Showing papers on "Tridymite published in 1981"
TL;DR: The experimental replacement of calcite and aragonite by dolomite under a variety of conditions indicates that dolmitization can take place in marine and lacustrine environments under two conditions: low dissolved sulfate concentrations and insubstantial contemporary silica diagenesis.
Abstract: The experimental replacement of calcite and aragonite by dolomite under a variety of conditions indicates that dolomitization can take place in marine and lacustrine environments under two conditions: (i) low dissolved sulfate concentrations and (ii) insubstantial contemporaneous silica diagenesis. Common sites for dolomite formation are areas where the dissolved sulfate concentration is reduced by microbial sulfate reduction, through the mixing of seawater with large amounts of fresh water, or where low-sulfate alkaline lacustrine environments prevail. Even under these conditions, dolomite formation may be inhibited by the concurrent transformation of opal-A (amorphous silica) to opal-CT (disordered cristobalite and tridymite), whereas the subsequent transformation of opal-CT to quartz favors the formation of dolomite.
559 citations
TL;DR: In this paper, the effect of thermal decomposition of rice hulls on the amorphous structure of silica ash was investigated by X-ray diffraction, and the results obtained clarify the optimum conditions for production of amorphized silica by combustion of Rice hulls in fixed beds.
86 citations
TL;DR: Twinning on the unit cell level of the idealized cristobalite structure, using a mirror plane as the twin and composition plane, provides a simple relationship between 14 tetrahedral frameworks as discussed by the authors.
13 citations
TL;DR: In this article, the phase transitions of KLiWO4 and KLiMoO4 were investigated using a high-temperature X-ray powder diffractometer and phase transitions were observed at 350°C and 360°C, respectively.
12 citations
TL;DR: The liquidus surface for the high silica (>60 wt%) portion of the ternary system Na2O-B2O3-SiO2 is presented in this article.
Abstract: The liquidus surface for the high silica (>60 wt%) portion of the ternary system Na2O-B2O3-SiO2 is presented. Determinations were made by quench runs and solubility studies. The compound, reedmergnerite, NaBSi3O8 was not observed. Tridymite is the major primary phase.
8 citations
7 citations
TL;DR: In this article, the amount of cristobalite was calculated from the thermal expansion coefficient, the area of the differential thermal expansion together with specific heat measurements and specific gravity determinations.
5 citations
TL;DR: In this article, the phase relations in the CaAl2O4|CaGa2O 4 system were examined by using three kinds of starting materials; A (CaCO3 + (Al,Ga)2O3), B (CaAl 2O4 + CaGa 2 O4) and C (Ca CO3 + Al 2O3 + Ga 2 O3 + G 2 O 3 + Ga 3 O 3 ) in the stuffed tridymite structure.
1 citations
Patent•
26 Mar 1981
TL;DR: Binder for chemically resistant concrete comprises 30-80 % wt. of tridymite and/or cristobalite particles contg. on the surface 0.5-6% mole Na2O and/ or K2O as mentioned in this paper.
Abstract: Binder for chemically resistant concrete comprises 30-80 % wt. quartz sand with specific surface area 1000-5000 cm2/g and 20-70 % wt. of tridymite and/or cristobalite particles contg. on the surface 0.5-6% mole Na2O and/or K2O. Binder is made by heating at 1000-1550 degrees C a mixt. of quartz sand and 0.7-15% of >=1 of Na2CO3, K2CO3, NaOH, KOH to form the tridymite and/or cristobalite contg. Na2O and/or K2O. Cooled mixt. is ground and mixed with ground quartz sand. Used for producing finishing blocks and panels bearing structural members for use in chemically aggressive environment. The binder has increased water resistance and is more economically produced with lower energy consumption.
1 citations