Slide 1Przemyslaw Dera University of Hawaii
School of Ocean and Earth Science and Technology Hawaii Institute of Geophysics & Planetology
ARL Summer Meeting Honolulu, HI, August 20, 2015
Partnership for eXtreme Xtallography: https://sites.google.com/site/partnershipx2/
Our research is supported by: NSF (Geophysics, GeoInformatics, EarthCube and SISI) CDAC/DOE-NNSA NASA (ASTID and SERA)
These phenomena can significantly affect mechanical/elastic and transport properties, which are often critical for the material’s performance in the field setting. In particular, some phase transitions may lead to catastrophic mechanical failure of armor ceramics or may affect sensitivity of molecular explosives or solid propellants.
Factors that can trigger phase transitions include: • Pressure • Temperature • Stress anisotropy (shear component) • Stress/strain rate
Structural transformations and energetic materials
Polymorphic pressure-induced transformation in Be(OH)2, hydrogen-bonded analog of silica Shelton, Dera et. al. in press
• Effects of temperature and hydrostatic pressure defining stable phase diagrams are fairly routine to measure, and for most fundamental systems have already been established.
• The effects of stress anisotropy and stress/strain rate are even more important/realistic for technological applications, but they are also much more elusive (e.g. path-dependent), harder to quantitatively control and often lead to metastable behavior.
• All of these effects can be measured using novel synchrotron in situ X-ray diffraction techniques developed by our group.
Stress anisotropy and stress/strain rate are capable of: • changing pressure/temperature at which known stable phase
transitions take place (e.g. SiO2 quartz) • inducing new metastable phase transitions (e.g. CuGeO3) • suppressing known phase transitions (e.g. SiO2 cristobalite) • changing deformation mechanism (e.g. SiO2 quartz)
Stress-rate controlled metastability
0.1mm
Polymorphism related to hydrogen bond transformations plays important role in controlling explosive materials stability
• Stable and unstable molecules that have compatible molecular geometries and H-bond formation capabilities can often be combined in co-crystals that inherit a combination of properties of the parent compounds.
• Hydrothermal conditions (high p and T) often promote co-crystal formation
• This route offers possibility for synthesis of hybrid molecular materials with improved properties (e.g. high energy storage and high stability)
Stable molecular analogs of explosives provide convenient test cases to understand hydrogen bond transformations
• s-triazine ring • 6 out of 9 non-H atoms are nitrogen • The molecule in the crystal is not flat because of extensive
intermolecular hydrogen bonding • Stable, fire-retardant properties (used for kitchen laminate
applications) • Molecular geometry compatible with TATB and TNB • Forms co-crystals with some molecular explosives • Synchrotron in situ single crystal X-ray diffraction (below)
provides unparalleled insight into the atomic details of compression behavior
Melamine
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Series1 Series2 Series3 Series4 Power (Series1) Log. (Series1)
benzene
graphite
melamine
• Two experiments carried out in Ne and He pressure media • No symmetry change or volume discontinuity detected up to 35 GPa • Displacive phase transition at 35 GPa to a triclinic phase • Amorphisation observed above 45 GPa
V/ V0
x10^3
p [GPa] P=30 GPa
P=1 GPa
de-distance to the nearest atom outside Normalized contact distance dnorm
Synchrotron single-crystal X-ray diffraction and Hirshfeld surface analysis
In situ Raman spectroscopy
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1.561
0.6987466428
2.234
0
0
1
0.5043
0.1813
0
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1
0.96
-0.0017
0.9983
0.4963
0.1816
0.96
0.9983
0.9841364267
1.0016547159
2.86
-0.0097
0.9903
0.4925
0.1889
2.86
0.9903
0.9766012294
1.0419194705
4.73
0.006
1.006
0.4875
0.1845
4.73
1.006
0.9666864961
1.0176503034
7.72
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0.4833
0.1912
7.72
1.001
0.9583581202
1.054605626
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0.995
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0.1951
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0.9551854055
1.0761169333
16.82
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0.4789
0.1966
16.82
1.005
0.9496331549
1.084390513
19.8
0.0081
1.0081
0.47362
0.1983
19.8
1.0081
0.9391631965
1.0937672366
23.54
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-18.3333333333
-20.3333333333
8.6666666667
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7.6666666667
5.6666666667
16.3333333333
14.3333333333
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PX2 Partnership for eXtreme Xtallography New Advanced Experimental Facility of HIGP at Argonne National Laboratory
X-ray beam: Bending magnet source, 30 keV fixed energy, 10x15 micrometers focal spot size
Goniometer: Unique six-circle diffractometer high rotation speed (up to 15deg/sec), high precision of rotation ( less than 10 micrometers sphere of confusion) High load capacity (up to 25 lb)
Detectors: Mar165 CCD Ultrafast Perkin Elmer XRD1642 flat panel pixel array detector (30 exposures/sec)
Laser optics: Online Raman spectroscopy Unique laser heating system for single crystal experiments including 200 W NIR fiber laser
Mission: Advanced research at conditions of extreme pressure, temperature and strain rates, exploring structure, defects, strain, and transformations of minerals and materials of technological interest
Access: Up to 50% beam time available for high pressure experiments
In house facilities for extreme conditions research at HIGP:
Diamond anvil cells Dynamic compression membrane setup NIR laser heating CO2 laser heating In situ ambient and high temperature Raman
spectroscopy in DAC Large volume presses for sample synthesis
Our facilities
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Polymorphism related to hydrogen bond transformations plays important role in controlling explosive materials stability
Stable molecular analogs of explosives provide convenient test cases to understand hydrogen bond transformations
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