雷达检测系统和电磁设备工作频率范围的不断拓宽，对吸波材料宽频吸收性能的要求越来越高，在宽频范围内研究同时满足薄厚度、轻质量、强吸收等综合性能优异的新型吸波材料已经成为当前的研究热点。超材料是一类由人工设计的亚波长周期性结构单元构成的材料，通过合理设计结构单元的形状、尺寸和排布方式等实现对电磁波定制化的调控，在电磁波吸收、隐身技术、反雷达探测、电磁能量收集等领域具有广阔的应用前景。本文基于吸波超材料可设计强的特性，围绕超宽频吸波、超薄、轻质等多功能化展开吸波材料的设计制备与性能研究工作，通过仿真模拟和实验研究相结合的方式开展宽频吸波特性设计优化，并对其多尺度吸波机理进行深入分析。本文主要研究内容和结论如下：

     （1）设计并制备了一种三明治结构水基吸波超材料。利用水在微波频率固有的高介电损耗及特有的频散特性，通过超材料的结构单元设计在多频点处激发产生多个谐振峰叠加作用实现宽频吸收。通过将介质水填充于3D打印树脂壳通道中制备的三明治型水基吸波超材料，实现了7.74-36.76 GHz范围大于90%的宽频电磁波吸收，相对带宽达131.2%，并兼具广角入射、极化不敏感、热稳定性、光学透明和可弯曲等特性。通过不同吸收峰值频率下的电场、磁场和功率损耗密度截面分布，分析了其宽频吸收机理，明确了超材料设计涉及在拓宽材料吸波频段、增强吸波性能中的作用方式及相关机制。

     （2）设计并制备了一种电磁协同强损耗的梯度椎体吸波超材料。以介电损耗材料碳纤维（C_f）和磁损耗材料羰基铁粉（CIP）作为吸波剂，将其分散于环氧树脂（EP）基体中形成具有特定微结构的CIP/C_f/EP复合材料，通过吸波剂含量可调节实现复合材料的电磁参数可调。基于CIP/C_f/EP复合材料设计了一种梯度锥体复合吸波超材料，所制备的吸波超材料在相对较小的厚度下实现了3.84-40 GHz范围内的超宽频电磁波有效吸收，相对带宽达167.8%。基于电磁波与超材料的相互作用，分析了梯度椎体吸波超材料的阻抗匹配特性和多重电磁损耗协同损耗机制。

     （3）设计并制备了一种轻质纤维素气凝胶双层台阶吸波超材料。以碳纳米管（CNT）为吸波剂，利用“溶解、再生、冷冻干燥”工艺制备了CNT/纤维素气凝胶，通过调节CNT的含量实现了纤维素气凝胶电磁参数可调。并在此基础上，设计了一种CNT/纤维素气凝胶双层台阶吸波超材料，然后将纤维素气凝胶填充于3D打印的柔性树脂外壳中，所制备的超轻质吸波超材料实现了4.36-40 GHz范围的超宽频电磁波有效吸收，相对带宽达160.7%。基于多尺度结构设计分析了不同尺度结构设计引发的多重电磁波损耗机制。

        With the continuous expansion of the working frequency range of radar detection systems and electromagnetic equipment, the demand for broadband absorption of materials absorber is becoming increasingly high. Research on new materials absorber with excellent comprehensive performance such as thin thickness, light weight, and strong absorption within the broadband range has become a current research hotspot. Metamaterials are a class of materials composed of artificially designed subwavelength periodic structural units, which realize customized regulation of electromagnetic waves by reasonably designing the shape, size and arrangement of structural units, and have broad application prospects in the fields of electromagnetic wave absorption, stealth technology, anti-radar detection, and electromagnetic energy harvesting. In this paper, based on the designability of metamaterial absorber, the design, preparation and performance of materials absorber are focused on the multi-functionalization of ultra-wideband wave absorption, ultra-thin and lightweight, and the design optimization of wide-band wave absorption characteristics is carried out through a combination of simulation and experimental studies, and the multi-scale wave absorption mechanism is analyzed in depth. The main research and findings of this paper are as follows:

     (1) A sandwich structured water-based metamaterial absorber was designed and prepared. Using the inherent high dielectric loss of water at microwave frequencies and the unique dispersion characteristics, the structural unit of the metamaterial is designed to generate multiple resonant peaks superimposed at multiple frequency points to achieve broadband absorption. The sandwich type water-based metamaterial absorber prepared by filling dielectric water in the 3D printing resin shell channel has realized the broadband electromagnetic wave absorption in the 7.74-36.76 GHz range of more than 90%, with the relative bandwidth of 131.2%, and has the characteristics of wide-angle incidence, polarization insensitivity, thermal stability, optical transparency and bendability. The broadband absorption mechanism was analyzed by cross-sectional distribution of electric field, magnetic field and power loss density at different absorption peak frequencies. The action mode and related mechanism of metamaterial design in broadening the absorbing frequency band and enhancing the absorbing performance of materials are clarified.

     (2) A novel metamaterial with periodic square frustums was designed and prepared. Carbon fiber (C_f), a dielectric loss material, and carbonyl iron powder (CIP), a magnetic loss material, are used as absorbents, which are dispersed in epoxy resin (EP) matrix to form CIP/C_f/EP composites with specific microstructures, and the electromagnetic parameters of the composites can be adjusted by the absorbent content. A square frustum metamaterial absorber was designed based on CIP/C_f/EP composites, and the prepared absorbing metamaterial achieved effective absorption of ultra-wide band electromagnetic waves in the range of 3.84-40 GHz with a relative bandwidth of 167.8% at a relatively small thickness. Based on the interaction between electromagnetic waves and metamaterials, the impedance matching characteristics of square frustum metamaterial absorber and the multiple electromagnetic loss synergistic absorption mechanism are analyzed.

     (3) A lightweight cellulose aerogel bilayer step metamaterial absorber was designed and prepared. The CNT/cellulose aerogel was prepared by dissolving, regenerating and freeze-drying process using carbon nanotubes (CNT) as wave absorbers, and the electromagnetic parameters of the cellulose aerogel were adjustable by adjusting the content of CNT. On this basis, a CNT/cellulose aerogel double-layer step metamaterial absorber was designed, and then the cellulose aerogel was filled in a 3D printed flexible resin shell, and the prepared metamaterial absorber achieved effective absorption of ultra-broadband electromagnetic waves in the range of 4.36-40 GHz with a relative bandwidth of 160.7%.