E. F. Abo Zeid

Fine Structure Effect of PdCo electrocatalyst for Oxygen Reduction Reaction Activity: Based on X-ray Absorption Spectroscopy Studies with Synchrotron Beam

In this study, we have demonstrated the fine structure effect of PdCo electrocatalyst on oxygen reduction reaction activity with different alloy composition and heat-treatment time. In order to identify the intrinsic factors for the electrocatalytic activity, various X-ray analyses were used, including inductively coupled plasma-atomic emission spectrometer, transmission electron microscopy, X-ray diffractometer, and X-ray Absorption Spectroscopy technique. In particular, extended X-ray absorption fine structure was employed to extract the structural parameters required for understanding the atomic distribution and alloying extent, and to identify the corresponding simulated structures by using FEFF8 code and IFEFFIT software. The electrocatalytic activity of PdCo alloy nanoparticles for the oxygen reduction reaction was evaluated by using rotating disk electrode technique and correlated to the change in structural parameters. We have found that Pd-rich surface was formed on the Co core with increasing heating time over 5 hours. Such core shell structure of PdCo/C showed that a superior oxygen reduction reaction activity than pure Pd/C or alloy phase of PdCo/C electrocatalysts, because the adsorption energy of adsorbates was apparently reduced by lowering the dband center of the Pd skin due to a combination of the compressive strain effect and ligand effect.

A novel heterometallic compound for design and study of electrical properties of silver nanoparticles-decorated lead compounds

A new heterometallic compound AgPb(C2O4)(NO3) (AgPb-1) was constructed for the first time using a precipitation reaction. Then, different silver nanoparticles (Ag-NPs)-decorated lead compounds were obtained from AgPb-1via thermal annealing at different temperatures. The compounds Ag·PbCO3 (AgPb-2), Ag·α-PbO (AgPb-3), Ag·α-PbO + β-PbO (AgPb-4) and Ag·β-PbO (AgPb-5) were obtained by annealing at 523 K, 623 K, 723 K and 873 K, respectively. The formed powders were investigated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). The dispersion of Ag-NPs on the surface of lead compounds as decorated layers was proven by SEM and TEM micrographs. The electrical conductivity and dielectric constant of the precursor in the temperature range of 293–673 K were investigated. Furthermore, the electrical behaviours of the different phases are described.

New Polymer Syntheses Part: 55#. Novel Conducting Arylidene Polymers and Copolymers Based on Methyl-Cyclohexanone Moiety

A new interesting class of conducting polymers based on methyl-cyclohexanone in the polymer main chain has been synthesized by solution polycondensation of terephthalaldehyde with methyl-cyclohexanone. Copolymers containing different cycloalkanone moieties were also synthesized using solution polycondensation technique. The model compound I was synthesized by the interaction of methyl-cyclohexanone monomer with benzaldehyde, and its structure was confirmed by elemental and spectral analyses. The resulting new polymers and copolymers were characterized by elemental and spectral analyses, beside solubility and viscometry measurements. The thermal properties of those polymer and copolymers were evaluated by TGA, DrTGA and DTA measurements and correlated to their structural units. PDT as well as T 10 was in the range from 205 to 370 ÂoC. In addition, T 10 thermal stability for all the polymers was in theorder: VI> II > III > IV > V. X– ray analysis showed that it has some degree of crystallinity in the region 2q = 5 – 60 degree.The UV– visible spectra of some selected polymers were measured in DMSO solution and showed absorption bands in the range 265-397 nm, due to n – p* and p – p* transition. The morphological properties of copolymer IV as selected examples were tested by SEM. The electrical conductivities of the synthesized polymers and copolymers enhanced to become in the range of 10 -9 -10 -8 S cm -1 by doping with iodine.Â

Investigation of nanoscale precipitates developed in Al–0·73Mg–0·45Si–0·34Cu–0·21Cr–0·20Fe alloy

Abstract In the present work, the developed nanoscale precipitates in Al–0·73Mg–0·45Si–0·34Cu–0·21Cr–0·20Fe (wt-%) alloy have been investigated by means of differential scanning calorimetry, electron microscopy (SEM and TEM) and microhardness measurements (HV). The addition of Cu assists the formation of Q′ phase which positively changes the alloy strength. The precipitation of β′′ nanoparticles is followed by the precipitation of β′ and/or Q′ precipitates. Both coherent and semicoherent precipitates have a positive contribution to the strengthening of the alloy. The average activation energy associated with the precipitation of β(Mg2Si)+Q phases is very close to that for Q″ and/or Q′ phase which suggests that the two phase precipitation might be characterised by the same mechanism. The reaction order of the precipitation processes suggests that β′ and/or Q′ precipitates grow radially; whereas, β-precipitates grow in the three directions.