Increasing the maximum strain and efficiency of bucky gel actuators by pyrrole oxidative polymerization on carbon nanotubes dispersed in an ionic liquid

Oxidative polymerization of pyrrole directly on preformed bucky gel slurry was carried out in order to combine the remarkable properties of ionic actuators based on carbon nanotubes and polypyrrole. Bimorph solid state ionic actuators were prepared with this novel hybrid material and compared with classical bucky gel actuators. A small amount of polypyrrole is sufficient to dramatically improve the overall actuator performance. The maximum strain is five times larger than the one of actuators prepared only with carbon nanotubes. Moreover, for the same applied charge, the strain generated increases up to twenty-five times.     

Ionic electroactive polymer actuators based on nano‐carbon electrodes

This review paper focuses on the recent studies of electroactive polymer actuators that have a triple‐layered configuration composed of an ionic‐gel electrolyte layer sandwiched by nano‐carbon dispersed ionic‐liquid gel electrode layers (bucky‐gel actuator) for the purpose of development of practical devices. The review covers recent studies of the developments of the materials of the bucky‐gel actuators and their electromechanical modeling. In the final section, the application to an ultra‐thin and ultra‐light Braille display based on the bucky‐gel actuator is described. © 2013 Society of Chemical Industry     

Single‐walled nanotube bucky paper and nanocomposite

A new processing method for the fabrication of single‐walled nanotube (SWNT)‐reinforced nanocomposites was developed to achieve uniform dispersion and high composition of the nanotubes in the nanocomposites. In this method, SWNTs were preformed as bucky paper by multi‐step dispersion and micro‐filtration of a suspension of nanotubes. The nanocomposites were then fabricated by infiltration of diluted epoxy resin through the bucky paper and hot pressing. The wetting of the nanocomposites was examined using scanning electron microscopy and atomic force microscopy. The results showed that the epoxy resin completely penetrated the bucky paper through the nanoporous structures. The results of dynamic mechanical analysis of the nanocomposites showed that the storage moduli of the nanocomposites increased by 200–250%. The tan δ curves indicated that the nanotubes had a strong influence on the damping properties of the nanocomposites. This processing technique is an effective method for fabricating nanocomposites with uniform dispersion and high composition of SWNTs. Copyright © 2006 Society of Chemical Industry     

Interaction of 1-allyl-3-methyl-imidazolium chloride and carbon black and its influence on carbon black filled rubbers

The interactions of the ionic liquid 1-allyl-3-methyl-imidazolium chloride (AMIMCl) with different grades of carbon black have been investigated using rheological measurements, differential scanning calorimetry and Raman spectroscopy. We could prove strong attractive interactions of AMIMCl with the carbon black surface, which result, for example, in the formation of an AMIMCl–carbon black–bucky gel and in an increased glass transition temperature of the ionic liquid in the presence of carbon black. Raman spectroscopy revealed that the AMIMCl is preferably attached to the edges of graphitic crystals at the carbon black surface, which have the highest adsorption energies. A surface treatment of different grades of carbon black with AMIMCl led to significant changes of the mechanical and electrical properties of different rubber compounds filled with carbon black, which can be attributed to a decreased filler–polymer interaction and a local plasticising effect of the AMIMCl at the carbon black surface.     

Improved interlaminar shear properties of multiscale carbon fiber composites with bucky paper interleaves made from carbon nanofibers

The effects of bucky paper interleaves made from carbon nanofibers on interlaminar shear properties of carbon fiber reinforced composites (CFRPs) are studied. The study includes fabrication of bucky papers, resin impregnation by different techniques, i.e., soaking, hot-compression and vacuum filtration, followed by β-stage curing and the integration with carbon fiber prepregs to produce CFRP composites with bucky paper interleaves. The vacuum infiltration technique results in the best quality of polymer impregnation through bucky papers. Remarkable 31% and 104% improvements in interlaminar shear strength and mode-II shear interlaminar fracture toughness of the multiscale composites, respectively, are achieved with the incorporation of interleaves at failure-prone locations. The pertinent mechanisms responsible for the ameliorating effects of interleaves include improved interfacial adhesion and matrix shear strength for the interlaminar strengthening and crack-tip bridging and meandering for the toughening. The present technique can be used to incorporate carbon nanotubes (CNTs) or carbon nanofibers (CNFs) of high contents to strengthen/toughen at selective locations in FRP composites, which has not been possible previously because of the high viscosity caused by randomly-oriented CNTs/CNFs in a polymer resin.     

单壁碳纳米管/再生纤维素复合纤维的制备及性能

将经过酸化处理和十二烷基苯磺酸钠处理后的单壁碳纳米管(SWNTs)与离子液体和再生纤维素共混制得纺丝溶液,通过干湿法纺丝制得SWNTs/再生纤维素复合纤维.考察了SWNTs处理前后的结构及在离子液体中的分散性;研究了复合纤维的力学性能和热性能.结果表明:经酸化和功能化处理后的SWNTs的直径有所减小,SWNTs在离子液...     

Cross-linking super-growth carbon nanotubes to boost the performance of bucky gel actuators

Chemical cross-linking of super-growth carbon nanotubes was performed to increase bucky gel actuators efficiency in transferring motion from the nano-scale to the micro-scale. The modification was achieved by a three-step reaction i.e. first an oxidation with nitric acid, then a chlorination process with thionyl chloride and finally the cross-linking with an aromatic diamine. The use of cross-linked nanotubes in bucky gel results in a threefold increase of the charge transfer capability of the composite material and an increase up to ten times of the strain generated by the resulting actuators. To our knowledge, such bucky gel actuators, prepared using cross-linked super growth carbon nanotubes, outperform any other electrochemical carbon nanotube actuator presented so far.     

Carbon nanomaterial–ionic liquid hybrids

Carbon nanomaterial–ionic liquid hybrids represent a very interesting class of materials because of their exceptional properties and potential use in a wide range of application fields. Their unique properties, arising from the synergistic combination of both components, can be exploited as elements of electrochemical and energy storage devices, as supports for catalysis and as nanofillers for polymeric composites. Owing to the specific interactions between ionic liquids (ILs) and carbon nanomaterials, the surface properties of the nanomaterials can be modified, leading to their improved dispersion in various media, thus providing an alternative solution to the most fundamental problem in processing of these materials. Since the discovery of bucky gel, the synthesis and processing methods of carbon nanotube–ionic liquid (CNT–IL) hybrids have been extensively studied. This review is aimed at giving an overview of the main synthetic routes and potential applications of CNT–IL hybrids. Graphene has lately emerged as a promising material, and received world-wide attention due to its exceptional properties. The synthesis of graphene-IL hybrids and the role of IL in the exfoliation process of graphene sheets are also discussed along with the potential applications of these new materials.     

Composites based on acrylic polymers and carbon nanotubes as precursors of carbon materials

The effect of carbon nanotubes on the properties of composite fibers and films based on polyacrylonitrile is analyzed. It is shown that the introduction of carbon nanotubes makes it possible to improve the mechanical characteristics of the composite material. Data on the effect of carbon nanotubes on chemical reactions occurring during the thermal stabilization and carbonization of these materials are cited.     

Graphene or carbon nanofiber-reinforced zirconia composites: Are they really worthwhile for structural applications?

The use of allotropic phases of carbon (i.e. nanotubes, graphene or carbon nanofibers) as second phases to design ceramic composites is a hot topic at present. Researchers try to provide a remarkable improvement of the parent ceramic assuming that some of the outstanding mechanical properties of these phases migrate to the resultant composite. This reasonable idea has been questioned severely in the case of nanotubes addition but there is not any analysis for the other two phases cited previously. To elucidate this question, zirconia was selected as a model ceramic. This paper reports the mechanical properties of zirconia composites reinforced either with graphene or carbon nanofibers, with special emphasis on the high-temperature plasticity.     

Important issues in a molecular dynamics simulation for characterising the mechanical properties of carbon nanotubes

This paper discusses several important issues in a molecular dynamics simulation for analysing carbon nanotubes and their mechanical properties. In particular, the paper addresses the problems in selecting appropriate inter-atomic potentials, number of thermostat atoms, thermostat techniques, time and displacement steps and number of relaxation steps to reach the dynamic equilibrium. Based on these, the structural changes of armchair and zigzag nanotubes and their mechanical properties are investigated. The Young's modulus and Poisson's ratio of the armchair tube are 3.96 and 0.15 TPa, respectively, and those of the zigzag tube are 4.88 and 0.19 TPa, respectively. The best simulation technique identified in this study predicts that the ultimate tensile strain of a carbon nanotube is around 40% before atomic bond breakage.     

Multiwall carbon nanotube elastomeric composites: A review

Nanostructured materials gained great importance in the past decade on account of their wide range of potential applications in many areas. A large interest is devoted to carbon nanotubes that exhibit exceptional electrical and mechanical properties and can therefore be used for the development of a new generation of composite materials. Nevertheless, poor dispersion and poor interfacial bonding limit the full utilization of carbon nanotubes for reinforcing polymeric media.In this paper, recent advances on carbon nanotubes and their composites will be presented through results of the author's research, essentially based on filled elastomeric networks. The intrinsic potential of carbon nanotubes as reinforcing filler in elastomeric materials will be demonstrated. It will be shown that, despite a poor dispersion, small filler loadings improve substantially the mechanical and electrical behaviors of the soft matrix. With the addition of 1 phr of multiwall carbon nanotubes in a styrene-butadiene copolymer, a 45% increase in modulus and a 70% increase in the tensile length are achieved. Straining effects investigated by atomic force microscopy and infrared and Raman spectroscopies, provide interesting results for the understanding of the mechanical behavior of these nanotube-based composites. All the experimental data lead to the belief that the orientation of the nanotubes plays a major role in the mechanical reinforcement. The strong restriction in equilibrium swelling in toluene with the MWNT content is not ascribed to filler-matrix interfacial interactions but to the occlusion of rubber into the aggregates. On the other hand, carbon nanotubes impart conductivity to the insulator matrix. Between 2 and 4 phr, the conductivity increases by five orders of magnitude reflecting the formation of a percolating network. Changes in resistivity under uniaxial extension completed by AFM observations of stretched composites bring new insights into the properties of these composites by highlighting the contribution of orientational effects.     

Enhanced mechanical and electrical properties of carbon fiber/poly(ether ether ketone) laminates via inserting carbon nanotubes interleaves

The carbon fiber/(carbon nanotubes/polyetherimide)/poly ether ether ketone (CF/(CNTs/PEI)/PEEK) laminates are prepared by inserting carbon nanotubes/polyetherimide (CNTs/PEI) interleaves into interlaminar region. The mechanical properties and electrical conductivities of the developed laminates are evaluated. The results indicate that the interlaminar shear strength and flexural strength of CF/(CNTs/PEI)/PEEK laminates are increased by 42.9% and 24.7%, after inserting CNTs2.91/PEI interleaves, respectively. The cross-sectional images of laminates after mechanical tests verify strong fiber-resin adhesion by scanning electron microscope observation. The pertinent mechanism responsible for the improvement of mechanical properties is mechanical interlocking effect of CNTs. After incorporating CNTs/PEI interleaves, the electrical conductivity of laminates is markedly improved due to the formation of conductive pathway. This work suggests that this method is compatible with the preparation process of thermoplastic composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48658.     

Investigation of a postprocessing method to tailor the mechanical properties of carbon nanotube/polyamide fibers

The incorporation of carbon nanotubes to thermoplastic fibers can potentially improve mechanical, thermal and electrical properties. In this article, a methodology to tailor the mechanical properties of carbon nanotube/nylon fibers is presented. Multiwalled nanotubes (MWNT) were combined to polyamide 12 through melt compounding and twin‐screw extrusion. Pellets containing between 0 and 5.0 wt % MWNT were extruded and subsequently melt spun with a capillary rheometer to produce filaments. To further promote the alignment of the polymer chains and MWNTs, postdrawing parameters were systematically investigated: temperature, drawing speed and elongation. The best improvements in terms of elastic modulus and yield strength were measured at 140°C and 500% elongation, whereas drawing speed was shown to have a negligible effect. It was confirmed through electron microscopy and X‐ray diffraction that these enhancements were mainly induced by the alignment of the polymer chains along the fibers' axis. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4375–4382, 2013     

Epoxy resin nanocomposites reinforced with ionized liquid stabilized carbon nanotubes

Epoxy resin nanocomposites reinforced with three different ionic liquid functionalized carbon nanotubes (f-CNTs) were fabricated by an in situpolymerization method. The influence of the anions on the curing process was studied through differential scanning calorimetry (DSC) and normalized Fourier transform infrared (FTIR) spectroscopy. The composition of the nanocomposites was analyzed by X-ray photoelectron spectroscopy. Two different mechanisms are proposed to explain the curing process of the neat epoxy and its composites. The electric conductivity and mechanical properties of the nanocomposites are also reported. The tensile strength was increased dramatically due to the insertion of f-CNTs. Scanning electron microsopy fracture surface analysis indicates a strong interfacial bonding between the carbon nanotubes and the polymer matrix.     

Carbon nanotubes for optical limiting

This paper reviews the optical limiting properties of carbon nanotubes. The nonlinear optical properties of nanotubes were investigated in water and in chloroform suspensions. Nonlinear transmittance measurements were reported for various pulse durations and wavelengths and show that carbon nanotubes are good candidates for effective optical limiting over broad temporal and laser energy ranges. Z-Scans and pump-probe time-resolved experiments were achieved to identify the origin of optical limiting in nanotubes. The main phenomenon is a strong nonlinear scattering, originating from solvent vapour bubble growth and sublimation of nanotubes at high fluences. Heat transfer from particles to solvent is particularly effective as compared to carbon black suspensions because of the large surface area of the carbon nanotubes.     

Investigation on morphology and properties of melt compounded polyoxymethylene/carbon nanotube composites

Polyoxymethylene nanocomposites containing different contents of carbon nanotubes were produced by a two‐step melt compounding process using a twin‐screw extruder. The dispersion quality, thermal and mechanical properties, and the creep as well as the tribological behaviors of the nanocomposites were investigated. Morphological investigations show that the masterbatch dilution process significantly improves the dispersion quality of carbon nanotubes within polyoxymethylene matrix, and as a consequence, enhanced mechanical properties and creep resistance are gained. Furthermore, to predict the long‐term property based on the short‐term experimental data, the time–temperature superposition principle and Findley model were used. Master curves with extended time scale are constructed using time–temperature superposition principle to horizontally shift the short‐term experimental data. The simulated results confirm the reinforced creep resistance by incorporation of the carbon nanotubes into the polymer matrix even at extended long time scale. By contrast, the tribological performance of polyoxymethylene was remarkably impaired after adding carbon nanotubes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42639.     

Ionic liquid assisted polyetheretherketone-multiwalled carbon nanotubes nanocomposites: An environmentally friendly approach

Reinforcement of PEEK by nanoparticles such as multiwalled carbon nanotubes (MWCNTs), is a promising technique to prepare PEEK nanocomposites with improved properties for promising biomedical applications. However, proper dispersion of MWCNTs in the polymer matrices is a primary processing challenge. The present study reports a novel and environmentally beneficial approach for homogeneous dispersion of MWCNT in PEEK by using ionic liquid (IL) 1-ethyl-3-methylimidazolium hydrogen sulfate ([EMIM][HSO₄]). Neat PEEK, PEEK-MWCNTs (using conventional organic solvent dimethylformamide), and PEEK-MWCNTs-IL (using [EMIM][HSO₄]) nanocomposites were fabricated via melt-compounding and compression molding techniques. The fabricated composites were characterized for morphological, thermal, and mechanical properties and compared to those of neat PEEK and PEEK-MWCNTs. Ionic liquid provoked proficient dispersion of the MWCNTs in PEEK, as confirmed by FESEM and optical micrographs. The thermal stability of PEEK-MWCNTs-IL composite was significantly superior to that of the neat PEEK and PEEK-MWCNTs. Analysis of tensile strength and nanoindentation depicted that the modulus of elasticity of PEEK-MWNCTs-IL was significantly increased by 76% as compared to that of neat PEEK. We believe that the present work could provide a new and green platform for the manufacturing of PEEK nanocomposites with enhanced dispersion of nanofillers for biomedical applications.     

Mechanical and morphological characterization of polymer-carbon nanocomposites from functionalized carbon nanotubes

Carbon nanotubes were functionalized with poly(vinyl alcohol) (PVA). The water-soluble PVA-functionalized carbon nanotubes were then embedded into PVA matrix via a wet-casting method, resulting in polymer-carbon nanocomposite films with homogeneous nanotube dispersion. Composites with pristine and functionalized nanotubes were tested in tension. It was found that the mechanical properties of these nanocomposite films were significantly improved compared to the neat polymer film. Functionalization allowed good distribution of the nanotubes in the matrix, leading to higher film strength. Scanning electron microscopy shows an apparent good wetting of the nanotubes by the PVA matrix. These results are supportive of good interfacial bonding between the functionalized carbon nanotubes and the hosting polymer matrix.     

Improving glass-fiber epoxy composites via interlayer toughening with polyacrylonitrile/multiwalled carbon nanotubes electrospun fibers

The development of innovative engineered epoxy composites aiming to manufacture cost-efficient materials with reduced weight and enhanced physical properties remains as a current industrial challenge. In this work we report an original procedure for manufacturing glass-fiber epoxy reinforced nanocomposites (GFECs) by employing electrospun fiber-mats as a reinforcing phase. These fibers have been produced from polyacrylonitrile and multiwalled carbon nanotubes solutions. Optimal protocols are designed by combining Taguchi method with the morphological, structural and mechanical properties obtained by scanning electron microscopy, profilometry and tensile tests. It is demonstrated that GFECs fabricated using GF800 glass fiber show an improvement/enhancement of the mechanical properties with a fracture strain up to 500 MPa (around 20% higher than the non-reinforced epoxy composite counterpart). It is also shown that GFECs fabricated using GF3M glass fiber exhibited a reduction of the roughness up to 56%, which corresponds with a roughness improvement from N8 to N7 following the guidelines provided by the ISO 1302. These results suggest that this type of nanocomposites would be suitable to be used in the aeronautics and automotive industries.