Magnetic lubricants: Preparation, physical mechanism, and application

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.