Complex permittivity of graphite, carbon black and coal powders in the ranges of X-band frequencies (8.2 to 12.4 ghz) and between 1 and 10 ghz

The real and imaginary parts of the relative complex permittivity (ε_r' and ε_r") were measured in the ranges of X-band frequencies (8.2 to 12.4 GHz) and between 1 and 10 GHz for graphite, carbon black and coal powders at room temperature so as to clarify the relation between the complex permittivities of carbonaceous materials and their characteristics, i.e., graphitization, porosity (i.e., specific surface area) and ash contained in coals. It is found that the complex permittivities increase with increasing crystallite size and specific surface area. It is also found that the dependency of the permittivities on the ash content seems be negligible within the range of the ash content in the present study.