1. Small Angle Scattering Beam Line for Materials Sciences
Stanford Synchrotron Radiation Laboratory
Small Angle Scattering Beam Line for Materials Sciences
Mike Toney & John Pople (SSRL)
Why new SAXS beam line?
What, where & cost?
Some examples
Fuel cell catalysts
Particles on surfaces
Polymers
Summary
Appendix: (SAXS basics & how proposal developed)

2. Materials Sciences SAXS Beam Line
nanoparticles: metal alloy (fuel cells), oxides, minerals
polymers: fibrels, co-polymers
supramolecular assemblies
metallic glasses
nanoporous materials
colloids
particles on surfaces/films
Requirements:
simultaneous WAXS/SAXS
large Q range:
SAXS: Q ≈ – 0.5 Å-1
WAXS: Q ≈ 0.5 – 6 Å-1
E = keV
ca 0.1 x 0.5 mm2 spot size at detector
ca 0.1 sec time-scale
sample environments: furnaces, electrochemical cells, windowless chamber
near-surface facility (grazing incidence SAXS)

3. SAXS Beam Line: Why?
small angle scattering probes nm length scales
same length scales as nanoscale materials
nanoparticles
metal alloys for fuel cell catalysts
minerals & oxides
metals for nanowires
supramolecular assemblies
polymers
arborols and fibrels
phase transitions in co-polymers
metallic glasses
nanoporous materials
surface particles and thin films (giSAXS)
colloids (e.g., TiO2)
hydrogen storage materials

4. New SAXS Beam Line: Why?
need large Q range: dispersion in particle sizes & morphology reconstruction
windowless SAXS: weak scatterers
anomalous SAXS (tune energy): element specificity
reactions and phase transitions
real time measurements (ca 0.1 sec)
furnaces, reaction chambers, electrochemical cells
simultaneous SAXS/WAXS

5. SAXS Beam Line: What Sample environments: WAXS detector slits: h & v
bend magnet
between
beamlines
4 and 5
mono:
multilayers
& Si(111)
focusing
mirror (h & v)
SAXS detector
up to 5m flight path
Sample environments:
furnace to ≈800o C
multi-sample holder (≈12) up to 200o C
stopped-flow cell
chamber for windowless SAXS
space for simultaneous optics & other instrumentation
heated shear cell
grazing incidence-SAXS chamber
Specifications:
Focused flux ~ 1e12 hn/s
E = keV
0.1 x 0.5 mm2 focus on detector
SAXS: Q ≈ – 0.5 Å-1
WAXS: Q ≈ 0.5 – 6 Å-1

6. SAXS Beam Line: Where between beam lines 4 (present) & 5
Bending magnet satisfies most requirements; flux frequently not limiting factor
unused bending magnet
enough space for long hutch

7. SAXS Beam Line: What & How Much
WAXS
detector
slits: h & v
bend magnet
between
beamlines
4 and 5
mono:
multilayers
& Si(111)
focusing
mirror (h & v)
SAXS detector
up to 5m flight path
Estimated Cost
Front end & optics: $3.0M
Hutch (slits, detector): $0.7M
Sample environments: $0.3M
Total: $4.0M
Sample environments:
furnace to ≈800o C
multi-sample holder (≈12) up to 200o C
chamber for windowless SAXS
grazing incidence-SAXS chamber

8. Membrane-Electrode Assembly
SAXS: Fuel Cell Catalysts
Fuel Cells: Efficient conversion of chemical energy into electrical energy
Goals:
reduce cost: reduce Pt catalyst loading from present ~0.5mg/cm2
improve durability
Membrane-Electrode Assembly
(PEM Fuel Cells)
Fundamental Breakthroughs needed:
reaction mechanisms
catalyst corrosion
activity/efficiency
Understanding properties of nanostructured electrocatalysts

9. SAXS: Fuel Cell Catalysts
4-2 with Strasser, Leisch, Koh, Fu
Determine nanoparticle size distribution & changes during operation in Pt-alloys
Use SAXS to determine particle size
Problem: strong SAXS from carbon support
Solution: use anomalous SAXS
tune energy near Pt LIII edge and vary Pt scattering strength
Before testing
After corrosion
Particle Size
SAXS: Pt-M Alloy Catalysts

10. In-Situ SAXS: Fuel Cell Catalysts
In-Situ SAXS: Watch the Changing World Monitor reaction progress: What are the changes accompanying a reaction? - corrosion (breaking bonds) - synthesis (making bonds)
Fuel Cell Catalysts:
First Generation In-situ Cell
In-Situ SAXS Electrochemical Cell
Electrically Active Materials: Catalysts, medical implants, energy conversion devices, electronics
When/how do the catalysts change during operation (corrosion, stability)?
What effect does the structure have on the activity? How does this change over time of operation?
Do better designs exist for a more robust material set?

11. Nanoparticles on surfaces: gi-SAXS
nanoparticles on surfaces or in films
precipitation
dissolution (pits)
templates
grazing incidence
(gi)-SAXS:
incidence angle < critical angle for total reflection
limit penetration into sample
near surface sensitivity
gi-SAXS
Renaud et al., Science 300, 1416 (2003)

12. Nanoparticles on surfaces: gi-SAXS
Fe2O3 nanoparticles on surfaces
determine particle size and size distribution
New beam line
need large Q range
windowless slits & chamber
tune energy
dedicated chamber for gi-SAXS
YS Jun & Waychunas (LBL), Pople & Toney (SSRL)

13. Self-Assembly of Block Co-Polymers
Formation process of ordered domains in block co-polymers (Balsara group UCB);
oxidation state of redox-active species controls order
New Beam line
larger Q range
tune energy

14. Collaborators/beam line users
nanoparticles
fuel cell catalysts: Strasser (UHouston), Leisch (SSRL),
oxides: Bargar (SSRL), Gilbert (LBL), Waychunas (LBL), Sposito (UCB)
nanowires: Stevens (IRL, NZ), Ingham (SSRL)
supramolecular assemblies: Safinya (UCSB)
polymers
fibers: Balsara (UCB)
co-polymers: Russso (LSU)
metallic glasses: Huffnagel (Johns Hopkins)
nanoporous materials: Miller (IBM), Kim (IBM), Leisch (SSRL)
surface particles and thin films: Waychunas (LBL), Tolbert (UCLA)
colloids (e.g., TiO2): Strasser (UHouston), Gilbert (LBL)
hydrogen storage materials: Clemens (SU)

15. Materials Sciences SAXS Beam Line
nanoparticles: metal alloy (fuel cells), oxides, minerals
polymers: fibrels, co-polymers
supramolecular assemblies
metallic glasses
nanoporous materials
colloids
particles on surfaces/films
Requirements:
simultaneous WAXS/SAXS
large Q range:
SAXS: Q ≈ – 0.5 Å-1
WAXS: Q ≈ 0.5 – 6 Å-1
E = keV
ca 0.1 x 0.5 mm2 spot size at detector
ca 0.1 sec time-scale
sample environments: furnaces, electrochemical cells, windowless chamber
near-surface facility (grazing incidence SAXS)

16. Materials Science Review
Director's Materials Science Review - June 9-10, 2003
Review of Opportunities with SPEAR3 exploring possible new initiatives in SSRL's chemical and materials science.
Sunil Sinha (UCSD, co-chair)
Russ Chianelli (UTEP, co-chair)
Franz Himpsel (Univ. of Wisconsin)
Bennett Larson (ORNL)
Simon Mochrie (Yale Univ.)
Cyrus Safinya (UCSB)
Sarah Tolbert (UCLA)
Don Weidner (SUNY).
The panel was charged with evaluating several proposed initiatives based on the increased performance of SPEAR3.

17. Panel's Recommendation
Area 1: Proposals that would have the most immediate impact on the materials synchrotron community.
Priority #1 – Super SAXS (ID beamline, wiggler) - A new full beamline with the following properties would have a great impact on the materials and biology community because of the simultaneous short range and long-range information obtained.
SAXS: Å-1 < q < 0.6 Å-1
WAXS: 0.6 Å-1 < q < 6 Å-1
Time resolution and timing
Anomalous Scattering, 6 keV < E < 35 keV
Range of spot sizes, as small as 10 μm2
Robotic sample control
Temperature control from very cold to very hot
Elevated gas pressures

18. SAXS: Basics scattered k’ k incident Q = k’ - k Q 2q
|Q| = (4p/l)sin q
Measure I(Q) with Q  – 1 Å-1
Scattering from nm density inhomogeneities

19. SAXS: Basics Need large Q range: 1/D Q 10/D <~ Isolated particles
or pores with
diameter D
Hexagonal packed
cylinders
p/D
Q-4
Need large Q range:
1/D Q 10/D
<~

20. Nanoporous Films: SAXS
Find:
reasonably small pores (good)
board distribution of pore sizes (bad)
size increases with loading => agglomeration (bad)
Huang et al, Appl. Phys. Lett. 81, 2232 (2002)