Ceramic Substrates for High-temperature Electronic Integration

One of the most attractive ways to increase power handling capacity in power modules is to increase the operating temperature using wide-band-gap semiconductors. Ceramics are ideal candidates for use as substrates in high-power high-temperature electronic devices. The present article aims to determine the most suitable ceramic material for this application

Universal aspects of vacancy-mediated disordering dynamics: the effect of external fields

We investigate the disordering of an initially phase-segregated binary alloy, due to a highly mobile defect which couples to an electric or gravitational field. Using both mean-field and Monte Carlo methods, we show that the late stages of this process exhibit dynamic scaling, characterized by a set of exponents and scaling functions. A new scaling variable emerges, associated with the field. While the scaling functions carry information about the field and the boundary conditions, the exponents are universal. They can be computed analytically, in excellent agreement with simulation results.Comment: 15 pages, 6 figure

Precipitate Redistribution During Creep of Alloy 617

Nickel-based superalloys are being considered for applications within advanced nuclear power generation systems due to their high temperature strength and corrosion resistance. Alloy 617, a candidate for use in heat exchangers, derives its strength from both solid solution strengthening and the precipitation of carbide particles. However, during creep, carbides that are supposed to retard grain boundary motion are found to dissolve and re-precipitate on boundaries in tension. To quantify the redistribution, we have used electron backscatter diffraction and energy dispersive spectroscopy to analyze the microstructure of 617 after creep testing at 900 and 1000°C. The data were analyzed with respect to location of the carbides (e.g., intergranular vs. intragranular), grain boundary character, and precipitate type (i.e., Cr-rich or Mo-rich). We find that grain boundary character is the most important factor in carbide distribution; some evidence of preferential distribution to boundaries in tension is also observed at higher applied stresses. Finally, the results suggest that the observed redistribution is due to the migration of carbides to the boundaries and not the migration of boundaries to the precipitates

Desenvolvimento e avaliação de uma fonte DC de alta tensão para utilização em sistema de deposição de filmes finos por pulverização catódica

RESUMO O trabalho em questão está relacionado ao projeto e construção de uma fonte de alta tensão em corrente contínua utilizando materiais e dispositivos adquiridos no comércio local visando sua aplicação no processo de pulverização catódica. Essa técnica permite a deposição de filmes finos de metais, óxidos e nitretos sobre substratos sólidos. Como teste de funcionamento e aplicação da fonte DC, com a mesma instalada em canhão de pulverização em alto vácuo, filmes finos de diferentes espessuras de cobre, aço inoxidável 304 e tungstênio foram depositados e estudados. Análise de espessura, morfologia, e resistência elétrica e resistividade foram conduzidas. Filmes com resistividade elétrica dependente das espessuras foram obtidos. A fonte DC se mostrou confiável em operação e permite a deposição de uma infinidade de materiais nas mais diferentes espessuras sobre vários tipos de substratos