Reduction of supercooling of water by TiO₂ nanoparticles as observed using differential scanning calorimeter

Aqueous dispersions of Titania nanoparticles were cooled using differential scanning calorimetry (DSC). The nanoparticles reduce the supercooling of water by acceleration of nucleation. The experimental results demonstrated the important role in water crystallisation by the internal surface of the sample holder, and that stable nanofluids are required for the measurements to investigate the effect of nanoparticles on freezing. But for dispersions at low concentrations, such as 0.05 wt% and 0.1 wt%, the starting temperatures of freezing were found to be unusual at the cooling rates of 3°C/min and 4.5°C/min, namely they were even lower than that of the deionised (DI) water. It is found that surface controlled nucleation (SCN) is dominant at low cooling rates, while volumetric controlled nucleation (VCN) is dominant at high cooling rates.