Sulfur hexafluoride (SF6) is commonly used as an insulation gas for electrical equipment due to its non-toxic and non-flammable properties. However, SF6 is also a greenhouse gas with a very high global warming potential, and there is a need for an environmentally friendly alternative. Chen et al. computationally and experimentally studied the decomposition of C4F7N, which has good insulation properties, with the potential to replace SF6.

“Many engineering-oriented tests have been performed on the technical performance of these gases, and some of them have been successfully used in pilot projects,” said author Boya Zhang. “However, the power industry remains cautiously optimistic about their large-scale applications, particularly because some critical fundamental physicochemical properties for these relatively novel compounds are still poorly understood and need further investigation.”

To help realize the practical limitations of C4F7N, the authors identified six potential decomposition pathways – some of which lead to the same stable products or reform C4F7N itself. The presence of ions allows for recombination to occur, further complicating the process. Luckily, the authors say the byproducts occur in very small amounts and often have good insulation strength, so the decomposition pathway should have little impact on insulation performance.

The authors also conducted density functional theory calculations and verified the theoretical results with a partial discharge experiment.

Some of C4F7N’s properties require additional study before it can be used in practical applications. There are lingering questions that need to be answered by future research, such as its decomposition from overheating or breakdown, its compatibility with other component materials and its arc quenching behaviors.

Source: “Decomposition pathway of C4F7N gas considering the participation of ions,” by Li Chen, Boya Zhang, Xingwen Li, and Tao Yang, Journal of Applied Physics (2020). The article can be accessed at