Melt atomization

Spherical particles proved to be superior in several applications owing to their favorable properties. Thus, they are used in thermal spraying for their excellent flowabil-ity, in powder metallurgy because of their excellent reproducibility in manufacturing parts with controlled porosity and as a filler material, as well. Metal microspheres can be easily produced by melt atomization. Similar method in the case of ceramics is impractical. Micron-sized ceramic particles, however, can be smelted by thermal plasmas that provide exceptional conditions for spheroidization due to its high temperature. In terms of purity and residence time of the particles in the hot temperature core, RF plasmas provide better conditions as compared to arc plasmas. 

The processing and surface preparation of silver particles is critical to their performance as a filler. The first step in manufacturing silver flakes is to produce silver powder. Powdered silver may be produced by chemical precipitation, electrolytic precipitation, or melt atomization. Most commercially available silver powders are precipitated by reducing silver from a silver nitrate solution. Particle sizes of powdered silver range from submicron to 5 pm." Silver powders are selected based on size and... 

Salmaso, S., Elvassore, N., Bertucco, A., and Caliceti, P Production of solid lipid submicron particles for protein delivery using a novel supercritical gas-assisted melting atomization process. Journal of... 

Abstract The science and technology underlying the process of melt atomization is introduced, paying particular attention to relevant thermal, solidification and other transport phenomena. Melt atomization has now been developed as one of major produce methods for various metal and alloy powder, and hence it is of both scientific and technological interest. The mechanisms of melt disintegration, the design of typical atomization devices, the influence of key process parameters, the thermal transport in the atomized droplets, and the characteristics of the size distribution are briefly described and discussed. 

The melt atomization is generally referred to as two-phase atomization (or twin fluid atomization). The fluid being atomized is typically a molten metal, while a secondary fluid is used as the atomization media to break-up the molten metal into droplets. During atomization, jets of the secondary fluid are formed and accelerated using a stream injector. These jets are then focused onto a stream of molten metal to promote disintegration. 

Melt atomization processes can be classified into various categories, according to the physical properties and flow characteristics of the atomization fluid water atomization, oil atomization, and gas atomization. Gas atomization can be further classified into subsonic gas atomization, supersonic gas atomization, and ultrasonic gas atomization. The considerations in selecting a particular melt atomization method include economic factors, production scale, the physical and chemical properties of fluid to be atomized and powder to be produced, and the morphology of the powder desired [3, 5]. 

In summary, melt atomization is a primary and widely used powder metallurgy process, in which an alloy melt jet is energetically disintegrated into micrometersized powders under a controlled environment and non-equihbrium thermal and solidification conditions. It is widely used to produce a variety of powders from almost any metal. 

In more efficiently designed and operated sulfur burners such as those used in the paper industry and in the manufacture of sulfuric acid (Shreve, 1944), the sulfur is melted, atomized in compressed air, and burnt in a separate combustion chamber. In these burners gas of a constant composition, 19-20 volume per cent SOa, without any sublimation and with only 0.14% of the sulfur transformed into SOs, can be obtained. Sulfur dioxide is a colorless gas having a characteristic odor, a normal molecular volume of 21.89 1., and a molecular weight of 64.06 g. It is soluble to the extent of 36.4 volumes in one volume of water at 20° C. Its solubility in water decreases from 8.6% by weight at 20° C. to 0.1% at 100° C. At atmospheric pressure SO2 liquefies at —10° C. at 20° C. liquid SO2 exerts a pressure of 3.25 atm. or 40.6 p.s.i. The solubility of sulfur dioxide in water has been determined accurately by Beuschlein and... 

Czisch, C., Fritsching, U. (2008). Atomizer design for viscous-melt atomization. Materials... 

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