Preparation And Properties Of Graphite-base Composite Materials

Expanded graphite has unique pore structure,good floating performance,can stay in the air for a long time.It is a new type of millimeter wave passive interference material.In order to improve the millimeter wave interference ability of expanded graphite,based on the millimeter wave attenuation theory,graphite-iron oxide composite and graphite-silver doped polypyrrole composite were prepared by using ferric nitrate and silver nitrate as raw materials and the millimeter wave attenuation performance test was carried out.The results show that compared with pure expanded graphite,the prepared composites have improved millimeter wave attenuation performance.The specific content is as follows:(1)A graphite intercalation compound was prepared by using nitric acid and potassium permanganate as composite oxidants,glacial acetic acid and perchloric acid as composite intercalation agents.The effects of different oxidant relative masses,expansion temperatures on the expansion volume of graphite intercalation compounds were investigated.The experimental results show that when glacial acetic acid and perchloric acid are used as composite intercaling agents,4.7 g of nitric acid and potassium permanganate composite oxidant are added to 5 g of flake graphite,the expansion volume of graphite intercalation compound reaches 401 mL/g at 700℃.(2)According to the design principle of pyrotechnic composition,nanometer iron oxide was prepared by sol combustion synthesis using iron nitrate as oxidant and citric acid as reducing agent.The particle size ranged from 40 nm to 70 nm.(3)The graphite-iron oxide composite was prepared by adding graphite intercalation compound to an iron nitrate and citric acid precursor sol under high temperature conditions.When the expansion temperature was 700℃,the expansion volume reached 379 mL/g.(4)Based on the preparation method of silver-doped polypyrrole,graphite intercalation compound was added during the reaction to prepare graphite-silver doped polypyrrole composite material,which has a core-shell structure with graphite as the core and silver-doped polypyrrole as the shell.The structure has a conductivity of 18.037 S/cm when the pyrrole monomer concentration is 0.2 mol/L,the molar ratio is 2,the reaction temperature is 40℃,the reaction time is 4 h,and the pH is 1.9.(5)Through the 3 mm and 8 mm wave attenuation performance test,the 3 mm wave attenuation of graphite-iron oxide composite can reach 8.35 dB,and theattenuation of 8 mm wave can reach 13.14 dB.The attenuation of 3 mm wave of graphite-silver doped polypyrrole composite can reach 6.62 dB,the 8 mm wave attenuation can reach 7.58 dB.The above studies show that graphite-iron oxide composites can be prepared by sol combustion synthesis method,and graphite-silver doped polypyrrole composites can be prepared by in-situ polymerization of pyrrole,both of them have good attenuation effect on millimeter waves.