Soot particle properties in the microwave range

This paper outlines the study of Diesel soot particle properties in the frequency band 2.0-40.0 GHz. Using a transmission/reflection as well as a cavity perturbation method, the complex dielectric constant ¿* = ¿1 - j¿2 was measured for multiple of samples (soot particles produced in a Diesel engine and deposited on paper filter). From the analysis of the experimental data the following conclusions appear: The complex dielectric constant - i.e. the HF electrical conductivity and the microwave power absorption efficiency - are dependent on the frequency and the soot particle thickness. Increasing the soot particle thickness causes the reflection to be stronger and results in less influence on deeper particle layers from incident microwave energy. The HF electrical conductivity has a maximum value between 5 and 10 GHz. The maximum power absorption efficiency appears in the same frequency band and decreases with increasing soot particle thickness.