聚合物转化SiHfCN陶瓷的制备及其吸波性能OA北大核心CSTPCD

Polymer-derived SiCN ceramics benefiting from advantages of light mass and low coefficient of thermal expansion,have received wide attention in electromagnetic wave absorption field.However,the wave absorptive performance of SiCN ceramics needs to be further improved due to its monomer loss mechanism and insufficient temperature resistance.Enhancing their wave absorptive performance with the aid of multicomponent synergy is a feasible way,but still facing some challenges in preparation and wave absorption.In this work,four types of nanoceramics,SiHfCN,SiHfCN-C,SiHfCN-B,and SiHfCN-N were obtained by single-source modification of polysilazane combining different compounds.The results showed that SiHfCN generated HfO2 and SiO2 for up to 13.5％(in mass)oxygen content in the Hf source,resulting in the minimum reflection loss(RLmin)of only-13.8 dB and the effective absorption bandwidth(EAB)of only 0.42 GHz.Compared to SiHfCN,the co-modification of the Hf-containing polymer with C,B and N sources increased the interface and conductive phases of polymer-derived ceramics,real and imaginary parts of SiHfCN-C,SiHfCN-B,and SiHfCN-N gave rise to 1.4-1.8 and 2.7-3.9 times higher,respectively,with RLmin of-50.6,-57.3 and-63.5 dB,and EAB of 3.53,3.99 and 4.01 GHz,showing a significant improvement in their wave absorptive properties.The SiHfCN-C inhibited the generation of HfO2 for massive free carbon,which could enhance the conductivity loss.The SiHfCN-B generated B-N and B-C bonds,and precipitated nanorods of HfSiO4 to provide more heterogeneous interfaces,increasing the polarization loss.The SiHfCN-N increased the content of N-C bond due to the introduction of abundant N,enhancing the dipole polarization loss,while the generated carbon nanosheets not only enhanced the conductivity loss but also provided rich interfaces,which improved the impedance matching and amplified the polarization loss,thus exhibiting excellent wave absorptive performance.