Rachel Guarriello 1
Thermo Chemistry Phase Diagrams Ge-Sc system Choi’s project Sightseeing! 2
Being only a sophomore, I have not yet taken a class in thermo chemistry During the first week I was here, Alyson worked with me to tech me the things I would need to know to work on experiments I spent 3 days learning Gibbs Free energy, energy diagrams, Mixing, reaction orders, energy potential, and the relationship between the Gibbs energy diagrams of a system and the Phase Diagram. 3
I also had a lot to learn about Phase Diagrams when I got here. I haven’t worked with them much until now. I had to learn about the relationship between Gibbs Energy Curves and phase boundaries ◦ Common Tangent Lines I also had to learn how to identify and label the different phases in a Phase Diagram 4
Other aspects of Phase Diagrams that I had to learn were: Invariant reactions ◦ 3 phases exist in equilibrium at a single point ◦ Eutectic, peritectic, peritectoid, eutectoid Congruent melting ◦ A single liquid phase cools to a single solid phase Reading Ternary Phase Diagrams 5
During my Second week, I began working with Choi on his Ge-Sc binary system experiment We made a 0.65 mole fraction sample of Ge- Sc ◦ This means it was 75 weight % Ge Looking to see if it is a eutectic point on the phase diagram at that composition 6
Procedure: The sample was 75% by weight Ge and 25% Sc The sample was melted in an ARC melter, flipped a few times and re-melted to ensure homogeneity ◦ We don’t have an ARC melter at PSU, so it was really neat to learn how to use one. The sample was sliced in half by a diamond saw and then placed in a coil of pure Mo wire, and sealed in a glass vacuum tube ◦ I had also never seen anyone prepare or mount a sample in this manner. The whole thing was placed in the furnace for 15 days 7
After the sample comes out of the furnace, Choi will perform DTA, SEM, EDS, EPMA, and XRD tests on it ◦ These tests will be used to confirm the composition of the sample and clarify the phase relations. ◦ The results will also be compared to the literature results. ◦ So far, the results have been similar to the diagram, but have differed around 65 atomic % Ge 8
Not much work has been done on this binary system ◦ Choi told me that the Ge-Sc system is important when working with aluminum, so it surprised me that there was not much previous work with it. Only one or two other phase diagrams can be found The original paper on the system cannot be found, so the liquidus line is inaccurate 9
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Tha hank nk Yo You to u to eve veryon yone e I I wa was able to wo work wi with h and nd sp spend nd time me wi with h wh while I wa le I was he here!! !! 11
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