现代轨道交通摩擦集电材料及相关载流摩擦磨损研究进展

简述了现代轨道交通摩擦集电材料的发展历史,介绍了铜基粉末冶金、浸金属碳、碳纤维等几种摩擦集电材料的性能特点和研究现状,肯定了其应用价值和进一步研究的必要性。同时,对与之相关的载流摩擦磨损研究进行了比较全面的综述,提出了载流摩擦磨损研究过程中存在的问题和可能的发展方向。

电力机车用滑动集电材料的研究及其选用

详细介绍了受电弓滑板材料以及国内外的研究与发展状况。滑板材料的选用应从材料的性能、匹配性、机务段的使用要求三方面进行综合评价。指出

紫铜摩擦集电材料在阴雨环境中的腐蚀与磨损行为

在HST-100载流高速摩擦磨损试验机上,考察了紫铜摩擦集电材料在阴雨环境下的腐蚀与磨损行为,采用扫描电镜(SEM)对磨损表面形貌进行了观测,并对磨损表面宏观温度进行了测量。结果表明,阴雨环境中的水雾,一方面降低了磨损面的温度起到润滑及减磨作用;另一方面电弧产生的频率增加了电弧侵蚀的几率,但总的来说,水雾可以有效地改善该摩擦集电材料的腐蚀与磨损行为。紫铜摩擦集电材料在阴雨环境中的腐蚀与磨损机理表现为电弧侵蚀和轻微的粘着磨损。

一种新型滑动集电材料的研制及性能研究

利用粉末冶金 /挤压的方法制作了一种新型的Cu C滑动集电材料 ,并对该材料的机械物理、摩擦磨损性能进行了检测 ,结果证明该材料具有较高的抗拉强度、适中的表面硬度、较低的电阻率、优良的摩擦磨损性能 ,是一种较为优良的电力机车滑板材料。其性能测试结果和铁道部标准要求相比 ,优于铁道部标准要求。

集电材料在流动电流作用下的磨损机理

对氧化层类薄膜电阻作了介绍,提出电接触模型,阐述了电势和温度在触点附近分布的分析方法。通过分析,发现调节电势和温度之间的关系定律,使用计算接触电阻和薄膜电阻的因数确立一种计算温升的公式。最后,提出一种表示磨损模式之间转变条件的量化图。

一种新型滑板材料的研制及性能研究

采用粉末冶金/挤压的方法制作了一种新型的Cu-C滑动集电材料,对该材料的机械性能进行了检测,结果证明该材料具有较高的抗拉强度,适中的表面硬度,较低的电阻率,是一种较为优良的电力机车滑板材料。将其性能测试结果与铁标要求对比,优于铁标的要求。

Steel-Tinplate as a Solar Wall Panel and Its Effectiveness

The aim of the research was to investigate black colored steel-tinplate use for absorber and covering material of the collector and compare the efficiency of three types of air heating collectors. This heated air can be exploited for drying of agricultural products, room ventilation and room heating etc. 0.1 × 0.5 × 1.0 meter long FPC （fiat-plate collector） with a sun following platform was built. Air velocity at the experiments was v = 0.9 m/s. Collectors of insulated and un-insulated surfaces with steel-tinplate absorber as a covering material warmed the ambient air up to 10-12 and 5-6 degrees correspondingly （at irradiance 800 W/m^2）. This difference indicates the great importance of insulating the collector body. It can be explained with intense heat exchange between the absorber and ambient air which reduces the efficiency of the collector. There was good correlation with irradiance and the air heating degree. The investigations showed that more effective FPC had the collector with absorber tinplate in the middle of the collector body. At favorable weather conditions the heating degree of the ambient air at the outlet reaches 6-8 degrees more that at the outlet of the insulated collector covered by steel-tinplate.

Towards active plasmonic response devices

Given the interdisciplinary challenges in materials sciences, chemistry, physics, and biology, as well as the demands to merge electronics and photonics at the nanometer scale for miniaturized integrated circuits, plasmonics serves as a bridge by breaking the limit in the speed of nanoscale electronics and the size of terahertz dielectric photonics. Active plasmonic systems enabling active control over the plasmonic properties in real time have opened up a wealth of potential applications. This review focuses on the development of active plasmonic response devices. Significant advances have been achieved in control over the dielectric properties of the active surrounding medium, including liquid crystals, polymers, photochromic molecules and inorganic materials, which in turn allows tuning of the reversible plasmon resonance switch of neighboring metal nanostructures.

Magnetically induced micropillar arrays for an ultrasensitive flexible sensor with a wireless recharging system

Significant efforts have been devoted to enhancing the sensitivity and working range of flexible pressure sensors to improve the precise measurement of subtle variations in pressure over a wide detection spectrum. However,achieving sensitivities exceeding 1000 kPa^(-1) while maintaining a pressure working range over 100 kPa is still challenging because of the limited intrinsic properties of soft matrix materials. Here, we report a magnetic field-induced porous elastomer with micropillar arrays(MPAs) as sensing materials and a well-patterned nickel fabric as an electrode. The developed sensor exhibits an ultrahigh sensitivity of 10,268 kPa^(-1)(0.6–170 kPa) with a minimum detection pressure of 0.25 Pa and a fast response time of 3 ms because of the unique structure of the MPAs and the textured morphology of the electrode. The porous elastomer provides an extended working range of up to 500 kPa with long-time durability. The sophisticated sensor system coupled with an integrated wireless recharging system comprising a flexible supercapacitor and inductive coils for transmission achieves excellent performance. Thus, a diverse range of practical applications requiring a low-to-high pressure range sensing can be developed. Our strategy, which combines a microstructured high-performance sensor device with a wireless recharging system, provides a basis for creating next-generation flexible electronics.

Ferroelectric materials for vibrational energy harvesting

Energy harvesting is an appealing technology that makes use of the ambient energy which is otherwise wasted. Piezoelectric materials directly convert the elastic energy to the electric energy, and thus have a great advantage in scavenging vibrational energy for simplicity in device structure with relatively high power density. This paper provides an overview on the research of piezoelectric materials in energy harvesting in recent decades, from basics of piezoelectricity and working principle of energy harvesting with piezoelectric materials, to the progress of development of high-performance piezoelectrics including ceramics, single crystals and polymers, then to experimental attempts on the device fabrication and optimization, finally to perspective applications of piezoelectric energy harvesting(PEH). The criteria for selection of materials for PEH applications are introduced. Not only the figure of merit but also maximum allowable stress of materials are taken into account in the evaluation of their potential in achieving high energy density and output power density. The influence of the device configuration on the performance is also acknowledged and discussed. The magnitude and distribution of induced stress in the piezoelectric unit upon excitation by the vibration source play an important role in determining the output power density and can be tuned via proper design of device configuration without changing its resonant frequency. Approaches to address the issue of frequency match accompanying with the resonant mode are illustrated with literature examples. Usage of PEH devices can be extended to a variety of vibration sources in everyday life as well as in nature. Some appealing applications of PEH, such as in implantable and wearable devices, are reviewed.

Design, optimization, and measurement of closed-loop Hall effect current sensor

A kind of closed-loop Hall effect sensor is designed and fabricated by considering several factors such as iron core material, Hall device, as well as selected integrated circuit. Through studying the effect of the iron material and structures of current sensor, a kind of optimal Hall effect current sensor is found. The experimental results show that the presented closed-loop Hall effect current sensor achieves 1 mA/A sensitivity. And its lineafity and accuracy are 0.1% and 0.35% FS, respectively, at cur- rents ranging from 0 to 50 A.