Diffusion-Thermal Phase Transformations in Titanium Hydride Containing a Multi-Barrier Systems of Hydrogen Traps

Abstract

Diffusion-thermal phase transformations in modified titanium hydride containing a multi-barrier system of hydrogen traps are considered. Modification of titanium hydride was carried out by the method of layer-by-layer electrochemical precipitation of metallic titanium and copper from organic and inorganic solutions of their salts. The creation of a multilayer coating (Ti–Cu) on the surface of the titanium hydride by the electrochemical precipitation method increases the thermal stability of the metal hydride system by 229.7°C. By using the methods of X-ray-phase, X-ray structural, and electron-probe microanalysis, it has been shown that the phase composition of the modified titanium hydride in a temperature range 100–700°C is constant. The most significant changes in the crystal lattice in the modified titanium hydride occur at a temperature of 500 °C owing to hydrogenation of the modified titanium shell and blocking of the microcracks of the surface with a copper coating; the period of the unit cell and the volume of the hydride-phase crystal change. The highest concentration of hydrogen in the surface layer (up to 87.9%) occurs in the temperature range of 300–500°C, which ensures the maximum defect density in the crystal lattice. At 700°C, one can observe a decrease in the dislocation density and a decrease in the crystal cell parameters associated with the annealing mode of titanium hydride and hydrogen thermal diffusion into the volume of material. The metallic titanium precipitated on the titanium hydride surface is an effective structural trap of hydrogen diffusing into the surface layers during thermal heating; the creation of an additional protective copper sheath prevents thermal diffusion of hydrogen into the environment.