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Cu–W nano-multilayered films show great potential applications in microelectronic, plasma and nuclear fields due to the unique interfacial structure. In this paper, Cu–W films with different microstructures were synthesized by co-sputtering at different deposition temperatures. At room temperature, a nano-multilayered structure with the modulation period (λ) of 5 nm appears with alternatively arrayed W-rich and Cu-rich regions. With the increase of the deposition temperature, the periods of the nano-layers become larger and fuzzy, and finally the totally separated phases of Cu and W grains can be identified at temperature higher than 300 °C. The dominant mechanism of such microstructural evolution can be ascribed by the surface diffusion ability of the deposited atoms as evidenced by temperature as well as deposition time. The hardness of the films declines with the elevated temperatures and by analyzing the hardening mechanisms, the interfacial strengthening effect was verified due to the high hardness in nano-multilayered Cu–W films.

The flashover of the DC basin insulator is the limiting factor for the safe and stable operation of DC-GIL and DC-GIS. It is of great significance to study the probability distribution model of the flashover. In this paper, the DC voltage experiment platform is built for the basin insulator in DC-GIL. The relationship between the flashover voltage and the flashover time of the basin insulator is obtained through experimental measurements. The probability distribution of flashover is established by using the Weibull distribution. The experimental results show that the flashover probability is related to the flashover voltage and flashover time. The higher the applied voltage, the greater the flashover probability, and the longer the applied time, the greater the flashover probability, and the steady state flashover voltage of this basin insulator is obtained. U 0.1% is 300kV.

A charge transport model based on ion drift in gases of strong electron affinity has been studied in details and validated against experimental results in air and SF 6 at different pressure and voltage levels. The size of the insulators also differs significantly. The choice of the model parameters, i.e. the solid and gas material properties, is carefully examined with information from existing literature. Results show that using the selected parameters, satisfactory agreement between predicted and measured potential distribution and surface charge density along the insulator surface can be obtained. Computational results for an 1100 kV epoxy spacer for use in HVDC wall bushing show that the concept of electrical conductivity as a material property is no longer valid in strong electric field for the gas surrounding the insulator. The polarity and density of the accumulated surface charge depend on the relative largeness of the electrical conductivity of the insulator material and the effective conductivity of the gas. The nonlinear effect due to ion generation and recombination becomes significant at very high voltage. The metallic cap providing shielding to the triple junction at the high voltage end of the insulator can induce much stronger local electric field near the insulator surface, by a factor of 1.48, if its shape is not optimized against the insulator geometry.