International audiencePt-Co/C electrocatalysts with Pt loadings near 30 wt. % prepared by the impregnation method in water - ethylene glycol solutions were investigated by X-ray diffraction and correlated with electrochemical measurements. We show that the composition of the binary solvent controls the average particle size and its distribution. The unit cell parameter of the Pt3Co alloy decreases nonlinearly with decreasing particle size. The ORR activity of the prepared Pt-Co/C catalysts in H2SO4 solution enhances with decreasing particle size and unit cell parameter as well as with narrowing of the particle size distribution. Corrosion treatment of the synthesized Pt-Co/C materials causes an increase of ca. 1 nm in average particles size accompanied by broadening of the particle size distribution and decreasing Co content in the Pt-Co alloy. All of the synthesized Pt-Co/C materials show higher ORR activities than do the commercial Pt/C electrocatalysts

In the present work, the effect of grain size distribution on the diffraction profile shape is inspected via analysis of the mutual ratio of Lorentz and Gauss components in pseudo-Voigt function which is used for simulating X-ray profiles of nanoparticles. As established from the plotted dependences, the error in the average Pt nanoparticles size determination reaches 56% and the discrepancy between calculated Pt nanoparticle surface areas attains 60%. Furthermore, the determination error becomes greater with increasing the Lorentz contribution to pseudo-Voigt function, or, in fact, with enlarging particle size distribution. The empirically found electrochemical surface area of Pt/C electrocatalyst is compared with that evaluated from XRD data using the Scherrer formula and particle size distribution data analysis.

The frequency dependence of scattering parameters of interdigital surface acoustic wave transducers placed on ferroelectric barium titanate (BaTiO 3 ) epitaxial film in c-phase coated over magnesium oxide has been studied using the finite-element method (FEM) approach along with the perfectly matched layer (PML) technique. The interdigital transducer which has a comb-like structure with aluminum electrodes excites the mechanical wave. The distance between the fingers allows tuning the frequency properties of the wave propagation. The magnesium oxide is taken as the substrate. The two-dimensional model of two-port surface acoustic wave filter is created to calculate scattering parameters and to show how to design the fixture in COMSOL TM . Some practical computational challenges of finite element modeling of SAW devices in COMSOL TM are shown. The effect of lattice misfit strain on acoustic properties of heterostructures of BaTiO 3 epitaxial film in c-phase at room temperature is discussed in present article for two lowfrequency surface acoustic resonances. ARTICLE HISTORY

We study excitation of magnetostatic backward volume waves on the microstrip line. The relation between the current density in the line and the normal component of the magnetic induction is found. The impedance of the line per unit length, i.e., its reactance and radiation resistance per unit length, is represented as a functional of the current density. The dependence of the operating-wave radiation resistance on the transverse size of the line and the width of the dielectric gap is studied. The radiation resistances of multistrip array and meander-type converters of magnetostatic backward volume waves are calculated.

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