Carbon Nanotube Blend Research Articles

Flexible Supercapacitors With Improved Energy Density Using OPBI-Coated Polyaniline- Carbon Nanotube Blends

Flexible Supercapacitors With Improved Energy Density Using OPBI-Coated Polyaniline- Carbon Nanotube Blends

Ignition Delay and Burning Rate Analysis of Diesel–Carbon Nanotube Blends Stabilized by a Surfactant: A Droplet-Scale Study

In this study, the effects of pristine carbon nanotubes (CNTs), sodium dodecylbenzene sulfonate (SDBS), and diesel blends on the ignition delay and burning rate are examined experimentally. For this purpose, single-droplet combustion tests were conducted in a combustion system for 21 days using CNTs at concentrations of 50 ppm and 100 ppm, which were dispersed in Colombian commercial diesel and stabilized by SDBS. Videos of the diesel droplet burning were obtained using a high-speed camera, and the Shadowgraph optical technique was used to observe the development of the droplet size during combustion. Thus, records of the process were collected, and the treatment was carried out using a MATLAB algorithm. The measurements and processing were carried out along with a stability study, which included measurements of dynamic light scattering (DLS), pH, potential Zeta, and properties such as thermal conductivity and surface tension. The results demonstrated that the temporal stability has a direct impact on the single-droplet combustion tests because a concentration of CNTs of 100 ppm showed a higher stability than those achieved by 50 ppm. Consequently, improvements were found with a concentration of 100 ppm—for instance, the thermal conductivity increased by about 20%, the ignition delay time increased by 16.2%, and the burning rate increased by 30.5%.

Organic compound gas detector based on polylactic acid/poly (styrene‐co‐acrylonitrile)/multi‐walled carbon nanotube blend composite with co‐continuous microstructure

AbstractA conductive polymer composite (CPC) based on polylactic acid (PLA)/poly (styrene‐co‐acrylonitrile) (SAN)/multi‐walled carbon nanotubes (MWNT) blend was prepared and used as a sensitive layer for detecting methanol, ethanol, toluene, and water vapor. The response behavior of polymer blend nanocomposite in comparison with PLA‐MWNT and SAN‐MWNT sensitive layers was studied as well as the influence of solution blending on the morphology, electrical behavior, and performance parameters of prepared sensitive layers. The scanning electron microscopy micrograph results showed that the PLA/SAN solution blended with a 50/50 wt% ratio had formed the co‐continuous morphology. In addition, the electrical conductivity investigation revealed that the percolation threshold of sensitive layers decreased from 1.5 vol%, related to PLA‐MWNT, to 0.8 vol%, related PLA/SAN blend nanocomposite. Thermodynamic investigation revealed that, in the solution blended conductive composites, MWNTs are preferentially localized in the PLA phase. The relative response (Rrel) of blended conductive composite, in comparison with PLA‐MWNT, was increased toward ethanol and toluene vapor while it was decreased against the methanol vapor. The sensitivity behavior of polymer blend composite was investigated based on the double percolated conductive network as well as the thermodynamic parameters such as Flory‐Huggins interaction parameter and solubility parameters.

Semiconducting carbon nanotubes in photovoltaic blends: The case of pTB7:PC60BM:(6,5) SWNT

Blends of carbon nanotubes with conjugated polymer and fullerene derivatives are complex nanocomposite systems, which have recently attracted great research interest for their photovoltaic ability. Therefore, gaining a better understanding of the excitonic dynamics in such materials can be important to boost the efficiency of excitonic solar cells. Here, we studied the photophysics of a ternary system in which the polymer PTB7 and the fullerene derivative PCBM are integrated with (6,5) single walled carbon nanotubes. We highlight the contribution of SWNTs in the exciton dissociation and in the charge transfer process. These findings can be useful for the exploitation of these multi-component systems for organic photovoltaic and, in general, optoelectronic applications.

Combustion characteristics, engine performances and emissions of a diesel engine using nanoparticle-diesel fuel blends with aluminium oxide, carbon nanotubes and silicon oxide

This research investigates the effect of nanoparticle-diesel fuel blends on combustion characteristics, performances and exhaust emissions of a four-stroke single-cylinder diesel engine. Three types of nanoparticles employed in this experiment were aluminium oxide, carbon nanotubes and silicon oxide. The nanoparticles were dispersed in a dosage of 25 ppm, 50 ppm and 100 ppm with pure diesel and were labelled as DA25, DA50, DA100 (aluminium oxide blends), DC25, DC50, DC100 (carbon nanotubes blends) and DS25, DS50, DS100 (silicon oxide blends). The ultraviolet-visible spectrophotometer analysis was done for 200 h to quantify the stability of the nanoparticle-diesel fuel blends. The blended fuels were experimentally tested with YANMAR TF120M diesel engine at engine loads of 0%, 25%, 50%, 75% and 100% at a constant 1800 rpm engine speed. The results revealed that the brake specific fuel consumption reduced by up to 19.8% and brake thermal efficiency enhanced by 18.8%. Silicon oxide blends show better results than aluminium oxide blends in many aspects, such as higher combustion pressure, lower brake specific fuel consumption and lower carbon monoxide emissions. Aluminium oxide and silicon oxide show stable blend conditions with 28.1% and 22.0% absorption ratio at 200 h sedimentation time, while carbon nanotube blends were least stable with absorption ratio reducing to less than 30% after 10 h. Combustion analysis of carbon nanotube blends with diesel show that carbon nanotubes have the potential to be further researched as an additive for diesel fuel due to significant combustion improvement in NOx emissions. However, the issue on the stability of carbon nanotube blends must be resolved before its potential can be fully utilized.

Tunable electrical conductivity of polystyrene/polyamide-6/carbon nanotube blend nanocomposites via control of morphology and nanofiller localization

The electrical conductivity and percolation behavior of polymer blend nanocomposites were investigated asa consequence of polymer-filler interaction and blend morphology. The nanocomposites were derived from melt compounding of carbon nanotubes (CNTs) in polystyrene (PS)/polyamide 6 (PA6) blends. The electrical conductivity of co-continuous PS/PA6 (50/50) blends remained constant in the semi-conductive region (6.75×10−8–1.50×10−7S·cm−1) over a wide range of CNT loading (0.5–3.5 phr). Nevertheless, (50/50) blends presented higher electrical conductivity than PA6/CNT nanocomposites with the same effective CNT concentration. Contrary to common intuitions, at high loadings of CNTs, higher electrical conductivity was observed for the blends wherein the CNT-rich PA6 phase was in the form of dispersed droplet morphology rather than co-continuous one. For instance, at the CNT loading of 3.5 phr, the conductivity of blend with PS/PA6 volume ratio of (90/10) is approximately 4 orders of magnitude higher than co-continuous (50/50) blend. This observation is attributed to a two-level percolation mechanism (primary and secondary), as verified by optical and transmission electron microscopy. The primary percolation occurs by selective localization of CNTs in PA6 droplets due to their thermodynamic affinity for the PA6 phase. Once the PA6 droplets are impregnated with CNTs, the excess CNTs (at high loadings) localize in the PS phase and act as effective electrical bridges for the highly conductive PA6 droplets (secondary percolation).

Fabrication of mediator-free hybrid nano-interfaced electrochemical biosensor for monitoring cancer cell proliferation

Glucose, a chief energy source in cellular metabolism, has a significant role in cell proliferation. Cancer cells utilize more glucose than normal cells to meet the energy demand arising due to their uncontrolled proliferation. The present work reports the development of a nano-interfaced amperometric biosensor for rapid and accurate monitoring of glucose utilization by cancer cells. A hybrid nano-interface comprising a blend of carbon nanotubes (CNTs) and graphene (GR) was employed to enhance the surface area of the working electrode and favour direct electron transfer. Glucose oxidase (GOx) immobilized on the interface serves as the sensing element due to its high selectivity and sensitivity towards glucose. Utilization of glucose was monitored at pre-determined time intervals in MiaPaCa-2 cancer cells. The results obtained from the amperometric technique were compared with the values obtained from a commercial glucometer. Alamar blue assay was performed to check the proliferation rate of the cells. A good correlation was obtained between the proliferation rate and glucose utilization. The designed biosensor was found to be unaffected by the presence of potential interferents and hence may serve as a novel in vitro tool to rapidly quantify the proliferation rates of cancer cells in response to different treatment strategies.

Thermal conductivity and stability of a three‐phase blend of carbon nanotubes, conductive polymer, and silver nanoparticles incorporated into polycarbonate nanocomposites

ABSTRACTMetallic and non‐metallic nanofillers can be used together in the design of polycarbonate (PC) nanocomposites with improved electrical properties. Here, the preparation of three‐phase blend (carbon nanotubes (CNT), silver nanoparticles, and conductive polymer) in a two‐step process before incorporation in the PC is reported. First, ethylene diamine functionalized multiwall carbon nanotubes (MWCNT‐EDA) were decorated with Ag nanoparticles. Next, the Ag‐decorated CNTs were coated with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT : PSS). Due to the high thermal conductivity instrinsic to both metallic and non‐metallic phases, it is expected that the thermal properties of the resulting nanocomposite would largely differ from those of pristine PC. We thus investigated in detail how this hybrid conductive blend affected properties such as the glass transition temperature, the thermal stability, and the thermal conductivity of the nanocomposite. It was found that this strategy results in improved thermal conductivity and thermal stability of the material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42281.

Progress on Carbon Nanotubes in Health Monitoring of Polymer Composites

Carbon nanotubes have a widely potential application in health monitoring of polymer composites due to the excellent electromechanical properties. Research advances in carbon nanotubes sensing in polymer composites are reviewed: carbon nanotubes filler, carbon nanotubes coated fiber, carbon nanotubes yarn and carbon nanotubes paper. This paper also focuses on the analysis of the common core principle of carbon nanotubes sensing,namely using carbon nanotubes sensing network to monitor structural strain injury. Carbon nanotubes paper can resolve problems such as the hard dispersion in the blending of carbon nanotubes and resin, the collaborative deformation of carbon nanotubes coated fiber and the whole structure monitoring of carbon nanotubes yarn. Carbon nanotubes paper provides the engineering application condition for carbon nanotubes sensing. The engineering application of carbon nanotubes sensing in health monitoring of polymer composites is the future research direction.

Wearable and sensitive heart-rate detectors based on PbS quantum dot and multiwalled carbon nanotube blend film

Wearable and sensitive photodetectors (PDs) have been demonstrated based on a blend film of PbS quantum dots (QDs) and QDs modified multiwalled carbon nanotubes (MWCNTs). Owing to the synergetic effect from high light sensitivity of PbS QDs and excellent conductive and mechanical properties of MWCNTs, the blend PDs show high sensitivity and flexibility performance: device responsivity and detectivity reach 583 mA/W and 3.25 × 1012 Jones, respectively, and could stand large number (at least 10 000 cycles) and wide angle (up to 80°) bending. Furthermore, the wearable and sensitive PDs have been applied to measure the heart rate in both red and near infrared (NIR) ranges. The presented PDs are expected to work as sensor candidates in integrated electronic skin.

Effects of carbon nanotube and conducting polymer coated microelectrodes on single-unit recordings in vitro.

Neuronal networks cultured on microelectrode arrays (MEAs) have been utilized as biosensors that can detect all or nothing extracellular action potentials, or spikes. Coating the microelectrodes with carbon nanotubes (CNTs), either pristine or conjugated with a conductive polymer, has been previously reported to improve extracellular recordings presumably via reduction in microelectrode impedance. The goal of this work was to examine the basis of such improvement in vitro. Every other microelectrode of in vitro MEAs was electrochemically modified with either conducting polymer, poly-3,4-ethylenedioxythiophene (PEDOT) or a blend of CNT and PEDOT. Mouse cortical tissue was dissociated and cultured on the MEAs to form functional neuronal networks. The performance of the modified and unmodified microelectrodes was evaluated by activity measures such as spike rate, spike amplitude, burst duration and burst rate. We observed that the yield, defined as percentage of microelectrodes with neuronal activity, was significantly higher by 55% for modified microelectrodes compared to the unmodified sites. However, the spike rate and burst parameters were similar for modified and unmodified microelectrodes suggesting that neuronal networks were not physiologically altered by presence of PEDOT or PEDOT-CNT. Our observations from immunocytochemistry indicated that neuronal cells were more abundant in proximity to modified microelectrodes.

Light-Controlled Resistance Modulation in a Photochromic Diarylethene–Carbon Nanotube Blend

Photochromic molecules are part of a large class of materials in which light stimulus not only induces a color variation but also affects other physicochemical properties. However, the change of bulk electrical properties (e.g., electrical conductivity) via light excitation remains difficult to control because the intrinsically switchable molecules may lose their functionality when wired with conductive electrodes. In contrast with previous work based on single molecules, here we demonstrate a facile and accessible “wet-chemical” method to produce light-induced electrical switching. The electrical conductivity of a photochromic blend composed of diarylethene polymer and single-walled carbon nanotubes (SWNTs) is reversibly tuned according with UV–vis excitation. The devices present good thermal stability and remarkable fatigue resistance under ambient conditions. Supported by electrical and spectroscopic evidence, we show that the intertube electrical coupling, mediated by the light-induced electrocyclization of the diarylethene unit, is the mechanism responsible for the modulation.

Platinum-sputtered electrode based on blend of carbon nanotubes and carbon black for polymer electrolyte fuel cell

A novel Pt-sputtered electrode based on a blend layer of carbon black (CB) and carbon nanotubes (CNTs) is developed for polymer electrolyte fuel cells. The Pt is sputtered on the surface of the blend to form a catalyst layer. The CNTs generate a pore in the blend layer, and the CB provides a high surface roughness for the blend layer. At a CNT content of 50 wt.%, the maximum value (20.6 m 2 g −1) for the electrochemical area of the Pt is obtained, which indicates that the surface area of the blend layer exposed for Pt deposition is the largest. The power density of a membrane-electrode assembly (MEA) employing the Pt-sputtered electrodes shows a linear increase with electrochemical area. The mass activity of the optimized Pt-sputtered electrode with a Pt loading of 0.05 mg cm −2 is 8.1 times that of an electrode with a Pt loading of 0.5 mg cm −2 prepared using a conventional screen-printing technique. Excellent mass transfer is obtained with the Pt-sputtered electrode.

Crystalinity Properties of Carbon Nanotube-Polyvinylidene Fluoride Composites

AbstractSingle-wall and multi-wall carbon nanotube blends (0 to 0.5 vol% ) with polyvinylidene fluoride (PVDF) have been prepared using solution cast method and characterized. By acid treatment, it has been observed that nanotube has been well functionalized and uniformly dispersed into the polymer. X-ray diffraction analysis coupled with differential scanning calorimetry (DSC) has revealed that carbon nanotube alters the crystallinity of PVDF and thereby enhances the β-phase in PVDF. Experimental results have demonstrated that enhancement of β-phase is a function of carbon nanotube concentration.

Shear-induced conductor-insulator transition in melt-mixed polypropylene-carbon nanotube dispersions

The blending of carbon nanotubes (CNTs) into polymer matrices leads to intrinsically nonequilibrium materials whose properties can depend strongly on flow history. We have constructed a rheodielectric spectrometer that allows for the simultaneous in situ measurement of both the electrical conductivity $\ensuremath{\sigma}(\ensuremath{\omega})$ and dielectric constant $\ensuremath{\epsilon}(\ensuremath{\omega})$ as a function of frequency $\ensuremath{\omega}$, as well as basic rheological properties (viscosity, normal stresses), as part of an effort to better characterize how flow alters the properties of these complex fluids. Measurements of $\ensuremath{\sigma}$ indicate a conductor-insulator transition in melt-mixed dispersions of multiwall CNTs in polypropylene over a narrow range of CNT concentrations that is reasonably described by the generalized effective medium theory. A conductor-insulator transition in $\ensuremath{\sigma}$ can also be induced by shearing the fluid at a fixed CNT concentration $\ensuremath{\phi}$ near, but above, the zero shear CNT conductivity percolation threshold ${\ensuremath{\phi}}_{c}$. We find that the shear-induced conductor-insulator transition has its origin in the shear-rate dependence of ${\ensuremath{\phi}}_{c}$, which conforms well to a model introduced to describe this effect. Surprisingly, $\ensuremath{\sigma}$ of these nonequilibrium materials fully recovers at these elevated temperatures upon cessation of flow. We also find that the frequency dependence of $\ensuremath{\sigma}(\ensuremath{\omega})$ follows a ``universal'' scaling relation observed for many other disordered materials.

Rheological and dynamic-mechanical behavior of carbon nanotube/vinyl ester–polyester suspensions and their nanocomposites

Rheological properties of vinyl ester–polyester resin suspensions containing various amounts (0.05, 0.1 and 0.3 wt.%) of multi walled carbon nanotubes (MWCNT) with and without amine functional groups (–NH 2) were investigated by utilization of oscillatory rheometer with parallel plate geometry. Dispersion of corresponding carbon nanotubes within the resin blend was accomplished employing high shear mixing technique (3-roll milling). Based on the dynamic viscoelastic measurements, it was observed that at 0.3 wt.% of CNT loadings, storage modulus ( G′) values of suspensions containing MWCNTs and MWCNT–NH 2 exhibited frequency-independent pseudo solid like behavior especially at lower frequencies. Moreover, the loss modulus ( G″) values of the resin suspensions with respect to frequency were observed to increase with an increase in contents of CNTs within the resin blend. In addition, steady shear viscosity measurements implied that at each given loading rate, the resin suspensions demonstrated shear thinning behavior regardless of amine functional groups, while the neat resin blend was almost the Newtonian fluid. Furthermore, dynamic mechanical behavior of the nanocomposites achieved by polymerizing the resin blend suspensions with MWCNTs and MWCNT–NH 2 was investigated through dynamic mechanical thermal analyzer (DMTA). It was revealed that storage modulus ( E′) and the loss modulus ( E″) values of the resulting nanocomposites increased with regard to carbon nanotubes incorporated into the resin blend. In addition, at each given loading rate, nanocomposites containing MWCNT–NH 2 possessed larger loss and storage modulus values as well as higher glass transition temperatures ( T g) as compared to those with MWCNTs. These findings were attributed to evidences for contribution of amine functional groups to chemical interactions at the interface between CNTs and the resin blend matrix. Transmission electron microscopy (TEM) studies performed on the cured resin samples approved that the dispersion state of carbon nanotubes with and without amine functional groups within the matrix resin blend was adequate. This implies that 3-roll milling process described herein is very appropriate technique for blending of carbon nanotubes with a liquid thermoset resin to manufacture nanocomposites with enhanced final properties.

Electrospun Nanofiber of Nylon 610/Multi-Walled Carbon Nanotube Composites

Multi-walled carbon nanotubes (MWNTs) were incorporated in electrospun Nylon 610 fibers. The MWNTs used were synthesized by a thermal CVD method. To eliminate metallic catalyst residues in as synthesized MWNTs, they were treated in HNO3 and HCl. The potential adhesion between the MWNTs and Nylon 610 was expected by the interaction between the amide group of Nylon 610 and the oxygen-containing species on the MWNTs such as carboxylic acid group introduced during the purification step. Contrary to the previous works on electrospinning using a simple blend of carbon nanotubes with polymeric materials, we incorporated MWNTs as nanoscale fillers by in-situ interfacial polymerization. We also investigated morphology of the electrospun Nylon 610 fibers with MWNTs.

Electrically conductive yarns based on PVA/carbon nanotubes

Electrically conductive yarns from carbon nanotubes (CNTs) and polyvinyl alcohol (PVA) were prepared by two different methods, wet-spinning and coating processes. For the wet-spinning process, the CNTs/PVA mixed solution was extruded into a coagulant bath which contained high concentration coagulating agent. The coating process was carried out on five common fibers, including natural fibers and synthetic fibers, by using a blend of CNTs and PVA. Then, the conductive yarns were treated by an acetylization process in order to decrease the solubility of PVA to water. Their conductivity and the mechanical property were investigated. Additionally, the influence of acidic hydrolysis by strong acids used for the acetylization process on mechanical properties of the materials was investigated.

Polymer–nanotube composites for transparent, conducting thin films

Highly conductive, highly transparent thin films have been fabricated from polymer–single walled carbon nanotube blends. Using poly-3,4-ethylenedioxythiophene doped with poly(styrenesulfonate) as a host material, excellent dispersion of single wall nanotubes could be achieved enhancing the conductivity with relatively low loadings <3 wt%. Raman spectroscopy indicates that there is little bundling of the single wall nanotubes in the matrix and that the nanotubes are sensitive to residual stress within the film. As the host bulk conductivity is increased, enhancements of the overall composite conductivity are observed to be proportional. These results suggest that the energy barrier to nanotube–nanotube carrier hopping within the matrix can be modified in accordance with a heterogeneous conduction model.

Filler blend of carbon nanotubes and organoclays with improved char as a new flame retardant system for polymers and cable applications

Multi wall carbon nanotubes (MWCNTs) or single wall carbon nanotubes (SWCNTs) were used as fillers in polyethylene (PE). Only MWCNTs reduced the heat release rates caused by polymer degradation. MWCNTs can be more effective in heat release reduction than organoclays. The char generated by the filler blend 'MWCNTs and organoclays' as a synergistic flame retardant system in an ethylene vinylacetate (EVA) based polymer blend was improved compared with the char generated by the only organoclay based nanocomposite. Initial results indicated that there was a strengthening effect of the char by MWCNTs. The synergistic improvement for heat release reduction by a blend of the two fillers 'MWCNTs and organoclays' was used for the development of a flame retardant cable compound. 1.5 kg of MWCNTs was compounded on a Buss ko-kneader to generate 60 kg of a nanocomposite based on the filler blend. The flame retardant properties of insulated wires made either by the filler blend or by 'classical' organoclays were measured.