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In this paper, the dispersion stability of zirconium diboride (ZrB 2 ) slurries and their anti-oxidation behavior to prevent re-oxidation in the ZrB 2 slurries were studied. SPEX-milled ZrB 2 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 ZrB 2 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 ZrB 2 slurries. By using 2 wt % PEI, the isoelectric point (IEP) of the ZrB 2 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 % ZrB 2 slurry at pH values of 212. The oxygen content of the ZrB 2 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 % ZrB 2 slurry could be reduced from 3.79 to 2.6 and 2.8 wt %, respectively. Consequently, a 50 vol % ZrB 2 slurry with an oxygen content was 2.92 wt % could be prepared in the pH range of 69 using 2 wt % PEI.

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In this study, two pretreatment methods were used to improve the sinterability of zirconium diboride (ZrB 2). As a mechanical treatment, as-received ZrB 2 powder was crushed using SPEX mill from an average size of 2.61 µm to 0.35 µm. As a chemical treatment, oxygen contents of ZrB 2 powder were decreased from 4.20 wt% to 2.22 wt% using a dilute hydrofluoric solution. The relative density of sintered ZrB 2 increased with decreasing particle size and oxygen contents. But it is considered that particle size is more effective than oxygen contents for ZrB 2 densification. Through the two pretreatment processes, we produced sintered ZrB 2 ceramic with a full density without sintering additives. The sinterability of ZrB 2 was improved by using mechanical and chemical pretreatment methods.