Cordierite glass ceramic

Phase Assemblages during Crystallization of Corning 9606 Glass-Ceramic  

A glass-ceramic material was produced with the formation of the primary crystal phase of cordierite. This glass-ceramic material is distinguished for its high fracture toughness of approximately 2.2 MPa m -, a high degree of hardness (Knoop hardness 700), and thermal conductivity of 37.7 W/(m K). The linear thermal expansion coefficient is 45 x 10 K  

The growth of -quartz solid solution is also preferred if the crystals impinge on each other. This process takes place at different temperatures, e.g., at 1150 C/2 min of heat treatment. During heat treatment at 1150 C for 60 min the conversion of the -quartz solid solution into cordierite was observed by TEM (Winter et al., 1995). Cordierite grows dendritically into the cores of the -quartz solid solution. The final glass produced with controlled crystallization features a-cordierite as the primary crystal phase. 

It must be noted, however, that other crystal phases apart from the P-quartz solid solution are also involved in the crystal phase formation of primary crystal phases up to a-cordierite. These crystal phases render the solid-state reaction highly complex. Hence, several unknown crystal phases with flat, almost two-dimensional habits were observed and could not be identified as Mg-petalite or osumilite as shown by Schreyer and Schairer (1961). 

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Cordierite glass-ceramics, 12 639-640 Cordilox, molecular formula and structure, 5 97t, 119t... 

Diaz, C., Valle-Fuentes, F. J., Zayas, M. E. Avalos-Borja, M. 1999. Cordierite glass-ceramic from geothermal waste. American Ceramic Society Bulletin, 78, 62-64. 

Knickerbocker, S.H., Kumar, A.H. and Herron, L.W. (1993) Cordierite glass-ceramics for multilayer ceramic packaging. Am. Ceram. Soc. Bull. 72, 90-5. 

R. Chaim and V. Talanker, Microstmctuie and Mechanical Properties of SiC Platelet/Cordierite Glass-Ceramic Composites, 7. Am. Ceram. Soc. 78, 166 172 (1995). 

Figure 1.14 The microstructure of a commercial cordierite glass ceramic (Coming Code 9606). The predominant phase with somewhat rounded grains is cordierite and the angular, needle-shaped crystals are magnesium aluminum titanate. (From Ref. 85.)...

Figure 2-11 SiOj-AlgOg-MgO phase diagram (Levin et al., 1964) indicating the base-glass composition of Corning 9606 cordierite glass-ceramic ( ). (wt%, t in °C).

Based on the developments by Budd (1993) and Partridge et al. (1989), cordierite glass-ceramics have been produced as advanced microwave... 

Figure 4.14 Schematics for the production of cordierite glass ceramics. The temperatures...

Figure 4. Plot of the equilibrium indentation applied stress crack length, c, extension behavior for cordierite glass ceramic in air. The data are well described by an ideal indentation response based on the penny crack model of Fig. 2.

Figure 5. Plot of the equilibrium indentation crack extension behavior for cordierite glass ceramic in air using parameters related to the residual and applied stress intensity factors. A straight line best fit to the data allows the crack geometry terms to be evaluated from the intercepts.

Figure 6. Plot of relative toughness as a function of crack length for cordierite glass ceramic containing silicon nitride whiskers at the volume fractions indicated. Adding whiskers enhances the toughness over the base material by over a factor of two, approximately 1 MP m / for this material in air.

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