In-situ XAFS study on structures and devitrifications of Ni–B nano-amorphous alloys

The local structures and the devitrifications of Ni70B30 nano-amorphous alloys prepared by chemical reduction method were studied by in-situ X-ray absorption fine structure (XAFS). The results indicate that the preparation temperature strongly affects the local structures of Ni70B30 amorphous alloys. The coordination geometry surrounding Ni atoms is a structure of amorphous Ni-like for the Ni70B30 (273 K) while the Ni70B30 (313 K) has amorphous Ni3B-like structure. In-situ XAFS analysis revealed that the Ni70B30 amorphous alloy prepared at the low temperature of 273 K is directly crystallized into the metallic Ni in a wide temperature range from 498 to 598 K. However, the crystallization of the sample prepared at the high temperature of 313 K is accomplished in two steps: the generation of intermediate product of crystalline Ni3B starting from 548 K and finishing at about 573 K; the unique formation of crystalline Ni at about 598 K.