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1.
R Srinivasan V Sankaranarayanan N P Raju S Natarajan U V Varadaraju G V Subba Rao 《Pramana》1987,29(2):L225-L230
The absolute thermopower of single phase YBa2Cu3O7 and Y0.8Er0.2Ba2Cu3O7 has been measured in the range 250 K to the superconducting transition temperature. It is found that these compounds show
a large enhancement of thermopower in the range 150 K down toT
c. This enhancement shows a steep exponential drop as the temperature increases from the transition temperature. The temperature
variation of the enhancement is too steep to be accounted for by electron-phonon or electron-local structural excitation mechanisms. 相似文献
2.
Studies on the superconductivity behaviour of pure and doped (Pb,TI) Bi4Sr3Ca3Cu4O16 phases are reported. Effect of oxide additives PbO, BaPbO3 and BaBiO3 has also been examined. Results show that an oxygen treatment at 600°C for 12 h during the final stages of the synthesis has the beneficial effect of sharpening the Tc zero of the 4334 Bi-composition. Pb and TI substitution has only a marginally beneficial effect on the Tc , though it is not definitely known whether substitution is actually occurring in the system. PbO as an additive raises the Tc zero to 89 K, whereas other additives do not basically affect the properties of the 4334 system. 相似文献
3.
Photoluminescence (PL) of Eu3+ was studied in SrIn2O4 host lattice. A complete solid solubility of Eu3+ has been found in the series SrIn2−xEuxO4 [x=0-2.0]. The phase formation at a relatively low temperature and in a very short duration was achieved by combustion synthesis (CS). Concentration quenching of luminescence has been observed in SrIn2−xEuxO4 [x=0.1-2.0] and the critical concentration for maximum emission was found to be with x=0.3. In order to find the role of crystallite size on the PL properties of SrIn2O4:Eu3+, the results obtained with phosphors synthesized by solid state reaction (SSR) and CS methods were compared. 相似文献
4.
M. Anji Reddy V. Pralong V. Caignaert U.V. Varadaraju B. Raveau 《Electrochemistry communications》2009,11(9):1807-1810
The monoclinic form of FeOHSO4 was prepared by dehydration of FeSO4·7H2O. We show that reversible insertion of up to 1Li/f.u. is possible in this compound at an average voltage of 3.2 V. The insertion/deinsertion is a biphasic process. The high voltage plateau, a reversible capacity of 110 mAh/g after 20 cycles and good cycling behavior make this compound an attractive positive electrode material for rechargeable Li-ion batteries, suggesting also that transition metal sulphates need to be explored. 相似文献
5.
Dr. Sourav Khan Dr. Rayappan Pavul Raj Dr. Laurel George Dr. G. S. Kamali Kannangara Dr. Adriyan Milev Prof. Dr. Upadhyayula V. Varadaraju Prof. Dr. Parasuraman Selvam 《ChemistryOpen》2020,9(1):23-31
The synthesis of morphology-controlled carbon-coated nanostructured LiFePO4 (LFP/Carbon) cathode materials by surfactant-assisted hydrothermal method using block copolymers is reported. The resulting nanocrystalline high surface area materials were coated with carbon and designated as LFP/C123 and LFP/C311. All the materials were systematically characterized by various analytical, spectroscopic and imaging techniques. The reverse structure of the surfactant Pluronic® 31R1 (PPO-PEO-PPO) in comparison to Pluronic® P123 (PEO-PPO-PEO) played a vital role in controlling the particle size and morphology which in turn ameliorate the electrochemical performance in terms of reversible specific capacity (163 mAh g−1 and 140 mAh g−1 at 0.1 C for LFP/C311 and LFP/C123, respectively). In addition, LFP/C311 demonstrated excellent electrochemical performance including lower charge transfer resistance (146.3 Ω) and excellent cycling stability (95 % capacity retention at 1 C after 100 cycles) and high rate capability (163.2 mAh g−1 at 0.1 C; 147.1 mAh g−1 at 1 C). The better performance of the former is attributed to LFP nanoparticles (<50 nm) with a specific spindle-shaped morphology. Further, we have also evaluated the electrode performance with the use of both PVDF and CMC binders employed for the electrode fabrication. 相似文献
6.
Schneiderman S Varadaraju H Zhang L Fong H Menkhaus TJ 《Journal of chromatography. A》2011,1218(51):9121-9127
A mathematical model has been investigated to predict protein breakthrough during membrane adsorption/chromatography operations. The new model incorporates a non-uniform boundary condition at the column inlet to help describe the deviation from plug flow within real membrane adsorption devices. The model provides estimated breakthrough profiles of a binding protein while explicitly accounting for non-uniform flow at the inlet of the separation operation by modeling the flow distribution by a polynomial. We have explored experimental breakthrough curves produced using commercial membrane adsorption devices, as well as novel adsorption media of nanolayered nanofiber membranes, and compare them to model predictions. Further, the impact of using various simplifying assumptions is considered, which can have a dramatic effect on the accuracy and predictive ability of the proposed models. The new model, using only simple batch equilibrium and kinetic uptake rate data, along with membrane properties, is able to accurately predict the non-uniform and unsymmetrical shape for protein breakthrough during operation of membrane adsorption/chromatography devices. 相似文献
7.
The photoluminescence (PL) studies on NaIn1?xRExW2O8, with RE=Eu3+, Tb3+, Dy3+ and Tm3+ phases have shown that the relative contribution of the host lattice and of the intra-f–f emission of the activators to the PL varies with the nature of the rare earth cation. In the case of Dy3+ and Tm3+ activators, with yellow and blue emission, respectively, the energy transfer from host to the activator plays a major role. In contrast for Eu3+, with intense red emission, the host absorption is less pronounced and the intra-f–f transitions of the Eu3+ ions play a major role, whereas for Tb3+ intra-f–f transitions are only observed, giving rise to green emission. 相似文献
8.
A new series of gallozincates LnBaZn3GaO7 (Ln=La, Nd, Sm, Eu, Gd, Dy, Y) and new aluminozincates LnBaZn3AlO7 (Ln=Y, Eu, Dy) have been synthesized. Their structure refinements show that these phases belong to the “114” series, with hexagonal P63mc space group previously described for SmBaZn3AlO7. The photoluminescence study of these oxides shows that the Eu3+ activated LnBaZn3MO7 oxides with Ln=Y, La, Gd; and M=Al, Ga exhibit strong magnetic and electric dipole transitions (multiband emission) which is of interest for white light production. These results also confirm that the site occupied by Eu3+ is not strictly centrosymmetric. The electric dipole transition intensity is the highest in GdBaZn3MO7 [M=Al, Ga]: 0.05Eu3+ as compared with other Eu3+ activated compositions. This is due to the layer distortion around GdO6 octahedra when compared with YO6 and LaO6 octahedra. 相似文献
9.
An efficient and convergent route for the synthesis of the natural product (+)-lithospermic acid, which possesses anti-HIV activity, was accomplished. The (±)-trans-dihydrobenzo[b]furan core therein was prepared by two different strategies. The first strategy involved the use of a palladium-catalyzed annulation to generate an appropriately substituted benzo[b]furan ester followed by a stereoselective reduction of a carbon-carbon double bond with Mg-HgCl(2)-MeOH. The second strategy relied on an aldol condensation between a suitably substituted methyl arylacetate and 3,4-dimethoxybenzaldehyde, followed by cyclization. Finally, a total synthesis of (+)-lithospermic acid was completed via coupling of a trans-dihydrobenzo[b]furan cinnamic acid with an enantiomerically pure methyl lactate. 相似文献
10.
The LiInW2O8:Eu3+, LiInW2O8:Dy3+ and LiInW2O8:Eu3+/Dy3+ phosphors were synthesized by solid-state reaction and their photoluminescence properties were studied. Under UV excitation, the LiInW2O8:Eu3+ phosphor exhibits an intense red emission whereas the LiInW2O8:Dy3+ and LiInW2O8:Dy3+/Eu3+ phosphors show a white emission. The WO6 octahedra play a major role in the luminescence of the host lattice, characterized by a blue emission under UV excitation. The emission of activator ion results from an efficient energy transfer from the LiInW2O8 host lattice to the Eu3+ and Dy3+ ions. The LiIn0.97Dy3+0.03W2O8 and LiIn0.965 Dy3+0.03Eu3+0.005W2O8 samples, optimized for white emission, are interesting candidates for solid-state lighting applications. 相似文献