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Thermal Healing of Laser‐Induced Internal Cracks in Lithium Fluoride Crystals
Author(s) -
Wang Zhanyi,
Li Yan Z.,
Harmer Martin P.,
Chou Ye T.
Publication year - 1992
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1992.tb04231.x
Subject(s) - shrinkage , materials science , composite material , annealing (glass) , activation energy , arrhenius equation , thermal diffusivity , lithium fluoride , thermal , thermal treatment , mineralogy , chemistry , thermodynamics , inorganic chemistry , physics , organic chemistry
Laser‐induced internal cracks in LiF single crystals were annealed and healed at various temperatures in the absence of environmental contamination. The thermal healing process consists of three distinct stages: (a) pinching off of the crack into radially directed cylindrical pores within the rim of the crack front and within inner regions close to 〈110〉 directions, (b) ovulation of the 〈110〉 pores into rows of isolated, square‐shaped pores and, simultaneously, regression of the plate‐shaped subcracks situated near 〈100〉 directions, and (c) shrinkage of the isolated pores. A modified Arrhenius relationship between the rate of subcrack shrinkage and the annealing temperature was obtained. The apparent activation energy was found to be 2.0 eV (192.7 kJ/mol), suggesting that the healing process is controlled by volume diffusion.