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Dimpling: The Final Frontier. It’s not just for golf balls and grandmothers anymore! Student: Jason Burbey Faculty Advisor: Professor Eric Stach. Outline. Background Objective Sample Preparation/Characterization Sample Prep. Instruments Work Completed Future Work Acknowledgements

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dimpling the final frontier

Dimpling: The Final Frontier

It’s not just for golf balls and grandmothers anymore!

Student: Jason Burbey

Faculty Advisor: Professor Eric Stach

outline
Outline
  • Background
  • Objective
  • Sample Preparation/Characterization
  • Sample Prep. Instruments
  • Work Completed
  • Future Work
  • Acknowledgements
  • Questions
background
Background
  • Professor Ravi Chandran
    • University of Utah
  • Laminated Steel and Brass
    • Repeated cold rolling
    • Continuation of previous study
  • Evaluated Mechanical Properties
    • Inverse relationship between yield strength and bilayer thickness
    • Yield strengths as high as 850 MPa
  • Why?
    • Microstructural characterization needed

Ravichandran, K. “Nanoscale Steel-Brass Multilayer Laminates Made By Cold Rolling: Microstructure and Tensile Properties.” Scripta Materialia Vol 42: 949,951

objective
Objective
  • Microstructural Characterization of laminates
    • Bright Field Images in TEM
  • Features of interest:
    • Bilayer thickness
    • Interlamellar structure
    • Dislocation density and distribution
sample preparation characterization
Sample Preparation/Characterization
  • Dimple specimens to 10-15um
  • Ion Mill to produce very small hole in specimen
    • Electron Transparent
  • Take bright-field images of specimen using TEM
the dimpler
The Dimpler
  • Model 2000 Sample Prep System
  • Diamond Slurries and pastes
    • 6,3,1, .25 micron
the ion mill
The Ion Mill
  • Gatan Model 600 Duo-Mill
  • Ar+ ions directed at specimen from both sides at a set angle
  • Fairly time consuming
transmission electron microscope
Transmission Electron Microscope
  • JEOL Model 2000FX
  • Uses an Ultra High Vacuum (UHV)
    • 10^-9 -10^-11 atm
  • Capable of high resolution images at high magnifications
    • 1,000,000X or higher
    • Resolution of < 3Å
work completed
Work completed
  • Dimpled metallic laminates
    • SS grinding wheel
      • Ion Mill attempt
    • Micarta grinding Wheel
  • Dimpled Ta/Si specimens
  • Dimpled InAs/GaP specimens
metallic laminates ss grinding wheel
Metallic Laminates: SS grinding Wheel
  • Thicknesses varied from 90-290um
  • Used 3um slurry and dimpled to 20um
    • Not all specimens were 20um
    • Used optical microscope to check thickness
    • Re-dimpling difficult
  • Specimens 10-15um achieved
    • Ion Mill trials
    • Inefficient
  • Start Over!
    • Made more specimens
    • New dimpling progression
    • Used different wheel
dimpling laminates micarta grinding wheel
Dimpling Laminates: Micarta Grinding Wheel
  • Micarta Wheel is flatter and thicker than the SS grinding wheel
  • Dimple the whole specimen surface
    • Used 6um slurry
    • Sped up dimpling progress
  • Much smoother surface
    • Very important for Ion Milling
  • Successful specimens created
    • Stopped after 1um slurry
    • More scratches observed with .25um paste
ta si specimens
Ta/Si Specimens
  • Checking phase transformation of Ta
  • Blue side = Si
  • Reflective = Ta
  • Use diamond scribe to cleave specimens
sample prep problem
Dimple on Si side

SS grinding wheel

Specimens thicker than laminates

470-520um

Same progression as laminates

Same force exerted by grinding arm

Sample Prep Problem
  • Destruction of specimens
    • Force too much
    • Si is fragile!
    • Would crack at approx. 20um
solution for ta si specimens
Solution for Ta/Si specimens
  • Use less force!
  • Progressively decrease force
    • Before switching slurry/paste
  • 3 specimens from each bulk sample ready for Ion Milling
in as specimens
In/As specimens
  • Thicknesses between 310-320um
  • Dimpled on GaP side
    • Used SS grinding wheel
    • Same dimpling progression as Ta/Si
    • Like butter!
    • It smells…
  • 3 specimens ready for Ion Milling
future work
Future Work
  • Ion Mill all of the different specimens
  • Characterize specimens in TEM with help from Professor Stach
  • Publish characterization results
acknowledgements
Acknowledgements
  • Dr. King
  • Professor Stach
  • Cheryl Waller
  • Vijay Rawat
  • Rocco Cerchiara from Fischione
  • Jan Eberle
  • MSE Dept.