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61.
近年来,人们对二次锂电池的正极进行了不少研究。许多过渡金属氧化物或硫化物,如V_6O(13),Li_(1+x)V_3O_8,TiS_2,MoS_2等被认为是较好的正极材料。Pistoia等研究了Li_(1+x)V_3O_8钒青铜的电化学性能得出,当Li浓度高时,由于电子定域作用使电荷屏蔽效应 相似文献
62.
The mechanism is investigated for CptBuRh(OH)2-catalyzed annulation of 2-biphenylboronic acid with three activated alkenes using M06-2X functional. The reaction comprises transmetalation via two steps and following C-H activation producing reactive Rh-biphenyl complex with two Rh—C σ bonds. After the coordination/insertion of alkenes, respective fused or bridged cyclic products are yielded depending on different alkenes accompanied by the release of CptBuRh. The promotion of CptBuRh(OH)2 lies in the barrier decrease of transmetalation and C-H activation ready for coordination/insertion ensuring the smooth progress of common rate-limiting reductive elimination. The stereoselective transfer and ring rotation are specific for benzoquinone and cyclopropenone. The role of Rh(III) catalyst and release of Rh(I) is supported by Multiwfn analysis on frontier molecular orbital(FMO) of specific transiton states(TSs) and Mayer bond order(MBO) value of vital bonding, breaking. 相似文献
63.
《中国化学》2017,35(11):1731-1738
The copolymerization of ethylene and styrene can be efficiently carried out by using Cp*TiCl2 (N = Ct Bu2)/MAO (Cp*=η 5‐C5Me5 ) system, yielding the poly(ethylene‐co ‐styrene)s with isolated styrene units. In order to investigate the reasons for formation of the structure, the mechanism of copolymerization, especially the selective insertion of ethylene and styrene, is studied in detail by density functional theory (DFT ) method. At the initiation stage, insertion of ethylene is kinetically more favorable than insertion of styrene, and insertion of styrene kinetically and thermodynamically prefers 2,1‐insertion. That is different from the conventional half‐titanocene system, in which the 1,2‐insertion is favorable. At chain propagation stage, the computational results suggest that the continuous insertion of styrene is hard to occur at room temperature due to the high free energy barriers (28.90 and 35.04 kcal/mol for 1,2‐insertion, and 29.15 and 34.00 kcal/mol for 2,1‐insertion) and thermodynamically unfavorable factors in two different conditions. That is mainly attributed to the steric hindrance between the coming styrene and chain‐end styrene or ketimide ligand. The computational results are in good agreement with the experimental data. 相似文献
64.
《Angewandte Chemie (International ed. in English)》2017,56(40):12064-12084
Magnesium metal is a superior anode which has double the volumetric capacity of lithium metal and has a negative reduction potential of −2.37 V vs. the standard hydrogen electrode. A major benefit of magnesium is the apparent lack of dendrite formation during charging which is one of the crucial concerns of using a lithium metal anode. In this Review, we highlight the foremost research in the development of electrolytes and cathodes and discuss some of the significant challenges which must be overcome in realizing a practical magnesium battery. 相似文献
65.
V. Lj. Marković M. M. Pejović Z. Lj. Petrović 《Plasma Chemistry and Plasma Processing》1996,16(2):195-208
The late afterglow in nitrogen with iron electrode is studied by the breakdown time delay method, i.e., by measuring the breakdown time delay td as a function of the afterglow time . It is proposed that the cause of the secondary electrons initiating the breakdown is the energy of the surface recombination of nitrogen atoms on the iron electrode. The gas-phase and macrokinetic diffusive models are used to describe the experimental breakdown time delay data. By fitting the theoretical curve to the experimental data: (1) it has been confirmed that the recombination on the molybdenum glass is of the second order and the value of the surface recombination coefficient is determined at 4 mbar; (2) it has been shown that the surface recombination on the iron electrode is of the second order, and the effective recombination coefficients are determined; (3) the analytical form of the recombination coefficient as a function of the adsorption characteristics of surfaces and the pressure of the parent gas has been derived. In addition, the orders of surface recombination on the molybdenum-, aluminum-, and gold-plated electrode were determined by the same method. 相似文献
66.
67.
《Macromolecular bioscience》2018,18(8)
Two bis(diaryldiazomethane)s substituted with amino groups are synthesized and used for the surface modification of membranes electrospun from gelatin. These membranes are then reacted with tolylene‐2,4‐diisocyanate to give urea‐functionalized materials, so that hydrogen peroxide can be reversibly bound onto their surface. These membranes are characterized by scanning electron microscopy, XPS, differential scanning calorimeter, and tensile test to show their surface properties and bulk properties. The surface modification with amino‐substituted diazomethanes and the subsequent cross‐linking reaction with diisocyanates contribute to high loadings of hydrogen peroxide, and greatly increase the antibacterial activity of gelatin‐derived membranes, which open a new horizon in the preparation of high loading antiseptic/antibacterial biomacromolecular surfaces and interfaces. 相似文献
68.
This paper is concerned with a nonlinear Timoshenko system with a time delay term in the internal feedback together with initial data and Dirichet boundary conditions. Under some suitable assumptions on the weights of feedback, we obtain the existence of a global attractor with finite fractal dimension for the case of equal speed wave propagation. Furthermore, the existence of exponential attractors is also derived. 相似文献
69.
Dependence of stability of Nicholson's blowflies equation with maturation stage on parameters 下载免费PDF全文
The stability of Nicholson''s blowflies equation with maturation stage is investigated by reducing the number of parameters in the original model. We derive the condition on the stability of the positive equilibrium of the model, and discuss the dependence of the stability on the parameters by analyzing geometrically the dependence of real parts of eigenvalues of the characteristic equation with fewer parameters on the parameters. By restoring parameters, the condition on the stability of the positive equilibrium of the original model are formulated explicitly, and the corresponding regions are depicted for some different cases. The obtained result shows that the parameter determining the maximum reproductive success of the population affects only the size of the positive equilibrium, but plays no role in determining its stability. 相似文献
70.
In this paper, We investigate Hopf-zero bifurcation with codimension 2 in a delayed predator-prey model with dormancy of predators. First we prove the specific existence condition of the coexistence equilibrium. Then we take the mortality rate and time delay as two bifurcation parameters to find the occurrence condition of Hopf-zero bifurcation in this model. Furthermore, using the Faria and Magalhases normal form method and the center manifold theory, we obtain the third order degenerate normal form with two original parameters. Finally, through theoretical analysis and numerical simulations, we give a bifurcation set and a phase diagram to show the specific relations between the normal form and the original system, and explain the coexistence phenomena of several locally stable states, such as the coexistence of multi-periodic orbits, as well as the coexistence of a locally stable equilibrium and a locally stable periodic orbit. 相似文献