| Micro Energy and Chemical Systems (MECS) devices enable at least two areas of benefit due to the accelerated heat and mass transfer that can be accomplished in microchannels. First, MECS devices enable process intensification; the ability to reduce the volume of space needed to implement systems of thermal and chemical unit operations. Second, MECS devices permit new capabilities for material synthesis and process control not possible at larger scales. Recent interest in high temperature MECS applications, such as catalytic combustion, fuel reforming, and waste heat recovery, has given rise to the need for materials that support high temperature microreactors. This dissertation investigates new microlamination methods for producing economical, intermetallic microchannel arrays that can resist high temperatures and have a high aspect ratio. The first part of the research shows the capability of fabricating two fluid microchannel array design from Ni3Al and FeAl foils, produced using existing aluminide foils. FeAl foil is found to be superior from an economical vantage. However, NiAl is a much better choice for high temperature catalytic reactions. Therefore, the second part of this dissertation investigates the effects of foil and processing conditions, primarily surface roughness and Ni plating, on diffusion bonding of reactively synthesized NiAl foils. Carbon inclusion is minimized in the matrix and better surface roughness obtained by using pyrolytic boron nitride platens of smoother texture. Void free bonds and better homogenization are accomplished by virtue of smoother surface roughness and thinner nickel layer. It is expected that economical NiAl foils could be produced using powder roll compaction techniques. The roughness wavelength and perhaps the amplitude of foils made in this manner would need to have less than 20% variation with excellent bonding results anticipated at around 5% variation. |
