1,721,059 research outputs found
Superconducting-normal phase transition in (Ba1-xKx)BiO3,x=0.40, 0.47
No full text[[abstract]]Specific-heat measurements on (Ba1-xKx)BiO3, x = 0.40 and 0.47, 0.7 less than or equal to T less than or equal to 35 K, 0 less than or equal to H less than or equal to 9 T, have determined the coefficient (gamma) of the normal-state conduction electron specific heat, and shown well-defined specific-heat anomalies at T-c that are consistent with the value of gamma and BCS expressions. These results contradict the suggestion in a recent Letter that gamma is several orders of magnitude greater than these experimental values and that the absence of a correspondingly large specific-heat anomaly constitutes evidence that the transition is an Ehrenfest fourth-order transition.[[note]]SC
Local electronic structure of LiMn2O4 probed by solid state Li-7-NMR
No full text[[abstract]]Crystalline LiMn2O4 materials were synthesized through a low temperature reflux (LTR) process. The LTR material exhibits an essential electrochemical behavior to present only one transition during the charge/discharge process and gives promises for the future application. The X-ray data hardly distinguishes either conventional high temperature (HT) or LTR material since both materials possess similar molecular structure. However, solid-state NMR results suggest substantial difference for their electronic structure. The Li-7-NMR of HT material exhibits the isotropic peak at 529 ppm and spreads for 160 kHz wide indicating the interaction between the lithium nucleus and the conducting electrons around the nucleus. The LTR material presents the main isotropic peak at 217 ppm but spreads for almost 400 kHz wide asymmetrically implying the existence of multiple electronic environments. (C) 2001 Elsevier Science Ltd. All rights reserved.[[note]]SC
Crystallization and anisotropic properties of water-stabilized potassium cobalt oxides
No full text[[abstract]]A low-temperature electrochemical synthesis of water-stabilized K(x)CoO(2)(.)yH(2)O crystal has been demonstrated. Temperature variable X-ray diffractions display a sandwiched structure with mobile water molecules. The crystal has hexagonal characteristic with four adjustable phases K(0.35)CoO(2)(.)0.40H(2)O, K(0.35)CoO(2)(.)0.34H(2)O, K(0.22)CoO(2)(.)0.21H(2)O, and anhydrous K0.15CoO2. Lattice water removal in a step-by-step process with the reduction of interlayer spacing in a single crystal can be achieved. Strong anisotropic conducting at low temperature and weak interlayer coupling in the ab plane have been demonstrated.[[note]]SC
High conductivity LiFePO4/C composite thin films with Ti underlayers deposited by radio frequency sputtering
No full text[[abstract]]LiFePO4/C thin films have been deposited on Ti-coated Si and stainless-steel substrates by radio frequency magnetron sputtering. Negative electric bias (0,-50,-80 V) and postdeposition vacuum annealing (150-650 degrees C) was applied to modify the film properties. Suitable substrate bias resulted in films with finer grains and pure olivine phase. The films deposited with Ti underlayers exhibited enhanced crystallization, grain sizes, and conductivity, as compared with films deposited without Ti underlayers. Composition depth profiles showed interdiffusion at the film/underlayer interfaces after annealing. Charge-discharge and cyclic voltammetry curves revealed the different electrochemical characteristics of the films. The films with Ti underlayers displayed lower initial capacity than those without underlayers due to heavy doping of Ti. However, the cycling stability is greatly improved, which was attributed to the enhanced adhesion property of the Ti underlayers to the substrates and films.[[note]]SC
Electrochemical synthesis of alpha-MnO2 octahedral molecular sieve
No full text[[abstract]]The alpha-MnO2, octahedral molecular sieve (OMS) with 2 x 2 hollandite-type structure can be electrochemically synthesized with a subsequent self-assembly process at 80degreesC. Powdery OMS material is prepared by the electrochemical oxidation of Mn2+ ion in an acidic medium followed by a hydrolysis reaction. Counter ion effects of H+, Li+, Na+, K+, Cs+ and Mg+2 are studied for the formation of alpha-MnO2 in this self-assembled system. Powder X-ray diffraction (XRD) is used to characterize the relationships among counter ions, electrolysis potential, and phase formation during synthesis. Li-7 nuclear magnetic resonance is used to probe the lithium environment in the hollandite-type structure of the Li+-exchanged and lithiated manganese oxides. (C) 2003 Elsevier Science B.V. All rights reserved.[[note]]SC
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Surface Treatment of Li(Li0.08Ni0.34Co0.08Mn0.5)O-2 Oxide for High Voltage Lithium Ion Battery
No full text[[abstract]]The high capacity cathode materials with charge voltage above 4.5 V are widely being developed. To reduce surface reactivity at high voltage, Al2O3 and pullulan are used for coating on the Li(Li0.08Ni0.34Co0.08Mn0.5)O-2 surface and are characterized by electrochemical analysis. Charge/discharge and electrochemical results reveal that the organic coating sustains in high voltage cycles. Ionic conductivity of surface coating plays a key role in the battery performance.[[note]]SC
Electrocrystallization and characterization of polymorphic forms of barium metaplumbate
No full text[[abstract]]The conducting oxide of BaPbO3 crystallized in KOH melt at various pH(2)O and voltage E-v values are systematically Studied by the electrochemical method. For crystals prepared in a low pH(2)O environment, the electrolysis product displays the Pb3O4 phase, whereas the single phase of BaPbO3 can be produced under high pH(2)O condition. The grown phases are found to depend on the concentration of superoxide [O-2(-)] and peroxide [O-2(2-)] intermediates in the melt. By adjusting the concentration of [O-2(-)]/[O-2(2-)] intermediates via careful control of the pH(2)O and atmosphere of the electrochemical cell, the formation temperature of BaPbO3 can be reduced to as low as 200 degrees C, which is significantly lower than the temperature used in other synthetic techniques. The BaPbO3 crystals with cubic, tetragonal, and orthorhombic structures are grown at 450, 340, and 260 degrees C, respectively. The symmetry of crystalline BaPbO3 structure prepared under these temperatures can be sustained at ambient conditions to allow a detailed study of the distorted perovskite structure.[[note]]SC
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