Dispersion stability and anti-oxidation of an aqueous Zirconium Diboride slurry with a high solid loading

In this paper, the dispersion stability of zirconium diboride (ZrB2) slurries and their anti-oxidation behavior to prevent re-oxidation in the ZrB2 slurries were studied. SPEX-milled ZrB2 powder was used to improve the dispersion stability, and the viscosity and zeta potential as a function of pH were measured in order to confirm the dispersion behavior in aqueous ZrB2 slurries using various additives [polyethylenimine (PEI), polyacrylicacid (PAA), polyvinyl pyrrolidone (PVP), and polyvinyl alcohol (PVA)]. In addition, the oxygen contents were measured before and after processing to evaluate the oxidation behavior in the ZrB2 slurries. By using 2 wt % PEI, the isoelectric point (IEP) of the ZrB2 slurry increased from a pH of 5.8 to above a pH of 12. Also, the viscosity was below 6.27 mPa.s in the 20 vol % ZrB2 slurry at pH values of 2-12. The oxygen content of the ZrB2 powders increased from 2.42 to 3.79 wt % after preparing an aqueous slurry, but by using 2 wt % PVP and 2 wt % PEI, the oxygen contents of the 20 vol % ZrB2 slurry could be reduced from 3.79 to 2.6 and 2.8 wt %, respectively. Consequently, a 50 vol % ZrB2 slurry with an oxygen content was 2.92 wt % could be prepared in the pH range of 6-9 using 2 wt % PEI. (C)2013 The Ceramic Society of Japan. All rights reserved.