缅北强奸

Control of friction and wear is a ubiquitous challenge in numerous machined interfaces ranging from biomedical implants, to engines, to nano- and micro-scaled electromechanical systems (MEMS) devices. Control of friction is also essential to reducing energy waste.¹ Central to developing boundary lubrication schemes for such applications is how to reduce wear at the rough surfaces of such surfaces, where nanoscaled asperities dominate the interfacial contacts that can lead to wear. The robust mechanical properties and general chemical inertness of two-dimensional (2D) nanomaterials, such as graphene and MoS₂, has made them of interest as friction modifiers. While single layer graphene and MoS₂ can readily adapt to surface structure on the atomic scale, when deposited on substrates with nanoscopic roughness of ~ 10 nm rms (as is common in many machined interfaces) a conformal coating generally cannot be fully formed, due to competition between adhesion to the substrate nanoscopic asperities and the bending rigidity of the material.^2,3 This often leaves a mixture of supported and unsupported regions which respond differently to applied load, with spatial variations in mechanical properties and chemical bonding. Modification of the frictional properties may also be tuned by controlling substrate interactions using self-assembled monolayers.^4,5 It has also been observed that increased strain in these materials on rough surfaces has also been seen to increase their chemical reactivity.⁶ This has recently led us to examine force-driven chemical reactions with graphene as a model approach to understanding mechanochemical reactions at surfaces. Here, we describe a combination of AFM nanomechanical, confocal Raman microspectroscopic and near-field IR scattering studies of graphene and MoS₂ on silica surfaces with controlled nanoscopic roughness, to examine the how this impacts their frictional properties, and alters their electronic properties and chemical reactivity, where strain dependent reactions can be driven by applied forces. Studies of MoS₂ on metal surfaces, such as Au(111) will also be described, where even within single layer MoS₂, varying phases of the MoS₂ are found to occur.⁷

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1. J.C. Spear, B.W. Ewers and J.D. Batteas, 鈥�2D-Nanomaterials for Controlling Friction and Wear at Interfaces,鈥� 10 Nano Today (2015) 301-314.

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2. M.B. Elinski, Z. Liu, J.C. Spear and J.D. Batteas, 鈥�2D or not 2D? The impact of Nanoscale Roughness and Substrate Interactions on the Tribological Properties of Graphene and MoS₂,鈥� J. of Phys. D: Appl. Phys. 50 (2017)103003.

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3. J.C. Spear, J.P. Custer and J.D. Batteas, 鈥淭he Influence of Nanoscale Roughness and Substrate Chemistry on the Frictional Properties of Single and Few Layer Graphene,鈥� Nanoscale 7 (2015) 10021-10029.

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4. M.B. Elinski, B.D. Menard, Z. Liu and J.D. Batteas, 鈥淎dhesion and Friction at Graphene/Self-Assembled Monolayer Interfaces Investigated by Atomic Force Microscopy,鈥� J. Phys. Chem. C 121 (2017) 5635-5641.

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5. M. Negrito, M.B. Elinski, N. Hawthorne, M.P. Pedley, M. Han, M. Sheldon, R.M. Espinosa-Marzal, and J.D. Batteas, 鈥淯sing Patterned Self-Assembled Monolayers to Tune Graphene-Substrate Interactions,鈥� Langmuir 37 (2021) 9996-10005.

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6. S. Raghuraman, M. B. Elinski, J. D. Batteas and J. R. Felts. 鈥淒riving Surface Chemistry at the Nanometer Scale Using Localized Heat and Stress,鈥� Nano Lett. 17 (2017) 2111-2117.

Bio:

Dr. James Batteas is the D. Wayne Goodman Professor of Chemistry and Professor of Materials Science and Engineering at Texas A&M University (TAMU). He earned a B.S. in Chemistry at the University of Texas at Austin in 1990 and a Ph.D. in Chemistry from the University of California at Berkeley in 1995. He is an expert in materials chemistry of surfaces and interfaces, with research activities spanning a broad range of fundamental surface and interfacial phenomena. These include studies of charge transport in organic molecular assemblies on surfaces, measured by scanning tunneling microscopy (STM) and modeled by density functional theory (DFT), nanoparticle catalysis, plasmonics, tribology, 鈥渟mart鈥� surfaces, and self-organizing nanoscale materials for device applications in optoelectronics and chemical sensing. His research in tribology focuses on the bridge between chemistry and mechanics, were his lab conducts atomic force microscopy (AFM) studies of atomic scale friction and wear of oxides and 2D nanomaterials. He had recently extended this work into fundamental studies of mechanochemistry and directs the new NSF Center for the Mechanical Control of Chemistry. He has been recognized twice by TAMU for excellence in teaching, receiving Association of Former students Distinguished Teaching awards at both the college and university levels. He was elected a Fellow of the Royal Society of Chemistry in 2012 and is an Editorial Board Member of RSC Advances and sits on the Editorial Advisory Board of ACS Central Science.

7.F. Wu, Z. Liu, N. Hawthorne, M. Chandross, Q. Moore, N. Argibay, J. Curry and J.D. Batteas, 鈥淔ormation of Coherent 1H-1T Heterostructures in Single Layer MoS₂ on Au(111),鈥� ACS Nano 14 (2020) 16939-16950.