Spinnable sols, formation

C is the concentration oftitanoxane polymer, rjsp/Cis the reduced viscosity and [> ] is the intrinsic viscosity), while the non-spinnable sols ( ) show only a small concentration dependence of the viscosity. This fact indicates the formation of linear type titanoxane polymers in the spinnable sols. Ti02 gel fibers were easily drawn by hand from the TIP sols with r-values of less than 4-5. It was also reported that Zr02 gel fibers were drawn... 

In the spinnable sols, the viscosity increase is caused by one-dimensional growth of linear particles, while in non-spinnable sols, the viscosity increase in the final stage is caused by the formation of bonding between granular particles. 

Fully dense fibers consisting of pure YAG phase were obtained by the 1600°C-heat-treatment of the gel fibers drawn from the solution of yttrium acetate hydrate/aluminum formate hydrate/H20/formic acid/ethylene glycol. The bending strength of the fibers was 1.7 0.2 GPa (Liu et al, 1998). Pullar et al. (1998a, 1999) also fabricated pure YAG fibers from aqueous sol-gel precursors. They blow-span the stoichiometric mixture of the alumina sol and silica sol by using PEO as a spinning aid. The HCl added to the sol as a peptizer was found to stabilize the sol, and to play important roles for the appearance of spinnability and also to improve the sinterability of the fibers. Fully dense YAG fibers obtained by them at 1600°C exhibited improved friability. 

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