Increase Of Carbon Nanotubes Concentration Research Articles

Removal of carboxylated multi-walled carbon nanotubes (MWCNT-COOH) from the environment by Trametes versicolor: a simple, cost-effective, and eco-friendly method

Nanotechnology has increased the release of nanoparticles into the environment, which poses a risk to human health and the ecosystem. Therefore, finding ways to eliminate these hazardous particles from the environment is crucial. This research studied the ability of Trametes versicolor fungi to remove carboxylated multi-walled carbon nanotubes. The study analyzed the impact of pH, MWCNT-COOH concentration, and initial fungal growth time on the removal process. The properties of the adsorbent were measured before and after the biosorption process using SEM, FTIR, and EDS techniques. The results showed that the live biomass of T. versicolor was more effective in removing nanoparticles than dead biomass at 30 °C and pH 7. An increase in carbon nanotube concentration from 5 to 20 mg. mL−1 decreased biosorption potential from 100% to 28.55 ± 1.7%. The study also found that an increase in initial fungal growth time led to higher biomass production and adsorption capacity, increasing biosorption ability for concentrations > 5mg. ml−1. The biosorption kinetics followed a pseudo-second-order model and corresponded most closely to the Freundlich isotherm model. The adsorption capacity of live fungal biomass to remove multi-walled carbon nanotubes was 945.17 mg. g−1, indicating that T. versicolor fungi have significant potential for removing carbon nanostructures from the environment.

Study on the kinetics of methane hydrate formation in the carbon microtube system

The current studies focused mostly on the promotion effects of nano-sized carbon nanotubes on hydrates, while the effect of carbon microtubes on the kinetics of methane hydrate formation is rarely mentioned. Therefore, this paper added 3–15 μm multi-walled carbon microtubes (MWCMTS) to a 4L autoclave (under the conditions of 3–6 MPa, and 0–5 ℃) to investigate the influence of the micron-medium concentration on the kinetics of hydrate formation. The results demonstrated that the addition of micro-carbon nanotubes could reduce the nucleation time of methane hydrate; a higher degree of subcooling could shorten the reaction time. Furthermore, the increase in carbon nanotube concentration could lead to higher gas storage capacity. Gas storage capacity was the highest at 32.4 V/V under the condition of 13:3 gas–liquid ratio; this rate was over 3 times larger than that of the pure water system. Micro-carbon nanotube-pure water system methane hydrate formation process was prone to the “platform period” phenomenon. However, this phenomenon would have on impact the final water conversion rate under the conditions of a sufficient driving force. Therefore, this study proved that carbon microtubes had an obvious effect on the promotion of methane hydrate formation and could be used as a cost-effective promoter.

Optical Properties of Cu2O Thin Films Impregnated with Carbon Nanotube (CNT)

This study investigates CNT-doped Cu2O thin film deposited by spray pyrolysis technique at a substrate temperature of 100°C. The samples were annealed at temperatures of 200°C and 230°C for 30 minutes. The effect of CNT doping on certain optical properties, such as extinction and absorption coefficients, a refractive index of doped Cu2O thin films were examined. The absorbance of the doped samples increases within the visible range and decreases in the ultraviolet range of the electromagnetic spectrum (EM). Both absorbance and extinction coefficients increased with temperature making the samples a good candidate for use as absorbance layer in device fabrication. In addition, there was an increase in direct bandgap with the increase in CNT concentration of the thin films. The result of the study revealed that CNT doping has a significant effect on the properties of Cu2O.

Hydration model for the OPC-CNT mixture: Theory and experiment

The experimental challenges in the application of spectroscopic techniques are resolved by using the theoretical tools. The material systems present in the ordinary Portland cement (OPC) are, for the first time, subjected to the density functional theory (DFT). A hydration model is constructed for the ordinary Portland cement (OPC) paste and its mixture with the carbon nanotubes (CNTs) by using theoretical and experimental Raman spectra. The model conceptualizes the water-cement interaction at the molecular level and contends the notion that the CNTs are chemically bonded to the silicates in the cement paste matrix. An agreement between the theoretical and the experimental Raman spectra verifies the model. The major material phases in the cement powder are of tri- and dicalcium silicates which interact with the water to form hydrated products such as the alite hydrate, the belite hydrate and the calcium silicate hydrate (C–S–H) with a chemical formula, CaH2O5Si−2. The Raman spectra from the CNT-cement paste mixture shows that the formation of the hydrated products does not depend on the concentration of CNTs. However, the defect density increases in the cement paste matrix with an increase of CNTs concentration.

Stability enhancement of MWCNT/water nanofluids using PVA surfactant

Nanofluids are prepared by dispersing MWCNT into aqueous polyvinyl alcohol (PVA) suspensions used as base fluids. This paper investigates the effectiveness of PVA as surfactant in stabilising MWCNT/water nanofluids. The stability of nanofluids is measured by Zetasizer Nano-ZS of only the stable samples. The morphology of carbon nanotube (CNT) and its interaction with PVA dispersant was analysed using SEM and in order to observe the dispersion characteristics of all samples, image analysis was carried out using TEM. The results demonstrated that zeta potential is affected by the concentration of CNT (0.01-0.1 wt.%). The zeta potential values (-19.96 mV to -33.3 mV) increased with an increase in CNT concentration. The SEM and TEM results showed that the amount of PVA added to each CNT concentration is sufficient to provide maximum stability to the CNT-water nanofluids, no excessive agglomerations or significant clusters of PVA are observed from the surface of CNT.

Fabrication and characterisation of low density polyethylene (LDPE)/multi walled carbon nanotubes (MWCNTs) nano-composites

Carbon nanotubes (CNT) have shown extraordinary electrical, mechanical properties as well as many other physical properties. The aim of this study is to explore the scope of CNT/LDPE nano-composites for engineering applications. Nano-composites of LDPE and MWCNT are generally prepared by using the melt blending method but in the present investigation these have been prepared by using solvent mixing method. Xylene has been used as a solvent which can dissolve low density polyethylene (LDPE) at about 125°C. The solution of LDPE in xylene has been ultrasonicated with various percentages of MWCNT (0, 1, 2, 5, 10wt% of MWCNT) composite to form thin film after drying. MWCNT used in this study have been synthesised by electric arc discharge method. Characteristics of these composites have been determined by Raman spectroscopy and scanning electron microscopy (SEM). Raman spectroscopy revealed variation in intensity of CNT's peak with variation in concentration of CNT. The results indicated that intensity of CNT's peak was found to increase with the increase in concentration of CNT which indicated the type of interaction between polymer and CNT. SEM analysis reveals CNT-polymer interfacial adhesion and shows agglomeration of CNT's at some locations and presence of individual tubes at other locations. These investigations show that LDPE/MWCNT composites can be fabricated using simple solvent mixing method. Further investigation on the effect of MWCNT on mechanical, electrical and thermal properties of LDPE based composites are in progress.

Electrical and dielectric behaviors of dry-mixed CNT/UHMWPE nanocomposites

Carbon nanotube (CNT)/ultrahigh-molecular weight polyethylene (UHMWPE) nanocomposite with an electrical percolation threshold of only 0.1 wt% was prepared by simple dry mixing followed by compression molding. The nanocomposite microstructure, direct current and alternating current (AC) electrical conductivities, conduction mechanisms, and dielectric properties in the 101–105 Hz frequency range have been investigated. Due to the localization of the nanofiller at the surface of UHMWPE powder particles, a segregated microstructure within the polymer matrix was created. Nanocomposites filled with 0.125–0.5 wt% CNT were found to follow the typical universal dynamic response behavior, and the characteristic frequency was found to increase with the increase in CNT concentration. At CNT concentration ≥ 0.5 wt%, the AC conductivity was found to be frequency independent over the entire frequency range studied.

Dispersion and its relation to carbon nanotube concentration in polyimide nanocomposites

Characterization of Carbon Nanotube (CNT) dispersion in a polyimide matrix and its effect on nanocomposite mechanical properties is presented in this paper. CNT bundle aspect ratio, measured by voltage-contrast scanning electron microscopy, is determined to be the quantitative measurement of dispersion and is found to decrease with increase in nanotube concentration. The reduction of CNT bundle aspect ratio with concentration is shown to explain the less effective reinforcement observed in composites as CNT concentration is increased beyond the electrical percolation concentration. It is shown that increase in CNT concentration beyond percolation concentration does not yield proportional improvement in elastic modulus because CNT aspect ratio systematically decreases as concentration increases. A modified Cox micromechanical model that accounts for the actual nanotube bundle aspect ratio as a function of concentration, nanotube waviness and orientation is shown to predict the observed nanocomposite elastic modulus dependence upon concentration.

Rheological Behavior of Carbon Nanotubes as an Additive on Lithium Grease

The rheological behaviors of carbon nanotubes (CNTs) as an additive on lithium grease at different concentrations were examined under various settings of shear rate, shear stress, and apparent viscosity. The results indicated that the optimum content of the CNTs was 2%. These experimental investigations were evaluated with a Brookfield Programmable Rheometer DV-III ULTRA. The results indicated that the shear, stress and apparent viscosity increase with the increase of CNTs concentration. The microstructure of CNTs and lithium grease was examined by high resolution transmission electron microscope (HRTEM) and scanning electron microscope (SEM). The results indicated that the microscopic structure of the lithium grease presents a more regular and homogeneous network structure, with long fibers, which confirms the rheological stability.

Investigation of Thermal Conductivity and Viscosity of Carbon Nanotubes–Ethylene Glycol Nanofluids

Conventional fluids used for heat transfer applications in automobiles limit the performance enhancement and compactness of the heat exchangers. These problems can be overcome by using the technology of nanofluids. The objectives of this work are to prepare nanofluids and to study their dynamic viscosity and thermal conductivity. Chemically treated carbon nanotubes (CNTs) were added with ethylene glycol (EG) and sonicated using a bath sonicator to have a homogeneous dispersion of CNTs in EG. In this study, the nanofluids were prepared with different concentrations of CNTs varying from 0.12 to 0.4 wt%. The dynamic viscosity of nanofluids was measured using a rheometer over a temperature range of 25°C to 60°C. It was observed that the viscosity of nanofluids decreases with an increase of temperature and enhances with CNT concentration. The nanofluid follows the characteristic behavior of Newtonian fluids. A linear rise in thermal conductivity of ethylene glycol was observed with an increase of CNT concentration. It is concluded that EG–CNT nanofluids are promising to meet the challenges required by automobile systems.

In vitro cytotoxicity of functionalized single walled carbon nanotubes for targeted gene delivery applications

Carbon nanotubes are a novel class of nanomaterials that have great potential in the field of biomedical research. This study investigates the cytotoxic effects of functionalized single walled carbon nanotubes (SWNTs) at different concentrations on a colon cancer cell line. Colorectal cancer cells were exposed to single walled carbon nanotubes functionalized with a green fluorescent protein expressing plasmid. The internalization of the nanotube-plasmid DNA complexes and their cytotoxicity were analyzed. The results indicate successful functionalization of the nanotubes and subsequent internalization of the nanotube-plasmid DNA complex by the cancer cells. The cytotoxicity was found to be significantly lower compared to a control. Cell viability was shown to have reduced with an increase in carbon nanotube concentration implying that SWNTs can be cytotoxic at higher dosages. The results show that SWNTs can be successfully used in gene delivery applications and their cytotoxic effects can be limited by optimizing the dosage levels.

Polyaniline/single-walled carbon nanotube composite electronic devices

Composites of high molecular weight polyaniline (PANI) and various weight percentages of single-walled carbon nanotubes (SWNT) were fabricated using solution processing. Electrical characteristics of metal–semiconductor (MS) devices fabricated from the PANI/SWNT composites were studied. Current–voltage ( I– V) characteristics of these devices indicate a significant increase in current with an increase in carbon nanotube concentration in the composite. The dominant transport mechanisms operating in these devices were investigated by plotting the forward I– V data on a log–log scale, which revealed two power-law regions with different exponents. In the lower voltage range, the exponent is approximately 1, implying that the charge transport mechanism is governed by Ohm's law. The charge transport mechanism in the higher voltage range, where the exponent varies between 1.1 and 1.7, is consistent with space-charge-limited (SCL) emission in the presence of shallow traps. The critical voltage ( V c), which characterizes the onset of SCL conduction, decreases with increasing SWNT concentration. In addition, V c was observed to increase with temperature. These initial results indicate that with further improvements in material consistency and reduction in defect densities, the polyaniline/single-walled carbon nanotube composite material can be used to fabricate organic electronic devices leading to many useful applications in microelectronics.

Electronic Device Fabricated From Polyaniline / Single walled Carbon Nanotubes Composite

AbstractComposites of high molecular weight polyaniline and single walled carbon nanotubes are investigated for applications to electronic devices. Electrical characteristics of devices fabricated using this composite show an order magnitude higher current level than those measured in the neat polyaniline devices. Composite materials and devices with various weight percentages of single walled carbon nanotubes were also fabricated. Current-voltage (I-V) characteristics of these devices indicate a significant increase in current with an increase in carbon nanotube concentration in the composite. Analysis of the forward I-V characteristics of these composite devices on a log-log scale shows two power law regions. In the lower voltage range, the exponent is 1, which is consistent with ohmic conduction, while in the higher voltage range, the exponent is between 1.1 and 1.5, which is consistent with space-charge-limited conduction.