Multi-walled Carbon Nanotubes Network Research Articles

Engineering carbon nanotubes enhanced hydrophobic membranes with high performance in membrane distillation by spray coating

The commonly used commercial hydrophobic membranes are facing great challenges in wetting and low permeation when used in membrane distillation (MD) because of the limited materials and structures. To address these problems, we herein fabricated a kind of carbon nanotubes (CNTs) enhanced membrane with high flux and stable performance in membrane distillation, where a porous hydrophobic network of multi-walled carbon nanotubes (MWCNTs) was spray-coated onto the commercial flat-sheet hydrophobic membrane surface. Then, we systematically investigated the impact of the CNTs loading on the substrate surface properties, membrane structures and MD performance (flux and rejection), and experimentally illustrated the role of CNTs towards improving MD performance. Results illustrate that there is an optimal match of the CNTs spray amount with the substrate pore size and the substrate materials to achieve the maximum specific surface area of membrane, and thus the maximum flux and salt rejection of the resultant CNTs-enhanced membrane, which is governed by the interfacial energy of the CNTs and the substrate, and thus the CNTs packing density. Results find that the CNTs packing density decreases with the decrease of the substrate free surface energy, and the loosest CNTs packing is formed on the polytetrafluoroethylene (PTFE) membrane with the lowest free surface energy. Under the optimized conditions, the CNTs enhanced PTFE membrane exhibited salt rejection of >99.9% and water flux of 33.2 LMH in MD, which was three times as high as that of the pristine PTFE membrane under the temperature difference of 40 °C between hot and cold streams when operated in direct contact membrane distillation. Our research here provides an efficient method to enhance the permeation and stability of commercial membranes by spray-coating CNTs and also supplies some insights on the design of next-generation MD membranes.

Multi-Functional Properties of MWCNT/PVA Buckypapers Fabricated by Vacuum Filtration Combined with Hot Press: Thermal, Electrical and Electromagnetic Shielding.

The applications of pure multi-walled carbon nanotubes (MWCNTs) buckypapers are still limited due to their unavoidable micro/nano-sized pores structures. In this work, polyvinyl alcohol (PVA) was added to a uniform MWCNTs suspension to form MWCNT/PVA buckypapers by vacuum infiltration combined with a hot press method. The results showed an improvement in the thermal, electrical, and electromagnetic interference (EMI) shielding properties due to the formation of dense MWCNTs networks. The thermal and electrical properties rose from 1.394 W/m·k to 2.473 W/m·k and 463.5 S/m to 714.3 S/m, respectively. The EMI performance reached 27.08 dB. On the other hand, ABAQUS finite element software was used to simulate the coupled temperature-displacement performance. The electronic component module with buckypapers revealed a homogeneous temperature and thermal stress distribution. In sum, the proposed method looks promising for the easy preparation of multi-functional nanocomposites at low-cost.

Using a Novel Approach to Estimate Packing Density and Related Electrical Resistance in Multiwall Carbon Nanotube Networks.

In this work, we use contrast image processing to estimate the concentration of multi-wall carbon nanotubes (MWCNT) in a given network. The fractal dimension factor (D) of the CNT network that provides an estimate of its geometrical complexity, is determined and correlated to network resistance. Six fabricated devices with different CNT concentrations exhibit D factors ranging from 1.82 to 1.98. The lower D-factor was associated with the highly complex network with a large number of CNTs in it. The less complex network, having the lower density of CNTs had the highest D factor of approximately 2, which is the characteristic value for a two-dimensional network. The electrical resistance of the thin MWCNT network was found to scale with the areal mass density of MWCNTs by a power law, with a percolation exponent of 1.42 and a percolation threshold of 0.12 g/cm. The sheet resistance of the films with a high concentration of MWCNTs was about six orders of magnitude lower than that of less dense networks; an effect attributed to an increase in the number of CNT–CNT contacts, enabling more efficient electron transfer. The dependence of the resistance on the areal density of CNTs in the network and on CNT network complexity was analyzed to validate a two-dimension percolation behavior.

Impedance spectroscopy of short multiwalled carbon nanotube networks deposited on a paper substrate: tracking the evolution of in-plane and thru-plane electronic properties

Multiwalled carbon nanotubes (MWNT) were deposited via dropcasting and dried using vacuum filtration. Because of the slightly larger pore size (5–10 µm) of the paper substrate used as compared to the length of the nanotubes (0.5–2 µm), a variety of MWNT networks were formed both on the surface and through the thickness of the paper. Using a combination of impedance spectroscopy, equivalent circuit modeling, and microscopy techniques, it was possible to describe in detail how the electrical properties change as a function of how the MWNTs are distributed on the porous substrate by varying the number of deposited layers (1–20) as well as the dispersion concentration (0.1–5 mg/mL). In the in-plane, four different electrical responses were observed and modeled: (1) a substrate dominated spectrum representing unconnected MWNTs, (2) one that included bundle and junction responses as well as some inductances representing sparsely distributed MWNT networks, (3) followed by a parallel RL circuit for partially connected MWNT networks, and (4) finally a series RL circuit for fully connected MWNT networks. In the thru-plane, only two different electrical responses were observed and modeled. The results for the in-plane and thru-plane properties were used to generate percolation curves that show that electrical conductivity can change as much as 10 orders of magnitude for the same exact MWNTs. These results indicate that not only do the characteristics of the nanotubes themselves play a role but also the structure of the underlying substrate and the details of how the films are deposited.

Preparation and Characterization of Highly Elastic Foams with Enhanced Electromagnetic Wave Absorption Based on Ethylene-Propylene-Diene-Monomer Rubber Filled with Barium Titanate/Multiwall Carbon Nanotube Hybrid.

Hybrid ethylene-propylene-diene-monomer (EPDM) nanocomposite foams were produced via compression molding with enhanced electromagnetic wave absorption efficiency. The hybrid filler, consisting of 20 phr ferroelectric barium titanate (BT) and various loading fractions of multi-wall carbon nanotubes (MWCNTs), synergistically increased the electromagnetic (EM) wave absorption characteristics of the EPDM foam. Accordingly, while the EPDM foam filled with 20 phr BT was transparent to the EM wave within the frequency range of 8.2–12.4 GHz (X-band), the hybrid EPDM nanocomposite foam loaded with 20 phr BT and 10 phr MWCNTs presented a total shielding effectiveness (SE) of ~22.3 dB compared to ~16.0 dB of the MWCNTs (10 phr). This synergistic effect is suggested to be due to the segregation of MWCNT networks within the cellular structure of EPDM, resulting in enhanced electrical conductivity, and also high dielectric permittivity of the foam imparted by the BT particles. Moreover, the total SE of the BT/MWCNTs loaded foam samples remained almost unchanged when subjected to repeated bending due to the elastic recovery behavior of the crosslinked EPDM foamed nanocomposites.

Electro-mechanical properties of thermoplastic polyurethane films and tubes modified by hybrid carbon nanostructures for pressure sensing

Electrical and piezoresistive properties of hybrid nanocomposite films and tubes made of a segmented aliphatic polyurethane modified with multilayer graphene sheets (MLGSs), multiwall carbon nanotubes (MWCNTs), and hybrid mixtures of both, were investigated. Hybrid nanocomposites were fabricated at a total weight concentration () of 5 wt.%, with relative weight concentration of MLGSs with respect to MWCNTs ( of 25%, 50% and 75%. The electrical conductivity of these films is dominated by the MWCNT network, observing electrical MLGS-MWCNT collaborative effects only for = 25%. Dielectric impedance spectroscopy indicates that the nanocomposites display capacitive effects at frequencies higher than tens of Hz, which is explained by interfacial polarization. The burst pressure and circumferential stiffness of internally pressurized tubes fabricated from these films is slightly higher for tubes containing only MWCNTs. The strain fields in the pressurized tubes, determined by digital image correlation, showed localized strain gradients, and the piezoresistive response of the electro-conductive tubes was nonlinear. The highest pressure sensitivity factor (4.59 kPa−1) was obtained for hybrid nanocomposite tubes with = 25%.

Facile Fabrication of 3D Porous Sponges Coated with Synergistic Carbon Black/Multiwalled Carbon Nanotubes for Tactile Sensing Applications.

Recently, flexible tactile sensors based on three-dimensional (3D) porous conductive composites, endowed with high sensitivity, a wide sensing range, fast response, and the capability to detect low pressures, have aroused considerable attention. These sensors have been employed in different practical domain areas such as artificial skin, healthcare systems, and human–machine interaction. In this study, a facile, cost-efficient method is proposed for fabricating a highly sensitive piezoresistive tactile sensor based on a 3D porous dielectric layer. The proposed sensor is designed with a simple dip-coating homogeneous synergetic conductive network of carbon black (CB) and multi-walled carbon nanotube (MWCNTs) composite on polydimethysiloxane (PDMS) sponge skeletons. The unique combination of a 3D porous structure, with hybrid conductive networks of CB/MWCNTs displayed a superior elasticity, with outstanding electrical characterization under external compression. The piezoresistive tactile sensor exhibited a high sensitivity of (15 kPa−1), with a rapid response time (100 ms), the capability of detecting both large and small compressive strains, as well as excellent mechanical deformability and stability over 1000 cycles. Benefiting from a long-term stability, fast response, and low-detection limit, the piezoresistive sensor was successfully utilized in monitoring human physiological signals, including finger heart rate, pulses, knee bending, respiration, and finger grabbing motions during the process of picking up an object. Furthermore, a comprehensive performance of the sensor was carried out, and the sensor’s design fulfilled vital evaluation metrics, such as low-cost and simplicity in the fabrication process. Thus, 3D porous-based piezoresistive tactile sensors could rapidly promote the development of high-performance flexible sensors, and make them very attractive for an enormous range of potential applications in healthcare devices, wearable electronics, and intelligent robotic systems.

Growth mechanisms and related thermoelectric properties of innovative hybrid networks fabricated by direct deposition of Bi2Se3 and Sb2Te3 on multiwalled carbon nanotubes

Flexible thermoelectric generators are an emerging trend in the field of waste heat conversion, as well as wearable and autonomous devices. However, the energy conversion efficiency of the state-of-the-art flexible thermoelectric devices is too low for their wide application and commercialization. In this work, n- and p-type multiwalled carbon nanotube (MWCNT)-thermoelectric material hybrid networks that may become a promising building block for the fabrication of flexible thermoelectric devices are presented. The hybrid networks were fabricated by direct deposition of thermoelectric material (Bi2Se3, Sb2Te3) on the MWCNT networks using physical vapor deposition technique. Growth mechanisms of Bi2Se3 and Sb2Te3 on MWCNTs were investigated. The Seebeck coefficient and charge transport properties of MWCNT-Bi2Se3 and MWCNT-Sb2Te3 hybrid networks were studied as function of MWCNT wt% in the networks. Variable-range hopping models were applied for the interpretation of conductance mechanisms in the hybrid networks. The Seebeck coefficients of the MWCNT-Sb2Te3 and MWCNT-Bi2Se3 hybrid networks with low MWCNT wt% were found to be comparable with the Seebeck coefficients of pure inorganic Sb2Te3 and Bi2Se3 thin films. At the same time, flexibility tests of the MWCNT-Sb2Te3 and MWCNT-Bi2Se3 hybrid networks with MWCNT 50% showed no significant increase in the resistance when they were bent to a radius of 5 mm. This makes hybrid networks, presented in this work, the perspective for applications in flexible thermoelectrics as thermoelectric coatings for flexible substrates and fillers for polymers-based composites.

Improved mechanical and dielectric properties of PLA/EMA-GMA nanocomposites based on ionic liquids and MWCNTs

Synergistically improved mechanical and dielectric properties of poly(lactic acid)/ethylene–methyl acrylate–glycidyl methacrylate random terpolymer (PLA/EMA-GMA) based nanocomposites containing ionic liquids (ILs) and multi-walled carbon nanotubes (MWCNTs) can be related to the morphological evolution and interface properties of the composites. ILs can catalyze the reaction between PLA and EMA-GMA and MWCNTs can induce morphology transformation from sea-island structure to quasi-cocontinuous structure. The rheological tests show that the G′ of samples significantly increased and G″ decreased with increasing the MWCNTs content. This indicates that a crosslink structure at PLA/EMA-GMA interface and a solid network structure of EMA-GMA/MWCNTs with quasi-cocontinuous morphology were formed by incorporation of ILs. Morphology transformation and interfacial enhanced compatibilization significantly improved the mechanical and dielectric properties of composites owing to the formation of MWCNTs network in EMA-GMA phase and interfacial crosslinked structure.

Flavin Mononucleotide-Mediated Formation of Highly Electrically Conductive Hierarchical Monoclinic Multiwalled Carbon Nanotube-Polyamide 6 Nanocomposites.

Although the multiwalled carbon nanotube (MWNT) is a promising material for use in the production of high electrical conductivity (σ) polymer nanocomposites, its tendency to aggregate and distribute randomly in a polymer matrix is a problematic issue. In the current study, we developed a highly conductive and monoclinically aligned MWNT-polyamide 6 (PA) nanocomposite containing interfacing flavin moieties. In this system, the flavin mononucleotide (FMN) initially serves as a noncovalent aqueous surfactant for individualizing MWNTs in the form of FMN-wrapped MWNTs (FMN-MWNT), and then partially decomposed FMN (dFMN) induces crystallization of the PA on the MWNTs. The results of experiments performed using material subjected to partial dissolution of PA matrix show that the nanocomposite PA-dFMN-MWNT, formed by melt extrusion of PA and dFMN-MWNT, contains a three-dimensional monoclinic MWNT network embedded in an equally monoclinic PA matrix. An increase in monoclinic network promoted by an increase in the content of MWNT increases σ of the nanocomposite up to 100 S/m, the highest value reported for a polymer-MWNT nanocomposite. X-ray diffraction along with transmission electron microscopy reveal that the presence of dFMN induces the formation of monoclinic PA on dFMN-MWNT. The high σ of the PA-dFMN-MWNT nanocomposite is also a consequence of a minimization of defect formation of MWNT by noncovalent functionalization. Hierarchical structural ordering, yet individualization of MWNTs, provides a viable strategy to improve the physical property of nanocomposites.

A Glucose Monitoring System With Remote Data Access.

A cost-effective portable glucose monitoring system with remote data access based on a novel e-oscilloscope was developed using a glucose biofuel cell and a capacitor circuit interfaced to an ESP8266 microcontroller programmed to convert the charge/discharge rates of the capacitor functioning as a transducer. The capacitor charge/discharge rates were converted into glucose concentration readings that is monitored remotely. The glucose monitoring system comprise a glucose biofuel cell, a charge pump circuit, a capacitor and an ESP microcontroller. The anode was fabricated by modifying a gold microwire with nanoporous colloidal platinum (Au-co-Pt) and the cathode was constructed using a mesh dense network of multiwalled carbon nanotubes modified with bilirubin oxidase, respectively. The glucose monitoring system showed sensitivity of 1.18 Hz/mM · cm2 with a correlation coefficient of 0.9939 with increasing glucose concentration from 1 mM to 25 mM. In addition, the glucose monitoring system exhibited optimal operation at a pH of 7.4 and 37 °C, which is ideal for physiological glucose monitoring.

Double-segregated multiwalled carbon nanotube/silicone composites with large electrical to thermal conductivity ratios via in-situ silicone emulsion polymerization

Polymer composites with a high electrical conductivity ( σ) to thermal conductivity ( k) ratio have been intensively investigated in recent years. While highly conductive materials, such as metallic fillers or conducting polymers, were used to enhance σ, microstructural engineering was used to decrease k by forming porous structures, such as aerogels or 3D networks. These structures, however, were mechanically vulnerable and could only have limited applications. In this study, multiwalled carbon nanotube /silicone composites with a high σ/k ratio were developed by forming a double-segregated multiwalled carbon nanotube network in the porous body of the composites. The unique microstructure of the composites was created by a novel fabrication process: layer-by-layer deposition with in-situ polymerization of silicone emulsion particles dispersed in a water solvent. This novel process yielded very thick films, >200 µm, with high σ/k values, ∼2 × 104 (S/m)/(W/m·K). These high σ/k composites can be used for various applications, such as resistive heating elements, thermoelectric materials, and wearable thermotherapy.

Accelerated Shape Forming and Recovering, Induction, and Release of Adhesiveness of Conductive Carbon Nanotube/Epoxy Composites by Joule Heating.

The versatile properties of a nanopaper consisting of a porous network of multi-walled carbon nanotubes were applied to enhance the mechanical and electrical properties of a thermosetting epoxy polymer. The embedded nanopaper proved useful both in the monitoring of the curing process of the epoxy resin by the self-regulating Joule heating and in the supervising of tensile deformations of the composite by detecting changes in its electrical resistance. When heated by Joule heating above its glass transition temperature, the embedded carbon nanotube nanopaper accelerated not only the modelling of the composites into various shapes, but also the shape recovery process, wherein the stress in the nanopaper was released and the shape of the composite reverted to its original configuration. Lastly, in comparison with its respective epoxy adhesive, the internally heated electro-conductive carbon nanotube nanopaper/epoxy composite not only substantially shortened curing time while retaining comparable strength of the adhesive bonding of the steel surfaces, but also enabled a release of such bonds by repeated application of DC current.

Electrical Conductivity of Multiwalled Carbon Nanotube/Acrylonitrile Butadiene Styrene Polymer Nanocomposites prepared by Melt Mixing: Comparison of Twin Screw Extrusion and Batch Mixing

Most polymeric materials are insulators. They can be rendered conductive by the addition of appropriate fillers [1]. To obtain the desired conductivity and to ensure spatial homogeneity of the composite, excellent dispersion of the fillers is considered necessary [1,2]. To prepare the composite, solution casting has been widely used and past work suggests that it can adequately disperse the filler in a polymer matrix [3,4]. However, the method involves long preparation times and large quantities of organic solvents, and is not easily scalable. Melt mixing [4-6] offers an attractive alternative as past work [4,5] suggests that it can yield polymer nanocomposites with conductivities similar to that of solution cast samples. They however utilized laboratory scale batch mixing but industrial scale compounding is often performed using melt extrusion [6]. Therefore, in this work, we have investigated the feasibility of twin-screw melt extrusion for nanocomposite preparation by comparing the electrical conductivity of multiwalled carbon nanotubes (MWCNT) filled acrylonitile-butadiene-styrene (ABS) nanocomposites thus prepared to those obtained using internal batch mixing.First, we measured the electrical conductivity of the polymer nanocomposites prepared by the two methods. As can be seen from Fig. 1, for the samples prepared using the batch mixer, the conductivity exhibited a rapid increase of several orders of magnitude upon addition of a small quantity of MWCNT (less than 1 vol%). Upon further addition of MWCNT, the conductivity increase became less steep. The observed behavior is consistent with results in the literature [1,4] and can be interpreted using percolation theory, which suggests that the sharp increase in the conductivity observed at a certain volume fraction arises because the filler forms a conducting path that percolates across the polymer matrix [1]. Unexpectedly however, for the samples prepared using the twin screw extruder, the results were markedly different in that very little increase in conductivity was observed. If the above interpretation using percolation theory [1] is well founded, this suggests the absence of a percolation path consisting of the MWCNT.Due to van der Waals attraction, MWCNT tend to aggregate into micron scale clusters. During nanocomposite preparation these clusters must be broken down to facilitate the dispersion of the MWCNT in the matrix. As sufficient dispersion is believed to be necessary for the formation of the conducting path [1,2], we performed dynamic viscoelasticity measurements of the samples prepared by both methods to assess the dispersion state of MWCNT. At 0.227 vol% MWCNT, the storage modulus, G’, at low frequencies is lower for the samples prepared using the batch mixer when compared to that prepared using the extruder. Following [1,4], this can be taken to suggest that the dispersion of the MWCNT is poorer in the extruded samples and can be hypothesized to be the reason for the low conductivity. Upon increasing the MWCNT content, the low frequency G’ of the samples prepared by both methods differed little from each other and exhibited a plateau. A low frequency plateau in G’ is typically considered indicative of the presence of a network structure [1,4]. Data in Fig. 2 would suggest that, at the higher volume fractions, both preparation methods results in the formation of a MWCNT network structure. However, the conductivity values for the two methods are vastly different. If high electrical conductivity cannot arise in the absence of a percolating path, that would suggest the absence of a network structure and directly contradicts the implications of the rheology data. Future work will focus on resolving this contradiction using other methods to characterize the dispersion of the MWCNT in the ABS matrix.[1] R. M. Mutiso and K. I. Winey, in Polymer Science: A Comprehensive Reference, edited by K. Matyjaszewski and M. Möller, (Elsevier, Amsterdam, 2012), pp. 327.[2] M. H Kim et al., Korea – Australia Rheology Journal, 31, 179 (2019).[3] M. H. Al-Saleh, H. K. Al-Anid, and Y. A. Hussain, Composites Part A: Applied Science and Manufacturing, 46, 53 (2013).[4] S. K. Sukumaran et al., Journal of The Electrochemical Society, 166, B3091 (2019).[5] S. Dul, A. Pegoretti, and L. Fambri, Nanomaterials, 8, 674 (2018).[6] A. Dorigato, V. Moretti, S. Dul, S. H. Unterberger, and A. Pegoretti, Synthetic Metals, 226, 7 (2017).Fig.1 Variation of σ with ϕ: comparison of nanocomposites prepared using a twin-screw extruder (■) and using an internal batch mixer (●).Fig. 2 Variation of G’ with ω at 200℃ for several ϕ: melt extrusion (solid symbols) and batch mixing (hollow symbols). The data for neat ABS is also shown. Figure 1

Characterization of PVC/MWCNTs Nanocomposite: Solvent Blend

Abstract Polyvinyl Vinyl Chloride (PVC) multiwall carbon nanotubes (MWCNTs) nanocomposite flexible films were prepared using the solvent blend technique. Chloroform (CHCl3) and tetrahydrofuran ((CH2)4O) were used as solvents for MWCNTs and PVC, respectively. The effect of the solvents’ blend on electrical, optical and thermal properties of PVC/MWCNTs were investigated. The results of the Raman spectrum showed that all the characteristic bands of PVC polymer have a slight shift due to addition of MWCNTs. Electrical results showed that the nanocomposite samples with chloroform volume ratios of 10% and 25% had nearly the same conductivity. This is attributed to the formation of the MWCNTs network, which assisted in electrical conductivity. The I-V hysteresis curve decreases as the temperature increases and as it approaches the glass transition temperature. The non-isothermal kinetics analysis for PVC and PVC/MWCNTs were investigated by Thermogravimetry Analysis (TGA) using the model-free kinetic method. The non-isothermal measurements were carried out at five heating rates of 5 to 40∘C/min. The results show that the main decomposition process has constant apparent activation energies for all samples. The use of the bi-solvent method has improved the dispersion of untreated MWCNTs, and this has been reflected on the stability of both electrical and thermal properties.

Effects of dispersants and defoamers on the enhanced electrical performance by carbon nanotube networks embedded in cement-matrix composites

Cementitious composites incorporating multi-walled carbon nanotubes (MWCNTs) were fabricated in this study. The effects of additive dispersants and defoamer concentrations on the electrical characteristics of the composites were experimentally investigated. Both electrically conductive (i.e., PEDOT:PSS) and insulating (i.e., SDBS) dispersants were used to enhance the colloidal dispersibility of the MWCNTs. Observations indicate that MWCNT networks embedded in cementitious composites with junctions supported by a conductive dispersant demonstrated a seven-fold enhancement in electrical conductivity. Additionally, the use of defoamers resulted in the suppressed formation of voids during the hydration process. Conductivity measurements showed that voids are disadvantageous as they result in the isolation of MWCNT networks, which are responsible for inferior electrical conductivity. Furthermore, observations revealed that the percolation threshold could be shifted by controlling the formation of voids; thus, percolation can be achieved at lower MWCNT concentrations (i.e., 0.125–0.25 wt%) than in those samples produced without defoaming additives (i.e., 0.25–0.35 wt%).

Carbon nanotube network as an electron pathway in nanocomposite films

AbstractThe role of a multiwalled carbon nanotube (MWCNT) network embedded in polymer nanocomposite is a key factor to study. Polyvinyl alcohol was used as the polymer matrix for 0.1 –0.4 wt.% functionalised nanotubes in an effort to establish the nanotube's role in nanocomposite films. The fabrication of nanocomposite film was conducted using an easy and simple procedure via the casting technique. Nanocomposite properties show that in the early addition of 0.1 wt.% MWCNT, an isolator–semiconductor transition with 1.1 × 10−8S cm−1conductivity occurred. Nanocomposite films were shown to be sensitive to UV light at 250–400 nm and tended to have a high transmission (approximately ∼90 %) within the visible region. Additionally, an MWCNT concentration of 0.3 wt.% in the electron pathway carried charge carriers of approximately 2.1 × 10−7S cm−1via a complete electrically-conductive path. As such, the network nanotubes displayed extraordinary properties as reinforcement for nanocomposite films when viewed in terms of mechanical strength and elongation increased in respective ranges of 7.3–18.8 % and 14.9–25.02 %. Upshift of the G-band occurred at approximately 7–26 cm−1, which was indicative of an electron transfer between the nanotube and the matrix.

A facile approach to the scalable preparation of thermoplastic/carbon nanotube composites

Disentangling and dispersing multiwalled carbon nanotubes (MWCNTs) in thermoplastics by the existing melt compounding facilities where neither solvent nor liquid chemicals are allowed remains a great challenge. This challenge is addressed herein by combining ball milling with melt compounding. Specifically, ball milling is applied to disentangle MWCNTs and to eventually liberate each tube from agglomeration, and then the tubes are melt compounded with SSFs (PA6). A uniformly distributed MWCNT network is observed; obvious load transfer from the matrix to the tubes is evidenced by the presence of many firmly embedded tubes on the fracture surface. The electrical conductivity percolation threshold of PA6/MWCNT composites is found to be 2.5–3.0 wt%, in comparison with 5.0–8.0 wt% for PA6/stainless steel fiber composites. The PA6/MWCNT composite at 10.0 wt% shows a 76% increase in flexural modulus and 58% in flexural strength.

The key role of processing in tuning nonlinear viscoelastic properties and microwave absorption in CNT-based polymer nanocomposites

Multi-walled carbon nanotube (MWCNT)/polymer nanocomposites exhibit excellent microwave shielding properties by forming interconnected networks of MWCNT in the polymer matrix. However, the final properties of MWCNT-based nanocomposites greatly depend on the quality of MWCNT dispersion, and hence on the mixing technique. In the current work, for the first time, we show the effect of different mixing methods on nonlinear viscoelastic response and electromagnetic interference shielding effectiveness (EMI SE) of MWCNT/polymer nanocomposites. To do this, MWCNT/poly(styrene) (PS) nanocomposites were prepared by two frequently-used approaches, namely, melt mixing and solution mixing. Nonlinear rheological response of the samples reveals higher intra-cycle and inter-cycle viscoelastic nonlinearity for solution-mixed samples. Imaging analysis of the solution-mixed sample showed heterogeneous dispersion with highly interconnected networks of MWCNT in PS matrix. The interconnected network of MWCNT developed by solution mixing leads to significantly enhanced EMI shielding performance over melt-mixed nanocomposites containing big clusters of MWCNT in micro-scale but smaller agglomerates in nano-scale. Hence, an optimum state of dispersion (i.e., heterogeneous dispersion or small agglomerates connected with individual MWCNT) of MWCNT is necessary to achieve maximum EMI shielding performance.

Three-dimensional assembly of multiwalled carbon nanotubes for creating a robust electron-conducting network in silicon-carbon microsphere-based electrodes

We present a strategic approach to improve the cycle performance of a polymeric binder-free anode based on nano-Si@C microspheres by incorporating a multiwalled carbon nanotubes (MW-CNTs) network and performing carbodiimide-based condensation coupling to form a robust molecular-junction between MW-CNTs and nano-Si@C microspheres. Field-emission scanning electron microscopy reveals that one-dimensional MW-CNTs homogeneously wrapped the individual Si@C microspheres and they interwove through the intergranular nanospace. The incorporation of amide bonds at the junction primarily contributes to the stabilization and reinforcement of the hybrid electrodes. Their reversible capacity after 50 cycles with 0.5 A g−1 was significantly improved from 81 mAh·g−1 to 520 mAh·g−1. Such robustness associated with the supramolecularly assembled MW-CNTs is expected to facilitate electron conductivity and mass transfer kinetics, leading to enhanced electrochemical performance of the Si@C anode.