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Magnetic shielding is a specific magnetic topology that can increase the lifespan of Hall thrusters by an order of magnitude. Magnetically shielded thrusters have similar performances as standard unshielded thrusters in the 5–15 kW power range. A comparison of the performances of two 200 W shielded (ISCT200-MS) and unshielded (ISCT200-US) Hall thrusters is presented here. The effects of replacing...
Vacuum deterioration at the most upstream of the front-end was predicted quantitatively under the assumption that a rupture of windows and subsequent inrush of air might occur in the SPring-8 beamline. A 10-m-long shock tube was employed to simulate an inrush of air into a region with rarefied gas dynamics. The shock Mach number (Ma) and pressure increase were measured with the fast-closing shutter...
The electric propulsion hollow cathode is a thermal electron emission device that can be used as an electron source and a neutralizer for aerospace electric propulsion systems. As a serial structure, the cathode's life reliability is the key to its application in orbit. The heater is used to start the hollow cathode, and short-circuit and open-circuit failure are important forms of hollow cathode...
Hot deformation behaviors of a solution-treated Ni-based superalloy are investigated. There are two types of hot compressive tests. Type A means that the strain rate keeps constant, while Type B denotes that the strain rate firstly keeps a high value in stage I, then a low one in stage II. It can be found that the deformation parameters and deformation history have great effects on the flow behavior...
Carbon foams are characterised by their high specific surface areas (SSAs) in combination with ultra-low densities. Due to these unique properties, carbon foams are particularly suitable for applications such as catalysts, where high surface area is essential. Metals or metal oxides are added to the carbon structure to increase the catalytically effectiveness. In this study, we present a new and efficient...
Graphitization micro-diamond composites are prepared by spark plasma sintering and which was modified by Ag nanoparticles subsequently. The samples are characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller analysis and Raman spectroscopy. Results show that the 1400-15 min diamond/graphite composite with core/shell...
Six series of cermet samples with Cr contents between 0 and 12.5 wt.% in 2.5 wt.% increments were prepared by vacuum sintering. The transverse rupture strength (TRS), hardness (HRA) and fracture toughness (K1C) were also measured. It was discovered that the grain size was affected by the Cr content. As the Cr addition increased, the average grain size and aspect ratio of the Mo2FeB2 hard phase decreased,...
NiCoCrAlY coatings were prepared on GH3128 nickel-based superalloy substrates using radio-frequency magnetron sputter deposition. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy measurements showed different particle growth in the thin films after annealing the as-deposited coatings at various heat treatment conditions. In addition, X-ray diffraction data revealed that...
In this report, large scale WO3 nanorods (NRs) and nanosheets (NSs) are prepared successfully by a facile one-step microwave irradiation method, using tungstic acid as tungsten source and CTAB & PEG as surfactants. TEM images showed that CTAB assisted microwave produced WO3 nanorods (diameter of 20–50 nm, length of 400–500 nm) and nanosheets (widths of 250–300 nm and thicknesses of about 15 nm)...
The structure evolution and surface modification of the ZnSb, ZnSb-Bi and ZnSb-NiO phase-change films are detected by in situ Raman laser irradiation with the different laser power and irradiation time. The results show that undoped ZnSb films exhibit a phase transformation from amorphous to metastable phases at 250 mW. The Bi-doped ZnSb films exhibit two different crystallization behaviors as the...
This paper reports the first-time evaluation of the time-dependent dielectric breakdown of recessed AlGaN/GaN-on-Si metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with plasma enhanced chemical vapor deposition (PECVD) SiO2 gate oxide. The interface fixed charge density and oxide bulk charge density extracted from the flat-band voltage characteristics were 2.7 × 1011...
In the present study, the Al/Al alloy reinforced with ZrB2 composite is produced by the combination of powder metallurgy (PM) and Vacuum arc melting (VAM) techniques. The composite powder is milled for homogenous composition and uniaxially cold compacted to form green compacts which are used as raw materials in VAM. The composites are remelted by tumbling the melts after completion of each melt to...
Burnett equations were originally derived in 1935 by Burnett by employing the Chapman-Enskog expansion to Classical Boltzmann equation to second order in Knudsen number Kn. Since then several variants of these equations have been proposed in the literature; these variants have differing physical and numerical properties. In this papers, we considered four such variants which are known in the literature...
LiF-NaF-KF (46.5-11.5-42 mol %, FLiNaK) molten salt was used in the thermal diffusion (TD) process to form chromium carbide coatings on gray cast iron HT250 at 900 °C for 8 h. The structure and chemical composition of the coating were observed by scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX) and X-ray diffraction (XRD). Both the nanoindentation hardness...
Highly resistive and sufficiently stiff insulation layers are an important prerequisite for the direct integration of piezoceramic modules into microstructured aluminium alloy sheets to produce smart adaptronic metal parts. In this study, we evaluate the mechanical and electrical properties of amorphous, hydrogenated silicon carbonitride films (a-SiCN:H) deposited by electron cyclotron resonance plasma...
This article deals with poly crystalline Zinc Oxide (ZnO) thin film fabricated on ultrasonicated clean glass substrate by sol-gel spin coating. X-Ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV–Visible spectroscopy (UV–Vis.), have been utilized to describe the fabricated ZnO film. The X-Ray diffraction (XRD) pattern infers that the ZnO thin film is polycrystalline...
The multilayered CoO-CoAl2O4 solar selective films were prepared on Co-WC coatings with different mole ratio of Co and Al by sol-gel process. The thin film has high and low refractive indices, respectively. The inner layer can improve surface condition of Co-WC coating as a high absorbing film and buffer lay, annealed at 650 °C in vacuum. The outer layer was annealed at the same condition. The absorptance...
Polycrystalline α-phase mercuric iodide (α-HgI2) film arrays have been prepared on ITO-coated glass substrates by hot-wall physical vapor deposition (HWPVD) method with the mask of 4 × 4 arrays. Film arrays are prepared based on one-step mask method. It is found that there exist differences between central parts and marginal parts of arrays in two aspects including surface morphology and electrical...
The doping of metal oxides with rare-earth element is an effective way of enhancing the optical properties of ZnO nanoparticles. The ZnO nanoparticles were prepared using co-precipitation method with different concentrations of Eu, constant N doping and characterized through X-ray diffraction, scanning electron microscopy, Raman spectroscopy and UV-visible spectroscopy. The Rietveld refined XRD of...
Nanorod-structured ZnO (NR-ZnO) films were formed on glass substrates by thermal treatment of Zn acetate films in a closed-type tube furnace. The formation mechanism of the NR-ZnO films is proposed as follows: the volatile Zn acetate was vaporized from the top region of the Zn acetate films; the mixture of ZnO and Zn acetate groups in the intermediate region acted as a seed layer; and ZnO NRs were...
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