摘要
数字设备的普及和雷达探测技术的飞速发展为我们的生活带来了便利，但是也造成了大量的电磁污染问题，并对人类的身体健康产生负面影响。吸波材料可有效抑制电磁波危害，为公共安全提供保障。在高科技领域，电磁防护对精密仪器的发展起着至关重要的作用；在军事领域，吸波材料可以保护军事人员和武器免受电磁干扰，提高作战效能。然而，传统吸波材料存在损耗机制单一、有效吸波频带窄、密度高等缺陷，其综合性能难以满足现代商业化和军事化对吸波材料“薄、轻、强、宽”的要求。本论文设计了多种方案制备还原石墨烯，并以环氧树脂为基体制备了吸波材料，多种测试与表征结果表明高还原程度的石墨烯拥有更好的介电损耗性能。通过纳米表面效应使石墨烯与银纳米线自组装形成三维网络纳米结构，利用石墨烯强介电损耗能力和银纳米线高电导率的特点使二者产生协同作用，改善了石墨烯片层的团聚问题，丰富了银纳米线的介电损耗形式，二者形成的复合材料具有优异的吸波性能，为石墨烯和银单质在电磁波吸收领域提供了新思路。本文主要研究内容如下： （1）分别采用VC和HI为还原剂制备RGO，并通过改变VC用量控制RGO 的还原程度。在VC法中，RGO的还原程度随着还原剂用量增加而提高，而HI 法制备的RGO-HI中碳原子相对含量高达85.7%，具有最高的还原程度。研究结果表明高度还原的石墨烯具有更强的介电损耗能力，在环氧树脂基体中，RGO-HI添加量仅为1 wt%时，2.5 mm厚度的吸波体在16.6 GHz具有最强吸收峰值-10.1 dB，其吸波效果主要来源于高还原程度的RGO引起更多的电子极化弛豫、电阻损耗和界面极化弛豫等介电损耗机制。
（2）通过乙二醇还原法制备了尺寸均一的高纯银纳米线，单组份的AgNWs 在树脂基体中的吸波效果并不明显，当AgNWs添加量达到15 wt%时，其复合材料的最低反射损耗值仅为-4.2 dB，这是因为AgNWs具有较高的导电性但电磁损耗机制单一，使复合材料拥有较高的介电常数实部和较低的虚部而导致材料的阻抗匹配率极低，电磁波难以进入材料内部实现有效的吸波效果。
（3）利用纳米表面效应产生的吸附作用使一维AgNWs与二维RGO自组装，制备了具有优异吸波性能的三维网络纳米结构的RGO-AgNWs复合材料，
材料的吸波性能随着AgNWs含量的增加而逐渐提高。当含量仅为1 wt%的RGO 与15 wt%的AgNWs复合时，在环氧树脂基体中具有优异的吸波性能，厚度为1.8 mm的RGO-AgNWs3吸波体在11.5 GHz具有最强吸收峰值-33.2 dB且有效吸波频宽为3.3 GHz（9.9~13.2 GHz）。这是因为AgNWs和RGO自主装产生协同作用，极大的提高了复合材料的介电虚部，一方面有效的改善了吸波体的阻抗匹配率，另一方面极大地提高了对入射电磁波的衰减能力，弥补了AgNWs和RGO单独作为吸波剂的不足。
无动力排风帽关键词：银纳米线；石墨烯；电磁波吸收；三维网络结构
Abstract
The prevalence of digital devices and the rapid development of radar detecting technology can make
our life more convenient. But these also generate a large amount of electromagnetic pollution and make a remarkable negative effect on physical health. Microwave absorbing materials can effectively eliminate the harm of electromagnetic waves and provide protection for public safety. In the high-tech field, electromagnetic protection plays a vital role in the development of precision instruments; in the military field, absorbing materials can protect military personnel and weapons from electromagnetic interference to enhance combat effectiveness.However, the traditional absorbing materials have the defects of single loss mechanism, narrow bandwidth and high density. The comprehensive performance of these materials is difficult to meet the requirements of modern commercialization and militarization with the performances of thin thickness, light weight, strong absorption capacity and wide absorption bandwidth. In this paper, a variety of schemes were designed to prepare reduced graphene oxide, and dispersed RGO in epoxy resin matrix to obtain the absorbing materials. A variety of tests and characterizations show that graphene with high degree of reduction has better dielectric loss performance. In addition, nano-surface effect is employed to promote the self-assembly of graphene and silver nanowires to form 3D network nanostructures. The RGO with strong dielectric loss capability and AgNWs with high conductivity can create a synergistic effect. It not only improves the impedance matching characteristics but also enhances the attenuation ability of electromagnetic energy, and a composite material with excellent
microwave absorbing properties is obtained. It provides a new idea for the field of electromagnetic wave absorption for graphene and silver.The main contents are as follows:
(1) RGO was prepared with VC method and HI method respectively, and the degree of reduction of RGO was controlled by changing the amount of VC. In the VC method, the reduction degree of RGO increases as the amount of VC increases, while the relative content of carbon atoms in the RGO-HI sample is as high as 85.7% which
胡纯玉
has the highest degree of reduction.The results show that RGO with high degree of reduction has a stronger dielectric loss capability. In the epoxy resin matrix, the RGO-HI composite has the most excellent absorbing performance. When the RGO addition is only 1 wt%, the absorber with 2.5 mm thickness has the reflection loss peak -10.1 dB at 16.6 GHz, and its absorbing effect is mainly due to the high reduction degree of RGO, which cause more dielectric loss mechanisms such as electron polarization delay, resistance loss and interface polarization delay.
(2) High-purity silver nanowires with uniform size were prepared by ethylene glycol reduction method.The microwave absorbing effect of single-component AgNWs in the resin matrix was not obvious. When the amount of AgNWs reached 15 wt%, the minimum reflection loss of the composite
is only -4.2 dB. The silver nanowire has high conductivity but a single electromagnetic loss mechanism, so that the composite material has a high effective permittivity real part and a low imaginary part, resulting in extremely low impedance matching rate of the material, which make it difficult for microwaves to enter the interior of the material.
(3) The 3D network nanostructured RGO-AgNWs composite with excellent absorbing performance was prepared by self-assembly of 1D AgNWs and 2D RGO by the nano-surface effect. The absorption capacity of the material increase as the amount of AgNWs increases. When RGO with a content of only 1 wt% was combined with 15 wt% AgNWs, the composite has excellent absorbing properties, and the RGO-AgNWs3 absorber with a thickness of 1.8 mm has the strongest absorption peak(-33.2 dB) at 11.5 GHz with an effective absorbing bandwidth of 3.3 GHz (9.9 to 13.2 GHz). This remarkable absorbing effect is due to the synergistic effect of AgNWs and RGO, which greatly improves the dielectric imaginary part of the composite. On the one hand, it effectively increases the impedance matching ratio, and on the other hand, the attenuation ability of the incident electromagnetic wave is greatly enhanced. Therefore, the shortage of AgNWs and RGO alone as the absorbing agent is compensated. Keywords: Ag nanowires; graphene; microwave absorption; 3D network structure
目录
摘要........................................................................................................................................ I Abstract ................................................................................................................................... III 第1章绪论 (1)
1.1 引言 (1)
1.2 吸波材料理论研究概述 (1)
1.2.1 吸波材料设计原则 (3)
1.2.2 吸波材料技术要求 (4)
1.2.3 吸波材料的分类 (6)
1.2.4 吸波材料的测试方法 (8)
1.3 吸波材料国内外研究进展 (9)
1.3.1 磁性吸波材料 (9)
whca1.3.2 导电聚合物吸波材料 (11)
1.3.3 石墨烯吸波材料 (13)
1.3.3 银纳米吸波材料 (14)
彩铅芯
1.4 本文的选题及研究内容 (16)
1.4.1 本文研究目的及意义 (16)
沉砂池1.4.2 本文主要研究内容 (16)
第2章吸波剂的制备与表征方法 (18)
2.1 引言 (18)
2.2 实验方案设计 (18)水溶液锂电池
2.3 实验原料及设备 (19)
2.3.1 实验原料 (19)
2.3.2 实验设备 (21)
2.4 石墨烯的制备 (21)
2.4.1 氧化石墨烯GO的制备 (21)
2.4.2 还原石墨烯RGO的制备 (22)
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