Mechanochemical synthesis investigations on the ternary and quaternary B₂O₃/TiO₂/Mg/C systems

In this study, mechanochemical synthesis (MCS) was performed on the ternary and quaternary B₂O₃/TiO₂/Mg/C system in order to investigate the probable reaction products. As being a high-energy ball milling (HEBM) technique, MCS was conducted on the B₂O₃–TiO₂–Mg, B₂O₃–Mg–C and B₂O₃–TiO₂–Mg–C powder blends. Various milling times were applied for MCS optimization. Besides, the effect of excess amount of Mg on the MCS process was investigated. Subsequently, a purification step was carried out on the milled powders to remove MgO by-product. The MgO content in the as-synthesized powders was leached out using 6 M HCl solution. Thermodynamic evaluations were made utilizing both the FactSage 7.1 and HSC thermochemical software to predict the reactions and products for each system. The as-synthesized and purified powders were characterized by using X-ray diffractometry (XRD), scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), transmission electron microscopy (TEM), particle size analysis (PSA) and differential scanning calorimetry (DSC) techniques. Pure TiB₂, B₄C and TiC–TiB₂ powders were synthesized from stoichiometric B₂O₃–TiO₂–Mg, B₂O₃–Mg–C and B₂O₃–TiO₂–Mg–C powder blends after MCS for 4 h, 10 h and 6 h, respectively. High purity TiB₂, B₄C and TiC–TiB₂ powders were obtained with an average particle size of 50.20 nm, 330 nm and 17 nm, respectively.