Design And Research Of The Cement Based Absorbing Coating

With the continuous progress of human science and technology,electromagnetic pollution has become the world's fourth pollution,which threatens the survival of mankind.Besides,the progress of radar technology has made the country's important military targets under threat.Aiming to endow the large number of buildings with electromagnetic wave absorption capacity to solving electromagnetic pollution and protecting significant military targets,the following works had been done.The effect of the pretreatment of distilled water,HCl and NaOH solution on the properties of activated carbon?AC?has been studied through nitrogen adsorption method,mercury intrusion method and SEM method.Based on the preparation of MnO₂/activated carbon composite,cement based absorbing coating has been prepared and its tensile bond strength,water resistance,wear resistance and wave absorbing properties have been studied.Based on the adsorption capacity of AC,KMnO4 and Mn?CH3COO?2 has been used to prepare MnO₂/activated carbon composite through precipitation method.The effects of pretreatment methods on the pore structure,micro morphology,and KMnO4 adsorption capacity of AC were studied.The results show that the average particle size of AC pretreated with HCl was significantly reduced.It is beneficial to open the micro-pore of AC and increase its porosity,and the BET specific surface area is increased by 15.7%.The NaOH solution has an etching effect on the AC,which can increase its porosity and average particle size.The AC treated by HCl and NaOH had the largest absorption quality,increased by 14.5%.Rubber particles was added in the wave absorbing coating to alleviate the problem of coating cracking.The tensile bond strength,wear resistance and water resistance of the coating were studied.The results show that rubber particles would reduce the tensile bond strength,but if the tensile bond strength is higher than 1.5MPa,the rubber particles is beneficial to the wear resistance.The MnO₂/activated carbon composite absorber can absorb some water,which is not conducive to the hydration of cement.The maximum tensile bond strength in 14 d of the coating was 2.4MPa.The minimum grinding pit length is 16.3mm when the wear resistance reaches maximum.The coating has excellent water resistance and only a few deformation,falling off and cracking.The reflectivity of the cement based absorbing coating was measured by the bowing method,and the wave absorbing properties were studied.Research results show that the minimum reflection of the coating is-15.38 dB.The band width of reflection below-10 dB is up to 8.8GHz.The band width of reflectivity below-5dB is up to 14 GHz,which accounted for 90% of the test band,so the cement based absorbing coating have practical significance.The mass ratio of the absorbing coating components which has the best absorbing property is 7.5:7.5:1:1:5.5.The number indicate the mass of cement,manganese zinc ferrite,MnO₂/activated carbon composite absorber,rubber particles and H₂O,respectively.