Elisabeth Restrepo Parra

• Prof. Dr.
• Professor (Full) at National University of Colombia

In this work, we present the preparation of a hybrid material constituted by a Metal-Organic Framework (type MIL-101(Fe)) and a natural clay ceramic monolith (NCCM), the materials were successfully assembled through an in-situ hydrothermal method. The composites were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA)...

TiO2/SO4 2- surfaces obtained by plasma electrolytic oxidation were used for the reduction of Cr(VI) to Cr(III) present in wastewater, in order to study the behavior of TiO2/SO4 2- in Cr(VI) and Cr(III) ion adsorption by X-ray photoelectron spectroscopy and density functional theory calculations. Highresolution X-ray photoelectron spectra showed th...

Isothermal molecular dynamics simulations were carried out with the embedded-atom method as a potential to predict the melting and crystallization temperatures of nanometric sized aluminum particles in the range of 2-4nm. Simulated data predicted a decrease in the melting point T m of aluminum nanoparticles with an increase in their inverse radius...

Dissociative adsorption of H2 was carried out on the @13 cluster (@ = Ag, Co, Cu and Ru) according to the number of nH2 molecules (n=1-10) and it was compared with H2 adsorption on the surface (111) of the same metals using Density Functional Theory. The adsorption of H2 is energetically more favorable on the @13 clusters than on the surfaces for a...

Density-functional theory calculations based on the GGA-PBE (generalized gradient approximation Perdew–Burke–Ernzerhof) exchange correlation functional were used to investigate the effect of hydrogen on the diffusion of adsorbed carbon, oxygen and hydrogen on the surface of Fe(100). The diffusion energy barrier was calculated for both clean surface...

In this paper, the mechanical properties of TaNx/TaCx bilayers obtained by direct current magnetron sputtering are studied. The materials were manufactured by stacking bilayers formed by the periodic alternation TaN and TaC. Initially, samples of 40 bilayers were produced varying the deposition temperature (200, 300, 400 and 500°C), finding the bes...

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 determ...

Biogenic hydroxyapatite (BHAp) is a widely used material in the biomedical area due to its similarities with the bone tissue mineral phase. Several works have been spotlighted on the thermal behavior of bone. However, little research has focused on determining the influence of calcination temperature in the physicochemical and bioactive properties...

This study focused on the influence of the CH4/Ar flow ratio on the microstructure, chemical composition, morphology, and mechanical properties of TaCx coatings deposited on (111) silicon substrates using magnetron sputtering. To characterize the coatings, X-ray diffraction for the microstructural analysis, auger electron spectroscopy (AES) for the...

In this work, we investigate the thermodynamic behavior of exchange graded ferromagnetic films using Monte Carlo simulations. The systems are modeled by using a classical Heisenberg Hamiltonian, considering only nearest neighbor exchange interactions and a linear depth-dependent effective magnetic exchange coupling strength profile. Our quantitativ...

The characterization of the magnetic field distribution is essential in experiments and devices that use magnetic field coil systems. We present an open-source application software, MFV (Magnetic Field Visualizer), for the visualization of the distribution of the magnetic field produced by circular coil systems. MFV models, simulates, and plots the...

This work presents a model for the simulation of plasmatic transmembrane ionic transport that may be exposed to a static gradient magnetic field. The simulation was carried out using the Monte Carlo method to simulate the transmembrane cell transport of five types of ions and obtain observables such as membrane potential, ionic current, and osmotic...

In this work, WTiN thin films were produced on silicon substrates using the DC magnetron sputtering technique varying the working pressure and keeping the power constant at 90 W and conducting the process at room temperature. The structure and morphology of the coatings were analyzed using the x-ray diffraction technique, which allowed the identifi...

A study on the physical, chemical and electrochemical (properties) behavior of bismuth oxide thin films is presented in this work. Thin films were grown on 316 L stainless steel substrates via Unbalanced Magnetron Sputtering (UMS) in reactive phase, varying the DC power applied to the target between 20 and 80 W with 10 W step, keeping the gases flo...

In this work, a study of magnetic properties of nanogranular films constructed with different grain sizes is presented. The total energy of the system is proposed by mean a Hamiltonian with four contributions, which was solved using the Monte Carlo Method. The proposed terms include: (i) The exchange interactions, which consider the stress at grain...

Chiral magnets have been vastly studied in the last years due to their potential applications as information carrying devices. In this work, it was studied the influence of the magnetocrystalline anisotropy term on the magnetic properties of two-dimensional chiral magnets, by means of Monte Carlo simulations. On the obtained magnetic arrangements,...

We provide a guide to implementing the particle-in-cell algorithm, which is useful for simulating diverse phenomena in plasmas. We focus on two-dimensional systems which have vector fields with three Cartesian components but depend only on two spatial coordinates. We describe the algorithm in detail, including particle-to-grid interpolation, the fa...

The characterization of the magnetic field distribution is essential in experiments and devices that use magnetic field coil systems. We present an open-source application software, MFV (Magnetic Field Visualizer), for the visualization of the distribution of the magnetic field produced by circular coil systems. MFV models, simulates, and plots the...

The magnetocaloric effect and the universal character for the magnetic entropy change regarding the cubic crystal structures (SC, BCC, FCC) were investigated, in a qualitative way, using Monte Carlo simulations. A classical Heisenberg Hamiltonian with nearest neighbors, and next nearest neighbors interactions was implemented. In order to compute th...

Manganitesof La0.7Ca0.3−xSrx MnO3 have been produced using the hydrothermal method. The influence of the concentration of La, Ca, and Sr on the structural, morphological, and magnetic properties was studied and analyzed. The x-ray diffraction studies showed the occurrence of orthorombic and trigonal symmetries in the crystalline structure, dependin...

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We evaluate the influence of the shape on hysteretic properties in ferromagnetic/antiferromagnetic core/shell nanoparticles using Monte Carlo simulations. Exchange bias and coercive fields were estimated in nanoparticles with shapes ranging from octahedra to spheres to cubes. The net magnetic moment in the shell interface, produced by uncompensated...

La1−x(Ca,Sr)x MnO3 manganites have been produced using the hydrothermal method. The influence of the concentration of La, Ca, and Sr on the structural, morphological, and magnetic properties was studied and analyzed. The X-ray diffraction analysis showed that samples crystallized in rhombohedral or trigonal symmetries depending on the stoichiometry...

La0.5Ca0.5Mn0.5Fe0.5O3 was synthesized using the solid state reaction method. This method consists of two main processes: a milling process and a subsequent thermal treatment. Two samples at different conditions were produced: one using 2 h of milling time and 900°C (M-I), and the other using 6 h of milling time and 1200°C of thermal treatment (M-I...

The automatic diagnosis of melanoma is usually affected by the noise that is often included in an image, during the acquisition stage or by superficial factors such as hair. Specifically, hair on the surface of a lesion can cause enough distortion, resulting in an erroneous diagnosis of the region of interest. To solve this issue, several technique...

In this work is proposed a new fully automated methodology using computer vision and dynamic programming to obtain a 3D reconstruction model of surfaces using scanning electron microscope (SEM) images based on stereovision. The horizontal stereo matching step is done with a robust and efficient algorithm based on semi-global matching. The cost func...

This work introduces a combination of three factors for explaining the possible causes of “magnetic domains” presented in experimental reports. The first factor is the combination of a ferromagnetic (FM) interaction between first neighbors with an antiferromagnetic (AFM) interaction at relatively long distances. The second factor is the presence of...

In this work, we present an investigation of the magnetization reversal times for a ferromagnetic/antiferromagnetic core/shell nanoparticle, by means of Monte Carlo simulations. The magnetic behavior of the nanoparticle was evaluated with a classical Heisenberg Hamiltonian, which includes terms for the exchange interaction, external magnetic field...

Bacterial degradation is an alternative method to degrade cocaine and amphetamines

In this work, we present a study of the plasma evolution during tungsten carbon nitride (WCN) coatings production using the repetitive pulsed arc technique. For the coatings production, a tungsten carbide (WC) target, and a mixture of argon and nitrogen as the filled gas were used. The study was carried out for discharges generated with one, two, t...

The magnetic properties and magnetocaloric effect in NdMnO3 have been investigated, as well as the effect of magnetic anisotropy in the magnetocaloric properties of the perovskite-type compound. A classical Heisenberg Hamiltonian with nearest and next-nearest neighbors interactions was implemented. Hamiltonian parameters were fitted in order to rep...

In the present work, we have studied the magnetic behavior of a ternary alloy nanoparticle of the form ABpC1−p by Monte Carlo simulations. The nanoparticle was modeled by three types of magnetic sites, A-sites with spin-3/2, B-sites with spin-1 and C-sites with spin-5/2, distributed in a simple cubic lattice. The magnetic behavior was modeled by me...

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 magneti...

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 magneti...

The magnetocaloric behavior of LaCaMn1-xFexO3 for x = 0.00, 0.02, 0.03, 0.05, 0.07, 0.08 and 0.10 under the influence of an external magnetic field was simulated and analyzed. Simulations were carried out using the Monte Carlo method and the classical Heisenberg model under the Metropolis algorithm. These mixed valence manganites are characterized...

This work presents a study of dynamic phase transitions in samples of perovskite type manganites of La23Ca13MnO3, when they were submitted to the influence of an external magnetic field that includes both a time dependent and a time independent magnetic fields. This study was carried out based on Monte Carlo simulations and using the Metropolis alg...

Thin films of CrN were synthesized in a DC magnetron sputtering system using a mixture of Ar + N2. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS) revealing CrN bonds. The stoichiometry variation dependence on the N2 flow was also analyzed using Auger spectroscopy. Both, The XPS and Auge...

In this work, a complete model for studying the magnetic behaviour of polycrystalline thin films at nanoscale was processed. This model includes terms as exchange interaction, dipolar interaction and various types of anisotropies. For the first term, exchange interaction dependence of the distance n was used with purpose of quantify the interaction...

In this work, Monte Carlo simulations based on Metropolis algorithm were performed to study the critical and compensation temperatures of a core-shell nanowire with spins S=±5/2,±3/2,±1/2 and σ=±3/2,±1/2, respectively, considering an Ising antiferromagnetic system. The influence of nearest neighbors exchange interactions and crystal field anisotrop...

This document presents a study of the influence of the dipolar interactions and geometrical parameters on the magnetic properties of single-walled ferromagnetic nanotubes built by using square and hexagonal unit cells. For this study, a Hamiltonian, which includes dipolar interactions and nearest neighbor classical Heisenberg model, was used; furth...

An atomistic scale study of ultra-thin ferromagnetic films was carried out using Monte Carlo simulations with Metropolis dynamics, and the simulations were performed using a Heisenberg Hamiltonian, surface and crystalline anisotropies, and dipolar interaction. We defined an 𝜖 parameter to bind the dipolar interaction with the anisotropy in order to...

In this work, the production of RuN thin films using the reactive direct current magnetron sputtering technique is presented. Samples were grown with varying Ar/N2 ratio with values of 60/40, 80/20, 85/15, 90/10, 95/5, and 100/0. X-ray photoelectron spectroscopy was employed to determine the presence of RuN before and after a sputtering etching pro...

We have studied the effects of surface shape anisotropy in the magnetization behavior of a torus nanoring by means of Monte Carlo simulations. Stable states (vortex and reverse vortex states) and metastable states (onion and asymmetric onion states) were found in the torus nanoring. The probability of occurrence of the metastable states (stable sta...

WTiN films were grown on silicon and stainless-steel substrates using the DC magnetron sputtering technique. The substrate temperature was varied taking values of 100 °C, 200 °C, 300 °C, and 400 °C. X-ray diffraction analysis allowed us to identify a rock salt-type face centered cubic (FCC) structure, with a lattice parameter of approximately 4.2 n...

The time independent Schrodinger 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...

Un trabajo realizado para la obtención del título de Ingeniero Físico, una revisión de presaberes requeridos para la determinación de estructuras cristalinas mediante algoritmos de optimización global y una citación de 3 repercusivos autores en estos (Particle Swarm Optimization, Evolutionary Algorithms, Simulated Annealing).

The direct bonded copper (DBC) process was carried out between Cu and Al2O3 foils and CuO thin films were grown on the surface of Cu foils to reduce the defects produced by the DBC on the surface. CuO thin films were synthesized using a magnetron sputtering system, employing a target of Cu with 99.99% of purity and substrates of Cu foils. The disch...

We have studied the magnetic properties of the mixed spin View the MathML source and spin View the MathML source Ising ferrimagnetic system in a graphene layer by means of Monte Carlo simulations. The effects of next-nearest neighbors exchange interactions and crystal field anisotropy on the critical and compensation behavior of the system have bee...

Thermal and hysteretic magnetic properties of La2/3Ca1/3MnO3 nanoparticles were studied using Monte Carlo simulations, with emphasis on the influence of anisotropy. In this work, several nanoparticle sizes ranging from 2.32 to 11.58 nm were analyzed and their properties were compared to those of the bulk material. The magnetic behavior of the mater...

In this study, a methodology, for polycrystalline magnetic thin films construction composed by nano-grains, was developed. The size and shape of grains and samples under scale considerations of magnetic materials were developed, taking into account periodic boundary conditions. A comparative analysis of results obtained with experimental grains’ di...

Thermal and hysteretic magnetic properties of nanoparticles were studied using Monte Carlo simulations, with emphasis on the influence of anisotropy. In this work, several nanoparticle sizes ranging from 2.32 nm to 11.58 nm were analyzed and their properties were compared to those of the bulk material. The magnetic behavior of the material was mode...

Magnetic behaviour of nanotubes with square cell has been studied by the Monte Carlo Method, under the Metropolis algorithm and Heisenberg model. The Hamiltonian used includes nearest neighbour exchange interaction and radial and tangential direction for uniaxial anisotropy. Periodic boundary conditions were implemented at the sample's edges. Simul...

In this work, titanium doped tungsten disulfide thin films (WS2-Ti) were deposited on AISI 304 stainless-steel substrates using the magnetron co-sputtering DC technique. Films were produced with varying titanium-cathode power from 0 to 25 W. The titanium content of the WS2 structure was determined using energy dispersive spectroscopy (EDS), thereby...

The use of color as a strategy for enhancing the contrast is useful for conducting feature extraction procedures in images with high illumination disorders; hence, in order to correct contrast problems in images that were erroneously acquired, a method that automatically searches the discriminant projections of the color map depending on the origin...

In this work, a software for simulating nanoindentation in thin films was implemented. For the software constructions, the Molecular Dynamics technique was used. The model applied for the graphic interface (software) is an approximation that reproduces the characteristic curves tendencies in test of materials hardness; on the other hand, the softwa...

AC magnetic susceptibility of La1−x Cax MnO3 (x = 0.25, 0.33, 04, 0.5) thin films was obtained using Monte Carlo simulations combined with Fourier transform. The material stoichiometry was varied depending on the combination of Mn 4+ and Mn 3+ ions. Hamiltonian used includes the Heisenberg interaction, magnetocrystalline anisotropy, and Zeeman effe...

Fission gas release in nuclear fuels can be modeled in the framework of percolation theory, where each grain boundary is classified as open or closed to the release of the fission gas. In the present work, two-dimensional grain boundary networks were assembled both at random and in a crystallographically consistent manner resembling a general textu...

Samples of La0.5Ca0.5Mn1−xFexO3+δ (0≤x≤0.5) were synthesized using a solid-state reaction method involving a milling process and thermal treatment up to 1200 °C in an air atmosphere. Samples were characterized structurally with X-ray diffraction analysis and Rietveld refinement with morphology characterization using scanning electron microscopy. Ma...

In this work we present a new design of Co based bit pattern media with out-of-plane uni-axial anisotropy induced by interface effects. Our model features the inclusion of magnetic impurities in the non-magnetic matrix. After the material model was refined during three iterations using Monte Carlo simulations, further simulations were performed usi...

En este trabajo se implementó el software de simulación para la nanoindentación de películas delgadas. El software desarrollado empleó la técnica de Dinámica Molecular. El modelo con el cual opera la interfaz gráfica (software), es un modelo aproximado, que reproduce las tendencias de las curvas características en pruebas de dureza de materiales. P...

This work has two main purposes: (i) introducing the basic concepts of molecular dynamics analysis to material scientists and engineers, and (ii) providing a better understanding of instrumented indentation measurements, presenting an example of nanoindentation and scratch test simulations. To reach these purposes, three-dimensional molecular dynam...

Monte Carlo simulations combined with the Heisenberg model and Metropolis algorithm were used to study the equilibrium magnetic properties of magnetic multi-core nanoparticles of magnetite. Three effects were considered in this simulation: the Zeeman effect, magneto crystalline anisotropy, and dipolar interaction. Moreover, the influence of the siz...

The ferroelectric response of bismuth titanate Bi4Ti3O12 (BIT) thin film is studied through a Monte Carlo simulation of hysteresis loops. The ferroelectric system is described by using a Diffour Hamiltonian with three terms: the electric field applied in the z direction, the nearest dipole-dipole interaction in the transversal (x-y) direction, and...

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 t...

Mechanical and tribological properties of CrN coatings grown on steel substrates AISI 304 and AISI 4140 using the magnetron sputtering technique were analyzed. Coatings were grown at two pressures of work, 0.4 and 4.0 Pa. The films grown on AISI 304 at a pressure of work of 0.4 showed the highest hardness because it presented a larger grain size an...

This work develops a model that mimics the growth of diatomic, polycrystalline thin films by artificially splitting the growth into deposition and relaxation processes including two stages: (1) a grain-based stochastic method (grains orientation randomly chosen) is considered and by means of the Kinetic Monte Carlo method employing a non-standard v...

This work presents a study of the effect of film thickness on the static and dynamic critical behavior of thin magnetic Ising films. Monte Carlo simulations using the Wolff algorithm were performed to determine the static and dynamic critical exponents of the films. A dimensionality crossover from 2D to 3D (due to the finiteness of the films) in th...

The Metropolis algorithm and the classical Heisenberg approximation were implemented by the Monte Carlo method to design a computational approach to the magnetization and resistivity of La2/3Ca1/3MnO3, which depends on the Mn ion vacancies as the external magnetic field increases. This compound is ferromagnetic, and it exhibits the colossal magneto...

TixAl1-xN coatings were grown using the triode magnetron sputtering technique with various bias voltages between -40 V and -150 V. As the bias voltage increased, an increase in the Al atomic percentage was observed, presenting a competition with Ti and producing structural changes. Moreover, the grain size and roughness were also strongly influence...

The pulsed cathodic arc deposition technique was used to synthesize titanium–zirconium nitride (TiZrN) thin films at different substrate temperatures. A microstructural analysis extracted from the X-ray powder diffraction pattern was performed to identify the dependence of crystallite size and microstrain on TS. The residual stress state was also d...

In this work, different methods employed for the analysis of emission spectra are presented. The proposal is to calculate the excitation temperature (Texc), electronic temperature (Te) and electron density (ne) for several plasma techniques used in the growth of thin films. Some of these techniques include magnetron sputtering and arc discharges. I...

Bismuth thin films were grown onto glass substrates through the DC magnetron sputtering technique. The effects of substrate temperature on the microstructure of the films were evaluated. The structural behavior was analyzed via X-ray diffraction, and it showed a marked influence of the substrate temperature on the crystallite size and the micro-str...

Monte Carlo method is a tool that has been widely used in materials science and engineering since its beginning in the decade of the 1940, but is also applicable in subjects as diverse as economics, society and its behavior, biology and even medicine. The working of the Monte Carlo method is based on the use of random numbers and to get to describe...

RESUMEN Se realizó síntesis de autopolimerización del polimetacrilato de metilo (PMMA) e hidroxiapatita (HA) por precipitado. Se sintetizó a partir de una mezcla de 1 g de ((C5O2H8)n) con 17% y 20% de incorporación de HA. La HA fue sintetizada en precipitado con sustitución de iones de calcio por iones de magnesio. Los materiales precursores (PMMA/...

Amorphous carbon nitride films have been obtained by pulsed cathodic arc at substrate temperatures of 20, 100, 150 and 200 °C. Film structure was investigated by Fourier Transformed infrared spectroscopy (FTIR) and Raman spectroscopy. Nitrile bands at approximately 2200 cm-1 were identified in all films. As the temperature increased a reduction in...

Three-dimensional molecular dynamics (MD) simulations of a nanoindentation technique using the hard sphere method for Cr (bcc) and Al (fcc) thin films and (Cr/Al)n (n=1,2) systems were carried out. For the model implementation, Morse interatomic potential was used for describing the single crystal interaction and the contact between Cr and Al struc...

TixAl1-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...

In this work the polarization and hysteresis response of Lead Zirconate Ti-tanate (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...

In this work, a study of some magnetotransport properties of manganite bilayers of ferromagnetic/Antiferromagnetic (FM/AF) La2=3Ca1=3MnO3/ La1=3Ca2=3MnO3 is presented. This study was carries out using the Monte Carlo method combined with Drude and Kronig-Penney models. For doing the simulations, graphic interfaces for allowing a suitable user inter...

W/WC bilayers were grown using the DC magnetron sputtering technique and varying substrate temperature. The mechanical and tribological behaviors were characterized using the nanoindentation and pin-on-disk techniques. The hardness and Youngs modulus tended to increase, while the coef fi cient of friction tended to be stable with increasing substrat...

Se realizó síntesis de autopolimerización del polimetacrilato de metilo (PMMA) e hidroxiapatita (HA) por precipitado. Se sintetizó a partir de una mezcla de 1 g de ((C5O2H8)n) con 17% y 20% de incorporación de HA. La HA fue sintetizada en precipitado con sustitución de iones de calcio por iones de magnesio. Los materiales precursores (PMMA/HA) se t...

Bismuth titanate (BixTiyOz) thin films were grown using the r.f. magnetron sputtering technique on (100) silicon substrates. In the process, annealing was performed in both oxygen and dry air atmospheres at 600°C for 30 and 120 min. The structure of the thin films was characterized through X-ray diffraction (XRD), and the ferroelectric response was...