Extreme Thermal Stability and Dissociation Mechanisms of Purified Boron Nitride Nanotubes: Implications for High-Temperature Nanocomposites

Abstract

A fundamental understanding of the thermal behavior of reinforcement materials is crucial to fully exploit their properties in composites. Boron nitride nanotubes (BNNTs), structural analogues to carbon nanotubes, are a strong candidate for nanofillers in high-temperature composites due to their high thermal stability, oxidation resistance, excellent mechanical properties, and high thermal conductivity. In this paper, samples of high-quality, high-purity BNNTs were tested to thermal failure in an inert atmosphere for the first time up to 2500 °C. A significant fraction of the BNNTs survived temperatures as high as 2200°, and the BNNT samples were completely undamaged at temperatures as high as 1800 °C. Boron nitride (BN) nanopowders were tested identically to perform a comparative study, as hexagonal BN is commonly found in purified BNNT samples. Observed color darkening, significant weight loss, an increased boron atomic level, significant weight gain upon oxidation, the presence of boron oxide compounds in an oxidized sample, and the observed boron clusters at the nanoscale indicate dissociation of B-N bonds in the BNNT sample at 2200 °C. The stability of BNNT structures was observed up to 2000 °C, with local/partial wall dissociation or unzipping, and complete survivability of highly crystalline BNNTs is demonstrated up to 1800 °C. This paper presents the first-ever study on extreme temperature thermal stability of purified BNNTs in an inert atmosphere analogous to manufacturing processes for high-temperature nanocomposites.

Manufacturing of stereolithographic 3D printed boron nitride nanotube-reinforced ceramic composites with improved thermal and mechanical performance

“…While sintering the silica particles, the stability of the fillers must be confirmed at high temperatures to prevent nanofillers from being damaged. Previously, studies have reported that the BNNTs have high oxidation resistance of ∼850 • C [16,17], and a recent study confirms the complete stability of the BNNTs up to 1800 • C in inert environments [19]. In order to prevent oxidation of BNNTs above 850 • C in air during the sintering process, the sintering process was divided into two steps (1) polymer burnout stage in the air up to 750 • C (figure 4 The green state samples first underwent a polymer burnout cycle where samples were heated at a 2 • C ramp rate up to 750 • C with a hold of 2 h at 240 • C and 1 h at 300 • C in a Lindberg/Blue M box furnace (ThermoFisher Scientific, Waltham, MA) in air to burn out binder polymer from the printed samples.…”

“…It was estimated that the dissociation of the B-N bond and failure of nanotubes occurred at temperatures up to 1900 • C depending on tube geometry. A recent study reported that B-N structures of BNNTs are completely stable up to 1800 • C in inert environments, introducing confident use of high-temperature manufacturing processing on BNNT composites [19].…”

Polymer-Derived Silicon Carbide and Boron Nitride Nanotube Composites with High Thermal Shock Resistance

“…To prepare the SiC-BNNT composites, BNNTs (Figure a) were dispersed in acetone with probe sonication. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the BNNTs were shown in an earlier publication . The BNNT/acetone dispersion (Figure b) was added with a commercial poly­(carbosilane) preceramic polymer (SMP-10, Starfire) and thoroughly mixed with probe sonication.…”

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

“…1(a)). 14,15 Their high thermal conductivity and mechanical strength make them suitable for applications in various fields, such as electronics, energy storage, and biomedicine. [16][17][18][19][20][21][22][23] This comprehensive review seeks to delve into the intricate world of BNNTs, with a particular focus on their growth methodologies and applications in neutron shielding, particularly in aerospace engineering and cancer therapy (Fig.…”

“…1(a)). 14,15 Their high thermal conductivity and mechanical strength make them suitable for applications in various fields, such as electronics, energy storage, and biomedicine. 16–23…”