Manufacturing catalyst-coated membranes by ultrasonic spray deposition for PEMFC: Identification of key parameters and their impact on PEMFC performance

This study deals with the manufacturing of catalyst-coated membranes (CCMs) for newcomers in the field of coating. Although there are many studies on electrode ink composition for improving the performance of proton-exchange membrane fuel cells (PEMFCs), there are few papers dealing with electrode coating itself. Usually, it is a know-how that often remains secret and constitutes the added value of scientific teams or the business of industrialists. In this paper, we identify and clarify the role of key parameters to improve coating quality and also to correlate coating quality with fuel cell performance via polarization curves and electrochemical active surface area measurements. We found that the coating configurations can affect the performance of lab-made CCMs in PEMFCs. After the repeatability of the performance obtained by our coating method has been proved, we show that: (i) edge effects, due to mask shadowing - cannot be neglected when the active surface area is low, (ii) a heterogeneous thickness electrode produces performance lower than a homogeneous thickness electrode, and (iii) the origin and storage of platinum on carbon powders are a very important source of variability in the obtained results.     

Ultrasonic tomographic velocimeter for visualization of axial flow fields in pipes

An ultrasonic tomographic velocimeter to provide quantitative images of axial flow fields in pipes is developed and presented in this work. To detect the flow in various directions and positions, a novel transducer configuration strategy is proposed. All-in-one transducers are mounted in two sectional planes of the pipe. In each plane, N transducers are equally spaced along the circumference. Overlapped propagation paths are introduced by the configuration strategy, and the influence of the vortex flow can be eliminated theoretically by averaging the line velocities of the overlapped paths. To achieve a fast detection speed, the projection data is collected via an electrical scan in a fan-beam mode. After rearrangement and interpolation of the projection data, the parallel beam filtered back projection (FBP) algorithm is implemented to reconstruct the axial flow field. Numerical simulations with the theoretical velocity profiles were performed. The compensation method for the vortex flow is proved to be effective and necessary, and the number of transducers required for reconstruction of common flow profiles was estimated. Accordingly, an ultrasonic tomographic velocimeter consisting of 2×12 transducers was fabricated. Experiments were conducted in the straight pipe and downstream of a single bend pipe and compared with the computational fluid dynamics (CFD) simulation results. As demonstrated, the ultrasonic tomographic velocimeter was capable of visualizing both symmetric and asymmetric axial flow fields with high reliability.     

A review on ultrasonic spot welding of copper alloys

As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided.     

Process and joint quality of ultrasonic vibration enhanced friction stir lap welding

In order to improve the process effectiveness and joint quality, ultrasonic vibrations were integrated with friction stir lap welding. Effect of ultrasonic exertion on the process and joint quality of AA 6061-T6 were investigated. Upon ultrasonic exertion, joints owned larger effective lap width, shorter hooks and improved strength. Weld fracture mode changed from a ductile–brittle mixed mode to a more ductile mode while the fracture path shifted from lap interface to beyond the stir zone. Material flow and interface defects were characterised using lap welded dissimilar aluminium alloy joints. Ultrasonic vibration improved the material flow and reduced the interfacial defects. Variations in failure load of joints were found in accordance with the variations in material flow and interfacial defects.     

污水汽提系统的化学除臭清洗

文章简要介绍了化学除臭清洗剂JX-518的组成,并对采用该清洗剂对污水汽提系统进行化学除臭清洗的清洗过程及注意事项进行了详细介绍。实践证明,清洗后系统残液中硫化物及氨氮可降至很低,取得了很好的清洗效果。     

高导电性原油电脱盐工艺研究

南阳原油中金属含量较高,掺有部分3次采油采出原油,加工时易造成电脱盐装置原油乳化,电导率高,脱盐难度较大。装置投产十几年来脱后含盐一直不合格,经过改造仍然超标,常压塔顶腐蚀严重。为此,对原油进行了电脱盐工艺条件及破乳剂研究,研制出了高效电脱盐设备和生物复合脱盐剂及降电流剂,采用平流弓形电极进行改造,解决了该原油的电脱盐问题,使脱后含盐达到3 mg/L。     

油井参数对超声透射系数的影响

为了研究油井各参数对超声波透射系数的影响，根据超声波在媒质中的波函数和边界条件，求出了油井中超声波的透射系数。当井液和水泥层的声速和密度增大时，超声波的透射系数也随之增大，但变化幅度不大，特别是水泥层密度对超声波的透射系数影响很小；当岩层的声速增大时，超声波的透射系数会出现一个极大值；岩层密度对超声波的透射系数影响较大，且随岩层密度的增大超声波的透射系数随之降低。     

CSTN-LCD用铬版清洗效果的改善

利用铬版清洗机对CSTN-LCD用铬版进行清洗处理,分析了清洗过程中出现的铬层脱落现象,铬层脱落与轴向喷射压力和水平切力密切相关,通过调整转速和喷射压力探索了安全使用条件:在转速不超过1000r/min,喷射压力低于0.5×105Pa的情况下使用铬版清洗机进行清洗是相对安全的。同时采用预清洗处理的方法满足清洁要求,使换线时间由平均3h缩短到平均1h以内,年产能提高270000片。     

超声波清洗在贵/廉金属复合材料生产过程的应用研究

本文结合“ODS清洗剂消费淘汰项目”的实施，并对新型超声波清洗机及新型ODS清洗液进行了工艺试验，阐述了超声波清洗技术是贵／廉金属复合材料生产过程中无可替代的清洗技术。     

牛奶加工过程中的清洗(二)

五．牛奶厂的清洗。目前，牛奶厂采用的清洗方式主要是CIP清洗(Cleaning in place)，原地清洗或称定置清洗，即在基本不拆卸或挪动机械装置和管线的情况下对生产过程中能与牛奶发生接触的设备表面进行的清洗。其冲刷、清洗、灭菌的整个过程全部实现了自动化因此大大降低了劳动强度。而有一些不