Rheological and related colloidal aspects of aqueous processing that affect the development of microstructure
Shear flow in {alpha}-Al{sub 2}O{sub 3} suspensions having a volume fraction of solids ({phi}) in the range between 0.17 and 0.50 was investigated between pH 4 and 12. It is Newtonian if the magnitude of the zeta potential exceeds a critical value which depends on {phi}; its value is 39 mV if {phi} = 0.40 and 74 mV if {phi} = 0.50. If this potential is less than the critical value, shear flow is pseudoplastic; its yield value markedly changes (e.g., 0 to {gt}100 Pa) in a slightly {phi}-dependent, narrow pH range ({lt}0.5 units). If a second oxide, t-ZrO{sub 2}, is present, its pH-dependent colloidal behavior governs the overall rheology, though its concentration may be only 11 % that of {alpha}-Al{sub 2}O{sub 3}. Scanning electron microscopy of composite pieces indicates that a detrimental, rheologically detectable interaction between {alpha}-Al{sub 2}O{sub 3} and t-ZrO{sub 2} can be avoided and the distribution of t-ZrO{sub 2} can be optimized during pressure casting by control of pH to ensure Newtonian flow or a very low yield value when the flow is pseudoplastic.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6965416
- Report Number(s):
- CONF-900466-16; ON: DE90010124
- Country of Publication:
- United States
- Language:
- English
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ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
COLLOIDS
CRYSTAL STRUCTURE
DISPERSIONS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PROCESSING
RHEOLOGY
SHEAR
SUSPENSIONS
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES