Silver etching

GP 2] [R 2] A comparative study with laser-LIGA OAOR silver, etched OAOR silver and sawn Aluchrom catalyst was reported (Table 3.2) [4]. The selectivity was 44-69% (laser-LIGA OAOR silver), 38-69% (etched OAOR silver) and 42-58% (sawn Aluchrom catalyst) for details of the experimental protocols, see [4]. The conversions were 2-15% (laser-LIGA OAOR silver) 5-20% (etched OAOR silver), and 2-6% (sawn Aluchrom catalyst). The space-hme yields were 0.01-0.07 t h m (laser-LIGA OAOR silver), 0.03-0.13 t h m (etched OAOR silver), and 0.01-0.061 h m (sawn Aluchrom catalyst). 

Hondros and Moore (22) also found that heating under vacuum or in nitrogen did not lead to the formation of facets. The latter produced smooth surfaces, and the former led to pit formation. From these data and the studies of earlier workers, the authors concluded that the mechanism of silver etching is the preferential evaporation of silver oxide from certain surface planes. 

Minor and potential new uses include flue-gas desulfurization (44,45), silver-cleaning formulations (46), thermal-energy storage (47), cyanide antidote (48), cement additive (49), aluminum-etching solutions (50), removal of nitrogen dioxide from flue gas (51), concrete-set accelerator (52), stabilizer for acrylamide polymers (53), extreme pressure additives for lubricants (54), multiple-use heating pads (55), in soap and shampoo compositions (56), and as a flame retardant in polycarbonate compositions (57). Moreover, precious metals can be recovered from difficult ores using thiosulfates (58). Use of thiosulfates avoids the environmentally hazardous cyanides. 

Fig. 9. Corrosion model of silver development. As the haUde ion, X, is removed into solution at the etch pit, the silver ion,, travels interstitiaHy, Ag/ to the site of the latent image where it is converted to silver metal by reaction with the color developer, Dev. Dev represents oxidized developer.

Chemical reduction is used extensively nowadays for the deposition of nickel or copper as the first stage in the electroplating of plastics. The most widely used plastic as a basis for electroplating is acrylonitrile-butadiene-styrene co-polymer (ABS). Immersion of the plastic in a chromic acid-sulphuric acid mixture causes the butadiene particles to be attacked and oxidised, whilst making the material hydrophilic at the same time. The activation process which follows is necessary to enable the subsequent electroless nickel or copper to be deposited, since this will only take place in the presence of certain catalytic metals (especially silver and palladium), which are adsorbed on to the surface of the plastic. The adsorbed metallic film is produced by a prior immersion in a stannous chloride solution, which reduces the palladium or silver ions to the metallic state. The solutions mostly employed are acid palladium chloride or ammoniacal silver nitrate. The etched plastic can also be immersed first in acidified palladium chloride and then in an alkylamine borane, which likewise form metallic palladium catalytic nuclei. Colloidal copper catalysts are of some interest, as they are cheaper and are also claimed to promote better coverage of electroless copper. 

GP 2] [R 2] The smooth surface of the laser-LIGA OAOR silver is roughened and pitted after OAOR treatment and used during more than 1000 h of ethylene oxide synthesis [4]. The etched OAOR silver shows pronounced sintering and agglomeration for the same type of treatment. 

In order to silver Dewar flasks the jacket is cleaned and filled about two thirds full with the prepared solution. The Dewar should be rolled or shaken during the severing. The end-point is determined by occasionally pouring out a little of the solution, and when a flocculent precipitate is formed the solution should be removed from the flask as quickly as possible to prevent blooming. The flask is then cleaned and dried. If the glass is first etched with a dilute solution (about 0-7 molar) of hydrofluoric acid before its final cleaning, the... 

Burdinski, D. Brans, H. J. A. Deere, M. M. J. 2005. Single etch patterning of stacked silver and molybdenum alloy layers on glass using microcontact wave printing. I. Amer. Chem. Soc. 127 10786-10787. 

Silver nitrate is probably the most important silver salt. It is used to make most silver salts. It is used in photographic film, indelible ink, and hair dyeing. Other uses are in making silver mirrors, etching ivory, and as a catalyst... 

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