SOL-GEL DERIVED SIO2 ZRO2 NANOCOMPOSITE FIBERS - INFLUENCE OF COMPOSITION, THERMAL-TREATMENT AND MICROSTRUCTURE ON TENSILE-STRENGTH

Fibers of the SiO2-ZrO2 system with 70130 and 50/50 (wt%) compositions were prepared by the sol-gel method, using Si and Zr alkoxides as pre cursors. Green fibers were heated at different temperatures up to 1500 -degrees-C. Chemical processes in solution and heating procedures prov ided a particular microstructure of the final Material in which spheri cal particles of tetragonal zirconia were embedded in an amorphous mat rix. The tensile strength of the fibers was determined as a function o f cross-sectional area for samples treated at different temperatures w ith variable heating times. Fractographical analysis allowed determina tion of fracture toughness. Mechanical properties are discussed in ter ms of ZrO2 crystallization (tetragonal habit), fiber densification and microstructure.