Carbon Nanotubes Loading Research Articles

Mode II Interfacial Fracture Toughness of Multi-Walled Carbon Nanotubes Reinforced Nanocomposite Film on Aluminum Substrate.

In this investigation, various loadings of multi-walled carbon nanotubes (MWCNTs) ranging from 0.3–1.0 wt % were incorporated into the epoxy to fabricate the nanocomposites. Nanocomposite film with a thickness of 0.2 mm was deposited on an aluminum substrate through a hot-pressing process. Theoretical expression of the model II strain energy release rate for the film/substrate composite structure was derived. End-notched flexure (ENF) tests were performed to characterize the mode II fracture energy of the composite structure. Experimental results indicate that the elastic modulus, ultimate strength, and mode II fracture energy increase as the MWCNT loading in the nanocomposite increases. In the case of nanocomposite film with 1.0 wt % of MWCNTs, the elastic modulus, ultimate strength, and mode II interfacial fracture toughness are increased by 20.6%, 21.1%, and 54.4%, respectively in comparison with neat epoxy. In addition, the dispersion of MWCNTs in the epoxy-based matrix was investigated using scanning electron microscope (SEM). The SEM images depict that MWCNTs are well dispersed leading to the enhancement of the mechanical properties of the nanocomposite.

Influences of pristine carbon nanotube on the rheological properties of compatibilized polylactic acid/natural rubber nanocomposite

Polylactic Acid (PLA) was blended with Natural Rubber (NR) and compatibilized by PLA grafted maleic anhydride (PMA) and NR grafted maleic anhydride (NMA) to achieve high performance of PLA/NR blends. Pristine carbon nanotube (CNT) was then added into PLA/NR blends with different CNT loading (1–8 part per hundred resin) using melt blending technique to form nanocomposites. A systematic investigation of the rheological properties of the nanocomposites as a function of pristine CNT content were carried out. Rheological analysis exhibited an enhancement in the storage and loss moduli of nanocomposites compared to blends without CNT. The compatibilizers PMA and NMA have shown contrasting results in terms of rheological values. Rheological analysis showed that the both sets of nanocomposites behaved solid-like at lower frequencies. When the CNT loading was increased the nanocomposites showed no dependence of frequency.

High-performance styrene-butadiene rubber nanocomposites based on carbon nanotube/nanodiamond hybrid with synergistic thermal conduction characteristics and electrically insulating properties

Reinforcement of rubbery materials with carbon nanotube (CNT) has gained much attention over the last few decades due to the inherent ability of CNT to improve the physical and mechanical properties of polymer composites. However, CNT renders electrical conductivity to the rubber composites, which could be problematic for a number of applications. In an attempt to overcome such issues, we controlled the insulating properties of styrene-butadiene rubber (SBR) nanocomposites by hybridization of CNT with nanodiamond (ND) particles without scarifying desirable features of the nanoparticles. In this respect, the effects of carbon nanotube (CNT) and nanodiamond (ND), either individually or in hybrid form, on mechanical, physical, morphological and thermal properties of styrene-butadiene rubber (SBR) nanocomposites were well characterized in the present research using bound rubber, tensile, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), electrical, and thermal conductivity characterizations. The SBR nanocomposites holding nanoparticle concentrations ranging from 1 to 5 phr were fabricated at various CNT/ND compositions. The results indicated that the hybridization of nanoparticles improved the dispersion state of individual nanoparticles in SBR, successfully controlled the insulating behavior of the SBR nanocomposite and enhanced the thermal conductivity of SBR in synergistic manner; while the mechanical improvement retained as CNT filled SBR. The SBR nanocomposites holding 5 phr hybrid-nanoparticles with appropriate nanoparticles composition possessed thermal conductivity more than two-fold of unfilled SBR and 20% more than nanocomposite with 5 phr loading of single CNT.

Self-healing and flexible carbon nanotube/polyurethane composite for efficient electromagnetic interference shielding

Electromagnetic interference (EMI) shielding composites are inevitably damaged in the long-term usage which would affect the regular operation of the devices. Hence, the demand for materials with healable and reliable EMI shielding performance has increased. Here, a flexible conductive composite owning both self–healing and EMI shielding functions is facilely developed, with carbon nanotubes (CNTs) as conductive filler and dynamically crosslinked polyurethane bearing Diels–Alder bonds (PUDA) as polymer matrix. The PUDA/CNT composite shows a high EMI shielding effectiveness (EMI SE) of 30.7 dB at 5.0 wt% CNT loading in the range of X-band (8.2–12.4 GHz). And the EMI SE can recover from 16.8 dB for damaged state to 29.8 dB after three times cut/healing cycles, revealing excellent EMI SE retention of 97.1%. The PUDA/CNT composite also exhibits healable tensile properties with an elongation at break up to 571% ± 31% at 2.0 wt% CNT content and self-healing efficiency of 89.2% after the repeatable healing. This work demonstrates a healable EMI shielding composite, which ensures the reliability and long-time use under harsh conditions.

Effect of fungal degradation on technological properties of carbon nanotubes reinforced polypropylene/rice straw composites

Effects of fungal decay period on the technological properties of polypropylene/rice straw composites reinforced with different amount of carbon nanotubes (CNTs) were evaluated in this research work. The composite specimens were prepared using an internal mixer followed by compression molding. The specimens were then subjected to the fungal decay using white-rot fungus ( Coriolus versicolor) for 1, 2, 3, and 4 months. The degree of fungal attack was recorded by determining the weight loss of the specimens. The physical and mechanical properties including water uptake, flexural strength, and impact strength (IS) were investigated. The results indicated that the weight loss of the specimens was significantly reduced by increasing the CNT loading levels. The weight loss ratio of the specimens with the CNT was lower than that of the specimens without the CNT. The modulus of rupture, modulus of elasticity, and IS of the specimens exposed to the fungal degradation increased in the presence of CNT. Furthermore, the decayed specimens without CNT had higher water uptake than those of the specimens with CNT. This was attributed to the decrease in the number of cavities on the surface of the composites containing CNT. Based on the findings obtained from the present study, it was concluded that the amount of the CNT should be considered according to the severity and duration of the fungal exposure.

Synthesis and performance evaluation of nanocomposite soy protein isolate/carbon nanotube (SPI/CNTs) adhesive for wood applications

In this article, effect of the incorporation of carbon nanotubes (CNTs) into soy-based adhesive, obtained from soy protein isolate (SPI), on the performance of the nanocomposite adhesive is presented. Multifunctional and exceptional properties of carbon nanotubes (CNTs) in nanofiller in polymer matrix were explored in this study to develop nanocomposite soy-based adhesive with improved shear strength and water resistance. Consequently, nanocomposite SPI/CNT adhesives having different CNT loading were synthesized and evaluated. Morphology, thermal stability and chemical functionalities of the synthesized nanocomposite adhesives were checked using scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy, respectively. The bond strength test of the adhesives was carried out according to European standards, EN-204 and EN-205. The results showed that CNTs improved the shear strength of the nanocomposite SPI/CNT adhesive at reduced percentage loading. About 100% increase in the shear strength and water resistance was recorded for the nanocomposite SPI/CNTs adhesive when compared with an alkaline modified adhesive without carbon nanotubes. The shear strength of the nanocomposite adhesive increased from 3.48 MPa (adhesive without CNTs) to 6.91 MPa (adhesive with 0.3 wt% CNT loading) and then decreased afterwards as the CNT loading was increased beyond 0.3%. Enhanced shear strength of soy-based adhesives using different fillers has been reported in the literature, but at relatively high loading of the filler. In this study, relatively small amount of CNTs (0.3%) has shown a substantial enhancement in shear strength as compared to other fillers. It is expected that the newly developed adhesive could pave the way to solving the challenge of low shear bond strength and poor water resistance of soy-based adhesives for wood applications in the industry.

Effect of Loading and Functionalization of Carbon Nanotube on the Performance of Blended Polysulfone/Polyethersulfone Membrane during Treatment of Wastewater Containing Phenol and Benzene.

In this study, a carbon nanotube (CNT)-infused blended polymer membrane was prepared and evaluated for phenol and benzene removal from petroleum industry wastewater. A 25:75 (by weight %) blended polysulfone/polyethersulfone (PSF/PES) membrane infused with CNTs was prepared and tested. The effect of functionalization of the CNTs on the quality and performance of the membrane was also investigated. The membranes were loaded with CNTs at different loadings: 0.5 wt. %, 1 wt. %, 1.5 wt. % pure CNTs (pCNTs) and 1 wt. % functionalized CNTs (fCNTs), to gain an insight into the effect of the amount of CNT on the quality and performance of the membranes. Physicochemical properties of the as-prepared membranes were obtained using scanning electron microscopy (SEM) for morphology, Raman spectroscopy for purity of the CNTs, Fourier transform infrared (FTIR) for surface chemistry, thermogravimetric analysis (TGA) for thermal stability, atomic force microscopy (AFM) for surface nature and nano-tensile analysis for the mechanical strength of the membranes. The performance of the membrane was tested with synthetic wastewater containing 20 ppm of phenol and 20 ppm of benzene using a dead-end filtration cell at a pressure ranging from 100 to 300 kPa. The results show that embedding CNTs in the blended polymer (PSF/PES) increased both the porosity and water absorption capacity of the membranes, thereby resulting in enhanced water flux up to 309 L/m2h for 1.5 wt. % pCNTs and 326 L/m2h for 1 wt. % functionalized CNT-loaded membrane. Infusing the polysulfone/polyethersulfone (PSF/PES) membrane with CNTs enhanced the thermal stability and mechanical strength. Results from AFM indicate enhanced hydrophilicity of the membranes, translating in the enhancement of anti-fouling properties of the membranes. However, the % rejection of membranes with CNTs decreased with an increase in pCNTs concentration and pressure, while it increased the membrane with fCNTs. The % rejection of benzene in the pCNTs membrane decreased with 13.5% and 7.55% in fCNT membrane while phenol decreased with 55.6% in pCNT membrane and 42.9% in the FCNT membrane. This can be attributed to poor CNT dispersion resulting in increased pore sizes observed when CNT concentration increases. Optimization of membrane synthesis might be required to enhance the separation performance of the membranes.

Reinforcing Microwave Absorption Multiwalled Carbon Nanotube–Epoxy Composites Using Glass Fibers for Multifunctional Applications

Glass fiber reinforced epoxy composites with various carbon nanotube loadings are fabricated and studied by Guang-Lin Zhao and co-workers in their article, number 1900780. The composites show high microwave absorption and low mass density with much enhanced tensile strength, which provides a multifunctional potential for various applications.

Piezoresistive characterization of epoxy based nanocomposites loaded with SWCNTs‐DWCNTs in tensile and fracture tests

AbstractStrain sensing capability of carbon nanotubes (CNTs) doped epoxy under tensile and flexural tests were broadly studied, while the piezoresistive behavior of nanocomposites in precracked specimen, that is, in fracture toughness tests, have not been addressed deeply in the literature. Therefore, in the current paper, both the strain and crack sensing capabilities of single wall carbon nanotubes‐double wall carbon nanotubes (SWCNTs‐DWCNTs) doped epoxy subjected to tensile and mode I fracture tests were investigated. Different CNT loadings including 0.5 and 0.75 wt% were used to compare the effect of various states of CNTs dispersion, including uniformly dispersed CNTs and aggregates, on electromechanical properties. Results showed that specimens loaded at 0.5 wt% of CNTs possessed proper tensile strength, fracture toughness, piezoresistivity, and sensitivity. A nonlinear trend in normalized resistance change with respect to strain was noticed under tensile test resulting from tunneling effect which induced nonlinearity in the electrical signals. During fracture tests, prior to crack propagation, different trends in piezoresistivity as a function of displacement were observed, depending on the CNT loading, that is, linear and nonlinear behavior at CNT content of 0.5 and 0.75 wt%, respectively. The nanocomposite could simultaneously monitor damage initiation and extension with the onset of crack growth by showing abrupt increase in normalized resistance, and two different failure modes can be distinguished including abrupt and crack extensions. It was concluded that any abrupt jump in normalized resistance could be used as an indicator for damage initiation in the specimen.

Shaping and Locomotion of Soft Robots Using Filament Actuators Made from Liquid Crystal Elastomer–Carbon Nanotube Composites

Soft robots, with their agile locomotion and responsiveness to environment, have attracted great interest in recent years. Liquid crystal elastomers (LCEs), known for their reversible and anisotropic deformation, are promising candidates as embedded intelligent actuators in soft robots. So far, most studies on LCEs have focused on achieving complex deformation in thin films over centimeter‐scale areas with relatively small specific energy densities. Herein, using an extrusion process, meter‐long LCE composite filaments that are responsive to both infrared light and electrical fields are fabricated. In the composite filaments, a small quantity of cellulose nanocrystals (CNCs) is incorporated to facilitate the alignment of liquid crystal molecules along the long axis of the filament. Up to 2 wt% carbon nanotubes (CNTs) is introduced into a LCE matrix without aggregation, which in turn greatly improves the mechanical property of filaments and their actuation speed, where the Young's modulus along the long axis reaches 40 MPa, the electrothermal response time is within 10 s. The maximum work capacity is 38 J kg−1 with 2 wt% CNT loading. Finally, shape transformation and locomotion in several soft robotics systems achieved by the dual‐responsive LCE/CNT composite filament actuators are demonstrated.

An efficient approach for prediction of the nonlocal critical buckling load of double-walled carbon nanotubes using the nonlocal Donnell shell theory

This paper aims to apply the nonlocal Donnell shell theory to study the buckling of double-walled carbon nanotubes (DWCNTs) under axial compression taking into account the effects of internal small length scale and the Van der Waals interactions between layers. The DWCNTs is modeled as nonlocal double circular cylindrical elastic shells. On the basis of nonlocal elasticity theory, governing equations for buckling of Donnell shells are obtained taking into account the Van der Waals force. The nonlocal buckling load of DWCNT is derived without any assumption on radius tubes. However, it is a very difficult task to obtain the analytical solution of nonlocal critical buckling load. In this paper, we develop an approach for prediction of the nonlocal critical buckling load of DWCNTs.

N-doped bamboo-like carbon nanotubes loading Co as ideal electrode material towards superior catalysis performance

A two-step thermal polarization process was developed to create N-doped bamboo-like carbon nanotubes with Co loading. Co-doped graphite carbon nitride (g-C3N4) nanosheets were prepared through the thermal polymerization of melamine. N-doped bamboo-like carbon nanotubes confirmed by Raman spectra were fabricated via further thermal polymerization at 750 °C using g-C3N4 nanosheets. Co nanoparticles were loaded during the thermal polymerization. Electrochemical tests indicate that Co-loaded samples revealed superior hydrogen evolution reaction (HER) performance. The Pt clusters were deposited on the Co-loaded nanotube. When the loading amount of Pt clusters is 0.21% wt, the HER performance of Co-loaded nanotubes was better than that of commercial Pt/C (20% wt of Pt loading) electrode. In contrast, those Ni loaded nanotubes exhibited excellent selectivity in the catalytic direction of furfural hydrogenation, in which 99.3% of furfural was converted to tetrahydrofurfuryl alcohol at 120 °C. These results inject new vitality into the research and application of ultra-thin g-C3N4 materials.

Automated Mixed Matrix Membrane Microextraction Prior to Liquid Chromatography for the Determination of Chlorophenoxy Acid Herbicides in Sewage Water Samples

A new automated flow-through adsorption/desorption procedure using a multiwalled carbon nanotube immobilised mixed matrix membrane is described. The membrane consisted of 25% (w/w) multiwall carbon nanotube loading in a cellulose triacetate polymer matrix as support and was cast and embedded in a flow-through cell with a channel of an approximate length of 20 mm, a width of 2 mm, and a depth of 1.5 mm. The membrane immobilised with nanoparticles was activated using 1-octanol as a conditioning solvent. For the analyte adsorption process, 6 mL of the sample was passed through the cell at a flow rate of 0.2 mL min−1. The entrapped target analytes were then desorbed dynamically with 60 µL of 2-propanal at a flow rate of 5 µL min−1 prior to HPLC/UV analysis. The performance of the system was demonstrated for the determination of chlorinated phenoxyacetic acid herbicides in sewage water samples. Under the optimum conditions, the linearity of this method ranged from 50 to 1000 ng mL−1, with a correlation coefficient (r) ≥ 0.993 and a detection limit varying from 15 to 20 ng mL−1. Enrichment factors of up to 55 were achieved with relative recoveries of 95–99% and precision values of 6.1–7.5%.

Calculation of tunneling distance in carbon nanotubes nanocomposites: effect of carbon nanotube properties, interphase and networks

In this paper, two developed models for electrical conductivity of polymer nanocomposites are linked to express an equation for tunneling distance between adjacent carbon nanotubes (CNT) by the effective properties of polymer matrix, CNT, interphase and networks. The tunneling distance is calculated for some samples at different CNT concentrations. In addition, the suggested equation is applied to justify the impacts of all parameters on the tunneling distance. The tunneling distance decreases as CNT concentration increases, but its variation reduces at high CNT loading. The suggested equation demonstrates that a thick interphase, thin and short CNT, high filler concentration, poor percolation threshold, low surface energy of polymer and high CNT surface energy produce a short tunneling distance.

A multifunctional carbon nanotube reinforced nanocomposite modified via soy protein isolate: A study on dispersion, electrical and mechanical properties

Excellent multifunctional polymeric nanocomposite cannot be achieved without good dispersion and well protection of nanofillers, for which a highly efficient, cost-effective and environmental benign nanofiller treatment approach is demanded. Herein, we report that soy protein isolate (SPI), an extracted protein from soybean, is applied as a highly performed bio-surfactant to treat carbon nanotubes (CNTs), resulting in nanocomposite with tremendously improved dispersion, electrical and mechanical properties. TEM, UV–vis and dynamic light scattering (DLS) and real-time optical microscopic characterizations show that, compared with a conventional surfactant, sodium dodecylsulfate (SDS), SPI more effectively and efficiently functionalize CNTs with less agglomerates and more stable particle size distribution. The electrical conductivity of the SPI-CNTs/epoxy increased by 6 orders of magnitude at 0.5 wt% vs pure epoxy, which is 4 orders higher than the pristine CNTs/epoxy and even 1 order higher than that of the SDS treated counterpart. The tensile modulus, strength and fracture toughness of the SPI-CNTs/epoxy increased by 27%, 24% and 32% at 1.0 wt% loading of CNTs, respectively, which is 20%, 26% and 18% higher than the pristine CNTs/epoxy and 10%, 23% and 21% higher than the SDS-CNTs/epoxy. The in-situ tensile test accompanied by digital image correlation technique (DIC) shows that cracks are effectively arrested by the SPI-CNTs while SDS-CNTs cannot. These results establish a solid foundation for the application of SPI in the polymeric nanocomposite fields.

Electrically conductive high-performance thermoplastic filaments for fused filament fabrication

Conductive polyetherimide (PEI)-based filaments can fill the gap between the design and manufacturing of functional and structural components through additive manufacturing. This study systematically describes the fabrication of carbon nanotube (CNTs)-reinforced PEI filaments, complemented by a custom-built extrusion process facilitating low weight fraction of nanomaterials. Neat PEI and CNTs/PEI filaments at different CNTs fractions ranging from 0.1 to 7 wt% were fabricated. Supported by morphology analysis, the rheological percolation was found to be higher (0.25 wt% CNTs/PEI) than electrical percolation (0.1 wt% CNTs/PEI) since the system reached an electrical percolation within the formation of a continuous conductive path at lower CNTs loadings. With the 7 wt% CNTs loading, the highest electrical conductivity of CNTs/PEI filaments was reported as 2.57×10-1 S/cm. A 55% enhancement in tensile modulus was achieved when 5 wt% CNTs were introduced, but in a trade-off in elongation at break ca. 65%.

Carbon nanotubes reinforced alumina matrix nanocomposites for conductive ceramics by additive manufacturing

Alumina has been extensively used due to its high toughness and hardness, low bulk density, and thermal stability without interaction with the matrix at high temperature. However, the non-conductivity at room temperature narrows its broader applications. Carbon nanotube (CNT) is a suitable candidate to adjust the electrical property of alumina matrix composites due to its high electrical conductivity. By using material extrusion 3D printing (ME3DP), we fabricated 3D CNT/alumina green bodies using inks with controlled rheological properties for high printability. The printed green bodies with CNT loading from 3 wt% to 10 wt% were thermally treated to remove binders and sinter the 3D parts at temperatures from 900 to 1400 °C. The sintered samples showed a good dispersion of CNT in the alumina matrix and improved electrical conductivity. The electrical conductivity of the composites measured up to 10-1 S/m at 7 wt.% CNT loading, compared to the electrical conductivity of 10-13 S/m of pure alumina.

Effect of Multiwall Carbon Nanotubes (Mwcnt, Mwcnt-Cooh and Mwcnt-Thiazol) in the Mechanical Compression Properties of a Cement-Based Material

This study focuses on determine the mechanical compression properties of Guatemalan cement-based materials as a function of the carbon nanotubes chemical composition and loading. Multiwall Carbon Nanotubes oxidized (MWCNT-COOH) and Multiwall Carbon Nanotubes funcionalized with thiazol (MWCNT-Thiazol) were synthesized in an environment friendly reaction with urea instead of the traditional acid reaction. The samples were characterized by FT-IR, RAMAN, X-Ray diffraction (XRD)and TGA. Different weight ratios of the MWCNTs were added to a cement mortar to provide mechanical properties (0.01%, 0.03%, 0.05% w/w); additionally, a super plasticizer was employed. Adding 0.01% of MWCNT the mechanical compression of Portland-type cement marketed in Guatemala was improved with 3867.17 psi and 5212 psi, representing an improvement of 5.26 and 2.02% in comparison to the control sample at 7 and 28 days, respectively. The UV-Vis of the super plasticizer andMWCNT (16:1 21.2:1 and 41:1) was done to understand the optimal dispersion. The performance of the mechanical compression of MWCNT in comparison to the MWCNT-COOH and MWCNT-Thiazol is analyzed according to the non-covalent interaction with the polycarboxylate superplasticizer and the matrix cement.

Efficient Solvent-Free Microwave Irradiation Synthesis of Highly Conductive Polypropylene Nanocomposites with Lowly Loaded Carbon Nanotubes

Efficient Solvent-Free Microwave Irradiation Synthesis of Highly Conductive Polypropylene Nanocomposites with Lowly Loaded Carbon Nanotubes

Analysis of the conductive behavior of a simplified sediment system and its computational simulation

Because of the important contributions of electrochemical redox reactions to biochemical cycles and their potential application for the in-situ remediation of contaminated sediment, the mechanisms of long-distance electron transport coupling spatially separated redox half reactions in sediment have drawn much attention. To explore a preliminary mechanism of long-distance electron transport in sediment, in the current study, two simplified composite systems are constructed consisting of spherical ferroferric oxide (Fe3O4) nanoparticles and rod-like carbon nanotubes (CNTs) as conductive fillers and silica (SiO2) particles as the matrix. Two different constructed composite systems (e.g., SiO2/Fe3O4 and SiO2/Fe3O4/CNTs) were used to model a three-dimensional sediment framework instead of sediment with quite complex components. The effects of the loading of conductive fillers (e.g., Fe3O4, CNTs) and the particle size of SiO2 matrix on the conductive behavior of the composite system were investigated. The results showed that both of the electrical properties of SiO2/Fe3O4 and SiO2/Fe3O4/CNTs composite systems typically exhibited a non-linear conductive behavior that the electrical conductivity increased with the increasing of filler loading and showed an abrupt increase at critical filler loading. The conductivity of the SiO2/Fe3O4 and SiO2/Fe3O4/CNTs composite systems with micro-sized SiO2 as the matrix was higher than that of the composite systems with nano-sized SiO2 as the matrix. Compared with the SiO2/Fe3O4 composite system, the electrical conductivity of the SiO2/Fe3O4/CNTs composite system was enhanced by several orders of magnitude and only a small loading of CNTs could make the conductivity of the SiO2/Fe3O4/CNTs composite system reach a higher level. The electrical conductivity predicted by the electrical conductivity model of a two-phase composite system showed a similar trend as the experimental results and the two-dimensional (2D) percolation-based model filled with rods gave a good estimation of percolation probability.