Table of contents

Crystalline silicon, including p-type czochralski (CZ) mono-crystalline and multi-crystalline (mc) silicon, has been the workhorse for solar cell production for decades. In recent years, there has been many developments in n-type c-Si solar cells basically due to the advantages of n-type c-Si wafers over p-type wafers. However, there are some limitations in making n-type solar cells considering the technologies involved to fabricate p-type cells. In this paper, different advantages of n-types wafers, their limitations in solar cell production, and an analysis of total market coverage are discussed.

The structural, electronic and optical properties of PbZrTiO₃ (PZT) and PbSnZrTiO₃ (PSnZT) have been studied by a quantum-mechanical calculation using a total-energy pseudopotential code. This compound has a tetragonal crystal structure with space group P4mm of a ferroelectric phase. Different compositions of titanium (Ti) and zirconium (Zr) in PZT and PSnZT were varied with Ti/Zr composition of 33/66, 50/50, and 66/33. It is found that the different compositions of Ti/Zr have changed the lattices and the band structure of both materials. The cohesive energy was calculated to predict the most suitable composition for modification in PZT and PSnZT. The refractive index under the change of Ti/Zr composition was also investigated. The PZT and PSnZT compounds may be promising materials for future ferroelectric and piezoelectric applications.

A high power Nd: YAG laser has been employed to produce magnetic colloids (ferrofluids) of iron oxide nanoparticles (NPs) in double distilled water. It is found that FeO (Wüstite) phase of iron oxide has been produced as an initial product; after oxidation and agglomeration it appears as Fe₂O₃ a stable composition of iron oxide. UV–visible absorption spectroscopy has been employed to distinguish both phases of iron oxide NPs. Absorption band gap of as synthesized ferrofluids at different pulse energies (30, 40, 50, 60 mJ) has been calculated. The absorption band gap of as synthesized FeO magnetic colloids is found in the range of (2.91–3.13 eV) and (3.37–3.91 eV) respectively which arises due to pair excitation and charge transfer. Absorption band gaps of Fe₂O₃ are found in the range of (2.16–2.28 eV) and (2.68–3.10 eV) respectively again due to pair excitation and charge transfer. Magnetic measurement was performed using VSM which confirms antiferromagnetic nature of FeO NPs with coercivity 47 Oe and magnetic domain size 73.50 Å at 300 K. Zero field cooled and field cooled magnetization confirms blocking and Néel temperature 245  ±  2 K and 181  ±  2 K respectively.

Highlight for review

1. As synthesized colloidal suspension of iron oxide NPs can be used as efficient cooling agent.

2. FeO composition of iron oxide has been synthesized using PLA

3. Optical band gap of colloidal suspension of iron oxide NPs is calculated at different laser energy.

4. Magnetic properties of iron oxide NPs have been studied.

InN/InGaN single quantum well (SQW) was fabricated on 100 nm GaN buffer layer which was deposited on GaN template by plasma assisted molecular beam epitaxy (PA-MBE). The In composition and the surface morphology were measured by x-ray diffusion (XRD) and atom force microscope (AFM), respectively. Afterwards, the sample was fabricated into site-controlled nanowires arrays by hot-embossing nano-imprint lithography (HE-NIL) and ultraviolet nanoimprint lithography (UV-NIL). The nanowires were uniform along the c-axis and aligned periodically as presented by scanning electron microscope (SEM). The single nanowire showed disk-in-a-wire structure by high angle annular dark field (HAADF) and an In-rich or Ga deficient region was observed by energy dispersive x-ray spectrum (EDXS). The optical properties of the SQW film and single nanowire were measured using micro photoluminescence (µ-PL) spectroscopy. The stimulating light wavelength was 632.8 nm which was emitted from a He-Ne laser and the detector was a liquid nitrogen cooled InGaAs detector. A blue peak shift from the film material to the nanowire was observed. This was due to the quantum confinement Stark Effect. More importantly, the 1.55 µm emission was given from the single disk-in-a-wire structure at room temperature. We believe the arrays of such nanowires may be useful for quantum communication in the future.

α-Fe₂O₃ films are deposited on fluorine-doped tin oxide (FTO) and indium-doped tin oxide (ITO) substrates for 1, 4 and 6 min using a spray pyrolysis technique. We also deposited α-Fe_2−xCr_xO₃ (x  =  0.0, 0.1, 0.2, 0.3, 0.4, 0.7 and 0.9) films on the FTO substrate for a deposition time of 35 s. The structural and optical properties of these films were then studied. The x-ray diffraction (XRD) patterns show that all the films are crystalline in nature with a hexagonal crystal structure. The average grain size and unit cell volume were calculated using XRD data. It is found that the average grain size and unit cell volume increase with an increasing film thickness and Cr-doping concentration. The value of strain decreases with an increasing film thickness and Cr-doping content. It is also found that films with the same deposition time on the ITO substrate are more crystalline than on the FTO substrate. Furthermore, the average grain size is obtained from field emission scanning electron microscopy (FESEM) images. FESEM analysis confirms that the average grain size increases with the film thickness and Cr-doping concentration. The optical absorption spectra of the films show that the absorbance increases with an increasing deposition time and Cr concentration. The energy band gap (E_g) of all the films has been calculated using Tauc's relation. A narrowing of the band gap was observed with an increase in film thickness and Cr-doping content. The reduction of the band gap with the increase in film thickness of the films deposited on the ITO substrate is larger than for the film deposited on the FTO substrate. The refractive index is also obtained from the absorption spectra of the films using the Moss relation: n  =  $\sqrt[4]{\left(k/{{E}_{\text{g}}}\right)}$, where k  =108 eV. The refractive index decreases with an increase in the optical band gap. The band gaps of the films are also calculated from the FTIR spectra. This is in good agreement with the UV data. The correlation between the structural and optical properties of the deposited films has been discussed.

Effects of boron and phosphorus doping on the structural, electrical, and optical properties of silicon nanocrystals in superlattice thin films were investigated. Silicon nanocrystals were fabricated via magnetron sputtering of stoichiometric silicon rich oxide and silicon dioxide bilayers followed by high temperature annealing at 1100 degrees Celsius. The characterization techniques used include: high-resolution transmission electron microscopy with energy filtering, grazing incidence x-ray diffraction, Raman, photoluminescence, and photothermal deflection spectroscopy, as well as electrical measurements. Results showed that phosphorus doping causes the loss of the bilayer structure and an increase in the average size of the silicon nanocrystals due to softening of the silicon dioxide matrix during post-sputter annealing. The result was a decrease in quantum confinement and a redshift in photoluminescence spectrum with an absorption profile similar to crystalline silicon. The undoped (intrinsic) sample maintained its bilayer structure and displayed stronger quantum confinement with higher photoluminescence peak energy and higher absorption coefficient. In-between, the boron doped sample was more similar structurally to the intrinsic sample, although merging between bilayers resulted in an extensive silicon nanocrystalline network. Optically, it displayed different effects due to photoluminescence quenching and free carrier absorption. Finally, both doped samples exhibited a decrease in electrical resistivity.

We prepared a 3D monolith by integrating graphite nanosheet encapsulated iron nanoparticles (Fe@GNS) into graphite felt (GF) supports. The structural properties of the resulting Fe@GNS/GF monolith are characterized by x-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and N₂ adsorption–desorption isotherms. The Fe@GNS/GF monoliths are utilized as a bifunctional sorbent and catalyst for water remediation. Using Congo red and methyl violet 2B as model pollutants, the sorption and catalytic performance of the Fe@GNS/GF composite are examined. The Fe@GNS/GF monolith possesses maximum sorption capacities of 177 and 142 mg g⁻¹ for the sorption of CR and MV-2B, respectively. It also exhibits rate constants of 0.0563 and 0.0464 min⁻¹ for the catalytic degradation of CR and MV-2B, respectively. As a proof of concept, the Fe@GNS/GF is successfully utilized to decontaminate simulated organic waste water via a combination of sorption and catalytic degradation processes.

Graphene oxide decoration with europium was carried out using SDS (sodium dodecyl sulfate) as the surfactant. The reaction was performed in a microwave oven and subsequently underwent thermal treatment under hydrogen flow. The results found in the present work demonstrate that through the use of SDS surfactant aggregates of hemi-cylindrical and onion-like structures could be obtained; which propitiate an enhanced synergistic photoluminescence located at the red wavelength. On the other hand, after thermal treatment the aggregates disappear providing a good dispersion of europium, however a decrease in the photoluminescence signal is observed. The graphene oxide decorated with europium was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier infrared transform spectroscopy (FTIR), RAMAN spectroscopy, x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques, showing the characteristic features of graphene oxide and europium.

In this paper, we report temperature dependent photoluminescence (PL) characteristics of CdSe colloidal QDs with average diameter ~2.8 nm. Temperature dependence of strongly confined exciton PL peak position, linewidth and intensity were investigated in 30 K to 300 K temperature range. Our studies reveal nearly four times weaker exciton-LO phonon coupling than bulk CdSe crystal. Theoretically, it should be vanishingly small due to near identical electron and hole charge distributions in strongly confined QDs. On the other hand, exciton-acoustic phonon coupling is an order of magnitude larger than its bulk counterpart. Observed finite value of exciton-LO phonon coupling and enhanced exciton-acoustic phonon coupling are due to piezoelectric strain fields. PL intensity exhibits anomalous behavior in the temperature range 100–230 K. This has been explained by thermally activated detrapping of the charge carriers trapped in the potential wells formed at the interface adjoining dislocations/stacking faults developed during the synthesis process. Above 230 K, PL is partially quenched by thermal escape of charge carriers from luminescing exciton state to higher lying nonluminescing states.

Uniform peony-like FeWO₄ (average diameter 430 nm) was synthesized by using a convenient solvothermal route in the presence of ethylene glycol and β-cyclodextrin. Using some research techniques, it was verified that the product is phase-pure and well-crystalline peony-like FeWO₄, which was made up of many small nanosheets with a thickness of about 10 nm. The specific surface area and the band gap energy of the peony-like FeWO₄ were 67.836 m² g⁻¹ and 1.87 eV, respectively. The product showed an extremely fast adsorbent speed and an excellent adsorbtion capacity for organic dyes. In particular, for methylene blue (MB), the adsorption capacities of the peony-like FeWO₄ reached as high as 69.4 mg g⁻¹ in only 5 min. The pseudo-second-order model and Langmuir isotherm model showed good fit with the adsorption data. According to the Langmuir isotherm model, the maximum adsorption capacity was 79.18 mg g⁻¹ for MB. In addition, in the presence of H₂O₂, the peony-like FeWO₄ showed good catalytic performance such that 98% of MB was degraded in only 32 min.

A highly qualitative NiO nanostructure was synthesized using thermal dry oxidation of metallic Ni thin films on ITO/glass using the RF sputtering technique. The deposited nickel thin films were oxidized in air ambient at 550 °C inside a furnace. The structural and surface morphologies, and the electrical and gas sensing properties of the NiO nanostructure were examined. An x-ray diffraction analysis demonstrated that the NiO nanostructure has a cubic structure with orientation of the most intense peak at (2 0 0), and shows good crystalline quality. Finite-element scanning electron microscopy and energy dispersive x-ray spectroscopy results revealed O and Ni present in the treated samples, indicating a pure NiO nanostructure composition obtained with high porosity. The electrical properties of the oxidize Ni thin films showed a p-type NiO thin film semiconductor. A hydrogen gas sensing measurement was made at different operating temperatures and different gas concentrations with a detection limit of 30 ppm concentration. The sensor device shows great sensing properties with an excellent sensitivity (310%) at room temperature, which decreases with an increase in the operating temperature. Superfast response and recovery times of 6 and 0.5 s, respectively, were observed with the device at 150 °C operating temperature.

Ge_(x)[SiO₂]_(1−x) (0.1  ⩽  x  ⩽  0.4) films were deposited onto Si(0 0 1) or fused quartz substrates using co-evaporation of both Ge and SiO₂ in high vacuum. Germanium nanocrystals were synthesized in the SiO₂ matrix by furnace annealing of Ge_x[SiO₂]_(1−x) films with x  ⩾  0.2. According to electron microscopy and Raman spectroscopy data, the average size of the nanocrystals depends weakly on the annealing temperature (700, 800, or 900 °C) and on the Ge concentration in the films. Neither amorphous Ge clusters nor Ge nanocrystals were observed in as-deposited and annealed Ge_0.1[SiO₂]_0.9 films. Infrared absorption spectroscopy measurements show that the studied films do not contain a noticeable amount of GeO_x clusters. After annealing at 900 °C intermixing of germanium and silicon atoms was still negligible thus preventing the formation of GeSi nanocrystals. For annealed samples, we report the observation of infrared photoluminescence at low temperatures, which can be explained by exciton recombination in Ge nanocrystals. Moreover, we report strong photoluminescence in the visible range at room temperature, which is certainly due to Ge-related defect-induced radiative transitions.

Carbon nanostructured materials have been widely investigated and explored all over the world. However, the frontiers of applications and basic examinations related to these materials have yet to be opened in terms of their stability and robustness in the required environment. I report the temperature-dependent transport properties of vertically aligned graphene nanoflakes (GNFs) at room temperature to 800 K. Investigation of GNFs incorporated with nitrogen (N₂) of varying concentration in situ and their possible conduction mechanism has been carried out over the entire range of temperatures mentioned above. N-type conductivity, carrier concentration, mobility and modulation at various temperatures are observed by means of Hall-effect measurements. The film of GNFs incorporated with nitrogen in situ persists in a linear trend, satisfying conduction behaviour expectations for all measured transport parameters with only a small discrete-point anomaly. Supporting evidence of N₂ incorporation and structural modifications is studied by scanning electron microscopy, Raman spectroscopy and x-ray photoemission spectroscopy. The observation findings also provide the thermal stability of N₂ incorporated into two-dimensional vertically standing GNFs.

A simple route to prepare Gd_0.7Sr_0.3MnO₃ nanoparticles by ultrasonication of their bulk powder materials is presented in this article. For comparison, Gd_0.7Sr_0.3MnO₃ nanoparticles are also prepared by ball milling. The prepared samples are characterized by x-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive x-ray (EDX), x-ray photoelectron spectroscope (XPS), and superconducting quantum interference device (SQUID) magnetometer. XRD Rietveld analysis is carried out extensively for the determination of crystallographic parameters and the amount of crystalline and amorphous phases. FESEM images demonstrate the formation of nanoparticles with average particle size in the range of 50–100 nm for both ultrasonication and 4 h (h) of ball milling. The bulk materials and nanoparticles synthesized by both ultrasonication and 4 h ball milling exhibit a paramagnetic to spin-glass transition. However, nanoparticles synthesized by 8 h and 12 h ball milling do not reveal any phase transition, rather show an upturn of magnetization at low temperature. The degradation of the magnetic properties in ball milled nanoparticles may be associated with amorphization of the nanoparticles due to ball milling particularly for milling time exceeding 8 h. This investigation demonstrates the potential of ultrasonication as a simple route to prepare high crystalline rare-earth based manganite nanoparticles with improved control compared to the traditional ball milling technique.

Implantation of hydrogen in single-crystal silicon (c-Si) is known to affect its machining. However, very little is reported on the material and mechanical properties of hydrogen-implanted silicon (Si). In this article, near-surface regions (~0–500 nm) of lightly doped (1 0 0) Si were modified by varying the hydrogen concentration using ion implantation. The maximum hydrogen concentration was varied from ~4  ×  10²⁰ to ~3.2  ×  10²¹ cm⁻³. The implanted Si was investigated by nanoindentation. From the dynamic nanoindentation test, it was found that in hydrogen-implanted Si hardness is increased significantly, while the elastic modulus is reduced. The nanoindentation-induced Si phase transformation was studied under different load/unload rates and loads. Raman spectroscopy revealed that the hydrogen implantation tends to suppress Si-XII and Si-III phases and facilitates amorphous Si formation during the unloading stage of nanoindentation. Both the mechanical properties and phase transformations were qualitatively related not only to the hydrogen concentration, but also to the implantation-generated defects and strain.

The employment of mechanophores and mechanochemistry in materials has enabled the development of novel force-responsive materials. Studies exploring the force sensing capabilities of the UV-dimerized cinnamoyl moiety have shown that after severing its cyclobutane bond under an external force, the moiety will revert back to its initial fluorescent state. Current fluorescent detection methods, however, fail to properly detect cyclobutane mechanophore activation in highly opaque samples. In this study, we apply Fourier transform infrared spectroscopy technique to measure a composite's chemical structure and examine activation of the cinnamoyl moiety's cyclobutane bond, regardless of sample transparency. Samples containing 10 wt% poly(vinyl cinnamate) as the active mechanophore, as well as set of samples with an additional 0.5 wt% carbon nanotubes, used to create a completely opaque composite, were developed. Both composites showed an increase in peaks at 1650 cm⁻¹ and 1635 cm⁻¹ after strain, which correspond to the cis and trans isomers of the fluorescent double-bond in the cinnamoyl group. A statistical difference in peak height occurs as early as 4% strain—before the yield point of the composites—indicating that early signal detection is possible. This improved sensing method provides a simpler, faster method for early signal detection over fluorescent imaging.

In the present work, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to ascertain the grafting of an organic layer of polyvinyl alcohol (PVA) onto the surface of semiconducting SiC nanocrystals using a novel method. FTIR spectroscopy reveals the introduction of new peaks corresponding to various functional groups of PVA alongwith the presence of characteristic Si–C vibrational peak in the spectra of grafted SiC nanocrystals. Raman spectra depict the presence of changes introduced in the characteristic TO and LO mode of vibration of SiC nanocrystals after grafting procedure. XRD analysis confirmed that the grafting procedure did not alter the crystalline geometry of SiC nanocrystals. TEM and SEM images further support the FTIR and Raman spectroscopic results and confirm the presence of PVA layer around SiC nanocrystals. Thermal degradation behavior of PVA-g-SiC nanocrystals has been studied using TGA analysis.

Diabetes mellitus is the most common endocrine disorder due to carbohydrate metabolism. Also, zinc and its supplements have been used in Indian traditional medicines for treating urinary tract infections. In this work, an attempt has been made to compare the properties of 'Yashadha Bhasma' a traditional ayurvedic ZnO supplement for diabetic treatment with the laboratory-synthesized ZnO nanoparticles. The nano-sized ZnO particles are synthesized using co-precipitation method and calcined at 400 °C for further purification. Confirmation of ZnO and presence of Ca and K elements additional to Zn in Yashadha Bhasma is confirmed from XPS. The morphology of ZnO is found to be spherical with average diameter of 15 nm. TEM results show that ZnO rods of Yashadha Bhasma are porous and non-uniform. Glucose degradation studies revealed good performance with ZnO nanoparticles with 80% degradation occurring within 15 min itself. Antibacterial studies also performed well establishing efficacy of ZnO nanoparticles against both gram-positive and gram-negative bacterial strains, thereby establishing suitable material for treating diabetes mellitus and also curing bacterial wound infections arising due to diabetes mellitus.

In this study, we have demonstrated that the multilayer nanoshells with dual symmetry breaking including the offset both dielectric layer and Au core can realize highly tunable extinction properties which are sensitively dependent on the relative offset direction between the Au core and dielectric layer. By controlling the offset direction of the Au core relative to the dielectric layer, the distinct multipeaked spectra with highly tunable multiple plasmon resonances can be excited selectively. The plasmon hybridization theory is applied to elucidate the origin of these resonances from the interactions of an admixture of both primitive and multipolar modes between the core and the broken nanoshell. Furthermore, the electromagnetic hot spots in dual symmetry breaking is accompanied by local-field enhancements, depending on the offset direction of the Au core relative to the dielectric layer, significantly larger than those obtainable for the single broken nanoparticle case.

Modern agriculture calls for a decrease in pesticide application, particularly in order to decrease the negative impact on the environment. Therefore the development of new active substances and plant protection products (PPP) to minimize the chemical load on ecosystems is a very important problem. Substances based on silver nanoparticles are a promising solution of this problem because of the fact that in correct doses such products significantly increase yields and decrease crop diseases while displaying low toxicity to humans and animals.

In this paper we for the first time propose application of polymeric guanidine compounds with varying chain lengths (from 10 to 130 elementary links) for the design and synthesis of modified silver nanoparticles to be used as the basis of a new generation of PPP. Colloidal solutions of nanocrystalline silver containing 0.5 g l⁻¹ of silver and 0.01–0.4 g l⁻¹ of polyhexamethylene biguanide hydrochloride (PHMB) were obtained by reduction of silver nitrate with sodium borohydride in the presence of PHMB. The field experiment has shown that silver-containing solutions have a positive effect on agronomic properties of potato, wheat and apple. Also the increase in activity of such antioxidant system enzymes as peroxidase and catalase in the tissues of plants treated with nanosilver has been registered.

Nanocrystalline materials (NcMs) are multi-phase composites containing nanograins, nanovoids and interface. Dynamic behavior of nanocrystalline silicon mass sensors on an elastic substrate is analyzed based on a two-variable refined plate model. Due to the experimental observation of grains micro-rotation and strain gradients near interfaces, the strain gradient based couple stress theory is employed to describe the size-dependent behavior of the nanocrystalline sensors. A micromechanical model is employed to incorporate the effects of inclusions and their surface energies. Galerkin's method is implemented to obtain the frequency shifts of the nanocrystalline mass sensor with different boundary conditions. One can see that the nanoparticle mass, nanograins size, nanograins surface energy, nanovoids size, void percentage, interface region, scale parameter, foundation constants and boundary conditions have a great influence on the frequency shifts of nanocrystalline mass sensors.

To replace traditional preparation methods of silica aerogels, a small-molecule 1,2-epoxypropane (PO) has been introduced into the preparation process instead of using ammonia as the cross-linking agent, thus generating a lightweight, high porosity, and large surface area silica aerogel monolithic. We put forward a simple solution route for the chemical synthesis of silica aerogels, which was characterized by scanning electron microscopy (SEM), TEM, XRD, FTIR, thermogravimetric analysis (TGA) and the Brunauer–Emmett–Teller (BET) method In this paper, the effect of the amount of PO on the microstructure of silica aerogels is discussed. The BET surface areas and pore sizes of the resulting silica aerogels can be freely adjusted by changing the amount of PO, which will be helpful in promoting the development of silica aerogels to fabricate other porous materials with similar requirements. We also adopted a new organic solvent sublimation drying (OSSD) method to replace traditional expensive and dangerous drying methods such as critical point drying and freeze drying. This simple approach is easy to operate and has good repeatability, which will further facilitate actual applications of silica aerogels.

Localized surface plasmon resonance has been a unique and intriguing feature of silver nanoparticles (AgNPs) that has attracted immense attention. This has led to an array of applications for AgNPs in optics, sensors, plasmonic imaging etc. Although numerous applications have been reported consistently, the importance of buffer and reaction parameters during the synthesis of AgNPs, is still unclear. In the present study, we have demonstrated the influence of parameters like pH, temperature and buffer conditions (0.1 M citrate buffer) on the plasmonic resonance of AgNPs. We found that neutral and basic pH (from alkali metal) provide optimum interaction conditions for nucleation of plasmon resonant AgNPs. Interestingly, this was not observed in the non-alkali metal base (ammonia). Also, when the nanoparticles synthesized from alkali metal base were incorporated in different buffers, it was observed that the nanoparticles dissolved in the acidic buffer and had reduced plasmonic resonance intensity. This, however, was resolved in the basic buffer, increasing the plasmonic resonance intensity and confirming that nucleation of nanoparticles required basic conditions. The above inference has been supported by characterization of AgNPs using UV–Vis spectrophotometer, Fluorimetry analysis, Infrared spectrometer and TEM analysis. The study concluded that the plasmonic resonance of AgNPs occurs due to the interaction of alkali (Na) and transition metal (Ag) salt in basic/neutral conditions, at a specific temperature range, in presence of a capping agent (citric acid), providing a pH tune to the overall system.

Platinum and palladium bimetal nanoparticles on ferroferric oxide (PtPd/Fe₃O₄ NPs) nanocomposite catalysts were successfully synthesized with polyvinyl pyrrolidone as a stabilizing agent. The resultant samples were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, inductively coupled plasma, and magnetic studies. The catalytic performance of the PtPd/Fe₃O₄ NPs in the Heck and Suzuki coupling reactions was evaluated. Results showed that the cubic phase of Pt and Pd bimetal nanoparticles coexists with that of Fe₃O₄. The PtPd/Fe₃O₄ NP catalysts, which were approximately 22 nm in size, showed excellent catalytic activity in the Heck and Suzuki reactions. Moreover, the catalyst can be recovered with a magnet and reused several times without the significant loss of catalytic activity.

In this study, nitrogen-doped rutile TiO₂ nanorod arrays (N–TiO₂) were prepared through a facile hydrothermal process for the first time, using ammonia and butyl titanate as nitrogen and titanium source, respectively. The crystal structure and morphology of N–TiO₂ were investigated by x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), which showed that the length and diameter of the nanorods as well as the intensity of (0 0 2) diffraction peak increased sharply with doping concentration. According to the x-ray photoelectron spectroscopy (XPS), only a small amount of nitrogen in reactants was deposited on the surface of TiO₂ nanorods, and even less could enter into bulk TiO₂ and form O–Ti–N structure. With the increase of doped nitrogen content, photoelectrical conversion efficiency of all-solid-state dye-sensitized solar cells first increased and then decreased, with the highest value of 2.88%, which was much higher than that of un-doped samples (1.57%). The improvement of the solar cells could be mainly attributed to vertical growth of the nanorod caused by the addition of nitrogen. After sintering treatment, the growth of (1 0 1) crystal face further increased the photoelectrical conversion efficiency to about 3.86%. Meanwhile, commercial liquid iodic electrolyte was also chosen to fabricate solar cells for comparison, and an efficiency of 5.36% was reached.

Carbon-encapsulated Fe–Ni alloy nanoparticles were synthesized through detonation using two composite explosive precursors doped with Fe (NO₃)₃ · 9H₂O and Ni(NO₃)₂ · 6H₂O · The morphology, components, and magnetism of the synthesized carbon-encapsulated alloy nanoparticles were characterized through x-ray diffraction studies (XRD, Rigaku, D/Max 2400, Japan), Raman spectroscopy (Raman, Thermo Fisher, DXR Microscope, USA), Transmission electron microscopy (TEM, FEI, Technai F30, USA) attached with energy dispersive x-ray spectroscopy (EDS), and vibrating sample magnetometer (VSM, JDM-13, China) analyses. The denotation products of the two precursors were compared. The influence of the components of the two precursors on the products was also analyzed. Results showed that both precursors detonated and synthesized the carbon-encapsulated Fe–Ni nanoparticles with a core–shell structure. The grains exhibited sizes ranging from 10 nm to 100 nm and were uniformly distributed. The encapsulated metal core was mainly composed of different proportions of Fe and Ni. The outer shell was composed of graphite and amorphous carbon. VSM analysis indicated that the detonated composite nanoparticles showed superparamagnetism at room temperature.

A simple thermal decomposition technique has been executed for the synthesis of cadmium ferrite (CdFe₂O₄) nanoparticles. With the help of x-ray diffraction; scanning electron microscopy, energy-dispersive x-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy the prepared nanoparticles were identified. The crystal size of the average particles aggregated and was found approximately to be 10–14 nm by means of XRD studies. However, the results of high-resolution transmission electron microscopy (HR-TEM) investigation ensured distinguished nanoparticles, and also the polycrystalline nature of those nanoparticles was confirmed by selected area diffraction (SAED) patterns. The scanning electron microscopy (SEM) images explored a random distribution of grains within the sample. Thin film surface topology of roughness and surface current measurement were studied by atomic force microscopy (TP-AFM, C-AFM). Hence, from the ultraviolet–visible (UV) spectroscopic absorption illustrated significant optical properties. Moreover, the optical energy band gap (E_g) of CdFe₂O₄ nanoparticle was determined to be 1.74 eV. By studying the variation of dielectric constant and dielectric loss with respect to frequency, the CdFe₂O₄ nanoparticles electrical properties were analyzed. Analysis in the real and imaginary part of impedance explained their frequency and temperature dependence of the CdFe₂O₄ nanoparticles. The traditional solution-phase organometallic approach provides an effective way to synthesize high quality hydrophobic semiconductor-CdFe₂O₄ nanoparticles. Our simple, cost-effective approach is quite general, which is applicable to other nanomaterials, and it utilizes the currently mature in Nano-chemistry. The nanocomposite assemblies' exhibit strong anisotropic optical and electrical properties are open up new possibilities in remarkable applications for optoelectronics in the near future.

The effects of the wetting layer thickness (t_WL) on the electronic properties of direct band gap type-I strained dome shaped Ge_(1−x)Sn_x quantum dot (QD) embedded in Ge matrix is numerically studied. The emission wavelength and the energy difference between S and P electron levels have been evaluated as a function of t_WL for different QD size and composition with constant height to diameter ratio. The emission wavelength is found to be red shifted by increasing the wetting layer thickness, with smaller size QD being more sensitive to the variation of t_WL. Furthermore, the minimum Sn composition required to fit the directness criteria is found to reduce by increasing the wetting layer thickness.

Surface enhanced Raman scattering (SERS) spectroscopy, a powerful contemporary tool for studying low-concentration analytes via surface plasmon induced enhancement of local electric field, is of utility in biochemistry, material science, threat detection, and environmental studies. We have developed a simple, fast, scalable, and relatively low-cost optical method of fabricating and characterizing large-area, reusable and broadband SERS substrates with long storage lifetime. We use tightly focused, intense infra-red laser pulses to write gratings on single-crystalline, Au (1 1 1) gold films on mica which act as SERS substrates. Our single-crystalline SERS substrates compare favourably, in terms of surface quality and roughness, to those fabricated in poly-crystalline Au films. Tests show that our SERS substrates have the potential of detecting urea and 1,10-phenantroline adulterants in milk and water, respectively, at 0.01 ppm (or lower) concentrations.

Commercial coolants such as water, ethylene glycol and triethylene glycol possess very low thermal conductivity, high vapor pressure, corrosion issues and low thermal stability thus limiting the thermal enhancement of the nanofluids. Thus, a new type of base fluid known as deep eutectic solvents (DESs) is proposed in this work as a potential substitute for the conventional base fluid due to their unique solvent properties such as low vapor pressure, high thermal stability, biodegradability and non-flammability. In this work, 33 different DESs derived from phosphonium halide salt and ammonium halide salts were synthesised. Carbon nantubes (CNTs) with different concentrations (0.01 wt%–0.08 wt%) were dispersed into DESs with the help of sonication. Stability of the nanofluids were determined using both qualitative (visual observation) and quantitative (UV spectroscopy) approach. In addition, thermo-physical properties such as thermal conductivity, specific heat, viscosity and density were investigated. The stability results indicated that phosphonium based DESs have higher stability (up to 4 d) as compared to ammonium-based DESs (up to 3 d). Thermal enhancement of 30% was observed for ammonium based DES-CNT nanofluid whereas negative thermal enhancement was observed in phosphonium based DES-CNT nanofluid.

Microwave absorption materials such as traditional ferrite have received increasing attention owing to wide applications in national defense, electronics industry and physical electromagnetic protection. However, the insufficient absorption intensity coupled with the large application thickness have limited the practical application of the traditional materials in absorbing area. To address such issues, the PANI/Ni_0.5Zn_0.5Fe₂O₄ nanoparticles were fabricated, and the microscopic morphologies, x-ray diffraction (XRD) spectras, dielectric parameters and microwave absorption property of the as-prepared samples were charaterizated. The qualified absorption bandwidth (5.1 GHz) was remarkably broadened at a small thickness (1.78 mm), suggesting a novel platform for designing tunable qualified bandwidth lightweight absorbing materials.

Nanocrystalline diamond (NCD) films are being used in a large number of applications. Also, diamond nanorods (DNRs) exhibit distinctive features that are not present in diamond films, because of the tunable large surface-to-volume ratio and tubular configuration. In this work, we report on the synthesis of DNRs by means of the bottom-up and template-free method from NCD films by the hot filament chemical vapor deposition system. The substrate materials used for diamond deposition were stainless steel (AISI 316) and chromium nitride-coated stainless steel. On both substrates, NCD films and then DNRs have been synthesized. The micro-Raman confirms that the synthesized structure is NCD. In addition, the grazing incident x-ray diffraction pattern confirms the presence of cubic diamond and rhombohedral diamond as a film on the CrN and Cr₂N interlayer. Also, the DNRs are encased in an amorphous carbon (a-C) shell. The DNRs are grown on the NCD grains by a bottom-up technology and template-free method. Their orientations are almost random in the diamond thin-film surface. In addition, the density of DNRs on the NCD film for the CrN interlayer is more than for the stainless-steel substrate. The NCD/DNR films are dense, adhesive, continuous, and almost uniform on the CrN-coated stainless-steel substrate.

SrFe₁₂O₁₉/FeCo composite particles with different mass ratios of SrFe₁₂O₁₉ to FeCo were synthesized through a cryogenic ball milling process. The corresponding products were characterized with scanning electron microscopy (SED), transmission electron microscopy (TEM), x-ray diffraction (XRD) and vibrating sample magnetometer (VSM) for crystal morphology, elemental distribution, crystal phases, and magnetic properties. The results showed that when the mass percentage of FeCo was less than 15%, smooth magnetic hysteresis loops could be obtained from SrFe₁₂O₁₉/FeCo composite particles, indicating effective magnetic exchange coupling between the SrFe₁₂O₁₉ and FeCo particles. A further FeCo mass increase resulted in kinks in the magnetic hysteresis loop and destroyed the magnetic exchange coupling. As a comparison, room temperature ball milling of SrFe₁₂O₁₉/FeCo (95/5 wt%) cannot achieve magnetic exchange coupling between SrFe₁₂O₁₉ and FeCo due to FeCo nanoparticle agglomeration.

Atomic layer deposition (ALD) followed by microwave hydrothermal processing was successfully employed for producing doped and vertically aligned ZnO nanorod arrays with different aspect ratio. Firstly, a textured ZnO layer with preferential orientation normal to the c-axis was formed on substrate (1 1 1) silicon single crystals by means of the ALD technique. This was achieved through the decomposition of diethylzinc at 190 °C and 3.289  ×  10⁻⁴ atm, which provided an adequate template with nucleation sites, favoring further growth of vertical nanorods. Subsequently, nanorod array growth was produced on the same surfaces through solvothermal synthesis using as promoter a solution of Zn(NO₃)₂. In addition, growth of indium-doped ZnoO nanorods over the substrates was produced by using In(CH₃COO)₃ as a doping agent. The method presented allows good quality ZnO and Zn_1−xIn_xO thin films to be obtained. Photoluminiscence spectra show clear evidence of the inclusion of indium in the ZnO matrix. The higher intensity ratio Zn_0.96In_0.4O/ZnO was increased 40-fold, demonstrating such an effect.

The strong polarization of isolated finite-length single-walled carbon nanotubes (CNTs) or bundles of CNTs has been predicted to lead to a strong near field enhancement effect that provokes additional electromagnetic energy dissipation in a conductive host (Shuba et al 2010 J. Appl. Phys. 108 114302). Here, we theoretically and experimentally show that this effect can be observed in the microwave frequency range via measurements of the spectra of the effective permittivity of CNT-based suspensions. Microwave effective permittivity of the suspensions comprising both annealed and doped CNTs has been measured in the temperature range from 300 to 330 K. The experimental data gives evidence of the unique properties of CNTs—to enhance electromagnetic fields in a volume as much as 100 times larger than the volume occupied by the nanotube itself.

Phase pure tin oxide (SnO₂) and indium doped SnO₂ nanocrystalline powders were synthesized in a single step by a flame spray pyrolysis method. The as-synthesized powders were characterized by standard techniques of x-ray diffraction, scanning and transmission electron microscopy, x-ray photoelectron spectroscopy and absorption spectroscopy. Using x-ray diffraction, it was established that the powders had the rutile (cassiterite) structure with tetragonal unit cells in the space group P4₂/mnm. Using the Rietveld refinement method, structural analysis was carried out in order to obtain the lattice parameters, volume and density. X-ray photoelectron spectra confirmed the presence of indium in the doped samples. Absorption spectra revealed that the powders were transparent to the visible spectrum with a sharp absorption below 350 nm. Energy bandgaps, estimated by Tauc plots, established that increasing the doping concentration reduced the bandgap.

The mechanical properties and deformation mechanism of alumina (Al₂O₃) ceramic nanopillars and microstructures have been studied using in situ transmission electron microscopy (TEM) compression and nanoindentation experiments. It has been found that the Young's modulus of Al₂O₃ nanopillars significantly increases with a decrease of its thickness; it ranges from 54.8 GPa for the nanopillar of radius 175 nm to 347.5 GPa for the one of radius of 75 nm. The hardness of Al₂O₃ microstructures estimated by the nanoindentation is between 3.19 to 20.60 GPa. The Raman spectra of Al₂O₃ substrate has a production peak (577.3 cm⁻¹) between 418.3 and 645.2 (cm⁻¹) peaks. The strain hardening behavior of Al₂O₃ microstructures has been observed and the impact of size on the compressive and bending behavior of Al₂O₃ micro-pillared structures is also examined and explained.

The effect of sintering temperature and Ti:Zn ratio of precursor solutions on the structural, morphological and thermoelectric properties of Zinc titanate (TZO) nanocrystals have been investigated. TZO nanocrystals were synthesized by changing the molar ratio of precursors of Zn and Ti sources by sol-gel method. The synthesized materials were sintered at different temperatures and the formation of multi phases of TZO were analysed by x-ray diffraction studies. The morphological properties and composition of TZO samples were studied by FESEM, TEM and XPS analysis. The thermoelectric properties of the TZO have been studied by measuring the Seebeck coefficient of the materials at various temperature. It was observed that the Seebeck coefficient of TZO sample increases with increasing Zn content in the sample especially at high temperature.

ZnO/g-C₃N₄ nanocomposite photocatalysts were prepared using a simple and cost-effective pyrolysis method. The structural, optical, surface morphological and photocatalytic properties of the nanocomposites were analyzed and compared with those of g-C₃N₄. X-ray diffraction results revealed that all the ZnO/g-C₃N₄ samples have a hexagonal wurtzite phase of ZnO. Spectroscopic results obtained via FT-IR technique were consistent with the layered structure of sp² hybridized bonding features of C and N in g-C₃N₄, besides Zn–O stretching vibrations. Photoluminescence results revealed that ZnO hybridization with g-C₃N₄ showed efficient separation and delayed recombination of photoinduced electron–hole pairs. TEM analysis clearly displayed that ZnO nanoparticles are anchored on g-C₃N₄ and showed the interface between the ZnO and g-C₃N₄. The ZnO/g-C₃N₄ nanocomposites exhibited enhanced visible light photocatalytic degradation against methylene blue dye when compared to g-C₃N₄. A plausible mechanism has been proposed for the observed enhanced photocatalytic activity.

We have calculated the implicit shift for various modes of frequency in a pure graphene sheet. Thermal expansion and Grüneisen parameter which are required for implicit shift calculation have already been studied and reported. For this calculation, phonon frequencies are obtained using force constants derived from dynamical matrix calculated using VASP code where the density functional perturbation theory (DFPT) is used in interface with phonopy software. The implicit phonon shift shows an unusual behavior as compared to the bulk materials. The frequency shift is large negative (red shift) for ZA and ZO modes and the value of negative shift increases with increase in temperature. On the other hand, blue shift arises for all other longitudinal and transverse modes with a similar trend of increase with increase in temperature. The q dependence of phonon shifts has also been studied. Such simultaneous red and blue shifts in transverse or out plane modes and surface modes, respectively leads to speculation of surface softening in out of plane direction in preference to surface melting.

In this paper, interactions of carbon monoxide (CO) and hydrogen sulfide (H₂S) with doped and decorated graphene were investigated by using density functional theory and quantum-espresso packages. First of all, impurity effects and properties like adsorption mechanism, the more probable position, binding energy, bond length, Lowdin charge analyze and density of state (DOS) have been determined and then the properties of CO and H₂S adsorption calculated, and a brief comparison with other studies has been done. All of these lead to tuning the electronic structure of graphene sheet with impurities that show higher affinities with H₂S and CO molecules in comparison to pristine graphene. The obtained results from DOS and charge transfer show that electrical conductance of the B doped graphene sheet and CuO Nano particle decorated—Boron doped graphene sheets are significantly changed compared to the pristine graphene sheet by an increase in the electronic states of near the Fermi's energy states.

The Ni/Cu/Ni tri-layer film with different thickness of Cu layer was deposited using pulsed electrodeposition method. The XRD pattern of all the films show the formation of fcc structure of nickel and copper. This shows the orientated growth in the (2 2 0) plane of the layered films as calculated from the relative intensity ratio. The layer formation in the films were observed from cross sectional view using FE-SEM and confirms the decrease in Cu layer thickness with decreasing deposition time. The magnetic anisotropy behaviour was measured using VSM with two different orientations of layered film. This shows that increasing anisotropy energy with decreasing Cu layer thickness and a maximum of  −5.13  ×  10⁴ J m⁻³ is observed for copper deposited for 1 min. From the K_eff.t versus t plot, development of perpendicular magnetic anisotropy in the layered system is predicted below 0.38 µm copper layer thickness.

Composites and hybrids of BN and Zn₃P₂ nanowires were made by consolidating respectively BN micropowder-Zn₃P₂ nanowire mixtures and non-conformally BN decorated Zn₃P₂ nanowires. The intent here is to study whether mere solid-state mixing of a thermal conductor and a thermal insulator leads to the engineering of the thermal conductivities of the resulting composites and hybrids. The results demonstrated that contrary to intuition, mere mixing of two materials, a thermal conductor (BN) and a thermal insulator (Zn₃P₂ nanowires), does not result in composites and hybrids that have thermal conductivities higher than those of the thermal insulator and lower than those of the thermal conductor. This contrary result is especially true in instances where microparticles or nanoparticles of a high thermal conductivity material are introduced into a matrix of the thermal insulator for achieving spatially uniform composites/hybrids and engineering the resulting materials' thermal conductivities. Here, both the size of the filler material and the type of interfaces formed between the matrix and the filler material play a major role in determining the ultimate thermal conductivities of the composites/hybrids. Imperfect interface formed between materials that have high lattice mismatches lead to lowering of the thermal conductivities of the composites/hybrids.

In this report, random nickel nanowires (Ni-NWs) meshes are fabricated by ions beam irradiation-induced nanoscale welding of NWs on intersecting positions. Ni-NWs are exposed to beam of 50 KeV Argon (Ar⁺) ions at various fluencies in the range ~10¹⁵ ions cm⁻² to 10¹⁶ ions cm⁻² at room temperature. Ni-NWs are welded due to accumulation of Ar⁺ ions beam irradiation-induced sputtered atoms on crossing positions. Ar⁺ ions irradiated Ni-NWs meshes are optically transparent and optical transparency is enhanced with increase in beam fluence of Ar⁺ ions. Ar⁺ ions beam irradiation-induced welded and optically transparent mesh is then exposed to 2.75 MeV hydrogen (H⁺) ions at fluencies 1  ×  10¹⁵ ions cm⁻², 3  ×  10¹⁵ ions cm⁻² and 1  ×  10¹⁶ ions cm⁻² at room temperature. MeV H⁺ ions irradiation-induced local heat cause melting and fusion of NWs on intersecting points and eventually lead to reduce contact resistance between Ni-NWs. Electrical conductivity is enhanced with increase in beam fluence of H⁺ ions. These welded highly transparent and electrically conductive Ni-NWs meshes can be employed as transparent conducting electrodes in optoelectronic devices.

1D nanocables consisting of metal core with high conductivity and protective polymer shell are promising for electronic devices. In this paper, silver nanowire/polyvinylidene fluoride (AgNW/PVDF) composite nanocables with excellent thermal stability were successfully fabricated by facile direct electrospinning (e-spinning), in which a slurry of AgNWs were uniformly dispersed into N,N-dimethylformamide/acetone solution containing 20% PVDF to form the e-spinning precursor solution. The decomposed temperature of resultant AgNW/PVDF nanocables is up to 460 °C. Interestingly, the as-spun nanocables exhibit more β phase of PVDF than that of pure PVDF nanofibers. The as-spun AgNW/PVDF nanocables could be applied in fields of antibacterial, ultrathin cables and optoelectronic devices.

Co–C core–shell nanoparticles have been synthesized in large quantity (in grams) by metal-organic chemical vapor deposition with analytical cobalt (III) acetylacetonate as precursor. Extremely small nanoparticles with an average core diameter of 3 nm and a shell thickness of 1–2 nm, and relatively large nanoparticles with an average core diameter of 23 nm and a shell thickness of 5–20 nm were obtained, depending on the deposition regions. The 3 nm Co nanocores are thermally stable up to 200 °C in air atmosphere, and do not exhibit visible structural and morphological changes after exposure to air at room temperature for 180 d. The extremely small core–shell nanoparticles exhibit typical superparamagnetic behaviors with a small coercivity of 5 Oe, while the relative large nanoparticles are a typical ferromagnetic material with a high coercivity of $584$ Oe. In the microwave absorption tests, a low reflection loss (RL) of  −80.3 dB and large effective bandwidth (frequency range for $\text{RL}\leqslant -10~$ dB) of 10.1 GHz are obtained in the nanoparticle-paraffin composites with appropriate layer thicknesses and particle contents. This suggests that the as-synthesized Co–C core–shell nanoparticles have a high potential as the microwave-absorbing materials.

We successfully prepared synthetic nanocomposite (SNC) by dispersing graphene quantum dots (GQD) in cellulose acetate (CA) polymer system. The dispersion and occupied network of GQD were foreseen by microscopic techniques. The variation of plane to crossed linked array network was observed by the polarizing optical microscopic (POM) technique. The scanning electron microscopy (SEM) revealed the leaves like impressions of GQD in host polymer system. The series network of GQD occupied in CA at higher resolution was confirmed by transmission electron microscopy (TEM). The two dimensional (2D) topographic images demonstrated an entangled polymer network to plane morphology. The variation in surface roughness was evaluated from the dimensional (3D) topography. The influence of temperature on AC conductivity with highest value (4  ×  10⁻⁵ S cm⁻¹), contributes to the decrease in activation energy. The DC conductivity obeys the percolation criteria co-related to the GQD loading by weight fraction. Furthermore, this synthetic nanocomposite is feasible for the development of sensing and electrical applications.

Present work deals with the effect Al doping on structural, optical and electrical properties of ZnS nanoparticles synthesized using chemical co-precipitation technique. The SEM imaging depicted the formation of ZnS agglomerates with narrow size distribution. The elemental composition of the nanoparticles was confirmed using energy dispersive spectroscopy (EDS). It was observed by XRD analysis that incorporation of Al ions does not alter the ZnS crystal structure significantly, but at higher doping levels the crystallanity of the nanoparticles deteriorates. Absorption spectrum shows an increase in the band gap of ZnS (from 3.97 to 4.06 eV) with increase in doping from 0–5 mol %. Photoluminescence spectra revealed that Al incorporation reduces band edge emission and enhances emission pertaining to S vacancies. Electrical conductivity of the as prepared nanoparticles was also found to increase by ~5 times for 5 mol% doped ZnS nanoparticles with respect to pristine samples.

A facile hydrothermal route without additives was used to prepare novel Ba bismuthate nanobelts. The Ba bismuthate nanobelts were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM and electrochemical method. The obtained nanobelts are composed of single crystalline monoclinic BaBiO_2.5 phase with the thickness, width and length of about 50 nm, 1 µm and several dozens of micrometers, respectively. The formation of the Ba bismuthate nanobelts is dependent on the temperature and reaction time. Electrochemical measurements display that the Ba bismuthate nanobelts modified glassy carbon electrode has good electrochemical activity toward tartaric acid. A pair of semi-reversible cyclic voltammetry (CV) peaks are observed at  −0.49 V and  +0.01 V, respectively. The peak current is linearly relative to the scan rate and tartaric acid concentration. The limit of detection (LOD) is 0.12 µM with the linear range of 0.001–2 mM. The work provides new electrode modified materials for the sensor to detect tartaric acid.

Three different purification methods for CdTe-MPA quantum dot (QD) were performed in aqueous medium: acid titration (HCl, HClO₄, H₂SO₄ and CH₃COOH), non-selective precipitation by addition of acetone and co-precipitation of the QD in the presence of inorganic salts. The QD stock solutions were prepared by an electrochemical method of synthesis, in four different heating times (1 h, 4 h, 8 h and 12 h). After purifications, the QD solids were redispersed in distilled water and analyzed by absorption and emission spectra. The λ_abs and λ_em of the purified QDs showed similar data observed for QD stock solutions, and the recovery rate varied from 71% to 99%. Co-precipitation method showed some advantages: quantum yield maintenance of the QD redispersed solution, longer period of storage (over 6 months) in solution and in solid state (QD embedded into the KCl crystal lattice). CdSe-MPA and CdS-MPA solutions were also purified by co-precipitation method with KCl, showing good results as observed for CdTe-MPA.

Fluorescence emission of molecules is strongly influenced by the plasmonic field of metal nanoparticles, with significant enhancement induced under optimal conditions. Nanocomposite ultrathin films fabricated with citrate-stabilized Ag nanoparticles and LB film of a cationic hemicyanine amphiphile, are shown to produce opposing fluorescence emission trends upon subtle variation in the assembly sequence. Monolayer LB films of the pure amphiphile show aggregation-induced quenching with increasing deposition pressure. Composite films formed by adsorption of Ag nanoparticles on the Langmuir film (self-assembly together with steered assembly) followed by LB transfer, show further quenching. However, adsorption of Ag nanoparticles on the pre-formed amphiphile LB film (self-assembly following steered assembly), causes the fluorescence to increase with the extent of adsorption. Spectroscopy and microscopy provide insight into the contrasting, tunable emission. Formation of Ag nanoparticle chains on the Langmuir film and their direct contact with the monolayer cause the fluorescence quenching; adsorption of isolated Ag nanoparticles on the LB film along with multilayer formation leads to the enhancement. The study illustrates the versatility of LB film—metal nanoparticle composites in producing distinct materials responses through subtle changes in the mode of assembly.

Incorporation of good magnetic moment and conductivity in a weakly magnetic matrix via doping of an impurity projects huge applications in the domain of magneto-electronics and spintronics. This is quite challenging because the system has to work in unison so that the there is an exchange of electrons and spins between the magnetic grains and the host matrix. Graphene-nano-ribbons (GNRs) possess defect states at their edges and shows good conductivity with weak magnetism. Such systems are studied as host matrix, in which 10% manganite (La_0.7Sr_0.3MnO₃ (LSMO)) has been incorporated using octadecyl-amine (ODA) as the conjugating agent to form a GNR-LSMO complex. While Raman analysis of GNR shows reduction in disorder after complex formation, the system shows magnetic transition at 350 K. The magnetic-force-microscopy shows direct evidence of enhanced magnetism as compared to only GNR, especially in the regions where the manganite grains are in proximity to the GNR matrix. A novel magneto-electronic material can be envisaged with further careful grain-boundary engineering.

Water dispersible Fe₃O₄ nanoparticles (NPs) were prepared, forming a durable suspension for several days. The zero field cooled magnetization peak temperature is ~4.5 times larger than the average blocking temperature, suggesting the presence of interparticle interactions. Frequency dependent AC magnetic susceptibility revealed superspin glass state at low temperatures. Also a signature of size dependent surface spin glass state was observed associated with a hump in in-phase and a peak in out-of phase susceptibility curves. Magnetic hyperthermia studies indicated that interparticle interactions influence the heat generation of NPs in an AC magnetic field. The temperature rise of 7 nm particles obtained was 8 times larger than that of 5 nm particles. This study shows the important role of interparticle interactions on magnetic and hyperthermia properties of magnetic NPs.

Silver nanowires (Ag NWs) of different aspect ratios have emerged as promising materials toward manufacturing optoelectronic devices for various applications. We report herein a facile, polyol-based one-pot strategy that has allowed us to synthesize Ag NWs ranging in length from 4–7 to 20–34 µm and diameter of 49  ±  10 nm, by simply controlling the concentration of MnCl₂ and KBr. The kinetics of Ag⁺ converted to Ag⁰ have been thoroughly investigated, revealing that the introduction of MnCl₂ and KBr plays a key role toward the growing of Ag NWs with a high aspect ratio. Cl⁻ and Br⁻ would significantly influence the reaction rate of Ag⁺ as well as the reaction activation energy, which controls the nucleation, seeding and growth process of Ag NWs. In addition, MnCl₂ and KBr promote an efficient conversion of Ag⁺ and thus, productivity of Ag NWs up to 90% and 70%, respectively. Without further post-treatment, the conductive film made of this Ag NWs on glass had a sheet resistance of 24 Ω/sq and the specular transmittance of it were 92.4%, which proved it is highly potential for optoelectronic applications.

We study the processes occurring inside carbon nanotubes during their growth. Carbon nanotubes were grown by the chemical vapor deposition method on iron catalyst. We observed the presence of α-, γ- and ε-phases of iron as well as its carbides inside the nanotubes. Stacking faults were found in (0 0 1) of cementite appearing due to the deformation of the cementite inside the nanotubes. Orientation relationships between different phases of iron are established. They allow one to conclude on the mechanisms of mutual transformations of the iron phases and carbides inside the nanotubes.

Mechanofluorochromic (MFC) materials are smart materials in that their absorption and/or emission can respond to mechanical stimuli. They have received much attention recently. Although there have been several new material systems designed, little work has been done regarding the influence of molecular conformation on MFC properties. Herein, to disclose the relationship between molecular conformation and MFC properties, two molecules based on a 6, 12-Dihydro-6, 12-diaza-indeno[1,2-b]fluorine (DDIF) building block with thienyl linker, BDDIF-Th and BDDIF-BTh, have been designed and synthesized. Optical and electrochemical properties have been studied by UV–vis spectrometer and cyclic voltammetry measurements. Weak aggregation-induced emission (AIE) phenomena were obtained in the tetrahydrofuran (THF)/water solution. MFC behaviors suggest that BDDIF-Th is more sensible to the external mechanical forces than BDDIF-BTh. The color change could be attributed to the appearance of new emission peak instead of a bathochromic or hypsochromic effect. Theoretical calculations reveal that MFC performance is highly related to the molecular conformation, meaning that the BDDIF-BTh with perpendicular conformation is more difficult to flatten than the comparatively planar BDDIF-Th.

Yb³⁺ single-doped glasses show a strong excitation band in the 300–400 nm region, and efficiently emit photons with wavelengths of 920–1150 nm, and have potential applications in solar cells operating in an extraterrestrial situation. In this work, we systematically study the broadband near-infrared downconversion and upconversion of Yb³⁺-doped silicate, germanate, phosphate, tellurite and tungsten tellurite glasses. All samples show a broad excitation band in the 300–400 nm range, which is attributed to the charge transfer of the Yb³⁺–O²⁻ couple. The position of the charge transfer band (CTB) shifts from 300 nm to longer wavelengths around 350 nm when the length of the R–O(Si, P, Ge, Te) increases. The longer R–O gives rise to a smaller central void for Yb³⁺, thus resulting in a small proportion of Yb³⁺ ions, thus leading to the blue-shift of the CTB. A smaller proportion of Yb³⁺ in silicate glasses causes in the strongest upconversion emission at 500 nm.

We report the effect of cobalt ferrite ($\text{CoF}{{\text{e}}_{2}}{{\text{O}}_{4}}$) nanoparticles on dielectric and ferroelectric properties of poly(vinylidene fluoride)(PVDF). Large enhancements in dielectric constant and remanent polarization upon addition of 5 wt.% $\text{CoF}{{\text{e}}_{2}}{{\text{O}}_{4}}$ nanoparticles to PVDF have been observed. Nearly 17% increase of dielectric constant and 31% increase in remanent polarization was observed in PVDF-$\text{CoF}{{\text{e}}_{2}}{{\text{O}}_{4}}$ nanocomposite films as compared to pristine PVDF films prepared under identical conditions. These enhancements were accompanied by a decrease in crystallinity and an increase in electroactive β-phase content as evidenced by x-ray diffraction and fourier transform infrared spectroscopy, respectively. A 5% increase in the amount of β-phase content is also observed in nanocomposite films. These enhancements in dielectric constant and remanent polarization are attributed to the influence of $\text{CoF}{{\text{e}}_{2}}{{\text{O}}_{4}}$ nanoparticles on nucleation, morphology, dipole aligning and dipole pinning behavior of PVDF.

In this work, multiwall carbon nanotubes (MWCNT) were dispersed in water with the assistance of water based surfactant and then sonicated in order to obtain a very well dispersed solution. The suspension was filtrate under vaccum conditions, generating a thin film called buckypapers (BP). Poly (phenylene sulphide) (PPS) reinforced carbon fiber (CF) and PPS reinforced CF/BP composites were manufactured through hot compression molding technique. Subsequently the samples were exposed to extreme humidity (90% of moisture) combined with high temperature (80 °C). The mechanical properties of the laminates were evaluated by dynamic mechanical analysis, compression shear test, interlaminar shear strength and impulse excitation of vibration. Volume fraction of pores were 10.93% for PPS/CF and 16.18% for PPS/BP/CF, indicating that the hot compression molding parameters employed in this investigation (1.4 MPa, 5 min and 330 °C) affected both the consolidation quality of the composites and the mechanical properties of the final laminates.

Glass fiber reinforced polyvinylchloride (PVC) composite is used widely because of its low price, chemical resistance, and dimensional stability, but most are short fiber reinforced PVC composites. Fabric reinforced composite have undulated regions, which is the only region without fiber, due to the characteristics of the weave construction, and it limits increasing the mechanical properties. Therefore, in this study, to increase the mechanical properties, the undulated regions of the glass fiber fabric/PVC composite were filled with a silane coupling agent treated chopped fiber. The physical properties, dynamic mechanical thermal properties, and mechanical properties of the prepared composite were observed. The critical fiber aspect ratio of the chopped fiber is different for each mechanical property. This shows that the fabric-reinforced composite of chopped fibers affect each of the mechanical properties differently. In addition, the silane coupling treatment increases the compatibility of the composite components, improving the mechanical properties.

Polymers such as polytetrafluoroethylene (PTFE) are widely used in artificial organs where long-term anti-bacterial properties are required to avoid bacterial proliferation. Copper or silver ion implantation on the polymer surface is known as a viable method to generate long-term anti-bacterial properties. Here, we have tested pulsed DC plasma with copper cathodic cage for the PTFE surface treatment. The surface analysis of the treated specimens suggests that the surface, structural properties, crystallinity and chemical structure of the PTFE have been changed, after the plasma treatment. The copper release tests show that copper ions are released from the polymer at a slow rate and quantity of the released copper increases with the plasma treatment time.

A novel hybrid organic silicon thermoplastic elastomer (Si-TPE) was copolymerized by adopting branched organic polysiloxane and diphenyl methane diisocyanate, and the thermal processing mechanism and the effect of hard segments on the thermal processability and mechanical properties of Si-TPE were studied. The results showed that Si-TPE presents excellent thermal processability ascribed to its reversible physical crosslinking, i.e. hydrogen bonding between NH–C=O of the hard chains, and could be stably thermally processed into different products including films, tubes, tapes and sheets at 160–180 °C. With increasing hard segment content, the hydrogen bonding in the system was enhanced, leading to increases in both the melt viscosity and the softening temperature of Si-TPE. Simultaneously, the mechanical properties of Si-TPE were improved. When the hard segments increased to 20.3%, the tensile strength and Young's modulus of Si-TPE reached 13.4 MPa and 43.8 MPa, respectively.

Polydimethylsiloxanes (PDMS) are used in a wide range of soft devices including lab-on-chip, soft robots and flexible electronics. These technologies are currently considered for space exploration applications. We experimentally study the effects of vacuum pressure on the dynamics of PDMS resonator and demonstrate that, unlike hard materials, it exhibits an appreciable change in modulus manifested as a shift in resonance frequency with varying pressure. To reveal this dependence, we carefully probe the dissipation due to air pressure damping acting on the surface of the membrane. For a 1 µm thick membrane, the modulus of the PDMS decreases when the pressure is below P_t  =  3.175 Torr, whereas at pressures above ${{P}_{\text{t}}}$ the dynamics are dominated by gas damping in the free molecular flow and viscous regimes. We conjecture that the observed effect is a consequence of a change in shear modulus resulting in a logarithmic linear relationship between pressure and stiffness for a circular PDMS membrane. These results are important for the application of PDMS microdevices at low pressure.

In this article, we systematically investigated the effects of process parameters such as melamine to formaldehyde (M/F) ratio taken in the initial feed on the yield percent, core content, solvent wash stability, morphology, mean particle size distribution and thermal stability of the microcapsules. Epoxy loaded poly(melamine-formaldehyde) (PMF) microcapsules were prepared by in situ polymerization using emulsion technique. Capsules core content and solvent wash stability increased as the formaldehyde content increased. Structural (FTIR and ¹H-NMR), morphological (optical microscopy (OM) and scanning electron microscopy (SEM)) and thermal (thermogravimetry and differential scanning calorimetry) characterization was done to investigate the effects of M/F ratio on the synthesized microcapsules. The analysis of core material by FTIR and ¹H-NMR spectra confirmed the presence of epoxy as the core material. OM and SEM micrographs showed that the prepared capsules were almost spherical with a perfect periphery, but showed the tendency to agglomerate as the ratio of M/F decreased. The mean particle size of epoxy filled PMF microcapsules decreased (from 87.1 µm to 67 µm) as the ratio of M/F increased. Thermal analysis showed that the microcapsules were thermally stable up to 373 °C. Thermal stability of microcapsules increased as the ratio of M/F increased. Such microcapsules are expected to find applications in the preparation of polymeric self-healing composites for aerospace industry.

The antibacterial effect of zinc oxide (ZnO#1) as prepared and annealed (ZnO#2) at 400 °C, Cu doped ZnO (CuZnO), and Ag doped ZnO (AgZnO) nanoplates on Staphylococcus epidermidis was investigated for the inhibition and inactivation of cell growth. The results shows that pure ZnO and doped ZnO samples exhibited antibacterial activity against Staphylococcus epidermidis (S. epidermidis) as compared to tryptic soy broth (TSB). Also it is observed that S. epidermidis was extremely sensitive to treatment with ZnO nanoplates and it is clear that the effect is not purely depend on Cu/Ag. Phase identification of a crystalline material and unit cell dimensions were studied by x-ray powder diffraction (XRD). The scanning electron microscopy (SEM) provides information on sample's surface topography and the EDX confirms the presence of Zn, O, Cu and Ag. X-ray photo-electron spectroscopy (XPS) was used to analyze the elemental composition and electronic state of the elements that exist within the samples. These studies confirms the formation of nanoplates and the presence of Zn, O, Ag, Cu with the oxidation states  +2, −2, 0 and  +2 respectively. These results indicates promising antibacterial applications of these ZnO-based nanoparticles synthesized with low-cost hydrothermal methods.

The Ti–Nb alloy binary system has been widely studied with regard to biomedical applications due to the high biocompatibility and excellent mechanical properties of the alloys. Regarding physical-chemical stability, Ti–Nb alloys maintain the properties of Ti metal, which is highly resistant to corrosion in aggressive media due to a spontaneous stable oxide layer (TiO₂) formed on its surface. The objective of this study was to evaluate the corrosion resistance of the Ti–40Nb alloy in artificial blood. The thermodynamic stability was studied using the open circuit potential technique and the corrosion resistance was assessed by potentiodynamic measurements and electrochemical impedance spectroscopy. The electrochemical results indicated that the Ti–40Nb alloy has high corrosion resistance and good thermodynamic stability, with an OCP of around  −485 mV, and the alloy remained electrochemically stable in potentiodynamic conditions with initial and final potentials of  −1.0 V to  +2.0 Vsce, respectively, in low current densities (~µA cm⁻²) with an absence of hysteresis, aspure Ti. The results obtained showed that this specific alloy has the potential to be used in biomedical applications.

A drug-loaded implantable scaffold is a promising substitute for the treatment of tissue defects after a tumor resection operation. In this work, natural pearl powder with good biocompatibility and osteoconductivity was incorporated into polylactic (PLA) nanofibers via electrospinning, and doxorubicin hydrochloride (DOX) was also loaded in the PLA/pearl scaffold, resulting in a drug-loaded composite nanofibrous scaffold (DOX@PLA/pearl). In vitro drug delivery of DOX from a PLA/pearl composite scaffold was measured and in vitro anti-tumor efficacy was also examined, in particular the effect of the pearl content on both key properties were studied. The results showed that DOX was successfully loaded into PLA/pearl composite nanofibrous scaffolds with different pearl content. More importantly, the delivery rate of DOX kept rising as the pearl content increased, and the anti-tumor efficacy of the drug-loaded scaffold on HeLa cells was improved at an appropriate pearl powder concentration. Thus, we expect that the prepared DOX@PLA/pearl powder nanofibrous mat is a highly promising implantable scaffold that has great potential in postoperative cancer treatment.

Advanced approaches to the application of nanomaterials for environmental studies, such as waste-water treatment and pollution removal/adsorption, have been considered in recent decades. In this research, hydrogen sulfide removal from water-based drilling fluid by ZnO and TiO₂ nanoparticles and a ZnO/TiO₂ nanocomposite was studied experimentally. The ZnO and TiO₂ nanoparticles were synthesized by sedimentation and the sol–gel method. A sol-chemical was employed to synthesize the ZnO/TiO₂ nanocomposite. X-ray diffraction, scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface analysis, inductively coupled plasma mass spectrometry (ICP), dynamic light scattering (DLS) and Fourier transform infrared spectroscopy were used to characterize the produced ZnO and TiO₂ nanoparticles, and the ZnO/TiO₂ nanocomposite. The results showed that the concentration of hydrogen sulfide decreased from 800 ppm to about 250 ppm (about 70% removal) and less than 150 ppm (more than 80% removal) using the TiO₂ and ZnO nanoparticles with a 0.67 wt% concentration, respectively. Hydrogen sulfide removal using the ZnO/TiO₂ nanocomposite with a 0.67 wt% showed the highest value of removal in comparison with the TiO₂ and ZnO nanoparticles. The hydrogen sulfide level was lowered from 800 ppm to less than 5 ppm (99% removal) by the nanocomposite.

The thermoelectric performance of CdO ceramics was optimized by synergistically tuning their electrical and thermal transport properties via Cu doping. The introduction of Cu led to an increase in carrier concentration and mobility simultaneously for samples with Cu content less than 3%. An improvement in power factor was obtained due to decreased electrical resistivity and a moderate Seebeck coefficient. A small amount of Cu doping was also verified to be effective in suppressing the heat transfer of CdO ceramics owing to the enhanced phonon scattering from point defects and grain boundaries. Benefiting from the increase in power factor and decrease in thermal conductivity, enhanced ZT values were achieved in all doped samples, indicating that Cu doping is an effective strategy to promote the thermoelectric performance of CdO ceramics.

A symmetric supercapacitor with porous activated carbon as the active material and trihexyl (tetradecyl) phosphonium bis (trifluoromethanesulfonyl) imide [PC₆C₆C₆C₁₄][Tf₂N] as the electrolyte was fabricated. Scanning electron microscopy, atomic force microscopy, x-ray diffraction, Fourier transform infrared spectroscopy and a zeta particle size analysis were conducted to examine the surface morphology and other physical properties. Differential scanning calorimetry and a thermal gravimetric analysis were performed to study the thermal stability of the ionic liquid based electrolyte. The binary mixture route was taken with acetonitrile and ionic liquid for reducing the viscosity to enhance the ionic mobility. Cyclic voltammetry, impedance spectroscopy and charge–discharge investigations were conducted to assess the performance of the supercapacitor. A very high specific capacitance of 300 F g⁻¹, an ultra high energy density of 110 Wh kg⁻¹, a high rate scalability (up to 1000 cycles) and an increased operation voltage of 3.5 V were achieved to propose this electrode electrolyte combination as a potential candidate for future ionic liquid based supercapacitor.

Manganese-doped lithium iron phosphate (LFMP) integrated with reduced graphene oxide (RGO) has been prepared via microwave-assisted synthesis and investigated as lithium-ion energy storage system in aqueous Li₂SO₄ electrolyte. The doping of the LFP was achieved with a low-cost commercial electrolytic manganese oxide (EMD) precursor using a microwave-assisted solvothermal technique. When compared to the undoped counterpart (LFP/RGO), obtained under similar experimental conditions, the LFMP/RGO nanohybrid showed an improved electrochemical performance. The LFMP/RGO gave a maximum areal capacitance of ca. 39.48 mF cm⁻², power density of 70.3 mW cm⁻² and energy density of 8 mWh cm⁻² compared to the values for the pristine complex (LFP/RGO); ca. 16.85 mF cm⁻², 54.4 mW cm⁻² and 4.8 mWh cm⁻². In addition, when the two types of electrochemical storage systems were subjected to voltage-holding (floating) experiment for 50 h, LFMP/RGO maintained 98% capacitance retention while LFP/G maintained 94% capacitance retention. The findings in this work prove that Mn-doping is capable of enhancing the electrochemical performance of the LFP material for energy storage.

This study entailed modeling a perovskite absorber involving band-gap grading at the back of the absorber and double-grading profiles of hole-transporting layer-free perovskite solar cells. Device simulation based on continuity equations and Poisson's equation was carried out by using AMPS-1D software. The optimum grading profile consisted of a band gap of 1.7 eV at the interface between the TiO₂ and absorber with a graded thickness of 300 nm, uniform 1.5 eV of 50 nm, and back surface 2.1 eV with a graded thickness of 50 nm. The attained simulated efficiency was 22.68% (open-circuit voltage, V_oc  =  1.34 V; short-circuit current density, J_sc  =  19.98 mA cm⁻²; fill factor, FF  =  0.84), which is close to the uniform band gap of 1.5 eV of the whole absorber with a hole-transporting layer (Spiro-OMeTAD). This was mainly because of back grading forming a conduction band energy barrier to suppress the transportation of photo-generated electrons from the absorber to the back electrode, thereby improving carrier collection. The results indicate that the hole-transporting layer could be replaced by optimal band-gap profiling of the absorber, with near to no decayed performance of the perovskite solar cells.

One chemical sand-fixing materials based on poly(acrylic acid)-corn starch (PACS) blend was studied in this work. The PACS blend was prepared by solution mixing method between PA and CS. In order to prepare sand-fixing materials for environmental applications using the well-established method of spraying evenly PACS blend solution on the surfaces of fine sand. Fourier transform infrared spectroscopy (FT-IR) revealed the existence of the intermolecular interactions between the blend components. Scanning electron microscope (SEM) analysis showed a continuous phase of blend, and it also showed the good sand-fixing capacity. The test results of hygroscopicity and water retention experiments indicated that the blends had excellent water-absorbing and water-retention capacity. The results of contact angle measurements between the PACS solutions and fine sand showed that the PACS blend has a satisfactory effect on fine sand wetting. And the PACS, as a sand-fixation material, has excellent sand-fixation rate up to 99.5%.

Thermoelectric devices employing magnesium silicide (Mg₂Si) offer an inexpensive and non-toxic solution for green energy generation compared to other existing conventional thermoelectric materials in the mid-temperature range. However, apart from the thermoelectric performance, their mechanical properties are equally important in order to avoid the catastrophic failure of their modules during actual operation. In the present study, we report the synthesis of Mg₂Si co-doped with Bi and Sb employing in situ spark plasma reaction sintering and investigate its broad range of mechanical properties. The mechanical properties of the sintered co-doped Mg₂Si suggest a significantly enhanced value of hardness ~5.4  ±  0.2 GPa and an elastic modulus ~142.5  ±  6 GPa with a fracture toughness of ~1.71  ±  0.1 MPa  √m. The thermal shock resistance, which is one of the most vital parameter for designing thermoelectric devices, was found to be ~300 W m⁻¹, which is higher than most of the other existing state-of-the-art mid-temperature thermoelectric materials. The friction and wear characteristics of sintered co-doped Mg₂Si have been reported for the first time, in order to realize the sustainability of their thermoelectric modules under actual hostile environmental conditions.

Understanding charge carrier transport in Na₂O₂, being one of the possible storage materials in the non-aqueous Na–O₂ battery, is key to the development of this type of energy storage system. The electronic and dynamic properties of Na₂O₂ are expected to greatly influence the overall performance and reversibility of the discharge process. Thus far experimental studies on this topic are rare. To measure the extremely low conductivities setups with sufficiently high sensitivity are needed. Here we studied the partial electronic conductivity σ_eon of nanocrystalline Na₂O₂ by potentiostatic polarization measurements which we carried out at room temperature. σ_eon turned out to be in the order of 8.8  ×  10⁻¹⁴ S cm⁻¹; with a very poor total conductivity of σ_total  =  17  ×  10⁻¹⁴ S cm⁻¹ we obtained σ_total/σ_eon  ≈  2 clearly showing that ionic transport of Na ions is strongly coupled to electronic dynamics.

In this work, we propose to boost the thermoelectric performance of bulk magnesium silicide using isotropic strain. The effect of strain on the electronic and thermoelectric properties of Mg₂Si is analyzed using first principles calculations combined with semi-classical Boltzmann theory. The Seebeck coefficient, power factor and electrical conductivity are strongly modified with strain. The lattice thermal conductivity is also tuned with strain. However, the strain effect on the lattice thermal conductivity of Mg₂Si has not yet been systematically studied. The effect of strain on lattice thermal conductivity, specific heat, phonon dispersion curves and phonon density of states of Mg₂Si are studied for the first time in this paper. The lattice thermal conductivity of bulk Mg₂Si is shown to decrease continuously when applied strain changes from compressive to tensile. The results obtained in this paper have great importance in the thermoelectric field.

The growth dynamics of CH₃NH₃PbI₃ (MAPbI₃) perovskite thin films, deposited by thermal evaporation, has been investigated by atomic force microscope and height–height correlation function analysis. The unstable scaling behavior of initial perovskite films exhibiting the growth of islands, resulting in rougher film formation has been observed. After the formation of continuous film, the roughening has been characterized by analyzing the scaling exponent α ~ 0.70, growth exponent β  =  0.79  ±  0.057, 1/z  =  0.78  ±  0.038, and 2D fast Fourier transform. Anomalous scaling behavior of the MAPbI₃ thin films and the formation of the rapid surface roughening are discovered. It is demonstrated that step-edge barrier induced mound growth may play the dominate role in the growth mechanism of MAPbI₃ thin films on Si substrates. Further, the growth behavior of MAPbI₃ film on ITO substrates is investigated as a comparison, and it reveals that the growth of MAPbI3 thin films is largely affected by the initial substrates underneath the growing films.

Graphene is an attractive candidate for use as an electrode material in electrochemical energy storage due to its unique structure and excellent properties. Compared with graphene, nanoporous graphene is a superior electrode material, owing to the porous structure of its graphene sheets, which facilitates cross-plane lithium ion transportation and provides more binding sites for the lithium ions during the lithiation/delithiation process. In this work, we demonstrate a simple and efficient strategy for obtaining nanoporous graphene on a large scale. Nanoporous graphene can be generated through the oxidation of graphene oxide by H₂O₂ under high-power UV irradiation with a subsequent reduction process. The morphology, chemical composition and defects of the as-generated nanoporous graphene were studied. The electrochemical evaluation of the nanoporous graphene sheets showed that it delivered higher specific capacity and better charge/discharge rate capability compared with chemically reduced graphene sheets for use as an anode material in lithium ion batteries.

The anisotropy in thermal conductivity (κ), induced by temperature gradient (TG), of thorium dioxide (ThO₂) and cerium dioxide (CeO₂) has been investigated by molecular dynamics (MD) simulations, in combination with non-equilibrium method, from 100 to 900 K. Anisotropy is observed in the systems with shorter length, in the direction of heat transfer, and is attributed to the large TG. The anisotropic response elevates with the increase in effective TG. Our results indicate that the higher temperature gradient is resulted from the significant phonon scattering, which in turn affects the transfer of thermal energy and leads to anisotropy in conductivity. It is found that the rate of change of thermal conductivity with TG is the largest for 〈1 0 0〉 crystallographic direction. At the highest TG, observed in this study, the anisotropy in thermal conductivity follows κ₁₀₀  <  κ₁₁₀  <  κ₁₁₁. The effect of anisotropy reduces with the increase in temperature.

Graphene-based thermocells for the conversion of low grade waste heat into electrical energy are investigated. A maximum current and power density of 0.63 A m⁻² and 0.19 W m⁻² respectively for 1 mV s⁻¹ at a temperature gradient of 50 °C is obtained. The maximum energy conversion efficiency relative to Carnot efficiency is 1.57% which is 1.1 times higher than the literature data. A constant ohmic overpotential of 0.07 V is calculated from equivalent circuit analysis. This low value of ohmic overpotential indicates higher ionic conductivity in the electrolyte medium. The mass transfer overpotential is low and is calculated as 0.2133 V for all load variations, indicating constant redox behaviour and an increased energy conversion efficiency of the device. The double layer capacitance is estimated as 3.72 F at a very low load (ca. 1 mV s⁻¹) and 0.32 F at a very high load (ca. 100 mV s⁻¹) thereby demonstrating the functioning ability of the device at higher loads. The Seebeck coefficient for a graphene electrode is evaluated to be 0.0117 V K⁻¹ and is in satisfactory agreement with the literature value of 0.02 V K⁻¹ for carbon-based devices.

Graphene, a two-dimensional (2D) material, is an important constituent part for the development of mechanic, electronic and photonic systems due to its remarkable properties, however, wrinkling is a ubiquitous phenomenon in 2D membranes. As a 2D material with atomic thickness, graphene is found to be wrinkled easily because of its relatively low bending rigidity, and besides, wrinkle affects graphene's remarkable physical property severely. Despite their prevalence and potential impact on large-scale graphene properties, only a several approaches have been dedicated to control their structural morphology and orientation by transferring graphene onto polymer substrates. Here we report a new route to control the orientation of wrinkles by directly applying external mechanical strains to metal substrates until plastic deformation happens. By changing direction and magnitude of tension strain, wrinkles with different spacing but all with orientations perpendicular to the tensile direction can be obtained.

The templated-rGO fabric, featuring high conductivity (<1.0 Ω □⁻¹) and low density (160 mg cm⁻²), is prepared by a simple dip-coating technique with sequentially coating nickel via polymer-assisted metal deposition (PAMD) and reduced-graphene oxide (rGO) on textile fabric templates at very mild conditions and is used in the fabrication of energy storage devices. As a proof of concept, both the layered and planar supercapacitors (SCs) are successfully fabricated using the rGO fabrics as templates, and both exhibit excellent electrochemical performance, ultrahigh stability with 2000 charge–discharge cycles and mechanical flexibility at bending (r  =  3 mm) and even folding states. It is found that the material of textile fabric used has a profound effect on the electrochemical property of SCs. The comparison result reveals that loose natural cotton fabrics are more suitable than tight man-made nylon fabrics for preparing high-performance SCs. In addition, such supercapacitor can be sewed into commercial textiles and powers a LED light, indicating promising applications in wearable electronics.

Porous graphene with nanoscaled pores on the sheets was prepared by a carbon thermal reduction method, in which the molybdenum oxide nanoparticles generated from the thermal decomposition of molybdate were used as the etching reagent, and the pores were formed on the surface of the reduced graphene oxide under the conditions of 650 °C and a nitrogen atmosphere. The morphology of pores on the graphene sheets may affect their potential applications in various fields, especially in the enhancement of mass transfer. Previous studies have shown that the reduction temperature and the amount of metal oxide are the key factors affecting the morphology of porous graphene, but in fact the reduction time is a more important affecting factor according to the present study. The results of SEM/TEM showed that a disordered large sheet-like structure with wrinkles was obtained at 120 min in the carbon-thermal reaction. The structural integrity of the PG was further destroyed after the reaction time of 140 min, in which the edge exhibited slightly crush and significant fold. The PG exhibited a hollow rod-like structure at the reaction time of 180 min. FTIR, Raman, XRD, and XPS studies were performed to characterize the morphology of porous graphene prepared at different reduction times.

Generally, the role of carbon defects in the corrosion of graphene is investigated by the experimental methods. Defects and cracks are considered to be the major cause of corrosion. Thus far, the intrinsic corrosion mechanism at the nanoscale is still not understood. In this work, using a first principles method, the energy barriers and average potentials of Cl anion diffusion cross the defective graphene are calculated in order to better understand the role of carbon defects in the corrosion of graphene at the nanoscale. The calculated results show that the reconstructed nanopores have a significant effect on retaining the anticorrosion of graphene.

Cementitious composites are quasi-brittle and susceptible to damage under dynamic loads. The addition of nanoscale fillers into cementitious composites is an effective approach to address this issue. In this paper, multi-layer graphenes (MLGs) are incorporated into cementitious composites to enhance its damping property. The underlying modification mechanism of MLGs to cementitous composites is also investigated. Experimental results showed that the addition of MLGs can effectively modify the damping property of cementitious composites. Compared with cementitious composites without MLGs, the damping ratio of cementitious composites filled with 1% and 5% of MLGs increases by 16.22% and 45.73%, respectively. The improvement of MLGs to damping property of cementitious composites can be attributed to the interlayer slip of MLGs, viscous friction between MLGs and matrix, and excellent thermal conductivity of MLGs. Moreover, the damping ratio measured by time-domain exponential decay method and frequency-domain half-power bandwidth method is consistent.

This study appraised the potential application of graphitic carbon nitride (g-C₃N₄) as an adsorbent for removal of Pb²⁺ ion from aqueous solution. The g-C₃N₄ was prepared by direct calcination of the low-cost melamine, and its morphology and microstructure were analyzed. Moreover, the effects of initial solution pH, initial Pb²⁺ ion concentration, adsorption time, and adsorbent dosage on the adsorption properties of the g-C₃N₄ were investigated. Two widely used isotherm models were used to describe the experimental equilibrium data, and the Freundlich isotherm model described well. Two widely used kinetic models were used to the fit of the adsorption experimental data, and the pseudo-second-order kinetic model fitted well. The maximum adsorption percentage and maximum adsorption capacity were 98.5% and 7.4 mg g⁻¹, respectively. In addition, the recycling of g-C₃N₄ for the removal of Pb²⁺ was investigated, and the results indicated that g-C₃N₄ owned a good reusability.

A kitchen mixer is one of the possible tools for the exfoliation of graphene. While organic solvents such as NMP or DMF are suitable for the exfoliation of graphite, the majority are toxic and dangerously harmful when exposed to humans and the environment. Therefore, an alternative solvent must be proposed for green and sustainable production of graphene. In this initial work, we have developed a new synthesis method for graphene through the direct exfoliation of graphite in commercial black tea. We found that our maximum yield concentration of graphene is Y  =  0.032 mg ml^−l after 15 min of mixing. From the data of Raman, the level of defects in our produced graphene is suggested as being very minor (I_D/I_G  =  0.17), despite possible graphene functionalization by oxygen groups in tea. Incorporation of our graphene into PMMA results in shifting the onset temperature from 300 °C to 326 °C, which impressively validates the potential of the produced graphene as a thermal reinforcement material for polymer composites.

Shape memory alloys (SMAs) have many thermo-mechanical characteristics which can return to their original value once exposed to a specific temperature. These materials are able to change their mechanical features such as shape, displacement or frequency in response to stress or heating; this may be useful for actuators in many fields such as aircraft, robotics and microsystems. In order to know the effect of the Sun's radiation on SMAs we have conducted a numerical study that simulates a SMA actuator.

A novel design for a planar artificial magnetic conductor (AMC) with meander line element is used to achieve miniaturization, reduction in the second/first resonant frequency ratio, and multi-band operation. It is known that various parameters—such as geometry, dielectric substrate thickness, the gap between patches, the length and width of a patch, the size of unit cell, permittivity, and permeability—strongly affect the resonant frequency. To obtain a miniaturized AMC, in this paper, we investigate the role of the metallic patch effective length on resonant frequency. Meander-shape is used to change the effective length in the direction of the incident wave polarization. A discussion of the design parameters and the electric field distribution is presented. Six different configurations are proposed. Miniaturization and reduction in the first/second resonant frequency ratio is achieved. In addition, the meander-shape allows the appearance of different operating bands that depend on the number of meanders. For instance, four bands are observed for one meander (U-shape). Therefore, a simple way to obtain AMC miniaturization and multi-band devices is proposed. The results are obtained by the finite element method. To validate our design some results have been compared against experimental testing presented in literature.

Effects of hydrogen plasma treatment on the electrical properties of a sol-gel-derived polycrystalline zinc oxide (ZnO) system have been studied by employing impedance spectroscopy. Complex impedance data were analyzed by employing an equivalent circuit. Hydrogen plasma treatment markedly increased the low-frequency range of constant values of the real part of complex impedance. As a result of plasma treatment, electrical conductivity was found to increase by about two orders of magnitude, with the activation energy being reduced from 0.62 eV to 0.30 eV. The dielectric constant also showed a two-fold increase following the plasma treatment.

The relative stability, electronic structure, and optical properties of (Ga–Al)-codoped ZnO were investigated by first-principles calculations based on density functional theory (DFT). To study the doping effects, ZnO supercells with 32 atoms were built. The results were obtained by using Material Studios 8.0 provided by Accelrys. Ab initio spin-polarized all-electron DFT computations have been performed for substitution. The results indicate that the energy band shifts towards the higher-energy region for Al- and/or Ga-doped ZnO, which endorsed the doping of Al and/or Ga. It has been observed that the preparation of (Ga–Al)-codoped ZnO is difficult compared to Al/Ga-doped ZnO due to the considerably larger formation energy required. The imaginary part of the dielectric function ε₂(ω), reflectivity R(ω), absorption coefficient α(ω), and refractive index n(ω) were calculated. The contribution of different density of states in the formation of the conduction and valence band has been analyzed for different configurations of ZnO.

Tin Oxide (SnO₂) nanostructures were synthesized by a microwave oven assisted solvothermal method using with and without cetyl trimethyl ammonium bromide (CTAB) capping agent. XRD confirmed the pure rutile-type tetragonal phase of SnO₂ for both uncapped and capped samples. The presence of functional groups was analyzed by Fourier transform infrared spectroscopy. Scanning electron microscopy shows the morphology of the samples. Transmission electron microscopy images exposed the size of the SnO₂ nanostructures. Surface defect-related g factor of SnO₂ nanoparticles using fluorescence spectroscopy is shown. For both uncapped and capped samples, UV–visible spectrum shows a blue shift in absorption edge due to the quantum confinement effect. Defect-related bands were identified by electron paramagnetic resonance (EPR) spectroscopy. The magnetic properties were studied by using vibrating sample magnetometer (VSM). A high value of magnetic moment 0.023 emu g⁻¹ at room temperature for uncapped SnO₂ nanoparticles was observed. Capping with CTAB enhanced the saturation magnetic moment to high value of 0.081 emu g⁻¹ by altering the electronic configuration on the surface.

CdS thin films were grown on flexible PET and PET/ITO substrates by chemical bath deposition varying the deposition time. The structural analysis indicates that CdS films are composed of nano-crystalline and amorphous material. CdS films grown on PET substrates have hexagonal phase, while those grown on PET/ITO substrates have a cubic phase. The bandgap values of CdS films grown on PET substrates are in the range 2.31–2.45 eV, and the E_g of CdS films grown on PET/ITO substrates are 2.18–2.42 eV. A strong green photoluminescence emission was observed in all the samples, which is associated to near band edge transitions. CdS films grown on PET/ITO substrates have an additional emission at 2.80 eV, which can be attributed to the presence of nano-crystals, in agreement with TEM analyses.

We demonstrate robust p-type doping of Cu₂O using low/medium energy ion implantation. Samples are made by controlled oxidation of annealed Cu metal foils, which results in Cu₂O with levels of doping close to intrinsic. Samples are then implanted with nitrogen ions using a kinetic energy in the few keV range. Using this method, we are able to produce very high levels of doping, as evidenced by a 350 meV shift in the Fermi level towards the VB maximum.

The robustness of the nitrogen implanted samples are tested by exposing them to atmospheric contaminants, and elevated temperatures. The samples are found to survive an increase in temperature of many hundreds of degrees. The robustness of the samples, combined with the fact that the materials used are safe, abundant and non-toxic and that the methods used for the growth of Cu₂O and N⁺ implantation are simple and cheap to implement industrially, underlines the potential of Cu₂O:N for affordable intermediate band photovoltaics.

X-ray photoelectron spectroscopy (XPS) was proposed as a feasible method to study the impurity phases and their distribution in the ZnGeP₂ single crystals grown by Bridgman method while these impurity phases can't be detected by x-ray diffraction (XRD) measurements because of their low content. The quality of ZnGeP₂ single crystal were characterized by XRD as well. Optical properties and crystal homogeneity were analyzed by Fourier transform infrared spectrophotometry (FTIR). XPS results manifest that impurities phases of ZnP₂ and Zn₃P₂ exist on the tail of the crystal rather than the main body which result in component inhomogeneity. These impurities lead to a lower IR transmittance of the tail part than that of the main crystal body. The study of impurities and its effect on optical properties provide important reference for optimizing the growth progress and its post heat treatment which can improve the IR transmittance.

This paper reports the controlled synthesis of highly ordered arrays of rutile TiO₂ rods with tunable size and properties on electrospun PVDF Fibers by using a low-temperature hydrothermal growth strategy. Well-defined, highly ordered, vertically oriented TiO₂ rod arrays covering on the PVDF fibers backbone were obtained. In order to study the morphology-dependent optical and photocatalytic properties of the hierarchical composites, the hydrothermal treatment time was varied, resulting in rime-like (6 h) and rod bundles (4 h and 10 h) morphologies. By contrast, the crystallinity, grain size and optical properties of the sample depended on the hydrothermal treatment time. After being irradiated for 600 min with an 18 W UV lamp, the photocatalytic efficiency of rhodamine B for the sample hydrothermal treated for 4 h, 6 h and 10 h was about 28%, 37% and 85%, respectively. A slight decrease in the photodegradation efficiency can be detected after five times recycled experiments. Moreover, further study indicates that the rime-like branched structure promote photocatalytic efficiency.

Ordered compact TiO₂ nanotubes have been fabricated by using third generation electrolyte on employing the electrochemical anodisation technique. The titania nanotube growth is intiated by etching the oxide layer due to fluoride ions in the prepared electrolyte therby results the pore formation which continue to deepen in the oxide layer by maintaining the atmosphere of high and low pH at the mouth and bottom of the titania nanotubes, respectively. Using field emission scanning electron microscope (FESEM) and anodization current time spectra, detailed fabrication mechanism of compact TiO2 nanotubes have been explained. Moreover, the resulting TiO₂ nanotubes were studied for light absorption using diffuse reflectance spectroscopy and photo-eletrochemical property using electrochemical analyzer. The absorption and photo-electrochemical spectra of the resulting titania nanotubes show the band gap of ~3.2 eV and photocurrent density of ~4.85 mA cm⁻² respectively. The elemental composition and phase purity of the finally prepared compact TiO₂ nanotubes (anatase) were confirmed by EDAX coupled with FESEM and x-ray diffractogram, respectively.

Oxide semiconductors with high expectations are regarded as the best candidate in the next generation thin film transistors. Flexible structure endows perovskite oxide semiconductors with the potential to satisfy different application requirements. In this letter, LaFeO₃ epi-films (epitaxial films) were deposited on Nd-SrTiO₃ to construct p-n junctions. The junctions show distinct rectification characteristic with a high rectification ratio of ~5  ×  10³ at  ±2 V. Through annealing in deficient oxygen ambience, changes in LaFeO₃ structure by introducing oxygen vacancies lead to the different turn-on voltages. Confirmed by XPS data, oxygen vacancies result in the slight reduction of Fe³⁺ to Fe²⁺ and the increase in holes concentration. Simultaneously, the location of Fermi Level shifts toward the top of valance band and barrier height for carriers increases gradually. Correspondingly, the turn-on voltage increases as lowering anneal oxygen pressure.

Thin films of magnetic garnet materials, e.g. yttrium iron garnet (Y₃Fe₅O₁₂, YIG), are useful for a variety of applications including microwave integrated circuits and spintronics. Substitution of rare earth ions, such as cerium, is known to enhance the magneto-optic Kerr effect (MOKE) as compared to pure YIG. Thin films of Ce_0.75Y_2.25Fe₅O₁₂ (Ce:YIG) have been grown using the pulsed laser deposition (PLD) technique and their crystal structure examined using high resolution scanning transmission electron microscopy. Homogeneous substitution of Ce in YIG, without oxidation to form a separate CeO₂ phase, can be realized in a narrow process window with resulting enhancement of the MOKE signal. The thermally generated signal due to spin Seebeck effect for the optimally doped Ce:YIG films has also been investigated.

The effect of Ti doping in Bi_0.3Ca_0.7Mn_1−xTi_xO₃ (where x  =  0.0, 0.015, 0.03, 0.05, 0.08, 0.12 and 0.16) on structural, magnetic and transport properties have been studied. The charge-ordering temperature (T_CO) decreases gradually with increasing Ti doping content, and finally disappears completely for x  =  0.12. The Neel temperature (T_N) also decreases with increasing Ti doping content. A transition to a cluster glass like state is observed at T  ⩽  T_N. The zero field cooled/field cooled (ZFC/FC) magnetization decreases at high temperature (T  >  200 K) with increasing Ti content, whereas an opposite trend is observed at low temperature (T  <  200 K). Small exchange bias effect is also observed for x  =  0.08 at 10 K. The resistivity increases with increasing Ti doping content. The disorder induced by Ti doping on the Mn site plays a key role in explaining the observed magnetic and electrical properties.

We have studied the structural and magnetic properties and electronic structure of the compound InCuPO₅ synthesized by a solid state reaction method. The structure of InCuPO₅ comprises S  =  ½ uniform spin chains formed by corner-shared CuO₄ units. Magnetic susceptibility (χ(T)) data show a broad maximum at about 65 K, a characteristic feature of one-dimensional (1D) magnetism. The χ(T) data are fitted to the coupled S  =  ½ Heisenberg antiferromagnetic (HAFM) uniform chain model that gives the intra-chain coupling (J/k_B) between nearest-neighbor Cu²⁺ ions as  −100 K and the ratio of inter-chain to intra-chain coupling (J'/J) as about 0.07. The exchange couplings estimated from the magnetic data analysis are in good agreement with the values computed from the electronic structure calculations based on the density functional theory  +  Hubbard U (DFT  +  U) approach. The combination of theoretical and experimental analysis confirms that InCuPO₅ is a candidate material for weakly coupled S  = ½ uniform chains. A detailed theoretical analysis of the electronic structure further reveals that the system is insulating with a gap of 2.4 eV and a local moment of 0.70 µ_B/Cu.

In this manuscript, we have investigated the effect of Fe and Ni doping on the structure and magnetic properties of YCr_1−xM_xO₃ ceramics (M  =  Fe, Ni and x  =  0, 0.1). X-ray diffraction analysis of the samples accompanied with, Rietveld refinement suggested no change in the structure upon doping, with structure of the samples being orthorhombic (space group: Pnma). Raman spectroscopic analysis of the samples revealed that doping induced disorder leads to broadening of the certain Raman modes of the system. While, both B_3g(5) and B_1g(3) modes are broadened in Ni and Fe doped samples, in addition Fe doped samples also show broadening of B_1g(4) mode. In doped samples a new mode, A_1g(3) appears due to the induced lattice disorder. Temperature dependent magnetic measurements suggested a negative value of Curie–Weiss temperature (θ_cw) indicating that all the samples are antiferromagnetic. However, the Neel temperature (T_N) increased for Fe doping and decreased with Ni doping. These changes in the Neel temperature upon doping can be correlated to the changes in the nearest neighbor and next nearest neighbor exchange interactions.

CoFe₂O₄ (S:Y-1:0) and Sr₂Co₂Fe₁₂O₂₂ (S:Y-0:1) ferrites were synthesized separately by using chemical coprecipitation technique and calcined at 1000 °C for 5 h. The mixed ferrite composites (S:Y-3:7, 4:6, 5:5, 6:4 and 7:3) were prepared by physical mixing of individual ferrite powders in required weight proportions. The prepared composites were heated at 1150 °C for 5 h in a muffle furnace and then slowly cooled to room temperature. The prepared ferrites were characterized using various instrumental techniques like FTIR, XRD, SEM, VSM and dielectric measurements. The x-ray diffraction studies of pure Sr₂Co₂Fe₁₂O₂₂ ferrite sample show the presence of M and Y-type hexagonal phases, while the composites consist of spinel and Y-type phases. FTIR spectra of all samples show two bands of Fe–O stretching vibrations. VSM results of composites reveal that the values of the saturation magnetization (M_s) vary from 50.44 emu g⁻¹ to 31.21 emu g⁻¹, while remanent magnetization values found from 11.18 emu g⁻¹ to 3.70 emu g⁻¹. A higher value of coercivity (H_c  =  562 emu g⁻¹) is observed in the composite S:Y-3:7 but M_r/M_s ratio of pure and composites is found to be less than 0.5. The dielectric behavior is explained using Maxwell–Wegner type interfacial polarization and N. Rezlescu's model.

The crystal structure features and the unit cell parameters were refined using the powder x-ray method for the solid solutions BaFe_12−xGa_xO₁₉ (x = 0.1–1.2) barium hexagonal ferrites of M-type at 300 K. With increase of substitution level the unit cell parameters monotonically decrease. The temperature and field dependences of the specific magnetization were investigated by the vibration magnetometry method. The concentration dependence of the T_C Curie temperature as well as the M_S spontaneous specific magnetization and the H_C coercive force at 300 K is constructed. With increase of substitution level the magnetic parameters monotonically decrease. The microwave properties of the considered solid solutions in the external magnetic bias field are also investigated at 300 K. With increase of Ga³⁺ concentration from x = 0.1 to x = 0.6 the frequency value of the natural ferromagnetic resonance (NFR) decreases in the beginning, and at further increase in concentration up to x = 1.2 it increases again. With increase in Ga³⁺ concentration the line width of the NFR increases that indicates the increase of frequency range where there is an intensive absorption of electromagnetic radiation (EMR). At the same time the peak amplitude of the resonant curve changes slightly. The frequency shift of the NFR in the external magnetic bias field takes place more intensively for the samples with small Ga³⁺ concentration. It is shown the prospects of use of the Ga-substituted barium hexagonal ferrite as the material effectively absorbing the high-frequency EMR.

The complex impedance spectroscopy and the electric modulus of Mo doped Cobalt–Zinc inverse spinel ferrite has been investigated in detail. The conventional ceramic technique has been used to prepare the CZMO. The HRXRD technique has been used to study the structural analysis which confirms the inverse spinel structure of the material and also suggest the material have Fd3m space group. The complex impedance spectroscopic data and the electric modulus formalism have been used to understand the dielectric relaxation and conduction process. The contribution of grain and grain boundary in the electrical conduction process of CZMO has been confirmed from the Cole–Cole plot. The activation energy is calculated from both the IS (Impedance Spectroscopy) and electric modulus formalism and found to be nearly same for the materials.

Thin films of NiFeW were fabricated by gradient composition deposition technique and their static and dynamic magnetic properties were characterized at various temperatures. The doping composition of W was controlled by varying the deposition power of W. It was found that when the doping composition of W is low, the temperature dependence of the magnetic anisotropy is negative, i.e. it is decreased with temperature. This result can be interpreted in terms of the dominant contribution of the pair-ordering magnetic anisotropy. However, when the doping composition of W is high enough, it becomes positive with magnetic anisotropy being significantly increased with the increasing of temperature. The peculiar observation of the increasing of magnetic anisotropy with temperature is due to the fact that the contribution of the stress-induced magnetic anisotropy becomes dominant when the W composition is increased. Because of the increasing of the stress upon the heating of the films, this stress-induced magnetic anisotropy increases with temperature.

Structural, optical and magnetic properties of Zn_0.96Li_0.02Cu_0.02O and Zn_0.98−xMg_xCu_0.02O (x  =  0.00, 0.02, 0.08) films grown by pulsed laser deposition (PLD) on a glass substrate coated with indium tin oxide (ITO) are presented in this paper. X-ray diffraction (XRD) measurements confirmed good structural quality without any impurity. No E₂(high) mode is observed in Raman spectra, possibly due to the breaking of translational symmetry caused by the intrinsic defects or by the dopant. Optical measurements show an increase in the bandgap of Mg- and Li-doped Cu:ZnO films with respect to that of Cu:ZnO film. Extended x-ray absorption fine structure spectroscopy (EXAFS) measurements at the Zn K-edge show some change in the coordination number, but no significant change was observed in the bond distances of the first and the second shells. The mean square relative displacement σ² increases with doping, indicating higher disorder in films caused by Mg and Li doping. No evidence of ferromagnetism is found in these films at 300 K.

Multiferroic Co_1−xCu_xCr₂O₄ (x  =  0.0, 0.5) chromites are synthesized by low temperature fired sol-gel auto combustion method. Synchrotron and lab x-ray diffraction (XRD) pattern confirms the single-phase crystalline nature. Structural phase transition is observed from cubic (CoCr₂O₄ (space group Fd3m)) to tetragonal (Co_0.5Cu_0.5Cr₂O₄ (space group I4₁/amd)). Scanning electron micrograph of sintered chromites discerns less agglomeration with average grain size distribution ranging from ~100 to 150 nm. High intense Raman mode (A_1g) is shifted lower wave number (red shift) for Jahn–Teller [JT] Cu²⁺ ion doped: Co_0.5Cu_0.5Cr₂O₄ chromites. Dielectric dispersion of CoCr₂O₄ and Co_0.5Cu_0.5Cr₂O₄ is attributed to hopping mechanism. Minimum power loss for Cu²⁺ as JT ion Co_0.5Cu_0.5Cr₂O₄ is observed as compare to CoCr₂O₄ chromite. JT (Cu²⁺) ions substitution does not show the existence of electric polarization in chromites.

Silver nanocluster-doped glasses are attractive materials for various photonic applications. In this paper, bulk silica glasses doped with luminescent silver nanoclusters have been prepared using the sol-gel technique. As a first step, dense silica glasses doped with ionic silver have been loaded with hydrogen. Thereafter, a heat-treatment in air atmosphere was performed to enable the growth of silver nanoclusters at different temperatures in the range 100–600 °C. The optical properties of the obtained nanocomposites have been studied, as a function of the post-annealing temperature, using optical absorption and photoluminescence spectroscopies. It has been shown that, under UV photoexcitation, the hydrogenated samples, heat-treated between 200 and 500 °C present visible luminescence due to cationic and neutral molecular-like silver clusters, consisting of a small number of Ag atoms or ions. After annealing at 600 °C, further Ag aggregation led to 2 nm-size silver nanoparticles, resulting in a quenching of the visible luminescence.

A simple and cost-effective flexible plasmonic sensor is developed using a gold-coated polymer nanograting structure prepared via soft UV nanoimprint lithography. The sub-wavelength nanograting patterns of digital versatile discs were used as a template to prepare the polydimethylsiloxane stamp. The plasmonic sensing substrate was achieved after coating a gold thin film on top of the imprinted nanograting sample. The surface plasmon resonance (SPR) modes excited on the gold-coated nanograting structure appeared as a dip in the reflectance spectrum measured at normal incidence under white light illumination in the ambient air medium. Electromagnetic simulation based on the finite element method was carried out to analyze the excited SPR modes. The simulated result shows very close agreement with the experimental data. The performance of the sensor with respect to changing the surrounding dielectric medium yields a bulk refractive index sensitivity of 788  ±  21 nm per refractive index unit. Further, label-free detection of proteins using a plasmonic sensing substrate was demonstrated by monitoring specific interactions between bovine serum albumin (BSA) and anti-BSA proteins, which gave a detection limit of 123 pg mm⁻² with respect to target anti-BSA protein binding. Thus, our proposed plasmonic sensor has potential for the development of an economical and highly sensitive label-free optical biosensing device for biomedical applications.

We report on the synthesis of photo luminescent zinc oxide (ZnO) quantum dots, their deployment on the window side of photovoltaic structures and the measured influence on the power conversion efficiency. Down-shifting effects were characterized by exciting the synthesized nanostructures with photons in the 340–350 nm range, and measuring the wavelength of the emitted photons observed to be ~500 nm. The colloidal ZnO quantum dots were synthesized in an ethanol-based solution, obtaining different sized nanostructures centered at 4 nm, optically recognizable by their emission in various colors. Subsequently, different concentrations of zinc oxide quantum dots were prepared and dispersed in poly-methyl-methacrylate (PMMA) to be spin cast on the window side of previously characterized solar cells. The observations made to date indicate an improvement of ~4.8% in the PCE. In this work, we discuss the results obtained and suggest pathways to further increase the power conversion efficiency of photovoltaic devices employing quantum dots.

Hydrogenated ZrO₂ microspheres were directly prepared by cathode plasma electrolysis (CPE) in an aqueous solution of Zr(NO₃)₄•5H₂O. Owing to the energy of plasma and the cathodic hydrogen evolution reactions, the CPE method combined the preparation of ZrO₂ ceramic and the hydrogen treatment into only one step. The results showed regular microspheres consisting of tetragonal-ZrO₂ and monoclinic-ZrO₂ with 1–10 µm in diameter were formed at relatively high concentration of Zr(NO₃)₃•5H₂O. These ZrO₂ microspheres contained about 52.54 µg g⁻¹ hydrogen which caused a narrow band gap (3.10 eV). Thus, the microspheres showed good photocatalytic activity under simulated sunlight, and the degradation of RhB dye reached nearly 58% for 3 h of irradiation, much better than the ZrO₂ microspheres after dehydrogenation treatment.

Yb³⁺, Er³⁺ and Tm³⁺ co-doped Gd₂O₂S sub-micro phosphors were synthesized by solid-state sulfurization of the oxide powders derived from sol-gel method. The crystal structure, morphology and upconversion luminescence properties of the phosphors were characterized by x-ray diffraction, scanning electron microscopic and fluorescence spectrum analysis methods. The phosphors exhibited typical hexagonal Gd₂O₂S phase when sulfurized at 800 °C for 2 h. Under the excitation of 980 nm laser diode, the Gd₂O₂S: Yb³⁺, Er³⁺, Tm³⁺ phosphors displayed distinct blue, green and red upconversion emissions centered at 481, 546 and 669 nm, respectively. The Gd₂O₂S phosphors using acetic acid as a chelating agent in the sol-gel process had the optimal upconversion emission property. The upconversion mechanism analysis revealed that the two-photon absorption was mainly responsible for the green and red upconversion emission of Er³⁺ ions, and the three-photon absorption was responsible for the blue upconversion emission of Tm³⁺ ions in the Gd₂O₂S: Yb³⁺, Er³⁺, Tm³⁺ phosphors.

Magnesium phthalocyanine (MgPc) based Schottky diode on indium tin oxide (ITO) substrate was fabricated by thermal evaporation method. The dark current voltage characteristics of the prepared ITO–MgPc–Al heterojunction Schottky diode were measured at different temperatures. The diode showed the non-ideal rectification behavior under forward and reverse bias conditions with a rectification ratio (RR) of 56 at  ±1 V at room temperature. Under forward bias, thermionic emission and space charge limited conduction (SCLC) were found to be the dominant conduction mechanisms at low (below 0.6 V) and high voltages (above 0.6 V) respectively. Under reverse bias conditions, Poole–Frenkel (field assisted thermal detrapping of carriers) was the dominant conduction mechanism. Three different approaches namely, I–V plots, Norde and Cheung methods were used to determine the diode parameters including ideality factor (n), barrier height (Φ_b), series resistance (R_s) and were compared. SCLC mechanism showed that the trap concentration is 5.52  ×  10²² m⁻³ and it lies at 0.46 eV above the valence band edge.

CaCu₃Ti₄O₁₂ (CCTO) was prepared by a chemical reaction method. The pellets prepared from the calcined powder of the material were sintered at 1100 °C. Analysis of x-ray diffraction pattern, recorded on CCTO powder, confirms the phase formation of CCTO. Studies of dielectric (ε_r, tanδ) and impedance parameters using dielectric and impedance spectroscopy of the compound have provided information about the electrical properties and the dielectric relaxation mechanism of the material. Detailed studies on the variation of electrical conductivity (dc) with temperature show semi-conducting nature of the material. Study of frequency (of applied electric field) dependence of ac conductivity at different temperatures suggests that the compound follows the Jonscher's power law. Complex impedance spectroscopic analysis suggests that the semicircles formed in the Nyquist plot are connected to the grains, grain boundary and interface effects. An optical energy band gap of ~1.9 eV is obtained from the UV–visible absorbance spectrum. The magnetic data related to magneto-electric (ME) coefficient, measured by varying dc bias magnetic field, have been obtained at room temperature.

Transparent heaters have become important owing to the increasing demand in automotive and display device manufacturing industries. Indium tin oxide (ITO) is the most commonly used material for the production of transparent heaters, but the fabrication cost is high as the indium resources are diminishing fast. This has been the driving force behind the intense research for discovering more durable and cost-effective alternatives. Tin oxide, with its high temperature stability and coexisting high levels of conductivity and transparency, can replace expensive ITO in the fabrication of transparent heaters. Here, we propose nanograined tin oxide films deposited using ultrasonic spray pyrolysis as the raw material for the fabrication of transparent heaters. Silver contacts are paste printed on the deposited SnO₂ layers, which provide the necessary connections to the external circuitry. Deposition of films having sheet resistance in the 120 Ω □⁻¹ range takes only ~5 min and the utilized methods are fully scalable to the mass production level. Durability tests, carried out for weeks of continuous operation at different elevated temperatures, demonstrated the long load life of the produced heaters.

The aim of the research is to obtain conductive elastomer based composites with different degree of filling and specific properties that are applicable for manufacturing of small flexible wearable antennas. The mechanical, electrical and magnetic properties of the composites based on butadiene-acrylonitrile rubber and conductive carbon black have been determined and the possibilities for their use have been analyzed.

It has been found that regarding the requirements for elastomer composites application as substrates in such kind of antennas for the 2.4–2.5 GHz frequency range (in respect to the tensile strength, elasticity, volume resistivity, real part of permittivity and permeability, tangent of dielectric and magnetic losses), the most suitable composites are those containing conductive carbon black at 5–10 phr. The prepared composites have been used as monolayered or multilayered substrates for manufacturing prototypes of small flexible wearable antennas for medical, sport and military applications for the 2.4–2.5 GHz frequency range, which demonstrate reliable performance and meet the requirements of the Federal Communication Commission.

Development of new and efficient metal-free electrocatalysts for replacing Pt to improve the sluggish kinetics of oxygen reduction reaction (ORR) is of great importance to emerging renewable energy technologies such as metal-air batteries and polymer electrolyte fuel cells. Herein, 3D sulfur-doping carbon nitride (S-CN) as a novel metal-free ORR electrocatalyst was synthesized by exploiting commercial melamine sponge as raw material. The sulfur atoms were doping on CN networks uniformly through numerous S–C bonds which can provide additional active sites. And it was found that the S-CN exhibited high catalytic activity for ORR in term of more positive onset potential, higher electron transfer number and higher cathodic density. This work provides a novel choice of metal-free ORR electrocatalysts and highlights the importance of sulfur-doping CN in metal-free ORR electrocatalysts.

Synthesis of tungsten (W) and tungsten tri-oxide (WO₃) thin films on alumina substrate by a peculiar Red-ox reaction route using hot-filament chemical vapor deposition technique is described. The resulting tungsten and tungsten oxide films were characterized using various techniques such as x-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM). XRD results revealed the complete conversion of cubic phase of pure tungsten into monoclinic phase of tungsten oxide. Raman spectroscopic analysis also confirmed the formation of WO₃. SEM images show considerable alteration in morphology from well faceted particles to wafers when pure W-film was converted to WO₃ film. The wafer like morphology of WO₃ films is found to be suitable for gas sensing towards hazardous gases such as NO₂ and NH₃. The WO₃ films showcased their highly responsive nature towards NO₂ gas with exceptionally high gas sensitivity ~32. WO₃ film demonstrated longer recovery time towards NO₂ gas unlike NH₃ gas making them attractive for their utilization in 'Newer application' such as a catalyst support material in catalytic converter devices which are potential representatives to arrest pollutant gases (NO₂) getting flown into the living environment.

Thin film deposition of SnS₂ was done by spin coating technique at ambient temperature. Deposition was done for different spin speed and spin time. The film thickness dependence on spin speed and spin time was studied. The spin speed was varied from 1000 rpm to 2000 rpm and spin time from 2 s to 6 s for constant speed of 1000 rpm. The elemental composition and crystal structure along with the phase of the as-deposited thin film was determined by the energy dispersive analysis of x-ray (EDAX) and x-ray diffraction (XRD) techniques respectively. The as-deposited thin film was found to be near stoichiometric and possess hexagonal crystal structure with determined lattice parameters in good agreement with the reported values. The crystallite size calculated from the XRD data using Scherrer's formula and Hall–Williamson relation came out to be 9.77 nm and 6.49 nm, respectively. The transmission electron microscopy (TEM) study of spin deposited thin films showed the film to be continuous. Surface study of the as-deposited thin film was done by simple optical microscope and scanning electron microscope (SEM). The study showed that the deposited thin film to be flat and uniform without visible cracks and pores. The optical spectroscopy study of the as-deposited thin film showed that the optical bandgap value decreases with increase in film thickness. The d.c. electrical resistivity variation with temperature for spin coating as-deposited SnS₂ film showed that the resistivity decreases with increase in temperature corroborating the semiconducting nature. The resistivity variation plot possesses two slopes. The temperature ranges showing two slopes lay between 300 to 383 K and 384 to 423 K having activation energy values for the two temperature ranges as 0.072 eV and 0.633 eV, respectively. The achieved results are deliberated in details.

Pure and gold-doped diamond-like carbon (Au-DLC) thin films are deposited at room temperature by using RF magnetron sputtering in an argon gas-filled chamber with a constant flow rate of 100 sccm and sputtering time of 30 min for all DLC thin films. Single-crystal silicon (1 0 0) substrates are used for the deposition of pristine and Au-DLC thin films. Graphite (99.99%) and gold (99.99%) are used as co-sputtering targets in the sputtering chamber. The optical properties and structure of Au-DLC thin films are studied with the variation of gold concentration from 1%–5%. Raman spectroscopy, atomic force microscopy (AFM), Vickers hardness measurement (VHM), and spectroscopic ellipsometry are used to analyze these thin films. Raman spectroscopy indicates increased graphitic behavior and reduction in the internal stresses of Au-DLC thin films as the function of increasing gold doping. AFM is used for surface topography, which shows that spherical-like particles are formed on the surface, which agglomerate and form larger clusters on the surface by increasing the gold content. Spectroscopy ellipsometry analysis elucidates that the refractive index and extinction coefficient are inversely related and the optical bandgap energy is decreased with increasing gold content. VHM shows that gold doping reduces the hardness of thin films, which is attributed to the increase in sp²-hybridization.

Present study reports the effect of vacuum (10⁻⁵ mbar) heat treatment (300 °C–900 °C) on the microstructural, electronic, thermo-optical, mechanical and tribological properties of commercially pure (CP) titanium (Ti) ultra thin (75 µm) foil. Phase analysis and surface morphology of the as-received and vacuum heat treated Ti foil samples were investigated by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and profilometry techniques. X-ray photoelectron spectroscopy (XPS) was employed to understand the electronic structure of the Ti foil surfaces. The solar absorptance (α_s), solar reflectance (ρ_s) and IR emittance (ε_ir) of the as-received and vacuum heat treated Ti foil samples were evaluated. For vacuum heat treatment temperatures above 700 °C these properties were significantly altered. Nanoindentation study was carried out to evaluate hardness and elastic modulus while single pass scratch tests were performed to understand the tribological behaviour of the as-received and vacuum heat treated Ti foil samples. Further, yield strength and elongation of the as-received and vacuum heat treated Ti foil samples were measured from the tensile tests. Based on the experimental results it is suggested that the nanoindentation response of the as-received and vacuum heat treated Ti foil samples can be significantly affected by presence or absence of residual stress and pile-up around the nanoindents. Moreover, the results implied that possibly the formation of hard and brittle TiC phase during vacuum heat treatment temperature at and above 700 °C had influenced the thermo-optical, mechanical and tribological properties of the thin Ti foils.

Polymethyl methacrylate (PMMA) tube is widely used in biomedical and mechanical engineering fields. However, it is hampered for some special applications as the inner surface of PMMA tube exhibts a hydrophobic characteristic. The aim of this work is to explore the hydrophilic modification of the inner surface of the PMMA tubes using an atmospheric pressure plasma jet (APPJ) system that incorporates the acylic acid monomer (AA). Polar groups were grafted onto the inner surface of PMMA tube via the reactive radicals (•OH, •H, •O) generated in the Ar/O₂/AA plasma, which were observed by the optical emission spectroscopy (OES). The deposition of the PAA thin layer on the PMMA surface was verified through the ATR-FTIR spectra, which clearly showed the strengthened stretching vibration of the carbonyl group (C=O) at 1700 cm⁻¹. The XPS data show that the carbon ratios of C–OH/R and COOH/R groups increased from 9.50% and 0.07% to 13.49% and 17.07% respectively when a discharge power of 50 W was used in the APPJ system. As a result, the static water contat angle (WCA) of the modified inner surface of PMMA tube decreased from 100° to 48°. Furthermore, the biocompatibility of the APP modified PMMA tubes was illustrated by the study of the adhesion of the cultured MC3T3-E1 osteocyte cells, which exhibted a significantly enhanced adhesion density.

Ag-doped barium strontium titanate (Ag/BST) thin films deposited on Si (1 0 0) substrates at various substrate temperatures and oxygen partial pressures via pulsed laser deposition were investigated. The effects of the substrate temperature and oxygen partial pressure on the crystalline structure, chemical state, and morphology were investigated via x-ray diffraction analysis, field-emission scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), and atomic force microscopy. The as-deposited thin films were found to be amorphous in nature. However, as the substrate temperature increased, the crystallinity of the films increased. The crystallite size varied from approximately 13 to 33 nm with respect to the substrate temperature. A uniform film with low roughness was obtained at high substrate temperatures with lattice parameters of a  =  3.8272 Å and c  =  4.4545 Å. A film prepared at 600 °C exhibited a better crystalline structure and a low surface roughness of approximately 70 nm. XPS revealed the core-level spectra of Ba3d, Sr3d, Ti2p, O1s, and Ag3d. An orange emission band at 571 nm was observed in photoluminescence studies of the Ag/BST thin films.

The authors report a method to grow high quality strain-relaxed Ge epilayer on a combination of low temperature Ge seed layer and Si_1−xGe_x/Si superlattice buffer layer by reduced pressure chemical vapor deposition system without any subsequent annealing treatment. Prior to the growth of high quality Ge epilayer, an ultrathin Si_1−xGe_x/Si superlattice buffer layer with the thickness of 50 nm and a 460 nm Ge seed layer were deposited successively at low temperature. Then an 840 nm Ge epilayer was grown at high deposition rate with the surface root-mean-square roughness of 0.707 nm and threading dislocation density of 2.5  ×  10⁶ cm⁻², respectively. Detailed investigations of the influence of ultrathin low-temperature Si_1−xGe_x/Si superlattice buffer layer on the quality of Ge epilayer were performed, which indicates that the crystalline quality of Ge epilayer can be significantly improved by enhancing the Ge concentration of Si_1−xGe_x/Si superlattice buffer layer.

Several papers have reported the grown self-organized nanotube arrays on pure Ti and its alloys to improve the surface of these materials for biomedical applications. The growth of nanotubes can be influenced by microstructure of material; however, few papers concerning this topic have been published. The aim of this work was to investigate the morphology, the cross-section view and the oxides in nanotube arrays in relationship to the microstructure of the Ti-10Nb alloy. The growth of nanotubes on the Ti-10Nb alloy obtained by anodic oxidation (AO). The Ti-10Nb alloy is composed by alfa and beta phases that were investigated by metallographic analysis, patterns of x-ray diffraction and EDS analysis. SEM images and EDS analysis revealed the morphology was composed by self-organized nanotube arrays on the alpha phase and walls with transversal holes on beta phase. X-ray patterns show crystalline oxides formation. Raman spectrum confirms the presence of anatase and Nb₂O₅ oxides. A significant contribution of the Nb₂O₅ was observed by bi-dimensional (x, y) Raman mapping, which also showed that the all oxide film was homogeneous oxide distributed on Ti-10Nb alloy. The nanostructured films have higher thickness in the beta than in the alpha phase, and have a small different in structure and oxide composition; as observed by SEM and Raman mapping. The results indicate that the microstructure of the Ti-10Nb affects the nanotubes morphology and the cross-section view, but the oxide formation was similar for all regions analyzed.

We report on the synthesis, characterization and photocatalytic activity of ZnO: Co thin films coated onto amorphous glass substrates by sol–gel spray coating technique. Structural and optical properties of the films were evaluated using x-ray diffractometer (XRD) and uv–vis spectrophotometer (UV–Vis), respectively. XRD patterns showed that the samples exhibited hexagonal wurtzite structure. The addition of cobalt reduced the (0 0 2) peak. This doping also reduces transparency and optical band gap. The band gap (E_g) markedly decreased from 3.20 eV to 3.00 eV for undoped ZnO and ZnO: Co with 10 mol% of doping concentration, respectively. Our thin films exhibited good structural, optical and photo cataytic properties. In this study, ZnO with 4 mol% of Co was observed to have the highest photocatalytic activity with methylene blue (MB) degradation of about 76.31% for 2 h under UV irradiation.

A thin film of Gd³⁺ doped Mn–Cr ferrite of the chemical formula MnCr_0.5Gd_0.02Fe_1.48O₄ was prepared by pulsed laser deposition from the bulk sample at room temperature. The optical absorption, transmission and reflection spectra were measured and discussed in the wavelength range from 300 to 2500 nm. The optical parameters were calculated following the single oscillator model. The optical band gap was found to be 2.75 eV, the dispersive energy of the electric dipoles was estimated using Wemple–Di Domenico relation to be 6.395 eV, while the oscillating energy of the dipole is found to be 4.997 eV. The optical dielectric constant was determined to be 3.886. The reported values could be taken as an indication to the crystal field deformation due to the large size Gd³⁺ ion in compensation to the physical deformation of the spinel structure.

The effects of the conventional shot peening and severe shot peening process on the mechanical and tribological properties of shot peened AISI 4340 high strength steel were systematically investigated. Compared with the conventional shot peened sample, the ultrafine grain surface layer with a depth of about 20 µm generated by the severe shot peening process can enhance the hardness and wear resistance of the treated material. However, deeper dimples generated by the high media velocity in the severe shot peening process resulted in a higher surface roughness, which is considered as a side effect of this method reducing the fatigue life of the material. Applying a smaller shot size with an appropriate intensity can be used to peen the severe shot peened samples to not only reduce the surface roughness and friction coefficient but also improve the wear resistance for these samples.

A revised nucleation theory in undercooled melt with applied electric field is derived based on the Classical Nucleation Theory, and the undercooling decrease caused by Joule heat release is also considered. The effect of applied electric field on the nucleation process in undercooling melts is calculated and discussed. Taking pure Al as the validation example, results indicate that with increasing electric field, the nucleation rate keeps increasing with a decreased undercooling, and the enhancement of nucleation rate caused by the electric field is the reason for grain refinement during solidification with electric treatment, which can be observed from the experimental investigation.

Inoculation plays an effective role to refine the microstructure of as-cast aluminium alloys, which strongly depend on the effectiveness of the inoculants. In this work, a new concept of nano-(TiNb)C/(NbTi)/Al complex powder as an inoculant for refining the as-cast aluminium alloys was proposed, and the nano-(TiNb)C/(NbTi)/Al complex powder was prepared by mechanical alloying (MA) method, furthermore, the refining effectiveness of inoculation on A356 alloy was investigated. Results show that the nano-(TiNb)C/(NbTi)/Al complex powder consists of three phases of α-Al, nano-(TiNb)C and (NbTi) solid solution. The nano-(TiNb)C/(NbTi)/Al complex powder as an inoculant have higher refining effectiveness as well as good recyclability on the microstructure of cast A356 alloy, and improve the mechanical properties, especially the ductility.

Microwave processing of metals is an emerging area. Melting of bulk metallic materials through microwave irradiation is still immature. In view of this, the present paper discusses the melting of bulk Al 1050 metallic material through microwave irradiation. The melting process is carried out successfully in a domestic microwave oven with 900 W power at 2450 MHz frequency. Metallurgical and mechanical characterization of the processed and as-received material is carried out. Aluminium phase is found to be dominant in processed material when tested through x-ray diffraction (XRD). Microstructure study of as-cast metal through scanning electron microscopy (SEM) reveals the formation of uniform hexagonal grain structure free from pores and cavities. The average tensile strength of the cast material is found to be around 21% higher, when compared to as-received material. Vickers' microhardness of the as-cast metal is measured and is 10% higher than that of the as-received metal. Radiography on as-cast metal shows no significant defects. Al 1050 material melted through microwave irradiation has exhibited superior properties than the as-received Al 1050.

Density functional theory calculations were used to study the vacancy and hydrogen interaction behavior in nickel, through calculation of the energetics and electronic interactions. Divacancy interactions in the nickel bulk depend on the position of the vacancies, where 1NN sites have an attractive interaction, 2NN sites have a repulsive interaction and 3NN sites have almost no interaction. Hydrogen-vacancy interactions have binding energies of 0.51 eV and 0.41 eV for a hydrogen atom at the shared octahedral 'O_s' site of a 2NN divacancy and 1NN divacancy, respectively. The calculated energy is in good agreement with previous observations. A monovacancy in nickel can trap up to six hydrogen atoms at the nearest octahedral site. However, a divacancy can accommodate almost four times as many hydrogen atoms as a monovacancy. 1NN octahedral sites can strongly bond with the hydrogen atoms, while hydrogen atoms at 2NN octahedral sites show a noticeably decreased segregation energy; however, the structures are still stable. A vacancy can significantly modify the charge density of the lattice. Hydrogen atoms at octahedral sites receive electrons from the NN metal atoms, forming bonds. As more hydrogen atoms are added, the isosurface is reduced, and there are fewer available optimal-density sites to accommodate additional hydrogen. Hydrogen at the 'O_s' site of a 2NN divacancy receives more electrons from the nearest metal atoms, and as a result, a strong interaction occurs. A divacancy can trap almost four times as many hydrogen atoms as a monovacancy, leading to an increase in the hydrogen content in the metal.

The novel thermomechanical treatment employed by Wang Z et al (2014 Mater. Sci. Eng. A 607 313–7) in enhancing the mechanical and microstructure properties of 6000 series aluminium alloys has been replicated for AA2139 aerospace aluminium alloys. The novel route which involves under-ageing, cold-rolling reductions and re-ageing at a fixed temperature has been carried out focusing on the effect of pre-straining and pre-ageing on the alloy properties. The influence of varying cold-rolling reductions and pre-ageing has been examined by tensile testing, hardness testing, differential scanning calorimetry, thermoelectric power measurements and scanning electron microscope (SEM). Further analyses were conducted with DSC and TEP measurements to check for precipitation sequence and solute retention respectively. On comparing the hardness and strength of the non pre-aged to the pre-aged samples, there is a remarkable increase in the hardness and strength of the aerospace alloy showing the huge influence of both pre-ageing and pre-straining stage of the novel thermomechanical treatment as observed in the 6000 series alloy, albeit at a higher rate. The treatments that exhibited the most promising mechanical properties (hardness, yield and ultimate tensile strength, elongation to failure) were found to be at a pre-ageing temperature of 175 °C for 1.5 h, 40% cold-rolling and re-ageing at 150 °C. The material was found to have yield strength of 590 MPa and 8.1% uniform elongation, which is well above the 5% acceptable value for structural applications and with strength levels adaptable for aerospace industries. The presence of higher volume fraction of well dispersed precipitates observed in the SEM further shows that intermediate cold-rolling reductions combines well with pre-ageing to give the best mechanical properties in this alloy.

A Fe/TiO₂ photocatalyst was synthesized and used as the catalyst in paraquat degradation as a test reaction to examine the photo-properties. The TEM, XRD, FTIR, UV–vis diffuse reflectance spectrometer, XPS and BET surface area analysis methods were used as the characterization techniques to investigate the physical and chemical properties of the prepared catalyst. Moreover, some of the preparation parameters, such as the preparation method, the content of Fe loading, thermal treatment and source of light irradiation, were also examined. According to the characterization and the expressed catalytic activity, it was found that the factor that significantly responded to the catalyst activity was the –OH surface species on the catalyst surface. Moreover, the lower band gap energy of the Fe/TiO₂ catalyst was also an important parameter that gave high catalytic properties because of the higher light adsorption. The preparation scheme and the photodegradation mechanism were proposed.

Density functional theory studies combined with the method of quasi-harmonic phonons have been undertaken to describe structural, bonding, elastic, vibrational and thermal properties of Ti₆Si₂B, which is a new ternary phase in the Ti–Si–B system. Analysis of the results is performed in relation to selected compounds from the Ti–Si and Ti–B systems as well as available experimental data. Titanium borosilicide exhibits covalent-type bonds of different strength as indicated by the calculated electron localization functions and the Bader charges. Its elastic and thermal properties are anisotropic due to higher out-of-plane than in-plane lattice compressibility and thermal expansivity. Polycrystalline Ti₆Si₂B is predicted to be a brittle material with quite high Vicker's hardness. It is shown that on one hand Ti₆Si₂B shares many common features with titanium silicides and borides, but on the other hand its mechanical, vibrational and thermal properties are distinct from those of compounds forming the Ti–Si and Ti–B systems. Theoretical phonon and Raman spectra, which are simulated at conditions close to experimental ones, may serve as a guide for interpretation and refinement of experimental spectra as well as symmetry mode assignment. The present work can be considered as a prediction study, still awaiting an experimental verification.

In the present study, we propose an aging parameter based on the aging temperature and the holding time, in order to quantify the degree of aging in aluminum alloys. The variations in hardness and tensile properties associated with different aging conditions were experimentally observed and expressed on a single curve according to the aging progression, which was quantitatively evaluated using the proposed parameter. The use of the proposed parameter provides a map of the hardness distribution and enables the determination of the optimum condition of the aging treatment, not only for maximizing the hardness value, but also for preventing the over-aging phenomenon.

To investigate the flow properties of constituent grains in ferrite–martensite dual phase steel, both the flow curve of individual grain and the flow behavior difference among different grains were investigated both using a classical dislocation-based model and nanoindentation technique. In the analysis of grain features, grain size, grain shape and martensite proximity around ferrite grain were parameterized by the diameter of area equivalent circular of the grain d, the grain shape coefficient λ and the martensite proximity coefficient p, respectively. Three grain features influenced significantly on the grain initial strength which increases when the grain size d decreases and when grain shape and martensite proximity coefficients enlarge. In describing the flow behavior of single grain, both single-parameter and multi-parameter empirical formulas of grain initial strength were proposed by defining three grain features as the evaluation parameters. It was found that the martensite proximity is an important determinant of ferrite initial strength, while the influence of grain size is minimal. The influence of individual grain was investigated using an improved flow model of overall stress on the overall flow curve of the steel. It was found that the predicted overall flow curve was in good agreement with the experimental one when the flow behaviors of all the constituent grains in the evaluated region were fully considered.

In this experimental investigation, the mechanical and tribological behaviour of aluminium (Al)-based silicon carbide (SiC, microparticles) and zirconium oxide (ZrO₂, nanoparticles) particle-reinforced hybrid composites were investigated. The contents of ZrO₂ (0, 3%, 6% and 9%, weight fraction) were added to Al–5%SiC composites by powder metallurgy (PM) technique. An x-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectrum (EDS) and elemental mapping were used for characterization of composites. Elemental mapping of the composites showed uniform distribution of SiC and ZrO₂ in the matrix. The wear test was conducted using a pin-on-disc apparatus with various input parameters like sliding distance (300, 500, 700 and 900 m), sliding speed (1, 1.5, 2 and 2.5 m s⁻¹) and applied load (20, 30 and 40 N). The hardness and wear resistance of the Al  +  SiC  +  ZrO₂ hybrid composites were found to be increased by increasing ZrO₂ content. The worn surface of hybrid composites and pure aluminium were analyzed through SEM to understand the wear mechanism.

In this study, the free vibration analysis of first-order shear-deformable orthotropic nanoplates are conducted in the frameworks of the nonlocal strain gradient elasticity theory. The equations of motion and also the associated boundary conditions are derived using the extended Hamilton's principle.

The multi-term extended Kantorovich method (MTEKM) in conjunction with the generalized differential quadrature method (GDQM) is employed to solve the equations of motion. For clamped and simply supported boundary conditions the problem is solved. In addition, a modified Mindlin plate model is introduced by excluding the nonlocality in the shear constitutive equations.

Numerical results have shown that the two material length scale parameters have opposite effects on the frequency response of the nanoplate. Also, the excluding the nonlocality in the shear constitutive equations is associated with the stiffness-softening phenomenon.

Concatenation of Silver nanowires (Ag-NWs) networks upon ion-beam irradiation is a novel annealing process with various opto-electronics and nano-electronics applications. In the present study, the Ag-NWs have been irradiated with copper (Cu) ion having MeV energy. The effect of ion fluencies on optical (ultraviolet and visible ranges) and electrical properties of Cu ion irradiated Ag NWs are investigated. It has been observed that electrical conductivity and optical transmittance rises with the increase of Cu ion fluences i.e. at 1  ×  10¹⁵ ions cm⁻², optical transmittance of Ag-NWs thin film increased up to 34% in the visible and 19% in the ultraviolet ranges with reference to un-irradiated Ag-NWs thin film. At the equivalent dose, the electrical conductivity raised twice to the pristine value. The increase in optical transmittance has been attributed to the ion beam induced localized heating source causing slicing of Ag-NWs, whereas ion beam induced fusion of Ag-NWs at contact position is the main reason to increase the electrical conductivity. This study offers a base for the future design of transparent metal NWs thin films in various photovoltaic applications, specifically in harsh irradiation environment.

Nanowires can be manipulated using an ion beam via a phenomenon known as ion-induced bending (IIB). While the mechanisms behind IIB are still the subject of debate, accumulation of point defects or amorphisation are often cited as possible driving mechanisms. Previous results in the literature on IIB of Ge and Si nanowires have shown that after irradiation the aligned nanowires are fully amorphous. Experiments were recently reported in which crystalline seeds were preserved in otherwise-amorphous ion-beam-bent Si nanowires which then facilitated solid-phase epitaxial growth (SPEG) during subsequent annealing. However, the ion-induced alignment of the nanowires was lost during the SPEG. In this work, in situ ion irradiations in a transmission electron microscope at 400 °C and 500 °C were performed on Ge and Si nanowires, respectively, to supress amorphisation and the build-up of point defects. Both the Ge and Si nanowires were found to bend during irradiation thus drawing into question the role of mechanisms based on damage accumulation under such conditions. These experiments demonstrate for the first time a simple way of realigning single-crystal Ge and Si nanowires via IIB whilst preserving their crystal structure.

Taking advantage of plasma technology using mixing gas CF₄/H₂, a fluorination process was performed on LDPE samples in the present paper. Different exposure times and discharge voltage levels were applied to produce four different types of samples. It has been found that after fluorination, space charge injection is obviously suppressed. And with longer fluorination times and higher discharge voltage, injected homocharges are reduced. By employing x-ray photoelectron spectroscopy, new chemical groups of C–F bindings are confirmed to be introduced by fluorination process of the plasma treatment. The charge suppression effect can be explained as: surface traps introduced by fluorination will reduce the interface field at both electrodes. Moreover, for fluorinated samples, heterocharge emerges obviously under 30 kV $\text{m}{{\text{m}}^{-1}}$, which are considered as charges ionized from degradation products of etching and/or lower weight molecular specifies. Through the conductivity measurements also performed at 30 kV $\text{m}{{\text{m}}^{-1}}$, it is found that, for the fluorinated samples with the better charge blocking effect, the conductivity is lowered. However, the conductivity of the fluorinated sample with the lightest degree of fluorination is found to be higher than that of normal samples.

Zn-Rich non-stoichiometric Ba(Zn_1/3Nb_2/3)_1−xZn_xO₃ (BZNZ) (x  =  0.01, 0.02, 0.03, 0.04) ceramics were prepared by the solid-state reaction method at 1500 °C for 2 h. The crystal structures and morphologies were analyzed by x-ray diffraction (XRD) and scanning electron microscopy. The vibration modes were obtained by Raman scattering spectroscopy and Fourier transform far-infrared (FTIR) reflectance spectroscopy. Rietveld refinement was performed for the XRD data. The relationship between crystal structures, dielectric properties, and phonon modes was analyzed in detail. XRD results show that the main phase is Ba(Zn_1/3Nb_2/3)O₃. The Raman results displayed that the ordering structure of BZNZ transformed from 1:2 to 1:1 when x changed from 0.02 to 0.04, and the dielectric losses have a positive correlation with the full width at half maximum values of the A_1g(O) and E_g(O) modes. The FTIR spectra were analyzed by the Kramers–Krönig method to obtain the real parts (ε') and the imaginary parts (ε'') of the dielectric constant. When x  =  0.02, the sample possesses uniform grains with clear boundaries and the lowest dielectric loss value (tanδ  =  5.5  ×  10^‒4) due to the largest packing fraction.

This work is focused on investigating the effects of deposition time and Ag ions implantation on structural and optical properties of ZnO film. The ZnO film was prepared on glass substrate by pulsed DC magnetron sputtering of pure Zn target in reactive oxygen environment for 2 h, 3 h, 4 h and 5 h respectively. X-ray diffraction results revealed polycrystalline ZnO film whose crystallinity was improved with increase of the deposition time. The morphological features indicated agglomeration of smaller grains into larger ones by increasing the deposition time. The UV–vis spectroscopy analysis depicted a small decrease in the band gap of ZnO from 3.36 eV to 3.27 eV with increase of deposition time. The Ag ions implantation in ZnO films deposited for 5 h on glass was carried out by using Pelletron Accelerator at different ions fluences ranging from 1  ×  10¹¹ ions cm⁻² to 2  ×  10¹² ions cm⁻². XRD patterns of Ag ions implanted ZnO did not show significant change in crystallite size by increasing ions fluence from 1  ×  10¹¹ ions cm⁻² to 5  ×  10¹¹ ions cm⁻². However, with further increase of the ions fluence, the crystallite size was decreased. The band gap of Ag ions implanted ZnO indicated anomalous variations with increase of the ions fluence.

The Phase stability, electronic structure, elastic properties and hardness of Ru–Ir alloys (Ru₅Ir₁₅, Ru₆Ir₁₄, Ru₈Ir₁₂) were investigated by first principles calculations. The negative values of cohesive energy and formation enthalpy show that these compounds are thermodynamically stable, and Ru–Ir alloys tend to exist in the form of Ru₅Ir_15, Ru₆Ir₁₄ and Ru₈Ir₁₂. The calculated results of electronic structure reveal that strong hybridizations exist near the Fermi level, being characteristic of Ru-d and Ir-d states, as a result, it is mainly composed of Ru–Ir bond in Ru–Ir alloy. The elastic properties were calculated, which included bulk modulus, shear modulus, Young's modulus, Poisson's ratio and hardness. The calculated results reveal that Ru₆Ir₁₄ compound has the highest hardness, and Ru₈Ir₁₂ compound has the maximal elastic anisotropy ratio. Meanwhile, Ru₅Ir₁₅, Ru₆Ir₁₄, Ru₈Ir₁₂ are brittle, and the vickers hardness values of these alloys are 25.29 GPa, 27.96 GPa, 27.39 GPa, respectively.

Cylindrical specimens of (1 0 4) oriented zinc single crystal (diameter  =  6 mm and length  =  5 mm) were irradiated with 500 keV C⁺¹ ions with the help of a Pelletron accelerator. Six specimens were irradiated in an ultra-high vacuum (~10^‒8 Torr) with different ion doses, namely 3.94  ×  10¹⁴, 3.24  ×  10¹⁵, 5.33  ×  10¹⁵, 7.52  ×  10¹⁵, 1.06  ×  10¹⁶, and 1.30  ×  10¹⁶ ions cm⁻². A field emission scanning electron microscope (FESEM) was utilized for the morphological study of the irradiated specimens. Formation of nano- and sub-micron size rods, clusters, flower- and fork-like structures, etc, was observed. Surface roughness of the irradiated specimens showed an increasing trend with the ions dose. Energy dispersive x-ray spectroscopy (EDX) helped to determine chemical modifications in the specimens. It was found that carbon content varied in the range 22.86–31.20 wt.% and that oxygen content was almost constant, with an average value of 10.16 wt.%. The balance content was zinc. Structural parameters, i.e. crystallite size and lattice strain, were determined by Williamson–Hall analysis using x-ray diffraction (XRD) patterns of the irradiated specimens. Both crystallite size and lattice strain showed a decreasing trend with the increasing ions dose. A good linear relationship between crystallite size and lattice strain was observed. Surface hardness depicted a decreasing trend with the ions dose and followed an inverse Hall–Petch relation. FTIR spectra of the specimens revealed that absorption bands gradually diminish as the dose of singly-charged carbon ions is increased from 3.94  ×  10¹⁴ ions cm⁻¹ to 1.30  ×  10¹⁶ ions cm⁻¹. This indicates progressive deterioration of chemical bonds with the increase in ion dose.