Plasma chemical decomposition

The first experiments on the plasma chemical decomposition of fluoride solutions containing tantalum or niobium to obtain tantalum and niobium oxides were reported about fifteen years ago [524]. Subsequent publications were devoted to further development and expansion of the method for other refractory rare metals such as titanium and zirconium [525 - 532]. 

The plasma chemical decomposition method is based on rapid heating, decomposition and hydrolysis of fluoride compounds to obtain powdered oxides following interaction with water. Rakov and Teslenko [533] showed that the following hydrolysis equilibrium... 

Niobium oxide obtained by plasma chemical decomposition is an ultra-fine powder with a specific surface area, as determined by the BET method, of about 20-30 m2/g. The estimated average particle size does not exceed 0.1 pm. 

Additional confirmation of the approach can be found in the fact that mere thermal treatment of powder obtained from fluoride solutions by plasma chemical decomposition at 1000-1200K for 2-3 hours in air brings about a 100-300 fold reduction in fluorine content. Hence, the plasma chemical process and subsequent thermal treatment of the powder enables to obtain final products with fluorine contents as low as 10 2-10 3 % wt. 

Investigations of the plasma chemical decomposition of tantalum-containing fluoride solutions indicated no significant differences in the process and product parameters compared to the corresponding decomposition of niobium-containing fluoride solution [529, 532]. The particle diameter, shape and specific surface area of both niobium oxide and tantalum oxide powders attest to a gas-phase mechanism of the interaction, with sequential condensation and agglomeration of the oxides. 

Phase transition irreversible, 225 order - disorder, 224-228 reversible, 225, 229, Physicochemical properties of ammonium hydrofluoride, 39 deviations from ideal, 149 ideal system, 148 NbF5 and TaFs, 25 niobium containing melts, 150 tantalum containing melts, 151 M5Nb3OFlg, 234-235 Piezoelectric properties, 245-247 Plasma chemical decomposition equipment, 311... 

Plasma-chemical decomposition of water in a double-stage C02 cycle. 

Futamura, S. and Yamamoto, T. Byproduct identification and mechanism detennination in plasma chemical decomposition of trichloroethylene IEEE Trans. Ind. Applicat., 1997, 33.447-453... 

I. I. Plasma-Chemical Decomposition of Hydrogen Halides Example of HBr Dissociation with Formation of Hydrogen and Bromine... 

As discussed earlier, the most effective plasma-chemical decomposition of hydrogen sulfide (10-58) occurs when the process starts with thermal decomposition (10-60) and is followed by sulfur clusterization (10-61) and product separation in a centrifugal field. Consider the kinetics of the process beginning with thermal decomposition (Potapkin et al., 1988). The elementary endothermic reaction initiating the total process (10-58) is the thermal dissociation of hydrogen sulfide ... 

Effect of Additives (CO2, O2, and Hydrocarbons) on Plasma-Chemical Decomposition of H2S... 

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