Mullite Formations

Mullite is the most important crystalline phase in fired products belonging to the Al2O3-SiO2 mullite system, such as whiteware articles used in daily life (e.g., low- and high-temperature hard porcelain, sanitaryware, and structural clay products). Mullite has attracted increasing interest due to its excellent high-temperature strength and creep resistance, good chemical and thermal stability, low thermal expansion coefficient, and good dielectric properties. Mullitization has been a subject of extensive and controversial investigations. This book comprehensively covers the synthesis and six types of phase transformation of mullite. Part I reviews previous research on the synthesis of mullite gels, advantages and disadvantages of different chemical routes of synthesis, and phase transformation processes. Part II discusses the nature and characterization of spinel and mullite phases and different mechanisms of mullite formation, as conjectured by various researchers. Part III deals with the critical analysis of the spinel and mullite phases and evolution of mullite formation routes. Every chapter is accompanied by detailed diagrams and a comprehensive list of references.

Akshoy Kumar Chakraborty is a retired research scientist with more than 40 years of experience in the clay/mullite research field of ceramics. He obtained his BTech in Chemical Engineering (1969), MTech in Glass and Ceramics (1970), and PhD (Sc; 1976) from Calcutta University, India. In collaboration with the National Physical Laboratory, New Delhi, India, he worked on the characterization of a certified silicon powder for X-ray diffraction and with Dr. K.J.D. Mackenzie (Gracefield Research Centre, New Zealand) on solid-state nuclear magnetic resonance studies on leached and heat-treated kaolinites. Dr. Chakraborty has received the International Plato Award for Educational Achievement by the International Biographic Centre, Cambridge, UK, and the Marquis Award. He has authored a book, Phase Transformation of Kaolinite Patents, and co-authored 45 articles and holds a few patents. He is a life member of the Indian Ceramic Society, the Indian Thermal Analysis Society, and the Indian Institute of Ceramics and a reviewer for the American Ceramic Society and Material Science.

1. Introduction Part 1: Review 2. Mullite Precursors Synthesized by the Monophasic Gelation Method 3. Mullite Precursors Synthesized by the Coprecipitation Method 4. Mullite Precursors Synthesized by the Colloidal Gelation Method 5. Mullite Precursors Synthesized by Codecomposition Processes 6. Mullite Precursors Synthesized from Other Miscellaneous Sources/by Other Processes 7. Phase Evolution Sequences of Mullite Precursors Synthesized by Different Methods Based on Components Used and Processing Variables 8. Phase Evolution Studies of Various Mullite Gels/ Precursors by IR and Raman Spectral Techniques 9. Phase Evolution Studies of Various Mullite Precursors/Gels by MAS-NMR 10. Chemistry of Mullite Formation through the Sol-Gel Process 11. Homogeneity of Al2O3-SiO2 Gels/Precursors 12. Comparison of Thermal Transformation Processes of Six Mullite Precursors Part 2: Identification: Characterization of Four Phases of Gel-to-Mullite Transformation Series 13. Nature and Its Characterization of the Noncrystalline Al2O3-SiO2 Mullite Precursor Phase 14. Final Dehydroxylation of Noncrystalline Al2O3-SiO2 Mullite Precursors 15. Spinel Phase: A Concise Review 16. Mullite Phase: A Concise Review 17. Nature of Residual Noncrystalline Aluminosilicate Phases Associated with Mullite Formation Part 3: Critical Analysis 18. Critical Analysis and Characterization of Spinel Phase 19. Critical Analysis and Characterization of Mullite Phase 20. Emergence of Only Three Routes of Phase Transformation Sequences of Mullite Precursors and Critical Analysis of Intermediates 21. Critical Analysis of Classification Scheme of Mullite Gels