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排序方式: 共有47条查询结果,搜索用时 15 毫秒
1.
Yu. V. Shaldin S. Matyjasik N. E. Novikova M. Tseitlin E. Mozhaev M. Roth 《Crystallography Reports》2010,55(6):1012-1018
The temperature dependences of the pyroelectric coefficients of KTiOAsO4 and RbTiOAsO4 single crystals grown by flux crystallization have been investigated in the temperature range of 4.2–300 K. With an increase
in temperature, superionic conductivity first arises in KTiOAsO4 (at T > 200 K) and then (at T > 270 K) in RbTiOAsO4. This conductivity is much higher in the samples polarized at T = 4.2 K. An exponential change in the crystal resistivity along the polar direction is simultaneously observed. The results
of measurements in the range of 4.2–200 K indicate larger values of pyroelectric coefficients when compared with potassium
and rubidium titanyl-phosphate crystals. A correlation between the pyroelectric coefficients and a change in the lattice constants
at isomorphic substitutions of K atoms for Rb and P atoms for As has been revealed within the symmetry approach. 相似文献
2.
V.M. Polyaev A.P. Mozhaev B.M. Galitseysky A.L. Lozhkin 《Experimental Thermal and Fluid Science》1996,12(4):426-432
The results of theoretical and experimental studies of heat transfer and pressure drop in nonuniform porous materials and systems are presented. In experiments, measurements were made of the air flow rate, inlet and outlet air pressures, and air and porous sample temperatures. Experimental determination of the heat transfer coefficient in porous structures is associated with certain difficulties. The problem of determining a temperature difference between coolant and porous skeleton is the most complex. As a rule, under laboratory conditions this difference is small and cannot be found with sufficient accuracy. In the present work, the method of determination of the internal heat transfer coefficient is based on solving the inverse unsteady heat transfer problem for porous structures. Using this approach, the heat transfer coefficient is calculated indirectly or on the basis of the porous material temperature variation over time. 相似文献
3.
I. K. Bdikin A. D. Mashtakov P. B. Mozhaev G. A. Ovsyannikov 《Physics of the Solid State》1998,40(4):558-560
X-ray diffraction is used to investigate YBa2Cu3O7?x (YBCO) films on NdGaO3(110) and a ${{(100)CeO_2 } \mathord{\left/ {\vphantom {{(100)CeO_2 } {(1\bar 102)}}} \right. \kern-0em} {(1\bar 102)}}Al_2 O_3 $ heterostructure. Symmetric, asymmetric, and axial geometries for θ and θ/2θ scans are used to obtain diffraction spectra from different crystallographic planes. The orientational and quantitative twinning characteristics of the films are determined. While the crystallographic parameters of these two types of film (the films are c-axis oriented with c=11.67 Å) are similar, there are differences in the twin structure. In particular, the features of the NdGaO3 structure lead to the appearance of an angle differing from 90° (90.20°) between the possible (110) and θ/2θ twin planes in a YBCO film and a different number of twin components in each system of twins. It is concluded from an analysis of the broadening of reflections, which are sensitive to twinning, that there is not twinning in a 60% film of YBCO on Al2O3 with a CeO2 buffer layer. 相似文献
4.
P. A. Nikul’shin A. V. Mozhaev D. I. Ishutenko P. P. Minaev A. I. Lyashenko A. A. Pimerzin 《Kinetics and Catalysis》2012,53(5):620-631
Using the Anderson-type heteropoly compounds (HPCs) [X(OH)6Mo6O18] n− (X = Co, Ni, Mn, Zn) and [Co2Mo10O38H4]6− and cobalt (or nickel) nitrate, XMo/Al2O3 and Co(Ni)-XMo/Al2O3 catalysts were prepared. The catalysts were studied by low-temperature nitrogen adsorption, X-ray diffraction, and high-resolution transmission electron microscopy. The average length of the active-phase particles of the catalysts was 3.5 to 3.9 nm, and the average number of MoS2 layers in a packet was 1.4 to 2.1. The catalytic properties of the samples, which were estimated in dibenzothiophene (DBT) hydrodesulfurization and in the hydrotreating of the diesel fraction, are considerably dependent upon both the type and composition of the HPC, and the nature of the applied promoter (Ni or Co). As compared to the Ni-promoted catalysts, the Co-promoted samples exhibit a higher desulfurization activity, whereas the hydrogenation ability of the Ni-XMo/Al2O3 catalysts surpasses that of the Co-XMo/Al2O3 ones. The catalytic properties depend on the morphology of the nanostructured active phase. With a growing number of MoS2 layers in the packet of the catalysts’ active phase, the DBT hydrodesulfurization rate constants for both the direct desulfurization route and the preliminary hydrogenation rote rise linearly and the selectivity falls linearly for the hydrogenation route. The selectivity of Ni-XMo/Al2O3 decreases to a greater extent than that of Co-XMo/Al2O3. The dependences of the catalytic properties on the morphology of the catalysts’ active phase are consistent with the “dynamic” model of the functioning of the active sites of transition metal sulfides. 相似文献
5.
S. I. Kuzina P. S. Mozhaev D. P. Kiryukhin A. I. Mikhailov I. M. Barkalov 《Russian Chemical Bulletin》1996,45(4):814-818
The photolysis of solid hydrogen cyanide and the effects of UV light on60Co--irradiated HCN at 77 K were studied using an ESR technique. As in the case of radiolysis, the HZ2C=N radical formed due to sticking of the H atom to the triple bond of the HCN molecule is the main radical product of low-temperature HCN photolysis. The C=N– radicals are accumulated at 77 K in insignificant amounts (3 %). It was established that radical and ionic products stabilized in y-irradiated HCN possess photochromism and under the action of UV light enter photochemical reactions leading to their decomposition. Upon photobleaching, the concentration of H2C=N– radicals first increases two- to threefold because of the decomposition of H2C=N– ions and then decreases. The presence of radicals and ions formed upon the low-temperature radiolysis of HCN broadens the optical absorption band of the system, and the boundary of the action spectrum shifts from 280 nm (for nonirradiated HCN) to the visible region at 400–440 nm.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 859–863, April, 1996. 相似文献
6.
E. Kemnitz A. A. Galkin T. Olesch S. Scheurell A. P. Mozhaev G. N. Mazo 《Journal of Thermal Analysis and Calorimetry》1997,48(5):997-1010
The oxygen diffusion and exchange behaviour of NdBa2Cu3O7–x is investigated by means of isothermal and dynamic-thermal analytical techniques. From the results it is concluded that oxygen anions move along vacancies in the CuO2-layers of the perovskite-like structure. In temperature regions where the diffusion rate is low (665 K<T<773 K) heterogeneous oxygen exchange reactions take place on the phase boundary. The higher the exchange rate the more the partially heterogeneous exchange is favoured in comparison to the completely heterogeneous isotope exchange. Depending on the oxygen deficiency of NdBa2Cu3O7–x the out-diffusion of oxygen becomes dominating at higher temperatures. 相似文献
7.
A discrete computer model of multistage processes of formation of porous clusters in a crystalline matrix is developed and
constructed. A package of computer programs simulating dynamic processes of formation of a cluster in the bulk of crystals
is developed taking into account the processes occurring at the surface, external fields, and chemical reactions accompanying
these processes. The morphological pattern of formed pores is correlated with the regularities associated with the shape of
the current-voltage characteristic of anodization. 相似文献
8.
Reflection of bulk acoustic waves in a TeO2 acoustooptic single crystal is studied for the case of a grazing incidence on the free crystal-vacuum boundary. The propagation and reflection of elastic waves is considered in the XOY plane of the material cut out in the form of a rectangular prism. An extraordinary case of reflection at the grazing incidence, when the energy flow of one of the two reflected waves in the crystal is directed opposite to that of the incident wave, is studied. It is shown that the transformation of the incident elastic energy into the energy of the backward-reflected wave can occur with an efficiency close to 100% and can be observed in a wide range of crystal cut angles. An abrupt change of the reflection coefficients in the vicinity of the critical angle is predicted. 相似文献
9.
Use of time-of-flight mass spectrometry for monitoring helium microcontamination in the industrial manufacture of extra high purity inert gases 总被引:1,自引:0,他引:1
V. T. Zhdan A. V. Kozlovskii A. N. Mozhaev I. I. Pilyugin 《Journal of Analytical Chemistry》2010,65(14):1532-1536
A time-of-flight EMG-20-9 mass spectrometer was designed for the online monitoring of helium impurity at the 0.05 ppm level.
The spectrometer was introduced for the continuous control of the gas mixture composition in the technology of neon purification
from the helium impurity in spite of the large difference in the concentrations of components. The instrument was certified
as a measuring facility and introduced into the State Register of Measurement Instrumentation of the Russian Federation. The
characteristics of the mass spectrometer and its modifications were overviewed and its possibilities for monitoring xenon
and krypton production from air were shown. 相似文献
10.