Microstructure and interfacial reactions between B6O and (Ni, Co) couples

The search for suitable additives for boron suboxide (B6O) materials which could improve densification, reduce sintering temperature and tailor the microstructure has been of great importance. In an earlier study it was shown that transition metal borides qualify as sintering aids for B6O, but partial segregations of the boride secondary phases were found. In this work, efforts have been made to understand the chemical interaction between the B6O and boride phase. A reaction couple of sintered B6O, nickel and green compact B6O were assembled and heat-treated at 1850 °C for 20 min. XRD and SEM examinations of the reaction zone show the formation of nickel boride, diffusing into the B6O matrix and a substantial grain growth of B6O at the interface.