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1.
The effect of the removal of zinc from brass nanoparticles has been experimentally discovered upon irradiating their suspension in ethanol by laser radiation. The analysis of the absorption spectra of nanoparticles shows that brass nanoparticles are transformed to copper nanoparticles during irradiation. The results are interpreted in terms of the high-pressure-induced modification of the phase diagram of nanoparticles. This pressure is caused by, first, the small radius of nanoparticles and, second, the pressure of the surrounding-liquid vapors upon the laser heating of nanoparticles. 相似文献
2.
S. I. Dolgaev A. A. Lyalin G. A. Shafeev Shafeev Voronov 《Applied Physics A: Materials Science & Processing》1996,63(1):75-79
The etching of polycrystalline SiC is studied with the help of radiation of a copper-vapor laser either in air or under the layer of a liquid (H2O, DMSO). The etching rate in air is as high as 0.24 m/pulse, in DMSO 0.07 gm/pulse at an energy density of 16 J/cm2. The etched surface is characterized with Scanning Electron Microscopy (SEM) and X-ray diffractometry. Etching of SiC ceramics in air revealed the partial amorphization of SiC and the formation of microcrystals of elementary Si with an average size of 300 Å. The etched surface of SiC ceramics takes on the ability to reduce Cu from a corresponding electroless plating solution. The adherence of the deposit is as high as 30 N/mm2 and is a function of the scanning velocity of the laser beam. 相似文献
3.
2-Trifluoromethyl-4H-thiochromene-4-thione obtained from 2-trifluoromethyl-4H-thiochromen-4-one and P2S5 reacts with aromatic amines, hydrazine hydrate, phenylhydrazine, and hydroxylamine at the C(4) atom of the chromene ring
to give the corresponding anils, azine, hydrazones, and oxime of thiochromone. 2-Trifluoromethyl-4H-thiochromen-4-one is oxidized by hydrogen peroxide in AcOH into 4-oxo-2-trifluoromethyl-4H-thiochromene 1,1-dioxide and reduced by NaBH4 to 2-trifluoromethyl-4H-thiochromen-4-ol or cis-2-(trifluoromethyl)thiochroman-4-ol. When treated with hydrazine hydrate, thiochromen-4-one gives 3(5)-(2-mercaptophenyl)-5(3)-trifluoromethylpyrazole.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 504–509, March, 2006. 相似文献
4.
S. F. Timashev A. V. Simakin G. A. Shafeev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(11):1980-1988
A brief review of results on initiation of nuclear transformations under conditions of the laser ablation of metals in aqueous media upon exposure to picosecond laser impulses with peak intensity J E ~ 1010–1013 W/cm2, which is orders of magnitude less than required for the direct initiation of nuclear processes, J E ~ 1018–1019 W/cm2, is presented. It is shown that the decay rate of radioactive nuclei (using the example of uranium 238) increases significantly (by orders of magnitude), nucleus transmutation processes are initiated (using the example of the transmutation of mercury 196 nuclei into gold 197), and the nuclear fusion of light elements occurs (using the example of tritium nuclei) under such conditions. Concepts regarding the processes of inelastic (with the generation of neutrino-antineutrino pair) interactions between electrons of high (on the chemical scale) energies (~5–10 eV) and nuclei are developed in order to understand the totality of the current experimental data on the initiation of such processes under conditions of the laser ablation of metals in solutions of ordinary and heavy water. This is reflected in the definition of such processes as nuclear-chemical. It is suggested that the state of nuclear matter in nuclei formed during such interactions is in an unbalanced in-shake-up state, and cannot be pictured in the standard manner, as an ensemble of a certain number of nucleons. Such states are reactive for a wide class of nuclear transformations. 相似文献
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6.
Boris I. Usachev Vyacheslav Ya. Sosnovskikh Mikhail A. Shafeev Gerd-Volker Röschenthaler 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1315-1319
Abstract Alkyl 2-mercaptophenyl ketones react with trifluoroacetic anhydride in the presence of triethylamine to give 2-(trifluoromethyl)-4H-thiochromen-4-ones, which are transformed into the corresponding pyrazoles by treatment with hydrazine hydrate and into 1,1-dioxides by oxidation with H2O2 in AcOH. 相似文献
7.
Laser irradiation of suspensions of Hg nanodrops in D2O induces partial transformation of Hg into Au. The Hg-Au conversion depends on the characteristics of the laser source used
(Cu vapor, femtosecond Ti:sapphire, 90-ps Nd:YAG, 350-ps Nd:YAG) and on the initial Hg isotopic composition. For Hg of natural
isotopic composition, the conversion gives the 196Hg content close to initial (0.15%). Starting with 196Hg-enriched (52%) Hg, the conversion yields 10 %. This transmutation is assigned to the generation of thermal neutrons during
laser exposure of Hg nanodrops in D2O. Possible mechanisms of neutron release are discussed. 相似文献
8.
A.V. Simakin E.N. Loubnin G.A. Shafeev 《Applied Physics A: Materials Science & Processing》1999,69(7):S267-S269
A novel effect is studied of self-limitation of the diamond-like film thickness during laser irradiation of the interface of transparent substrates with liquid aromatic hydrocarbons. The interface is exposed through the transparent substrate to radiation of a copper vapor laser (wavelength of 510.6 nm, pulse duration of 20 ns). The thickness of diamond-like film increases linearly to 80-100 nm with the number of laser pulses and then saturates, while the substrate is ablated with nearly constant rate. This ablation rate depends on the thermal expansion coefficient of the substrate (glass, fused silica, sapphire, or CaF2). The absorption of extinction coefficient of deposited films measured by ellipsometry is of order of 104 cm-1 and is sufficient to cause the significant heating of the interface. The ablation of the transparent substrates is due to their unequal thermal expansion compared to the diamond-like film having different thermal expansion coefficient. The measured ablation rates scale from 0.2 Å/pulse for glass to 4.5 Å/pulse for CaF2. A 7m spatial resolution of the ablation process has been demonstrated for fused silica. 相似文献
9.
A.V. Simakin V.V. Voronov N.A. Kirichenko G.A. Shafeev 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1127-1132
A review of results on nanoparticles formation is presented under laser ablation of Ag, Au, and Ti solids targets in liquid environments (H2O, C2H5OH, C2H4Cl2, etc.). X-ray diffractometry (XRD), UV-Vis optical transmission spectrometry, and high-resolution transmission electron microscopy (HRTEM) characterise the nanoparticles. The morphology of nanoparticles is studied as a function of both laser fluence and nature of the liquid. The evidence of an intermediate phase of Au-Ag alloy is presented under exposure of a mixture of individual nanoparticles to laser radiation. Self-influence of the beam of a femtosecond laser is discussed under the ablation of the Ag target in liquids under Ti:sapphire laser. The factors are discussed that determine the distribution function of particle size under laser ablation. The influence of laser parameters as well as the nature on the liquid on the properties of nanoparticles is elucidated. PACS 42.62.-b; 61.46.+w; 78.66.-w 相似文献
10.
Laser-induced accelerated alpha-decay of 232U nuclei under laser exposure of Au nanoparticles in aqueous solutions of uranium salt has been experimentally studied. It is demonstrated that the decrease in the alpha-activity depends strongly on the peak intensity of laser radiation in the liquid and reaches a maximum at 1012–1013Wcm?2. The decrease in the alpha-activity of the exposed solutions is accompanied by deviation of gamma-activities of daughter nuclides of 232U from their equilibrium values. Experimental data on the accelerated alpha-decay of 238U under similar experimental conditions are also presented. Possible mechanisms of laser effect on the alpha-activity are discussed in terms of the amplification of the electric field of laser wave on metallic nanoparticles. 相似文献