The Experts below are selected from a list of 38394 Experts worldwide ranked by ideXlab platform
Isak I. Beilis - One of the best experts on this subject based on the ideXlab platform.
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Vacuum arc Cathode spot motion in oblique magnetic fields: An interpretation of the Robson experiment
Physics of Plasmas, 2016Co-Authors: Isak I. BeilisAbstract:A model was developed of vacuum arc Cathode spot motion in a magnetic field that obliquely intercepts the Cathode Surface. The model takes into account a force under an electric field caused by retrograde spot motion across the normal component of the magnetic field, producing a drift velocity component in the direction of the acute angle between the magnetic field and the Cathode Surface. The relationship between velocity of the retrograde direction and drift velocity of the Cathode spot motion to the acute angle was developed. The dependencies of the drift angle θ on the acute angle φ, magnetic field strength B, and arc current I were calculated. It was found that the calculated θ increased with φ, B, and I in accordance with Robson's measurements.
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A model of vacuum arc Cathode spot motion in an oblique magnetic field
2016 27th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV), 2016Co-Authors: Isak I. BeilisAbstract:A model of vacuum arc Cathode spot motion in a magnetic field which obliquely intercepts the Cathode Surface was developed. The model takes in account an electrical force generated by spot motion across the normal component of the magnetic field, which accelerates plasma in the direction of the opening of the acute angle. A relation between the drift angle (between the retrograde direction and the Cathode spot motion) and the acute angle formed by the intersection of the magnetic field lines with the Cathode Surface, was developed. The dependencies of the drift angle on the acute angle and magnetic field strength measured in Robson's experiment were analyzed.
Weidong Xia - One of the best experts on this subject based on the ideXlab platform.
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spot and diffuse mode of Cathode attachments in a magnetically rotating arc plasma generator at atmospheric pressure
Journal of Applied Physics, 2019Co-Authors: Cheng Wang, Qiang Sun, Lu Sun, Weiluo Xia, Weidong XiaAbstract:Adjusting the strength of an axial magnetic field is an effective method to control the Cathode attachment. In this paper, a magnetically rotating arc plasma generator is constructed to study the Cathode attachment modes under different magnetic fields. Two Cathode attachment modes are observed: a spot mode and a diffuse mode. Images of Cathode attachments, temperature distribution of the Cathode Surface, and arc voltage characteristics correlating to different Cathode attachment modes are investigated. Results show that the spot mode is favored by the low magnetic field. With an increase in the magnetic field, the Cathode attachment region expands gradually, until the spot mode evolutes to the diffuse mode. The diffuse mode is associated with a significantly increased arc voltage, indicating that the transition is an abrupt process rather than a gradual process. For the diffuse mode, the Cathode end has a higher average and lower peak temperature, but there exists varying temperature distribution on the Cathode end, such as the ring-shaped high temperature region. Additionally, a two-dimensional coupled model is applied to qualitatively discuss the effect of magnetic field on the Cathode attachment modes. Simulation results reveal that energy flux to the Cathode Surface increases with the increase of the magnetic field, and the major increment is thermal conduction heating from the arc column to the Cathode Surface, which possibly arises from the axial compression of arc plasma. Thus, the diffuse mode tends to always operate in the large magnetic field.
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Diffuse and spot mode of Cathode arc attachments in an atmospheric magnetically rotating argon arc
Journal of Physics D: Applied Physics, 2016Co-Authors: Tang Chen, Cheng Wang, Meng-ran Liao, Weidong XiaAbstract:A model including the Cathode, near-Cathode region, and arc column was constructed. Specifically, a thermal perturbation layer at the arc fringe was calculated in order to couple sheath/presheath modelling with typical arc column modelling. Comparative investigation of two modes of attachment of a dc (100, 150, 200 A) atmospheric-pressure arc in argon to a thermionic Cathode made of pure tungsten was conducted. Computational data revealed that there exists two modes of arc discharge: the spot mode, which has an obvious Cathode Surface temperature peak in the arc attachment centre; and the diffuse mode, which has a flat Cathode Surface temperature distribution and a larger arc attachment area. The modelling results of the arc attachment agree with previous experimental observations for the diffuse mode. A further 3D simulation is obviously needed to investigate the non-axisymmetrical features, especially for the spot mode.
Zhengcheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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methodology for understanding interactions between electrolyte additives and Cathodes a case of the tris 2 2 2 trifluoroethyl phosphite additive
Journal of Materials Chemistry, 2018Co-Authors: Ritu Sahore, Cameron Peebles, Chen Liao, Zhengcheng Zhang, Adam Tornheim, Juan C Garcia, Fulya Dogan, Daniel C Ohanlon, Hakim Iddir, Javier BarenoAbstract:Use of electrolyte additives is a promising route to address Surface destabilization issues of lithium transition metal (TM)-oxide Cathodes (for example, lithium nickel-manganese-cobalt oxides (NMCs)) that occur as they are charged to high voltages (>4.3 V vs. Li/Li+). Despite the successful discovery of several additives, their working mechanisms are often vaguely understood. In this work, we provide a methodology to comprehensively understand additive/Cathode interactions in lithium-ion batteries. A case of the tris(2,2,2-trifluoroethyl)phosphite (TTFP) additive is presented where its decomposition behavior was investigated at 4.6 V vs. Li/Li+ in a Li4Ti5O12 (LTO)/Li1.03(Ni0.5Mn0.3Co0.2)0.97O2 (NMC532) cell. Overall, we found that while some of the additive does modify the Surface film on the Cathode and binds at the Surface, it does not passivate the Cathode Surface towards electrolyte oxidation. Rather, the majority of the TTFP forms stable, free tris(2,2,2-trifluoroethyl)phosphate (TTFPa) molecules by removing O atoms from the charged NMC Cathode Surface, some of which then further react with the electrolyte solvents and stay in solution. Finally, we propose a stable configuration in which TTFP is bound to the Cathode Surface via a P–O–TM bond, with one of the –CH2CF3 side groups removed, leading to the formation of BTFPa (bis(2,2,2-trifluoroethyl)phosphate). We anticipate that these techniques and findings could be extended to other additives as well, especially phosphite-based additives, allowing the effective design of future additives.
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mechanistic insight in the function of phosphite additives for protection of lini0 5co0 2mn0 3o2 Cathode in high voltage li ion cells
ACS Applied Materials & Interfaces, 2016Co-Authors: Cameron Peebles, Zhenxing Feng, Justin G Connell, Chen Liao, Yan Wang, Ilya A Shkrob, Zhengcheng ZhangAbstract:Triethlylphosphite (TEP) and tris(2,2,2-trifluoroethyl) phosphite (TTFP) have been evaluated as electrolyte additives for high-voltage Li-ion battery cells using a Ni-rich layered Cathode material LiNi0.5Co0.2Mn0.3O2 (NCM523) and the conventional carbonate electrolyte. The repeated charge/discharge cycling for cells containing 1 wt % of these additives was performed using an NCM523/graphite full cell operated at the voltage window from 3.0-4.6 V. During the initial charge process, these additives decompose on the Cathode Surface at a lower oxidation potential than the baseline electrolyte. Impedance spectroscopy and post-test analyses indicate the formation of protective coatings by both additives on the Cathode Surface that prevent oxidative breakdown of the electrolyte. However, only TTFP containing cells demonstrate the improved capacity retention and Coulombic efficiency. For TEP, the protective coating is also formed, but low Li(+) ion mobility through the interphase layer results in inferior performance. These observations are rationalized through the inhibition of electrocatalytic centers present on the Cathode Surface and the formation of organophosphate deposits isolating the Cathode Surface from the electrolyte. The difference between the two phosphites clearly originates in the different properties of the resulting phosphate coatings, which may be in Li(+) ion conductivity through such materials.
Robert Franz - One of the best experts on this subject based on the ideXlab platform.
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insights into Surface modification and erosion of multi element arc Cathodes using a novel multilayer Cathode design
Journal of Applied Physics, 2020Co-Authors: Mehran Golizadeh, Andre Anders, Francisca Mendez Martin, Szilard Kolozsvari, Robert FranzAbstract:Nowadays, multi-element Cathodes are frequently employed to grow multi-element thin films and coatings using cathodic arc deposition processes. During Cathode erosion, the Cathode spot sequentially ignites on the Cathode Surface and imposes melting–solidification cycles that lead to material intermixing and the formation of a modified layer on the Cathode Surface. To allow us to study these Surface modifications, a 10 μm thick Mo/Al multilayer coating was sputter-deposited onto a standard Ti arc Cathode. This Cathode was eroded by a dc steered arc discharge for a short duration enabling the observation of single craters formed by type 1 and 2 Cathode spots. Furthermore, separated clusters of overlapping craters and a fully eroded Surface caused by different stages of erosion were differentiated when scanning the erosion track in the lateral direction. Cross sections of single craters were prepared by focused ion beam techniques while metallographic methods were applied to obtain cross sections of overlapping craters and the modified layer. The layers of the multilayer coating acted as trace markers providing new insights into the material intermixing within craters, the material displacements during crater formation, the plasma pressure acting on the craters, and the temperature gradient (heat-affected zone) below the craters. The observations are discussed within the framework of established arc crater formation models.Nowadays, multi-element Cathodes are frequently employed to grow multi-element thin films and coatings using cathodic arc deposition processes. During Cathode erosion, the Cathode spot sequentially ignites on the Cathode Surface and imposes melting–solidification cycles that lead to material intermixing and the formation of a modified layer on the Cathode Surface. To allow us to study these Surface modifications, a 10 μm thick Mo/Al multilayer coating was sputter-deposited onto a standard Ti arc Cathode. This Cathode was eroded by a dc steered arc discharge for a short duration enabling the observation of single craters formed by type 1 and 2 Cathode spots. Furthermore, separated clusters of overlapping craters and a fully eroded Surface caused by different stages of erosion were differentiated when scanning the erosion track in the lateral direction. Cross sections of single craters were prepared by focused ion beam techniques while metallographic methods were applied to obtain cross sections of overlapp...
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cathodic arc deposition of al cr 2o3 macroparticles and Cathode Surface modifications
Surface & Coatings Technology, 2011Co-Authors: Markus Pohler, Robert Franz, Peter Polcik, J Ramm, Christian MittererAbstract:The present work investigates the microstructure and chemical composition of macroparticles incorporated in arc evaporated (Al,Cr)2O3 coatings. According to scanning and transmission electron microscopy analysis, two different types of macroparticles with a distinct difference in their shape and a noticeable variation in their chemical composition, i.e. the Al/Cr ratio, can be distinguished. In addition, the transformations on the Surface of the corresponding Al–Cr compound Cathodes during the evaporation process in O2 atmosphere are studied by scanning electron microscopy and X-ray diffraction. Beside the virgin Cathode material, a reaction layer consisting of various intermetallic AlxCry phases with a fine-grained morphology and pillar-shaped Al2O3 islands was found. Correlations between the origin of the macroparticles and the observed modifications at the Surface of the Al–Cr Cathode are discussed.
Bruce E Logan - One of the best experts on this subject based on the ideXlab platform.
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increasing power generation for scaling up single chamber air Cathode microbial fuel cells
Bioresource Technology, 2011Co-Authors: Shaoan Cheng, Bruce E LoganAbstract:Scaling up microbial fuel cells (MFCs) requires a better understanding the importance of the different factors such as electrode Surface area and reactor geometry relative to solution conditions such as conductivity and substrate concentration. It is shown here that the substrate concentration has significant effect on anode but not Cathode performance, while the solution conductivity has a significant effect on the Cathode but not the anode. The Cathode Surface area is always important for increasing power. Doubling the Cathode size can increase power by 62% with domestic wastewater, but doubling the anode size increases power by 12%. Volumetric power density was shown to be a linear function of Cathode specific Surface area (ratio of Cathode Surface area to reactor volume), but the impact of Cathode size on power generation depended on the substrate strength (COD) and conductivity. These results demonstrate the Cathode specific Surface area is the most critical factor for scaling-up MFCs to obtain high power densities.
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multi electrode continuous flow microbial electrolysis cell for biogas production from acetate
International Journal of Hydrogen Energy, 2010Co-Authors: Geoffrey Rader, Bruce E LoganAbstract:Abstract Most microbial electrolysis cells (MECs) contain only a single set of electrodes. In order to examine the scalability of a multiple-electrode design, we constructed a 2.5 L MEC containing 8 separate electrode pairs made of graphite fiber brush anodes pre-acclimated for current generation using acetate, and 304 stainless steel mesh Cathodes (64 m2/m3). Under continuous flow conditions and a one day hydraulic retention time, the maximum current was 181 mA (1.18 A/m2, Cathode Surface area; 74 A/m3) within three days of operation. The maximum hydrogen production (day 3) was 0.53 L/L-d, reaching an energy efficiency relative to electrical energy input of ηE = 144%. Current production remained relatively steady (days 3–18), but the gas composition dramatically shifted over time. By day 16, there was little H2 gas recovered and methane production increased from 0.049 L/L-d (day 3) to 0.118 L/L-d. When considering the energy value of both hydrogen and methane, efficiency relative to electrical input remained above 100% until near the end of the experiment (day 17) when only methane gas was being produced. Our results show that MECs can be scaled up primarily based on Cathode Surface area, but that hydrogen can be completely consumed in a continuous flow system unless methanogens can be completely eliminated from the system.