Topic
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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TL;DR: The solubility of all fractions between 0.5 and 70μ of a Belgian glass sand (Snowit) was found to be proportional to the surface area available for solution as mentioned in this paper.
Abstract: Measurements have been made of the silica solubility of quartz samples in the size range 0.5–500μ, prepared from different sources. The solubility of all fractions between 0.5 and 70μ of quartz from a Belgian glass sand (‘Snowit’) was found to be proportional to the surface area available for solution; with quartz from Madagascar the same proportionality was found for samples with sizes between 4 and 50μ, but particles below 2μ in diameter had a much higher solubility per unit area. No colloidal polymerised silicic acid was found in the extracts of the quartz samples of sizes from 0.5 to 500μ, and its alleged occurrence could be explained by quartz and kaolin of small particle size.
The solubility characteristics of quartz, tridymite, cristobalite and fused silica were found to be very similar.
The heat of wetting by water of unetched and etched samples of quartz and tridymite was found to be of the order of 260 ergs./cm.2, which was attributed to the presence of silanol groups on the surface.
6 citations
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TL;DR: In this article, structural characterization and X-ray reference powder pattern determination have been conducted for the Co and Zn-containing tridymite derivatives Ba(Co1−xZnx)SiO4 (x = 0.2, 0.4,0.6, 0., 0.8).
Abstract: Structural characterization and X-ray reference powder pattern determination have been conducted for the Co- and Zn-containing tridymite derivatives Ba(Co1−xZnx)SiO4 (x = 0.2, 0.4, 0.6, 0.8). The bright blue series of Ba(Co1−xZnx)SiO4 crystallized in the hexagonal P63 space group (No. 173), with Z = 6. While the lattice parameter “a” decreases from 9.126 (2) A to 9.10374(6) A from x = 0.2 to 0.8, the lattice parameter “c” increases from 8.69477(12) A to 8.72200(10) A, respectively. Apparently, despite the similarity of ionic sizes of Zn2+ and Co2+, these opposing trends are due to the framework tetrahedral tilting of (ZnCo)O4. The lattice volume, V, remains comparable between 626.27 A3 and 626.017 (7) A3 from x = 0 to x = 0.8. UV-visible absorption spectrum measurements indicate the band gap of these two materials to be ≈3.3 and ≈3.5 eV, respectively, therefore potential UV photocatalytic materials. Reference powder X-ray diffraction patterns of these compounds have been submitted to be included in the Powder Diffraction File (PDF).
6 citations
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TL;DR: In this article, the results of the structural determination of barium calcium tetragallium octaoxide, BaCaGa 4 O 8, from X-ray (Cu Kα) powder diffraction data and refinement by the Rietveld technique are presented.
Abstract: The results of the structural determination of barium calcium tetragallium octaoxide, BaCaGa 4 O 8 , from X-ray (Cu Kα) powder diffraction data and refinement by the Rietveld technique are presented. In BaCaGa 4 O 8 , GaO 4 tetrahedra are arranged in a tridymite-like framework. The arrangement of GaO 4 tetrahedra has not previously been found among compounds with the stuffed tridymite structure.
5 citations
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01 Jan 2018
TL;DR: In this paper, the micromorphological characteristics and interpretation of pedogenic siliceous features in soils and regoliths are discussed, and the most common pedofeatures are typic and laminar coatings and infillings with various silica phases such as opal, opal-CT, cristobalite, chalcedony, and non-fibrous microcrystalline quartz.
Abstract: This chapter deals with the micromorphological characteristics and interpretation of pedogenic siliceous features in soils and regoliths. Pedogenic siliceous features occur as crystalline forms, such as quartz, tridymite, and cristobalite, and as poorly ordered or non-crystalline forms, such as opal-A and opal-CT. Silica may be concentrated in varying degrees through weathering, vertical and lateral translocation, and precipitation and dissolution, resulting in the formation of cemented horizons (silcretes and duripans) and non-cemented or poorly cemented horizons (fragipans). Typic coatings, infillings, and nodules, mainly consisting of opal, are commonly observed in fragipan thin sections. In duripans and silcretes, the most common pedofeatures are typic and laminar coatings and infillings with various silica phases such as opal, opal-CT, cristobalite, chalcedony, and non-fibrous microcrystalline quartz. Transformation of poorly ordered to more crystalline forms with aging is frequently observed. Dissolution of quartz is commonly observed in strongly weathered materials.
5 citations