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Kinetics of Cristobalite Formation from Silicic Acid
Author(s) -
VERDUCH A. G.
Publication year - 1958
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1958.tb12890.x
Subject(s) - cristobalite , nucleation , silicic acid , activation energy , atmospheric temperature range , silicic , thermodynamics , superstructure , materials science , kinetics , crystallization , chemistry , crystallography , mineralogy , metallurgy , geology , organic chemistry , physics , quantum mechanics , quartz , volcano , seismology
Rate experiments made on the transformation of silicic acid into cristobalite, in the temperature range 945° to 1085° C, have demonstrated the existence of a measurable nucleation period. From its variation with temperature, a value of 102.8 kcal. per mole has been calculated for the activation energy of the nucleation process. A second step of the transformation, involving the growth and perfecting of the new phase, has been shown to occur with an activation energy of 50.9 kcal. per mole. From the shape of the rate curves it has been calculated that a superstructure having fairly well‐defined sequence rhythms of alternating three‐ and two‐layer structural units might be the end product of heating silicic acid in the temperature range covered by the present experiments. It also has been demonstrated that the degree of disorder increases from the core to the surface of the transforming cristobalite crystals.