Preparation and characterization of continuous alumina based fiber reinforced with orientated mullite whisker

• The orientated mullite whisker-reinforced alumina based fibers were prepared using spinnable sol.
• The axial direction of whiskers was consistent with the fibrous matrix.
• The addition of whisker enhanced the spinning viscosity while lowered the zeta potential of the sol.
• The addition of whisker reduced the spinning length but did not affect the compactness of the fiber.
• The tensile strength increased from 535.9 to 637.9 MPa at a whisker content of 1 wt.%.

Single crystal mullite whiskers were directly added into the precursor sols to synthesis the orientated whisker-reinforced continuous alumina based fibrous matrix composite. The solid content and spinnable viscosity range were enhanced but the zeta potential was reduced by the addition of the mullite whiskers into the sol. The Al oligomers content increased while monomer and Al13 decreased with the increase of mullite whisker. After sintering at 1250 °C, the obtained compact nano grains fibers were reinforced with accordant axial direction whiskers which were orientated by the axial force derived from the spinning process. The phase composition and compact structure were not affected by the presence of the mullite whiskers, while the continuous spinning length became low. Although tensile strength of single composite fiber was decreased at a high mullite whisker content due to the low densification and cracks of composite fiber, whisker bridging and pullout during fiber fracture may have increased the strength at a mullite whisker content of 1 wt.% to 642.6 MPa.