Tensile strength of SiO sub 2 -ZrO sub 2 fibers prepared by the sol-gel method; Effects of preparation artifacts and thermal treatments

This paper reports that fibers of composition 80SiO{sub 2}.20ZrO{sub 2} (mol%) were prepared by the sol-gel method, starting from silicon and zirconium alkoxides, and heated up to 1500{degrees}C. Chemical processes in solution and heating procedure provided well-densified products. ZrO{sub 2} crystallization afforded stable tetragonal ZrO{sub 2} crystallites with an average dimension smaller than 30 nm; SiO{sub 2} crystallized as cristobalite above 1200{degrees}C. The tensile strength was determined as a function of diameter for samples heated at 900{degrees} and 1200{degrees}C. Strength data, analyzed using a Weibull approach, showed that surface and bulk defects are responsible for the measured tensile strength.