CNT Dispersion Research Articles

Effect of CNT Dispersion of Nanocarbon Fiber Silicone-matrix Composites Sheet on Sliding Property of Water Droplet

Effect of CNT Dispersion of Nanocarbon Fiber Silicone-matrix Composites Sheet on Sliding Property of Water Droplet

Effect of diazotization and magnetic assembly on CNT dispersion observed with hardness and modulus measurement of their epoxy composite of low CNT volume fraction

Polymer composites with small amount of CNTs (< 5 wt%) have been studied as a light-weight wear-resistant material with low friction, among other applications, but their modulus improvement often plateaus or diminishes with increasing CNT fraction due to agglomeration. Here, polymer nanocomposites were fabricated with randomly oriented or aligned CNTs across their volume (up to 5 mm length) by CNT surface diazotization and by static magnetic field application (400 G for 40 min). With the improved CNT dispersion and thus less agglomeration, the reduced moduli of PNCs stayed improved with addition of up to 1 vol% (or 1.3 wt%) of CNTs. In this work, the PNCs with randomly oriented CNTs exhibited higher stiffness than the PNCs with magnetically aligned and assembled CNTs, indicating again the negative effect of CNT agglomeration on stiffness. In future, other CNT structuring methods with controlled inter-CNT contacts will be conducted to dissociate alignment from local agglomeration of CNTs and thus to simultaneously improve hardness and modulus of PNCs with small CNT addition.

Tribological and Electrochemical Characterization of UHMWPE Hybrid Nanocomposite Coating for Biomedical Applications.

A new approach of using a polymer hybrid nanocomposite coating to modify the surface of titanium and its alloys is explored in this study. Electrostatic spray coating process is used to deposit the coating on the plasma-treated substrates for better adhesion. Ultra-high molecular weight polyethylene (UHMWPE) has been selected as the parent matrix for the coating due to its biocompatibility and excellent tribological properties. However, to improve its load-bearing capacity carbon nanotubes (CNT’s) (0.5, 1.5, and 3 wt.%) are used as reinforcement and to further enhance its performance, different weight percent of hydroxyapatite (HA) (0.5, 1.5, 3, and 5 wt.%) are introduced to form a hybrid nanocomposite coating. The dispersion of CNT’s and HA was evaluated by Raman spectroscopy and scanning electron microscopy. The electrochemical corrosion behavior of the nanocomposite coatings was evaluated by performing potentiodynamic polarization and electrochemical impedance spectroscopic tests in simulated body fluid. Tribological performance of the developed hybrid nanocomposite coating was evaluated using a 6.3 mm diameter stainless steel (440C) ball as the counterface in a ball-on-disk configuration. Tests were carried out at different normal loads (7 N, 9 N, 12 N, and 15 N) and a constant sliding velocity of 0.1 m/s. The developed hybrid nanocomposite coating showed excellent mechanical properties in terms of high hardness, improved scratch resistance, and excellent wear and corrosion resistance compared to the pristine UHMWPE coatings.

Performance evaluation of bitumen with a homogeneous dispersion of carbon nanotubes

Nano-modified bitumen binders can be tailored to exhibit excellent properties for potential application in pavement engineering. However, a homogeneous dispersion of nano-materials in bitumen is still a challenge, which obscures the maximum property improvement of bitumen that can be achieved. In this study, a CNT sponge, which is a macroscopic assembly of nanotubes and represents one of the most promising lightweight carbon nanomaterials with homogeneous three-dimensional network and a high porosity, was used to reinforce bitumen. Bitumen can autonomously penetrate into the porous CNT sponge, and fill up all the pores, forming a bitumen/CNT nanocomposite with homogeneous CNT dispersion quality. We found that, the addition of CNTs significantly improves the performance of bitumen at elevated temperatures, as indicated by the much improved properties of stiffness, rutting resistance, creep and recovery behavior as well as high-temperature stability. Such effective modification of bitumen by CNT are ascribed to the highly uniform dispersion of CNTs, as well as the percolation structure formed throughout bitumen matrix. This study highlights the importance of CNT dispersion quality, and sheds light on the bitumen property improvement that could be achieved.

Sulfate Surfactant Assisted Approach to Fabricate Sulphur‐Doped Supported Nanodiamond Catalyst on Carbon Nanotube with Unprecedented Catalysis for Ethylbenzene Dehydrogenation

AbstractDirect dehydrogenation (DDH) of ethylbenzene is an efficient chemical process for styrene production. Nanocarbon materials, as clean and low‐cost catalysts, have drawn more and more attention in this field. In this work, inspired by the promoting effect of support modulation on the catalytic performance of the general supported‐type catalyst, we present a facile sulfate surfactant assisted dispersion with subsequent annealing (SADA) approach for preparing sulphur‐doped supported nanodiamond catalyst on carbon nanotube (ND/CNT‐SDS) with abundant active sites by using sodium dodecyl sulfate (SDS) as both the dispersing agent for promoting the dispersion of catalytically active ND motif and the CNT support and the sulphur source for sulphur doping, yielding an outstanding supported ND catalyst for DDH of ethylbenzene to styrene with 7.7 mmol g−1cat. h−1 of styrene rate and 98.2 % of styrene selectivity. ND/CNT‐SDS catalyst demonstrates 3.0 times higher styrene rate of the pristine ND. Moreover, ND/CNT‐SDS catalyst shows 1.5 times higher styrene rate of the previously reported defect‐enriched N,O‐codoped ND/CNT (N,O‐ND/CNT‐d) with up to 98 % of similar styrene selectivity, ascribed to its more exposed C=O active sites and higher specific surface area originating from the promoted dispersion of both ND and CNT by SDS, as well as the sulphur‐doping. Moreover, this work also presents a novel and efficient method for the designing the other supported nanocarbon catalysts from dispersion‐required catalytically active nanocarbon motif and the nanocarbon carrier.

The dispersion of CNT in TPU matrix with different preparation methods: solution mixing vs melt mixing

Melt mixing and solution mixing are two commonly used methods for the preparation of polymer nanocomposites. In this work, thermoplastic polyurethane (TPU) composites with unmodified MWCNTs and carboxyl MWCNTs (MWCNT-COOH) were prepared using melt mixing and solution mixing. The dispersion of filler in TPU matrix and the macro-properties of composites under different processing conditions were systematically investigated. It was found that for pristine MWCNTs, a better dispersion was obtained using solution method at relatively low content of fillers (≤2.5 wt%); but when the content of MWCNT was above 2.5 wt%, melt mixing under high shear force was more effective to achieve a homogeneous dispersion. The similar result was confirmed in TPU/MWCNT-COOH composites, with the critical concentration shifted to 5.0 wt%, indicating that the interaction between CNT and TPU also played role on the dispersion of CNT in TPU matrix via solution mixing. Our finding is important for the preparation of polymer/CNT nanocomposites with good dispersion depending on the filler content and mixing methods.

Synergetic effects of carbon nanotubes and triblock copolymer on the lap shear strength of epoxy adhesive joints

This paper investigated the effect of functionalized CNTs and triblock copolymer addition on the lap shear strength of the epoxy adhesive joints. CNTs were functionalized using an ultrasonicated-ozonolysis process to enhance the uniform and stable dispersion of CNT, and 3-roll mill was employed to achieve the uniform distribution of CNT in the epoxy matrix. Two different triblock copolymers named as SBM and MAM were used as toughening agents to improve the shear strength of the nanocomposite adhesive material. Single lap shear tests were performed on the aluminum adhesively bonded joints using pure and modified epoxy adhesives to determine the shear strength of the adhesive. The effect of different weight fractions of untreated CNTs, functionalized CNTs, and the hybrid effect of CNTs and triblock copolymer addition on the shear strength of the adhesive joints was studied. It was found that the use of functionalization and 3-roll mill methods are effective to achieve stable and even dispersion of the CNTs and the shear strength was improved by 26% (23.6 MPa) compared to that of pure epoxy. The hybrid effect of functionalized CNTs and SBM showed the maximum shear strength of 44.7 MPa, with an increase of 137% compared to that the of the pure epoxy demonstrating the effectiveness of the triblock copolymer addition in improving the shear strength. Fracture analysis revealed that the nano-additives acted synergistically to increase fracture ductility which contributed to increase the shear strength. In addition, glass transition temperature and thermal stability of the modified epoxy were found to be relatively unaffected.

Comparative study of structure, mechanical and electromagnetic interference shielding properties of carbon nanotube buckypapers prepared by different dispersion media

In order to prepare multi-wall carbon nanotube (MWCNT) buckypapers (BPs) with excellent comprehensive properties, an investigation was conducted regarding the effect of dispersing medium on CNT dispersions and resultant BPs. Three types of MWCNTs with different lengths and diameters, denoted as CNT-A, CNT-B and CNTC, were dispersed into water, ethanol and 1-methyl-2-pyrrolidone, respectively. The dispersion stability was monitored by UV–vis spectroscopy and conductivity meter. The results showed that all MWCNT/water dispersions were far superior to MWCNT/ethanol dispersion in stability, but slightly inferior in monodispersity. Subsequently, BPs prepared by vacuum filtration using the above-mentioned dispersions were investigated to clarify the pore structure, electrical, mechanical and electromagnetic shielding properties. Compared with BPs prepared with CNT-A/ethanol dispersion (BP-A-E), the BP prepared with CNT-A/water dispersion (BP-A-W) showed smaller pore size, and exhibited significantly improvement in electrical conductivity (74%), strength (665%). A super high absorption-dominated electromagnetic interference shielding effectiveness (SE) of 101.7 dB was achieved by BP-A-W of 450 μm thick in the range of 8.2–18 GHz, which was 26% higher than that of BP-A-E. A notable SE of 48.4 dB and a high specific SE of 29,300 dB·cm2/g were obtained by BP of 45 μm thick prepared with CNT-C/water dispersion.

Preparation of WO3/CNT catalysts in presence of ionic liquid [C16mim]Cl and catalytic efficiency in oxidative desulfurization

AbstractBACKGROUNDWith the strict regulation for environmental protection, the removal of sulfur compounds from fuels is becoming more and more urgent. Hydrodesulfurization is one of the most widely used technologies in chemical industry, but its application is limited because of the harsh reaction conditions and the low efficiency in removal of aromatic organic sulfide. In this work, catalysts consisting of tungsten trioxide immobilized on carbon nanotubes (WO3/CNT) in the presence of ionic liquid [C16mim]Cl were prepared for the oxidative desulfurization of aromatic organic sulfide.RESULTSThe catalysts were systematically characterized by TG‐DSC, XRD, UV–visible, FTIR, Raman, SEM, TEM, XPS and BET. The dispersion of CNT and the crystal phase of WO3 on the carrier (CNT) were changed in the presence of ionic liquid [C16mim]Cl. The WO3 exists in tetrahedral form when the mass ratio of [C16mim]Cl to CNT is 2. The WO3/CNT catalyst demonstrates better activity in the oxidative desulfurization system, with the removal of dibenzothiophene (DBT) reaching 90.73% under optimal conditions. The oxidation process of DBT follows pseudo‐first‐order kinetics, and the activation energy is about 29.69 kJ mol−1. Dibenzothiophene sulfone (DBTO2) was determined to be the oxidative product of DBT.CONCLUSIONThe results illustrated that the oxidative desulfurization efficiency of different forms of WO3 loaded on the same carrier (CNT) followed the order tetrahedral WO3 &gt; tetragonal phase WO3 &gt; monoclinic phase WO3. © 2019 Society of Chemical Industry

Enhanced performance of 3D printed highly elastic strain sensors of carbon nanotube/thermoplastic polyurethane nanocomposites via non-covalent interactions

Strain sensors based on conductive polymer composites have been widely investigated due to their excellent elasticity and sensitivity. Such sensors may be manufactured using additive manufacturing techniques but there are some challenges to overcome in terms of performance if this technique is to be used. In this work, a high-performance strain sensor of carbon nanotube/thermoplastic polyurethane (CNT/TPU) nanocomposites was printed by fused deposition modeling (FDM), and 1-pyrenecarboxylic acid (PCA) was introduced to non-covalently modify the CNTs and improve the polymer-nanofiller interactions. It is shown that the tensile and electrical properties of the modified composites are increased as a result of more uniform CNT dispersion. The 3D printed sensors demonstrate excellent properties with high gauge factor (GF = 117213 at a strain of 250%), large detectable strain (0–250%), good stability (up to 1000 loading/unloading cycles) and wide frequency response range of 0.01–1 Hz. Also, the strain sensing ability of the sensor is greatly improved with the introduction of PCA. The working mechanism of strain sensor was further studied based on the Simmons’ tunneling theory. In addition, the sensor demonstrates the capability to monitor human body movements and voice, showing its potential for applications in intelligent robots and wearable electronics where customizability is demanded.

Carbon aerogel/carboxylated carbon nanotubes: porous structure and electrical conductivity properties

The aim of this study is to investigate the effect of various weight percentages of multi-walled-carbon nanotubes (CNT) with carboxyl groups on the properties of carbon aerogels (CA). The electrical conductivity, shrinkage and morphology of carbon aerogel- functionalized carboxylated carbon nanotubes composites (COO-CNT sample) were characterized and compared with carbon aerogel composites synthesized by CNT dispersed by sodium dodecyl sulfate (SDS-CNT sample) and carbon aerogel composites with raw CNT (R-CNT sample). According to the obtained results, the shrinkage of R-CNT sample does not noticeably change with increasing CNT weight percentages (wt%), while the decreased significant shrinkage of COO-CNT and SDS-CNT samples might be due to better dispersion of CNT. In addition, while the electrical conductivity of R-CNT is maintained at the same level, it is enhanced by increasing the CNT wt% for COO-CNT and SDS-CNT samples which could be attributed to the pathways with higher conductivity in their matrix. Moreover, the higher mechanical strength (lower shrinkage) of SDS-CNT sample compared to COO-CNT sample can be ascribed to a more uniform arrangement of CNT inner network, as observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

Effect of Carbon Nanotubes on Solution Treatment Temperature and Dissolution Characteristics of Precipitates in Al Alloy Produced by High-Energy Milling and Hot Extrusion

The present study discusses the effect of CNT on the solution treatment temperature for Al alloy (AA), i.e. Al–4.4Cu–0.5 Mg, Al alloy–CNT (AC) and Al alloy–Ni-coated CNT (ANC) composites fabricated by mechanical milling and hot extrusion. Differential scanning calorimetry indicated that dispersion of CNT in Al alloy increased the dissolution temperature of θ phase precipitates. X-ray diffraction (XRD) and scanning electron microscopy illustrated complete dissolution of θ phase in both AA and AC samples when solution-treated at 520 °C, whereas ANC sample exhibited the same behaviour at 500 °C itself. XRD patterns of ANC sample revealed the presence of an additional intermetallic Al7Cu4Ni phase, which remains undissolved even after the solution treatment at 540 °C. Utilisation of Cu atoms to form Al7Cu4Ni phase resulted in significant reduction in size and number density of θ phase in ANC. The hardness of AC and ANC samples was found to be higher compared to AA owing to dispersion strengthening by CNT and Al7Cu4Ni particles.

Effect of CNT dispersion methods on the strength and fracture mechanism of interface in epoxy adhesive/Al joints

The tensile and shear strengths of adhesively bonded aluminum (Al) joints were inspected in the presence of amino functionalized multi-wall carbon nanotubes (MWCNTs). Tensile and shear tests were carried out using butt and lap-shear joints. The main goal was to compare the effects of dispersion methods of functionalized-CNT into epoxy on the mechanical performances and failure mechanisms of Al joints. Two different types of dispersion procedures, distributing CNT in the hardener (HH method) and distributing CNT in the resin (RR method), were applied. To identify the failure mechanisms, the morphology of fracture surfaces were analyzed using scanning electron microscopy (SEM). Comparing two dispersion methods against one another ascertained that following the RR method for dispersing CNTs in the adhesive displayed larger shear strength, while applying HH method offered fairly greater tensile strength. Moreover, dispersing CNTs in the resin induced more uniform dispersion of CNTs as compared to distributing nanofillers in the hardener. Following RR method, CNTs good dispersion as well as the presence of effective crack growth dissipating mechanisms, increased the shear strength of CNT reinforced adhesive joint. Incorporating CNTs using HH approach encouraged the plastic void formation of epoxy around the agglomerated CNTs, and as a consequence, promoted the plastic deformation under tension.

Role of CNT/clay hybrid on the mechanical, electrical and transport properties of NBR/NR blends

Hybrid fillers are making a remarkable improvement in the properties of polymeric systems. In the present study, the influence of hybrid of multiwalled carbon nanotube (MWCNT) and nanoclay on the mechanical, electrical and transport properties of nitrile rubber (NBR)/natural rubber (NR) blends has been investigated. Attempts were made to prepare NBR/NR/CNT/nanoclay composites on a two-roll mill and to study various mechanical properties such as tensile strength, tear resistance, abrasion loss and compression set percent. Transport, thermal and electrical properties were also investigated. By virtue of the synergism between MWCNT and nanoclay, the composites exhibited enhancement in the mechanical properties by the immobilization of rubber chains via coupling action between the filler surface and the rubber molecules. The fine and uniform dispersion of both CNT and clay in composite samples supported the observation. The hybrid filler system had a great impact on the thermal and electrical properties of the composites.

CNT dispersion effect on weld strength of fiber reinforced plastics

CNT dispersion effect on weld strength of fiber reinforced plastics

Relationship between the carbon nanotube dispersion state, electrochemical impedance and capacitance and mechanical properties of percolative nanoreinforced OPC mortars

The homogeneous dispersion of carbon nanotubes, (CNTs), in a cementitious matrix is a crucial procedure that affects both mechanical properties and electrical conductivity of the nanocomposite. Electrochemical Impedance Spectroscopy, (EIS), can be very useful in studying and characterizing the impact of the CNT content in nanoreinforced cementitious materials in a quantitative way. In this study, measurements of the resistance, reactance and capacitance reveal the nature of circuit elements formed by the nanotube network in cement mortars reinforced with various amounts of carbon nanotubes and provide insight of the nanotubes’ dispersion state. Resistivity results show that percolation threshold was reached between CNT weight fractions of 0.1% and 0.15 wt%. Below percolation, a consistency between resistive and capacitive phases exists, i.e., resistivity, reactance and capacitance were found to decrease as the nanotube content increases. After the continuous conductive network was formed, and percolative behavior was achieved, resistivity values show a little dependence on the CNT content. However, the presence of CNT entanglements was found to contribute to an amplified energy storage ability, as both the imaginary part of impedance (reactance) and capacitance were increased. A correlation between capacitance, flexural strength and modulus of elasticity was observed for the first time. Capacitance values provide valuable information on the energy storage ability of the material and how the actual CNT dispersion state affects the mechanical properties of percolative nanoreinforced cementitious materials. Finally, a general micromechanics model, modified by taking into account the conductive mechanisms below and above percolation threshold, was successfully implemented. The theoretically determined values of the overall electrical conductivity are in good agreement with the experimental results.

Stability and vibration analysis of CNT-Reinforced functionally graded laminated composite cylindrical shell panels using semi-analytical approach

The present paper examined the buckling, postbuckling and vibration characteristics of pre-buckled and post-buckled laminated CNT reinforced composite (CNTRC) cylindrical shell panel made up of single walled carbon nanotubes (SWCNTs) and isotropic matrix. The effective material properties of CNTRC panel are computed using extended rule-of mixture (ROM) method. Higher order shear deformation theory (HSDT) with von Kármán type of nonlinearity is adopted to model the CNTRC cylindrical shell panel. Four different boundary conditions are considered. Besides uniform loading, different types of non-uniform in-plane load distribution such as triangular, trapezoidal, parabolic and partial edge loadings are considered. The internal stress distribution within the shell panel due to applied non-uniform loadings is evaluated by prebuckling analysis. Subsequently, via Hamilton's principle the governing partial differential equations of CNTRC laminated cylindrical shell panel are derived. Employing Galerkin's method and by neglecting the inertia terms the partial differential equations are reduced to a set of non-linear algebraic equation for the static problem. However, for dynamic problem the partial differential equations are converted to a set of ordinary differential equations. Beside parametric study the obtained numerical results from the present semi-analytical study illustrates the effects of CNT volume fraction, CNT dispersion profile, non-uniform load distribution and boundary conditions on the stability and vibration characteristics of CNTRC cylindrical panel.

Nonlinear bending analysis of FG-CNTRC annular plates with variable thickness on elastic foundation

As a first endeavor, the nonlinear bending behavior of functionally graded carbon nanotube reinforced composite (FG-CNTRC) annular plates with variable thickness on an elastic foundation is scrutinized in this research. The nonlinear governing equations are established according to the third-order shear deformation theory (TSDT) in conjunction with the nonlinear von Karman strain field. A Pasternak elastic foundation is assumed to be in contact with the annular plate during deformation. To discretize the nonlinear governing equations and boundary conditions, the generalized differential quadrature method (GDQM) is adopted and the nonlinear system of equations is solved via the Newton-Raphson iterative method. Through the numerical results, effects of the elastic foundation, geometrical parameters, boundary conditions, CNT dispersion and volume fraction, thickness-to-radius ratio and thickness profile are investigated in detail. It is shown that CNT volume fraction and dispersion have a remarkable effect on improving bending behavior of the annular plate. It is found that thickness profile plays an essential role in the bending response of the annular plate.

The effect of CNT-reinforced polyurethane foam cores to flexural properties of sandwich composites

In foam cored sandwich composites, it is crucial to understand micromechanical characteristics of foam in relation with its properties to understand synergetic effects of adding nanomaterials such as CNTs. In this study, effects of CNT dispersion and distribution on cell morphology and foamability of rigid polyurethane (PU), which is directly related to microstructure and mechanical performance of overall structures were investigated. Raw and functional CNTs were added to rigid polyurethane foams up to 0.2 wt.% and their compressive strength is evaluated. The results showed that dispersion media such as PMDI with low viscosity revealed a better CNT dispersion and resulted with an enhancement of 13% in compressive strength compared to neat PU foams. This enhancement in foam core properties reflected in sandwich composites with an enhancement approximately 30% in both core shear and face ultimate strength. Hence, core shear found to be the common failure mechanism for all sandwich composites.

Experimental Investigation on 3D Graphene-CNT Hybrid Foams with Different Interactions.

Due to the exceptional properties of graphene, numerous possibilities for real applications in various fields have been provided. However, it is a challenge to fabricate bulk graphene materials with properties arising from the nature of individual graphene sheets, and which assemble into monolithic three-dimensional structures. If 3D structured graphene foam were made instead of 2D structured graphene, it is expected that it would be a facile fabrication, with relatively low cost with the possibility of scale-up, and would maintain the intrinsic properties of graphene. To solve the weaknesses of 2D structured graphene, this study aimed to fabricate a 3D graphene-carbon nanotubes (CNT) hybrid foam. In this study, CNT was used to reinforce the graphene foams. In addition, two different surfactants, known as sodium dodecylbenzene sulphonate (SDBS) and cetyltrimethylammonium bromide (CTAB), were applied to help CNT dispersion. The π–π interaction was induced by SDBS/CNT, while ionic interaction was derived from CTAB/CNT. To confirm the charge effect with different surfactants, SEM, Zeta-potential, FT-IR, Raman spectroscopy, and compression tests were performed. When using a cationic surfactant, CTAB, compressive modulus, and strength increased due to the formation of relatively strong ionic bonding.