Synthesis Of Boron Nitride Nanomaterials Using Precursors

Hexagonal boron nitride material is an important non-oxide ceramic material with many excellent performance and promising applications.Its corresponding boron nitride nanomaterials are attracted by a wide range of researchers because of their unique structure with more special properties.The current method of synthesizing boron nitride nanomaterials is diverse,but it is still difficult to obtain high yield,high purity and high crystallinity products.At the same time,some synthetic methods have the shortcomings of high raw material risks,high synthesis temperature,high reaction pressure,and the appearance and size of products is not easy to control.Therefore,the development of a synthetic method which is simple and efficient,environmentally friendly and can obtain high purity and high yield,controllable size boron nitride nanomaterials for the follow-up material performance research and practical industrial applications is of great significance.In this paper,boron nitride nanotubes and boron nitride nanosheets were synthesized by organic-inorganic hybrid precursors and inorganic precursors.The main contents and results are as follows:(1)The organic-inorganic hybrid precursors were prepared by a wet chemical synthesis using boric acid as boron source,ethylenediamine as transition metal chelating agent and ferric nitrate as catalyst precursor.Boron nitride nanotubes were synthesized at 1200 °C under ammonia gas.It was found that the type of catalyst and reaction atmosphere had a decisive effect on the morphology of the final product.The content of the catalyst also has an important effect on the diameter and aspect ratio of the obtained boron nitride nanotubes.The reaction temperature determines the quality and purity of the product.When the reaction temperature is too low,the product is boron nitride nanotubes with irregular tube diameter,large diameter and curved irregular morphology.The effect of reaction time is the smallest effect factor,and the boron nitride nanotubes can be obtained by considering the optimal reaction time.Finally,the optimum technological conditions for the synthesis of boron nitride nanotubes were explored.The precursor which was synthesized with the ferric nitrate as the catalyst and 2.5% adding content was used to fabricate boron nitride nanotube at 1200 °C under ammonia gas flow for 3 h.The obtained boron nitride nanotubes have the diameter of 80-200 nm,tens of microns length,smooth surface and large aspect ratio.The VLS growth mechanism of boron nitride nanotubes was also proposed.(2)Using borax as boron source and transition metal nitrate as catalyst precursor,the inorganic precursors were prepared by a wet chemical synthesis method.Boron nitride nanosheets can be synthesized at 1050-1350 °C under ammonia gas flow using this precursor.The morphology of boron nitride nanosheets obtained with ferric nitrate as the catalyst is the best,and no impurity morphology exists.The addition of iron nitrate and the reaction time had little effect on the morphology of the final product,all of which were boron nitride nanosheets,except that the size uniformity of the nanosheets was somewhat different.However,the reaction temperature has an important effect on the synthesis of boron nitride nanomaterials by inorganic precursors.When the reaction temperature is too low,only short columnar boron nitride with very small aspect ratio can be obtained.When the temperature is too high,round sheet of boron nitride is obtained.The thermogravimetric analysis and photoluminescence analysis of the obtained boron nitride nanosheets found that the boron nitride nanosheets had good thermal stability and good photoluminescence properties and could be used in the harsh environment of high temperature and light emitting device.