钇硅酸盐材料力学性能的第一性原理研究

First Principle Study of Mechanical Properties of Yttrium Silicates

为深入研究C_f/SiC复合材料钇硅酸盐涂层材料Y_2SiO_5与Y_2Si_2O_7的力学性能,为钇硅酸盐涂层体系的设计提供理论依据,基于第一性原理广义梯度近似,研究钇硅酸盐理想晶体X1-Y_2SiO_5和γ-Y_2Si_2O_7的电子结构、力学性能。结果表明:X1-Y_2SiO_5和γ-Y_2Si_2O_7均为机械稳定结构,X1-Y_2SiO_5与γ-Y_2Si_2O_7的体模量、剪切模量、弹性模量、泊松比分别为112,49,128GPa,0.31和114,55,142GPa,0.29。可见X1-Y_2SiO_5的模量较γ-Y_2Si_2O_7低。同时研究二者理想晶体的韧性、热膨胀系数、残余应力。结果表明:X1-Y_2SiO_5韧性较γ-Y_2Si_2O_7好,热膨胀系数较γ-Y_2Si_2O_7高,残余应力较γ-Y_2Si_2O_7低。

In order to investigate mechanical properties of Y2SiO5 and Y2Si2O7 yttrium silicates coatings on Cf/SiC composites and design thermal environment barrier coatings, first-principles calculations were performed to investigate electronic and mechanical properties of X1-Y2SiO5 and γ-Y2Si2O7 using gradient generalized approximation （GGA） based on first principles.The results indicate that they are both mechanically stable structures.Bulk, shear modulus, Young＇＇s modulus of X1-Y2SiO5 and γ-Y2Si2O7 are 112GPa, 49GPa, 128GPa, 0.31 and 114GPa, 55GPa, 142GPa, 0.29, respectively.These mechanical properties of X1-Y2SiO5 are lower than those of γ-Y2Si2O7.At the same time, toughness, thermal expansion coefficient and residual stress of two ideal crystals were studied.The results show that X1-Y2SiO5 has better ductile properties than γ-Y2Si2O7 and its thermal expansion coefficient is larger than that of γ-Y2Si2O7 and while, the residual stress of Y2SiO5 is lower.