碳基纳米吸波材料制备的研究进展

为探索民用电磁屏蔽和军用隐形碳基高性能吸波材料的制备,研究了碳纳米管和磁性金属复合,碳纳〖JP2〗米管和铁氧体复合,碳纳米管/聚合物复合,碳、石墨基复合等碳基吸波材料的不同复合和制备方法,比较了其反射损耗等不同的特点、影响因素和性能特点及其相关应用。结果表明,多元复合、低维化、工艺优化是其制备的有效途径。     

Fe-MOFs衍生碳基吸波材料研究进展

随着社会的快速发展和电子设备的普及,电磁辐射污染问题变得尤为突出,也带来了潜在的危害。因此,开发高效的电磁波吸收材料以解决电磁辐射污染问题迫在眉睫。铁基金属有机框架(Fe-MOFs)具有高度不饱和的铁金属中心离子和多样的结构类型。通过将Fe-MOFs作为前驱体进行碳化,可以制备出铁/铁氧化物/铁碳化物均匀分布的衍生碳基化合物。这些Fe-MOFs衍生碳基化合物表现出较高的介电损耗和磁损耗能力,可有效克服当前吸波材料存在的吸收频带窄、阻抗匹配性差等问题,成为近年来备受关注的一种新型吸波材料。首先简要介绍了电磁波吸收机制,然后综述了近年来关于单金属、双金属、三金属Fe-MOFs以及由Fe-MOFs与其他材料(包括碳材料、导电聚合物、MXene和生物质)复合制备的衍生碳基吸波材料的研究进展,最后对MOFs衍生碳基吸波材料的未来发展方向进行了展望。     

磁性碳纳米复合吸波材料的研究进展

碳纳米材料具有独特的微观结构和介电性能,将这类材料与磁损耗材料复合可以有效提高吸波性能。从制备方法、吸波性能和吸波机理等方面,综述了石墨烯、碳纳米管、碳纳米纤维等碳纳米材料与磁性材料复合的吸波特性的最新研究成果,并对其发展前景进行了展望。     

石墨烯基吸波材料研究新进展

石墨烯以其独特的二维结构和极佳的电性能被用作介电损耗基材,将石墨烯与磁损耗基材复合,可达到优异的吸波性能。介绍了石墨烯基复合吸波材料的制备方法、吸波机理和吸波特性等,并对其发展趋势进行了展望。     

不同形状特征的碳基复合材料吸波性能分析

基于短切碳纤维、碳纳米纤维、石墨烯及炭黑,分析研究碳基复合材料中吸收剂形状比对电磁特性,尤其是吸波性能的影响。采用矢量网络分析仪测试基于不同形状比吸收剂形成碳基复合材料的电磁参数,并且计算出样品理论反射损耗。结果发现,随着频率的增加,碳基复合材料的介电常数逐渐减小;碳纳米纤维样品厚度为2 mm,在8 GHz时反射损耗达到-8 d B;炭黑与石墨烯质量比为1∶1时,在0. 5~12. 8 GHz频段内损耗角正切tanδ随频率的增大而增大且样品厚度为2mm时,其在12~16. 2 GHz反射损耗小于-10 d B,且在12. 8 GHz时反射损耗达到-22. 5 d B。通过对不同形状比吸收剂形成碳基复合材料的电磁参数分析,发现具有一定长径比或较大比表面积的吸收剂复合有利于提升碳基复合材料的吸波性能。     

电磁吸波材料研究进展

阐述了常见的吸波材料种类及其特点,吸波材料的研究现状,重点介绍了纳米铁氧体吸波材料及其制备方法。笔者采用柠檬酸盐sol-gel法制得了均匀包覆铁氧体的空心微珠为基的复合材料,其吸波性能良好。最后指出吸波材料的发展趋势为纳米化、多元化和多介质化。     

水泥基复合吸波材料的性能研究

对吸波剂和添加剂改性水泥基复合材料的吸波性能和力学性能进行了研究。结果表明：炭粉、MnO_2和SiC三种电损耗型吸波剂对水泥的吸波性能有较大改善,其中炭粉的改性效果最明显;EPS、炭包EPS、珍珠岩和页岩四种添加剂对水泥基体的波阻抗有较好的改善作用,可以提高水泥的吸波能力,其中EPS的效果最明显。以水泥为基体,EPS为添加剂的复合吸波材料,在8~18 GHz范围内,最高反射率可达到-20 d B,低于-10 d B的带宽为6.6 GHz。     

石墨烯基纳米红外吸波材料的制备及消光性能研究

作为单原子厚度的碳材料,石墨烯因具有低密度、高比表面积和电子迁移率的特性,易于满足吸波材料所需的要求。目前,单一的吸波材料难以达到多波段、宽频带的吸收效果,为了拓宽其红外吸收频带,通过将氧化石墨烯与纳米γ-Al2O3复合,并采用水合肼原位还原制备石墨烯基吸波材料。利用Raman、XRD、FT-IR、EDX和SEM对复合材料的结构与形貌进行了分析,同时测试了烟幕对1.06 m激光和8～12 m波段的红外消光特性,结果表明,石墨烯基吸波材料对红外激光系统以及红外热像仪均具有一定的干扰作用。     

阵列式碳纤维复合材料的制备与微波吸收机理研究

以碳纤维为代表的碳材料具有质轻、导电性好、化学稳定性强等突出的物理化学性质,将其作为吸波剂使用可以提升材料的吸波性能、使用寿命并有效降低重量。通过“电场取向优化+基体灌封固化”的工艺完成了不同组分阵列式碳纤维复合材料的制备,采用SEM、FT-IR等手段对材料的形貌和化学成分进行表征,利用矢量网络分析仪对材料在2～18 GHz频段内的复介电常数和复磁导率进行表征,分析了微观结构对材料电磁参数、界面阻抗匹配及电磁波吸收性能的影响规律,最后研究碳纤维空间排布形式、复配粉体成分对其吸波性能的影响机制。结果表明,材料的电磁损耗机制由电介质损耗、干涉相消、界面极化弛豫、磁损耗共同构成;当复合材料厚度为2.0 mm时,反射率<-10 dB(6.1～7.6 GHz),在6.5 GHz处最大衰减值为-15.2 dB,热导率达到3.2 W/(m·K);验证所制备的材料在满足电磁波吸收功能的同时还具有一定的导热性。     

偶联剂处理对吸波材料电磁特性影响的研究进展

偶联剂是常见的表面改性剂,广泛应用在复合材料表面改性处理领域,其应用于吸波材料表面改性的技术也是吸波材料的研究热点之一。首先总结了制备方法、偶联剂的种类和添加量这些因素对偶联剂改性吸波材料电磁特性影响的研究现状,然后分析了这些因素对吸波材料的电磁参量调控的重要作用,最后展望了偶联剂处理技术改善吸波材料吸波性能的未来前景。     

Ordered Mesoporous Carbon/Fused Silica Composites

A series of novel, dense, and interesting ordered mesoporous carbon (OMC)/fused silica composites with different carbon contents has been prepared by a controllable but simple sol‐gel method followed by hot‐pressing. In the as‐sintered OMC/fused silica composites the carbon particles still exist in the form of perfectly ordered carbon nanowires. Conductivity measurements on the composites indicate that these novel composites are electrically conductive and have a typical percolation threshold of 3.5–5 vol% OMC. The electromagnetic interference (EMI) shielding efficiency (SE) of an OMC/fused silica composite containing 10 vol% OMC is as high as 40 dB in the X band which is higher than that of a carbon nanotube (CNT)/ fused silica composite with the same carbon content (～30 dB). This indicates that these conductive OMC/fused silica composites are very suitable for an application as EMI shielding materials. Upon increasing the volume content of OMC in the composite the overall contribution as well as the increase rate of the microwave absorption are larger than those of the microwave reflection, which suggest that OMC/fused silica composites may also be promising electromagnetic (EM) wave absorbing materials. Based on the promising properties of these composites this work will hopefully lead to the development of new low‐cost and highly efficient EMI shielding or EM wave absorbing materials.     

正交排布碳纤维材料的电磁防护性能研究

分别研究微量改性碳纤维/环氧树脂复合微波电磁防护材料不同排布的电磁防护性能。简要讨论了电磁防护机理以及影响电磁防护效果的因素。实验结果表明:改性碳纤维复合材料电磁防护性能与改性碳纤维的排布方式以及纤维含量密切相关;正交排布试样的电磁防护效果总体上优于原纤维布排布试样;原纤维含量为3000根/束,间距1cm时的正交排布方式获得-30dB以下的反射衰减。     

Advance in Using Plasma Technology for Modification or Fabrication of Carbon-Based Materials and Their Applications in Environmental,Material, and Energy Fields

Plasma technology is an eco-friendly way to modify or fabricate carbon-based materials (CBMs) due to plasmas’ distinctive abilities in tuning the surface physicochemical properties by implanting functional groups or incorporating heteroatoms into the surface without changing the bulk structure. However, the mechanisms of functional groups formation on the carbon surface are still not clearly explained because of the variety of different discharge conditions and the complexity of plasma chemistry. Consequently, this paper contains a comprehensive review of plasma-treated carbon-based materials and their applications in environmental, materials, and energy fields. Plasma-treated CBMs used in these fields have been significantly enhanced in recent years because these related materials possess unique features after plasma treatment, such as higher adsorption capacity, enhanced wettability, improved electrocatalytic activity, etc. Meanwhile, this paper also summarizes possible reaction routes for the generation of functional groups on CBMs. The outlook for future research is summarized, with suggestions that plasma technology research and development shall attempt to achieve precise control of plasmas to synthesize or to modify CBMs at the atomic level.     

An Interface‐Induced Co‐Assembly Approach Towards Ordered Mesoporous Carbon/Graphene Aerogel for High‐Performance Supercapacitors

Hierarchically porous composites with mesoporous carbon wrapping around the macroporous graphene aerogel can combine the advantages of both components and are expected to show excellent performance in electrochemical energy devices. However, the fabrication of such composites is challenging due to the lack of an effective strategy to control the porosity of the mesostructured carbon layers. Here an interface‐induced co‐assembly approach towards hierarchically mesoporous carbon/graphene aerogel composites, possessing interconnected macroporous graphene networks covered by highly ordered mesoporous carbon with a diameter of ≈9.6 nm, is reported. And the orientation of the mesopores (vertical or horizontal to the surface of the composites) can be tuned by the ratio of the components. As the electrodes in supercapacitors, the resulting composites demonstrate outstanding electrochemical performances. More importantly, the synthesis strategy provides an ideal platform for hierarchically porous graphene composites with potential for energy storage and conversion applications.     

炭基/锌掺杂铁磁体复合材料制备及其消光性能研究

为了实现抗红外烟幕高效环保的要求,同时实现质轻、宽波段吸波性能,采用一步水热法制备了炭基-锰锌铁氧体/镍锌铁氧体/钴锌铁氧体复合材料的前驱体,并在500~900 ℃的温度区间进行焙烧得到了炭基/锌掺杂铁磁体复合材料。通过X射线粉末衍射仪（XRD）、傅里叶红外光谱仪（FT-IR）、扫描电子显微镜（SEM）等表征方法,分析了复合材料的物相和形貌。根据朗伯比尔定律,采用傅里叶红外光谱仪的KBr压片法测试并计算了各材料在2.5~25 μm区间的红外消光系数,并且研究了焙烧温度对材料消光性能的影响。研究结果表明:炭基/锌掺杂铁氧体前驱体焙烧后生成的炭基/锌掺杂铁磁体复合材料的红外消光性能均有所增强,经过700 ℃焙烧后的炭/钴锌铁磁体红外消光系数最大,为0.25 m2/g,具有较好的红外消光性能。     

镀镍中间相沥青基碳纤维的吸波性能

为了改善中间相沥青基碳纤维的磁性能和吸波性能,通过化学镀工艺在中间相沥青基碳纤维表面均匀包覆了金属镍,研究了镀镍中间相沥青基碳纤维的磁性能和微波吸收性能。以镀镍中间相沥青基碳纤维作为吸收剂,环氧树脂为基体制备了单层吸波涂层,涂层的厚度为1.02 mm时,吸波涂层在15.4~18 GHz反射率R小于-10 dB,最大吸收峰在18 GHz,反射率R为-20.74 dB。探讨了镀镍中间相沥青基碳纤维的吸收机理,在含镀镍中间相沥青基碳纤维的吸波涂层中,镀镍中间相沥青基碳纤维作为偶极子在电磁场的作用下,会产生耗散电流,在周围基体作用下,耗散电流被衰减,从而电磁波能量转换为其它形式的能量,主要为热能,这是镀镍中间相沥青基碳纤维偶极子吸波涂层的主要吸波机理。     

尖晶石型铁氧体/TiO2复合材料的水热法制备及性能研究进展

综述了尖晶石型铁氧体/TiO₂复合材料的水热法制备与性能研究进展,包括零维、一维结构的尖晶石型铁氧体/TiO₂复合材料和特殊形貌的尖晶石型铁氧体/TiO₂/石墨烯复合材料的水热法制备研究现状,以及复合材料电化学性能、光催化性能、吸波性能的研究进展。总结了二元或三元复合材料由于充分发挥了各组分材料间的协同作用以及复合材料具有的独特结构,使复合材料具有优异的电化学性能、光催化性能和吸波性能。指明未来应以水热法制备尖晶石型铁氧体/TiO₂/石墨烯三元复合材料为目标,向着引入中空过渡层以及制备具有特殊结构的三元复合材料方向发展。     

Low-cost and low-electromagnetic-interference packaging of optical transceiver modules

The low-cost and low-electromagnetic-interference (EMI) packaging of optical transceiver modules employing housings of plastic composites are developed and fabricated. Optical transceiver modules fabricated by the plastic composites with transmission rates of 1.25 and 2.5 Gb/s are tested to evaluate the electromagnetic (EM) shielding against emitted radiation from the plastic packaging. The results show that these packaged optical transceiver modules with their high shielding effectiveness (SE) are suitable for use in low-cost and low-EMI Gigabit Ethernet lightwave transmission systems. By comparison of cost, weight, and shielding performance for optical transceiver modules fabricated by the housings of nylon and liquid-crystal polymer with carbon fiber filler composites, woven continuous carbon fiber (WCCF), and nanoscale hollow carbon nanocapulses (HCNCs) epoxy composites, the WCCF composite shows lower cost, lighter weight, and higher EM shielding than the other types of composites. Future studies may develop the low-cost and low-EMI optical transceiver modules using nanoscale HCNCs that have the combination of excellent physical and mechanical properties, light weight, and thinness compared with the conventional fabrication techniques.