Preparation and Characterization of BN Nanotubes with Controllable Sizes by Template-aided Synthesis
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Preparation and Characterization of BN Nanotubes with Controllable Sizes by Templateaided Synthesis Yuting WANG, Shiro SHIMADA, Hajime KIYONO, and Yasunori YAMAMOTO Graduate School of Engineering, Hokkaido University, sapporo, 060-8628, Japan ABSTRACT In this study, an efficient approach to prepare high quality BN nanotubes (BNNTs) was developed. BNNTs with specific sizes were prepared by sublimation of ammonia borane complex (BH3NH3) using two kinds of porous alumina anodic membrane template in two independently temperature controlled furnaces in a glovebox filled with N2. The BNNTs with template were nitrided at different temperatures 1300 ~ 1700 °C in NH3. The BNNTs of 200 300 nm wide×60 μm long, and 70 - 80 nm wide×40 μm long were finally collected after removal of the template by etching of with 40 wt% NaOH solution. The fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results confirmed the formation of BN from BH3NH3. Ordered arrays of BNNTs were observed by scanning electron microscopy (SEM), and the microstructure of these BNNTs was investigated by transmission electron microscopy (TEM). It was found that the diameters of the BNNTs can be easily controlled by using templates with different pore sizes. The wall thickness of the nanotubes was increased by increasing the sublimation time or the amount of the starting BH3NH3. The crystallinity of BNNTs was improved at higher temperatures (1700 °C) in NH3. INTRODUCTION In recent years, one-dimensional (1D) nanostructure materials such as nanotubes, nanowires and nanobelts have attracted much attention on account of their novel chemical and physical properties. Boron nitride nanotubes (BNNTs), structurally similar to carbon nanotubes (CNTs), display several outstanding properties for future technological applications [1-8] and they are sometimes considered to be more suitable than carbon nanotubes; BNNTs demonstrate high oxidation resistance up to 800 °C in air, in contrast to CNTs that are readily oxided around 400 °C. Although there have been significantly more studies concerning CNTs, there have been relatively less reports about preparation, properties and applications of BNNTs. Because preparation of high quality BNNTs in large quantity and the control of their size is more difficult than that of CNTs. Currently, BNNTs were synthesized by arc discharge [9], substitution reaction with CNTs, ball milling [10], thermal annealing of a mixed powder of boron and hexagonal boron nitride h-BN [11], and the chemical vapor deposition (CVD) method by using a mixture of B2O2 and Mg vapors [4]. Almost all these methods require complicated and expensive apparatus or severe preparation conditions. In particular, it is difficult to control the diameter, the inner space, or the length of the nanotubes by using the aforementioned techniques. Therefore, a new, simple and efficient technique to prepare high purity BN nanotubes which allows for control of geometry is highly desired. The template-aided synthesis has been consi
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