Structure characterization and physical properties of a complex with supramolecular architectures Co-2(2,6-DPC2Co(H2O)5 center dot 2H(2)O (DPC=2,6-pyridinedicarboxylate)

Reaction of 2,6-pyridinedicarboxylic with CoCl2 . 6H(2)O in aqueous solution give rise to a three-dimensional Complex CO2(2,6-DPC)(2)Co(H2O)(5).2H(2)O (DPC = 2,6-pyridinedicarboxylate) 1. It has been characterized by elemental analyses, infrared spectra (IR) spectrum, thermogravimetric (TG) analysis, EPR spectrum, and single crystal X-ray diffraction. The complex crystallizes in the P2(1)/c space group with a = 8.3906(3) Angstrom, b = 27.4005(8) Angstrom, c = 9.6192(4) A, alpha = 90.00degrees, beta = 98.327(2)degrees, gamma = 90.00degrees, V = 2188.20(14) Angstrom(3), Z = 4. There are two types of cobalt environments: Co(1) is coordinated by four oxygen atoms from four carboxyl groups and two nitrogen 2 atoms which are all from pdc(2). Co(2) is coordinated by six oxygen atoms, five from coordinated water molecules and one from a carboxyl of pdc(2) - of which the other oxygen atom is linked to the Co(1). The extensive intermolecular hydrogen bonds are formed in the crystal by means of the five coordinated water molecules.

Physical and electrochemical characterizations of PtRu/C catalysts by spray pyrolysis for electrocatalytic oxidation of methanol

In this paper, it was reported that the carbon-supported Pt-Ru(Pt-Ru/C) catalyst used as the anodic catalyst in the direct methanol fuel cell (DMFC) was synthesized with a two-step spray pyrolysis (SP) method using the Pt and Ru metal salt as the precursors and polyethylene glycol (PEG) with the different molecular weights (Mw= 200,600,and 1000 analytical reagent) as cosolvent. PEG as a cosolvent plays a crucial role in producing PtRu/C catalysts. It was found that the Mw of PEG could affect the electrocatalytic activity of Pt-Ru and the morphology of the Pt-Ru particles in the Pt-Ru/C catalysts prepared with this method. When the Mw of PEG is 600, the Pt-Ru particles in the Pt-Ru/C catalyst prepared with this method possess the small average size, narrow size distribution, uniform dispersion, and high electrochemically active specific surface area. The electrocatalytic activity of the Pt-Ru/C catalyst prepared with this method using the cosolvent PEG with Mw = 600 for the methanol oxidation is much higher than that of the commercial E-TEK Pt-Ru/C catalyst. Therefore, the two-step SP method is an excellent method for the preparation of the Pt-Ru/C catalyst used in DMFCs.

Effect of physical aging on fracture behavior of polyphenylquinoxaline films

The influence of physical aging on the tensile fracture behavior of notched Polyphenylquinoxaline (PPQ-E) samples has been studied. The dependence of fracture stress and strain on physical aging has been explained. The glass transition temperature (T-g) and the endothermic peak at the end of T-g transition with different physical aging were characterized using differential scanning calorimetry (DSC) and the results have also been explained. The morphology of fracture surface was observed by scanning electron microscopy (SEM). (C) 2000 John Wiley & Sons, Inc.

The effects of physical ageing on crazing of polyphenylquinoxaline films

The effects of physical ageing on the crazing of polyphenylquinoxaline (PPQ-E) films were studied. The DSC endothermic peak at the glass transition region of the samples was interpreted in terms of the cohesional entanglement theory. The free volume cavity size and free volume intensity of the samples were characterized by positron annihilation life spectroscopy. The difference in free volume cavity size and free volume intensity between two samples reflect the strength and density of cohensional entanglement point. The critical strain for craze initiation and craze stability depended on physical ageing of the samples. The relationships between physical ageing and crazing were interpreted initially.

Effect of physical aging on the microstructure and the crystallization of amorphous poly(aryl ether ether ketone ketone) (PEEKK)

Physical aging of poly(aryl ether ether ketone ketone) (PEEKK) has been investigated. Heat flow responses were measured after annealing the amorphous samples obtained by quenching the melt into an ice-water bath close to, but below, the glass transition temperature. The extent of aging is related to the supercooling from the glass transition temperature and to the aging time. The activation energy of the aging process, which was estimated by a Williams-Watt expression, is similar in magnitude to that obtained for the cold crystallization for the aged samples. The quenched glass is a metastable glass. The conformation of molecular chains rearranges with physical aging which results in the formation of a denser packing in the amorphous phase. The dense amorphous phase may form an initial nucleus for crystallization. Isothermal cold crystallization of the aged samples was carried out. The Avrami equation was used to determine the kinetic parameters, and the Avrami constant n is about 2. An Arrhenius expression was used to evaluate the activation energy of relaxation upon physical aging and the activation energy of transportation upon isothermal crystallization. The activation energy of relaxation is similar in magnitude to that of crystallization for aged samples. Results obtained are interpreted as kinetic effects associated with the glass formation process.

Morphologies and physical properties of PA1010/HIPS/HIPS-g-MA ternary blends

The effect of the content of a copolymer consisting of high impact polystyrene grafted with maleic anhydride (HIPS-g-MA) on morphological and mechanical properties of PA1010/HIPS blends has been studied. Blend morphologies were controlled by adding HIPS-g-MA during melt processing, thus the dispersion of the HIPS phase and interfacial adhesion between the domains and matrices in these blends were changed obviously. The weight fractions of HIPS-g-MA in the blends increased from 2.5 to 20, then much finer dispersions of discrete HIPS phase with average domain sizes decreased from 6.1 to 0.1 mu m were obtained. It was found that a compatibilizer, a graft copolymer of HIPS-g-MA and PA1010 was synthesized in situ during the melt mixing of the blends. The mechanical properties of compatibilized blends were obviously better than those of uncompatibilized PA1010/HIPS blends. These behaviors could be attributed to the chemical interactions between the two components of PA1010 and HIPS-g-MA and good dispersion in PA1010/HIPS/HIPS-g-MA blends. Evidence of reactions in the blends was seen in the morphology and mechanical behaviour of the solid. The blend containing 5 wt % HIPS-g-MA component exhibited outstanding toughness. (C) 1999 Kluwer Academic Publishers.

Physical aging and crystallization of amorphous poly(aryl ether ether ketone ketone)

Physical aging of poly(aryl ether ether ketone ketone) (PEEKK) was investigated. Heat flow responses were measured after annealing the amorphous samples that were obtained by quenching the melt into an ice-water bath at just below the glass transition temperature. Isothermal cold crystallization of the aged samples was carried out. The Avrami equation was used to determine the kinetic parameters, and the Avrami constant it is about 2. An Arrhenius form was used to evaluate the relaxation activation energy of physical aging and the transport activation energy of isothermal crystallization. The activation energy of physical aging was similar in magnitude to that observed for the temperature dependence of crystallization under conditions of transportation control. Results obtained were interpreted as purely kinetic effects associated with the glass formation process. (C) 1998 John Wiley & Sons, Inc.

Physical diffusion and electron-transfer dynamics of electroactive solutes in polymer electrolytes .2. Effect of the ionic size of supporting electrolytes

The diffusion coefficients(D-app) and the heterogeneous electron-transfer rate constants(k(s)) for ferrocene in MPEG/salt electrolytes were determined by using steady-state voltammetry. The temperature dependence of the two parameters obeys the Arrhenius equation. The effect of the ionic size of six supporting electrolytes on diffusion and electron transfer dynamics of ferrocene was discussed.

Physical diffusion and electron-transfer dynamics of electroactive solutes in polymer electrolytes .3. Effect of the polymer solvents

The diffusion coefficients(D-app) and the heterogeneous electron transfer rate constants(k(s)) for ferrocene in several polymer solvents were determined by using steady-state voltammetry. The temperature dependence of the two parameters indicates Arrhenius behavior, The polymer solvent effects on diffusion and electron transfer dynamics of ferrocene were discussed.

Physical diffusion and electron-transfer dynamics of electroactive solutes in polymer electrolytes .1. Effect of the nature of electroactive solutes

The diffusion coefficients(D-app) and the heterogeneous electron-transfer rate constants(k(s)) for ferrocene and its seven derivatives in MPEG/LiClO4 electrolyte were determined by using steady-state voltammetry. The two parameters increase with increasing temperature, indicating Arrhenius behavior. The effects of the nature of electroactive solute molecules on D-app, k(s), and the half-wave potentials(E-1/2) are discussed.

Preparation, structure and some physical properties of scheelite-related AgLnMo(2)O(8) compounds

We present the synthesis of the AgLnMo(2)O(8) oxides with Ln = La-Nd, Sm, Gd, Tb and Y. These compounds represent a scheelite-related structure type characterized by MoO42- tetrahedrons. The IR spectra show three transmittance bands in the region of 1000-400 cm(-1), which correspond respectively to the nu(1), nu(2), and nu(3) modes of the tetrahedral MoO42- groups. All of AgLnMo(2)O(8) are insulator materials at room temperature. The temperature dependence of the magnetic susceptibilities of AgLnMo(2)O(8) (Ln = Ce-Nd, Sm, Gd, Tb) show Curie-Weiss Law behaviors with two anomalies occurring at low temperature, whereas AgLaMo2O8 and AgYMo2O8 both exhibit diamagnetic properties as expected. The magnetic moments at room temperature fit very well with those corresponding to rare earth sesquioxides. This suggests that rare earth ions exist in +3 oxidation state in all AgLnMo(2)O(8) compounds.

Effect of physical aging on phenolphthalein polyethersulfone/poly(phenylene sulfide) blend .1. Mechanical properties

The effect of physical aging at 210 degrees C on the mechanical properties of phenolphthalein polyether sulfone (PES-C) and a PES-C/poly(phenylene sulfide) (PPS) blend, with 5% content of PPS, were studied using DMA, tensile experiments, an instrumented impact tester, and SEM observations. The blend shows good mechanical properties in comparison with the corresponding PES-C. The mechanical properties of both materials exhibit characteristics of physical aging, with only the aging rate of the blend relatively slower, which should be attributed to the constraint effect of PPS particles and the good interfacial adhesion. The morphology of the PPS phase in the blend did not change with aging time. The principal role of PPS particles is to induce crazes, which dissipate energy, under applied loading; thus, the blend shows good toughness. On the other hand, the multiple crazing mechanism depends on the molecular mobility or structural state of the matrix. (C) 1996 John Wiley & Sons, Inc.

THE EFFECT ON PHYSICAL-PROPERTIES OF THE SUBSTITUTION OF CA OR BA FOR SR IN NDSRNIO4

A new solid solution series, NdSr(1-x)M(x)NiO(4) (M = Ca: 0.0 less than or equal to x less than or equal to 1.0; M = Ba: 0.0 less than or equal to x less than or equal to 0.6), was synthesized by solid state reaction, and the structures, magnetic and electrical properties and optical spectra of this series have been studied. All the samples crystalized in tetragonal systems, with the exception of NdCaNiO4, which crystallized in the orthohombic system. IR spectra of NdSr1-xCaxNiO4 indicated that the lengths of two Ni-O bonds decrease with increasing Ca content. The electrical conduction changed from metallic-type to semiconductive-type when x greater than or equal to 0.4 (M = Ca, Ba), and the room temperature resistivities of NdSr1-xCaxNiO4 increased with the increase of Ca content. Magnetic susceptibility measurements revealed that Ni+3 ions in all the samplies were in low-spin state over the temperature range 77-300 K.

PREPARATION STRUCTURE AND PHYSICAL-PROPERTIES OF NEW SILVER LANTHANIDE MOLYBDENUM OXIDES [AGLNMO(2)O(8)(LN=LA-ND AND SM)]

We present the synthesis of AgLnMo(2)O(8) compounds with Ln = La-Nd and Sm. These compounds represent a scheelite-type structure characterized by MoO4- tetrahedrons. IR spectra show five absorption peaks in the region of 1000-400cm(-1), around 800cm(-1) and 400cm(-1), which correspond to the modes of the tetrahedral MoO42- groups. All of AgLnMo(2)O(8) (Ln = La-Nd and Sm) oxides are dielectric materials at room temperature. The temperature dependence of the magnetic susceptibility ofAgLnMo(2)O(8) (Ln = Ce-Nd and Sm) shows Curie-Weiss law behavior from 100K to 300K. This indicates that both Ce and Pr exist in +3 oxidation state in AgLnMo(2)O(8). For AgLaMo2O8, diamagnetic properties are found as expected.

STRUCTURE AND PHYSICAL-PROPERTIES OF NEW PHASE OXIDE LA2MOO5

The compound La2MoO5 has a cubic fluorite symmetry. There is strong interaction between the two molybdenum ions (IV). The cubic-La2MoO5 oxide contains separated Mo2O8 clusters and is a semiconductor. The electrical resistivity measurement shows a semiconductor-metal transition around 250 degrees C. Temperature dependence of magnetic susceptibility represents the Curie-Weiss law. The compound La2MoO5 exhibits a paramagnetic behaviour from 170-250 K.