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Crystallization and Chemical Strengthening of Nepheline Glass‐Ceramics
Author(s) -
DUKE D. A.,
MacDowell J. F.,
KARSTETTER B. R.
Publication year - 1967
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.1151-2916.1967.tb15041.x
Subject(s) - nepheline , materials science , crystallization , nepheline syenite , phase (matter) , mineralogy , ceramic , nucleation , chemical engineering , composite material , chemistry , organic chemistry , engineering
Electron micrographic and X‐ray diffraction techniques were used to study the nucleation and growth of titania‐nucleated nepheline in glass. On heating, the glasses phase‐separated as a prelude to the crystallization sequence. The first crystalline phase identified was the metastable phase, carnegieite. With time, the equilibrium phase, nepheline, crystallized and the titania crystallized to anatase. The resulting materials were nonporous and largely crystalline. These nepheline glass‐ceramics were chemically strengthened by treatments in molten potassium salts. A K + → Na + exchange took place and effected transformation of nepheline to kalsilite. This transformation was a function not only of the exchange treatment, but of the composition of the initial nepheline crystals. Confining the kalsilite surface against a volume increase during the phase transformation created a surface compressive stress. Glass‐ceramics containing nepheline crystals with an appropriate structure were chemically strengthened in this manner to yield bulk, abraded modulus of rupture values above 200,000 psi.