A Study of the Reaction Rates between (a) Silica, (b) Alumina, (c) Mullite, (d) Zirconia and Other Oxides at Various Temperatures
JSGT 1953 V37 T269-T301
Additional work on reactions between silica and one or more metallic oxides was carried out with a view to investigating how the reaction rates are modified by: (a) introduction of lime as CaO and as CaC03, (b) the presence of alumina or zirconia, (c) the particle size of the silica; and (d) the forms in which the silica is introduced. Reaction rates between alumina, mullite or zirconia and one or more of the other metallic oxides were also investigated by the x-ray-diffraction method. The results obtained showed that: (1) The reaction rates in silica–lime–soda mixtures are independent of whether the lime is introduced as calcium oxide or carbonate. (2) The addition of alumina or zirconia to a silica–soda mixture decreases the reaction rates in the initial stages of firing, but after a certain period of firing at 1400° the reaction rates are higher. (3) The reaction rates in a silica–soda mixture increase with the diminishing size of the silica particles. (4) At 1200° and' 1300°, cristobalite reacts with soda at a higher rate than quartz, but at 1400° and 1450° the reaction rates are almost identical. (5) Zirconia reacts with the other metallic oxides more slowly than mullite or silica, and also reacts more slowly than alumina, except with the alkalis or boric oxide. (6) The various metallic oxides react with mullite at a much slower rate than with silica. (7) Each of the metallic oxides, when present alone, reacts with alumina at a much slower rate than with mullite or silica; the presence of silica gel or boric oxide considerably increases the rate of reaction of the metallic oxides with alumina, but has only a small effect on the rates of reaction with mullite or silica. (8) The various alkali-metal oxides and alkaline earths, arranged in decreasing order of their reaction rates with silica, alumina, mullite or zirconia, can be placed as follows: K2O, Na2O, Li2O and BaO, CaO, ZnO and MgO respectively, when they are present in molecularly equivalent quantities.
Abd-El-Moneim Abou-El-Azm
