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Synergistic Tribo-Activity of Nanohybrids of Zirconia/Cerium-Doped Zirconia Nanoparticles with Nano Lamellar Reduced Graphene Oxide and Molybdenum Disulfide

1
Department of Chemistry, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005, India
2
Department of Chemistry, Prof. Rajendra Singh (Rajju Bhaiya) Institute of Physical Sciences for Study & Research, V.B.S. Purvanchal University, Jaunpur 222003, India
3
Department of Mechanical Engineering, College of Engineering, Kyung Hee University, Yongin 446-701, Korea
*
Authors to whom correspondence should be addressed.
Nanomaterials 2020, 10(4), 707; https://doi.org/10.3390/nano10040707
Received: 5 March 2020 / Revised: 3 April 2020 / Accepted: 3 April 2020 / Published: 8 April 2020
(This article belongs to the Section Nanocomposite Thin Films and 2D Materials)
Zirconia and 10%, 20%, and 30% cerium-doped zirconia nanoparticles (ZCO), ZCO-1, ZCO-2, and ZCO-3, respectively, were prepared using auto-combustion method. Binary nanohybrids, ZrO2@rGO and [email protected] (rGO = reduced graphene oxide), and ternary nanohybrids, ZrO2@[email protected]2 and [email protected]@MoS2, have been prepared with an anticipation of a fruitful synergic effect of rGO, MoS2, and cerium-doped zirconia on the tribo-activity. Tribo-activity of these additives in paraffin oil (PO) has been assessed by a four-ball lubricant tester at the optimized concentration, 0.125% w/v. The tribo-performance follows the order: [email protected]@MoS2 > ZrO2@[email protected]2 > [email protected] > ZrO2@rGO > MoS2 > ZrO2 > rGO > PO. The nanoparticles acting as spacers control restacking of the nanosheets provided structural augmentation while nanosheets, in turn, prevent agglomeration of the nanoparticles. Doped nanoparticles upgraded the activity by forming defects. Thus, the results acknowledge the synergic effect of cerium-doped zirconia and lamellar nanosheets of rGO and MoS2. There is noncovalent interaction among all the individuals. Analysis of the morphological features of wear-track carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in PO and its formulations with various additives is consistent with the above sequence. The energy dispersive X-ray (EDX) spectrum of [email protected]@MoS2 indicates the existence of zirconium, cerium, molybdenum, and sulfur on the wear-track, confirming, thereby, the active role played by these elements during tribofilm formation. The X-ray photoelectron spectroscopy (XPS) studies of worn surface reveal that the tribofilm is made up of rGO, zirconia, ceria, and MoS2 along with Fe2O3, MoO3, and SO42− as the outcome of the tribo-chemical reaction. View Full-Text
Keywords: doped nanoparticles; nanohybrids; X-ray photoelectron spectroscopy; friction; wear; tribo-activity doped nanoparticles; nanohybrids; X-ray photoelectron spectroscopy; friction; wear; tribo-activity
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MDPI and ACS Style

Verma, D.K.; Shukla, N.; Kumar, B.; Singh, A.K.; Shahu, K.; Yadav, M.; Rhee, K.Y.; Rastogi, R.B. Synergistic Tribo-Activity of Nanohybrids of Zirconia/Cerium-Doped Zirconia Nanoparticles with Nano Lamellar Reduced Graphene Oxide and Molybdenum Disulfide. Nanomaterials 2020, 10, 707.

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