Study On The Preparation Of PDCs/biomass Carbon Composites And Their Electromagnetic Wave Absorbing Properties

Biomass carbon-based absorbing materials is an important research direction for the development of EMW（Electromagnetic Wave）absorbing materials,which have been widely concerned due to their low cost,extensive source,environmentally friendly and recyclability,especially for their internal rich natural excellent pore structure.However,there are some problems such as single loss mechanism,impedance mismatch and narrow absorption band.Therefore,in order to solve the above problems,Ni/PDCs/BCMs composite absorbing materials with different BCMs（Biomass Carbon Materials）as carriers were designed and prepared by vacuum assisted impregnation process and carbothermal reduction process,which introducing nickel source as magnetic modified metal into PDCs（Polymer-Derived Ceramics）precursor.The main research contents are as follows:（1）Ni/PDCs/PS composite absorbing materials were prepared by using PS（Peanut Shell）as carrier.The effects of different content of nickel source on the final phase composition,microstructure and absorbing properties of composite absorbing materials were studied,and the absorbing mechanism was further explored.The results shown that the prepared Ni/PDCs/PS composite absorbing material had a hierarchical porous structure,which could not only provide a large number of heterogeneous interfaces and enhance the interfacial polarization of the absorbing material,but improve the multiple reflection of the incident EMW as well.The PDCs after thermally decomposed and Ni/Ni₃Si in-situ formed effectively regulated the impedance matching and magnetic loss of the composites.When the addition amount of nickel source was 1 wt%and the filler content was 50 wt%,NPP-1sample had good EMW absorption performance.The RL_min（Minimum Reflection Loss）at1.74 mm was-66.38 d B,and the EAB（Effective Absorption Bandwidth）at 1.45 mm was3.54 GHz（14.46-18 GHz）.（2）Ni/PDCs/SS composite absorbing materials were prepared by using SS（Sorghum Straw）as carrier.The effects of different content of nickel source on the final phase composition,microstructure and absorbing properties of composite absorbing materials were studied,and the absorbing mechanism was further explored.The results shown that the PDCs after pyrolysis and Ni₂Si in-situ generated effectively adjusted the impedance matching of the composite absorbing material,and improved the conductivity of the sample along with graphite carbon.BCMs and in-situ generated CNTs（Carbon Nanotubes）provided a large number of heterogeneous interfaces,which promoted interfacial polarization and dipole polarization.When the nickel source content was 2 wt%and the filler content was 30 wt%,the RL_min reached-69.44 d B when the thickness was only 1.33 mm,and the EAB at 1.49mm was 4.27 GHz（13.73-18 GHz）.In addition,the low frequency RL_min at 4.22 mm was-45.80 d B,the EAB between 4.20 mm and 5 mm remained above 2.4 GHz and the widest reached 2.48 GHz.（3）Ni/PDCs/CF composite absorbing materials were prepared by using CF（Cotton Fiber）as carrier.The effects of different content of nickel source on the final phase composition,microstructure and absorbing properties of composite absorbing materials were studied,and the absorbing mechanism was further explored.The results shown that the PDCs after pyrolysis and Ni in-situ generated effectively adjusted the impedance matching of the composite absorbing material.The in-situ generated Ni not only endowed the composite absorbing materials with good magnetic properties and magnetic loss ability,but possessed excellent catalytic activity too.A large number of CNTs were in-situ generated on the surface of CF,which together formed a double-layer core-shell structure with the precursor impregnation surface,and greatly improved the graphite carbonization degree of the material,enhanced the dielectric loss ability and multiple reflections.Especially when the nickel source content was 2 wt%,the filler content was 50 wt%,the thickness was only 1.15 mm,and the EAB was 4.92 GHz（13.08-18 GHz）.When the nickel source content was 3 wt%,the RL_min reached-82.23 d B at a thickness of 1.79 mm.