Ni-B非晶态合金超细微粒的表面性质

非晶态合金具有短程有序和长程无序的结构特点,其优良的催化性能引人注目.但通常熔体急冷法制备的非晶样品表面积甚小.近年来采用化学还原方法制备使非晶态合金兼具超细微粒的性质,从而为非晶态合金在多相催化过程中的应用展示了诱人的前景.因此,研究非晶态合金超细微粒的表面性质就具有重要意义.Okamoto 等发现在用NaBH_4还原水溶液中Ni~(2+)离子制得的Ni-B 超细微粒表面除存在以合金方式结合的Ni、B 物类外还存在由B 水解产生的硼氧化物类,但未能将微粒表面性质与合金结构进行关联.本文报导不同结构状态下Ni-B 超细微粒表面性质的研究结果.

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

The effect of thermal treatment on the surface properties of ultrafine amorphousNiB alloy particles has been studied by H_2 chemisorption,X-ray photoelectronspectroscopy and surface area measurments.It is found that when heating temperatureis lower than 623K the amount of H_2 chemisorbed on NiB alloy catalyst increaseswith increasing temperature due to the aggregation of oxidized boron species existedin the surface layers of NiB alloy particles.However,thermal treatment at tempera-ture higher than 623K results in a remarkable decrease in the H_2 uptake.This iscorrelated with not only the sintering of NiB alloy particles but also the migration ofboron species alloying with nickel atoms from bulk to surface caused by completecrystallization of amorphous NiB alloy catalyst.