A potentially exciting material for membrane separations were metallic glass materials due to their low cost, high elastic toughness and resistance to hydrogen embrittlement as compared to crystalline Pd-based membrane systems. However, at elevated temperatures and extended operation times structural changes including partial crystallinity may appear in these amorphous metallic systems. This study reports on the investigation of time and temperature dependent crystalline phase formation in conjunction with in situ crystallization/hydrogen permeation experiments at elevated temperatures. At temperatures near to 400C a FeNi crystalline phase appeared as 22vol% inside the host amorphous matrix and the resulting composite structure remains stable for over 3h at temperature. The hydrogen permeation at 400C of the partially crystalline material was similar to the fully amorphous material near 5 x 10−9molH2/msPa1/2, while ambient temperature electrochemical permeation at 25C revealed an order of magnitude decrease in the permeation of partially crystalline materials due to differences in the amorphous versus crystalline phase activation energy for hydrogen permeation.

The Role of Partial Crystallinity on Hydrogen Permeation in Fe–Ni–B–Mo Based Metallic Glass Membranes. K.Brinkman, E.Fox, P.Korinko, D.Missimer, T.Adams, D.Su: Journal of Membrane Science, 2011, 378[1-2], 301-7