Preparation and mechanical properties of ZrO2-reinforced polymer-derived SiCNO composite ceramics

Polymer derived ceramics (PDCs) technology has the advantages of simple manufacturing and adjustable composition, providing an effective way to prepare new types of ceramics. However, due to the escape of tiny molecules during the pyrolysis process, the pore defects are formed, and amorphous polymer derived SiCNO ceramics (PDCs SiCNO ceramics) produced by precursor technique have poor mechanical properties. To solve the aforementioned problems, enhancement of the polymer-derived ceramics is achieved by adding a second phase (particles reinforcement) to the ceramic matrix. A method was proposed to obtain ZrO2 reinforced PDCs-SiCNO composite ceramics (PDCs-SiCNO-ZrO2) by ball-milling of polyvinylsilazane (PVSZ) and ZrO2 followed by pyrolyzing. The phase structure and mechanical properties of PDCs-SiCNO-ZrO2 composite ceramics were investigated, respectively. The results show that the introduced ZrO2 fillers are embedded in the matrix of PDCs-SiCNO ceramic as a reinforcement, which not only can effectively reduce the linear shrinkage, but also greatly enhance the mechanical properties of the PDCs-SiCNO-ZrO2 composite ceramics. PDCs-SiCNO-ZrO2 composite ceramics with a 10%(mass fraction) ZrO2 addition have the flexural and compressive strengths of 197.03 MPa and 375.2 MPa, which are 64% and 267% greater than those of PDCs-SiCNO ceramics. The highest hardness value can reach 20.92 GPa, and the fracture toughness can reach 2.76 MPa·m1/2. The addition of appropriate content of ZrO2 contributes to the densification of the PDCs-SiCNO ceramic matrix, which enhances the mechanical properties of the PDCs-SiCNO-ZrO2 composite ceramics.