Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
2003. 9. 이병주 포항공과대학교 신소재공학과 [email protected] Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction – Historical Background Maxwell · Newton → Classical Mechanics → Electromagnetism → Quantum Mechanics · Lagrangian · Rationalism · Hamiltonian · Time Reversible · Experimental fact (산업혁명) · Heat → Concept of Temperature · PV work → Concept of Pressure → Thermodynamics · Empirical Rule · Time irreversible · Thompson → Rumford · Davy · Mayor · Carnot · Joule · Thomson → Kelvin · Clausius · Maxwell · Gibbs Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - J. W. Gibbs ※ Expansion in scope has been made to embrace not only thermal, mechanical and chemical effects, but also the kinetic energy and the complete set of potentials energies: gravitational, electrical, magnetic and body forces, (with the exception of atomic energy). ※ J. Willard Gibbs, 1883 : On the Equilibrium of Heterogeneous Substances Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Microscopic vs. Macroscopic Point of View · macroscopic : no special assumption on the structure of matter, directly measured · microscopic : assumption on the structure of matter (molecules), unmeasurable. can only be justified by comparing some deduction with that from macroscopic point of view. · quantum mechanics Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Role of Thermodynamics · Foundation of materials science · Phase Diagrams, Chemical Reactions, Adsorption, Capillarity effects and Electrochemistry, …, etc. Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Basic Terminology · System / Surrounding (reservoir) · State (Properties: description of state), Change of state (properties) during a process · Measurable and unmeasurable properties : Unmeasurable property는 다른 측정 가능한 특성치로부터 결정 ⇔ Property 간의 관계식 (EOS) ※ Thermodynamic systems, thermodynamic properties, thermodynamic relationships Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Terminology for System · Unary / multicomponent · Homogeneous / Heterogeneous · Closed / Open · Non-reacting / reacting · Exchange of energies / No exchange (※ Isolated) Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - State Function & Process Variable · Thermodynamics State or State of Thermodynamic Equilibrium Mechanical, Chemical and Thermal Equilibrium Uniform and well defined thermodynamic coordinates No tendency to change with time of thermodynamic coordinates · path independence → ∂V ∂V dV = dP + dT ∂P T ∂T P · Extensive and Intensive Properties · Process variable (only have meaning for changing systems) · work & heat Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Equation of State of an ideal gas · Boyle’s law (1660): · Charles’ law (1787): P∝ 1 V → PoV (T , Po ) = PV (T , P ) V ∝T → V ( Po , To ) V ( Po , T ) = To T PV PoVo = · = constant = 1atm×22.414 liters ∕ 273.16 degree-mole T To = 0.082057 liter-atm/degree-mole · EOS of the ideal gas: PV = RT ▶ unit of Work 1atm = 76 cm of mercury = 76.0×13.595×980.665 = 1.013×106 dyne/cm2 1atm-liter = 1.013 × 102 joule Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Universal Equation of State for pure Substances E u ( r ) = − Ec (1 + a * )e − a* a = α ( r / re − 1) * 1/ 2 9 BΩ α = Ec H. Rose, J.R. Smith, F. Guinea and J. Ferrante, Phys. Rev. B 29 (1984) 2963. Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Temperature Scale ▷ Thermal equilibrium and zeroth law of thermodynamics ▷ Temperature concept the temperature of a system is a property that determines whether or not a system is in thermal equilibrium with other systems. ▷ Gay-Lussac (1802): thermal expansion coefficient of "permanent gases" is a constant. α= 1 Vo ∂V T ∂ P where Vo is the volume at 0.0(1) oC. α = 1/267. · for ideal gas α = 1/273.16 → absolute zero of temperature, -273.16 ▷ Measurement of Temperature · thermometric property, X · thermometric function, θ(X) = aX Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Temperature Scale Thermometers and thermometric properties Thermometers Gas (const. volume) Electric resistor (const. tension) Thermocouple (const tension) Helium vapor (saturated) Paramagnetic salt Blackbody radiation Thermometric properties Pressure Electric Resistance Thermal Emf Pressure Magnetic susceptibility Radiant emittance Symbol P R ε P χ RB,λ Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Temperature Scale Thermometer 마다 scale이 달라, 물의 삼중점을 제외한 나머지 온도에 대해서는 다른 값을 나타냄. Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Temperature Scale 저압에서 error가 작은 gas thermometer를 empirical temperature scale을 정의하기 위한 standard thermometer로 선정 ▷ Gas thermometer의 발달 : 측정오차의 원인 분석 및 보완 과정 그림 Simplified constant-volume gas thermometer Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Temperature Scale ▷ Ideal-Gas Temperature, θ Gas thermometer로 1기압 수증기의 온도를 재었을 때 그 온도는 thermometer에 사용된 gas의 종류에 따라 값이 약간씩 다르나, PTP를 작게 하면 할수록 동일한 값에 수렴한다. (그림) P θ = 273.16 lim PTP →0 P TP (const. V) ※ 가장 적합한 gas로 Pt 용기 속으로 확산되지 않고, 비등점이 낮은 He 선정 → 0.5 K 까지 측정 가능 ※ It will be shown that in the temperature region in which a gas thermometer may be used, the ideal gas scale and the Kelvin scale are identical. Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Temperature Scale ▷ Celsius Temperature Scale Ideal Gas temperature scale과 크기가 같으나 물의 삼중점이 0.01oC 가 되도록 zero point 만 shifted 됨. ⇒ t(℃) = θ(K) - 273.15 NMP of H2O NBP of H2O = 0.00℃ = 99.975℃ ※ The only Celsius temperature which is fixed by definition is that of the triple point. ▷ Electric Resistance Thermometry Platinum resistance thermometer : very accurate within the range -253 to 1200oC. : Empirical formula RPt = Ro (1 + At + Bt2) ⇒ A, B 항의 수가 늘어날수록 여러 개의 standard temperature 필요. ▷ Thermocouple : Platinum+10%rhodium/platnum thermocouple: 0 to 1600oC. : Empirical formula ε = a + bt + ct2 + dt3 Byeong-Joo Lee www.postech.ac.kr/~calphad Introduction - Temperature Scale Table Defining fixed points of the ITS-90 (International Temperature Scale) Number 1 2 7 9 16 17 Temperature T90/K T90/℃ 3 to 5 -270.15 to 268.15 13.8033 -259.3467 83.8058 -189.3442 273.16 0.01 1337.33 1064.18 1357.77 1084.62 Substance(a) State(b) Wr (T90) He e-H2 Ar H2O Au Cu V T T T F F 0.00119007 0.21585975 1.00000000 - (a) All substances except 3He are of natural isotopic composition. e-H2 is hydrogen at the equilibrium concentration of the ortho and para molecular forms. (b) For complete definitions and advice on the realization of these various states. See "Supplementary Information for the ITS-90". The symbols have the following meanings: V : vapour pressure point T : triple point (temperature at which the solid, liquid and vapor phases are in equilibrium) G : gas thermometer point M, F : melting point, freezing point (temperature, at a preassure of 101 325 Pa, at which the solid and liquid phases are in equilibrium). Byeong-Joo Lee www.postech.ac.kr/~calphad