Modification Of MWCNTs Research Articles

Eco-friendly Functionalization of MWCNTs with Deep Eutectic Solvents

The unique features of deep eutectic solvents (DESs) have sparked interest in their use for various applications due to their capacity to introduce new functional groups and other surface alterations. In this study, DESs were employed for the surface modification of MWCNTs. Twelve distinct varieties of Choline chloride-based DESs were prepared and characterized. Prior to the MWCNTs functionalization process, further tests, including viscosity, density, and TGA analysis, were carried out to evaluate the stability of the prepared solvents. The surface functionalization of MWCNTs was then carried out using the most stable solvent. The DESs-functionalized samples were tested for dispersibility and solubility, and FTIR was used to confirm the functional groups present. In comparison to the pristine MWCNTs, the result showed that samples D1, D2, and D4 had several functional groups on their surfaces. Also, in comparison to other DESs-functionalized samples, D1, D2, and D4 had more oxygen-containing groups, as further corroborated by CHNS analysis.As a result, DESs comprising glycerol and ethylene glycol provide an environmentally benign route to alter the surface of MWCNTs, making them suitable functional materials for a range of uses such as Adsorbents, Catalysts, Li batteries, EMI shielding materials, and Supercapacitor electrolytes.

A comparative study of polymer nanocomposites containing multi-walled carbon nanotubes and graphene nanoplatelets

Featuring exceptional mechanical and functional performance, MWCNTs and graphene (nano)platelets (GNPs or GnPs; each platelet below 10 ​nm in thickness) have been increasingly used for the development of polymer nanocomposites. Since MWCNTs are now cost-effective at US$30 per kg for industrial applications, this work starts by briefly reviewing the disentanglement and surface modification of MWCNTs as well as the properties of the resulting polymer nanocomposites. GNPs can be made through the thermal treatment of graphite intercalation compounds followed by ultrasonication; GNPs would have lower cost yet higher electrical conductivity over 1,400 ​S ​cm −1 than MWCNTs. Through proper surface modification and compounding techniques, both types of fillers can reinforce or toughen polymers and simultaneously add anti-static performance. A high ratio of MWCNTs to GNPs would increase the synergy for polymers. Green, solvent-free systhesis methods are desired for polymer nanocomposites. Perspectives on the limitations, current challenges and future prospects are provided.

Characterization and electrochemical studies of MWCNTs decorated with Ag nanoparticles through pulse reversed current electrodeposition using a deep eutectic solvent for energy storage applications

Carbon nanotubes (CNTs) are receiving special attention due to their remarkable thermal, electrical, and mechanical properties. The present work reports an innovative synthesis procedure to decorate MWCNTs with silver nanoparticles (Ag-NPs) via pulsed reverse deposition technique using a deep eutectic solvent (DES) based on choline chloride and glycerol as an electrolyte at room temperature, not requiring any previous surface modification of MWCNTs. MWCNTs decorated with Ag-NPs disclose a significant enhancement of their electrochemical performance as demonstrated by the increase of electrode stability and specific capacitance. Electrochemical characterization of the composite material was performed using cyclic voltammetry and charge/discharge curves, achieving a specific capacitance up to 28.50 F. g −1 , against 4.70 F. g −1 for the commercial MWCNTs in a three-electrode system. Retention of the specific capacitance up to 99% for the Ag-MWCNTs composites compared with a value of 78% for electrodes modified with commercial MWCNTs. The Ag-MWCNTs composites were characterized through SEM/EDX analysis, ultrahigh-resolution STEM, in which the Z – Contrast image was collected, and Raman analysis to prove the successful attachment of the Ag-NPs to the MWCNTs surface. AFM was performed to evaluate the conductivity of the composites.

Combining hydrophilic MXene nanosheets and hydrophobic carbon nanotubes for mechanically resilient and electrically conductive elastomer nanocomposites

It is challenging to process elastomers with two types of fillers having disparate morphologies and surface properties. In this study, hydrophilic Ti3C2Tx MXene nanosheets and hydrophobic carbon nanotubes (CNTs) were compounded with an elastomer latex to prepare 3-phase nanocomposites that demonstrated highly improved mechanical and functional properties. Multi-walled CNTs were modified with hexadecyltrimethylammonium bromide (CTAB) to produce an overall positive surface charge. The modification yielded not only a spontaneous electro-static interaction between MWCNTs and the negatively charged MXene nanosheets but also promoted a relatively uniform dispersion of the hybrid nanofiller in the elastomer matrix. Raman and X-ray photoelectron spectroscopy confirmed the modification of MWCNTs and the structural integrity of both nanofillers. The hybrid fillers achieved remarkable compatibility with the matrix through the reactions between Ti in Ti3C2Tx MXene and N in both the elastomer (nitrile rubber) and the modifier (CTAB). Micrographs revealed an enhanced degree of filler dispersion compared with those nanocomposites containing non-assembled fillers. Due to the bridged and interconnected structures of the hybrid fillers, the electrical conductivity of the resulting nanocomposites was markedly increased and the mechanical properties (e.g., tensile strength and tangent modulus) displayed much improved synergism. In addition, the chemical resistance was substantially increased due to the network formed between the hybrid fillers and the elastomer macromolecules.

Influence of multiwalled carbon nanotubes on the structure and properties of poly(ethylene‐co‐vinyl acetate‐co‐carbon monoxide) nanocomposites

AbstractIn this work, composites of poly(ethylene‐co‐vinyl acetate‐co‐carbon monoxide) (EVACO)/surface‐modified multiwalled carbon nanotubes (m‐MWCNTs) were prepared using a solution casting technique. Acid treatment was employed for the surface modification of MWCNTs to improve the compatibility between polar EVACO and MWCNTs. The influences of m‐MWCNTs on the crystalline, mechanical, thermal, and electrical properties of EVACO at very low filler loading were systematically evaluated. The presence of m‐MWCNTs in the EVACO matrix influenced the crystallinity, and the respective changes were determined and quantified using dynamic scanning calorimetry and X‐ray diffraction. The mechanical properties of the composites were improved remarkably by the addition of a minute quantity (0.05, 0.1, 0.15, 0.2, and 0.25 wt%) of m‐MWCNTs. Additionally, m‐MWCNTs in the EVACO matrix improved the thermal stability and electrical properties of EVACO. However, the filler loading is below the threshold loading of the fillers, and there was no drastic improvement in the electrical conductivity of the composite.

Fabrication of CNTs reinforced copper composite powders by electrochemical co-deposition

ABSTRACTCarbon nanotubes (CNTs) reinforced copper composite powders were fabricated by electrochemical co-deposition. The purification and modification of MWCNTs and the effect of surfactants on deposition process were studied to improve uniform distribution of CNTs in copper matrix and the interfacial adhesion between them. The results indicate that MWCNTs treated by mixture concentrated acid generate many functional groups, such as hydroxyl group and carboxyl group, which greatly improve the hydrophily of CNTs and the co-deposition of CNTs and copper cation in the electrolyte. Further, a good adhesion of CNTs in copper matrix is obtained in the present study as revealed through the micrograph analysis of as-deposited Cu/CNTs composite powders by means of scanning electron microscope (SEM) and transmission electron microscope (TEM).

Surface modification of MWCNT and its influence on properties of paraffin/MWCNT nanocomposites as phase change material

ABSTRACTMultiwalled carbon nanotubes (MWCNTs) were modified by an organo‐silane in order to improve their dispersion state and stability in paraffin wax. A family of paraffin‐based phase change material (PCM) composites filled with MWCNTs was prepared with different loadings (0, 0.1, 0.5, and 1 wt%) of pristine MWCNTs and organo‐silane modified MWCNTs (Si‐MWCNT). Structural analyses were performed by means of Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and rheological studies using temperature sweeps. Moreover, phase change transition temperatures and heat of fusion as well as thermal and electrical conductivities of the developed PCM nanocomposites were determined. The SEM micrographs and FTIR absorption bands appearing at approximately 1038 and 1112 cm−1 confirmed the silane modification. Differential scanning calorimetery (DSC) results indicate that the presence of Si‐MWCNTs leads to slightly favorable enhancement in the energy storage capacity at the maximum loading. It was also shown that the thermal conductivity of the PCM nanocomposites, in both solid and liquid phases, increased with increasing the MWCNT content independent of the kind of MWCNTs by up to about 30% at the maximum loading of MWCNTs. In addition, the modification of MWCNTs made the samples completely electrically nonconductive, and the electrical surface resistivity of the PCMs containing pristine MWCNTs decreased with increasing MWCNTs loading. Furthermore, the rheological assessment under consecutive cyclic phase change demonstrated that the samples containing modified MWCNTs are more stable compared to the PCM containing pristine MWCNTs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48428.

Improvement of Mechanical Strength, Thermal Stability, Swelling, Moisture Content of Triple Network Hydrogels by Carbon Nanotubes

In this study, we prepared a novel carbon nanotubes reinforced three network hydrogels composed of carbon nanotubes, polyacrylic acid(PAA), agar and polyvinyl alcohol(PVA), consisting of an agar gel as the first physical network, a PAA-Fe3+ gel as the second physical network and a polyvinyl alcohol as the third physical network. The surface modification of MWCNTs was carried out by oxyfluorination to introduce the functional groups on the hydrophobic MWCNTs. Agar/PAA-Fe3+/PVA/MWCNTs hydrogels with high tensile and compression strength(σf of 1.5 Mpa, Ɛf of 14.24 mm/mm) and (σf of 1.69 Mpa, the deformation of 80%), thermal stability, low-swelling, high moisture content properties were successfully prepared by a simple three-step method. The addition of carbon nanotubes has significantly improved the thermal stability of the gels, its thermogravimetric curve drops obviously until 387°C. Under the joint action of hydrogen bonding and ion coordination interaction, the gel achieves a perfect balance of swelling and moisture content. The research provide a new method to improve mechanical, swelling, thermal stability, moisture content ability by adjusting the compositions and interactions in the gels.

Noncovalent functionalization of carbon nanotubes via co-deposition of tannic acid and polyethyleneimine for reinforcement and conductivity improvement in epoxy composite

In this paper, a novel strategy via one-pot co-deposition of tannic acid (TA) and polyethyleneimine (PEI) to modify the MWCNTs was reported, which allows to modify MWCNTs with polymer via robust linkage in a convenient, green and nondestructive way. The obtained TA-PEI modified MWCNTs (TA-PEI/MWCNTs) with abundant amine and imine groups have good dispersibility in various solvents as well as epoxy resin. Epoxy composites reinforced with TA-PEI/MWCNTs were prepared and their mechanical properties was studied in detail. The modification of MWCNTs by TA-PEI could not only enhance the compatibility of MWCNTs with epoxy resin, but also improve the interface interaction between MWCNTs and epoxy matrix caused by the curing reaction between epoxy and amine groups on MWCNTs surface. With the 0.4 wt% loading of TA-PEI/MWCNTs, the impact strength and tensile strength of the composite reach 40.51 kJ/m2 and 80.83 MPa, improved by 154% and 148% compared with pristine MWCNTs/epoxy composites, respectively, clearly demonstrating the important role of TA-PEI modification. In addition, the glass transition temperature (Tg) of the composite is 152.4 °C which is significantly higher than pure epoxy resin (136.9 °C) and MWCNTs/epoxy (142.0 °C). Furthermore, the electrical conductivity of the epoxy composite was also remarkably enhanced.

Numerical study of turbulent heat transfer of nanofluids containing eco-friendly treated carbon nanotubes through a concentric annular heat exchanger

In this study, we conducted numerical simulations using finite volume method to examine thermal and hydrodynamic characteristics of clove-treated multi-walled carbon nanotube (C-MWCNT)/distilled water nanofluids in a concentric annular heat exchanger exposed to uniform and constant heat flux boundary conditions. We devised an environmentally friendly functionalization method to synthesize the MWCNTs where the MWCNTs were covalently treated with clove buds in one pot using free radical grafting reaction for preparation of homogeneous MWCNT nanofluid without involving existing corrosive, hazardous acid based conventional functionalization methods of carbon nanomaterials. We analysed the C-MWCNTs using Fourier transform infrared spectroscopy in order to assess the surface modification of MWCNTs. Next, we performed numerical simulations in order to predict the convective heat transfer and hydrodynamic characteristics of the nanofluids considering three concentrations of C-MWCNTs: 0.075, 0.125, and 0.175 wt.%. The effective thermo-physical properties of the nanofluids, which we obtained experimentally, were used in our three-dimensional simulations in order to solve the governing equations of fluid dynamics (continuity, momentum and energy), along with the k-ω turbulence model. We found that there is a good agreement between the simulation and experimental results. We also noticed that the addition of a small fraction of C-MWCNTs into distilled water significantly enhances the convective heat transfer coefficient relative to distilled water. Our results are also encouraging because we observed that the friction factor does not vary significantly for the nanofluids at their concentration range. In general, we conclude that our simulation model can be used to predict the convective heat transfer and hydrodynamic characteristics of C-MWCNT/distilled water nanofluids in a concentric annular heat exchanger with reasonable accuracy and the results show the promising capabilities of these nanofluids as coolants.

Improvement of amoxicillin removal from aqueous environment by applying functionalized carbon nanotube

ABSTRACTMultiwalled carbon nanotubes (MWCNTs) were applied for amoxicillin removal from aqueous environment. To enhance the adsorption capacity of adsorbent, MWCNT with modified surface was applied. A functional group as 8-hydroxyquinoline (8-HQ) and carboxyl group were selected to modify the surface of MWCNT. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed the successful surface modification of MWCNTs. Some important parameters associated with the adsorption capacity such as pH, initial concentration of amoxicillin and equilibrium time of adsorption were investigated for pristine and functionalized MWCNTs. Adsorption results suggested that the maximsum removal efficiency of pollutant was achieved at pH = 5 for pristine and 8-HQ functionalized carbon nanotube (CNT) and pH = 3 for the functionalized CNT with carboxylic groups. The equilibrium time of adsorption was 4 h for the pristine and 2 h for the functionalized CNTs. The maximum adsorption capacity of 8-HQ CNTs was nearly 50% higher than that of pristine MWCNT. The modeling of adsorption process suggested that adsorption of amoxicillin on pristine and functionalized MWCNTs was best fitted with Langmuir model. Moreover, pseudo-second-order kinetic model was found to be the best kinetic model for the adsorption process. In conclusion, functionalized MWCNT with 8-HQ functional groups offers a novel alternative for removing amoxicillin from water.

Enhancing energy density of carbon-based supercapacitors using Prussian Blue modified positive electrodes

The modification of MWCNTs with Prussian Blue (PB) represents a significant improvement of the energy density values of asymmetric carbon based supercapacitors (CBSCs) in neutral media (KCl). The development of the faradaic processes associated with the presence of PB on the positive electrode increases not only the capacitance but also the operational voltage of these devices (up to 1.4V) due to the high electrode potentials at which the Prussian Blue/Berlin Green (PB/BG) redox reactions occur. Accordingly, in asymmetric CBSCs assembled using an activated carbon as negative electrode and MWCNTs as the positive one, suitable modification of MWCNTs with PB increases the energy density of the device fivefold (from 1.46 to 7.68W h kg−1). The resultant system becomes an asymmetric hybrid device in which the energy is stored due to the double layer formation in the negative electrode and the development of the PB faradaic processes in the positive electrode, which acts as a battery.

Mechanical and electrical properties of chemically modified MWCNTs/3Y-TZP composites

In the present work, homogeneous dispersion of MWCNTs in ZrO2 matrix was achieved by the chemical modification of MWCNTs and the formation of noncovalent attachment between carboxyl acid (–COOH) groups on MWCNTs and ZrO2 particles to obtain better compatibility of MWCNTs in ZrO2 matrix. 3Y-TZP/4wt% MWCNTs composite exhibited the best indentation toughness of 6.24MPam1/2 increasing 31% over monolithic ZrO2. Nanoindentation measurements showed that Young׳s modulus, hardness and contact-damage-resistance decreased with increasing the MWCNTs content. Moreover, the electrical conductivity slightly increased for MWCNTs weight fraction below 1wt% and displayed a dramatic increment with a maximum corresponding to MWCNTs weight fraction of 4wt%, which can be described by the percolation theory.

3D hierarchical honeycomb structured MWCNTs coupled with CoMnAl–LDO: fabrication and application for ultrafast catalytic degradation of bisphenol A

Schematic illustration for the synthesis of CNTs–LDH. (I): The surface modification of MWCNTs. (II): The adsorption of metal ions. (III): The formation of 2D CNTs–LDH nanosheets. (IV): The formation of 3D hierarchical honeycomb nano-structure.

Chemical modification of MWCNTs with 5-aminoisophthalic acid and its effects on the thermal and morphological properties of chiral poly (ester-imide)/MWCNT nanocomposites having N-trimellitylimido-L-isoleucine moieties

In this article, carboxylated-multiwalled carbon nanotubes (MWCNT) s were functionalized with 5-aminoisophthalic acid under microwave irradiation conditions as a simple and efficient technique. Functionalized MWCNTs were incorporated into a chiral poly (ester-imide) (PEI) matrices using solution mixing and ultrasonic dispersion method. The optically active PEI was prepared by direct polycondensation reaction of chiral diacid with 4,4′-thiobis (2-tert-butyl-5-methylphenol) promoted by tosyl chloride in pyridine and N,N-dimethyl formamide solution. The nanocomposites (NC) s containing functionalized MWCNTs with loading levels of 5, 10, 15 wt.% were produced and studied in terms of morphology, thermal stability and chemical structure by X-ray diffraction, FT-IR spectroscopy, thermogravimetric analysis (TGA), transmission electron microscopy, and field emission scanning electron microscopy. It was found from TGA data that the NCs show improved thermal stability by comparison with the pure PEI as a result of uniform and efficient dispersion of functionalized MWCNTs in the PEI matrices. Microscopic observations indicated good filler dispersion and improved compatibility of the filler with polymer.

Preparation and electrochemical characterization of polyaniline functionalized copper bridges carbon nanotube for supercapacitor applications.

Supercapacitor is an alternative power source due to its high energy density, fast charge/discharge time, low level of heating, safety, long-term operation stability. MWCNTs are used for supercapacitor applications due to their unique properties, structure, high surface area. In the present work nanocomposites were prepared from Cu modified MWCNTs (binary) from which ternary composite also prepared with HCI doped polyaniline (PANI). Cu modified MWCNTs were prepared by the reduction of copper sulphate with sodium borohydride in basic medium. The uniform coating of polymer, upon the Cu modified MWCNTs, was evidenced from the field emission scanning electron microscopic (FESEM) and high resolution transmission electron microscopic (HRTEM) images. The modification of MWCNTs with Cu, was confirmed from the X-ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Cyclic voltammetry (CV) measurement and charge discharge test shows higher capacitance for the ternary composites (264 F/g) compared to the binary system (125 F/g). The cyclic stability and retention of specific capacitance also shows the better result for ternary system.

Core/shell, protuberance-free multiwalled carbon nanotube/polyaniline nanocomposites via interfacial chemistry of aryl diazonium salts

Highly uniform core–shell like multi-walled carbon nanotubes–polyaniline (MWCNT–PANI) nanocomposites were prepared in two steps (i) surface modification of MWCNTs with a 4-aminodiphenylamine group via in situ diazonium generation process; and (ii) polymerization of aniline onto surface modified MWCNTs. This functionalization helped to easily disperse the MWCNTs in acidic solutions; hence it is suitable for the chemical oxidative polymerization of aniline. It was found that MWCNT–PANI nano-composites with higher MWCNTs loading yield PANI chains with more quinoid units than the pure PANI, which results in significant improvement in the conductivity of the composites. This facile approach of synthesizing core–shell nanocomposites highlights the efficiency of the interfacial chemistry of aryl diazonium salts in generating conductive polymer/MWCNT nanocomposites with enhanced conductivity and high surface area.

Synthesis and characterization of multi-walled carbon nanotubes modified with octadecylamine and polyethylene glycol

Chemical modification of MWCNTs via oxidation followed by side wall functionalization using polyethylene glycol (PEG) and octadecylamine (ODA); separately, was studied. Different characterization techniques such as FTIR spectrometry, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and solubility in different solvents were performed for the oxidized MWCNTs, MWCNTs–PEG and MWCNTs–ODA. The characterization techniques proved the presence of the functional groups on the MWCNT surface. Thermal gravimetric analysis revealed that nearly 16% (by weight) of the MWCNTs were functionalized with PEG and 39% (by weight) was functionalized with ODA.

Oxidative treatment of multi-wall carbon nanotubes with oxygen dielectric barrier discharge plasma

The surface chemical properties and morphology changes that occurred on carbon nanotubes after modification by oxygen dielectric barrier discharge (DBD) at atmospheric pressure were investigated by dispersion test, XPS, FTIR, Raman, SEM and nitrogen adsorption. The effects of plasma treatment parameter, such as discharge power and treatment time, have been conducted. At the power of 15 W following 40 min exposure to the discharge, the surface atomic oxygen percentage could increase from 1.90% to 7.47%. Meanwhile, the surface area increased from 125 m 2/g to 156 m 2/g and the total volume from 0.309 cm 3/g to 0.358 cm 3/g. The possible mechanism is drawn for the modification process. Firstly, the plasma would attack on the defect site, transformed the sp 2-hybridized carbons in nanotubes framework into sp 3-hybridization and introduce the oxygen-containing functional groups including OH, COOH groups within 10 min. Furthermore, the hydroxyl groups could be further oxidized to form carboxyl groups. Moreover, the COOH groups were further oxidized to CO 2 and H 2O under excessive exposure time causing the decrease of the amount of oxygen atom. This investigation may be a simple and nonpolluting method for the modification of MWCNTs.