Preparation and Characterization of TiB₂/Al₃Ti/Al₂O₃ Composite Nano-powder

TiB₂/Al₃Ti/Al₂O₃ composite nano-powder has been prepared by sintering TiO₂, Al powder, and B₂O₃ with molten salt as the medium. The sintered powder was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy–energy dispersive spectroscopy (TEM–EDS), and x-ray photoelectron spectroscopy (XPS). The results illustrated the successful synthesis of TiB₂/Al₃Ti/Al₂O₃ nano-powder when the mass ratio of molten salt to reactants was 3 after calcination at 1000°C for 3 h. The synthesized powder comprises baseball-like, lamellar, and spheroidal nanoparticles, with TiB₂ and Al₂O₃ presenting a nano-scale mosaic structure which was used to reinforce aluminum-based composites. The synthesis mechanism of TiB₂/Al₃Ti/Al₂O₃ nano-powder was also investigated. With the increase in temperature, Al₂O₃, Al₃Ti, and Al₈B₂O₁₅ intermediate phases were first generated. Then, the further increase in temperature promoted the dissolution and diffusion of the unstable Al₈B₂O₁₅ phase in the molten salt, increasing the contact between Ti and B, thus producing the TiB₂ phase. By adding the TiB₂/Al₃Ti/Al₂O₃ powder to the A6061 aluminum alloy at a 5% mass fraction, the Vickers hardness of the original alloy increased by 55.30%.