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Effect of TiO 2 on Initial Sintering of Al 2 O 3
Author(s) -
BAGLEY RODNEY D.,
CUTLER IVAN B.,
JOHNSON D. LYNN
Publication year - 1970
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1970.tb12055.x
Subject(s) - sintering , diffusion , grain boundary diffusion coefficient , materials science , effective diffusion coefficient , solubility , volume fraction , volume (thermodynamics) , particle (ecology) , particle size , grain size , grain growth , grain boundary , surface diffusion , kinetics , chemical engineering , mineralogy , metallurgy , analytical chemistry (journal) , composite material , microstructure , chemistry , thermodynamics , chromatography , oceanography , magnetic resonance imaging , engineering , adsorption , quantum mechanics , radiology , medicine , physics , geology
Alpha alumina with additions of TiO 2 sintered more rapidly than “pure” alumina. The rate of initial sintering increased approximately exponentially with titania concentration up to a percentage beyond which the rate of sintering remained approximately constant or decreased slightly with additional titania. The concentration which produces the maximum rate of sintering is thought to be the solubility limit of TiO 2 in Al 2 O 3 . For alumina particles larger than about 2 μm, the kinetic process was mainly grain‐boundary diffusion. With smaller particles, volume diffusion increased. The “solubility limit” increased with decreasing particle size, indicating an excess surface concentration of TiO 2 . The data may be interpreted in terms of a region of enhanced diffusion at the grain boundary that increases with TiO 2 concentration. With small alumina particles, this region is large enough to become a significant portion of the volume of the particle, and the small particles appear to sinter by volume diffusion kinetics, but the diffusion coefficient corresponds to an enhanced diffusion coefficient.