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Showing 1 to 16 of 16 for “"devitrification"”.
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Bonding Characteristics and Devitrification Behavior in Iron-Containing Sodium-Silicate Glasses
… upon either the melting conditions or the devitrification behavior. The fraction of tetrahedral sites in the glassy matrix decreases proportionally with increasing K(,Fe) values, or equivalently, the crystallinity of (gamma)-Na(,2)Si(,2)O(,5). From the overall consideration, the addition of …
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Devitrification Kinetics and Optical Stability of Optical Fibers at High Temperatures
… One of the limitations of such systems is the devitrification of the fused silica based core and cladding glass at elevated temperatures. Crystallites can nucleate on the surface of the cladding and grow into the core. The formation of these crystalline flaws in the optical fiber causes stress …
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Microstructure Control and Crystallization Kinetics in Amorphous Cadmium-Germanium - Arsenide (Devitrification, Differential Scanning, Calorimetry)
CdGeAs(,2) is a member of the II-IV-V chalcopyrite semiconductor family. The crystallization of the amorphous form of this compound was investigated using Differential Scanning Calorimetry. The basic operating principles of the two currently most popular DSC instruments (the DuPont 1090 DSC and the …
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Multinuclear NMR Investigations of Sol-Gel Systems
… oxides, followed by rapid cooling to avoid devitrification. A topic of current interest in materials research is the preparation of oxide glasses by the hydrolysis and polymerization of metal alkoxides in solution to form a gel, which may then be fired to form a glass. This so-called sol-gel …
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Amorphization and De-vitrification in Immiscible Copper-Niobium Alloy Thin Films
… competing supersaturated crystalline phases. The devitrification of the immiscible Cu-Nb thin film of composition Cu-45% Nb has been studied in detail with the discussion on the mechanism of phase transformation. The initial phase separation in the amorphous condition seems to play a vital role in …
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Phase Formation, Liquid Structure, and Physical Properties of Amorphous- and Quasicrystal-forming Alloys
… and discussed on changes in microstructure and devitrification mechanisms with the addition of Ag in Mg65Cu(25-x)AgxGd10 BMGs, interesting for their light weight and resistance to oxygen during casting, using transmission electron microscopy: TEM), SEM, and differential scanning calorimetry: …
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Application of through-vial impedance spectroscopy as a novel process analytical technology for freeze drying
… ice being formed on annealing. The phenomenon of devitrification (and the production of more ice, and hence larger ice crystals) was therefore discounted as the mechanism by which annealing impacts the drying time. Having excluded devitrification from the mechanism of annealing enhanced drying, it …
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Investigation of the thermodynamics of iron phosphate melts and stability of iron phosphate glasses: effects of composition and iron redox ratio
… chain lengths are most stable against devitrification. Heterogeneous crystallization occurs on the glass surface and is dependent on iron valence state, particle size, heating rate, temperature and oxygen availability in the atmosphere. Oxidation of ferrous iron on the glass surface …
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OXIDATION OF SILICON CARBIDE AND GRAPHITE FOR HIGH TEMPERATURE GAS-COOLED REACTOR APPLICATIONS
… of SiC fibers with regards to stress relief and devitrification in the SiO<sub>2</sub> scale. By comparing the oxide layer thickness of TRISO particles oxidized in atmospheres containing 0.2 and 20 kPa O<sub>2</sub>, it was found that the mechanism responsible for oxide growth was different at …
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A study of obsidian in prehistoric central and Eastern Europe, and it's trace element characterization. An analytically-based study of archaeological obsidian in Central and Eastern Europe, an investigation of obsidian sources in this area, and the characterization of these obsidians using neutron activation analysis.
… sources, and which are not badly affected by devitrification and hydration of the obsidian, for example the rare earth elements. The analytical data was processed using Cluster Analysis. 242 of the archaeological samples came from Slovak sources, 22 from Hungarian sources, 9 from Lipari and 5 …
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Development of Optimal Electromagnetic Resonance Rewarming Technology for Cryopreservation
… cooling process, the slow rewarming can lead to devitrification and recrystallization, introducing considerable ice crystals that should be avoided. On the other hand, the non-uniform temperature profile brought by the convective heating method leads to the thermal stress induced fractures, which …
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Immobilization of radioactive materials in iron phosphate glass
… decreased melt viscosity and reduced devitrification tendency. The chemical durability of all but one of the glassy wasteforms containing SNF was as good as, or better than a borosilicate reference glass (10<sup>-9</sup> g/cm<sup>2</sup>/min) in distilled water at 90°C.</p> <p>The …
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Petroleum coke slags: characterization and dissolution
… materials, sulfide exsolution processes, glass devitrification. and the development of chemical zonation in some spinels. This information offers some perspectives on the potential of resource reclamation. Resource reclamation for petroleum coke slags is best assessed with a knowledge of phases, …
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Volcanic stratigraphy and lithochemistry of the lower Jurassic Hazelton group, host to the Eskay Creek precious and base metal volcanogenic deposit
… facies displays vapor phase volcanic features, devitrification, and enrichment in K, Sb, Ag, Hg. Intense K-silicate, sericitic, and silicic alteration, with precious and base metal mineralization, occurs in the feeder dikes to the rhyolite flow domes. The 21 Zone deposit is located within 200 …
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Lithium at the Thacker Pass deposit, Humboldt County, Nevada, U.S.A.
… This study postulates that degassing and devitrification of the underlying McDermitt Tuff was responsible for the enrichment of Li in the caldera and Thacker Pass deposit. Observation of vapor phase altered, degassed and devitrified McDermitt Tuff with 30-40 ppm Li beneath the Thacker Pass …