Synthesis And Microwave Absorption Properties Of D-Xylose-based Carbon Composites

Biomass-based carbon materials are a class of carbon materials formed by different forms of carbonization reactions using carbon-rich biomass as carbon precursors.The residual functional groups contained on the surface of biomass carbon materials can be used as polarization centers to convert electromagnetic energy,and the defective sites existing inside their materials can produce spatial potential resistance and interfacial polarization,which are beneficial to electromagnetic wave absorption.In this work,a series of xylose-based carbon composites were prepared,and the components and morphological structures of the materials were characterized and analyzed by XRD,XPS,FT-IR,SEM,TEM and Raman spectroscopy,and the electromagnetic parameters of the samples were tested by vector network analyzer(VNA).The results are as follows.(1)CuFe2O4/carbon microsphere composites were synthesized by a two-step hydrothermal method using xylose,Cu(NO3)2·3H2O and Fe(NO3)3·9H2O as raw materials.The effects of the addition of carbon microspheres,microscopic morphology and magnetic properties on the microwave absorption performance of the materials were investigated.The results showed that the CuFe2O4 modification formed a heterogeneous interface on the surface of carbon microspheres and enhanced the interfacial polarization;the introduction of CuFe2O4 magnetic particles improved the dielectric loss and magnetic loss of the composites and enhanced the microwave absorption performance;when the addition amount of carbon microspheres was 0.3 g,the CuFe2O4/carbon microsphere composites achieved good microwave absorption capacity at 14.64 GHz The minimum reflection loss was-50.4 dB and the effective absorption bandwidth was 6.24 GHz at a sample matching thickness of 2.5 mm.(2)Nitrogen-doped carbon nanosheet composites were prepared by hydrothermal and high-temperature calcination using xylose and adenine as raw materials.The effects of calcination temperature,nitrogen doping and morphological structure on the microwave absorption properties of the composites were investigated.The results show that the doping of heterogeneous atoms of nitrogen in the carbon layer can increase the dipole polarization center and cause the increase of dipole polarization loss;the formed nanosheet layer structure increases the contact surface and generates the charge aggregation phenomenon,which is beneficial to enhance the interfacial polarization,and also can occur multiple reflections;when the calcination temperature is 700 degrees and the matched thickness of the sample is 2 mm,the minimum reflection loss reaches-14.65 dB,and the corresponding effective absorption bandwidth is 5.44 GHz.(3)The ZnAl2O4/nitrogen-doped carbon nanosheet composites were prepared by hydrothermal method using xylose,adenine,zinc nitrate and aluminum nitrate as raw materials.The effects of raw material mass ratio and morphological structure on the microwave absorption properties of the composites were investigated.The results showed that:the presence of a large number of interfaces inside the composite,resulting in interfacial polarization,the formation of conductive networks between the material particles,further increasing the loss to microwaves;the appropriate ratio of reactants and the introduction of zinc aluminate can adjust the impedance matching of the material;when the mass ratio of carbon nanosheets,zinc nitrate and aluminum nitrate is 1:6:15,the minimum reflection loss reaches-40.8 dB at the sample matching thickness of 2 mm,and the maximum effective reflection loss reaches-40.8 dB at the sample matching thickness.40.8dB,and the maximum effective absorption bandwidth is 5.6 GHz.Figures[31]Tables[5]References[101]...