Investigation of corrosion properties with Ni–P/TiNO coating on aluminum alloy bipolar plates in proton exchange membrane fuel cell

Aluminum alloy bipolar plates have unique application potential in proton exchange membrane fuel cell (PEMFC) due to the characteristics of lightweight and low cost. However, extreme susceptibility to corrosion in PEMFC operation condition limits the application. To promote the corrosion resistance of aluminum alloy bipolar plates, a Ni–P/TiNO coating was prepared by electroless plating and closed field unbalanced magnetron sputter ion plating (CFUMSIP) technology on the 6061 Al substrate. The research results show that Ni–P interlayer improves the deposition effect of TiNO outer layer and increase the content of TiN and TiO_xN_y phases. Compared to Ni–P and TiNO single-layer coatings, the Ni–P/TiNO coating samples exhibited the lowest current density value of (1.10 ± 0.02) × 10^?6 A·cm^?2 in simulated PEMFC cathode environment. Additionally, potential cyclic polarization measurements were carried out aiming to evaluate the durability of the aluminum alloy bipolar plate during the PEMFC start-up/shut-up process. The results illustrate that the Ni–P/TiNO coating samples exhibit excellent stability and corrosion resistance.     

Electromagnetic shielding properties of iron oxide impregnated kenaf bast fiberboard

The electromagnetic shielding effectiveness of kenaf fiber based composites with different iron oxide impregnation levels was investigated. The kenaf fibers were retted for removing the lignin and extractives from the fibers and magnetized. Using the unsaturated polyester and the magnetized fibers, kenaf fiber based composites were manufactured by the compression molding process. The transmission energies of the composites were characterized when the composite samples were exposed under the irradiation of electromagnetic (EM) wave with a variable frequency from 9 GHz to 11 GHz. Using the Scanning Electron Microscope (SEM), the iron oxide nanoparticles were observed on the surfaces and inside the micropore structures of single fibers. As the Fe content increased from 0% to 6.8%, 15.9% and 18.0%, the total surface free energy of kenaf fibers with the magnetizing treatments increased from 44.8 mJ/m² to 46.1 mJ/m², 48.8 mJ/m² and 53.0 mJ/m², respectively, while the modulus of elasticity reduced from 2875 MPa to 2729 MPa, 2487 MPa and 2007 MPa, respectively. Meanwhile, the shielding effectiveness was increased from 30–50% to 60–70%, 65–75% and 70–80%, respectively.     

铝质量分数对FeCrAl合金多孔材料性能的影响

铁铬铝（FeCrAl）合金是一种典型的耐热合金,由其开发而成的耐高温金属多孔材料已经在煤气净化、高温催化剂载体等方面获得了广泛的应用。在反应合成制备FeCrAl合金多孔材料过程中,铝质量分数在多孔材料孔结构、力学性能及抗氧化性能等方面具有重要影响。本文在Fe?20%Cr合金（质量分数）基础上添加不同质量分数的铝粉（0～20%）,以铁、铝、铬元素混合粉为原料,通过反应合成方法制备了一系列FeCrAl合金多孔材料（Fe?20Cr?xAl,x=0～20%,质量分数）,研究了铝质量分数对Fe?20Cr?xAl多孔材料物相、孔结构、力学性能以及抗氧化性能的影响。结果表明,添加5%铝（质量分数）的Fe?20Cr?xAl多孔材料具有较优的孔隙度和力学性能,同时在600～800 ℃高温氧化实验中表现出最优的抗氧化性能和力学性能稳定性。     

Nanotribological study of PECVD DLC and reactively sputtered Ti containing carbon films

Amorphous carbon film, also known as DLC film, is a promising material for tribological application. It is noted that properties relevant to tribological application change significantly depending on the method of preparation of these films. These properties are also altered by the compositions of these films. DLC films are well known for their self-lubricating properties, as well. In view of this, the objective of the present work is to compare the tribological properties of diamond like carbon (DLC) film obtained by plasma enhanced chemical vapour deposition (PECVD) with the Ti containing nanocrystalline carbon (Ti/a-C:H) film obtained by unbalanced magnetron sputter deposition (UMSD) in nN load range. Towards that purpose, DLC and Ti/a-C:H films are deposited on silicon substrate by PECVD and UMSD processes respectively. The microstructural features and the mechanical properties of these films are determined by scanning electron microscope (SEM), transmission electron microscope (TEM) and nano indenter. The surface topographies and the friction force surfaces of these films are evaluated by means of an atomic force microscope (AFM). The results show that although PECVD DLC film has higher elastic modulus and higher hardness than UMSD Ti/a-C:H film, the surface roughness and the friction coefficient of PECVD film is significantly higher than that of UMSD Ti/a-C:H film.     

环氧丙烯酸酯合成及应用的研究进展

介绍了环氧丙烯酸酯从双酯合成到双酯的改性,以及近几年新提出的单酯合成及应用的研究现状,评述了环氧丙烯酸酯,尤其是环氧丙烯酸单酯合成的研究进展。     

Vapour phase hydrogenation of phenol over Pd/C catalysts: A relationship between dispersion,metal area and hydrogenation activity

A series of palladium supported on activated carbon catalysts, with Pd varying from 0.5 to 6.0 wt%, were prepared via wet impregnation method using PdCl₂ · xH₂O as a precursor salt. The dried samples were further reduced at 573 K in hydrogen and characterized by CO adsorption at room temperature in order to determine the dispersion, metal area and particle size. The catalysts were tested for vapour phase phenol hydrogenation in a fixed-bed all glass micro-reactor at a reaction temperature of 453 K under normal atmospheric pressure. The decrease in metal surface area as well as dispersion with corresponding increase in turn-over frequency (TOF) against palladium loadings suggest the unusual inverse relationship that exist between Pd dispersion and phenol hydrogenation activity over Pd/carbon catalysts. The stability of TOF at larger crystallite size indicates that phenol hydrogenation is less sensitive reaction especially beyond 3 wt% of Pd content. It is evident from the results that structural properties of the catalysts strongly influence the availability of Pd atoms on the surface for CO chemisorption and hence for phenol hydrogenation. A comparison between selectivity and product yield of the reaction against overall phenol conversion indicates that changes in reaction selectivity for cyclohexanone or cyclohexanol is independent of phenol conversion level and either of the product is not formed at the cost of another. The stability of the catalysts with reaction time suggests that coke formation on the surface of the catalyst is less significant and the formation of cyclohexanone remains almost total even at higher reaction temperatures.     

Microstructural and tribological behavior of TiAlN/MoS2-Ti coatings

1. Introduction The search for a better wear resistant coating has resulted in the development of a class of hard, solid-lubricated coatings. The driving force behind the coating industry was the need to develop a proc-ess that will extend the life of steel machine parts, cutting tools, molding dies, and sliding parts. For example, in the stamping industry, severe abrasive wear and galling (cold metal welding) are expected. There is the need for an efficient application of lu-bricants both for…     

Plasma Enhanced Lithium Coupled with Cobalt Fibers Arrays for Advanced Energy Storage

Construction of high efficiency and stable Li metal anodes is extremely vital to the breakthrough of Li metal batteries. In this study, for the first time, groundbreaking in situ plasma interphase engineering is reported to construct high-quality lithium halides-dominated solid electrolyte interphase layer on Li metal to stabilize & protect the anode. Typically, SF₆ plasma-induced sulfured and fluorinated interphase (SFI) is composed of LiF and Li₂S, interwoven with each other to form a consecutive solid electrolyte interphase. Simultaneously, brand-new vertical Co fibers (diameter: ≈5 µm) scaffold is designed via a facile magnetic-field-assisted hydrothermal method to collaborate with plasma-enhanced Li metal anodes (SFI@Li/Co). The Co fibers scaffold accommodates active Li with mechanical integrity and decreases local current density with good lithiophilicity and low geometric tortuosity, supported by DFT calculations and COMSOL Multiphysics simulation. Consequently, the assembled symmetric cells with SFI@Li/Co anodes exhibit superior stability over 525 h with a small voltage hysteresis (125 mV at 5 mA cm⁻²) and improved Coulombic efficiency (99.7%), much better than the counterparts. Enhanced electrochemical performance is also demonstrated in full cells with commercial cathodes and SFI@Li/Co anode. The research offers a new route to develop advanced alkali metal anodes for energy storage.     

A new insight into promotion action of Co2+ in Ni-diamond composite electrodeposition

A new insight into the promotion action of Co²⁺ on both particle and metal deposition in Ni-diamond composite electrodeposition system was analyzed according to electrochemical measurements. The results showed that the addition of Co²⁺ made particles content in deposits increased remarkably. The change of particles content in deposits was related inversely to the change of cathodic zero potential with the increase of the concentration of cobalt sulfate. Zero charge potential of cathode was shifted to much more negative region. The negative shift of the zero potential, combining with positive shift of the zeta potential, increased the electrostatic force between the particle-adsorbed metallic cations and the cathode. It not only benefits to the transportation of particles in solution towards cathode, but also shortens their residence time on cathodic surface. Meanwhile, entry of particles is also promoted. For metals deposition, reduction resistance of metallic cations rises greatly and deposition current at cathodic potentiodynamic polarization decreases after cobalt sulfate has been added into electrolyte. These factors are favorable for increasing particles content in deposits. In addition, physical model of diamond particles deposition state before and after the addition of Co²⁺ has been discussed.     

超临界CO2流体辅助合成Si-Fe-Fe3O4-C复合材料及储锂性能

硅碳负极是未来锂离子电池材料发展的重点方向之一,本文针对传统球磨法制备硅碳负极复合不均匀、界面融合差等问题,提出了一种超临界二氧化碳(scCO₂)流体介质球磨合成Si-Fe-Fe₃O₄-C复合材料的新方法。研究发现,纳米硅和中间相碳微球(MCMB)在scCO₂介质球磨混合过程中,CO₂和Fe反应先得到均匀分散的Si-FeCO₃-C前驱体,然后FeCO₃原位高温固相分解得到Si-Fe-Fe₃O₄-C复合材料。同时,在scCO₂流体渗透下,MCMB剥离成石墨片,并与纳米硅和Fe-Fe₃O₄实现较好的界面融合,Fe-Fe₃O₄的引入显著提升了硅碳负极的储锂容量、循环稳定性和倍率性能,Si-Fe-Fe₃O₄-C复合材料在0.2 A·g?1下100次循环后可逆容量保持在1065 mA·h·g?1。本方法利用超临界流体渗透性好、扩散能力强等特点,合成工艺简便,容易工业化实施,具有商业化开发潜力。