Preparation Of Amino-functionalized Boron Nitride Nanosheets And Their Application In Composites

Boron nitride nanosheets（BNNS）are highly promising two-dimensional inorganicnanomaterials due to their exceptional mechanical strength,wide band gap,excellent chemical stability,high-temperature resistance,high thermal conductivity,and superior insulation properties.However,the large-scale production of BNNS with both thin layers and large lateral dimensions remains a major challenge for both academic research and industry.In this study,BNNS were prepared through mechanical peeling using the semi-solid milling method,and their surfaces were functionalized.The application of modified BNNS in sensors and PVA composite membrane was explored.Firstly,amino-functionalized boron nitride nanosheets（BNNS-NH₂）were prepared using hexagonal boron nitride（h-BN）,urea,and deionized water as raw materials through the semi-solid milling method.Urea,deionized water,and h-BN were premixed into a semi-solid state and added to a stone mill.Under the action of shear force,the lamellae of h-BN sheets were continuously peeled off.At the same time,urea wrapped on the surface of h-BN sheets underwent a chemical reaction with the B-N bond,forming new chemical bonds on the surface.This allowed for simultaneous exfoliation and surface modification,resulting in BNNS-NH₂ with a large aspect ratio.The morphology of BNNS-NH₂ showed good lattice structures with a lateral dimension of approximately 2μm and a thickness of about 10 nm.Surface group and elemental analysis confirmed that amino groups were successfully grafted onto the surface of BNNS.Next,the applications of BNNS in fire alarms,solvent sensors,and humidity sensors were explored.An asymmetric composite membrane of BNNS/graphene oxide（GO）was prepared by vacuum filtration using BNNS-NH₂ and GO as raw materials.In fire alarm tests,the BNNS/GO asymmetric composite membrane showed a warning response time of only 0.2 s and a fire resistance time of up to 52 s,outperforming the pure GO membrane.This is attributed to the ability of the GO layer to be thermally reduced to electrically conductive reduced graphene oxide during combustion,while the BNNS layer provides rapid heat conduction and excellent fire resistance.Additionally,the asymmetric layer of the BNNS/GO composite membrane can rapidly move and bend in volatile solvent atmospheres or humidity,making it suitable for highly sensitive self-driving switches.Lastly,the application of BNNS in polyvinyl alcohol（PVA）membranes was explored.BNNS/PVA composite membrane were prepared using BNNS-NH₂ and PVA as raw materials through the solution blending method.Compared to pure PVA membranes,adding only 5%BNNS-NH₂ significantly improved the thermal conductivity of BNNS/PVA composite membrane.When the BNNS/PVA composite membrane is used as the thermal interface materials（TIM）,the surface temperature of the LED lamp is only 28℃,which decreases by 24.1℃compared to the PVA membrane as the TIM.Additionally,in UV-shielding performance tests,as the content of BNNS-NH₂ increased,the BNNS/PVA composite membrane maintained excellent transmittance while the UV shielding rate gradually increased.When the addition amount of BNNS-NH₂ reached 15 wt%,the transmittance of the BNNS/PVA composite membrane exceeded 70%and the UVC shielding exceeded 60%.