Micro-mechanical properties of a novel silicon nitride fiber reinforced silicon carbide matrix composite via in situ nano-indentation method

A novel Si3N4 fiber reinforced SiC matrix composite has been prepared and the micro-mechanical properties of the composites in situ have been explored. For the Si3N4 fibers, the micro-mechanical properties in situ remained almost unchanged with the increasing fabrication temperatures. In comparison, for the PCS derived SiC matrix, higher fabrication temperature could trigger more beta-SiC formations, which led to enlarging the corresponding micro-mechanical properties. The microstructure analysis of the interfacial zones in the composites revealed strong interfacial reactions existing in the composites fabricated at >= 800 degrees C. Therefore, the interfacial shear strength of the composite was significantly increased from similar to 420 MPa to similar to 535 MPa with the fabrication temperature increasing from 800 degrees C to 1200 degrees C, thus impeding the toughening mechanisms of the composites. After introducing BN interphase, the interfacial shear strength was significantly reduced to similar to 140 MPa and the flexural strength was increased from similar to 140 MPa to similar to 250 MPa. The work highlights the efficiency of introducing BN interphase to weaken the interfacial interaction, thus to enhance the macro-mechanical properties.