Integrated study of the ceramic processing of yttria

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:7241031

Voigt, J A

Preparation of a yttria ceramic, beginning with the continuous precipitation of a yttrium hydroxynitrate precursor by the reaction between yttrium nitrate and ammonium hydroxide, was studied to find the interrelationships among the various processing steps. Emphasis was placed on the effect of precipitation conditions on the characteristics of the precursor powder; the effect of these initial powder properties on the product from the subsequent calcination, pressing, and sintering operations was then examined. The precipitation process was modeled using a population balance approach which included the competitive kinetic rate effects of nucleation, crystal growth, agglomeration, and agglomerate breakup. Physically reasonable values for the rate constants were found when the model was fit to experimentally determined population density distributions. The model described a three-particle system, as found experimentally, in which the precipitate consisted of primary crystallites (less than 0.1 ..mu..m in size), which were nucleated from solution, tightly bonded aggregates (approx.1 ..mu..m in size) of crystallites, and less tightly bonded flocs (1 to 30 ..mu..m in size), which were agglomerates of crystallites and aggregates.

• Research Organization: Iowa State Univ. of Science and Technology, Ames (USA)
• OSTI ID: 7241031
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
AMMONIUM COMPOUNDS
AMMONIUM HYDROXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
FABRICATION
HYDROGEN COMPOUNDS
HYDROXIDES
NITRATES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
POWDERS
PRECIPITATION
SEPARATION PROCESSES
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM NITRATES
YTTRIUM OXIDES