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Callister - An introduction - 8th edition

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Summary • 529<br />

This chapter also discussed the structural transformation that occurs during<br />

crystallization—from a glassy (noncrystalline) structure (Chapters 3 and 12) to a<br />

fine-grained polycrystalline one, as represented by the following relational diagram.<br />

Glass-Ceramics<br />

(Structure)<br />

Structure of<br />

noncrystalline solids<br />

(Chapter 3)<br />

Structure of<br />

silica glasses<br />

(Chapter 12)<br />

Structure of glass-ceramics<br />

(fine-grained,<br />

polycrystalline)<br />

(Chapter 13)<br />

Property alterations are also possible as a result of crystallization. The glassceramic<br />

piece may remain transparent (as the precursor glass) or become opaque,<br />

depending on grain size. Very fine-grained materials are transparent, as discussed<br />

in Section 21.10. The following diagram depicts this relationship.<br />

Glass-Ceramics<br />

(Properties)<br />

Degree of<br />

transparency/opacity<br />

(Chapter 13)<br />

Scattering of light in<br />

polycrystalline and<br />

pore-free ceramics<br />

(Chapter 21)<br />

This concludes our processing/structure/properties/performance commentary<br />

for glass-ceramics. For the most part, the individual components found in the interrelationships<br />

shown above are conceptual in nature—that is, they represent the scientific<br />

(as opposed to engineering) aspects of materials. We have also generated a<br />

processing/structure/properties/performance relational diagram for glass-ceramics<br />

taken from the materials engineering perspective, which is shown in Figure 13.19.<br />

Important Terms and Concepts<br />

abrasive (ceramic)<br />

annealing point (glass)<br />

calcination<br />

cement<br />

crystallization (glass-ceramics)<br />

firing<br />

glass-ceramic<br />

glass transition temperature<br />

green ceramic body<br />

hydroplastic forming<br />

melting point (glass)<br />

microelectromechanical system<br />

(MEMS)<br />

optical fiber<br />

refractory (ceramic)<br />

sintering<br />

slip casting<br />

softening point (glass)<br />

strain point (glass)<br />

structural clay product<br />

thermal shock<br />

thermal tempering<br />

vitrification<br />

whiteware<br />

working point (glass)<br />

Processing Structure Properties Performance<br />

Composition specification<br />

(silica, other oxides,<br />

nucleating agent)<br />

Heat to elevated temp.<br />

(melt or soften)<br />

Form/shape<br />

(e.g., pressing,<br />

drawing)<br />

Heat-treat<br />

(crystallize)<br />

Fine-grained,<br />

polycrystalline<br />

Grain size<br />

Biocompatible<br />

Thermally shock<br />

resistant<br />

Strength<br />

Transparent or<br />

opaque<br />

Applications<br />

(Section 13.3)<br />

Figure 13.19 Schematic diagram that summarizes the elements of processing, structure,<br />

properties, and performance for glass-ceramics—from a materials engineering perspective.

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