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1.
André Ricard Jean-Philippe Sarrette Soo-Ghee Oh Yu Kwon Kim 《Plasma Chemistry and Plasma Processing》2016,36(6):1559-1570
We report a detailed comparison between RF and microwave (HF) plasmas of N2 and Ar–20 %N2 as well as in the corresponding afterglows by comparing densities of active species at nearly the same discharge conditions of tube diameter (5–6 mm), gas pressure (6–8 Torr), flow rate (0.6–1.0 slm) and applied power (50–150 W). The analysis reveals an interesting difference between the two cases; the length of the RF plasma (~25 cm) is measured to be much longer than that of HF (6 cm). This ensures a much longer residence time (10?2 s) of the active species in the N2 RF plasma [compared to that (10?3 s) of HF], providing a condition for an efficient vibrational excitation of N2(X, v) by (V–V) climbing-up processes, making the RF plasma more vibrationally excited than the HF one. As a result of high V–V plasma excitation in RF, the densities of the vibrationally excited N2(X, v > 13) molecules are higher in the RF afterglow than in the HF afterglow. Destruction of N2(X, v) due to the tube wall is estimated to be very similar between the two system as can be inferred from the γv destruction probability of N2(X, v > 3–13) on the tube wall (2–3 × 10?3 for both cases) obtained from a comparison between the density of N2(X, v > 3–9) in the plasmas to that of the N2(X, v > 13) in the long afterglows. Interestingly enough, densities of N-atoms and N2(A) metastable molecules in the afterglow regions, however, are measured to be very similar with each other. The measured lower density of N2 + ions than expected in the HF afterglow is rationalized from a high oxygen impurity in our HF setup since N2 + ions are very sensitive to oxygen impurity . 相似文献
2.
ZHU Chuan-Zheng YANG Bao-Lin ZHAO Hong GU Wen-Xiu AI Shi-YunDepartment of Chemistry East China Normal University Shanghai China 《中国化学》1997,15(1):68-75
The dissociation constant of each step for TB-chlorosulphophenol has been determined by potentiometric method, and the thermodynamic constants, △G°, △H° and △S°, of the dissociation process have been calculated. The protonation constants were measured by the spectrophotometric method. The pH values of various forms of anions of the chromogenic reagent at their concentrations were also calculated. 相似文献
3.
L. T. Denisova Yu. F. Kargin L. T. Chumilina V. M. Denisov K. S. Gavrichev M. A. Ryumin A. V. Tyurin 《Russian Journal of Inorganic Chemistry》2016,61(1):1-6
The heat capacity of TbVO4 has been measured by the adiabatic calorimetry (5–346 K) and differential scanning calorimetry (344–859 K) methods. The Cp = f(T) plot has an extreme point (32 K). The thermodynamic properties of the oxide compounds have been calculated from the experimental data. A general equation that describes the heat capacity of terbium orthovanadate as a function of temperature in the range 35–859 K has been derived. 相似文献
4.
Xiao-Qing Yang Li-Jun Yang Ka-Ma Huang Wen-Yan Tian Hui Shang 《Journal of solution chemistry》2010,39(6):849-856
This paper focuses on the measurement of the permittivity of dimethyl sulfoxide (DMSO)–water (H2O) mixture solutions, at 2.45 GHz by using a resonant cavity perturbation method. A specific phenomenon was found, in that
the imaginary part of the permittivity for the mixture solution was larger than the imaginary part for each component. Theoretical
calculation indicated that the reason for that phenomenon was that the high frequency friction of the mixture was larger than
that of each component. When comparing the theoretical results with the experimental data, it was found that the classical
Debye equation must be modified in order to calculate the complex permittivity. 相似文献
5.
Leszek Rycerz Ewa Ingier-Stocka Slobodan Gadzuric Marcelle Gaune-Escard 《Journal of Thermal Analysis and Calorimetry》2010,101(2):455-461
Differential Scanning Calorimetry was used to study phase equilibrium in EuBr2–RbBr binary system. It was established that this system includes two eutectics and three stoichiometric compounds. First
of them, Rb2EuBr4, decomposes peritectically at 778 K. Second one, RbEuBr3, undergoes the solid–solid phase transition at 732 K and melts incongruently at 852 K. Third compound, RbEu2Br5, melts congruently at 888 K. The composition and temperature values of eutectics were determined as x(EuBr2) = 0.316; T
eut = 776 K and x(EuBr2) = 0.797; T
eut = 859 K. Mixing enthalpy was measured by direct calorimetry on the whole composition range. The minimum of the mixing enthalpy
occurs around the composition x(EuBr2) ≈ 0.4. The electrical conductivity of liquid mixtures was also investigated over the whole composition range and measured
down to temperatures below solidification. The specific conductance (liquid phase) plotted against the mole fraction of EuBr2 shows a broad minimum at x(EuBr2) ~ 0.6. The activation energy for conductivity changes with temperature. Results obtained are discussed in terms of possible
complex formation. 相似文献
6.
T.L. Egorova M.V. Kalinina E.P. Simonenko N.P. Simonenko G.P. Kopitsa O.V. Glumov N.A. Mel’nikova I.V. Murin L. Almásy O.A. Shilova 《Russian Journal of Inorganic Chemistry》2017,62(10):1275-1285
Two alternative chemical synthesis methods—cryotechnological coprecipitation of hydroxides and cocrystallization of salts—were used for preparing (CeO2)1–x (Y2O3) x nanopowders (x = 0.10, 0.15, 0.20) with a mean coherent scattering domain size of ~7–11 nm and S sp = 2.1–97.5 m2/g. From these nanopowders, ceramic nanomaterials with mean coherent scattering domain sizes of ~61–85 nm were synthesized. It was studied how the phase composition, microstructure, and electrical transport properties of the produced samples depend on the Y2O3 content of a CeO2-based solid solution and on the synthesis method. It was shown that, in the series (CeO2)1–x (Y2O3) x (x = 0.10, 0.15, 0.20), the solid solution (CeO2)0.90(Y2O3)0.10 has the highest ionic conductivity with the ion transport number t i = 0.73 (600°C). In its physicochemical characteristics, this ceramic can be used as a solid electrolyte of intermediate-temperature fuel cells. 相似文献
7.
N. Mabrouk H. Berriche 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(8):1474-1485
Calculations of the adiabatic potential energy curves and the transition dipole moments between the ground (A1Σ+) and the first excited (A1Σ+) states have been determined for the LiCs and NaCs molecules. The calculations are performed using an ab initio approach based on non-empirical pseudopotentials for Cs+, Li+ and Na+ cores, parameterized l-dependent polarization potentials and full configuration interaction calculations. The potential energy curves and the transition dipole moment are used to estimate the radiative lifetimes of the vibrational levels of the A+Σ+ state using the Franck–Condon (FC) approximation and the approximate sum rule method. The radiative lifetimes associated with the A+Σ+ state are presented here for the first time. These data can help experimentalists to optimize photoassociative formation of ultracold molecules and their longevity in a trap or in an optical lattice. 相似文献
8.
Russian Chemical Bulletin - 相似文献
9.
A. A. Komlev V. V. Panchuk V. G. Semenov O. V. Almjasheva V. V. Gusarov 《Russian Journal of Applied Chemistry》2016,89(12):1932-1938
Specific features of the process in which oxide nanopowders are formed in a hydrothermal treatment of coprecipitated magnesium and iron oxides were studied. It was shown that the rate at which oxide nanoparticles are formed increases when reagents structurally close to the final product are used. It was found that, with the hydrothermal treatment of coprecipitated magnesium and iron hydroxides at 450°C combined with the subsequent thermal treatment in air at temperatures of 400–600°C, it is possible to obtain a homogeneous mixture of nanocrystalline powders based on an iron-containing spinel phase and magnesium oxide. 相似文献
10.
O. B. Bel’skaya O. V. Maevskaya A. B. Arbuzov T. V. Kireeva V. K. Duplyakin V. A. Likholobov 《Kinetics and Catalysis》2010,51(1):98-104
The interaction of platinum(IV) and palladium(II) chloro complexes with the γ-Al2O3 surface in a wide range of surface metal concentrations is reported. Varying the concentration of the adsorbed metal complex
on the alumina surface causes changes both in the proportions of weakly and strongly bound desorbable platinum species and
in the proportions of desorbable (ion-exchanged) and nondesorbable (coordinatively bound) complexes. The adsorbed palladium
complexes are more uniform in chemical composition and binding strength and consist largely of desorbable species removable
from the surface by competitive sorption of anions. The absolute amount of coordinatively bound platinum and palladium species
increases as the total metal content of the sample is raised to 1.0% and remains almost invariable at higher metal contents. 相似文献
11.
Garrigosa AM Ariño C Díaz-Cruz JM Esteban M 《Analytical and bioanalytical chemistry》2008,391(6):2209-2218
A comparison of a differential pulse polarographic with a phase sensitive alternating current polarographic study of the Cd-Cys-Gly
and Cd-PC2 systems [PC2 being a phytochelatin of general structure (γ-Glu-Cys)
n
-Gly, with n = 2] has been performed. The chemometric multivariate curve resolution method with alternating least squares was applied
in the experimental data analysis. The results obtained by both polarographic techniques have made it possible to find out
the formation sequences of the complexes and their final stoichiometries. The alternating current polarograms compared with
the differential pulse ones show some differences (a new signal and an important shift of peak potentials), which anyway are
consistent with some of the conclusions obtained by differential pulse polarography. This fact implies that although the alternating
current polarography results need some corrections before data treatment, they provide extra information that complements
the conclusions achieved by differential pulse polarography.
Figure Voltammograms at ACP(−10°), ACP(−65°) and corrected ACP during the titration of a 10−5 mol L−1 Cd(II) solution with PC2 at pH 8.5 in 0.05 L−1 Tris. 相似文献
12.
M. I. Afanasov P. B. Fabrichnyi M. V. Korolenko T. M. Ivanova 《Russian Journal of Inorganic Chemistry》2008,53(8):1288-1291
Analysis of the Mössbauer spectra of dopant 119Sn in cubic MgO has demonstrated that the Sn2+ ions can be stabilized on the surface of crystallites of an oxide with a structure differing from the corundum structure. The Mössbauer parameters (at 100 K, the isomer shift is δ = 2.50 ± 0.01 mm/s and the quadrupole splitting is Δ = 2.30 ± 0.02 mm/s) point to the stereochemical activity of the lone pair of Sn2+. Being in contact with oxygen at 295 K, tin is rapidly converted to the tetravalent state (δ = 0.08 ± 0.01 mms, Δ = 0.58 ± 0.01 mm/s). The lack of formation of Sn2+ on the surface of another cubic oxide (MnO) can be explained by rapid segregation of tin from the bulk of crystallites as stannate clusters. 相似文献
13.
P. P. Fedorov M. N. Mayakova S. V. Kuznetsov V. A. Maslov N. I. Sorokin A. E. Baranchikov V. K. Ivanov A. A. Pynenkov M. A. Uslamina K. N. Nishchev 《Russian Journal of Inorganic Chemistry》2016,61(11):1472-1478
The phase diagram of the NaF–CaF2 system was studied by thermal analysis and X-ray powder diffraction analysis with the determination of the chemical composition. The system was found to be of the eutectic type. A narrow range of the existence of solid solution Ca1–xNaxF2–x was established. The NaF solubility reaches a maximal value of x = 0.035 at 1200 ± 50°C (the temperature at which there is a diffuse phase transition in fluorite). At 920 ± 25°C, the NaF solubility reaches a minimum (<0.4 mol %) and increases again to 2.2 ± 0.2 mol % at a eutectic temperature (818°C). The ionic conductivity increases by three orders of magnitude after adding NaF to CaF2. 相似文献
14.
Summary. The CD exciton chirality method was applied to various phenylacetylene alcohols to determine their absolute configurations; the long axis polarized –* transition (max=252nm) of the 4-methoxyphenylacetylene chromophore couples with the transition (max=257nm) of the 4-methoxybenzoate group to generate intense exciton split CD Cotton effects, from the signs of which the absolute configurations of phenylacetylene alcohols were unambiguously determined. As an extension of the results, a new methodology for determining the absolute configurations of acetylene alcohols having the HCCCH(OH)-moiety by combination of the Sonogashira reaction and the CD exciton chirality method has been developed and applied. Since the –* transition of acetylene triple bond is located below 180nm, it is difficult to observe ideal bisignate CD Cotton effects due to the exciton coupling between acetylene and benzoate chromophores. To observe the ideal exciton split Cotton effects necessary for the unambiguous determination of absolute configuration, the terminal acetylene group was converted, by the Sonogashira reaction, to the 4-methoxyphenylacetylene moiety, which exhibits an intense –* absorption band polarized along the long axis of the chromophore at 252nm. As a partner of exciton coupling, 4-methoxybenzoate showing a –* band at 257nm was introduced into the alcohol moiety, and the benzoates formed showed intense bisignate CD Cotton effects, from the signs of which the absolute configurations of original acetylene alcohols could be determined in an unambiguous manner. 相似文献
15.
T. I. Krasnenko R. F. Samigullina M. V. Rotermel I. V. Nikolaenko N. A. Zaitseva A. V. Ishchenko T. A. Onufrieva 《Russian Journal of Inorganic Chemistry》2017,62(3):269-274
A promising yellow phosphor, α-Zn2V2O7, was synthesized at temperatures below the phase transition temperature (610 ± 5°C) by three different methods: solid-phase and microwave processes and thermolysis of a water–salt composition. According to powder X-ray diffraction, the structures of all samples belonged to space group C/2c. Depending on the method of synthesis, the particle size varied from 500 nm (thermolysis of a water–salt composition) to 5–8 μm (ceramic and microwave methods). The excitation spectra of all samples are in the UV region (220–400 nm) and the emission spectra are in the 400–750 nm wavelength range. The photoluminescence spectra of the samples are non-elementary, which is caused by specific features of the electronic charge transfer in the structural VO4 tetrahedra. 相似文献
16.
V. M. Bondareva E. V. Ishchenko T. Yu. Kardash A. V. Ishchenko V. I. Sobolev 《Russian Journal of Applied Chemistry》2016,89(8):1279-1285
Supported oxide catalysts of the overall composition V0.3Mo1Te0.23Nb0.12/n SiO2 (n = 0, 10, 25, 35, and 50 wt %) were tested in oxidative conversion of ethane to ethylene and were characterized by chemical analysis, X-ray diffraction, and high-resolution transmission electron microscopy. On introducing SiO2, coarse crystals of the active М1 phase become partially coated with layers of amorphous SiO2. The support does not influence the selectivity with respect to the reaction products. The catalysts with 10–25 wt % SiO2 content exhibit the highest activity owing to the presence of nanodomains of the M1 phase. 相似文献
17.
The high-field 19F and 91Zr NMR method is used to study the hydrolysis and polycondensation of hexafluorozirconate ZrF62− in aqueous and water-peroxide solutions. During hydrolysis in aqueous solutions only ZrF62− and F− ions were observed by NMR, however, in the water-peroxide medium, an intermediate product of hydrolysis ([F5Zr-OO-ZrF5]4− dimer) was detected. The dimer structure is confirmed by 19F and 91Zr NMR. In high fields (19F NMR frequency > 200 MHz), the fluorine exchange between ZrF62− and F− is slow in the 19F NMR scale and has a multisite character. 相似文献
18.
E. A. Miroshnichenko T. S. Kon’kova Ya. O. Inozemtsev Yu. N. Matyushin 《Russian Chemical Bulletin》2011,60(1):36-41
Based on the experimentally determined values and published data, the enthalpies of formation of nitroalkanes C4–C7 in the standard state and in the gas phase were recommended. The dissociation energies of bonds in these compounds were determined
taking into account the enthalpies of atomization and the energies of nonvalent interactions of nitro groups with one another.
The calculated values were compared with the available thermal decomposition kinetic data. The dissociation energies of bonds
in C4–C7 nitroalkane radicals were also calculated using the enthalpies of atomization and the energies of nonvalent interactions
of nitro groups. Regularities of changes in the bond dissociation energies of nitroalkanes C1–C7 and their radicals are established. 相似文献
19.
L. T. Denisova Yu. F. Kargin L. G. Chumilina V. M. Denisov 《Russian Journal of Inorganic Chemistry》2016,61(4):420-423
Heat capacity of NdVO4 was determined in the temperature range of 384–859 K using differential scanning calorimetry. The thermodynamic functions (H°(T)–H°(384 K), S°(T)–S°(384 K), and Φ°) of neodymium orthovanadate were calculated using the experimental Cp = f(T) values. The structure of NdVO4 was studied at 298 and 973 K. 相似文献
20.
Dejan Zagorac Dr. Klaus Doll Prof. Dr. J. Christian Schön Prof. Dr. Martin Jansen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(35):10929-10936
Recently, we have investigated the energy landscape of PbS for many different pressures on the ab initio level by using Hartree–Fock and density functional theory to globally search for possible thermodynamically stable and metastable structures. The perhaps most fascinating observation was that besides the experimentally known modification exhibiting the rock salt structure a second minimum exists close‐by on the landscape showing the low‐temperature α‐GeTe‐type structure. In the present study, we investigate the possible reasons for the existence of this metastable modification; in particular we address the question, whether the α‐GeTe‐type modification might be stabilized (and conversely the rock salt modification destabilized) by steric effects of the non‐bonding electron pair. 相似文献