3 March 1995 Reduction of aluminum, silicon, and boron oxides in a carbon plasma of pulsed-power microwave discharge
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The high stability of aluminum, silicon and boron oxides is well known. A thermodynamic analysis of usual reactions of a carbon reduction of these oxides indicates that a degree of their conversion is quite low: for example, less than 0.3% for the alumina reduction at temperatures approximately equals 1900 K. On the other hand, a high efficiency of plasma-chemical processes and advantages of the user of microwave produced plasmas for materials processing are not a secret too. It was very interesting, from this viewpoint, to conduct mentioned reactions in a plasma of the pulsed power microwave (PPMW) discharge. Experiments were carried out in the focal zone of a focused PPMW beam at intensities up to 5 X 104 MW/cm2 (wavelength - 4 cm, pulse duration - 1...1000 microsecond(s) , repetition rate - 10 Hz). Quartz retorts containing powdered mixtures of outlined oxides with stoichiometric quantities of a carbon-black were pumped down to initial pressures of approximately equals 1 Torr. During the plasma treatment the pressure inside retorts grew and reached values of 100-200 Torr. After that retorts were pumped down again, and the process was continued. The total time of powders processing was of 20-60 min, and the samples' temperatures did not exceed 1300 K. Thus, for example, at the time of reduction of mixtures Al2O3 + C in amounts of 2 g, about 0.3 'normal' liters of gases were evolved, that corresponds to approximately equals 30% degree of the alumina conversion. Simultaneously, a strong influence of the steamer-like PPMW discharge in the atmosphere outside retorts on the reduction process was observed. Obviously, the reactions proceed at a higher rate due to the inducing role of a intense UV- radiation of such discharges. It is an important practical result too.
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Alexander A. Ravaev, Alexander A. Ravaev, Iskander K. Tagirov, Iskander K. Tagirov, Pavel S. Chernyshev, Pavel S. Chernyshev, } "Reduction of aluminum, silicon, and boron oxides in a carbon plasma of pulsed-power microwave discharge", Proc. SPIE 2374, Novel Applications of Lasers and Pulsed Power, (3 March 1995); doi: 10.1117/12.205005; https://doi.org/10.1117/12.205005

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