Magnetic lubricants are emerging as advanced lubricants with controlled flowability and enhanced lubrication and heat transfer capabilities, showing potential for use in extreme conditions such as aerospace. Although their excellent properties have been preliminarily confirmed, the mechanisms by which these properties influence performance—including fluid dynamics, electromagnetism, and chemistry—require systematic investigation. This paper addresses this gap by systematically reviewing the preparation, physicochemical properties, and potential applications of magnetic lubricants. First, the formulations of magnetic lubricants, including the base fluid and stabilizing additives, are thoroughly examined, considering various magnetic materials and preparation methods to elucidate the mechanisms influencing dispersion stability and magnetic response. Next, the physical properties, such as saturation magnetization, viscosity, and flowability, are analyzed through theoretical and experimental studies, and constitutive models for the fluid dynamics of magnetic lubricants are summarized. Furthermore, the advanced tribological and thermal properties, as well as the physical behavior under magnetic fields, are discussed, highlighting the superior antifriction, antiwear, cooling, and controlled flowability performance compared to traditional lubricants. Finally, current applications and potential fields, such as bearings, machining, and heat exchangers, are reviewed. This paper provides a valuable reference for both theoretical studies and engineering applications of magnetic lubricants.

Minimum quantity lubrication (MQL) is a relatively efficient and clean alternative to flooding workpiece machining. Electrostatic atomization has the merits of small droplet diameter, high uniformity of droplet size, and strong coating, hence its superiority to pneumatic atomization. However, as the current research hotspot, the influence of jet parameters and electrical parameters on the average diameter of droplets is not clear. First, by observing the shape of the liquid film at the nozzle outlet, the influence law of air pressure and voltage on liquid film thickness (h) and transverse and longitudinal fluctuations are determined. Then, the mathematical model of charged droplet volume average diameter (VAD) is constructed based on three dimensions of the liquid film, namely its thickness, transverse wavelength (λ_h), and longitudinal wavelength (λ_z). The model results under different working conditions are obtained by numerical simulation. Comparisons of the model results with the experimental VAD of the droplet confirm the error of the mathematical model to be less than 10%. The droplet diameter distribution span value Rosin–Rammler distribution span (R.S) and percentage concentrations of PM10 (particle size of less than 10 μm)/PM2.5 (particle size of less than 2.5 μm) under different working conditions are further analyzed. The results show that electrostatic atomization not only reduces the diameter distribution span of atomized droplets but also significantly inhibits the formation of PM10 and PM2.5 fine-suspension droplets. When the air pressure is 0.3 MPa, and the voltage is 40 kV, the percentage concentrations of PM10 and PM2.5 can be reduced by 80.72% and 92.05%, respectively, compared with that under the pure pneumatic atomization condition at 0.3 MPa.

Metal cutting fluids (MCFs) under flood conditions do not meet the urgent needs of reducing carbon emission. Biolubricant-based minimum quantity lubrication (MQL) is an effective alternative to flood lubrication. However, pneumatic atomization MQL has poor atomization properties, which is detrimental to occupational health. Therefore, electrostatic atomization MQL requires preliminary exploratory studies. However, systematic reviews are lacking in terms of capturing the current research status and development direction of this technology. This study aims to provide a comprehensive review and critical assessment of the existing understanding of electrostatic atomization MQL. This research can be used by scientists to gain insights into the action mechanism, theoretical basis, machining performance, and development direction of this technology. First, the critical equipment, eco-friendly atomization media (biolubricants), and empowering mechanisms of electrostatic atomization MQL are presented. Second, the advanced lubrication and heat transfer mechanisms of biolubricants are revealed by quantitatively comparing MQL with MCF-based wet machining. Third, the distinctive wetting and infiltration mechanisms of electrostatic atomization MQL, combined with its unique empowering mechanism and atomization method, are compared with those of pneumatic atomization MQL. Previous experiments have shown that electrostatic atomization MQL can reduce tool wear by 42.4% in metal cutting and improve the machined surface R_a by 47% compared with pneumatic atomization MQL. Finally, future development directions, including the improvement of the coordination parameters and equipment integration aspects, are proposed.