This paper presents a study on the perrnittivities of the earbon black/epoxy composite at mierowave frequeney. The measurements were performed at the frequeney band of 1 GHz-18 GHz. The experimental data show that the complex permittivities of composites depend strongly on the natures and concentrations of the carbon black dispersion. The frequeney characteristics of dielectric constants and ac conductivities of composites show the good conformity with descriptions of the percolation theory, satisfying the general scaling relation. The measuring frequeney band is over the critical frequency, below that the ac conductivities of composites are constant to the frequency. The values of dielectric constants and ac conductivities have consistent relationships with the carbon black concentration. The A new scheme, that is a branch of Lichteneeker-Rother formula, is proposed to obtain a mixing law to describe the complex permittivities of the composites as function frequeney and concentration of carbon black.

Keywords: Dielectric, Conductivity, Carbon Black, Epoxy, Composite, Simulation, Microwave, Complex permittivity