Characterisation of UV-absorbent nanoceramic powders

Nanoceramic powders were produced via a plasma processing route by QinetiQ Nanomaterials Ltd. The powders were characterised in terms of agglomerate size, morphology, phase analysis and surface chemistry. The powders were made into suspensions and the UV absorbency properties were investigated. It was found that the mixtures produced different products depending on the concentration of titania in the starting material. Powders containing less than 30% titania were solid mixtures of zinc oxide and titania; these powders absorbed UV radiation as well and in some cases better than the individual powders. The powders containing more than 30% titania were shown to have titanium ions incorporated into the zinc oxide structure. This reduced the band gap of the powder which meant that the powders did not absorb UV radiation. For all the powders that absorbed UV radiation, it was found that particles around 100 nm absorbed large amounts of UV radiation and did not interact with visible radiation, producing a clear, transparent suspension which gives ideal characteristics for a sunscreen formulation. The suspensions were found to absorb the most UV radiation above 3 wt %. The powder containing 95 % zinc oxide 5 % titania was shown to absorb more UV radiation and scatter less visible radiation than the individual powders, showing the potential to provide an improvement to the properties of sunscreen formulations.