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Hajeeassa, Khdejah S., Mahmoud A. Hussein, Yasir Anwar, Nada Y. Tashkandi e Zahra M. Al-amshany. "Nanocomposites containing polyvinyl alcohol and reinforced carbon-based nanofiller". Nanobiomedicine 5 (1 gennaio 2018): 184954351879481. http://dx.doi.org/10.1177/1849543518794818.
Testo completoAbstract (sommario):
A new class of biologically active polymer nanocomposites based on polyvinyl alcohol and reinforced mixed graphene/carbon nanotube as carbon-based nanofillers with a general abbreviation (polyvinyl alcohol/mixed graphene–carbon nanotubes) has been successfully synthesized by an efficient solution mixing method with the help of ultrasonic radiation. Mixed graphene and carbon nanotubes ratio has been prepared (50%:50%) wt by wt. Different loading of mixed graphene–carbon nanotubes (2, 5, 10, 15, and 20 wt%) were added to the host polyvinyl alcohol polymer. In this study, polyvinyl alcohol/mixed graphene–carbon nanotubesa–e nanocomposites were characterized and analyzed by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, and the thermal stability was measured by thermogravimetric analysis and derivative thermal gravimetric. Fourier transform infrared and X-ray diffraction spectra proved the addition of mixed graphene–carbon nanotubes into polyvinyl alcohol matrix. X-ray diffraction patterns for these nanocomposites showed 2 θ = 19.35° and 40° due to the crystal nature of polyvinyl alcohol in addition to 2 θ = 26.5° which attributed to the graphite plane of carbon-based nanofillers. Thermal stability of polyvinyl alcohol/mixed graphene–carbon nanotubes nanocomposites was enhanced comparing with pure polyvinyl alcohol. The main degradation step ranged between 360° and 450°C. Moreover, maximum composite degradation temperature has appeared at range from 285°C to 267°C and final composite degradation temperature (FCDT) displayed at a temperature range of 469–491°C. Antibacterial property of polyvinyl alcohol/mixed graphene–carbon nanotubesa–e nanocomposites were tested against Escherichia coli bacteria using the colony forming units technique. Results showed an improvement of antibacterial property. The rate percentages of polyvinyl alcohol/mixed graphene–carbon nanotubesb, polyvinyl alcohol/mixed graphene–carbon nanotubesc, and polyvinyl alcohol/mixed graphene–carbon nanotubesd nanocomposites after 24 h are 6%, 5%, and 7% respectively. However, polyvinyl alcohol/mixed graphene–carbon nanotubese nanocomposite showed hyperactivity, where its reduction percentage remarkably raised up to 100% which is the highest inhibition rate percentage. In addition, polyvinyl alcohol and polyvinyl alcohol/graphene–carbon nanotubesa–d showed colony forming units values/ml 70 × 106 and 65 ± 2 × 106 after 12 h. After 24 h, the colony forming units values/ml were in the range of 86 × 106–95 × 106.
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Jin, Wei, Wen Chen, Bai Tao Dong, Chun Xia Zhao, Li Qiang Mai e Ying Dai. "V2O5 Nanotubes Novel Gas Sensor with High Sensitivity for Ethanol". Key Engineering Materials 421-422 (dicembre 2009): 328–31. http://dx.doi.org/10.4028/www.scientific.net/kem.421-422.328.
Testo completoAbstract (sommario):
Vanadium oxide nanotubes were synthesized via a rheological self-assembling process followed by a hydrothermal reaction. V2O5 gas sensors were fabricated from vanadium oxide nanotubess with an average diameter of around 90 nm and their gas-sensing properties were investigated. It was found that the sensors based on vanadium oxide nanotubes exhibit high responses ethanol gas at 270°C. The results indicate that vanadium oxide nanotube sensors will be promising candidates for practical detectors for ethanol.
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Prasad, Shiva, Harish Venkat Reddy e Ashok Godekere. "Properties of Carbon Nanotubes and their applications in Nanotechnology – A Review". Mapana Journal of Sciences 20, n. 4 (1 ottobre 2021): 49–64. http://dx.doi.org/10.12723/mjs.59.4.
Testo completoAbstract (sommario):
One of the most distinctive inventions in the world of nanotechnology is the carbon nanotube (CNT). Many scholars around the world have been studying carbon nanotubes (CNTs) over the past two decades due to their enormous potential in a variety of sectors. Single-wall CNTs with dimensions in the nanometer range are commonly referred to as carbon nanotubes. Carbon nanotubes are also known as multi-wall CNTs, which are made up of nested single-wall CNTs that are weakly bonded together in a tree ring-like structure by van der Waals interactions. Tubes having an unknown carbon wall structure and diameters smaller than 100 nanometers are also referred to as carbon nanotubes. A carbon nanotube's length is often substantially longer than its diameter, according to standard manufacturing methods. Carbon nanotubes are capable of exhibiting a variety of remarkable properties. CNTs have distinct electrical, mechanical and optical properties that have all been thoroughly investigated. The properties and applications of carbon nanotubes are the focus of this review.
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Hou, Wenyi, e Shaoping Xiao. "Mechanical Behaviors of Carbon Nanotubes with Randomly Located Vacancy Defects". Journal of Nanoscience and Nanotechnology 7, n. 12 (1 dicembre 2007): 4478–85. http://dx.doi.org/10.1166/jnn.2007.862.
Testo completoAbstract (sommario):
In this paper, 10 0 zigzag nanotubes and (6, 6) armchair nanotubes are considered to investigate the effects of randomly distributed vacancy defects on mechanical behaviors of single-walled carbon nanotubes. A spatial Poisson point process is employed to randomly locate vacancy defects on nanotubes. Atomistic simulations indicate that the presence of vacancy defects result in reducing nanotube strength but improving nanotube bending stiffness. In addition, the studies of nanotube torsion indicate that vacancy defects prevent nanotubes from being utilized as torsion springs.
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Lin, Tong, Vardhan Bajpai, Tao Ji e Liming Dai. "Chemistry of Carbon Nanotubes". Australian Journal of Chemistry 56, n. 7 (2003): 635. http://dx.doi.org/10.1071/ch02254.
Testo completoAbstract (sommario):
Judicious application of site-selective reactions to non-aligned and aligned carbon nanotubes has opened a rich field of carbon nanotube chemistry. In order to meet specific requirements demanded by particular applications (e.g. biocompatibility for nanotube biosensors and interfacial strength for blending with polymers), chemical modification of carbon nanotubes is essential. The tips of carbon nanotubes are more reactive than their sidewalls, allowing a variety of chemical reagents to be attached at the nanotube tips. Recently, some interesting reactions have also been devised for chemical modification of both the inner and outer nanotube walls, though the seamless arrangement of hexagon rings renders the sidewalls relatively unreactive. This review provides a brief summary of very recent progress in the research on chemistry of carbon nanotubes.
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ACAR, Muhammet Taha. "Investigation of the effects of Sr and Mn doping on corrosion tribocorrosion and cyclic voltammetry performances of TiO2 nanotubes". European Mechanical Science 7, n. 3 (20 settembre 2023): 138–45. http://dx.doi.org/10.26701/ems.1265161.
Testo completoAbstract (sommario):
In this study, manganese (Mn) and strontium (Sr) were doped into TiO2 nanotubes (TNT), which are frequently used in energy storage equipment. The aim of this study is to compare the corrosion tribocorrosion and cyclic voltammetry performances of doped TNTs after examining their structural characteristics. XRD and SEM were used to characterize the nanotubes. After the anodization processes, the inclusion of Mn and Sr in the TNT structure was confirmed by XRD analysis. In SEM analysis, it was observed that with the addition of Mn and Sr into the solution, longer nanotubes were formed with increased electrical conductivity. Increasing the nanotube length and shrinking the nanotube's inner diameter provided increased corrosion resistance. Increased surface hardness resulted in increased tribocorrosion resistance. In cyclic voltammetry experiments, the capacitance increased approximately 5 times in Sr-doped TNT compared to undoped TNT, while it increased 10 times in Mn-doped TNT.
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Le, Minh Tai, e Shyh Chour Huang. "Modeling and Analysis the Effect of Helical Carbon Nanotube Morphology on the Mechanical Properties of Nanocomposites Using Hexagonal Representative Volume Element". Applied Mechanics and Materials 577 (luglio 2014): 3–6. http://dx.doi.org/10.4028/www.scientific.net/amm.577.3.
Testo completoAbstract (sommario):
Carbon nanotubes (CNTs) are the ultimate reinforcing materials for the development of an entirely new class of composites. However, they have the complicated shapes and do not usually appear as straight reinforcements when introduced in polymer matrices. This decreases nanotube’s effectiveness in enhancing the matrix mechanical properties. In this paper, nanostructure having hexagonal representative volume element (RVE), theory of elasticity of anisotropic materials and finite element method (FEM) are used to investigate the effect of helical CNT morphology on effective mechanical properties of nanocomposites. CNT with different helical angles are modeled to estimate the nanocomposite mechanical properties. The results of helical nanotube models are compared with the effective mechanical properties of nanocomposites reinforced with straight nanotubes.
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Syahriza Ismail, Khairil Azwa Khairul, Zainovia Lockman e Zhwan Dilshad Ibrahim Sktani. "Mechanism of Co3O4-TiO2 Nanocomposite Formation with Enhanced Photocatalytic Performance". Journal of Advanced Research in Micro and Nano Engineering 23, n. 1 (2 ottobre 2024): 49–60. http://dx.doi.org/10.37934/armne.23.1.4960.
Testo completoAbstract (sommario):
TiO2 nanotubes are tubular structures that have garnered significant attention in materials science and engineering due to their unique properties and diverse applications. In this study, highly ordered and well aligned TiO2 nanotubes were successfully synthesized through anodization of Ti foil in ethylene glycol (C2H6O2) containing ammonium fluoride (NH4F) and hydrogen peroxide (H2O2) at 60 V for 30 minutes. The effectiveness of TiO2 as a photocatalyst under solar light is limited by its wide band gap and high recombination rate of charge carriers. To address these limitations, TiO2 nanotubes were modified with cobalt oxide. The resulting Co3O4-TiO2 nanocomposite was synthesized using a wet impregnation technique, aiming to enhance the photocatalytic performance of TiO2 nanotubes across a broader range of the solar spectrum. The formation of Co3O4-TiO2 nanocomposite is by immersing the TiO2 nanotubes in the metal salt precursor solution of Co(NO3)2 for a certain soaking period. The soaking cycle was repeated a few times to ensure the deposition of cobalt oxide nanostructures on the TiO2 nanotube samples. This diffusion interstitial process via wet impregnation was time dependent, which altered the amount of cobalt loaded on the nanotube's surface. The addition of cobalt significantly improved the photodegradation activity of the nanotubes under visible light, outperforming bare TiO2 nanotubes. This enhancement is likely due to the cobalt acting as shallow traps, which effectively promote the separation of photogenerated charge carriers.
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Gábor, T., D. Aranyi, Katalin Papp, F. H. Kármán e Erika Kálmán. "Dispersibility of Carbon Nanotubes". Materials Science Forum 537-538 (febbraio 2007): 161–68. http://dx.doi.org/10.4028/www.scientific.net/msf.537-538.161.
Testo completoAbstract (sommario):
Availability of a stable carbon nanotube suspension is a prerequisite for production of polymer composites with carbon nanotube as additives. In this work nanotube suspensions, which have been prepared from various nanotubes in different dispersion agents, were compared. Dispersibility of the samples was investigated by scanning electon microscopy and atomic force microscopy. Solution of a non-ionic surfactant was also used successfully as a new dispersion agent. Geometrical parameters of the carbon nanotubes were determined by using atomic force microscopy. Correlation was found between the dispersibility and the parameters of the nanotubes and relative permittivity of the different solvents.
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Jinkins, Katherine, Michael S. Arnold e Sean Foradori. "Aligned Semiconducting Carbon Nanotubes for Commercial Logic and RF Electronics". ECS Meeting Abstracts MA2024-01, n. 15 (9 agosto 2024): 1177. http://dx.doi.org/10.1149/ma2024-01151177mtgabs.
Testo completoAbstract (sommario):
Carbon nanotubes are exceptional semiconductors that offer larger current densities and faster switching than conventional Si and GaAs devices, making nanotubes promising for meeting the performance and energy efficiency needs of next-generation electronics. However, the successful commercialization of carbon nanotubes necessitates the control over semiconducting purity, alignment, packing density, and scalability. The simultaneous control of these characteristics has been a major challenge preventing the integration of nanotubes in industrial electronics and the full exploitation of their electronic properties. This talk will present an overview of recent technological developments and methods that progress towards these goals. In these methods, semiconducting (purity of >99.99%) carbon nanotubes are deposited on target substrates via scalable alignment methods at room temperatures. These individual methods separately enable the deposition of quasi-aligned (±28°) nanotube arrays (~50 nanotubes µm-1) demonstrated across 100 mm substrates, highly-aligned (±6°) nanotube arrays (~100 nanotubes µm-1) demonstrated across 100 mm substrates, and the selective-area deposition of highly-aligned nanotube (±7°) arrays (~up to 250 nanotubes µm-1). The nanotube arrays with high packing density (~250 nanotubes μm-1) yield exceptional current densities of 2 mA μm-1 and transconductances of 1 mS μm-1 at VD of -0.6V. Importantly, due to the low-temperature nature of the deposition processes, these techniques offer a direct path towards the alignment of carbon nanotubes directly on Si and other materials, such as GaN or plastics, to enable high-performance 3D integrated circuits.
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Levchenko, I., K. Ostrikov e M. Keidar. "Plasma-Assembled Carbon Nanotubes: Electric Field–Related Effects". Journal of Nanoscience and Nanotechnology 8, n. 11 (1 novembre 2008): 6112–22. http://dx.doi.org/10.1166/jnn.2008.sw10.
Testo completoAbstract (sommario):
The paper presents results of comparative investigation of carbon nanotubes growth processes in dense low-temperature plasma and on substrate surface. Hybrid/Monte-Carlo numerical simulations were used to demonstrate the differences in the ion fluxes, growth rates and kinetics of adsorbed atoms re-distribution on substrate and nanotubes surfaces. We show that the plasma parameters significantly affect the nanotubes growth kinetics. We demonstrate that the growth rates of the nanotubes in plasma and on surface can differ by three orders, and the specific fluxes to the nanotube in the plasma can exceed the flux to surface-grown nanotube by six orders. We also show that the metal catalyst used for the nanotubes production on surface and in arc is a subject to very different conditions and this may be a key factor for the nanotube growth mode. The obtained dependencies for the ion fluxes to the nanotubes and nanotubes growth rates on the plasma parameters may be useful for selection of the production methods.
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Zhang, J. W., Zhen Luo, Y. L. Li, J. D. Zhu e J. Hao. "A Welding Method for Carbon Nanotubes". Advanced Materials Research 160-162 (novembre 2010): 737–42. http://dx.doi.org/10.4028/www.scientific.net/amr.160-162.737.
Testo completoAbstract (sommario):
A simple and reliable welding method was developed to weld carbon nanotubes with the power supply here. The carbon nanotubes were synthesized chemical vapor deposition method and Multi-walled carbon nanotubes was uesd here. Firstly, apply less than 5 V voltages between carbon nanotubes when they were in close proximity under direct view of optical microscope. Then, let carbon nanotube contact with each other and increase the external voltage to 7–8V until carbon nanotube was attached to the end of the other, the two carbon nanotube join into a carbon nanotube. Furthermore, some experiments were implemented to analyze the reliability, the images of the weld joint and the weld strength all indicted this method were reliable.
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Li, Yun, Nan Nan Wang, Hai Feng Cheng, Yong Jiang Zhou e Ting Ting Li. "Microstructure Evolution of Hybrid TiO2 Nanowire-Nanotube Structure Fabricated by Anodization". Materials Science Forum 852 (aprile 2016): 428–32. http://dx.doi.org/10.4028/www.scientific.net/msf.852.428.
Testo completoAbstract (sommario):
Hybrid TiO2 nanowire–nanotube structure was synthesized by a facile anodization on Ti substrate. To study the origin and evolution of TiO2 nanotubes, the morphology of TiO2 nanotubes was investigated. It was found that nanotubes corrode gradually into nanowires, and the critical time was about 8.5 h after the beginning of anodization. Uniform nanotubes were obtained by ultrasonic cleaning. It was demonstrated experimentally that the inner diameter of TiO2 nanotube increased with the extension of anodization time, but the outer diameter of TiO2 nanotubes, which were fabricated under different anodization time, was almost the same.
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Yang, Seunghwa. "Understanding Covalent Grafting of Nanotubes onto Polymer Nanocomposites: Molecular Dynamics Simulation Study". Sensors 21, n. 8 (8 aprile 2021): 2621. http://dx.doi.org/10.3390/s21082621.
Testo completoAbstract (sommario):
Here, we systematically interrogate the effects of grafting single-walled (SWNT) and multi-walled carbon nanotubes (MWNT) to polymer matrices by using molecular dynamics (MD) simulations. We specifically investigate key material properties that include interfacial load transfer, alteration of nanotube properties, and dispersion of nanotubes in the polymer matrix. Simulations are conducted on a periodic unit cell model of the nanocomposite with a straight carbon nanotube and an amorphous polyethylene terephthalate (PET) matrix. For each type of nanotube, either 0%, 1.55%, or 3.1% of the carbon atoms in the outermost nanotubes are covalently grafted onto the carbon atoms of the PET matrix. Stress-strain curves and the elastic moduli of nanotubes and nanocomposites are determined based on the density of covalent grafting. Covalent grafting promotes two rivalling effects with respect to altering nanotube properties, and improvements in interfacial load transfer in the nanocomposites are clearly observed. The enhanced interface enables external loads applied to the nanocomposites to be efficiently transferred to the grafted nanotubes. Covalent functionalization of the nanotube surface with PET molecules can alter the solubility of nanotubes and improve dispersibility. Finally, we discuss the current limitations and challenges in using molecular modelling strategies to accurately predict properties on the nanotube and polymers systems studied here.
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Liu, Yuan Chao, Ya Jie Zhang, Ya Jun Wu e Bao Min Sun. "Carbon Nanotubes with Special Structure from the Pyrolysis Flame". Advanced Materials Research 261-263 (maggio 2011): 909–12. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.909.
Testo completoAbstract (sommario):
Carbon nanotube is the one-dimensional carbon nano-materials. The synthesis of carbon nanotubes from pyrolysis flame is a new method. Variety of carbon nanotubes with special structure can be seen from pyrolysis flame due to the influence of key factors such as the concentration of reactants and catalyst particle size. The morphology and structural of carbon nanotubes were characterized by scanning electron microscope and transmission electron microscopy respectively. Carbon nanotubes with special structure such as bamboo-like, pod-like and coil-like can be seen in the experiment. The bamboo-like carbon nanotube has a bamboo-like structure clearly. The shape of pod-like carbon nanotube is very similar with the peasecod. The coil-like carbon nanotube is similar to carbon nanofiber in structure. It was discussed and analyzed that the formation mechanism of bamboo-like, pod-like and coil-like carbon nanotubes from the V-type pyrolysis flame.
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Brown, Alan S. "Positive Reinforcement". Mechanical Engineering 132, n. 03 (1 marzo 2010): 36–39. http://dx.doi.org/10.1115/1.2010-mar-3.
Testo completoAbstract (sommario):
This article focuses on the future applications and challenges of nanotube-enhanced composites. In spite of their well-known strength and stiffness, nanotubes have proved incredibly difficult to harness, especially in composites. Researchers have eventually found ways to compatibilize nanotubes by attaching molecules to the nanotube surface. Some formulators compatibilize nanotubes for infusion processes, which pump resin into reinforcing fiber preforms. Electric hybrid car designer Velozzi is working with Bayer Materials Science LLC, a subsidiary of Germany’s Bayer AG, to use nanotube-based composites in its high-performance electric Supercar and its more affordable plug-in hybrid Solo. Lockheed Martin is investigating a complete range of applications for carbon nanotubes in both materials and electronics. The company wants to incorporate nanotubes into its established production methods. Nanotubes improve resistance to impact, fatigue, and microcracking, all properties related to resins. The result is a much stronger and more durable composite.
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Susi, Bryan T., e Jay F. Tu. "Digital Synthesis of Realistically Clustered Carbon Nanotubes". C 8, n. 3 (22 giugno 2022): 34. http://dx.doi.org/10.3390/c8030034.
Testo completoAbstract (sommario):
A computational approach for creating realistically structured carbon nanotubes is presented to enable more accurate and impactful multi-scale modeling and simulation techniques for nanotube research. Much of the published literature to date involving computational modeling of carbon nanotubes simplifies their structure as being long and straight, and often existing as isolated individual nanotubes. However, imagery of nanotubes has shown over several decades that nanotubes agglomerate together and exhibit looping and curvature due both to inter- and intra-nanotube attraction. The research presented in this paper leverages multi-scale simulations consisting of a simple bead-spring model for initial nanotube relaxation followed by a differential geometry approach to create an atomic representation of carbon nanotubes, and then finalized with molecular dynamics simulations using the Tersoff potential model for carbon that allows dynamic bonding and cleavage. The result is atomically accurate representations of carbon nanotubes that exist as single nanotubes, or as clusters of multiple nanotubes. The presented approach is demonstrated using (5,5) single-walled carbon nanotubes. The synthesized nanotubes are shown to relax into the curving and looping structures observed in transmission or scanning electron microscopy, but also exhibit nano-scale defects due to buckling, crimping, and twisting that are resolved during the molecular dynamics simulations. These features locally compromise the desired strength characteristics of nanotubes and therefore the presented procedure will enable more accurate modeling and simulation of nanotubes in subsequent research by representing them less as the theoretically straight and independent entities, but as realistically imperfect.
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Le, D. T., E. V. Butyrskaya e T. V. Eliseeva. "Cluster Adsorption of L-Histidine on Carbon Nanotubes in Aqueous Solutions at Different Temperatures". Russian Journal of Physical Chemistry A 96, n. 8 (agosto 2022): 1719–23. http://dx.doi.org/10.1134/s003602442208012x.
Testo completoAbstract (sommario):
Abstract Adsorption isotherms are obtained for L-histidine on carbon nanotubes using aqueous solutions at temperatures of 25, 35, 45, 55, 65, and 80°C. The isotherms are interpreted by using the cluster adsorption model and analyzing the dependence of the strength of the bond nanotube–amino acid on temperature. Equations of the adsorption isotherms are obtained for all temperatures. The calculated results indicate that L-histidine is fixed on a nanotube’s surface in the form of monomers and different clusters. The equilibrium characteristics of adsorption are found to change as the temperature rises. Values obtained for the coefficients of equilibrium are used to calculate apparent enthalpy ΔH* of L-histidine adsorption by nanotubes, according to the van’t Hoff equation.
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SUENAGA, Kazutomo. "Nanotube. Hetero-Nanotubes." SHINKU 42, n. 8 (1999): 735–40. http://dx.doi.org/10.3131/jvsj.42.735.
Testo completo
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ALDAJAH, S., J. CHATTERJEE, M. ALRAWADEH, A. KOSURI e Y. HAIK. "ALIGNMENT OF CARBON NANOTUBES USING MAGNETIC NANOPARTICLES". International Journal of Nanoscience 08, n. 03 (giugno 2009): 251–59. http://dx.doi.org/10.1142/s0219581x09006067.
Testo completoAbstract (sommario):
Carbon nanotubes are driving scientific research nowadays. This field has several important directions in basic research, including chemistry, electronic transport, mechanical, and field emission properties. The most eye-catching features of carbon nanotubes are their electronic, mechanical, optical, and chemical characteristics, which open a way to future applications. One of the most important applications of nanotubes based on their properties will be as reinforcements in composite materials. One of the biggest concerns to nanotube industry is the alignment problem which has limited the usage and utilizations of carbon nanotubes in composites. The ability to impose a preferred alignment of carbon nanotubes in a composite will increase the effectiveness of utilizing nanotubes in composite applications. The alignment of nanotubes will maximize the interfacial bonding across the nanotube matrix interface. In this research, we developed a methodology and a process to align nanotubes in polymer nanocomposites by means of a magnetic field. By doing so, we will get a very strong nanocomposite that can be used in the composites industry. The proposed mechanism aims at aligning the carbon nanotubes by means of nanomagnetic particles that are adsorbed on the nanotube surfaces and by applying an external magnetic field. SEM analysis have shown that nanomagnetic particles with the assistance of the magnetic field were able to align the carbon nanotubes in the desired direction.
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Yang, Yang, Xiao Hui Wang e Long Tu Li. "Zinc-Doped TiO2 Nanotube Arrays". Key Engineering Materials 434-435 (marzo 2010): 446–47. http://dx.doi.org/10.4028/www.scientific.net/kem.434-435.446.
Testo completoAbstract (sommario):
Zinc-doped TiO2 nanotube arrays were fabricated by immersing TiO2 nanotube arrays in zinc-containing solution for hours. And subsequent heat-treatment was crucial for Zn2+ coming into the crystal lattice of TiO2 nanotubes. TEM analysis was used as main technique to investigate the structure of zinc-doped TiO2 nanotubes, and found that the Zn2+ ions only combine into the lattice of TiO2 nanotubes. This kind of doping can change the valence structure in the surface of TiO2 nanotube array. The obtained zinc-doped TiO2 nanotube arrays have potential application in photocatalysis.
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Huseynov, Asgar, Aydin Israfilov, Samira Mammadova, Sevda Abdullayeva, Sergey Sokolov, Alexey Goryunkov e Akif Guliyev. "Fabrication and characterization of MWCNT/natural Azerbaijani bentonite electroconductive ceramic composites". Journal of Composite Materials 53, n. 26-27 (13 maggio 2019): 3909–23. http://dx.doi.org/10.1177/0021998319848798.
Testo completoAbstract (sommario):
Multi-walled carbon nanotubes have been synthesized by Aerosol-Chemical Vapor Deposition method. Carbon nanotubes firstly have been used as filler in affordable and prevalent natural Azerbaijani bentonite clays for fabrication electroconductive ceramic composites. In this paper, multi-walled carbon nanotubes/natural Azerbaijani bentonite ceramic composites were prepared by two-factor mechanical method and followed by calcination at 1050℃ in an inert atmosphere. The ceramic composites were characterized by scanning electron microscope, atomic force microscope, X-ray diffraction and thermogravimetric-differential-thermal analysis. X-ray diffraction analysis confirmed the presence of two principal components – multi-walled carbon nanotube and bentonite in composites. From the thermogravimetric-differential-thermal data, it was revealed that multi-walled carbon nanotube/ bentonite ceramic composites demonstrate thermo-oxidative stability up to 580–640℃. Scanning electron microscope images demonstrated a sufficiently high dispersibility of carbon nanotubes and satisfactory homogeneity in the composites. Experimental results demonstrated that by increasing the mass fraction of multi-walled carbon nanotubes from 1% to 8% in multi-walled carbon nanotube/bentonite ceramic composites, the electrical conductivity enhances substantially. The enhancement of electrical conductivity of the composites explained the mass fraction of multi-walled carbon nanotubes, as well as the uniform dispersion of multi-walled carbon nanotubes in the bentonite clays. Compared with other 8% multi-walled carbon nanotubes/bentonite ceramic composites, the electrical conductivity of heptane-multi-walled carbon nanotube/Gobu bentonite (σ = 397 S·m−1) and heptane-multi-walled carbon nanotubes/Atyali (σ = 305 S·m−1) composites is 2–5 times higher than the conductivity of composites obtained with cyclohexane carbon nanotubes- cyclohexane-multi-walled carbon nanotube/Atyali (σ = 78 S·m−1), cyclohexane-multi-walled carbon nanotube/Gobu (σ = 111,5 S·m−1). These results can be explained with the structure, the number of layers, purity and diameter distribution, as well as the type and amount of defects in internal and external layers of Hep-multi-walled carbon nanotubes which cause better dispersion in bentonite clays. Due to the high conductivity and high temperature stability, these composites can be used as promising material for fabrication heating elements, electrodes, substrates for microelectronic devices, etc.
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Kumar, Ponnusamy Senthil, e G. Janet Joshiba. "Carbon Nanotube Composites". Diffusion Foundations 23 (agosto 2019): 75–81. http://dx.doi.org/10.4028/www.scientific.net/df.23.75.
Testo completoAbstract (sommario):
The discovery of carbon nanotubes is one of the remarkable achievement in the field of material science and it is a great advancement of Nanotechnology. A carbon nanotube is an expedient material used in several domains and paves way for the welfare of humans in many ways. Carbon nanotubes are nanosized tubes made from graphitic carbons and it is well known for its exclusive physical and chemical properties. The market demand for the nanotubes has increased progressively due to its size dependent, structure and mechanical properties. The carbon nanotubes possess high tensile strength and it is also found to be the durable fibre ever known. It is also found to possess exceptional electrical properties. The carbon nanotube composites have an excellent young’s modulus and higher tensile strength same as graphite carbon. This review plots the properties of carbon nanotubes and portrays the planning and properties of carbon nanotube composites. The wide application of carbon nanotube composites is also explained.
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Winey, Karen I., Takashi Kashiwagi e Minfang Mu. "Improving Electrical Conductivity and Thermal Properties of Polymers by the Addition of Carbon Nanotubes as Fillers". MRS Bulletin 32, n. 4 (aprile 2007): 348–53. http://dx.doi.org/10.1557/mrs2007.234.
Testo completoAbstract (sommario):
AbstractThe remarkable electrical and thermal conductivities of isolated carbon nanotubes have spurred worldwide interest in using nanotubes to enhance polymer properties. Electrical conductivity in nanotube/polymer composites is well described by percolation, where the presence of an interconnected nanotube network corresponds to a dramatic increase in electrical conductivity ranging from 10−5 S/cm to 1 S/cm. Given the high aspect ratios and small diameters of carbon nanotubes, percolation thresholds are often reported below 1 wt% although nanotube dispersion and alignment strongly influence this value. Increases in thermal conductivity are modest (∼3 times) because the inter facial thermal re sis tance between nanotubes is considerable and the thermal conductivity of nanotubes is only 104 greater than the polymer, which forces the matrix to contribute more toward the composite thermal conductivity, as compared to the contrast in electrical conductivity, >1014. The nanotube network is also valuable for improving flame-retardant efficiency by producing a protective nanotube residue. In this ar ticle, we highlight published research results that elucidate fundamental structure–property relationships pertaining to electrical, thermal, and/or flammability properties in numerous nanotube-containing polymer composites, so that specific applications can be targeted for future commercial success.
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Kim, Jeong-Hyeon, Jong-Min Kim, Sungkyun Park, Kang Hyun Park e Jae-Myung Lee. "Synthesis and cryogenic mechanical properties of CO2-blown carbon-reinforced polyurethane foam". Journal of Cellular Plastics 54, n. 4 (29 dicembre 2017): 743–63. http://dx.doi.org/10.1177/0021955x17750389.
Testo completoAbstract (sommario):
In the present study, carbon-nanotube-polyurethane foams were synthesized by adding (0.02, 0.1, and 0.3 wt%) carbon nanotubes during the polymerization reaction between polyol and isocyanate liquids. After the synthesis process, the microstructural cell morphology of the carbon-nanotube-polyurethane foams, based on the amount of carbon nanotubes, was observed using field emission scanning electron microscopy. To evaluate the mechanical characteristics of the carbon-nanotube-polyurethane foams, temperature-dependent (20°C, −90°C, and −163°C) compressive tests were performed, and the results were compared to those of the pure polyurethane foam to verify the effectiveness of the developed carbon-nanotube-polyurethane foams. Specifically, the effects of the weight percent of carbon nanotubes, density, and temperature on the overall behavior of the carbon-nanotube-polyurethane foams were considered. Finally, the permanent deformation ratio and material failure characteristics were investigated. The results showed that the cell morphology and compressive strength of the carbon-nanotube-polyurethane foam with 0.02 wt% carbon nanotubes were superior to those of pure polyurethane foam, and these properties showed a significant dependence on the weight percent of carbon nanotubes, test temperatures, and the density.
26
Mei, Hui, Qianglai Bai, Konstantinos Dassios, Haiqing Li, Laifei Cheng e Costas Galiotis. "Morphological and Microstructural Property Comparison of Bulk and Aligned Cvd-Grown Carbon Nanotubes". Advanced Composites Letters 23, n. 1 (gennaio 2014): 096369351402300. http://dx.doi.org/10.1177/096369351402300101.
Testo completoAbstract (sommario):
Carbon nanotubes are one-dimensional materials found in various forms, the most important of which are bulk unordered carbon nanotubes of lengths of few microns and aligned tubes regularly a few millimeters long. Differences in length, orientation, alignment, nanotube graphitization and purity will influence the eventual performance of the material. Herein four characterization methods are used to characterize and compare bulk and aligned carbon nanotubes. Results show that the diameters of the millimeter-long aligned carbon nanotubes are approximately 60 ∼ 80 nm with thick nanotube walls of about 25–30 nm, while the diameters of the bulk carbon nanotubes are about 15–20 nm with much thinner walls. The aligned carbon nanotubes have significantly larger graphitization degrees, higher purity and greater orientation than the bulk carbon nanotubes that tend to self-agglomerate under no external stimulus. Silicon carbide matrix nanocomposites reinforced by the aligned carbon nanotubes were found to be denser that those reinforced by the bulk carbon nanotubes and also exhibit extensive, uniform, and long pullout of carbon nanotubes.
27
ZHU, YINGCHUN. "INSIGHT INTO THE STRUCTURE AND FORMATION OF TITANIUM OXIDE NANOTUBES". Functional Materials Letters 01, n. 03 (dicembre 2008): 239–46. http://dx.doi.org/10.1142/s1793604708000435.
Testo completoAbstract (sommario):
Titanium oxide nanotube is a promising material for versatile applications. However, its structure and formation mechanism were quite confusedly reported. Therefore, it is essential to fully understand its structure, formation mechanism and stability. In this study, the structure, formation and stability of titanium oxide nanotube were studied in detail. New experimental findings on the morphology of titanium oxide nanotubes were reported, demonstrating close-opened nanotubes, cone-shaped nanotubes, twin and ternary nanotubes etc. A structural model of the titanium oxide nanotubes is proposed on the basis of cylinders of smoothly curved sheets of TiO 6 octahedra, among which H + and H 3 O + are intercalated. The formation mechanism of titanium oxide nanotubes was deduced and discussed on the basis of their structural characteristics and chemical bonding behaviors of constituent atoms. The stability of the nanotubes was also studied under different conditions.
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Majidi, Roya, Hamid Reza Taghiyari e Mahsa Ekhlasi. "Adsorption Patterns of Helium on Carbon and Cellulose Nanotubes: Molecular Dynamics Simulations". Nano 12, n. 03 (marzo 2017): 1750036. http://dx.doi.org/10.1142/s1793292017500369.
Testo completoAbstract (sommario):
Molecular dynamics simulations were performed to study helium adsorption on carbon and cellulose nanotubes. Adsorption isotherms were analyzed at different temperatures and pressures. All adsorption isotherms for carbon and cellulose nanotubes were predicted to be of Langmuir shape type I. Helium adsorption was observed both inside and outside of open-ended tubes. Increasing temperatures caused lower helium adsorption on carbon and cellulose nanotubes. The calculated quantities confirmed that the adsorption capacity of the cellulose nanotube was greater than that of the carbon nanotube. The adsorption capacity, isosteric heat of adsorption and binding energy indicated that cellulose nanotubes as well as carbon nanotubes are proper materials for gas storage.
29
Marquis, Fernand D. S. "Carbon Nanotube Nano Composites for Multifunctional Applications". Materials Science Forum 561-565 (ottobre 2007): 1397–402. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.1397.
Testo completoAbstract (sommario):
Owing to their exceptional stiffness, strength, thermal and electrical conductivity, carbon nanotubes have the potential for the development of nano composites materials for a wide variety of applications. In order to achieve the full potential of carbon nanotubes for structural, thermal and electrical multifunctional applications, both single wall carbon nanotubes (SWNTs), double wall nanotubes (DWNTs) and multi wall nanotubes (MWNTs) need to be developed into fully integrated carbon nanotube composites. Full integration of nanotubes requires their development beyond conventional composites so that the level of the non-nanotube material is designed to integrate fully with the amount of nanotubes and where the nanotubes are part of the matrix rather than a differing component, as in the case of conventional composites. In order to advance the development of multifunctional materials from nanotubes, this research is focused on the simultaneous control of structural properties, thermal and electrical conductivity of fully integrated carbon nanotube composites. These are hybrid material systems designed to surpass the limits of rule of mixtures engineering and composite design. The goals are to implement designs to fully mimic the properties of carbon nanotubes on larger scales for enhanced thermal and electrical management in addition to controlled strength and toughness. These new approaches involve, functionalization, dispersion, stabilization, alignment, polymerization and reaction bonding, in order to achieve full integration. Typical examples of polymeric and ceramic matrices, as well as other material systems are presented and discussed.
30
ROLAND, C., M. BUONGIORNO NARDELLI, H. GUO, H. MEHREZ, J. TAYLOR, J. WANG e Y. WEI. "THEORETICAL INVESTIGATIONS OF QUANTUM TRANSPORT THROUGH CARBON NANOTUBE DEVICES". Surface Review and Letters 07, n. 05n06 (ottobre 2000): 637–42. http://dx.doi.org/10.1142/s0218625x00000774.
Testo completoAbstract (sommario):
By combining a nonequilibrium Green's function analysis with a standard tight-binding model, we have investigated quantum transport through carbon nanotube devices. For finite-sized nanotubes, transport is dominated by resonant tunneling, with the conductance being strongly dependent on the length of the nanotubes. Turning to nanotube devices, we have investigated spin-coherent transport in ferromagnetic–nanotube–ferromagnetic devices and nanotube-superconducting devices. The former shows a significant spin valve effect, while the latter is dominated by resonant Andreev reflections. In addition, we discuss AC transport through carbon nanotubes and the role of photon-assisted tunneling.
31
Shi, Dong-Li, Xi-Qiao Feng, Yonggang Y. Huang, Keh-Chih Hwang e Huajian Gao. "The Effect of Nanotube Waviness and Agglomeration on the Elastic Property of Carbon Nanotube-Reinforced Composites". Journal of Engineering Materials and Technology 126, n. 3 (29 giugno 2004): 250–57. http://dx.doi.org/10.1115/1.1751182.
Testo completoAbstract (sommario):
Owing to their superior mechanical and physical properties, carbon nanotubes seem to hold a great promise as an ideal reinforcing material for composites of high-strength and low-density. In most of the experimental results up to date, however, only modest improvements in the strength and stiffness have been achieved by incorporating carbon nanotubes in polymers. In the present paper, the stiffening effect of carbon nanotubes is quantitatively investigated by micromechanics methods. Especially, the effects of the extensively observed waviness and agglomeration of carbon nanotubes are examined theoretically. The Mori-Tanaka effective-field method is first employed to calculate the effective elastic moduli of composites with aligned or randomly oriented straight nanotubes. Then, a novel micromechanics model is developed to consider the waviness or curviness effect of nanotubes, which are assumed to have a helical shape. Finally, the influence of nanotube agglomeration on the effective stiffness is analyzed. Analytical expressions are derived for the effective elastic stiffness of carbon nanotube-reinforced composites with the effects of waviness and agglomeration. It is found that these two mechanisms may reduce the stiffening effect of nanotubes significantly. The present study not only provides the relationship between the effective properties and the morphology of carbon nanotube-reinforced composites, but also may be useful for improving and tailoring the mechanical properties of nanotube composites.
32
Siregar, Syahril, Sri Oktamuliani e Yoshifumi Saijo. "A Theoretical Model of Laser Heating Carbon Nanotubes". Nanomaterials 8, n. 8 (28 luglio 2018): 580. http://dx.doi.org/10.3390/nano8080580.
Testo completoAbstract (sommario):
We present a theoretical model of laser heating carbon nanotubes to determine the temperature profile during laser irradiation. Laser heating carbon nanotubes is an essential physics phenomenon in many aspects such as materials science, pharmacy, and medicine. In the present article, we explain the applications of carbon nanotubes for photoacoustic imaging contrast agents and photothermal therapy heating agents by evaluating the heat propagation in the carbon nanotube and its surrounding. Our model is constructed by applying the classical heat conduction equation. To simplify the problem, we assume the carbon nanotube is a solid cylinder with the length of the tube much larger than its diameter. The laser spot is also much larger than the dimension of carbon nanotubes. Consequently, we can neglect the length of tube dependence. Theoretically, we show that the temperature during laser heating is proportional to the diameter of carbon nanotube. Based on the solution of our model, we suggest using the larger diameter of carbon nanotubes to maximize the laser heating process. These results extend our understanding of the laser heating carbon nanotubes and provide the foundation for future technologically applying laser heating carbon nanotubes.
33
Lv, Yan. "Fabrication of Nickel Nanotube Using Anodic Oxidation and Electrochemical Deposition Technologies and Its Hydrogen Storage Property". Journal of Nanomaterials 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/4057829.
Testo completoAbstract (sommario):
Electrochemical deposition technique was utilized to fabricate nickel nanotubes with the assistance of AAO templates. The topography and element component of the nickel nanotubes were characterized by TEM and EDS. Furthermore, the nickel nanotube was made into microelectrode and its electrochemical hydrogen storage property was studied using cyclic voltammetry. The results showed that the diameter of nickel nanotubes fabricated was around 20–100 mm, and the length of the nanotube could reach micron grade. The nickel nanotubes had hydrogen storage property, and the hydrogen storage performance was higher than that of nickel powder.
34
CAVNESS, B., N. McGARA e S. WILLIAMS. "SPECTRA OF RADIATION EMITTED FROM OPEN-ENDED AND CLOSED CARBON NANOTUBES EXPOSED TO MICROWAVE FIELDS". International Journal of Nanoscience 12, n. 04 (agosto 2013): 1350028. http://dx.doi.org/10.1142/s0219581x13500282.
Testo completoAbstract (sommario):
We performed experiments in which both open-ended and closed carbon nanotubes were exposed to 2.46 GHz microwaves over the course of several irradiation and cooling cycles at a pressure of ~ 10-6 torr. The spectra of the radiation emitted from the nanotubes indicate that the intensity of the emitted radiation with wavelengths of 650–1000 nm increased during the irradiation cycles. However, the intensity of the radiation emitted from untreated nanotubes increased substantially more than the intensity of the radiation emitted from nanotubes that had been chemically treated in order to open nanotube ends. As open-ended nanotubes have a lower work function than closed nanotubes, and as nanotube ends are known to open as they are heated, our results suggest that the mechanism responsible for the emission of infrared, visible and ultraviolet radiation from carbon nanotubes exposed to microwaves is field emission-induced luminescence.
35
Han, Ki Bong, e Yong Ho Choi. "Characterization of Contact Resistance between Carbon Nanotubes Film and Metal Electrodes". Advanced Materials Research 683 (aprile 2013): 238–41. http://dx.doi.org/10.4028/www.scientific.net/amr.683.238.
Testo completoAbstract (sommario):
Carbon nanotube has attracted great research attentions due to its outstanding electrical, physical, mechanical, chemical properties. Based on its excellent properties, the carbon nanotube is promising nanoscale material for novel electrical, mechanical, chemical, and biological devices and sensors. However, it is very difficult to control the structure of carbon nanotube during synthesis. A carbon nanotubes film has 3 dimensional structures of interwoven carbon nanotubes as well as unique properties such as transparency, flexibility and good electrical conductivity. More importantly, the properties of carbon nanotubes are ensemble averaged in this formation. In this research, we study the contact resistance between carbon nanotubes film and metal electrode. For most of electrical devices using carbon nanotubes film, it is necessary to have metal electrodes on the film for current path. A resistance at the contact lowers the electrical efficiencies of the devices. Therefore, it is important to measure and characterize the contact resistance and lower it for better efficiencies. The device demonstrated in this study using classical technique for metal contacts provides relatively reliable contact resistance measurements for carbon nanotubes film applications.
36
Kaplan-Ashiri, I., S. R. Cohen, K. Gartsman, R. Rosentsveig, G. Seifert e R. Tenne. "Mechanical behavior of individual WS2 nanotubes". Journal of Materials Research 19, n. 2 (febbraio 2004): 454–59. http://dx.doi.org/10.1557/jmr.2004.19.2.454.
Testo completoAbstract (sommario):
The Young's modulus of WS2 nanotubes is an important property for various applications. Measurements of the mechanical properties of individual nanotubes are challenged by their small size. In the current work, atomic force microscopy was used to determine the Young's modulus of an individual multiwall WS2 nanotube, which was mounted on a silicon cantilever. The buckling force was measured by pushing the nanotube against a mica surface. The average Young's modulus of an individual WS2 nanotube, which was calculated by using Euler's equation, was found to be 171 GPa. First-principle calculations of the Young's modulus of MoS2 single-wall nanotubes using density-functional–based tight-binding method resulted in a value (230 GPa) that is close to that of the bulk material. Furthermore, the diameter dependence of the Young's modulus in both zigzag and armchair configuration was studied and was found to approach the bulk value for nanotubes with few-nanometer diameters. Similar behavior is expected for WS2 nanotubes. The mechanical behavior of the WS2 nanotubes as atomic force microscope imaging tips gave further support for the measured Young's modulus.
37
Cui, Zhi Min, Cui Zhi Dong, Ying Chen e Qing Jun Zhang. "Hollow Structure of Nano-Crystals by Microemulsion Method". Advanced Materials Research 391-392 (dicembre 2011): 260–63. http://dx.doi.org/10.4028/www.scientific.net/amr.391-392.260.
Testo completoAbstract (sommario):
Nano-crystals with hollow structure were synthesized by microemulsion method. XRD(X-rays Diffraction), EDS(Energy Dispersive Spectrometer) and TEM(Transmission Electron Micrograph) techniques were used to characterize the structure, composition and morphology of nano-crystals. Results of XRD and ED(Electron Diffraction) revealed that nano-crystals were the mixture of CdSe and CdSeO3. TEM images shows nanotube and bamboo-like nanotube, CdSe nano-particles are observed in bamboo-like nanotubes. Reports on nanotubes and bamboo-like nanotubes by microemulsion method are little. In this experiment nanotubes and bamboo-like nanotubes are successfully prepared. In this experiment just through one step nano-crystals with hollow structure are obtained, which greatly simplify the experiment process to removing core.
38
Treacy, M. M. J., e T. W. Ebbesen. "Mechanical Properties of Carbon Nanotubes Inferred from TEM". Microscopy and Microanalysis 3, S2 (agosto 1997): 393–94. http://dx.doi.org/10.1017/s1431927600008850.
Testo completoAbstract (sommario):
The discovery of carbon nanotubes by Iijima has stimulated considerable research into their structural, chemical, electrical and mechanical properties. Apart from their intrinsic beauty as macromolecules, and their possibilities as one-dimensional conductors, researchers are stimulated by the notion that a structurally perfect nanotube may be one of the strongest known materials.It is known that when nanotubes are bent through large angles, regions of high curvature buckle to develop crimps, similar to those observed when metal pipes are bent too much. Figure la shows a multi-walled nanotube that has one end embedded in a ceramic matrix. The other end is snagged so that the tube is bent. Several crimps are visible on the nanotube. Figure lb shows the same nanotube imaged a few moments later. Remarkably, the nanotube has sprung straight and the crimps have disappeared. This demonstrates that buckling in nanotubes does not involve plastic deformation, and that nanotubes can maintain their structural integrity even after severe deformation.
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Alanka, Sandeep, Chanamala Ratnam e Balla Srinivasa Prasad. "Characterization of cubic tumbler rod milled dispersed carbon nanotubes–Aluminum composites". Journal of Composite Materials 52, n. 28 (1 maggio 2018): 3973–85. http://dx.doi.org/10.1177/0021998318773437.
Testo completoAbstract (sommario):
In this work, cubic tumbler rod milling was used to disperse X wt% multiwalled carbon nanotubes (X = 0.5, 0.75, 1.0) in an aluminum matrix. Dispersed precursor of aluminum–multiwalled carbon nanotube composite was subsequently consolidated by cold compaction followed by sinter-forged process. Microstructural and mechanical behaviors of as-produced aluminum–multiwalled carbon nanotube composites with different concentration were investigated. Findings revealed that the as-produced Al–0.75 wt% carbon nanotube sinter-forged composite exhibits homogenous distribution and embedded nanotubes confirmed by the scanning electron microscope and the properties were observed to be increased significantly up to addition of 0.75 wt% of carbon nanotubes concentration than the pure aluminum as well as extruded composite and decrease to 1.0 wt% carbon nanotube due to the agglomeration of multiwalled carbon nanotube. However, enhancement of hardness, tensile strength, and Young’s modulus of the nanocomposites, compared with pure aluminum are 48.5, 83.8, and 30%, respectively. The tensile fractography of sinter-forged composite shows carbon nanotubes act like a bridge and barring the crack growth of aluminum matrix, remaining are pullout. Hence, it can be concluded that aluminum carbide phase starting from 0.75 wt% carbon nanotube and a strong interfacial bonding in as-produced aluminum–carbon nanotube composite has been observed which gives effective load transfer between aluminum matrix and carbon nanotubes.
40
Rouhi, S., R. Ansari e A. Nikkar. "On the vibrational characteristics of single-walled boron nitride nanotubes/polymer nanocomposites: A finite element simulation". Modern Physics Letters B 31, n. 22 (10 agosto 2017): 1750208. http://dx.doi.org/10.1142/s0217984917502086.
Testo completoAbstract (sommario):
The finite element method is used here to investigate the vibrational behavior of single-walled boron nitride nanotube/polymer nanocomposites. The polymer matrix is modeled as a continuous media. Besides, nanotubes are modeled as a space-frame structure. It is shown that increasing the length of nanotubes at a constant volume fraction leads to decreasing of the nanocomposite frequency. By investigating the effect of volume percentage on the frequencies of the boron nitride nanotube-reinforced polymer nanocomposites, it is observed that for short nanotubes, the nanocomposites with larger nanotube volume fractions have larger frequencies. Also, through studying the first 10 frequencies of nanocomposites reinforced by armchair and zigzag nanotubes, it is shown that the effect of chirality on the vibrational behavior of nanocomposite is insignificant.
41
RAMESH, PALANISAMY, KENICHI SATO, YUJI OZEKI, MASAHITO YOSHIKAWA, NAOKI KISHI, TOSHIKI SUGAI e HISANORI SHINOHARA. "MICROSCOPIC CHARACTERIZATION OF THIN-MULTIWALL CARBON NANOTUBES SYNTHESIZED BY CATALYTIC CVD METHOD WITH MESOPOROUS SILICA". Nano 01, n. 03 (novembre 2006): 207–12. http://dx.doi.org/10.1142/s1793292006000227.
Testo completoAbstract (sommario):
Carbon nanotubes with 1–6 walls have been grown on cobalt-loaded mesoporous silica (i.e., MCM41) by using acetylene catalytic chemical vapor deposition. It is found that titanium grafting on the MCM41 pore walls prior to cobalt loading promotes the growth of nanotubes with 1–6 walls. As-grown nanotube material is found to be a mixture of single-wall carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs) and thin-multiwall carbon nanotubes (t-MWNTs) with 3–6 walls. Annealing of the as-grown nanotubes has reduced the amount of SWNTs in the nanotube mixture. Several structural deformations of the t-MWNTs are observed during transmission electron microscopy (TEM) analysis. Complete or partial collapse of the t-MWNTs is also found due to these structural deformations. Graphite-like domains developed at the collapsed regions stabilize these structural deformations.
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Kono, Junichiro. "(Invited, Digital Presentation) Macroscopically Aligned Carbon Nanotubes for Photonics, Electronics, and Thermoelectrics". ECS Meeting Abstracts MA2022-01, n. 10 (7 luglio 2022): 775. http://dx.doi.org/10.1149/ma2022-0110775mtgabs.
Testo completoAbstract (sommario):
The remarkable flexibility, stable chemical structure, and extraordinary thermal, electrical, and optical properties of carbon nanotubes (CNTs) are promising for a variety of applications in flexible and/or high-temperature electronics, optoelectronics, and thermoelectrics, including wearables, refractory photonics, and waste heat harvesting [1]. However, the long-standing goal in the preparation of CNT ensembles is how to maintain the extraordinary properties of individual CNTs on a macroscopic scale. The polydispersity and randomness remain two main challenges. Here, we will discuss different methods for creating macroscopically aligned CNTs, including spontaneous formation of wafer-scale aligned CNT films via controlled vacuum filtration [2-4] and production of ultrahigh-conductivity CNT fibers and films through solution spinning and coating [5,6]. We will then describe the optical [2,7-11], dc and ac electrical [2,12-17], thermal [18], and thermoelectric [19-21] properties of these materials. These results are promising for device applications in various fields such as flexible CNT broadband detectors [22-26], spectrally selective thermal emitters [11], and thermoelectric devices [20,21]. W. Gao et al., “Macroscopically Aligned Carbon Nanotubes for Flexible and High-Temperature Electronics, Optoelectronics, and Thermoelectrics,” Journal of Physics D: Applied Physics 53, 063001 (2020). X. He et al., “Wafer-Scale Monodomain Films of Spontaneously Aligned Single-Walled Carbon Nanotubes,” Nature Nanotechnology 11, 633 (2016). W. Gao and J. Kono, “Science and Applications of Wafer-Scale Crystalline Carbon Nanotube Films Prepared through Controlled Vacuum Filtration,” Royal Society Open Science 6, 181605 (2019). N. Komatsu et al., “Groove-Assisted Global Spontaneous Alignment of Carbon Nanotubes in Vacuum Filtration,” Nano Letters 20, 2332 (2020). N. Behabtu et al., “Strong, Light, Multifunctional Fibers of Carbon Nanotubes with Ultrahigh Conductivity,” Science 339, 182 (2013). L. W. Taylor et al., “Improved Properties, Increased Production, and the Path to Broad Adoption of Carbon Nanotube Fibers,” Carbon 171, 689 (2021). K. Yanagi et al., “Intersubband Plasmons in the Quantum Limit in Gated and Aligned Carbon Nanotubes,” Nature Communications 9, 1121 (2018). W. Gao et al., “Continuous Transition between Weak and Ultrastrong Coupling through Exceptional Points in Carbon Nanotube Microcavity Exciton–Polaritons,” Nature Photonics 12, 362 (2018). M. E. Green et al., “Bright and Ultrafast Photoelectron Emission from Aligned Single-Wall Carbon Nanotubes through Multiphoton Exciton Resonance,” Nano Letters 19, 158 (2019). F. Katsutani et al., “Direct Observation of Cross-Polarized Excitons in Aligned Single-Chirality Single-Wall Carbon Nanotubes,” Physical Review B 99, 035426 (2019). W. Gao et al., “Macroscopically Aligned Carbon Nanotubes as a Refractory Platform for Hyperbolic Thermal Emitters,” ACS Photonics 6, 1602 (2019). X. Wang et al., “High-Ampacity Power Cables of Tightly-Packed and Aligned Carbon Nanotubes,” Advanced Functional Materials 24, 3241 (2014). A. Zubair et al., “Carbon Nanotube Fiber Terahertz Polarizer,” Applied Physics Letters 108, 141107 (2016). D. Tristant et al., “Enlightening the Ultrahigh Electrical Conductivities of Doped Double-Wall Carbon Nanotube Fibers by Raman Spectroscopy and First-Principles Calculations,” Nanoscale 18, 19668 (2016). N. Komatsu et al., “Modulation-Doped Multiple Quantum Wells of Aligned Single-Wall Carbon Nanotubes,” Advanced Functional Materials 27, 1606022 (2017). F. R. G. Bagsican et al., “Terahertz Excitonics in Carbon Nanotubes: Exciton Autoionization and Multiplication,” Nano Letters 20, 3098 (2020). A. Baydin et al., “Giant Terahertz Polarization Rotation in Ultrathin Films of Aligned Carbon Nanotubes,” Optica 8, 760 (2021). S. Yamaguchi et al., “One-Directional Thermal Transport in Densely Aligned Single-Wall Carbon Nanotube Films,” Applied Physics Letters 115, 223104 (2019). K. Fukuhara et al., “Isotropic Seebeck Coefficient of Aligned Single-Wall Carbon Nanotube Films,” Applied Physics Letters 113, 243105 (2018). Y. Ichinose et al., “Solving the Thermoelectric Trade-Off Problem with Metallic Carbon Nanotubes,” Nano Letters 19, 7370 (2019). N. Komatsu et al., “Macroscopic Weavable Fibers of Carbon Nanotubes with Giant Thermoelectric Power Factor,” Nature Communications 12, 4931 (2021). S. Nanot et al., “Broadband, Polarization-Sensitive Photodetector Based on Optically-Thick Films of Macroscopically Long, Dense, and Aligned Carbon Nanotubes,” Scientific Reports 3, 1335 (2013). X. He et al., “Photothermoelectric p-n Junction Photodetector with Intrinsic Broadband Polarimetry Based on Macroscopic Carbon Nanotube Films,” ACS Nano 7, 7271 (2013). X. He et al., “Carbon Nanotube Terahertz Detector,” Nano Letters 14, 3953 (2014). X. He, F. Léonard, and J. Kono, “Uncooled Carbon Nanotube Photodetectors,” Advanced Optical Materials 3, 989 (2015). A. Zubair et al., “Carbon Nanotube Woven Textile Photodetector,” Physical Review Materials 2, 015201 (2018).
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Tomilin O. B., Rodionova E. V., Rodin E.A., Poklonski N. A., Anikeyev I. I. e Ratkevich S. V. "Dependence of the energy of emission molecular orbitals in short open carbon nanotubes on the electric field". Physics of the Solid State 64, n. 3 (2022): 347. http://dx.doi.org/10.21883/pss.2022.03.53191.201.
Testo completoAbstract (sommario):
On the examples of short open carbon nanotubes of armchair type (n,n), for n=3, 4, and zigzag (n,0), for n=5, 6, 7, the influence of the magnitude and direction of the external constant electric field vector on their field emission properties was studied. It is shown that the deviation of the field vector from the nanotube axis leads to an increase in the field strength to generate electron field emission. Emission orbitals in carbon nanotubes (n,n) found as a result of a new type of conjugation of p-electrons in cylindrical conjugated systems are more sensitive to a change in the direction of the electric field vector compared to emission orbitals in nanotubes (n,0). When the electric field vector deviates from the nanotube axis, the emission orbitals of carbon nanotubes change the less, the larger the nanotube diameter. Keywords: short open carbon nanotubes, field emission, conjugation of p-electrons, emission molecular orbital.
44
Andersson, M., P. Alberius-Henning, K. Jansson e M. Nygren. "Preparation of Carbon Nanotubes from CO and in situ Formed Nano-sized Pd Particles". Journal of Materials Research 15, n. 8 (agosto 2000): 1822–27. http://dx.doi.org/10.1557/jmr.2000.0263.
Testo completoAbstract (sommario):
Carbon nanotubes, typically of 0.5-μm length and 20-nm diameter, were prepared with good selectivity by disproportionation of CO in He over a Pd/La2O3 catalyst. The catalyst was formed in situ by reduction of a La4PdO7 precursor. The obtained nanotubes had the so-called fishbone structure with the graphitic planes inclined at an angle to the long axis of the nanotube. The effect of CO concentration was studied at 673 °C, and it was found that, among the concentrations studied, 20 vol% CO in the gas was suitable for nanotube growth. The obtained nanotube/La2O3/Pd composite contained typically only 3 wt% nanotubes after 8 h of CO treatment. A process for selective dissolution of La2O3 and Pd was applied, and a product containing 85 wt% nanotubes was obtained. The nanotubes were characterized by high-resolution, transmission, and scanning electron microscope studies, combined with element analyses using energy dispersive spectrometers, x-ray powder diffraction studies, and thermogravimetric analysis.
45
Kharlamova, Marianna V. "Investigation of growth dynamics of carbon nanotubes". Beilstein Journal of Nanotechnology 8 (11 aprile 2017): 826–56. http://dx.doi.org/10.3762/bjnano.8.85.
Testo completoAbstract (sommario):
The synthesis of single-walled carbon nanotubes (SWCNTs) with defined properties is required for both fundamental investigations and practical applications. The revealing and thorough understanding of the growth mechanism of SWCNTs is the key to the synthesis of nanotubes with required properties. This paper reviews the current status of the research on the investigation of growth dynamics of carbon nanotubes. The review starts with the consideration of the peculiarities of the growth mechanism of carbon nanotubes. The physical and chemical states of the catalyst during the nanotube growth are discussed. The chirality selective growth of nanotubes is described. The main part of the review is dedicated to the analysis and systematization of the reported results on the investigation of growth dynamics of nanotubes. The studies on the revealing of the dependence of the growth rate of nanotubes on the synthesis parameters are reviewed. The correlation between the lifetime of catalyst and growth rate of nanotubes is discussed. The reports on the calculation of the activation energy of the nanotube growth are summarized. Finally, the growth properties of inner tubes inside SWCNTs are considered.
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Komane, Patrick P., Yahya E. Choonara, Lisa C. du Toit, Pradeep Kumar, Pierre P. D. Kondiah, Girish Modi e Viness Pillay. "Diagnosis and Treatment of Neurological and Ischemic Disorders Employing Carbon Nanotube Technology". Journal of Nanomaterials 2016 (2016): 1–19. http://dx.doi.org/10.1155/2016/9417874.
Testo completoAbstract (sommario):
Extensive research on carbon nanotubes has been conducted due to their excellent physicochemical properties. Based on their outstanding physicochemical properties, carbon nanotubes have the potential to be employed as theranostic tools for neurological pathologies such as Alzheimer’s disease and Parkinson’s disease including ischemic stroke diagnosis and treatment. Stroke is currently regarded as the third root cause of death and the leading source of immobility around the globe. The development and improvement of efficient and effective procedures for central nervous system disease diagnosis and treatment is necessitated. The main aim of this review is to discuss the application of nanotechnology, specifically carbon nanotubes, to the diagnosis and treatment of neurological disorders with an emphasis on ischemic stroke. Areas covered include the conventional current diagnosis and treatment of neurological disorders, as well as a critical review of the application of carbon nanotubes in the diagnosis and treatment of ischemic stroke, covering areas such as functionalization of carbon nanotubes and carbon nanotube-based biosensors. A broad perspective on carbon nanotube stimuli-responsiveness, carbon nanotube toxicity, and commercially available carbon nanotubes is provided. Potential future studies employing carbon nanotubes have been discussed, evaluating their extent of advancement in the diagnosis and treatment of neurological and ischemic disorders.
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Tadi Beni, Yaghoub, Fahimeh Mehralian e Mehran Karimi Zeverdejani. "Free vibration of anisotropic single-walled carbon nanotube based on couple stress theory for different chirality". Journal of Low Frequency Noise, Vibration and Active Control 36, n. 3 (29 marzo 2017): 277–93. http://dx.doi.org/10.1177/0263092317700153.
Testo completoAbstract (sommario):
In the present work, using the couple stress theory, a new model is provided for vibrating behavior of anisotropic carbon nanotubes. Carbon nanotubes have many applications, and careful analysis of their behavior is important. So far, using the isotropic models, several studies have been conducted on carbon nanotube vibration. According to the arrangement of carbon atoms on the nanotube walls, their properties will be different in various directions. Therefore, the behavior of carbon nanotubes must be considered as anisotropic materials. In this article, initially, using the Hamilton's principle, motion equations, and boundary conditions of carbon nanotubes are extracted based on couple stress theory. Afterwards, the equations are solved using the analytical solution method. In the results section, the effect of different parameters, particularly the anisotropic effect, on the carbon nanotube natural frequency is investigated.
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Jin, Weifeng, Ying Tao e Rongzhong Cheng. "Coupled Effect of Carbon Nanotubes and Crushing on Shear Strength and Compression of Calcareous Sand Seeped by Colloidal Silica". Geofluids 2022 (12 agosto 2022): 1–17. http://dx.doi.org/10.1155/2022/9335126.
Testo completoAbstract (sommario):
Colloidal silica, which has a low viscosity, can seep quickly through sand and subsequently form silica gel to stabilize the sand. The addition of carbon nanotubes can improve the strength of the sand-gel composite. However, previous literature has not investigated the coupled effect of carbon nanotubes and sand crushing on the strength and compression of colloidal-silica-stabilized calcareous sand. So we prepared 86 specimens with 2 different concentrations of colloidal silica and 9 different contents of carbon nanotubes. Then, we performed triaxial shearing and isotropic compression tests based on the triaxial system. The test results show the following: (1) The same carbon nanotube content at the higher concentration of colloidal silica results in higher shear strength, but increasing crushing makes the shear strengths, respectively, caused by 10 wt% and 40 wt% colloidal silica dispersed with carbon nanotubes tend to be the same. (2) The optimal content of carbon nanotubes, which leads to the maximum shear strength, is distributed differently in different concentrations of colloidal silica; i.e., as crushing increases, the optimal carbon nanotube content drifts from 0.03 wt% to 0.10 wt% in 10 wt% colloidal silica, while 40 wt% colloidal silica stabilizes the optimal carbon nanotube content around 0.08 wt%. (3) Compared with carbon nanotubes in 10 wt % colloidal silica, carbon nanotubes in 40 wt% colloidal silica cause higher cohesion rather than internal friction angle, which is the mechanism of higher shear strength at higher colloidal silica concentration with the same carbon nanotube content. (4) For isotropic compression, minimal compression is caused by 40 wt% colloidal silica plus 0.1 wt% carbon nanotubes.
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Khaleghian, Mehrnoosh, e Fatemeh Azarakhshi. "Quantum Mechanical Investigation of Geometrical Structure and Dynamic Behavior of h-BNNT (9,9-5) and h-AlNNT (9,9-5)Single-Walled Nanotubes: NBO Analysis". Letters in Organic Chemistry 16, n. 9 (5 luglio 2019): 705–17. http://dx.doi.org/10.2174/1570178615666181022152818.
Testo completoAbstract (sommario):
In the present research, B45H36N45 Born Nitride (9,9) nanotube (BNNT) and Al45H36N45 Aluminum nitride (9,9) nanotube (AlNNT) have been studied, both having the same length of 5 angstroms. The main reason for choosing boron nitride nanotubes is their interesting properties compared with carbon nanotubes. For example, resistance to oxidation at high temperatures, chemical and thermal stability higher rather than carbon nanotubes and conductivity in these nanotubes, unlike carbon nanotubes, does not depend on the type of nanotube chirality. The method used in this study is the density functional theory (DFT) at Becke3, Lee-Yang-Parr (B3LYP) method and 6-31G* basis set for all the calculations. At first, the samples were simulated and then the optimized structure was obtained using Gaussian 09 software. The structural parameters of each nanotube were determined in 5 layers. Frequency calculations in order to extract the thermodynamic parameters and natural bond orbital (NBO) calculations have been performed to evaluate the electron density and electrostatic environment of different layers, energy levels and related parameters, such as ionization energy and electronic energy, bond gap energy and the share of hybrid orbitals of different layers.
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George, Jinu Jacob, Rajatendu Sengupta e Anil K. Bhowmick. "Influence of Functionalization of Multi-Walled Carbon Nanotubes on the Properties of Ethylene Vinyl Acetate Nanocomposites". Journal of Nanoscience and Nanotechnology 8, n. 4 (1 aprile 2008): 1913–21. http://dx.doi.org/10.1166/jnn.2008.18256.
Testo completoAbstract (sommario):
Commercially available multiwalled carbon nanotubes (MWNT) were chemically modified by amine, acid and silane and their ethylene vinyl acetate (EVA) based nanocomposites were prepared. Unmodified and modified nanotubes were characterized by thermogravimetry, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. Early degradation of modified nanotubes from the thermogravimetry study proved the presence of functional groups on nanotube surface. Increase in D-band to G-band ratio and a shift in radial breathing mode peaks from the Raman spectra indicated the generation of surface defects due to functionalization and variation in van der Waals force of attraction between nanotube aggregates on modification. The unmodified nanotubes improved the tensile strength by 30% with 4 weight% of filler. Amine modification imparted further increase in strength due to the presence of functional groups on the nanotube surface and the subsequent better dispersion of the nanotubes in the polymer matrix. The silane treatment imparted maximum improvement in various properties of the nanocomposites. The nanotubes provided better thermal degradation stability and also higher thermal conductivity to virgin EVA. The results were well supported by the morphological as well as swelling study of the various samples.