The effect of oxidized and oxide-free boron on the Mg-B-H nanohydrides transformation in the nearly nanosized powders

Authors

R. A. Varin, University of WaterlooFollow
Ch. Chiu, University of WaterlooFollow
Zbig Wronski, CANMETFollow
Andrzej Calka, University of WollongongFollow

RIS ID

16674

Publication Details

Varin, R., Chiu, C., Wronski, Z. Calka, A. (2007). The effect of oxidized and oxide-free boron on the Mg-B-H nanohydrides transformation in the nearly nanosized powders. Solid State Phenomena, 128 47-52. >

Abstract

In this work oxidized and oxide-free amorphous boron (a-B) powder and elemental Mg were used in an attempt to directly synthesize the Mg(BH4)2 complex hydride by controlled reactive mechanical alloying (CRMA) under hydrogen in a magneto-mill up to 200h. The particle size was refined to the 100-200nm range. Nanocrystalline MgH2 (~6nm crystallite size) was formed within the particles when an oxidized a-B is used. In contrast, a mixture of MgB2 and an amorphous hydride MgHx was formed when an oxide-free a-B was used. Differential scanning calorimetry (DSC) test up to 500°C produced a single endothermic heat event at 357.7°C due to hydrogen desorption. In addition, desorption conducted in a Sieverts-type apparatus revealed ~1.4wt.% of hydrogen release. The X-ray diffraction pattern after DSC test of the 200h milled sample made with oxide-free boron showed the presence of MgB2.