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Assignment 2.1 (Problem 7.2) Glass ceramics are a new class of high-technology crystalline ceramic. They are made by taking complex amorphous glasses (like SiO2-Al2O3-Li2O) and making them devitrify (crystallize). For a particular glass, it is found that: (a) no devitrification occurs above a temperature of 1000 °C; (b) the rate of devitrification is a maximum at 950 °C and (c) the rate of devitrification is negligible below 700 °C. Give reasons for this behaviour. Answers: Assignment 2.2 (Problem 8.5) A classic set of experiments on homogeneous nucleation was published by the brilliant scientist David Tumbull (GE R&D Labs, NY) in 1952. Tumbull used mercury (TM=234.33K, - 38.87C) as the sample material. 5 cm3 of liquid Hg was mixed with 150 cm2 of silicone oil using a food blender (“health and safety” would not like that these days!), which broke the Hg up into a large number of isolated droplets having a mean diameter of 3.27 micron. The sample was the quenched to various temperatures below