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Sample records for aleacion al-si tipo

  1. Experiencias de calorimetría diferencial de barrido en aleaciones Al-Si

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    Carolina López-Eckerdt

    2016-01-01

    Full Text Available La observación de agujas características de una transformación displaciva en aleaciones U-Al-Si en el entorno del compuesto U3Si5 evidencia la necesidad de analizar las distintas transformaciones que ocurren durante el enfriamiento utilizando una técnica dinámica de identificación de transformaciones (calorimetría diferencial de barrido. Para evaluar la versatilidad de esta técnica, se estudiaron aleaciones Al-Si con concentraciones de Si entre 0,6% y 7,1% en peso. Se determinaron las temperaturas liquidus y eutéctica de cada aleación y se estimó la entalpía de formación de los precipitados de Si y de la reacción eutéctica. Los resultados reproducen las temperaturas de ambas reacciones según el diagrama de equilibrio del sistema binario Al-Si. Para el cálculo de las entalpías de transformación resulta indispensable obtener el porcentaje de fase transformada por otras técnicas de caracterización una vez finalizado el ensayo.

  2. Comportamiento a tracción a temperaturas ambiente y elevadas de nuevos composites basados en aleaciones hipereutécticas de Al-Si

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    Valer, J.

    1997-02-01

    Full Text Available This work shows the improvement obtained on tensile stress at room and high temperatures of hypereutectic Al-Si alloys. These alloys are produced by a combination of spray-forming, extrusión and thixoforming process, in comparison with conventional casting alloys. Al-25%Si-5%Cu, Al- 25%Si-5%Cu-2%Mg and Al-30%Si-5%Cu alloys have been studied relating their microstructural parameters with tensile stress obtained and comparing them with conventional Al-20%Si, Al-36%Si and Al-50%Si alloys. Al-25%Si-5%Cu alloy was tested before and after semi-solid forming, in order to distinguish the different behaviour of this alloy due to the different microstructure. The properties obtained with these alloys were also related to Al-SiC composites formed by similar processes.

    En este trabajo se muestra la mejora obtenida en la resistencia a la tracción a temperatura ambiente y a elevadas temperaturas de aleaciones hipereutécticas de Al-Si producidas por una combinación de un proceso de solidificación rápida y del conformado en estado semisólido, en comparación con aleaciones obtenidas por procedimientos convencionales de inyección en estado líquido. Se han estudiado las aleaciones Al-25%Si-5%Cu, Al-25%Si-5%Cu-2%Mg y Al-30%Si-5%Cu, relacionando sus parámetros microestructurales con las resistencias a tracción obtenidas, y se han comparado con las aleaciones binarias Al-20%Si, Al-36%Si y Al-50%Si. La aleación Al-25%Si-5%Cu se ha ensayado antes y después del conformado en estado semisólido, lo que ha permitido conocer la diferencia en el comportamiento de la aleación como consecuencia de la distinta microestructura. También se comparan las propiedades obtenidas en estas aleaciones con las que presentan composites de aleaciones de aluminio reforzados con partículas de SiC y procesados por métodos similares.

  3. Effect of NaCl upon an Al-Si casting alloy hipoeutec; Efecto del NaCl sobre una aleacion de Al-Si hipoeutectica vaciada

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    Martinez Delgado, E.J.; Ortega de la Rosa, R. [Istituto Tecnologico de Zacatecas, Zacatecas (Mexico)]. E-mail: enriquemartinez_1999@yahoo.com; rubin_ortega_2002@yahoo.com.mx; Cisneros Guerrero, M.A. [Instituto Tecnologico de Saltillo, Saltillo, Coahuila (Mexico)]. E-mail: cisneros@its.mx; Haro Rodriguez, S. [Universidad Autonoma de Zacatecas, Zacatecas, Zacatecas (Mexico)]. E-mail: haros907@hotmail.com

    2009-10-15

    This work, comprehends the study about the effect of NaCl kind Halite upon the morphology of eutectic Silicon and porosity in a cast hipoeutectic Al-Si alloy. The melting was carried out in two furnaces, the first to combustion of LP gas in graphite crucible to increase the content of Si in the alloy from 0.13 to 5% wt using metallic silicon with a purity of 99.35% wt, and the second of electric resistances in the same kind of crucible to control the temperature at 750 degrees Celsius. The melting material was casting into molds of sand shell. To add the salt into the metallic bath, two techniques were used; one with injection by means of Argon gas and the other on by gravity, both cases three quantities of salt were used, 0.5, 1.5 and 2.5% wt respectively, powdered and preheated at 150 degrees Celsius during 60 min. The obtained samples were analyzed metallographily evidencing the modification of the eutectic Si, presenting the best results the samples with 1.5 and 2.5% wt of salt added by gravity. Too was obtained effect of Salt upon the degassing of bath metallic, where the simples with 1.5% wt presented the best results. Finally, by means of Scanning Electron Microscopy, the precipitates present were characterized in the samples. [Spanish] Este trabajo comprende el estudio del efecto del NaCl tipo Halita sobre la morfologia del Si eutectico y la porosidad en una aleacion fundida Al-Si hipoeutectica. La fusion se llevo a cabo en dos hornos, el primero a combustion con gas LP en crisol de grafito con la finalidad de incrementar el contenido de Si en la aleacion de 0.13 a 5% en peso, utilizando silicio metalico con una pureza de 99.35%, y el segundo de resistencias electricas en el mismo tipo de crisol para controlar la temperatura a 750 grados Celsios. El material fundido fue vaciado en modelos de arena. La sal se anadio al bano metalico a 0.5, 1.5 y 2.5% en peso, respectivamente, pulverizada y precalentada a 150 grados Celsios durante 60 min, mediante dos

  4. Comportamiento a la corrosión electroquímica de aleaciones MgAl con recubrimientos de materiales compuestos Al/SiCp mediante proyección térmica

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    Pardo, A.

    2010-04-01

    Full Text Available The corrosion protection of Mg-Al alloys by flame thermal spraying of Al/SiCp composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiC particles (SiCp varied between 5 and 30%. The as-sprayed Al/SiCp composite coatings revealed a high number of micro-channels, largely in the vicinity of the SiC particles, that facilitated the penetration of the electrolyte and the subsequent galvanic corrosion of the magnesium substrates. The application of a cold-pressing post-treatment reduced the degree of porosity of the coatings and improved the bonding at the coating/substrate and Al/SiC interfaces. This resulted in improved corrosion resistance of the coated specimens. The effectiveness of the coatings slightly decreased with the addition of 5-30 vol.% SiCp compared with the unreinforced thermal spray aluminium coatings.

    Se estudia, mediante espectroscopía de impedancia electroquímica en solución 3,5 % NaCl, la protección frente a la corrosión de aleaciones Mg-Al recubiertas por proyección térmica con materiales compuestos Al/SiCp. Se varió la fracción de volumen de las partículas de SiC (SiCp entre 5 y 30 %. Los recubrimientos efectuados por proyección térmica revelan un elevado número de microcanales, en la vecindad de las partículas de SiC, que facilitan la penetración del electrolito originando procesos de corrosión galvánica en los substratos de las aleaciones de magnesio. Un tratamiento posterior mediante la aplicación de una presión en frío reduce el grado de porosidad de los recubrimientos y mejora la unión, tanto entre el substrato y el recubrimiento como entre las partículas de aluminio y SiC, mejorando la resistencia a la corrosión de las aleaciones recubiertas. La efectividad de los recubrimientos disminuye ligeramente con la adición de SiCp cuando se comparan con los mismos recubrimientos de aluminio sin refuerzo.

  5. Prediction of hardness of the Zn-Al-Cu alloys of agreement by composition in weight; Prediccion de la dureza de la aleacion Zn-Al-Cu de acuerdo a su composicion en peso

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    Villegas-Cardenas, Jose David; Camarillo-Villegas, Alejandra; Juanico-Loran, Antonio [Universidad Politecnica del Valle de Mexico, Tultitlan, Estado de Mexico (Mexico)]. E-mails: jdvc76@yahoo.com.mx; v_c_a_77@hotmail.com; ajuanico@yahoo.com.mx; Espinosa-Rojas, Raul [Universidad Autonoma Metropolitana, Unidad Azcapotzalco (Mexico)]. E-mail: rer21@hotmail.com; Camacho-Olguin, Carlos [Universidad Politecnica del Valle de Mexico, Tultitlan, Estado de Mexico (Mexico)]. E-mail: ccamacho@upvm.edu.mx

    2013-07-15

    Ten alloys Zn-Al-Cu were developed in two parts, in agreement to two zones presented in the isopleth diagrams (Villas et al., 1995). The percentage of Cu and Al was systematically varied. Subsequently, hardness measurements were performed. These measurements allowed establishing two equations that predict the hardness with an error lower than 5%. With these equations, it is possible to obtain alloys that replace Al base alloys by a Zn base alloy, having the same hardness. This implicates also the elimination of the volumetric change in the presence of e phase. [Spanish] Se desarrollaron diez aleaciones Zn-Al-Cu divididas en dos partes, de acuerdo a dos zonas presentadas en los diagramas isopleticos de Hans (Villas et al., 1995). Se incremento el porcentaje de Cu y Al paulatinamente. Posteriormente se desarrollaron pruebas de macrodureza y de ese analisis se obtuvieron dos ecuaciones que permiten pronosticar y disenar aleaciones de una dureza determinada de acuerdo a su porcentaje en peso de cada elemento, con un error menor que 5%. Como se demuestra en este trabajo, con estas ecuaciones es posible desarrollar aleaciones sustitutas base aluminio por una aleacion base zinc o viceversa, teniendo la misma dureza para cada tipo de aleacion y eliminando el problema del cambio volumetrico debido a la presencia de la fase e.

  6. Metalografía a color en aleaciones Al-Si comerciales. Optimización de las técnicas de caracterización microestructural mediante microscopía óptica de reflexión

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    Vander-Voort, G. F.

    2010-10-01

    Full Text Available The present demand on alloy production with improved quality requires the optimization of the metallographic procedures used on its characterization. Traditional etching techniques commonly employed for phase identification by optical metallography in aluminium alloys are not always suitable for a detailed analysis of existing phases, nor to accurately predict the mechanisms that govern the solidification process in certain detail. This work explores the potential of colour metallography to reveal at its best as-cast microstructures in Al-Si 12 alloys. For this purpose a colour etching technique, specifically developed for aluminium alloys and based on the Weck reagent. The application of such etchant has allowed the qualitative characterization of the microstructure. And it has also shown the advantages of colour metallography over black and white (B&W etching techniques.La demanda de aleaciones con calidades optimizadas conlleva la mejora continua de estas calidades, lo que viene suscitando la necesidad de mejora y optimización permanentes de las técnicas de caracterización metalográfica. Las técnicas de ataque tradicionales, utilizadas en la observación microscópica de las aleaciones de aluminio, no permiten un análisis detallado de la evolución microestructural de las fases presentes ni de parte de los mecanismos que rigen la solidificación. En el presente trabajo, se explora el potencial de la metalografía en color aplicada a las estructuras de solidificación de aleaciones Al-Si 12. Se ha utilizado un procedimiento de ataque en color, basado en un reactivo desarrollado porWeck para aleaciones de aluminio. El empleo de esta técnica ha permitido la evaluación cualitativa de la microestructura. La técnica ha permitido revelar características microestructurales que los métodos de ataque en blanco-negro no revelan.

  7. Fabricación de la aleación Au-Si para utilización como soldadura blanda de aleaciones de oro

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    Julián Tobón

    2013-09-01

    Full Text Available La Aleación Au-Si en su composición eutéctica presenta un punto de fusión cercano a los 369ºC y color similar al oro de alta ley. En este estudio se presentan resultados de fabricación de las aleaciones de oro con 2,5; 2,8 y 3,0 % de silicio, por medio de la fusión en un horno de plasma con atmósfera inerte de argón. Se realizó caracterización de composición química por espectroscopía de dispersión de energía (EDS y espectrometría de dispersión de longitud de onda (WDS, análisis metalográfico y microestructural por microscopía óptica, SEM y DRX, dureza y microdureza Vickers, evaluación del punto de fusión por DSC y determinación de las coordenadas colorimétricas SCIELab. A nivel microestructural las aleaciones muestran pequeñas formaciones dendríticas ricas en oro y el constituyente eutéctico formado por precipitados de silicio aciculares en una matriz de oro. Los resultados de dureza y microdureza dieron valores alrededor de los 110HV, presentándose un importante aumento en las propiedades mecánicas con respecto a las aleaciones tradicionales de oro de alta pureza. La temperatura de fusión para las aleaciones se ubicó en los 374°C, además de presentar un color muy cercano a los valores del oro puro.

  8. Microstructural effects of phosphorus on pressure die cast Al-12Si components

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    Suárez-Peña, B.

    2007-10-01

    Full Text Available The refinement of cuboidal silicon in eutectic Al-Si alloys by phosphorus additions used to manufacture pressure die cast components was studied. The results show that the addition of phosphorus in the form of AlFeP mother alloy before process degassing, leads to the best refinement of the size of the Si-cuboids phase, among several phosphorus additions analysed in the present research.

    Se ha estudiado el afino del silicio cuboidal en aleaciones eutécticas Al-Si por acción del fósforo, en piezas obtenidas mediante la técnica de fundición a presión. Tras la adición de fósforo en pruebas industriales, en las que dicho elemento se incorpora al baño con diversas composiciones, los mejores resultados se obtienen con la adición de la aleación madre AlFeP, previa al desgasificado industrial.

  9. Elaboración de aleaciones de Cu-Al-Ni con efecto memoria de forma mediante pulvimetalurgia

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    Pérez-Sáez, R. B.

    1998-05-01

    Full Text Available During the production of shape memory alloys, a very fine grain size should be obtained in order to obtain better mechanical properties and a good thermomechanical behaviour during cycling. The classically used grain refiners show some secondary effects on the martensitic transformations that could be at the origin of some technological problems. For this reason, a new processing method by powder metallurgy has been developed for this kind of alloys. The three proceeding stages are described: Atomization, hot isostatic pressing and hot rolling. The microstructure of the materials is characterized. The martensitic transformation and the thermomechanical properties are also studied.

    En la elaboración de aleaciones Cu-Al-Ni con efecto memoria de forma es importante conseguir un tamaño de grano fino, para mejorar las propiedades mecánicas y el comportamiento durante el ciclado termomecánico. Clásicamente, esto se ha conseguido mediante la adición de refinadores de grano; sin embargo, los efectos secundarios que éstos producen pueden ser problemáticos. Por esta razón, se ha desarrollado un nuevo método de procesado de este tipo de aleaciones mediante pulvimetalurgia. En este trabajo se presenta el proceso de elaboración consistente en tres etapas: atomización, compactación isostática en caliente y laminación en caliente. Se estudia la microestructura del material, se caracteriza la transformación martensítica y se determinan las propiedades termomecánicas.

  10. An electrochemical investigation of the corrosion behavior of Al-Si-Cu hypereutectic alloys in alcoholic environments

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    Traldi, S. M.

    2003-12-01

    Full Text Available Al-Si-Cu hypereutetic alloys produced by spray forming are mostly used in the automotive industry, especially for cylinder liners. They have the advantage of low weight associated with low coefficient of thermal expansion and excellent mechanical properties - mainly wear resistance at high temperatures. The corrosion resistance of these alloys in fuels, particularly alcoholic media, however is not yet known. In this investigation, electrochemical impedance spectroscopy (EIS and potentiodynamic polarisation have been used to evaluate the corrosion resistance of a hypereutectic Al-Si-Cu alloy in alcoholic environments. The EIS tests were carried out in pure ethanol, and ethanol with small additions (1 mM of acid and chloride, to investigate the effect of these contaminants on corrosion resistance. The corrosion resistance of a grey cast iron has also been evaluated in pure ethanol for comparison. The Al-Si-Cu alloy showed high corrosion resistance in pure ethanol, far superior to that of grey cast iron in the same medium.

    Aleaciones hipereutécticas producidas por conformación por spray son muy empleadas en la industria automovilística, especialmente en los revestimientos de los cilindros. Tienen la ventaja de añadir menos peso con bajo coeficiente de expansión térmica y excelentes propiedades mecánicas, sobre todo resistencia al desgaste en altas temperaturas. Todavía, la resistencia a la corrosión de estas aleaciones en combustibles no es conocida. En este estudio fueron utilizadas las técnicas de espectroscopia de impedancia electroquímica y polarización potenciodinámica, para evaluar la resistencia a la corrosión de una aleación hipereutéctica Al-Si-Cu en medio alcohólico. Las pruebas fueron conducidas en etanol puro y etanol con pequeñas adiciones (1 mM de ácido y cloruro, con la finalidad de investigar el efecto de estos contaminantes en la resistencia a la corrosión. Hierro fundido gris, también fue

  11. Aleaciones de aluminio amorfas y nanoestructuradas

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    García-Escorial, A.

    1998-05-01

    Full Text Available The work carried out in CENIM on amorphous and nanostructured aluminium alloys is described. Results about Al-LTM-ETM, Al-Fe-Nb and Al-Cu-Zr, and Al-LTM-RE, Al-Fe-Nd (LTM = Late Transition Metal, ETM = Early Transition Metal y RE = Rare Earth alloys obtained by rapid solidification, inert gas atomization and melt-spinning, as well as mechanical alloying are presented.

    En este trabajo se recoge la labor desarrollada en el CENIM en aleaciones de base aluminio amorfas y nanoestructuradas. Se presentan los resultados obtenidos hasta ahora en el estudio de aleaciones Al-LTM-ETM, Al-Fe-Nb y Al-Cu-Zr, y Al-LTM-RE, Al-Fe-Nd (LTM = Late Transition Metal, ETM = Early Transition Metal y RE = Rare Earth, procesadas por solidificación rápida, mediante atomización por gas inerte y temple ultrarrápido sobre rueda, así como por aleado mecánico en molino de bolas de alta energía.

  12. Estudio de aleaciones amorfas Hf1-x Cux mediante correlaciones angulares perturbadas

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    Damonte, Laura Cristina

    1988-01-01

    Con la intención de contribuir a un mejor entendimiento de la estructura atómica local en aleaciones del tipo MT-MT, en este trabajo de tesis se realiza un estudio, mediante la aplicación de la técnica TDPAC, sobre aleaciones amorfas Hf1-x Cux (x=0.33, 0.44, 0.50, 0.59) y sus contrapartes cristalinas. Muy pocos trabajos han sido publicados sobre este sistema. El objetivo general de este trabajo es analizar el orden local en estas aleaciones, su evolución con tratamientos térmicos (r...

  13. Desarrollo de aleaciones multifuncionales con base titanio

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    Pareja, Ramiro

    2007-01-01

    El Laboratorio de Materiales Nano-estructurados y Multifuncionales del Departamento de Física de la Universidad Carlos III de Madrid se dedica al desarrollo, procesado y caracterización de aleaciones con propiedades mejores que las preparadas por métodos convencionales. La mejora de las propiedades se consigue produciendo las aleaciones con un tamaño de grano nanométrico o ultrafino, o introduciendo una dispersión de nano-partículas de óxido en la matriz. El grupo está interesado en algún tip...

  14. Desarrollo calorimétrico del proceso de precipitación en aleaciones Cu-Co-Si

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    Donoso, E.

    2005-12-01

    Full Text Available Using differential scanning calorimetry (DSC the precipitation processes of supersaturated solid solutions of three Cu-Co-Si alloys, with a constant cobalt composition, were studied. Thermograms, and previous studies, reveal that the decomposition begins with cobalt precipitation. Clustering of cobalt initiates the silicon precipitation, finally Co2Si stoichiometric particles are formed. Volume fractions are determined by the amount of cobalt present in these alloys. It is inferred that surplus silicon atoms retained in the solution increase the reaction rate. Kinetic parameters were calculated by a method based in the Mehl-Johnson-Avrami (MJA formalism. The lower activation energy obtained, associated with cobalt clustering is attributed to the contribution of quenched-in vacancies.

    Mediante calorimetría diferencial de barrido (DSC se estudió el proceso de precipitación de soluciones sólidas supersaturadas de tres aleaciones de Cu-Co-Si, con composición de cobalto constante. Evaluaciones entalpimétricas y estudios previos, revelaron que la descomposición comienza con la precipitación de cobalto. El agrupamiento de átomos de cobalto inicia la precipitación del silicio, formándose finalmente partículas de composición estequiométricas de Co2Si. Las fracciones volumétricas fueron determinadas en función de la cantidad de cobalto presente en estas aleaciones. Se infiere que el superávit de átomos de silicio retenidos en la solución aumenta la velocidad de reacción. Los parámetros cinéticos fueron calculados a partir de un método basado en el formalismo de Mehl- Johnson-Avrami (MJA. La energía de activación más baja obtenida, asociada con el apilamiento de cobalto, se atribuyó a la contribución de las vacantes retenidas por temple.

  15. Corrosion of high temperature resisting alloys exposed to heavy fuel ash; Corrosion de aleaciones resistentes a altas temperaturas expuestas a ceniza de combustoleo pesado

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    Wong Moreno, Adriana del Carmen

    1998-03-01

    content of vanadium and very low content of sulfur at temperatures near the point of fusion of he vanadium compounds that constitute them. The development of the processes of metallic deterioration that are included in the proposed model was documented through this investigation, for an alloy range, from low alloy steels to nickel based super alloys, as well as for a series of ash deposits whose composition covers a part of the spectra of combinations of sodium/sulfate vanadates that little has been explored. Among the more relevant aspects that were documented and included in the proposed global mechanism, stand out the following ones: The global mechanism of corrosion by ashes of heavy fuel oil based on 3 primary processes of alloy degradation is described: metallic dissolution, accelerated oxidation and sulfidazation. The influence that the temperature and the composition of the ash on the predominance of one or another degradation mechanism has. It is also analyzed how the transformation of the underlying zone to the metal/deposit interphase by diffusion processes and precipitation accelerates the kinetics of degradation of the alloy, particularly, it has been considered the change in the concentrations of Cr, Al and Si, and the sulfide precipitation. Finally, the results obtained contribute in addition with practical information on the alloy performance, which allows to establish an order of merit among the evaluated alloys as far as its resistance to the corrosion, and on the roll of the main alloyings in its behavior of corrosion by fuel oil ash deposits. [Espanol] El objetivo de la investigacion realizada fue estudiar el proceso de degradacion por corrosion a alta temperatura de aleaciones expuestas a cenizas de combustoleo pesado a traves de una evaluacion experimental comparativa de su desempeno que permitio establecer los mecanismos involucrados en el fenomeno. La experimentacion llevada a cabo involucro la determinacion de la resistencia a la corrosion de 14

  16. Electrochemical corrosion behaviour of Mg-Al alloys with thermal spray Al/SiCp composite coatings; Comportamiento a la corrosion electroquimica de aleaciones MgAl con recubrimientos de materiales compuestos Al/SiCp mediante proyeccion termica

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    Pardo, A.; Feliu Jr, S.; Merino, M. C.; Mohedano, M.; Casajus, P.; Arrabal, R.

    2010-07-01

    The corrosion protection of Mg-Al alloys by flame thermal spraying of Al/SiCp composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiC particles (SiCp) varied between 5 and 30%. The as-sprayed Al/SiCp composite coatings revealed a high number of micro-channels, largely in the vicinity of the SiC particles, that facilitated the penetration of the electrolyte and the subsequent galvanic corrosion of the magnesium substrates. The application of a cold-pressing post-treatment reduced the degree of porosity of the coatings and improved the bonding at the coating/substrate and Al/SiC interfaces. This resulted in improved corrosion resistance of the coated specimens. The effectiveness of the coatings slightly decreased with the addition of 5-30 vol.% SiCp compared with the un reinforced thermal spray aluminium coatings. (Author) 31 refs.

  17. Propiedades mecánicas y mecanismos de deformación en aleaciones del sistemas Fe-xMn-3,2Al-0,2C (12 ≤ x ≤ 43

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    Rodríguez, V. F.

    1998-05-01

    Full Text Available Microstructure and mechanical properties of Fe-xMn-3,2Al-0,23C alloys with 12 ≤ x ≤ 43 (mass % at 77 and 290 K have been studied to determine the mechanisms controlling plastic deformation. Austenitic alloys (Mn ≥ 22 show an increase of elongation to failure with decreasing temperature of testing (inverse ductility. This behavior has been related to formation of deformation twins, which is favored at 77 K. Alloys with manganese content lower than 17 % present a two-phase microstructure (α' + γ. The martensite volume fraction increases as the manganese content decreases. These alloys show a loss of ductility, especially at 77 K. In contrast to asutenitic alloys, this different mechanical behavior has been associated with a TRIP mechanism (transformationinduced plasticity.

    Se han estudiado la microestructura y las propiedades mecánicas a 77 y 290 K de una serie de aleaciones Fe-xMn-3,2Al-0,23C con 12 ≤ x ≤ 43 (% en masa con objeto de determinar los mecanismos que controlan la deformación plástica. Se ha comprobado que, en las aleaciones con estructura austenítica (Mn ≥ 22, el alargamiento a rotura aumenta al disminuir la temperatura de ensayo (ductilidad inversa. Este comportamiento se ha relacionado con un proceso de deformación por maclaje favorecido a 77 K. Las aleaciones con contenidos de manganeso < 17 % presentan una estructura bifásica (α' + γ, siendo mayor la fracción de volumen de martensita a medida que disminuye la concentración de manganeso. Estas aleaciones presentan una disminución del alargamiento a rotura especialmente a 77 K. El diferente comportamiento mecánico con respecto al de las aleaciones austeníticas se asocia a un proceso de transformación a martensita inducida por deformación (TRIP.

  18. Description of hypoeutectic Al-Si-Cu alloys based on their known chemical compositions

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    Djurdjevic, M. B.

    2013-10-01

    interés durante las últimas décadas, y la cantidad de programas de simulación existentes en el mercado es un buen indicador del interés de la industria en este campo. La mayoría de los datos empleados en estos programas se basan en los diagramas de fase binarios, ternarios o incluso superiores. Desafortunadamente, excepto para los diagramas binarios, el ajuste de los datos no es lo suficiente bueno. Teniendo en cuenta que la mayoría de los sistemas binarios del aluminio están bien definidos se ha intentado convertir los sistemas multi-componentes en un pseudo binario sistema Al-Xi (en este caso el diagrama de fase Al-Si es el elegido como sistema de referencia. El nuevo algoritmo del Silicio Equivalente (SiEQ expresa la cantidad de los elementos de la aleación que son mayoritarios y minoritarios, a través de una cantidad “equivalente” de silicio. Este sistema puede emplearse para calcular varias características termo-físicas y de solidificación de sistemas multicomponentes, como las aleaciones de aluminio. Esto permite al modelo tener la capacidad de realizar predicciones de las características de la solidificación de las piezas fundidas, donde las velocidades de enfriamiento son bajas y las características del proceso de solidificación son bien conocidas, para evitar posibles problemas en la fundición. Este trabajo demuestra cómo el algoritmo del SiEQ puede ser empleado para el cálculo de las características de las temperaturas de solidificación de las aleaciones multi-componentes Al-Si, así como sus calores latentes y el factor de restricción del crecimiento del grano. El análisis estadístico de los resultados obtenidos en un amplio rango de composiciones químicas de la aleación, muestra una muy buena correlación entre los datos experimentales y los cálculos realizados con el SiEQ. La misma aproximación matemática podría ser aplicada para otros sistemas metálicos como el hierro y el magnesio, empleando el carbono equivalente en el

  19. Transformaciones de fase en aleaciones Zn-22%Al-2%Cu y Zn-22%Al-2%Cu-X (X = 1, 2 y 3%Ag envejecidas isotérmicamente

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    Flores-Ramos, Alfredo

    2014-12-01

    Full Text Available The study of phase transformations that take place in Zn-22%Al-2%Cu and Zn-22%Al-2%Cu-X (X = 1, 2 and 3%Ag alloys was carried out using X-Ray Diffraction (XRD and Scanning Electron Microscopy (SEM. Alloys were homogenized at 350 °C during 10 days and quenched at ~2 °C. Subsequently, samples were aged at 200 °C for different times. The initial microstructure consists in a matrix of fine equiaxial grains of α and η phases for all the alloys. Besides isolated particles of ε and Φ were observed without and with Ag addition, respectively. During the aging, the four phase reaction, α + ε→η + τ’, takes place to obtain the equilibrium η, α and τ’ phases. However, the Ag addition promotes the formation of the Φ phase, which retards or inhibits the four phase reaction. The stability of the Φ phase is obtained with 3%Ag, which could improve the dimensional stability of the alloy for future industrial applications.En el presente estudio sobre las transformaciones de fase en las aleaciones Zn-22%Al-2%Cu y Zn-22%Al-2%Cu-X (X = 1, 2 y 3%Ag se utilizó Difracción de Rayos X (DRX y Microscopía Electrónica de Barrido (MEB. Las aleaciones fueron homogeneizadas a 350 °C durante 10 días, templadas a ~2 °C y posteriormente envejecidas a 200 °C durante diferentes tiempos. Todas las aleaciones ensayadas presentaron una microestructura inicial formada por una matriz de granos finos y equiaxiales de las fases α y η. Además, para las aleaciones sin Ag se observa la presencia de partículas de la fase ε (CuZn4 y de Φ ((Ag, Cu Zn4 en las que se adicionó Ag. Durante el envejecido, ocurre la reacción de cuatro fases, α + ε→η + τ’, para obtener las fases de equilibrio η, α y τ’. Sin embargo, la adición de Ag promueve la formación de la fase Φ, la cual retarda e incluso inhibe la reacción de cuatro fases. La estabilidad de la fase Φ se obtiene con 3%Ag, lo que podría mejorar la estabilidad dimensional de la aleación para

  20. Influencia de la composición y el tratamiento térmico en las propiedades mecánicas de aleaciones de bronce al aluminio

    Directory of Open Access Journals (Sweden)

    Cenoz-Echeverría, I.

    2007-08-01

    Full Text Available Aluminium bronzes are copper-base alloys containing aluminium within the limits between 5-12 %. Additions of Fe, Ni and Mn are used as alloying elements forming a family of complex alloys noted for their exceptional strength and corrosion resistance. In present paper the Ni:Fe ratio and heat treatments have been analyzed by determining the mechanical properties for three different aluminium bronze alloys containing Cu-Al10-Fe3, Cu-Al10-Fe5-Ni5 and Cu-Al10-Fe4-Ni8. The effect of as cast, quenched and quenched and tempered structures has been investigated regarding hardness, proof and ultimate tensile strength, elongation, modulus of elasticity, Poisson ratio, fracture toughness, fatigue strength, crack propagation and Charpy impact properties. The influence of temperature has been studied by testing the elastic modulus, Poisson ratio, the proof stress, tensile strength and the Charpy impact properties at –20 °C, 24 °C and 100 °C.

    Los cuproaluminios son aleaciones de cobre con contenidos de aluminio del 5-12 % que pueden incorporar hierro, níquel, y manganeso para formar una familia de aleaciones con unas excelentes propiedades de resistencia mecánica y a la corrosión. En el presente artículo se estudia el efecto que la relación Ni:Fe y que los tratamientos térmicos ocasionan en las propiedades mecánicas como dureza, límite elástico, tensión de rotura, alargamiento, módulo de elasticidad, coeficiente de Poisson, tenacidad a la fractura estática, resiliencia, fatiga y propagación de grieta. Para ello, se analizan tres aleaciones en tres estados. Las composiciones nominales son Cu-Al10-Fe3, Cu-Al10-Fe5-Ni5 y Cu- Al10-Fe4-Ni8. Las estructuras de las aleaciones son las correspondientes a: bruto de colada, temple y temple seguido de revenido. La caracterización del módulo de elasticidad y coeficiente de Poisson, así como los ensayos de tracción y resiliencia, se realizan a –20 °C, 24 °C y 100 °C.

  1. Efecto magnetocalórico en aleaciones ferromagnéticas con memoria de forma monocristalinas de NiFeCoGa.

    OpenAIRE

    Vázquez Risco, Alain

    2017-01-01

    Este trabajo se centrará en el estudio del efecto magnetocalórico de una aleación monocristalina ferromagnética de composición Ni-Fe-Co-Ga. Este tipo de material entra dentro de las denominadas aleaciones con memoria de forma o SMA (Shape Memory Alloys). Estas aleaciones presentan los efectos de memoria de forma de las propias SMA y otras características como las uperelasticidad, los efectos magnetocalóricos directo e inverso. El interés de estos materiales se debe a que pued...

  2. Recubrimiento por láser de aleaciones cuasicristalinas

    Directory of Open Access Journals (Sweden)

    Audebert, F.

    1998-04-01

    Full Text Available Quasicrystals are a new class of ordenated structures with metaestable characteristics at room temperature. Quasicrystalline phases can be obtained by rapid quenching from the melt of some alloys. In general, quasicrystals present properties which make these alloys promising for wear and corrosion resistant coatings applications. During the last years, the development of quasicrystalline coatings by means of thermal spray techniques has been impulsed. However, no references have been found of their application by means of laser techniques. In this work four claddings of quasicrystalline compositions formed over aluminum substrate, produced by a continuos CO2 laser using simultaneous powders mixture injection are presented. The claddings were characterized by X ray diffraction, scanning electron microscopy and Vickers microhardness.

    Los cuasicristales constituyen un nuevo tipo de estructuras ordenadas con características metaestables a temperatura ambiente. En general, en determinadas aleaciones, pueden obtenerse por enfriamiento rápido desde el estado líquido. Han demostrado poseer buenas propiedades para su aplicación como recubrimientos resistentes al desgaste y a la corrosión. En este sentido, desde hace unos años, se ha impulsado el desarrollo de su aplicación mediante técnicas de thermal spray, aunque no se han encontrado referencias de su aplicación mediante técnicas de láser. En este trabajo, se presenta la formación de cuatro recubrimientos de aleaciones con composiciones cuasicristalinas sobre un sustrato de aluminio, utilizando un láser continuo de CO2, con inyección simultánea del material en forma de mezcla de polvos. Los mismos fueron caracterizados por difracción de rayos X, microscopía electrónica de barrido y microdureza Vickers.

  3. on Ti6AL4V for biomedical applications

    Directory of Open Access Journals (Sweden)

    Juan José Pavón

    2006-01-01

    Full Text Available La fijación al tejido receptor de implantes para el reemplazo de hueso puede ser mejorada si poseen una superficie bioactiva con la capacidad de precipitar hidroxiapatita in vivo. Las aleaciones de titanio, a pesar de sus buenas propiedades mecánicas y comportamiento no-tóxico, no son bioactivas y, por tanto, no se enlazan directamente al hueso. Una de las maneras de modificar una superficie metálica bioinerte es recubriéndola con material bioactivo. En este trabajo se presenta la evaluación del comportamiento a fatiga mediante indentación hertziana (esférica de un recubrimiento de vidrio sobre Ti6Al4V. Este recubrimiento pertenece al sistema SiO2-CaO-MgO-Na2O-K2O-P2O5 y, a pesar de que puede usarse para protección contra la corrosión, ha sido específicamente diseñado para ser utilizado como capa interna de un recubrimiento bicapa bioactivo con una capa externa de bajo contenido en SiO2 para garantizar la bioactividad. Los ensayos hertzianos monotónicos permitieron obtener una secuencia de daños comenzando con tres eventos de daño tipo frágil (agrietamiento tipo anillo, cono y radial seguidos por la delaminación del recubrimiento asociada a la deformación plástica del substrato. El primer daño frágil, el agrietamiento tipo anillo, fue usado como criterio para la evaluación del agrietamiento por corrosión bajo tensión y por carga cíclica, en aire y agua destilada. Los resultados mostraron la sensibilidad del recubrimiento a la degradación bajo ambos tipos de carga, estática y cíclica, siendo esta degradación considerablemente mayor en agua destilada debido a la susceptibilidad del vidrio a la corrosión. La delaminación fue también sensible a la carga cíclica hertziana presentando dos mecanismos diferentes dependiendo de la máxima carga aplicada.

  4. Relación estructura-propiedades en aleaciones inteligentes con memoria de forma Cu-Al-Ag de alta temperatura de transformación martensítica termoelástica

    Directory of Open Access Journals (Sweden)

    Guilemany, J. M.

    1998-05-01

    Full Text Available New shape memory alloys have been developed in the last few years with high martensitic transformation temperatures. However, the highest martensitic transformation temperatures are lower than 200°C and they are achieved with very complex alloys. New Cu-Al-Ag shape memory alloys have been developed with martensitic transformation temperatures ranging from 250 to 400°C. It is really interesting to increase the knowledge of the phase stability behaviour when cycling the alloy above or below the martensitic transformation temperature because of the high temperatures involved. Two Cu-Al-Ag shape memory alloys with very different composition have been thermal cycled in a DSC following the amount of energy release during the forward and reverse transformation and the changes of the martensitic transformation temperatures in order to follow the phase changes that takes place during cycling.

    En los últimos años, se han desarrollado nuevas aleaciones con memoria de forma, de altas temperaturas de transformación martensítica. Sin embargo, las temperaturas de transformación martensítica más elevadas son inferiores a 200°C e implican aleaciones de gran complejidad. Nuevas aleaciones con memoria de forma Cu-Al-Ag han sido desarrolladas con temperaturas de transformación entre 250 y 400°C. Es de gran importancia incrementar el conocimiento de la estabilidad de las fases durante el ciclado por encima o por debajo de la temperatura de transformación martensítica a causa de las altas temperaturas involucradas. Dos aleaciones con memoria de forma Cu-Al-Ag con muy diferente composición química han sido cicladas en el DSC midiendo la cantidad de energía liberada durante las transformaciones directa e inversa, así como los cambios en las temperaturas de transformación, con objeto de caracterizar las transformaciones de fase que tienen lugar durante el ciclado.

  5. Predicción de la dureza de aleaciones Al-Cu-Zn en estado de colada y templado

    Directory of Open Access Journals (Sweden)

    Villegas-Cárdenas, José D.

    2014-06-01

    Full Text Available This work presents a new experimental and numerical methodology in order to predict the hardness in the as-cast, and solution treated and quenched Al-Cu-Zn alloys. Chemical composition of alloys is located inside two straight lines represented by two equations. Eight different compositions were selected from each line. All the alloys were characterized for light microscope, scanning electron microscope, X-ray diffraction and Rockwell B hardness test. The equilibrium phases were obtained at different temperatures by Thermo-Calc. The microstructure characterization and regression analysis enabled to determine the phase transformations and two equations of hardness assessment. The combination of hardness equations and composition line equations permitted to estimate the hardness of any alloy composition inside this zone. This was verified by calculating hardness with the information reported in other works, with an error lower than 7% in the estimated hardness.Este trabajo presenta una nueva metodología experimental y numérica para pronosticar la dureza de las aleaciones Al-Cu-Zn, tanto en estado de colada como solubilizadas y templadas, cuyas composiciones químicas se encuentren dentro de dos líneas limítrofes, representadas por dos ecuaciones. De cada una de las líneas limítrofes se seleccionaron ocho composiciones diferentes que se caracterizaron por metalografía óptica, microscopía electrónica de barrido, difracción de rayos X y dureza. Las fases en equilibrio a diferentes temperaturas se obtuvieron por medio del programa Thermo-Calc. De la caracterización microestructural y análisis de regresión se obtuvieron los diferentes cambios de fase y dos ecuaciones de dureza. Al combinar las ecuaciones de dureza con las ecuaciones limítrofes se puede deducir la dureza de cualquier aleación con composición química dentro de esta zona. Para comprobar la exactitud de este método, se pronosticó la dureza de aleaciones a partir de los

  6. Aluminio pulvimetalúrgico: desarrollo y mejora de sus aleaciones y materiales compuestos

    Directory of Open Access Journals (Sweden)

    Ruiz-Navas, E. M.

    2008-06-01

    Full Text Available Powder metallurgy components demand is increasing in the last few years mainly due to the necessity of products assigned to automotive and aerospace industries, which has allow an important development of aluminium alloys and composites (AMCs. Consolidation of aluminium alloys by sintering present a main problem: the oxide layer that cover aluminium particles. Several alternatives are studied in this work as solution to the oxide layer problem during the sintering of series 2xxx aluminium alloys. One of these solutions is related to the addition of tin traces, and the other is the addition of a second alloy. Moreover, aluminium metal matrix composites are characterized by excellent properties as combination of properties which comes from the matrix and from the reinforcement. The last part of this study is focused to the analysis of one aluminium matrix composite as the influence of several quantities of reinforcement.

    El auge en la demanda de componentes pulvimetalúrgicos destinados principalmente al sector automovilístico y aeroespacial ha permitido un fuerte desarrollo tanto de aleaciones como de MMCs base aluminio (AMCs. El principal problema a la hora de consolidar estos materiales vía pulvimetalúrgica es la capa de óxido que recubre a las partículas de aluminio. En este trabajo se presentan varias alternativas como solución a este problema, aplicadas a la consolidación de aleaciones de aluminio pertenecientes a la serie 2xxx, entre ellas, la adición de trazas de estaño y la adición de una aleación Al-Si. En cuanto a los materiales compuestos de matriz de aluminio, se caracterizan por presentar propiedades únicas como combinación de las propiedades individuales que caracterizan tanto a la matriz como al refuerzo. En la última parte de este trabajo se estudia la consolidación de un material compuesto así como la influencia de las distintas cantidades de refuerzo.

  7. Recubrimientos vítreos de cerio para la protección activa de aleaciones de aluminio

    OpenAIRE

    Yhasmin Reyes; Alicia Durán; Yolanda Castro

    2015-01-01

    Las buenas propiedades mecánicas, alta conductividad eléctrica y térmica y bajo coste de mecanización del aluminio y sus aleaciones, permiten su uso en un amplio campo de aplicaciones. Sin embargo, al exponerse a ambientes agresivos, el aluminio sufre corrosión localizada. En este trabajo, se estudia la preparación de recubrimientos vítreos de óxido de cerio, sintetizados a partir de nitrato de cerio y diversos complejantes para mejorar la resistencia a la corrosión de las aleaciones AA2024 y...

  8. Comportamiento de la corrosión de diferentes aleaciones de titanio y tantalio en contacto con fluidos fisiológicos

    OpenAIRE

    Dueñas Santacruz, Ernesto Diego

    2013-01-01

    Programa de doctorado: Tecnología industrial El objetivo de la tesis es el estudio del comportamiento de diferentes aleaciones de titanio y tantalio en contacto con fluidos fisiológicos. En concreto, se trata de tres aleaciones con un contenido de un cinco, un quince y un veinticinco por ciento de tantalio. En cuanto al fluido fisiológico, se trata de una disolución Ringer.

  9. Comparison of brazed joints made with BNi-1 and BNi-7 nickel-base brazing alloys

    Directory of Open Access Journals (Sweden)

    Zorc, Borut

    2000-04-01

    Full Text Available Kinetics of the processes are different with different types of brazing alloys. Precipitation processes in the parent metal close to the brazing gap are of great importance. They control the mechanical properties of the joint area when the brittle eutectic has disappeared from the gap. A comparative study of brazed joints on austenitic stainless alloys made with BNi-7 (Ni-P type and BNi-1 (Ni-Si-B type brazing alloys was made. Brazing alloys containing phosphorus behave in a different manner to those containing boron.

    Las aleaciones de níquel se producen mediante tres sistemas de aleación: Ni-P, Ni-Si y Ni-B. Durante las reacciones metalúrgicas con el metal de base, la eutéctica frágil en la separación soldada puede transformarse en la solución dúctil-sólida con todas aleaciones. La cinética del proceso varía según el tipo de aleación. Los procesos de precipitación en el metal de base cerca de la separación soldada son de mucha importancia, ya que controlan las propiedades mecánicas de la área de unión después de desaparecer la eutéctica frágil de la separación. Se ha hecho un análisis comparativo de uniones soldadas en aleaciones austeníticas inoxidables realizadas con aleaciones BNi-7 (tipo Ni-P y BNi-1 (tipo Ni-Si-B. Las aleaciones que contienen fósforo se comportan de una manera diferente, tanto con el cambio de la eutéctica a la solución sólida, como con los procesos de precipitación en el metal de base cerca de la unión soldada.

  10. U-Mo/Al-Si interaction: Influence of Si concentration

    International Nuclear Information System (INIS)

    Allenou, J.; Palancher, H.; Iltis, X.; Cornen, M.; Tougait, O.; Tucoulou, R.; Welcomme, E.; Martin, Ph.; Valot, C.; Charollais, F.; Anselmet, M.C.; Lemoine, P.

    2010-01-01

    Within the framework of the development of low enriched nuclear fuels for research reactors, U-Mo/Al is the most promising option that has however to be optimised. Indeed at the U-Mo/Al interfaces between U-Mo particles and the Al matrix, an interaction layer grows under irradiation inducing an unacceptable fuel swelling. Adding silicon in limited content into the Al matrix has clearly improved the in-pile fuel behaviour. This breakthrough is attributed to an U-Mo/Al-Si protective layer around U-Mo particles appeared during fuel manufacturing. In this work, the evolution of the microstructure and composition of this protective layer with increasing Si concentrations in the Al matrix has been investigated. Conclusions are based on the characterization at the micrometer scale (X-ray diffraction and energy dispersive spectroscopy) of U-Mo7/Al-Si diffusion couples obtained by thermal annealing at 450 deg. C. Two types of interaction layers have been evidenced depending on the Si content in the Al-Si alloy: the threshold value is found at about 5 wt.% but obviously evolves with temperature. It has been shown that for Si concentrations ranging from 2 to 10 wt.%, the U-Mo7/Al-Si interaction is bi-layered and the Si-rich part is located close to the Al-Si for low Si concentrations (below 5 wt.%) and close to the U-Mo for higher Si concentrations. For Si weight fraction in the Al alloy lower than 5 wt.%, the Si-rich sub-layer (close to Al-Si) consists of U(Al, Si) 3 + UMo 2 Al 20 , when the other sub-layer (close to U-Mo) is silicon free and made of UAl 3 and U 6 Mo 4 Al 43 . For Si weight concentrations above 5 wt.%, the Si-rich part becomes U 3 (Si, Al) 5 + U(Al, Si) 3 (close to U-Mo) and the other sub-layer (close to Al-Si) consists of U(Al, Si) 3 + UMo 2 Al 20 . On the basis of these results and of a literature survey, a scheme is proposed to explain the formation of different types of ILs between U-Mo and Al-Si alloys (i.e. different protective layers).

  11. Revisión sobre nitruraciones láser de aleaciones de titanio

    Directory of Open Access Journals (Sweden)

    Pérez-Artieda, M. G.

    2010-12-01

    Full Text Available A common technique used to improve the wear response of titanium alloys is to nitride the surface, using chemical or physical vapour deposition, ion implantation or surface remelting in a nitrogen atmosphere. In this revision nitriding systems with laser technology are studied, used in titanium alloys surface treatments.For high temperature, high strength applications, titanium based alloys are an attractive light-weight alternative to steel, due to their high strength to weight ratio and corrosion resistance. In applications that require good wear resistance, titanium alloys pose a problem due to their poor tribological characteristics.Titanium alloys used with a suitable nitriding treatment could allow the replacement of steel in different applications, obtaining weight savings in fabricated components.

    Una técnica comúnmente utilizada para la mejora de la resistencia a desgaste de las aleaciones de titanio es la nitruración de la superficie, utilizando la deposición física o química de vapor, la implantación iónica o el refundido de la superficie en atmósferas que contienen nitrógeno. En esta revisión se estudian los sistemas de nitruración con tecnología láser, utilizados para tratar la superficie de diferentes aleaciones de titanio. Las aleaciones de titanio son un material alternativo al acero, muy atractivo para aplicaciones que requieren alta resistencia a temperaturas elevadas, puesto que tienen una relación resistencia-dureza elevada y buena resistencia a corrosión. En aplicaciones que requieren buena resistencia a desgaste, las aleaciones de titanio suponen un problema, debido a sus pobres características tribológicas. La utilización de aleaciones de titanio junto con un tratamiento de nitruración adecuado, podría permitir la sustitución del acero en diferentes aplicaciones, consiguiendo una disminución en el peso de los componentes fabricados.

  12. Formation of AlFeSi phase in AlSi12 alloy with Ce addition

    Directory of Open Access Journals (Sweden)

    S. Kores

    2012-04-01

    Full Text Available The influence of cerium addition on the solidification sequence and microstructure constituents of the Al-Si alloys with 12,6 mass % Si was examined. The solidification was analyzed by a simple thermal analysis. The microstructures were examined with conventional light and scanning electron microscopy. Ternary AlSiCe phase was formed in the Al-Si alloys with added cerium during the solidification process. AlSiCe and β-AlFeSi phases solidified together in the region that solidified the last. Cerium addition influenced on the morphology of the α-AlFeSi phase solidification.

  13. Hot Corrosion Behavior of Stainless Steel with Al-Si/Al-Si-Cr Coating

    Science.gov (United States)

    Fu, Guangyan; Wu, Yongzhao; Liu, Qun; Li, Rongguang; Su, Yong

    2017-03-01

    The 1Cr18Ni9Ti stainless steel with Al-Si/Al-Si-Cr coatings is prepared by slurry process and vacuum diffusion, and the hot corrosion behavior of the stainless steel with/without the coatings is studied under the condition of Na2SO4 film at 950 °C in air. Results show that the corrosion kinetics of stainless steel, the stainless steel with Al-Si coating and the stainless steel with Al-Si-Cr coating follow parabolic laws in several segments. After 24 h corrosion, the sequence of the mass gain for the three alloys is the stainless steel with Al-Si-Cr coating coating coating. The corrosion products of the three alloys are layered. Thereinto, the corrosion products of stainless steel without coating are divided into two layers, where the outside layer contains a composite of Fe2O3 and FeO, and the inner layer is Cr2O3. The corrosion products of the stainless steel with Al-Si coating are also divided into two layers, of which the outside layer mainly consists of Cr2O3, and the inner layer is mainly SiO2. The corrosion film of the stainless steel with Al-Si-Cr coating is thin and dense, which combines well with substrate. Thereinto, the outside layer is mainly Cr2O3, and the inside layer is Al2O3. In the matrix of all of the three alloys, there exist small amount of sulfides. Continuous and protective films of Cr2O3, SiO2 and Al2O3 form on the surface of the stainless steel with Al-Si and Al-Si-Cr coatings, which prevent further oxidation or sulfide corrosion of matrix metals, and this is the main reason for the much smaller mass gain of the two alloys than that of the stainless steel without any coatings in the 24 h hot corrosion process.

  14. Precipitation and strengthening phenomena in Al-Si-Ge and Al-Cu-Si-Ge alloys

    International Nuclear Information System (INIS)

    Mitlin, D.; Morris, J.W.; Dahmen, U.; Radmilovic, V.

    2000-01-01

    The objective of this work was to determine whether Al rich Al-Si-Ge and 2000 type Al-Cu-Si-Ge alloys have sufficient hardness to be useful for structural applications. It is shown that in Al-Si-Ge it is not possible to achieve satisfactory hardness through a conventional heat treatment. This result is explained in terms of sluggish precipitation of the diamond-cubic Si-Ge phase coupled with particle coarsening. However, Al-Cu-Si-Ge displayed a uniquely fast aging response, a high peak hardness and a good stability during prolonged aging. The high hardness of the Cu containing alloy is due to the dense and uniform distribution of fine θ' precipitates (metastable Al 2 Cu) which are heterogeneously nucleated on the Si-Ge particles. High resolution TEM demonstrated that in both alloys all the Si-Ge precipitates start out, and remain multiply twinned throughout the aging treatment. Since the twinned section of the precipitate does not maintain a low index interface with the matrix, the Si-Ge precipitates are equiaxed in morphology. Copyright (2000) AD-TECH - International Foundation for the Advancement of Technology Ltd

  15. Validated thermodynamic prediction of AlP and eutectic (Si) solidification sequence in Al-Si cast alloys

    International Nuclear Information System (INIS)

    Liang, S M; Schmid-Fetzer, R

    2016-01-01

    The eutectic microstructure in hypoeutectic Al-Si cast alloys is strongly influenced by AlP particles which are potent nuclei for the eutectic (Si) phase. The solidification sequence of AlP and (Si) phases is, thus, crucial for the nucleation of eutectic silicon with marked impact on its morphology. This study presents this interdependence between Si- and P-compositions, relevant for Al-Si cast alloys, on the solidification sequence of AlP and (Si). These data are predicted from a series of thermodynamic calculations. The predictions are based on a self-consistent thermodynamic description of the Al-Si-P ternary alloy system developed recently. They are validated by independent experimental studies on microstructure and undercooling in hypoeutectic Al-Si alloys. A constrained Scheil solidification simulation technique is applied to predict the undercooling under clean heterogeneous nucleation conditions, validated by dedicated experimental observations on entrained droplets. These specific undercooling values may be very large and their quantitative dependence on Si and P content of the Al alloy is presented. (paper)

  16. Interface reactions in the Al-Si-SiC and Mg-Al-Al{sub 2}O{sub 3} composite systems

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, P.K. [Commission of the European Communities, Petten (Netherlands). Inst. for Advanced Materials; Fazal-Ur-Rehman [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Dept. of Materials; Fox, S. [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Dept. of Materials; Flower, H.M. [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Dept. of Materials; West, D.R.F.

    1995-12-31

    Structural and compositional observations are reported on the influence of the interfaces on the mechanisms and kinetics of liquid metal-ceramic reactions in Al-SiC, Al-Si-SiC, Mg-Al{sub 2}O{sub 3} and Mg-Al-Al{sub 2}O{sub 3} composites. The aluminium based materials contained up to 20 vol% SiC in particulate form, and were produced by a spray casting process; subsequently the interface reactions were studied in samples heated to temperatures up to 1100 C. The reaction product was Al{sub 4}C{sub 3} in both Al-SiC and Al-Si-SiC composites. The influence of the crystallography and topology of the SiC particle surfaces on the nucleation of the Al{sub 4}C{sub 3} has been demonstrated; surface asperities play an important role. Growth of nuclei proceeds to form continuous reaction product layers which control the subsequent kinetics. The magnesium based composites contained 5 vol% Al{sub 2}O{sub 3} fibres (3 {mu}m in diameter), and were produced by a liquid infiltration process. SD Safimax fibres with relatively low and high porosity, and also RF Saffil fibres, with a silica binder, were investigated. Fibre porosity plays a major role in accelerating the penetration of Mg into the fibres with reaction to form MgO. Silica binder on the fibre surface transforms to MgO. The reaction rate was reduced by the presence of aluminium in the matrix. The factors controlling the reactions in the aluminium and magnesium based composites are compared. (orig.)

  17. Al-Si/B{sub 4}C composite coatings on Al-Si substrate by plasma spray technique

    Energy Technology Data Exchange (ETDEWEB)

    Sarikaya, Ozkan [Sakarya University, Faculty of Engineering, Department of Mechanical Engineering, Esentepe Campus, Sakarya 54187 (Turkey); Anik, Selahaddin [Sakarya University, Faculty of Engineering, Department of Mechanical Engineering, Esentepe Campus, Sakarya 54187 (Turkey); Aslanlar, Salim [Sakarya University, Faculty of Technical Education, Department of Mechanical Engineering, Esentepe Campus, Sakarya 54187 (Turkey); Cem Okumus, S. [Sakarya University, Faculty of Engineering, Department of Metallurgical and Materials Engineering, Esentepe Campus, Sakarya 54187 (Turkey); Celik, Erdal [Dokuz Eylul University, Engineering Faculty, Department of Metallurgical and Materials Engineering, Buca, Izmir 35160 (Turkey)]. E-mail: erdal.celik@deu.edu.tr

    2007-07-01

    Plasma-sprayed coatings of Al-Si/B{sub 4}C have been prepared on Al-Si piston alloys for diesel engine motors. The Al-Si/B{sub 4}C composite powders including 5-25 wt% B{sub 4}C were prepared by mixing and ball-milling processes. These powders were deposited on Al-Si substrate using an atmospheric plasma spray technique. The coatings have been characterised with respect to phase composition, microstructure, microhardness, bond strength and thermal expansion. It was found that Al, Si, B{sub 4}C and Al{sub 2}O{sub 3} phases were determined in the coatings with approximately 600 {mu}m thick by using X-ray diffraction analysis. Scanning electron microscope observation revealed that boron carbide particles were uniformly distributed in composite coatings and B{sub 4}C particles were fully wetted by Al-Si alloy. Also, no reaction products were observed in Al-Si/B{sub 4}C composite coatings. It was found that surface roughness, porosity, bond strength and thermal expansion coefficient of composite coatings decreased with increasing fraction of the boron carbide particle. It was demonstrated that the higher the B{sub 4}C content, the higher the hardness of coatings because the hardness of B{sub 4}C is higher than that of Al-Si.

  18. Desempeño ante la corrosión y tribocorrosión de aleaciones comerciales de aluminio anodizadas

    OpenAIRE

    Rodríguez, Samantha; Carrasquero, Edwuin J.; López, Luis M.; Fajardo, Jorge I.

    2016-01-01

    El presente trabajo muestra la evaluación del desempeño de dos aleaciones comerciales de aluminio anodizadas ante la corrosión y tribocorrosión. Para el anodizado se emplearon dos tipos de electrolitos distintos (H2SO4 y H2C2O4), un valor constante de densidad de corriente y dos tiempos de anodizado (30 y 45 minutos). Usando una de las técnicas de microscopía electrónica de barrido (MEB) y espectroscopía por dispersión de la energía de rayos X (EDX) se caracterizaro...

  19. EIS, Mott Schottky and EFM analysis of the electrochemical stability and dielectric properties of Ca-P-Ag and Ca-P-Si-Ag coatings obtained by plasma electrolytic oxidation in Ti6Al4V

    Directory of Open Access Journals (Sweden)

    Sara María Leal-Marin

    2017-01-01

    Full Text Available El Ti6Al4V ELI (ASTM F136 es una de las aleaciones más empleadas en dispositivos de osteosíntesis y reemplazo articular. Sin embargo, las propiedades de esta aleación pueden ser mejoradas respecto a su biocompatibilidad y osteointegración con el tejido óseo a través de recubrimientos. El objetivo de este trabajo fue evaluar el comportamiento electroquímico de un recubrimiento obtenido por oxidación por plasma electrolítico sobre Ti6Al4V ELI empleando soluciones electrolíticas enriquecidas con iones de PO4 2-, Ca+2, Si+4 y varias concentraciones de Ag+1. Los recubrimientos se caracterizaron mediante espectroscopia de impedancia electroquímica (EIS y Mott-Schottky (M-S en una celda de tres electrodos con una solución fisiológica simulada. El comportamiento electroquímico se contrastó con microscopía de fuerza electrostática (EFM, donde se analizó el potencial eléctrico del recubrimiento. Los resultados de EIS mostraron mejores propiedades de estabilidad frente a la corrosión en los sustratos recubiertos con Ca- P-Ag, comparados con los recubiertos con Ca-P-Si-Ag. Los espectros de Nyquist y Bode mostraron relajaciones relacionadas con la transferencia de carga hacia la doble capa electroquímica como reflejo de los cambios microestructurales y de conductividad de los recubrimientos, dada por la presencia particular en cada caso, de los elementos contenidos en estos. De acuerdo con los resultados de M-S, todas las muestras ensayadas presentaron un comportamiento con dopado tipo n, cuya conductividad incrementó con la inclusión de plata. Mediante EFM se observaron mayores contrastes en el potencial, fase y la amplitud de los recubrimientos con mayor cantidad de plata respecto al Ti6Al4V sin recubrir.

  20. Electroluminescence of erbium in Al/α-Si:H(Er)/p-c-Si/Al structure

    International Nuclear Information System (INIS)

    Kon'kov, I.O.; Kuznetsov, A.N.; Pak, P.E.; Terukov, E.I.; Granitsyna, L.S.

    2001-01-01

    It is informed for the first time on the observation of the erbium intensive electroluminescence from the amorphous hydrated silicon layer by application of the Al/α-Si:H(Er)/p-c-Si/Al structure in the direct shift mode. The above structure is the n-p-heterostructure with the barrier values of 0.3-0.4 eV for the electrons and 0.9-1.1 eV for the holes. The electroluminescence efficiency is evaluated at the level ∼ 2 x 10 -5 . The electroluminescence effect in the Al/α-Si:H(Er)/p-c-Si/Al structure is connected with the hole tunneling from the crystal silicon by the amorphous silicon localized states with the subsequent release into the valent zone [ru

  1. Soldadura de aleaciones de aluminio con láseres de Nd:YAG de alta potencia

    Directory of Open Access Journals (Sweden)

    García Orza, J. A.

    1998-04-01

    Full Text Available Aluminium alloys have good mechanical properties (high strength-to-weight ratio, corrosion resistance and good workability. Their applications are growing up, specially in the transportation industry. Weldability is however poorer than in other materials; recent advances in high power YAG lasers are the key to obtain good appearance welds and higher penetration, at industrial production rates. Results of the combination of high power YAG beams with small fiber diameters and specific filler wires are presented. It is also characterized the airborne particulated material, by-product of the laser process: emission rates, size distribution and chemical composition are given for several aluminium alloys.

    El uso del Al y sus aleaciones es creciente en la fabricación de vehículos de transporte. Su soldabilidad es menor que la de otros materiales y las aleaciones presentan cierta disminución de propiedades por pérdida de aleantes y/o de su tratamiento térmico. Se revisa brevemente el uso de láseres de Nd:YAG de potencia en soldeo de aleaciones de aluminio y se presentan resultados de la combinación de haces de potencia guiados por fibras de pequeño diámetro, con focos ligeramente superpuestos en la pieza. Finalmente, se caracterizan los humos producidos en la soldadura con láser continuo de 2 kW.

  2. Evolution of a novel Si-18Mn-16Ti-11P alloy in Al-Si melt and its influence on microstructure and properties of high-Si Al-Si alloy

    Directory of Open Access Journals (Sweden)

    Xiao-Lu Zhou

    Full Text Available A novel Si-18Mn-16Ti-11P master alloy has been developed to refine primary Si to 14.7 ± 1.3 μm, distributed uniformly in Al-27Si alloy. Comparing with traditional Cu-14P and Al-3P, Si-18Mn-16Ti-11P provided a much better refining effect, with in-situ highly active AlP. The refined Al-27Si alloy exhibited a CTE of 16.25 × 10−6/K which is slightly higher than that of Sip/Al composites fabricated by spray deposition. The UTS and elongation of refined Al-27Si alloy were increased by 106% and 235% comparing with those of unrefined alloy. It indicates that the novel Si-18Mn-16Ti-11P alloy is more suitable for high-Si Al-Si alloys and may be a candidate for refining hypereutectic Al-Si alloy for electronic packaging applications. Moreover, studies showed that TiP is the only P-containing phase in Si-18Mn-16Ti-11P master alloy. A core-shell reaction model was established to reveal mechanism of the transformation of TiP to AlP in Al-Si melts. The transformation is a liquid-solid diffusion reaction driven by chemical potential difference and the reaction rate is controlled by diffusion. It means sufficient holding time is necessary for Si-18Mn-16Ti-11P master alloy to achieve better refining effect. Keywords: Hypereutectic Al-Si alloy, Primary Si, Refinement, AlP, Thermal expansion behavior, Si-18Mn-16Ti-11P master alloy

  3. Biomorphous SiSiC/Al-Si ceramic composites manufactured by squeeze casting: microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zollfrank, C.; Travitzky, N.; Sieber, H.; Greil, P. [Department of Materials Science, Glass and Ceramics, University of Erlangen-Nuernberg (Germany); Selchert, T. [Advanced Ceramics Group, Technical University of Hamburg-Harburg (Germany)

    2005-08-01

    SiSiC/Al-Si composites were fabricated by pressure-assisted infiltration of an Al-Si alloy into porous biocarbon preforms derived from the rattan palm. Al-Si alloy was found in the pore channels of the biomorphous SiSiC preform, whereas SiC and carbon were present in the struts. The formation of a detrimental Al{sub 4}C{sub 3}-phase was not observed in the composites. A bending strength of 200 MPa was measured. The fractured surfaces showed pull-out of the Al-alloy. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  4. Computer aided cooling curve analysis for Al-5Si and Al-11Si alloys ...

    African Journals Online (AJOL)

    The effect of grain refiner, modifier, and combination of grain refiner cum modifier was studied on Al-5Si and Al-11Si alloys using computer aided cooling curve analysis. For combined grain refinement and modification effect, Al-Ti-B-Sr single master alloy was developed that acted as both grain refiner and modifier.

  5. Addition of iron for the removal of the {beta}-AlFeSi intermetallic by refining of {alpha}-AlFeSi phase in an Al-7.5Si-3.6Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Belmares-Perales, S. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon (Mexico); Zaldivar-Cadena, A.A., E-mail: azaldiva70@hotmail.com [Facultad de Ingenieria Civil, Departamento de Ecomateriales y Energia, Instituto de Ingenieria Civil, Av. Fidel Velasquez and Av. Universidad S/N, Cd. Universitaria, San Nicolas de los Garza, N.L. 66450 (Mexico)

    2010-10-25

    Addition of iron into the molten metal for the removal of the {beta}-AlFeSi intermetallic by refining of {alpha}-AlFeSi phase has been studied. Solidification conditions and composition determine the final microstructure and mechanical properties of a casting piece. It is known that increasing the iron content will produce an increasing of the {alpha}-AlFeSi and {beta}-AlFeSi phases. This phenomenon was confirmed with calculations made by Thermo-Calc{sup TM} software and validated with experimental results, however, the technique of iron addition in this study plays an important role on the solidification kinetics of these iron phases because the refining of {alpha}-AlFeSi and removal of {beta}-AlFeSi phases can be improved. Final results showed an improvement in mechanical properties by removal and refining of {beta}-AlFeSi and {alpha}-AlFeSi phases, respectively. This study shows a new method of removal of {beta}-AlFeSi that could be adopted in the aluminum smelting industry in aluminum alloys with a low cooling rate with a secondary dendritic spacing of about 37 {mu}m.

  6. Addition of iron for the removal of the β-AlFeSi intermetallic by refining of α-AlFeSi phase in an Al-7.5Si-3.6Cu alloy

    International Nuclear Information System (INIS)

    Belmares-Perales, S.; Zaldivar-Cadena, A.A.

    2010-01-01

    Addition of iron into the molten metal for the removal of the β-AlFeSi intermetallic by refining of α-AlFeSi phase has been studied. Solidification conditions and composition determine the final microstructure and mechanical properties of a casting piece. It is known that increasing the iron content will produce an increasing of the α-AlFeSi and β-AlFeSi phases. This phenomenon was confirmed with calculations made by Thermo-Calc TM software and validated with experimental results, however, the technique of iron addition in this study plays an important role on the solidification kinetics of these iron phases because the refining of α-AlFeSi and removal of β-AlFeSi phases can be improved. Final results showed an improvement in mechanical properties by removal and refining of β-AlFeSi and α-AlFeSi phases, respectively. This study shows a new method of removal of β-AlFeSi that could be adopted in the aluminum smelting industry in aluminum alloys with a low cooling rate with a secondary dendritic spacing of about 37 μm.

  7. Sr-Al-Si co-segregated regions in eutectic Si phase of Sr-modified Al-10Si alloy.

    Science.gov (United States)

    Timpel, M; Wanderka, N; Schlesiger, R; Yamamoto, T; Isheim, D; Schmitz, G; Matsumura, S; Banhart, J

    2013-09-01

    The addition of 200 ppm strontium to an Al-10 wt% Si casting alloy changes the morphology of the eutectic silicon phase from coarse plate-like to fine fibrous networks. In order to clarify this modification mechanism the location of Sr within the eutectic Si phase has been investigated by a combination of high-resolution methods. Whereas three-dimensional atom probe tomography allows us to visualise the distribution of Sr on the atomic scale and to analyse its local enrichment, transmission electron microscopy yields information about the crystallographic nature of segregated regions. Segregations with two kinds of morphologies were found at the intersections of Si twin lamellae: Sr-Al-Si co-segregations of rod-like morphology and Al-rich regions of spherical morphology. Both are responsible for the formation of a high density of multiple twins and promote the anisotropic growth of the eutectic Si phase in specific crystallographic directions during solidification. The experimental findings are related to the previously postulated mechanism of "impurity induced twinning". Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Influencia del cobre en la transformación de fase de la aleación Zn - 22 % p Al, durante la homogenización

    OpenAIRE

    Rangel Lara, S.; Bernal, J. L.; Ita de la Torre, A. de

    2011-01-01

    Las aleaciones fueron producidas por fundición y enfriadas en aire quieto a temperatura ambiente, la microestructura dendrítica fue analizada en un trabajo anterior [1]. Muestras de las aleaciones obtenidas fueron sometidas a un tratamiento de homogenización a 375 °C por 120 horas, se observó la modificación de la microestructura a 60, 100 y 120 horas en las aleaciones Zn - 22 % p Al y Zn - 22 % p Al - 2 % p Cu. Las fases presentes en las aleaciones se identificaron por microscopia óptica. Se...

  9. Modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy

    International Nuclear Information System (INIS)

    Wu Yuying; Liu Xiangfa; Jiang Binggang; Huang Chuanzhen

    2009-01-01

    Modification effect of Ni-38 wt.%Si on the Al-12 wt.%Si alloy has been studied by differential scanning calorimeter, torsional oscillation viscometer and liquid X-ray diffraction experiments. It is found that there is a modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy, i.e. primary Si can precipitate in the microstructure of Al-12 wt.%Si alloy when Ni and Si added in the form of Ni-38 wt.%Si, but not separately. Ni-38 wt.%Si alloy brings 'genetic materials' into the Al-Si melt, which makes the melt to form more ordering structure, promotes the primary Si precipitated. Moreover, the addition of Ni-38 wt.%Si, which decreases the solidification supercooling degree of Al-12 wt.%Si alloy, is identical to the effect of heterogeneous nuclei.

  10. Modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yuying [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China)], E-mail: wyy532001@163.com; Liu Xiangfa [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China); Shandong Binzhou Bohai Piston Co., Ltd., Binzhou 256602, Shandong (China); Jiang Binggang [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China); Huang Chuanzhen [School of Mechanical Engineering, Shandong University, Jinan 250061 (China)

    2009-05-27

    Modification effect of Ni-38 wt.%Si on the Al-12 wt.%Si alloy has been studied by differential scanning calorimeter, torsional oscillation viscometer and liquid X-ray diffraction experiments. It is found that there is a modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy, i.e. primary Si can precipitate in the microstructure of Al-12 wt.%Si alloy when Ni and Si added in the form of Ni-38 wt.%Si, but not separately. Ni-38 wt.%Si alloy brings 'genetic materials' into the Al-Si melt, which makes the melt to form more ordering structure, promotes the primary Si precipitated. Moreover, the addition of Ni-38 wt.%Si, which decreases the solidification supercooling degree of Al-12 wt.%Si alloy, is identical to the effect of heterogeneous nuclei.

  11. The Effect of Si Morphology on Machinability of Al-Si Alloys

    Directory of Open Access Journals (Sweden)

    Muhammet Uludağ

    2015-12-01

    Full Text Available Many of the cast parts require some sort of machining like milling, drilling to be used as a finished product. In order to improve the wear properties of Al alloys, Si is added. The solubility of Si in Al is quite low and it has a crystallite type structure. It behaves as particulate metal matrix composite which makes it an attractive element. Thus, the wear and machinability properties of these type of alloys depend on the morphology of Si in the matrix. In this work, Sr was added to alter the morphology of Si in Al-7Si and Al-12Si. Cylindrical shaped samples were cast and machinability characteristics of Sr addition was studied. The relationship between microstructure and machinability was evaluated.

  12. Defining and comparing vibration attributes of AlSi10 foam and CFRP coated AlSi10 foam materials

    Science.gov (United States)

    Çolak, O.; Yünlü, L.

    2017-06-01

    Now, Aluminum materials have begun being manufactured as porous structures and being used with additive composite materials through emerging manufacturing technologies. These materials those porous structures have also begun being used in many areas such as automotive and aerospace due to light-weighted structures. In addition to examining mechanical behavior of porous metallic structures, examining vibration behavior is important for defining characteristic specifications. In this study, vibration attributes belong to %80 porous AlSi10 foam and CFRP coated %80 porous AlSi10 foam are determined with modal analysis. Modal parameters such as natural frequencies and damping coefficient from frequency response functions at the end of hammer impact tests. It is found that natural frequency of CFRP coated AlSi10 foam’s is 1,14 times bigger than AlSi10 foam and damping coefficient of CFRP coated AlSi10 foam is 5 times bigger than AlSi10 foam’s with tests. Dynamic response of materials in various conditions is simulated by evaluating modal parameters with FEM. According to results of the study, CFRP coating on AlSi10 foam effect vibration damping and resonance avoidance ability positively.

  13. Marbled texture of sputtered Al/Si alloy thin film on Si

    Energy Technology Data Exchange (ETDEWEB)

    Gentile, M.G. [Physics Department and NIS Interdepartmental Center, University of Torino, via P. Giuria 1, 10125 Torino (Italy); Vishay Intertechnology, Diodes Division, Via Liguria 49, 10071 Borgaro Torinese, Turin (Italy); Muñoz-Tabares, J.A.; Chiodoni, A. [Istituto Italiano di Tecnologia, Center for Space Human Robotics, Corso Trento 21, 10129 Torino (Italy); Sgorlon, C. [Vishay Intertechnology, Diodes Division, Via Liguria 49, 10071 Borgaro Torinese, Turin (Italy); Para, I. [Department of Applied Science and Technology (DISAT), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Carta, R.; Richieri, G. [Vishay Intertechnology, Diodes Division, Via Liguria 49, 10071 Borgaro Torinese, Turin (Italy); Bejtka, K. [Istituto Italiano di Tecnologia, Center for Space Human Robotics, Corso Trento 21, 10129 Torino (Italy); Merlin, L. [Vishay Intertechnology, Diodes Division, Via Liguria 49, 10071 Borgaro Torinese, Turin (Italy); Vittone, E. [Physics Department and NIS Interdepartmental Center, University of Torino, via P. Giuria 1, 10125 Torino (Italy)

    2016-08-01

    DC magnetron sputtering is a commonly used technique for the fabrication of silicon based electronic devices, since it provides high deposition rates and uniform large area metallization. However, in addition to the thickness uniformity, coating optical uniformity is a crucial need for semiconductor industrial processes, due to the wide use of optical recognition tools. In the silicon-based technology, aluminum is one of the most used materials for the metal contact. Both the pre-deposition substrate cleaning and the sputtering conditions determine the quality and the crystalline properties of the final Al deposited film. In this paper is shown that not all the mentioned conditions lead to good quality and uniform Al films. In particular, it is shown that under certain standard process conditions, Al/Si alloy (1% Si) metallization on a [100] Si presents a non-uniform reflectivity, with a marbled texture caused by flakes with milky appearance. This optical inhomogeneity is found to be caused by the coexistence of randomly orient Al/Si crystal, with heteroepitaxial Al/Si crystals, both grown on Si substrate. Based on the microstructural analysis, some strategies to mitigate or suppress this marbled texture of the Al thin film are proposed and discussed. - Highlights: • Sputtered Al/Si layers deposited on Si present evident optical non-uniformity • It could be an issue for optical recognition tools used in semiconductor industries • Optical non-uniformity is due to randomly oriented growth of Al grains. • Substrate misorientation and process temperature can mitigate the problem.

  14. Solid-state 27Al and 29Si NMR investigations on Si-substituted hydrogarnets

    International Nuclear Information System (INIS)

    Rivas Mercury, J.M.; Pena, P.; Aza, A.H. de; Turrillas, X.; Sobrados, I.; Sanz, J.

    2007-01-01

    Partially deuterated Ca 3 Al 2 (SiO 4 ) 3-x (OH) 4x hydrates prepared by a reaction in the presence of D 2 O of synthetic tricalcium aluminate with different amounts of amorphous silica were characterized by 29 Si and 27 Al magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The 29 Si NMR spectroscopy was used for quantifying the non-reacted silica and the resulting hydrated products. The incorporation of Si into Ca 3 Al 2 (SiO 4 ) 3-x (OH) 4x was followed by 27 Al NMR spectroscopy: Si:OH ratios were determined quantitatively from octahedral Al signals ascribed to Al(OH) 6 and Al(OSi)(OH) 5 environments. The NMR data obtained were consistent with the concentrations of the Al and Si species deduced from transmission electron microscopy energy-dispersive spectrometry and Rietveld analysis of both X-ray and neutron diffraction data

  15. Structure and optical properties of aSiAl and aSiAlHx magnetron sputtered thin films

    Directory of Open Access Journals (Sweden)

    Annett Thøgersen

    2016-03-01

    Full Text Available Thin films of homogeneous mixture of amorphous silicon and aluminum were produced with magnetron sputtering using 2-phase Al–Si targets. The films exhibited variable compositions, with and without the presence of hydrogen, aSi1−xAlx and aSi1−xAlxHy. The structure and optical properties of the films were investigated using transmission electron microscopy, X-ray photoelectron spectroscopy, UV-VisNIR spectrometry, ellipsometry, and atomistic modeling. We studied the effect of alloying aSi with Al (within the range 0–25 at. % on the optical band gap, refractive index, transmission, and absorption. Alloying aSi with Al resulted in a non-transparent film with a low band gap (1 eV. Variations of the Al and hydrogen content allowed for tuning of the optoelectronic properties. The films are stable up to a temperature of 300 °C. At this temperature, we observed Al induced crystallization of the amorphous silicon and the presence of large Al particles in a crystalline Si matrix.

  16. Comparative study of anisotropic superconductivity in CaAlSi and CaGaSi

    International Nuclear Information System (INIS)

    Tamegai, T.; Uozato, K.; Kasahara, S.; Nakagawa, T.; Tokunaga, M.

    2005-01-01

    In order to get some insight into the origin of the anomalous angular dependence of H c2 in a layered intermetallic compound CaAlSi, electronic, superconducting, and structural properties are compared between CaAlSi and CaGaSi. The angular dependence of H c2 in CaGaSi is well described by the anisotropic GL model. Parallel to this finding, the pronounced lattice modulation accompanying the superstructure along the c-axis in CaAlSi is absent in CaGaSi. A relatively large specific heat jump at the superconducting transition in CaAlSi compared with CaGaSi indicates the presence of strong electron-phonon coupling in CaAlSi, which may cause the superstructure and the anomalous angular dependence of H c2

  17. Caracterización microestructural de aleaciones base cobre obtenidas mediante molienda reactiva

    Directory of Open Access Journals (Sweden)

    Palma, R.

    2010-06-01

    Full Text Available The micro and nanostructure of Cu-Al, Cu-V and Cu-Ti alloys produced by reactive milling were analyzed using X-ray diffraction (XRD and transmission electron microscopy (TEM. Samples with different milling times (t= 0, 10, 20 and 30 h were considered. The grain size, dislocation density and residual microstrain were evaluated form the XRD data using the Williamson-Hall and Klug-Alexander methods. The evolution of texture as a function of milling time was also studied using XRD. It was found, using TEM, that the grain size and dispersoid size were nanometric in all three alloys considered.

    Se analizó la micro y nano estructura de aleaciones Cu-Al, Cu-V y Cu-Ti obtenidas por molienda reactiva, mediante difracción de rayos X (XRD y microscopía electrónica de transmisión (TEM. Se consideraron muestras con distintos tiempos de molienda (t= 0, 10, 20 y 30 h. A partir de los datos XRD, usando los métodos de Williamson- Hall y Klug-Alexander, se evaluaron el tamaño de grano, la densidad de dislocaciones y la microdeformación residual; también se estudió la evolución de la textura de la matriz de cobre en función del tiempo de molienda. En los polvos molidos durante 30 h, de las tres aleaciones consideradas, se encontró, por TEM, que los tamaños de grano y de los dispersoides desarrollados son nanométricos.

  18. Experimental and thermodynamic assessments of substitutions in the AlFeSi, FeMnSi, FeSiZr and AlCaFeSi systems (65 wt % Si) - solidification simulation

    International Nuclear Information System (INIS)

    Gueneau, C.; Ansara, I.

    1994-01-01

    The substitutions of Al Si, Fe Mn and Fe Zr in some intermetallic compounds of the Al-Fe-Si, Fe-Mn-Si and Fe-Si-Zr systems are modelled in the Si-rich corner using a two sublattice model. The solidification paths of the studied alloys are determined at equilibrium. The ascalculated phase volume fractions of the alloys are compared to the experimental ones. Finally, a solidification simulation using the Gulliver-Scheil's model is performed in order to explain the formation of some precipitates experimentally observed. (authors). 14 figs., 19 refs

  19. Efecto de la adición de un 10 % en volumen de cromo en el comportamiento a tracción de aleaciones pulvimetalúrgicas NiAlCr

    Directory of Open Access Journals (Sweden)

    García-Barriocanal, J.

    2005-08-01

    Full Text Available The mechanical properties of Ni3Al-Cr reinforced with 10% in volume fraction of chromium particles produced by powder metallurgy have been studied. For this purpose, milled powders with composition of Ni-20.9Al-8Cr-0.49B (% at. with and without the addition of 10% in volume fraction of chromium particles have been produced. Both alloys were consolidated by hot isostatic pressing (HIP. After HIP, heat treatment was applied to homogenize the microstructure. The chromium reinforcement has an important effect in the yield strength and ultimate strength increase. The reinforced alloy presents a yield strength of 1300 MPa at room temperature with respect to 800 MPa for the un-reinforced material. After heat treatment, the yield strength of both alloys does not change significantly. However, a decrease in ductility and ultimate tensile strength have been observed

    En este trabajo se estudia la influencia de la adición de un 10 % en volumen, de cromo en las propiedades mecánicas de aleaciones Ni3Al-Cr procesadas por vía pulvimetalúrgica. Para ello se prepararon dos aleaciones: la primera, se obtuvo por molienda de polvo de composición Ni-20,9Al-8Cr-0,49B (% at. y, a la segunda, se le añadió un 10 % en volumen de partículas de cromo, mediante un proceso de mezcla, previo al de molienda. Ambas, fueron consolidadas mediante compactación isostática en caliente (HIP y, por último, se les aplicaron tratamientos térmicos para homogeneizar la microestructura. Los resultados experimentales han mostrado que el refuerzo de cromo tiene como efecto un importante aumento del límite elástico y de la resistencia. Así, el material reforzado presenta un límite elástico cercano a 1.300 MPa, a temperatura ambiente, frente a los 800 MPa que presenta el material sin reforzar, a la misma temperatura. En relación con las propiedades mecánicas de los materiales tratados térmicamente, se observa que ambos experimentan un acusado

  20. Diferencias en Estrés Percibido, Salud Mental y Física de acuerdo al Tipo de Relación Humano-Perro

    OpenAIRE

    MÓNICA TERESA GONZÁLEZ RAMÍREZ; RENÉ LANDERO HERNÁNDEZ

    2011-01-01

    Con el propósito de evaluar si los niveles de estrés y salud percibidos difieren de acuerdo al tipo de relación entre el humano y el perro, así como de evaluar la correlación de estrés y salud percibidos con la frecuencia en que se realizan algunas actividades con el perro, se aplicaron cuestionarios de autoinforme a 247 voluntarios, dueños de al menos un perro. Los principales resultados muestran puntajes más bajos de estrés percibido y más altos de salud mental en quienes consideran a su pe...

  1. Synthesis of Vertically-Aligned Carbon Nanotubes from Langmuir-Blodgett Films Deposited Fe Nanoparticles on Al2O3/Al/SiO2/Si Substrate.

    Science.gov (United States)

    Takagiwa, Shota; Kanasugi, Osamu; Nakamura, Kentaro; Kushida, Masahito

    2016-04-01

    In order to apply vertically-aligned carbon nanotubes (VA-CNTs) to a new Pt supporting material of polymer electrolyte fuel cell (PEFC), number density and outer diameter of CNTs must be controlled independently. So, we employed Langmuir-Blodgett (LB) technique for depositing CNT growth catalysts. A Fe nanoparticle (NP) was used as a CNT growth catalyst. In this study, we tried to thicken VA-CNT carpet height and inhibit thermal aggregation of Fe NPs by using Al2O3/Al/SiO2/Si substrate. Fe NP LB films were deposited on three typed of substrates, SiO2/Si, as-deposited Al2O3/Al/SiO2/Si and annealed Al2O3/Al/SiO2/Si at 923 K in Ar atmosphere of 16 Pa. It is known that Al2O3/Al catalyzes hydrocarbon reforming, inhibits thermal aggregation of CNT growth catalysts and reduces CNT growth catalysts. It was found that annealed Al2O3/Al/SiO2/Si exerted three effects more strongly than as-deposited Al2O3/Al/SiO2/Si. VA-CNTs were synthesized from Fe NPs-C16 LB films by thermal chemical vapor deposition (CVD) method. As a result, at the distance between two nearest CNTs 28 nm or less, VA-CNT carpet height on annealed Al2O3/Al/SiO2/Si was about twice and ten times thicker than that on SiO2/Si and that on as-deposited Al2O3/Al/SiO2/Si, respectively. Moreover, distribution of CNT outer diameter on annealed Al2O3/Al/SiO2/Si was inhibited compared to that on SiO2/Si. These results suggest that since thermal aggregation of Fe NPs is inhibited, catalyst activity increases and distribution of Fe NP size is inhibited.

  2. Core–shell structured FeSiAl/SiO{sub 2} particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite cores with tunable insulating layer thicknesses

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xi’an, E-mail: groupfxa@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Wang, Jian, E-mail: snove418562@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Wu, Zhaoyang, E-mail: wustwuzhaoyang@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Li, Guangqiang, E-mail: ligq-wust@mail.wust.edu.cn [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China)

    2015-11-15

    Graphical abstract: - Highlights: • FeSiAl/SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores were prepared. • SiO{sub 2} surrounding FeSiAl were replaced by Al{sub 2}O{sub 3} during sintering process. • Fe{sub 3}Si particles were separated by Al{sub 2}O{sub 3} with tunable thickness in composite cores. • Fe{sub 3}Si/Al{sub 2}O{sub 3} had lower core loss and better frequency stability than FeSiAl core. • The insulating layer between ferromagnetic particles can reduce core loss. - Abstract: FeSiAl/SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores with tunable insulating layer thicknesses have been synthesized via a modified Stöber method combined with following high temperature sintering process. Most of the conductive FeSiAl particles could be coated by insulating SiO{sub 2} using the modified Stöber method. During the sintering process, the reaction 4Al + 3SiO{sub 2} ≣ 2α-Al{sub 2}O{sub 3} + 3Si took place and the new Fe{sub 3}Si/Al{sub 2}O{sub 3} composite was formed. The Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher resistivity and lower core loss than the raw FeSiAl core. Based on this, several types of FeSiAl/SiO{sub 2} particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores with tunable insulating layer thicknesses were selectively prepared by simply varying TEOS contents. The thickness of Al{sub 2}O{sub 3} insulating layer and resistivity of Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores increased with increasing the TEOS contents, while the permeability and core loss changed in the opposite direction.

  3. Photoluminescence of Er-doped Si-SiO2 and Al-Si-SiO2 sputtered thin films

    International Nuclear Information System (INIS)

    Rozo, C.; Fonseca, L.F.; Jaque, D.; Sole, J.Garcia

    2008-01-01

    Er-doped Si-SiO 2 and Al-Si-SiO 2 films have been deposited by rf-sputtering being annealed afterwards. Annealing behavior of the Er 3+ : 4 I 13/2 → 4 I 15/2 emission of Er-doped Si-SiO 2 yields a maximum intensity for annealing at 700-800 deg. C. 4 I 13/2 → 4 I 15/2 peak emission for Er-doped Al-Si-SiO 2 at 1525 nm is shifted from that for Er-doped Si-SiO 2 at 1530 nm and the bandwidth increases from 29 to 42 nm. 4 I 13/2 → 4 I 15/2 emission decays present a fast decaying component related to Er ions coupled to Si nanoparticles, defects, or other ions, and a slow decaying component related to isolated Er ions. Excitation wavelength dependence and excitation power dependence for the 4 I 13/2 → 4 I 15/2 emission correspond with energy transfer from Si nanoparticles. Populating of the 4 I 11/2 level in Er-doped Si-SiO 2 involves branching and energy transfer upconversion involving two or more Er ions. Addition of Al reduces the populating of this level to an energy transfer upconversion involving two ions

  4. The constitution of alloys in the Al-rich corner of the Al-Si-Sm ternary system

    International Nuclear Information System (INIS)

    Markoli, B.; Spaic, S.; Zupanic, F.

    2001-01-01

    The constitution of alloys and the liquidus surface in the Al-rich corner of the Al-Si-Sm ternary system were determined by the examination of controlled heated and cooled specimens, as well as heat-treated specimens by means of optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential thermal analysis and X-ray diffraction. The Al-rich corner of the Al-Si-Sm ternary system comprises five regions of primary crystallisation (α Al , β Si , Al 3 Sm, Al 2 Si 2 Sm and AlSiSm) with following characteristic invariant reaction sequences: ternary eutectic reaction L → α Al + β Si + Al 2 Si 2 Sm, and two liquidus transition reactions, i. e., L + Al 3 Sm → α Al + AlSiSm, and L + AlSiSm → α Al + Al 2 Si 2 Sm. Along with the position of ternary eutectic and both interstitial points in the Al-rich corner of the Al-Si-Sm ternary system, the temperatures for each reaction were determined. (orig.)

  5. Karakterisasi Paduan AlMgSi Untuk Kelongsong Bahan Bakar U3Si2/Al Dengan Densitas Uranium 5,2 gU/cm3

    Directory of Open Access Journals (Sweden)

    Aslina Br. Ginting

    2018-03-01

    Full Text Available Meningkatnya densitas uranium dari 2,96 gU/cm3 menjadi 5,2 gU/cm3 bahan bakar U3Si2/Al harus diikuti dengan penggunaan kelongsong yang kompatibel. Bahan bakar berdensitas tinggi mempunyai kekerasan yang tinggi, sehingga bila menggunakan paduan AlMg2 sebagai kelongsong dapat menyebabkan terjadi dogbone pada saat perolan. Selain fenomena dogbone, pada saat bahan bakar tersebut digunakan di reaktor dapat terjadi swelling karena meningkatnya hasil fisi maupun burn up. Oleh karena itu, perlu dicari pengganti bahan kelongsong untuk bahan bakar U3Si2/Al densitas tinggi. Pada penelitian ini telah dilakukan karakterisasi paduan AlMgSi sebagai kandidat pengganti kelongsong AlMg2. Karakterisasi yang dilakukan meliputi analisis termal, kekerasan, mikrostruktur dan laju korosi. Analisis termal dilakukan menggunakan DTA (Differential Thermal Analysis dan DSC (Differential Scanning Calorimetry. Analisis kekerasan menggunakan alat uji kekerasan mikro, mikrostruktur menggunakan SEM (Scanning Electron Microscope dan analisis laju korosi dilakukan dengan pemanasan pada temperatur 150 oC selama 77 jam di dalam autoclave. Hasil analisis menunjukkan bahwa kelongsong AlMgSi maupun AlMg2 mempunyai kompatibilitas panas dengan bahan bakar U3Si2/Al cukup stabil hingga temperatur 650 oC. Kelongsong AlMgSi mempunyai kekerasan sebesar 115 HVN dan kelongsong AlMg2 sebesar 70,1 HVN. Sementara itu, analisis mikrostruktur menunjukkan bahwa morfologi ikatan antarmuka (interface bonding kelongsong AlMgSi lebih baik dari kelongsong AlMg2, demikian halnya dengan laju korosi bahwa kelongsong AlMgSi mempunyai laju korosi lebih kecil dibanding kelongsong AlMg2. Hasil karakterisasi termal, kekerasan, mikrostruktur dan laju korosi menunjukkan bahwa PEB U3Si2/Al densitas 5,2 gU/cm3 menggunakan kelongsong AlMgSi lebih baik dibanding PEB U3Si2/Al  densitas 5,2 gU/cm3  menggunakan kelongsong AlMg2. Kata kunci: U3Si2/Al, densitas 5,2 gU/cm3, kelongsong AlMgSi dan AlMg2.

  6. Synthesis of geopolymer from spent FCC: Effect of SiO2/Al2O<3 and Na2O/SiO2 molar ratios

    Directory of Open Access Journals (Sweden)

    Trochez, J. J.

    2015-03-01

    Full Text Available This paper assesses the feasibility of using a spent fluid catalytic cracking catalyst (SFCC as precursor for the production of geopolymers. The mechanical and structural characterization of alkali-activated SFCC binders formulated with different overall (activator + solid precursor SiO2/Al2O3 and Na2O/SiO2 molar ratios are reported. Formation of an aluminosilicate ‘geopolymer’ gel is observed under all conditions of activation used, along with formation of zeolites. Increased SiO2/Al2O3 induces the formation of geopolymers with reduced mechanical strength, for all the Na2O/SiO2 ratios assessed, which is associated with excess silicate species supplied by the activator. This is least significant at increased alkalinity conditions (higher Na2O/SiO2 ratios, as larger extents of reaction of the spent catalyst are achieved. SiO2/Al2O3 and Na2O/SiO2 ratios of 2.4 and 0.25, respectively, promote the highest compressive strength (67 MPa. This study elucidates the great potential of using SFCC as precursor to produce sustainable ceramic-like materials via alkali-activation.Este artículo estudia la factibilidad de usar un catalizador gastado del proceso de craqueo (SFCC para la producción de geopolímeros. Se evalúan las características mecánicas y estructurales de los geopolímeros producidos con diferentes relaciones molares (activador + precursor solido de SiO2/Al2O3 y Na2O/SiO2. La formación de un gel geopolimérico de tipo aluminosilicato se observa a las diferentes condiciones evaluadas, así como la formación de zeolitas. Un incremento en la relación SiO2/Al2O3 genera geopolímeros de baja resistencia mecánica, a las diferentes relaciones molares Na2O/SiO2 evaluadas, como consecuencia del exceso de especies silicato provenientes del activador. Este efecto es menos significativo al incrementar las condiciones de alcalinidad (mayores relaciones Na2O/SiO2, ya que un mayor grado de reacción del catalizador gastado es alcanzado. Las

  7. The constitution of alloys in the Al-rich corner of the Al-Si-Sm ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Markoli, B.; Spaic, S. [Ljubljana Univ. (Slovenia). Faculty of Natural Science and Engineering; Zupanic, F. [Maribor Univ. (Slovenia). Faculty of Mechanical Engineering

    2001-09-01

    The constitution of alloys and the liquidus surface in the Al-rich corner of the Al-Si-Sm ternary system were determined by the examination of controlled heated and cooled specimens, as well as heat-treated specimens by means of optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential thermal analysis and X-ray diffraction. The Al-rich corner of the Al-Si-Sm ternary system comprises five regions of primary crystallisation ({alpha}{sub Al}, {beta}{sub Si}, Al{sub 3}Sm, Al{sub 2}Si{sub 2}Sm and AlSiSm) with following characteristic invariant reaction sequences: ternary eutectic reaction L {yields} {alpha}{sub Al} + {beta}{sub Si} + Al{sub 2}Si{sub 2}Sm, and two liquidus transition reactions, i. e., L + Al{sub 3}Sm {yields} {alpha}{sub Al} + AlSiSm, and L + AlSiSm {yields} {alpha}{sub Al} + Al{sub 2}Si{sub 2}Sm. Along with the position of ternary eutectic and both interstitial points in the Al-rich corner of the Al-Si-Sm ternary system, the temperatures for each reaction were determined. (orig.)

  8. Effect of Al and AlP on the microstructure of Mn-30 wt.%Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yuying [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jing Shi Road 73, Jinan 250061 (China); Liu Xiangfa [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jing Shi Road 73, Jinan 250061 (China)], E-mail: xfliu@sdu.edu.cn

    2008-04-15

    Effect of Al and AlP particles on the microstructure of near eutectic Mn-Si alloy (Mn-30 wt.%Si) was studied by Electron Probe Micro-analyzer (EPMA) and Differential Scanning Calorimeter (DSC). Crystal lattice correspondence analyses show that both Al and AlP have good lattice matching coherence relationships with MnSi phase, and the addition of Al and AlP particles results in an abnormal eutectic structure, i.e. the eutectic constitution MnSi and Mn{sub 5}Si{sub 3} precipitate separately: MnSi precipitates firstly, and then the Mn{sub 5}Si{sub 3} phase.

  9. Surface acoustic wave devices on AlN/3C–SiC/Si multilayer structures

    International Nuclear Information System (INIS)

    Lin, Chih-Ming; Lien, Wei-Cheng; Riekkinen, Tommi; Senesky, Debbie G; Pisano, Albert P; Chen, Yung-Yu; Felmetsger, Valery V

    2013-01-01

    Surface acoustic wave (SAW) propagation characteristics in a multilayer structure including a piezoelectric aluminum nitride (AlN) thin film and an epitaxial cubic silicon carbide (3C–SiC) layer on a silicon (Si) substrate are investigated by theoretical calculation in this work. Alternating current (ac) reactive magnetron sputtering was used to deposit highly c-axis-oriented AlN thin films, showing the full width at half maximum (FWHM) of the rocking curve of 1.36° on epitaxial 3C–SiC layers on Si substrates. In addition, conventional two-port SAW devices were fabricated on the AlN/3C–SiC/Si multilayer structure and SAW propagation properties in the multilayer structure were experimentally investigated. The surface wave in the AlN/3C–SiC/Si multilayer structure exhibits a phase velocity of 5528 m s −1 and an electromechanical coupling coefficient of 0.42%. The results demonstrate the potential of AlN thin films grown on epitaxial 3C–SiC layers to create layered SAW devices with higher phase velocities and larger electromechanical coupling coefficients than SAW devices on an AlN/Si multilayer structure. Moreover, the FWHM values of rocking curves of the AlN thin film and 3C–SiC layer remained constant after annealing for 500 h at 540 °C in air atmosphere. Accordingly, the layered SAW devices based on AlN thin films and 3C–SiC layers are applicable to timing and sensing applications in harsh environments. (paper)

  10. Laser cladding of Al-Si/SiC composite coatings : Microstructure and abrasive wear behavior

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Vilar, R.; Ocelik, V.; De Hosson, J.Th.M.

    2007-01-01

    Surface coatings of an Al-Si-SiC composite were produced on UNS A03560 cast Al-alloy substrates by laser cladding using a mixture of powders of Al-12 wt.% Si alloy and SiC. The microstructure of the coatings depends considerably on the processing parameters. For a specific energy of 26 MJ/m2 the

  11. State diagram of U-Al-Si as a basis for analysis of the processes in nuclear fuel compositions based on U(Al, Si)3 and U3Si compounds

    International Nuclear Information System (INIS)

    Chebotarev, N.T.; Konovalov, L.N.; Zhmak, V.A.; Chebotarev, Ya.N.

    1996-01-01

    Results of studies into the Al-UAl 3 -USi 3 -Si of the U-Al-Si ternary system are presented. It is established that phase equilibrium between the intermetallic compound U(Al, Si) 3 and the aluminium-silicon alloys may be presented in form of conodes on the isothermal cross-section of the state diagram. It is shown that the U(Al, Si) 3 intermetallic compound, containing up to 6.5 at.% silicon, interacts both with liquid and solid aluminium with the U(Al, Si) 4 phase formation [ru

  12. Solid-state {sup 27}Al and {sup 29}Si NMR investigations on Si-substituted hydrogarnets

    Energy Technology Data Exchange (ETDEWEB)

    Rivas Mercury, J.M. [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain); Pena, P. [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain)]. E-mail: ppena@icv.csic.es; Aza, A.H. de [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain); Turrillas, X. [Instituto de Ciencias de la Construccion Eduardo Torroja, CSIC, Serrano Galvache, 4, 28033 Madrid (Spain); Sobrados, I. [Instituto de Ciencia de Materiales, CSIC, Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco-Madrid (Spain); Sanz, J. [Instituto de Ciencia de Materiales, CSIC, Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco-Madrid (Spain)

    2007-02-15

    Partially deuterated Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-x}(OH){sub 4x} hydrates prepared by a reaction in the presence of D{sub 2}O of synthetic tricalcium aluminate with different amounts of amorphous silica were characterized by {sup 29}Si and {sup 27}Al magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The {sup 29}Si NMR spectroscopy was used for quantifying the non-reacted silica and the resulting hydrated products. The incorporation of Si into Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-x}(OH){sub 4x} was followed by {sup 27}Al NMR spectroscopy: Si:OH ratios were determined quantitatively from octahedral Al signals ascribed to Al(OH){sub 6} and Al(OSi)(OH){sub 5} environments. The NMR data obtained were consistent with the concentrations of the Al and Si species deduced from transmission electron microscopy energy-dispersive spectrometry and Rietveld analysis of both X-ray and neutron diffraction data.

  13. Óxidos de estaño: nuevos anodos para baterías de Ion-Litio

    OpenAIRE

    Morales Palomino, Julián; Sánchez, L.

    1999-01-01

    La reacci n entre el litio y xidos aleaciones de esta o es reversible cuando se realiza por m todos electroqu micos y a bajos potenciales con respecto al electrodo de litio. Esta propiedad permite el uso de estos materiales como electrodos negativos en el dise o y construcci n de bater as tipo ion-litio. En el caso de xidos de esta o la reacci n de inserci n de litio en la matriz conduce a la formaci n de aleaciones Li-Sn. La presencia de agregados grandes de tomos de esta o, fo...

  14. Fabrication and Analysis of the Wear Properties of Hot-Pressed Al-Si/SiCp + Al-Si-Cu-Mg Metal Matrix Composite

    Science.gov (United States)

    Bang, Jeongil; Oak, Jeong-Jung; Park, Yong Ho

    2016-01-01

    The aim of this study was to characterize microstructures and mechanical properties of aluminum metal matrix composites (MMC's) prepared by powder metallurgy method. Consolidation of mixed powder with gas atomized Al-Si/SiCp powder and Al-14Si-2.5Cu-0.5Mg powder by hot pressing was classified according to sintering temperature and sintering time. Sintering condition was optimized using tensile properties of sintered specimens. Ultimate tensile strength of the optimized sintered specimen was 228 MPa with an elongation of 5.3% in longitudinal direction. In addition, wear properties and behaviors of the sintered aluminum-based MMC's were analyzed in accordance with vertical load and linear speed. As the linear speed and vertical load of the wear increased, change of the wear behavior occurred in order of oxidation of Al-Si matrix, formation of C-rich layer, Fe-alloying to matrix, and melting of the specimen

  15. Effect of Heat Treatment on Commercial AlSi12Cu1(Fe) and AlSi12(b) Aluminum Alloy Die Castings

    Science.gov (United States)

    Battaglia, E.; Bonollo, F.; Ferro, P.; Fabrizi, A.

    2018-03-01

    High-pressure die castings (HPDCs) cannot normally be heat-treated at a high temperature because of the presence of inner air/gas- or shrinkage-porosity that may lead to the formation of undesired surface blisters. In this paper, an unconventional heat treatment is proposed. Two secondary Al-Si alloys, AlSi12(b) and AlSi12Cu1(Fe), were stabilization heat-treated at 624 K (350 °C) with soaking times ranging from 1 to 8 hours. Enhancement of both static and dynamic mechanical properties was found to be related to the fragmentation of interconnected eutectic Si particles and the smoothing of coarser crystals. Increased ductility after heat treatment was correlated with a decrease in hardness and Si particle roundness. The formation of Si precipitates within the α-Al matrix was also observed.

  16. The Co-60 gamma-ray irradiation effects on the Al/HfSiO4/p-Si/Al MOS capacitors

    Science.gov (United States)

    Lok, R.; Kaya, S.; Karacali, H.; Yilmaz, E.

    2017-12-01

    In this work, the initial interface trap density (Nit) to examine device compability for microelectronics and then the Co-60 gamma irradiation responses of Al/HfSiO4/p-Si/Al (MOS) capacitors were investigated in various dose ranges up to 70 Gy. Pre-irradiation response of the devices was evaluated from high frequency (HF) and low frequency (LF) capacitance method and the Nit was calculated as 9.91 × 1011 cm-2 which shows that the HfSiO4/p-Si interface quality is convenient for microelectronics applications. The irradiation responses of the devices were carried out from flat-band and mid-gap voltage shifts obtained from stretch of capacitance characteristics prior to and after irradiation. The results show that the flat band voltages very slightly shifted to positive voltage values demonstrating the enhancement of negative charge trapping in device structure. The sensitivity of the Al/HfSiO4/p-Si/Al MOS capacitors was found to be 4.41 mV/Gy for 300 nm-thick HfSiO4 gate dielectrics. This value approximately 6.5 times smaller compared to the same thickness conventional SiO2 based MOS devices. Therefore, HfSiO4 exhibits crucial irradiation tolerance in gamma irradiation environment. Consequently, HfSiO4 dielectrics may have significant usage for microelectronic technology as a radiation hard material where radiation field exists such as in space applications.

  17. Growth of CNTs on Fe-Si catalyst prepared on Si and Al coated Si substrates

    International Nuclear Information System (INIS)

    Teng, F-Y; Ting, J-M; Sharma, Sahendra P; Liao, Kun-Hou

    2008-01-01

    In this paper we report the effect of Al interlayers on the growth characteristics of carbon nanotubes (CNTs) using as-deposited and plasma etched Fe-Si catalyst films as the catalysts. Al interlayers having various thicknesses ranging from 2 to 42 nm were deposited on Si substrates prior to the deposition of Fe-Si catalysts. It was found that the Al interlayer diffuses into the Fe-Si catalyst during the plasma etching prior to the CNT growth, leading to the swelling and amorphization of the catalyst. This allows enhanced carbon diffusion in the catalyst and therefore a faster growth rate of the resulting CNTs. It was also found that use of an Al interlayer having a thickness of ∼3 ± 1 nm is most effective. Due to the effectiveness of this, the normally required catalyst etching is no longer needed for the growth of CNTs

  18. Growth of CNTs on Fe-Si catalyst prepared on Si and Al coated Si substrates.

    Science.gov (United States)

    Teng, F-Y; Ting, Jyh-Ming; Sharma, Sahendra P; Liao, Kun-Hou

    2008-03-05

    In this paper we report the effect of Al interlayers on the growth characteristics of carbon nanotubes (CNTs) using as-deposited and plasma etched Fe-Si catalyst films as the catalysts. Al interlayers having various thicknesses ranging from 2 to 42 nm were deposited on Si substrates prior to the deposition of Fe-Si catalysts. It was found that the Al interlayer diffuses into the Fe-Si catalyst during the plasma etching prior to the CNT growth, leading to the swelling and amorphization of the catalyst. This allows enhanced carbon diffusion in the catalyst and therefore a faster growth rate of the resulting CNTs. It was also found that use of an Al interlayer having a thickness of ∼3 ± 1 nm is most effective. Due to the effectiveness of this, the normally required catalyst etching is no longer needed for the growth of CNTs.

  19. Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen

    Science.gov (United States)

    Zhirkov, I.; Landälv, L.; Göthelid, E.; Ahlgren, M.; Eklund, P.; Rosen, J.

    2017-02-01

    Al2O3 alloyed with Cr is an important material for the tooling industry. It can be synthesized from an arc discharge using Al-Cr cathodes in an oxygen atmosphere. Due to formation of Al-rich oxide islands on the cathode surface, the arc process stability is highly sensitive to oxygen pressure. For improved stability, the use of Al0.70Cr0.25Si0.05 cathodes has previously been suggested, where Si may reduce island formation. Here, we have investigated the effect of Si by comparing plasma generation and thin film deposition from Al0.7Cr0.3 and Al0.7Cr0.25Si0.05 cathodes. Plasma ion composition, ion energies, ion charge states, neutral species, droplet formation, and film composition have been characterized at different O2 flow rates for arc currents of 60 and 90 A. Si and related compounds are detected in plasma ions and in plasma neutrals. Scanning electron microscopy and energy dispersive X-ray analysis show that the cathode composition and the film composition are the same, with Si present in droplets as well. The effect of Si on the process stability, ion energies, and ion charge states is found to be negligible compared to that of the arc current. The latter is identified as the most relevant parameter for tuning the properties of the reactive discharge. The present work increases the fundamental understanding of plasma generation in a reactive atmosphere, and provides input for the choice of cathode composition and process parameters in reactive DC arc synthesis.

  20. Evolución Microestructural en Uniones de la Aleación Ti-6Al-4V Mediante el Proceso de Soldadura de Punto por Fricción-agitación

    Directory of Open Access Journals (Sweden)

    Flor Araceli Garcia-Castillo

    Full Text Available Resumen La soldadura de punto por fricción-agitación (Friction Stir Spot Welding, FSSW es un tema de reciente desarrollo e interés, principalmente en aleaciones de Titanio, ya que existen estudios previos realizados en aleaciones de aluminio, magnesio, aceros y polímeros. Las aleaciones de Titanio tienen una amplia aplicación en la industria aeronáutica, principalmente como componentes en el tren de aterrizaje en aviones comerciales, por lo cual este trabajo se centra en la aleación Ti-6Al-4V, este tipo de aleación presenta fases alfa (α y beta (β, brindado mejor balance en propiedades mecánicas de dureza y esfuerzo a la tensión. El proceso FSSW se realizó mediante un centro de maquinado de alta velocidad, utilizando una velocidad de rotación de 500 RPM, una velocidad de penetración de la herramienta de 2 mm/s y 3 s en tiempo de sostenimiento, en láminas con un espesor de 1,5 mm y una longitud de traslape de 20 mm. Los resultados mostraron el efecto de las variables del proceso de soldadura FSSW sobre la microestructura de la aleación Ti-6Al-4V ocasionada por el efecto térmico y la deformación plástica del proceso de la soldadura, concluyendo que una adecuada combinación de parámetros permite realizar una unión sin defectos.

  1. Studies on SiC(p) reinforced Al-Al sub 3 Ni eutectic matrix composites

    International Nuclear Information System (INIS)

    Masrom, A.K.; Foo, L.C.; Ismail, A.B.

    1996-01-01

    An investigation on processing of Al-5.69wt% Ni eutectic with SiC particulate composites is reported. The intermetallic composites are prepared by elemental powder metallurgy route and sintered at two different temperatures, i.e., 600 degree C and 620 degree C. Results show that the metal matrix was Al-Al sub 3 Ni eutectic. The phase analysis by XRD identified the presence of Al sub 3 Ni and Al as dominant phases together with silicon and Al sub 4 C sub 3 phase as minor phases. The Al sub 4 C sub 3 and Si phases are formed during sintering due to SiC-Al interface reaction. SEM micrographs also reveal the formation of microvoid surrounding the SiC particle

  2. The electrochemical properties of melt-spun Al-Si-Cu alloys

    International Nuclear Information System (INIS)

    Zhang Linping; Wang Fei; Liang Pu; Song Xianlei; Hu Qing; Sun Zhanbo; Song Xiaoping; Yang Sen; Wang Liqun

    2011-01-01

    Highlights: → Non-equilibrium Al 75-X Si 25 Cu X alloys exhibit high lithiation storages. → The lithiation mechanism is different from melt-spun Al-Si-Mn system. → The structural evolution is mitigated in the non-equilibrium alloys. → Volume variation is alleviated due to the co-existence of Al 2 Cu, α-Si and α-Al. - Abstract: Melt spinning was used to prepare Al 75-X Si 25 Cu X (X = 1, 4, 7, 10 mol%) alloy anode materials for lithium-ion batteries. A metastable supersaturated solid solution of Si and Cu in fcc-Al, α-Si and Al 2 Cu co-existed in the alloys. Nano-scaled α-Al grains, as the matrix, formed in the as-quenched ribbons. The Al 74 Si 25 Cu 1 and Al 71 Si 25 Cu 4 anodes exhibited initial discharge specific capacities of 1539 mAh g -1 , 1324 mAh g -1 and reversible capacities above 472 mAh g -1 , 508 mAh g -1 at the 20th cycle, respectively. The specific capacities reduced as the increase of the Cu content. AlLi intermetallic compound was detected in the lithiated alloys. It is concluded that the lithiation mechanism of the Al-Si-based alloys can be affected by the third component. The structural evolution and volume variation can be mitigated due to the formation of non-equilibrium state and the co-existence of nano-scaled α-Al, α-Si, and Al 2 Cu for the present alloys.

  3. On compensation in Si-doped AlN

    Science.gov (United States)

    Harris, Joshua S.; Baker, Jonathon N.; Gaddy, Benjamin E.; Bryan, Isaac; Bryan, Zachary; Mirrielees, Kelsey J.; Reddy, Pramod; Collazo, Ramón; Sitar, Zlatko; Irving, Douglas L.

    2018-04-01

    Controllable n-type doping over wide ranges of carrier concentrations in AlN, or Al-rich AlGaN, is critical to realizing next-generation applications in high-power electronics and deep UV light sources. Silicon is not a hydrogenic donor in AlN as it is in GaN; despite this, the carrier concentration should be controllable, albeit less efficiently, by increasing the donor concentration during growth. At low doping levels, an increase in the Si content leads to a commensurate increase in free electrons. Problematically, this trend does not persist to higher doping levels. In fact, a further increase in the Si concentration leads to a decrease in free electron concentration; this is commonly referred to as the compensation knee. While the nature of this decrease has been attributed to a variety of compensating defects, the mechanism and identity of the predominant defects associated with the knee have not been conclusively determined. Density functional theory calculations using hybrid exchange-correlation functionals have identified VAl+n SiAl complexes as central to mechanistically understanding compensation in the high Si limit in AlN, while secondary impurities and vacancies tend to dominate compensation in the low Si limit. The formation energies and optical signatures of these defects in AlN are calculated and utilized in a grand canonical charge balance solver to identify carrier concentrations as a function of Si content. The results were found to qualitatively reproduce the experimentally observed compensation knee. Furthermore, these calculations predict a shift in the optical emissions present in the high and low doping limits, which is confirmed with detailed photoluminescence measurements.

  4. Influence of secondary ageing temperature on hardening and residual elastic stresses in AlMgSi and AlMgSiCu alloys

    International Nuclear Information System (INIS)

    Milosavlevich, A.Ya.; Shiyachki-Zheravchich; Rogulin, M.Ya.; Milenkovich, V.M.; Prokich-Tsvetkovich, R.M.

    1993-01-01

    The investigations were conducted on samples of AlMgSi and AlMgSiCu alloys quenched, aged and cold worked with 20, 40, 60 and 85 % reduction in area. Secondary ageing was carried out at 200 and 250 deg C. Residual stresses wee determined by X-ray diffraction method. It was shown that cold deformation effect on hardness and residual stresses is dependent on alloy composition. The hardening due to secondary ageing is more pronounced for AlMgSi alloy at 200 deg C and for AlMgSiCu alloy at 250 deg C. Positive residual stresses increase with secondary ageing temperature

  5. PRODUCCIÓN Y CARACTERIZACIÓN DE PARTÍCULAS Y FIBRAS CORTAS DE β-SiC OBTENIDAS A PARTIR DE CÁSCARA DE ARROZ

    Directory of Open Access Journals (Sweden)

    Marco Valencia

    Full Text Available El aprovechamiento de la cáscara de arroz (CA es mínimo en la mayoría de los países latinoamericanos y solo una pequeña porción se utiliza eficientemente como abono o combustible. Los productos obtenidos por pirólisis de CA son, sin embargo, útiles para la fabricación de productos abrasivos y refractarios a base de carburo de silicio (SiC. Hay aplicaciones de reciente desarrollo y de mayor exigencia que consisten en usar el SiC como refuerzo de aleaciones metálicas para la fabricación de composites metálicos. En esta investigación se han obtenido fibrillas cortas y partículas finas de SiC por pirólisis controlada de CA. La síntesis del SiC se llevó a cabo en un horno de gas diseñado y puesto a punto durante el desarrollo del proyecto. El proceso fue optimizado mediante un diseño experimental que incluyó como variables la temperatura, el tiempo de pirólisis, el tipo de catalizador y la atmósfera de proceso.

  6. The electrochemical properties of melt-spun Al-Si-Cu alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Linping; Wang Fei; Liang Pu; Song Xianlei; Hu Qing [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Sun Zhanbo, E-mail: szb@mail.xjtu.edu.cn [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Song Xiaoping; Yang Sen; Wang Liqun [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

    2011-10-03

    Highlights: {yields} Non-equilibrium Al{sub 75-X}Si{sub 25}Cu{sub X} alloys exhibit high lithiation storages. {yields} The lithiation mechanism is different from melt-spun Al-Si-Mn system. {yields} The structural evolution is mitigated in the non-equilibrium alloys. {yields} Volume variation is alleviated due to the co-existence of Al{sub 2}Cu, {alpha}-Si and {alpha}-Al. - Abstract: Melt spinning was used to prepare Al{sub 75-X}Si{sub 25}Cu{sub X} (X = 1, 4, 7, 10 mol%) alloy anode materials for lithium-ion batteries. A metastable supersaturated solid solution of Si and Cu in fcc-Al, {alpha}-Si and Al{sub 2}Cu co-existed in the alloys. Nano-scaled {alpha}-Al grains, as the matrix, formed in the as-quenched ribbons. The Al{sub 74}Si{sub 25}Cu{sub 1} and Al{sub 71}Si{sub 25}Cu{sub 4} anodes exhibited initial discharge specific capacities of 1539 mAh g{sup -1}, 1324 mAh g{sup -1} and reversible capacities above 472 mAh g{sup -1}, 508 mAh g{sup -1} at the 20th cycle, respectively. The specific capacities reduced as the increase of the Cu content. AlLi intermetallic compound was detected in the lithiated alloys. It is concluded that the lithiation mechanism of the Al-Si-based alloys can be affected by the third component. The structural evolution and volume variation can be mitigated due to the formation of non-equilibrium state and the co-existence of nano-scaled {alpha}-Al, {alpha}-Si, and Al{sub 2}Cu for the present alloys.

  7. Construction and evaluation of multi-component Zn-Al based bearing alloys (Zn-Al-Si, Zn-Al-Cu)

    International Nuclear Information System (INIS)

    Shahmiri, M.; Shahin, K.

    2001-01-01

    Zn-Al based alloys, with excellent mechanical properties, are finding increasing applications in various industries, especially bearing and bushing fields. Observed dimensional instabilities, in their multicomponent systems, (e. g. Zn-Al-Si and, Zn-Al Si-Cu), is believed to be as the result of some kinds of phase transformation, due to the temperature variations, while in service. Profound understanding of the phase transformations due to the temperature variation, requires detailed evaluations of the isothermal sections of the multi-components phase diagrams of Zn-Al-Si and, Zn-Al-Si-Cu alloy systems. In the present article, the isothermal sections of the aforementioned ternary and quaternary systems in the solid state regions have been investigated and observed phase transitions have been critically evaluated

  8. Low silicon U(Al,Si)3 stabilization by Zr addition

    International Nuclear Information System (INIS)

    Pizarro, L.M.; Alonso, P.R.; Rubiolo, G.H.

    2009-01-01

    Previous knowledge states that (U,Zr)Al 3 and U(Al,Si) 3 phases with Zr and Si content higher than 6 at.% (7.7 wt%) and 4 at.% (1.4 wt%), respectively, does not partially transform to UAl 4 at 600 o C. In this work, four alloys within the quaternary system U-Al-Si-Zr were made with a fixed nominal 0.18 at.% (0.1 wt%) Si content in order to assess the synergetic effect of both Zr and Si alloying elements to the thermodynamic stability of the (U,Zr)(Al,Si) 3 phase. Heat treatments at 600 deg. C were undertaken and samples were analyzed by means of XRD, EPMA and EDS techniques. A remarkable conclusion is that addition of 0.3 at.% Si in the (U,Zr)(Al,Si) 3 phase reduces in 2.7 at.% the necessary Zr content to inhibit its transformation to U(Al,Si) 4 .

  9. Structure and wear behavior of AlCrSiN-based coatings

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yun [School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Chengdu Tool Research Institute Co., Ltd., Chengdu 610500 (China); Du, Hao [School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065 (China); Chen, Ming, E-mail: mchen@sjtu.edu.cn [School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Yang, Jun [Chengdu Tool Research Institute Co., Ltd., Chengdu 610500 (China); Xiong, Ji [School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065 (China); Zhao, Haibo [The Analysis and Testing Centre, Sichuan University, Chengdu 610065 (China)

    2016-05-01

    Graphical abstract: - Highlights: • AlCrSiN based coating showed amorphous structure. • AlCrSiN/Me{sub x}N coatings obtained better wear resistance. • Molybdenum and niobium increased the coating hardness and wear resistance. - Abstract: AlCrN, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings have been deposited on high-polished WC–Co cemented carbide substrate and tools by mid-frequency magnetron sputtering in Ar/N{sub 2} mixtures. Al{sub 0.6}Cr{sub 0.4}, Al{sub 0.6}Cr{sub 0.3}Si{sub 0.1}, and C/Mo/Nb targets were used during the deposition. The microstructure and mechanical properties of as-deposited coatings were investigated. Investigations of the wear behaviors of coated tools were also performed. The results showed that cubic structure was formed in the coatings. Broader CrAlN (1 1 1) and (2 0 0) peaks without SiN{sub x} peak were formed in the AlCrSiN/Me{sub x}N coatings, which showed a nanocomposited structure. Meanwhile, according to SEM micrographs, AlCrN exhibited a columnar structure, while, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings showed nanocrystalline morphology. The nano-multilayered coatings performed higher hardness, H/E, and H{sup 3}/E{sup 2} ratios compared with AlCrN coating. Through the Rockwell adhesion test, all the coatings exhibited adhesion strength quality HF1. After turning Inconel 718 under dry condition, the nano-multilyered coatings showed better wear resistance than AlCrN coating. Due to the molybdenum and niobium in the coating, AlCrSiN/MoN and AlCrSiN/NbN coatings showed the best wear resistance.

  10. Microstructure and properties of an Al-Ti-Cu-Si brazing alloy for SiC-metal joining

    Science.gov (United States)

    Dai, Chun-duo; Ma, Rui-na; Wang, Wei; Cao, Xiao-ming; Yu, Yan

    2017-05-01

    An Al-Ti-Cu-Si solid-liquid dual-phase alloy that exhibits good wettability and appropriate interfacial reaction with SiC at 500-600°C was designed for SiC-metal joining. The microstructure, phases, differential thermal curves, and high-temperature wetting behavior of the alloy were analyzed using scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and the sessile drop method. The experimental results show that the 76.5Al-8.5Ti-5Cu-10Si alloy is mainly composed of Al-Al2Cu and Al-Si hypoeutectic low-melting-point microstructures (493-586°C) and the high-melting-point intermetallic compound AlTiSi (840°C). The contact angle, determined by high-temperature wetting experiments, is approximately 54°. Furthermore, the wetting interface is smooth and contains no obvious defects. Metallurgical bonding at the interface is attributable to the reaction between Al and Si in the alloy and ceramic, respectively. The formation of the brittle Al4C3 phase at the interface is suppressed by the addition of 10wt% Si to the alloy.

  11. United modification of Al-24Si alloy by Al-P and Al-Ti-C master alloys

    Institute of Scientific and Technical Information of China (English)

    韩延峰; 刘相法; 王海梅; 王振卿; 边秀房; 张均艳

    2003-01-01

    The modification effect of a new type of Al-P master alloy on Al-24Si alloys was investigated. It is foundthat excellent modification effect can be obtained by the addition of this new type of A1-P master alloy into Al-24Simelt and the average primary Si grain size is decreased below 47 μm from original 225 μm. It is also found that theTiC particles in the melt coming from Al8Ti2C can improve the modification effect of the Al-P master alloy. Whenthe content of TiC particles in the Al-24Si melt is 0.03 %, the improvement reaches the maximum and keeps steadywith increasing content of TiC particles. Modification effect occurs at 50 min after the addition of the Al-P master al-loy and TiC particles, and keeps stable with prolonging holding time.

  12. Microestructura y propiedades mecánicas de materiales compuestos de matriz Al-Mg-Si-Cu reforzada con AlNp, procesados por extrusión de polvos

    Directory of Open Access Journals (Sweden)

    Ortiz, José Luis

    2000-10-01

    Full Text Available This article presents an experimental investigation on the structure and mechanical properties of an Al-Mg-Si-Cu P/M alloy reinforced with 5 %, 10 % and 15 % aluminum nitride, produced by extrusión of cold compacted powders mixtures. Mechanical properties in "as extruded" and T6 conditions are compared. Differential Scanning Calorimetry and Dilatometric analysis were conducted to gain further insight into the precipitation process of these materials. Low cost 6061Al/AlNp composites can be produced with rare and small porosity by extrusión of cold compacted shapes without canning. The mechanical properties of the MMCs obtained by this process have limitations for high particles fractions because of clustering effects. All materials are always harder than the matrix and shows a similar behavior during aging processes but kinetics is changed. Potential applications of dilatometric techniques in the aging investigations of aluminum alloys and aluminum matrix composites have been established.

    Se presenta una investigación experimental sobre la relación entre la estructura y las propiedades mecánicas de materiales obtenidos mediante la extrusión en caliente de preformas de polvos compactados en frío y cuya matriz es una aleación Al-Mg-Si-Cu con composición cercana a la AA6061, reforzada con tres proporciones diferentes (5, 10 y 15 % en volumen de partículas de AlN. Se utilizó Calorimetría Diferencial de Barrido y Dilatometría sobre las muestras solubilizadas y templadas para complementar el estudio del efecto de las partículas sobre el envejecimiento de la aleación base. Se establece que es posible producir, a bajo costo, materiales compuestos de matriz metálica, MMCs, de matriz de aleación AA6061 reforzada con partículas de AlN con baja porosidad y buenas propiedades mecánicas, mediante la extrusión de mezclas de polvos compactados en frío, sin necesidad de enlatado. Sin embargo, las aglomeraciones de partículas, para

  13. Gerichtete Erstarrung von Al-Si und Al-Si-Mn Legierungen unter dem Einfluss von magnetischen Wechselfeldern

    OpenAIRE

    Orth, Andreas

    2013-01-01

    In this work, samples of two alloys, Al-Si7 and Al-Si7-Mn1, are directionally solidified and their structure microscopically analysed. Thereby, the combined influence of induced current flow and intermetallic precipitates is of particular interest. A newly modified "Artemis" setup at the institute of material physics at the DLR in Cologne allows controlled solidification velocities of 30 to 240 micron/s under a constant temperature gradient of 3 K/mm. In using silica aerogels as part of the c...

  14. Precipitation kinetics of Al-1.12 Mg{sub 2}Si-0.35 Si and Al-1.07 Mg{sub 2}Si-0.33 Cu alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gaber, A. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Gaffar, M.A. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt)]. E-mail: mgaafar@aucegypt.edu; Mostafa, M.S. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Zeid, E.F. Abo [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt)

    2007-02-21

    The kinetics of hardening precipitates of Al-1.12 wt.% Mg{sub 2}Si-0.35 wt.% Si (excess Si) and Al-1.07 wt.% Mg{sub 2}Si-0.33 wt.% Cu (balanced + Cu) alloys have been investigated by means of differential scanning calorimetry and hardness measurements. The excess Si enhances the precipitation kinetics and improves the strength of the material. On the other hand, however addition of Cu assist formation of the Q' phase which positively changed the alloy strength. The high binding energy between vacancies and solute atoms (Si and Mg) enhances the combination of Si, Mg and vacancies to form Si-Mg-vacancy clusters. These clusters act as nucleation sites for GP-zones. The coexistence of the {beta}'- and Q'-precipitates in the balanced + Cu alloy results in a higher peak age hardening compared to the alloy with Si in excess.

  15. Chemical leaching of rapidly solidified Al-Si binary alloys

    International Nuclear Information System (INIS)

    Yamauchi, I.; Takahara, K.; Tanaka, T.; Matsubara, K.

    2005-01-01

    Various particulate precursors of Al 100-x Si x (x = 5-12) alloys were prepared by a rapid solidification process. The rapidly solidified structures of the precursors were examined by XRD, DSC and SEM. Most of Si atoms were dissolved into the α-Al(fcc) phase by rapid solidification though the solubility of Si in the α-Al phase is negligibly small in conventional solidification. In the case of 5 at.% Si alloy, a single α-Al phase was only formed. The amount of the primary Si phase increased with increase of Si content for the alloys beyond 8 at.% Si. Rapid solidification was effective to form super-saturated α-Al precursors. These precursors were chemically leached by using a basic solution (NaOH) or a hydrochloric acid (HCl) solution. All Al atoms were removed by a HCl solution as well as a NaOH solution. Granules of the Si phase were newly formed during leaching. The specific surface area was about 50-70 m 2 /g independent of Si content. The leaching behavior in both solutions was slightly different. In the case of a NaOH solution, the shape of the precursor often degenerated after leaching. On the other hand, it was retained after leaching by a HCl solution. Fine Si particles precipitated in the α-Al phase by annealing of as-rapidly solidified precursors at 773 K for 7.2 x 10 3 s. In this case, it was difficult to obtain any products by NaOH leaching, but a few of Si particles were obtained by HCl leaching. Precipitated Si particles were dissolved by the NaOH solution. The X-ray diffraction patterns of leached specimens showed broad lines of the Si phase and its lattice constant was slightly larger than that of the pure Si phase. The microstructures of the leached specimens were examined by transmission electron microscopy. It showed that the leached specimens had a skeletal structure composed of slightly elongated particles of the Si phase and quite fine pores. The particle size was about 30-50 nm. It was of comparable order with that evaluated by Scherer

  16. Crystallization in Y-Si-Al-O-N glasses

    Energy Technology Data Exchange (ETDEWEB)

    Leng-Ward, G; Lewis, M H

    1985-05-01

    The development of crystallization in oxynitride glasses has been characterized using transmission electron microscopy and scanning electron microscopy, X-ray (energy-dispersive) microanalysis, and powder X-ray diffraction techniques. A series of glasses was prepared while maintaining the ratio of yttrium-to-silicon-to-aluminium, but replacing oxygen with nitrogen up to the nitrogen solubility limit. On annealing at 1250 C, the oxide glass fully crystallized into yttrium disilicate (Y2Si2O7). Al2O3 and mullite (Al6Si2O13) while, with increasing nitrogen content, the disilicate phase was progressively replaced by yttrium aluminium garnet (Y3Al5O12) and nitrogen was mainly incorporated into Si2N2O. Annealing of the nitrogen glasses at 1100 C produced partial crystallization involving an intermediate phase related to nitrogen-wollastonite. Phase separation in an as-quenched SiO2-rich Y-Si-Al-O composition glass is illustrated. 9 references.

  17. First-principle study of the AlP/Si interfacial adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Dai Hongshang [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China); Du Jing [School of Science, Shandong Jianzhu University, Jinan 250101 (China); Wang Li; Peng Chuanxiao [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China); Liu Xiangfa, E-mail: xfliu@sdu.edu.c [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China); Shandong Binzhou Bohai Piston Co. Ltd., Binzhou 256602, Shandong (China)

    2010-01-15

    AlP is heterogeneous nucleation substrate of primary Si in hypereutectic Al-Si alloys, while studies on the nucleation mechanism at atomic level are absent. The pseudopotential-based DFT calculations have been carried out to investigate the atomic and electronic structure, bonding and adhesion of the AlP/Si interface. In total, eight geometries have been investigated, in which the interfacial stacking sequence is different. The favorable interfaces can be deduced for the reason that adhesive interface energies (W{sub ad}) are different, which cannot be obtained from the traditional mismatch theory. The interfacial density of states and Mulliken population are also investigated. It is found that the main bond between AlP and Si is covalent Al-Si or P-Si bond, accompanying some ionic characteristic.

  18. Comportamiento térmico de aleaciones de aluminio de la serie 2XXX sinterizadas : estudio de la influencia de la aleación mecánica y adiciones de SN y TICN

    OpenAIRE

    Santos Sánchez, Enrique

    2011-01-01

    Las principales propiedades que hacen del aluminio un material atractivo son su baja densidad, su buena resistencia mecánica específica, su ductilidad y su elevada resistencia a la corrosión. Debido a la combinación única de estas propiedades, los materiales base aluminio están cada vez más integrados y demandados en la sociedad actual. Las propiedades termomecánicas de los metales y sus aleaciones se pueden mejorar mediante la utilización de diversos tipos de refuerzos; pueden ser fibras de ...

  19. Study on Microstructure and Mechanical Properties of Hypereutectic Al-18Si Alloy Modified with Al-3B.

    Science.gov (United States)

    Gong, Chunjie; Tu, Hao; Wu, Changjun; Wang, Jianhua; Su, Xuping

    2018-03-20

    An hypereutectic Al-18Si alloy was modified via an Al-3B master alloy. The effect of the added Al-3B and the modification temperature on the microstructure, tensile fracture morphologies, and mechanical properties of the alloy were investigated using an optical microscope, Image-Pro Plus 6.0, a scanning electron microscope, and a universal testing machine. The results show that the size of the primary Si and its fraction decreased at first, and then increased as an additional amount of Al-3B was added. When the added Al-3B reached 0.2 wt %, the fraction of the primary Si in the Al-18Si alloy decreased with an increase in temperature. Compared with the unmodified Al-18Si alloy, the tensile strength and elongation of the alloy modified at 850 °C with 0.2 wt % Al-3B increased by 25% and 81%, respectively. The tensile fracture of the modified Al-18Si alloy exhibited partial ductile fracture characteristics, but there were more areas with ductile characteristics compared with that of the unmodified Al-18Si alloy.

  20. Centrifugally cast Zn-27Al-xMg-ySi alloys and their in situ (Mg2Si + Si)/ZA27 composites

    International Nuclear Information System (INIS)

    Wang Qudong; Chen Yongjun; Chen Wenzhou; Wei Yinhong; Zhai Chunquan; Ding Wenjiang

    2005-01-01

    Effects of composition, mold temperature, rotating rate and modification on microstructure of centrifugally cast Zn-27Al-xMg-ySi alloys have been investigated. In situ composites of Zn-27Al-6.3Mg-3.7Si and Zn-27Al-9.8Mg-5.2Si alloys were fabricated by centrifugal casting using heated permanent mold. These composites consist of three layers: inner layer segregates lots of blocky primary Mg 2 Si and a litter blocky primary Si, middle layer contains without primary Mg 2 Si and primary Si, outer layer contains primary Mg 2 Si and primary Si. The position, quantity and distribution of primary Mg 2 Si and primary Si in the composites are determined jointly by alloy composition, solidification velocity under the effect of centrifugal force and their floating velocity inward. Na salt modifier can refine grain and primary Mg 2 Si and make primary Mg 2 Si distribute more evenly and make primary Si nodular. For centrifugally cast Zn-27Al-3.2Mg-1.8Si alloy, the microstructures of inner layer, middle layer and outer layer are almost similar, single layer materials without primary Mg 2 Si and primary Si are obtained, and their grain sizes increased with the mold temperature increasing

  1. Electrochemical corrosion behaviour of Mg-Al alloys with thermal spray Al/SiCp composite coatings

    International Nuclear Information System (INIS)

    Pardo, A.; Feliu Jr, S.; Merino, M. C.; Mohedano, M.; Casajus, P.; Arrabal, R.

    2010-01-01

    The corrosion protection of Mg-Al alloys by flame thermal spraying of Al/SiCp composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiC particles (SiCp) varied between 5 and 30%. The as-sprayed Al/SiCp composite coatings revealed a high number of micro-channels, largely in the vicinity of the SiC particles, that facilitated the penetration of the electrolyte and the subsequent galvanic corrosion of the magnesium substrates. The application of a cold-pressing post-treatment reduced the degree of porosity of the coatings and improved the bonding at the coating/substrate and Al/SiC interfaces. This resulted in improved corrosion resistance of the coated specimens. The effectiveness of the coatings slightly decreased with the addition of 5-30 vol.% SiCp compared with the un reinforced thermal spray aluminium coatings. (Author) 31 refs.

  2. Production of 26Al by spallation of Fe, Si, Al nuclei

    International Nuclear Information System (INIS)

    Paillard, P.

    1977-01-01

    Cross sections for 7 Be, 10 Be and 26 Al formation in Al, Si and Fe targets bombarded with 0.6 and 24GeV protons have been measured by using highly selective chemical separation and low level background counters. Results for 26 Al at 0.6GeV are in mb: 17.9 + or - 2.7 in Al, 12.5 + or - 2.5 in Si and 0.45 + or - 0.14 in Fe; at 24GeV 2.6 + or - 0.5mb in Fe. Results for 10 Be are not valid on account of experimental difficulties. It is deduced from these values of aluminium in cosmic ray propagation that 26 Al is not yet cosmic ray chronometer [fr

  3. Electrochemical corrosion behavior of Ni-containing hypoeutectic Al-Si alloy

    Directory of Open Access Journals (Sweden)

    Abul Hossain

    2015-12-01

    Full Text Available Electrochemical corrosion characteristics of the thermally treated 2 wt % Ni-containing Al-6Si-0.5Mg alloy were studied in NaCl solutions. The corrosion behavior of thermally treated (T6 Al-6Si-0.5Mg (-2Ni alloys in 0.1 M NaCl solution was investigated by electrochemical potentiodynamic polarization technique consisting of linear polarization method using the fit of Tafel plot and electrochemical impedance spectroscopy (EIS techniques. Generally, linear polarization experiments revealed a decrease of the corrosion rate at thermal treated Al-6Si-0.5Mg-2Ni alloy. The EIS test results showed that there is no significant change in charge transfer resistance (Rct after addition of Ni to Al-6Si-0.5Mg alloy. The magnitude of the positive shift in the open circuit potential (OCP, corrosion potential (Ecorr and pitting corrosion potential (Epit increased with the addition of Ni to Al-6Si-0.5Mg alloy. The forms of corrosion in the studied Al-6Si-0.5Mg alloy (except Al-6Si-0.5Mg-2Ni alloy are pitting corrosion as obtained from the scanning electron microscopy (SEM study.

  4. Effect of Si and Zr on the Microstructure and Properties of Al-Fe-Si-Zr Alloys

    Directory of Open Access Journals (Sweden)

    Anna Morozova

    2017-11-01

    Full Text Available The effects of Si and Zr on the microstructure, microhardness and electrical conductivity of Al-Fe-Si-Zr alloys were studied. An increase in the Zr content over 0.3 wt. % leads to the formation of primary Al3Zr inclusions and also decreases mechanical properties. Therefore, the Zr content should not be more than 0.3 wt. %, although the smaller content is insufficient for the strengthening by the secondary Al3Zr precipitates. The present results indicate that high content of Si significantly affects the hardness and electrical conductivity of the investigated alloys. However, the absence of Si led to the formation of harmful needle-shaped Al3Fe particles in the microstructure of the investigated alloys after annealing. Therefore, the optimum amount of Si was 0.25–0.50 wt. % due to the formation of the Al8Fe2Si phase with the preferable platelet morphology. The maximum microhardness and strengthening effects in Al-1% Fe-0.25% Si-0.3% Zr were observed after annealing at 400–450 °C due to the formation of nanosized coherent Al3Zr (L12 dispersoids. The effect of the increasing of the electrical conductivity can be explained by the decomposition of the solid solution. Thus, Al-1% Fe-0.25% Si-0.3% Zr alloy annealed at 450 °C has been studied in detail as the most attractive with respect to the special focus on transmission line applications.

  5. Alternativas al cromo en la industria del acabado superficial del aluminio. Tratamientos superficiales de bajo impacto ambiental

    Directory of Open Access Journals (Sweden)

    Aballe Villero, Álvaro

    2001-02-01

    Full Text Available Chromates are one of the most commonly used compounds in anticorrosive protection systems because of its excellent rate efficiency/cost. In the case of aluminium alloys, these compounds are employed as inhibitors as well as in the anticorrosive pretreatments to develop protective films. However, chromates are highly toxic and its use involves a high risk for health and environment. Consequently, in the last years intensive efforts have been achieved in the surface treatment industry to find ecological alternatives to this kind of compounds. In this work, the main alternatives proposed in literature to substitute chromates in the surface treatments of aluminium alloys are reviewed. To begin with, the role of chromates in these systems and their environmental consequences has been briefly reviewed.

    Los cromatos son unas de las sustancias más comúnmente empleadas en los sistemas de protección frente a la corrosión de aleaciones metálicas, debido a su excelente relación eficacia/coste. En el caso de las aleaciones de aluminio, estos compuestos se aplican tanto como inhibidores, incorporados al medio agresivo, como en pretratamientos anticorrosivos para la formación de películas protectoras. Sin embargo, los cromatos son altamente tóxicos y su uso conlleva un elevado riesgo para la salud laboral y el medio ambiente. Por esta razón, dentro de la industria del acabado superficial, en los últimos tiempos, se ha venido realizando un intenso esfuerzo para buscar alternativas ecológicamente aceptables a este tipo de compuestos. En este trabajo se revisan las principales alternativas planteadas en la bibliografía para sustituir a los cromatos en los tratamientos superficiales de las aleaciones de aluminio. Como punto de partida, se ha llevado a cabo un breve repaso al papel que juegan los cromatos en los sistemas de protección frente a la corrosión y las implicaciones medioambientales que conlleva su uso.

  6. Cu-segregation at the Q'/α-Al interface in Al-Mg-Si-Cu alloy

    International Nuclear Information System (INIS)

    Matsuda, Kenji; Teguri, Daisuke; Uetani, Yasuhiro; Sato, Tatsuo; Ikeno, Susumu

    2002-01-01

    Cu segregation was detected at the Q ' /α-Al interface in an Al-Mg-Si-Cu alloy by energy-filtered transmission electron microscopy. By contrast, in a Cu-free Al-Mg-Si alloy no segregation was observed at the interface between the matrix and Type-C precipitate

  7. Study of polarization curves from AlSi12, AlSi5Mg and AlMg5 alloys due to corrosion problems in telecomunication equipment

    International Nuclear Information System (INIS)

    Silva, J.R.A. da

    1984-01-01

    The corrosion behaviour of three aluminium based alloys (AlSi 12, AlMg5 and AlSi 5Mg) when exposed to aqueous media containing chloride is investigated; these alloys are used in the manufacturing of telecomunication equipment. Accelerated corrosion testing and salt spray tests were carried out. The results include polarization curves obtained with three kinds of aqueous solutions (the first containing only 3% NaCl and the others, 3% NaCl and small amounts of Fe 3+ and Cu 2+ ions). (C.L.B.) [pt

  8. Separation of stress-free AlN/SiC thin films from Si substrate

    International Nuclear Information System (INIS)

    Redkov, A V; Osipov, A V; Mukhin, I S; Kukushkin, S A

    2016-01-01

    We separated AlN/SiC film from Si substrate by chemical etching of the AlN/SiC/Si heterostructure. The film fully repeats the size and geometry of the original sample and separated without destroying. It is demonstrated that a buffer layer of silicon carbide grown by a method of substitution of atoms may have an extensive hollow subsurface structure, which makes it easier to overcome the differences in the coefficients of thermal expansion during the growth of thin films. It is shown that after the separation of the film from the silicon substrate, mechanical stresses therein are almost absent. (paper)

  9. A new technique to modify hypereutectic Al-24%Si alloys by a Si-P master alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yaping; Wang Shujun; Li Hui [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China); Liu Xiangfa [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China)], E-mail: xfliu@sdu.edu.cn

    2009-05-27

    The modification effect of a Si-P master alloy on Al-24%Si alloy was investigated by using electron probe micro-analyzer (EPMA) and optical microscopy (OM). The dissolution problem of the Si-P master alloys was solved by changing the sequence of addition. When the Si-P master alloy was added into Al melt before the addition of silicon, the best modification effect could be achieved. The modification parameters of the master alloy on Al-24%Si alloy were optimized through designing and analyzing the orthogonal experiment, and their influences on the modification effect were discussed. The results show that the influence of temperature on the modification effect is the greatest, followed by the addition level, and the holding time is the least. The optimized modification parameters are the modification temperature of 810 deg. C, the addition level of 0.35 wt.%, the holding time of 30 min + 50 min whose meaning is that the Si-P master alloy is added firstly to the molten Al, and silicon is added 30 min later, then holding another 50 min. In addition, the modification mechanism of the Si-P master alloy on Al-24%Si alloy was also discussed.

  10. Effect of Si addition to Al-8Mg alloy on the microstructure and thermo-physical properties of SiCp/Al composites prepared by pressureless infiltration

    International Nuclear Information System (INIS)

    Ren Shubin; He Xinbo; Qu Xuanhui; Humail, Islam S.; Li Yan

    2007-01-01

    Fifty-five volume percentage of SiCp/Al composites were prepared by pressureless infiltration to investigate the effect of Si addition to Al-8Mg alloy from 0 wt% to 18 wt% on the interfacial reaction between Al and SiC and the thermo-physical properties of the prepared composites. TEM and X-ray analysis showed that the degree of interfacial reaction decreased as the Si content increased, and that it ceased at 1273 K when the Si addition to the aluminum was greater than 12 wt%. The Si addition to Al-8Mg alloy reduced the CTE of the composites and increased their thermal conductivity (TC), but Si beyond 12 wt% led to the reduction of TC, though the CTE was lower. This is attributable to the combined action of the Si on the wettability, interfacial reaction and the TC and CTE of the matrix itself

  11. Adherencia al tratamiento nutricional en pacientes con diabetes mellitus tipo 2 que asisten a un programa educativo

    OpenAIRE

    Mariela A. Carvajal

    2017-01-01

    El objetivo de este estudió fue evaluar la adherencia al tratamiento nutricional por medio de la hemoglobina glicosilada en pacientes con diabetes mellitus tipo 2 que asistieron a un programa educativo en diabetes en la ciudad de Guatemala, así como evaluar los principales factores que influyen en ella. Se realizó un estudio de tipo prospectivo, longitudinal, experimental, pareado de intervención no medicamentosa. Se utilizó la prueba de Morinsky-Green Levine para evaluar la adherencia al tra...

  12. Assessment of circumferential cracks in hypereutectic Al-Si clutch housings

    Directory of Open Access Journals (Sweden)

    M. Haghshenas

    2017-04-01

    Full Text Available As in situ natural composites with silicon phase acting as the reinforcing phase, Al-Si alloys are among most commonly used aluminum alloys in automotive applications (i.e. engine component. Silicon contributes to the strength of Al-Si alloys through load transfer from the Al matrix to the hard (rigid Si phase in the microstructure (load-carrying capacity. Casting parameters (i.e. solidification rate, elemental segregation, secondary dendrite spacing… as well as the size and distribution of the microstructural constituents in Al-Si alloys (i.e. morphology of Si particles, intermetallic compounds, secondary dendrite spacing contribute directly to the mechanical response and failure (or fracture behavior of the alloy within the service. In hyper-eutectic Al-Si alloys (i.e. B390.0, distribution of coarse pre-eutectic Si particle mainly contribute to stress concentration, crack initiation and propagation during the actual service condition. In the present paper, the parameters contribution to the formation of the circumferential cracks in clutch housings made of die cast hyper-eutectics B390.0 Al-Si alloys are assessed through optical microscopy and scanning electron microscopy. Casting variable, cooling rate, their effect on the cracks as well some of the possible causes are also discussed in detail.

  13. Synthesis, microstructure and magnetic properties of Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite core

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jian, E-mail: snove418562@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Fan, Xi’an, E-mail: groupfxa@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Wu, Zhaoyang, E-mail: wustwuzhaoyang@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Li, Guangqiang [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China)

    2015-11-15

    Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite core have been synthesized via a modified stöber method combined with following high temperature sintering process. Most of conductive Fe{sub 3}Si{sub 0.7}Al{sub 0.3} particles could be uniformly coated by insulating SiO{sub 2} using the modified stöber method. The Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles exhibited good soft magnetic properties with low coercivity and high saturation magnetization. The reaction 4Al+3SiO{sub 2}=2α-Al{sub 2}O{sub 3}+3Si took place during the sintering process. As a result the new Fe{sub 3}Si/Al{sub 2}O{sub 3} composite was formed. The Fe{sub 3}Si/Al{sub 2}O{sub 3} composite core displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher electrical resistivity and lower core loss than the pure Fe{sub 3}Si{sub 0.7}Al{sub 0.3} core. The method of introducing insulating layers surrounding magnetic particles provides a promising route to develop new and high compact soft magnetic materials with good magnetic and electric properties. - Graphical abstract: In Fe{sub 3}Si/Al{sub 2}O{sub 3} composite, Fe{sub 3}Si phases are separated by Al{sub 2}O{sub 3} layers and the eddy currents are confined in Fe{sub 3}Si phases, thus increasing resistivity and reducing core loss. - Highlights: • Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} cores were prepared. • Fe{sub 3}Si{sub 0.7}Al{sub 0.3} particles could be uniformly coated by nano-sized SiO{sub 2} clusters. • Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} cores showed good soft magnetic properties. • Fe{sub 3}Si/Al{sub 2}O{sub 3} had lower core loss and better frequency stability than Fe{sub 3}Si{sub 0.7}Al{sub 0.3} cores.

  14. Deimanto tipo anglies nanokompozicinių (SiOx turinčių deimanto tipo anglies plėvelių struktūros, cheminės sudėties, savybių ir taikymo sričių apžvalga

    Directory of Open Access Journals (Sweden)

    Šarūnas MEŠKINIS

    2011-11-01

    Full Text Available Straipsnyje apžvelgiama dabartinė būklė nanokompozicinių deimanto tipo anglies plėvelių (SiOx turinčių deimanto tipo anglies dangų tyrimų srityje. Aptariami įvairūs šių dangų formavimo metodai bei sintezei naudojamos medžiagos. Įvairiais būdais ir įvairiomis sąlygomis užaugintų deimanto tipo anglies nanokompozicinių plėvelių cheminė sudėtis nagrinėta atsižvelgiant į tyrimų duomenis, gautus taikant skirtingus analizės metodus (rentgeno spindulių fotoelektronų spektroskopiją, infraraudonųjų spindulių spektroskopiją. Taip pat aprašyti skirtingų autorių siūlomi nanokompozicinių deimanto tipo anglies plėvelių struktūros modeliai. Apžvelgtos SiOx turinčių DTA plėvelių, suformuotų įvairiais būdais, mechaninės, optinės, elektrinės savybės bei plėvelių paviršiaus energija. Straipsnio pabaigoje aprašomos nanokompozicinių deimanto tipo anglies plėvelių dabartinės naudojimo sritys ir ateities perspektyvos.http://dx.doi.org/10.5755/j01.ms.17.4.770

  15. Fabrication of Al-20 wt%Si powder using scrap Si by ultra high-energy milling process

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Won-Kyung [Division of Advanced Materials Engineering and Institute for Rare Metals, Kongju National University, 275, Budae-dong, Cheonan, Chungnam 330-717 (Korea, Republic of); Y Latin-Small-Letter-Dotless-I lmaz, Fikret [Department of Physics, Faculty of Art and Science, Gaziosmanpasa University, Tasliciftlik Campus, 60240 Tokat (Turkey); Kim, Hyo-Seob; Koo, Jar-Myung [Division of Advanced Materials Engineering and Institute for Rare Metals, Kongju National University, 275, Budae-dong, Cheonan, Chungnam 330-717 (Korea, Republic of); Hong, Soon-Jik, E-mail: hongsj@kongju.ac.kr [Division of Advanced Materials Engineering and Institute for Rare Metals, Kongju National University, 275, Budae-dong, Cheonan, Chungnam 330-717 (Korea, Republic of)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer High energy ball milling process has been successfully employed to produce Al-20Si alloy using scrap Si powders. Black-Right-Pointing-Pointer Fully finer and homogenous structure could be achieved after 60 min of milling time. Black-Right-Pointing-Pointer Si particles were not dissolved but uniformly dispersed in the Al matrix in a milled state. Black-Right-Pointing-Pointer The hardness of as-milled Al-20Si powder increased steadily with the increase of milling time. Black-Right-Pointing-Pointer Grain size and dispersion strengthening are two mechanisms being responsible for hardness increment. - Abstract: In this study, microstructural evolution and mechanical properties of Al-20 wt%Si and pure Al powders fabricated by ultra high-energy ball milling technique were investigated as a function of milling time. The microstructure and mechanical properties of the as-milled powders were examined by scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffractometer (XRD) and Vickers hardness tester. SEM observation showed that the particle size increased at an early stage of milling, and then decreased drastically with further milling. XRD and cross-sectional EDS-mapping analyses revealed that Si particles were not dissolved but uniformly dispersed in the Al matrix in a milled state. Vickers hardness of both pure Al and Al-Si powder increases with milling time, which attributes to the grain size strengthening and dispersion strengthening.

  16. Microstructure and Mechanical Properties of Multiphase Strengthened Al/Si/Al_2O_3/SiO_2/MWCNTs Nano composites Sintered by In Situ Vacuum Hot Pressing

    International Nuclear Information System (INIS)

    Li, J.; Jiang, X.; Zhu, D.; Zhu, M.; Shao, Z.; Johnson, S.; Luo, Z.

    2015-01-01

    Eutectic Al/Si binary alloy is technically one of the most important Al casting alloys due to its high corrosion resistance, evident shrinkage reduction, low thermal expansion coefficient, high fluidity, and good weldability. In this work, multi phased Al/Si matrix nano composites reinforced with Al_2O_3 and multi walled carbon nano tubes (MWCNTs) have been sintered by an in situ vacuum hot-pressing method. The alumina Al_2O_3 nanoparticles were introduced by an in situ reaction of Al with SiO_2. Microstructure and mechanical properties of the sintered Al/Si/Al_2O_3/SiO_2/MWCNTs nano composites with different alumina contents were investigated. The mechanical properties were determined by micro-Vickers hardness and compressive and shear strength tests. The results demonstrated that in situ alumina and MWCNTs had impacts on microstructure and mechanical properties of the nano composites. Based on the mechanical properties and microstructure of the nano composites, strengthening and fracture mechanisms by multiple reinforcements were analyzed

  17. Obtenção de substratos cerâmicos no sistema Si-Al-O-N-C empregando polissiloxanos e carga de Si e Al2O3 Ceramic tapes of Si-Al-O-N-C compounds using mixtures of polyssiloxane and Si-Al2O3 fillers

    Directory of Open Access Journals (Sweden)

    R. M. Rocha

    2005-03-01

    Full Text Available A técnica de processamento de colagem por fita (tape casting tem sido amplamente utilizada na obtenção de cerâmicas para diferentes aplicações: substratos cerâmicos e estruturas planares em multicamadas para circuitos integrados e capacitores; eletrólitos sólidos para células a combustível e sensores; cerâmicas piezoelétricas para atuadores e transdutores; membranas de separação para micro-filtragem; compósitos estruturais e trocadores de calor. Neste trabalho, a técnica convencional de colagem por fita foi adaptada com a utilização do processo de pirólise controlada de misturas de polímeros e carga, empregando-se polissiloxanos e cargas de silício e alumina nas suspensões. Foram preparadas suspensões com 60% vol. de fase polimérica (polissiloxanos e metil-trietoxi-silano e 40% vol. de carga (Si e Al2O3, com diferentes concentrações dos polímeros e das cargas. As amostras na forma de substratos foram pirolisadas em atmosfera de nitrogênio a 1400 °C/2 h e 1500 °C/2 h, sendo convertidas em materiais cerâmicos no sistema Si-Al-O-N-C. O processo de pirólise foi caracterizado até a temperatura de 1000 ºC por análise termogravimétrica. As cerâmicas foram caracterizadas quanto às fases formadas, microestrutura, massa específica aparente e condutividade térmica. Os substratos cerâmicos apresentaram porosidade relativamente alta (entre 12 e 22% e baixa condutividade térmica (entre 3 e 8 W/m.K, sendo constituídos por fases cristalinas de beta-SiC, Si2ON2, O'-SiAlON, Al2O3, mulita e fase amorfa de SiOC; o Si foi observado nas amostras pirolisadas a 1400 ºC.The tape casting technique has been widely used to prepare ceramic tapes for different applications: ceramic substrates and multilayer planar structures for integrated circuits and capacitors, solid electrolytes for fuel cells and sensors, piezoelectric ceramics for actuators and transducers, membrane systems for micro-filtration, structural composites and

  18. Oxidation behavior of arc evaporated Al-Cr-Si-N thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tritremmel, Christian; Daniel, Rostislav; Mitterer, Christian; Mayrhofer, Paul H.; Lechthaler, Markus; Polcik, Peter [Christian Doppler Laboratory for Advanced Hard Coatings, Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); Christian Doppler Laboratory for Application Oriented Coating Development, Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); OC Oerlikon Balzers AG, Iramali 18, LI-9496 Balzers (Liechtenstein); PLANSEE Composite Materials GmbH, Siebenbuergerstrasse 23, D-86983 Lechbruck am See (Germany)

    2012-11-15

    The impact of Al and Si on the oxidation behavior of Al-Cr-(Si)-N thin films synthesized by arc evaporation of powder metallurgically prepared Al{sub x}Cr{sub 1-x} targets with x = Al/(Al + Cr) of 0.5, 0.6, and 0.7 and (Al{sub 0.5}Cr{sub 0.5}){sub 1-z}Si{sub z} targets with Si contents of z = 0.05, 0.1, and 0.2 in N{sub 2} atmosphere was studied in detail by means of differential scanning calorimetry, thermogravimetric analysis (TGA), x-ray diffraction, and Raman spectroscopy. Dynamical measurements in synthetic air (up to 1440 Degree-Sign C) revealed the highest onset temperature of pronounced oxidation for nitride coatings prepared from the Al{sub 0.4}Cr{sub 0.4}Si{sub 0.2} target. Isothermal TGA at 1100, 1200, 1250, and 1300 Degree-Sign C highlight the pronounced improvement of the oxidation resistance of Al{sub x}Cr{sub 1-x}N coatings by the addition of Si. The results show that Si promotes the formation of a dense coating morphology as well as a dense oxide scale when exposed to air.

  19. Structural, bonding, anisotropic mechanical and thermal properties of Al4SiC4 and Al4Si2C5 by first-principles investigations

    Directory of Open Access Journals (Sweden)

    Liang Sun

    2016-09-01

    Full Text Available The structural, bonding, electronic, mechanical and thermal properties of ternary aluminum silicon carbides Al4SiC4 and Al4Si2C5 are investigated by first-principles calculations combined with the Debye quasi-harmonic approximation. All the calculated mechanical constants like bulk, shear and Young's modulus are in good agreement with experimental values. Both compounds show distinct anisotropic elastic properties along different crystalline directions, and the intrinsic brittleness of both compounds is also confirmed. The elastic anisotropy of both aluminum silicon carbides originates from their bonding structures. The calculated band gap is obtained as 1.12 and 1.04 eV for Al4SiC4 and Al4Si2C5 respectively. From the total electron density distribution map, the obvious covalent bonds exist between Al and C atoms. A distinct electron density deficiency sits between AlC bond along c axis among Al4SiC4, which leads to its limited tensile strength. Meanwhile, the anisotropy of acoustic velocities for both compounds is also calculated and discussed.

  20. Growth and Device Performance of AlGaN/GaN Heterostructure with AlSiC Precoverage on Silicon Substrate

    Directory of Open Access Journals (Sweden)

    Jae-Hoon Lee

    2014-01-01

    Full Text Available A crack-free AlGaN/GaN heterostructure was grown on 4-inch Si (111 substrate with initial dot-like AlSiC precoverage layer. It is believed that introducing the AlSiC layer between AlN wetting layer and Si substrate is more effective in obtaining a compressively stressed film growth than conventional Al precoverage on Si surface. The metal semiconductor field effect transistor (MESFET, fabricated on the AlGaN/GaN heterostructure grown with the AlSiC layer, exhibited normally on characteristics, such as threshold voltage of −2.3 V, maximum drain current of 370 mA/mm, and transconductance of 124 mS/mm.

  1. Comportamiento en fluencia de un material compuesto de matriz metálica Al6061-15 vol % SiCw pulvimetalúrgico

    Directory of Open Access Journals (Sweden)

    González-Doncel, G.

    2005-12-01

    Full Text Available The creep behavior of a powder metallurgy (PM Al6061-15 vol % SiCw metal matrix composite has been studied. This behavior has been compared to that of 6061Al cast alloy and 6061Al PM alloy. The creep response of the PM unreinforced alloy is better than that of the cast 6061Al alloy. Similarly, the behavior of the composite is better than that of the PM unreinforced alloy. Two microstructural factors have been considered the responsible ones of this improvement. The first one is the dispersion of Al2O3 oxide particles of nanometric scale. The second one, is the presence of the SiC whisker reinforcement of micrometric scale. Despite the similar strengthening effect, the intrinsic nature of the reinforcing mechanism is, however, different for each type of particle due to the different microstructural scale.Se ha realizado un estudio de las propiedades en fluencia del material compuesto pulvimetalúrgico Al6061-15 vol % SiCw. Su comportamiento se ha comparado con el de la aleación Al6061 pulvimetalúrgica y la aleación Al6061 de colada. El comportamiento del material pulvimetalúrgico sin reforzar mejora respecto al del material de colada. Al mismo tiempo, el del material compuesto mejora respecto al comportamiento del material pulvimetalúrgico sin reforzar. Se consideran dos factores microestructurales como los principales responsables de la mejora de las propiedades en fluencia de este material compuesto. Por un lado, las partículas de Al2O3 de tamaño nanométrico y, por otro, las partículas de fibra corta cerámicas de SiC de tamaño micrométrico. Aunque ambos tipos de partículas dan lugar a un efecto de refuerzo similar, los mecanismos intrínsecos asociados a la presencia de estas partículas tienen una naturaleza diferente debido a la diferencia en la escala microestructural.

  2. Investigation of the Electrical Characteristics of Al/p-Si/Al Schottky Diode

    International Nuclear Information System (INIS)

    Şenarslan, Elvan; Güzeldir, Betül; Sağlam, Mustafa

    2016-01-01

    In this study, p-type Si semiconductor wafer with (100) orientation, 400 μm thickness and 1-10 Ω cm resistivity was used. The Si wafer before making contacts were chemically cleaned with the Si cleaning procedure which for remove organic contaminations were ultrasonically cleaned at acetone and methanol for 10 min respectively and then rinsed in deionized water of 18 MΩ and dried with high purity N 2 . Then respectively RCA1(i.e., boiling in NH 3 +H 2 O 2 +6H 2 O for 10 min at 60°C ), RCA2 (i.e., boiling in HCl+H 2 O 2 +6H 2 O for 10 min at 60°C ) cleaning procedures were applied and rinsed in deionized water followed by drying with a stream of N 2 . After the cleaning process, the wafer is immediately inserted in to the coating unit. Ohmic contact was made by evaporating of Al on the non-polished side of the p-Si wafer pieces under ∼ 4,2 10 -6 Torr pressure. After process evaporation, p-Si with omic contac thermally annealed 580°C for 3 min in a quartz tube furnace in N 2 . Then, the rectifier contact is made by evaporation Al metal diameter of about 1.0 mm on the polished surface of p-Si in turbo molecular pump at about ∼ 1 10 -6 Torr. Consequently, Al/p-Si/Al Schottky diode was obtained. The I–V measurements of this diode performed by the use of a KEITLEY 487 Picoammeter/Voltage Source and the C–V measurements were performed with HP 4192A (50–13 MHz) LF Impedance Analyzer at room temperature and in dark. (paper)

  3. Investigation of the Electrical Characteristics of Al/p-Si/Al Schottky Diode

    Science.gov (United States)

    Şenarslan, Elvan; Güzeldir, Betül; Sağlam, Mustafa

    2016-04-01

    In this study, p-type Si semiconductor wafer with (100) orientation, 400 μm thickness and 1-10 Ω cm resistivity was used. The Si wafer before making contacts were chemically cleaned with the Si cleaning procedure which for remove organic contaminations were ultrasonically cleaned at acetone and methanol for 10 min respectively and then rinsed in deionized water of 18 MΩ and dried with high purity N2. Then respectively RCA1(i.e., boiling in NH3+H2O2+6H2O for 10 min at 60°C ), RCA2 (i.e., boiling in HCl+H2O2+6H2O for 10 min at 60°C ) cleaning procedures were applied and rinsed in deionized water followed by drying with a stream of N2. After the cleaning process, the wafer is immediately inserted in to the coating unit. Ohmic contact was made by evaporating of Al on the non-polished side of the p-Si wafer pieces under ~ 4,2 10-6 Torr pressure. After process evaporation, p-Si with omic contac thermally annealed 580°C for 3 min in a quartz tube furnace in N2. Then, the rectifier contact is made by evaporation Al metal diameter of about 1.0 mm on the polished surface of p-Si in turbo molecular pump at about ~ 1 10-6 Torr. Consequently, Al/p-Si/Al Schottky diode was obtained. The I-V measurements of this diode performed by the use of a KEITLEY 487 Picoammeter/Voltage Source and the C-V measurements were performed with HP 4192A (50-13 MHz) LF Impedance Analyzer at room temperature and in dark.

  4. Irradiation mixing of Al into U3Si

    International Nuclear Information System (INIS)

    Birtcher, R.C.; Ding, F.R.; Kestel, B.J.; Baldo, P.M.; Zaluzec, N.J.

    1995-11-01

    Thermal and irradiation induced intermixing of uranium silicide reactor fuels with the aluminum cladding is an important consideration in understanding their fission gas and fuel swelling behavior. The authors have used Rutherford backscattering to follow the behavior of an Al thin film on U 3 Si and U 3 Si 2 during 1.5 MeV Kr ion irradiation at temperatures of 30 and 350 C. After an initial dose during which no intermixing occurs, the Al mixes quickly into U 3 Si. The threshold dose is believed to be associated with an oxide layer between the Al and the uranium silicide. At 300 C and doses greater than threshold, rates of mixing and aluminide phase growth are extracted

  5. Weld microstructure in cast AlSi9/SiC(p metal matrix composites

    Directory of Open Access Journals (Sweden)

    J. Wysocki

    2009-04-01

    Full Text Available Welded joint in cast AlSi9/SiC/20(p metal matrix composite by manual TIG arc welding using AlMg5 filler metal has been described inhis paper. Cooling curves have been stated, and the influence in distribution of reinforced particles on crystallization and weldmicrostructure. Welded joint mechanical properties have been determined: hardness and tensile.

  6. Microstructure and mechanical properties of spray deposited hypoeutectic Al-Si alloy

    International Nuclear Information System (INIS)

    Ferrarini, C.F.; Bolfarini, C.; Kiminami, C.S.; Botta F, W.J.

    2004-01-01

    The microstructure and the tensile properties of an Al-8.9 wt.% Si-3.2 wt.% Cu-0.9 wt.% Fe-0.8% Zn alloy processed by spray forming was investigated. The alloy was gas atomized with argon and deposited onto a copper substrate. The microstructure was evaluated by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Small faceted dispersoids observed surrounding equiaxial α-Al matrix were identified by SEM-EDS as silicon particles. Sand cast samples with the same composition showed a columnar dendritic α-Al matrix, Al-Si eutectic, polyhedric α-AlFeSi and needle-like β-AlFeSi intermetallics. In the spray formed material the formation of the Al-Si eutetic was suppressed, and the formation of the α-AlFeSi and β-AlFeSi intermetallics was strongly reduced. The fine and homogeneous microstructure showed an aluminium matrix with grain size ranging from 30 to 40 μm, and particle size of the silicon dispersoids having a mean size of 12 μm. Room temperature tensile tests of the spray formed alloy showed relative increasing of strength and elongation when compared with the values observed for the conventionally cast counterparts. These results can be ascribed to the refined microstructure and the scarce presence of intermetallics of the spray formed material

  7. Development and cytotoxicity evaluation of SiAlONs ceramics

    International Nuclear Information System (INIS)

    Santos, C.; Ribeiro, S.; Daguano, J.K.M.F.; Rogero, S.O.; Strecker, K.; Silva, C.R.M.

    2007-01-01

    SiAlONs are ceramics with high potential as biomaterials due to their chemical stability, associated with suitable mechanical properties, such as high fracture toughness and fracture resistance. The objective of this work was to investigate the mechanical properties and the cytotoxicity of these ceramic materials. Three different compositions were prepared, using silicon nitride, aluminum nitride and a rare earth oxide mixture as starting powders, yielding Si 3 N 4 -SiAlON composites or pure SiAlON ceramics, after hot-pressing at 1750 deg. C, for 30 min. The sintered samples were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Furthermore, hardness and fracture toughness were determined using the Vicker's indentation method. The biological compatibility was evaluated by in vitro cytotoxicity tests. Ceramic with elevated hardness, ranging between 17 and 21 GPa, and high fracture toughness of 5 to 6 MPa m 1/2 were obtained. Since a nontoxic behavior was observed in the cytotoxicity tests, it may be assumed that SiAlON-based ceramics are viable materials for clinical applications

  8. Diferencias en Estrés Percibido, Salud Mental y Física de acuerdo al Tipo de Relación Humano-Perro

    Directory of Open Access Journals (Sweden)

    MÓNICA TERESA GONZÁLEZ RAMÍREZ

    2011-01-01

    Full Text Available Con el propósito de evaluar si los niveles de estrés y salud percibidos difieren de acuerdo al tipo de relación entre el humano y el perro, así como de evaluar la correlación de estrés y salud percibidos con la frecuencia en que se realizan algunas actividades con el perro, se aplicaron cuestionarios de autoinforme a 247 voluntarios, dueños de al menos un perro. Los principales resultados muestran puntajes más bajos de estrés percibido y más altos de salud mental en quienes consideran a su perro miembro de la familia. Además, se encontraron correlaciones significativas entre entrenar al perro y el estrés y la salud mental; entre jugar con el perro y la vitalidad y la salud mental, y entre pasearlo y la vitalidad. Se concluye que quienes consideran al perro un miembro de la familia y realizan más actividades con él tienen más beneficios en su salud física y mental, y en el nivel de estrés percibido.

  9. Dissolution of Si in Molten Al with Gas Injection

    Science.gov (United States)

    Seyed Ahmadi, Mehran

    Silicon is an essential component of many aluminum alloys, as it imparts a range of desirable characteristics. However, there are considerable practical difficulties in dissolving solid Si in molten Al, because the dissolution process is slow, resulting in material and energy losses. It is thus essential to examine Si dissolution in molten Al, to identify means of accelerating the process. This thesis presents an experimental study of the effect of Si purity, bath temperature, fluid flow conditions, and gas stirring on the dissolution of Si in molten Al, plus the results of physical and numerical modeling of the flow to corroborate the experimental results. The dissolution experiments were conducted in a revolving liquid metal tank to generate a bulk velocity, and gas was introduced into the melt using top lance injection. Cylindrical Si specimens were immersed into molten Al for fixed durations, and upon removal the dissolved Si was measured. The shape and trajectory of injected bubbles were examined by means of auxiliary water experiments and video recordings of the molten Al free surface. The gas-agitated liquid was simulated using the commercial software FLOW-3D. The simulation results provide insights into bubble dynamics and offer estimates of the fluctuating velocities within the Al bath. The experimental results indicate that the dissolution rate of Si increases in tandem with the melt temperature and bulk velocity. A higher bath temperature increases the solubility of Si at the solid/liquid interface, resulting in a greater driving force for mass transfer, and a higher liquid velocity decreases the resistance to mass transfer via a thinner mass boundary layer. Impurities (with lower diffusion coefficients) in the form of inclusions obstruct the dissolution of the Si main matrix. Finally, dissolution rate enhancement was observed by gas agitation. It is postulated that the bubble-induced fluctuating velocities disturb the mass boundary layer, which

  10. Response of Si- and Al-doped graphenes toward HCN: A computational study

    International Nuclear Information System (INIS)

    Rastegar, Somayeh F.; Peyghan, Ali Ahmadi; Hadipour, Nasser L.

    2013-01-01

    Highlights: ► Sensitivity of Si- and Al-doped graphene (SiG and AlG) toward HCN is investigated. ► The electronic properties of AlG are significantly changed in the presence of HCN. ► It is established that AlG can be a good sensor for HCN molecule. - Abstract: Sensitivity of Si- and Al-doped graphenes (SiG and AlG) toward toxic HCN has been investigated using density functional theory (DFT) in terms of energetic, geometric and electronic properties. Optimized configurations corresponding to physisorption and, subsequently, chemisorption of HCN on each surface have been identified. It is found that HCN molecule can be adsorbed on impurity atoms with adsorption energies about −27.20 and −38.75 kcal/mol on the SiG and the AlG, respectively. By comparing to HCN adsorption on SiG, it can be inferred that molecular HCN adsorbed on AlG can induce significant change in AlG conductivity. On the basis of calculated changes in the HOMO/LUMO energy gap it is found that electronic properties of AlG are sensitive toward adsorption of HCN and the reverse is correct for SiG, suggesting that the AlG may be a promising sensor for HCN.

  11. Improving the characteristics of foundry alloys AlSiCuMg during manufacturing

    Science.gov (United States)

    Fragoso, Bruno Filipe Marques

    As piroxenas sao um vasto grupo de silicatos minerais encontrados em muitas rochas igneas e metamorficas. Na sua forma mais simples, estes silicatos sao constituidas por cadeias de SiO3 ligando grupos tetrahedricos de SiO4. A formula quimica geral das piroxenas e M2M1T2O6, onde M2 se refere a catioes geralmente em uma coordenacao octaedrica distorcida (Mg2+, Fe2+, Mn2+, Li+, Ca2+, Na+), M1 refere-se a catioes numa coordenacao octaedrica regular (Al3+, Fe3+, Ti4+, Cr3+, V3+, Ti3+, Zr4+, Sc3+, Zn2+, Mg2+, Fe2+, Mn2+), e T a catioes em coordenacao tetrahedrica (Si4+, Al3+, Fe3+). As piroxenas com estrutura monoclinica sao designadas de clinopiroxenes. A estabilidade das clinopyroxenes num espectro de composicoes quimicas amplo, em conjugacao com a possibilidade de ajustar as suas propriedades fisicas e quimicas e a durabilidade quimica, tem gerado um interesse mundial devido a suas aplicacoes em ciencia e tecnologia de materiais. Este trabalho trata do desenvolvimento de vidros e de vitro-cerâmicos baseadas de clinopiroxenas para aplicacoes funcionais. O estudo teve objectivos cientificos e tecnologicos; nomeadamente, adquirir conhecimentos fundamentais sobre a formacao de fases cristalinas e solucoes solidas em determinados sistemas vitro-cerâmicos, e avaliar a viabilidade de aplicacao dos novos materiais em diferentes areas tecnologicas, com especial enfase sobre a selagem em celulas de combustivel de oxido solido (SOFC). Com este intuito, prepararam-se varios vidros e materiais vitro-cerâmicos ao longo das juntas Enstatite (MgSiO3) - diopsidio (CaMgSi2O6) e diopsidio (CaMgSi2O6) - Ca - Tschermak (CaAlSi2O6), os quais foram caracterizados atraves de um vasto leque de tecnicas. Todos os vidros foram preparados por fusao-arrefecimento enquanto os vitro-cerâmicos foram obtidos quer por sinterizacao e cristalizacao de fritas, quer por nucleacao e cristalizacao de vidros monoliticos. Estudaram-se ainda os efeitos de varias substituicoes ionicas em composicoes de

  12. The Effectiveness of Al-Si Coatings for Preventing Interfacial Reaction in Al-Mg Dissimilar Metal Welding

    Science.gov (United States)

    Wang, Yin; Al-Zubaidy, Basem; Prangnell, Philip B.

    2018-01-01

    The dissimilar welding of aluminum to magnesium is challenging because of the rapid formation of brittle intermetallic compounds (IMC) at the weld interface. An Al-Si coating interlayer was selected to address this problem, based on thermodynamic calculations which predicted that silicon would change the reaction path to avoid formation of the normally observed binary Al-Mg IMC phases ( β-Al3Mg2 and γ-Al12Mg17). Long-term static heat treatments confirmed that a Si-rich coating will preferentially produce the Mg2Si phase in competition with the less stable, β-Al3Mg2 and γ-Al12Mg17 binary IMC phases, and this reduced the overall reaction layer thickness. However, when an Al-Si clad sheet was tested in a real welding scenario, using the Refill™ friction stir spot welding (FSSW) technique, Mg2Si was only produced in very small amounts owing to the much shorter reaction time. Surprisingly, the coating still led to a significant reduction in the IMC reaction layer thickness and the welds exhibited enhanced mechanical performance, with improved strength and fracture energy. This beneficial behavior has been attributed to the softer coating material both reducing the welding temperature and giving rise to the incorporation of Si particles into the reaction layer, which toughened the brittle interfacial IMC phases during crack propagation.

  13. Separation of primary solid phases from Al-Si alloy melts

    Directory of Open Access Journals (Sweden)

    Ki Young Kim

    2014-07-01

    Full Text Available The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical, physical and chemical properties of the alloys should be removed. On the other hand, Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process. One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts. This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation, draining, filtration, electromagnetic separation and centrifugal separation, focused on the iron removal and on the separation of silicon in the solvent refining process.

  14. Corrosion analysis of AlMg2 and AlMgSi using electrochemical method

    International Nuclear Information System (INIS)

    Dian A; Maman Kartaman; Rosika K; Yanlinastuti

    2014-01-01

    Corrosion test of cladding materials and structures of research reactor fuel, AlMgSi and AlMg2 have been performed in demineralized water of pH 2 and 6.7 using an electrochemical method. Corrosion phenomenon is affected by several factor such as composition and condition of solution. The purpose of this activity is to investigate the corrosion phenomena through the determination of the parameters of corrosion and polarization curve. The materials used are AlMg2 and AlMgSi alloy in circular dish shape with an area of 1 Cm"2. Preparation of the test sample is performed through several stages polishing, cleaning and drying procedures followed ASTM G3. The electrochemical method is done by measuring the open circuit potential (OCP), polarization resistance and potentiodynamic in demineralized water of pH 2 and pH 6.7 at temperature of 25°C. The results of the OCP is the corrosion potential (Ecorr) of AlMg2 and AlMgSi each of -906.1 mV and -619.8 mV at pH 2 and -868.6 and -756.7 mV at pH 6.7 mV. The results of measurements by polarization resistance technique showed that the corrosion rate of AlMg2 and AlMgSi in safe category (<2 mpy) at pH 6.7 and at pH 2 corrosion rate increased significantly, but still in the lightweight category (<20 mpy). Potentiodynamic curves showed that the passivation at pH 6.7 is very low while the passivation at pH 2 occurs within a relatively short range potential and followed events corroded. (author)

  15. Effects of Al-Mn-Ti-P-Cu master alloy on microstructure and properties of Al-25Si alloy

    Directory of Open Access Journals (Sweden)

    Xu Chunxiang

    2013-09-01

    Full Text Available To obtain a higher microstructural refining efficiency, and improve the properties and processing ability of hypereutectic Al-25Si alloy, a new environmentally friendly Al-20.6Mn-12Ti-0.9P-6.1Cu (by wt.% master alloy was fabricated; and its modification and strengthening mechanisms on the Al-25Si alloy were studied. The mechanical properties of the unmodified, modified and heat treated alloys were investigated. Results show that the optimal addition amount of the Al-20.6Mn-12Ti-0.9P-6.1Cu master alloy is 4wt.%. In this case, primary Si and eutectic Si as well as メ-Al phase were clearly refined, and this refining effect shows an excellent long residual action as it can be heat-retained for at least 5 h. After being T6 heat treated, the morphology of primary and eutectic Si in the Al-25Si alloys with the addition of 4wt.% Al-20.6Mn-12Ti-0.9P-6.1Cu alloy changes into particles and short rods. The average grain size of the primary and eutectic Si decreases from 250 レm (unmodified to 13.83 レm and 35 レm (unmodified to 7 レm; the メ-Al becomes obviously finer and the distribution of Si phases tends to be uniform and dispersed. Meanwhile, the tensile properties are improved obviously; the tensile strengths at room temperature and 300 ìC reach 241 MPa and 127 MPa, increased by 153.7% and 67.1%, respectively. In addition, the tensile fracture mechanism changes from brittle fracture for the alloy without modification to ductile fracture after modification. Modifying the morphology of Si phase and strengthening the matrix can effectively block the initiation and propagation of cracks, thus improving the strength of the hypereutectic Al-25Si alloy.

  16. Study on the preparation of the SiCp/Al-20Si-3Cu functionally graded material using spray deposition

    International Nuclear Information System (INIS)

    Su, B.; Yan, H.G.; Chen, G.; Shi, J.L.; Chen, J.H.; Zeng, P.L.

    2010-01-01

    Research highlights: → The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. → The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. → In the experimental setup, the novel devices play an important role in adjusting the output of SiCp to prepare the FGM. → The experiment results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. → The fraction of SiC particles has no obvious influence on the phase constitutions of the SiCp/Al-20Si-3Cu FGM. - Abstract: The SiCp/Al-20Si-3Cu functionally gradient material (FGMs) was successfully prepared via the spray deposition technique accompanied with an automatic control system. The results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. The part with the higher SiCp weight fraction exhibits a relatively smaller density than that with the lower SiCp weight fraction. However, the microhardness and the porosity increase with the increasing SiCp weight fraction in the as-deposited preform. The X-ray diffraction results exhibit that the secondary phases in the regions with the different amount of SiC particles are the same such as Al 2 Cu and AlCuMg. The spray deposition technology is promising to produce a wide range of other FGMs.

  17. Study of Ni/Si(1 0 0) solid-state reaction with Al addition

    International Nuclear Information System (INIS)

    Huang Yifei; Jiang Yulong; Ru Guoping; Li Bingzong

    2008-01-01

    The characteristics of Ni/Si(1 0 0) solid-state reaction with Al addition (Ni/Al/Si(1 0 0), Ni/Al/Ni/Si(1 0 0) and Al/Ni/Si(1 0 0)) is studied. Ni and Al films were deposited on Si(1 0 0) substrate by ion beam sputtering. The solid-state reaction between metal films and Si was performed by rapid thermal annealing. The sheet resistance of the formed silicide film was measured by four-point probe method. The X-ray diffraction (XRD) was employed to detect the phases in the silicide film. The Auger electron spectroscopy was applied to reveal the element profiles in depth. The influence of Al addition on the Schottky barrier heights of the formed silicide/Si diodes was investigated by current-voltage measurements. The experimental results show that NiSi forms even with the addition of Al, although the formation temperature correspondingly changes. It is revealed that Ni silicidation is accompanied with Al diffusion in Ni film toward the film top surface and Al is the dominant diffusion species in Ni/Al system. However, no Ni x Al y phase is detected in the films and no significant Schottky barrier height modulation by the addition of Al is observed

  18. Phase relations in the SiC-Al2O3-Pr2O3 system

    International Nuclear Information System (INIS)

    Pan, W.; Wu, L.; Jiang, Y.; Huang, Z.

    2016-01-01

    Phase relations in the Si-Al-Pr-O-C system, including the SiC-Al 2 O 3 -Pr 2 O 3 , the Al 2 O 3 -Pr 2 O 3 -SiO 2 and the SiC-Al 2 O 3 -Pr 2 O 3 -SiO 2 subsystems, were determined by means of XRD phase analysis of solid-state-reacted samples fabricated by using SiC, Al 2 O 3 , Pr 2 O 3 and SiO 2 powders as the starting materials. Subsolidus phase diagrams of the systems were presented. Two Pr-aluminates, namely PrAlO 3 (PrAP) and PrAl 11 O 18 (β(Pr) β-Al 2 O 3 type) were formed in the SiC-Al 2 O 3 -Pr 2 O 3 system. SiC was compatible with both of them. Pr-silicates of Pr 2 SiO 5 , Pr 2 Si 2 O 7 and Pr 9.33 Si 6 O 26 (H(Pr) apatite type) were formed owing to presence of SiO 2 impurity in the SiC powder. The presence of the SiO 2 extended the ternary system of SiC-Al 2 O 3 -Pr 2 O 3 into a quaternary system of SiC-Al 2 O 3 -SiO 2 -Pr 2 O 3 (Si-Al-Pr-O-C). SiC was compatible with Al 2 O 3 , Pr 2 O 3 and the Pr-silicates. The effect of SiO 2 on the phase relations and liquid phase sintering of SiC ceramics was discussed.

  19. Preparation and study of nanostructured TiAlSiN thin films

    Directory of Open Access Journals (Sweden)

    Jakab-Farkas L.

    2011-12-01

    Full Text Available TiAlSiN thin film coatings were deposited by DC reactive magnetron sputtering of TiAlSi target with 40 at.% Ti, 40 at.% Al and 20 at.% Si, performed in N2-Ar gas mixture. The sputtering power used in these experiments was controlled for 400 W. The bias voltage of the substrates was kept at -20 V DC and the temperature at 500 0C. All the samples were prepared with a constant flow rate of Ar and different nitrogen flow rates, which were selected from 1.25 sccm to 4.0 sccm. Nanostructured TiAlSiN coatings were developed on Si(100 and HSS substrates. Microstructure investigation of the coatings was performed by transmission electron microscopy investigation, structure investigation was performed by XRD analysis, and the mechanical properties of the coatings have been tested by ball-on-disk tribological investigation and micro-Vickers hardness measurements. In this paper will be shown that for optimized nitrogen concentration the microstructure of TiAlSiN coating evolve from a competitive columnar growth to a dendritic growth one with very fine nano-lamellae like morphology. The developed nanostructured TiAlSiN coatingshave hardness HV exceeding 40 GPa and show an increased abrasive wear resistance

  20. Study of Bending Fatigue Properties of Al-Si Cast Alloy

    Directory of Open Access Journals (Sweden)

    Tillová E.

    2017-09-01

    Full Text Available Fatigue properties of casting Al-alloys are very sensitive to the microstructural features of the alloy (e.g. size and morphology of the eutectic Si, secondary dendrite arm spacing - SDAS, intermetallics, grain size and casting defects (porosity and oxides. Experimental study of bending fatigue properties of secondary cast alloys have shown that: fatigue tests up to 106-107cycles show mean fatigue limits of approx. 30-49 MPa (AlSi9Cu3 alloy - as cast state, approx. 65-76 MPa (AlSi9Cu3 alloy after solution treatment and 60-70 MPa (self-hardened AlZn10Si8Mg alloy in the tested casting condition; whenever large pore is present at or near the specimen’s surface, it will be the dominant cause of fatigue crack initiation; in the absence of large casting defects, the influence of microstructural features (Si morphology; Fe-rich phases on the fatigue performance becomes more pronounced.

  1. Rare earth concentration in the primary Si crystal in rare earth added Al-21 wt. % Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Chang, J.Y.; Kim, G.H. [Korea Inst. of Science and Technology, Seoul (Korea, Republic of); Moon, I.G.; Choi, C.S. [Yonsei Univ., Seoul (Korea, Republic of). Dept. of Metallurgical Engineering

    1998-07-03

    Al-Si alloys containing more than about 12 wt. % Si exhibit a hypereutectic microstructure, normally consisting of a primary silicon phase in an eutectic matrix. The primary silicon in normal hypereutectic alloys is usually very coarse and thus leads to poor properties to these alloys. Therefore, alloys with a predominantly coarse primary silicon crystal must be modified to ensure adequate mechanical strength and ductility. Further improvement of mechanical properties of these alloys can be achieved by the modification of eutectic microstructure. Therefore, development of a modifier or refiner that can produce both fine primary and eutectic Si is a major factor which can lead to significant enhancement of mechanical properties in hypereutectic Al-Si alloys. Refinement of primary silicon is usually achieved by the addition of phosphor to the melt. On the other hand, it is reported that the rare earth (RE) elements are capable of modifying the eutectic structure of cast Al-Si alloys. According to the literature, Phosphor acts as a heterogeneous nucleation site of Si crystal by forming AlP intermetallic particles at high temperature, i.e., above liquidus temperature of Al-Si alloy. Unlike phosphor, RE was not known to form a stable compound with Al that can act as a nucleation site at high temperature. Therefore, the role of RE as a refiner should be considered by examining the behavior of RE as a solute in the melt. The distribution of RE within the primary Si and in the matrix of the alloy will provide a clue to the role of RE on the modification of primary Si during solidification.

  2. Rapid solidification growth mode transitions in Al-Si alloys by dynamic transmission electron microscopy

    International Nuclear Information System (INIS)

    Roehling, John D.; Coughlin, Daniel R.; Gibbs, John W.; Baldwin, J. Kevin; Mertens, James C.E.; Campbell, Geoffrey H.; Clarke, Amy J.; McKeown, Joseph T.

    2017-01-01

    In situ dynamic transmission electron microscope (DTEM) imaging of Al-Si thin-film alloys was performed to investigate rapid solidification behavior. Solidification of alloys with compositions from 1 to 15 atomic percent Si was imaged during pulsed laser melting and subsequent solidification. Solely α-Al solidification was observed in Al-1Si and Al-3Si alloys, and solely kinetically modified eutectic growth was observed in Al-6Si and Al-9Si alloys. A transition in the solidification mode in eutectic and hypereutectic alloys (Al-12Si and Al-15Si) from nucleated α-Al dendrites at lower solidification velocities to planar eutectic growth at higher solidification velocities was observed, departing from trends previously seen in laser-track melting experiments. Comparisons of the growth modes and corresponding velocities are compared with previous solidification models, and implications regarding the models are discussed.

  3. Annealing Behavior of Al-Implantation-Induced Disorder in 4H-SiC

    International Nuclear Information System (INIS)

    Zhang, Yanwen; Weber, William J.; Jiang, Weilin; Shutthanandan, V.; Thevuthasan, Suntharampillai; Janson, Martin; Hallen, Anders

    2004-01-01

    Single crystal 4H-SiC films were implanted at 150 K with 1.1 MeV Al 2 2+ and subsequently annealed at elevated temperatures. Rutherford backscattering spectrometry (RBS) results indicate that the relative Si disorder at the damage peak recovers significantly as the annealing temperature increases. However, the residual Si disorder is more resistant to high-temperature annealing in the region of the implanted Al. The maximum concentration of Al profile measured by secondary ion mass spectroscopy (SIMS) is a factor of 1000 lower than the level of the residual Si disorder at the same region. Analysis of these results indicates that the excess residual Si disorder around the implanted Al projected range cannot be accounted for by just the Al interstitials; instead, it appears that each implanted Al stabilizes or inhibits recovery for an equivalent of a few hundred Si interstitials under the current experimental conditions

  4. Quality analysis of the Al-Si-Cu alloy castings

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2007-04-01

    Full Text Available The developed design methodologies both the material and technological ones will make it possible to improve shortly the quality of materials from the light alloys in the technological process, and the automatic process flow correction will make the production cost reduction possible, and - first of all - to reduce the amount of the waste products. Method was developed for analysis of the casting defects images obtained with the X-ray detector analysis of the elements made from the Al-Si-Cu alloys of the AC-AlSi7Cu3Mg type as well as the method for classification of casting defects using the artificial intelligence tools, including the neural networks; the developed method was implemented as software programs for quality control. Castings were analysed in the paper of car engine blocks and heads from the Al-Si-Cu alloys of the AC-AlSi7Cu3Mg type fabricated with the “Cosworth” technological process. The computer system, in which the artificial neural networks as well as the automatic image analysis methods were used makes automatic classification possible of defects occurring in castings from the Al-Si-Cu alloys, assisting and automating in this way the decisions about rejection of castings which do not meet the defined quality requirements, and therefore ensuring simultaneously the repeatability and objectivity of assessment of the metallurgical quality of these alloys.

  5. Influence of silicon concentration on linear contraction process of Al-Si binary alloy

    Directory of Open Access Journals (Sweden)

    J. Mutwil

    2008-12-01

    Full Text Available Investigations of shrinkage phenomena during solidification and cooling of aluminium and aluminium-silicon alloys (AlSi5, AlSi7, AlSi9, AlSi11, AlSi12.5, AlSi18, AlSi21 have been conducted. A vertical shrinkage rod casting with circular cross-section (constant or fixed: tapered has been used as a test sample. By constant cross-section a test channel mould was parted and allowed a constrained contraction to examine. No parted test channel mould was tapered and allowed an unconstrained contraction to investigate. In the experiments the dimensions changes of solidifying test bar and the test mould have been registered, what has allowed to explain a mechanism of pre-shrinkage extension of solidifying metals and alloys. Registered time dependence of the test bar and the test mould dimension changes have shown, that so-called pre-shrinkage extension has been by mould thermal extension caused. The investigation results have also shown that time- and temperature dependences of shrinkage of Al-Si alloys have been on silicon concentration depended.

  6. Structural transformation in mechanosynthesized bcc Fe-Al-Si(Ge) solid solutions during heating

    International Nuclear Information System (INIS)

    Kubalova, L.M.; Sviridov, I.A.; Vasilyeva, O.Ya.; Fadeeva, V.I.

    2007-01-01

    X-ray diffractometry and Moessbauer spectroscopy study of Fe 50 Al 25 Si 25 and Fe 50 Al 25 Ge 25 alloys obtained by mechanical alloying (MA) of elementary powders was carried out. Phase transformation during heating of synthesized products was studied using differential scanning calorimetry (DSC). After 2.5 h of MA monophase alloys containing bcc Fe(Al, Ge) solid solutions Fe(Al, Si) are formed. Fe(Al, Si) is partially ordered B2 type and Fe(Al, Ge) is completely disordered. DSC curves of synthesized alloys displayed the presence of exothermal peaks caused by phase transformation. The metastable Fe(Al, Si) solid solution transformed into FeAl 1-x Si x (B2) and FeSi 1-x Al x (B20) equilibrium phases. The Fe(Al, Ge) solid solution transformed into equilibrium phases through intermediate stage of Fe 6 Ge 3 Al 2 metastable phase formation. The Fe 6 Ge 3 Al 2 phase dissociated into three equilibrium phases: FeAl 1-x Ge x (B2), χ-Fe 6 Ge 5 and η-Fe 13 (Ge, Al) 8 (B8 2 ). The structure of Fe 6 Ge 3 Al 2 was calculated by Rietveld method, the distribution of Al and Ge in the elementary cell and its parameters were calculated. Moessbauer study showed that Fe(Al, Si) and Fe(Al, Ge) solid solutions are paramagnetic. In the equilibrium state the alloy containing Si is also paramagnetic while the alloy with Ge showed ferromagnetic properties

  7. Study of Physical Properties of SiCw/Al Composites During Unloaded Thermal Cycling

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xin-ming; TIAN zhi-gang; CHENG hua; ZHU Xiao-gang; CHEN Wen-li

    2004-01-01

    The thermal expansion coefficient of SiCw/Al composites squeeze cast during unloaded thermal cycling was determined and analyzed. The study had shown that the thermal expansion coefficient of SiCw/Al composites reduced greatly with temperature raising. The thermal expansion coefficient of artificial ageing treatment SiCw/Al composites during unloaded thermal cycling reduced gradually, while the thermal expansion coefficient of squeezing SiCw/Al composites increased gradually. In addition, the thermal expansion coefficient of SiCw/Al composites reduced drastically with fiber fraction increasing.

  8. Síntese de Al2O3/SiC em forno de microondas: estudo de parâmetros do processo Synthesis of Al2O3/SiC in microwave oven: study of the processing parameters

    Directory of Open Access Journals (Sweden)

    T. P. Deksnys

    2005-12-01

    Full Text Available Estudos demonstram a eficiência do método de moagem prévia do aluminossilicato precursor para a síntese da fase Al2O3/SiC por meio da reação de redução carbotérmica em forno de microondas. No presente trabalho, além da moagem do precursor, outros parâmetros de reação foram estudados, como tempo de reação, potência da radiação emitida e fluxo de gás. As reações foram realizadas em forno de microondas semi-industrial, com adaptação para inserção de gás inerte. Dois tipos de reatores foram avaliados: um reator cilíndrico, termicamente isolado, e um reator tubular de leito fixo, nos quais foram colocados os precursores peletizados. Existe uma relação direta entre a saturação da atmosfera de reação com a cinética de redução carbotérmica do aluminossilicato. Esse comportamento, aliado a elevadas potências de emissão, favorecem a formação da fase Al2O3/SiC em períodos de tempo reduzidos.Results presented elsewhere have confirmed the feasibility of the previous milling process of the starting materials for the synthesis of Al2O3/SiC by the microwave-assisted carbothermal reduction. In the present work, parameters such as precursor milling, reaction time, microwave's power level and gas flow have been investigated. Reactions were carried out in a semi-industrial microwave oven (Cober Inc., USA, which allowed the inert gas insertion. Two reactions arrangement were developed to perform the synthesis: a cylindrical reactor, thermally insulated and a pipe fluidized bed reactor. Into both reactors, the precursor was applied in a palletized form to react. There is a direct relation between the reaction atmosphere saturation and the kinetics of the carbothermal reduction. This behavior, in addiction to high power levels of microwave radiation (>1.5 KW, favors the formation of Al2O3/SiC in a short time.

  9. CVD of SiC and AlN using cyclic organometallic precursors

    Science.gov (United States)

    Interrante, L. V.; Larkin, D. J.; Amato, C.

    1992-01-01

    The use of cyclic organometallic molecules as single-source MOCVD precursors is illustrated by means of examples taken from our recent work on AlN and SiC deposition, with particular focus on SiC. Molecules containing (AlN)3 and (SiC)2 rings as the 'core structure' were employed as the source materials for these studies. The organoaluminum amide, (Me2AlNH2)3, was used as the AlN source and has been studied in a molecular beam sampling apparatus in order to determine the gas phase species present in a hot-wall CVD reactor environment. In the case of SiC CVD, a series of disilacyclobutanes (Si(XX')CH2)2 (with X and X' = H, CH3, and CH2SiH2CH3), were examined in a cold-wall, hot-stage CVD reactor in order to compare their relative reactivities and prospective utility as single-source CVD precursors. The parent compound, disilacyclobutane, (SiH2CH2)2, was found to exhibit the lowest deposition temperature (ca. 670 C) and to yield the highest purity SiC films. This precursor gave a highly textured, polycrystalline film on the Si(100) substrates.

  10. Fabrication and structure of bulk nanocrystalline Al-Si-Ni-mishmetal alloys

    International Nuclear Information System (INIS)

    Latuch, Jerzy; Cieslak, Grzegorz; Kulik, Tadeusz

    2007-01-01

    Al-based alloys of structure consisting of nanosized Al crystals, embedded in an amorphous matrix, are interesting for their excellent mechanical properties, exceeding those of the commercial crystalline Al-based alloys. Recently discovered nanocrystalline Al alloys containing silicon (Si), rare earth metal (RE) and late transition metal (Ni), combine high tensile strength and good wear resistance. The aim of this work was to manufacture bulk nanocrystalline alloys from Al-Si-Ni-mishmetal (Mm) system. Bulk nanostructured Al 91-x Si x Ni 7 Mm 2 (x = 10, 11.6, 13 at.%) alloys were produced by ball milling of nanocrystalline ribbons followed by high pressure hot isostating compaction

  11. Influencia de la distribución de las fibras en la conductividad térnnica de materiales compuestos con matrices de aleaciones de titanio y de magnesio

    Directory of Open Access Journals (Sweden)

    Alcaraz, D.

    2005-12-01

    Full Text Available Metal matrix composites are materials with an increasing use in industrial applications. Generally, the estimation of their thermal conductivity does not take into account the type of reinforcements distribution within the matrix. By applying the Network Simulation Method, a 2-D network model is designed and simulated to determinate precise numerical values of thermal conductivity of composites with random distributions. The proposed model is applied to titanium and magnesium matrix composites reinforced with different types of continuous fibers.

    Los "composites" de matriz metálica son materiales de uso creciente en distintas aplicaciones industriales. En general, la determinación de su conductividad térmica no considera el tipo de distribución de los refuerzos en el seno de las matrices. Aplicando el Método de Redes, se diseña un modelo (2D cuya simulación numérica permite obtener valores precisos de conductividad en "composites" con distribuciones aleatorias. El modelo se aplica a "composites" con matrices de aleaciones de titanio y magnesio reforzados con diferentes tipos de fibras continuas.

  12. Effect of alumina on grain refinement of Al-Si hypereutectic alloys

    Science.gov (United States)

    Majhi, J.; Sahoo, S. K.; Patnaik, S. C.; Sarangi, B.; Sachan, N. K.

    2018-03-01

    The size, volume fraction and distribution of primary as well as eutectic silicon affect the mechanical properties of the Al-Si hypereutectic alloys. It is very difficult for the simultaneous refinement and modification of primary and secondary Si particles in hypereutectic Al-Si alloys through traditional processes. This paper explores the role of γ-Al2O3 nanoparticles on Si particles in the course of solidification in hypereutectic Al-Si alloys at particular pouring temperature. The present study involves incorporation of varying contents dispersed γ-Al2O3 nanoparticles into a molten base metal during stir casting and followed by solidification. It has been reported that the synthesized composites having good interfacial bonding (wetting) between the dispersed phase and the liquid matrix was achieved in order to provide improved mechanical properties of the composite. The cast product of hypereutectic Al-16Si alloy with the reinforcement of nanoparticles, illustrated a significant improvement in both wear behaviour and hardness. The dry sliding wear test has been performed on a group of specimens with varying parameters (different loads and sliding velocities) in a pin on disc wear testing machine. Moreover, the wear rate and specific wear rate also affected in different load and different sliding velocities. However in XRD analysis of the samples, the enhancement of wear resistance as well as hardness was due to the formation of brittle phases like SiO2, Al2O3 and Al-rich intermetallic compounds. The hardness value of the materials increases nearly 6% in addition to increase in the density of only 0.8%. As per literature, the large plate eutectic Si particles were modified in to the fine core particles and it acquires enough potential for various applications.

  13. Neural network potential for Al-Mg-Si alloys

    Science.gov (United States)

    Kobayashi, Ryo; Giofré, Daniele; Junge, Till; Ceriotti, Michele; Curtin, William A.

    2017-10-01

    The 6000 series Al alloys, which include a few percent of Mg and Si, are important in automotive and aviation industries because of their low weight, as compared to steels, and the fact their strength can be greatly improved through engineered precipitation. To enable atomistic-level simulations of both the processing and performance of this important alloy system, a neural network (NN) potential for the ternary Al-Mg-Si has been created. Training of the NN uses an extensive database of properties computed using first-principles density functional theory, including complex precipitate phases in this alloy. The NN potential accurately reproduces most of the pure Al properties relevant to the mechanical behavior as well as heat of solution, solute-solute, and solute-vacancy interaction energies, and formation energies of small solute clusters and precipitates that are required for modeling the early stage of precipitation and mechanical strengthening. This success not only enables future detailed studies of Al-Mg-Si but also highlights the ability of NN methods to generate useful potentials in complex alloy systems.

  14. Monolithic integration of AlGaInP laser diodes on SiGe/Si substrates by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Kwon, O.; Boeckl, J. J.; Lee, M. L.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A.

    2006-01-01

    Room temperature operation of visible AlGaInP laser diodes epitaxially integrated on Si was demonstrated. Compressively strained laser heterostructures were grown by molecular beam epitaxy (MBE) on low dislocation density SiGe/Si substrates, where the threading dislocation density of the top relaxed Ge layers was measured in the range of 2x10 6 cm -2 . A threshold current density of J th ∼1.65 kA/cm 2 for the as-cleaved, gain-guided AlGaInP laser grown on SiGe/Si was obtained at the peak emission wavelength of 680 nm under pulsed mode current injection. These results show that not only can high quality AlGaInP materials grown by MBE be achieved on Si via relaxed SiGe interlayers, but the prototype demonstration of laser diode operation on Si illustrates that very defect sensitive optoelectronics in the III-P system can indeed be integrated with Si substrates by heteroepitaxial methods

  15. Preparation and Anodizing of SiCp/Al Composites with Relatively High Fraction of SiCp.

    Science.gov (United States)

    Wang, Bin; Qu, Shengguan; Li, Xiaoqiang

    2018-01-01

    By properly proportioned SiC particles with different sizes and using squeeze infiltration process, SiCp/Al composites with high volume fraction of SiC content (Vp = 60.0%, 61.2%, 63.5%, 67.4%, and 68.0%) were achieved for optical application. The flexural strength of the prepared SiC p /Al composites was higher than 483 MPa and the elastic modulus was increased from 174.2 to 206.2 GPa. With an increase in SiC volume fraction, the flexural strength and Poisson's ratio decreased with the increase in elastic modulus. After the anodic oxidation treatment, an oxidation film with porous structure was prepared on the surface of the composite and the oxidation film was uniformly distributed. The anodic oxide growth rate of composite decreased with SiC content increased and linearly increased with anodizing time.

  16. Preparation and Anodizing of SiCp/Al Composites with Relatively High Fraction of SiCp

    Directory of Open Access Journals (Sweden)

    Bin Wang

    2018-01-01

    Full Text Available By properly proportioned SiC particles with different sizes and using squeeze infiltration process, SiCp/Al composites with high volume fraction of SiC content (Vp = 60.0%, 61.2%, 63.5%, 67.4%, and 68.0% were achieved for optical application. The flexural strength of the prepared SiCp/Al composites was higher than 483 MPa and the elastic modulus was increased from 174.2 to 206.2 GPa. With an increase in SiC volume fraction, the flexural strength and Poisson’s ratio decreased with the increase in elastic modulus. After the anodic oxidation treatment, an oxidation film with porous structure was prepared on the surface of the composite and the oxidation film was uniformly distributed. The anodic oxide growth rate of composite decreased with SiC content increased and linearly increased with anodizing time.

  17. Preparation and Anodizing of SiCp/Al Composites with Relatively High Fraction of SiCp

    Science.gov (United States)

    2018-01-01

    By properly proportioned SiC particles with different sizes and using squeeze infiltration process, SiCp/Al composites with high volume fraction of SiC content (Vp = 60.0%, 61.2%, 63.5%, 67.4%, and 68.0%) were achieved for optical application. The flexural strength of the prepared SiCp/Al composites was higher than 483 MPa and the elastic modulus was increased from 174.2 to 206.2 GPa. With an increase in SiC volume fraction, the flexural strength and Poisson's ratio decreased with the increase in elastic modulus. After the anodic oxidation treatment, an oxidation film with porous structure was prepared on the surface of the composite and the oxidation film was uniformly distributed. The anodic oxide growth rate of composite decreased with SiC content increased and linearly increased with anodizing time. PMID:29682145

  18. Application of Al-2La-1B Grain Refiner to Al-10Si-0.3Mg Casting Alloy

    Science.gov (United States)

    Jing, Lijun; Pan, Ye; Lu, Tao; Li, Chenlin; Pi, Jinhong; Sheng, Ningyue

    2018-05-01

    This paper reports the application and microstructure refining effect of an Al-2La-1B grain refiner in Al-10Si-0.3Mg casting alloy. Compared with the traditional Al-5Ti-1B refiner, Al-2La-1B refiner shows better performances on the grain refinement of Al-10Si-0.3Mg alloy. Transmission electron microscopy analysis suggests that the crystallite structure features of LaB6 are beneficial to the heterogeneous nucleation of α-Al grains. Regarding the mechanical performances, tensile properties of Al-10Si-0.3Mg casting alloy are prominently improved, due to the refined microstructures.

  19. Positron annihilation studies of the AlOx/SiO2/Si interface in solar cell structures

    International Nuclear Information System (INIS)

    Edwardson, C. J.; Coleman, P. G.; Li, T.-T. A.; Cuevas, A.; Ruffell, S.

    2012-01-01

    Film and film/substrate interface characteristics of 30 and 60 nm-thick AlO x films grown on Si substrates by thermal atomic layer deposition (ALD), and 30 nm-thick AlO x films by sputtering, have been probed using variable-energy positron annihilation spectroscopy (VEPAS) and Doppler-broadened spectra ratio curves. All samples were found to have an interface which traps positrons, with annealing increasing this trapping response, regardless of growth method. Thermal ALD creates an AlO x /SiO x /Si interface with positron trapping and annihilation occurring in the Si side of the SiO x /Si boundary. An induced positive charge in the Si next to the interface reduces diffusion into the oxides and increases annihilation in the Si. In this region there is a divacancy-type response (20 ± 2%) before annealing which is increased to 47 ± 2% after annealing. Sputtering seems to not produce samples with this same electrostatic shielding; instead, positron trapping occurs directly in the SiO x interface in the as-deposited sample, and the positron response to it increases after annealing as an SiO 2 layer is formed. Annealing the film has the effect of lowering the film oxygen response in all film types. Compared to other structural characterization techniques, VEPAS shows larger sensitivity to differences in film preparation method and between as-deposited and annealed samples.

  20. Thermodynamic aspects of grain refinement of Al-Si alloys using Ti and B

    Energy Technology Data Exchange (ETDEWEB)

    Groebner, Joachim [Technical University of Clausthal, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Mirkovic, Djordje [Technical University of Clausthal, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Schmid-Fetzer, Rainer [Technical University of Clausthal, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)]. E-mail: schmid-fetzer@tu-clausthal.de

    2005-03-25

    A thermodynamic assessment of ternary Al-Si-Ti phases was performed. Published datasets for the other subsystems were checked and adapted. Based on that, a consistent thermodynamic description of quaternary Al-Si-Ti-B alloys was generated. This was applied in a calculation of Al-Si-Ti-B phase diagram sections for practically relevant temperatures and compositions of Al-Si alloys from Al-rich to typical Al-Si foundry alloys. These stable and metastable phase diagrams could be correlated to many detailed aspects of possible reactions observed or suggested in experimental studies of grain refining. Understanding the mechanisms of grain refining of Al wrought alloys and Al-Si foundry alloys using titanium and boron requires a fundamental knowledge of both thermodynamic and kinetic aspects of this complex process. This work focuses exclusively on the thermodynamic aspects and the phase diagrams, which were not available for the quaternary alloys and partly incomplete and inconsistent for the ternary subsystems.

  1. Effects of Eutectic Si and Secondary Dendrite Arm Spacing on the Mechanical Properties of Al-Si-Cu Cast Alloys

    International Nuclear Information System (INIS)

    Lee, Kyungmin; Kim, Yumi; Kim, Youngman; Hong, Sungkil; Choi, Seweon; Kim, Youngchan; Kang, Changseok

    2014-01-01

    The present study aims at investigating the effects of eutectic Si and Secondary dendrite arm spacing (SDAS) on mechanical properties of Al-Si-Cu alloy. Heat treatment and controlling of solidification rate affect to microstructure of Al-Si-Cu alloy. Al-Si-Cu alloy was dissolved in an electric furnace. The alloy cast in STD61 mold which had been pre-heated to 95 ℃ and 200 ℃. Eutectic Si and SDAS were finer as cooling rate increased. Image analysis technique has been utilized to examine the microstructure. Microstructure observation results showed that T6 heat treatment has a strong influence eutectic Si particle morphology. The mechanical properties, such as tensile strength, yield strength, elongation, were improved by ASTM E8 standard. Tensile properties of the Al-Si-Cu alloys prepared by different cooling rates were the same as each other by T6 heat treatment.

  2. Structural and magnetic study of mechanically deformed Fe rich FeAlSi ternary alloys

    International Nuclear Information System (INIS)

    Legarra, E.; Apiñaniz, E.; Plazaola, F.

    2012-01-01

    Highlights: ► Addition of Si to binary Fe–Al alloys makes the disordering more difficult. ► Si addition opposes the large volume increase found in FeAl alloys with deformation. ► Disordering induces a redistribution of non-ferrous atoms around Fe atoms in Fe 75 Al 25−x Si x and Fe 70 Al 30−x Si x . ► Addition of Si to binary Fe 75 Al 25 and Fe 70 Al 30 alloys opposes the magnetic behavior induced by Al in the magnetism of Fe. ► Si inhibits the para-ferro transition found in Fe 60 Al 40 alloy with disordering. - Abstract: In this work we study systematically the influence of different Al/Si ratios on the magnetic and structural properties of mechanically disordered powder Fe 75 Al 25−x Si x , Fe 70 Al 30−x Si x and Fe 60 Al 40−x Si x alloys by means of Mössbauer spectroscopy, X-ray diffraction and magnetic measurements. In order to obtain different stages of disorder the alloys were deformed by different methods: crushing induction melted alloys and ball milling annealed (ordered) alloys using different number of balls and speed. X-ray and Mössbauer data show that mechanical deformation induces the disordered A2 structure in these alloys. The results indicate that addition of Si to binary Fe–Al alloys makes the disordering more difficult. In addition, X-ray diffraction patterns show that the normalized lattice parameter variation of the disordered alloys of each composition decreases monotonically with Si content, indicating clearly that Si addition opposes the large volume increase found in FeAl alloys with deformation. The study of the hyperfine fields indicates that there is a redistribution of non-ferrous atoms around Fe atoms with the disordering; indeed, there is an inversion of the behavior of the hyperfine field of the Fe atoms. On the other hand, the magnetic measurements indicate that addition of Si to binary Fe 75 Al 25 and Fe 70 Al 30 alloys opposes the magnetic behavior induced by Al in the magnetism of Fe.

  3. Mechanical properties of Al-Cu alloy-SiC composites

    Science.gov (United States)

    Anggara, B. S.; Handoko, E.; Soegijono, B.

    2014-09-01

    The synthesis of aluminum (Al) alloys, Al-Cu, from mixture 96.2 % Al and 3.8 % Cu has been prepared by melting process at a temperature of 1200°C. The adding 12.5 wt% up to 20 wt% of SiC on Al-Cu alloys samples has been investigated. The structure analyses were examined by X-Ray Diffractometer (XRD) and scanning electron microscope (SEM). Moreover, the morphology of Al-Cu alloys has been seen as structure in micrometer range. The hardness was measured by hardness Vickers method. According to the results, it can be assumed that the 15 wt% of SiC content is prefer content to get better quality of back to back hardness Vickers of Al-Cu alloys.

  4. Mechanical properties of Al-Cu alloy-SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Anggara, B. S., E-mail: anggorobs1960@yahoo.com [Jurusan Fisika, FMIPA Universitas Negeri Jakarta, Indonesia 13220 and PPS Ilmu Material, Department Fisika, FMIPA, Universitas Indonesia (Indonesia); Handoko, E. [Jurusan Fisika, FMIPA Universitas Negeri Jakarta, 13220 (Indonesia); Soegijono, B. [PPS Ilmu Material, Department Fisika, FMIPA, Universitas Indonesia (Indonesia)

    2014-09-25

    The synthesis of aluminum (Al) alloys, Al-Cu, from mixture 96.2 % Al and 3.8 % Cu has been prepared by melting process at a temperature of 1200°C. The adding 12.5 wt% up to 20 wt% of SiC on Al-Cu alloys samples has been investigated. The structure analyses were examined by X-Ray Diffractometer (XRD) and scanning electron microscope (SEM). Moreover, the morphology of Al-Cu alloys has been seen as structure in micrometer range. The hardness was measured by hardness Vickers method. According to the results, it can be assumed that the 15 wt% of SiC content is prefer content to get better quality of back to back hardness Vickers of Al-Cu alloys.

  5. Acero de alto silicio producido por inmersión en Al-Si y recocido de difusión

    Directory of Open Access Journals (Sweden)

    Ros-Yáñez, Tanya

    2000-10-01

    Full Text Available It is difficult to process steel sheet with a high Si content (>3.5%Si, mainly because of its brittleness and the appearance of cracks during rolling and oxidation. However, there is a market for this steel in electrical applications because of the favourable influence of Si on magnetostriction and electrical resistivity. As an alternative process, 3% Si-steel substrates were coated with hypereutectic Al-Si-alloys in a "hot-dip simulator" using different preheating and dipping times. The obtained layers were characterised by SEM and EDS analysis. Diffusion annealing experiments were performed to obtain sufficient amount of Si in the steel. It was observed that:

    • intermetallic phases appear in the coating layers as according to the ternary Fe-Si-Al diagram
    • with a double dipping primary silicon crystals are formed in the surface layer
    • the ordered DO3 structure is present if the dipping and/or diffusion time is long enough
    • homogeneous silicon gradients in the whole substrate thickness have not yet been achieved
    • theoretic calculations show that Si-gradient, also have beneficial effects on magnetic behaviour


    Es difícil procesar aceros eléctricos de alto contenido en silicio (>3,5 % Si. Esto se debe principalmente, a problemas de fragilidad, aparición de grietas durante la laminación y oxidación. Sin embargo, existe un importante mercado para este tipo de acero en aplicaciones eléctricas debido a la favorable influencia que ejerce el Si sobre la magnetoestricción, las pérdidas eléctricas y la resistividad eléctrica. Como proceso alternativo, se sumergieron substratos de acero con 3 % de silicio en una aleación hipereutéctica Al-25 % Si, en un simulador de recubrimiento por inmersión en caliente. En los ensayos se utilizaron diferentes tiempos de precalentamiento y de inmersión. En la segunda fase de la investigación se llevaron a cabo recocidos de difusión en el

  6. Hardness and microstructural characteristics of rapidly solidified Al-8-16 wt.%Si alloys

    International Nuclear Information System (INIS)

    Uzun, O.; Karaaslan, T.; Gogebakan, M.; Keskin, M.

    2004-01-01

    Al-Si alloys with nominal composition of Al-8 wt.%Si, Al-12 wt.%Si, and Al-16 wt.%Si were rapidly solidified by using melt-spinning technique to examine the influence of the cooling rate/conditions on microstructure and mechanical properties. The microstructures of the rapidly solidified ribbons and ingot samples were investigated by the optical microscopy, electron microscopy and X-ray diffraction (XRD) techniques. The results showed that the structures of all melt-spun ribbons were completely composed of finely dispersed α-Al and eutectic Si phase, and primary silicon was not observed. The XRD analysis indicated that the solubility of Si in the α-Al matrix was greatly increased with rapid solidification. Additionally, mechanical properties of both conventionally cast (ingot) and melt-spun ribbons were examined by using Vickers indenter for one applied load (0.098 N). The hardness values of the melt-spun ribbons were about three times higher than those of ingot counterparts. The high hardness of the rapidly solidified state can be attributed to the supersaturated solid solutions. Besides, hardness values with different applied loads were measured for melt-spun ribbons. The results indicated that Vickers hardness values (H v ) of the ribbons depended on the applied load. Applying the concept of Hays-Kendall, the load independent hardness values were calculated as 694.0, 982.8 and 1186.8 MN/m 2 for Al-8 wt.%Si, Al-12 wt.%Si and Al-16 wt.%Si, respectively

  7. Microstructural characteristics and aging response of Zn-containing Al-Mg-Si-Cu alloy

    Science.gov (United States)

    Cai, Yuan-hua; Wang, Cong; Zhang, Ji-shan

    2013-07-01

    Al-Mg-Si-Cu alloys with and without Zn addition were fabricated by conventional ingot metallurgy method. The microstructures and properties were investigated using optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), tensile test, hardness test, and electrical conductivity measurement. It is found that the as-cast Al-Mg-Si-Cu-Zn alloy is composed of coarse dendritic grains, long needle-like β/δ-AlFeSi white intermetallics, and Chinese script-like α-AlFeSi compounds. During high temperature homogenization treatment, only harmful needle-like β-AlFeSi phase undergoes fragmentation and spheroidizing at its tips, and the destructive needle-like δ-phase does not show any morphological and size changes. Phase transitions from β-AlFeSi to α-AlFeSi and from δ-AlFeSi to β-AlFeSi are also not found. Zn addition improves the aging hardening response during the former aging stage and postpones the peak-aged hardness to a long aging time. In T4 condition, Zn addition does not obviously increase the yield strength and decrease the elongation, but it markedly improves paint-bake hardening response during paint-bake cycle. The addition of 0.5wt% Zn can lead to an increment of 99 MPa in yield strength compared with the value of 69 MPa for the alloy without Zn after paint-bake cycle.

  8. The effect of Si content on the fracture toughness of CrAlN/Si3N4 coatings

    International Nuclear Information System (INIS)

    Liu, S.; Wheeler, J. M.; Davis, C. E.; Clegg, W. J.; Zeng, X. T.

    2016-01-01

    CrAlN/Si 3 N 4 nanocomposite coatings with different Si contents were deposited to understand how Si influences the microstructure and mechanical behaviour of the coatings, in particular, the fracture toughness. The coating composition, chemical bonding, microstructure, and mechanical properties were studied by energy dispersive spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and nanoindentation, respectively. Using a micro double cantilever beam sample, it was found that the fracture toughness of CrAlN/Si 3 N 4 coatings was higher than that of both the CrN and CrAlN coatings and increased with increasing Si content. Cross-sectional transmission electron microscopy suggested that this was caused by the suppression of cracking at columnar boundaries

  9. EFFECT OF SILICON CONTENT ON MACHINABILITY OF Al-Si ALLOYS

    Directory of Open Access Journals (Sweden)

    Birol Akyüz

    2016-09-01

    Full Text Available In this study the effect of the change in the amount of Silicon (Si occuring in Al-Si alloys on mechanical and machinability properties of the alloy was investigated. The change in mechanical properties and microstructure, which depends on the increase in Si percentage, and the effects of this change on Flank Build-up (FBU, wear on the cutting edge, surface roughness, and machinability were also studied. Alloys in different ratios of Si (i.e. 2 to 12 wt %, were employed in the study. The specimens for tests were obtained by casting into metal moulds. The results obtained from experimental studies indicate improved mechanical properties and machinability, depending on the rise in Si percentage in Al-Si alloys. It is also observed that the increase in Si percentage enhanced surface quality.

  10. Interracial Structure and Formation Mechanism of Ultrasonic-assisted Brazed Joint of SiC Ceramics with Al-12Si Filler Metals in Air

    Institute of Scientific and Technical Information of China (English)

    Xiaoguang Chen; Ruishan Xie; Zhiwei Lai; Lei Liu; Jiuchun Yan; Guisheng Zou

    2017-01-01

    Ultrasonic-assisted brazing of SiC ceramics was performed by filling with an Al--12Si alloy at a low temperature of 620 ℃ in air.The interfacial characteristics and formation mechanism were investigated.The joint shear strength reached 84-94 MPa using the ultrasonic time of 2-16 s.The fracture morphology showed that the fracture path initiated and propagated in the joint alloy.The thin film of amorphous SiO2 that formed on the SiC surface was non-uniformly decomposed and diffused into the liquid Al-12Si alloy under the cavitation erosion effect of ultrasound.Abnormal isolated blocks of Al2SiO5 compounds formed at the interface between Al--12Si and a thicker SiO2 layer formed during the thermal oxidation treatment of the SiC ceramic.The SiO2 layer on the SiC ceramic did not hinder or impair the wetting and bonding process,and a stronger bond could form between Al-12Si and SiO2 or SiC in ultrasonicassisted brazing.

  11. Net-shape forming and properties of high volume fraction SiCp/Al composites

    International Nuclear Information System (INIS)

    Ren Shubin; Qu Xuanhui; Guo Jia; He Xinbo; Qin Mingli; Shen Xiaoyu

    2009-01-01

    High performance SiCp/Al composites have been realized their net-shape forming by use of a novel process-ceramic injection molding (CIM) for the preparation of SiC preform and pressureless infiltration of aluminum alloys. The dimension precision of prepared SiCp/Al parts could reach about ±0.3%, and their properties could also better meet the requirement of electronic packaging on the materials. In this paper, the CIM process to fabricate SiC preform and the infiltration of SiC preform by Al alloys have been discussed in detail. Additionally, the properties of prepared SiCp/Al composites have also been given research and evaluation.

  12. Micro-nano filler metal foil on vacuum brazing of SiCp/Al composites

    Science.gov (United States)

    Wang, Peng; Gao, Zeng; Niu, Jitai

    2016-06-01

    Using micro-nano (Al-5.25Si-26.7Cu)- xTi (wt%, x = 1.0, 1.5, 2.0, 2.5 and 3.0) foils as filler metal, the research obtained high-performance joints of aluminum matrix composites with high SiC particle content (60 vol%, SiCp/Al-MMCs). The effect of brazing process and Ti content on joint properties was investigated, respectively. The experimental results indicate that void free dense interface between SiC particle and metallic brazed seam with C-Al-Si-Ti product was readily obtained, and the joint shear strength enhanced with increasing brazing temperature from 560 to 580 °C or prolonging soaking time from 10 to 90 min. Sound joints with maximum shear strength of 112.5 MPa was achieved at 580 °C for soaking time of 90 min with (Al-5.25Si-26.7Cu)-2Ti filler, where Ti(AlSi)3 intermetallic is in situ strengthening phase dispersed in the joint and fracture occured in the filler metal layer. In this research, the beneficial effect of Ti addition into filler metal on improving wettability between SiC particle and metallic brazed seam was demonstrated, and capable welding parameters were broadened for SiCp/Al-MMCs with high SiC particle content.

  13. Caracterización superficial, electroquímica y de composición de aleaciones zinc níquel electrodepositadas

    OpenAIRE

    PIRATOBA, ULISES; VERA, ENRIQUE; ORTIZ, CESAR

    2008-01-01

    La gran demanda de láminas de acero recubiertas con Zinc o con aleaciones de Zinc, es atendida conprocesos de electro deposición en continuo; estos requieren de altas densidades de corriente, obtenidas en electrolitos ácidos. En este trabajo se presenta la composición, morfología superficial y la caracterización electroquímica de aleaciones Zinc Níquel fase gamma sobre láminas de acero, depositadas con altas densidades de corriente. Estas fueron determinadas mediante Análisis de Energía Disp...

  14. Residual Stress Measurement of SiC tile/Al7075 Hybrid Composites by Neutron Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Bok; Lee, Jun Ho; Hong, Soon Hyung; Ryu, Ho Jin [KAIST, Daejeon (Korea, Republic of); Lee, Sang Bok; Lee, Sang Kwan [Korea Institute of Materials Science, Changwon (Korea, Republic of); Muslihd, M. Rifai [Center for Advanced Materials Science and Technology, Tangerang (India)

    2016-05-15

    In this research, SiC which has low density, high compressive strength, and high elastic modulus was used to fabricate the armor plate. In addition, Al which has low density and high toughness was used for a metal matrix of the composites. If two materials are combined, the composite can be effective materials for light weight armor applications. However, the existence of a large difference in coefficients of thermal expansion (CTE) between SiC and Al matrix, SiC/Al composites can have residual stresses while cooled in the fabrication process. Previous research reported that residual stresses in the composites or microstructures have an effect on the fatigue life and their mechanical properties. Some researchers reported about the residual stresses in the SiCp/Al metal matrix composites by numerical simulation systems, X-ray diffraction, and destructive methods. In order to analyze the residual stress of SiC/Al composites, the neutron diffraction as the non-destructive method was performed in this research. The 50 vol.% SiC{sub p}/Al7075 composites and SiC tile inserted 50 vol.% SiC{sub p}/Al7075 hybrid composites were measured to analyze the residual stress of Al (111) and SiC (111). Both samples had the tensile residual stresses in the Al (111) and the compressive residual stresses in the SiC (111) due to the difference in CTE.

  15. The Effectiveness of Al-Si Coatings for Preventing Interfacial Reaction in Al - Mg Dissimilar Metal Welding

    OpenAIRE

    Wang, Yin; Al-Zubaidy, Basem; Prangnell, Philip

    2017-01-01

    The dissimilar welding of aluminum to magnesium is challenging because of the rapid formation of brittle intermetallic compounds (IMC) at the weld interface. An Al-Si coating interlayer was selected to address this problem, based on thermodynamic calculations that predicted silicon would change the reaction path to avoid formation of the normally observed binary Al-Mg IMC phases (-Al3Mg2 and -Al12Mg17). Long-term static heat treatments confirmed that a Si-rich coating will preferentially pr...

  16. Thermal shock behavior of nano-sized SiC particulate reinforced AlON composites

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, X.J. [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Ru, H.Q., E-mail: ruhq@smm.neu.edu.cn [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Chen, D.L., E-mail: dchen@ryerson.ca [Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Zhang, N.; Liang, B. [Key Laboratory of Advanced Materials Manufacturing Technology of Liaoning Province, Shenyang University, Shenyang, Liaoning 110044 (China)

    2012-03-25

    Highlights: Black-Right-Pointing-Pointer Addition of nano-SiC particles enhances residual strength and critical temperature. Black-Right-Pointing-Pointer Young's modulus decreases with increasing quenching temperature. Black-Right-Pointing-Pointer Linear relationship between residual strength and thermal shock times is obtained. Black-Right-Pointing-Pointer Rougher fracture surfaces in the SiC-AlON composites are observed. - Abstract: Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications. Thermal shock resistance is a major concern and an important performance index of high-temperature ceramics. While silicon carbide (SiC) particles have been proven to improve mechanical properties of AlON ceramic, the high-temperature thermal shock behavior was unknown. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of AlON ceramic and 8 wt% SiC-AlON composites over a temperature range between 175 Degree-Sign C and 275 Degree-Sign C. The residual strength and Young's modulus after thermal shock decreased with increasing quenching temperature and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. A linear relationship between the residual strength and thermal shock times was observed in both pure AlON and SiC-AlON composites. The addition of nano-sized SiC particles increased both residual strength and critical temperature from 200 Degree-Sign C in the monolithic AlON to 225 Degree-Sign C in the SiC-AlON composites due to the toughening effect, the lower coefficient of thermal expansion and higher thermal conductivity of SiC. The enhancement of the thermal shock resistance in the SiC-AlON composites was directly related to the change of fracture mode from intergranular cracking along with cleavage-type fracture in the AlON to a rougher fracture surface with ridge

  17. A comparative wear study on Al-Li and Al-Li/SiC composite

    Energy Technology Data Exchange (ETDEWEB)

    Okumus, S. Cem, E-mail: cokumus@sakarya.edu.tr; Karslioglu, Ramazan, E-mail: cokumus@sakarya.edu.tr; Akbulut, Hatem, E-mail: cokumus@sakarya.edu.tr [Sakarya University Engineering Faculty, Department of Metallurgical and Materials Engineering, Esentepe Campus, 54187, Sakarya (Turkey)

    2013-12-16

    Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al{sub 2}O{sub 3} ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms{sup −1} and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.

  18. Influence of powder particle injection velocity on the microstructure of Al-12Si/SiCp coatings produced by laser cladding

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Vilar, R.; Ocelik, V.; De Hosson, J. Th M.

    2009-01-01

    The influence of powder particle injection velocity on the microstructure of coatings consisting of an Al-Si matrix reinforced with SiC particles prepared by laser cladding from mixtures of powders of Al-12 wt.% Si alloy and SiC was investigated both experimentally and by modeling. At low injection

  19. Enhanced field emission from Si doped nanocrystalline AlN thin films

    International Nuclear Information System (INIS)

    Thapa, R.; Saha, B.; Chattopadhyay, K.K.

    2009-01-01

    Si doped and undoped nanocrystalline aluminum nitride thin films were deposited on various substrates by direct current sputtering technique. X-ray diffraction analysis confirmed the formation of phase pure hexagonal aluminum nitride with a single peak corresponding to (1 0 0) reflection of AlN with lattice constants, a = 0.3114 nm and c = 0.4986 nm. Energy dispersive analysis of X-rays confirmed the presence of Si in the doped AlN films. Atomic force microscopic studies showed that the average particle size of the film prepared at substrate temperature 200 deg. C was 9.5 nm, but when 5 at.% Si was incorporated the average particle size increased to ∼21 nm. Field emission study indicated that, with increasing Si doping concentration, the emission characteristics have been improved. The turn-on field (E to ) was 15.0 (±0.7) V/μm, 8.0 (±0.4) V/μm and 7.8 (±0.5) V/μm for undoped, 3 at.% and 5 at.% Si doped AlN films respectively and the maximum current density of 0.27 μA/cm 2 has been observed for 5 at.% Si doped nanocrystalline AlN film. It was also found that the dielectric properties were highly dependent on Si doping.

  20. Effects of Mn addition on microstructure and hardness of Al-12.6Si alloy

    Science.gov (United States)

    Biswas, Prosanta; Patra, Surajit; Mondal, Manas Kumar

    2018-03-01

    In this work, eutectic Al-12.6Si alloy with and without manganese (Mn) have been developed through gravity casting route. The effect of Mn concentration (0.0 wt.%, 1 wt%, 2 wt% and 3 wt%) on microstructural morphology and hardness property of the alloy has been investigated. The eutectic Al-12.6 Si alloy exhibits the presence of combine plate, needle and rod-like eutectic silicon phase with very sharp corners and coarser primary silicon particles within the α-Al phase. In addition of 1wt.% of Mn in the eutectic Al-12.6Si alloy, sharp corners of the primary Si and needle-like eutectic Si are became blunt and particles size is reduced. Further, increase in Mn concentration (2.0 wt.%) in the Al-12.6Si alloy, irregular plate shape Al6(Mn,Fe) intermetallics are formed inside the α-Al phase, but the primary and eutectic phase morphology is similar to the eutectic Al-12.6Si alloy. The volume fraction of Al6(Mn,Fe) increases and Al6(Mn,Fe) particles appear as like chain structure in the alloy with 3 wt.% Mn. An increase in Mn concentration in the Al-12.6Si alloys result in the increase in bulk hardness of the alloy as an effects of microstructure modification as well as the presence of harder Al6(Mn,Fe) phase in the developed alloy.

  1. Study on characteristics of U-Mo/Al-Si interaction layers of dispersion fuel plates

    International Nuclear Information System (INIS)

    Liu Lijian; Yin Changgeng; Chen Jiangang; Sun Changlong; Liu Yunming

    2014-01-01

    In this paper, we analyzed the characteristics of U-Mo/Al-Si interaction layers of dispersion fuel plates. The results show that the interaction layers (IL) are with irregular morphology and uneven thickness, and are mainly formed in the internal micro cracks of the dispersion fuel particles or at the interface between the particles and the substrates. The diffusion mechanism of U-Mo/Al-Si is the vacancy diffusion, Al and Si are migrating elements, and the diffusion reaction is that Al and Si diffuse to U-Mo alloy. Inside the interaction layers, the Al content keeps constant basically, but the Si content gradually increases with the substrate-fuel direction, and the maximum content of Si appears interaction layers near the U-Mo side. Adding about 5 wt% Si into Al matrix can restrain the diffusion reaction, and improve the performance of dispersion fuel plates finally. (authors)

  2. Fabrication of SiCp/Al Alloy Composites by In-situ Vacuum Hot Press Process

    Energy Technology Data Exchange (ETDEWEB)

    Choi, S. W.; Hong, S. K.; Kim, Y. M.; Kang, C. S. [Chonnam National University, Kwangju (Korea); Chang, S. Y. [Hanyang University, Seoul (Korea)

    2001-07-01

    SiCp/pure Al and SiCp/2024Al MMCs were fabricated by in-situ VHP process designed specially just in this study which is composed of the vacuum hot press at range from R.T. to 500 deg.C and the continuous extrusion without canning process at 520 deg.C. It was investigated the effect of SiC particle size, volume fraction and extrusion ratio on the tensile properties and micro structure in all composites. In case of the 10:1 extrusion ratio, but SiCp/pure Al and SiCp/2024Al composites were shown a sound appearance and a good micro structure without crack of SiCp as well as uniform distribution of SiCp. However, in case of the 16:1 extrusion ratio, the number of cracked SiC particles more than increased in a higher volume fraction composite and 2024Al matrix composite compared with pure Al matrix one. The tensile strength of the composites reinforced smaller SiCp was higher than that of the bigger SiCp reinforced in same volume fraction and extrusion ratio. (author) 14 refs., 14 figs.

  3. Soldadura TIG y MIG de las aleaciones de aluminio 6061 y 7020. Estudios microestructurales y de propiedades mecánicas

    Directory of Open Access Journals (Sweden)

    Gómez de Salazar, J. M.

    1998-05-01

    Full Text Available The aluminium alloys of the 6XXX and 7XXX series, are actually considered of medium and high strength, and are been profusely used in different industries such as aeronautical, automotive, etc. However, its wide application as structural material needs of the proper development of their joining process. The present work describes the results obtained from the microstructural evaluation, both with optical and scanning electronic microscopies (OM and SEM, and of the mechanical one (hardness changes of the weld produced in the alloys using two different are welding techniques: GTAW (TIG and GMAW (MIG. For the last one, a filler metal with a composition of Al-5Mg, AWS denomination A5.10-92 (AA5356, has been used.

    Las aleaciones de las series AA6XXX y AA7XXX están consideradas como de media y alta resistencia, y se utilizan con gran profusión en tecnologías como: aeronáutica, automoción, etc. Pero su aplicación como materiales estructurales pasa, sin duda, por el adecuado desarrollo de sus procesos de unión. En este trabajo, se realiza una evaluación microestructural, tanto mediante técnicas de microscopía óptica (MO como electrónica (MEB-EDS y de las propiedades mecánicas (evolución de la dureza de estas aleaciones, una vez que han sido sometidas a procesos de soldadura con arco, como son GTAW (TIG y GMAW (MIG, empleando un aporte de aleación de aluminio de composición Al-5Mg, cuya denominación es AWS A5.10-92 (AA5356.

  4. Synthesis and structural characterization of Al4SiC4-homeotypic aluminum silicon oxycarbide, [Al4.4Si0.6][O1.0C2.0]C

    International Nuclear Information System (INIS)

    Kaga, Motoaki; Iwata, Tomoyuki; Nakano, Hiromi; Fukuda, Koichiro

    2010-01-01

    A new quaternary layered oxycarbide, [Al 4.39(5) Si 0.61(5) ] Σ5 [O 1.00(2) C 2.00(2) ] Σ3 C, has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy (EDX). The title compound was found to be hexagonal with space group P6 3 /mmc, Z=2, and unit-cell dimensions a=0.32783(1) nm, c=2.16674(7) nm and V=0.20167(1) nm 3 . The atom ratios Al:Si were determined by EDX, and the initial structural model was derived by the direct methods. The final structural model showed the positional disordering of one of the three types of Al/Si sites. The maximum-entropy methods-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were R wp =3.73% (S=1.20), R p =2.94%, R B =1.04% and R F =0.81%. The crystal was an inversion twin. Each twin-related individual was isostructural with Al 4 SiC 4 (space group P6 3 mc, Z=2). - Graphical abstract: A new oxycarbide discovered in the Al-Si-O-C system, Al 4 SiC 4 -homeotypic [Al 4.4 Si 0.6 ][O 1.0 C 2.0 ]C. The crystal is an inversion twin, and hence the structure is represented by a split-atom model. The three-dimensional electron density distributions are determined by the maximum-entropy methods-based pattern fitting, being consistent with the disordered structural model.

  5. Electroluminescence of doped and undoped AlN/SiC-heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Bruesewitz, Christoph; Vetter, Ulrich; Hofsaess, Hans [II. Physikalisches Institut, Georg-August-Universitaet Goettingen (Germany)

    2010-07-01

    AlN with its large and direct bandgap is a useful host for optoelectronic applications. Grown on 6H-SiC, a heterojunction is created, forming a diode. The light emitted by n-doped 6H-SiC via electroluminescence forms a broad band with a maximum at a wavelength of 475 nm. With the AlN layer on the surface, nitrogen atoms can diffuse into the 6H-SiC, creating new energy levels. Depending on the direction of the current and additional dopants in the AlN layer, the carrier concentration changes and new levels are available, resulting in different colours. It is shown that in this heterojunction blue, red and white colours are feasible.

  6. Silicon nitride and YMgSiAlON glass study by mechanical spectroscopy

    International Nuclear Information System (INIS)

    Doen, B.; Gadaud, P.

    1996-01-01

    Si 3 N 4 /TiN and YMgSiAlON/SiC composites have been studied by isothermal mechanical spectroscopy over a large frequency range. Internal friction curves obtained for the composite Si 3 N 4 -TiN(30% vol)-Al 2 O 3 , Y 2 O 3 (7.5% vol) exhibit a thermally activated pseudo peak superposed on a non purely exponential background. We can assume that this maximum is due to relaxations in the compressed intergranular glassy films. The apparent dynamical parameters deduced from its shift (11.2 eV and 3.10 -45 s) are unusual as observed in amorphous materials. YMgSiAlON glass has a composition very similar to the one of the intergranular phase of Si 3 N 4 /TiN composite. The damping curves obtained for YMgSiAlON/SiC composites above the glass transition temperature are pure exponential backgrounds. An original analysis of these curves allows to determine an activation energy of about 3.6 eV. This value is more realistic for an elementary diffusion mechanism in a glass near Tg. (orig.)

  7. Effect of Carbon in Fabrication Al-SiC Nanocomposites for Tribological Application

    Directory of Open Access Journals (Sweden)

    Bartosz Hekner

    2017-06-01

    Full Text Available Aluminium-based hybrid composites are a new class of advanced materials with the potential of satisfying the demands in engineering applications. This paper describes the effects of carbon addition on the formation and properties of AMC with SiC nanoparticles reinforcement. The composites were produced via mechanical alloying followed by hot pressing. Three forms of carbon, graphite (GR, multiwalled carbon nanotubes (CNTs, and, for the first time, glassy carbon (GC, were used for the hybrid composites manufacturing and compared with tribological properties of Al-SiC composite without carbon addition. GC and CNTs enhanced formation of Al-SiC composite particles and resulted in a homogeneous distribution of reinforcing particles. On the other hand, GR addition altered mechanochemical alloying and did not lead to a proper distribution of nanoparticulate SiC reinforcement. Hot pressing technique led to the reaction between Al and carbon as well as SiC particles and caused the formation of Al4C3 and γ-Al2O3. The subsistence of carbon particles in the composites altered the predominant wear mechanisms since the wear reduction and the stabilization of the friction coefficient were observed. GC with simultaneous γ-Al2O3 formation in the hybrid Al-SiC(n-C composites turned out to be the most effective additive in terms of their tribological behaviour.

  8. Superplastic forming of the Cd-17.4Zn alloy; Conformado superplastico de la aleacion Cd-17.4Zn

    Energy Technology Data Exchange (ETDEWEB)

    Llanes-Briceno, J. A.; Torres-Villasenor, G. [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

    2000-06-01

    In the present work the necessary steps to carry on the superplastic forming of the Cd-17.4Zn alloy are defined. The use of either atmospheric pressure or gas pressure as forming tools is analyzed. The optimum values of the variable involved (temperature, maximum strain and sensitivity index) are determined while a method for the characterization of futures superplastic alloys is set forth. The experimental characterization of the superplastic forming is achieved with free bulging of circular membranes of 12, 16, 24, 32 and 40 mm in diameter and with three different membrane thicknesses (0.4, 0.6, 0.8 mm). [Spanish] Se definen los pasos necesarios para el conformado superplastico de la aleacion Cd-17.4 Zn. Se comparan la presion atmosferica y el gas a presion como herramientas de conformado. Se determinan los valores optimos de la variables involucradas (temperatura, deformacion maxima e indice de sensibilidad) y se plantea una metodologia para la caracterizacion de futuras aleaciones superplasticas. El conformado superplastico se caracteriza experimentalmente mediante el inflado libre de membranas circulares de 12, 16, 24, 32 y 40 mm de diametro y tres diferentes espesores (0.4, 0.6 y 0.8 mm). Se muestra la estructura perlitica (enfuiada al aive Cd-17.4Zn) y la estructura grano fino. Se muestra la profundidad de deformacion en tres espesores (0.4, 0.6, 0.8 mm) a P=200 Kpa y T = 200 y a T = 230.

  9. Stress Wave attenuation in SiC3D/Al Composite

    International Nuclear Information System (INIS)

    Yuan Chunyuan; Wang Yangwei; Li Guoju; Zhang Xu; Gao Jubin

    2013-01-01

    SiC 3D /Al composite is a kind of special composite with interpenetrating network microstructure. The attenuation properties of stress wave propagation along the SiC 3D /Al composite are studied by a Split Hopkinson Pressure Bar system and FEM simulations, and the attenuation mechanism is discussed in this paper. Results show that the attenuation rate of the stress wave in the composite is up to 1.73MPa·mm −1 . The reduction of the amplitude of waves is caused by that plenty of interfaces between SiC and Al within the composite acting with stress waves. When the incident plane wave reaches the SiC 3D /Al interface, reflection wave and transmission wave propagates in different directions along the irregular interface between SiC phase and aluminium phase due to the impedance mismatch of them, which leads to the divergence of stress wave. At the same time, some stress micro-focuses occurs in the aluminium phase for the complex wave superimposition, and some plastic deformation may take place within such micro-regions, which results in the consumption of stress wave energy. In conclusion, the stress wave attenuation is derived from divergence and consumption of stress wave.

  10. Microstructure and bonding mechanism of Al/Ti bonded joint using Al-10Si-1Mg filler metal

    International Nuclear Information System (INIS)

    Sohn, Woong H.; Bong, Ha H.; Hong, Soon H.

    2003-01-01

    The microstructures and liquid state diffusion bonding mechanism of cp-Ti to 1050 Al using an Al-10.0wt.%Si-1.0wt.%Mg filler metal with 100 μm in thickness have been investigated at 620 deg. C under 1x10 -4 Torr. The effects of bonding process parameters on microstructure of bonded joint have been analyzed by using an optical microscope, AES, scanning electron microscopy and EDS. The interfacial bond strength of Al/Ti bonded joints was measured by the single lap shear test. The results show that the bonding at the interface between Al and filler metal proceeds by wetting the Al with molten filler metal, and followed by removal of oxide layer on surface of Al. The interface between Al and filler metal moved during the isothermal solidification of filler metal by the diffusion of Si from filler metal into Al layer. The interface between Al and filler metal became curved in shape with increasing bonding time due to capillary force at grain boundaries. The bonding at the interface between Ti and filler metal proceeds by the formation of two different intermetallic compound layers, identified as Al 5 Si 12 Ti 7 and Al 12 Si 3 Ti 5 , followed by the growth of the intermetallic compound layers. The interfacial bond strength at Al/Ti joint increased with increasing bonding time up to 25 min at 620 deg. C. However, the interfacial bond strength of Al/Ti joint decreased after bonding time of 25 min at 620 deg. C due to formation of cavities in Al near Al/intermetallic interfaces

  11. Electronic Structure and Chemical Bond of Ti3SiC2 and Adding Al Element

    Institute of Scientific and Technical Information of China (English)

    MIN Xinmin; LU Ning; MEI Bingchu

    2006-01-01

    The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation (DFT-DVM) method. When Al element is added into Ti3SiC2, there is a less difference of ionic bond, which does not play a leading role to influent the properties. After adding Al, the covalent bond of Al and the near Ti becomes somewhat weaker, but the covalent bond of Al and the Si in the same layer is obviously stronger than that of Si and Si before adding. Therefore, in preparation of Ti3SiC2, adding a proper quantity of Al can promote the formation of Ti3SiC2. The density of state shows that there is a mixed conductor character in both of Ti3SiC2 and adding Al element. Ti3SiC2 is with more tendencies to form a semiconductor. The total density of state near Fermi lever after adding Al is larger than that before adding, so the electric conductivity may increase after adding Al.

  12. Formation of Al15Mn3Si2 Phase During Solidification of a Novel Al-12%Si-4%Cu-1.2%Mn Heat-Resistant Alloy and Its Thermal Stability

    Science.gov (United States)

    Suo, Xiaojing; Liao, Hengcheng; Hu, Yiyun; Dixit, Uday S.; Petrov, Pavel

    2018-02-01

    The formation of Al15Mn3Si2 phase in Al-12Si-4Cu-1.2Mn (wt.%) alloy during solidification was investigated by adopting CALPHAD method and microstructural observation by optical microscopy, SEM-EDS, TEM-EDS/SAD and XRD analysis; SEM fixed-point observation method was applied to evaluate its thermal stability. As-cast microstructural observation consistently demonstrates the solidification sequence of the studied alloy predicted by phase diagram calculation. Based on the phase diagram calculation, SEM-EDS, TEM-EDS/SAD and XRD analysis, as well as evidences on Al-Si-Mn-Fe compounds from the literature, the primary and eutectic Mn-rich phases with different morphologies in the studied alloy are identified to be Al15Mn3Si2 that has a body-centered cubic (BCC) structure with a lattice constant of a = 1.352 nm. SEM fixed-point observation and XRD analysis indicate that Al15Mn3Si2 phase has more excellent thermal stability at high temperature than that of CuAl2 phase and can serve as the major strengthening phase in heat-resistant aluminum alloy that has to face a high-temperature working environment. Results of tension test show that addition of Mn can improve the strength of Al-Si-Cu alloy, especially at elevated temperature.

  13. Estudio de la corrosión de diferentes aleaciones en sales de carbonatos fundidos con la técnica de espectroscopía de impedancia electroquímica

    Directory of Open Access Journals (Sweden)

    Pérez, F. J.

    2000-06-01

    Full Text Available In the present work the corrosion behavior of different alloys (AISI 304, AISI 430 and TiAl6V in molten carbonates at 650EC are compared. By using the Electrochemical Impedance Technique different corrosion parameters such as the corrosion rate and the oxyde concentration and others features of the different layers of corrosion products are "in situ" determined. Take into account, the corrosion product characterization by X-ray Diffraction (XRD, Scanning Electron Microscopy (SEM and Electrochemical impedance Spectroscopy (EIS a corrosion mechanism for every tested alloy is proposed. In all cases, the corrosion mechanisms during the first hours are similar to a high temperature oxidation mechanism. When the equilibrium is established, the lithiation began by the formation of different double-layers on the surface of Li-metal oxydes. At the end of the corrosion process, one or two inner layers of metallic oxydes and one or two outer layers of Li-metal oxydes were formed. The corrosion mechanisms of the stainless steels (AISI 304 ans AISI 310S are a function of their chromium contents. TiAl6V alloy showed the best behavior against the corrosion of molten carbonates by the formation of a protective layer of mixed Li-Ti oxydes.

    En el presente trabajo se compara el comportamiento frente a la corrosión de diferentes aleaciones (aceros inoxidables AISI 304 y AISI 310S y aleación TiAl6V en un electrolito de carbonatos fundidos a 650°C. Con la técnica de impedancia se determina “in situ” la velocidad de corrosión de las aleaciones, la resistencia del electrolito, es decir, la concentración del óxido disuelto y otras características de las capas de productos de corrosión. Teniendo en cuenta la caracterización de los productos de corrosión mediante difracción de rayos X (XRD y microscopía electrónica de barrido (SEM y los resultados de espectroscopía de impedancia (EIS, se propone un mecanismo para cada una de las aleaciones. En

  14. Fabrication of Spherical AlSi10Mg Powders by Radio Frequency Plasma Spheroidization

    Science.gov (United States)

    Wang, Linzhi; Liu, Ying; Chang, Sen

    2016-05-01

    Spherical AlSi10Mg powders were prepared by radio frequency plasma spheroidization from commercial AlSi10Mg powders. The fabrication process parameters and powder characteristics were investigated. Field emission scanning electron microscope, X-ray diffraction, laser particle size analyzer, powder rheometer, and UV/visible/infrared spectrophotometer were used for analyses and measurements of micrographs, phases, granulometric parameters, flowability, and laser absorption properties of the powders, respectively. The results show that the obtained spherical powders exhibit good sphericity, smooth surfaces, favorable dispersity, and excellent fluidity under appropriate feeding rate and flow rate of carrier gas. Further, acicular microstructures of the spherical AlSi10Mg powders are composed of α-Al, Si, and a small amount of Mg2Si phase. In addition, laser absorption values of the spherical AlSi10Mg powders increase obviously compared with raw material, and different spectra have obvious absorption peaks at a wavelength of about 826 nm.

  15. Evaluaciones calorimétricas de la precipitación en aleaciones Cu-Co-Si, ricas en Cu

    Directory of Open Access Journals (Sweden)

    Donoso, Eduardo

    2001-08-01

    Full Text Available The precipitation process of cobalt and silicon atoms from supersaturated solid solutions of Cu-Co-Si for two compositions was studied by differential scanning calorimetry (DSC. Calorimetric traces analysis showed the presence of two overlapping exothermic reactions (stages 1 and 2, which can are attributed to two precipitation processes. First stage correspond to the preceding formation of a cobalt precipitate, while the second stage correspond to the formation of stoichiometric CO2Si composition which takes place by silicon diffusion to the first precipitate. Heat contents during the stages 1 and 2 are proportional to precipitates volume fractions. Activation energies of both precipitates, calculated from the Kissinger method, are consistent with those corresponding to diffussion of Co in Cu and Si in Cu. Both processes can be decribed by the Johnson-Mehl Avrami (JMA equation. Values of n are compatible with precipitate nucleation from the solid solution (stage 1 and with growth of paticles from preexisting Co precipitates. Furthermore,, the kinetic of the concentration decay of Co and Si in the matrix was estimated as function of the transformated fraction for each thermal event and from their respective volume fractions.

    Mediante calorimetría diferencial de barrido (DSC se estudió el proceso de precipitación de átomos de cobalto y silicio a partir de dos soluciones sólidas supersaturadas de Cu-Co- Si. El análisis de las trazas calorimétricas muestra la presencia de dos reacciones exotérmicas traslapadas (etapas 1 y 2, que se interpretan como la formación de dos tipos de precipitados. La primera etapa corresponde a la formación precursora de un precipitado de cobalto, en tanto que la etapa 2 corresponde a la formación de un precipitado de composición estequiométrica CO2Si producido por difusión de silicio hacia la primera partícula. Los calores liberados durante las etapas 1 y 2 son proporcionales a

  16. Influence wt.% of SiC and borax on the mechanical properties of AlSi-Mg-TiB-SiC composite by the method of semi solid stir casting

    Science.gov (United States)

    Bhiftime, E. I.; Guterres, Natalino F. D. S.; Haryono, M. B.; Sulardjaka, Nugroho, Sri

    2017-04-01

    SiC particle reinforced metal matrix composites (MMCs) with solid semi stir casting method is becoming popular in recent application (automotive, aerospace). Stirring the semi solid condition is proven to enhance the bond between matrix and reinforcement. The purpose of this study is to investigate the effect of the SiC wt.% and the addition of borax on mechanical properties of composite AlSi-Mg-TiB-SiC and AlSi-Mg-TiB-SiC/Borax. Specimens was tested focusing on the density, porosity, tensile test, impact test microstructure and SEM. AlSi is used as a matrix reinforced by SiC with percentage variations (10, 15, 20 wt.%). Giving wt.% Borax which is the ratio of 1: 4 between wt.% SiC. The addition of 1.5% of TiB gives grain refinement. The use of semi-solid stir casting method is able to increase the absorption of SiC particles into a matrix AlSi evenly. The improved composite presented here can be used as a guideline to make a new composite.

  17. Influence of PECVD deposited SiNx passivation layer thickness on In0.18Al0.82N/GaN/Si HEMT

    International Nuclear Information System (INIS)

    Singh, Sarab Preet; Liu, Yi; Ngoo, Yi Jie; Kyaw, Lwin Min; Bera, Milan Kumar; Chor, Eng Fong; Dolmanan, S B; Tripathy, Sudhiranjan

    2015-01-01

    The influence of plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiN x ) passivation film thickness on In 0.18 Al 0.82 N/GaN/Si heterostructures and HEMTs has been investigated. The formation of Si 3 N 4 was confirmed by x-ray photoelectron spectroscopy (XPS) measurements. X-ray reflectivity (XRR) measurements reveal that both the density and roughness of the SiN x film increase with increasing film thickness. With an increase in SiN x film thickness, a significant increase in two-dimensional electron gas (2DEG) density, drain current, extrinsic transconductance and negative threshold voltage shift of the In 0.18 Al 0.82 /GaN/Si HEMTs are observed. An optimal thickness of SiN x is ∼100 nm and it yields a substantial increase in 2DEG density (∼30%) with a minimum sheet resistance for In 0.18 Al 0.82 N/GaN/Si heterostructures. Furthermore, we correlate the observed SiN x film thickness-dependent electrical characteristics of In 0.18 Al 0.82 /GaN/Si HEMTs with the density of the SiN x film. (paper)

  18. THE THERMODYNAMIC PROPERTIES OF MELTS OF DOUBLE SYSTEM MgO – Al2O3, MgO – SiO2, MgO – CaF2, Al2O3 – SiO2, Al2O3 – CaF2, SiO2 – CaF2

    Directory of Open Access Journals (Sweden)

    В. Судавцова

    2012-04-01

    Full Text Available Methodology of prognostication of thermodynamics properties of melts is presented from the coordinatesof liquidus of diagram of the state in area of equilibria a hard component is solution, on which energies ofmixing of Gibbs are expected in the double border systems of MgO – Al2O3, MgO – SiO2, MgO – CaF2,Al2O3 – SiO2, Al2O3 - CaF2, SiO2 - CaF2. For the areas of equilibrium there is quasibinary connection(MgAl2O4, Mg2SiO4, Al6Si2O13 – a grout at calculations was used equalization of Hauffe-Wagner. Theobtained data comport with literary

  19. GaN nanorods and LED structures grown on patterned Si and AlN/Si substrates by selective area growth

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shunfeng; Fuendling, Soenke; Soekmen, Uensal; Neumann, Richard; Merzsch, Stephan; Peiner, Erwin; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig (Germany); Hinze, Peter; Weimann, Thomas [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany); Jahn, Uwe; Trampert, Achim; Riechert, Henning [Paul-Drude-Institut fuer Festkoerperelektronik, Berlin (Germany)

    2010-07-15

    GaN nanorods (NRs) show promising applications in high-efficiency light emitting diodes, monolithic white light emission and optical interconnection due to their superior properties. In this work, we performed GaN nanostructures growth by pre-patterning the Si and AlN/Si substrates. The pattern was transferred to Si and AlN/Si substrates by photolithography and inductively-coupled plasma etching. GaN NRs were grown on these templates by metal-organic vapour phase epitaxy (MOVPE). GaN grown on Si pillar templates show a truncated pyramidal structure. Transmission electron microscopy measurements demonstrated clearly that the threading dislocations bend to the side facets of the GaN nanostructures and terminate. GaN growth can also be observed on the sidewalls and bottom surface between the Si pillars. A simple phenomenological model is proposed to explain the GaN nanostructure growth on Si pillar templates. Based on this model, we developed another growth method, by which we grow GaN rod structures on pre-patterned AlN/Si templates. By in-situ nitridation and decreasing of the V/III ratio, we found that GaN rods only grew on the patterned AlN/Si dots with an aspect ratio of about 1.5 - 2. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Obtención de aleaciones eutécticas PbLi mediante procesos de fusión

    Directory of Open Access Journals (Sweden)

    Barrena, M. I.

    2012-12-01

    Full Text Available The development of thermonuclear experimental reactor (ITER, whose objective is to produce energy from nuclear fusion, has raised the study of Pb-Li eutectic alloys, as they have been selected for the manufacture of test blanket modules (TBM. However, during the manufacturing process of the Pb-Li alloys, thermal conditions used result in a loss of litium element, which inhibits the formation of eutectic structures. In this work we have done fusion of pure lead and lithium, evaluating different process parameters to obtain Pb-Li (17 at. % eutectic alloys. The alloys manufactured were characterized by DSC, SEM-EDX and microhardness tests. From these studies we noted that the used of an induction reactor and the process parameters optimized to obtain Pb-Li alloy allow for completely eutectic ingots and high chemical homogeneity and microstructural.

    El desarrollo del reactor experimental termonuclear (ITER, cuyo objetivo es la producción de energía a partir de la fusión nuclear, ha suscitado el estudio de las aleaciones eutécticas Pb-Li, ya que éstas han sido seleccionadas para la fabricación de las envolturas regeneradoras del reactor (TBM. Sin embargo, durante el proceso de fabricación de las aleaciones Pb-Li se produce una pérdida de litio, que inhibe la formación de estructuras eutécticas. En el presente trabajo se han realizado fusiones partiendo de plomo y litio puros evaluando diferentes parámetros de proceso para la obtención de aleaciones eutécticas Pb-Li (17 % at.. Las aleaciones obtenidas fueron caracterizadas mediante calorimetría diferencial de barrido, microscopía SEM-EDX y microdureza. De estos estudios podemos señalar, que la utilización de hornos de inducción y los parámetros de proceso optimizados para la obtención de la aleación Pb-Li, permiten obtener lingotes completamente eutécticos y con gran homogeneidad química y microestructural.

  1. Effect of Ni on eutectic structural evolution in hypereutectic Al-Mg2Si cast alloys

    International Nuclear Information System (INIS)

    Li Chong; Wu Yaping; Li Hui; Wu Yuying; Liu Xiangfa

    2010-01-01

    Research highlights: → By the injection of rod-like NiAl 3 phase in Al-Mg 2 Si alloys, Al-Mg 2 Si binary eutectic structure gradually evolves into Al-Mg 2 Si-NiAl 3 ternary eutectic. → The ternary eutectic presents a unique double rod structure that rod-like NiAl 3 and Mg 2 Si uniformly distribute in Al matrix. → The mechanism of structural evolution was analyzed in terms of the detailed microstructural observations. → The high temperature (350 deg. C) tensile strength of the alloy increases by 23% due to the eutectic structural evolution. - Abstract: The aim of this work is to investigate the eutectic structural evolution of hypereutectic Al-20% Mg 2 Si with Ni addition under a gravity casting process. Three-dimensional morphologies of eutectic phases were observed in detail using field emission scanning electron microscopy, after Al matrix was removed by deep etching or extraction. The results show that Al-Mg 2 Si binary eutectic gradually evolves into Al-Mg 2 Si-NiAl 3 ternary eutectic with the increase of Ni content, and flake-like eutectic Mg 2 Si transforms into rods. The ternary eutectic presents a unique double rod structure that rod-like NiAl 3 and Mg 2 Si uniformly distribute in Al matrix. Further, the high temperature (350 deg. C) tensile strength of the alloy increases by 23% due to the eutectic structure evolution, and the mechanism of structural evolution was discussed and analyzed in terms of the detailed microstructural observations.

  2. Ion beam mixing to produce disordered AlSi superconducting alloys

    International Nuclear Information System (INIS)

    Xi Xiaoxing; Ran Qize; Liu Jiarui; Guan Weiyan

    1987-01-01

    Multilayered Al/Si films were bombarded with Ar ions at LHe temperature and superconducting transition temperature Tsub(c) was measured in situ. The highest Tsub(c) thus obtained was 7.53 K. The systematic studies on samples with different compositions suggest that ion induced disorder might be the main reason for Tsub(c) enhancement in these AlSi alloys. (author)

  3. Growth of GaN on SiC/Si substrates using AlN buffer layer by hot-mesh CVD

    International Nuclear Information System (INIS)

    Tamura, Kazuyuki; Kuroki, Yuichiro; Yasui, Kanji; Suemitsu, Maki; Ito, Takashi; Endou, Tetsuro; Nakazawa, Hideki; Narita, Yuzuru; Takata, Masasuke; Akahane, Tadashi

    2008-01-01

    GaN films were grown on SiC/Si (111) substrates by hot-mesh chemical vapor deposition (CVD) using ammonia (NH 3 ) and trimetylgallium (TMG) under low V/III source gas ratio (NH 3 /TMG = 80). The SiC layer was grown by a carbonization process on the Si substrates using propane (C 3 H 8 ). The AlN layer was deposited as a buffer layer using NH 3 and trimetylaluminum (TMA). GaN films were formed and grown by the reaction between NH x radicals, generated on a tungsten hot mesh, and the TMG molecules. The GaN films with the AlN buffer layer showed better crystallinity and stronger near-band-edge emission compared to those without the AlN layer

  4. Creep behaviour of a casting titanium carbide reinforced AlSi12CuNiMg piston alloy at elevated temperatures; Hochtemperaturkriechverhalten der schmelzmetallurgisch hergestellten dispersionsverstaerkten Kolbenlegierung AlSi12CuNiMg

    Energy Technology Data Exchange (ETDEWEB)

    Michel, S.; Scholz, A. [Zentrum fuer Konstruktionswerkstoffe, TU Darmstadt (Germany); Tonn, B. [Institut fuer Metallurgie, TU Clausthal (Germany); Zak, H.

    2012-03-15

    This paper deals with the creep behaviour of the titanium carbide reinforced AlSi12CuNiMg piston alloy at 350 C and its comparison to the conventional AlSi12Cu4Ni2MgTiZr piston alloy. With only 0,02 vol-% TiC reinforcement the creep strength and creep rupture strength of the AlSi12CuNiMg piston alloy are significantly improved and reach the level of the expensive AlSi12Cu4Ni2MgTiZr alloy. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Adsorption properties of AlN on Si(111) surface: A density functional study

    Science.gov (United States)

    Yuan, Yinmei; Zuo, Ran; Mao, Keke; Tang, Binlong; Zhang, Zhou; Liu, Jun; Zhong, Tingting

    2018-04-01

    In the process of preparing GaN on Si substrate by MOCVD, an AlN buffer layer is very important. In this study, we conducted density functional theory calculations on the adsorption of AlN molecule on Si(111)-(2 × 2) surface, with the AlN molecule located horizontally or vertically above Si(111) surface at different adsorption sites. The calculations revealed that the lowest adsorption energy was at the N-top-Al-bridge site in the horizontal configuration, with the narrowest band gap, indicating that it was the most preferential adsorption growth status of AlN. In the vertical configurations, N adatom was more reactive and convenient to form bonds with the topmost Si atoms than Al adatom. When the N-end of the AlN molecule was located downward, the hollow site was the preferred adsorption site; when the Al-end was located downward, the bridge site was the most energetically favorable. Moreover, we investigated some electronic properties such as partial density of states, electron density difference, Mulliken populations, etc., revealing the microscale mechanism for AlN adsorption on Si(111) surface and providing theoretical support for adjusting the processing parameters during AlN or GaN production.

  6. Al-Si-Re Alloys Cast by the Rapid Solidification Process / Stopy Al-Si-Re Odlewane Metodą Rapid Solidification

    Directory of Open Access Journals (Sweden)

    Szymanek M.

    2015-12-01

    Full Text Available The aim of the studies described in this article was to present the effect of rare earth elements on aluminium alloys produced by an unconventional casting technique. The article gives characteristics of the thin strip of Al-Si-RE alloy produced by Rapid Solidification (RS. The effect of rare earth elements on structure refinement, i.e. on the size of near-eutectic crystallites in an aluminium-silicon alloy, was discussed. To determine the size of crystallites, the Scherrer X-ray diffraction method was used. The results presented capture relationships showing the effect of variable casting parameters and chemical composition on microstructure of the examined alloys. Rapid Solidification applied to Al-Si alloys with the addition of mischmetal (Ce, La, Ne, Pr refines their structure.

  7. Properties of P/M forged Al-Si alloys made by premixed powders. 1. Influences of dispersion and sizes of proeutectic Si on wear resistance; Kongoho ni yotte sakuseishita Al-Si kei shoketsu tanzo gokin no tokusei. 1. Taimamosei ni oyobosu shosho Si no bunsan jotai to ryukei no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Ishijima, Z.; Ichikawa, J.; Sasaki, s.; Shikata, H. [Hitachi Powdered Metals Co. Ltd., Tokyo (Japan)

    1995-10-15

    Influences of dispersion and sizes of proeutectic Si on wear resistance of P/M Al-Si alloys using the prealloying method and premixing method have been investigated. As a result, discretely dispersed proeutectic Si showed excellent wear resistance in compassion with uniformly dispersed one. The cause is considered to be the unclosed Si soft phase which has been preferentially worn away, consequently acting on forming oil grooves and burying worn particles. Further more the existence of the optimum size of proeutectic Si on wear resistance was confirmed. In the case of finer particles, only Al-Si alloy (pin) was warned away substantially. On the other handgun the case of larger particles, both the Al-Si alloy (pin) and the mating malarial (steel disc) were excessively warned away. It is assumed therefore that the finer proeutectic Si particles are not effective as hard particles, on the contrary, larger proeutectic Si particles increase the abrasive wear against the mating material, and those buried into the mating material initiate wear of Al-Si alloy at the same time. 2 refs., 10 figs., 1 tab.

  8. Reduced interaction layer growth of U-Mo dispersion in Al-Si

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeon Soo, E-mail: yskim@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Park, Jong Man; Ryu, Ho Jin; Jung, Yang Hong [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong, Daejeon 305-353 (Korea, Republic of); Hofman, G.L. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2012-11-15

    Development of high U-density U-Mo fuel particle dispersion in Al is needed to convert high power research and test reactors from HEU to LEU. Interaction layer growth between U-Mo and Al poses a challenge to this goal. The KOMO-4 test was designed at KAERI and irradiated in the HANARO reactor to {approx}50% burnup of initial 19.75% U-235 enrichment at {approx}200 Degree-Sign C. The main objective of the test was to examine the effect of the Si content in the matrix up to 8 wt.%. U-Mo/Al-Si dispersion samples with a Si addition in the range 0-8 wt.% in the matrix were tested. A sample with pre-irradiation Si-containing interaction layers (ILs) was also tested. As the Si content in the matrix increases, the IL growth was progressively reduced. Contrary to the thermodynamics prediction and out-of-pile observations, however, Si accumulation in the ILs occurred near the IL-matrix interface with only a slight increase in concentration. The effect of the pre-formed ILs was insignificant in reducing IL growth.

  9. HIDRODENITROGENACION DE CARBAZOL SOBRE CATALIZADORES NiMo/Al2O3-SiO2(x

    Directory of Open Access Journals (Sweden)

    Felipe Sánchez-Minero

    2012-01-01

    Full Text Available En este trabajo se estudió la velocidad de reacción del carbazol sobre catalizadores NiMo soportados sobre Al2O3 modificada superficialmente con SiO2 (0 y 10 % en peso de SiO2 en el soporte. Los catalizadores fueron evaluados en un reactor intermitente a cuatro temperaturas (287, 300, 312 y 325oC, presión de 4.0 MPa y relación molar hidrogeno/carbazol de 2400. A partir de los resultados experimentales se realizó un estudio cinético utilizando ecuaciones del tipo Langmuir-Hinshelwood (L-H. Luego, los parámetros cinéticos fueron estimados mediante la minimización de Powell (programa Scientist de MicroMath. Los resultados muestran que el catalizador con sílice (NiMo-SAC 10 alcanza una mayor actividad para la HDN de carbazol debido a que presenta un mayor número de sitios activos (valor de A, así como una menor fuerza de adsorción entre el reactante y la superficie catalítica (valor de KN, lo cual posiblemente favorece una mejor regeneración de sitios activos.

  10. Ostwald ripening of faceted Si particles in an Al-Si-Cu melt

    International Nuclear Information System (INIS)

    Shahani, A. J.; Xiao, X.; Skinner, K.; Peters, M.; Voorhees, P. W.

    2016-01-01

    The microstructural evolution of an Al-Si-Cu alloy during Ostwald ripening is imaged via synchrotron-based, four-dimensional (i.e., space and time resolved) X-ray tomography. Samples of composition Al-32 wt%Si-15 wt%Cu were annealed isothermally at 650 °C, in the two-phase solid-liquid regime, while tomographic projections were collected in situ over the course of five hours. Advances in experimental methods and computational approaches enable us to characterize the local interfacial curvatures and velocities during ripening. The sequence of three-dimensional reconstructions and interfacial shape distributions shows highly faceted Si particles in a copper-enriched liquid, that become increasingly isotropic or rounded over time. In addition, we find that the coarsening rate constant is approximately the same in the binary and ternary systems. By coupling these experimental measurements with CALPHAD modeling and ab initio molecular dynamics simulation, we assess the influence of Cu on the coarsening process. Lastly, we find the unusual “pinning” of microstructure at the junction between rough and smooth interfaces and suggest a mechanism for this behavior.

  11. Microstructure analysis of the automotive Al-Si-Cu castings

    Directory of Open Access Journals (Sweden)

    M. Krupiński

    2008-04-01

    Full Text Available The developed design methodologies both the material and technological ones will make it possible to improve shortly the quality of materials from the light alloys in the technological process, and the automatic process flow correction will make the production cost reduction possible, and - first of all - to reduce the amount of the waste products. In the metal casting industry, an improvement of component quality depends mainly on better control over the production parameters.Castings were analysed in the paper of car engine blocks and heads from the Al-Si-Cu alloys of the AC-AlSi7Cu3Mg type fabricated with the “Cosworth” technological process. In this work the AC-AlSi7Cu3Mg alloy structure was investigated, of this alloy samples were cut of for structure analysis of the cylinder part as well of crankshaft of a fuel engine. The investigation shows a difference in the (phase structure morphology as a result of cast cooling rate.

  12. The role of Si as surfactant and donor in molecular-beam epitaxy of AlN

    International Nuclear Information System (INIS)

    Lebedev, V.; Morales, F.M.; Romanus, H.; Krischok, S.; Ecke, G.; Cimalla, V.; Himmerlich, M.; Stauden, T.; Cengher, D.; Ambacher, O.

    2005-01-01

    The growth of Si-doped AlN(0001) thin films on Al 2 O 3 (0001) substrates by plasma-induced molecular-beam epitaxy is reported. We have found that Si positively affects the epitaxy being an effective surfactant for AlN growth with a remarkable impact on the crystal quality. It was proven that the characteristic surface reconstruction sequences frequently related to the Al adatoms are obviously Si induced on AlN(0001) surfaces. It was also observed that heavy doping conditions result in volume segregation of Si on the threading dislocation network and in the formation of an amorphous (AlO)(SiO)N cap layer caused by surface oxidation of the accumulated Al and segregated Si. The electron affinity was measured to be smaller than 0.5 eV on the clean AlN surface after removing of the cap layer using Ar + sputtering

  13. Reciprocating Wear Behaviour of 7075Al/SiC and 6061Al/Al2O3 Composites: A study of Effect of Reinforcement, Stroke and Load

    Directory of Open Access Journals (Sweden)

    J. Lakshmipathy

    2014-06-01

    Full Text Available The wear behaviour comparison of Al/SiC and Al/Al2O3 composites prepared by stir casting technique is investigated to find out the effects of weight percentage of SiC/Al2O3, load and the number of strokes on a reciprocating wear testing machine. The MMC pins are prepared with different weight percentage of SiC and Al2O3 (10, 15 and 20 %. The tests are carried out with different load conditions (25, 50 and 75 N and different number of strokes (420,780 and 1605 strokes. Wear surfaces of tested samples are examined in Scanning Electron Microscope (SEM. Hardness test and impact test are also carried out on the MMC samples. The experimental results shows that hardness of composites increases with increase in SiC and Al2O3 particle and the impact strength decreases with increase in SiC and Al2O3 content. The volume loss of MMC specimens are less than that of the matrix alloy. The temperature rise near the contact surface of the MMC specimens increases with increase in wt% of SiC and Al2O3, load and number of strokes. The coefficient of friction decreases with increase in the number of strokes. The WVAS (Wireless Vibration Acquisition System interfaced with MAT Lab software is used to record the amplitudes during the test.

  14. Effects of La and Ce Addition on the Modification of Al-Si Based Alloys

    Directory of Open Access Journals (Sweden)

    Emad M. Elgallad

    2016-01-01

    Full Text Available This study focuses on the effects of the addition of rare earth metals (mainly lanthanum and cerium on the eutectic Si characteristics in Al-Si based alloys. Based on the solidification curves and microstructural examination of the corresponding alloys, it was found that addition of La or Ce increases the alloy melting temperature and the Al-Si eutectic temperature, with an Al-Si recalescence of 2-3°C, and the appearance of post-α-Al peaks attributed to precipitation of rare earth intermetallics. Addition of La or Ce to Al-(7–13% Si causes only partial modification of the eutectic Si particles. Lanthanum has a high affinity to react with Sr, which weakens the modification efficiency of the latter. Cerium, however, has a high affinity for Ti, forming a large amount of sludge. Due to the large difference in the length of the eutectic Si particles in the same sample, the normal use of standard deviation in this case is meaningless.

  15. Microstructure and properties of TiAlSiN coatings prepared by hybrid PVD technology

    International Nuclear Information System (INIS)

    Yu Donghai; Wang Chengyong; Cheng Xiaoling; Zhang Fenglin

    2009-01-01

    TiAlSiN coatings with different Si content were prepared by hollow cathode discharge (HCD) and mid-frequency magnetron sputtering (MFMS) hybrid coating deposition technology. The chemical composition, microstructure, mechanical properties of these coatings were systematically investigated by means of energy dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nanoindentation measurement, scratch and high speed milling hardened steel tests. The coatings prepared by this method showed the structure of crystalline phase was corresponding to that of TiAlN, however, different preferred orientation with addition of Si. Proper content of Si into TiAlN led to increase of microhardness and adhesion. TiAlSiN coated end mill with Si content of 4.78 at.% had the least flank wear, which was improved about 20% milling distance than TiAlN coated end mill.

  16. Microstructure and properties of TiAlSiN coatings prepared by hybrid PVD technology

    Energy Technology Data Exchange (ETDEWEB)

    Yu Donghai [Faculty of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Wang Chengyong, E-mail: cywang@gdut.edu.c [Faculty of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Cheng Xiaoling; Zhang Fenglin [Faculty of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

    2009-07-01

    TiAlSiN coatings with different Si content were prepared by hollow cathode discharge (HCD) and mid-frequency magnetron sputtering (MFMS) hybrid coating deposition technology. The chemical composition, microstructure, mechanical properties of these coatings were systematically investigated by means of energy dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nanoindentation measurement, scratch and high speed milling hardened steel tests. The coatings prepared by this method showed the structure of crystalline phase was corresponding to that of TiAlN, however, different preferred orientation with addition of Si. Proper content of Si into TiAlN led to increase of microhardness and adhesion. TiAlSiN coated end mill with Si content of 4.78 at.% had the least flank wear, which was improved about 20% milling distance than TiAlN coated end mill.

  17. Microstructure and mechanical properties of Al-Si-X alloys fabricated by gas atomization and extrusion process

    International Nuclear Information System (INIS)

    Lee, T.H.; Hong, S.J.

    2009-01-01

    In order to develop good wear resistant and high-strength alloys, Al 81 Si 19 alloy was reinforced with transition elements such as Ni and Ce. The solubility of Si in aluminum was amplified, with increasing the Ni and Ce content in the rapidly solidified powders. The extruded bars consist of homogeneously dispersed fine Si particles along with Al 3 Ni and Al 3 Ce compounds (30-120 nm) in aluminum matrix (grain size below 500 nm). The tensile strength at room temperature for Al 81 Si 19 , Al 78 Si 19 Ni 2 Ce 0.5 and Al 76 Si 19 Ni 4 Ce 1 bars extruded at 400 deg. C was estimated as 281, 521, and 668 MPa, respectively. In addition, the maximum tensile strength of 730 MPa was attained in Al 73 Si 19 Ni 7 Ce 1 bulk alloy. The uniform dispersion of precipitates (Si, Al 3 Ni and Al 3 Ce particles) from the supersaturated Al matrix of ternary and quaternary alloys after extrusion was effective for enhanced mechanical properties.

  18. Improved mechanical properties of near-eutectic Al-Si piston alloy through ultrasonic melt treatment

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Jae-Gil; Lee, Sang-Hwa [Implementation Research Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of); Lee, Jung-Moo, E-mail: jmoolee@kims.re.kr [Implementation Research Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of); Cho, Young-Hee [Implementation Research Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of); Kim, Su-Hyeon [Metal Materials Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of); Yoon, Woon-Ha [Implementation Research Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of)

    2016-07-04

    The effects of ultrasonic melt treatment (UST) on the microstructure and mechanical properties of Al-12.2Si-3.3Cu-2.4Ni-0.8Mg-0.1Fe (wt%) piston alloy were systematically investigated. Rigid colonies consisting of primary Si, eutectic Si, Mg{sub 2}Si and various aluminides (ε-Al{sub 3}Ni, δ-Al{sub 3}CuNi, π-Al{sub 8}FeMg{sub 3}Si{sub 6}, γ-Al{sub 7}Cu{sub 4}Ni, Q-Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and θ-Al{sub 2}Cu) were observed in the as-cast alloys. The sizes of the secondary phases, eutectic cell and grain were significantly decreased by UST because of the enhanced nucleation of each phase under ultrasonic irradiation. The yield strength, tensile strength and elongation at 25 °C were significantly improved by UST mainly because of the refinement of the microstructures. Both tensile strength and elongation at 350 °C were also improved by UST despite the unchanged yield strength.

  19. UV and IR laser induced ablation of Al2O3/SiN:H and a-Si:H/SiN:H

    Directory of Open Access Journals (Sweden)

    Schutz-Kuchly T.

    2014-01-01

    Full Text Available Experimental work on laser induced ablation of thin Al2O3(20 nm/SiN:H (70 nm and a-Si:H (20 nm/SiN:H (70 nm stacks acting, respectively, as p-type and n-type silicon surface passivation layers is reported. Results obtained using two different laser sources are compared. The stacks are efficiently removed using a femtosecond infra-red laser (1030 nm wavelength, 300 fs pulse duration but the underlying silicon surface is highly damaged in a ripple-like pattern. This collateral effect is almost completely avoided using a nanosecond ultra-violet laser (248 nm wavelength, 50 ns pulse duration, however a-Si:H flakes and Al2O3 lace remain after ablation process.

  20. Growth of GaN on SiC/Si substrates using AlN buffer layer by hot-mesh CVD

    Energy Technology Data Exchange (ETDEWEB)

    Tamura, Kazuyuki [Nagaoka University of Technology, Nagaoka 940-2188 (Japan)], E-mail: kazuyuki@stn.nagaokaut.ac.jp; Kuroki, Yuichiro; Yasui, Kanji [Nagaoka University of Technology, Nagaoka 940-2188 (Japan); Suemitsu, Maki; Ito, Takashi [Center of Interdisciplinary Research, Tohoku University, Sendai 980-8578 (Japan); Endou, Tetsuro [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Nakazawa, Hideki [Faculty of Science and Technology, Hirosaki University, Hirosaki 036-8561 (Japan); Narita, Yuzuru [Center of Interdisciplinary Research, Tohoku University, Sendai 980-8578 (Japan); Takata, Masasuke; Akahane, Tadashi [Nagaoka University of Technology, Nagaoka 940-2188 (Japan)

    2008-01-15

    GaN films were grown on SiC/Si (111) substrates by hot-mesh chemical vapor deposition (CVD) using ammonia (NH{sub 3}) and trimetylgallium (TMG) under low V/III source gas ratio (NH{sub 3}/TMG = 80). The SiC layer was grown by a carbonization process on the Si substrates using propane (C{sub 3}H{sub 8}). The AlN layer was deposited as a buffer layer using NH{sub 3} and trimetylaluminum (TMA). GaN films were formed and grown by the reaction between NH{sub x} radicals, generated on a tungsten hot mesh, and the TMG molecules. The GaN films with the AlN buffer layer showed better crystallinity and stronger near-band-edge emission compared to those without the AlN layer.

  1. Irradiation-induced changes in the local environment of Si and Al in LnSiAlON glasses as probed by {sup 27}Al and {sup 29}Si NMR

    Energy Technology Data Exchange (ETDEWEB)

    Sangleboeuf, J.C. [Univ Rennes 1, CNRS, FRE 2717, LARMAUR, F-35042 Rennes (France); Dauce, R.; Le Floch, M.; Verdier, P. [Univ Rennes 1, Inst Chem, UMR 6512, CNRS, F-35042 Rennes (France); Dauce, R. [CE Cadarache, DEC/SESC, F-13018 St Paul Les Durance (France)

    2007-03-15

    Two compounds have been studied: an oxide glass from the Y-Si-Al-O system and an oxynitride glass from the Y-Si-Al-O-N system, both bombarded with Sn-ions (975 MeV, fluences ranging from 10{sup 12} to 2.7 * 10{sup 13} Sn/cm{sup 2}). The changes in the environment of the silicon and the aluminium were investigated using NMR spectroscopy. Irradiation by Sn ions leads to a loss of nitrogen in the silicon and probably the aluminium environments. Part of the aluminium changes from a network former coordination to a network modifier coordination while the oxide silicate network exhibits a higher cross-linking due to an increase of the population of bridging oxygen. Part of the aluminium in five-fold coordination is formed at the expense of aluminium in six-fold coordination in the case of the oxynitride glass and the changes in the silicon environment occur at lower fluences than for the oxide glass. (authors)

  2. Utilisation of mould temperature change in eliminating the Al5FeSi phases in secondary AlSi7Mg0.3 alloy

    Directory of Open Access Journals (Sweden)

    Bolibruchová D.

    2017-03-01

    Full Text Available This article describes the impact of the metal mould temperature change in eliminating the adverse effect of iron in the AlSi7Mg0.3 alloy. The kind of phases based on iron to be formed in aluminium alloys is determined by the alloy chemical composition, the melt overheating temperature prior to casting, and the cooling rate during crystallisation. In the experiment, we used three various mould temperatures, and their impact on the possible change in the adverse Al5FeSi phase, excreted in a needle form to a more compact form of Chinese writing or skeleton units. The experimental part did not use melt overheat that would result in impairment of the melt, for example due to increased gassing of the melt, as well as in a greater load on the smelting unit, thus resulting in increased energy expenditure. We can conclude from the obtained results that the mould temperature change does not have an adequate effect in eliminating the adverse effect of iron in Al-Si-Mg alloys.

  3. The high temperature synthesis of CsAlSiO 4-ANA, a new polymorph in the system Cs 2OAl 2O 3SiO 2. I. The end member of ANA type of zeolite framework

    Science.gov (United States)

    Dimitrijevic, R.; Dondur, V.; Petranovic, N.

    1991-12-01

    High temperature phase transformations of Cs + exchanged zeolites were investigated. Above 1000°C, CsX, CsY (FAU), and Cs, ZK-4 (LTA) frameworks recrystallized in a pollucite phase. A Cs + loaded mordenite recrystallized at 1300°C in the orthorhombic CsAlSi 5O 12 phase. A Cs + exchanged zeolite A at 960°C recrystallized in a mixture of two polymorphic CsAlSiO 4 phases having different (Al,Si)O 4 frameworks. The unstable orthorhombic CsAlSiO 4ABW phase has a topotactic transition at 1150°C into an ordered low CsAlSiO 4-ANA framework. Further calcination produces, at 1200°C, transformation of the low CsAlSiO 4-ANA phase to the more stable high CsAlSiO 4-ANA polymorph having cubic ( a 0 = 13.6595 (5) Å) symmetry and an ordered SiAl distribution. The crystal structure of high CsAlSiO 4ANA, a new polymorph in the system Cs 2OAl 2O 3SiO 2, was determined using X-ray Rietveld analyses and 29Si MAS NMR spectroscopy.

  4. Modeling of Eutectic Formation in Al-Si Alloy Using A Phase-Field Method

    Directory of Open Access Journals (Sweden)

    Ebrahimi Z.

    2017-12-01

    Full Text Available We have utilized a phase-field model to investigate the evolution of eutectic silicon in Al-Si alloy. The interfacial fluctuations are included into a phase-field model of two-phase solidification, as stochastic noise terms and their dominant role in eutectic silicon formation is discussed. We have observed that silicon spherical particles nucleate on the foundation of primary aluminum phase and their nucleation continues on concentric rings, through the Al matrix. The nucleation of silicon particles is attributed to the inclusion of fluctuations into the phase-field equations. The simulation results have shown needle-like, fish-bone like and flakes of silicon phase by adjusting the noise coefficients to larger values. Moreover, the role of primary Al phase on nucleation of silicon particles in Al-Si alloy is elaborated. We have found that the addition of fluctuations plays the role of modifiers in our simulations and is essential for phase-field modeling of eutectic growth in Al-Si system. The simulated finger-like Al phases and spherical Si particles are very similar to those of experimental eutectic growth in modified Al-Si alloy.

  5. Oxidation resistance of quintuple Ti-Al-Si-C-N coatings and associated mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Wu Guizhi; Ma Shengli; Xu Kewei; Ji, Vincent; Chu, Paul K. [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); ICMMO/LEMHE, Universite Paris-Sud 11, 91405 Orsay Cedex (France); Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon (Hong Kong)

    2012-07-15

    The oxidation behavior of Ti-Al-Si-C-N hard coatings with different Al contents deposited on high-speed steel and Si substrates by hybrid arc-enhanced magnetron sputtering is investigated in the temperature range of 500 Degree-Sign C-1000 Degree-Sign C. The coating hardness is maintained at around 35 GPa, and the parabolic oxidation rate constant K{sub p} at 1000 Degree-Sign C decreases to 3.36 Multiplication-Sign 10{sup -10} kg{sup 2} m{sup -4} s{sup -1} when the Al concentration is increased to 30 at. %, indicating that Ti-Al-Si-C-N coatings with larger Al concentrations have better oxidation resistance. X-ray diffraction, cross-sectional scanning electron microscopy, and x-ray photoelectron spectroscopy reveal a protective surface layer consisting of Al{sub 2}O{sub 3}, TiO{sub 2}, and SiO{sub 2} that retards inward oxygen diffusion. A mechanism is proposed to elucidate the oxide formation. As a consequence of the good oxidation resistance, the Ti-Al-Si-C-N coatings have a large potential in high-speed dry cutting as well as other high temperature applications.

  6. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    Directory of Open Access Journals (Sweden)

    Zhang Zhongtao

    2008-08-01

    Full Text Available Functionally graded materials (FGM have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and fi nally to the hypoeutectic with numerous primary Al dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of Al/Si FGM.

  7. Production of Al2O3–SiC nano-composites by spark plasma sintering; Producción de nano-composites – SiC–Al2O3 por spark plasma sinterizado

    Energy Technology Data Exchange (ETDEWEB)

    Mansour Razavi; Ali Reza Farajipour; Mohammad Zakeri; Mohammad Reza Rahimipour; Ali Reza Firouzbakht

    2017-11-01

    In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600°C for 10min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5h. The milled powders were sintered in a SPS machine. After sintering process, phase studies, densification and mechanical properties of Al2O3–SiC composites were examined. Results showed that the specimens containing micro-sized SiC have an important effect on bulk density, hardness and strength. The highest relative density, hardness and strength were 99.7%, 324.6 HV and 2329MPa, respectively, in Al2O3–20wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale. [Spanish] En este trabajo se muestran compuestos de Al2O3-SiC producidos por SPS, en vacío, a 1.600 °C durante 10 min. Para la preparación de muestras, se molieron polvos de Al2O3 durante 5 h con la segunda fase de micro-y-nano polvo de SiC. Posteriormente, estos polvos molidos se sinterizaron mediante SPS. Después del proceso de sinterización, se realizaron estudios de fase, densificación y propiedades mecánicas de los compuestos de Al2O3-SiC obtenidos. Los resultados mostraron que micro-SiC en las muestras tiene un efecto importante en su densidad aparente, dureza y resistencia. La mayor densidad relativa, dureza y resistencia fueron respectivamente del 99,7%, 324,6 HV y 2.329 MPa para Al2O3 con un 20% en peso micro-SiC. Debido al corto tiempo de sinterización, el crecimiento los granos fue limitado y se mantuvieron en escala nanométrica.

  8. Stainless-Steel-Gadolinium Alloys; Alliages Acier Inoxydable-Gadolinium; Splavy iz nerzhaveyushchej stali i gadoliniya; Aleaciones de Acero Inoxidable-Gadolinio

    Energy Technology Data Exchange (ETDEWEB)

    Copeland, M.; Kato, H. [Albany Metallurgy Research Center, Bureau Of Mines, United States Department of the Interior, Albany, OR (United States)

    1964-06-15

    mineures ont une grande influence sur les structures resultant de traitements equilibrants et sur les possibilites de transformation des aciers. Lorsque le gadolinium est melange a de l 'acier au chrome et au nickel, deux phases mineures, Fe{sub 9}Gd et Ni{sub 7}Gd, fondent a 1080 Degree-Sign C, ce qui impose une limite superieure aux temperatures de traitement a chaud et de transformation. Les auteurs ont pu facilement transformer des alliages comprenant jusqu'a 5 Degree-Sign Io en poids de gadolinium et determiner leurs caracteristiques mecaniques et leur resistance a la corrosion. Ils n'ont observe aucun changement dans les caracteristiques mecaniques de l'acier ou sa resistance a la corrosion par l'eau chaude, lorsqu'ils lui ont ajoute'jusqu'a 3% en poids de gadolinium. En raison des limites imposees aux temperatures de transformation des aciers au chrome et au nickel par le point de fusion des phases mineures, les auteurs ont etudie les effets du gadolinium sur des aciers au chrome. Ils ont releve une seule phase mineure qui fond a 1320 Degree-Sign C en etudiant l 'isoplethe du gadolinium a 10% en poids dans l 'alliage chrome-fer-gadolinium. Cette propriete permettrait d'equilibrer et de transformer ces aciers au gadolinium aux temperatures auxquelles on opere normalement. (author) [Spanish] En vista de la excelente resistencia a la corrosion de los aceros inoxidables y del interes que presenta el gadolinio como veneno nuclear, se han estudiado aleaciones de esos dos metales. El gadolinio fue aleado con aceros inoxidables de tipo AISI-304 y al cromo, y se estudiaron las relaciones de fase, la facilidad de trabajo y las propiedades de estas aleaciones. Se observo que en las aleaciones que contienen bajos porcentajes de gadolinio, los puntos de fusion de las fases menores ejercen un efecto muy marcado sobre las estructuras resultantes de los tratamientos de equilibracion y sobre la facilidad de trabajo de los afceros. Cuando se alea el gadolinio con acerce al cromo

  9. Sulfur passivation for the formation of Si-terminated Al{sub 2}O{sub 3/}SiGe(0 0 1) interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sardashti, Kasra [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA (United States); Hu, Kai-Ting [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA (United States); Tang, Kechao [Department of Materials Science and Engineering, Stanford University, CA (United States); Park, Sangwook; Kim, Hyonwoong [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA (United States); Madisetti, Shailesh [Department of Nanoscale Science and Engineering, University at Albany—State University of New York, Albany, NY (United States); McIntyre, Paul [Department of Materials Science and Engineering, Stanford University, CA (United States); Oktyabrsky, Serge [Department of Nanoscale Science and Engineering, University at Albany—State University of New York, Albany, NY (United States); Siddiqui, Shariq; Sahu, Bhagawan [TD Research, GLOBALFOUNDRIES USA, Inc., Albany, NY (United States); Yoshida, Noami; Kachian, Jessica [Applied Materials, Inc., Santa Clara, CA (United States); Kummel, Andrew, E-mail: akummel@ucsd.edu [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States)

    2016-03-15

    Graphical abstract: - Highlights: • Effect of wet sulfur passivation on the electrical properties of Al{sub 2}O{sub 3}/SiGe(0 0 1) interfaces has been determined. • EOT of 2.1 nm has been achieved for ALD Al{sub 2}O{sub 3} deposited directly on SiGe(0 0 1) surfaces. • Sulfur passivation has been found to passivate the Al{sub 2}O{sub 3} interface with Si−O−Al bonds. • Sulfur passivation is found to significantly reduce the GeO{sub x} or Ge−O−Al content at the Al{sub 2}O{sub 3}/SiGe interface therefore improving the reliability. • Sulfur passivation extends the surface stability prior to oxide ALD to up to an hour with no dramatic change in D{sub it}, C{sub ox} or V{sub FB} of the resulting devices. - Abstract: Sulfur passivation is used to electrically and chemically passivate the silicon–germanium (SiGe) surfaces before and during the atomic layer deposition (ALD) of aluminum oxide (Al{sub 2}O{sub 3}). The electrical properties of the interfaces were examined by variable frequency capacitance–voltage (C–V) spectroscopy. Interface compositions were determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The sulfur adsorbs to a large fraction of surface sites on the SiGe(0 0 1) surface, protecting the surface from deleterious surface reactions during processing. Sulfur passivation (a) improved the air stability of the cleaned surfaces prior to ALD, (b) increased the stability of the surface during high-temperature deposition, and (c) increased the Al{sub 2}O{sub 3} ALD nucleation density on SiGe, thereby lowering the leakage current. S passivation suppressed formation of Ge−O bonds at the interface, leaving the majority of the Al{sub 2}O{sub 3}–SiGe interface terminated with direct Si−O−Al bonding.

  10. The effect of Si content on the fracture toughness of CrAlN/Si{sub 3}N{sub 4} coatings

    Energy Technology Data Exchange (ETDEWEB)

    Liu, S. [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore); Gordon Laboratory, Department of Materials Science and Metallurgy, 27 Charles Babbage Rd., Cambridge CB3 0FS (United Kingdom); Wheeler, J. M. [Laboratory for Nanometallurgy, ETH Zürich, Vladimir-Prelog-Weg 5, 8093 Zurich (Switzerland); Davis, C. E.; Clegg, W. J. [Gordon Laboratory, Department of Materials Science and Metallurgy, 27 Charles Babbage Rd., Cambridge CB3 0FS (United Kingdom); Zeng, X. T. [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore)

    2016-01-14

    CrAlN/Si{sub 3}N{sub 4} nanocomposite coatings with different Si contents were deposited to understand how Si influences the microstructure and mechanical behaviour of the coatings, in particular, the fracture toughness. The coating composition, chemical bonding, microstructure, and mechanical properties were studied by energy dispersive spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and nanoindentation, respectively. Using a micro double cantilever beam sample, it was found that the fracture toughness of CrAlN/Si{sub 3}N{sub 4} coatings was higher than that of both the CrN and CrAlN coatings and increased with increasing Si content. Cross-sectional transmission electron microscopy suggested that this was caused by the suppression of cracking at columnar boundaries.

  11. Effects of Si content on microstructure and mechanical properties of TiAlN/Si3N4-Cu nanocomposite coatings

    Science.gov (United States)

    Feng, Changjie; Hu, Shuilian; Jiang, Yuanfei; Wu, Namei; Li, Mingsheng; Xin, Li; Zhu, Shenglong; Wang, Fuhui

    2014-11-01

    TiAlN/Si3N4-Cu nanocomposite coatings of various Si content (0-5.09 at.%) were deposited on AISI-304 stainless steel by DC reactive magnetron sputtering technique. The chemical composition, microstructure, mechanical and tribological properties of these coatings were systematically investigated by means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), nanoindentation tester, a home-made indentation system, a scratch tester and a wear tester. Results indicated that with increasing Si content in these coatings, a reduction of grain size and surface roughness, a transformation of the (1 1 1) preferred orientation was detected by XRD and FESEM. Furthermore the hardness of these coatings increase from 9.672 GPa to 18.628 GPa, and the elastic modulus reveal the rising trend that increase from 224.654 GPa to 251.933 GPa. However, the elastic modulus of TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content dropped rapidly and changed to about 180.775 GPa. The H3/E2 ratio is proportional to the film resistance to plastic deformation. The H3/E2 ratio of the TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content possess of the maximum of 0.11 GPa, and the indentation test indicate that few and fine cracks were observed from its indentation morphologies. The growth pattern of cracks is mainly bending growing. The present results show that the best toughness is obtained for TiAlN/Si3N4-Cu nanocomposite coating containing 3.39 at.% Si content. In addition, the TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content also has good adhesion property and superior wear resistance, and the wear mechanism is mainly adhesion wear.

  12. Tribological Properties of AlSi11-SiCp Composite Castings Produced by Pressure Die Casting Method

    Directory of Open Access Journals (Sweden)

    Konopka Z.

    2014-08-01

    Full Text Available The measurement results concerning the abrasive wear of AlSi11-SiC particles composites are presented in paper. The method of preparing a composite slurry composed of AlSi11 alloy matrix and 10, 20% vol.% of SiC particles, as well as the method of its high-pressure die casting was described. Composite slurry was injected into metal mould of cold chamber pressure die cast machine and castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. Very good uniform arrangement of SiC particles in volume composite matrix was observed and these results were publicated early in this journal. The kinetics of abrasive wear and correlation with SiC particles arrangement in composite matrix were presented. Better wear resistance of composite was observed in comparison with aluminium alloy. Very strong linear correlation between abrasive wear and particle arrangement was observed. The conclusion gives the analysis and the interpretation of the obtained results.

  13. Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

    Science.gov (United States)

    Marszałek, Konstanty; Winkowski, Paweł; Jaglarz, Janusz

    2014-01-01

    Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

  14. The Evaluation of the Corrosion Resistance of the Al-Si Alloys Antimony Alloyed

    Directory of Open Access Journals (Sweden)

    Svobodova J.

    2014-06-01

    Full Text Available This paper deals with the evaluation of the corrosion resistance of the Al-Si alloys alloyed with the different amount of antimony. Specifically it goes about the alloy AlSi7Mg0,3 which is antimony alloyed in the concentrations 0; 0,001; 0,005; 0,01 a 0,05 wt. % of antimony. The introduction of the paper is dedicated to the theory of the aluminium alloys corrosion resistance, testing and evaluation of the corrosion resistance. The influence of the antimony to the Al-Si alloys properties is described further in the introduction. The experimental part describes the experimental samples which were prepared for the experiment and further they were exposed to the loading in the atmospheric conditions for a period of the 3 months. The experimental samples were evaluated macroscopically and microscopically. The results of the experiment were documented and the conclusions in terms of the antimony impact to the corrosion resistance of the Al-Si alloy were concluded. There was compared the corrosion resistance of the Al-Si alloy antimony alloyed (with the different antimony content with the results of the Al-Si alloy without the alloying after the corrosion load in the atmospheric conditions in the experiment.

  15. Simulation of spheroidisation of elongated Si-particle in Al-Si alloys by the phase-field model

    International Nuclear Information System (INIS)

    Kovacevic, I.

    2008-01-01

    The application of the phase-field model for spheroidisation of undissolvable particles during high-temperature treatment of alloys is pointed out. Modelling of the spheroidisation of elongated Si-particles during annealing of Al-Si alloy is elaborated in this paper. The driving force for spheroidisation is the minimization of the total free-energy of the system or the minimization of the ratio between the interface areas and the particle volumes. The spheroidisation kinetics of elongated Si-particle for binary Al-Si system during homogenisation of aluminium alloys simulated by the phase-field model is demonstrated. The influences of the interface energy and the homogenisation temperature on the spheroidisation kinetics is presented. The lack of knowledge of the interface energy anisotropy between Si-particle and the aluminium phase is the only reason for using isotropic interface energy in simulations. The thermodynamic driving force for the phase transformation of the silicon into the aluminium phase is computed from the data obtained from the JMatPro software for aluminium alloys

  16. Effect of Cold Forging on Microstructure and MechanicalProperties of Al/SiC Composites

    Science.gov (United States)

    Hanamantraygouda, M. B.; Shivakumar, B. P., Dr; Siddappa, P. N.; Sampathkumar, L.; Prashanth, L.

    2018-02-01

    The objective of this work was to investigate the effect of cold forging on mechanical properties and microstructural study of Al MMCs, at different wt% of SiC and forging cycle. The Al-SiC composite material was fabricated by stir casting method at different weight percentage of SiC such as 2.5, 5, 7.5 and 10%. Further, the deformation characteristics during open-die forging of Al-SiC composite at cold conditions was investigated. Cast and forged composite material was subjected to hardness test, tensile test and impact test. The grain size, microstructure behaviour was investigated using optical microscope. The results show that hardness and strength of Al-SiC composite increases and ductility decreases as compared to Al alloy in both as-cast and forged conditions. Optical microscope images showed that the distribution of SiC in Al matrix was more homogeneous in a forged composite as compared to cast one and reduction of porosity was found. Further, it showed that due to forging cycle the grain size was reduced by 30% to 35% from initial size.

  17. Covalent bonds and their crucial effects on pseudogap formation in α-Al(Mn,Re)Si icosahedral quasicrystalline approximant

    International Nuclear Information System (INIS)

    Kirihara, K.; Nagata, T.; Kimura, K.; Kato, K.; Takata, M.; Nishibori, E.; Sakata, M.

    2003-01-01

    X-ray charge densities of Al-based icosahedral quasicrystalline approximant crystals α-AlReSi, α-AlMnSi, and Al 12 Re were observed by a combination of the maximum entropy method with the Rietveld method. We successfully obtained the clear images of interatomic covalent bonds between Al and transition metals (Mn, Re) and those in the Al (or Si) icosahedron in Mackay icosahedral clusters of both α-AlReSi and α-AlMnSi approximant crystals. The bonding nature of the three kinds of glue atom sites connecting Mackay icosahedral clusters was also clarified. This covalent bonding nature should strongly relate with the enhancement of the electron density-of-states pseudogap near the Fermi level. In addition, the interatomic covalent bonds of α-AlReSi are stronger than those of α-AlMnSi. This fact leads to the low effective carrier density of α-AlReSi in comparison with that of α-AlMnSi. Unlike the covalent bonding nature of an icosahedron in α-AlReSi and α-AlMnSi crystals, the Al icosahedron with an Re center atom exhibits no Al-Al interatomic covalent bonds in the Al 12 Re crystal. The tendency for metallic-covalent bonding conversion in the Al icosahedron, which is related to the atom site occupancy of the icosahedral cluster center, is also strongly supported

  18. Blistering in ALD Al2O3 passivation layers as rear contacting for local Al BSF Si solar cells

    NARCIS (Netherlands)

    Vermang, B.; Goverde, J.C.; Uruena, A.; Lorenz, A.; Cornagliotti, E.; Rothschild, A.; John, J.; Poortmans, J.; Mertens, R.

    2012-01-01

    Random Al back surface field (BSF) p-type Si solar cells are presented, where a stack of Al2O3 and SiNx is used as rear surface passivation layer containing blisters. It is shown that no additional contact opening step is needed, since during co-firing local Al BSFs are induced at the location of

  19. Characterization of fuel miniplates fabricated with U(Mo) particles dispersed in Al-Si matrices

    International Nuclear Information System (INIS)

    Arico, S F; Mirandou, M I; Balart, S N; Fabro, J O

    2012-01-01

    In 2011 ECRI facility (Depto. ECRI, GCCN, CNEA) restarted the development for the fabrication of dispersion miniplates fuel elements in Al-Si matrix. This miniplates are fabricated with atomized U-7wt%Mo particles dispersed in a matrix formed by a mixture of pure Al and pure Si powders. The first results for an Al-4wt%Si matrix were presented at the AATN 2011 Annual Meeting. In this work, new results from the microstructural characterization of the meat in Al- 2wt%Si and pure Al miniplates are presented and compared with the previous ones. It is the intention to study the influence of the fabrication parameters as well as different Si concentration in the matrix, on the formation and characteristics of the interaction layer formed between the particles and the matrix at the end of the fabrication process. According to the results presented in this work an improvement can be observed on miniplates with Al-Si matrix respect to the one with pure Al. On the miniplates with Al- Si matrix, almost 100 % of the U(Mo) particles presented, at least in some fraction of its surface, an interaction layer composed by phases that contain Si. Moreover its morphological characteristics are independent of the crystallographic state of the U(Mo) particles. However, the oxide layer formed on the U(Mo) during the hot rolling acts as a barrier to the formation of the interaction layer. As a consequence, it is then mandatory to introduce some changes on the fabrication parameters to avoid, or at least minimize, this oxide layer (author)

  20. The application of cast SiC/Al to rotary engine components

    Science.gov (United States)

    Stoller, H. M.; Carluccio, J. R.; Norman, J. P.

    1986-01-01

    A silicon carbide reinforced aluminum (SiC/Al) material fabricated by Dural Aluminum Composites Corporation was tested for various components of rotary engines. Properties investigated included hardness, high temperature strength, wear resistance, fatigue resistance, thermal conductivity, and expansion. SiC/Al appears to be a viable candidate for cast rotors, and may be applicable to other components, primarily housings.

  1. Interfacial reaction in SiC_f/Ti-6Al-4V composite by using transmission electron microscopy

    International Nuclear Information System (INIS)

    Huang, Bin; Li, Maohua; Chen, Yanxia; Luo, Xian; Yang, Yanqing

    2015-01-01

    The interfacial reactions of continuous SiC fiber reinforced Ti-6Al-4V matrix composite (SiC_f/Ti-6Al-4V composite) and continuous SiC fiber coated by C reinforced Ti-6Al-4V matrix composite (SiC_f/C/Ti-6Al-4V composite) were investigated by using micro-beam electron diffraction (MBED) and energy disperse spectroscopy (EDS) on transmission electron microscopy (TEM). The sequence of the interfacial reactions in the as-processed and exposed at 900°C for 50h SiC_f/Ti-6Al-4V composites can be described as SiC||TiC||Ti_5Si_3 + TiC||Ti-6Al-4V and SiC||TiC||Ti_5Si_3||TiC||Ti_5Si_3||TiC||Ti_5Si_3||Ti-6Al-4V, respectively. Additionally, both in as-processed and exposed composites, Ti_3SiC_2 and Ti_3Si are absent at the interfaces. For the SiC_f/C/Ti-6Al-4V composite exposed at 900 °C for 50 h, the sequence of the interfacial reaction can be described as SiC||C||TiC_F||TiC_C||Ti-6Al-4V before C coating is completely consumed by interfacial reaction. When interfacial reaction consumes C coating completely, the sequence of the interfacial reaction can be described as SiC||TiC||Ti_5Si_3||TiC||Ti-6Al-4V. Furthermore, in SiC_f/C/Ti-6Al-4V composite, C coating can absolutely prevent Si diffusion from SiC fiber to matrix. Basing on these results, the model of formation process of the interfacial reaction products in the composites was proposed. - Highlights: • We obtained the sequence of the interfacial reactions in the as-processed and exposed at 900 °C for 50 h SiC_f/Ti-6Al-4 V composites as well as in the SiC_f/C/Ti-6Al-4 V composite exposed at 900 °C for 50 h. • We verified that both in as-processed and exposed SiC_f/Ti-6Al-4 V composites, Ti_3SiC_2 and Ti_3Si are absent at the interfaces. • Carbon coating can absolutely prevent silicon diffusion from SiC fiber to matrix. • Basing on these results, the model of formation process of the interfacial reaction products in the composites was proposed.

  2. DIFERENCIAS EN ESTRÉS PERCIBIDO, SALUD MENTAL Y FÍSICA DE ACUERDO AL TIPO DE RELACIÓN HUMANO-PERRO / DIFFERENCES IN PERCEIVED STRESS, MENTAL HEALTH, AND PHYSICAL HEALTH ACCORDING TO TYPES OF HUMAN-PET DOG RELATIONSHIPS

    OpenAIRE

    MÓNICA TERESA GONZÁLEZ RAMÍREZ; RENÉ LANDERO HERNÁNDEZ

    2011-01-01

    Con el propósito de evaluar si los niveles de estrés y salud percibidos difieren de acuerdo al tipo de relación entre el humano y el perro, así como de evaluar la correlación de estrés y salud percibidos con la frecuencia en que se realizan algunas actividades con el perro, se aplicaron cuestionarios de autoinforme a 247 voluntarios, dueños de al menos un perro. Los principales resultados muestran puntajes más bajos de estrés percibido y más altos de salud mental en quienes consideran a su pe...

  3. Formation of Si clusters in AlGaN: A study of local structure

    International Nuclear Information System (INIS)

    Somogyi, A.; Martinez-Criado, G.; Homs, A.; Hernandez-Fenollosa, M. A.; Vantelon, D.; Ambacher, O.

    2007-01-01

    In this study, the authors report on the application of synchrotron radiation x-ray microprobe to the study of Si impurities in plasma-induced molecular beam epitaxy grown Al 0.32 Ga 0.68 N. Elemental maps obtained by μ-x-ray fluorescence spectrometry show inhomogeneous distributions of Si, Al, and Ga on the micron scale. X-ray absorption near-edge structure spectra taken at the Si and Al K edges provided information about their local chemical environment and revealed the change of the spectral features as depending on the position compared to the sample surface and on the concentration of Si

  4. The structure-property relationships of powder processed Fe-Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Prichard, Paul D. [Iowa State Univ., Ames, IA (United States)

    1998-02-23

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D84 < 32 μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 μm. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 μm to 104 μm. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase α + DO3 structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

  5. A Study of Thin Film Resistors Prepared Using Ni-Cr-Si-Al-Ta High Entropy Alloy

    Directory of Open Access Journals (Sweden)

    Ruei-Cheng Lin

    2015-01-01

    Full Text Available Ni-Cr-Si-Al-Ta resistive thin films were prepared on glass and Al2O3 substrates by DC magnetron cosputtering from targets of Ni0.35-Cr0.25-Si0.2-Al0.2 casting alloy and Ta metal. Electrical properties and microstructures of Ni-Cr-Si-Al-Ta films under different sputtering powers and annealing temperatures were investigated. The phase evolution, microstructure, and composition of Ni-Cr-Si-Al-Ta films were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, and Auger electron spectroscopy (AES. When the annealing temperature was set to 300°C, the Ni-Cr-Si-Al-Ta films with an amorphous structure were observed. When the annealing temperature was at 500°C, the Ni-Cr-Si-Al-Ta films crystallized into Al0.9Ni4.22, Cr2Ta, and Ta5Si3 phases. The Ni-Cr-Si-Al-Ta films deposited at 100 W and annealed at 300°C which exhibited the higher resistivity 2215 μΩ-cm with −10 ppm/°C of temperature coefficient of resistance (TCR.

  6. New investigation of phase equilibria in the system Al-Cu-Si.

    Science.gov (United States)

    Ponweiser, Norbert; Richter, Klaus W

    2012-01-25

    The phase equilibria and invariant reactions in the system Al-Cu-Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ(1) and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the β-phase of Cu-Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al-Cu and Cu-Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable.

  7. Hydrometallurgical extraction of Al and Si from kaolinitic clays

    Directory of Open Access Journals (Sweden)

    Eliana G. Pinna

    Full Text Available Abstract Herein is presented the results of a study on the hydrometallurgic extraction and recovery of aluminum and silicon by leaching of kaolinitic clays with HF. The studied extraction parameters were: temperature, reaction time, solid/liquid ratio, concentration, and precipitating agent mass. In the leaching process, mineral dissolutions near 100% were obtained when working at 348 K, solid/liquid ratio 2% w/v, HF 12% v/v, for 120 minutes. The HF leach liquor generated from the dissolution of kaolinitic clays contains H2SiF6and H3AlF6. Studies were conducted to recover the two valuable fluorides as K2SiF6and Na3AlF6by precipitation with alkaline salts from the leach liquor. Phases of precipitated fluorides were identified by XRD and surface morphology by SEM. The purity of the K2SiF6precipitate was 98.8%, whereas for Na3AlF6, it was 89.3%. Also, both synthesized solids are of high commercial value due to their industrial applications.

  8. Evaluation of the behavior of PtPd/MWCNT electrocatalysts as ethylene glycol-tolerant electrodes for oxygen oxidation reaction (ORR); Evaluacion del comportamiento de electrocatalizadores tipo PtPd/MWCNT como electrodos para la reaccion de oxidacion del oxigeno (ORR) tolerantes al etilenglicol

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Acosta, D.; Arriaga, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Pedro Escobedo, Queretaro (Mexico)]. E-mail: dmorales@cideteq.mx; Alvarez-Contreras, L. [Centro de Investigacion en Materiales Avanzados S. C., Chihuahua, Chihuahua (Mexico); Fraire Luna, S.; Rodriguez Varela, F.J. [Cinvestav, Unidad Saltillo, Ramos Arizpe, Coahuila, (Mexico)

    2009-09-15

    Pt-Pd/MWCNTs (atomic ratio Pt:Pd 43:57) and Pt/MWCNTs electrocatalysts were synthesized and evaluated as cathodes for oxygen reduction reaction (ORR) with the application of direct ethylene glycol fuel cells (DEGFC). A commercial PtC material was also evaluated as a reference. It was found that Pt-Pd/MWCNT has a capability for high tolerance to ethylene glycol (EG) and higher selectivity for ORR compared to a single Pt- cathode. As a result, the change in onset potential of the ORR, Eonset, in Pt-Pd/MWCNTs was considerably less than the change in Pt/MWCNTs or Pt/C. The average particle size (XRD) was 3.5nm and 4nm for Pt/MWCNTs and Pt-Pd/MWCNTs, respectively. A moderate degree of alloying was determined for the material. The application of Pt-Pd electrocatalysts in DEGFCs should be advantageous. [Spanish] Electrocatalizadores Pt-Pd/MWCNTs (relacion atomic Pt:Pd 43:57) y Pt/MWCNTs fueron sintetizados y evaluados como catodos para la reaccion de reduccion del oxigeno (ORR) con aplicacion del celdas de consumo directo de etilenglicol (Direct Ethylene Glycol Fuel Cells, o DEGFC). Como referencia, un material comercial tipo Pt/C fue tambien evaluado. Se encontro que Pt-Pd/MWCNTs tiene una alta capacidad de tolerancia al etilenglicol (EG) y una selectividad mayor hacia la ORR comparado con el catodo basado en Pt-solo. Como resultado, el cambio en potencial de inicio de la ORR, Eonset, en Pt-Pd/MWCNTs fue considerablemente menor que el cambio en Pt/MWCNTs o Pt/C. La talla de particula promedio (de XRD) fue 3.5 nm y 4 nm para Pt/MWCNTs y Pt-Pd/MWCNTs, respectivamente. Un moderado grado de aleacion fue determinado para el material. Una aplicacion ventajosa para electrocatalizadores tipo Pt-Pd debe ser en DEGFCs.

  9. Two directional microstructure and effects of nanoscale dispersed Si particles on microhardness and tensile properties of AlSi7Mg melt-spun alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xixi, E-mail: dongxx09@mails.tsinghua.edu.cn [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); He, Liangju [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); School of Aerospace, Tsinghua University, Beijing 100084 (China); Mi, Guangbao [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); Li, Peijie [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China)

    2015-01-05

    Highlights: • Both surface and cross-sectional microstructure of AlSi7Mg ribbon were characterized. • 13–50 nm and 50-hundreds of nm Si particles were dispersed both in α-Al and its boundary. • Tensile property of AlSi7Mg ribbon was studied with UTS 1.5 times higher than ingot. • Effects of nanoscale Si particles on hardness and tensile properties were provided. - Abstract: The two directional microstructure and multiple mechanical properties of the AlSi7Mg ribbon produced by melt-spun were investigated by optical microscopy (OM), field emission gun scanning electron microscope (FEGSEM), X-ray diffraction (XRD), microhardness and tensile tests. Both the surface and cross-sectional microstructure of the melt-spun ribbon were characterized in detail to give a clear and integrated description of the microstructure. Two kinds of nanoscale Si particles were observed, i.e., small Si particles ranging from 13 to 50 nm and large Si particles ranging from 50 nm to several hundreds of nanometers with clear size boundary were dispersed both in the interior and boundary of fine α-Al. XRD results revealed supersaturated solution of Si in Al matrix to be 0.62 at.%. The ultimate tensile strength, yield strength, and hardness of the ribbon were 1.53, 1.75 and 1.56 times higher than that of the conventional cast ingot separately. The breaking elongation of the ribbon was 1.73% with intergranular fracture feature. The effects of nanoscale dispersed Si particles on the significant improvement of both hardness and tensile properties of the AlSi7Mg melt-spun ribbon were discussed in detail.

  10. Distribution of Al and in impurities along homogeneous Ge-Si crystals grown by the Czochralski method using Si feeding rod

    Science.gov (United States)

    Kyazimova, V. K.; Alekperov, A. I.; Zakhrabekova, Z. M.; Azhdarov, G. Kh.

    2014-05-01

    A distribution of Al and In impurities in Ge1 - x Si x crystals (0 ≤ x ≤ 0.3) grown by a modified Czochralski method (with continuous feeding of melt using a Si rod) have been studied experimentally and theoretically. Experimental Al and In concentrations along homogeneous crystals have been determined from Hall measurements. The problem of Al and In impurity distribution in homogeneous Ge-Si single crystals grown in the same way is solved within the Pfann approximation. A set of dependences of Al and In concentrations on the crystal length obtained within this approximation demonstrates a good correspondence between the experimental and theoretical data.

  11. FEM Analysis of Sezawa Mode SAW Sensor for VOC Based on CMOS Compatible AlN/SiO2/Si Multilayer Structure

    Directory of Open Access Journals (Sweden)

    Muhammad Zubair Aslam

    2018-05-01

    Full Text Available A Finite Element Method (FEM simulation study is conducted, aiming to scrutinize the sensitivity of Sezawa wave mode in a multilayer AlN/SiO2/Si Surface Acoustic Wave (SAW sensor to low concentrations of Volatile Organic Compounds (VOCs, that is, trichloromethane, trichloroethylene, carbon tetrachloride and tetrachloroethene. A Complimentary Metal-Oxide Semiconductor (CMOS compatible AlN/SiO2/Si based multilayer SAW resonator structure is taken into account for this purpose. In this study, first, the influence of AlN and SiO2 layers’ thicknesses over phase velocities and electromechanical coupling coefficients (k2 of two SAW modes (i.e., Rayleigh and Sezawa is analyzed and the optimal thicknesses of AlN and SiO2 layers are opted for best propagation characteristics. Next, the study is further extended to analyze the mass loading effect on resonance frequencies of SAW modes by coating a thin Polyisobutylene (PIB polymer film over the AlN surface. Finally, the sensitivity of the two SAW modes is examined for VOCs. This study concluded that the sensitivity of Sezawa wave mode for 1 ppm of selected volatile organic gases is twice that of the Rayleigh wave mode.

  12. Crack-resistant Al2O3-SiO2 glasses.

    Science.gov (United States)

    Rosales-Sosa, Gustavo A; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki

    2016-04-07

    Obtaining "hard" and "crack-resistant" glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3-(100-x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3-SiO2 glasses. In particular, the composition of 60Al2O3 • 40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses.

  13. Development of an efficient grain refiner for Al-7Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kori, S.A.; Murty, B.S.; Chakraborty, M. [Indian Inst. of Technol., Kharagpur (India). Dept. of Metall. and Mater. Eng.

    2000-03-15

    The response of Al-7Si alloy towards grain refinement by Al-Ti-B master alloys (with different Ti-B ratios) at different addition levels has been studied in detail. The results indicate that high B-containing master alloys are powerful grain refiners when compared to conventional grain refiners like Al-5Ti-lB master alloys. In the present study, indigenously developed master alloys have been used for the grain refinement of alloys Al-7Si and LM-25. Significant improvements in mechanical properties have been obtained with a combination of grain refiner and Sr as modifier. (orig.)

  14. Four-branched compounds coupled Si and iron-rich intermetallics in near eutectic Al-Si alloys

    International Nuclear Information System (INIS)

    Wu, Yuying; Liu, Xiangfa; Jiang, Binggang; Bian, Xiufang

    2007-01-01

    Many four-branched compounds coupled Si and iron-rich intermetallics were observed in near eutectic Al-Si alloy modified with Al-P master alloy. Such four-branched compounds have never been reported before, but in our case it seems to be commonly observed. In this work the growth characterization of the four-branched compounds are scrutinized with a JXA-8800 electron microprobe (EPMA). More deep study of the formation of four-branched compounds is performed by SEM and TEM analysis. The characterization of the four-branched compounds is that of a primary silicon in the center with four iron-rich intermetallics around. Experimental results also show that the precipitation of primary silicon is the key factor for the formation of four-branched compounds. And WHS-theory explains the growth mechanism of the four-branched compounds. In detail, subsequent twinning within the primary silicon provides four-fold coordination sites on the surface, and then the α-Al(Fe,Mn)-Si phase nucleates on the surface of the primary silicon

  15. Influence of Iron in AlSi10MgMn Alloy

    Directory of Open Access Journals (Sweden)

    Žihalová M.

    2014-12-01

    Full Text Available Presence of iron in Al-Si cast alloys is common problem mainly in secondary (recycled aluminium alloys. Better understanding of iron influence in this kind of alloys can lead to reduction of final castings cost. Presented article deals with examination of detrimental iron effect in AlSi10MgMn cast alloy. Microstructural analysis and ultimate tensile strength testing were used to consider influence of iron to microstructure and mechanical properties of selected alloy.

  16. Influence of Preparation Conditions on Electrical Properties of the Al/Alq3/Si Diode Structures

    Directory of Open Access Journals (Sweden)

    Irina ČERNIUKĖ

    2013-12-01

    Full Text Available Hybrid organic-inorganic diode structures, Al/Alq3/n-Si and Al/Alq3/p-Si based on thin films of tris(8-hydroxyquinoline aluminum (Alq3 have been investigated. The Alq3 films were evaporated in vacuum and spin coated onto patterned areas of crystalline n- and p-type Si substrates with chemically removed native SiO2 layer. Current-voltage characteristics of the diode structures demonstrated improved rectification property compared to similar Al/n-Si and Al/p-Si device structures. Increased barrier height values (0.90 eV ÷ 1.1 eV and 0.77 eV ÷ 0.91 eV for the Al/Alq3/n-Si and Al/Alq3/p-Si device structures, respectively certified presence of an interface dipole induced by the organic interlayer. Non-ideal behavior of forward current-voltage characteristics has been explained assuming non-uniformity of barrier height, presence of interface states, and influence of the organic film on diode series resistance and space charge limited current. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2733

  17. Investigating the effect of silicon surface chemical treatment on Al/Si contact properties in GaP/Si solar cells

    Science.gov (United States)

    Kudryashov, D.; Gudovskikh, A.

    2018-03-01

    In the present work, experimental studies have been carried out to reveal how chemical treatment of a silicon surface affects the properties of the Al/Si contact. It has been shown that for p-type monocrystalline silicon substrates with a resistivity of 10 ohm cm, it is possible to form an ohmic Al/Si contact by magnetron sputtering of an aluminum thin film and its further annealing at temperatures of 400 - 450 °C. In the range of annealing temperatures of 250 - 400 °C, the Si substrate treatment in the HF solution leads to a significant increase in currents on the current-voltage curves of the Al/Si contact, while in the range of 450 - 700 °C, the effect of chemical treatment of the silicon is not detected.

  18. Ab initio study of 3C-SiC/M (M = Ti or Al) nano-hetero interfaces

    International Nuclear Information System (INIS)

    Tanaka, Shingo; Kohyama, Masanori

    2003-01-01

    Ab initio pseudopotential calculation of 3C-SiC(1 1 1)/Al nano-hetero interfaces have been performed and interface atom species dependence (IASD) and interface orientation dependence (IOD) of nano-hetero interfaces between 3C-SiC ((1 1 1) or (0 0 1) orientation) and metal (Ti or Al) have been studied systematically. Stable atomic configurations of the 3C-SiC(1 1 1)/Al interfaces are quite different from those of the 3C-SiC(1 1 1)/Ti interfaces. Two terminated, Si-terminated (Si-TERM) and C-terminated (C-TERM), 3C-SiC(1 1 1)/Al interfaces have covalent bonding nature. In 3C-SiC/M (M = Ti or Al) nano-hetero interfaces, the C-terminated interface has relative strong, covalent and ionic C-Ti or C-Al bonds as TiC or SiC while the Si-terminated interface has various type of bonding nature, relative weak Si-Ti or Si-Al bonds from metallic character at the (0 0 1) interface to covalent character at the (1 1 1) interface. Adhesive energy (AE) shows strong IASD and IOD. The AE of the C-terminated interface is larger than that of the Si-terminated one. In the C-terminated interface, the AE of the (1 1 1) interface is smaller than that of the (0 0 1) one while in the Si-terminated interface there exists opposite interrelation. Schottky barrier height (SBH) also shows strong IASD and IOD. The SBH of the C-terminated interface is smaller than that of the Si-terminated one. The C-terminated SiC/Al interfaces have extremely small SBHs. In comparison with some experimental SBH, the present result is reliable as the difference of SBH between the two terminated interfaces and qualitative properties

  19. Effect of Al-5Ti-0.62C-0.2Ce Master Alloy on the Microstructure and Tensile Properties of Commercial Pure Al and Hypoeutectic Al-8Si Alloy

    Directory of Open Access Journals (Sweden)

    Wanwu Ding

    2017-06-01

    Full Text Available Al-5Ti-0.62C-0.2Ce master alloy was synthesized by a method of thermal explosion reaction in pure molten aluminum and used to modify commercial pure Al and hypoeutectic Al-8Si alloy. The microstructure and tensile properties of commercial pure Al and hypoeutectic Al-8Si alloy with different additions of Al-5Ti-0.62C-0.2Ce master alloy were investigated. The results show that the Al-5Ti-0.62C-0.2Ce alloy was composed of α-Al, granular TiC, lump-like TiAl3 and block-like Ti2Al20Ce. Al-5Ti-0.62C-0.2Ce master alloy (0.3 wt %, 5 min can significantly refine macro grains of commercial pure Al into tiny equiaxed grains. The Al-5Ti-0.62C-0.2Ce master alloy (0.3 wt %, 30 min still has a good refinement effect. The tensile strength and elongation of commercial pure Al modified by the Al-5Ti-0.62C-0.2Ce master alloy (0.3 wt %, 5 min increased by roughly 19.26% and 61.83%, respectively. Al-5Ti-0.62C-0.2Ce master alloy (1.5 wt %, 10 min can significantly refine both α-Al grains and eutectic Si of hypoeutectic Al-8Si alloy. The dendritic α-Al grains were significantly refined to tiny equiaxed grains. The morphology of the eutectic Si crystals was significantly refined from coarse needle-shape or lath-shape to short rod-like or grain-like eutectic Si. The tensile strength and elongation of hypoeutectic Al-8Si alloy modified by the Al-5Ti-0.62C-0.2Ce master alloy (1.5 wt %, 10 min increased by roughly 20.53% and 50%, respectively. The change in mechanical properties corresponds to evolution of the microstructure.

  20. Alleviation of process-induced cracking of the antireflection TiN coating (ARC-TiN) in Al-Cu and Al-Cu-Si films

    CERN Document Server

    Peng, Y C; Yang, Y R; Hsieh, W Y; Hsieh, Y F

    1999-01-01

    The alleviation of cracking of the TiN-ARC layer on Al-Cu and Al-Cu-Si films after the development process has been achieved. For the TiN-ARC/Al-Cu system, the stress-induced defects decreased with increasing TiN-ARC layer thickness. In contrast, for the TiN-ARC/Al-Cu-Si system, Si nodules formed during cooling, thereby inducing poor coverage with high aspect-ratio holes. As a result, the photoresist developer penetrated through the films. Chemical vapor deposition of TiN-ARC or predeposition of a Ti Interposing layer was used to eliminate the formation of Si nodules.

  1. Aleaciones moleculares. Sincristalizacion en la serie de paradihalosubstituidos del benceno

    OpenAIRE

    Calvet Pallàs, Maria Teresa

    1990-01-01

    La sincristalización orgánica constituye un campo de investigación relativamente nuevo, en el que entran en juego interacciones muy diversas, y variaciones en las propiedades de los materiales a menudo muy sensibles a las condiciones de temperatura, presión y sobre todo a la composición. Por lo tanto, cualquier estudio sobre el tema debe comprender muchas líneas de enfoque: control de pureza de los materiales de partida, síntesis de las aleaciones, estudio de los equilibrios de las fases que ...

  2. Electron density distribution and disordered crystal structure of 15R-SiAlON, SiAl4O2N4

    International Nuclear Information System (INIS)

    Banno, Hiroki; Hanai, Takaaki; Asaka, Toru; Kimoto, Koji; Fukuda, Koichiro

    2014-01-01

    The crystal structure of SiAl 4 O 2 N 4 was characterized by laboratory X-ray powder diffraction (CuKα 1 ). The title compound is trigonal with space group R3-bar m. The hexagonal unit-cell dimensions (Z=3) are a=0.301332(3) nm, c=4.18616(4) nm and V=0.3291825(5) nm 3 . The initial structural model was successfully derived by the charge-flipping method and further refined by the Rietveld method. The final structural model showed the positional disordering of one of the three (Si,Al) sites. The maximum-entropy method-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were R wp =5.05%, S (=R wp /R e )=1.21, R p =3.77%, R B =1.29% and R F =1.01%. The disordered crystal structure was successfully described by overlapping three types of domains with ordered atom arrangements. The distribution of atomic positions in one of the three types of domains can be achieved in the space group R3-bar m. The atom arrangements in the other two types of domains are noncentrosymmetrical with the space group R3m. These two structural configurations are related by the pseudo-symmetry inversion. -- Graphical abstract: A bird's eye view of electron densities up to 75.3% (0.133 nm −3 ) of the maximum on the plane parallel to (110) with the corresponding atomic arrangements of SiAl 4 O 2 N 4 . Highlights: • Crystal structure of SiAl 4 O 2 N 4 is determined by laboratory X-ray powder diffraction. • The atom arrangements are represented by the split-atom model. • The maximum-entropy method-based pattern fitting method is used to confirm the validity of the model. • The disordered structure is described by overlapping three types of domains with ordered atom arrangements

  3. Development and application of graphite-SiO2/Al2O3/Nb2O5-methylene blue (GRP-SiAlNb-MB composite for electrochemical determination of dopamine

    Directory of Open Access Journals (Sweden)

    Juliana de Fátima Giarola

    2017-03-01

    Full Text Available In the present paper an amperometric sensor based on graphite-SiO2/Al2O3/Nb2O5-methylene blue (GRP-SiAlNb-MB composite has been successfully prepared for dopamine (DA determination in real samples. The electrochemical behavior of DA at the GRP-SiAlNb-MB has been evaluated by employing cyclic voltammetry. The best ratio (m/m of GRP-SiAlNb-MB composite was found to be 1:0.54. Under optimized conditions (pH 7.5 in 0.15 mol L−1 phosphate buffer the amperometry method responds linearly to DA from 5.0 up to 500.0 μmol L−1 (r = 0.995 with limits of detection and quantification of 1.49 and 4.97 μmol L−1, respectively. The developed method was successfully applied for DA determination in real samples of pharmaceutical formulations and can be used for routine quality control analysis of pharmaceutical formulations containing DA. The use of inorganic matrix SiAlNb was found to be very useful to adsorb MB in the composite material with further improvement of the anodic peak current of DA.

  4. Characterization and properties Ti-Al-Si-N nanocomposite coatings prepared by middle frequency magnetron sputtering

    Science.gov (United States)

    Zou, C. W.; Zhang, J.; Xie, W.; Shao, L. X.; Guo, L. P.; Fu, D. J.

    2011-10-01

    TiN-containing amorphous Ti-Al-Si-N (nc-TiN/a-Si 3N 4 or a-AlN) nanocomposite coatings were deposited by using a modified closed field twin unbalanced magnetron sputtering system which is arc assisted and consists of two circles of targets, at a substrate temperature of 300 °C. XRD, XPS and High-resolution TEM experiments showed that the coatings contain TiN nanocrystals embedded in the amorphous Si 3N 4 or AlN matrix. The coatings exhibit good mechanical properties that are greatly influenced by the Si contents. The hardness of the Ti-Al-Si-N coatings deposited at Si targets currents of 5, 8, 10, and 12 A were 45, 47, 54 and 46 GPa, respectively. The high hardness of the deposited Ti-Al-Si-N coatings may be own to the plastic distortion and dislocation blocking by the nanocrystalline structure. On the other hand, the friction coefficient decreases monotonously with increasing Si contents. This result would be caused by tribo-chemical reactions, which often take place in many ceramics, e.g. Si 3N 4 reacts with H 2O to produce SiO 2 or Si(OH) 2 tribolay-layer.

  5. Determination of Al, Si and P in certified reference materials by Instrumental Neutron Activation Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Noyori, Amanda; Saiki, Mitiko, E-mail: anoyori@gmail.com, E-mail: mitiko@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-11-01

    Neutron analysis activation is not commonly used for aluminum, phosphorus and silicon determination, due to the difficulty to obtain reliable results. In this study, Al was determined by measuring {sup 28}Al and the contribution of P and Si due to {sup 28}Al formed in {sup 31}P(n,α){sup 28}Al and {sup 28}Si(n,p){sup 28}Al reactions were corrected using correction factors determined experimentally. Phosphorus was determined by measuring {sup 32}P (pure beta emitter) formed in reaction {sup 31}P(n,γ){sup 32}P. Silicon was determined by epithermal neutron analysis activation (ENAA) and measuring {sup 29}Al radionuclide formed in {sup 29}Si(n,p){sup 29}Al reaction. Aliquots of certified reference materials (CRMs) and synthetic standards of the elements were irradiated together, using the pneumatic transfer station of IEA-R1 nuclear research reactor. Results obtained for biological and geological CRMs showed good precision and accuracy with |Z-score| < 2 for Al, P and Si determinations. The detection limits for Al, P and Si determinations CRMs were also evaluated. Results obtained in this study demonstrated the viability of applying INAA procedures in the determination of Al, P and Si. (author)

  6. Determination of Al, Si and P in certified reference materials by Instrumental Neutron Activation Analysis

    International Nuclear Information System (INIS)

    Noyori, Amanda; Saiki, Mitiko

    2017-01-01

    Neutron analysis activation is not commonly used for aluminum, phosphorus and silicon determination, due to the difficulty to obtain reliable results. In this study, Al was determined by measuring "2"8Al and the contribution of P and Si due to "2"8Al formed in "3"1P(n,α)"2"8Al and "2"8Si(n,p)"2"8Al reactions were corrected using correction factors determined experimentally. Phosphorus was determined by measuring "3"2P (pure beta emitter) formed in reaction "3"1P(n,γ)"3"2P. Silicon was determined by epithermal neutron analysis activation (ENAA) and measuring "2"9Al radionuclide formed in "2"9Si(n,p)"2"9Al reaction. Aliquots of certified reference materials (CRMs) and synthetic standards of the elements were irradiated together, using the pneumatic transfer station of IEA-R1 nuclear research reactor. Results obtained for biological and geological CRMs showed good precision and accuracy with |Z-score| < 2 for Al, P and Si determinations. The detection limits for Al, P and Si determinations CRMs were also evaluated. Results obtained in this study demonstrated the viability of applying INAA procedures in the determination of Al, P and Si. (author)

  7. Fabrication of V-Cr-Ti-Y-Al-Si alloys by levitation melting

    Energy Technology Data Exchange (ETDEWEB)

    Chuto, Toshinori; Satou, Manabu; Abe, Katsunori [Department of Quantum Science and Energy Engineering, Tohoku University, Sendai, Miyagi (Japan); Nagasaka, Takuya; Muroga, Takeo [National Inst. for Fusion Science, Toki, Gifu (Japan); Shibayama, Tamaki [Center for Advanced Research of Energy Technology, Hokkaido University, Sapporo, Hokkaido (Japan); Tomiyama, Shigeki [Daido Bunseki Research Inc., Nagoya, Aichi (Japan); Sakata, Masafumi [Daido Steel Co. Ltd., Nagoya (Japan)

    2000-09-01

    Three allows of V-4Cr-4Ti type containing Si, Al and Y were fabricated by 2.5 kg scale levitation melting in this study. Workability and recrystallization behavior of the alloys were studied in order to establish the fabrication method of high-purity large ingot of V-Cr-Ti-Si-Al-Y type alloys, especially reducing interstitial impurity levels. Oxygen contents decreased with increasing yttrium contents and were kept below 180 mass ppm over wide region in the ingots. Nitrogen contents in the V-Cr-Ti-Y-Si-Al type alloys were only 100 mass ppm, which were as low as that in the starting materials. Only the V-4Cr-4Ti-0.1Y, Si, Al alloy could be cold-rolled at as-melted condition. Because large yttrium inclusions were observed in the alloys containing 0.5 mass%Y, it is necessary to optimize yttrium contents to avoid large inclusions and to obtain good workability. (author)

  8. Fabrication of V-Cr-Ti-Y-Al-Si alloys by levitation melting

    International Nuclear Information System (INIS)

    Chuto, Toshinori; Satou, Manabu; Abe, Katsunori; Nagasaka, Takuya; Muroga, Takeo; Shibayama, Tamaki; Tomiyama, Shigeki; Sakata, Masafumi

    2000-01-01

    Three allows of V-4Cr-4Ti type containing Si, Al and Y were fabricated by 2.5 kg scale levitation melting in this study. Workability and recrystallization behavior of the alloys were studied in order to establish the fabrication method of high-purity large ingot of V-Cr-Ti-Si-Al-Y type alloys, especially reducing interstitial impurity levels. Oxygen contents decreased with increasing yttrium contents and were kept below 180 mass ppm over wide region in the ingots. Nitrogen contents in the V-Cr-Ti-Y-Si-Al type alloys were only 100 mass ppm, which were as low as that in the starting materials. Only the V-4Cr-4Ti-0.1Y, Si, Al alloy could be cold-rolled at as-melted condition. Because large yttrium inclusions were observed in the alloys containing 0.5 mass%Y, it is necessary to optimize yttrium contents to avoid large inclusions and to obtain good workability. (author)

  9. Mechanisms of aluminium-induced crystallization and layer exchange upon low-temperature annealing of amorphous Si/polycrystalline Al bilayers.

    Science.gov (United States)

    Wang, J Y; Wang, Z M; Jeurgens, L P H; Mittemeijer, E J

    2009-06-01

    Aluminium-induced crystallization (ALIC) of amorphous Si and subsequent layer exchange (ALILE) occur in amorphous-Si/polycrystalline-Al bilayers (a-Si/c-Al) upon annealing at temperatures as low as 165 degrees C and were studied by X-ray diffraction and Auger electron spectroscopic depth profiling. It follows that: (i) nucleation of Si crystallization is initiated at Al grain boundaries and not at the a-Si/c-Al interface; (ii) low-temperature annealing results in a large Si grain size in the continuous c-Si layer produced by ALILE. Thermodynamic model calculations show that: (i) Si can "wet" the Al grain boundaries due to the favourable a-Si/c-Al interface energy (as compared to the Al grain-boundary energy); (ii) the wetting-induced a-Si layer at the Al grain boundary can maintain its amorphous state only up to a critical thickness, beyond which nucleation of Si crystallization takes place; and (iii) a tiny driving force controls the kinetics of the layer exchange.

  10. The Prognosis of the Phase Equilibrium Diagram of the System Al-Cu-Si

    Directory of Open Access Journals (Sweden)

    Florentina Cziple

    2007-10-01

    Full Text Available The paper presents a model for establishing the mathematical functions of the liquidus and solidus curves, from the binary diagrams Al-Si, Si-Cu, Cu-Al and their use in the prognosis of the phase equilibrium diagram from the ternary system Al-Cu-Si. We have studied the model of the non-ideal liquid solution of the regular type. The calculus and graphic plotting of the equations for the binary systems has been performed on the computer

  11. Microstructure and corrosion resistance of Sm-containing Al-Mn-Si-Fe-Cu alloy

    Directory of Open Access Journals (Sweden)

    Han Yuyin

    2017-12-01

    Full Text Available Optimizing alloy composition is an effective way to improve physical and chemical properties of automobile heat exchanger materials.A Sm-containing Al-Mn-Si-Fe-Cu alloy was investigated through transmission electron microscopy,scanning electron microscopy,and electrochemical measurement.Experimental results indicated that main phases distributed in the alloy wereα-Al(Mn,FeSi,Al2Sm and Al10Cu7Sm2.Alloying with Sm element could refine the precipitated α-Al(Mn,FeSi phase.Polarization testing results indicated that the corrosion surfacewas mainly composed of pitting pits and corrosion products.Sea water acetic acid test(SWAAT showed that corrosion loss increased first and then slowed downwith increase of the corrosion time.

  12. AlN metal-semiconductor field-effect transistors using Si-ion implantation

    Science.gov (United States)

    Okumura, Hironori; Suihkonen, Sami; Lemettinen, Jori; Uedono, Akira; Zhang, Yuhao; Piedra, Daniel; Palacios, Tomás

    2018-04-01

    We report on the electrical characterization of Si-ion implanted AlN layers and the first demonstration of metal-semiconductor field-effect transistors (MESFETs) with an ion-implanted AlN channel. The ion-implanted AlN layers with Si dose of 5 × 1014 cm-2 exhibit n-type characteristics after thermal annealing at 1230 °C. The ion-implanted AlN MESFETs provide good drain current saturation and stable pinch-off operation even at 250 °C. The off-state breakdown voltage is 2370 V for drain-to-gate spacing of 25 µm. These results show the great potential of AlN-channel transistors for high-temperature and high-power applications.

  13. Characterization of Si3N4-Al interface after corrosion tests Caracterização da interface Si3N4-Al após testes de corrosão

    Directory of Open Access Journals (Sweden)

    C. dos Santos

    2003-12-01

    Full Text Available Silicon nitride is a covalent ceramic material of high corrosion resistance and mechanical stability at elevated temperatures. Due to these properties, its use in metallurgical processes, such as the casting of alloys, is increasing. Therefore, the characterization of the interface between Si3N4 and the casted metal is of great importance to investigate possible interactions, which might deteriorate the ceramic mould or contaminate the metal. In this work, the use of Si3N4 as crucible material for Al-casting has been studied, by investigating the corrosion attack of liquid Al at a temperature of 1150 ºC during 30 days in air. The interface was characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. It has been found that due to superficial oxidation two oxide layers form - SiO2 on Si3N4 and Al2O3 on Al - which effectively hinder further reactions under the conditions studied, confering high corrosion resistance to the Si3N4 crucible.Nitreto de silício (Si3N4 é um material cerâmico covalente de elevada resistência à corrosão e estabilidade mecânica em temperaturas elevadas. Devido a essas propriedades, sua utilização em processos metalúrgicos, tais como em fundição de ligas metálicas, é crescente. Desta forma, a caracterização da interface entre Si3N4 e metais fundidos é de grande interesse para investigar possíveis interações as quais poderão deteriorar o material cerâmico e/ou contaminar o metal. Nesse trabalho o uso de Si3N4 como material base de cadinhos para fundição de alumínio foi estudado, pela investigação do ataque corrosivo de Al líquido a 1150 ºC durante 30 dias, ao ar. A interface foi caracterizada por difração de raios X, microscopia eletrônica de varredura e espectroscopia de energia dispersiva. É encontrado que devido à oxidação superficial dois óxidos se formam - SiO2 no Si3N4 e Al2O3 no Al - os quais evitam possíveis reações sob as condi

  14. Electrical transport characterization of Al and Sn doped Mg 2 Si thin films

    KAUST Repository

    Zhang, Bo

    2017-05-22

    Thin-film Mg2Si was deposited using radio frequency (RF) magnetron sputtering. Al and Sn were incorporated as n-type dopants using co-sputtering to tune the thin-film electrical properties. X-ray diffraction (XRD) analysis confirmed that the deposited films are polycrystalline Mg2Si. The Sn and Al doping concentrations were measured using Rutherford backscattering spectroscopy (RBS) and energy dispersive X-ray spectroscopy (EDS). The charge carrier concentration and the charge carrier type of the Mg2Si films were measured using a Hall bar structure. Hall measurements show that as the doping concentration increases, the carrier concentration of the Al-doped films increases, whereas the carrier concentration of the Sn-doped films decreases. Combined with the resistivity measurements, the mobility of the Al-doped Mg2Si films is found to decrease with increasing doping concentration, whereas the mobility of the Sn-doped Mg2Si films is found to increase.

  15. Thermoelectric properties of Al doped Mg{sub 2}Si material

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Kulwinder, E-mail: kulwindercmp@gmail.com; Kumar, Ranjan [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh-160 014 (India); Rani, Anita [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh-160 014 (India); Guru Nanak College for Girls, Sri Muktsar Sahib, Punjab (India)

    2015-08-28

    In the present paper we have calculated thermoelectric properties of Al doped Mg{sub 2}Si material (Mg{sub 2−x}Al{sub x}Si, x=0.06) using Pseudo potential plane wave method based on DFT and Semi classical Boltzmann theory. The calculations showed n-type conduction, indicating that the electrical conduction are due to electron. The electrical conductivity increasing with increasing temperature and the negative value of Seebeck Coefficient also show that the conduction is due to electron. The thermal conductivity was increased slightly by Al doping with increasing temperature due to the much larger contribution of lattice thermal conductivity over electronic thermal conductivity.

  16. AlSiTiN and AlSiCrN multilayer coatings: Effects of structure and surface composition on tribological behavior under dry and lubricated conditions

    International Nuclear Information System (INIS)

    Faga, Maria Giulia; Gautier, Giovanna; Cartasegna, Federico; Priarone, Paolo C.; Settineri, Luca

    2016-01-01

    Graphical abstract: - Highlights: • The demand for high performance nanostructured coatings has been increasing. • AlSiTiN and AlSiCrN nanocomposite coatings were deposited by PVD technique. • Coatings were analyzed in terms of structure, hardness and adhesion. • Tribological properties under dry and lubricated conditions were studied. • The effects of surface and bulk properties on friction evolution were assessed. - Abstract: Nanocomposite coatings have been widely studied over the last years because of their high potential in several applications. The increased interest for these coatings prompted the authors to study the tribological properties of two nanocomposites under dry and lubricated conditions (applying typical MQL media), in order to assess the influence of the surface and bulk properties on friction evolution. To this purpose, multilayer and nanocomposite AlSiTiN and AlSiCrN coatings were deposited onto tungsten carbide-cobalt (WC-Co) samples. Uncoated WC-Co materials were used as reference. Coatings were analyzed in terms of hardness and adhesion. The structure of the samples was assessed by X-ray diffraction (XRD), while the surface composition was studied by XPS analysis. Friction tests were carried out under both dry and lubricated conditions using an inox ball as counterpart. Both coatings showed high hardness and good adhesion to the substrate. As far as the friction properties are concerned, in dry conditions the surface properties affect the sliding contact at the early beginning, while bulk structure and tribolayer formation determine the main behavior. Only AlSiTiN coating shows a low and stable coefficient of friction (COF) under dry condition, while the use of MQL media results in a rapid stabilization of the COF for all the materials.

  17. Irradiation behaviour of U-Si-Al with peripheral voidage

    International Nuclear Information System (INIS)

    Fehrenbach, P.J.; Feraday, M.A.; Cotnam, K.D.; Morel, P.A.

    1977-12-01

    Peripheral voidage in the form of longitudinal slots on the surface of the fuel is effective in accommodating the irradiation induced swelling of U-Si-Al rods clad in cold-worked Zr-2.5 wt% Nb. Diametral increases in elements operated at steady powers between 50 and 80 kW/m to a burnup of 240 MW.h/kg U were less than 1.25%. Similar to U 3 Si elements, lower sheath strength or higher temperatures resulted in greater diametral increases. An oxide or graphite interlayer between the fuel and sheath was shown to be effective in preventing the development of a fuel/sheath bond. The ability of U-Si-Al elements to successfully survive a power increase from 35 to 70 kW/m after appreciable burnup at the lower power has also been demonstrated. (author)

  18. Relación entre factores micro- estructurales e impacto repetido en aleaciones de alto cromo para bolas de molino.

    Directory of Open Access Journals (Sweden)

    E. Albertin

    2008-01-01

    Full Text Available Las aleaciones de alto cromo son empleadas para la fabricación de bolas de molino en industrias de procesamiento de minerales. Los usuarios y fabricantes requieren lograr mejores resultados técnicos-económicos en sus aplicaciones, por lo que necesitan aumentar los conocimientos relacionados con los aspectos estructurales de estos materiales. En este trabajo se realiza una investigación con vistas a establecer relaciones entre la estructura de las aleaciones y su comportamiento ante el impacto repetido que es un fenómeno característico en estos procesos. Se funden bolas con varias aleaciones hipo eutécticas, eutécticas, e hipereutécticas; se prueban en un equipo que simula el impacto repetido. Los resultados permiten comprobar los buenos resultados de aleaciones hipo eutécticas con relaciones de Cr/C altas y a su vez altos contenidos de Cr y de aleaciones eutécticas para menores relaciones de Cr/C y menores contenidos de Cr, en ambos casos los carburos eutécticos son de forma simétrica, regulares y no forman redes continuas de carburos asimétricos bordeando los granos, que presentan peores comportamiento en el impacto repetido y que son el caso de las hipoeutécticas con bajas relaciones Cr/C y las hipereutécticas donde aparecen también grandes carburos primarios.High Chromium alloys are used to manufacture grinding balls for the Industry of Construction Materials. Customers and users need to improve their knowledge about the relationships between microstructure and the parts damage in these alloys to obtain better technical-economics results. In this paper the results of a research to obtain different microstructures of eutectics, hipoeutectics and hipereutectics alloys are presented, searching for the lesser damage in these alloys. These alloys are tested in a repeated impact testing machine that simulate its mechanical behaviour .The results show a good behaviour for hipoeutectic alloys with high relations of Cr/C and high

  19. Apego al tratamiento farmacológico en pacientes con diagnóstico de diabetes mellitus tipo 2

    Directory of Open Access Journals (Sweden)

    Durán-Varela Blanca Rosa

    2001-01-01

    Full Text Available Objetivos. Establecer la frecuencia de apego al tratamiento farmacológico en pacientes diabéticos tipo 2, relacionarla con el control metabólico e identificar factores que influyen para el no apego. Material y métodos. Estudio transversal comparativo, efectuado en 150 pacientes con diabetes mellitus tipo 2 de la unidad de medicina familiar No. 33 del Instituto Mexicano del Seguro Social de Chihuahua, Chih., México, hecho entre 1997 y 1998. Se midió el apego con cuenta de tabletas en su domicilio. El control metabólico se midió con hemoglobina glucosilada. Un cuestionario investigó factores relacionados. Se utilizó estadística descriptiva, t de Student y razón de momios. Resultados. El apego correspondió a 54.2%. Los factores asociados al no apego fueron la escolaridad primaria y la falta de información sobre la enfermedad (phttp://www.insp.mx/salud/index.html

  20. The annealing behavior of hydrogen implanted into Al-Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Masahiko; Yamaji, Norisuke; Imai, Makoto; Itoh, Akio; Imanishi, Nobutsugu [Kyoto Univ. (Japan). Faculty of Engineering

    1997-03-01

    We have studied effects of not only defects but also an added elements on trap-sites of hydrogen in metals. For the purpose, we observed depth profiles and thermal behaviors of hydrogen implanted into Al-1.5at.%Si alloy samples in an implantation-temperature range of liquid nitrogen temperature (LNT) to 373K at different doses. The results were compared with those for pure aluminum samples. It was found that hydrogen is trapped as molecules in grain boundaries of Al/Si. (author)

  1. Friction stir welding of SiCp/2009Al composite plate

    International Nuclear Information System (INIS)

    Wang, D.; Xiao, B.L.; Wang, Q.Z.; Ma, Z.Y.

    2013-01-01

    Highlights: ► SiCp/2009Al plates were successfully friction stir welded using an ultra-hard tool. ► Under T4 temper condition, the joint coefficient of tensile strength was 95.9%. ► Coarsen Al 2 Cu in the nugget zone dissolved and precipitated after T4. - Abstract: Six milimeter thick hot-rolled SiCp/2009Al composite plates were successfully joined by friction stir welding (FSW) using an ultra-hard material tool. After FSW, the distribution of the SiC particles in the nugget zone (NZ) was more homogeneous than that in the base material (BM). Scanning electron microscopic examinations (SEM) and X-ray analysis (XRD) indicated that part of the Al 2 Cu was dissolved into the aluminum matrix in the NZ due to intense plastic deformation and high temperature during FSW. The undissolved Al 2 Cu particles remained in the NZ and coarsened during the cooling process after FSW. The ultimate tensile strength (UTS) of the as-welded joint is only 321 MPa and failed in the BM zone due to the low strength of the BM. After T4 heat treatment, the strength of the joint increased and became close to that of the BM with T4 temper, because most of the Al 2 Cu particles were dissolved into the matrix and re-precipitated homogeneously as the GP zones, which are the major strengthening precipitates for T4-tempered 2009Al alloy

  2. Preparation of mullite whiskers reinforced SiC/Al2O3 composites by microwave sintering

    Directory of Open Access Journals (Sweden)

    Wei Li

    2016-12-01

    Full Text Available Mullite whiskers reinforced SiC/Al2O3 composites were prepared by microwave sintering in a microwave chamber with TE666 resonant mode. Original SiC particles were coated with SiO2 using sol-gel processing and mixed with Al2O3 particles. Mullite was formed in the reaction between SiO2 and Al2O3. The isostatically pressed cylindrical pellets were sintered from 1350 °C to 1600 °C for 30 min. Physical and chemical responses were investigated by detecting changes in reflected power during the microwave sintering process. XRD was carried out to characterize the samples and showed that mullite could be formed at 1200 °C. Bridging of mullite whiskers between Al2O3 and SiC particles was observed by SEM and is due to a so-called local hot spot effect, which was the unique feature for microwave sintering. The optimized microwave sintering temperature was 1500 °C corresponding to the maximum amount of mullite whiskers within SiC/Al2O3 composites. The high electro-magnetic field enhanced the decomposition of mullite at higher temperatures above 1550 °C. The mechanical properties of mullite whiskers reinforced SiC/Al2O3 composites are much better than the SiC/Al2O3 composites without mullite whiskers.

  3. Solid-state 27Al and 29Si NMR characterization of hydrates formed in calcium aluminate-silica fume mixtures

    International Nuclear Information System (INIS)

    Pena, P.; Rivas Mercury, J.M.; Aza, A.H. de; Turrillas, X.; Sobrados, I.; Sanz, J.

    2008-01-01

    Partially deuterated Ca 3 Al 2 (SiO 4 ) y (OH) 12-4y -Al(OH) 3 mixtures, prepared by hydration of Ca 3 Al 2 O 6 (C 3 A), Ca 12 Al 14 O 33 (C 12 A 7 ) and CaAl 2 O 4 (CA) phases in the presence of silica fume, have been characterized by 29 Si and 27 Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca 3 Al 2 (OH) 12 and Al(OH) 3 phases were detected. From the quantitative analysis of 27 Al NMR signals, the Al(OH) 3 /Ca 3 Al 2 (OH) 12 ratio was deduced. The incorporation of Si into the katoite structure, Ca 3 Al 2 (SiO 4 ) 3-x (OH) 4x , was followed by 27 Al and 29 Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of 27 Al MAS-NMR components associated with Al(OH) 6 and Al(OSi)(OH) 5 environments. The 29 Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C-S-H and C-A-S-H for short. From 29 Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures. - Graphical abstract: Transmission electron micrograph of CaAl 2 O 4 -microsilica mixture hydrated at 90 deg. C for 31 days showing a cubic Ca 3 Al 2.0±0.2 (SiO 4 ) 0.9±0.2 (OH) 1.8 crystal surrounded by unreacted amorphous silica spheres

  4. Effect of high power ultrasound on mechanical properties of Al-Si alloys

    Science.gov (United States)

    Srivastava, N.; Gupta, R.; Chaudhari, G. P.

    2018-03-01

    Effect of high power ultrasonic treatment on the solidification microstructures of Al-Si alloys containing varying content of solute Si (1, 2, 3 and 5 wt %) is investigated. Large variation in microstructures is seen and refinement of primary α-Al grains is observed. It is observed that increasing the weight percentage of solute along with ultrasonic treatment resulted in finer primary phase. By increasing the solute content from 1% to 5 wt.% in Al-Si alloys, hardness increased by about 38% without and 48% with ultrasonic treatment. Tensile strength of the alloys with ultrasonic treatment is higher as compared to those without ultrasonic treated.

  5. Al and Si Influences on Hydrogen Embrittlement of Carbide-Free Bainitic Steel

    Directory of Open Access Journals (Sweden)

    Yanguo Li

    2013-01-01

    Full Text Available A first-principle method based on the density functional theory was applied to investigate the Al and Si influences on the hydrogen embrittlement of carbide-free bainitic steel. The hydrogen preference site, binding energy, diffusion behaviour, and electronic structure were calculated. The results showed that hydrogen preferred to be at the tetrahedral site. The binding energy of the cell with Si was the highest and it was decreased to be the worst by adding hydrogen. The diffusion barrier of hydrogen in the cell containing Al was the highest, so it was difficult for hydrogen to diffuse. Thus, hydrogen embrittlement can be reduced by Al rather than Si.

  6. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    International Nuclear Information System (INIS)

    Huang, Yiqin; Li, Heqin; Zuo, Min; Tao, Lei; Wang, Wei; Zhang, Jing; Tang, Qiong; Bai, Peiwen

    2016-01-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB. - Highlights: • The same thick Al, SiC and SiC/Al films are deposited on NdFeB by magnetron sputtering. • 510 nm SiC/Al bilayer films can improve the corrosion resistance of the NdFeB evidently. • Al buffer layer improves effectively the surface roughness of the SiC thin film. • SiC/Al bilayer films do not deteriorate the magnetic properties of NdFeB.

  7. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yiqin [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Li, Heqin, E-mail: lhqjs@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zuo, Min; Tao, Lei; Wang, Wei [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zhang, Jing; Tang, Qiong [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009 (China); Bai, Peiwen [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China)

    2016-07-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB. - Highlights: • The same thick Al, SiC and SiC/Al films are deposited on NdFeB by magnetron sputtering. • 510 nm SiC/Al bilayer films can improve the corrosion resistance of the NdFeB evidently. • Al buffer layer improves effectively the surface roughness of the SiC thin film. • SiC/Al bilayer films do not deteriorate the magnetic properties of NdFeB.

  8. Chinese Script vs Plate-Like Precipitation of Beta-Al9Fe2Si2 Phase in an Al-6.5Si-1Fe Alloy

    Science.gov (United States)

    Ferdian, Deni; Josse, Claudie; Nguyen, Patrick; Gey, Nathalie; Ratel-Ramond, Nicolas; de Parseval, Philippe; Thebault, Yannick; Malard, Benoit; Lacaze, Jacques; Salvo, Luc

    2015-07-01

    The microstructure of a high-purity Al-6.5Si-1Fe (wt pct) alloy after solidification at various cooling rates was investigated. In most of the cases, the monoclinic beta-Al9Fe2Si2 phase was observed as long and thin lamellae. However, at a very slow cooling rate, Fe-bearing precipitates with Chinese script morphology appeared together with lamellae. Further analysis showed all these Chinese script precipitates correspond also to the monoclinic beta phase. This finding stresses that differentiating second phases according to their shape may be misleading.

  9. Investigations on Mechanical Behaviour of Micro Graphite Particulates Reinforced Al-7Si Alloy Composites

    Science.gov (United States)

    Nagaraj, N.; Mahendra, K. V.; Nagaral, Madeva

    2018-02-01

    Micro particulates reinforced metal matrix composites are finding wide range of applications in automotive and sports equipment manufacturing industries. In the present study, an attempt has been made to develop Al-7Si-micro graphite particulates reinforced composites by using liquid melt method. 3 and 6 wt. % of micro graphite particulates were added to the Al-7Si base matrix. Microstructural characterization was done by using scanning electron microscope and energy dispersive spectroscope. Mechanical behaviour of Al-7Si-3 and 6 wt. % composites were evaluated as per ASTM standards. Scanning electron micrographs revealed the uniform distribution of micro graphite particulates in the Al-7Si alloy matrix. EDS analysis confirmed the presence of B and C elements in graphite reinforced composites. Further, it was noted that ultimate tensile and yield strength of Al-7Si alloy increased with the addition of 3 and 6wt. % of graphite particulates. Hardness of graphite reinforced composites was lesser than the base matrix.

  10. Effects of combined additions of Sr and AlTiB grain refiners in hypoeutectic Al-Si foundry alloys

    International Nuclear Information System (INIS)

    Lu, L.; Dahle, A.K.

    2006-01-01

    Strontium is the most widely used and a very effective element for modifying the morphology of eutectic silicon, while Ti and B are commonly present in the commercial grain refiners used for Al-Si alloys. Systematic studies on the effects of combined additions of Sr and different AlTiB grain refiners on the Al + Si eutectic and primary aluminium solidification have been performed. While slight coarsening of both eutectic Si and primary aluminium grains occurs during holding, no obvious interactions are observed between Sr and AlTiB grain refiners when the addition level of grain refiners is low. As a result, a well-modified and grain refined structure was obtained. However, strong negative interactions between Sr and Al1.5Ti1.5B were observed as the addition level of the grain refiner increases. It was found that these interactions have a much more profound impact on the eutectic solidification than the primary Al solidification. The melt treated with combined additions of Sr and Al1.5Ti1.5B still shows good grain refinement efficiency even after losing its modification completely. The mechanism responsible for such negative interactions is further discussed

  11. Effects of combined additions of Sr and AlTiB grain refiners in hypoeutectic Al-Si foundry alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lu, L. [CSIRO Minerals, P.O. Box 883, Kenmore, Qld. 4069 (Australia)]. E-mail: Liming.Lu@csiro.au; Dahle, A.K. [CRC for Cast Metals Manufacturing, Division of Materials, School of Engineering, University of Queensland, Brisbane, Qld. 4072 (Australia)

    2006-11-05

    Strontium is the most widely used and a very effective element for modifying the morphology of eutectic silicon, while Ti and B are commonly present in the commercial grain refiners used for Al-Si alloys. Systematic studies on the effects of combined additions of Sr and different AlTiB grain refiners on the Al + Si eutectic and primary aluminium solidification have been performed. While slight coarsening of both eutectic Si and primary aluminium grains occurs during holding, no obvious interactions are observed between Sr and AlTiB grain refiners when the addition level of grain refiners is low. As a result, a well-modified and grain refined structure was obtained. However, strong negative interactions between Sr and Al1.5Ti1.5B were observed as the addition level of the grain refiner increases. It was found that these interactions have a much more profound impact on the eutectic solidification than the primary Al solidification. The melt treated with combined additions of Sr and Al1.5Ti1.5B still shows good grain refinement efficiency even after losing its modification completely. The mechanism responsible for such negative interactions is further discussed.

  12. Stability of the Al/TiB2 interface and doping effects of Mg/Si

    Science.gov (United States)

    Deng, Chao; Xu, Ben; Wu, Ping; Li, Qiulin

    2017-12-01

    The Al/TiB2 interface is of significant importance in controlling the mechanical properties of Al-B4C composites and tuning the heterogeneous nucleation of Al/Si alloys in industry. Its stability and bonding conditions are critical for both purposes. In this paper, the interfacial energies were investigated by first-principles calculations, and the results support the reported grain refinement mechanisms in Al/Si alloys. Moreover, to improve the mechanical properties of the interface, Mg and Si were doped at the interface, and our simulations show that the two interfaces will both weaken after doping Mg/Si, thus the formation of TiB2 is inhibited. As a result, the processability of the Al-B4C composites may be improved. Our results provide a theoretical basis and guidance for practical applications.

  13. Osteoblast Adhesion on Cathodic Arc Plasma Deposited Nano-Multilayered TiCrAlSiN Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sun Kyu [University of Ulsan, Ulsan (Korea, Republic of); Pham, Vuong Hung [Hanoi University of Science and Technology (HUST), Hanoi (Viet Nam)

    2014-03-15

    Adhesion of osteoblast cells to TiCrAlSiN thin films was evaluated in vitro. Ti and TiCrAlSiN thin films were deposited on glass substrates by cathodic arc deposition. Surface roughness and chemistry of the TiCrAlSiN thin films was characterized by AFM and EPMA, respectively. Ti and TiCrAlSiN thin films and glass coverslips were cultured with human osteoblast cells (hFOB 1.19). The cell cytoskeleton was analyzed by observing the organization of actin stress fibers and microtubules. Cell proliferation was investigated by MTT assay and visualization. Focal contact adhesion was studied by observing the vinculin density. The results indicated that the TiCrAlSiN coating significantly influenced the actin cytoskeleton and microtubule organization. Human osteoblasts hFOB attached and proliferated better on TiCrAlSiN thin films with more focal contact adhesions than on Ti thin films or glass surfaces. These results suggest that TiCrAlSiN thin films can be an implantable material where the maximum cell adhesion is required.

  14. Adherencia al tratamiento nutricional en pacientes con diabetes mellitus tipo 2 que asisten a un programa educativo

    Directory of Open Access Journals (Sweden)

    Mariela A. Carvajal

    2017-03-01

    Full Text Available El objetivo de este estudió fue evaluar la adherencia al tratamiento nutricional por medio de la hemoglobina glicosilada en pacientes con diabetes mellitus tipo 2 que asistieron a un programa educativo en diabetes en la ciudad de Guatemala, así como evaluar los principales factores que influyen en ella. Se realizó un estudio de tipo prospectivo, longitudinal, experimental, pareado de intervención no medicamentosa. Se utilizó la prueba de Morinsky-Green Levine para evaluar la adherencia al tratamiento nutricional, el cual consiste en cuatro preguntas de auto informe sobre la adherencia. La muestra estuvo conformada por 126 pacientes que recibieron una intervención educativa durante cinco meses. La metodología utilizada permitió analizar la adherencia al tratamiento por medio de la prueba de hemoglobina glicosilada, una encuesta de adherencia, evaluación del consumo por grupos de alimentos al inicio y al final. Uno de los principales hallazgos fue que los pacientes están convencidos que su plan nutricional les beneficia y les evitaría complicaciones. El apoyo familiar también juega un papel muy importante en la adherencia de estos pacientes al tratamiento nutricional. Los indicadores de adherencia que se encontraron más afectados son los relacionados al costo del plan de alimentación y la dificultad para seguirlo. Se concluye que es posible utilizar la hemoglobina glicosilada como un indicador efectivo de adherencia, ya que el porcentaje de pacientes con hemoglobina glicosilada controlada aumentó de un 50 a un 65.9% después de la intervención.

  15. Pitting Corrosion of Ni3(Si,Ti+4Al Intermetallic Compound at Various Chloride Concentrations

    Directory of Open Access Journals (Sweden)

    Gadang Priyotomo

    2014-04-01

    Full Text Available The pitting corrosion of Ni3(Si,Ti with 4 at% Al consisting of two regions of a Ni3(Si,Ti single-phase of L12 structure and two phases of L12 and fcc Niss was investigated as function of chloride concentrations by using electrochemical method, scanning electron microscope and energy dispersive X-Ray spectroscopy in neutral sodium chloride solutions at 293 K.  In addition, the pitting corrosion of Ni3(Si,Ti and  type C276 alloy were also studied under the same experimental condition for comparison.  The pitting potential obtained for the Ni3(Si,Ti with 4 at%Al decreased with increasing chloride concentration.  The specific pitting potential and pitting potential of Ni3(Si,Ti with 4at%, Ni3(Si,Ti and C276 were the lowest, the moderate and the highest, respectively, which means that the pitting corrosion resistance of Ni3(Si,Ti was higher than Ni3(Si,Ti with 4at% Al, but lower than that of C276.  A critical chloride concentration of Ni3(Si,Ti with 4at% Al was found to be lower than that of Ni3(Si,Ti.  The Pitting corrosion of Ni3(Si,Ti with 4at% Al occurred in the two phase mixture (L12 + Niss.

  16. Microstructure of the irradiated U 3Si 2/Al silicide dispersion fuel

    Science.gov (United States)

    Gan, J.; Keiser, D. D.; Miller, B. D.; Jue, J.-F.; Robinson, A. B.; Madden, J. W.; Medvedev, P. G.; Wachs, D. M.

    2011-12-01

    The silicide dispersion fuel of U 3Si 2/Al is recognized as the best performance fuel for many nuclear research and test reactors with up to 4.8 gU/cm 3 fuel loading. An irradiated U 3Si 2/Al dispersion fuel ( 235U ˜ 75%) from the high-flux side of a fuel plate (U0R040) from the Reduced Enrichment for Research and Test Reactors (RERTR)-8 test was characterized using transmission electron microscopy (TEM). The fuel was irradiated in the Advanced Test Reactor (ATR) for 105 days. The average irradiation temperature and fission density of the U 3Si 2 fuel particles for the TEM sample are estimated to be approximately 110 °C and 5.4 × 10 27 f/m 3. The characterization was performed using a 200-kV TEM. The U/Si ratio for the fuel particle and (Si + Al)/U for the fuel-matrix-interaction layer are approximately 1.1 and 4-10, respectively. The estimated average diameter, number density and volume fraction for small bubbles (<1 μm) in the fuel particle are ˜94 nm, 1.05 × 10 20 m -3 and ˜11%, respectively. The results and their implication on the performance of the U 3Si 2/Al silicide dispersion fuel are discussed.

  17. Heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-Si alloys investigated by entrained droplet technique and DSC

    International Nuclear Information System (INIS)

    Li, J H; Schumacher, P; Albu, M; Hofer, F; Ludwig, T H; Arnberg, L

    2016-01-01

    Entrained droplet technique and DSC analyses were employed to investigate the influence of trace elements of Sr, Eu and P on the heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-5wt.% Si alloys. Sr and Eu addition was found to exert negative effects on the nucleation process, while an increased undercooling was observed. This can be attributed to the formation of phosphide compounds having a lower free energy and hence may preferentially form compared to AlP. Only a trace P addition was found to have a profound effect on the nucleation process. The nucleation kinetics is discussed on the basis of the classical nucleation theory and the free growth model, respectively. The estimated AlP patch size was found to be sufficient for the free growth of Si to occur within the droplets, which strongly indicates that the nucleation of Si on an AlP patch or AlP particle is a limiting step for free growth. The maximum nucleation site density within one droplet is directly related to the size distribution of AlP particles or AlP patches for Si nucleation, but is independent of the cooling rates. Although the nucleation conditions were optimized in entrained droplet experiments, the observed mechanisms are also valid at moderate cooling conditions, such as in shape casting. (paper)

  18. Influence of copper content on microstructure development of AlSi9Cu3 alloy

    Directory of Open Access Journals (Sweden)

    Brodarac Zovko Z.

    2014-01-01

    Full Text Available Microstructure development and possible interaction of present elements have been determined in charge material of EN AlSi9Cu3 quality. Literature review enables prediction of solidification sequence. Modelling of equilibrium phase diagram for examined chemical composition has been performed, which enables determination of equilibrium solidification sequence. Microstructural investigation indicated distribution and morphology of particular phase. Metallographic analysis tools enable exact determination of microstructural constituents: matrix αAl, eutectic αAl+βSi, iron base intermetallic phase - Al5FeSi, Alx(Fe,MnyCuuSiw and/or Alx(Fe,MnyMgzCuuSiw and copper base phases in ternary eutectic morphology Al-Al2Cu-Si and in complex intermetallic ramified morphology Alx(Fe,MnyMgzSiuCuw. Microstructure development examination reveals potential differences due to copper content which is prerequisite for high values of final mechanical, physical and technological properties of cast products.

  19. Microstructure of as-fabricated UMo/Al(Si) plates prepared with ground and atomized powder

    Science.gov (United States)

    Jungwirth, R.; Palancher, H.; Bonnin, A.; Bertrand-Drira, C.; Borca, C.; Honkimäki, V.; Jarousse, C.; Stepnik, B.; Park, S.-H.; Iltis, X.; Schmahl, W. W.; Petry, W.

    2013-07-01

    UMo-Al based fuel plates prepared with ground U8wt%Mo, ground U8wt%MoX (X = 1 wt%Pt, 1 wt%Ti, 1.5 wt%Nb or 3 wt%Nb) and atomized U7wt%Mo have been examined. The first finding is that that during the fuel plate production the metastable γ-UMo phases partly decomposed into two different γ-UMo phases, U2Mo and α'-U in ground powder or α″-U in atomized powder. Alloying small amounts of a third element to the UMo had no measurable effect on the stability of the γ-UMo phase. Second, the addition of some Si inside the Al matrix and the presence of oxide layers in ground and atomized samples is studied. In the case with at least 2 wt%Si inside the matrix a Silicon rich layer (SiRL) forms at the interface between the UMo and the Al during the fuel plate production. The SiRL forms more easily when an Al-Si alloy matrix - which is characterized by Si precipitates with a diameter ⩽1 μm - is used than when an Al-Si mixed powder matrix - which is characterized by Si particles with some μm diameter - is used. The presence of an oxide layer on the surface of the UMo particles hinders the formation of the SiRL. Addition of some Si into the Al matrix [7-11]. Application of a protective barrier at the UMo/Al interface by oxidizing the UMo powder [7,12]. Increase of the Mo content or use of UMo alloys with ternary element addition X (e.g. X = Nb, Ti, Pt) to stabilize the γ-UMo with respect to α-U or to control the UMo-Al interaction layer kinetics [9,12-24]. Use of ground UMo powder instead of atomized UMo powder [10,25] The points 1-3 are to limit the formation of the undesired UMo/Al layer. Especially the addition of Si into the matrix has been suggested [3,7,8,10,11,26,27]. It has been often mentioned that Silicon is efficient in reducing the Uranium-Aluminum diffusion kinetics since Si shows a higher chemical affinity to U than Al to U. Si suppresses the formation of brittle UAl4 which causes a huge swelling during the irradiation. Furthermore it enhances the

  20. Cast AlSi9Cu4 alloy with hybride strenghtened by Fe{sub x}Al{sub y}-Al{sub 2}O{sub 3} composite powder

    Energy Technology Data Exchange (ETDEWEB)

    Piatkowski, J [Department of Materials Technology, Silesian University of Technology, Krasinskiego 8, 40-019 Katowice (Poland); Formanek, B, E-mail: jaroslaw.piatkowski@polsl.pl, E-mail: boleslaw.formanek@polsl.pl [Department of Materials Science, Silesian University of Technology, Krasinskiego 8, 40-019 Katowice (Poland)

    2011-05-15

    The main objective of the study was to develop a technology of dispersion strenghtened hypoeutectic Al-Si alloy. The article presented the materials and technology conception for producing aluminium matrix composite AlSi9Cu4Fe alloy with hybride reinforcement of Al{sub x}Fe{sub y} intermetallic and aluminium oxide powders. Composite powder obtained in mechanical agllomerisation mixture of elemental powders. Changes in the structure were confirmed by TA and ATD thermal analyses plotting the solidification curves, which showed a decrease in temperature T{sub liq} compared to the unmodified alloy and an exothermic effect originating from the crystallisation of eutectics with alloying elements. The examinations carried out by SEM and BSE as well as the determination of local chemical composition by EDX technique have characterised the structure of the alloy as containing some binary Al-Si-Al-Cu and Al-Fe eutectics and multicomponent eutectics.

  1. Microstructure of AlSi17Cu5 alloy after overheating over liquidus temperature

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2015-01-01

    Full Text Available The paper presents microstructure tests of alloy AlSi17Cu5. In order to disintegrate the primary grain of silicon the so-called time-temperature transformation TTT was applied which was based on overheating the liquid alloy way over the temperature Tliq., soaking in it for 30 minutes and casting it to a casting mould. It was found that such process causes the achievement of fine-crystalline structure and primary silicon crystals take up the form of pentahedra or frustums of pyramids. With the use of X-ray microanalysis and X-ray diffraction analysis the presence of intermetallic phases Al2Cu, Al4Cu9 which are the ingredients of eutectics α - AlCu - β and phase Al9Fe2Si which is a part of eutectic α - AlFeSi - β was confirmed.

  2. Structure and chemistry of the Si(111)/AlN interface

    Science.gov (United States)

    Radtke, G.; Couillard, M.; Botton, G. A.; Zhu, D.; Humphreys, C. J.

    2012-01-01

    We investigate the atomic structure and the chemistry of the Si(111)/AlN interface for an AlN film grown at low-temperature (735 °C) by metalorganic vapor phase epitaxy. A heterogeneous interface is formed from the alternation of crystallographically abrupt and partly amorphous regions. The polarity of the AlN film, along with the projected atomic structure of the crystalline interface, is retrieved using high-angle annular dark field imaging, and a model, based on these experimental observations, is proposed for the bonding at the interface. Electron energy-loss spectrum-imaging, however, also reveals a chemical intermixing, placing our growth conditions at the onset of SiNx interlayer formation.

  3. Kinetic studies of oxidation of MgAlON and a comparison of the oxidation behaviour of AlON, MgAlON, O'SiAlON-ZrO{sub 2}, and BN-ZCM ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xidong; Seetharaman, S. [Div. of Metallurgy, Royal Inst. of Tech., Stockholm (Sweden); Li Wenchao [Dept. of Physical Chemistry, Univ. of Science and Technology Beijing (USTB), Beijing, BJ (China)

    2002-06-01

    The kinetics and morphology of the oxidation process of magnesium-aluminium oxynitride (MgAlON), aluminium oxynitride (AlON), O'SiAlON-ZrO{sub 2}, and BN-ZCM have been studied in the temperature range 1373-1773 K (ZCM=30 wt% ZrO{sub 2}, 52 wt% Al{sub 2}O{sub 3} and 18 wt% 3 Al{sub 2}O{sub 3}.2 SiO{sub 2}). Oxidation experiments with powder and plate samples of the above materials have been carried out in air. MgAlON shows the best resistance to oxidation at lower temperatures (< 1473 K), whereas at higher temperatures ({proportional_to} 773 K), AlON shows the best resistance. O'SiAlON-ZrO{sub 2} shows very good oxidation resistance up to 1673 K. But its oxidation rate increases strongly above 1673 K, presumably due to the formation of liquid phase. BN-ZCM has the poorest oxidation resistance due to the evaporation of B{sub 2}O{sub 3}. The activation energies for the chemical oxidation reaction of AlON, MgAlON, and O'SiAlON-ZrO{sub 2} are 214, 330 and 260 kJ/mol, respectively. The overall diffusion activation energies for AlON, MgAlON, O'SiAlON-ZrO{sub 2} and BN-ZCM are 227, 573, 367 and 289 kJ/mol, respectively. (orig.)

  4. Semisolid casting with ultrasonically melt-treated billets of Al-7mass%Si alloys

    Directory of Open Access Journals (Sweden)

    Yoshiki Tsunekawa

    2012-02-01

    Full Text Available The demand for high performance cast aluminum alloy components is often disturbed by increasing impurity elements, such as iron accumulated from recycled scraps. It is strongly required that coarse plate-like iron compound of モ-Al5FeSi turns into harmless form without the need for applying refining additives or expensive virgin ingots. The microstructural modification of Al-7mass%Si alloy billets with different iron contents was examined by applying ultrasonic vibration during the solidification. Ultrasonically melt-treated billets were thixocast right after induction heating up to the semisolid temperature of 583 ìC, the microstructure and tensile properties were evaluated in the thixocast components. Globular primary メ-Al is required to fill up a thin cavity in thixocasting, so that the microstructural modification by ultrasonic melt-treatment was firstly confirmed in the billets. With ultrasonic melt-treatment in the temperature range of 630 ìC to 605 ìC, the primary メ-Al transforms itself from dendrite into fine globular in morphology. The coarse plate-like モ-Al5FeSi compound becomes markedly finer compared with those in non-treated billets. Semisolid soaking up to 583 ìC, does not appreciably affect the size of モ-Al5FeSi compounds; however, it affects the solid primary メ-Al morphology to be more globular, which is convenient for thixocasting. After thixocasting with preheated billets, eutectic silicon plates are extremely refined due to the rapid solidification arising from low casting temperature. The tensile strength of thixocast samples with different iron contents does not change much even at 2mass% of iron, when thixocast with ultrasonically melt-treated billets. However, thixocast Al-7mass%Si-2mass%Fe alloy with non-treated billets exhibits an inferior strength of 80 MPa, compared with 180 MPa with ultrasonically melt-treated billets. The elongation is also improved by about a factor of two in thixocastings with

  5. Investigation of nanocrystalline Epi-Si/γ-Al2O3 heterostructure deposited on Si substrate by spectroscopic ellipsometry

    International Nuclear Information System (INIS)

    Khatun, Mosammat Halima; Shahjahan, Mohammad; Ito, Ryoki; Sawada, Kazuaki; Ishida, Makoto

    2006-01-01

    In this work, micro-structural and interfacial studies of the epi-Si/γ-Al 2 O 3 heterostructure were undertaken by spectroscopic ellipsometry, and compared with the results of atomic force microscopy and X-ray photoelectron spectroscopy. The experimental ellipsometric data were fitted with the theoretical calculations using effective medium approximation for each layer of the structure. It was observed that the epitaxial silicon layer consists of a fraction of amorphous Si and crystalline Si. The percentage of amorphous silicon increases with the decrease of deposition temperature and with the increase of the deposition rate. The γ-Al 2 O 3 layer produces a hydrostatic pressure on the Si substrate and the amount of hydrostatic pressure was measured to be 8 x 10 9 dyn/cm 2

  6. Tensile behaviour at room and high temperatures of novel metal matrix composites based on hyper eutectic Al-Si alloys

    International Nuclear Information System (INIS)

    Valer, J.; Rodriguez, J.M.; Urcola, J.J.

    1997-01-01

    This work shows the improvement obtained on tensile stress at room and high temperatures of hyper eutectic Al-Si alloys. These alloys are produced by a combination of spray-forming, extrusion and thixoforming process, in comparison with conventional casting alloys.Al-25% Si-5%Cu. Al-25%Si-5%Cu-2%Mg and Al-30%Si-5%Cu alloys have been studied relating their microstructural parameters with tensile stress obtained and comparing them with conventional Al-20%Si. Al-36%Si and Al-50%Si alloys. Al-25%Si-5%Cu alloy-was tested before and after semi-solid forming, in order to distinguish the different behaviour of this alloy due to the different microstructure. The properties obtained with these alloys were also related to Al-SiC composites formed by similar processes. (Author) 20 refs

  7. Thermal phase separation of ZrSiO4 thin films and frequency- dependent electrical characteristics of the Al/ZrSiO4/p-Si/Al MOS capacitors

    Science.gov (United States)

    Lok, R.; Kaya, S.; Yilmaz, E.

    2018-05-01

    In this work, the thermal phase separation and annealing optimization of ZrSiO4 thin films have been carried out. Following annealing optimization, the frequency-dependent electrical characteristics of the Al/ZrSiO4/p-Si/Al MOS capacitors were investigated in detail. The chemical evolution of the films under various annealing temperatures was determined by Fourier transform infrared spectroscopy (FTIR) measurements. The phase separation was determined by x-ray diffraction (XRD) measurements. The electrical parameters were determined via the capacitance–voltage (C–V), conductance–voltage (G/ω) and leakage-current–voltage (Ig–Vg ). The results demonstrate that zirconium silicate formations are present at 1000 °C annealing with the SiO2 interfacial layer. The film was in amorphous form after annealing at 250 °C. The tetragonal phases of ZrO2 were obtained after annealing at 500 °C. When the temperature approaches 750 °C, transitions from the tetragonal phase to the monoclinic phase were observed. The obtained XRD peaks after 1000 °C annealing matched the crystalline peaks of ZrSiO4. This means that the crystalline zirconium dioxide in the structure has been converted into a crystalline silicate phase. The interface states increased to 5.71 × 1010 and the number of border traps decreased to 7.18 × 1010 cm‑2 with the increasing temperature. These results indicate that an excellent ZrSiO4/Si interface has been fabricated. The order of the leakage current varied from 10‑9 Acm‑2 to 10‑6 Acm‑2. The MOS capacitor fabricated with the films annealed at 1000 °C shows better behavior in terms of its structural, chemical and electrical properties. Hence, detailed frequency-dependent electrical characteristics were performed for the ZrSiO4 thin film annealed at 1000 °C. Very slight capacitance variations were observed under the frequency variations. This shows that the density of frequency-dependent charges is very low at the ZrSiO4/Si interface. The

  8. Coating of Si3N4 fine particles with AlN by fluidized bed-CVD; Ryudoso CVD ho ni yoru Si3N4 biryushi no AlN hifuku

    Energy Technology Data Exchange (ETDEWEB)

    Chiba, S.; Oyama, Y. [Hokkaido National Industrial Research Institute, Sapporo (Japan); Harima, K.; Kondo, K.; Shinohara, K. [Hokkaido University, Sapporo (Japan)

    1996-03-10

    Agglomerates of 100-250 {mu}m consisting of Si3N4 primary particles of 0.76 {mu}m were made with a rotary vibrating sieve. Si3N4 fine particles were coated with AlN by gas phase reaction with AlCl3 and NH3 in some fluidized beds of the agglomerates. The cross sectional distribution of AlN in the agglomerate was measured by EPMA analysis. As a result, uniform deposition of AlN was obtained at a relatively low reaction temperature and low gas velocity. 4 refs., 3 figs.

  9. A study of Al/Si interface by photoemission, Auger electron yield and Auger electron spectroscopies

    International Nuclear Information System (INIS)

    Kobayashi, K.L.I.; Barth, J.; Gerken, F.; Kunz, C.; Deutsches Elektronen-Synchrotron

    1980-06-01

    Photoemission, Auger electron yield and Auger electron spectra were observed for Al/Si(111) interfaces with various Al coverage prepared by successive deposition using a molecular beam source. The Al 3p derived states are introduced at around the top of the valence band by the Al coverage of less than one monolayer. The Al surface layer behaves as a 'metal' and the Fermi level is stabilized in the Al 3p derived states at about 0.3 eV above the top of the valence band of Si. The Schottky barrier height in this stage is about 0.8 eV and further increase in Al coverage does not change the barrier height. A covalent bonding model of the Al/Si interface based on the experimental results is proposed. The present result favors the on-top geometry of Al atoms on Si(111) surface among the geometries used in the pseudopotential calculation by Zhang and Schlueter. (orig.)

  10. Y-Si-Al-O-N Glass Fibers.

    Science.gov (United States)

    The excellent mechanical properties and outstanding water corrosion resistance of Y -Si-Al-O- N glasses indicate that they are attractive candidate...materials for forming into high performance glass fibers. Fibers of glasses containing, respectively,3.2 and 6.6 wt% N were drawn freehand in air, and

  11. Electron excitations in BeAl2O4, Be2SiO4 and Be3Al2Si6O18 crystals

    International Nuclear Information System (INIS)

    Ivanov, V.Yu.; Pustovarov, V.A.; Shlygin, E.S.; Korotaev, A.V.; Kruzhalov, A.V.

    2005-01-01

    Low-temperature (T = 7 K) time-resolved selectively photoexcited luminescence spectra (2-6 eV) and luminescence excitation spectra (8-35 eV) of wide-bandgap chrysoberyl BeAl 2 O 4 , phenacite Be 2 SiO 4 , and beryl Be 3 Al 2 Si 6 O 18 crystals have been studied using time-resolved VUV spectroscopy. Both the intrinsic luminescence of the crystals and the luminescence associated with structural defects were assigned. Energy transfer to impurity luminescence centers in alexandrite and emerald was investigated. Luminescence characteristics of stable crystal lattice defects were probed by 3.6-MeV accelerated helium ion beams [ru

  12. Thermal stability and chemical bonding states of AlOxNy/Si gate stacks revealed by synchrotron radiation photoemission spectroscopy

    International Nuclear Information System (INIS)

    He, G.; Toyoda, S.; Shimogaki, Y.; Oshima, M.

    2010-01-01

    Annealing-temperature dependence of the thermal stability and chemical bonding states of AlO x N y /SiO 2 /Si gate stacks grown by metalorganic chemical vapor deposition (MOCVD) using new chemistry was investigated by synchrotron radiation photoemission spectroscopy (SRPES). Results have confirmed the formation of the AlN and AlNO compounds in the as-deposited samples. Annealing the AlO x N y samples in N 2 ambient in 600-800 deg. C promotes the formation of SiO 2 component. Meanwhile, there is no formation of Al-O-Si and Al-Si binding states, suggesting no interdiffusion of Al with the Si substrate. A thermally induced reaction between Si and AlO x N y to form volatile SiO and Al 2 O is suggested to be responsible for the full disappearance of the Al component that accompanies annealing at annealing temperature of 1000 deg. C. The released N due to the breakage of the Al-N bonding will react with the SiO 2 interfacial layer and lead to the formation of the Si 3 -N-O/Si 2 -N-O components at the top of Si substrate. These results indicate high temperature processing induced evolution of the interfacial chemistry and application range of AlO x N y /Si gate stacks in future CMOS devices.

  13. Abrasive Wear of AlSi12-Al2O3 Composite Materials Manufactured by Pressure Infiltration

    Directory of Open Access Journals (Sweden)

    Kremzer M.

    2016-09-01

    Full Text Available The aim of this study is to investigate tribological properties of EN AC-AlSi12 alloy composite materials matrix manufactured by pressure infiltration of Al2O3 porous preforms. In the paper, a technique of manufacturing composite materials was described in detail as well as wear resistance made on pin on disc was tested. Metallographic observations of wear traces of tested materials using stereoscopic and confocal microscopy were made. Studies allow concluding that obtained composite materials have much better wear resistance than the matrix alloy AlSi12. It was further proved that the developed technology of their preparation consisting of pressure infiltration of porous ceramic preforms can find a practical application.

  14. Effect of AlN doping on the growth morphology of SiC

    Energy Technology Data Exchange (ETDEWEB)

    Singh, N.B.; Jones, E.; Berghmans, A.; Wagner, B.P.; Jelen, E.; McLaughlin, S.; Knuteson, D.J.; Fitelson, M.; King, M.; Kahler, D. [Northrop Grumman Corporation, ES-ATL, Linthicum, MD (United States)

    2009-09-15

    AlN doped SiC films were deposited on on-axis Si-face 4H-SiC(0001) substrates by the physical vapor transport (PVT) method. Thick film in the range of 20 {mu}m range was grown and morphology was characterized. Films were grown by physical vapor deposition (PVD) in a vertical geometry in the nitrogen atmosphere. We observed that nucleation occurred in the form of discs and growth occurred in hexagonal geometry. The X-ray studies showed (001)orientation and full width of half maxima (FWHM) was less than 0.1 indicating good crystallinity. We also observed that film deposited on the carbon crucible had long needles with anisotropic growth very similar to that of pure AlN. Some of the needles grew up to sizes of 200{mu}m in length and 40 to 50 {mu}m in width. It is clear that annealing of SiC-AlN powder or high temperature physical vapor deposition produces similar crystal structure for producing AlN-SiC solid solution. SEM studies indicated that facetted hexagons grew on the top of each other and coarsened and merged to form cm size grains on the substrate. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. On the stability of large-area Al-p-Si junction

    International Nuclear Information System (INIS)

    Tsyganov, Yu.S.

    2006-01-01

    Design of silicon radiation detector made of 12 kΩ · cm p-silicon with both amine- and amine-free hardeners epoxy resin junction edge passivation is presented. Before producing large-area detectors for measurements of efficiency of evaporation residues collection at the focal plane of the Dubna Gas-Filled Recoil Separator (DGFRS), a set of small-area test detectors was produced. Stability of the Al-(p)Si junction has been studied for a long time. Estimate of a realistic lifetime for the mentioned type of Al-Si rectifying junction is done

  16. Competitiveness of ALS inhibitors resistant and susceptible biotypes of Greater Beggarticks (Bidens subalternans Competitividade de biótipos de Picão-Preto (Bidens subalternans Resistente e euscetível aos inibidores da ALS

    Directory of Open Access Journals (Sweden)

    F.P. Lamego

    2011-06-01

    Full Text Available The continuous use of ALS-inhibiting herbicides has led to the evolution of herbicide-resistant weeds worldwide. Greater beggarticks is one of the most troublesome weeds found in the soybean production system in Brazil. Recently, a greater beggarticks biotype that is resistant (R to ALS inhibitors due to Trp574Leu mutation in the ALS gene was identified. Also, the adaptive traits between susceptible (S and R to ALS inhibitors biotypes of greater beggarticks were compared. Specifically, we aimed to: (1 evaluate and compare the relative growth rates (RGR between the biotypes; (2 analyze the seed germination characteristics of R and S biotypes under different temperature conditions; and (3 evaluate their competitive ability in a replacement series study. The experiments were conducted at the University of Arkansas, USA, in 2007 and at Universidade Federal do Rio Grande do Sul (Federal University of Rio Grande do Sul, Brazil, in 2008. Plant proportions for replacement series studies were respectively 100:0, 75:25, 50:50, 25:75 and 0:100, with a total population of 150 plants m-2. There was no difference in RGR between R and S biotypes. The R-biotype germination rate was lower than that of the S biotype. However, at low temperature conditions (15 ºC, the reverse was observed. In general, there is no difference in the competitive ability between R and S greater beggarticks biotypes.O uso contínuo de herbicidas inibidores da ALS tem levado à evolução de plantas daninhas resistentes mundialmente. Picão-preto é uma das mais importantes plantas daninhas no sistema de produção de soja no Brasil. Recentemente, foi identificado um biótipo de picao-preto resistente (R aos inibidores da ALS devido à mutação Trp574Leu no gene ALS. Também, foram comparadas características adaptativas entre biótipos de picao-preto suscetível (S e R aos inibidores da ALS. Especificamente, os objetivos deste trabalho foram: (1 avaliar e comparar o crescimento

  17. Characteristics of heterojunctions of amorphous LaAlO2.73 on Si

    International Nuclear Information System (INIS)

    Huang Yanhong; Zhao Kun; Lu Huibin; Jin Kuijuan; He Meng; Chen Zhenghao; Zhou Yueliang; Yang Guozhen

    2006-01-01

    High-quality heterojunctions consisting of n-type amorphous LaAlO 3- δ and p-type Si without Si interfacial layer were prepared using a thin film deposition system normally used for laser-molecular beam epitaxy. Good I-V rectifying property, ferroelectricity of interface enhancement and fast photovoltaic effect have been observed in the LaAlO 3- δ /Si p-n heterojunctions. We expect that the multifunctional properties of rectification, ferroelectricity and photovoltaic effect should open up new possibilities in device development and other applications

  18. Thermal Conductivity and High-Frequency Dielectric Properties of Pressureless Sintered SiC-AlN Multiphase Ceramics

    Directory of Open Access Journals (Sweden)

    Jialin Gu

    2018-06-01

    Full Text Available SiC-AlN multiphase ceramics with 10 wt. %Y2O3-BaO-SiO2 additives were fabricated by pressureless sintering in a nitrogen atmosphere. The effects of SiC contents and sintering temperatures on the sinterability, microstructure, thermal conductivity and high-frequency dielectric properties were characterized. In addition to 6H-SiC and AlN, the samples also contained Y3Al5O12 and Y4Al2O9. SiC-AlN ceramics sintered with 50 wt. % SiC at 2173 K exhibited the best thermal diffusivity and thermal conductivity (26.21 mm2·s−1 and 61.02 W·m−1·K−1, respectively. The dielectric constant and dielectric loss of the sample sintered with 50 wt. % SiC and 2123 K were 33–37 and 0.4–0.5 at 12.4–18 GHz. The dielectric constant and dielectric loss of the samples decreased as the frequency of electromagnetic waves increased from 12.4–18 GHz. The dielectric thermal conductivity properties of the SiC-AlN samples are discussed.

  19. Cell adhesion to cathodic arc plasma deposited CrAlSiN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sun Kyu, E-mail: skim@ulsan.ac.kr [School of Materials Science and Engineering, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Pham, Vuong-Hung [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kim, Chong-Hyun [Department of Food Science, Cornell University, Ithaca, NY 14853 (United States)

    2012-07-01

    Osteoblast cell response (cell adhesion, actin cytoskeleton and focal contact adhesion as well as cell proliferation) to CrN, CrAlSiN and Ti thin films was evaluated in vitro. Cell adhesion and actin stress fibers organization depended on the film composition significantly. Immunofluorescent staining of vinculin in osteoblast cells showed good focal contact adhesion on the CrAlSiN and Ti thin films but not on the CrN thin films. Cell proliferation was significantly greater on the CrAlSiN thin films as well as on Ti thin films than on the CrN thin films.

  20. In Situ Synthesis of Al-Si-Cu Alloy During Brazing Process and Mechanical Property of Brazing Joint

    Directory of Open Access Journals (Sweden)

    LONG Wei-min

    2016-06-01

    Full Text Available The Al-Si-Cu alloy system is considered to be a promising choice of filler metal for aluminium alloys brazing due to its high strength and low melting point. The greatest obstacle is its lack of plastic forming ability and being difficult to be processed by conventional methods. This disadvantage is ascribed to the considerable amount of brittle CuAl2 intermetallic compound which forms when alloy composition is around the ternary eutectic point. In order to overcome this deficiency, authors of this article proposed to synthesize Al-Si-Cu filler metal by using in situ synthesis method, and the structure and properties of brazing joints were studied. The results show that AlSi alloy is used as the wrap layer, and CuAl alloy is used as the powder core in the composite brazing wire, the two alloys have similar melting points. The machinability of the composite brazing wire is much superior to the traditional Al-Si-Cu filler metal. During the induction brazing of 3A21 alloy, when using AlSi-CuAl composite filler wire, AlSi and CuAl alloys melt almost simultaneously, then after short time holding, Al-Si-Cu braze filler is obtained, the brazing seam has uniform composition and good bonding interface, also, the shearing strength of the brazing joints is higher than the joint brazed by conventional Al-Si-Cu filler metal.

  1. The [sup 26]Al(p,[gamma])[sup 27]Si reaction at low stellar temperature

    Energy Technology Data Exchange (ETDEWEB)

    Champagne, A E [North Carolina Univ., Chapel Hill, NC (United States). Dept. of Physics and Astronomy Duke Univ., Durham, NC (United States). Triangle Universities Nuclear Lab.; Brown, B A [Michigan State Univ., East Lansing, MI (United States). Dept. of Physics and Astronomy Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab.; Sherr, R [Princeton Univ., NJ (United States). Dept. of Physics

    1993-05-03

    Shell-model calculations have been used to predict the locations of states in [sup 27]Si which are analogous to well-studied states in [sup 27]Al. From this, we have determined the resonance properties of the known states in [sup 27]Si near the [sup 26]Al+p threshold. The resulting thermonuclear reaction rate is uncertain by about a factor of ten at low temperatures, but it appears that the [sup 26]Al(p, [gamma])[sup 27]Si reaction is too slow to destroy a significant amount of [sup 26]Al at these temperatures. (orig.)

  2. Novel composites of β-SiAlON and radome manufacturing ...

    Indian Academy of Sciences (India)

    2017-07-08

    Jul 8, 2017 ... radome applications, (ii) designing of an AlN-free precursor mixture for consolidating ... radomes with very high-production yields and (vi) development of an ... (about 4 mm thick) of β-SiAlON prototype radome manufactured at.

  3. The chemical phenol extraction of intermetallic particles from casting AlSi5Cu1Mg alloy.

    Science.gov (United States)

    Mrówka-Nowotnik, G; Sieniawski, J; Nowotnik, A

    2010-03-01

    This paper presents a chemical extraction technique for determination of intermetallic phases formed in the casting AlSi5Cu1Mg aluminium alloy. Commercial aluminium alloys contain a wide range of intermetallic particles that are formed during casting, homogenization and thermomechanical processing. During solidification, particles of intermetallics are dispersed in interdendritic spaces as fine primary phases. Coarse intermetallic compounds that are formed in this aluminium alloy are characterized by unique atomic arrangement (crystallographic structure), morphology, stability, physical and mechanical properties. The volume fraction, chemistry and morphology of the intermetallics significantly affect properties and material behaviour during thermomechanical processing. Therefore, accurate determination of intermetallics is essential to understand and control microstructural evolution in Al alloys. Thus, in this paper it is shown that chemical phenol extraction method can be applied for precise qualitative evaluation. The results of optical light microscopy LOM, scanning electron microscopy SEM and X-ray diffraction XRD analysis reveal that as-cast AlSi5Cu1Mg alloy contains a wide range of intermetallic phases such as Al(4)Fe, gamma- Al(3)FeSi, alpha-Al(8)Fe(2)Si, beta-Al(5)FeSi, Al(12)FeMnSi.

  4. Crack-resistant Al2O3–SiO2 glasses

    Science.gov (United States)

    Rosales-Sosa, Gustavo A.; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki

    2016-01-01

    Obtaining “hard” and “crack-resistant” glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3–(100–x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3–SiO2 glasses. In particular, the composition of 60Al2O3•40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses. PMID:27053006

  5. Electron density distribution and disordered crystal structure of 8H-SiAlON, Si3−xAl1+xOxN5−x (x∼2.2)

    International Nuclear Information System (INIS)

    Banno, Hiroki; Asaka, Toru; Fukuda, Koichiro

    2014-01-01

    The 8H-SiAlON crystal with general formula Si 3−x Al 1+x O x N 5−x was characterized using laboratory X-ray powder diffraction (CuKα 1 ), transmission electron microscopy and energy dispersive X-ray spectroscopy. The [Si: Al] molar ratios were determined to be [0.21(1): 0.79(1)], corresponding to x=2.2(1). The Si 0.8(1) Al 3.2(1) O 2.2(1) N 2.8(1) compound is hexagonal with space group P6 3 /mmc (Z=2). The unit-cell dimensions are a=0.298877(8) nm, c=2.30872(5) nm and V=0.178602(8) nm 3 . The initial structural model was successfully derived by the charge-flipping method and further refined by the Rietveld method. The final structural model showed the positional disordering of two of the three (Si,Al) sites. The maximum-entropy method-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were R wp =4.74%, S (=R wp /R e )=1.30, R p =3.40%, R B =1.04% and R F =0.74%. The disordered crystal structure was successfully described by overlapping four types of domains with ordered atom arrangements. The distribution of atomic positions in each of the domains can be achieved in the space group P6 3 mc. Two of the four types of domains are related by a pseudo-symmetry inversion, and the two remaining domains also have each other the inversion pseudo-symmetry. - Graphical abstract: Bird's eye view of electron densities up to 49.3% (0.071 nm −3 ) of the maximum on the plane parallel to (110) with the corresponding atomic arrangements of Si 0.8 Al 3.2 O 2.2 N 2.8 . - Highlights: • Crystal structure of Si 0.8 Al 3.2 O 2.2 N 2.8 is determined by laboratory X-ray powder diffraction. • The atom arrangements are represented by the split-atom model. • The maximum-entropy method-based pattern fitting method is used to confirm the validity of the model. • The disordered structure is described

  6. Natural gels: crystal-chemistry of short range ordered components in Al, Fe, and Si systems

    International Nuclear Information System (INIS)

    Ildefonse, Ph.; Calas, G.

    1997-01-01

    In this review, the most important inorganic natural gels are presented: opal, aluminosilicate (allophanes) and hydrous iron oxides and silicates. It is demonstrated that natural gels are ordered at the atomic scale. In allophanes, Al is distributed between octahedral and tetrahedral sites. The amount of Al increases as Al/Si ratio decreases. Si-rich allophane have a local structure around Al and Si very different of that is known in kaolinite or halloysite. Transformation of Si-rich allophanes to crystallized minerals implies dissolution-recrystallization processes. On the contrary, in iron silicate with Fe/Si = 0.72, Si and Fe environments are close to those found in nontronite. The gel transformation to Fe-smectite may occur by long range ordering during ageing. In ferric silicate gels, the similarity of local structure around Fe in poorly ordered precursors and what is known in crystallized minerals suggests a solid transformation during ageing. This difference between iron and aluminium is mainly due to the ability of Al to enter both tetrahedral and octahedral sites, while the affinity of iron for octahedral sites is higher at low temperature

  7. Properties of U3Si2-Al dispersion fuel element and its application

    International Nuclear Information System (INIS)

    Yin Changgeng

    2001-01-01

    The properties of U 3 Si 2 fuel and U 3 Si 2 -Al dispersion fuel element are introduced, which include U-loading; the banding quality, U-homogeneity and 'dog-bone' phenomenon, the minimum thickness of cladding and the corrosion performances. The fabrication technique of fuel elements, NDT for fuel plates, assemble technique of fuel elements and the application of U 3 Si 2 -Al dispersion fuel elements in the world are introduced

  8. Formation of coarse Al13Fe4 particles and their effects in an RS/PM Al-Fe-V-Si alloy

    International Nuclear Information System (INIS)

    Lee, Sunghak; Lee, D.Y.; Ahn, Sangho.

    1991-01-01

    The present paper analyzed the fracture behavior of an RS/PM Al-Fe-V-Si alloy after high temperature exposure, in particular the effects of coarse Al13Fe4 particles formed during the exposure at 480 C. In situ SEM observations of crack opening processes found that brittle cleavage fracture occurred at these coarse Al13Fe4 particles, leading to the reduction in strength, fracture toughness, and ductility of the Al-Fe-V-Si alloy exposed to high temperatures. The results of fracture toughness were also interpreted using a simplified ductile fracture initiation model based on a basic assumption that crack extension starts to occur at a certain critical strain over a microstructurally significant critical distance. This model correlates microstructure to fracture toughness, confirming that the presence of coarse Al13Fe4 particles is the main metallurgical factor for the embrittlement phenomenon in the Al-Fe-V-Si alloy after high temperature exposure. 12 refs

  9. Room temperature mechanosynthesis and microstructure characterization of nanocrystalline Si{sub 0.9}Al{sub 0.1}C

    Energy Technology Data Exchange (ETDEWEB)

    Bandyopadhyay, S. [Department of Physics, The University of Burdwan, Golapbag, Burdwan, 713104, West Bengal (India); Dutta, H. [Department of Physics, Vivekananda College, Burdwan, 713103, West Bengal (India); Kar, T. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, West Bengal (India); Pradhan, S.K., E-mail: skp_bu@yahoo.com [Department of Physics, The University of Burdwan, Golapbag, Burdwan, 713104, West Bengal (India)

    2016-02-01

    This article reports the synthesis and microstructure characterization of nanocrystalline Si{sub 0.9}Al{sub 0.1}C powder obtained by mechanical milling the mixture of Si, Al and graphite powders at room temperature under inert atmosphere. XRD patterns of ball-milled powders clearly reveal the nucleation of Si{sub 0.9}Al{sub 0.1}C phase after 5 h of milling and the stoichiometric cubic Si{sub 0.9}Al{sub 0.1}C is formed after 10 h of milling with crystallite size of ∼3 nm. Microstructure of ball-milled powders in terms of different lattice imperfections is characterized by employing both Rietveld's method of structure refinement using XRD data and high resolution transmission electron microscope (HRTEM). HRTEM micrographs of 10 h milled powder substantiate the formation of nanocrystalline Si{sub 0.9}Al{sub 0.1}C compound without any contamination and confirm the findings of Rietveld analysis using XRD data. - Highlights: • Cubic Si{sub 0.9}Al{sub 0.1}C is formed after 5 h of milling of Si, Al and graphite powders. • Nanocrystalline Si{sub 0.9}Al{sub 0.1}C with particle size ∼3 nm is obtained after 10 h milling. • Average particle size of Si{sub 0.9}Al{sub 0.1}C from XRD analysis and HRTEM is very close.

  10. Carbon monoxide sensing properties of B-, Al- and Ga-doped Si nanowires

    Science.gov (United States)

    de Santiago, F.; Trejo, A.; Miranda, A.; Salazar, F.; Carvajal, E.; Pérez, L. A.; Cruz-Irisson, M.

    2018-05-01

    Silicon nanowires (SiNWs) are considered as potential chemical sensors due to their large surface-to-volume ratio and their possible integration into arrays for nanotechnological applications. Detection of harmful gases like CO has been experimentally demonstrated, however, the influence of doping on the sensing capacity of SiNWs has not yet been reported. For this work, we theoretically studied the surface adsorption of a CO molecule on hydrogen-passivated SiNWs grown along the [111] crystallographic direction and compared it with the adsorption of other molecules such as NO, and O2. Three nanowire diameters and three dopant elements (B, Al and Ga) were considered, and calculations were done within the density functional theory framework. The results indicate that CO molecules are more strongly adsorbed on the doped SiNW than on the pristine SiNW. The following trend was observed for the CO adsorption energies: E A[B-doped] > E A[Al-doped] > E A[Ga-doped] > E A[undoped], for all diameters. The electronic charge transfers between the SiNWs and the adsorbed CO were estimated by using a Voronoi population analysis. The CO adsorbed onto the undoped SiNWs has an electron-acceptor character, while the CO adsorbed onto the B-, Al-, and Ga-doped SiNWs exhibits an electron-donor character. Comparing these results with the ones obtained for the NO and O2 adsorption, the larger CO adsorption energy on B-doped SiNWs indicates their good selectivity towards CO. These results suggest that SiNW-based sensors of toxic gases could represent a clear and advantageous application of nanotechnology in the improvement of human quality of life.

  11. The impact of major alloying elements and refiner on the SDAS of Al-Si-Cu alloy; Der Einfluss von Hauptlegierungselementen und Kornfeinern auf den sekundaeren Dendritenarmabstand der Al-Si-Cu-Legierung

    Energy Technology Data Exchange (ETDEWEB)

    Djurdjevic, Mile; Byczynski, Glenn [Nemak Europe GmbH, Frankfurt am Main (Germany). Frankfurt Airport Center 1; Pavlovic, Jelena [Magdeburg Univ. (Germany). Inst. fuer Fertigungstechnik und Qualitaetssicherung

    2009-02-15

    This paper investigates the effect of some major alloying elements (silicon and copper) and the effect of grain refiner (titanium boride) on the size of the secondary dendrite arm spacing (SDAS) in series of Al-Si-Cu alloys. It has been shown that both silicon and copper have significant influence on this solidification parameter. The addition of grain refining master alloys to aluminium alloys is common practice in many commercial foundries aiming to reduce the grain size of Al-Si alloys. However, it was shown in the present paper that master alloy based on TiB had an unexpected impact on the SDAS, decreasing the size of SDAS. In addition, there is a minimum of SDAS corresponding to the presence of 0.12 wt% of titanium in Al-Si alloy. Such findings could have important implications for Al-Si alloys in particular, due to their wide spread applications in the automotive industry. (orig.)

  12. Selective laser melting of carbon/AlSi10Mg composites: Microstructure, mechanical and electronical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xiao; Song, Bo, E-mail: bosong@hust.edu.cn; Fan, Wenrui; Zhang, Yuanjie; Shi, Yusheng

    2016-04-25

    Carbon nanotubes/AlSi10Mg composites has drawn lots of attention in structural engineering and functional device applications due to its extraordinary high elastic modulus and mechanical strength as well as excellent electrical and thermal conductivities. In this study, the CNTs/AlSi10Mg composites was firstly prepared and then processed by selective laser melting. The powder preparation, SLM process, and microstructure evolution, properties were clarified. The results showed that CNTs were decomposed due to the direct interaction with the laser beam. The SLMed composites displayed a similar microstructure to that of SLMed AlSi10Mg. The common brittleness phase Al{sub 4}C{sub 3} didn't form, and the carbon dispersion strengthening was observed. The electrical resistivity of the composites was reduced significantly and the hardness was improved. - Highlights: • Carbon nanotubes/AlSi10Mg powder were prepared by slurry ball milling process. • Carbon nanotubes/AlSi10Mg composites were firstly prepared by SLM. • The electrical resistivity of the composites was significantly reduced and hardness was improved.

  13. Effects of AlN on the densification and mechanical properties of pressureless-sintered SiC ceramics

    Directory of Open Access Journals (Sweden)

    Qisong Li

    2016-02-01

    Full Text Available In the present work, SiC ceramics was fabricated with AlN using B4C and C as sintering aids by a solid-state pressureless-sintered method. The effects of AlN contents on the densification, mechanical properties, phase compositions, and microstructure evolutions of as-obtained SiC ceramics were thoroughly investigated. AlN was found to promote further densification of the SiC ceramics due to its evaporation over 1800 °C, transportation, and solidification in the pores resulted from SiC grain coarsening. The highest relative density of 99.65% was achieved for SiC sample with 15.0 wt% AlN by the pressureless-sintered method at 2130 °C for 1 h in Ar atmosphere. Furthermore, the fracture mechanism for SiC ceramics containing AlN tended to transfer from single transgranular fracture mode to both transgranular fracture and intergranular fracture modes when the sample with 30.0 wt% AlN sintered at 1900 °C for 1 h in Ar. Also, SiC ceramics with 30.0 wt% AlN exhibited the highest fracture toughness of 5.23 MPa m1/2 when sintered at 1900 °C.

  14. Effect of surface passivation by SiN/SiO2 of AlGaN/GaN high-electron mobility transistors on Si substrate by deep level transient spectroscopy method

    International Nuclear Information System (INIS)

    Gassoumi, Malek; Mosbahi, Hana; Zaidi, Mohamed Ali; Gaquiere, Christophe; Maaref, Hassen

    2013-01-01

    Device performance and defects in AlGaN/GaN high-electron mobility transistors have been correlated. The effect of SiN/SiO 2 passivation of the surface of AlGaN/GaN high-electron mobility transistors on Si substrates is reported on DC characteristics. Deep level transient spectroscopy (DLTS) measurements were performed on the device after the passivation by a (50/100 nm) SiN/SiO 2 film. The DLTS spectra from these measurements showed the existence of the same electron trap on the surface of the device

  15. Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

    Science.gov (United States)

    Ahmad, R.; Asmael, M. B. A.

    2016-07-01

    The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

  16. Liquidus Temperature of SrO-Al2O3-SiO2 Glass-Forming Compositions

    DEFF Research Database (Denmark)

    Abel, Brett M.; Morgan, James M.; Mauro, John C.

    2013-01-01

    . In the composition range of interest for industrial glasses, Tliq tends to decrease with increasing strontium-to-alumina ratio. We find that cristobalite, mullite, and slawsonite are the dominant devitrification phases for the compositions with high SiO2, SiO2+Al2O3, and SrO contents, respectively. By comparison...... with the phase diagrams for CaO-Al2O3-SiO2 and MgO-Al2O3-SiO2 systems, we have found that for the highest [RO]/[Al2O3] ratios, Tliq exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging...... to the SrO-Al2O3-SiO2 family may be designed with a more exact control of the glass-forming ability by avoiding the regions of high liquidus temperature....

  17. Corrosion performance of SiCsubp/6061 Al metal matrix composites in sodium chloride solution

    International Nuclear Information System (INIS)

    Mohmad Soib bin Selamat

    1995-01-01

    The corrosion performance of silicon carbide particle/aluminium metal matrix composites (SiCsubp/Al) were studied in sodium chloride solution by means of electrochemical, microscopic, gravimetric and analytical techniques. The materials under investigation were compocasting processed 6061 Al reinforced with increasing amounts of SiC particles. Potentiostatic polarization tests were done in 0.1M NaCl solutions that were aerated or deaerated to observe overall corrosion behaviour. It was seen that the corrosion potentials did not vary greatly in relation to the amounts of SiCsubp reinforcement. Corrosion tests showed that the degree of corrosion increased with increasing SiCsubp content. SEM analysis technique was used to study the corroded samples and the pitting morphology. By TEM, no intermetallic layer was found at SiC/Al interface. A model for pitting process was proposed

  18. Effect of Si and Co on the crystallization of Al-Ni-RE amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.H. [Key Lab of Liquid structure and Heredity of Materials, Ministry of Education, South Campus of Shandong University, Jinan 250061 (China); Bian, X.F. [Key Lab of Liquid structure and Heredity of Materials, Ministry of Education, South Campus of Shandong University, Jinan 250061 (China)], E-mail: xfbian@sdu.edu.cn

    2008-04-03

    Crystallization of Al{sub 83}Ni{sub 10}Si{sub 2}Ce{sub 5}, Al{sub 85}Ni{sub 10}Ce{sub 5}, Al{sub 87}Ni{sub 7}Nd{sub 6} and Al{sub 87}Ni{sub 5}Co{sub 2}Nd{sub 6} amorphous alloys has been studied by using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The multiple transition metal (TM) (containing metalloid element) have significant effect on the crystallization behavior. A small addition of Si transforms a eutectic crystallization (Al{sub 85}Ni{sub 10}Ce{sub 5}) to a primary crystallization (Al{sub 83}Ni{sub 10}Si{sub 2}Ce{sub 5}); while a small addition of Co transforms a primary crystallization (Al{sub 87}Ni{sub 7}Nd{sub 6}) to a eutectic crystallization (Al{sub 87}Ni{sub 5}Co{sub 2}Nd{sub 6}). In addition, the activation energies for crystallization (E{sub a}) are obtained to be 191, 290, 221 and 166 kJ/mol for the Al{sub 83}Ni{sub 10}Si{sub 2}Ce{sub 5}, Al{sub 85}Ni{sub 10}Ce{sub 5}, Al{sub 87}Ni{sub 5}Co{sub 2}Nd{sub 6} and Al{sub 87}Ni{sub 7}Nd{sub 6} amorphous alloys based on the Kissinger method, respectively. It is found that the primary crystallization of fcc-Al is characteristic of a lower E{sub a}, as compared with eutectic crystallization.

  19. Epitaxial growth and properties of AlGaN-based UV-LEDs on Si(111) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Saengkaew, Phannee

    2010-07-08

    An increasing demand for bright and efficient ultraviolet light emitting diodes (UVLEDs) is generated by numerous applications such as biochemical sensors, purification and sterilization, and solid-state white lighting. Al{sub x}Ga{sub 1-x}N is a promising material to develop UVLEDs due to the direct wide-bandgap material for emission wavelengths in the UV range and the capability of n- and p-type doping. To develop UV-LEDs on Si substrates is very interesting for low-cost UV-light sources since the Si substrate is available at low cost, in large-diameter size enabling the integration with well-known Si electronics. This work presents the first crack-free AlGaN-based UV-LEDs on Si(111) substrates by MOVPE growth. This AlGaN-based UV-LED on Si(111) substrate consists of Al{sub 0.1}Ga{sub 0.9}N:Si layers on LT-AlN/HT-AlN SL buffer layers and an active layer of GaN/Al{sub 0.1}Ga{sub 0.9}N MQWs followed by Mg-doped (GaN/Al{sub 0.1}Ga{sub 0.9}N) superlattices and GaN:Mg cap layers. It yields a {proportional_to}350 nm UV electroluminescence at room temperature and a turn-on voltage in a range of 2.6-3.1 V by current-voltage (I-V) measurements. The novel LT-AlN/HT-AlN superlattice buffer layers efficiently improve the crystalline quality of Al{sub x}Ga{sub 1-x}N layers and compensate a thermal tensile strain in Al{sub x}Ga{sub 1-x}N layers after cooling as observed by in-situ curvature measurements. The dislocation density could be reduced from 8.4 x 10{sup 10} cm{sup -2} in the AlN-based SLs to 1.8 x 10{sup 10} cm{sup -2} in the Al{sub 0.1}Ga{sub 0.9}N layers as determined by cross-sectional transmission electron microscopy (TEM) measurements. Crack-free Al{sub x}Ga{sub 1-x}N layers grown on these LT-AlN/HT-AlN superlattices with 0.05{<=}x{<=} 0.65 are achieved on Si substrates with good crystalline, optical, and electrical properties. The best crystalline quality of Al{sub 0.1}Ga{sub 0.9}N is obtained with {omega}-FWHMs of the (0002) and (10-10) reflections of

  20. Influence of Al addition on phase transformation and thermal stability of nickel silicides on Si(0 0 1)

    International Nuclear Information System (INIS)

    Huang, Shih-Hsien; Twan, Sheng-Chen; Cheng, Shao-Liang; Lee, Tu; Hu, Jung-Chih; Chen, Lien-Tai; Lee, Sheng-Wei

    2014-01-01

    Highlights: ► The presence of Al slows down the Ni 2 Si–NiSi phase transformation but significantly promotes the NiSi 2−x Al x formation. ► The behavior of phase transformation strongly depends on the Al concentration of the initial Ni 1−x Al x alloys. ► The Ni 0.91 Al 0.09 /Si system exhibits remarkably improved thermal stability, even after high temperature annealing for 1000 s. ► The relationship between microstructures, electrical property, and thermal stability of Ni(Al) silicides is discussed. -- Abstract: The influence of Al addition on the phase transformation and thermal stability of Ni silicides on (0 0 1)Si has been systematically investigated. The presence of Al atoms is found to slow down the Ni 2 Si–NiSi phase transformation but significantly promote the NiSi 2−x Al x formation during annealing. The behavior of phase transformation strongly depends on the Al concentration of the initial Ni 1−x Al x alloys. Compared to the Ni 0.95 Pt 0.05 /Si and Ni 0.95 Al 0.05 /Si system, the Ni 0.91 Al 0.09 /Si sample exhibits remarkably enhanced thermal stability, even after high temperature annealing for 1000 s. The relationship between microstructures, electrical property, and thermal stability of Ni silicides is discussed to elucidate the role of Al during the Ni 1−x Al x alloy silicidation. This work demonstrated that thermally stable Ni 1−x Al x alloy silicides would be a promising candidate as source/drain (S/D) contacts in advanced complementary metal–oxide-semiconductor (CMOS) devices

  1. Ab-initio electronic and magnetic properties of Fe-Al alloys

    Directory of Open Access Journals (Sweden)

    Apiñaniz, E.

    2000-06-01

    Full Text Available This work presents ab-initio self-consistent calculations performed with the TB-LMTO code to study the different phases of the Fe-Al phase diagram, corresponding to the ordered structures B2, DO3 and B32 and for Fe50Al50 and Fe3Al compositions. Both, unpolarized and spin-polarized calculations have been performed to deduce the energetic difference between the paramagnetic and ferromagnetic state of the corresponding structure. Calculations for the disordered structures have also been performed for the previously mentioned compositions. These results show that by disordering the alloy magnetism is enhanced and that the equilibrium lattice parameter increases.

    En este trabajo se presentan cálculos autoconsistentes ab-initio realizados con el método TB-LMTO (Tight Binding Linear Muffin Tin Orbital con el fin de estudiar las diferentes estructuras que se presentan en el diagrama de fases de las aleaciones Fe-Al. Se han estudiado las estructuras ordenadas B2, DO3 y B32 para las siguientes concentraciones: Fe50Al50 y Fe3Al. Asimismo, se han realizado cálculos teniendo y sin tener en cuenta la polarización de spin con el fin de poder deducir la diferencia energética entre los estados ferromágneticos y paramágneticos de la misma estructura. Por otra parte se han realizado estos mismos cálculos para estructuras desordenadas y las mismas concentraciones. Los resultados muestran que mediante el desorden aumenta el magnetismo de estas aleaciones y crece el parámetro de red.

  2. Corrosion study of the passive film of amorphous Fe-Cr-Ni-(Si, P, B alloys

    Directory of Open Access Journals (Sweden)

    López, M. F.

    1996-12-01

    Full Text Available Amorphous Fe62Cr10Ni8X20 (X = P, B, Si alloys in 0.01M HCl solution have been investigated by means of standard electrochemical measurements in order to evaluate their corrosion resistance. The study reveals that the best corrosion behaviour is given by the Si containing amorphous alloy. X-ray photoelectron spectroscopy (XPS and Auger electron spectroscopy (AJES have been employed to study the composition of the passive layers, formed on the surface of the different amorphous alloys. The results on Fe62Cr10Ni8X20 show that a protective passive film, mainly consisting of oxidized chromium, greatly enhances its corrosion resistance.

    La resistencia a la corrosión de las aleaciones amorfas Fe62Cr10Ni8X20 (X = P, B, Si inmersas en HCl 0,01M se evaluó usando técnicas electroquímicas. Las técnicas de espectroscopia de fotoemisión de rayos X y espectroscopia Auger se emplearon para estudiar la composición de las capas pasivas, formadas en aire sobre la superficie de las aleaciones amorfas. Del estudio realizado se concluye que el mejor comportamiento frente a la corrosión viene dado por la aleación amorfa que contiene como metaloide Si. Esto es debido a que la capa pasiva de dicha aleación está formada principalmente de óxido de cromo, lo cual confiere una alta resistencia a la corrosión.

  3. Atomic structures of a monolayer of AlAs, GaAs, and InAs on Si(111)

    International Nuclear Information System (INIS)

    Lee, Geunjung; Yoon, Younggui

    2010-01-01

    We study atomic structures of a monolayer of AlAs, GaAs, and InAs on a Si(111) substrate from first-principles. The surface with the stacking sequence of ...SiSiMAsSiAs is energetically more stable than the surface with the stacking sequence of ...SiSiSiAsMAs, where M is Al, Ga, or In. The atomic structure of the three top layers of the low-energy surfaces are quite robust, irrespective of M, and the atomic structure of the AlAsSiAs terminated surface and that of the GaAsSiAs terminated surface are very similar. For the high-energy AsMAs terminated surfaces, the broken local tetrahedral symmetry plays an important role in the atomic structures. The calculated atomic structures of InAs on the Si(111) substrate depart most from the structure of crystalline Si.

  4. Effect of Si/Al2 Ratio on 2-butanol Dehydration over HY Zeolite Catalysts

    International Nuclear Information System (INIS)

    Jung, Euna; Choi, Hyeonhee; Jeon, Jong-Ki

    2015-01-01

    Synthesis of butenes through dehydration of 2-butanol was investigated over HY zeolite catalysts. 2-Butanol dehydration reaction was carried out in a fixed bed catalytic reactor. 2-Butanol conversion was increased with increase of Si/Al 2 ratio of HY zeolite catalysts, which can be ascribed to increase of acid strength with increase of Si/Al 2 ratio. Selectivities to 1-butene, trans-2-butene, and cis-2-butene were not greatly influenced by the change of the Si/Al 2 ratio of HY zeolite. As a result, it was advantageous to use a HY zeolite catalyst with 60 Si/Al 2 ratio for maximizing the yield of 1-butene in the dehydration of 2-butanol. The optimal reaction temperature for maximizing the yield of 1-butene was 250 .deg. C over HY (60) catalyst

  5. Al- or Si-decorated graphene oxide: A favorable metal-free catalyst for the N2O reduction

    International Nuclear Information System (INIS)

    Esrafili, Mehdi D.; Sharifi, Fahimeh; Nematollahi, Parisa

    2016-01-01

    Highlights: • The reduction of N 2 O by CO molecule is investigated over Al- and Si-decorated graphene oxides (Al-/Si-GO). • The N 2 O decomposition process can take place with a negligible activation energy over both surfaces. • Al-GO and Si-GO can be used as an efficient metal-free catalyst for the reduction of N 2 O molecule at ambient conditions. - Abstract: The structural and catalytic properties of Al- or Si-decorated graphene oxide (Al-/Si-GO) are studied by means of density functional theory calculations. The relatively large adsorption energy together with the small Al−O or Si−O binding distances indicate that the epoxy groups over the GO surface can strongly stabilize the single Al or Si atom. Hence, Al-GO and Si-GO are stable enough to be utilized in catalytic reduction of N 2 O by CO molecule. It is found that the adsorption and decomposition of N 2 O molecule over Si-GO is more favorable than over Al-GO, due to its larger adsorption energy (E ads ) and charge transfer (q CT ) values. On the other hand, the CO molecule is physically adsorbed over both surfaces, with relatively small E ads and q CT values. Therefore, at the presence of N 2 O and CO molecules as the reaction gas, the Al or Si atom of the surface should be dominantly covered by N 2 O molecule. Our results indicate that the N 2 O decomposition process can take place with a negligible activation energy over Al-/Si-GO surface, where the N 2 molecule can be easily released from the surface. Then, the activated oxygen atom (O ads ) which remains over the surface reacts with the CO molecule to form the CO 2 molecule via the reaction O ads + CO → CO 2 . Based on the calculated activation energies, it is suggested that both Al-GO and Si-GO can be used as an efficient metal-free catalyst for the reduction of N 2 O molecule at ambient conditions.

  6. Structural investigation of ZnO:Al films deposited on the Si substrates by radio frequency magnetron sputtering

    International Nuclear Information System (INIS)

    Chen, Y.Y.; Yang, J.R.; Cheng, S.L.; Shiojiri, M.

    2013-01-01

    ZnO:Al films 400 nm thick were prepared on (100) Si substrates by magnetron sputtering. Energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM) revealed that in the initial stage of the deposition, an amorphous silicon oxide layer about 4 nm thick formed from damage to the Si substrate due to sputtered particle bombardment and the incorporation of Si atoms with oxygen. Subsequently, a crystalline Si (Zn) layer about 30 nm thick grew on the silicon oxide layer by co-deposition of Si atoms sputtered away from the substrate with Zn atoms from the target. Finally, a ZnO:Al film with columnar grains was deposited on the Si (Zn) layer. The sputtered particle bombardment greatly influenced the structure of the object films. The (0001) lattice fringes of the ZnO:Al film were observed in high-resolution TEM images, and the forbidden 0001 reflection spots in electron diffraction patterns were attributed to double diffraction. Therefore, the appearance of the forbidden reflection did not imply any ordering of Al atoms and/or O vacancies in the ZnO:Al film. - Highlights: • ZnO:Al films were deposited on (100) Si substrate using magnetron sputtering. • An amorphous silicon oxide layer with a thickness of 4 nm was formed on Si substrate. • Crystalline Si (Zn) layer about 30 nm thick grew on amorphous silicon oxide layer. • ZnO:Al film comprising columnar grains was deposited on the Si(Zn) layer. • Lattice image of the ZnO:Al film has been interpreted

  7. Comparative study of gamma ray shielding and some properties of PbO–SiO2–Al2O3 and Bi2O3–SiO2–Al2O3 glass systems

    International Nuclear Information System (INIS)

    Singh, K.J.; Kaur, Sandeep; Kaundal, R.S.

    2014-01-01

    Gamma-ray shielding properties have been estimated in terms of mass attenuation coefficient, half value layer and mean free path values, whereas, structural studies have been performed in terms of density, optical band gap, glass transition temperature and longitudinal ultrasonic velocity parameters. X-ray diffraction, UV–visible, DSC and ultrasonic techniques have been used to explore the structural properties of PbO–SiO 2 –Al 2 O 3 and Bi 2 O 3 –SiO 2 –Al 2 O 3 glass systems. - Highlights: • Bi 2 O 3 –SiO 2 –Al 2 O 3 and PbO–SiO 2 –Al 2 O 3 glasses can replace conventional concretes as gamma-ray shielding materials. • Gamma-ray shielding properties improve with the addition of heavy metals. • Rigidity deteriorates with the increase in the content of heavy metals. • Bi 2 O 3 –SiO 2 –Al 2 O 3 glass system is better than PbO–SiO 2 –Al 2 O 3 glass system in terms of gamma-ray shielding as well as structural properties

  8. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    Science.gov (United States)

    Huang, Yiqin; Li, Heqin; Zuo, Min; Tao, Lei; Wang, Wei; Zhang, Jing; Tang, Qiong; Bai, Peiwen

    2016-07-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB.

  9. Brazing of AlN to SiC by a Pr silicide: Physicochemical aspects

    Energy Technology Data Exchange (ETDEWEB)

    Koltsov, A. [SIMAP - UMR CNRS 5266, INP Grenoble-UJF, Domaine Universitaire, BP 75, 1130 rue de la Piscine, 38402 Saint Martin d' Heres, Cedex (France)], E-mail: alexey.koltsov@arcelor.com; Hodaj, F.; Eustathopoulos, N. [SIMAP - UMR CNRS 5266, INP Grenoble-UJF, Domaine Universitaire, BP 75, 1130 rue de la Piscine, 38402 Saint Martin d' Heres, Cedex (France)

    2008-11-15

    In view of their very different thermomechanical properties, joining of metals to ceramics by brazing is usually performed by means of one or more interlayers. In a recent investigation AlN was chosen as interlayer material for brazing SiC to a superalloy. The aim of the present study is to determine an alloy with a high melting point (close to 1200 deg. C) enabling brazing of AlN to SiC. Two types of experiments are performed with a Si-17 at.% Pr eutectic alloy (T{sub m} = 1212 deg. C): sessile drop experiments to determine wetting and brazing of AlN and SiC plates to determine gap filling. Experiments are carried out in high vacuum to promote deoxidation. Interfacial reactivity, joint microstructure and type of failure occurring during cooling are examined by optical and scanning electron microscopy.

  10. Brazing of AlN to SiC by a Pr silicide: Physicochemical aspects

    International Nuclear Information System (INIS)

    Koltsov, A.; Hodaj, F.; Eustathopoulos, N.

    2008-01-01

    In view of their very different thermomechanical properties, joining of metals to ceramics by brazing is usually performed by means of one or more interlayers. In a recent investigation AlN was chosen as interlayer material for brazing SiC to a superalloy. The aim of the present study is to determine an alloy with a high melting point (close to 1200 deg. C) enabling brazing of AlN to SiC. Two types of experiments are performed with a Si-17 at.% Pr eutectic alloy (T m = 1212 deg. C): sessile drop experiments to determine wetting and brazing of AlN and SiC plates to determine gap filling. Experiments are carried out in high vacuum to promote deoxidation. Interfacial reactivity, joint microstructure and type of failure occurring during cooling are examined by optical and scanning electron microscopy

  11. Viscosity of Industrially Important Zn-Al Alloys Part II: Alloys with Higher Contents of Al and Si

    Science.gov (United States)

    Nunes, V. M. B.; Queirós, C. S. G. P.; Lourenço, M. J. V.; Santos, F. J. V.; Nieto de Castro, C. A.

    2018-05-01

    The viscosity of Zn-Al alloys melts, with industrial interest, was measured for temperatures between 693 K and 915 K, with an oscillating cup viscometer, and estimated expanded uncertainties between 3 and 5 %, depending on the alloy. The influence of minor components, such as Si, Mg and Ce + La, on the viscosity of the alloys is discussed. An increase in the amount of Mg triggers complex melt/solidification processes while the addition of Ce and La renders alloys viscosity almost temperature independent. Furthermore, increases in Al and Si contents decrease melts viscosity and lead to an Arrhenius type behavior. This paper complements a previous study describing the viscosity of Zn-Al alloys with quasi-eutectic compositions.

  12. Local Structures around Si, Al and Na in Hydrated Silicate Glasses

    International Nuclear Information System (INIS)

    Farges, Francois; Wispelaere, Sidoine de; Rossano, Stephanie; Munos, Manuel; Wilke, Max; Flank, Anne-Marie; Lagarde, Pierre

    2007-01-01

    XANES spectra were collected at the Si-, Al-, and Na K-edge in hydrous silicate glasses to understand the effect of water on the local structure around these cations. Around network forming Si and Al, no drastic changes are observed. Around Na, the dissolution of water creates more ordered environments in Al-bearing glasses and less ordered environment in Al-free glasses. Ab-initio XANES calculations were undertaken to understand the structural origins for these features. Based on these results, a bond valence model was refined that considers not only the present XANES experiments and models but also NMR information. The double percolation model refined explains, among others, the explosive properties of water-bearing hydrous melts, at the origin of a number of cataclysmic eruptions in subduction zones

  13. Investigation of the fabrication processes of AlGaN/AlN/GaN HEMTs with in situ Si3N4 passivation

    International Nuclear Information System (INIS)

    Tomosh, K. N.; Pavlov, A. Yu.; Pavlov, V. Yu.; Khabibullin, R. A.; Arutyunyan, S. S.; Maltsev, P. P.

    2016-01-01

    The optimum mode of the in situ plasma-chemical etching of a Si 3 N 4 passivating layer in C 3 F 8 /O 2 medium is chosen for the case of fabricating AlGaN/AlN/GaN HEMTs. It is found that a bias of 40–50 V at a high-frequency electrode provides anisotropic etching of the insulator through a resist mask and introduces no appreciable radiation-induced defects upon overetching of the insulator films in the region of gate-metallization formation. To estimate the effect of in situ Si 3 N 4 growth together with the heterostructure in one process on the AlGaN/AlN/GaN HEMT characteristics, transistors with gates without the insulator and with gates through Si 3 N 4 slits are fabricated. The highest drain current of the AlGaN/AlN/GaN HEMT at 0 V at the gate is shown to be 1.5 times higher in the presence of Si 3 N 4 than without it.

  14. Effect of electric pulse modification on mircostructure and properties of Ni-rich Al-Si piston alloy

    Directory of Open Access Journals (Sweden)

    Bing Wang

    2016-03-01

    Full Text Available In order to improve the properties of Ni-rich (2.5wt.% Al-Si piston alloy, electric pulse modification was applied in fabricating the Ni-rich Al-Si piston alloy in this study. The effect of electric pulse modification on the mechanical properties of the Ni-rich Al-Si piston alloy was studied using optical microscope (OM, scanning electron microscope (SEM, X-ray diffraction (XRD, microhardness measurement and tensile strength testing. The results showed that the microstructures of Ni-rich Al-Si piston alloy treated by electric pulse modification were refined, the solid solubility of Cu, Ni, Si, etc. in α-Al matrix was improved, and furthermore, the microhardness and high-temperature tensile strength were increased by 9.41% and 17.5%, respectively. The distribution of second phases was also more uniform compared with that of a non-modified sample.

  15. Preliminary study of the characteristics of a high Mg containing Al-Mg-Si alloy

    International Nuclear Information System (INIS)

    Yan, F; McKay, B J; Fan, Z; Chen, M F

    2012-01-01

    An Al-20Mg-4Si high Mg containing alloy has been produced and its characteristics investigated. The as-cast alloy revealed primary Mg 2 Si particles evenly distributed throughout an α-Al matrix with a β-Al 3 Mg 2 fully divorced eutectic phase observed in interdendritic regions. The Mg 2 Si particles displayed octahedral, truncated octahedral, and hopper morphologies. Additions of Sb, Ti and Zr had a refining influence reducing the size of the Mg 2 Si from 52 ± 4 μm to 25 ± 0.1 μm, 35 ± 1 μm and 34 ± 1 μm respectively. HPDC tensile test samples could be produced with a 0.6 wt.% Mn addition which prevented die soldering. Solution heating for 1 hr was found to dissolve the majority of the Al 3 Mg 2 eutectic phase with no evidence of any effect on the primary Mg 2 Si. Preliminary results indicate that the heat treatment has a beneficial effect on the elongation and the UTS.

  16. Enhanced performance of nano-sized SiC reinforced Al metal matrix nanocomposites synthesized through microwave sintering and hot extrusion techniques

    Directory of Open Access Journals (Sweden)

    M. Penchal Reddy

    2017-10-01

    Full Text Available In the present study, nano-sized SiC (0, 0.3, 0.5, 1.0 and 1.5 vol% reinforced aluminum (Al metal matrix composites were fabricated by microwave sintering and hot extrusion techniques. The structural (XRD, SEM, mechanical (nanoindentation, compression, tensile and thermal properties (co-efficient of thermal expansion-CTE of the developed Al-SiC nanocomposites were studied. The SEM/EDS mapping images show a homogeneous distribution of SiC nanoparticles into the Al matrix. A significant increase in the strength (compressive and tensile of the Al-SiC nanocomposites with the addition of SiC content is observed. However, it is noticed that the ductility of Al-SiC nanocomposites decreases with increasing volume fraction of SiC. The thermal analysis indicates that CTE of Al-SiC nanocomposites decreases with the progressive addition of hard SiC nanoparticles. Overall, hot extruded Al 1.5 vol% SiC nanocomposites exhibited the best mechanical and thermal performance as compared to the other developed Al-SiC nanocomposites. Keywords: Al-SiC nanocomposites, Microwave sintering, Hot extrusion, Mechanical properties, Thermal expansion

  17. Development of an efficient grain refiner for Al-7Si alloy and its modification with strontium

    Energy Technology Data Exchange (ETDEWEB)

    Kori, S.A.; Murty, B.S.; Chakraborty, M. [Indian Inst. of Technol., Kharagpur (India). Dept. of Metall. and Mater. Eng.

    2000-05-15

    The grain refining response of Al and Al-7Si alloy has been studied with various Al-Ti, Al-B and Al-Ti-B master alloys at different addition levels. The results show that Al-B and B rich Al-Ti-B master alloys cannot grain refine Al, while they are efficient grain refiners to Al-7Si alloy. The level of grain refinement saturates after 0.03% of Ti or B for most of the master alloys studied both at short and long holding times. The grain refining efficiency of some elements other than Ti and B on Al-7Si alloy has also been studied. Interestingly, all the elements studied (B, Cr, Fe, Mg, Ni, Ti and Zr) have resulted in some grain refinement of Al-7Si alloy at short holding time and have shown fading/poisoning on long holding, which increased in the order of B (no poisoning), Ti, Cr, Ni, Fe, Mg, Zr. Sr (0.02%) has been found to provide complete modification of the eutectic in Al-7Si alloy within 2 min, which is not lost even after long holding up to 120 min. Significant improvements in the mechanical properties have been obtained by a combination of grain refinement and modification to an extent that was not possible by either of them alone. (orig.)

  18. Production of Al2O3–SiC nano-composites by spark plasma sintering

    International Nuclear Information System (INIS)

    Mansour Razavi; Ali Reza Farajipour; Mohammad Zakeri; Mohammad Reza Rahimipour; Ali Reza Firouzbakht

    2017-01-01

    In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600°C for 10min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5h. The milled powders were sintered in a SPS machine. After sintering process, phase studies, densification and mechanical properties of Al2O3–SiC composites were examined. Results showed that the specimens containing micro-sized SiC have an important effect on bulk density, hardness and strength. The highest relative density, hardness and strength were 99.7%, 324.6 HV and 2329MPa, respectively, in Al2O3–20wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale. [es

  19. Material dimensionality effects on the nanoindentation behavior of Al/a-Si core-shell nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Robert A. [Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Center for Advanced Surface Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Goss, Josue A. [Center for Advanced Surface Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Zou, Min, E-mail: mzou@uark.edu [Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Center for Advanced Surface Engineering, University of Arkansas, Fayetteville, AR 72701 (United States)

    2017-08-01

    Highlights: • Nanoindentation behavior of Al/a-Si core-shell nanostructures were studied. • 3D core confinement enables significant deformation recovery beyond elastic limit. • As the confinement is reduced, the deformation recovery is reduced or suppressed. • Atomistic simulations suggest core confinement affects dislocation dynamics. • 3D confinement has the highest percentage of dislocation removal after unloading. - Abstract: The nanoindentation behavior of hemispherical Al/a-Si core-shell nanostructures (CSNs), horizontally-aligned Al/a-Si core-shell nanorods (CSRs) with various lengths, and an Al/a-Si layered thin film has been studied to understand the effects of geometrical confinement of the Al core on the CSN deformation behavior. When loaded beyond the elastic limit, the CSNs have an unconventional load-displacement behavior with no residual displacement after unloading, resulting in no net shape change after indentation. This behavior is enabled by dislocation activities within the confined Al core, as indicated by discontinuous indentation signatures (load-drops and load-jumps) observed in the load-displacement data. When the geometrical confinement of the core is slightly reduced, as in the case of CSRs with the shortest rod length, the discontinuous indentation signatures and deformation resistance are heavily reduced. Further decreases in core confinement result in conventional nanoindentation behavior, regardless of geometry. Supporting molecular dynamics simulations show that dislocations nucleated in the core of a CSN are more effectively removed during unloading compared to CSRs, which supports the hypothesis that the unique deformation resistance of Al/a-Si CSNs are enabled by 3-dimensional confinement of the Al core.

  20. Material dimensionality effects on the nanoindentation behavior of Al/a-Si core-shell nanostructures

    International Nuclear Information System (INIS)

    Fleming, Robert A.; Goss, Josue A.; Zou, Min

    2017-01-01

    Highlights: • Nanoindentation behavior of Al/a-Si core-shell nanostructures were studied. • 3D core confinement enables significant deformation recovery beyond elastic limit. • As the confinement is reduced, the deformation recovery is reduced or suppressed. • Atomistic simulations suggest core confinement affects dislocation dynamics. • 3D confinement has the highest percentage of dislocation removal after unloading. - Abstract: The nanoindentation behavior of hemispherical Al/a-Si core-shell nanostructures (CSNs), horizontally-aligned Al/a-Si core-shell nanorods (CSRs) with various lengths, and an Al/a-Si layered thin film has been studied to understand the effects of geometrical confinement of the Al core on the CSN deformation behavior. When loaded beyond the elastic limit, the CSNs have an unconventional load-displacement behavior with no residual displacement after unloading, resulting in no net shape change after indentation. This behavior is enabled by dislocation activities within the confined Al core, as indicated by discontinuous indentation signatures (load-drops and load-jumps) observed in the load-displacement data. When the geometrical confinement of the core is slightly reduced, as in the case of CSRs with the shortest rod length, the discontinuous indentation signatures and deformation resistance are heavily reduced. Further decreases in core confinement result in conventional nanoindentation behavior, regardless of geometry. Supporting molecular dynamics simulations show that dislocations nucleated in the core of a CSN are more effectively removed during unloading compared to CSRs, which supports the hypothesis that the unique deformation resistance of Al/a-Si CSNs are enabled by 3-dimensional confinement of the Al core.

  1. Ti-Al-Si-C-N hard coatings synthesized by hybrid arc enhanced magnetron sputtering

    International Nuclear Information System (INIS)

    Wu, Guizhi; Liu, Sitao; Ma, Shengli; Xu, Kewei; Vincent, Ji; Chu, Paul K.

    2010-01-01

    Ti-Al-Si-C-N coatings are deposited by hybrid arc-enhanced magnetic sputtering and characterized by various micro- and macro-tools. X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy reveal that the coatings are nanocomposites consisting of nanocrystallites and amorphous phases. They are generally in the form of nc-(Ti,Al)(C,N)/a-Si_3N_4/a-C depending on the composition of the coatings. With increasing Al concentrations, the X-ray diffraction peaks shift to a lower angle indicating compressive stress in the coatings. The measured hardness also diminishes implying reduced contributions from the self-organized stable nanostructure. The dry friction coefficients of the Ti-Al-Si-C-N coatings are found to be about 0.3 which is lower than that of conventional Ti-Si-N coatings. These coatings can find potential applications requiring high temperature with heavy contact loading. (author)

  2. AlGaInN-based ultraviolet light-emitting diodes grown on Si(111)

    International Nuclear Information System (INIS)

    Kipshidze, G.; Kuryatkov, V.; Borisov, B.; Holtz, M.; Nikishin, S.; Temkin, H.

    2002-01-01

    Ultraviolet light-emitting diodes grown on Si(111) by gas-source molecular-beam epitaxy with ammonia are described. The layers are composed of superlattices of AlGaN/GaN and AlN/AlGaInN. The layers are doped n and p type with Si and Mg, respectively. Hole concentration of 4x10 17 cm -3 , with a mobility of 8 cm2/Vs, is measured in Al 0.4 Ga 0.6 N/GaN. We demonstrate effective n- and p-type doping of structures based on AlN/AlGaInN. Light-emitting diodes based on these structures show light emission between 290 and 334 nm

  3. Crack-free AlGaN-based UV LED on Si(111) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Saengkaew, P.; Dadgar, A.; Blaesing, J.; Witte, H.; Mueller, M.; Guenther, K.M.; Fey, T.; Bastek, B.; Bertram, F.; Kurnatowski, M. von; Wieneke, M.; Hempel, T.; Veit, P.; Clos, R.; Christen, J.; Krost, A. [FNW/IEP/AHE Otto-von-Guericke-Universitaet Magdeburg (Germany)

    2010-07-01

    To achieve low-cost UV LEDs on large-diameter substrates it is a very interesting approach to grow AlGaN on low-cost Si substrates. Here, AlGaN layers and AlGaN LED structures grown on Si(111) were additionally monitored by in-situ curvature measurements. They show that with the insertion of AlN-based SL buffer layers and LT-AlN interlayers, the AlGaN layers are under compressive stress during growth enabling to compensate tensile stress after cooling. To characterize the crystalline quality, HR-XRD measurements were performed. Cross-sectional TEM to investigate dislocation propagation and annihilation. n- and p- conductivities were achieved by Si and Mg doping of the layers, respectively. By C-V and Hall-effect measurements, the maximum free-electron concentration of 2.6{sup +18} cm{sup -3} and free-hole concentration of 2.4{sup +17} cm{sup -3} by using a structure of Mg-doped GaN/Al{sub 0.1}Ga{sub 0.9}N multilayers for the latter were determined. A GaN/Al{sub 0.1}Ga{sub 0.9}N MQW structure showed near UV-luminescence around 350-360 nm. The optical and electrical properties of AlGaN-based LED samples were further characterized by I-V, EL, PL and CL measurements. The I-V measurements show forward-diode characteristics with turn-on voltage about 2.6-3.1 V.

  4. Mechanical Properties And Microstructure Of AlN/SiCN Nanocomposite Coatings Prepared By R.F.-Reactive Sputtering Method

    Directory of Open Access Journals (Sweden)

    Nakafushi Y.

    2015-06-01

    Full Text Available FIn this work, AlN/SiCN composite coatings were deposited by r.f.-reactive sputtering method using a facing target-type sputtering (FTS apparatus with composite targets consisting of Al plate and SiC chips in a gaseous mixture of Ar and N2, and investigated their mechanical properties and microstructure. The indentation hardness (HIT of AlN/SiCN coatings prepared from composite targets consisting of 8 ~32 chips of SiC and Al plate showed the maximum value of about 29~32 GPa at a proper nitrogen gas flow rate. X-ray diffraction (XRD patterns for the AlN/SiCN composite coatings indicated the presence of the only peeks of hexagonal (B4 structured AlN phase. AlN coatings clarified the columnar structure of the cross sectional view TEM observation. On the other hand, microstructure of AlN/SiCN composite coatings changed from columnar to equiaxed structure with increasing SiCN content. HR-TEM observation clarified that the composite coatings consisted of very fine equiaxial grains of B4 structured AlN phase and amorphous phase.

  5. Electronic properties of Al/DNA/p-Si MIS diode: Application as temperature sensor

    International Nuclear Information System (INIS)

    Guellue, O.; Tueruet, A.

    2011-01-01

    Research highlights: → This work proposes that DNA molecules should be considered, among other candidates, as a potential organic thin film for metal-interface layer-semiconductor devices. → We successfully fabricated Al/DNA/p-Si device with interlayer by a simple cast method. → The temperature is found to significantly effect the electrical properties of the Al/DNA/p-Si device. → The facts: (i) that the technology of the fabrication of a Al/DNA/p-Si Schottky diode much simpler and economical than that for the Si p-n junction and (ii) the sensibility of the Al/DNA/p-Si Schottky diode as temperature sensor is 42% higher than that of a Si p-n junction, indicate that the Al/DNA/p-Si Schottky diode is a good alternative as temperature sensor. - Abstract: The current-voltage (I-V) measurements were performed in the temperature range (200-300 K) on Al/DNA/p-Si Schottky barrier type diodes. The Schottky diode shows non-ideal I-V behaviour with ideality factors n equal to 1.34 ± 0.02 and 1.70 ± 0.02 at 300 K and 200 K, respectively, and is thought to have a metal-interface layer-semiconductor (MIS) configuration. The zero-bias barrier height Φ b determined from the I-V measurements was 0.75 ± 0.01 eV at 300 K and decreases to 0.61 ± 0.01 eV at 200 K. The forward voltage-temperature (V F -T) characteristics were obtained from the I-V measurements in the temperature range 200-300 K at different activation currents (I F ) in the range 20 nA-6 μA. The V F -T characteristics were linear for three activation currents in the diode. From the V F -T characteristics at 20 nA, 100 nA and 6 μA, the values of the temperature coefficients of the forward bias voltage (dV F /dT) for the diode were determined as -2.30 mV K -1 , -2.60 mV K -1 and -3.26 mV K -1 with a standard error of 0.05 mV K -1 , respectively.

  6. Electronic properties of Al/DNA/p-Si MIS diode: Application as temperature sensor

    Energy Technology Data Exchange (ETDEWEB)

    Guellue, O., E-mail: omergullu@gmail.com [Batman University, Science and Art Faculty, Department of Physics, 72060 Batman (Turkey); Osmaniye Korkut Ata University, Science and Art Faculty, Department of Physics, 80000 Osmaniye (Turkey); Tueruet, A. [Atatuerk University, Science Faculty, Department of Physics, 25240 Erzurum (Turkey)

    2011-01-21

    Research highlights: > This work proposes that DNA molecules should be considered, among other candidates, as a potential organic thin film for metal-interface layer-semiconductor devices. > We successfully fabricated Al/DNA/p-Si device with interlayer by a simple cast method. > The temperature is found to significantly effect the electrical properties of the Al/DNA/p-Si device. > The facts: (i) that the technology of the fabrication of a Al/DNA/p-Si Schottky diode much simpler and economical than that for the Si p-n junction and (ii) the sensibility of the Al/DNA/p-Si Schottky diode as temperature sensor is 42% higher than that of a Si p-n junction, indicate that the Al/DNA/p-Si Schottky diode is a good alternative as temperature sensor. - Abstract: The current-voltage (I-V) measurements were performed in the temperature range (200-300 K) on Al/DNA/p-Si Schottky barrier type diodes. The Schottky diode shows non-ideal I-V behaviour with ideality factors n equal to 1.34 {+-} 0.02 and 1.70 {+-} 0.02 at 300 K and 200 K, respectively, and is thought to have a metal-interface layer-semiconductor (MIS) configuration. The zero-bias barrier height {Phi}{sub b} determined from the I-V measurements was 0.75 {+-} 0.01 eV at 300 K and decreases to 0.61 {+-} 0.01 eV at 200 K. The forward voltage-temperature (V{sub F}-T) characteristics were obtained from the I-V measurements in the temperature range 200-300 K at different activation currents (I{sub F}) in the range 20 nA-6 {mu}A. The V{sub F}-T characteristics were linear for three activation currents in the diode. From the V{sub F}-T characteristics at 20 nA, 100 nA and 6 {mu}A, the values of the temperature coefficients of the forward bias voltage (dV{sub F}/dT) for the diode were determined as -2.30 mV K{sup -1}, -2.60 mV K{sup -1} and -3.26 mV K{sup -1} with a standard error of 0.05 mV K{sup -1}, respectively.

  7. Effect of Heat Treatment on the Microstructure and Wear Properties of Al-Zn-Mg-Cu/In-Situ Al-9Si-SiCp/Pure Al Composite by Powder Metallurgy

    Science.gov (United States)

    Yu, Byung Chul; Bae, Ki-Chang; Jung, Je Ki; Kim, Yong-Hwan; Park, Yong Ho

    2018-03-01

    This study examined the effects of heat treatment on the microstructure and wear properties of Al-Zn-Mg-Cu/in-situ Al-9Si-SiCp/pure Al composites. Pure Al powder was used to increase densification but it resulted in heterogeneous precipitation as well as differences in hardness among the grains. Heat treatment was conducted to solve this problem. The heat treatment process consisted of three stages: solution treatment, quenching, and aging treatment. After the solution treatment, the main dissolved phases were η'(Mg4Zn7), η(MgZn2), and Al2Cu phase. An aging treatment was conducted over the temperature range, 100-240 °C, for various times. The GP zone and η'(Mg4Zn7) phase precipitated at a low aging temperature of 100-160 °C, whereas the η(MgZn2) phase precipitated at a high aging temperature of 200-240 °C. The hardness of the sample aged at 100-160 °C was higher than that aged at 200-240 °C. The wear test was conducted under various linear speeds with a load of 100 N. The aged composite showed a lower wear rate than that of the as-sintered composite under all conditions. As the linear speed was increased to 1.0 m/s, the predominant wear behavior changed from abrasive to adhesive wear in all composites.

  8. Effect of Heat Treatment on the Microstructure and Wear Properties of Al-Zn-Mg-Cu/In-Situ Al-9Si-SiCp/Pure Al Composite by Powder Metallurgy

    Science.gov (United States)

    Yu, Byung Chul; Bae, Ki-Chang; Jung, Je Ki; Kim, Yong-Hwan; Park, Yong Ho

    2018-05-01

    This study examined the effects of heat treatment on the microstructure and wear properties of Al-Zn-Mg-Cu/in-situ Al-9Si-SiCp/pure Al composites. Pure Al powder was used to increase densification but it resulted in heterogeneous precipitation as well as differences in hardness among the grains. Heat treatment was conducted to solve this problem. The heat treatment process consisted of three stages: solution treatment, quenching, and aging treatment. After the solution treatment, the main dissolved phases were η'(Mg4Zn7), η(MgZn2), and Al2Cu phase. An aging treatment was conducted over the temperature range, 100-240 °C, for various times. The GP zone and η'(Mg4Zn7) phase precipitated at a low aging temperature of 100-160 °C, whereas the η(MgZn2) phase precipitated at a high aging temperature of 200-240 °C. The hardness of the sample aged at 100-160 °C was higher than that aged at 200-240 °C. The wear test was conducted under various linear speeds with a load of 100 N. The aged composite showed a lower wear rate than that of the as-sintered composite under all conditions. As the linear speed was increased to 1.0 m/s, the predominant wear behavior changed from abrasive to adhesive wear in all composites.

  9. Tensile Strength of the Al-9%Si Alloy Modified with Na, F and Cl Compounds

    Directory of Open Access Journals (Sweden)

    T. Lipiński

    2010-01-01

    Full Text Available The modification of the Al-9%Si alloy with the use of a complex modifier containing Na, F and Cl was investigated in the study. The modifier was composed of NaCl, Na3AlF6 and NaF compounds. The modifier and the liquid Al-Si alloy were kept in the crucible for 15 minutes. The modifier's effect relative to the weight of the processed alloy on its tensile strength was presented in graphic form. The results of the study indicate that the complex modifier altered the investigated properties of the eutectic Al-9%Si alloy.

  10. Low temperature route synthesis of SiC–Al2O3 hetero-structural nanofibers

    International Nuclear Information System (INIS)

    Dai, Xiao; Wang, Hao; Cao, Fengfeng; Yi, Qinghua; Cong, Shan; Wang, Yun; Song, Pingyuan; Zhai, Pengfei; Zou, Guifu; Dong, Chao

    2014-01-01

    SiC–Al 2 O 3 hetero-structural nanofibers have been synthesized by the chemical solution approach at 200 ° C. The diameters of nanofibers are in the range of 60–100 nm while the lengths are from tens of micrometers to hundreds of micrometers. The microstructural analysis shows that the fibers possess a like-epitaxial relationship between (104) of hexagonal Al 2 O 3 and (111) of cubic SiC. Additionally, the optical investigation of the nanofibers suggests there are some defects in the low annealing temperature synthesized SiC–Al 2 O 3 nanofibers. (paper)

  11. Application of the Raman technique to measure stress states in individual Si particles in a cast Al-Si alloy

    International Nuclear Information System (INIS)

    Harris, Stephen J.; O'Neill, Ann; Boileau, James; Donlon, William; Su, Xuming; Majumdar, B.S.

    2007-01-01

    While Raman spectroscopy is often used to measure stresses, the analyses are almost always limited to cases with simple stress states (uniaxial, equibiaxial). Recently we provided an experimental methodology to determine the full state of stress in Si wafers. Here we extend that methodology to interrogate stress states in Si particles embedded in an Al-Si alloy. Such determinations will ultimately be valuable for predicting ductility of cast Al, since a primary source of damage is cracking of eutectic Si particles. We combine electron back-scattered diffraction with the frequency shift, polarization and intensity of the Raman light to determine stress states. Stress states are measured both in the as-received residually stressed state and under in situ uniaxial loading. Comparison with finite element calculations shows good agreement. As an application of the technique, we show the determination of strength of an individual Si particle and compare the stress evolution with various models

  12. XPS and EELS characterization of Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Grosvenor, A.P., E-mail: andrew.grosvenor@usask.ca [Department of Chemistry, University of Saskatchewan, Saskatoon, SK S7N 5C9 (Canada); Bellhouse, E.M., E-mail: erika.bellhouse@arcelormittal.com [Global R & D—Hamilton, ArcelorMittal Dofasco, 1330 Burlington St. E, Hamilton, ON L8N 3J5 (Canada); Korinek, A., E-mail: korinek@mcmaster.ca [Canadian Centre for Electron Microscopy, Brockhouse Institute for Materials Research, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada); Bugnet, M., E-mail: bugnetm@mcmaster.ca [Canadian Centre for Electron Microscopy, Brockhouse Institute for Materials Research, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada); McDermid, J.R., E-mail: mcdermid@mcmaster.ca [Steel Research Centre, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada)

    2016-08-30

    Graphical abstract: XPS and EELS spectra were acquired from Mn2Al2O4, MnSiO3 and Mn2SiO4 standards and unique features identified that will allow unambiguous identification of these compounds when studying the selective oxidation of advanced steels. - Highlights: • Mn2Al2O4, MnSiO3 and Mn2SiO4 standards were synthesized and characterized using both XPS and EELS. • Unique features in both the XPS high resolution and EELS spectra were identified for all compounds. • The spectra can be used to identify these compounds when studying the selective oxidation of steels. - Abstract: X-ray Photoelectron Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS) are strong candidate techniques for characterizing steel surfaces and substrate-coating interfaces when investigating the selective oxidation and reactive wetting of advanced high strength steels (AHSS) during the continuous galvanizing process. However, unambiguous identification of ternary oxides such as Mn{sub 2}SiO{sub 4}, MnSiO{sub 3}, and MnAl{sub 2}O{sub 4} by XPS or EELS, which can play a significant role in substrate reactive wetting, is difficult due to the lack of fully characterized standards in the literature. To resolve this issue, samples of Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4} were synthesized and characterized by XPS and EELS. The unique features of the XPS and EELS spectra for the Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4} standards were successfully derived, thereby allowing investigators to fully differentiate and identify these oxides at the surface and subsurface of Mn, Si and Al alloyed AHSS using these techniques.

  13. X-ray nano-diffraction study of Sr intermetallic phase during solidification of Al-Si hypoeutectic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Manickaraj, Jeyakumar; Gorny, Anton; Shankar, Sumanth, E-mail: shankar@mcmaster.ca [Light Metal Casting Research Centre (LMCRC), Department of Mechanical Engineering, McMaster University, 1280 Main Street W, Hamilton, Ontario L8S 4L7 (Canada); Cai, Zhonghou [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

    2014-02-17

    The evolution of strontium (Sr) containing intermetallic phase in the eutectic reaction of Sr-modified Al-Si hypoeutectic alloy was studied with high energy synchrotron beam source for nano-diffraction experiments and x-ray fluorescence elemental mapping. Contrary to popular belief, Sr does not seem to interfere with the Twin Plane Re-entrant Edge (TPRE) growth mechanism of eutectic Si, but evolves as the Al{sub 2}Si{sub 2}Sr phase during the eutectic reaction at the boundary between the eutectic Si and Al grains.

  14. Particle stabilization of plastic flow in nanostructured Al-1 %Si Alloy

    DEFF Research Database (Denmark)

    Huang, Tianlin; Li, Chao; Wu, Guilin

    2014-01-01

    A nanostructured Al-1 %Si alloy containing a dispersion of Si particles in ultrapure aluminum (99.9996 %) was produced by heavy cold rolling to study the effect of second-phase particles on the occurrence of plastic instability during tensile testing of a nanostructured metal. Tensile tests were...

  15. Effect of Copper on Corrosion of Forged AlSi1MgMn Automotive Suspension Components

    Science.gov (United States)

    Koktas, Serhan; Gokcil, Emre; Akdi, Seracettin; Birol, Yucel

    2017-09-01

    Recently, modifications in the alloy composition and the manufacturing process cycle were proposed to achieve a more uniform structure with no evidence of coarse grains across the section of the AlSi1MgMn alloys. Cu was added to the AlSi1MgMn alloy to improve its age hardening capacity without a separate solution heat treatment. However, Cu addition degrades the corrosion resistance of this alloy due to the formation of Al-Cu precipitates along the grain boundaries that are cathodic with respect to the aluminum matrix and thus encourage intergranular corrosion. The present work was undertaken to identify the impact of Cu addition on the corrosion properties of AlSi1MgMn alloys with different Cu contents. A series of AlSi1MgMn alloys with 0.06-0.89 wt.% Cu were tested in order to identify an optimum level of Cu addition.

  16. Influence of Annealing on Mechanical Properties of Al-20Si Processed by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Pan Ma

    2014-01-01

    Full Text Available The microstructure and mechanical properties of Al-20Si produced by selective laser melting (SLM are investigated for different heat treatment conditions. As a result of the high cooling rate during processing, the as-built SLM material displays a microstructure consisting of a supersaturated Al(Si solid solution along with heavily refined eutectic Si and Si particles. The Si particles become coarser, and the eutectic Si gradually changes its morphology from fibrous to plate-like shape with increasing annealing temperature. The microstructural variations occurring during heat treatment significantly affect the mechanical behavior of the samples. The yield and ultimate strengths decrease from 374 and 506 MPa for the as-built SLM material to 162 and 252 MPa for the sample annealed at 673 K, whereas the ductility increases from 1.6 to 8.7%. This offers the possibility to tune microstructure and corresponding properties of the Al-20Si SLM parts to meet specific requirements.

  17. Fabrication and characterization of Al2O3 /Si composite nanodome structures for high efficiency crystalline Si thin film solar cells

    Directory of Open Access Journals (Sweden)

    Ruiying Zhang

    2015-12-01

    Full Text Available We report on our fabrication and characterization of Al2O3/Si composite nanodome (CND structures, which is composed of Si nanodome structures with a conformal cladding Al2O3 layer to evaluate its optical and electrical performance when it is applied to thin film solar cells. It has been observed that by application of Al2O3thin film coating using atomic layer deposition (ALD to the Si nanodome structures, both optical and electrical performances are greatly improved. The reflectivity of less than 3% over the wavelength range of from 200 nm to 2000 nm at an incident angle from 0° to 45° is achieved when the Al2O3 film is 90 nm thick. The ultimate efficiency of around 27% is obtained on the CND textured 2 μm-thick Si solar cells, which is compared to the efficiency of around 25.75% and 15% for the 2 μm-thick Si nanodome surface-decorated and planar samples respectively. Electrical characterization was made by using CND-decorated MOS devices to measure device’s leakage current and capacitance dispersion. It is found the electrical performance is sensitive to the thickness of the Al2O3 film, and the performance is remarkably improved when the dielectric layer thickness is 90 nm thick. The leakage current, which is less than 4x10−9 A/cm2 over voltage range of from -3 V to 3 V, is reduced by several orders of magnitude. C-V measurements also shows as small as 0.3% of variation in the capacitance over the frequency range from 10 kHz to 500 kHz, which is a strong indication of surface states being fully passivated. TEM examination of CND-decorated samples also reveals the occurrence of SiOx layer formed between the interface of Si and the Al2O3 film, which is thin enough that ensures the presence of field-effect passivation, From our theoretical and experimental study, we believe Al2O3 coated CND structures is a truly viable approach to achieving higher device efficiency.

  18. Production of Al2O3–SiC nano-composites by spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Mansour Razavi

    2017-07-01

    Full Text Available In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600 °C for 10 min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5 h. The milled powders were sintered in a SPS machine. After sintering process, phase studies, densification and mechanical properties of Al2O3–SiC composites were examined. Results showed that the specimens containing micro-sized SiC have an important effect on bulk density, hardness and strength. The highest relative density, hardness and strength were 99.7%, 324.6 HV and 2329 MPa, respectively, in Al2O3–20 wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale.

  19. Tritium release in Li{sub 4}SiO{sub 4} and Li{sub 4.2}Si{sub 0.8}Al{sub 0.2}O{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Linjie, E-mail: zhaolinjie1989@163.com; Long, Xinggui, E-mail: xingguil@caep.cn; Peng, Shuming, E-mail: pengshuming@caep.cn; Chen, Xiaojun; Xiao, Chengjian; Ran, Guangming; Li, Jiamao

    2016-12-15

    Li{sub 4+x}Si{sub 1−x}Al{sub x}O{sub 4} solid solution materials, which were designed as the advanced tritium breeders, were obtained by indirect solid state reactions. The behaviors of tritium release from Li{sub 4}SiO{sub 4} and Li{sub 4.2}Si{sub 0.8}Al{sub 0.2}O{sub 4} powders were investigated by temperature programmed desorption. The tritium release curves show different characteristics for the Li{sub 4}SiO{sub 4} and Li{sub 4.2}Si{sub 0.8}Al{sub 0.2}O{sub 4} ceramics. The main tritium release peak in the Li{sub 4}SiO{sub 4} and Li{sub 4.2}Si{sub 0.8}Al{sub 0.2}O{sub 4} powders is at approximately 600 °C after a high dose irradiation. Moreover, the temperature of the tritium release from Li{sub 4.2}Si{sub 0.8}Al{sub 0.2}O{sub 4} was lower than that of the release from Li{sub 4}SiO{sub 4}. This suggests a possible advantage to using the solid solutions as the advanced tritium breeding materials.

  20. Identification of intermetallic phases in a eutectic Al-Si casting alloy using electron backscatter diffraction pattern analysis

    International Nuclear Information System (INIS)

    Kral, M.V.; McIntyre, H.R.; Smillie, M.J.

    2004-01-01

    Intermetallic phases in sand cast eutectic Al-Si alloys were characterized using a combination of SEM, EDS and EBSD pattern analysis. Chinese script α-phase particles were consistent with cubic Al 19 (Fe,Mn) 5 Si 2 . Plate-shaped β-phase particles were consistent with tetragonal Al 3 (Fe,Mn)Si 2

  1. Device Performance and Reliability Improvements of AlGaBN/GaN/Si MOSFET

    Science.gov (United States)

    2016-02-04

    AFRL-AFOSR-JP-TR-2016-0037 Device Performance and Reliablity Improvements of AlGaBN/GaN/Si MOSFET Robert Wallace UNIVERSITY OF TEXAS AT DALLAS Final...GaN/Si MOSFET 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-14-1-4069 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) Robert Wallace 5d.  PROJECT...AOARD Grant FA2386-14-1-4069 Device Performance and Reliability Improvements of AlGaN/GaN/Si MOSFET US 12 month extension (2014 – 2015) for current

  2. Effect of Nuclear Reactions on the Properties of Al-Mg-Si Alloys after Long-Time Exploitation in Research Reactors

    CERN Document Server

    Hofmann, A; Szteke, W; Hajewska, E; Wagner, T; Semina, V K

    2004-01-01

    Effect of fast neutron ($E>$ 0.1~?eV) irradiation on the mechanical properties and fracture morphology of the Al-Mg-Si alloys (PAR-1 and ???-1) after 40 years of exploitation in research nuclear reactors has been studied. Tested specimens were cut from structural elements of reactor EWA ($\\acute{\\rm S}$wierk, Poland). Irradiation induces degradation in mechanical properties, namely yield strength and ultimate strength increase, but elongation reduces. The mechanical property changes are caused by ageing of Al--Mg--Si alloy. During irradiation Si is formed from Al by the Al($n, \\gamma $)Si reaction. The presence of Si might cause strengthening of the Al--Mg--Si alloys by increasing precipitation of Mg$_{2}$Si or pure Si in the Al matrix. Post-irradiation activity studies of EWA reactor structural elements show that the high-activity $^{60}$Co and $^{65}$Zn isotopes have been formed by the nuclear reactions.

  3. Effect of nuclear reactions on the properties of Al-Mg-Si alloys after long-time exploitation in research reactors

    International Nuclear Information System (INIS)

    Hofman, A.; Didyk, A.Yu.; Semina, V.K.; Szteke, W.; Hajewska, E.; Wagner, T.

    2004-01-01

    Effect of fast neutron (E > 0.1 MeV) irradiation on the mechanical properties and fracture morphology of the Al-Mg-Si alloys (PAR-1 and CAB-1) after 40 years of exploitation in research nuclear reactors has been studied. Tested specimens were cut from structural elements of reactor EWA (Swierk, Poland). Irradiation induces degradation in mechanical properties, namely yield strength and ultimate strength increase, but elongation reduces. The mechanical property changes are caused by ageing of Al-Mg-Si alloys. During irradiation Si is formed from Al by the Al(n, γ)Si reaction. The presence of Si might cause strengthening of the Al-Mg-Si alloys by increasing precipitation of Mg 2 Si or pure Si in the Al matrix. Post-irradiation activity studies of EWA reactor structural elements show that the high-activity 60 Co and 65 Zn isotopes have been formed by the nuclear reactions

  4. DISOCIACIONES EN EL RENDIMIENTO PRÁXICO EN PACIENTES CON DEMENCIA TIPO ALZHEIMER: IMITACIÓN DE GESTOS TRANSITIVOS, INTRANSITIVOS Y NO FAMILIARES

    Directory of Open Access Journals (Sweden)

    PABLO GUILLERMO GÓMEZ

    2011-01-01

    Full Text Available En el contexto de evaluación de praxias, los gestos pueden clasificarse en tres categorías: transitivos, intransitivos y no familiares. Si bien ha sido reportada la disociación entre los distintos tipos de gestos, es usual que en la evaluación de praxias o en el análisis del desempeño de los pacientes no se consideren por separado estas tres categorías de gestos, o se varíe la definición de ellas. El objetivo del estudio que se informa fue eva luar si en un mismo grupo de pacientes con demencia tipo Alzheimer se encuentran disociaciones entre gestos transitivos, intransitivos y no familiares, previamente descriptas en el rendimiento práxico de pacientes con lesiones focales (González Rothi, Mack, Verfaellie, Brown & Heilman, 1988; Negri et al., 2007. Se evaluaron 50 pacientes con diagnóstico de demencia tipo Alzheimer probable en imitación de praxias (gestos transitivos, gestos intransitivos y gestos no familiares y uso de objetos. Los estímulos fueron tomados de la batería cognitiva de evaluación de praxias (Politis, 2003. Los gestos eran inicialmente realizados por el examinador, quien mantenía su ejecución durante la imitación del paciente. El grupo con diagnóstico de demencia tipo Alzheimer rindió significativamente peor que el grupo de los controles sanos. En el grupo de pacientes, las cuatro pruebas de praxias correlacionaron entre si. Sin embargo, se hallaron disociaciones en el rendimiento individual de cada paciente en esas mismas pruebas. La disociación entre gestos transitivos, intransitivos y no familiares apoya la posibilidad de que estos diferentes tipos de gestos involucren sistemas de procesamiento distintos.

  5. Aqueous suspensions of {alpha}Al{sub 2}O{sub 3}/SiC mixed systems

    Energy Technology Data Exchange (ETDEWEB)

    Pagnoux, C.; Baklouti, S.; Chartier, T.; Baumard, J.F. [ENSCI, Limoges (France). LMCTS

    1997-12-31

    The preparation of aqueous {alpha}-Al{sub 2}O{sub 3}, {alpha}-SiO{sub 2} and {alpha}-SiC suspensions with polyelectrolytes, respectively the NH{sub 4}{sup +} salt of polymethacrylic acid (PMA-NH{sub 4}{sup +}) and acidic form polyethylene imine (PEI-H{sup +}) is investigated. It is based on the adsorption of these polyelectrolytes which in turn depends mainly on the nature of the polyelectrolyte, and the charge density which develops on the powder surface in water. Good dispersion and stability of dispersions are then obtained through electrostatic and steric stabilization. As an application, the preparation of an Al{sub 2}O{sub 3}-SiC aqueous mixed slurry was investigated as a preliminary step for processing of Al{sub 2}O{sub 3}/SiC nanocomposites. (orig.) 2 refs.

  6. Thermal stability of Ni/Ti/Al ohmic contacts to p-type 4H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hailong; Shen, Huajun, E-mail: shenhuajun@ime.ac.cn; Tang, Yidan; Bai, Yun; Liu, Xinyu [Microwave Device and IC Department, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029 (China); Zhang, Xufang [School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Wu, Yudong; Liu, Kean [Zhuzhou CSR Times Electric Co., Ltd, ZhuZhou 412001 (China)

    2015-01-14

    Low resistivity Ni/Ti/Al ohmic contacts on p-type 4H-SiC epilayer were developed, and their thermal stabilities were also experimentally investigated through high temperature storage at 600 °C for 100 h. The contact resistance of the Al/Ti/Ni/SiC contacts degraded in different degrees, and the contact morphology deteriorated with the increases of the average surface roughness and interface voids. X-ray spectra showed that Ni{sub 2}Si and Ti{sub 3}SiC{sub 2}, which were formed during ohmic contact annealing and contributed to low contact resistivity, were stable under high temperature storage. The existence of the TiAl{sub 3} and NiAl{sub 3} intermetallic phases was helpful to prevent Al agglomeration on the interface and make the contacts thermally stable. Auger electron spectroscopy indicated that the incorporation of oxygen at the surface and interface led to the oxidation of Al or Ti resulting in increased contact resistance. Also, the formation of these oxides roughened the surface and interface. The temperature-dependence of the specific contact resistance indicated that a thermionic field emission mechanism dominates the current transport for contacts before and after the thermal treatment. It suggests that the Ni/Ti/Al composite ohmic contacts are promising for SiC devices to be used in high temperature applications.

  7. Elimination of Iron Based Particles in Al-Si Alloy

    Directory of Open Access Journals (Sweden)

    Bolibruchová D.

    2015-03-01

    Full Text Available This paper deals with influence on segregation of iron based phases on the secondary alloy AlSi7Mg0.3 microstructure by chrome. Iron is the most common and harmful impurity in aluminum casting alloys and has long been associated with an increase of casting defects. In generally, iron is associated with the formation of Fe-rich phases. It is impossible to remove iron from melt by standard operations, but it is possible to eliminate its negative influence by addition some other elements that affect the segregation of intermetallics in less harmful type. Realization of experiments and results of analysis show new view on solubility of iron based phases during melt preparation with higher iron content and influence of chrome as iron corrector of iron based phases. By experimental work were used three different amounts of AlCr20 master alloy a three different temperature of chill mold. Our experimental work confirmed that chrome can be used as an iron corrector in Al-Si alloy, due to the change of intermetallic phases and shortening their length.

  8. Spin accumulation in Si channels using CoFe/MgO/Si and CoFe/AlOx/Si tunnel contacts with high quality tunnel barriers prepared by radical-oxygen annealing

    International Nuclear Information System (INIS)

    Akushichi, T.; Shuto, Y.; Sugahara, S.; Takamura, Y.

    2015-01-01

    We investigate spin injection into Si channels using three-terminal spin-accumulation (3T-SA) devices with high-quality CoFe/MgO/n-Si and CoFe/AlO x /n-Si tunnel spin-injectors whose tunnel barriers are formed by radical oxidation of Mg and Al thin films deposited on Si(100) substrates and successive annealing under radical-oxygen exposure. When the MgO and AlO x barriers are not treated by the radical-oxygen annealing, the Hanle-effect signals obtained from the 3T-SA devices are closely fitted by a single Lorentz function representing a signal due to trap spins. On the other hand, when the tunnel barriers are annealed under radical-oxygen exposure, the Hanle-effect signals can be accurately fitted by the superposition of a Lorentz function and a non-Lorentz function representing a signal due to accumulated spins in the Si channel. These results suggest that the quality improvement of tunnel barriers treated by radical-oxygen annealing is highly effective for spin-injection into Si channels

  9. High-Temperature Corrosion of AlCrSiN Film in Ar-1%SO2 Gas

    Directory of Open Access Journals (Sweden)

    Poonam Yadav

    2017-03-01

    Full Text Available AlCrSiN film with a composition of 29.1Al-17.1Cr-2.1Si-51.7N in at. % was deposited on a steel substrate by cathodic arc ion plating at a thickness of 1.8 μm. It consisted of nanocrystalline hcp-AlN and fcc-CrN, where a small amount of Si was dissolved. Corrosion tests were carried out at 800 °C for 5–200 h in Ar-1%SO2 gas. The major corrosion reaction was oxidation owing to the high oxygen affinity of Al and Cr in the film. The formed oxide scale consisted primarily of (Al,Cr2O3, within which Fe, Si, and S were dissolved. Even after corrosion for 200 h, the thickness of the scale was about 0.7–1.2 μm, indicating that the film had good corrosion resistance in the SO2-containing atmosphere.

  10. Iron Intermetallic Phases in the Alloy Based on Al-Si-Mg by Applying Manganese

    Directory of Open Access Journals (Sweden)

    Podprocká R.

    2017-09-01

    Full Text Available Manganese is an effective element used for the modification of needle intermetallic phases in Al-Si alloy. These particles seriously degrade mechanical characteristics of the alloy and promote the formation of porosity. By adding manganese the particles are being excluded in more compact shape of “Chinese script” or skeletal form, which are less initiative to cracks as Al5FeSi phase. In the present article, AlSi7Mg0.3 aluminium foundry alloy with several manganese content were studied. The alloy was controlled pollution for achieve higher iron content (about 0.7 wt. % Fe. The manganese were added in amount of 0.2 wt. %, 0.6 wt. %, 1.0 wt. % and 1.4 wt. %. The influence of the alloying element on the process of crystallization of intermetallic phases were compared to microstructural observations. The results indicate that increasing manganese content (> 0.2 wt. % Mn lead to increase the temperature of solidification iron rich phase (TAl5FeSi and reduction this particles. The temperature of nucleation Al-Si eutectic increase with higher manganese content also. At adding 1.4 wt. % Mn grain refinement and skeleton particles were observed.

  11. Effect Of SiC Particles On Sinterability Of Al-Zn-Mg-Cu P/M Alloy

    Directory of Open Access Journals (Sweden)

    Rudianto H.

    2015-06-01

    Full Text Available Premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder was analyzed as matrix in this research. Gas atomized powder Al-9Si with 20% volume fraction of SiC particles was used as reinforcement and added into the alloy with varied concentration. Mix powders were compacted by dual action press with compaction pressure of 700 MPa. High volume fraction of SiC particles gave lower green density due to resistance of SiC particles to plastic deformation during compaction process and resulted voids between particles and this might reduce sinterability of this mix powder. Sintering was carried out under ultra high purity nitrogen gas from 565°-580°C for 1 hour. High content of premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder gave better sintering density and reached up to 98% relative. Void between particles, oxide layer on aluminum powder and lower wettability between matrix and reinforcement particles lead to uncompleted liquid phase sintering, and resulted on lower sintering density and mechanical properties on powder with high content of SiC particles. Mix powder with wt90% of Alumix 431D and wt10% of Al-9Si-vf20SiC powder gave higher tensile strength compare to another mix powder for 270 MPa. From chemical compositions, sintering precipitates might form after sintering such as MgZn2, CuAl2 and Mg2Si. X-ray diffraction, DSC-TGA, and SEM were used to characterize these materials.

  12. Influence of LaSiOx passivation interlayer on band alignment between PEALD-Al2O3 and 4H-SiC determined by X-ray photoelectron spectroscopy

    Science.gov (United States)

    Wang, Qian; Cheng, Xinhong; Zheng, Li; Shen, Lingyan; Zhang, Dongliang; Gu, Ziyue; Qian, Ru; Cao, Duo; Yu, Yuehui

    2018-01-01

    The influence of lanthanum silicate (LaSiOx) passivation interlayer on the band alignment between plasma enhanced atomic layer deposition (PEALD)-Al2O3 films and 4H-SiC was investigated by high resolution X-ray photoelectron spectroscopy (XPS). An ultrathin in situ LaSiOx interfacial passivation layer (IPL) was introduced between the Al2O3 gate dielectric and the 4H-SiC substrate to enhance the interfacial characteristics. The valence band offset (VBO) and corresponding conduction band offset (CBO) for the Al2O3/4H-SiC interface without any passivation were extracted to be 2.16 eV and 1.49 eV, respectively. With a LaSiOx IPL, a VBO of 1.79 eV and a CBO of 1.86 eV could be obtained across the Al2O3/4H-SiC interface. The difference in the band alignments was dominated by the band bending or band shift in the 4H-SiC substrate as a result of different interfacial layers (ILs) formed at the interface. This understanding of the physical details of the band alignment could be a good foundation for Al2O3/LaSiOx/4H-SiC heterojunctions applied in the 4H-SiC metal-oxide-semiconductor field effect transistors (MOSFETs).

  13. Scanning Electron Microscopic Studies of Microwave Sintered Al-SiC Nanocomposites and Their Properties

    Directory of Open Access Journals (Sweden)

    M. A. Himyan

    2018-01-01

    Full Text Available Al-metal matrix composites (AMMCs reinforced with diverse volume fraction of SiC nanoparticles were synthesized using microwave sintering process. The effects of the reinforcing SiC particles on physical, microstructure, mechanical, and electrical properties were studied. The phase, microstructural, and surface analyses of the composites were systematically conducted using X-ray diffraction (XRD, scanning electron microscope (SEM, and surface profilometer techniques, respectively. The microstructural examination revealed the homogeneous distribution of SiC particles in the Al matrix. Microhardness and compressive strength of nanocomposites were found to be increasing with the increasing volume fraction of SiC particles. Electrical conductivity of the nanocomposites decreases with increasing the SiC content.

  14. Corrosion and wear behavior of functionally graded Al2024/SiC composites produced by hot pressing and consolidation

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, Fatih; Canakci, Aykut, E-mail: aykut@ktu.edu.tr; Varol, Temel; Ozkaya, Serdar

    2015-09-25

    Highlights: • Functionally graded Al2024/SiC composites were produced by hot pressing. • Effect of the number of graded layers was investigated on the corrosion behavior. • Functionally graded composites has the most corrosion resistant than composites. • Wear mechanisms of Al2024/SiC composites were explained. - Abstract: Functionally graded Al2024/SiC composites (FGMs) with varying percentage of SiC (30–60%) were produced by hot pressing and consolidation method. The effects of SiC content and number of layers of Al2024/SiC FGMs on the corrosion and wear behaviors were investigated. The microstructures of these composites were characterized by a scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5% NaCl solution. Corrosion experiments shows that corrosion rate (1109 mpy) of two layered FGMs which containing 50 wt.% SiC were much higher than Al2024 matrix (2569 mpy) and Al2024/50 wt.% SiC composite (2201 mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disk wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40 wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role.

  15. Comparative study of initial growth stage in PVT growth of AlN on SiC and on native AlN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Epelbaum, B.M.; Heimann, P.; Bickermann, M.; Winnacker, A. [Department of Materials Science 6, University of Erlangen-Nuernberg, Martensstr. 7, 91058 Erlangen (Germany)

    2005-05-01

    The main issue in homoepitaxial growth of aluminum nitride (AlN) on native seed substrates appears to be aluminum oxynitride poisoning of seed surface leading to polycrystalline growth at 1750-1850 C. This is well below the lowest growth temperature appropriate for physical vapor transport (PVT) of bulk AlN, which is about 2150 C. Contrary, heteroepitaxial growth of AlN on SiC is relatively easy to achieve because of natural formation of a thin molten layer on the seed surface and VLS growth of AlN via the molten buffer layer. The most critical issue of AlN growth on SiC is cracking of the grown layer upon cooling as a result of different thermal expansion. Optimization of seeded growth process can be achieved by proper choice of SiC seed orientation and by use of ultra-pure starting material. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Effect of Si/Al{sub 2} Ratio on 2-butanol Dehydration over HY Zeolite Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Euna; Choi, Hyeonhee; Jeon, Jong-Ki [Kongju National University, Cheonan (Korea, Republic of)

    2015-02-15

    Synthesis of butenes through dehydration of 2-butanol was investigated over HY zeolite catalysts. 2-Butanol dehydration reaction was carried out in a fixed bed catalytic reactor. 2-Butanol conversion was increased with increase of Si/Al{sub 2} ratio of HY zeolite catalysts, which can be ascribed to increase of acid strength with increase of Si/Al{sub 2} ratio. Selectivities to 1-butene, trans-2-butene, and cis-2-butene were not greatly influenced by the change of the Si/Al{sub 2} ratio of HY zeolite. As a result, it was advantageous to use a HY zeolite catalyst with 60 Si/Al{sub 2} ratio for maximizing the yield of 1-butene in the dehydration of 2-butanol. The optimal reaction temperature for maximizing the yield of 1-butene was 250 .deg. C over HY (60) catalyst.

  17. Development of dispersion U(Mo)/Al–Si miniplates fabricated at 500 °C with Al 6061 as cladding

    Energy Technology Data Exchange (ETDEWEB)

    Mirandou, M.I., E-mail: mirandou@cnea.gov.ar [Gerencia Materiales-GAEN-CNEA, Avda. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Aricó, S.F. [Gerencia Materiales-GAEN-CNEA, Avda. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Instituto Sabato UNSAM-CNEA, Avda. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Balart, S.N. [Gerencia Materiales-GAEN-CNEA, Avda. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Fabro, J.O. [Departamento ECRI, Gerencia de Ciclo del Combustible Nuclear, CNEA, Avda. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina)

    2015-02-15

    In the frame of U(Mo) dispersion fuel elements qualification, Si additions to Al matrix arose as a promising solution to the unacceptable failures found when pure Al is used. Analysis of as-fabricated fuel plates made with Al–Si matrices demonstrated that good irradiation behavior is correlated with the formation during fabrication of a Si-containing interaction layer around the U(Mo) particles. Thus, the analysis of the influence of fabrication parameters becomes important. Studies on Al–Si dispersion miniplates fabricated in CNEA, Argentina, have been initiated to determine how to obtain the better interaction layer characteristics with the lesser modifications to the fabrication process and the smaller amount of Si in the matrix. In this work results for miniplates made of atomized U–7 wt%Mo particles dispersed in Al–2 wt%Si and Al–4 wt%Si matrices, obtained by mixing pure Al and Si powders, and Al 6061 as cladding are presented. Interaction layer grown during fabrication process (500 °C) consists of Si-containing phases being U(Al, Si){sub 3} its principal component. Its uniformity is not satisfactory due to the formation of an oxide layer.

  18. Mechanisms controlling the artificial aging of Al-Mg-Si Alloys

    International Nuclear Information System (INIS)

    Pogatscher, S.; Antrekowitsch, H.; Leitner, H.; Ebner, T.; Uggowitzer, P.J.

    2011-01-01

    Highlights: → Artificial aging of Al-Mg-Si alloys in the range of 150 and 250 deg. C. → We study precipitation kinetics caused by various thermal histories. → Natural pre-aging affects kinetics at low artificial aging temperatures. → Natural pre-aging promotes kinetics at high artificial aging temperatures. → A vacancy-prison mechanism explains the effect of natural pre-aging. - Abstract: In this study the artificial aging behavior of the Al-Mg-Si alloy AA 6061 was investigated in the temperature range 150-250 deg. C using atom probe tomography, hardness and resistivity measurements for various thermal histories. It was found that the precipitation kinetics and age-hardening response of artificial aging at temperatures below 210 deg. C are lowered by prior natural aging but enhanced above this temperature. An analysis of hardness data was used to evaluate the temperature dependence of precipitation kinetics and dissolution processes. Supported by theoretical considerations, it is assumed that artificial aging of Al-Mg-Si alloys is controlled via the concentration of mobile vacancies. The 'vacancy-prison mechanism' proposed determines the mobile vacancy concentration in the case of natural pre-aging by temperature-dependent dissolution of co-clusters and solute-vacancy interactions.

  19. Microstructure and Properties of AlSi10Mg Powder for Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    TANG Pengjun

    2018-02-01

    Full Text Available The AlSi10Mg powder was prepared by supersonic gas atomization. After classified, the powder was fabricated into block by selective laser melting (SLM. The microstructure, phase, and evolutions of powder and block were investigated by optical microscope, scanning electron microscope and X-Ray Diffraction. The tensile properties of SLM block were tested by tensile experiments at room temperature. The results show that the size distribution of AlSi10Mg powder after classified can meet the requirements of SLM technology. The powder always is spherical and spherical-like. Meanwhile, the microstructure of powders is fine and uniform, which contain α(Al matrix and (α+Si eutectic. In addition, the melt pool boundaries of SLM block are legible. The microstructure is also uniform and densified, the relative density approaches to 99.5%. On the other hand, only α(Al and few Silicon phase are detected in this condition, due to the most alloying elements are dissolved in α(Al matrix. At room temperature, the ultimate tensile strength of SLM block reaches up to 442 MPa.

  20. Raman spectra of MgSiO3 . 10% Al2O3-perovskite at various pressures and temperatures

    International Nuclear Information System (INIS)

    Liu Lingun; Irifune, T.

    1995-01-01

    Variations of Raman spectra of MgSiO 3 . 10% Al 2 O 3 -perovskite were investigated up to about 270 kbar at room temperature and in the range 108-425 K at atmospheric pressure. Like MgSiO 3 -perovskite, the Raman frequencies of MgSiO 3 . 10% Al 2 O 3 -perovskite increase nonlinearly with increasing pressure and decrease linearly with increasing temperature within the experimental uncertainties and the range investigated. A comparison of these data with those of MgSiO 3 -perovskite suggests that MgSiO 3 . 10% Al 2 O 3 -perovskite is slightly more compressible than MgSiO 3 -perovskite, and that the volume thermal expansion for MgSiO 3 . 10% Al 2 O 3 -perovskite is also slightly greater than that for MgSiO 3 -perovskite. (orig.)

  1. Dispersão e comportamento reológico de concretos refratários ultra-baixo teor de cimento no sistema Al2O3-SiC-SiO2-C

    Directory of Open Access Journals (Sweden)

    Oliveira I. R. de

    2003-01-01

    Full Text Available Concretos refratários no sistema Al2O3-SiC-SiO2-C vêm sendo amplamente utilizados em indústrias siderúrgicas como revestimento de canais de corrida de altos-fornos, em virtude principalmente da sua elevada refratariedade aliada a altas resistências ao choque térmico e ao ataque por escória e metal fundido. Neste trabalho, investigou-se a influência de diferentes tipos de aditivos na trabalhabilidade e dispersão de concretos refratários de ultra-baixo teor de cimento nesse sistema. Apesar da sua alta capacidade de complexar íons de cálcio, moléculas de citrato não foram capazes de controlar adequadamente o tempo de pega do concreto estudado, contradizendo a idéia geral de que os íons de citrato devem ser utilizados para controlar a sua trabalhabilidade. Por outro lado, o aditivo polimetacrilato de sódio mostrou-se eficiente na otimização simultânea da dispersão e da trabalhabilidade do concreto devido provavelmente ao retardamento da dissolução dos íons advindos do cimento.

  2. Ni3Si(Al)/a-SiOx core shell nanoparticles: characterization, shell formation, and stability

    Science.gov (United States)

    Pigozzi, G.; Mukherji, D.; Gilles, R.; Barbier, B.; Kostorz, G.

    2006-08-01

    We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni3Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni3Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiOx). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

  3. Dynamic magnetization of NiZn ferrite doped FeSiAl thin films fabricated by oblique sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Xiaoxi, E-mail: xiaoxi.zhong@gmail.com [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China); Phuoc, Nguyen N. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, Singapore 117411 (Singapore); Soh, Wee Tee [Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Ong, C.K. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, Singapore 117411 (Singapore); Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Li, Lezhong [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China)

    2017-06-15

    Highlights: • We prepared NiZn ferrite doped FeSiAl-based thin films using oblique deposition technique. • The magnetic properties of FeSiAl-based thin films were systematically studied. • Two ferromagnetic resonance peaks were observed in the permeability spectra. • The thermal stability of microwave properties of FeSiAl-based films was studied. • The thermal stability of properties we studied was relatively good. - Abstract: In this study, we comprehensively investigate the dynamic magnetic properties of FeSiAl-NiZnFeO thin films prepared by the oblique deposition method via a shorted microstrip perturbation technique. For the films with higher oblique angle and NiZn ferrite doping amount, there are two ferromagnetic resonance peaks observed in the permeability spectra, and both of the two peaks originate from FeSiAl. Furthermore, the magnetic anisotropy field H{sub K} of the ferromagnetic resonance peak at higher frequency is enhanced with increasing doping amount, which is interpreted in terms of the contribution of reinforced stress-induced anisotropy and shape anisotropy brought about by doping elements and oblique sputtering method. In addition, the thermal stability of the ferromagnetic resonance frequency f{sub FMR} of FeSiAl-NiZnFeO films with oblique angles of 35° and 45° with respect to temperature ranging from 300 K to 420 K is deteriorated with increasing ferrite doping amount, which is mainly ascribed to the influence of pair-ordering anisotropy and/or the reduction of the FeSiAl grain size.

  4. Application progress of solid 29Si, 27Al NMR in the research of cement-based materials

    International Nuclear Information System (INIS)

    Feng Chunhua; Wang Xijian; Li Dongxu

    2014-01-01

    Background: The solid-state Nuclear Magnetic Resonance (NMR) is an effective method for the research of cement-based materials. Now it focuses on using solid 29 Si and 27 Al NMR to research the hydration structure of the cement-based materials in cement chemistry. Purpose: A theoretical guidance is proposed for solid 29 Si and 27 Al NMR technology used in cement chemistry research. Methods: We reviewed the application of solid 29 Si and 27 Al NMR in the cement-based materials and analyzed the problem among the researches. Results: This paper introduced an fundamental, relevant-conditions and basic parameters of NMR, and studied the technical parameters of solid 29 Si and 27 Ai NMR together with the relationship among the hydration structure of cement based material. Moreover, this paper reviewed the related domestic and overseas achievements in the research of hydration structure of the cement-based materials using solid 29 Si and 27 Al NMR. Conclusion: There were some problems in the research on cement-based materials by technology of solid 29 Si and 27 Al NMR. NMR will promote the Hydration theory of cement-based material greatly. (authors)

  5. Excellent Passivation of p-Type Si Surface by Sol-Gel Al2O3 Films

    International Nuclear Information System (INIS)

    Hai-Qing, Xiao; Chun-Lan, Zhou; Xiao-Ning, Cao; Wen-Jing, Wang; Lei, Zhao; Hai-Ling, Li; Hong-Wei, Diao

    2009-01-01

    Al 2 O 3 films with a thickness of about 100 nm synthesized by spin coating and thermally treated are applied for field-induced surface passivation of p-type crystalline silicon. The level of surface passivation is determined by techniques based on photoconductance. An effective surface recombination velocity below 100 cm/s is obtained on 10Ω ·cm p-type c-Si wafers (Cz Si). A high density of negative fixed charges in the order of 10 12 cm −2 is detected in the Al 2 O 3 films and its impact on the level of surface passivation is demonstrated experimentally. Furthermore, a comparison between the surface passivation achieved for thermal SiO 2 and plasma enhanced chemical vapor deposition SiN x :H films on the same c-Si is presented. The high negative fixed charge density explains the excellent passivation of p-type c-Si by Al 2 O 3 . (cross-disciplinary physics and related areas of science and technology)

  6. Effect of SiO2 passivation overlayers on hillock formation in Al thin films

    International Nuclear Information System (INIS)

    Kim, Deok-kee

    2012-01-01

    Hillock formation in Al thin films with varying thicknesses of SiO 2 as a passivation layer was investigated during thermal cycling. Based on the stress measurements and the number of hillocks, 250 nm thick SiO 2 was thick enough to suppress the hillock formation and the suppression of hillock at 250 nm passivation and the lack of suppression at thinner passivation is related to the presence/absence of protection against the diffusive flow of atoms from the surrounding area to the surface due to the biaxial compressive stresses present in the film through the weak spots in the passivation layer. The stress state of Al films measured during annealing (the driving force for hillock formation) did not vary much with SiO 2 thickness. A small number of hillocks formed during the plasma enhanced chemical vapor deposition of SiO 2 overlayers at 300 °C. - Highlights: ► We examined the effect of SiO 2 overlayers on hillock formation in Al thin films. ► Thin overlayers were not effective in suppressing diffusive flow to the surface. ► A thick overlayer suppressed the diffusive flow from the interior to the surface. ► The stress state of Al films did not vary much with SiO 2 passivation thickness. ► High mechanical strength provided a large driving force for the large grain growth.

  7. Valence electron structure analysis of the cubic silicide intermetallics in rapidly solidified Al-Fe-V-Si alloy

    International Nuclear Information System (INIS)

    Wang, J.Q.; Qian, C.F.; Zhang, B.J.; Tseng, M.K.; Xiong, S.W.

    1996-01-01

    The application of rapid solidification for the development of elevated temperature aluminum alloys has resulted in the emergence of several alloys based on the Al-Fe alloy system. Of particular interest are Al-Fe-V-Si alloys which have excellent room temperature and high temperature mechanical properties. In a pioneering study, Skinner et al. showed the stabilization of the cubic phase in ternary Al-Fe-Si alloy by the addition of a quaternary element, vanadium. The evolution of the microstructure in these alloys both during rapid solidification and subsequent processing is of crucial importance. Kim has demonstrated that the composition of the silicide phase in rapidly solidified Al-Fe-V-Si alloy is very close to Al 12 (Fe,V) 3 Si with the body centered cubic (bcc) structure. The structure is closely related to that of quasicrystals.In view of the structural features and the relationship between the α 12 and α 13 phases, the researching emphasis should firstly be put on the α 12 phase. In this paper the authors analyzed the α -(AlFeSi)(α 12 -type) phase from the angle of atomic valence electron structure other than the traditional methods of obtaining the diffraction spots of the phase. Several pieces of information were obtained about the hybrid levels and bond natures of every kind of atom in the α -(AlFeSi) phase. Finally the authors explained the phenomenon which V atom can substitute for Fe atom in the α 12 phase and improve the thermal stability of the phase in Al-Fe-V-Si alloy

  8. Segregation and Microstructure in the Fusion zones of Laser joints of Al-10%Si coated Boron Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Min-Suck [Hyundai Hysco Co., Ltd, Ulsan (Korea, Republic of); Kang, Chung-Yun [Pusan National University, Busan (Korea, Republic of)

    2016-01-15

    During laser welding of Al-10 wt%Si coated boron steel, which is used in the automotive industry, Al and Si, which are elements of the coated layer, are diluted in the fusion zone; then, the concentration of Al and Si is distributed randomly. The segregation can be roughly classified into two types. The first forms along the fusion boundary in a long comet shape in the depth direction of the fusion zone. The Al concentration of this comet shape is Fe3(Al, Si)and the material is composed of a single phase. This segregation phase is formed at the same time as the melting of the base metal and the diluting of the coated layer of Fe(Al, Si), without reaction of the molten metal. Then, a static dissolution reaction of the diluted coated layer occurs, scarcely stirring the molten metal; the concentration of Al and Si is reduced to 1/2. The second type of segregation is formed by martensite and bainte in the fusion zone of the segregated zone; the composition of Al is 1.28⁓0.48 wt%. Considering the results of the analysis of the Fe(Si,C, Mn,Cr)-xwt%Al quasi binary phase diagram, performed using Thermo-Calc, segregated zones are solidified in the form “L→L+α→γ”. Also, and as a result, it was found that the phase transformation from γ under-cooling results in the solid phase, which undergoes bainite transformation and is transformed to martensite.

  9. Segregation and Microstructure in the Fusion zones of Laser joints of Al-10%Si coated Boron Steel

    International Nuclear Information System (INIS)

    Kwon, Min-Suck; Kang, Chung-Yun

    2016-01-01

    During laser welding of Al-10 wt%Si coated boron steel, which is used in the automotive industry, Al and Si, which are elements of the coated layer, are diluted in the fusion zone; then, the concentration of Al and Si is distributed randomly. The segregation can be roughly classified into two types. The first forms along the fusion boundary in a long comet shape in the depth direction of the fusion zone. The Al concentration of this comet shape is Fe3(Al, Si)and the material is composed of a single phase. This segregation phase is formed at the same time as the melting of the base metal and the diluting of the coated layer of Fe(Al, Si), without reaction of the molten metal. Then, a static dissolution reaction of the diluted coated layer occurs, scarcely stirring the molten metal; the concentration of Al and Si is reduced to 1/2. The second type of segregation is formed by martensite and bainte in the fusion zone of the segregated zone; the composition of Al is 1.28⁓0.48 wt%. Considering the results of the analysis of the Fe(Si,C, Mn,Cr)-xwt%Al quasi binary phase diagram, performed using Thermo-Calc, segregated zones are solidified in the form “L→L+α→γ”. Also, and as a result, it was found that the phase transformation from γ under-cooling results in the solid phase, which undergoes bainite transformation and is transformed to martensite.

  10. Oxidation precursor dependence of atomic layer deposited Al2O3 films in a-Si:H(i)/Al2O3 surface passivation stacks.

    Science.gov (United States)

    Xiang, Yuren; Zhou, Chunlan; Jia, Endong; Wang, Wenjing

    2015-01-01

    In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al2O3 stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al2O3 stacks, the minimum interface trap density was reduced from original 3 × 10(12) to 1 × 10(12) cm(-2) eV(-1), the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 10(12) cm(-2) for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

  11. TEM Nanostructural Study of Al-6Si-3Cu-Mg Melt-Spun Ribbons

    Directory of Open Access Journals (Sweden)

    Ismeli Alfonso López

    2008-01-01

    Full Text Available Three quaternary Al-6Si-3Cu-xMg (x = 0.59, 3.80, and 6.78 wt.% alloys were produced by melt-spun and characterized using X-ray diffractometry (XRD, transmission electron microscopy (TEM, and microhardness techniques. Obtained second phases were Al2Cu( for the alloy with 0.59% Mg and Al5Cu2Mg8Si6 (Q for the alloys with 3.80 and 6.78% Mg. These phases are present as 30–50 nm or as 5–10 nm nanoparticles. Alloying elements content in solid solution increased, mainly for Si and Mg. The high alloying elements content in solid solution and the small -Al cell size for melt-spun alloys leads to microhardness values about 2 times higher than those of ingot counterparts. The microhardness increase for melt-spun alloys with 3.80 and 6.78% Mg depends on Mg content in solid solution.

  12. Low temperature internal friction in La75Al20Si5 metallic glass

    International Nuclear Information System (INIS)

    Zolotukhin, I.V.; Kalinin, Yu.E.

    1991-01-01

    Results of investigation of temperature dependence of internal friction (IF) in amorphous alloy La 75 Al 20 Si 5 are presented. The amorphous state was atteined by quenching from liquid melt at a rate of 10 5 -10 6 K/s. Two IF maxima at Q -1 (T) dependence are observed at the temperatures of 185 and 230 K. Increase in the frequency of mechanical vibrations results in the shift of IF maxima to the side of high temperatures, which indicates their relaxation origin. The first peak of IF in the studied alloy La 75 Al 20 Si 5 is in all probability related to reorientation of chemical bonds La-La and La-Al. The maximum at T∼230 K is related to the switching of La-Si chemical bonds

  13. Evaluación del efecto de modificadores y refinadores en el comportamiento mecánico y magnitud del rechupe de aleaciones Al-Si-Mg. // Modifier and refiners effect evaluation in the magnitude and mechanical shrinkage behavior of Al-Si-Mg alloys.

    Directory of Open Access Journals (Sweden)

    V. Lavaert

    2002-05-01

    Full Text Available Se estudia la influencia del Na, Sr y Ti y sus combinaciones (Na-Ti y Sr-Na en las propiedades mecánicas y el rechupe(superior y lateral de la aleación hipoeutéctica AlSi7Mg Aunque todos estos elementos y combinaciones tienden aneutralizar la formación del rechupe substancialmente, el Sr se presenta como el más eficaz para disminuir el rechupesuperior mientras la combinación Na-Ti llevó a la menor formación de rechupe lateral.Se observó una acción modificadora excelente para 0.02% de Sr y 0.02% de Na, pero a diferencia del Sr, el efectomodificador del Na comienza a desvanecerse después de 30 min afectando el alargamiento notablemente. El estroncio, sinembargo, mostró un efecto de la modificación muy duradero (aproximadamente 3 h. Otro hallazgo interesante es laexistencia de un cierto periodo de incubación de aproximadamente 90 minutos después de agregar Sr. Contrariamente a loesperado el uso de titanio no mejoró las propiedades mecánicas a pesar de un eficaz refinamiento de grano.Palabras claves: Rechupe superior, acción modificadora, propiedades mecánicas, metalurgia no ferrosa._________________________________________________________________________AbstractThe influence of Na, Sr and Ti and their combinations (Na-Ti and Sr-Na on the mechanical properties and the shrinkage(top macro shrinkage and lateral macro shrinkage of hypoeutectic aluminium-silicon alloys (AlSi7xMg has been studied.Although all these elements and combinations tend to counteract substantially the shrinkage formation, Sr appeared to bethe most effective to decrease top macro shrinkage whereas the combination Na-Ti led to the least formation of lateralmacro shrinkage. An excellent modifying action was observed for 0.02% Sr and 0.02% Na, but unlike Sr the modifyingeffect provided by Na started fading after 30 min of holding which affected the elongation markedly. However, strontiumshowed a very lasting modification effect (about 3 h. Another interesting

  14. Tunable Luminescence of CeAl11O18 Based Phosphors by Replacement of (AlO)+ by (SiN)+ and Co-Doping with Eu

    NARCIS (Netherlands)

    Yin, L.J.; Chen, G.Z; Wang, C.; Xu, X.; Hao, L.Y.; Hintzen, H.T.J.M.

    2014-01-01

    A series of Si-N or Eu-Li doped CeAl11O18 and CeAl12O18N phosphors are prepared by solid–state reaction. Their structure and luminescence are researched carefully. Si-N doping with the concentration less than 8% can be successfully dissolved into CeAl11O18 crystal lattice and doesn't change the

  15. Evolution of Primary Fe-Rich Compounds in Secondary Al-Si-Cu Alloys

    Science.gov (United States)

    Fabrizi, Alberto; Capuzzi, Stefano; Timelli, Giulio

    Although iron is usually added in die cast Al-Si foundry alloys to prevent die soldering, primary Fe-rich particles are generally considered as "hardspot" inclusions which compromise the mechanical properties of the alloy, namely ductility and toughness. As there is no economical methods to remove the Fe excess in secondary Al-Si alloys at this time, the control of solidification process and chemical composition of the alloy is a common industrial practice to overcome the negative effects connected with the presence of Fe-rich particles. In this work, the size and morphology as well as the nucleation density of primary Fe-rich particles have been studied as function of cooling rate and alloy chemical composition for secondary Al-Si-Cu alloys. The solidification experiments were carried out using differential scanning calorimetry whereas morphology investigations were conducted using optical and scanning electron microscopy. Mcrosegregations and chemical composition of primary Fe-rich particles were examined by energy dispersive spectroscopy.

  16. Wear behaviour of plasma-sprayed AlSi/B4C composite coatings

    International Nuclear Information System (INIS)

    Sarikaya, Ozkan; Anik, Selahaddin; Celik, Erdal; Okumus, S. Cem; Aslanlar, Salim

    2007-01-01

    This paper describes the wear behaviour of AlSi/B 4 C composite coatings with 0-25 wt% B 4 C particles for diesel engine motors. These coatings were successfully fabricated on AlSi substrates using an atmospheric plasma spray technique. The produced samples were characterized by means of an optical microscope, scanning electron microscope and microhardness tester. The obtained results pointed out that an increase of B 4 C particles in AlSi coatings was caused on the rising of the microhardness values and the decrease of the thermal expansion coefficient of the coatings. The friction and wear experiments were performed under dry conditions using a ball-on-dics configuration against WC/Co counter material for different loads. It was concluded that wear resistance of the coatings produced using B 4 C powders is greatly improved compared with the substrate material. The highest wear resistance of the coatings were also determined in the 20% B 4 C coating

  17. Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy

    Directory of Open Access Journals (Sweden)

    Sonia C. Ferreira

    2014-12-01

    Full Text Available Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiCnp produced by powder metallurgy (PM were anodized under voltage control in tartaric-sulfuric acid (TSA. In this work, the influence of the amount of SiCnp on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050 anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiCnp. The current peaks and the steady-state current density recorded at each voltage step increases with the SiCnp volume fraction due to the oxidation of the SiCnp. The formation mechanism of the anodic film on Al/SiCnp composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiCnp in the anodic film.

  18. Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy

    Science.gov (United States)

    Ferreira, Sonia C.; Conde, Ana; Arenas, María A.; Rocha, Luis A.; Velhinho, Alexandre

    2014-01-01

    Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiCnp) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiCnp on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiCnp. The current peaks and the steady-state current density recorded at each voltage step increases with the SiCnp volume fraction due to the oxidation of the SiCnp. The formation mechanism of the anodic film on Al/SiCnp composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiCnp in the anodic film. PMID:28788295

  19. Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy.

    Science.gov (United States)

    Ferreira, Sonia C; Conde, Ana; Arenas, María A; Rocha, Luis A; Velhinho, Alexandre

    2014-12-19

    Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiC np ) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiC np on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiC np . The current peaks and the steady-state current density recorded at each voltage step increases with the SiC np volume fraction due to the oxidation of the SiC np . The formation mechanism of the anodic film on Al/SiC np composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiC np in the anodic film.

  20. Magnetocrystalline anisotropy constants, rotational hysteresis energy and magnetic domain structure in UFe6Al6, UFe9AlSi2 and ScFe10Si2 intermetallic compounds

    International Nuclear Information System (INIS)

    Wyslocki, J.J.; Pawlik, P.; Wochowski, K.; Kotur, B.; Bodak, O.I.

    1996-01-01

    The magnetic torque, T, was applied to determine the anisotropy constants K 1 and K 2 of the UFe 6 Al 6 , UFe 9 AlSi 2 and ScFe 10 Si 2 compounds. The mechanism of magnetization reversal processes in these compounds was investigated on the basis of the analysis of the rotational hysteresis energy, W r and rotational hysteresis integral, R, calculated from the magnetic torque curves. Applying the powder pattern method, magnetic domain structures were observed. Moreover, the fundamental parameters of the domain structure were determined. (orig.)

  1. Al- or Si-decorated graphene oxide: A favorable metal-free catalyst for the N2O reduction

    Science.gov (United States)

    Esrafili, Mehdi D.; Sharifi, Fahimeh; Nematollahi, Parisa

    2016-11-01

    The structural and catalytic properties of Al- or Si-decorated graphene oxide (Al-/Si-GO) are studied by means of density functional theory calculations. The relatively large adsorption energy together with the small Alsbnd O or Sisbnd O binding distances indicate that the epoxy groups over the GO surface can strongly stabilize the single Al or Si atom. Hence, Al-GO and Si-GO are stable enough to be utilized in catalytic reduction of N2O by CO molecule. It is found that the adsorption and decomposition of N2O molecule over Si-GO is more favorable than over Al-GO, due to its larger adsorption energy (Eads) and charge transfer (qCT) values. On the other hand, the CO molecule is physically adsorbed over both surfaces, with relatively small Eads and qCT values. Therefore, at the presence of N2O and CO molecules as the reaction gas, the Al or Si atom of the surface should be dominantly covered by N2O molecule. Our results indicate that the N2O decomposition process can take place with a negligible activation energy over Al-/Si-GO surface, where the N2 molecule can be easily released from the surface. Then, the activated oxygen atom (Oads) which remains over the surface reacts with the CO molecule to form the CO2 molecule via the reaction Oads + CO → CO2. Based on the calculated activation energies, it is suggested that both Al-GO and Si-GO can be used as an efficient metal-free catalyst for the reduction of N2O molecule at ambient conditions.

  2. Effect of nano Cu coating on porous Si prepared by acid etching Al-Si alloy powder

    International Nuclear Information System (INIS)

    Li, Chunli; Zhang, Ping; Jiang, Zhiyu

    2015-01-01

    As a promising anode material for lithium ion battery, nano-Cu coated porous Si powder was fabricated through two stages: first, preparation of porous nano Si fibers by acid-etching Al-Si alloy powder; second, modified by nano-Cu particles using an electroless plating method. The nano-Cu particles on the surface of nano-Si fibers, not only increase the conductivity of material, but also inhibit the fuse process between nano Si fibers during charge/discharge cycling process, resulting in increased cycling stability of the material. In 1 M LiPF 6 /EC: DMC (1:1) + 1.5 wt% VC solution at current density of 200 mA g −1 , the 150th discharge capacity of nano-Cu coated porous Si electrode was 1651 mAh g −1 with coulombic efficiency of 99%. As anode material for lithium ion battery, nano-Cu coated porous Si nano fiber material is easier to prepare, costs less, and produces higher performance, representing a promising approach for high energy lithium ion battery application

  3. Preparation and characterization of the electrodeposited Cr-Al{sub 2}O{sub 3}/SiC composite coating

    Energy Technology Data Exchange (ETDEWEB)

    Gao Jifeng, E-mail: readlot@tom.com [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Suo Jinping, E-mail: jpsuo@yahoo.com.cn [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2011-09-01

    To increase the SiC content in Cr-based coatings, Cr-Al{sub 2}O{sub 3}/SiC composite coatings were plated in Cr(VI) baths which contained Al{sub 2}O{sub 3}-coated SiC powders. The Al{sub 2}O{sub 3}-coated SiC composite particles were synthesized by calcining the precursor prepared by heterogeneous deposition method. The transmission electron microscopy analysis of the particles showed that the nano-SiC particle was packaged by alumina. The zeta potential of the particles collected from the bath was up to +23 mV, a favorable condition for the co-deposition of the particles and chromium. Pulse current was used during the electrodeposition. Scanning Electron Microscopy (SEM) indicated that the coating was compact and combined well with the substrate. Energy dispersive X-ray analysis of Cr-Al{sub 2}O{sub 3}/SiC coatings demonstrated that the concentration of SiC in the coating reached about 2.5 wt.%. The corrosion behavior of the composite coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The data obtained suggested that the Al{sub 2}O{sub 3}/SiC particles significantly enhanced the corrosion resistance of the composite coating in 0.05 M HCl solution.

  4. Crack resistance behaviour of an intermetallic Ti-Al-Si-Nb alloy at room temperature

    International Nuclear Information System (INIS)

    Wittkowsky, B.U.; Pfuff, M.J.

    1996-01-01

    The room temperature crack growth behaviour of a Ti-Al-Si-Nb alloy consisting of the two intermetallic phases (Ti, Nb) 3 (Al, Si) and (Ti, Nb) 5 (Si, Al) 3 is investigated in the present paper. The material exhibits a heterogeneous disordered microstructure and fails in a brittle manner. Crack growth is associated with a pronounced crack resistance behaviour. For a sample of nominally identical specimens the R-curves scatter around a mean curve with a standard deviation which remains roughly constant as the crack grows. A natural extension of the bundle model introduced in a previous paper is used to simulate R-curves and their scatter is in reasonably good agreement with the experimental findings. (orig.)

  5. Low Z elements (Mg, Al, and Si) K-edge X-ray absorption spectroscopy in minerals and disordered systems

    International Nuclear Information System (INIS)

    Ildefonse, P.; Calas, G.; Flank, A.M.; Lagarde, P.

    1995-01-01

    Soft X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy have been performed at the Mg-, Al- and Si-K edges in order to establish the ability of this spectroscopy to derive structural information in disordered solids such as glasses and gels. Mg- and Al-K XANES are good structural probes to determine the coordination state of these elements in important minerals, glasses and gels. In a CaO-MgO-2SiO 2 glass Mg XANES spectra differ from that found in the crystalline equivalent, with a significant shift of the edge maxima to lower energy, consistent with a CN lower than 6. Mg-EXAFS on the same sample are in agreement and indicate the presence of 5-coordinated Mg with Mg-O distances of 2.01 A. In aluminosilicate gels, Al-K XANES has been used to investigate the [4]Al/Al total ratios. These ratios increase as the Al/Si ratios decrease. Aluminosilicate and ferric-silicate gels were studied by using Si-K edge XANES. XANES spectra differ significantly among the samples studied. Aluminosilicate gels with Al/Si=1 present a different Al and Si local environment from that known in clay minerals with the same Al/Si ratio. The gel-to-mineral transformation thus implies a dissolution-recrystallization mechanism. On the contrary, ferric-silicate gel presents a Si local environment close to that found in nontronite which may be formed by a long range ordering of the initial gels. (orig.)

  6. Si diffusion in compositional disordering of Si-implanted GaAs/AlGaAs superlattices induced by rapid thermal annealing

    International Nuclear Information System (INIS)

    Uematsu, Masashi; Yanagawa, Fumihiko

    1988-01-01

    The Si diffusion in Si-implanted GaAs/Al 0.5 Ga 0.5 As superlattices intermixed in the disrodering process induced by rapid thermal annealing (RTA), is investigated by means of secondary ion mass spectroscopy (SIMS). The SIMS profiles indicate that no fast Si diffusion occurs during the disordering, and the disordering occurs when the Si concentration exceeds 1 x 10 19 cm -3 , which is about three times larger than the threshold value for the disordering by furnace annealing (FA). The number of Si atoms which are allowed to pass through the heterointerface is considered to be essential for disordering. (author)

  7. Microstructure, mechanical and tribological properties of CrSiC coatings sliding against SiC and Al{sub 2}O{sub 3} balls in water

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zhiwei [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics and Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology, Nanjing 210016 (China); College of Mechanical and Electrical Engineering, Nanjing Forestry University, Nanjing 210037 (China); Zhou, Fei, E-mail: fzhou@nuaa.edu.cn [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics and Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology, Nanjing 210016 (China); Chen, Kangmin [Center of Analysis, Jiangsu University, Zhenjiang 212013 (China); Wang, Qianzhi [Department of Mechanical Engineering, Keio University, Yokohama 2238522 (Japan); Zhou, Zhifeng [Advanced Coatings Applied Research Laboratory, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong (China); Yan, Jiwang [Department of Mechanical Engineering, Keio University, Yokohama 2238522 (Japan); Li, Lawrence Kwok-Yan [Advanced Coatings Applied Research Laboratory, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong (China)

    2016-04-15

    Graphical abstract: CrSiC coatings were speculated to be X-ray amorphous (A). Although the hardness of coatings fluctuated slightly (13.2–13.8 GPa), the CrSiC coatings showed poor wear resistance due to the decline of the crack resistance and toughness. Moreover, the friction coefficient (0.24–0.31) and the wear rate (2.97–7.66 × 10{sup −6} mm{sup 3}/Nm) of CrSiC/SiC trobopairs were lower than those of CrSiC/Al{sub 2}O{sub 3} tribopairs (B and C). - Highlights: • CrSiC coatings with Si content of 2.0–7.4 at.% were deposited via adjusting the TMS flow. • The amorphous structure in the CrSiC coatings was presented. • No obvious fluctuations of hardness (about 13 GPa) were observed with TMS flow. • CrSiC/SiC tribopairs showed better tribological performance than CrSiC/Al{sub 2}O{sub 3} tribopairs. - Abstract: CrSiC coatings with different silicon contents were prepared using unbalanced magnetron sputtering via adjusting trimethylsilane (Si(CH{sub 3}){sub 3}H) flows. Their phase structure, bonding structure, microstructure and hardness were characterized by X-ray diffraction (XRD), X-ray photoelectrons spectroscopy (XPS), a field emission scanning electron microscope (FESEM) and nano-indenter, respectively. The tribological properties of CrSiC coatings sliding against SiC and Al{sub 2}O{sub 3} balls were investigated in water. The results showed that the CrSiC coatings were speculated to be X-ray amorphous. Although the hardness of coatings fluctuated slightly (13.2–13.8 GPa), the coatings showed poor wear resistance due to the decline of the crack resistance and toughness. Moreover, the friction coefficient (0.24–0.31) and the wear rate (2.97–7.66 × 10{sup −6} mm{sup 3}/Nm) of CrSiC/SiC trobopairs were lower than those of CrSiC/Al{sub 2}O{sub 3} tribopairs.

  8. Surface passivation by Al2O3 and a-SiNx: H films deposited on wet-chemically conditioned Si surfaces

    NARCIS (Netherlands)

    Bordihn, S.; Mertens, V.; Engelhart, P.; Kersten, K.; Mandoc, M.M.; Müller, J.W.; Kessels, W.M.M.

    2012-01-01

    The surface passivation of p- and n-type silicon by different chemically grown SiO2 films (prepared by HNO3, H2SO4/H2O2 and HCl/H2O2 treatments) was investigated after PECVD of a-SiNx:H and ALD of Al2O3 capping films. The wet chemically grown SiO2 films were compared to thermally grown SiO2 and the

  9. Scanning electron microscopy analysis of fuel/matrix interaction layers in highly-irradiated U-Mo dispersion fuel plates with Al and Al-Si alloy matrices

    Energy Technology Data Exchange (ETDEWEB)

    Keiser, Dennis D. Jr; Jue, Jan Fong; Miller, Brandon D.; Gan, Jian; Robinson, Adom B.; Medvedev, Pavel; Madden, James; Wachs, Dan; Meyer, Mitch [Nuclear Fuels and Materials Division, Idaho National Laboratory (United States)

    2014-04-15

    In order to investigate how the microstructure of fuel/matrix-interaction (FMI) layers change during irradiation, different U-7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electron microscopy (SEM). Specifically, samples from irradiated U-7Mo dispersion fuel elements with pure Al, Al-2Si and AA4043 (-4.5 wt.%Si) matrices were SEM characterized using polished samples and samples that were prepared with a focused ion beam (FIB). Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. For the Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface and evidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U-7Mo fuel was observed for samples with Si in the Al matrix, which resulted in a change of the size (larger) and shape (round) of the fission gas bubbles. Additionally, solid fission product phases were observed to nucleate and grow within these bubbles. These changes in the localized regions of the microstructure of the U-7Mo may contribute to changes observed in the macroscopic swelling of fuel plates with Al-Si matrices.

  10. Three-dimensional rigid multiphase networks providing high-temperature strength to cast AlSi10Cu5Ni1-2 piston alloys

    International Nuclear Information System (INIS)

    Asghar, Z.; Requena, G.; Boller, E.

    2011-01-01

    The three-dimensional (3-D) architecture of rigid multiphase networks present in AlSi10Cu5Ni1 and AlSi10Cu5Ni2 piston alloys in as-cast condition and after 4 h spheroidization treatment is characterized by synchrotron tomography in terms of the volume fraction of rigid phases, interconnectivity, contiguity and morphology. The architecture of both alloys consists of α-Al matrix and a rigid long-range 3-D network of Al 7 Cu 4 Ni, Al 4 Cu 2 Mg 8 Si 7 , Al 2 Cu, Al 15 Si 2 (FeMn) 3 and AlSiFeNiCu aluminides and Si. The investigated architectural parameters of both alloys studied are correlated with room-temperature and high-temperature (300 deg. C) strengths as a function of solution treatment time. The AlSi10Cu5Ni1 and AlSi10Cu5Ni2 alloys behave like metal matrix composites with 16 and 20 vol.% reinforcement, respectively. Both alloys have similar strengths in the as-cast condition, but the AlSi10Cu5Ni2 is able to retain ∼15% higher high temperature strength than the AlSi10Cu5Ni1 alloy after more than 4 h of spheroidization treatment. This is due to the preservation of the 3-D interconnectivity and the morphology of the rigid network, which is governed by the higher degree of contiguity between aluminides and Si.

  11. Multiscale tomographic analysis of heterogeneous cast Al-Si-X alloys.

    Science.gov (United States)

    Asghar, Z; Requena, G; Sket, F

    2015-07-01

    The three-dimensional microstructure of cast AlSi12Ni and AlSi10Cu5Ni2 alloys is investigated by laboratory X-ray computed tomography, synchrotron X-ray computed microtomography, light optical tomography and synchrotron X-ray computed microtomography with submicrometre resolution. The results obtained with each technique are correlated with the size of the scanned volumes and resolved microstructural features. Laboratory X-ray computed tomography is sufficient to resolve highly absorbing aluminides but eutectic and primary Si remain unrevealed. Synchrotron X-ray computed microtomography at ID15/ESRF gives better spatial resolution and reveals primary Si in addition to aluminides. Synchrotron X-ray computed microtomography at ID19/ESRF reveals all the phases ≥ ∼1 μm in volumes about 80 times smaller than laboratory X-ray computed tomography. The volumes investigated by light optical tomography and submicrometre synchrotron X-ray computed microtomography are much smaller than laboratory X-ray computed tomography but both techniques provide local chemical information on the types of aluminides. The complementary techniques applied enable a full three-dimensional characterization of the microstructure of the alloys at length scales ranging over six orders of magnitude. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  12. Modeling and optimization of cylindrical grinding of Al/SiC composites using genetic algorithms

    OpenAIRE

    Thiagarajan, C.; Sivaramakrishnan, R.; Somasundaram, S.

    2012-01-01

    The Al/SiC composites have received more commercial attention than other kinds of Metal Matrix Composites (MMCs) due to their high performance. However, a continuing problem with MMCs is that they are difficult to machine, due to the hardness and abrasive nature of the SiC particles. Grinding is often the method of choice for machining Al/SiC composites to acquire high dimensional accuracy and surface finish in large scale production. Based on the full factorial design (3(4)), a total of 81 e...

  13. (SiC/AlN)2 multilayer film as an effective protective coating for sintered NdFeB by magnetron sputtering

    Science.gov (United States)

    You, Yu; Li, Heqin; Huang, Yiqin; Tang, Qiong; Zhang, Jing; Xu, Jun

    2017-08-01

    SiC/AlN and (SiC/AlN)2 multilayer films with a well-arranged bilayer structure and a four-layer structure are prepared respectively on NdFeB substrates by a magnetron sputtering method. Crystal phase and microstructures of the SiC/AlN and (SiC/AlN)2 films are investigated using x-ray diffraction (XRD), field-emission scanning electron microscope (FESEM) and atomic force microscope (AFM). It is observed that the surface of the (SiC/AlN)2 four-layer film is much denser and smoother than that of the SiC/AlN bilayer film. Corrosion behaviors of the NdFeB substrates coated with SiC/AlN and (SiC/AlN)2 films as well as the bare NdFeB substrate are evaluated by potentiodynamic polarization curve tests. It is revealed that the lateral growth structures developed in interfaces are favorable for an enhanced corrosion resistance. Corrosion current densities of the (SiC/AlN)2 coated NdFeB measured in acid, alkali and salt solutions are 2.796  ×  10-9, 3.65  ×  10-6, and 2.912  ×  10-6 A cm-2, respectively, which are much lower than those of the bare NdFeB and the SiC/AlN coated NdFeB.

  14. Effect of compound field on horizontal continuous casting of Al-1wt.%Si alloy

    Directory of Open Access Journals (Sweden)

    Zhong-tao Zhang

    2015-03-01

    Full Text Available A travelling magnetic field, a power ultrasonic field, and a compound field were used separately during the horizontal continuous casting process of Al-1wt.%Si alloy. The samples obtained were characterized using an optical microscope, a scanning electron microscope, a tensile testing machine, and an electron probe microscopic analyzer to test the microstructures, properties, and element distribution of the samples. The results show that the application of a single field can enhance the mechanical properties and reduce the segregation of Si element in Al-1wt.%Si alloy to some extent. The application of a compound field can obtain the best refinement and homogeneity of the Si element in the alloy, leading to the highest increase of tensile strength and elongation among the three applied fields. The mechanism of the action of external fields on the refinement of microstructures and homogeneity of the Si element is discussed and the compound field is considered to be an effective method to achieve high quality Al alloys.

  15. Phase Diagram of Al-Ca-Mg-Si System and Its Application for the Design of Aluminum Alloys with High Magnesium Content

    Directory of Open Access Journals (Sweden)

    Nikolay A. Belov

    2017-10-01

    Full Text Available The phase transformations in the Al-Ca-Mg-Si system have been studied using thermodynamic calculations and experimental methods. We show that at 10% Magnesium (Mg, depending on the concentrations of calcium (Ca and silicon (Si, the following phases crystallize first (apart from the aluminum (Al solid solution: Al4Ca, Mg2Si, and Al2CaSi2. We have found that the major part of the calculated concentration range is covered by the region of the primary crystallization of the Al2CaSi2 phase. Regardless of the Ca and Si content, the solidification of the aluminum-magnesium alloys ends with the following nonvariant eutectic reaction: L → (Al + Al4Ca + Mg2Si + Al3Mg2. With respect to the temperature and composition of the liquid phase, this reaction is close to the eutectic reaction in the Al-Mg binary system. The addition of Ca and Si to the Al-10% Mg base alloy increases its hardness, reduces its density, and has no negative influence on its corrosion resistance. We have also established that the near-eutectic alloy containing about 3% Ca and 1% Si has the optimum structure.

  16. Calculation of solidification microstructure maps for the system Al-Fe-Si

    International Nuclear Information System (INIS)

    Gilgien, P.

    1996-01-01

    Computer programs have been developed in order to calculate solidification microstructure maps for binary and ternary alloys. These programs are based on recent analytical models for the constrained growth of dendrites and eutectics. Due to the importance of phase diagrams data, programs for the calculation of growth kinetics are coupled with ThermoCalc, a commercial software for phase diagram calculations. These programs have been used to calculate a solidification microstructure map for the Al-Fe system from 0 to 4 at%Fe. Comparison of the calculated results with an experimental solidification microstructure map from the literature shows that all microstructure transitions were predicted. Nevertheless there remain significant discrepancies between some calculated and experimental transition velocities. The programs were also used to calculate solidification microstructure maps in the Al-rich corner of the Al-Fe-Si system (0 to 8 at% Fe and 0 to 8 at% Si). In this case also, calculated results were in satisfactory agreement with experimental solidification microstructure maps, although the comparison was only partial since experimental ternary microstructure maps are less complete than for the binary system, and because the available thermodynamic database does not, as yet, include metastable phases. Laser surface remelting experiments were carried out on an Al-4 at% Fe alloy in order to link results from the literature, obtained at high solidification rates by laser surface remelting and at low solidification rates by Bridman experiments. Finally, Bridman experiments were carried out with an Al-2.63 wt% Fe alloy in order to determine the critical velocity at which a planar Al-Al 13 Fe 4 eutectic front is destabilised in a cellular eutectic by a small amount of Si. The critical solidification velocity thus obtained was in agreement with a criterion of constitutional undercooling. (author) figs., tabs., refs

  17. Crystallization kinetics of BaO-Al2O3-SiO2 glasses

    Science.gov (United States)

    Bansal, Narottam P.; Hyatt, Mark J.

    1989-01-01

    Barium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system were studied by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt percent) 10BaO-38Al2O3-51SiO2-1MoO3 (glass A) and 39BaO-25Al2O3-35SiO2-1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3-2SiO2) and hexacelsian (BaO-Al2O3-2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 C. It undergoes structural transformation into the orthorhombic form at approximately 300 C accompanied by a large volume change which is undesirable for structural applications. A process needs to be developed where stable monoclinic celsian, rather than hexacelsian, precipitates out as the crystal phase in glass B.

  18. Electrical properties of reactive-ion-sputtered Al{sub 2}O{sub 3} on 4H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Madhup, E-mail: madhup.iit@gmail.com [Microelectronics and MEMS Laboratory, Electrical Engineering Department, Indian Institute of Technology Madras, Chennai 600036 (India); Dutta, Gourab [Microelectronics and MEMS Laboratory, Electrical Engineering Department, Indian Institute of Technology Madras, Chennai 600036 (India); Mannam, Ramanjaneyulu [Department of Physics and Nano Functional Materials Technology Centre, Indian Institute of Technology Madras, Chennai 600036 (India); DasGupta, Nandita [Microelectronics and MEMS Laboratory, Electrical Engineering Department, Indian Institute of Technology Madras, Chennai 600036 (India)

    2016-05-31

    Al{sub 2}O{sub 3} was deposited on n-type 4H-SiC by reactive-ion-sputtering (RIS) at room temperature using aluminum target and oxygen as a reactant gas. Post deposition oxygen annealing was carried out at a temperature of 1100 °C. Metal-oxide-semiconductor (MOS) test structures were fabricated on 4H-SiC using RIS-Al{sub 2}O{sub 3} as gate dielectric. The C-V characteristics reveal a significant reduction in flat band voltage for oxygen annealed RIS-Al{sub 2}O{sub 3} samples (V{sub fb} = 1.95 V) compared to as-deposited Al{sub 2}O{sub 3} samples (V{sub fb} > 10 V), suggesting a reduction in negative oxide charge after oxygen annealing. Oxygen annealed RIS-Al{sub 2}O{sub 3} samples also showed significant improvement in I-V characteristics compared to as-deposited RIS-Al{sub 2}O{sub 3} samples. A systematic analysis was carried out to investigate the leakage current mechanisms present in oxygen annealed RIS-Al{sub 2}O{sub 3} on 4H-SiC at higher gate electric field and at different operating temperature. For measurement temperature (T) < 303 K, Fowler–Nordheim (FN) tunneling was found to be the dominant leakage mechanism and for higher temperature (T ≥ 303 K), a combination of FN tunneling and Poole-Frenkel (PF) emission was confirmed. The improvement in I-V characteristics of oxygen annealed RIS-Al{sub 2}O{sub 3}/4H-SiC MOS devices is attributed to large effective barrier height (Φ{sub B} = 2.53 eV) at Al{sub 2}O{sub 3}/SiC interface, due to the formation of an interfacial SiO{sub 2} layer during oxygen annealing, as confirmed from X-ray Photoelectron Spectroscopy results. Further improvement in C-V characteristics for oxygen annealed RIS-Al{sub 2}O{sub 3}/4H-SiC MOS devices was observed after forming gas annealing at 400 °C. - Highlights: • O{sub 2} annealed RIS-Al{sub 2}O{sub 3} on 4H-SiC showed better performance than other reported result. • FN, FN + PF tunneling was found in O{sub 2} annealed RIS-Al{sub 2}O{sub 3} for different temp. ranges. • Al

  19. First-principles study of the structure properties of Al(111)/6H-SiC(0001) interfaces

    Science.gov (United States)

    Wu, Qingjie; Xie, Jingpei; Wang, Changqing; Li, Liben; Wang, Aiqin; Mao, Aixia

    2018-04-01

    This paper presents a systematic study on the energetic and electronic structure of the Al(111)/6H-SiC(0001) interfaces by using first-principles calculation with density functional theory (DFT). There are all three situations for no-vacuum layer of Al/SiC superlattics, and two cases of C-terminated and Si-terminated interfaces are compared and analyzed. Through the density of states analysis, the initial information of interface combination is obtained. Then the supercells are stretched vertically along the z-axis, and the fracture of the interface is obtained, and it is pointed out that C-terminated SiC and Al interfaces have a better binding property. And, the fracture positions of C-terminated and Si-terminated interfaces are different in the process of stretching. Then, the distance variation in the process of stretching, the charge density differences, and the distribution of the electrons near the interface are analyzed. Al these work makes the specific reasons for the interface fracture are obtained at last.

  20. Comparison of AlCrN and AlCrTiSiN coatings deposited on the surface of plasma nitrocarburized high carbon steels

    International Nuclear Information System (INIS)

    Chen, Wanglin; Zheng, Jie; Lin, Yue; Kwon, Sikchol; Zhang, Shihong

    2015-01-01

    Highlights: • The duplex coatings were produced by combination of nitrocarburizing and multi-arc ion plating. • The γ′-phase plays the nucleation sites for the coating nitrides. • The compound layers (CL) considerably enhance mechanical and tribological properties of the duplex PVD coatings. • The main wear mechanisms of the PVD coatings with and without CL are oxidation wear, the combination of spalling, chipping and oxidation wear, respectively. - Abstract: The AlCrN and AlCrTiSiN coatings were produced on the surface of plasma nitrocarburized T10 steels by multi-arc ion plating. The comparison of the microstructures and mechanical properties of the duplex coatings were investigated by means of X-ray diffraction, optical microscope, scanning electron microscope and transmission electron microscope, in association with mechanical property measurement. The results show that the AlCrN coatings with columnar grown are mainly composed of nanocrytalline fcc-(Cr,Al)N phases with {111} preferred orientation, whereas the superlattice and nanocomposite AlCrTiSiN coatings with planar growth mainly consist of nanocrystalline fcc-(Cr,Al)N phases with {100} perfected orientation, hcp-AlN and Si 3 N 4 amorphous phases. The AlCrTiSiN duplex coating with the compound layer reveals higher hardness, adhesion strength, load capacity and lower friction coefficient when compared with the other duplex coatings, which is due to its superlattice and nanocomposite structure. Additionally, these improved properties are related to the appearance of the γ′-phase which plays the nucleation sites for the coating nitrides and provides a strong supporting effect for the AlCrN and AlCrTiSiN coatings. The main wear mechanism of the duplex coatings without compound layer is spalling and chipping wear as well as tribooxidation wear, whereas the main wear mechanism of the duplex coatings with compound layer is tribooxidation wear

  1. Hyperfine-field distribution in Fe3Si/sub 1-x/Al/sub x/ alloys and a theoretical interpretation

    International Nuclear Information System (INIS)

    Burch, T.J.; Raj, K.; Jena, P.; Budnick, J.I.; Niculescu, V.; Muir, W.B.

    1979-01-01

    In Fe 3 Si/sub 1-x/Al/sub x/ alloys with small x the Si and Al nuclear magnetic resonances are 31.5 and 16.1 MHz, respectively. The concentration dependences of the frequencies of these resonances are linear, the Si resonance shifting to lower frequencies, the Al resonance to higher frequencies. Both the magnitudes and concentration dependences of the Si and Al internal fields are in agreement with the predictions of a simple model which Jena and Geldart, following the approach of Daniel and Friedel, have found successful in calculating the fields of sp elements in Heusler alloys. A positive sign is predicted for the Si internal field, and a negative sign for the Al field. Magnetization and lattice-parameter data required for the comparison of experiment and theory are also reported

  2. Friction and wear behaviour of hypereutectic Al-Si alloy/steel tribopair under dry and lubricated conditions

    Directory of Open Access Journals (Sweden)

    Parveen Kumar

    2017-12-01

    Full Text Available Dry and lubricated sliding tribological tests on hypereutectic Al-25Si alloy was performed using a ball- on- disk configuration at room temperature. Hypereutectic Al-25Si alloy were prepared by rapid solidification process under T6 condition. Friction coefficient (COF and wear rate of the alloy were measured under different applied loads ranging from 5–100 N. It is found that the friction coefficient varies with load, first declines (from 5-50 N, then increases (from 50-80 N and then again decreases (80-100 N. The wear rate of the samples of hypereutectic Al-25Si alloy, first increases and then decreases with increasing the applied normal load. Hypereutectic Al-25Si alloy presents higher wear rate at 50 N due to the participation of a large amount of needle-like precipitates, but shows low wear rate under high load of 100 N because of the work hardening layer. Worn surface morphologies were analyzed using optical and scanning electron microscope (SEM coupled with an energy dispersive spectrometer (EDS. The improvements in COF and wear rate were mainly attributed to morphology, size and distribution of Si particles due to its fabrication process. The dominant wear mechanism for hypereutectic Al-25Si alloy was adhesive wear, abrasive wear and plastic deformation.

  3. Thermodynamic description of the Al-Cu-Mg-Mn-Si quinary system and its application to solidification simulation

    International Nuclear Information System (INIS)

    Chang, Keke; Liu, Shuhong; Zhao, Dongdong; Du, Yong; Zhou, Liangcai; Chen, Li

    2011-01-01

    By means of the first-principles calculations, the enthalpy of formation for the quaternary phase in the Al-Cu-Mg-Si system was computed. A set of self-consistent thermodynamic parameters for the Al-Cu-Mg-Si and Al-Cu-Mn-Si systems was then obtained using CALPHAD approach taking into account the reliable experimental data and the first-principles calculations. The thermodynamic database for the Al-Cu-Mg-Mn-Si system was developed based on the constituent binary, ternary, and quaternary systems. Comprehensive comparisons between the calculated and measured phase diagrams and invariant reactions showed that the experimental information was satisfactorily accounted for by the present thermodynamic description. The obtained database was used to describe the solidification behavior of Al alloys B319.1 (90.2Al-6Si-3.5Cu-0.3Mg, in wt.%) and B319.1 + xMn (x = 0.5-2, in wt.%) under Gulliver-Scheil non-equilibrium condition. The reliability of the present thermodynamic database was also verified by the good agreement between calculation and experiment for Gulliver-Scheil non-equilibrium solidification.

  4. Solidification, growth mechanisms, and associated properties of Al-Si and magnesium lightweight casting alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hosch, Timothy [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings

  5. Proton threshold states in sup 27 Si and the destruction of sup 26 Al at low stellar temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Wang, T F [Yale Univ., New Haven, CT (USA). Wright Nuclear Structure Lab.; Argonne National Lab., IL (USA)); Champagne, A E; Hadden, J D [Princeton Univ., NJ (USA). Dept. of Physics; Magnus, P V; Smith, M S; Howard, A J; Parker, P D [Yale Univ., New Haven, CT (USA). Wright Nuclear Structure Lab.

    1989-07-31

    Using the {sup 27}Al({sup 3}He,t){sup 27}Si reaction, we have located and measured accurate excitation energies for seven states in {sup 27}Si between the {sup 26}Al+p threshold and the lowest observed {sup 26}Al(p,{gamma}){sup 27}Si resonance. By examining the mirror states in {sup 27}Al via the {sup 26}Mg({sup 3}He, d){sup 27}Al and {sup 26}Mg({alpha},t){sup 27}Al reactions, we find that in the {sup 26}Al+p channel there can be at most only one s-wave resonance that lies below the lowest directly observed resonance; this possible l=0 resonance most probably corresponds to either the 7589, 7557 or 7533 keV state in {sup 27}Si. The remaining six states are most probably formed via l{ge}2 proton capture. Upper limits for the reduced proton widths of these states have been used to estimate an upper limit for the {sup 26}Al(p,{gamma}){sup 27}Si thermonuclear reaction rate. (orig.).

  6. Influence of the Si/Al ratio on the separation properties of SSZ-13 zeolite membranes

    NARCIS (Netherlands)

    Kosinov, N.; Auffret, C.; Borghuis, G.J.; Sripathi, V.G.P.; Hensen, E.J.M.

    2015-01-01

    SSZ-13 (CHA) zeolite membranes supported by a-alumina hollow fibers were prepared by a hydrothermal secondary growth method. The gel Si/Al ratio was varied between 5 and 100. The water adsorption depended strongly on the Si/Al ratio. Comparatively, ethanol adsorption varied less with membrane

  7. Resonant X-ray Raman scattering for Al, Si and their oxides

    International Nuclear Information System (INIS)

    Szlachetko, J.; Berset, M.; Dousse, J.-Cl.; Fennane, K.; Szlachetko, M.; Barrett, R.; Hoszowska, J.; Kubala-Kukus, A.; Pajek, M.

    2005-01-01

    High-resolution measurements of the resonant X-ray Raman scattering (RRS) of Al and Si and their oxides were performed at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, using a von Hamos Bragg-type curved crystal spectrometer. To probe the influence of chemical effects on the RRS X-ray spectra, Al 2 O 3 and SiO 2 samples were also investigated. The X-ray RRS spectra were measured at different photon beam energies tuned below the K-absorption edge. The measured spectra are compared to results of RRS calculations based on the second-order perturbation theory within the Kramers-Heisenberg approach

  8. El proceso de Toma de Decisiones en pacientes con Demencia tipo Alzheimer

    Directory of Open Access Journals (Sweden)

    Jose R. Alameda

    2012-04-01

    Full Text Available Tomar decisiones es algo común en nuestra vida y contribuye a la adaptación al medio en que vivimos, por ello es relevante conocer cómo es el proceso de toma de decisiones y las posibles disfunciones que puedan darse a causa de su deterioro. En el caso de los pacientes con demencia tipo Alzheimer, los problemas en la toma de decisiones parecen incluso ya en fases leves, lo que dificulta la correcta interacción con el entorno, especialmente en situaciones de incertidumbre. Este proceso ha sido analizado desde varios enfoques, siendo la hipótesis del marcador somático y la tarea de la Iowa Gambling Task (IGT uno de los más utilizados. El objetivo de este trabajo es el de analizar la toma de decisiones en pacientes con DTA frente a un grupo de sujetos control, y analizar el tipo de elecciones de ambos grupos en situaciones de incertidumbre mediante la una versión modificada de la IGT, observar si son tendentes al riesgo o no, y la relación que guarda su ejecución con el status cognitivo en cada una de las áreas evaluadas por los tests. Además de la IGT, utilizaremos como test de cribado en demencias el Miniexamen Cognoscitivo de Lobo, Test del Reloj a la Orden y Copia y Test de Fluidez Verbal de Isaacs. En nuestros resultados, los sujetos con DTA presentan una ejecución deficitaria en la IGT, tanto en el cómputo global como en su análisis por bloques, con una estrategia de elección de cartas aleatoria, por lo que podríamos considerar ciertas tendencias al riesgo, si bien su ejecución muestra cierta capacidad de aprendizaje a lo largo de los bloques. Por último, el deterioro cognitivo y el grado de afectación en las distintas áreas analizadas se relacionan con la forma en que toman decisiones los pacientes con DTA.

  9. Hydrogen release at metal-oxide interfaces: A first principle study of hydrogenated Al/SiO{sub 2} interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jianqiu, E-mail: jianqiu@vt.edu [Department of Mechanical Engineering, Virginia Tech, Goodwin Hall, 635 Prices Fork Road - MC 0238, Blacksburg, VA 24061 (United States); Tea, Eric; Li, Guanchen [Department of Mechanical Engineering, Virginia Tech, Goodwin Hall, 635 Prices Fork Road - MC 0238, Blacksburg, VA 24061 (United States); Hin, Celine [Department of Mechanical Engineering, Virginia Tech, Goodwin Hall, 635 Prices Fork Road - MC 0238, Blacksburg, VA 24061 (United States); Department of Material Science and Engineering, Virginia Tech, Goodwin Hall, 635 Prices Fork Road-MC 0238, Blacksburg, VA 24061 (United States)

    2017-06-01

    Highlights: • Hydrogen release process at the Al/SiO{sub 2} metal-oxide interface has been investigated. • A mathematical model that estimates the hydrogen release potential has been proposed. • Al atoms, Al−O bonds, and Si−Al bonds are the major hydrogen traps at the Al/SiO{sub 2} interface. • Hydrogen atoms are primarily release from Al−H and O−H bonds at the Al/SiO{sub 2} metal-oxide interface. - Abstract: The Anode Hydrogen Release (AHR) mechanism at interfaces is responsible for the generation of defects, that traps charge carriers and can induce dielectric breakdown in Metal-Oxide-Semiconductor Field Effect Transistors. The AHR has been extensively studied at Si/SiO{sub 2} interfaces but its characteristics at metal-silica interfaces remain unclear. In this study, we performed Density Functional Theory (DFT) calculations to study the hydrogen release mechanism at the typical Al/SiO{sub 2} metal-oxide interface. We found that interstitial hydrogen atoms can break interfacial Al−Si bonds, passivating a Si sp{sup 3} orbital. Interstitial hydrogen atoms can also break interfacial Al−O bonds, or be adsorbed at the interface on aluminum, forming stable Al−H−Al bridges. We showed that hydrogenated O−H, Si−H and Al−H bonds at the Al/SiO{sub 2} interfaces are polarized. The resulting bond dipole weakens the O−H and Si−H bonds, but strengthens the Al−H bond under the application of a positive bias at the metal gate. Our calculations indicate that Al−H bonds and O−H bonds are more important than Si−H bonds for the hydrogen release process.

  10. Structure of multilayered Cr(Al)N/SiO{sub x} nanocomposite coatings fabricated by differential pumping co-sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Kawasaki, Masahiro [JEOL USA Inc., 11 Dearborn Road, Peabody, Massachusetts 01960 (United States); Nose, Masateru [Faculty of Art and Design, University of Toyama, 180 Futagami-machi, Takaoka 933-8588 (Japan); Onishi, Ichiro [JEOL Ltd. 3-1-2 Musashino, Akishima, Tokyo 196-8558 (Japan); Shiojiri, Makoto [Kyoto Institute of Technology, Kyoto 606-8585 (Japan)

    2013-11-11

    A Cr(Al)N/38 vol. % SiO{sub x} hard coating was prepared on a (001) Si substrate at 250 °C in a differential pumping co-sputtering system, which has two chambers for radio frequency (RF) sputtering and a substrate holder rotating on the chambers. The composite coating was grown by alternate sputter-depositions from CrAl and SiO{sub 2} targets with flows of N{sub 2}+Ar and Ar at RF powers of 200 and 75 W, respectively, on transition layers grown on the substrate. Analytical electron microscopy reveled that the Cr(Al)N/SiO{sub x} coating had a multilayered structure of Cr(Al)N crystal layers ∼1.6 nm thick and two-dimensionally dispersed amorphous silicon oxide (a-SiO{sub x}) particles with sizes of ∼1 nm or less. The a-SiO{sub x} particles were enclosed with the Cr(Al)N layers. The coating had a low indentation hardness of ∼25 GPa at room temperature, due to a high oxide fraction of 38 vol. % and a low substrate rotational speed of 1 rpm. Faster rotation and lower oxide fraction would make a-SiO{sub x} particles smaller, resulting in the formation of Cr(Al)N crystal including the very fine a-SiO{sub x} particles with small number density. They would work as obstacles for the lattice deformation of the Cr(Al)N crystals. We have fabricated a superhard coating of Cr(Al)N/17 vol. % SiO{sub x} with a hardness of 46 GPa prepared at 12 rpm.

  11. Application of a grain refiner and modifier to an Al-12 Si cast alloy

    International Nuclear Information System (INIS)

    Haro R, Sergio; Goytia R, Rafael E; Santos B, Audel; Dwivedi, D.K

    2008-01-01

    The refining and modification of an alloy of cast aluminum Al-12Si was studied, using sample alloys of Al-5Ti-1B as a refiner and Al-10Sr as a modifier. Two levels of each one were tested and added separately. The results show that the addition of titanium as well as of strontium favored the improvement of the tension properties of the cast Al-12Si alloy, by modifying the microstructure. But the addition of 0.06% Sr in the form of a master alloy produced a more adequate microstructure and presented the best combination of mechanical properties (au)

  12. Epitaxial growth of higher transition-temperature VO2 films on AlN/Si

    Directory of Open Access Journals (Sweden)

    Tetiana Slusar

    2016-02-01

    Full Text Available We report the epitaxial growth and the mechanism of a higher temperature insulator-to-metal-transition (IMT of vanadium dioxide (VO2 thin films synthesized on aluminum nitride (AlN/Si (111 substrates by a pulsed-laser-deposition method; the IMT temperature is TIMT ≈ 350 K. X-ray diffractometer and high resolution transmission electron microscope data show that the epitaxial relationship of VO2 and AlN is VO2 (010 ‖ AlN (0001 with VO2 [101] ‖   AlN   [ 2 1 ̄ 1 ̄ 0 ] zone axes, which results in a substrate-induced tensile strain along the in-plane a and c axes of the insulating monoclinic VO2. This strain stabilizes the insulating phase of VO2 and raises TIMT for 10 K higher than TIMT single crystal ≈ 340 K in a bulk VO2 single crystal. Near TIMT, a resistance change of about four orders is observed in a thick film of ∼130 nm. The VO2/AlN/Si heterostructures are promising for the development of integrated IMT-Si technology, including thermal switchers, transistors, and other applications.

  13. Influencia de tratamientos térmicos de temple en las propiedades de la transformación martensítica en aleaciones metamagnéticas Ni-Mn-In-Co

    OpenAIRE

    Velasco Albéniz, Fernando

    2013-01-01

    El objetivo de este proyecto fin de carrera es el estudio del efecto de tratamientos térmicos de templado y envejecimiento post-templado en la transformación martensítica y en la temperatura de Curie en una aleación en base Ni-Mn-In-Co. En estudios anteriores se han analizado la influencia de tratamientos de temple y envejecimiento en aleaciones Ni-Mn-In, pero hasta la fecha no se ha realizado ningún estudio similar en aleaciones Ni-Mn-In-Co. Es por ello que en este proyecto se...

  14. Influencia del rayado sobre la resistencia electroquímica de les aleaciones de NiTi tratadas por un nuevo tratamiento térmico para aplicaciones biomédicas

    OpenAIRE

    Soualah, Lakhdar

    2005-01-01

    Las aleaciones de níquel-titanio son aleaciones que se utilizan cada vez más en aplicaciones biomédicas, por sus propiedades interesantes de superelasticidad, de memoria de forma, de resistencia a la corrosión y de biocompatibilidad. Sin embargo, los resultados obtenidos de su resistencia a la corrosión son muy variables, dependiendo del estado de superficie. Así, para mejorar, la resistencia a la corrosión de este material, se diseñó en un trabajo anterior un nuevo tratamie...

  15. Modeling of Precipitation Sequence and Ageing Kinetics in Al-Mg-Si Alloys

    NARCIS (Netherlands)

    Bahrami, A.

    2010-01-01

    Al-Mg-Si alloys are heat treatable alloys in which strength is obtained by precipitation hardening. Precipitates, formed from a supersaturated solid solution during ageing heat treatment, are GP-zones, B", B´ and B-Mg2Si. Precipitation kinetics and strength vary with alloy composition and process

  16. Thermal description of hypoeutectic Al-Si-Cu alloys using silicon equivalency

    Directory of Open Access Journals (Sweden)

    Mile B. Đurđević

    2012-01-01

    Full Text Available The modeling of casting processes has remained a topic of active interest for several decades, and availability of numerous software packages on the market is a good indication of the interest that the casting industry has in this field. Most of the data used in these software packages are read or estimated from the binary or multi-component phase diagrams. Unfortunately, except for binary diagrams, many of ternary or higher order phase diagrams are still not accurate enough. Having in mind that most of the aluminum binary systems are very well established, it has been tried to transfer a multi-component system into one well known Al-Xi pseudo binary system (in this case the Al-Si phase diagram was chosen as a reference system. The new Silicon Equivalency (SiEQ algorithm expresses the amounts of major and minor alloying elements in the aluminum melts through an 'equivalent' amount of silicon. Such a system could be used to calculate several thermo-physical and solidification characteristics of multi component as cast aluminum alloys. This lends the model the ability to make predictions of solidification characteristics of cast parts, where cooling rates are slow and the solidification process has to be known in great detail in order to avoid problems in the casting. This work demonstrates how the SiEQ algorithm can be used to calculate characteristic solidification temperatures of the multi-component hypoeutectic Al-Si-Cu alloys as well as their latent heats. SA statistical analysis of the results obtained for a wide range of alloy chemical compositions shows a very good correlation with the experimental data and the SiEQ calculations.

  17. Simulation, microstructure and microhardness of the nano-SiC coating formed on Al surface via laser shock processing

    International Nuclear Information System (INIS)

    Cui, C.Y.; Cui, X.G.; Zhao, Q.; Ren, X.D.; Zhou, J.Z.; Liu, Z.; Wang, Y.M.

    2014-01-01

    Highlights: • Nano-SiC coating is successfully fabricated on pure Al surface via LSPC. • Movement states of the nano-SiC particles are analyzed by FEM. • Formation mechanism of the nano-SiC coating is put forward and discussed. • Microhardness of the Al is significantly improved due to the nano-SiC coating. - Abstract: A novel method, laser shock processing coating (LSPC), has been developed to fabricate a particle-reinforced coating based on laser shock processing (LSP). In this study, a nano-SiC coating is successfully prepared on pure Al surface via LSPC. The surface and cross section morphologies as well as the compositions of nano-SiC coating are investigated. Moreover, a finite element method (FEM) is employed to clarify the formation process of nano-SiC coating. On the basis of the above analyzed results, a possible formation mechanism of the nano-SiC coating is tentatively put forward and discussed. Furthermore, the nano-SiC coating shows superior microhardness over the Al substrate

  18. A computational study on the electronic and field emission properties of Mg and Si doped AlN nanocones

    Science.gov (United States)

    Saedi, Leila; Soleymanabadi, Hamed; Panahyab, Ataollah

    2018-05-01

    Following an experimental work, we explored the effect of replacing an Al atom of an AlN nanocone by Si or Mg atom on its electronic and field emission properties using density functional theory calculations. We found that both Si-doping and Mg-doping increase the electrical conductivity of AlN nanocone, but their influences on the filed emission properties are significantly different. The Si-doping increases the electron concentration of AlN nanocone and results in a large electron mobility and a low work function, whereas Mg-doping leads to a high hole concentration below the conduction level and increases the work function in agreement with the experimental results. It is predicted that Si-doped AlN nanocones show excellent filed emission performance with higher emitted electron current density compared to the pristine AlN nanocone. But the Mg-doping meaningfully decreases the emitted electron current density from the surface of AlN nanocone. The Mg-doping can increase the work function about 41.9% and the Si-doping can decrease it about 6.3%. The Mg-doping and Si-doping convert the AlN nanocone to a p-type and n-type semiconductors, respectively. Our results explain in a molecular level what observed in the experiment.

  19. Effect of re-melting on particle distribution and interface formation in SiC reinforced 2124Al matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

    2013-12-15

    The interface between metal matrix and ceramic reinforcement particles plays an important role in improving properties of the metal matrix composites. Hence, it is important to find out the interface structure of composite after re-melting. In the present investigation, the 2124Al matrix with 10 wt.% SiC particle reinforced composite was re-melted at 800 °C and 900 °C for 10 min followed by pouring into a permanent mould. The microstructures reveal that the SiC particles are distributed throughout the Al-matrix. The volume fraction of SiC particles varies from top to bottom of the composite plate and the difference increases with the decrease of re-melting temperature. The interfacial structure of re-melted 2124Al–10 wt.%SiC composite was investigated using scanning electron microscopy, an electron probe micro-analyzer, a scanning transmission electron detector fitted with scanning electron microscopy and an X-ray energy dispersive spectrometer. It is found that a thick layer of reaction product is formed at the interface of composite after re-melting. The experimental results show that the reaction products at the interface are associated with high concentration of Cu, Mg, Si and C. At re-melting temperature, liquid Al reacts with SiC to form Al{sub 4}C{sub 3} and Al–Si eutectic phase or elemental Si at the interface. High concentration of Si at the interface indicates that SiC is dissociated during re-melting. The X-ray energy dispersive spectrometer analyses confirm that Mg- and Cu-enrich phases are formed at the interface region. The Mg is segregated at the interface region and formed MgAl{sub 2}O{sub 4} in the presence of oxygen. The several elements identified at the interface region indicate that different types of interfaces are formed in between Al matrix and SiC particles. The Al–Si eutectic phase is formed around SiC particles during re-melting which restricts the SiC dissolution. - Highlights: • Re-melted composite shows homogeneous particle

  20. Vanadium Influence on Iron Based Intermetallic Phases in AlSi6Cu4 Alloy

    Directory of Open Access Journals (Sweden)

    Bolibruchová D.

    2014-10-01

    Full Text Available Negative effect of iron in Al-Si alloys mostly refers with iron based intermetallic phases, especially Al5FeSi phases. These phases are present in platelet-like forms, which sharp edges are considered as main cracks initiators and also as contributors of porosity formation. In recent times, addition of some elements, for example Mn, Co, Cr, Ni, V, is used to reduce influence of iron. Influence of vanadium in aluminium AlSi6Cu4 alloy with intentionally increased iron content is presented in this article. Vanadium amount has been graduated and chemical composition of alloy has been analysed by spectral analysis. Vanadium influence on microstructural changes was evaluated by microstructural analysis and some of intermetallic particles were reviewed by EDX analysis.

  1. Influence of Fuel Meat Porosity on Heat Capacities of Fuel Element Plate U3Si2-Al

    International Nuclear Information System (INIS)

    Ginting, Aslina Br.; Supardjo; Sutri Indaryati

    2007-01-01

    Analyze of heat capacities of Al powder, AIMg 2 cladding, U 3 Si 2 powder and PEB U 3 Si 2 -Al with the meat porosity of 4.9; 5.53 ; 6.25 ; 6.95 %; 7.90; 8.66% have been done. Analysis was conducted by using Differential Scanning Calorimeter (DSC) at temperature 30℃ to 450℃ with heating rate 1℃ /minute in Argon gas media. The purpose of analyze is to know the influence of increasing of fuel meat porosity on heat capacities because increasing of percentage of meat porosity will cause degradation the of heat capacities of PEB U 3 Si 2 -Al. Result of analysis showed that the heat capacities of Al powder, AIMg 2 cladding increase by temperature, while heat capacities of U 3 Si 2 powder was stable with increasing of temperature up to 450℃. Analysis of heat capacities toward PEB U 3 Si 2 -Al indicate that increasing of fuel meat porosity of caused degradation of the heat capacities of PEB U 3 Si 2 -Al. Data obtained were expected to serve the purpose of input to fabricator of research reactor fuel in for design of fuel element type silicide with high loading. (author)

  2. Al-oxynitride interfacial layer investigations for Pr{sub X}O{sub Y} on SiC and Si