Enhancing the electromagnetic interference shielding effectiveness of carbon-fiber reinforced cement paste by coating the carbon fiber with nickel

The effectiveness of electromagnetic interference (EMI) shielding is valuable for construction materials and can be enhanced by the addition of carbon fiber to cement. This work reports for the first time that nickel coating on carbon fiber enhances the shielding effectiveness (200-2000 MHz, radio wave) of carbon-fiber cement by increasing the absorption loss SEA, due to the increase in electrical conductivity and magnetic permeability. The SEA/thickness enhancement by the coating decreases with increasing fiber content, because the fiber content increase enhances the conductivity, thereby promoting SEA and diminishing the magnetic influence of the nickel. The SEA/SET (SET = total loss) tends to be higher with the coating. The reflection loss SER is not affected by the coating, because the coating increases both conductivity and permeability, which affect SER oppositely, and the skin depth is smaller for nickel than carbon. The SEA/thickness and SER increase with increasing fiber content, which promotes the conductivity. The trend is less clear with the coating, due to the coating affecting both conductivity and permeability. The SEA/thickness tends to increase with increasing frequency, whereas SER trends oppositely.