Surface Modification On Boron Nitride Micro/nano-materials And Their Property Studies

Hexagonal boron nitride?BN?has a graphite-like layered structure and possesses a number of highly desirable properties including high thermal conductivity,excellent electrical resistivity,lubrification,very good chemical stability,high temperature oxidation resistance and thermal stability.By structural engineering of BN material at micro/nano scale,the performance of BN can be well modulated,so renders the BN effective in many applications,such as polymer reinforcement,water treatment,gas adsorption,hydrogen storage,advanced catalyst,luminescent materials,etc.In spite of that,the restrictions/limitations for practical utilization of BN micro/nanomaterials in some cases may directly lie in the intrinsic characteristics of BN e.g.chemical inertness,low wettability or non-magnetic properties.Surface modification and/or consciously assembling of BN micro/nanomaterialscould be utilized to tailor the properties of BN micro/nanomaterials for specific applications,so are very importantboth scientific and technological reasons.In the thesis,I report our effort to prepare new functional materials via surface modification to BN-based micro/nanomaterials,i.e.BN nanospheres and porous BN micro/nanofibers,as well as the functional assembling of porous BN microfibers into hierarchical porous materials.The applications of the prepared materials as adsorbents,photocatalyst,etc.were also explored.The main contents of the thesis are listed below.1?Fe₃O₄ nanoparticles with an average diameter of 10 nm and high crystallinity were uniformly coated on the surface of BN nanospheres?BNNSs?by ethanol-thermal reaction to obtain a magneto-operable nanocomposites.The impact of the reaction time on the compositions,morphologies and magnetic properties of the products were investigated and the coating mechanism was discussed.By adjusting the growth parameters,nanocomposites with superparamagnetism were obtained.We also performed the studies on the biocompatibility of BNNSs@Fe₃O₄ nanocomposites.The Cell viability experiments indicated a low toxicity of the nanocomposites to the cell lines of MCF-7,MCF-10 and Hela.The nanocomposites are expected to be useful in biomedical applications,such as cancer therapy and magnetic targeting drug delivery.2?Surface modification to hydrophobic porous BN nanofibers was carried out via one-step ethanol-thermal method.With copper nitrate as the copper source,CuO semiconductor nanoparticles were successfully grown on the surface of the porous BN nanofibers.The obtained nanocomposites turned to be hydrophilic,and possessed a large number of micropores and mesopores.The specific surface area and pore volume of the nanocomposites could be up to 226 m²/g and 0.323 cm³/g,respectively.Compared with the porous BN nanofibers,the nanocomposites showed wider range optical absorption from deep UV to visible light.Thus the nanocomposites exhibited very good photocatalytic performance.3?We modified the traditional method for synthesis of porous BN microfibers by introducing the techniques of ultrasonic-assisted growth.As a result,the structures of the BN microfibers could be modified and the microfibers were self-assembled into ultralight monoliths.A novel BN foam consisting of porous BN microfibers was obtained.We studied the optical contact angle,adsorption performance and mechanical properties of the as-prepared BN foams.The results indicated that the BN foams were resilient,possessing super oleophilic and hydrophobic properties,excellent oil absorption performance and could be easily recycled.