Tribological behavior and electrical insulation properties of micro-and nanoscale graphene/β-Si3N4 whisker-reinforced Si3N4 ceramics at low temperature

Si 3 N 4 ceramics are ideal materials for liquid rocket turbopump bearings due to their excellent properties such as low-temperature resistance, low density, and wear resistance. To further enhance the sustained self-lubricating performance of bearings in low-temperature environments, novel Si 3 N 4 ceramic composites containing micro- and nanoscale graphene and β-Si 3 N 4 whisker were prepared via spark plasma sintering. The low-temperature tribological properties and electrical conductivity of Si 3 N 4 ceramic composites were thoroughly analyzed. Results indicated that the dry sliding friction coefficient of Si 3 N 4 ceramics at 10–20 N load and 77 K ranged from 0.11 to 0.28, representing a significant reduction of 6.67 %–64.52 % compared to that at 298 K. The enhanced tribological properties under cryogenic conditions was attributed to increased interatomic forces and improved frictional heat transfer. Additionally, the incorporation of 1 wt% graphene did not alter the insulating state of Si 3 N 4 ceramics, as the limited graphene content hindered the formation of an effective electron transfer pathway within the matrix. This work provides new insights into the design of advanced ceramic composites for extreme environments.