Abstract The effect of growth conditions and post treatments on the properties of calcium phosphate films electrodeposited by a potentiostat of the authors’ design and construction is presented. The electrolyte used was formed with 0.025 M (NH4)H2PO4 and 0.042 M Ca(NO3)2.4H2O, and its pH was kept at 5. A voltametric analysis was performed to determine the necessary potential values to obtain the films. Additionally, the temperature of the electrolyte was varied to determine its influence on the properties of the deposited films. The films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The films deposited at -1.4 V and -1.7 V present the brushite phase. The thermal post-treatment favored the formation of octagonal calcium phosphate in amorphous phase, while the basic treatment provided the OH- groups necessary for the formation of hydroxyapatite. The low cost potentiostat implemented presents excellent characteristics for obtaining films with similar characteristics to those obtained with a conventional potentiostat.

Abstract The cathodic arc discharge is a deposition technique widely used to synthesize hard coatings and thin films. The structure of the plasma generated by the electrical discharge and its interaction with neutral particles was studied using numerical simulations. Typical plasma parameters were characterized considering their spatial and temporal dependence, as well as several cathode materials that are commonly used in these systems. For the evolution of the ion density, it was observed the formation of Knudsen layer, and also a dependence of pressure gradients in the global behavior. With respect to the kinetic energy, it was found a deceleration of ions, which is represented by a shock front produced in the plasma−neutrals interaction. On the other hand, the energy releasing was generated due to the heat transference between electrons and ions. The plasma potential follows a behavior, which is similar to that of the ion density, and it is caused by the dynamics of charged particles which is directly affected by the concentration of neutrals and ions. In general, the physical quantities are directly affected by electrical and thermal conductivity of the cathode material. Our results can be applied to understand the plasma phenomena produced in a cathodic arc discharge.

Abstract We present an open-source software package, Vegas, for the atomistic simulation of magnetic materials. Using the classical Heisenberg model and the Monte Carlo Metropolis algorithm, Vegas provides the required tools to simulate and analyze magnetic phenomena of a great variety of systems. Vegas stores the history of the simulation, i.e. the magnetization and energy of the system at every time step, allowing to analyze static and dynamic magnetic phenomena from results obtained in a single simulation. Also, standardized input and output file formats are employed to facilitate the simulation process and the exchange and archiving of data. We include results from simulations performed using Vegas, showing its applicability to study different magnetic phenomena.

The time independent Schrödinger equation is a differential equation of great interest in computational physics. In many cases, it is impossible to reach an analytical solution for it, due to the potential function complexity, therefore numerical methods play an important role in its solution for practical cases. By means of numerical methods it is possible to solve the stationary Schrödinger equation for arbitrary potentials, allowing the study of interesting potentials that exhibit fascinating phenomena. Some of these potentials are the Kronig-Penney and pseudo-Coulomb potential functions, or more single like barrier potential function. Nevertheless, in many cases, the implementation of the sequence of steps needed to solve the differential equation is not straightforward. In this work we present and explain a sequence of steps to solving the time independent Schrödinger equation by means of the variational method, and apply it to solve non-periodic potential functions, like the harmonic oscillator potential well and rectangular potential barrier, and periodic potential functions like the Kronig-Penney and pseudo-Coulomb. Our main purpose is for this work to be an introduction to the computational quantum mechanics field.

Preparation and characterization of TiO2 films were made. Films were synthesized on glass substrates by the SILAR (Successive Ionic Layer Adsorption and Reaction) method. The preparation consisted of 150 cycles of a successive and alternate immersion of substrates in the precursor solution and in distilled water at 353 K. Growing was conducted at two conditions of the precursor solution which contained TiCl3 and NH2CONH2: at room temperature and at 343 K. After the growth, films were annealed at 723 K for 2 hours. Regarding characterization, samples were studied using XRD, SEM and UV-Vis. Structural characterization results showed that, in general, the films presented an amorphous crystalline structure except those which were grown with precursor solution at 343 K and thermally treated after the growths, which presented an anatase crystalline structure. Concerning their morphology, a granular structure and a random distribution of a flower-like structure were observed. Grain sizes did not change significantly after annealing. The optical study was carried out taking into account an indirect transition allowed determining the band gap energy to be around 3.1 eV. This value, which is typical for TiO2, decreases after annealing, usual for this type of films.

Se prepararon y caracterizaron películas de TiO2 sobre sustratos de vidrio por el método SILAR (del inglés Successive Ionic Layer Adsorption and Reaction, adsorción y reacción iónica en capas sucesivas). La preparación consistió en una inmersión sucesiva y alternada de los sustratos en una solución precursora y en agua destilada a 353 K durante 150 ciclos. Se hicieron crecimientos a dos condiciones de la solución precursora, la que contenía TiCl3 y NH2CONH2: a temperatura ambiente y a 343 K. Después de los crecimientos, las películas se trataron térmicamente a 723 K durante dos horas. En relación con la caracterización, las muestras fueron estudiadas empleando XRD, SEM y UV-Vis. Los resultados de la caracterización estructural mostraron que las películas, en general, presentaron una estructura cristalina amorfa excepto aquellas que crecieron con solución precursora a 343 K y que fueron tratadas térmicamente después del crecimiento, las que presentaron la fase cristalina anatase. En cuanto a la morfología, se observó una estructura granular y una distribución aleatoria tipo flores cuyos tamaños de grano no cambiaron significativamente con el tratamiento térmico. El estudio óptico se llevó a cabo teniendo en cuenta una transición indirecta permitida, lo que permitió determinar una energía de la brecha prohibida alrededor de 3.1 eV; este valor, típico para TiO2, disminuyó con el tratamiento térmico, lo que es común para este tipo de películas.

En este trabajo se estudió la respuesta de polarización y de histéresis en películas delgadas de titanato zirconato de plomo (PZT) a la variación de temperatura, presión, campo eléctrico y contenido de impurezas no ferroeléctricas, mediante simulación Monte Carlo. La simulación se basó en un Hamiltoniano DIFFOUR, que tiene en cuenta el efecto de un esfuerzo uniaxial, además de la interacción entre dipolos vecinos y el efecto de un campo eléctrico externo. Los resultados obtenidos para ciclos de histéresis y curvas de polarización se ajustan a los datos experimentales reportados para este material.

In this work the polarization and hysteresis response of Lead Zirconate Titanate (PZT) ferroelectric thin films was studied in relation to the variation on temperature, stress, electric field and the content of non-ferroelectric impurities by using a Monte Carlo simulation. The simulation was based on a DIFFOUR Hamiltonian that takes into account the effect of uniaxial stress, in addition to the nearest neighbor dipoles interaction and the effect of an external electric field. The obtained results for hysteresis loops and polarization curves correspond with reported experimental data for this material.

Se crecieron recubrimientos de Ti xAl1-xN empleando la técnica de magnetron sputtering tríodo, variando el voltaje de polarización entre -40 V y -150V. Por medio de espectroscopía de energía dispersiva, difracción de rayos x y miscroscopía de fuerza atómica, se analizó la influencia del voltaje de polarización sobre las propiedades morfológicas y estructurales de los recubrimientos. A medida que el voltaje bias se incrementó, se observó un aumento en el porcentaje atómico de Al, compitiendo con la concentración de Ti y produciendo cambios estructurales. A bajas concentraciones de Al, la pelcula exhibió una estructura cristalina FCC; sin embargo, a medida que le porcentaje de Al disminuyó, se pudo detectar una mezcla de fases FCC y HCP. Por otro lado, el incremento en el voltaje de polarización produjo una disminución en el espesor de las películas, debido al aumento en el número de colisiones. Además, el tamaño de grano y la rugosidad se vieron fuertemente afectados por el voltaje bías.

Ti xAl1-xN coatings were grown using the triode magnetron sputtering technique varying the bias voltage between -40 V and -150V. The influence of bias voltage on structural and morphological properties was analyzed by means of energy dispersive spectroscopy, x-ray diffraction and atomic force microscopy techniques. As the bias voltage increased, an increase in the Al atomic percentage was observed competing with Ti and producing structural changes. At low Al concentrations, the film presented a FCC crystalline structure; nevertheless, as Al was increased, the structure presented a mix of FCC and HCP phases. On the other hand, an increase in bias voltage produced a decrease films thickness due to an increase in collisions. Moreover, the grain size and roughness were also strongly influenced by bias voltage.

Las interfaces gráficas son útiles para especificar y examinar estructuras químicas y propiedades físicas de materiales. En este artículo se presenta el software SIMMON (Simulación de propiedades magnéticas de manganitas) como un programa de visualización cuyo objetivo es mostrar la magnetización, la susceptibilidad magnética, la energía, el calor específico, los ciclos de histéresis y la resistividad de materiales magnéticos. Estas propiedades pueden ser obtenidas a partir de la simulación de diferentes manganitas del tipo Re2/3A1/3MnO3, donde Re son iones de una tierra rara metálica como La, Nd y Pr con valencia 3+, los cuales se enlazan con iones Mn3+-3d4 y A es una tierra alcalina con valencia 2+ tal como Ba, Ca, Sr, entre otras, enlazadas con Mn4+-3d3. En estas simulaciones se emplea el método Monte Carlo combinado con el algoritmo de Metrópolis y el modelo de Heinsenberg.

The graphics interface is useful in specifying and examining chemical structures and physical properties. In this scientific and technological research paper, the SIMMON (MMSP - Manganite magnetic simulation properties) software is presented, as a visualization program, that allows to observe, the magnetization, susceptibility, energy, specific heat, the hysteresis loops and the resistivity of magnetic materials. This properties can be obtained from the simulation of different manganites Re2/3A1/3MnO3, where Re is a rare earth metal ions as La, Nd and Pr with valence 3+, which are bonded with Mn3+-3d4 ions and A is a 2+ alkaline earth ion such as Ba, Ca, Sr, among others, bonded with Mn4+-3d3. The based method for the simulations is Monte Carlo combined with Metropolis algorithm and Heisenberg model.

En este trabajo se presenta el estudio de propiedades mecánicas de multicapas de Zr/ZrN y TiN/ZrN variando el número de bicapas en 1, 2, 5 y 10, es decir, períodos de 2, 1, 0,4 y 0,2 µm, con espesor constante de 2 µm en una relación de 1:1 y 1:3. Para esta simulación se empleó el software ANSYS, el cual se basa en el método de elementos finitos. Se obtuvieron curvas de Esfuerzo- Deformación, dureza y módulo de Young en función del número de bicapas. De acuerdo al análisis realizado, las bicapas de TiN/ZrN con relación 1:3 presentan mayor dureza (31±1 GPa) en relación a los demás sistemas y un módulo de Young de aproximadamente 460 GPa. Los resultados de las simulaciones de las propiedades mecánicas de materiales basados en Ti y Zr, empleando métodos como el de elementos finitos, son prometedores en el campo de los nuevos materiales para predecir su desempeño en aplicaciones tecnológicas e industriales como recubrimientos duros sobre diferentes herramientas y piezas de maquinaria y así disminuir costos de producción. Además, las simulaciones presentadas en este trabajo pueden extenderse a sistemas compuestos de otros materiales de gran utilidad.

In this work mechanical properties of Zr/ZrN and TiN/ZrN multilayers varying the bilayerd number in 1, 2, 5 and 10, that is, multilayer periods of 2, 1, 0.4 y 0.2 µm, with thickness constant of 2 µm in a ratio 1:1 y 1:3 were studied. For the simulation the ANSYS software was employed, based on the finite elements method. Strain-stress curves, the hardness and Young's Modulus were obtained as function of the bilayer numbers. According, the analysis carried out, the TiN/ZrN bilayers with 1:3 ratio presented the highest hardness (31±1 GPa) regarding the others and a Young's modulus approximately of 460 GPa. Results obtained from the mechanical properties simulations of materials based on Ti and Zr, by using methods like finite elements are promising in the new materials field, in order to predict their performance in industrial and technological applications as hard coatings grown on several tools and machine pieces and from this way reducing the production costs. Moreover, simulations presented in this work can be extended to systems composed by other materials with great utilization.

Este trabalho apresenta o estudo das propriedades mecânicas das multicapas de Zr/ZrN e TiN/ZrN variando o número de bicapas em 1, 2, 5 e 10, ou seja, os períodos de 2, 1, 0.4 e 0.2 µm, com uma espessura constante de 2 µm em uma proporção de 1:1 e 1:3. Para esta simulação foi utilizado o software ANSYS, que é baseado no método dos elementos finitos. Foram obtidas curvas de esforço-deformação, dureza e módulo de Young em função do número de bicapas. Conforme a o análise, as bicapas de TiN/ZrN com proporção de 1:3 têm uma maior dureza (31 ± 1 GPa) em comparação com outros sistemas e um módulo de Young de cerca de 460 GPa. Os resultados das simulações das propriedades mecânicas de materiais basiados de Ti e Zr, utilizando métodos como elementos finitos, são promissoras no domínio dos novos materiais para prever o seu desempenho em aplicações tecnológicas e industriais, como revestimentos duros, em ferramentas diferentes e peças da máquina e, assim, reduzir os custos de produção. Além disso, as simulações apresentadas neste trabalho podem se estender para sistemas compostos de outros materiais de grande utilidade.