【摘要】 用经典的有效媒质公式 (包括 Maxwell Garnet公式、Bruggeman公式、Polder-van Santen公式和相干准晶近似公式 (quasicrystalline approximation with coherentpotential,QCA-CP) )研究了含纳米 Si C(N)粉体的复合材料的微波介电特性 ,计算结果表明 ,经典的有效媒质公式对含纳米 Si C(N)粉体的复合材料是不适合的 ,应寻求新的方法来求解纳米复合材料的微波介电常数。研究表明 ,不同纳米 Si C(N)粉体含量的复合材料的介电常数实测值与纳米粉体体积分数 (f )之间有非常好的拟合关系 ,复合材料微波介电常数的实部 (ε′)和虚部 (ε" )与纳米粉体体积分数之间符合二次多项式 (ε′、ε" =Af 2 +Bf +C)关系 ,根据二次多项式可以非常方便而准确地计算纳米复合材料的微波介电常数更多还原

【Abstract】 Our aim was to predict the microwave permittivity of SiC(N) composite powder. We tried first to use the classical effective medium functions, which had not been subjected to scrutiny at microwave frequencies and had not been tested for SiC(N) composite powder. We successfully prepared the nano SiC(N) composite powder from hexamethyldisilazane ((Me 3Si) 2NH) (Me∶CH 3) by a laser induced gas phase reaction. The powders are spherical, loosely agglomerate with a size range of 20~30 nm. The microwave permittivities of a mixture containing paraffin and nano SiC(N) composite powders were measured between 8.2 GHz and 12.4 GHz. The classical effective medium functions such as Maxwell Garnet function, Bruggeman function, Polder van Santen function, QCA CP (quasicrystalline approximation with coherent potential) function, were used to calculate the microwave permittivities of the mixture containing nano SiC(N) composite powders. We found that the real part (ε′) and imaginary part (ε") of the microwave permittivity and dissipation factor (tg δ=(ε"/ε′) of the mixture increase with the volume filling factor ( f ) of nano SiC(N) composite powder. The calculation results indicate that the classical effective medium functions can not effectively model the microwave permittivities of these nano composites. So we tried using second order polynomials. The ε′ and ε" of composites containing nano SiC(N) composite powders at 10 GHz can be effectively modeled by the following second order polynomials respectively: ε′= -12.934 f 2+85.552f+2.717 3; ε"=591.35f 2+51.888f+0.847 8 .更多还原