Abstract In this work, compositions containing transparent glass bottles and banana leaves (desiccated and crushed), with different mass fractions (30-50%), were prepared for obtaining cellular materials for thermal insulation purposes. The formulated and prepared compositions were uniaxially pressed (10 MPa) and the compact powders fired between 700 and 850°C for 30 min in order to investigate the effect of the banana leaves on the formation of pores and on the thermal and mechanical properties of the processed glass foams. The results indicated that the obtained glass foams with porosities between 58.5 and 87.5%, compressive strength ranging between 1.17 and 3.50 MPa and thermal conductivity ranging between 0.06 and 0.15 W/mK, are potential candidates to work as thermal insulators with appropriate properties for a specific application.

RESUMO Resíduos de vidro podem ser reutilizados para o desenvolvimento de materiais alternativos. Uma opção viável são os materiais celulares para isolamentos térmicos já que, apresentando poros isolados, possuem baixa condutividade térmica, baixa densidade aparente e temperaturas de serviço mais altas que a dos materiais isolantes poliméricos. Neste trabalho, foi preparada uma suspensão aquosa com resíduos de vidro previamente moídos, Ágar-ágar (gelificante) e Emustab(r) (emulsificante), a qual foi adicionada diferentes frações de óleo de soja (50, 70 e 90% em massa). Subsequentemente, foi realizada a emulsificação do óleo vegetal no líquido da suspensão por meio de agitação em misturador mecânico de alto cisalhamento. Corpos de prova cilíndricos foram produzidos via colagem por gelificação e queimados a 700 °C/30 min. Os resultados mostraram que os vidros celulares obtidos apresentaram porosidade entre 74 e 93% com poros bem definidos e distribuídos e baixas condutividades térmicas (0,05 a 0,09 W/m.K). Tais resultados indicam que os materiais obtidos são potenciais candidatos para atuarem como isolantes térmicos, como por exemplo, painéis para revestimentos utilizados na construção civil.

ABSTRACT Glass wastes can be reused for the development of alternative materials. A viable option are the cellular materials for thermal insulation since with isolated pores they show low thermal conductivity, low density and service temperatures higher than those of the polymeric insulating materials. In this work an aqueous suspension was prepared with previously milled glass wastes, agar (gelling) and Emustab(r) (emulsifier), in which different soy oil fractions (50, 70 and 90 wt% ) were added. Subsequently, the emulsification of the vegetable oil was carried out in the liquid suspension by stirring in a mechanical mixer at high shear. Cylindrical samples were produced by gelation slip casting and fired at 700 °C/30 min. The results showed that the obtained cellular glasses had porosity between 74 and 93% with well-defined and distributed pores and low thermal conductivity (0.05 to 0.09 W/mK). These results indicate that the obtained materials are potential candidates to act as thermal insulators, such as panels for coatings used in construction.

Copper-substituted bismuth vanadate has been considered a promising material for composite cathodes in SOFC. However, high reactivity of BICUVOX.10 towards the electrolytes still has been its greatest shortcoming. This paper describes reactions between BICUVOX.10 and yttria-stabilized zirconia (YSZ) electrolytes. Secondary phases formed were evaluated by X-ray diffraction, scanning electron microscopy and a.c. impedance spectroscopy. A deleterious interaction between BICUVOX.10 and YSZ was observed, mainly regarding the yttrium depletion from ZrO2 lattice through reaction with VO2.5, resulting in YVO4 phase nucleation and destabilization of the tetragonal and cubic ZrO2 polymorphs to monoclinic. The ZrO2 destabilization and YVO4 nucleation are related phenomena and were interpreted through a theoretical mechanism using charge-compensating dopants description. Thus, these reactions were seen as detrimental to the cathode/electrolyte contact, especially regarding the highly resistive layer formed in the BICUVOX.10/YSZ junction, discouraging further usage of BICUVOX.10 as a cathode in yttria-stabilized zirconia electrolytes.