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Nitride Nanotubes (nitride + nanotube)
Kinds of Nitride Nanotubes Selected AbstractsSuperparamagnetic Nanoparticles: Facile Fabrication and Superparamagnetism of Silica-Shielded Magnetite Nanoparticles on Carbon Nitride Nanotubes (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Mater. The superparamagnetic response of silica-coated magnetite nanoparticles on carbon nitride nanotubes in water is depicted in this cover image. The silica shell helps maintain the superparamagnetic fluid while magnetite nanoparticles on carbon nitride nanotubes without silica layers show a significant degradation of magnetic performance in water. On page 2213, Jeung Ku Kang and co-workers report a facile fabrication of these silica-shielded magnetite nanoparticles on carbon nitride nanotubes via the liquid polyol process. [source] Facile Fabrication and Superparamagnetism of Silica-Shielded Magnetite Nanoparticles on Carbon Nitride NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Jung Woo Lee Abstract Using conventional methods to synthesize magnetic nanoparticles (NPs) with uniform size is a challenging task. Moreover, the degradation of magnetic NPs is an obstacle to practical applications. The fabrication of silica-shielded magnetite NPs on carbon nitride nanotubes (CNNTs) provides a possible route to overcome these problems. While the nitrogen atoms of CNNTs provide selective nucleation sites for NPs of a particular size, the silica layer protects the NPs from oxidation. The morphology and crystal structure of NP,CNNT hybrid material is investigated by transmission electron microscopy (TEM) and X-ray diffraction. In addition, the atomic nature of the N atoms in the NP,CNNT system is studied by near-edge X-ray absorption fine structure spectroscopy (nitrogen K-edge) and calculations of the partial density of states based on first principles. The structure of the silica-shielded NP,CNNT system is analyzed by TEM and energy dispersive X-ray spectroscopy mapping, and their magnetism is measured by vibrating sample and superconducting quantum interference device magnetometers. The silica shielding helps maintain the superparamagnetism of the NPs; without the silica layer, the magnetic properties of NP,CNNT materials significantly degrade over time. [source] Boron Nanotube,Polymer Composites: Towards Thermoconductive, Electrically Insulating Polymeric Composites with Boron Nitride Nanotubes as Fillers (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Mater. Composites formed through embedding of high-concentration boron nitride nanotubes in polymers are reported by C. Y. Zhi et al. on page 1857. The composites possess high thermal conductivity, high break-over voltage, low coefficient of thermal expansion, and other favorable properties. These polymeric composites are promising highly thermoconductive electrically insulating materials for a range of applications. [source] Towards Thermoconductive, Electrically Insulating Polymeric Composites with Boron Nitride Nanotubes as FillersADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Chunyi Zhi Abstract Ultilizing boron nitride nanotubes (BNNTs) as fillers, composites are fabricated with poly(methyl methacrylate), polystyrene, poly(vinyl butyral), or poly(ethylene vinyl alcohol) as the matrix and their thermal, electrical, and mechanical properties are evaluated. More than 20-fold thermal conductivity improvement in BNNT-containing polymers is obtained, and such composites maintain good electrical insulation. The coefficient of thermal expansion (CTE) of the BNNT-loaded polymers is dramatically reduced because of interactions between the polymer chains and the nanotubes. Moreover, the composites possess good mechanical properties, as revealed by Vickers microhardness tests. This detailed study indicates that BNNTs are very promising nanofillers for polymeric composites, allowing the simultaneous achievement of high thermal conductivity, low CTE, and high electrical resistance, as required for novel and efficient heat-releasing materials. [source] Energetic stability of boron nitride nanostructures doped with one carbon atomINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2010Rebeca D. Gonçalves Abstract We have investigated, using first-principles calculations, the role of a substitutional carbon atom on the geometric stability of boron nitride monolayers, nanotubes, and nanocones. It is shown that the formation of energy depends on the number of atoms for the monolayers and on the diameter for the tubes. It is also found, for the carbon-doped boron nitride nanotubes, that the value for the strain energy approaches the one obtained for nondoped tubes with increasing diameter. For the structural stability, we have verified that the doping, which introduces an excess of nitrogen or boron, makes each structure more favorable in its reverse atmosphere, i.e., excess of nitrogen is more stable in a boron-rich growth environment, whereas excess of boron is preferred in a nitrogen-rich condition. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Formation of Silicon-Doped Boron Nitride Bamboo Structures Via Pyrolysis of a Polymeric PrecursorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006Yi Fan In this paper, we report the growth of bamboo-like silicon-doped boron nitride nanotubes via catalyst-assisted pyrolysis of a boron-containing polymeric precursor. The morphologies and structures of the nanotubes were characterized using electron microscopy and Raman spectroscopy. Two types of nanotubes are observed, one from a base-growth mode and the other from a tip-growth mode. The type II nanotubes contain encapsulated catalytic nanoparticles at the tip of every compartment. This unique structure is a promising candidate for applications in many nanodevices. [source] Exciton luminescence of boron nitride nanotubes and nano-archesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 14 2006B. Berzina Abstract We report photoluminescence (PL) and PL-excitation spectroscopy of BN nanotubes (nt-BN) mixed with some residual hexagonal crystalline (h-BN) starting material, and of pure h-BN microcrystalline powder. The nanotube phase exhibits a broad-band PL near 380 nm, in agreement with a published report of cathodoluminescence from a sample comprising >90% nanotubes. This emission is almost 3 eV lower in energy than unrelaxed exciton states found in recent all-electron theories of nt-BN and h-BN and about 1.4 eV lower than the lowest (perturbed dark?) exciton seen in absorption of nt-BN. This may suggest that excitons in nt-BN vibrationally relax to self-trapped states before emitting, a path found in many wide-gap solids, especially in quasi-1-dimensional forms. Exciton emission from bulk single-crystal h-BN has been shown to occur from vibrationally unrelaxed (free-exciton) states. We suggest a hypothesis in which known nano-arch reconstructions on the surface of h-BN may provide the low-dimensional environment to make exciton self-trapping on the surfaces of h-BN likely. This allows consistent interpretaton of the surface-related 380 nm emission from h-BN powder within a half-nanotube self-trapped exciton hypo- thesis. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Double-helix structure in multiwall boron nitride nanotubesACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2005Ayten Celik-Aktas A new nanotube structural form is reported that resembles a double helix in multiwall boron nitride nanotubes (MW-BNNT) grown by a carbon-free chemical-vapor-deposition process as documented by evidence obtained by transmission electron diffraction and microscopy. The double-helix structure is found in MW-BNNTs exhibiting the same chirality in its different walls. The MW-BNNTs deviate from the structure of ideal nested coaxial cylindrical tubes. Most significantly, bright- and dark-field electron imaging reveals regular zigzag dark and bright spots on the side walls of the nanotubes. The repeating distance between the bright, or dark, spots is related to the chiral angle of the nanotube. Electron diffraction patterns recorded from individual nanotubes show additional diffraction spots belonging to the ,201, zone axes, which are not allowed in a perfectly cylindrical nanotube. These additional diffraction spots become asymmetrical as smaller sections of the nanotube are probed. A series of diffraction patterns recorded along the tube axis showed that the imperfections giving rise to these spots move in a regular fashion around the circumference of the tube. It is shown that all experimental evidence supports the structure model of two helices; one is polygonal in cross section and highly crystalline and the other is circular and less ordered. It is further suggested that the double-helix structure is a result of stronger wall,wall interactions associated with the ionic bonding in boron nitride. [source] Cytocompatibility, interactions, and uptake of polyethyleneimine-coated boron nitride nanotubes by living cells: Confirmation of their potential for biomedical applicationsBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2008Gianni Ciofani Abstract Boron nitride nanotubes (BNNTs) have unique physical properties, which can be exploited in the biomedical field. Hence, the surprising lack of reported studies on their biocompatibility and interactions with living cells, addressed by the present paper which deals the results of such an investigation based on 72 h culture of human neuroblastoma cell line (SH-SY5Y) in the presence of an aqueous suspension of polyethyleneimine (PEI)-coated BNNTs. BNNTs conjugated with fluorescent markers (quantum dots) are employed to enable tracking of their uptake by living cells. The results demonstrate good cytocompatibility together with unequivocal BNNT cellular uptake by an energy-dependent endocytic process. Biotechnol. Bioeng. 2008;101: 850,858. © 2008 Wiley Periodicals, Inc. [source] | |||||||||||||