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  • 1 North Shore College of SONY Institute Atsugi, Kanagawa 243-8501 Japan Atsugi, Kanagawa 243-8501 Japan
  • | 2 Tokyo Metropolitan University Minami-osawa, Hachioji, Tokyo 192-0397 Japan Minami-osawa, Hachioji, Tokyo 192-0397 Japan
  • | 3 Seiko Instruments, Inc. Mihama, Chiba, Chiba 261-8507 Japan Mihama, Chiba, Chiba 261-8507 Japan
  • | 4 Japan Fine Ceramics Center Atsuta-ku, Nagoya, Aichi 456-8587 Japan Atsuta-ku, Nagoya, Aichi 456-8587 Japan
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Abstract  

Gamma-alumina membrane was prepared from anodic (amorphous) alumina (AA) obtained in a sulphuric acid electrolyte. The transformation scheme, i.e., the crystallization to form metastable alumina polymorphs and the final transition to α-Al2O3 with heating was studied by TG-DTA and X-ray diffraction (XRD) using fixed time (FT) method. When heating at a constant rate, the crystallization occurred at 900C or higher and the final formation of α-Al2O3 occurred at 1250C or higher, which temperatures were higher than the case of using anodic (amorphous) alumina prepared from oxalic acid electrolyte. Relative content of S of the products was obtained by transmission electron microscope (TEM)-energy dispersive spectroscopy (EDS). The proposed thermal change of anodic alumina membrane prepared from sulphuric acid is as follows: 1. At temperatures lower than ca 910C: Formation of a quasi-crystalline phase or a polycrystalline phase (γ-, δ- and θ-Al2O3); 2. 910–960C: Progressive crystallization by the migration of S toward the surface within the amorphous or the quasi-crystalline phase, forming S-rich region near the surface; 3. 960C: Change of membrane morphology and the quasi-crystalline phase due to the rapid discharge of gaseous SO2; 4. 960–1240C: Crystallization of γ-Al2O3 accompanying δ-Al2O3; and 5. 1240C: Transition from γ-Al2O3 (+tr. δ-Al2O3) into the stable α-Al2O3. The amorphization which occurs by the exothermic and the subsequent endothermic reaction suggests the incorporation of SO3 groups in the quasi-crystalline structure.

Manuscript Submission: HERE

  • Impact Factor (2019): 2.731
  • Scimago Journal Rank (2019): 0.415
  • SJR Hirsch-Index (2019): 87
  • SJR Quartile Score (2019): Q3 Condensed Matter Physics
  • SJR Quartile Score (2019): Q3 Physical and Theoretical Chemistry
  • Impact Factor (2018): 2.471
  • Scimago Journal Rank (2018): 0.634
  • SJR Hirsch-Index (2018): 78
  • SJR Quartile Score (2018): Q2 Condensed Matter Physics
  • SJR Quartile Score (2018): Q2 Physical and Theoretical Chemistry

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Journal of Thermal Analysis and Calorimetry
Language English
Size A4
Year of
Foundation
1969
Volumes
per Year
4
Issues
per Year
24
Founder Akadémiai Kiadó
Founder's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher
Chief Executive Officer, Akadémiai Kiadó
ISSN 1388-6150 (Print)
ISSN 1588-2926 (Online)