STUDIES ON THE SURFACE PROPERTIES OF ULTRAFINE AMORPHOUS Ni-B ALLOY PARTICLES

The effect of thermal treatment on the surface properties of ultrafine amorphous NiB alloy particles has been studied by H-2 chemisorption, X-ray photoelectron spectroscopy and surface area measurments. It is found that when heating temperature is lower than 623K the amount of H-2 chemisorbed on NiB alloy catalyst increases with increasing temperature due to the aggregation of oxidized boron species existed in the surface layers of NiB alloy particles. However, thermal treatment at temperature higher than 623K results in a remarkable decrease in the H-2 uptake. This is correlated with not only the sintering of NiB alloy particles but also the migration of boron species alloying with nickel atoms from bulk to surface caused by complete crystallization of amorphous NiB alloy catalyst.