Structure and dynamics of high-current arc cathode spots in vacuum

Beilis, I. I.; Djakov, B. E.; Jüttner, B.; Pursch, H.

doi:10.1088/0022-3727/30/1/015

Cited by 99 publications

(56 citation statements)

References 14 publications

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“…The electrons concentrate at asperities and the electric field of the cathode is amplified. The field attracts ions existing in the plasma, which bombard and heat the asperity [74], [75]. Due to the combination of high field with heat, some electrons are liberated from the cathodic surface, which results in electron-atom collisions producing positive ions.…”

Section: Cathodic Arc Plasma Depositionmentioning

confidence: 99%

Cavitation erosion resistance of NiTi thin films produced by Filtered Arc Deposition

Yang

Tieu

Dunne

et al. 2009

Wear

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AcknowledgementsFirst and foremost, I would like to thank my principal supervisor, Professor A. Kiet.Tieu., for providing timely and insightful advice, financial and spiritual support. My supervisor's implicit trust in my research abilities not only allowed me to freely pursue my goals, but also gave me an opportunity to learn how to manage time and allocate resources. Special thanks go to Professor Druce Dunne, for his insightful instruction and for all the generous attention and time he devoted to my research work. Tables Table 5. List of List of Figures AbstractThe objective of this work was to produce near-equiatomic NiTi thin films by filtered arc deposition system (FADS) to improve the cavitation erosion resistance of a steel base working in liquid. First, deposition conditions were optimized in order to obtain near-equiatomic NiTi films. Energy dispersive spectroscopy (EDS) was used to measure the composition of films. It was found that both the substrate bias voltage and arc current affect the compositions of as-deposited NiTi films. X-ray diffractometry (XRD) and transmission electron microscopy (TEM) were used to investigate the microstructures of Ni-rich, Ti-rich and near-equiatomic films. Their thermal behaviours were tested using differential scanning calorimetry (DSC). Atomic force microscopy (AFM), ultra micro-indentation system (UMIS) and Romulus scratch testing were used to measure the roughness, hardness and adhesive force of a near-equiatomic thin film.The cavitation erosion resistance of the near-equiatomic NiTi film was assessed using ASTM Test Method G32. It was found that NiTi thin films showed significantly higher cavitation erosion resistance than 316 austenitic stainless steel. The improved cavitation erosion resistance was attributed to the recoverable deformation associated with pseudoelasticity of the NiTi thin film.The effect of substrate temperature on the properties of NiTi thin films was investigated by preheating substrates to different temperatures (130 C, 300 C, 430 C and 600 C). temperature of 600 C was more resistant to cavitation erosion than films deposited at other bias voltages with a similar substrate temperature.The effect of substrate material on the properties of NiTi thin films was investigated by comparing films on mild steel and on austenitic stainless steel. For similar deposition conditions, the NiTi film deposited on mild steel consisted of B2, B19' and R phases, while the NiTi film on stainless steel was dominated by B2 parent phase. This is probably because the lower thermal conductivity of austenitic stainless steel resulted in a higher deposition temperature.The dominance of the B2 phase for deposition with a high substrate temperature, a high bias voltage and the use of stainless steel substrate was not found to be due to Ni-enrichment of the films, but is consistent with stabilization of the parent phase by possible pick-up oxygen and nitrogen from the chamber atmosphere when the deposition temperature is high.The research program successfully pro...

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Section: Cathodic Arc Plasma Depositionmentioning

confidence: 99%

Cavitation erosion resistance of NiTi thin films produced by Filtered Arc Deposition

Yang

Tieu

Dunne

et al. 2009

Wear

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“…lifetime is thought to be in the nanosecond range based on modeling 12,13 and optical experiments with very high temporal resolution 14,15 . However, longer "characteristic times" have been seen in optical emission 16 , too, which have led to the formulation of self-consistent models for the cathodic arc spot not based on the ecton concept. In such models, strong evaporation and ionization of vapor in some distance from he solid cathode surface is assumed 17 .…”

Section: Experimental Setup and Measurementsmentioning

confidence: 99%

Material-dependent high-frequency current fluctuations of cathodic vacuum arcs: Evidence for the ecton cutoff of the fractal model

Anders

Окс

2006

Journal of Applied Physics

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Current fluctuations of cathodic arcs were recorded with high analog bandwidth (up to 1 GHz) and fast digital sampling (up to 5 Gsamples/sec). The power spectral density of the arc current was determined by fast Fourier transform clearly showing material dependent, non-linear features in the frequency domain. These features can be associated with the non-linear impedance of the conducting channel between cathode and anode, driven by the explosive nature of electron emission and plasma formation. The characteristic times of less than 100 ns can be associated with individual explosive processes, "ectons," and therefore represent the short-time physical cutoff for the fractal model of cathodic arcs.

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“…The number of group spots increases with the current, as does the fraction of the cathode area covered by spots, so that the average current per group spot and the current density within the active cathode area is approximately constant. 19 Taking this into account, we assume in the present model that plasma and current density are constant, and as a result the effective initial plasma jet radius R 0 increases with arc current. The initial jet radius R 0 is computed from: R 0 ϭ( f i I)/(Z i eN 0 V 0Z ) 0.5 , where f i is the ion current fraction ( f i ϭ0.1), I is the arc current, V OZ ϭ1.1ϫ10 4 m/s is the initial axial ion velocity for copper, and the ionicity 20 is Z i ϭ1.8.…”

Section: A Starting Planementioning

confidence: 99%

Theoretical study of plasma expansion in a magnetic field in a disk anode vacuum arc

Beilis

Keidar

Boxman

et al. 1998

Journal of Applied Physics

131

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The low-density plasma flow in an axial magnetic field to a disk-shaped anode in a vacuum arc was studied theoretically using a two-dimensional model. The plasma expansion was modeled using the sourceless steady-state hydrodynamic equations, where the free boundary of the plasma was determined by a self-consistent solution of the gas-dynamic and electrical current equations. The anode was modeled as a current and plasma collector, which does not influence the plasma flow field. Magnetic forces from both the azimuthal self-magnetic field, and the imposed axial magnetic field were taken into account. It was found that the self-magnetic field does not substantially influence either the plasma jet shape, density, velocity, or the current density distribution for arc currents I⩽200 A. On the other hand, the plasma jet angle (α0) at the starting plane and the radial plasma density gradient force in the expansion region do have a strong influence on the plasma and current flow. The mass and current flow in a 500 A arc are compressed in the near axis region, leading to an increase in the plasma and axial current density by a factor of 1.5 at a distance of about two plasma jet radii from the starting plane. The calculated arc current–voltage characteristics agree qualitatively with experiments on arc behavior in an axial magnetic field.

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Structure and dynamics of high-current arc cathode spots in vacuum

Cited by 99 publications

References 14 publications

Cavitation erosion resistance of NiTi thin films produced by Filtered Arc Deposition

Cavitation erosion resistance of NiTi thin films produced by Filtered Arc Deposition

Material-dependent high-frequency current fluctuations of cathodic vacuum arcs: Evidence for the ecton cutoff of the fractal model

Theoretical study of plasma expansion in a magnetic field in a disk anode vacuum arc

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