The Synthesis of Titanium Dioxide Powders for Cold Spray

Titanium dioxide (TiO₂) is a unique material that can be used as an excellent photocatalyst, hence it will be very useful to solve the current world pollution problem. For photocatalytic application, the cold spray process, which uses supersonic high velocity technique at moderate temperature is considered to be a suitable technique as it will inhibit the phase transformation of TiO₂. It is known that obtaining a thick coating of TiO₂ is difficult as it is a hard ceramic material. However, we have successfully synthesised TiO₂ powders that can be cold sprayed. Our synthesis technique is a simple hydrolysis method of titanyl sulphate (TiOSO₄) in distilled water. It was discovered that the cold sprayability of TiO₂ powders is depended on the powder morphology and using our synthesis method, powder morphology can be easily altered. Addition of (NH₄)₂SO₄ during hydrolysis and post synthesis hydrothermal treatment result in a unique oriented aggregated nanostructure of TiO₂. Only TiO₂ with this nanostructure can be cold sprayed.