不同还原铁粉掺量下混凝土的电磁屏蔽和吸波特性

Electromagnetic shielding and wave absorption of concrete with different contents of reduced iron powder

建筑工程材料的电磁防护能力对于信息安全日趋重要。针对常规混凝土无法达到电磁屏蔽性能,而钢纤维或碳纤维混凝土无法兼顾宽频电磁波的屏蔽和吸波能力的问题,提出利用还原铁粉(Fe3O4)作为掺料,制备一种新型电磁屏蔽混凝土。设计基于端口法和弓架法的电磁波反射率和透射率试验,定量评价了不同掺量水平和厚度条件下混凝土试件对于电磁波的屏蔽和吸波特性。结果表明:1)加入还原铁粉可以显著提升材料的吸波能力,但是铁粉掺量对于反射率影响不大。2)当掺量超过200 kg/m^3时,试样受谐振特性影响其透射率反而降低。3)通过对比分析得出,当掺量为200 kg/m^3、混凝土板厚度为20 mm时,试样在10 GHz以下的电磁辐射环境中获得了较好的屏蔽和吸收性能;在10~15 GHz的电磁环境中,20 mm和40 mm厚的混凝土板电磁防护性能相当;当频率高于15 GHz时,采用40 mm厚混凝土在电磁屏蔽和吸收特性上更优。该混凝土材料试样在电磁屏蔽性能上均有显著提高,具有一定宽频吸波性能,可为电磁波防护工程建筑材料的研究提供一定的参考和借鉴。

The electromagnetic protection ability of building materials is becoming more and more important for information security.Conventional concrete can not achieve the electromagnetic shielding performance,while steel fiber or carbon fiber concrete can not take into account the shielding and absorbing capacity of broadband electromagnetic wave.In this paper,a new type of electromagnetic shielding concrete was prepared by using reduced iron powder(Fe3O4)as admixture.Based on the experiments of reflectivity and transmissivity of electromagnetic wave by port method and bow frame method,the shielding and absorbing characteristics of concrete specimens under different mixing levels and thicknesses were evaluated quantitatively.The results show that 1)adding reduced iron powder can significantly improve the absorption ability of the material,but the amount of iron powder has little effect on the reflectivity;2)When the dosage was more than 200 kg/m^3,the transmissivity of the sample decreased under the influence of resonance characteristics;3)Through comparative analysis,it is concluded that when the dosage was 200 kg/m^3 and the thickness of concrete slab was 20 mm,the sample had good shielding and absorption performance in the electromagnetic radiation environment below 10 GHz;in the electromagnetic environment of 10-15 GHz,the electromagnetic protection performance of 20 mm-thick and 40 mm-thick concrete slab was equivalent;when the frequency was higher than 15 GHz,40 mm-thick concrete was better in electromagnetic shielding and absorption characteristics.The concrete sample had a significant improvement in electromagnetic shielding performance,and had a certain broadband absorption performance,which can provide certain reference and reference for the research of electromagnetic wave protection engineering building materials.