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Reducing the Sintering Temperature for MgO–Al 2 O 3 Mixtures by Addition of Cryolite (Na 3 AlF 6 )
Author(s) -
Chen SweKai,
Cheng MinYuan,
Lin SuJien
Publication year - 2002
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.1151-2916.2002.tb00130.x
Subject(s) - spinel , corundum , cryolite , sintering , materials science , quenching (fluorescence) , atmospheric temperature range , phase (matter) , stoichiometry , metallurgy , calcination , analytical chemistry (journal) , aluminium , mineralogy , nuclear chemistry , chemistry , catalysis , chromatography , thermodynamics , physics , organic chemistry , quantum mechanics , fluorescence , biochemistry
The preparation of near stoichiometric spinel and alumina‐rich spinel composites from Al 2 O 3 and MgO powders with the addition of Na 3 AlF 6 up to 4 wt% in the temperature range 700°–1600°C was studied; 98 wt% spinel containing 72 wt% Al 2 O 3 can be produced from the mixture of 72 wt% (50 at.%) Al 2 O 3 + 28 wt% (50 at.%) MgO powders with the addition of 1 wt% Na 3 AlF 6 fired at 1300°C for 1 h. Spinels containing 81–85 wt% Al 2 O 3 can be produced from either the mixture of 90 wt% (78 at.%) Al 2 O 3 + 10 wt% (22 at.%) MgO or the mixture of 95 wt% (88 at.%) Al 2 O 3 + 5 wt% (12 at.%) MgO powders with the addition of 4 wt% Na 3 AlF 6 in the temperature range 1300°–1600°C by using a torch‐flame firing for 3 min, followed by quenching in water, while the same system under slow cooling in a furnace results in spinel containing 74–76 wt% Al 2 O 3 . Microscopic studies indicate that the alumina‐rich spinel composites consist of a continuous majority spinel phase and an isolated minority corundum phase, regardless of slow cooling in a furnace or quenching in water.