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991.
《International Journal of Hydrogen Energy》2019,44(13):6674-6686
A nanostructured NiSn alloy/multi-walled carbon nanotube (MWCNT) composite was successfully synthesized for highly reversible sodium and hydrogen ions storage by using an electrochemical deposition process on porous Cu foam. The surface morphology of the resulting NiSn alloy/MWCNT nanocomposite was characterized using a field-emission scanning electron microscope, indicating the formation of sphere-like NiSn alloy nanoparticles with an average size of 190 nm. On the other hand, X-ray diffraction analysis, energy dispersive and Fourier transform infrared spectroscopies were employed to determine the crystalline structure, elemental surface and chemical composition of the nanocomposite electrode. The initial sodium discharge capacity of the electrode was maximized at ∼550 mAh g−1 under the current density of 1000 mA g−1, and a high hydrogen discharge capacity of 5200 mAh g−1 was obtained at 1100 mA g−1 after 20 cycles. A comprehensive comparison between the sodium and hydrogen ions capacities in this study and those of the literature for different materials and structures was also performed. Accordingly, the resulting nanocomposite electrode with dual capacity may offer promising applications in both sodium-ion battery and hydrogen storage. 相似文献
992.
Xiao-Tao Luo Gregory M. Smith Yan Wang Edward Gildersleeve Sanjay Sampath Chang-Jiu Li 《Ceramics International》2019,45(4):4718-4728
HVOF sprayed WC based cermet coatings have been widely used in industries as barriers against wear and hydrodynamic cavitation due to their high hardness and relatively high toughness. However, cracking of the coatings can occur during coating production or in service, which can reduce operational performances. It can be difficult to assess the performance impact due to cracks within the coating and as to whether the cracked coatings should be resprayed or removed from service. In this work, artificial cracks of different widths were introduced to liquid fuel HVOF sprayed WC-12Co coating through uniaxial tension of the coated steel substrate to assess the implications of such cracking. Tribological performances of the cracked coatings were examined using rubber wheel dry abrasion, ‘ball on disc’ sliding wear, and ultrasonic cavitation erosion. The results show that the crack deteriorates the abrasive wear resistance of the coating at the initial stage due to preferable mass loss at the cracks. However, after 30?min of abrasion, all the cracked coatings showed the same wear rate as compared to the non-cracked coating, with the abrasive wear resistance acting independent to the crack characteristics. Because the cracks could store wear debris and thus minimize the debris induced abrasion to the coating surface during sliding wear test, both improvement in wear resistance and reduction in coefficient of friction (COF) were detected in the cracked coatings. During the cavitation test, it was found that the mass loss of the specimen increased significantly (up to 75%)with crack width and density suggesting that the crack presence greatly deteriorated the cavitation resistance of the cermet coatings. 相似文献
993.
The effect of chlorite on the flotation of pyrrhotite was systematically investigated through flotation tests, adsorption studies, optical microscopy experiments, inductively coupled plasma emission spectrometer tests, zeta potential measurements, and X-ray photoelectron spectroscopy analysis. Results showed that fine chlorite impaired the flotation of pyrrhotite due to slime coating. To eliminate the adverse effect of chlorite, two different methods were employed. Carboxymethyl cellulose and quartz could remove the slime coating of chlorite and improve the flotation recovery of pyrrhotite, whereas the addition of quartz provided better results. The key to eliminating the adverse effect of chlorite on the flotation of pyrrhotite is to remove the slime coating of chlorite by changing the surface charge of chlorite. 相似文献
994.
Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed(HVOF) technique WC-17 Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope(SEM), energy dispersive X-ray spectroscopy(EDX), and X-ray diffractrometry(XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy(OM), and surface topography. The experimental results reveal that the WC-17 Co coating adjusted the boundary between the partial slip regime(PSR) and the slip regime(SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17 Co coating in prevention of rotational fretting wear. 相似文献
995.
996.
研究了聚碳硅烷(PCS)粉末的高温裂解特性及PCS粉末与锆粉间的化学反应机理,并在900 ℃制备了SiC涂层。研究发现,900 ℃开始,PCS裂解产物由无定形态SiC向结晶态转变。不同温度下,PCS粉末与锆粉的混合物发生一系列化学反应,产物为ZrC、Zr2Si、Si3Zr5,通过调节反应温度,可控制该化学反应的程度,进而实现对涂层成分的调节。采用先驱体转化法(PIP)在锆合金包壳表面制备了SiC涂层,经PCS溶液浸涂-裂解3次循环可得到SiC陶瓷层,厚度为4 μm,涂层成分为SiC,ZrC为过渡层。划痕法测试得到涂层附着力等级为1~2级。 相似文献
997.
998.
Non-treated Galvalume (55% Al, 43.4% Zn and 1.6% Si by weight) coatings have been studied through a combination of surface, near surface and bulk analysis after exposure at marine conditions, and for comparison also in an urban test site and in successively more complex short-term laboratory exposures. Slightly polished Galvalume surfaces exhibit dendritic aluminum-rich areas with higher Volta potential compared with interdendritic zinc-rich areas. These effects were not observed on bare as-received surfaces due to the overall presence of aluminum oxide. As a result, preferential corrosion occurred initially in interdendritic areas. The zinc release rate followed the same time-dependence as the surface coverage of zinc-containing phases at the marine exposure condition with zinc predominantly released compared to aluminum. Short term laboratory exposures generated the same main phases as formed at marine conditions. This confirms that the evolution of corrosion products and time dependence of zinc release rates can be explained by the uniform formation of less soluble Al2O3, AlOOH and Al(OH)3 compared to observed zinc-containing phases, e.g. ZnO, zinc hydroxycarbonate and zinc hydroxychloride. The same underlying mechanism is believed to operate also during exposure of Galvalume in the urban site studied. 相似文献
999.
《金属精饰学会汇刊》2012,90(6):305-311
ABSTRACTCorrosion processes can compromise the durability of metallic materials. One way to minimise the effects of corrosion is to coat them with corrosion-resistant alloys. In this study, Co–W alloys were produced by electrodeposition and their anticorrosive performance was evaluated at different levels of current density, Co bath concentration and bath temperature, using factorial experiment design and ANOVA techniques. This evaluation consisted of measuring corrosion current and using electrochemical impedance spectroscopy. Adherent and corrosion resistant alloys were obtained at the lowest temperature of experimental design (25°C) and current density (10?mA?cm?2) values. From the corrosion tests, X-ray Diffraction and Scanning Electron Microscopy analysis it was possible to conclude that the increase in the tungsten percentage in the composition of the alloy generated an increase in corrosion resistance. Although the alloys’ chemical composition has influence on the corrosion resistance, their physical aspect, such as the presence of cracks, are more significant for the resistance to corrosion. 相似文献
1000.