碳纳米管吸波材料研究进展

介绍了碳纳米管的结构和性能特点,归纳和分析了碳纳米管吸波材料的最新进展,并提出了现有研究中存在的不足及进一步研究的方向。目前碳纳米管吸波材料的研究主要集中在不同结构碳纳米管吸波材料、磁性金属/碳纳米管复合吸波材料、稀土/碳纳米管复合吸波材料、铁氧体/碳纳米管复合吸波材料、聚合物/碳纳米管复合吸波材料以及陶瓷/碳纳米管复合吸波材料。对碳纳米管进行形貌控制、结构优化、表面修饰、复合掺杂改性以及界面结合和耐温性能的强化,是碳纳米管吸波材料今后的发展方向。     

多壁碳纳米管/环氧树脂复合材料的吸波性能

本文将高温碱处理多壁碳纳米管分散到环氧树脂中制成多壁碳纳米管/环氧树脂吸波复合材料,并研究了该复合材料的微波吸收性能。改变碳纳米管高温碱处理的浓度可以使复合材料的最大吸收峰向高频方向移动,与此同时,吸收峰强度和吸波频宽也有所提高,这对于调整雷达吸波材料的吸波频段、吸波强度和吸波频宽有着十分重要的意义。测试结果还表明,这种新型吸波复合材料的体积电阻率在106~107Ω.cm数量级,具有良好的抗静电的能力。     

碳化硅颗粒填充的碳纳米管/环氧树脂复合材料的吸波性能

以碳纳米管、碳化硅颗粒为原料制备环氧树脂复合吸波材料,并对其吸波性能进行测试,研究了碳纳米管、碳化硅颗粒含量与复合材料吸波性能的关系.结果表明碳纳米管、碳化硅颗粒的含量对复合材料的吸波性能有较大影响.随碳纳米管含量的增加,碳纳米管/环氧树脂复合材料的吸波性能先提高后降低,碳纳米管含量存在最佳值(12%,质量分数).将碳...     

多壁碳纳米管复合材料在8 mm波段的吸波性能

将相同厚度不同碳纳米管含量, 以及不同厚度相同碳纳米管含量的多壁碳纳米管加入玻璃纤维增强复合材料中, 并研究了其在26. 5～40. 0 GHz 频段的吸波性能。结果发现, 多壁碳纳米管具有吸波性能, 而且吸波性能随着多壁碳纳米管含量的增加而提高。多壁碳纳米管/ 玻璃纤维/ 环氧树脂复合材料层板在26. 5～40. 0 GHz频段表现出较好的吸收效果, 其吸波性在于碳纳米管本身具有吸波性能, 此外还与吸波材料的谐振吸波原理有关。通过对该复合材料的电磁参数的测定并计算, 证明实验结果与吸波原理相符合。      

炭纤维及其复合材料的吸波性能和吸波机理

炭纤维和炭纤维复合材料在隐身技术中已经得到了广泛应用。通过分析连续炭纤维、短切炭纤维、螺旋形炭纤维、异形截面炭纤维、掺杂改性炭纤维及其复合材料的微波电磁特性和吸波性能,探讨了以上几种炭纤维的吸波机理,其中螺旋形炭纤维和异形截面炭纤维是最有发展前景的两种吸波炭纤维。     

稀土掺杂碳纳米管/聚氯乙烯复合材料的吸波性能研究

利用La(NO3)3和Ce(NO3)3掺杂的碳纳米管(MWCNTs-La(NO3)3和MWCNTs-Ce(NO3)3)作为吸收剂、聚氯乙烯(PVC)作为基体,制备出MWCNT-La(NO3)3(或Ce(NO3)3)/PVC复合材料。运用透射电子显微镜和X射线衍射仪对MWCNTs、MWCNTs-La(NO3)3、MWCNTs-Ce(NO3)3的微观结构进行表征分析,使用同步热分析仪和矢量网络分析仪对MWCNT/PVC、MWCNT-La(NO3)3/PVC、MWCNT-Ce(NO3)3/PVC复合材料的热解行为和吸波性能进行测试分析。结果表明,在2～18GHz频率范围内,适量掺杂La(NO3)3或Ce(NO3)3可以使MWCNT/PVC复合材料的吸波性能大幅度提高,而热解行为变化不明显。在反射率R<-10dB的范围内,MWCNT-Ce(NO3)3/PVC复合材料的吸收频宽(约为5.4GHz)虽然不及MWCNT-La(NO3)3/PVC的吸收频宽(约为5.6GHz)宽,但是吸收频段和吸收峰峰值均向高频区域移动,有利于提高复合材料的高频吸波性能。     

碳纳米管吸波材料的研究现状与展望

碳纳米管因其独特的物理和化学性能10多年来一直备受关注,已有研究将其运用于军事科技领域,如吸波材料,但目前国内关于此类研究的报道还不多.较为全面地总结了近年来国内外对碳纳米管作为吸波材料的研究成果及其目前的研究现状,即简述碳纳米管的吸波机理;详细介绍碳纳米管薄膜、活性碳纳米管、磁性金属(合金)/碳纳米管、碳纳米管/聚合物基复合吸波材料的研究现状;展望未来吸波材料的发展方向.     

含结晶水无机盐对复合材料吸波性能的影响——材料研究新思路探索

通过在毕业论文研究中对乙炔炭黑(CB)和含结晶水无机盐吸波剂填充丁腈橡胶(NBR)吸波性能的探索，不但对得到了具有良好吸波性能的材料，而且还得到了良好的科学研究思想方法的训练，提高了动手能力。     

双层结构型吸波复合材料的制备与吸波性能研究

依据传输线理论和阻抗匹配原则,设计并制备了一种以磁性金属微粉为面层、多壁碳纳米管为底层、玻璃纤维布为环氧树脂基体增强体的低频段双层结构型吸波复合材料。采用透射电镜和扫描电镜对多壁碳纳米管和磁性金属微粉的微观形貌进行了表征,采用HP8722ES矢量网络分析仪测量了材料在2～18GHz频率范围内的复介电常数和复磁导率,采用弓形法测试了复合材料在2～8GHz扫频范围内的反射率特性。研究表明,该双层结构型吸波复合材料在低频S波段具有良好的吸波效果,当其匹配厚度为dm=4.0mm时,最大吸收峰在3.08GHz时达到-17dB,反射率小于-10dB的频宽为1.82GHz。     

Mechanical properties of multi-walled carbon nanotube/epoxy composites

Untreated and acid-treated multi-walled carbon nanotubes (MWNT) were used to fabricate MWNT/epoxy composite samples by sonication technique. The effect of MWNT addition and their surface modification on the mechanical properties were investigated. Modified Halpin–Tasi equation was used to evaluate the Young’s modulus and tensile strength of the MWNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. There was a good correlation between the experimentally obtained Young’s modulus and tensile strength values and the modified Halpin–Tsai theory. The fracture surfaces of MWNT/epoxy composite samples were analyzed by scanning electron microscope.     

Polydiphenylamine/carbon nanotube composites for applications in rechargeable lithium batteries

Polydiphenylamine/single walled carbon nanotube (PDPA/SWNT) composites were synthesized electrochemically aiming at their application as active electrode materials for rechargeable lithium batteries. The electrochemical polymerization of diphenylamine (DPA) on a SWNT film immersed in a 1 M HCl solution was studied by cyclic voltammetry. Comparing cyclic voltammograms recorded on a blank Pt electrode with those obtained for a SWNT film deposited on Pt electrode one observes in the latter case a decrease of the DPA reduction potential. To elucidate electrochemical polymerization mechanism, photoluminescence studies on DPA/SWNT and PDPA/SWNT systems were carried out. Additional information concerning the functionalization process of SWNT with PDPA was obtained by Raman and IR spectroscopy. Using the PDPA/SWNT composite as active material for the positive electrode of a rechargeable lithium cell (LiPF₆ electrolyte), the charge-discharge tests show a specific discharge capacity of ca. 245 mA h g⁻¹, much higher than the 35 mA h g⁻¹ for pure PDPA.     

纳米碳管结构差异对树脂炭包覆硅/纳米碳管复合材料电化学性能的影响

采用聚乙烯醇（PVA）树脂炭化的方法，制备了PVA树脂炭包覆硅／不同纳米碳管复合材料，通过X-射线、高分辩电镜观察和电化学性能测试等手段比较研究了单壁、双壁和多壁纳米碳管作为弹性导电网络缓解硅在充放电过程中体积变化方面的效果。结果表明，单壁纳米碳管和双壁纳米碳管比多壁纳米碳管能够更好地缓解硅在循环过程中产生的结构和体积变化，这主要是因为其长径比大，缠裹效果更好。单壁纳米碳管和双壁纳米碳管具有相近的直径、长径比及宏观分布形式，但在循环过程中，双壁纳米碳管的结构稳定性好于单壁纳米碳管，进而其缓解硅结构变化的效果更好。     

Properties of composites of carbon nanotube fibres

Composites have set the standard for high strength materials for several decades. With the discovery of nanotubes, new possibilities for reinforced composites have arisen, with potential mechanical properties superior to those of currently available materials. This paper reports the properties of epoxy matrix reinforced with fibres of carbon nanotubes (CNTs) which, in many ways, are similar to standard composites reinforced with commercial fibres. The composites were formed by the back diffusion of the uncured epoxy into an array of aligned fibres of CNTs. The fibre density and volume fraction were measured from thermogravimetric analysis (TGA). Properties in tension and compression were measured, and the level of fibre–matrix interaction analysed fractographically. The results show the significant potential for this route to CNT reinforcement.     

Effect of carbon nanotube (CNT) content on the mechanical properties of CNT-reinforced aluminium composites

The interest in carbon nanotubes (CNTs) as reinforcements for aluminium (Al) has been growing considerably. Efforts have been largely focused on investigating their contribution to the enhancement of the mechanical performance of the composites. The uniform dispersion of CNTs in the Al matrix has been identified as being critical to the pursuit of enhanced properties. Ball milling as a mechanical dispersion technique has proved its potential. In this work, we use ball milling to disperse up to 5 wt.% CNT in an Al matrix. The effect of CNT content on the mechanical properties of the composites was investigated. Cold compaction and hot extrusion were used to consolidate the ball-milled Al–CNT mixtures. Enhancements of up to 50% in tensile strength and 23% in stiffness compared to pure aluminium were observed. Some carbide formation was observed in the composite containing 5 wt.% CNT. In spite of the observed overall reinforcing effect, the large aspect ratio CNTs used in the present study were difficult to disperse at CNT wt.% greater than 2, and thus the expected improvements in mechanical properties with increase in CNT weight content were not fully realized.     

Dielectric, magnetic, and microwave absorbing properties of multi-walled carbon nanotubes filled with Sm2O3 nanoparticles

This study investigates the dielectric, magnetic, and microwave absorbing properties of Sm₂O₃-filled multi-walled carbon nanotubes (MWCNTs) synthesized by wet chemical method. The complex permittivity and permeability were measured at a microwave frequency range of 2-18 GHz. Sm₂O₃ nanoparticles encapsulated in the cavities enhance the magnetic loss of MWCNTs. The calculated results indicate that the bandwith of absorbing peak of the modified MWCNTs is much broader than that of unfilled MWCNTs. The maximum reflectivity (R) is about − 12.22 dB at 13.40 GHz and corresponding bandwidth below − 5 dB is more than 5.11 GHz. With the increase of thickness, the peak of R shifts to lower frequency, and multiple absorbing peaks appear, which helps to broaden microwave absorbing bandwidth.     

Viscoelastic and mechanical properties of multi walled carbon nanotube/epoxy composites with different nanotube content

The viscoelastic and mechanical properties of composites multi walled carbon nanotube (MWNT)/epoxy at different weight fractions (0.1, 0.5, 1 and 2 wt.%) were evaluated by performing tensile and dynamic-mechanical thermal analysis (DMTA) tests. The MWNT/epoxy composite were fabricated by sonication and a cast molding process. The results showed that addition of nanotubes to epoxy had significant effect on the viscoelastic and mechanical properties. However, the use of 0.5 wt.% increased the viscoelastic properties more significantly. Concerning viscoelastic modeling, the COLE–COLE diagram has been plotted by the results of DMTA test. These results show a good agreement between the Perez model and the viscoelastic behavior of the composite.     

添加纳米碳管对高密度聚乙烯力学行为和结晶过程的影响

利用熔融法制备了一系列具有不同纳米碳管含量的纳米碳管(Q盯)／高密度聚乙烯(HDPE)复合材料。对其拉伸性能的研究结果表明，添加质量分数分别为2％，5％和10％的纳米碳管使HDPE的拉伸模量分别提高了7．4％，27．0％和28．6％，屈服强度分别提高了3．3％，14．4％和18．5％，但是会降低HDPE的断裂强度和断裂伸长率。同时，对复合材料中HDPE结晶过程的研究表明，纳米碳管可以提高HDPE的开始结晶温度，降低结晶活化能，但是会使HDPE的结晶速率下降，结晶度降低。     

Effect of short carbon fibers and MWCNTs on microwave absorbing properties of polyester composites containing nickel-coated carbon fibers

Multiphase composite materials filled with multiwall carbon nanotubes (MWCNTs), short nickel-coated carbon fibers and millimeter-long carbon fibers with various weight fractions and compositions are developed and used for the design of wide-band thin radar-absorbing screens. The effective complex permittivity of several composite samples is measured in the frequency range from 8 GHz to 18 GHz. The obtained results show that the addition of the MWCNTs into the mixture allows tuning the EM properties of the composite filled with the short nickel-coated fibers. Numerical simulations are also performed in order to design new radar-absorbing shields. Single-layer and bi-layer thin dielectric Salisbury screens are designed to exhibit minimum reflection coefficient at 10 GHz and at 15 GHz, and maximum bandwidth at −10 dB. It results that the total thickness of the screen can be reduced below 2 mm by using a lossy sheet made with the composite filled with MWCNTs and nickel-coated carbon fibers, whereas the bandwidth at −10 dB can exceed 6 GHz in a bi-layer structure.     

空气氧化处理对三维编织炭复合材料性能的影响

利用真空浸渍法制得三维编织炭纤维增强环氧复合材料,研究了空气氧化处理前后炭纤维表面状态的变化以及表面处理对三维编织复合材料力学性能的影响。结果表明:空气氧化处理使炭纤维的比表面积和表面粗糙度发生了变化,随着氧化温度和氧化时间的增加,炭纤维的比表面积有不同程度的增加;但同时伴随着炭纤维强度的下降。经450℃-1h空气氧化处理后,复合材料的弯曲强度、弯曲模量和剪切强度分别提高了149%,91%和29%,但冲击强度下降了23%。