Controlled Fabrication And Performance Studies Of Flexible BN Nanoribbon Aerogels

With the advent of 5G era,electronic devices are becoming more and more important in our life,and tend to more and more miniaturized,integrated and intelligent.Therefore,the thermal management of electronic devices requires more efficiency and multiple functions for their practical applications,especially for the coming portable 5G electronic devices,as the undesired heating will bring discomfort and even heat damage to the users.Boron nitride?BN?possesses a similar structure to graphene and consists of the same number of B and N atoms.BN nanoribbon aerogel is a novel porous ceramic material with intertwined nanoribbons and they form a three-dimensional porous network structure.Compared with traditional materials,these BN aerogels not only have high specific surface area,low density and a large number of reactive sites,but also have excellent chemical inertia and thermal insulation effect,high thermal stability and antioxidant performance.The main research contents and results are as follow:?1?Boric acid as source of boron,melamine as the nitrogen source,water and tert-butyl alcohol as a co-solvent.The boric acid and melamine were dissolved into the co-solvent at high temperature,and then cooling crystallization at low temperature,and after frozen drying,high temperature pyrolysis,the flexibile BN nanoribbon aerogels were obtained.Through the SEM,element mapping,TEM,XRD,nitrogen adsorption desorption?BET? and other tests,the nanoribbon microstructure,element distribution and pore diameter distribution of BN aerogels were studied.The specific surface area of the optimal BN aerogel is up to 981.72 m²/g.Thermogravimetric analysis?TG? showed that almost no weight change after the BN aerogel was heating to 900°C under N₂,which indicated the excellent thermal stability of the BN aerogel.Moreover,the obtained BN aerogels exhibited temperature–invariant flexibility over a wide temperature range from liquid nitrogen to flame.?2?Cutting the melamine diborate?M·2B?monolith into slices and followed as press assembled and high-temperature pyrolysis,the flexible BN aerogel film was obtained.The resulting films possessed a thickness range from 50 to 200 m,a density range from 150 to200 mg/cm³ and a high specific surface area?624 m²/g?.According to the thermocouple recording,infrared thermal imaging and flame experiment,the thermal stability and thermal insulation performances were investigated systematic and visually.This excellent thermal insulation performance and the light,thin and flexible characters of the BN aerogel film make it could serve as a thermal barrier in portable electronics to provide a comfort environment for users,especially to the wearable electronics in the near further.?3?Introducing the paraffin into the BN aerogel film,and obtained the BN phase change composite film.The filling amount and enthalpy of phase change materials in boron nitride aerogel films can be as high as 89wt% and 201 J/g,respectively.By changing the type of PCMs,different phase change temperatures and different phase change enthalpies can be realized.This film can effectively cool the portable electronics as that the organic phase change materials filled in the aerogel matrix can serve as a smart thermal-regulator to absorb the undesired heat via solid-liquid phase transition.The thermal energy confinement based peak-load shifting behavior of BN/paraffin composite film could be used in the portable electronics to dissipate the undesired heat.