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Загальна кількість знайдених документів : 3
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Kuzio I.
Substantiation of the Shape of a Solid Oxide Fuel Cell Anode Using the Stress-Strain and Shape-Dependent Crack Deceleration Approaches [Електронний ресурс] / I. Kuzio, B. Vasyliv, V. Korendiy, V. Borovets, V. Podhurska // Ukrainian journal of mechanical engineering and materials science. - 2019. - Vol. 5, Num. 1. - С. 29-38. - Режим доступу: http://nbuv.gov.ua/UJRN/ujmems_2019_5_1_6
Stress and strain distributions in the YSZ - NiO spheroidal shape anode-substrate for a solid oxide fuel cell (SOFC) under pressure of operating environment were calculated using the finite element analysis. The features were then compared with ones of the cylindrical shape anode. The radii ranges for the cylindrical and spheroidal (segments of a sphere) parts of the anode ensuring its improved deformation resistance and more uniform stress distribution were suggested. Based on the calculations, an anode of the cylindrical shape with top and bottom convex surfaces (a spheroidal shape anode), with the spheroid to cylinder radii ratio R/Rc in the range from 5 to 20 is suggested. Its specific volume V/Sc is in the range from 1 to 2,5 mm. The stresses in the most dangerous areas (i. e. along the axis and the closed-loop fixing) and maximum strain, caused by external gas pressure on the anode working surface, are decreased by 10 - 30 % and 20 - 40 % respectively as compared to an anode of the cylindrical shape of the same radius and volume features. This increases the lifetime of a solid oxide fuel cell. A three-dimensional curve of intersection of the surfaces of stress distribution in the anode along its axis and the closed-loop fixing was approximated which displays the values of balanced stresses depending on V/Vc and R/Rc parameters. Also, the advantage of the spheroid shaped SOFC anode-substrate over conventional flat one was substantiated using a shape-dependent crack deceleration approach.Stress and strain distributions in the YSZ - NiO spheroidal shape anode-substrate for a solid oxide fuel cell (SOFC) under pressure of operating environment were calculated using the finite element analysis. The features were then compared with ones of the cylindrical shape anode. The radii ranges for the cylindrical and spheroidal (segments of a sphere) parts of the anode ensuring its improved deformation resistance and more uniform stress distribution were suggested. Based on the calculations, an anode of the cylindrical shape with top and bottom convex surfaces (a spheroidal shape anode), with the spheroid to cylinder radii ratio R/Rc in the range from 5 to 20 is suggested. Its specific volume V/Sc is in the range from 1 to 2,5 mm. The stresses in the most dangerous areas (i. e. along the axis and the closed-loop fixing) and maximum strain, caused by external gas pressure on the anode working surface, are decreased by 10 - 30 % and 20 - 40 % respectively as compared to an anode of the cylindrical shape of the same radius and volume features. This increases the lifetime of a solid oxide fuel cell. A three-dimensional curve of intersection of the surfaces of stress distribution in the anode along its axis and the closed-loop fixing was approximated which displays the values of balanced stresses depending on V/Vc and R/Rc parameters. Also, the advantage of the spheroid shaped SOFC anode-substrate over conventional flat one was substantiated using a shape-dependent crack deceleration approach.
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Vasyliv B.
Estimation of the effect of redox treatment on microstructure and tendency to brittle fracture of anode materials of YSZ–NiO(Ni) system [Електронний ресурс] / B. Vasyliv, V. Kulyk, Z. Duriagina, D. Mierzwinski, T. Kovbasiuk, T. Tepla // Восточно-Европейский журнал передовых технологий. - 2020. - № 6(12). - С. 61-71. - Режим доступу: http://nbuv.gov.ua/UJRN/Vejpte_2020_6(12)__8
The effect of reduction treatment in a high-temperature (600 <^>oC) hydrogen-containing environment on the microstructure and tendency to brittle fracture of YSZ - NiO(Ni) materials for solid oxide fuel cell anodes has been studied. To assess the crack growth resistance of the ceramics, the Vickers indentation technique was adapted, which allowed estimating the microhardness and fracture toughness of the material in the complex. The requirements for high porosity of the anodes to ensure functional properties show that the strength may be an insufficient characteristic of the bearing capacity of the anode. More structurally sensitive characteristics are needed to assess its crack growth resistance. The average levels of microhardness of YSZ - NiO ceramics in the as-sintered state and YSZ - NiO(Ni) cermets (2,0 GPa and 0,8 GPa, respectively) and their fracture toughness (3,75 MPa-m<^>1/2 and 2,9 MPa-m<^>1/2, respectively) were experimentally determined. It was found that the microstructure of YSZ - NiO(Ni) cermet after redox treatment is formed by a YSZ ceramic skeleton with refined Ni-phase grains combined in a network, which provides increased electrical conductivity. Along with higher porosity of the cermet, its fracture toughness is not lower than that of the one-time reduced cermet due to the implementation of the bridging toughening mechanism of fracture. The proposed treatment method allowed forming the microstructure of the anode material, resistant to crack propagation under mechanical load. The propensity of the anode material to brittle fracture on the basis of evaluation of its crack growth resistance and analysis of the microstructure and fracture micromechanism was substantiated. This result is interesting from a theoretical point of view. From a practical point of view, the developed technique allows determining the conditions of redox treatment in the technology of manufacturing fuel cell anodes.
| | 3. |
Kuzio I.
Optimization of geometric parameters of a semi-spheroidal solid oxide fuel cell anode using the 3D stress and strain distribution graphs [Електронний ресурс] / I. Kuzio, B. Vasyliv, V. Korendiy, V. Borovets // Ukrainian journal of mechanical engineering and materials science. - 2019. - Vol. 5, Num. 2. - С. 33-42. - Режим доступу: http://nbuv.gov.ua/UJRN/ujmems_2019_5_2_6
The purpose. Determination of radii ranges for cylindrical and convex (semispheroidal) parts of the solid oxide fuel cell (SOFC) semi-spheroidal shape anode based on stress and strain parameters calculated; comparison of 3D graphs of stress/strain distribution in anodes of proposed and spheroidal shapes; substantiation of the semi-spheroidal anode potential to withstand deformation and stress gradient under operational conditions. The research method. The object of research is a solid oxide fuel cell anode of a semispheroidal shape loaded with a fixing pressure along the closed-loop fixing and with an external gas pressure applied to the anode working surface. Stress and strain distributions in the anode were calculated by finite element analysis using software for calculating three-dimensional tasks Mechanical Desktop 6 Power Pack. Three-dimensional (3D) dependences of stress/strain distribution in anodes of proposed and spheroidal shapes at a variety of R/Rc ratios were plotted. Based on these curves, 3D surfaces of stress distribution along the axis and closed-loop fixing of semi-spheroidal shape anodes were constructed. Results. Three-dimensional curves of the graphic intersections of the surfaces of stress distribution along the axis and closed-loop fixing of semi-spheroidal shape anodes, with their projections on three coordinate planes, were plotted. The curves display the values of balanced stresses depending on geometric parameters. Domains of these curves were also defined. The scientific novelty. The proposed method of building 3D surfaces of stress/strain distribution in anodes depending on their geometric parameters shows for the first time that there exists an area of geometric parameters that allows the appropriate stress level to be reached ensuing safe long-term operation of the semi-spheroidal shape anode. The domain of this area was graphically defined. Based on the plotted isolines showing levels of strain in anodes with the 0,5, 1 and 1,5 mm thick cylindrical parts and a variety of spheroid to cylinder radii ratios, an advantage of a semi-spheroidal shape anode over spheroidal one was substantiated. The practical value. The obtained calculation results and their 3D graphical interpretation can be used in the study of the stress state and, respectively, to evaluate the strength and stiffness of the anode supported SOFCs of various shapes.
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