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1.
LnBaCuCoO5 + δ (Ln = Y, Dy) cuprocobaltites were prepared. Their unit cell parameters were determined and their thermal expansion, electrical conductivity (σ), and Seebeck coefficient (S) were studied in air in the range 300–1100 K. The compounds have tetragonal structures (space group P4/mmm). Their unit cell parameters are a = 0.3867(2) nm, c = 0.7550(7) nm, V = 112.9(2) × 10?3 nm3 for YBaCuCoO4.98; and a = 0.3872(2) nm, c = 0.7562(7) nm, V = 113.4(2) × 10?3 nm3 for DyBaCuCoO5.01. They are p-type semiconductors. The electrical conductivity of DyBaCuCoO5 + δ is slightly lower and its Seebeck coefficient is 1.5–2 times higher than the respective values for YBaCuCoO5 + δ apparently because of different electronic configurations of the rare-earth cations in LnBaCuCoO5 + δ (4d 0 for Y3+ and 4f 9 for Dy3+). Dilatometric measurements show that the LnBaCuCoO5 + δ phases in the range 300–1100 K do not experience structural phase transitions, and their linear thermal expansion coefficients (LTEC) are 14.3 × 10?6 K?1 for Ln = Y and 14.7 × 10?6 K?1 for Ln = Dy.  相似文献   

2.
Densities for aqueous solutions of magnesium tetraborate MgB4O7(aq) at the molalities of (0.00556–0.03341) mol·kg?1 were measured with an Anton Paar Digital vibrating-tube densimeter at temperature intervals of 5 K from 283.15 to 363.15 K and 0.1 MPa. Apparent molar volumes were obtained based on the experimental density data, and the 3D diagrams of the apparent molar volume (V ? ) of MgB4O7(aq) against temperature (T) and molality (m) were plotted. On the basis of the Vogel–Tamman–Fulcher equation, the coefficients of the correlation equation for densities of MgB4O7(aq) against temperature and molality were parameterized. According to the Pitzer ion-interaction model of the apparent molar volume, the temperature correlation equations of Pitzer single-salt parameters F(i,p,T)?=?a0?+?a1?×?T?+?a2?×?T 2?+?a3/T?+?a4?×?ln(T)?+?a5?×?T 3 (where T is temperature in Kelvin, a i are model parameters) for MgB4O7 were obtained for the first time.  相似文献   

3.
An organic-inorganic hybrid Keggin compound, [4,4′-bipyH2][4,4′-bipyH]2[VW12O40] · 4,4′-bipy · 7.5H2O (bipy-bipyridine) (1), has been prepared under hydrothermal conditions and characterized by IR spectroscopy, single crystal X-ray diffraction, thermal analysis, and ESR spectroscopy. 1 crystallized in the monoclinic space group P21/c with a = 18.7350(15) Å, b = 14.0253(12) Å, c = 26.434(2) Å, β= 105.0810(10)°, V = 6706.6(10) Å3 and Z = 4. The crystal structure of 1 consists of diprotonated and monoprotonated 4,4′-bipyridine cations, free 4,4′-bipyridine molecule, lattice water molecules, and a typical Keggin-type polyoxoanion [VW12O40]4?. The polyoxoanion is constructed by four {W3O16} trinuclear groups, each of which is made up of three edge-sharing {WO6} octahedra, and the {VO4} tetrahedron is in the center of the cage.  相似文献   

4.
A complex [Zn(C8H7O3)2(H2O)2] (C8H8O3 is vanillin) has been synthesized and characterized by IR, elemental analysis, and X-ray diffraction single-crystal analysis. The crystals are monoclinic, space group C2/c, a = 22.236(8) Å, b = 10.594(2) Å, c = 7.8190(16) Å, α = 89.90(3)°, β = 106.87(4)°, γ = 89.99(3)°, V = 1762.6(8) Å3, Z = 4, F(000) = 832, S = 1.079, ρ c = 1.521g cm?3, R = 0.0221, R w = 0.0604, μ = 1.433 mm?1. The Zn2+ ion is six-coordinated with a distorted octahedron geometry. The complex forms a three-dimensional network through intermolecular hydrogen bonds. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal conditions by the TG and DTG methods. The kinetic equation can be expressed as dα/dt = Ae?E/RT 2(1 ? α)[1 ? ln(1 ? α)]1/2. The kinetic parameters (E, A), activation entropy ΔS , and activation free-energy ΔG were also gained.  相似文献   

5.
Single crystals of bismuth oxoborate Bi4B2O9 have been grown by slowly cooling the melt of a stoichiometric Bi2O3 + H3BO3 mixture. The structure of the borate (monoclinic space group P21/c, a = 11.107 Å, b = 6.629 Å, c = 11.044 Å, β = 91.04°, Z = 4) has been studied at 20, 200, and 450°C. The structure is described not only in terms of full BiO6 ? and BiO7 polyhedra but also in terms of truncated BiO3 ? and BiO4 ? polyhedra and BO3 triangles, as well as oxo-centered OBi3 triangles and OBi4 tetrahedra. It is shown that both the B-O and Bi-O bond lengths are practically unaffected by temperature. Only the angles between polyhedra change with temperature, being responsible for the strong anisotropy of Bi4B2O6 thermal expansion, which was measured by high-temperature powder X-ray diffraction: α11 = 20, α22 = 15, α33 = 6 × 10?6 °C?1, and μ = (c, α33) = ?19°.  相似文献   

6.
By using dc and ac polarography, the kinetics of electroreduction of the palladium (II) complexes with β-alanine at a dropping mercury electrode was studied in solutions with the palladium (II) concentration from 2 × 10?5 to 2 × 10?4 M and variable β-alanine and sodium perchlorate concentrations (pH 6–12). One polarographic wave was observed in solutions with pH 9 and 10 at the β-alanine overall concentration of c βala = 1 × 10?3 to 5 × 10?2 M; two waves, at lower pH or higher c βala. It was concluded on the formation of different forms of palladium (II) complexes in the studied solutions; the complexes contained two to four β-alanine coordinated anions. Using the limiting diffusion currents for the two waves at pH 9–11 and c βala = 0.1 and 0.5 M, the stepwise stability constant for the Pd(βala) 4 2? complex was calculated. Using two ac peaks observed at pH 7–8 and c βala = 1 × 10?2 to 0.1 M, the stepwise stability constant for the Pd(βala) 3 ? . was calculated. The perchlorate ions adsorbed at the dropping mercury electrode, as well as βala? anions at their higher concentrations, hamper the electroreduction of the palladium (II) complexes with β-alanine.  相似文献   

7.
The heat capacities of Pb2V2O7 and Pb3(VO4)2 as a function of temperature in the range 350–965 K have been studied by the differential scanning calorimetry method. The CP = f(T) curve for Pb2V2O7 is described by the equation Cp = (230.76 ± 0.51) + (73.60 ± 0.50)×10-3T ? (18.38 ± 0.54)×105T-2 in the entire temperature range. For Pb3(VO4)2, there is a well-pronounced extreme point in the CP = f(T) curve at T = 371.5 K, which is caused by the existence of a structural phase transition. The thermodynamic properties of the oxide compounds have been calculated.  相似文献   

8.
The chemical diffusion coefficient of oxygen vacancies and oxygen ion conductivity in lanthanum cobaltite LaCoO3 were determined by the polarization method as functions of oxygen partial pressure \(p_{O_2 } \) (atm) and temperature T(K) over the ranges ?4 ≤ log \(p_{O_2 } \) ≤ 0 and 1173 K ≤ T ≤ 1323 K. The mobilities (cm2/(V s)) of oxygen vacancies calculated over the temperature range studied satisfy the inequalities 1.8 × 10?5\(v_{v_0 } \) ≤ 3.4 × 10?5. The transfer numbers of oxygen vacancies were calculated. These numbers change depending on oxygen partial pressure over the range 5 × 10?7t 0 ≤ 1 × 10?5. The activation energy of self-diffusion of oxygen vacancies was found to be E a= 104 ± 10 kJ/mol (1.1 ± 0.1 eV).  相似文献   

9.
The kinetics of 1,1-dimethylpropyl peroxy radicals recombination in polar solvents—water, methanol, and their mixtures—was studied by EPR spectroscopy in combination with the stopped-flow method, and the rate constants of this reaction were determined. Peroxyl radicals were generated by mixing solutions of Ce4+ sulfate and 1,1-dimethylpropyl hydroperoxide. The observed EPR signal of the peroxyl radical is a singlet with a g-factor of 2.015 ± 0.001, and a line width of ΔH = (1.36 ± 0.02) × 10?3 T for methanol and ΔH = (9.7 ± 0.2) × 10?4 T for water. The measured rate constants of (CH3)2C(O2·)CH2CH3 radical recombination at 298 K are 2kt = (3.9 ± 0.4) × 104 L mol?1 s?1 for water and 2kt = (5.2 ± 0.5) × 103 L mol?1 s?1 for methanol. A linear relationship between ln(2kt) and the Kirkwood function (ε?1)/(2ε + 1), where e is the dielectric constant of the medium, has been established, indicating an important role of nonspecific solvation in the recombination of tertiary peroxyl radicals.  相似文献   

10.
New crystal structure of Eu(DMF)4(H2O)3Co(CN)6·H2O (DMF = N,N′-dimethylformamide) (Eu-Co) has been determined to be monoclinic, P2(1)/n, a = 19.796(12) Å, b = 8.862(11) Å, c = 17.525(10) Å, β = 96.26(5)°, V = 3056(5) Å3, Z = 4. The Eu(III) ion adopts an antiprismatic eight-coordination and forms a cyano bridge with r(Eu-N) = 2.496(7) Å and Θ(Eu-N-C) = 165.7(7)° to the Co(III) ion. The complex exhibits some common features with the Eu-Fe complex. Diffuse reflectance electronic spectra and magnetic susceptibility of Eu-Cr, Eu-Mn, Eu-Fe, and Eu-Co complexes were compared. By substituting the metal ions, both electronic and structural features affected the charge transfer bands and superexchange interactions concerning cyanide ligands. In addition, only Eu-Co exhibited 5 D 07 F 2 and 5 D 07 F 1 luminescence bands at 16300 cm?1 and 16900 cm?1, respectively at 298 K (λex = 360 nm (27000 cm?1)), because quenching by cyano-bridged ions did not prevent Eu(III) ion from exhibiting emission. Thus, only Eu-Co may be suitable for verification of an assumption of mechanism concerning drastic photoinduced magnetic changes for Nd-Fe. Merely small decrease of magnetization was observed for Eu-Co after UV light irradiation at 2.0 K. This result was attributed to slight structural changes around cyano bridges without transitions of spin states.  相似文献   

11.
The kinetics of gas reaction \(HOCl\underset{{k_r }}{\overset{{k_f }}{\longleftrightarrow}}H(^2 S) + OCl(X^2 \Pi _i )\) was analyzed by the MP4 method. In the temperature range of 100–373 K the rate constants k f and k r and equilibrium constant K were changed from 1.10 × 10?220 to 1.17 × 10?52 s?1, from 2.89 × 10?16 to 1.68 × 10?5s?1 and from 3.80 × 10?205 to 6.96 × 10?48 respectively. In the above temperature range, the activation energy of the forward reaction (E f) is 105.05 kcal/mol. In the same temperature interval there are two kinetic domains for the reverse reaction with activation energies (E r1 = 5.53 kcal/mol when T is 100–273 K and E r2 = 14.50 kcal/mol when T is 273–373 K, respectively.  相似文献   

12.
The interaction between oxygen and polycrystalline palladium (Pd(poly)) at \(P_{O_2 } \) = 2.6 × 10?6–10 Pa and T = 300–1300 K was studied by the thermal desorption (TD) method. The interaction between O2 and Pd(poly) is governed by the O2 pressure and the sample temperature. At low pressures of \(P_{O_2 } \) (≤1.3 × 10?5 Pa), O2 is chemisorbed dissociatively on the Pd(poly) surface. During chemisorption, the Oads-surface bond energy and the O2 sticking coefficient gradually decrease as the surface coverage θ increases. At \(P_{O_2 } \) ≥ 10?2 Pa and T ≤ 500 K, after the saturation of the Oads layer (θ ~ 0.5), Oads atoms penetrate under the surface layer of the metal to form surface palladium oxide. At \(P_{O_2 } \) ≥ 1 Pa and T > 500 K, after the saturation of the surface oxide film 2 ML in thickness (n ~ 2), Oads atoms penetrate into the oxide film and then into the subsurface palladium layer and diffuse deep into the metal bulk. As a result, the oxygen uptake at 700 K is n ~ 50. Upon heating, the surface oxides decompose, desorbing O2, which gives rise to a low-temperature TD peak with T max = 715 K. The release of oxygen inserted in the subsurface layers of palladium shows itself as a distinct high-temperature TD peak with T max ≥ 750 K.  相似文献   

13.
The phase diagram of system DyCuS2–EuS has been first constructed, and the phase equilibria in the Cu2S–Dy2S3–EuS triangle at 970 K have been studied. Compound EuDyCuS3 (1DyCuS2 : 1EuS), space group Pnma, a = 10.1901(3) Å, b = 3.9270(1) Å, c = 12.8468(3) Å, melts incongruently at 1727 ± 7 K according to the reaction: EuDyCuS3solid ? 0.17 SS EuS (90 mol % EuS, 10 mol % DyCuS2) + 0.83 liq (42 mol % EuS, 58 mol % DyCuS2), ΔH = 2.9 ± 0.6 kJ/mol; microhardness of the phase is 3080 ± 35 MPa. Compound EuDyCuS3 is transparent in the range 3000–1800 cm–1. In system DyCuS2–EuS, the solid solution (SS) based on EuS extends from 91 to 100 mol % at 1770 K and from 92 to 100 mol % at 1170 K. In γ-DyCuS2, 2 mol % EuS dissolves at 1487 K. The eutectic is formed between compounds DyCuS2 and EuDyCuS3 at 12 mol % EuS, T = 1487 ± 8 K. In system Cu2S?Dy2S3?EuS, 10 secondary systems have been isolated. At 970 K, tie-lines are located between compound EuDyCuS3 and solid solutions based on compounds β-Cu2S, EuS, DyCuS2, β-(DyCu3S3), and EuDy2S4; between DyCuS2 and the solid solution of α-Dy2S3, DyCuS2, and EuDy2S4.  相似文献   

14.
Ferrites of composition ErMIFe2O5 (MI = Li, Na, K, Cs) were synthesized by a solid-phase method. The structure of the ferrites was for the first time studied by X-ray powder diffraction. Crystal systems, unit cell parameters, and X-ray and pycnometric densities were determined. For ErLiFe2O5, a = 10.510 Å, c = 14.270 Å, V°= 1616.16 Å3, Z = 16, V subcell ° = 101.01 Å3, ρx = 6.01 g/cm3, ρpyc = 5.97 ± 0.04 g/cm3; for ErNaFe2O5, a = 10.519 Å, c = 15.510 Å, V° = 1759.56 Å3, Z = 16, V subcell ° = 109.90 Å3, ρx = 5.77 g/cm3, ρpyc = 5.72 ± 0.08 g/cm3; for ErKFe2O5, a = 11.050 Å, c = 15.480 Å, V° = 1937.33 Å3, Z = 16, V subcell ° = 121.08 Å3, ρx = 5.46 g/cm3, ρpyc = 5.41 ± 0.04 g/cm3; and for ErCsFe2O5, a = 10.78 Å, c = 16.01 Å, V° = 1905.37 Å3, Z = 16, V subcell ° = 119.09 Å3, ρx = 6.86 g/cm3, ρpyc = 6.61 ± 0.01 g/cm3.  相似文献   

15.
A new V6O13-based material has been synthesized via the sol–gel route. This sol–gel mixed oxide has been obtained from an appropriate heat treatment of the chromium-exchanged V2O5 xerogel performed under reducing atmosphere. This new compound, with the chemical formula Cr0.36V6O13.50, exhibits a monoclinic structure (C2/m) with the following unit cell parameters, a=11.89 Å, b=3.68 Å, c=10.14 Å, β=101.18°. The electrochemical characterization of this compound has been performed using galvanostatic discharge–charge experiments in the potential range 4–1.5 V and completed by ac impedance spectroscopy measurements. It exhibits a specific capacity of about 370 mAh g?1, which makes the compound Cr0.36V6O13.50 the best one in the V6O13-based system: 85% of the initial capacity (315 mAh g?1) after the 35th cycle is still available at C/25 without any polarization. From impedance spectroscopy, a high kinetics of Li transport (D Li=1.8×10?9 cm2 s?1) is found at mid-discharge.  相似文献   

16.
The synthesis and determination of the crystal and molecular structure of the binuclear complex fu-4,4′-bipyridyl-bis-[trans-C,0-nitrate-2-(2′-thienyl–3-ido)pyridine-palladium] is described (C28H20N6O6Pd2S2: a = 12.3914(11) Å, b = 9.8929(7) Å, c = 12.4058(12) Å, α = 90(0)β, ß = 105.440(40)α, γ = 90(0)α, V = 1465.9(0) Å3, monoclinic symmetry, P2 1/n (14), Z = 4, d x = 1.843 g/cm3 ). The pyridine rings of 4,4′-bipyridyl are shown to be in the orthogonal position with respect to the coordination planes of palladium centers both in the solid state and solution  相似文献   

17.
It is found that the tertiary amine N,N,N′,N′-tetramethyl-para-phenylenediamine (TMPD) causes the decomposition of α-phenylethyl hydroperoxide (ROOH), and the interaction between the components occurs in accordance with a complicated rate law. It is demonstrated that more than 30 hydroperoxide molecules (n) can be degraded at a molecule of TMPD; this fact suggests that the amine has a catalytic effect on the process. The value of n increases with the [ROOH]0/[TMPD]0 ratio. The initial rates of consumption of ROOH and TMPD linearly increase with the initial concentrations of both of the reactants. The apparent rate constant of the reaction is k = 0.4 l mol?1 s?1 (393 K), as calculated from the initial rates of ROOH consumption. As a result of the interaction, TMPD is converted into an inhibitor. The rate constant of the reaction of this inhibitor with ethylbenzene peroxy radicals is about 2 × 104 l mol?1 s?1.  相似文献   

18.
A nickel(II) complex, [Ni(taetacn)](ClO4)2 ? H2O, where taetacn = 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane was synthesized. The crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. The complex crystallizes in the orthorhombic space group Pna21 with a = 16.004(2) Å, b = 10.186(1) Å, c = 13.937(2) Å, V = 2271.9(5) Å3, Dx = 1.56 g cm?3, Dm = 1.59 g cm?3 (floatation method), and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values are 0.0636 and 0.1672, respectively, for all 4845 independent reflections. The compound is composed of octahedral nickel(II) cation with three 2-aminoethyl pendant groups of taetacn, tetrahedral ClO 4 ? anion, and a water molecule of crystallization. Electronic spectra are consistent with the octahedral geometry. Temperature dependence of the magnetic susceptibility (4.5–300 K) can be interpreted considering the zero-field splitting of the nickel(II) ion (g = 2.14, D = 3.72 cm?1, and = 300 × 10?6 cm3 mol?1). Cyclic voltammetry in DMF showed quasi-reversible and irreversible oxidation waves (Epa = 0.54 V, Epc = 0.45 V; Epa = 1.16 V, Epc = 0.71 V vs. Ag/Ag+).  相似文献   

19.
A new coordination polymer, [Cd(HMal)(Bipy)(H2O) · 2H2O (I) (H3Mal is malic acid, Bipy is 4,4′-bipyridine), has been synthesized from H3Mal and Bipy under hydrothermal conditions and characterized by elemental analysis, IR, TG, and single-crystal X-ray diffraction. The X-ray diffraction analysis reveals that I (C14H16N2O7Cd) crystallizes in the orthorhombic system, space group Ibam. The adjacent cadmium(II) atoms were first interconnected by the HMal ligands via carboxylate oxygen atoms and its adjacent hydroxyl group to generate an infinite zigzag [Cd(HMal)] n chain, which are further linked by Bipy ligands to form a 2D wavelike layer. Interestingly, the adjacent layers are further connected via hydrogen bonds, giving rise to a 3D porous framework with a cross-sectional area of 11.690 × 9.326 Å2. The unit cell parameters for I: a = 8,457(1), b = 22.030(7), c = 23.066(7) V = 4297(2) Å3, Z = 4.  相似文献   

20.
The complex [Pd(bipy)Cl2] (1) (bipy = 2,2′-bipyridyl) has been synthesized and characterized by NMR spectroscopy, elemental analysis and X-ray diffraction method. The first step hydrolysis reaction kinetics for the complex was studied by UV-absorption spectroscopy; the speed constant (k 1) was found to be 3.0×10?4 s?1. The fluorescence spectra have been collected to investigate the interaction of complex (1) with fish sperm DNA (FS-DNA) and the results indicate that the complex (1) has an effective intercalation within DNA. The reaction of complex (1) with adenine in ethanol/water results in the compound [Pd2(bipy)2(ade)2]Cl2·3H2O (2) (ade = adenine) whose crystal structure was determined by X-ray diffraction method. The structure is orthorhombic, Pmmn, a = 12.993(4) Å, b = 14.512(5) Å, c = 9.837(3) Å, V = 1854.8(11) Å3, Z = 2 (C30H30Cl2N14O3Pd2), final R 1 = 0.0675. The palladium complex is a binuclear cation, where two ade ligands bridge two Pd(II) centers, while each Pd(II) is also chelated by one bipy ligand.  相似文献   

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