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Gas sensors are the key equipment in transformer fault online monitoring systems, and developing new and efficient gas sensing materials is an important prerequisite for breaking through existing monitoring performance. Herein, the first-principles density functional theory (DFT) is employed to study the adsorption and gas-sensing performance of two metal atomic clusters (Pt 3 and Rh 3) anchored on a WTe 2 monolayer (C-WTe 2) for four typical fault characteristic gases (CO, CO 2 , H 2 , and C 2 H 2). These results suggest that four gases can stably bind to C-WTe 2 and exist in the form of chemical adsorption due to the high adsorption energy. Also, Rh 3 -WTe 2 exhibits high selectivity and repeatability towards CO and CO 2 due to its strong response and fast recovery characteristics when used in resistive sensors; Pt 3 -WTe 2 can detect and distinguish the four types of gases due to the significant and differentiated changes in work function when used in work function sensors. Therefore, both Pt 3 -WTe 2 and Rh 3 -WTe 2 monolayers are promising gas-sensing materials for the dissolved gases detection in oil. This investigation sheds light on devices of designing metal atomic cluster anchored WTe 2 -based gas sensor for improved transformer fault monitoring performances. [Display omitted] [ABSTRACT FROM AUTHOR]

Acetylene (C2H2) gas sensors were developed by synthesizing a reduced graphene oxide (rGO)-loaded SnO2 hybrid nanocomposite via a facile two-step hydrothermal method. Morphological characterizations showed the formation of well-dispersed SnO2 nanoparticles loaded on the rGO sheets with excellent transparency and obvious fold boundary. Structural analysis revealed good agreement with the standard crystalline phases of SnO2 and rGO. Gas sensing characteristics of the synthesized materials were carried out in a temperature range of 100-300 °C with various concentrations of C2H2 gas. At 180 °C, the SnO2-rGO hybrid showed preferable detection of C2H2 with high sensor response (12.4 toward 50 ppm), fast response-recovery time (54 s and 23 s), limit of detection (LOD) of 1.3 ppm and good linearity, with good selectivity and long-term stability. Furthermore, the possible gas sensing mechanism of the SnO2-rGO nanocomposites for C2H2 gas were summarized and discussed in detail. Our work indicates that the addition of rGO would be effective in enhancing the sensing properties of metal oxide-based gas sensors for C2H2 and may make a contribution to the development of an excellent ppm-level gas sensor for on-line monitoring of dissolved C2H2 gas in transformer oil. [ABSTRACT FROM AUTHOR]

The development of functionalized metal oxide/reduced graphene oxide (rGO) hybrid nanocomposites concerning power equipment failure diagnosis is one of the most recent topics. In this work, WO3 nanolamellae/reduced graphene oxide (rGO) nanocomposites with different contents of GO (0.5 wt %, 1 wt %, 2 wt %, 4 wt %) were synthesized via controlled hydrothermal method. X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analyses-derivative thermogravimetric analysis-differential scanning calorimetry (TG-DTG-DSC), BET, and photoluminescence (PL) spectroscopy were utilized to investigate morphological characterizations of prepared gas sensing materials and indicated that high quality WO3 nanolamellae were widely distributed among graphene sheets. Experimental ceramic planar gas sensors composing of interdigitated alumina substrates, Au electrodes, and RuO2 heating layer were coated with WO3 nanolamellae/reduced graphene oxide (rGO) films by spin-coating technique and then tested for gas sensing towards multi-concentrations of acetylene (C2H2) gases in a carrier gas with operating temperature ranging from 50 °C to 400 °C. Among four contents of prepared samples, sensing materials with 1 wt % GO nanocomposite exhibited the best C2H2 sensing performance with lower optimal working temperature (150 °C), higher sensor response (15.0 toward 50 ppm), faster response-recovery time (52 s and 27 s), lower detection limitation (1.3 ppm), long-term stability, and excellent repeatability. The gas sensing mechanism for enhanced sensing performance of nanocomposite is possibly attributed to the formation of p-n heterojunction and the active interaction between WO3 nanolamellae and rGO sheets. Besides, the introduction of rGO nanosheets leads to the impurity of synthesized materials, which creates more defects and promotes larger specific area for gas adsorption, outstanding conductivity, and faster carrier transport. The superior gas sensing properties of WO3/rGO based gas sensor may contribute to the development of a high-performance ppm-level gas sensor for the online monitoring of dissolved C2H2 gas in large-scale transformer oil.

Acetylene (C2H2) gas sensors were developed by synthesizing a reduced graphene oxide (rGO)-loaded SnO2 hybrid nanocomposite via a facile two-step hydrothermal method. Morphological characterizations showed the formation of well-dispersed SnO2 nanoparticles loaded on the rGO sheets with excellent transparency and obvious fold boundary. Structural analysis revealed good agreement with the standard crystalline phases of SnO2 and rGO. Gas sensing characteristics of the synthesized materials were carried out in a temperature range of 100–300 °C with various concentrations of C2H2 gas. At 180 °C, the SnO2–rGO hybrid showed preferable detection of C2H2 with high sensor response (12.4 toward 50 ppm), fast response-recovery time (54 s and 23 s), limit of detection (LOD) of 1.3 ppm and good linearity, with good selectivity and long-term stability. Furthermore, the possible gas sensing mechanism of the SnO2–rGO nanocomposites for C2H2 gas were summarized and discussed in detail. Our work indicates that the addition of rGO would be effective in enhancing the sensing properties of metal oxide-based gas sensors for C2H2 and may make a contribution to the development of an excellent ppm-level gas sensor for on-line monitoring of dissolved C2H2 gas in transformer oil.

• Selective discrimination of acetylene and ethylene with LaFeO 3 based gas sensors. • The operation temperature controls the selectivity. • The sensor has shown very stable responses to acetylene during cross sensitivity with ethylene. Gas sensing using metal oxides can be a highly cost effective and reliable technology in a variety of medical and industrial applications. However, selectively sensing a specific gas in a complex gas mixture continues to be a significant challenge. Here, we focus on acetylene and ethylene sensing with LaFeO 3 (LFO) based sensors with novel applications, such as online monitoring and maintenance of electrical power transformers, in mind. We prepared LFO's via sol gel method at five different calcined temperatures (500–900 °C). X-ray diffraction (XRD) patterns showed that all five materials were single phased with a perovskite crystal structure. We then used these materials as active sensing layers during exposure to various test gases, including C 2 H 2 , C 2 H 4 , CH 4 , C 2 H 6 , CO, CO 2 and H 2 at different operating temperatures (150 °C, 200 °C, 250 °C and 300 °C). All of our sensors showed a significant response to unsaturated hydrocarbons, namely acetylene and ethylene, but not to the other gases. We further improved this high selectivity of our sensors, to only detect acetylene and not ethylene, by controlling the operating temperature. We then tested the effects of different backgrounds, such as humidity, and CO 2 levels, on our LFO sensors. The sensors were saturated faster in humid than dry conditions, in particular at lower operating temperatures, and there was no influence of CO 2. Therefore, our results demonstrate novel oxide-based sensors capable of distinguishing between acetylene and ethylene, enabling interesting new industrial applications. [ABSTRACT FROM AUTHOR]

The development of functionalized metal oxide/reduced graphene oxide (rGO) hybrid nanocomposites concerning power equipment failure diagnosis is one of the most recent topics. In this work, WO3 nanolamellae/reduced graphene oxide (rGO) nanocomposites with different contents of GO (0.5 wt %, 1 wt %, 2 wt %, 4 wt %) were synthesized via controlled hydrothermal method. X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analyses-derivative thermogravimetric analysis-differential scanning calorimetry (TG-DTG-DSC), BET, and photoluminescence (PL) spectroscopy were utilized to investigate morphological characterizations of prepared gas sensing materials and indicated that high quality WO3 nanolamellae were widely distributed among graphene sheets. Experimental ceramic planar gas sensors composing of interdigitated alumina substrates, Au electrodes, and RuO2 heating layer were coated with WO3 nanolamellae/reduced graphene oxide (rGO) films by spin-coating technique and then tested for gas sensing towards multi-concentrations of acetylene (C2H2) gases in a carrier gas with operating temperature ranging from 50 °C to 400 °C. Among four contents of prepared samples, sensing materials with 1 wt % GO nanocomposite exhibited the best C2H2 sensing performance with lower optimal working temperature (150 °C), higher sensor response (15.0 toward 50 ppm), faster response-recovery time (52 s and 27 s), lower detection limitation (1.3 ppm), long-term stability, and excellent repeatability. The gas sensing mechanism for enhanced sensing performance of nanocomposite is possibly attributed to the formation of p-n heterojunction and the active interaction between WO3 nanolamellae and rGO sheets. Besides, the introduction of rGO nanosheets leads to the impurity of synthesized materials, which creates more defects and promotes larger specific area for gas adsorption, outstanding conductivity, and faster carrier transport. The superior gas sensing properties of WO3/rGO based gas sensor may contribute to the development of a high-performance ppm-level gas sensor for the online monitoring of dissolved C2H2 gas in large-scale transformer oil. [ABSTRACT FROM AUTHOR]