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Kwak, Ja Hun
Molecular Catalysis lab
Research Interests
  • Heterogeneous catalysis, molecular catalysis, ASlumima, zeolites

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Unraveling the Origin of Structural Disorder in High Temperature Transition Al2O3: Structure of θ-Al2O3

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Title
Unraveling the Origin of Structural Disorder in High Temperature Transition Al2O3: Structure of θ-Al2O3
Author
Kovarik, LiborBowden, MarkShi, DachuanWashton, Nancy M.Andersen, AmityHu, Jian ZhiLee, JaekyoungSzanyi, JanosKwak, JahunPeden, Charles H. F.
Issue Date
2015-10
Publisher
AMER CHEMICAL SOC
Citation
CHEMISTRY OF MATERIALS, v.27, no.20, pp.7042 - 7049
Abstract
The crystallography of transition Al2O3 has been extensively studied in the past, because of the advantageous properties of the oxide in catalytic and a range of other technological applications. However, existing crystallographic models are insufficient to describe the structure of many important Al2O3 polymorphs, because of their highly disordered nature. In this work, we investigate structure and disorder in high-temperature-treated transition Al2O3 and provide a structural description for θ-Al2O3 by using a suite of complementary imaging, spectroscopy, and quantum calculation techniques. Contrary to current understanding, our high-resolution imaging shows that θ-Al2O3 is a disordered composite phase of at least two different end-members. By correlating imaging and spectroscopy results with density functional theory (DFT) calculations, we propose a model that describes θ-Al2O3 as a disordered intergrowth of two crystallographic variants at the unit-cell level. One variant is based on β-Ga2O3, and the other on a monoclinic phase that is closely related to δ-Al2O3. The overall findings and interpretations afford new insight into the origin of poor crystallinity in transition Al2O3, and we also provide new perspectives on structural complexity that can emerge from intergrowth of closely related structural polymorphs.
URI
https://scholarworks.unist.ac.kr/handle/201301/17843
URL
http://pubs.acs.org/doi/10.1021/acs.chemmater.5b02523
DOI
10.1021/acs.chemmater.5b02523
ISSN
0897-4756
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