139,064 research outputs found
Direct measurements of electrostatic potentials at grain boundaries: mechanism for current improvement in high-T-c superconductors
No full textGrain boundaries (GBs) in high-temperature superconductors represent the major factor limiting high current applications. Via magneto-optical imaging and direct transport measurements, we observed an increase of the intergranular J(c) in 4degrees and 8degrees [001] low-angle grain boundaries via substitution of Y by Ca in YBa2Cu3O7-x by up to 100%. Since Ca substitution leads to hole overdoping, these results suggest that charge depletion and band bending may be responsible for the suppression of superconductivity in GBs. By using electron holography, we directly observe ail electrostatic potential at the dislocation cores. The radius as well as the value of the potential are reduced in Ca-doped grain boundaries, directly reflecting the improved transport properties. (C) 2004 Elsevier B.V. All rights reserved
Numerical simulation of performance of concrete-filled FRP tubes under impact loading
No full textC. Wu, T. Ozbakkaloglu, G. Ma and Z. Y. Huanghttp://www.rpsonline.com.sg/proceedings/9789810844554/html/tp.htm
Ti–C bonds reinforced TiO2@C nanocomposite Na-ion battery electrodes by fluidized-bed plasma-enhanced chemical vapor deposition
No full textCarbon coatings hold great promise for next-generation non-conductive energy storage nanomaterials. However, simplicity, stable, uniformity and high-performance remain unresolved issues. Here, unique synergy of the fluidized bed reactor with plasmas enables highly-effective, single-step fluidized-bed plasma-enhanced chemical vapor deposition (FB-PECVD) of uniform, low-temperature carbon coatings on TiO2 nano-powder (TiO2@C). Plasma-specific effects induce the formation of new phases that are beneficial for energy storage. The 6 nm carbon layer is grown within only 10 min, while the TiO2 maintains its anatase phase. The unique plasma conditions make it possible to form Ti–C bonds at the Ti/C interface at much lower temperatures than achievable otherwise. The electronic transport at the interface and structural stability are thus greatly improved. Consequently, TiO2@C shows excellent electrochemical performances as a negative electrode of sodium ion battery, such as specific discharge capacity of 290.2 mA h g−1 at 50 mA g−1 and very stable long-term cyclability (101.2% capacity retention over 300 cycles at 4000 mA g−1). Our results show that FB-PECVD is not only a versatile method for bond-reinforced interface nanoparticle coating with carbon, but also provide a new strategy for designing hybrid-phase electrochemically active nanocomposite materials.No Full Tex
Superconducting HgBa2CaCu2Oy thin films growth on NdGaO3, SrTiO3, LaAlO3 and Y-ZrO2 substrates
No full textSuperconducting HgBa2CaCu2Oy (Hg-1212) films have been fabricated on (110) NdGaO3, (100) SrTiO3, (100) LaAlO3 and (100) Y-ZrO2 substrates by a two-step process. Good reproducible superconducting properties, zero resistance temperatures (T-c) > 115 K and critical current density (J(c)) > 4000 MA/m(2) at 77 K in zero field, are obtained. X-ray diffraction patterns indicate that the films have an epitaxial structure with the c-axis perpendicular to the surface. Scanning electron microscopy measurements show a layered growth structure with square and octagonal grains on the Hg-1212 film surfaces. (110) NdGaO3 is demonstrated to be a good substrate for growing the Hg-cuprate thin films. A lower superconducting transition temperature is observed in films deposited on Y-ZrO2 substrates, which can be attributed to variations of the microstructure in the films. (C) 1999 Elsevier Science B.V. All rights reserved.Physics, AppliedSCI(E)EI18ARTICLE3-4197-20131
THE INVESTIGATION OF EFFECTIVE MATERIAL CONCEPT FOR THE TRANSIENT WAVE PROPAGATION IN MULTILAYERED MEDIA
No full textBreaking of ground-state symmetry in core-excited ethylene and benzene
No full textThe observation of C-H bending, and C-C and C-H stretching vibrational levels in high-resolution C 1s-1π* photoabsorption spectra of ethylene and benzene demonstrates that, within the validity of the Franck-Condon principle, both molecules have broken symmetry in this core-excited state. A simple model based on the antibonding character of the π* electron, and on the local rehibridization of the bonding orbitals on the excited C atom, is utilized to explain our observations and to show that both core-excited molecules become nonplanar. Our results also show that the core hole is localized on the excited carbon atom
Nucleophilicity of diatomic Lewis bases MA in hydrogen-bonded complexes MA⋯HX: influence of the group and row of M in the periodic table
No full textNucleophilicities NMA of diatomic Lewis bases MA acting as hydrogen-bond acceptors in complexes MA⋯HX are reported. The molecules MA were chosen so that the atom M adjacent to the atoms A directly involved in the hydrogen bonds belongs to Groups 13, 14, 15, 16 and 17 of the periodic table. The effects of changing atom M from rows 1 to 4 within a given group were also investigated. The hydrogen-bond donors HX involved in the complexes were HF, HCl, HBr, HI, HCCH, and HCP. Nucleophilicities NMA were determined from dissociation energies De for the process MA⋯HX = MA + HX by using De = cNMA·EHX + d, where EHX are electrophilicities of the Lewis acids HX, and c and d are constants. The order of NMA values was found to be Row 4 > Row 3 ∼ Row 2 ≫ Row 1 in each of the Groups 13, 15, 15, 16 and 17. The effect of adding an H atom to MA to give linear triatomic molecules HMA were considered. The reduced nucleophilicities ИMA = NMA/σmin (σmin is the minimum value of the molecular electrostatic surface potential of MA) as a function of the group and row of atom M were also discussed for diatomic molecules MA
Investigation of Dynamic Responses for Piezoceramic Plates in Resonance by Using Fiber Bragg Grating
No full text- …
