Abstract: Si/C/N nano powders with 11.61% nitrogen were prepared by CVD. XRD pattern and permittivity of the powders were investigated. On the basis of permittivity of
the powders, radar absorber structures of single- and double-layer were designed. A single-layer absorber coating with a reflection coefficient less than --5dB in
the frequency range of 8--15GHz was designed with a thickness of 2.7mm. A double-layer radar absorber coating with a reflection coefficient less than --5dB
in the frequency range of 8--18GHz was also designed with a thickness of 2.8mm. The range of the reflection coefficient being less than --8dB was 6GHz for the designed
double-layer radar absorber. The radar absorbing mechanism of Si/C/N nano powders was also interpreted. The SiC microcrystalline in the nano composite powder dissolves
a great deal of nitrogen. The charged defects are caused by N atoms occupying the sites of C in SiC moved in response to the electric field. The dielectric relaxation caused
by the charged defects moved in response to the electric field is the main way of the Si/C/N nano powders with absorbing properties.

Key words: Si/C/N nano powder, permittivity, structure design, absorbing mechanism