Super Electrical Insulating Materials Based on Honeycomb‐Inspired Nanostructure: High Electrical Strength and Low Permittivity and Dielectric Loss

Abstract

The high breakdown field strength is the most important index to evaluate the performance of insulating materials. It is theoretically found that the breakdown field strength of dielectric samples can be significantly improved by up to 1–2 orders of magnitude by constructing nanopore structures. Thus, bridged silsesquioxane super electrical insulating materials (BSSEIM) are developed with nanosized pore structures and their extremely high electrical insulation performance is realized. The results indicate that the breakdown field strength of the BSSEIM is dramatically higher than aluminosilicate fiber insulating materials (ASFIM) by 570.5% for dry samples and 118.1% for oil‐impregnated samples. Specifically, the prepared BSSEIM samples have excellent dielectric performances with permittivity and dielectric losses that are only 51.3% and 1.1% of ASFIM, which are significantly lower than most existing insulating materials. Finally, the theoretical analysis indicates that the nanopore structures can effectively limit the scale of the head size for an electron avalanche and significantly reduce the number of effective gas molecules by dividing the gas into nanounits. This significantly inhibits the ionization of gas molecules and improves the breakdown field strength of samples. This discovery overturns previous understandings of traditional insulating materials and opens an avenue toward super electrical insulating materials.

High flashover strength and superhydrophobic coatings by constructing porous surface structure

“…Previous studies have shown that the collision ionisation can be inhibited by nanosized pore structures with pore size close to or slightly larger than the average electron free path [15, 16]. It is noted that OTS coating has a large number of pores and pits at the level of 100 nm.…”

“…Since the sandpaperpolishing and sandblasting surface treatment methods used in existing researches mainly produce micron-scale topography, the existing research mainly focuses on the effect of micronscale morphology. Lei et al [15] and Sima et al [16] found that the breakdown voltage can be significantly improved by preparing porous-structure insulating materials with pores from 10 nm to one-micron level, in which the electron avalanche process is suppressed by nanoscale pores with size below or equal to the mean free path of electrons. Similarly, the flashover strength may also be improved by structuring surface topography on the scale of hundreds of nanometres, but to the best of our knowledge, the effect of nanoscale topography is still rarely explored.…”

Regulation mechanism of porous structures on flashover performances: combined effect of hindering collision ionization and corona stabilization

“…The mean free path of electrons is one of the main factors affecting the collisional ionization of gas molecules. Previous studies have shown that the collision ionization can be effectively inhibited by porous structures with pore diameter close to or slightly larger than the mean free path of electrons [21,23,24]. The mean free path of electrons can be expressed by [39]:…”

“…However, due to the complex correlation between matrix and filler of composite coatings, the role of nanoscale morphology cannot be clearly distinguished. Xin et al [23] and Sun et al [24] found that porous materials with pore diameter close to the electron mean free path could improve the breakdown strength owing to the inhibition effect on collision ionization and avalanche breakdown. The influence of pore diameter on breakdown performance is clarified.…”

“…Potential scanning test, partial discharge (PD) measurement and optical photography were adopted to characterize the surface discharge properties. The collision ionization of gas molecules is inhibited by the obstruction effect of high-density solid structures on electrons [23,24]. At the same time, due to the influence of pores, porous materials are prone to form the corona stabilization effect [25][26][27], which weakens the electric field strength at the triple junction point, thus increasing the flashover voltage.…”