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

Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN ACADEMY OF SCIENCES

WP 2. Lead-acid batteries for POEMES, LABD

Scanning Electron Microscopy

(SEM) -

construction, components, features and

applications



e-Electron gun

Vacuum tube

- Tungsten filament- Lanthanum hexaboride (LaB6) single crystal- field emission gun

Focussed e- beam

- accelerating voltage 20 – 200 keV

SEM construction, components and features

Spot size – nm to m range

Magnification: 100 – 200,000 xResolurion: 0,7 nm to 50 nm

Electron optics

Objective (final lens)JEOL JSM-890 field emission:

Magnification: 900,000 x35 keV, Resolurion: 0,7 nm

Microstructure of the specimen surface



Sample (one / several)

e-

Condensing magnetic coils


Objective (final lens)

Electron optics

Au: sputter coater



e-

Sample

Feature: images of morphology or topology - “3-d” view

Scan coils

Scan mode




Electron optics



e-

Scan coils


Secondary e-

0,1 - 1 eVTopography

Sample Amplifier & detector



B/W photoCCD matrix

wwwvideo

PC control



e-

Secondary X rays (element microanalysis, X-ray mapping)

Detector

Sample




Scan coils

WD(crystal)S: B – Am,EDS (Si,Ge,Li, Be): B–U(AM), spot 1 m, 0,1%

EPMA



e-

EBS: crystallography,EBSD: local phase identification and orientation meas., EBS mapping: sp. lattice features, grain boundary misorientation

Scan coils

Back scattered e-

50-200 keVAtomic Nr, topogr. Sample Amplifier &

detector






e-

Magnification: up to 50,000 x, resolution 10 nm.

Sample

E (environmental) SEM

Environment:T: -200 to +1000oC

Humidity, Atmosphere

Real time videoVHS recording

- Effect of wetting/drying on fibres. - Water reactions with cement to produce bulk properties, -Soil science, catalysis, -Polymers, ceramics, -- Microelectronics.



PbO2 crystals morphology vs. electrolyte concentration

6 M, 1.34 s.g. 5 M, 1.28 s.g.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



2.8 M, 1.17 s.g. 1.56 M, 1.095 s.g.


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



0.18 M, 1.010 s.g.

0.5 M, 1.030 s.g.


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



Our secret goal: “green” battery, 100% natural products

Nephrolepis(fern)

Polypodium(fern)



PAM, charged, after thermal rise

1 m

1 m

1 m

1 m

Source: D. Pavlov, B. Monahov, and A. Kirchev, to be published



NAM, formed, before thermal rise

1 m3.3 m




NAM, charged, after thermal rise

1 m 1 m




Determinations in PAM/AMCL/CL1. XRD: - phase composition,

- average crystallite size;2. SEM: - crystal morphology,

- structure

SGT positive plate structure studies setupSample collecting points

Pb CL AMCL PAM

PAM

Pb strap gridinterface

- sample collecting point



Morphology of PbO2 in the corrosion layer

dense aggregates on the metal surface fine, globular, hydrated PbO2 particles, almost no pores



dense structure

porous structure

Morphology of PbO2 in the AMCL



e-

TEM construction, components and features

The internal structure of the specimen (2-d imaging)

Electron gunUacc - up to 1000 keV

Sample: 0,2 m

Magnification: 350 - 600,000 xResolurion: down to 0,2 nm

JEOL JEM-4010 - atomsMagnification: 2,000,000x

40-100 keV, Resolurion: 0,15 nm

Mesh, goniometer specimen stages

Secondary X rays (element microanalysis)

TEM microprobe

TEM nanoprobe

STEMEDS

CCD camera Cryogenic facility



Source: D. Pavlov, I. Balkanov, and P. Rachev, J. Electrochem. Soc., 134 (1987) 2390.

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



1. Structure of the Pb/PbSO4 electrode system. Membrane model of PbSO4.

2. Structure of the Pb/PbO/PbSO4 electrode system. Semiconductor model of PbOn.

3. 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.

4. Structure of NAM. Skeleton and energetic structures.

5. Structure of the CL. CL/AMCL/PAM model.

6. Mapping of PAM and the corrosion layer.

Battery knowledge developed using SEM/TEM microscopy

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

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