Most previous studies have employed surface patterning to improve the performance of lubrication systems. However, few have experimentally analyzed improved effects on friction reduction in SiC mechanical seals by ultra-fast laser pulse texturing. This work applies surface texturing on a non-contact mechanical seal and analyzes the characteristics of the resultant surface morphology. A femtosecond laser system is employed to fabricate micro/nanostructures on the SiC mechanical seal, and generates microscale-depth stripes and induces nanostructures on the seal surface. This work examines the morphology and cross section of the SiC nanostructures that correspond to the different scanning speeds of the laser pulse. Results show that varying the scanning speed enables the application of nanostructures of different amplitudes and widths on the surface of the seal. The friction coefficient of the introduced SiC full-textured seal is about 20% smaller than that of a conventional SiC mechanical seal. Hence, femtosecond laser texturing is effective and enables direct fabrication of the surface micro/nanostructures of SiC seals. This

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Traditional magnetic metal and alloy materials suffer from easy oxidation and high density, which hinders their practical application as high-performance microwave absorbers. Lightweight and durability have become new goals in the fabrication of the next generation of microwave absorbers. Herein, we report the synthesis of polypyrrole (PPy) nanosphere/reduced graphene oxide (rGO) composites through chemical reduction of self-assembly PPy nanosphere/GO hybrids. PPy nanospheres and GO are integrated effectively by π–π interaction of dual conjugated systems. When the mass ratio of PPy nanospheres to rGO is 0.6:1, the resultant composite, PPy/rGO-0.6, presents comparable/superior reflection loss characteristics to those magnetic metals and their related graphene-based composites in previous studies. Electromagnetic analysis reveals that well-matched characteristic impedance, multiple polarization loss, and good conductivity loss are, together, responsible for the excellent microwave absorption performance of PPy/rGO-0.6. More importantly, PPy/rGO-0.6 also exhibits good microwave absorption after being treated at 423 K for a long time. This work provides a new idea for designing and preparing a high-performance microwave absorber with lightweight and durable features.

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