| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 93 === This research was study the sintering behaviors of nanometer-sized α-alumina powders The nanometer-sized α-alumina powders was manufactured with aluminum hydroxide gel precursor mixing with oleic acid and stir-milled for 120 mins. to form an emulsion and calcined.
Green body of sintering was prepared by the alumina powders adding up aluminum hydroxide gel or zirconium hydroxide gel as binders. After pelleting with 100 mesh screen and drying, the green compact were formed with 600 MPa automatic uniaxial hydraulic press. These green bodies were sintered at 1200℃ to 1500℃ for 2 hours and furnace-cooling to room temperature. The sintered ceramic bodies were identified by relative apparent density, volume shrinkage rate, micro-structure observation and grain size distribution measurement.
The aluminum hydroxide gel mixed with oleic acid needed to heat until 1200℃ for 20 mins. to transform into nanometer-sized α-alumina powders. XRD indicated that the average size of this α-alumina powders of individual crystal diameters was 38 nm, and the BET calculated that was 60nm. The relative density of green compacts were measured 60% of adding aluminum hydroxide gel, 57% of adding zirconium hydroxide gel and 52% with no gel binders. The volume shrinkage rate of sintered body’s were measured 40% of adding aluminum hydroxide gel, 46% of adding zirconium hydroxide gel and 48% with no gel binders. The relative density of sintered body were calculated 95% of the α-alumina powders with alumina hydroxide gel binder in sintering conditions of 1400℃for 2 hours duration. This sintering temperature was 100℃ lower than that of no gel binder green compact. The grain’s size of sintered bodies were identified 650nm, which was the finest of the sintered bodies. The microstructure of the sintered body prepared by adding zirconium hydroxide gel was observed the zirconia grains in the boundary of
alumina grains.
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