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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: The most likely cause of cavity formation is transient tensional stress that produces a mechanical opening and widening at the interface between the crystallization front and the host melt (e.g., where T ǫ> T g ≥ 0).
Abstract: High-temperature crystallization domains (HTCDs) including spherulites and lithophysae form during cooling of silica-rich lava and welded ignimbrites. Spherulites grow in silicate melts or hot glass and they display a radiating or microcrystalline texture, typically consisting of cristobalite, tridymite, and sanidine. Lithophysae are HTCDs comprising one or more cavities. This contribution reviews the research and discussions on HTCDs carried out over the last 200 years. The emphasis, here, is on lithophysae and summarizes current knowledge of their formation. A number of parameters influence the initiation and growth of lithophysae, as well as, their shapes and internal textures. The most likely cause of cavity formation is transient tensional stress that produces a mechanical opening and widening at the interface between the crystallization front and the host melt (e.g., where T > T g ). Cavity growth and expansion forced by rising vapor pressure is considered less important. In some cases, further growth of HTCD cavities results from vapor phase corrosion and brecciation.

71 citations

Journal ArticleDOI
TL;DR: Two novel framework compounds have been synthesized by a self-assembly reaction and contain an unexpected framework, Ag2I4(2-) with tridymite topology, and the discrete M(en)3(2+) cations are located in the channels.
Abstract: Two novel framework compounds, Zn(en)3Ag2I4 (1) and Ni(en)3Ag2I4 (2), have been synthesized by a self-assembly reaction. Both of them contain an unexpected framework, Ag2I42− with tridymite topolop...

70 citations

Journal ArticleDOI
A. Proctor1
TL;DR: The structure and composition of processed rice hull ash were studied to better understand its adsorption of the soy oil components, lutein and free fatty acids as discussed by the authors, and the silica-rich ash was composed largely of low order cristobalite and tridymite in the form of opal CT, with variable particle size.
Abstract: The structure and composition of processed rice hull ash were studied to better understand its adsorption of the soy oil components, lutein and free fatty acids. The silica-rich ash was composed largely of low order cristobalite and tridymite in the form of opal CT, with variable particle size. On heating of the ash there was conversion to a more ordered form of opal C, fusing of particles, and loss of potassium. Acid washing, following heating, also removed potassium and slightly reduced particle size further. Crystal form, particle size, particle fusion and potassium content may be important factors influencing ash adsorption of soy oil components.

69 citations

Journal Article
TL;DR: In this paper, the thermally induced amorphous-to-crystalline transition has been studied for bulk sheets and micrometre-sized particles of magnesium silicate glass (MgSiO3), nanometresized amorphized magnesium silicates (mssO3 and mssO4 smokes) and amorphised silica particles (SiO2) using laser ablation technique.
Abstract: The thermally induced amorphous-to-crystalline transition has been studied for bulk sheets and micrometre-sized particles of magnesium silicate glass (MgSiO3), nanometresized amorphous magnesium silicate (MgSiO3 and Mg2SiO4 smokes) and amorphous silica particles (SiO2) Silicate glass was produced by the shock-quenching of melts Samples of nanometre-sized smoke particles have been obtained by the laser ablation technique Both the MgSiO3 and the Mg2SiO4 smokes have been found to consist of two particle species; particles of smaller size ranging in diametre from 10 nm to about 100 nm and bigger size ranging from a few 100 nm to almost 3 micrometres in diametre Nanometre-sized particles have been shown to be depleted in magnesium whereas the micrometre-sized particles were found to be enriched in Mg Generally, the particles are composed of nonstoichiometric magnesium silicates with compositions varying even inside of the particles Frequently, the particles contained internal voids that are assumed to have been formed by thermal shrinkage or outgassing of the particles’ interior during cooling Annealing at 1000 K transformed the magnesium silicate smokes into crystalline forsterite (c-Mg2SiO4), tridymite (a crystalline modification of SiO2) and amorphous silica (a-SiO2) according to the initial Mg/Si-ratio of the smoke Crystallization took place within a few hours for the Mg2SiO4 smoke and within one day for the MgSiO3 smoke The MgSiO3 glass evolved more slowly because crystallization started at the sample surface It has been annealed at temperatures ranging from 1000 to 1165 K In contrast to the smoke samples, MgSiO3 glass crystallized as orthoenstatite (MgSiO3) Only after 50 hours of annealing at 1000 K, weak indications of forsterite and tridymite formation have been found in the X-ray diffraction spectra At a temperature of 1000 K, amorphous silica nanoparticles showed distinctly lower rates of thermal evolution compared with the magnesium silicates At 1220 K, the timescale of crystallization of a-SiO2 into cristobalite and tridymite amounts to 45 h Send offprint requests to: D Fabian (fabian@astrouni-jenade) From the experiments, crystallization parameters have been obtained: activation energy and velocity of crystal growth The spectra shown in this study will be made publically available in the electronic database (http://wwwastrounijenade)

69 citations

Journal ArticleDOI
TL;DR: In this article, it is shown that although cristobalite can be produced from pure quartz by heating it is not possible to produce tridymite in this fashion; a flux or mineralizer is required for tridymyite formation and even in this case cristsobalite is produced before any tridye is observed.
Abstract: A study of the stability relations of pure silica phases is described. It is shown that although cristobalite can be produced from pure quartz by heating it is not possible to produce tridymite in this fashion; a flux or mineralizer is required for tridymite formation and even in this case cristobalite is produced before any tridymite is observed. Thus it is concluded that the stability relations for the silica minerals proposed by Fenner are incorrect and that tridymite is not a stable phase in the pure silica system.

69 citations


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