ENGR 240 - 9.12.07

ENGR 240 - 9.12.07 - ENGR 240 September 12, 2007 Impurities...

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ENGR 240 – September 12, 2007 Impurities – point defects which are foreign atoms in the structure o Metals Always have impurities The most pure a metal can be is 99.9999% Very expensive to find a metal this pure Still have 10 16 – 10 17 impurities in 1 cm 3 o You get either a solid solution or two phases Solid solution – foreign atoms dissolve into the crystal structure of the host material Homogeneous mixture Solvent host atom type (higher concentration) Solute guest atom type (lower concentration) if not a solid solution you get a 2 nd phase Types of solid solutions o Substitutional Impurities replace the host atom o Interstitial Fill spaces between host atoms Concentration of interstitial impurities is less than 10% Metals are too closely packed o Factor Required for Complete Solubility 1. Crystal Structure Both must have same structure
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ENGR 240 - 9.12.07 - ENGR 240 September 12, 2007 Impurities...

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