Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session V4: NM.2 Nanomaterials |
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Chair: Takahiro Matsuoka, Osaka University Room: Vashon |
Thursday, July 11, 2013 1:45PM - 2:00PM |
V4.00001: Shock--Induced Nanostructure Formation in Copper Yurii Meshcheriakov, Natalia Zhigacheva, Alexandre Divakov, Grigorii Konovalov, Boris Barakhtin Shock-induced nanostructure in polycrystalline copper of varied purity is found to be nucleated within narrow range of strain rates 5$\cdot $10$^{6} \div 5.7 \cdot $10$^{6}$s$^{-1}$. Shock loading of plane targets was conducted in two ways. The first way allows interference of longitudinal and lateral release waves whereas in the second configuration the studied material was conically pressed inside the copper disks, which allows to avoid a passage of lateral waves through the material of interest. The chaotically distributed within grains 3D-nanostructure formations of 15 $\div$ 25 $\mu$m in diameter are the result of dynamic response of material on combined loading with longitudinal and lateral release waves, which can be provided only in the first way of shock loading i.e. under 3D conditions. The formations consist of 3D-network of mutual perpendicular microtwins of 100$\div$200 \textit{nm} spacing. Energy and momentum expended on formation of the structures is shown to be quantitatively characterized by ``defect of particle velocity'' - difference between impact velocity under symmetrical collision and free surface velocity. There is a threshold strain rate at which defect of particle velocity begins to grow very fast, dimension of formations increases, and simultaneously hardness and spall-strength of material grow as well. [Preview Abstract] |
Thursday, July 11, 2013 2:00PM - 2:15PM |
V4.00002: High-Pressure Nanocrystals: New Structure and New Phase Transition Sequence Bo Zou High-pressure studies offer a potential strategy to the synthesis of nanocrystals with new phases, and provide new insights into the phase stability in metastable NCs. We have studied the stability of metastable ZB- and WZ-MnS NCs under high pressure and found ZB-nanoparticles and ZB/WZ-nanobipods are stable below 5.3 and 2.9 GPa, respectively. With further compression, all these metastable MnS NCs directly convert to the stable RS-MnS. The WZ-CuGaS$_{2}$ nanocrystals undergo a transition to another disordered RS phase above 15.9 GPa, which is stable up to 30.3 GPa. Upon release of pressure, the sample was irreversible and intriguingly converted into the energetically more favorable and ordered Chalcopyrite (CH) structure. The YPO$_{4}$ nanoparticles exhibit a distinct transition sequence: zircon to scheelite phase ($\sim$18 GPa) without the metastable monazite phase. Additionally, this transition sequence was investigated on the YV$_{\mathrm{1-x}}$P$_{\mathrm{x}}$O$_{4}$ nanoparticles. The transition pressure is reduced with more VO$_{4}$ substituting for PO$_{4}$ units.\\[4pt] [1] Nanoscale, 2012, 4, 7443\\[0pt] [2] JPCC, 2012, 116, 3292\\[0pt] [3] JPCC, 2012, 116, 24837 [Preview Abstract] |
Thursday, July 11, 2013 2:15PM - 2:30PM |
V4.00003: Molecular monolayers under high pressure: a study using surface enhanced Raman scattering and vibrational sum frequency generation spectroscopy Yuanxi Fu, Dana Dlott Vibrational spectra of molecular monolayers in a diamond anvil cell (DAC) reveal the conformation and packing state of the monolayers undergoing large-amplitude deformations. Measuring monolayer spectra under high pressure can be difficult due to the small number of molecules. We used surface enhanced Raman scattering (SERS) and vibrational sum frequency generation (VSFG) spectroscopy in a DAC to address the challenge. Localized surface plasmon resonance generated on curved metal surfaces enhances the adsorbates' Raman scattering cross-sections by factors of 10$^{\mathrm{6}}$, allowing SERS spectra of monolayers formed by organic thiols on silver coated polystyrene nanospheres and dyes on silver colloidal nanoparticles to be studied up to several GPa. To better understand the role of curvature, monolayers on planar surfaces were studied using a new diamond anvil cell for VSFG spectroscopy. VSFG is a nonlinear coherent vibrational spectroscopy that uses converging IR and visible femtosecond laser pulses. The VSFG spectra of long-chain alkane monolayers were studied up to several GPa. [Preview Abstract] |
Thursday, July 11, 2013 2:30PM - 2:45PM |
V4.00004: Characterization of Elastic and Vibrational Properties of Dense BC$_{\mathrm{x}}$ Nano-Phases Synthesized under High-Pressure and High-Temperature Pavel Zinin, Katherine Burgess, Ruth Jia, Eric Hellebrand, Tayro Acosta, Li-Chung Ming We use Raman scattering to study cold phase transitions in the graphitic $g$-BC$_{8}$ phase and graphite under high pressure up to 84 GPa. It is shown that the $E_{2g}$ Raman active mode of graphite ($G $peak) can be detected up to 84 GPa. We demonstrate that (a) there is a phase transition in graphite and in $g$-BC$_{8}$ at 35 GPa and (b) above 35 GPa the graphite and $g$-BC$_{8}$ transform in a high pressure phase, fully \textit{sp}$^{3}$ bonded $a$-BC$_{8}$ phases, Below the phase transition a polynomial fit to the G peak position versus pressure data yielded the following quadratic relation; above 35 GPa it exhibits linear behavior for graphite as well as for $g$-BC$_{8}$ phase. A direct transformation of graphitic phases in the BC$_{\mathrm{x}}$ system with high concentration of boron (1.5 \textless\ x 8) under high pressure and high temperature was studied. It was found that graphitic phases transform to new cubic BC$_{\mathrm{x}}$ (c-BC$_{3}$, c-B$_{2}$C$_{3})$ phases in a diamond anvil cell (DAC) at high temperature, 2200 K, and high pressure, 31 GPa. The atomic structure, bonding between atoms, and nanostructure was determined using transmission electron microscopy (TEM), x-ray diffraction and transmission electron microscopy-electron energy-loss spectroscopy (EELS). Elastic properties of the BC$_{\mathrm{x}}$ phases were determined by Laser Ultrasonic and Brillouin scattering techniques. [Preview Abstract] |
Thursday, July 11, 2013 2:45PM - 3:15PM |
V4.00005: Extreme synthesis and characterization of an ultrananocrystalline diamond aerogel in a diamond anvil cell Invited Speaker: Peter Pauzauskie High-surface-area mesostructured carbon materials have attracted a great amount attention in recent years because of a growing number of applications in energy storage, chemical catalysis, separations, and sensing. In particular, amorphous carbon aerogels have attracted much interest since the 1980's due to their low density, large intrinsic surface areas (\textgreater 1000 m$^{2}$/g), large pore volume, low dielectric constant, and high strength. In this talk we present the use of high-pressure (\textgreater 20 GPa) laser-heating (\textgreater 1500$^{\circ}$C) within a diamond anvil cell (DAC) to convert the amorphous network of a low-density (40 mg/cc) carbon aerogel into an ultrananocrystalline diamond aerogel. Raman spectroscopy is used to probe the amorphous-to-diamond phase transition at pressure within the DAC. High-resolution transmission electron microscopy images of recovered material indicate diamond crystallite sizes range from 1 to 100 nm, with electron diffraction and electron energy loss confirming the presence of the diamond phase.~ Photoluminescence spectroscopy and confocal time-correlated single-photon counting indicate the recovered material contains both negatively-charged and neutral nitrogen-vacancy (NV) complexes. Synchrotron scanning transmission x-ray microscopy (STXM) is used to compare the carbon electronic density-of-states of the amorphous starting material with the recovered diamond aerogel with \textless 100 meV energy resolution. Finally, we use nanoscale secondary ion mass spectrometry to investigate doping of the resorcinol-formaldehyde starting material with the aim of chemically tuning heteroatomic point defects within this diamond material system. [Preview Abstract] |
Thursday, July 11, 2013 3:15PM - 3:30PM |
V4.00006: Morphology-Tuned Phase Transitions of Anatase TiO$_{2}$ Nanowires under High Pressure Quanjun Li, Benyuan Cheng, Xue Yang, Ran Liu, Bo Liu, Jing Liu, Zhiqiang Chen, Bo Zou, Tian Cui, Bingbing Liu The phase transitions of one-dimensional (1D) anatase TiO$_{2}$ nanowires were studied by in situ high pressure synchrotron X-ray diffraction (XRD) and Raman scattering. A direct anatase-to-baddeleyite transformation was observed at $\sim$9 GPa, which is clearly different from the size-dependent phase transition behaviors for nanocrystalline TiO$_{2}$. We found the higher compressibility in the c-axis compared to the a-axis for anatase nanowires which may be attributed to both the crystal structural feature and the growth direction of the nanowires. This phase transition of the TiO$_{2}$ nanowires shows obvious morphology-tuned behaviors. Upon decompression, the baddeleyite phase transformed into $\alpha $-PbO$_{2}$ phase. The morphology of the TiO$_{2}$ nanowires shows excellent stability and TiO$_{2}$ nanowires with $\alpha $-PbO$_{2}$ phase were obtained at ambient conditions through a compression-decompression cycle. These results indicate that the nanoscale quasi-1D structure of TiO$_{2}$ nanowires may contribute to the high pressure phase transitions showing unique morphology-tuned behaviors. [Preview Abstract] |
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