共查询到20条相似文献,搜索用时 31 毫秒
1.
X. H. Liang K. Tsukada A. Toyoshima Z. J. Li M. Asai T. K. Sato N. Sato Y. Nagame 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(2):917-922
Adsorption of carrier-free radiotracers 181W and 93mMo produced in the 181Ta(p, n) and natNb(p, n) reactions, respectively, on anion-exchange resin was studied in mixed solution of HF and HNO3 in a concentration range of 10−4–10−1 M HF/0.1 M HNO3. Distribution coefficients (K
d) of 181W and 93mMo at 70 °C showed the V-shaped variation with the minimum at around 10−1 M HF/0.1 M HNO3, although variation of the K
d values for 93mMo was quite small compared with that for 181W. Formation of oxofluoro complexes for W and Mo is briefly discussed. 相似文献
2.
I. V. Kuz’min V. N. Solkan G. M. Zhidomirov V. B. Kazanskii 《Kinetics and Catalysis》2011,52(2):192-196
The thermodynamic parameters of the formation of the perylene radical cation in anhydrous hydrogen fluoride containing dissolved
dioxygen were calculated by the ab initio method MP2. The protonated product of HF autoprotolysis was modeled as the H(FH)3+ cluster. The 3O2 molecule was found to bind to the linear H(FH)3+ cluster via a hydrogen bond. As the charge and multiplicity of the system change upon the capture of an electron, the oxygen-hydrogen
fluoride cluster complex undergoes rearrangement to yield the hydroperoxyl radical OOH incorporated in a cycle formed by HF
molecules. The free energy of electron transfer from the perylene molecule to the 3O2 molecule in the HF medium is about −38 kcal/mol. 相似文献
3.
Sh. Sh. Nabiev I. I. Ostroukhova N. V. Revina L. P. Sukhanov 《Russian Chemical Bulletin》1998,47(3):417-422
The Raman spectra of ClOF2
+ cation in solutions of anhydrous HF were studied. In the ClOF2
+HF2
− and ClOF2
+BF4
−−HF systems, this cation exists as a pyramidal structure (C
s
symmetry), while in the ClOF2
+AuF6
−−HF system, it exists as a planar structure (C
2v
symmetry). Based on nonempirical calculations by the Hartree-Fock-Roothaan method, an explanation for the dependence of the
structure of the ClOF2
+ cation on the nature of the anion was proposed. For the Cl−O bond vibrations, the correlation functions of vibrational and
rotational relaxations were calculated, and the characteristic times of these processes were determined. The main contribution
to the formation of the band contours corresponding to the above-mentioned modes is made by the vibrational dephasing.
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 432–437, March, 1998. 相似文献
4.
Jinzhang Gao Yingying Zhang Jie Ren Ming Li Wu Yang 《Central European Journal of Chemistry》2010,8(3):602-606
A sensitive and convenient method for the determination of trace europium ions using an oscillating chemical reaction involving
Ce(IV) - KBrO3 - acetone - oxalic acid - H2SO4 was proposed. The results indicated that the changes in oscillating period (T) was linearly proportional to the negative
logarithmic concentration of Eu3+ (-log C) in the range of 1.41 × 10−8 ˜ 1.41 × 10−4 mol L−1 (r = 0.9982) with a detection limit of 1.04 × 10−9 mol L−1. The recoveries were limited to the range of 99.5% to 100.8%. Under the same conditions, other rare earth ions did not interfere
with the determination of Eu3+. In addition, a perturbation mechanism was also discussed briefly.
相似文献
5.
Liquid-phase reduction NO
3
−
using monometallic and bimetallic catalysts (5% Rh/Al2O3, 5% Rh-0.5% Cu/Al2O3, 5% Rh-1.5% Cu/Al2O3, 5% Rh-5% Cu/Al2O3 and a physical mixture of 5% Rh/Al2O3 and 1.5% Cu/Al2O3) was studied in a slurry reactor operating at atmospheric pressure. Kinetic measurements were performed for a low concentration
of nitrate (0.4 × 10−3−3.2 × 10−3 mol dm−3) and the temperature range 293–313 K. From the experimental data, it was found that the reduction of nitrate is first order
with respect to nitrate. On the basis of the rate constants, the apparent activation energy was established using a graphic
method.
Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 6, pp. 881–886.
This article was submitted by the authors in English. 相似文献
6.
H. López-González M. Jiménez-Reyes M. Solache-Ríos A. Rojas-Hernández 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):103-108
Solubility product (Lu(OH)3(s)⇆Lu3++3OH−) and first hydrolysis (Lu3++H2O⇆Lu(OH)2++H+) constants were determined for an initial lutetium concentration range from 3.72·10−5 mol·dm−3 to 2.09·10−3 mol·dm−3. Measurements were made in 2 mol·dm−3 NaClO4 ionic strength, under CO2-free conditions and temperature was controlled at 303 K. Solubility diagrams (pLuaq vs. pC
H) were determined by means of a radiochemical method using 177Lu. The pC
H for the beginning of precipitation and solubility product constant were determined from these diagrams and both the first
hydrolysis and solubility product constants were calculated by fitting the diagrams to the solubility equation. The pC
H values of precipitation increases inversely to [Lu3+]initial and the values for the first hydrolysis and solubility product constants were log10
β*
Lu,H
= −7.92±0.07 and log10
K*sp,Lu(OH)3 = −23.37±0.14. Individual solubility values for pC
H range between the beginning of precipitation and 8.5 were S
Lu3+ = 3.5·10−7 mol·dm−3, S
Lu(OH)2+ = 6.2·10−7 mol·dm−3, and then total solubility was 9.7·10−7 mol·dm−3. 相似文献
7.
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
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.
I. E. Animitsa E. N. Dogodaeva S. S. Nokhrin O. A. Kosareva A. Ya. Neiman 《Russian Journal of Electrochemistry》2010,46(7):734-740
Perovskite phases Ba3In2ZrO8 and Ba4In2Zr2O11 with the nominal concentration of structural oxygen vacancies 1/9 and 1/12, respectively, were synthesized by solid-phase
and solution methods. X-ray diffraction showed cubic symmetry of both phases with the unit cell parameter a = 0.4193(2) and 0.4204(3) nm, respectively. The absence of superstructural lines resulted in the conclusion on statistical
arrangement of oxygen vacancies. Thermogravimetry and mass spectrometry proved that both phases can reversibly absorb water
from gas phase (pH2O = 2 × 10−2 atm) with observed correlation between the concentration of oxygen vacancies and amount of absorbed water. The total water
amount was up to 0.9 mol per formula unit or, if recalculated for perovskite unit ABO3, 0.3 and 0.23 mol H2O, respectively. The temperature curves of coductivity in the atmosphere with various partial water vapor pressures (pH2O = 3 × 10−5 and 2 × 10−2 atm) showed significantly higher conductivity and lower activation energy (0.52 eV) in humid atmosphere due to proton transfer.
The proton conductivity is up to 5 × 10−4 Ohm−1 cm−1 at 300°C for Ba3In2ZrO8 specimen. IR spectrometry showed that protons in the structure exist primarily in OH-groups. 相似文献
10.
I. G. Fomina Zh. V. Dobrokhotova G. G. Aleksandrov O. Yu. Proshenkina M. L. Kovba A. S. Bogomyakov V. N. Ikorskii V. M. Novotortsev I. L. Eremenko 《Russian Chemical Bulletin》2009,58(1):11-20
Methods were developed for the controlled thermal synthesis of high-spin cubane-like pivalates {MII
4(μ3−OR)4} (M = Co or Ni; R = H or Me) starting from mono-and polynuclear complexes. The solid-state thermal decomposition of the known
pivalate clusters [MII
4(μ3−OMe)4−(μ2−OOCBut)2(η2−OOCBut)2(MeOH)4] and the new clusters [M4II(μ3)−OH4(η1−OOCBut)3−(μ−(NH2)2C6H2Me2)3(η1−(NH2)2C6H2Me2)3]+(OOCBut)− (M = Co or Ni) was studied by differential scanning calorimetry and thermogravimetry. The thermolysis of cubane-like CoII
and NiII pivalates is a destructive process. The phase composition of the decomposition products is determined by the nature
of coordinated ligands and the structural features of the metal core. 相似文献
11.
Electrocatalytic oxygen reduction was studied on a RuxFeySez(CO)n cluster catalyst with Vulcan carbon powder dispersed into a Nafion film coated on a glassy carbon electrode. The synthesis
of the electrocatalyst as a mixture of crystallites and amorphous nanoparticles was carried out by refluxing the transition
metal carbonyl compounds in an organic solvent. Electrocatalysis by the cluster compound is discussed, based on the results
of rotating disc electrode measurements in a 0.5 M H2SO4. A Tafel slope of −80.00±4.72 mV dec−1 and an exchange current density of 1.1±0.17×10−6 mA cm−2 was calculated from the mass transfer-corrected curve. It was found that the electrochemical reduction reaction follows the
kinetics of a multielectronic (n=4e−) charge transfer process producing water, i.e. O2+4H++4e−→2H2O.
Electronic Publication 相似文献
12.
The rate constants of the reactions of the chlorine atom with C3F7I (k
1) and CF3I (k
2) have been measured using the resonance fluorescence of chlorine atoms in a flow reactor at 295 K: k
1 = (5.2 ± 0.3) × 10−12 cm3 molecule−1 s−1 and k
2 = (7.4 ± 0.6) × 10−13 cm3 molecule−1 s−1. No iodine atoms have been detected in the reaction products. 相似文献
13.
S. Y. Sawant V. M. S. Verenkar S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2007,88(3):669-672
Samples of water based commercial acrylic resin paints were spread in a film form on slides, dried at room temperature and
exposed to solar radiation for up to eight months.
The characterization and quantification of resins and charges in the white paint emulsion were carried out for the thermal
decomposition. Besides this, X-ray diffractometry was used to identify CaCO3 as charge and TiO2 (rutile phase) as pigment.
It was observed through thermal techniques similar behavior to the samples even though with varied exposure time.
Kinetic studies of the samples allowed to obtain the activation energy (E
a) and Arrhenius parameters (A) to the thermal decomposition of acrylic resin to three different commercial emulsion (called P1, P2, P3) through non-isothermal procedures. The values of E
a varied regarding the exposition time (eight months) and solar radiation from 173 to 197 kJ mol−1 (P1 sample), from 175 to 226 kJ mol−1 (P2 sample) and 206 to 197 kJ mol−1 (P3 sample).
Kinetic Compensation Effect (KCE) observed for samples P2 and P3 indicate acrylic resin s present in these may be similar in nature. This aspect could be observed by a small difference in the thermal behavior of
the TG curves from P1 to P2 and P3 sample.
The simulated kinetic model to all the samples was the autocatalytic Šesták-Berggreen. 相似文献
14.
Summary. Calcium sulfate occurs in nature in form of three different minerals distinguished by the degree of hydration: gypsum (CaSO4·2H2O), hemihydrate (CaSO4·0.5H2O) and anhydrite (CaSO4). On the one hand the conversion of these phases into each other takes place in nature and on the other hand it represents
the basis of gypsum-based building materials. The present paper reviews available phase diagram and crystallization kinetics
information on the formation of calcium sulfate phases, including CaSO4-based double salts and solid solutions.
Uncertainties in the solubility diagram CaSO4–H2O due to slow crystallization kinetics particularly of anhydrite cause uncertainties in the stable branch of crystallization.
Despite several attempts to fix the transition temperatures of gypsum–anhydrite and gypsum–hemihydrate by especially designed
experiments or thermodynamic data analysis, they still vary within a range from 42–60°C and 80–110°C. Electrolyte solutions
decrease the transition temperatures in dependence on water activity.
Dry or wet dehydration of gypsum yields hemihydrates (α-, β-) with different thermal and re-hydration behaviour, the reason
of which is still unclear. However, crystal morphology has a strong influence.
Gypsum forms solid solutions by incorporating the ions HPO4
2−, HAsO4
2−, SeO4
2−, CrO4
2−, as well as ion combinations Na+(H2PO4)− and Ln3+(PO4)3−. The channel structure of calcium sulfate hemihydrate allows for more flexible ion substitutions. Its ion substituted phases
and certain double salts of calcium sulfate seem to play an important role as intermediates in the conversion kinetics of
gypsum into anhydrite or other anhydrous double salts in aqueous solutions. The same is true for the opposite process of anhydrite
hydration to gypsum. Knowledge about stability ranges (temperature, composition) of double salts with alkaline and alkaline
earth sulfates (esp. Na2SO4, K2SO4, MgSO4, SrSO4) under anhydrous and aqueous conditions is still very incomplete, despite some progress made for the systems Na2SO4–CaSO4 and K2SO4–CaSO4–H2O.
Corresponding author. E-mail: daniela.freyer@chemie.tu-freiberg.de
Received December 17, 2002; accepted January 10, 2003
Published online April 3, 2003 相似文献
15.
F. Poineau T. Hartmann G. W. Chinthaka Silva G. Jarvinen K. Czerwinski 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):43-48
A new method for the preparation of Tc metal from pertechnetate is described. Metallic technetium was prepared from TcO4− by initial reduction in dry argon atmosphere at 300 °C followed by a wet argon atmosphere in the presence of carbon between
700 and 910 °C. The higher temperature conditions in the presence of H2O and carbon form H2 and CO, which can drive the reduction of TcO2. This method was applied to the recovery of pertechnetate sorbed on anion-exchange resins resulting in the formation of Tc
metal microspheres. The resulting Tc was characterized by XRD analysis and SEM. 相似文献
16.
The complex impedance method in the temperature range of 291–660 K was used to study conductivity of oxofluoride BiO0.1F2.8 belonging to the tysonite structural type (LaF3). Bismuth oxofluoride was synthesized using a solid-phase method at 770–870 K for 1–2 h in an argon atmosphere. Heterovalent
substitution of fluoride ions F− by oxygen ions O2− in the anionic BiF3 matrix sublattice results in high ionic conductivity (∼0.1 S/cm at 660 K) of BiO0.1F2.8 ceramic samples. 相似文献
17.
Qingyang Liu 《Central European Journal of Chemistry》2010,8(2):326-330
This work presents a nano-Al2O3 solid phase extraction technique for the determination of ultra-trace amounts of inorganic selenium species in aqueous systems
using ion chromatography inductively coupled plasma-mass spectrometry (IC-ICP-MS). In this experiment, the inorganic selenium
species were successfully extracted on a nano-Al2O3 solid phase column and then quantitative eluted with a 100 mmol L−1 NaOH solution. Extraction conditions such as solvent identity, solvent concentration, solvent volume, solvent pH and salt
addition were optimized. Under the optimum extraction conditions (elute solvent: 100 mmol L−1 NaOH, solvent volume: 4 mL, pH: 7.0), low detection limits (Se (IV): 6 ng L−1, Se (VI): 11 ng L−1; RSD<5.0%) and good linear range (0.5–100 ng mL−1, R2 > 0.999) were obtained for all of the analytes. Good spiked recoveries over the range of 80–98% were obtained by applying
the proposed method on real environmental water samples. These results indicated that this method is very sensitive and reliable
when monitoring trace levels of inorganic selenium species in aqueous samples.
相似文献
18.
A. N. Mansurova R. I. Gulyaeva V. M. Chumarev V. P. Mar’evich 《Journal of Thermal Analysis and Calorimetry》2010,101(1):45-47
Homogeneous manganocolumbite (MnNb2O6) was synthesized from Nb2O5 and MnO oxides. Powder sample was orthorhombic with unit cell parameters: α = 0.5766 nm, b = 1.4439 nm, c = 0.5085 nm and V = 0.4234 nm3. Heat capacity over the temperature range of 313–1253 K was measured in an inert atmosphere with combined thermogravimetry
and calorimetry using NETZSCH STA 449C Jupiter thermoanalyzer. Melting point was 1767 ± 3 K, enthalpy of melting was 144 ± 4 kJ mol−1. Experimental heat capacity of MnNb2O6 is fitted to polynomial C
pm = 221.46 + 3.03 · 10−3 T + −39.79 · 105 T
−2 + 40.59 · 10−6 T
2. 相似文献
19.
D. V. Vrazhnov T. A. Kochina A. A. Alferova I. S. Ignat’ev 《Russian Journal of General Chemistry》2011,81(6):1131-1136
B3LYP method with the LANL2DZ basis for tin and aug-cc-pVDZ basis for carbon and hydrogen were used to obtain the equilibrium
geometry of the main (with a positive charge on the tin) isomers in the C4H11Sn+ system and the transition states at their interconversion. As in the case of silicon and germanium, the cations of lighter
elements of the 14th group, the most stable isomer is shown to be the tertiary ion, however, the energy of its complexes with
ethane and propane is higher only by several kJ mol−1. Nevertheless, the formation of these complexes from the tertiary ion requires overcoming a rather high barrier (293 and
272 kJ mol−1, respectively). The barrier for isomerization of the secondary ion in the ethane complex is somewhat lower (222 kJ mol−1), but still is significantly greater than the energy gained at the appearance of the nucleogenic ion. The most probable transformation
pathways of the nucleogenic stannylium ions are the formation of complexes with ethylene, which requires overcoming barriers
of 130 and 117 kJ mol−1 for the tertiary and secondary ions, respectively. 相似文献
20.
I. A. Sokolov I. V. Murin V. E. Kriyt A. A. Pronkin 《Russian Journal of Electrochemistry》2011,47(4):410-415
The influence of the SO42− ion on the temperature and concentration dependences of electric conductivity and the structure of sodium phosphate oxide
glasses was studied. The increased electric conductivity of sulfate-phosphate glasses was explained by the formation of mixed
sulfate-phosphate fragments with terminal SO42− ions in the structure of glasses in the Na2SO4-NaPO3 system. The dissociation energies of the sodium sulfate fragments are lower than those of pure oxide sodium phosphate structural
units. As a result, the number of dissociated sodium ions increases, the activation energy of electric conductivity falls,
and the conductivity (at 25°C) increases approximately 270-fold relative to the conductivity of NaPO3. The arrangement of SO42− ions in the structure was evaluated from the IR spectra of the glasses. 相似文献