The electromagnetic characteristics of carbon foams

Three different pore size carbon foams with variable electric conductivities were prepared by a polymer sponge replication method. The electromagnetic parameters of these carbon foams and their corresponding pulverized powders were measured by a resonant cavity perturbation technique at a frequency of 2450 MHz. The results show that carbon foams have smaller dielectric constants but several times larger dielectric loss compared with their corresponding pulverized powders. Moreover, carbon foams show magnetic loss while no magnetic loss can be observed from their corresponding pulverized powders. The magnetic loss of carbon foams is apparently a kind of extrinsically magnetic loss and believed to be able to maintain at high temperatures. The electromagnetic characteristics of carbon foams demonstrate that macrostructure modification is an effective way to modulate electromagnetic properties of such materials. (C) 2007 Elsevier Ltd. All rights reserved.