Oxygen permeation properties and surface modification of acceptor-doped CeO2/MnFe2O4 composites |
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Authors: | Hitoshi Takamura Hiroshi Sugai Masato Watanabe Takehiro Kasahara Atsunori Kamegawa Masuo Okada |
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Affiliation: | (1) Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aramaki Aza Aoba, Sendai 980-8578, Japan;(2) CREST, Japan Science and Technology Agency, Japan;(3) Three-R Corporation, 4-10-3 Chuo, Sendai 980-0021, Japan;(4) MHW Informatics, Inc., 406-33-3 Yagiyama-kasumicho, Sendai 982-0831, Japan;(5) Tohoku University, Japan |
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Abstract: | The preparation and oxygen permeation properties of the (Ce0.8Pr0.2)O2−δ − x vol% MnFe2O4 composites, where x = 0 to 35, have been investigated. The samples were prepared by the Pechini method. In the case of Ce0.8Pr0.2O2−δ, an oxygen flux density of 6 μmol⋅cm−2⋅s−1 (L = 0.0247 cm) and the maximum methane conversion of 50% were attained at 1000∘C. Unlike composites consisting of Gd-doped CeO2 and MnFe2O4, the oxygen permeability of the (Ce0.8Pr0.2)O2−δ – x vol% MnFe2O4 composites was almost constant regardless of the volume fraction of MnFe2O4; however, the optimum volume fraction of MnFe2O4 was determined to be 5 to 25 in the context of the chemical and mechanical stabilities under methane conversion atmosphere. In addition, the surface modification of the (Ce0.8Gd0.2)O2−δ – 15 vol% MnFe2O4 composite was performed by using the FePt nanoparticles. The catalyst loading of 2.8 mg/cm2 on the both side of the 0.3 mm-thick (Ce0.8Gd0.2)O2−δ – 15vol% MnFe2O4 composite increased the oxygen flux density from 0.30 to 0.76 μmol⋅cm−2⋅s−1 in the case of He/air gradients; however, the effect seems to be reduced in the case of high oxygen flux density caused by a large pO2 gradient. Moreover, the Langmuir-Blodgett film of the FePt nanoparticles were successfully prepared on the tape-cast (Ce0.8Gd0.2)O2−δ – 15vol% MnFe2O4 composite. Hydrophobic treatments for the surface of the composite were crucial to achieve high transfer ratio for the deposition of the LB film. |
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Keywords: | Oxygen permeable ceramics Pr-doped ceria Methane conversion FePt nanoparticles Langmuir-Blodgett film |
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