Vapor phase manufacture of porous TiN deposits on/in porous supports

Abstract

Particle Precipitation aided Chemical Vapor Deposition (PP-CVD) is a modification of the conventional CVD process. In PP-CVD an aerosol is formed in the gas phase at an elevated temperature, and particles are deposited on a substrate surface. The synthesis of titanium nitride (TiN) using titanium tetrachloride vapor, nitrogen, ammonia, and hydrogen is studied. TiN is formed by a heterogeneous reaction involving a titanium containing species and nitrogen, whereas simultaneously a TiN aerosol is formed by a reaction involving ammonia. Dense columnar microstructures are formed in the absence of a temperature gradient. At low temperature differences between substrate and gas phase only dense microstructures with virtually equiaxed grains are observed. Porous coherent layers are found in experiments, where larger temperature differences are applied. The observed interconnection of the particles originates from a heterogeneous reaction. A further increase in temperature difference between the susceptor and the gas phase only leads to loose powder deposits.