E98mtm - Engineering 45 The Structure and Properties of...

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The Structure and Properties of Materials Midterm Exam March 18, 1998 Problem 1: (a) Describe how the Cu 3 Au, NaCl and ß-ZnS structures are derived from FCC. (b) Only one of these structures is commonly found in compound semiconductors. Which? Why? Problem 2: An interface between two phases is an open system with work function S = σ A 2.1 where A is the area of the interface and σ is its interfacial tension. Given this equation explain the following observations. (a) A drop of water in free fall takes a spherical shape. (b) A particle of table salt takes a cubic shape. (c) It is a good idea to clean superficial oxides and adsorbed films off of a surface before trying to wet it or bond to it. Problem 3: The solidification of SiO 2 is governed by kinetic relations that are roughly reproduced in the figure below, where τ is the time necessary to initiate solidification and T is the undercooling below the melting point. ln
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E98mtm - Engineering 45 The Structure and Properties of...

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