Selective coatings

Base Metal Finishes. The low cost of base metal finishes obviates selective coating. Electro deposition is used for 0.5—5 p.m thick coatings of tin and tin—lead alloy, usually about 50 wt % Sn, 50 wt % Pb, on electronic connector contacts, on contacts at the edges of printed circuit boards, and on terminals. Sheet copper alloys that have been coated with tin—lead alloy are widely used for contacts that are stamped and then formed into the desired shapes, such as pins having a closed end and sockets. Aluminum connectors that have utility—industrial appHcations are more thickly coated, and hot-dipping in molten tin is common. 

The phosphate concentration in the tailings is upgraded to a level adequate for commercial exploitation through removal of the nonphosphate sand particles by flotation [32], in which the silica solids are selectively coated with an amine and floated off following a slurry dewatering and sulfuric acid treatment step. The commercial quality, kiln-dried phosphate rock product is sold directly as fertilizer, processed to normal superphosphate or triple superphosphate, or burned in electric furnaces to produce elemental phosphorus or phosphoric acid, as described in Section 9.2. 

Selig reported a potentiometric titration method for the analysis of procaine and some other organic cations precipitated by tetraphenylborate [67]. The development of ion selective coated-wire electrodes, and their application in the titration of procaine and other pharmaceutically important substances, was reported [68]. 

Collectors arc chemical reagents that selectively coat the particles to be floated with a water-repellanl surface that will adhere to air bubhlcs. Collectors generally are classified as cationic, anionic, or nonionic. Examples of collectors include the xanlhales, dithiophosphates. thiocarbonilides. and ihionocarbonales, all of which are anionic collectors... 

Figure 10. An hypothetical model for a cyclic water splitting system, based on a semiconductor particle immobilized in a polymerized membrane and having access to both aqueous solutions on each side of the membrane. Specific and selective coating by catalysts leads to simultaneous and separate hydrogen and oxygen generation on each side of the polymerized membrane.

Inherent in the oscillation of any object is the existence of different modes of oscillations and of higher harmonics. In addition to the lateral modes there is also the torsional mode. All modes can be detected in the x-y-directions by the PSD (Fig. 4.22). In the case of resonant cantilevers, the different modes have different mass sensitivity (Kim et al., 2001). They are well separated on the amplitude spectrum (Fig. 4.24), and show different sensitivities to absorption of vapors into the selective coating applied to the cantilever (Fig. 4.25). 

Figure 3.36 Apparatus to make composite hollow fiber membranes by coating a hollow fiber support membrane with a thin selective coating [105]...

Another way to improve on the solar energy efficiency w is to apply selective coating on the converter s absorbing and emitting surface. These coatings... 

FIGURE 3.6 A neutral (TRITC-Arg A and D), a singly charged anion (TRITC-Gly B and E), or a doubly charged anion (TRITC-Asp C and F) is continuously electrophoresed. Preferential transport of anions into the field-free channel (ff) at a tee intersection. The electro-osmotic velocity in the side or ground channel (g) has been reduced relative to that in the separation channel (sep) by selectively coating the ground channel with a viscous polymer [387]. Reprinted with permission from the American Chemical Society. 

The selectivity of the sensor is determined by the efficiency of the coating material. Developing selective coatings is an ongoing research area. Figure 3 shows a useful metric for sensor performance called the receiver operating characteristic (ROC) curve [16]. 

To be used in an array, the coatings will have to be selected by testing out many different candidate coatings. We have tested each selective coating individually to characterize... 

In both shielding and decorative work demand has been growing for processes that will coat only selected parts of a component. For shielding usually it is only necessary to coat one surface (the inside) and any additional coating just adds to cost. Also, when an outer surface is coated there may be difficulty over the external colour finish—problems, say, over adhesion of paint to metallic film. Un-metallized plastics are comparatively easy to paint and if the outer surface is natural it either may be left like that or painted without trouble. For decorative applications selective coating can be helpful for visual effects—as an example, by contrast between bright nickel-chromium and matt black surfaces. 

Acetylcholineesterase Enzyme was covalently immobilized on a bovine serum albumin-modified H +-selective coated wire electrode. The sensor was used in 5mM phosphate buffer pH 7 at 30°C. The response time was 3-10 min for O.l-lOmM ACh. pH change of 6-8 had little effect. Coefficient of variation was 5.7 and 5.8%. [72]... 

An attractive feature of acoustic-wave-based chemical sensors is that they impose relatively few constraints on the materials that can be used as chemically selective coatings. In brief, the film must be uniform, adherent, thin, chemically and physically stable when in contact with its working medium (gas or liquid), and it must not electrically short-circuit the IDTs. 

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