Fundamental Concepts of Thermodynamics First, second, and third law Entropy Heat capacity, enthalpy Reaction enthalpies and thermochemical cycles Phase transitions Calorimetry

Why I Count Calories for a Living They are fascinating –Energetics whisper secrets of the strength of chemical bonds –Entropies sing of vibrating atoms, moving electrons, and structural disorder –Systematics have predictive power They pay –thermodynamic data are essential to good materials processing –Environmental science needs thermodynamics, both for issues of stability and as a starting point for kinetics –Mineralogy, petrology, and deep Earth geophysics need thermodynamic data.

Calorimetry Measures Heat capacities Heats of phase transitions’ Heats of formation

From these data one calculates Entropies and free energies Solubililities Phase diagrams Petrologic and geochemical processes Materials synthesis and compatibility

Phase Transitions

Low temperature heat capacity and standard entropy, Fe 2 SiO 4 olivine and spinel, calorimetry on a chip

Thermal Analysis and Scanning Calorimetry Measure a signal (mass, heat, evolved gas, lemgth, X-ray pattern) at a variable heating (cooing) rate Systems –Room temp to 600 o C, common – o C, less common but we have – o C, uncommon but we have

Example: HfO 2

TMA on HfO 2 TMA traces of HfO 2 (1.5 % Zr) in Ar flow. (HfO 2 pellet L 2.5 mm Ø 5 mm sintered at 1700 °C for 2 hours). Heating rate 10 °C/min. 5 gram load. \

High Temperature Oxide Melt Solution Calorimetry Dissolve oxide samples (5-15 mg) in a molten oxide solvent (20 g) at to form a dilute solution Difference in heat of solution of reactants and products gives heat of reaction Oxidative reactions for nitrides, sulfides, selenides, carbides Needed for ceramic materials which do not dissolve in aqueous solvents

Solvents and Systems Lead borate (2PbO-4B 2 O 3, sodium molybdate (3Na 2 O-4MoO 3 ), alkali borate Oxides dissolve H 2 O and CO 2 evolve as gases Nitride oxidized to evolved N 2 Sulfide oxidized to dissolved sulfate

High-Temperature Calorimetry 700 o C 25 o C 700 o C 25 o C 700 o C 25 o C DSTTDSOL

Thermochemical Cycles - Perovskites 1. AO(xl, 298K) = AO(dissolved, 973K) 2. BO 2 (xl, 298K) =BO 2 (dissolved, 973K) 3. ABO 3 (xl, 298K) = ABO 3 (dissolved, 973K) ______________________________ 4. AO(xl, 298K) + BO 2 (xl, 298K) = ABO 3 (xl, 298K), H4 = H1 + H2 – H3 Tolerance factor t = d AO /1.414d BO

Gas Adsorption Calorimetry Combine sensitive microcalorimeter with automated gas dosing system Measure heat of adsorption and adsorption isotherm simultaneously Apply to high surface area and microporous materials

Differential (a) and integral (b) heats of H 2 O adsorption for anatase with surface area of 90, 200 and 240 m 2 /g and rutile of 61 and 103 m 2 /g (Levchenko et al. 2006).

The Peter A. Rock Thermochemistry Laboratory A unique suite of equipment and expertise Can design a calorimetric experiment to suit almost any material and problem