QUIZ7-2008key

QUIZ7-2008key - PRINT NAME _ INTRODUCTION TO MATERIALS...

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PRINT NAME ____________________________________ INTRODUCTION TO MATERIALS SCIENCE MSE-150 QUIZ 7 I PLEDGE MY HONOR THAT I HAVE NEITHER GIVEN OR RECEIVED AID ON THIS EXAMINATION. SIGNATURE ______________________________________ (2 points each) Label the graph of free energy versus radius of a spherical nucleus for solidification by homogeneous nucleation; a) the driving force, b) the retarding force, and c) the critical radius for nucleation. (1 point each) Which type of nucleation is more likely to occur? a) homogeneous b) heterogeneous For the following diffusion conditions, circle the condition with faster diffusion? vacancy mechanism (Cr in Fe) or interstitial mechanism (C in Fe) large concentration gradient or small concentration gradient low temperature self-diffusion or high temperature self-diffusion (3 points) Phosphorus is diffused into a thick slice of silicon with no previous phosphorus. The goal is to achieve a phosphorus concentration of 2 x 10 16 atoms/cm 3 at 1 micron below the surface by keeping the surface
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