1,721,036 research outputs found
Fabrication and electrochemical characterization of LiCoO2 cathode powder by mechanochemical process
No full textLiCoO2 cathode powders with a grain size of 1-1.5 mum were synthesized by a mechanochemical process. The Li-Co precursor was prepared by a freeze drying method using a Li and Co acetate as starting raw materials. The surface was modified by lapping the precursor using K2SO4 in a simple ballmill. After the surface modification, the Li-Co precursor was heated at 800degreesC to form a high-temperature polymorph. The K2SO4 coat on the Li-Co precursor prevented the Li-Co precursors from contacting one another, due to the high decomposition temperature of K2SO4 above 1000degreesC and constrains grain growth. Because of this, the modified Li-Co precursor is converted to very small crystalline LiCoO2 particles by phase transformation. The as-synthesized LiCoO2 powder had well-developed facets and a very uniform grain size distribution. A small capacity fade for high discharge rate was observed in the as-synthesized powder, which can be attributed to the diffusion of Li ions at the grain boundary. Thus, it is possible not only to synthesis LiCoO2 powder to a desired grain size but also to control the grain size distribution using this method. These results indicated that the synthesis of a high-temperature polymorph of LiCoO2 with a small grain size is possible by constraining growth during the heat-treatment. The LiCoO2 powder synthesized here represents a very good candidate for use in fabricating not only of high power bulk batteries but high power slim batteries as well, when a thin and thick film process is used. (C) 2004 The Electrochemical Society.National Research Laboratory program (development of monolithic high performance battery
SURFACE MORPHOLOGIES OF BATIO3 THIN-FILMS BY ATOMIC-FORCE MICROSCOPY
No full textSurface morphologies of BaTiO3 thin films have been studied by atomic force microscopy (AFM). The films on (111)InSb, indium tin oxide (ITO)-coated glass and (100)Si substrates are deposited by in-situ metalorganic chemical vapor deposition (MOCVD) at different deposition temperatures of 300-degrees-C, 400-degrees-C and 600-degrees-C, respectively. AFM under ambient conditions showed that the BaTiO3 film deposited on the ITO-coated glass had a smooth surface consisting of large hemispherical grains, while the film on (100)Si had a slightly rough surface with [110]textured rectangular grains. As-grown film on the (111)InSb substrate was in the amorphous phase except near the interface, resulting in a rough surface. Our results of dependence on the kind of substrates and growth temperature suggest that the surface morphology of the as-grown films is strongly influenced by the crystallinity and growing characteristic of the film. For low-temperature growth below the deposition temperature of 600-degrees-C, surface roughness of the BaTiO3 film is strongly dependent on growth temperature rather than crystallinity of the films related to substrates
Cost-minimizing construction of a unidirectional SHR with diverse protection
No full textThe widespread use of SONET technology makes the self-healing ring (SHR) architecture the most basic building-block in designing a large fiber-optic network which is not only survivable but also cost-effective, We address the design problem of placing a single SONET unidirectional ring with a single gateway hub in a region administered by a community of interest, Introduced for the purpose of further cost-saving in our problem setting is the flexibility that some offices, instead of being included in the ring, can be homed to the ring via two are-disjoint paths, Given the set of offices and potential arcs, the objective is then to determine at the minimum total cost both the ring location and the homing to the ring of its nonmember nodes. We formulate the problem as a mixed integer programming model and develop an efficient solution procedure by devising six improvement heuristics, Extensive computational experiments are conducted with input data instances selected from the data ranges of the real-world environments, The practical value of the solution procedure for network planners is well evidenced by its excellent and consistent performance of quickly generated good-quality solutions over various input data instances
Room-temperature growth of Cu thin films by nozzle-type partially ionized beam deposition with various acceleration voltages
No full textNozzle-type partially ionized beam deposition of Cu thin films at a system pressure of 5 x 10(-6) to 7 x 10(-6) Torr was conducted in order to fabricate Cu metallization with high-quality Cu/Si interfaces. In order to prevent diffusion of the Cu toward the Si and silicide formation, the depositions with various acceleration voltages were performed at room temperature. X-ray diffraction patterns showed all the as-grown films having the [111] Cu direction normal to the (100) Si plane regardless of the acceleration voltage. Anger electron spectroscopy demonstrated that there was no residual carbon detection in the bulk of the as-grown films. The thickness of the all as-grown Cu films was 2 000 Angstrom as confirmed by low-magnitude cross-sectional transmission electron microscopy, i.e. growth rates of the Cu film by partially ionized beam deposition at room temperature were almost independent of the acceleration voltage. Furthermore, cross-sectional transmission electron microscopy showed a sharp Cu/Si interface and large-grain polycrystalline Cu films with twin defects. Atomic force microscopy under ambient conditions showed all the films had very smooth surfaces which were greatly reduced with the acceleration voltage. A scratch test showed good adhesion in all the films. These results indicate that the nozzle-type partially ionized beam deposition at room temperature can be used for Cu thin film metallization for semiconducting applications
Characteristics of ZnO thin film deposited on various metal bottom electrodes
No full textZnO films for electronic applications were deposited by radio-frequency (rf) sputtering onto various metal bottom electrodes (Pt/Ti, W Ni) to investigate such structural properties as crystallinity and surface morphology. The crystallinity, surface morphology and composition of the as-deposited films were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS), respectively. The preferred orientation and surface morphologies were strongly influenced by the type of bottom electrodes. The ZnO films with (200) texturing deposited on Pt/Ti/SiO2/Si showed a smoother and smaller grain size than those deposited on W and Ni. The ZnO films on Pt and W electrodes exhibited compressive residual stress
Preparation and electrochemical characterization of size controlled SnO2-RuO2 composite powder for monolithic hybrid battery
No full textTin oxide (SnO2) powders with a particle size of similar to20 nm were synthesized by a gas condensation method. Ruthenium oxide was loaded by an incipient-wetness method, in which an aqueous solution of RuCl3 was added to the manufactured SnO2 powder in an amount that was just sufficient to wet completely the powder. And then, the resulting solution was obtained after freeze-drying to synthesis the smallest particle. The as-synthesized SnO2 powder with 1.5 wt.% ruthenium oxide (RuO2) exhibited well-developed facets and had a very uniform particle size. The first discharge capacity was lower than comparing to commercial powder because of forming the second phase, but showed good cyclability. A maximum specific electrode capacitance of similar to20 F/g and a maximum specific power of similar to80 W/kg were achieved by manufactured SnO2 With 1.5 wt.% RuO2. This result indicated that the synthesized SnO2-RuO2 composite powder of nano-size scale is candidate for use in fabricating monolithic hybrid batteries using suitable electrolyte as well. (C) 2004 Elsevier Ltd. All rights reserved.R&D supporting by National ResearchL aboratory program (Development of monolithic
high power hybrid batter
-InP heterostructures
Full text linkIon-beam-assisted deposition of Pt on p-InP at room temperature was performed in order to produce Pt epitaxial films with high quality and Pt/p-InP (100) heterostructures with sharp interfaces. From the x-ray diffraction analysis, the grown film was found to be a Pt heteroepitaxial film. Anger electron spectroscopy measurements showed that the composition of the as-grown film was Pt and that the interface quality between the Pt and the InP was relatively good. Transmission electron microscopy showed that the grown Pt was an epitaxial film. These results indicate that the Pt epitaxial films grown on p-InP (100) can be used for both stable contacts in optoelectronic devices and Pt/InP metal-semiconductor-field-effect transistors and that the Pt/InP heterostructures can give good motivation for the fabrication of Pt/InP superlattices. (C) 1996 American Institute of Physics
Design of TR-EFPI fiber-optic pressure sensor for the medical application
No full textThe conventional reflection-type extrinsic Fabry-Perot interferometric (EFPI) fiber optic sensor has good sensitivity and resolution compared with other types of fiber optic sensors. However, it has the disadvantage that the EFPI fiber optic sensor is difficult to know the direction of physical properties, because of the measurement method by only fringe counting. So, it is hard to use the practical measurement. But the total reflected extrinsic Fabry-Perot interferometric (TR-EFPI) fiber optic sensor can measure the direction of the physical properties without adding other mechanisms and complex signal process equipments. This paper presents the newly designed fiber optic pressure sensor using the TR-EFPI fiber optic sensor with a single mode fiber (SMF), and a micro fabricated diaphragm. The output signal of this type of fiber optic pressure sensor can be easily analyzed based on the spliced based model proposed by D. Marcuse and large deflection theory. Then, we can design the optimal length between the thin film of diaphragm and the end of single mode fiber. Therefore, we can know the relation between the deflection of thin film and applied pressure using the large deflection theory. From these analyses, the relation between the applied pressure and the output signal of TR-EFPI fiber optic sensor can be simulated. It means that we can design the TR-EFPI fiber optic pressure sensor measuring various conditions by changing the size of thin film. As the newly designed TR-EFPI fiber optic pressure sensor can be fabricated in small size and has good sensitivity, it can be applied to medical instrument like pressure sensor and force sensor for catheter and minimumally invasive surgery robot for safer surger
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
- …
