Tridymite

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

Theoretical Study on Atomic Structures of Thermally Grown Silicon Oxide/Silicon Interfaces

Abstract: The reason why previous researchers have repoterd many different atomic structures such as cristobalite, tridymite, and quartz for the thermally grown silicon oxide/silicon interfaces is studied by following the possible interface structures during the oxidation processes using the first-principles calculations. The results show that the cristobalite-like structures can be easily formed from the silicon diamond structure. Proceeding with the oxidation, compressive strains are accumulated in these cristobalite-like regions. To significantly release these accumulated strains, it is considered that the cristobalite-like regions change into less strained tridymite-like structures and finally more relaxed quartz-like structures. If the transformation occurs without lateral ordering, then the transformed interfacial structure does not have any order and should be amorphous. This explanation provides us with a unified understanding of the interfacial atomic structures. [DOI: 10.1380/ejssnt.2006.584]

Effect of Cu and Zr Co-doped SiO2 Nanoparticles on the Stability of Phases (Quartz-Tridymite-Cristobalite) and Degradation of Methyl Orange at High Temperature

Abstract: SiO2 nanoparticles doped by 10 mol% Zr and 10 mol% Cu were prepared via the sol-gel method in a controled process The effects of doping and calcination temperature on the structural and photo-catalytic properties of SiO2 nanopowders were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis absorption spectroscopy The phases of cristobalite, quartz and tridymite were found at a calcinations temperature range of 800 to 1000 °C and only cristobalite phase was formed at a temperature of 1200 °C The degradation of methyl orange was examined under visible light radiation indicating that the effect of doped elements (Zr, Cu) on SiO2 reduces the band gap effectively

Caracterización por XANES, análisis mineralógico y aplicación industrial de un depósito de caolín de México

Abstract: A kaolin obtained from Villa de Reyes, a region near to San Luis Potosi (Mexico) was characterized by means of X-ray powder diffraction (XRD, optical microscopy (OM), scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-Ray Absorption Near Edge Spectroscopy (XANES), thermal analysis (DTA/TGA), dilatometry (DIL), and chemical analysis. Mineralogical and morphological characteristics of the mineral are presented. The kaolin sample was formed mainly by kaolinite, but other minor phases were also detected such as quartz, cristobalite, tridymite, and dolomite. The high content of volcanic glass detected, by optical microscopy, revealed an incomplete kaolinization process of the raw material. The reddish color of the kaolin was associated with the free iron content in the form of limonite [FeO(OH)], which was determined by XANES. The influence of the particle size on the whiteness of kaolin was evaluated. Dilatometric analysis revealed a strong thermal expansion between 110 y 240 °C, which would difficult the use of this material in traditional ceramic applications. On the other hand the presence of glass and high temperature phases of SiO2, such as cristobalite and tridymite will favor its use in the cement industry.

Experimental study of phase equilibria in the “SnO”–CaO–SiO2 system in equilibrium with tin metal

Abstract: Experimental studies have been conducted to determine the primary phases and liquidus temperatures in the binary “SnO”–SiO2 and ternary “SnO”–CaO–SiO2 systems in equilibrium with tin metal between 1 148 and 1 673 K, using a high temperature equilibration and quenching technique followed by measurement of phase compositions using electron probe X-ray microanalysis. The melting temperature of cassiterite (SnO2) in equilibrium with tin metal was found to be between 1 398 and 1 403 K. The following primary phase fields were identified in the system: malayaite (CaSiSnO5), pseudo-wollastonite (CaSiO3), tridymite and cristobalite (SiO2), and cassiterite (SnO2). The liquidus of the “SnO”–CaO–SiO2 system is dominated by the tridymite or cristobalite (SiO2), and pseudo-wollastonite (CaSiO3) primary phase fields in the range of compositions studied.