Effect of cobalt ion contamination on proton conduction of ultrathin Nafion film

With the wide use of platinum alloy electrocatalysts proton exchange membrane fuel cells, the dissolution of transition metal in the acid environment of catalyst layer becomes a major concern due to the decreased catalytic activity during long-term operation. Although great efforts have been done, few attention is paid to the effect of transition metal ion contamination of Nafion ionomer that wrapped around catalyst particles within catalyst layer which might greatly influence the proton conduction. To elucidate such effect, ultrathin Nafion film on SiO₂ model substrate is prepared via self-assembly method to represent the ionomer in fuel-cell catalyst layers, and the ultrathin film with specific thickness is further equilibrated in Co(NO₃)₂/HNO₃ solutions with different Co²⁺ concentration to achieve different doping level. Conductivity measurements demonstrate that the non-precious metal contamination severely worsens proton conduction of Nafion ionomer, but it is always ignored before. In addition, when the occupation of H⁺ in Nafion ionomer is less than 50%, the activation energy shows a sharp increase, indicating a possible change in proton conduction mechanism.     

微型离心泵泵叶三层式滑块机构三板模具设计

针对微型离心泵泵叶塑件成型模具设计困难的问题，设计了一种改进型三板点浇口模以用于该泵叶塑件的成型。塑件的浇注成型应用3个点浇口来进行平衡注塑，以控制塑件成型变形。模腔布局为1模1腔。针对塑件叶槽区域脱模困难问题，设计了一种3层3次复合抽芯脱模用于难脱模叶槽部位特征的脱模，机构中，将叶槽部位特征的成型块分割成2层成型件后，机构的第一次抽芯动作由弹簧驱动上层滑块实施上层成型块的抽芯；机构的第二次抽芯由斜导柱驱动实施下层成型块的抽芯；最后，由弯销驱动基座滑块带动2个侧抽芯滑块向外抽芯，以让出塑件完全顶出脱模的运动空间。第二次抽芯、第三次抽芯的驱动动力分别由模架模板的第三次开模、第四次开模打开来进行驱动。塑件的最终脱模由油缸驱动顶针板及顶杆顶出而实现塑件的完全脱模。基于塑件、流道脱模及抽芯机构的动作需要，将典型三板点浇口模架改进为四板4次开模点浇口，从而能使塑件、流道废料及驱动滑块机构分次按序来实施抽芯脱模。模具脱模机构动作设置合理，机构结构设计巧妙，模具整体工作可靠，有较好的设计参考价值。     

Improvement of fuel cell performances through the enhanced dispersion of the PTFE binder in electrodes for use in high temperature polymer electrolyte membrane fuel cells

In high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), it is important that the structure of the electrode catalyst layer is formed uniformly. To achieve this, the binder must be well dispersed; however, polytetrafluoroethylene (PTFE), which is commonly employed in the preparation of HT-PEMFCs, is difficult to disperse during electrode manufacture due to its high hydrophobicity. In this study, we fabricate electrodes containing a surfactant to improve the dispersion of the PTFE binder and to enhance reproducibility during electrode manufacture. The electrodes are commonly prepared via a bar coating method, which is known to exhibit poor dispersion due to the small amounts of solvent employed compared to the spraying method. We then compare the properties of the obtained electrodes prepared in the presence and absence of the surfactant through physical and electrochemical characterization. It is found that the electrode containing the surfactant is structurally superior, and its single cell performance is significantly higher (i.e., 0.65 V at 0.2 Am cm⁻²). The single cells are suitable for operation at 150 °C using H₂/air at atmospheric pressure and a total platinum loading of 2.0 mg cm⁻².     

热处理工艺对22MnB5钢铝硅镀层氧化层厚度和组织演变的影响

目的探究奥氏体化工艺对铝硅镀层氧化层厚度和微观组织的影响规律及其演变机理。方法以热浸镀Al-10%Si的22MnB5为研究对象,采用扫描电子显微镜(SEM)、辉光放电光谱仪(GD-OES)和X射线衍射仪(XRD)等仪器,观察镀层在奥氏体化过程中氧化层厚度的变化和微观组织的演变规律。结果当试样以15℃/s的速率升温到900℃后立即水淬,镀层氧化层最薄,当试样升温到900℃保温5 min后水淬,镀层氧化层出现了不同程度的开裂,镀层表面出现孔洞和脱落的现象,氧化层厚度明显增加。结论奥氏体化保温时间比奥氏体化升温速率对镀层氧化层厚度的影响更大,保温时间越长,氧渗入镀层的深度越深,氧化层越厚,奥氏体化时间的延长不利于镀层氧化层保持完整性,影响镀层对钢基体的保护功能。镀层及其氧化层的微观组织演变规律为:镀层中首先形成Al2Fe3Si3(τ1)和Fe2Al5相,随后Fe2Al5相生长并伴随FeAl2相形成,而后FeAl2+Fe2Al5相生长且有FeAl析出,随后FeAl相生长,氧化层出现孔洞,最后氧化层破裂,镀层表面孔洞增加,最终组织为FeAl2+Fe2Al5+FeAl。     

玻璃沉积物对La2Ce2O7/YSZ涂层高温下热冲击性能的影响

目的 为了探究玻璃沉积物CMAS(CaO-MgO-Al2O3-SiO2)对新型结构热障涂层在1250 ℃下的热冲击寿命的影响，揭示热障涂层的失效行为。方法 通过火焰喷涂技术将制备的CMAS粉体均匀地沉积到铈酸镧/氧化钇部分稳定二氧化锆双陶瓷层热障涂层(LC/YSZ DCL-TBCs)和梯度热障涂层(LC/YSZ FGM-TBCs)的表面，于1250 ℃热冲击实验中进行涂层样品的抗热冲击性能及失效机理研究。利用扫描电镜(SEM)和能谱仪(EDS)追踪CMAS的位置，观察CMAS与涂层反应层的厚度与形貌。采用X射线衍射仪(XRD)测试反应层产物，并总结其失效方式。结果 高温热冲击结果显示梯度涂层的热冲击寿命(435次)远高于双陶瓷层热障涂层的寿命(229次)，约为铈酸镧/氧化锆双陶瓷层热障涂层寿命的1.9倍。铈酸镧层与梯度层都能在一定程度上阻碍CMAS渗入涂层内部，提高其CMAS腐蚀条件下的热冲击寿命。双陶瓷层热障涂层与梯度热障涂层的失效均是以层状剥落为主，剥落层主要是CMAS与LC的反应层以及反应层下的烧结层，反应层是由Ca2(LaxCe1-x)8(SiO4)6O6-4x、萤石相和MgAl2O4等难熔氧化物组成，这层致密氧化物类似于密封层，能阻止CMAS继续渗入。结论 功能梯度结构具有比双陶瓷层结构更优异的抗CMAS热冲击性能和更好的应力耐受性。     

Enhanced thermal stability of Bi2Te3-based alloys via interface engineering with atomic layer deposition

The ease of Te sublimation from Bi₂Te₃-based alloys significantly deteriorates thermoelectric and mechanical properties via the formation of voids. We propose a novel strategy based on atomic layer deposition (ALD) to improve the thermal stability of Bi₂Te₃-based alloys via the encapsulation of grains with a ZnO layer. Only a few cycles of ZnO ALD over the Bi₂Te_2.7Se_0.3 powders resulted in significant suppression of the generation of pores in Bi₂Te_2.7Se_0.3 extrudates and increased the density even after post-annealing at 500 °C. This is attributed to the suppression of Te sublimation from the extrudates. The ALD coating also enhanced grain refinement in Bi₂Te_2.7Se_0.3 extrudates. Consequently, their mechanical properties were significantly improved by the encapsulation approach. Furthermore, the ALD approach yields a substantial improvement in the figure-of-merit after the post-annealing. Therefore, we believe the proposed approach using ALD will be useful for enhancing the mechanical properties of Bi₂Te₃-based alloys without sacrificing thermoelectric performance.     

厚松散层薄基岩坚硬顶板工作面覆岩破坏电法监测

掌握导水裂缝带发育高度对于厚松散层薄基岩煤矿工作面安全开采具有重要的意义。在煤层采动影响前,在工作面巷道向煤层工作面顶板施工1个仰孔,布置孔中电极电缆,形成钻孔电法监测系统。在巷道中连接并行电法仪器和钻孔电缆,数据采集方式称为AM法。随采煤工作面位置逐渐接近并进入钻孔控制范围,监测电极电流值和视电阻率值发生变化。结果表明:对潘北煤矿厚松散层薄基岩坚硬顶板工作面电法监测显示,弯曲下沉带电极电流值和视电阻率值较为稳定,受采动影响程度较小;导水裂缝带内,电极电流值明显下降,视电阻率值明显升高;顶板高度0~40 m采动超前影响范围可达410 m左右;工作面坚硬顶板砂岩地层为控制覆岩破坏的关键层,采空区上方坚硬顶板岩层垮落滞后工作面9~16 m;工作面导水裂缝带高度为37 m,导水裂缝带未发育到基岩面,风化砂质泥岩裂隙在采动应力作用下存在闭合现象。     

Composite mixed matrix membranes incorporating microporous carbon molecular sieve as filler in polyethersulfone for CO2/CH4 separation

Membrane technology has been considered a key factor for sustainable growth in high-efficiency gas separation. Current mixed matrix membranes (MMMs) technology is rising, but these membranes in the dense structure are having difficulties in operating at high pressures and scale up for commercialization. The purpose of this research is to synthesize composite MMMs (CMMMs) consisting of polyethersulfone (PES), carbon molecular sieve (CMS 1–5 wt %), and Novatex 2471 nonwoven fabric (support layer). The membranes' physical, chemical, and thermal properties were evaluated by different analytical equipment. The morphology of both PES and PES-CMS composite membranes had a porous and asymmetric structure, in which CMS was uniformly distributed in the polymer matrix. The thermal properties showed that the membranes were stable up to 350 °C with a single glass transition temperature. The functional groups in the membrane were confirmed by spectral analysis. The gas performance results showed that carbon dioxide permeance increased with increased CMS concentration and methane permeance decreased due to the hindering effect of CMS under similar operating conditions. The highest selectivity achieved was 12.774 using CMMM of 5 wt % of CMS at 10 bar, which on average was 137.80%, improved selectivity compared to pure PES membrane. The support layer was able to withstand high operating pressures and showed the ability to scale up. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48476.     

Ni对铁基合金粉块氩弧堆焊层组织和性能的影响

通过氩弧焊在基体材料Q235钢板上熔敷铁合金混合粉末压块,研究了压块成分及堆焊工艺对堆焊层组织及性能的影响。结果表明:在固定压块粉末总质量为16 g、镍铁含量为0.64 g、堆焊电流为180 A时,堆焊层的硬度最大,达到HRC48.9;耐磨性最高,相对磨损量为0.013 4 g/(cm^2·min)。     

低碳钢电弧熔覆增材层摩擦磨损及抗腐蚀性能

目的 针对低碳钢零件的破损失效采用TIG焊电弧熔覆增材制造工艺，研究低碳钢电弧熔覆修复使其达到再制造零件性能要求的可行性，为实现TIG焊修复应用提供保证。方法 通过TIG焊熔覆在低碳钢坡口处，对熔覆接头的显微组织进行分析，并测试修复后的增材层表面硬度性能。使用Nanovea Tribometer摩擦磨损仪和NanoveaPS50表面轮廓仪，对基体和增材层进行摩擦性能测试，并表征摩擦磨损后的表面形貌，探究磨损机理。采用电化学工作站对基体和增材层的腐蚀性能进行分析。结果 修复后的增材层显微硬度（220.17HV）高于基体且其摩擦性能和腐蚀性能优于基体，随着磨损载荷的增加，增材层的摩擦系数逐渐降低，磨损机制主要为磨粒磨损和粘着磨损。增材层表面组织均匀细小，在NaCl溶液中点蚀坑小且分散，增材层的腐蚀电流密度（1.8349×10-6 A/cm2）小于基体的腐蚀电流密度（6.5251×10-5 A/cm2），增材层表面的抗腐蚀能力明显提高。结论 电弧熔覆低碳钢可满足低碳钢零部件现场电弧快速修复对再制造性能的要求，实现了低碳钢破损零部件的表面修复与强化。