title: Self-dispersed crumpled graphene balls in oil for friction and wear reduction.
abstract: Ultrafine particles are often used as lubricant additives because they are capable of entering tribological contacts to reduce friction and protect surfaces from wear. They tend to be more stable than molecular additives under high thermal and mechanical stresses during rubbing. It is highly desirable for these particles to remain well dispersed in oil without relying on molecular ligands. Borrowing from the analogy that pieces of paper that are crumpled do not readily stick to each other (unlike flat sheets), we expect that ultrafine particles resembling miniaturized crumpled paper balls should self-disperse in oil and could act like nanoscale ball bearings to reduce friction and wear. Here we report the use of crumpled graphene balls as a high-performance additive that can significantly improve the lubrication properties of polyalphaolefin base oil. The tribological performance of crumpled graphene balls is only weakly dependent on their concentration in oil and readily exceeds that of other carbon additives such as graphite, reduced graphene oxide, and carbon black. Notably, polyalphaolefin base oil with only 0.01-0.1 wt % of crumpled graphene balls outperforms a fully formulated commercial lubricant in terms of friction and wear reduction.
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208;
authors.forename: Xuan
authors.initials: X
authors.lastname: Dou
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208;
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Koltonow
authors.affiliation: Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208;
authors.forename: Xingliang
authors.initials: X
authors.lastname: He
authors.affiliation: Rare Metals Research Center, Korea Institute of Geoscience & Mineral Resources, Daejeon, 305-350, South Korea.
authors.forename: Hee Dong
authors.initials: HD
authors.lastname: Jang
authors.affiliation: Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208; qwang@northwestern.edu ywchung@northwestern.edu jiaxing-huang@northwestern.edu.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208; Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208; qwang@northwestern.edu ywchung@northwestern.edu jiaxing-huang@northwestern.edu.
authors.forename: Yip-Wah
authors.initials: YW
authors.lastname: Chung
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208; qwang@northwestern.edu ywchung@northwestern.edu jiaxing-huang@northwestern.edu.
authors.forename: Jiaxing
authors.initials: J
authors.lastname: Huang
keywords: aggregation-resistant particles; graphene; lubrication; tribology
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