SILICA FIBER/CORE-SHEATH FIBER.

The report describes work on a program which called for 1 a study of fused quartz fiber forming from a fluid melt contained in a bushing of tungsten and other materials in an argon atmosphere, and 2 the development of a composite ceramic-glass fiber of core-sheath configuration. High-Temperature Fiber Forming - Continuous fused quartz fiber forming was achieved from silica melts contained in both tungsten and yttria-stabilized zirconia bushings operated in an argon atmosphere. Fiber forming temperatures ranged from approximately 1900C to 2300C. Fiber tensile strengths approaching 600,000 psi were obtained. Bushings were indirectly heated, which permitted flexibility of design and materials. Core-Sheath Fiber Development - A systematic study of the crystalline core vitreous sheath concept was conducted using a doublecompartmented platinum alloy bushing in which the inner compartment contained a core material and the outer compartment the sheath material. Fourteen candidate core materials and four sheath glasses were evaluated. Narmco found that fibers with a core volume as high as 80 could be successfully formed with this bushing design. The fibers so formed were vitreous and the core was crystallized by subsequent heat treatments. After core crystallization, modulus increases up to 75 were obtained, with values approaching 0.00002 psi. Tensile strengths over 100,000 psi were measured. Author