Molecular dynamics simulations of the effect of static electric field on progressive ice formation.

Ice accumulation under static electric fields presents a significant hazard to transmission lines and power grids. Contemporary computational studies of electrofreezing predominantly probed excessive electric fields (109 V/m) that are significantly higher than those typically encountered in proximity to transmission lines. To elucidate the influence of realistic electric fields (105 V/m) on ice crystallization, we run extensive molecular dynamics (MD) simulations across dual ice-water coexistence systems. Three aspects of work were accordingly examined. First, we investigated the influence of the effect of static electric fields, with a strength of 105 V/m, along three orthogonal axes on the phase transition during the encountered freezing and melting processes. Second, we established the mechanism of how the direction of an electric field, the initial ice crystallography, and the adjacent crystal planes influence the solidification process. Third, the results of our MD simulations were further post-processed to determine the dipole moment, radial distribution, and angle distribution resulting from the static electric field. Our results indicate that while weak electric fields do not cause complete polarization of liquid water molecules, they can induce a transition to a more structured ice-like geometry of the water molecules at the ice-water interphase region, particularly when applied perpendicular to the ice-water interphase. Notably, the interface adjacent to cubic ice exhibits a greater response to the electric fields than that adjacent to hexagonal ice. This is attributable to the intrinsic differences in their original hydrogen bonding networks.

Effect of Ultraviolet-A Radiation on Alicyclic Epoxy Resin and Silicone Rubber Used for Insulators.

Compared with the high-temperature vulcanized silicone rubber (HTVSR) insulator, the alicyclic epoxy resin insulator has higher hardness and better bonding between the core and the sheath. This makes the latter very promising in the coastal area of Southern China. Outdoor insulators are often subjected to high intensity of ultraviolet (UV)-A radiation. The influence of UV-A radiation is significant for alicyclic epoxy resin insulators. To help address the concern, the surface of two kinds of samples, namely the alicyclic epoxy resin insulator and HTVSR insulator, with UV-A aging time was characterized by tests of scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The operation properties (mechanical properties, hydrophobicity) for outdoor insulators were also analyzed. It was found that the appearance color of the alicyclic epoxy resin has changed greatly, and there is a certain degree of fading. The mechanical properties of the alicyclic epoxy resin are maintained well and, the hydrophobicity decreases gradually. For silicone rubber, the appearance color change of silicone rubber is smaller, and the mechanical properties of silicone rubber decreased greatly. In addition, although the hydrophobicity of silicone rubber decreased gradually, it is still better than that of alicyclic epoxy resin. Both materials have broken chemical bonds, but the degree is relatively light, which meets the requirements of insulators for outdoor operation.