THERMODYNAMIC AND KINETIC ANALYSES OF SYNTHESIZING ZrB₂@Al(OH)₃–Y(OH)₃ CORE–SHELL COMPOSITE PARTICLES

Abstract

ZrB 2 has some excellent performances, but it is easily oxidized at high temperatures to impact the high-temperature strength, which restricts its applied range. To protect from the oxidization and improve the strength of ZrB 2 at high temperature, the surface of ZrB 2 particles is coated with the Al ( OH ) 3 – Y ( OH ) 3 shell to synthesize ZrB 2 @ Al ( OH ) 3 – Y ( OH ) 3 core–shell composite particles. Through the thermodynamic and kinetic analyses of the heterogeneous nucleation and homogeneous nucleation, the concentration product of precursor ion ( Y 3+ or Al 3+ ) and OH - (Q i ) must be greater than the solubility product (K sp ), respectively; the conditions of Y 3+ and Al 3+ are reached to produce Al ( OH ) 3 – Y ( OH ) 3 shell on the ZrB 2 surface between the Y 3+ line and the AlO 2 - line. Through TEM and XRD analyses, ZrB 2 @ Al ( OH ) 3 – Y ( OH ) 3 core–shell composite particles are successfully synthesized by the co-precipitation method, the shell layer quality is better at pH = 9, which established the foundation for preparing high-performance YAG / ZrB 2 and Al 2 O 3 – YAG / ZrB 2 multiphase ceramic materials.