Porous materials for EMI shielding

This chapter discusses the synthesis methods and electromagnetic interference (EMI) shielding mechanisms and performance of porous materials. Electronic devices need shielding from external EMI to properly function. Also, sources of EM waves such as communication systems and medical imaging equipment need to be isolated to protect humans from exposure. Current trends and practices of designing, fabricating, and using lightweight porous materials for EMI shielding applications are covered. Various methods and innovative solutions for producing porous materials by modifying either the matrix or filler type/shape are examined. The presence of porosity in the material results in several novel mechanisms for EMI mitigation, which include multiple internal reflections from pore walls providing greater interaction of EM waves with the material leading to increased absorption for same thickness of the shield. It is also observed that using conducting fillers such as metallic particles or carbon nanotubes in foam microstructure is very effective because the filler is located in thin cell walls and forms a conducting network at low filler loading, improving the shielding effectiveness. An assessment of economic implications of weight reduction in EMI shields is also presented. Future directions in research and applications of new EMI shielding materials are also discussed.