Amount Of Multi-walled Carbon Nanotubes Research Articles

Effect of Processing Temperature and the Content of Carbon Nanotubes on the Properties of Nanocomposites Based on Polyphenylene Sulfide.

The study aimed to investigate the effect of processing temperature and the content of multi-wall carbon nanotubes (MWCNTs) on the rheological, thermal, and electrical properties of polyphenylene sulfide (PPS)/MWCNT nanocomposites. It was observed that the increase in MWCNT content influenced the increase of the complex viscosity, storage modulus, and loss modulus. The microscopic observations showed that with an increase in the amount of MWCNTs, the areal ratio of their agglomerates decreases. Thermogravimetric analysis showed no effect of processing temperature and MWCNT content on thermal stability; however, an increase in stability was observed as compared to neat PPS. The differential scanning calorimetry was used to assess the influence of MWCNT addition on the crystallization phenomenon of PPS. The calorimetry showed that with increasing MWCNT content, the degree of crystallinity and crystallization temperature rises. Thermal diffusivity tests proved that with an increase in the processing temperature and the content of MWCNTs, the diffusivity also increases and declines at higher testing temperatures. The resistivity measurements showed that the conductivity of the PPS/MWCNT nanocomposite increases with the increase in MWCNT content. The processing temperature did not affect resistivity.

Room-temperature power factor of CuAlO2 composite tablets enhanced by MWCNTs

CuAlO2 with high theoretical thermoelectric performance has potential applications in thermal energy conversion. Herein, multi-wall carbon nanotubes (MWCNTs)/CuAlO2 composite tablets are prepared by using different amounts of MWCNTs and solid paraffin binder, where MWCNTs served as a conductive agent and rendered three orders of magnitude increase in electrical conductivity. Seebeck coefficient of the composites was reduced with increasing MWCNTs content. Consequently, an optimal room-temperature thermoelectric power factor (PF) of 1.31 μW m−1K−2 has been rendered by MWCNTs/CuAlO2 composite tablet with 1 wt % MWCNTs. Moreover, PF value increased with increasing temperature after a slight decrease at 333 K, which can be ascribed to the modulation of electrical conductivity. Current work provides an effective strategy to improve thermoelectric performance of CuAlO2 materials.

Highly Thermally Conductive Yet Electrically Insulative Polycarbonate Composites with Oriented Hybrid Networks Assisted by High Shear Injection Molding

AbstractIn this work, a facile strategy is proposed to construct thermal conductive network in polycarbonate (PC)/boron nitride (BN) composites via incorporating a small amount of multiwalled carbon nanotubes (CNTs) assisted by high shear injection molding process. A synergy is achieved between BN and CNTs in building thermal conductive pathways within PC, as confirmed by scanning electron microscopy observations and rheological analysis. The obtained thermal conductivities are well fitted with the Agari model, which further confirms the efficacy of constructing thermal conductive pathways within PC/BN/CNT composites. The thermal conductivity of PC/BN 30 wt%/CNT 2 wt% composite reaches as high as 2.05 W mK−1, which is ≈832% and 45.4% higher than that of pure PC and PC/BN 30 wt% composite, respectively. In addition, PC/BN/CNT composites exhibit excellent electrical insulation, low dielectric properties as well as reasonable mechanical performance, which show potential applications in advanced engineering fields.

Experimental investigations and optimization of MWCNTs-mixed WEDM process parameters of nitinol shape memory alloy

Excellent characteristics of multi-walled carbon nanotubes (MWCNTs), such as higher toughness and stiffness, enlarged strength, and high thermal conductivity, make them an attractive choice to improve surface characteristics and machining performance. In the current study, MWCNTs mixed with dielectric fluid in the wire electrical discharge machining (WEDM) process was used to enhance the machining performance of Nitinol shape memory alloy (SMA). Significance of WEDM machining variables such as current, pulse-on time (Ton), pulse-off time (Toff), and variation in powder concentration of MWCNTs are studied on material removal rate (MRR) and surface roughness (SR). The addition of MWCNTs substantially improves the machining performance by increasing MRR and simultaneously reducing the SR. Improvement in the MRR of 75.42% and SR of 19.15% is achieved with the use of MWCNTs at 1 g/L in comparison to the conventional WEDM process. An advanced parameterless TLBO algorithm is used for simultaneous optimization of multiple responses. An advanced parameterless TLBO algorithm is used to find the optimal solution of multiple responses. Single objective optimization result has yielded maximum MRR of 0.5262 g/min at a current of 5 A, Ton 110 μs, Toff 1 μs and MWCNTs amount of 1 g/L while minimum SR of 1.27 μm at a current of 1 A, Ton 1 μs, Toff 24 μs and MWCNTs amount of 1 g/L. MOTLBO algorithm is used for simultaneous optimization of MRR and SR. Lastly, the surface integrity of machined surfaces using a field emission scanning electron microscope (FESEM) is also studied to evaluate the effect of MWCNTs on recast layer thickness (RLT) and other surface defects. The incorporation of MWCNTs has shown a substantial reduction in RLT and other surface defects such as reduction in globules of debris, melted material deposition, micro-crack-free, and micro-pores-free surfaces.

Poly(acrylated epoxidized soybean oil)‐modified carbon nanotubes and their application in epoxidized soybean oil‐based thermoset composites

AbstractPoly(acrylated epoxidized soybean oil) (PAESO) has been grafted on the surface of multiwalled carbon nanotubes (MWCNTs) by reversible addition–fragmentation chain‐transfer reaction (RAFT). MWCNTs–PAESO as reinforcement has been successfully applied to prepare epoxidized soybean oil/maleopimaric‐based thermosetting composites with good dispersion through probe ultrasonic treatment in ethyl acetate. Micromorphology analyses on composites by transmission electron microscopy and scanning electron microscopy show that MWCNTs–PAESO has better dispersion stability in both ethyl acetate and epoxy matrix and better interface bonding effect with cured matrix, resulting in more uniformly and separately dispersed behavior than hydroxylated multiwalled carbon nanotubes. Correspondingly, by the method of molecular dynamics simulation, it is verified that the nonbond energy and van der Waals force of CNTs–PAESO in solvent can be relatively reduced, and that CNTs–PAESO possesses higher binding energy with matrix compared with CNTsOH. Therefore, MWCNTs–PAESO and PAESO have synergistic enhancement on the mechanical properties of composites demonstrated by rheology testing and dynamic mechanical analysis. The appropriate amount of MWCNTs–PAESO loading at 0.15 wt% can increase the glass transition temperature (Tg) of thermoset from 83.8 to 96.3°C, resulting in the improvement of both mechanical and thermal properties. These results show that surface‐grafting MWCNTs with homologous polymer can effectively increase the interfacial compatibility between matrix and MWCNTs, thereby improving the thermal and mechanical properties of composites.

Estimating the Reducing Power of Carbon Nanotubes and Granular Activated Carbon Using Various Compounds

Determining the degree of the reducing power of multi-walled carbon nanotubes (MWCNTs) and granular activated carbon (GAC) enables their effective application in various fields. In this study, we estimate the reducing power of carbon nanotubes (CNTs) and GAC by measuring the reduction degree of various compounds with different reduction potentials. MWCNTs and GAC materials can reduce Cr(VI), Fe(III) and PMo12O403−, where the reduction potentials range from +1.33 V to +0.65 V. However, no reduced forms of PW12O403− and SiW12O404− compounds were detected, indicating that the reducing power of MWCNTs and GAC is insufficient for reduction potentials in the range +0.218 V to +0.054 V. MWCNTs exhibit a short reduction time (5 min), whereas GAC exhibits a gradually increasing reduction degree of all the compounds assessed until the end of the reaction. This indicates a higher reduction degree than that of MWCNTs systems. Acidic initial pH values favor reduction, and the reduction degree increases as the pH becomes lower than 4.0. Moreover, large quantities of MWCNTs and GAC increase the concentrations of the reduced compounds.

The enhancement in dielectric properties for PVDF based composites due to the incorporation of 2D TiO2 nanobelt containing small amount of MWCNTs

Film capacitors can be used as energy storage for fast storage and release energy, but the low energy density limits their applications. In our previous study, we have demonstrated that a small amount of 2D titanium dioxide (TiO2) nanobelts in PVDF could significantly enhance the energy density of these composite films. In order to increase the dielectric constant and energy density of these composites, multi-walled carbon nanotubes (MWCNTs) are introduced into these 2D TiO2 nanobelts obtained during electrospinning, and parallelly oriented along these 2D nanobelts. The shell formed by insulating TiO2 can avoid the formation of conductive network and realize high polarization efficiency. It’s shown that when the ratio of MWCNTs and TiO2 in the composite filler is 1:30, the breakdown voltage of the filler can achieve 478 kV/mm, the polarizability is 8.34 μC/cm2, and the energy density is increased from 2.87 J/cm3 to 17.97 J/cm3 comparing with neat PVDF.

A Highly Stretchable and Sensitive Strain Sensor Based on Dopamine Modified Electrospun SEBS Fibers and MWCNTs with Carboxylation

AbstractWearable flexible electronic strain sensor devices have developed rapidly in recent years due to their potential capacity to detect human motion in various situations. However, it still remains still a big challenge to fabricate strain sensors with high sensitivity over a wide workable strain range. In order to meet this challenge, a new type of strain sensor based on elastomer/carbon nanotube composite fiber is reported in this work. Elastomer fibers are initially prepared via the electrospinning of styrene ethylene butene styrene block copolymer (SEBS). The resultant SEBS fibers are then functionalized by sequentially coating with dopamine (DA) coating and carboxyl group (‐COOH) grafted multi‐walled carbon nanotubes (MWCNTs) under vacuum filtration and ultrasonication. Scanning electron microscopy (SEM) and thermogravimetric analysis reveals that a large amount of MWCNTs is firmly bonded onto the SEBS fibers and evenly distributed. SEBS@PDA/MWCNTs composite fibers based strain sensors exhibit excellent performance, including a high gauge factor of 3717 and large workable strain range up to 530%. Furthermore, the developed sensors demonstrate excellent washing fastness and superior sensitivity in monitoring both small strains (e.g., pulse beats and vocal cord vibrations) and large strains (e.g., finger, elbow, and knee bending).

Flexible Electronics: Flexible, Strong, Anisotropic Wood‐Derived Conductive Circuit (Adv. Sustainable Syst. 6/2021)

In article number 2100040, Min Xu and co-workers fabricate an electrically conductive wood-derived circuit with excellent flexibility and high mechanical strength through a simple top-down wood nanotechnology. The wood-derived circuit presents a high electrical conductivity and anisotropic conductivity when the addition amount of multi-walled carbon nanotube is 4.06 vol%. Therefore, the sustainable wood-derived conductive circuit shows potential applications in the field of flexible electronics.

Mechanical, Thermal and Electromagnetic Shielding Effectiveness of MWCN-ABS Films

The multi-walled carbon nanotubes (MWCNTs) and the poly(acrylonitrile-co-butadiene-co-styrene) (ABS) granulates are dispersed in acetone separately using a magnetic stirrer followed by ultrasonication. Further, both the solutions were mixed with magnetic stirring followed by ultrasonication. Neat-ABS film, 0.25 wt%, 0.5 wt% and 1 wt% of MWCNT-ABS nanocomposite films of the average thickness of 140 µm are fabricated by the solution molding using a petri dish, followed by room temperature curing and further hot compression to maintain uniform thickness. The tensile properties, thermal stability, electrical conductivity, and EMSE of all films are investigated. The results indicate that the addition of MWCNTs to ABS enhanced the mechanical properties and electrical conductivity, thermal stability, and EMSE. The 0.25 wt% MWCNT-ABS nanocomposite films show attractive mechanical, electrical, thermal, and EMSE as compared to neat-ABS films. More than 0.25 wt% MWCNTs in the ABS matrix deteriorates the tensile strength. However, 0.5 wt% MWCNT-ABS nanocomposites exhibit better tensile strength, Young’s modulus, electrical conductivity, and EMSE than neat-ABS. In this research, we used a low quantity of MWCNTs and followed a one-time heating process in the entire fabrication, and produced MWCNT-ABS nanocomposite films with reasonable properties. Hence, this may be one of the options to produce nanocomposites suitable for EMS materials. We recommend that these films may be used as interlayers to develop an X-band range electromagnetic wave shielding material.

Natural rubber nanocomposites: effect of carbon black/multi-walled carbon nanotubes hybrid fillers on the mechanical properties and thermal conductivity

ABSTRACT This work presents the effect of carbon black (CB)/multiwall carbon nanotubes (MWCNT) hybrid filler system on the mechanical properties and thermal conductivity of natural rubber (NR) based nanocomposites. A 30 phr (parts per hundred of rubber) of CB nanocomposite was used as a reference for which various amounts (0.5, 1, 2 and 5 phr) of MWCNT were incorporated as a CB replacement. Scanning electron microscopy (SEM) was used to investigate the state of dispersion of the CB/MWCNT fillers inside the NR matrix, while dynamic mechanical analysis (DMA) was performed to characterize their storage and loss moduli, Payne effect and loss factor (tan δ). The scorch time (t10) and optimum curing time (t90) gradually increased with increasing MWCNT content due to the shape difference between CB and MWCNT, as well as the adsorption of curatives onto the MWCNT. Finally, due to the intrinsic properties of MWCNT and its synergy with CB, substantial improvements in thermal conductivity and mechanical properties were achieved by the substitution of 5 phr CB with MWCNT. For example, a thermal conductivity of 0.602 W/m.K was achieved, which corresponds to a 80% increase compared to the reference sample. Furthermore, a 72% and 54% increase of the modulus at 100% and 300% strain (M100 and M300) was respectively achieved, while the elongation at break decreased by only 20%.

Effect of multi-walled carbon nanotubes with different diameters on morphology and thermal and mechanical properties of flexible polyurethane foams

We report flexible polyurethane foams (PUFs) containing –OH functionalized multi-walled carbon nanotubes (MWCNTs) with different diameters (10–20 nm, 20–30 nm, >50 nm) from 0.1–0.6 wt% (per 100 resins of polyol by weight) prepared via in situ polymerization. After synthesis, the morphology of the MWCNT/PUF composites was observed through scanning electron microscopy (SEM) based on MWCNT amount. The MWCNTs acted as nucleating agents and increased the matrix viscosity. The pore size of the composites decreased and the number of pores increased with increasing MWCNT concentration. Dynamic mechanical analysis (DMA) showed that the storage modulus of the composites increased, the loss modulus decreased, and the Tg gradually decreased with increasing MWCNT content. The incorporation of MWCNTs induced remarkable thermal stabilization of the matrix. The increase in the degradation temperature from 294°C to 304°C resulted in a 50% weight loss. The mechanical properties of the MWCNT/PUF materials increased with increasing MWCNT proportion because of the excellent compatibility and strong interface interaction between the MWCNT and flexible PUF.

Multi-objective optimization of process variables for MWCNT-added electro-discharge machining of 316L steel

Fabrication of 316L steel with the desired surface integrity and thin modified recast layer for manufacturing various devices is very challenging using the traditional techniques and requires post-processing. Nevertheless, electro-discharge machining (EDM) is an evolving candidate among the non-traditional processes offering concurrent machining and surface alteration for the instrument manufacturing industry. To explore its full potential, this research work provides a thorough investigation of process variables on the machining performances and surface features primarily required for processing 316L steel in the industry. In this study, nano multi-walled carbon nanotubes (MWCNT) are utilized to improve the machining and surface responses. In addition to this, the parametric optimization is conducted through a Taguchi-based design which assists to obtain the highest material removal rate (MRR) of 42.25 mg/min corresponding to a 10-A peak current, 16-μs pulse-on time, 1-g/l MWCNT amount, and 45% duty cycle while the lowest surface roughness (SR) and recast layer thickness (RLT) of 1.58 μm and 5.243 μm respectively are attained at a 5-A peak current, 8-μs pulse-on time, 0.7-g/l MWCNT amount, and 45% duty cycle. Analysis of variance (ANOVA) reports peak current being the most momentous parameter complied by the MWCNT amount, pulse-on time, and duty cycle for MRR, SR, and RLT. The best 21 solution sets predicted through the multi-objective optimization tool called non-dominated sorting genetic algorithm-II (NSGA-II) obeying the set objective functions are proposed which are obtained from the Pareto optimal frontiers. Accuracy levels of the predicted solution sets are verified by the confirmatory experiments showing the estimated errors of less than 10%. SEM analyses confirm excellent surface integrity with a comparatively thin recast layer formation.

Nanocomposites of Multi-walled Carbon Nanotubes and Titanium dioxide (MWCNTs/TiO2) as affective counter electrode materials for Platinum-free Dye-Sensitized Solar Cells (DSSCs)

Platinum is commonly used as a catalyst to regenerate the redox mediator in Dye-Sensitized Solar Cells (DSSCs). This work intends to replace the expensive and rare platinum with conventional and economical materials. Nanocomposites of Multi-walled Carbon Nanotubes (MWCNTs) and TiO2 can be used as active catalyst materials for the counter-electrode of DSSC. In these composites, MWCNTs provide catalytic properties, and TiO2 acts as a binder. The interaction between MWCNTs and TiO2 has been investigated by Transmission Electron Microscopy (TEM). It has been observed that DSSCs photovoltaic performance significantly depends on the concentration of MWCNTs in nanocomposites. The amount of MWCNTs has been optimized for the best performance of DSSC. The solar cell assembled with 4%MWCNTs catalyst material showed an efficiency of 8.81%, comparable to Pt-based device (9.40%), fabricated under analogous environment.

Flexible, Strong, Anisotropic Wood‐Derived Conductive Circuit

AbstractFlexible electronics have attracted tremendous attention because of the potential applications in flexible sensors and wearable electronics. Herein, a wood‐derived conductive circuit is prepared through a simple top‐down wood nanotechnology. Wood scaffolds with layered structure and aligned micro‐nano channels are used as the flexible substrate and multi‐walled carbon nanotubes (MWCNTs) are used as the conductive materials. Driven by the hydroxyl groups‐induced hygroscopicity of wood scaffold, the MWCNTs are uniformly embedded into the wood scaffold. The conductive circuit exhibits excellent flexibility and high mechanical performance with the tensile strength of 66.07 MPa when the addition amount of MWCNT is 4.06 vol%. Moreover, the conductive circuit presents a high electrical conductivity and anisotropic conductivity. The high conductivity along the fiber direction is 132.42 S m–1 and the conductivity perpendicular to the fiber direction is 43 S m–1. Compared with the wood film, the conductivity of the wood circuit is significantly improved by 109. Therefore, the sustainable wood‐derived conductive circuit shows potential applications in the field of flexible electronics.

Investigation of microhardness properties of the multi-walled carbon nanotube additive MgB2 structure by using the vickers method

In this study, the effect of multi-walled carbon nanotube doping to MgB2 compound on microhardness properties of MgB2 was investigated by using solid-state reaction method. The amount of multi-walled carbon nanotubes was chosen as 0, 1, 2, 3 and 4% by weight of total MgB2. All samples were obtained by sintered at 650 °C temperatures. The microhardness properties of the samples obtained were examined using the Vickers method. At the same time, the samples obtained were analyzed according to Meyer’s Law, proportional sample resistance (PSR) model, Hays-Kendall (HK) approach and elastic/plastic deformation (EPD) model. Samples were found to exhibit indentation size effect (ISE) behavior. It was understood that the multi-walled carbon nanotubes doped to the samples made MgB2 softer by reducing the intergranular bonding of the MgB2 structure. In addition, it was found that the force applied to the samples caused both plastic and elastic deformation on the samples.

Enhancing Microwave Absorbing Properties of Nickel-Zinc-Ferrite with Multi-walled Carbon Nanotubes (MWCNT) Loading at Higher Gigahertz Frequency

The rapid growth of electronic systems and devices operating within the gigahertz (GHz) frequency range has increased electromagnetic interference. In order to eliminate or reduce the spurious electromagnetic radiation levels more closely in different applications, there is strong research interest in electromagnetic absorber technology. Moreover, there is still a lack of ability to absorb electromagnetic radiation in a broad frequency range using thin thickness. Thus, this study examined the effect of incorporating magnetic and dielectric materials into the polymer matrix for the processing of radar absorbing materials. The experiment evaluated the sample preparation with different weight percentages of multi-walled carbon nanotubes (MWCNT) mixed with Ni0.5Zn0.5Fe2O4 (Nickel-Zinc-Ferrite) loaded into epoxy (P) as a matrix. The prepared samples were analysed by examining the reflectivity measurements in the 8 – 18 GHz frequency range and conducting a morphological study using scanning electron microscopy analyses. The correlation of the results showed that different amounts of MWCNT influenced the performance of the microwave absorber. As the amount of MWCNTs increased, the reflection loss (RL) peak shifted towards a lower frequency range and the trend was similar for all thicknesses. The highest RL was achieved when the content of MWCNTs was 2 wt% with a thickness of 2 mm with an RL of – 14 dB at 16 GHz. The 2.5 GHz bandwidth corresponded to the RL below -10 dB (90% absorption) in the range of 14.5 – 17 GHz. This study showed that the proposed experimental route provided flexible absorbers with suitable absorption values by mixing only 2 wt% of MWCNTs.

Effect of curing time on thermal response characterization of carbon-nano cementitious composites

Introducing small amounts of multi-walled carbon nanotubes (MWCNTs) into cement-based materials changes the thermal and electrical characteristics of the composites. The heat generation of cement materials can be enhanced by incorporating MWCNTs. The thermal response of cement composites incorporating MWCNTs under dry curing conditions was experimentally investigated by varying the curing time and MWCNT concentrations of the composite. The temperature change in each specimen was measured by connecting the electrode to the power supply and supplying a constant voltage. The heat generation of the MWCNT cementitious composite increased with the number of curing days. In addition, the heat generation of the composite increased in a quadratic form with increasing MWCNT concentration. The electrical resistance of the composite depended on the progress of the hydration reaction. In the case of cementitious composites containing relatively high concentrations of MWCNTs, the electrical resistance decreased as the number of curing days increased.

Dielectric Relaxation Spectroscopy and Synergy Effects in Epoxy/MWCNT/Ni@C Composites

The dielectric/electric properties of the Ni@C (carbon-coated Ni)/epoxy composites and Ni@C/MWCNTs (multi-walled carbon nanotubes)/epoxy composites loaded with fixed MWCNTs amount just below the percolation threshold (0.09 vol.%) and Ni@C at different concentrations up to 1 vol.% were investigated in broad frequency (20 Hz–40 GHz) and temperature (30 K–500 K) regions. In composites with the only Ni@C nanoparticles, the electrical percolation threshold was determined between 10 and 15 vol.%. Above the percolation threshold the dielectric permittivity (ε’) and the electrical conductivity (σ) of the composites loaded with Ni@C only are high enough, i.e., ε’ = 105 and σ = 0.6 S/m at 100 Hz for composites with 30 vol.% Ni@C, to be used for electromagnetic shielding applications. The annealing to 500 K was proved to be an effective and simple tool to decrease the percolation threshold in epoxy/Ni@C composites. For hybrid composites series an optimal concentration of Ni@C (0.2 vol.%) was determined, leading to the conductivity absolute values several orders of magnitude higher than that of a composite filled with MWCNTs only. The synergy effects of using both fillers have been discussed. Below room temperature the electrical transport is mainly governed by epoxy resin compression in all composites, while the electron tunnelling was observed only in hybrid composites below 200 K. At higher temperatures (above 400 K), in addition to the nanoparticles redistribution effects, the electrical conductivity of epoxy resin makes a significant contribution to the total composite conductivity. The dielectric relaxation spectroscopy allows estimating the nanoparticles distributions in polymer matrix and could be used as the non-destructive and fast alternate to microscopy techniques for general polymer composite fabrication control.

Rheological behavior, electrical conductivity, and morphology of multi‐walled carbon nanotube filled poly(ethylene‐co‐vinyl acetate)/poly(methyl methacrylate) nanocomposites: Effect of nanofiller content

AbstractNanocomposites derived from poly(methyl methacrylate) (PMMA) and poly(ethylene‐co‐vinyl acetate) (EVA) with 30 wt% EVA and 0–10 wt% multi‐walled carbon nanotube (MWCNT) content were prepared. Scanning electron microscope images showed a two‐phase morphology for the unfilled blend in which the EVA droplets were dispersed within the PMMA domain. However, the size of EVA droplets was considerably smaller in the nanocomposites than that of the unfilled blend. The tensile results revealed that the maximum elastic modulus, tensile strength, yield stress, and strain at break were achieved for the nanocomposite containing 5 wt% MWCNT. The electrical conductivity sharply increased for the nanocomposite containing 2.5 wt% MWCNT, in comparison with that of the unfilled blend, beyond which the conductivity was less dependent on the MWCNT content. The rheological characterization showed that the normalized relaxation time increased up to 5 wt% nanofiller and remained reasonably constant for higher amounts of MWCNT.