Accelerated Test of Silicone Rubbers Exposing to PEMFC environment

The durability of sealing material is one of the major challenges to the overall lifetime of proton exchange membrane fuel cell (PEMFC). In order to study the failure mode and aging mechanism of fuel cell seals, this paper focuses on the most widely used commercial silicone rubber, and an ex-situ accelerated aging method was employed by simulating the circumstance of PEMFC, including higher temperature and clamping force, lower pH value and F⁻ with higher concentration. The main factors that affect the performance of the seal were obtained through the test of their morphologies and mechanical properties. The failure mode of the aging mechanism of the rubbers were analyzed through scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), attenuated-total-reflection infrared spectroscopy (ATR-IR), mass loss, compression set (CS), etc. It was found that temperature played an important role in the deterioration of seal performance, and the change of the parameters of the compression set with time conformed the dynamic empirical formula, which provides the experimental basis for the lifetime prediction of the seals.     

聚丙烯纤维混凝土耐久性与冻融损伤模型研究

掺入适量聚丙烯纤维即可以提高混凝土力学性能,又能够很好地改善混凝土耐久性。通过完成不同纤维掺量聚丙烯纤维混凝土抗水渗透试验、抗冻试验,得出耐久性最佳配合比。利用现有理论,结合数值分析最小二乘拟合方法,建立以相对动弹性模量和冻融累积损伤为损伤变量聚丙烯纤维混凝土的冻融损伤模型,完善现有软岩隧道喷层支护耐久性理论,对于软岩隧道支护技术发展具有广泛推广意义。     

Pyrolysis of Iron(III) porphyrin coated Pt/C toward oxygen reduction reaction in acidic medium

Design and synthesis of highly active and durable electrocatalysts toward oxygen reduction reaction (ORR) is of particular importance for proton exchange membrane fuel cells (PEMFCs), yet remains a grand challenge. Herein, we report the deposition of iron (III) porphyrin (FeP) on house-made Pt/C by rotary evaporation of the mixture of FeP and house-made Pt/C dispersed in chloroform, followed by pyrolysis at 650 °C in argon atmosphere. This approach led to the synthesis of new non-precious metal electrocatalyst (NPME)-Pt/C composites (Pt/C–FeP) with an average nanoparticle diameter of 3.1 ± 1.5 nm without aggregation. According to X-ray photoelectron spectroscopy (XPS), the binding energy of Pt 4f_7/2 became larger due to the presence of pyrolyzed FeP. In addition, the electrochemically active surface area (ECSA) of Pt/C–FeP-650 is 65 m²/g less than that of house-made Pt/C (80.2 m²/g). This implies that the pyrolyzed FeP may have partially covered the surface of Pt nanoparticles and thus lowering the ECSA. Interestingly, the mass activity (MA) of Pt/C–FeP turns out to be 349.0 mA/mg_Pt @0.9 V vs. RHE, which is 2.6 times and 1.5 times of house-made Pt/C and commercial Pt/C, respectively. It is speculated that the electronic interaction and possible synergy between Pt and pyrolyzed FeP as NPME might have contributed to the ORR activity improvement despite of partial loss of ECSA. During accelerated durability tests (ADTs), the MA of Pt/C–FeP-650 degrades 64.3% inferior to commercial Pt/C (52.2%). The main reason likely arises from the degradation of pyrolyzed FeP, which is a bottleneck problem confronting NPMEs.     

谈混凝土结构耐久性的防护认识

混凝土结构的耐久性是当前困扰土建基础设施工程的世界性问题。本文对混凝土结构的耐久性现状进行了综合简单介绍,并陈述了影响混凝土结构耐久性的主要因素,同时提出解决影响混凝土结构耐久性的保防护措施。     

涤棉双面针织物透湿等性能分析

针对我国流行的涤棉双面针织物，本文研究了纱线粗细、编织密度和组织结构等对织物透湿性、耐磨性、抗起毛起球性等影响。从热湿舒适性、服用性能角度出发，提出了有关原料选择、编织密度和组织结构等方面的新见解。     

再生骨料对高钙粉煤灰基地聚物混凝土力学及耐久性能的影响

试验分别采用再生骨料和天然骨料作为粗骨料,制备了碱激发高钙粉煤灰基地聚物再生骨料混凝土和地聚物天然骨料混凝土。测试了其密度、抗压强度、劈裂抗拉强度、抗折强度、吸水率、渗透孔隙率、氯离子渗透深度及抗硫酸侵蚀等指标,探讨比较了再生骨料与天然骨料高钙粉煤灰基地聚物混凝土物理力学性能和耐久性的差异;并进一步分析了不同NaOH溶液浓度(6 mol·L~(-1)、12 mol·L~(-1)和18 mol·L~(-1))对其相关性能的影响。结果表明:再生骨料可以用作粗骨料制备高钙粉煤灰基地聚物混凝土,其抗压强度在30.64~38.22 MPa之间,略低于天然骨料制备的地聚物混凝土。随着NaOH溶液浓度的增加,粉煤灰基地聚物混凝土的力学性能及耐久性能均显著改善,且当NaOH浓度为12 mol·L~(-1)时,其各项性能综合较优。     

谈混凝土耐久性及提高措施

论述混凝土耐久性问题的重要性,探讨影响混凝土耐久性的因素,分析混凝土过早劣化的起因,并提出提高混凝土耐久性的几项措施。     

生物高分子HCP与聚丙烯酰胺HPAM的交联性能与应用

研制了一种生物高分子交联剂HCP,并使其与部分水解聚丙烯酰胺HPAM的水溶液进行交联.通过光度分析、室内岩心实验及测试电导率和粘度等方法评价了交联聚合物的性能.实验结果表明,交联剂HCP与HPAM之间的确可以产生交联作用,而且交联得到的凝胶具有良好的增粘、耐温性能;交联产物可以用于窜聚井的封窜和注聚井剖面调整.     

CRTSⅡ型水泥乳化沥青砂浆施工质量控制

本文以京沪高速铁路和京津城际客运专线工程施工实践为基础,阐述了水泥乳化沥青砂浆层施工质量控制要点,对施工中常见病害进行了描述与原因分析,最后基于弹性地基梁理论与有限元方法,研究了砂浆层离缝对轨道结构受力和变形的影响。结果表明轨道板与水泥乳化沥青砂浆层之间的离缝将加剧轨道结构的变形,为了保证高速列车行车品质与轨道结构的耐久性,必须严格控制水泥乳化沥青砂浆的施工质量,防止灌浆时砂浆离缝的出现,并及时进行施工工艺调整与养护维修。     

改进的DFR法在轨道车辆结构疲劳寿命预测中的应用

为满足高速化和重载化设计需要,耐久性疲劳设计已经成轨道车辆关键部件疲劳设计的主要方法.本文在结构细节疲劳额定值法分析的基础上,提出了针对轨道车辆结构细节的疲劳额定值法,推导了中长寿命范围(104～∞)内基于肋RDFR法的疲劳寿命预测公式,并编写了RDFR朋法的计算程序.最后结合轨道车辆牵引梁的特殊结构细节,验证了此方法可以被用来进行评估和分析国内车辆主要结构部件的疲劳寿命.