Alumina Fiber Reinforced Zirconia / Alumina Composites Preparation Process

Fiber reinforced ceramic matrix composite is one of the most active research field in composite for the moment because of the excellence of high temperature-resistant, abrasion-resistant, high temperature creep-resistant, low thermal conductivity coefficient, low thermal expand coefficient and chemical corrosion-resistant. However, the shortage of non oxide fiber reinforced ceramic matrix composite is the decline of mechanics performance because of oxidation reaction in high temperature and oxidation environment. Oxide fiber/oxide ceramic matrix composite can work in high temperature and oxidation environment, and can not fracture catastrophically because of oxidation. It is the most promising material for gas turbines hot section parts because of low cost. Gel-casting has the advantage of near net-shape forming technique, and the bodies can be machined to get accurated and complicated shape parts. This paper can make oxide fiber/oxide ceramic matrix composite by gel-casting. Al₂O₃ fiber is used for reinforced material and ZrO₂ toughened Al₂O₃ ceramic is used for matrix material.The paper investigated the gel-casting of ZrO₂ toughened Al₂O₃ matrix material, and studied various of factors which affected the gel-casting. The slurry had better flowability and stability when pH was 10, the dispersion content was 0.6wt% and solid volume fraction was 50vol%. The surface-exfoliation of green bodies could be prohibited by adding a proper amounts of soluble macromolecule PEG and using terrace molds; solid volume fraction affected the strength of green bodies, and the most value of green bodies's bending strength was 43.94MPa when solid volume fraction was 50vol%.Bulk density, porosity and mechanic properties of different fiber amounts (0～40wt%) composite in different sintering temperature(1300℃～1600℃) were investigated. The testing results show that the sintering temperature and fiber amounts influenced great on the bulk density and porosity, the bulk density of composite increased and porosity decreased when sintering temperature was elevated, the bulk density decreased and porosity increased when fiber amounts increased. The most value of sample's bending strength was achieved when fiber amounts were 30wt% in different sintering temperature, sample's bending strength was increased to 55.15 %,92.07%,147.63% and 83.29% in the sintering temperature 1300°C, 1400°C, 1500°C and 1600°C respectively; The most value of samples bending strength and fracture toughness are 461.17MPa and 6.03 MPa·m^1/2 by adding sintering aid in 1600°C and increased 44.81% and 47.79% respectively.The microstructures of different fiber amounts (0～40wt%) composite in different sintering temperature(1300°C～1600°C) were investigated. The results show that the samples began to be compact when sintering temperature was 1500°C, and the samples were compact much more when sintering temperature was 1600°C, the fibers and matrix materials were close; the better dispensability was achieved when fiber amounts were 30wt%. The surface of fiber changed when sintering temperature increased. The surface of fiber was smooth when sintering temperature was 1300°C; the surface of fiber was rough when sintering temperature was 1400°C; the hole defect could be seen in the surface of fiber when sintering temperature was 1500°C;the surface of fiber was coarsed obviously because of fiber grain growth when sintering temperature was 1600°C. The fiber evulsion effect was seen clearly in different sintering temperature. It was the basic reason that the bending strength and fracture toughness of composites were increased when fibers were added.