Light weight expanded graphite (EG) flakes are synthesized from natural graphite flakes of size ～ 2 nm employing chemical oxidation and thermal treatment method. Scanning electron microscope investigation shows that EG flakes consist of numerous graphite sheets of nanometers thickness and micrometer in diameter. EG flakes are mechanically mixed with novolac phenolic resin (NPR) in different weight ratios (30wt%, 40wt% & 50wt%) and compressed with thermal treatment to develop expanded graphiteovolac phenolic resin (EG/NPR) composites. Nicolson-Ross method is used to determined the complex permittivity (ε_r = ε_r' - jε_r~") of the developed composites using Agilent E8362C vector network analyzer. A high value of dielectric loss tangent (ε_r~"/ε_r~') > 1 has been observed for the three compositions in the entire X band. Shielding effectiveness of developed composites of thickness 3.7 mm measured in the frequency range of 8 to 12 GHz shows a maximum value of -48 dB for 50 wt% EG/NPR composites. The material production is simple and cost effective, and the absorbing material is light weight and thus, is beneficial for installation in some strategic components.
展开▼
