Si₃N₄ nanowires@pyrolytic carbon nanolayers coupled with hydroxyapatite nanosheets as reinforcement for carbon matrix composites with boosting mechanical and friction properties

Extensive attention has been drawn to the development of carbon-matrix composites for application in the aerospace and military industry, where a combination of high mechanical strength and excellent frictional properties are required. Herein, carbon-matrix composites reinforced by Si₃N₄ nanowires@pyrolytic carbon nanolayers (Si₃N_4nws@PyC_nls) coupled with hydroxyapatite nanosheets is reported. The Si₃N_4nws@PyC_nls (SP) with coaxial structure could increase the surface roughness of Si₃N_4nws and promote the stress transfer to the carbon matrix, whereas the porous hydroxyapatite nanosheets favor the infiltration of the carbon matrix and promote the interfacial bonding between the SP and carbon matrix. The carbon matrix composites reinforced by SP coupled with hydroxyapatite nanosheets (Si₃N_4nws@PyC_nls-HA-C) exhibit excellent mechanical strength. Compare with the conventional Si₃N_4nws reinforced carbon composites, Si₃N_4nws@PyC_nls-HA-C (SPHC) have 162% and 249% improvement in flexural strength and elastic modulus, respectively. Moreover, the friction coefficient and wear rate decreased by 53% and 23%, respectively. This study provides a co-reinforcement strategy generated by SP coupled with hydroxyapatite nanosheets for effective improvement of mechanical and frictional properties of carbon matrix composites that are used for aerospace and military industry applications.