Electroless plating, metal deposition

During electroless plating, metal is deposited onto the desired surface from solution through an autocatalytic redox process [36]. Specifically, a reductant in the... 

The metal was deposited by electro and electroless plating, vacuum deposition and deposition by the decomposition of organometallic compounds. 

Electroless plating The deposition is due to an autocatalyzed reaction of a metallic salt complex on the target surface, which is left in a hath of the complex salt and a reducing agent... 

Electroless plating and deposition Spent electroless copper bath Waste rinse water Acids, palladium, complexed metals, chelating agents, formaldehyde... 

Traditionally, where good shielding was required, equipment cases were made from metal, but more recently polymers have become widely used. These polymers are rendered conductive by processes such as electroplating, electroless plating, vacuum deposition, sputtering and flame spraying. Alternatively, they can be compounded with conductive fillers such as carbon blacks, carbon fibres, aluminium flakes, stainless steel fibres and various metal-coated fillers. 

In electroless deposition, the substrate, prepared in the same manner as in electroplating (qv), is immersed in a solution containing the desired film components (see Electroless plating). The solutions generally used contain soluble nickel salts, hypophosphite, and organic compounds, and plating occurs by a spontaneous reduction of the metal ions by the hypophosphite at the substrate surface, which is presumed to catalyze the oxidation—reduction reaction. 

Electrodeposition of Metals. Citric acid and its salts are used as sequestrants to control deposition rates in both electroplating and electroless plating of metals (153—171). The addition of citric acid to an electroless nickel plating bath results in a smooth, hard, nonporous metal finish. 

Modem electroless plating began in 1944 with the rediscovery that hypophosphite could bring about nickel deposition (7,8). Subsequent work led to the first patents on commercially usable electroless nickel solutions. Although these solutions were very useful for coating metals, they could not be used on most plastics because the operating temperature was 90—100°C. The first electroless nickel solution capable of wide use on plastics was introduced in 1966 (9). This solution was usable at room temperature and was extremely stable (see Nickel and nickel alloys). 

The ideal electroless solution deposits metal only on an immersed article, never as a film on the sides of the tank or as a fine powder. Room temperature electroless nickel baths closely approach this ideal electroless copper plating is beginning to approach this stabiHty when carefully controUed. Any metal that can be electroplated can theoretically also be deposited by electroless plating. Only a few metals, ie, nickel, copper, gold, palladium, and silver, are used on any significant commercial scale. 

Electroless plating rates ate affected by the rate of reduction of the dissolved reducing agent and the dissolved metal ion which diffuse to the catalytic surface of the object being plated. When an initial continuous metal film is deposited, the whole surface is at one potential determined by the mixed potential of the system (17). The current density is the same everywhere on the surface as long as flow and diffusion are unrestricted so the metal... 

Plating T anks. An electroless plating line consists of a series of lead-lined (for plastics etching) or plastic-lined tanks equipped with filters and heaters, separated by rinse tanks (24). Most metal tanks, except for passivated stainless steel used for electroless nickel, cannot be used to hold electroless plating baths because the metal initiates electroless plating onto itself. Tank linings must be stripped of metal deposits using acid at periodic intervals. 

Electroless Plating formation of a metallic coating by chemical reduction catalysed by the metal deposited. 

Electroless plating is a chemical reduction process that depends upon the catalytic reduction of a metallic ion in an aqueous solution containing a reducing agent and the subsequent deposition of metal without the use of external electric energy. 

The second method, i.e. electroless plating, has been used also to produce graphite - Sn, Sn02 composite materials. The chemical deposition of metals on the graphite supports is performed through two principal steps. 

Synthetic lipids and peptides have been found to self-assemble into tubules [51,52]. Several groups have used these tubules as templates [17,51,53-56]. Much of this work has been the electroless deposition of metals [51,54]. Electrolessly plated Ni tubules were found to be effective field emission cathode sources [55]. Other materials templated in or on self-assembled lipid tubules include conducting polymer [56] and inorganic oxides [53]. Nanotubules from cellular cytoskeletons have also been used for electroless deposition of metals [57]. 

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