Morphological Changes in Process-Related Large Pores of Granular Compacted and Sintered Alumina

Large pore defects clearly develop in Al2O3 ceramics during sintering. These large pores originate from voids caused by the incomplete deformation and adhesion of powder particles in collapsed dimples at the centers and boundaries of granules in the green compacts. The coalescence of pores, with limited shrinkage, during densification and grain growth in the late intermediate to final stages of sintering, is considered responsible for the development of the large pores. The mechanism of pore coalescence is explained by thermodynamic arguments, which demonstrate that the largest pores result in a stable system.

[1]  K. Uematsu,et al.  Seasonal Variation of Microstructure and Sintered Strength of Dry‐Pressed Alumina , 2004 .

[2]  K. Uematsu,et al.  Formation mechanisms of processing defects and their relevance to the strength in alumina ceramics made by powder compaction process , 1999 .

[3]  K. Uematsu,et al.  Characterization of processing pores and their relevance to the strength in alumina ceramics , 1999 .

[4]  K. Uematsu,et al.  Origin of strength change in ceramics associated with the alteration of spray dryer , 1999 .

[5]  K. Uematsu,et al.  Effect of seasons on density, strength of alumina , 1999 .

[6]  K. Uematsu.  Immersion microscopy for detailed characterization of defects in ceramic powders and green bodies , 1996 .

[7]  K. Uematsu,et al.  Effect of Moisture on the Structure and Fracture Strength of Ceramic Green Bodies , 1994 .

[8]  K. Uematsu,et al.  Liquid Immersion-Polarized Light Microscopy as a Powerful Tool in the Research of Ceramic Processing , 1993 .

[9]  F. Lange,et al.  Densification of Large Pores: II, Driving Potentials and Kinetics , 1993 .

[10]  M. Inoue,et al.  Effect of processing conditions on the characteristics of pores in hot isostatically pressed alumina , 1993, Journal of Materials Science.

[11]  J. S. Reed,et al.  Study of the Bimodal Pore Structure of Ceramic Powder Compacts by Mercury Porosimetry , 1992 .

[12]  F. Lange,et al.  Densification of Large Pores: I, Expriments , 1992 .

[13]  M. Harmer,et al.  Effect of Pore Distribution on Microstructure Development: III, Model Experiments , 1992 .

[14]  K. Uematsu,et al.  Direct Study of the Behavior of Flaw‐Forming Defect in Sintering , 1992 .

[15]  J. S. Reed,et al.  The different roles of forming and sintering on densification of powder compacts , 1992 .

[16]  Z. Kato,et al.  Effect of Forming Pressure on the Internal Structure of Alumina Green Bodies Examined with Immersion Liquid Technique , 1991 .

[17]  K. Uematsu,et al.  Direct observation of internal structure in spray-dried alumina granules , 1990 .

[18]  Z. Kato,et al.  Direct Observation Method for Internal Structure of Ceramic Green Body , 1990 .

[19]  B. Kellett,et al.  Thermodynamics of densification. II: Grain growth in porous compacts and relation to densification , 1989 .

[20]  B. Kellett,et al.  Thermodynamics of Densification: I, Sintering of Simple Particle Arrays, Equilibrium Configurations, Pore Stability, and Shrinkage , 1989 .

[21]  F. Lange,et al.  Powder Processing Science and Technology for Increased Reliability , 1989 .

[22]  M. Harmer,et al.  Effect of Pore Distribution on Microstructure Development: II, First‐ and Second‐Generation Pores , 1988 .

[23]  Frederick F. Lange,et al.  Sinterability of Agglomerated Powders , 1984 .

[24]  R. Coble,et al.  Spheroidization of Tubular Voids in Al2 O3 Crystals at High Temperatures , 1972 .