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Nitrile butadiene rubber (NBR) is a water-lubricated bearing material that demonstrates excellent vibrational absorption and impact resistance; however, rapid wear under abnormal conditions is still a serious problem. Graphene (Gra) and carbon nanotubes (CNTs) are two types of carbon nanomaterials with different dimensions and excellent mechanical and friction properties. In this work, Gra and CNTs were used to fill the NBR, and a multifunctional friction and wear testing machine was used to study their impacts on the friction between NBR and ZCuSn10Zn2 under water lubrication conditions. The results indicate that both Gra and CNTs can effectively reduce the adhesion and the friction coefficient of NBR during the friction process. The two-dimensional lamellar structure of Gra is more likely to precipitate from the NBR matrix to generate a surface lubrication film, which can effectively reduce the friction coefficient. Both Gra and CNTs can prevent crack initiation and propagation in NBR during the wear process, thereby effectively reducing the wear of NBR. Compared with the two-dimensional structure of Gra, the one-dimensional linear structure of carbon nanotubes can "trap" the NBR molecular chains more effectively during the friction process, thus reducing the initiation and propagation of wear cracks and further improving the wear performance of NBR. • Effect of different dimensions of carbon nanomaterials on friction behavior of NBR. • Effect mechanism of two-dimensional graphene and one-dimensional carbon nanotubes on friction behavior of NBR. • NBR wear mechanism enhanced by two-dimensional graphene and one-dimensional carbon nanotubes. [ABSTRACT FROM AUTHOR]

The friction and wear of water-lubricated bearings has always been an engineering problem that we need to solve urgently. To investigate the influence of SiO 2 particle size and dispersion on the friction and wear properties of nitrile rubber. The friction and wear performance of rubber compounds (SiO 2 (nano) /NBR, SiO 2 (micr) /NBR and SiO 2 (TESP) /NBR) was tested by American Rtec multifunctional friction and wear test machine under the conditions of water lubrication and constant temperature. The results showed that the particle size of SiO 2 has a great impact on its dispersion in nitrile rubber, and the surface modification of SiO 2 can significantly improve its dispersion. SiO 2 (TESPT) /NBR showed a good friction coefficient under low-speed and high-load conditions. The wear of SiO 2 (nano) /NBR and SiO 2 (micr) /NBR, which was mainly the fatigue wear, was relatively serious. In contrast, the modified SiO 2 had a smaller particle size, better dispersion and stronger interfacial bonding with the nitrile rubber matrix. This significantly reduced the wear of SiO 2 (TESPT) /NBR, which was mainly the abrasive wear, and improved its wear resistance. • TESPT was used to modify the hydroxyl groups on the surface of nano-silica. • The escape and disintegration of SiO 2 (micr) and SiO 2 (nano) agglomerates during the wear process were characterized. • The effect of particle size and dispersion of SiO 2 on tribological properties of nitrile rubber was revealed. [ABSTRACT FROM AUTHOR]

Nitrile Butadiene Rubber (NBR) is widely used in ship water-lubricated stern tube bearings. Sediments in the water would cause a serious effect on friction and wear properties of the water-lubricated bearings. In this study, the tribological performance of water-lubricated rubber bearings under different sediment particle sizes and sand types were analyzed. Two sediment sand types are involved in the research, (i) SiO 2 particles with sizes of 0–25 μm, 48–60 μm, 75–90 μm and 150–200 μm, respectively; (ii) Sediment particles collected from the Yangtze River with sizes of 48–60 μm, 75–90 μm and 120–150 μm, respectively. The friction coefficients and wear volumes as well as surface morphology were measured. It was found that NBR worn by SiO 2 particles was worse than that by the sediment within a certain particle size range. On the other hand, the particle sizes exhibited significant effects on the tribological properties. As the particle size increased, the largest wear volume of NBR occurred at particle size of 75–90 μm, While the friction coefficient grew firstly and then fell down, and reached its maximum at particle size of 48–60 μm. Additionally, the friction coefficient demonstrated a negative correlation with sliding speed regardless of the sediment type and particle size. The particle sizes were prevented from flowing into the friction pair as applied load increased. In conclusion, this research offers a great insight for designing water-lubricated bearings. [ABSTRACT FROM AUTHOR]