Table of contents

Preface

These proceedings present the written contributions of the participants of the 4th International Meeting for Researchers in Materials and Plasma Technology (4th IMRMPT) which was held from 23 to May 26, 2017, at the Santa Marta city, Colombia, organized by Foundation Of Researchers In Science and Technology Of Materials (FORISTOM). This was the fourth version of biennial meetings that began in 2011.

The proceedings consist of 75 contributions that were presented as plenary talks at the conference. The abstracts of all participants contributions were published in the Abstract Book with ISSN 2422-3824. The website of the conference is available at http://foristom.org:8080/4imrmpt.

The four-day scientific program of the 4th IMRMPT consisted of 7 Magisterial Conferences, 64 Oral Presentations, 112 Poster Presentations, 3 Courses and 1 Discussion Panel with the participation of undergraduate and graduate students, professors, researchers and entrepreneurs from Colombia, Russia, Spain, Unite Kingdom, Mexico, 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 advance 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.

List of Organizing Committee, National Scientific Committee, International Scientific Committee, Sponsor and Partners are available in this pdf.

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.

Based on structural spin-polarized density functional theory, the electronic and magnetic properties of carbon-doped zincblende AlN were investigated. The calculations were carried out by means of the pseudopotential method employed exactly as implemented in Quantum Espresso code. For 0.625% C-doped AlN, we found a ferromagnetic and half-metallic behaviour. Per supercell, the AlC_0.0625N_0.9375 has a net magnetic moment of 1.0μ_β. The main contribution to the magnetic moment comes from the 2p-C orbitals, with a lesser contribution of the 2p-N and 2p-Al orbitals. Our results suggest that C-doped AlN has potential applications in semiconductor spintronic devices.

This work describes the synthesis and the structural characterization of the La_3.5-xBa_4.5+x-yCa_yCu₈O₁₈ (0.2<x<0.4 and 0.3<y<0.5) systems, obtained by the conventional solid-state reaction method. The samples were characterized by X-ray diffraction comparing the main signals of the experimental and theoretical diffractograms with the PCW software, revealed the obtaining of an orthorhombic structure with space group Pmm2 (25) and unit cell volume V=465.5370ų. The analysis by Raman spectroscopy allows to determine the main modes of vibration of the different bonds that are formed between the atoms in the synthesized perovskite structure.

This article proposes an alternative to the use of phosphorus slag and blast furnace dust, by-products of the steel industry, due to the negative environmental impact caused by its accumulation. Taking into account the above, the pertinence of the use of these by-products in asphalt mixtures for the construction of roads is studied. In this way, the origin and its properties are presented, as well as their physical and chemical characteristics. Once the tests have been carried out, it is determined that these by-products have adequate characteristics for their use since they do not present toxicity problems. Following this, the design of the mixtures is carried out to determine the mechanical and dynamic properties and thus determine the proportion to be replaced with the conventional materials. Taking into account the results it is concluded that its use is feasible since the mixture with these by-products presents acceptable resilient modulus parameters and improvement in some verification parameters.

The present work report, the synthesis and characterization of the CuIn_0.5Ga_0.5Se₂ system (abbreviated CIGS), by the implementation of a hydrothermal route, in order to obtain a solid with appropriate properties in terms of surface, morphological and texture properties for potential applications in the design of photovoltaic cells. The synthesis was carried out using the corresponding stoichiometric quantities (Cu:In:Ga:Se 1:0.5:0.5:2), which were mixed in a Teflon vessel under stirring conditions. The homogeneous solution was treated in a steel autoclave at 300°C for 72 hours at the end of which the resulting material was characterized by X-Ray Diffraction (XRD) and Rietveld refinement. The results of the structural characterization allowed to confirm the obtaining of a chalcopyrite type structure, with a I-42 d (122) structure and cell parameters a=0.570, b=0.570, c=1.140nm, α=90, β=90, γ=90° oriented along (1 0 4) facet, detecting the presence of a secondary phases, related with CuInSe and CuIn metallic selenides, derived from synthesis process. The structural refinement allowing to validate the obtaining of a nanometric crystalline material (10-20nm) for potential applications in field of photovoltaic technology.

This research describes the synthesis and characterization of the Pr_1.5Eu_1.5Ba₅Cu₈O₁₈ system, obtained by the solid-state reaction method. For the synthesis of this material, oxides of Pr₆O₁₁, Eu₂O₃, BaO and CuO were used. The sintering temperature was 900°C. The structural analysis of the synthesized systems was carried out using X-Ray Diffraction (XRD), with a comparison with theoretical patterns and validated with Rietveld refinement analysis, obtaining a type P2mm crystallographic orthorhombic system with a=3.892454Å, b=3.894411Å and c=31.155851Å. The characterization by means of Scanning Electron Microscopy (SEM) let us conclude that the material presents homogeneous granular morphology. Finally, the magnetic response of this material is determined by the magnetization curves as a function of the applied magnetic field 50K and as a function of temperature 2000Oe.

This research paper aims to analyse the behaviour of MDC-19 hot dense asphalt mixtures with steel slag as coarse aggregate, by using asphalt 80-100, in order to verify if this residue has suitable characteristics that allow its use. The physical and mechanical characterization was accomplished using phosphorous slag from the company Acerías Paz del Río S.A. The working formula was then determined for each mixture using the RAMCODES methodology, the briquettes were produced in the laboratory and then, the design verification was performed. Taking into account the results obtained, it is concluded that the use of phosphorous slag as coarse aggregate in asphalt mixtures is workable, since acceptable design parameters and verification are obtained that meet the specifications for use as a rolling layer.

This work reports on the synthesis and characterization of the Bi_x-1Sm_xFeO₃ (x=0.04 and 0.07) systems, produced by the solid-state reaction method. The samples obtained were characterized by X-Ray Diffraction (XRD), Rietveld refinement and magnetization measurements as a function of the magnetic field applied and temperature. The structural characterization was performed by Rietveld refinement and allowed the identification of a perovskite type structure on all the materials with rhombohedral crystalline system and R3_C space group. The characterization by Scanning Electron Microscope (SEM) allowed to determine that the sintered solids present a homogenous microstructure. The magnetization curves as a function of magnetic field applied at 50 and 300K and as a function of the temperature at 5000Oe of the sintered solids exhibited a ferromagnetic behavior, with a rise of the permanent magnetization (Mr), the coercive field (Hc) and the magnetic susceptibility when the samarium concentration rose up. The structural and magnetic characteristics that are generated in the obtained solids make these materials of great interest as multiferroic components.

The work focuses on the use and exploitation of the mineral concentrates from phosphate rock (PR) coming from mines with a low percentage of phosphorus. The procedure was based on the collection of a source of phosphate rock from the department of Boyacá (municipality of Turmequé), using a randomized design with three replications. The samples were initially milled and sifted using meshes between 140 and 200 US standard, homogenizing them and improving the process of solubility of the phosphorus in the soil. We conduced Z-potential tests, which show that by performing a prior wash on the mineral and maintaining certain concentrations and pH defined, better results are achieved in terms of the buoyancy of the particles in the flotation process. The results obtained from the microflotation tests; both direct and inverse, and the results of chemical composition, with X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD), before and after the microflotation process, were carried out to obtain of commercial laws grade phosphate rock concentrate, confirm that the protocol used increases by 9% the value of total phosphorus in the collected sample. These concentrates from phosphate rock, could be used in the future for the attainment of simple superphosphate (SSP), with the help of sulphuric acid and ammonium thiosulphate mixtures.

Semiconductor type Cu₂ZnTiS₄ (CZTiS) and Cu₂ZnSnS₄ (CZTS),were synthetized starting from a hydrothermal route from precursor powders such as copper, zinc, tin, titanium isopropoxide and tiocarbammide metal nitrates dissolved in deionized water in concentrations of 1molL_-1. Dosed and placed in a steel autoclave equipped with a Teflon jacket under magnetic stirring (150rpm) and at a temperature of 300°C for 24 hours in order to promote the formation of the respective ceramic phases. Segregates have been repeatedly washed with ethanol at all times until obtaining crystalline-looking solids. Subsequently, in order to promote the production of pure crystalline phases, the materials were subjected to a second reaction stage in a tubular furnace at 400°C in flow (50mLmin-1) for the purpose of Reduce the concentration of secondary phases of sulphides. The characterization of the CZTiS and CZTS materials was performed by X-ray Diffraction (XRD) and Raman spectroscopy where the presence of Kesterite type crystalline structures was confirmed in the two materials revealing that the effect of titanium with a higher ionic radius than tin produces a distortion in the cell of the CZTiS material compared to the report for the CZTS system. The results of Scanning Electron Microscopy (SEM), confirm the regular aggregates obtained with composition consistent with the proposal theoretically and validated by Energy-Dispersion X-ray Spectroscopy (EDX) techniques and comparison between secondary emission spectra and Retro-dispersed.

The present work includes the first advances in the development of investigations that seek to include Ground Grinding Glass (GRR) and the Electric Arc Furnace Slag (EAFS) in the production of mixtures of hydraulic concrete mixing them simultaneously, so that it satisfies the specifications techniques to be used in the construction of rigid pavements. Firstly, we cite the tests carried out on the different materials to obtain their physical, chemical and mechanical characterization and determine their compliance, as well as the measurement of certain characteristics that may be somewhat empirical to standardize their control. Technique such as X-Ray Diffraction (XRD), X-ray Fluorescence Spectrometry (XFR) and Scanning Electron Microscopy (SEM) have been used. Once the results of the characterization tests and their correspondence with the Colombian technical standards have been obtained, it has become possible to select the use of the Transparent Recycled Ground Glass (TRGG) as the most suitable for the replacement of the sand in the dosage of new mixtures modified concrete.

In this study, the removal capacity of low cost adsorbents during the adsorption of Methylene Blue (MB) and Congo Red (CR) at different concentrations (50 and 100mg·L^-1) was evaluated. These adsorbents were produced from wood wastes (cedar and teak) by chemical activation (ZnCl₂). Both studied materials, Activated Cedar (AC) and activated teak (AT) showed a good fit of their experimental data to the pseudo second order kinetic model and Langmuir isotherms. The maximum adsorption capacities for AC were 2000.0 and 444.4mg·g^-1 for MB and CR, respectively, while for AT, maximum adsorption capacities of 1052.6 and 86.4mg·g^-1 were found for MB and CR, respectively.

Cedarwood (Cedrela Angustifolia) and teak (Tectona Grandis) woods are typically used for furniture manufacture because they have high durability, are light and easy to work. During these manufacturing process, large amount of these wastes is generated causing disposal environmental problems. In this paper, the residual wastes (sawdust) of Cedar (C) and Teak (T) are transformed into an activated material. The chemical composition of both biomass (C and T) was determinate by TGA (Thermogravimetric Analysis). Activated materials were characterized in surface area following the BET (Brunauer, Emmett and Teller) method, morphology using SEM (Scanning Electron Microscopy) and to know their functional groups a FTIR (Fourier Transform Infrared Spectroscopy) analysis was done. Their adsorption capacity was evaluated by removal of Methylene Blue (MB) and Congo Red (CR) from aqueous solutions.

Zn₂TiO₄ + Ag compounds were synthesized by the solution combustion path seeking to enhance their photocatalytic and photodynamic response in the visible. X-ray diffraction tests confirmed the formation of the phase and the presence of metallic silver. Field emission electron microscopy evidenced the formation of aggregates formed by grains lower than 100nm. The diffuse reflectance tests allowed to detect compound absorption in the visible region and activation energy of 2.8eV. The evaluation of the photocatalytic properties was performed by the degradation of methylene blue while the photodynamic response in biological systems was performed by the antilesihmanicidal response of the compounds in promastigotes of Leishmania amazonensis. Indirect measurement of ROS species confirmed the formation of oxygen singlets and OH radicals of the compounds when subjected to the action of visible light.

This work studies the reinforcing effect of Multi Walled Carbon Nanotubes (MWCNT) on cement pastes. A 0.35% solid concentration of MWCNT in powder was dispersed in deionized water with sodium dodecyl sulfate (cationic surfactant), cetylpyridinium chloride (anionic surfactant) and triton X-100 (amphoteric surfactant) using an ultrasonic tip processor. Three concentrations of each surfactant (1mM, 10mM and 100mM) were tested, and all samples were sonicated until an adequate dispersion degree was obtained. Cement pastes with additions of carbon nanotubes of 0.15% by mass of cement were produced in two steps; first the dispersions of MWCNT were combined with the mixing water using an ultrasonic tip processor to guarantee homogeneity, and then cement was added and mixed until a homogeneous paste was obtained. Direct tensile strength, apparent density and open porosity of the pastes were measured after 7 days of curing. It was found that the MWCNT/surfactants dispersions decrease the mechanical properties of the cement based matrix due to an increased porosity caused by the presence of surfactants.

This work shows the results obtained by replacing Type I Portland®, by cementitious geopolymers materials, derived from minerals, in concrete mixtures. Synthesis of both geopolymers through alkaline activation of two alluminosilicates: Bentonite and Pumice with sodium silicate (Na₂SiO₃). XRD, SEM and XRDE are used to structural study of new geopolymers. Concrete mixtures with replacement of Portland have 10% and 30% of geopolymer. Finally, concrete mortars formed were mechanically analysed according to ICONTEC 220 at 7, 14, 28, 41, 90 and 120 days of cure. Results shows that compressive strength of concrete from Bentonite and Pumice are almost the same for the standard concrete at 28 days of cure. At 90 days of cure, compression resistance of concrete from Pumice at 10% is even higher than those that standard concrete shows.

This paper presents results of a research project related to the development of alkali-activated geopolymers, synthesized from alumina-silicate minerals (fly ash and pumice) which are added to concrete. Alkali sources used in geopolymer synthesis were sodium hydroxide and sodium silicate solution. New materials were structurally characterized by Infra-Red spectroscopy (IR) and X-Ray Diffraction (XRD). Concretes obtained after geopolymers addition as Portland cement substitutes at 10%, 20% and 30%, were mechanically analysed by compression resistance at 7, 14, 28 and 90 drying days. Results were referred to standard (concrete of Portland cement) allows to know cementitious characteristics of geopolymers are lower than those for standard, but it keeps growing at longer drying time than Portland cement. By Electrochemical Impedance Spectroscopy (EIS) it is found that this new material shows high electrical resistance and have been proved as a protection agent against corrosion in reinforced concrete exhibiting anticorrosive properties higher than those showed by the conventional concrete mixture.

In some Engineering fields, we need that conductive materials have a mechanic performance and specific electrical for that they maintain conditions or corrosive attack if they are in the environment or if they are closed structure. The stainless steels have an inert film on their surface and it has the function to act in contrast to external agents who generates the corrosion, especially for stings, spoiling the film until to fail. We found a solution taking into account the electrical performance and the anticorrosive; into the process we put recovering of specific oxides on, stainless steel using the method of sputtering with Unbalanced Magnetron, (UBM) varying the oxygen in the reactive environment. The coating obtained had a thickness one micron approximately and we saw on serious structural uniformity [1]. The corrosion resistance was evaluated through the potentiodynamics polarization and electrochemical spectroscopy impedance in NACL according to the standard. The cathode protection is the most important method employed for the corrosion prevention of metallic structures in the soil or immersed on the water. The electrical resistivity was evaluated with the four points methods and it showed a behaviour of diode type in some substrates with a threshold potential in several volts. We noticed a simple resistance solution when it was analysed in the Nyquist graphics whit the Electrochemical Impedance Spectroscopy technique. With on equivalent circuit, for this reason we determinate a variation in the corrosion speed in almost two orders of magnitude when we analysed the potentiodynamics curve by Tafel approximation. The data obtained and analysed show that this type of surface modification maintains the conductivity condition at the interface, improving the resistance in relation whit the corrosion of these elements where the recovering allowed the ionic flow wished for overcoming threshold voltage, acting as an insulator in different cases.

Surface engineering seeks the development of new techniques to improve the performance and life of components of machines or industrial facilities, always looking for low costs and the least possible environmental damage. Thermal projection is one of the techniques that is based on the projection of particles of compounds and alloys on properly prepared and heated substrates, these particles are driven by a stream of air passing through an oxyacetylene flame which gives the energy to the process; These coatings give the possibility to improve the properties of the materials or the maintenance of components to maximize the availability of service. In order to reduce the damage caused by wear and corrosion of a low carbon AISI 1020 steel, they were coated with a metal based alloy, studying the effect of the cobalt-chromium-silicon-tungsten carbide alloy coating (DIAMALLLOY 4060 NS). The coating was deposited with two different pressures in the gases supplied to the torch, obtaining two flames and working three thicknesses of coating that oscillate between 100-500μm, according to the number of deposited layers, making use of a projection gun Castolin Eutectic. Powder and substrate characterization was performed using X-Ray Diffraction (XRD) techniques, X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), spark emission spectroscopy and metallographic analysis. The results confirm the chemical nature and structure of the powder of the alloy and the substrate to be used, in addition, the thermal stability of the system was verified. The evaluation of the adhesion of the deposited layers was carried out by the implementation of pull-off tests according to ASTM D4541, in order to determine the type of failure that is presented. Mechanical wear was determined using a MT/60/NI microtest tribometer while electrochemical tests were performed using a suitable experimental unit for this purpose, confirming that the substrate exhibits lower wear levels when coated with Layers between 300-400μm, demonstrating that the implemented methodology allows to reduce the process of wear of mechanical parts subjected to aggressive operating conditions.

In all material treated in Sbnormal Glow Discharge (AGD) the phenomenon of sputtering occurs. In this work we study the sputtering suffered at different temperatures by AISI 1020 steel subjected to a DC discharge in two types of atmospheres. The steel samples were previously sanded until obtaining mirror brightness and subjected to the AGD plasma in the gaseous atmospheres of H₂ and Ar. The temperature for each sputtering process was set in the range of 420°C to 600°C. In these samples the mass variation was measured and the yield sputtering processes was determined. Next, the simulation of the sputtering process was performed in the SRIM/TRIM 2008 software, by adjusting sputtering yield computational computations to those experimentally measured, in order to determine the energy with which the responsible ions of the sputtering collide with studied target.

Changes in the behaviour of steels to carbon, for three different finishes, surfaces were determined to be nitride by atmospheric pressure dielectric barrier discharge. The surfaces were characterized both morphologically and structurally before and after the treatment. The techniques used were: measurement of roughness and electrochemical testing (Tafel). Results show changes differential depending on the type of finish, but in any case, an improvement of corrosion resistance.

Evaluated the wear resistance and the coatings corrosion behaviour of Al₂O₃-TiO₂ prepared by thermal spraying by flame on AISI 1020 carbon steel substrates, previously coated with an alloy base Ni. For this purpose, were controlled parameters of thermal spraying and the use of powders of similar but different chemical composition is taken as a variable commercial reference for ceramic coating. SEM images allowed to know the morphology of the powders and coatings. Electrochemical techniques (Tafel) were applied to evaluate the protection against corrosion. Coatings were tested for wear with a tribometer configuration bola-disco. It was determined that the phases present in coatings are directly relate to the behaviour against corrosion and wear them. Keywords: wear, corrosion, thermal imaging.

A numerical simulation was performed with the software Jets et Poudres, the results let choose the parameters to deposit zirconia-alumina-ceria coatings of different composition on substrates of red clay, by thermal spraying with the oxyacetylene flame to obtain homogeneous coatings with good adhesion to the substrate. The effect of the projection distance (7, 10 and 12cm) between the substrate and the torch, the fusion percentage of particles and the K-Sommerfeld number was determined. This number is dimensionless and is affected by the projection distance and by the chemical composition of the particles. For a projection distance of 9cm, the fusion percentage of the particles varies between 83.8% and 100%, and the K-Sommerfeld number between 47.3 and 50 for the different compounds. This makes possible to obtain uniform coatings with good wettability, therefore, good adhesion to the substrate, while for the distance of 7cm the fusion percentage varies between 22% and 38%, due to the short time of the particles in the flame which causes low adhesion, when the projection distance is 12cm the particles do not have sufficient kinetic energy to reach the substrate and therefore the coating is not deposited.

The K-Sommerfeld values (K) and the melting percentage (% F) obtained by numerical simulation using the Jets et Poudres software were used to find the projection parameters of zirconia-alumina coatings by thermal spraying flame, in order to obtain coatings with good morphological and structural properties to be used as thermal insulation. The experimental results show the relationship between the Sommerfeld parameter and the porosity of the zirconia-alumina coatings. It is found that the lowest porosity is obtained when the K-Sommerfeld value is close to 45 with an oxidant flame, on the contrary, when superoxidant flames are used K values are close 52, which improve wear resistance.

This report shows the results obtained researching the flank wearing resistance performed by the high-speed steel (HSS) burins without any surface treatment (reference substrate) and others with surface treatment based on Titanium ions. The flank wearing was carried out by means of an industrial process by chip removal with repetitive tests of dry finished turning of AISI/SAE 1045 steel bars. The useful service life of the burins was evaluated according to ISO 3685:1993, and it was found that the burins treated with Titanium ions showed an increase in the flank wearing resistance with respect to the ones used as reference.

Scanning electron microscopy was used to investigate the anatase-rutile transformation of self-organized TiO₂ nanotubes obtained on titanium foil by anodizing and subsequent heat treatment. The anodizing was carried out at 20V in an 1% v/v HF acid and ethylene glycol:water (50:50) electrolyte at room temperature. The anodized samples were initially pre-heat treated at 450°C for 4 hours to modify the amorphous structure of TiO₂ nanotubes into anatase structure. Then, the samples were heated between 600 to 800°C for different times, in order to promote the transformation to rutile structure. The formation of TiO₂ nanotubes is evident by SEM images. Notably, when the samples are treated at high temperature, the formation of rutile crystals starts to become evident at the nanotubes located on the originally grain boundaries of the titanium. Thus, the anatase - rutile transformation has a close relationship with the microstructure of the titanium, more exactly with grain boundaries.

We study properties of exciton in a weakly coupled concentric quantum rings, penetrated by an axially directed magnetic flux and subjected to an electric field in the ring's plane. To this end, we adopt a simple model of quasi-one-dimensional rotator, for which the wave functions and the corresponding energies we found by using the double Fourier series expansion method. Revealed multiple intersections of the energy levels provide conditions for abrupt changes of the radial and the angular quantum numbers, making possible the tunnelling of carriers between rings and allowing the formation of a permanent large dipole moment. We show that the electric and magnetic polarizability of concentric quantum rings with a trapped exciton are very sensible to external electric and magnetic fields.

Due to their excellent surface properties, gold nanoparticles have been used in a wide range of applications from optics and catalysis to biology and cancer treatment by thermal therapy. Gold nanoparticles can absorb a large amount of radiation according to their geometry, such as nanospheres and nanorods. The importance of gold nanoparticles geometry is based on the electromagnetic spectrum wavelength where exists a greater absorption of radiation, which belongs to the visible region for nanospheres and ranges between visible and near infrared regions for nanorods, conferring greater biomedical applicability to the latter. When using photochemical synthesis method, which consists of reducing gold atoms to their metallic state with UV radiation, the geometry of gold nanoparticles depends on different variables such as: 1) pH, 2) concentration of chloroauric acid, 3) the surfactant, 4) concentration of silver nitrate, 5) temperature and 6) irradiation time. Therefore, in this study the geometry of the gold nanoparticles obtained by photochemical synthesis was determined as a function of solution pH and chloroauric acid concentration, using Spectrophotometry in the Ultraviolet Visible region (UV-vis) as characterization technique. From the analysis of the UV-vis spectra, it was determined that at an acidic pH the particles have two absorption bands corresponding to nanorods geometry, while at a basic pH only nanospheres are found and at a neutral pH the lower relative intensity of the second band indicates the simultaneous existence of the two geometries. The increase in the concentration of chloroauric acid produces a decrease in the amount of synthesized nanorods, seen as a decrease of the relative intensity of the second absorption band. Therefore, obtaining gold nanoparticles with nanorods geometry favours fields such as biomedicine, because they are capable of absorbing infrared radiation and can be used as photosensitive agents in localized thermal therapy against cancer.

The La_2/3Sr_1/3MnO₃ (LSMO) with Curie temperature above room temperature is the leading compound of the manganite perovskite family. Therefore, the physical properties are desirable for practical applications as magnetic sensors. However, when the dimensions are reduced the ferromagnetic properties of material are weakened. In this research, we have grown La_2/3Sr_1/3MnO₃/SrTiO₃ thin films by sputtering DC at high oxygen pressure at 830°C. X-Ray Diffraction (XRD) analysis reveals that only (0 0 2) LSMO peak are present, indicating a textured growth. The samples morphology was characterized by Atomic Force Microscopy (AFM). Additionally, LSMO microwires were patterned by UV lithography; the devices are a well-defined channel with current and voltage leads enabling four points resistance measurements. Resistivity versus temperature curves displays typical manganite behaviour with metal-insulator transition ∼350K. We study the electric and magnetotransport properties in LSMO film and in wire channel and their dependence with size (width and length) for potential applications like magnetic sensors.

Antiferromagnetic/Ferromagnetic coupling mechanics have been studying by growing successfully BiFeO₃/La_2/3Sr_1/3MnO₃ bilayers on SrTiO₃ single crystals by using rf and dc sputtering technique at pure oxygen pressures. We have investigated the magnetic behaviour of this samples, field cooling loops evidence interfacial coupling effect when antiferromagnetic ferroelectric BiFeO₃ is placed in contact with ferromagnetic La_2/3Sr_1/3MnO₃ indicate by the shift of the magnetization loop to negative values of the applied magnetic field. Our samples exhibited an exchange bias of 76Oe at 5K after field cooling the sample under 5000Oe. Temperature dependence of the exchange bias field showed exponential decay. The BFO/LSMO bilayer exhibits excellent ferroelectric behaviour (P_s=65μC/cm² at 4V and 100Hz). Coexistence of ferroelectric and ferromagnetic properties in the BFO/LSMO bilayer make it a promising candidate system for applications where the magnetoelectric behaviour is required.

In the present study, coatings of Chitosan - Polyethylene Glycol was obtained by dip coating on Ti6Al4V from polymer mixtures (30-70, 50-50, 70-30). The aim of our study was analysed their ability to formation of apatite and their electrochemical behaviour in the presence of a simulated physiological fluid. The coating properties were evaluated by electrochemical impedance, atomic absorption, SEM and FTIR techniques. The results showed that surfaces coated with a 50-50 ratio of chitosan PEG stimulate the formation of calcium phosphates on the surface of the material. On the other hand, it was found that the number of layers generate a very significant effect on the resistance to the degradation of the alloy in the presence of SBF, generating an increase of up to 1 and 3 orders of magnitude in the impedance of the coating of 5 and 7 layers respectively compared to the Ti6Al4V alloy.

The formation of PEO ceramic coatings on Ti6Al4V ELI alloy was investigated using a phosphate/calcium containing electrolyte at 300 and 400V at 310K for different times. The Plasma Electrolytic Oxidation (PEO) coated specimens were then heat treated at 873 and 1073K for 2 hours. Scanning electron microscopy, Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray diffraction analysis were used to study the composition and the morphology of the ceramic coatings. The corrosion behaviour of the coatings was studied by Electrochemical Impedance Spectroscopy (EIS) in Simulated Body Fluid (SBF). The PEO-treated specimens primarily revealed a porous structure with thickness between 4 and 12μm, according to the voltage and process time used. The coatings are mainly composed of hydroxyapatite; however, as the voltage and anodizing time increase, the Ca/P ratio decreases. Generally, the corrosion resistance of the alloy was improved by the PEO-treated coatings, although the specimens treated at 1073K showed the presence of cracks that reduced the protective effect of the coatings.

Pulse current electrodeposition is a technique of special interest, due to the advantages it has, like easy operation, high control in the amount, homogeneity and purity of the deposited material, and low cost. This work studies the influence of the pulsed electrodeposition parameters variation on the characteristics of calcium phosphates coatings, including the composition, crystallinity and morphology. The influence of the current density and pulse on and off time on the physicochemical properties of the obtained coatings were evaluated. The coatings were electrodeposited on Ti₆Al₄V using Ca(NO₃)₂·H₂O and NH₄H₂PO₄ with a Ca/P molar ratio of 1.67. The coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The analysis of DRX confirmed the formation of HAP. The results revealed that the variation of the current density modified the morphology of the coating. Also, the amount of material deposited increases as the off-time pulse increases, allowing the diffusion of the ions in the solution towards the working electrode.

The purpose of our study was to evaluate the corrosion behavior of Ti₆Al₄V ELI surfaces textured with linear geometry using a CO₂ laser. The linear geometry of the textures was obtained using a laserpro X380RX device with a 40W power supply. The characterization of the textured surface was performed by scanning electron microscope and X-ray dispersive energy spectroscopy. The effect of the separation distance of the linear textures on the corrosion resistance of the Ti₆Al₄V ELI alloy was evaluated by resistance to linear polarization, electrochemical impedance spectroscopy and potentiodynamic polarization curves in SBF. The results showed that the separation distance of the linear textures does not generate a significant effect on the corrosion resistance of the material. However, all the textured surfaces presented less resistance to corrosion than the unmodified material. This decrease in the corrosion resistance is attributed to the inclusion of elements such as molybdenum, silicon and phosphorus that are present in the lines due to the implementation of the cermark coating prior to the laser textured process.

In this work, the response of HOS cells on Ti₆Al₄V ELI textured surfaces by a CO₂ laser was evaluated. The test surfaces were; smooth Ti₆Al₄V, used as the control, and four textured surfaces with linear geometry. These four surfaces had different separation distances between textured lines, D1 (1000 microns), D2 (750 microns), D3 (500 microns) and D4 (250 microns). Toxicity of textured surfaces was assessed by MTT and the cellular adhesion test was performed using HOS ATCC CRL 1543 line cells. This test was done after 5 days of culture in a RPMI 1640 medium supplemented with 10% fetal bovine serum and 1% antibiotics. The results showed that the linear textures present 23% toxicity after 30 days of incubation, nevertheless, the adhesion tests results are inconclusive in such conditions and therefore the effect of the line separation on the cell adhesion cannot be determined.

Repairing tissues and organs has been the main goal of surgical procedures. Since the 1990s, the main goal of tissue engineering has been reparation, using porous scaffolds that serve as a three-dimensional template for the initial fixation of cells and subsequent tissue formation both in vitro and in vivo. A scaffold must have specific characteristics of porosity, interconnectivity, surface area, pore volume, surface tortuosity, permeability and mechanical properties, which makes its design, manufacturing and characterization a complex process. Inspired by nature, triply periodic minimal surfaces (TPMS) have emerged as an alternative for the manufacture of porous pieces with design requirements, such as scaffolds for tissue repair. In the present work, we used the technique of 3D printing to obtain ceramic structures with Gyroid, Schwarz Primitive and Schwarz Diamond Surfaces shapes, three TPMS that fulfil the geometric requirements of a bone tissue scaffold. The main objective of this work is to compare the mechanical properties of ceramic pieces of three different forms of TPMS printed in 3D using a commercial ceramic paste. In this way it will be possible to clarify which is the TPMS with appropriate characteristics to construct scaffolds of ceramic materials for bone repair. A dependence of the mechanical properties with the geometry was found being the Primitive Surface which shows the highest mechanical properties.

Calcium phosphates are bioceramics that have been widely used as bone substitutes because they encourage the formation of bone on their surface and can improve the healing of the bone. Hydroxyapatite HA (calcium/phosphorus ratio of 1.67) and tricalcium phosphate TCP (calcium/phosphorus ratio of 1.50) are the most common calcium phosphates. Natural materials have begun to be tested to make HA or TCP such as shells of cardiidae (family of mollusks) and eggshells. The calcium phosphate obtained has a high ability to precipitate apatite. In this work, the mixed phase ceramic of beta-Tri-calcium phosphate / hydroxyapatite (β-TCP/HA) was synthesized by aqueous precipitation from fish otoliths, which are monomineralic species composed of aragonite. Otoliths of the specie Plagioscion squamosissimus, commonly called the river croaker, were used. Techniques such as DRX, Raman spectroscopy and SEM-EDS were used to characterize the raw material and the obtained material. X-ray diffraction analysis revealed the presence of two crystalline phases of calcium phosphates with 86.2% crystallinity. SEM micrographs showed agglomeration of particles with porous structure and submicron particle sizes.

In this work, the rheological and hyperfine properties of a magnetorheological fluid (MRF) under the action of a uniform external magnetic field are analysed. Powders of native mineral magnetite of micrometric particle size, after a pulverization process, form the solute of these fluids. The sizes of these samples are selected by sieving in order to obtain sizes of around 20µm and 45µm. The powders are characterized by means of Mössbauer spectroscopy to analyse their stoichiometry giving rise to a non-stoichiometric magnetite Fe_2.96O₄ in addition to a hematite component. Result of viscosity and shear stress in the low-speed regime were analysed using the Hershel Buckley method. In particular, the case of surface tension it decreases with the application of a uniform magnetic flux density, which is understood in terms of a phase separation due to the formation of mesoscopic structures, thus decreasing the cohesion force and increasing the adhesion force.

The electrical and structural properties of the LaCr_0.4Co_0.4Fe_0.2O₃ perovskite are investigated. The oxide is synthetized by polymerization-combustion method, using citric acid as a chelating agent and low calcination temperature. The X-ray diffraction, Raman spectroscopy and transmission electron microscopy analysis show conformation of a pure phase with rhombohedral (R-3c) structure and confirmed high structural crystallinity facilitated by synthesis method. The characterization by means of impedance spectroscopy is performed at room temperature. It is observed that the oxides behave as materials of the semiconductor type and that the conductivity increase in accordance to a thermal excitation phenomenon.

This article presents the structural and thermal characterization of fly ash, the waste from blast furnace slag and the glass hull, generated as common residues in industry, which cannot be recycled easily or destroyed in a simple and fast way. In the particular case of fly ash, at present are being used as a lightweight aggregate in the production of cement, concrete and additive in the production of glass and glass ceramics. As far as the slag and hull, are being used as additives for the asphalt and concretes, however its use still is restricted, reason why its use in alternative ways are necessary. Initially the chemical composition of residues was established, determining that the fly ashes contains SiO₂, Al₂O₃ and Fe₂O₃ oxides; 90% of the total composition, was confirmed by X-ray diffraction analysis. As minor constituents, small percentages of Mg, P, S, K, Na and Ti were found. For the slag case, the phases of Fe₃O₄, Ca₃Mg (SiO₂)₄ and Ca(MgAl)(Si,Al)₂O₆ were identified, observing the presence of amorphous phase higher than 94% of the total phase of the system. Meanwhile, the glass hull sample showed a higher percentage of 95% amorphicity, mainly identifying a weak signal associated with silicon oxide SiO₂. The thermal analyses of the samples, exhibit a decrease in mass for samples between 25-1000°C was observed, which can be attributed to different physical-chemical events that occur in the materials. The heat flow for each sample is related with the removal of the water retained by the physisorption processes around 92-110°C in all cases. With this previous characterization of the precursors, a sample was composed using 70% fly ash, 10% slag and 20% of glass hull was composed and treated at 1200°C/1.5 hours, obtaining a dense black glassy material for potential applications in field of the glass ceramics.

The aluminizing of a T91 martensitic ferritic steel was carried out by a novel modification to the traditional technique of packed cementation, with the objective of producing a diffusion coating of aluminum in a shorter time and operating cost, from a technique that allows the reuse of powder packaging and which the coating of metal parts with complex shapes can be secured. As an aluminum source, commercial foil is used to wrap the piece to be coated, while the powder packaging contains aluminum oxide Al₂O₃ and an activating salt, ammonium chloride NH₄Cl. During the deposition process of the coating, the NH₄Cl is decomposed by reacting with foil, and thus, aluminum halides can be transferred to the metallic substrate, which deposit aluminum on the T91 steel surface while Al₂O₃ can be recycled for subsequent processes. The results of the diffractograms and micrographs indicated the strong influence of temperature, exposure time and ammonium chloride concentration in the formation and growth evolution of a stable coating of iron-aluminum and iron-aluminum-nickel on the T91 steel surface, which was effectively deposited at a temperature of 700°C and an exposure period of 9 hours. The coating formed on the T91 steel surface could play a protective role towards the material by acting as a physical barrier between the alloy and other corrosive species in high temperature operated systems.

This project aims to determine the coefficient of dynamic friction between micrometric size coatings of alumina and metallic materials (Steel and aluminium); the methodology used to achieve the proposed objective consisted of 4 phases, in the first one was developed a procedure that allowed, from a Pin on Disk machine built based on the specifications given by the ASTM G99-05 standard (Standard test method for wear tests with a Pin on Disk machine), to determine the coefficient of dynamic friction between two materials in contact; subsequently the methodology was verified through tests between steel-steel and steel-aluminium, due to these values are widely reported in the literature; as a third step, deposits of alumina particles of micrometric size were made on a steel substrate through thermal spraying by flame; finally, the tests were carried out between pins of steel of aluminium and alumina coating to determine the coefficients of dynamic friction between these two surfaces. The results of the project allowed to verify that the developed methodology is valid to obtain coefficients of dynamic friction between surfaces in contact since the percentages of error were of 3.5% and 2.1% for steel-steel and aluminium-steel, respectively; additionally, it was found that the coefficient of friction between steel-alumina coatings is 0.36 and aluminium-alumina coating is 0.25.

The city walls of Cartagena between the Baluarte of San Lucas and Santa Clara reflects the consequences of poor stormwater drainage. In the present investigation the current drainage state of this area have been evaluated, assessing its sizing and conditions to be then modelled through SWMM 5 software for return periods of 5, 10, 15 and 20 years respectively. Finally, it has been determined that the physical deterioration of the drainage elements justifies the malfunction of the whole system, therefore cleaning and periodic maintenance of the drainage elements is strongly suggested.

In this research work, we studied the conditions for formation and decomposition of siderite FeCO₃ from hematite Fe₂O₃ along with carbon dioxide CO₂ at suitable thermodynamic conditions. As reductant agents were used mixtures of two elements, metallic iron and graphite. Best levels of carbonation were found in mixtures with bigger amounts of metallic iron. It was demonstrated that CO₂ capture capacity by hematite depends of temperature, CO₂ pressure, and reaction time. Temperatures between 100 and 150°C, pressures between 10 and 30bar and reaction times between 1 and 4h were adjusted for analyse the carbonation behaviour; siderite formation was improved by increases of these three variables. There was no carbonation without water in the mixtures, due to kinetic limitations. CO₂ capture capacity was calculated from Rietveld refinement results. Using vacuum system and Dielectric Barrier Discharge, DBD plasma, the siderite was decomposed at 300°C, and 320°C respectively. Techniques as X-ray diffraction, and surface area analysis were employed to study the material.

The Nopal (opuntia ficus indica) from remote times has contributed like food and additive product in prehispanic constructions; although it grows in all the Colombian territory is very little used and its contribution in mixtures of Colombian cement is unknown. In order to evaluate the hydration characteristics of Nopal, several Thermogravimetric Analysis (TGA) were performed to evaluate the optimal temperature of dehydration. Initially, the results show that around 175°C the weight loss is approximately 95%, this mass loss corresponds to the process of physical removal, suggesting that at least a remaining amount of 5% (w/w) has the ability to retain large amounts of water which is stored in the micro-structural deposits of Nopal. The evaluation by means Scanning Electron Microscopy (SEM), confirm that the whole cactus structure enables the water storage at cellular level. The results of infrared spectroscopy (FT-IR) and Energy Dispersive X-ray (EDX) analysis allowed the qualitative and semi-quantitative evaluation of the presence of functional groups and elemental chemical composition of Nopal respectively, mainly related with polysaccharide functional groups, which corresponds to 85% of the total composition. Other functional groups, are related with protein and mineral components. This found characteristics are relevant for the water retention in process that require the decrease of water consumption and the reinforcing of mechanical properties and durability, due to ability of Nopal mucilage to restore its hydration characteristics.

This work the effect of the addition of Calcium Oxide (CaO) in the compaction and sintering of powder metallurgical iron Ancoor Steel 1000® is studied. Iron samples were made with proportions of: 0.5%, 1%, 1.5% and 2% by weight of CaO. The samples were sintered in a luminescent discharge furnace, in an atmosphere of H2+Ar at a temperature of 1150°C. XRD analysis was used to determine the formation of compounds, this analysis evidenced the formation of: hematite and magnetite, which were found both on the surface and in the volume. A characterization of the ability to protect against corrosive effects was carried out using the EIS electrochemical impedance spectroscopy method on the samples, in a solution of 1000ppm of chloride, with this procedure it was found that at a concentration of 0.5% and 1% CaO, the electrochemical impedance value is increased with values of 11.7MΩ, 2.2MΩ respectively.

In this study Mn-modification (at 1%, 2.5%, 5% and 10%) on Nb₂O₅ was carried out through the Pechini method; the annealing temperatures: 400°C, 500°C, 600°C and 700°C, were used to study the thermal stability of the system and the crystalline growth. The crystallization at high temperatures has been investigated because low annealing temperature cannot improve the crystallization and the effect of Mn-modification concentration is worthy of a further investigation. Before annealing the samples were analysed by TGA. The structural analysis through XRD is carried out to study a possible increase of the crystallite size (L) by increasing the Mn concentration; for the samples at 700°C and 1% and 2.5% concentrations, L is increased from 39.81 to 46.45nm while L changes from 32.67 to 35.63 with 5% and 10%, respectively. After Mn-modification the evolution of (100) and (180) peaks Nb₂O₅ was observed suggesting that they were well defined only until 2.5%. IR and Raman spectroscopies allowed to analyse vibrational modes present in the samples: the IR spectrums for the samples at 400°C, 500°C and 600°C showed a band around 1100cm^-1 which can be associated to C-C(ν_C-C) and C-O(ν_C-O) vibrations; at 700°C the shoulder was distinguished around 750cm^-1 characteristics of the Nb₂O₅ orthorhombic structure. Vibration modes associated with Nb₂O₅ were found with the Raman spectroscopy; these become less intense after Mn-modification. The band gap energy was obtained through UV-Vis spectrophotometry which revealed a slight increase at 700°C.

A liquid crystal display is an optoelectronic device contains molecules in an intermediate state between solid and liquid. In this work are showed numerical and experimental results of the azimuthal polarization states, which are used to optimize the pure-phase modulation of a Sony LCX038ARA LCD liquid crystal display for a linear polarized light beam with wavelength 632.8nm.

The goal of this work is to do mechanical and chemical characterization of puzzolanic materials using compressive strength measurements and X-Ray Diffraction (XRD). These materials are composed of red clay and aluminous sludge produced by the treatment of potable water at Planta Algodonal, Ocaña, Norte de Santander, Colombia. Ceramic bricks were sintered to 1100°C and ten were characterized in their physically, mechanically and chemically properties. The results showed that the relationships with which the Colombian standards according to NTC 4017 (100KGF/cm2) for non-structural bricks are maintained for those containing 10% (105Kgf/cm²) and 20% (102.9Kgf/cm²) of sludge with respect to clay.

For over five decades, the high-temperature behaviour of ammonium dihydrogen phosphate, NH4H2PO4, has been a controversial subject; while initial works associate ionic conductivity increase around Tt=153°C to a physical transformation (structural phase transition), later research supports the chemical nature of the transformation. However, currently, the origin of the ionic conductivity increase is still not clear. To provide a possible interpretation for this phenomenon, a careful high-temperature thermal examination of this acid salt was conducted by means of Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Mass Spectroscopy (MS). The results show that when this acid salt is heated through Tt, a chemical decomposition into phosphoric acid (H₃PO₄) and ammonia (NH3) takes place. Considering that H₃PO₄ exhibits conductivity values around 10^-3S·cm^-1, our results suggest that the conductivity increase observed at around Tt is an exclusive consequence of the presence of this decomposition product.

Naphthenic acids present in oil from most regions worldwide currently stand as the main responsible for the naphthenic corrosion problems, affecting the oil-refining industry. The phenomenon of sulfidation, accompanying corrosion processes brought about by naphthenic acids in high-temperature refining plant applications, takes place when the combination of sulfidic acid (H₂S) with Fe forms layers of iron sulphide (FeS) on the material surface, layers with the potential to protect the material from attack by other corrosive species like naphthenic acids. This work assessed corrosion products formed by sulfidation as inhibitors of naphthenic corrosion rate in AISI-316 steel exposed to processing conditions of simulated crude oil in a dynamic autoclave. Calculation of the sulfidation and naphthenic corrosion rates were determined by gravimetry. The surfaces of the AISI-316 gravimetric coupons exposed to acid systems; were characterized morphologically by X-Ray Diffraction (XRD) and X-ray Fluorescence by Energy Dispersive Spectroscopy (EDS) combined with Scanning Electron Microscopy (SEM). One of the results obtained was the determination of an inhibiting effect of corrosion products at 250 and 300°C, where lower corrosion rate levels were detected. For the temperature of 350°C, naphthenic corrosion rates increased due to deposition of naphthenic acids on the areas where corrosion products formed by sulfidation have lower homogeneity and stability on the surface, thus accelerating the destruction of AISI-316 steel. The above provides an initial contribution to oil industry in search of new alternatives to corrosion control by the attack of naphthenic acids, from the formation of FeS layers on exposed materials in the processing of heavy crude oils with high sulphur content.

This work studies the corrosion behaviour of Colombian galvanized steel in solutions of chloride and sulphate ions. The effect of the thickness and exposure time on the film's breakdown susceptibility and protectiveness of the corrosion products were studied using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The corrosion products were analysed using SEM-EDS and XRD. The samples with a higher thickness level in the zinc film (Z180) have the lowest corrosion rate. In this case, one of the products that was formed by the chemical reactions that occurred was Zinc hydroxide, which exhibits a passive behaviour as observed in the Pourbaix curves of the obtained potentials and in how the different Ph levels of the solutions worked. The sheets with the highest thickness (Z180) had the best performance, since at the end of the study they showed the least amount of damage on the surface of the zinc layer. This is because the thickness of the zinc layer favours the formation of simonkolleite, which is the corrosion product that protects the material under the conditions of the study.

For all Industrial sector is important to extend the useful life of the materials that they use in their process, the scales of CaCO₃ are common in situation where fluids are handled with high concentration of ions and besides this temperatures and CO₂ concentration dissolved, that scale generates large annual losses because there is a reduction in the process efficiency or corrosion damage under deposit, among other. In order to find new alternatives to this problem, the citric acid was evaluated as scale of calcium carbonate inhibition in critical condition of temperature and concentration of CO₂ dissolved. Once the results are obtained it was carried out the statistical evaluation in order to generate an equation that allow to see that behaviour, giving as result, a good efficiency of inhibition to the conditions evaluated the scales of products obtained were characterized through scanning electron microscopy.

In this work, DC electrochemical techniques were used to determine the corrosion rate of copper and stainless-steel electrodes used in grounding, varying the level of humidity, in sandy loam and clay loam soils. The maximum corrosion potentials were: for copper -211 and -236mV and for stainless steel of -252 and -281mV, in sandy loam and clay loam respectively, showing that in sandy loam the values are higher, about 30mV. The mechanism by which steel controls corrosion is by diffusion, whereas in copper it is carried out by transfer of mass and charge, which affects the rate of corrosion, which in copper reached a maximum value of 5mm/yr and in Steel 0.8mm/yr, determined by Tafel approximations. The behaviour of the corrosion rate was mathematically adjusted to an asymptotic model that faithfully explains the C.R. as a function of humidity, however, it is necessary to define the relation between the factor □ established in the model and the precise characteristics of the soil, such as the permeability or quantity of ions present.

The integrity of structures buried in earthing becomes relevant when analysing maintenance and replacement costs of these systems, as the deterioration is mainly due to two factors, namely: the failures caused in the electrical systems, which are due to the system. Failure in earthing due to corrosion at the interface cause an alteration in the structure of the component material and generates an undesirable resistivity that cause malfunction in this type of protection systems. Two local soils were chosen that were categorized as sandy loam and clay loam type, whose chemical characteristics were simulated by means of an electrolyte corresponding to the amount of ions present determined by a soil characterization based on the CICE (effective cation exchange coefficient), which allows us to deduce the percentage of chloride and sulphate ions present for the different levels established in the experimental matrix. The interaction of these soils with grounding electrodes is a complex problem involving many factors to consider. In this study, the rates and corrosion currents of the different soils on two types of electrodes, one copper and the other AISI 304 stainless steel, were approximated by electrochemical techniques such as potentiodynamic curves and electrochemical impedance spectra. Considerably higher speeds were determined for copper-type electrodes when compared to those based on steel. However, from the Nyquist diagrams, it was noted that copper electrodes have better electrical performance than steel ones. The soil with the highest ionic activity turned out to be the sandy loam. The clay loam soil presents a tendency to water retention and this may be the reason for the different behaviour with respect to ionic mobility. The diffusion control in the steel seems to alter the ionic mobility because its corrosion rates proved to be very similar regardless of the type of soil chemistry. In general, corrosion rates fell since tenths of a millimetre every year to the hundredths of a millimetre in the case of the steel-based electrode, which are relatively small corrosion rates.

This research studies the physical and chemical changes in steel ASTM A335 P92, produced from a typical refinery corrosion environment. The environment evaluated was oxidation-nitridation with the presence of water vapor. In this study five (5) exposure times were selected: 1, 20, 50, 100 and 200 hours; As well as two (2) analysis temperatures: 450 and 550°C. The working pressure used was one (1) atmosphere. Bearing in mind the kinetic study, the behaviour shown in ASTM A335 P92 steel describes an accelerated growth until 50 hours, after this time growth is less. For the tests carried out at 450°C, the kinetic constant was 2x10-8g²mm^-4h^-1, as well as for 550°C the calculated kinetic constant was 3.1×10-7g²mm^-4h^-1; through the SEM-EDS characterization techniques, it was possible to appreciate a good adhesion and homogeneity of the layers formed on the metal matrix until a time of exposure of 100 hours at 450 and 550°C, different from that evidenced to 200 hours of exposure where the layer formed near to the substrate showed detachment, this is attributed to the formation of hydroxides product of water vapor. Among the results obtained are the elemental composition, the presence of nitrides such as Si₃N₄, also NSiO₂ and NSi₂O, molybdenum oxides: MoO₂ and MoO₃ and iron oxides: FeO and Fe₂O₃ can be evidenced.

Corrosion studies are key element that ensure the correct functioning of equipment in the industrial sector. The oxidation phenomena were evaluated, taking as a case study steel ASTM A335 P91 (P91), a steel of typical use in equipment that work at high temperatures. Five (5) exposure times were selected for the experimental development: 1, 20, 50, 100 and 200h; as well as four (4) analysis temperatures: 450, 550, 650 and 750°C. Through the metallographic analysis was possible to evidence the presence of multiple carbide precipitates and a ferritic structure, after all the temperatures tested. On the other hand, the analysis of hardness and microhardness showed an increase for all the evaluated temperatures. These increases were mainly related to the precipitation of carbides in the coupons of P91. Regarding to the chemical analysis, it was possible to conclude that after 200h of experimentation in each temperature, a layer of duplex oxide, composed mainly of hematite, magnetite and spinel iron-chromium, was formed in the O₂/H₂O atmosphere. Finally, the kinetic study demonstrated that the oxide layer formed on each coupon of P91 was of protective character.

In Colombia, energy companies neglect the distribution that represents the main and most valuable process, presenting shortcomings in prevention and forecasting programs, using contractors who perform corrective maintenance of the components without guaranteeing the quality and performance of the materials. Within the process, the terminals determine the effective connection between the voltage line and the transformer, which have faults that are evidenced by the thermal deterioration of the material. In this work, a diagnosis of the thermal performance of these components was carried out and it was correlated with the microstructure, observing variations of the working temperature, with a thermography camera, for three types of terminals, which were classified by X-ray fluorescence in brass Z20, Z40 and Z60, and for two types of connection, copper and aluminium. The microstructure results showed that copper is the conductor that degrades the terminals faster, evidencing cracking of the material; on the other hand, the Z40 brass was the most stable with the lowest temperature variation regardless of the conductor diameter; however, in all cases the behaviour of higher temperature to lower calibre is satisfied.

Fouling is a common problem related to different industries in which the solubility of dissolved minerals in water changes leading to the formation of deposits on the surface of the equipment, for instance, in oil production the scale can be formed on the wellbore, on the well tubing or superficial facilities. Over the last years, several studies have been carried out in order to determine the effect of operational conditions in the scale growth but there are no conclusive results. This paper presents the results of calcium carbonate deposition on the surface of stainless steel AISI 316 at 71°C, and the influence of rotating velocity on the quantity and morphology of the generated scale. The tests were carried out by using a rotating cylinder electrode and X-Ray Diffraction (DRX), and Scanning Electron Microscopy (SEM) of the scale obtained was analysed. The results show that the amount of scale formed changes regarding the velocity of the fluid, as well as the morphology of the deposited crystals.

Operating conditions at the head of oil wells are critical, in addition to injecting water to increase the pressure while maintaining production cause deterioration in the metallic structures that transport fluids. One way to maintain integrity is the injection of inhibitors which plays an important role in protecting the pipes. In this study a molecule N-PHENYL NITRONE was obtained, which was evaluated by electrochemical tests (LPR) and Tafel Polarization Curves in a reactor controlling environments containing different dosages, pressure values, temperatures and flow velocity using working electrodes tubing API N 80, the reactor was connected to a potentiostat to determine corrosion rates, allowing the analysis of the influence of each variable on the protective behaviour of the inhibitor, and its efficiency against the decrease of the deterioration of the pipes. Corrosion products are analysed by X-Ray Diffraction (XRD). Photographic records of the surface verify the formation of iron carbonate (FeCO₃). In addition, a mathematical analysis of the independent variables is performed to evaluate the effect that it has on the efficiency of corrosion inhibition.

a study on the performance of a forced solar heating system in which a comparative analysis of two control strategies, including the classic on-off control and PID control is presented. From the experimental results it was found that the two control strategies show a similar behaviour in the solar heating system forced an approximate settling time of 60 min and over-elongation 2°C for the two control strategies. Furthermore, the maximum temperature in the storage tank was 46°C and the maximum efficiency of flat plate collector was 76.7% given that this efficiency is the ratio of the energy of the radiation on the collector and the energy used to heat water. The efficiency obtained is a fact well accepted because the business efficiencies of flat plate collectors are approximately 70%.

The energy potential of the osmotic pressure gradient of cyanide waters is evaluated using two membrane modules, horizontal and vertical, operated under dead-end flow. The membrane was characterized using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS). The membrane is mainly composed of carbon, oxygen, and sulphur. The properties of the membrane were unchanged and had no pore clogging after exposure to the cyanide waters. Potentials of 1.78×10^-4 and 6.36×10^-5Wm^-2 were found for the horizontal and vertical modules, respectively, using the Van't Hoff equation. Likewise, the permeability coefficient of the membrane was higher in the vertical module. Although the energy potential is low under the studied conditions the vertical configuration has a greater potential due to the action of gravity and the homogenous contact of the fluid with the membrane.

In this paper is presented a model that analyses the options to provide energy to an interconnected house in Lagos del Cacique, Bucaramanga, Colombia. Three power supplies were considered: photovoltaic, 1 kW wind turbine, and a 2.6kW gasoline generator, as well as a battery for energy storage. The variables considered for the sensitivity analysis correspond to the price of gasoline and the variation in loads. The simulation results suggest an optimal configuration of microgrids in generator-photovoltaic panel-battery. Sensitivity variables were specified in order to evaluate the effect of uncertainty. The simulation was done through the Homer software and the results of the combinations of sources are suggestions of the same.

This work reports the obtaining, study and mathematical modeling of a photovoltaic material type CZTiS (Cu₂ZnTiS₄), in function of two thermodynamic variables such as temperature and hydrothermal synthesis time. The obtention the materials had to be validated through the implementation of characterization techniques such as X-Ray Diffraction (XRD) and solid state Impedance Spectroscopy (IS). The results of the characterization, allowed to confirm in all cases the obtention of the materials, with a crystalline structure concordant with a tetragonal geometry space group of I-42m, a preferential crystalline orientation in the plane (1 1 2), with crystal sizes in the nanometric order (5-6nm). The electrical characterization, showed a semiconductor behavior of the solids concordant with values of conductivity that can be modeled by the analysis of variance and verified through the Kramers-kronig transform. The information obtained confirms that the temperature variable is the most strong influence in the electrical behavior of the CZTiS material, which is in agreement with similar works evaluated with alternative techniques [1].

This paper describes the results of the synthesis and characterization of a quaternary semiconductor based on Cu₂ZnTiS₄ (abbreviated CZTiS), using a hydrothermal technique. The results confirm that time (24, 48 and 72 hours) and temperature (250, 275, and 300°C) factors, used in synthesis process, regulate different levels of electrical conductivity in these materials. The results of ultraviolet spectroscopy (UV) analysis, confirm the production of semiconductor solids with Band-gap values around 1.4eV, being coherent with a strong absorption in the ultraviolet region. The X-Ray Diffraction analysis (XRD), confirm that there is an opposite and proportional relationship between the crystal sizes, the reaction times and the synthesis temperature. In all cases, the particle sizes were 50-100nm. The results derived from Scanning Electron Microscopy (SEM), confirm the obtaining of homogenous materials with optimal morphological properties in accordance with synthesis method. Similarly, the composition values derived from the Energy-Dispersion X-ray Spectroscopy analysis (EDS), shown that obtained compositions are in agree with expected values. Finally, the results of electric characterization, confirm that used synthesis parameters show a strong dependence on the conductive behaviour of solids being the most relevant result the shown by the solid obtained at 300°C and 72 hours of reaction in accordance with preliminary works.

This paper describes the synthesis and characterization of two spinel and olivine-type multicomponent oxides based on LiMO₂ and LiM₂O₄ systems (M=Co and Mn), which represent the current state of the art in the development of cathodes for Li-ion batteries. A simple combustion synthesis process was employed to obtain the nanometric oxides in powder form (crystal sizes around 5-8nm), with a number of improved surface characteristics. The characterization by X-Ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (SEM, TEM) and X-Ray Fluorescence (XRF), allowed to evaluate the morphology and the stoichiometric compositions of solids, obtaining a concordant pure crystalline phase of LiCoO₂ and LiMn₂O₄ oxides identified in a rhombohedral and cubic phase with punctual group R-3m (1 6 6) and Fm-3m (2 2 5) respectively. The electrical characterization of materials developed by impedance spectroscopy solid state, allowed to determine a p-type semiconducting behaviour with conductivity values of 6.2×10^-3 and 2.7×10^-7 S for LiCoO₂ and LiMn₂O₄ systems, consistent with the state of the art for such materials.

Plasma Electrolytic Oxidation (PEO) is used to synthetize titanium dioxide (TiO₂) ceramic coatings with the appropriate selection of an electrolyte. The dimension of the micro-cavities and the particle size at the surface can be controlled through the pulse frequency of the voltage that is applied between the electrodes. The change of surface morphology can increase the surface area-to-volume ratio. In this work, PEO of an ASME SB-265 titanium substrate (20×20×1mm) was made in a water solution containing 8g/L Na₃PO₄ and 0.4g/L NaOH. Hence, the coatings were fabricated using voltage pulses of 340V for 10 minutes with a 10% duty cycle and frequencies of 1000, 1500 and 2000Hz. According to the X-ray diffractograms of the obtained samples, the sintering process at 500°C during 1 hour generated Anatase titanium dioxide porous coatings. The grain size decreased approximately from 29nm for 1000 and 1500Hz pulse frequencies until 21nm for 2000Hz. On the other hand, from the micrographs of scanning electron microscopy was possible to see the uniform formation of the micro-cavities with the largest diameter, 900nm, for the lowest frequency value used in PEO.

In this work, we study the quantum electron transport through a Quantum Dots Structure (QDs), with different geometries, embedded in a Quantum Well (QW). The behaviour of the current through the nanostructure (dot and well) is studied considering the orbital spin coupling of the electrons and the Rashba effect, by means of the second quantization theory and the standard model of Green's functions. Our results show the behaviour of the current in the quantum system as a function of the electric field, presenting resonant states for specific values of both the external field and the spin polarization. Similarly, the behaviour of the current on the nanostructure changes when the geometry of the QD and the size of the same are modified as a function of the polarization of the electron spin and the potential of quantum confinement.

Using the cross-platform game engine Unity, we develop virtual laboratories for PC, consoles, mobile devices and website as an innovative tool to study physics. There is extensive uptake of ICT in the teaching of science and its impact on the learning, and considering the limited availability of laboratories for physics teaching and the difficulties this causes in the learning of school students, we design the virtual laboratories to enhance studentâĂŹs knowledge of concepts in physics. To achieve this goal, we use Unity due to provide support bump mapping, reflection mapping, parallax mapping, dynamics shadows using shadows maps, full-screen post-processing effects and render-to-texture. Unity can use the best variant for the current video hardware and, if none are compatible, to use an alternative shader that may sacrifice features for performance. The control over delivery to mobile devices, web browsers, consoles and desktops is the main reason Unity is the best option among the same kind cross-platform. Supported platforms include Android, Apple TV, Linux, iOS, Nintendo 3DS line, macOS, PlayStation 4, Windows Phone 8, Wii but also an asset server and Nvidia's PhysX physics engine which is the most relevant tool on Unity for our PhysLab.

A theoretical procedure to obtain the Ginzburg-Landau (GL) equations with the inclusion of localized anisotropy in the superconducting sample is shown. Using this theory, it is possible to study the vortex structures in two-dimensional mesoscopic superconductors with defects in the presence of a uniform magnetic field. The defects would be included through variation of parameter γ(x, y, z) considering different shapes into the sample. This theory would allow to find unconventional vortex states which can show vortex clusters or exhibiting asymmetry. In samples with defects the vortex strings are formed owing to the interactions of vortices with variable Meissner currents through the sample due to spatial change of the anisotropy, but also the thermodynamics parameters of the superconducting sample could be determined as a function of the degree of the anisotropy generated in the defect.

Information and Communication Technologies (ICT) are essential in the transfer of knowledge, and the Web tools, as part of ICT, are important for institutions seeking greater visibility of the products developed by their researchers. For this reason, we implemented an application that allows the information management of the FORISTOM Foundation (Foundation of Researchers in Science and Technology of Materials). The application shows a detailed description, not only of all its members also of all the scientific production that they carry out, such as technological developments, research projects, articles, presentations, among others. This application can be implemented by other entities committed to the scientific dissemination and transfer of technology and knowledge.

The present work has the objective to model a simple masonry building, through two different modelling methods in order to assess their validity in terms of evaluation of static stresses. Have been chosen two of the most commercial software used to address this kind of problem, which are of S.T.A. Data S.r.l. and Sismicad12 of Concrete S.r.l. While the 3Muri software adopts the Frame by Macro Elements Method (FME), which should be more schematic and more efficient, Sismicad12 software uses the Finite Element Method (FEM), which guarantees accurate results, with greater computational burden. Remarkably differences of the static stresses, for such a simple structure between the two approaches have been found, and an interesting comparison and analysis of the reasons is proposed.

Now there are numerous sources for multicharged ions production, each being designed for certain science or technological objectives. Electron cyclotron resonance ion sources (ECRIS) are best suited for designing heavy ion accelerators of very high energies, because they can generate multicharged ion beams at relatively great intensities. In these sources, plasma heating and its confinement are effected predominantly in minimum-B magnetic traps, this type of magnetic trap consist of two current coils used for the longitudinal magnetic confinement and a hexapole system around the cavity to generate a transversal confinement of the plasma. In an ECRIS, the electron cyclotron frequency and the microwave frequency are maintained equal on a quasi-ellipsoidal surface localized in the trap volume. It is crucial to heat electrons to energies sufficient to ionize K- and L-levels of heavy atoms. In this work, we present the preliminary numerical results concerning the space distribution of TE₁₁₁ microwave field in a cylindrical cavity. The 3D microwave field is calculated by solving the Maxwell equations through the Yee's method. The magnetic field of minimum-B configuration is determined using the Biot-Savart law. The parameters of the magnetic system are that which guarantee the ECR surface location in a zone of a reasonably high microwave tension. Additionally, the accuracy of electric and magnetic fields calculations are checked.

Adsorption using metal oxide materials has been demonstrated to be an effective technique to remove hazardous materials from water, due to its easy operation, low cost, and high efficiency. The high number of oxyanions in aquatic ecosystems causes serious pollution problems. Removal of arsenate (H₂AsO₄^-), is one of the major concerns, since it is a highly toxic anion for life. Within the metal oxides, the iron oxide is considered as a suitable material for the elimination of oxyanions. The adsorption of H₂AsO₄^- on Fe-(hydr)oxide is through the formation of inner or outer sphere complexes. In this work, through computational methods, a complete characterization of the adsorbed surface complexes was performed. Three different pH conditions were simulated (acidic, intermediate and basic), and it was found that, the thermodynamic favourability of the different adsorbed complexes was directly related to the pH. Monodentate complex (MM₁) was the most thermodynamically favourable complex with an adsorption energy of -96.0kJ/mol under intermediate pH conditions.

We study the effect of nonparabolicity of the conduction band on the energy spectrum of the off-axis donors in InAs crater-like quantum rings in framework of the Kane Hamiltonian. By using ta simple numerical procedure we find the low-lying energies dependencies on the radius, height and width of the ring and on the distance of the donor location from the axis. The comparison of our results with those obtained in one-band effective mass approximation reveals an essential influence of the non-parabolicity of the conduction band on the off-axis energy spectra in InAs/GaAs quantum rings. In addition, we analyse the effect of the external magnetic field applied along the symmetry axis on the Aharonov-Bohm oscillations of lower energy levels.

The relativistic dynamics of an electron accelerated in a cylindrical cavity mode TE₁₁₃ in the presence of a static inhomogeneous magnetic field is studied. This type of acceleration is known as Spatial AutoResonance Acceleration (SARA). The magnetic field profile is such that it keeps the phase difference between the electric microwave field and the electron velocity vector within the acceleration phase band. We study the dynamic of the electron through simulations of the relativistic Newton-Lorentz equation. Numerical experiments with TE₁₁₃ cylindrical microwave fields of a frequency of 2.45GHz and an amplitude of the order of 7kV/cm show that it is possible accelerate the electrons up to energies of the order of 300keV. This energy is about of 30% higher than those obtained in previous studies by using the TE₁₁₂ mode.