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Carbon nanomaterials (CNMs) have recently been used to form superhydrophobic coatings on metals, synthetic polymers or textiles. Here we investigate the possibility of using carbon black (CB), graphene (Gr) and carbon nanotubes (CNTs), as water repellent agents on naturally hydrophilic wood. We show that it is possible to form homogeneous CNM coatings on any type of wood via simple methods of drop casting and dip coating, using CNMs dispersed in organic solvents or water. Contact angle measurements of wood coated with only 0.05 g/m 2 CNTs and 0.25 g/m 2 Gr gave the results exceeding 130°, indicating apparent hydrophobicity. Yet, high adhesion of the droplets was observed, simultaneously suggesting a “rose petal” type of superhydrophobic behavior. That may be explained by the formation of micro-nano architectures in which low surface energy CNMs deposited on microrough surface of wood cause superhydrophobicity. Yet, due to heterogeneity of wood, some part of hydrophilic surface is still uncovered, resulting in high adhesion of water. Finally, although Gr and CNT were only physically bond to wood surface, the hydrophobic properties of CNM coatings were maintained after sandpaper abrasion test. Moreover, wood fibers and particles covered with Gr showed the decrease of water absorption equal 98% and 87%, respectively.

The human activity of heating homes contributes a significant amount of CO2 in the total of the UK Green House Gases and the process of retrofitting residential stock and equipping new dwellings with lower and carbon neutral technologies could be complex, costly and physically challenging. This paper investigates the feasibility of a composite mixture of carbon nanotubes (CNT) and graphene material applied as a printed layer to the underside of a cementitious flooring substrate, acting as a radiant underfloor heater. Screening sample tests confirm instant radiant heating at low DC voltages with remarkably low conduction heat losses through the substrate.

The surrounding gas atmosphere can have a significant influence on the electrical properties of multi-walled carbon nanotube (CNT) ensembles. In this study, we subjected CNT films to various gaseous environments or vacuum to observe how such factors alter the electrical resistance of networks at high temperatures. We showed that the removal of adsorbed water and other contaminants from the surface under reduced pressure significantly affects the electrical conductivity of the material. We also demonstrated that exposing the CNT films to the hydrogen atmosphere (as compared to a selection of gases of inert and oxidizing character) at elevated temperatures results in a notable reduction of electrical resistance. We believe that the observed sensitivity of the electrical properties of the CNT films to hydrogen or vacuum at elevated temperatures could be of practical importance.

We report on the development of a method of formation of free-standing gold-carbon nanotube (CNT) composites. It is based on a quick and simple decoration of CNT films with the application of chloroauric aqueous solution. Flexible and conductive macroassemblies of any size and shape can be created with ease. Addition of as little as 1% of Au by weight allowed for reduction of resistance by more than a quarter. Higher Au doping resulted in further decrease of resistance, but not so significant. From the practical point of view, these composites are a new type of materials with high electrical conductivity, but also offer resistance to corrosion.

Individual carbon nanotubes are highly interesting electrical conductors which could well complete with superconductors. Yet, the possibility of production of top-performance carbon nanotube electrical conductors beyond nanoscale, is the question currently challenging scientists. This study discusses theoretical potential of macroscopic fibres made purely of carbon nanotubes, in charge transport and electrical applications. It also examines various aspects of their electrical conductivity including both direct and alternating current transport, weight-conductivity ratios, current density and doping issues. The reasons for the constraints in electrical transport in fibres manufactured today are explained, as are possible routes to achieving significant improvements in the performance.

This research details the spontaneous electroless and electrodeposition of copper onto carbon nanotube (CNT) film from a copper sulfate electrolyte. Inhomogeneous electrodeposition was found to occur on pristine CNT film due to differences in available active nucleation sites and the hydrophobic nature of the film. In order to improve the electrochemical response of CNT films, oxidative pre-treatments such as heat treatment and anodization were investigated. These treatments were shown to increase the amount of oxygen containing defects at the surface of CNT film material. Incorporation of functional groups were shown to enhance the wetting of the aqueous electrolyte and created a highly active surface suitable for homogenous electrodeposit. Cathodic polarization curves showed that the presence of functional groups decreased the required level of polarization for copper deposition. Nevertheless, after a certain level of functionalization the polarization starts to decrease due to increased resistivity of the CNT film. Oxygen grafted CNT films were also shown to exhibit enhanced adsorption and reduction of copper without applied voltage due to redox replacement reactions, which were observed to increase with enhanced levels of functionalization.

Carbon nanotubes (CNT) fibres were printed from liquid suspension. The resulting fibres are highly conductive, with conductivity close to the one of standard CNT fibres, flexible and very versatile. The printed fibres are comparable to fibres that can be gained from direct spinning, carpet spinning and spinning from superacids, but offer broader range of composition and are simpler and safer to produce as no high-temperature equipment and dangerous chemicals need to be used. Any CNT material can be implemented, allowing the use of a variety of CNT structures, different densities of the fibres and various shapes for the final product. Keywords: Carbon nanotubes, Electrical conductivity, Macroassemblies, Fibre, Tape

International audience; Microwave plasma splitting of biogas to solid carbon forms is a promising technique to produce large quantities of sustainable carbon based nano materials. Well defined graphitic nano carbons have been produced exhibiting graphene multilayers in turbostratic packing. After heat treatment, the purified material has been used to formulate stable, aqueous dispersions. These dispersions are used directly as inks, allowing the preparation of conductive membranes with remarkable resistivity. Nano carbonsderived by plasma processes constitute a promising alternative to carbon black because they can be prepared from renewable sources of methane or natural gas, are calibrated in size, exhibit high conductivity, and have promising perspectives for chemical and material science purposes.

In this study we examine multiwall carbon nanotube (MWCNT) based nanosystems i.e. aligned MWCNT matrices, as potential scaffolds for cell growth and tissue engineering. We present the effect of samples purification and surface modification on the viability, adhesiveness and morphology of human normal gingival fibroblasts (HGF-1) and human osteosarcoma (U2OS) cell lines. We employ spectroscopic and analytical techniques (Scanning Electron Microscopy, Thermal Gravimetric Analysis, Atomic Force Microscopy, Raman and Fourier Transform Infrared Absorption Spectroscopy and Confocal Microscopy) in order to characterize the obtained structures. Furthermore, we analyze the expression level of selected cell adhesion-related genes by the quantitative real-time (qRT-PCR) method and the cell viability for MWCNT powders. We show that the surface structure of MWCNTs carpets contributes to the adhesion of cells. Additionally, we report the increased expression level of integrin, talin and fibronectin, proteins which are involved in cell attachment. We speculate that carbon nanotube based materials can be consider as potential candidates for biomedical purposes and as a biocompatible scaffold for cell growth.

Working towards improvement of the electrical performance of carbon fibre (CF) reinforced polymer composites used in aircrafts, we have developed new routes of production of hybrid carbon nanotube (CNT)/CF epoxy composites. It was shown that the use of CNT films produced via one-step chemical vapour deposition (CVD) based method and in-process control of films morphology combined with standard vacuum bagging based manufacture of the composites results in very good electrical performance of the final material, delivering high potential for lightning strike related applications including electromagnetic interference (EMI) shielding and static dissipation for the composite components used in aerospace and transport sector. Simultaneously, the process is much simpler, inexpensive and easy to upscale than previously proposed methods.

Copper is probably one of the most important metal used in the broad range of electronic applications. It has been developed for many decades, and so it is very hard to make any further advances in its electrical and thermal performance by simply changing the manufacture to even more oxygen-free conditions. Carbon nanotubes (CNTs) due to their excellent electrical, thermal and mechanical properties seem like an ideal component to produce Cu-CNT composites of superior electrochemical performance. In this report we present whether Cu-CNT contact has a beneficial influence for manufacturing of a new type of carbon-based supercapacitor with embedded copper particles. The prepared electrode material was examined in symmetric cell configuration. The specific capacity and cyclability of composite were compared to parent CNT and oxidized CNT.

Copper–CNT (carbon nanotube) composite materials are promising alternatives to conventional conductors in applications ranging from interconnects in microelectronics to electrical cabling in aircraft and vehicles. Unfortunately, exploiting the full potential of these composites is difficult due to the poor Cu–CNT electro-mechanical interface. We demonstrate through large-scale ab initio calculations and sonication experiments that this problem can be addressed by CNT surface modification. Our calculations show that covalent functionalization of CNTs below 6.7 at% significantly improves Cu–CNT wetting and the mechanical properties of the composite. Oxidative pre-treatment of CNTs enhances the Young's modulus of the composite by nearly a factor 3 above that of pure Cu, whereas amination slightly improves the electrical current density with respect to the unmodified Cu–CNT system in the high bias regime. However, only nitrogen doping can effectively improve both the mechanical and electrical properties of the composite. As the experiments show, consistent with the calculations, substitutional doping with nitrogen effectively improves adhesion of the CNT to the Cu matrix. We also predict an improvement in the mechanical properties for the composite containing doped double-wall CNTs. Moreover, the calculations indicate that the presence of nitrogen dopants almost doubles locally the transmission through the nanotube and reduces the back scattering in the Cu matrix around the CNT. The computed electrical conductance of N-doped Cu–CNT “carpets” exceeds that of an undoped system by ∼160%.

First, sputtering deposition of Au, Ag, Pt and Pd resulted in changes to the electrical resistance of carbon nanotube (CNT) films due to electron localization followed by creation of percolation pathways. Metal-CNT composites created this way showed different reaction of electrical resistance to temperature as well as thermal stability. Furthermore, their surface properties show much higher affinity towards aqueous media than as-made CNT films. Finally, we have developed an easy way of tailoring the size of metal clusters on the surface of CNT films depending on the employed deposition and heating conditions. Electrothermal sintering yielded metal clusters of controlled size that showed big potential for the application in catalyst-assisted chemical transformations.

Aligned carbon nanotube fibers are macroscopic materials with remarkable properties, such as high specific strength, stiffness, extreme flexibility as well as electrical and thermal conductivity. It is demonstrated that when subjected to negative potentials, these structures undergo the process of swelling in which the increase of their external dimension is observed. Swelling is believed to be caused by cation insertion in the process similar to intercalation. The efficiency of swelling was determined both in organic and aqueous solutions of different pH. Chronocoulometry was used as the technique to monitor the charging-discharging processes of swollen ACNT fibers in a presence of different electrolytes, i.e. LiCl, NaCl and KCl. The possibility of performing the charging-discharging cycles multiple times indicates that the swollen ACNT fibers can be considered as an advantageous material for electrodes in ion batteries and supercapacitors. Keywords: Aligned carbon nanotubes, Swelling, Intercalation, Charging, Discharging

Electrochemical deposition of copper on a carbon nanotube (CNT) fiber from a copper sulfate – sulfuric acid bath was studied in order to produce a carbon nanotube-copper composite wire. The high resistivity of the aerogel-spun fiber causes a non-uniform current distribution during deposition, which results in a drastic drop in the copper nuclei population density as sufficient overpotential is not available beyond a certain distance from the current feed point. Copper was found to fill the pores between CNT bundles from Focused Ion Beam (FIB) cut cross-sections confirming that aqueous based electrolytes can fill micropores between as-spun CNTs in a fiber network. The speed at which copper grows on the fiber surface was identified at ca. 0.08 mm/s with 1 mA applied current. The copper cladding showed columnar growth with a grain size an order of magnitude higher than the CNT-Cu region. The resulting composite was found to have specific conductivity similar to that of pure copper i.e. 98% of copper with 0.2 w-% of CNT, exhibiting a ninefold increase from the pure CNT fiber. Self-annealing was shown to decrease the resistance of the composite.

In this work, functionalized Multiwall Carbon Nanotubes of specified length and containing well-defined iron particles (O-MWCNT/Fe) were prepared. A significant enhancement in contrast in Magnetic Resonance Imaging was found for the investigated composites. The magnetic characterization revealed the ferromagnetic nature of iron particles embedded within O-MWCNTs. The enhancement of the 1 H spin–spin relaxation time of MRI scans using hydrophilic O-MWCNT/Fe as potential contrast agents was estimated for selected dispersive media. Moreover, the cytotoxicity of the hybrids was studied in two cell lines, i.e. cancer cells (HeLa) and fibroblasts (GM07492). The intracellular impact of O-MWCNT/Fes in HeLa cells was observed after staining of selected organelles (nuclei and mitochondria). Significant changes in cell morphology were found for water soluble MWCNT/Fes with diameters above 30 nm.

Carbon nanotube fibres are a new class of materials highly promising for many electrical/electronic applications. The range of applications could be extended through the modification of their electrical transport properties by inclusions of foreign materials. However, the changes in electrical transport are often difficult to assess. Here, we propose that the analysis of resistance–temperature dependencies of modified fibres supported by a recently developed theoretical model may aid research in this area and accelerate real life applications of the fibres.

Carbon nanotube assemblies are expected to find application in many areas of technology. Therefore, it is of paramount importance to understand and predict their performance in different ambient conditions. Here, we explore the influence of air exposure on the electrical conduction in carbon nanotube fibres and films produced via floating catalyst chemical vapour deposition. We recognise that on top of the previously well-explored oxygen doping effect these macroscopic materials are also significantly affected by humidity. The adsorption of water vapour causes an increase in the weight of the assemblies, increase in electrical conductivity at room temperature or changes in the resistance-temperature dependence at low temperatures. It is suggested that the water vapour is mainly adsorbed by the standard clustering mechanisms observed in other carbon materials, but the mechanisms responsible for the improvement in electrical performance are much more debatable. We present a strong indication that the carbon nanotubes are neither n-doped nor p-doped by water molecules and provide further discussion on the potential role of water in the electrical transport of carbon nanotube assemblies.

We developed the first self-heated catalytic membrane made of carbon nanotubes (CNT) and used it for steam reforming of alcohols. After exploring a variety of Ni catalyst preparation methods, we selected the most promising route and made Ni@CNT membranes. Then, we used them to produce hydrogen from methanol, ethanol and iso-propanol whilst current was passed through to deliver thermal energy required for the catalytic reaction to take place. By employing Joule heating, we were able to reach temperatures up to about 450 °C and probe the catalytic activity of the system. Despite that such self-heated metal–CNT hybrid is still in early phase of development, it has already shown promises for microscale steam reforming and many other chemical transformations that require efficient and uniform heating conditions.

The process of conjugated polymer deposition on the surface of horizontally aligned multi-walled carbon nanotube, HA-CNT, electrode is described. Poly(3,4-ethylenedioxythiophene), PEDOT, was grown electrochemically under variable conditions in both aqueous and non-aqueous solutions of selected electrolytes. It is shown that the mechanism of nucleation highly depends on the reaction environment. The presence of a surfactant or non-aqueous medium favors the process of progressive nucleation in which the polymer growth is uniform and a homogeneous film of PEDOT is formed. It is demonstrated that the conditions make it is possible to cover the outer walls of individual HA-CNTs instead of forming thick polymer layer. The application of overpotential is proven to be a necessary condition to generate radical cations and cause relatively fast growth of polymer layer.

The electrical transport of a carbon nanotube assembly is determined by its morphology and composition. These vary with the assembly production processes and post-process treatments applied. Here, we present the study of the electrical – structural dependence of wire like assemblies of carbon nanotubes i.e. carbon nanotube fibres produced via floating catalyst chemical vapour deposition processes. We propose that the analysis of resistance – temperature characteristics of the fibres provides vast amount of information for the assessment of the quality of the fibres and thus the efficacy of fibre production and post-production processes. To aid qualitative and quantitative analysis of the experimental results we propose a new universal model which allows the fitting of experimental data in the full range of temperatures and a straightforward comparison of the recorded characteristics.

We explored high-field (60 T) magneto-resistance (MR) with two carbon nanotube (CNT) material classes: (1) unaligned single-wall CNTs (SWCNT) films with controlled metallic SWCNT concentrations and doping degree and (2) CNT fiber with aligned, long-length microstructure. All unaligned SWCNT films showed localized hopping transport where high-field MR saturation definitively supports spin polarization instead of a more prevalent wave function shrinking mechanism. Nitric acid exposure induced an insulator to metal transition and reduced the positive MR component. Aligned CNT fiber, already on the metal side of the insulator to metal transition, had positive MR without saturation and was assigned to classical MR involving electronic mobility. Subtracting high-field fits from the aligned fiber’s MR yielded an unconfounded negative MR, which was assigned to weak localization. It is concluded that fluctuation induced tunnelling, an extrinsic transport model accounting for most of the aligned fiber’s room temperature resistance, appears to lack MR field dependence.

Films and fibers made of carbon nanotubes were found to be promising materials for future electrical and electronic engineering. Despite of many advantages provided by these materials, they are not without problems. The biggest issue is that the macroscopic CNT structures, such as films or fibers, have much lower electrical conductivity values than it is for individual carbon nanotubes. And therefore researchers worldwide try to increase electrical properties of those macroscopic structures. One of the approaches scientists are currently investigating is chemical doping. Despite chemical doping has been already reported there is still a huge list of compounds that are capable to increase the conductivity values and has not been tested yet. In this work one of such compounds has been examined. It is a strong p-dopant 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). The solution of F4TCNQ in three different solvents (chloroform, acetic acid and dimethylsulfoxide) has been prepared and applied on purified CNT films. Both electrical conductivity and specific conductivity was measured. The best electrical conductivity value achieved is 5,24·106 S·m-1. Samples were also observed under SEM.

Improving the interface between copper and carbon nanotubes (CNTs) offers a straightforward strategy for the effective manufacturing and utilisation of Cu–CNT composite material that could be used in various industries including microelectronics, aerospace and transportation. Motivated by a combination of structural and electrical measurements on Cu–M–CNT bimetal systems (M = Ni, Cr) we show, using first principles calculations, that the conductance of this composite can exceed that of a pure Cu–CNT system and that the current density can even reach 1011 A cm−2. The results show that the proper choice of alloying element (M) and type of contact facilitate the fabrication of ultra-conductive Cu–M–CNT systems by creating a favourable interface geometry, increasing the interface electronic density of states and reducing the contact resistance. In particular, a small concentration of Ni between the Cu matrix and the CNT using either an “end contact” and or a “dot contact” can significantly improve the electrical performance of the composite. Furthermore the predicted conductance of Ni-doped Cu–CNT “carpets” exceeds that of an undoped system by ∼200%. Cr is shown to improve CNT integration and composite conductance over a wide temperature range while Al, at low voltages, can enhance the conductance beyond that of Cr.

The electronic properties of carbon nanostructures such as carbon nanotubes (CNTs) or graphene can easily be tuned by the action of various doping agents. We present an experimental study and numerical analysis of how and why metallic and semiconductive CNTs can be p-doped by exposing them to two interhalogens: iodine monochloride and iodine monobromide. Simple application of these compounds was found to reduce the electrical resistance by as much as 2/3 without causing any unfavorable chemical modification, which could disrupt the highly conductive network of sp2 carbon atoms. To gain better insight into the underlying mechanism of the observed experimental results, we provide a first principles indication of how interhalogens interact with model metallic (5,5) and semiconductive (10,0) CNTs.

We have demonstrated fire-retardancy properties of a polymer matrix-free CNT film for the first time. As compared with classical fire-retardant materials such as Kevlar, Twaron or Nomex, the CNT film showed a spectrum of advantages. The material is lightweight, flexible and well-adherent to even the most complicated shapes. The results have showed that by using CNTs for fire-retardancy we can extend the operational time almost two-fold, what makes CNTs a much better protection than the solutions employed nowadays. We believe that among other great properties of CNT, their macroscopic assemblies such as CNT films show significant potential for becoming a fire protective coating, which exhibits high performance in not sustaining fire.

Carbon nanotubes are very promising materials for many electrical and electronic application. Particularly, it is expected that macroscopic assemblies made purely of carbon nanotubes may form highly efficient and reliable electrical conductors for the next generation of electrical wires. It has already been demonstrated that wire-like nanotube assemblies—carbon nanotube fibres can successfully work as electrical wires, however, their performance needs further research and development. This paper presents the possible method of enhancement of electrical conductivity and current-carrying capacity of the carbon nanotube fibres via incorporation of silver nanoparticles into the nanotube network and formation of a hybrid carbon nanotube fibre–silver conductor.

The effect of the functionalization of multi-walled carbon nanotubes (MWCNTs) on the process of electrochemical co-deposition of MWCNTs and polypyrrole (PPy), as well as the morphology of obtained composites have been demonstrated. As the nanotube components of the hybrids, three types of MWCNT were used, namely c-CVD derived (pristine) MWCNTs, their oxidized counterparts MWCNT-Ox and pyrrole-modified MWCNT-Py. The stability of pristine and functionalized MWCNTs (f-MWCNT) dispersions in tetrahydrofuran and water was studied together with the description of the process of formation PPy/(f-)MWCNT hybrid materials via electrochemical co-deposition. The structural and morphological properties of the hybrids were characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy revealing substantial differences among hybrid materials in their surface morphology and the influence of MWCNT functionalization on the orientation of growing PPy chains.

Aligned carbon nanotube (CNT) polymer composites are envisioned as the next-generation composite materials for a wide range of applications. In this work, we investigate the erosive wear behavior of epoxy matrix composites reinforced with both randomly dispersed and aligned carbon nanotube (CNT) arrays. The aligned CNT composites are prepared in two different configurations, where the sidewalls and ends of nanotubes are exposed to the composite surface. Results have shown that the composite with vertically aligned CNT-arrays exhibits superior erosive wear resistance compared to any of the other types of composites, and the erosion rate reaches a similar performance level to that of carbon steel at 20° impingement angle. The erosive wear mechanism of this type of composite, at various impingement angles, is studied by Scanning Electron Microscopy (SEM). We report that the erosive wear performance shows strong dependence on the alignment geometries of CNTs within the epoxy matrix under identical nanotube loading fractions. Correlations between the eroded surface roughness and the erosion rates of the CNT composites are studied by surface profilometry. This work demonstrates methods to fabricate CNT based polymer composites with high loading fractions of the filler, alignment control of nanotubes and optimized erosive wear properties.

We report a new method to modify electrical properties of carbon nanotubes (CNTs). Single-, double- and multi-wall CNTs were subjected to treatment with a polar interhalogen compound, i.e. iodine monochloride (ICl) for 8 h at room temperature or briefly at 350 °C to assess kinetics and thermodynamics of the reactions. The results showed a powerful p-doping, which enabled us to decrease electrical resistance of the material by more than 60% eventually reaching specific conductivity of 1.24 S m 2 g −1 . Functionalization of CNTs with halogen atoms resulted in evident changes to the material microstructure and composition. To illustrate viability of this technique for manufacturing highly conductive wires, we have produced an ICl-doped CNT-based USB cable. The tests unequivocally revealed that the cable could be successfully used for power or data transmission on the verge of USB 2.0 capabilities.

We report an innovative approach to halogenation of carbon nanotube (CNT) films. Application of bias voltage across horizontally aligned CNT films resulted in the electrothermal effect, which enabled us to chemically modify CNT films at the entirely controlled range of temperatures up to 300 °C. Such heated CNT membranes were exposed to gaseous halogens (Cl 2 , Br 2 , I 2 ) whilst their electrical properties were monitored. The experiments were carried out at room temperature and 100–300 °C (in 50 °C steps) until no further change in electrical resistance could be seen. The procedure lasted less than one minute, during which we were able to successfully introduce up to 6.7%, 6.0% and 1.5% at. of Cl, Br and I into the CNT framework. In parallel, we observed a permanent increase in conductivity of the films and mild purification of the starting material due to the removal of various carbon–oxygen functional groups.

We determine the three-dimensional structure of melt-mixed carbon nanotube (CNT) networks in an amorphous polymer matrix via confocal microscopy and image analysis. We find that the CNT networks consist of ramified clusters whose size distribution scales with cluster mass according to exponents typical of percolating systems. Remarkably, these scaling relationships hold over a wide range of concentrations, processing operations (squeezing, shearing, annealing) and subsequent electrical conductivity levels. Our results suggest that the power law scaling of cluster mass with size and frequency might be an important principle governing multi-wall carbon nanotube (MWCNT) structure in processed composites. We suggest that subtle changes in MWCNT-polymer interface structure may play a significant role in composite electrical direct current DC conductivity. Also, we find that residual flow plays a key role in the phenomenon of conductivity recovery during post-process annealing.

The effect of annealing on multi-walled carbon nanotube (MWCNT) arrays grown via catalytic Chemical Vapour Deposition ( c -CVD) was studied. The treatment enabled to decrease number of defects/imperfections in the graphene walls of MWCNTs’, which was reflected in Raman spectroscopy by reduction of the I D / I G ratio by 27%. Moreover, the vertical alignment from the as-synthesized nanotube arrays was found intact after annealing. Not only graphitization of the nanotube walls occurred under annealing, but the amount of metal iron-based catalyst residues (interfering with numerous physicochemical properties, and hence applications of MWCNTs) was reduced from 9.00 wt.% (for pristine MWCNTs) to 0.02 wt.% as detected by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). This value, established by a new analytical protocol, is the lowest recorded by now for purified c -CVD MWCNTs and, due to operating under atmospheric pressure, medium temperature regime (as for annealing processes), reasonable time-scale and metal residue non-specificity, it could lay the foundation for commercial purification of c -CVD derived MWCNTs.

The production of continuous fibers made purely of carbon nanotubes has paved the way for new macro-scale applications which utilize the superior properties of individual carbon nanotubes. These wire-like macroscopic assemblies of carbon nanotubes were recognized to have a potential to be used in electrical wiring. Carbon nanotube wiring may be extremely light and mechanically stronger and more efficient in transferring high frequency signals than any conventional conducting material, being cost-effective simultaneously. However, transfer of the unique properties of individual CNTs to the macro-scale proves to be quite challenging. This Feature Article gives an overview of the potential of using carbon nanotube fibers as next generation wiring, state of the art developments in this field, and goals to be achieved before carbon nanotubes may be transformed into competitive products.

The excellent electrical and mechanical performance of individual carbon nanotubes combined with their extremely low weight make these structures highly interesting materials for electrical wiring applications. The recent manufacture of macroscopic wire-like assemblies made purely of carbon nanotubes – carbon nanotube fibres – has opened up new prospects in this area. The extensive research on the optimization of the morphology of the fibres indicates that it will be soon possible to produce carbon nanotube fibres exceeding both the electrical and mechanical performance of conductive metals currently used in electrical engineering. To enable the application carbon nanotube fibres as wires in everyday electrical circuits it is necessary to provide them with electrical insulation. This paper proposes, for the first time, a method of insulation of the fibres and analyses the parameters which control the successful development of insulating coating on the surface of these highly porous carbon materials. It is shown that the applied insulation does not compromise either the electrical or mechanical performance of the fibres. The proposed insulation method is inexpensive, easy to integrate into a production process for the carbon nanotube fibres and it can be scaled up.

We have developed a benign technique for the modification of electrical and structural properties of horizontally aligned carbon nanotube (CNT) films. The as-made CNT films were immersed in 30 %wt aqueous solution of hydrogen peroxide whilst current was passed through the nanotube bundles to bring the temperature of CNTs up to 200 °C. Depending on the employed conditions, we either successfully removed extraneous material contaminating CNT films and decreased its resistance by 40% or initiated the introduction of functional groups. The whole process lasted only for 1 min and was more straightforward, less expensive and more ecologically friendly than the current post-processing technologies. We imagine that such a method of tweaking up electrical and/or structural properties could be successfully employed to a range of nanomaterials with a particular focus on carbon C-sp2 nanostructures.

A melt processing route was successfully applied in the manufacturing of aligned multi-wall carbon nanotube/isotactic polypropylene (MWCNT-iPP) composites. As high as 25 wt% content of the catalytic Chemical Vapour Deposition (c-CVD) derived nanotube filler could be introduced into the iPP matrix. The composite was characterised by a practically retained nanotube alignment as well as an enhanced crystallisation of iPP. Analysis of the phase iPP composition in the composite using XRD and DSC revealed a dominating α-phase with polymer molecules uniaxially oriented in the same direction as the nanotube alignment. Furthermore, kinetic in situ Synchrotron XRD studies verified that the enhanced crystallisation was induced mainly by shear stress occurring in the initial stage of infiltration MWCNT arrays by flowing molten polymer and, to a lesser extent, by the template-based growth of iPP crystallites.

With current level of development, mankind is about to face many energy-related problems unless we find ways for more efficient power generation and transmission. In this paper, we depicted the operation of high- performance carbon nanotube film heaters, which show a clear advantage over traditionally employed materials. The material was synthesized by a facile one-step method and used as resistive heating element. The results have shown very effective conversion of electric power into heat. To improve the homogeneity of the heaters electrical resistance, we explored a selection of volatile solvents. Such a pretreatment step prior to heaters use caused densification of the material and favorable changes to the electrothermal behavior.

For electromagnetic absorbing and shielding applications, carbon nanotubes (CNT) are widely used due to their excellent electrical and physical properties. Fabrication of microwave absorbing materials involves the use of compounds capable of generating dielectric and/or magnetic losses when impinged by an electromagnetic wave. The presence of lattice defects e.g. vacancies and dislocations contributes to the loss and attenuation in the electromagnetic waves, which in turn remarkably enhance the absorption ability of the material. With the CVD technique which is known to produce several lattice defects in the final product, aligned MWCNTs were successfully synthesized by pyrolizing toluene and ferrocene in an inert argon environment. The morphology analysis of the aligned MWCNTs was conducted via FESEM and TEM analysis, to reveal the average length of approximately 295 μm, with diameters in the range of 60-200 nm. EDS analysis indicates the high yield of CNTs, with more than 90% in weight composition, with less than 5 % Fe impurities presence. Textural properties of MWCNTs were studied by measuring pore size and BET surface area. To understand the response of CNTs to an electromagnetic field, permeability and permittivity measurement were conducted in the frequency range of 100 Hz to 110 MHz. In conclusion, the presence of defects in MWCNTs is desirable for enhanced electromagnetic absorption ability.

Field emission (FE) measurements are reported from carbon nanotube (CNT) fibers and laser-patterned free standing films fabricated by direct online condensation from a floating catalyst chemical vapor deposition reactor. Fiber and film cathodes showed stable emission in the 1–2 mA current (I) range at maximum cathode temperatures less than 1000 °C; film cathodes show localized heating at the triangular tips and higher maximum temperatures than the fibers. Fowler-Nordheim (FN) analysis indicated a change in the morphology of the emitters with increasing external electrical field (Eext). Fiber cathode I-Eext data are interpreted as FN emission from the fiber tip which is eventually limited by space-charge effects. At higher Eext, FN emission from the fiber sidewall occurs. The single fiber cathode stopped emitting abruptly when field induced self-heating effects became significant. For CNT films, self-heating effects can destroy a portion of the film, but FE can still occur from other areas.

We developed carbon nanotube wires (CNWs) and monitored in situ their electrical properties at high temperature conditions for the first time. The dominant type of CNTs present in the material and packing density of thereof proved to have a dominant effect on the thermal stability of CNWs. Furthermore, we showed that kinetics of CNW oxidation plays an important role and slow heating rates or prolonged heating times are essential for the proper determination of thermal stability of CNTs. To enhance the stability at high temperatures, we applied SiC coating onto the CNWs, what allowed a 300 °C improvement to the operational window, eventually reaching 700 °C in the long-haul. Correlation of the change in electrical properties with thermogravimetric response showed that the loss of electrical percolation takes place at 100 °C lower temperature than the last observed weight loss in CNTs content. Finally, we demonstrated feasibility of SiC-coated CNWs under high temperature conditions, by creating a heating device out of them. The presence of SiC layer gave rise to a significant improvement to the thermal stability of the CNT heaters, which now offer unprecedented range of operation reaching 700 °C, as compared to 400 °C when uncoated.

Fe3þ ions were anchored via complexation onto the oxidized multiwall carbon nanotubes containing encapsulated iron-based nanoparticles (Fe@O-MWCNTs) yielding hybrids Fe(III)/Fe@O-MWCNTs for application as MRI contrast agents. After washing, no free Fe3þ ions were observed in the solution. A 120 mg Fe3þ was coordinated by each 1 gram of Fe@O-MWCNTs with a formation of stable hybrids. Relaxation times T1 and T2 of water protons were measured for the suspensions of hybrids. At 7.1 T relaxivity, r2 of Fe@O-MWCNT and Fe(III)/Fe@O-MWCNT was 25 and 35 s -1 ml mg -1 , respectively, whereas at 0.4 T r2-values were equal. Additionally, T1/T2 ratio was found in a range of 17-104, which is a promising value in the light of application of the proposed materials as potential T2 MRI contrast agents.

A novel chemical approach was established to produce carbon nanotube/Nylon-6,6 hybrid materials from readily available substrates, that is, Nylon-6,6 salt and oxidized multiwall carbon nanotubes (O-MWCNTs). The key synthetic precursor hexane-1,6-diaminium adipate and “carbon nanotubate”—“Binary nanotube salt”—was obtained and isolated as stable and easy-to-handle solid in over 80% yield and with no nanotube losses. The final hybrid materials of various nanotube loadings were synthesized at 270°C and were easily purified from the homopolymer. Purified hybrids were comprehensively analyzed (yields and grafting ratios, SEM, TEM, FT-IR) revealing a two-phase characteristics—individually grafted nanotubes and cross-linked nanotube material. Isothermal TGA kinetic studies showed that in the “binary salts” diamine and diacid molecules were anchored to the nanotube outer shells and then held electrostatically enabling growth of polymer immobilized on O-MWCNTs (“grafting-from” mechanism). Depending on the density and type of nanotube functionalities and filler concentration in the “binary salt,” the O-MWCNT/Nylon-6,6 hybrids can be treated as hybrid material of a proportion of aliphatic polyamide and polyaramide properties. POLYM. COMPOS., 35:523–529, 2014. © 2013 Society of Plastics Engineers

Carbon nanotube/tungsten dioxide (CNT/WO2) hybrids were prepared by in-situ formation and coating of WO2 nanoparticles on CNTs using two alternative routes, both based on an aqueous solution processing technique and carried out at room temperature. In the first route, functionalized CNTs were used, whereas the other utilized pristine CNTs with benzyl alcohol as a surfactant to enhance the adhesion of nanoparticles. Microstructural and phase characterizations of the samples were carried out using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. For both types of CNTs, a 30% ethanol-70% water solution led to continuous coatings, however, weaker interaction between the CNTs and oxide particles was obtained when pristine CNTs were used for coating. Moreover, it was seen that the amount of ethanol in the solution had a crucial role on forming the coating when pristine CNTs were used.

Carbon nanotubes, with their unique physical properties, have the potential to outperform conventionally used electrical wiring metals. Any improvement in this area of technology would be of great importance to industry, the economy, and the environment, as the global need for electrical energy and its efficient transfer and conversion rapidly increases. Carbon nanotube fibers, which are assemblies made purely of carbon nanotubes, can uniquely be used in macroscopic electrical applications including electrical wires and devices where the operation is enabled by these conductors. This paper presents details of the working prototype of an electrical machine, a transformer, where conventional copper wires have been replaced with conducting wires made purely of carbon nanotube fibers.

We report a simple approach of tailoring electronic properties of carbon nanotube (CNT) films. The process was carried out in the gas phase using fuming nitric acid vapors, gases generated from piranha solution or ozone in high and low concentration in O2 as reactants. The results showed a significant alteration in terms of electrical resistance, wherein it was changed by –50% up to +1,300% depending on the employed conditions. Furthermore, as a result of chemical functionalization of the CNT backbone, we witnessed changes to the sample morphology both on the micro- and nanoscale, what could be an asset. Most interestingly, fuming HNO3 treatment introduced carboxylic and phenolic groups to the structure and as a result of hydrogen bonding, we observed bundling up of the material. This strategy could be a tool to yield CNT macroassemblies of predetermined electronic and structural properties without the need of problematic multi-step solution processing.

Electrothermal materials, which convert electric energy into heat have been known for many years now. They are the heart of plethora of devices surrounding us, but their isotropic structure does not allow for tailoring of operating conditions. The carbon nanotube film heaters developed in house were built for the first time on a counter-intuitive concept to pass electric current against the alignment axis. They render superior and time-independent performance reaching terminal temperature without lag. Just 1 mg of these ultra-light free-standing films outperforms 120 g of nichrome, most commonly used resistive material. They are envisioned to become the next generation heating materials particularly in the applications, in which weight (aviation and aerospace industry), size (microreactor technology) or speed (kinetic systems) is of importance.

We synthesized highly porous composite films of vertically aligned carbon nanotubes (CNTs) and polypyrrole (PPy) by employing a simple in situ electropolymerisation process from aqueous pyrrole solutions. By contacting the entire CNT array, each CNT acts as a highly active anode that facilitates uniform deposition and immediate polymerization of pyrrole directly on the CNT surface. As a result, each individual CNT was coated with a thin layer of PPy with a tunable thickness between 4 and 38 nm. At the same time the vertical array structure of the CNTs was preserved. A major advantage of this route is that the resulting composite film is highly porous and can be post-filled with other polymers, metals or ceramics to create new multifunctional composites and hybrid structures.

MWCNTs in the ‘nanotube–drug’ hybrids can play a role of carriers or additives (enhancers) in the more complex formulations. This work reviews qualitative and quantitative analyses of Drug Delivery Systems (DDSs) based on multi-wall carbon nanotubes (MWCNTs) and their chemically modified analogues (mainly oxidised MWCNTs). A special emphasis was placed on the chemical interactions between drug molecules and the nanotube carrier critical both in the stage of preparation/synthesis of the hybrids and liberation of the drug.