Study of the Process of Destructive Hydrogenation of Powder Intermetallic Systems. II. Rate of the First Destructive Hydrogenation of the Intermetallic TiNi

摘要

We have studied the rate of the first destructive hydrogenation of the as-poured bulk powder and compacts of TiNi. We have established that it is determined on the whole by the rate of processes that occur on the surface of the particles and are connected with formation of catalytic sites for dissociation of hydrogen, and by the rate of processes within the volume of the particles that is controlled by the rate of hydrogen diffusion and decomposition of TiNi. The first destructive hydrogenation of bulk TiNi powders is a lengthy process that can take tens of hours. Its rate increases as the temperature and hydrogen pressure increase. The effect of particle size is nonmonotonic because of the competing action of oxygen on the particle surface. Pressing TiNi powders made it possible to shorten the time required for the first destructive hydrogenation ten-fold (down to a few hours). This is connected with formation during pressing of fresh catalytic surfaces in closed cracks and on interparticle contacts. The rate of the first destructive hydrogenation of TiNi compacts increases as the temperature rises, and does not depend on particle size.