The dispersibility of ZrB2 particles in aqueous medium had a significant effect on colloidal forming processes of ZrB2 based ultra high temperature ceramics. To improve the dispersibility of ZrB2, surface preoxidation was developed. After preoxidation, a layer of oxides composed of ZrO2 and B2O3 formed on particle surfaces. The dispersibility of ZrB2 particles in aqueous medium was investigated using zeta potential measurements, sedimentation tests and viscosity measurements. The surface oxygen of ZrB2 particle preoxidised at 800°C was 2·66±0·12 wt-%. It was found that ZrB2 had the best dispersibility and the lowest viscosity after surface preoxidation at 800°C for 1 h.
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