New anti-ablation candidate for carbon/carbon composites: Preparation, composition and ablation behavior of Y2Hf2O7 coating under an oxyacetylene torch

Y2Hf2O7 possesses low thermal conductivity and high melting point, which make it promising for a new anti ablation material. For evaluating the thermal stability and the potential applications of Y2Hf2O7 on anti-ablation protection of C/C composites, Y2Hf2O7 ceramic powder was synthesized by solution combustion method and Y2Hf2O7 coating was prepared on the surface of SiC coated C/C composites using SAPS. Results shown that the coating exhibits good ablation resistance under the heat flux of 2.4 MW/m(2) with the linear and mass ablation rates are 0.16 mu m s(-1) and -0.028 mg s(-1), respectively, after ablation for 40 s. With the prolonging of the ablation time, the increasing thermal stress causes the increase of cracks. Moreover, the chemical erosion from SiO2 and the physical volatilization of low temperature molten products aggravate failure of the Y2Hf2O7 coating.