Short Multi-walled Carbon Nanotubes Research Articles

Short Multi‐Walled Carbon Nanotubes Loaded Sulfur Nanoparticles for High Performance Lithium‐Sulfur Batteries

AbstractLithium‐sulfur (Li−S) batteries have been regarded as a promising candidate for next‐generation high‐performance energy storage devices because of their advantages in high energy density. However, practical uses of Li−S batteries have been hindered by their poor rate performances and dissatisfactory capacity decay during cycling. In this work, we demonstrate carbon based coating material combined with short multi‐walled carbon nanotubes (S‐CNTs) to form coating cathode (S‐CNTs@S) in the Li−S battery system. The S‐CNTs@S cathode not only facilitates fast diffusion of electrons, but also efficiently inhibits diffusion of poly‐sulfide components. Importantly, the inter‐shell space of S‐CNTs is conducive to the diffusion of electrolyte, which improves the migration efficiency of lithium‐ions, then improves the rated performances of the Li−S battery. Thus, the excellent cycle stability and Coulombic efficiency with high sulfur loading (3 mg cm−2) were demonstrated in durable Li−S coin cell.

Nanomaterials in concrete: Enhancing strength and durability

Carbon nanotubes (CNTs) have received great attention for their applications in concrete due to their unique properties such as high strength, flexibility, and electrical conductivity. This study aims to investigate the effect of adding carbon nanotubes on the energy combination of the material. Concrete samples were prepared with different concentrations of carbon nanotubes and their mechanical properties were measured and compared with control samples without carbon nanotubes. The results show that the addition of carbon nanotubes increases the compressive and flexural strength of concrete. The findings suggest that incorporating carbon nanotubes into concrete could be a good way to improve concrete's mechanical properties and improve its performance in construction. Compared with white cement M20 samples aged 7, 14 and 28 days. The 28day maximum strength is stated below for 0.0045 wt.% SWCNT and MWCNT and 0.0030 wt.% SWCNT and MWCNT. It was determined that nanocomposites containing a lower proportion of long MWCNTs had properties comparable to nanocomposites containing a higher proportion of short MWCNTs. Many of the walls of the carbon nanotubes reach microcracks, indicating that the carbon nanotubes are cracked and pulled out. Besides the compression test, we also calculated the slit tensile strength by adding different percentages of carbon nanotubes. The usage percentage increased for 0.0015% MWCNTs and 0.0030% and 0.0045% SWNTs.

Construction of activated-CNT/carbon composite aerogel for supercapacitor electrode with ultra high cycle stability

Double layer supercapacitors are widely used for energy storage devices due to their excellent characteristics such as high stability and good cycling performance. In this work, a novel carbon aerogel doped with activated short multi-walled carbon nanotube (CA/AMWCNT composite aerogel) was constructed by sol-gel and carbonization process. The effects of the activated short multi-walled carbon nanotube (AMWCNT) addition amount on the microstructure and electrochemical properties of the composite aerogels were investigated. The composite aerogels with appropriate AMWCNT addition amount exhibited improved specific surface area, pore diameter and pore volume. In particular, the composite aerogel CA/AMWCNT-2.5, with higher specific surface area (640 m2 g−1) and pore volume (1.985 cm3 g−1), exhibited improved electrochemical performance with the equivalent series resistance and specific capacitance at a current density of 1 A g−1 being 0.36 Ω and 115.11 F g−1, respectively. Moreover, the composite aerogel CA/AMWCNT-2.5 electrode showed excellent cycle stability, with the retention rate maintaining 99.9 % even after 10,000 cycles, and three prepared symmetrical supercapacitors could supply power for a light emitting diode bulb for a long time. This work provides a new strategy for developing electric double layer supercapacitors with ultra high cycling stability, and the obtained CA/AMWCNT composite aerogels will have promising applications in the field of energy storage devices that require a long service lifetime.

Effect of size of multiwalled carbon nanotubes on thermal conductivity and viscosity of ethylene glycol-based nanofluids for solar thermal applications

The paper investigates the influence of the length of multi-walled carbon nanotubes (MWCNTs) dispersed as an additive in solar thermic fluids to enhance thermal conductivity. Here, pure ethylene glycol was chosen as solar thermic fluid due to its low viscosity, high boiling point, excellent chemical stability, and compatibility with the materials used in solar thermal systems. Pristine multi-walled carbon nanotubes are ball milled for 5, 10, and 20 h to reduce the length due to attrition. The effect of ball milling duration on the defect formation and damage to the tubular structure is assessed using Raman spectroscopy. Furthermore, the ball-milled MWCNTs were oxidized to separate amorphous carbon produced during ball milling, increasing their purity. The pristine long nanotubes and ball-milled nanotubes are mixed in pure ethylene glycol in 0.25 wt. %, and the stability of liquids is estimated using Ultraviolet–Visual (UV-Vis) spectroscopy for two months. The stability of the fluids and thermal conductivity have considerably enhanced with the dispersion of shortened MWCNTs. The dispersion of short MWCNTs in ethylene glycol resulted in a 20%–30% increase in thermal conductivity compared to pure ethylene glycol. It was also found that higher ball milling times resulted in ultra-high stability but the properties deteriorated due to the destruction of the MWCNTs' tubular structure, making them useless.

Nanoindentation and nano-scratch testing on cement paste

Carbon nanotubes are an attractive reinforcement material for several composites. This is due to their inherently high tensile strength and high modulus of elasticity. This study focused on the nanomechanical characteristics of cement paste with and without short multi-walled carbon nanotubes (MWCNTs). The objective behind studying the nanomechanical properties of cement paste is to better understand the fundamental behaviour of cement at the nanoscale level. Cement paste is a complex material that consists of various phases, including cement hydrates, unhydrated cement particles and porosity. By studying the mechanical properties of cement paste at the nanoscale, researchers can gain insights into the mechanisms that govern the behaviour of this material. Following earlier tests, the amount of MWCNTs was kept constant (0.30% by weight of cement). The nanomechanical parameters explored included the localised Young's modulus and hardness. According to the test results, short MWCNTs increased the proportion of high-density calcium silicate hydrate in the cement paste. The nanomechanical properties (localised Young's modulus and hardness) of cement paste with short MWCNTs were found to be greater than those of cement paste without MWCNTs. According to nano-scratching experiments, the cement matrix with short MWCNTs was substantially more durable than the matrix without them.

Novel electrochemical biosensor for Escherichia coli using gold-coated tungsten wires and antibody functionalized short multiwalled carbon nanotubes

Rapid and easy detection of pathogens, especially bacteria, plays an important role in daily life in the face of increasing environmental pollution. Nanosensors focus on carbon nanotubes, which can bind various molecules to large surfaces and have high electron conductivity. They are widely used in the development of electrochemical biosensors. In this study, a new design of electrochemical biosensors is presented by integrating gold-coated tungsten wires (GC-TW) and acid-functionalized multi-walled carbon nanotubes (MWCNTs) in a two-step coating process. GC-TWs are coated with acid-functionalized short MWCNTs. Fourier transforms infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) results show efficient immobilization of the electrodes. The performance for Escherichia coli (E. coli) K-12 is evaluated based upon the change in current following antibody-antigen interactions. Bioimpedance measurements are performed from 50 Hz to 10 MHz to achieve optimal coverage of impedance changes. The measurements show that the electrode has a detection limit of 0.8 CFU/mL. The response of the electrode saturates when the bacterial concentration is increased to 1.70 x 102 CFU/mL. The biosensor is capable of detecting E. coli between 0.8 and 1.70 × 102 CFU/mL. The data show that this MWCNT-based biosensor can be developed into a highly sensitive device for E. coli.

To Improve the Strength of Concrete by Using Carbon Nanotubes (CNTs)

Abstract: The use of carbon nanotubes (CNTs) in concrete has been gaining attention due to their unique properties, such as high strength, flexibility, and electrical conductivity. This study focuses on investigating the effect of adding CNTs to concrete mixtures on the strength of the resulting material. The concrete specimens were prepared with different percentages of CNTs, and their mechanical properties were measured and compared to those of control specimens without CNTs. The results showed that the addition of CNTs significantly improved the compressive and flexural strength of the concrete. The findings suggest that the incorporation of CNTs in concrete mixtures could be an effective way to enhance the mechanical properties of concrete and improve its performance in construction applications. Compared to the plain cement sample at 28 days. The highest increase in strength at 28 days for the 0.0045 wt.% MWCNTs and the 0.0030 wt.% MWCNTs was 43.4% and 37.79% respectively. It is concluded that nano composites with low concentration of long MWCNTs give comparable mechanical performance to the nano composites with higher concentration of short MWCNTs. Many of the MWCNIs were stretching across the micro-cracks showing CNT's breakage and pull-out. In addition to the compression test we had calculated the split tensile strength by adding the multi-walled carbon nano tubes by increasing the proportion as per the percentage. For 0.0015% MWCNT's, 0.0030% and 0.0045% the percentage of strength increased by 25.6%, 44.63% and 51.21% respectively.

A Comparative Study of Short Multi-Walled Carbon Nanotubes with Different Bulk Densities

A Comparative Study of Short Multi-Walled Carbon Nanotubes with Different Bulk Densities

Fabrication and Characterization of Functionalized Multi-Wall Carbon Nanotubes Flexible Network Modified by a Layer of Polypyrrole Conductive Polymer and Metallic Nanoparticles

Short Multi-Walled Carbon Nanotubes functionalized with OH group (MWCNTs-OH) were used to synthesize flexible MWCNTs networks. The MWCNTs suspension was synthesized using Benzoquinone (BQ) and N, N Dimethylformamide alcohol (DMF) in specific values and then deposited on filter paper by filtration from suspension (FFS) method. Polypyrrole (PPy) conductive polymer doped with metallic nanoparticles (MNPs) prepared using in-situ chemical polymerization method. To improve the properties of the MWCNTs networks, a coating layer of (PPy) conductive polymer, PPy:Ag nanoparticles, and PPy: Cu nanoparticles were applied to the network. The fabricated networks were characterized using an X-ray diffractometer (XRD), UV-Vis. spectrometer, and Atomic Force Microscope (AFM). XRD results revealed that the broadening for the (002) peak decreased after being coated with PPy and increased for the doped samples with MNPs, indicating on decrease in the crystalline size (MWCNTs/PPy) sample and increasing for doped ones with Ag and Cu MNPs. AFM images revealed that the surface roughness of the MWCNTs-OH network decreased after being coated with PPy, PPy: Ag, and PPy: Cu. With the help of AFM and XRD results, the CNTs contain 14 layers, while the inner and outer diameters were 18.2 nm and 27 nm receptivity. The UV-Vis. spectrum of MWCNTs showed several peaks, the highest in the 350 nm range. The coated of MWCNTs greatly affected the absorption spectrum, with many bands appearing between 300 to 450 nm and increasing the absorbance along the overall spectrum. For samples doped with Ag NPs and Cu NPs, a weak absorption peak of the plasmonic resonance frequency of the metallic nanoparticles. Analysis of Raman spectra shows that (ID/IG) ratios for all networks are less than one, which prove that the fabricated networks have few impurities and have good homogeneity. This work aimed to synthesize and characterize a flexible MWCNTs network and develop it by coated with a layer of conductive polymer and metallic nanoparticles for gas sensing application using quick and straightforward preparation methods.

Toxicity of short multi-walled carbon nanotubes in Caenorhabditis elegans

Carbon nanotubes have become widely used due to their superior physiochemical properties, and so knowledge of their toxicity has become important. In this study, the toxic effects of nanotubes on Caenorhabditis elegans have been investigated. Multi-walled carbon nanotubes were characterized by transmission electron microscopy and particle size analysis. Upon exposure to the nanotubes at concentrations of 100 to 500 mg/L for 3 to 15 days, numbers and body lengths of the nematodes were not altered, but body thickness was raised and body movements were slightly decreased. A new type of toxicity-reproduction assay was performed to see the effect of multi-walled carbon nanotubes. The circular-form aggregation of starved larvae was counted. The number of aggregations was reduced with the increasing nanotube concentration by ∼27%. The concentration-dependent reduction was confirmed by counting the eggs in a single worm which demonstrated the negative effect of multi-walled carbon nanotubes on reproduction when the nematodes were subjected to prolonged exposure.

Purification use and toxicity of paramagnetic short multi-walled carbon nanotubes

ABSTRACT Carbon nanotubes (CNT) have high surface area and absorption capabilities and the absorption capacity of multi-walled CNTs (MWNTs) enables paramagnetic nanotubes to be obtained by absorbing iron salts. Characterization of paramagnetic MWNTs was performed with TEM, FTIR, DSC, and VSM. Paramagnetic CNTs are used for the purification of water from heavy metals and plastic originated compounds. Most of the PVC-based materials contain phthalate acid esters (PAE) which have considerable effects on human health. In this study, MWNTs were used for removing diethyl phthalate (DEP) from methanol after their toxicity evaluation. Concentration-dependent absorption of 494, 1461, and 2950 ppm, respectively, were measured from the mixture containing 13.3, 33.3, and 66.6% DEP in 40 mg paramagnetic MWNT solution. Although it was concluded that magnetic nanotubes would exhibit significant toxic effects compared to untreated MWNTs, GC-MS results were showed a reliable absorption capacity of magnetic nanotubes for purification applications. The results demonstrated that the use of magnetic MWNTs for the extraction of PAEs is an efficient way from liquids.

Synergistically assembled nitrogen-doped reduced graphene oxide/multi-walled carbon nanotubes composite aerogels with superior electromagnetic wave absorption performance

In this work, ultralight nitrogen-doped reduced graphene oxide/multi-walled carbon nanotubes (NRGO/MWCNTs) composite aerogels were fabricated via a facile hydrothermal and lyophilization two-step strategy. Results of morphology analysis showed that the as-synthesized binary composite aerogels displayed unique three-dimensional porous netlike structure with a pore size around dozens of microns, which was composed of the partial stack of neighboring porous RGO flakes attached by some tiny MWCNTs. Moreover, the effects of complexing with MWCNTs, lengths of MWCNTs and filler contents on the electromagnetic wave (EMW) absorption properties of obtained composite aerogels were investigated. Significantly, the as-prepared NRGO/MWCNTs composite aerogel with long MWCNTs exhibited notably enhanced EMW absorption capacity than that of binary composite aerogel with short MWCNTs and single NRGO aerogel. Specifically, the composite aerogel with long MWCNTs and doped nitrogen content of 7.07 wt% (bulk density ~ 7.2 mg cm−3) presented the optimal reflection loss of −53.3 dB at 6.5 GHz (C band) and broad absorption bandwidth of 5.2 GHz (from 11.1 to 16.3 GHz) under a small matching thickness of merely 2.0 mm and low filler content of 15 wt%. Interestingly, the reflection loss values were all less than −20 dB with matching thicknesses changing from 1.5 to 4.5 mm. Furthermore, the relationship between reflection loss and filler contents was revealed. Additionally, the underlying EMW absorption mechanisms were clarified. Therefore, the as-fabricated NRGO/MWCNTs composite aerogels could be promising candidates as light-weight and high-performance EMW absorbers.

Effect of Different Multi-Walled Carbon Nanotubes MWCNTs on Mechanical and Physical Properties of Epoxy Nanocomposites

Different types of long and short multiwalled carbon nanotubes (MWCNTs) were used as structural support in epoxy resin with a percentage of weight (0.1,0.2,0.5,1.0,1.5,2.0,2.5,3.0,3.5,4.0,4.5,&5) wt. percent, Utilization of direct mixing processes to prepare Nano-Composites (Epoxy/MWCNTs). The ultrasonic mixing method has been used to disperse the nanotubes into the epoxy resin system. SEM was used to demonstrate the dispersion in the epoxy polymer matrix of different MWCNT concentrations. The findings show that electrical conductivity properties boost effect, thermal conductivity coefficient, and A.C with percentage enhancement of less than 2 percent, and then raising with further raise in the content of MWCNTs.

Length difference of multi-walled carbon nanotubes generates differential cytotoxic responses.

Carbon nanotubes have recently been rated as an effective biomaterial owing to their functionalization ability. However, the safety of multi-walled carbon nanotubes (MWCNTs) has yet to be clearly understood. To investigate how cells differentially react to minor geometric differences, we prepared well-dispersed and stable long and short MWCNTs showing an approximately 100-nm length difference in an in vitro system. Through an optimal combination of bovine serum albumin (BSA) and fetal bovine serum (FBS) biosurfactants and ultrasonication, we first confirmed that the MWCNTs were maintained without aggregation throughout the experiments. Internalized MWCNTs in human coronary artery smooth muscle cells were then quantified in a label-free manner using coherent anti-Stokes Raman scattering, followed by an analysis of their localization via two-photon excitation fluorescence. Intracellular MWCNTs were found to primarily localize in mitochondria with abnormal morphologies. Mitochondrial dysfunction, which was found to result from early stages of oxidative stress that consequently lead to cell death, was then proved via decreasing mitochondrial membrane potentials, with short MWCNTs showing significantly greater cytotoxicity than long MWCNTs. Our results suggest that even small length differences of MWCNTs may lead to differential responses in cells.

Impedance spectroscopy of short multiwalled carbon nanotube networks deposited on a paper substrate: tracking the evolution of in-plane and thru-plane electronic properties

Multiwalled carbon nanotubes (MWNT) were deposited via dropcasting and dried using vacuum filtration. Because of the slightly larger pore size (5–10 µm) of the paper substrate used as compared to the length of the nanotubes (0.5–2 µm), a variety of MWNT networks were formed both on the surface and through the thickness of the paper. Using a combination of impedance spectroscopy, equivalent circuit modeling, and microscopy techniques, it was possible to describe in detail how the electrical properties change as a function of how the MWNTs are distributed on the porous substrate by varying the number of deposited layers (1–20) as well as the dispersion concentration (0.1–5 mg/mL). In the in-plane, four different electrical responses were observed and modeled: (1) a substrate dominated spectrum representing unconnected MWNTs, (2) one that included bundle and junction responses as well as some inductances representing sparsely distributed MWNT networks, (3) followed by a parallel RL circuit for partially connected MWNT networks, and (4) finally a series RL circuit for fully connected MWNT networks. In the thru-plane, only two different electrical responses were observed and modeled. The results for the in-plane and thru-plane properties were used to generate percolation curves that show that electrical conductivity can change as much as 10 orders of magnitude for the same exact MWNTs. These results indicate that not only do the characteristics of the nanotubes themselves play a role but also the structure of the underlying substrate and the details of how the films are deposited.

Investigation on Mode I Fracture Toughness of Woven Carbon Fiber-Reinforced Polymer Composites Incorporating Nanomaterials.

This study experimentally investigated the effects of nanomaterials and interface fiber angle on the mode I fracture toughness of woven carbon fiber-reinforced polymer (CFRP) composites. Three different types of nanomaterials were used: COOH-functionalized short multi-walled carbon nanotubes (S-MWCNT-COOH), multi-walled carbon nanotubes (MWCNTs), and graphene nanoplatelets (GnPs). Double cantilever beam specimens were composed of 12 woven carbon fiber fabrics with/without 1 wt% nanomaterials, and were manufactured using the hand lay-up method. Furthermore, two different stacking sequence series were used; the first series comprised only on-axis carbon-fiber fabrics (0° or 90°), and the second series comprised both on- and off-axis carbon-fiber fabrics (0° or 90° and ±45°). The test results showed that adding S-MWCNT-COOH, MWCNTs, and GnPs significantly increased the mode I fracture toughness of the CFRP composites for both the stacking sequence series. Moreover, the specimens that used only on-axis carbon fiber fabrics exhibited higher fracture toughness values than those of the specimens that used on- and off-axis carbon fiber fabrics together. In addition, an empirical model was established to predict the fracture toughness of the CFRP composites with nanomaterials by using on- and off-axis carbon fiber fabrics together, and the prediction results showed a good agreement with the experimental results.

Fabrication of BaTiO3@super short MWCNTs core-shell particles reinforced PVDF composite films with improved dielectric properties and high thermal conductivity

For present ceramic particles/polymer dielectric composite materials, their dielectric properties and thermal conductivity haven't met the application requirement at the same time. In this research, to achieve this goal, barium titanate@super short MWCNTs (BT@SSCNT) core-shell particle was prepared in a confinement reactive space built by water phase and oil phase. Polyvinylidene fluoride (PVDF) based composite flexible films reinforced by the BT@SSCNT particles possessed desired dielectric and excellent thermal behaviors. Especially for the composite film with 60 wt% (containing less than 17 wt% SSCNT) loading, at 102 Hz and in the wide temperature range of −40–140 °C, dielectric constant and dielectric loss varied from 476 to 764 and from 2.74 to 4.58, respectively. Meanwhile the thermal conductivity of this film reaches 25.43 W/(m K). The promising dielectric properties and high thermal conductivity of the films are attributed to multiple roles of SSCNT shell layer including external electric field applying on BT particles, tremendous interfacial polarization area, restricted electron motion and electron efficient in transporting heat. The BT@SSCNT/PVDF composite films can be a promising candidate for the modern electronic industry.

Effect of short multi-walled carbon nanotubes on the mode I fracture toughness of woven carbon fiber reinforced polymer composites

The present study experimentally and theoretically investigated the effects of short multi-walled carbon nanotubes on the mode I fracture toughness of woven CFRP composites. COOH-functionalized short multi-walled carbon nanotubes (S-MWCNT-COOH) with three different amounts of 0.5, 1, and 1.5 wt% (by weight) of epoxy resin/hardener mixture were used. In total, 32 test specimens were fabricated and tested. The mode I fracture toughness was performed under double cantilever beam (DCB) test, and was evaluated using three different data reduction methods: modified beam theory method (MBT), compliance calibration method (CC), and modified compliance calibration method (MCC). The test results with the addition of 0.5, 1, and 1.5 wt% S-MWCNT-COOH showed 1.6, 31.0, and 31.7% increase on average, respectively, of the mode I fracture toughness of the CFRP composites. The mode I fracture toughness evaluated using the three data reduction methods of MBT, CC, and MCC was almost the same. Furthermore, an analytical model was constructed using the trilinear curves based on bridging law describing the pullout force–displacement response of short CNTs from an epoxy matrix, and the predicted results showed good agreement with the experimental results. Finally, idealized load–displacement curves of the CFRP composites were proposed based on the linear elastic fracture mechanics (LEFM) using initiation fracture toughness, and the predictions showed good agreement with the experimental curves.

Strengthening of poly (ethylene terephthalate) by filling with short glass fibers and multi-wall carbon nanotubes

The effect of hybrid filling of poly (ethylene terephthalate) (PET) with short glass fibers (GF) and multi-walled carbon nanotubes (MWCNTs) on the static and dynamic mechanical properties of composites, as well as the structural features and rheological behavior of melts were investigated. Compounding materials was carried out by the PET melt blending with the use of the reaction extrusion method. The studied composites contained from 15 to 60 wt. % GF, the concentration of MWCNTs was 0.5 and 1.6 wt. %. It was shown that the PET hybrid filling led to a synergistic increase in the strength, the elastic modulus and the dynamic shear modulus of composites under tension and bending in a wide temperature range. MWCNT additives intensified interfacial adhesion, had a nucleating effect on the crystallization of the binder, and increased its thermal stability.

High efficiency heat transfer and antifriction characteristics of SMWCNTs nanofluids

In this paper, the thermal conductivity and tribological properties of ethylene glycol/water-based nanofluids with hydroxylated short multi-walled carbon nanotubes (SMWCNTs(OH)) were investigated. Long-term stable ethylene glycol/water-based nanofluids were prepared by a two-step method. The morphology and surface functional group characteristics of SMWCNTs(OH) were characterized by field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The kinematic viscosity of the base fluid and nanofluids at different temperatures was measured using a rotary rheometer. The dispersion stability of nanofluids was analyzed by dynamic light scattering. Thermal conductivity test was performed using the transient hot wire method. The reciprocating friction test was carried out by UMT5 test machine, and the appearances of wear scars were analyzed by white light morphology. Results show that a significant enhancement of thermal conductivity could be achieved by increasing the temperature of the nanofluids and adjusting the concentration of the carbon nanotubes compared with the corresponding base. At 60 °C, the thermal conductivity of the nanofluids increases significantly and reaches 6.0%at the volume fraction of 25% for ethylene glycol/water. It is shown that the SMWCNTs(OH) have good self-lubrication antifriction effect in the water base nanofluids for the GCr15 friction pair. Meanwhile, the wear loss of the wear scar is greatly reduced, and the friction coefficient is reduced by 15.4% compared with the pure water, which shows a good application prospect of nanofluids in pump drive fluid loops.