Epitactic Nucleation of Spinel in Aluminosilicate Gels and Its Effect on Mullite Crystallization

Jeffrey C. Huling, Gary Lynn Messing

Research output: Contribution to journalArticle

145 Citations (Scopus)

Abstract

Control over the structure of hybrid (colloidal + molecular) aluminosilicate gels was utilized to demonstrate that precursor chemistry has a direct and controllable effect on the ∼1000°C crystallization of spinel and mullite in molecular precursor systems. Synthesis or preparation conditions leading to the development of a cubic, transition alumina result in the epitactic nucleation of spinel at ∼1000°C in gels that otherwise crystallize directly to mullite at ∼1000°C. Thus, the preference for spinel nucleation in gels derived from solution precursor systems whose chemistries promote formation of transition alumina readily explains the reported inability to obtain substantial mullite yields at ∼1000°C. Isothermal transformation kinetics of colloidal and hybrid gels show that in the absence of direct mullite formation at ∼1000°C, the release of alumina from the spinel‐type crystal structure becomes the rate‐controlling step in the transformation. This necessitates higher temperatures for mullite formation and limits the kinetic enhancement possible with extrinsic increases in mullite nucleation frequency.

Original languageEnglish (US)
Pages (from-to)2374-2381
Number of pages8
JournalJournal of the American Ceramic Society
Volume74
Issue number10
DOIs
StatePublished - Jan 1 1991

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Mullite
Aluminosilicates
Crystallization
Nucleation
Gels
Aluminum Oxide
Alumina
Kinetics
spinell
aluminosilicate
Crystal structure

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

Cite this

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abstract = "Control over the structure of hybrid (colloidal + molecular) aluminosilicate gels was utilized to demonstrate that precursor chemistry has a direct and controllable effect on the ∼1000°C crystallization of spinel and mullite in molecular precursor systems. Synthesis or preparation conditions leading to the development of a cubic, transition alumina result in the epitactic nucleation of spinel at ∼1000°C in gels that otherwise crystallize directly to mullite at ∼1000°C. Thus, the preference for spinel nucleation in gels derived from solution precursor systems whose chemistries promote formation of transition alumina readily explains the reported inability to obtain substantial mullite yields at ∼1000°C. Isothermal transformation kinetics of colloidal and hybrid gels show that in the absence of direct mullite formation at ∼1000°C, the release of alumina from the spinel‐type crystal structure becomes the rate‐controlling step in the transformation. This necessitates higher temperatures for mullite formation and limits the kinetic enhancement possible with extrinsic increases in mullite nucleation frequency.",
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Epitactic Nucleation of Spinel in Aluminosilicate Gels and Its Effect on Mullite Crystallization. / Huling, Jeffrey C.; Messing, Gary Lynn.

In: Journal of the American Ceramic Society, Vol. 74, No. 10, 01.01.1991, p. 2374-2381.

Research output: Contribution to journalArticle

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AU - Messing, Gary Lynn

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AB - Control over the structure of hybrid (colloidal + molecular) aluminosilicate gels was utilized to demonstrate that precursor chemistry has a direct and controllable effect on the ∼1000°C crystallization of spinel and mullite in molecular precursor systems. Synthesis or preparation conditions leading to the development of a cubic, transition alumina result in the epitactic nucleation of spinel at ∼1000°C in gels that otherwise crystallize directly to mullite at ∼1000°C. Thus, the preference for spinel nucleation in gels derived from solution precursor systems whose chemistries promote formation of transition alumina readily explains the reported inability to obtain substantial mullite yields at ∼1000°C. Isothermal transformation kinetics of colloidal and hybrid gels show that in the absence of direct mullite formation at ∼1000°C, the release of alumina from the spinel‐type crystal structure becomes the rate‐controlling step in the transformation. This necessitates higher temperatures for mullite formation and limits the kinetic enhancement possible with extrinsic increases in mullite nucleation frequency.

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