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Due to some excellent properties of YAG, it is researched and applied widely. The YAG porous ceramics are prepared via the vacuum sintering technology. The results show that a certain relationship is existed between carbon emissions time and increasing temperature speed, increasing temperature speed is faster, carbon emission time is shorter, entire sintering cycle is shorter, which makes porosity similar, but higher compressive strength is shown, therefore, the increasing temperature speed slightly faster is advantageous to the performance of YAG porous ceramics, that is to say the heating rate of 5℃/min. By appearance, porosity, compressive strength performance comparison that carbon emissions at 800℃ is more appropriate, porous ceramic YAG prepared under 1500℃ and 1h shows the white surface, 59.4% porosity and compressive strength of 8.55MPa.

ZrB2 belongs to a class of ceramics defined ultra-high-temperature ceramics with extremely high melting temperatures; however, ZrB2 ceramics is easily oxidized. To make ZrB2 ceramics possess the better oxidation resistance in the air at high temperature, in this paper, the effect of surface modification on the properties of YAG–ZrB2 ceramics were investigated. Fracture toughness of sintered ceramics with coated raw materials is higher than that of sintered ceramics with mixed raw materials under the same phase and phase content conditions. Oxidation layer thickness of sintered ceramics with coated raw materials is thinner than that of sintered ceramics with mixed raw materials. The results indicate that the sintered coated structure ceramics with coated raw materials help to increase the mechanical property and oxidation resistance of YAG–ZrB2 ceramics.

ZrB2 are widely applied because of some excellent performances; however, ZrB2 is easily oxidized in the high-temperature air. To reach better Al(OH)3–Y(OH)3 composite shell and higher coating ratio on the ZrB2 particles surfaces, ZrB2 particles must be adequately dispersed in the ZrB2 suspension during the coating process. The dispersion of ZrB2 particles and the influence of dispersion on coating effect of ZrB2@Al(OH)3–Y(OH)3 core-shell composite particles were investigated. The dispersion of ZrB2 suspension adding the polyelectrolyte dispersant is better than that of ZrB2 suspension adding the nonionic dispersant; the dispersant content is 2 vol% of ZrB2 suspension to reach the best dispersion. The best dispersion is obtained by the ultrasonic dispersion for 10 min. ZrB2 particles are coated using the dispersant and the ultrasonic dispersion in the ZrB2 suspension to obtain the better coating effect. The dispersion of ZrB2 particles is increased with increasing the coating content.

Silicon nitride (Si3N4) has attracted substantial interest because of its extreme chemical and physical properties, but the sintering densification of Si3N4 is difficult, and it is easily oxidized in the high-temperature air to impact high-temperature strength, which restricts its applied range. In order to decrease the oxidization and improve the strength of Si3N4 at high temperature, the surface of Si3N4 is coated with Al(OH)3 and Y(OH)3 to synthesis Si3N4@Al(OH)3–Y(OH)3 core-shell composite particles. Through TEM, XRD, and BET analysis, when pH is about 9, Si3N4@Al(OH)3–Y(OH)3 core-shell composite particles are successfully synthesized by co-precipitation methods. Coating layer is about 200 nm, which is compaction and conformability. Dispersion of coated Si3N4 with Al(OH)3 and Y(OH)3 particles are very good. Synthesis of Si3N4@Al(OH)3–Y(OH)3 core-shell composite powder will lay the foundation for preparing high-performance YAG/Si3N4 multiphase ceramic materials.

With the fast development of new materials investigation, attention is paid to. The performance of superfine powders, which must be modified on the surface to acquire some points. Coating technology of particles is one especial method of surface modification. In this paper, coating methods of particles are classified into solid state, liquid state, and gaseous state, main methods and mechanisms during current time are reviewed, respectively, and some research examples are listed. The choice of diversified coating technologies is decided synthetically based on powder materials, performance of the modified substance, and application of coated powders. In the future, the researches of the core-shell modification mechanism, coated particles with an ordered arrangement coating layer, a new surface active agent, the facilities of suiting surface modification, and the evaluation methodology of the surface coating effect are very exigent and necessary for the preparation and application of superfine powders.

Zirconium diboride is widely applied to high-temperature materials, but it is easily oxidized at high temperature. To increase the oxidation resistance of zirconium diboride at high temperature, the A1(OH)3–Y(OH)3 is coated on the ZrB2 surface to prepare A1(OH)3–Y(OH)3/ZrB2 composite particles. In this paper, the effect of coating content on the properties of A1(OH)3–Y(OH)3/ZrB2 composite particles is investigated. It is analyzed that the particle size and particle size distribution of A1(OH)3–Y(OH)3/ZrB2 composite particles is increased with the coating content. The dispersion of ZrB2 particles is largely increased with the coating content of 0%–20%; the dispersion of ZrB2 particles is similar when the coating content is from 20% to 30%. The oxidation resistance ratio of the ZrB2 particles with 30% coating content is the best than that of other conditions—it is about three times more than that of the original ZrB2 particles.

Although Zirconium diboride (ZrB2) is a desirable combination with some good properties, it is easily oxidized in the high-temperature air to impact high-temperature properties, which dwindles the applied range. In order to decrease oxidization and improve the high-temperature properties of ZrB2, the surface of ZrB2 is coated with Al(OH)3–Y(OH)3 to synthesize Al(OH)3–Y(OH)3/ZrB2 composite particles. In this paper, the conditions of synthesizing Al(OH)3–Y(OH)3/ZrB2 composite particles by the co-precipitation method are investigated. Al(OH)3–Y(OH)3/ZrB2 composite particles are synthesized under different conditions, but the conditions of synthesizing Al(OH)3–Y(OH)3/ZrB2 composite particles with the better coating quality require pH = 9, the appropriate concentration (Al3+ = 0.017 mol/L, Y3+ = 0.01 mol/L) of composite solution, reaction time of 60 min, titration speed of 0.05 ml/s, using the dispersant in the ZrB2 suspension and the ultrasonic dispersion, respectively.