Extremely low friction coefficient

Graphitic BN (h-BN) is used as lubricant with low friction in numerous applications. Compared to graphite the h-BN can be used as lubricant in an oxidizing atmosphere up to 900 °C as well as at extremely low temperatures, e.g., in space because no water inclusions between the atomic sheet layers are present (graphite always contains small amounts of water between the layers). Due to its excellent resistance against oxidation, its extremely low friction coefficient, and its chemical inertness, h-BN can be inserted into alloys or ceramics [105]. It can be used as a solid surface lubricant [106] or added to a liquid to get dispersions with lubricating properties. 

Table V shows a typical coiqiarison of the test data recorded of the various anti-friction ccn ounds at cne shaft speed and one loading. I obably the most outstanding characteristic of the PPS formulation is its extremely low friction coefficient. The effect of this very low friction coefficient is clearly shown in its extremely low bearing teiqierature build-up at various loads compared to the other materials.

High heat resistivity, stability against oxygen, extremely low friction coefficient. 

Abstract Aqueous biocompatible tribosystems are desirable for a variety of tissue-contacting medical devices. L-3,4-dihydroxyphenylalanine (DOPA) and lysine (K) peptide mimics of mussel adhesive proteins strongly interact with surfaces and may be useful for surface attachment of lubricating polymers in tribosystems. Here, we describe a significant improvement in lubrication properties of poly (dimethylsiloxane) (PDMS) surfaces when modified with PEG-DOPA-K. Surfaces were characterized by optical and atomic force microscopy, contact angle, PM-IRRAS, and X-ray photoelectron spectroscopy. Sudi surfaces, tested over the course of 200 rotations ( 8 m in length), maintained an extremely low friction coefficient (p) (0.03 0.00) compared to bare PDMS (0.98 0.02). These results indicate... 

Extremely low friction coefficients are feasible with some solid lubricants, and when combined with liquids, such low friction may persist over much longer sliding distances or much heavier loads. 

Electronics. Owing to its relatively high electrical conductivity, low friction coefficient, and extremely high resistance to corrosion, gold metal is critically important in microelectrical circuitry, particularly in printed circuit boards, connectors, keyboard contactors, and miniaturized circuitry. 

Looking for materials with a low surface friction has been one of the classical and everlasting research topics for material scientists and engineers. Despite many efforts, it has been shown that snrface modification or adding Inbricants is not a very effective way to reduce the steady-state sliding friction between two solids, which show a frictional coefficient p = 10 even in the presence of a Inbricant. The discovery of an extremely low-friction gel should enable hydrogels to find wide application in many fields where low friction is required. 

Very small coefficients of friction are observed on ice. A typical value is p sa 0.03. There have been several attempts to explain this extremely low friction (for a history of research on this topic, see Ref. [918]). One attempt is related to the abnormal behavior of ice with respect to pressure and density. James Thompson in 1850 developed an expression showing the hnear dependence between pressure and freezing point depression, which was verified experimentally by his brother Lord Kelvin. In 1886, John Joly calculated that the local pressure below skater slides leads to... 

You are probably most familiar with Teflon as a nonstick coating for kitchen utensils (Figure 23.2). The slippery surface of Teflon-coated fry pans and muffin tins results from Teflon s extremely low coefficient of friction. 

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