Zirconium diboride (ZrB2) and ZrB2 ceramics containing 10, 20, and 30 vol% SiC particulates were prepared from commercially available powders by hot pressing. Four‐point bend strength, fracture toughness, elastic modulus, and hardness were measured. Modulus and hardness did not vary significantly with SiC content. In contrast, strength and toughness increased as SiC content increased. Strength increased from 565 MPa for ZrB2 to >1000 MPa for samples containing 20 or 30 vol% SiC. The increase in strength was attributed to a decrease in grain size and the presence of WC.

Zirconium diboride (ZrB 2 ) ceramics were sintered to a relative density of B98% without applied external pressure. Densification studies were performed in the temperature range of 19001-21501C. Examination of bulk density as a function of temperature revealed that shrinkage started at B21001C, with significant densification occurring at only 21501C. At 21501C, isothermal holds were used to determine the effect of time on relative density and microstructure. For a hold time of 540 min at 21501C, ZrB 2 pellets reached an average density of 6.0270.04 g/cm 3 (98% of theoretical) with an average grain size of 9.075.6 lm. Four-point bend strength, elastic modulus, and Vickers' hardness were measured for sintered ZrB 2 and compared with values reported for hot-pressed materials. Vickers' hardness of sintered ZrB 2 was 14.572.6 GPa, which was significantly lower when compared with 23 GPa for hot-pressed ZrB 2 . Strength and elastic modulus of the ZrB 2 were 444730 MPa and 454 GPa, which were comparable with values reported for hot-pressed ZrB 2 . The ability to densify ZrB 2 ceramics without hot pressing should enable near-net shape processing, which would significantly reduce the cost of fabricating ZrB 2 components compared with conventional hot pressing and machining.J ournal

Zirconium diboride-silicon carbide ceramics with relative densities in excess of 95% were produced by reactive hot pressing (RHP) at temperatures as low as 16501C. The ZrB 2 matrix was formed by reacting elemental zirconium and boron. Attrition milling of the starting powders produced nanosized (o100 nm) Zr particulates that reacted with B below 6001C. The reaction resulted in the formation of nanoscale ZrB 2 crystallites that could be densified more than 2501C below the temperatures required for conventional ZrB 2 powder. Because of the low-temperature densification, the resulting ZrB 2 grain sizes were as small as 0.570.30 lm for specimens densified at 16501C and 1.571.2 lm for specimens densified at 18001C. Vickers hardness, elastic modulus, and flexure strength of fully dense materials produced by RHP were 27, 510, and 800 MPa, respectively.

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