Tridymite

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

Influence of dipalmitoylphosphatidylcholine on the dissolution of Brazilian chrysotile.

Abstract: It is known that Brazilian chrysotile is rapidly removed from the lungs, but quantitative studies about the influence of lung surfactants on chrysotile dissolution have not been investigated. In this work, the chemical behavior of chrysotile and its dissolution in the presence of dipalmitoylphosphatidylcholine (DPPC) were investigated in physiological conditions. The dissolution was investigated through quantification of magnesium and silicon released by chrysotile. At 37 degrees C, the magnesium concentration is similar to control (without DPPC), which is about 2.0x10(-4)molL(-1), meaning that the dissolution process is not affected by the presence of this surfactant. The same was observed for silicon. The silicon concentration released by chrysotile is similar in all media tested. It is known that the dissolution mechanisms of brucite and tridymite layers are different. From our results, we propose that under physiological conditions, the mechanism of brucite dissolution is based on its interaction with hydrogen ions and that the mechanism of tridymite dissolution is based on a hydrolysis process.

The microstructure of some raw lead mat glazes

Abstract: This is a report on the microstructure of mats found in the following composition range: These were fired at cones 03, 2, 4, and 6. The compounds present recognized as crystals were anorthite, cession (probably), tridymite, and wollastonite. Willemite was not observed. The good mats were due to crystal separations. A high alumina content was not essential. Anorthite was the principal crystalline form present in mat glazes containing lime.

Nuclear magnetic resonance investigations of the structural phase transitions of AlPO4 tridymite

Abstract: 27Al and 31P NMR spectroscopic data are presented for the tridymite polymorph of AlPO4 (AlPO4 −1) through its structural phase transition at about 80 °C. The RT 27Al and 31P spectra of AlPO4−t both contain doublets of broad peaks, indicating two well-separated groups of sites in the RT structure with mean Al-O-P bond angles per tetrahedron of ∼ 147.8°and 153.1°(±1). With increasing temperature, the doublets remain the same up to about 74 °C, where the relative intensities of the two peaks start to change. The peak corresponding to smaller Al-O-P bond angles disappears, and above ∼88 °C the 27Al and 31P spectra contain single symmetrical peaks, corresponding to a mean Al-O-P bond angle of 153.4°. This bond angle increases gradually with increasing temperature to 153.7°at ∼150 °C and remains constant to about 500 °C. 27Al quadrupole echo experiments suggests that the 27Al nuclear quadrupole coupling constant (QCC) is small and decreases with increasing temperature. QCC remains nonzero in the high temperature phase of AlPO4−t, consistent with the previously proposed 3m local symmetry of Al in the high-temperature structure.

Preparation of sodium silicate

Abstract: The hydrothermal method of preparing sodium silicate (waterglass) is capable of providing high, ie above 26, molar SiO₂/Na₂O ratio by using cristobalite or tridymite as the silica source