Droplet generation metal

This section describes the atomization processes and techniques for metal droplet generation. Advantages and drawbacks of the atomization systems are discussed along with typical ranges of operation conditions, design characteristics, and actual and potential applications. Commonly used atomization media and their thermophysical properties are also included. 

Ultrasonic atomization is sometimes also termed capillary-wave atomization. In its most common form, 142 a thin film of a molten metal is atomized by the vibrations of the surface on which it flows. Standing waves are induced in the thin film by an oscillator that vibrates vertically to the film surface at ultrasonic frequencies. The liquid metal film is broken up at the antinodes along the surface into fine droplets once the amplitude of the capillary wave exceeds a certain value. The most-frequent diameter of the droplets generated is approximately one fourth of the wavelength of the capillary wave,1 421 and thus decreases with increasing frequency. 

Many hypotheses for initiation of liquid expls have been proposed, of which Bowden et al (Refs 13, 14a 27) suggested adiabatic compression of gas bubbles Johansson et al (Ref 28) - vapor or droplet burning Andreev (Ref 29) - droplet formation or suspension behind a burning front is capable of causing a transition to detonation Bolkhovitinov (Ref 33a) - crystallization of the material under pressure Cook et al (Ref 34b) - initiation occurs with the development of a pressure-generated metallic state accompanied by a plasma that provides the postulated requirement of high heat conductivity... 

There are many liquids capable of rapidly generating a solid product, when their droplets dispersed in an inert gas are contacted with a vapor coreactant. Such compounds include metal alkoxides, halides, and oxyhalides that react with water, hydrogen sulfide, etc., and organic monomers that can undergo either addition or condensation polymerization in the presence of appropriate initiators. The resulting powders consist of spherical particles, the size distribution of which depends on the method and conditions of droplet generation. 

In the present section, we restrict ourselves to the version of droplet generators working with (mostly metal) nozzle plates carrying the orifice hole(s). The design of the nozzle plate concerns both the diameter and the shape of the... 

It may be assumed that the mean diameter of molten metal droplets generated in the presence of bubbles is also predicted by (6.21). Furthermore, the following... 

The experimental apparatus and fluids used as models for molten metal and slag are the same as those described in Sect. 6.2. When the air flow rate is relatively high, a number of small metal droplets that later accumulated at the slag-metal interface are generated, as shown schematically in Fig. 6.1. Droplet generation ceases below a certain critical air flow rate. 

This process uses a moving laser beam, directed by a computer, to prepare the model. The model is made up of layers having thicknesses about 0.005-0.020 in. (0.012-0.50 mm) that are polymerized into a solid product. Advanced techniques also provides fast manufacturing of precision molds (152). An example is the MIT three-dimensional printing (3DP) in which a 3-D metal mold (die, etc.) is created layer by layer using powdered metal (300- or 400-series stainless steel, tool steel, bronze, nickel alloys, titanium, etc.). Each layer is inkjet-printed with a plastic binder. The print head generates and deposits micron-sized droplets of a proprietary water-based plastic that binds the powder together. 

White P, either in bulk or in soln, is a good example of the burning type of smoke generator. The resulting colloidal suspension of P pentoxide is quickly hydrolyzed by moisture to become phosphoric acid droplets which are the actual visible constituent of the smoke. Various other burning type smoke generators exist such as those used for signaling purposes and which use red P, metallic phosphides, or P trichloride as the source of the particulate cloud... 

A water droplet on an iron surface is a miniature electrochemical cell that corrodes iron metal and generates iron oxide (rust). 

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