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Chapt 7 Vacancies

Chapt 7 Vacancies - EMA4120 Physical Metallurgy I Chapt 7...

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EMA4120 Physical Metallurgy I, Chapt 7 Vacancies University of Florida, Dept. of Materials Science and Engineering EMA4120 Physical Metallurgy I Chapter 7: Vacancies Paul Holloway 202 Rhines Hall 846-3330 [email protected]

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EMA4120 Physical Metallurgy I, Chapt 7 Vacancies University of Florida, Dept. of Materials Science and Engineering Outline Thermodynamics Gibbs free energy, enthalpy, entropy Internal energy, heat, work Reversible, irreversible Spontaneous reactions Entropy of mixing Point defects Vacancies Enthalpy of formation, concentration vs T Enthalpy of motion, rate of hopping Interstitial atoms Enthalpy of formation, concentration vs T Enthalpy of motion, rate of hopping Complex point defects Divacancies Frenkel-Poole defects
EMA4120 Physical Metallurgy I, Chapt 7 Vacancies University of Florida, Dept. of Materials Science and Engineering Thermodynamics Gibbs free energy: G = H -T S H = enthalpy, S = entropy, T = temperature H = U + W = U + (PV) where U = internal energy, W = work, P = pressure, V = volume S ≥ Q/T where Q = heat; reversible reactions are equal, irreversible are greater than Reversible reactions, G = 0 due to H = U = S = T( Q/T) [assuming (PV) = 0], G = 0 = Q - T( Q/T) Irreversible reactions are spontaneous, G < 0 and S > Q/T Entropy is determined by statistics S = k ln(P) where k = Boltzman’s constant, P = probability 2200 ∆ S = k ln(P 2 /P 1 ) • P 2 > P 1 , entropy increases Randomness increase, entropy increase Order increase, entropy decrease Entropy of mixing

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EMA4120 Physical Metallurgy I, Chapt 7 Vacancies University of Florida, Dept. of Materials Science and Engineering Entropy of Mixing
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Chapt 7 Vacancies - EMA4120 Physical Metallurgy I Chapt 7...

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