PRODUCTION OF SO2F2, SOF4, (SOF2+SF4), S2F10, S2OF10 AND S2O2F10 IN SF6 AND (50-50) SF6-CF4 MIXTURES EXPOSED TO NEGATIVE CORONAS

摘要

This study concerns the production of SO2F2, SOF4, (SOF2 + SF4), S2F10, S2OF10 and S2O2F10 when SF6 is subjected to negative polarity corona discharges of varying durations (with transported charges of 1.5, 4 and 6 C) performed with a point-to-plane set-up using a stainless steel or aluminium plane electrode. During the experiments, the parameters varied were the way the measurement cell was prepared (clean and very clean), the SF6 pressure (50 to 400 kPa), the concentration of additives such as CF4 (0 to 50%) for total gas pressures of 200 kPa and 300 kPa, water (0 to 0.2%) and oxygen (0 to 1%) for a total pressure of 300 kPa. Analyses were carried out using gas phase chromatography. The mode of preparation of the cell proved to be representative of the action of impurities such as water and oxygen on each of the compounds studied. This effect was all the stronger when the SF6 pressure was low, In the very clean conditions (effect of H2O and O-2 reduced to a minimum) we observed a decrease of the quantities of the main products formed as the SF6 pressure or the percentage of CF4 was increased. Concerning the effect of the small quantities of added water and oxygen studied in both pure SF6 and in the 50-50 SF6-CF4 mixture, the results showed that, overall, the oxygen and the water enhance the production of ail the sulphur oxyfluorides from the SF6 fragments (except for SOF2 which is inhibited by oxygen to the benefit of SOF4) and inhibit the production of S2F10. The presence of 50% CF4, a fluorine source, inhibited the production of all the compounds studied independently of the transported charge, the metal used for the plane electrode and the percentages of impurities (H2O, O-2) added. [References: 24]