Green And Scalable Preparation Of Electrically Insulating Nanosheets And Their Applications In Nacre-inspired Insulating Paper

Insulating paper is a critical component in power systems,providing effective isolation of current and electric field to protect electrical equipment from electric shock and arc damage.As modern power systems continue to evolve,with increasing demands for high voltage,high current,and frequency conversion applications,the electrical insulation performance and mechanical properties of insulating paper have become even more crucial.In recent years,nacre-like nano-insulating papers have garnered significant attention due to their exceptional properties,such as enhanced breakdown strength,corona resistance,and mechanical robustness.These papers are fabricated by assembling electrical insulating nanosheets and polymer,taking inspiration from the laminar microstructure of nacre.However,the lack of green and scalable preparation methods for the electrical insulating nanosheets has limited the further development and application of these high-performance nano-insulating papers.In view of this,this thesis provides a comprehensive review of the preparation methods of electrically insulating nanosheets and the progress made in exfoliating layered silicates and boron nitride through mechanical exfoliation,liquid phase exfoliation,and intercalation exfoliation.Furthermore,the author analyzes and discusses the structural design of nanocomposites inspired by the natural nacre,highlighting its potential for enhancing the mechanical,thermal,electrical,and other properties of nanocomposites.Building on this foundation,the authors explore the exfoliation of layered silicates,particularly mica,and prepare boron nitride nanosheets and nacre-inspired nano-insulating papers with them as reinforcing units inspired by the nacre layered structure and its high performance.The specific results of the study are as follows.1.A novel method of protonated glycine intercalation-assisted sand-mill exfoliation of layered silicates is developed,which yields a high percentage of 86.5%at a feeding rate of 100 g natural mica for 2 h.The effects of different intercalators and intercalators protonated or not on the intercalation-assisted sand-mill exfoliation of mica are investigated through both experimental and theoretical calculations in detail.The solution system and intercalators utilized in this method are discussed and compared with commonly used organic solvents and intercalators in terms of sustainability.The method is extended to the green and scalable preparation of a series of silicate nanosheets,such as synthetic mica and phlogopite;2.Using the above mentioned method of exfoliating layered silicates,the intercalator is optimized for the structure of boron nitride,and functionalized boron nitride nanosheets are prepared using sucrose-saturated solution-assisted sand-mill exfoliation.The symmetric gradient nacre-inspired boron nitride nanosheets-polyimide insulating paper is then successfully prepared by compounding them with boron nitride nanosheets as reinforcing units,and their electrical and mechanical properties are significantly improved compared with original polyimide.Notably,the corona resistance life is 71 times that of the original polyimide at 2 kV and 20 kHz for 389 min.