Influence of viscous deformation at the contact point of primary particles on compaction of alkoxide-derived fine SiO{sub 2} granules under ultrahigh isostatic pressure
- Tokyo Univ. of Agriculture and Technology (Japan). Graduate School of Bio-Applications and Systems Engineering
- Shizuoka Univ., Hamamatsu (Japan). Dept. of Materials Science
- Nagoya Univ. (Japan). Dept. of Chemical Engineering
Viscous deformation and the adhesion force at the contact point between amorphous silica particles under ultrahigh isostatic pressure (up to 1 GPa) are important in the densification of powder compacts. The amount of viscous deformation and the strength of adhesion force have been changed in the present study by altering the calcination temperature and particle diameter, and the new values have been determined successfully using a diametral compression test. The diameter of spherical and monosized alkoxide-derived silica powders has been controlled within the range of 10--400 nm. Close-packed granules of these powders have been produced by spray drying. Because of viscous deformation, as-spray-died ultrafine silica powders without calcination could be consolidated into highly dense compacts (>74% of theoretical density) by applying ultra-high isostatic pressure (1 GPa). Relatively high temperature in the calcined particles (>400 C) causes viscous deformation at the contact point to disappear almost completely and clearly increases the adhesion force, because of neck growth that has resulted from viscous sintering. At temperatures >200 C, the green density of the calcined powders decreases to 65% of theoretical density, even under 1 GPa pressure. The relationship between green density and viscous deformation in silica particles at the point of contact has been analyzed quantitatively by the Hertz and Rumpf model. The relationship between granule strength and neck growth at the contact point with calcination has been estimated Quantitatively.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 417734
- Journal Information:
- Journal of the American Ceramic Society, Vol. 79, Issue 9; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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