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1.
Ji-min Yang Yan Yao Qi-ying Xia Bao-hui Li Shu-yong Xu Jie Yang 《Journal of solution chemistry》2008,37(3):377-389
Isopiestic molalities and water activities have been measured for the Li2B4O7+LiCl + H2O system at T=298.15 K using an improved isopiestic apparatus. Two types of osmotic coefficients, φ
S and φ
E, were determined, where φ
S is based on the stoichiometric molalities of the solute Li2B4O7(aq) and φ
E is based on equilibrium molalities calculated by consideration of the equilibrium speciation of Li2B4O7 to partially form H3BO3, B(OH)4− and B3O3(OH)4−. The stoichiometric equilibrium constant K
m for the aqueous speciation reaction was estimated. Two representations of the osmotic coefficients of Li2B4O7 + LiCl + H2O were made with Pitzer’s ion-interaction model. Model (1) involved representing the φ
S values with six parameters based on considering the ionic interactions between Li+, Cl−, and B4O72−; and model (2) involved representing the φ
E values based on the calculated equilibrium speciation. Reasonable agreements were obtained between the experimental osmotic
coefficient data and those calculated using the above models, with standard deviations of 0.075 and 0.0229, respectively,
for these two models. The thermodynamic osmotic coefficients for the complex system containing polymeric boron anions and
lithium cation was modelled and explained by use of Pitzer’s ion-interaction model, with minor modifications in combination
with speciation reaction equilibria. 相似文献
2.
Zhi-Heng Zhang Guo-Yin Yin Zhi-Cheng Tan Yan Yao Li-Xian Sun 《Journal of solution chemistry》2006,35(10):1347-1355
The molar heat capacities of an aqueous Li2B4O7 solution were measured with a precision automated adiabatic calorimeter in the temperature range from 80 to 356 K at a concentration of 0.3492 mol⋅kg−1. The occurrence of a phase transition was determined based on the changes in the curve of the heat capacity with temperature. A phase transition was observed at 271.72 K corresponding to the solid-liquid phase transition; the enthalpy and entropy of the phase transition were evaluated to be Δ H
m = 4.110 kJ⋅mol−1 and Δ S
m = 15.13 J⋅K−1⋅mol−1, respectively. Using polynomial equations and thermodynamic relationship, the thermodynamic functions [H
T
−H
298.15] and [S
T
−S
298.15] of the aqueous Li2B4O7 solution relative to 298.15 K were calculated in temperature range 80 to 355 K at intervals of 5 K. Values of the relative apparent molar heat capacities of the aqueous Li2B4O7 solution, C
p,φ, were calculated at every 5 K in temperature range from 80 to 355 K from the experimental heat capacities of the solution and the heat capacities of pure water. 相似文献
3.
SiO2/Sb2O3 (SiSb), having a specific surface area, S
BET, of 788 m2 g−1, an average pore diameter of 1.9 nm and 4.7 wt% of Sb, was prepared by the sol-gel processing method. Meldola's blue (MeB),
methylene blue (MB) and toluidine blue (TB) were immobilized on SiSb by an ion exchange reaction. The amounts of the dyes
bonded to the substrate surface were 12.49, 14.26 and 22.78 μmol g−1 for MeB, MB and TB, respectively. These materials were used to modify carbon paste electrodes. The midpoint potentials (E
m) of the immobilized dyes were −0.059, −0.17 and −0.18 V vs. SCE for SiSb/MeB, SiSb/MB and SiSb/TB modified carbon paste electrodes,
respectively. A solution pH between 3 and 7 practically did not affect the midpoint potential of the immobilized dyes. The
electrodes presented reproducible responses and were chemically stable under various oxidation-reduction cycles. Among the
immobilized dyes, MeB was the most efficient to mediate the electron transfer for NADH oxidation in aqueous solution at pH 7.
In this case, amperometric detection of NADH at an applied potential of 0 mV vs. SCE gives linear responses over the concentration
range of 0.1–0.6 mmol L−1, with a detection limit of 7 μmol L−1. 相似文献
4.
Large-scale Li1+x
V3O8 nanobelts were successfully fabricated using filter paper as deposition substrate through a simple surface sol–gel method.
The nanobelts were as long as tens of micrometers with widths of 0.4–1.0 μm and thickness of 50–100 nm. The nanobelts were
characterized by X-ray diffration (XRD), Fourier infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission
electron microscopy (TEM). The formation mechanism of the nanobelts was investigated, showing that the morphology of the nanobelts
is mainly determined by the calcination temperature. Electrochemical properties of the Li1+x
V3O8 nanobelts were characterized by charge–discharge experiments, and the results demonstrate that the Li1+x
V3O8 nanobelts exhibit a high discharge capacity (278 mAh g−1) and excellent cycling stability. 相似文献
5.
A differential pulse voltammetric (DPV) method for the determination of bromate in drinking water, after pre-concentration
on γ-Al2O3, is proposed. The reduction peak of bromate has been observed at the potential E
p
-−1.6 V in an ammonia buffer as a supporting electrolyte. The method has been successfully applied to determine a bromate
concentration of 2.5 μg·l−1 in drinking water (RSD=6.1%, n=7). A sample pre-treatment with a column filled with mixed cation-exchange resin in Ag, Ba
and H forms was needed before pre-concentration of bromate on alumina. 相似文献
6.
The enthalpies of dilution, Δdil
H
m, have been measured for LiCl+Li2B4O7+H2O system at T=298.15 K by using a RD496-III microcalorimeter. A suitable measurement method was used to obtain the better data of the enthalpies
of dilution for the ternary mixing solutions to low concentrations. The relative apparent molar enthalpies, L
ϕ, have been determined and the relationships between L
ϕ and ionic strength I at different molal fractions of Li2B4O7 were obtained. The effect of the borate Li2B4O7 on the heat properties for the studied system was discussed. 相似文献
7.
2CaO·3B2O3·H2O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and
TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B2O3·H2O in HCl·54.572H2O was determined. From a combination of this result with measured enthalpies of solution of H3BO3 in HCl·54.501H2O and of CaO in (HCl+H3BO3) solution, together with the standard molar enthalpies of formation of CaO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol−1 of 2CaO·3B2O3·H2O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method. 相似文献
8.
S. -X. Wang Z. -C. Tan Y. -S. Li L. -X. Sun Y. Li 《Journal of Thermal Analysis and Calorimetry》2008,92(2):483-487
Synthesis, characterization and thermal analysis of polyaniline (PANI)/ZrO2 composite and PANI was reported in our early work. In this present, the kinetic analysis of decomposition process for these
two materials was performed under non-isothermal conditions. The activation energies were calculated through Friedman and
Ozawa-Flynn-Wall methods, and the possible kinetic model functions have been estimated through the multiple linear regression
method. The results show that the kinetic models for the decomposition process of PANI/ZrO2 composite and PANI are all D3, and the corresponding function is ƒ(α)=1.5(1−α)2/3[1−(1-α)1/3]−1. The correlated kinetic parameters are E
a=112.7±9.2 kJ mol−1, lnA=13.9 and E
a=81.8±5.6 kJ mol−1, lnA=8.8 for PANI/ZrO2 composite and PANI, respectively. 相似文献
9.
R. G. Bulgakov Yu. G. Ponomareva Z. S. Muslimov F. G. Valyamova R. A. Sadykov R. F. Tuktarov 《Russian Chemical Bulletin》2007,56(2):211-219
Fullerenyl radicals (FR) RC60
· and chemiluminescence (CL) are generated in the presence of O2 in C60—R3Al (R = Et, Bui) solutions in toluene (T = 298 K). The FR are formed due to the addition of the R· radical, which is an intermediate of R3Al autooxidation, to C60. Mass spectroscopy and HPLC were used to identify EtnC60Hm (n, m = 1–6), EtpC60 (p = 2–6), and dimer EtC60C60Et as stable products of FR transformations. As found by ESR, the EtC60
· radical (g = 2.0037) is also generated by photolysis of solutions obtained after interaction in the (C60— R3Al)—O2 system. In the presence of dioxygen, the FR is not oxidized but yields complexes with O2, which appear as broadening of the ESR signals. Chemiluminescence arising in the (C60—R3Al)—O2 system is much brighter (I
max = 1.86·108 photon s−1 mL−1) than the known background CL (I
max = 6.0·106 photon s−1 mL−1) for the autooxidation of R3Al and is localized in a longer-wavelength spectral region (λmax = 617 and 664 nm). This CL is generated as a result of energy transfer from the primary emitter 3CH3CHO* to the products of FR transformation: RnC60Hm, RpC60, and EtC60C60Et.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 205–213, February, 2007. 相似文献
10.
H. M. Wu J. P. Tu X. T. Chen Y. Li X. B. Zhao G. S. Cao 《Journal of Solid State Electrochemistry》2007,11(2):173-176
Spinel LiMn2−x
Ni
x
O4 compounds doped with a range of Ni (x=0–0.06) were synthesized by a spray-drying method. The structure and morphology characteristics of the powders were studied in detail by means of X-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy. The XRD data reveal that all the samples have well-defined spinel structure, but, with the increase in Ni content, the doped lithium manganese spinels have smaller lattice constant. The undoped and doped spinel LiMn2O4 particles are fine, narrowly distributed, and well crystallized. The electrochemical characteristics of the samples are measured in the coin-type cells in a potential range of 3.2–4.35 V vs Li/Li+. All cyclic voltammogram curves exhibit two pairs of redox reaction peaks, but, among them, there are some differences about the peak split. With the increase in the Ni content, the specific capacities of the samples decrease slightly, but their cyclic ability increases. 相似文献
11.
Klaartje De Buysser Philippe F. Smet Bart Schoofs Els Bruneel Dirk Poelman Serge Hoste Isabel Van Driessche 《Journal of Sol-Gel Science and Technology》2007,43(3):347-353
This paper describes the synthesis of ZrW2O8 by the use of an aqueous citrate-gel method in order to prepare a fine, pure and homogeneous oxide mixture suitable for ceramic
processing. The thermal expansion coefficient thus obtained for α-ZrW2O8 is −10.6 × 10−6 °C−1 (50–125 °C) whereas for the β-ZrW2O8 a value of −3.2 × 10−6 °C−1 (200–300 °C) is obtained. The advantages of the use of a sol–gel method is expressed in the very homogeneous end-products.
The paper describes crystallographic data, morphological structure and the thermal expansion properties of the ZrW2O8 material. Moreover, photoluminescence and photochromic properties specific to the precursor gel are described and analyzed.
These effects support our views that the precursors show homogeneity up to nanometer level. 相似文献
12.
N. I. Matskevich 《Journal of Thermal Analysis and Calorimetry》2007,90(3):955-958
Enthalpy of formation of the perovskite-related oxide BaCe0.9In0.1O2.95 has been determined at 298.15 K by solution calorimetry. Solution enthalpies of barium cerate doped with indium and mixture
of BaCl2, CeCl3, InCl3 in ratio 1:0.9:0.1 have been measured in 1 M HCl with 0.1 M KI. The standard formation enthalpy of BaCe0.9In0.1O2.95 has been calculated as −1611.7±2.6 kJ mol−1. Room-temperature stability of this compound has been assessed in terms of parent binary oxides. The formation enthalpy of
barium cerate doped by indium from the mixture of binary oxides is Δox
H
0 (298.15 K)=−36.2±3.4 kJ mol−1. 相似文献
13.
Among the various positive electrode materials investigated for Li-ion batteries, spinel LiMn2O4 is one of the most important materials. Small particles of the active materials facilitate high-rate capability due to large
surface to mass ratio and small diffusion path length. The present work involves the synthesis of submicron size particles
of LiMn2O4 in a quaternary microemulsion medium. The precursor obtained from the reaction is heated at different temperatures in the
range from 400 to 900 °C. The samples heated at 800 and 900 °C are found to possess pure spinel phase with particle size <200 nm,
as evidenced from XRD, SEM, and TEM studies. The electrochemical characterization studies provide discharge capacity values
of about 100 mAh g−1 at C/5 rate, and there is a moderate decrease in capacity by increasing the rate of charge–discharge cycling. Studies also
include charge–discharge cycling and ac impedance studies in temperature range from −10 to 40 °C. Impedance data are analyzed
with the help of an equivalent circuit and a nonlinear least squares fitting program. From temperature dependence of charge-transfer
resistance, a value of 0.62 eV is obtained for the activation energy of Mn3+/Mn4+ redox process, which accompanies the intercalation/deintercalation of the Li+ ion in LiMn2O4. 相似文献
14.
Er3+-doped Al2O3 nanopowders have been prepared by the non-aqueous sol-gel method using the aluminum isopropoxide as precursor, acetylacetone
as a chelating agent, nitric acid as a catalyzer, and hydrated erbium nitrate as a dopant under isopropanol environment. The
different phase structure, including three crystalline types of (Al, Er)2O3 phases, α, γ, θ, and an Er–Al–O stoichiometric compound phase, Al10Er6O24, was observed for the 0.01–0.5 mol% Er3+-doped Al2O3 nanopowders at the sintering temperature of 1,000 °C. The green and red up-conversion emissions centered at about 523, 545
and 660 nm, corresponding respectively to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+, were detected by a 978 nm semiconductor laser diodes excitation. With increasing Er3+ doping concentration from 0.01 to 0.1 mol%, the intensity of the green and red emissions increased with a decrease of the
intensity ratio of the green to red emission. When the Er3+ doping concentration rose to 5 mol%, the intensity of the green and red emissions decreased with an increase of their intensity
ratio. The maximum intensity of both the green and red emissions with the minimum of intensity ratio was obtained, respectively,
for the 0.1 mol% Er3+-doped Al2O3 nanopowders composed of a single α-(Al,Er)2O3 phase. The intensity ratio of the green emission at 523 and 545 nm increased monotonously for all Er3+ doping concentrations. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions
of the Er3+-doped Al2O3 nanopowders. 相似文献
15.
Ca3Co4O9 powder was prepared by a polyacrylamide gel route in this paper. The effect of the processing on microstructure and thermoelectric
properties of Ca3Co4O9 ceramics via spark plasma sintering were investigated. Electrical measurement shows that the Seebeck coefficient and conductivity
are 170 μV/K and 128 S/cm, respectively, at 700 °C, yielding a power factor value of 3.70 × 10−4 W m−1 K−2 at 700 °C, which is larger than that of Ca3Co4O9 ceramics via solid-state reaction processing. The polyacrylamide gel processing is a fast, cheap, reproducible and easily
scaled up chemical route to improve the thermoelectric properties of Ca3Co4O9 ceramics by preparing the homogeneous and pure Ca3Co4O9 phase. 相似文献
16.
Ben Hui Wang Ji De Wang RuiQuan Liu Ya Hong Xie Zhi Jie Li 《Journal of Solid State Electrochemistry》2007,11(1):27-31
A new type of oxide–salt composite electrolyte, yttrium doped ceria YDC–Ca3(PO4)2–K3PO4, was developed and demonstrated for its promising use for ammonia synthesis. Using this composite electrolyte, ammonia was
synthesized from nitrogen and natural gas at atmospheric pressure in the solid-state proton conducting cell reactor, and the
optimal condition for ammonia production was determined . The evolved rate of ammonia is up to 6.95×10−9 mol s−1 cm−2. 相似文献
17.
N. A. Sanina T. N. Rudneva S. M. Aldoshin A. N. Chekhlov R. B. Morgunov E. V. Kurganova N. S. Ovanesyan 《Russian Chemical Bulletin》2007,56(1):28-34
The neutral dinuclear iron nitrosyl complex [Fe2(SC3H5N2)2(NO)4] (1) of the “g = 2.03” family with a ligand analogous to natural mercaptohistidine was synthesized by the metathesis reaction
of the thiosulfate ligands in the [Fe2(S2O3)2(NO)4]2− anion with imidazolidine-2-thiolate ligands. The electrochemical determination of nitrogen oxide in solution showed that
compound 1 has a lower NO-donor ability compared to the iron complexes with 1-methylimidazole-2-thiol and imidazole-2-thiol synthesized
earlier. Study of the magnetic properties of polycrystals of 1 demonstrated that the effective magnetic moment at room temperature is ca. 2.45 μB and corresponds to a molecule containing a pair of the noninteracting spins S = 1/2. This is evidence that each iron coordination
unit in complex 1 contains one unpaired electron, and the iron atom is in the low-spin state.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 28–34, January, 2007. 相似文献
18.
Areas of fusion and crystallization peaks of K3TaO2F4 and KTaF6 were measured using the DSC mode of a high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities, considering
the temperature dependence of the calorimeter sensitivity, values of the fusion enthalpy of K3TaO2F4 at the fusion temperature of 1181 K of (43 ± 4) kJ mol−1 and of KTaF6 at the fusion temperature of 760 K of (8 ± 1) kJ mol−1 were determined. 相似文献
19.
Merlin C. E. Bandeira Joseph A. Crayston Norberto S. Gonçalves Lúcia K. Noda Andrew Glidle César V. Franco 《Journal of Solid State Electrochemistry》2007,11(2):231-239
The electropolymerization of trans-[RuCl2(vpy)4] (vpy=4-vinylpyridine) on Au or Pt electrodes was studied by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM) technique, and Raman spectroscopy. Cyclic voltammetry of the monomer at a microelectrode shows the typical Ru(III/II) and Ru(IV/III) waves, together with the vinyl reduction waves at −1.5 and −2.45 V and adsorption wave at −0.8 V. Electrodeposition on EQCM technique performed under potential cycling between −0.9 and −2.0 V revealed that the polymerization proceeded well in advance of the vinyl reduction waves. At potentials more positive than −0.9 V, soluble oligomers were deposited irreversibly on the electrode during the oxidative sweep. The film also showed reversible mass changes due to the oxidation and accompanying ingress of charge-balancing anions and solvent into the film. In contrast, potentiostatic growth of the polymer at −1.6 V was slower because the oligomeric material was lost completely from the electrode. Unreacted vinyl groups were detected by in situ Raman spectroscopy for films grown at −0.7, −0.9, and −1.6 V but were absent when the polymerization was carried out at −2.9 V vs Ag/Ag+. 相似文献
20.
A. D. Chervonnyi 《Russian Journal of Inorganic Chemistry》2010,55(4):556-559
The A1, O, AlO, A12O, Al2O2, WO2, and WO3, partial pressures in the vapor over Al2O3 in a tungsten Knudsen effusion cell between 2300 and 2600 K were derived from A1+, O+, AlO+, A12O+, Al2O2+, WO2+, and WO3+, ion intensities. The mass spectrometer was calibrated against the equilibrium constant of the WO3(g) = WO2(g) + O(g) reaction. Refined values of the ionization cross sections of AlO and A12O2 were used in the partial pressure calculations. The enthalpies of atomization of aluminum suboxides were determined to be
Δat
H
o(AlO, g, 0) = 510.7 ± 3.3 kJ mol−1, Δat
H
o(Al2O, g, 0) = 1067.2 ± 6.9 kJ mol−1, and Δat
H
o(Al2O2, g, 0) = 1556.7 ± 9.9 kJ mol−1. 相似文献