Characterization Of Multi-walled Carbon Nanotubes Research Articles

Multi-Walled Carbon Nanotube Functionalization by Radical Addition Using Hydroxymethylene Groups.

Synthetic methodology and characterization of multi-walled carbon nanotubes (MWCNTs) function- alized with hydroxymethylene groups are reported. The MWCNTs were synthesized by the spray pyrolysis technique using toluene as carbon source and ferrocene as catalyst. Hydroxymethylation of MWCNTs was carried out by methanol using benzoyl peroxide (BPO) at different quantities (300 to 900 mg); the optimum BPO quantity was 300 mg. The resulting materials were characterized by FT-IR, Raman Spectroscopy, Thermal Gravimetric Analysis (TGA) and Transmission Electron Microscopy (TEM). The presence of the hydroxymethylene group on the MWCNTs surface was demonstrated by FT-IR, Raman Spectroscopy, TGA, EDS, TEM and Mass Spectrometry. The func- tionalized MWCNTs were not damaged by this methodology.

Preface to the tenth volume of Express Polymer Letters

The editorial of the first issue of the tenth volume provides a short review of the results and statistics of the previous years. 931 articles were published in the past 9 years, a mere 16% of the submitted ones. 84% was rejected, although a part of them contained results of the acceptable high quality, but we strove to select only cutting edge topics. This is reflected in the fact that about 60% of the articles published in eXPRESS Polymer Letters has been downloaded at least 1000 times, which means that these topics attracted the attention of our readers. The download statistics are also reflected in the number of citations. The most downloaded article is Starch-based completely biodegradable polymer materials (DOI: 10.3144/expresspolymlett.2009.46), with about 11000 downloads. The most cited article in the Web of Science (WoS) is The present status and key problems of carbon nanotube based polymer composites (DOI: 10.3144/expresspolymlett.2007.39), which has already 178 citations. Further seven articles have more than ten citations per annum with the following titles: Self healing in polymers and polymer composites. Concepts, realization and outlook: A review (DOI: 10.3144/expresspolymlett.2008.29); Advances in synthetic optically active condensation polymers – A review (DOI: 10.3144/expresspolymlett. 2011.15); Dielectric relaxations in PVDF/BaTiO3 nanocomposites (DOI: 10.3144/expresspolymlett. 2008.35); Raman spectroscopic characterization of multiwall carbon nanotubes and of composites (DOI: 10.3144/expresspolymlett.2012.63); How carbon nanotubes affect the cure kinetics and glass transition temperature of their epoxy composites? – A review (DOI: 10.3144/expresspolymlett.2009.73); Multi-walled carbon nanotube filled polypropylene nanocomposites based on masterbatch route: Improvement of dispersion and mechanical properties through PP-g-MA addition (DOI: 10.3144/ expresspolymlett.2008.87); Crystallization kinetics of poly(lactic acid)-talc composites (DOI: 10.3144/ expresspolymlett.2011.84). The journals which cite the articles of eXPRESS Polymer Letters most frequently are Polymer, Journal of Applied Polymer Science and Macromolecules. The h-index of eXPRESS Polymer Letters in WoS is 37, the present impact factor is 2.761. This indicator is being presently fiercely attacked but we consider it important as it is still one of the most important evaluation tools of scientific journals. Impact factor is a helpful compass for the young scientist generation to evaluate the relative rank and quality of various journals. Otherwise, there would be no quality-related orientation where to send their manuscripts. Additionally, nowadays the internet is full of ‘predator’ journals having titles, appearance and websites which resemble those of high quality journals with good impact factors, and WoS can help to exclude these journals. When launching the 10th volume of eXPRESS Polymer Letters I wish all authors, readers and referees a successful new year and achievement of highly cited research results. Sincerely yours,

Dispersion Characteristics of Multi-Walled Carbon Nanotubes with Gallic Acid.

Dispersions of multi-walled carbon nanotubes (MW-CNTs) assisted by non-covalent surface modification and covalent surface modification were prepared using different concentration of gallic acid aqueous solution. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the dispersion states and effect of MWNTs. FTIR results demonstrate that concentration of gallic acid has great effect on the surface modification of multi-walled carbon nanotubes. With the content of gallic acid increasing, modification effect were firstly increased and then decreased in that the optimal concentration is about 10 μg/ml as it is its solubility in water. SEM and TEM results also show that gallic acid not only can ensure the integrity of the MW-CNTs, but also can purify it. These results confirmed achievement of a good dispersion state and effect of MW-CNTs with gallic acid. The dispersion mechanism of non-covalent surface modification and covalent surface modification was analyzed.

Aerosol generation and characterization of multi-walled carbon nanotubes exposed to cells cultured at the air-liquid interface.

Aerosol generation and characterization are critical components in the assessment of the inhalation hazards of engineered nanomaterials (NMs). An extensive review was conducted on aerosol generation and exposure apparatus as part of an international expert workshop convened to discuss the design of an in vitro testing strategy to assess pulmonary toxicity following exposure to aerosolized particles. More specifically, this workshop focused on the design of an in vitro method to predict the development of pulmonary fibrosis in humans following exposure to multi-walled carbon nanotubes (MWCNTs). Aerosol generators, for dry or liquid particle suspension aerosolization, and exposure chambers, including both commercially available systems and those developed by independent researchers, were evaluated. Additionally, characterization methods that can be used and the time points at which characterization can be conducted in order to interpret in vitro exposure results were assessed. Summarized below is the information presented and discussed regarding the relevance of various aerosol generation and characterization techniques specific to aerosolized MWCNTs exposed to cells cultured at the air-liquid interface (ALI). The generation of MWCNT aerosols relevant to human exposures and their characterization throughout exposure in an ALI system is critical for extrapolation of in vitro results to toxicological outcomes in humans.

Heat transfer, pressure drop and fouling studies of multi-walled carbon nanotube nano-fluids inside a plate heat exchanger

This work presents the results of an experimental research on the heat transfer and pressure drop characteristics of multi-walled carbon nanotube (MWCNT), aqueous nano-fluids inside a plate heat exchanger (PHE), with the consideration of fouling formation of carbon nanotubes (CNTs). Influence of operating parameters such as flow rate (700<Re<25,000), volumetric concentration of nano-fluids (vol.%=0.5–1.5), inlet temperature of nano-fluid (Tin=50–70°C) on the overall heat transfer coefficient and pressure drop was experimentally investigated. Results demonstrated that the heat transfer coefficient could be intensified, when flow rate and concentration of nano-particles increase. In addition, increase of temperature of inlet flow can cause a slight increase in heat transfer coefficient. In terms of pressure drop, it was seen that with increasing the flow rate and mass concentration of nano-fluids, pressure drop was intensified such that for flow rate, enhancement rate was significant, while for concentration, a small penalty was registered. Although MWCNT/water nano-fluids presented higher pressure drop and friction factor in comparison with the base fluid, they provided better overall thermal performance in comparison with the base fluid. For long-operating condition, significant fouling resistance was also measured, which was amplified by increasing the volumetric concentration of nano-fluids. A none-linear fouling behavior over the extended time was registered for nano-fluids and for the decrease of heat transfer coefficient as well.

Characterization of multiwalled carbon nanotube filled, palm‐oil‐based polyalkyds: Effects of loading and in situ reaction

ABSTRACTIn this study, the contribution of multiwalled carbon nanotubes (MWCNTs) was studied for the evaluation of the performances of polyalkyd‐based films produced from dehydrated palm oil. Initially, different percentages of MWCNTs, including 0.5, 1.0, and 1.5 wt %, were considered for loading into the resin with the help of sonication. Additionally, a 1.0 wt % loading was considered for in situ conditions during the esterification process to achieve better dispersion and obtain improved properties of the film. The loading was evaluated by different performance tests, such as those of tensile, elongation, pencil hardness, swelling ratio, gel content, wettability, chemical resistivity, adhesion, and surface morphology. The results of mechanical testing showed that the addition of 1.0 wt % MWCNTs enhanced the tensile strength by 50%, whereas in situ conditions were found to be favorable for significantly improving the tensile strength by 75%. Moreover, the wettability, surface morphology, and thermal properties were also found to be in favor of in situ conditions for the dispersion of the MWCNTs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42934.

Characteristics of multi-walled carbon nanotube toughened ZrB2–SiC ceramic composite prepared by hot pressing

Monolithic zirconium diboride ceramic as well as ZrB2–20vol% SiC and ZrB2–20vol% SiC–10vol% carbon nanotube ceramic matrix composites were hot pressed at 1850°C for 60min under 20MPa. The effects of adding carbon nanotubes on the densification process, microstructural development, and mechanical properties of ZrB2–SiC were investigated. The results showed that the relative density and the mean ZrB2 grain size in the final microstructure did not change significantly by adding 10vol% carbon nanotube to the ZrB2–20vol% SiC composite. Compared to the monolithic ZrB2, the grain growth was effectively stopped when the composite was reinforced by SiC and was doped with carbon nanotubes. Indentation fracture toughness of the carbon nanotube reinforced sample was measured about 5.1MPam½, which is meaningfully higher than those of unreinforced ceramics. The remaining nanotubes in the final microstructure also led to the activation of some toughening mechanisms such as carbon nanotubes pull out and crack deflections. On the other hand, the Vickers hardness value (8.6GPa) decreased due to the presence of carbon nanotubes as a soft reinforcement phase.

Carbon nanotubes versus polyaniline nanoparticles; which transducer offers more opportunities for designing a stable solid contact ion-selective electrode

Sensors that exploit the unique properties of nanomaterials establish the most rapidly growing sensor research area. Remarkable achievements in nanotechnology and ion selective electrodes (ISEs) lead to explore a wide variety of approaches that develop completely calibration-free ISEs. This work offers construction and comparative evaluation of the performance characteristics of multiwall-carbon nanotubes (CNTs) and polyaniline nanoparticles (PANI) as ion-to-electron transducers between an ionophore-doped PVC membrane and glassy carbon electrodes. With respect to the previously published reports, the current comparison was performed side by side under similar experimental conditions and hence the advantages and shortcomings of each transducer nanoparticles were directly highlighted in light of ISE figures of merit. Apparently, the inclusion of CNTs and PANI nanoparticles added more stability to the electrical signal due to their excellent electronic and chemical properties. Moreover, the fast ion-to-electron transduction allows obtaining short response times and the hydrophobic behavior avoids the formation of water layers at the electrode/membrane interface. These results enabled the production of a series of SC-ISEs with improved piece-to-piece reproducibility where the potential was stable over 60 and 45days with drift of 0.8mVh−1 and 0.7mVh−1 for CNT and PANI based sensors, respectively. The electrodes were utilized for determination of buspirone as a model pharmaceutical drug.

Heat Transfer and Pressure Drop Characteristics of Nanofluid Flows Inside Corrugated Tubes

An experimental investigation is carried out to study the heat transfer and pressure drop characteristics of multiwalled carbon nanotubes (MWCNTs)/heat transfer oil nanofluid flows inside horizontal corrugated tubes under uniform wall temperature condition. To provide the applied nanafluids, MWCNTs are dispersed in heat transfer oil with mass concentrations of 0.05, 0.1, and 0.2 wt%. The Reynolds number varies between 100 and 4,000. Three tubes with hydraulic diameters of 11.9, 13.2, and 15.5 mm are applied as the test section in the experimental setup. Tubes are corrugated four times on the cross section; that is, there are four different helices around the tube. Depths of the corrugations are chosen as 0.9, 1.1, and 1.3 mm, and pitch of corrugation is 14 mm. The acquired data confirm the increase of heat transfer rate as a result of utilizing nanofluids in comparison with the base fluid flow. However, corrugating the tubes decreases the heat transfer rate at low Reynolds numbers. The highest increase in heat transfer rate is observed for the Reynolds numbers for which the smooth tube is in the transition regime and the corrugated tube reaches the turbulent flow, that is, Reynolds number in the range of 1,000 to 3,000. Rough correlations are proposed to predict the Nusselt number and friction factor.

Dispersion Characteristics of Multi-Walled Carbon Nanotubes and Carbon Nanoflakes with Oxygen Plasma

Dispersion Characteristics of Multi-Walled Carbon Nanotubes and Carbon Nanoflakes with Oxygen Plasma

Designing Of MWCNT/ Ferrofluid/ Flyash Multiphase Composite As Safeguard For Electromagnetic Radiation

Utilization of flyash which is produced at large scale in coal based thermal power plant is a challenge. In this regard, our investigation provides distinctive way of utilizing flyash for designing and preparing high-performance EMI shielding materials. Herein, we report synthesis and characterization of multiwalled carbon nanotubes (MWCNT) based multiphase composites. The multiphase composites were synthesized by in-situ co-precipitation with conductive filler (MWCNT) and magnetic filler (Ferrofluid). Scanning electron microscopy results confirm the presence of fly ash particles covered with Ferrofluid nanoparticles along with MWCNTs. Multiphase composites show total shielding effectiveness of 48 dB (>99.998 % attenuation) in the Ku-band (12.4–18 GHz) frequency range. The electromagnetic attributes, dielectric and permeability parameters have been calculated from the measured scattering parameters (S11, S22, S12, S21) using the Nicolson–Ross–Weir algorithm. The synthesized multiphase composites were characterized using XRD, FTIR, VSM and SEM. The results suggested that the MPC composites showed great potential as a radar absorbing material.

Removal of methyl orange by multiwall carbon nanotube accelerated by ultrasound devise: Optimized experimental design

This study investigates the methyl orange (MO) removal from aqueous solution through the application of ultrasound onto multiwalled carbon nanotubes (MWCNTs). Characterization of MWCNT was carried out using scanning electron microscopy (SEM) and tunneling electron microscopy (TEM). The influences of various parameters on the removal percentage were studied and optimized by a central composite design (CCD) and response surface methodology (RSM). Results indicate that a small amount of proposed adsorbent (0.025g) is responsible for successful removal of 15mgL−1 of MO (RE>99%) in a short time (3.4min) and pH of 1–2. Adsorption kinetic data are fitted well with pseudo second order model. Equilibrium data followed Langmuir isotherm model with maximum adsorption capacity of 53.76mgg−1.

Characterization of multi-walled carbon nanotubes and application for Ni2+ adsorption from aqueous solutions

Multi-walled carbon nanotubes (MWCNTs) were used to remove Νi2+ from aqueous solutions. Batch experiments performed to examine the effects of initial Νi2+ solution concentrations, pH, and contact time on Νi2+ sorption process. MWCNTs were characterized by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, micro-Raman spectroscopy, thermogravimetric analysis, and specific surface area (BET) techniques. The tested MWCNTs exhibit purity >95%, average diameter 20–30 nm, and specific surface area >150 m2/g. The results showed that 60–95% of Ni2+ was absorbed depending on the initial solution concentrations. As it is suggested by the distribution coefficient (kd) values, increased initial Νi2+ solution concentrations resulted to lower Νi2+ adsorption intensity onto MWCNTs, while the total amount of Ni2+ that removed from the equilibrating solutions increased. The adsorption of nickel onto MWCNTs was significantly affected by the solution pH; higher Ni2+ adsorption was observed at pH > 6.0. According to the contact time experiments, the sorption process reached equilibrium at 60 min. This study suggests that MWCNTs can be utilized for the removal of nickel ions from aqueous solutions and that they can be a promising candidate adsorbent for environmental applications and wastewater treatment.

Thermo-mechanical characterization of multi-walled carbon nanotube reinforced polycarbonate composites: A molecular dynamics approach

The present study aims at examining the mechanical properties of multi-walled carbon nanotubes–polycarbonate composites (MWCNT–PC), through a molecular dynamics (MD) simulation. Composites of MWCNT–PC were modeled using Materials Studio 5.5 software. Multiwall carbon nanotubes (MWCNTs) compositions in polycarbonate (PC) were varied by weight from 0.5% to 10% and also by volume from 2% to 16%. Forcite module in Materials Studio was used for finding mechanical properties. A marked increase in the elastic modulus (up to 89%) has been observed, even with the addition of a small quantity (up to 2 weight %) of MWCNTs. Also, upon addition of about 2 volume % of MWCNTs, the elastic modulus increases by almost 10%. The increase in mechanical properties is found to supplement earlier experimental investigations of these composites using nano-indentation techniques. Better load transfer property of MWCNTs, larger surface area and interaction between reinforcement with base matrix are the suggested reasons for this increase in mechanical properties.

Electrical and morphological characterization of multiwalled carbon nanotubes functionalized via the Bingel reaction

Covalent sidewall functionalization of multiwalled carbon nanotubes (MWCNTs) has been performed using two approaches, direct and indirect cycloaddition through diethyl malonate, based on the Bingel reaction. The results revealed that functionalized MWCNTs demonstrated enhanced electrical properties and significantly lower sheet resistance, especially after electric field thermal assisted annealing at 80°C was performed. The presence of 1,3-dicarbonyl compounds caused the surface of MWCNTs to be more hydrophilic, approachable for the electrolyte and improved the capacitance performance of Au/MWCNTs electrodes. The modified MWCNTs have been incorporated into nanocomposites by using solution mixing method with polyaniline and drop-casting resulting mixture on the paper substrate. The reduction in the sheet resistance with increasing the content of MWCNTs in the prepared nanocomposite films has been achieved.

Effect of microstructure and morphological properties of carbon nanotubes on the length reduction during melt processing

Abstract Length of multi-walled carbon nanotube (MWCNT) has strong impact on mechanical strength of MWCNT/polymer composite. In this paper, MWCNT/polyamide 6, 6 (PA 66) composites using ten different MWCNTs were prepared by melt processing. The harsh mixing process used to achieve a fine dispersion of MWCNTs in the polymer matrix broke and severely reduced the lengths of the MWCNTs. The characteristics of MWCNTs that influence the breakage and length reduction were systematically and experimentally explored. Insights into designing the microstructures and morphological properties of pristine MWCNTs were provided, based on the correlation data and statistical evaluation results, in an effort to preserve the high aspect ratio of the MWCNTs during the melt mixing process, thereby expecting the enhanced mechanical properties of the composite.

Preparation and characterization of multi-walled carbon nanotubes impregnated with polyethyleneimine for carbon dioxide capture

In this work, multi-walled carbon nanotubes impregnated with polyethyleneimine (MWCNT/PEI) have been prepared by wet-impregnation method with various PEI loadings for CO2 capture. The surface features and morphology were observed by scanning electron microscopy (SEM) and the textural properties were analyzed by N2/77 K adsorption–desorption isotherms. The CO2 adsorption capacity was evaluated by thermogravimetric analysis (TGA) method at 15% CO2 partial pressure. The MWCNT/PEI exhibited higher CO2 adsorption capacity than pristine MWCNTs. This result suggested that amine groups were attached on carbon surfaces in the impregnation process, leaving CO2 affinity sites on MWCNT surfaces. MWCNT/PEI exhibited superior cycle stability for CO2 capture, indicating great potential for application in post-combustion technology.

Preparation and Characterization of Multiwall Carbon Nanotube (MWCNT) Reinforced Chitosan Nanocomposites: Effect of Gamma Radiation

Nanocomposites of biodegradable chitosan and multiwalled carbon nanotubes (MWCNTs) were prepared using two kinds of MWCNTs, i.e., pristine multiwalled carbon nanotubes (p-MWCNTs) and carboxyl-functionalized multiwalled carbon nanotubes (f-MWCNTs). The nanocomposites were subjected to gamma irradiation (60Co) at different intensities (1–50 kGy), and the variation of different physicomechanical properties has been extensively studied. Various techniques such as Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), optical microscopy (OM), thermogravimetric analysis (TGA), differential scanning colorimetry (DSC), and universal testing machine (UTM) were used to investigate the physicochemical, morphological, and thermomechanical properties of the nanocomposites. FTIR spectra and OM confirmed that oxygen-containing functional groups were present on the surface of the tubes that helped better dispersion of f-MWCNTs in chitosan solution. The experimental results demonstrated that the tensile strength (TS) and modulus (TM) of nanocomposites were increased by 57 and 48 %, respectively, through the addition of 1 % MWCNTs with the chitosan matrix; however, no significant changes of TS and TM are observed for more MWCNTs (above 1 %) in the composites. Considering the effect of irradiation doses, it was observed that low irradiation doses (up to 10 kGy) significantly increases thermal stability and tensile properties of the nanocomposite compared with the nonirradiated samples.

Effect of Chemical Treatment on Multi-Walled Carbon Nanotubes/Epoxy Composite

Multi-walled carbon nanotubes (MWCNT) was first treated by concentrated H2SO4/HNO3, and then epoxy (EP) was filled with as-received and acid treated MWCNT. Fourier transform infrared spectroscopy (FT-IR) was used to analyze the surface characteristics of MWCNT. Result of electrical conductivity analysis reveals that the surface treatment could affect the formation of conductive network. Dynamical mechanical analysis indicates that the loss factor of composite was impaired by the incorporation of acid treated MWCNT. The tensile strength was increased with the increasing content of acid treated MWCNT.

Analysis of the Electrochemical Performance of Ptni/MWCNT in Alkaline Media

It is well known that the outstanding properties and characteristics of multi-walled carbon nanotubes (MWCNT) make them attractive materials for diverse applications. For electrocatalytic systems, MWCNT are being exhaustively studied all over the world, and it is been corroborated that this type of materials are appropriate to be used as support of metallic nanoparticles, having a synergistic effect in the electroactivity. However, it has been found also that the MWCNT characteristics as quality (graphitization grade) and purity (amount of amorphous carbon) have a direct influence on the metal anchorage, the electrocatalytic activity as well as the stability. On the other hand, Pt-Ni system is attracting the attention in recent years for its application as PEM fuel cell electrode. The addition of a non-noble metal (Ni in this case) could decrease the cost of the electrocatalyst as well as improve the performance. The research group involved in the present work has been working during years in the design and synthesis of PtNi/MWCNT electrocatalysts using homemade MWCNT of high quality and purity, and analyzing their performance in acidic media for the application in PEM fuel cells. The obtained results are interesting and promising, high activities have been achieved as well as good stability. Nevertheless, in order to diversify the applications, as well as have a complete understanding of the PtNi/MWCNT systems, studies in alkaline media are necessary. Hence, the aim of this paper was to study the electrochemical performance in alkaline media of PtNi/MWCNT homemade electrocatalysts towards the PEM fuel cell reactions. In order to achieve this goal, the studies were performed in a conventional three electrodes cell, using a glassy carbon rod as working electrode, a Pt wire as counter electrode, a Ag/AgCl (KCl Sat) electrode as reference, and 1M NaOH solution as electrolyte. The interesting results obtained as well as the discussion will be presented at the conference. Acknowledgments: Authors recognize the support to FOMIX-QRoo under grant no. QR00-2011-001-174895