Thermal plasma synthesis

I. Mohai, J. Szepvolgyi, I. Bertoti, M. Mohai, J. Gubicza, T. Ungar, Thermal plasma synthesis of zinc ferrite nanopowders, Solid State Ionics 141-142 (2001) 163-168. 

Thermal Plasma Synthesis of Reactive Mixtures for Production of Vinyl Chloride... 

Non-Thermal Plasma Synthesis of Aldehydes, Alcohols, and Organic Acids in Mixtures of Carbon Oxides with Hydrogen Organic Synthesis in CO2-H2O Mixture... 

Non-Thermal Plasma Synthesis of Formic Acid in CO2-H2O Mixture. Determine the minimum energy efficiency of the plasma-chemical HCOOH synthesis in the CO2-H2O mixture (9-60) required for effective hydrogen production in the double-step cycle (9-60) and (9-61). Assume that thermodynamically about 70% of the total energy required for hydrogen production from water should be consumed in this case for decomposition of formic acid (9-61) to form hydrogen and to recycle carbon dioxide back to the plasma process. 

Thermal plasma synthesis has been used to make colloidal scale and nanoscale aerosol particles. The high temperature and inert atmosphere of the plasma enable the synthesis of materials that cannot be made in flame reactors (see, for example. Reference [46]). 

The methane conversion and hydrogen yield were investigated as a function of with respect to methane flow rate and both of the two were very high more than 90%. Particle size and sinface area of synthesized carbon were strongly dependent on methane flow rate. Hydrogen produced finm thermal plasma can be applied to fuel cell due to its high purity and carbon black can be applied for the synthesis of rubber industry. 

It could be concluded that thermal plasma process for methane decomposition is very effective for the production of high purity of the hydrogen as well as synthesis of the carbon black. 

Simplified schematics of a thermal plasma reformer for the production of synthesis gas from hydrocarbons. 1 = Anode, 2 = cathode, 3 = discharge, and 4 = insulator. 

Continuous production of fullerenes was possible by pyrolysis of acetylene vapor in a radio-frequency induction heated cylinder of glassy polymeric carbon having multiple holes through which the gas mixture passes [44]. Fullerene production is seen at temperatures not exceeding 1500 K. The yield of fullerenes, however, generated by this method is less than 1%. A more efficient synthesis (up to 4.1% yield) was carried out in an inductively coupled radio-frequency thermal plasma reactor [45]. 

Plasma methods. Plasmas are discharges in a low-pressure gas environment (0.01-0.02 Pa), that can be used for the direct synthesis of fine powders, or for the deposition of coatings.63,64 Two major types of plasmas are used in materials processing.65 In thermal plasmas (equilibrium, high-temperature, or plasma torch) electrons and gas molecules are at comparable temperatures, which are typically thousands of degrees. Solid... 

Contrary to the above mentioned technologies, which are based on arc plasma furnaces, a radiofrequency (RF) plasma system can process fine powders without granulation in a continuous operation. This possibility, together with the advantageous features of the thermal plasmas mentioned above, offer great perspectives for the synthesis of special ceramic powders such as spinel ferrites [5]. The RF plasma treatment produces nanosized metal and/or oxide powders depending on the parameters of processing. In this paper application of an RF thermal plasma system for the treat-... 

The top-down approach starts with a bulk material and attempts to break it down into nanoscaled materials through physical methods. Hence, most of these techniques are really forms of fabrication rather than synthesis. For nanostructured bulk phases, including powders, the common methods are milling, devitrification of metallic glass, and severe plastic deformation. For nanocrystalline thin films (films with nanosized crystallites), methods include thermal vaporization (under high vacuum), laser ablation, and sputtering (thermal plasma), all of which were... 

Figure 2. Schematic diagram of various CVD techniques for diamond synthesis, (a) HFCVD (b) MW PACVD (c) ECR MW PACVD (d) DC PACVD (e) RF PACVD (0 DC thermal plasma CVD (g) RF thermal plasma CVD (h) flame (combustion) CVD.l (Reproduced with permission.)...

The low temperature synthesis of diamond films has been investigated in the substrate temperature range of 350-800°C in RF thermal plasma CVD, and diamond films of reasonable quality have been obtained at 550-600°C which are considerably lower than those generally considered as... 

A. Dissociation of molecular oxygen. This process is mostly investigated in strongly nonequilibrium atmospheric-pressure plasma conditions in relation to ozone synthesis (Section 6.5). Here we discuss the characteristics of thermal plasma decomposition of molecular... 

Mechanisms of NO Synthesis Provided in Non-Thermal Plasma by Excitation of Neutral Molecules Zeldovich Mechanism... 

N2 dissociation in non-thermal plasma has been discussed in Section 5.11.4. The rate coefficients of the process (6-5) are shown in Fig. 6-2 as a function of electron temperature for the cases of dissociation by direct electron impact from the ground state as well as stepwise dissociation through the electronic excitation sequence. The dissociation rate coefficient can reached = 10 "cm satTe = leV. After dissociation of N2, NO synthesis takes place in the exothermic reaction (6-3). The energy efficiency of NO synthesis through... 

The rate coefficient of the recombination (6-6) is kf 10 cm /s at electron temperature Te = 1 eV. After formation of atomic nitrogen, NO synthesis takes place in the exothermic reaction (6-3). Nj ions in non-thermal plasmas at elevated pressures have a tendency to form complex ions Nj N2 (or N4 see Fridman Keimedy, 2004), which decreases the yield of N atoms in the recombination. 

The energy cost of NO generation varies between different plasma-chemical mechanisms. The energy efficiency of NO synthesis in thermal plasma is not high and is limited by three major factors ... 

Stability of Products of Plasma-Chemical Synthesis to Reverse Reactions in Active Zone of Non-Thermal Plasma... 

Protection of products from active species in the active plasma zone seriously restricts the yield of non-thermal plasma-chemical NO synthesis. The most important fast barrierless reverse reaction, leading to destraction of NO inside the active discharge zone, is... 

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