Study On Preparation And Microwave Absorption Properties Of Coal-based Carbon/Cobalt Matrix Composites

In order to further protect the ecological environment and realize the sustainable development strategy,China has formulated the development goals of"carbon peak"and"carbon neutralization",which are reflected in promoting the adjustment of industrial structure and eliminating backward production capacity on the basis of the traditional utilization of carbon materials.Among them,the problem of greenhouse gases and toxic and harmful gases produced in the combustion of fossil fuels represented by coal is particularly prominent.Therefore,taking coal as raw material and converting it into coal-based derived carbon materials with high added value is one of the effective methods to effectively solve the above problems.This is highly consistent with Chinese established new development concept,high-quality development,and ecological civilization construction.On the other hand,in the information age,the application of various electronic products not only brings convenience and efficiency to human beings but also brings various electromagnetic pollution problems.In order to deal with this problem,various carbon matrix composites also came into being.Based on the problems of coal conversion and electromagnetic pollution,taking Ningxia anthracite as carbon matrix material,different types and contents of cobalt sources were introduced,and coal-based carbon/Co matrix composites were prepared at different temperatures.The results show that coal-based carbon/Co matrix composites have significant microwave absorption properties,which not only realize the efficient and clean utilization of coal to a certain extent but also provide a new research idea for microwave absorbing materials.The main conclusions of this paper are as follows:（1）Coal-based carbon/Co（CBC/Co）composites were prepared by in-situ reaction.Ningxia anthracite was mixed with cobalt chloride hexahydrate in different proportions and activated by adding potassium hydroxide.CBC/Co composites with different cobalt additions were prepared by in-situ reaction with reducing gas produced by anthracite heating.The results show that the material surface has a large number of layered textures,and cobalt nanoparticles are distributed in the inner layer and surface of the composite.When the ratio of anthracite to cobalt chloride hexahydrate is 1:0.4 and the reaction temperature is 800°C,the CBC/Co composites show the best microwave absorption performance.Specifically,the reflection loss of CBC/Co composites at 10.48GHz and 15.84 GHz are-57.05 d B and-50.35 d B respectively,the effective absorption bandwidth is 2.8 GHz,and 4.1 GHz,Corresponding thickness is 2.13 mm and 1.35 mm.（2）Coal-based carbon/Fe Co（CBC/Fe Co）composites were prepared by hydrothermal method combined with thermal carbonization and alkali activation.Firstly,Fe Co is prepared by low-temperature hydrothermal method,then Fe Co is placed in anthracite system and potassium hydroxide is added to form anthracite/Fe Co mixed system.Anthracite is transformed into coal-based carbon in the N₂ atmosphere.At the same time,coal-based carbon and Fe Co alloy are compounded to form CBC/Fe Co composites.The carbonization and activation of anthracite are carried out simultaneously in the whole process,which greatly improves the efficiency of the preparation process.In all the CBC/Fe Co samples,the sample with the addition of 0.3 g of Fe Co alloy at the process temperature of 800°C showed better microwave absorption performance than other proportions and temperatures.The minimum reflection loss of CBC/Fe Co composites at 8.96 GHz and 16.80 GHz.It is-49.82 d B and-60.81 d B respectively,and the thickness is only 2.45 mm and 1.38 mm.（3）Coal-based carbon/Co/Co₇Fe₃（CBC/Co/Co₇Fe₃）composites were prepared by the in-situ reaction.With anthracite as the carbon source,the ratio of ferrous sulfate heptahydrate to cobalt chloride hexahydrate is 1:3.The reducing gas produced by coal under high heat and oxygen-free conditions will reduce the iron source and cobalt source to Co₇Fe₃ and Co magnetic particles,which can well realize the synergy of dielectric and magnetism.This work explores the electromagnetic parameters and microwave absorption properties of CBC/Co/Co₇Fe₃ at different temperatures.The results show that the structure of graphene is observed in CBC/Co/Co₇Fe₃ magnetic composites,which may be related to the graphitization of coal-based carbon at high temperatures,and the degree of graphitization also increases with the increase of temperature.In particular,the samples prepared at 850°C have the best microwave absorption performance,that is,the reflection loss at the thickness of 3.31 mm and 2.41mm is-68.73 d B and-51.85 d B respectively,covering C-band and X-band respectively.In order to verify that the material in the ratio has the best microwave performance,we added the experimental verification that the ratio of iron source to cobalt source is 1:2and 1:4 at 850°C.The results further show that the samples carbonized and activated at the process temperature of 850°C show excellent microwave absorption performance when the ratio of iron source to cobalt source is 1:3.Using coal as raw material and introducing magnetic particles to prepare coal-based composites not only realizes the transformation and clean utilization of coal but also shows the application potential in microwave absorption.Figure[48]Table[13]References[160]...