1. Dimpling: The Final Frontier It’s not just for golf balls and grandmothers anymore! Student: Jason Burbey Faculty Advisor: Professor Eric Stach

2. Outline Background Background Objective Objective Sample Preparation/Characterization Sample Preparation/Characterization Sample Prep. Instruments Sample Prep. Instruments Work Completed Work Completed Future Work Future Work Acknowledgements Acknowledgements Questions Questions

3. Background Professor Ravi Chandran Professor Ravi Chandran University of UtahUniversity of Utah Laminated Steel and Brass Laminated Steel and Brass Repeated cold rollingRepeated cold rolling Continuation of previous studyContinuation of previous study Evaluated Mechanical Properties Evaluated Mechanical Properties Inverse relationship between yield strength and bilayer thicknessInverse relationship between yield strength and bilayer thickness Yield strengths as high as 850 MPaYield strengths as high as 850 MPa Why? Why? Microstructural characterization neededMicrostructural characterization needed Ravichandran, K. “Nanoscale Steel-Brass Multilayer Laminates Made By Cold Rolling: Microstructure and Tensile Properties.” Scripta Materialia Vol 42: 949,951

4. Objective Microstructural Characterization of laminates Microstructural Characterization of laminates Bright Field Images in TEMBright Field Images in TEM Features of interest: Features of interest: Bilayer thicknessBilayer thickness Interlamellar structureInterlamellar structure Dislocation density and distributionDislocation density and distribution

5. Sample Preparation/Characterization Dimple specimens to 10-15um Dimple specimens to 10-15um Ion Mill to produce very small hole in specimen Ion Mill to produce very small hole in specimen Electron TransparentElectron Transparent Take bright-field images of specimen using TEM Take bright-field images of specimen using TEM

6. The Dimpler Model 2000 Sample Prep System Model 2000 Sample Prep System Diamond Slurries and pastes Diamond Slurries and pastes 6,3,1,.25 micron6,3,1,.25 micron

7. The Ion Mill Gatan Model 600 Duo-Mill Gatan Model 600 Duo-Mill Ar + ions directed at specimen from both sides at a set angle Ar + ions directed at specimen from both sides at a set angle Fairly time consuming Fairly time consuming

8. Transmission Electron Microscope JEOL Model 2000FX JEOL Model 2000FX Uses an Ultra High Vacuum (UHV) Uses an Ultra High Vacuum (UHV) 10 ^-9 -10 ^-11 atm10 ^-9 -10 ^-11 atm Capable of high resolution images at high magnifications Capable of high resolution images at high magnifications 1,000,000X or higher1,000,000X or higher Resolution of < 3ÅResolution of < 3Å

9. Work completed Dimpled metallic laminates Dimpled metallic laminates SS grinding wheelSS grinding wheel Ion Mill attempt Ion Mill attempt Micarta grinding WheelMicarta grinding Wheel Dimpled Ta/Si specimens Dimpled Ta/Si specimens Dimpled InAs/GaP specimens Dimpled InAs/GaP specimens

10. Metallic Laminates: SS grinding Wheel Thicknesses varied from 90-290um Thicknesses varied from 90-290um Used 3um slurry and dimpled to 20um Used 3um slurry and dimpled to 20um Not all specimens were 20umNot all specimens were 20um Used optical microscope to check thicknessUsed optical microscope to check thickness Re-dimpling difficultRe-dimpling difficult Specimens 10-15um achieved Specimens 10-15um achieved Ion Mill trialsIon Mill trials InefficientInefficient Start Over! Start Over! Made more specimensMade more specimens New dimpling progressionNew dimpling progression Used different wheelUsed different wheel

11. Dimpling Laminates: Micarta Grinding Wheel Micarta Wheel is flatter and thicker than the SS grinding wheel Micarta Wheel is flatter and thicker than the SS grinding wheel Dimple the whole specimen surface Dimple the whole specimen surface Used 6um slurryUsed 6um slurry Sped up dimpling progressSped up dimpling progress Much smoother surface Much smoother surface Very important for Ion MillingVery important for Ion Milling Successful specimens created Successful specimens created Stopped after 1um slurryStopped after 1um slurry More scratches observed with.25um pasteMore scratches observed with.25um paste

12. SS vs. Micarta

13. 1um slurry vs..25um paste w/micarta wheel

14. Ta/Si Specimens Checking phase transformation of Ta Checking phase transformation of Ta Blue side = Si Blue side = Si Reflective = Ta Reflective = Ta Use diamond scribe to cleave specimens Use diamond scribe to cleave specimens

15. Sample Prep Problem Dimple on Si side Dimple on Si side SS grinding wheelSS grinding wheel Specimens thicker than laminates Specimens thicker than laminates 470-520um470-520um Same progression as laminates Same progression as laminates Same force exerted by grinding arm Same force exerted by grinding arm Destruction of specimens Destruction of specimens Force too muchForce too much Si is fragile!Si is fragile! Would crack at approx. 20umWould crack at approx. 20um

16. Solution for Ta/Si specimens Use less force! Use less force! Progressively decrease force Progressively decrease force Before switching slurry/pasteBefore switching slurry/paste 3 specimens from each bulk sample ready for Ion Milling 3 specimens from each bulk sample ready for Ion Milling

17. In/As specimens Thicknesses between 310-320um Thicknesses between 310-320um Dimpled on GaP side Dimpled on GaP side Used SS grinding wheelUsed SS grinding wheel Same dimpling progression as Ta/SiSame dimpling progression as Ta/Si Like butter!Like butter! It smells…It smells… 3 specimens ready for Ion Milling 3 specimens ready for Ion Milling

18. Future Work Ion Mill all of the different specimens Ion Mill all of the different specimens Characterize specimens in TEM with help from Professor Stach Characterize specimens in TEM with help from Professor Stach Publish characterization results Publish characterization results

19. Acknowledgements Dr. King Dr. King Professor Stach Professor Stach Cheryl Waller Cheryl Waller Vijay Rawat Vijay Rawat Rocco Cerchiara from Fischione Rocco Cerchiara from Fischione Jan Eberle Jan Eberle MSE Dept. MSE Dept.

20. Questions?