pr3+ 激活的CaMoO4红色荧光粉的发光性质

采用高温固相法制备了稀土pr3+激活的Ca1-xPrxMoO4(0.005≤x≤0.02)系列红色荧光粉.荧光光谱表明:在453 nm激发下,样品产生了红光发射,其中对应于pr3+的特征跃迁3 P0→3F2位于654 nm的红色发射峰最强.分析了pr3的掺杂摩尔分数x对样品发光强度的影响,确定pr3+的最佳掺杂摩尔分数...     

N2��Ƶ�ŵ��������(e,N2+, N+)��PIC-MCģ��

采用PIC-MC自洽模型,模拟了氮气电容性耦合射频放电的微观等离子体过程及带电粒子(e,N2+,N+)的行为。结果表明,离子(N2+,N+)的运动状态滞后瞬时射频电场的变化;在两极附近,N2+具较高密度,但能量较低,N+具较低的密度但能量较高,两者的密度差6倍左右。两种离子轰击射频电极的能量分布变化规律类似,随放电参数变化,离子(N2+,N+)能量变化显著,其密度变化不明显。模拟的电子能量几率分布与测量结果一致。     

Effect of Mg doping and MgO-surface modification on the cycling stability of LiCoO2 electrodes

Two synthetic routes including Mg doping and MgO-surface modification were applied to the preparation of LiCoO₂ showing enhanced reversible cycling behaviour as cathode material in lithium ion batteries. Mg-doped LiCoO₂ was obtained by the citrate precursor method in the temperature range 750–900°C. The surface of LiCoO₂ was modified by coating with Mg(CH₃COO)₂ and subsequent heating at 600°C. XRD, chemical oxidative analysis and electron paramagnetic resonance (EPR) of Ni³⁺ spin probes were used to characterize the Mg distribution in LiCoO₂. Substitution of Co by Mg in the CoO₂-layers was found to have a positive effect on the cycling stability, while Mg dopants in LiO₂-layers did not influence the capacity fade. The accumulation of MgO on the surface of LiCoO₂ improves the cycling stability without loss of initial capacity.     

Nonextensive thermostatistics and deformed structures

We obtain a generalized Planck law within the framework of nonextensive statistics making use of a deformed oscillator system. Our results are used to fit the data from the COBE (Cosmic Background Explorer) satellite. Best fit values for the entropy parameter q, the deformation parameter r and for the temperature are found.     

Kinetic resolution of vic-diols by Bacillus stearothermophilus diacetyl reductase

The kinetic resolution of several racemic syn- and anti-1,2-diols by enzymatic oxidation with Bacillus stearothermophilus diacetyl reductase is described. The enantiomerically pure (R,R)- and (R,S)-diols are recovered in almost quantitative yield.     

Microstructure and rheology of polymer melts reinforced by long glass fibres: direct simulations

The two stages of classical modelling (formulation of the governing equations and finding their solutions) become particularly difficult, in fact practically unfeasable, in the case of concentrated suspensions of long fibres in polymer melts. In such situations it may be useful to explore a completely different route. One such route is offered by the idea of direct simulations. On this route the model is formulated by specifying the fibre–solvent and the fibre–fibre interactions. The passage from the single-fibre point of view to the macroscopic view on which rheological properties and the microstructure are observed is made by first calculating trajectories of all fibres in a model-system composed of several hundreds of fibres and making appropriate averages. The preliminary results of such simulations are in a good qualitative agreement with experimental observations for a polypropylene melt reinforced by long glass fibres. For examples, dilution and migration of fibres away from die walls are predicted; it is also observed that in concentrated situations the fibres form bundles which could in the entry flow generate large energy dissipation and oscillations.     

Organic Moiety-Regulated Photocatalytic Performance of Phosphomolybdate Hybrids for Hexavalent Chromium Reduction

Visible-light-driven photocatalytic Cr(VI) reduction is a promising pathway to moderate environmental pollution, in which the development of photocatalysts is pivotal. Herein, three hourglass-type phosphomolybdate-based hybrids with the formula of: (H₂bpe)₃[Zn(H₂PO₄)][Zn(bpe)(H₂O)₂]H{Zn[P₄Mo₆O₃₁H₆]₂} ⋅ 6H₂O ( 1 ) Na₆[H₂bz]₂[ZnNa₄(H₂O)₅]{Zn [P₄Mo₆O₃₁H₃]₂} ⋅ 2H₂O ( 2 ) and (H₂mbpy) {[Zn(mbpy)(H₂O)]₂[Zn(H₂O)]₂}{Zn[P₄Mo₆O₃₁H₆]₂} ⋅ 10H₂O ( 3 ) (bpe=trans-1,2-bi(4-pyridyl)-ethylene; bz=4,4′-diaminobiphenyl; mbpy=4,4’-dimethyl-2,2’bipyridine) were synthesized under the guidance of the functional organic moiety modification strategy. Structural analysis showed that hybrids 1 – 3 have similar 2D layer-like spatial arrangements constructed by {Zn[P₄Mo₆]₂} clusters and organic components with different conjugated degree. With excellent redox properties and wide visible-light absorption capacities, hybrids 1 – 3 display favourable photocatalytic activity for Cr(VI) reduction with 79%, 70% and 64% reduction rates, which are superior to that of only inorganic {Zn[P₄Mo₆]₂} itself (21%). The investigation of organic components on photocatalytic performance of hybrids 1 – 3 suggested that the organic counter cations (bpe, bz and mbpy) can effectively affect the visible-light absorption, as well as the recombination of photogenerated carriers stemmed from {Zn[P₄Mo₆]₂} clusters, further promoting their photocatalytic performances towards Cr(VI) reduction. This work provides an experimental basis for the design of functionalized photocatalysts via the modification of organic species.