Synthesis and characterization of carbon nanotube/polypyrrole core–shell nanocomposites via in situ inverse microemulsion

We demonstrate here a feasible approach to the preparation of multiwalled carbon nanotube (MWNT)/polypyrrole (PPy) core–shell nanowires by in situ inverse microemulsion. Transmission electron microscopy and scanning electron microscopy showed that the carbon nanotubes were uniformly coated with a PPy layer with a thickness of several to several tens of nanometers, depending on the MWNT content. Fourier transform infrared spectra suggested that there was strong interaction between the π‐bonded surface of the carbon nanotubes and the conjugated structure of the PPy shell layer. The thermal stability and electrical conductivity of the MWNT/PPy composites were examined with thermogravimetric analysis and a conventional four‐probe method. In comparison with pure PPy, the decomposition temperature of the MWNT/PPy (1 wt % MWNT) composites increased from 305 to 335 °C, and the electrical conductivity of the MWNT/PPy (1 wt % MWNT) composites increased by 1 order of magnitude. The current–voltage curves of the MWNT/PPy nanocomposites followed Ohm's law, reflecting the metallic character of the MWNT/PPy nanocomposites. The cyclic voltammetry measurements revealed that PPy/MWNT composites showed an enhancement in the specific charge capacity with respect to that of pure PPy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6105–6115, 2005     

An electrically heated ionic-liquid/multi-wall carbon nanotube composite electrode and its application to electrochemiluminescent detection of ascorbic acid

A heated composite electrode consisted of multi-wall carbon nanotube (MWNT) and ionic liquids (ILs) was designed and fabricated. The non-conductive binders were replaced by a conductive IL, n-octylpyridinum hexafluorophosphate (OPFP). This heated OPFP/MWNT composite electrode was applied for electrochemiluminescent (ECL) sensor, and the performance of ECL sensor was evaluated by ascorbic acid (AA)/lucigenin ECL system. The new heated electrode combines the advantages of ILs/CNT and heated electrode, showing high thermal stability and conductivity, simple heating setups, improved reproducibility, renewable surface, simplicity of fabrication and enhanced sensitivity with detection limit (S/N = 3) of 0.01 μmol/L for AA.     

Significance of the Dispersion Stability of Carbon Nanotubes on the Thermal Conductivity of Nylon 610 Nanocomposite

Herein, the effect of the dispersion uniformity of multi-wall carbon nanotubes (MWNTs) on the thermal conductivity of nylon 610/MWNTs nanocomposite was investigated. Compared to raw MWNTs, the carboxylated MWNTs (MWNT-COOH) were well dispersed in aqueous hexamethylenediamine solution and the dispersion stability was further improved by the presence of poly(vinyl alcohol). By means of interfacial polymerization between the aqueous hexamethylenediamine solution containing the MWNTs and a sebacoyl chloride phase, nylon 610/MWNT composites were prepared. It was found that the stable dispersion state of MWNTs in aqueous solutions greatly improved the thermal conductivity of the ultimate nanocomposites. It is noted that the thermal conductivity of nylon 610/MWNT-COOH/PVA nanocomposite was 135% higher than that of nylon 610/raw MWNTs for the same 0.1 wt% content of MWNTs.     

多壁碳纳米管对聚甲醛性能的影响

将多壁碳纳米管(MWCNTs)和聚甲醛(POM)在转矩流变仪中熔融混合得到POM/MWCNT复合材料.研究了复合材料的形态,导热性能,导电性能,流变性能和结晶性能.结果表明,MWCNTs在没有经过处理的情况下能够均匀地分散在POM基体中;当向POM中添加1.0 wt%含量MWCNTs时,复合材料的导热系数上升到0.5289 W/(K m),比纯POM的导热系数0.198 W/(K m)提高1.5倍,通过有效介质方法(EMA)验证了体系导热系数提高幅度不大的原因是MWCNTs与POM之间形成了很高的界面热阻;当MWCNTs的含量为1.0 wt%时,体系产生了导电逾渗效应,逾渗值在0.5 wt%~1.0 wt%之间;MWCNTs对POM有显著的成核作用,当向POM中添加0.5 wt%含量的MWCNTs时,POM的结晶温度提高6℃左右,但当MWCNTs的添加量进一步增加时,结晶温度几乎不再变化,成核效果呈现"饱和"状态.另外,材料的复数黏度,储能模量和损耗模量随MWCNTs含量的增加而增加.     

Enhanced conductivity composites for aircraft applications: carbon nanotube inclusion both in epoxy matrix and in carbonized electrospun nanofibers

The potential of carbonized electrospun nanofiber mats to render epoxy resin composites for aircraft applications electrically and thermally more conductive was investigated. The effect of carbon nanotube inclusion both inside the carbon nanofiber and in the epoxy resin matrix material was studied, in order to reveal any synergistic effects of multilevel presence of nanosized reinforcements on the conductivity and mechanical properties. The carbon nanotube inclusion into the carbonized nanofibers increased the electrical conductivity of the samples by 20–50% and the thermal conductivity by approximately three times leading to a higher value than that of the conventional composites. The preparation of layered composites with a conductive upper layer containing nonwoven carbon nanofabric and a load bearing lower layer with conventional unidirectional carbon fiber reinforcement can offer a cost‐effective and weight‐saving solution for the replacement of metal meshes in structural aircraft composites. Copyright © 2014 John Wiley & Sons, Ltd.     

聚噻吩/多壁碳纳米管复合材料结构与导电机理的研究

从结构和相互作用方面对聚噻吩(PTh)/多壁碳纳米管(MWNTs)复合材料进行了研究, 结果表明: 一方面聚噻吩本身的结构对其导电性能有一定的影响, 另一方面MWNTs作为一种掺杂剂, 和聚噻吩之间存在强的相互作用, 电子从MWNTs转移到聚噻吩. MWNTs和它周围被掺杂的聚噻吩通过π-π共轭作用形成相对独立的导电单元, 在复合材料的导电体系中起到主要作用, 随着这种导电单元数量的增加直至相互接触, 形成大的导电体系, 复合材料的电导率达到最大值.     

Oriented UHMW-PE/CNT composite tapes by a solution casting-drawing process using mixed-solvents

Ultra-high molecular weight polyethylene/multi-wall carbon nanotube (UHMW-PE/MWNT) composites have been prepared by a novel approach which involves the use of a mixture of solvents during the gelation process. By combining one of the best known organic solvents for nanotubes, N,N-dimethylformamide (DMF) with xylene and use this mixed-solvent in the gelation/crystallisation process for UHMW-PE/MWNT composite fabrication, an attempt is made to improve the dispersion of carbon nanotubes in UHMW-PE. The obtained films were drawn to obtain highly oriented tapes, which were characterized in terms of electrical and mechanical properties. The conductivity of the drawn tapes is maintained at 10⁻⁴ S/m at draw ratio 30, two orders of magnitude higher than the minimum level required to provide electrostatic discharge. Although the mechanical properties are compromised by use of DMF and MWNTs, the Young’s modulus still remains at 25 GPa, in comparison with 35 GPa for pure UHMW-PE tape at draw ratio 30.     

Evaluation of Mechanical Properties of Epoxy/Nanoclay/Multi-Walled Carbon Nanotube Nanocomposites using Taguchi Method

This paper reports the improvement of the mechanical properties of epoxy/nanoclay/multi-walled carbon nanotube (MWNT) nanocomposites prepared by the solution casting method for a range of pre-cure temperatures (room temperature, 50, and 70 °C), cure temperature (120, 130, and 140 °C), nanoclay content (0.5, 1.0, 1.5 wt%) and content of MWNT (0.2, 0.6, 1.0 wt%) for three levels. The influence of these parameters on the mechanical properties of epoxy/nanoclay/MWNT has been investigated using Taguchi's experimental design. The output measured responses are the tensile properties (tensile modulus, tensile strength and strain at break), impact strength and fracture toughness. From the Analysis of Mean (ANOM) and Analysis of Variance (ANOVA), MWNT content, pre-cure temperature and cure temperature had the most significant effects for the impact strength with contribution percentages of 38%, 28% and 23% respectively. However, for the fracture toughness and strain at break, the enhancements of properties come from the nanoclay content (59%), MWNT content (18%) and pre-cure temperature (23%). While the improvement in tensile strength was influenced by nanoclay and MWNT content, the cure temperature has a stronger effect on the tensile modulus. In this respect, Taguchi method points to the Taguchi method, in this way, points to the dominant parameters and gives the optimum parameter settings for each mechanical property. Confirmation experiments were performed with the optimum parameter settings and the mechanical properties were measured compared with the predicted results.     

聚3-辛基噻吩/MWNTs复合材料的导电性能研究

采用在氯仿溶液中超声共混, 制备聚3-辛基噻吩(P3OT)和多壁碳纳米管(MWNTs)复合材料. 当MWNTs掺杂量为3%时复合材料的电导率为1.43 S•m－1, 达到纯MWNTs的电导率水平. 用FTIR光谱, TG, UV-Vis光谱, XPS和FESEM进行研究分析, 认为MWNTs的离域电子与P3OT主链上的π电子之间形成π-π共轭, 增加了P3OT主链的有效共轭度, 被掺杂的P3OT具有很高的电导率, 提高了复合材料的导电性能. MWNTs与被掺杂的P3OT组成相对独立的导体单元, 对复合材料的导电网络形成起着主要作用.     

Positive Temperature Coefficient Characteristics of Multi-walled Carbon Nanotube Filled Polyvinylidene Fluoride Nanocomposites

Composites of polyvinylidene fluoride (PVDF) and multi-wall carbon nanotubes (MWNT) were prepared by a melt mixing process. Temperature dependence of electrical properties of the nanocomposites was investigated for composites containing different amounts of MWNT. An obvious positive temperature coefficient was observed. It was found that resistivity of the composites was decreased with increasing MWNT content and the electrical percolation threshold was formed at 3 wt% MWNT, which were caused by the formation of conductive chains in the composites. The mechanism of the positive temperature coefficient behavior of the nanocomposites is discussed. The rheological results showed that the materials experience a fluid–solid transition at the composition of 2 wt%, beyond which a continuous MWNT network forms throughout the matrix leading to a percolated network structure, which further indictes the nanotubes were dispersed uniformaly, in the PVDF matrix.     

Effect of carbon nanotubes on phase transitions of nematic liquid crystals

Phase diagrams of multi-wall carbon nanotube (MWNT)/nematic liquid crystal (E7) and buckminsterfullerene (C₆₀-I _h)/nematic liquid crystal (E7) binary systems have been investigated by means of polarizing optical microscopy and differential scanning calorimetry. It was found that the isotropic-nematic phase transition temperature (T _NI) of the liquid crystal component was enhanced by the incorporation of MWNT within a small composition gap. A chimney-type phase diagram can be identified in the MWNT/E7 mixture over a narrow range of ∼0.1-0.2% MWNT concentration. Upon substituting the nanotubes with isotropic fillers such as fullerene, the (C₆₀-I _h)/E7 blend showed no discernible change of T _NI in the same concentration range of the chimney of the MWNT/E7 mixture, suggesting a significant contribution of anisotropy (or the aspect ratio) of the nanotubes to the entropy of the system containing liquid crystal molecules. This enhanced T _NI phenomenon may be attributed to anisotropic alignment of liquid crystal molecules along the carbon nanotube bundles.     

高性能环氧树脂/碳纳米管复合物的热分析研究

用差示扫描量热仪(DSC)、热失重分析仪(TGA)和动态力学热分析仪(DMTA)研究了多壁碳纳米管(MWNTs)/高性能4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)复合物的热性能.Kissinger和Flynn-Wall-Ozawa的非等温固化动力学研究发现,随着MWNTs含量的增加,复合物固化反应的活化能先减小后增大.TGA研究表明,MWNTs的添加对环氧树脂热稳定性影响很小.碳纳米管填充到TGDDM/DDS体系后,复合物的储存模量随着MWNTs含量的增加而增大,而玻璃化温度却随之减小.     

Effect of aspect ratio of vertically aligned copper nanowires in the presence of cellulose nanofibers on the thermal conductivity of epoxy composites

The composites comprising vertically aligned network of copper nanowires (CuNWs) in the presence of cellulose nanofibers were fabricated by using the freeze‐templating method and the effect of aspect ratio (A/R) of CuNWs on the thermal conductivity of epoxy composites was investigated. The thermal conductivity of epoxy composites increased to 0.79 W m^?1 K^?1 at 1.12 vol% of high A/R CuNWs loading, corresponding to the thermal conductivity enhancement of 365% as compared to the pure epoxy. The thermal conductivity of vertically aligned higher A/R CuNWs/epoxy, which is 38.5% and 51.9% higher than those of the lower A/R CuNWs and the randomly aligned CuNWs, respectively. The application of the epoxy composites in heat dissipation was demonstrated by the temperature changes of composites on a hot plate with the increase of heating time. These results indicate that the thermally conductive composites in this study could be applied for thermal dissipating materials in electronic devices.     

Electrical properties study of multi-walled carbon nanotubes/hybrid-glass nanocomposites

Electrical properties of multi-walled carbon nanotubes (MWNTs)/hybrid-glass nanocomposites prepared by the fast-sol–gel reaction were investigated in light of percolation theory. A good correlation was found between the experimental results and the theory. We obtained a percolation threshold ? _c  = 0.22 wt%, and a critical exponent of t = 1.73. These values are reported for the first time for a silica-based system. The highest conductivity measured on the MWNT/hybrid-glass nanocomposites was σ ≈ 10^?3(Ω cm)^?1 for 2 wt% carbon nanotube (CNT) loading. The electrical conductivity was at least 12 orders of magnitude higher than that of pure silica. Electrostatic force microscopy and conductive-mode atomic force microscopy studies demonstrated conductivity at the micro-level, which was attributed to the CNT dispersed in the matrix. It appears that the dispersion in our MWNT/hybrid-glass system yields a particularly low percolation threshold compared with that of a MWNT/silica-glass system. Materials with electrical conductivities described in this work can be exploited for anti-static coating.     

Influence of aspect ratio of carbon nanotubes on crystalline phases and dielectric properties of poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVDF)-multiwalled carbon nanotube (MWNT) composites with different aspect ratios of MWNT were prepared by a coagulation method. Field emission scanning electron and transmission electron microscopic studies reveal that MWNT are well dispersed in the PVDF matrix. The X-ray diffraction and differential scanning calorimeter data indicate that the composites with high aspect ratio of MWNT have the β phase structure at the MWNT loading level of 2.0wt%, and have a mixture of α and β phase below 2wt% MWNT, and that those composites with low aspect ratio of MWNT, however, always have a mixture of α and β phase for MWNT concentrations ?2.0wt%. The dielectric constant values increase with the increase in MWNT loading level and the percent increase in dielectric constant is much greater in the composite filled with high aspect ratio of MWNT than in that loaded with low aspect ratio. And also, it has been found that the dielectric loss of the composites with MWNT loading level ?2.0wt% is still as low as neat PVDF, which is of significance for dielectric application.     

Segregated network polymer/carbon nanotubes composites

In this work we present the preparation of conductive polyethylene/carbon nanotube composites based on the segregated network concept. Attention has been focused on the effect of decreasing the amount of filler necessary to achieve low resistivity. Using high- and low-grade single-walled carbon nanotube materials we obtained conductive composites with a low percolation threshold of 0.5 wt.% for high-grade nanotubes, about 1 wt% for commercial nanotubes and 1.5 wt% for low-grade material. The higher percolation threshold for low-grade material is related to low effectiveness of other carbon fractions in the network formation. The electrical conductivity was measured as a function of the single-walled carbon nanotubes content in the polymer matrix and as a function of temperature. It was also found that processing parameters significantly influenced the electrical conductivity of the composites. Raman spectroscopy was applied to study single wall nanotubes in the conductive composites.     

Thermal and spectroscopic characterization of polypropylene-carbon nanotube composites

Thermogravimetric (TG) and varied temperature Raman spectroscopic measurements of melt-blended polypropylene composites (PP) with double wall (DWNT) and multi-wall carbon nanotubes (MWNT) revealed that the incorporation of carbon nanotubes into polymer matrix increased the thermal stability comparing to the virgin polypropylene. The characterization of reference nanotubes was also done by Raman microscopy and TG measurements. Varied temperature rheological analysis provided further information about the thermal decomposition of the composites indicating the formation of high strength char in case of MWNT and limited applicability of DWNT at high temperature. The residue of the decomposition of PP-MWNT nanocomposites consists of nanotubes of spectroscopically higher purity comparing to the original one indicating the thermally induced chemical changes in the solid phase.     

纳米金/碳纳米管复合材料修饰电极催化鲁米诺电致发光体系的研究

制备了纳米金/多壁碳纳米管(MWNT)复合材料修饰电极,并将此电极应用于鲁米诺电化学发光体系.电化学发光实验表明,此复合材料修饰电极同时具备了纳米金和碳纳米管的催化性能.此外通过电极活性表面积测算、电化学交流阻抗实验等方法研究了纳米金和碳纳米管在此体系催化过程中的作用.纳米金/碳纳米管修饰电极具有良好的重现性,可以广泛应用于鲁米诺电化学发光测定体系.     

Morphological and mechanical properties of carbon nanotube/polymer composites via melt compounding

The mechanical properties and morphology of multiwall carbon nanotube (MWNT)/polypropylene (PP) nanocomposites were studied as a function of nanotube orientation and concentration. Through melt mixing followed by melt drawing, using a twin screw mini‐extruder with a specially designed winding apparatus, the dispersion and orientation of MWNTs was optimized in PP. Tensile tests showed a 32% increase in toughness for a 0.25 wt % MWNT in PP (over pure PP). Moreover, modulus increased by 138% with 0.25 wt % MWNTs. Transmission electron microscopy and scanning electron microscopy demonstrated qualitative nanotube dispersion and orientation. Wide angle X‐ray diffraction was used to study crystal morphology and orientation by calculating the Herman's orientation factor for the composites as function of nanotube loading and orientation. The addition of nanotubes to oriented samples causes the crystalline morphology to shift from α and mesophase to only α phase. Furthermore, the addition of nanotubes (without orientation) was found to cause isotropization of the PP crystal, and drawing was shown to improve crystal orientation through the orientation factor. In addition, differential scanning caloriometry qualitatively revealed little change in overall crystallinity. In conclusion, this work has shown that melt mixing coupled with melt drawing has yielded MWNT/PP composites with a unique combination of strength and toughness suitable for advanced fiber applications, such as smart fibers and high‐performance fabrics. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 864–878, 2006     

Enhancement of water barrier properties and tribological performance of hybrid glass fiber/epoxy composites with inclusions of carbon and silica nanoparticles

Water barrier properties and tribological performance (hardness and wear behavior) of new hybrid nanocomposites under dry and wet conditions were investigated. The new fabricated hybrid nanocomposite laminates consist of epoxy reinforced with woven and nonwoven tissue glass fibers and two different types of nanoparticles, silica (SiO₂) and carbon black nanoparticles (C). These nanoparticles were incorporated into epoxy resin as a single nanoparticle (either SiO₂ or C) or combining SiO₂ and C nanoparticles simultaneously with different weight fractions. The results showed that addition of carbon nanoparticles with 0.5 and 1 wt% resulted in maximum reduction in water uptake by 28.55% and 21.66%, respectively, as compared with neat glass fiber reinforced epoxy composites. Addition of all studied types and contents of nanoparticles improves hardness in dry and wet conditions over unfilled fiber composites. Under dry conditions, maximum reduction of 47.26% in weight loss was obtained with specimens containing 1 wt% carbon nanoparticles; however, in wet conditions, weight loss was reduced by 17.525% for specimens containing 0.5 wt% carbon nanoparticles as compared with unfilled fiber composites. Diffusion coefficients for different types of the hybrid nanocomposites were computed using Fickian and Langmuir models of diffusion. Copyright © 2017 John Wiley & Sons, Ltd.