Showing papers on "Tridymite published in 1993"
TL;DR: The crystal structures of the compounds BaMSiO4 (M = Co, Mg, Zn) have been refined by using single-crystal X-ray data and powder neutron data as discussed by the authors.
54 citations
TL;DR: In this paper, the changes occurring in SAPO-37 upon heating it to 1273 K are studied using 29Si, 27Al and 31P magic-angle-spinning nuclear magnetic resonance (MAS NMR), X-ray diffraction (XRD) and infrared spectroscopy.
Abstract: The changes occurring in SAPO-37 upon heating it to 1273 K are studied using 29Si, 27Al and 31P magic-angle-spinning nuclear magnetic resonance (MAS NMR), X-ray diffraction (XRD) and infrared spectroscopy. The removal of the template at 873 K leads to a shift of both 29Si and 27Al MAS NMR peaks, suggesting an interaction of the template with some SiO4 and AlO4 tetrahedra. A further solid-state transformation is shown to occur between 1073 and 1173 K. This involves the formation of siliceous islands, generating silicoaluminate domains. The faujasite crystal structure is maintained. At 1273 K the material is fully transformed to a mixture of tridymite and cristobalite structures. A model is proposed for the migration of atoms in the framework.
31 citations
TL;DR: The morphology, mineralogy, chemistry and size distribution of nonspherical particles collected in the stratosphere between 34 and 36 km altitude during May, 1985 were determined by analytical electron microscope analysis as discussed by the authors.
23 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
TL;DR: The framework structure of a new sodium zinc arsenate, produced by dehydration of the Na 6 (ZnAsO 4 ) 6 ·8 H 2 0 sodalite analog, has been solved by a simulated annealing method as mentioned in this paper.
18 citations
TL;DR: In this article, the amorphous structure of aluminium phosphate thin film obtained from the pyrosol process was investigated and it was shown that the structure of these thin films is constituted of two types of chain with Al atoms in both tetrahedral and octahedral sites.
13 citations
Patent•
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04 Jun 1993
TL;DR: In this article, the authors proposed a structurally dense silica brick having excellent heat conductivity, pressure resistance and wear resistance at high temp., prolonging the service life of the body of a furnace and capable of saving the energy.
Abstract: PURPOSE:To provide a structurally dense silica brick having excellent heat conductivity, pressure resistance and wear resistance at high temp., prolonging the service life of the body of a furnace and capable of saving the energy. CONSTITUTION:This dense silica brick has a compsn. contg. cristobalite and tridymite subjected to transition as crystal phases in (10-40):(90-60) ratio (wt.%) and 2-12wt.% metal oxide other than SiO2 and existing as an amorphous phase and has >=1.95 bulk density and <=15% porosity. When colloidal silica is impregnated into this silica brick, a denser silica brick having higher wear resistance is obtd.
7 citations
Journal Article•
TL;DR: In this article, solid-state synthesis of a new caesium-beryllium monoarsenate and its crystal growth by an original flux process are detailed and followed by a complete crystallographic characterization pointing out it belongs to the well-known stuffed tridymite structural family.
6 citations
Patent•
23 Mar 1993
TL;DR: In this article, a composite material is obtained by mixing 45-95vol.% low- melting glass powder with 5-50vol.%.% tridymite powder and 0-40vol.%).
Abstract: PURPOSE:To obtain a composite material, having a high thermal expansion coefficient and mechanical strength and suitable for covering IC packages or thermistors made of a metal. CONSTITUTION:A composite material is obtained by mixing 45-95vol.% low- melting glass powder with 5-50vol.% tridymite powder and 0-40vol.% ceramic powder. Furthermore, oxide powder such as alumina, zirconia, magnesia, calcia, zinc stannate or calcium stannate is used as the ceramic powder.
3 citations
Patent•
14 Jan 1993
TL;DR: In this article, a kind of silica rock is incorporated with 0.2-5wt.% of a soda lime silicate-based melt to promote the transition of the silica to cristobalite and tridymite.
Abstract: PURPOSE:To obtain the title brick useful as a refractory for industrial furnaces by promoting silica transition using silica rock, as raw material, which is resistant in the transition of silica to cristobalite and tridymite. CONSTITUTION:A raw material, a kind of silica rock, is incorporated with 0.2-5wt.% of a soda lime silicate-based melt. Thereby, reaction of this melt with the silica in the raw material will promote the transition of the silica to cristobalite and tridymite.
3 citations
TL;DR: In this article, it was found that the thermal expansion is controllable by the amount of silica polymorphs, particularly tbat of tridymite, in silica/glass composites.
Abstract: Sintered composites of silica-containing Na2WO4 as a phase transformation agent and sodium borosilicate glass were prepared, and silica polymorphs in silica/glass sintered composites were identified and quantitatively analyzed by means of XRD. The amount of tridymite increased with the addition of Na2WO4. It was found that the thermal expansion is controllable by the amount of silica polymorphs, particularly tbat of tridymite, in silica/glass composites. Addition of Na2WO4 to the composites increased the dielectric constant, which may be attributed to the increase in the amounts of sodium and tungsten ions which have high polarizabilty.
Patent•
09 Mar 1993
TL;DR: In this article, the authors proposed to obtain a sealing material having a high thermal expansion coefficient of approximately 120-220 X 10 / deg.C, capable of sealing at low temperatures, and having high mechanical strength.
Abstract: PURPOSE:To obtain a sealing material having a high thermal expansion coefficient of approximately 120-220 X 10 / deg.C, capable of sealing at low temperatures, and having a high mechanical strength. CONSTITUTION:The objective sealing material comprises 45-80vol.% of the powder of low temperature melting point glass having a transition point of <=350 deg.C, 5-50vol.% of the powder of cristobalite and/or tridymite, and 0-40vol.% of the powder of a ceramic. The powder of the cristobalite and the powder of the tridymite, each having the maximum particle diameter of <=45mum, are employed. The ceramic powder includes the oxide powder of alumina, zirconia, magnesia, calcia, zinc stannate, calcium stannate, etc.
TL;DR: In this paper, the authors investigated the possibility of selective dissolution of silicate components of TUFF in alkaline water solution (NaOH) and found that the slime mainly contains minerals of clay type as well as indefinite quantities of quartz, tridymite and amorphous SiO2.
Abstract: Possibility of selective dissolution of silicate components of TUFF in alkaline water solution (NaOH) has been investigated. Insoluble slime mainly contains minerals of clay type as well as indefinite quantities of quartz, tridymite and amorphous SiO2. By changing Na2O/SiO2 and H2O/SiO2 ratios, temperature and duration of treatment we searched for conditions of simultaneous maximum silicate and minimum aluminosilicate component solubility. In our experiments composition of the slime was successfully determined by IR method.