Synthesis of Nanocrystalline Cubic Hafnium Nitride by Reactive Mechanical Alloying

Nanocrystalline cubic hafnium nitride (HfN_x) powders are prepared by the mechanical milling of Hafnium and hexagonal boron nitride (h-BN) powder mixtures. The prepared nanocrystalline HfN_x is analyzed and characterized using x-ray diffraction and Raman spectroscopy. HfN_x formation mechanisms in both mechanical milling and annealing processes are also studied in detail. It is found that HfN_x is probably formed via the phase separation of Hf(N) solid solution alloy driven by reactive mechanical milling in which Hf(N) solid solution alloy is formed by Hf and N atoms through a diffusion reaction process. Meanwhile, a phase separation can also be induced in Hf (N) solid solution as the N content exceeding its solubility limit, leading to an additional way to produce HfN_x. No HfB₂ has been found during both milling and annealing processes.