共查询到19条相似文献,搜索用时 156 毫秒
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空间材料二次电子发射过程的理论研究 总被引:2,自引:0,他引:2
航天器充放电效应故障大多都会引起卫星灾难性事故,对航天器在轨安全运行产生较大的影响。空间材料的二次电子发射系数是决定卫星表面带电速率和充电平衡电位水平的重要材料特征参数,对于卫星表面带电的预测及卫星带电设计选材具有重要的意义。基于蒙特卡洛方法,从理论上分析了材料二次电子的产生、转移及逃逸过程,获得了材料二次电子发射系数的计算方法。实验结果表明该方法能较好地拟合材料二次电子发射系数随入射电子能量的变化趋势,为航天器充放电效应数值模拟和防护设计提供数据支持。 相似文献
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水热合成磷酸铁锂粉体的形貌控制 总被引:3,自引:0,他引:3
以氢氧化锂、硫酸亚铁、磷酸为原料,采用水热法合成磷酸铁锂.研究了表面活性剂,加料温度、降温速度对产物形貌及性能的影响.用X射线衍射(XRD)、扫描电子显微镜(SEM)和激光粒度仪、恒流充放电测试表征材料的性能.结果表明:表面活性剂选择CTAB,40℃加料,降温速度选择5℃·min-1,可以得到平均粒径为1.5μm的粉体,在30℃的环境温度下,材料0.2C、1C和5C首次充放电比容量分别为157、152和136mAh·g-1,经过35次5C倍率充放电循环后,比容量无衰减. 相似文献
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采用鳞片石墨粉作为铝离子电池正极材料,其不同粒度大小对正极材料的表面特性和电化学性能都有影响。通过X射线衍射、X射线光电子能谱、充放电测试、倍率特性测试和循环性能测试分析该正极材料的晶体结构、化学价态和电化学性能。结果表明:铝离子电池正极材料鳞片石墨粉为良好的层状结构,P63/mc空间群,六方晶系。其中鳞片石墨粉325目(粒度45μm)在1C倍率下的充放电比容量分别为104.76和104.46mAh/g,其5C倍率较1C倍率的容量保持率为71.4%,循环100次后容量保持率为95.19%,因此其充放电比容量、倍率性能、循环性能等电化学性能较佳。 相似文献
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家用空调热交换器的发展 总被引:1,自引:0,他引:1
本文主要介绍为适应家用空调热交换器的技术革新而开发的铜管、铝箔材料的情况:如内螺纹铜管的齿型及其高度导热性的原理,铝箔的成型与材料特性的关系,翅片材料的表面机能与特性要求以及给予这些机能特性的表面处理方法等。 相似文献
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空间材料二次电子发射特性测试 总被引:6,自引:4,他引:6
空间材料的二次电子发射系数是表征航天器表面充电状态的重要参数 ,对于卫星表面带电的预测及卫星防带电设计选材具有重要的作用。为了测量空间材料二次电子发射特性 ,研制了专门的测试装置。介绍了该实验装置的主要结构、性能及技术指标等 ,通过应用计算机数据采集系统 ,并研制专门的数据处理软件 ,提高了装置的自动测量能力。实验说明 ,该装置用于空间材料的二次电子发射特性测试中测量方便、准确 相似文献
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J. Pavl? A. Velyhan I. Richterová J. Šafránková Z. Něme?ek J. Wild M. Jer¨áb 《Vacuum》2006,80(6):542-547
Dust grains in space are charged by various processes. Impacts of energetic ions lead to deposition of positive charge on the grain, increasing the grain potential and, as a consequence, the electric field at its surface. The accumulated charge is spontaneously released as an emission current when the electric field reaches a threshold. This discharging current is usually attributed to field ionization of any gas surrounding the grain or to ion field emission and would thus be predominantly a function of the surface potential. However, preliminary studies [Velyhan A, Z?ilavý P, Pavl? J, S?afránková J, Něme?ek Z. Ion beam effects on dust grains. Vacuum 2004;76:447-55] using melamine formaldehyde spheres have shown that the discharging current depends strongly on the energy of primary ions. The present paper continues these investigations with the motivation to understand the whole charging/discharging process. The experiment is based on the capture of a single dust grain in an electrodynamic quadrupole. The trapped grain is exposed to an ion beam with different energies up to 5 keV and its charge and surface potential are estimated from the frequency of its oscillations in the quadrupole. The charging/discharging currents are determined from temporal changes of the grain charge. Our results suggest that the grain charge is accumulated in a thick surface layer of non-conducting samples. The thickness of this layer depends on the mass and energy of primary ions. On the other hand, the beam ions probably recombine on the metallic surfaces and create an adsorbed layer there. We believe that the main discharging process is field desorption complemented in this particular case with post-ionization. 相似文献
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Analysis of Power-Supply Interference Effects on Direct Sensor-to-Microcontroller Interfaces 总被引:1,自引:0,他引:1
Reverter F. Gasulla M. Pallas-Areny R. 《IEEE transactions on instrumentation and measurement》2007,56(1):171-177
This paper analyzes the effects of power-supply interference on direct sensor-to-microcontroller interfaces based on measuring the charging/discharging time of an RC circuit that includes the sensor. Power-supply interference becomes a source of trigger noise that affects the measurement of the charging/discharging time and, hence, the measurement of the sensor resistance or capacitance. The measurement uncertainty increases proportionally to the amplitude of the interference and depends on its frequency. Such interference effects are smaller when measuring the discharging time and can be further reduced by placing an additional resistor in the interface circuit. Experimental data obtained from a PIC microcontroller agree with the theoretical predictions 相似文献
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石墨烯作为一种锂离子电池负极材料表现出优异的电化学性能,但石墨烯在充放电过程中容易团聚,导致其容量衰减特别快。而金属氧化物在充放电过程中体积膨胀大,因此其容量衰减也非常快;另外,金属氧化物的电导率低,导致其倍率性能差。将金属氧化物与石墨烯复合,两者性能互补,石墨烯可提高复合材料的电导率,缓解金属氧化物在充放电过程中的体积效应;金属氧化物可提高复合材料的储锂容量,并能阻止石墨烯在充放电过程中团聚。本文介绍了石墨烯/CuO锂离子电池负极材料的制备方法,分析了石墨烯与氧化铜及其复合材料的储锂机制,展望了石墨烯/CuO锂离子电池负极材料的应用前景,并指出了当前研究中存在的问题。 相似文献
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锂空气电池以其超高的能量密度而备受关注, 然而充、放电过电位高等问题严重限制了其实际应用。金属钯作为催化剂可而降低锂空气电池的充、放电过电位, 但其充、放电反应催化机制尚不完善。本研究运用第一原理计算方法, 建立了钯/氧气/过氧化锂(Pd/O2/Li2O2)的三相界面催化模型, 从微观角度揭示钯催化剂在锂空气电池充、放电反应中的催化机制。研究表明, Pd/O基底通过促进Li2O2在界面处的电荷转移提高自身对LiO2吸附作用, 从而加速放电产物在电极表面的形成, 有效降低了充电过电位0.43 V。 相似文献
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Identifying the Origin and Contribution of Surface Storage in TiO2(B) Nanotube Electrode by In Situ Dynamic Valence State Monitoring 下载免费PDF全文
Yuxin Tang Yanyan Zhang Oleksandr I. Malyi Nicolas Bucher Huarong Xia Shibo Xi Zhiqiang Zhu Zhisheng Lv Wenlong Li Jiaqi Wei Madhavi Srinivasan Armando Borgna Markus Antonietti Yonghua Du Xiaodong Chen 《Advanced materials (Deerfield Beach, Fla.)》2018,30(33)
Fundamental insight into the surface charging mechanism of TiO2(B) nanomaterials is limited due to the complicated nature of lithiation behavior, as well as the limitations of available characterization tools that can directly probe surface charging process. Here, an in situ approach is reported to monitor the dynamic valence state of TiO2(B) nanotube electrodes, which utilizes in situ X‐ray absorption spectroscopy (XAS) to identify the origin and contribution of surface storage. A real‐time correlation is elucidated between the rate‐dependent electrode performance and dynamic Ti valence‐state change. A continuous Ti valence state change is directly observed through the whole charging/discharging process regardless of charging rates, which proves that along with the well‐known non‐faradaic reaction, the surface charging process also originates from a faradaic reaction. The quantification of these two surface storage contributions at different charging rates is further realized through in situ dynamic valence state monitoring combined with traditional cyclic voltammetry measurement. The methodology reported here can also be applied to other electrode materials for the real‐time probing of valence state change during electrochemical reactions, the quantification of the faradaic and non‐faradaic reactions, and the eventual elucidation of electrochemical surface charging mechanisms. 相似文献
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以氧化石墨为碳前驱体, 利用含氧官能团与金属离子的价键结合, 一步水热工艺同时实现石墨烯的制备及均匀负载团簇结构CoFe2O4。微观形貌显示CoFe2O4为一次颗粒组成的团簇结构。复合材料独特的结构有助于充分发挥石墨烯高导电性、大比表面积的优势, 相比单纯的CoFe2O4, 该复合材料具有优异的倍率特性和循环稳定性。石墨烯的高导电性提升了复合材料的整体导电和导锂特性。同时, 独特的团簇结构及石墨烯的限制作用抑制了活性纳米颗粒在充放电过程中的体积变化, 提高了活性材料的稳定性。 相似文献