α-Alumina Fiber with Platelet Morphology Through Wet Spinning

Highly loaded Al(OH)(3) slurries were prepared in a 2 vol% aqueous acetic acid medium up to 33.3 wt% powder loading. The slurries were blended with 4 wt% chitosan in 2 vol% acetic acid and formed into ceramic fibers through wet spinning in sodium tripolyphosphate (STPP) bath. A gelation kinetics study of the chitosan-blended slurry also showed instantaneous gelation behavior under oscillatory mode rheological measurement. The slurries with moderate viscosities up to 150 Pa's were spinnable in STPP bath due to ionotropic gelation. Low viscous slurries were formed into a lump during spinning due to low powder loading and less chitosan present in the blend. The green fibers crystallized into a-alumina during sintering at similar to 950 degrees C with an average diameter varying between 70 and 120 mu m. alpha-alumina platelets were formed at 1350 degrees C and changed to hexagonal platelets at 1550 degrees C. The crystallite size of alpha-alumina varied between 26 and 112 nm which was measured from XRD data using Scherrer formula. The grain size of sintered fibers was similar to 4.5 lm at 1350 degrees C. The fibers were assembled into a cylindrical scaffold and sintered to produce a crushing strength of 0.9 MPa with density 0.9 g/cm(3)