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Nitrogen Temperature (nitrogen + temperature)
Kinds of Nitrogen Temperature Selected AbstractsFracture behaviour of cracked carbon nanotube-based polymer composites: Experiments and finite element simulationsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2010Y. KURONUMA ABSTRACT This paper studies the fracture behaviour of cracked carbon nanotube (CNT)-based polymer composites by a combined numerical,experimental approach. Tensile tests were conducted on single-edge cracked plate specimens of CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K), and the critical loads for fracture instabilities were determined. Elastic,plastic finite element simulations of the tests were then performed to evaluate the,J -integrals corresponding to the experimentally determined critical loads. Scanning electron microscopy examinations were also made on the specimen fracture surfaces, and the fracture mechanisms of the CNT-based composites were discussed. [source] Raman spectroscopy of dimethyl sulphoxide and deuterated dimethyl sulphoxide at 298 and 77 KJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2002Wayde N. Martens Raman spectroscopy was used to determine the molecular behaviour of DMSO and DMSO- d6, and to compare it with that of DMSO in DMSO-intercalated kaolinites. For DMSO at 298 K two bands are observed at 2994 and 2913 cm,1 and are assigned to the antisymmetric and symmetric CH stretching modes. At 77 K the degeneracy of these bands is lost. Bands are now observed as antisymmetric bands at 3001, 2995 and 2988 cm,1 and symmetric bands at 2923, 2909 and 2885 cm,1, respectively. For the DMSO-intercalated low-defect kaolinite, the 2913 cm,1 band resolves into five component bands at 2882, 2907, 2917, 2920 and 2937 cm,1. The CD antisymmetric and symmetric stretching modes in the 298 K spectrum are found at 2250 and 2125 cm,1, respectively. Both bands show some asymmetry and further bands may be resolved at 2256 and 2244 cm,1 in the antisymmetric stretching region and at 2118 cm,1 in the symmetric stretching region. The spectra of the SO stretching region of DMSO and DMSO- d6 are complex with a band profile centred at 1050 cm,1. Three bands are curve resolved at 1058, 1042 and 1026 cm,1 attributed to the unassociated monomer and the out-of-phase and the in-phase vibrations of the dimer, respectively. Upon cooling to liquid nitrogen temperature, these three bands are observed at 1057, 1038 and 1019 cm,1. The spectra of the SO stretching region of DMSO- d6 are more complex because of the overlap of the DCD deformation modes with the SO stretching modes. The antisymmetric and symmetric stretching CS modes of DMSO are observed at 698 and 667 cm,1, shifting at 77 K to 705 and 672 cm,1. It is concluded that the structure of DMSO in DMSO-intercalated kaolinite is different from those of both liquid DMSO at 298 K and solid DMSO measured at 77 K. Copyright © 2002 John Wiley & Sons, Ltd. [source] Vibrational spectra of barium formate crystalJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2001Jianjun Liu The Raman spectra of barium formate were investigated at room temperature and liquid nitrogen temperature and the infrared absorption and reflection spectra at room temperature. The presence of two crystallographically non-equivalent sets of formate ions in the lattice results in the doubling of the internal modes in the vibrational spectra. The observed high-wavenumber vibrational bands are assigned to the internal vibrations of formate ions. Copyright © 2001 John Wiley & Sons, Ltd. [source] Raman scattering of Nd0.9Ca0.1Ba2Cu3O7,, with different oxygen contentsJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2001Yun Zhao A series of Nd0.9Ca0.1Ba2Cu3O7,, samples with different oxygen contents were fabricated by the solid-state reaction method and thermally treated under different conditions. The superconducting transition temperatures Tc were measured to be above liquid nitrogen temperature. The measurements of the thermopower S showed a monotonic decrease with increasing oxygen content. The Raman peak of the apical oxygen O(4) stretching vibration shifts to higher wavenumber, which also shows a monotonic increase in oxygen content. Two modes at 224 and 597 cm,1 are assigned to the disorder-induced stretching vibrations of copper and oxygen atoms, respectively. They arise from symmetry breaking from short-chain fragments and are not due to impurity phases. Copyright © 2001 John Wiley & Sons, Ltd. [source] Thin film formation by rf sputtering with EuGa2S4 target and photoluminescence of the prepared filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006M. Dohi Abstract Thin films were deposited on Si and fused quartz substrates by rf sputtering with EuGa2S4 target. The deposited films were annealed in the mixed atmosphere of S and He, which led crystallization of the film from amorphous phase. Photoluminescence of the annealed films, characteristic to the Eu2+ ion, was observed with room temperature quantum efficiency of 17%. Decay time constants at room temperature and liquid nitrogen temperature were measured to be 140 ns, and 430 ns, respectively. The latter value is close to the reported radiative lifetime of the EuGa2S4 crystal. Construction possibility of a surface-emitting laser is discussed with data on behaviour of excitation intensity dependent time-resolved spectra under pulsed laser excitation and on surface roughness of the film. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural changes of hexamethylenetetramine and undecanedioic acid co-crystal (HMT-C11) as a function of the temperatureACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2003Carlos Basílio Pinheiro HMT-C11 belongs to the family of adducts formed by the co-crystallization of N4(CH2)6 molecules (hexamethylenetetramine or HMT) and aliphatic dicarboxylic acids HOOC(CH2)n, 2COOH with 5 ,n, 13 (Cn). The adducts exhibit a layered structure in which the packing between HMT and Cn is determined by strong hydrogen bonds. The compounds in this family studied so far present thermotropic structural phase transitions and, depending on the chain length, disordered, twinned and modulated phases. The structure refinement of HMT-C11 based on X-ray diffraction experiments indicates three distinct phases from the melting point down to liquid nitrogen temperature: phase I is not crystalline; phase II is disordered (stacking fault) and its average structure is described in space group Bmmb; phase III is partially disordered and its symmetry is P21/c. The systematic study of the structure evolution of phase III upon cooling revealed that the disorder has a dynamic character (anharmonicity). The main structural change observed from 293,K down to 93,K is the increase of the tilting angle of the C11 chains relative to the layer plane and the rotation of the HMT molecules. Both HMT and C11 behave like rigid bodies in the temperature range investigated. The quality of the refinements leads to a conclusive model for the O,H,N hydrogen bonds linking HMT and C11. [source] YBaCuO and REBaCuO HTS for ApplicationsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2007Herbert C. Freyhardt The discovery of electrical conductors that carry loss-less currents at liquid nitrogen temperatures and above, high-temperature superconductors (HTS), inspired the imaginations of scientists and engineers in an unprecedented way. It culminated in a broad search for an understanding of their basic phenomena and properties, but also for new classes of the HTS. The availability of these materials created novel ideas of their use for effective and economical generation, transport, and use of electric energy. YBaCuO and related REBaCuO HTS compounds still belong to the most attractive workhorses. This contribution intends to illustrate the efforts to manufacture from these HTS bulk monoliths, wires, tapes, or conductors, which would be needed for novel components and devices for electrical and power engineering, devices that offer not only an effective use of energy but also broad environmental benefits and, furthermore, help to safe resources. The research and developments discussed are mainly focused on efforts in Europe. [source] Commercial Exploration of High-Temperature SuperconductivityLASER TECHNIK JOURNAL, Issue 4 2010Excimer Lasers Enable Novel Coated Superconductor Cylinders Superconductivity, which is the condition in which the electrical resistance of a material drops to zero, was discovered nearly 100 years ago. Since that time, large superconducting magnets such as those used in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR) and big physics experiments have been developed and can now be regarded as being commercial products extending our capabilities in medicine and science. Yet many industrial applications of high temperature superconductivity (HTS) are on the horizon waiting to enter the marketplace. Currently, numerous manufacturers are working on improving and upscaling HTS materials, which operate at liquid nitrogen temperatures, and the most promising configuration for these materials is in the form of long tapes also known as coated conductors. These coated conductors are wound into coils in order to produce electrical components such as motors, magnets, transformers etc. Depending on the component to be made, there is an alternative to fabricating long unit lengths of superconducting tape, and in forming stable robust windings utilizing them. Now, a new technique has been developed which is using pulsed laser deposition (PLD) to deposit a series of layers of superconducting material directly on to the surface of a cylinder and patterning them into coils. This configuration provides a very direct route for the production of components that conventionally involve winding processes. This article explores how coated conductor cylinders can be produced utilizing this technique and explains why industriallyproven excimers represent the optimum choice of laser source for this emergingtechnology. [source] | ||||||||||||||||