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# HW4-new - ME311 MATERIALS ENGINEERING SPRING 2012...

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ME311 MATERIALS ENGINEERING SPRING 2012 HOMEWORK #4 DUE DATE: February 16, before class PROBLEM 1: The measured density of a sample of bcc iron is 7.87 g/cm 3 . If the lattice parameter of this sample is 0.2866 nm, calculate the percentage of vacancies in this sample. Assume the atomic weight of iron to be 55.85 g/mole. Hint: In the absence of vacancies, bcc iron has 2 atoms/unit cell. Consider that the density is mass/volume. PROBLEM 2: You are an engineer working in a nuclear plant. In order to select the appropriate material for the reactor you perform a series of experiments to determine the equilibrium mole fraction of vacancies as a function of the working temperature. The results from your experiments are shown in the table below. Based on the data you have generated, determine a) the entropy/mole of vacancies, b) the enthalpy of vacancy formation /mole of vacancies and c) the equilibrium mole fraction of vacancies at 400 o C. 27

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HW4-new - ME311 MATERIALS ENGINEERING SPRING 2012...

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