Table of contents

These proceedings present the written contributions of the participants of the 3rd International Meeting for Researchers in Materials and Plasma Technology (3rd IMRMPT) and the 1st Symposium on Nanoscience and Nanotechnology which was held from 4 to May 9, 2015 at the Dann Carlton Hotel Bucaramanga, Colombia, organized by the faculty of science of the Universidad Industrial de Santander (UIS) and the basic science department of the Universidad Pontificia Bolivariana. This was the third version of biennial meetings that began in 2011.

The five-day scientific program of the 3rd IMRMPT consisted of 24 Magisterial Conferences, 70 Oral Presentations, 185 Poster Presentations, 3 Courses and 1 Discussion Panel with the participation of undergraduate and graduate students, professors, researchers and entrepreneurs from Colombia, Russia, Germany, France, Spain, England, United States, Mexico, Argentina, Uruguay, Brazil, Venezuela, among others. Moreover, the objective of IMRMPT was to bring together national and international researchers in order to establish a network of scientific cooperation with a global impact in the area of the science and the technology of materials; to promote the exchange of creative ideas and the effective transfer of scientific knowledge, from fundamental research to innovation applied to industrial solutions and to advances in the development of new research allowing to increase the lifetime of the materials used in the industry by means of efficient transference of the knowledge between sectors academia and industry.

The topics covered in the 3rd IMRMPT include New Materials, Surface Physics, Structural Integrity, Renewable Energy, Online Process Control, Non Destructive Evaluation, Characterization of Materials, Laser and Hybrid Processes, Thin Films and Nanomaterials, Surface Hardening Processes, Wear and Corrosion/Oxidation, Plasma Applications and Technologies, Modelling, Simulation and Diagnostics, Biomedical Coatings, Surface Treatments and Surface Modification (Ion Implantation, Ion Nitriding, PVD, CVD). The editor hopes that those interested in the area of the science and the technology of materials and plasma enjoy the reading that reflect a wide range of topics.

It is a pleasure to thank the sponsors, partners and all the participants and contributors for making possible this international meeting of researchers.

It should be noted that the event organized by UIS, through of the research groups FITEK and CMN, was a very significant contribution to the national and international scientific community, achieving the interaction of different research groups from academia and business sector.

On behalf of the research groups FITEK and CMN of the UIS, we greatly appreciate the support provided by the Sponsors and Partners, who allowed to continue with the dream of research which contributing to Innovation and development in the present and future of Colombia.

The Editor

Ely Dannier V. Niño

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Energy assets and especially those deployed offshore are subject to a variety of harsh operational and environmental conditions which lead to deterioration of their performance and structural capacity over time. The aim of reduction of CAPEX in new installations shifts focus to operational management to monitor and assess performance of critical assets ensuring their fitness for service throughout their service life and also to provide appropriate and effective information towards requalification or other end of life scenarios, optimizing the OPEX. Over the last decades, the offshore oil & gas industry has developed and applied various approaches in operational management of assets through Structural Health and Condition Monitoring (SHM/CM) systems which can be, at a certain level, transferable to offshore renewable installations. This paper aims to highlight the key differences between offshore oil & gas and renewable energy assets from a structural integrity and reliability perspective, provide a comprehensive overview of different approaches that are available and applicable, and distinguish the benefits of such systems in the efficient operation of offshore energy assets.

One of the problems that affect the mechanical integrity of pipelines transporting aqueous fluids is the formation of fouling deposits as CaCO₃. Today different theoretical models that establish criteria trend but are not decisive in establishing the true rate of growth of scale in a pipeline there. This paper presents experimental development which was conducted to deposit scale of calcium carbonate by using a loop in which the deposits formed into a capillary of stainless steel AISI 316 and thus study the influence of various physical - chemical factors such as the composition of the solution, flow rate, and surface temperature and the presence of CO₂ generated on amount of scale. The evolution of the thickness and the amount of fouling obtained by tests was subsequently determined and by X-ray diffraction (XRD) and scanning electron microscopy (SEM) were characterized the deposits. With the results of the study show a strong influence of carbon dioxide in the amount of fouling obtained and according to the composition of the solution the flow rate fouling can generate greater or lesser scale. Under the test conditions is not possible to obtain deposits at room temperature.

This paper is intended to use a process model stochastic renewal to analyze the disintegration of the pipeline due to the time of use and service conditions, classifying the pipeline into segments according to the conditions to which it is exposed (temperatures, pressures, speed flow, environmental conditions, etc.). The model will determine the material wear over time, periods of renewal of the material and life chances at any time.

The power company feature infrastructure, which are generally shaped so the transmission and distribution lines, here is why it is necessary to characterize the process of electrochemical corrosion of these components. In this case the steel wire coated with zinc or aluminium, as it is undergoes the rigor of corrosive environments. Given the geographical diversity and different climatic environments, atmospheric corrosion carried affecting service life of structures. For example in very humid environments such as coasts and high altitudes, wetting time (TOW), parameter that meets the conditions of temperature and relative humidity, it affects large proportion, accelerating the corrosion of ferrous materials. Given the importance of establishing mechanisms that lessen the impact on degradation in transmission and distribution lines of both the reliability and the availability of the same. This paper presents the implementation in nitride steels as an alternative or complement to zinc coating.

The experimental set for artificially modulated structures production through an advanced vacuum arc evaporator with a magnetically-driven cathode spots on the cathode surface is described. The main features of vacuum arc as a vapor source with time-modulated compositions are discussed. The characteristics of the obtained multilayer coatings with artificially modulated Ti/TiB structures are presented.

4d and 5d series of the transition metals are used to the obtaining nitrides metallic, due to the synthesis of PtN, AgN and AuN in the last years. Different nitrides are obtained in the Plasma Assisted Physics Vapour Deposition system, due to its ionization energy which is necessary for their formation. In this paper a Magnetron Sputtering system was used to obtain Au thin films on Si wafers in Nitrogen atmosphere. The substrate temperature was varied between 500 to 950°C. The samples obtained at high temperatures (>500°C) show Au, Si and N elements, as it is corroborated in the narrow spectrum obtained for X-Ray Photoelectron Spectroscopy; besides the competition of orientation crystallographic texture between (111) and (311) directions was present in the X-Ray Diffraction analysis to the sample heated at 950°C.

The main purpose of this project was to elaborate a comparison between three water heating systems; using two plane water heating solar collector and another using a vacuum tube heater, all of them are on top of the cafeteria's roof on building of the "Universidad Pontificia Bolivariana" in Bucaramanga, Colombia. Through testing was determined each type of water heating systems' performance, where the Stainless Steel tube collector reached a maximum efficiency of 71.58%, the Copper Tubing Collector a maximum value of 76.31% and for the Vacuum Tube Heater Collector a maximum efficiency of 72.33%. The collector with copper coil was the system more efficient. So, taking into account the Performance and Temperature Curves, along with the weather conditions at the time of the testing we determined that the most efficient Solar Heating System is the one using a Vacuum Tube Heater Collector. Reaching a maximum efficiency of 72.33% and a maximum temperature of 62.6°C.

In this work we carried out the texturization of surfaces of multicrystalline silicon type-p in order to decrease the reflection of light on the surface, using the chemical etching method and then a treatment with laser. In the first method, it was immersed in solutions of HF:HNO₃:H₂O, HF:HNO₃:CH₃COOH, HF:HNO₃:H₃PO₄, in the proportion 14:01:05, during 30 seconds, 1, 2 and 3 minutes. Subsequently with a laser (ND:YAG) grids were generated beginning with parallel lines separated 50μm. The samples were analyzed by means of diffuse spectroscopy (UV-VIS) and scanning electron micrograph (SEM) before and after the laser treatment. The lowest result of reflectance obtained by HF:HNO₃:H₂O during 30 seconds, was of 15.5%. However, after applying the treatment with laser the reflectance increased to 17.27%. On the other hand, the samples treated (30 seconds) with acetic acid and phosphoric acid as diluents gives as a result a decrease in the reflectance values after applying the laser treatment from 21.97% to 17.79% and from 27.73% to 20.03% respectively. The above indicates that in some cases it is possible to decrease the reflectance using jointly the method of chemical etching and then a laser treatment.

This document shows the estimate of the total solar irradiance incident for the set of solar collectors to be located on the roof of cultural and sports university centre (CSUC) of the Foundation University Los Libertadores (FULL) in Bogotá, Colombia, and they will be part of the climate control system of the pool built inside. The calculation was based on experimental data of global solar radiation on the horizontal surface on March, July, October, November and December, through the three most commonly models used to determine the total solar radiation on tilted surfaces: isotropic sky, HDKR and Perez. The results show differences of less than 5% between the values calculated by the three models for December, the month with lower irradiance. For this month, reductions up to 15% and 19% were observed in the estimated irradiance, relative to those obtained on a horizontal surface on a surface under ideal orientation and inclination, respectively.

A method for tracking 3D objects using sensitivity phase of its Fourier transform to determine the position, displacement and orientation of a moving object is presented. The orientation and 3D position of the object from the 3D imaging system with subvoxel accuracy are calculated. A reference pattern should be fixed on the surface of the object and should be registered by the system of 3D images. This method is based on a prior knowledge of the association between the phase of the reference pattern and object motion, inherent property of the Fourier Transform. The reference pattern consists of a regular distribution of intensity that can be represented mathematically by three fringes of orthogonal patterns of volume whose 3D spectrum it allows to generate a 3D distribution of continued phase and absolute for each strip of the pattern orthogonal. A local maximum intensity value in the reference pattern represents a phase value 2nN where N corresponds to the fringe where is encountered the desired value. Reconstruction of the absolute phase associated with each set of fringes of volume in each direction orthogonal allows obtaining an exact point of the pattern, leading to the determination of the position of the object's location with subvoxel accuracy. The displacements from two consecutive positions are calculated. The accuracy of this method considering the parameters such as sampling, the number of holes, noise and contrast is evaluated numerically. Also its efficiency measuring the orientation is evaluated.

In recent years the use of Infrared Thermography (IRT) has reached a special importance in the industrial sector as a method of Non-Destructive Testing (NDT), for inspection of surface and subsurface defects of different types of materials. In order to determine the size of such defects by implementing the technique of Infrared Active Thermography, a Plexiglass sample (PMMA) with circular defects of different diameters and depths was designed and built. The sample was thermally stimulated by a continuous radiation from a halogen lamp, and subsequently the thermographic images were acquired by using the time-resolved infrared radiometry technique (TRIR). Images were obtained using Fluke TI-30 and TI-32 cameras, and a program was designed in Matlab for its further processing. Through a user interface, the program can display and filter the image; then it chooses a particular defect and calculates the diameter with their respective uncertainties. The best results for the calculated diameter were obtained with Ti-32 camera. The estimated uncertainties were below of 1.2mm, regard of defect diameter. Importantly, uncertainties grew when the diameter/depth ratio was 1 for depths of 4.0mm.

The cell adhesion of the implant is determinate by the chemical composition, topography, wettability, surface energy and biocompatibility of the biomaterial. In this work the interaction between human osteosarcoma HOS cells and textured Ti₆Al₄V surfaces were evaluated. Ti₆Al₄V surfaces were textured using a CO₂ laser in order to obtain circular spots on the surfaces. Test surfaces were uncoated (C1) used as a control surface, and surfaces with points obtained by laser engraving, with 1mm spacing (C2) and 0.5mm (C3). The HOS cells were cultured in RPMI-1640 medium with 10% fetal bovine serum and 1% antibiotics. No cells toxicity after one month incubation time occurred. The increased cell adhesion and cell spreading was observed after 1, 3 and 5 days without significant differences between the sample surfaces (C2 and C3) and control (uncoated) at the end of the experiment.

In the present work hybrid sol-gel coatings were synthesized on different magnesium alloys with potential interest in the fabrication of orthopaedic implants. Hybrid sols were obtained from a mixture of the inorganic precursor tetraethoxysilane (TEOS) and the organic precursor 3-glycidoxypropyltrimethoxysilane (GPTMS), employing ethanol as solvent and acetic acid as catalyst. The characterization of the sols was performed using pH measurements, rheological tests and infrared spectroscopy (FTIR) for different aging times. On the other hand, the coatings were characterized by scanning electron microscopy (SEM), while the corrosion resistance was evaluated using anodic polarization in SBF solution at 37±2°C. The results confirmed that, under specific conditions, uniform and homogeneous sol-gel coatings were obtained, which enhanced the corrosion resistance so that the corrosion current density was reduced in about two orders of magnitude with regard to the parent alloy.

In the present work multilayer hybrid sol-gel coatings were synthesized on the AISI 316L austenitic stainless steel employed in the fabrication of orthopaedic implants. Hybrid sols were obtained from a mixture of inorganic precursor, TEOS, and organic, GPTMS, using ethanol as solvent, and acetic acid as catalyst. The characterization of the sols was performed using pH measurements, rheological tests and infrared spectroscopy (FTIR) for different ageing times. On the other hand, the coatings were characterized by scanning electron microscopy (SEM), while the corrosion resistance was evaluated using anodic potentiodynamic polarization in SBF solution at 37±2°C. The results confirmed that sol-gel synthesis employing TEOS-GPTMS systems produces uniform and homogeneous coatings, which enhanced the corrosion resistance with regard to the parent alloy. Moreover, corrosion performance was retained after applying more than one layer (multilayer coatings).

This project aims to compare the behaviour of an AISI 1045 steel's abrasive wear resistance when is covered with aluminium oxide (Al2O3) or Titanium dioxide (TiO2), of nanometric size, using the technique of thermal hot spray, which allows to directly project the suspension particles on the used substrate. The tests are performed based on the ASTM G65-04 standard (Standard Test Method for Measuring Abrasion Using the Dry Sand/Rubber Apparatus). The results show that the amount of, lost material increases linearly with the travelled distance; also determined that the thermal treatment of hardening-tempering and the alumina and titanium dioxide coatings decrease in average a 12.9, 39.6 and 29.3% respectively the volume of released material during abrasive wear test.

Fouling in heat exchangers is produced by the deposition of undesired materials on metal surfaces. As fouling progresses, pressure drop and heat transfer resistance is observed and therefore the overall thermal efficiency of the equipment diminishes. Fouling is mainly caused by the deposition of suspended particles, such as those from chemical reactions, crystallization of certain salts, and some corrosion processes. In order to understand the formation of fouling deposits from Colombian heavy oil (API≈12.3) on carbon steel SA 516 Gr 70, a batch stirred tank reactor was used. The reactor was operated at a constant pressure of 340psi while varying the temperature and reaction times. To evaluate the formation of deposits on the metal surfaces, the steel samples were characterized by gravimetric analysis and Scanning Electron Microscopy (SEM). On the exposed surfaces, the results revealed an increase in the total mass derived from the deposition of salt compounds, iron oxides and alkaline metals. In general, fouling was modulated by both the temperature and the reaction time, but under the experimental conditions, the temperature seems to be the predominant variable that controls and accelerates fouling.

In this work electrochemical techniques were used to determine the corrosion behaviour of copper and stainless steel electrodes, used in grounding varying soil type with which they react. A slight but significant change in the corrosion rate, linear polarization resistance and equivalent parameters in the technique of electrochemical impedance spectroscopy circuit was observed. Electrolytes in soils are slightly different depending on laboratory study, but the influence was noted in the retention capacity of water, mainly due to clays, affecting ion mobility and therefore measures such as the corrosion rate. Behaviour was noted in lower potential for copper corrosion, though the corrosion rate regardless of the type of soil, was much higher for electrodes based on copper, by several orders of magnitude.

The Atmospheric corrosion is a phenomenon we see every day in our environment that arises due to environmental pollution we generate, there is currently very little information on atmospheric corrosion in the department of Boyacá and in general, in Colombia. The aim of this paper is to analyse which of these two environments is more aggressive and wherein the steel corrodes faster. To analyse these phenomenon specimens made in steel SAE 105 exposed for five months to the atmosphere in the municipalities of Tunja and Nobsa (an urban atmosphere and other industrial atmosphere) were installed, a control was carried to verify the amount of time that will be exposed each of these samples to the atmosphere, of Thus it may determine the lifetime of a structural steel. For the analysis of these samples electrochemical tests were carried out to calculate the rate of corrosion and resistance to polarization, also the gravimetric method be conducted to compare what was the amount of mass lost during the time of exposure to each of the samples.

Farmers and ranchers depend on the successful combination of livestock and crops. However, they have lost in the production by nitrate pollution. Nitrate poisoning in cattle is caused by the consumption of an excessive amount of nitrate or nitrite from grazing or water. Both humans and livestock can be affected. It would appear that well fertilised pasture seems to take up nitrogen from the soil and store it as nitrate in the leaf. Climatic conditions, favour the uptake of nitrate. Nitrate poisoning is a noninfectious disease condition that affects domestic ruminants. It is a serious problem, often resulting in the death of many animals. When nitrogen fertilizers are used to enrich soils, nitrates may be carried by rain, irrigation and other surface waters through the soil into ground water. Human and animal wastes can also contribute to nitrate contamination of ground water. A possible method to decontaminate polluted water by nitrates is with methods of fabrication of zero valent iron nanoparticles (FeNps) are found to affect their efficiency in nitrate removal from water.

In this work was studied the CO₂ carbon dioxide treatment, which is a pollutant gas and the main cause of global warming. For this aim, plasma was generated, through dielectric barrier discharges DBD, using hydrogen H₂ together with the CO₂ as reaction gases. There were used as dielectrics, alumina and quartz tubes of identical geometry. It was studied the CO₂ conversion in function of mixture composition CO₂+H₂, of the electrical power and the operation frequency, for three different gas flows. In all cases it was achieved better conversion levels with the alumina; this is because the alumina has a relative dielectric permittivity coefficient higher than the quartz. As products of CO₂ conversion in the chemical reactions, water H₂O and methane gas CH₄ were identified. The CO₂ conversion percentage to fixed work conditions was higher with the decrease the quantity of this gas in the mixture, with increase the active electrical power, and with decrease the operation electrical frequency.

In this study, an evaluation of the elastic-plastic surface hardening on Ti6Al4V ELI titanium nitride films obtained by glow discharge method was carried out by nanoindentation tests according to the standard ISO 14577. The nanotribological properties (metal-metal) were also evaluated using the pin-on-disc system Ti6Al4V surface deposition ELI with nitrogen, obtaining a correlation between the coefficient of friction of Ti6Al4V ELI treated by PVD and the Young's modulus of the respective substrate modified by PVD. To characterize the substrate for the characterization tests, scanning electron microscopy, atomic force microscopy and X-ray diffraction and contact angle were carried out. The results demonstrated that the substrates nitrided improved mechanical and tribological properties, hardness, Young's modulus and coefficient of friction, making the alloy Ti6Al4V ELI support axial loads in tension and compression.

As a contribution to the computational simulation of magnetic confinement and heating of plasmas ECR (Electron Cyclotron Resonance), this work is dedicated to the calculation and subsequent analysis of the magnetic fields generated by permanent magnets and coils required in magnetic traps between which we can mention the mirror trap, minimum- B and zero-B. To do this, we solved numerically the Biot-Savart law in the case of the coils with stationary current and the Ampere law in the case of the permanent magnets. The study includes the characterization of the ECR areas as well as the display of the vector field all of this applied to the magnetic traps mentioned above. Additionally, in the case of the mirror type trap and minimum-B trap, it is determined the ratio of the mirror, because it is important in the description of confinement.

The magneto-statics field from a parallelepiped magnet which can turn around an axis, is the first step to find the whole magnetic field in a multipolar configuration. This configuration is present in the ion sources, which are heated by electron cyclotron resonance. We present the analytic formulas to calculate this magnetic field outside the volume of the magnet. To model the magnet, we considered a constant magnetization vector inside of magnet volume. Therefore, the magnetic scalar potential method can be used. We present the results by a hexapolar system. Their magnetic field components are calculated on confinement region, several graphics are shown with directions and magnitude's gradients of the magnetic field to help understand better the confinement system. Our results are confronted with experimental ones. These formulas are very useful in research of plasma magnetic confinement in ion sources through computational simulations.

In this study, a sintering methodology is presented by using abnormal glow discharge to metal matrix composites (MMC), consisting of 316 steel, reinforced with titanium carbide (TiC). The wear behaviour of these compounds was evaluated according to the standard ASTM G 99 in a tribometer pin-on-disk. The effect of the percentage of reinforcement (3, 6, and 9%), with 40 minutes of mixing in the planetary mill is analysed, using compaction pressure of 700MPa and sintering temperature of 1,100°C±5°C, gaseous atmosphere of H₂ - N₂, and sintering time of 30 minutes. As a result of the research, it shows that the best behaviour against wear is obtained when the MMC contains 6% TiC. Under this parameter the lowest percentage of pores and the lowest coefficient of friction are achieved, ensuring that the incorporation of ceramic particles (TiC) in 316 austenitic steel matrix significantly improves the wear resistance. Also, it is shown that it is possible to sinter such materials using the abnormal glow discharge, being a novel and effective method in which the working temperature is reached in a short time.

Composite samples of 316 stainless steel and SiC were produced by powder metallurgy. Starting materials were mixed in different proportions and compacted to 700MPa. Sintering stage was performed by abnormal glow discharge plasma with direct current in an inert atmosphere of argon. The process was conducted at a temperature of 1200°C±5°C with a heating rate of 100°C/min. This work shows, the effectiveness of plasma sintering process to generate the first contacts between particles and to reduce vacancies. This fact is confirmed by comparing green and sintered density of the material. The results of porosity show a decrease after plasma sintering. Wear tests showed the wear mechanisms, noting that at higher SiC contents, the wear resistance decreases due to poor matrix-reinforcement interaction and by the porosity presence which causes matrix-reinforcement sliding.

The orbital angular momentum of light has a big contribution in many engineering applications like optical communications, because this physical property allows eigenstates characteristic of the wavefront rotation when the beam is propagated. The nature of these eigenstates allows that information can be encoded and gives immunity to electromagnetic interference, allowing an increase of bandwidth, cadence and capacity of the communication channel. This work shown the methodology using nanometric thin films like Titanium based (TiO₂) grown over strontium titanate (SrTiO₃) support, to distinguish and discriminate a well- defined integer value of the topological charge of an OAM beam.

A systematic study of the morphology evolution of ZnO nanostructures grown by physical vapour transport was carried out. The evolution of the shape with the growth time is shown to depend on the different gas-phase supersaturation and temperature conditions encountered in the crystallization zone of the tube furnace. The observed morphology transitions are discussed, and a growth model for ZnO nanostructures is given.

ZnO thin films have been elaborated by Pulsed Laser Deposition (PLD) onto glass substrates, at room temperature. Post-growth annealing treatment was applied to the films in air background. Morphology, chemical composition and optical characteristics of ZnO films were evaluated as a function of annealing temperature. With the increase in annealing temperature, the 002 axis peak intensity is improved and optical band gap is shifted to lower values. The PL peak positions shift are associated at stoichiometry change, it is confirmed with the experimental results. The films elaborated with this experimental setup could be used to applications in short wavelength optoelectronic devices, chemical and optical sensors.

In this work an easy, reproducible and inexpensive technique for the production of solid state nanopores and micropores using silicon wafer substrate is proposed. The technique is based on control of pore formation, by neutralization etchant (KOH) with a strong acid (HCl). Thus, a local neutralization is produced around the nanopore, which stops the silicon etching. The etching process was performed with 7M KOH at 80°C, where 1.23µm/min etching speed was obtained, similar to those published in literature. The control of the pore formation with the braking acid method was done using 12M HCl and different extreme conditions: i) at 25°C, ii) at 80°C and iii) at 80°C applying an electric potential. In these studies, it was found that nanopores and micropores can be obtained automatically and at a low cost. Additionally, the process was optimized to obtain clean silicon wafers after the pore fabrication process. This method opens the possibility for an efficient scale-up from laboratory production.

Bi_xSi_yO_z type coatings via sol-gel synthesized from bismuth nitrate pentahydrate, and tetraethyl orthosilicate as precursors; glacial acetic acid and 2-ethoxyethanol as solvents, and ethanolamine as complexing. The coatings were supported on AISI 316L stainless steel substrate through dip-coating and spin-coating techniques. The study showed that the spin-coating technique is efficient than dip-coating because it allows more dense and homogeneous films.

The medical science and the engineering, work to improve the materials used in the manufacture of joint implants, since they have a direct impact on the quality of people life. The surgical interventions are increasing worldwide with a high probability of a second or even a third intervention. Around these circumstances, it was evaluated the behaviour against microabrasion-corrosion phenomena on SiO₂ TiO₂ ZrO₂ coatings, synthesized by the sol-gel method with concentration of the Si/Ti/Zr precursors: 10/70/20 and 10/20/70. The coatings were deposited on AISI 316 LVM stainless steel substrates. The morphological characterization of the wear was made by AFM techniques. It was observed that the coatings with higher levels of titanium have a good response to the phenomena of microabrasion-corrosion.

In this work is presented the synergistic behaviour among corrosion/wear (tribocorrosion) of the multilayer coatings hafnium nitride/vanadium nitride [HfN/VN]n. The multilayers were deposited on AISI 4140 steel using the technique of physical vapor deposition PVD magnetron sputtering, the tests were performed using a pin-on-disk tribometer, which has an adapted potentiostat galvanostat with three-electrode electrochemical cell. Tribocorrosive parameters such as: Friction coefficient between the coating and the counter body (100 Cr6 steel ball); Polarization resistance by means of electrochemical impedance spectroscopy technique and corrosion rate by polarization curves were determined. It was observed an increase in the polarization resistance, a decrease in the corrosion rate and a low coefficient of friction in comparison with the substrate, due to an increase on the number of bilayers.

It was studied the green synthesis of silver nanoparticles (AgNPs) from the reduction of a silver nitrate solution (1 and 10mM) in the presence of an extract of mangifera indica leaves. Phytochemicals components present in extracts of mango leaves were determined using a GC-MS chromatograph. The results showed the presence of the phenolic compound pyrogallol (26.9% wt/5mL of extract) and oleic acid (29.1% wt/5mL of extract), which are useful for the reduction of the metallic salt AgNO₃ and the stabilization of silver nanoparticles. The synthesized nanoparticles were characterized by UV visible spectroscopy (UV-vis), evidencing absorbances at wavelengths of 417nm (AgNPs-1) and 414nm (AgNPs- 10), which are characteristic peaks of this metallic nanoparticles. Scanning Electron Microscopy (SEM) was used to determine the size of the synthesized nanoparticles. A particle size of about 28±7nm was observed for the AgNPs-1 sample and 26±5nm for the AgNPs-10. This suggests the advantages of green chemistry to obtain silver nanoparticles with a narrow size distribution.

Photocatalytic activity of iron oxide (IO) nanoparticles functionalized with TiO₂ was evaluated through photodegradation of phenol under UV irradiation. For this, magnetic nanoparticles were synthesized by co-precipitation method obtaining aggregates with a size of 46nm. The IO nanoparticles were encapsulated in a polysiloxane matrix and then functionalized with TiO₂ at 25°C (sample A: 0.1g TiO₂ and B: 0.3g TiO₂). Photodegradation experiments were carried out for six hours at pH 3.0 using concentrations of IO-TiO₂ nanoparticles of 0.2, 0.5, and 1.0g/L. A maximum amount of 89% of phenol photodegradation was achieved by using 0.2g/L of the IO-TiO₂-B sample. In addition, it was evaluated the possibility to re-using the nanomaterial after magnetic separation. For this, 0.2g/L of B sample were submitted for five cycles of photodegradation. A stable photocatalytic activity was observed as well as the nanoparticles were regenerated by calcination among cycles, which suggests the versatility of these nanoparticles for the photodegradation of organic pollutants.

This project aims to determine the possibility of obtaining nanometric size particles of aluminium oxide (Al₂O₃) and titanium dioxide (TiO₂) from commercial micron-sized powders, through the physical principle of ultrasonic cavitation, in order to be used as supply material in coatings made through a process of thermal spray by flame. The tests are performed on a Hielscher UIP 1000hd Ultrasonics equipment, in a 20 micron wave amplitude and in times of 6, 8, 12, 18 and 24 hours. The determination of the particle size is done through image processing using ImageJ software, obtained by the technique of scanning electron microscopy (SEM); while the elemental composition of the processed samples is analyzed through the technique of energy dispersing spectroscopy (EDS). The results show that Al2O3 and TiO2 have a reduction behaviour of the particles size after being subjected to ultrasonic cavitation, however is only reached the nanometric size in the TiO2 samples.

ZnMnO thin films were grown by Pulsed Laser Deposition (PLD) technique onto Silicon (100) substrates at different growth conditions. Thin films were deposited varying Mn concentration, substrate temperature and oxygen pressure. ZnMnO samples were analysed by using Raman Spectroscopy that shows a red shift for all vibration modes. Raman spectra revealed that nanostructure of thin films was the same of ZnO bulk, wurzite hexagonal structure. The structural disorder was manifested in the line width and shape variations of E₂(high) and E₂(low) modes located in 99 and 434cm^-1 respectively, which may be due to the incorporation of Mn ions inside the ZnO crystal lattice. Around 570cm^-1 was found a peak associated to E₁(LO) vibration mode of ZnO. 272cm^-1 suggest intrinsic host lattice defects. Additional mode centred at about 520cm-1 can be overlap of Si and Mn modes.

The growth of PEO ceramic coatings on AA 2024-T3 aluminium alloy in an aqueous Na₂SiO₃ (10.5g/l), KOH (2.8g/l) solution at 310 and 400V for 500 and 710s, was investigated. The morphology, roughness and thickness of the coatings were determined by SEM, digital microscopy, XRD diffraction analysis and thickness measuring instrument. The results show that thicker coatings are produced with longer process times and high applied voltages. Due to the nature of the PEO process, the roughness of the surface coatings increases as the coating become thicker, due to the development of sparks. The coatings are porous, with a crater like morphology and they are mainly amorphous.

CuGaSe₂ thin films have been synthesized by one-step electrodeposition on titanium and SnO₂/glass substrates from aqueous solutions that contain thiocyanate ion as a complexing agent. According to composition, and morphology analysis at deposition potential of -0.55V vs SCE (Standard Calomel Electrode) for 20 minutes from aqueous solutions of 4.6mM CuCl, 25.0mM GaCl₃ y 9.2mM SeO₂ in 2.0M de KSCN at pH 2.5 was found the optimum condition for obtain the CuGaSe₂ thin films with good morphology and good stoichiometric. The samples were annealed at temperature of 520°C in inert atmosphere for 30 minutes to improve their crystallinity. The obtained CuGaSe₂ thin film has a direct band gap (E_g) of 1.65eV. In addition, the cyclic voltammetry (CV) studies were performed in order to elucidate the electrodic processes that occur for the formation of semiconductor CuGaSe₂. Therefore, the electrochemical behaviour for each ion (Cu⁺, Ga³⁺ and Se⁴⁺), for binary (Cu-Se, Ga-Se, and Cu- Ga) and for ternary (Cu-Ga-Se) systems are described. This material has potential application in solar cells.

The local nanolithography oxidation technique is implemented by using an atomic force microscope (AFM) for the fabrication of nanoscale patterning structures on a silicon substrate covered whit a thin film of silicon nitride. During the fabrication process, the microscope is operated on air and contact mode utilizing a silicon tip covered whit a hard Cobalt- Chromium coat. The dependence of the oxide growth with the applied voltage was investigated varying this parameter in a range of 1 to 10V to constant scanning speed; the influence of the writing speed in the dimensions of the oxide formed is also analysed varying the speed values between 0.1 to 1μm/s. Is found that the dimensions of lines depend of scanning speed and voltages applied.

SrTi_1-xCo_xO3 (0.2≥x≥0) polycrystalline samples were prepared by solid-state reaction. X-ray diffraction (XRD) analysis shown the perovskite type structure is conserved for all samples without impurities. A small increase in the lattice parameters were observed for x≥0.05. Morphology and composition were analysed by scanning electron microscopy (SEM- EDX). Impedance spectroscopy measurements form 50Hz to 1MHz were made at different temperatures (25-400°C). The spectra were analysed by Z' vs Z'' plots, which reveal 3 contributions associated to electrodes, grain boundary and grain. From the fits the frequency f) and times relaxation (τ) of the grain were estimated, with values of f∼15KHz and τ∼67µs for 20% Co samples at RT. A dispersion in the permittivity ε* at low frequency (<300Hz) were observed, which increase with the temperature. Each component of ε* converge for frequencies up to ∼300kHz. Finally, a behaviour and activation energy analysis of the electrical conductivity is presented from ln(σ) vs 1/T plots.

Results regarding optical and structural properties of Cu₂ZnSnS₄ (CZTS) thin films prepared by co-evaporation using a novel procedure are compared with those obtained with CZTS films grown using a solution based route. The lattice strain ε and crystallite size D of CZTS films prepared by co-evaporation and by spray pyrolysis were estimated through X-ray diffraction (XRD) measurements using Williamson-Hall-isotropic strain model. The results of estimated average crystallite size of CZTS films by Scherrer and Williamson-Hall plot methods were compared with AFM (atomic force microscopy) measurements. It was found that the average crystallite size measured by Williamson-Hall plot methods agree quite well with AFM results. Further, information regarding the influence of preparation method on both, crystalline phases and the formation of structural defects was achieved through Raman and Urbach energy measurements.

In this study, a methodology for obtaining a conductive cassava starch biofilm doped with lithium perchlorate (LiClO₄) is shown, as well as the electrochemical technique for the synthesis of polypyrrole films, which are used for developing the trilayer artificial muscle PPy/Biopolymer/PPy designed to operate in air. Furthermore, results from the trilayer movement using chronoamperometric techniques are shown.

We investigated the structural, electronic, and magnetic properties of Mg, in the CS (simple cubic), NiAs (Nickel arsenide), FCC (rock-salt), R (Rhombohedral), Diamond and WZ (wurtzite) phases. Calculations were performed using the first-principles pseudo-potential method within the framework of spin-density functional theory (DFT).

Chemical oxidation is one of the many different methods of removing contaminants that has emerged recently, is an alternative method to traditional techniques. According to this research calcium peroxide is suitable choice for contaminant biodegradation in soil and ground water, but it happens at a very low speed. We hope that the method of synthesis of calcium peroxide in nano size by increased ratio of surface to volume can increase the speed of reaction and solve the problem. In the first synthesis of the material we obtained CaO instead of CaO₂. Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound in obtaining hypochlorite and to neutralize acidic soils. In this study we characterize the material by X-ray scanning electron microscopy, and ultraviolet-visible spectroscopy.

Coal tar is a by-product of coal distillation in the absence of oxygen to obtain metallurgical coke; its colour varies from dark coffee to black, slightly viscous and its density is greater than that of water. Taking into account the previous characteristics, this document presents a study of the feasibility of using coal tar for the improvement of physical properties, mechanics and dynamics of materials used in road engineering. In this way, the origin, characteristics, and properties of tar are first described. Next, its combination with which granular-based material is evaluated through the CBR test procedure to determine its resistance and to compare it with the non-stabilized material. Finally, the behaviour of the material when subjected to dead loads by means of resistant modules found with the NAT (Nottingham Asphalt Tester) is explored. As a result, the option of using coal tar as a stabilizer was identified due to its use under specific conditions.

This work reports the synthesis and the characterization of six oxides; it is based on Ce_1-xPr_xO₂ (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) system, which is obtained by the polymerization- combustion technique for potential applications on design of advanced electrodic components, for solid oxide fuel cells (SOFC). Initially the solid precursors are characterized by infrared spectroscopy (FTIR) and thermal analysis (TGA-DTA), allowing to determine the formation of prevalent citrate species and the optimal temperature for the consolidation of the desired crystalline phases. The X-ray diffraction (XRD) and the transmission electron microscopy analysis (TEM) are performed over calcined samples which provided information about the formation of a fluorite phase with grain distribution, surface, textural and morphological properties consistent with the nanometric obtaining crystallites (30nm), it is oriented along the (1 1 1) facet, with d spacings of 0.31nm for the main diffraction signal. These results indicate the effectiveness of the proposed synthesis method for potential applications in the design of advanced anodic materials for solid oxide fuel cells.

The triple perovskite La₂SrFe₂CoO₉ was prepared by the solid state reaction method from the high purity precursor powders La₂O₃, SrCO₃, Fe₂O₃, Co₂O₃ (99.9%). The crystalline structure was studied by X-ray diffraction experiments and Rietveld refinement analysis. Results reveal that this material crystallizes in an orthorhombic triple perovskite belonging to the space group Pnma (#62) with lattice constants a=5.491978(2)Ǻ, b=7.719842(2)Ǻ and c=5.436260(3)Ǻ. The granular surface morphology was studied from images of Scanning Electron Microscopy. The electric response was studied by the Impedance Spectroscopy technique from 10.0mHz up to 0.1MHz, at different temperatures (77-300K). Measurements of magnetization as a function of temperature permitted to determine the occurrence of a paramagnetic - ferromagnetic transition for a Curie temperature of 280K, which suggests it application in nanoelectronic devices. From the fit of the magnetic response with the Curie- Weiss equation it was concluded that the effective magnetic moment is particularly large due to the contribution of La, Fe and Co cations.

In this work we used first principles calculations in the frame of density functional theory (DFT) in order to study the structural and electronic properties of GaN doped with carbon. The computational calculations were carried out by a method based on plane waves pseudopotentials, as implemented in the Quantum Espresso code. In the wurtzite type GaN supercell the nitrogen atoms were replaced by carbon atoms (C by N) and then also the gallium atoms by carbon atoms (C by Ga). The carbon concentrations in the GaN volume was set as x=25, 50 y 75%. For each concentration x of carbon the formation energy was calculated for the substitutions C by N and CxGa. We found that it is more energetically favourable that the carbon atoms occupy the positions of the nitrogen atoms (C by N), because in all the x concentrations of carbon the formation energies were lower than that in the substitutions (C by Ga). It was found that the new compounds C_xGaN_1-x have higher bulk moduli. So they are very rigid. This property makes them good candidates for applications in hard coatings or devices for high power and temperatures. Analysis of the density of states show that the new C_xGaN_1-x ternary compound have metallic behaviour that comes essentially from the hybridization states N-p and C-p cross the Fermi level.

A polyanhydride was synthesized through microwave radiation using azelaic acid and dodecanedioic dicarboxylic acid at concentrations of 75:25, 50:50, and 25:75%w/w with acetic anhydride as crosslinking agent. Polymerization was carried out during 3 and 5 minutes. The copolymer with the highest molecular weight was selected using the intrinsic viscometry technique and by Huggin/Kraemer and Solomon/Ciuta methods. Based on these measurements, the 50:50 copolymer was selected with a polymerization time of 3 minutes in the microwave. This sample displayed the highest intrinsic viscosity (41.82cm³/g), demonstrating the relevance of the microwave technique for the synthesis of biopolymers.

Mercury is one of the persistent pollutants in wastewater; it is becoming a severe environmental and public health problem, this is why nowadays its removal is an obligation. Iron oxide nanoparticles are receiving much attention due to their properties, such as: great biocompatibility, ease of separation, high relation of surface-area to volume, surface modifiability, reusability, excellent magnetic properties and relative low cost. In this experiment, Fe₃O₄ and γ-Fe₂O₃ nanoparticles were synthesized using iron salts and NaOH as precipitation agents, and Aloe Vera as stabilizing agent; then these nanoparticles were characterized by three different measurements: first, using a Zetasizer Nano ZS for their size estimation, secondly UV-visible spectroscopy which showed the existence of resonance of plasmon at λ_max∼360 nm, and lastly by Scanning Electron Microscopy (SEM) to determine nanoparticles form. The results of this characterization showed that the obtained Iron oxides nanoparticles have a narrow size distribution (∼100nm). Mercury removal of 70% approximately was confirmed by atomic absorption spectroscopy measurements.

In this paper computational calculations were performed based on the density functional theory DFT, to investigate the structural, electronic and magnetic properties of CuAl_1-xCr_xS₂ (x=0.0, 0.50 and 1.00) alloys. Pseudopotential method was used, as is implemented in the Quantum-Espresso code. We found that the alloys crystallize in a tetragonal structure belonging to space group 122 (I-42d) with lattice constants a=5.290Å, c=10.378Å for x=0.5 and a=5.283Å, c=10.366Å for x=1.00. These values are in good agreement with experimental results. Additionally, we found that the alloys possess an antiferromagnetic behaviour with magnetic moments 4,20μ_β/cell and 4,05μ_β/cell, respectively. From the analysis of the density of states, it is clear that the alloys have a half-metallic behaviour due to the Cr-d and Cu-d states crossing the Fermi level. This compounds can be used in spintronic.

In this work we execute computational calculations to investigate the structural, electronic and magnetic properties of the GaN/MnN/GaN and MnN/GaN/MnN interlayers. The calculations were carried out by a method based on pseudopotentials, as implemented in the Quantum ESPRESSO code. For the description of the electron-electron interaction, generalized gradient approximation (GGA) was used. The total energy calculation reveal that the GaN/MnN/GaN interlayer is energetically most favourable that the MnN/GaN/MnN. Analysis of the density of states show that the interlayers have metallic behaviour that comes essentially from the hybridization and polarization states Mn-d and N-p cross the Fermi level. The interlayers have magnetic properties with a magnetic moment of 8μ_β/cell. Due these properties the superlattices can be potentially used in the field of spintronic.

We report first-principles calculations to determine the structural and electronic properties of Er_0.5Lu_0.5B₂ and LuB₂ compounds, by using Density Functional Theory (DFT) and Full Potential Linearized Augmented Plane-Waves (FP-LAPW) method. For the description of the electron-electron interaction was used the Local Density Approximation (LDA), Generalized Gradient Approximation of Perdew-Burke-Ernzerhof (GGA-PBE) and PBE0 hybrid functional. From the density of states (DOS), it is found that the addition of a fraction of the exact Hartree- Fock exchange energy in PBE approximation, evidence the localization of the 4f-Er and 4f-Lu orbitals, which favours the polarization of the electronic spins of these orbitals in LuB₂ and Er_0.5Lu_0.5B₂ compounds. The PBE0 scheme is justified because it describes of more appropriate manner the electronic and magnetic properties of strongly correlated systems than the LDA and PBE approaches.

In this work we study relative stability, structural and electronic properties of pure BN and with substitutions of carbon by boron and nitrogen atoms, e.i. for B_0.9375C_0.0625N and BC_0.0625N_0.9375, respectively. Using first-principles calculations in the Density Functional Theory (DFT), we found that it is more energetically favourable that the carbon atoms occupy the positions of the boron atoms (C by B). It was found that the new compounds BC_0.0625N_0.9375 (C by N) and B_0.9375C_0.0625N (C by B) have high bulk modulus, so they are very rigid. This property makes them good candidates for applications in hard coatings or devices for high power and temperatures. The density of state calculations shows that compound has metallic behaviour due to the hybridization of the orbitals C-2p and N-2p that cross the Fermi level.

The stabilization products often used to improve the support of granular layers in the construction of road surfaces may be expensive and difficult to get. Therefore, it is necessary to test different materials, which are cheap and easy to obtain, and which will enhance the physical and mechanical properties of pavement layers. This document evaluates the use of coal tar, as a stabilizer for granular subbase. Initially, with a description of tar properties, determining the optimal conditions for the granular subbase material compaction, by means of modified proctor tests and the calculation of the resistance of the unaltered material by using CBR lab tests (California Bearing Ratio). Afterwards, with the design and development of granular material mixes with different percentages of coal tar and determining its CBR as comparative parameter with that of the unaltered material. Finally, by calculating the optimal coal tar percentage in order to stabilize the subbase granular, the results showed an improvement in the resistance of the granular material and a decrease in its expansion due to the use of coal tar.

Modification techniques have been developed to achieve changes in the processing of polymers, and modification of their mechanical, thermal and morphological properties, as well as their hydrophobicity and conductivity. Sulfonation improves ion conductivity, antistatic behaviour, hydrophilicity and solubility of the polymers. These characteristics are related to the presence of sulfonic groups in the polymer matrix. This research project focuses on the evaluation of mechanical, physical and chemical properties of membranes that are based on a sulfonated Styrene-Ethylene-Propylene-Styrene (SEPS) copolymer. The membranes were functionalized with diethanolamine at 5, 15 and 30% w/w, to separate carbon dioxide. FTIR and XRD analyses were used to characterize the membranes. The sulfonated-loaded membrane with 15% of diethanolamine showed the best results in each characterization.

Hydrogen storage and microstructure the TiCrV_0.9, TiCrV_0.9Zr_0.2 and TiCrV_0.7Zr_0.4 alloys were investigated. The alloys were melted in arc furnace, the structure was analysed by X- ray diffraction and hydrogen absorption times were analysed by Sievert's type apparatus. The results showed that the addition of Zr replacing the V decreases in the absorption capacity passing of 3.8%wt to 2.0%wt in contrast the speed of hydrogen absorption increases considerably.

This research seeks to implement a web application to estimate the total charge in an electric discharge from the experimental parameters established in reactors such as the JUPITER-MOSMET [1-5], used to perform surface modifications of metallic and nonmetallic species in solids substrates by hybrid discharges pulsed of high voltage and electric arc at low pressures [6-13]. Estimate the total charge generated in an electric discharge will allow to know the approximate value of the dose of ions implanted in the material surface [14-15], which are of great importance in each one of the experiments performed in the plasma laboratory of the Universidad Industrial de Santander (UIS), where the reactor is installed. Currently there are no applications developed to ease the process optimization and estimate the total charge generated in a pulsed electric discharge.

This work analyzes through computational methods the phenomenon of confinement and heating of plasmas, in open magnetic traps, Minimum-B, and zero-B under conditions of resonance electron cyclotron (ECR). This simulation is made using electrostatic particle in cell method. First, it simulates the minimum-B trap, which has been studied both numerically and experimentally, by which is accomplished the confrontation of 6 different types of results that help us to validate our code. In the same way the zero-B trap is analysed. Proposed by Dr. Dugar-Zhabon, the main characteristic of the trap is the nullity of the magnetic field in the centre of the trap. The results show the detailed behaviour of the electronic component in the initial stage of the formation of plasma. Given the computational cost of the used model that allowed us to simulates fine details of the dynamics of plasma. Results were only reached in the time of half-life of the electrons. During this period the minimum-B trap proved to be better for the production of ions than the zero-B trap. Due to the huge amount of equations needed to solve the motion equations and the charge density, they are calculated in a Parallel way by GPU clustering.

The properties of a metallic matrix composites materials (MMC's) reinforced with particles can be affected by different events occurring within the material in a manufacturing process. The existence of residual stresses resulting from the manufacturing process of these materials (MMC's) can markedly differentiate the curves obtained in tensile tests obtained from compression tests. One of the themes developed in this work is the influence of residual stresses on the mechanical behaviour of these materials. The objective of this research work presented is numerically estimate the thermal residual stresses using a unit cell model for the Mg ZC71 alloy reinforced with SiC particles with volume fraction of 12% (hot-forging technology). The MMC's microstructure is represented as a three dimensional prismatic cube-shaped with a cylindrical reinforcing particle located in the centre of the prism. These cell models are widely used in predicting stress/strain behaviour of MMC's materials, in this analysis the uniaxial stress/strain response of the composite can be obtained through the calculation using the commercial finite-element code.

Mechanical properties of materials are strongly affected by increasing temperature, showing behaviors that could cause failure as creep. This article provides a brief theoretical description about fracture of materials, deepening on creep and intergranular creep. Some parameters as creep strain, strain rate, time to failure and displacement of the crack tip of a metallic glass selected at high temperature were studied. This paper shows a computer numerical model that permits establish mechanical behavior of a metal composite material Zr_52.5Cu₁₈Ni_14.5Al₁₀Ti₅, bulk metallic glass. In the presence of cracking when the material is subjected to temperatures exceeding 30% of the melt temperature of material. The results obtained by computer simulation show correlation with the results about the behavior of the material viewed through the creep test. From the results we conclude that the mechanical properties of the material generally do not undergo major changes at high temperatures. However, at temperatures greater than 650C, the effect of the application of stress during creep entails failures in this kind of material.

We study the ground state of a Kondo lattice model where the free carries undergo a superlattice potential. Using the density matrix renormalization group method, we establish that the model exhibits a ferromagnetic phase and spiral phase whose boundaries in the phase diagram depend on the depth of the potential. Also, we observed that the spiral to ferromagnetic quantum phase transition can be tuned by changing the local coupling or the superlattice strength.

Using the density matrix renormalization group method, we study a system of ¹⁷¹Yb atoms confined in a one-dimensional optical lattice. The atoms in the ¹So state undergo a double-well potential, whereas the atoms in the ³P₀ state are localized. This system is modelled by the Kondo lattice model plus a double-well potential for the free carries. We obtain phase diagrams composed of ferromagnetic and spiral phases, where the critical points always increase with the interwell tunneling parameter. We conclude that this quantum phase transition can be tuned by the double-well potential parameters as well as by the common parameters: local coupling and density.

Recently optical lattices allow us to observe phase transition without the uncertainty posed by complex materials, and the simulations of these systems are an excellent bridge between materials-based condensed matter physics and cold atoms. In this way, the computational physics related to many-body problems have increased in importance. Using the density matrix renormalization group method, we studied a Hubbard model for anyons, which is an equivalent to a variant of the Bose-Hubbard model in which the bosonic hopping depends on the local density. This is an exact mapping between anyons and bosons in one dimension. The anyons interlope between bosons and fermions. For two anyons under particle exchange, the wave function acquires a fractional phase e^iθ. We conclude that this system exhibits two phases: Mott-insulator and superfluid. We present the phase diagram for some angles. The Mott lobe increases with an increase of the statistical. We observed a reentrance phase transition for all lobes. We showed that the model studied is in the same universality class as the Bose-Hubbard model with two-body interactions.

We study the ground-state phase diagram of boson chains on a 2-period superlattice using the density matrix renormalization group method. New insulators for commensurate densities were found, differentiated by the arrangement of the particles in the unit cell, which was corroborated by analysis of the density versus the potential strength. Also, phase transitions between insulators for ρ ≥ 1 were seen, and a maximum in the behavior of the von Neumann entropy in the critical region was revealed, which suggests a superfluid phase between the insulators.

A fermionic chain is a one-dimensional system with fermions that interact locally and can jump between sites in the lattice, in particular an AB_n chain type, where A and B are sites that exhibit a difference in energy level of Δ and site B is repeated n-times, such that the unit cell has n +1 sites. A limit case of this model, called the ionic Hubbard model (n = 1), has been widely studied due to its interesting physics and applications. In this paper, we study the ground state of an AB₂ chain, which describes the material R₄[Pt₂(P₂O₅H₂)₄X] · nH₂O. Specifically, we consider a filling with two electrons per unit cell, and using the density matrix renormalization group method we found that the system exhibits the band insulator and Mott correlated insulator phases, as well as an intermediate phase between them. For couplings of Δ = 2,10 and 20, we estimate the critical points that separate these phases through the structure factor and the energy gap in the sector of charge and spin, finding that the position of the critical point rises as a function of Δ.

In this article theoretical models and some existing data sets were examined in order to model the two main causes (hydrogen embrittlement and corrosion-cracking under stress) of the called environmentally assisted cracking phenomenon (EAC). Additionally, a computer simulation of flat metal plate subject to mechanical stress and cracking due both to hydrogen embrittlement and corrosion was developed. The computational simulation was oriented to evaluate the effect on the stress-strain behavior, elongation percent and the crack growth rate of AISI SAE 1040 steel due to three corrosive enviroments (H₂ @ 0.06MPa; HCl, pH=1.0; HCl, pH=2.5). From the computer simulation we conclude that cracking due to internal corrosion of the material near to the crack tip limits affects more the residual strength of the flat plate than hydrogen embrittlement and generates a failure condition almost imminent of the mechanical structural element.

This paper shows the mathematical modeling of heat and mass transfer in transient state of cylindrical bars of low carbon steel subjected to carburizing process. The model solution for the two phenomena was performed using a one-dimensional analysis in the radius direction, using the numerical method of finite differences; also a sensitivity analysis by varying the coefficient of convective heat transfer (h) is performed. The modeling results show that this carburization steel is strongly dependent on h. These results suggest that if it can increase the value of h in this kind of process could reduce the time of process for this heat treatment. Additionally, an experimental procedure was established by carburization of a steel AISI SAE 1010, which develops cementing solid phase and the specimen steel and micrographic hardness profiles obtained from samples of the specimen analysis was performed, to determine the penetration depth of the carbon and validate this result over the values obtained by the computer model.

We employed density functional theory (DFT) in order to study the electronic and magnetic properties of (VN)₁/(AlN)₁, (VN)₁/(GaN)₁ and (VN)₁/(InN)₁ superlattices, in the wurtzite structure. The calculations were carried out using the pseudopotential method, employed exactly as implemented in Quantum Espresso code. For the description of the electron-electron interaction, generalized gradient approximation (GGA) was used. We found that the superlattices exhibit a half-metallic ferromagnetic behaviour and all the superlattices have magnetic properties with a magnetic moment of 2μ_β/cell. Analysis of the density of states show that ferromagnetic behaviour of the superlattices can be explained by the strong hybridization between states V-d and N-p crossing of the Fermi level. Due these properties the superlattices can be potentially used in the field of spintronics or spin injectors.

Cracking of metallic engineering materials is of great importance due cost of replacing mechanical elements cracked and the danger of sudden structural failure of these elements. One of the most important parameters during consideration of the mechanical behavior of machine elements having cracking and that are subject to various stress conditions is the stress intensity factor near the crack tip called factor Kic. In this paper a computational model is developed for the direct assessment of stress concentration factor near to the crack tip and compared with the results obtained in the literature in which other models have been established, which consider continuity of the displacement of the crack tip (XBEM). Based on this numerical approximation can be establish that computational XBEM method has greater accuracy in Kic values obtained than the model implemented by the method of finite elements for the virtual nodal displacement through plateau function.

We study spin-1 bosons confined in a one-dimensional optical lattice, taking into consideration both ferromagnetic and antiferromagnetic interaction. Using the density matrix renormalization group, we determine the phase diagram for the two firsts lobes and report the evolution of the first and second Mott lobes with respect to the spin-exchange interaction parameter (U₂). We determine that for the antiferromagnetic case, the first lobe is suppressed while the second grows as |U₂| increases. For the ferromagnetic case, the first and second Mott lobes are suppressed by the spin-exchange interaction parameter. We propose an expresion to describe the evolution of the critical point with the increase in |U₂| for both cases.

Particle-In-Cell(PIC) method is widely used for simulating plasma kinetic models. A 2D-PIC electrostatic algorithm is implemented for simulating the expansion of a laser- induced plasma plume. For potential and Electric Field calculation, Dirichlet and periodic boundary conditions are used in the X (perpendicular to the ablated material) and Y directions, respectively. Poisson-solver employs FFTW3 library and the five-point Laplacian to compute the electric potential. Electric field calculation is made by central finite differences method. Leap-frog scheme updates particle positions and velocities at each iteration. Plume expansion anlysis is done for the Emission and Post-Emission stages. In the Emission phase (while the laser is turned on), fast electron expansion is observed and ion particles remain near the surface of the ablated material. In the post-emission stage (with the laser turned off) the charge separation produces an electric field that accelerates the ions leading to the formation of a KeV per particle Ion-Front. At the end of the expansion, fastest electrons escape from the simulation space; an almost homogeneous ion-electron distribution is observed, decreasing the electric field value and the Coulomb interactions.

Using the atomic levels previously employed to demonstrate a two-photon maser, we show that the atom-atom entanglement produced by the successive passage of two three-level Rydberg atoms across a single-mode lossless cavity can be enhanced using the Stark shift. The atoms are assumed to be prepared in their excited states and to interact with the field during the same amount of time. Employing a physically motivated perturbation-theory approach, we obtain an effective two-level Hamiltonian. We show that, within the limits of validity of the approximation, atomic entanglement can be controlled by changing the frequency of the cavity field, and can be enhanced up to a maximum where the squared concurrence attains the value 16/27.

The sequential to correlated-tunneling transition of two identical bosons confined in a symmetrical double well potential is studied using a time-dependent variational formalism. Increasing the strength of the short-range boson-boson interaction, the probability of finding both bosons in the same well allow to identify three regimes. For small values of the boson- boson coupling constante, this probability display beatings. Then, the probability of finding both bosons in the same well becomes quasi-periodical in time, for almost all values of the coupling constant; however, there is a zero-measure set, which contains an infinity of points, for which this probability is time-periodic. Finally, for larger values of the coupling constant, this probability changes periodically. Based on the dynamics of the probability of finding one boson on each well and increasing the boson-boson interaction, we find that tunnelling changes from a regime where one boson tunnels after the other to a regime in which they tunnel together.

In this paper we present the preliminary results of morphological analysis of Fe₅₉Mn_36.5Al_3.10C_3.56Cu_0.237%Wt alloy. This alloy was prepared by mechanical alloying with various milling times, then hot compacted at various pressures and finally underwent presented a sintering process. The samples were characterized structurally by experimental techniques such as: X-ray diffraction and scanning electron microscopy. Each micrograph was analysed by fractal dimension using the Box Counting method in 2D; this type of tool allows you to assign a numerical value to the region which has been applied the technic. This numerical value is associated with the properties obtained by experimental techniques such as microhardness.

The space cyclotron autoresonance interaction of an electron beam with microwaves of TE₁₀₂ rectangular mode is simulated. It is shown that in these conditions the beam electrons can achieve energies which are sufficient to generate hard x-rays. The physical model consists of a rectangular cavity fed by a magnetron oscillator through a waveguide with a ferrite isolator, an iris window and a system of dc current coils which generates an axially symmetric magnetic field. The 3D magnetic field profile is that which maintains the electron beam in the space autoresonance regime. To simulate the beam dynamics, a full self-consistent electromagnetic particle-in-cell code is developed. It is shown that the injected 12keV electron beam of 0.5A current is accelerated to energy of 225keV at a distance of an order of 17cm by 2.45GHz standing microwave field with amplitude of 14kV/cm.

The results of full electromagnetic simulations of the electron beam acceleration by a TE₁₁₂ linear polarized electromagnetic field through Space Autoresonance Acceleration mechanism are presented. In the simulations, both the self-sustaned electric field and selfsustained magnetic field produced by the beam electrons are included into the elaborated 3D Particle in Cell code. In this system, the space profile of the magnetostatic field maintains the electron beams in the acceleration regime along their trajectories. The beam current density evolution is calculated applying the charge conservation method. The full magnetic field in the superparticle positions is found by employing the trilinear interpolation of the mesh node data. The relativistic Newton-Lorentz equation presented in the centered finite difference form is solved using the Boris algorithm that provides visualization of the beam electrons pathway and energy evolution. A comparison between the data obtained from the full electromagnetic simulations and the results derived from the motion equation depicted in an electrostatic approximation is carried out. It is found that the self-sustained magnetic field is a factor which improves the resonance phase conditions and reduces the beam energy spread.

This paper present novel virtual laboratories of electromagnetism, mechanics and optics to be used in the teaching of physic for the students as well as to the teacher in the classroom. The model used is friendly with the users and also is responsible for displaying data and its manipulation. The Vista/model, implements the behavior of the view to respond to user actions and expose model data in a way that is easy to use bindings, it is the mechanisms by which we can link the elements of the user interface objects containing the information to be displayed in the view. During the process of application of virtual laboratories the students shown a increasing ability to learn this specifics physics topics using a Web-based learning environment and a guide of work with the virtual laboratories framed in the meaningful learning pedagogical model.

A theoretical study of the current-voltage characteristics of a double-barrier heterostructure doped with a layer of shallow donors in the middle of the well and subjected to a magnetic field tilted with respect to the growth direction is reported. The parent materials are assumed to possess simple cubic lattices, the electronic structure of the system is modeled by means of a one-band tight-binding Hamiltonian, and the current is evaluated employing the Keldysh nonequilibrium formalism. The results reveal the magnetocompression of the donor wavefunction, in good qualitative agreement with the experimental report of Patané et al [Phys Rev Lett 105 236804 (2010)].

This paper presents theoretical results of a study that analyzed the effect of a high- frequency laser in the ground state binding energy of a hydrogenic donnor impurity. For these results, the trigonometric sweep method and framework of the effective mass approximation is applied. The results showed that the binding energy changes depending on the laser intensity and the impurity position across of the nanocone axis. The results agree with previous results obtained in similar systems.

We study in this paper the spin-polarized current density components in diluted magnetic semiconductor tunnelling diodes with different sample geometries. We calculate the resonant JxV and the density of states. The differential conductance curves are analyzed as functions of the applied voltage and the magnetic potential strength induced by the magnetic ions.

This study reports the biosynthesis of gold nanoparticles using an extract of Tamarindus indica L. leaves. Phenols, ketones and carboxyls were present in the leaves of T. indica. These organic compounds that allowed the synthesis of nanoparticles were identified by gas chromatography coupled to mass spectrometry (GC/MS) and High Pressure Liquid Chromatographic (HPLC). Synthesis of gold nanoparticles was performed with the extract of T. indica leaves and an Au⁺³ aqueous solutions (HAuCl₄) at room temperature with one hour of reaction time. Characterization of gold nanoparticles was performed by UV visible spectroscopy, scanning electron microscopy (SEM) and EDX. The results indicated the formation of gold nanoparticles with a wavelength of 576nm and an average size of 52±5nm. The EDX technique confirmed the presence of gold nanoparticles with 12.88% in solution.

This work studies the flux effect of borax (di sodium tetraborate decahydrate) on sintering of iron Ancor Steel 1000^® in abnormal glow discharge. The incidence of the percentage by weight of borax and the sintering temperature in the process were observed. Samples of powder metallurgical iron were prepared with proportions of 0.50%, 2.0%, 4.0% and 6.0% by weight of borax using the procedures of powder metallurgy. The samples were sintered at 800 and 1100°C for 30min, by glow discharge at low pressure in a reducing atmosphere composed of 20% H₂+80% Ar. The samples in compact green-state were analyzed by TGA-DSC to determine the fusion process and mass loss during sintering. The analysis of microhardness and density, shows that at a sintering temperature of 800°C the sample density decreases and the sample microhardness increases with respect to sintered samples without borax. Sintered samples were analysed by DRX showing the absence of precipitates.

Niobium pentoxide (Nb₂O₅) nanoparticles were prepared by the polymeric precursor method using citric acid as a chelating agent and ethylene glycol as a polymerizing agent. The powders obtained were characterized by X-ray diffraction and scanning electron microscopy. The results showed that the presence of HNO₃, HCl or NH₄OH in the employed aqueous solution favour the solubility of the used precursor salt, as well as also inside the oxide phase formation. The initial Nb₂O₅ powders were amorphous. The amorphous powders heated at 500°C contained Nb₂O₅ TT-phase, whereas at 650°C the Nb₂O₅ T-phase was obtained. In this way an increase in the synthesis temperature is related to the increase of the crystallinity, according to the values of the crystallite sizes that were estimated using the Scherrer method.

Wave equations describing the quasi-degenerated two-beam coupling in the photorefractive crystals for high frequency gratings have been solved. In the case of the quasi-degenerate two-beam coupling, equations depend upon the coupling coefficient, the response time of the medium, the input beams frequencies, the absorption coefficient and the input intensity ratio. The response time of the medium is function of the diffusion field, the drift field, the saturation field and the concentration ratio, i.e., the ratio between N_A density of acceptor impurities and N_D density of donor impurities. The effect of these parameters on the gain has been studied in details.

The tensile strength and bending strength, structure and thermal behaviour of mixtures of polyester resin (P-2000) and powders (ASTM sieve 200, <75μm) of dental ceramic wastes (dentals impressions, alginate and gypsum) was reported. The samples consisted of mixtures with percentage weights of 50-50%, 60-40%, 70-30%, 80-20%, 90-10%, where the resin was the majority phase, the Mekc (4% wt) was used as catalyst. The structure was studied using SEM and XRD, the thermal behaviour using DSC, TGA and DMA, while the mechanical strength was tested using standards ASTM D790 and D638. Irregular morphology and presence of small agglomerations was observed, with particle sizes between 29.63 and 38.67μm, the presence of different phases of calcium sulphate was found, and that to the increasing the concentration of the powder, the materials becomes more crystalline, increasing its density. An average service temperature of 69.15±4.60°C was found. Vickers hardness values are reported in ranges from 18.65 to 27.96. Considering the elastic modules was established that the materials become more rigid by having more powder concentration.

In this paper we presents the synthesis process of the GdMn_1-xFe_xO₃ perovskite material by conventional solid state reaction method. Crystalline phase evolution during the synthesis was studied by X-ray Diffraction (XRD) in powder of the materials, observing that the chemical reaction of the precursor oxides was significant above 1000°C. Rietveld refinement of DRX patterns shows a perovskite structure with octahedral distortions (space group Pbnm, # 62) for studied values of x (0, 0.1 and 0.2). The degree of substitution generates an increasing tendency on lattice parameters a and c, while for b is decreasing just as for the volume of the unit cell. The effect of the change in the lattice parameters directly affects the octahedral distortions, ie, with increasing degree of substitution (increased parameter c) octahedra tend to arrange one above the other aligned with the c axis. Magnetization measurements as a function of temperature were performed above room temperature between 300K and 860K with an applied field of 20Oe and below room temperature in Field Cooling (FC) and Zero Field Cooling modes (ZFC) between 4.2K and 300K with an applied field of 200Oe. Magnetic behavior above room temperature is paramagnetic for used values of x, on the other hand at low temperatures (T<30K) magnetic phase transitions associated to the apparition of an antiferromagnetic phase are observed. In addition for x=0.1 the derivative of magnetization shows a peak around 31K, associated to the ferrimagnetic transition for this material. Curie-Weiss fit reveals the antiferromagnetic (ferrimagnetic) behavior of the materials, also shows that the configurations with x=0 and x=0.2 have an effective magnetic moment very similar to the reported value of undoped material, while for x=0.1 a higher value is observed confirming the ferrimagnetic behavior of this configuration.

This project aims to mechanically characterize through compression resistance and shore hardness tests, the mixture of hevea brasiliensis natural rubber with butadiene synthetic rubber (BR), styrene-butadiene rubber (SBR) and ethylene-propylene-diene monomer rubber (EPDM). For each of the studied mixtures were performed 10 tests, each of which increased by 10% the content of synthetic rubber in the mixture; each test consisted of carrying out five tests of compression resistance and five tests of shore hardness. The specimens were vulcanized on a temperature of 160°C, during an approximate time of 15 minutes, and the equipment used in the performance of the mechanical tests were a Shimadzu universal machine and a digital durometer. The results show that the A shore hardness increases directly proportional, with a linear trend, with the content of synthetic BR, SBR or EPDM rubber present in the mixture, being the EPDM the most influential. With respect to the compression resistance is observed that the content of BR or SBR increase this property directly proportional through a linear trend; while the EPDM content also increases but with a polynomial trend.

The production and structural & magnetic characterization of new superconductor system TR:3811 (TR=Sm, Y, Yb) is presented in this work. The samples were produced by the solid state reaction method. The analysis of the measures of the diffraction X-ray, were made with the Rietveld refinement technique, that allowed to infer that the system presents a Pmm2 type structure with the following lattice parameters (a=3.88Å, b=3.82Å, c=42.82Å). The magnetization measurements were made by using the VSM-VERSALAB equipment with a magnetic field variation from a 100Oe to 7000Oe, and a temperature from 50K to 350K, showing the superconducting transition of the order of 90K.

The magnetoelectric effect is the phenomenon whereby through a magnetic stimulation can be produced an electrical response or vice versa. We implement a magnetoelectric voltage measuring device through the dynamic method for a different range of temperatures. The system was split into an electric set and an instrumentation and control set. Design and element selection criteria that the experimenter must take into account are presented, with special emphasis in the design of the sample holder, which is the fundamental component that differentiates the system operating at high temperature and the one operating at room temperature. The experimental equipment consists of an electromagnet with DC magnetic flux density (B) in a range of (0.0 to 1.6) KOe, a Helmholtz coil which operates with a sinusoidal B between (0.0 and 0.016) KOe and a PT100 temperature sensor. A tubular heating resistance, a Checkman temperature control and an SSR 40A were used for controlling the temperature. As an application of the system, the transverse and longitudinal magnetoelectric coefficient was measured for a thin film of BiFeO₃ at room temperature and 307K. It was observed that the behaviour of the longitudinal and transverse magnetoelectric coefficient matches the reported value and decreased with increasing temperature.

Yttrium-substituted Bi_1-xY_xFeO₃ (x=0, 0.03, 0.07, 0.15, 0.2 and 0.5) samples were prepared by solid state reaction technique. Morphological analysis was obtained by Scanning Electron Microscopy (SEM) technique indicating mainly granular behaviour. In addition, the substitution of yttrium promotes smaller particle size of BiFeO₃. The obtained samples were also studied by X-ray diffraction (XRD). The crystal structure and the lattice parameters were confirmed by XRD. Rietveld refinement of experimental X-ray diffraction patterns showed that substituted BiFeO₃ compounds crystallize in a R3c type structure and the lattice parameters decrease as Y concentration increases.

According to the trend of the heavy crudes and high demand of fuels, it is projected a considerable increase in the production of vacuum residues. With the purpose of taking advantage of these loads, the refineries have been improving conversion processes for the production of better quality distillates. However, as increasing the severity conditions and the species content of resins and asphaltenes high concentrations of coke are obtained. To provide an insight into the quality and cokes properties, in this study fifty (50) coke samples obtained from vacuum residues processed under conditions of thermal cracking and hydroconversion were selected. Each coke was analysed in detail with properties such as fixed carbon, volatile material, ash, and calorific value. Subsequently, a characterization methodology was developed to predict the properties of cokes, by using partial least squares regression, and infrared spectroscopy (FTIR-ATR) in the spectral range from 4000 to 500cm^-1. The models obtained by chemometrics allowed to predict the quality of the coke produced from vacuum residues with reliable responses in short periods of time.

The use of the probability functions for the prediction of crude distillation curves has been implemented in different characterization studies for refining processes. The study of four functions of probability (Weibull extreme, Weibull, Kumaraswamy and Riazi), was analyzed in this work for the fitting of curves of distillation of vacuum residue. After analysing the experimental data was selected the Weibull extreme function as the best prediction function, the fitting capability of the best function was validated considering as criterions of estimation the AIC (Akaike Information Criterion), BIC (Bayesian information Criterion), and correlation coefficient R2. To cover a wide range of composition were selected fifty-five (55) vacuum residue derived from different hydrocarbon mixture. The parameters of the probability function Weibull Extreme were adjusted from simple measure properties such as Conradson Carbon Residue (CCR), and compositional analysis SARA (saturates, aromatics, resins and asphaltenes). The proposed method is an appropriate tool to describe the tendency of distillation curves and offers a practical approach in terms of classification of vacuum residues.

This study focused on the process reactivity of thermal cracking of vacuum residues from crude oils mixtures. The thermal cracking experiments were carried out under a nitrogen atmosphere at 120psi between 430 to 500°C for 20 minutes. Temperature conditions were established considering the maximum fractional conversion reported in tests of thermogravimetry performed in the temperature range of 25 to 600°C, with a constant heating rate of 5°C/min and a nitrogen flow rate of 50ml/min. The obtained products were separated in to gases, distillates and coke. The results indicate that the behaviour of thermal reactivity over the chemical composition is most prominent for the vacuum residues with higher content of asphaltenes, aromatics, and resins. Finally some correlations were obtained in order to predict the weight percentage of products from its physical and chemical properties such as CCR, SARA (saturates, aromatics, resins, asphaltenes) and density. The results provide new knowledge of the effect of temperature and the properties of vacuum residues in thermal conversion processes.

In this paper the use of a liquid homogeneous catalyst has been studied in reactivity vacuum residues by hydroconversion under different conditions. To cover a wide range of compositions, six (6) vacuum residues were selected from crude mixtures. Hydroconversion test were performed in batch reactor with hydrogen atmosphere at about 2000psi in a temperature range between 430 and 480°C. The results allowed to establish that the reactivity hydroconversion conditions about coke formation is higher in vacuum residues with higher content of resins and asphaltenes. The reaction conditions promote distillate formation, however, with increasing stringency conditions, the distillate yield decreases due to distillate transformation into temperature range 430 and 460°C compared to the tests performed without catalyst demonstrating that the use of homogeneous catalyst is an alternative to treating vacuum residues and results are satisfactory in the conversion processes. Finally, predictive expressions have been developed in the formation of products depending on the conditions of temperature and physicochemical properties of processed vacuum residue.

We have studied the effect of ⁵⁷Fe substitution on structural and magnetic properties of La_2/3Ca_1/3Mn_1-xFe_xO₃ (LCMFO; x=0, 5 and 10%) manganites. The powders were prepared by the solid state reaction method, and the final products were characterized by X-Ray Diffraction (XRD), Mössbauer Spectrometry and Magnetic Measurements. Only one single phase corresponding to the manganite phase was detected without the presence of impurities or iron phases. The hyperfine parameters of Mossbauer spectra (MS), taken at different temperatures for the doped samples, reveal the only presence of Fe³⁺ ions in octahedral coordination. At low temperatures, the MS spectra were fitted with a model of three components associated to three magnetic phases of iron (ferromagnetic and paramagnetic states). These ordered and not ordered magnetic phases are related to the effects of grain size distribution in LCMFO samples. Finally, significant changes were observed in the saturation magnetization, Curie temperature and coercivity field with increasing of iron doping level.

In this paper we show the characterization of two kinds of quantum dots: hydrophilic and hydrophobic, with core and core/shell respectively, using spectroscopy techniques such as UV-Vis, fluorescence and Raman. We determined the quantum yield in the quantum dots using the quinine sulphate as standard. This salt is commonly used because of its quantum yield (56%) and stability. For the CdTe excitation, we used a wavelength of 549nm and for the CdSe/ZnS excitation a wavelength of 527nm. The results show that CdSe/ZnS (49%) has better fluorescence, better quantum dots, and confirm the fluorescence result. The quantum dots have shown a good fluorescence performance, so this property will be used to replace dyes, with the advantage that quantum dots are less toxic than some dyes like the rhodamine. In addition, in this work we show different techniques to find the quantum dots emission: fluorescence spectrum, synchronous spectrum and Raman spectrum.

The light passing through a ferroelectric crystal tends to split into several separate beams due to refraction and reflection at the domain walls. This interaction of light with ferroelectric domains becomes one of the most important features of modern optoelectronic and nonlinear optics materials. Recently, lanthanum modified lead titanate, Pb_(1-x)La_xTiO₃, (PLT) has become popular because it possesses interesting properties such as a lower Curie temperature, a lower coercive field, and smaller remanent polarizations than PZT and has great potential for nonlinear optical and electro optical applications. In this work, we propose a simple model taking into account the optical transmission and rearrangement of the ferroelectrics domains structure on the PLT21 ceramic in temperature function. The variation of dielectrical and optical measurements in function of temperature were observed and correlated with the optical visualization of ferroelectric domains.

The photocatalysis process using semiconductor materials, in particular TiO₂, is one of the most attractive treatment for polluted waters decontamination because of its advantages over other oxidation processes [1-6]. In this study the effect on the physical properties of TiO₂ due to the pH used during the manufacturing of the semiconductor is studied. Different samples were synthesized using ammonium hydroxide (NH₄OH) and nitric acid (HNO₃) as catalysts to provide basic and acid pH environments, respectively. Changes in composition, structure and morphology of the samples were studied and its dependence with the pH of the synthesis is discussed. Results indicate that the base catalysis favours the formation of anatase TiO₂ crystalline phase with crystallite size ∼ 26nm obtained by Rietveld refinement; the spherical particles formed agglomerates of ∼100nm; the average pore size is in the range of mesopores and the surface area increases with the amount of NH₄OH added in the process. On the other hand, with acid catalysis, a mixture of two crystalline phases, anatase and rutile, was obtained with crystallite sizes around 26 and 49nm, respectively. The grain size is several orders of magnitude higher than those obtained by basic catalysis. The photocatalytic activity was measured using methylene blue solutions to determine their degradation with radiation. Greater efficiency was observed in the photocatalysts synthesized with NH₄OH.

The nonlinear effects characterization by using the Z-Scan transmission technique in many materials has generated great in forest according to the technological necessities. The majority part of the nonlinear effects can be described by the classic electromagnetic theory, with the electrical susceptibility in the constitutive equation that relates the electrical polarization with the electrical field. In this work the sign and refractive index magnitude and the nonlinear absorption coefficient of the following organic substance were determined: methylene-blue, rodamine LD, vegetable powder and gentian violet a hundred percent pure dissolved in isopropyl alcohol, a laser Nd: YAG was used as a source excitation. The bunch of laser was focused with a lens of ten centimeters of focal length; by using a displacement system the sweeping of twenty centimeters was realized. The following results of the normalized curves of the transmittance in function of the z position were obtained applying the Sheik- Bahae theory: The nonlinear refractive index of the dye shows an increase in function of its concentration and the power of exciting of the laser with negative nonlinear sign in the majority of the sample.

A tetrapolar probe to measure the electrical properties of electrolyte solutions was implemented with gold electrodes according to the van der Pauw method. Electrical impedance spectroscopy (EIS) measurements of different concentrations of phosphate buffer saline (PBS) solution and an oral mucosal tissue sample dispersed in PBS were performed in the galvanostatic mode using a four-electrode cell (tetrapolar probe). Taking advantage of using a potentiostat/galvanostat for carrying out the electrical measurements, a simple and rapid method using a three-electrode electrochemical cell is described for: a) cleaning of electrodes, b) verification of surface chemical state of electrode material and c) choice of current supplied to electrodes for EIS measurements. Results of this research shown a depolarization effect due to the addition of oral mucosa tissue cells into the PBS solution.

In this work the study of viscosity is presented for a magnetorheological fluid made from iron oxides micrometre, under an external magnetic field. The material was characterized by magnetic loops in a vibrating sample magnetometer and its crystal structure by X-ray diffraction. The results show that saturation magnetization and coercive field have dependence with the powder size. The material has different crystal structure which lattice parameters were determined by Rietveld refinement. The viscosity of the magnetorheological fluid was measured by a viscometer with rotational symmetry with and without external field. This result evidence a dependency on the size, percentage iron oxide and the applied magnetic field, it is due to the hydrodynamic volume of iron oxide interacts with the external magnetic field, increasing the flow resistance.

In this paper, the Linear Thermal Expansion Coefficient of Guadua angustifolia- Kunth samples was measured using the Photoacoustic (PA) technique in a heat transmission configuration and considering the thermoelastic bending as a PA signal generation mechanism in addition to the thermodiffusion ones. The obtained value of (27±7)x10^-6K^-1 is a reasonable value compared with that reported for similar materials such as wood.

In this work we report synthesis of the LaYbO₃ ceramics material by the solid state reaction technique and its structural and morphological characterization from X-ray diffraction and Scanning Electron Microscopy experiments. Rietveld refinement of the diffraction patterns reveals that this material crystallizes in an orthorhombic perovskite, Pnma space group (#62) with lattice parameters a=6.0233Å, b=8.2080Å and c=5.7203Å. Systematic monitoring of the synthesis process is carried out through analysis of results of X-ray diffraction. The surface morphology of the samples was qualitatively analysed as a function of the sintering process.

Parameters required for the preparation of coatings of aluminium oxide deposited on AISI 1020 steels were determined according to their thickness and type of flame to differentiate their behaviour against corrosion. Commercial powders were used by the method of thermal spraying deposition. The coatings were analysed by OM (optical microscopy), the thickness was measured by means of a coating thickness gauge and electrochemical techniques variables measured was the Linear Polarization Resistance (LPR) and approximation Tafel potentiodynamic curves. The corrosion current for steel 1020 with Na₂SO₄ electrolyte of 3.5% is of the order of hundreds of A/cm² and coated steel given in the order of A/cm², which leads to think that the projection produces coatings uniform low closed porosity, although techniques DC indicate a significant porosity as is observable current response to the potentiodynamic curve. The observed thicknesses fall into the hundreds of microns and little uniformity was noted in this coatings. The coatings deposited by oxidizing flame was better performance in corrosion than the coating deposited by neutral flame.

In this work we have studied the behaviour of the electrochemical corrosion of structural steel AISI SAE 1007 with epoxy coatings, using epoxy-type paints, through techniques such as DC resistance Polarization and Potentio-dynamic tests. In order to determine potential and corrosion rates of these coatings, have been correlated this results with different used electrolytes. For this, coatings were characterized by thickness measurement and continuity measurements. The coatings showed a slight degradation in the testing time, due to defects present in their structure, and the attack by the electrolyte; however, epoxy coating system tends to react with the electrolytes based on their chemical composition.

Rechargeable Ni-MH batteries contain strategic metal values which are worth to be recovered. In the present work, a preliminary sequential chemical and electrochemical procedure is proposed, in order to reclaim materials bearing Ni, Co and rare earth elements (REE) from Ni-MH spent batteries. Initially, spent batteries are disassembled to separate the electrode materials (anode and cathode), which are then leached with an aqueous solution of 5w% sulphuric acid. The metal content of this solution is checked by atomic absorption spectrometry techniques. The obtained solution is pH-adjusted (with NaOH), until pH is between 4.0 and 4.3; then, it is heated up to 70°C to precipitate a rare earth elements sulphate (Nd, La, Pr, Ce), as determined by means of x-ray fluorescence techniques. The solids-free solution is then electrolyzed, in order to recover a Ni-Co alloy. The electrolysis conditions were established through a cyclic voltammetry technique.

The study of geometric, electronic properties and intrinsic chemical reactivity is presented for the case of Quinoline and three-derived molecules (4-Amino-Quinoline, 3- Phenyl-Quinoline, 4-Amino-3-phenylquinoline). The study was carried for the ground state in gas phase in the context of the functional theory density using B3LYP/6 31+G (d) model. The purpose of the study is aimed for identifying a compound derived from quinoline, on based to mono- or bi-substitution, using the amino fragment and the phenyl group.

This work presents a study of AC magnetic susceptibility and the influence of heat treatment on obtaining the nanocrystalline structure for the amorphous alloy of Fe₃₇Co₃₅Nb₆B₁₁Si₁₀Cu₁ composition. AC magnetic susceptibility at different frequencies and sample lengths, using a variable magnetic field was measured. The influence of heat treatment on obtaining the sample nanocrystalline structure was evidenced by means of XRD technique. The crystallite size, the crystalline volume fraction and the distance between grains for each heat treatment temperature were calculated using the XRD peaks refinement software GSAS. Samples were obtained in the amorphous state by melt spinning technique and all measurements by AC magnetic susceptibility and XRD were performed at room temperature.

In this work, the effect of mullite dopant (mull) on the structural and electrical properties of two conductive polymers: polyaniline (PAni) and polypyrrole (PPy), which have great interest in science and materials engineering, has been evaluated. Doped polymers were synthesized with different contents of mineral and at two polymerization times (t_P) by an in situ chemical synthesis in acidic aqueous solution and using Ammonium Persulfate (APS) as the reaction initiator. Structural characterization was performed by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The conductivity values (σ_ac) were estimated from Electrochemical Impedance Spectroscopy (EIS). It was found that, at concentrations of work, were obtained higher values σ_ac of conductivity at the highest concentration of the mineral, however, in some compounds the conductivity decreased. The variations in conductivity were attributed to PC-dopant interactions.

In the present study, optical microscopy in stereoscopic mode coupled to laser- induced p-breakdown spectroscopy (μ-LIBS) was applied for analysing HP-40 steel samples. microLIBS (μ-LIBS) is a new growing area that employs low energy laser pulses for the generation of plasma emission, which allow the realization of localized microanalysis [1]. This new LIBS instrument was used for the surface characterization of the steel samples in the spectral range from 356 to 401nm. Elements such as Cr, Ni, Fe, Nb, Pb, Mo, C, Mn and Si in the steel samples were investigated. The results allowed the construction of elemental distribution profiles of the samples. Complementary the HP-40 steel samples were superficially characterized by Scanning Electron Microscope (SEM).

Surface Enhanced Raman Spectroscopy (SERS) has been used to investigate the somatostatin (SST) analogue Vapreotide (VAP) in gold colloids. The optimum conditions to detect SERS signals of VAP have been studied. The observed SERS bands correspond to different vibrational modes of the peptide; being the most dominant SERS signals the ones derived from the aromatic amino acids Tryptophan (Trp), Phenylalanine (Phe) and Tyrosine (Tyr). Changes in enhancement and wavenumber of the proper bands upon adsorption on gold colloid are consistent with VAP adsorption, primarily through Tryptophan residues.

Eight vacuum residues and their delayed coking liquids products from Colombian crude were study by infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and principal component analysis (PCA). For the samples the structural parameters of aromaticity factor (fa), alifaticity (A2500-3100cm^-1), aromatic condensation degree (GCA), length of aliphatic chains (LCA) and aliphatic chain length associated with aromatic (LACAR) were determined through the development of a methodology, which includes the previous processing of spectroscopy data, identifying the regions in the IR spectra of greatest variance using PCA and molecules patterns. The parameters were compared with the results obtained from proton magnetic resonance (¹H-NMR) and ¹³C-NMR. The results showed the influence and correlation of structural parameters with some physicochemical properties such as API gravity, weight percent sulphur (% S) and Conradson carbon content (% CCR)

We present ab-initio calculations in the pseudopotential approximation for the carbon atoms substitutions by aluminium and nitrogen sites at the AlN compound in wurtzite phase. Structural parameters for the AlN with and without carbon were optimized. Subsequently, the electronic and magnetic properties are determined by the density of states (DOS). Also it was determined that Carbon substitutions (AlN:C) are quite stable. This substitution exhibits magnetic properties, indicating that these compounds are good candidates for possible application in diluted magnetic semiconductors, spin injectors, and other spintronics applications.