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A simple hydrothermal process was used to synthesize the assembled leaf-like copper oxide (CuO) from copper hydroxide and urea in aqueous solution. The field emission scanning electron microscopy revealed that the individual CuO leaf-like nanostructure has a dimension of about 0.5–1.5 μm in length, 50–70 nm in thickness, and 80–110 nm in width, respectively. These CuO nanostructures were structurally characterized by X-ray diffraction and Raman spectroscopy, which showed that the CuO nanostructures prepared from the hydrothermal process have high crystalline properties with a monoclinic structure. X-ray photoelectron spectroscopy studies confirmed that the as-prepared sample is composed of CuO, which is consistent with X-ray diffraction patterns. The CuO nanostructures were used as electrode materials for lithium-ion batteries, demonstrating electrochemical properties of a high initial discharge capacity of approximately 1,028 mAh/g along with good cycle stability. [ABSTRACT FROM AUTHOR]

It is our interest to design and develop a high-power pulser system employing an electrical discharge in a spark gap. The type of discharge generates short electric pulses capable of both the characteristics of a fast rise time and a high repetition rate. Such a switch pulser has wide applications in the industry. To generate the electrical discharge in the spark gap in an efficient manner is very important for the switching operation. The regime of the operation utilizes the residual plasma in the interpulse recovery of the spark gap to increase the repetition rate. Therefore, the mechanisms of the discharge in a controlled manner following the electrical breakdown of the spark gap, such as the plasma generation in the spark channel and the dielectric recovery process as well as the residual plasma in the post-spark-discharge period, are of great importance. The understanding of the type of the spark-gap discharge for the switching at a high repetition rate beyond 1 MHz has been the primary goal. The typical voltage and current ratings are below 1 kV and several amperes, respectively. In particular, this paper addresses the optimal set of several parameters, such as the spark-gap geometry, electrode gap distance, gas pressure, and gas type, in conjunction with a unique circuit scheme to drive the discharge in the controlled fashion. [ABSTRACT FROM PUBLISHER]

It is our endeavor to develop switching technology for the breakdown reliability and reproducibility at extremely high voltages above 1 MV. One of the key objectives of the endeavor is to derive precise breakdown criteria for use in high-voltage applications. We have developed empirical criteria by which the breakdown field strength of a high-pressure \SF6-filled spark gap can be computed. The validity of the computed result has been verified with several experimental data from different investigators. The computed result has shown good agreement in an extended range of pd (pressure times gap distance) and field enhancement factor of the spark gap geometry. Furthermore, a spark gap has been designed and constructed with particular intention of generating a high-pulsed-power source in Pohang Accelerator Laboratory. In parallel, field modeling has been performed to verify the appropriate shape of the highly stressed insulator and electrode design in the spark gap and to evaluate their field enhancements. A series of breakdown voltage tests has demonstrated the function of the spark gap switch as intended up to 9 bars of \SF6. Aside from this, the limitation of the switching behavior has been examined with an aim of operating the designed spark gap to its maximum capability. [ABSTRACT FROM PUBLISHER]

The article discusses various reports published within the issue, including one on repetitive pulsed power for directed energy research and applications, and high voltage issues in power electronics.

An introduction to the journal is presented in which the editors discuss an article about repetitive pulsed power for commercial research and applications, one on closing and opening plasma switches and another about advanced dielectric materials in repetitive and high voltage applications.