Runling Peng

This study prepared graphene/molybdenum disulphide (RGO/MoS ₂ ) composite additives via freeze‐drying to enhance their dispersion stability and oxidation resistance. The tribological properties and lubrication mechanisms of these nano‐additives in lubricating oils were systematically investigated through experimental characterisation and molecular dynamics simulations. Results demonstrated that MoS ₂ 's interlayer sliding intensifies with increasing load/speed, though excessive mechanical stress induces structural degradation; graphene provides stable support for MoS ₂ , reducing atomic slippage and improving synergistic lubrication. A comparison between the experimental and molecular dynamics simulation results leads to the following conclusions: MoS ₂ demonstrates superior friction performance under high‐speed and light‐load conditions compared to RGO/MoS ₂ . Conversely, RGO/MoS ₂ exhibits better friction performance under high‐load and low‐speed conditions than MoS ₂ alone. Importantly, across various testing conditions, the trends in the friction coefficient curves obtained from molecular dynamics simulations align well with the experimental data.

In order to investigate the anti‐friction and anti‐wear performance of different crystal forms nano MoS₂ in paraffin oil. Freeze‐drying method combined with hydrothermal was used to prepare different crystal forms nano MoS₂ and their microstructures were characterised by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The anti‐friction and anti‐wear performance of MoS₂ nanoparticles as lubricat additives under different working conditions was investigated by the ball‐and‐disk friction and wear testing machine and the mechanism of friction and wear reduction was investigated. The results showed that the thickness of the floral sheet MoS₂ flakes was about 10 nm and the particle size of the spherical MoS₂ was about 90 nm. When the addition concentration was 3 wt%, the friction coefficient of the floral sheet MoS₂ in paraffin oil was lower at 0.094, which was 29.3% lower than that of the pure paraffin oil, the width of the abrasion marks was 24.2% lower than that of the pure paraffin oil and the wear rate was 71.6% lower than that of the pure paraffin oil; The friction coefficient of the spherical MoS₂ with 2.5 wt% addition was 0.082, which was 38.3% lower than the friction coefficient of pure paraffin oil, 24.1% lower than that of paraffin oil in terms of wear scar width and 81.9% lower than that of paraffin oil in terms of wear rate.

To reduce the agglomeration of graphene and improve the synergistic friction‐reducing and anti‐wear action of graphene loading copper, one‐step preparation of reduced graphene oxide/copper(RGO/Cu) nanoparticles by freeze‐drying method was used, the influence of process parameters on particles size of RGO/Cu is studied by orthogonal experiments. The microstructures of RGO/Cu nanoparticles are characterized by SEM and AFM, and the tribological properties of RGO/Cu nanoparticles are studied on a tribometer. The results show that the purity of RGO/Cu nanoparticles prepared by freeze‐drying was higher, and the copper nanoparticles 100–200 nm are uniformly attached to the graphene surface. It was found that RGO/Cu nanoparticles have better friction reduction and anti‐wear properties than graphene mono‐agent as lubricant additive. The synergistic anti‐friction and anti‐wear performance are better at the addition of 0.10 wt% for RGO/Cu nanoparticles. Compared with the base oil, the friction coefficient decreases by 23.1%, and the width of wear scar decreases by 62.5%.

Monodispersed nano-copper particles were prepared, and the optimized method of preparation procedure was established through orthogonal experiments under four different factors. The experimental results show that the particle size of freeze-dried nano-copper particles can be adjusted by rotational speed, freezing rate, types of active agents and freezing mode, and freezing mode is the most important among all of the four factors. Tribological results of the nano-copper particles from the best optimized procedure can be improved 5%–10% than that of pure paroline oil and the lowest coefficient of friction 0.12 can be obtained for the sample of 0.05 wt%. The lubrication mechanism mostly attributed to the appropriate concentration of copper particles filling the surface pits, which is beneficial for the improvement of the tribological performance.

Molybdenum disulfide quantum dots (MoS₂ QDs) are a promising lubricant additive for enhanced engine efficiency. In this study, MoS₂ QDs were used as lubricating oil additives for ball-on-disc contact and had adequate dispersity in paroline oil, due to their super small particle size (~3 nm). Tribological results indicate that the friction coefficient of paroline oil with 0.3 wt.% MoS₂ QDs reached 0.061, much lower than that of pure paroline oil (0.169), which is due to the formation of a stable tribo-film formed by the MoS₂, MoO₃, FeS, and FeSO₄ composite within the wear track. Synergistic lubrication effects of the tribo-film and ball-bearing effect cooperatively resulted in the lowest friction and wear.

This paper proposes a watermark scheme for lenslet-based light field imaging operating on its 4D Fourier domain. In this scheme, the computational light field of the 2D watermark is first obtained. A slice of its frequency spectrum is then generated. After that, the watermark is embedded into the host light field by slice displacement. The experimental simulations show that the proposed scheme is simple in complexity while the robustness is strong. In addition, it does not bring significant artifacts or distortion into the refocused image or the depth map.