Filled Carbon Nanotubes Research Articles

Tribological Behavior of Poly(tetrafluoroethylene) and Its Composites Reinforced by Carbon Nanotubes and Graphene Sheets: Molecular Dynamics Simulation

Low‐dimensional fillers play an important role in improving the tribological properties of poly(tetrafluoroethylene) (PTFE) composites. However, the reinforcement mechanism is not fully understood, since few in situ experiments are able to capture the dynamics evolution and interfacial behavior of fillers. Herein, the tribological behavior of PTFE composites filled with graphene (Gr) sheets and carbon nanotubes (CNT) at the nanoscale is investigated. The results demonstrate that the composites filled with the CNT and Gr fillers have much better wear resistance than that of the pure PTFE, and the wear amounts are reduced by 76.2% and 85.7%, respectively. The relative bond and angle energy of PTFE indicate less deformation in the reinforced composite matrices. The calculations of interfacial interaction energy and radial distribution function reveal that the Gr fillers have better reinforcements than CNT due to stronger interactions at the Gr/PTFE interfaces.

A Prospective Concept on the Fabrication of Blend PES/PEG/DMF/NMP Mixed Matrix Membranes with Functionalised Carbon Nanotubes for CO2/N2 Separation.

With an ever-increasing global population, the combustion of fossil fuels has risen immensely to meet the demand for electricity, resulting in significant increase in carbon dioxide (CO2) emissions. In recent years, CO2 separation technology, such as membrane technology, has become highly desirable. Fabricated mixed matrix membranes (MMMs) have the most desirable gas separation performances, as these membranes have the ability to overcome the trade-off limitations. In this paper, blended MMMs are reviewed along with two polymers, namely polyether sulfone (PES) and polyethylene glycol (PEG). Both polymers can efficiently separate CO2 because of their chemical properties. In addition, blended N-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF) solvents were also reviewed to understand the impact of blended MMMs’ morphology on separation of CO2. However, the fabricated MMMs had challenges, such as filler agglomeration and void formation. To combat this, functionalised multi-walled carbon nanotube (MWCNTs-F) fillers were utilised to aid gas separation performance and polymer compatibility issues. Additionally, a summary of the different fabrication techniques was identified to further optimise the fabrication methodology. Thus, a blended MMM fabricated using PES, PEG, NMP, DMF and MWCNTs-F is believed to improve CO2/nitrogen separation.

A Multi-Scale Method for Designing Hybrid Fiber-Reinforced Composite Drive Shafts with Carbon Nanotube Inclusions

In this paper, the modal and linear buckling analysis of a laminated composite drive shaft reinforced by 11 multi-walled carbon nanotubes (MWCNTs) was carried out using an analytical approach, as well as the finite element method (FEM). The theoretical model is based on classical laminated theory (CLT). The fundamental frequency and the critical buckling torque were determined for different fiber orientation angles. The Halpin–Tsai model was employed to calculate the elastic modulus of composites having randomly oriented nanotubes. The effect of various carbon nanotube (CNT) volume fractions in the epoxy resin matrix on the material properties of unidirectional composite laminas was also analyzed. The fundamental frequency and the critical buckling torque obtained by the finite element analysis and the analytical method for different fiber orientation angles were in good agreement with each other. The results were verified with data available in the open literature, where possible. For the first time in the literature, the influence of CNT fillers on various composite drive shaft design parameters such as the fundamental frequency, critical speed, and critical buckling torque of a hybrid fiber-reinforced composite drive shaft is finally predicted.

Ni–P alloy@carbon nanotubes immobilized on the framework of Ni foam as a 3D hierarchical porous self-supporting electrode for hydrogen evolution reaction

The development of self-supporting electrodes that exhibited both high efficiency and good durability remained a challenge in the field of hydrogen energy utilisation. Here, we designed a self-supporting 3D hierarchical porous electrode by filling carbon nanotubes (CNTs) loaded with Ni–P alloy into the framework of nickel foam (NF). Firstly, CNTs were decorated with a catalytically active Ni–P alloy via electroless plating (Ni–P@CNTs). Then, the Ni–P@CNTs were filled and anchored onto the framework of NF via electroplating to synthesise a self-supporting electrode (Ni–P@CNTs/NF). The Ni–P@CNTs/NF exhibited an excellent catalytic performance toward the hydrogen evolution reaction (HER) in 1 M KOH electrolyte, with an overpotential of 53 mV at 10 mA cm−2, a small Tafel slope of 101.56 mV dec−1 and excellent long-term durability. This facile and effective strategy might provide a new path to the design of self-supporting electrodes with enhanced HER catalytic.

One-dimensional Sub-stoichiometric W3O8Nanowires Filled Carbon Nanotubes

One-dimensional Sub-stoichiometric W₃O₈Nanowires Filled Carbon Nanotubes

Investigation on hybrid nanofluids based on carbon nanotubes filled with metal nanoparticles: Stability, thermal conductivity, and viscosity

In recent years, nanofluids as heat transfer fluids have shown huge potential in heat exchange systems. However it is still needed to discover new types of nanofluids with excellent thermal conductivity, dispersion stability and low viscosity to expand its applications. In the present work metal nanoparticles (copper or silver)-filled carbon nanotubes (Cu@CNT, Ag@CNT) have been synthesized by a simple ultrasonic-assisted impregnation combined with chemical reduction. The morphology, phase structure, and degree of crystallization of the prepared nanocomposites have been characterized in detail. Two kinds of nanofluids, including water-based and ethylene glycol-based, have been prepared employing the nanocomposites without adding any surfactant. The dispersion stability, thermal conductivity, and viscosity of the hybrid nanofluids with different mass fraction are studied systematically. The results show that the hybrid nanofluids process good dispersion stability and high thermal conductivity. No obvious delamination can be observed in all nanofluids (0.01–0.05 wt%) after standing for 6 months. The maximum enhancement in thermal conductivity for water-based and ethylene glycol-based Ag@CNT nanofluids with mass fraction of 0.05 wt% reach 52.37% and 40.42% respectively at 65 °C, compared to the base fluid. And the Cu@CNT and Ag@CNT hybrid nanofluids exhibit higher thermal conductivity and lower viscosity than functionalized CNT nanofluids. These results indicate that the metal nanoparticles-filled CNTs composites can be used to improve the thermal conductivity of nanofluids and promote the development of new thermal conductive agents.

Enhancement of dielectric permittivity in carbon nanotube/polyvinylidene fluoride composites by constructing of segregated structure

A segregated structure was constructed based on pristine multi-walled carbon nanotubes (MWCNTs) fillers and polyvinylidene fluoride (PVDF) matrix to enhance the dielectric permittivity of the composites. It is found that the MWCNTs could disperse uniformly in the PVDF matrix through grinding method and a low percolation threshold of 2.7 vol% was achieved. The effect of MWCNTs on the dielectric properties of MWCNTs/PVDF composites was investigated at measuring voltage 4 V. A giant dielectric permittivity with the value of 53460 at 100 Hz is achieved in the composites with 6.1 vol% MWCNTs, while the loss tangent is only 134. Furthermore, the dielectric permittivity decreases slowly and a high value of 11815 still can be seen when the measuring frequency was 104 Hz. The main reason for the giant dielectric permittivity can be attributed to the polarization effect coming from the interface between PVDF powder and MWCNTs. The results suggest that the giant dielectric permittivity can be achieved in pristine MWCNTs/PVDF composites with segregated structure. It is promising for bypass capacitor applications.

Shape-Programmable Interfacial Solar Evaporator with Salt-Precipitation Monitoring Function.

Interfacial solar evaporators (ISEs) for seawater desalination have garnered enormous attention in recent decades due to global water scarcity. Despite the progress in the energy conversion efficiency and production rate of ISE, the poor portability of large-area ISE during transportation as well as the clogging of water transport pathways by precipitated salts during operation remain grand challenges for its fielded applications. Here, we designed an ISE with high energy conversion efficiency and shape morphing capability by integrating carbon nanotube (CNT) fillers with a light-responsive shape memory polymer (SMP, cross-linked polycyclooctene (cPCO)). Utilizing the shape memory effect, our ISE can be folded to an origami with 1/9 of its original size to save space for transportation and allow for on-demand unfolding upon sunlight irradiation when deployed in service. In addition, the ISE is equipped with a real-time clogging monitoring function by measuring the capacitance of the electric double layer (EDL) formed at the evaporator/seawater nanointerface. Due to its good energy conversion efficiency, high portability, and clogging monitoring capability, we envisage our ISE as a promising selection in solar evaporation technologies.

Silicate-Enhanced Heterogeneous Flow-Through Electro-Fenton System Using Iron Oxides under Nanoconfinement.

Herein, a silicate-enhanced flow-through electro-Fenton system with a nanoconfined catalyst was rationally designed and demonstrated for the highly efficient, rapid, and selective degradation of antibiotic tetracycline. The key active component of this system is the Fe2O3 nanoparticle filled carbon nanotube (Fe2O3-in-CNT) filter. Under an electric field, this composite filter enabled in situ H2O2 generation, which was converted to reactive oxygen species accompanied by the redox cycling of Fe3+/Fe2+. The presence of the silicate electrolyte significantly boosted the H2O2 yield by preventing the O-O bond dissociation of the adsorbed OOH*. Compared with the surface coated Fe2O3 on the CNT (Fe2O3-out-CNT) filter, the Fe2O3-in-CNT filter demonstrated 1.65 times higher kL value toward the degradation of the antibiotic tetracycline. Electron paramagnetic resonance and radical quenching tests synergistically verified that the dominant radical species was the 1O2 or HO· in the confined Fe2O3-in-CNT or unconfined Fe2O3-out-CNT system, respectively. The flow-through configuration offered improved tetracycline degradation kinetics, which was 5.1 times higher (at flow rate of 1.5 mL min-1) than that of a conventional batch reactor. Liquid chromatography-mass spectrometry measurements and theoretical calculations suggested reduced toxicity of fragments of tetracycline formed. This study provides a novel strategy by integrating state-of-the-art material science, Fenton chemistry, and microfiltration technology for environmental remediation.

Barium Titanate-reinforced Acrylonitrile-Butadiene Rubber: Synergy Effect of Carbon-based Secondary Filler

Acrylonitrile rubber (NBR) composites filled with barium titanate (BT) were prepared using an internal mixer and a two-roll mill. Also, a secondary filler, namely carbon nanotubes (CNT), was added in order to find a potential synergistic blend ratio of BT and CNT. The cure characteristics, tensile and dielectric properties (dielectric constant and dielectric loss) of the composites were determined. It was found that NBR/BT composites with CNT secondary filler, at a proper BT:CNT ratio, exhibited shorter scorch time (ts1) and cure time (tc90) together with superior tensile properties and reinforcement efficiency, relative to the one with only the primary filler. In addition, the NBR/BT-CNT composite with 80 phr BT and 1–2 phr CNT had dielectric constant of 100–500, dielectric loss of 12–100 and electrical conductivity below 10−4 S/m together with high thermal stability. Thus, with a proper BT:CNT mix and filler loading, we can produce mechanically superior rubber composites that are easy to process and low-cost, for flexible dielectric materials application.

Prediction of influences of MWCNT fillers on the vibration characteristics of laminated hybrid honeycomb core sandwich GFRP composite plate

In this paper, the prediction of influences of multi-wall carbon nanotubes (MWCNT) fillers on the vibration characteristics of laminated hybrid honeycomb core sandwich GFRP composite plate has been performed based on the higher-order shear deformation theory using finite element formulations. The parametric study on the dynamic behavior of honeycomb sandwich composite plates hybrid with MWCNT with the influence of the weight percentage of CNTs for core material and upper and bottom skins with CCCC boundary conditions, different ply configuration was performed. The numerical study clearly shows that the bending frequency increase with an increase in the weight percentage of MWCNTs. It can be observed that the influence of MWCNT in the core is least contributing to increasing the stiffness with the influence of MWCNT in the skins on the bending characteristics. Finally, the ANN technique is used to predict effectively the dynamic characteristics of honeycomb sandwich composite plates hybrid with MWCNT with the influence of intermittent the weight percentage of CNTs for core material and upper and bottom skins which reduces the computational effort.

Karbon Nanotüp ile Modifiye Edilmiş Fiber Takviyeli Laminelerin Isıl ve Elektriksel Özelliklerinin Teorik Analizi

In the present study, the effect of the multi-walled carbon nanotubes (MWCNTs) fillers weight fraction on the mechanical, electrical, and thermal properties of the epoxy was calculated analytically. The results were then compared and it was found out that the MWCNTS has a significant effect on the electrical conductivity of the epoxy. The MWCNT modified epoxy composites were considered as the matrix material to design quasi-isotropic carbon fibre/epoxy composite. The change of the weight fraction of the MWCNTs on the mechanical, electrical, and thermal properties of the carbon fibre/epoxy laminates was also calculated. Finally, the hygrothermal load and the bending load response of the laminated composites were researched. MWCNTs fix the mismatch between the hygrothermal properties of the epoxy matrix and the carbon fiber.

Synergistic Effect of MWCNT and Carbon Fiber Hybrid Fillers on Electrical and Mechanical Properties of Alkali-Activated Slag Composites

Herein, we investigated the synergistic effect of multi-walled carbon nanotube (MWCNT) and carbon fiber (CF) hybrid fillers on electrical and mechanical characteristics of alkali-activated slag (AAS) composites. Many studies on AAS composites have been conducted in the past; however, not much progress has been made regarding characteristics of AAS composites with hybrid conductive fillers. The specimens with different mix proportions were fabricated in the present study, and numerous material characteristics, including flowability, electrical resistivity, and compressive strength of AAS composites were measured. In addition, the synergistic effects were investigated through scanning electron microscopy and thermogravimetric analysis. It was found that the 0.5 wt.% of MWCNTs and CFs lead the effects of the bridging and reducing crack propagation, thereby improving its electrical and mechanical performances. The filler exceeding a percolation point improved the electrical performance of the AAS composites; however, it interfered with the hydration process during the curing period, and caused a decrease in compressive strength of AAS composites.

1-Amino 2-Naphthol Modified Solvent Filled Carbon Nanotubes for Enhanced Electrochemical Sensing of Bioanalytes

My research interest is mainly on developing cost-effective electrochemical sensors for bioanalytes sensing. For example, bioanlytes such as ascorbic acid, dopamine, and uric acid present together in human body poses challenge for selective sensing of one over other. As these molecules play a vital role in controlling the body’s metabolism, it is paramount to develop a sensor tool with high sensitivity towards these bioanlytes for diagnosing diseases, including AIDS, Parkinsonism, etc. Development of fast and reliable methods for sensing these biomolecules is of considerable importance in offering rapid diagnosis.1–3 In the present experimental work, it is shown for the first time that liquid-filled multi-walled carbon nanotubes (MWCNT) exhibit remarkably enhanced characteristics for sensor applications, the detection threshold being lowered by as much as an order of magnitude, while detection sensitivity is doubled for a number of molecules including ascorbic acid, dopamine, and uric acid. 1H NMR relaxometry at a moderately low field, i.e., 14.6 MHz (0.34 T), confirms that the improved sensor characteristics are correlated with the filling of MWCNTs with solvents such as acetonitrile, dimethyl sulfoxide, etc. The molecular motions are slowed down when solvent molecules fill MWCNTs, thus increasing motional correlation times, and hence, longitudinal relaxation rate increases under extreme narrowing conditions. The filling of MWCNTs appears to relate to solvent-CNT interactions that are in line with the principle of hard and soft acids and bases, and also correlates with solvent dipole moments.4 We have further enhanced the detection limit and selectivity towards ascorbic acid by modifying the MWCNTs surface with amino naphthol. References K. Iriyama, M. Yoshiura, T. Iwamoto, and Y. Ozaki, Anal. Biochem., 141, 238–243 (1984).L. Jothi, S. Neogi, S. kumar Jaganathan, and G. Nageswaran, Biosens. Bioelectron., 105, 236–242 (2018).M. Jahan, Z. Liu, and K. P. Loh, Adv. Funct. Mater., 23, 5363–5372 (2013).T. Gurusamy, A. Banerjee, N. Chandrakumar, and K. Ramanujam, J. Electrochem. Soc., 166, B1186–B1195 (2019).

Synergistic effect of carbon nanotubes and nano-hydroxyapatite on mechanical properties of polyetheretherketone based hybrid nanocomposites

Hybrid nanocomposites utilize the benefits of properties of different fillers to enhance its desired properties. Polyetheretherketone (PEEK) based hybrid nanocomposites have immense potential applications in aerospace, automobile, high-temperature electrical applications, and medical and health care. The present work is an attempt to improve the elastic modulus, hardness, fracture resistance, and storage modulus simultaneously by reinforcing the PEEK matrix with multiwall carbon nanotubes (MWCNTs) filler and 30 wt.% nano hydroxyapatite (nHA)-MWCNT hybrid filler. The nanocomposites having 0,1,3,5 and 7 wt.% of MWCNTs were fabricated by the Ball Mixing and Compression Molding Method. Customized Die Heater setup was used to ensure uniform heating and cooling during compression molding. The morphology was examined by Field Emission Scanning Electron Microscopy (FESEM) and Energy-Dispersive X-ray Spectroscopy (EDS) and uniform distribution of nano-fillers was observed. The nanoindentation method was adopted to investigate the Static Mechanical Analysis (SMA) and Dynamic Mechanical Analysis (DMA) at varying frequencies of loading, of nanocomposites. At 5 wt.% of MWCNTs, the enhancements in elastic modulus, hardness, fracture resistance, and storage modulus were observed to be 80%, 36%, 32%, and 58% respectively in case of PEEK/(0–7%)MWCNT nanocomposite and 104%, 76%, 16%, and 80% respectively in case of PEEK/30%nHA-(0–7%)MWCNT hybrid nanocomposite. The decrements in loss factor indicated the improvement in elastic behavior of nanocomposites with increasing wt.% of MWCNTs. The elastic modulus of PEEK/30%nHA-5%MWCNT hybrid nanocomposite was observed to be 7.67 GPa, which falls within the range of elastic modulus of the human cortical bone. The results revealed that 5 wt.% of MWCNTs is optimum filler composition for improving the mechanical properties.

Raman resonance tuning of quaterthiophene in filled carbon nanotubes at high pressures

Filling carbon nanotubes with molecules is a route for the development of electronically modified one-dimensional hybrid structures for which the interplay between the electronic structure of molecules and nanotubes is a key factor. Tuning these energy levels with external parameters is an interesting strategy for the engineering of new devices and materials. Here we show that the hybrid system composed by quaterthiophene (4T) molecules confined in single-walled carbon nanotubes, presents a piezo-Raman-resonance of the molecule vibrational pattern. This behavior manifests as a rapid pressure induced enhancement of the 4T Raman mode intensities compared to the tubes G-band Raman modes. Density functional theory calculations allow to explain the spectral behaviour through the pressure-enhanced quaterthiophene resonance evolution. By increasing pressure, the tube cross-section deformation leads to a reduction of the intermolecular distance, to the splitting of the molecular levels and then to an increase of resonance channels. Calculations and experiments converge to the 4T piezo-resonance scenario associated with the pressure-induced nanotube radial collapse observed at about 0.8 GPa. Our findings offer possibilities for the development of pressure transducers based on molecule-filled carbon nanotubes.

Electrically conductive cotton fabric coatings developed by silica sol-gel precursors doped with surfactant-aided dispersion of vertically aligned carbon nanotubes fillers in organic solvent-free aqueous solution

HypothesisFrom the end of the twentieth century, the growing interest in a new generation of wearable electronics with attractive application for military, medical and smart textiles fields has led to a wide investigation of chemical finishes for the production of electronic textiles (e-textiles). ExperimentsHerein, a novel method to turn insulating cotton fabrics in electrically conductive by the deposition of three-dimensional hierarchical vertically aligned carbon nanotubes (VACNT) is proposed. Two VACNT samples with different length were synthesized and then dispersed in 4-dodecylbenzenesulfonic acid combined with silica-based sol-gel precursors. The dispersed VACNT were separately compounded with a polyurethane thickener to obtain homogeneous spreadable pastes, finally coated onto cotton surfaces by the “knife-over-roll” technique. FindingsShorter VACNT-based composite showed the best electrical conductivity, with a sheet resistance value less than 4.0 · 104 ± 6.7 · 103 Ω/sq. As demonstrated, developed e-textiles are suitable for application as humidity sensing materials in wearable smart textiles by exhibiting adequate response time for end-users and repeatability at several exposure cycles, still maintaining excellent flexibility. The proposed environmentally-friendly and cost-effective method can be easily widened to the scalable production of CNT-containing conductive flexible coatings, providing additional support to the development of real integration between electronics and textiles.

Functionalized carbon nanotubes based thermo-responsive shape memory blends with enhanced mechanical properties for potential robotics applications

A two-step approach was used to synthesize a thermo-responsive polyurethane and its blends with amino-functionalized-polystyrene (PS) and multiwall carbon nanotubes (MWCNTs) aiming at enhanced mechanical, thermal and shape memory properties. The synthesis of novel shape-memory polyurethane was confirmed by FTIR spectroscopy. SEM analysis of samples revealed excellent interfacial interaction due to chemical and physical interlinking between both polymers (PU synthesized and polystyrene functionalized) and functionalized multiwall carbon nanotubes (FMWCNTs) filler. The significant improvement in mechanical and thermal properties was observed for synthesized blends (PU/modified PS) as the filler content increased. The mechanical properties of PU/modified-PS blend having 3% loading amount of FMWCNTs were enhanced from 28.6 to 59.3 MPa as compared to those of neat PU. Due to proper fabrication and strong interfacial interaction, enhancement in thermal properties was also evident from the results with increasing filler loading amount. A sharp decrease in thermal, mechanical and recovery properties was also evident due to agglomerates net-points formation when loading amount of carbon filler increased from a certain level. Almost 100% shape recoveries were achieved for all samples, but the recovery durations of the samples were different. Modified-PS and FMWCNTs with PU formed three-dimensional interlocked networks which provided excellent mechanical strength, thermal stabilities and efficient shape recovery to the synthesized blends. Shape recovery response time of blends and nanocomposite was also found to decrease almost half of that of the pristine PU (less than 37 s for blends). Enhanced thermal stabilities, tensile properties, smaller shape recovery time, almost 100% shape recovery capabilities and sustainability, all factors favor the potential use of these blended composite materials in robotics, aeronautics, medical devices and high-performance materials in auto-industry.

Mechanical, thermal and morphological properties of thermoplastic polyurethane composite reinforced by multi-walled carbon nanotube and titanium dioxide hybrid fillers

A suitable material for wind turbine blades has promoted great interest in carbon-based thermoplastic polyurethane (TPU) composites as they are flexible, lightweight, and mechanically robust. However, these carbon-based fillers deteriorate the thermal and mechanical properties in the long run due to the high agglomeration of the nanoparticles. In addition to that, these fillers also increase the production cost because of the chemical treatment conducted on the fillers. Therefore, a new approach is essential for maintaining the mechanical and thermal properties without using expensive chemical treatment in a low-cost platform. In this work, we present low agglomeration with even distribution of reinforcing fillers in the TPU matrix and robust mechanical and thermal properties by incorporating TiO2 in the carbon-based TPU matrix (TiO2/MWCNT/TPU), without inclusion of costly chemical treatments. TiO2 improves morphology due to the low valency of Ti2+, which may decrease the particle size and thus, reduces agglomeration. Moreover, the enhanced morphology assists in sustaining the rigidity of its molecular structure at high temperatures. The composite also reveals excellent mechanical properties of high tensile stress (4.46 MPa), more extended elongation at break (49%), and high Young's Modulus (9.17 MPa). The thermal analysis using DMA and TGA revealed that the sample TiO2/MWCNT/TPU is a good heat insulator and has a high glass transition temperature compared to the neat TPU indicating its ability to sustain rigidity at high temperatures overall, this composite can perform in elevated weather conditions.

Tritium Effects on Aromatic Carbon–Loaded Polymers

By incorporating carbon nanotubes (CNTs) and graphene nanomaterials with aromatic sp2 carbon structures, we have specifically tuned filled ethylene propylene diene monomer elastomer (EPDM) seal and gasket composite materials for radiation resistance. Our results show that CNTs and graphene have an increased ability to stabilize the EPDM matrix compared to standard carbon black (CB) as a radiation-resistant filler. Graphene outperforms both CNT and CB fillers when considering surface damage under conditions where beta exposure is an issue. Both graphene and CNT fillers offer significantly reduced changes in glass transition temperature under prolonged exposure to tritium compared to CB-filled standards, with a 2.5-fold and almost 5-fold reduction, respectively. Thus, CNT- and graphene-filled O-ring materials could be designed that would maintain acceptable seals significantly longer than currently used composites.