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Tridymite

About: Tridymite is a research topic. Over the lifetime, 840 publications have been published within this topic receiving 14831 citations.


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Journal ArticleDOI
TL;DR: In this article, phase equilibrium experimental data in the FeO-Fe2O3-SiO2-CaO-MgO-Al 2O3 system at oxygen partial pressure of 10−8m within the range of temperatures and compositions directly relevant to copper smelting was provided.
Abstract: Copper concentrates and fluxes can contain variable levels of SiO2, CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational temperature. Optimal control of the slag chemistry in the copper smelting, therefore, is essential for high recovery and productivity; this, in turn, requires detailed knowledge of the slag phase equilibria. The present work provides new phase equilibrium experimental data in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 system at oxygen partial pressure of 10−8 atm within the range of temperatures and compositions directly relevant to copper smelting. For the range of conditions relevant to the Kennecott Utah Copper (South Magna, UT) smelting furnace, it was confirmed experimentally that increasing concentrations of MgO or CaO resulted in significant decreases of the tridymite liquidus temperature and in changes in the position of the tridymite liquidus in the direction of higher silica concentration; in contrast, the spinel liquidus temperatures increase significantly with the increase of MgO or CaO. Olivine and clinopyroxene precipitates appeared at high MgO concentrations in the liquid slag. The liquidus temperature in the spinel primary phase field was expressed as a linear function of 1/(wt pctFe/wt pctSiO2), wt pctCaO, wt pctMgO, and wt pctAl2O3. The positions of each of the liquidus points (wt pctFe)/(wt pctSiO2) at a fixed temperatures in the tridymite primary phase field were expressed as linear functions of wt pctCaO, wt pctMgO, and wt pctAl2O3.

21 citations

Journal ArticleDOI
01 Mar 2010
TL;DR: In this article, the diffraction pattern of the high pressure phase CO2-V is consistently interpreted in terms of a tetragonal uni_t cell (Z = 4, a = 3.584, c = 5.908 ) at 50 GPa.
Abstract: Synchrotron X-ray diffraction study for solid CO2 at 40?100 GPa and around 2,000 K has shown that the diffraction pattern of the high pressure phase CO2-V is consistently interpreted in terms of a tetragonal uni_t cell (Z = 4, a = 3.584 ?, c = 5.908 ? at 50GPa). A ?-cristobalite structure (space group I2d) gives a good account of our data qualitatively. Isothermal molar volume (300K) of the CO2-V in the present study is smaller than that indexed as a tridymite structure proposed by previous studies at any pressures.

20 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated regolith breccia 15299, which was returned by the Apollo 15 mission, using the combined techniques of focused ion beam (FIB), synchrotron X-ray diffraction (XRD), and transmission electron microscopy (TEM), and inferred that the stishovite possibly formed by the Imbrium impact or subsequent local impact event in the Procellarum KREEP Terrane (PKT) of the nearside of the Moon.
Abstract: High-pressure polymorphs recovered in terrestrial craters are evidence of meteoroid impact events on the Earth’s surface. Despite countless impact craters on the Moon, high-pressure polymorphs have not been reported to date in returned Apollo samples. On the other hand, recent studies report that the high-pressure polymorphs of silica, coesite, and stishovite occur in shocked lunar meteorites. We investigated regolith breccia 15299, which was returned by the Apollo 15 mission, using the combined techniques of focused ion beam (FIB), synchrotron X-ray diffraction (XRD), and transmission electron microscopy (TEM). The regolith breccia 15299 studied here consists of a mafic impact melt breccia with millimeter-sized, coarse-grained, low-Ti basalt clasts. The mafic melt breccia consists of fragments of minerals (olivine, pyroxene, plagioclase, silica, and ilmenite) and glass. Several quartz, tridymite, and cristobalite grains of 10–100 μm across occur in the mafic impact melt breccia. Vesicular melt veins of less than ~200 μm wide cut across the mafic melt breccia matrix and mineral fragments. Some silica grains are entrained in the melt veins. One of the silica grains entrained in the melt veins consist of stishovite [ a = 4.190(1), c = 2.674(1) A, V = 46.95 A3, space group P 42/ mnm ] along with tridymite and silica glass. This is the first report of high-pressure polymorphs from returned lunar samples. TEM images show that the stishovite is needle-like in habit, and up to ~400 nm in size. Considering the lithologies and shock features of 15299, it is inferred that the stishovite possibly formed by the Imbrium impact or subsequent local impact event(s) in the Procellarum KREEP Terrane (PKT) of the nearside of the Moon.

20 citations

Journal Article
TL;DR: In this article, changes in 29 Si MAS NMR Spectra of synthetic tridymite from room temperature to 504°C are consistent with the structural phase transitions previously observed by x-ray diffraction and by oatical and calorimetric methods.
Abstract: Changes in 29 Si MAS NMR Spectra of synthetic tridymite from room temperature to 504°C are consistent with the structural phase transitions previously observed by x-ray diffraction and by oatical and calorimetric methods. The results also provide evidence for a disordered or incommensurate structure for the OP and OS phases (stable from about 110 to 200°C) and for dynamical disordering of the O atoms at greater than kilohertz frequencies for at least the higher temperature OC and HP phases

20 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202315
202231
202125
202027
201920
201826