Surface Forces and Nanorheology of Molecularly Thin Films
In this chapter, we describe the static and dynamic normal forces that occur between surfaces in vacuum or liquids and the different modes of friction that can be observed between (i) bare surfaces in contact (dry or interfacial friction), (ii) surfaces s
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Surface Forces 18.1 Introduction: Types of Surface Forces ..... 544 18.2 Methods Used to Study Surface Forces .... 18.2.1 Force Laws ................................. 18.2.2 Adhesion Forces .......................... 18.2.3 The SFA and AFM ......................... 18.2.4 Some Other Force-Measuring Techniques ................................. 18.3 Normal Forces Between Dry (Unlubricated) Surfaces ......................... 18.3.1 Van der Waals Forces in Vacuum and Inert Vapors ......................... 18.3.2 Charge Exchange Interactions ....... 18.3.3 Sintering and Cold Welding .......... 18.4 Normal Forces Between Surfaces in Liquids ............................................ 18.4.1 Van der Waals Forces in Liquids .... 18.4.2 Electrostatic and Ion Correlation Forces............ 18.4.3 Solvation and Structural Forces ..... 18.4.4 Hydration and Hydrophobic Forces 18.4.5 Polymer-Mediated Forces............. 18.4.6 Thermal Fluctuation Forces ........... 18.5 Adhesion and Capillary Forces................ 18.5.1 Capillary Forces ........................... 18.5.2 Adhesion Mechanics .................... 18.5.3 Effects of Surface Structure, Roughness, and Lattice Mismatch................... 18.5.4 Nonequilibrium and Rate-Dependent Interactions: Adhesion Hysteresis.....................
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18.6 Introduction: Different Modes of Friction and the Limits of Continuum Models ...... 569 18.7 Relationship Between Adhesion and Friction Between Dry (Unlubricated and Solid Boundary Lubricated) Surfaces 18.7.1 Amontons’ Law and Deviations from It Due to Adhesion: The Cobblestone Model ................ 18.7.2 Adhesion Force and Load Contribution to Interfacial Friction 18.7.3 Examples of Experimentally Observed Friction of Dry Surfaces... 18.7.4 Transition from Interfacial to Normal Friction with Wear ........
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Part C 18
In this chapter, we describe the static and dynamic normal forces that occur between surfaces in vacuum or liquids and the different modes of friction that can be observed between (i) bare surfaces in contact (dry or interfacial friction), (ii) surfaces separated by a thin liquid film (lubricated friction), and (iii) surfaces coated with organic monolayers (boundary friction). Experimental methods suitable for measuring normal surface forces, adhesion and friction (lateral or shear) forces of different magnitude at the molecular level are described. We explain the molecular origin of van der Waals, electrostatic, solvation and polymer mediated interactions, and basic models for the contact mechanics of adhesive and nonadhesive elastically deforming bodies. The effects of interaction forces, molecular shape, surface structure and roughness on adhesion and friction are discussed. Simple models for the contributions of the adhesion force and external load to interfacial friction are illustrated with experimental data on both unlubricated and lubricated systems, as measured with the surface forces apparatus. We dis
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