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为了研究激光触发真空开关的靶材激光诱导击穿光谱和电弧光谱,分析影响时延抖动的微观因素,利用单脉冲纳秒激光轰击位于开关阴极的靶材激发等离子体,采用滤光片和光电倍增管组合使用的方法,取得了离散波长光强的数据,建立拟合曲线,进行了理论分析。结果表明,脉冲激光能量增大可以提高靶材激光诱导击穿光谱的强度,但几乎不影响电弧光谱的强度;增大开关两端电压可以提高电弧光谱强度;在开关强电场作用下,电弧等离子体碰撞激发,等离子体的成分比例随电压大小发生变化;时延抖动与电压大小无关,与自由电子运动状态和电弧离子种类无关,主要在触发阶段受影响,而相比激光能量,开关电压大小对导通时的电压下降沿陡度起主要作用。这一结果对激光触发真空开关中激光与靶材相互作用、脉冲电弧和时延抖动的进一步研究是有帮助的。 相似文献
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在真空断路器中,当电流达到几千安时会产生电弧集聚,我们使用两种触头来克服由于这种现象而产生的不良后果。横磁触头产生的横磁场使集聚电弧旋转,电有量均匀地分布在触头表面。纵磁触头可以防止电弧集聚到很高的能量。为了提高这两种真空断路器的开断容量,了解电流零点附近真空电弧等离子体(即真空电弧)的特性和变化过程,如等离子体的密度、等离子体的衰变以及能量就十分重要。在本文中,我们主要是用延迟场分析仪来研究电流过零前最后3ms内电弧电流的有效值达到了7.5kA时真空电弧等离子体中离子能量的分布状况。研究发现:横磁和纵磁触头的电弧离子能量存在着明显的差别。在电流超过5kA时,这两种触头上电弧离子能量的分布接近于麦克期韦(Maxwellian)分布,这是一种由离子碰撞决定的等离子体的特有分布。也就是说,在电流接近零点时,横磁触头中电弧离子的运动具有很强的方向性,而纵磁触头中能量的分布却明显受到离子碰撞的影响。 相似文献
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自持体放电又称大气压脉冲放电或脉冲辉光放电,是一种利用微秒-亚微秒量级脉冲在大气压下获得大体积等离子体的放电形式。为了测量自持体放电过程中气体温度的演化,采用光谱拟合的方法,对氮分子第二正带光谱进行了理论分析。并对两套横向激励大气压(TEA)气体激光器放电系统(准分子放电腔快放电系统,TEA CO2激光器放电腔慢放电系统)的等离子体时域分辨分子光谱进行了测量,并拟合了气体转动温度,取得了两种不同放电结构放电过程中气体温度演化的数据。结果表明,准分子放电腔快放电过程中总的能量注入密度为1.3105J/m3时,温度升高92K,TEA CO2激光器放电腔慢放电过程中总的能量注入密度为7104J/m3时,温度升高约50K,两套系统温度升高比对应于总的注入能量密度比。这一结果对研究自持体放电机理提高放电稳定性是有帮助的。 相似文献
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利用脉冲电化学沉积技术,以NiSO4·6H2O为电镀液在镀Cr硅基片上沉积低密度、直径在150nm左右的Ni催化剂颗粒,在此基础上,采用乙炔、氨气作为气源,采用等离子体增强化学气相沉积(PECVD)技术制备分散定向的碳纳米管阵列。研究了等离子体预处理技术对纳米管制备的影响以及该阵列的场发射性能,证明低密度的碳纳米管阵列阴极能有效地降低场屏蔽效应,进而提高场发射性能,其场发射的开启电场强度约为2.39V/μm。 相似文献
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Kang Zhang Qing Zhang Cao Liu Nicola Marzari Francesco Stellacci 《Advanced functional materials》2012,22(24):5216-5223
Dichlorocarbene is added to the sidewalls of single‐walled carbon nanotubes (SWNTs) with diameters ranging from 1.2 to 2.2 nm. Small diameter SWNTs are found to react much more easily than large diameter SWNTs. Upon functionalization, the conductance could be largely preserved for almost all SWNTs, while an effective bandgap increase for functionalized metallic SWNTs (m‐SWNTs) and a bandgap reduction for functionalized semiconducting SWNTs (s‐SWNTs) are generally observed. The results suggest that [2 + 1] cycloaddition is an excellent choice of processing, resulting in SWNTs over a large diameter range with electronic properties that are almost unaffected. Furthermore, possible separation of SWNTs according to their diameters could be achieved due to the apparent diameter‐dependent reactivity. 相似文献
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采用回流法成功制备甲苯胺蓝(TB)-羧甲基壳聚糖 (cmCs)-碳纳米管(CNTs)复合光敏剂,研究CNTs直径对复合光敏剂光谱性能的影响。通过透 射电镜(TEM)、红外吸收光谱和可见光吸收光谱对复 合光敏剂的形貌和光学性质进行分析表征,并通过实验观察其在水溶液中的分散性和稳定性 。结果表明:TB可较好地复合到cmCs修饰的CNTs;CNTs直径的不同对复合光敏剂的合成影 响较小,但其半径较小时,复合光敏 剂在水中易团聚;复合光敏剂在可见光波段的吸收峰位于611nm处; 复合光敏剂在水溶液中有较好的分散性。本文研究将 为TB-cmCs-CNTs复合光敏剂在生物医学的应用提供重要的实验依据。 相似文献
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G.P. Zhu C.X. Xu X.F. Wu Y. Yang X.W. Sun Y.P. Cui 《Journal of Electronic Materials》2007,36(4):494-497
The arc discharge method was employed to fabricate zinc oxide (ZnO) nanorods with wurtzite structure. The microstructure analysis
by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that the ZnO nanorods grew along
the [0001] direction. On average, the diameter and length of the nanorods were about 40 nm (some are as thin as 5 nm) and
several hundred nanometers, respectively. The photoluminescence (PL) of the nanorods showed an ultraviolet band, a violet
band, and a green band. The PL mechanism was discussed with the growth process and Raman spectroscopy. 相似文献
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Romain Fleurier Jean‐Sébastien Lauret Ugo Lopez Annick Loiseau 《Advanced functional materials》2009,19(14):2219-2223
Diameter separation of single‐walled carbon nanotubes is achieved via the density gradient ultracentrifugation process. Statistical analysis of the separated samples is performed using high‐resolution transmission electron microscopy (HRTEM). The evolution of the diameter distribution with respect to the gradient density is extracted by analyzing hundreds of HRTEM images, and the results are found to be consistent with those estimated by UV–vis–IR spectroscopy. The efficiency of the separation process can be quantitatively characterized by the standard deviation of the diameter distribution, which is determined from the TEM analyses. This particular study indicated that for electric arc nanotubes dispersed in sodium cholate, diameter sorting is more efficient in the upper part of the gradient. 相似文献
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采用射频等离子体增强化学气相沉积(RF-PECVD),以Fe作为催化剂,在Si基片上生长了碳纳米管(CNT),采用扫描电子显微镜(SEM),高分辨透射电子显微镜(HR TEM)以及显微Raman光谱等对制备的CNT的形貌及结构进行了表征.结果表明:700℃和800℃温度下生长的CNT均取向无序、弯曲缠结,由整齐排列的圆... 相似文献
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G. Gu G. Philipp X. Wu M. Burghard A. M. Bittner S. Roth 《Advanced functional materials》2001,11(4):295-298
Single‐walled carbon nanotubes have been grown by chemical vapor deposition from methane and hydrogen on catalyst patterns prepared by microcontact printing on 20 nm thick silicon nitride substrates. A higher yield of single‐walled carbon nanotubes was obtained by the simple expedient of introducing hydrogen during deposition. Based on atomic force microscopy and transmission electron microscopy measurements, we found that high‐quality single‐walled carbon nanotubes with a broad diameter distribution were obtained. 相似文献
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ZnO nanotubes have been fabricated through a carbon thermal reduction deposition process. Structure characterization results show that the ZnO nanotubes have a single crystalline wurtzite hexagonal structure pref- erentially oriented in the c-axis. The diameters of ZnO nanotubes are in the range of 90-280 nm and the wall thickness is about 50-100 nm. Room-temperature photoluminescence measurements of the ZnO nanotubes exhibit an intensive ultraviolet peak at 377 nm and a broad peak centered at about 517 nm. The UV emission is caused by the near band edge emission while the green emission may be attributed to both oxygen vacancy and the surface state. Raman and cathodoluminescence spectra are also discussed. Finally, a possible growth mechanism of the ZnO nanotubes is proposed. 相似文献