Reducing the Sintering Temperature for MgO–Al2O3Mixtures by Addition of Cryolite (Na3AlF6) |
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Authors: | Swe-Kai Chen Min-Yuan Cheng Su-Jien Lin |
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Affiliation: | Materials Science Center, National Tsing Hua University, Hsinchu 30043 Taiwan, Republic of China;Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30043 Taiwan, Republic of China |
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Abstract: | The preparation of near stoichiometric spinel and alumina-rich spinel composites from Al2O3and MgO powders with the addition of Na3AlF6up to 4 wt% in the temperature range 700°–1600°C was studied; 98 wt% spinel containing 72 wt% Al2O3can be produced from the mixture of 72 wt% (50 at.%) Al2O3+ 28 wt% (50 at.%) MgO powders with the addition of 1 wt% Na3AlF6fired at 1300°C for 1 h. Spinels containing 81–85 wt% Al2O3can be produced from either the mixture of 90 wt% (78 at.%) Al2O3+ 10 wt% (22 at.%) MgO or the mixture of 95 wt% (88 at.%) Al2O3+ 5 wt% (12 at.%) MgO powders with the addition of 4 wt% Na3AlF6in 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% Al2O3. 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. |
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Keywords: | sinter/sintering magnesium oxide alumina |
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