| Electro-magnetic wave absorption properties of polymer matrix composites made by blending polymer with nanometer powders and ordinary absorbers were investigated in the paper. Main work includes three parts. Firstly,the electro-magnetic parameters of nanometer SiOx, CB,their mixture and CNTs were researched by means of waveguide. Secondly, electro-magnetic wave absorption properties of composites made by mixing nanometer SiOx, CB, nanometer zonic, ZnOw, CNTs and their mixture with polymer were measured in the method of freespace. Thirdly, different depth and different structure composites were designed in order to improve electro-magnetic absorption properties of materials. Main results include:1. Investigation of electro-magnetic parameters shows that nanometer SiOx,CB and CNTs are dielectric loss materials, ' of CB decreases and " and tg8 of CB are largely improved when a little quantity of nanometer SiOx is added to CB.2. Research shows that absorption properties of composite powders are better than those of single absorber.The minimum reflectivity of 25 phr CB can decrease from -10. 54dB to -28. 71dB and the absorption frequency width <-10 dB of 25 phr CB can be increased from 0. 66 GHz to 2. 78 GHz when CB is mixed with 5 phr nanometer SiOx.3. Results of absorption properties of different depth composites prove that the absorption peak is shifted to high frequency as the depth of materials decreases.4. Investigation of absorption properties of different structure composites shows that , on the condition of the reasonable structure design, absorption properties of multi-layer materials are better than those of single-layer materials. The minimum reflectivity of multi-layer ZnOw/CB/NBR ( 100/25/25) composites compared with single-layer ZnOw/CB/NBR (100/25/25) composites decreases from -14. 34dB to -46. 37dB, and the absorption frequency width <-10dB increases from 1. 32 GHz to 1.91GHz.The complex permittivity peak of nanometer SiOx and two dielectric losses of CNTs are discovered in our experiment which are different from properties of other nanometer materials. We should do the further research to reveal the truth. |
