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  • 2005-2009  (686)
  • 1925-1929
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  • 11
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 600-603 (Sept. 2008), p. 995-998 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A 10 kV 4H-SiC PiN diode with an improved junction termination structure has beenfabricated. An improved bevel mesa structure, nearly vertical side-wall at the edge of pn junctionand rounded corner at mesa bottom, has been formed by reactive ion etching (RIE). The junctiontermination extension (JTE) region has been optimized by device simulation, and simulatedbreakdown voltage has been compared with experimental results. The locations of electric fieldcrowding and diode breakdown have been discussed
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  • 12
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 124 (1929), S. 480-480 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] WITH a condensed spark discharge (10-40 thousand volts transformer with two Minos-jars of 4000 cm. capacity each) between tungsten and carbon electrodes 1 cm. apart in an atmosphere of hydrogen at about 7–10 cm. pressure as a source, a system of CH-bands is observed. The band with its intensity ...
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  • 13
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In the 21st century, the optical computation is likely to be the basic technology forprocessing lots of information at high speed. The aim of the present research work is to develop optical logic gates or memory chips. For this purpose, we have examined the suitability of organic nonlinear optical dye material Vanadyl-phthalocyanine (VOPc). Large single crystals of this material have been fabricated by using Molecular Beam Epitaxy (MBE) technique. The epitaxial films were formed on the substrate under optimum operating conditions. However, the epitixial growth is observed only up to a limited thickness. Above this thickness, the films become non-epitaxial, which can be improved by annealing. The reformation of the epitaxial films has been confirmed. We have also reported the effects of the environment of high temperature on the multilayered tetra-tert-butyl-Vanadyl-phthalocyanine ((t-bu)4VOPc) films, formed by Langmuir-Blodgett (LB) method. The solvent used to dissolve ((t-bu)4VOPc) was 1,2-dichloroethane. The monolayer on the surface of the water was transferred to a glass substrate by the vertical dipping method. If the multilayered stack is too thick, the molecular arrangement of the film may get disturbed. The improvement in the molecular arrangement of the LB films was examined and confirmed by measuring it’s nonlinear optical susceptibility, using Maker Fringe Method. Monolayer formation onwater surface depends on the surface pressure-area isotherm. If this monolayer formation is not perfect, multiplayer stacks cannot be formed. The molecular films were aligned almost perpendicular to the substrate, as estimated from the limiting molecular area of surface pressure-area isotherm. The molecular organization of the monolayer on the substrate and the molecular structure of the multilayered ((t-bu)4VOPc) films are discussed
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  • 14
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 556-557 (Sept. 2007), p. 129-132 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fast homoepitaxial growth of 4H-SiC has been carried out on off-axis (0001) substrates byhorizontal hot-wall CVD at 1600οC. High growth rate up to 24 μm/h has been achieved withmirror-like surface in the C/Si ratio range of 1.0-2.0. The Z1/2 and EH6/7 concentrations can be kept aslow as 7 × 1011 cm-3 and 3 × 1011 cm-3, although an unknown trap (UT1) is observed with theconcentration in the 1011 cm-3 range. The photoluminescence spectra are dominated by strong freeexciton peaks, and the L1 peak is not observed. The basal-plane dislocation (BPD) density hasdecreased with increase in growth rate, and it can be reduced to 22 cm-2 when epilayers are grown onChemical Mechanically Polished (CMP) substrates at a growth rate of 24 μm/h
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  • 15
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 556-557 (Sept. 2007), p. 35-40 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Homoepitaxial growth of 4H-SiC and characterization of deep levels obtained mainly inthe authors’ group have been reviewed. The growth rate has been increased to 24 om/h with keepingvery good surface morphology and low trap concentration on 8o off-axis 4H-SiC(0001) by hot-wallchemical vapor deposition at 1650oC. The increased growth rate has resulted in the enhancedconversion of basal-plane dislocations into threading edge dislocations in epilayers. The Z1/2 andEH6/7 concentrations can be decreased to about 1·1012 cm-3 by increasing the C/Si ratio during CVD.Extensive investigation on as-grown and electron-irradiated epilayers indicates that both the Z1/2 andEH6/7 centers may be attributed to the same origin related to carbon displacement, probably a carbonvacancy. Deep levels observed in as-grown and irradiated p-type 4H-SiC are also presented
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  • 16
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 558-559 (Oct. 2007), p. 207-212 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In order to improve deep drawability of 6000 series aluminum alloys for automotive bodypanels, texture control for increasing r-value of the sheets was attempted by combination ofsymmetric and asymmetric rolling. Asymmetric warm rolling at relatively low reduction aftersymmetric rolling made it possible to form TD-rotated β-fiber texture including {111} components.Recrystallization textures of the T4-treated materials varied significantly depending on roll speedratio and reduction in asymmetric warm rolling. On appropriate rolling conditions, {111}〈110〉orientation with high r-value was formed as a main component of recrystallization texture. On theother hand, two-stage heat treatment consisting of low temperature annealing and subsequentT4-treatment led to a significant change in recrystallization texture. In the sample annealed for longtime at a low temperature, TD-rotated β-fiber rolling texture was retained even after solutiontreatment at a much higher temperature, because recovery or recrystallization took place to someextent during low temperature annealing
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  • 17
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 591-593 (Aug. 2008), p. 811-815 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: It well known that the operational conditions of rotary kilns affect strongly the quality ofquicklime produced. This work presents a study about parametric optimization of rotary kilns forquicklime production (CaO) from thermal decomposition of calcite limestone (CaCO3). Theapproach used is based on the technique of design of experiments (DOE) to identify the mostsignificant variables which affect the quality of oxide and, in addition, to determine betterconditions of production. An experimental setup in laboratory scale was build in order to carry outthe experiments. Calcination temperature, calcination time, rotation speed, particle mean diameter,heat flow and air flow rate were evaluate using a fractional factorial design. The parametricoptimization shows that the raise of time and temperature of calcinations produces an increase offree CaO terms. However this operation is not useful due to sintering process observed in the BETsurface area results. A correlation between quicklime reactivity and specific surface area could beestablished, in way that reactive quicklimes presented bigger areas. Finally, it was possible todetermine the best conditions of quicklime production and to estimate a quadratic model by using acentral composite design and a like surface response model. It was found that the best region ofoperation is about 900oC and 45 minutes of calcination time
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  • 18
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Slaked lime is a suspension of hydrated lime in water that can contain up to 40% ofsolids in suspension. The quality of the suspensions of slaked lime depends on the quality of limeused and on a careful choice of the conditions during the hydration process. A high quality slakedlime is a product with a small quantity of insoluble residues, high specific surface area, highalkaline content and small particle size. Therefore, the objective of this work was to study the bestconditions of temperature and concentration to produce a superior slaked lime. A statistic analysiswas performed using the experimental results in order to optimize the operational conditions of thehydration process. The use of hydration water around 74 °C, of small particles of CaO (0.144 mm)and of a CaO/H2O ratio around 220 g/L contributed to the production a slaked lime suspension offine quality
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  • 19
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advances in science and technology Vol. 48 (Oct. 2006), p. 119-126 
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: Carbon nanowalls (CNWs), i.e., two-dimensional carbon nanostructures, were fabricatedusing fluorocarbon capacitively coupled plasma-enhanced chemical vapor deposition assisted by Hradical injection. The correlation between CNW growth and the fabrication conditions wasinvestigated. The morphologies of CNWs were dependent on the types of carbon source gases andthe amount of H radicals injected. In addition, H and CFx (x=1-3) radical densities in the plasmawere measured using vacuum ultraviolet absorption spectroscopy and appearance massspectrometry, respectively, to clarify the growth mechanism of CNWs. The density ratio of Hradicals to CFx radicals was found to be an important factor responsible for the formation of CNWsfrom fluorocarbon/hydrogen systems and increased drastically as a result of H radical injection
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  • 20
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 301 (Jan. 2006), p. 155-158 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The interfacial resistances of La1-xSrxCo1-yFeyO3-δ (denoted LSCF(10(1-x)/10x/10(1-y)/10y)) cathodes, and the catalytic activities of a Ni-Ce0.85Y0.15O1.925 (Ni-YDC) anode and an LSCF(2/8/8/2) cathode of a single-chamber solid oxide fuel cells (SOFCs) were investigated. LSCF cathodes with high oxide ion conductivities gave low interfacial resistances. LSCF cathodes with suitable thermal expansion coefficients formed favorable interfacial structures with a ceria-based electrolyte. Ni-YDC showed a higher conversion efficiency for CH4 and a lower selectivity for CO2 than LSCF(2/8/8/2). The single-chamber SOFC based on the Sm-doped ceria electrolyte with the Ni-YDC anode and LSCF(2/8/8/2) cathode showed a maximum power density of 186 mW/cm2 at 800ºC
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