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1.
V. I. Vettegren V. A. Marikhin V. B. Kulik L. S. Titenkov 《Physics of the Solid State》2002,44(12):2341-2346
The temperature dependence of the expansion ?C of trans conformers of the carbon skeleton of macromolecules in crystallized and amorphous poly(ethylene terephthalate) (PET) due to zero-point and thermal atomic vibrations is investigated by IR spectroscopy. It is found that the thermal expansion coefficient βC jumpwise increases at the characteristic temperatures T t and T b. This increase is associated with the crossover from the quantum to classical statistics of torsional and bending vibration modes. The quantum and classical contributions to the expansion ?C are determined for each mode. The quantum and classical contributions of the torsional vibrational mode in the amorphous polymer are approximately 1.5 times larger than those in the crystallized polymer. This effect is caused by an increase in the anharmonicity of torsional vibrations in the amorphous polymer. 相似文献
2.
M. E. Kompan I. I. Novak V. B. Kulik 《Journal of Experimental and Theoretical Physics》2002,94(4):739-744
Spectra of second-order Raman scattering in porous silicon are investigated. A band shift towards lower energies in second-order spectra is observed, as well as the correlation between the values of band shift in first-and second-order spectra. It is demonstrated that the observed effect cannot be interpreted using the conventional concepts of the mechanisms of scattering in microcrystalline samples. An interpretation of the revealed effect is suggested. 相似文献
3.
V. I. Kulik E. V. Meshkov A. S. Nilov Z. T. Upitis 《Mechanics of Composite Materials》1991,27(2):159-166
4.
(Fe,Co)–Zr,Hf)–Cu–B (HITPERM-type) alloys with variable Hf, Zr and Co content were isothermally crystallised at 500–650 °C for 1 h, and the optimum nanocrystallisation temperature was selected on the basis of the minimum coercive field at room temperature. The quasistatic hysteresis loops were measured at temperature from 20 to 650 °C. Subsequently, the optimally annealed alloys were subjected to long-term annealing at 500, 550 and 600 °C. Working temperature of 600°C is too high for the investigated alloys to maintain stable magnetic properties. Temperature of 550 or 500 °C permits the material to be magnetically stable for a long period. The magnetic hysteresis loops recorded for the nanocrystalline alloys, where Fe:Co ratio is close to 1 and refractory metals content is 7 at.%, prove that coercive field increases slightly with temperature, but remains in the range of 20–40 A/m (depending on the alloy composition) from 20 to 550 °C. This proves that the investigated alloys, after optimisation of chemical composition, may be suitable for high temperature use. 相似文献
5.
A new Co–Fe-based ferromagnetic bulk metallic glass (BMG) was synthesized by copper mould casting method. The thermal stability and crystallization processes were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The soft magnetic behavior was studied by DC magnetic measurements. The high glass formation ability was interpreted in terms of the effective suppression of nucleation and growth of the intermetallic compounds which appear in the multicomponent system during solidification. The high thermal stability indicates that the new Co–Fe-based BMG could be used as high-temperature magnetic material. The low coercivity which was as low as 8 A/m for the as-cast sample was found in the Co–Fe-based metallic glass cylinder with a diameter of 1.5 mm. 相似文献
6.
Irradiation of suspensions of CdS in water-ethanol mixtures containing nibrobenzene with light at > 320 run does not in practical terms lead to the reduction of the nitrobenzene to aniline. It has been shown that the formation of aniline occurs when solvato complexes of vanadium(III) (PhNH2=18.1·10–3) and vanadium(IV) (PhNH2= 2.84·10–3) are added to the system. The photocatalytic reduction of nitrobenzene is accompanied by oxidation of the alcohol to acetaldehyde and acetal. The proposed process mechanism includes stages and acceptance of an electron photogenerated in the semiconductor by vanadium compounds and of a hole by molecules of the alcohol and subsequent stages of reaction of the reduced forms of vanadium, and also of the ethoxy radicals with nitrobenzene, which leads to its reduction.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 550–557, September–October, 1989. 相似文献
7.
A. I. Kryukov S. Ya. Kuchmii A. V. Korzhak N. F. Guba S. V. Kulik 《Theoretical and Experimental Chemistry》1994,29(3):182-184
We have obtained new semiconductor materials with microheterojunctions by substitution of surface cadmium ions in CdS by Cu(I), Cu(II), and Bi(III) ions. We have shown that the photocatalytic activity of their dispersions in the reaction of evolution of H2 from alcohol-water mixtures is considerably higher than in the original cadmium sulfide.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 3, pp. 270–274, May–June, 1993.We would like to acknowledge Academician V. D. Pokhodenko of the Academy of Sciences of Ukraine for drawing our attention to the prospects for investigation of complex photocatalytic systems based on semiconductors with different types of conductivity. 相似文献
8.
V. R. Khabibulin A. V. Kulik I. V. Oshanina L. G. Bruk O. N. Temkin V. M. Nosova Yu. A. Ustynyuk V. K. Bel’skii A. I. Stash K. A. Lysenko M. Yu. Antipin 《Kinetics and Catalysis》2007,48(2):228-244
The formation mechanism of the active catalyst in the oxidative carbonylation of terminal alkynes at the ≡C-H bond has been investigated for the catalytic system Pd(OAc)2-PPh3-p-benzoquinone (Q)-MeOH. It has been demonstrated by NMR spectroscopy, X-ray crystallography, and kinetic measurements that the catalytically active palladium is in the oxidation state 0 and is bound into complexes stabilized by p-benzoquinone (PdL2Q, where L = PPh3). A mechanism is suggested for the catalytic process, which includes the formation of the complex PdL2Q, the oxidative addition of the alkyne to this complex at the ≡C-H bond, the insertion of CO into the Pd-C bond, and steps in which hydride hydrogen is intramolecularly transferred to the p-quinone. 相似文献
9.
T. V. Kulik V. N. Barvinchenko B. B. Palyanitsa O. V. Smirnova V. K. Pogorelyi A. A. Chuiko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(1):83-90
The interaction of cinnamic acid with the surface of highly dispersed silica is studied. The mechanisms of adsorption, chemisorption, and thermal transformations of cinnamic acid on the silica surface are proposed. The kinetic parameters of the chemical reactions on the surface of silica are calculated. 相似文献
10.
A comparative study of anisotropic relaxation in two-pulse primary and three-pulse stimulated electron spin echo decays provides a direct way to distinguish fast (correlation time tau(c)<10(-6) s) and slow (tau(c)>10(-6) s) motions. Anisotropic relaxation is detected as a difference of the decay rates for different resonance field positions in anisotropic electron paramagnetic resonance spectra. For fast motion anisotropic relaxation influences the primary echo decay and does not influence the stimulated echo decay. For slow motion it is seen in both two-pulse echo and three-pulse stimulated echo decays. For nitroxide spin probes dissolved in glassy glycerol only fast motion was found below 200 K. Increase of temperature above 200 K results in the appearance of slow motion. Its amplitude increases rapidly with temperature increase. While in glycerol glass slow motion appears above glass transition temperature T(g), in ethanol glass it is observable below T(g). The scenario of motional dynamics in glasses is proposed which involves the broadening of the correlation time distribution with increasing temperature. 相似文献