Cristobalite - Wikipedia
Cristobalite (/ k r ɪ ˈ s t oʊ b ə ˌ l aɪ t /) is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, Si O 2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the quartz group, which also include coesite, tridymite and ...
Cristobalite formation from the thermal treatment of amorphous …
2018年10月1日 · Cristobalite is a low-density homogeneous duo of the SiO 2 polymorph that crystallises from a thermodynamically stable SiO 2 melt zone with atmospheric pressures and temperatures of 1470–1728°C.
The Mineral cristobalite - The Mineral and Gemstone Kingdom
Cristobalite is an odd form of silica. It is composed of the same elements as Quartz but has a different crystal structure, making it a separate mineral. Cristobalite is found in volcanic sources almost always associated with the natural glass rock obsidian. It usually forms in vesicles and gas pockets with the obsidian.
Compressional pathways of α-cristobalite, structure of cristobalite …
2017年6月7日 · We demonstrate that under hydrostatic pressure α-cristobalite remains untransformed up to at least 15 GPa. In quasi-hydrostatic experiments, above 11 GPa cristobalite X-I forms—a monoclinic...
Cristobalite - an overview | ScienceDirect Topics
Cristobalite forms several types of pedofeatures, such as coatings in andesitic lava (Nieuwenhuyse & Verburg, 2000), typic and amiboidal nodules in alluvial fans (Bustillo & Alonso-Zarza, 2003), and microlaminated coatings and fissure infillings in duripans (Gutiérrez-Castorena et al., 2006, 2007; Quantin, 2010).
Silica fume was thermally treated to 700–1100°C in air to transform it into crystals and cause it to reach the metastable cristobalite state. The phase transition behaviour of the silica fume crystallisation process and the main factors influencing the crystallisation behaviour were
In many silica applications, it is crucial to control the transformation to cristobalite. Cristobalite formation sets the upper temperature bound for use of fused silica glassware; whereas, in glass ceramics and silica refractories, the forma-tion of cristobalite is a vital part of processing.
The nature and formation of cristobalite at the Soufrière Hills …
2013年2月21日 · Feathery crystallites and micro-crystals of cristobalite and quartz associated with volcanic glass, identified using SEM-Raman, are interpreted to have formed by varying amounts of devitrification. We discuss mechanisms of silica transport and cristobalite formation, and their implications for petrological interpretations and dome stability.
A kinetic study of the quartz–cristobalite phase transition
2013年12月1日 · Ex-situ observations have demonstrated that the formation of cristobalite from quartz after 50 min, 2, 4 and 6 h at 1200 and 1300 °C, exhibits a remarkable dependence on 〈d〉 of quartz, showing comparable behaviours in the case of 〈d〉 equal to 15.8 and 28.4 μm, but significant differences for 〈d〉 of 4.1 μm.
Cristobalite formation from thermal treatment of Texas lignite fly ash
1999年9月1日 · This study shows that thermal treatments, at ≥900°C, of fly ash favor the preferential formation of cristobalite, a conclusion supported by our XRD, FT-IR and SEM studies. Furthermore, the cristobalite is found to crystallize instead of tridymite eventhough the latter is the thermodynamically stable phase because kinetics of formation is an ...
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