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October 16-20, 2011 – Columbus, Ohio
Effect of Ytterbium on Grain Boundary Structure and
Grain Growth in Magnesium Aluminate Spinel
George Ferko, Animesh Kundu, Martin P. Harmer
Applications of Spinel
October 16-20, 2011 – Columbus, Ohio
Courtesy of TA&T
Courtesy of Armorline• Armored windows
• Radomes
Desirable Properties
•Hardness
•Fracture toughness
•Transparency
LiF in Spinel
October 16-20, 2011 – Columbus, Ohio
Reimanis and Kleebe, J. Am. Ceram. Soc., 92 [7] (2009)
Spinel and Ytterbium
October 16-20, 2011 – Columbus, Ohio
Courtesy of JM Perkins and MH Lewis
Complexions
October 16-20, 2011 – Columbus, Ohio
S.J. Dillon et al. / Acta Materialia 55 (2007)
Experimental Procedure for Bi-crystals
• Cleaning of single crystals• Yb-doping (99.99% pure)• Hot-pressing (1200ºC, ~4MPa,
1Hrs)• Annealing (1600ºC, 2Hrs)• Polishing• FIB• TEM
October 16-20, 2011 – Columbus, Ohio
Spinel (100)
Spinel (111)
Yb(NO3)3•xH2O
Experimental Procedure for Pressureless Sintering
• Powder doping (500 ppm Yb)• Uniaxial pressing (35 Mpa)• CIPing (275 Mpa)• Sintering (1800°C)• Sectioning, grinding, and
polishing• EBSD
October 16-20, 2011 – Columbus, Ohio
Baikowski S30CR Powder Purity
S (ppm) 800-900
K(ppm) 40
Na(ppm) 11
Fe(ppm) <10
Ca(ppm) <10
Si(ppm) <10
Benameur et al., J. Am. Ceram. Soc. 94[5] (2011)
EBSD Data Processing
October 16-20, 2011 – Columbus, Ohio
Raw Data Grain Dilation Pore Data Removal
SEM Signal Overlay SEM Signal Grain Size Data
Identifying Abnormal Grains
October 16-20, 2011 – Columbus, Ohio
Grain Diameter (μm)
Freq
uenc
y
Grain Growth
October 16-20, 2011 – Columbus, Ohio
3.5 3.6 3.7 3.8 3.9 4 4.1 4.20
0.20.40.60.8
11.21.41.61.8
2
Undoped
500 ppm Yb-doped
log(t) (s)
log(
Ḡ) (
μm)
1 Hour Sample Comparison
October 16-20, 2011 – Columbus, Ohio
Freq
uenc
y
Grain Diameter (μm) Grain Diameter (μm)
2 Hour Sample Comparison
October 16-20, 2011 – Columbus, Ohio
Freq
uenc
y
Grain Diameter (μm) Grain Diameter (μm)
4 Hour Sample Comparison
October 16-20, 2011 – Columbus, Ohio
Freq
uenc
y
Grain Diameter (μm) Grain Diameter (μm)
October 16-20, 2011 – Columbus, Ohio
Grain Size Distribution Comparison
Yb-doped Samples
1 Hour
2 Hour
4 Hour
Undoped Samples
1 Hour
2 Hour
4 Hour
Freq
uenc
y
Grain Diameter (μm) Grain Diameter (μm)
Freq
uenc
y
STEM of Bi-crystal
October 16-20, 2011 – Columbus, Ohio
Bright Field STEM Dark Field STEMSTEM work performed by Animesh Kundu
STEM of Bi-crystal
October 16-20, 2011 – Columbus, Ohio
Bright Field STEM Dark Field STEMSTEM work performed by Animesh Kundu
Future Work
October 16-20, 2011 – Columbus, Ohio
Hot-pressing (1200ºC, 60 Mpa)
Annealing (1400°C, 1600°C, 1800°C)
Polycrystals
Yb-doped Undoped
Grain Size Measurements (EBSD)
Density Measurements
Quantitative Analysis of Grain Boundary Kinetics
Hot-pressing (1200ºC, 4 Mpa)
Annealing (1400°C, 1600°C, 1800°C)
Bi-crystals
Yb-doped
FIB Lift-out Method
HRTEM
HAADF STEM
Acknowledgements • My advisor Prof. Martin P. Harmer• Animesh Kundu for his unending assistance• Funding provided by:
– NSF MERSEC (CMMI-1131408)
October 16-20, 2011 – Columbus, Ohio
Thank you!
