Titanium nitride coatings to inner wall of narrow tube

Abstract

Titanium nitride TiN has considerable hydrogen impermeability and is expected as a prevention coating of hydrogen gas parmiation for a cladding tube of metal hydride fission fuel. The TiN coating produced with plasma process is very complicated because the cladding tube is not wide enough to create stable plasma. A simple reactive evaporation process was selected for coationg process of TiN films to inner wall of narrow tube or stainless steal tube. The films were thermally deposited on stainless steel sheets coiled around inner wall of silica glass tubes. Nitrogen as a reactive gas was introduced into the vacuum chamber with pressure range of 5.0×10^-2 Pa ∼ 3.0×10^-1 Pa. Thin films with gold color were obtained. From XRD measurement of films, distinct diffraction patterns of TiN phase were observed. A reactivity of N₂ gas molecules with Ti atoms in Ti-N film formation has measured quantitatively. The reaction probability of N₂ molecules r_N2 is defined as the ratio of the absorbing rate of N₂ on Ti surface A_N2 to the rate of N₂ impingement Z_N2. Reactive evaporation process exhibits the highest N₂ reaction probability r_N2 ≅ 0.05. It was the similar value of r_N2 with Ti film prepared by ARE plasma processes.