摘要
以α-Si_3N_4粉末为原料、Al_2O_3–RE_2O_3(RE=Lu,Y,Gd和La)为烧结助剂,在1 800℃压烧结制备氮化硅陶瓷,研究了不同烧结助剂对材料的相组成、微观结构和力学性能的影响。结果表明:样品中α-Si_3N_4完全转化为β-Si_3N_4,所形成的长柱状晶粒生长发育良好。随着稀土阳离子半径的增大,材料的相对密度和力学性能呈增加趋势,其中Si_3N_4–Al_2O_3–Gd_2O_3的抗弯强度和断裂韧性分别达到860 MPa和7.2 MPa·m~(1/2)。由于稀土离子对烧结液相黏度的影响,Si_3N_4–Al_2O_3–Lu_2O_3和Si_3N_4–Al_2O_3–Y_2O_3中出现了晶粒异常长大的现象,而Si_3N_4–Al_2O_3–La_2O_3的基体与柱状晶粒界面结合较大导致材料力学性能降低。
Silicon nitride ceramics were prepared via hot-pressing at a sintering temperature of 1800℃withα-silicon nitride as a raw material and Al_2O_3–RE_2O_3(RE=Lu,Y,Gd and La)as sintering additives.The effect of sintering additives on the phase composition,microstructure and mechanical properties of silicon nitride ceramics was investigated.The results show thatα-Si_3N_4 in the sample can completely convert toβ-Si_3N_4 with long columnar grains.The relative density and mechanical properties of the material increase with the increase of the rare-earth element ion radius,and the flexural strength and fracture toughness of Si_3N_4–Al_2O_3–Gd_2O_3 are 860MPa and 7.2 MPa m~(1/2),respectively.Due to the effect of rare earth element ions on the viscosity of the sintered liquid phase,the growth of exaggerated grains occurs in the samples of Si_3N_4–Al_2O_3–Lu_2O_(3 )and Si_3N_4–Al_2O_3–Y_2O_3,and Si_3N_4–Al_2O_3–La_2O_3 has a strong grain interface bonding between the matrix and columnar grain,leading to the reduction of their mechanical properties.
引文
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