Abstract
Vacuum cold spray is a promising method to deposit nanocrystalline ceramic coating. The effective control of porous structure within nanostructured coating is essentially important to enhance the performance of the mesoporous nanocrystalline coatings for applications to catalyst and photo-electrode. In this study, the ceramic-polymer composite powders were employed as spray feedstocks for vacuum cold spray to control the pore structure in the deposits. The ceramic-polymer composite powders were made from nano-sized TiO2 (25nm), ZrO2 (30nm) and Al2O3 (30nm) and polyethylene glycol (PEG). The surface morphologies and the cross-sectional microstructures of the coatings were characterized using scanning electron microscope (SEM). The pore size distribution was measured using a nitrogen adsorption approach. The results showed that the deposition during spraying was implemented through the composite particles in a size ranging from submicrometers to several micrometers. Through post-spray heat treatment of the deposit, the PEG can be completely removed to increase the porosity in the deposit. The pores exhibited a bimodal distribution. The small pores present the size from several nanometers to tens of nanometers. Moreover, the size of large pores is in micrometer scale. The porosity and pore size distribution can be controlled by the composition of the composite powder.
