MgO calcination for easy direct coagulation casting of aqueous alumina slurries |
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Authors: | Sree-Laxmi Nair Rakesh Krishnan Sujith Vijayan Praveen Wilson K. Prabhakaran |
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Affiliation: | Department of Chemistry, Indian Institute of Space Science and Technology, Thiruvananthapuram 695547, India |
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Abstract: | The reactivity of MgO with ammonium poly(acrylate) and diammonium hydrogen citrate dispersants was decreased by high-temperature calcination which enabled easy preparation of direct coagulation casting slurries without cooling. The decrease in reactivity of MgO with an increase of calcination temperature (30–1200?°C) was due to the decrease of surface area (52.7–0.7?m2/g) as a result of an increase of average particle size (285–2075?nm) as well as a change of particle morphology from flaky to near spherical. The MgO calcined at a temperature of 1000?°C and above provided sufficient time for mixing with aqueous alumina slurries by ball milling at room temperature (~30?°C) without producing an adverse increase in viscosity before casting. The setting time of 55?vol% alumina slurries was in the ranges of 260–1070 and 10–50?min at room temperature and at 70?°C, respectively, at MgO concentrations in the range of 0.1123–1.2?wt%. The faster setting at 70?°C was due to a combination of faster dispersant-MgO reaction, faster hydration of MgO and high valance counter ion effect. |
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Keywords: | A. Calcination A. Suspension D. Alumina D. MgO Direct coagulation casting |
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