Preparation And Study Of Mullite-alumina Composite Continuous Fiber

In this paper,mullite-alumina composite continuous fiber was prepared,which not only has high strength,high hardness,corrosion resistance and wear resistance of alumina ceramic fiber,but also improves its toughness and the resistance to high temperature creep.In the present work,the precursor of ?-AlOOH was prepared by means of hydrothermal treatment,and ?-AlOOH with uniform particle size and good dispersion was prepared at different temperatures and pH values.Then,the uniform dispersion of?-Al2O3 was obtained by sintering ?-AlOOH.Using the prepared aluminum sol,?-Al2O3 and silicon sol as precursors,spinnable sol was obtained by removing solvent under vacuum using sol-gel method in presence of spinning additive.Continuous gel fibers were prepared by dry spinning technique using the above spinnable sol as precursor.The effect of spinning conditions and spinning additives on gel fibers were studied.The role of ?-Al2O3 in the process of fiber sintering is discussed.The addition of ?-Al2O3 as homogenous seeds can accelerate the formation of alumina nucleus,increase the nucleation center,reduce the nucleation barrier of alumina.The formation temperature of ?-Al2O3 crystal phase is decreased,and the formation temperature difference between ?-Al2O3 and mullite phase is reduced,which can effectively prevent the growth of crystalline mullite and ?-Al2O3 particles at high temperature to obtain the dense ceramic fibers.It also improves the mechanical properties of the fiber.Due to the massive effusion of gases derived from solvent volatilization and the decomposition of spinning additives in the gel fiber,the slow heating rate is adopted in the low-temperature stage.And during the late stages of crystallization,the rapid high-temperature sintering is used to inhibit the rapid crystal growth.The as-prepared mullite-alumina composite continuous fiber has excellent heat resistance and high-temperature creep resistance,uniform fiber diameter,the smooth fiber surface and the dense internal structure,which exhibits high strength and good flexibility.The tensile strength of the fiber monofilament after the heat treatment at 1350? is up to 2.5GPa,which can still be kept ca.85%at the temperature of 1350?.The fiber can be used for reinforcing the metal base or the ceramic-based composite material,and shows wide application potentials in the fields of aerospace,automobile,energy,and so on.