Preparation and spinnability of precursor sols for alumina continuous fibers
Aluminum(Al)sol was prepared using Al powder and aluminum chloride hexahydrate(AlCl3·6H2O)as Al source and neutral silica sol(SiO2)as Si source by sol-gel method and was exposed to concentration and ageing to produce spin-nable precursor Al sol.The effects of feed ratio,reaction time,concentration temperature and time on the preparation of Al sol,as well as the effects of concentration,aging and dilute hydrochloric acid(HCl)addition on the spinnability of precursor Al sol,were studied.And the rheological property of spinnnable precursor Al gel was measured.The results showed that Al sol with a solid content of 20%was synthesized under the conditions of 80℃ water bath and electric stirring speed of 1 000 r/min,and the optimal feed ratio was Al powder/AlCl3·6H2O mass ratio of 1:1 and the rational reaction time was 3 h;Al sol with a solid con-tent of 20%and a dynamic viscosity(μ)of 20 mPa·s was concentrated at 80℃ for 5 h before ageing at 28℃ for 40 h to obtain a precursor Al sol with good spinnability and μ of approximately 60 000 mPa·s;the addition of dilute HCl can effectively inhibit the sol gel in the preparation of spinnable precursor Al sol,and the appropriate amount of HCl was 1.5 g in 25 g Al sol;a spin-nable precursor Al sol exhibited a shear thinning pseudoplastic fluid,with the μ of the sol of 50 000-70 000 mPa·s at a temper-ature of 25-35℃ and a shear rate of 0-1 000 s-1,indicating a good spinnability.
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