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  • 1
    Electronic Resource
    Electronic Resource
    Rehabilitation of Semiarid Landscapes in Australia. I. Restoring Productive Soil Patches (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 4 (1996), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A rehabilitation procedure designed to reestablish resource control processes in a degraded Acacia aneura woodland was successful in improving soil nitrogen and carbon content, exchange properties, and water infiltration rates. Soil respiration rates and soil fauna populations increased, and soil temperatures were moderated. The procedure comprised laying piles of branches in patches on the contour of bare, gently sloping landscapes, with the expectation that soil, water, and litter would accumulate in these branch piles, thus improving the soil habitat and its productive potential. The procedure was derived from landscape function analysis, indicating that surface water flow was the principal means of resource transfer in these landscapes. Under degradation such overland flow results in a loss of resources. This rehabilitation procedure reversed loss processes, resulting in gains in the productive potential of soils within patches. This procedure was successful despite grazing pressure being maintained throughout the experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1526-100X.1996.tb00191.x
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  • 2
    Electronic Resource
    Electronic Resource
    Rehabilitation of Semiarid Landscapes in Australia. II. Restoring Vegetation Patches (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 4 (1996), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This paper describes a practical technique, tested experimentally, for rehabilitating degraded semiarid landscapes in Australia. This rehabilitation technique is based on the ecological principle that semiarid landscapes are spatially organized as patchy, source-sink systems; this patchy organization functions to conserve limited water and nutrients within the system. The aim was to rebuild vegetation patchiness, lost through decades of utilization of these landscapes as rangelands. Patches were reconstructed from large tree branches and shrubs obtained locally and placed in elongated piles along contours. These piles of branches were very effective in recreating productive soil patches within the landscape, as described in part I of this study. These new patchy habitats promoted the establishment and growth of perennial grasses. Although the foliage cover of these grasses declined into a drought, which started before the end of the experiment, plant survivorship remained high. This suggests that patches also function as refugia for organisms during droughts. The patches of branches remained robust and functional, even under grazing impacts, although plant growth and survival were significantly higher within an ungrazed paddock than in a grazed paddock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1526-100X.1996.tb00192.x
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental Phase-Diagram Study and Thermodynamic Optimization of the Silver-Strontium-Copper-Oxygen (Ag-Sr-Cu-O) and Silver-Calcium-Copper-Oxygen (Ag-Ca-Cu-O) Systems (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    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 relations in the silver-strontium-copper-oxygen (Ag-Sr-Cu-O) and silver-calcium-copper-oxygen (Ag-Ca-Cu-O) systems were studied in oxygen, air, and nitrogen environments, using differential thermal analysis and energy-dispersive X-ray spectrometry. The presence of silver reduces the melting temperature of the oxide liquid to a monotectic in the strontium- and calcium-containing systems by 62 and 82 K, respectively (to 1222 and 1244 K, respectively) in oxygen. The oxide liquid dissolves silver (up to a metallic ratio of 0.17) in the Ag-Sr-Cu-O system in oxygen at a temperature slightly higher than that required for monotectic reaction. In the Ag-Ca-Cu-O system, the silver content has been measured to be 0.29 (metallic ratio). The oxide systems have been optimized using the experimental data from monotectics and those from lower-order systems that have been published previously. This work is part of a project to evaluate the phase relations within the silver-bismuth-strontium-calcium-copper-oxygen (Ag-Bi-Sr-Ca-Cu-O) system and, in particular, to focus on the influence of silver on the phase equilibria around the superconducting phases during partial-melt processing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02283.x
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  • 4
    Electronic Resource
    Electronic Resource
    Processing of β-Silicon Nitride from Water-Based alpha-Silicon Nitride, Alumina, and Yttria Powder Suspensions (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    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 water-based route for processing ß-Si3N4 from alpha-Si3N4, Al2O3, and Y2O3 powder mixtures was established. The surface charges and isoelectric points of the three different powders were investigated within the pH range from pH 3 to pH 12. Citric acid diammonium salt was found to be an effective deflocculant for shifting the isoelectric points to pH 3.5 for Al2O3 and to pH 6 for Y2O3. Aluminum hydroxide (Al(OH)3) showed strong interaction with the Si3N4 powder, shifting the isoelectric point from pH 7 to pH 5.5. Low-viscosity, high-solids-loading suspensions (60-63 vol%) thus were possible at pH 9.7. The preparation of homogeneous and stable suspensions with a solids content of ≤61 vol% and a viscosity 〈1 Pa·s was limited to a pH regime between pH 9 and pH 10.5 because of the high solubility of yttria. The homogeneous suspensions were easily solidified by direct coagulation casting (DCC), using the urease-catalyzed decomposition of urea at pH 9 to pH 10, by forming salt. No shrinkage cracking, sedimentation, or phase separation was observed during coagulation or drying. The green-density distribution was homogeneous throughout all bodies, even for complex geometries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02037.x
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  • 5
    Electronic Resource
    Electronic Resource
    Experimental Phase Diagram in the Ag-Cu2O-CuO System (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    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: Phase equilibria in the Ag-CuO-Cu2O system were experimentally determined using thermal analysis, and structural and compositional studies. Three reactions were observed in air: (1) L1= CuO + Ag, (2) L2= CuO + L1, and (3) Cu2O = CuO + L2. The evolution and absorption of oxygen accompanied these reactions. At oxygen partial pressures below 0.02 bar, the reactions L1= Cu2O + Ag and L2= Cu2O + L1 were found. Based on isobaric projections in the Ag-CuO-Cu2O system, two invariant reactions, L1= CuO + Cu2O + Ag and L2= CuO + Cu2O + L1, were deduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02604.x
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  • 6
    Electronic Resource
    Electronic Resource
    Thermodynamic Assessment of the Silver–Oxygen System (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    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: An assessment of the silver–oxygen system has been made, and a consistent set of thermodynamic parameters has been optimized. The calculated thermodynamic properties and phase relations are in good agreement with the experimental data. Ag2O is the only phase that is commonly found within the system. In air, it decomposes to silver and oxygen gas at 420 K. There is a eutectic between silver and Ag2O at a temperature of 804 K, an oxygen partial pressure (PO2) of 526 bar (5.26 × 107 Pa), and an oxygen mole fraction in the liquid phase of 0.25. Uncertainties remain on the Ag2O liquidus for PO2 〉 108 Pa. An ionic two-sublattice model has been used to describe the liquid phase. This work is part of a study of interactions between compounds from the bismuth-strontium-calcium-copper-oxygen system and silver.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03232.x
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  • 7
    Electronic Resource
    Electronic Resource
    Thermodynamic Assessment of the Bismuth–Strontium–Oxygen Oxide System (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    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 experimental data on the oxide portion of the Bi–Sr–O system have been reviewed, and an optimized thermodynamic description is presented. There are at least seven stable ternary oxide phases, two of which show considerable solid-solution ranges. At least two phases—δ-Bi2O3 and the rhombohedral β-phase—are good oxygen-ion conductors. Most of the phases are confined to the Bi2O3-SrO line at ambient oxygen partial pressure; however, in the SrO-rich portion, there are at least two phases with oxygen in excess, i.e., with bismuth in the oxidation state Bi5+ instead of the usual Bi3+. There are rather large differences between different experimental data sets; nevertheless, a reasonably consistent set of data can be chosen for the optimization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb02950.x
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  • 8
    Electronic Resource
    Electronic Resource
    Experimental Phase Diagram Study and Thermodynamic Optimization of the Ag-Bi-O System (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    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 Ag-Bi-O system has been experimentally studied using differential thermal analysis (DTA) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), and thermodynamically optimized. The temperatures of the eutectic, monotectic, and Bi2O3 allotropic transformations have been measured in N2, in air, and in O2 by DTA. There are no ternary phases stable at ambient pressure. Presently measured transformation temperatures have been combined with existing oxygen activity measurements in the metal liquid to optimize thermodynamic parameters describing the liquid phase. The resulting fit is excellent. EDX measurements of the composition in the oxide liquid have a rather low precision but confirm the thermodynamic optimization. However, some uncertainties remain concerning the liquid composition at the eutectic transformation and the shape of the miscibility gap at higher temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01821.x
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  • 9
    Electronic Resource
    Electronic Resource
    Direct Coagulation Casting of Silicon Carbide Components (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    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: Direct coagulation casting is a novel near-net-shape method for forming ceramic green bodies from homogenous high-solids-loaded particle suspensions. It is based on the principle of the in situcoagulation of a powder suspension via a reaction-rate-controlled internal-enzyme(urease)-catalyzed reaction after casting. Low-viscosity (〈3 Pas) suspensions with a high solids loading (〉62 vol%) of SiC, boron, and carbon powder mixtures with a high surface area (〉7-10 m2/g) have been prepared at pH = 10. Salt ions (up to 1-2 mol/L) are created by the urease-catalyzed decomposition of urea, to destabilize the suspensions. The coagulation kinetics and the strength of the wet green bodies have been investigated. The reaction rate is strongly dependent on the temperature (in the range of 5°-30°C) and the enzyme concentration (for the range of 4-16 units/g SiC) and is independent of the substrate (urea) concentration for urea concentrations of 〈2 wt%, based on the powder content. The resulting green bodies show no shrinkage during coagulation and 1%-2% linear shrinkage during drying. The compressive strengths of the wet green bodies are as high as 60 kPa and increase as the coagulation time increases. The wet green strength of the coagulated suspensions scales with the solids content, according to a power law with an exponent of 11, in the range of 56-61 vol% solids content. The possibilities of fabricating high-solids-containing complex SiC green and sintered components with homogenous microstructures and high sintered densities are demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01886.x
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  • 10
    Electronic Resource
    Electronic Resource
    Thermodynamic Assessment of the Strontium–Copper–Oxygen System (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    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 diagram and thermodynamic data on the Sr–Cu–O system at a total pressure of 105 Pa (1 bar) have been reviewed and assessed. Gibbs energy functions for the ternary oxides Sr2CuO3, SrCuO2, Sr14Cu24O41, SrCu2O2, and the liquid phase have been optimized, and a consistent thermodynamic description is presented. Calculated SrOCuOx phase diagrams in air and in 1.01 ×105 Pa (1.01 bar) O2, the oxygen potential diagram, and various thermodynamic properties are shown and compared to experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb02864.x
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