Preparation Of Low Dimensional Carbon Composites For Microwave Absorption Property

The wide application of electromagnetic wave technology brings convenience to daily life for many people,but also brings invisible electromagnetic pollution.The research of electromagnetic shielding and microwave absorption is very important."Light,thin,wide and strong" is the evaluation criteria of high-performance absorbers,so the application of traditional absorbers is greatly limited.With the development of carbon-based materials,this kind of carbon nanomaterials with low density,stable properties and outstanding performance have attracted attention of researchers in the field of microwave absorbents.The manufacturing conditions of carbon nanomaterials are strict.Conventional pyrolysis often leads to structural collapse,powder agglomeration,or material inequality.Based on these premises,the purpose of this experiment is to adjust the formation of inorganic materials with the help of salt template,further reduce the material density,improve the impedance matching,and explore a convenient,efficient and low-cost manufacturing method of low dimensional carbon materials.In this paper,carbon nanosheets with different morphologies are prepared by pyrolysis using sodium chloride as template,and then applied to the field of microwave absorbents.The materials obtained have excellent properties such as light weight,thin thickness,wide effective absorption band and strong reflection loss.The main contents of this paper are as follows:(1)Synthesis and electromagnetic wave absorption properties of a kind of vesicular carbon nanosheets:A kind of vesicular carbon nanosheets is prepared by molten salt method using metal-free phthalocyanine as carbon source.We have characterized the composition,morphology and structure,tested the electromagnetic parameters and studied the microwave absorption properties.The experimental data show that the increase of pyrolysis temperature is conducive to the introduction of defects and graphitization,and the impedance matching ability of the absorber is improved.The experimental data reveal that the maximum loss is-21.05 d B from 0.5 GHz to 18 GHz,and the bandwidth is 8.58 GHz.(2)Synthesis and electromagnetic wave absorption properties of a kind of corrugated copper phthalocyanine carbon nanosheets:A kind of corrugated carbon nanosheets is prepared by molten salt method using copper phthalocyanine as carbon source.We have characterized the composition,morphology and structure,also tested the electromagnetic parameters and studied the microwave absorption properties.The experimental data show that the unique wavy structure is beneficial to increase the specific surface area and provide more polarization centers.The experimental data show that the maximum loss is-13.36 d B and the bandwidth is 3.7 GHz from 0.5 GHz to 18 GHz when the sample is treated at900 ? for 2.0 mm thickness.(3)Synthesis and electromagnetic wave absorption properties of micron scale square carbon materials:A kind of micron scale square carbon material is prepared by doping molten salt method,and using 5,10,15,20-tetra(4-pyridyl)porphyrin as carbon source.We have characterized the composition,morphology and structure,also tested the electromagnetic parameters and studied the microwave absorption properties.The experimental data show that the square holes and rough lamellar surface help to reduce the reflection of electromagnetic wave,and the flocculent carbon film increases the specific surface area of the materials.With the increase of heat treatment temperature,the values of?' and ?'' of the products increase to a certain extent.The experimental data reveal that the maximum loss between 0.5 GHz and 18 GHz is-33.58 d B and 9.4 GHz in the thickness of2.6 mm at 850 ? compared with 800 ?,the performance of the sample is increased by10% and the effective bandwidth is increased by 25.3%.