Tribological and tribochemical properties of magnetite nanoflakes as additives in oil lubricants--颗粒学报PARTICUOLOGY

Xiang, L., Gao, C., Wang, Y., Pan, Z., & Hu, D. (2014). Tribological and tribochemical properties of magnetite nanoflakes as additives in oil lubricants. Particuology, 17, 136–144. https://doi.org/10.1016/j.partic.2013.09.004

Tribological and tribochemical properties of magnetite nanoflakes as additives in oil lubricants

Longhua Xiang ^a, Chuanping Gao ^a, Yanmin Wang ^{a b *}, Zhidong Pan ^{a b}, Dawei Hu ^a

a College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China b Key Laboratory of Specially Functional Material under Ministry of Education, Guangzhou 510640, China

10.1016/j.partic.2013.09.004

Volume 17, December 2014, Pages 136-144

Received 28 April 2013, Revised 14 September 2013, Accepted 28 September 2013, Available online 14 December 2013.

E-mail: wangym@scut.edu.cn

Highlights

• Friction coefficient with base oil of 1.5 wt% Fe₃O₄ nanoflakes decreased by 18.06%.

• After 48-h friction, chemical composition of the base oil did not change.

• During friction, Fe₃O₄ particle size decreased due to lattice distortion.

• Formation of tribochemical film on friction surface may improve the friction properties.

Abstract

This detailed the tribological and tribochemical properties of magnetite (Fe₃O₄) nanoflakes used as additives in #40 base oil in a four-ball tribo-tester. The average friction coefficient of the friction pair for lubricant containing the Fe₃O₄ nanoflakes of 1.5 wt% as a lubricant additive in the base oil is decreased by 18.06% compared to that of solely base oil. The chemical composition of base oil with the Fe₃O₄ nanoflake additives did not change during the 48-h friction assessment. The decreased saturation magnetization and increased coercivity of magnetite nanoflakes occurred due to the distortion of the basal planes and the presence of hematite (α-Fe₂O₃) generated by the tribochemical reactions during the friction process. The multi-layer low-shear-stress tribochemical lubrication films on the surface of the friction pair could form because the nanoflake particles arrange and adhere onto the surface of the friction pair in an orderly manner, and the tribochemical reactions of the friction pair in the presence of the nanoflakes occur as Fe → FeO → Fe₃O₄ → γ-FeOOH → γ-Fe₂O₃ → α-Fe₂O₃. The formation of the films can improve the tribological properties.

Graphical abstract

Keywords

Nanoflake particles； Magnetite； Lubricant additive； Tribology； Tribochemical properties

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