Novel device for simultaneous volumetric and x-ray diffraction measurements on metal-hydrogen systems

B. A. TALAGAÑIS; F. J. CASTRO; A. BARUJ; G. MEYER

Reykjavik, Islandia

Conferencia; International Symposium on Metal-Hydrogen Systems (MH2008); 2008

MH2008 Organizing Commitee

Volumetric techniques provide useful and precise information on the equilibrium and kinetic properties of the interaction of hydrogen with a solid material. However, in multiphase systems, the identification of intermediate compounds is impossible without stopping the experiment and, frequently, modifying sample environment and the properties of interest. In this work we present an automatic Sieverts-type apparatus equipped with a reactor that can be used in an X-ray difractometer, allowing simultaneous hydrogen content determination and phase identification through structural characterization. The operation range of the reactor is 0-60 bar and room temperature-450 degC. Two beryllium windows allow to perform measurements in a 2-theta range of 10-90 deg. Pressure and temperature in the sample, hydrogen flow, valve settings and goniometer position are measured and controlled by software designed specifically for this device. Static and dynamic pressure-composition isotherms, isothermal reaction kinetics at constant volume and/or pressure, thermal desorption spectroscopy and hydriding and dehydriding cycling are the experimental runs that can be made in conjunction with structural determination. As an example of the potential uses of this equipment, we present the measurement of phase coexistence during LaNi5H6 decomposition from 40 bar to vacuum at 120 degC. LaNi5H6, LaNi5H6 + LaNi5H3, LaNi5H3, LaNi5H3 + LaNi5 and LaNi5 phases were detected and identified following the 28-32 deg 2-theta range during dehydriding.