Small Amount Of Carbon Nanotubes Research Articles

Manufacturing and properties of Carbon Nanotube Composites with Nbr, Sbr and Nr

Carbon nanotubes (CNTs) were incorporated as a filler in various elastomers in order to obtain rubbers with improved electrical and thermal conductivity. Composites with very low electrical percolation thresholds were successfully produced by direct mixing of elastomers and CNTs in an internal mixer. The effect of CNTs on vulcanisation behaviour and crosslink density of the rubbers was examined and it was shown that very small amounts of CNTs accelerate the curing reaction with sulfur curing systems and contribute to an increase in crosslink density. It was also confirmed that composites of elastomers and CNTs are suitable in principle for manufacturing heating elements with controllable surface temperatures.

The effect of the addition of multiwalled carbon nanotubes on the uniform distribution of TiC nanoparticles in aluminum nanocomposites

Aluminum matrix composites reinforced by TiC nanoparticles (with volume fractions of 1.5% and 3%) or a combination of TiC nanoparticles and carbon nanotubes (CNTs) were fabricated using a combination of ball-milling and sheath-rolling techniques. Hybridization of TiC nanoparticles with a small amount of CNTs (0.7 vol.%) significantly enhanced the distribution of TiC nanoparticles in the matrix, indicating that CNTs can be used as carriers to improve the dispersion of nanoparticles in metal–matrix composites.

Effect of Carbon Nanotubes on Properties of Graphite/Carbon Black/Polypropylene Nanocomposites

High chemical corrosion, low manufacturing cost and light of total mass of bipolar plate in Proton Exchange Membrane Fuel Cell (PEMFC) lead most of the PEMFCs researchers over the world attracted their interest to replace pure graphite or metal based bipolar plate with conductive polymer composites (CPCs) bipolar plate. CPCs is fabricate from the mixed of conductive fillers such as and Graphite (G) andCarbon Black (CB) had been incorporated in Polypropylene (PP) matrix for fabrication of electrical conductive polymer composite plate. Most researchers reported only at high loading of fillers (more than 90 wt.%), are gave electrical conductivity above 100 S/cm, which is target from Department of Energy (USA). Higher loading of fillers cause change in rheological properties and increase the difficulties in polymer processing. Thus will decreasing the electrical and mechanical properties of CPCs as bipolar plate. Therefore, in this study carbon nanotubes (CNTs) which have 1000 time electrical conductivity than copper wire are introduced into G/CB/PP composite to compensate above problems. But the main problems of CNTs, at high loading it tend to agglomerate and thus will affect the properties of CPCs. So that, small amount of CNTs which is 0.2, 0.4, 0.6 and 0.8 wt.% will be added into G/CB/PP composite. But weight percentage of CB and PP has been fixed which is 25 wt.% and 20 wt.% respectively and the weight percentage of G will various from 55 wt.% to 54.2 wt.% according to CNTs loading. The result shows that the G/CB/CNTs/PP composite with 0.2 wt% CNTs has the higher electrical conductivity 295.78 S/cm.

Highly loaded nanocomposite films as fire protective coating for polymeric substrates

The main fire retardancy mechanism of polymer–clay nanocomposites involves the progressive build-up of an inorganic-rich layer at the sample surface during combustion, by a combination of ablative reassembling and migration of the nanoparticles, reducing heat and mass transfer between gas and condensed phases. In this process, a non-negligible amount of polymer needs to be sacrificed before the entire surface of the residual material is shielded. This study aims to improve the fire behaviour of polymer–clay nanocomposites by accelerating the physical barrier formation through the development of new hybrid structures. For that purpose, a system based on polyamide 12 and halloysite nanotubes is chosen as reference and highly loaded nanocomposite films are coated on a virgin PA12 substrate. Both the influence of clay fraction in the nanocomposite film and its thickness on the flammability performance of the coated samples are evaluated by mass loss calorimetry and compared to that of homogeneous ‘bulk’ nanocomposites. Results show unambiguously that hybrid materials are more effective than conventional nanocomposites to flame retard polymers while substantially reducing the total filler loading, and so the cost of the final product. Moreover, a small amount of carbon nanotubes can be incorporated in the polymer substrate and/or in the nanocomposite film to suppress the vigorous bubbling of evolved degradation products as well as to reduce the flexibility of the thin protective skin, which can cause detrimental effects on its barrier properties.

Barrier, mechanical and morpho-structural properties of gelatin films with carbon nanotubes addition

The effect of a small amount of carbon nanotubes (CNT) on the water content and physical properties of gelatin films with glycerol were evaluated. Control films and those with 0.001% (w/w) CNT addition were prepared. Water isotherms adsorption and water vapor permeability, were undertaken on the gelatin films to asses barrier characteristics. Tensile strength and elongation at break were evaluated with a texture meter, while hardness and elastic modulus were measured with a nanoindentation tester, all these tests were measured at 22%, 40%, 58% and 75% RH. Atomic force, environmental and field emission scanning electron microscopy, were used to see the films morpho-structure. The data adsorption isotherms fitted well all models tried. An increase in RH decreased the tensile strength, and increased the elongation at break of all films. The CNT addition did not affect significantly the films barrier properties (p>0.05), but it caused an increase of about 11.36% on the elongation at break of films, at any RH higher than 40%; with no effect on the tensile strength and hardness. Films image analysis, showed a morpho-structure with high ordering, which might well correlate with CNT addition to the protein matrix. CNT were found embedded in the polymeric matrix.

Effects of Functionalization on Thermal Properties of Single-Wall and Multi-Wall Carbon Nanotube–Polymer Nanocomposites

Carboxylic functionalization (-COOH groups) of carbon nanotubes is known to improve their dispersion properties and increase the electrical conductivity of carbon-nanotube-polymer nanocomposites. We have studied experimentally the effects of this type of functionalization on the thermal conductivity of the nanocomposites. It was found that while even small quantities of carbon nanotubes (~1 wt %) can increase the electrical conductivity, a larger loading fraction (~3 wt %) is required to enhance the thermal conductivity of nanocomposites. Functionalized multi-wall carbon nanotubes performed the best as filler material leading to a simultaneous improvement of the electrical and thermal properties of the composites. Functionalization of the single-wall carbon nanotubes reduced the thermal conductivity enhancement. The observed trends were explained by the fact that while surface functionalization increases the coupling between carbon nanotube and polymer matrix, it also leads to formation of defects, which impede the acoustic phonon transport in the single-wall carbon nanotubes. The obtained results are important for applications of carbon nanotubes and graphene flakes as fillers for improving thermal, electrical and mechanical properties of composites.

Transparent, Conductive, and Printable Composites Consisting of TEMPO-Oxidized Nanocellulose and Carbon Nanotube

Ultrastrong, transparent, conductive and printable nanocomposites were successfully prepared by mixing single-walled carbon nanotubes (CNTs) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs) with abundant sodium carboxyl groups on the crystalline nanocellulose surfaces. The surface-anionic cellulose nanofibrils had reinforcing and nanodispersing effects on the CNTs both in water used as the dispersed medium and in the dried composite film, providing highly conductive and printable nanocomposites with a small amount of CNTs. TOCNs are therefore expected as an effective flexible matrix that can be used as an alternative to conventional polymers for various electrical materials, when nanocomposited with CNTs and also graphene. Our findings provide a promising route to realize green and flexible electronics.

Carbon nanotubes–reinforced copper matrix composites produced by melt stirring

Due to their geometry and extraordinary mechanical properties, carbon nanotubes have been envisioned as promising enhancements for metal matrix composites. In this article, we report on our melt stirring approach for incorporation of carbon nanotubes into a copper alloy matrix and on the experimental results obtained by assessing the material properties. The existence of carbon nanotubes in the copper matrix after processing was proven by Raman analysis. We found that the small amounts of carbon nanotubes (0.1 wt%) in the composites influenced mechanical and abrasive wear properties.

A novel visible-light-response plasmonic photocatalyst CNT/Ag/AgBr and its photocatalytic properties

A facile, one-step synthesis of carbon nanotube (CNT)-loaded Ag/AgBr is reported. The as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), UV/Vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopy (EIS). The CNT/Ag/AgBr composite exhibited much higher photocatalytic activity than pure Ag/AgBr in degrading methyl orange (MO) dye solution. The loading amount of CNT had a significant influence on the photoactivity of the CNT/Ag/AgBr composite. When the CNT loading amount was 1.4 at%, the hybrid material showed the highest photocatalytic ability. The result showed that a small amount of CNT was beneficial for photo-generated electron transfer, which could enhance the photoactivity of CNT/Ag/AgBr. The degradation dye solution was tested by liquid chromatography/mass spectrometry (LC/MS) and total organic carbon (TOC) analysis. Based on the results, the structure of the synthesized CNT/Ag/AgBr hybrid material was verified and the possible degradation path of the MO dye was proposed. A possible visible-light photocatalytic degradation mechanism was also discussed.

Isothermal crystallization behavior and mechanical properties of polylactide/carbon nanotube nanocomposites

Carbon nanotube (CNT)–reinforced polylactide (PLA) nanocomposites were prepared using a melt compounding process employing a twin-screw extruder. The isothermal crystallization kinetics of PLA/CNT nanocomposites according to Avrami’s theory were analyzed using differential scanning calorimetry in the temperature range 90–120°C. There was a significant dependence of CNT on the crystallization behavior of the PLA matrix. The incorporation of CNT improved effectively the crystallization rate of PLA/CNT nanocomposites through heterogeneous nucleation. The nucleating effect of CNTs which increased the number of nucleation sites and decreased the average spherulite size was confirmed using polarized optical microscopy. The rheological properties of the PLA/CNT nanocomposites were also investigated. Changes in the microstructure of the PLA/CNT nanocomposites occurred by incorporating CNT. Furthermore, the tensile strength/modulus and thermal stability of PLA/CNT nanocomposites were enhanced when a very small quantity of CNT was added. This research accounts for the effect of CNTs, which significantly influenced the isothermal behavior, thermal stability, mechanical, and rheological properties of the PLA/CNT nanocomposites, providing a design guide for PLA/CNT nanocomposites in industrial fields.

Hot extruded carbon nanotube reinforced aluminum matrix composite materials

Carbon nanotube (CNT) reinforced aluminum (Al) matrix composite materials were successfully fabricated by mechanical ball milling followed by powder hot extrusion processes. Microstructural analysis revealed that the CNTs were well dispersed at the boundaries and were aligned with the extrusion direction in the composites obtained. Although only a small quantity of CNTs were added to the composite (1 vol%), the Vickers hardness and the tensile strength were significantly enhanced, with an up to three-fold increase relative to that of pure Al. From the fractography of the extruded Al–CNT composite, several shapes were observed in the fracture surface, and this unique morphology is discussed based on the strengthening mechanism. The damage in the CNTs was investigated with Raman spectroscopy. However, the Al–CNT composite materials were not only strengthened by the addition of CNTs but also enhanced by several synergistic effects. The nanoindentation stress–strain curve was successfully constructed by setting the effective zero-load and zero-displacement points and was compared with the tensile stress–strain curve. The yield strengths of the Al–CNT composites from the nanoindentation and tensile tests were compared and discussed. We believe that the yield strength can be predicted using a simple nanoindentation stress/strain curve and that this method will be useful for materials that are difficult to machine, such as complex ceramics.

High strain rate behavior of multi-walled carbon nanotubes–polycarbonate composites

Multi-walled carbon nanotubes–polycarbonate composites (MWCNT–PC) were prepared by a two-step method of solvent casting followed by compression molding and their dynamic impact strength was studied. Split Hopkinson Pressure Bar (SHPB) was deployed as the instrument for impact testing of the composite samples. The impact tests were performed under varying strain rates ranging from 1096 to 4017/s. The present studies report the stress–strain behavior of MWCNT–PC composites under a high strain rate of 2000–2600/s. A comparison of stress at various strains ranging from 5% to 20% was done by varying MWCNT concentration in the range 0.1, 0.5, 1, 2 and 5wt.% in PC. Stress tolerance of these composites was studied to analyze effectiveness of small amounts of carbon nanotubes (CNTs) for impact/stress absorption in comparison to pure PC samples. It was found that the stress behavior for specific strains varies with concentration of CNTs in polycarbonate. At very low (about 0.1wt.%) and high concentrations (about 5wt.%) of carbon nanotubes the stress did not vary much as compared to pure PC for the above mentioned strain range. At concentration levels of 0.5, 1 and 2wt.% CNTs, the impact absorption (nearly 105MPa) increased by 10–20% as compared to pure PC (nearly 90MPa) depending upon the amount of strain in the samples. The role of functionalized CNTs in impact studies was also studied by using 0.5wt.% and 2wt.% functionalized MWCNT. The use of functionalized CNTs was found to result in reduced impact absorption (nearly 95MPa) as compared to as-synthesized CNTs (nearly 105MPa). The effect of concentration of CNTs on impact strength of MWCNT–PC composites was analyzed by studying the SEM images of composite samples after impact.

Dynamic mechanical behavior of magnetorheological nanocomposites filled with carbon nanotubes

Magnetorheological (MR) elastomer composites with the addition of multi-walled carbon nanotubes are developed. The dynamic mechanical responses of the MR nanocomposites to applied magnetic fields are investigated through dynamic mechanical analysis. It is found that a small amount of carbon nanotubes can effectively improve the mechanical performance of conventional MR elastomers. The MR nanocomposites have shown not only large jumps in zero-field dynamic stiffness and damping, but also higher magnetic-field-induced improvement in these dynamic mechanical properties.

탄소나노튜브 적용 나노유체의 임계 열유속까지의 비등 열전달계수

In this study, the nucleate pool boiling heat transfer coefficients (HTCs) and critical heat flux (CHF) for a smooth and square flat heater in a pool of pure water with and without carbon nanotubes (CNTs) dispersed at 60 o C were measured. Tested aqueous nanofluids were prepared using CNTs with volume concentrations of 0.0001%, 0.001%, and 0.01%. The CNTs were dispersed by chemically treating them with an acid in the absence of any polymers. The results showed that the pool boiling HTCs of the nanofluids are higher than those of pure water in the entire nucleate boiling regime. The acid-treated CNTs led to the deposition of a small amount of CNTs on the surface, and the CNTs themselves acted as heat-transfer-enhancing particles, owing to their very high thermal conductivity. There was a significant increase in the CHF up to 150% when compared to that of pure water containing CNTs with a volume — — concentration of 0.001%. This is attributed to the change in surface characteristics due to the deposition of a very thin layer of CNTs on the surface. This layer delays nucleate boiling and causes a reduction in the size of the large vapor canopy around the CHF. This results in a significant increase in the CHF.

Magnetic Susceptibility Studies on a Ternary Lyotropic Liquid Crystal System

We have carried out mass diamagnetic susceptibility studies on (SdS)/decanol/water system for two different concentrations of the constituents namely 41.6/6.6/51.8 wt% and 35.47/7/57.5 wt%. This system exhibits calamitic nematic (Nc), isotropic (I) and hexagonal phases (H) on heating from room temperature. We find the isotropic phase susceptibility is temperature dependent at low temperatures and temperature independent at high temperatures. The susceptibility in the nematic phase of sample 1 is temperature independent while that of sample 2 is temperature dependent. We find marked differences in the diamagnetic anisotropy of these two samples. We infer that this may be related to the difference in the shape of the micelles in these samples. We also report the changes in the nematic phase susceptibility in the sample 1 on dispersing a small amount of carbon nanotubes.

Dye-sensitized solar cells based on anatase TiO 2 hollow spheres/carbon nanotube composite films

Dye-sensitized solar cells (DSSCs) based on anatase TiO 2 hollow spheres (TiO2HS)/multi-walled carbon nanotubes (CNT) nanocomposite films are prepared by a directly mechanical mixing and doctor blade method. The prepared samples are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–vis absorption spectroscopy and N 2 adsorption–desorption isotherms. The photoelectric conversion performances of the DSSCs based on TiO2HS/CNT composite film electrodes are also compared with commercial-grade Degussa P25 TiO 2 nanoparticles (P25)/CNT composite solar cells at the same film thickness. The results indicate that the photoelectric conversion efficiencies ( η) of the TiO2HS/CNT composite DSSCs are dependent on CNT loading in the electrodes. A small amount of CNT clearly enhances DSSC efficiency, while excessive CNT loading significantly lowers their performance. The former is because CNT enhance the transport of electrons from the films to FTO substrates. The latter is due to high CNT loading shielding the visible light from being adsorbed by dyes.

Improvement of thermal management of high-power GaN-based light-emitting diodes

The thermal management of high-power light-emitting-diode (LED) devices employing various die-attach materials is analyzed. Three types of die-attach materials are tested, including silver paste, Sn–3wt.% Ag–0.5wt.% Cu (SAC305) solder, and SAC305 solder added with a small amount of carbon nanotubes (CNTs). The analysis of thermal management is performed by comparing the temperatures of the LED chips in use and the total thermal resistances of the LED devices obtained respectively from the thermal infrared images and thermal transient analysis. Due to the high thermal conductivity of CNT, the addition of CNTs into the SAC305 solder reduces the total thermal resistance and chip temperature of the LED device, and the thermal management of the LED devices is improved accordingly.

Nematic electroclinic effect in a carbon-nanotube-doped achiral liquid crystal

A small quantity of carbon nanotubes (CNTs) dispersed in an achiral liquid crystal (LC) matrix transmits chirality a short distance into the LC, and the LC+CNT mixture is found to exhibit a bulklike electroclinic effect in the nematic phase. The magnitude of the effect increases rapidly on cooling, showing significant pretransitional behavior on approaching the nematic-smectic-A transition temperature (T(NA)) from above. The variation of the electroclinic coefficient is negligible over the frequency range 100 Hz to 100 kHz in the in the nematic phase well above T(NA) and in the smectic-A phase, whereas the electroclinic coefficient falls off significantly with increasing frequency just above T(NA).

Carbon nanotube-induced macroscopic helical twist in an achiral nematic liquid crystal

An achiral nematic liquid crystal was doped with a small quantity of carbon nanotubes having a net chirality, and the mixture was found to exhibit an average mechanical twist over macroscopic dimensions. The nanotube-induced chiral pitch length P was determined as a function of the average nanotube concentration by measuring the radii of curvature of reverse twist disclination lines in 90° nematic twist cells. The results suggest that the nanotubes’ spatial concentration can vary significantly across the cell and that at high average concentration, the nanotubes undergo aggregation, resulting in an apparent saturation of P−1 at high concentrations. The macroscopic helical twisting power of the nanotubes has been estimated from the results.

Effects of processing conditions on rheological, thermal, and electrical properties of multiwall carbon nanotube/epoxy resin composites

AbstractWe report on the effect of processing conditions on rheology, thermal and electrical properties of nanocomposites containing 0.02–0.3 wt % multiwall carbon nanotubes in an epoxy resin. The influence of the sonication, the surface functionalization during mixing, as well as the application of external magnetic field (EMF) throughout the curing process was examined. Rheological tests combined with optical microscopy visualization are proved as a very useful methodology to determine the optimal processing conditions for the preparation of the nanocomposites. The Raman spectra provide evidence for more pronounced effect on the functionalized with hardener compositions, particularly by curing upon application of EMF. Different chain morphology of CNTs is created depending of the preparation conditions, which induced different effects on the thermal and electrical properties of the nanocomposites. The thermal degradation peak is significantly shifted towards higher temperatures by increasing the nanotube content, this confirming that even the small amount of carbon nanotubes produces a strong barrier effect for the volatile products during the degradation. The ac conductivity measurements revealed lower values of the percolation threshold (pc) in the range of 0.03–0.05 wt %. CNTs for the nanocomposites produced by preliminary dispersing of nanotubes in the epoxy resin, compared to those prepared by preliminary functionalization of the nanotubes in the amine hardener. This is attributed to the higher viscosity and stronger interfacial interactions of the amine hardener/CNT dispersion which restricts the reorganization of the nanotubes. The application of the EMF does not influence the pc value but the dc conductivity values (σdc) of the nanocomposites increased at about one order of magnitude due to the development of the aforementioned chain structure. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011