Effect of coating layers on nano-TiO₂ particles on the preparation of nanocrystalline λ-Ti₃O₅ by carbonthermal reduction

Three different kinds of rutile TiO₂ nanoparticles with different surface coating conditions were prepared by precipitation method for synthesizing λ-Ti₃O₅. The effect of surface layers on nano rutile TiO₂ particles on the preparation of λ-Ti₃O₅ was firstly investigated. X-ray diffraction, scanning electron microscope, energy dispersive spectrometer and transmission electron microscope were used to characterize these powders. The nano rutile TiO₂ powders were mixed with carbon black separately and then annealed at an isothermal heat condition. The phase structures of the products demonstrate that high purity nanocrystalline λ-Ti₃O₅ powders can be synthesized by carbothermal reduction of the Al₂O₃–SiO₂ dual-coated TiO₂ powders, but not by the uncoated and SiO₂-coated TiO₂ powders. Thus, the coating layers of the TiO₂ nanoparticles played a decisive role in the formation of nanocrystalline λ-Ti₃O₅. It proposed that both of the coating layers and metal ion (i.e. Al³⁺) make a contribution to stabilize the metastable phase λ-Ti₃O₅ to ambient temperature in the carbothermal reduction of the TiO₂/C system. This study provided considerable insights into the preparation of nanocrystalline λ-Ti₃O₅.