查看更多>>摘要：In this study the possibility to employ magnetron-based gas aggregation source for the effective and facile production of mesoporous vanadium films composed of individual vanadium nanoparticles is investigated. It is demonstrated that due to the high deposition rate of V nanoparticles under optimized conditions, their low impact energies, and the directionality of the deposition process, it is possible not only to produce porous nanoparticle coatings, but also coatings with columnar structures. Furthermore, it is shown that such produced coatings may be easily transformed into vanadium pentoxide ones by their annealing in air at the temperature of 550 ?C, without loosening the mesoporous character of resulting films.
查看更多>>摘要：A straightforward approach for preparing a hierarchical carbon nanofiber (CNF) electrode through surface engineering of a stainless steel microwire mesh (SS) current collector is developed. Surface-engineering is achieved via controlled chemical etching SS and subsequent flame depsotion of a CNF coating. In contrast to pristine SS, the surface-engineered SS do not only comprise a unique surface texture but also a higher catalytic activity facilitating the direct growth of CNFs in an ethanol flame. Therefore, the as-fabricated electrode exhibits a high specific capacitance of 2988 F/g at 25 mA/cm(2) in a redox active electrolyte containing Fe2+/(3+) optimized for this electrode/electrolyte system. To maximize their capacitive performance, supercapacitors in a newly designed dual-asymmetric electrode/electrolyte (DASCs) configuration are assembled. Both the CNF positive electrode and the alpha-molybdenum oxide (MoO3) nanobelt negative electrode are capable to operate in their most suitable electrolyte. Consequently, the DASCs deliver an ultrahigh energy density of 96 Wh/kg at 114 W/Kg and a remarkable capacitance retention. Our results demonstrate the effectiveness of this surface engineering approach for fabricating electrodes, the redox activity modulation of the electrolyte, and the newly designed configuration of the capacitors, on enhancing their performance.
查看更多>>摘要：In view of the good thermal insulation, good high-temperature phase stability, high thermal expansion coefficients and ferroelastic transformation of YTaO4 ceramics, which can be prepared as thermal insulation and anti-oxidation coating material on Ti6Al4V alloy (TC4). Herein, a bond coating (BC, NiCrAlY) and top coating (TC, YTaO4) were deposited on a TC4 surface via atmospheric plasma spraying (APS), the microstructure, multi scale mechanical properties and failure mode of TC were investigated. XRD results demonstrate YTaO4 coating has good phase stability below 900 ?, both average particle size and intrinsic strain are calculated by Williamson-Hall (W-H) method. The surface hardness, wear resistance and service life of YTaO4 coating deposited on TC4 is higher than that of pure TC4, and thermal shock tests results (> 300 times at 900 ?; 269 times at 1000 ?; 79 times at 1100 ?) exhibits YTaO4 coating has an excellent protective effect against thermal shock and oxidation for TC4.
查看更多>>摘要：The growth processes of trivalent chromium-based conversion (TCC) coatings on galvanized steel at room temperature (298.15 K) were studied using the potential-time curve, polarization curves, electrochemical impedance spectroscopy and scanning electron microscopy. Results display the integrity of bi-layers at stage II around 50 s causes enhanced corrosion resistance and film compactness. The protection of surficial film, dominated by inner Cr(III)-rich barrier layer, is weakened after stage III, where it presents defective bi-layers with the mixed kinetic-diffusion control. Thermodynamic stability, layer growth and structural evolution of the film formation above Zn are discussed by the Pourbaix diagrams, molecular dynamics and schematic models, respectively.
查看更多>>摘要：In this research, multilayer DLC-Si films were effectively formed on the 2024 Al alloy utilizing cage-like hollow cathode discharge plasma-enhanced chemical vapour deposition (PECVD). A scanning electron microscopy (SEM), atomic force microscope (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Nano Indenter G200 device were utilized to characterize the microstructural features of the coatings. Various electrochemical methods were used to investigate the anticorrosion performance of DLC films in 3.5 wt% electrolytic solution. The findings revealed that an increment in the bias voltage increases the condensation of the DLC layer and increments the thickness of the coatings. Furthermore, the outcomes revealed that the anodic current density and passive current decrements with an increment of bias voltage. This behavior is attributable to a good barrier impact of the amorphous DLC film. The multilayer film introduces new interfaces, resulting in the deterrence of Cl- ions penetrations. Further, the values of activation energy (delta E), enthalpy (delta H), and entropy of activations (delta S) for the samples in 3.5 wt% NaCl were determined and presented.
查看更多>>摘要：Spiral blades are the main working mechanism of shearers, and the service life of blades directly affects the coal-rock cutting progress and enterprise production efficiency. To repair the damaged spiral blade and improve the wear resistance, FeCrSiB coatings having different amounts of reinforcing TiC particles were fabricated on the blade material 34CrNiMo6 by laser additive manufacturing technology. The effects of the TiC particle weight fraction on the microstructure, phase, hardness and wear resistance of the TiC/FeCrSiB composite coating were systematically studied. A laser additive remanufacturing repair experiment of damaged spiral blades based on reverse engineering technology was performed. The results indicated that the composite coating had good metallurgical bonding with the 34CrNiMo6 substrate, and the TiC particles converged towards the top of the coating via Marangoni convection and dynamic viscosity. The composite coatings mainly consisted of gamma-(Fe, Cr) solid solution, M23C6, Fe2B/Cr2B and TiC. By increasing the TiC concentration in the composites, the hardness and wear resistance of the coating were significantly improved. The Rockwell hardness, microhardness and wear rate of the 30%-TiC-reinforced coating were 74.82 HRC, 1143.61 HV0.5 and 0.45 x 10(-2) mm(3)N(-1) mm(-1), respectively, and the wear resistance of the composite coating was 9 times higher than that of the substrate. The experimental results show that the laser additive remanufacturing TiC reinforced coating was an effective method to repair damaged spiral blades and improve the service performance.
查看更多>>摘要：This study is critical for aiding the development of a hybrid treatment consisting of a tungsten-doped diamondlike carbon coating (WC/C) deposited atop shot-peened Ti-6Al-4V surfaces. Residual stresses, considered a key indicator of fatigue performance, were measured by X-ray diffraction (XRD). Rotating bending fatigue tests were carried out while microscopy allowed for fractographic analysis of resultant surfaces. Results show that despite the pronounced surface roughness produced by the shot peening treatment, the high residual compressive stresses, together with the refined and cold-worked microstructure were capable of marginally improving the fatigue performance of the shot peened Ti-6Al-4V compared to the untreated alloy. Conversely, following fatigue testing, the WC/C coating displayed extensive cracking which propagated prematurely into the substrate and yielded a reduction in fatigue limit. On the other hand, despite some annealing of the compressive residual stresses during the coating deposition treatment, the hybrid treatment yielded a reasonable improvement in the fatigue limit over the untreated condition. This result, coupled with the high coating hardness and adhesion, confirm this hybrid treatment's capability in retaining both the adhesive and fatigue performance of the Ti-6Al4V alloy.
查看更多>>摘要：To enhance the adhesion strength and tribological properties of hydrogenated diamond-like carbon (H-DLC) films, the multi-layered H-DLC films consisting of a function layer with chromium and boron doping, Cr-C and Cr-H-DLC transition layer and a Cr bonding layer were prepared on 52100 steel through the unbalanced magnetron sputtering system. The influence of Cr and B doping on the mechanical properties and tribological performance were investigated. The results indicated that the structure of H-DLC, Cr-H-DLC and B-H-DLC films was compact. There were no peelingflake, delamination, and crack between the films and substrate. Raman spectra showed that the value of I-D/I-G increased with the Cr and B doping, which indicated that the sp(3) content inside the H-DLC film decreased. Compared with the atmospheric condition, the coefficient of friction and wear rate of those films were higher than that in vacuum. According to the Raman spectra of the wear track, it was found that the graphitization of sliding interface theory had its limitations. The mechanical wear of those films was dominated by the abrasive and oxidative wear in the atmospheric environment. Owing to the passivation of the hydrogen atoms, the abrasive wear and adhesive wear was the main failure mechanism in vacuum.
查看更多>>摘要：The durability and service performance of thermal barrier coatings (TBCs) is influenced by its microstructure. One type of yttria stabilized zirconia coating containing irregular microcracks (mc-YSZ) was prepared by atmospheric plasma spraying (APS) method in this study, and the differences in hot corrosion behavior and thermal shock resistance between the conventional YSZ coating and the mc-YSZ coating were investigated. Results showed that the presence of irregular microcracks facilitated the penetration of corrosive salt (V2O5 and Na2SO4) and accelerated the hot corrosion reaction. The deflection effect of irregular microcracks in the early stage of hot corrosion could suppress the propagation of cracks generated by corrosion; but irregular microcracks would merge with corrosion cracks in the later stages of corrosion and aggravate the failure of the coatings. Thermal shock tests showed no significant difference of the thermal shock lifetime between YSZ coating and mcYSZ coating, which proved that this irregular microcrack could not effectively improve the strain tolerance. The present study provides a reference for the structure design of thermal barrier coatings: when designing the structure of the coating, the appearance of that irregular microcracks should be avoided.
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Elsevier