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排序方式: 共有156条查询结果,搜索用时 31 毫秒
91.
Osmane Camara Anamul H. Mir Krzysztof Dzieciol Graeme Greaves Shibabrata Basak Hans Kungl Matteo Bosi Luca Seravalli Steve E. Donnelly Rüdiger A. Eichel Jonathan A. Hinks 《Particle & Particle Systems Characterization》2021,38(12):2100154
Once nanomaterials have been synthesized, inducing further structural modifications is challenging. However, being able to do so in a controlled manner is crucial. In this context, germanium nanowires are irradiated in situ within a transmission electron microscope (TEM) by a 300 keV xenon ion beam at temperatures ranging from room temperature (RT) to 500 °C. The ion irradiation is performed in situ and the evolution of nanowires during irradiation is monitored. At 300 °C and below, where the temperature is low enough to allow amorphization, the ion beam causes the formation of nanostructures within the nanowires. Formation of nanopores and swelling of nanowires is observed for a very low fluence of 2.2 × 1014 and up to 4.2 × 1015 ions cm−2. At higher fluences, the thickness of the nanowires decreases, the nanowires lose their wire-like cylindrical shape and the nanostructuring caused by the ion beam becomes more complex. The nanostructures are observed to be stable upon crystallization when the nanowires are annealed at 530 °C. Furthermore, in situ imaging allows the growth of nanopores during irradiation to be followed at RT and at 300 °C providing valuable insights into the mechanism responsible for the nanostructuring. 相似文献
92.
Brayton DF Tanabe K Khiterer M Kolahi K Ziller J Greaves J Farmer PJ 《Inorganic chemistry》2006,45(15):6064-6072
S-oxygenation of dithiocarbamate (DTC) complexes has been implicated in their function as industrial anti-oxidants, as well as in their use as pesticides and most recently in their cumulative toxicity, but little is known of the species generated. Several S-oxygenated derivatives of N,N-disubstituted DTCs have been synthesized, characterized by a variety of methods, and their structure and reactivity examined. Low-temperature reaction of bis(N,N-diethyldithiocarbamato)zinc(II), Zn(deDTC)2 1, with oxygenating reagents (hydrogen peroxide, m-chloroperbenzoic acid, urea hydrogen peroxide) yields mono-oxygenated DTC complexes (N,N-peroxydiethyldithiocarbamato)(N,N-diethyldithiocarbamato)zin(II), Zn(O-deDTC)(deDTC), 2 and bis(N,N-peroxydiethyldithiocarbamato)zinc(II), Zn(O-deDTC)2, 3. The tetraoxygenated derivative bis(N,N-diethylthiocarbamoylsulfinato)zinc(II), Zn(O(2)-deDTC)2, 4, was cleanly obtained by initial reaction of the DTC salts with stoichiometric oxidant prior to complexation with Zn(II). X-ray crystallographic analysis of 2, 3, and 4 show that the peroxydithiocarbamate ligands are S,O-bound. Similar derivatives were obtained from the homoleptic dimethyl and pyrollidine DTC Zn complexes. These oxygenated species display unique 1H and 13C NMR variable-temperature spectra, as the symmetry of DTC ligand is broken upon oxygenation; total line shape analysis (TLSA) was used to compare the energetic parameters for rotation about the C-N bond in several derivatives. Compounds 2, 3, and 4 were deoxygenated by alkyl phosphine, regenerating the parent dithiocarbamate 1. The peroxydithiocarbamate complexes were susceptible to base-catalyzed hydrolytic decomposition, giving ligand-based products indicative of S-oxidation and S-extrusion. 相似文献
93.
Ricardo Castell Eduardo D. Greaves Lyzeth Abdala Haydn Barros 《Applied physics. B, Lasers and optics》2012,109(1):47-53
A new procedure with minimum sample preparation has been developed for a fast and serial analysis of cryolite with varying concentrations of dissolved alumina by liquid-phase laser ablation followed by Total Reflection X-Ray Fluorescence and induced coupled plasma optical emission spectroscopy. The analysis supplies the sodium/aluminium ratio of bath samples taken from industrial Hall-Herault reduction cells, as well as trace element relative concentrations. Two different types of molten samples taken directly from the aluminium production plant were placed under distilled de-ionized water in a quartz cell and subjected to pulsed laser ablation using the beam from a third harmonic Nd:YAG laser. Scanning electron microscopy examination shows the nanoparticles nature of the ablated material. The water-suspension is deposited on quartz reflectors for Total Reflection X-ray Fluorescence analysis or directly aspirated to the induced coupled plasma yielding the aluminium and sodium signals. Instrument quantification of the elements is performed by the use of aqueous standards. Validation tests were done with cryolite sample digestion and standard methods of sample quantification. The procedure can provide the aluminium/sodium ratio with adequate precision for aluminium production plant cell diagnostics and reveals the trace elements that could be considered as contamination. 相似文献
94.
G.N. Greaves M.C. Wilding S. Fearn F. Kargl L. Hennet W. Bras O. Majérus C.M. Martin 《Journal of Non》2009,355(10-12):715-721
Employing small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) combined with laser-heated aerodynamic levitation has enabled different transitions in supercooled yttrium oxide–aluminium oxide to be distinguished. These include liquid–liquid phase transitions as well as high temperature crystallization for different compositions. Prerequisites for avoiding crystallization in order to reveal polyamorphic phase separation in the supercooled state are established. We also show how the rise in SAXS intensity at low wavevectors can be used to identify correlation distances in long range fluctuations in high temperature melts. These distances appear to scale with melt viscosity and to extend temporarily during liquid–liquid transitions. 相似文献
95.
Greaves TL Weerawardena A Drummond CJ 《Physical chemistry chemical physics : PCCP》2011,13(20):9180-9186
The ability of low molecular weight amides to support amphiphile self-assembly is shown to be a general feature for this class of solvents. This report extends the number of known polar solvents which can support amphiphile self-assembly by five new amides; more than doubling the number of known amides able to serve as amphiphile self-assembly media. The formation of lyotropic liquid crystalline phases by cationic and non-ionic surfactants in these liquid amides is reported. The ability of a solvent to promote amphiphile self-assembly is governed by the "solvophobic effect" and is linked to the solvent cohesiveness. The Gordon parameter which is a measure of the solvent cohesiveness was found to provide a guide to an amides capacity to support lyotropic liquid crystalline phase diversity and thermal stability ranges of those phases. The "solvophobic effect" and steric hindrance factors were compared between amide's and protic ionic liquids possessing analogous chemical structures and also being able to promote amphiphile self-assembly. 相似文献
96.
Recent electrochemical studies involving in situ Mössbauer spectroscopy are reviewed. The principal application has been the development of new electrodes for lithium-ion batteries, where Mössbauer spectroscopy plays an important complementary role to XRD in characterizing, and usually identifying, nanocrystalline and intermediate phases of iron and tin. Other applications include the crystallography of Prussian Blue, taken using a recently developed spectrometer for acquiring multiple spectra during continuous cyclic voltammetry, valence interconversion in clay minerals and electrochemical oxygen reduction. 相似文献
97.
Deborah Greaves 《国际流体数值方法杂志》2004,44(10):1093-1117
A new adaptive quadtree method for simulating laminar viscous fluid problems with free surfaces and interfaces is presented in this paper. The Navier–Stokes equations are solved with a SIMPLE‐type scheme coupled with the Compressive Interface Capturing Scheme for Arbitrary Meshes (CICSAM) (Numerical prediction of two fluid systems with sharp interfaces, Ph.D. Thesis, Imperial College of Science, Technology and Medicine, London, 1997) volume of fluid (VoF) method and PLIC reconstruction of the volume fraction field during refinement and derefinement processes. The method is demonstrated for interface advection cases in translating and shearing flow fields and found to provide high interface resolution at low computational cost. The new method is also applied to simulation of the collapse of a water column and the results are in excellent agreement with other published data. The quadtree grids adapt to follow the movement of the free surface, whilst maintaining a band of the smallest cells surrounding the surface. The calculation is made on uniform and adapting quadtree grids and the accuracy of the quadtree calculation is shown to be the same as that made on the equivalent uniform grid. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
98.
S. T. Lees I. Gameson M. O. Jones P. P. Edwards C. Greaves F. Wellhofer P. Woodall I. Langford M. Slaski 《Physica C: Superconductivity and its Applications》1996,270(3-4):305-310
Pulsed laser ablation has been used to fabricate La2CuO4 thin films. Superconducting properties have been successfully induced in the films by an ex-situ, post-ablation annealing process in F2 gas resulting in a Tc (onset) of 36 K. The presence of two slightly different c-axis expanded phases in the X-ray diffraction data of the fluorinated films implies a degree of inhomogeneity in F2 uptake. Critical current densities (Jc) and the irreversibility line have been established from hysteresis cycles. A Jc of 106 A cm−2 for a typical film was observed at 10 K in zero field. 相似文献
99.
J. E. Koch W. Krieg E. E. Harris R. L. Mitchell F. W. Klingstedt W. H. Dore Erich Schmidt A. W. Schorger P. Klason Bror Holmberg und C. Greaves 《Fresenius' Journal of Analytical Chemistry》1940,119(5-6):237-240
Ohne Zusammenfassung 相似文献
100.
Discrete track media were simulated and compared with conventional, continuous media. The optimum write pole width was determined for discrete track media with 60 nm land/30 nm grooves, subject to the condition that there be no adjacent track erasure. Under optimal conditions discrete track media outperformed continuous media in terms of both on-track and off-track SNR. The performance difference became greater at higher linear densities, demonstrating the potential of discrete track media. 相似文献