Nanocomposite based on modified multiwalled carbon nanotubes: Fabrication by an oriented spinning process and electrical conductivity

We have produced nanocomposite films consisting of modified multiwalled carbon nanotubes (MWCNTs) and a polymer (MWCNT/polymer weight ratio of 95/5). The nanocomposite has been applied to a paper substrate by an oriented spinning process from a liquid phase. The resistivity of the films has been measured as a function of temperature in the range 20–140°C along and across the preferential orientation direction of the nanotubes in the nanocomposite. The results point to an irreversible transition from semiconducting to metallic behavior of the conductivity of the films.     

Carbon nanotube/polycarbonate composites as multifunctional strain sensors

In this study we demonstrate that multiwalled carbon nanotube fillers can impart a strain sensing functionality to a composite. The nanocomposite is fabricated by dispersing 5% weight of multiwalled nanotube fillers into a polycarbonate matrix. When subjected to linear and sinusoidal dynamic strain inputs, the instantaneous change in the electrical resistance (deltaR/R0) of the nanocomposite responds in a manner similar to a strain gage. The sensitivity of the nanocomposite sensor was measured to be approximately 3.5 times that of a typical strain gage. This sensitivity of the nanocomposite's electrical properties to mechanical stress implies that in addition to enhancing mechanical properties (strength, stiffness, structural damping, etc.), these multifunctional materials show the potential to provide real-time structural health monitoring and self-diagnostic functionalities.     

聚合物基纳米复合材料的研究进展

对聚合物基纳米复合材料的研究进展进行了介绍,报道了有关聚合物基纳米复合材料制备方法的研究进展情况,并分别对聚合物/粘土纳米复合材料、环氧树脂基纳米复合材料、聚酯纳米复合材料、聚合物/碳纳米管纳米复合材料的研究发展情况给予了评述,同时对每种体系特点和存在的问题进行了论述,最后着重指出纳米复合材料制备方法、应用以及开发新的聚合物基纳米复合体系是今后的主要研究方向.     

MWCNTs/Cu(OH)2 nanoparticles/IL nanocomposite modified glassy carbon electrode as a voltammetric sensor for determination of the non-steroidal anti-inflammatory drug diclofenac

This paper describes the development and utilization of a new nanocomposite consisting of Cu(OH)₂ nanoparticles, hydrophobic ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate (EMIMPF₆) and multiwalled carbon nanotubes for glassy carbon electrode modification. The nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy (EDX). The modified electrode was used for electrochemical characterization of diclofenac. Using differential pulse voltammetry, the prepared sensor showed good sensitivity and selectivity with low overpotential for the determination of diclofenac in the range from 0.18 to 119 μM, with a detection limit of 0.04 μM. Electrochemical studies suggested that the MWCNTs/Cu(OH)₂ nanoparticles/IL nanocomposite modified electrode provided a synergistic augmentation on the voltammetric behavior of electrochemical oxidation of diclofenac, which was indicated by the improvement of anodic peak current.     

Effect of Polyaniline Functionalized Carbon Nanotubes Addition on the Positive Temperature Coefficient Behavior of Carbon Black/High-Density Polyethylene Nanocomposites

The influence of addition of polyaniline functionalized multiwalled carbon nanotubes (PANI-MWNTs) on the positive temperature coefficient (PTC) characteristics of carbon black (CB) filled high-density polyethylene (HDPE) nanocomposite materials have been studied. Polymer nanocomposites were prepared by the combined solution and melt-mixing process. The experimental results showed that the PTC intensity and maximum resistivity of the hybrid nanocomposites were obviously influenced by the polyaniline functionalization of multiwalled carbon nanotubes (MWNTs). A noticeable PTC of resistivity was observed for PANI-MWNTs/CB/HDPE hybrid nanocomposites near the melting point of HDPE. This is due to the significant volume expansion near the melting point of the HDPE in presence of hybrid fillers and a sudden increase of the resistivity due to the disconnection of the conductive paths. The PTC effect of CB/HDPE composites can be effectively modified by the addition of PANI-MWNTs.     

Electrogenerated chemiluminescence of tris (2,2'-bipyridyl)ruthenium(II) ion-exchanged in nafion-silica composite films

The voltammetry and electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3 2+) ion-exchanged in Nafion and Nafion-silica composite materials have been investigated. The major goal of this work was to investigate and develop new materials and immobilization approaches for the fabrication of ECL-based sensors with improved reactivity and long-term stability. Nation-silica composite materials with varying contents of Nation (53-100 wt% relative to silica) were prepared via the two-step acid/base hydrolysis and condensation of tetramethoxysilane. The Nafion doped sols were spin cast on glassy carbon electrodes, dried, and then ion-exchanged with Ru(bpy)3 2+. The shapes of the cyclic voltammetric curves and the amount of Ru(bpy)3 2+ exchanged into the films strongly depends on the amount of Nafion incorporated into the hybrid sol. Nafion-silica films with a low content of Nafion ion-exchanged less Ru(bpy)3 2+ and exhibited tail-shaped voltammetry at 100 mV/s. The ECL of immobilized Ru(bpy)3 2+ in the presence of either tripropylamine or sodium oxalate in pH 5 acetate buffer was also strongly dependent on the amount of Nafion introduced into the composite with greater ECL observed for the Nafion-silica films relative to pure Nafion.     

PVK/MWNT electrodeposited conjugated polymer network nanocomposite films

The facile preparation of poly (N-vinyl carbazole) (PVK) and multiwalled carbon nanotubes (MWNTs) solution and conjugated polymer network (CPN) nanocomposite film is described. The stable solutions of PVK/MWNT were prepared in mixed solvents by simple sonication method, which enabled successful deaggregation of the MWNTs with the polymer matrix. MWNT was most effectively dissolved in N-cyclohexyl-2-pyrrolidone (CHP) compared to other solvents like N-methyl pyrrolidone (NMP), dimethyl formamide, and dimethyl sulfoxide (DMSO). The composite solution was relatively stable for months with no observable precipitation of the MWNTs. Thermogravimmetric analysis (TGA) revealed the thermal stability of the nanocomposite while the differential scanning calorimetry (DSC) showed an increasing melting (T(m)) and glass transition (T(g)) temperatures as the fraction of the MWNTs in the nanocomposite was increased. Cyclic voltammetry (CV) allowed the electrodeposition of the nanocomposite film on indium tin oxide (ITO) substrates and subsequent cross-linking of the carbazole pendant group of the PVK to form CPN films. Ultraviolet-visible (UV-vis), fluorescence, and Fourier transform infrared (FTIR) confirmed film composition while atomic force microscopy (AFM) revealed its surface morphology. Four-point probe measurements revealed an increase in the electrical conductivity of the CPN nanocomposite film as the composition of the MWNTs was increased: 5.53 × 10(-4) (3% MWNTs), 0.53 (5%), and 1.79 S cm(-1) (7%). Finally, the interfacial charge transfer resistance and ion transport on the CPN nanocomposite film was analyzed by electrochemical impedance spectroscopy (EIS) with a measured real impedance value of ～48.10 Ω for the 97% PVK and 3% MWNT ratio of the CPN nanocomposite film.     

Highly conductive and mechanically robust multiwalled carbon nanotube-polyamide nanocomposites via noncovalent functionalization

Journal of Materials Science - Electrically conductive multiwalled carbon nanotube (MWNT)/polyamide 6 (PA 6) nanocomposite films with high mechanical strength were fabricated by blending modified...     

Design of an Assembly of Poly(benzimidazole), Carbon Nanotubes,and Pt Nanoparticles for a Fuel‐Cell Electrocatalyst with an Ideal Interfacial Nanostructure

A newly designed and fabricated novel nanocomposite composed of multiwalled carbon nanotubes (MWNTs), poly(benzimidazole) (PBI), and Pt nanoparticles. This composite is fabricated by the preparation of PBI‐wrapped MWNTs (MWNT/PBI), followed by Pt loading onto the MWNT/PBI. As a result of the PBI wrapping, the loading efficiency of the Pt nanoparticles onto the MWNTs is dramatically improved up to 58.8% compared to that of the pristine MWNTs (41.0%). The process also allows homogeneous Pt immobilization onto the surface of MWNTs without any strong oxidation process for the MWNTs that is typically used for metal supporting on carbon nanotubes. Far‐IR spectroscopy of the composite shows a peak from the Pt? N bonding, indicating that these improvements are derived from the coordination of the Pt ion with the PBI molecules. Cyclic voltammogram measurements reveal that the Pt nanoparticles deposited on the MWNT/PBI shows higher utilization efficiency (74%) for electrocatalysts compared to that on the pristine MWNT (39%).     

Hierarchical assembly of carbon nanotubes-liquid crystal nanocomposite

Fabrication of liquid crystalline (LC) nanomaterials in an aligned pattern along the multiwalled carbon nanotubes (CNT) has been reported here. The nanocomposite was prepared by sonicating esterified CNTs and the ferroelectric liquid crystal (FLC) in chloroform. The nanohybrid shish kebab (NHSK) like pattern was observed in SEM analysis. The nanocomposite materials were characterized by Fourier transform infrared spectroscopy (FTIR), polarizing optical microscopy and electron microscopy. The DC and AC electrical properties of the composite materials were investigated. The DC conductivity of the nanocomposite increased by 2 order from the FLC materials and AC relaxation has been observed, in the nanocomposite, which was totally absent in the FLC materials.     

Carbon nanotube reinforced aluminum nanocomposite via plasma and high velocity oxy-fuel spray forming

Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites.     

以预锂化多壁碳纳米管为负极的锂离子电容器性能

采用内部短路方式对多壁碳纳米管负极进行不同程度的预嵌锂处理,预嵌锂时间为5,30,60min,以预嵌锂多壁碳纳米管极片作为负极,活性炭极片作为正极,组装成锂离子电容器。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)对多壁碳纳米管及电极极片进行表征分析,采用恒流充放电(GCD)和交流阻抗谱(EIS)研究预嵌锂多壁碳纳米管负极和未预嵌锂处理多壁碳纳米管负极锂离子电容器的性能。电化学测试结果表明,多壁碳纳米管负极预嵌锂大幅提高了电容器充放电性能,对比未嵌锂多壁碳纳米管电容器,在相同的电流密度下(100mA/g),能量密度提高400%。预嵌锂60min,电流密度100mA/g时,其比容量达到57F/g。在电流密度为100～3200mA/g范围内,其最高能量密度与功率密度分别达到90Wh/kg,4130W/kg。1000次充放电循环后,容量保持率维持在85%以上,表现出良好的超级电容器性能。     

Increasing the antibacterial effect of lysozyme by immobilization on multi-walled carbon nanotubes

We report a facile strategy to obtain multiwalled carbon nanotubes (MWCNTs) functionalized with covalently bonded lysozyme. The functionalization procedure has been investigated by means of several techniques, including thermogravimetry, Raman spectroscopy, transmission electron microscopy, and cyclic voltammetry. A functionalization of about 1 lysozyme molecule every 4000 carbon atoms is obtained. The modified lysozyme-CNTs nanocomposite shows a significant increase of the antibacterial activity towards the Gram-positive S. aureus if compared with lysozyme in solution.     

The relationship of crystallization behavior,mechanical properties,and morphology of polypropylene nanocomposite fibers

This study aimed at the fabrication of lightweight and high performance nanocomposite fibers. Polypropylene/multiwalled carbon nanotubes (PP/MWCNTs) nanocomposite fibers (0–5 wt% of MWCNTs) were prepared via melt spinning process. The MWCNTs were dispersed in the dispersing agent before mixing with PP powder. After mixing, the dispersing agent was removed. Then the nanocomposites were spun into fibers. The fibers were spun and stretched with 7.5 draw ratios. Crystallization behavior and thermal properties of PP/MWCNTs nanocomposite fibers were studied using the differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA). The DSC curves of PP/MWCNTs nanocomposite fibers showed the crystallization peak at a temperature higher than that of neat PP fibers. These results revealed that the MWCNTs acted as nucleating sites for PP crystallization. The additions of MWCNTs into PP leaded to an increase in both crystallization temperature and crystallization enthalpy. However, no significant changes in the melting temperatures of the PP nanocomposites were detected. Degradation temperature of samples obtained from the TGA curves showed increase thermal degradation behavior for the PP/MWCNTs with the content of MWCNTs. It was found that the increase of tensile strength and modulus corresponded well with the increase of crystallinity of the composite fibers.     

Enhanced reaction kinetics and impact strength of cyanate ester reinforced with multiwalled carbon nanotubes

In this work, the effect of multiwalled carbon nanotubes on the properties of a unique, low viscosity bisphenol E cyanate ester (BECy) resin is characterized during various stages of nanocomposite preparation. The effect of surface functionalization, with nanotubes containing hydroxyl groups (OH CNTs) and carboxylic acid groups (COOH CNTs), on the rheological, cure, thermal, and impact properties of the nanocomposite properties are also examined. Based on rheology measurements prior to cure, the unfunctionalized nanotube suspensions are found to exhibit the highest viscosity and the most dramatic shear thinning behavior. Cure characterization using differential scanning calorimetry (DSC) reveals that the nanotubes catalyze the cure of BECy and the OH CNTs exhibiting the most dramatic catalytic effect. The DSC data is well described by an nth order autocatalytic model. The impact strength of fully cured BECy is found to increase by 91% and 63% upon incorporation of 1 wt% COOH and OH CNTs, respectively. While incorporation of 1 wt% unfunctionalized nanotubes results in an 8 degrees C decrease in the glass transition temperature (T(g)) of BECy, chemical functionalization greatly mitigates the magnitude of the reduction.     

Phenoxy nanocomposite carriers for delivery of nanofillers in epoxy matrix for resin transfer molding (RTM)-manufactured composites

The use of phenoxy nanocomposite films as carriers of nanofillers involving multiwalled carbon nanotubes and nanoclays is successfully demonstrated for application in epoxy carbon fibers reinforced composites (CFRC) processed by RTM. Model studies on individual nanocomposite filaments embedded in epoxy precursors show that the nanofillers are passively transported by the interdiffusion gradient during heating over distance around 800 μm. A morphology gradient is generated after reaction induced phase separation and the nanofillers end up in the epoxy, despite their initial dispersion in the phenoxy. The proof of concept is extended to CFRC panels where nanocomposite phenoxy films are prepositioned between every odd carbon layer of the preform. Carbon nanotubes are filtered by the carbon fabrics, which limits their full diffusion and that of phenoxy through the preform. This has negative consequences on fracture toughness (G_Ic)_. For nanoclay, G_Ic is rather slightly improved although the origin is not fully clear.     

Four-dimensional spectral tomography of carbonaceous nanocomposites

There is considerable interest in the adhesion of polymers to carbon nanotubes for nanocomposite applications.(1-4) One example is multiwalled carbon nanotubes (MWCNTs) dispersed in nylon 6,6.(5) We will show that high-contrast tomographic reconstructions can be created from plasmon-loss electrons that show the three-dimensional structural complexity of the MWCNT-nylon composite at the nanoscale. Further, by recording a series of energy-loss images at successive tilts, it is possible to interrogate subvolumes to extract energy-loss spectra from the reconstructed "volume spectra".     

Effect of multiwalled carbon nanotubes on the crystallization and dielectric properties of BP-PEN nanocomposites

In this work, polymer-based nanocomposite films formed from biphenol poly(arylene ether nitrile) (BP-PEN) and multiwalled carbon nanotubes (MWCNTs) were successfully prepared by the solution casting method combined with continuous ultrasonic dispersion technology. The micromorphology, thermal, mechanical and dielectric properties of the nanocomposite films were investigated in detail. Non-isothermal crystallization behavior studies indicate that the presence of MWCNTs enhances the crystallization of BP-PEN in the nanocomposites, which is consistent with the XRD analysis. Most importantly, it could be observed that the film containing 0.8 wt% MWCNTs reached the maximum crystallinity. Although, incorporation of MWCNTs did not obviously increase the mechanical of the films, all the nanocomposite films still exhibited excellent mechanical strength. The SEM micrographs of the nanocomposite films showed that the MWCNTs were uniformly coated by BP-PEN crystals, and indicating significantly improved nucleation ability of MWCNTs for polymer crystallization.     

Mechanical,tribological and heat resistant properties of fluorinated multi-walled carbon nanotube/bismaleimide/cyanate resin nanocomposites

Bismaleimide containing cyanate resin(BMI/CE) pre-ploymer was used as resin matrix. Fluorinated multiwalled carbon nanotubes(F-MWCNTs) were used as fillers to prepare F-MWCNT/BMI/CE nanocomposites via a solution intercalation method. The influence of F-MWCNT content on the mechanical, tribological and heat resistant properties of the nanocomposites was investigated. The morphology of the fracture surface and the wear surface of nanocomposites were characterized by scanning electron microscopy.Results show that the addition of F-MWCNTs is beneficial to improving the mechanical and tribological properties of the nanocomposites. It's worth noting that when the content of F-MWNTs was 0.6 wt%, the performances of nanocomposite are optimized(i.e., highest impact strength, lowest frictional coefficient and wear rate). In addition, the nanocomposites exhibit good thermal stability in comparison with BMI/CE.     

Electro-active shape memory properties of poly(ε-caprolactone)/functionalized multiwalled carbon nanotube nanocomposite

One type of electroactive shape memory nanocomposite was fabricated, including cross-linked poly(ε-caprolactone) (cPCL) and conductive multiwalled carbon nanotubes (MWNTs). The cross-linking reaction of the pristine poly(ε-caprolactone) (PCL) was realized by using benzoyl peroxide (BPO) as an initiator. The raw MWNTs (Raw-M) were prefunctionalized by acid-oxidation process and covalent grafting with poly (ethylene glycol) (PEG), respectively. Three kinds of nanocomposites containing cPCL/Raw-M, cPCL/acid-oxidation MWNTs (AO-M) and cPCL/PEG grafted MWNTs (PEG-M) were obtained, and the mechanical, electrical and shape memory properties were further investigated. The influence of in vitro degradation on their shape memory and mechanical properties was also evaluated. The methyl thiazolyl tetrazolium (MTT) assay was performed to estimate their biocompatibility. The results displayed that these nanocomposites could perform favorable shape memory recovery both in hot water at 55 °C and in electric field with 50 V applied voltage. In addition, compared with cPCL/Raw-M and cPCL/AO-M, cPCL/PEG-M composite possessed more favorable properties such as mechanical, biocompatible, and electroactive shape memory functions. Therefore, the nanocomposite may be potential for application as smart bioactuators in biomedical field.