Interaction of oxygen functionalized multi-walled carbon nanotube nanofluids with copper

We investigate the influence of an applied electric field on the separation of a water-ethanol solution inside a carbon nanotube (CNT) using a series of molecular dynamics simulations. The electric field is applied at an angle θ with respect to the axis of the CNT. The study uncovers that with the application of a 'small-angle' electric field (e.g. smaller θ), the water molecules exhibit preferential occupancy inside the CNT, whereas the application of the same electric field at a 'wide-angle' mode (e.g. higher θ) fills the CNT with ethanol molecules in place of water. Remarkably, the direction of the electric field plays a pivotal role because the field exerts a contrasting influence on the behaviours of the water and ethanol molecules. The water dipoles are favourably aligned at small values of θ creating an ordered water structure inside the CNT. Increasing θ disrupts the water dipole orientation and leads to the preferential occupancy of the CNT by ethanol molecules. An in-depth analysis on the simulated systems unveil that, at lower values of θ, multiple layers of water molecules are physically adsorbed near the CNT walls, which is found to diminish as θ is increased. In comparison, at higher magnitudes of θ, the ethanol molecules are preferentially adsorbed inside the CNT. The average interaction energy per ethanol (water) molecule is found to increase (reduce) when θ is monotonically increased, which can be ascribed to the increase (decrease) in the intermolecular hydrogen bonding capacity of the ethanol (water) molecules at larger values of θ. Consequently, inside the CNT, the average occupancy of water molecules decreases and ethanol molecules increases, as θ is monotonically increased, leading to the separation of the ethanol-water mixture. The proposed methodology can convert an equimolar mixture (1 : 1) of ethanol-water into a concentrated one (14 : 1) when the electric field is applied orthogonal to the axis of the CNT. The separation efficiency is found to improve with an increase in the intensity of the externally applied electric field.

A new application of carbon nanotubes nanofluid as working fluid of low-temperature direct absorption solar collector

8 - π-Stacking, conjugated, polymer-supported carbon nanotubes (CNTs) composite materials for light-emitting diode (LED) application

Carbon nanotubes (CNTs) are widely used in drug delivery systems (DDSs) due to their unique chemical and physical properties. Investigation of interactions between biomolecules and CNTs is an interesting and important subject in biological applications. In this study, we used molecular dynamics (MD) simulation to investigate the adsorption mechanism of the anticancer drug paclitaxel (PTX) on pristine and functionalized CNTs (f-CNT) in aqueous solutions. Our theoretical results show that PTX can be adsorbed on sidewalls of CNT in different methods. In the case of f-CNTs, PTX can be adsorbed on the functional groups due to the existence of polar interactions. These interactions in the CNT functionalized with polyethylene glycol (PEG), are more than the other investigated systems. Furthermore, it was found that the solubility of CNTs in aqueous solution is increased by functionalization. This is related to the intermolecular hydrogen bonds between functional groups and solvent molecules. The PEG group has the greatest effect on the solubility of the CNT in aqueous solution due to more polar interactions.

Synthesis and characterization of polytetrafluoroethylene/oleic acid-functionalized carbon nanotubes composite membrane for desalination by vacuum membrane distillation

Carbon nanotubes (CNTs) and magnetic nanoparticles (MNPs) are amalgamated to produce a new type of sensing ink. The combined properties of CNTs and MNPs also justify their use as additives in composite materials. These developments open new windows for nanotechnology applications. This chapter elucidates the methods of synthesizing MNPs, using them to functionalize and chaperone CNTs, and the capabilities of these MNP-CNT conjugates. Section 2.1 provides a general introduction to CNTs (Section 2.1.1) and MNPs (Section 2.1.2). Different ways of functionalizing CNTs are discussed in Section 2.2. The process of covalent functionalization of CNTs when co-precipitated MNPs are attached to the surfaces of nanotubes is explained in Section 2.3, including a detailed methodology (Section 2.3.1) and the formulation of a magnetoresponsive and electrically conductive ink (Section 2.3.2). Different methods of noncovalent functionalization of CNTs are discussed in Section 2.4 with an emphasis on electroless plating of CNTs (Section 2.4.1), entanglement of MNPs with CNTs (Section 2.4.3), and an example of how to print sensors (Section 2.4.4). Endohedral functionalization of CNTs is described in Section 2.5 with future perspectives elucidated in Section 2.6.

Effect of amide-functionalized carbon nanotubes as commercial diesel and palm-oil biodiesel additives on the ignition delay: A study on droplet scale

Chapter 6 - Carbon nanotubes and other carbon nanomaterials: Prospects for functionalization

Adsorption of uranyl ions from its aqueous solution by functionalized carbon nanotubes: A molecular dynamics simulation study

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2012. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. The conclusions are as follows : (1) The research works on thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and valves, fuel cells and power plants, ground-coupled heat pumps, and general heat and mass transfer systems. Research issues are mainly focused on new and renewable energy systems, such as fuel cells, ocean thermal energy conversion power plants, and ground-coupled heat pump systems. (2) Research works on the heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, and industrial heat exchangers. Researches on heat transfer characteristics included the results for natural convection in a square enclosure with two hot circular cylinders, non-uniform grooved tube considering tube expansion, single-tube annular baffle system, broadcasting LED light with ion wind generator, mechanical property and microstructure of SA213 P92 boiler pipe steel, and flat plate using multiple tripping wires. In the area of pool boiling and condensing heat transfer, researches on the design of a micro-channel heat exchanger for a heat pump, numerical simulation of a heat pump evaporator considering the pressure drop in the distributor and capillary tubes, critical heat flux on a thermoexcel-E enhanced surface, and the performance of a fin-and-tube condenser with non-uniform air distribution and different tube types were actively carried out. In the area of industrial heat exchangers, researches on a plate heat exchanger type dehumidifier, fin-tube heat exchanger, an electric circuit transient analogy model in a vertical closed loop ground heat exchanger, heat transfer characteristics of a double skin window for plant factory, a regenerative heat exchanger depending on its porous structure, and various types of plate heat exchangers were performed. (3) In the field of refrigeration, various studies were executed to improve refrigeration system performance, and to evaluate the applicability of alternative refrigerants and new components. Various topics were presented in the area of refrigeration cycle. Research issues mainly focused on the enhancement of the system performance. In the alternative refrigerant area, studies on CO2, R32/R152a mixture, and R1234yf were performed. Studies on the design and performance analysis of various compressors and evaporator were executed. (4) In building mechanical system research fields, twenty-nine studies were conducted to achieve effective design of mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, renewable energy systems, and lighting systems in buildings. New designs and performance tests using numerical methods and experiments provide useful information and key data, which can improve the energy efficiency of buildings. (5) In the fields of the architectural environment, studies for various purposes, such as indoor environment, building energy, and renewable energy were performed. In particular, building energy-related researches and renewable energy systems have been mainly studied, reflecting interests in global climate change, and efforts to reduce building energy consumption by government and architectural specialists. In addition, many researches have been conducted regarding indoor environments.

In heat exchangers, heat transfer between the cold and the hot fluid consumes pumping power. Evaluating the energy efficiency of this process scientifically and quantitatively is an urgent issue for both academic research and industrial applications, and has important significance to energy saving and emission reduction. We comprehensively analyzed the flow and heat transfer characteristics of water-water heat transfer process without phase-change in a heat exchanger, and proposed the energy efficiency index (= k / N p n , k is overall heat transfer coefficient and N p is flow pressure gradient). EEI reflects the inherent energy efficiency properties of a heat exchanger, which represents the overall heat transfer coefficient per equivalent flow pressure drop consumption. At a given temperature difference and fluid flow rate, for the heat exchangers with the same heat transfer area and fluid flow length, bigger EEI means a lager heat transfer rate per equivalent pumping power consumption. EEI is independent on the heat transfer area; no dependence or weak dependence on the flow velocity can be achieved by choosing the index n reasonably, indicating a good stability of EEI . Evaluation result based on national standard of heat exchanger performance test measured could represent the energy efficiency of the heat exchanger. Combined with the water-water heat transfer process without phase-change flow and heat transfer performance database of the plate heat exchangers, the value of index n and the overall EEI distribution of plate heat exchangers in industry are obtained, providing a basis for the classification of the energy efficiency of plate heat exchangers.

Industrial hydrodesulfurization method has not been efficient for removal of dibenzothiophene (DBT) from petroleum distillates. Therefore, in this current study, adsorptive desulfurization (investigated in batch mode) was carried out using functionalized carbon nanotubes (FCNTs) to reduce the amount of DBT in a model diesel. Different techniques, such as, scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX), were used to check the morphological structure and the elemental compositions of the adsorbent; Fourier transmission infrared (FTIR) was used to check the chemical functionalities of the adsorbent; and nitrogen physisorption at 77K was used to check the surface area, pore size, and pore volume of the adsorbent. The results show that the FCNTs outperformed the non-functionalized carbon nanotubes (CNTs) during the desulfurization by about 10%, indicating the functionalization did improve the desulfurization performance of the CNTs. The % removal of DBT by the FCNTs and CNTs was 70.48 and 60.88%, respectively. It can be concluded that the acid treatment of CNTs enhanced its surface affinity for DBT, thus contributing to the improved adsorption performance of the adsorbent. The isotherm results show that Freundlich isotherm model described well the mechanism of the adsorption process for both CNTs and FCNTs. In addition, pseudo second-order kinetics describes the behavior of the adsorbents during the adsorption process. The results obtained in this study therefore show that functionalized CNTs could be efficient and potential adsorbent for removal of DBT in petroleum distillate (e.g., diesel), to meet up with the stringent policies regarding emission of sulfur oxides.

The ecology and general public health are badly impacted by the prolonged usage of chemical fertilizers. Applying carbon-based nanomaterials is one of the best options available for accelerating plant growth while reducing harm to the environment. The current study aims to assess the effects of graphene oxides (GO), functionalized carbon nanotubes (FCNTs), and carbon nanotubes (CNTs) on plant growth and soil nutrient content. To observe the impact on gram plant growth and soil parameters, we synthesized and applied GO, FCNTs, and CNTs at a rate of 100µg/mL (120 g per kg soil) in the corresponding pots. After 90 days of seed sowing, GO-treated crops showed a 41% increase in crop height compared to the control (no nanomaterials), but this increase was 33% and 40% in CNTs - and FCNTs-treated crops, respectively. When compared to the control, the GO-treated plants shown a twofold increase in root length; in contrast, the FCNTs and CNTs-treated plants showed increases of 60% and 25%, respectively. The highest increases in plant biomass, soil organic matter, total nitrogen, microbial biomass, and enzymatic activity were observed in plants treated with GO. A 52% increase in SDA was seen in the GO-treated soil as compared to the control; in the FCNTs and CNTs-treated soils, this increase was 32% and 19%, respectively. An organic material with a carbon base is a carbon-based nanomaterial, which has the ability to control the soil microenvironment and activate soil enzyme activity. The results verified that incorporating carbon-based nanomaterials, particularly GO, into the soil might enhance the growth of gram plants and the sustainability of the soil.

High energy supercapacitors based on functionalized carbon nanotubes: Effect of atomic oxygen doping via various radiation sources

Carbon nanotubes (CNTs) can be used as atomic force microscope (AFM) probes due to their robust mechanical properties, high aspect ratio and small diameter. In this study, a model of CNTs clamped in an elastic medium is proposed as CNT AFM probes. The buckling instability of the CNT probe clamped in elastic medium is analyzed based on the nonlocal Euler–Bernoulli beam model and the Whitney–Riley model. The clamped length of CNTs, and the stiffness of elastic medium affect largely on the stability of CNT AFM probe, especially at high buckling mode. The result shows that the buckling stability of the CNT AFM probe can be largely enhanced by increasing the stiffness of elastic medium. Moreover, the nonlocal effects of buckling instability are investigated and found to be lager for high buckling mode. The theoretical investigation on the buckling stability would give a useful reference for designing CNT as AFM probes.