Callister - An introduction - 8th edition

13.9 Fabrication and Processing of Glasses and Glass-Ceramics • 513
Figure 13.5 A
classification scheme
for the ceramicforming
techniques
discussed in this
chapter.
Glass-forming
processes
Ceramic fabrication techniques
Particulate-forming
processes
Cementation
Pressing Blowing Drawing Fiber
forming
Powder
pressing
Hydroplastic
forming
Slip
casting
Tape
casting
Hot Uniaxial Isostatic
Drying
13.9 FABRICATION AND PROCESSING OF
GLASSES AND GLASS-CERAMICS
Glass Properties
Before we discuss specific glass-forming techniques, some of the temperature-sensitive
properties of glass materials must be presented. Glassy, or noncrystalline, materials
do not solidify in the same sense as do those that are crystalline. Upon cooling, a
glass becomes more and more viscous in a continuous manner with decreasing temperature;
there is no definite temperature at which the liquid transforms to a solid
as with crystalline materials. In fact, one of the distinctions between crystalline and
noncrystalline materials lies in the dependence of specific volume (or volume per
unit mass, the reciprocal of density) on temperature, as illustrated in Figure 13.6.
Firing
Specific volume
Supercooled liquid
Glass
Liquid
Crystallization
Figure 13.6 Contrast of specific volumeversus-temperature
behavior of crystalline
and noncrystalline materials. Crystalline
materials solidify at the melting temperature
T m . Characteristic of the noncrystalline state
is the glass transition temperature T g .
Crystalline
solid
T g
T m
Temperature