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ZrB2, YAG, and Al2O3 are widely applied because of some excellent performance qualities, but ZrB2 is easily oxidized in high-temperature air. To make the ZrB2 ceramics obtain better oxidation resistance, high-density ZrB2–YAG–Al2O3 ceramics were prepared. The oxidation behavior of ZrB2–YAG–Al2O3 ceramics was investigated. The weight gain of ceramics was increased with increasing oxidation temperature, and the weight gain of ceramics was reduced with increasing YAG–Al2O3 content and Al2O3 proportion, especially above 1500°C. The weight gain was increased with prolonged oxidation time, but the rate of weight gain was decreased gradually after 2 h, and the weight gain was reduced with increasing YAG–Al2O3 content and Al2O3 proportion. Increasing YAG–Al2O3 content and Al2O3 proportion may raise the oxidation resistance of ZrB2–YAG–Al2O3 ceramics. Through the above analysis, the oxidation resistance model of ZrB2–YAG–Al2O3 ceramics was constructed to fully comprehend the oxidation process and mechanism.

ZrB2 belongs to a class of ceramics defined ultra-high-temperature ceramics (UHTCs) with extremely high melting temperatures, but ZrB2 ceramics are difficult for densification. To make high relative density and good high-temperature property ZrB2 ceramics, in this article, the effect of YAG content on the property of YAG–ZrB2 multiphase ceramics is investigated. The sintering shrinkage is increasing with the increasing of the YAG content from 10% to 40%. The relative density increases with the increase of the YAG content from 10% to 40%, but the rate of increasing relative density from 10% to 30% is higher than that of 40%. When the content of YAG is higher than 30%, fracture toughness increases a little. The YAG content is more, and the weight gain is less, which shows that the oxidation layer thickness is thinner.

Although ZrB2 has some excellent performances, it is difficult to prepare the high relative-density ZrB2 ceramics, which limits the application of ZrB2 materials. To obtain higher relative-density ZrB2 ceramics for increasing the good oxidation resistance, YAG/ZrB2 multiphase ceramics is prepared with the spark plasma sintering, the sintering mechanism of preparing YAG/ZrB2 multiphase ceramic materials is investigated. Al2O3 reacts with Y2O3 to form YAG above 700°C during the sintering process. YAG is filled and melted the space of ZrB2 particles to bind the ZrB2 particles during reaction and sintering process, which increases the density of YAG/ZrB2 multiphase ceramic materials. The YAG/ZrB2 multiphase ceramic materials was successfully prepared under sintering temperature of 1700°C, holding temperature time for 4 min, and sintering pressure of 20 MPa; the density is 5.63 g/cm3, the relative density is 99.78%.

To obtain the better ZrB2/Al(OH)3–Y(OH)3 core-shell composite particles, ZrB2 particles must be adequately dispersed during the coating process. In this article, the dispersibility of ZrB2 particles in the ZrB2 suspension is investigated via the sedimentation method. Through test and analysis, the dispersibility is rapidly increased with prolonging the ultrasonic dispersion time before 10 minutes. After 30 minutes, the sedimentation grads using ultrasonic dispersion basically reach the sedimentation balance, but the grads using mechanical agitating dispersion does not basically change after 5 minutes. The ultrasonic dispersion is one of more effective ways between ultrasonic and mechanical agitating dispersion, the dispersion time for 10 minutes is chosen in the dispersibility of ZrB2 particles via ultrasonic dispersion.