Kinetics and Mechanism of Hydrogen Sorption in Yttrium-Silicon D88- Structure Phases, Part I
Keywords:
Hydrogen storage material, Interstitial alloys, Gas-solid reactions, Kinetics, Thermal analysisAbstract
A relationship between the size of the z-axis lattice parameter and the
rate of hydrogenation of D88 phases has been established. Materials with caxis
in the range 0.632-0.642 nm are most resistant to hydrogen content
increase whilst maintaining a fast sorption capability for 0.9-10 H (fu)-1.
From this Y5Si2Ge and Y5Si2GeN0.1 have been prepared and used to establish
the hydrogen sorption kinetics at a range of temperatures and pressures of
hydrogen. The effect that nitrogen has on the alloy is to increase reaction
rates by a factor of approximately 3. Thermogravimetric plots were first
analysed by the J-M-A equation as used by Goudy (6). Arrhenius
representation of the first and second order equations indicate a significant
change in reaction mechanism at 740-745 K. Activation energies are in the
range 84-166 kJ (mol)-1 depending on order and temperature.
