Morphology Of Carbon Nanotubes Research Articles

Facile synthesis of homogeneously dispersed carbon nanotubes on TC4 alloy powder by in-situ CVD and its growth behavior

We developed a simple method of in-situ synthesize carbon nanotubes (CNTs) on Ti–6Al–4V (TC4) alloy powder to fabricate CNTs/TC4 compound powders through plasma-enhanced chemical vapor deposition (PECVD). By this approach, CNTs on TC4 alloy powder exhibit better uniform dispersion and morphology compared with the traditional CVD methods. In order to reveal the growth behavior of CNTs during the PECVD process, XRD, SEM, TEM, and Raman spectroscopy were used to analyze the morphology and graphitization of CNTs at different synthesis conditions. The plasma is benefit to the pyrolysis of CH4, but overmuch plasma bombardment also reduces the yield and quality of CNTs. The number of CNTs can be significantly improved with appropriately increasing the temperature and time, but excessive temperature, time and carbon concentration can increase the number of impurities such as amorphous carbon. Significantly, the growth mechanism of CNTs synthesized in TC4 powders is following tip-growth mode in PECVD process. Additionally, the quantity and quality were satisfactory at 600 °C for 30 min with 50 W plasma power. This study about PECVD process lays a foundation for improving the comprehensive properties of CNTs/TC4 composites in the future.

Enhancing Tensile Properties and Surface Roughness of (Gr + CNTs)/Cu Composite Foils

Graphene (Gr) and carbon nanotubes (CNTs) were successfully deposited into the copper matrix by direct current electrodeposition, and the dispersion of their composites was improved by π–π bonds constructed by Gr and CNTs. The microscopic morphology of Gr and CNTs and the morphology, organization, tensile properties, and surface roughness of composite foils were characterized. The results show that Gr–CNT reinforcements were distributed in the copper foil matrix. As the concentration of Gr–CNTs in the electrolyte (gelatin 21 g/L, SPS 7 g/L) increased, the tensile strength increased from 271 ± 6 to 429 ± 10 MPa and then decreased to 375 ± 9 MPa, and the surface roughness (Sa) decreased from 1.720 ± 0.080 to 0.889 ± 0.090 μm and then increased to 1.371 ± 0.091 μm. The self-dispersing effect of Gr and CNTs and good concentration ratios of additives in this work provide a production possibility for the field of electrolytic copper foils.

Preparation of Multi-walled Carbon Nanotubes with Ni/SiO2 Composites

Using carbon monoxide as carbon source to manufacture Multi-walled carbon nanotubes on the supported of Ni/SiO2 by chemical vapor deposition. The effects of nickel loading and raw gas to carbon nanotubes were studied. When the content of Ni is 5%, the yield of carbon is very low. As the content of Ni increases from 5% to 35%, the yield gradually increases. When Ni loading exceeds 35%, the yield of carbon decreases. Through the TEM, HRTEM and XRD to characterized carbon nanotubes. The results showed that the morphology of carbon nanotubes became worse with the Ni conten increased In terms of yield and quality,the best synthesis temperature is 600°C. In the absence of hydrogen in the feedgas, the diameter of carbon nanotubes is in the narrow range of 10 to 20 nm. When hydrogen is introduced into the system, the amount of carbon increases, but the form deteriorates.

Modifying the Molecular Structure of Carbon Nanotubes through Gas-Phase Reactants.

Current approaches to carbon nanotube (CNT) synthesis are limited in their ability to control the placement of atoms on the surface of nanotubes. Some of this limitation stems from a lack of understanding of the chemical bond-building mechanisms at play in CNT growth. Here, we provide experimental evidence that supports an alkyne polymerization pathway in which short-chained alkynes directly incorporate into the CNT lattice during growth, partially retaining their side groups and influencing CNT morphology. Using acetylene, methyl acetylene, and vinyl acetylene as feedstock gases, unique morphological differences were observed. Interwall spacing, a highly conserved value in natural graphitic materials, varied to accommodate side groups, increasing systematically from acetylene to methyl acetylene to vinyl acetylene. Furthermore, attenuated total reflectance Fourier-transfer infrared spectroscopy (ATR-FTIR) illustrated the existence of intact methyl groups in the multiwalled CNTs derived from methyl acetylene. Finally, the nanoscale alignment of the CNTs grown in vertically aligned forests differed systematically. Methyl acetylene induced the most tortuous growth while CNTs from acetylene and vinyl-acetylene were more aligned, presumably due to the presence of polymerizable unsaturated bonds in the structure. These results demonstrate that feedstock hydrocarbons can alter the atomic-scale structure of CNTs, which in turn can affect properties on larger scales. This information could be leveraged to create more chemically and structurally complex CNT structures, enable more sustainable chemical pathways by avoiding the need for solvents and postreaction modifications, and potentially unlock experimental routes to a host of higher-order carbonaceous nanomaterials.

Bisphenol-A-Carbon Nanotube Nanocomposite: Interfacial DFT Prediction and Experimental Strength Testing.

Epoxies, their derivatives, and composites, due to superior specific strength, are preferred for many potential applications in the field of automobiles, aircraft, bonding of structures, protective coatings, water filtration, etc. As structural members in automobiles and aircraft, the epoxy-based components are exposed to various static/dynamic mechanical loading conditions during their service life. The interfacial interactions, between the matrix and reinforcement, greatly affect the final properties of the composites. The present study demonstrates that the solvent used for the preparation of the composite can also contribute toward interfacial interactions. Present research systematically finds out a suitable solvent (acetone) and reinforcement type [multi-walled carbon nanotube (CNT)] for epoxy [bisphenol-A (BPA)] nanocomposites. Dynamic and static strengths of the as-prepared epoxy-CNT nanocomposites were carefully investigated. Well dispersed CNTs in acetone were mixed with an ester of BPA under constant magnetic stirring conditions. Samples of tablet shape were prepared for testing static and dynamic performance of the composite using a nano-indentation technique. Considerable enhancement by 55 and 22% in the static elastic modulus and hardness of BPA-CNT composites, respectively, was observed (compared with that of pristine BPA). The storage modulus and tan-delta of the nanocomposites were also improved by 14 and 46%, respectively. Improved static and dynamic performance, reported in this work, significantly enhances the scope of utilization of BPA-CNT-based nanocomposites under severe static and dynamic loading conditions simultaneously. Static and dynamical analysis of CNT-reinforced epoxy provides more realistic understanding of the mechanical performance of the nanocomposite. Density functional theory (using QuantumATK software) simulations were performed to investigate and identify the alterations in the atomic morphology of CNTs during interfacial interaction with the acetone molecule and epoxy matrix. The calculations predicted that CNTs with mild defects as compared to pristine CNTs were better suited for synthesis of the nanocomposite and also assisted in a homogeneous distribution of CNTs in BPA without aggregation (with acetone as the solvent). Furthermore, structural changes in CNTs after treatment with BPA and the curing agent and the role of defects are studied in detail.

Highly proton conductive and mechanically robust SPEEK composite membranes incorporated with hierarchical metal–organic framework/carbon nanotubes compound

The preparation of composite proton exchange membranes (PEMs) by incorporating metal- organic frameworks (MOFs) into polymeric substrates has become a hot research topic in the field of fuel cells in recent years. In this work, ZSC was prepared by in-suit reacted with the precursor of ZIF-8 (Zeolitic Imidazolate Framework 8) and silica coated carbon nanotubes (SiO2@CNTs). The as-prepared ZSC was introduced into sulfonated poly (ether ether ketone) (SPEEK) to fabricate a series of composite proton exchange membranes SPEEK/ZSC-x (where x is the mass percentage between ZSC and SPEEK). The coating treatment of carbon nanotubes (CNTs) by silica not only can avoid the direct contacting among CNTs and enhance the dispersion in SPEEK matrix, but also realize the regulation of nucleation and crystallization process of ZIF-8 particles along the morphology of CNTs. The obtained SPEEK/ZSC composite membranes show improved performance owing to construction of interconnected network architecture and the compositional advantages of the ZSC materials. The proton conductivity of SPEEK/ZSC-0.5 membrane was up to 38.10 mS/cm at 80 °C, which was 1.8 times that of the pure SPEEK membrane (21.12 mS/cm) under the same condition. Moreover, the SPEEK/ZSC-0.5 showed better performance with peak power density of 38.9 mW/cm2 in 2 M methanol solution, which was 1.3 times that of the pure SPEEK membrane of 30.3 mW/cm2, the further stability tests confirmed that the composite film maintained good voltage stability even after 100 h of continuous operation at 80 °C. These results indicate that the strategy of construction MOFs and functional CNTs hybrid materials show promising application prospects in the preparation of high performance PEMs.

Steam reforming of ethanol, acetaldehyde, acetone and acetic acid: Understanding the reaction intermediates and nature of coke

The small aliphatic organics like ethanol, acetaldehyde, acetone and acetic acid are frequently used as feedstocks for hydrogen production via steam reforming. These organics have distinct functionalities, which might result in formation of different reaction intermediates and coke. This was investigated in this study with Ni/KIT-6 as a catalyst under normalized conditions. The results indicated that dehydration to ketene but not cracking was major route for dissociative adsorption of acetic acid on Ni/KIT-6 from 100 °C. Thermally stable CH and CC in alkenes, formed via dehydration of ethanol and aromatization of acetone/intermediates via bimolecular Aldol-condensation, were important precursors of coke in ethanol and acetone reforming. Although acetone strongly adsorbed on Ni/KIT-6, it did not polymerize to heavy oxygen-containing organics that were difficult to be gasified with steam. In comparison, the similar strong adsorption of acetaldehyde led to rapid polymerization even at 100 °C, forming the polymeric coke of highly aliphatic nature. The coking tendency in reforming followed the order: acetone > acetic acid > ethanol > acetaldehyde. Nevertheless, the amorphous form of coke in acetaldehyde reforming led to the rapid deactivation of Ni/KIT-6. The coke in ethanol, acetone and acetic acid reforming were mainly the catalytic type with the highly aromatic nature, high carbon crystal crystallinity, high thermal stability, high resistivity towards oxidation and the carbon nanotube morphology. Nevertheless, the varied reaction intermediates involved in reforming of these varied feedstock also formed the coke of some unique features.

Pyrolysis of typical plastics and coupled with steam reforming of their derived volatiles for simultaneous production of hydrogen-rich gases and heavy organics

Pyrolysis is a thermochemical route for converting waste plastics into hydrocarbons that might be further upgraded to fine chemicals via the process such as hydrotreatment. In this study, the pyrolysis of five typical plastics (PE, PP, PVC, PS and PET) and steam reforming of their derived volatiles were coupled in one process, named as pyro-reforming. The reaction behaviors, especially the property of their derived cokes, in the pyro-reforming were investigated. The results indicated that the volatiles from the pyrolysis of PE had the highest reactivity with steam to produce H2 of the highest yield, followed by that of PP, PVC, PET and PS. The Cl in PVC promoted nickel sintering, enhanced formation of heavy aromatics through aromatization. Moreover, the existence of Cl interrupted formation of carbon nanotube, forming the highest amount of coke with hemp rope-like fiber form of very coarse surface. This was very different from the carbon nanotube form of coke with smooth surface and uniform outer/inner diameters from the pyro-reforming of PE or PP. The pyro-reforming of PET or PS generated mainly the aromatic intermediates that were chemically more inert in steam reforming, forming polymeric type of coke with no carbon nanotube morphology and very low crystallinity.

Progress on research of construction of carbon nanotubes/carbon fiber cross-scale interface enhancement systems

<p indent="0mm">Carbon fiber reinforced composites (CFRP) have a broad application prospect in aerospace, military equipment and other fields because of their many excellent properties such as high strength and stability. However, the inert surface structure of carbon fiber (CF) seriously affects the load transfer efficiency with the matrix, which hinders the full play of the excellent performance of the composites. Therefore, the optimization and design of the interfacial structure between the two phases has become a hot research topic. Carbon nanotubes (CNTs) with excellent mechanical properties were deposited on the surface of CF to form a three-dimensional network hybrid structure with multiple orders of magnitude, thereby improving the interfacial bonding ability between the CF and the matrix. This paper introduces four process routes for the construction of cross-scale enhancement systems, including chemical vapor deposition (CVD), electrophoretic deposition (EPD), chemical grafting and dip-coating spraying process. The advantages, limitations and key process parameters of each method are summarized. The study of CVD method focuses on the influence of process parameters such as catalysts (type, morphology, concentration), growth time, treatment temperature, carbon source and carrier gas (type, mixing ratio, inlet speed) on the growth morphology (length, density, thickness) of CNTs. This method achieves the direct directional growth of CNTs on the CF surface, but the CF is affected by the pre-activation treatment, metal catalyst etching, and high-temperature environment, which leads to a significant decrease in its own strength. In the EPD method, the adjustment of key process parameters (applied voltage, energization time, electrode distance, and electrode shape) becomes the key to successful application of the EPD method. Although the EPD method is capable of producing textured CNT coatings or thin films on the CF, the weak van der Waals force bonding form and the “disorder” of deposition are the main pain points of this method. In the chemical grafting process, the reaction between multiple reactive functional groups and the use of macromolecular coupling agents provide a more diversified preparation scheme, and the bonding strength between CNTs and CF is greatly enhanced by chemical bonding. The construction of CNTs/CF interfacially enhanced structures, using two different processes, surface dip coating and spraying, is considered to be simple and effective, and the degree of dispersion of CNTs in sizing agents or different solvents becomes an important consideration for good deposition on the CF surface. Although the combination between CNTs and CF is not strong, the simple operation process and reasonable economic cost show a high suitability for industrialization. In this paper, three different attachment types of CNTs, namely radial embedding, random topology and surface attachment, are proposed in summary to investigate the stress transfer paths between the composite matrix and the form of interfacial enhancement. The three different attachment types contribute to the enhancement of the interface properties in different ways and to different degrees, with radially embedded structures contributing the most to the enhancement of the interface properties, vertically oriented CNTs significantly weakening the radial stresses between the CF and the matrix, and surface-applied CNTs suppressing the shear stresses more significantly than the radial stresses. Finally, the application of the CNTs/CF cross-scale interfacial reinforcement system in composites is explored, resulting in CFRP exhibiting superior properties in a number of ways, but only in terms of the mechanical properties of the system, which are exploited. Therefore, the development and application of multi-functional materials such as heat and electricity, as well as the preparation of high efficiency, high quality and low cost CNTs/CF/matrix three-phase composites will be the main development direction in the field of nano-reinforced CF composites in the future.

The effect of electrophoretic deposition of carbon nanotubes onto carbon fiber on the interlaminar resistance of carbon reinforced aluminum laminates

Functionalized multi-walled carbon nanotubes were deposited on the carbon fabric using ultrasonic-assisted electrophoretic deposition. The effect of carbon nanotubes (CNTs) deposition time and morphology on the mode I interlaminar fracture resistance of carbon reinforced aluminum laminates (CARALL) was investigated. The formation of a proper network of CNTs on the carbon fabric favorably deviated the crack growth into the carbon fabric layer and intensified the fiber bridging during the delamination. The CNT coating on the carbon fiber in conjunction with the alkaline-acid treatment on the Al substrate significantly promoted the interlaminar fracture initiation and propagation energies and stabilized the fracture behavior.

Effect of catalyst support layers on emissivity of carbon nanotubes grown via floating catalyst chemical vapor deposition

We propose an efficient method of growing carbon nanotube (CNT) arrays on a variety of metals using chemical vapor deposition (CVD) assisted by a simple surface treatment of the substrate materials. The main feature of this method is the application of shot blasting with fine alumina shot to create the catalyst support layer that is required for the effective growth of CNTs on the various conductive materials, including the ultrahard metal tungsten. Energy dispersive X-ray spectroscopy shows that the shot blasting forms a noncontinuous layer where alumina nanoparticles are embedded as residue from the blasting media on the treated surfaces. Such a noncontinuous alumina layer can behave as the catalyst support layer, which is normally prepared via sputtering or a vacuum evaporation coating process. The influence of shot size on the characteristics of the nonuniform alumina buffer layer as well as the resultant multiwalled CNT arrays grown via CVD in conjunction with a floating iron catalyst are investigated. The results show that the morphology, crystallinity, and spectral emissivity of CNTs depend on the size of alumina shot used in the shot blasting treatment. The characteristics of the CNTs grown on various metal substrates with a discontinuous and continuous alumina buffer layers are compared with each other. These comparisons indicate that the degrees of hardness and the redox property of the substrates moderately affect the characteristics of CNTs on the discontinuous layer in contrast to the continuous layer.

Microwave-assisted pyrolysis of plastics with iron-based catalysts for hydrogen and carbon nanotubes production

This study presents a microwave-assisted pyrolysis (MAP) for plastics using iron-based catalysts with the aim to convert high-density polyethylene into hydrogen and carbon nanotubes (CNTs). A multistep mechanism was proposed based on the microwave-induced ‘micro-hot spots’ theory, indicating that the yield and composition of pyrolytic products are mainly determined by the microwave absorbing property and the activity of the catalysts. To validate the mechanism, iron-based catalysts with different microwave-absorbing properties were prepared using different catalyst supports including activated carbon, silicon carbide, and silicon dioxide. The experimental results showed that the catalysts with high dielectric loss promoted the gas yield and the growth of CNTs. This was due to the local high-temperature domains generated over the catalyst surface under microwave irradiation. In addition, the role of catalytic activity was explored by designing FeAlOx catalysts with different iron loadings. An increase in iron content from 7% to 22% improved the gas yield from 86.3% to 93.7% but has insignificant effect on the morphology of CNTs. Conclusions drawn from this study can guide the future design and development of microwave-responsive catalysts for the microwave-assisted pyrolysis of plastic wastes towards circular economy.

Preparation of carbon nanotubes with high filling rate of copper nanoparticles

Performance of carbon nanotubes (CNTs) can be adjusted by filling their cavities with guest materials. In this study, Cu nanoparticles are filled into CNTs via wet chemical method. To improve the filling efficiency, oxygen-containing functional groups (OCFGs) are introduced onto the tube walls of CNTs by acid treatment. The defects and pore size distribution on CNTs are detected and quantified by N2 adsorption-desorption experiment, Raman spectra, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Morphologies of CNTs before and after filling treatment are observed by transmission electron microscope (TEM). The filling rate is characterized by inductively coupled plasma emission spectrometer (ICP) and thermal gravimetric analysis (TGA). The results indicate that the OCFGs can not only improve the hydrophilicity of CNTs, but also greatly affect the filling rate of CNTs. The filling rate of CNTs acid-treated for 24 h (1.99 wt% tested by TGA) is significantly lower than that of acid-treated for 8 h (12.11 wt% tested by TGA), which can be ascribed to the fact that excessive OCFGs could hinder Cu2+ ions from entering the cavity of CNTs. The obtained results can provide a new perspective for the application of CNTs in composite preparation and related fields.

Investigation of the effect of catalyst type, concentration, and growth time on carbon nanotube morphology and structure

Investigation of the effect of catalyst type, concentration, and growth time on carbon nanotube morphology and structure

Smart Self-Sensing Piezoresistive Composite Materials for Structural Health Monitoring

The use of fiber-reinforced composite materials has widely spread in various sectors, including aerospace, defense, and civil industry. The assessment of these heterogeneous material systems is important for safer and risk-free applications and has contributed to the need for self-sensing composites. This work is focused on the development of piezoresistive composites, the prediction of their performance and structural health monitoring (SHM). Additionally, this work unpacks the complexity of carbon nanotubes (CNTs) micro-fabrication and the development of piezoresistive and electromagnetic (EM) waves detection electrodes. Scanning electron microscopy (SEM) was used to characterize the CNTs structure and morphologies. The manufactured CNTs were incorporated in epoxy systems to fabricate glass fiber reinforced polymer (GFRP)-CNTs smart composites with piezoresistive properties. The detection of micro-damage onset and its progression was carried out in mode I, to evaluate the sensitivity of the smart composites to damage development. The change in electrical conductivity of the nanotubes-reinforced composite systems due to localized mechanical strains enabled crack propagation detection. The relationship between crack propagation, fracture toughness, and electrical resistivity of the smart composite was analyzed.

Highly Sensitive, Stretchable Pressure Sensor Using Blue Laser Annealed CNTs.

A piezoresistive sensor is an essential component of wearable electronics that can detect resistance changes when pressure is applied. In general, microstructures of sensing layers have been adopted as an effective approach to enhance piezoresistive performance. However, the mold-casted microstructures typically have quite a thick layer with dozens of microscales. In this paper, a carbon microstructure is formed by blue laser annealing (BLA) on a carbon nanotube (CNT) layer, which changes the surface morphology of CNTs into carbonaceous protrusions and increases its thickness more than four times compared to the as-deposited layer. Then, the pressure sensor is fabricated using a spin-coating of styrene–ethylene–butylene–styrene (SEBS) elastomer on the BLA CNTs layer. A 1.32 µm-thick pressure sensor exhibits a high sensitivity of 6.87 × 105 kPa−1, a wide sensing range of 278 Pa~40 kPa and a fast response/recovery time of 20 ms, respectively. The stability of the pressure sensor is demonstrated by the repeated loading and unloading of 20 kPa for 4000 cycles. The stretchable pressure sensor was also demonstrated using lateral CNT electrodes on SEBS surface, exhibiting stable pressure performance, with up to 20% stretching.

Morphology and Electrical Characteristics of Single-Walled Carbon Nanotubes Film Prepared by Air Brush Technique

This study is to investigate the morphology and electrical characteristics of single-wall carbon nanotubes (SWCNTs) thin film deposition using air brush technique. A deposition setup consisting of a conventional artist air brush was developed and used to deposit SWCNT thin films and therefore the resulting film’s characteristics need to be investigated to gauge its suitability in producing uniform monolayer. The SWCNTs used were synthesized via Direct Injection Pyrolytic Synthesis (DIPS) method, with diameters ranging from 0.8 to 3 nm. The substrate was deposited using an airbrush with varying nozzle to study its effect to the resulting SWCNTs thin films’ characteristics. Subsequently, scanning electron microscope (SEM) were used to inspect the morphology and surface topography, and followed by preliminary electrical measurements. The result shows that good dispersion promotes uniform distribution of SWCNTs over large area of glass substrate. Moreover, the electrical measurement revealed that at 1 V, best morphology produced highest current at a nozzle distanceof 10 mm (15.3 μA) and the lowest current at a nozzle height of 4 mm (3.24 μA). From the results presented, it is demonstrated that conventional artist airbrush setup can be effectively used to deposit monolayer thin film of SWCNT with high degree of uniformity. This research is necessary for the process of depositing-controlled CNT thin film network, which can influence the material characteristics and performance of the variety of CNT-based device applications.

Development of biofuel cell based on anode modified by glucose oxidase, Spirulina platensis-based lysate and multi-walled carbon nanotubes

In this study, the GC/PEI/CNT/S.p./GOx bioanode was successfully designed using the chemical oxidized multi-walled carbon nanotubes (CNT) and Spirulina platensis-based lysates that facilitate the electron transfer and reduce the open circuit potential (OCP) drop along the electron transfer pathway. Composition, morphology and chemical modification efficiency of CNT was examined using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and simultaneous thermal analysis (STA) coupled with mass spectrometric (MS) analysis of evolving gaseous species (TG/DTA–MS). The power density generated by GC/PEI/CNT/S.p./GOx bioelectrode was 21.8 times higher if S. platensis-based lysates were applied in bioanode design (than GC/PEI/CNT/GOx bioelectrode). The magnitude of maximal power density evaluated by linear sweep voltammetry (LSV) measurements was estimated to be 3.2 µW cm−2 at 213 mV voltage, whereas the bioelectrode act as a bioanode and bare glassy carbon as a cathode in a single-compartment biofuel cell design. Furthermore, the GC/PEI/CNT/S.p./GOx bioanode shows high long-term stability, while the magnitude of power density after seven days achieved approximately 89.6 % (2.87 µW cm−2) of its initial value. The initial OCP value of bioanode with S. platensis-based lysates was found to be -156 mV, which was reduced after the addition of 12.5 mM glucose. The equilibrated average value of OCP (-259 mV vs Ag/AgCl (3 M KCl)) indicates that glucose oxidase (GOx) immobilized on CNT functionalized with S. platensis-based lysates possess superior electron transfer and reduce the OCP drop along the electron transfer pathway.

A route towards metal-free electrical cables via carbon nanotube wires

Carbon nanotubes (CNTs) have unique properties with promise to outperform the electrical characteristics of bulk copper, giving rise to its primary driver for use in electronic devices. The challenge still hindering their full exploitation stems from an inability to manufacture them to long lengths, resulting in a requirement to align and entwine them into a yarn or wire. There have been several methods presented in achieving this, however, the common disadvantage has been that they are only applicable to specific types and morphologies of CNTs. In the work reported here, using electrospinning as a universally applicable route for any CNT type, we re-engineer and optimise the various formulation, fabrication and processing steps required to manufacture CNT wires. Through a series of investigations using a materials agnostic approach, we experimentally probe the choice of solvent, surfactant and thermal treatment temperature of the CNT inks, demonstrating the CNT-type optimum using a range of commercially available single- double- and multiwalled CNTs. Finally, this allowed us to develop and probe an electrical conditioning process to further enhance the electrical performance, achieving the highest reported un-doped electrical conductivity of 36,000 S⋅ m − 1 for electrospun CNT wires, or a specific conductivity of 0.2 × 10 6 S · m − 1 / g · c m − 3 .

Microstructure-sensitive investigation on the mechanical behavior of CNT-reinforced composites considering debonding damage based on cohesive finite element method

In this paper, an analytical modeling and numerical approach based on the finite element (FE) method are introduced to study the influence of the real morphology (e.g., length and waviness) and distribution of carbon nanotubes (CNTs) on the mechanical behavior of the CNT-reinforced composites. The analytical model has considered the real morphology effect using the equivalent curved CNTs with perfect bonding. The equivalent chord length, diameter, and waviness have been computed using the abundance of different values of measured parameters in an actual microstructure of the CNTs in the matrix. In the FE method, a computational tool is used to map an actual composite microstructure onto a FE representative volume element (RVE) with the exact shape, size, distribution, and waviness of CNTs. FE analysis has been carried out in both well-bonded and interface-debonding conditions. The cohesive zone model (CZM) with bilinear traction-separation law for both opening and sliding modes has been utilized to capture the debonding at the CNT-matrix interface. Results indicate that in the presence of weak bonding, CNT waviness can enhance the composite stiffness rather than reduce it. A quite different conclusion to what can be obtained with the assumption of perfect adhesion. In the presence of poor bonding, the curvature has a positive effect on composite properties and improves the load transferring from the matrix. FE analysis for different RVEs highlights that the curvature and length of the CNTs are essential features of the microstructure, and they can effectively influence the mechanical properties of the material. Results demonstrate that the equivalent curved CNTs cannot appropriately represent the real microstructure.