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Characterisation of porous materials using Electron Microscopy. Dr. Patricia J. Kooyman DelftChemTech / National Centre for HREM Delft University of Technology p.j.kooyman@tudelft.nl. Bulk (structural) information. Transmission Electron Microscopy (TEM). Surface information.

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characterisation of porous materials using electron microscopy

Characterisation ofporous materials usingElectron Microscopy

Dr. Patricia J. Kooyman

DelftChemTech / National Centre for HREM

Delft University of Technology

p.j.kooyman@tudelft.nl

surface information

Bulk (structural) information

Transmission Electron Microscopy (TEM)

Surface information

Scanning techniques

Scanning probe microscopy: STM, AFM

Scanning Electron Microscopy (SEM)

what is tem
What is TEM?
  • A technique using high-energy electrons to obtain a 2D projection of a 3D structure.
  • The highest possible resolution is currently about 0.1 nm.
electron solid interactions
Electron-solid interactions

TEM

EDX

Specimen

Element

Elastically

specific X-rays

scattered

Secondary

electrons

electrons

ED / HREM

Visible light

Incident electrons

Direct beam

Backscattered

SEM

Inelastically

electrons

scattered

Auger electrons

electrons

EELS

slide7

SEMTEM

particle morphology(particle morphology)

surface morphology2D projection - internal structure

elemental analysis elemental analysis

5 nm - 500 micron1 nm - 5 micron

electr backscatter diffr electron diffraction

EELS

general features of sem
General features of SEM
  • Electrons interact with specimen
  • High vacuum necessary
  • Specimen should be conducting (sputter with Au)
  • Particle morphology
  • Surface imaging
  • Elemental analysis
  • Resolution ~ 1 nm
general features of tem
General features of TEM
  • Electrons interact with specimen
  • High vacuum necessary (~ 10-7 Torr for HREM)
  • Specimen should be very thin (< 10 nm for HREM)
  • 2D projection of 3D structure
  • Structural analysis
  • Elemental analysis
  • Resolution ~0.1 nm
optical systems
Optical systems

http://www.vcbio.sci.kun.nl/fesem/info/

optical system of a tem
Optical system of a TEM

specimen

focus plane

for

diffraction

intermediate 1

focus plane

for

image

image cross-section TEM

intermediate 2

final image

imaging

diffraction

electron diffraction tem
Electron diffraction (TEM)

MFI

HR bright-field image

ED

pattern

Fourier

transform

electron backscatter diffraction ebsd sem1
Electron backscatter diffraction (EBSD - SEM)

MFI

SEM image

Stavinski et al.

Angew. Chem.

120 (2008) 5719

EBSD patterns spots A and D

Indexed EBSD patterns spots A and D

tem imaging
TEM imaging

centered

dark field

HREM

bright field

dark field

ru alumina soede dut
Ru/aluminaSoede, DUT

Bright field

image

slide17

d-spacing

Ru/aluminaSoede, DUT

Electron

Diffraction

Pattern

slide18

Dark field

image with

Ru-diffracted

beam

Bright field

image

Ru/alumina

Soede

DUT

tem information obtained
TEM - information obtained
  • Method Information
  • * bright-field * microstructural
  • imaging nb: 2D info of 3D
  • * high resolution structure!
  • imaging

* electron diffraction * crystallographic

pattern (cf XRD)

* generated X-rays *elemental analysis (EDX)

sample preparation crushing
Sample preparation: crushing

suspension in

eg ethanol

crush

deposit on

grid with

carbon film

3 mm

tem fe mfi
TEM Fe-MFI

Taboada, TUD

sample preparation ion milling
Sample preparation: ion milling

specimen

polishing holder

polishing

5-10 micron thick

Ar ion beams

sample preparation ultramicrotomy
Sample preparation: ultramicrotomy

catalyst core

slices < 50 nm

glue mantle

diamond knife

slices on grid

water bath

also possible at liquid nitrogen temperature

ultramicrotomy
Ultramicrotomy

powder

specimen

ultramicrotomed

specimen

mcm 41
MCM-41

mesoporous zeotype material

pore size > 3 nm

possibility to convert larger molecules

different phases are found

hpa mcm 41 fresh
HPA/MCM-41 fresh

Verhoef, TUD

Ordered Disordered

fe si sba 15 tem
Fe-Si-SBA-15: TEM

Li, Hensen, TU/e

J. Phys. Chem. B 110 (2006) 26114 -26121

slide39

Pt-Rh/alumina (Grisel, UL)

Particle size distribution?

Alloying?

Use TEM/HREM in combination with EDX

slide40

overview

cluster

Pt-Rh/alumina (Grisel, UL)

slide41

full scale

enlarged scale

Pt-Rh/alumina (Grisel, UL)

pt zeolite

optimal imaging

zeolite

5 degree tilt

zeolite amorphised

Pt/zeolite
tio 2 in tud 1
TiO2 in TUD-1

Hamdy-Saad, TUD

Peeters, TUE

3d tem
3D TEM

Reconstruct 3D structure

from tilt series at different angles

of the same area of material

“Electron Tomography”

3d tem1
3D TEM

Procedure:

Acquire tilt series of a particle from +70 to -70 degrees at 1 or 2 degrees steps

Recombine these images to 3D reconstruction

Depict as slices through the particle or as volume rendering

3d tem result
3D TEM - result

Single image from series Slice of reconstruction

Jansen et al., Utrecht University

new mesoporous mat tem
New mesoporous mat: TEM

MSU-3

Prouzet et al.,

J.Mater.Chem.

12 (2002) 1553

new mesoporous mat 3d tem
New mesoporous mat: 3D-TEM

Single images from series

new mesoporous mat 3d tem1
New mesoporous mat: 3D-TEM

Single slices from reconstruction

slide54

E, energy of 200 kV electron

E-DE

Electron Energy Loss Spectroscopy

  • electron excitations, like
  • plasmons, phonons
  • secondary electrons (ionisation)
  • electron transitions to unoccupied states

Energy loss DE depends on for example

slide55

EELS spectrum

  • Zero loss and peak broadening due to
  • energy resolution ~ 1 eV.
  • + phonon scattering 0-0.1 eV
  • Low loss: plasmons 0-50 eV
  • Plural scattering in thick specimens
slide56

Ionisation edges,

K,L,M,… For element characterisation

slide58

EELS for elemental analysis

  • especially useful for low Z elements

C, diamond

slide60

EFTEM

  • higher spatial resolution than EDS elemental mapping
  • much better sensitivity for low Z elements than EDS
  • much shorter acquisition times than EDS
slide61

Example: Si-L2,3 EFTEM in MOSFET structure

M. Worch et al, Thin Solid Films 405 (2002) 198.

slide62

Si

BF

SiO2

Si3N4

50 nm

slide63

O

N

air sensitive materials sem
Air-sensitive materials - SEM

Normally, samples prepared in air

Problem for air-sensitive samples

Quasi in situ: prevent exposure to air

Real in situ: insert gas in microscope

prevents charging

slide65
ESEM

http://www.egr.msu.edu/cmsc/esem/gallery/index.html

slide66
ESEM

Lee et al.,

Journal of the European Ceramic Society 27 (2007) 561-564

air sensitive materials tem
Air-sensitive materials - TEM

Normally, samples prepared in air

Problem for air-sensitive samples

Quasi in situ: prevent exposure to air

Real in situ: perform reactions in microscope

nanoparticles

calc 823 K

sulph 613 K

calc 673 K

sulph 823 K

calc 823 K

sulph 673 K

Nanoparticles

Tungsten sulphide

real in situ commercially available
Real in situ: commercially available

E-TEM

Max 50 mbar

Resolution lost > 5 mbar

Complete sample holder is

heated and can react

Now sold by FEI

Haldor Topsoe

ASU

real in situ commercially available2
Real in situ: commercially available

New FEI Titan E-TEM

http://www.fei.com/

towards higher pressure
Towards higher pressure

A few mbar is NOTclose to realistic conditions!

NCHREM / Kavli Institute of NS / TUD

develop new concept - nanoreactor

Fredrik Creemer, Henny Zandbergen

towards higher pressure1
Towards higher pressure

Closed nanoreactor

towards higher pressure2
Towards higher pressure

MEMS nanoreactor

towards higher pressure4
Towards higher pressure

1.2 bar H2

500 oC

J.F. Creemer et al.

Atomic-scale

electron microscopy

at ambient pressure

Ultramicroscopy 2008

main problems
Main problems
  • representativity of specimen area
  • preparation damage
  • electron beam damage
  • very small particle imaging (< 1 nm)
  • visibility of monolayers
  • effect of support on image of supported phase