Synthesis Of Porous Boron Nitride Nanofibers And Their Adsorption Properties

As a new type of non-oxide porous material,one-dimensional?1D?porous BN nanofibers have high specific surface area,large pore volume,high aspect ratios and excellent chemical and thermal stability,thus can be considered as a promising nanomaterials in many application fields,such as catalyst carriers,hydrogen storage,and wastewater treatment,etc.In this thesis,we report the first synthesis of 1D porous BN nanofibers with high aspect ratios via a three-step method using boric acid and melamine as the starting materials.Then their adsorption properties have been studied in detail.The main contents are as follows:1.We developed a green and low cost method to synthesize porous BN nanofibers with diameter of less than 100 nm in a high purity and high yield.Firstly,melamine diborate?M·2B?were synthesized using boric acid and melamine as raw materials.Then the ultrafine nanofiber precursors were fabricated via the freeze-drying of hot melamine diborate solution.After a high-temperature pyrolysis process in N₂ atmosphere,porous BN nanofibers were obtained in a high yield and high purity.In order to characterize the morphology,composition,structure,pore size distribution,specific surface area and pore volume of the product,the samples were analyzed by scanning electron microscope?SEM?,transmission electron microscope?TEM?,electron energy loss?EELS?,X-ray diffraction?XRD?and physical-chemical adsorption?BET?,and so on.The ultrafine porous BN nanofibers were fabricated in a large scale and high purity,and their diameter distribution is 20-60 nanometres.2.Then we studied the adsorption properties of porous BN nanofibers prepared in an optimized condition.The adsorption performance of porous BN nanofibers for the removal of methylene blue?MB?,congo red?CR?and rhodamine B?RhB?was investigated,repectively.The testing results were fitted with isothermal adsorption and kinetics.Finally,we also studied the cycle performance of the BN nanofibers.3.In the last chapter of this thesis we studied the luminescence properties of the RhB/BN composite fibers.The excitation and emission spectra,quantum efficiency,and the thermal stability of the composite phosphor were studied in detail.The results indicate that porous BN can be used as an ideal host to improve the efficiency and thermal stability of RhB.The as-synthesized RhB/BN composites can be considered as a promising red emitting phosphor with high efficiency and high thermal stability.