Multi-walled Carbon Nanotubes Support Research Articles

Surfactant assisted synthesis of Pt-Pd/MWCNT and evaluation as cathode catalyst for proton exchange membrane fuel cell

This study evaluates the role of two types of surfactants, the anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB) on the synthesis and properties of multi-walled carbon nanotube (MWCNT) supported bi-metallic Pt-Pd (atomic ratio 1:1) nanoparticles (NPs) and assess their performance as cathode catalyst in proton exchange membrane fuel cell (PEMFC). Pt-Pd/CNT catalysts are prepared through microwave assisted, polyol route in presence of SDS (Pt-Pd/CNT-S) or CTAB (Pt-Pd/CNT-C) and their performance is compared with Pt-Pd/CNT prepared in an identical way without any surfactant. The study shows the prominent influence of the type of surfactant in disaggregation of MWCNT bundles and the dispersion of Pt-Pd NPs on MWCNT support, which in turn controls their catalytic activity for oxygen reduction reaction. In-situ electrochemical characterization studies show improvement in the catalytic activity of Pt-Pd/CNT-S compared to Pt-Pd/CNT-C and Pt-Pd/CNT, demonstrating SDS as an efficient disperser for MWCNT. High fuel cell performance achieved with Pt-Pd/CNT-S having less Pt content (∼12 wt %) than the commonly employed pure Pt or Pt/C (20 wt %) catalysts demonstrates that it is a potential cathode catalyst for PEMFC that can help its wider commercialization.

Carbon nanotubes reinforced reactive powder concrete

In this paper, four types of multi-walled carbon nanotubes (MWCNTs) were incorporated into reactive powder concrete (RPC) with water or heat curing. The enhancing effects of MWCNT types and curing methods on mechanical properties of RPC were investigated. Experimental results indicate that adding proper type and content of MWCNTs can effectively improve mechanical properties of RPC including flexural strength, fracture energy, compressive strength/toughness and flexural strength to compressive strength ratio. In general, these mechanical properties of MWCNTs filled RPC with heat curing are superior to that with water curing, which indicates that heat curing is more beneficial for reinforcing impact of MWCNTs to RPC than water curing. In most cases, the critical length of MWCNTs in RPC is smaller than actual length, which indicates MWCNTs will be snapped when damage occurs in RPC. In addition, the reinforcement of MWCNTs to RPC results from crack bridging and pull out effects.

Effect of MWCNTs on piezoelectric and ferroelectric properties of KNN composites

The aim of the research work was to investigate the effect of multiwall carbon nanotubes (MWCNTs) reinforcement (0.3–1.2wt.%) on functional properties of microwave sintered Potassium sodium niobate (KNN) composites. Sintered composites are characterized for crystal structure, morphology and temperature stability of piezo-electric, ferroelectric and dielectric properties. KNN composites showed perovskite phase with improved tetragonal symmetry, fine grained porous microstructure, reduced dielectric loss and enhanced effective permittivity. The optimum functional properties and thermal stability obtained for KNN-MWCNT (0.9 wt.%) composites over the range of 20–100 °C, makes the idea of using the addition of MWCNTs to KNN ceramics an interesting approach in searching new structures for temperature stability.

The influence of topology and morphology of fillers on the conductivity and mechanical properties of rubber composites

Herein, the comparison of butadiene rubber (BR) composites based on the thermally reduced graphene (TrG), multi-walled carbon nanotubes (MWCNTs) and carbon black (CB) on conductivity and mechanical properties was reported. SEM images of the composites showed that the TrG exhibited better dispersion and compatibility with the BR matrix than that of MWCNTs and CB. Therefore, a significant enhancement of electrical conductivity and mechanical properties of the BR/TrG nanocomposites were obtained at low graphene content. The electrical conductivity of the BR/TrG nanocomposites increased from 1 × 10−13 S cm−1 to 1.8 × 10−4 S cm−1 in the presence of 7 phr TrG and the electrical percolation threshold was about 4.3 phr, compared with 9.5 phr and 44 phr for MWCNTs and CB, respectively. A 448% improvement of tensile strength and a nearly 2 times improvement of elongation at break were obtained at the graphene content of 7 phr. Compared with the MWCNTs and CB, the content of graphene in composites was much lower than that of MWCNTs and CB when the mechanical properties was similar. The dynamic mechanical properties showed that the TrG efficiently reinforced the storage modulus and reduced the loss factor of the composites relative to MWCNTs and CB. The different reinforcement of TrG, MWCNTs and CB mainly came from the different topology and morphology of the three fillers. Different contact specific area provided different interface interaction, which induced the different dispersity, which influenced the properties of the composites at last.

MWCNTs toward superior strength of epoxy adhesive joint on mild steel adherent

Abstract In this work, the characteristics of the lap shear joints of MWCNT-epoxy adhesive on mild steel adherend are investigated. In this paper, multiwall carbon nanotubes (MWCNTs) are homogeneously and cluster-freely reinforced in epoxy matrix by simultaneously applying ultrasonic waves and an axial flow impeller on epoxy resin to develop toughened epoxy adhesives. Here, we describe details pertaining to mild steel surface morphology, the bond line thickness of the adhesive, the wettability of MWCNT-epoxy resin on the mild steel surface and the impact of the presence of MWCNTs in epoxy resin on the performance of lap shear joints. The experimental observations indicate that the reinforcement of MWCNTs in epoxy with uniform cluster-free dispersion and a change in the morphology of the mild steel adherend significantly improve the strength of lap shear joints and change their failure mode. The inclusion of 0.75 wt% of MWCNTs in epoxy adhesive resulted in the largest enhancement in the lap shear strength and as the weight percentage of MWCNTs increased from 0.75 wt%, the lap shear strength began to degrade.

Effect of MWCNT reinforcement on the precipitation-hardening behavior of AA2219

Aluminum alloy matrix composites have found a predominant place in research, and their applications are explored in almost all industries. The aerospace industry has been using precipitation-hardenable alloys in structural applications. However, insufficient literature is available on the influence of multiwalled carbon nanotubes (MWCNTs) on precipitation-hardenable alloy composite materials; thus, this work was designed to elucidate the effect on MWCNT reinforcement on AA2219 with and without precipitation hardening. Reinforcement with MWCNTs has been reported to accelerate precipitation and to achieve greater hardness within a much shorter time. The addition of 0.75wt% MWCNTs resulted in maximal hardness at 90 min, which is approximately 27% of improvement over the maximum hardness achieved by the corresponding monolithic alloy after 10 h of aging. The sample reinforced with 0.75wt% MWCNTs showed an improvement of 82% in hardness by solutionizing and aging compared to that achieved by sintering.

Characterization of poly(para-phenylene)-MWCNT solvent-cast composites

Poly(para-phenylene) (PPP) is one of the strongest and stiffest thermoplastic polymers due to its aromatic backbone structure. However, because of this chemistry, this also means that typical processing techniques require high temperatures and pressures to allow for formability. This study demonstrates that, unlike similar aromatic thermoplastics, PPP has the unique ability to be solvent-cast using conventional solvents, which allows for facile fabrication of thin films and coatings under ambient conditions. The purpose of this research was to investigate the properties of solvent-cast PPP, which is not currently available in literature. In addition, through the solvent-casting technique, composite materials can be created by combining PPP with multi-walled carbon nanotubes (MWCNTs) in attempts to enhance structural properties and electrical conductivity. A method was developed for solvent-casting of PPP through chloroform evaporation and subsequent methanol soaking, resulting in homogenous average thicknesses of 0.10 ± 0.04 mm. Mechanical testing of solvent-cast PPP resulted in an elastic modulus of 4.2 ± 0.2 GPa with 13 ± 2.3% strain-to-failure. The addition of MWCNT reinforcement increased ultimate tensile strength at the expense of ductility. Composites maintained a yielding response up to 6 vol.% of MWCNTs, which also corresponded to the largest strength values observed. Ultimate tensile strength increased from 96 MPa from the matrix to a maximum of 121 MPa. Electrical conductivity of the composites increased from 4.5 × 10 −6 to 1.02 × 10 −3 S/cm from 3 to 20 vol.% MWCNTs, although values plateau at 5 vol.%.

Surface functionalizing effect of fillers on the tribological properties of MWCNT reinforcement HSGFs/phenolic laminate composites under water lubrication

Multi‐wall carbon nanotubes (MWCNTs) and high strength glass fabrics (HSGFs) were modified by polydopamine and polyethyleneimine, respectively. The aim is to improve the friction and wear performance of the synthesized laminate composites in water environment. In this work, polydopamine was used to improve the dispersibility of MWCNTs in phenolic resin matrix, and polyethyleneimine was utilized to enhance the wettability and reactivity of HSGFs. The modified results showed that the dispersibility of MWCNTs treated by polydopamine in water had a distinct improvement in comparison with that of the pristine MWCNTs. Furthermore, it can be clearly observed that good dispersibility can improve the friction and wear performance of the laminate composites. After functionalizing HSGFs by polyethyleneimine, the laminate composites exhibited excellent interfacial bonding, also greatly enhancing the friction and wear properties of the composites.

An effective route for the fabrication of multi-walled carbon nanotubes-reinforced ROMP-based nanocomposites by solution casting technique

This work reports the solvent-soluble multi-walled carbon nanotubes (MWCNTs), which can be used for the fabrication of ring-opening metathesis polymerization (ROMP)-based nanocomposites by solution casting technique. As the first and most important step of the solution casting technique, the excellent dispersibility of the MWCNTs in different solvents is achieved by the functionalization of the nanotube surface with norbornene oligomers. The norbornene-functionalized MWCNTs (nMWCNTs) have outstanding dispersion stability in water, tetrahydrofuran (THF), acetone, and ethanol, especially the maximum nanotube concentration of 3.9mg/mL in THF. The incorporation of nMWCNTs into poly(5-ethylidene-2-norbornene) (poly(ENB)) by solution casting technique results in significant improvements in the mechanical properties over the neat poly(ENB) and the pristine MWCNT-reinforced poly(ENB) nanocomposites. The route developed here not only avoids the dramatic increase of the viscosity occurring in the bulk polymerization but also provides the feasibility of high loadings of MWCNT reinforcements, consequently broadening the potential applications of ROMP-based nanocomposites.

Effect of Multiwall Carbon Nanotubes (MWCNs) Reinforcement on the Mechanical Behavior of Synthesis 7075 Aluminum Alloy Composites by Mechanical Milling

Effect of Multiwall Carbon Nanotubes (MWCNs) Reinforcement on the Mechanical Behavior of Synthesis 7075 Aluminum Alloy Composites by Mechanical Milling

Time-concentration superpositioning principle accounting for reinforcement and dissipation of multi-walled carbon nanotubes filled polystyrene melts

Nanoparticle reinforcement at low and moderately high loadings has been assigned to the hydrodynamic and networking effects, respectively while the conclusions are ambiguous without specifying the “frequency”-dependent polymer dynamics. Herein a unique time-concentration superpositioning (TCS) principle is disclosed for accounting for the hydrodynamic-to-jamming regime transition associated with the apparent liquid-to-solid transition of multi-walled carbon nanotubes (MWCNTs) filled polystyrene (PS) melt. This principle is applicable to both reinforcement and dissipation of the composites at different temperatures. It is also testified for the pure filler effect introduced by MWCNTs to the dynamically retarded bulk phase. The new findings may shed light on the creation of rheological models that include the polymer dynamics beyond the conventional studies under the guidance of hydrodynamic and jamming theories.

Enhancing Fatigue Life of Filament Winding Laminar and Curved Pipes Containing Carbon Nanotubes, and Their Fatigue Failure

In this study, the fatigue life of glass fibre-epoxy matrix material produced by the filament winding composite pipes and matrix material reinforced with multi-walled carbon nanotubes (MWCNTs) nanocomposite filament winding tubes were studied experimentally under the influence of internal pressure. Glass-reinforced plastic (GRP) pipes which were reinforced with carbon nanotubes were tested in the conditions of an open-ended test. The winding angle of test specimens was ±55° and they had six layers. During all the experiments, the fatigue life effect of reinforced carbon nanotubes was investigated. Unreinforced glass, as a reference material, was compared with reinforced plastic with the addition of nano-reinforced material using two different rates of 0.5% and 1%. Fatigue tests of specimens have been carried out in accordance with ASTM D-2992. Later on, the results obtained by determining the material properties with the reinforcement of carbon nanotubes GRP pipes were evaluated. As a result of this study, it has been found that MWCNTs reinforcement increases the fatigue life of the GRP tubes. Inter-laminar fracture strength was developed via the mechanical locking of MWCNTs. The critical MWCNTs usage value was between 0.5% and 1%.

Improvement in skin–core adhesion of multiwalled carbon nanotubes modified carbon fiber prepreg/Nomex honeycomb sandwich composites

An experimental investigation on the sandwich composites composed of the carbon fiber face sheets and Nomex honeycomb core has been carried out in this study. Multiwalled carbon nanotubes were added into the matrix of prepreg for converting the traditional pure resin adhesive fillet to composites. Resin viscosity was measured to evaluate the effect of the additive amount of multiwalled carbon nanotubes on the rheological properties. The size of adhesive fillet was obtained from the optical microscopy to assess the forming quality. Climbing drum peel test and edgewise compression test were employed for the mechanical assessment. The results showed that the addition of multiwalled carbon nanotubes reinforcement to epoxy resin in the prepreg was very effective in improving the skin–core adhesion. The peel load and peel energy release rate as well as the edgewise compressive strength and edgewise compressive modulus of the sandwich composites varied with different magnitudes due to the additive amount of multiwalled carbon nanotubes. Reinforcing mechanism of the adhesive fillet with multiwalled carbon nanotubes reinforcement was discussed on the basis of the fractographic observations by scanning electron microscopy.

Comparison of the flexural strength of polymethyl methacrylate resin reinforced with multiwalled carbon nanotubes and processed by conventional water bath technique and microwave polymerization.

Purpose:This in vitro study was done to compare the flexural strength of polymethyl methacrylate resin reinforced with multiwalled carbon nanotubes (MWCNTs) and processed by conventional water bath technique and using microwave energy.Materials and Methods:A total of 180 acrylic resin specimens measuring 65 mm × 10 mm × 2.5 mm were fabricated, with conventional water bath groups and microwave group having ninety specimens each. Ninety specimens were divided into thirty specimens as control and subgroups containing 0.025% MWCNTs and 0.050% MWCNTs with thirty specimens each. The specimens were tested for flexural strength by three-point bending test on universal testing machine. The statistical analysis was done using Student's t-test and one-way analysis of variance, and the intercomparison between each group was done using Tukey's post hoc analysis.Results:The mean flexural strength of specimens cured by water bath technique was 95.563 MPa and microwave technique was 118.416 MPa. Control Group B possesses highly significant increase in flexural strength than Control Group A with P < 0.01. Unpaired Student's t-test showed that Subgroup B1 and Subgroup B2 possess highly significant increase in flexural strength than Subgroup A1and Subgroup A2.Conclusion:Heat polymerized denture base resin with and without reinforcement of MWCNTs and polymerized by microwave technique possess higher flexural strength than heat polymerized fiber reinforced denture resin polymerized by water bath technique. MWCNTs could be used as an effective reinforcement material for denture base resin polymerized by either water bath technique or microwave energy.

Metal Matrix Composite Solar Cell Metallization

Advanced solar cells are moving to ever thinner formats in order to save mass and in some cases improve performance. As cells are thinned, the possibility that they may fracture or cleave due to mechanical stresses is increased. Fractures of the cell can degrade the overall device performance if the fracture propagates through the contact metallization, which frequently occurs. To address this problem, a novel semiconductor metallization system based on multi-walled carbon nanotube (CNT) reinforcement, termed metal matrix composite (MMC) metallization is under investigation. Electro-mechanical characterization of MMC films demonstrate their ability to provide electrical conductivity over >40 micron wide cracks in the underlying semiconductor, with the carbon nanotubes bridging the gap. In addition, these materials show a “self-healing” behaviour, electrically reconnecting at ~30 microns when strained past failure. Triple junction (TJ) space cells with MMC metallization demonstrated no loss in J sc after intentional fracture, whereas TJ cells with conventional metallization suffer up to 50% J sc loss.

Strengthening in and fracture behaviour of CNT and carbon-fibre-reinforced epoxy–matrix hybrid composite

Advanced materials such as continuous fibre-reinforced polymer matrix composites offer significant enhancements in strength and fracture resistance properties as compared with their bulk, monolithic counterparts. In the present work, mode-I (tensile) fracture behaviour of the neat epoxy (without nano- or hybrid reinforcements), nanocomposite (with amino-functionalized multi-walled carbon nanotube (MWCNT) reinforcement to neat epoxy) and hybrid composite (with amino MWCNT and carbon fibre reinforcements to neat epoxy) along with their flexural strength and interlaminar shear strength has been reported and discussed. Limited topological studies have also been conducted to understand the nature of material fracture and its dependence on the notch orientation. The results thus obtained are analysed and discussed in detail to elucidate: (i) alignment of fibre and its influence on the anisotropy in strength and fracture resistance, (ii) dependence of notch root radii on the apparent fracture toughness and concurrence to strain-controlled fracture and (iii) finally, the nature of J–R curves. The results thus obtained have revealed that the resistance to fracture is significantly increased with the addition of amino-functionalized MWCNTs and carbon fibres. In the hybrid composite, fracture resistance is greater in the longitudinal orientation of fibres than in the transverse orientation and it exhibits a significantly higher strength–fracture toughness combination.

Improved shape memory effects in multiwalled‐carbon‐nano‐tube reinforced thermosetting polyurethane composites

ABSTRACTShape memory thermosetting polyurethane (SMPU) composites containing different amount of multiwalled carbon nanotube (MWCNT) ranging from 0 to 0.250 phr were prepared. The shape memory behavior, tensile stress, and recovery stress were determined by using conventional thermomechanical cycle; however, the modified thermomechanical cycle designated as progressive stretch–relax–stretch (PSRS) cycle was also employed to create shape memory effects in studied composites. The test was carried out in water bath which was equipped with an electric heater, temperature controller, and tensile stress and strain measuring setup. The recovery and tensile stresses both were showing higher values for PSRS samples as compared with conventional samples. Loading of MWCNT improved the recovery stress of SMPU, thereby confirming reinforcing effect. The maximum recovery stress of 2.17 MPa for 0.188 phr MWCNT loading was observed as compared with 1.09 MPa of unreinforced SMPU specimen. The recovery time was also improved on reinforcement as demonstrated in this article. The morphology of fractured surface and degree of dispersion of MWCNT was studied using Field Emission Scanning Electron Microscope. The impact on glass transition temperature was also observed for MWCNT reinforcement on SMPU, which depends on the degree of dispersion and loading of MWCNT in the specimen. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44389.

Effect of Argon Plasma Treatment on Tribological Properties of UHMWPE/MWCNT Nanocomposites.

Ultra-high molecular weight polyethylene (UHMWPE) is widely used in artificial joints in the replacement of knee, hip and shoulder that has been impaired as a result of arthritis or other degenerative joint diseases. The UHMWPE made plastic cup is placed in the joint socket in contact with a metal or ceramic ball affixed to a metal stem. Effective reinforcement of multi-walled carbon nanotubes (MWCNTs) in UHMWPE results in improved mechanical and tribological properties. The hydrophobic nature of the nanocomposites surface results in lesser contact with biological fluids during the physiological interaction. In this project, we investigate the UHMWPE/MWCNTs nanocomposites reinforced with MWCNTs at different concentrations. The samples were treated with cold argon plasma at different exposure times. The water contact angles for 60 min plasma-treated nanocomposites with 0.0, 0.5, 1.0, 1.5, and 2.0 wt % MWCNTs were found to be 55.65°, 52.51°, 48.01°, 43.72°, and 37.18° respectively. Increasing the treatment time of nanocomposites has shown transformation from a hydrophobic to a hydrophilic nature due to carboxyl groups being bonded on the surface for treated nanocomposites. Wear analysis was performed under dry, and also under biological lubrication, conditions of all treated samples. The wear factor of untreated pure UHMWPE sample was reduced by 68% and 80%, under dry and lubricated conditions, respectively, as compared to 2 wt % 60 min-treated sample. The kinetic friction co-efficient was also noted under both conditions. The hardness of nanocomposites increased with both MWCNTs loading and plasma treatment time. Similarly, the surface roughness of the nanocomposites was reduced.

Development of Carbon Nanotube Reinforced Bulk Polycrystalline Ceramics with Intragranular Carbon Nanotube Reinforcement

In the bulk polycrystalline ceramic–carbon nanotube (CNT) composites developed to date, reinforcing CNTs have been present just at the matrix grain boundaries, with the grain interiors being nearly completely devoid of CNT; thus severely limiting the improvements achieved in fracture and wear properties. Against this backdrop, bulk polycrystalline Al2O3‐based composites, having multi‐walled CNTs (MWCNTs) present within the matrix grain interiors (not just at grain boundaries), have been developed in this work for the first time. Such microstructure development has been rendered possible by an innovative, but facile, wet‐chemical synthesis route (sans ball‐milling) involving incorporation of well‐dispersed MWCNTs directly into matrix sol, followed by rapid gelation (within a few seconds) and sintering (inclusive of crystallization step). Intragranular MWCNT reinforcements (in “sol–gelled” composites) led to significant improvements in indentation‐induced crack propagation resistances and abrasive wear resistances, as compared to “conventionally” prepared Al2O3–MWCNT composites (i.e., “ball‐milled” counterpart) having the same contents of MWCNT, but present only at grain boundaries. Wear rates recorded with the “sol–gelled” Al2O3‐2.5 vol%MWCNT are lower than those for monolithic Al2O3 and “ball‐milled” counterpart by ~95% and ~90%, respectively. Such improvements, as never achieved before, are a consequence of reinforcing the matrix grain interiors with MWCNTs.

Fabrication and evaluation of thin layer PVDF composites using MWCNT reinforcement: Mechanical, electrical and enhanced electromagnetic interference shielding properties

Radar X-band electromagnetic interference shielding (EMS) is one of the prime requirements for any air vehicle coating; with limitations on the balance between strength and thickness of the EMS material. Nanocomposite of multiwalled-carbon-nanotubes (MWCNT) has been homogeneously integrated (0 – 9 wt%) with polymer, poly (vinylidene fluoride, PVDF) to yield 300 micron film. The PVDF + 9 wt% MWCNT sample of density 1.41 g/cm3 show specific shielding effectiveness (SSE) of 17.7 dB/(g/cm3) (99.6% EMS), with maintained hardness and improved conductivity. With multilayer stacking (900 microns) of these films of density 1.37 g/cm3, the sample showed increase in SSE to 23.3 dB/(g/cm3) (99.93% EMS). Uniform dispersion of MWCNTs in the PVDF matrix gives rise to increased conductivity in the sample beyond 5 wt% MWCNT reinforcement. The results are correlated to the hardness, reflection loss, absorption loss, percolation threshold, permittivity and the conductivity data. An extremely thin film with maximum EMS property is hence proposed.