Melting plasma flame

Plasma Discharge. The low-voltage and high-current-density process in plasma gas is often called arc plasma or hot plasma. A high-power ion beam formed in the plasma flame hits the target substances to heat them to several thousand kelvins, which is enough to melt all solid materials. Under the inert gas flow, the vaporized... 

Temperatures above 1800°C would be required to contain a fiber forming silica melt in a bushing. A requirement like this would by far exceed the practical capability of most precious metal and/or other practical alloy materials. As a result, pure silica glass fibers are downdrawn from solid silica preform rods (Figure 14). Gas flame or electrical furnaces soften the ends of the quartz rods, and thereby facilitate the formation of continuous silica fibers. Preforms made from natural silica contain 99.99% Si02 and impurities include 20-50 ppm Al, <5 ppm OH", and <4 ppm Na. Preforms made by oxidation of SiCl4 in a plasma flame [60] afford even purer silica fibers (<1 ppm Al, <0.1 ppm OH, <1 ppm Na, and <50 ppm Cl). 

Flame spray n. Any process whereby a material is brought to its melting point and sprayed onto a surface to produce a coating. The process includes (1) Metallizing. (2) Thermospray. (3) Plasma flame. 

Hydroxyapatite has been coated on metaUic dental and orthopedic implants by high-temperature plasma thermal spray since the 1980s [24,25]. In this process, HA powders are fed into a plasma flame (temperature 5,000 to 15,000°C). The powders are quickly melted and quenched on the metallic implant substrate to... 

Transparent Vitreous Silica. Clear, transparent, bubble-free vitreous sihca may be obtained by melting natural quart2 minerals, ie, fused quart2, by flame or plasma vapor deposition (synthetic fused siUcas), and by sol—gel processing. 

Transparent vitreous sihca is made by electric melting of natural quartz minerals such as sand in vacuum. It also may be made by fusing quartz in flame or by vapor phase hydrolysis or oxidation of pure silicon compounds by heating electrically or using a flame or plasma. Translucent form is made by fusion of high purity quartz sand crystals. 

In the Verneuil method, the powdered sample is melted in a high temperature, oxy-hydrogen flame and droplets allowed to fall on to a seed crystal where they crystallize. This is an old method used originally to produce artificial ruby. Using the same method but using a plasma torch to melt the powder, can achieve even higher temperatures. 

The highest melting material that can be grown by the flame fusion method is determined by the maximum temperature of the flame. A plasma torch may be used as an alternative heat source for materials that decompose in a hydrogen-oxygen or coal gas-oxygen flame. 

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