Electron Microscopy of Hydride Precipitation in Vanadium

Abstract

Precipitation of hydride from the solid solution of vanadium-hydrogen containing a small amount of hydrogen was observed at temperatures ranging between 300 K and 77 K using the cold stage of a 500 kV electron microscope. Two types of precipitates were found at low temperatures. One has a cubic superstructure with a unit cell twice as large as that of vanadsum matrix. The other has a tetragonal structure in which vanadium atoms form a body-centered tetragonal lattice with c⁄a=1.1−1.3. On heating these precipitates dissolved to the matrix at certain temperatures depending on the hydrogen concentration of the specimens. These facts give a direct confirmation to the postulation that the ‘anomalies’ in vanadium metal are caused by the precipitation as the hydride phase of a trace of hydrogen involved.