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Search Results: 1 - 10 of 297743 matches for " J. Porcayo-Calderon "
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Corrosion Behavior of Fe40Al Alloy with Additions of Ti, Ag, and Cr in Molten KCl+
R. Ademar,J. G. Gonzalez-Rodriguez,J. Uruchurtu,J. Porcayo-Calderon,V. M. Salinas-Bravo,G. Dominguez-Pati?o,A. Bedolla-Jacuinde
International Journal of Corrosion , 2012, DOI: 10.1155/2012/146486
Abstract: The effect of 2.5?at.% Cr, Ti, and Ag on the corrosion behavior of Fe40Al intermetallic alloy in KCl-ZnCl2 (1?:?1?M) at 670°C has been evaluated by using electrochemical techniques. Techniques included potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) measurements. Results have shown that additions of both Cr and Ti were beneficial to the alloy, since they decreased its corrosion rate, whereas additions of Ag was detrimental, since its additions increased the corrosion rate, although the alloy was passivated by adding Ag or Cr. The best corrosion performance was obtained with the addition of Cr, whereas the highest corrosion rate was obtained by adding Ag. This is explained in terms of the stability of the corrosion products formed film. 1. Introduction Sodium and potassium impurities present in the form of chloride or sulfates are very corrosive constituents under certain combustion conditions such as waste incinerators and biomass-fired boilers [1, 2]. Early failure of the thermal components frequently occurs due to the complex reactions between the metallic materials and the hostile combustion environment. Incineration has become a viable technology for disposing of various types of wastes, including municipal, hospital, chemical, and hazardous. Problems with process equipment resulting from fireside corrosion have been frequently encountered in incinerators. The major problem is the complex nature of the feed (waste) as well as corrosive impurities which form low-melting point compounds with heavy and alkali metal chloride which prevents the formation of protective oxide scales and then causes an accelerated degradation of metallic elements [1]. In particular, under reducing conditions such as those typical of the operation of waste gasification plants or even under localized reducing conditions, which frequently arise in the case of incorrect operation of waste incineration systems, it is difficult to form protective oxide scales such as Cr2O3, SiO2, and Al2O3 on the surface of structural materials. Thus, the corrosion attack can be further enhanced under reducing atmospheres in the presence of salt deposits [2]. The effect of individual KCl, NaCl, and their mixtures with heavy metal chlorides or sulfates on the corrosion behavior of a series of alloy systems has been studied in detail so far [3–9]. It is generally realized that Cr is not as effective element for corrosion resistance of Fe-base and Ni-based alloys due to chloride attack. In contrast, alumina- (Al2O3) forming
Hot Corrosion Behavior of High-Chromium, High-Carbon Cast Irons in NaCl-KCl Molten Salts
S. Vuelvas-Rayo,J. G. Gonzalez-Rodriguez,J. Porcayo-Calderon,V. M. Salinas-Bravo,S. I. Maldonado-Ruiz
International Journal of Corrosion , 2012, DOI: 10.1155/2012/479761
Abstract: A study on the corrosion behavior of a series of experimental high-chromium (18.53–30.48?wt.%), high-carbon (3.82–5.17%) cast irons in NaCl-KCl (1?:?1?M) at 670°C has been evaluated by using weight loss technique and compared with a 304-type stainless steel. It was found that all castings had a higher corrosion rate than conventional 304SS and that the addition of Cr increased the degradation rate of the cast irons. Additionally, corrosion rate increased by increasing the C contents up to 4.29%, but it decreased with a further increase in its contents. Results are discussed in terms of consumption of the Cr2O3 layer by the melt. 1. Introduction The molten salt technology has been widely used in the industrial world because of its physical and chemical characteristics, especially its high electrical conductivity, high processing rate, and high diffusion rate. Recently, it has attracted much attention in the fields of jet engines, fuel cells, catalysts, metal refinement, as well as certain combustion conditions such as waste incinerators, biomass-fired boilers, and power stations [1–5]. Therefore, the studies on the corrosion of structural materials for handling high-temperature molten salts have also been continuously carried out. It is generally realized that Cr is not an effective element for corrosion resistance improvement of Fe-based and Ni-based alloys due to chloride salt attack [6–15]. However, by increasing the Cr contents, the corrosion resistance of Fe-based alloys could be increased. Problems with process equipment resulting from fireside corrosion have been frequently encountered in waste incinerators and biomass-fired boilers. The major problem is the complex nature of the feed (waste) as well as corrosive impurities which form low-melting point compounds with heavy and alkali metal chlorides which prevent the formation of protective oxide scales and then cause an accelerated degradation of metallic elements [1]. In particular, under reducing conditions such as those typical of the operation of waste gasification plants or even under localized reducing conditions, which frequently arise in the case of incorrect operation of waste incineration systems, it is difficult to form protective oxide scales such as , SiO2, and on the surface of structural materials. Thus, the corrosion attack can be further enhanced under reducing atmospheres in the presence of salt deposits [2]. High-chromium, high-carbon cast irons are commonly used in industrial conditions subjected to attrition and wear similar to the environment found in mining or coal cement
Effect of Minor Alloying Elements on the Corrosion Behavior of Fe40Al in NaCl-KCl Molten Salts
G. Salinas,J. G. Gonzalez-Rodriguez,J. Porcayo-Calderon,V. M. Salinas-Bravo,M. A. Espinoza-Medina
International Journal of Corrosion , 2012, DOI: 10.1155/2012/185842
Abstract: The hot corrosion behavior of Fe40Al intermetallic alloyed with Ag, Cu, Li, and Ni (1–5 at.%) in NaCl-KCl (1?:?1?M) at 670°C, typical of waste gasification environments, has been evaluated by using polarization curves and weight loss techniques and compared with a 304-type stainless steel. Both gravimetric and electrochemical techniques showed that all different Fe40Al-base alloys have a much higher corrosion resistance than that for stainless steel. Among the different Fe40Al-based alloys, the corrosion rate was very similar among each other, but it was evident that the addition of Li decreased their corrosion rate whereas all the other elements increased it. Results have been explained in terms of the formation and stability of an external, protective Al2O3 layer. 1. Introduction Sodium and potassium impurities present in the form of chloride or sulfates are very corrosive constituents under certain combustion conditions such as waste incinerators and biomass-fired boilers [1, 2]. Early failure of the thermal components frequently occurs due to the complex reactions between the metallic materials and the hostile combustion environment. Problems with process equipment resulting from fireside corrosion have been frequently encountered in incinerators. The major problem is the complex nature of the feed (waste) as well as corrosive impurities which form low-melting point compounds with heavy and alkali metal chlorides which prevent the formation of protective oxide scales and then causes an accelerated degradation of metallic elements [1]. In particular, under reducing conditions such as those typical of the operation of waste gasification plants or even under localized reducing conditions, which frequently arise in the case of incorrect operation of waste incineration systems, it is difficult to form protective oxide scales such as Cr2O3, SiO2, and Al2O3 on the surface of structural materials. Thus, the corrosion attack can be further enhanced under reducing atmospheres in the presence of salt deposits [2]. The effect of individual KCl, NaCl, and their mixtures with heavy metal chlorides or sulfates on the corrosion behavior of a series of alloy systems has been studied in detail so far [2–9]. It is generally realized that Cr is not as effective element for corrosion resistance of Fe-based and Ni-based alloys due to chloride attack. In contrast, alumina-(Al2O3-) forming alloys exhibit promising candidate materials considering the better high temperature resistance of alumina over chromia and their properties such as lower cost, low density, high
Caracterización de recubrimientos Ni-P depositados por reducción química autocatalítica en superficies internas
Porcayo-Calderón, J.,Sarmientos-Bustos, E.
Revista de Metalurgia , 1995,
Abstract: Electroless nickel deposition with sodium hypophosphite forms a Ni-P amorphous deposit with 4 to 12 % (in mass) P content. The corrosion resistance of this kind of coating depends on phosphorus content, and the phosphorus content depends on the operational conditions of the bath. Usually, this coatings are deposited by total immersion of the part, but when it is wished to coat only internal surfaces (as in tubes), it is necessary to recirculate the electroless nickel solution through the tube, in order to prevent the external surface from coating. This work shows the results of the characterization of electroless coatings deposited to protect internal surfaces. Based on this study we can say that it is possible to coat internal surfaces by this technique, and that the flow regimen does not affect the coating phosphorus content; on the other hand, the deposition rate and morphological characteristics are affected. El níquel depositado por reducción química autocatalítica con hipofosfito forma un depósito amorfo de Ni-P con un contenido de fósforo entre el 4 y el 12 % en masa. Su resistencia a la corrosión depende de la cantidad de fósforo codepositado, y éste, a su vez, de las condiciones de operación del ba o niquelante. Normalmente, este tipo de recubrimientos se aplica por inmersión total de la pieza, pero, cuando se desea proteger selectivamente la superficie interna (p. ej., en el caso de tuberías) es necesario recircular la solución niquelante y evitar que la superficie externa se niquele. Este trabajo presenta los resultados del estudio y caracterización de la aplicación de este tipo de recubrimientos para la protección de la superficie interna de las tuberías. Los resultados muestran que es posible proteger dicha superficie por medio de esta técnica y que el régimen de flujo no tiene efecto significativo alguno sobre el contenido de fósforo del recubrimiento, aunque sí lo tiene sobre las características morfológicas y su velocidad de deposición.
Comportamiento espacial de las larvas del mosquito verde Jacobiasca lybica, en un vi edo de secano en Andalucía, Espa a
J. F. Ramírez Dávila,E. Porcayo Camargo
Ciencia Ergo Sum , 2009,
Abstract: Se determina la distribución espacial de las poblaciones de larvas del mosquito verde Jacobiasca lybica en una parcela experimental de secano en Cádiz, Espa a. Los resultados demostraron que las poblaciones de larvas presentaron una distribución en agregados, lo que se observa en los mapas elaborados. Se determinó que el grado de infestación no alcanzaba el 100% de la parcela experimental, lo cual resulta interesante para poder dirigir las medidas de control sobre áreas específicas de infestación. Se logró determinar una estabilidad espacial y temporal a corto plazo de las poblaciones de larvas.
Quasiparticle spectrum of grain boundaries in d-wave superconductors
M. J. Calderon,E. Bascones
Physics , 1997,
Abstract: A grain boundary which separates domains with different orientation along the c-axis is analyzed. The coupling of two parallel superconducting planes whose order parameters are rotated leads to interesting properties which are expected to be common to other kinds of grain boundary. The density of states is enhanced at low energies. The number of localized states depends on the degree of misfit across the boundary. A continuum of zero energy states appears at certain values of the angle rotation.
Skyrmion Strings and Anomalous Hall Effect in Double Exchange Systems
M. J. Calderon,L. Brey
Physics , 2000, DOI: 10.1103/PhysRevB.63.054421
Abstract: We perform Monte Carlo simulations to obtain quantitative results for the anomalous Hall resistance, R_A, observed in colossal magnetoresistance manganites. R_A arises from the interaction between the spin magnetization and topological defects via spin-orbit coupling. We study these defects and how they are affected by the spin-orbit coupling within the framework of the double exchange model. The obtained anomalous Hall resistance is, in sign, order of magnitude and shape, in agreement with experimental data.
Composite Spin Waves, Quasi-Particles and Low Temperature resistivity in Double Exchange Systems
M. J. Calderon,L. Brey
Physics , 2000, DOI: 10.1103/PhysRevB.64.140403
Abstract: We make a quantum description of the electron low temperature properties of double exchange materials. In these systems there is a strong coupling between the core spin and the carriers spin. This large coupling makes the low energy spin waves to be a combination of ion and electron density spin waves. We study the form and dispersion of these composite spin wave excitations. We also analyze the spin up and down spectral functions of the temperature dependent quasi-particles of this system. Finally we obtain that the thermally activated composite spin waves renormalize the carriers effective mass and this gives rise to a low temperature resistivity scaling as T ^{5/2}.
Monte Carlo Simulations for the Magnetic Phase Diagram of the Double Exchange Hamiltonian
M. J. Calderon,L. Brey
Physics , 1998, DOI: 10.1103/PhysRevB.58.3286
Abstract: We have used Monte Carlo simulation techniques to obtain the magnetic phase diagram of the double exchange Hamiltonian. We have found that the Berry's phase of the hopping amplitude has a negligible effect in the value of the magnetic critical temperature. To avoid finite size problems in our simulations we have also developed an approximated expression for the double exchange energy. This allows us to obtain the critical temperature for the ferromagnetic to paramagnetic transition more accurately. In our calculations we do not observe any strange behavior in the kinetic energy, chemical potential or electron density of states near the magnetic critical temperature. Therefore, we conclude that other effects, not included in the double exchange Hamiltonian, are needed to understand the metal-insulator transition which occurs in the manganites.
Evaluación de Velocidades para la Deposición de FeSi y MoS2 por Triboadhesión en Aceros SAE 4140 y AISI 304
Rodríguez,J.M.; Colín,J.; Porcayo,J.; López,M.I.;
Información tecnológica , 2005, DOI: 10.4067/S0718-07642005000300004
Abstract: in this work a theoretical and experimental evaluation of the velocities required to deposit fesi and mos2 on sae 4140 and aisi 304 steels is presented. to achieve this goal, the friction factor between the cotton mop and the base material was determined. the deposition process by triboadhesion is caused by the heat generated by friction between the cotton mop and the base material. during the friction, the contact between these two elements generates high instant temperatures. in the study, it was experimentally demonstrated the deposition of the material, using the tangential velocity obtained from a theoretical analysis.
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