Thermodynamic Study of the Mg-Ca-Zn system

Shanae HenryPhiladelphia, Pennsylvania, Sophomore, Lankenau High School

Hakeem JacksonPhiladelphia, Pennsylvania, Junior, Lankenau High School

Ryan RobinsonPhiladelphia, 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

Materials

• 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

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.

Microstructural Analysis

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

Any Questions?

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