Effect of adding fiber on the microstructure and mechanical properties of NiFe2O4 composite ceramics

NiFe2O4 composite ceramics reinforced with carbon fibers (Cf), nickel-coated carbon fibers (NiCf) and ZrO2 fibers (ZrO2f) were fabricated by the conventional high-temperature solid state reaction at 1300 °C for 6 hs. The effects of the three kinds of fibers on microstructure and mechanical properties of NiFe2O4 composite ceramics were investigated. The fracture surfaces of NiFe2O4 composite ceramics were observed by scanning electron microscopy (SEM). Elemental analysis of micro-structural phases was performed using energy dispersive spectroscopy (EDS), attached with SEM. Flexural strength by three-point bending techniques and fracture toughness were measured. It was found that leaving holes after reactions between the carbon fiber and matrix led to decreased mechanical properties. The ZrO2f-doped composite had an improved fracture toughness of 3.05±0.1 MPa m1/2 compared to NiFe2O4 composite ceramics having 1.91±0.2 MPa m1/2 due to fiber debonding, fiber pull-out and fiber bridging as well as microcracking toughening. The results presented here show that ZrO2f can serve as a potential toughening agent for NiFe2O4 composite ceramics.