Micro- and Macrostructures of Aligned Boron Nitride Nanotube Arrays

Abstract

Boron nitride nanotubes (BNNTs) possess a broad range of applications because of several engineering-relevant properties, including high specific strength and stiffness, thermal stability, and transparency to visible light. The morphology of these nanoscale fibers must be controlled to maximize such properties, which can be achieved by synthesizing long aligned arrays of crystalline hexagonal boron nitride (hBN) nanotubes. Herein, we synthesize high-quality millimeter length, vertically aligned (VA-) BNNTs using free-standing carbon nanotube (CNT) arrays as scaffolds. In addition to high optical transparency of the VA-BNNTs, we also demonstrate several micro- and macrostructures of BNNTs via patterning and/or postprocessing of the arrays, including engineering of either disconnected or interconnected tubes in VA-, horizontally aligned (HA-), or coherently buckled BNNTs. The internanotube spacings and interconnections between aligned BNNT can thus be tailored to create BN macrostructures with complex shapes and advantaged morphologies for hierarchical materials and devices.

Methods for Preparation of Hexagonal Boron Nitride Nanomaterials

“…189 Wardle et al further expanded upon this method. 190 They initially utilized a freestanding array of CNTs as a scaffold to synthesize highquality, optically transparent millimeter-long VA-BNNTs. Subsequently, they engineered disconnected or interconnected BNNTs through array patterning and varied processing methodologies.…”

“…Copyright 2015 American Chemical Society. (q) Reprinted with permission from ref . Copyright 2022 American Chemical Society.…”

“…The coating mechanism of the h -BN layer was elucidated through NanoSIMS characterization, revealing a top-down deposition process from the top to the bottom of the VA-SWCNT array . Wardle et al further expanded upon this method . They initially utilized a freestanding array of CNTs as a scaffold to synthesize high-quality, optically transparent millimeter-long VA-BNNTs.…”

“…Additionally, they coated diverse carbon scaffolds (bucky paper, carbon fibers, and "fuzzy" carbon fibers) via CVD and then transformed them into "BN twins" through thermal oxidation to create intricate macroscopic BN structures (Figure 10q), yielding BNNTs with distinct characteristics tailored to specific requirements. 190 4.4. Thermal Plasma Method.…”

“…Subsequently, they engineered disconnected or interconnected BNNTs through array patterning and varied processing methodologies. Additionally, they coated diverse carbon scaffolds (bucky paper, carbon fibers, and “fuzzy” carbon fibers) via CVD and then transformed them into “BN twins” through thermal oxidation to create intricate macroscopic BN structures (Figure q), yielding BNNTs with distinct characteristics tailored to specific requirements …”