Premium
Effect of Trace A1 2 O 3 on Transformation of Quartz to Cristobalite
Author(s) -
CHAKLADER A. C. D.
Publication year - 1961
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.1151-2916.1961.tb13740.x
Subject(s) - cristobalite , quartz , tridymite , mineralogy , materials science , chemistry , analytical chemistry (journal) , metallurgy , chromatography
The effect of additions of 0.22, 0.44, 0.88, and 1.76% A1 2 O 3 (Si 4+ /A1 3+ ratio of 200:1, 100:1, 50:1, and 25:1) on the transformation of Brazilian quartz to cristobalite was studied at 1500°, 1530°, and 1570°C. The smaller percentages of A1 2 O 3 (0.22 and 0.44%) catalyzed the transformation of quartz and the formation of cristobalite considerably. The rates of transformation of quartz with 0.88 and 1.76% A1 2 O 3 were slower than with 0.22 or 0.44%, indicating a critical A1 3+ /Si 4+ ratio where the catalytic effect was found to be maximum. This appeared to occur at about 0.5% A1 2 O 3 . The transformation rate of quartz indicated that the reaction was first order. Cristobalite, however, showed two different rates; the initial rapid growth was followed by a slower rate. The point of changeover was found to be at about 30 ± 5% cristobalite. The critical nature of the A1 3− /Si 4+ ratio at about 0.01 (or A1 2 O 3 /SiO 2 ± 0.005) may have some bearing on the properties of silica refractories with more or less than 0.5% A1 2 O 3 .