Fabrication and characterization of hot pressed Al۲O۳–SiCfibrous monolithic ceramics

Fibrous Monolithic Ceramics (FMs) in many of cases are inexpensive alternatives for replacingthe ceramic composites that reinforced with continuous fibers. Additionally, the FMs compositesprovide higher fracture toughness. For fabrication of monolithic specimens, alumina-basedcomposites with ۵, ۱۰, ۱۵, ۲۰ and ۲۵ wt% of silicon carbide and ۰.۵ wt% of titanium hot pressedat ۱۵۵۰ °C under the pressure of ۳۰ MPa for ۱ h. Then, the fibrous monolithic ceramics,containing core and shell with the diameter of ۱ mm manufactured. The core of (FMs) containing۹۰ wt% alumina, ۱۰ wt% silicon carbide and ۰.۵ wt% titanium dioxide, surrounded by graphiticshells. core to shell volume fraction ratios (۶۵: ۳۵ and ۷۵: ۲۵) produced by extrusion method. Forthe second step, the fibers were laid out in the cold press in two different directions of ۰°, ۰ /۹۰°.then they were pressed with a load of ۳۰ MPa. After that, the specimens hot pressed under thepressure of ۳۰ MPa at ۱۵۵۰ °C for ۱ hour. For the monolithic composites containing ۵ wt %silicon carbide, maximum fracture toughness and hardness measured and values about ۵.۹(MPa.m۱/۲) and ۲۰۸۵ HV. The highest flexural strength of ۶۳۴.۷۵ MPa was obtained for thespecimen with ۲۵ wt% silicon carbide. For the FMs specimens, due to the reduction of the cellboundary thickness, the crack deflection and crack delamination in the cell boundary increased,and the maximum value of fracture toughness increased up to ۸.۹ MPa .m۱/۲.

Keywords:

Fibrous monolithic ceramics , Alumina , Silicon carbide , Hot pressing , microstructure , mechanical properties.