随着智能化时代的到来，电磁波技术广泛应用于民生和国防领域，大大促进社会发展，保卫了国家安全。但过量电磁辐射也造成了环境第四大污染——电磁污染。为有效解决电磁污染问题，大量科研工作者开发“强、宽、轻、薄”的高性能电磁波吸收材料，一方面可以提高电子设备的稳定性和信息的安全性，保护人体免受电磁辐射危害，另一方面作为隐身飞机、军舰等军事设备表面涂覆层可有效吸收敌方雷达信号，降低被探测的概率实现电磁隐身，增强突防和生存能力。过去几十年内，以金属硫化物、碳材料、磁性材料等为主的电磁波吸收材料被广泛研究。硫化铜(CuS)因物理化学性能优异、合成方法简便、微观结构可调而在电磁波吸收领域展现了巨大的潜力。CuS优异的导电性作为一把双刃剑，既使其在交变电磁场中展现出优异的介电损耗能力，同时也带来了阻抗失配导致性能不佳的问题，此外CuS可调的形貌结构也有助于增强极化弛豫、促进电磁波衰减。因此本论文以CuS为基底，从介电性能调控与微观结构优化两个角度出发，通过优化阻抗匹配和发挥结构优势两方面来提升电磁波反射损耗(Reflection Loss，RL)，主要研究内容与结果如下：
(1) 以优化CuS多组分间协同作用、丰富损耗机制为出发点，采用溶剂热法合成了一种凹立方多面体状CuS/γ-Fe2O3复合结构。凹多面体CuS表面为γ-Fe2O3纳米粒子提供大量锚定位点以更好调节介电常数，又有效的避免了γ-Fe2O3纳米粒子的团聚，从而在提高复合材料的复磁导率、优化阻抗匹配的同时，增强材料的界面极化作用。上述改进使得CuS/γ-Fe2O3复合结构的电磁波吸收性能相比于单一组分大大提升，2.6 mm下10.48 GHz处最小反射损耗(Minimum Reflection Loss，RLmin)为-48 dB，此时有效吸收带宽(Effective Absorption Bandwidth，EAB)为3.2 GHz (8.56-11.76 GHz)，2 mm时的EAB则可以达到4 GHz (11.76-15.76 GHz)，通过调节样品的厚度(2-7 mm)，可以实现从2.64 GHz至15.76 GHz范围的有效吸收，GHz频带覆盖率可达82%，为合理设计介电-磁复合吸波材料提供了思路。
(2) 为更准确探讨结构调控与电磁波吸收性能之间的关系，通过简单溶热法可控地合成了不同比例的花状 CuS/γ-Fe2O3异质结构。在精细调节电磁参数并优化阻抗匹配的基础上，三维(3D)花状结构带来了多重极化弛豫和丰富的损耗机制。更值得注意的是，花状CuS与γ-Fe2O3之间形成的数量更为丰富的异质结结构，进一步增强界面极化作用。多种结构优势协同使得 CuS/γ-Fe2O3异质结构的电磁波吸收性能显著增强。厚度仅为1.6 mm时，15.6 GHz处的RLmin为-49.36 dB，EAB达到4.64 GHz。通过调整吸收体的厚度(1.6-7.0 mm)，EAB 达到 15.36 GHz，覆盖了96%的GHz频带。此外，通过调节Fe2O3的添加量，可实现在中频区域(7.6 GHz) -61.53 dB的强吸收，为吸波材料微观结构调控以及构效关系分析提供了参考。
(3) 为解决过渡金属硫化物在复合磁损耗材料以调节介电常数过程中所导致的填充率高、吸收带宽窄的问题，通过简单的碳化法结合原位溶剂热法，成功制备了生物质衍生无序多孔碳复合CuS的双介电复合材料(PC/CuS)。生物质材料煅烧后形成的无序多孔导电网络结构一方面提供更连续的电流通路增强导电损耗能力，另一方面使CuS均匀分散，材料密度大大减低，促使复合材料拥有良好的阻抗匹配和更强的衰减能力。通过生物质材料碳化温度及组分比例的调节，800 ℃下煅烧得到的样品在20 wt%的填充率下表现出了优异的吸波性能，在厚度仅为1.9 mm的条件下，RLmin为-50 dB，EAB可达6.08 GHz，实现了厚度薄、吸收强且频带宽的目标。而PC添加量更多的样品在填充率调整为15 wt%后依旧能达到在9.2 GHz处的-50 dB的性能，实现中频范围的有效吸收，通过调节样品的厚度(1.6-7.0 mm)，GHz波段覆盖率高达97%，为轻量化、环保、性能优异的可持续电磁波吸收材料提供了候选者。

With the advent of the intelligent era, electromagnetic wave (EMW)technology is widely used in the field of livelihood and defense, which greatly promotes social development and defends national security. But excessive electromagnetic radiation has also caused the fourth major environmental pollution - electromagnetic pollution. In order to effectively solve the problem of electromagnetic pollution, a large number of researchers develop high-performance EMW absorbing materials with strong absorption, wide bandwidth, light weight and thin thickness. On the one hand, they can improve the stability of electronic equipment and security of information, while protecting the human body from electromagnetic radiation. On the other hand, as the surface coating layer of stealth aircraft, military ships and other military equipment, they can effectively absorb the enemy's radar signals, reduce the probability of being detected to realize EMW stealth, and enhance the ability of surprise defense and survival. In the past few decades, materials for EMW absorption, mainly metal sulfides, carbon materials, magnetic materials, etc., have been widely studied. Copper sulfide (CuS) has shown great potential in the field of EMW absorption due to its excellent physicochemical properties, simple synthesis method, and tunable microstructure. The excellent electrical conductivity of CuS serves as a double-edged sword, which not only enables it to exhibit excellent dielectric loss capability in alternating electromagnetic field, but also brings about the problem of impedance mismatch leading to poor performance that needs to be solved. In addition, the tunable morphology of CuS contributes to the enhancement of polarization relaxation and EMW attenuation. Therefore, in this thesis, CuS is used as a substrate to enhance the EMW reflection loss (RL) by optimizing the impedance matching and taking advantage of the structure from the perspectives of dielectric property tuning and microstructure optimization. The main research contents and results are as follows: 
(1) With the starting point of optimizing the synergistic interaction between CuS multicomponents and enriching the loss mechanism, a concave cubic polyhedral-like CuS/γ-Fe2O3 composite structure was synthesized by solvent-thermal method. The concave polyhedral CuS surface provides a large number of anchor localization points for γ-Fe2O3 nanoparticles to better regulate the dielectric constant, and effectively avoids the agglomeration of γ-Fe2O3 nanoparticles, which enhances the interfacial polarization of the material while improving the complex permeability of the composite material and optimizing the impedance matching. The above improvements have led to a significant enhancement of the EMW absorption performance of the CuS/γ-Fe2O3 composite structure compared to that of the single component, with a minimum reflection loss (RLmin) of -48 dB at 10.48 GHz for 2.6 mm, where the effective absorption bandwidth (EAB) is 3.2 GHz (8.56-11.76 GHz), and an EAB of 4 GHz (11.76-15.76 GHz) for 2 mm. By adjusting the thickness of the samples (2-7 mm), effective absorption from 2.64 GHz to 15.76 GHz can be realized, and the GHz band coverage can be up to 82%, which provides ideas for the rational design of dielectric-magnetic composite EMW absorbing materials.
(2) To more precisely explore the relationship between structural modulation and EMW absorption performance, flower-like CuS/γ-Fe2O3 heterostructures with different ratios were controllably synthesized by a simple solvothermal method. Based on the fine tuning of electromagnetic parameters and optimization of impedance matching, the three-dimensional (3D) flower-like structures bring multiple polarization relaxation and rich loss mechanisms. More notably, the more abundant heterojunction structure between the flower-like CuS and γ-Fe2O3 further enhances the interfacial polarization. The multiple structural advantages synergize to enhance the EMW absorption performance of the CuS/γ- Fe2O3 heterostructure. With a thickness of only 1.6 mm, the RLmin at 15.6 GHz is -49.36 dB and the EAB reaches 4.64 GHz, while by adjusting the thickness of the absorber (1.6-7.0 mm), the EAB reaches 15.36 GHz, which covers 96% of the GHz band. In addition, a strong absorption of -61.53 dB in the mid-frequency region (7.6 GHz) can be achieved by adjusting the addition amount of Fe2O3, which provides a reference for the microstructure tuning as well as the conformational relationship analysis of EMW absorbing materials.
(3) In order to solve the problems of high doping and narrow absorption bandwidth caused by transition metal sulfides in the process of composite magnetic loss materials to regulate the dielectric constant, dual dielectric composites of biomass-derived disordered porous carbon composite with CuS (PC/CuS) were successfully prepared by a simple carbonization method combined with an in-situ solvent-thermal method. The disordered porous conductive network structure formed after calcination of the biomass material provides a more continuous current pathway to enhance the conductive loss capability on the one hand, and on the other hand, the CuS is uniformly dispersed, which greatly reduces the density of the material, and contributes to the composites with good impedance matching and stronger attenuation capability. By adjusting the carbonization temperature of biomass materials and the proportion of components, the sample obtained by calcination at 800 ℃ shows excellent EMW absorption performance at 20 wt% filling rate, with RLmin of -50 dB and EAB of up to 6.08 GHz under the condition of thickness of only 1.9 mm, realizing the goals of thin thickness, strong absorption and wide bandwidth. The sample with more PC additions still achieve -50 dB at 9.2 GHz after the filling rate is adjusted to 15 wt%, realizing effective absorption in the mid-frequency range, and by adjusting the thickness of the sample (1.6-7.0 mm), the GHz band coverage is as high as 97%, which is a candidate for lightweight, environmentally friendly, and high-performance sustainable EMW absorbing materials.