Addition Of MWCNT Research Articles

Vitamin C functionalized multi-walled carbon nanotubes and its reinforcement on poly(ester-imide) nanocomposites containing L-isoleucine amino acid moiety

The aim of this research was to prepare poly(ester–imide) (PEI)-based nanocomposites (NCs) through the functionalization of carboxylated-multiwalled carbon nanotubes (MWCNT)s with ascorbic acid, in order to ensure better filler dispersion and good interfacial adhesion between filler and matrix. Chiral and biodegradable PEI was synthesized from amino acid-based diacid with 4,4′-thiobis(2-tert-butyl-5-methylphenol) by a direct polycondensation method. Using the solution mixing technique, the NCs containing modified MWCNTs with different loading levels of 5,10, 15 wt% were produced and examined in terms of chemical structure, morphology, and thermal stability by FT-IR spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). TEM and FE-SEM photographs of the obtained NCs indicated well-dispersed morphologies and strong interaction between the functionalized MWCNTs and the polymer matrix. TGA results revealed that the addition of MWCNT resulted in a significant increase of the thermal stability and char yields of the NCs compared to those of the neat PEI.

Enhanced photocatalytic activity of MWCNT/TiO2 heterojunction photocatalysts obtained by microwave assisted synthesis

Herein reported are the synthesis and the photocatalytic activity of MWCNT/TiO2 heterojunction photocatalysts obtained by microwave-assisted method using titanium butoxide as precursor. The obtained materials were characterized by XRD, Raman, SEM, TEM, UV–vis, FTIR, surface area (BET) and photoluminescence. The characterization results showed that the addition of MWCNT did not provide structural changes on TiO2. The photocatalytic activities of the synthesized materials were investigated using acid blue 9 dye as a model molecule. The results indicate an enhancement on photocatalytic activity by the addition of low amount of MWCNT (1 and 3wt%). The improvement is attained to the synergic effect between TiO2 and MWCNT which reduces the electron–hole pair recombination according with the photoluminescence study. In this way, a proposed schema for the enhanced photoactivity of the MWCNT/TiO2 heterojunction photocatalyst is discussed.

Effect of MWCNT addition on improving the electrical conductivity and activation energy of electrospun nylon films

Nylon 6/with (0, 0.1, 0.2, 0.4, 0.6 and 0.8) wt. % MWCNTs films conductive polymers were prepared by electrospinning technique. Prepared films morphology test by SEM and the average fibers diameters measure statically was 140 nm for (nylon/0.4 wt. % MWCNTs film). The nanofibers films show enhancing the electrical conductivity by increase MWCNTs concentration, from (2.9 × 10−9 S/cm) for pure nylon film to (1.042 × 10−6 S/cm) for 0.8 wt. % MWCNT. The activation energy decreased with increasing the MWCNTs concentration, the activation energy was (0.068, 0.057, 0.0536, 0.0523, and 0.045 and 0.077) eV for (pure nylon, nylon/0.1, 0.2, 0.4, 0.6, 0.8% wt. % MWCNTs) films. The calculated result of 0.077 eV is even higher than the activation energy of the pure film which is 0.068 eV, this is may be due to changing the state of MWCNTs dispersion in the host polymer (nylon 6) as concentration of MWCNTs increased.

Enhanced rate performance of multiwalled carbon nanotube encrusted olivine type composite cathode material using polyol technique

Olivine type multi-walled carbon nanotube encrusted LiFePO4/C composites have been prepared using economic and energy efficient simple polyol technique without any subsequent heat treatment. The prepared material has an olivine type orthorhombic phase. Also, the iron oxidation state is 2+, which is identified by X-ray diffraction and X-ray photoelectron spectroscopy. It is possible to attain the discharge capacity almost close to theoretical capacity of LiFePO4 as in high temperature methods with ∼100% coulombic efficiency. The specific surface area has been increased upon encrusting multi walled carbon nano tube on LiFePO4/C, which results in enhanced reversible capacity upto 166 mAh g−1 at C/10. Also, it exhibits 89 mAh g−1 even at 30 C rate. This is due to the formation of conductive networks by carbon nanotube, and excellent attachment of LiFePO4/C composite particles on multi-walled carbon nanotube, which induced the kinetics during intercalation/deintercalation process. Multi-walled carbon nanotube acts as the electro-conductive filler on the LiFePO4 surface. The direct addition of MWCNT would result better performances than blending the MWCNT with LiFePO4/C.

Effect of Carbon Nanotubes on Thermoelectric Properties in Zn0.98Al0.02O

Thermoelectric oxides can provide the advantage of high-temperature stability in oxygen-containing atmospheres. It is known that the incorporation of multiwalled carbon nanotubes (mw-CNT) can change the thermoelectric as well as the structural properties of oxides. Here, we report the influence of mw-CNT on the thermoelectric properties of Al-doped ZnO (AZO). The preparation of the mw-CNT-added AZO was done using an ultrasonic mixing of the starting materials followed by a spark plasma sintering process under vacuum. The Seebeck coefficient S, thermal conductivity λ and electrical conductivity σ were determined in the temperature range between 300 K and 900 K. It was observed that the thermal conductivity is significantly reduced by the incorporation of the mw-CNT. At the same time, the electrical conductivity is increased by a factor of 21 from 8700 S/m to 190,000 S/m. The Power factor \({\rm PF} = S^{2} \sigma\) indicates that the addition of mw-CNT improves the thermoelectric properties of Al doped ZnO in comparison to the reference sample prepared with same process but without mw-CNT.

In vitro toxic effects of different types of carbon nanotubes

We have carried out a comparative assessment of industrial single- and multiwalled carbon nanotubes (SWCNTs / MWCNTs) toxic effects in the cultures of macrophages (RAW 264.7) and bronchial epithelial cells (BEAS-2B). Lactate dehydrogenase (LDH) levels were measured directly in the medium. Intracellular reduced glutathione levels (GSH) were determined in culture lysates. Cell viability was determined by fluorescence method. RAW 264.7 were much more sensitive to the effects of carbon nanotubes (CNTs): MWCNT addition was not accompanied by a significant reduction in the viability of macrophages, but caused damage to cell membranes (release of LDH) with a dose and time-dependent oxidative stress. SWCNTs caused a significant decrease in viability and induction of oxidative stress. Improved darkfield microscopy revealed adsorption and accumulation of MWCNTs on the surface and inside the macrophages. Adding SWCNTs to BEAS-2B culture caused small statistically significant dose-and time-dependent decrease in viability and pronounced reduction in glutathione only at the highest concentration of nanoparticles. Bronchial epithelial cells BEAS- 2B appeared to be much less susceptible to MWCNTs. The findings suggest that there are differences in the toxic action of different CNTs and there is a need for thoughtful approach to the assessment of nanomaterials toxicity.

Measurement of properties and performance prediction of the new MWCNT-embedded zeolite 13X/CaCl2 composite adsorbents

In this study, MWCNT embedded zeolite 13X/CaCl2 composite adsorbents with different MWCNT mass ratios were synthesized for use in adsorption cooling systems. XRF, XPS, BET, TGA and thermal conductivity tests were conducted and the properties of the composite adsorbents are presented. The MWCNT embedded composite adsorbent prepared with the highest MWCNT mass ratio, 100:1, has the highest carbon concentration, 12.91wt%. The addition of MWCNT in the composite adsorbent can increase the overall specific surface area and total pore volume of the adsorbent. The useful range of water adsorption of composite adsorbents is much higher than for zeolite 13X. The operational range of water uptake for zeolite 13X is 0.09kg/kg and that of the composite adsorbents is 0.5kg/kg. It is possible that the composite adsorbents can perform 5 times better than zeolite 13X. The effective thermal conductivity is improved significantly, and reached 0.27–0.8W/mK in the temperature range of 30–70°C, where the thermal conductivity of zeolite 13X is only 0.08–0.13W/mK in the same temperature range. The addition of MWCNT does not have noticeable drawbacks on adsorption capacity and can improve the effective thermal conductivity of the composite adsorbent.A FEM simulation model of an adsorber was built to predict the performance of different adsorbents, namely zeolite 13X, zeolite 13X/CaCl2 composite adsorbent and MWCNT embedded 13X/CaCl2 adsorbent (CNT-CA-1). Under the same operation conditions, in which the evaporation pressure is 872.5Pa, condensation pressure is 4247Pa, heating water temperature is 80°C and cooling water temperature is 30°C, the CNT-CA-1 performs much better than zeolite 13X and the zeolite 13X/CaCl2 composite adsorbent. The SCP of the adsorber using CNT-CA-1 is improved by 6.5 times to 1113.4W/kg compared to zeolite 13X. The total cooling power is significantly enhanced by 13.4 times to 1783.2W. By comparing the adsorber performance using CNT-CA-1 against that using zeolite 13X/CaCl2, simply adding the MWCNT can improve the COP and SCP by more than 20%.

Hybrid Nanocomposite Material for EMI Shielding in Spacecrafts

In this study lightweight carbon fiber and multiwalled carbon nanotubes filled hybrid nanocomposite was fabricated for electromagnetic interference (EMI) shielding in spacecraft. Electrical conductivity was conducted to assess the affect of MWCNT addition on composite. EMI shielding effectiveness (SE) was tested in the frequency range of 1-18 GHz. Comparison of SE was also made with AA6061-T6 sheet. Dispersion of nanotubes in the matrix was examined through microscopy. Results indicated that the conductivity was increased with increasing MWCNTs up to 0.25 wt%. Higher loading level of MWCNTs has resulted in decrease in conductivity due to agglomeration in cured samples. Hybrid nanocomposite exhibited improved SE than AA6061-T6 in 1-8 GHz frequency range. Best SE and electrical conductivity was witnessed in 0.25 wt% MWCNT sample. EMI SE in range of-20 dB to-40 dB can be easily achieved in our developed material.

Carbon nanotubes and carbon onions for modification of styrene–acrylate copolymer nanocomposites

Styrene acrylate polymer (SAC) nanocomposites with various carbon nanofillers (multi‐walled carbon nanotubes, MWCNT, and onion like carbons, OLCs, annealed at two different temperatures) are manufactured by means of latex based and combined routes. Concentration of the carbon nanofillers is changed in a broad interval starting from 0.01 up to 10 wt%. Elastic, dielectric, and electromagnetic interference (EMI) shielding efficiency of SAC nanocomposites are investigated. Dynamic elastic modulus, electrical conductivity, and EMI shielding efficiency of the investigated SAC nanocomposites increase along with rising nanofiller content. The effect of the addition of anisodiametric MWCNT on the elastic properties as well as EMI shielding characteristics of the SAC nanocomposites is higher than in the case of the addition of OLCs. Modification effectiveness of the polymer matrix in respects to elastic and EMI shielding performance provided by the OLC, annealed at higher temperature, is greater in comparison with the OLC, annealed at lower temperature, generally because of more perfect structure of the first. POLYM. COMPOS., 36:1048–1054, 2015. © 2015 Society of Plastics Engineers

CNT and PDCs: A fruitful association? Study of a polycarbosilane–MWCNT composite

The effect of MWCNT introduction in a polycarbosilane based ceramic on its electrical properties is presented. The electrical conductivity of two MWCNT powders was measured under dynamic compaction up to 20MPa when it reached 3–5S/cm. The compaction behavior was also analyzed and modeled. A composite was then realized using allylhydridopolycarbosilane SMP10® and divinylbenzene as matrix. Intact 10mm MWCNT-SiC ceramic discs samples with 2wt.% filler load were produced pressure-less via liquid route despite the linear shrinkage of about 30%. Nanotubes microstructure and distribution in the matrix were confirmed after pyrolysis with TEM and SEM analysis. Anyhow similar electrical conductivity values after pyrolysis between the loaded and unloaded samples were measured. The microstructure analysis via XRD and TEM revealed that the percolative carbon network formed through the use of divinylbenzene improves the electric conductivity more than that of MWCNT addition and also simplifies the whole process.

Construction of novel xanthine biosensor by using polymeric mediator/MWCNT nanocomposite layer for fish freshness detection

A novel nanocomposite host matrix for enzyme immobilization of xanthine oxidase was developed by incorporating MWCNT in poly(GMA-co-VFc) copolymer film. In the food industry fish is a product with a very low commercial life, and a high variability as well elevated level of xanthine is an important biomarker as a sign of spoilage. The fabricated process was characterized by scanning electron microscopy (SEM), and the electrochemical behaviors of the biosensor were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The prepared enzyme electrodes exhibited maximum response at pH 7.0 and 45°C +0.35V and reached 95% of steady-state current in about ∼4s and its sensitivity was 16mAM−1. Linear ranges (2–28μM, 28–46 and 46–86μM), analytical performance and a low detection limit 0.12μM obtained from the xanthine biosensor gives reliable results in measuring xanthine concentration in the fish meat. All the results indicating that the resulting biosensor exhibited a good response to xanthine that was related to the addition of MWCNT in the polymeric mediator film which played an important role in the biosensor performance. In addition, the biosensor exhibited high good storage stability and satisfactory anti-interference ability.

Effect of MWCNT functionalization on thermal and electrical properties of PHBV/MWCNT nanocomposites

Abstract

Effect of field cooling heights on the levitation force of pure and starch/polystyrene/MWCNT added bulk MgB2 superconductors

A series of MgB2 pellets with and without addition of carbon from different sources (viz. starch, polystyrene and carbon nanotubes) have been synthesized by solid state reaction under argon atmosphere. XRD analysis indicates a decrease in lattice parameters of MgB2 with addition of starch, polystyrene (PS) and MWCNT and confirms substitution of carbon in boron sites. The presence of nanosized carbon inclusions between the grain boundaries in the present set of samples is evident in TEM photographs. Resistivity data confirms a decrease in superconducting transition temperature (Tc0) for MgB2 doped with starch/PS/MWCNT. The effect of different field cooling heights (HIFC) at 20K on maximum levitation force (FMLF) and maximum attractive force (FMAF) of pure MgB2 and MgB2 doped with starch/PS/MWCNT have been investigated. Except for MWCNT, doping of starch and PS in MgB2 is found to improve FMLF and FMAF and the best result is obtained for MgB2 doped with 1wt.% PS. Levitation force measured as a function of decreasing initial field cooling height indicates exponential dependence of both maximum levitation force (FMLF) and maximum attractive force (FMAF). However, the gap distance between PM and the sample (H0AF and HMAF) corresponding to maximum attractive force (FMAF) and zero attractive force (F0AF) varies linearly and their difference remains constant. This constancy in (HMAF−H0AF) is understood in terms of constant reduction rate of magnetic flux density between H0AF and HMAF.

Visible light photocatalytic degradation of cyanide using Au–TiO2/multi-walled carbon nanotube nanocomposites

Au–TiO2 nanocatalyst-supported multi-walled carbon nanotubes were effectively prepared by the sol–gel modified technique. The Au–TiO2/MWCNT nanocomposite was used to remove cyanide by photocatalytic oxidation under visible light irradiation. The Au–TiO2/MWCNT nanocomposite photocatalyst was characterized by XRD, TEM, UV–vis, and BET techniques. Results revealed the nanoparticles TiO2 and Au were well dispersed into MWCNT. Addition of Au and MWCNT can eliminate recombination pairs of electron holes in the Au–TiO2/MWCNT nanocomposite. Also, the presence of the MWCNT in the Au–TiO2/MWCNT nanocomposite transfers absorption of TiO2 from the UV region to visible region of the spectrum. The optimum weight ratio of MWCNTs:TiO2:Au was 0.06:1.0:0.10, which resulted in experimental performance photocatalyst oxidation of about 100% of the cyanide in a solution of 100mg/L over 40min, with 1.2g/L of catalyst used.

Influence of different β-nucleating agent on crystallization behavior, morphology, and melting characteristic of multiwalled carbon nanotube-filled isotactic polypropylene nanocomposites

To obtain isotactic polypropylene (iPP) nanocomposites with high β-crystal content, TMB5, calcium pimelate and calcium pimelate supported on the surface of nano-CaCO3 were used as β-nucleating agent and MWCNT filled β-nucleated iPP nanocomposites were prepared. The effect of different β-nucleating agent and MWCNT on the crystallization behavior and morphology, melting characteristic and β-crystal content of β-nucleated iPP nanocomposites were investigated by DSC, XRD and POM. The results indicated that addition of MWCNT increased the crystallization temperature of iPP and MWCNT filled iPP nanocomposites mainly formed α-crystal. The β-nucleating agent can induce the formation of β-crystal in MWCNT filled iPP nanocomposites. The β-nucleating ability and β-crystal content in MWCNT filled β-nucleated iPP nanocomposites decreased with increasing MWCNT content and increased with increasing β-nucleating agent content due to the nucleation competition between MWCNT and β-nucleating agents. It is found that the calcium pimelate supported on the surface of inorganic particles as β-nucleating agent has stronger heterogeneous β-nucleation than calcium pimelate and TMB5. The MWCNT filled iPP nanocomposites with high β-crystal content can be obtained by supported β-nucleating agent. POLYM. COMPOS., 36:635–643, 2015. © 2014 Society of Plastics Engineers

Optoelectronic properties of solution synthesis of carbon nanotube/ZnO:Al:N nanocomposite and its potential as a photocatalyst

A novel multiwalled carbon nanotubes/aluminum–nitrogen co-doped ZnO (MWCNT/ZnO:Al:N) nanocomposite film was synthesized by a sol–gel deposition method and used for the photodegradation of organic dye under UV light illumination. The MWCNT/ZnO:Al:N composite film was extensively characterized through scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence measurements (PL) and UV–vis spectroscopy. Photocatalytic measurements reveal that the addition of MWCNT enhances photocatalytic degradation of MB by providing conduction path for electron transfer and reactive oxygen groups.

Transition in micro/nano-scale mechanical properties of ZrO<sub>2</sub>/multi-wall carbon nanotube composites

ZrO2/multi-wall carbon nanotube (MWCNT) composites were consolidated using a spark plasma sintering technique. Micro- and nano-scale mechanical properties of sintered composites with various MWCNT contents were investigated using X-ray diffraction and instrumented indentation techniques. Transitional behavior in the hardness and elastic modulus of the composites was observed and attributed to the contrasting effects of the MWCNT addition; i.e., beneficial effects such as inhibition of crystal growth and phase transition and detrimental effects due to the agglomerated MWCNTs.

Effect of modified filler surfaces and filler-tethered polymer chains on morphology and physical properties of poly(azo-pyridyl-urethane)/multi-walled carbon nanotube nanocomposites

Poly(azo-pyridyl-urethane)/multi-walled carbon nanotube (PAPU/MWCNT) nanocomposites were prepared by first synthesizing polyurethane followed by solution dispersing MWCNT in the matrix. We have used two different MWCNTs: the first set of MWCNT contained carboxylic acid group (MWCNT-COOH) and the second set contained acid chloride group (MWCNT-COCl). Afterward, these MWCNT particles were used in the preparation of PAPU/MWCNT nanocomposites. In the first set of nanocomposites, MWCNT-COOH and PAPU were just physically mixed and were designated as PAPU/MWCNT-A. In the second set of nanocomposites, PAPU chains were tethered onto the surfaces of MWCNT-COCl particles and designated as PAPU/MWCNT-AC. Two types of nanocomposites were thus fabricated, including acid functionalized nanotube-based non-tethered PAPU/MWCNT and acid chloride functionalized MWCNT-based tethered system. We have incorporated hydroxyl end-terminated polyurethane via “ grafting to” approach to acid chloride functional MWCNT through esterification. Fourier transform infrared spectra confirmed that the matrix was covalently attached to sidewalls of nanotube. Various nanotube loading levels and surface-modified groups were considered to regulate mechanical, thermal and electrical performance of PAPU/MWCNT. The experimental results showed that a moderate loading level of 5 wt. % MWCNT produced the maximum tensile strength (63.1 MPa) in tethered nanocomposites, while the presence of surface carboxylation of MWCNT relatively decreased the tensile strength (49.7 MPa). Comparative studies based on scanning and transmission electron microscopy of the chemically bonded samples revealed unique nano-fibriller morphology. Dynamic mechanical analysis of nanocomposite films showed an increased segmental rigidity with Tg of 144–153℃ in the tethered system relative to pristine PAPU (133℃). Addition of acid chloride functional MWCNT also contributed to an enhancement in the conductivity (2.9–4.7 S cm−1), relative to PAPU/carboxylated MWCNT (2.0–2.7 S cm−1).

Facile scalable synthesis of Co3O4/carbon nanotube hybrids as superior anode materials for lithium-ion batteries

In this report, Co3O4/multiple-wall carbon nanotube (MWCNT) hybrid materials were synthesized via strong ultrasonication-assisted shaking and magnetic stirring processes. The prepared samples were well characterized by utilizing powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy techniques. Results indicated that the resulting Co3O4 nanoparticles were highly dispersed in the MWCNT network backbone and further form Co3O4/MWCNT hybrid materials. The obtained Co3O4/MWCNT hybrids can be employed as anode electrode in Lithium-ion batteries and deliver as high as discharge capacity of 1250mAhg−1 at a current density of 0.2C, additionally, 81% of the discharge capacity for sample 2 with 20wt.% MWCNT loading could be retained after 70 cycles, which could be associated with the specific hybrid structure of the electrode as well as the addition of MWCNT. Most importantly, the present synthetic approach is facile, controllable, and scalable, which allowing it more easily adapted to prepare other hybrid materials with specific architectures.

Enhancement of thermal and mechanical properties of flexible graphene oxide/carbon nanotube hybrid films though direct covalent bonding

The thermal conductivity and mechanical properties of graphene oxide/multiwalled carbon nanotube (GO/MWCNT) hybrid films with and without covalent bonding were examined. Chlorinated GO and amino-functionalized MWCNT were bonded covalently to fabricate chemically bonded GO/MWCNT hybrid films. Mixtures of surface-modified GO and MWCNT were filtered and then subjected to hot-pressing to fabricate stacked films. Examination of these chemically bonded hybrid films revealed higher thermal conductivity than in physically bonded hybrid films, because of the synergetic interaction of functional groups in GO and MWCNT in the films. However, the addition of excess MWCNT to the films led to an increased phonon scattering density and a decreased thermal conductivity. The hybrid films fabricated by the optimized process endured about 20000 bending cycles without rupturing or losing their thermal conductivity. The mechanical properties showed enhanced performance after increased MWCNT loading at elevated temperature due to the reinforcement effect of the MWCNT between GO layers.