Solid lubrication, graphite

Molybdenum disulhde (M0S2), graphite, hexagonal boron nitride, and boric acid are examples of lamella materials commonly applied as solid lubricants. The self-lubricating nature of the materials results from the lamella crystalline structure that can shear easily to provide low friction. Some of these materials used to be added to oils and greases in powder forms to enhance their lubricity. Attention has been shifted in recent years to the production and use of nanosize particles of M0S2, WS2, and graphite to be dispersed in liquid lubricants, which yields substantial decreases in friction and wear. 

Several oxides and sulfides display the characteristics of network solids. The bond network of silica appears in Section 9-. Other examples are titania (Ti02) and alumina (AI2 O3). These two substances have extremely high melting points because their atoms are held together by networks of strong a covalent bonds. Like graphite, M0S2 is a two-dimensional network solid that serves as a solid lubricant. 

The extrusion process requires the use of a lubricant to prevent adhesion of the aluminum to the die and ingot container walls. In hot extrusion, limited amounts of lubricant are applied to the ram and die face or to the billet ends. For cold extrusion, the container walls, billet surfaces, and die orifice must be lubricated with a thin film of viscous or solid lubricant. The lubricant most commonly used in extrusion is graphite in an oil or water base. A less common technique, spraying liquid nitrogen on the billet prior to extrusion, is also used. The nitrogen vaporizes during the extrusion process and acts as a lubricant. 

Kokkoris et al. (1991, 1995) suggested another method to impair catalyst attrition. In a small scale slugging bed they reduced the attrition rate of zeolites by addition of only very small quantities of various fine solid lubricants. In the case of graphite the reduction was up to 30%. The fines were assumed to reduce attrition by forming a protective coating that... 

Fluorinated carbon, CFX, where x is between 0 and 1.3, is prepared by the direct fluorination of carbon at high temperatures [108]. Many varieties of fluorinated carbon can be prepared depending on the type of carbon used in the process (e.g. graphite, petroleum coke, carbon black, etc.) and the level of fluorination (i. e. the value of ). Fluorinated carbons, such as those manufactured by Allied-Signal (Accufluor ), Central Glass Co. (Cefbon ) and Daikin, are used for the fabrication of cathodes in lithium anode batteries and as solid lubricants [109]. 

Because of the weak interaction between the sandwiches, M0S2 is a useful solid lubricant. It feels slippery like graphite. The M0S2 structure is found for WS2, MoSe2, WSe2, and MoTe2- Because of the greater polarizabilities of Se and Te compared with S, selenides and tellurides should be better solid lubricants than sulfides but the toxicity and unpleasant odors of selenides and tellurides make them poor choices. 

If a powder does not have all the required qualities, one can add lubricants to aid the sliding and positioning of the microgranules. Such lubricants can be liquid (water, mineral oil) or solid (tale, graphite, stearic acid, and various stearates). Binders are also added to increase the post-compression adhesion, as for example starch is added for pelletizing active carbon. An increase in the adhesive forces title to chemical bonds resulting from contact between the granules can also be... 

Graphite fluoride (CF) has unique properties, which include heat-resistance, electrical capabilities, and solid lubrication. Numerous studies on (CF) have been performed from the view points of electronic/crystal structures and chemical states/properties [1-5]. For example, Motoyama et al. [5] have... 

R.L. Fusaro, H.E. Sliney, Preliminary investigation of graphite fluoride (CFT) as a solid lubricant, NASA Tech, Note D-5097, March 1969. 

Where does molybdenum disulphide fit into this picture Certainly the use of solid lubricants must be ancient. Loose sand, ice and powdered snow have already been mentioned, but other slippery solids which were available and even locally abundant were graphite, mica, talc and molybdenum disulphide. 

Graphite has been known as a lubricant for over 2000 years, and until about 1960 was the most extensively-used solid lubricant. In terms of annual consumption, it may still be the leading solid lubricant, because of its major application in carbon brushes in electrical equipment. Its technology is highly developed, and there are several comprehensive books about a comparison... 

A major advantage of solid lubricants is their very low tendency to cause contamination of industrial products such as foods, pharmaceuticals and textiles. Many of them, including PTFE, graphite and molybdenum disulphide, are also virtually... 

For less critical applications the choice of solid lubricant will also be less critical, and will often be made on a cost basis. The three most commonly-used lubricants in low-technology applications and consumer products are PTFE, molybdenum disulphide and graphite. Their characteristics are compared in Table... 

Bahun, C.J. and Jones, J.R., Influence of Load, Speed and Coating Thickness on the Wear Life of a Bonded Solid Lubricant, Lubric. Eng., 25, 351, (1969). Hopkins, V., Discussion, p. 6, on Rabinowicz, E., Variation of Friction and Wear of Solid Lubricant Films with Film Thickness, ASLE Trans., 10, 1, (1967). Whitehouse, G.D., Nandan, D. and Whitehurst, C.A., The Effect of Film Thickness on Friction Coefficients for Solid Lubricants CaF2, MoSj and Graphite, ASLE Trans., 13, 159, (1970). 

Fusaro, R.L., A Comparison of the Lubricating Mechanisms of Graphite Fluoride and Molybdenum Disulfide Films, Proc. 2nd Inti. Conf. on Solid Lubrication, (15 -18 August 1978), ASLE SP-6, p. 59. 

Paxton, R.R., Carbon, Graphite and Metal-Bonded Molybdenum Disulphide Solid Lubricant Bearings, Tribology Inti., 15, 285, (1982). 

Atkinson, I.B. and Waghorne, R.M., Tribo-Chemistry of Graphite Fluoride Studied Using X-Ray Photoelectron Spectroscopy, Wear, 37, 123, (1976). Gisser, H., Petronio, M. and Shapiro, A., Graphite Fluoride as a Solid Lubricant, Proc. ASLE Inti. Conf. on Solid Lubricants, Denver, Colorado, (24-27 Aug. 1971), ASLE SP-3, p. 217. 

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