Chemical durability of crystalline and vitreous oxides in alkaline solutions
The durability in sodium hydroxide solution of crystalline oxides including SiO/sub 2/, MgO, Al/sub 2/O/sub 3/, and ZrO/sub 2/, as well as silicates containing such oxides and/or CaO, was studied by scanning electron microscopy and by a weight loss method. The chemical resistance of glassy forms of similar silicates was also investigated. Special attention was given to silica glass and quartz; measurements were done on bulk and powdered samples in aqueous KOH, LiOH and NaOH solutions of different strength. Dissolution rates of oxides were compared with thermodynamic stability data. It was determined that, for the same family of glassy and crystalline silicates, the alkaline durability is directly proportional to the packing density. Hydration product layers were formed on many oxide surfaces after immersion in alkaline solutions. The dissolution rate of silica glass in NaOH solution at 90/sup 0/C is approximately 60 to 80 times faster than that of quartz. Measured dissolution rates of silica glass are influenced by the type of surface finish; studied were surfaces which were mechanically polished, fire polished, as well as fracture surfaces. Upon immersion in NaOH solution, mechanically polished surfaces begin to develop characteristic dissolution patterns, and thereby give rise to increased surface areas. The dependence of dissolution rate on crystallographic direction and on pH was determined. Activation energies for chemical attack in alkaline solutions were determined for silica glass and quartz.
- Research Organization:
- California Univ., Los Angeles (USA)
- OSTI ID:
- 5033760
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM OXIDES
STABILITY
CRYSTALS
MAGNESIUM OXIDES
SILICA
ZIRCONIUM OXIDES
ALKALI METAL COMPOUNDS
HYDROXIDES
VITRIFICATION
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
HYDROGEN COMPOUNDS
MAGNESIUM COMPOUNDS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
SILICON COMPOUNDS
SILICON OXIDES
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
400201 - Chemical & Physicochemical Properties