Synthesis of Double-Walled Boron Nitride Nanotubes from Ammonia Borane by Thermal Plasma Methods

Abstract

Highly crystalline double-walled boron nitride nanotubes (DWBNNTs ∼60%) were synthesized from ammonia borane (AB; H3B–NH3) precursors using a high-temperature thermal plasma method. The differences between the synthesized BNNTs using the hexagonal boron nitride (h-BN) precursor and AB precursor were compared using various techniques such as thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and in situ optical emission spectroscopy (OES). The synthesized BNNTs were longer and had fewer walls when the AB precursor was used than when the conventional method was used (with the h-BN precursor). The production rate significantly improved from ∼20 g/h (h-BN precursor) to ∼50 g/h (AB precursor), and the content of amorphous boron impurities was significantly reduced, implying a self-assembly mechanism of BN radicals rather than the conventional mechanism involving boron nanoballs. Through this mechanism, the BNNT growth, which was accompanied by an increased length, a decreased diameter, and a high growth rate, could be understood. The findings were also supported by in situ OES data. Considering the increased production yield, this synthesis method using AB precursors is expected to make an innovative contribution to the commercialization of BNNTs.

Growth methodologies of boron nitride nanotubes and their neutron shielding applications: a review

“…Typically, they do not employ catalyst particles and are grown by flowing hydrogen gas along with reactants. 37,40,42,44 Similar to laser ablation, they exhibit few-walled, small diameters, and long lengths, forming macroscale bucky paper. BNNTs synthesized via CVD initiate the reaction at temperatures above 1000 K with relatively low surrounding pressures.…”

“…Bae et al 44 reported the growth of BNNTs using an ammonia-borane precursor. The synthesized BNNTs were highly crystalline, long, and double-walled (∼60%) with minimal amorphous boron impurities (Fig.…”

“…The complex atomic structure of BNNTs necessitates precise control over the growth process, which is influenced by various factors, such as temperature, pressure, and choice of catalysts. Different growth methods, including laser ablation, [30][31][32][33][34][35][36] thermal plasma, [37][38][39][40][41][42][43][44][45][46] chemical vapor deposition (CVD), [47][48][49][50][51][52][53][54][55] and ball milling, [56][57][58][59][60][61][62][63][64][65][66][67] have intricacies and yield BNNTs of different qualities. This review examines these growth techniques and highlights their mechanisms, advantages, and limitations.…”

Methods for Preparation of Hexagonal Boron Nitride Nanomaterials

“…Recent studies have expanded the range of raw materials for this method to include ammonia borane (AB). In comparison to BNNTs synthesized using traditional h -BN or B powders, those prepared from AB exhibit longer lengths, fewer walls, and lower levels of amorphous B impurities. , Bae et al demonstrated a substantial increase in BNNT production yield, from approximately 20 g/h (using h -BN precursors) to around 50 g/h by utilizing AB precursors, promoting the commercialization process of BNNTs …”

“…Additionally, the synthesized BNNTs contain a significant amount of impurities, including amorphous boron and h -BN, requiring further refinement through purification processes. Further research will focus on optimizing the thermal plasma reactor, , feedstock materials, , as well as purification techniques to reduce costs and enhance the quality of BNNTs.…”