Microwave absorption properties of SiCN ceramics doped with cobalt nanoparticles

Polymer-derived SiCN ceramics containing cobalt was prepared with SiCN ceramics as matrix and cobalt nanoparticles as doping phase. Phase composition, Raman analysis, electromagnetic parameters and microwave absorption properties of SiCN ceramics with different cobalt content pyrolyzed at 1100 ℃ and cobalt content of 2 wt% but different pyrolysis temperature were carried out. The microstructures and magnetic properties of SiCN ceramics with cobalt content of 2 wt% and pyrolysis temperature of 900 ℃ were analyzed. The results show that some cobalt particles can react with carbon to form magnetic Co₃C particles, which is one of the reasons for the magnetism of the sample. The good dielectric property of SiCN ceramics matches the magnetic property, which makes the material have excellent microwave absorption property. When the cobalt content is 2 wt% and the pyrolysis temperature is 900 ℃, the sample has the best microwave absorption performance. The minimum R_L reaches − 10.9 at about 15 GHz, and the effective absorption bandwidth (R_L < − 10 dB) is 3.3 GHz with a thickness of 3 mm. When the thickness became 6 mm, the minimum R_L of the sample can reach − 11.8 dB and the effective absorption bandwidth (R_L < − 10 dB) is 4.2 GHz, showing the excellent microwave absorption performance of materials we obtained.