Crystallographic and electrochemical characteristics of Ti-Zr-Ni-Pd quasicrystalline alloys

Ti45Zr35Ni20-xPdx (x = 0, 1, 3, 5 and 7, at%) alloys were prepared by melt-spinning. The phase structure and electrochemical hydrogen storage performances of melt-spun alloys were investigated. The melt-spun alloys were icosahedral quasicrystalline phase, and the quasi-lattice constant increased with increasing x value. The maximum discharge capacity of alloy electrodes increased from 79 mAh/g (x = 0) to 148 mAh/g (x = 7). High-rate dis-chargeability and cycling stability were also enhanced with the increase of Pd content. The improvement in the electrochemical hydrogen storage characteristics may be ascribed to better electrochemical activity and oxidation resistance of Pd than that of Ni.

Influence of metal particle size on the hydrogenation of maleic anhydride over Pd/C catalysts in scCO(2)

Hydrogenation of maleic anhydride (MAH) with Pd/C catalysts in supercritical carbon dioxide (scCO(2)) was investigated. The selectivity for gamma-butyrolactone (GBL) reached 97.3% in scCO(2) at 100% conversion of MAH, which was notably higher than that of 77.4% obtained in organic solvent of ethylene glycol dimethyl ether (EGDME). The particle size of Pd exhibited large influence on the reaction rate and selectivity of GBL. Higher selectivity of GBL was obtained with Pd/C catalyst of smaller Pd particle size, and the rate of GBL selectivity increase as a function of CO2 pressure was found to be significantly correlated with Pd particle size.

Synthesis and characterization of rigid-rod sulfonated polyimides bearing sulfobenzoyl side groups as proton exchange membranes

A novel wholly aromatic diamine, 2,2 '-bis(3-sulfobenzoyl)benzidine (2,2 '-BSBB), was successfully prepared by the reaction of 2,2 '-dibenzoylbenzidine (2,2 '-DBB) with fuming sulfuric acid. Copolymerization of 1,4,5,8-naphathlenetetracarboxylic dianhydride with 2,2 '-BSBB and 2,2 '-DBB generated a series of rigid-rod sulfonated polyimides. The synthesized copolymers with the -SO3H group on the side chain of polymers possessed high molecular weights revealed by their high viscosity and the formation of tough and flexible membranes. The copolymer membranes exhibited excellent oxidative stability and mechanical properties due to their fully aromatic structure extending through the backbone and pendent groups. They displayed clear anisotropic membrane swelling in water with negligibly small dimensional changes in the plane direction of the membrane. The proton conductivities of copolymer membranes increased with increasing IEC and temperature, reaching value above 1.25 x 10(-1) S/cm at 20 degrees C, which is higher than that of Nafion (R) 117 at the same measurement condition. They displayed reasonably high proton conductivity due to the higher acidity of benzoyl sulfonic acid group, the larger interchain spacing, which is available for water to occupy, taking their lower water uptake (WU) into account. Consequently, these materials proved to be promising as proton exchange membrane.

纳米GdPO_4:Eu~(3+)的制备、结构和发光特性

采用沉淀法,在不同pH值、EDTA二钠盐参加和不同温度等条件下制备出纳米GdPO4:Eu3+。利用X射线衍射,扫描电镜和荧光光谱等测试手段对制备的纳米GdPO4:Eu3+的结构,形貌和发光性能进行了研究。XRD和SEM研究结果表明:所有样品均为纯GdPO4相,纳米粒子的大小、形貌和晶面的发育与合成条件有关;发射光谱和激发光谱的研究结果表明:5D0-7FJ特征发射峰强度和激发光谱的强度随pH值和烧结温度的提高而增强,EDTA二钠盐参加合成的样品,由于在表面残留有机基团使发光强度降低。纳米粒子的猝灭浓度约为8%(摩尔分数,下同)。

Atomic force microscope investigation of large-circle DNA molecules

A circular bacterial artificial chromosome of 148.9 kbp on human chromosome 3 has been extended and fixed on bare mica substrates using a developed fluid capillary flow method in evaporating liquid drops. Extended circular DNA molecules were imaged with an atomic force microscope (AFM) under ambient conditions. The measured total lengths of the whole DNA molecules were in agreement with sequencing analysis data with an error range of +/-3.6%. This work is important groundwork for probing single nucleotide polymorphisms in the human genome, mapping genomic DNA, manipulating biomolecular nanotechnology, and studying the interaction of DNA-protein complexes investigated by AFM.

Ordered pattern formation from dewetting of polymer thin film with surface disturbance by capillary force lithography

The dewetting process of thin polystyrene (PS) film with built-in ordered disturbance by capillary force lithography (CFL) has. been investigated in situ by AFM. Two different phenomena are observed depending on the excess surface energy (DeltaF(gamma)) of the system. When DeltaF(gamma) is less than a certain critical value (i.e., the disturbance amplitude is under a critical value), the PS film would be flattened and become stable finally by heating above T-g. While, if the size of the disturbance amplitude is larger than the critical value, ordered PS liquid droplets form by further dewetting. The pattern formation mechanisms and influencing factors have been discussed in detail.

Electropolymerization of azure B on a screen-printed carbon electrode and its application to the determination of NADH in a flow injection analysis system

The electrooxidation polymerization of azure B on screen-printed carbon electrodes in neutral phosphate buffer was studied. The poly(azure B) modified electrodes exhibited excellent electrocatalysis and stability for dihydronicotinamide adenine dinucleotide (NADH) oxidation in phosphate buffer (pH 6.9), with an overpotential of more than 400 mV lower than that at the bare electrodes. Different techniques, including cyclic voltammetry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy have been employed to characterize the poly (azure B) film. Furthermore, the modified screen-printed carbon electrodes were found to be promising as an amperometric detector for the flow injection analysis (FIA) of NADH, typically with a dynamic range of 0.5 muM to 100 muM.

Complex aggregates of spherical colloids via modified micromolding in capillaries

This paper describes a simple approach to fabricate aggregates composed of monodispersed silica microspheres by modified micromolding in capillaries (MIMIC). Two different kinds of contact modes, namely, conformal contact and non-conformal contact, between the poly(dimethylsiloxane) (PDMS) mold and the underlying prepatterned substrate, can be controlled during the micromolding, which result in the formation of different aggregates under the influence of template confinement and capillary forces. These aggregates, including woodpile structure, discoid, conoid and rectangular clusters, possess well-controlled sizes and orientation. The possible mechanisms for the formation of different aggregates are discussed in detail.

几种CPP树脂的pVT特性

利用 PVT- 100分析仪对几种不同牌号的流延聚丙烯 (CPP)进行了 p VT特性测量 ,得到了比容随温度和压力变化的关系。通过公式法计算出热膨胀系数 α和等温压缩系数 β与温度和压力的依赖关系 ,并与由 Tait方程计算出的 α和 β结果进行了比较。另外从比容随温度和压力变化的关系图得到了各种牌号 CPP熔融温度 Tm 与压力的关系。最后通过高温凝胶渗透色谱 GPC法测量实验前后样品的分子量表明 CPP在 p VT特性测试过程中有部分降解

UV-VUV excited luminescence of SrBPO5 : Sm phosphor prepared in air

The high-resolution luminescent spectrum of divalent samarium excited by 355 nm UV light at 77 K, the VUV excitation spectra, the VUV excited emission spectra and EXAFS at Sm-L-3 edge were reported for samarium doped strontium borophosphate, SrBPO5:Sm prepared by solid state reaction in air at high temperature. The high-resolution luminescent spectrum showed that the divalent samarium ions occupied the C-2upsilon lattice sites. The VUV excitation spectra indicated that the sample exhibited absorption bands with the maxima at 129 and 148 nm, respectively. The performance of EXAFS at Sm-L3 absorption edge suggested that the samarium ions were nine-coordinated and the mean distances of bond Sm-O were 2.38 Angstrom.

Hydrothermal synthesis and crystal structure of a novel compound: [Ni(phen)(3)](2)[(SiMo10V2O40)-O-IV((VO)-O-IV)2]center dot 2H(2)O

A novel compound [Ni(phen)(3)](2)[(SiMo10V1/2O40)-O-V((VO)-O-IV)(2)] . 2H(2)O has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The compound crystallizes in the triclinic, system, space group P-1, a = 12.378(4) Angstrom, b = 14.148(5) Angstrom, c = 14.316(2) Angstrom, alpha = 105.91(2)degrees, beta = 95.31(2)degrees, gamma = 96.89(3)degrees, V = 2373.0(12) Angstrom(3), Z = 1, (lambdaMo(Kalpha)) = 0.71073 Angstrom, R1 (wR2) = 0.0869(0.2174). Data were collected on a Siemens P4 four-circle diffractometer at 293 K in the range of 1.51 < theta < 22.50degrees using the omega-scan technique. Empirical absorption correction (psi scan) was applied. The structure was solved by the direct method and refined by the Full-matrix least-squares on F-2 using the SHELXL-97 software. X-ray crystallographic study showed that the title compound contained a bi-capped alpha-Kegin-type [(SiMo10V2O40)-O-IV((VO)-O-IV)(2)](4-) polyoxoanion.

Study on the transesterification of poly(beta-hydroxybutyrate) and poly(epsilon-caprolactone)

The transesterification of poly(beta-hydroxybutyrate) (PHB) and poly(epsilon-caprolactone) (PCL) was carried out by using stannous octoate as catalyzer in liquid phase. The effects of reaction conditions on the transesterification, including reaction temperature, reaction time and catalyzer content, were investigated. The sequence distribution, crystallization behavior and thermal stability of PHB-co-PCL copolyesters were studied by C-13-NMR, FTIR, DSC, WAXD and TGA. The results showed that the transesterification of PHB with PCL was confirmed to produce a block copolymer, and enhancing reaction temperature and increasing reaction time were advantageous to the transesterification. With the increase in PCL content in the block copolymer, the crystallization behavior of PHB-co-PCL copolyesters changed evidently. On the other hand, the introduction of PCL segment into PHB chains did not change its crystalline structure; moreover, thermal stability of PHB-co-PCL copolyesters was a little improved in air, comparing with that of pure PHB.

聚β-羟基丁酸酯和聚ε-己内酯的酯交换反应

以辛酸亚锡为催化剂 ,研究了聚 β 羟基丁酸酯 (PHB)与聚ε 己内酯 (PCL)在液相条件下的酯交换反应 .讨论了反应时间 ,反应温度和催化剂浓度对酯交换反应的影响 .采用1 3C NMR ,FTIR ,DSC ,WAXD和TGA等方法对PHB和PCL共聚酯 (PHB co PCL)的结构进行了表征 ,并对其结晶行为、晶体结构和热稳定性进行了研究 .结果表明 ,通过酯交换反应 ,所得到的共聚酯为嵌段共聚物 .提高反应温度和延长反应时间有利于酯交换反应的发生 .随着酯交换量的增加 ,PHB co PCL的结晶行为发生很大的变化 .但是 ,PHB co PCL晶体结构并没有因为PCL链段的引入而发生变化 ,而且它的热稳定性在空气气氛中略有提高

溶胶对辐射交联高密度聚乙烯的熔融行为及非等温结晶动力学的影响

通过差示扫描热分析对辐射交联高密度聚乙烯的纯溶胶、纯凝胶及溶凝胶混合体系的熔融和非等温结晶动力学行为进行了研究。结果表明，在相同辐射剂量下，含有溶胶的试样的熔点及结晶峰温均高于纯凝胶试样。含有溶胶的试样，其Avrami指数基本上高于相应的纯凝胶的Avrami指数，且前者的数值更接近原始高密度聚乙烯。因此，溶胶的存在与否，对辐射交联高密度聚乙烯的熔融行为及非等温结晶动力学有很大的影响。