Polymeric ytterbium(ii) complex with pyridyl amido ligands

The reaction of potassium pyridyl amido ligand {L = [N(R)(2-C5H3N-6-Me)]–, R = CH2But} with YbI2(thf)2 afforded the linear polymeric complex [K0.5(L)3YbiiK0.5]n, which was characterized by X-ray structure analysis.     

Numerical Simulation on the Production Mechanism of Surface-Wave Plasmas Sustained along a Metal Rod

For interpreting the production mechanism of surface-wave plasmas sustained along a metal rod, electromagnetic simulation on the electromagnetic field distributions and particle-in-cell/Monte Carlo collision （PIC/MCC） simulation of the ionization process are present. The results show that the enhanced electric field of surface plasmon polaritons （SPPs） can be excited in the ion sheath layer between the negative-voltage metal rod and the surface-wave plasmas, which is responsible for maintaining the plasma discharge. Moreover, the spatio-temporal evolutions of plasma density and electric fields are simulated by the PIC/MCC model. It is further suggested that the expanded ion sheath layer can extend the length of plasma domain by increasing the plasma absorbed energy from SPPs.     

A theoretical study of the Y$\mathsf{_{3}}$O clusters

Hybrid density functional calculations are performed to study the structural and electronic properties of neutral, anionic and cationic Y₃O clusters. The most stable structures of these clusters are found to be triply bridging oxygen atom structures with C_S symmetry. The ground states of Y₃O, Y₃O^- and Y₃O ⁺ are doublet (²A), triplet (³A) and singlet (¹A), respectively. The calculated electron affinities and ionization potentials are in good agreement with the available experimental data. Time-dependent density functional theory is used to calculate the low-lying excited states. A theoretical assignment for the features in the experimental photoelectron spectra is given.Received: 5 November 2003, Published online: 20 January 2004PACS: 36.40.Mr Spectroscopy and geometrical structure of clusters - 31.15.Ew Density-functional theory - 34.50.Gb Electronic excitation and ionization of molecules; intermediate molecular states (including lifetimes, state mixing, etc.)     

Hierarchically assembled porous ZnO microstructures and applications in a gas sensor

This paper presents a facile, low-cost and pollution-free route to prepare porous metal oxide nanomaterials. Hierarchically assembled ZnO microstructures with multi-scaled porosity were obtained by calcining the flower-like assembly of a basic zinc carbonate (BZC) precursor which was synthesized by a facile low-temperature (100 ^°C) homogenous precipitation without using any organic solvent or surfactant. A gas sensor based on the porous ZnO sample exhibited higher response to ethanol and formaldehyde gases than commercial ZnO powder. The facile preparation method and the improved property derived from the hierarchically porous microstructure are of great significance in the synthesis and application of nanomaterials.     

Geometry dependence of the elongation behavior of a polypropylene melt through a micro die

A series of rheological experiments was performed for a polypropylene (PP) melt to explore its elongation behavior through a capillary die. Using an advanced twin-bore capillary rheometer with dies measuring 1.0, 0.5, and 0.25 mm in diameter, the experiments were performed at 210, 220, and 230 °C. The results indicated that the temperature of the PP melt had a significant effect on its extensional viscosity. The different decreases in the extensional viscosity values in the tested dies revealed the geometry dependence of the extensional viscosity. In the case of PP in the 0.25 mm die at 210 °C, the extensional viscosity values under different extensional strain rates were much higher than those in the other dies. Only in the 1.0 mm die did the relationship between the extensional viscosity of PP and its temperature obey the Arrhenius equation due to the larger die size which related to a slight size effect on its elongation behavior. The calculated deviations of the extensional viscosity in the tested dies demonstrated that the increasing pressure applied to the PP melt in the micro channel was related to the geometry dependence of the elongation behavior of the PP melt. The change in the extensional viscosity eventually relied on the interaction of the die geometry, the temperature, and the extensional stress of the PP melt.     

6-NO2-BTAMB与钴显色反应的研究与应用

研究了6-NO2-BTAMB与钴显色反应。实验表明,在pH6.2—7.4(CH2)6N4-HCl体系中,钴与试剂定量地形成稳定的蓝绿色络合物,表观摩尔吸光系数ε650=1.18×105L·mol-1.cm-1;钴浓度在0—6μg/10mL范围内符合比耳定律。用于VB12和钴分子筛中微量钴的测定,结果令人满意。