Preparation and characterization of nanoscale nickel metal powder through sodium-ammonia solution

Nanoscale nickel metal powder was prepared by a two-step process. In the first step, nanoscale nickel nitride powder was prepared via reduction and nitridation of nickel chloride in sodium-ammonia solution. In the second step, nanoscale nickel metal powder was successfully obtained through the vacuum thermal decomposition of the nanoscale nickel nitride powder. The experimental results show that the nanoscale nickel nitride powder obtained from sodium-ammonia solution exhibites hexagonal crystal structure and average crystalline size of 19 nm. Furthermore, after vacuum heat treatment at 300°C, the nanoscale nickel nitride powder is completely decomposed, then the nanoscale nickel metal powder is produced, with cubic crystal structure, average crystalline size of 21.4 nm, and specific surface area of 30.5 m²·g^-1. During vacuum heat treatment of the nanoscale nickel metal powder at 300-700°C, its average crystalline size gradually increases to 36.8 nm, and its specific surface area gradually decreases to 13.2 m²·g^-1.