resumo
The influence of adding 0-5 mol% zirconia (ZrO2) to a series of melt-quenched alkaline-earth aluminosilicate glasses designed in the gehlenite (Ca2Al2SiO7)-akermanite (Ca2MgSi2O7) system has been investigated for their potential application as sealants for solid oxide fuel cells (SOFCs). The work was implemented with a dual aim of improving the sintering ability of the glass system under consideration and gaining insight into the structural changes induced by ZrO2 additions in the glasses consequentially leading to their enhanced long-term thermal stability. That the degree of condensation of SiO4 tetrahedra increased with increasing amounts of zirconia was confirmed by Si-29 magic-angle (MAS) NMR. 1D Al-27, B-11 MAS as well as two-dimensional (2D) B-11 MQMAS/STMAS NMR experiments gave structural insight into the number and nature of aluminum and boron sites found in the glass and glass-ceramic (GC) samples. Irrespective of the heat treatment time, increasing the zirconia content in glasses suppressed their tendency towards devitrification, while the glasses exhibited good sintering behavior resulting in mechanically strong GCs with higher amounts of residual glassy phase making them suitable for self-healing during SOFC operation. All the GCs exhibited low total electrical conductivity; appropriate coefficients of thermal expansion (CTE), good joining and minimal reactivity with SOFC metallic components at the fuel cell operating temperature, thus, qualifying them for further appraisal in SOFC stacks.
palavras-chave
SI-29 MAS-NMR; ALUMINOSILICATE GLASSES; QUADRUPOLAR NUCLEI; SINTERING BEHAVIOR; PLANAR SOFCS; SILICATE; SPECTROSCOPY; CALCIUM; CRYSTALLIZATION; OPTIMIZATION
categoria
Chemistry; Energy & Fuels; Materials Science
autores
Reddy, AA; Tulyaganov, DU; Goel, A; Sardo, M; Wiper, PV; Pascual, MJ; Kharton, VV; Kolotygin, VA; Tsipis, EV; Mafra, L; Ferreira, JMF
nossos autores
Allu Amarnath Reddy
Estudante de doutoramento
José Maria da Fonte Ferreira
Professor(a) Jubilado(a)
Luís Mafra
Investigador Principal
Mariana Coutinho Sardo
Investigador Auxiliar
Paul Vincent Wiper
Bolseiro de pós-Doutoramento
Vladislav Kharton
Investigador Principal CovidadoProjectos
agradecimentos
This study was financially supported by CICECO, University of Aveiro, Portugal, and by FCT, Portugal (PTDC/CTM-CER/114209/2009, PTDC/QUI-QUI/100998/2008 and PEst-C/CTM/LA0011/2011). M. S. thanks FCT for the post-doc grant (SFRH/BPD/65978/2009). We acknowledge the Portuguese NMR Network (RNRMN) for funding and BP Amoco Chemical Company for sponsoring P.V.W.'s postdoc grant.