Synthesis of hafnium diboride on a vacuum free electric arc furnace

This study reports the successful synthesis of hafnium diboride (HfB2) powder by vacuum-free electric arc synthesis. The method employs an autonomous gas environment in which an arc discharge between graphite electrodes in air generates a protective atmosphere of carbon monoxide and carbon dioxide. This in situ gas mixture shields the reactants from atmospheric oxygen, eliminating the need for vacuum. Optimal charge preparation parameters were determined, including starting component ratios, ball-milling homogenisation conditions, and arc reactor discharge energy settings. X-ray diffraction confirmed that the product obtained under the recommended conditions consists predominantly of the desired HfB2 phase, with no impurities detectable within the method’s sensitivity limits. The oxidation resistance of the synthesised powder was evaluated: the HfB2 phase remains stable up to 600 °C, while significant degradation begins at 700–800 °C, accompanied by hafnium dioxide (HfO2) formation. This work demonstrates a cost-effective and efficient route for producing high-purity HfB2.