Tridymite

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

Heat-repair material for coke oven head and preparation method thereof

Abstract: The invention discloses a heat-repair material for a coke oven head. The heat-repair material comprises, by weight, 10-25% of silica brick, 15-25% of high-alumina bauxite, 10-15% of a binding agent, 15-20% of a cosolvent, 5-10% of a water reducer and 15-55% of alumina silicate. The silica brick comprises, by weight, 75-80% of tridymite and 15-20% of cristobalite. The binding agent is industrial aluminum dihydrogen phosphate. The cosolvent comprises at least three of potassium oxide, silica, alumina and sodium oxide. The water reducer comprises at least one of an M water reducer, a FDN water reducer and an MF water reducer. The heat-repair material has good shock resistance and good wear resistance. The silica brick powder in the raw materials has a high tridymite degree, improves material high temperature volume stability, improves material binding performances, can be bonded with a silica brick base, prevents cracking and shrinkage in a thermal state, effectively prolongs a coke oven head service life, and guarantees uniformity, adhesion and brick internal structure strength by use of the water reducer.

Mineralogical and geochemical studies of hardened subsurface layers in soils of the Azufres and Atecuaro volcanic calderas, southwestern Mexico

Abstract: Free silica and halloysite-bearing hardened subsurface layers in the ash fall deposits of the Azufres and Atecuaro volcanic calderas (Michoacan State, southwestern Mexico), known as “tepetates”, have been characterized by chemical analysis, X-ray diffraction (XRD), Raman and Infrared spectrometry, optical (OM) and scanning (SEM) microscopy with energy dispersive X-ray analysis (EDXRA). Chemical analysis of these weathered and hardened formations shows the oxidation of Fe2+, enrichment of Al, Fe3+ and Ti, loss of Si, Na, Ca, K, Mg, and formation of minerals with hydroxyls groups. Tepetates are characterized by elevated SiO2/Al2O3 molar ratios (4.86–8.82) that show part of the SiO2 has crystallized in free siliceous phases. X-ray analysis reveals hydrated (1.0 nm) and dehydrated halloysite (0.7 nm), sanidine, plagioclases, cristobalite, and tridymite. Raman and infrared spectra confirm the presence of these mineral phases and show that the structural transformations occur in opal neoformations. SEM shows a ...

Thermal phase transformation of turquoise

Abstract: The process and product of thermal phase transformation of the apatite pseudomorphic turquoise from maanshan,Anhui province were analyzed by differential thermal analysis,infrared spectra and Raman spectrum and X-ray powder diffraction.The results indicate that the thermal phase transformation can be divided into six stages:the removal of the absorption water in the range of 100–200 ℃;the release of the hydroxyl and lattice water in the range of 250–330 ℃;the formation of non-crystalline structure in the range of 330–750 ℃;the formation of a new phase at 750 ℃;the generation of aluminum phosphate with tridymite structure in the range of 750–1200 ℃.The increase of the degree of crystalline order of aluminum phosphate increases at 1200 ℃.

Silica crown refractory corrosion in glass melting furnaces

Abstract: The critical parameters of silica refractories, such as compressive strength, bulk, density, quantity of silica, microstructure and porosity were evaluated of unused and used bricks to line the crowns of glass furnaces, when the rate of corrosion of crowns were about 2 times greater. The change of these parameters, the chemical composition and formation of the microcracks in the used silica refractories material were studied. It was established that the short time at service of container glass furnace crown can be related to low quality of silica brick: high quantity of CaO and impurities, low quantity of silica, low quantity of silica, transferred to tridymite and cristobalite and formation of 5-10 μm and more than 100 μm cracks in the crown material. The main reason of corrosion high quality silica bricks used to line the crown of electrovacuum glass furnace is the multiple cyclic change of crown temperature at 1405 - 1430°C range in the initial zone of crown and at 1575 - 1605°C range in the zone of highest temperatures.