Facture toughness measurements by COD of SrO-MgO-Al2O3-B2O3-SiO2 glass-ceramics composites for use as SOFC sealants

Reference	Presenter	Authors (Institution)	Abstract
10-014	Francisco Carlos Serbena	Sant'Ana Gallo, L.(State University of Ponta Grossa); Moreira Justo, V.(State University of Ponta Grossa); de Souza Just, L.(State University of Ponta Grossa); Antunes da Silva, A.(State University of Ponta Grossa); Mathias, I.(State University of Ponta Grossa); Rodríguez-Lopez, S.(Universidad Autónoma de Madrid); Pascual-Francisco, M.J.(Universidad Autónoma de Madrid); Serbena, F.C.(State University of Ponta Grossa);	The study of solid oxide fuel cells (SOFC) is an alternative to the production of electricity and glass-ceramic (GC) sealants play an important role on SOFC performance to avoid the mixture of the reactive gases of the stack. To avoid stresses due to mismatch of the thermal expansion coefficient (?) of the cell components, the developed GC must present ? ranging from 9–12.10-6 K-1. The GCs studied attend this criterion. One of the main mechanical properties to be characterized is the critical stress intensity factor, KTIP. It is obtained by measuring the crack opening displacement (COD) of a crack generated at the corner of a Vickers imprint. Four proposed compositions were analyzed, a parent composition (PC) and three ones derived from it. One of the derived compositions (DC1) had the addition of 15wt% of ZrO2 fibers to enhance the mechanical properties. A second derived composition (DC2), the addition of 5mol% of Al2O3 and the third derived composition (DC3) has a lesser amount of SiO2 and higher amount of MgO. Samples from all compositions were sintered at 750°C for 24h, 100h and 800h. Images of the cracks were obtained by scanning electron microscopy and COD measurements were conducted using ImageJ software. PC presented the highest values of KTIP of the analyzed compositions, although also presenting the highest scatter. The highest KTIP was obtained for the sample heat treated at 750ºC for 800h (2.2±0.2 MPa.m1/2). PC1 presented the highest value of KTIP for the sample heat treated at 750ºC for 24h (0.40±0.02 MPa.m1/2). Longer heat treatment times lead to a decrease on KTIP. PC2 presented the highest value of KTIP for the sample heat treated at 750ºC for 100h (0.45±0.05 MPa.m1/2). It was not possible to obtain KTIP measurements for this composition after 800h at 750ºC due to high porosity. PC3 presented equal values of KTIP within the experimental error. the highest value of KTIP for the sample heat treated at 750ºC for 100h (0.22±0.05 MPa.m1/2).
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