Tridymite

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

Properties of sandstones as a refractory material

Abstract: Sandstories from Chungking were tested for their properties as a refractory material. Chemical, petrographical, rational, and sieve analyses were made; properties, such as porosity, refractoriness, specific gravity, thermal expansion, and resistance to spalling. were determined; and studies were made on changes in firing up to 1550°C. No inversion of the quartz grains in the rock into tridymite or cristohalite could be detected. The interstitial clay substances fused first, and the quartz grains then dissolved gradually into the glassy matrix on firing at high temperatures. Being free from mineralogical and structural changes, unusually low in thermal expansion and porosity, and good in spalling resistance after firing at high temperatures, sandstones are shown to be an excellent refractory if properly employed. Of the two kinds of rocks, the dense and the porous, the former was found much better in test for refractoriness under load. Prefiring of the material before lining in a furnace structure is desirable to eliminate the permanent expansion and to improve the resistance to spalling in the raw state.

Examination of polished specimens of refractories by reflected light

Abstract: A discussion is presented of the preparation of the sample specimen and the polishing, etching, and identification of phases when the technique is applied to basic and silica refractories. This method shows the relationship of high-iron slag to tridymite and cristobalite in the silica brick and it aids in the explanation of the bursting of chrome-magnesite brick by iron oxide.

Thermal stability of V-loaded AlPO4-5 materials

Abstract: A progressive sintering of the porosity of both V-free and V-loaded AlPO4-5 samples is observed upon calcination in air at increasing temperatures. This sintering leads to the coexistence of porous AlPO4-5 and dense tridymite. As established by cristallinity and pore volume measurements. the presence of vanadium decreases by 100 to 300°C the threshold temperature at which this sintering begins, in spite of the low V amount in the samples (V/(V+Al+P) atomic ratio of 0.5–1%). This threshold temperature depends on the method used to introduce V (by hydrothermal synthesis, under static conditions or agitation, and/or by grinding vanadia with a V-free AlPO4-5) and on the morphology of the AlPO4-5 crystals as observed by scanning electron microscopy. These factors are related to the dispersion of the V species within the porosity. Since only very small amounts of intraporosity VIV species (VIV/VT<1%) are detected by ESR, whatever the extent of the Sintering which generates tridymite, it is concluded that the thermal stability of V-loaded AlPO4-5 is determined by the dispersion of Vv species within the porosity. This conclusion is in line with earlier propositions made to explain the thermal behaviour of V-loaded zeolites and V-contamined FCC catalysts.

Entaxy of tridymite in the gangue of a Pb-Cu-Zn occurrence

Abstract: Tridymite identified in the gangue of Dunbrack Prospect, Musquodoboit River, Halifax County, Nova Scotia, shows in addition to twinning in six-sided sectorial pattern an t'ornamentation" in alternating sectors. This "ornamentation" consists of a distinct crystalline phase, with an axial angle 2V " 30o as against 2V" \7" of the main part of-the composite crystal. The intergrowth of the two crystalline phases is regular and oriented. The term entaxy is suggested for such intergrowths.