Effect of processing parameters on the formation of TiB2 nanopowder by mechanically induced self-sustaining reaction

The influence of milling parameters on the formation of titanium diboride nanopowders by mechanically induced self-sustaining reaction (MSR) was studied. A high-energy planetary ball mill was used to provide necessary conditions for the occurrence of MSR. Results showed that the formation and structural features of titanium diboride nanopowders were notably influenced by ball to powder weight ratio (BPR), total powder mass and weight fraction of diluent (NaCl). With BPRs of 10:1, 15:1 and 20:1, combustion reaction occurred after 73, 34 and 40min, respectively. The mechanosynthesized nanopowders were composed of TiB2 (major compound), MgO and Mg2TiO4 (unwanted phases). With a BPR of 15:1, the addition of 5wt% NaCl delayed the combustion reaction to 60min and led to the formation of TiB2, MgO and Mg2TiO4 with the crystallite size of around 24, 40 and 45nm, respectively. After leaching in 18% HCl aqueous solution at 60°C for 30min, the unwanted phases were completely removed and consequently a single-phase titanium diboride nanopowder with crystallite size of about 92nm was formed. According to the scanning electron microscope images, the leached powder was comprised of nanoparticles with an average size of about 140nm.