Friction deposition

Tin—Nickel. AHoy deposits having 65% fin have been commercially plated siace about 1951 (135). The 65% fin alloy exhibits good resistance to chemical attack, staining, and atmospheric corrosion, especially when plated copper or bron2e undercoats are used. This alloy has a low coefficient of friction. Deposits are solderable, hard (650—710 HV ), act as etch resists, and find use ia pfinted circuit boards, watch parts, and as a substitute for chromium ia some apphcafions. The rose-pink color of 65% fin is attractive. In marine exposure, tin—nickel is about equal to nickel—chromium deposits, but has been found to be superior ia some iadustfial exposure sites. Chromium topcoats iacrease the protection further. Tia-nickel deposits are bfitde and difficult to strip from steel. Temperature of deposits should be kept below 300°C. 

N Tanigaki, K Yase, and A Kaito, Oriented films of poly(p-phenylene) by friction-deposition and oriented growth in polymerization, Mol. Cryst. Liq. Cryst., 267 335-340, 1995. 

Lattice Visualization of Poly(tetrafluoro ethylene) (PTFE) by CM-AFM Sample Preparation Friction Deposition... 

PPP films can also be prepared by electropolymerisation imder either reductive or oxidative conditions, but the EL properties have been found to be highly dependent on the polymerisation conditions [51]. A study of the PL efficiency of PPP thin films of varying chain length concluded that for highly ordered PPP films a chain length of 25-30 units was optimal [52]. Oriented films of PPP have been prepared by a friction deposition method and found to show highly polarised fluorescence [53]. 

Breiby, D., Spiling, T.I., Bunk, O., Nyberg, R.B., Norrman, K., Nielsen, M.M., 2005. Structural surprises in friction-deposited films of poly(tetrafluoroethylene). Macromolecules 38, 2383-2390. 

Deposited monolayers of such RX-type compounds as fatty acids and amines can be extremely tenaciously held, as evident for example, in frictional wear experiments (see Section XII-7) and in their stability against evaporation under... 

Carbon Composites. Cermet friction materials tend to be heavy, thus making the brake system less energy-efficient. Compared with cermets, carbon (or graphite) is a thermally stable material of low density and reasonably high specific heat. A combination of these properties makes carbon attractive as a brake material and several companies are manufacturing carbon fiber—reinforced carbon-matrix composites, which ate used primarily for aircraft brakes and race cats (16). Carbon composites usually consist of three types of carbon carbon in the fibrous form (see Carbon fibers), carbon resulting from the controlled pyrolysis of the resin (usually phenoHc-based), and carbon from chemical vapor deposition (CVD) filling the pores (16). 

Eunctional or hard chromium plating (169,175) is a successfljl way of protecting a variety of industrial devices from wear and friction. The most important examples are cylinder liners and piston rings for internal combustion engines. Eunctional chromium deposits must be appHed to hard substrates, such as steel, and are appHed in a wide variety of thicknesses ranging from 2.5 to 500 ]Am. 

Investigation into the effect has been mainly devoted to reactions with red fuming nitric acid . It seems that in red fuming nitric acid a preliminary reaction results in the formation of a surface deposit of finely divided metallic titanium ignition or pyrophoricity can then be initiated by any slight impact or friction. The tendency to pyrophoricity increases as the nitrogen dioxide content of the nitric acid rises from zero to maximum solubility at about 20%, but decreases as the water content rises, the effect being nearly completely stifled at about 2% water. 

Composite deposits of electroless nickel and PTFE are characterised by a very low coefficient of friction . They contain 18-25% by volume of PTFE, and have found considerable application in the automobile, textile machinery and paper-making industries, among others. 

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