Chapter 41. Thermal Stability of Single Crystal and Polycrystalline Alumina Fibers and 85% Al2O3-15 % SiO2 Fibers

  1. John B. Wachtman Jr.
  1. Gopal Das

Published Online: 26 MAR 2008

DOI: 10.1002/9780470314784.ch41

Proceedings of the 19th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures - B: Ceramic Engineering and Science Proceedings, Volume 16, Issue 5

Proceedings of the 19th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures - B: Ceramic Engineering and Science Proceedings, Volume 16, Issue 5

How to Cite

Das, G. (1995) Thermal Stability of Single Crystal and Polycrystalline Alumina Fibers and 85% Al2O3-15 % SiO2 Fibers, in Proceedings of the 19th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures - B: Ceramic Engineering and Science Proceedings, Volume 16, Issue 5 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314784.ch41

Author Information

  1. Pratt & Whitney P.O. Box 109600 West Palm Beach, FL 33410-9600

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1995

ISBN Information

Print ISBN: 9780470375389

Online ISBN: 9780470314784

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Keywords:

  • polycrystalliie;
  • precrystallized;
  • nextel;
  • homogeneous;
  • fractography

Summary

Room temperature tensile strengths of single crystal α-Al2O3 fiber (Saphikon), polycrystalline α-Al2O3 fiber (Nextel 610) and 85% Al2O3 -15% SiC2 fiber (Nextel 720) were evaluated in the as-received condition and after long term exposure at 982°C in air. Following an initial 25% loss of strength after a thermal exposure for 100 h, the Saphikon fibers appeared to suffer a gradual strength degradation with increasing thermal exposure. The Nextel 610 fibers did not appear to lose strength for thermal exposure up to 2000 h. The strengths of crystallized and precrystallized Nextel 720 fibers also remained unaffected by thermal exposures for 500 h at 982°C. The tensile strengths of precrystallized Nextel 720 fibers heat treated at 1093–1427°C in air were determined. The precrystallized Nextel 720 fibers started to show a loss of strength after heat treatment at 1093°C/4 h and the strength deterioration was exacerbated for heat treatment at 1204°C/4 h and above. The increased degradation of strength in precrystallized Nextel 720 fibers heat treated at 1204°C/4 h coincided with the formation of mullite, grain coarsening, and pores. Fractographic analysis revealed that fracture originated predominantly at the fiber surface in all fibers in the as-received and thermally treated conditions.