Si3N4@SiO2/PEEK core-shell structure ceramic matrix composite prepared by cold sintering and its tribological properties

The traditional high-temperature sintering method cannot achieve the combination of ceramics and polymers for the huge sintering temperature difference. The insufficient interfacial bonding strength of the ceramic matrix is the difficulty in the low-temperature preparation of ceramic-polymer composites. To improve the interfacial bonding strength of Si 3 N 4 (Silicon nitride) ceramic matrix composite, an easy-bonding SiO 2 (Silica) shell was introduced onto the surface of the hard-bonding Si 3 N 4 core by Stober method, to obtain Si 3 N 4 @SiO 2 composite. Si 3 N 4 @SiO 2 /PEEK (Polyetheretherketone) composites were prepared by the cold sintering process (500 MPa, 240 °C, and transient liquid phase is NaOH solution). The dry tribological properties of Si 3 N 4 @SiO 2 /PEEK composites with different PEEK percentages were studied by a ball-disc contact form. It is shown that an amorphous SiO 2 shell with a thickness of 25 nm is chemically bonded onto the surface of the Si 3 N 4 core. The presence of the SiO 2 shell improves the interface bonding strength between Si 3 N 4 ceramic particles. The friction coefficients of Si 3 N 4 @SiO 2 /PEEK composites decrease with the increase of PEEK percentage. Compared with Si 3 N 4 @SiO 2 composite, the friction coefficient and wear rate of Si 3 N 4 @SiO 2 /50 vol% PEEK composite decrease by about 40% and 26%, respectively. The main wear forms of Si 3 N 4 @SiO 2 /PEEK composites are abrasive wear and adhesive wear. A mixed lubrication layer, mainly including PEEK, Si 3 N 4 , and SiO 2 , exists simultaneously on the surfaces of Si 3 N 4 @SiO 2 /PEEK composite and the counterpart ball, respectively, playing the role of reducing friction and wear.