Oh-Hun Kwon - Academia.edu (original) (raw)
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Norwegian University of Science and Technology
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Papers by Oh-Hun Kwon
Journal of The American Ceramic Society, 2006
Alumina-glass composites with a small amount of a continuous glassy phase and closed pores were p... more Alumina-glass composites with a small amount of a continuous glassy phase and closed pores were prepared and isostatically hot-pressed under varied conditions. Induced macropore structure showed partiallcomplete pore filling with glass and some evidence of pore collapsing. Pore filling was achieved by viscous from of the glass from the grain boundary to the macropores, which causes a simultaneous localized rearrangement of the alumina grain structure.
Journal of The American Ceramic Society, 1989
Kwon, O.-H. and Messing, GL (1989), Gas Diffusion During Containerless Hot Isostatic Pressing of ... more Kwon, O.-H. and Messing, GL (1989), Gas Diffusion During Containerless Hot Isostatic Pressing of Liquid-Phase Sintered Ceramics. Journal of the American Ceramic Society, 72: 10111015. doi: 10.1111/j. 1151-2916.1989. tb06260. x
Journal of The American Ceramic Society, 2005
Seeding boehmite with α-Al2O2, followed by calcination at 600°C, results in an agglomerated alumi... more Seeding boehmite with α-Al2O2, followed by calcination at 600°C, results in an agglomerated alumina powder (<53 μm) that can be sinter forged to full density at 1250°C. Compressive strains as high as ɛx=−0.9, and radial flow (ɛx= 1.0) during sinter forging remove large, interagglomerate pores. The fully dense alumina has a grain size of 0.4 pm and is visually transparent. It is proposed that deformation of dense agglomerates is the primary mecha- nism responsible for large pore elimination and compact densification. The sinter forging of sol-gel-derived alumina powders offers a new technology to prepare highly transparent, optical ceramics at lower temperatures than conventional routes.
Journal of The American Ceramic Society, 1990
Densification controlled by solution-precipitation during liquid-phase sintering was analyzed for... more Densification controlled by solution-precipitation during liquid-phase sintering was analyzed for the aluminamagnesium aluminosilicate glass system. As a model system for liquid-phase sintering, narrowly sized alumina powders and up to 20 vol% magnesium aluminosilicate glass samples were isothermally sintered at 1550" to 1650°C. Densification rate increases with increasing liquid content and sintering temperature but decreases with increasing density. For samples with <15% grain growth, the densification rate during the solution-precipitation stage of sintering was proportional to (particle size)-' and thus interface reactioncontrolled. Activation energies ranged from 270 to 500 kJ/mol over the relative density range of 66% to 96%, respectively. The low activation energy is attributed to densification by particle rearrangement, whereas the higher activation energy is due to densification controlled by interface-reactioncontrolled solution-precipitation. Intermediate activation energies are attributed to simultaneous densification by the two mechanisms. [
Journal of The American Ceramic Society, 2006
Alumina-glass composites with a small amount of a continuous glassy phase and closed pores were p... more Alumina-glass composites with a small amount of a continuous glassy phase and closed pores were prepared and isostatically hot-pressed under varied conditions. Induced macropore structure showed partiallcomplete pore filling with glass and some evidence of pore collapsing. Pore filling was achieved by viscous from of the glass from the grain boundary to the macropores, which causes a simultaneous localized rearrangement of the alumina grain structure.
Journal of The American Ceramic Society, 1989
Kwon, O.-H. and Messing, GL (1989), Gas Diffusion During Containerless Hot Isostatic Pressing of ... more Kwon, O.-H. and Messing, GL (1989), Gas Diffusion During Containerless Hot Isostatic Pressing of Liquid-Phase Sintered Ceramics. Journal of the American Ceramic Society, 72: 10111015. doi: 10.1111/j. 1151-2916.1989. tb06260. x
Journal of The American Ceramic Society, 2005
Seeding boehmite with α-Al2O2, followed by calcination at 600°C, results in an agglomerated alumi... more Seeding boehmite with α-Al2O2, followed by calcination at 600°C, results in an agglomerated alumina powder (<53 μm) that can be sinter forged to full density at 1250°C. Compressive strains as high as ɛx=−0.9, and radial flow (ɛx= 1.0) during sinter forging remove large, interagglomerate pores. The fully dense alumina has a grain size of 0.4 pm and is visually transparent. It is proposed that deformation of dense agglomerates is the primary mecha- nism responsible for large pore elimination and compact densification. The sinter forging of sol-gel-derived alumina powders offers a new technology to prepare highly transparent, optical ceramics at lower temperatures than conventional routes.
Journal of The American Ceramic Society, 1990
Densification controlled by solution-precipitation during liquid-phase sintering was analyzed for... more Densification controlled by solution-precipitation during liquid-phase sintering was analyzed for the aluminamagnesium aluminosilicate glass system. As a model system for liquid-phase sintering, narrowly sized alumina powders and up to 20 vol% magnesium aluminosilicate glass samples were isothermally sintered at 1550" to 1650°C. Densification rate increases with increasing liquid content and sintering temperature but decreases with increasing density. For samples with <15% grain growth, the densification rate during the solution-precipitation stage of sintering was proportional to (particle size)-' and thus interface reactioncontrolled. Activation energies ranged from 270 to 500 kJ/mol over the relative density range of 66% to 96%, respectively. The low activation energy is attributed to densification by particle rearrangement, whereas the higher activation energy is due to densification controlled by interface-reactioncontrolled solution-precipitation. Intermediate activation energies are attributed to simultaneous densification by the two mechanisms. [