US EPA

6588346 

Journal Article 

Spark decomposition of SF6 and SF6+50% CF4 mixtures 

Pradayrol, C; Casanovas, AM; Hernoune, A; Casanovas, J; , 

1996 

Yes 

Journal of Physics D: Applied Physics
ISSN: 0022-3727
EISSN: 1361-6463 

IOP PUBLISHING LTD 

BRISTOL 

29 

7 

1941-1951 

10.1088/0022-3727/29/7/031 

WOS:A1996UZ48500031 

The spark decomposition of SF6 and of SF6 + 50% CF4 mixtures was studied principally at a gas pressure of 200 kPa. The sparks were generated between a point and a plane either under 50 Hz ac voltage (0.09 J per spark) or by discharging a capacitor (3.59 J per spark). Our attention was only focused on the gaseous SF6 by-products: SOF2 + SF4, SOF4, SO2F2, S2F10, S2OF10, S2O2F10 and S2O3F6 which were assayed by gas chromatography. The last three compounds were principally observed under the higher energy sparks. Their yields were studied varying the cell preparation technique, the metal constituting the plane electrode (aluminium, copper, stainless steel) and the concentrations of two additives, O-2 (between 0 and 1%) and H2O (between 0 and 0.2%). The cell preparation procedure had a strong effect on the formation of all products except SOF2; the S2F10 yield was for example multiplied by similar or equal to 17 when the cell was carefully dried and outgassed and with an aluminium electrode. The aluminium led, whatever the procedure used, to the highest levels of products.Under the high-energy sparks an increase of the oxygen content of SF6 or of the SF6-CF4 mixture led to a decrease of the SOF2 + SF4 and S2F10 formation rates and to an increase of that of the other compounds. An increase of the H2O content had very little effect on SOF2 + SF4 production and led to increased production of S2OF10 and SO2F2 + SOF4 and to a lowering of the formation of other compounds. Under the low-energy sparks the addition of O-2 to SF6 or to the SF6-CF4 mixture led to a lowering of the SOF2 + SF4 and S2F10 yields like under high-energy sparks and to an increase of S2OF10 (which became observable) and of SO2F2 + SOF4. Addition of water resulted in an increase of the SOF2 + SF4 and SO2F2 + SOF4 yields, in a lowering of S2F10 and had no effect on S2OF10 which remained unobservable. Finally it should be noted that the addition of 50% of CF4 to the SF6 had very little effect on the rates of formation of the gaseous SF6 by-products except under low-energy sparks where the SF6-SF4 mixture led to lower production rates for SOF2 + (SF4) and S2F10.