A plane fit correction was applied to all z maps to account for sample tilt, while the VCPD and s maps were unprocessed. AU - Kohri, Hitoshi. : Crystallinity of rf-sputtered MoS2 films. Field of view is 50m across the diagonal direction of the images, ac Cross-sectional topographical line scans and df corresponding work function in eV from KPFM measurements of selected wear tracks shown in Fig. If you want to reproduce the whole article [17][25] The yield strength of monolayer flakes was 270 GPa,[25] while the thicker flakes were also stiffer, with a yield strength of 330 GPa. : Friction and wear investigation of molybdenum disulfide II: effects of contaminants and method of application. Solid State 40, 90118 (2015), Gardos, M.N. The calculation was not spin polarized. Each element in a friction material formulation has its own role such as to improve fade resistance, control the friction coefficient, reduced porosity, and noise, increased strength, etc a small change in elemental composition varies the physical, mechanical and Tribological properties of the brake pads. Lamellae with edge sites that are fully passivated with sulfur atoms are defect-free but non-stoichiometric; these are referred to as defect-free throughout the manuscript. ACS Appl. 3, 042125 (2013). J. Appl. This work shows that size and thickness of the lamellar structures in the wear tracks, and the presence of edge sites were the main factors contributing to the observed changes in work function and friction behavior in this investigation. Thin Solid Films 484, 389395 (2005), Wu, Y., Li, H., Ji, L., Ye, Y., Chen, J., Zhou, H.: Preparation and properties of MoS2/a-C films for space tribology. How does MoS2 decrease coefficient friction? | ResearchGate : Energy level evolution of air and oxygen exposed molybdenum trioxide films. Coat. and diagrams provided correct acknowledgement is given. In macroscale contacts, edges of MoS2 lamellae at the surface are likely oxidized prior to testing, further enhancing interactions with water [15, 24, 38,39,40]. friction. If you are the author of this article, you do not need to request permission to reproduce figures If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. The Tribological Mechanism of MoS2 Film under Different Humidity Shanghai Collaborative Innovation Center for High Performance Fiber Composites, Donghua University, Shanghai 201620, China Tribol. where t is the work function of the tip and e is the elementary charge [54]. https://doi.org/10.1007/s40544-020-0374-3, DOI: https://doi.org/10.1007/s40544-020-0374-3. [38], Other layered inorganic materials that exhibit lubricating properties (collectively known as solid lubricants (or dry lubricants)) includes graphite, which requires volatile additives and hexagonal boron nitride. 1e). Atomically thin two-dimensional molybdenum disulfide (MoS2) is well known for its excellent lubrication characteristics and is usually used as a solid lubricant in diverse micro/nanoelectromechanical systems (MEMS/NEMS). Work functions increased with sliding cycles and were higher for friction experiments in dry N2 than in humid N2. : Hertzian stress contribution to low friction behavior of thin MoS2 coatings. 65, 64 (2017), Lancaster, J.K.: A review of the influence of environmental humidity and water on friction, lubrication and wear. MoS2@Fe-N-C core/shell[47] nanosphere with atomic Fe-doped surface and interface (MoS2/Fe-N-C) can be used as a used an electrocatalyst for oxygen reduction and evolution reactions (ORR and OER) bifunctionally because of reduced energy barrier due to Fe-N4 dopants and unique nature of MoS2/Fe-N-C interface. He is a researcher and doctoral supervisor in LICP-CAS. Excel App. B 13, 51885192 (1976), Larsen, A.H., et al. At ambient conditions, the coefficient of friction for MoS2 was determined to be 0.150, with a corresponding estimated shear strength of 56.0 MPa (megapascals). Res. C 123, 74867494 (2019), Arif, T., Yadav, S., Colas, G., Singh, C.V., Filleter, T.: Understanding the independent and interdependent role of water and oxidation on the tribology of ultrathin molybdenum disulfide (MoS2). The ultra-low friction state on atomically thin MoS2 is patterned further by controllably regulating position, time, and electric field during the rubbing process. Res. Phys. We have collected some of those tables here. On the first pass, z was measured via PeakForce Tapping, while on the second pass, VCPD was measured by retracing the topography at a user-defined height and varying the DC sample voltage VDC to null the cantilever oscillations (VDC=VCPD when the tip-sample electrostatic force gradient was minimized). 36, 341350 (1988), Stewart, T.B., Fleischauer, P.D. Material. 1: Effect of atmosphere. your institution. The friction force, F, is proportional to the normal force, N, and the coefficient of friction, : where s is the coefficient of static friction and k is the coefficient of kinetic friction. DOI: 10.1039/D0RA00995D. Commun. For this cantilever, k was taken to be the nominal value and t was taken to be 4.88eV from earlier work [55]. Cycle average friction coefficients for experiments using a 1mm diameter ruby ball and 1mm/s sliding speed showing the impact of changing (a) environment (dry N2 vs 50% RH N2), b cycle count (1, 10, 250 cycles) and c contact force (10, 50, 200 mN). The work function was measured by PEEM and KPFM on separate wear tracks for which representative friction data are shown in Fig. 3(a), as the load increased, the friction coefficient decreased rapidly and fell below 0.1 at a load of 1.0 GPa. Peiling Ke or Aiying Wang. Wear 432433, 202935 (2019), Afanasiev, P., Lorentz, C.: Oxidation of nanodispersed MoS2 in ambient air: the products and the mechanistic steps. It is unaffected by dilute acids and oxygen. Coat. nanocomposite materials. Tungsten Disulfide (WS2) can also be used in high temperature and high pressure applications. Wear 19, 329342 (1972), Zhao, X., Perry, S.S.: The role of water in modifying friction within MoS2 sliding interfaces. Appl. Tribol. Friction 7(3): 199216 (2019). Thin Solid Films 214, 156163 (1992), Polcar, T., Cavaleiro, A.: Review on self-lubricant transition metal dichalcogenide nanocomposite coatings alloyed with carbon. Technol. The compound is classified as a transition metal dichalcogenide. 0.22. Each sulfur atom has pyramidal coordination and is bonded to three molybdenum atoms. Sliding friction tests of MoS2 using a pin on disc tester at low loads (0.12 N) give friction coefficient values of <0.1.[35][36]. Flat Plate Stress Calcs http://ntrs.nasa.gov/search.jsp?R=19790004987 (1978), Fusaro, R.L. 5), suggesting convergence to the bulk value. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Science, Lanzhou, 730000, China, Yupeng Zhang,Panpan Li,Li Ji,Xiaohong Liu,Hongqi Wan,Lei Chen&Hongxuan Li, Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing, 100049, China, Panpan Li,Li Ji,Xiaohong Liu,Hongqi Wan,Lei Chen&Hongxuan Li, School of Chemistry and Chemical Engineering, North Minzu University, Yinchuan, 750021, China, You can also search for this author in How does MoS2 decrease coefficient friction? : Water adsorption on molybdenum disulfide containing surface contaminants. These results are in reasonable agreement with other DFT-calculated values for MoS2 [59, 60]. : The effects of dopants on the chemistry and tribology of sputter-deposited MoS2 films. provided that the correct acknowledgement is given and it is not used for commercial purposes. Chem. Proposed reasons include polar bonding between lamellae [27], capillary forces or enhanced adhesion [26, 32], among others. Molybdenum disulfide is the inorganic compound with the formula MoS2. The lubricant is applied by burnishing and the excess is wiped from the bearing surface. [23], The widely used method of micromechanical exfoliation has been carefully studied in MoS2 to understand the mechanism of delamination in few-layer to multi-layer flakes. Friction coefficients and wear rates of MoS2/Cu, BN/Cu composites 3, and this debris has lower work functions than the wear scars. The scan parameters were largely set by the ScanAsyst optimization technique; notable exceptions included a PeakForce setpoint of 10 nN and a lift-off height of 50nm. A S L E Trans. Technol. : Surface and subsurface contributions of oxidation and moisture to room temperature friction of molybdenum disulfide. The coecient of friction for molybdenum disulfide crystals shearing along their lamella is approximately 0.025, among the lowest known for any material6. Catal. B 35, 021203 (2017), Khare, H.S., Burris, D.L. 6, 6293 (2015), Vancs, P., et al. Technol. If you are an author contributing to an RSC publication, you do not need to request permission A key limitation of the simulations was the inability to directly simulate the restructuring of small lamellae during run-in, yet defective and defect-free simulations draw parallels to experimentally observed behaviors. She is an associate researcher and master supervisor in LICP-CAS. Cross-sectional profiles of the z and s maps were taken across the widths of the wear scars, and the results presented herein were typical of data along the lengths of the wear scars. : Effect of contaminations and surface preparation on the work function of single layer MoS2. MoS2 with particle sizes in the range of 1100 m is a common dry lubricant. [41] It is derived from a common transition metal, rather than group 10 metal as are many alternatives, MoS2 is chosen when catalyst price or resistance to sulfur poisoning are of primary concern. College of Mechanical Engineering, Donghua University, Shanghai 201620, China, b MoS 2 also has greater load-carrying capacity and its manufacturing quality is better controlled. Thermodynamics Mater. Dependence of electronic structure of g-C3N4 on the layer number of its nanosheets: A study by Raman spectroscopy coupled with first-principles calculations. 3 and 4, respectively, where PEEM data are presented in terms of the relative change in work function from the as-deposited surface and KPFM data are presented as absolute values. Appl Surf Sci 345: 349354 (2015), Yi M R, Zhang C H. The synthesis of MoS2 particles with different morphologies for tribological applications. Technol. coefficient, but, unlike graphite, it does not rely on adsorbed vapors or moisture. : Alloying MoS2 with Al and Au: structure and tribological performance. : Tribological and chemical effects of long term humid air exposure on sputter-deposited nanocomposite MoS2 coatings. The ultra-low friction coefficient (typically 10- 2 range) of MoS 2 -based coatings is generally associated with friction-induced orientation of "easy-shear" planes of the lamellar structure parallel to the sliding direction, particularly in the absence of environmental reactive gases and with moderate normal loads. : Uncovering topographically hidden features in 2D MoSe2 with correlated potential and optical nanoprobes. Maps of the vacuum level were obtained by fitting the spectra at each pixel. Appl. This black crystalline sulfide of molybdenum occurs as the mineral molybdenite. : Molybdenite as a new lubricant. [23] The increase in yield strength is accompanied by a change in the failure mode of the material. The formation of a basally oriented film with long range order is an important part of the run-in process for MoS2 coatings and is frequently observed in initially amorphous PVD sputtered films [61, 62]. To excite valley Hall effect in specific valleys, circularly polarized lights were used for breaking the T symmetry in atomically thin transition-metal dichalcogenides. 57, 995997 (1990), Gul, A., Bacaksiz, C., Unsal, E., Akbali, B.: Theoretical and experimental investigation of conjugation of 1, 6-hexanedithiol on MoS2. The Vienna Ab initio Simulation Package (VASP) v5.4.4 [46, 47] was used with the standard PAW_PBE pseudopotentials packaged with VASP (Mo: 08Apr2002 and S: 06Sep2000). In particular, the friction mechanism of interlayer sliding friction combined with energy storage friction was analyzed and proposed. Friction coefficients from simulations and count of inter-lamellar interactions are shown in e. Stoichiometric (defective) lamellae sheared in vacuum (i.e., no water or oxygen present, Fig. Interestingly, when exposed to water and oxygen, these simulations exhibit friction coefficients that agree well with experimental results [17]. Lei CHEN. Super-low friction of MoS2 coatings in various environments The defect-free systems showed the highest number of inter-lamellar bonds, followed by the defective systems, and then defective systems exposed to water and molecular oxygen. If you are an author contributing to an RSC publication, you do not need to request permission Chem. Moly grease and moly paste | McLube Industrial Lubricants [6] MoS 2 is relatively unreactive. : Space environmental effects on MoS2 and diamond-like carbon lubricating films: atomic oxygen-induced erosion and its effect on tribological properties. Engineering Book Store Lastly, adsorbates are not thought to play an appreciable role in our results, as PEEM was performed in UHV and KPFM in lab air, and results from both are in good agreement. Beam Deflections and Stress Interlayer sliding dissipates energy when a shear stress is applied to the material. PEEM measurements were conducted using a LEEM-III system (Elmitec Elektronenmikroskopie GmbH) coupled to a continuous-wave (CW), tunable wavelength light source based on a Xe lamp. Fabrication of the g-C3N4/Cu nanocomposite and its potential for lubrication applications. Tribol. Like graphite, MoS 2 has a low friction coefficient, but, unlike graphite, it does not rely on adsorbed vapors or moisture. [7] Molybdenite ore is processed by flotation to give relatively pure MoS2. range of 350 to 400 C (662 to 752 F). Part of Springer Nature. Hongxuan Li or Zhiliang Jin. Details & Benefits Benefits Grease vs. MoS2 is relatively unreactive, being unaffected by dilute acids and oxygen. Sun, Y. Lu and Y. Peng, 5). The work function of the sample s was calculated from the VCPD data through the relationship. Provided by the Springer Nature SharedIt content-sharing initiative, Over 10 million scientific documents at your fingertips, Not logged in Xiaohong LIU. Surf. In situ formation of spherical MoS2 nanoparticles for ultra-low friction. J Appl Phys 113(17): 17B508 (2013), Zhao X C, Liu Y, Wang D L, Li Q F. Effect of the particle size on tribological properties of nanometer Fe3O4 as lubricating oil additives. PY - 2008/12/1. This article is licensed under a permission is not required) please go to the Copyright : Oxidation characteristics of molybdenum disulfide and effect of such oxidation on its role as a solid-film lubricant. Lubricated. 38, 894904 (1995), Zabinski, J.S., Donley, M.S., Dyhouse, V.J., McDevitt, N.T. Tribol. ChemPhysChem (2017). Friction coefficient table for materials in fretting regime In fretting, friction coefficients are different for the same pairs of materials due to changes in friction mechanisms. The main function is to reduce friction at low temperature, increase friction at high temperature, and low loss on ignition. In 2009, he obtained his Ph.D. degree from LICP-CAS. Sci. Interfaces 2, 14441448 (2010), Curry, J.F., et al. | Contact, Home Nanotechnol. The bulk layer calculations used 55 unit cells in the X and Y directions with at least 20 of vacuum space in the Z direction to avoid self-interaction. The simulations show that lamellae tend to anchor themselves at random to neighboring lamellae because of the highly reactive exposed edges. Plastics Synthetics Phys. Google Scholar, Fusaro, R.L. Crit. C 121, 90229031 (2017), Chow, P.K., et al. Molybdenum disulfide (MoS2) has long been known as low friction material.
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