Rf plasma torch

Ultrafme refractory carbide and nitride powders can be produced in an inductively coupled radio-frequency (rf) plasma torch.a schematic drawing of a plasma torch for the production of silicon carbide powder is shown in Fig. 14.1. 

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RF-Plasma Torch Reactor. A diagram of a radiofrequency (RF) plasma torch reactor (25) is shown in Figure 8.1.3. The apparatus consists of an RF-plasma reactor with frequency of 4.0 MHz, a powder feeder, a gas supply system, and an exhaust system. The torch is composed of a work coil and three concentric quartz tubes for three independent gas flows outer, inner, and center carrier gas flows. For TiN UFPs synthesis, N2 is added to the outer flow of Ar, and titanium powder sieved in advance to a size less than 25 p.m is fed into the plasma by the carrier gas of Ar... 

Table 8.1.5 Processing Conditions for the Synthesis of Silicon Nitride UFPs by an Inductively Coupled RF-Plasma Torch Reactor...

Miller and Ayen (40) investigated the hydrogen reduction of titanium tetrachloride in an RF plasma torch. They obtained conversions of TiCl4 to TiClg of between 60 and 80%, at feed rates of 1.5... 

From additional calculations of the thermodynamics of the SiCl4 decomposition, Vurzel and Polak predicted that the decomposition would be favored by reducing conditions and confirmed this experimentally, obtaining high-purity silicon by use of an RF plasma torch. 

Salinger (44) reported the successful conversion of methyltrichloro-silanes to silicon carbide in a 50-kW RF plasma torch. The liquid methyltrichlorosilanes were fed to the tail flame of various plasmas and the solid products were recovered in an acid-resistant bag filter. Up to 85% recovery of theoretical solid product was reported, which was subsequently heated at 500°C to remove elemental carbon. Under the best condition (20-25% vol. hydrogen in argon plasma at 36 kW), up to 70%o conversion to j3-SiC was obtained with ca. 10% conversion to amorphous SiC. Salinger suggested that the good crystallinity of the )3-SiC so obtained meant that the reaction occurred in a gas temperature range in which )3-SiC was the stable crystalline form (i.e., < 2300°C). 

Figure 4-63. Schematic of kilowatt power level inductively coupled radio-frequency (ICP-RF) plasma torch.

Fig. 23a. Torch geometry and system of coordinates, b Stream lines and c temperature fields in a RF plasma torch working with argon. Reprinted from...

Powder Chemical preparation Vapor-ph e chemical reaction RF-plasma torch Sol-gel Self-propagating high-temperature synthesis... 

High-quality powders of refractory carbides and nitrides can be obtained by the more recent processing techniques of chemical-vapor deposition (CVD), RF-plasma torch, combustion synthesis, and sol-gel.l H l... 

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