Industrial Grade Multiwalled Carbon Nanotubes Research Articles

SCILL-SILP hybrid catalytic system by employing carbon nanotubes as a support for the selective oxidation of ethylbenzene to acetophenone

Hydrocarbon oxidation to more valuable products is one of the most crucial industrial petrochemical processes. To improve efficiency, economic effectiveness, and reduction of waste production by conventional processes, the development of active and selective catalysts is still an important area of research. To cope with these challenges, we developed a catalytic system that utilized molecular oxygen to oxidize ethylbenzene (EB) to acetophenone (AcPO). The catalyst was prepared by coating a thin layer of a mixture of selected ionic liquid 1-ethyl-3-methylimidazolium octylsulfate and N-hydroxyphthalimide over industrial-grade multiwalled carbon nanotubes functionalized with copper(II) ions. This unique catalyst represented a hybrid catalytic system via the combination of solid catalyst with an ionic liquid layer (SCILL) and a supported ionic liquid phase (SILP) system. The oxidation reactions were performed at 80 °C and 0.1 MPa for 6 h. SCILL-SILP hybrid catalytic system exhibited exceptional performance with ∼27 % EB conversion and ∼77 % AcPO selectivity. The recyclability and reusability of the prepared catalysts were also investigated. The copper content was determined using inductively coupled plasma mass spectrometry (ICP-MS). Scanning electron microscopy (SEM) and transmission electron microscopy(TEM)were used to study the morphologies of the catalysts. Energy dispersive spectroscopy (EDS) was used to detect the immobilized copper on the functionalized CNTs while N2 physisorption analysis was employed to study the textural properties of the catalysts. Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to study the freshly synthesized and recycled catalysts.

On the thermal and thermodynamic analysis of parabolic trough collector technology using industrial-grade MWCNT based nanofluid

The thermal and thermodynamic performance of parabolic trough solar collector (PTC) could be enhanced by using nanofluids due to their enhanced thermophysical properties. In this work, numerical and experimental investigations were carried out to study the effect of suspended industrial-grade multi-walled carbon nanotubes (MWCNTs) in distilled water (DW) for low to medium temperature PTCs. Stable nanofluids were prepared at various volume concentration of 0.05%, 0.1%, and 0.3%. Moreover, a one-dimensional numerical model is developed to investigate the optical and thermo-hydraulic performance of the commercial IST-PTC at different locations in the United Arab Emirates (UAE). The results of simulations show that Abu Dhabi is the best location with the highest annual thermal efficiency of 49.52%. Also, the suspension of MWCNTs nanoparticles in water results in an improvement of Nusselt number by 12%, 16%, and 21% for nanoparticle concentrations of 0.05%, 0.1%, and 0.3%, respectively. The impact of inlet temperature and flow rate are also investigated, and a thermodynamic analysis is carried out to study the entropy generation. The use of nanofluid at low concentrations could enhance the thermo-hydraulic performance for flow rates lower than 0.2 L/s, while nanoparticles concentration should be increased at higher flow rates for better heat transfer. • Stable industrial grade MWCNT/DW nanofluid are prepared and characterized. • Abu Dhabi is the most suitable location in UAE for PTC technology. • Nusselt number is enhanced by up to 21% for 0.3% nanoparticle loading. • Thermo-hydraulic performance enhanced for flow rates below 0.2L/s. • Adding nanoparticle concentrations is needed for higher flow rates.

Fabrication of all-solid-state textile supercapacitors based on industrial-grade multi-walled carbon nanotubes for enhanced energy storage

Textile supercapacitors (TESCs) are an emerging energy storage solution to power smart gadgets integrated on clothes. Herein, efficient solid-state TESCs with different active areas (2–8 cm2) were produced based on cotton fabrics coated with industrial grade multi-walled carbon nanotubes (MWCNTs) as electrodes and a safe polyelectrolyte. The textile electrodes were fabricated by an optimized eco-friendly scalable dip-pad-dry process. The lowest electrical resistance (2.62 Ω cm−2) and most uniform coating of the electrodes were achieved using 10 mg mL−1 CNTs dispersion and 8 dip-pad-dry steps. The TESCs exhibited a specific capacitance of 8.01 F g−1 (9.18 F cm−2) and high cyclability (5000 cycles). The energy and power densities were tuned by changing the electrode area: the largest TESC presented the highest energy density of 6.30 Wh kg−1, which was 14× higher than those of other EDLC-type carbon-based TESCs reported in the literature; the smallest TESC presented the highest power density of 2.72 kW kg−1, being 49× higher than the values reported for comparable systems. Finally, a sensor was powered for 47 min by coupling two TESCs in series (14 cm2). This work demonstrated the ability to produce efficient TESCs using industrial grade MWCNTs by processes implemented in the Textile Industry, boosting technological transfer for high-tech applications.

Performance assessment of linear Fresnel solar reflector using MWCNTs/DW nanofluids

In this study industrial grade Multi-walled carbon nanotubes (MWCNTs) nanoparticles dispersed in distilled water (DW) are investigated to evaluate its impact on the thermal behavior of linear Fresnel solar reflector technology. The stability and thermophysical properties of the MWCNTs/DW nanofluids are obtained experimentally. Stable nanofluids that showed higher thermal conductivity compared to DW were obtained. Thermal conductivity (TC) of the nanofluids increased by 3%, 6% and 7% for the volume fractions of 0.05%, 0.1% and 0.3% at 25 °C, respectively. TC also increased with the increase in temperature (i.e. 11% for 0.3% volume fraction at 70 °C). A one-dimensional model is developed to evaluate the transient behavior of the nanofluid within the linear solar reflector. Matlab code based on the finite difference method is developed to solve the energy balance equations at the different components of the studied solar collector. The numerical model is then validated with experimental results, where a maximum experimental thermal efficiency of 29.205% at 14:00 is achieved. MWCNTs/DW nanofluid with 0.3% volume fraction has the highest thermal efficiency of 33.81% and the highest PEC value as well as the lowest entropy generation.

Evaluating industrial grade functionalized multiwalled carbon nanotubes by X-ray photoelectron spectroscopy

Utilization of carbon nanotubes in various applications is a function of their dispersion in respective matrix which effectively depends on the functionalization employed. Functional group distribution on Carbon Nanotube surface is usually a complex mixture of groups depending on the oxidizing agent employed. In this regard, nine varieties of Industrial grade multiwalled carbon nanotubes belonging to 10–30, 20–40 and 50–80 nm outer diameter ranges but differing in functionality (carboxyl and hydroxyl) were analyzed. X-ray photoelectron spectroscopy was employed to quantify the different functionalities on pristine, hydroxyl and carboxyl functionalized multiwalled carbon nanotubes and high-resolution transmission electron microscopy was used to image the internal structure including the side wall damage in functionalized varieties. X-ray photoelectron spectroscopy measurements on nine batches have suggested the presence of carbonyl, carboxyl and hydroxyl functional groups on all multiwalled carbon nanotubes in different proportions. This implies that it is not possible to have exclusive hydroxyl or carboxyl functionalization on a CNT surface Additionally, comparison is drawn between already existing deconvolution procedures from literature.

A wide potential window symmetric supercapacitor by TEMPO functionalized MWCNTs

In this paper, we report a simple and effective method to functionalize industrial-grade multi-walled carbon nanotubes (MWCNTs) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), via oxidation of MWCNTS and followed by carbodiimide coupling of amino-TEMPO. The effective coupling is confirmed and studied by EPR, HRTEM, BET, XPS, FTIR, TGA and XRD techniques. Electrochemical studies reveal the capacitive enhancement of MWCNTs-TEMPO, where MWCNTs-TEMPO shows capacitance value (66 F g−1 at 0.25 A g−1) that is 5-times higher than that of industrial grade MWCNTs (13.5 F g−1 at 0.25 A g−1). This can be due to the reversible redox reaction of nitroxide radicals on TEMPO that contributes to pseudocapacitance. A symmetrical supercapacitor is assembled with MWCNTs-TEMPO as electrode material and optimized with wide operating voltage (2 V) to produce high energy density of 26.6 Wh kg−1 with high stability (90% capacitance retention over 4000 cycles). The findings propose a facile approach to modify industrial grade MWCNTs as the electrode materials in supercapacitors.

Coating carbon nanotubes with humic acid using an eco-friendly mechanochemical method: Application for Cu(II) ions removal from water and aquatic ecotoxicity

In this work, industrial grade multi-walled carbon nanotubes (MWCNT) were coated with humic acid (HA) for the first time by means of a milling process, which can be considered an eco-friendly mechanochemical method to prepare materials and composites. The HA-MWCNT hybrid material was characterized by atomic force microscopy (AFM), scanning electron microscopies (SEM and STEM), X-ray photoelectron spectroscopy (XPS), termogravimetric analysis (TGA), and Raman spectroscopy. STEM and AFM images demonstrated that the MWCNTs were efficiently coated by the humic acid, thus leading to an increase of 20% in the oxygen content at the nanotube surface as observed by the XPS data. After the milling process, the carbon nanotubes were shortened as unveiled by SEM images and the values of ID/IG intensity ratio increased due to shortening of the nanotubes and increasing in the number defects at the graphitic structure of carbon nanotubes walls. The analysis of TGA data showed that the quantity of the organic matter of HA on the nanotube surface was 25%. The HA coating was responsible to favor the dispersion of MWCNTs in ultrapure water (i.e. −42mV, zeta-potential value) and to improve their capacity for copper removal. HA-MWCNTs hybrid material adsorbed 2.5 times more Cu(II) ions than oxidized MWCNTs with HNO3, thus evidencing that it is a very efficient adsorbent material for removing copper ions from reconstituted water. The HA-MWCNTs hybrid material did not show acute ecotoxicity to the tested aquatic model organisms (Hydra attenuata, Daphnia magna, and Danio rerio embryos) up to the highest concentration evaluated (10mgL−1). The results allowed concluding that the mechanochemical method is effective to coat carbon nanotubes with humic acid, thus generating a functional hybrid material with low aquatic toxicity and great potential to be applied in environmental nanotechnologies such as the removal of heavy metal ions from water.

Preparation and characterization of high-performance wood polymer nanocomposites using multi-walled carbon nanotubes

Effect of industrial grade multi-walled carbon nanotubes on mechanical, decay, and thermal properties of wood polymer nanocomposites was investigated. To meet this objective, pine wood flour, polypropylene with and without coupling agent (maleic anhydride grafted polypropylene), and multi-walled carbon nanotube (0, 1, 3, 5 wt%) were compounded in a twin screw co-rotating extruder. The mass ratio of the wood flour to polypropylene was 50/50 (w/w) in all compounds. Test specimens were produced using injection molding machine from the pellets. The flexural and tensile properties, biological durability, and thermal analysis (thermogravimetric analysis and differential scanning calorimetry) of the nanocomposites were investigated. The flexural and tensile properties of the wood polymer nanocomposites increased with increasing content of the industrial grade multi-walled carbon nanotubes (from 1 to 5 wt%) and maleic anhydride grafted polypropylene (3 wt%). The mass loss rates of the wood polymer nanocomposites decreased with increasing amounts of the maleic anhydride grafted polypropylene and industrial grade multi-walled carbon nanotube. The differential scanning calorimetry analysis showed that the melt crystallization enthalpies of the wood polymer nanocomposites increased with increasing amount of the industrial grade multi-walled carbon nanotubes. The increase in the Tc indicated that the industrial grade multi-walled carbon nanotubes were the efficient nucleating agent for the wood polymer nanocomposites.

Carbon Dioxide Capture with Polyethylenimine-Functionalized Industrial-Grade Multiwalled Carbon Nanotubes

Industrial grade multiwalled carbon nanotubes (IG-MWCNTs) were functionalized with polyethylenimines (PEIs) for CO2 capture from simulated flue gas. Ethylenediamine end-capped PEI (PEI-EC) impregnated IG-MWCNTs was found to exhibit a significantly higher adsorption capacity than other branched PEIs impregnated IG-MWCNTs. The PEI-EC impregnated IG-MWCNTs were characterized with various experimental methods including N2 adsorption/desorption isotherms, X-ray diffraction, and thermogravimetric analysis. The CO2 adsorption behavior of the PEI-EC impregnated IG-MWCNTs is influenced by PEI loading and adsorption temperature. The PEI-EC impregnated IG-MWCNTs exhibit a CO2 adsorption capacity as high as 2.538 mmol/g at 343 K, and can be completely regenerated higher than 403 K. The CO2 adsorption/desorption kinetics of the PEI-EC impregnated IG-MWCNTs was investigated with Avrami’s fractional order kinetic model. The activation energy of the CO2 adsorption/desorption was calculated from Arrhenius equation and use...

Enhanced Tolerance to Flue Gas Contaminants on Carbon Dioxide Capture Using Amine-Functionalized Multiwalled Carbon Nanotubes

The adsorption behavior of adsorbents for carbon dioxide can be significantly affected by flue gas contaminants. In this work, we examined the performance of tetraethylenepentamine (TEPA) impregnated industrial grade multiwalled carbon nanotubes (IG-MWCNTs) in trace amounts of flue gas contaminants such as H2O, NO, and SO2. It was observed that H2O and NO had a minimal impact on CO2 adsorption capacity, while the effect of SO2 on CO2 adsorption was influenced by adsorption temperature and SO2 concentration. Compared with silica-based adsorbents, i.e., TEPA-impregnated MCM-41, amine-functionalized IG-MWCNTs show significantly better tolerance to H2O and SO2. In addition, we examined the variation of CO2 adsorption with and without SO2 with various experimental methods (N2 adsorption/desorption isotherms, X-ray diffraction, and differential scanning calorimetry analysis) and molecular simulation. Experimental results show that irreversible sulfate/sulphite species deposited into the adsorbent contributes to the decrease on CO2 adsorption, while the results from simulation studies reveal that the enthalpy difference between the isolated TEPA with SO2 and TEPA···SO2 (ΔH(TEPA···SO2)) is larger than that of CO2 (ΔH(TEPA···CO2)), indicating that SO2 has a stronger reaction activity with TEPA than CO2. The increase of the ratio of ΔH(TEPA···SO2)/ΔH(TEPA···CO2) with increasing temperature illustrates that the difference of CO2 adsorption capacity with and without SO2 increases with elevated temperatures.

Kinetics Studies of CO2 Adsorption/Desorption on Amine-Functionalized Multiwalled Carbon Nanotubes

The adsorption/desorption kinetics of carbon dioxide on tetraethylenepentamine (TEPA) impregnated industrial grade multiwalled carbon nanotubes (IG-MWCNTs) was investigated to obtain insight into the underlying mechanisms on the fixed bed. After evaluating four kinetic models for CO2 adsorption at various adsorption temperatures, CO2 partial pressure, and amine loadings, it was found that Avrami’s fractional-order kinetic model provided the best fitting for the adsorption behavior of CO2. In order to find the optimal regeneration method, three desorption methods were evaluated for the regeneration of solid sorbents. The activation energy Ea of CO2 adsorption/desorption was calculated from Arrhenius equation and used to evaluate the performance of the adsorbent. The Ea decreased with increasing CO2 concentration, indicating that CO2 adsorption of amine-functionalized IG-MWCNTs is possibly intraparticle controlled. Meanwhile, because of the energy input of a vacuum pump, Ea for the vacuum swing regeneration...

Amine-functionalized low-cost industrial grade multi-walled carbon nanotubes for the capture of carbon dioxide

Industrial grade multi-walled carbon nanotubes (IG-MWCNTs) are a low-cost substitute for commercially purified multi-walled carbon nanotubes (P-MWCNTs). In this work, IG-MWCNTs were functionalized with tetraethylenepentamine (TEPA) for CO2 capture. The TEPA impregnated IG-MWCNTs were characterized with various experimental methods including N2 adsorption/desorption isotherms, elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. Both the adsorption isotherms of IG-MWCNTs-n and the isosteric heats of different adsorption capacities were obtained from experiments. TEPA impregnated IG-MWCNTs were also shown to have high CO2 adsorption capacity comparable to that of TEPA impregnated P-MWCNTs. The adsorption capacity of IG-MWCNTs based adsorbents was in the range of 2.145 to 3.088 mmol/g, depending on adsorption temperatures. Having the advantages of low-cost and high adsorption capacity, TEPA impregnated IG-MWCNTs seem to be a promising adsorbent for CO2 capture from flue gas.

Properties of normal-strength concrete and mortar with multi-walled carbon nanotubes

This investigation studied the strength and performance of cementitious materials, such as concrete and mortar, with multi-walled carbon nanotubes (MWNTs). One hundred cylindrical specimens 10 cm in diameter and 20 cm in height were used to investigate strength variation and changes in the durability of concrete and mortar as a function of the weight percent (0∼1·5 wt%) of MWNTs and the effectiveness of a dispersion method that used a sodium naphthalene sulfonate formaldehyde solution. Industrial-grade MWNTs (purity: >90%, diameter: >50 nm) were used for the test. Ball milling with 1·5 wt% MWNT was processed for 7 h, followed by a dilution process with 0·25, 0·5, 0·75, 1·0, 1·25 and 1·5 wt% dispersive solutions. Ultrasonication treatments were then applied to each diluted solution for 20 min. Compressive strength, splitting tensile strength, permeability, electrical conductivity and the relative dynamic modulus of the concrete cylinders were tested under a 24 MPa mix design by increasing the wt% MWNT using standard ASTM guidelines. In parallel, MWNT mortar tests were performed for compressive strength, flexural bending and shrinkage with 50 prismatic specimens (4 × 4 × 16 cm in size).

Polyetherimide/Bucky Gels Nanocomposites with Superior Conductivity and Thermal Stability

Polyetherimide (PEI) nanocomposites comprising bucky gels of industrial-grade multiwalled carbon nanotubes (MWCNTs) and ionic liquid (IL, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM][PF6])) were prepared. The processing framework for this nanocomposite is simple, reproducible, and easily scalable. The strong interaction between IL and MWCNTs caused the latter to uniformly disperse in the PEI matrix while IL flowed into the gaps between the nanotubes' walls. The nanocomposite exhibited an enhanced conductivity of 2.01 × 10(4) Ω·cm volume resistivity at room temperature; the value decreased dramatically by 12 orders of magnitude, compared to pristine PEI. The IL free ions and MWCNTs networks provided excellent channels for electron transfer. PEI/bucky gels nanocomposites also showed improved thermal stability and high tensile strength. Other than having antiwear properties, this material can have numerous applications in the aerospace and electronics industries. Moreover, our work presents a "green" method toward modified nanocomposites industrial production as IL is environmentally safe and is easily recyclable.

Temperature effects on the nitric acid oxidation of industrial grade multiwalled carbon nanotubes

In this study, we report an oxidative treatment of multiwalled carbon nanotubes (MWCNTs) by using nitric acid at different temperatures (25–175 °C). The analyzed materials have diameters varying from 10 to 40 nm and majority lengths between 3 and 6 μm. The characterization results obtained by different techniques (e.g., field emission scanning electron microscopy, thermogravimetric analysis, energy-filtered transmission electron microscopy, Braunauer, Emmet and Teller method, ζ-potential and confocal Raman spectroscopy) allowed us to access the effects of temperature treatment on the relevant physico-chemical properties of the MWCNTs samples studied in view of an integrated perspective to use these samples in a bio-toxicological context. Analytical microbalance measurements were used to access the purity of samples (metallic residue) after thermogravimetric analysis. Confocal Raman spectroscopy measurements were used to evaluate the density of structural defects created on the surface of the tubes due to the oxidation process by using 2D Raman image. Finally, we have demonstrated that temperature is an important parameter in the generation of oxidation debris (a byproduct which has not been properly taken into account in the literature) in the industrial grade MWCNTs studied after nitric acid purification and functionalization.

Carbon nanotubes enhanced the lead toxicity on the freshwater fish

Carbon nanotubes are promising nanostructures for many applications in materials industry and biotechnology. However, it is mandatory to evaluate their toxicity and environmental implications. We evaluated nitric acid treated multiwalled carbon nanotubes (HNO3-MWCNT) toxicity in Nile tilapia (Oreochromis niloticus) and also the lead (Pb) toxicity modulation after the nanotube interaction. Industrial grade multiwalled carbon nanotubes [Ctube 100, CNT Co. Ltd] were treated with 9M HNO3 for 12h at 150°C to generate oxygenated groups on the nanotube surface, to improve water dispersion and heavy metal interaction. The HNO3-treated multiwalled carbon nanotubes were physico-chemically characterized by several techniques [e.g. TEM, FE-SEM, TGA, ζ-potential and Raman spectroscopy]. HNO3-MWCNT did not show toxicity on Nile tilapia when the concentration ranged from 0.1 to 3.0 mg/L, and the maximum exposure time was 96h. After 24, 48, 72 and 96h the LC50 values of Pb were 1.65, 1.32, 1.10 and 0.99 mg/L, respectively. To evaluate the Pb-nanotube interaction influence on the ecotoxicity, we submitted the Nile tilapia to different concentrations of Pb mixed with a non-toxic concentration of HNO3-MWCNT (1.0 mg/L). After 24, 48, 72, 96 h the LC50 values of Pb plus nanotubes were: 0.32, 0.25, 0.20, 0.18 mg/L, respectively. These values showed a synergistic effect after Pb-nanotube interaction since Pb toxicity increased over five times. X-ray energy dispersive spectroscopy (EDS) was used to confirm lead adsorption on the carbon nanotube oxidized surface. The exposure of Nile tilapia to Pb plus HNO3-MWCNT caused both oxygen consumption and ammonium excretion decrease, when compared to the control. Finally, our results show that carbon nanotubes interact with classical pollutants drawing attention to the environmental implications.

An empirical equation for electrical resistivity of thermoplastic polymer/multi-walled carbon nanotube composites

Industrial grade multi-walled carbon nanotubes (Nanocyl 7000) were incorporated into various thermoplastic polymers, such as polyamide 6, polyamide 11, polyamide 12, high-density polyethylene, polypropylene and polycarbonate, by a simple melt mixing process. An empirical equation has been fit to electrical measurements obtained by several experiments. The proposed empirical equation fit all of the experimental data above the percolation threshold concentration very well, and it has been proven that each parameter of the empirical equation has a strong correlation with the state of dispersion of the carbon nanotubes. Furthermore, for the first time, the Hansen solubility parameter has been used to predict compatibility between carbon nanotubes and thermoplastic polymers, and the predicted result strongly resembles data obtained in several other reports.

Synthesis of Multiwalled Carbon Nanotubes on Fly Ash Derived Catalysts

Carbon nanotubes (CNTs) are an allotrope of carbon with unique properties that make them potentially useful in a vast range of applications. However, CNTs are predominantly produced using expensive and/or nonrecyclable catalyst supports, e.g., mesoporous silica and alumina. In this work, coal combustion fly ash, a bulk waste product with limited uses, was impregnated with iron nitrate and successfully used as a substrate to produce industrial grade multiwalled carbon nanotubes (MWNTs) by fluidized bed chemical vapor deposition. CNTs were analyzed using thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The most successful catalyst trialed at 650 degrees C using ethylene as a carbon source was a 5 wt % Fe fly ash catalyst, which produced a CNT yield in respect to metal loading of approximately 82.5%. The MWNTs had outer diameters of between 12 and 20 nm with a reasonable degree of wall graphitization (I(G)/I(D) of 1.17). Advantages of utilizing fly ash as a catalyst support are its availability at low cost at the megaton scale, its high thermal stability, and suitability for use in industrial fluidized bed reactors. Potential applications for the fly ash produced CNTs include use in composite materials.