Gas sensor based on micro fiber coated with carboxylated carbon nanotubes to detect new environmentally friendly insulating gas C4F7N

Abstract

C₄F₇N gas mixtures, due to its high insulation strength and low global warming potential, is gradually replacing SF₆ gas in gas-insulated equipment. To ensure the safe and reliable operation of new C₄F₇N gas mixture insulated equipment, real-time monitoring of the C₄F₇N gas concentration in the equipment is of significant engineering importance. In this paper, a micro fiber coated with carboxylated carbon nanotubes gas detection method based on fiber-loop ring-down (FLRD) technology is presented. Firstly, based on Density Functional Theory (DFT), the study establishes four adsorption systems: C₄F₇N-SWNT, C₄F₇N-SWNT-COOH, O₂-SWNT-COOH, and CO₂-SWNT-COOH, to explore the potential application of carboxyl-functionalized carbon nanotubes as selective adsorbents for C₄F₇N. Subsequently, a FLRD demodulation system was constructed, incorporating a micro fiber coated with carboxylated carbon nanotubes for experimental validation. The results showed that the sensor exhibited selective detection capability for C₄F₇N in the gas mixture. Finally, the detection performance of the FLRD system was analyzed using the least squares method. The results showed that the linear fit between the C₄F₇N gas concentration and the ring-down time had a coefficient of determination (R²) of 0.997, with a maximum relative error of 4.088%. Under a background of 4% C₄F₇N gas mixture, the detection repeatability of the system was 0.00698. The research results provide a theoretical foundation and technical reference for the online monitoring of the new C₄F₇N gas mixture insulated equipment.