S canning E lectron M icroscopy ( SEM ) - construction, components, features and applications

1. Scanning Electron Microscopy (SEM) - construction, components, features and applications

2. e- SEM construction, components and features • - Tungsten filament • Lanthanum hexaboride (LaB6) • single crystal • - field emission gun Electron gun - accelerating voltage 20 – 200 keV Vacuum tube Electron optics Magnification: 100 – 200,000 x Resolurion: 0,7 nm to 50 nm Objective (final lens) JEOL JSM-890 field emission: Magnification: 900,000 x 35 keV, Resolurion: 0,7 nm Focussed e- beam Spot size – nm to mm range Microstructure of the specimen surface

3. e- SEM construction, components and features Condensing magnetic coils Electron optics Objective (final lens) Au: sputter coater Sample (one / several)

4. e- SEM construction, components and features Condensing magnetic coils Electron optics Scan coils Objective (final lens) Sample Scan mode Feature: images of morphology or topology - “3-d” view

5. e- SEM construction, components and features PC control B/W photo Condensing magnetic coils CCD matrix video www Scan coils Objective (final lens) Secondary e- 0,1 - 1 eV Topography Amplifier & detector Sample

6. e- SEM construction, components and features EPMA WD(crystal)S: B – Am, EDS (Si,Ge,Li, Be): B–U(AM), spot 1 mm, 0,1% Condensing magnetic coils Scan coils Objective (final lens) Detector Sample Secondary X rays (element microanalysis, X-ray mapping)

7. e- SEM construction, components and features Condensing magnetic coils Scan coils Objective (final lens) Back scattered e- 50-200 keV Atomic Nr, topogr. Amplifier & detector Sample EBS: crystallography, EBSD: local phase identification and orientation meas., EBS mapping: sp. lattice features, grain boundary misorientation

8. e- E (environmental) SEM • - Effect of wetting/drying on fibres. • - Water reactions with cement to produce bulk properties, • Soil science, catalysis, • Polymers, ceramics, - • Microelectronics. Environment: T: -200 to +1000oC Humidity, Atmosphere Real time video VHS recording Sample Magnification: up to 50,000 x, resolution 10 nm.

9. 6 M, 1.34 s.g. 5 M, 1.28 s.g. PbO2 crystals morphology vs. electrolyte concentration Source: D. Pavlov, A. Kirchev, M. Stoycheva and B. Monahov, Influence of H2SO4 concentration on the mechanism of the processes and on the electrochemical activity of the Pb/PbO2PbSO4 electrode, accepted for publication in J.Power Sources, 2004

10. 2.8 M, 1.17 s.g. 1.56 M, 1.095 s.g. PbO2 crystals morphology vs. electrolyte concentration Source: D. Pavlov, A. Kirchev, M. Stoycheva and B. Monahov, Influence of H2SO4 concentration on the mechanism of the processes and on the electrochemical activity of the Pb/PbO2PbSO4 electrode, accepted for publication in J.Power Sources, 2004

11. 0.5 M, 1.030 s.g. 0.18 M, 1.010 s.g. PbO2 crystals morphology vs. electrolyte concentration Source: D. Pavlov, A. Kirchev, M. Stoycheva and B. Monahov, Influence of H2SO4 concentration on the mechanism of the processes and on the electrochemical activity of the Pb/PbO2PbSO4 electrode, accepted for publication in J.Power Sources, 2004

12. Our secret goal: “green” battery, 100% natural products Polypodium (fern) Nephrolepis (fern)

13. 1 mm 1 mm 1 mm 1 mm PAM, charged, after thermal rise Source: D. Pavlov, B. Monahov, and A. Kirchev, to be published

14. 1 mm 3.3 mm NAM, formed, before thermal rise Source: D. Pavlov, B. Monahov, and A. Kirchev, to be published

15. 1 mm 1 mm NAM, charged, after thermal rise Source: D. Pavlov, B. Monahov, and A. Kirchev, to be published

16. PAM Pb strap grid interface - sample collecting point CL Pb AMCL PAM SGT positive plate structure studies setup Sample collecting points • Determinations in PAM/AMCL/CL • XRD: - phase composition, - average crystallite size; • SEM: - crystal morphology, - structure

17. Morphology of PbO2 in the corrosion layer • dense aggregates on the metal surface • fine, globular, hydrated PbO2 particles, almost no pores

18. Morphology of PbO2 in the AMCL dense structure porous structure

19. TEM microprobe TEM nanoprobe e- STEM EDS TEM construction, components and features Electron gun Uacc - up to 1000 keV Magnification: 350 - 600,000 x Resolurion: down to 0,2 nm JEOL JEM-4010 - atoms Magnification: 2,000,000x 40-100 keV, Resolurion: 0,15 nm Sample: 0,2 mm Mesh, goniometer specimen stages CCD camera Cryogenic facility Secondary X rays (element microanalysis) The internal structure of the specimen (2-d imaging)

20. a: TEM micrograph of an active mass agglomerate after discharge; b: electronogram of the crystals in the defined area with interpretation of its interplanar spacings TEM micrograph and electron diffractogram of a PbO2 particle Source: D. Pavlov, I. Balkanov, and P. Rachev, J. Electrochem. Soc., 134 (1987) 2390.

21. Battery knowledge developed using SEM/TEM microscopy • Structure of the Pb/PbSO4 electrode system. Membrane model of PbSO4. • Structure of the Pb/PbO/PbSO4 electrode system. Semiconductor model of PbOn. • Structure of PAM. PbO2 agglomerates, aggregates and particles. Hydrated structures in PAM and in the corrosion layer. Gel-crystal model of PbO2. Influence of the electrolyte concentration on the crystal morphology of PbO2. • Structure of NAM. Skeleton and energetic structures. • Structure of the CL. CL/AMCL/PAM model. • Mapping of PAM and the corrosion layer.