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A Detailed TEM Study of Carbon Nano-Onions’ Structure
Chethan K. Gaddam | Randy L. Vander Wal
Introduction SAED
Bright and Dark Field Tomography
Conclusions
Dr. Trevor Clark & Dr. Ke Wang (EM-2010F, EM-2010 LaB6) Dr. Missy Hazen (EM-FEI Tecnai G2) Chung-Hsuan Huang (Lattice Fringe Analysis)
References 1. D. Ugarte, Nature, 359(1992)707-708
2. R. L. Vander Wal, Combust. Sci. and Tech., 126(1997)333-357
3. Y. Gao et al., Carbon, 51(2013)52-58
4. F. Banhart et al., Nature, 382(1996)433-435
5. W. A. de Heer et al., Chem. Phys. Letters, 207(1993)480-486
6. D. Pech et al., Nature, 5(2010)651-654
7. S. Tomita et al., Chem. Phys. Letters, 305(1999)225-229
8. S. Iijima, J. Crys. Growth, 50(1980)675-683
9. K. Yehliu et al., Combust. Flame, 158(2011)1837-1851
John and Willie Leone Family Dept. of Energy and Mineral Engineering & The EMS Energy Institute The Pennsylvania State University, University Park
(a) (b) (c)
Figure 1. Ray diagrams showing how the objective lens and objective aperture are used in combination to produce (a) a Bright Field imaging, (b) off-axis Dark Field, and (c) on-axis Dark Field
Figure 2. Bright and Dark Field TEM images of CNOs at different magnifications (a)–(b) 40,000x, (c)–(d) 60,000x, and (e)–(f) 100,000x. Dark field images were acquired using the (002) diffraction
Figure 3. Illustration of Bragg diffraction from atomic layer planes
Figure 4. SAED pattern of CNOs. the pattern shows diffraction rings corresponding to graphite (002), (100), (004), and (110) layer planes, respectively.
Carbon Nano-Onions (CNOs) • Polyhedral carbon nanoshells • Fabrication by graphitization • Applications include lubrication, catalyst support,
conductive filler Transmission Electron Microscopy (TEM) • TEM analyses provide crystalline structure and carbon
bonding information • Techniques include:
• Bright-field & Dark-field imaging • Selected area electron diffraction (SAED) • Electron energy loss spectroscopy (EELS)
• We expand these using image analysis algorithms to quantify crystallite parameters evident in bright field imaging, and by tomography, for morphology and dimensionality
HRTEM & Fringe Analysis
EELS
X =1.4nm X =1.12 X = 0.34nm
Figure 6. HRTEM images of CNOs acquired at a magnification of 500,000x
(a)
(b) (c) (d)
Figure 7. Lattice fringe analysis (a) schemes for calculating fringe length, tortuosity and separation, (b)–(d) histograms and overlaid lognormal fits and parameterized mean values, respectively
σ*
π*
Figure 5. Images recorded from a specimen at different tilt-angle positions (as labeled)
Figure 8. A schematic of the EELS and EFTEM experimental setup for a Gatan imaging filter (GIF)
Acknowledgements
• Bright field images show ordered lamella • SAED "spotty" pattern demonstrates well developed
crystal structure (along with lattice structure) • Dark field shows that structure is spatially localized • EELS indicates bonding is predominantly sp2
• Image analysis algorithms permit quantification of crystallite parameters
• Tomography confirms 3D nature of this novel carbon morphology
θ θIncident Angle
Reflection Angle
θθλd
dAtomic Layer Planes
nλ#=#2d#sinθ
Optic AxisObjective Aperture
Direct Beam
Direct Beam
Diffracted Beam
2θ
θSpecimen
ReflectingPlane
IncidentBeam
Optic AxisObjective Aperture
Diffracted Beam
Direct Beam
Diffracted Beam
ObjectiveLens
2θ
θSpecimen
ReflectingPlane
Optic Axis
IncidentBeam
Optic AxisObjective Aperture
Diffracted Beam
Diffracted Beam
Direct Beam
ObjectiveLens
θSpecimen
Optic Axis
2θ = Angle of tilt of incident beam
Objective Aperture
Direct Beam
Objective Aperture
Optic Axis
Tilted Incident Beam
DiaphragmDiaphragm
(a) (b)
(c) (d)
(e) (f)
Electron Beam
Specimen
EntranceAperture
Magnetic Prism
Energy SelectingSlit
Lens Array
CCD Camera
Fringe Length
End point distance
Fringe Separation
(002)(100)
(004)
(110)
~2.45Å (100)
~1.41Å (110)
~3.5Å (002)
Crystallite Structure
(600)
(-200) (00)
(200)
(400)
(-600)
(-200)
(-400)