Preparation of Garlic Oil-Functionalized Carbon Nanomaterials for Tribological Application

In daily life and industrial production, friction can lead to the loss of energy, which will reduce the efficiency of machinery and even reduce the service life of equipment. The pursuit of effective anti-wear and wear reduction strategies has aroused great interest. Lubricating oil is an effective solution to reduce friction and wear. However, the base oil with limited performance is difficult to keep up with the rapid development of modern industry. Lubrication additives are essential to compensate for these deficiencies and provide an effective method to improve lubrication performance. Carbon nanomaterials are known for their exceptional chemical stability, mechanical properties, and thermal conductivity, making them ideal candidates for lubricant additives. In this paper, polyaniline pyrrole (PACP) was prepared by interfacial polymerization of aniline and pyrrole, which was used as a precursor and carbonized at a certain temperature to prepare a class of organic carbon nanomaterials (PCN). Then, the PCN was modified with KH590 to obtain the–SH groups functionalized PCN (SH-PCN). Finally, SH-PCN was further functionalized with garlic oil (GO) to improve their dispersion stability and tribological performance in base oil. Garlic oil, rich in organic sulfides such as diallyl disulfide and isobutylene sulfide, demonstrated excellent extreme pressure capabilities. The GO was chemically bonded to the surface of carbon nanomaterials via a coupling agent, resulting in garlic oil-functionalized carbon nanomaterials. The structure, morphology and composition of the synthetic materials were analyzed comprehensively. It could be seen from the morphology that PCN still maintained good spheroid morphology after carbonization at high temperature, which was due to the hypercross linked conjugated structure of PACP. These test results of FI-IR, XPS and Zeta potential clearly indicated the successful grafting of garlic oil (GO) onto the PCN carbon nanomaterials. Subsequently, their tribological performances were evaluated under different test conditions (different addition amount, changing loads, changing temperatures and frequencies). The prepared GO-SH@PCN-500 as a lubricant additive could increase the load resistance of base oil from 200 N to 450 N, reduce the average friction coefficient from 0.18 to 0.11, and reduce the wear volume from 2.5×10⁵ μm³ to 0.13×10⁵ μm³. The excellent tribological performances were due to the formation of a strong protective film through the tribochemical reaction between the friction pairs, which effectively prevented direct contact between the friction pairs and significantly reduced friction and wear. This research not only provided a viable approach for the preparation of carbon nanomaterials as lubricating additives but also identifies the factors influencing the tribological properties of these additives, which contributing to the development of carbon-based lubricant additives with improved tribological performance for practical applications.