Performance Of Multiwalled Carbon Nanotubes Research Articles

Enhanced Rate Capability of Polymer-Derived SiCN Anode Material for Electrochemical Storage of Lithium with 3-D Carbon Nanotube Network Dispersed in Nanoscale.

Electrochemical performances of multi-walled carbon nanotubes (CNT)-SiCN composite have been investigated. The sample was synthesized by a simple ultrasonication assisted method combined with high-temperature pyrolysis and characterized by Fourier transform infrared spectra, Raman spectra, X-ray diffraction, field emission scanning electron microscopy and transmission electronic microscopy. In this composite, CNT were uniformly distributed in the SiCN ceramic matrix, it retained the structural integrity during the polymer-ceramic conversion and had a relatively strong bonding with the SiCN ceramic matrix. When tested as anode in the half cell, the obtained composite exhibited enhanced rate capability and cyclic capacity than that of pristine SiCN powder, CNT and graphite, it could supply a capacity of 222.7 mA h/g when charged at 2000 mA/g, while the SiCN anode showed nearly no capacity even at the low current density of 200 mA/g. It is expected that the CNT-SiCN composite, perhaps the series of CNT-PDC composites, may be prospective candidate for high power applications.

Adsorption performance of multiwall carbon nanotubes and graphene oxide for removal of thiophene and dibenzothiophene from model diesel fuel

Multiwall carbon nanotubes (MWCNT) and graphene oxide (GO) are promising compressible nano adsorbents that can be used in the deep desulfurization process for mobile applications. In this study, the adsorption isotherm and the adsorption kinetics of thiophene and dibenzothiophene (DBT) introduced in hexane as a model diesel fuel have been investigated. The adsorption performance of thiophene and DBT on MWCNT and GO were compared with the adsorption performance on activated carbon (AC) as a reference material. In addition, the effect of agitation speed and adsorbent dosage amount were studied. The DBT adsorption results on the three adsorbents were represented by Langmuir and Freundlich isotherm models. The Freundlich isotherm was found to be more favorable with squared correlation coefficient (R 2) >0.97. The thiophene adsorption isotherm was fitted only by the Freundlich isotherm model with R 2 > 0.989. The adsorption rate for these sulfur compounds follows the pseudo-second-order adsorption kinetic. The removal efficiency of DBT using the MWCNT was 68.8 % almost twice the GO removal efficiency but lower than the AC removal efficiency by about 25 %. In addition, the ability of these adsorbents to remove the DBT from the model fuel was much higher than their capability to remove the thiophene.

Oil Adsorption and Reuse Performance of Multi-Walled Carbon Nanotubes

Multi-walled carbon nanotubes (MWCNTs) have aroused widespread attention as a new type of adsorbents due to their outstanding ability for oil adsorption. In this work, the effects of recycling method, different types oil, metal ions and surfactants on the adsorption capacity and reuse performance of MWCNTs were investigated. The results showed that with the increase of the number of reuse, oil adsorption ability of MWCNTs decreased and stabilized gradually. Through the study on the methods of oil removing from MWCNTs and re-adsorption performance of MWCNTs, it was found that the re-adsorption capacity of incinerated MWCNTs is higher than those extruded ones. This may due to the destruction of the gap between carbon nanotubes during the extrusion process, which leading to lower oil adsorption capacity. The oil adsorption capacity on the extruded MWCNTs increased with the increase of carbon chain length of the oil, while that on the incinerated ones decreased. With the existing of mental ions and surfactant, it was found that the oil adsorption capacity increased with the increasing of ions and surfactant concentration.

Enhanced vacuum sensing performance of multiwalled carbon nanotubes: role of defects and carboxyl functionalization

The presence of surface active carboxylic sites and the nature of the (ordered and defective) stacking of graphite layers in the nanotubes determined the vacuum sensing characteristics.

Enhancement in the performance of multi-walled carbon nanotube: Poly(methylmethacrylate) composite thin film ethanol sensors through appropriate nanotube functionalization

We report for the first time, development of an efficient ethanol sensor using mild functionalized multiwalled carbon nanotubes (MWCNTs). A unique technique to functionalize MWCNT is reported to enhance the performance of the ethanol sensor based on it. The conventional functionalization techniques tend to damage physical structure of carbon nanotubes (CNTs) to a large extent and convert most of their sp2 bonds into sp3 bonded carbon atoms. This results in reduction of the available adsorption sites for ethanol vapors on the CNT surface and hence deteriorates the sensitivity. In this work, the functionalization of nanotubes is achieved through direct cycloaddition to π electrons of the CNT that does not hamper the physical structure of the nanotube. High resolution transmission electron microscopy (HRTEM) and Raman spectroscopy studies were employed to confirm the appropriate functionalization for better performance of the sensor. Electrical transport properties of the composites were also studied to understand the quality of the established CNT network. Out of the other functionalization technique, Diels Alder cyclo addition reaction based composite sensor was found to exhibit excellent performance and has an edge over the other reported CNT based sensor.

Catalytic performance of carbon nanotubes in H2O2 decomposition: Experimental and quantum chemical study

The catalytic performance of multi-walled carbon nanotubes (MWCNTs) with different surface chemistry was studied in the decomposition reaction of H2O2 at various values of pH and temperature. A comparative analysis of experimental and quantum chemical calculation results is given. It has been shown that both the lowest calculated activation energy (∼18.9kJ/mol) and the highest rate constant correspond to the N-containing CNT. The calculated chemisorption energy values correlate with the operation stability of MWCNTs. Based on the proposed quantum chemical model it was found that the catalytic activity of carbon materials in electron transfer reactions is controlled by their electron donor capability.

Performance of MWCNTs and a low-cost adsorbent for Chromium(VI) ion removal

In the present study, adsorption of Cr(VI) ions from aqueous solutions was investigated and compared under various conditions using two different nano-structured adsorbents, i.e., carbon nanotubes (CNTs) and low-cost activated carbons (AC). Walnut shell, an agricultural solid waste, was used as a raw material for the preparation of ACs. Multi-walled CNTs (MWCNTs) with average diameter of 20 nm and length of about 2 mm were also used for comparison purposes. Adsorption studies were carried out by varying the parameters such as: treatment time, metal ion concentration, adsorbent amount and pH. The adsorption capacities of AC and MWCNT for Cr(VI) ions were measured as 35 and 24 mg g−1, respectively. The efficiency was observed fairly high at pH = 2–3 for AC and pH = 5–6 for MWCNTs. The adsorption was significantly enhanced by increasing the adsorbent dose up to 0.4 and 0.3 g for AC and MWCNTs, respectively. It was also determined that Cr(VI) adsorption behavior follows both Langmuir and Freundlich isotherms. The content of functional groups, which was obtained by applying the Boehm’s method, revealed that phenolic groups are mostly present on the surface of MWCNTs, while basic groups are predominant on the walnut shell AC structures.

Abrasive Wear Performance of CNT/PP Composites

In this work, abrasive wear performance of multi-walled carbon nanotube (CNT) reinforced polypropylene (PP) has been studied. Various weight percentage of CNT/PP nanocomposites were prepared through melt intercalation with the aid of twin screw extruder. Prepared composites were subjected to sliding wear against silicon carbide abrasive paper with the aid of pin-on-disc configuration. Worn out surface morphology were observed under microscope and non-contact profilometer to understand the wear mechanism. Since the dominant friction mechanism observed to be is ploughing, no lubrication effect of CNT was observed. CNT/PP composite exhibits inferior wear resistance than unfilled PP due to its brittleness. With increased CNT, wear resistance found to decreases.

Comparisons of heat treatment on the electrochemical performance of different carbons for lithium-oxygen cells

Lithium-oxygen (Li-O2) cells are a promising power source, and carbons are an attractive non-metal catalyst for air electrodes. To improve the electrochemical performance, various carbons are heated in an inert atmosphere. It is found that heat treatment at 900°C can differently improve the electrochemical performance of multiwalled carbon nanotubes (CNTs), acetylene carbon black (AB) and activated carbon (AC), but the improvement of CNTs is the most obvious. After heat treatment, the peak current density of the oxygen reduction reaction (ORR) and the 1st discharge capacity of CNTs increase ∼30% and ∼125%, respectively, while the charge transfer reaction resistance and the Warburg diffusion resistance decrease ∼7.0% and ∼11.1%, respectively. AC has the highest charge capacities and capacity retention ratio in spite of little influence by heat treatment. The possible mechanism and reasons are analyzed using different techniques. Microstructure is superior to conductivity for enhancing the rechargeability and the cyclability, and heat treatment is effective for some carbon materials in improving the electrochemical performance of Li-O2 cells.

Adhesive Wear Performance of PP/MWCNT Composites

In this work, tribological performance of multi-walled carbon nanotube reinforced polypropylene has been studied. Various amount of nano composites prepared through melt intercalation with the aid of twin screw extruder. Developed composites were tested for adhesive wear performance with the aid of pin on disc tribometer. Worn out surfaces of nano composites were examined under non-contact optical profilometer to understand the friction wear mechanism. In spite of reduction in friction coefficient due to the presence of carbon nanotubes, composite exhibit inferior wear resistance than polypropylene. Worn out surface of test specimens reveals polypropylene ability to form substantial transfer film on the counter face and hence confirms the superior wear performance than that of carbon nanotube composite.

Effect of nano-filler on the performance of multiwalled carbon nanotubes based electrochemical double layer capacitors

This article presents the main features of electrochemical double layer capacitor (EDLC), made up of multiwalled carbon nanotubes as electrode materials and electrolyte based on nano silica dispersed in poly(vinylidene fluoride-co-hexafluoropropylene)-based magnesium ion conducting nano composite gel polymer electrolyte. The capacitance value was stable up to 5000 voltammetric cycles and even more. The performance characteristics of EDLC have been tested using cyclic-voltammetry, impedance spectroscopy, and charge-discharge techniques. Analysis shows that the nano-filler based EDLC has relatively larger capacitance value as compared to filler-free based electrolyte. The maximum capacitance of 92 mF cm−2, equivalent to single electrode specific capacitance of 92 F g−1 was achieved. It corresponds to energy-density of 10.5 W h kg−1 and power-density of 3.25 kW kg−1.

Investigation of Reactive Red Dye 198 removal using multiwall carbon nanotubes in aqueous solution

The present study evaluates the performance of multiwalled carbon nanotubes (MWCNTs) for removing Reactive Red Dye 198 (RR198) from the color wastewater. In this study, the influence of pH, adsorbent dose, initial dye concentration, and contact time on the RR198 adsorption by MWCNTs was investigated. The results showed increasing the dye concentration from 20 to 200mg/L, removal efficiency decreased from 99.62% to 66.99%. Moreover, by increasing the pH from 3 to 10, the efficiency of dye removal decreased from 76.34% to 54.98%. Freundlich isotherm and pseudo-second-order kinetic model were the best models for describing the adsorption reactions.

Microstructure and Performance of Multiwalled Carbon Nanotube/m-Aramid Composite Films as Electric Heating Elements

We report microstructure of thermomechanically stable multiwalled carbon nanotube (MWCNT)/poly(m-phenylene isophthalamide) (m-aramid) composite films containing 0.0-10.0 wt % MWCNTs and their performance as electric heating elements. FE-SEM images show that the MWCNTs are well dispersed in the composite films and are wrapped with m-aramid chains and that the interfacial thickness of m-aramid wrapped MWCNTs decreases with the MWCNT content. The electrical resistivity of films varies from ∼10(13) Ω cm for the neat m-aramid to ∼10(0) Ω cm of the film with 10.0 wt % MWCNT owing to the formation of a conductive three-dimensional network of MWCNTs. Accordingly, the performance of MWCNT/m-aramid films as electric heating elements is strongly dependent on MWCNT content as well as applied voltage. For the composite film with 10.0 wt % MWCNT, a maximum temperature of ∼176 °C is attained even at a low applied voltage of 10 V. The excellent performance such as rapid temperature response and high electric power efficiency at given applied voltages is found to be related with the microstructural features of the MWCNT/m-aramid films.

Alkaline lipase from Pseudomonas fluorescens non-covalently immobilised on pristine versus oxidised multi-wall carbon nanotubes as efficient and recyclable catalytic systems in the synthesis of Solketal esters

In order to produce effective and recyclable catalysts for enantioselective transesterification in the industrial applications, alkaline lipase from Pseudomonas fluorescens was non-covalently immobilised (ca. 6wt%) on pristine multi-wall carbon nanotubes (MWCNTs) and oxidised MWCNTs (O-MWCNTs) using an adsorption technique. Mesoporous silica modified with n-octyl groups was used as a reference support. Irreversible transesterifications of three vinyl esters (acyl donors) by racemic Solketal with a chromatographically (GC) traced kinetics were selected as model reactions. The undertaken comparative studies revealed that different morphology and chemical functionalisation of the supports led to various enzyme loadings, catalytic activities and enantioselectivities. MWCNT–lipase emerged as the exceptionally active (yield up to 98%, t=1h, 1320Ug−1, i.e. 9 times more active than native enzyme) whereas lipase immobilised on O-MWCNTs as the most enantioselective system, particularly for longer acyl chain esters (e.e. up to 72% after 30min at yield of 20%, 340Ug−1). Moreover, the activity of all nanotube-based catalysts after 10 cycles of transesterification remained practically unchanged. The differences in performance of MWCNTs and O-MWCNTs as solid supports were found to be based on geometry of pores, dominating hydrophobic interactions and absence/presence of the surface polar groups. Due to an excellent activity and reusability of the nanotube–lipase catalysts one can propose (O-)MWCNT as supports of a prospective industrial relevance.

Enhanced electrochemical detection performance of multiwall carbon nanotubes functionalized by aspartame

Inexpensive, non-toxic, and biocompatible materials that can disperse multiwall carbon nanotubes (MWCNTs) in aqueous solutions through a non-covalent approach while retaining their unique electronic and photonic properties are highly preferred. In this article, we introduce the use of an amphiphilic dipeptide derivative, aspartame, as an effective dispersing agent in preparing highly stable suspensions under ultrasonication. The results demonstrate that aspartame was absorbed by the nanotube surface possibly because of non-covalent π–π stacking between the aromatic group of aspartame and the CNT backbone. In addition, the resulting MWCNT/aspartame composites remained stably dispersed over a wide range of pH values. The chronoamperometric measurements of MWCNT/aspartame composite-coated electrodes for hydrogen peroxide demonstrated better electrochemical detection performance, as characterized by significantly enhanced step current, higher sensitivity, and reduced potential compared with bare electrodes.

Enhanced electrochemical performance of multi-walled carbon nanotubes modified Li2FeSiO4/C cathode material for lithium-ion batteries

The multi-walled carbon nanotubes (MWCNTs) modified Li2FeSiO4/C composite is synthesized via a citric acid-based sol–gel method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, galvanostatic charge/discharge measurements, cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) tests. The Li+ diffusion coefficient in Li2FeSiO4/C/MWCNTs is larger than that in Li2FeSiO4/C. Compared with Li2FeSiO4/C, Li2FeSiO4/C/MWCNTs electrode can extract more than 1mol Li+ and exhibit better electrochemical performance with a high discharge capacity of 206.8mAhg−1 in the second cycle, especially, an excellent high-rate capacity and cycle stability. The enhanced electrochemical performance is attributed to the reduced particle size and the high conducting network between the MWCNTs and the Li2FeSiO4/C particles.

Thermal performance of multi-walled carbon nanotubes (MWCNTs) in aqueous suspensions with surfactants SDBS and SDS

The surfactants of sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS) are used in multi-walled carbon nanotubes (MWCNT) aqueous solution respectively due to the hydrophobic nature of MWCNT. Thermal conductivities of nanofluid solutions are measured via the LAMBDA measuring system by transient hot wire method and compared as function of dispersing two different surfactants. MWCNT (hereinafter sometime referred to as CNTs) nanofluid gets a good dispersion and long time stability with both surfactants within 3/1 relative ratio mixture. However, the thermal conductivity of nanofluid decreases with increasing the concentration of both surfactants, and CNT nanofluid with SDBS exhibits better thermal conductivity than that with SDS dispersant. Finally the proper mixture ratio of CNT nanofluid with SDBS and pH value is examined and results show that 0.5wt.% CNT nanofluids with 0.25wt.% SDBS, at pH≈9.0 condition display the best thermal performance which increases by 2.8% totally on thermal conductivity compared with that of base fluid distilled water (DW).

Decoration of Magnetic Nanoparticles on Functionalized Multi-Wall Carbon Nanotubes by<i> In Situ </i>Method

To increase the magnetic performance of multi-wall carbon nanotubes (MWCNTs)/Fe3O4 nanocomposites, Fe3O4-polymer-MWCNTs with a novel nanostructure was prepared by in-situ method. The low molecular weight poly (acrylic acid) was grafted on the surface of acid-oxidized MWCNTs, forming numerous carboxyl groups from the original hydroxyl groups on the surface of acid-treated MWCNTs. And then, the ferric and ferrous ions would be adsorbed on the surface of PAA-g-MWCNTs through the electrostatic interaction. At last, the ammonia solution was added into the above solution to form Fe3O4 nanoparticles on the surface of MWCNTs through hydrothermal treatment. The experimental results showed that large quantities of Fe3O4 nanoparticles were coated on the surface of PAA-g-MWCNTs via in-situ method and our products possessed high magnetic saturation and magnetic sensitivity.

Grafting 3-mercaptopropyl trimethoxysilane on multi-walled carbon nanotubes surface for improving on-line cadmium(II) preconcentration from water samples

In the present study, the performance of multi-walled carbon nanotubes (MWCNTs) grafted with 3-mercaptopropyltrimethoxysilane (3-MPTMS), used as a solid phase extractor for Cd2+ preconcentration in a flow injection system coupled to flame atomic absorption spectrometry (FAAS), was evaluated. The procedure involved the preconcentration of 20.0mL of Cd2+ solution at pH 7.5 (0.1molL−1 buffer phosphate) through 70mg of 3-MPTMS-grafted MWCNTs packed into a minicolumn at 6.0mLmin−1. The elution step was carried out with 1.0molL−1 HCl. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to estimate the extent of the MWCNT chemical modification. The 3-MPTMS-grafted MWCNTs provided a 1.68 times improvement in the sensitivity of the Cd2+ FAAS determination compared to the unsilanized oxidized MWCNTs. The following parameters were obtained: preconcentration factor of 31.5, consumptive index of 0.635mL, sample throughput of 14h−1, and concentration efficiency of 9.46min−1. The analytical curve was constructed in the range of 1.0–60.0μgL−1 (r=0.9988), and the detection and quantification limits were found to be 0.15μgL−1 and 0.62μgL−1, respectively. Different types of water samples and cigarette sample were successfully analyzed, and the results were compared using electrothermal atomic absorption spectrometry (ETAAS) as reference technique. In addition, the accuracy of proposed method was also checked by analysis of certified reference material NIST SRM 1573a (tomato leaves) and standard reference material NIST SRM 1643e (trace elements in natural waters).

Influence of the different oxidation treatment on the performance of multi-walled carbon nanotubes in the catalytic wet air oxidation of phenol

Multi-walled carbon nanotubes (MWCNTs) functionalized by different oxidants (HNO3/H2SO4, H2O2, O3 and air) have been used as catalysts for the wet air oxidation of phenol. To investigate the effect of the oxidation conditions on the structure of the functionalized MWCNTs, various characterization techniques, e.g., scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) have been used. The MWCNTs treated with O3 and H2O2 show higher amounts of oxygen-containing functional groups and carboxylic acid groups, and a weaker acidic nature, in comparison with those treated with other oxidizing agents. All the functionalized MWCNTs exhibit good activity in the catalytic wet air oxidation (CWAO) of phenol. However, the MWCNTs treated with O3 show the highest activity with desirable stability in comparison with other functionalized MWCNTs, indicating that the functionalization of carbon nanotubes with O3 is a very promising strategy in synthesizing efficient catalysts for CWAO.