EXPLORATORY INVESTIGATION OF NOVEL FILAMENT FORMATION TECHNIQUES FOR CONTINUOUS CRYSTALLINE ALUMINA.
Technical summary rept. 15 Aug 65-15 Jun 66,
TYCO LABS INC WALTHAM MA
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Sapphire filaments up to six inches in length, with diameters in the range of 5-20 mils, have been grown from the melt. The growth process, which is almost certainly dendritic namely, occurring below rather than above the melt surface, involves a novel configuration - the floating orifice technique FOT. The growth technique is essentially continuous and offers promise for the preparation of indefinitely long filaments. Filaments have been grown at rates up to 150 mmmin it is probable, however, that much higher speeds can be used, limited only by thermal considerations involving the rate of rejection of the latent heat of solidification. A theoretical analysis of the process is included. Four recognizably different types of filaments have been grown X-ray examination indicates that some of the filaments may be multicrystalline. Preliminary measurements of the mechanical properties of nonsmooth, nonuniform filaments indicate an elastic modulus of 30-50 times 10 to the 6th power psi, as measured by a vibrating reed technique 25 times 10 to the 6th power psi, as measured by flexure and a strength of 125,000 psi. Author