Table of contents

In the present volume of Journal of Physics: Conference Series we publish the proceedings of the "II Colombian Congress of Electrochemistry (CCEQ) and 2nd Symposium on Nanoscience and Nanotechnology (SNN)", that was held from, October 4-7, 2016, at the Bucarica headquarters of the Universidad Industrial de Santander (UIS), Bucaramanga, Colombia. The proceedings consist of 45 contributions that were presented as plenary talks at the event. The abstracts of all participants' contributions were published in the Abstract Book with ISBN 978-958-8819-39-6. The website of the symposium is available at http://cceq.uis.edu.co/.

The scientific program of the II CCEQ and 2nd SNN consisted of 5 Plenary Lecture, 3 Magisterial Conferences, 2 Keynote, 54 Oral and 78 Poster Presentations and 3 Courses with the participation of undergraduate and graduate students, professors, researchers and entrepreneurs from Colombia, Spain, Mexico, Brazil and Venezuela. Moreover, the II CCEQ and 2nd SNN provided a forum of exchange in the research and innovation that enrich the area of electrochemistry, Nanoscience and Nanotechnology of the materials and the industrial applications.

All papers in these Proceedings refer to one from the following topics: New Materials, Thin Film, Surface Physics, Simulation and Diagnosis, Laser and Hybrid Processes, Biomedical Coatings, Preparation/Characterization/Application Nanomaterials, Surface Modification (Ionic Implantation, Ion Nitriding, PVD, CVD), Electrochemistry of Materials (Electrodeposits, Electropolymerization, Nanoelectrochemistry, Semiconductors), Corrosion, Analytical Electrochemistry, Electrochemistry in Mineral Processing and Metals (Extractive Metallurgy), Storage and Conversion Electrochemical Energy and Environmental Electrochemistry and Water Treatment involving Electrochemical Nature Phenomena. The editor hopes that those interested in the area of the science of materials can to enjoy this reading that reflects a wide variety of current issues.

On behalf of the organizing committee of the II CCEQ and 2nd SNN, we are extremely thankful to all authors for providing their valuable contributions for these Proceedings as well as the reviewers for their constructive recommendations and criticism aiding to improve the presented articles. Besides, especially we appreciate the great support provided by the Sponsors and Partners.

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.

A pH sensitive nanovalve was fabricated using different smart surfaces covalently attached to an anodized aluminium oxide membrane (AAO). The smart surfaces were synthesized using a mixture of aliphatic and aminated silanes. Effect on the contact angle of the aliphatic silane chain length was evaluated. The smart surface, in conjunction with a nanoporous membrane, allowed the formation of a hydrophobic plug which controlled the transport of the molecule safranine depending on the pH of the solution. It was demonstrated that mixtures of butyl and methyl-trimethoxysilane with aminopropyl-trimethoxysilane were able to perform as effective nanovalves creating a plug that remained closed at pH>7 and opened up at pH<5.

In the present work, synthesis of Al-based composites reinforced with carbon nanotubes has been carried out using solid–state manufacturing routes exclusively to consolidate Al–1100/CNTs laminates. Preliminary results regarding consolidation of Al/CNTs nanocomposites in which pressure and temperature are combined in a single step are presented. Preliminary Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) characterization allow us to conclude that CNTs were effectively set on the Al matrix.

Polymeric nanocomposites have been in the scope of scientists for the last decade due to their multiple applications and simple synthesis. Self-assembly fabrication can be performed through different methods such as layer-by-layer or the controlled growth of nanostructures on a surface. These methods allow fast elaboration of nanocomposites that can be readily integrated in sensors or films. The current work exposes the self-assembly of nanocomposites for the modification of material's macroscopic properties such as hydrophobicity and temperature's resistance on textiles. Hydrophobicity properties of cotton textiles were modified by the application of functionalized silica nanoparticles on their surfaces. Thermal resistance of cotton textiles was achieved by incorporating TiO₂ nanoparticles into the matrix, increasing the scope of their applications. Functionalization was attained by chloro-trimethyl-silane (CTS) and γ-amino(propyl) triethoxy silane (APTES) in organic and inorganic solvents. Wetting phenomena characteristics appeared to highly depend on the synthesis parameters.

We presents the study carried out by the technique Z-Scan, to analyse the nonlinear optical properties of (E)-4-(4-dimetylaminophenyl) but-3-en-2-one and (E)-4-(4-nitrophenyl) but-3-en-2-one, diluted in Ethyl Acetate with concentration levels of [0.02M, 0.08M, 0.23M] and [0.0047M, 0.013M, 0.041M] respectively. The measurements were performed using a Nd:YAG laser emitting at 532nm, for samples with L_eff =1mm thickness, and a automated scanning of 10cm symmetric to the lens focus, the iris diameter was 1mm, the samples were also characterized by an UV-Vis Spectroscopy. We calculated the nonlinear refractive index (η2), the nonlinear absorption coefficient (β) and the the third-order nonlinear optical susceptibility (χ3) of the two researched compounds. The results show a combination of thermal response and nonlinear self-defocusing and self-focusing, which make their application interesting as new optoelectronic materials.

The study of the nonlinear optical properties of new organic molecules in solution was performed. Z-Scan technique was used to investigate the nonlinear optical properties of 2-amino-4,6-diphenylnicotinenitrile depending on the solution concentration and the laser power; This compound was diluted in ethyl acetate at fixed concentration of 0.024M. Through this technique, nonlinear parameters such as the nonlinear refractive index (η₂), the nonlinear absorption coefficient (β) and the third-order electric susceptibility (χ³) were determined. For these measurements, a laser Nd: YAG emitting at 532nm, a lens 10 cm focus, an iris of 1mm and a cell with a thickness of 1mm were used. The study was performed with laser powers of 55mW, 100mW, 145mW and 195mW; All measurements were made by transmission in closed and open configurations. Finally the sample was characterized by absorption spectroscopy UV-Vis. This study allows us to relate the molecular design with the optical properties.

A model of non-uniform core-shell type nanostructure with a donor located at a bottleneck point of the core is considered. It is shown that such structure can have a giant polarizability, which, besides can be controlled by applying of the external magnetic field. Presented theoretical analysis reveals a new possibility for the coupling between the polarization and magnetization arising from the quantum-size effect in non-uniform semiconductor nanowires.

The effect of the external magnetic field on the spectral properties of one-electron non-uniform quantum ring with radially directed hills is analysed. The corresponding one-particle wave equation is separable in the adiabatic limit, when the layer thickness is essentially smaller than its lateral dimension. Our calculations show that the presence of a single axially directed hill as well as a rise of the central hole thickness produce a quenching of the Aharonov-Bohm (AB) oscillations of the lower energy levels and of the magnetic momentum. However, as the number of radially directed hills is increased, the system exhibits again oscillations, resulted from an enhancement of tunnelling circular currents.

Laser induced breakdown spectroscopy (LIBS), is a kind of spectral method of atomic emission that uses pulses of radiation high energy laser as excitation source. One of the advantages of technical LIBS lies in the possibility of analyse the substances in any State of aggregation, already is solid, liquid or gaseous, even in colloids as aerosols, gels and others. Another advantage over other conventional techniques is the simultaneous analysis of elements present in a sample of multielement. This work is made in the use of this technique for the identification of metal pollutants in the Swan Lake sediment samples, collected by drilling cores. Plasmas were generated by focusing the radiation of Nd: YAG laser with an energy per pulse 13mJ and 4ns duration, wavelength of 532nm. The spectra of radiation from the plasmas of sediment were recorded with an Echelle spectrograph type coupled to an ICCD camera. The delay times were between 0.5μs and 7μs, while the gate width was of 2μs. To ensure the homogeneity of the plasmas, the sediment sample was placed in a positioning system of linear and rotary adjustment of smooth step synchronized with the trigger of the laser pulse. The registration of the spectra of the sediment to different times of delay, allowed to identify the lines prominent of the different elements present in the sample. The analysis of the Spectra allowed the identification of some elements in the sample as if, Ca, Na, Mg, and Al through the measurement of wavelengths of the prominent peaks.

This work shows experimental and theoretical results of the characterization of a nematic liquid-crystal spatial light modulator Sony model LCX038ARA for the parameters angle of molecular rotation, the birefringence and angle of the molecular axis, using the retarder-rotor model without electric field applied in the amplitude regime-coupled.

Due to its outstanding properties, the titanium and its alloys have been widely used in the dental and orthopaedic fields as biomaterials. The TiO₂ nanotubes surface and the texturized process by laser engraving enables significantly accelerated osteoblast adhesion on the biomaterial. For this reason in this paper, the HOS cell responses on TiO₂ nanotubes fabricated on Ti6Al4V alloy and texturized by laser engraving were evaluated. The test surfaces were carried out on smooth Ti6Al4V as control, TiO₂ nanotubes (NT) and surfaces with micropoints obtained by laser engraving, with 1mm spacing (NTP1) and 0.5mm (NTP2). The results show that the texturized process enables decreases the contact angle thus improving wettability of the TiO₂ nanotubes surface. The NTP1 and NTP2 surfaces show excellent cell adhesion and spreading on the surface, which is evident in epifluorescence microscopy images. Furthermore, the NTP1 and NTP2 surfaces improved the cell proliferation at 18% and 16% respectively in relation with NT surface, showing that the laser texturing improves cell response of TiO₂ nanotubes.

In order to determine the variation in the mechanical properties of AISI 1020 standardized steel, heat treated by a quenching and tempering process and with a Tungsten Carbide coating, was performed a microstructural and chemical characterization of the coating material through electron microscopy scanning and X-ray energy dispersive spectroscopy. The steel received a heat treatment of quenching performed by heating to 850°C, followed by cooling in water and tempering at a temperature of 450°C with air cooling. Tests of a) microhardness with a Wilson-Wolpert Tukon 2100B micro durometer and b) resistance to adhesive and abrasive wear following the ASTM G99-05 "Standard test method for wear testing with a pin-on-disk machine" and ASTM G65-04 "standard test method for measuring abrasion using dry sand and rubber Wheel" standards respectively. The results show that the microhardness of the steel do not vary with the load used to perform the test; in addition, the heat treatment of quenching and tempering improves by 5.5% the property while the coating increase it by 124.2%. Regarding the abrasive wear resistance, it is observed that the amount of material lost increases linearly with the distance covered. It was determined that the heat treatment decreased on average by 17.5% the volume of released material during the tests while the coating recued it by 66.7%. The amount volume of material lost during the adhesive wear tests increases linearly with the distance covered while the heat treatment decreased on average by 10.5% the volume of released material during the trial and the coating reduced it by 66.5%.

In the literature, it is common to find that the size of the particles used in coatings through thermal spraying processes influences the hardness and wear resistance thereof; this project aimed to quantify the importance of this parameter in the adhesive and abrasive wear resistance when aluminium oxide is deposited on a substrate of AISI 1020 steel, through a thermal spraying by flame process. The methodology consisted of: a) morphological characterization of the powder used in the coatings by scanning electron microscopy, b) deposition of coatings, c) testing of adhesive and abrasive wear (ASTM G99-05 Standard test method for wear testing with a pin-on-disk apparatus and ASTM G65–04 Standard test method for measuring abrasion using dry sand/rubber wheel apparatus), and d) statistical analysis to determine the influence of particle size on wear resistance. The average size of the powder used for coatings was 92, 1690, 8990 and 76790nm. The obtained results allow to identify an inversely proportional behaviour between particle size and wear resistance, in both types of wear (adhesive and abrasive) is shown a logarithmic trend indicating an increase in loss mass during the test as the particle size is also increased and therefore a decrease in wear resistance of the coating.

In this research, a technical study of induction hardening in a grey cast iron used in engine cylinder liners manufactured by LAVCO Ltda., a Colombian foundry company, was carried out. Metallurgical parameters such as austenitization temperature, cooling rate, and quenching severity were determined. These factors are exclusively dependent on chemical composition and initial microstructure of grey cast iron. Simulations of induction heating through finite elements method were performed and, the most appropriate experimental conditions to achieve the critical transformation temperature was evaluated to reach a proper surface hardening on the piece. Preliminary results revealed an excellent approximation between simulation and heating test performed with a full bridge inverter voltage adapted with local technology.

The article presents some details about the synthesis and evaluation of photovoltaic materials related with the Cu₂ZnSnS₄ system (abbreviated CZTS), using a hydrothermal route that provide the optimal way to synthesize the proposed materials. The ceramic was obtained starting from corresponding metal nitrates and thiourea as sulphur source in stoichiometric amounts. Corresponding reagents were dossed in a steel Teflon lined vessel and treated at different temperatures to evaluate the effect of external variables in synthesis process. The structure was evaluated by means scanning electron microscopy (SEM) and X-ray diffraction. The electrical characteristics were evaluated by solid state spectroscopy using a statistical analysis coupled with a simple model fitted to the data of electrical conductivity of the material as function of synthesis temperature, for this, the mathematical formulation of the impedance was analyzed, with the use of the Kramers-Kronig transform (KK), (mathematical equations that describe the relationship between the real and imaginary parts of certain complex functions analytic) as well as documentation and research related with the subject of this article. The results show a good behavior of the material, showing that the higher synthesis temperatures promotes a corresponding increase in the electrical conductivity in accordance with previous works [1].

In the present research a web application is designed and implemented allowing us to calculate the dose of implanted ions on solid substrates from experimental parameters (repetition rate and pulse duration of current, potential difference, work pressure and treatment time) and current pulses acquired during start-up and shutdown of high voltage electrical discharges at low pressures. By physical and mathematical processing, it is achieved at first estimate the value of the ionic charge, and then the areal density. This study will provide more accurate and suitable developments in relation to applications of ion implantation as an alternative technique to increase the service life of the surfaces of the materials used in various industrial sectors developments.

A computational thermo-mechanical insertion model was implemented considering the incorporation of carbon nanotubes (CNTs) into semisolid aluminium. A shell surface of CNTs within an aluminium matrix was obtained using the Particles Dynamic Method (PDM). Also, energy absorption simulations were performed through computational impact tests in order to characterize the behaviour of the nanocomposite under high strain rates. Theoretical results are useful in the design of nanocomposites and the experimental processing of Al/CNTs nanocomposites for different applications.

YBCO-BYTO6% and YBCO-BZO10% YBa₂Cu₃O_7-d-Ba₂YTaO₆ 6% (YBCO-BYTO6%) and YBa₂Cu₃O_7--BaZrO₃ 10% (YBCO-BZO 10%) nanostructured films were grown by the Chemical Solution Deposition method, and compared with YBCO pure films. Films were deposited on YSZ substrates, with Ce_0.9Zr_0.1O₂ and Ce_0.6Zr_0.4O₂ buffer layers. They were characterized by GADDS X-ray diffraction, scanning electron microscopy (SEM) and inductive (SQUID) measurements of the critical temperature (T_c) and critical current density (J_c). It was found that YBCO-BZO10% films presented better superconducting properties (T_c=89.2K and J_c=1.3MA/cm²), probably due to an enhanced pinning force, originated by BZO nanoparticles. Additionally, it was found that these films have lower reactivity with the buffer layer.

In this paper, the evaluation microscopic of hot corrosion of 8mol% Yttria Stabilized Zirconia (8YSZ) coatings was studied in the presence of V₂O₅ and Na₂SO₄ as corrosive molten salt, for 40h at 1050°C. First, the substrates of Inconel 718 super-alloy were sprayed with a NiCrCoAl-Y₂O₃ bond coat by atmospheric plasma spraying (APS). Then this bond coat was polished for elaborated the 8YSZ layer by suspension plasma spraying (SPS). The microstructure of the cross-section and surface of the coating was evaluated by scanning electron microscopy (SEM). After the hot corrosion test, the delamination of 8YSZ coatings was occurred in the ceramic layer due to the creation of stress resulting from the chemical reaction between the molten salts and the yttria (Y₂O₃) of 8YSZ coating at high temperature. According to EDS-SEM analysis, the evaluation of fractured sections of 8YSZ coating showed mainly the formation of crystals composed by Y, V, O and the surface was mainly composed by Zr and O. Those crystals can be related with the tetragonal phase of YVO₄, which they were commonly found by other researchers in studies of hot corrosion of YSZ-based TBCs when its surface reacts with the corrosive salts.

Highly open polyhedral networks were fabricated using an economical and environmentally friendly template route. Recycled cellulose foams were impregnated with a sucrose resin and then pyrolyzed in order to produce reticulated vitreous carbon foams with morphological features that closely resemble trabecular bone. Also, cell sizes ~1mm were achieved, a trait that will allow the mechanical reinforcement of such scaffolds using a biomaterial coating without compromising the pore size that favors osteoblast cell infiltration and growth (200-500µm). Moreover, initial studies showed that carbonization conditions have an effect on the mechanical properties of the synthesized foams and, therefore, such process parameters could be further evaluated towards the enhancement of the mechanical resistance of the scaffolds. The materials developed here are visualized as the porous component of a synthetic bone graft with features that could help overcome the current limitations associated with the medical treatments used for bone defect repair.

Silver nanoparticles have a wide range of applications in the medical field, textile and food industries. These and other applications can be found due to the relation between its size and morphology. In this study the influence of bath temperature on the morphology and size of silver nanoparticles are evaluated, which are obtained by chemical reduction of AgNO₃ using three reducing agents: sodium borohydride, ascorbic acid and sodium citrate. The evaluation carried out by the traditional UV-vis Spectrophotometric analysis and with High Resolution Transmission Electron Microscopy. The UV-vis spectrum of the silver colloids obtained by chemical reduction using three different reducing agents shows the effect of the temperature change on the growing and aggregative process. The final effect on the morphology, size and aggregation of the particles was confirmed by TEM. The result suggests a change in the growing mechanism, conducted by aggregation of atoms at 5 and 20°C degrees and aggregation of clusters at higher temperatures. Moreover in this work the main synthesis methods of nanomaterials are described.

The increasing demand for equipment to remove organic compounds in industry and research activity has led to evaluate nanometric zinc oxide (ZnO). In this work, we present the ZnO nanoparticles synthesis for reusing of discarded columns, as a low-cost alternative. The compound was obtained by sol-gel technique using zinc chloride and sodium hydroxide as precursors and a drying temperature of 169°C. An X-ray diffractometer was used to estimate the average particle size at 20.3±0.2nm; the adsorption capacity was 0.0144L/g and the chemical resistance was tested with HCl and NaOH. The ZnO nanopowder was packed with 100psi pressure in an empty C-18 column cavity. The column packing resolution was evaluated using a high performance liquid chromatographer (HPLC-Thermo Scientific Dionex UltiMate 3000); using a caffeine standard, the following parameters were established: solvent flow: 1.2mL/min, average column temperature: 40°C, running time: 10 minutes, mobile phase acetonitrile-water composition (9:1). These results validate the potential of ZnO nanopowder as a column packing material in HPLC technique.

A systematic study of the inorganic surface functionalization of ZnO nanostructures by sol-gel method is shown. We have emphasized on the evolution of morphology properties of samples as a function of functionalization parameters. In addition, the effects on thermal stability and some optical properties of samples are discussed.

This paper report the synthesis, characterization and magnetic evaluation of Ce_0.6Pr_0.4O₂ system using a chemical route that involves the combustion of citrate species. The precursors were characterized by Fourier transform infrared spectroscopy (FTIR), to identify, the main vibrational bands associated with the organic material after combustion process. The structural analysis by X-ray diffraction (XRD) revealed the obtaining of an Fm-3m (225) cubic phase with a particle size around 10nm. Finally, the measurement of the magnetization as a function of applied magnetic field and of susceptibility showed a perfect paramagnetic behaviour.

Bioactive hydroxyapatite (HA) coatings were fabricated by a precipitation, sol-gel and dip-coating method. The effects of the aging time and the base used to adjust pH and substrate materials on the phases and microstructures of HA coatings were studied by field emission scanning electron microscopy FESEM, energy dispersive spectroscopy EDS, X-ray photoelectron spectroscopy XPS, and the vibrations of the phosphate groups were determined by Raman spectroscopy. The results showed that all the films were composed of the phases of TiO₂ and HA. With coated titanium substrate with TiO₂, the crystallinity of the HA coating increases, the structure became more compact and the Ca/P ratio increased because of the loss of P in the films. The addition of sodium hydroxide (adjusting the pH level to about 10) can increase the HA content in the coating. XPS and EDS results for steel substrate and titanium showed poor calcium content as obtained with a Ca/P ratio of 1.38 and 1.58, respectively, composition is similar to that of natural apatite. However, spectroscopic results suggest the presence of a mixture of hydroxyapatite and octacalcium phosphate. The different substrate materials have a high influence on the microstructure of the separated double films. However, hydroxyapatite nanopowders coatings were obtained using a simple method, with potential biomedical applications.

This document compares homogeneous and heterogeneous catalysts used by production of biodiesel of sunflower oil and cooking oil used in frying. For this, NaOH was used as a catalyst homogeneous, and K₂CO₃ and Na₂CO₃ supported in gamma-alumina (K₂CO₃/γ Al₂O₃ y Na₂CO₃ /γ-Al₂O₃) were synthesized as heterogeneous catalysts, which were characterized by X-ray diffraction. The transesterification tests were carried out for the sunflower oil and used cooking oil, in a reflux system, to different molar relations methanol/oil, depending on the type of oil and characterization of the same. The reflux system is performed at a temperature of 55-60°C for one hour. Finally, biofuel was characterized and the yield of the reaction was calculated.

This research is focused on the synthesis and characterization of a perovskite oxide based on La_0.8Sr_0.2CrO₃ system by the combustion method. The material was obtained in order to contribute to analyse the effect of synthesis route in the obtaining of advanced anodic materials for solid oxide fuel cells (SOFC). The obtaining of solid was achieved starting from corresponding nitrate dissolutions, which were polymerized by temperature effect in presence of citric acid. The solid precursor as a foam citrate was characterized by infrared (FTIR) and ultraviolet (UV) spectroscopy, confirming the effectiveness in synthesis process. The solid was calcined in oxygen atmosphere at 800°C and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive of X-ray spectroscopy (EDX) and solid state impedance spectroscopy (IS). Results confirm the obtaining of an orthorhombic solid with space group Pnma (62) and cell parameters a=5.4590Å, b=7.7310Å and c=5.5050Å. At morphological level the solid showed a heterogeneous distribution with an optimal correspondence with proposed and obtained stoichiometry. The electrical characterization, confirm a semiconductor behaviour with a value of 2.14eV Band-gap according with previous works.

This paper focuses on the synthesis and characterization of a ceramic material based on the Cu₂ZnSnS₄ system, through the implementation of a hydrothermal route. For this purpose, we started from nitrate dissolutions in a 1.0mol L^-1 concentration, which were mixed and treated in a teflon lined vessel steel at 280°C for 48h. The Physicochemical characterization of the solid was evaluated by means of ultraviolet visible spectroscopy (UV-VIS), X-ray diffraction (XRD), Raman spectroscopy, scanning and transmission electron microscopy (SEM-TEM) and solid state impedance spectroscopy (IS). The initial characterization through UV measurements confirms a Band-gap around 1.46eV obtained by the Kubelka-Munk method, which demonstrates the effectiveness of the synthesis method in the obtaining of a semiconductor material. The XRD results confirm the obtaining of a crystalline material of pure phase with tetragonal geometry and I-42m space group. The preferential crystalline orientation was achieved along (2 2 0) facet, with crystallite sizes of nanometric order (6.0nm). The morphological aspects evaluated by means electron microscopy, confirmed the homogeneity of the material, showing specifically a series of textural and surface properties of relevant importance. Finally, the electrical characterizations allow to validate the semiconductor behaviour of CZTS system for development of photovoltaic technologies.

Current work is focused on the synthesis and characterization of a Cu₂ZnSnS₄ material (Abbreviated CZTS), identified as a potential candidate for the manufacture of photovoltaic cells. The material was obtained by means of a hydrothermal route which permits a simple and economical alternative to synthesize advanced materials for photovoltaic applications. The synthesis of a solid started from corresponding metal nitrates of Cu(NO₃)₂.6H₂O, Zn(NO₃)₂, Sn(NO₃)₄.6H₂O and thiourea as S source, which were dissolved in deionized water until complete a 1.0mol L^-1 concentration. The solution was kept in a Teflon lined steel vessel with magnetic stirring (150 rpm) and treated at 300°C for 12 hours to form the crystalline phase. The initial characterization of solid was done using UV spectroscopy to validate the chemical process and identify the corresponding Band-gap around (1.43eV). The structural characterization by X-ray diffraction, confirmed the presence of nanometric solids (140-260nm). The morphological characterization by SEM analysis evidenced a homogeneous material in the form of micrometric aggregates, by a related synthesis method. Finally, the electrical characterization by means of solid state impedance spectroscopy demonstrated a semiconductor behaviour which evidenced the transport phenomena associated with a Warburg resistance.

The present work shows the effect of a modification on LaCrO₃ oxide using Fe and Co cations over the structural and electrical properties in order to evaluate its response to applications as electrode in solid oxide fuel cells (SOFC). The LaCr_0.8Fe_0.2O₃ and LaCr_0.6Co_0.2Fe_0.2O₃ oxides were synthetized by polymerization-combustion method using citric acid as complexing agent. The characterizations by means of X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Raman spectroscopy revealed the conformation of a LaCrO₃ single phase with an orthorhombic structure (Pnma 62) in both ceramics and average crystal size of 131nm. The images of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the conformation of materials with relevant morphological characteristics obtained because of synthesis method used. Analysis by Impedance spectroscopy (IS) from room temperature to 800°C, indicated that both oxides were semiconductor type in accordance to thermal activation process.

Calcium phosphates were obtained by reducing nitrate ions to produce hydroxide ions on TiO₂/stainless steel and TiO₂/titanium electrodes. TiO₂ coatings on metallic substrates were prepared by sol-gel dip-coating method. The morphology of deposits was observed by FESEM. Chemical nature of calcium phosphate deposits was identified by Raman micro-spectroscopy and FESEM/EDS microanalysis. Electrochemical behavior of nitrate and nitrite reduction on stainless steel and titanium electrodes was studied by linear sweep voltammetry. In addition, voltammetric study of the calcium phosphate electrodeposition on both electrodes was performed. From these measurements was selected the potential to form a calcium phosphate. A catalytic current associated to nitrate reduction reaction was obtained for stainless steel electrode, leading to significant deposition of calcium phosphate. Ca/P ratio for both substrates was less than 1.67. The formation of calcium deficient hydroxyapatite was confirmed by Raman spectroscopy.

The behaviour of enriched Al-0.7at.%Cu alloy is investigated using cyclic voltammetry. Enriched alloy layers at the interface between the alloy/oxide film were developed by alkaline etching at 5mAcm^-2 in 0.1M sodium hydroxide solution at 298K, with the time of etching determining the extent of enrichment. Cyclic voltammograms were recorded at a scan rate of 10mV s^-1 in naturally aerated 0.1M ammonium pentaborate solution at 298K. The current overshoot of the enriched alloys was different from that for non-enriched alloy. The latter material revealed the usual single peaks, which are very similar. In contrast, the overshoot comprised two or more components for the enriched alloys. The behaviour is suggested to be associated with the atomic bonding of aluminium in copper-rich and aluminium-rich regions of the enriched alloy layer, with influence on the activation potentials for oxidation of aluminium.

Aluminium alloys are widely used in various sectors of industry. The 7075-T6 alloy corresponding to an Al-Zn T6, is mostly used as structural component in the aviation industry, due to the good relationship between weight and mechanical properties. However, the negative point of this alloys is the resistance to corrosion, which is why they need to be coated with an anodic film. Different surface treatments, such as anodizing, are used to improve corrosion resistance. Anodizing is an electrolytic process by which a protective layer on aluminium known as "alumina" is formed, this is formed by the passage of an electric current in an acidic electrolyte. This investigation presents a study of the effect of the thickness of layers of alumina deposited by anodized method, in the corrosion resistance of 7075-T6 aluminium. This study was performed by using in a solution of tartaric acid - sulfuric acid and an inorganic salt. To evaluate the influence alumina layer thickness on the corrosion properties some tests were carried out by using the electrochemical spectroscopy impedances (EIS) technique and Tafel polarization curves. It was found that the grown of the thickness of film favourably influences in the corrosion resistance.

A hydrometallurgical recycling procedure for the recovery of a mixed rare earths sulfate and an electrodeposited Ni-Co alloy has been described. The latter step was found to be complex, due to the presence of several ions in the battery electrode materials. Electrochemical evaluation of the influence of the ions on the Ni-Co alloy deposition was carried out by cyclic voltammetry test. It was found that ions such as K⁺, Fe²⁺ and Mn²⁺ improved the current efficiency for the Ni-Co deposition process on a copper surface. On the other hand, Na⁺ and Zn²⁺ ions exhibited a deleterious behaviour, minimizing the values of the reduction current. The results were used to suggest the inclusion of additional steps in the process flow diagram of the recycling operation, in order to eliminate deleterious ions from the electroplating solution.

Alloy 22 is a nickel base alloy highly resistant to all forms of corrosion. It was designed to resist to most aggressive environments for industrial applications. Electrochemical studies such as Potentiodynamic-Galvanostatic-Potentiostatic (PD-GS-PD) tests and Electrochemical Impedance Spectroscopy (EIS) and Scanning Electron Microscopy (SEM) observations were performed to determine the corrosion behaviour of alloy 22 (N06022). The effect of sulphate ion in chloride containing solutions at 90°C, were studied in this work under aggressive conditions where this material might be susceptible to crevice corrosion. The electrolyte solution, which consisted of 0.1M and 1M NaCl and different sulphate concentrations. It was observed that there were complete inhibitions of crevice corrosion for R_crit=[SO₄⁼]/[Cl^-]=1 in the 0.1mol/L NaCl solutions and R_crit=2 in the 1mol/L NaCl solutions. The corrosion rate obtained was about 0.1μm/year at 24 hours of immersion.

Samples of ASTM A53 steel grade B underwent 500 oxidation cycles at 600°C. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) were performed to study the morphology, composition and phase structure of Fe₂O₃ y Fe₃O₄ layers on oxidation surface. Such layers were homogenous and poorly adhesive. Mass loss was significant due to absence of protective oxides and inevitable flaking, leaving the substrate exposed to corrosive environment.

1020 steel is a material very used for surface treatment in the abnormal glow discharge. Because the composition of the gaseous atmosphere has an important influence on the results of plasma treatment, in this work the oxidation process of 1020 steel is verified on the abnormal glow discharge under different concentrations of air (20% to 100%) at temperatures of 600°C and 900°C. For each atmosphere used mass variation is measured during the process of surface oxidation, the structure and microstructure of the oxide film formed is observed and also its mechanical properties through its microhardness.

Cr_1-xAl_xN hard coatings were successfully deposited by R.F. reactive magnetron co-sputtering in an Ar/N2 gas mixture using chromium and aluminium targets on 316L stainless steel substrates. Crystallographic orientations associated to the Cr_1-xAl_xN FCC based in the conjugate complex of CrN and w-AlN phases, with ao=4.18Å lattice parameter for the ternary Cr_1-xAl_xN compound were identified by X-Ray diffraction. The thickness and roughness of the deposited coatings are 1.00±0.05nm and 2.65±0.6nm, respectively. The mechanical properties were determined by nanoindentation leading to a hardness of 27.8±2.6GPa and elastic modulus of 346GPa. The corrosion resistance of the coated 316L/Cr_1-xAl_xN system under simulated body fluid (SBF, Hank's solution) was determined via electrochemical impedance spectroscopy. A reduction in the corrosion rate of 99% in relation to uncoated 316L stainless steel substrate was found by Tafel. Thus, these coatings seem to be excellent candidates to be used in biomedical applications.

Surfactant inhibitors also called active surface agents are molecules composed of a polar hydrophilic group and a non-polar hydrophobic group, with characteristics of adsorption on metal surfaces, high efficiency of inhibiting, low price, low toxicity and easy production. In this work, the corrosion inhibition was study by CO₂ steel AISI-SAE 1020 with the addition of 0.01M Tween 80 surfactant to a brine solution (3% NaCl). Electrochemical Impedance Spectroscopy and potentiodynamic polarization testing investigated the phenomenon. The results revealed that the surfactant studied acts as an excellent corrosion inhibitor and inhibition efficiency (E%) increases with increasing fluid velocity. The morphology of the steel surface after exposure to the solution of 3% NaCl with and without surfactant indicates the inhibition phenomenon is due to the adsorption of the surfactant molecules, which insulate the surface of the corrosive medium and reduces the attack surficial.

Primary causes of corrosion in components and equipment used in the petroleum industry are due to the density differences present in the multiphase system Water/Hydrocarbon/CO₂ as well as the presence of weak particles of carbonic acid. The present research is focus on the study of the corrosion rate of the steel AISI-SAE 1020 under a saturated CO₂ multiphase system. The effects of fluid speed, temperature and oil content on the steel corrosion were carried out in an electrode of rotator cylinder and also using electrochemical impedance spectroscopy, and potentiodynamic polarization measurements. The results show that the effect of oil content in the rate of steel corrosion is inversely proportional with the speed of the rotor. Our observations indicate that increasing the rotor speed in systems containing 60% oil or higher produce a simultaneous increase in the degradation rate of materials. Similarly, temperatures higher than 60°C generate layers of siderite that reduce the electrochemical effect.

Ochratoxin A (OTA) is a nephrotoxic metabolite, hepatotoxic and carcinogenic produced mainly by Aspergillus and Penicillium fungi. Usually, the mycotoxin analysed through the technique of high performance liquid chromatography. This method is expensive and takes a lot of time. Therefore, expected to automate a device of low cost, minimal instrumentation micropolarographic (MIMP) for the analysis. For this purpose, the right programming environment and the manufacturing of the software for the graphical user interface selected automation of the MIMP through the design and simulation of the circuit, imprint and assembled in a container with connection ports. Lastly, validation and analysis of Ochratoxin A by cyclic voltammetry from analogous MIMP, automatic MIMP and a potentiostat, in order to corroborate the registered data. This way, voltammetry analysis of coumarin is obtained and the simulation of the MIMP electric circuit. Therefore, this are the key data during the investigation, because the molecule of OTA can be monitored through an acid hydrolysis of amides, composed by a phenylalanine and coumaric acid group, generating the significant decrease in the costs and time of analysis.

Coulometry is a primary method for measuring high purity substances. This is used to certify the primary reference materials required in a chemical analysis process. This paper describes the coulometric titration system developed by the National Metrology Institute (NMI) of Colombia for the certification of hydrochloric acid 0.1mol/kg reference materials. In addition, it also shows preliminary studies for future development of potassium chloride (KCl) and ethylenediaminetetraacetic acid disodium salt (EDTA-Na₂) certification.

Dissolution of platinum group metals (PGM; herein Pt, Pd and Rh) in different chloride-based leaching systems from spent auto catalysts was performed. Response surface methodology and a five-level-five-factor central composite design were used to evaluate the effects of 1) temperature, 2) liquid-to-solid ratio, 3) stirring speed, 4) acid concentration and 5) particle size on extraction yield of PGM by aqua regia. Analysis of variance was used to determine the optimum conditions and most significant factors affecting the overall metal extraction. In the optimum conditions, leaching of Pt, Pd and Rh was 91.58%, 93.49% and 60.15%, respectively. The effect of different oxidizing agents on the PGM dissolution in chloride medium was studied comparatively in the following leaching systems: a) aqua regia/sulfuric acid mixture, b) hydrogen peroxide in sulfuric acid (piranha solution), c) sodium hypochlorite and d) copper(II). Dissolution of Rh is increased in both aqua regia and hydrogen peroxide/hydrochloric acid solutions by adding sulfuric acid.

Herein, kinetics extraction of platinum from spent auto catalysts, using nitric acid as an oxidant in hydrochloric acid solution, was investigated. The parameters such as temperature, hydrochloric and nitric acid concentrations, stirring speed, particle size and liquid/solid ratio, were analysed. The kinetic data were analysed using the shrinking core model. A variant of this model fits the kinetic data more appropriately. At a temperature of 90°C, the values of R² in surface chemical reactions and diffusion were 0.819 and 0.937, respectively. With the alternative model, however, 0.991 was obtained. The activation energy for the dissolution was 35.75kJ/mol.

In order to fabricate a solar cell, ordered TiO₂ nanotube (TNT) arrays were prepared by double anodization. TNT arrays with variable lengths were obtained by changing the duration of the anodizing process of up to 3h. TNT membranes were transferred to indium tin oxide substrates and attached with a B-TiO₂ sol. TNT photoanode with the best photoelectrochemical performance was sensitized with CdS by SILAR method. On other hand, CdTe quantum dots prepared via colloidal synthesis were deposited on TNT photoanodes for 2h, 4h and 6h. In addition, TNT/CdS was loaded with CdTe quantum dots for 4 h. Morphology and chemical modification of TiO₂ were characterized by FESEM and XPS, while their photoelectrochemical performance was measured by open-circuit photopotential and photovoltammetry under visible light. TiO₂ nanotubes grown during 2.5h showed the highest photocurrent due to presence of Ti³⁺ donor states by N and F co-doping, increasing the number of photogenerated electrons transported to back collector. TNT/CdS/CdTe photoanode reach the highest conversion efficiency under AM 1.5G simulated solar illumination.

To investigate whether different metal surface treatments, performed on meshes of stainless steel 304 and titanium, affect the photocatalytic activity (PCA) of supported modified anodic TiO₂ films, metallic substrates were coated with titanium isopropoxide sol-gel precursor modified with thiourea. Substrates were pretreated by some of the following techniques: a) sandblasting, b) pickling, c) hydroxylation and d) passivation. The as-prepared electrode materials were characterized by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and voltammetry in the dark and under light UVA irradiation. PCA of modified N-S-TiO₂ electrodes was evaluated by electrochemically assisted photocatalytic degradation of methyl orange. The results of XPS revealed that N and S were incorporated into the lattice of TiO₂. FESEM showed that surface roughness and thickness of films varies depending on surface treatment. Voltammetric and XPS characterization of N-S co-doped TiO₂ films supported on stainless steel revealed that their surface contains alpha-Fe₂O₃/FeOOH. Accordingly, iron contamination of the films coming from stainless steel was detrimental to the degradation of methyl orange. Prior to sol-gel coating process, sandblasting followed by nitric acid passivation for stainless steel or hydrofluoric acid pickling process in the case of titanium improved the PCA of N-S co-doped TiO₂ films.

Plasma electrolytic oxidation (PEO) is an environmentally friendly technique that allows the growth of ceramic coatings without organic solvents and non-toxic residues. This method was applied to ASME SB-265 titanium (Ti) plates (2×2×0.1cm) using voltage pulses from a switching power supply (340V) for 10 minutes at frequency of 1000Hz changing duty cycle at 10, 60 and 90% and the electrolytes were Na₃PO₄ and NaOH. The treated sheets surfaces were analysed by X-ray diffraction and scanning electron microscopy. According to the diffractograms, the duty cycle increase produces amorphous TiO₂ coating on Ti sheets and the thickness increases. After sintering at 900°C during 1 hour, the 10% duty cycle generated a combination of anatase and rutile phases at the sample surface with weight percentages of 13.3 and 86.6% and particle sizes of 32.461±0.009nm and 141.14±0.03 nm, respectively. With this sample, the total reduction of hexavalent chromium was reached at 50 minutes for 1ppm solution. This photocatalytic activity was measured following the colorimetric method ASTM-3500-Cr B.