The influence of fiber coating conditions on the mechanical properties of alumina/alumina composites

Alumina fibers as a form of fabric cloth are slurry coated by a vacuum enhanced dip-coating (VEDC) method for the reinforcement of an alumina matrix. Three kinds of precursors including YPO4, CePO4 and LaPO4 are prepared and applied to the coating of alumina cloth. SEM observation shows that the fibers in the bundle are uniformly coated by this method. The coated fibers are debonded from the matrix during fracture of the composites. Mechanical properties of these composites using the vacuum enhanced dip-coated fibers are affected by the properties of coating slurry, including concentration and pH value. The three kinds of coating have shown no significant difference when they are coated under the same conditions. Increase of the concentration of the coating slurry causes increase of the bulk density of the composites, while the optimum coating thickness corresponding to the highest maximum fracture strength is obtained by the medium slurry concentration. When pH of the coating slurry is nearly neutral, the coating becomes uniform and the highest maximum strength as well as the highest density of the composites are achieved.