Time-dependent transformations & off-hugoniot processes

Transcription

1 Time-dependent transformations & off-hugoniot processes The scientific understanding of the dynamics of chemical and structural transitions can be dramatically advanced through the development of time-resolved x-ray diagnostics integrated with a variety of impulsive drives (pressure, temperature, photons, field) or pump-probe measurements. These advances will broadly address dynamic processes including reaction chemistry, phase changes, material performance, technological material synthesis, and basic science. geoscience Time-resolved chemical/structural changes Material synthesis Catalysis mechano-, photopressure-, thermal- Material performance

2 Time-dependent transformations & off-hugoniot processes 10 2 Strain rate /s Quasistatic, MTS, piezodevice Kolsky bar Gas gun, explosives Laser s-ms 100 µs 100 ns-µs fs-ns HPCAT HPCAT HPCAT as a complementary venue for time-resolved measurements to DCS and LCLS; opening to any new ideas.

3 Coherent x-ray diffraction imaging, W. Yang et al. A case: Void growth Molecular dynamics, Luo et al. WAX + SAX (high E) - CDI: individual voids - SAXS and WAXS to cover sufficient q range: statistics of voids. SAX + WAX (medium E) Sector 1 Helium chamber

4 Priority Research Directions and scientific challenges PRD: Pulsed P/T/photon/EM field induced structural/chemical changes and dynamics Non-equilibrium transformations and equilibrium phase boundary, e.g., superheating/supercooling, over-/under-pressurization. A wide variety of materials, hard/soft materials including proteins, and processes. Nano-, microscale microstructure interactions and evolution Scientific challenges: Atomic rearrangement: lattice structure and interface (scattering/imaging), including nanomaterials. Valance (XEAFS); spin (e.g., domain walls); photon, electron, spin, phonon interactions; chemistry (spectroscopy). Complementary physical properties: mechanical, electrical, magnetic, transport Dynamics/kinetics for thermo-mechano-chemical pathways: phonons, phase changes, chemical reactions, plasticity (loading, and detection).

5 Experimental Capabilities Diagnostics techniques: spatially/temporally resolved scattering/diffraction, imaging, spectroscopy measurement, others. CDI; XANES tomography (composition and microstructure). X-ray sources Spatially coherent + monochromatic; high flux; focused and unfocused beams. Time structure: 100 ps (time resolution limit); repetition rate (4 APS modes). Pulsed loading: P/T/photons/electromagnetic field Synchronization of loading, X-ray pulses and detectors. IR, UV lasers; fs laser. Detectors - High speed: gating (single pulse), and framing (exposure time 100s ns to ms) - Large area for diffraction. - Direct and indirect x-ray detection; indirect, scintillators. Software - Timing, loading, and detector controls. - Big data processing: storage, transfer, and processing, including physics and data mining. Offline capabilities.

6 Technical challenges X-ray sources Tunable, high flux, monochromatic light (radiation damage). Shorter pulses would be better (1 ps vs. 100 ps). Detectors - High speed: gating (single pulse), and framing (exposure time 100s ns to ms) - Large area for diffraction. - Direct and indirect x-ray detection; indirect, fast and efficient scintillators; point spread function. Loading: exact loading/unloading conditions, e.g., stress/t field? Synchronization of loading, X-ray pulses and detectors; sensor/detector damage. Software - Timing, loading, and detector controls. - Big data processing: storage, transfer, and processing, including physics and data mining. A learning curve: acquisition of knowledge and experience.

7 Contributors W. Evans and S. Luo (chairs) M. Armstrong (panelist) J.-Y. Chen (panelist) E. Chronister (panelist) D. Hooks (panelist) N. Velisavljevich (panelist) W. Yang (panelist) G. Boman Y. Gupta S. Gramsch D. Funk T. Sekine Many others

8 Nanoscale interactions Use low angle scattering/imaging to characterize the evolution of nanoscale material distributions in time and space upon rapid heating or compression Nanoscale mixing kinetics/chemistry Quench/passivate nanoparticles for recovery at room pressure Characterize defect migration under dynamic conditions Scientific challenges Technical challenges How can nucleation at the nanoscale be controlled by pressure? How do surface chemistry and grain boundary interactions depend on pressure? Difficult to observe nanoscale material dynamics under a wide variety of initial conditions Requires precise control and characterization of the thermodynamic state

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10 Non-equilibrium transformations Characterize the formation of materials in non-equilibrium situations Coherent chemistry Very rapid quench Anisotropic chemistry Non-thermal kinetic energy distribution Scientific challenges Technical challenges Is it possible to find higher yield/cheaper synthesis methods using non-equilibrium phenomena? Is it possible to recover previously unknown metastable materials? Where to start? Potential synthesis methods are difficult to evaluate to estimate chances of success. Need to formulate some general principles

11 Time-resolved structural changes associated with µmscale chemical/physical changes chemical and structural changes in photo-mechanical microcrystals, kinetics of: a) polymorphic crystalline phase changes, b) photo-mechanical changes, and c) mechano-chemistry, d) protein folding kinetics, initiation by microsecond (or submicrosecond) dynamic pressure. Scientific challenges Structural changes in: macromolecules crystal structure crystalline disorder Technical challenges Time and Spatial constraints: µs or sub-µs time resolution 10µm scale samples µs or sub-µs dynamic pressure

12 Phase/Chemical Transition Dynamics Time-resolved diffraction and imaging studies Super-compressed liquid time-> Solid Scientific challenges Develop an understanding of the dynamics of phase transitions: Microscopic (nucleation) Macroscopic (growth) Influence of compression rate Microstructure evolution Technical challenges adequate flux High-speed, high-efficiency, highresolution detectors process/analyze large data sets drives (ddac, laser, explosive, strain, ) with micro-positioning X-ray beam with variable focus (submicron to mm s) Tunable energy to match experiment Large adaptable experimental bay

13 Time-dependent evolution of microstructure Time resolved structural evolution Variables: pressure, temperature, strain, particle size, phase Diagnostic Methods: Time resolved optical properties, x-ray diffraction, imaging, spectroscopy, transport property Scientific challenges Technical challenges Atomic rearrangement Charge transfer Spin transition Kinetics Pressure/temperature vs. Time order/disorder Recrystallization Chemical reaction/dissociation Fast and high sensitive detector High probing flux, but radiation damage Pump-probe Stability and repeatability Transport property in line with shock, pump probe Fast acquisition vs. S/N ratio