不同气氛制备的MoSi_2/Al_2O_3复合材料显微结构与介电性能

Microstructure and Dielectric Properties of MoSi_2/Al_2O_3 Composites Prepared in Different Atmospheres

采用固相烧结法制备MoSi_2/Al_2O_3复合材料,研究了空气、真空、Ar气氛对显微结构及介电性能的影响。结果表明:Ar气氛下试样烧结性能好于真空及空气气氛,MoSi_2颗粒被Al_2O_3包覆且分散均匀;3种气氛下烧成的试样均含MoSi_2、Al_2O_3和Mo_5Si_3相,而空气下发现有SiO_2,真空及Ar保护气氛有少量Mo;空气气氛下烧成的复合材料气孔率最大,断裂韧性与抗弯强度最低;Ar保护气氛烧成后试样的断裂韧性与抗弯强度分别达到9.70 MPa·m^(1/2)与179.5 MPa。随频率的增加,不同烧结气氛制备的MoSi_2/Al_2O_3复合材料的介电常数和介电损耗均降低;随着烧结气氛从空气、真空、Ar气的变化,复合材料介电常数的实部和虚部均增加。

MoSi2/Al2O3 composites were prepared by a solid-state sintering method. The microstructure and dielectric properties of the samples in different sintering atmospheres （i.e., air, vacuum and At） were investigated. The results show that the sintering performance of the specimens in Ar atmosphere is better than that in vacuum and in air atmospheres. The MoSi2 particles are coated with Al2O3 and dispersed evenly. MoSi2, Al2O3 and Mo5Si3 are in the composites after sintering in different atmospheres. SiO2 generates in air, and a small amount of Mo exists in vacuum and in Ar atmospheres. The porosity of composites sintered in air atmosphere is the greatest, and the fracture toughness and flexural strength are the lowest. The maximum fracture toughness and flexural strength of the composites after sintering in Ar atmosphere are 9.70 MPa·m1/2 and 179.5 MPa, respectively. The dielectric constant and loss of MoSi2/Al2O3 composite decrease with the increase of frequency in different atmospheres. The real and imaginary parts of the dielectric constant of the composite material increase with changing sintering atmosphere from air and vacuum to At.