Tribological Control

Recently, ultrathin organic thin films attract attention as new film lubricant [51]. Organosilane monolayer, which is one of the ultrathin films, has been identified as promising boundary lubricants. This is because organosilane molecules interact strongly with substrates and they are robust against solvent and temperature increase. Friction and wear tests of monolayers were carried out with a conventional ball-on-disk type friction tester (SHINTO Scientific Co. Ltd.) in air and tetradecane at 298 K. A 5.0 mm radius ball made of stainless steel was slid on a disk. The friction coefficient was determined by the distortion of a 

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New experimental techniqnes for the direct measurement of interparticle forces are now available and can be nsed to nnderstand the physicochemical factors that control adhesion, coating phenomena, tribology, and others. 

The implantation of low-to-medium energy ions changes only surfaee layer of polymers, with the thickness in nm-pm range, and preserves favorable bulk properties of polymers. By the ion implantation sueh surfaee properties as ehemieal strueture [108-111], wettability [109,110,112], eleetrieal eonduetivity [109,113-116], tribological properties [112,117,118] and bioaetivity [18,111-113,119] ean be ehanged in a manner which can be controlled by a proper ehoice of ion mass, energy and fluenee. 

The scope of the series covers the entire spectrum of solid mechanics. Thus it includes the foundation of mechanics variational formulations computational mechanics statics, kinematics and dynamics of rigid and elastic bodies vibrations of solids and structures dynamical systems and chaos the theories of elasticity, plasticity and viscoelasticity composite materials rods, beams, shells and membranes structural control and stability soils, rocks and geomechanics fracture tribology experimental mechanics biomechanics and machine design. 

Nagakari, M., Yamamoto, S., Sakurai, H. and Kubo, K., Study of the Influence of Organic Molybdenum Compound on Valve Train Wear Control Performance of Gasoline Engine Oil, World Tribology Congress, London, 8-12 September, 1997. 

In a different approach, Bruce and coworkers 210) described the preparation of liquid-crystalline derivatives of a N,C,N-Pt (II) Imninophore (Fig. 18). Interestingly, they foimd that emission in the liquid-crystal phase is characteristic of the monomeric complex, while excimer-like emission normally characterizes nonliquid-crystalline analogues. They showed that the emission of pure films is responsive to both method of preparation and tribological stimulation so that it is possible to switch in a controllable manner between monomer- and excimer-like states. 

The AFM probe tip interacts via various mechanisms with the sample surface, including simple quasi-static and dynamic normal and lateral forces. These (and other) interactions depend on local physical properties of the sample, on the scale of the probed area. Tribological, viscoelastic, and microhardness mechanical properties can be probed under (more or less) controlled environmental conditions. 

NVH As mentioned in the section on Tribology, some braking energy is converted into vibration and sound energy. Just as in the tests used for wear characterization, several dynamometer and vehicle tests have been developed to characterize the NVH-generating tendency of brake systems. Dynamometer tests are conducted with the brake corner or a whole vehicle mounted in a controlled environmental chamber. 

Potassium titanate whiskers were found to improve the tribological properties of NAO friction materials. These soft, synthetic refractory materials stabilize friction level, reduce pad wear, noise, fade, thermal conductivity, control porosity, and provide thermal reinforcement. Fibrous potassium titanates are being replaced by platelet and powder versions because of health concerns associated with respirable fibers. 

Self-Assembled Monolayer Coatings to Control MEMS Tribology... 

We are currently in the midst of a new revolution in tribology, driven by (a) the advent of experimental techniques that allow controlled friction measurements at atomic scales and (b) computers that allow the complex dynamics in atomic scale contacts to be analyzed. This new line of study, dubbed nanotribology, is playing a central role in the quest to build robust machines with nanometer-scale moving parts and is poised in turn to beneht from the resulting advances in nanotechnology. 

The three major new atomic-scale experimental methods developed in the last decade are the quartz crystal microbalance (QCM) [2 4], atomic and friction force microscopes (AFM/FFM) [5,6], and the surface force apparatus (SEA) [7,7a,8]. These new tools reveal complementary information about tribology at the nanometer scale. The QCM measures dissipation as an adsorbed him of submonolayer to several monolayer thickness slides over a substrate. AFM and FFM explore the interactions between a surface and a tip whose radius of curvature is 10 100 nm [9]. The number of atoms in the contact ranges from a few to a few thousand. Larger radii of curvature and contacts have been examined by gluing spheres to an AFM cantilever [10,11]. SEA experiments measure shear forces in even larger-diameter ( 10 pm) contacts, but with angstrom-scale control of the thickness of lubricating hlms. 

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