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Proceedings Paper

Compressive strengthening of sapphire by neutron irradiation
Author(s): Thomas M. Regan; Daniel C. Harris; Rhonda M. Stroud; John R. White; David W. Blodgett; Kevin C. Baldwin; Joseph A. Miragliotta; Michael E. Thomas; Milton J. Linevsky; John W. Giles; Thomas A. Kennedy; Mohammad Fatemi; David R. Black; K. Peter D. Lagerloef
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Paper Abstract

Neutron irradiation of sapphire with 1 x 1022 neutrons(<EQ MeV)/m2 increases the c-axis compressive strength by a factor of 3 at 600 degree(s)C. The mechanism of strength enhancement is the retardation of r-plane twin propagation by radiation-induced defects. 1-B and Cd shielding was employed during irradiation to filter our thermal neutrons (<EQ1 eV), thereby reducing residual radioactivity in the sapphire to background levels in a month. Yellow-brown irradiated sapphire is nearly decolorized to pale yellow by annealing at 600 degree(s)C with no loss of mechanical strength. Annealing at sufficiently high temperature (such as 1200 degree(s)C for 24 h) reduces the compressive strength back to its baseline value. Neutron irradiation decreases the flexure strength of sapphire at 600 degree(s)C by 0-20% in some experiments. However, the c- plane ring-on-ring flexure strength at 600 degree(s)C is doubled by irradiation. Elastic constants of irradiated sapphire are only slightly changed by irradiation. Infrared absorption and emission and thermal conductivity of sapphire are not affected by irradiation at the neutron fluence used in this study. Defects that might be correlated with strengthening were characterized by electron paramagnetic resonance spectroscopy. Color centers observed in the ultraviolet absorption spectrum were not clearly correlated with mechanical response. No radiation-induced changes could be detected by x-ray topography or x-ray diffraction.

Paper Details

Date Published: 7 September 2001
PDF: 10 pages
Proc. SPIE 4375, Window and Dome Technologies and Materials VII, (7 September 2001); doi: 10.1117/12.439191
Show Author Affiliations
Thomas M. Regan, Aspen Systems and Univ. of Massachusetts/Lowell (United States)
Daniel C. Harris, Naval Air Warfare Ctr. (United States)
Rhonda M. Stroud, Naval Research Lab. (United States)
John R. White, Univ. of Massachusetts/Lowell (United States)
David W. Blodgett, The Johns Hopkins Univ. (United States)
Kevin C. Baldwin, The Johns Hopkins Univ. (United States)
Joseph A. Miragliotta, The Johns Hopkins Univ. (United States)
Michael E. Thomas, The Johns Hopkins Univ. (United States)
Milton J. Linevsky, The Johns Hopkins Univ. (United States)
John W. Giles, The Johns Hopkins Univ. (United States)
Thomas A. Kennedy, Naval Research Lab. (United States)
Mohammad Fatemi, Naval Research Lab. (United States)
David R. Black, National Institute of Standards and Technology (United States)
K. Peter D. Lagerloef, Case Western Reserve Univ. (United States)

Published in SPIE Proceedings Vol. 4375:
Window and Dome Technologies and Materials VII
Randal W. Tustison, Editor(s)

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