碳纳米复合材料在电磁屏蔽中的应用

发布时间：2018-04-10 06:28

本文选题：电磁屏蔽　切入点：石墨烯　出处：《山东大学》2017年硕士论文

【摘要】：电磁屏蔽材料对电磁波的屏蔽作用机理分为吸收和反射。本文所研究的材料为碳纳米材料及其与铁氧体材料的复合材料,碳材料属于良好的电阻型吸收剂,铁氧体属于磁介质型吸收剂,两者复合能更大的符合现代新型吸波剂向着频带宽,密度低,吸收高的性能发展要求。碳纳米材料包括碳纳米管和石墨烯表现出的巨大优异性质,能够结合传统碳材料频带宽,质量轻的特点,又能将纳米材料比表面积大,导电率好等优势发挥出来,但吸波能力较弱,限制了其应用。而相比较CNT和石墨烯材料,Fe_3O_4的吸波能力更强,但吸波频带较窄,将其与碳材料复合,发挥两类材料的特点,具有重要的意义。本文中主要讨论了 CNT,石墨烯,Fe_3O_4及其复合材料的制备,优化制备参数,并利用TEM、SEM、XRD、Raman、TGA等对材料的形貌,结构,成分进行分析。利用VSM、VAN测试材料的磁学性能及吸波性能。主要内容如下:1)利用Hummers法制备高比表面积的氧化石墨烯(GO),改进洗涤工艺,缩短了实验过程,利用冷冻干燥法制得GO粉末。采用浮动催化法制备了 CNT,探究不同碳源、催化剂、气体流量、进液速度对CNT质量的影响,确定了批量制备CNT的优化参数。利用二甲苯为碳源,可以得到较高质量的CNT,但二甲苯有一定的毒性,且制备的CNT容易粘在石英管壁上不利于成膜;利用酒精为碳源,可制得高质量CNT,克服了二甲苯粘度大的缺点,成膜性能较好。确定了催化剂中二茂铁和噻吩的比例范围3.5/1～2.5/1,确定气流量比例Ar气流量为5L/min,H2为2L/min,进液速度为0.08ml/min。此法制得单壁CNT,管径为20nm。2)以聚乙二醇(PEG)为分散剂,以乙二醇为还原剂,在醋酸钠提供的碱性环境下,采用水热法将氯化铁还原制备Fe_3O_4纳米球,得到均匀实心球体。在反应溶液中添加GO的方式,制得了 Fe_3O_4纳米球/GO复合物,Fe_3O_4纳米球均匀的负载在GO片的表面,GO对Fe_3O_4纳米球的生长大小没有影响,只是提供形核场所。磁性能测试发现Fe_3O_4纳米球/GO复合物的磁饱和强度为28.7emu/g,磁滞回线较窄,为软磁材料。对Fe_3O_4纳米球/GO复合物的在2～18GHz的吸波特性进行表征,发现复合物在石蜡中含量为20%时在13.5GHz频率下最高反射损耗为-13dB,30%含量的复合物反射损耗在8.5GHz时最高为-19dB。将复合材料分散在环氧树脂中,利用刷涂法制备Fe_3O_4/GO@CNT@碳纤维布的四元材料,测试其在10MHz～2GHz内的吸波特性进行表征,在280MHz频率的电磁损耗达到峰值-45dB。对比不加入Fe_3O_4/GO复合物和单纯的碳纤维布的反射损耗-37dB和-32dB,发现Fe_3O_4/GO复合物能够提高电磁损耗,但相比于纯碳材料,其损耗峰值位置发生变化。3)以硫代硫酸钠为氧化剂,在氢氧化钠提供的碱性环境中,利用PEG400为模板剂,采用水热法制备Fe_3O_4纳米线,得到直径为100nm的均匀线体。不添加PEG400,仅以水溶液作为反应剂,得到的是晶粒尺寸为200nm的八面体结构的Fe_3O_4。在水溶剂中添加一定量的GO代替PEG400,同样得到纳米线结构的Fe_3O_4,证明GO具有类似于PEG400作为模板剂的作用,同时得到了Fe_3O_4纳米线/GO复合材料。GO在合成Fe_3O_4纳米线主要起两个作用,一是GO的片层结构均匀分散在水溶液中,降低了离子的结合速度,第二是GO表面的-OH等官能团对Fe_3O_4纳米线的不同晶面的生长有不同的影响。对Fe_3O_4纳米线/GO复合物的磁性能测试发现其磁饱和强度为37emu/g,磁滞回线较Fe_3O_4纳米球/GO复合物宽,但同为软磁材料。对Fe_3O_4纳米线/GO复合物的在2～18GHz的吸波特性进行表征,发现复合物在石蜡中含量为20%、30%时,他们的最高反射损耗分别为-9dB和-7dB,40%含量的复合物反射损耗在6.8GHz时最高为-17dB。
[Abstract]:The shielding mechanism of electromagnetic shielding material for electromagnetic wave absorption and reflection. This paper is divided into the composite material of carbon nano material and ferrite material, carbon material is a kind of good resistance type absorbent, ferrite magnetic medium absorbent belongs to the type, two more in line with modern composite energy absorbing model agent to frequency bandwidth, low density, high absorption performance requirements. The development of carbon nano materials including large excellent properties of carbon nanotubes and graphene exhibits, can be combined with traditional carbon materials with wide frequency band, light quality characteristics, and the nano material is bigger than the surface area, good conductivity and other advantages to play out, but the absorption wave ability is weak, which limits its application. Compared with CNT materials and graphene, absorbing ability of Fe_3O_4, but the absorption band is narrow, and the carbon composite, exert the characteristics of two kinds of materials, has important significance. This paper mainly discusses CNT, graphene, Fe_3O_4 and preparation of composite materials, optimization of preparation parameters, and the use of TEM, SEM, XRD, Raman, TGA and other materials on morphology, structure and composition analysis. Using VSM, magnetic properties and microwave absorption properties of VAN test materials. The main contents are as follows: 1) preparation of graphene oxide with high specific surface area by Hummers method (GO), to improve the washing process, shorten the process, using freeze drying method. Using CNT GO powder prepared by the floating catalyst method, explore the different carbon source, catalyst, gas flow, liquid inlet velocity effect on the quality of CNT, to determine the volume system parameter optimization of preparation of CNT. Using xylene as carbon source, can get higher quality of CNT, but the xylene has a certain toxicity, and the preparation of the CNT easy to stick in the quartz tube wall is not conducive to the film; using alcohol as carbon source, can be made of high quality CNT, overcome the viscosity of xylene The disadvantage of large, good film-forming properties. The two ferrocene and thiophene catalyst ratio in the range of 3.5/1 ~ 2.5/1, determine the gas flow ratio of Ar gas flow rate is 5L/min, H2 is 2L/min, the rate of the liquid is 0.08ml/min. this method of single wall CNT, diameter 20nm.2) with polyethylene glycol (PEG) as dispersant. Ethylene glycol as the reducing agent in alkaline environment of sodium acetate, via hydrothermal method preparation of Fe_3O_4 nanoparticles by homogeneous reduction of ferric chloride, solid sphere. The addition of GO in the reaction solution, prepared Fe_3O_4 nanoparticles /GO complexes, Fe_3O_4 nanoparticles uniformly loaded on the surface of GO film. The size of GO did not affect the growth of the Fe_3O_4 nanospheres, only provide nucleation sites. Magnetic test shows that Fe_3O_4 nanoparticles /GO complex magnetic saturation intensity is 28.7emu/g, the hysteresis loop is narrow, as soft magnetic materials. The Fe_3O_4 nanoparticles of /GO complex in 2~1 The microwave absorbing properties of 8GHz were characterized and found complex content in paraffin at 20% 13.5GHz under the highest frequency reflection loss is -13dB, the complex reflection loss of 30% content in 8.5GHz is the highest of -19dB. composite materials dispersed in epoxy resin, four yuan Fe_3O_4/ GO@CNT@ carbon fiber cloth material prepared by brush coating method. In the test, 10MHz ~ 2GHz wave absorbing properties were studied, and -45dB. reached the peak in contrast to add carbon fiber cloth Fe_3O_4/GO composite and pure reflection loss of -37dB and -32dB in the electromagnetic loss frequency of 280MHz, found that Fe_3O_4/GO complexes can improve the electromagnetic loss, but compared to pure carbon materials, the loss peak position the change of.3) on sodium thiosulfate as oxidant, sodium hydroxide in the alkaline environment in the use of PEG400 as template, Fe_3O_4 nanowires prepared by hydrothermal method, get the uniform diameter of 100nm Line body. Do not add PEG400, only with aqueous solution as reaction agent, the grain size is eight of 200nm structure Fe_3O_4. is added in the water solvent instead of GO PEG400, also obtained nanowires Fe_3O_4, proved that GO has similar to PEG400 as the template, obtained at the same time Fe_3O_4 /GO nanowires composite.GO mainly has two roles in the synthesis of Fe_3O_4 nanowires is a lamellar structure of GO dispersed in aqueous solution, the ion binding rate is second, the surface of GO -OH functional groups on Fe_3O_4 nanowires with different crystal surface growth have different effects on magnetic properties of Fe_3O_4. /GO nanowires composite test shows that the magnetic saturation intensity is 37emu/g, the hysteresis loop of Fe_3O_4 nanospheres /GO complex is wide, but the same as soft magnetic materials. The Fe_3O_4 nanowires of /GO complex in 2 ~ 18GHz absorption into Potter Row characterization showed that the maximum reflection loss of the composite was 20% and 30% in paraffin, respectively. Their highest reflection loss was -9dB and -7dB respectively, and the compound loss reflected by 40% was the highest when 6.8GHz was -17dB..

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TB33

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