Solvothermal synthesis and characterization of Ln (Eu3+, Tb3+) doped hydroxyapatite

Luminescent Ln (Eu3+, Tb3+) doped hydroxyapatite (Eu:HAp, Tb:HAp) phosphors were successfully fabricated via the cetyltrimethylammonium bromide (CTAB)/n-octane/n-butanol/water microemulsion-mediated solvothermal process. The structure, morphology, and optical properties were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectra as well as the kinetic decays, respectively.

Mo的掺杂对Ce_(0.8)Gd_(0.2)O_(1.9)烧结温度及电性能的影响

掺杂的CeO2基固体电解质因其在中低温条件下(500￣700℃)具有高氧离子电导率而成为有希望的IT-SOFCs(intermediate temperature-solid oxide fuel

Selective crystallization of BaF2 under a compressed Langmuir monolayer of behenic acid

Selective crystallization of BaF2 crystals under a compressed Langmuir monolayer of behenic acid [CH3(CH2)(20)COOH] has been studied by using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray analysis. It was found that, in the absence of a monolayer, three kinds of crystals (Ba2ClF3, BaClF, and BaF2) can be obtained by mixing BaCl2 with a NH4F solution. However, in the presence of the monolayer of behenic acid, only BaF2 crystals appear at the monolayer-subphase interface and crystals have a special crystal face (100). During this process of crystallization, the monolayer plays a very important role and acts as a template that can preferentially select a special crystal and a special crystal face. The above results can be explained in terms of a specific molecular interaction between ions and the headgroups of the monolayer and specific electrostatic, geometric, and stereochemical interactions at the organic-inorganic interface.

Isothermal and nonisothermal crystallization kinetics of nylon-11

Analysis of the isothermal, and nonisothermal crystallization kinetics of Nylon-11 is carried out using differential scanning calorimetry. The Avrami equation and that modified by Jeziorny can describe the primary stage of isothermal and nonisothermal crystallization of Nylon-11. In the isothermal crystallization process, the mechanism of spherulitic nucleation and growth are discussed; the lateral and folding surface free energies determined from the Lauritzen-Hoffman equation are sigma = 10.68 erg/cm(2) and sigma(e) = 110.62 erg/cm(2); and the work of chain folding q = 7.61 Kcal/mol. In the nonisothermal crystallization process, Ozawa analysis failed to describe the crystallization behavior of Nylon-ii. Combining the Avrami and Ozawa equations, we obtain a new and convenient method to analyze the nonisothermal crystallization kinetics of Nylon-11; in the meantime, the activation energies are determined to be -394.56 and 328.37 KJ/mol in isothermal and nonisothermal crystallization process from the Arrhonius form and the Kissinger method. (C) 1998 John Wiley & Sons, Inc.

Deformation process and mechanism of HDPE/LDPE blends

Blends of HDPE in more LDPE, with appropriate heat treatment, produce a dispersion of separate entities of HDPE in a matrix of LDPE. The system offered an especially favourable means of studying the deformation of melt-crystallized lamellae. It has been found that sheaf-like spherulites are transformed under tensile deformation into hourglass shapes i.e. a double cone aligned along the drawing direction with origin in the center of the object. This is a consequence of different modes of deformation according to the relation of an individual lamella to the tensile axis. The work shows that the lamellae have not undergone melting and recrystallization in the deformation process at room temperature.

HDPE/LDPE共混物形变过程中的结构变化及机理

聚合物熔体结晶由于链缠结等因素的影响，其形态结构非常复杂，这给研究结晶聚合物的微观结构，特别是聚合物在拉伸过程中的形态变化带来很大困难．本文将高密度聚乙烯（ＨＤＰＥ）和低密度聚乙烯（ＬＤＰＥ）两种不相容的组分进行共混，使少量ＨＤＰＥ分散在ＬＤＰＥ中，…

Nonisothermal melt and cold crystallization kinetics of poly(aryl ether ether ketone ketone)

Analysis of the nonisothermal melt and cold crystallization kinetics of poly(aryl ether ether ketone ketone) (PEEKK) was performed by using differential scanning calorimetry (DSC). The Avrami equation modified by Jeziorny could describe only the primary stage of nonisothermal crystallization of PEEKK. And, the Ozawa analysis, when applied to this polymer system, failed to describe its nonisothermal crystallization behavior. A new and convenient approach for the nonisothermal crystallization was proposed by combining the Avrami equation with the Ozawa equation. By evaluating the kinetic parameters in this approach, the crystallization behavior of PEEKK was analyzed. According to the Kissinger method, the activation energies were determined to be 189 and 328 kJ/mol for nonisothermal melt and cold crystallization, respectively.

Synthesis and characterization of novel polyimides from alicyclic dianhydride

New alicyclic Polyimides (PIs) were prepared from asymmetric alicyclic dianhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-cyclohexane-1,2-dicarboxylic anhydride (DOCDA) and the corresponding aromatic diamines such as p-phenylenediamine, m-phenylenediamine and oxydianiline etc. by the polycondensation in N-methyl-2-pyrrolidone (NMP) followed by chemical imidization as well as one step polyimidization in m-cresol in the presence of isoquinoline as a catalyst. The resulting PIs with glass transition temperatures ranging from 220 to 328 degrees C had the inherent viscosities within the range of 0.25 similar to 1.42 dL/g. These polymers were readily soluble in aprotic polar solvents such as NMP, dimethylacetamide (DMAc), dimethylesulfoxide (DMSO), etc. Furthermore, some of the polymers showed good solubility properties to common organic solvents like tetrahydrofurane and chlorform. Also, all of these polyimide films were tough, almost colourless, and transparent.

INFLUENCE ON THE THIN-LAYER SPECTROELECTROCHEMISTRY - DIFFUSION WITHIN A THIN-LAYER CELL

The potential step and cyclic voltammetric experiments in the thin layer cell were studied by the digital simulation method in this work. A relationship between the time needed for exhaustive electrolysis of the electroactive species and the thickness of the thin layer cell was obtained. On the basis of this formula, the lower time limit for a kinetic plot of the following chemical reaction can be estimated. For the cyclic voltammetry, a semiempirical formula was derived for the peak-peak potential difference (Delta Ep) in terms of the sweep rate (v), thickness of the cell (d), diffusion coefficient (D) and electron transfer number (n) 59 - n Delta Ep/n Delta Ep = 0.328(RT D/nF vd(2))(1.20).

Study on a new comb polymer electrolyte(II)

A comb polymer(CP350) with oligo-oxyethlene side chains was prepared from methyl vinyl ether/maleic anhydride copolymer. Homogeneous amorphous polymer electrolyte were made from the comb polymer and LiCF3SO3 by solvent casting from acetone, and their conductivities were measured as a function of temperature and salt concentration. Maximum conductivity close I to 5.08 x 10(-5)S/cm was achieved at room temperature at [Li]/[EO] ratio of about 0.12.

酞菁铜旁热式气敏元件的研究

酞菁铜旁热式气敏元件的研究冉祥海，车吉泰，张万喜，孙文霞（中国科学院长春应用化学研究所）０引言由于酞氰系列化合物具有良好的热、机械适应性，并对光电和某些气体有敏感特性，因此，近年来有人以酞氰化合物为气敏材料研究了ＮＯ２、ＮＯ、Ｏ２、ＳＯ２的气敏特性［...

环化顺1，4－聚丁二烯浓溶液的流动行为

大多数线型高聚物浓溶液的流动行为呈现非牛顿性，线型顺１，４－聚丁二烯（ＬＢＲ）亦然，而环化顺１，４－聚丁烯（ＣＢＲ）的浓溶液在浓度达１７．８％时仍表现为牛顿流体。ＣＢＲ溶液的临界缠结浓度明显地高于ＬＢＲ，ＣＢＲ分子链间的缠结效应比ＬＢＲ弱得多，这是ＣＢＲ的分子链结构特征所致。

聚电解质──壳聚糖浓溶液流变学性质研究：浓度、温度、溶剂pH值和外加盐对粘度及流动性的影响

本工作用日本岩本ＲＰＸ－７０５多功能流变仪测定了在不同浓度、温度、溶剂ｐＨ值和外加盐浓度对壳聚糖在甲酸水溶液中其浓溶液粘度η随剪切速率γ的变化关系．讨论了浓度、温度等对溶液粘度、流动活化能Ｅ_γ和流动指数ｎ的影响．发现溶剂ｐＨ值减小或溶液中外加盐浓度增加，溶液粘度变小，ｎ增大，表明非牛顿流动性减弱，并且进一步讨论了零剪切粘度η_０和外加盐浓度Ｃ_ｓ的依赖关系．

PHASE-BEHAVIOR IN THERMOTROPIC LIQUID-CRYSTALLINE POLYMER AND POLYARYLETHERSULFONE BLENDS

An experimental study of the phase morphology and miscibility of binary blends of poly-arylethersulfone (PES) and a liquid crystalline polymer (LCP) of p-oxybenzoate and ethylene terephthalate units in a 60/40 molar ratio (PET-60PHB) is described. Blends

ELECTROCHEMICAL STUDY OF ISOPOLY AND HETEROPOLY OXOMETALLATE FILM MODIFIED MICROELECTRODES .5. PREPARATION AND ELECTROCHEMICAL-BEHAVIOR OF A 2/18-MOLYBDODIPHOSPHATE ANION MONOLAYER MODIFIED ELECTRODE

In this paper a carbon fibre (CF) microelectrode modified with the 2:18-molybdodiphosphate anion by simple adsorption is described and its electrochemical behaviour is reported. The 2:18-molybdodiphosphate anion (alpha-P2Mo18O626-), which is a Dawson structure, undergoes five successive multielectron reductions in acidic solution. The first three redox waves correspond to the two-electron process, and the last two waves are four-electron and six-electron processes respectively. On the basis of the experimental results it is shown that the electrode process of alpha-P2Mo18O626- on the CF electrode in acidic solution is simultaneously controlled by the diffusion and adsorption of alpha-P2Mo18O626- anions. When the concentration of the alpha-P2Mo18O626- in the solution is reduced, the electrode process mainly exhibits non-diffusion-controlled behaviour, and the diffusion-limited process takes over as the concentration of alpha-P2Mo18O626- becomes higher. The CF electrode modified with a thin film of alpha-P2Mo18O626- exhibits very good stability and redox behaviour in aqueous acidic solution. The alpha-P2Mo18O626- is reduced to heteropoly blue, with an accompanying protonation process. The addition of more than six electrons to the alpha-P2Mo18O626- anion in an aqueous solution does not result in its decomposition. The result obtained is not the same as that reported previously.