Abstract:
We describe the development of a low temperature method for the deposition of 1-10 ?m thick films and bulk materials using a combination of powder processing technologies (colloidal suspension, die pressing, screen printing) and polymeric precursor processing methods (spin coating, impregnation). In this process the powder is first deposited onto the surface to provide a framework of connected particles into which the polymeric precursor impregnates to form an oxide particle/organic polymer composite film. Upon heating to about 300°C, the polymer decomposes to yield a nanocrystalline layer. Subsequent and multiple depositions of polymer precursor fill the space between the particles providing on demand: dense or porous and homogenous or composite structures. The homogenous structures are created when the oxide in the polymer precursor layer is of the same composition as the powder used to create the framework, while heterogeneous composites occur when the two differ. The advantage of this technology is related to low temperature processing, because the interfacial reactions between different layers can be avoided and the problems due to thermal expansion mismatch of different materials can be minimized. The low temperature processing also allows preparation of nanocrystalline structures, which is one of the ways to improve the catalytic properties of electrodes. In addition, the possibility of fabricating dense and nanocrystalline layers at low temperature gives a unique opportunity to investigate nanocrystalline properties of materials, which may be different from those of microcrystalline.
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