Continuous mullite ceramic fibers were fabricated by a sol-gel dry-spinning technique. The sot was prepared from an aqueous solution of aluminum nitrate, aluminum isopropoxide and tetraethylorthosilicate. The sol-gel transition was investigated by measuring the volume, the solid content, the viscosity and the rheological properties of the solution. Shear viscosity eta of the mullite sot varied dynamically with concentrating time and temperature of the sot. Combined with size analysis of sot particles and TEM analysis, the growth characteristics of sot particle agglomeration and its structural evolution were examined. By adjusting the temperature, the gelation degree could be stabilized at a certain value, and the sol-gel transition could be transferred to the spinning line. Continuous fibers were obtained from such sols using a laboratory dry-spinning apparatus. Sintering of the precursor fibers at 1100 degrees C yielded crack-free mullite ceramic fibers when the solid content of spinnable sot was above 50%. (C) 2009 Published by Elsevier Ltd.