1. Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004

2. What are TBCs? Ceramic Coating Most commonly used in the gas turbine engines Yttria Stabilized Zirconia (YSZ) ZrO 2 - 7 wt% Y 2 O 3

3. What makes TBCs Useful? Improves fuel efficiency –Allows for higher continuous service temperature –Low Thermal conductivity ( ~ 1 W/mK ) Improves engine reliability –Increases lifetime of parts –Prevent corrosion

4. Processing Plasma spray Lamella formation

5. Lamella Formation http://www.gordonengland.co.uk/tsc.htm

6. Research Investigation Varying starting powder will affect lamella microstructure 3 powder sizes separated from a single YSZ batch – 18-26 µm –37-52 µm –74-105 µm

7. Experimental Procedure Sample Preparation –Sprayed onto cylindrical and flat Copper substrates Archimedes Density –Total porosity is calculated from suspended, saturated, and dry mass –Measurements taken in as-sprayed condition and after heat treatments of 5 hours and 50 hours at 1400°C Dilatometer –Quantifies sintering of coatings as heat treated for 5 hours at 1400°C SEM –Use SEM micrographs to quantify lamella thickness XRD –Quantify phases present at each step during heat treatment –Based on intensity of t-ZrO 2 and c-ZrO 2 peaks

8. Archimedes Density Uniform decrease in porosity Large particle coatings displayed most porosity before and after heat treatment

9. Dilatometer Medium powder exhibited most shrinkage Driving force for densification

10. SEM Small MediumLarge

11. SEM Measured Lamella Thickness (µm) 195-8 Small1.34 ± 0.39 195-7 Medium2.01± 0.72 195-6 Large 2.95 ± 0.97

12. X-ray Diffraction Super Saturated Solid Solution of Y 2 O 3 in ZrO 2 As Y 2 O 3 diffuses out of ZrO 2, c-ZrO 2 is formed

13. X-ray Diffraction

14. Future Research to be Explored Study phase transformation during heat treatment with respect to varying lamella size Study thermal conductivity of coatings throughout heat treatment with respect to varying lamella size

15. Acknowledgments Prof. Trice and Prof. Kvam Kei Yamamoto and Jan Eberle Chris Petorak and Ben Iverson REU and Surf Students