Investigating the chemical bonding state of graphite powder treated with magnesium(II) phosphate through EELS, TEM, and XPS analysis

Graphite is often used as a solid lubricant owing to its unique layered structure. However, graphite powder is susceptible to oxidation at high temperatures. In this study, graphite powder was treated with magnesium(II) phosphate solution to obtain graphite powder with excellent oxidation resistance at high temperatures while retaining its lubricating properties. The oxidation resistance of the obtained graphite powder and original graphite was evaluated at temperatures ranging from room temperature (RT) to 1000 °C. The results show that the initial temperature of graphite oxidation increased by nearly 170 °C. Furthermore, this study confirmed that the treated powder still retains the unique layered structure of graphite, which contributes to its lubricating properties. In addition, to clarify the mechanism of using magnesium(II) phosphate to treat graphite for improving its oxidation resistance, the chemical bonding state was specifically analyzed using electron energy loss spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Therefore, the magnesium(II) phosphate-treated graphite maintains the graphite-based interlayer structure and magnesium(II) phosphate forms a C–O–P chemical bond on the graphite defect to cover the reaction site of graphite, which allows the treated graphite to improve oxidation resistance. [Display omitted] •Graphite suffers from oxidative degradation at high temperatures.•Herein, graphite was modified with a solution of magnesium(II) phosphate.•Oxidation resistance of the graphite powder and original graphite was evaluated.•Modified graphite maintained the desirable properties of unmodified graphite.•Verify the oxidation resistance improvement mechanism of modified graphite and propose a hypothesis