Large scale synthesis of N-doped multi-layered graphene sheets by simple arc-discharge method
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Electric arc
C4F7N-CO2 mixed gas as the potential substitute for SF6 has attracted more and more attention, so it is of great significance to study the arcing characteristics. In this paper, a set of experimental device was designed to study the arcing characteristics of 5%C4F7N/95%CO2sub> and 10%C4F7N/90%CO2. The arc images are captured by high-speed camera to visualize the motion characteristics of arc breaking process, and compared with SF6 gas under the same charging current and gas pressure conditions. The experimental results shown that: with the increase of pressure, the arc voltage increases, which can promote the arc extinguishing performance; The arc conductance of SF6 gas is the largest, and the fluctuation range of arc diameter of 10%C4F7N/90%CO2 is relatively smaller, with the average diameter of 5.5mm; With the increase of C4F7N content, the arc stability is improved, the arc voltage and arc conductance are close to SF6, and the arc extinguishing ability is enhanced.
Electric arc
Plasma arc welding
Sulfur hexafluoride
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Electric arc
Resistive touchscreen
Arc flash
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The self-extinguishing behavior of secondary arcs affects the single-phase re-closure time of transmission lines,so it is important to improve the power system's transmission capacity and reliability.Based on the classic Mayr arc model,the non-linear time-varying arc resistance was introduced to describe the condition of an arc channel,and the arc resistance equations were established.By analyzing the movement characteristics of the secondary arc,the arc's real time length was obtained to iteratively compute the arc resistance.Then an arc resistance criterion was proposed to judge whether arc extinguishes by itself or not according to the law of energy conservation.The equivalent circuit of the arc resistance connected with the system circuit was also put forward to calculate the arc characteristics,and the simulation flow for the self-extinguishing behavior of the secondary arc was further expressed in detail.With the arcing test data at low currents,the parameter estimation was performed for this arc model,and some waveforms of arc voltage,current,resistance and arcing duration were obtained.According to the obtained results,the potential gradient of secondary arc is in a range of 1 500~2 000 V/m.The calculation waveforms are close to the test results,and the arcing duration error is within the permission error of engineering.It is concluded that the presented secondary arc model and its simulation method are reasonable and practicable.
Electric arc
Plasma arc welding
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The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines,including half-wavelength power transmission lines.In this paper,a lowvoltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera.It was found that the arcing time of the secondary arc rendered a close relationship with its arc length.Through the input and output power energy analysis of the secondary arc,a new critical length criterion for the arcing time was proposed.The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria,and the simulation results were compared with the experimental data.The study showed that the arcing time calculated from the new critical length criterion gave more accurate results,which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines.
Electric arc
Arc length
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The new criterion of arc stability and instability is introduced, which enables one to find arc duration dependently on given circuit parameters and properties of contact material. The mathematical model of phase transformations inside electrodes during arcing is elaborated which describes dynamics of arc erosion in metallic and gaseous arc phases. Increasing of arc duration and erosion with inductance occurs on account of enlarging of gaseous arc phase, while variation of metallic phase is relatively small.
Electric arc
Plasma arc welding
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He notes that, since graphene's discovery, scientists working with natural graphite to produce graphene have used what is known as the Hummers method to turn graphene oxide into reduced graphene oxide (or rGO - a term which [Gordon Chiu] says has been incorrectly and interchangeably used with the term'graphene').
Because graphite has the same composition and arrangement as graphene, natural graphite is a popular and cost-effective precursor in the production of many graphene materials, including graphene nanoplatelets, reduced graphene and graphene oxide, Dr Elena Polakova, CEO of Graphene Laboratories told IM.
In order to restore some of graphene's natural properties - because graphene oxide is not conductive like graphene - we reduced the samples to create reduced graphene oxide. We then went a step further and converted the reduced graphene oxide into a paste with applications in conductive inks and coatings.
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Graphene foam
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Abstract The initial shape of the secondary arc considerably influences its subsequent shape. To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence, theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical. In this study, an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc. The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc. A secondary arc evolution model was developed based on this model. Moreover, the accuracy of the model was evaluated by comparison with physical experimental results. When the secondary arc current increased, the arcing time and dispersion increased. There is an overall trend of increasing arc length with increasing arcing time. Nevertheless, there is a reduction in arc length during arc ignition due to short circuits between the arc columns. Furthermore, the arcing time decreased in the range of 0°–90° as the angle between the wind direction and the x -axis increased. This work investigated the method by which short-circuit arcs evolve into secondary arcs. The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.
Electric arc
Pre-charge
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Possibilities of controlling electric arc-location burning between the butt-ends of cylindrical electrodes for the thermal treatment of metals are investigated. It is shown that the behavior of an electric arc in a nonuniform magnetic field can be determined by the diamagnetism of plasma, Holl-current and mechanical interaction of the arc with current-carrying elements. Methods of localizing or positioning the AC and DC arc discharges in the gap between electrodes are suggested.
Electric arc
Vacuum arc
Plasma arc welding
Diamagnetism
Electric current
Plasma channel
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The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines,including half-wavelength power transmission lines.In this paper,a lowvoltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera.It was found that the arcing time of the secondary arc rendered a close relationship with its arc length.Through the input and output power energy analysis of the secondary arc,a new critical length criterion for the arcing time was proposed.The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria,and the simulation results were compared with the experimental data.The study showed that the arcing time calculated from the new critical length criterion gave more accurate results,which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines.
Electric arc
Arc length
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Graphene 基于 graphene 有唯一的物理性质，和许多 proof-of-concept 设备是 demonstated。因为，为 graphene 的申请的一个前提是它以一种控制方式的生产在这些层的 graphene 层和缺点的数字显著地影响运输性质。在这份报纸，我们简短在 graphene 和基于 graphene 的 composites 的控制合成上考察我们的最近的工作，方法到的发展在干净精力应用并且为定序的快速的 DNA 描绘 graphene 的 graphene 层，和使用。例如，我们使用了钻电子光谱学描绘 graphene 层的数字和结构，在整个 Ni 电影底层上的生产单个层的 graphene，是的综合分散得好的减少的 graphene 氧化物一致地有唯一的金 nanodots 的 grafted，和制作 graphene nanoscrolls。我们也在器官的太阳能电池并且直接探索了 graphene 的应用，定序的 ultrafast DNA。最后，我们探讨挑战那 graphene 在它的合成和干净精力和生物察觉到应用的静止的脸。
Graphene foam
Bilayer graphene
Nanodot
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