Papers by armando sarmiento santos
Ciencia en Desarrollo, Dec 21, 2017
Resumen La tecnología del plasma es una ciencia que desde sus comienzos se encuentra en una const... more Resumen La tecnología del plasma es una ciencia que desde sus comienzos se encuentra en una constante evolución, desde aplicaciones para el tratamiento de materiales hasta aplicaciones ambientales. En particular el plasma de la descarga luminiscente ofrece una amplia gama de aplicaciones desde aplicaciones en plasmo-química hasta tratamientos termoquímicos de materiales. En el presente trabajo se busca aprovechar la generación de calor por parte de la descarga luminiscente de baja presión en corriente continua, debido a la transferencia de energía cinética desde el plasma hacia los electrodos. Para ello se diseñó un reactor cilíndrico que genera una descarga luminiscente de baja presión en una atmósfera de argón. El cátodo de la descarga lo constituye el electrodo interno, mientras que el ánodo, y al mismo tiempo la pared de la cámara, lo constituye un cilindro metálico externo, concéntrico al cátodo. Para mantener la descarga se utilizó una fuente de corriente continua pulsada y la descarga se generó a varias corrientes y en diferentes atmósferas gaseosas (N 2 , H 2 y Ar). Mediante medidas eléctricas de la descarga se determinó la potencia y consumo energético del reactor, comparándolo con los valores obtenidos para un dispositivo calefactor comercial basado en resistencias eléctricas.
Aleaciones inoxidables Fe-Cr con concentraciones de cromo entre 13,9 y 28,4% en peso, fueron prep... more Aleaciones inoxidables Fe-Cr con concentraciones de cromo entre 13,9 y 28,4% en peso, fueron preparadas a traves del metodo de pulvimetalurgia. Se correlaciona el comportamiento de la variacion de densidad de las muestras con su contenido de cromo y con los parametros del proceso. Despues de sinterizadas, las muestras fueron sometidas al proceso de sputtering en una descarga luminiscente anormal de baja presion en atmosfera de 80% de Ar y 20% de H2 a 10 torr de presion y una temperatura de 900°C. Las medidas de la variacion de masa despues del proceso de sputtering fueron comparadas con simulaciones realizadas mediante el programa SRIM-2003.20. Stainless Fe-Cr alloys with chromium content between 13,9 and 28,4% in weigh, were prepared through powder metallurgy method. Process parameters and chromium content were correlated with density variation in samples. After sinterized, the samples were submitted to sputtering process in a low pressure abnormal glow discharge with 80% Ar and 20% H2 atmosphere. The glow pressure and sample temperature were 10 torr and 900°C respectively. After sputtering process, samples weight variations were compared with SRIM-2003.20 software simulations.
Revista Colombiana de Física, Dec 4, 2011
Aleaciones inoxidables Fe-Cr con concentraciones de cromo entre 13,9 y 28,4% en peso, fueron prep... more Aleaciones inoxidables Fe-Cr con concentraciones de cromo entre 13,9 y 28,4% en peso, fueron preparadas a traves del metodo de pulvimetalurgia. Se correlaciona el comportamiento de la variacion de densidad de las muestras con su contenido de cromo y con los parametros del proceso. Despues de sinterizadas, las muestras fueron sometidas al proceso de sputtering en una descarga luminiscente anormal de baja presion en atmosfera de 80% de Ar y 20% de H2 a 10 torr de presion y una temperatura de 900°C. Las medidas de la variacion de masa despues del proceso de sputtering fueron comparadas con simulaciones realizadas mediante el programa SRIM-2003.20. Stainless Fe-Cr alloys with chromium content between 13,9 and 28,4% in weigh, were prepared through powder metallurgy method. Process parameters and chromium content were correlated with density variation in samples. After sinterized, the samples were submitted to sputtering process in a low pressure abnormal glow discharge with 80% Ar and 20% H2 atmosphere. The glow pressure and sample temperature were 10 torr and 900°C respectively. After sputtering process, samples weight variations were compared with SRIM-2003.20 software simulations.
Revista UIS Ingenierías
The formation of polymeric films by plasma has become an alternative for the coating of metallic ... more The formation of polymeric films by plasma has become an alternative for the coating of metallic materials that require varying their surface characteristics and improving their resistance to corrosion; because by this method it is possible, in principle, to polymerize any gaseous hydrocarbon. In this work, the study of the formation of acetylene polymer films on a copper substrate, previously treated in an abnormal luminescent discharge regime in argon-hydrogen atmosphere, is presented. The polymeric formation was carried out in a continuum current abnormal glow discharge in an atmosphere of 60% Ar, 35% H2 and 5% C2H2 at a pressure of 2 Torr, at a temperature of 600 °C and with deposition times between 5 and 120 s. The structural and morphological analysis of the polymeric film deposited at different temperatures was performed by Infrared Spectroscopy and Scanning Electron Microscopy. Additionally, a characterization of the materials was carried out using corrosion resistance analy...
Bulletin of the American Physical Society, Oct 13, 2015
this work we use the abnormal glow discharge (AGD) to produce the CaMn 0.9 Mo 0.1 O 3 perovskite ... more this work we use the abnormal glow discharge (AGD) to produce the CaMn 0.9 Mo 0.1 O 3 perovskite through decarbonize, calcination and sintering steps. Structural characterization was carry out by Rietveld refinement of X-ray diffraction on samples after sintering step. The magnetic properties was analysed through magnetization curves as a function of temperature for applied magnetic fields in the range of 20 Oe to 20 kOe by the ZFC-FC method and magnetization curves in function of the applied field at 50 K and 300 K temperatures. The CaMn 0.9 Mo 0.1 O 3 perovskite was also produced by conventional method in resistive furnace and its behaviour was compared with those of the plasma synthesized. The X-ray analysis reveals that the samples produced by both methods crystalized in a Pnma structure, the lattice parameters change and one second phase appears when the AGD is applied in the last production steps. The magnetization measurements allow analysing the behaviour of the sample at low temperatures and comparing the magnetic transitions in the samples produced by both methods; these are influenced according to production method employed. The results shows that the use of AGD is an alternative method to produce ceramic materials, which reduced ostensibly the production time and allow to obtain similar magnetic and structural properties with respect to conventional method.
Revista Facultad de Ingeniería, Jan 15, 2013
Brazilian Journal of Chemical Engineering, Apr 19, 2021
The decomposition of synthetic siderite (FeCO3) in air atmosphere at room temperature conditions ... more The decomposition of synthetic siderite (FeCO3) in air atmosphere at room temperature conditions was studied. Siderite was formed by mechanochemical reaction of Fe3O4 and graphite at high CO2 pressure in the presence of water. Kinetics of decomposition reaction was studied over period up to 9 days and it is shown that decomposition reaction obeys geometrical contraction solid-state reaction mechanism model. It was found that the water influences not only the kinetics of siderite formation but also its stability. Siderite completely decomposes at ambient conditions yielding magnetite (Fe3O4) and hematite (Fe2O3) which can reversibly re-absorb carbon dioxide.
Journal of physics, Dec 1, 2017
In all material treated in Sbnormal Glow Discharge (AGD) the phenomenon of sputtering occurs. In ... more 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.
Revista de Investigación, Desarrollo e Innovación, Dec 20, 2014
Journal of Superconductivity and Novel Magnetism, Feb 5, 2012
Revista Mexicana De Fisica, 2012
Journal of physics, Feb 1, 2016
Composite samples of 316 stainless steel and SiC were produced by powder metallurgy. Starting mat... more Composite samples of 316 stainless steel and SiC were produced by powder metallurgy. Starting materials were mixed in different proportions and compacted to 700MPa. Sintering stage was performed by abnormal glow discharge plasma with direct current in an inert atmosphere of argon. The process was conducted at a temperature of 1200°C±5°C with a heating rate of 100°C/min. This work shows, the effectiveness of plasma sintering process to generate the first contacts between particles and to reduce vacancies. This fact is confirmed by comparing green and sintered density of the material. The results of porosity show a decrease after plasma sintering. Wear tests showed the wear mechanisms, noting that at higher SiC contents, the wear resistance decreases due to poor matrix-reinforcement interaction and by the porosity presence which causes matrix-reinforcement sliding.
Journal of physics, Dec 1, 2017
This work reports on the synthesis and characterization of the Bix-1SmxFeO3 (x=0.04 and 0.07) sys... more This work reports on the synthesis and characterization of the Bix-1SmxFeO3 (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 R3C 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.
Journal of physics, 2017
1020 steel is a material very used for surface treatment in the abnormal glow discharge. Because ... more 1020 steel is a material very used for surface treatment in the abnormal glow discharge. Because the composition of the gaseous atmosphere has an important influence on the results of plasma treatment, in this work the oxidation process of 1020 steel is verified on the abnormal glow discharge under different concentrations of air (20% to 100%) at temperatures of 600°C and 900°C. For each atmosphere used mass variation is measured during the process of surface oxidation, the structure and microstructure of the oxide film formed is observed and also its mechanical properties through its microhardness.
Dyna, Sep 1, 2011
RESUMEN: La aplicación de la descarga luminiscente anormal al proceso de sinterización es una téc... more RESUMEN: La aplicación de la descarga luminiscente anormal al proceso de sinterización es una técnica reciente que representa disminución en el tiempo requerido para el proceso de sinterización de muestras, tanto metálicas como cerámicas, y un menor consumo de energía, debido a que el calentamiento se realiza en forma directa por el bombardeo de los iones y átomos neutros sobre la superficie del cátodo donde generalmente se localiza la muestra. En este trabajo se estudia la aplicación de la descarga luminiscente anormal de baja presión como método alternativo para realizar la etapa de sinterización del material cerámico YBa 2 Cu 3 O 7-δ , se comparan la estructura y la microestructura de muestras sinterizadas en la descarga luminiscente con las de muestras sinterizadas en horno resistivo, el cual es comúnmente utilizado para la producción de este tipo de materiales. Para ello se realiza el análisis estructural y morfológico por DRX y SEM, respectivamente, de las muestras obtenidas por los dos procedimientos. Los resultados experimentales permitieron establecer una estructura similar para ambos casos y una menor porosidad superficial en las muestras sinterizadas por plasma. Además, en el proceso de sinterización por plasma se observa una ligera contaminación de la superficie de las muestras debida a la pulverización catódica, la cual es fácilmente eliminada por métodos mecánicos.
IEEE Transactions on Plasma Science, Dec 1, 2016
In this paper, we use the abnormal glow discharge (AGD) in the synthesis process of the CaMn 0.9 ... more In this paper, we use the abnormal glow discharge (AGD) in the synthesis process of the CaMn 0.9 Mo 0.1 O 3 perovskite, varying the conventional route by solid-state reaction method, and the AGD was employed in decarbonizing, annealing, and sintering steps. Structural characterization was carry out by the Rietveld refinement of X-ray diffraction on samples after sintering step at room temperature. Magnetic properties were analyzed through magnetization curves as a function of temperature for applied magnetic field of 1 kOe by the zero-fieldcooled-field-cooled method. CaMn 0.9 Mo 0.1 O 3 perovskite was also produced by conventional method in resistive furnace, and its behavior was compared with these obtained for samples AGD produced. The X-ray analysis reveals that samples crystallize in a P nma structure. The magnetization measurements allow analyzing the behavior of the sample, at low temperatures, and comparing the magnetic transitions in the samples produced by both the methods. The results show that AGD can be an alternative to produce these ceramic materials with an important reduction in the production time with respect to conventional method.
Physica B-condensed Matter, Dec 1, 2014
ABSTRACT In this work, we report the production of TR3Ba5Cu8Oδ (TR=Ho, Y and Yb) superconducting ... more ABSTRACT In this work, we report the production of TR3Ba5Cu8Oδ (TR=Ho, Y and Yb) superconducting system using a usual solid state reaction method. The irreversibility line and the analysis of magnetization fluctuations for TR3Ba5Cu8Oδ (TR=Ho, Y and Yb) system were investigated. The curves of magnetization ZFC-FC were measured in magnetic fields of the 100-4000 Oe to obtain the values for T⁎ and TC temperatures. The penetration depth and the coherence length parameters as a function of the applied magnetic field were obtained. The data of the magnetization excess ΔM(T, H) was analyzed from the curves of magnetization as a function of logarithm of applied field for different values of temperature in the corresponding range. The Bulavskii, Ledvij and Kogan theory was employed for this purpose which considers fluctuations effects in the free energy and into the equilibrium magnetization.
Journal of Superconductivity and Novel Magnetism, Oct 15, 2014
Journal of Physics: Conference Series, 2017
This work the effect of the addition of Calcium Oxide (CaO) in the compaction and sintering of po... more 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.
Journal of Materials Research and Technology, 2020
With the aim to produce a material with magnetic and semiconductor properties, a lanthanide bismu... more With the aim to produce a material with magnetic and semiconductor properties, a lanthanide bismuth-ferrite type material is proposed in this work. Polycrystalline samples of Dy 2 Bi 2 Fe 4 O 12 were produced following the standard solid-state reaction method. Structural characterization through the X-ray diffraction technique evidences that the synthesized ceramic crystallizes in a perovskite-like orthorhombic structure, belonging to the Pnma (#62) space group. Scanning electron microscopy images revealed the granular nature of the samples with mean grain sizes of nanometric order. X-ray energy dispersion spectra allowed establishing that in the samples there are no elements different from those expected in the stoichiometric proportions suggested by the chemical formula of the compound. Studies of electrical behavior were carried out using I-V curves and electrical permittivity as a function of frequency and temperature, which show the diode varistor feature of this material with a marked Maxwell-Wagner-type trend. The semiconductor band gap was determined from the analysis of diffuse reflectance spectra that reveal E g = 1.88 eV. Temperature-dependent magnetization curves for applied fields of 1.0, 5.0 and 10 kOe showed the behavior expected for ferromagnetic type materials, with strong evidence of magnetic frustration causing irreversibility in curves obtained from Zero Field Cooling and Field Cooled measurement procedures. The magnetization hysteresis curves at temperatures of 50, 200 and 300 K exhibit a ferromagnetic response with evidence of superparamagnetic effects due to the significant presence of nano-sized ferromagnetic grains. Based on the obtained results, it can be affirmed that the material behaves like a soft ferrimagnetic semiconductor with low coercive field (between 500 Oe and 700 Oe) and remnant magnetization (between 2.15 × 10 −4 emu/g and 3.25 × 10 −4 emu/g) that would have eventual technological implications in the spintronic industry.
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Papers by armando sarmiento santos