TENSILE STRENGTH OF SAPPHIRE WHISKERS AT ELEVATED TEMPERATURES

Tensile tests have been carried out on 124 sapphire whiskers at temperatures in the range 350 to 1810° C. The effects of crystallographic orientation, growth process, purity and surface perfection have been investigated. The strength-temperature-dependences of different categories of whisker are compared with that to be expected for a Griffith fracture mechanism, and it is shown that such a mechanism may apply up to ∼1000° C to A-type (<hk.o>) whiskers grown by the wet-hydrogen process [1]. Chemically-polished whiskers of this type show a strength-temperature-dependence more consistent with a dislocation-induced fracture mechanism. There is some evidence that chemically-polished C-type (<0001>) whiskers grown by a chloride oxidation process [2] behave in the same manner. For other categories of whisker there are insufficient data to ascribe fracture mechanisms. © 1969 Chapman and Hall.