Síntese e caracterização de eletrólitos compósitos à base de céria e sais fundidos
Solid electrolyte is the part of the fuel cell has three essential functions: separate reagents, blocking electronic current and have high ionic conductivity of the elements that compose it. Composite electrolytes consisting of a ceria (CeO2) or ceria-gadolinia (Ce0,9Gd0,1O2, CGO) ceramic matrix...
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| Formato: | Dissertação |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/23682 |
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| Resumo: | Solid electrolyte is the part of the fuel cell has three essential functions: separate
reagents, blocking electronic current and have high ionic conductivity of the elements
that compose it. Composite electrolytes consisting of a ceria (CeO2) or ceria-gadolinia
(Ce0,9Gd0,1O2, CGO) ceramic matrix and eutectic mixtures of Na2CO3/Li2CO3 or
LiCl/KCl allow reducing the operating temperature of ceramic fuel cells from 600 -
800°C to 400 – 600 °C. In this paper, composite electrolytes based on ceria and molten
salts (eutectic mixtures of carbonates and chlorides) were obtained by the citrate
method. The adopted chemical route enabled the simultaneous synthesis of the two
phases, with precise control of composition and microstructure, providing substantial
chemical interaction between phases. The study evaluated the effects of composition
(carbonate or chloride content in the ceria based matrix) and processing (sintering
temperature) on microstructure and transport properties of the composites. The
structural characterization by X-ray diffraction showed that the carbonates and
chlorides exist as amorphous phases. Despite the low relative densities (between 52
and 75%), as a result of reduced sintering temperatures (ceria/carbonate at 690°C and
ceria/chloride between 400 and 600°C), it was observed that the fusion of the
amorphous phase acts as a seal that can prevent the flow of gases through the
samples. The correlation between the composition and the electrical behavior, using
the infrared spectroscopy techniques, scanning electron microscopy and impedance
spectroscopy, has observed a homogeneous microstructural distribution between
phases, indicating the formation of a ceramic skeleton based on ceria, surrounded by
a mixture of amorphous salts, obtaining a conductivity of 0.079 S cm-1 and 0,058 cm-1
S for the ceria composite and carbonates at 600 ° C and 0.0016 S cm-1 and 0.0011 S
cm-1 for composites ceria and chlorides at 450 ° C. |
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