碳纤维表面生长碳纳米管技术研究进展

介绍了碳纤维(CF)表面生长碳纳米管(CNTs)的制备方法研究情况,综述了沉积温度、沉积时间、碳源气体等因素对CNTs形态结构的影响,阐述了以CF为基底CNTs的生长机理及CNTs-CF复合增强材料的增强机制,展望了CNTs-CF复合增强材料的应用前景。     

碳纳米管填料静电自组装制备及在导电塑料中的应用

为了提高碳纳米管(CNTs)在塑料中的分散性能,设计碳纳米管填料(CNTs Filler)。阳/非离子表面活性剂复配在水中分散CNTs,并赋予CNTs表面正电性。与表面负电性的炭黑或聚苯乙烯微球复合,通过静电吸附作用自组装形成均匀稳定的复合物,制备出CNTs Filler。对比了CNTs Filler、CNTs和炭黑在PS和ABS塑料中,经不同成型工艺的导电结果,证明了使用碳纳米管填料提高了碳纳米管在塑料中的分散性能,总结了碳纳米管相对炭黑作为塑料导电功能体适合压延成型加工。推荐碳纳米管用于导电片材、导电薄膜和高导电塑料等领域。     

微波作用下反应结晶制备碱式碳酸镁

采用等初末温度比较法和等温法分别在微波及水浴加热下反应结晶合成了碱式碳酸镁颗粒。用扫描电镜（SEM）、X射线衍射（XRD）以及粒度分析表征不同阶段样品的晶体结构、表面形貌和粒度分布,用化学分析（滴定法）跟踪反应结晶过程中镁离子浓度的变化。实验结果表明：所得晶体由纳米片自组装而成,微波场对碳酸镁结晶具有促进作用,即微波对碳酸镁结晶中初级纳米颗粒的组装具有促进作用,可提高碱式碳酸镁的生长速率,增大颗粒粒度,但没有改变产物晶习;不同温度下碱式碳酸镁转变路径不同,较高温度时无定形颗粒直接组装成碱式碳酸镁,较低温度时将出现正碳酸镁中间态,经由不同相转变历程的碱式碳酸镁纳米片微观形貌和组装方式并不相同。     

以负载Fe的介孔分子筛为模板合成碳纳米管

以负载Fe的介孔分子筛Fe/MCM-41和Fe/ABW分别为催化剂,乙炔为碳源,采用化学气相沉积法对催化合成碳纳米管(CNTs)进行研究,讨论了反应温度、催化剂种类以及催化剂预处理对CNTs纯度和形貌的影响,通过场发射扫描电子显微镜、高分辨透射电子显微镜和X-射线衍射仪对产物的结构和形貌进行了表征和分析,并对CNTs的生长机理进行了推测.结果表明,在反应温度为700℃,两种不同的催化剂经H2还原后,催化生长出直径均匀(20nm～30nm)且晶化程度较好的CNTs.     

钴催化剂制备螺旋纳米炭纤维

以纳米钴粉为催化剂,采用化学气相沉积法制备了纳米螺旋炭纤维。重点探讨了气相沉积温度、碳源气体流量、气相沉积时间等参数对螺旋炭纤维形貌的影响。用SEM、XRD、拉曼光谱等对螺旋炭纤维的微观形貌和物相组成等进行表征。结果表明,随温度的升高,产品石墨化程度加剧,但会出现无定形碳等杂质,纤维直径变粗。气相沉积时间对纳米螺旋炭纤维直径有较大影响,适当的气相沉积时间是生成光滑螺旋纳米炭纤维的前提。在500℃,通入80 mL/min的乙炔,反应40 min,可获得纤维直径50~100 nm、表面光滑的纳米螺旋炭纤维。     

原子层沉积氧化锌功能化碳纳米管织物及其光催化特性

以二乙基锌和去离子水为前驱体,利用原子层沉积（ALD）在自支撑碳纳米管（CNT）织物上沉积氧化锌（ZnO）对其进行了功能化;考察了ALD沉积过程中功能化织物的微观形貌、晶型结构、表面性质及光催化性能。实验结果表明,ZnO最初在CNTs表面生长为纳米颗粒,随ALD循环次数的增加,逐渐形成包覆CNTs的保形生长层,改变ALD沉积条件可精确调控氧化物在CNT织物中的负载量,CNT织物逐渐由强疏水转变为高度亲水。CNTs与六方纤锌矿结构ZnO的结合有效增强了电子转移能力,同时降低了光生电子与空穴的复合几率,ALD功能化CNT织物展现出优异的光催化降解性能,表明ALD是一种能够拓展CNT织物应用领域的灵活且有效的功能化手段。     

CF/CNTs多尺度混杂填充PA6复合材料性能研究

以碳纤维/碳纳米管(CF/CNTs)多尺度混杂填充聚酰胺6(PA6)复合材料为研究对象,采用不同的方法处理CNTs,并考察了对应复合材料的力学性能、导电性能和导热性能。结果表明:CNTs经过表面化学镀镍处理后,明显改善了CF与基体界面间的结合强度和相容性。表面镀镍处理的碳纳米管(CNTs-Ni)吸附在CF表面,不仅可促进CF与基体间形成"钉扎效应",从而提高了复合材料的力学性能,还在CF与PA6基体间形成了导热桥路和导电网络,使材料的电阻率和界面热阻有所下降;CF和CNTs混杂填充基体树脂对复合材料的力学性能、导热性能及导电性能有着良好的协同增效作用;CNTs-Ni可明显改善CF增强复合材料的导热性能和导电性能。     

碳纳米管-石墨烯-碳纳米纤维复合电极的制备及应用

配制含乙酸钴和乙酸镍的氧化石墨烯-聚丙烯腈(Co~(2+)-Ni~(2+)/GO-PAN)纺丝液,经静电纺丝技术制成碳纳米级纤维GO-PAN,预氧化和碳化处理GO-PAN得到分级多孔碳纳米管/石墨烯-碳纳米纤维(CNTs/G-CNFs)复合材料,对其结构和性能进行表征。结果表明,GO还原的石墨烯(G)均匀分布CNTs/G-CNFs内部,碳纳米管(CNTs)大量生长在CNTs/G-CNFs表面,使材料比表面积高达223.8 m~2/g。将0.5 g CNTs/G-CNFs组装成电容去离子技术(CDI)电极,在Na Cl的质量浓度为200 mg/L、处理时间为10 min的条件下,对比发现其电吸附脱盐能力高于CNFs和G-CNFs电极,最大除盐量达8.17 mg/g、除盐效率20.47%;并且5次循环使用后,除盐量和除盐效率下降不大,证明这种分级多孔的电极材料具有优异的除盐性能和可再生循环吸附能力。     

碳纳米管填充PDMS膜的渗透汽化性能

将碳纳米管（CNTs）填充到PDMS中制备出CNTs/PDMS杂化膜,并将其用于乙醇/水体系的分离,发现由多壁碳纳米管制备的膜分离性能优于单壁碳纳米管填充膜,在40℃下,进料乙醇浓度为5%（质量分数）时,膜的分离因子可由8.3提高到10.0,渗透通量为206.2 g·（m²·h）^-1;采用十二烷基三氯硅烷对多壁碳纳米管进行修饰,并对修饰前后碳纳米管的性能进行表征,研究表明修饰后碳纳米管表面形成疏水层,碳纳米管的疏水性增强;将修饰后的碳纳米管填充到PDMS中,可进一步提高杂化膜对乙醇的选择性,膜的分离因子可提高到11.3,渗透通量为130.9 g·（m²·h）^-1。     

碳纳米管/碳纤维混杂多尺度增强体研究现状

碳纳米管(CNTs)优异的力学性能使其成为复合材料的理想增强材料,将CNTs引入到碳纤维(CF)表面制备CNTs/CF纳、微米复合增强体,可同时改善复合材料的界面剪切强度和冲击强度,从而获得具有优异综合性能的复合材料。本文综述了CNTs/CF混杂多尺度增强体的制备方法及其复合材料的性能。     

Lignin-based carbon fibers: Carbon nanotube decoration and superior thermal stability

Lignin-based carbon fibers (CFs) decorated with carbon nanotubes (CNTs) were synthesized and their structure, thermal stability and wettability were systematically studied. The carbon fiber precursors were produced by electrospinning lignin/polyacrylonitrile solutions. CFs were obtained by pyrolyzing the precursors and CNTs were subsequently grown on the CFs to eventually achieve a CF–CNT hybrid structure. The processes of pyrolysis and CNT growth were conducted in a tube furnace using different conditions and the properties of the resultant products were studied and compared. The CF–CNT hybrid structure produced at 850 °C using a palladium catalyst showed the highest thermal stability, i.e., 98.3% residual weight at 950 °C. A mechanism for such superior thermal stability was postulated based on the results from X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and electron energy loss spectroscopy analyses. The dense CNT decoration was found to increase the hydrophobicity of the CFs.     

Investigation into microstructure of carbon nanotube multi-yarn

Structural analysis at the nano and micro scale was performed on a carbon nanotube (CNT) multi-yarn. The yarns were made by a process of drawing CNTs into a ribbon and twisting the ribbon into a yarn. Scanning electron microscopy (SEM) was used to view the exterior of the yarn. Polarized microscopy was used to examine details of the 1-yarn, and it also identified ribbon–ribbon boundaries. Further examination of interior structure was done by NanoCT scans which showed that folding of the ribbons had occurred causing complicated structures. The interior folding was found by milling into the yarn with a focus ion beam gun (FIB) and imaging with SEM. These different methods thus provided various microstructural details (structure, ribbon–ribbon boundary, folding and void fraction) of CNT multi-yarn which could be used to compare with other yarns fabricated with different procedures/sources as well to provide parameters for analytical tools. Further, these microstructural details can be related to macro mechanical and physical properties.     

Direct measurement of grafting strength between an individual carbon nanotube and a carbon fiber

Hierarchical structures consisting of carbon nanotubes (CNTs) grafted onto a carbon fiber (CF) have the potential to improve the performance of fiber/polymer composites. The strength between a CNT and a CF is a key factor that influences the load-transfer behavior and inter-laminar properties. Here, we directly measured the grafting strength of a chemically bonded CNT–CF hierarchical structure by detaching individual CNT from the CF substrate and simultaneously recording the force–displacement characteristics in a scanning electron microscopy equipped with a nano-manipulator. We observed a relatively wide distribution of the maximum forces at complete detachment for different grafted CNTs, which ranges from below the van der Waals (vdW) force existing at the CNT–CF interface up to 7 times higher than that. For a typical configuration where a CNT is partially anchored on a CF, we obtained grafting strengths in the range of 5–90 MPa, which are dominated by the vdW force as well as other factors such as chemical bonding. Our results, based on the measurements at individual nanostructure level, might be useful for designing and fabrication of high performance hierarchical composites.     

Mechanical properties of carbon nanotube/carbon fiber reinforced thermoplastic polymer composite

Carbon nanotube (CNT)/carbon fiber (CF) hybrid fiber was fabricated by sizing unsized CF tow with a sizing agent containing CNT. The hybrid fiber was used to reinforce a thermoplastic polymer to prepare multiscale composite. The mechanical properties of the multiscale composite were characterized. Compared with the base composite (traditional commercial CF), the multiscale composite reinforced by the CNT/CF hybrid fiber shows increases in interlaminar shear strength (ILSS) and impact toughness. Laminate containing CNTs showed a 115.4% increase in ILSS and 27.0% increase in impact toughness. The reinforcing mechanism was also discussed by observing the impact fracture morphology. POLYM. COMPOS., 38:2001–2008, 2017. © 2015 Society of Plastics Engineers     

The controlled formation of hybrid structures of multi-walled carbon nanotubes on SiC plate-like particles and their synergetic effect as a filler in poly(vinylidene fluoride) based composites

Vertically aligned carbon nanotubes (CNTs) grown on plate-like SiC microparticles as nano/micro hybrid structures were produced by floating catalytic chemical vapor deposition. Acetylene and ferrocene were used as carbon source and catalyst precursor, respectively. The effect of experimental conditions on the structure of the CNT-SiC multi-scale hybrids produced was investigated. The results indicated that the organization mode of CNTs on SiC particles could be effectively tuned by changing the hydrogen content in the carrier gases. The effect of the substrate on the hybrid structures was also studied and their formation mechanism was discussed. According to X-ray diffraction and Raman spectra, the asymmetric surface properties of 6H-SiC tended to produce “single-direction” growth of CNTs on SiC particles, while the competition between the nature of the substrate and the experimental conditions can result in a “multi-direction” hybrid structure. The resultant well-organized CNT-SiC hybrid structures can be further used as conductive filler to prepare percolative poly(vinylidene fluoride) composites. The composites containing the “single-direction” hybrid structures exhibited a much lower percolation threshold than those with “multi-direction” hybrid structures. The percolation behavior of the composites can be tuned by controlling the structure of CNT-SiC hybrids.     

The role of grafting force and surface wettability in interfacial enhancement of carbon nanotube/carbon fiber hierarchical composites

The grafting force of carbon nanotube (CNT) on carbon fiber (CF) and the wettability of CF surface were experimentally studied, where hierarchical CNT/CF reinforcement was prepared using chemical vapor deposition (CVD). Then, their effects on interfacial improvement were experimentally and theoretically investigated. The results show that the CNT/CF grafting force is so strong, more than 5 μN, and CNT/CF attachment can sustain the fracture of the CNTs. This is expected to be contributed to the improvement of interfacial properties. However, the deposited catalyst deteriorates the wettability, which could seriously degrade the interfacial properties. As a result, experimental results from the micro-droplet test show that there is only a 30% increase in the interfacial shear strength of hierarchical CNT/CF reinforced composite comparing with that of as-received CF reinforced composite. An analytical model was developed to predict the effects of CNT/CF grafting force on interfacial improvement, and the predicted results are in agreement with the experimental one.     

Improved fracture toughness of carbon fiber composite functionalized with multi walled carbon nanotubes

Woven carbon fiber (CF) laminae are functionalized in situ with carbon nanotubes (CNTs) to test the hypothesis that growing CNTs on CF (i.e., carbon fiber bundles or tow) would enhance the properties of polymeric carbon composites, specifically epoxy–carbon composites that are used in aerospace applications. The CNT as-grown on the woven CF were shown to substantially improve the fracture toughness of the cured composite on the order of 50%. This was accompanied by no loss in structural stiffness of the final composite structure. In fact, the flexural modulus increased approximately 5%. The significant increase in the fracture toughness as tested under the ASTM D 5528 standard indicates that the damage tolerance of a composite structure would benefit from the CNT material applied in this way. Our approach has allowed for significantly larger samples to be uniformly functionalized with CNTs than is reported elsewhere in the open literature. In addition, this work demonstrated CNT functionalization on flexible substrates that remains flexible after functionalization, whereas most CNT growth substrates are rigid in order to withstand the high (>800 °C) growth temperatures often encountered in CNT synthesis.     

Easy synthesis of a nanostructured hybrid array consisting of gold nanoparticles and carbon nanotubes

A nanostructured hybrid consisting of a high-density and uniform assembly of gold nanoparticles (AuNPs) on carbon nanotubes (CNTs) was prepared using easy methods. The pyrolysis of iron(II) phthalocyanine (FePc) on a Si substrate under an atmosphere of hydrogen/argon was used to produce multiwalled carbon nanotubes (MWCNTs) with 12 nm in diameter and 4 μm in length. Then, Au nanocolloid solution, which contained dodecanethiol-capped Au nanoparticles synthesized by solution chemical method, was deposited on the synthesized CNT array and heated at 300 °C for 1 h under Ar. The synthesis temperature of CNT governs the AuNP-CNT hybrid structure and surface nitrogen concentration from decomposition of FePC. CNTs synthesized at 800 °C exhibit the finest particle size and most homogeneous dispersity of assembled AuNPs in comparison to hybrids whose CNTs are synthesized at other temperatures. These features are considered to correlate with the surface nature of the grown CNT; good dispersity of AuNPs on CNT results from interaction between the thiolate molecules capped on the AuNPs and the N atoms doped into the grown CNT. Assembling AuNPs to CNT contributes the electrical conductivity enhancement of the CNT hybrid array.     

CVD growth of secondary carbon nanotubes and its effect on field electron emission

Secondary carbon nanotubes (CNTs) were grown on primary ones by simply changing the methane concentration. No additional catalyst was used throughout the whole deposition process. The CNT growth was carried out using hot filament chemical vapor deposition in a gas mixture of methane and hydrogen. The structure and surface morphology of the deposited CNTs were studied and the field emission properties of the CNTs were tested. It was found that synthesizing primary CNTs at extremely low methane concentration is the key for the secondary growth without additional catalyst. The CNT samples grown with secondary nanotubes exhibited improved field emission properties.     

Synthesis of three-dimensional carbon nanotube/graphene hybrid materials by a two-step chemical vapor deposition process

A three-dimensional carbon nanotube (CNT)/graphene hybrid material was synthesized by a two-step chemical vapor deposition (CVD) process. Due to the separated CVD processes for graphene and CNTs, the structures of the hybrid materials could be easily controlled. It is revealed that graphene film was tightly connected with one end of the CNT arrays, forming “jellyfish” structures. Moreover, our results indicate that the presence of graphene influenced the precipitation and growth rate of CNTs. The precipitation of CNTs was postponed due to the existence of graphene. However, the average growth rate of CNTs in the graphene region for the whole process was faster than that in the region without graphene.