Corrosion behavior and electrical conductivity of niobium implanted 316L stainless steel used as bipolar plates in polymer electrolyte membrane fuel cells

The corrosion behavior and interfacial contact resistance (ICR) of niobium implanted SS316L used as the bipolar plate in a polymer electrolyte membrane fuel cell (PEMFC) are investigated. The ICR values of the bare and niobium implanted SS316L are measured to evaluate the electrical conductivity. The effects of ion implantation on the corrosion behavior are investigated by potentiodynamic and potentiostatic tests in the simulated PEMFC anode and cathode environments. The solutions after the potentiostatic test are analyzed by inductively-coupled plasma atomic emission spectrometry (ICP-AES). The surface topography of the samples before and after the potentiostatic test is monitored by SEM in order to investigate the mechanism and degree of corrosion. The XPS results indicate that the composition on the surface is altered by ion implantation. The electrochemical results reveal that the passivation current density of the Nb implanted SS316L decreases and has higher chemical stability in the simulated PEMFC environment. However, the ion implantation fluence affects the current density. The ICP results are in agreement with those of the electrochemical test disclosing that the bare SS316L has the highest dissolution rate in both the cathode and anode environments and niobium implantation reduces the dissolution rate significantly. SEM shows that the bare SS316L undergoes serious corrosion whereas after Nb ion implantation, corrosion is greatly retarded. The XPS depth profiles indicate that a passive film with a new composition consisting mainly of niobium oxide is formed after the potentiostatic test. Our results suggest that niobium implantation with proper ion fluences can significantly improve the corrosion resistance and the electric conductivity of SS316L in the simulated PEMFC environments.     

云南南坡铜矿床地质特征及找矿标志

文章结合区域成矿地质背景,以南坡铜矿床地质勘查成果资料为依据,对矿区地层、构造、矿体特征、矿石特征等进行了论述,分析了矿床成因成矿规律,总结控矿因素及找矿标志,指导下一步找矿工作。     

A Comparative Analysis of Primary and Extreme Characteristics of Dry or Wet Status between Asia and North America

In this study, the Palmer Drought Severity Index (PDSI) was used to analyze the average and extreme dry/wet states of Asia and North America from 1953 to 2003. The results indicate that the two continents underwent drying trends during this period. Compared with North America, Asia showed more severe drought trends. However, more significant and regular seasonal variation for drought was found in North America. The driest regions in Asia were located in the northern region of China, Mongolia, and eastern mid-Siberian plateau. Most regions in central North America were relatively wetter than other regions. The northern and southwestern regions of North America, as well as the Atlantic and Pacific coastal areas, experienced the most drought during this period. A sharp increase of the drought area and the number of extreme drought events took place from 1997 to 2003 in both Asia and North America. Severe drought events were more likely to occur during the summer on both continents. Asia had the most extreme drought events during July, but North America reached its highest drought frequency from June to September. In Asia, a persistent increasing trend of extreme drought emerged throughout the studied period. However, a more complex evolution of drought emerged in North America: a decreasing trend appeared before the mid-1960s and an increasing trend appeared after the late 1970s. A relatively steady dry/wet status was observed between the mid-1960s and the late 1970s. The role of exceptional, extreme drought events with respect to the La Nina event was considered during 1997-2003.     

高强钢激光复合焊接T型接头组织分析

采用15kW高功率激光复合焊接船用低合金高强钢T型接头构件.测定了接头截面的显微硬度,通过光学显微镜、扫描电镜和透射电镜分析了焊缝微观组织.结果表明:焊接接头没有气孔、裂纹等缺陷;焊缝和热影响区显微 硬度均高于母材,焊缝显微硬度最高为290HV;焊缝组织主要为细条状的粒状贝氏体和少量的M-A组元.贝氏体铁素体为细条状的铁索体,晶粒细小,晶界密度高.Cu、Ti等微合金元素形成的碳化物沉淀强化相分布于贝氏体铁素体内.细条状的粒状贝氏体组织的晶粒细化及其微合金碳化物(Cu,Ti)xCy的沉淀强化使得焊缝强度高于母材.     

Effect of gap on plasma and molten pool dynamics during laser lap welding for T-joints

The aim of the present research is to discuss the effect of gap on plasma plume, keyhole, and molten pool dynamics during laser lap welding for T-joints. The authors observe plasma plume, keyhole opening, and molten pool images by high-speed camera in different gaps during CO₂ laser overlap welding of T-joints. The results show that gap causes beam energy fluctuations in the keyhole and leads to the instability of welding process. In laser spot welding, zero-gap and small gap greatly affect the stability of plasma and keyhole, which causes the formation of cavities in the weld metal, while a proper gap can help prevent porosity formation. In laser continuous welding, the disruption and closure of front keyhole wall at the gap periodically changes with the gap, which causes the formation of plenty of porosities at the gap. The instability of keyhole is closely related to dynamics of plume and molten pool, which gives an insight into the mechanism of porosity formation during laser overlap welding.     

16MnL汽车大梁钢板冷弯性能研究

分析研究了影响16MnL宽冷弯性能的主要因素,结合安钢实际情况提出了提高16MnL综合性能的建议。     

基于综合油液监测的大型冲压自动生产线故障诊断专家系统

根据SGM公司大型冲压自动生产线的润滑和液压系统的实际情况,在综合应用油液监测技术对生产线设备进行状态监测和故障诊断的基础上,采用基于C/S模式的SQLServer2000数据库并且应用VisualBasic开发了专家系统,实现了油样信息的管理、趋势分析和故障诊断等的功能。     

云南省某岩溶隧洞涌水量预测

云南省牛栏江-滇池补水工程大五山隧洞6号支洞在施工过程中排水量持续不减,影响施工进度。为指导下步施工工作,选用Q-S曲线法、比拟法和大井法三种方法对支洞涌水量进行了预测,结果分别为25 088,17 580,24 528 m3/d。经对比,水文地质比拟法误差最小,与隧洞施工开挖实况吻合较好,涌水量计算结果可直接指导施工。     

基于特征点提取和旋转不变技术的锁片基体视觉检测

针对锁片基体漏装检测中高速、柔性、准确的要求，采用视觉检测的方式进行检测。运用基于Harris探测算法的特征点提取并结合Zernike矩图像旋转不变技术，成功地解决了基体在图像中位置不固定的情况下检测耗时的问题，实现了锁片基体手工安装是否漏装的自动化视觉检测。实验证明，该方法具有实用性和高效性。     

冲压生产线液压油光谱监测研究

采用GM(1，1)模型对所监测的冲压生产线在用液压油的光谱数据进行拟合和预测，计算结果表明，GM(1，1)是一种用来预测的有效的模型，同时探讨了油液污染度与设备磨损状态的关联度，初步揭示了油液污染度和元素光谱数据之间的关系。