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!