METAL HYDRIDE, REVERSIBLE HYDROGEN ASORBERS, ARE BEGINNING TO ENTER THE MARKET PLACE AS NEW ENGINEERING MATERIALS.

METAL HYDRIDE, REVERSIBLE HYDROGEN ASORBERS, ARE BEGINNING TO ENTER THE MARKET PLACE AS NEW ENGINEERING MATERIALS. AS THEY DO SO, IT IS BECOMING CLEAR THAT THEIR POTENTIAL USEFULNESS CANNOT BE REALIZED UNTIL THE PROBLEM OF HYSTERESIS IS CONSIDERABLY REDUCED. HYSTERESIS, THE GAP BETWENN THE ABSORPTION PRESSURE AND DESORPTION PRESSURE IN A METAL-HYDROGEN SYSTEM, VARIES GREATLY AMONST CURRENT HYDRIDE MATERIALS. A CONSENSUS EXISTS THAT HYSTERESIS IS LARGELY THE RESULT OF PLASTIC STRAIN IN THE METAL LATTICE ASIT ABSORBS AND DESORBS HYDROGEN. THERE ARE NO GENERAL RULES FOR EXPLAINING THE WIDE VARIATION IN HYSTERESIS AMONGST APPARENTLY SIMILAR INTERMETALLIC HYDRIDES. THE PROPOSED EFFORT WILL SEEK TRENDS IN THE CRYSTAL STRUCTURES OF LOW HYSTERESIS HYDRIDE ALLOYS AND COMPARE FRACTURE ENERGY DURING ACTIVATION OF HYDRIDE WITH THE ENERGY ABSORBED IN ITS HYSTERESIS BAND. IF THE PHENOMENON OF HYDRIDE HYSTERESISIS STRAIN-RELATED, IT SHOULD BE SENSITIVE TO CHANGES IN THE PHYSICAL PROPERTIES OF THE ALLOYS.