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RISS 인기검색어
- 검색키워드
- 저자 : Dell’Agli, G. (검색결과 5 건)
- 무료
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Dell’Agli, G.,Spiridigliozzi, L.,Pansini, M.,Accardo, G.,Yoon, S.P.,Frattini, D. Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.15
<P><B>Abstract</B></P> <P>Variously co-doped Samaria-20 mol% doped ceria (SDC20) nanopowders were synthesized through a combined co-precipitation/hydrothermal treatment method under different carbonate environments. Urea and ammonium carbonate were used as both precipitating and mineralizing agent. In all cases, the adopted powder composition was Ce<SUB>0.8</SUB>Sm<SUB>0.16</SUB> ×<SUB>0.04</SUB>O<SUB>1.9-δ</SUB>, where X was either Ca, Sr, Er or Pr and δ is 0 for trivalent cations (i.e. Er and Pr) or 0.02 for divalent cations (i.e. Ca and Sr). The effects of different synthesis parameters on powders morphology and crystalline phases have been pointed out. Differently synthesized powders underwent structural and morphological transformations during the hydrothermal treatment leading to different crystalline precursors for the desired co-doped ceria nanopowders, i.e. crystallized into the fluorite-like cubic structure after a calcination step at 700 °C for 1 h. The final properties of the calcined powders are strongly related to the corresponding parent powder features, consequently determining different sintering behaviours in the various pellets. In particular, except for Er/Sm co-doped ceria, all samples synthesized with ammonium carbonate as precipitating/mineralizing agent exhibited excellent sintering behaviour, with remarkable values of relative density (higher than 97% and up to 99.4%) and an almost ideal microstructure. Definitely, the present work gives several guidelines in terms of synthesis parameters and conditions to produce, with a relatively simple and cheap process, highly reactive co-doped ceria nanopowders with tuned properties and suitable as electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFCs).</P>
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Dell’Agli, G.,Spiridigliozzi, L.,Marocco, A.,Accardo, G.,Frattini, D.,Kwon, Y.,Yoon, S.P. Elsevier 2017 Ceramics international Vol.43 No.15
<P><B>Abstract</B></P> <P>Nanocrystalline Samarium (20mol%)-doped ceria (SDC20) nanopowders were prepared using a combined co-precipitation/hydrothermal treatment synthesis route carried out at reduced temperature (120°C). The amorphous precursor experiences some microstructural transformations during the hydrothermal treatment, and after 16h a Samarium-Cerium hydroxide carbonate, characterized by a hexagonal crystalline lattice, spherical morphology and particles of about 100nm in size, with a very low degree of agglomeration, is the only present phase in contrast to the initial amorphous state. After the calcination step, the powders which preserved this morphology are still characterized by the absence of hard agglomerates. As a consequence, these powders exhibited an excellent sintering behaviour with a microstructure characterized by regular, equiaxed and micrometric grain size. In fact, at 1500°C a nearly perfect densified sample was obtained, but also at 1300°C a very good sintering behaviour was observed. Finally, the electrochemical characterization carried out by EIS measurements showed a very good electrical behaviour with high ionic conductivity, i.e. at 800°C 5.2·10<SUP>−2</SUP> Scm<SUP>−1</SUP> and 4.8·10<SUP>−2</SUP> Scm<SUP>−1</SUP> for pellets sintered at 1500°C and 1300°C respectively, making them suitable for IT-SOFCs.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Spiridigliozzi, L.,Dell'Agli, G.,Accardo, G.,Yoon, S.P.,Frattini, D. Elsevier 2019 CERAMICS INTERNATIONAL Vol.45 No.4
<P><B>Abstract</B></P> <P>Gd<SUB>0.2-x</SUB>Pr<SUB>x</SUB>Ce<SUB>0.8</SUB>O<SUB>1.90</SUB>, (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) has been synthesized by means of a simple co-precipitation route based on ammonium carbonate as the precipitating agent. The as-synthesized precursors are cerium-gadolinium-praseodymium amorphous hydroxycarbonates, which are nanometric in size with highly homogeneous morphology, leading to reactive doped and co-doped nanocrystalline (≈13 nm) ceria after a mild thermal treatment (2 h at 600 °C). The obtained results highlight the very positive effect of Pr on the powders’ sintering behaviour, which favour a better densification of the final pellets, thus improving both their microstructure (with relative densities of 97–99% after sintering at 1250 °C for 3 h) and electrochemical properties (up to 1.25·10–1 S cm<SUP>−1</SUP> at 800 °C for sample 6Pr) compared to the state-of-art ceria-based electrolytes. Through a comprehensive characterization, a relation was formed between the Pr content and the microstructural features of the sintered pellets and their electrical behaviour. The amount of Pr doping was investigated over a wide range and 6 mol% has been established to be optimal (possessing the lowest electronic conductivity contribution). Definitely, these results indicate that Gd<SUB>0.2-x</SUB>Pr<SUB>x</SUB>Ce<SUB>0.8</SUB>O<SUB>1.90</SUB> has an excellent set of characteristics, both microstructural and electrical, and a convenient fabrication process, thus making it perfectly suitable for IT-SOFC practical applications.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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L. Spiridigliozzi,G. Dell’Agli,A. Marocco,G. Accardo,M. Pansini,S.P. Yoon,H.C. Ham,D. Frattini 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.59 No.-
Nanometric powders of doped and co-doped ceria based ceramics with spherical-like morphology and characterized by very low degree of agglomeration, were prepared by using a simple and cheap synthesis route, easily scalable on industrial level, based on an optimized co-precipitation process with ammonium carbonate as precipitating agent. The as-synthesized powders are completely converted to ceria with fluorite structure. The original morphology and the nanometric features are also preserved. Nearly perfect dense products were obtained after sintering at 1300 °C for 3 h, as by SEM and density measurements. Electrochemical measurements proved that they are all suitable as electrolytes for IT-SOFC.
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Gadolinium-doped ceria nanopowders synthesized by urea-based homogeneous co-precipitation (UBHP)
Accardo, G.,Spiridigliozzi, L.,Cioffi, R.,Ferone, C.,Di Bartolomeo, E.,Yoon, Sung Pil,Dell’Agli, G. Elsevier 2017 Materials chemistry and physics Vol.187 No.-
<P><B>Abstract</B></P> <P>Gadolinium (10%)-doped ceria was successfully synthesized by using an urea-based co-precipitation method (UBHP). A single fluorite phase was obtained after a low temperature (400 °C) calcination treatment. The resulting powders showed grains of nanometric size with some agglomerations and an overall good sinterability. Pellets were sintered at 1300 and 1500 °C for 3 h. The ionic conductivity was measured by electrochemical impedance spectroscopy measurements and a correlation between electrical properties and microstructure was revealed. The promising conductivity values showed that the synthesized powders are suitable for intermediate temperature solid oxide fuel cells (IT-SOFCs) applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Urea-based homogeneous co-precipitation is applied to synthesize nanocrystalline GDC. </LI> <LI> Dense GDC samples at different sintering temperatures were characterized. </LI> <LI> SEM and TEM revealed a well define microstructure and controlled composition. </LI> <LI> Correlation between electrochemical properties by EIS and microstructure was discussed. </LI> <LI> UBHP method can be used to prepare high performance GDC electrolytes. </LI> </UL> </P>
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