Bradley Allison Advisor: Prof. Rodney Trice

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Bradley AllisonAdvisor Prof. Rodney Trice

• Effects of Starting Powder Size on Sintering of
  YSZ Thermal Barrier Coatings
• REU Presentation
• August 5, 2004

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What are TBCs?

• Ceramic Coating
• Most commonly used in the gas turbine engines
• Yttria Stabilized Zirconia (YSZ)
• ZrO2 - 7 wt Y2O3

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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

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Processing

• Plasma spray
• Lamella formation

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

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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
  1400C
• Dilatometer
• Quantifies sintering of coatings as heat treated
  for 5 hours at 1400C
• SEM
• Use SEM micrographs to quantify lamella thickness
• XRD
• Quantify phases present at each step during heat
  treatment
• Based on intensity of t-ZrO2 and c-ZrO2 peaks

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Archimedes Density

• Uniform decrease in porosity
• Large particle coatings displayed most porosity
  before and after heat treatment

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Dilatometer

• Medium powder exhibited most shrinkage
• Driving force for densification

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SEM
Small
Medium
Large
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SEM
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X-ray Diffraction

• Super Saturated Solid Solution of Y2O3 in ZrO2
• As Y2O3 diffuses out of ZrO2 , c-ZrO2 is formed

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X-ray Diffraction
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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

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Acknowledgments

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