Search results for "OTU"
showing 10 items of 2539 documents
Synthesis and characterization of highly ordered cobalt-magnetite nanocable arrays.
2006
Magnetically tunable, high-density arrays of coaxial nanocables within anodic aluminum oxide (AAO) membranes have been synthesized. The nanocables consist of magnetite nanowires surrounded by cobalt nanotube sheaths and cobalt nanowires surrounded by magnetite nanotube sheaths. These materials are a combination of separate hard (Co) and soft (Fe3O4) magnetic materials in a single nanocable structure. The combination of two or more magnetic materials in such a radial structure is seen as a very powerful tool for the future fabrication of magnetoresistive, spin-valve and ultrafast spin-injection devices with nonplanar geometries. The nanocable arrays were prepared using a supercritical-fluid …
Electron Irradiation Effects in Carbon Nanostructures: Surface Reconstruction, Extreme Compression, Nanotube Growth and Morphology Manipulation
2008
It will be demonstrated, that irradiation exposure at elevated temperatures, can be used as an effective tool to covalently weld SWNTs in order to create molecular junctions of various geometries [1–3]. We have fabricated Y, X and T-like junctions that are stable [2]. Tight binding molecular dynamics calculations demonstrate that vacancies, formed under the electron beam, trigger the formation of molecular junctions involving seven or eight membered carbon rings. We envisage that these results will pave the way towards controlled fabrication of novel nanotube-based molecular circuits, nanotube fabrics and network architectures. In this context, novel super architectures, using carbon nanotu…
Fullerite crystal thermodynamic characteristics and the law of corresponding states.
2010
The existence of single-wall carbon nanotubes in organic solvents in the form of clusters is discussed. A theory is developed based on a bundlet model, which enables describing the cluster-size distribution function. Comparison of calculated solubilities with experiments would permit obtaining energetic parameters, characterizing the interaction of a nanotube with its surrounding. Fullerenes and nanotubes are objects whose behaviour in many physical situations is characterized by peculiarities, which show up in that these systems represent the only soluble forms of carbon, what is related to their molecular structures. The fullerene molecule is a virtually uniform closed spherical-spheroida…
Synthesis of Fullerene- and Nanotube-Like SnS2 Nanoparticles and Sn/S/Carbon Nanocomposites
2009
SnS2 nested fullerene-type (IF) nanoparticles, nanotubes, and SnS2/C hybrid nanostructures were obtained by vapor transport starting from elemental tin and CS2. The reaction was carried out in a single-step process by heating elemental tin metal powder in a horizontal tube furnace at 800−1000 °C. TEM analysis allowed proposing a plausible mechanism for the formation of fullerene-like particles of SnS2 as well as tubes and scrolls from nanosheets of SnS2. Pure material could be obtained by optimizing the reaction based on a product analysis using powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) combined with energy-dispersive X-ray spectroscopy (EDX…
High-Yield of Memory Elements from Carbon Nanotube Field-Effect Transistors with Atomic Layer Deposited Gate Dielectric
2008
Carbon nanotube field-effect transistors (CNT FETs) have been proposed as possible building blocks for future nano-electronics. But a challenge with CNT FETs is that they appear to randomly display varying amounts of hysteresis in their transfer characteristics. The hysteresis is often attributed to charge trapping in the dielectric layer between the nanotube and the gate. This study includes 94 CNT FET samples, providing an unprecedented basis for statistics on the hysteresis seen in five different CNT-gate configurations. We find that the memory effect can be controlled by carefully designing the gate dielectric in nm-thin layers. By using atomic layer depositions (ALD) of HfO$_{2}$ and T…
Adsorption Studies of Molecules on the Halloysite Surfaces: A Computational and Experimental Investigation
2017
We report the results of joint computational and experimental investigations on the adsorption capability of halloysite toward a set of common molecules (water, alcohols, halides, and carboxylic acids). The halloysite system has been modelized by means of a cluster approach choosing a portion of a spiral nanotube; it has a slight curvature, with a convex aluminic layer. The adsorption geometries are described in terms of hydrogen bond network structures; calculated interaction energies invariably indicate that the inner aluminic surface is the place for preferential adsorption of polar molecules. The presence of substitutional defects on the outer or inner surface of the halloysite model ca…
A study on the stability of carbon nanoforms–polyimidazolium network hybrids in the conversion of co2 into cyclic carbonates
2021
Three different carbon nanoforms (CNFs), single-walled and multi-walled carbon nanotubes (SWCNTs, MWCNTs) and carbon nanohorns (CNHs), have been used as supports for the direct polymerization of variable amounts of a bis-vinylimidazolium salt. Transmission electron microscopy confirmed that all CNFs act as templates on the growth of the polymeric network, which perfectly covers the nanocarbons forming a cylindrical (SWCNTs, MWCNTs) or spherical (CNHs) coating. The stability of these hybrid materials was investigated in the conversion of CO2 into cyclic carbonate under high temperature and CO2 pressure. Compared with the homopolymerized monomer, nanotube-based materials display an improved c…
Steric stabilization of modified nanoclays triggered by temperature.
2015
Halloysite clay nanotubes were modified through the adsorption of poly(N-isopropylacrylamide)-amine terminated (PNIPA-NH2) onto the external surface by exploiting electrostatic interactions at pH=6. In spite the amount of attached polymer is rather low (1 wt%), the properties of the nanotubes are deeply modified. The apparent specific volume and isentropic compressibilities of the hybrid nanomaterial dispersed in water evidenced the transferring of the termosensitive property from the polymer to halloysite. The hydrodynamic radius as well as the ζ-potential of the nanohybrid are consistent with the attachment of a positively charged polymer onto the negative surface of the nanotube. The col…
Ab initio simulations on N and S co-doped titania nanotubes for photocatalytic applications
2015
In this paper we present the results of quantum chemical modeling for energetically stable anatase (001) TiO2 nanotubes, undoped, doped, and codoped with N and S atoms. We calculate the electronic structure of one-dimensional (1D) nanotubes and zero-dimensional (0D) atomic fragments cut out from these nanotubes, employing hybrid density functional theory with a partial incorporation of an exact, nonlocal Hartree–Fock exchange within the formalism of the linear combination of atomic orbitals, as implemented in both CRYSTAL and NWChem total energy codes. Structural optimization of 1D nanotubes has been performed using CRYSTAL09 code, while the cut-out 0D fragments have been modelled using the…
Electronic properties of single-walled carbon nanotubes inside cyclic supermolecules
2006
Possible ways for manipulating carbon nanotubes (CNTs) with cyclic supermolecules are studied using density functional theory. Electronic structure calculations with structure optimizations have been performed for the (4,4) and (8,0) single-walled carbon nanotubes (SWNTs) complexed with crown ethers as well as for the (4,0) SWNT with beta-cyclodextrin. A slight polarization of charge in both the nanotube and the supermolecule is observed upon rotaxane complexation, but the interaction is mainly repulsive, and the systems stay 2.8-3.5 A apart. The supermolecule does not affect the electronic band structure of the nanotube significantly within such a configuration. The situation differs notic…