Abstract
Zirconium diboride based ultra-high temperature ceramics toughened by zirconia fiber (ZrB2–ZrO2f) were prepared by hot pressing and pressureless sintering, and the effect of two sintering techniques on the phase composition, microstructures and mechanical properties of ZrB2–ZrO2f ceramics were studied in detail. The densification behavior was investigated through the analysis of the density curves. The microstructures and mechanical properties of ZrB2–ZrO2f ceramics were analyzed and compared in order to research the influence of the two sintering techniques. Results indicated that the hot-pressing process was more suitable for preparing ZrB2–ZrO2f ceramics than pressureless sintering process. The comprehensive properties of ZrB2 plus 30vol.% ZrO2f ceramics obtained at temperature 1950°C by hot pressing for 2h were optimal, the flexural strength and fracture toughness reached 633MPa and 5.6MPa·m1/2, respectively. The higher flexural strength was attributed to the smaller size of grains and higher relative density, furthermore, the toughening mechanisms were fiber debonding, fiber pull-out, crack deflection and transformation toughening.
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