Crystal glass materials based on catalyzed cordierite glass synthesized under exposure to concentrated radiant flux

Abstract

The results of investigations of crystal glass materials based on cordierite glass containing TiO 2 as a catalyst are presented. It is established that the synthesis of glass under exposure to a concentrated radiant flux has the same effect on crystallization processes as increasing the catalyst content. The optimal composition and conditions for obtaining sintered sitals from glass powder are determined.There are a large number of works on the particularities of the crystallization of MgO -Al 2 O 3 -SiO 2 glasses. These works devote special attention to the crystallization of glass with cordierite composition, since it is precisely this type of glass that forms the base for crystal glass materials with the optimal combination of dielectric and thermomechanical properties. Cordierite crystallizes via the formation of a number of intermediate phases whose temperature intervals of formation and stability depend on a number of factors, including the conditions under which the glasses are synthesized. This article presents the results of investigations of the character of the crystallization of glass with cordierite composition obtained under exposure to a concentrated radiant flux.The initial components were magnesium and aluminum oxides as well as quartz-kaolinite-pyrophyllitic rock (SiO 2 source). Chemical analysis showed this mineral to contain the following (% 2 ): 77.64 SiO 2 . 17.43 Al 2 O 3 , 0.39 MgO, and trace impurities (Fe 2 O 3 , Na 2 O, K 2 O).The glasses were synthesized in a solar furnace as well as in a simulator where 10-kW xenon lamps served as the source of heat. The fused glass was poured into water. This method of quenching the melt made it possible to obtain brittle granules which could be easily milled.A DRON-UM1 diffractometer was used for x-ray phase analysis and a Q-1500 D derivatograph differential-thermal analysis. Glass powders with different particle size (from 1 -5 to 80 mm) as well as 2 -3 mm fragments of granules were analyzed.Previous investigations of glasses with stoichiometric cordierite composition without catalysts [1,2] showed that the crystallization process can be represented in terms of the following scheme:Since glass cannot undergo bulk crystallization without a catalyst, investigations were performed to determine the influence of TiO 2 as a catalyst on the crystallization process for glass with cordierite composition. The catalyst was introduced into the stoichiometric glass in amounts 2 -12% (above 100%). It was determined that when TiO 2 was introduced during the melting process the color of the castings ranged from straw-colored (2% TiO 2 ) to black (12% TiO 2 ), which could indicate an increase of the Ti 3+ content in the glass.The introduction of 2% TiO 2 had no appreciable effect on the crystallization rate of the glass. The main crystalline phase was a cordierite. As the amount of TiO 2 increased, the crystallization process changed sharply. The crystallization of m cordierite was already activated during sintering of

TNE Effect of Heating Radiation on the Synthesis and Crystallization of Cordierite Composition Glasses

“…Previously, our research [11,12] has shown that during the synthesis of glasses of the cordierite composition under the influence of concentrated radiant flux, the crystallization of α-cordierite occurs through the formation of solid solutions with the structure of hightemperature quartz (quartz-O) and μ-cordierite. On the DTA curves, obtained on the crushed granular samples, the presence of diffuse exothermic peaks in the temperature ranges 700-900°C and 900-1000°C and most pronounced at 1040-1050°C are observed ( Figure 1).…”

“…The nature of the curve of the latter spectrum is more like the absorption spectrum of a glass with less TiO 2 , synthesized using a Xenon lamp. α-cordierites, the presence of magnesium-aluminum-titanate (a solid solution nAl 2 TiO 5 • mMgTi 2 O 5 ) is observed, and its amount increases with increase of content of titanium dioxide [12].…”