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The impact of the gas mixing ratio on the insulation strength refers to the synergistic behavior of mixed gas. In this work, synergistic effects of various SF6 admix (SF6/N2, SF6/dry air, and SF6/Ar) are tested using HV co-axial sparkgap switch with different % by vol of SF6 under nonuniform field background (point-plane configuration). The experimental work is performed with 5%, 10%, 25%, and 50% by vol of SF6 for pressure levels 34.5–206.7 kPa in a gap length of 4 mm. For the subjected experimental constraint, SF6 admix with Ar, N2, and dry air exhibits a positive synergism. The breakdown voltage (BDV) of the SF6/N2 and SF6/dry air mixture with 5% SF6 is found to be ~60% of pure SF6. Furthermore, SF6/N2 admix shows a saturated growth trend with an increase in % by vol. of SF6. The binary mixtures of SF6 with N2, dry air, and Ar exhibit an increasing trend in the breakdown characteristics with an increase in the concentration levels of SF6. Besides the experimental study, a discharge model has been developed using 3-D particle-in-cell/Monte Carlo collision (PIC/MCC) code for binary mixtures of SF6 with N2 and Ar for the same volumetric proportions at which the experimentation work was carried out. In the simulations, ionization by interactions of SF6 with N2 and Ar atoms are considered, whereas dissociative ionization and plasma chemistry has been ignored. The BDV, electron number density, and temporal variation of the electric field during the discharge process are obtained through numerical simulations. The calculated BDV is found to have a good agreement with experimental breakdown data. From this study, one can predict the BDV of SF6 admix, thereby providing a reference for designing and manufacturing power equipment using SF6 admix.

An existing propulsion system is modified to obtain variable ISP capabilities that could be used to modulate thrust. This created an engine that is able to use low thrust and high ISP setting for interplanetary travel and use high thrust and low ISP setting for attitude control and compensating for atmospheric drag. A cold gas thruster (CGT) was created by using the body of a charge exchange thruster (CXT) effectively producing a dual mode CXT with CGT capabilities. The dual mode CXT was capable of a maximum thrust of 94 µN in electric engine mode. Experimentations showed that using Argon, the dual mode CXT in CGT mode produced a thrust of 4 mN, a 43-fold improvement. A convergent divergent nozzle was designed and validated via ANSYS Fluent for use with the dual mode CXT, it showed a 16-fold improvement in CGT performance at low mass flow rates < 50 sccm.

A highly active and stable Cu-based catalyst for CO2to CO conversion was demonstrated by creating a strong metal–support interaction (SMSI) between Cu active sites and the TiO2-coated dendritic fibrous nano-silica (DFNS/TiO2) support. The DFNS/TiO2–Cu10 catalyst showed excellent catalytic performance with a CO productivity of 5350 mmol g–1h–1(i.e., 53,506 mmol gCu–1h–1), surpassing that of almost all copper-based thermal catalysts, with 99.8% selectivity toward CO. Even after 200 h of reaction, the catalyst remained active. Moderate initial agglomeration and high dispersion of nanoparticles (NPs) due to SMSI made the catalysts stable. Electron energy loss spectroscopy confirmed the strong interactions between copper NPs and the TiO2surface, supported by in situ diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy. The H2-temperature programmed reduction (TPR) study showed α, β, and γ H2-TPR signals, further confirming the presence of SMSI between Cu and TiO2. In situ Raman and UV–vis diffuse reflectance spectroscopy studies provided insights into the role of oxygen vacancies and Ti3+centers, which were produced by hydrogen, then consumed by CO2, and then again regenerated by hydrogen. These continuous defect generation–regeneration processes during the progress of the reaction allowed long-term high catalytic activity and stability. The in situ studies and oxygen storage complete capacity indicated the key role of oxygen vacancies during catalysis. The in situ time-resolved Fourier transform infrared study provided an understanding of the formation of various reaction intermediates and their conversion to products with reaction time. Based on these observations, we have proposed a CO2reduction mechanism, which follows a redox pathway assisted by hydrogen.

In this work, we have designed and synthesized nickel-laden dendritic plasmonic colloidosomes of Au (black gold-Ni). The photocatalytic CO2hydrogenation activities of black gold-Ni increased dramatically to the extent that measurable photoactivity was only observed with the black gold-Ni catalyst, with a very high photocatalytic CO production rate (2464 ± 40 mmol gNi–1h–1) and 95% selectivity. Notably, the reaction was carried out in a flow reactor at low temperature and atmospheric pressure without external heating. The catalyst was stable for at least 100 h. Ultrafast transient absorption spectroscopy studies indicated indirect hot-electron transfer from the black gold to Ni in less than 100 fs, corroborated by a reduction in Au–plasmon electron–phonon lifetime and a bleach signal associated with Ni d-band filling. Photocatalytic reaction rates on excited black gold-Ni showed a superlinear power law dependence on the light intensity, with a power law exponent of 5.6, while photocatalytic quantum efficiencies increased with an increase in light intensity and reaction temperature, which indicated the hot-electron-mediated mechanism. The kinetic isotope effect (KIE) in light (1.91) was higher than that in the dark (∼1), which further indicated the electron-driven plasmonic CO2hydrogenation. Black gold-Ni catalyzed CO2hydrogenation in the presence of an electron-accepting molecule, methyl-p-benzoquinone, reduced the CO production rate, asserting the hot-electron-mediated mechanism. Operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that CO2hydrogenation took place by a direct dissociation path via linearly bonded Ni–CO intermediates. The outstanding catalytic performance of black gold-Ni may provide a way to develop plasmonic catalysts for CO2reduction and other catalytic processes using black gold.