An Evaluation of Two Methods for Producing Intermetallic Microchannels

Abstract

Microtechnology-based Energy and Chemical Systems (MECS) offer opportunities for portable power generation, distributed heat pumps, hydrogen separation for automotive fuel cells, on-site waste remediation and point-of-use chemical synthesis. In order to realize many of these applications, it is recognized that new techniques must be developed for producing microchannels within refractory materials. Material requirements include high-temperature resistance, chemical inertness and low-cost microfabrication. Advances in multilayer ceramics have allowed the microlamination of microreactor structures from ceramic tape. The tapes are formed in the green state and subsequently bonded through a sintering process. Problems include sagging, porosity, and volumetric shrinkage which can lead to dimensional instability. Intermetallics are another class of refractory materials which may hold some promise for high-temperature microchannel development. In this paper, several proposed methods of forming microchannel arrays in aluminide intermetallics are evaluated. These methods have the advantage of eliminating volumetric shrinkage due to binder removal. Results show that some NiAl systems may be suitable for microchannel designs. Issues to be addressed include cost, volumetric shrinkage due to phase changes or other creep-related phenomena incurred during phase changes.