IN-SITU SCANNING-TUNNELING-MICROSCOPY IMAGE OF A HIGHLY ORIENTED PYROLYTIC-GRAPHITE ELECTRODE MODIFIED WITH POTASSIUM BIS(11-MOLYBDOSILICATO) DYSPROSATE(III) IN SODIUM-SULFATE SOLUTION

The variation in molecule adsorption mode on pretreated highly oriented pyrolytic graphite electrodes, modified with the title complex K10H3[Dy(SiMo11O39)(2)] by cyclic voltammetry in the title complex solution, was observed in situ by electrochemical scanning tunnelling microscopy (ECSTM) with molecular resolution in sodium sulphate solution. According to the ECSTM images and the known molecular structure we conclude that the adsorption mode of the title complex modified electrode changed during potential cycling from ''vertical'' to ''inclined'' and then ''horizontal'' or ''flat'' mode, i.e. the title complex adsorbed on the surface of electrode by one ligand of the complex at first, then began to incline and was finally adsorbed by two ligands of the complex. This result indicates that the adsorption mode on the modified electrode surface changed during potential cycling in the sulphate solution and a much more stable molecular layer was formed. The change in adlattice of adsorbates on the modified electrode surface from hexagonal to rectangular was also observed by ECSTM. A plausible model was given to explain this process.

AN INTEGRATED CALCIUM-FLUORIDE CRYSTAL IR THIN-LAYER CELL AND ITS APPLICATION TO IDENTIFICATION OF ELECTROCHEMICAL REDUCTION PRODUCT OF BILIRUBIN

An integrated CaF2 crystal optically transparent infrared (ir) thin-layer cell was designed and constructed without using any soluble adhesive materials. It is suitable for both aqueous and nonaqueous systems, and can be used not only in ir but also in uv-vis studies. Excellent electrochemical and spectroelectrochemical responses were obtained in evaluating this cell by cyclic voltammetry and steady-state potential step measurements for both ir and uv-vis spectrolectrochemistry with ferri/ferrocyanide in aqueous solution, and with ferrocene/ferrocenium in organic solvent as the testing species, respectively. The newly designed ir cell was applied to investigate the electrochemical reduction process of bilirubin in situ, which provided direct information for identifying the structure of the reduction product and proposing the reaction mechanism.

ELECTRICAL CHARACTERIZATION INDUCED IN PERNIGRANILINE BY POTASSIUM-ION IMPLANTATION

The electrical conductivities of pernigraniline after ion implantation with potassium ions were studied experimentally. Pernigraniline films were irradiated with doses ranging from 1 x 10(13) to 1 x 10(17) K+ ions/cm2 at 40 keV. The electrical conductivit

RADIATION EFFECTS ON POLY(VINYLIDENE FLUORIDE)

Melt-crystallized poly(vinylidene fluoride)s (PVF2) with different crystallization histories were irradiated with gamma-rays within the range of irradiation doses 0-83 Mrad. The effects on the crystalline structure and mechanical properties have been measured, compared, and discussed. The degree of crystallinity of the samples was found to increase with radiation dose. The differential scanning calorimeter scans of the quenched samples indicate that there are two melting peaks, and that the area of the lower temperature peak increases while the area of higher temperature peak decreases with increasing dose. Yield stress and breaking stress for all samples are not significantly affected by irradiation but elongation at break is.

VALENCY AND ITS CHANGE PROCESS OF SAMARIUM ION IN SAMARIUM FLUORIDE SYSTEM

Nonstoichiometric series SmF(x) (2.0 less-than-or-equal-to x less-than-or-equal-to 3.0) have been synthesized by reduction of samarium trifluoride with hydrogen for several times, and the stoichiometric samarium difluoride has been obtained. The structure of nonstoichiometric samarium fluoride series and the valency of samarium ion are briefly discussed. The valent change process of samarium ion at high temperatures in different atmospheres is investigated.

STUDY ON GAMMA-RADIATION INDUCED LAMELLAR DAMAGE MECHANISM OF POLY(VINYLIDENE FLUORIDE)

This paper studies gamma-radiation induced lamellar damage mechanism of poly(vinylidene fluoride), using wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), electronic paramagnetic resonance (EPR) and gel fraction determination. We believe that it is ''lamellae core damage'' rather than ''lamellae surface damage'' that results in the decrease of the crystallinity.

XPS STUDIES OF RADIATION-INDUCED STRUCTURAL-CHANGES IN POLYVINYLIDENE FLUORIDE

In this work the radiation-induced structural changes in PVDF were studied using XPS. It was found that for PVDF irradiated at 150-degrees-C, double bonds were formed mainly through the further dehydrofluorination of crosslinked and/or branched molecules, whereas for samples irradiated at 20-degrees-C the dehydrofluorination of macromolecular radicals to form stable polyene radicals is the main source of unsaturated structures.

A NEW HYDROGEN SENSOR WITH RARE-EARTH COMPLEX FLUORIDE

A new type of solid-state galvanic cell for detecting a small amount of hydrogen in air at room temperature is proposed. The sensor cell is a potentiometric cell using Ce0.95Ca0.05F2.95 as solid-state electrolyte. The cell exhibits good sensing properties to hydrogen in air at room temperature.

CHARACTERIZATION OF A POTASSIUM-PROMOTED COBALT MOLYBDENUM ALUMINA WATER-GAS SHIFT CATALYST

A series of potassium-promoted CoMo/Al2O3 has been investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR). CoMoO4 was found in the CoMo/Al2O3 catalyst by XRD and is destroyed by the presence of potassium. The reducibility of molybdenum is enhanced by potassium in the CoMoK/Al2O3 catalyst and is easier to reduce to Mo(IV) during sulfidation. In the oxidic state catalyst cobalt is increased on the surface by the addition of potassium. After sulfidation this phenomena disappeared, the distribution of cobalt remains at a constant level and is unaffected by the potassium content. The addition of potassium leads to a monotonical decrease of the molybdenum dispersion with the impregnating amount of potassium in the oxidic state catalyst but is more complicated after sulfidation. Potassium is well dispersed on the surface in both the oxidic and sulfided state. The activity in the water-gas shift reaction was correlated with the potassium content of CoMoK/Al2O3.