The gas constant and the absolute tempera-ture

14.15 What influence does the presence of alloying elements (other than carbon) have on the shape of a hardenability curve? Briefly ex-plain this effect.

14.16 How would you expect a decrease in the austenite grain size to affect the hardenabil-ity of a steel alloy? Why?

(a) A 50-mm (2-in.) diameter cylindrical specimen of an 8640 steel alloy that has been quenched in moderately agitated oil.

(b) A 75-mm (3-in.) diameter cylindrical specimen of a 5140 steel alloy that has been quenched in moderately agitated oil.

14.22 What is the distinction between glass transi-tion temperature and melting temperature?

14.23 On the basis of mechanical characteristics associated with the behaviors shown in Fig-ure 14.15, explain why glass may be drawn into fibers whereas crystalline aluminum ox-ide may not.

14.27 For many viscous materials, the viscosity � may be defined in terms of the expression

where � and d�/dt are, respectively, the ten-sile stress and the strain rate. A cylindrical specimen of a soda–lime glass of diameter 5 mm (0.2 in.) and length 100 mm (4 in.) is subjected to a tensile force of 1 N (0.224 lbf) along its axis. If its deformation is to be less than 1 mm (0.04 in.) over a week’s time, using Figure 14.16, determine the maximum temperature to which the specimen may be heated.

14.29 Borosilicate glasses and fused silica are resis-tant to thermal shock. Why is this so?

14.34 Thick ceramic wares are more likely to crack upon drying than thin wares. Why is this so?

14.35 Explain why a clay, once having been fired at an elevated temperature, loses its hydro-plasticity.

14.38 Cite one reason why drying shrinkage is greater for slip cast or hydroplastic products that have smaller clay particles.

14.39 (a) Name three factors that influence the degree to which vitrification occurs in clay-based ceramic wares.

(a) Rapid initiation, slow propagation, and rapid termination.

(b) Slow initiation, rapid propagation, and slow termination.

14.44 Nylon 6,6 may be formed by means of a condensation polymerization reaction in which hexamethylene diamine [NH2U (CH2)6UNH2] and adipic acid react with one another with the formation of water as a by-product. Write out this reaction in the manner of Equation 14.5.

14.45 It is desired to produce nylon 6,6 by conden-sation polymerization using hexamethylene diamine and adipic acid as described in Problem 14.44. What masses of these two components are necessary to yield 37.5 kg of completely linear nylon 6,6?

14.47 What is the distinction between dye and pig- ment colorants?