Abstract:
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. FeA1 foil is found to be superior from an economical vantage.
However, NiA1 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 NiA1 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 NiA1 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.
