1. Stanford Synchrotron Radiation Laboratory Small Angle Scattering Beam Line for Materials Sciences Mike Toney & John Pople (SSRL) 1.Why new SAXS beam line? 2.What, where & cost? 3.Some examples a.Fuel cell catalysts b.Particles on surfaces c.Polymers 4.Summary 5.Appendix: (SAXS basics & how proposal developed)

2. Materials Sciences SAXS Beam Line Requirements: simultaneous WAXS/SAXS large Q range: SAXS: Q ≈ 0.001 – 0.5 Å -1 WAXS: Q ≈ 0.5 – 6 Å -1 E = 5.9 - 20 keV ca 0.1 x 0.5 mm 2 spot size at detector ca 0.1 sec time-scale sample environments: furnaces, electrochemical cells, windowless chamber near-surface facility (grazing incidence SAXS) Science: nanoparticles: metal alloy (fuel cells), oxides, minerals polymers: fibrels, co-polymers supramolecular assemblies metallic glasses nanoporous materials colloids particles on surfaces/films

3. SAXS Beam Line: Why? 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., TiO 2 ) hydrogen storage materials small angle scattering probes 1-100 nm length scales same length scales as nanoscale 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. bend magnet between beamlines 4 and 5 focusing mirror (h & v) mono: multilayers & Si(111) SAXS detector up to 5m flight path Sample environments: - furnace to ≈800 o C - multi-sample holder (≈12) up to 200 o C - stopped-flow cell - chamber for windowless SAXS - space for simultaneous optics & other instrumentation - heated shear cell - grazing incidence-SAXS chamber WAXS detector Specifications: Focused flux ~ 1e12 h /s E = 5.9 - 20 keV 0.1 x 0.5 mm 2 focus on detector SAXS: Q ≈ 0.001 – 0.5 Å-1 WAXS: Q ≈ 0.5 – 6 Å-1 slits: h & v SAXS Beam Line: What

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

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

8. SAXS: Fuel Cell Catalysts Goals:  reduce cost: reduce Pt catalyst loading from present ~0.5mg/cm 2  improve durability Membrane-Electrode Assembly (PEM Fuel Cells) Fuel Cells: Efficient conversion of chemical energy into electrical energy Fundamental Breakthroughs needed: reaction mechanisms catalyst corrosion activity/efficiency Understanding properties of nanostructured electrocatalysts

9. SAXS: Fuel Cell Catalysts 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 Determine nanoparticle size distribution & changes during operation in Pt-alloys 4-2 with Strasser, Leisch, Koh, Fu 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) 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? In-Situ SAXS Electrochemical Cell Electrically Active Materials: Catalysts, medical implants, energy conversion devices, electronics Fuel Cell Catalysts: First Generation In-situ Cell

11. Nanoparticles on surfaces: gi-SAXS 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 Renaud et al., Science 300, 1416 (2003)

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

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., TiO 2 ): Strasser (UHouston), Gilbert (LBL) hydrogen storage materials: Clemens (SU)

15. Materials Sciences SAXS Beam Line Requirements: simultaneous WAXS/SAXS large Q range: SAXS: Q ≈ 0.001 – 0.5 Å -1 WAXS: Q ≈ 0.5 – 6 Å -1 E = 5.9 - 20 keV ca 0.1 x 0.5 mm 2 spot size at detector ca 0.1 sec time-scale sample environments: furnaces, electrochemical cells, windowless chamber near-surface facility (grazing incidence SAXS) Science: nanoparticles: metal alloy (fuel cells), oxides, minerals polymers: fibrels, co-polymers supramolecular assemblies metallic glasses nanoporous materials colloids particles on surfaces/films

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. 1.SAXS: 0.0007 Å-1 < q < 0.6 Å -1 2.WAXS: 0.6 Å -1 < q < 6 Å -1 3.Time resolution and timing 4.Anomalous Scattering, 6 keV < E < 35 keV 5.Range of spot sizes, as small as 10 μm 2 6.Robotic sample control 7.Temperature control from very cold to very hot 8.Elevated gas pressures

18. Measure I(Q) with Q  0.0001 – 1 Å -1 Scattering from 1-100 nm density inhomogeneities |Q| = (4  )sin  k  incident scattered k’ Q = k’ - k Q SAXS: Basics

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

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