Poor lubrication performance of low-sulfur fuel leads to increased wear of diesel engine components. In order to improve the lubrication properties of low-sulfur fuel, we successfully prepared graphene lubricant additives by dielectric barrier discharge plasma-assisted ball milling. The tribological properties of graphene lubricant additives in two types of 0# diesel oils with different sulfur content were evaluated by high-frequency reciprocating rig (HFRR). The results indicated that the expanded graphite was exfoliated and refined into graphene sheets with nine layers by the synergistic effect of the heat explosive effect of the discharge plasma, the impact of mechanical milling function, and the cavitation effect of 0# diesel oil. The organic functional groups of 0# diesel oil were successfully grafted on the surface of graphene sheets. The addition of 0.03 wt % graphene resulted in 20% reduction in the friction coefficient (COF) and 28% reduction in wear scar diameter (WSD) compared to pure 0# diesel oil with a sulfur content of 310 mg/kg. The addition of 0.03 wt % graphene resulted in 24% reduction in the friction coefficient (COF) and 30% reduction in wear scar diameter (WSD) compared to pure 0# diesel oil with a sulfur content of 1.1 mg/kg. The formation of graphene tribofilm on rubbing surfaces improved the lubrication properties of low-sulfur fuel.

The unique structure and physical properties of graphene and anatase TiO2 make them suitable for use as additives for engine lubricants. This study describes the use of dielectric barrier discharge plasma-assisted ball milling to synthesize a multilayer graphene-reinforced TiO2 composite nanolubricant additive (MGTC). A variety of physical and chemical tests were performed to characterize the resulting experimental materials, including X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Four-ball friction and wear testing machines were used to study the tribological properties and extreme pressure anti-wear properties of a base oil containing 0.1, 0.5, 1.0, and 1.5 wt % of the modified TiO2. Raman spectroscopy, XPS, SEM, and energy-dispersive spectrometry (EDS) analyses were used to examine and analyze the microstructure of the friction pairs. As a result of the plasma-assisted ball milling process, expanded graphite was successfully separated into multilayer graphene nanosheets, and spherical TiO2 was successfully bonded to the nanosheets of the multilayer graphene. The 1.0 wt % composite oil was found to provide good friction reduction and wear resistance. It had a film thickness of 27.5 nm, which was 167% thicker than base oil. Due to its excellent dispersion stability, the MGTC nanocomposite exhibited excellent lubrication performance, which was attributed to the formation of carbon protective films, titanium dioxide deposition films, transfer films, and the occurrence of nano ball effects on the surface of friction pairs.

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In this experimental investigation, a core–shell-structured nano-lubricating additive was synthesized utilizing the dielectric barrier discharge plasma (DBDP)-assisted ball grinding technique for a duration of 5 h. The microstructural analysis of the nano-TiO2 powder was performed employing advanced methods such as X-ray diffraction (XRD) and thermogravimetry–differential scanning calorimetry (TG-DSC). The initial particle size of TiO2 was refined from 1 μm to a range of 150–200 nm, resulting in a remarkable increase in lattice distortion rate by 88.2% and an oil affinity enhancement of 200%. Through the introduction of CTAB’s oil-compatible group onto the surface of nano-TiO2 particles, a modified layer with a thickness of 21 nm possessing superior thermal stability and an activation energy (E a) of 600 kJ/mol was successfully produced. Molecular dynamics simulations were conducted to elucidate the mechanism underlying the surface modification of nano-TiO2 powder facilitated by DBDP-assisted ball grinding, thereby revealing the pivotal role of electrostatic forces in the organic modification of the TiO2 surface. It was found that electrostatic forces dominantly govern the cetyl trimethyl ammonium bromide (CTAB)–TiO2 composite interface model, contributing to 70% of the total energy with a maximum energy proportion of −187.84 kcal/mol. To evaluate the lubrication performance of the composite oil samples under boundary lubrication conditions, comprehensive assessments were carried out using the four-ball method and reciprocating friction experiments. The results demonstrated noteworthy enhancements in viscosity index, dynamic viscosity, and oil film thickness within the composite oil samples. Particularly, the composite oil containing 0.5 wt % TiO2@CTAB exhibited outstanding extreme pressure resistance, manifesting a significant reduction of 41.7% in the average friction coefficient, a considerable increase of 25.8% in wear spot diameter, and a substantial elevation of 66.9% in maximum nonseizure load. Compared to the base oil, the incorporation of 0.5 wt % TiO2@CTAB led to a notable increment of 34.7% in oil film thickness, 6.7% in dynamic viscosity, and 9% in viscosity index. In the tribological experiment simulating marine diesel engines, the friction coefficient witnessed a remarkable reduction by 65.8%, accompanied by a substantial decrease of 54.1% in wear rate. This noteworthy improvement in boundary lubrication conditions of the friction pair effectively mitigated friction and wear. For comprehensive characterization of the wear marks, energy-dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS) techniques were employed to analyze the physical structure and chemical composition. The implementation of TiO2@CTAB nano-lubricating additives resulted in nanobearing and deposition effects, leading to a reduction in contact area and surface roughness, thereby facilitating the restoration of the friction pairs. These findings possess significant implications for extending the service life of die...

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Phase change materials (PCMs) are widely used in new energy storage fields such as industrial waste heat recovery and solar heat recovery. However, the low thermal conductivity of PCMs causes the slow heat storage efficiency of PCMs, resulting in a large waste of waste heat. For the sake of increasing the heat storage rate of PCMs, a new type of pulsating heat pipe (PHP) phase change heat storage device is designed, which couples PHP with PCMs. For sake of further improve the heat storage efficiency of the novel device, a different filling working medium was used in the experiment. The results show that methanol is the best charging working fluid compared with water and ethanol, the corresponding heat storage time of methanol was reduced by 2500 seconds and 900 seconds, respectively. Therefore, methanol is the best charging medium, followed by water and ethanol. K E Y W O R D Sfilling working medium, heat storage rate, pulsating heat pipe (PHP)

In order to study the effect of high hydrostatic pressure on the corrosion of low-alloy steels in deepsea environments. The electrochemical corrosion behavior of single-metal system and triple-metal coupled system of 907A steel, 921A steel and 1# steel under different hydrostatic pressures were studied by electrochemical, weight loss and morphology observation methods. The results show that the high hydrostatic pressure promotes the corrosion of low-alloy steel by changing the composition and morphology of corrosion products. In addition, there was also severe galvanic corrosion between the couples with a low potential difference (< 60 mV),907A steel was used as the anode of the three-metal coupled system, and 921A steel and 1# steel as the cathode. The galvanic coupling effect accelerates the pitting corrosion of 907A steel as an anode metal. When using multi-metal couplers with low potential differences, they should be protected by both coating protection and cathodic protection.