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  • 1
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A GeS2 gel was prepared by sol–gel processing of Ge(OEt)4 and H2S in toluene solution. The effects of H2S and germanium ethoxide concentrations, concentration ratio, and temperature on the microstructure of the prepared GeS2 gels were studied. It was found that the concentrations of the reactants had the most significant influence on primary particle size and gel morphology. The microstructure of the dried gels was characterized by nitrogen BET analysis, SEM, powder XRD analysis, and infrared spectroscopy. Results indicate that the GeS2 gels are amorphous colloidal xerogels regardless of the reaction conditions and length of aging.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A range of compositions and temperatures below the monotectic temperature exists where there are thermodynamic restrictions that prevent the equilibrium solid from forming directly from the undercooled homogeneous liquid. In this region, the solid can form only after liquid-liquid phase separation has occurred. As suggested by earlier research, the thermodynamic restrictions on the crystallization process may be useful to control the crystallized grain structure in glass-ceramic systems. Thus, understanding the thermodynamic limitations on the formation of the solid in monotectic systems could have commercial significance. In the present paper, the metastable liquidus boundaries, liquid miscibility gaps, and spinodal curves in binary MgO-SiO2, CaO-SiO2, and SrO-SiO2 systems are calculated by using analytical expressions for the Gibbs free energies of the liquid phases. Calculating the metastable liquidus rather than using a simple extrapolation as originally proposed in the aforementioned previous research provides greater control of the heat-treatment processes and, thus, greater control over the resulting microstructure.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In an attempt to understand the liquid–liquid phase separation in the B2O3–MgO, B2O3–CaO, B2O3–SrO, and B2O3–BaO systems, the liquid miscibility gaps were calculated using the optimized interaction parameters of liquid phases. The Gibbs energies of liquid phases were derived in the form of a subregular solution from an optimization procedure based on phase diagram data. In addition, metastable liquidus boundaries and spinodal curves were also assessed by using the Gibbs energies of liquid phases. The present results were compared and discussed with other experimental and assessed data available in the literature.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The phase diagrams in the Al2O3–Cr2O3 and V2O3–Cr2O3 systems have been assessed by thermodynamic modeling with existing data from the literature. While the regular and subregular solution models were used in the Al2O3–Cr2O3 system to represent the Gibbs free energies of the liquid and solid phases, respectively, the regular solution model was applied to both phases in the V2O3–Cr2O3 system. By using the liquidus, solidus, and/or miscibility gap data, the interaction parameters of the liquid and solid phases were optimized through a multiple linear regression method. The phase diagrams calculated from these models are in good agreement with experimental data. Also, the solid miscibility gap and chemical spinodal in the V2O3–Cr2O3 system were estimated.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A solid oxide fuel cell (SOFC) is a complete solid-state energy conversion device with the potential advantages of high efficiency, silent operation, and low emissions. However, the current performance of SOFCs is still limited by a number of problems. Investigations in this field have indicated that it is imperative to fabricate efficient and compatible anodes for SOFCs to minimize polarization loss and to concurrently achieve long-term stability. In this paper, a critical review of previous studies is given and several criteria for the theoretically ideal anode are summarized. Accordingly, a newly developed vapor deposition technique, polarized electrochemical vapor deposition (PEVD), is applied to fabricate composite anodes to meet these criteria. The initial experimental results in the present study show that PEVD is capable of depositing a thin layer of yttria-stabilized zirconia on a porous metallic electrode to form a composite anode. This will not only provide continuous ionic and electronic conducting paths in the anode to reduce the overpotential loss and resistance, but also protect the metallic electrode from further sintering, vapor loss, and poisoning in the harsh SOFC operating conditions.
    Type of Medium: Electronic Resource
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