Synthesis and microwave characterization of expanded graphiteovolac phenolic resin composite for microwave absorber applications

摘要

Chemical oxidation and thermal treatment method is used to synthesize expanded graphite from natural graphite flakes of size ~2 μm. Novolac phenolic resin (NPR) is used as base matrix and mechanically mixed with expanded graphite (EG) in different weight ratios (30 wt.%, 40 wt.% & 50 wt.% of EG). The mixture is molded at 100-150 °C using compression molding technique to pellets of EG/NPR composite for electrical and microwave characterization. Surface morphology and structural characterization are investigated using scanning electron microscope and X-ray diffraction respectively. 50 wt.% EG composite shows a maximum value of electrical conductivity ~147 S/cm and thermal stability ~350°C The composite is highly dissipating with (ε~(11)_r/ε~1_r > 1) over the entire X band. Reflection loss >-13 dB is observed throughout out the frequency range. The composite has a potential for broadband microwave absorber application.