A new way to spinnable sols derived from modified aluminium alkoxides

The preparation of spinnable sols has been developed to obtain a new type of sol-gel derived pure aluminia fiber. The starting material was aluminium sec-butoxide, which was modified in a first step with glycolether, e.g., isopropoxyethanol. This leads to apartial replacement of alkoxy groups via alcoholysis an a change of the precursor structure from a trimetric to a terametric one. In the second step, carboxylation, the transformation to six-coordinated aluminium could be observed. Due to the formation of a sol with Newtonian flow behaviour after hydrolysis, gel fibers up to several kilometers long could be drawn directly from the clear colorless sol with spinning velocities up to 200m/min. The addition of an organic filament-forming polymer is not necessary. The sol is spinnable for periods up to one year. The transformation of gel fiber to a-Al2O3 occurs at 1150 deg C.