# Questions and Answers on Engineering Topics

Topics: Solid, Temperature, Ion Pages: 2 (618 words) Published: December 27, 2014

Engineering Materials Week 9
12.11 Iron titanate forms in the ilmenite crystal structure that consists of an HCP arrangement of ions. (a). Which type of interstitial site will the ions occupy? Why? Since this ratio is between 0.414 and 0.732, the ions will occupy octahedral sites (b). Which type of interstitial site will the ions occupy? Why? Since this ratio is between 0.414 and 0.732, the ions will also occupy octahedral sites. (c). What fraction of the total tetrahedral sites will be occupied? No tetrahedral sites will be occupied.

(d). What fraction of the total octahedral sites will be occupied? For every formula unit, there are three ions, and, therefore, three octahedral sites; since there is one ion in each of and, two-thirds of these octahedral sites will be occupied. 12.21 The unit cell for has cubic symmetry with a unit cell edge length of 0.839 nm. If the density of this material is 5.34, compute its atomic packaging factor.

12.30 Calculate the number of Frenkel defects per cubic meter in silver chloride at 350C. The energy for defect formation is 1.1 eV, while the density of AgCl is 5.50

12.47 The modulus of elasticity for titanium carbide (TiC) having 5 vol% porosity is 310 GPa. (a). Compute the modulus of elasticity for the nonporous material.

(b). At what volume percent porosity will the modulus of elasticity be 240 GPa?

Only the negative root is meaningful, and the value of the porosity is 17.1 vol%. 13.8 Compare the manner in which the aggregate particles become bonded together in clay-based mixtures during firing and in cements during setting. For clay-based aggregates, a liquid phase forms during firing, which infiltrates the pores between the unmelted particles; upon cooling, this liquid becomes a glass, which serves as the bonding phase. With cements, the bonding process is a chemical, hydration reaction between the water that has been added and the various cement constituents. The cement particles are bonded together...