Time and space resolved spectroscopy of nanoenergetic materials Dana Dlott

Transcription

1 Time and space resolved spectroscopy of nanoenergetic materials Dana Dlott Hyunung Yu Selezion A. Hambir School of Chemical Sciences and Fredrick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign

2 Outline of Effort Experimental measurements of engineered nanoenergetic materials dynamic response to heat and shock Response of isolated nanoparticles Interactions among nanoparticles Reaction propagation over short distances (100 nm to 1 mm)

3 Program Structure and Interactions Synthesis & Assembly PSU UIUC nano - macro Theoretical Modeling & Simulation USC PSU macro - nano NEEM Experimental Characterization & Diagnostics nano - macro UIUC PSU

4 Interactions with MURI team Experimental measurements of engineered nanoenergetic materials dynamic response to heat and shock Theoretical modeling and simulation: Test and verify simulations, suggest focus areas Synthesis and assembly: Performance testing of novel materials, suggestions for advanced materials PSU Experimental characterization and diagnostics: Microperformance testing of practical materials, suggestions to improve performance based on micro measurements

5 transparent polymer oxidizer 100 ps oxidizer 100 nm pulse 100 ps heating pulse is matched to metal particle thermal conduction. Particle is uniformly heat- ed, surroundings cold High repetition rate laser flash- heating (100/s) 40 mg sample (3 µm thick). Each shot 50 ng (150 µm diam) shots per sample 10 cm 1 mm

6 Picosecond CARS measurements of flash heated materials fixed delay attenuator variable delay SPS CARS pulses 100 ps heating pulse thin film narrow band CD dye laser XY spectrograph CCD 1. Heat pulse 1053 nm, 100 ps, µj energy 70 µm radius 2. Probe pulses visible, 10 µj 30 ps, 30 µm rad CD broad band CD dye laser YLF QS ML SHG 3. repetition rate = 80 per second

7 Picosecond laser system for flash- heating studies

8 Nitrate group consumption in Alex/NC ONO2 survival fraction 800 CARS of NC -ONO CARS wavenumber (cm -1 ) 0.0 J = 5.9 J/cm delay time (ns) 0.2% 0.5% 1.0% 2.0% abrupt abrupt transition transition when when reactions reactions coalsece coalsece ~300 ps conc. indep CARS intensity (arb)

9 Energy release via time-resolved emission intensity (arb) Al atoms AlO 1% in NC 5.6 J/cm J/cm J/cm J/cm 2 2ns 1% in NC 5.6 J/cm J/cm J/cm J/cm 2 several ns wavelength (nm) time (ns) Energy release ~2 ns at low concentration Slows down at higher fluence as reaction propagates over greater distances

10 d avg Average distance d avg between nanoparticles is a ruler average distance d avg (nm) 3 m ρ ox Al w m Al ρ ox Al = mass of Al in a nanoparticle ox = oxidizer density w = wgt fraction of nanoparticles 110nm 62nm NC/Al Teflon/Al 30nm Al concentration (wgt%)

11 Reaction distance for 7 Al particles in Teflon mean distancce (nm) (1.7) nm 30 (2.8) nm 60 (2.5) nm 62 (6.0) nm 101 (2.8) nm 111 (5.6) nm 215 (18) nm x x10 11 energy per unit volume Al (J/m 3 )

12 Longer distance and directional propagation sample glass substrate thickness 1 µm to 100 µm near-ir flash heating pulse streakscope

13 Ultrafast (sub ns) microscopy of laser-initiated materials delay generator computer & video frame grabber CCD camera solid-state near-ir laser PS S N 2 - laser dye laser optical fiber

14 Energetic laser-triggered materials for computer-to to-plate imaging 2 µs duration laser pulse PDMS (silicone rubber) 2.5 µm substrate EM substrate

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16 Femtosecond IR laser laser table 5W 532 fs osc 20W YLF 3 mj, 1kHz, 100 fs Titan amplifier pulse shaper PC shape control flash-heating/ IR transient absorption table shock pulse PC λ control IR OPA 4 pass amplifier 15W YLF IR probe IR ref spectrograph +IR array optical delay line spectrograph +CCD SFG SFG/shock table flip-in mirrors Fabry-Perot ètalons BB-IR NB-vis shock target array sample on motorized flashheating positioner pulse

17 Femtosecond IR laser ( µm) C-H, C-C, Al-O, Al-F, C-F, O-H, etc.

18 Time-resolved IR ( µm) signal BBIR Mirror beamsplitter reference dichroic beamsplitter spectrograph with IRFPA near-ir flash heating pulse signal

19 Shock spectroscopy of self- assembled monolayers on Au tethered ODT layer Ni Cr Au -CH 3 One 200 µm m x 200 µm element of a 50 mm x 50 mm array ~50,000 shots/array laser shock pulse glass substrate plasma contact liquid CaF 2 window SFG IR vis each SFG spectrum a few hundred shots

20 Properties of femtosecond laser- driven shock wave Pressure 5-10 GPa Material velocity ~0.8 km/s Shock velocity ~4 km/s (40Å/ps) Compression factor V = 0.2 Rise time 2-3 ps Fall time 15 ps

21 Shock data on 3 transitions of PDT (15 carbons) relative SFG signal I/I <4 ps rise ~15 ps fall 15-carbon chain ν s ν as ν FR delay time (ps) completely elastic recovery

22 Shock data on 3 transitions of ODT/Au (18 carbons) <4 ps rise ~15 ps fall relative SFG signal I/I 0 shock ~30 ps decay sym asym bend delay time (ps) viscoelastic compression

23 Model for viscoelastic compression of ODT θ = 23 θ = 85 θ = 85 θ = 12 Shock creates a mixture of single ( gt) and double g+g defects with high tilt angles that kill the SFG signal. tt -g t -g +g t +g 1% 10% 28% 5% V When shock unloads, the barriers are too high for either to relax to tt. However g+g can relax to upright t+g

24 Status of effort Status of effort Tools developed to study isolated nanoparticles and nanoscale propagation Ultrafast microscope upgrade completed Fast IR constructed, waiting for IR detector upgrade (Nov) Reaction propagation experiment constructed, waiting for detector upgrade (Oct) Monolayer shock experiments successful but difficult, need more development