Synthesis And Microwave Absorption Properties Of G-C₃N₄ And Composites

Graphitic carbon nitride(g-C3N4),which has a monolayer structure similar to graphene,is a non-metallic semiconductor material and a dielectric microwave absorbing material.The composite of spinel-type metal oxide and g-C3N4,prepared graphitic phase carbon nitride composite has good microwave absorption properties.In this work,g-C3N4,CoFe2O4/g-C3N4,and ZnCo2O4/g-C3N4 composites were prepared by hydrothermal method.SEM,TEM,XRD,FT-IR spectroscopy,XPS and vector network analyzer were used to characterize the compositional composition,morphological structure and electromagnetic parameters of the materials,and the results are as follows:(1)g-C3N4 materials were prepared by calcination in a muffle furnace at 550?for 4h and by hydrothermal method using melamine as raw material.The effects of hydrothermal reaction time on the morphological structure and microwave absorption properties of g-C3N4 materials were investigated.The results showed that the g-C3N4 materials prepared by different hydrothermal reaction times had rod,lamellar and needle cluster morphologies,and the lamellar g-C3N4 material with a hydrothermal reaction time of 15 h had the best microwave absorption capacity,with a minimum reflection loss of-18.08 dB and a maximum effective absorption bandwidth of 3.36 GHz at the sample matching thickness of 3.5 mm and a frequency of 10.16 GHz.(2)CoFe2O4/g-C3N4 composites were prepared by hydrothermal method using g-C3N4,FeSO4·7H2O,Co(NO3)2·6H2O as raw materials and NaOH to adjust the pH of the solution to 11.The effects of the morphological structure of the composites and the mass ratio of raw materials on the wave absorption properties of the composites were investigated.The results showed that the lamellar g-C3N4 distribution formed a heterogeneous interface in microspherical nano CoFe2O4,which caused interfacial polarization and enhanced the ability of multiple scattering and reflection of electromagnetic waves inside the material;when the g-C3N4:Co(NO3)2·6H2O:FeSO4·7H2O mass ratio was 1:0.97:0.46,the material had the best wave absorption performance,the minimum reflection loss value of-39.34 dB was obtained at the sample matching thickness of 3 mm and frequency of 10.24 GHz,and the maximum effective absorption bandwidth reached 4.96 GHz at the sample matching thickness of 2 mm.(3)ZnCo2O4/g-C3N4 composites were prepared using g-C3N4,CoCl2·6H2O and Zn(CH3COO)2·2H2O as raw materials and ammonium fluoride as surfactant by hydrothermal method and forged in a muffle furnace at 400? for 2 h.The effects of morphological structure and raw material mass ratio on the wave absorption properties of the composites were investigated.The results show that the flower-like structure of ZnCo2O4 grows on the lamellar g-C3N4 and forms into a conductive network structure,which enhances the interfacial polarization and conductivity loss;when the mass ratio of g-C3N4:Zn(CH3COO)2·2H2O:CoCl2·6H2O is 1:0.88:0.48,the material has excellent wave absorption performance,the minimum reflection loss value of-40.65 dB was achieved at the sample matching thickness of 2.5 mm and frequency of 12.4 GHz,and the maximum effective absorption bandwidth reached 4.88 GHz at the sample matching thickness of 2 mm.Figures[27]Tables[4]References[114]...