纳米SiC和SiC(N)粉体的微波介电特性及其与微波的作用机理  

Microwave Permittivity of Nano SiC(N) Composite Powder andNano SiC Powder and Interaction Mechanism with Microwave

作　　者：赵东林[1] 罗发[1] 周万城[1] 万伟[2] 

机构地区：[1]西北工业大学凝固技术国家重点实验室 [2]西北工业大学电子工程系,陕西西安710072

出　　处：《西北工业大学学报》2002年第2期167-171,共5页Journal of Northwestern Polytechnical University

基　　金：航空科学基金(99G53082)

摘　　要：研究了纳米SiC粉体和纳米SiC(N)复相粉体在8.2-12.4GHz频率范围的介电特性及其与微波的作用机理，发现纳米SiC(N）复相粉体介电常数的实部（ε′）和虚部（ε′′）在8.2-12.4GHz范围内随频率增大而减小，介电损耗（tgδ=ε′′/ε′）较高，是较为理想的微波吸收材料。纳米SiC粉体的ε′、ε′′和tgδ明显小于纳米SiC(N)复相粉体的，对微波的吸收不理想。提出了纳米SiC(N)复相粉体对微波的吸收机理。纳米SiC(N)复相粉体中的SiC微晶固溶了大量的N原子，在纳米SiC(N)复相粉体中形成大量的带电缺陷，这些带电缺陷在电磁波交变电场作用下产生极化耗散电流，强烈的极化驰豫过程导致大的介电损耗。To our best knowledge, there is no paper in the open literature on the microwave permittivity of the nano SiC and nano SiC(N) composite powder. So we studied the microwave permittivity of these two kinds of nano powders, in order to find a new good microwave absorber. We successfully prepared thenano SiC(N) composite powder and nano SiC powder from hexamethyldisilazane ((Me3Si)2NH) (Me: CH3) and SiH4-C2H2 respectively by a laser-induced gas-phase reaction. The powder agglomerated loosely into spheres. The microwave permittivities of the nano SiC(N) composite powder and nano SiC powder were measured. We found that the nano SiC(N) composite powder, compared with a mixture of pure SiC and Si3N4 phase, exhibits some new feature of dielectrical property at microwave frequencies. The nano SiC(N) composite powder is a new good microwave absorber. We found that the real part (ε') and imaginary part (ε') of the microwave permittivity, and dissipation factor (tgδε'/ε') of nano SiC(N)composite powder are much higher than those of nano SiC powder, especially the tgδ. The microwavepermittivity of the mixture of nano SiC(N) composite powder and paraffin wax (or any other dielectricalmaterials) can be adjusted by varying the amount of this composite powder. From this point on, weexplain the interaction mechanism between microwave and nano SiC powder, and between microwaveand nano SiC(N) composite powder. The promising new feature of nano SiC(N) composite powder may bedue to that, compared with a mixture of pure SiC and Si3N4 phase, the atomic chemical environment of Si, C, and N is more complicated. The SiC microcrystalline in the nano composite powder dissolves a great deal of nitrogen. So the charged defects and quasi-free electrons move in response to the electric field, and adiffusion or polarization current results from the field propagation. The higher ε' and dissipation facter tgδare due to the dielectrical relaxation. The β-SiC and α-SiC in nano SiC powder dissolve no nitrogen,therefore the charged defects and

关 键 词：微波 纳米SiC(N)复相粉体 纳米SIC粉体 微波介电特性 作用机理 纳米材料 复合材料 碳化硅 

分 类 号：TB332[一般工业技术—材料科学与工程] TB383