Study On Cement Based Electromagnetic Shielding Composite Materials Of Carbon Series

Electromagnetic radiation origined from electromagnetic wave menace people's health and safety in modern society. It leads to many series electromagnetic shielding materials were produced and researched. Cement based electromagnetic shielding materials will have broad application prospect in building electromagnetic protection for large scale protection, lower cost and easy operating.Cement based electromagnetic shielding composites filled with carbon fiber, graphite, carbon black and coke powder were prepared in this paper. The influence of content, fineness(length), modification, loss agent compounded on compressive strength, electrical resistivity and electromagnetic shielding effectiveness (SE)of composites. The electrical resistivity and SE of composites were measured with four-probe method and coaxial planar—spectrum analyzer method. Results show carbon fiber is an effective attenuation agent, the length of carbon fiber should chose 5-10mm, dispersant agent is carboxymethyl cellulose(CMC). As the carbon black mass fraction increased, the SE of cement composites will get obvious improvement, the electrical resistivity and compressive strength of composites will decline. The 28d compressive strength attained 47.8Mpa, the electrical resistivity reached 0.72Ω·m and the maximum of SE attained 21dB at carbon fiber content of 0.9%. Graphite as attenuation agent, the SE and conductive property of composites will improve,the compressive strength of composites will decline with the mass fraction of graphite increasing. The 28d compressive strength attained 38.16Mpa, the electrical resistivity reached 75.5Ω·m and the maximum of SE attained 10dB at graphite (120 mesh) content of 12%. Refinement of graphite help to improve the mechanical property, electrical conductive property and shielding property. The maximum of 28d compressive strength and SE attained 53.85Mpa and 15 dB, the electrical resistivity reached 4.97Ω·m when the fineness of graphite is 3500mesh. The SE and electrical conductive property of composites that simutaneously contain carbon black and carbon fiber is higher thansingly use these shielding agents. Like the graphite, adding carbon black in composites have good effect in improving SE and electrical conductivity, but having negative impact on mechanical property. The mechanical property of composites contain super conductive carbon black is inferior to containing conductive carbon black. The minimum electrical resistivity of super conductive carbon black composites attained 3.42Ω·m, the maximum of SE reached 19 dB. Adding carbon fiber into carbon black caomposites will improve the electrical conductive property and electromagnetic shielding property. The minimum electrical resistivity attained 0.12Q-m and the maximum of SE reached 27dB to c onductive carbon black—carbon fiber composites. Adding coke powder into cement paste havn't effective impact on improving the shileding and electrical conductive properties of composites, but declining the mechanical property of composites. Refinement of coke powder isn't an effective way to improving the mechanical and shileding property of composites. The electrical conductivity and SE of composites contain coke and carbon fiber profit from carbon fiber not coke powder.