质子交换膜燃料电池极板及其表面改性研究进展

在质子交换膜燃料电池（Proton exchange membrane fuel cells,PEMFCs）的部件中,双极板是重要组成部分。双极板约占燃料电池成本、质量、体积的40 %、80 %、50 %。传统的PEMFC因为石墨双极板的材料、工艺等问题,造成其体积和质量较大,这增加了汽车的重量,缩小了汽车底盘地可用空间,影响了质子交换膜燃料电池汽车的性能。因此开发体积小、成本低、制备工艺简单的双极板对推进质子交换膜燃料电池的商业化应用具有重要意义。金属双极板因其成本低、力学性能好、导电性、导热性、体积相对易控等特点,在PEMFC领域备受关注。但金属双极板在PEMFC环境中易生成钝化膜,导致其接触电阻增加。因此,如何在提高金属双极板耐蚀性的同时,保持良好的导电性,是当前对PEMFC研究的重点。本文综述了石墨、复合材料和金属双极板制备工艺及表面改性方法。讨论了双极板及其表面碳化物涂层、金属涂层和氮化物涂层的优缺点,并比较了这些涂层在PEMFC环境下的耐腐蚀性和界面接触电阻性能。     

质子交换膜燃料电池双极板防护涂层研究进展

质子交换膜燃料电池(PEMFC)作为第4代发电技术,具有结构紧凑、体积小、能量密度高、效率高、启动快、低温运行以及零排放的绝对优势,被认为是现阶段理想的清洁能源之一,是未来新能源汽车理想的供能部件,受到各国学者的广泛关注。双极板作为PEMFC重要的组成部件之一,不仅能够将单电池串联、并联或是混合联结形成电池堆,起到支撑作用,还能够隔绝阴极、阳极的反应气体,排出电池堆反应产生的热量和水,对PEMFC电池堆的性能至关重要。合适的双极板材料要具有优异的导电性和耐腐蚀性,已成为PEMFC研究领域的一个热点。简述了PEMFC的工作原理以及近年来石墨双极板、金属双极板以及复合双极板的研究情况,指出了PEMFC在工作条件下对金属双极板的性能要求及改性难题。着重对不锈钢双极板的表面涂层改性进行了研究,列举了碳基涂层、金属及其化合物涂层、导电高分子聚合物涂层、疏水涂层等一系列涂层的研究进展和性能,分析对比了它们在PEMFC双极板表面改性中的优缺点。分析结果表明,过渡金属碳、氮化物以及碳/陶瓷复合涂层具有良好的导电性和耐蚀性且成本较低,是当前以及未来的研究热点,同时如何增强涂层与基体的结合力,也是今后双极...     

氢燃料电池中钛双极板研究进展

钛及钛合金密度低、比强度高且在酸性环境中耐蚀性优异,在氢燃料电池双极板中具有较高的应用价值。回顾了近年来氢燃料电池用钛双极板的研究进展,详述了钛双极板表面改性技术的研究成果,包括掺杂合金元素、钛表面涂覆金属基涂层(贵金属、金属碳/氮化物等)和碳基涂层(石墨、无定型碳等)。涂层结构组织的复合化和纳米化,有利于提升钛双极板的耐蚀性、导电性和疏水性,其对于提升氢燃料电池的性能及保证其运行的稳定性和耐久性具有重要作用。     

质子交换膜燃料电池金属双极板材料研究进展

双极板在质子交换膜燃料电池(PEMFC)中具有隔离反应介质、收集电流、提供气体通道的作用，金属材料用于双极板面临腐蚀及表面层钝化影响电池性能等问题．在介绍了研究金属双极板性能的方法，包括接触电阻测试、电池极化性能测试、模拟电化学方法等测试方法的同时，着重介绍了在双极板中应用的不同种类铁基金属材料、轻金属材料的性能及各种表面涂层技术的研究进展．简单介绍了PEMFC中，金属双极板材料研究所应重点解决的技术问题．     

质子交换膜燃料电池不锈钢双极板的腐蚀行为及其表面防护的研究进展

质子交换膜燃料电池(PEMFCs)作为一种环境友好型电池装置,在倡导人与自然和谐相处的现代社会日渐受到重视.双极板是PEMFCs的重要组成之一,其性能的好坏与PEMFCs的发展密切相关.不锈钢双极板虽具有优异的导电性和强度,但在PEMFCs的严苛工作环境下,仍面临着腐蚀与钝化等问题.近年来,国内外的研究者为解决不锈钢双极板的表面防护问题展开了广泛的探索,深入研究发现,解决这一问题的有效途径是在其表面制备高导电性、高耐蚀性的防护涂层.简述了PEMFCs的工作原理以及对双极板的性能要求,从不锈钢双极板的运行环境和工作要求出发,提出其自身存在的问题和所面临的改性难题.另外,对近年来不锈钢双极板的表面防护涂层进行了分类,分别阐述了碳基涂层、金属及其化合物涂层和疏水涂层在不锈钢双极板防护上的研究进展,分析对比了不同方法制备涂层的优缺点,在此基础上,明确了不锈钢双极板表面防护的发展方向和未来表面改性技术的研究热点.     

空间燃料电池金属钛表面复合涂层制备与性能研究

金属 Ti 因其密度小（仅为不锈钢的 0.6 倍）和比强度高等特点,是轻量化空间燃料电池金属板材料的首要选择,但其在弱酸性环境中长时间工作容易被腐蚀。为了改善金属 Ti 双极板耐蚀性,采用多弧离子镀技术在金属 Ti 表面制备了由 Ti 过渡层及 TiN 表层构成的 Ti / TiN 复合涂层,研究制备工艺参数对 Ti / TiN 复合涂层微观结构及力学、电化学性能的影响规律。利用场发射扫描电子显微镜（SEM）分析涂层的微观形貌,利用 X 射线衍射仪分析涂层的相组成,利用纳米压痕仪评价涂层的力学性能,利用电化学工作站评价涂层在模拟质子交换膜燃料电池（PEMFC）阴极工作环境下的耐蚀性。结果表明：制备工艺参数优化后的 Ti / TiN 复合涂层具有优异的表面质量和良好的耐蚀性,腐蚀电流密度为 6.383 μA / cm² ,是金属 Ti 腐蚀电流密度的 0.6 倍,Ti / TiN 复合涂层显著提高了金属 Ti 的耐蚀性,可为空间燃料电池金属双极板表面改性提供技术支持。     

硅烷流量对钛合金双极板表面改性碳膜性能的影响

目的通过对钛合金基底进行表面改性,提高其作为质子交换膜燃料电池(PEMFC)金属双极板的耐蚀导电性能。方法通过等离子体增强化学气相沉积法(PECVD),调控不同的Si H4流量(0～10 mL/min),在钛基底表面制备了含硅非晶碳膜。利用电化学工作站、界面接触电阻测量仪、水接触角测量仪、纳米压痕仪,分别测试了薄膜的耐蚀性、导电性、疏水性和力学性能。通过拉曼光谱分析了腐蚀前后薄膜内部杂化比变化,并结合扫描电子显微镜和高分辨透射电子显微镜研究了薄膜厚度、腐蚀形貌和内部结构。结果 SiH4流量为8m L/min时,制备的含硅非晶碳膜具有最佳耐蚀性和导电性,该含硅非晶碳膜水接触角为102.91°,硬度为9.28 GPa,弹性模量为60.34 GPa,厚度为2.822μm。其动电位腐蚀电流密度为0.017μA/cm2,相比钛基底提升3个数量级(80.51μA/cm~2),在1.4 MPa压力下,其界面接触电阻为47.06 mΩ·cm~2。结论硅的引入诱导非晶碳膜生成类石墨烯结构,提高了非晶碳膜的导电性能和耐蚀性能,提升了薄膜的力学性能及疏水性。用含硅非晶碳膜对钛双极板进行表面改性,有望显著提高极板的燃料电池性能。     

质子交换膜燃料电池金属双极板改性碳基涂层技术研究进展

对比了碳基涂层改性金属极板、未涂覆的金属极板和传统石墨极板性能的优劣,阐述了碳基涂层在优化金属极板导电耐蚀性能方面取得的最新成果,以及在质子交换膜燃料电池(Proton exchange membrane fuel cells, PEMFCs)环境长期运行后,碳基涂层出现性能失效及寿命受限等问题。通过分析影响碳基涂层性能的因素,指出由于非晶碳材料设计、微观结构等对其性能影响规律的系统化研究不足,导致非晶碳涂层/金属极板损伤及退化机理不明确。重点阐述了国内外关于PEMFCs金属极板改性碳基涂层材料技术的研究进展,包括调控本征碳基涂层(a-C)微观形貌优化涂层性能;采用理论计算与实验相结合的方法制备金属掺杂碳基涂层(a-C:Me),解决涂层与特定金属基体间粘附性差、压应力高等问题;设计多层结构碳基涂层以减少贯穿性缺陷。探讨了几类涂层失效机制,并对金属极板改性用碳基涂层技术进行了展望。     

金属双极板表面改性碳基涂层研究进展

首先对比了贵金属涂层、氮化物涂层、碳基涂层的性能优劣,重点阐述了碳基涂层改性技术的最新研究进展。然后,以碳基涂层的设计及制备2个维度为研究切入点进行阐述。在膜系设计方面,着重分析了膜系设计和元素掺杂对碳基涂层的性能影响;在制备方面,分析了偏压、沉积时间和气体流量等对碳基涂层的化学组分、微观结构的调控作用。最后,总结了当前碳基涂层改性双极板存在的问题,主要为涂层运行寿命不足,无法达到服役标准;测试条件不统一,且模拟环境与电堆实际工况差距较大;涂层长时间服役后的失效机制不明确。同时,对金属双极板改性碳基涂层的进一步发展方向做出了展望。     

GO-PTFE-C涂层改性Ti金属板的防腐性能研究

目的提高钛金属板的抗腐蚀性能。方法采用水热浸渍两道工序在Ti双极板上制备GO-PTFE-C复合改性涂层。使用0.1 mol/L葡萄糖溶液作为碳源,在170℃+10 h条件下,于反应釜中完成碳涂层制备。对获得的涂层进行热处理,浸渍5%(质量分数)的聚四氟乙烯(PTFE)溶液和不同浓度氧化石墨烯(GO)的混合悬浮液后,在350℃热处理得到涂层。采用傅氏转换红外线光谱分析仪(FTIR)、扫描电子显微镜(SEM)和能谱仪(EDS)分析表面形貌和成分,选取三电极体系并利用电化学工作站(CHI 660e)表征改性前后双极板电化学性能,在模拟质子交换膜燃料电池(PEMFC)环境中测试其抗腐蚀性能。结果与单一的碳涂层相比,GO-PTFE表面具有更多的C=O官能团,同时由于聚四氟乙烯表面的F与含氧官能团的氧原子电子云的诱导效应,涂层附着力明显提高。其中,采用5%PTFE+3 g/L GO浸渍的涂层的腐蚀电流密度和接触角分别为0.008μA/cm~2和103.6°,恒电位极化测试(0.6 V和-0.1 V)显示,涂层的腐蚀电流密度均低于1μA/cm~2。结论以碳涂层为基体,浸渍GO和PTFE的混合液后,制备所得的钛基双极板在PEMFC的双极板中显示出巨大的应用前景。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.