Tunable nonlinear conductive behavior without percolation threshold and high thermal conductivity of epoxy resin/SiC ceramic foam co-continuous phase composites

Smart dielectrics with self-adaptive capabilities can exhibit desirable electric field-grading performance as the applied electric field exceeds a critical value. However, the conventional approaches to such dielectrics need heavy doping rate, which will not only increase the interface thermal resistance and limit the improvement of thermal conductivity, but also severely sacrifice the mechanical property. In this contribution, a new type of electric field-grading co-continuous phase composite (EP/SiCcf) composed of epoxy resin and SiC ceramic foam was prepared to realize tunable nonlinear conductive performance, while simultaneously improving thermal and mechanical properties. Results show that there is no percolation threshold for all EP/SiCcf composites. The volume loadings of EP/SiCcf composites range from 8.7 vol% to 15.6 vol%, while the nonlinear coefficient subjected to potential barrier height increases from 2.1 to 4.5 and the switching field tuned by barrier width decreases from 1008 kV/mm to 686 kV/mm. The EP/SiCcf40 still exhibits sharp thermal conductivity enhance-ment of about 1000% and glass transition temperature enhancement of 10.8 degrees C. The surface temperature fluc-tuation over time during heating and cooling has illustrated the prospective application of thermal management capability. In addition, the dynamic mechanical analysis reveals that all EP/SiCcf composites have the signifi-cantly improved storage modulus and crosslinking density ascribed to the intact SiC skeleton. The novel co-continuous phase composite provides a new approach for global enhancement of smart dielectric composites in potential applications.

Automated summary

Smart dielectrics with self-adaptive capabilities can show excellent electric field-grading performance when subjected to an applied electric field above a critical value. However, conventional approaches require high doping rates, which increase interface thermal resistance, limit thermal conductivity improvement, and negatively impact mechanical properties. In this study, a new type of electric field-grading co-continuous phase composite (EP/SiCcf) composed of epoxy resin and SiC ceramic foam was prepared to achieve tunable nonlinear conductive performance, while improving thermal and mechanical properties. The results demonstrate the potential application of the novel composite in smart dielectric materials.