颗粒级配对Si_(3)N_(4)w/Si_(3)N_(4)复合材料弯曲强度与介电性能的影响EI北大核心CSCD

为了获得一种弯曲和介电性能良好的氮化物陶瓷材料,本工作首先以氮化硅晶须(Si_(3)N_(4w))为原料,采用喷雾造粒工艺制备3种具有不同粒径分布的Si_(3)N_(4w)球形颗粒粉体,研究雾化盘转速对Si_(3)N_(4w)球形颗粒粉体粒径分布的影响。然后以喷雾造粒得到的Si_(3)N_(4w)球形颗粒为原料,采用干压法制备3种颗粒级配的Si_(3)N_(4w)预制体,研究颗粒级配Si_(3)N_(4w)预制体的孔径分布。采用化学气相渗透(CVI)和先驱体浸渍裂解(PIP)工艺在3种颗粒级配的Si_(3)N_(4w)预制体中进一步制备Si_(3)N_(4)基体,研究Si_(3)N_(4w)/Si_(3)N_(4)复合材料制备过程中的物相和微结构演变以及颗粒级配对Si_(3)N_(4w)/Si_(3)N_(4)复合材料的微结构、密度、弯曲强度和介电性能的影响。结果表明:3种颗粒级配的Si_(3)N_(4w)预制体均具有二级孔隙特征,其中小孔孔径均约为0.7μm,大孔孔径分别为45.2,30.1μm和21.3μm。在制备的3种颗粒级配的Si_(3)N_(4w)/Si_(3)N_(4)复合材料中,S13样品的颗粒级配效果最好,复合材料的弯曲强度达到81.59 MPa。此外,该样品的介电常数和介电损耗分别为5.08和0.018。良好的弯曲强度和介电性能表明制备的Si_(3)N_(4w)/Si_(3)N_(4)复合材料有望应用于导弹天线罩领域。

Effect of particle gradation on flexural strength and dielectric property of Si3N4w/Si3N4 composites

In order to obtain a nitride ceramic material with good flexural and dielectric properties, using silicon nitride whiskers (Si₃N_4w) as raw material, three kinds of Si₃N_4w spherical particle powders with different particle size distributions were prepared by spray drying process at first in this work, and the effect of the rotating speed of the atomizing disc on the particle size distribution of Si₃N_4w spherical particles was studied. Then, using the Si₃N_4w spherical particles obtained by spray drying as raw materials, three kinds of Si₃N_4w preforms with different particle gradations were prepared by dry pressing method, and the pore size distribution of the particle gradation Si₃N_4w preforms was studied. Si₃N₄ matrices were further prepared in three kinds of particle gradation Si₃N_4w preforms by chemical vapor infiltration (CVI) and precursor impregnation and pyrolysis (PIP) methods, and the phase and microstructure evolution of Si₃N_4w/Si₃N₄ composites during the preparation process were investigated. Finally, the effect of particle gradation on the microstructure, density, flexural and dielectric property of Si₃N_4w/Si₃N₄ composites was studied. The results show that the three kinds of particle gradation Si₃N_4w preforms all have bimodal pore structure characteristics, in which the pore sizes of small pores are all about 0.7 μm, and the pore sizes of large pores are 45.2, 30.1 μm and 21.3 μm, respectively. Among the as-prepared three types of Si₃N_4w/Si₃N₄ composites with particle gradation, the flexural strength of the S13 composites reaches 81.59 MPa since it has the best particle gradation effect. In addition, the dielectric constant and dielectric loss of this sample are 5.08 and 0.018, respectively. Good flexural strength and dielectric properties indicate that the as-prepared Si₃N_4w/Si₃N₄ composites are expected to be used in the field of missile radomes.