As solid lubricant

Calcium complex soap greases, obtained by the reaction of lime and a mixture of fatty acids and acetic acid. These greases offer good high temperature and anti-wear/extreme pressure properties related to the presence, in the soap, of calcium acetate that acts as solid lubricant they have good mechanical stability. 

The expectation of the structural dependence of lubrication motivated great numbers of investigations that intended to prepare and use highly ordered organic films, such as the Langmuir-Blodgett (L-B) hlms and Self-Assembled Monolayers (SAMs), as solid lubricant, which will be discussed more specihcally in Section 4. 

The most commonly used amphiphiles to build L-B hlms for tribological applications are the straight chain hydrocarbon compounds with simple functional groups such as the fatty acids, including stearic acids, arachidic acids, and behenic acids [32], but other amphiphilic molecules, e.g., 2,4-heneicosanedione and 2-docosylamina-5-nitropyridine, are also applied in some cases. There are two major systems of self-assembled monolayers, namely the alkylsilance derivatives (e.g., OTS, octadecyltrichlorosilane) on hydroxylated surfaces and the alkanethiols on metal substrates, which have been investigated extensively to examine their properties as solid lubricants and protective surface films [31 ]. 

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. 

Soft metals such as In, Ag, Sn, Pb, and Au can lead to reasonably low friction coefficients, when used as solid lubricants, due to their low shear strength. The metals were generally applied as thin films prepared by the vacuum deposition process. Especially, in applications to the high temperature conditions where liquid lubricants fail due to the evaporation, the thin films of soft metals can provide effective protection to the surfaces in sliding. 

These coatings are also employed as solid lubricants in engine components. Refractory materials such as MoS2 and WSe2 are lamellar compounds and provide very effective solid-state lubrication in spacecraft bearings and components used in radiation environments where conventional organic liquid lubricants are not stable (see Lubrication and lubricants). 

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]. 

The composites have an improved wear behaviour under load [580-582], In comparison to monolithic Si3N4 ceramics, the differences at 800 °C were more pronounced than at room temperature. This was attributed to the formation of TiOx layers, which are known as solid lubricants [580, 581],... 

The most likely application of the chalcogenide nanotubes is as solid lubricants. Mo and W chalcogenides are widely used as solid lubricants. It has been observed that the hollow nanoparticles of WS2 show better tribological properties and act as a better lubricant compared to the bulk phase in every respect (friction, wear and life-time of the lubricant).142 Tribological properties of 2H-MoS2 and WS2 powder can be attributed to the weak van der Waals forces between the layers which allow easy shear of the films with respect to each other. The mechanism in the WS2 nanostructures is somewhat different and the better tribological properties may arise from the rolling friction allowed by the round shape of the nanostructures. 

Even though the technology of lubrication by solids is largely empirical, it is useful to systematize classification and terminology. Substances that are used as solid lubricants can be grouped into the six... 

Many organic solids can be coated on metals and other hard materials to form rubbing interfaces with low friction, but most of them do not meet the other criteria required of solid lubricants, such as durability, resistance to high temperatures, and low volatility. Only a handful of organic substances have been given serious consideration as solid lubricants pcA it, the behavior of which depends on the properties of macroscopic coatings as distinct from a.diOJibe.d of fatty acids,... 

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