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31.
E. Zhecheva R. Stoyanova M. Gorova F. R. Alcantara J. Morales J. -L. Tirado 《Ionics》1997,3(1-2):1-15
A new method for the preparation of ultrafine LiCoO2 with a layered crystal structure was developed, which consists in thermal pyrolysis of homogeneous lithium-cobalt-citrate
precursors. Atomic scale mixing of Li and Co is achieved by citric acid acting as a chelating agent. Electron spectroscopy
of concentrated Li-Co-citrate solutions with Li:Co:Cit=1:1:1 and Li:Co:Cit=1:1:2 reveals that the predominant species at pH=7
are [Co(C6H5O7)]− and [Co(C6H5O7)2]4− complexes. Freeze-drying of the two types of solutions leads to the formation of LiCo(C6H5O7).nH2O and (NH4)3LiCo(C6H5O7)2.nH2O precursors, where Co2+ ions are complexed by one and two triionized citrate ions, respectively, and Li+ ions serve as counter ions. Between 400–600 °C, the thermal decomposition of these metal-citrate precursors yields LiCoO2 with layered and pseudo-spinel structure, the proportion between them being depending on: (i) the Co/citrate ratio; (ii)
the concentration of the freeze-dried solution; (iii) the heating rate. At 400 °C, the most defectless layered LiCoO2, consisting of hexagonal individual particles with dimensions of 120–170 nm, is a product of the bis-citrate decomposition
with a slow heating rate. For this sample, heating up to 600 °C does not affect the crystal size dimensions. For ultrafine
layered LiCoO2 and LiCoO2 obtained by solid state reaction at high-temperatures (850 °C), the deintercalation and intercalation reactions proceed in
the 3.95 – 3.99 and 3.86 – 3.88 voltage intervals, respectively. For defect trigonal LiCoO2, additional oxidation and reduction peaks at 3.7 – 3.8 and 3.4 – 3.5 V were observed. We did not succeed in preparing monophase
LiCoO2 with pseudo-spinel structure.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Sept. 14–21, 1996 相似文献
32.
33.
Vogliardi S Anichina K Stoyanova R Traldi P 《European journal of mass spectrometry (Chichester, England)》2005,11(1):43-51
The behaviour in electrospray conditions of a series of thiazol-benzimidazolones and 2- benzimidazolylsulphanyl ethanones has been studied by means of multiple tandem mass spectrometry experiments. Even though the experimental conditions were the same, different behaviour is observed for the two classes of compounds. In the case of thiazol-benzimidazolones, the formation of a protonated complex with CH3OH employed as solvent is observed, but in the case of 2-benzimidazolylsulphanyl ethanones the formation of MNa+ ions is privileged. This behaviour has been related to molecular structure. The collisionally-induced decompositions of MH+ ions have been rationalised in terms of the Stevenson-Audier and even-electron rules, as well as on the basis of proton affinity data. Thus, protonated thiazol-benzimidazolones undergo facile loss of CO and a series of different decomposition pathways involving cleavage of the thiazolone ring that reflect the structure of the neutral fragments. In contrast, the decompositions of the protonated 2-benzimidazolylsulphanyl ethanones are mainly related to the piperazine moiety, suggesting that the protonation takes place on this substructural unit. 相似文献
34.
C.H. Guendovitch K.S. Stoyanova P.S. Sharlandjiev 《Optics and Lasers in Engineering》1982,3(2):131-138
Two opto-electronic systems for seismic data information treatment are described. The possibilities of directional and frequency filtering and evaluation on the basis of the seismic section correlogram are discussed. 相似文献
35.
E. Zhecheva P. Zlatilova R. Stoyanova 《Journal of Physics and Chemistry of Solids》2010,71(5):848-986
The electrochemical performance of carbon-coated nanocrystalline LiFePO4 prepared by a freeze-drying method is examined. This method is based on the thermal decomposition of homogeneous phosphate-formate precursors. Structural and morphological characterization of LiFePO4 is carried out by powder XRD, BET measurements, SEM and XPS analyses. The electrochemical behaviour is tested in model lithium cells using galvanostatic mode. By changing the solution concentration, the freeze-drying method allows preparing LiFePO4 with mean particle sizes between 60 and 100 nm and different particle size distributions. The content of carbon appearing mainly on the particle surface depends on both the solution concentration and the annealing temperature. The effect of particle size distribution on the voltage profile of LiFePO4 is also demonstrated. The specific capacity is mainly determined by the amount of carbon deposited on the particle surfaces. 相似文献
36.
Radiative lifetimes of 8p2P3/1 (15.3 ns) and nf2F (7f2F5/2 - 24.7 m. 7f2F7/2 - 5.5 ns, 8f2F7/2 - 48.5 ns, 8f2F5/2 - 47.0 ns) levels of Hg+ have been measured employing delayed coincidence method. The dependencies of radiative lifetimes vs effective principal quantum number for np2P3/2 and np2F7/2 series are non linear. 相似文献
37.
Ivo Grabchev Evgenia Vasileva-Tonkova Desislava Staneva Paula Bosch Rositsa Kukeva Radostina Stoyanova 《International Journal of Polymer Analysis and Characterization》2018,23(1):45-57
A new polyamidoamine metallodendrimer modified with eight 1,8-naphthalimide units was synthesized. The Cu(II) complex has been investigated by EPR spectroscopy and it has shown that 17 copper ions have involved in the dendrimer complex. To confirm the presence of metallodendrimers on the cotton surface, scanning electron microscopy characterization has been used. In vitro antimicrobial activity of the metallodendrimer against different pathogens was investigated and compared to the dendrimer ligand free of copper ions. Both dendrimers were deposited on a cotton fabric and antibacterial activity of the treated cotton samples was investigated against model Gram-positive and Gram-negative bacteria. It has been shown that the studied dendrimers reduce bacterial growth and prevent the formation of biofilms. The metallodendrimer showed stronger antimicrobial and biofilm inhibiting abilities than those of the free of Cu(II) ions ligand. 相似文献
38.
Stoyanov ES Stoyanova IV Reed CA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(26):7880-7891
The competitive substitution of the anion (A(-)) in contact ion pairs of the type [Oct3NH+]B(C6F5)4 (-) by unsaturated hydrocarbons (L) in accordance with the equilibrium Oct3NH+...A(-) + nL right arrow over left arrow [Oct3NH+...Ln]A(-) has been studied in CCl4. On the basis of equilibrium constants, K, and shifts of nuNH to low frequency, it has been established that complexed Oct3NH...+Ln cations with n=1 and 2 are formed and have unidentate and bifurcated N--H+...pi hydrogen bonds, respectively. Bifurcated hydrogen bonds to unsaturated hydrocarbons have not been observed previously. The unsaturated hydrocarbons studied include benzene and methylbenzenes, fused-ring aromatics, alkenes, conjugated dienes, and alkynes. From the magnitude of the redshifts in the N--H stretching frequencies, Delta nuNH, a new scale for ranking the pi basicity of unsaturated hydrocarbons is proposed: fused-ring aromatics相似文献
39.
40.
T. V. Koksharova S. V. Kurando I. V. Stoyanova 《Russian Journal of General Chemistry》2012,82(9):1481-1484
Complexes of copper(II), nickel(II), cobalt(III), zinc(II), and iron(III) salicylates with thiosemicarbazide were synthesized. The resulting compounds were characterized by the elemental analysis data, infrared spectroscopy, diffuse reflectance spectroscopy, and thermogravimetry. 相似文献