Multi-walled Carbon Nanotube Composite Films Research Articles

In situ preparation and continuous fiber spinning of poly(p-phenylene benzobisoxazole) composites with oligo-hydroxyamide-functionalized multi-walled carbon nanotubes

A graft-from approach has been performed to achieve covalent functionalization of multi-walled carbon nanotubes (MWNTs) with oligo-hydroxyamide (oHA). Pristine MWNT was first oxidized to MWNT-COOH and then functionalized to MWNT-COCl by acyl chloride. MWNT-COCl was copolymerized with oHA to produce oHA-grafted MWNTs (MWNT-oHA). The thickness of the oHA shell in MWNT-oHA is about 7.5nm. MWNT-oHA has a remarkable solubility in polar solvents and a good thermal stability because characteristic dehydrative ring closure occurs upon heating and forms a thermally more stable benzoxazole component. MWNT-oHA has been further covalently incorporated with a rigid-rod polymer matrix, poly(p-phenylene benzobisoxazole) (PBO), through in situ polymerization. Continuous PBO–MWNT composite fibers with different MWNT compositions have been fabricated using dry-jet wet-spinning technique. The structure and morphology of PBO–MWNT composite fibers have been characterized and their mechanical, thermal, conducting properties have been investigated. The tensile modulus, tensile strength, and thermal stability of PBO–MWNT composite fibers have been improved because of a good dispersion and high alignment of MWNTs in PBO as well as enhanced interfacial interaction between these two components. Furthermore, increased conductivity has been discovered in the PBO–MWNT composite films and the inner core of the composite fibers; however, not on the outer surface. The phenomena can be interpreted using percolation model together with the heterogeneous fiber morphology and nanotube distribution over the cross-section of the fiber.

Preparation and characterization of poly[Ni( salen)(crown receptor)]/multi-walled carbon nanotube composite films

Nanocomposite films comprising multi-walled carbon nanotubes (MWCNTs) embedded within poly[Ni(3-Mesalophen-b15-c5)] were deposited on Pt and ITO electrode surfaces by the potentiodynamic polymerisation of [Ni(3-Mesalophen-b15-c5)] from solutions containing dispersed MWCNTs. Composites incorporating carbon nanotubes subject to a range of oxidising pre-treatments were compared with those incorporating untreated carbon nanotubes and with the pure polymer. In both cases, the use of CH 3CN and CH 2Cl 2 as fabrication and characterization media were explored. Films were characterized by voltammetry, electrochemical impedance spectroscopy and scanning electron microscope (SEM). The coating of the carbon nanotubes with polymer varied significantly with pre-treatment and solvent medium; this influenced the final composite morphology and electrical properties. Performance enhancement of the polymer component by the presence of the carbon nanotubes was manifested through the ability to store charge and the ease with which this could be accomplished; these were parameterized via increased redox capacitance and decreased charge-transfer resistance, respectively. Correlation of impedance parameters with SEM images provided a morphological rationale for composite electrical properties.

Preparation, fabrication and response behavior of a HTBN/TDI/MWCNT composite sensing film by in situ dispersed polymerization

A polyurethane inserted multi-wall carbon nanotube (MWCNT) composite conductive film was prepared by in situ dispersed polymerization reaction using hydroxyl-terminated poly(butadiene-acrylonitrile) liquid rubber as a linear diol, toluene diisocynate as a curative, ethylene glycol or glycerine or triethanolamine as a chain-extending agent and MWCNT as a conducive filler. The effect of various curing temperatures and chain-extending agents on vapor-induced electrical responsiveness of the conductive films was investigated. The structural characterization of the cured film was conducted by Fourier transformation infrared spectrophotometer (FTIR), differential scanning calorimeter (DSC), polarization microscope (POM) and wide angle X-ray diffraction (WAXD). The experimental results showed that the conductive composite film obtained in the present work exhibited a microphase separation resulting from the soft-hard segment domains, and possessed some crystalline behavior from the hard segment. The response intensity was enhanced with the curing temperature increased, while the reversibility could be improved at a relatively low curing temperature. The responsivity of the film produced by a linear difunctional group chain-extending agent was lower than that prepared by trifunctional group curatives, and the reversibility was vice versa. The experimental phenomena were explained from the viewpoint of the microphase separation, crystalline behavior, the structural characteristics of the soft-hard segment, and the electronic properties of multi-wall carbon nanotubes as well as a weak electrostatic or noncovalent interaction between polymer or analyte molecules and MWCNTs.

Poly(3-hydroxybutyrate)/Bioglass® composite films containing carbon nanotubes

Poly(3hydroxybutyrate)(P(3HB))/Bioglass® composites incorporating multiwalled carbon nanotubes (MWCNTs) have been successfullyprepared by the solvent casting technique. The microstructure, electrical properties andbioactivity of the composites were characterized using scanning electron microscopy, x-raydiffraction and current–voltage measurements. Different concentrations of MWCNTs wereused to determine their effect on the electrical properties of the composites. MWCNTs andBioglass® particles were found to be homogeneously dispersed throughout the P(3HB) matrix. Theelectrical resistance of the composite samples decreased on increasing the MWCNTconcentration, as expected. An in vitro degradation study in simulated body fluid (SBF)was carried out on composite samples. The formation of hydroxyapatite on the surfaces ofP(3HB)/Bioglass®/MWCNT composite films was confirmed after two months of immersion in SBF. This hydroxyapatite layerwas not formed on the neat polymeric films and on composites containing MWCNTs only (withoutBioglass®). It was found that the presence of MWCNTs did not hinder the bioactivity of theBioglass® particles, as confirmed by SEM and XRD studies on composite samples.

Electrochemical quartz crystal impedance study on the overoxidation of polypyrrole–carbon nanotubes composite film for amperometric detection of dopamine

The electrochemical quartz crystal impedance (EQCI) method was used to study the overoxidation of polypyrrole (PPy)–multiwalled carbon nanotubes (MWCNT) nanocomposite film in neutral and alkaline solutions. The values of molar mass per electron transferred (M/n) obtained during the overoxidation of PPy in 0.10molL−1 Na2SO4 and 0.20molL−1 NaOH aqueous solutions were estimated to be ca. 17 and 22gmol−1, respectively, suggesting the nucleophilic attack of solution OH− to the pyrrole units during the overoxidation, and the possible partial formation of carboxylic groups after the overoxidation in the NaOH solution. Also, the overoxidized PPy–MWCNT composite film prepared in the NaOH solution showed a notably larger affinity to dopamine (DA) dissolved in a neutral phosphate buffer than that prepared in the Na2SO4 solution. The modification of the overoxidized nanocomposite film improved substantially the sensitivity for DA assay in a neutral phosphate buffer, as compared with the modification of overoxidized PPy or MWCNT alone. At a −6kHz (201-nm thickness) nanocomposite film prepared in a polymerization bath containing 1.0mgmL−1 MWCNT and overoxidized in 0.20molL−1 aqueous NaOH, the peak current response from differential pulse voltammetric assay of DA was linear with DA concentration from 4.0×10−8 to 1.4×10−6molL−1, with a lower limit of detection of 1.7nmolL−1, good anti-interferent ability, as well as good stability and reproducibility.

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.

The effect of multi-walled carbon nanotubes on the molecular orientation of poly(vinyl alcohol) in drawn composite films

Poly(vinyl alcohol) (PVA)/multi-walled carbon nanotube (MWNT) composite films were prepared by casting a DMSO solution of PVA and MWNTs, whereby the MWNTs were dispersed by sonication. A significant improvement in the mechanical properties of the PVA drawn films was achieved by the addition of a small amount of MWNTs. The initial modulus and the tensile strength of the PVA drawn film increased by 30% and 45% respectively, with the addition of 1 wt% MWNTs, which are close to those calculated from the rule of mixtures, and were strongly dependent upon the orientation of the PVA matrix. The mechanical properties, however, were not improved with a further increase in the MWNT content. The orientation of MWNTs in the composite was not well developed compared to that of the PVA matrix. This result suggests that the improvement of the molecular orientation of the PVA matrix plays a major role in the increase of the mechanical properties of the drawn PVA/MWNT composite films.

Prussian Blue electrodeposited on MWNTs–PANI hybrid composites for H 2O 2 detection

A Prussian Blue (PB)/polyaniline (PANI)/multi-walled carbon nanotubes (MWNTs) composite film was fabricated by step-by-step electrodeposition on glassy carbon electrode (GCE). The electrode prepared exhibits enhanced electrocatalytic behavior and good stability for detection of H 2O 2 at an applied potential of 0.0 V. The effects of MWNTs thickness, electrodeposition time of PANI and rotating rate on the current response of the composite modified electrode toward H 2O 2 were optimized to obtain the maximal sensitivity. A linear range from 8 × 10 −9 to 5 × 10 −6 M for H 2O 2 detection has been observed at the PB/PANI/MWNTs modified GCE with a correlation coefficient of 0.997. The detection limit is 5 × 10 −9 M on signal-to-noise ratio of 3. To the best of our knowledge, this is the lowest detection limit for H 2O 2 detection. The electrode also shows high sensitivity (526.43 μA μM −1 cm −2) for H 2O 2 detection which is more than three orders of magnitude higher than the reported.

Adhesive strength of nano-size particles filled thermoplastic polyimides. Part-I: Multi-walled carbon nano-tubes (MWNT)–polyimide composite films

In this study, adhesive properties of thermoplastic polyimides (PI) filled with multi wall carbon nano-tubes (MWNT) are investigated. The PIs studied are ODPA/3, 4′-ODA/PA (amorphous) and BPDA/3, 4′-ODA/PA (semi-crystalline). The PIs are prepared via a two-step method involving poly(amide acid) (PAA) stage followed by thermal or chemical imidization to obtain polyimide in film or powder form. The MWNT are mixed in low wt% (0.1–1.5) during synthesis at PAA stage through mechanical agitation and sonication. PI-MWNT film composites were characterized using DMTA and tensile testing to determine viscoelastic behavior and mechanical properties. Adhesive strength and adhesive energy of bonded samples, prepared with PI-MWNT films and powder composites, were determined using single lap joints test and wedge test methods, respectively. The fractured bonded surfaces were examined by scanning electron microscope to determine failure patterns. The results showed that viscoelastic behavior of PI–MWNT composite films changes from liquid-like to solid-like by increasing MWNT content. Elastic modulus and strength at break of PI-MWNT composite films were found to increase with increase in MWNT wt%. However, elongation at break and breaking energy of PI–MWNT composite films and lap shear strength and adhesive energy of bonded samples were found to initially increase with increase in MWNT wt%, but then after a critical value decreases. The SEM analysis showed that bonded joints prepared with PI–MWNT composite films containing high wt% of MWNT failed in adhesive mode showing poor wetting of adherend surfaces.

Fabrication of Nickel–Multiwalled Carbon Nanotube Composite Films with Excellent Thermal Conductivity by an Electrodeposition Technique

Nickel-multiwalled carbon nanotube (MWCNT) composite films were fabricated by an electrodeposition technique, and their microstructure and thermal conductivity were characterized. Nickel-MWCNT composite films with a homogeneous dispersion of MWCNTs throughout the nickel matrix free of any significant voids were electrodeposited from a Ni plating bath containing effective additives and MWCNTs under galvanostatic conditions. The thermal conductivity of the composite films was as high as 109 Wm -1 K -1 , which is about twice that of a nickel film without MWCNTs.

Light emitting diodes of fully conjugated heterocyclic aromatic rigid-rod polymer dopedwith multi-wall carbon nanotubes

Poly-p-phenylenebenzobisoxazole (PBO) and carbon nanotubes have a fully conjugated rod-likebackbone entailing excellent mechanical properties, thermo-oxidative stability and solventresistance. Rigid-rod PBO is commonly processed by dissolving in methanesulfonic acid orLewis acid. A multi-wall carbon nanotube (MWNT) was dissolved in an isotropic Lewisacid solution of PBO for dispersion of nanotubes and for processing into thin film. TheMWNT concentration in the films was up to 5 wt%. Compared to pure PBO film, allPBO + MWNT composite films retained the same but enhanced UV–Vis absorption peaks,showing that MWNT and PBO did not have overlapping electron orbitals affecting theirenergy gaps. The films were excited at 325 nm using a He–Cd laser for photoluminescence(PL) emission. All PL spectra had the maximum intensity at 540 nm, indicative of ayellow–green light emission. Single-layer light emitting diodes of MWNT doped PBOdecreased the threshold voltage by 2 V. Up to 0.1 wt% of MWNTs, the diode emissioncurrent increased by about two orders of magnitude over those of the diodes withoutMWNT. Further increase of MWNT concentration caused a successive decrease inelectroluminescence emission intensity, that was attributed to a quench effect fromaggregation of MWNTs.

High Performance Nanotube‐Reinforced Plastics: Understanding the Mechanism of Strength Increase

AbstractPolymer–multiwalled carbon nanotube composite films were fabricated using two types of polymer matrices, namely poly(vinyl alcohol), (PVA) and chlorinated polypropylene. In the first case, the PVA was observed to form a crystalline coating around the nanotubes, maximising interfacial stress transfer. In the second case the interface was engineered by covalently attaching chlorinated polypropylene chains to the nanotubes, again resulting in large stress transfer. Increases in Young's modulus, tensile strength, and toughness of × 3.7, × 4.3, and × 1.7, respectively were observed for the PVA‐based materials at less than 1 wt.‐% nanotubes. Similarily for the polypropylene‐based composites, increases in Young's modulus, tensile strength and toughness of × 3.1, × 3.9, and × 4.4, respectively, were observed at equivalent nanotube loading levels. In addition, a model to describe composite strength was derived. This model shows that the tensile strength increases in proportion to the thickness of the interface region. This suggests that composite strength can be optimized by maximising the thickness of the crystalline coating or the thickness of the interfacial volume partially occupied by functional groups.

Mechanical Properties Of Polyaniline / Multi-walled Carbon Nanotube Composite Films

ABSTRACTHigh molecular weight polyaniline / multi-walled carbon nanotube composite films were fabricated using solution processing. Composite films with various weight percentages of multiwalled carbon nanotubes were fabricated. Physical properties of these composites were analyzed by thermogravimetric analysis, tensile testing, and scanning electron microscopy. These results indicate that the addition of multiwalled nanotubes to polyaniline significantly enhances the mechanical properties of the films. In addition, metal–semiconductor (composite) (MS) contact devices were fabricated, and it was observed that the current level in the films increased with increasing multiwalled nanotube content. Furthermore, it was observed that polyaniline containing one weight percent of carbon nanotubes appears to be the most promising composition for applications in organic electronic devices.