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Kwak, Ja Hun
Molecular Catalysis Lab.
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dc.citation.endPage 68 -
dc.citation.startPage 58 -
dc.citation.volume 500 - Lee, Jaekyoung - Jeon, Himchan - Oh, Dong Gun - Szanyi, Janos - Kwak, Ja Hun - 2023-12-22T01:07:55Z - 2023-12-22T01:07:55Z - 2015-08-03 - 2015-07 -
dc.description.abstract The phase transformations of platelet- and rod-shaped gamma-Al2O3 were investigated and compared to that of a commercial sample by XRD, BET surface area measurements, transmission electron microscopy (TEM), solid state Al-27-NMR, and ethanol temperature programmed desorption (TPD) after sequential annealing in air up to 1100 degrees C. After annealing at 1100 degrees C, commercial gamma-Al2O3 mostly transformed into alpha-Al2O3 with drastic surface area reduction (from 200 m(2)/g to 25 m(2)/g). Interestingly, platelet- and rod-shaped gamma-Al2O3 which showed exactly the same XRD patterns transformed into different phases upon the high temperature calcinations. Platelet-shaped gamma-Al2O3 transformed into theta-phase while the rod-shaped gamma-Al2O3 transformed into the delta-phase and not to the alpha-polymorph. Both platelet- and rod-shaped aluminas retained significantly higher surface area (similar to 60 m(2)/g) than the commercial one after the same treatment at 1100 degrees C. These results suggest that the phase transformation in gamma-Al2O3 is strongly affected by not only the crystal structure of the starting material, but its morphology as well. Ethanol TPD from platelet- and rod-shaped alumina after 1100 degrees C annealing, showed significantly different desorption profiles which suggest different surface characteristics even though they had almost the same surface areas. These different phase transformations were also supported by solid state Al-27-NMR. After 1100 degrees C annealing commercial alumina showed the presence of mostly octahedral Al3+ ions, but the other two samples displayed even higher number of tetrahedral Al3+ ions than the initial gamma-Al2O3. Morphological changes were also confirmed by TEM. All these results consistently suggest the morphology-dependent phase transformations of gamma-Al2O3 and the improved thermal stability of platelet- and rod-shaped gamma-Al2O3 in comparison to a commercial gamma-Al2O3. (C) 2015 Elsevier B.V. All rights reserved. -
dc.identifier.bibliographicCitation APPLIED CATALYSIS A-GENERAL, v.500, pp.58 - 68 -
dc.identifier.doi 10.1016/j.apcata.2015.03.040 -
dc.identifier.issn 0926-860X -
dc.identifier.scopusid 2-s2.0-84968764298 -
dc.identifier.uri -
dc.identifier.url -
dc.identifier.wosid 000357141700008 -
dc.language 영어 -
dc.publisher ELSEVIER SCIENCE BV -
dc.title Morphology-dependent phase transformation of γ-Al2O3 -
dc.type Article -
dc.description.isOpenAccess FALSE -
dc.relation.journalWebOfScienceCategory Chemistry, Physical; Environmental Sciences -
dc.relation.journalResearchArea Chemistry; Environmental Sciences & Ecology -
dc.description.journalRegisteredClass scie -
dc.description.journalRegisteredClass scopus -
dc.subject.keywordAuthor gamma-Al2O3 -
dc.subject.keywordAuthor Phase transformation -
dc.subject.keywordAuthor Morphology -
dc.subject.keywordAuthor TEM -
dc.subject.keywordAuthor Ethanol-TPD -
dc.subject.keywordPlus GAMMA-ALUMINA -
dc.subject.keywordPlus SURFACE-AREA -
dc.subject.keywordPlus HYDROTHERMAL SYNTHESIS -
dc.subject.keywordPlus TRANSITIONAL ALUMINAS -
dc.subject.keywordPlus ETHANOL DEHYDRATION -
dc.subject.keywordPlus THERMAL-STABILITY -
dc.subject.keywordPlus PARTICLE-SIZE -
dc.subject.keywordPlus BOEHMITE -
dc.subject.keywordPlus NANOPARTICLES -
dc.subject.keywordPlus MECHANISM -


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