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184. Effect of Ta5+ doping on the thermal physical properties of defective fluorite Y3NbO7 ceramics.

Author

Song, Dowon, Pyeon, Janghyeok, Ryu, Myeungwoo, Jeon, Hak‐Beom, Oh, Yoon‐Suk, Song, Taeseup, Paik, Ungyu, Yang, SeungCheol, and Jung, Yeon‐Gil

Subjects
THERMAL properties, AERODYNAMIC heating, FLUORITE, THERMOMECHANICAL properties of metals, CHEMICAL engineering, CERAMICS, THERMAL barrier coatings
Abstract

The effects of substituting the B cation in A3BO7 ceramics on their thermal physical properties were investigated by applying a large mass difference. Y3(Nb1‐xTax)O7 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) ceramics were synthesized, and their structural characteristics were determined. All the fabricated Y3(Nb1‐xTax)O7 ceramics showed defective fluorite structures and glass‐like low thermal conductivity (1.18−2.04 W/m∙K at 25°C) because of the highly distorted crystal structure and significant mass difference. Substitution with Ta5+ enhanced the sintering resistance, leading to superior thermal‐insulating performance via grain boundary scattering. Furthermore, the ceramics exhibited excellent coefficients of thermal expansion, implying the promising applicability of Y3(Nb1‐xTax)O7 as new thermal barrier materials. The effect of mass difference on the thermomechanical properties of the ceramics was examined, suggesting a simple strategy for engineering the chemical composition of new thermal barrier materials. [ABSTRACT FROM AUTHOR]

Published
2022
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186. Partial Dehydration in Hydrated Tungsten Oxide Nanoplates Leads to Excellent and Robust Bifunctional Oxygen Reduction and Hydrogen Evolution Reactions in Acidic Media

Author

Han, Hyuksu, Nayak, Arpan Kumar, Choi, Heechae, Ali, Ghulam, Kwon, Jiseok, Choi, Seunggun, Paik, Ungyu, Song, Taeseup, Han, Hyuksu, Nayak, Arpan Kumar, Choi, Heechae, Ali, Ghulam, Kwon, Jiseok, Choi, Seunggun, Paik, Ungyu, and Song, Taeseup

Abstract

The development of efficient, low-cost, and stable bifunctional catalysts is necessary for renewable energy storage and conversion, but it remains a challenge. Herein, we first report a novel strategy to develop WO3 center dot nH(2)O (n = 0.33, 1.00, or 2.00) as a highly active and durable bifunctional catalyst for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in acidic media by controlling the degree of hydration. The content of solvated water molecules in WO3 center dot nH(2)O can be precisely controlled by selectively using ethylenediaminetetraacetic acid or DL-malic acid for room-temperature precipitation synthesis. Structural flexibility associated with water solvation in WO3 center dot nH(2)O leads to excellent bifunctional catalytic activity as well as durability in acidic media. The bifunctional catalytic mechanism of WO3 center dot nH(2)O is mainly attributed to spontaneous partial dehydration during electrolysis, resulting in simultaneous formation of active phases for HER and ORR, respectively.

Published
2020

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