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High Pressure Research
An International Journal
Volume 20, 2001 - Issue 1-6
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Original Articles

Scientific basis of technology of fine-crystalline quartz and corundum

, , , , &
Pages 229-239 | Received 10 Jan 2000, Accepted 25 Feb 2000, Published online: 19 Aug 2006
 

Abstract

Authors have investigated the mechanism and the kinetics of fine-crystalline quartz and corundum synthesis in supercritical water. The thermovaporous treatment of raw materials has been carried out in laboratory (v=20 ml) and technical (v = 2m3 and v=4m3) autoclaves at temperatures between 390 and 410°C and vapor pressures of water from 20 to 27 MPa in the presence of miacroadditives of activators. The samples of products after thermovaporous treatment have been studied by X-ray diffraction, optical and electron microscopy, mass-spectroscopy, ESR-, IR-spectroscopy, thermal analysis and pycnometry. It was shown that microadditives of activator into silica or alumina might not only accelerate the attainment of the best hydroxylation, but also initiate the transformation of precursors in an ordered way. The control of the transformation mechanism by introducing activators into the starting materials has allowed us to obtain fine-crystalline quartz and corundum with desired properties: various habitues and size of crystals. On the basis of these data, technology of fine-crystalline quartz and corundum has been developed.

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