Measurement of hydrogen in alloys by magnetic and electronic techniques

摘要

As demonstrated in this paper, magnetic and electronic measurements can be used to quantify hydrogen availability, absorption, and desorption in materials for nickel metal-hydride batteries and hydrogen storage. The ability of a metal alloy to absorb and desorb hydrogen depends on the interaction of the metal's electronic bands with electrons donated or accepted by the hydrogen. The tendency of alloys to dissolve hydrogen and form hydrides depends on their performance as electron acceptors. Absorbed hydrogen may exist in either soluble (protonic) or bound phases. Magnetization and thermoelectric (Seebeck) coefficient were measured as functions of hydrogen content in powdered AB_5- and AB_2-type alloys. Magnetization decreases with increasing soluble hydrogen in ferromagnetic AB_5-type (La-Ce)(Ni-Mn)_5 and (La-Nd)(Ni-Co-Mn)_5. However, magnetization increases with increasing soluble hydrogen in AB_2-type (Zr-Ti)(Cr-Fe)_2. Finally, magnetization does not change with increasing bound hydrogen in AB_2-type (Zr-Ti)(Ni-Mn-Cr-V)_2. The Seebeck coefficient for AB_5-type (La-Nd)(Ni-Co-Mn)_5 is a monotonically decreasing function of hydrogen content. However, the effect of absorbed hydrogen on the Seebeck coefficient of the AB_2 alloys depends on whether the hydrogen is soluble or bound.