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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Improved Surface Flashover Characteristics of Ceramic Vacuum Interface by Surface Treatment
摘要： In this paper, influences of surface Cr2O3 coating treatment on ceramic vacuum interface under a long pulse-duration voltage are reported. The surface properties of the treated ceramics have been measured by SEM, LSCM and XRD methods. Compared with the original untreated ceramics, the treated ceramic has a smoother surface, a lower SEE coefficient and a lower surface resistivity. As a result, a higher surface flashover voltage has been obtained. The surface treatment is an easy and convenient method to improve surface flashover characteristics of ceramic vacuum interface under a long pulse-duration high voltage.
关键词： surface treatment,ceramic vacuum interface,surface flashover,secondary electron emission,Cr2O3 coating
更新于2025-09-23 15:22:29
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Remarkable reproducibility and significant sensitivity of ZnO nanoparticles covered by Chromium (III) oxide as a hydrogen sulfide gas sensor
摘要： ZnO nanoparticles covered by Chromium (III) oxide (Cr2O3) were fabricated using spray pyrolysis and thermal evaporation technique to increase the H2S gas sensor repeatability. Gas sensing analyses showed that the Cr2O3 cover on the ZnO nanoparticle increased the response at high concentrations without affecting the operating temperature. Furthermore, there was no change in the response and recovery time after coating Cr2O3. ZnO nanoparticles covered by Cr2O3 demonstrated considerable reproducibility.
关键词： H2S,Cr2O3,Sensor,ZnO,sensitivity.,longevity
更新于2025-09-23 15:22:29
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Construction of Cr2O3:ZnO Nanostructured Thin Film Prepared by Pulsed Laser Deposition Technique for NO2 Gas Sensor
摘要： Rhombohedral structure of chromium oxide (Cr2O3) thin-film doped hexagonal zinc oxide (ZnO) nanoparticles have been prepared using pulsed laser deposition technique at a different weight percent of ZnO from 0 to 9 wt%. The results of X-ray diffraction analysis shown that the doped films are polycrystalline, and the average crystallite size of the synthesized thin films is found to be dependent on the ZnO concentration. The surface morphology of the prepared thin films was characterized by atomic force microscopy. The optical properties are investigated using ultraviolet–visible light (UV–Vis) absorption spectroscopy. The optical bandgap ranged from 2.45 to 2.68 eV, showing the shift towards longer-wavelength compared to bulk Cr2O3 (~ 3 eV). The sensitivity, response, and recovery times of the sensor towards nitrogen dioxide (NO2) gas were studied and discussed. The sensitivity increase with increasing the doping concentration, and started to decrease when ZnO concentrations reach 7 wt%. The optimal ZnO concentrations for NO2 gas sensitivity is 5 wt%, which attain maximum sensitivity of 87.5% at temperature of 523 K.
关键词： Cr2O3:ZnO nanostructure,Structural properties,Optical properties,Gas sensitivity,PLD technique
更新于2025-09-23 15:19:57
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Facile microwave-assisted synthesis of Cr2O3 nanoparticles with high near-infrared reflection for roof-top cooling applications
摘要： Microwave-assisted solution synthesis was employed for the preparation of Cr2O3 nanoparticles using Cr(acac)3 and ethylene glycol. The optimum conditions for the completion of the reaction forming a green precipitate (yield-95%) were: irradiation for 40e60 min at 220 (cid:1)C solution temperature. The as-prepared sample was barely crystalline; annealing in air at above 300 (cid:1)C formed nanocrystalline Cr2O3, as shown by X-ray diffraction (XRD). High-resolution transmission electron microscopy (HRTEM) of the “700 (cid:1)C sample” con?rmed the well-crystallised Cr2O3 formation with ~37 nm average size. The as-prepared powder (bluish-green) showed high near-infrared (NIR) re?ectance, whereas the annealed samples showed bright-green re?ectance, whose International Commission on Illumination L*a*b* (CIE L*a*b*) values shifted towards the green region. The higher Dq/B value (3.76), suggested that Cr3t lies in a strong crystal ?eld. Stainless steel blocks covered with the as-prepared (intermediate) material reduced heating under sunlight by 5 (cid:1)C, indicating its suitability as an easily prepared tile coating for roof-top applications. The annealed samples are found suitable as an anti-dazzling coating for automobile windscreens and rear-view mirrors.
关键词： Chemical synthesis,Ceramics,Microwave-assisted synthesis,Oxide materials,Cr2O3 nanoparticles
更新于2025-09-19 17:15:36
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Effects of Cr2O3 active agent on the weld process dynamic behavior and joint comprehensive properties of fiber laser welded stainless steel thick plate
摘要： In this study, the dynamic behaviors of metal vapor, plasma, keyhole, and weld pool during activating laser welding of stainless steel thick plates are monitored in real time by employing a novel "sandwich" method in combination with a high-speed camera system. Meanwhile, the welding quality of specimens is inspected and analyzed from the aspects like joint weld formation, mechanical properties, microstructure, and element distribution. The effects of Cr2O3 active agent on the welding stability and quality of specimens are explored. According to the results, adequate coating of active agent on the specimen surface can weaken and suppress the generation and drastic changes of metal vapor and plasma inside and outside the keyhole, increase the keyhole depth, improve the keyhole shape, weaken the oscillation amplitude of weld pool, and prolong the change cycles of keyhole and weld pool. Consequently, the stability of welding process is enhanced, the generation of porosity and splash defects is inhibited preferably, the quality of weld formation is improved, the weld penetration is increased, the grain structure in weld zone is refined, the width of heat affected zone is narrowed, and the joint strength and toughness are enhanced, without showing apparent change of the relative element contents in the welded joint. In conclusion, coating of Cr2O3 active agent on the specimen surface is effective in improving the welding properties of laser welded stainless steel plates.
关键词： Welding quality,Fiber laser welding,Plasma morphology,Cr2O3 active agent,Weld pool behavior
更新于2025-09-19 17:13:59
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[IEEE 2018 2nd International Conference on Engineering Innovation (ICEI) - Bangkok (2018.7.5-2018.7.6)] 2018 2nd International Conference on Engineering Innovation (ICEI) - Schottky's Barrier Height of T91/Cr2O3 Heterojunction in Dry and Wet Conditions: Effects of WaterVapor Onto Accelerated High Temperature Oxidation
摘要： Increasing the operating temperature in thermal power plant will further accelerate the high temperature oxidation with the presence of water vapor. It is hypothesized that water vapor provides hydrogen that dissolves into the ferritic alloy susbstrate, hence altering their electronic state at the metal-semiconductor (oxide) interface. This study aims to quantitatively prove above postulation by comparing their Schottky’s Barrier Height (SBH) in dry and wet environment. The Schottky’s barrier was prepared by sputtering Cr2O3 onto the T91 boiler tube in high vacuum condition using RF power 150W for an hour. The T91/Cr2O3 junction was then connected with platinum wire for capacitance-voltage, C-V test at high temperature. The value of Vbi was used to calculate the SBH, which increase proportionately with built in voltage. It is clearly shown that the SBH value in wet condition is higher than that in dry condition by 10.3%. This is explained by the formation of space charge layer at metal/oxide interface due to dissolved hydrogen in metal, thus may change the transport property and accelerate the oxidation rate in water vapor.
关键词： T91 alloy,Cr2O3,Schottky’s barrier,High temperature oxidation
更新于2025-09-04 15:30:14