Spray techniques

Spray pyrolysis is a method that can be used to obtain a powder with particle size distribution that is narrow and controllable from micrometer to sub-micrometer order [62]. The size of the particles is reduced to 300 nm by a combinatimi of spray pyrolysis with dry ball milling [63]. To decrease the size of the particles down to 150 nm on average, a wet milling is needed, and performed owing to 45 ml zirconia vial, ethanol being used as a medium [64]. 

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Solutions of solids may need to be converted into aerosols by pneumatic or sonic-spraying techniques. After solvent has evaporated from the aerosol droplets, the residual particulate solid matter can be ionized by a plasma torch. 

Two basic methods are used for the appHcation of protective coatings to metal containers, ie, roUer coating and spraying. RoUer coating is used if physical contact is possible, eg, coating of metal in sheet and coil form. Spraying techniques are used if physical contact is not possible, eg, to coat the inside surface of two-piece drawn and ironed can bodies (see Coating processes). 

The speed of the pickle reaction is also dependent on the concentration and temperature of the pickle, the degree of agitation of either the metal part or the pickle solution, the alloy being pickled, and the acid used. Pickling solutions may be appHed by either spray or immersion techniques. However, because of the noxious fumes emitted, there must be adequate ventilation. Sometimes, particularly when spraying techniques are used, an enclosure to contain the fumes and mist is employed. 

Most plastics are now available as powders and can be applied as coatings by fluidized bed or spraying techniques. Nylon 11 and polyethylene have proved most useful for chemical plant applications. 

If the compound being extruded is not attacked by water, for example, conventional butadiene-acrylonitrile based compounds, the preforms are passed through a water cooling system. The water cooling system can be using either the spray technique or complete submersion. 

Flame sprayed molybdenum articles have poor corrosion resistance, no doubt owing to the porosity of the coating. However, modern plasma spraying techniques produce a dense coating and this should lead to more widespread use of clad materials such as molybdenum clad steel where the clad product should have the same corrosion resistance as the solid material. 

The more automatic the method of coating application, the more economical and efficient it is, since automation lends itself more readily to more even coatings than do manual methods, e.g. large surface areas lend themselves more readily to spraying techniques, whereas open work structures are more suitable for dipping methods. The coating should also be applied to a specified minimum thickness which is adequate for the service conditions and life envisaged. 

The vision of the late W E Ballard ensured that this chapter is still very relevant but there have been some changes in emphasis. Of the spraying techniques, the electric arc process is now generally more economical in operation than oxy-fuel gas processes. The rate of spraying is proportional to the current used and several types of equipment are available ranging from 200 to 1 000 A capacity. For manual operation, pistols using currents up to... 

Reininger, H., Further Developments in Metal Spraying Technique , Metalloberfldche, 15, 52, 88, 118, 148 (1961). (Translation available as TM460, Aluminium Federation, Brimingham) Scott, D. J., Aluminium Sprayed Coatings Their Use for the Protection of Aluminium Alloys and Steel , Trans. Inst. Met. Fin., 49 No. 3, 111-122 and 49 No. 4, 173-175 (1971) Sprowl, J. D., Aluminized Steel-A Description, Report of the Department of Metallurgical Research, Kaiser Aluminium and Chemical Corporation, April (1958)... 

A matter of considerable importance in the selection of an application method is its efficiency. Spray techniques are usually inefficient, since many droplets drift past the target and are lost. Even electrostatic spraying can waste as much as 35% of the paint. There is some loss of paint in most methods, but roller coating, curtain coating and electrodeposition are very efficient. Electrodeposition is also a very useful technique where corrosion resistance is important, since it applies a uniform coating over nearly all surfaces of even the most complex-shaped article. 

Thermosetting epoxy and polyurethane chemically-cured liquid resins can provide, among other characteristics, superior abrasion resistance coatings. Solvent-free formulation applied by hot spray techniques can achieve film thicknesses of up to 5 mm. 

They are applied by wet paint spray techniques and have the advantage, over other paint systems, of long-term flexibility. Conventional alkyd systems may have an initial degree of flexibility, but within 12 months outside become rigid and then crack due to thermal expansion and contraction of the substrate. This phenomenon is less likely to occur with a well formulated vinyl solution. 

Corrosion-inhibited petroleum-based waxes deposited from solvent are finding application in both the automotive and aircraft industries for the supplementary protection of hollow sections of the finished product. These waxes are applied by airless or air-assisted pressure-feed spraying techniques... 

Effects due to grain boundaries have been discussed by Chartier et al. [93] with respect to the CdS/polysulfide junction. The photoelectrochemical behavior of polycrystalline CdS layers obtained by the spraying technique was found to be... 

Samples of high area powders and of supported metals may be applied to the CaF2 support plate by a spraying technique, previously described In detall(ll). In Figure 1, we show a half plate design In which a supported metal deposit, produced by H2 reduction of metal Ions held on the support, occupies one half of the plate while the pure support occupies the other half. 

Both DDT and chlordan are used in colorless, odorless, deobase-type solvent DDT in 5% solution and chlordan in 2% solution. The oil solvent is used because it is a nonconductor and because experience has shown that the crystals from a film of oil solvent solution adhere more firmly to the surface sprayed. A pressure-type spray tank, either a hand pump or mechanical source of air pressure, is used, with a special nozzle which gives a fan-shaped nonmisting spray. A special dripless valve is used. Several valves and nozzles which meet these requirements are on the market. The appropriate areas are sprayed with this fan-shaped painting spray stream, so that the surface glistens with the wet film but there is not sufficient quantity to run down. Experience has shown that this will leave approximately 200 mg. of DDT per square foot or an equivalent amount of chlordan. This procedure is recommended by the U. S. Public Health Service in its spraying technique for residences and food establishments treated in its program of spraying DDT only for malaria control. It has not as yet recommended chlordan for this use. Specifications for the sprayer nozzles procedure can be obtained from this source. 

Table VI. The knockdown power of the organofluorine insecticides has been determined principally against members of the Diptera order and by a limited number of workers. There is general agreement that DFDT acts more rapidly than DDT, at least against those species with which they have been compared. Prill 92) found that twice the amount of DFDT compared to DDT was required to give the same knockdown against houseflies when tested by a space spray technique with added pyrethrins. The forced contact method of Fay and Buckner 27) revealed that without added pyrethrins DFDT was a more powerful knockdown agent than DDT.

Atmospheric Low to medium Liquid Corona Spray technique, even... 

Spray-forming, of particulate metal-matrix composites, 16 175 Spray functions, 23 174t Spray impact, 23 197 measurements, 23 194-195 Spraying processes, for sodium carbonate peroxohydrate, 18 412 Spraying techniques, in fluidized-bed encapsulation, 11 541-542 Spray instrumentation, 23 192-195 Spray irrigation... 

The differences in ionisation efficiencies, however, not only result from the use of FIA or LC but, as mentioned before, depend also on the application of the APCI or ESI interface for ionisation. Therefore the application of both API methods, APCI and ESI, is the only way to overcome discrimination problems because of interface type selection. Even the use of the ion spray technique instead of conventional ESI may influence the ionisation efficiency considerably. 

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