Incompletely carbonized polyacrylonitrile (PAN) cloths were prepared by heating stabilized PAN cloth at 600800 degrees C in different atmosphere. Their X-band dielectric and microwave-absorbing properties were investigated. Results showed that the complex permittivity constantly increased with the increasing heating temperature due to the growth of carbon sheets. Conversely, the cloths carbonized in air exhibit lower complex permittivity than those carbonized in nitrogen because the reaction with oxygen restricts the progress of carbonization. The reflection loss below 10 dB can be obtained in X band for the sample carbonized at 650 degrees C for 2 h in air. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013