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31.
We report on the discovery of a new solid, presumably amorphous n-butanol at ambient pressure. According to the literature data the melting point Tm of n-butanol is 183 K and the glass transition temperature Tg is 118 K. If kept isothermally at a fixed temperature between 130 and 160 K, the supercooled liquid n-butanol undergoes remarkable phase transformations to a solid phase. The new phase converts to liquid at a temperature of about 170 K. It is presumably amorphous because foreign substances dissolved in liquid n-butanol keep the same state in this new phase of butanol. The kinetics of free radical oxidation by dissolved oxygen in both solid amorphous phases is investigated in detail. 相似文献
32.
Andrey Yu. Manakov Andrey G. Ogienko Vladislav Yu. Komarov Aleksei I. Ancharov Michail A. Sheromov 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):317-320
X-ray diffraction study of quenched sample of acetone clathrate hydrate synthesized at 0.8 GPa was carried out. It was shown
that the host frameworks of the hydrate comprise uniform cavities which are similar to that of recently characterized structure
of high-pressure tetrahydrofurane hydrate. The unique peculiarity of investigated hydrate is decrease in the crystallographic
symmetry of the hydrate arising from ordering in guest subsystem. 相似文献
33.
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35.
CO2 laser-induced plasma CVD synthesis of diamond 总被引:1,自引:0,他引:1
V.I. Konov A.M. Prokhorov S.A. Uglov A.P. Bolshakov I.A. Leontiev F. Dausinger H. Hügel B. Angstenberger G. Sepold S. Metev 《Applied Physics A: Materials Science & Processing》1998,66(5):575-578
2 laser maintenance of a stationary optical discharge in a gas stream, exhausting over a substrate into the air (laser plasmatron).
Nano- and polycrystalline-diamond films were deposited on tungsten substrates from atmospheric-pressure Xe(Ar):H2:CH4 gas mixtures at flow rates of 2 ?/min. A 2.5-kW CO2 laser focused beam produced plasma. The deposition area was about 1 cm2 and growth rates were up to 30–50 μm/h. Peculiarities and advantages of laser plasmatrons are discussed.
Received: 15 January 1998/Accepted: 16 January 1998 相似文献
36.
Amorphous silica is an inorganic material that is central for many nanotechnology applications, such as nanoelectronics, microfluidics, and nanopore sensors. To use molecular dynamics (MD) simulations to study the behavior of biomolecules interacting with silica, we developed a force field for amorphous silica surfaces based on their macroscopic wetting properties that is compatible with the CHARMM force field and TIP3P water model. The contact angle of a water droplet on a silica surface served as a criterion to tune the intermolecular interactions. The resulting force field was used to study the permeation of water through silica nanopores, illustrating the influence of the surface topography and the intermolecular parameters on permeation kinetics. We find that minute modeling of the amorphous surface is critical for MD studies, since the particular arrangement of surface atoms controls sensitively electrostatic interactions between silica and water. 相似文献
37.
Ogienko AG Kurnosov AV Manakov AY Larionov EG Ancharov AI Sheromov MA Nesterov AN 《The journal of physical chemistry. B》2006,110(6):2840-2846
For the first time, the compositions of argon and methane high-pressure gas hydrates have been directly determined. The studied samples of the gas hydrates were prepared under high-pressure conditions and quenched at 77 K. The composition of the argon hydrate (structure H, stable at 460-770 MPa) was found to be Ar.(3.27 +/- 0.17)H(2)O. This result shows a good agreement with the refinement of the argon hydrate structure using neutron powder diffraction data and helps to rationalize the evolution of hydrate structures in the Ar-H(2)O system at high pressures. The quenched argon hydrate was found to dissociate in two steps. The first step (170-190 K) corresponds to a partial dissociation of the hydrate and the self-preservation of a residual part of the hydrate with an ice cover. Presumably, significant amounts of ice Ic form at this stage. The second step (210-230 K) corresponds to the dissociation of the residual part of the hydrate. The composition of the methane hydrate (cubic structure I, stable up to 620 MPa) was found to be CH(4).5.76H(2)O. Temperature dependence of the unit cell parameters for both hydrates has been also studied. Calculated from these results, the thermal expansivities for the structure H argon hydrate are alpha(a) = 76.6 K(-1) and alpha(c) = 77.4 K(-1) (in the 100-250 K temperature range) and for the cubic structure I methane hydrate are alpha(a) = 32.2 K(-1), alpha(a) = 53.0 K(-1), and alpha(a) = 73.5 K(-1) at 100, 150, and 200 K, respectively. 相似文献
38.
Galina F. Fedorova Viktoryia A. Lapina Valery A. Menshov Vladimir V. Naumov Aleksei V. Trofimov Yury B. Tsaplev Rostislav F. Vasil'ev Olga I. Yablonskaya 《Photochemistry and photobiology》2019,95(3):780-786
Updating the facile chemiluminescence oxygen‐aftereffect method, most suitable for determining the rate constant (kt) of the peroxy‐radical self‐reaction (main chemiluminescence channel), pertained to considering the sensitivity of such a method toward a disturbing influence of the peroxy radicals of the initiator of the chain oxidation process. Such a disturbance may derive from the side chemiluminescent reaction, which involves peroxy radicals of both hydrocarbon and initiator. To examine the applicability and limitations of the chemiluminescence method under present scrutiny, cyclohexene was used as the model oxidizable hydrocarbon substrate. Computer simulations of the reaction and chemiluminescence kinetics have demonstrated the validity of the considered methodology at the value of the rate constant of the propagation of the overall chain process by peroxy radicals of the initiator higher than 1 m ?1 s?1. Despite that the chemiluminescence time profile and the stationary level of the total chemiluminescence intensity depend on the kinetics of the side chemiluminescence channel and on the ratio of the excited‐state generation yields in the mentioned reaction channel and in the main chemiluminescence process, the value of kt assessed by the oxygen‐aftereffect method has been found independent of variation of these characteristics. 相似文献
39.
The microscopic mechanics of DNA stretching was characterized using extensive molecular dynamics simulations. By employing an anisotropic pressure-control method, realistic force-extension dependences of effectively infinite DNA molecules were obtained. A coexistence of B and S DNA domains was observed during the overstretching transition. The simulations revealed that strain softening may occur in the process of stretching torsionally constrained DNA. The latter observation was qualitatively reconciled with available experimental data using a random-field Ising model. 相似文献
40.
Impact of the Oxygen Defects and the Hydrogen Concentration on the Surface of Tetragonal and Monoclinic ZrO2 on the Reduction Rates of Stearic Acid on Ni/ZrO2 下载免费PDF全文
Sebastian Foraita Dr. John L. Fulton Zizwe A. Chase Aleksei Vjunov Pinghong Xu Dr. Eszter Baráth Dr. Donald M. Camaioni Dr. Chen Zhao Prof. Dr. Johannes A. Lercher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2423-2434
The role of the specific physicochemical properties of ZrO2 phases on Ni/ZrO2 has been explored with respect to the reduction of stearic acid. Conversion on pure m‐ZrO2 is 1.3 times more active than on t‐ZrO2, whereas Ni/m‐ZrO2 is three times more active than Ni/t‐ZrO2. Although the hydrodeoxygenation of stearic acid can be catalyzed solely by Ni, the synergistic interaction between Ni and the ZrO2 support causes the variations in the reaction rates. Adsorption of the carboxylic acid group on an oxygen vacancy of ZrO2 and the abstraction of the α‐hydrogen atom with the elimination of the oxygen atom to produce a ketene is the key to enhance the overall rate. The hydrogenated intermediate 1‐octadecanol is in turn decarbonylated to heptadecane with identical rates on all catalysts. Decarbonylation of 1‐octadecanol is concluded to be limited by the competitive adsorption of reactants and intermediate. The substantially higher adsorption of propionic acid demonstrated by IR spectroscopy and the higher reactivity to O2 exchange reactions with the more active catalyst indicate that the higher concentration of active oxygen defects on m‐ZrO2 compared to t‐ZrO2 causes the higher activity of Ni/m‐ZrO2. 相似文献