An apparatus for gravimetric analysis: its application to metal-hydrogen systems

We have developed a systematic analysis by gravimetry apparatus dedicated to metal-hydrogen processes under pressures ranging from 0.1 Pa to 10 MPa and temperatures ranging from 20 to 800 °C. This equipment allows us to study the metal-hydrogen phase diagram and the characteristic plateau pressure of definite hydride formation and to determine the related quantities that are the enthalpy and entropy of reaction. Moreover, it is possible to record the rate of absorption and desorption and thus to analyse relaxation phenomena parameters. The apparatus has been used to measure the enthalpy and entropy of reaction of LaNi5Hx as a standard system, and of ZrCr1.8Mo0.2Hx, a new system.