Search Results

You are looking at 1 - 4 of 4 items for

  • Author: M. Wyrwas x
Clear All Modify Search
Open access

M. Wyrwas

Abstract

The paper is devoted to the construction of observers for linear fractional multi–order difference systems with Riemann–Liouville– and Grünwald–Letnikov–type operators. Basing on the Z-transform method the sufficient condition for the existence of the presented observers is established. The behaviour of the constructed observer is demonstrated in numerical examples.

Open access

M. Dziubaniuk, J. Wyrwa, M. Bućko and M. Rękas

Abstract

The preparation and sintering conditions of the selected rare-earth oxychlorides REOCl (Re=La, Nd, Sm, Gd) were determined. The purity of materials phase compositions was confirmed by X-ray diffraction method. Further analysis of the data enabled lattice parameters and average grain size determination. The electrical properties of the single phase REOCl materials were investigated by Electrochemical Impedance Spectroscopy in wide temperature range in atmospheric air. The spectra were analyzed by the equivalent circuit fitting. Basing on the values of equivalent circuits parameters the specific conductivities were calculated and presented in the Arrhenius coordinates. Energies of activation were calculated. The determined structural and electrical properties of four different rare-earth oxychlorides were directly compared.

Open access

J. Cyran, J. Wyrwa, E. Drożdż, M. Dziubaniuk and M. Rękas

Abstract

The aim of this work was examination of gadolinium-doped 3YSZ electrical and structural properties. Such materials may be used as electrolytes in intermediate temperature solid oxide fuel cells (IT-SOFC). First step of the research was synthesis of 3YSZ with different contents of gadolinium (0.25; 0.5; 1.0 at %). Prepared materials were characterized by high porosity. No effect of gadolinium addition on grain size was observed. The experimentally determined values of grain interiors electrical conductivities for gadolinium doped samples are comparable to grain interior conductivities of gadolinium free tetragonal zirconia. On the other hand, a clear effect of gadolinium addition on electrical conductivity of grain boundaries was observed. It was found that 3YSZ containing 0.25 at. % Gd was the most promising from the investigated materials as a solid electrolyte for IT SOFC.

Open access

E. Drożdż, M. Jelonek, J. Wyrwa and M. Rękas

Abstract

Yttria-stabilized zirconia (YSZ) is the best known ceramic-oxide material employed as a component of either solid electrolyte or anode cermet material for intermediate solid oxide fuel cell (IT - SOFC). The properties of traditionally produced (by mechanical mixing of oxides) Al2O3/3YSZ composite with the same composition materials obtained by citrate and impregnation methods and with properties of pure tetragonal zirconia (3YSZ) were compared. The materials were characterised by X-ray diffraction, SEM observations with EDX analysis, density and impedance spectroscopy measurements. The results shown that Al2O3/3YSZ composites reveals higher conductivity than pure 3YSZ and that addition of alumina (regardless of methods) improve electric properties of resulting materials. Taking into account application of this materials as anode in IT-SOFC the determined values of energy activation of conductivity and microstructural properties of composites show that materials obtained by citric method are the most promising.