Some Thermodynamic Aspects of the Oxides of Chromium

To understand Cr emissions from slag melts to a vapor phase, an assessment of the stabilities of the chromium oxides at high temperatures has been carried out. The objective of the present study is to present a set of consistent data corresponding to the thermodynamic properties of the oxides of chromium, with special reference to the emission of hexavalent chromium from slags. In the current work, critical analysis of the experimental data available and a third analysis in the case of Cr2O3 have been carried out. Commercial databases, Fact Sage and ThermoCalc along with NIST-JANAF Thermochemical Tables, have been used for the analysis and comparisons of the results that are presented. The significant discrepancies in the available data have been pointed out. The data from NIST-JANAF Thermochemical Tables have been found to provide a set of consistent data for the various chromium oxides. An Ellingham diagram and the equations for the Delta G degrees (standard Gibbs free energy change) of formation of CrOx have been proposed. The present analysis shows that CrO3(g) is likely to be emitted from slag melts at high oxygen partial pressures. (C) The Minerals, Metals & Materials Society and ASM International 2014

Comparative Studies on the Bioremediation of Hexavalent and Trivalent Chromium using Citrobacter freundii: Part I-Effect of parameters controlling Biosorption

The potential of Citrobacter freundii, a Gram negative bacteria for the remediation of hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III))) from aqueous solutions was investigated. Bioremediation of Cr(VI) involved both biosorption and bioreduction processes, as compared to only biosorption process observed with respect to Cr(III) bioremediation. In the case of Cr(VI) bioremediation studies, about 59 % biosorption was achieved at an equilibrium time of 2 h, initial Cr(VI) concentration of 4 mg/L, pH 1 and a biomass loading of 5x10(11) cells/mL. The remainder, 41 %, was found to be in the form of Cr(111) ions owing to bioreduction of Cr(VI) by the bacteria resulting in the absence of Cr(VI) ions in the residue, there by meeting the USEPA specifications. Similar studies were carried out using Cr(III) solution for an equilibrium time of 2 h, Cr(III) concentration of 4 mg/L, pH 3 and a biomass loading of 6.3x10(11) cells/mL., wherein a maximum biosorption of about 30 % was achieved.

Effect of Pt doping on the gas sensing properties of porous chromium oxide films through a kinetic response analysis approach

The effect of doping trace amounts of noblemetals (Pt) on the gas sensing properties of chromium oxide thin films, is studied. The sensors are fabricated by depositing chromium oxide films on a glass substrate using a modified spray pyrolysis technique and characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The films are porous and nanocrystalline with an average crystallite size of similar to 30 nm. The typical p-type conductivity arises due to the presence of Cr vacancies, formed as a result of Cr non-stoichiometry, which is found to vary upon Pt doping. In order to analyze the effect of doping on the gas sensing properties, we have adopted a kinetic response analysis approach, which is based on Langmuir Adsorption isotherm (LA) theory. The sensor response is analyzed with equations obtained from LA theory and time constants as well as energies of adsorption-desorption are evaluated. It is seen that, Pt doping lowers the Schottky barrier height of the metal oxide semiconductor sensor from 222 meV to 172 meV. Subsequently the reduction in adsorption and desorption energies led to enhancement in sensor response and improvement in the kinetics of the sensor response i.e. the response time as well as recovery times of the sensor.

Damage mechanisms in stainless steel and chromium carbide coatings under controlled environment fretting conditions

Fretting is of a serious concern in many industrial components, specifically, in nuclear industry for the safe and reliable operation of various component and/or system. Under fretting condition small amplitude oscillations induce surface degradation in the form of surface cracks and/or surface wear. Comprehensive experimental studies have been carried out simulating different fretting regimes under ambient and vacuum (10(-9) MPa) conditions and, temperature up to 400 degrees C. Studies have been carried out with stainless steel spheres on stainless steel flats, and stainless steel spheres against chromium carbide, with 25% nickel chrome binder coatings. Mechanical responses are correlated with the damage observed. It has been observed that adhesion plays a vital role in material degradation process, and its effectiveness depends on mechanical variables such as normal load, interfacial tangential displacement, characteristics of the contacting bodies and most importantly on the environment conditions. Material degradation mechanism for ductile materials involved severe plastic deformation, which results in the initiation or nucleation of cracks. Ratcheting has been observed as the governing damage mode for crack nucleation under cyclic tangential loading condition. Further, propagation of the cracks has been observed under fatigue and their orientation has been observed to be governed by the contact conditions prevailing at the contact interface. Coated surfaces show damage in the form of brittle fracture and spalling of the coatings. Existence of stick slip has been observed under high normal load and low displacement amplitude. It has also been observed that adhesion at the contact interface and instantaneous cohesive strength of the contacting bodies dictates the occurrence of material transfer. The paper discusses the mechanics and mechanisms involved in fretting damage under controlled environment conditions. (C) 2015 Elsevier B.V. All rights reserved.

Conductometric Sensing of H-2 by Chromium Niobate

Investigations on chromium niobate (CrNbO4) have shown that the material responds to a wide hydrogen concentration range of 0.01%-0.40% at 613 K. The conductivity of CrNbO4 is independent of oxygen partial pressure and offers to be a promising candidate for monitoring H-2 in radioactive spent fuel storage facilities. Reduction of metal ions to lower valence states during hydrogen sensing was evidenced by X-ray photoelectron spectroscopic studies.

Characterization of a Laser-Discrete Quenched Steel Substrate/Chromium System by Dissolving Coatings

A laser-discrete quenched steel (LDQS) substrate/as-deposited chromium (top high-contraction (HC) and underlying low-contraction (LC) chromium) system was investigated by dissolving coatings in order to reveal the mechanism that the service life of the coated parts is largely improved using the hybrid technique of laser pre-quenching plus chromium post-depositing. It was found that the surface characteristics of the substrate, LC and HC chromium layer can be simultaneously revealed owing to the dissolution edge effect of chromium coatings. Moreover, the periodical gradient morphologies of the LDQS substrate are clearly shown: the surfaces of laser transformation-hardened regions are rather smooth; a lot of fine micro-holes exist in the transition zones; there are many micro-dimples in the original substrate. Furthermore, the novel method of dissolving coatings with sharp interfaces may be used to reveal the structural features of a substrate/coating system, explore the effect of the substrate on the initial microstructure and morphologies of coatings, and check the quality of the coated-parts.

Comportamiento agro-industrial de catorce variedades de caña de azúcar (Saccharum sp hibrido L.) en comparación con las variedades Ja 60-5 y C 87-51

El presente trabajo se llevó a cabo en el ciclo 92-93 en el Ingenio Victoria de Julio, donde se evaluaron 14 variedades de caña de azúcar en comparación con las variedades Ja 60 - 5 y C 87 - 51 para determinar el comportamiento agro-industrial de estos cultivares y seleccionar los genotipos más sobresalientes. El experimento fue establecido el 25 de enero de 1992, en un suelo arcilloso de la serie Chilamatillo, la cosecha se realizó a los 11 meses de edad del cultivo, el 16 de Dic 1992. El diseño utilizado fue de bloques completos al azar con 5 repeticiones, las variables estudiadas fueron: Germinación, población, altura de tallos, floración, diámetro de tallos, peso promedio de los tallos, rendimiento agrícola, rendimiento industrial y rendimiento agro-industrial. Los datos fueron sometidos a un análisis de varianza y prueba de tukey al 5% de margen de error. Los resultados obtenidos fueron los siguientes: Germinación; siendo las mejores RB 73-1012, CP 70-321 y Q 96. Población;las mejores numéricamente resultaron Méx 68-P 23,SP 70-1284 y SP 72-4790. Longitud de tallo; las mejores variedades fueron la SP 72-4790, Q 96, RB 73-1012 y RB 73-5220. Diámetro de los tallos; obtuvo el mejor resultado la variedad Méx 69-420 y en segundo lugar la Ja 60-5. Peso promedio de 100 tallos. ; presentando el mejor resultado el cultivar Méx 69-420 seguido de la RB 73-5220. Floración; todas las variedades florecieron a excepción del testigo C 87-51. Rendimiento agrícola; obtuvo el mejor resultado la variedad Méx 68-P 23 ocupando el segundo lugar SP 72-4790; Rendimiento industrial; entre las variedades sobresalieron numéricamente la Q 96 seguido de la C 87-51 y la CP 72-1210. Rendimiento Agro-Industrial; de acuerdo a los resultados de rangos múltiples la variedad Q 96 presenta un rendimiento estadísticamente superior a la variedad testigo Ja 60-5, superando numéricamente al resto de variedades. Las variedades que presentaron afectaciones por enfermedades fueron : RB 76-5288, SP 70-1284, SP 72-4790, CP 72-1210, SP 71-61801 CP 72-2086, Méx 69-420, Méx 68-P23, Ja 60-5 y e 87-51.

Efecto de aplicaciones de NPK sobre el crecimiento, desarrollo y rendimiento agroindustrial de la caña de azucar (Saccharum sp híbrido) variedad C87-51 en caña planta en el IBZ-CASUR S.A., Potosí, Rivas

El presente estudio se realizó en áreas de la finca "San Fernando" perteneciente al Ingenio Benjamin Zeledón (IBZ) de la Compañía Azucarera del Sur (CASUR, S.A.) ubicado en Potosí, departamento de Rivas (11005' LN y 86001' LO, a 70 msnm) con el objetivo de contribuir al incremento del rendimiento agroindustrial de la caña de azúcar se evaluaron el efecto de niveles de NPK: Nitrógeno (0, 80, 120 y 160 kg ha-1), Fósforo (0 y 60 kg ha-1) y Potasio (0, 60, 90 y 120 kg ha-1) sobre el crecimiento, desarrollo y rendimiento agroindustrial de la variedad C87-51. Los 32 tratamientos fueron distribuidos en un diseño de Bloques Completamente al Azar (BCA) con arreglo en Parcelas Subdivididas con tres réplicas. Se inició y estableció en la segunda semana de abril del 2003 y se cosechó en marzo del 2004. A los resultados de campo se les aplicó un análisis de varianza (ANDEVA) y separación de medias (Tukey ∞=0.05) sobre 13 variables cuantitativas. Asimismo, se utilizó un modelo estadístico de tendencia (lineal, cuadrática y cúbica) en el rendimiento agroindustrial para evaluar los niveles de N y K, y modelos de regresión múltiple en rendimiento. Se otuvieron efecto significativo en las variables de desarrollo y rendimiento, en el caso del P su efecto no fue significativo en el rendimiento. El mayor rendimiento agroindustrial se alcanzó en la combinación de 160–0–120 (9.34 Ton ha-1) y 160–60–120 (9.42 Ton ha-1), y presentó significancia estadística para una respuesta lineal y cúbica en N; para el caso del K la respuesta a los tres modelos establecidos fue significativa, pero con mayor significancia estadística la función lineal. La relación del rendimiento industrial a partir de rendimiento agrícola fue significativa con un ajuste cuadrático determinada por un R2 de 0.8671.

On the tensile behaviors of a hard chromium coating plated on a steel substrate with periodic subsurface inclusions

The tensile behaviors of a hard chromium coating plated on a steel substrate with periodic laser pre-quenched regions have been investigated by experimental and theoretic analysis. In the experiment, three specimens are adopted to study the differences between homogeneous and periodic inhomogeneous substrates as well as between periodic inhomogeneous substrate of relatively softer and stiffer materials. The unique characteristics have been observed in the specimen of periodic inhomogeneous substrate under quasi-static tension loading. With the periodic laser pre-quenched regions being treated as periodic subsurface inclusions (PSI), the unique stress/strain pattern of the specimen is obtained by analytical modeling and FEM analysis, and the mechanisms accounting for the experimental results is preliminarily illustrated.

Characteristics of the interface of a laser-quenched steel substrate and chromium electroplate

The interface of a laser-discrete-quenched steel substrate and as-deposited chromium electroplate was investigated by ion beam etching, dissolving-substrate-away and using a Vickers microhardness tester, in an attempt to reveal the mechanism that the service life of the chromium-coated parts is increased by the duplex technique of laser pre-quenching plus chromium post-depositing. The laser quenching of the steel substrate can reduce the steep hardness gradient at the substrate/chromium interface and improve the load-bearing capacity of chromium electroplate. Moreover, the laser quenching prior to plating has an extremely great effect on the morphologies and microstructure of the substrate/chromium interface: there is a transient interlayer at the original substrate/chromium interface while there is not at the laser-quenchedzone/chromium interface; the near-substrate surface microstructure and morphologies of the free-standing chromium electrodeposits, whose substrate was dissolved away with nital 30% in volume, inherit the periodically gradient characteristics of the laser-discrete-quenched substrate surface. (c) 2006 Elsevier B.V. All rights reserved.

Degradation failure features of chromium-plated gun barrels with a laser-discrete-quenched substrate

The effect of substrate laser-discrete quenching on the degradation failure of chromium-plated gun barrels was metallurgically investigated. The results show that substrate laser-discrete quenching changes the failure patterns of chromium coatings during firing, and some periodic through-thickness cracks in the fired chromium coatings are justly located at original substrate zones between two adjacent laser-quenched tracks. Moreover, chromium coatings and the laser-quenched zones on the substrate are simultaneously degraded in microstructure and property during firing. Furthermore, the periodic structure of the laser-discrete-quenched steel (LDQS) substrate near the breech remains after firing, and the hardness of the fired laser-quenched zones is still higher than that of original substrates. The specific failure features were utilized to illustrate the mechanism of the extended service life of chromium-plated gun barrels with the LDQS substrate. (c) 2007 Elsevier B.V All rights reserved.

Prudentia Iuris, 2000, n° 51 (número completo)

Contenido: Editorial – Romanística: Los aportes jurídicos de las “Noches Aticas” / Edmundo J. Carbone – Los riesgos de los viajeros en el Derecho Romano / Alfredo Gustavo Di Pietro – Derivación vulgar y bizantina del contrato estimatorio de Ulpiano / Alvaro DOrs – Derecho Internacional Privado: El contrato internacional de transporte de mercaderías a través de un sobrevuelo / Raúl Alberto Ramayo – La naturaleza de los tratados de extradición en los fallos de la Corte en los casos Priebke y Liendo Arriaga / Fernando Rolandelli – Las empresas de origen comunitario / María Luján Claro de Gandía – Derecho Ambiental Internacional / María Solange Jonas Aguilar – Régimen internacional de la propiedad inmaterial / Carlos J. Martínez Casado ; María Solange Jonas Aguilar – Derecho Internacional Público: El legado de Vietnam : la amenaza y el uso de la fuerza en la política exterior norteamericana / Hernando V. Cañardo – La personalidad jurídica de la soberana militar Orden de Malta / Juan Manuel Gramajo – Derecho Penal Internacional / Fernando Rolandelli – Documentos -- Recensiones

Efecto de siete niveles de nitrógeno, fósforo y zinc sobre algunos componentes de rendimiento del frijol variedad 510-51 (Phaseolus vulgaris L.)

El frijol es uno de los cultivos mas importantes en Nicaragua. Datos estadísticos indican que este cultivo ocupa el segundo lugar en importancia como alimento básico y el quinto lugar en cuanto al valor nutricional. Durante los últimos años se han obtenido bajos rendimientos y para 70-71 se obtuvo un rendimiento promedio de 537.2 kilogramos por hectárea (5). Como se puede observar el rendimiento promedio nacional es muy bajo. Para incrementar este rendimiento ademas de sembrar con variedades mejoradas se debe hacer necesario buscar los niveles mas adecuados de Fertilización. Se ha observado en la zona de Masatepe una aparente deficiencia de ciertos elementos menores y en especial del Zinc manifestándose con síntomas de necrosis general y deformaciones semejantes a rosetas en las yemas foliar en el cultivo de frijol (13). Este ensayo se llevo a efecto el 4 de octubre de 1973 en la Estación Regional de Diversificación Agrícola Campos Azules. El objetivo de este trabajo fue evaluar el efecto del Nitrógeno, Fósforo y Zinc respectivamente. En la evaluación de los datos de rendimiento se empleo el diseño Guadalupe y Bloque al azar con dos repeticiones. De acuerdo a los resultados para altura de planta, el efecto de los tratamientos fue estadisticamente significativo al nivel de 1 por ciento de probabilidad correspondiendo las mayores alturas para las dosis de 75-125-9, 75-150-9 y 150-150-18 kg/ha, de N-P-Zn respectivamente. El análisis de numero de vainas por planta muestra diferencias significativas entre tratamientos lo mismo que para el rendimiento de grano siendo los niveles adecuados para rendimiento en la zona de Masatepe el 150-150-0 y 75-75-0 kg/ha, de N-P-Zn con 1 101 y 1 044 kg/ha respectivamente.

Deputados brasileiros : repertório biográfico : 51ª legislatura, 1999-2003

Reúne as informações pessoais e sobre a vida profissional e política dos 513 deputados eleitos no pleito de outubro de 1998, no momento inicial da 51ª Legislatura, tendo por objetivo constituir-se em importante fonte de pesquisa e de preservação da memória da Câmara dos Deputados

Plano do carvão nacional : projeto nº 1.045/51

Registra a tramitação do Plano do Carvão Nacional, na Câmara dos Deputados e no Senado Federal, de 24 de agosto de 1951 a 25 de novembro de 1952. Inclui as sessões, atas de reuniões, relatórios, pareceres, emendas. Reúne debates de plenário e comissões, pareceres, vetos, discursos, atas de reuniões e outros documentos parlamentares, mensagens presidenciais, etc.