Abstract
Ceramic-based microchemical systems (μCSs) are more suitable for operation under harsh environments such as high temperature and corrosive reactants compared to the more conventional μCS materials such as silicon and polymers. With the recent renewed interests in chemical manufacturing and process intensification, simple, inexpensive, and reliable ceramic manufacturing technologies are needed. The main objective of this paper is to introduce a new powder-based fabrication framework, which is a one-pot, cost-effective, and versatile process for ceramic μCS components. The proposed approach employs the compaction of metal-oxide sub-micron powders with a graphite fugitive phase that is burned out to create internal cavities and microchannels before full sintering. Pure alumina powder has been used without any binder phase, enabling more precise dimensional control and less structure shrinkage upon sintering. The key process steps such as powder compaction, graphite burnout during partial sintering, machining in a conventional machine tool, and final densification have been studied to characterize the process. This near-full density ceramic structure with the combustion chamber and various internal channels was fabricated to be used as a micro-burner for gas sensing applications.
Highlights
Original polymer mold fabricated by micro-steoreolithography, which is used directly for low-pressure injection molding[29,30]
Figure 1c1 indicates that the graphite layer was completely burn out during the partial sintering at 800 °C as the decomposition temperature of the graphite phase is below 800 °C
We presented a unique ceramic powder processing method to fabricate the ceramic structures with internal cavities and channels for microchemical system applications
Summary
Original polymer mold fabricated by micro-steoreolithography, which is used directly for low-pressure injection molding[29,30]. The smallest feature size on the order of a few microns in ceramic structures has been fabricated using the soft-lithographic molding technique like micromolding in capillaries combined with sol-gel casting[26,31]. Unlike the various molding techniques, tape casting is capable of producing suspended structures, enclosed cavity or microchannels for μCSs. the suspended structures tend to deform and sag due to high lamination pressures and the softening of the glass component in the ceramic composite during sintering[35]. The advantages of the proposed powder-based technique include (1) a one-pot, cost-effective process to create either open or fully-enclosed ceramic microreactors and microchannels, (2) near-full density ceramic structures without any other phases (e.g. organic or glass materials) in the final devices, (3) partially-sintered ceramic structures facilitating machining, and (4) abilities to control the surface finish of the internal cavity walls and incorporate additional features on the cavity surface. As a proof-of-the-concept demonstration, a fully-enclosed ceramic structure with sub-millimeter internal cavities is used for micro-burner and micro flame ionization detector (μFID) applications
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