Preparation of Continuous Alumina Fiber with Nano Grains by the Addition of Iron Sol

Continuous alumina fiber exhibits excellent mechanical properties owing to its dense microstructure with fine grains. In this study, alumina fiber was prepared by the sol-gel method using iron sol as a nucleating agent. It was proposed that the alpha-Al2O3 grain size be adjusted based on the modification of colloidal particle size. The effect of holding temperature and reaction material ratio on the iron colloidal particle size was studied. The microstructure of alumina fiber was characterized by scanning electron microscopy (SEM). The experiment results indicated that iron colloidal particle size increases with the holding temperature and the NH4HCO3/Fe(NO3)(3)Greek ano teleia9H(2)O ratio. The alumina fiber with uniform nano alpha-Al2O3 grains was obtained by calcination at 1400 degrees C for 5 min. The mean grain size tends to rise with the mean colloidal particle size. Using the iron sol as a nucleating agent, the fiber with a mean grain size of 22.5 nm could be formed. The tensile strength of fibers increased with the decrease of grain size.