The Effect of CNT Doping on the Hydrogenation Behavior of Y5Si3 Phases
Keywords:
carbon nanotube CNT, D88-phases, Hydrogen Storage materials SEM, Hydrogen Sorption, Polymorphic Change, X-ray diffraction XRDAbstract
Abstract
The reactivity of the CNT-doped Y5Si3 compared to Y5Si3 phase system has been
investigated. Both alloys have been prepared by arc melting and their reactivity with
hydrogen has been studied. Single–phase CNT-doped Y5Si3 can only be made by melting
preformed Y5Si3 with the CNT. An activation process has been developed to induce
reaction of the doped alloy with hydrogen. It involves cycling in H2 gas pressures above
1.2 atm at temperature higher than 435oC depending on the CNT content. Conditioned
samples, will repeatedly (above 50 cycles) cycles 2.5 H (fu)-1 between room temperature
and 500oC with 0.9 and 1.2 H (fu)-1 being desorbed and absorbed with fast kinetic within
a very small temperature range. This behavior is believed to arise from the polymorphic
change between an α-form of the D88 structure and a supercell β-form. An attempt to
quantify the enhanced stability, compared to Y5Si3, is made by measuring reaction
enthalpies using Van’t Hoff isopleths.
