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Modern society everywhere in the electromagnetic waves generated by the electromagnetic radiation is a threat to human health and safety, and thus all kinds of electromagnetic protective material came into being. Electromagnetic shielding cement-based material has the protection area, construction is convenient, inexpensive, and will be very broad application prospects in building electromagnetic protection. This article was prepared by the composite material of carbon fibers, graphite, carbon black and coke as the cement-based electromagnetic shielding electromagnetic loss agent. Electromagnetic loss agent dosage, the fineness or length, modification, loss agent Admixed composite mechanical properties, electrical conductivity, electromagnetic shielding performance. Resistivity and electromagnetic shielding performance of the composite four-electrode method and the coaxial cable - spectrum analyzer for testing. The results show that the carbon fibers is an effective electromagnetic loss agent, a dispersing agent should be selected, carboxymethyl cellulose, chopped carbon fibers, length of 5-10mm is appropriate, as the carbon fiber content increases, the decline in the mechanical properties of the composite material, the conductive properties and shielding performance significantly enhance. Carbon fiber content of 0.9%, the 28d compressive strength of the composite 47.8MPa, the resistivity of 0.72Ω · m, screen efficiency maximum of 21dB. Graphite as loss agent, graphite dosage increased, the mechanical properties of the composites decreased significantly increase in electrical conductivity and electromagnetic shielding performance. 120 mesh graphite content is 12%, the composite 28d compressive strength 38.16MPa, and resistivity of 75.5Ω · m, a maximum of 10dB screen effect. Graphite refinement help to improve the mechanical properties of the composites, electrical conductivity and electromagnetic shielding performance, 28d compressive strength of the composite material and the screen effect in 3500 mesh graphite fineness maximum of 53.85MPa and 15dB, respectively, resistance rate 4.97Ω · m prepared composites of graphite carbon fiber composite doped conductivity and electromagnetic shielding performance is better than single doped graphite and carbon fibers prepared composite performance. Carbon black as electromagnetic loss agent, the mechanical properties of the composites significantly decreased significantly enhance conductivity and electromagnetic shielding performance. Conductive carbon black composite mechanical properties inferior to the conductive carbon black composites, conductive carbon black composites resistivity as low as 3.42Ω · m, the screen efficiency values ??of up to 19dB. Carbon black and carbon fiber composites can be doped conductive properties and further enhance the shielding performance, the lowest resistivity of conductive carbon black, carbon fiber composite materials 0.12Ω-· m, the screen efficiency values ??of up to 27dB. Coke introduced into the cement matrix, and can not effectively improve the conductive properties of composite materials and electromagnetic shielding performance, and will also reduce the mechanical properties of the composite material. Refinement of coke and does not significantly improve the performance and mechanical properties of the composite electromagnetic shielding. Coke and carbon fiber mixed to prepare a composite material, the conductive properties of the material and electromagnetic shielding performance entirely from the contribution of the carbon fibers, coke does not play a role in promoting.
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