Water-based superlubricity in vacuum
This study achieved water-based superlubricity with the lubrication of H3PO4 solution in vacuum (highest vacuum degree <10–4 torr) for the first time by performing a pre-running process in air before running in vacuum. The stable water-based superlubricity was sustainable in vacuum (0.02 torr) for 14 h until the test was stopped by the user for non-experimental factor. A further analysis suggested that the superlubricity may be attributed to the phosphoric acid–water network formed in air, which can efficiently lock water molecules in the liquid lubricating film even in vacuum owing to the strong hydrogen bond interaction. Such capability to lock water is strongly affected by the strength of hydrogen bond and environmental conditions. The realization of water-based superlubricity with H3PO4 solution in vacuum can lead to its application in space environment.
Keywordsfriction water-based superlubricity vacuum phosphoric acid
The authors are grateful for the financial support from the National Natural Science Foundation of China (Nos. 51527901, 51405256), and Self-developed Project of State Key Laboratory of Traction Power (No. 2017TPL_Z02).
- Erdemir A, Martin J M. Superlubricity. New York (USA): Elsevier, 2007.Google Scholar
- Kameno H, Kubo A, GÄCHTER S, Takahata R. Basic design of 1 kWh class compact flywheel energy storage system-application of active magnetic bearings with zeropower nonlinear control method. Koyo Eng J Engl Edit 163E: 44–48 (2003)Google Scholar
- Zhou G P, Wang Y B. Density function theory on intermolecular interactions of H3PO4 with H2O. J Northwest Norm Univ Nat Sci 48(1): 74–79 (2012)Google Scholar
- Jeffrey G A, Saenger W. Hydrogen Bonding in Biological Structures. Berlin (Germany): Springer, 2012.Google Scholar
- Israelachvili J N. Intermolecular and Surface Forces. Pittsburgh (USA): Academic Press, 2011.Google Scholar
- Ewig C S, Van Wazer J R. Ab initio structures of phosphorus acids and esters. 1. Phosphinic, phosphonic, and phosphoric acids. J Am Chem Soc 107(7): 1965–1971 (1985)Google Scholar
Open Access: The articles published in this journal are distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.