Criterion equation for calculation of the current limiting electrochemical machining by formation of sparks

The current density used in electrochemical machining can be increased only up to a certain value, above which the formation of electric sparks on the cathode (tool) is observed, whereby the latter and its insulation are damaged. The present work is devoted to the measurement of this critical current density for the case of electrochemical drilling of small holes by means of metal capillaries provided with an external insulation. The results are correlated by a criterion equation which gives the values of the limiting currents for sparking, IS , with an average error of ±9%.

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Examination of current limiting mechanisms in monocore Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ tape with high critical current density

IEEE Transactions on Applied Superconductivity ◽

10.1109/77.919760 ◽

2001 ◽

Vol 11 (1) ◽

pp. 3269-3272 ◽

Cited By ~ 16

Author(s):

A. Polyanskii ◽

D.M. Feldmann ◽

S. Patnaik ◽

J. Jiang ◽

X. Cai ◽

...

Keyword(s):

Critical Current Density ◽

Critical Current ◽

Current Density ◽

High Critical Current Density ◽

Current Limiting

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Statistical study of the void structure of Bi2212 multifilamentary superconducting wires and its effect on the critical current density

Engineering Computations ◽

10.1108/ec-10-2018-0476 ◽

2019 ◽

Vol 36 (8) ◽

pp. 2714-2725 ◽

Cited By ~ 1

Author(s):

Xin-Xin Zhou ◽

Feng Xue ◽

Xiaofan Gou ◽

Teng-Ming Shen

Keyword(s):

Critical Current Density ◽

Critical Current ◽

Current Density ◽

Superconducting Magnets ◽

Complex Structure ◽

Statistical Characterization ◽

Content Type ◽

Superconducting Wires ◽

Current Limiting ◽

Void Structure

Purpose Multifilamentary Bi2Sr2CaCu2Ox (Bi2212) superconductor composite wires are the only high-temperature superconducting round wires (RW) with sufficient critical current density (Jc) for superconducting magnets generating magnetic fields greater than 25 Tesla. Very complex microstructures of Bi2212 RWs including the voids or gas bubbles, filament to filament bridges and wire architecture strongly influence their electrical behavior. Especially, a large number of voids in Bi2212 superconducting filaments is believed to be the major current-limiting mechanism. However, the effect of the void structure on the Jc is not well understood yet. Design/methodology/approach In this paper, the authors first statistically analyzed the size and distribution of voids in filaments using the reported microscopic data, obtaining the essential statistical regularities. An electrical model was further developed to predict the Jc of multifilamentary wires while taking into account of the current limiting mechanisms of the void structure in filaments, and the current sharing roles of filament to filament bridges. Findings The model predicts the quantitative dependence of Jc on the number of Bi2212 filaments in each bundle of a double-restack wire and porosity. The results are useful optimizing design and fabrication of Bi2212 multifilamentary wires. Originality/value For the complex structure of voids and interfilamentary bridges inside Bi2212 multifilamentary superconducting wires, the authors took a statistical characterization and studied its effect on the critical current density Jc (the key index of evaluating the current carrying capacity).

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Microstructural characterization of YBa2Cu3O7-x thin films formed by metalorganic CVD

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089718 ◽

1991 ◽

Vol 49 ◽

pp. 1080-1081

Author(s):

P. Lu ◽

W. Huang ◽

C.S. Chern ◽

Y.Q. Li ◽

J. Zhao ◽

...

Keyword(s):

Thin Film ◽

Thin Films ◽

Critical Current Density ◽

Critical Current ◽

Current Density ◽

Film Growth ◽

Chemical Vapor ◽

Microstructural Characterization ◽

Ion Milling ◽

Conventional Grinding

The YBa2Cu3O7-x thin films formed by metalorganic chemical vapor deposition(MOCVD) have been reported to have excellent superconducting properties including a sharp zero resistance transition temperature (Tc) of 89 K and a high critical current density of 2.3x106 A/cm2 or higher. The origin of the high critical current in the thin film compared to bulk materials is attributed to its structural properties such as orientation, grain boundaries and defects on the scale of the coherent length. In this report, we present microstructural aspects of the thin films deposited on the (100) LaAlO3 substrate, which process the highest critical current density.Details of the thin film growth process have been reported elsewhere. The thin films were examined in both planar and cross-section view by electron microscopy. TEM sample preparation was carried out using conventional grinding, dimpling and ion milling techniques. Special care was taken to avoid exposure of the thin films to water during the preparation processes.

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Facet Topography and Dislocation Structure as a Possible Source for Electrical Heterogeneity in [001] TILT Bicrystals of YBa2Cu3O7-δ

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164155 ◽

1996 ◽

Vol 54 ◽

pp. 338-339

Author(s):

I-Fei Tsu ◽

D.L. Kaiser ◽

S.E. Babcock

Keyword(s):

Grain Boundary ◽

Critical Current Density ◽

Critical Current ◽

Current Density ◽

Electromagnetic Properties ◽

Length Scale ◽

Density Values ◽

Current Densities ◽

Applied Fields ◽

A Current

A current theme in the study of the critical current density behavior of YBa2Cu3O7-δ (YBCO) grain boundaries is that their electromagnetic properties are heterogeneous on various length scales ranging from 10s of microns to ˜ 1 Å. Recently, combined electromagnetic and TEM studies on four flux-grown bicrystals have demonstrated a direct correlation between the length scale of the boundaries’ saw-tooth facet configurations and the apparent length scale of the electrical heterogeneity. In that work, enhanced critical current densities are observed at applied fields where the facet period is commensurate with the spacing of the Abrikosov flux vortices which must be pinned if higher critical current density values are recorded. To understand the microstructural origin of the flux pinning, the grain boundary topography and grain boundary dislocation (GBD) network structure of [001] tilt YBCO bicrystals were studied by TEM and HRTEM.

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