The effect of CNT doping on the hydrogenation behavior of Y5Si3 phases

Abstract EN

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.