Microwave liquid characterization for the study of alcohol molecular relaxation process
Hsin Yu Yao1*, Chun Chen1, Tsun Hsu Chang1
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
* Presenter:Hsin Yu Yao, email:s5te633v@hotmail.com
A broadband system was developed to characterize liquid materials in the microwave regime. It is implemented by a rectangular waveguide system, where the liquid under test is fully filled in a waveguide flange and tightly enclosed by dielectric windows. The scattering coefficients of the stand-alone window as well as the overall system (with liquid) were both measured, and the transfer matrix method was employed to calibrate the window effect. A close form was derived to simultaneously retrieve the complex permittivity and permeability of samples from the well-calibrated overall scattering coefficients. Three common alcohols (methanol, ethanol, and propanol) were characterized in X-band (8-12 GHz), the static permittivity, the optical permittivity and the Debye relaxation time of which were further extracted. Strong dependence between relaxation time and molar mass was clearly observed. This work provides a standard measurement procedure for liquid characterization with decent accuracy, which will benefit the study of the molecule dynamics of liquids.

Keywords: liquid characterization, complex permittivity and permeability, liquid molecular dynamics