Preparation Of Boron Nitride Nanotubes By Chemical Vapor Desposition

Boron nitrogen nanotubes?BNNTs?possess many unique properties,such as superb thermal conductivity,high chemical inertness,electrical insulator,and excellent mechanical properties and so on.Such unmatched properties enable BNNTs as a promising nanomaterial in a variety of potential fields such as insulating fillers for making thermal conductive polymeric composites,ultraviolet-light emitters,and hydrogen accumulators,attracting increasing research interest.However,some fundamental scientific problems regarding the growth of BNNTs,especially growth mechanism,remain open questions.In the article,the structures,properties,and preparation of BNNTs are briefly reviewed.In our work,Chemical Vapor Deposition?CVD?method was used to synthesis BNNTs and the growth mechanism of BNNTs has also been explored and confirmed.The power BNNTs were also successfully synthesized by CVD method,which made it have an extremely impressive application in business.The major conclusions are summarized as the following:1.Based on the investigation of CVD method for synthesis of BNNTs,we designed a dual zone growth way for the independent temperature control for precursor reaction and BNNTs growth under low pressure.High quality BNNTs were obtained with length up to100?m and diameters about 10 nm.Furthermore,the as-grown BNNTs show a large band gap of 6.12 eV,approaching to hexagonal phase BN single crystals,and meanwhile exhibit an intense UV-emission band located at 345 nm as well a weak deep band at 237 nm.Their optical properties make them have promising for future nanoscale deep-UV light emitting devices.But most importantly,it is suggested that the Fe-Mg-O species derived from the precursor acted as the catalysts,which proved the catalyst growth mechanism for BNNTs.2.Boron nitrogen can be seen as alternating boron?B?and nitrogen?N?atoms in a hexagonal lattice structure.We first propose a way for synthesis bimetallic catalytic to increase the solubility of B and N atoms respectively and promoted the yield rate of product,through the phase diagrams of B and N atoms and the growth mechanism.We successfully prepared Ni,Mo,Y,Ni-Mo,and Ni-Y catalyst particles through the reverse micelle method.We used Ni-Mo and Ni-Y nanoparticles as the catalysts to successfully grow large amounts of BNNTs.This work offers a principle for catalyst design and an effective way for producing BNNTs.3.By exploiting catalyst species,we chose Li₃N as catalyst to effectively prepare BNNTs powder.It is worth emphasizing that Li₃N is not only supply the nitrogen source,but also catalyze BN nanostructures synthesis,which huge yield rate can reach over 96%.The BN nanosheets have also been observed in the product,which make it have a promising for building the 3D structure of conductivity to increases the thermal conductivity in composites.When 1.0 wt%BN was loaded,the thin film showed a TD of almost 7.31mm₂/s in in-plane,which improve more 400%than blank TPU without affecting the optical property.