Toughness mechanism in polypropylene composites: Polypropylene toughened with elastomer and calcium carbonate

Polypropylene (PP) was modified with elastomer or CaCO₃ particles of two different sizes (1 μm and 50 nm) in various volume fractions. The dispersion morphology and mechanical properties of the two systems were investigated as functions of the particle size and volume fraction of the modifier. The brittle‐to‐tough transition occurred when the matrix ligament thickness was less than the critical ligament thickness, which was about 0.1 μm for the PP used here, being independent of the type of modifier. At the same matrix ligament thickness, the improvement of the toughness was obviously higher with the elastomer rather than with CaCO₃, but adding CaCO₃ increased the modulus of PP. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1656–1662, 2004     

Colorimetric recognition of different enzymology-concerning transition metals based on a hybrid cluster complex.

A hybrid cluster complex, formed by chelating a chromogenic ligand to a [2Fe-2S] cluster, sensitively exhibited differential colorimetric responses towards Hg2+, Cd2+, Cr3+, Pb2, Sn2+, Cu2+, Zn2+, Fe3+ and Co2+ in water at physiological pH. Speciation of some of these metal elements, such as Cr(III) and Sn(IV), was also studied by UV/Vis absorption.     

NMR investigation of concentrated alumina and silica slurries

The longitudinal relaxation times (T₁) of water in concentrated silica and alumina slurries were measured as a function of solids content. It was shown that the results could be fit very well with a two-phase fast-exchange model between free and surface-bound water. As expected, values of T₁ for bound water were in the order of 20–2000 times lower than that for free water, indicating a higher effective viscosity of the surface-bound water. The strength of the interaction depended on the particular surface, and all of the aluminas examined interacted more strongly with water than the two silicas studied, which themselves differed considerably. The chemical mechanical polishing (CMP) removal rate of tantalum by silica slurries was shown to be directly correlated with the interaction parameters, derived from the NMR relation times rather than with total surface hydroxyl group concentration.     

Nowhere zero 4‐flow in regular matroids

Jensen and Toft 8 conjectured that every 2‐edge‐connected graph without a K₅‐minor has a nowhere zero 4‐flow. Walton and Welsh 19 proved that if a coloopless regular matroid M does not have a minor in {M(K_3,3), M*(K₅)}, then M admits a nowhere zero 4‐flow. In this note, we prove that if a coloopless regular matroid M does not have a minor in {M(K₅), M*(K₅)}, then M admits a nowhere zero 4‐flow. Our result implies the Jensen and Toft conjecture. © 2005 Wiley Periodicals, Inc. J Graph Theory     

因素空间理论与知识表示的数学框架(XⅢ)──描述架中概念的结构(2)

本文是［１，１２］的继续，研究描述架中概念的结构；本文讨论后半部分，内容涉及概念内涵与外延的转换，清晰关系的内投影与内变换，概念的结构＊以及有关问题的注记。     

Microstructural evolution of decagonal quasicrystal in the undercooled Al72Ni12Co16 alloy melts

The microstructure evolution of decagonal quasicrystals in Al₇₂Ni₁₂Co₁₆ alloy was investigated by the electromagnetic melting and cyclic superheating method. Single-phase decagonal quasicrystals have been obtained when the undercoolings were larger than 60 K. The decagonal quasicrystals formed at various undercoolings show different microstructural morphologies. Furthermore, grain refinement was found near the undercooling of 120 K. Based on current thermodynamic and dendrite growth theories, a dimensionless superheating parameter was adopted to explain the effect of processing conditions on the microstructure of Al₇₂Ni₁₂Co₁₆ alloy. The result indicate that the fine equiaxied microstructure of decagonal quasicrystal (D-phase) formed near on undercooling of 120 K originates from the break-up of dendrites.     

The study of lithium fast ion conductors of Li3xLa0.67−xScyTi1−2yNbyO3 system

Perovskite-type lithium fast ion conductors of Li_3xLa_0.67−xSc_yTi_1−2yNb_yO₃ system were prepared by solid state reaction. X-Ray powder diffraction shows that perovskite solid solution form in the ranges of x=0.10, y≤0.10. AC impedance measurements indicate that the bulk conductivities and the total conductivities are of the order of 10⁻⁴ S·cm⁻¹ and 10⁻⁵ S·cm⁻¹ at 25 °C respectively. The compositions have low bulk activation energies of about 17 kJ/mol in the temperature ranges of 298 – 523 K and total activation energies of about 37 kJ/mol in the temperature ranges of 298 – 523 K.     

Effect of end groups on complexation kinetics between cyclodextrins and guest polymers

α‐Cyclodextrin (α‐CD) has been complexed with various poly(ethylene glycol) (PEG) derivatives in aqueous solution. It has been found that the end groups of PEG derivatives affect the complexation kinetics greatly, but have only a little influence on the thermodynamic behavior. By increasing the hydrophobicity of end groups, the complexation speeds up rapidly. On the other hand, the bulky end groups slow down the threading of polymeric guests into the cavity of CD. By changing the hydrophobicity and the size of end groups, the complexation rate can be adjusted in the range of several orders of magnitudes, which should be quite useful in the design of new supramolecular systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2050–2057, 2006     

Crystal and molecular structure of (μ-p-CH3C6H4C2S) (μ-n-C3H7S)Fe2(CO)6Co2(CO)6

The crystal and molecular structure of the complex containing cobalt-carbon and iron-sulfur cluster cores, (μ-p-CH₃C₆H₄C₂S) (μ-n-C₃H₇S)Fe₂(CO)₆Co₂(CO)₆, has been determined by X-ray diffraction method. The crystals are triclinic, space group P&1bar;, with a — 9.139(2), b=9.610(1), c-17.183(2) Å, α = 84.36(1), β-89.45(1), γ=88.15(1)°, V-1501.0 ų; Z=2, D_c=1.74 g/cm³. R=0.072, Rw=0.081. The results of the structure determination show a cobalt-carbon cluster core formed through the reaction of (μ-p-CH₃C₆H₄C₂S)(μ-n-C₃H₇S)Fe₂(CO)₆ with Co₂(CO)₈. In the cobalt-carbon cluster core, the bond length of the original C≡C lengthened to 1.324 Å which is close to the typical value of carbon-carbon double bond. The groups connecting the carbons of the cluster core are in cis position and lie on the opposite side of cobalt atoms. In this complex, the conformation of —SC₃H₇ is e-type, while that of —SC₂C₆H₄CH₃ is a-type.