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Unformatted text preview: ENSC 3313, Spring 2004 Quiz 3 ANSWERS Name ________________________________ Answer any 4 questions only , 1 point each 1. To improve the wear resistance of steel gears, a process called carburizing utilizes diffusion to create a carbon rich, and hence harder, layer near the gear surface. Calculate the activation energy for carbon diffusion in the steel if at 1000 o C the diffusivity is 1.93 10-11 m 2 /s. Note: D o = 2.3 10-5 m 2 /s R=8.32 J/mole K = = ln D D RT Q e D D RT Q o Simple manipulation of exponential equation ( ) kJ/mol 148 10 39 . 8 ln 1273 32 . 8 7 = = Q 2. Calculate the number of vacancies per cm 3 for copper at 500 o C. The energy of vacancy formation is 0.9 eV, Boltzmanns constant is k = 8.62 10-5 eV/K, and Avagadros number is N A =6.023x10 23 mol-1 , copper density = 8.4 g/cm 3 and atomic weight = 63.5 g/mol....
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This note was uploaded on 01/10/2012 for the course ENSC 3313 taught by Professor Staff during the Fall '11 term at Oklahoma State.
- Fall '11