Study On Cement Based Composite Absorbing Materials With Resistance Gradual Changing Structure

With rapid development of modern electronic science and technology, the harm due to electromagnetic radiation which result in electronic equipment with high frequency and digitization is more and more serious. In order to prevent external electromagnetic interference and electromagnetic signals leak and reduce the harm of electromagnetic wave on human body and detecting ability on buildings, the study on cement-based composite materials with excellent absorbing property has important significance in defense, civil, and protecting human health.Cement based materials with resistance gradual changing structure are a kind of functional building materials. It can effectively will electromagnetic wave into electrical energy, heat or other forms of electromagnetic energy, which reached the electromagnetic wave absorbing attenuation, and also has excellent heat insulation performance. The article mainly aims at civil and military buildings at home and abroad for the urgency of electromagnetic protection and current cement base absorbing material existent problem, put forward with excellent the impedance gradient absorbing function of type cement base composite materials. Relative disciplines of composition, structure and performances were mastered, high-performance cement-based materials were designed and produced that were wave absorption, splitting resistance, heat preservation, durability and environmental protection. Significant basement and theoretical guidance were provided for designing, production and application of the materials.In this article, the main tasks and achievements are as below:According to the electromagnetic wave propagation law and impedance matching theory, combined with the characteristics of cement-based material itself, through optimization design on cement base material composition, matched layer and depletion layer, the design idea and method that the structure with different impedance layered cement matrix composites (matched layer+depletion layer) was put forward.Electromagnetic parameters change rule of matrix cementitious material was studied through adding steel slag, fly ash, high titanium heavy slag, etc.. Then dielectric and magnetic loss mechanism on electromagnetic wave of the matrix cementitious material was proved up. The article systematically analyzed the influence law of absorbing properties, which due to the mineral admixture and surface modification of polymer on matrix composite. Results showed that adding 10% mass fraction of rubber micro-powder and 30% mass fraction of steel slag could improve matching impedance of surface material and electromagnetic waves loss ability of internal material. On the basis of optimizing matrix, the influences of obturator perlite, basalt fiber and graphite powder as the absorbing losses components mixed in cement-based composites to absorbing properties were studied systematically. The results showed that, as the obturator materials with low electromagnetic parameters, perlite has excellent electromagnetic loss characteristics, whose optimal dosage from 50vol % to 60vol % (volume dosage); basalt fiber contains some dielectric loss substances, its internal structure is porous and it has microwave transparency function, adding about 0.5% to 1.0% will be best; as the resistance loss type absorbing agent, Graphite dosage should be controlled in 0.2% to 0.4%.On the basis of research on cement base composites matrix and absorbing performance factors, double-layer absorbing materials with resistance gradual changing structure were designed and produced:Graphite composite perlite as loss layer absorbing components; rubber micro-powder composite perlite as matched layer fillers. Through adjusting matched layer materials filled ratio to adjust material surface electromagnetic parameters, which make the input impedance on material surface and the wave impedance in free space matching. Through adjusting depletion layer absorbing component content and preparation technology, make absorbing agent evenly distributed in electromagnetic wave transmission channel formed by wave-permeating aggregate, this will realize the effective loss of electromagnetic wave. The result shows:filling the matched layer with 60% expanded pearlite and filling the depletion layer with 0.4% graphite,60% expanded pearlite and 0.5% basalt fibre, in test frequency within 8 to 18GHz, reflectivity will all below -10dB, the minimum reflectivity reach -23.35 dB, which have showed excellent absorbing performance. Combined with cement base composite insulation performance testing, reveals the lottery wave-aggregate obturator rate, high polymer modification and fiber disorderly to distribution form three-dimensional interpenetrating networks structure on the influence mechanism insulation materials, realized the cement base composite materials multifunction change.