摘要
As a novel member of the ultra-high temperature ceramic family,which have extremely high melting points and remarkable hardness,Ta1-xHfxC solid solution ceramics are promising for applications in thermal protection systems.Ta_(1-x)Hf_(x)C(x=0,0.2,0.5,0.8,and 1.0)with 2 vol%Cr_(3)C_(2),were densified up to 98.8%at 2000℃ using a two-step spark plasma sintering process.Effect of Cr_(3)C_(2) on the linear shrinkage of Ta1-xHfxC was investigated.Possible‘eutectic’reaction within TaCeCr_(3)C_(2) ceramic was inferred to contribute to the shrinkage at 1462 C.High-angle annular dark-field scanning transmission electron microscopy combined with energy-dispersive spectroscopy was employed to further confirm the mutual diffusion between rock-salt structured‘CrCx’and TaC.Flexural strength,fracture toughness and Vicker’s hardness of Ta1-xHfxC ceramics were in the range of 439e492 MPa,4.0e5.8 MPa∙m^(1/2) and 14.9e19.9 GPa respectively.The coefficient of thermal expansion(in the temperature range of 25e1000℃)and thermal conductivity(at 1000℃)of Ta_(1-x)Hf_(x)C varied from 7.17 to 7.51×10^(-6) K^(-1) and 31.9e42.9 W/m·K,respectively.The high-temperature strength of Ta_(0.5)Hf_(0.5)C decreased to 165 MPa up to 1600℃,approximately 34%of room-temperature strength,and a‘zig-zag’load-displacement curve was observed.
基金
support from:National Natural Science Foundation of China(No.52073299,51602325,91960102)
Youth Innovation Promotion Association,CAS,(No.2018289)
Natural Science Foundation of Shanghai(20ZR1465400)
ScienceFoundation for Youth Scholar and Opening Project of State Key Laboratory of High-Performance Ceramics and Superfine Microstructures,Shanghai Institute of Ceramics CAS(SKL201602,SKL201902SIC)
gratefully acknowledged.Buhao Zhang would also like to acknowledge the Chinese Scholarship Council(CSC)for financial support.
