A study of preparation and properties of epoxy resin/carbon fiber/phenolic residual carbon composites with adjustable negative permittivity behavior

In recent years, there have been more and more researches on the dielectric properties of carbon-based composites, and its dielectric tunability is a hot research topic. In this paper, epoxy resin/carbon fiber/phenolic residual carbon (EP/CF/C) was prepared by high-temperature sintering, vacuum liquid phase impregnation and hot-press curing methods. The AC conduction behavior, dielectric properties and impedance properties of composites with different CF/C compression ratios (1, 1.5, 2) are studied. With the increase of CF/C compression ratio, the negative dielectric properties of composites are getting stronger and stronger. The results show that when the CF/C compression ratio is 1, the composites occur percolation phenomenon and dielectric constant is negative. When the CF/C compression ratio is 2, the absolute value of the negative dielectric coefficient of the EP/CF/C composite reaches 9.8 × 104, and the conductivity reaches 0.54 S/cm. In addition, impedance analysis has further confirmed that the inductance properties lead to the negative dielectric properties of the material. The adjustable negative dielectric properties of EP/CF/C composites can provide some suggestions for the field of electromagnetic shielding and capacitors.