Preparation Of BNNAs On The Porous Stainless Steel

Along with the deeper study of the nanomaterials, boron nitride nanotubes(BNNTs) get widespread attention from the researchers at home and abroad. As wide-gap semiconductors, BNNTs have stable electrical property which is independent of atomic structure. Besides, BNNTs have some other properties such as good resistance to oxidization, good stability high thermal conductivity and high mechanical strength, etc. Due to these good properties, BNNTs show wide prospects of application in MEMS, composite materials, gas storage field and so on. For now, however, most methods for the preparation of BNNTs are facing high requirements of the equipments, low yield of production and low purity. Furthermore, the nanotubes always have random distributions and different alignments. These problems prevent the research on properties and the application exploitation. Therefore, in this paper, we focused on the preparation of boron nitride nanotube arrays(BNNAs) which are made of the nanotubes with highly same alignments.In this paper, a detailed review on the recent progress of both BNNTs and BNNAs was summarized by referring to many literatures. On basis of this review, a novel ball milling annealing method which was assisted with a porous stainless steel template for the preparation of BNNAs was developed. In the first stage of this study, the amorphous boron powder and Iron(?) nitrate nonahydrate were chosen as the raw materials for the synthesis of BNNTs, and the effects of different substrate on the growth of BNNTs were studied. The experimental results show that the synthesized BNNTs which were grown on the 314 stainless steel plate have the tube length range of 2~8 ?m and the diameter range of 75~100 nm. In the second stage, the stainless steel was prepared by electrochemical corrosion method to obtain porous structure and the experimental parameters such as the DC supply voltage, the electrolyte concentration and the reaction time were studied. It was found that as the DC supply voltage increased, the size of pores on stainless steel plate increased. When it increased too high, the porous structure was dissolved. In the situation of low electrolyte concentration, the pores were shallow. The depth of the pores deepened with the increase of electrolyte concentration. When the electrolyte concentration was too high, the porous structure became fuzzy. When the corrosion process lasted for a long time, the porous structure was destroyed. In the final stage, the novel ball milling annealing method which used the porous stainless steel plate as the substrate was developed for the preparation of BNNAs. After ball milling of the mixture which were made of amorphous boron and Iron(?) nitrate nonahydrate for 18 h, the ethanol was added to prepare the boron ink. After coated with the boron ink, the substrate was annealed under the atmosphere of the mixture of nitrogen and hydrogen in 1150?. White powder was found on the surface of the substrate. For further study, the white powder was taken for characterization. It was observed that the BNNAs which have highly orientation and high density of distribution were grown on the substrate. Furthermore, it was observed that BNNTs which were high crystallization had bamboo-like structure.