Abstract: The present invention relates to a lightweight and flexible material for prevention of electric waves having both absorbing properties and shielding properties against electric waves. In the present invention, carbon fiber or magnetic particles, or both and graphitized carbon black are dispersed and incorporated into an insulating substrate so that the weight ratio of the graphitized carbon black to the carbon fiber, the magnetic particles or the sum of the two may be 0.3 to 5.

Abstract: A wave absorber which is light in weight, rich in flexibility and excellent in wave absorption characteristics in a microwave frequency range. The wave absorber in which composite carbon black particles including crystalline graphite and amorphous carbon black are dispersed into an insulating matrix. In the wave absorber, dispersion of the composite carbon black particles is adjusted so that a ratio (.rho./R) of a volume resistivity .rho. measured at frequencies of 30, 100 and 500 kHz to a measured DC volume resistivity R is in a predetermined range and a volume ratio of the composite carbon black particles having particle diameters of 10 nm to 200 nm to all the composite carbon black particles is in a range of 5% to 95%. Thereby, a wave absorber excellent in absorption characteristics is obtained.