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161.
Qiong Yu Lai Ji Zheng LuXiao Bo Su Xiao Yang Ji 《Journal of solid state chemistry》2002,165(2):312-316
Spinel compound LiNi1−xMnxVO4 (0≤x≤0.4) had been prepared by using the moist chemical method. X-ray diffraction spectra showed that the lattice constant increased with x in the LiNi1−xMnxVO4, XPS spectra indicating that Li1s had a chemical shift towards lesser binding energy, and manganese in LiNi1−xMnxVO4 existing as the mixed valence of Mn2+ and Mn3+. The electrochemical charge and discharge testing at a current density of 0.1 mA/cm2 between the potentials of 4.0 and 3.0 V vs Li/Li+ in 1 mol/dm3 LiPF6/EC+DEC (1:1 by volume) at 25°C showed that LiNi1−xMnxVO4 cell has a better rechargeability, but a lower cell voltage of 4.0 V vs Li/Li+ than that without the doping sample, and the capacity and the cycle efficiency of the Li/LiNi1−xMnxVO4 cells increased with x in the LiNi1−xMnxVO4. 相似文献
162.
The antioxidative effect of flavonols and their glycosides against the peroxidation of linoleic acid has been studied in homogeneous solution (tBuOH/H(2)O, 3:2) and in sodium dodecyl sulfate and cetyl trimethylammonium bromide micelles. The peroxidation was initiated thermally by the water-soluble initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and the reaction kinetics were studied by monitoring the formation of linoleic acid hydroperoxides. The synergistic antioxidant effect of the flavonols with alpha-tocopherol (vitamin E) was also studied by following the decay kinetics of alpha-tocopherol and the alpha-tocopheroxyl radical. Kinetic analysis of the antioxidative process demonstrates that the flavonols are effective antioxidants in solution and in micelles, either alone or in combination with alpha-tocopherol. The antioxidative action involves trapping the initiating radicals in solution or in the bulk-water phase of the micelles, trapping the propagating lipid peroxyl radicals on the surface of the micelles, and regenerating alpha-tocopherol by reducing the alpha-tocopheroxyl radical. It was found that the antioxidant activity of the flavonols and their glycosides depends significantly on the position and number of the hydroxy groups, the oxidation potential of the molecule, and the reaction medium. The flavonols bearing ortho-dihydroxy groups possess significantly higher antioxidative activity than those without such functionalities, and the glycosides are less active than their parent aglycones. The activity of the flavonols is higher in micelles than in solution, while the activity of alpha-tocopherol is lower in micelles than in solution. This is because the predominant factor for controlling the activity is the hydrogen-bonding interaction of the antioxidant with the micellar surface in the case of hydrophilic flavonols, while it is the inter- and intramicellar diffusion in the case of lipophilic alpha-tocopherol. 相似文献
163.
Marián Kucharík František Šimko Vladimír Danielik Miroslav Boča Roman Vasiljev 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1211-1215
Summary. The phase diagram of the system Na3AlF6–NaVO3 was determined by means of thermal analysis. The system is a simple binary eutectic one. The eutectic point was estimated
at x(NaVO3) = 0.975 and t
eut = 617°C. The XRD patterns of samples after thermal analysis revealed the presence of cryolite and NaVO3 only supporting the above assumption of a simple eutectic binary system. 相似文献
164.
通过X射线衍射分析和超导量子干涉磁强计(SQUID)磁性测量,研究了Co替代Fe含量对居里温度在室温以上的磁制冷材料La(Fe1-xCox)11.7Al1.3(x=0.072,0.081)磁结构和磁性能的影响。La(Fe1-xCox)11.7Al1.3材料的居里温度随Co的含量增加而增加,La(Fe0.919Co0.081)11.7Al1.3的居里温度为311 K。当外场变化为1.9 T时磁熵变达到3.6 J·kg^-1·K^-1,RCP值为168.6 J·kg^-1,虽然它的磁熵变小于具有巨磁熵变的磁制冷材料,但是它在磁场为1.9 T时的制冷能力与这些材料相当。 相似文献
165.
166.
The charge transport properties of mer-tris(8-hydroxyquinolinato)aluminum(III) (mer-Alq), which is the most widely used electron transport material in OLED, were investigated by quantum chemistry calculations within the framework of the charge hopping model and Marcus electron transfer theory. Internal reorganization energies of 0.276 and 0.242 eV were calculated by the DFT-B3LYP method employing a 6-31 G* basis set for the electrons lambdai(e) and holes lambdai(h), respectively. The relative distances and orientations of Alq molecules in amorphous film were simulated by those in the beta-phase. The intermolecular charge-transfer integrals, Hda(h) and Hda(e), along all 14 hopping pathways were then calculated by the Koopmans Theorem in conjunction with the Hartree-Fock method employing a 6-31 G* basis set as well as by the direct coupling method. The results showed that there were some Hda(e) that were 1 order of magnitude larger than any Hda(h), because hopping pathways with effective overlaps of LUMOs can occur and, thus, large Hda(e). On the other hand, effective overlap of HOMO was absent in all pathways, resulting in a relatively small Hda(h). This difference in the magnitudes of Hda(e) and Hda(h) would predict a 2 orders of magnitude difference in the electron-transfer rate constants and account for the observed 2 orders of magnitude difference in the mobilities of electrons and holes. 相似文献
167.
Cyril Prknyi Hui Liang Yuan Bo H. E. Strmberg Ariella Evenzahav 《Journal of heterocyclic chemistry》1992,29(4):749-753
The synthesis of ten new substituted 1,3,4-thiadiazolyl-4(3H)-quinazolinones 8–11, 13, 17 , and 20–23 is reported. Compounds 8–11 were prepared by condensation of 5-fluoro-2-methyl-3,1-benzoxazin-4-one (3) and 5-substituted 2-amino-1,3,4-thiadiazoles 4–7. Compound 13 was obtained by condensation of 5-fluoro-2-methyl-3,1-benzoxazin-4-one (3) with DL-α-amino-?-caprolactam (12) . Compound 17 was synthesized by condensation of 6-bromo-2-methyl-3,1-benzoxazin-4-one (16) and 2-amino-5-t-butyl-1,3,4-thiadiazole (5) . Compounds 20–23 were obtained by condensation of 5-chloro-6,8-dibromo-2-methyl-3,1-benzoxazin-4-one (19) and 5-substituted 2-amino-1,3,4-thiadiazoles 4–7, respectively. The substituted 3,1-benzoxazin-4-ones 3, 16, and 19 were obtained in good yield by refluxing the appropriate anthranilic acid, 1,15 , and 18 with acetic anhydride (2) . 相似文献
168.
SincethediscoveryofphosphoniumylidebyWittig',carbanionsstabilizedbyadjacentfifthorsixthgrouponiumionshavebeendevelopedasavaluablereactiveintermediate.However,despitethegreateffortsinylidechemistryinthepastfewdecades',relativelylittleisknownaboutthethermodynamicstabilitiesofylidecarbanions.Itiswellknowthatthequantitativemeasuresofthecarbanionstabilityhavecontributedagreatdealtothedevelopmentoforganicchemistry,thereforeitshouldbeexpectedthattheknowledgeaboutylidestabilitywillalsoprovidavaluableg… 相似文献
169.
The electric field gradient (EFG) tensors at the deuterons in the water molecules in BeSO4 · 4D2O at 25°C are reported. The quadrupole coupling constants (e2Q/h) and asymmetry parameters (η) for the two independent deuterons are 181.1(4) and 194.8(3) kHz, and 0.226(4) and 0.123(3), respectively. The EFG tensor corresponding to the smallest e2qQ/h is considerably distorted by the beryllium ion, which causes a high η value as well as a deviation of the y-principal axis by 21.8(6)° from the normal to the water molecule plane. A redetermination of the EFG tensors at the deuterons in the water molecule in Li2SO4 · D2O at 25°C and ?110°C is also reported. The e2Q/h and η values for the two deuterons are 236.6(1.2) and 239.8(1.1) kHz, and 0.091(8) and 0.126(7), respectively, at ?110°C. The corresponding e2qQ/h and η values for the averaged EFG tensor at 25°C are 125.8(1.1) kHz and 0.813(13), respectively. The results are in good agreement with those from the pioneer work by Ketudat and Pound, 20 years ago on the same compound. 相似文献
170.
IntroductionTriazenereagentsareinterestingbecauseoftheirstrongcomplexationabilitieswithtransitionmetals .1 6However,littledecolorationofthemcatalyzedbysilverionhasbeenstudiedinanalyticalchemistry .Manyanal ysistshavereportedtheuseofcatalyticreactionsfort… 相似文献