Synthesis of cobalt-nickel-boron based composite powders using metal chloride powder blends

Abstract

This study reports an alternative route for obtaining crystalline metal boride composite powders at low temperatures using various chemical reactions. The ternary system of Co-Ni-B was studied by using anhydrous metal chlorides and sodium borohydride powder mixtures. The reactions were carried out in a sealed reactor under autogenic pressure, placed in a chamber furnace. The unwanted chloride phases were removed by hot water leaching after reaction. Some of the purified powders were annealed at 1100 °C to improve the crystallinity. Effects of different reaction conditions on the formation and microstructure of the final powders were investigated. Phase, chemical and microstructural characterizations and particle size measurements of the synthesized and annealed powders were conducted using X-ray diffractometer (XRD), X-ray fluorescence spectrometer (XRF), scanning electron microscope (SEM/EDX) and dynamic light scattering technique. The results revealed the positive effect of inorganic molten salt mixture (LiCl/KCl eutectic mixture) on the formed phases during the reaction between CoCl 2 , NiCl 2 and NaBH 4 powder blends. After their reaction at 750°C in a sealed reactor under autogenic pressure, crystalline cobalt-nickel-boron based composite powders were achieved with an average particle size of 60 nm.