Multi-walled Carbon Nanotubes Support Research Articles

Performance of a Newly Developed Multiwalled Carbon Nanotube Reinforced Alumina Tool Insert during Turning of AISI 1060 Steel

Due to the demand of the manufacturing industry for high production-rate machining, ceramic tool material plays an important role. In this work, alumina (Al 2 O 3 ) matrix composite reinforced with 0.3 vol.% multiwalled carbon nanotubes (MWCNTs) was prepared by hot-press sintering at a temperature of 1550°C under uniaxial load of 2.5 MPa. This developed nanocomposite having increased hardness, fracture toughness and flexural strength compared to monolithic Al 2 O 3 was then used as a cutting tool insert with a nose radius of 1 mm for machining AISI 1060 steel rod under different machining conditions. Cutting force was measured and chip forms were observed at different levels of machining parameters to evaluate the machining performance of the tool insert. Results obtained from turning experiments show promising applicability of the developed 0.3 vol.% MWCNT/Al 2 O 3 cutting tool insert.

Effect of multi-walled carbon nanotubes reinforcement and gamma irradiation on viscoelastic properties of ultra-high molecular weight polyethylene

Ultra-high molecular weight polyethylene (UHMWPE) has been used as a surface for acetabular in total joint replacements for the past 60 years. However, the performance of the implant is influenced by the increase in temperature because of the articulating motion and the contact asperities, which affects its longevity. The viscoelastic properties of multi-walled carbon nanotubes (MWCNTs) reinforced UHMWPE nanocomposites with respect to temperature and irradiation dose are not reported so far. Hence, an attempt was made to study the viscoelastic properties of UHMWPE by varying concentration of MWCNTs and intensity of irradiation dose. The test samples were subjected to sinusoidal loading in the temperature range of 30–80°C. Ultra-high molecular weight polyethylene nanocomposites were prepared at different concentrations of MWCNTs such as 0.5, 1.0, 1.5 and 2 wt-% using compression moulding process and the nanocomposites were subjected to 60Co gamma irradiation up to 100 kGy dose. The viscoelastic characteristics of UHMWPE, such as storage modulus, loss moduls and damping factor of the irradiated nanocomposites, were studied in detail. It was observed that the storage modulus of the pure UHMWPE was increased by 139% with the addition of 2 wt-% MWCNTs; however, it was found to be reduced by 83% with 100 kGy irradiation doses. The damping factor and loss modulus of the nanocomposites were reduced by 27.3 and 71.6% with 2 wt-% of MWCNTs concentration, but both were increased with 100 kGy irradiation dose by 74.7 and 69% compared to virgin UHMWPE. It is concluded that the storage modulus reduced with the increase in temperature and also irradiation dose, which may lead to higher static deformation of material. However, the presence of MWCNTs would minimise the deformation and pave way for the better functionality of the material.

Synthesis and electrochemical characterization of binary carbon supported Pd3Co nanocatalyst for oxygen reduction reaction in direct methanol fuel cells

Binary carbon supports are applied to make the membrane electrode assembly (MEA) of passive direct methanol fuel cells (PDMFCs) and their comprehensive electrochemical characterization is considered. Electrocatalytic properties for the oxygen reduction reaction (ORR) are evaluated using polarization curves and electrochemical impedance spectroscopy (EIS) in PDMFC. The best efficiency is obtained when the mass ratio of multi-walled carbon nanotubes (MWCNTs) and Vulcan XC-72R (VC) is 25:75. The results of the electrode kinetic parameters indicate that introduction of MWCNTs as a secondary support delivers high available surface area, good electronic conductivity, and fast ORR kinetics. In addition to the significant role of Pd3Co active surface area on kinetic of the system, the improvement of kinetic parameters is also associated with the decrease of activation energy for ORR on binary-support electrode resulting in a notable enhancement of kinetic parameters. An 8-h lifetime test is performed for the single cell to evaluate the durability in which the MEA is made using MWCNT/VC with the mass ratio of 25:75. The test results show that the mentioned ratio of MWCNT and VC support results in highest stability and durability.

Influence of a liquid-like MWCNT reinforcement on interfacial and mechanical properties of carbon fiber filament winding composites

A kind of liquid-like multiwalled carbon nanotube (MWCNT) reinforcements was prepared and dispersed into epoxy matrix. The effects of the liquid-like MWCNT reinforcements on the processing, mechanical and interfacial properties of carbon fiber filament wound composites were investigated. The results showed that the liquid-like MWCNT reinforcements can be uniformly dispersed in epoxy matrix which showed the good processing properties for winding technology. The liquid-like MWCNT reinforcements could participate in the cross-linking reaction with epoxy groups, improve the interfacial bonding between carbon fibers and resin matrix, and change the failure mode of the resulting composites. Compared to the neat epoxy system, the significant enhancement in tensile and compressive properties of resin matrix was realized by adding 3 wt% liquid-like MWCNT reinforcements. Meanwhile an increase of 8 °C in glass transition temperature, 8% in interlaminar shear strength and 17% in tensile strength of MT300 carbon fiber Naval Ordnance Laboratory rings was achieved.

A highly efficient and stable oxygen reduction reaction on Pt/CeOx/C electrocatalyst obtained via a sacrificial precursor based on a metal-organic framework

Advanced Pt/CeOx/C nanocomposite, where C=porous carbon and multi-walled carbon nanotube (MWCNT), was synthesized using a precursor based on Ce-containing metal organic framework (MOF), via carbonyl chemical route, followed by heat-treatment at 900°C under argon atmosphere. Based on the analyses of powder X-ray diffraction (pXRD) data, and via the Williamson-Hall method, the lattice parameter, stacking fault and micro-strain values on Pt/CeOx/C was found to decrease, whereas the crystallite size increased with respect to the as-prepared sample. Combined with the results of transmission electron microscopy (TEM), these changes were related to the in-situ formation of intimately contacted Pt/CeOx nanoparticles (NPs), well-dispersed onto MWCNT support. However, both the pXRD and TEM results showed that the Pt NPs were agglomerated upon heating and finally detached from the support in the MOF-free samples. Thus, MOF could protect Pt nanoparticles (NPs) from agglomeration at high temperature. The X-ray photoelectron spectroscopy (XPS) showed that the Pt surface was less oxidized in Pt/CeOx/C nanocomposite in comparison to as-prepared and MOF-free samples. Moreover, only the Ce3+ was detected in the nanocomposite. These facts together with Raman spectroscopy and surface electrochemistry experiments assessed the stabilization of the electronic state of Pt° and Ce3+ via the interaction between Pt and CeOx. In addition, enhanced catalytic activity towards the oxygen reduction reaction (ORR) was observed in acid medium. The specific and mass activity at 0.9V/RHE on Pt/CeOx/C were ca. 1279μAcm−2Pt and 870mAmg−1Pt, respectively, ca. 10–11 fold higher than commercial Pt/C (Johnson Matthey, JM) in half-cell. Accelerating durability tests (ADT), after 16,000 potential cycles, demonstrated higher stability of Pt/CeOx/C in contrast to oxide-free and Pt/C (JM) catalyst. Compared with other homemade or commercial Pt/C (JM) cathodes, the innovative cathode catalyst showed enhanced cell performance in a H2/O2 micro-laminar flow fuel cell system.

Design and Performance Evaluation of Hybrid Nanofiltration Membranes Based on Multiwalled Carbon Nanotubes and Polyelectrolyte Multilayers for Larger Ion Rejection and Separation

A polyelectrolyte multilayer (PEM) membrane of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4‐styrenesulfonate) (PSS) is deposited on top of a thick‐layer micrometer range of multiwalled carbon nanotubes (MWCNTs) assembled on a porous silicon carbide (SiC) tubular membrane support. MWCNTs are assembled “layer‐by‐layer” alternating oxidized CNTs and poly(allylamine hydrochloride)‐modified CNTs. The MWCNTs layer is crosslinked by annealing after the assembly. The MWCNT layer acts as a spacer between the PDADMAC/PSS PEM and the SiC support. The MWCNT support increases water permeability in 42% compared with the PEMs deposited without MWCNTs. Hybrid MWCNT–PEM membranes show high rejection for divalent ions, which increases directly with flux. A rejection up to 92% is measured for MgSO4 and there is up to a 60% rejection difference between MgCl2 and NaCl, making the hybrid MWCNT–PEMs highly appealing for nanofiltration and monovalent and divalent ion separations image

Electrical Resistivity, Tribological Behaviour of Multiwalled Carbon Nanotubes and Nanoboron Carbide Particles Reinforced Copper Hybrid Composites for Pantograph Application

This work focuses on the influence and contribution of multiwalled carbon-nanotube (MWCNT)–boron carbide (B4C) to the mechanical and tribological properties of copper matrix composites. Different weight fractions of nano- B4C-containing fixed-weight fractions of MWCNT-reinforced copper composites were prepared using the entrenched cold-press sintering method of powder metallurgy. The wear losses of sintered Cu–MWCNT–B4C composites were investigated by conducting sliding tests in a pin-on-disc apparatus. The addition of reinforcements showed enhancements in the hardness and wear properties of the composites due to the uniform dispersion of the secondary reinforcement in the copper matrix and the self-lubricating effect of the MWCNTs. The effects of the nanoparticle distribution in the matrix, the worn surface morphology, and the elemental composition of the composites were characterized using high-resolution scanning electron microscopy and X-ray diffraction analysis. The electrical resistivity of the fabricated copper hybrid composite preforms was evaluated using a four-point probe tester. Our results highlight the use of experiential reinforcing limits of B4C on the wear and electrical and mechanical behaviour of copper composites.

Electrical, Thermal and Mechanical Properties of CNT Treated Prepreg CFRP Composites

This study is part of Smart Intelligent Aircraft Structures (SARISTU) project, which aims considerable improvements in aircraft damage tolerance, electrical conductivity and weight reduction besides producibility in industrial scale. In this study, the effect of multiwalled carbon nanotube reinforcement on electrical, thermal and mechanical properties of T800/M21 carbon fibre reinforced plastic is studied experimentally. T800/M21 is a commercial prepreg carbon fibre/epoxy composite material considered for CNT treatment by means of CNT-doped thermoplastic-based dry powder. The CNTs are deposited on top of prepreg material uniformly using a controlled spraying machine selecting the best state-of-the art and innovative performing technology from the candidate technologies within the project. The electrical conductivity of the composite material with/without CNT is measured in longitudinal, transverse and thickness directions. The changes occurring in the electrical conductivity of the composite materials are investigated. In order to investigate thermal behaviour of the composite materials, differential scanning calorimetry and thermogravimetric analyses are performed. Detailed thermal analysis is conducted for with/without carbon nanotube reinforced material to obtain the thermal conductivity, specific heat and thermal expansion coefficient of the material. Finally, the effect of carbon nanotube reinforcement on mechanical behaviours is studied by tensile, bending and shear tests.

142 配向カーボンナノチューブ/エポキシ複合材料の熱膨張特性評価とその応用に関する研究

142 配向カーボンナノチューブ/エポキシ複合材料の熱膨張特性評価とその応用に関する研究

Investigation into the toughening mechanism of epoxy reinforced with multi-wall carbon nanotubes

Abstract This study reports the reinforcement and fracture toughening mechanism of pristine multi-walled carbon nanotubes (MWCNTs) on epoxy matrix. The tensile strength and fracture energy (G IC) of the epoxy polymer increased simultaneously upon the addition of a small amount of MWCNTs. The fracture surfaces of single-edge-notch three-point bending test specimens were analysed by scanning electron microscopy, and the double-notch four-point bending technique was used to investigate the fracture process by transmission electron microscopy, respectively. MWCNT pull-out and subsequent plastic void growth were found; meanwhile, fracture of MWCNTs was observed along the crack propagation path. The theoretical model of shearing band initiated by the stress concentrations around the MWCNTs is the dominant toughening mechanism. While the crack bridging of MWCNTs and the plastic void growth of epoxy also have a toughening effect.

Growth kinetics of intermetallic layer in lead-free Sn–5Sb solder reinforced with multi-walled carbon nanotubes

In this study, the effects of multi-walled carbon nanotubes reinforcement on the thickness and growth kinetics of interfacial intermetallic compound (IMC) layer in Sn–5Sb solder system are investigated. In the typical study, plain Sn–5Sb solder system and carbon nanotubes reinforced solder systems (Sn–5Sb−xCNT; x = 0.01, 0.05 and 0.1 wt%) were developed via the powder metallurgy approach. The solder/Cu joints subjected to the as-reflow and isothermal aging (170 °C) conditions were systematically characterised to evaluate the growth of the IMC layer. Results suggest that the composite solders showed better results for all subjected conditions compared with the plain solder. In particular, 0.05 wt % CNTs reinforced solder system exhibited the most appreciable IMC layer suppression and diffusion coefficient among all the samples analysed in this study.

Carbon nanotube reinforced metal binder for diamond cutting tools

Abstract The potential of carbon nanotube reinforcement of metallic binders for the improvement of quality and efficiency of diamond cutting wheels is studied. The effect of multi-walled carbon nanotube (MWCNT) reinforcement on the mechanical properties i.e. hardness, Young modulus, strength and deformation behavior of copper and iron based binder for diamond cutting wheels is investigated experimentally and numerically. Computational micromechanical studies were carried out to clarify the mechanisms of the MWCNT material strengthening. It is demonstrated that the adding of MWCNTs leads to the decrease of grain size of the structural constituents of the binder, what in turn leads to the improved simultaneously hardness, Young modulus, plastic extension, bending strength and performances of the metallic binders. Comparing service properties of diamond end-cutting drill bits with and without MWCNT one observed the drastic increase of the cutting speed as a result of MWCNT reinforcement.

Mechanical, Rheological, and Electrical Properties of Multiwalled Carbon Nanotube Reinforced Nanocomposites of 50/50 Acrylonitrile–Styrene–Acrylate/Zn+2 poly(ethylene-co-methacrylic acid) Ionomer Blend

The effect of variable amount of multiwalled carbon nanotubes on mechanical, rheological, and electrical properties of acrylonitrile–styrene–acrylate/Zn+2-poly(ethylene-co-methacrylic acid) ionomer blend system has been evaluated. Optical micrographs as well as alternating current conductivity data shows the formation of nanotube percolation network at 1 wt% nanotube content. The polymer/nanotube interaction increased the rate of tensile modulus to 55 GPa at low nanotube content. The polymer chain relaxation time was increased upto 1 wt% of nanotube content, but higher nanotube loading reduced the time. The zero-shear viscosity was function of nanotube content whereas the infinite-shear viscosity was independent of nanotube content.

Mechanical characterization and validation of poly (methyl methacrylate)/multi walled carbon nanotube composite for the polycentric knee joint

Trans femoral amputation is one of the most uncomfortable surgeries in patient׳s life, where the prosthesis consisting of a socket, knee joint, pylon and foot is used to do the walking activities. The artificial prosthetic knee joint imitates the functions of human knee to achieve the flexion–extension for the above knee amputee. The objective of present work is to develop a light weight composite material for the knee joint to reduce the metabolic cost of an amputee. Hence, an attempt was made to study the mechanical properties of multi walled carbon nanotubes (MWCNT) reinforced Poly (methyl methacrylate) (PMMA) prepared through melt mixing technique and optimize the concentration of reinforcement. The PMMA nanocomposites were prepared by reinforcing 0, 0.1, 0.2, 0.25, 0.3 and 0.4wt% of MWCNT using injection moulding machine via twin screw extruder. It is observed that the tensile and flexural strength of PMMA, which were studied as per ASTM D638 and D790, respectively, were increased by 32.9% and 26.3% till 0.25wt% reinforcement of MWCNT. The experimental results of strength and modulus were compared with theoretical prediction, where a good correlation was noted. It is concluded that the mechanical properties of PMMA were found to be increased to maximum at 0.25wt% reinforcement of MWCNT, where the Pukanszky model and modified Halpin-Tsai model are suggested to predict the strength and modulus, respectively, of the PMMA/MWCNT composite, which can be opted as a suitable materiel for the development of polycentric knee joint.

Restriction of Phase Transformation in Carbon Nanotube-Reinforced Yttria-Stabilized Zirconia

The present research aims to investigate the effect of multi-walled carbon nanotube (MWNT) reinforcement on the mechanism of transformation toughening in zirconia matrix, and consequently, its fracture toughness. Monoclinic zirconia (un-doped ZrO2), partially stabilized zirconia (3 mol pct yttria-stabilized zirconia (3 mol pct YSZ)), and fully stabilized cubic zirconia (8 mol pct YSZ) with and without 6 vol pct MWNT-reinforced nanocomposites were processed via multi-stage spark plasma sintering. Phase analysis of powders, and sintered and crushed pellets performed using X-ray diffraction reveals the absence of any phase transformation in monoclinic ZrO2, 8 mol pct YSZ and their MWNT-reinforced nanocomposites upon application of stress by means of crushing. However, a significant decrease in the stress-induced phase transformation (81.1 pct metastable tetragonal phase retained with 6 vol pct MWNT reinforcement when compared to that of 68.4 pct tetragonal phase in 3 mol pct YSZ) is observed in the crushed pellet samples of partially stabilized zirconia upon 6 vol pct MWNT reinforcement. Transmission electron microscopy has been utilized for complementary phase analysis. Evaluation of mechanical properties indicates enhancement in fracture toughness (~23.6 to 26.4 pct) with the incorporation of 6 vol pct MWNT. Isolation of the net toughening contribution suggests that MWNT toughening mechanisms are ~3.8 times more effective than transformation toughening in enhancing the fracture toughness of YSZ/MWNT nanocomposites.

Strengthening Mechanisms in Multiwalled Carbon Nanotubes Reinforced Co–W Pulse Electrodeposited Coatings

Cobalt–tungsten coatings reinforced with multiwalled carbon nanotubes (MWCNTs) were prepared by pulse electrodeposition (PED) from citrate bath dispersed with MWCNTs. Effect of MWCNTs and electrodeposition technique, i.e., PED on the microstructure and properties of these coatings was evaluated. The results show that the incorporations of MWCNTs, substantially improve the hardness of the deposited coatings. PED produces Co–W/MWCNT coatings that are featured by small grain size, low surface roughness, and uniform distribution of MWCNTs in matrix, and consequently display higher hardness. Grain refinement, thermal mismatch, Orowan looping, and shear lag mechanisms have played substantial role in strengthening of the Co–W coatings reinforced with MWCNTs. Investigations suggest that shear lag mechanism has a pronounced role in strengthening these coatings.

Enhanced Percolation Threshold and Dielectric of Multi-Walled Carbon Nanotube Reinforced Ethylene-Vinyl Acetate: The Role of Fillers Based Capacitor Applications

Enhanced Percolation Threshold and Dielectric of Multi-Walled Carbon Nanotube Reinforced Ethylene-Vinyl Acetate: The Role of Fillers Based Capacitor Applications

Influence of multi walled carbon nanotubes reinforcement and gamma irradiation on the wear behaviour of UHMWPE

Ultra high molecular weight polyethylene (UHMWPE) was reinforced by chemically treated multi walled carbon nanotubes (MWCNTs) up to 2.0wt% and later subjected to gamma irradiation up to 100kGy dose. The influence of MWCNTs on the hardness and wear resistance of UHMWPE was evaluated before and after the irradiation process. The hardness of UHMWPE was increased by 89% by homogeneous dispersion of 2wt% MWCNTs and 100kGy irradiation. Wear studies on the test samples revealed that the wear volume of unirradiated UHMWPE was reduced by 31%, 54% and 73% upon dispersing 2wt% MWCNTs, 100kGy irradiation and the combination of both, respectively. The surface morphology and topography of the wear tracks were examined to understand the wear mechanisms of UHMWPE and its composites. Though the wear mechanism observed in the polymer and composites under normal and irradiated condition is found to be the same, the severity of wear was found to be reduced for irradiated composites compared to unirradiated UHMWPE. The crosslink density (CLD) of composites was found to be higher than that of UHMWPE. It is concluded that the cumulative effect of the presence of MWCNTs and irradiation effectively increased the wear resistance of UHMWPE.

Mechanics of Deformation of Multi Walled Carbon Nanotube Reinforced Composites

Mechanics of Deformation of Multi Walled Carbon Nanotube Reinforced Composites

Dispersion fraction enhances cellular growth of carbon nanotube and aluminum oxide reinforced ultrahigh molecular weight polyethylene biocomposites.

Ultrahigh molecular weight polyethylene (UHMWPE) is widely used as bone-replacement material for articulating surfaces due to its excellent wear resistance and low coefficient of friction. But, the wear debris, generated during abrasion between mating surfaces, leads to aseptic loosening of implants. Thus, various reinforcing agents are generally utilized, which may alter the surface and biological properties of UHMWPE. In the current work, the cellular response of compression molded UHMWPE upon reinforcement of bioactive multiwalled carbon nanotubes (MWCNTs) and bioinert aluminum oxide (Al2O3) is investigated. The phase retention and stability were observed using X-ray diffraction, Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The reinforcement of MWCNTs and Al2O3 has shown to alter the wettability (from contact angle of ~88°±2° to ~118°±4°) and surface energy (from ~23.20 to ~17.75 mN/m) of composites with respect to UHMWPE, without eliciting any adverse effect on cytocompatibility for the L929 mouse fibroblast cell line. Interestingly, the cellular growth of the L929 mouse fibroblast cell line is observed to be dominated by the dispersion fraction of surface free energy (SFE). After 48 h of incubation period, a decrease in metabolic activity of MWCNT-Al2O3 reinforced composites is attributed to apatite formation that reduces the dispersion fraction of surface energy. The mineralized apatite during incubation was confirmed and quantified by energy dispersive spectroscopy and X-ray diffraction respectively. Thus, the dispersion fraction of surface free energy can be engineered to play an important role in achieving enhanced metabolic activity of the MWCNT-Al2O3 reinforced UHMWPE biopolymer composites.