Premium
THE MEASUREMENT OF REACTION RATES AT HIGH TEMPERATURES *
Author(s) -
CEESTERS J. H.,
PARMELEE C. W.
Publication year - 1934
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.1151-2916.1934.tb19284.x
Subject(s) - spinel , cristobalite , mineralogy , quartz , grain size , analytical chemistry (journal) , materials science , magnesium , millimeter , composite material , metallurgy , chemistry , optics , chromatography , physics
Cylindrical test pieces, rammed under a pressure of 10,000 pounds per square inch, were heated to temperatures varying between 1300°C and 1500°C. The rate of inversion of quartz to cristobalite and the rate of spinel formation in mixtures of electrically fused magnesia and alumina were determined from the slope of the expansion curve at constant temperature. The amount of cristobalite or spinel formed was calculated from the density determinations before and after firing. The products were identified by X‐ray and microscopic investigation. Unfired silica brick showed almost complete inversion to cristobalite after two hours at 15OO°C, the corresponding vertical expansion being about 6%. The addition of 2% CaO to unfired quartzite was found to increase the rate of inversion to cristobalite quite appreciably. A further addition of 1.5% Na 2 O + 1.5% Fe 2 O 8 so increased the rate of inversion at 1400° that after two hours only cristobalite appeared to be present. A mixture of electrically fused magnesia (0.15 to 0.06 millimeter grain size) and alumina (3.59 to 0.15 millimeter grain size) was found to contain about 25% spinel after two hours at 1500°C. The addition of 2% B 2 O 3 increased the amount of spinel formed under similar conditions to 75%. Test pieces made solely from magnesia and alumina of one grain size (0.06 millimeter) showed complete conversion to spinel after only ten minutes at 1450° C. The sensitivity of this method of studying reaction rates is such that an expansion of one scale division is equivalent to the formation of 0.1% of spinel.