This study presented a comprehensive investigation into the synergistic enhancement of tribological performance through the combination of MoS2 and TiO2 nanoparticles (NPs) in a water based nanofluid. An integrated methodology combining fundamental tribological experiments with atomic-scale molecular dynamics (MD) simulations was employed to dynamically reveal the underlying cooperative lubrication mechanisms. The experimental phase involved the preparation of three distinct nanofluids using a physical dispersion method: a 0.2wt.% MoS2 nanofluid, a 0.2wt.% TiO2 nanofluid, and a composite nanofluid containing 0.1wt.% MoS2+0.1wt.% TiO2. The base fluid was formulated with organic molybdenum, glycerol, triethanolamine, sodium hexametaphosphate and sodium dodecyl benzene sulfonate. The dispersion stability of these nanofluids was rigorously evaluated through sedimentation tests and Zeta potential measurements. Tribological performance was assessed with a four-ball friction and wear tester. Key parameters including the maximum nonseizure load, average friction coefficient, and wear scar diameter were measured under controlled conditions. Wear scar morphology was analyzed by laser confocal microscopy, while the structure and composition of the in-situ formed tribofilm were characterized via focused ion beam transmission electron microscopy (FIB-TEM) and X-ray photoelectron spectroscopy (XPS). Complementing the experiments, non-equilibrium MD simulations were performed to gain atomistic insights into the dynamic shear behavior at the friction interface. These simulations tracked parameters such as friction force, normal stress, and temperature distribution over time.
The results demonstrated a clear synergistic effect in the MoS2/TiO2 composite nanofluid. Dispersion stability tests showed that MoS2/TiO2 nanofluid exhibited the highest Zeta potential absolute value (41.5 mV), indicating excellent colloidal stability, attributed to the intercalation of spherical TiO2 by layered MoS2, which acted as a physical barrier against agglomeration. Tribological tests revealed that MoS2/TiO2 nanofluid significantly outperformed its single-component counterparts. It achieved a maximum nonseizure load of 922 N, representing improvements of 23.6% and 14.7% over pure MoS2 (746 N) and TiO2 (804 N) nanofluids, respectively. The average friction coefficient of MoS2/TiO2 nanofluid was 0.068, lower than that of MoS2 (0.075) and TiO2 (0.079) nanofluids. Furthermore, it produced the smallest wear scar diameter (0.705 mm) and the most uniform, shallow surface scratches, confirming its superior wear resistance. MD simulations provided a dynamic, atomic-scale visualization of the synergistic mechanism. In the composite system, the MoS2 nanosheets facilitated interlayer sliding, effectively reducing shear resistance. Concurrently, the TiO2 NPs primarily exhibited a rolling motion, which was maintained and protected from embedding into the iron surface by the shielding effect of the MoS2 layers. This cooperation resulted in the lowest average simulated friction force (0.003 nN) and normal stress (0.697 GPa), compared with the single-component systems. The temperature distribution along the contact region was also more uniform in the hybrid system, indicating better management of frictional heat due to the combined load-bearing and stress-dispersing actions of both NPs. Post-test analysis of the wear scar using FIB-TEM confirmed the formation of a dense, uniform, and adherent tribofilm approximately 20 nm thick on the steel ball surface under MoS2/TiO2 nanofluid lubrication. EDS mapping confirmed the diffusion of Mo, S, and O elements into the near-surface region. XPS analysis identified the tribofilm's chemical composition, revealing the presence of FeO, MoO3, and Fe2O3. These oxides were products of tribochemical reactions induced by the high pressure and temperature at the contact interface. They formed a protective layer that prevented direct metal-to-metal contact. Meanwhile, the fragmented NPs (MoS2 and TiO2) adsorbed onto this reacted layer, contributing through mechanisms such as interlayer shear (MoS2), rolling and polishing (TiO2), and filling, creating a multi-functional, synergistic lubrication system.
Key words
lubrication /
surface /
nanoparticles /
tribological behavior /
synergistic effect
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References
[1] LI P P, HE W H, JU P F, et al.Acquisition of Molecular Rolling Lubrication by Self-Curling of Graphite Nanosheet at Cryogenic Temperature[J]. Nature Communications, 2024, 15: 5747.
[2] GHOSH G K, PANDA S, KUMAR N, et al.A Multi- Faceted Review on Industrial Grade Nanolubricants: Applications and Rheological Insights with Global Market Forecast[J]. Results in Engineering, 2025, 25: 103628.
[3] HAI A, LI S S, HE J Q, et al.High-Temperature Wettable Water-Based Lubricants Toward Hot Rolling Lubrication[J]. Advanced Functional Materials, 2024, 34(30): 2316793.
[4] SUN J L, MENG Y N, ZHANG B M.Tribological Behaviors and Lubrication Mechanism of Water-Based MoO3 Nanofluid during Cold Rolling Process[J]. Journal of Manufacturing Processes, 2021, 61: 518-526.
[5] XU M R, ALI S, KURNIAWAN R, et al.Nanoparticle- Based Lubrication during Machining: Synthesis, Application, and Future Scope—A Critical Review[J]. The International Journal of Advanced Manufacturing Technology, 2025, 136(10): 4141-4174.
[6] 张铭建, 陈云龙, 李维民, 等. 二聚酸离子液体作为水基润滑添加剂的摩擦学性能研究[J]. 摩擦学学报(中英文), 2024, 44(12): 1739-1751.
ZHANG M J, CHEN Y L, LI W M, et al.Tribological Properties of Dimer Acid Ionic Liquids as Lubricant Additives in Water-Based Fluid[J]. Tribology, 2024, 44(12): 1739-1751.
[7] TANG W W, WANG Y, TAN Y H, et al. Surface and Core Dual-Designed Carbon Dots Toward High-Efficiency Nano-Lubricant Additives for Polyethylene Glycol[J]. Wear, 2024, 554/555: 205480.
[8] SHAN Z Q, FAN H Z, TIAN Q, et al.The Strong Mechanical Anchoring of ZIF-8 Nanoparticles on Graphene Oxide Surface to Enhance Frictional Energy Dissipation[J]. Tribology International, 2024, 192: 109303.
[9] 滕家皇, 邹帅, 彭茂珲, 等. 碳量子点的润滑机制及其作为润滑添加剂的研究进展[J]. 润滑与密封, 2024, 49(7): 168-180.
TENG J H, ZOU S, PENG M H, et al.Research Progress on Lubrication Mechanism and Applications of Carbon Quantum Dots as Lubricant Additives[J]. Lubrication Engineering, 2024, 49(7): 168-180.
[10] RAWAT S S, HARSHA A P, KHATRI O P, et al.Pristine, Reduced, and Alkylated Graphene Oxide as Additives to Paraffin Grease for Enhancement of Tribological Properties[J]. Journal of Tribology, 2021, 143(2): 021903.
[11] HE J Q, SUN J L, MENG Y N, et al.Improved Lubrication Performance of MoS2-Al2O3 Nanofluid through Interfacial Tribochemistry[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2021, 618: 126428.
[12] HASSANPOUR H, RASTI A, SABBAGHI FARSHI S, et al.Sustainable Micro-Milling of Ti6Al4V: Role of MoS2 and CuO Nanofluids in Minimum Quantity Lubrication[J]. Precision Engineering, 2026, 97: 226-234.
[13] LUO J B, LIU M, MA L R.Origin of Friction and the New Frictionless Technology—Superlubricity: Advancements and Future Outlook[J]. Nano Energy, 2021, 86: 106092.
[14] WANG C L, YANG J, ZHANG H S, et al.Research on the Synergistic Lubrication Mechanism of Graphene Oxide and MgO Nanoparticles: From Experiment to Simulation[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2026, 733: 139283.
[15] CUI Y H, XUE S H, LIU Z H, et al.Synergistic Effect of MXene and PTFE with Multi-Structure as Lubricant Additives for Tribological Applications[J]. Carbon, 2024, 220: 118896.
[16] WANG B, GAO K, WANG Y J, et al.Synergistic Dispersion, Adsorption, and Anti-Wear Effects of Magnesium Silicate Hydroxide Nanomaterials and Carboxylic Acid[J]. Applied Surface Science, 2024, 665: 160373.
[17] DU S N, SUN J L, WU P.Preparation, Characterization and Lubrication Performances of Graphene Oxide-TiO2 Nanofluid in Rolling Strips[J]. Carbon, 2018, 140: 338-351.
[18] MENG Y N, SUN J L, HE J Q, et al.Interfacial Interaction Induced Synergistic Lubricating Performance of MoS2 and SiO2 Composite Nanofluid[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2021, 626: 126999.
[19] LI G, DE WIJN A S. Molecular Dynamics Simulations of Nanoscale Friction on Illite Clay: Effects of Solvent Salt Ions and Electric Double Layer[J]. Journal of Colloid and Interface Science, 2026, 703: 139107.
[20] ZHAO L, CHEN H, ZHANG J J, et al.Effect of hBN/ MoS2 Hybrid Nanofluid Minimum Quantity Lubrication on the Cutting Performance of Self-Lubricating Ceramic Tools when Machining AISI 4340[J]. Tribology International, 2025, 201: 110249.
[21] EVANS D J, HOLIAN B L.The Nose-Hoover Thermostat[J]. The Journal of Chemical Physics, 1985, 83(8): 4069-4074.
[22] RAPPE A K, CASEWIT C J, COLWELL K S, et al.UFF, a Full Periodic Table Force Field for Molecular Mechanics and Molecular Dynamics Simulations[J]. Journal of the American Chemical Society, 1992, 114(25): 10024-10035.
[23] LIANG H Y, LI J H, BU Y F.Molecular Dynamics Simulations of Nanoparticles as Lubricant Additives: A Review[J]. Computational Materials Science, 2025, 259: 114174.
[24] XU J, LU H, MAHFOUDI W, et al.The Influence of the Particle Size and Size Synergistic Effect of Nano-Copper on the Tribological Properties of Lubricants[J]. Tribology International, 2025, 201: 110282.
[25] WANG C L, HE J Q, XIONG S, et al.Enhancement of Cold Rolling Lubrication Performance of Cu Nanofluid Induced by Tribochemical Reactions[J]. Applied Surface Science, 2026, 715: 164596.
[26] WANG J, YANG X, KLEMEŠ J J, et al.A Review on Nanofluid Stability: Preparation and Application[J]. Renewable and Sustainable Energy Reviews, 2023, 188: 113854.
[27] ABDEL-REHIM A A, AKL S, ELSOUDY S. Investigation of the Tribological Behavior of Mineral Lubricant Using Copper Oxide Nano Additives[J]. Lubricants, 2021, 9(2): 16.
[28] WANG J T, FU K, ZHANG X Y, et al.When MoS2 Meets TiO2: Facile Synthesis Strategies, Hybrid Nanostructures, Synergistic Properties, and Photocatalytic Applications[J]. Journal of Materials Chemistry C, 2021, 9(27): 8466-8482.
[29] MA C R, HOU D W, JIANG J L, et al.Elucidating the Synergic Effect in Nanoscale MoS2/TiO2 Heterointerface for Na-Ion Storage[J]. Advanced Science, 2022, 9(35): 2204837.
[30] CAO J J, BAI X, YE Z F, et al.Enhanced Transport of TiO2-Reduced Graphene Oxide Nanocomposites in Saturated Porous Media: The Impact of Loaded TiO2 Shape and Solution Conditions[J]. Water, Air, & Soil Pollution, 2020, 231(3): 124.
[31] WEN Y C, ZHANG C, ZHU G Y, et al.Combined Effects of Nanofluid and Surfactant on Enhanced Oil Recovery: An Experimental Study[J]. ACS Omega, 2025, 10(44): 52375-52386.
[32] RANJU M R, ABHILASH P M, KESAVAN D.Rolling Contact Fatigue Studies on AISI 4140 Steel under Formulated Lubrication Conditions with Nano Graphene Additives[J]. Wear, 2024, 544: 205311.
[33] HE J Q, XIONG S, LI H J.Synergistic Lubrication Effect of Graphene Oxide and MoS2 Nanoparticles in Water- Based Fluid: Experiment and Humid-Environmental MD Simulation Study[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2025, 707: 135900.
[34] XIONG S, YAN C Y, QI Y.Effect of N-Doped GO Quantum Dots with MoS2 and Al2O3 Nanofluids on the Surface Quality of Hot Rolling of Copper and Steel Plates[J]. Nano Materials Science, 2026, 8(1): 78-92.
[35] TANG H J, SUN J L, PAN J S.Electrochemical and Localized Corrosion Behavior of 316 L SS/Copper/316 L SS Sandwich Composite in Chloride-Containing Environment[J]. Corrosion Science, 2022, 209: 110719.
[36] TANG H J, SUN J L, ZHAO Z L, et al.Effect of Friction Velocity on Tribological Behavior of Coumarin as Mineral Oil Additive[J]. Journal of Tribology, 2021, 143(2): 021901.
Funding
Natural Science Foundation of Henan Province (262300421918)
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