In this paper, we have studied the structure and the phase transformations in thin films (obtained by evaporation from g-irradiated polyethylene bulks -ageing polymer) before and after laser irradiation. We made a comparison between the following samples: A -thin films obtained from g-irradiated polyethylene bulk and not subjected to laser irradiation; B -thin films obtained from g-irradiated polyethylene bulk and subjected to laser irradiation. We have revealed many modifications in the dielectric and structural properties of the thin films, depending on the dose, dose rate and the time of laser irradiation (in the case of samples B). The thickness of all deposited films was 90 nm. The samples (non-irradiated or irradiated) were analysed by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), in combination with selected area electron diffraction (SAED). We have also presented the structure of non-aged and non-irradiated thin polyethylene films (control polyethylene film), in which we observed a particularly puzzling phase between an incipient spherulitic phase and a fine structure of the spherulitic phase (specifically for thin PE films structure). After g-and laser irradiations, we observed a strong modification of the structure. The spherulitic phase was transformed. We observed large, amorphous, transparent crystals containing many defects, carbon precipitates, the beginning of crystallisation revealed by electron diffraction, treeing and breakdown figures (usually after laser irradiation).
Impedance Spectroscopy (IS) is considered one of the most popular methods to the characterization of ceramic materials used as electrolytes for fuel cells, such as, solid oxide fuel cells (SOFCs) and intermediate temperature -solid oxide fuel cells (IT-SOFCs). However, experimental data analysis requires developing a model describing the electrical behavior of the solid electrolyte.The aim of this paper is to characterize the electrical behavior of sintered composite based on ceria using a new model. Therefore, the measurements of impedance components (Z ' and Z '' ), of two composites based on ceria, designed to be used as solid electrolytes for intermediate temperature fuel cells (IT-SOFC) were performed by Impedance Spectroscopy (IS). The materials are two different composites based on ceria 10YDC + (10%) 150ppm YA (E1) and 10ScDC + (10%) 150ppm YA (E2), obtained by sol-gel method and sintered at temperature of 1500 0 C. Two models (microstructural and electric) were applied for determining the electrical conductivity and permittivity of grains ( g and rg ) and grain boundaries ( gb and rgb ) values and the components of the complex impedance Z (Z ' and Z '' ) at different frequencies. The composite E1 presents better conductivities ( g and gb ) than E2 and it is favorable for use as solid electrolyte fuel cells.
The paper applies the re-expansion method to analyze the sound radiation from a flanged circular pipe. The axial velocity in the aperture is expressed by means of some orthogonal polynomials combining the properties of Jacobi's polynomials and hypergeometric functions, and also accounting for the velocity singularities at the edge points of the aperture. This makes it possible to reveal the physical parameters of the problem with a very limited number of terms. Besides the classical case when the flange covers the whole plane outside the pipe, the method also permits one to study also the case of the flange extending with zero thickness over a part of the circular pipe. Finally, the paper includes the extension of the results beyond the plane wave region achieving good accuracy and convergence.
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