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Thermo%201%202009

Thermo%201%202009 - Mat E 510 Thermodynamics of Solids Mat...

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Mat E 510 Mat E 510 Thermodynamics of Solids Thermodynamics of Solids Based on Prof Roger Doherty’s course Based on Prof. Roger Doherty’s course Lecture #1 Y G t i Yury Gogotsi A.J. Drexel Nanotechnology Institute and Department of Materials Science & E i i D l U i it Engineering, Drexel University, Philadelphia, Pennsylvania, USA

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Introduction Historically - study of heat engines Heat, q , and work, w , are examples of transfer of energy, U ε = work out / heat in = ( T h T c ) / T h . Concept of Entropy S - Direction of Change Defines Temperature, T (K) Equilibrium Chemical reactions / Structures Gibbs Free Energy, G
How does thermo work? 4 basic postulates - the "Laws of Thermodynamics" Zeroth Law: Establishes Temperature as an intrinsic property (like pressure). First Law: Internal Energy is a State Function. Second Law: Defines Entropy S that seeks a maximum value. d S = d q / T Third Law: As T (K) -> 0, S -> 0 (usually if in Internal Equilibrium)

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Role of Thermo in Chemistry/ Materials These laws describe our world. They allow incredibly useful predictions starting from just simple thermal measurements: Specific heats, heats of reaction, vapor pressures, e.m.f. of electrochemical cells etc. - to predict all equilibrium structures, all chemical reactions, Phase diagrams, (usually easier to measure a PD and back calculate the thermodynamic properties) and the kinetics and thus resulting structures of structural transformations. So, an essential part of Materials Science and Engineering. Determines equilibrium. Compounds, Phases, Defects. Direction and kinetics of structural and chemical change. Hence Microstructure Phase diagrams Process design P. Atkins, Four Laws that drive the Universe, Oxford Univ. Press, 2007
Materials Science and Engineering (MSE) The Relationship of Properties and Performance to "Microstructure". The Relationship of Microstructure to Composition and Processing. Modification of Processing to give New or Improved Properties. Thermo occurs in first and last activities but predominantly in the second activity. Distinction from Physical Chemistry or Solid State Physics ? Useful properties of Engineering Materials MSE is still a largely empirical science but becoming, slowly, more predictive and steadily accelerating the pace of empirical development.

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Computational Thermodynamics
Phase diagrams as projections of Gibbs energy plots Ternary system, projection from G-x 1 -x 2 diagram

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Determination of most stable phase by Gibbs energy minimization Phase with lowest Gibbs energy is the most stable. 1358.00 K 2846.16 K 71236.5 J Points on the solid lines for P = 1 atm are given for copper. 216494.2 J
Effect of high pressure on the graphite to diamond transition Where available, density (i.e. molar volume) data for solids and liquids are employed in REACTION (the “ VdP ” term) although their effect only becomes significant at high pressures.

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