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How to evaluate plasma-derived heat (PDH) and the synergistic effect of plasma catalysis, especially for in-plasma catalysis (IPC), is still ambiguous. In this work, to exclude the reaction-heat impact on PDH, N2 plasma was first used to compare the heat-uninsulated and heat-insulated cases for empty and packed dielectric barrier discharge (DBD). Compared with the heat-uninsulated cases, the heat-insulation has nearly the same discharge characteristics, and a weak impact on N2 rotational temperature. The heat-insulation, whether for empty or packed DBD, gave much higher outgoing gas temperature (Tg) and reactor wall temperature (Tw) than the heat uninsulation. For methanol-steam reforming in the heat-insulated reactor over various supported catalysts on Al2O3 support (AS), the dependence of PDH indicated by Tw on reaction-heat power was observed. The synergistic effect of plasma and Au/CeZn/AS catalyst in the heat-insulated IPC reactor was verified. For the plasma alone case, methanol conversion was negligible, giving a Tw of 618 K. For the IPC case, the Tw decreased considerably to 545 K due to the effect of reaction-heat power on PDH. Methanol conversion of 46.8% was achieved, which is much higher than the catalysis alone case of 9.0%, even at a higher temperature of 573 K. Moreover, H2 selectivity increased from plasma alone from 80.0% to 95.1%. If the IPC case was heat-uninsulated, the Tw dropped down to 385 K, and accordingly methanol conversion became insignificant. This work demonstrated that heat-insulation is necessary for reliable evaluation of the PDH and the synergistic effect in plasma catalysis. [ABSTRACT FROM AUTHOR]

As an intermedia between cold and thermal plasmas, warm plasma generated by gliding arc (GA) discharge possesses high conversions and high energy efficiencies for CO2 conversion. However, there is little understanding for the arc characteristics in CO2-based atmosphere and reaction mechanism of CO2 in GA plasma from experimental approach. For this purpose, a magnetically driven GA plasma with a constant length of arc is designed to study GA characteristics and reaction mechanism by changing H2/CO2 molar ratio (from pure CO2 to pure H2). In the entire range of H2/CO2 ratio, the arc channel shows a glow-like feature. The plasma parameters are arc temperature of 2200–3600 K, electron density of ~1.6  ×  1014 cm−3 and electron temperature of ~3 eV. From pure CO2 to pure H2, arc diameter decreases from 1.3 to 0.6 mm, whereas rotational frequency increases from 20 to 64 Hz. Based upon the optical emission spectra of CO, OH, H and O species, chemluminescence spectra of CO and O recombination and CO production rate detected online by gas chromatographs, the reaction mechanism at low and high H2/CO2 molar ratios is disclosed. [ABSTRACT FROM AUTHOR]

We present a new method for achieving chemical reactions induced by plasmas with liquids—an in-liquid arc plasma jet system—designed to have a few advantages over the existing methods. High-speed imaging and optical emission spectroscopy were adopted to highlight the physical aspects of the in-liquid arc plasma jet system, and the feasibility of the system was investigated in a wastewater treatment case with phenol as the model contaminant. We found that the specific energy input is a reasonable parameter by which to characterize the overall process. The phenol removal reaction could be modeled as a pseudo-first-order reaction, and the reaction constant became smaller as the phenol concentration increased. However, complete decomposition of the phenol into water and carbon dioxide required very high energy because the final intermediate, oxalic acid, is relatively stable. Detailed chemical and physical analyses, including byproducts, ions, solution acidity, and conductivity, were conducted to evaluate this new method for use in the appropriate applications. [ABSTRACT FROM AUTHOR]

In this study, we deposited Fe films on MoS2 flakes, and investigated the microscopic magnetic behavior on individual flakes. The MoS2 flakes were fabricated on SiO2/Si(1 0 0) substrates using chemical vapor deposition. Fe coverage was deposited on the MoS2 flakes by e-beam evaporation with a thin Pd capping for protection. Investigations by atomic force microscope and Raman spectroscopy confirmed that the MoS2 flakes had a mean lateral size of 10–20 μ m and mostly single layer thick. After depositing 3.6 and 7.0 nm Fe on MoS2/SiO2, clear hysteresis loops were observable with the in-plane magnetic field. From the investigation using a magneto-optical Kerr microscope, we measured the hysteresis curves within individual MoS2 flakes. Although the Fe coverage was much thicker than the MoS2 atomic step height (∼0.66 nm) and the direct connection and strong ferromagnetic coupling between Fe/MoS2 and Fe/SiO2 were expected, a magnetic decoupling between the magnetic domains of Fe/MoS2 and Fe/SiO2 was surprisingly observed. For 3.6 nm Fe/MoS2, the magnetic coercivity (Hc) was 28  ±  5 Oe, while in contrast, the Hc of 3.6 nm Fe/SiO2 ranged 58  ±  5 Oe. With a thicker Fe coverage of 7.0 nm, the Hc of Fe/MoS2 and Fe/SiO2 converged and the magnetic decoupling became too weak to observe. The distinct interface magnetic anisotropy of Fe on different substrates was held responsible for the observed magnetic decoupling across the MoS2 atomic step between Fe/MoS2 and Fe/SiO2 domains. These observations will be valuable in combining a magnetic coverage with a single layer MoS2 for future spintronic applications. [ABSTRACT FROM AUTHOR]

Since carbon-based structures of various dimensions, including one-dimensional (1D) carbon nanotubes, two-dimensional (2D) graphene and three-dimensional (3D) carbon foams, have attracted significant attention as microwave absorption fillers, we present an exceptional hetero-junction filler with a 1D–2D–1D feature, achieved by manipulating 2D graphene into 1D carbon fibers in the fiber-extruding process under the electric field. The as-fabricated 1D–2D–1D structural fillers exhibited much-improved dielectric properties and promoted microwave absorption performance in their composites, which is linked to the establishment of enhanced polarization capability, the generation of increased electric loss pathway and the creation of more favorable electromagnetic energy consumption conditions. The results suggest that employing 2D graphene in the 1D–2D–1D nanostructures played the critical role in tuning the electromagnetic response ability, because of its intrinsic electric advantages and dimensional features. To broaden the effective absorption bandwidth, periodic pattern-absorbing structures were designed, which showed combined absorption advantages for various thicknesses. Our strategy for fabricating 1D–2D–1D structural fillers illuminates a universal approach for manipulating dimensions and structures in the nanotechnology. [ABSTRACT FROM AUTHOR]