Terahertz relaxation polarization modeling of micro-water inside nano-modified dielectrics and imaging distribution of free/bound water

The additional moisture can be easily introduced into dielectric materials with the nano-doping, which could have adverse impacts on the insulating properties. Herein, samples with different moisture absorption are tested using Terahertz (THz) waves. The relaxation resonance integrated polarization model is developed to illustrate the water absorption effect by the nano-filler on the THz spectrum, which is related to the hydrogen bond (HB) state of water molecular clusters. Detection of moisture content is realized by the polarized resonance intensity in the proposed model. The different HB states of free water and bound water are effectively distinguished using the Debye parameters in the model, and the formation process of water involved in the HB network is analyzed. Meanwhile, the proposed model is verified by molecular simulation. This work provides an application-worthy method to distinguish nuances in moisture contents and distribution in nano-dielectrics, with advantages of non-destructiveness, rapidity and 2D visualization. •This work provides a way to effectively differentiate the moisture content and the moisture distribution in nanodielectrics.•Relaxation resonance integrated polarization model reveals the water absorption effect of nanofillers on terahertz spectra.•The different HB states of free and bound water are effectively distinguished using the Debye parameter in the model.