Development of Nano-Porous Alumina Catalyst Support by Anodic Oxidation of Thermally and Kinetically Sprayed Aluminum Coatings

In order to minimize environmental burden, green technologies should be important in the 21st century. High-performance catalyst layer would make significant contribution through reforming of hydrocarbon fuels, removal of toxic molecules such as CO and NH₃ from exhaust gas, reduction of NOx formation in combustion, and efficient conversion of chemical energy to thermal energy in small scales. Among various kinds of catalyst support, nano porous alumina developed with anodic oxidation of aluminum (Al) layers attracts much attention due to its extremely-large specific area, easy controllability of porosity and coating thickness, and large bond strength with the substrate. In our previous studies, we have developed a micro-scale catalytic combustor with a Pd/nano-porus alumina catalyst layer, aiming at micro thermophotovoltaic power generation system, which enables higher energy density than Li-ion batteries. In this paper, we employ cold and plasma sprays for the deposition of Al, and examine effect of the Al deposition methods on the number density of nano pores. It is found that large internal stress in the Al layer provides much higher density for cold-spray-coated films.