Perparation And Performance Of Novel Cermet Microwave-absorbing Materials

With the development of the stealthy and anti-stealthy, the demand of vacuum devices for high-power, the widespread popularity of electronic communication, and the electromagnetic pollution increasing, the development of micro-wave absorbing material has been the one of the hotport in functional matrials.In this dissertation, the development of novel Mo/AlN cermet micro-wave absorbing materials is the primary object. The materials are expected to become the next high-performance novel micro-wave absorbing materials.The Mo/AlN and Mo/TiO₂ cermets were manufactured by a conventional pressing-sintering process with AlN, TiO₂ and Mo powders as the staring materials. Microstructure and composition of the sintered cermets were investigated by the SEM, XRD, EDS, and mechanical performances were also tested. Moreover the microwave-absorbing behaviors of the Mo/AlN and Mo/TiO₂ cermets were measured by the vector network analyzer. The results showed that Mo/AlN and Mo/TiO₂ cermets with relative densities of more than 97ï¼…and 94ï¼…, respectively, of the theoretical can be obtained by sintering their compacts at 1750℃and 1350℃, respectively, for 4h.The mechanical properties of the sintered cermets increase as Mo content increases. The bending strength and fracture toughness were 531.4 MPa and 4.61 MPa·m^1/2 respectively, for Mo/AlN cermets with 40 wtï¼…Mo, and its thermal conduction reached to 156.1 W·m^-1·K^-1. To the Mo/TiO₂ cermets, the bending strength and fracture toughness were 238.4Mpa and 2.23MPa·m^1/2 respectively.The introduction of Mo obviously improved the microwave-absorbing behaviors of Mo/AlN and Mo/TiO₂ cermets, and Mo content also had an obvious influence on the microwave-absorbing behaviors of the cermets. What'more, single frequency band atenuation performances were appeared on the Mo/TiO₂ cermets. Mo/AlN material with 40 wtï¼…Mo had a wider frequency absorbing band between 4 and 18GHz, the maximum reflection loss was almost negative-22dB. The maximum reflection loss of the Mo/TiO₂ cermets is found near to the 20 GHz, and it reached to-19dB.The frequency absorbing band was broadened by the Mo presence. We also studied on the Mo/AlN cermet microwave absorption mechanism. Farthermore, we found that the Mo/AlN cermets showed better microwave-absorbing property than the Mo/TiO₂ material.