Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Selected Abstracts

Poly(pyridine-3-boronic acid)/Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrodes for Simultaneous Determination of Ascorbic Acid, 3,4-Dihydroxyphenylacetic Acid and Uric Acid

Zhijiao Wu
Abstract Poly(pyridine-3-boronic acid) (PPBA)/multiwalled carbon nanotubes (MWCNTs) composite modified glassy carbon electrode (GCE) was used for the simultaneous determination of ascorbic acid (AA), 3,4-dihydroxyphenylacetic acid (DOPAC) and uric acid (UA). The anodic peaks for AA, DOPAC and UA at the PPBA/MWCNTs/GCE were well resolved in phosphate buffer solution (pH,7.4). The electrooxidation of AA, DOPAC and UA in the mixture solution was investigated. The peak currents increase with their concentrations increasing. The detection limits (S/N=3) of AA, DOPAC and UA are 5,M, 3,M and 0.6,M, respectively. [source]

Heterogeneous Electron Transfer and Oxygen Reduction Reaction at Nanostructured Iron(II) Phthalocyanine and Its MWCNTs Nanocomposites

Abstract Electron transfer and oxygen reduction dynamics at nanostructured iron(II) phthalocyanine/multi-walled carbon nanotubes composite supported on an edge plane pyrolytic graphite electrode (EPPGE-MWCNT-nanoFePc) platform have been reported. All the electrodes showed the category 3 diffusional behaviour according to the Davies,Compton theoretical framework. Both MWCNTs and MWCNT-nanoFePc showed huge current responses compared to the other electrodes, suggesting the redox processes of trapped redox species within the porous layers of MWCNTs. Electron transfer process is much easier at the EPPGE-MWCNT and EPPGE-MWCNT-nanoFePc compared to the other electrodes. The best response for oxygen reduction reaction was at the EPPGE-MWCNT-nanoFePc, yielding a 4-electron process. [source]

Simultaneous Determination of Trace Zinc(II) and Cadmium(II) by Differential Pulse Anodic Stripping Voltammetry Using a MWCNTs,NaDBS Modified Stannum Film Electrode

Qing Tian
Abstract A multiwalled carbon nanotubes,sodium dodecyl benzene sulfonate (MWCNTs,NaDBS) modified stannum film electrode was employed for the determination of cadmium(II) and zinc(II). The Sn/MWCNTs-NaDBS film electrode was prepared by applying MWCNTs,NaDBS suspension to the surface of the GCE, while the Sn film was plated in situ simultaneously with the target metal ions. Under optimal conditions, linear calibration curves were obtained in a range of 5.0 ,100.0,,g L,1 with detection limits of 0.9,,g L,1 for zinc(II) and 0.8,,g L,1 for cadmium(II), respectively. This film electrode was successfully applied to the determination of Zn(II) and Cd(II) in tap water sample. [source]

Electroanalysis of Bisphenol A at a Multiwalled Carbon Nanotubes-gold Nanoparticles Modified Glassy Carbon Electrode

Xinman Tu
Abstract A sensitive electrochemical method was developed for the determination of bisphenol A (BPA) at a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (MWCNTs)-gold nanoparticles (GNPs) hybrid film, which was prepared based on the electrostatic interaction between positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged MWCNTs and GNPs. The MWCNT-GNPs/GCE exhibited an enhanced electroactivity for BPA oxidation versus unmodified GCE and MWCNTs/GCE. The experimental parameters, including the amounts of modified MWCNTs and GNPs, the pH of the supporting electrolyte, scan rate and accumulation time, were examined and optimized. Under the optimal conditions, the differential pulse voltammetric anodic peak current of BPA was linear with the BPA concentration from 2.010,8 to 210,5 mol L,1, with a limit of detection of 7.5,nmol L,1. The proposed procedure was applied to determine BPA leached from real plastic samples with satisfactory results. [source]

Multiwalled Carbon Nanotubes Encased in Ruthenium Oxide Film as a Hybrid Material for Neurotransmitters Sensor

Chien-Chieh Ti
Abstract A hybrid film (MWCNTs-RuOx,nH2O) which contains multiwalled carbon nanotubes (MWCNTs) along with the incorporation of ruthenium oxide (RuOx,nH2O) has been synthesized on glassy carbon electrode (GCE), gold (Au), indium tin oxide (ITO) and screen printed carbon electrode (SPCE) by potentiostatic methods. The presence of MWCNTs in the hybrid film enhances surface coverage concentration (,) of RuOx,nH2O to ,2100%. The surface morphology of the hybrid film deposited on ITO has been studied using scanning electron microscopy and atomic force microscopy. These two techniques reveal that the RuOx,nH2O incorporated on MWCNTs. Electrochemical quartz crystal microbalance study too reveals the incorporation of MWCNTs and RuOx,nH2O. The MWCNTs-RuOx,nH2O hybrid film exhibits promising enhanced electrocatalytic activity towards the biochemical compounds such as epinephrine and norepinephrine. The electrocatalytic responses of these analytes at RuOx,nH2O, MWCNTs and MWCNTs-RuOx,nH2O hybrid films have been measured using cyclic voltammetry. The obtained sensitivity values from electrocatalysis studies of analytes for MWCNTs-RuOx,nH2O hybrid film are higher than the RuOx,nH2O and MWCNTs films. Finally, the flow injection analysis has been used for the amperometric studies of analytes at MWCNTs-RuOx,nH2O hybrid film modified SPCEs. [source]

Adsorptive Stripping Voltammetric Detection of Tea Polyphenols at Multiwalled Carbon Nanotubes-Chitosan Composite Electrode

Deyin Guo
Abstract This study reports the catalytic oxidation and detection of tea polyphenols (TPs) at glassy-carbon electrode modified with multiwalled carbon nanotubes-chitosan (MWCNTs-CS) film. The adsorption of TPs at the surface of the MWCNTs through ,,, conjugation prevents the aggregation of nanotubes and induces a stable MWCNTs suspension in water over 30 days. Based on the adsorptive accumulation of polyphenols at MWCNTs, TPs is sensitively and selectively detected by adsorptive stripping voltammetry. The accumulation conditions and pH effect on the adsorptive stripping detection were examined. The linear range was found to be 100 to 1000,mg L,1 with a detection limit of 10,mg L,1 (S/N=3) for 2.5,min accumulation. Additionally, the MWCNTs-CS electrode is easily renewed by applying positive potential to remove the adsorbed TPs. This method was successfully applied to determine TPs in commercially available teas with satisfied result compared with that of conventional spectrometric analysis. [source]

Improved Voltammetric Response of L -Tyrosine on Multiwalled Carbon Nanotubes-Ionic Liquid Composite Coated Glassy Electrodes in the Presence of Cupric Ion

Liqin Liu
Abstract L -Tyrosine can exhibit a small anodic peak on multiwalled carbon nanotubes (MWCNTs) coated glassy carbon electrodes (GCE). At pH,5.5 its peak potential is 0.70,V (vs. SCE). When an ionic liquid (i.e., 1-octyl-3-methylimidazolium hexafluorophosphate, [omim][PF6]) is introduced on the MWCNT coat, the peak becomes bigger. Furthermore, in the presence of Cu2+ ion the anodic peak of L -tyrosine increases further due to the formation of Cu2+ - L -tyrosine complex, while the peak potential keeps unchanged. Therefore, a sensitive voltammetry based on the oxidation of Cu2+ - L -tyrosine complex on MWCNTs-[omim][PF6] composite coated electrode is developed for L -tyrosine. Under the optimized conditions, the anodic peak current is linear to L -tyrosine concentration in the range of 110,8,510,6 M, and the detection limit is 810,9 M. The modified electrode shows good reproducibility and stability. In addition, the voltammetric behavior of other amino acids is explored. It is found that among them tryptophan (Trp) and histidine (His) can also produce sensitive anodic peak under same experimental conditions, and their detection limits are 410,9 M and 410,6 M, respectively. [source]

Study on Glucose Biofuel Cells Using an Electrochemical Noise Device

Yueming Tan
Abstract An electrochemical noise (ECN) device was utilized for the first time to study and characterize a glucose/O2 membraneless biofuel cell (BFC) and a monopolar glucose BFC. In the glucose/O2 membraneless BFC, ferrocene (Fc) and glucose oxidase (GOD) were immobilized on a multiwalled carbon nanotubes (MWCNTs)/Au electrode with a gelatin film at the anode; and laccase (Lac) and an electron mediator, 2,2,-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS), were immobilized on a MWCNTs/Au electrode with polypyrrole at the cathode. This BFC was performed in a stirred acetate buffer solution (pH,5.0) containing 40,mmol/L glucose in air, with a maximum power density of 8,,W/cm2, an open-circuit cell voltage of 0.29,V, and a short-circuit current density of 85,,A/cm2, respectively. The cell current at the load of 100,k, retained 78.9% of the initial value after continuous discharging for 15,h in a stirred acetate buffer solution (pH,5.0) containing 40,mmol/L glucose in air. The performance decrease of the BFC resulted mainly from the leakage of the ABTS mediator immobilized at the cathode, as revealed by the two-channel quartz crystal microbalance technique. In addition, a monopolar glucose BFC was performed with the same anode as that in the glucose/O2 membraneless BFC in a stirred phosphate buffer solution (pH,7.0) containing 40,mmol/L glucose, and a carbon cathode in Nafion-membrane-isolated acidic KMnO4, with a maximum power density of 115,,W/cm2, an open-circuit cell voltage of 1.24,V, and a short-circuit current density of 202,,A/cm2, respectively, which are superior to those of the glucose/O2 membraneless BFC. A modification of the anode with MWCNTs for the monopolar glucose BFC increased the maximum power density by a factor of 1.8. The ECN device is highly recommended as a convenient, real-time and sensitive technique for BFC studies. [source]

Inlaid Multi-Walled Carbon Nanotube Nanoelectrode Arrays for Electroanalysis

Jun Li
Abstract The rapid development in nanomaterials and nanotechnologies has provided many new opportunities for electroanalysis. We review our recent results on the fabrication and electroanalytical applications of nanoelectrode arrays based on vertically aligned multi-walled carbon nanotubes (MWCNTs). A bottom-up approach is demonstrated, which is compatible with Si microfabrication processes. MWCNTs are encapsulated in SiO2 matrix leaving only the very end exposed to form inlaid nanoelectrode arrays. The electrical and electrochemical properties have been characterized, showing well-defined quasireversible nanoelectrode behavior. Ultrasensitive detection of small redox molecules in bulk solutions as well as immobilized at the MWCNT ends is demonstrated. A label-free affinity-based DNA sensor has shown extremely high sensitivity approaching that of fluorescence techniques. This platform can be integrated with microelectronics and microfluidics for fully automated microchips. [source]

Nanostructured pillars based on vertically aligned carbon nanotubes as the stationary phase in micro-CEC

Ren-Guei Wu
Abstract We present a micro-CEC chip carrying out a highly efficient separation of dsDNA fragments through vertically aligned multi-wall carbon nanotubes (MWCNTs) in a microchannel. The vertically aligned MWCNTs were grown directly in the microchannel to form straight nanopillar arrays as ordered and directional chromatographic supports. 1-Pyrenedodecanoic acid was employed for the surface modification of the MWCNTs' stationary phase to adsorb analytes by hydrophobic interactions. This device was used for separating dsDNA fragments of three different lengths (254, 360, and 572,bp), and fluorescence detection was employed to verify the electrokinetic transport in the MWCNT array. The micro-CEC separation of the three compounds was achieved in less than 300,s at a field strength of 66,V/cm due to superior laminar flow patterns and a lower flow resistance resulting from the vertically aligned MWCNTs being used as the stationary phase medium. In addition, a fivefold reduction of band broadening was obtained when the analyte was separated by the chromatographic MWCNT array channel instead of the CE channel. From all of the results, we suggest that an in situ grown and directional MWCNT array can potentially be useful for preparing more diversified forms of stationary phases for vertically efficient chip-based electrochromatography. [source]

Carbon nanotube disposable detectors in microchip capillary electrophoresis for water-soluble vitamin determination: Analytical possibilities in pharmaceutical quality control

Agustn G. Crevilln
Abstract In this work, the synergy of one mature example from "lab-on-chip" domain, such as CE microchips with emerging miniaturized carbon nanotube detectors in analytical science, is presented. Two different carbon electrodes (glassy carbon electrode (GCE) 3,mm diameter, and screen-printed electrode (SPE) 0.3,mm2.5,mm) were modified with multiwalled carbon nanotubes (MWCNTs) and their electrochemical behavior was evaluated as detectors in CE microchip using water-soluble vitamins (pyridoxine, ascorbic acid, and folic acid) in pharmaceutical preparations as representative examples. The SPE modified with MWCNT was the best electrode for the vitamin analysis in terms of analytical performance. In addition, accurate determination of the three vitamins in four different pharmaceuticals was obtained (systematic error less than 9%) in only 400,s using a protocol that combined the sample analysis and the methodological calibration. [source]

Functionalized Multi-Wall Carbon Nanotubes for Lipase Immobilization,

I. V. Pavlidis
Abstract We examine the immobilization of lipase B from Candida antarctica on functionalized multi-wall carbon nanotubes (MWCNTs) through physical adsorption. MWCNTs functionalized with carboxyl-, amine- and ester- terminal groups on their surface are used as immobilization carriers. Dispersion of the nanotubes and the immobilization procedure take place in aqueous and low-water media. High enzyme loadings are attained, up to 25% of the weight of the carbon nanotubes. These novel biomaterials are characterized though FT-IR and Raman spectroscopy. The MWCNT,lipase bioconjugates exhibit high catalytic activity and increased storage and operational stability. The biomaterials retain more than 55% of their initial activity after 6 months at 4,C, while they retain approximately 25% of their initial activity after 30 d of incubation in hexane at 60,C. The catalytic behaviour of the immobilized enzyme depends on the terminal group of the carbon nanotubes, the concentration of the enzyme and the immobilization method employed. [source]

A Reusable Interface Constructed by 3-Aminophenylboronic Acid-Functionalized Multiwalled Carbon Nanotubes for Cell Capture, Release, and Cytosensing

Xue Zhong
Abstract A newly developed electrochemical cell sensor for the determination of K562 leukemia cells using 3-aminophenylboronic acid (APBA)-functionalized multiwalled carbon nanotubes (MWCNTs) films is demonstrated. The films are generated by the covalent coupling between the NH2 groups in APBA and the COOH group in the acid-oxidized MWCNTs. As a result of the sugar-specific affinity interactions, the K562 leukemia cells are firmly bound to the APBA-functionalized MWCNTs film via boronic acid groups. Compared to electropolymerized APBA films, the presence of MWCNTs not only provides abundant boronic acid domains for cell capture, their high electrical conductivity also makes the film suitable for electrochemical sensing applications. The resulting modified electrodes are tested as cell detection sensors. This work presents a promising platform for effective cell capture and constructing reusable cytosensors. [source]

Thermal and Structural Characterizations of Individual Single-, Double-, and Multi-Walled Carbon Nanotubes

Michael T. Pettes
Abstract Thermal conductance measurements of individual single- (S), double- (D), and multi- (M) walled (W) carbon nanotubes (CNTs) grown using thermal chemical vapor deposition between two suspended microthermometers are reported. The crystal structure of the measured CNT samples is characterized in detail using transmission electron microscopy (TEM). The thermal conductance, diameter, and chirality are all determined on the same individual SWCNT. The thermal contact resistance per unit length is obtained as 78,585,m,K,W,1 for three as-grown 10,14,nm diameter MWCNTs on rough Pt electrodes, and decreases by more than 2 times after the deposition of amorphous platinum,carbon composites at the contacts. The obtained intrinsic thermal conductivity of approximately 42,48, 178,336, and 269,343,W,m,1,K,1 at room-temperature for the three MWCNT samples correlates well with TEM-observed defects spaced approximately 13, 20, and 29,nm apart, respectively; whereas the effective thermal conductivity is found to be limited by the thermal contact resistance to be about 600,W,m,1,K,1 at room temperature for the as-grown DWCNT and SWCNT samples without the contact deposition. [source]

Specific Functionalization of Carbon Nanotubes for Advanced Polymer Nanocomposites

Nanda Gopal Sahoo
Abstract A novel approach to chemically functionalize multiwalled carbon nanotubes (MWCNTs) for making advanced polymeric nanocomposites with liquid crystalline polymers (LCPs) is presented. In this approach, two types of chemical moieties (i.e., carboxylic and hydroxyl benzoic acid groups) are selectively introduced onto the sidewalls of the MWCNTs. Fourier transform IR and Raman spectroscopy are used to examine the interaction between the functionalized MWCNTs and the LCP. The strong interaction between the functionalized MWCNTs and the LCP greatly improved the dispersion of MWCNTs in the polymer matrix as well as the interfacial adhesion. The dispersion of the MWCNTs in the LCP matrix is observed by optical microscopy and field-emission scanning electron microscopy. As a result, the addition of 1,wt% MWCNTs in the LCP resulted in the significant improvement (41 and 55%) in the tensile strength and modulus of the LCP. [source]

Signal-On Electrochemiluminescence Biosensors Based on CdS,Carbon Nanotube Nanocomposite for the Sensitive Detection of Choline and Acetylcholine

Xiao-Fei Wang
Abstract This work describes for the first time signal-on electrochemiluminescence (ECL) enzyme biosensors based on cadmium sulfide nanocrystals (CdS NCs) formed in situ on the surface of multi-walled carbon nanotubes (MWCNTs). The MWCNT,CdS can react with H2O2 to generate strong and stable ECL emission in neutral solution. Compared with pure CdS NCs, the MWCNT,CdS can enhance the ECL intensity by 5.3-fold and move the onset ECL potential more positively for about 400,mV, which reduces H2O2 decomposition at the electrode surface and increases detection sensitivity of H2O2. Furthermore, the ECL intensity is less influenced by the presence of oxygen in solution. Benefiting from these properties, signal-on enzyme-based biosensors are fabricated by cross-linking choline oxidase and/or acetylcholine esterase with glutaraldehyde on MWCNT,CdS modified electrodes for detection of choline and acetylcholine. The resulting ECL biosensors show wide linear ranges from 1.7 to 332,M and 3.3 to 216,M with lower detection limit of 0.8 and 1.7,M for choline and acetylcholine, respectively. The common interferents such as ascorbic acid and uric acid in electrochemical enzyme-based biosensors do not interfere with the ECL detection of choline and acetylcholine. Furthermore, both ECL biosensors possess satisfying reproducibility and acceptable stability. [source]

High-Conductivity Polymer Nanocomposites Obtained by Tailoring the Characteristics of Carbon Nanotube Fillers,

Nadia Grossiord
Abstract We present a detailed study of the influence of carbon nanotube (CNT) characteristics on the electrical conductivity of polystyrene nanocomposites produced using a latex-based approach. We processed both industrially-produced multi-wall CNT (MWCNT) powders and MWCNTs from vertically-aligned films made in-house, and demonstrate that while the raw CNTs are individualized and dispersed comparably within the polymer matrix, the electrical conductivity of the final nanocomposites differs significantly due to the intrinsic characteristics of the CNTs. Owing to their longer length after dispersion, the percolation threshold observed using MWCNTs from vertically-aligned films is five times lower than the value for industrially-produced MWCNT powders. Further, owing to the high structural quality of the CNTs from vertically-aligned films, the resulting composite films exhibit electrical conductivity of 103,S m,1 at 2,wt% CNTs. On the contrary, composites made using the industrially-produced CNTs exhibit conductivity of only tens of S m,1. To our knowledge, the measured electrical conductivity for CNT/PS composites using CNTs from vertically-aligned films is by far the highest value yet reported for CNT/PS nanocomposites at this loading. [source]

In Situ Growth of Mesoporous SnO2 on Multiwalled Carbon Nanotubes: A Novel Composite with Porous-Tube Structure as Anode for Lithium Batteries,

Z. Wen
Abstract A novel mesoporous-nanotube hybrid composite, namely mesoporous tin dioxide (SnO2) overlaying on the surface of multiwalled carbon nanotubes (MWCNTs), was prepared by a simple method that included in situ growth of mesoporous SnO2 on the surface of MWCNTs through hydrothermal method utilizing Cetyltrimethylammonium bromide (CTAB) as structure-directing agents. Nitrogen adsorption,desorption, X-ray diffraction and transmission electron microscopy analysis techniques were used to characterize the samples. It was observed that a thin layer tetragonal SnO2 with a disordered porous was embedded on the surface of MWCNTs, which resulted in the formation of a novel mesoporous-nanotube hybrid composite. On the base of TEM analysis of products from controlled experiment, a possible mechanism was proposed to explain the formation of the mesoporous-nanotube structure. The electrochemical properties of the samples as anode materials for lithium batteries were studied by cyclic voltammograms and Galvanostatic method. Results showed that the mesoporous-tube hybrid composites displayed higher capacity and better cycle performance in comparison with the mesoporous tin dioxide. It was concluded that such a large improvement of electrochemical performance within the hybrid composites may in general be related to mesoporous-tube structure that possess properties such as one-dimensional hollow structure, high-strength with flexibility, excellent electric conductivity and large surface area. [source]

Engineering Strong Intergraphene Shear Resistance in Multi-walled Carbon Nanotubes and Dramatic Tensile Improvements

Mehdi Estili
Strong intergraphene shear resistance is engineered in multi-walled carbon nanotubes (MWCNTs) by embedding the nanotubes into a compressive-stressing ceramic environment to exploit the exceptional strength of its inner graphene walls during tensile loading. A dramatic enhancement in the tensile failure load of MWCNT is achieved in the ceramic environment and a new "multi-wall" failure mechanism is discovered. [source]

Three-dimensional Electrical Property Mapping with Nanometer Resolution

Alexander Alekseev
The conductivity behavior of MWCNT networks within the volume of polymer nanocomposite samples is analyzed with nanometer resolution in all three dimensions. It is demonstrated that close to but above the percolation threshold for electrical conduction most of the MWCNTs do not contribute to the conductive network within the nanocomposite. [source]

Sharp Carbon-Nanotube Tips and Carbon-Nanotube Soldering Irons,

Abha Misra
The nano-electron beam assisted fabrication of atomically sharp iron-based tips (see figure) and the creation of a nano-soldering iron for nano-interconnects using Fe-filled multiwalled carbon nanotubes (MWCNTs) is reported. The technique allows carving of a MWCNT and a control of the flow of the encapsulated metal outward by regulating the e-beam exposure time and spot size. [source]

Production of Ultrahigh-Molecular-Weight Polyethylene/Pristine MWCNT Composites by Half-Titanocene Catalysts

Sungjin Park
MWCNT/ Ultrahigh-molecular-weight polyethylene (UHMWPE) composites, where pristine MWCNTs are well dispersed in the UHMWPE matrices, are produced using MWCNT/half-titanocene hybrids as catalysts. The diameter of the UHMWPE-coated MWCNT strands produced is about 30,70,nm, while the diameter of the pristine MWCNTs used is 10,15,nm. UHMWPE composites with a molecular weight greater than 2,,106 are produced. [source]

Degradation behavior of nanoreinforced epoxy systems under pulse laser

M. Calhoun
Abstract Nanocomposites using EPON 824 as their matrix were exposed to pulse laser at 532 nm for various time intervals. The developed nanomaterials used for this study were manufactured using EPON 824 with multiwalled carbon nanotubes (MWCNTs) at a loading rate of 0.15% by weight and nanoclays at a loading rate of 2% by weight as reinforcements. The effect of laser irradiation on polymer composites has been investigated. The degradation mechanism for the epoxy was of a laser induced burning nature. Of all specimens tested, the ultimate strength of the MWCNT-reinforced specimens decreased the most as a function of radiation time; the nanoclay-reinforced epoxy retained the most strength after 2 min of laser radiation. In addition, the threshold fluence for decomposition indicated that less energy was required to initiate decomposition in the MWCNT-reinforced epoxy than in the nanoclay-reinforced epoxy. This can be attributed to the high thermal conductivity of the carbon nanotubes. Measurement of surface damage in the material was observed via electron microscopy. Fourier transform infrared spectroscopy was used to investigate changes to the molecular structure as a function of exposure time. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

Rheological and thermal properties of poly(ethylene oxide)/multiwall carbon nanotube composites

T. N. Abraham
Abstract Poly(ethylene oxide) (PEO) based nanocomposites were prepared by the dispersion of multiwall carbon nanotubes (MWCNTs) in aqueous solution. MWCNTs were added up to 4 wt % of the PEO matrix. The dynamic viscoelastic behavior of the PEO/MWCNT nanocomposites was assessed with a strain-controlled parallel-plate rheometer. Prominent increases in the shear viscosity and storage modulus of the nanocomposites were found with increasing MWCNT content. Dynamic and isothermal differential scanning calorimetry studies indicated a significant decrease in the crystallization temperature as a result of the incorporation of MWCNTs; these composites can find applications as crystallizable switching components for shape-memory polymer systems with adjustable switching temperatures. The solid-state, direct-current conductivity was also enhanced by the incorporation of MWCNTs. The dispersion level of the MWCNTs was investigated with scanning electron microscopy. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Preparation and properties of plasticized starch/multiwalled carbon nanotubes composites

Xiaodong Cao
Abstract In this work we have studied the utilization of multiwalled carbon nanotubes (MWCNTs) as filler-reinforcement to improve the performance of plasticized starch (PS). The PS/MWCNTs nanocomposites were successfully prepared by a simple method of solution casting and evaporation. The morphology, thermal behavior, and mechanical properties of the films were investigated by means of scanning electron microscopy, wide-angle X-ray diffraction, differential scanning calorimetry, and tensile testing. The results indicated that the MWCNTs dispersed homogeneously in the PS matrix and formed strong hydrogen bonding with PS molecules. Compared with the pure PS, the tensile strength and Young's modulus of the nanocomposites were enhanced significantly from 2.85 to 4.73 MPa and from 20.74 to 39.18 MPa with an increase in MWCNTs content from 0 to 3.0 wt %, respectively. The value of elongation at break of the nanocomposites was higher than that of PS and reached a maximum value as the MWCNTs content was at 1.0 wt %. Besides the improvement of mechanical properties, the incorporation of MWCNTs into the PS matrix also led to a decrease of water sensitivity of the PS-based materials. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

Kinetic study of carbon nanotubes synthesis by fluidized bed chemical vapor deposition

AICHE JOURNAL, Issue 2 2009
R. Philippe
Abstract Multi-walled carbon nanotubes (MWCNTs) have been produced with high selectivity by fluidized bed catalytic chemical vapor deposition from ethylene on Fe/Al2O3 catalysts. The influence of operating parameters such as deposition duration, temperature, ethylene and hydrogen partial pressures, and iron loading on MWCNT productivity, process selectivity, characteristics of final powders, and chemical composition of the outlet gases has been analyzed. Using gas phase chromatography, methane and ethane have been detected, whatever are the conditions used. Between 650 and 750C, no catalyst deactivation occurs because nucleation remains active all along the synthesis, thanks to the explosion of the catalyst grains. Above 650C, ethane itself produces MWCNTs, whereas methane does not react in the temperature range, 550,750C. The formation of MWCNTs induces marked bed expansions and sharp decreases of grain density. Apparent kinetic laws have been deduced from the collected data. The apparent partial orders of reaction for ethylene, hydrogen, and iron were found to be 0.75, 0, and 0.28, respectively. 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

Kinetic modeling study of carbon nanotubes synthesis by fluidized bed chemical vapor deposition

AICHE JOURNAL, Issue 2 2009
R. Philippe
Abstract The kinetic and physical laws developed in the first part of the study have been implemented in a modified version of the bubbling bed Kato and Wen model to represent multiwalled carbon nanotubes (MWCNTs) synthesis by catalytic chemical vapor deposition from ethylene as carbon source and using an Fe/Al2O3 catalyst. The absolute deviation for MWCNT productivity between experimental results of Part 1 and simulations is of 17.3% when only considering experiments for which the bed is mainly in bubbling regime. The influence of the main operating parameters on the evolutions with time of the species molar fractions, the weight of MWCNTs formed, and the bed characteristics has been numerically studied. Such capabilities can help designing new reactors. Finally, the model has been used for scale up purposes, by increasing the reactor diameter and catalyst weight. Simulations have shown that the process productivity could reach 74 tons/year of MWCNTs in a reactor 45 cm in diameter. 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

Noncovalent functionalization of multiwalled carbon nanotubes using graft copolymer with naphthalene and its application as a reinforcing filler for poly(styrene- co -acrylonitrile)

Kyung Tae Kim
Abstract A new compatibilizer, poly(vinyl benzyloxy ethyl naphthalene)- graft -poly(methyl methacrylate), for poly(styrene- co -acrylonirile) (SAN)/multi-walled carbon nanotubes (MWCNTs) composites was synthesized. It has been identified that naphthalene unit in backbone of compatibilizer interacts with MWCNTs via ,, interaction and that the PMMA graft of the compatibilizer is miscible with the SAN matrix. When a small amount of compatibilizer was added to SAN/MWCNT composites, MWCNTs were more homogeneously dispersed in SAN matrix than the case without compatibilizer, indicating that the compatibilizer improves the compatibility between SAN and MWCNTs. As a consequence, mechanical and electrical properties of the composites with compatibilizer were largely improved as compared with those of composites without compatibilizer. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4184,4191, 2010 [source]

Modification of multiwall carbon nanotubes via soap-free emulsion polymerization of acrylonitrile

Zhenping Cheng
Abstract A novel method for the synthesis of polyacrylonitrile (PAN)-coated multiwall carbon nanotubes (MWCNTs) via a simple soap-free emulsion polymerization is presented for the first time. The polymerization was initiated with conventional anionic ammonium persulfate (APS) at 65 C. The modification of PAN on MWCNT surfaces was confirmed by Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy. It is found that all the surfaces of the MWCNTs were coated by PAN chains, and the PAN coating thickness could be controlled by simply adjusting the polymerization time. The obtained PAN-coated MWCNTs could be well dispersed in water. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2057,2062, 2010 [source]

Multi-walled carbon nanotubes encapsulated with polyurethane and its nanocomposites

Xiao Wang
Abstract Poly(acryloyl chloride) (PACl) was employed to enhance the surface of multi-walled carbon nanotubes (MWCNTs). MWCNTs were first acid treated to generate hydroxyl groups on the surface, which was reacted with PACl to obtain an encapsulation. The numerous acryloyl chloride groups on the out layer were esterified with a proper amount of ethylene glycol (EG). Subsequently, 4,4,-methylenebis (phenylisocyanate) (MDI) and 1,4-butanediol (BDO) were introduced into the system, and a polyurethane (PU) layer was formed in situ. The formation of PU layers on MWCNTs was confirmed by Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscope (XPS). The morphology of encapsulated MWCNTs was observed by transmission electron microscope (TEM) and scanning electron microscope (SEM). Thermo gravimetric analysis (TGA) showed the grafted polymer fraction was up to 90%. On introducing the modified MWCNTs into a PU matrix, an increase in tensile strength by 60.6% and improvement in modulus by 6.3% over neat PU was observed. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4857,4865, 2008 [source]