Reactive Preparation and Properties of ZrB_2 Coating

In order to improve the ablation property of C/SiC composite at ultra high temperatures,ZrB2 coatings upon C/SiC composite were prepared by pasting the slurry of zirconium powder,boron powder and phenolic resin,followed by high temperature sintering.The reactions in the sintering process were investigated,and the component,microstructure and ablation property of the coatings were characterized.The results show that zirconium powder reacts firstly with pyro-lytic carbon to form ZrC till 1200℃,and then ZrC reacts with boron to form ZrB2 during 1400℃-1600℃.When the mole ratio of Zr/B/C is 1.0/1.5/1.0,the coating sintered at 1600℃ is composed of mainly ZrB2,small amount of ZrC and ZrO2.After ablation for 60 s in oxyacetylene torch environment,the C/SiC composite with ZrB2 coating shows a linear reces-sion rate of zero,due to the ZrO2 formation from ZrB2 oxidation,while the C/SiC composite without coating shows a lin-ear recession ratio of 0.064mm/s.