Influence of Oxygen on the Thermal Decomposition Properties of C(4)F(7)N–N(2)–O(2) as an Eco-Friendly Gas Insulating Medium

[Image: see text] The C(4)F(7)N (fluorinated nitrile) gas mixture has been recognized as the most potential substitute gas to SF(6) used in gas-insulated equipment. In this paper, we explored the thermal stability and decomposition properties of the C(4)F(7)N–N(2)–O(2) gas mixture. The influence mechanism of oxygen content and temperature on the byproduct generation was obtained and analyzed. It was found that thermal decomposition of the C(4)F(7)N–N(2)–O(2) gas mixture mainly produces CO, C(3)F(6), C(3)F(8), CF(3)CN, (CN)(2), and COF(2). The addition of oxygen could accelerate the decomposition of C(4)F(7)N. The content of C(3)F(6) and (CN)(2) decreases, while the yield of CF(4), CO, C(3)F(8), and COF(2) increases with the oxygen content. Thermal decomposition of the C(4)F(7)N–N(2)–O(2) gas mixture at temperatures lower than 425 °C results from the interaction between C(4)F(7)N and the metal heating element, while the bond cleavage reactions occur at higher temperature. As for engineering application, the oxygen added in the 6%C(4)F(7)N–94%N(2) gas mixture should not exceed 6% to avoid the negative effect of oxygen on the thermal stability of C(4)F(7)N.