Thermodynamic Study of the Mg-Ca-Zn system Shanae Henry Philadelphia, Pennsylvania, Sophomore, Lankenau High School Hakeem Jackson Philadelphia, Pennsylvania, Junior, Lankenau High School Ryan Robinson Philadelphia, Pennsylvania, Senior, Lankenau High School
Presentation Outline: • Introduction • Background • Methods • Experiment • Results • Microstructural Analysis
What is Thermodynamics? Thermodynamics is the study of Gibbs free energy. • Gibbs free energy • G=H-TS • Phase stability • Lowest Gibbs free energy www.humanthermodynamics.com
Objective Purpose: Perform a Diffusion Couple to validate the existence of the Ca2Mg5Zn13 that was predicted by previous researchers. Hypothesis: The predicted phase Ca2Mg5Zn13 exists [ is stable] at 335 and 160 degrees Celsius.
What is Diffusion? Diffusion is the movement of molecules from an area of high concentration to an area of low concentration.
Materials Properties: Magnesium • Flexible • Light Weight Calcium: • Rather soft • Reacts with water Zinc: • Reasonable conductor of electricity • Good corrosion resistance
Phase Transformation • The process of one phase to another • The rate at which a phase will become stable • Also we can use Phase Transformations to see when two or more substances • co-exist
Phase Diagram Graphical representation that shows the phases that are present What can be seen by the phase diagram? Number of phases present Composition of each phase
70 wt% Mg-30 wt% Ca, pure Zn 600 Grit paper Diffusion couple Lathe Machine Didymium Glasses 335o Celsius furnace 160o Celsius furnace Vacuum Wet Saw Machine Glass Tube Fiber Glass Epoxy Resin Hardener Liquid nitrogen Oxygen Gloves Materials
Procedures Step 1- Initial Polishing Step 2- Make the Diffusion Couple Step 3-Turn on each furnace to the destination temperatures [335 and 160 degrees Celsius] Step 4-Place the samples inside each furnace for a period of two weeks Step 5- Microstructural Analysis
Results Due to lack of time there was not sufficient diffusion that took place. As a result- we could not predict whether the phase existed or not, although the surfaces of our samples were clearly different.
Conclusion/ Future References If scientists wish to conduct this experiment again then they should: • Allow more time for diffusion • Change the percentages of each metal • Increase the temperature to decrease the time for diffusion
Acknowledgements We will like to give special thanks to: EMS Faculty: Professor Zi-Kui-Liu EMS Graduate Students: Swetha Ganeshan, and Hui Zhang The College of Earth and Mineral Sciences EMS Glass Maker: Doug Smith UBMS Instructor: Mrs. Pam Monk UBMS Director: Ms. Jody Markley UBMS Assist. Director: Mrs. Annie Holmes UBMS Staff