Development of EMI shielding materials characterized by low secondary electromagnetic radiation pollution

Abstract-Present work is to develop a novel functional material for Electromagnetic Interference (EMI), which is characterized by low secondary pollution through enhanced absorption loss at high shielding effectiveness. The shielding materials were made by acrylic acid resin containing Ni powder and Ni+NiZnFe₂O₄ respectively. The effect of NiZnFe₂O₄ addition on EMI shielding effectiveness of shielding composite was investigated in terms of reflection loss and absorption loss in shielding effectiveness. There is no significant difference in conductivity of the composites with or without 2.5% volume fraction of NiZnFe₂O₄ powder addition. However, the EMI shielding effectiveness was increased obviously because NiZnFe₂O₄ addition. This can be attributed to enhancement of absorption capability of electromagnetic radiation because of NiZnFe₂O₄ soft magnetic characteristics. The enhancement of absorption capability for electromagnetic radiation is greatly beneficial to decrease the secondary pollution of EMI which is resulted from the reflection of electromagnetic radiation on shielding materials. The effect of NiZnFe₂O₄ addition on reflection and absorption in shielding effectiveness was discussed and evaluated based on the basic principle of electromagnetic theory.