LUCAS APARECIDO DOS SANTOS FERREIRA
3 resultados
Resultados de Busca
Agora exibindo 1 - 3 de 3
Artigo IPEN-doc 29908 Mechanical and electrical characterization of 8YSZ-ScCeSZ ceramics2023 - FUJIMOTO, T.G.; SERIACOPI, V.; FERREIRA, L.A.S.; MACHADO, I.F.; MUCCILLO, E.N.S.The effects of small amounts (up to 5 wt.%) of scandia- and ceria-stabilized zirconia on the electrical conductivity, and the elastic modulus and hardness of yttria-stabilized zirconia were investigated by impedance spectroscopy and nanoindentation tests, respectively. The main purpose of this work was to obtain solid electrolyte compounds with improved properties compared to those of the base materials. Solid electrolytes compounds were prepared by solid-state reaction synthesis with sintering at 1450 ĀŗC for 4 h. All prepared compounds exhibit a cubic fluorite-type structure. The microstructure of the compounds consists of polygonal grains with low (< 2%) porosity. The mean grain size estimated by the intercept method was 5 Ā± 1 Ī¼m. The electrical conductivity of the compound ceramics is lower than that of the base material. Addition of scandia-stabilized zirconia is found to exert a beneficial effect on the matrix by increasing the elastic modulus, achieving 221 MPa for 5 wt.% of the additive.Resumo IPEN-doc 28563 Electrical conductivity and grain growth of 12Ce-TZP2021 - FERREIRA, LUCAS A. dos S.; MUCCILLO, ELIANA N. dos S.Ceramic materials based on tetragonal zirconia polycrystals (TZP) with yttrium or cerium oxide have been thoroughly studied for a number of technological applications, due to their outstanding thermomechanical properties. In this work, tetragonal zirconia polycrystals containing 12 mol% cerium oxide (12Ce-TZP) were prepared by solid-state reaction using different sintering methods, to evaluate the influence of the final microstructure on the electrical conductivity. High purity zirconium oxide and cerium oxide starting chemicals were weighted in the stoichiometric proportion and ball-milled for 6 h for homogenization. Cylindrical specimens were prepared by pressing followed by sintering. Sintering experiments were carried out by the conventional and the two-stage methods. The mean grain size of specimens sintered by the conventional method achieved approximately 2.4 mm after sintering at 1450 ĀŗC/5 h, whereas those sintered by the two-stage method exhibit less than 1.5 mm even after 10 h at 1350 ĀŗC, in the second stage of sintering. The electrical conductivity determined by impedance spectroscopy shows the usual Arrhenius behavior for both the bulk (or intragrain) and grain boundary (intergrain) conductivities, with activation energies of ~0.97 (bulk) and 1.25 eV (grain boundary). The grain conductivity of specimens sintered by different methods does not depend on the grain size. In contrast, the grain boundary conductivity is higher for specimens sintered by the two-stage method, possibly due to dissolution of minor impurities located at grain boundaries into the bulk, during the long holding times of the two-stage method.Artigo IPEN-doc 28341 Influence of the sintering method on densification, microstructure and electrical conductivity of 12Ce-TZP2021 - FERREIRA, L.A.S.; MUCCILLO, E.N.S.Zirconia containing 12ā mol-% cerium oxide ceramics were prepared by solid state reaction utilising the conventional, fast firing and two-step sintering methods. The sintering temperature and time were varied aiming to determine ideal sintering profile for these methods. The monoclinic and tetragonal phase contents, microstructure and electrical conductivity of dense specimens were investigated. The linear shrinkage was found negligible up to 1100Ā°C and the maximum rate of shrinkage was achieved at 1150Ā°C. Densification increased up to 2ā h for conventional sintered specimens. Stabilisation of tetragonal phase in non-isothermally sintered specimens occurred at a high temperature (1500Ā°C). Specimens sintered by the two-step method attained high density along with small grain sizes. Optimised sintering profiles were determined for all the sintering methods used.