High-quality Boron Nitride Nanotubes Research Articles

Ti-B-O System for Catalyzing Boron Nitride Nanotube Growth.

Chemical vapor deposition (CVD) stands out as the most promising method for cost-effective production of high-quality boron nitride nanotubes (BNNTs). Catalysts play a crucial role in BNNT synthesis. This work delves into the impact of oxygen (O) on Ti-based catalysts during the CVD growth of BNNTs. In contrast to the B/TiB2 nanoparticles (NPs) and B/TiN NPs systems, the oxygen-containing precursor B/TiO2 NPs remarkably catalyzes the growth of high-quality and high-purity BNNTs across a wider range of synthesis parameters. Subsequent analyses reveal that TiBO3 acts as an active catalyst, facilitating BNNT growth in Ti-based catalyst systems. Moreover, the nanocomposite film synthesized from BNNTs and PVDF-HFP exhibits excellent mechanical properties and heat dissipation capabilities. Utilizing the nanocomposite film as a thermal interface material effectively enhances the heat dissipation for a 5 W light-emitting diode (LED) chip. Consequently, our research confirms the effectiveness of the Ti-B-O system in catalyzing BNNT growth.

Self-Catalytic Ternary Compounds for Efficient Synthesis of High-Quality Boron Nitride Nanotubes.

The large-scale synthesis of high-quality boron nitride nanotubes (BNNTs) has attracted considerable interests due to their applications in nanocomposites, thermal management, and so on. Despite decades of development, efficient preparation of high-quality BNNTs, which relies on the effective design of precursors and catalysts and deep insights into the catalytic mechanisms, is still urgently needed. Here, a self-catalytic process is designed to grow high-quality BNNTs using ternary W-B-Li compounds. W-B-Li compounds provide boron source and catalyst for BNNTs growth. High-quality BNNTs are successfully obtained via this approach. Density functional theory-based molecular dynamics (DFT-MD) simulations demonstrate that the Li intercalation into the lattice of W2 B5 promotes the formation of W-B-Li liquid and facilitates the compound evaporation for efficient BNNTs growth. This work demonstrates a high-efficient self-catalytic growth of high-quality BNNTs via ternary W-B-Li compounds, providing a new understanding of high-quality BNNTs growth.

Surfactant-Assisted Isolation of Small-Diameter Boron-Nitride Nanotubes for Molding One-Dimensional van der Waals Heterostructures.

Rolling two-dimensional (2D) materials into 1D nanotubes allows for greater functionality. Boron-nitride nanotubes (BNNTs) can serve as insulating 1D templates for the coaxial growth of guest nanotubes, without interfering with property characterization. However, their application as 1D templates has been greatly hindered by their poor dispersibility, inevitably resulting in the formation of thick bundles. Here we present the facile preparation of well-dispersed BNNT templates via surfactant dispersions and synthesis of 1D van der Waals heterostructures based on the BNNTs. Comprehensive microscopic analyses show the isolation of clean, high-quality BNNTs. Statistical analyses revealed that small-diameter double-walled BNNTs are highly enriched by chemical peeling of BN sidewalls through the sonication process. We further demonstrate that the isolated BNNTs can template the coaxial growth of carbon and MoS2 nanotubes by using chemical vapor deposition. The present strategy can be applied to the synthesis of a variety of nanotubes, thereby allowing for their characterization.

Spontaneous formation of boron nitride nanotube fibers by boron impurity reduction in laser ablation of ammonia borane

Highly crystalline and few-walled boron nitride nanotubes (BNNTs) had been synthesized by laser ablation using only ammonia borane as a precursor. As a molecular precursor, ammonia borane supplied both B and N atoms with a ratio of 1:1, and BNNTs were formed via the homogeneous nucleation of BN radicals, not the growth from boron nano-droplets, which is a generally accepted growth mechanism of the laser-grown BNNTs. Owing to the absence of amorphous boron impurities, the van der Waals interaction among BNNTs became effective and thus a BNNT fibers was formed spontaneously during the BNNT synthesis. The BNNT growth and the subsequent fiber formation are found to occur only at high pressures of a surrounding gas. The mechanism behind the critical role of pressure was elucidated from the perspective of reaction kinetics and thermal fluid behaviors. A polarized Raman study confirmed that the BNNT fiber formed exhibits a good alignment of BNNTs, which implies great potential for continuous production of high-quality BNNT fibers for various applications.

Insight into BN Impurity Formation during Boron Nitride Nanotube Synthesis by High-Temperature Plasma.

The high-temperature plasma process has demonstrated great potential in growing high-quality boron nitride nanotubes (BNNTs) with small diameters (∼5 nm) and few walls (3–4 walls) and led to successful commercialization with a high production rate approaching 20 g/h. However, the process is still accompanied by the production of BN impurities (e.g., a-BN, BN shell, BN flakes) whose physicochemical properties are similar to those of BNNTs. This renders the post-purification process very challenging and thus hampers the development of their practical applications. In this study, we have employed both experimental and numerical approaches for a mechanistic understanding of BN impurity formation in the high-temperature plasma process. This study suggests that the flow structure of the plasma jet (e.g., laminar or turbulent) plays a key role in the formation of BN impurities by dictating the transport phenomena of BNNT seeds (e.g., B droplets), which play an important role in BNNT nucleation. We discussed that the turbulence enhances the radial diffusion of B droplets as well as their interparticle coagulation, which leads to a significant reduction in the population of effective BNNT seeds in the BNNT growth zone (T < 4000 K). This results in the generation of unreacted BN precursors (e.g., B-N-H species) in the BNNT growth zone that eventually self-assemble into BN impurities. Our numerical simulation also suggests that a higher thermal energy input makes the flow more turbulent in the BNNT growth zone due to the elevated velocity difference between the plasma jet and ambient cold gas. This finding provides critical insight into the process design that can suppress the BN impurity formation in the high-temperature plasma process.

WITHDRAWN: A biocompatible and flexible piezoelectric generator with high-quality boron nitride nanotubes from human running

WITHDRAWN: A biocompatible and flexible piezoelectric generator with high-quality boron nitride nanotubes from human running

Synthesis of boron nitride nanotubes by combining citrate-nitrate combustion reaction and catalytic chemical vapor deposition

High-quality boron nitride nanotubes were successfully synthesized via a novel two-step method, including citrate-nitrate combustion reaction and catalytic chemical vapor deposition. The composition, bonding features and microstructures of as-synthesized sample were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, Raman microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, transmission electron microscopy and selected area electron diffraction techniques. The results show that the as-synthesized boron nitride nanotubes with smooth surface are relatively pure. The diameter ranges between 20 and 80 nm, while the length is about dozens of micrometers. During the synthesis process of boron nitride nanotubes, citric acid chelates the cobalt ions and reacts with nitrate to form the cobalt oxide, depositing on the surface of boron powder homogeneously. The catalyst content and annealing temperature have a significant impact on the composition and microstructures of the final products. Based on the experimental results and thermodynamic analysis, the possible chemical reactions are listed, and vapor-liquid-solid mechanism is proposed to be dominant for the formation of boron nitride nanotubes.

Low temperature synthesis of high quality BNNTs via argon supported thermal CVD

The anti-oxidant nature of Argon gas prevents the formation of water vapors and oxidation of as produced catalysts. These facts have made it possible to synthesize high quality boron nitride nanotubes via Argon supported thermal chemical vapor deposition at a relatively lower temperature of 900°C. The synthesized sample is the combination of straight, nearly straight and curve like morphologies of boron nitride nanotubes with diameter in the range of 20–80nm. Internally, each tube has bamboo like structure whereas the external part has lattice fringes with an interlayer spacing of~0.34nm. X-ray photoelectron spectroscopy shows B 1s and N 1s peaks at 191.4 and 398.7eV for hexagonal boron nitride nature of the synthesized nanotubes whereas, the recorded Raman spectrum reports a high intensity peak at 1372(cm−1) that corresponds to E2g mode of vibration in hexagonal boron nitride.

Scaled synthesis of boron nitride nanotubes, nanoribbons, and nanococoons using direct feedstock injection into an extended-pressure, inductively-coupled thermal plasma.

A variable pressure (up to 10 atm) powder/gas/liquid injection inductively coupled plasma system has been developed and used to produce high-quality boron nitride nanotubes (BNNTs) at continuous production rates of 35 g/h. Under suitable conditions, collapsed BN nanotubes (i.e., nanoribbons), and closed shell BN capsules (i.e., nanococoons) are also obtained. The process is adaptable to a large variety of feedstock materials.

Functionalization, Dispersion, and Cutting of Boron Nitride Nanotubes in Water

High-quality boron nitride nanotubes (BNNTs) were functionalized for the first time with water-soluble and biocompatible PEGylated phospholipid [methoxy-poly(ethylene glycol)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N conjugates (mPEG-DSPE)]. We found that BNNTs can be suspended in water for more than 3 months without precipitation. By comparing the dispersion stability of mPEG-DSPE/BNNTs in various solvents and the related Hansen solubility parameters, we found that polarized and hydrogen bonds between water and the hydrophilic mPEG play important roles in maintaining stable dispersion of BNNTs and preventing aggregation of mPEG-DSPE/BNNTs in the solutions. This has led to the formation of composite films with well-dispersed BNNTs and the coating of self-assembled monolayer (SAM) BNNTs. Furthermore, the lengths of these functionalized BNNTs can be shorterned, for the first time, from >10 μm to ∼500 nm by ultrasonication. Experiments suggest that effective dispersion of BNNT in solution is necessary for such cutting, where effective energy transfer from the sonicator to nanotubes is achieved. Our results will form the basis for stable functionalization, dispersion, and effective cutting of BNNTs with water-soluble and biocompatible PEGylated phospholipid, which are important for biomedical and composite applications.

Patterned Growth of Long and Clean Boron Nitride Nanotubes on Substrates

AbstractFor the first time, patterned growth of boron nitride nanotubes (BNNTs) on Si substrates has been achieved by catalytic chemical vapor deposition (CCVD). Following the boron oxide chemical pathway and our growth vapor trapping approach, high quality and quantity BNNTs can be produced. Effective catalysts have been found to facilitate the growth of BNNTs, while some critical parameters of the synthesis have also been identified to control the quality and density. The success of patterned growth of high quality BNNTs not only explains the roles of the effective catalysts during the synthesis process, but could also be of technologically important for future device fabrication.