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• C 5 F 10 O starts to decompose at 500 ℃ and CO 2 , C 3 F 6 , and C 4 F 10 are dominant by-products. • A unique by-products C 2 F 6 O 3 is produced under partial discharge in C 5 F 10 O-air mixture. • Decomposition products CF 4 , C 3 F 6 , CF 2 O, CHF 3 , and C 3 HF 7 have good compatibility with Al (1 1 1) and Cu (1 1 1) surfaces. • The O atoms in C 2 F 6 O 3 show strong reaction activity with Al (1 1 1) and Cu (1 1 1) surfaces. Perfluoroketone C 5 F 10 O has drawn much attention in recent years as a promising environmental-friendly gas to substitute SF 6 in power equipment. In this paper, the decomposition characteristics of C 5 F 10 O and C 5 F 10 O/air mixture under pyrolysis and partial discharge conditions were explored by experiments using a gas chromatography/mass spectrometer. Besides, the compatibility of decomposition products with the copper and aluminum was evaluated based on the density functional theory calculation. We found that C 5 F 10 O has good thermal stability at 300 ℃. At 500 ℃, C 5 F 10 O starts to decompose and it produces CO, CO 2 , C 2 F 6 , C 2 F 4 , C 3 F 8 , C 3 F 6 , C 4 F 10 , C 4 F 8 and CHF 3 , among which CO 2 , C 3 F 6 , and C 4 F 10 are dominant. For C 5 F 10 O/air mixtures, the pyrolysis products are mainly saturated fluorocarbons and more CO 2 is produced. Partial discharges in C 5 F 10 O/air mixture mainly produce CO 2 , saturated fluorocarbons and a unique compound C 3 F 6 O 3. It is found that CF 4 , C 3 F 6 , CF 2 O, CHF 3 , and C 3 HF 7 have good compatibility with Al (1 1 1) and Cu (1 1 1) surfaces, while the interactions between C 2 F 6 O 3 and Al (1 1 1), Cu (1 1 1) surfaces are relatively strong, which are chemisorption. The identified by-products of C 5 F 10 O and C 5 F 10 O/air mixture under different conditions as well as their compatibility with metal materials is essential for online fault-diagnostic and long-term maintenance in engineering applications. [ABSTRACT FROM AUTHOR]

• The interaction of C 4 F 7 N with α-Al 2 O 3 (0001) surface belongs to chemisorption. • The dissociation of C 4 F 7 N on α-Al 2 O 3 surface is difficult to occur. • C 4 F 7 N and α-Al 2 O 3 shows good thermal compatibility below 170 ℃. • The α-Al 2 O 3 -based materials can be used as insulators in C 4 F 7 N-filled electrical equipment. In this paper, the compatibility between C 4 F 7 N and α-Al 2 O 3 (0001) surface has been evaluated based on the density functional theory (DFT). The adsorption energy, total charge transfer, states analysis, and electron density difference were obtained to analyze the interaction behavior of C 4 F 7 N on α-Al 2 O 3 (0001) surface. The results demonstrated a chemisorption between C 4 F 7 N and α-Al 2 O 3 (0001) surface. Moreover, the pathway of C 4 F 7 N dissociated on α-Al 2 O 3 (0001) surface after the adsorption was determined. However, the activation energy required for the dissociation is too large to achieve, which means that the dissociation of C 4 F 7 N on α-Al 2 O 3 surface is difficult to occur. Additionally, the thermal compatibility between α-Al 2 O 3 and C 4 F 7 N were verified by experiments, which shows a certain compatibility between C 4 F 7 N and α-Al 2 O 3 (0001) under up to 170 ℃. The results demonstrate that α-Al 2 O 3 -based materials can be used as insulators in C 4 F 7 N-filled electrical equipment. [ABSTRACT FROM AUTHOR]