21) During the annealing process, which stage has the most dramatic change in dislocation density? a. Quenching b. Recovery c. Recrystallization d. Grain growth e. All stages about the same in terms of changes to dislocation density 22) Which of the following are common characteristics of thermoset polymers? a. Heavily networked or cross linked structures. b. Linear or slightly branched long chain molecules. C. Soften on heating and harden on cooling. d. Often recycled back into the same or similar applications. 23) What impact would substituting Ca2+ ions for zirconium ions (i.e. adding an impurity of calcium in the form of CaO) in a ZrO2 ceramic have on the material in terms of defects? a. For each Ca2+ substitution, one 02- vacancy would form b. For each Ca2+ substitutions, one O2 interstitial would form c. For each Ca2+ substitution, one Frenkel defect would form for oxygen d. For each Ca2+ substitution, one Schottky defect would form for Zr and O 24) The addition of a phosphorous (P) impurity to otherwise pure silicon (Si) will a. Decrease conductivity due to additional scattering of electrons due to the impurity b. Create an additional allowable energy level inside the band-gap called a donor level C. Create an extrinsic semiconductor with holes being the majority charge carrier d. Transform the silicon from a semiconductor to an insulator. e. Provide a mechanism to stabilize the cubic phase of silicon. 25) What do you expect to happen when heating a typical thermoplastic polymer? a. It will soften considerably and then eventually melt b. It will remain rigid and eventually degrade (burn) and not melt C. If it was first cold worked, it will go through recovery, recrystallization, and grain growth d. Depends on the phase diagram and the specific phases present e. Heating will cause any martensite present to temper which will slightly increase ductility