Introduction Of Multi-walled Carbon Nanotubes Research Articles

Polypyrrole–multi-walled carbon nanotube nanocomposites synthesized in oil–water microemulsion

An oil–water microemulsion system, having been successfully used for synthesizing polypyrrole (PPy) nanoparticles, is introduced for preparing PPy–multi-walled carbon nanotube (MWCNT) nanocomposites via in situ chemical oxidative polymerization. The structures and the physical properties of the PPy–MWCNT nanocomposites are also investigated. The studies show that PPy can coat MWCNTs to form core–shell structure. The backbone structure of PPy is not damaged by the introduction of MWCNTs, and the PPy in the PPy–MWCNT nanocomposites is still amorphous as pure PPy. The conductivities of PPy–MWCNT nanocomposites are higher than that of pure PPy and are enhanced with the increase in the MWCNT–monomer mass ratio. Furthermore, a model is supposed to be used for illustrating the mechanism for PPy–MWCNT nanocomposite formation via in situ microemulsion synthesis.

The effects of synthesis procedures on the morphology and photocatalytic activity of multi-walledcarbon nanotubes/TiO2 nanocomposites

This study investigates the microstructures of multi-walled carbon nanotubes(MWNTs)/TiO2 nanocomposites, obtained by sol–gel and hydrothermal processes. The synthesizednanocomposite materials were characterized by x-ray diffractometry (XRD),Brunauer–Emmett–Teller (BET) adsorption analysis, transmittance electronmicroscopy (TEM), scanning electron microscopy (SEM), photoluminescence(PL) spectroscopy, and x-ray photoelectron spectroscopy (XPS). The effects ofthe synthetic procedures and MWNTs on the morphology and photocatalyticactivity of the nanocomposites were studied. The photocatalytic activity of theMWNTs/TiO2 nanocomposite was elucidated based on the photooxidation ofNOx under UV light illumination. A fleck-like and well dispersedTiO2 microstructure on the surface of the MWNTs was observed in the sol–gel system, whilecompact and large aggregated particles were found in the hydrothermal procedure. Thenanocomposite prepared by the sol–gel system exhibits better photocatalytic activity forNO oxidation (from 20.52 to 32.14%) than that prepared by the hydrothermal method(from 22.58 to 26.51%) with the same MWNT loading (from 0 to 8 wt%), respectively.The optimal MWNT content in the nanocomposite was considered at 8 wt%.Additionally, results confirm that the introduction of MWNTs will cause theNO2 to be more consumed than NO in the photocatalytic experiments, leading to more completeNOx photooxidation. These observations indicate that the differentTiO2 distributions on the MWNT surfaces and MWNT contents in the materials woulddetermine the morphology, the physicochemical and photocatalytic characteristics for thenanocomposite materials.

Interlaminar shear strength of glass fiber reinforced epoxy composites enhanced with multi-walled carbon nanotubes

In this study, we examine the interlaminar shear strength (ILSS) of traditional glass fiber reinforced epoxy composites enhanced by strategically injecting multi-walled carbon nanotube (MWNT)–epoxy suspensions into stationary glass fiber mats. The suspensions were prepared by combining the techniques of high-speed mechanical stirring, ultrasonic agitation and acid oxidation. Two types of process designs were introduced to fabricate the hybrid MWNT/glass/epoxy composites and their relative merits were discussed. Short beam shear (SBS) and compression shear tests (CST) were conducted on the manufactured components to characterize the influence of the process and the weight percentage of nanotubes on the ILSS. The results show that the introduction of MWNT into the composite increased the ILSS by up to 33%. The preferential orientation of the MWNTs in the thickness direction was found to contribute to the increase in the interlaminar shear properties.

Materials investigation of multi-walled carbon nanotubes doped silica gel glass composites

Multi-walled carbon nanotubes (MWNTs) doped silica gel glass matrix nano-composites were successfully prepared by sol–gel technique. Morphology of the composites was characterized by scanning electrical microscope and transmittance electrical microscope images. Pore structure of net MWNTs, silica gel glass matrix and resulted MWNTs doped composites were studied and compared. The results show that MWNTs are well dispersed in the gel glass matrix and sol–gel processing does not appear to affect the morphology of MWNTs. Pore structure of the silica matrix is changed by the introduction of MWNTs.

Preparation and electrochemical characterization of polyaniline/multi-walled carbon nanotubes composites for supercapacitor

Polyaniline/multi-walled carbon nanotubes composites were synthesized by an in situ chemical oxidative polymerization method and were the new electrode materials used for supercapacitor. The composites were characterized physically by transmission electron microscope and X-ray diffraction. The electrochemical capacitance performance of the composites in neutral solution (NaNO 3) was investigated by cyclic voltammetry, galvanostatic charge–discharge tests and ac impedance spectroscopy with a three-electrode system. The polyaniline/multi-walled carbon nanotubes composites electrodes showed much higher specific capacitance (328 F g −1), better power characteristics and were more promising for application in capacitor than pure polyaniline electrodes. This may be attributed to the introduction of multi-walled carbon nanotubes. The improvement mechanisms of multi-walled carbon nanotubes in the composites electrode were also discussed in detail.

Carbon Nanotubes Incorporated within Lyotropic Hexagonal Liquid Crystal Formed in Room-Temperature Ionic Liquids

Multiwalled carbon nanotubes (MWCNTs) were evenly dispersed within hexagonal lyotropic liquid crystals (LLCs) formed in room-temperature ionic liquids (RTILs), ethylammonium nitrate (EAN). Characterization and tribological properties of dispersed system were studied in detail. Polarized optical microscopy images combined with small-angle X-ray scattering (SAXS) results indicate that the MWCNTs are well-dispersed and that the introduction of MWCNTs does not destroy the structure of hexagonal LLCs. The increase of d spacing demonstrates the integration of MWCNTs within the cylinders of the hexagonal LLCs. FT-IR and Raman spectra of the MWCNTs-LLC composites show the characteristic absorption peaks and Raman bands of MWCNTs. The tribological properties were explored to greatly extend the applications of MWCNTs-LLC composites in RTILs as lubricating materials. The rheological measurement results indicate that MWCNTs-LLC composites are highly viscoelastic and that the apparent viscosity is enhanced by the presence of the MWCNTs.

Electrochemical fabrication of polyaniline/multi-walled carbon nanotube composite films for electrooxidation of methanol

Polyaniline (PANI)/multi-walled carbon nanotubes (MWNTs) composite films were fabricated by electropolymerization of aniline containing well-dissolved MWNTs. The films can be used as catalyst supports for electro-oxidation of methanol. Cyclic voltammogram and Chronoamperogram results show that platinum particles deposited on PANI/MWNT composite films exhibit higher electrocatalytic activity towards methanol oxidation than that deposited on pure PANI films. The porous structure and electrical conductivity of PANI films has been significantly changed by introduction of MWNTs, higher surface areas of PANI/MWNT composites has been achieved therefore. It favors for platinum particles to be highly dispersed on the PANI/MWNT composite films and the better electrocatalytic activity of Pt/PANI/MWNT electrode is induced consequently.

Biosensor based on polyaniline–Prussian Blue/multi-walled carbon nanotubes hybrid composites

In this work, a novel route for fabrication polyaniline (PANI)–Prussian Blue (PB) hybrid composites is proposed by the spontaneous redox reaction in the FeCl 3–K 3[Fe(CN) 6] and the aniline solution. With the introduction of multi-walled carbon nanotubes (MWNTs), the PANI–PB/MWNTs system shows synergy between the PANI–PB and MWNTs which amplified the H 2O 2 sensitivity greatly. A linear range from 8 × 10 −8 to 1 × 10 −5 M and a high sensitivity 508.18 μA μM cm 2 for H 2O 2 detection are obtained. The composites also show good stability in neutral solution. A glucose biosensor was further constructed by immobilizing glucose oxidase (GOD) with Nafion and glutaraldehyde on the electrode surface. The performance factors influencing the resulted biosensor were studied in detail. The biosensor exhibits excellent response performance to glucose with the linear range from 1 to 11 mM and a detection limit of 0.01 mM. Furthermore, the biosensor shows rapid response, high sensitivity, good reproducibility, long-term stability and freedom of interference from other co-existing electroactive species.

Nanocomposites based on poly- d, l-lactide and multiwall carbon nanotubes

A possibility of poly- d, l-lactide modification by multiwall carbon nanotubes (MWCNT) has been shown. MWCNT were prepared from methane-air mixture upon atmospheric pressure without catalyst on high voltage atmospheric pressure discharge plasma set-up. According to scanning and transmission electronic microscope data carbon nanotubes diameters were within 12–60 nm. Quantities of MWCNT incorporated did not exceed 0.5%. Nanocomposites were obtained by sonification of mixture of a poly- d, l-lactide solution in chloroform and MWCNT followed by film casting on glass substrates. Tensile strength and thermomechanical properties of the dried composite films were investigated. Introduction of MWCNT into poly- d, l-lactide has been shown to cause the enhanced polymer stability to thermal oxidative destruction. Taking into account the results obtained one could anticipate that implants from nanocomposites of poly- d, l-lactide with MWCNT would be dispersed in a living organism more slowly as compared to implants from pure poly- d, l-lactide without additives.

Recent advances in microcavity plasma devices and arrays: a versatile photonic platform

Selected highlights in the recent development of microplasma devices are reviewed with emphasis on large arrays of Si-based hybrid plasma/semiconductor pixels. Arrays of 40 000 (200 × 200) pixels, excited by sinusoidal ac waveforms at frequencies of 5–20 kHz, have now been realized. The fabrication of these arrays and their electrical and optical performance with rare gases and Ar/N2 mixtures are briefly described. Metal/dielectric/metal devices having a piezoelectric dielectric (BaTiO3), a cylindrical microcavity 50 µm in diameter, and a total thickness of ∼ 110 µm are also discussed. Finally, the introduction of multiwall carbon nanotubes into microdischarge devices as an auxiliary source of current is presented as being exemplary of the opportunities afforded by the integration of nanotechnology into microcavity plasma structures.

Effects of Electrochemical Activation and Multiwall Carbon Nanotubes on the Capacitive Characteristics of Thick MnO2 Deposits

Thick composites composed of crystalline manganese dioxide and multiwall carbon nanotubes (MWCNTs) were successfully codeposited onto a graphite substrate from an solution. The rate/nucleation mechanism of deposition was significantly influenced by the introduction of MWCNTs in the plating baths. The specific capacitance of thick -MWCNT composites, measured from cyclic voltammetry (CV) or chronopotentiometry (CP) in a potential window of 1.0 V, is monotonously decreased from ca. 160 to 80 F/g with increasing the oxide loading from 1.5 to 4.5 mg/cm2. The lower specific capacitance of thick and -MWCNTs deposits is reasonably attributed to the relatively poorer utilization of electroactive species as well as the compact structure in comparison with a thin Mn oxide deposit (<1 μm). The capacitive performance of these thick deposits in 0.1 M is significantly improved by the application of electrochemical activation and the introduction of MWCNTs, revealing the promising improvement in the capacity of electrodes. © 2004 The Electrochemical Society. All rights reserved.

Nonlinear phenomena in flows of viscoelastic polymer fluids

Highly ordered honeycomb films were produced from arborescent graft polystyrene (AGPS) solutions using breath figures (BF). The structure of the BF pattern (whether single layered or multilayered) of pores depended on several factors such as the type of solvent used (CS2 or CHCl3), the length of the side chains, the generation number and the concentration of the polymer. When solutions of AGPS with shorter side chains (Mw ∼ 5000 g/mol) were used for the BF process, arborescent polymers generated a multilayer pore structure. However, when polymers with longer side chains (Mw ∼ 30,000 g/mol) were used, monolayer pore structures were mostly generated. The regularity and surface quality of the honeycomb pattern became worsened as the multilayered structures formed. The polymer concentration (ϕ) also played a critical role in determining the morphology of the BF films. Higher ϕ led to a multilayer pore structure while lower ϕ resulted in a monolayer pore structure. In general, the regularity of top layer pores was found to decrease with increasing generation number. The introduction of multiwall carbon nanotubes (MWCNTs) into AGPS solutions and application of the BF process using the solution blends yielded patterned hybrid films. SEM images showed that some CNTs were loaded into the honeycomb pattern of AGPS, but that most MWCNTs precipitated to form the bottom layer. In this work, the influence of concentration and surface modification of MWCNTs on the BF patterns obtained is discussed.