层状水泥基吸波材料结构设计、制备及其性能研究

The cement-based composites with the excellent wave-absorbed capabilities, mechanical performance and durability will be explored considering the detriment due to electromagnetic radiation and interference.Combined with the characteristics of the cement-based composites, a new cement-based material will be prepared by designing the multi-layer structure with the gradient electromagnetic impedance in according to the electromagnetic wave transmission theory and composites design principles. The influence of the composition and thickness of the impedance matching layer on reflectivity and absorption can be studied as well as the type of absorbing agent and its optimum dosage in each layer. The key electromagnetic parameters of cement-based materials and the factors with the influence on the reflectivity can be deterimined. The related mechanism and the effect of such factors as each composed layer, its thickness and characteristics on the microwave absorbing capability can be investigated. The model can be established to be used to estimate the properties of the microwave absorbing materials. This model is believed to be beneficial to the design of such kind of materials and its appplication. The role of ferrite as absorbing agent will be revealed in the process of cement hydration, evolution of the micro-structure as well as its influence on the workability, mechanical performance and durability. The work above can provide a theoretical support for the application of ferrite materials in cementitious system.

针对电磁辐射所造成的污染以及电磁干扰产生的危害，开发兼具电磁波吸收性能、优异力学性能和耐久性能的水泥基复合材料。以电磁波传输理论和复合材料设计原理为指导，结合水泥基材料自身的特点，设计具有阻抗渐变结构的层状水泥基吸波材料，分析阻抗匹配层材料的组成、厚度对吸波体透波性能的影响，损耗层中吸波剂的种类、掺量以及复合方式对材料吸波性能的影响；确定水泥基材料基本电磁参数及反射率的影响因素、机理以及层状水泥基吸波材料各层的材料组成、厚度及性质对吸波能力的影响规律；建立吸波材料性能预测模型，为材料的设计与应用提供理论与实验依据；揭示铁氧体类吸波剂对水泥基材料水化进程、水化产物、微观结构演变以及各种工作性能、力学性能及耐久性能影响，为铁氧体类材料在水泥基体系中的应用提供理论依据。课题为应对日益严重的电磁环境的挑战，提供新材料、新技术以及科学依据。

针对电磁辐射和电磁干扰开发具有电磁波吸收性能的水泥基材料具有重要理论与工程应用价值。本课题设计、制备了具有阻抗梯度变化的高吸收宽频带层状水泥基吸波体，并探讨了吸波体中阻抗匹配层和电磁波吸收层材料的组成、厚度对吸波体性能的影响，确定了水泥基材料基本电磁参数与反射率的关系，并对材料性能进行了预测。主要结论如下：.随着硅灰掺量的增大，水泥基材料的孔隙率逐渐减小，介电常数逐渐增大，材料材料表面的匹配性能变差，其透波率最大值从30.1%逐渐减小到27.8%；随着引气剂掺量的增大，材料的孔隙率也逐渐增大，介电常数则逐渐减小，阻抗匹配性能得到改善，透波率最大值从30.1%增到37.9%；掺有20%膨胀珍珠岩的水泥基材料制备的匹配层，其透波率最高接近于60%，对材料阻抗匹配性改善明显优于掺有引气剂。引入碳纳米管、铁氧体等具有导电和磁性的功能材料以达到电磁波损耗的目的。碳纳米管是较好的吸波功能材料，随着碳纳米管掺量的增加，水泥基材料介电常数逐渐增大。铁氧体加入也增加了复合材料的电磁参数，并降低材料的反射率。.设计制备了具有电磁参数梯度变化的多层水泥基吸波体结构，结果表明：多层水吸波体结构电磁波损耗性能明显优于单层水泥基样品，且表现为层数愈多，吸收性能越好，吸收带愈宽。三层吸波体结构反射率低于-7dB的带宽为11.0GHz，低于-10dB的带宽为7.65GHz。通过传输线理论预测了单层、双层及三层材料的平板材料微波反射率，计算结果与实测值相对比发现：单层材料预测值与实验值具有较好的相关性，而双层和三层水泥基材料，由于每层材料电磁参数难以精确测量，导致最终反射率预测值与实测值相差较大。