Oxidative Unzipping and Transformation of High Aspect Ratio Boron Nitride Nanotubes into “White Graphene Oxide” Platelets

Abstract

Morphological and chemical transformations in boron nitride nanotubes under high temperature atmospheric conditions is probed in this study. We report atmospheric oxygen induced cleavage of boron nitride nanotubes at temperatures exceeding 750 °C for the first time. Unzipping is then followed by coalescence of these densely clustered multiple uncurled ribbons to form stacks of 2D sheets. FTIR and EDS analysis suggest these 2D platelets to be Boron Nitride Oxide platelets, with analogous structure to Graphene Oxide, and therefore we term them as “White Graphene Oxide” (WGO). However, not all BNNTs deteriorate even at temperatures as high as 1000 °C. This leads to the formation of a hybrid nanomaterial system comprising of 1D BN nanotubes and 2D BN oxide platelets, potentially having advanced high temperature sensing, radiation shielding, mechanical strengthening, electron emission and thermal management applications due to synergistic improvement of multi-plane transport and mechanical properties. This is the first report on transformation of BNNT bundles to a continuous array of White Graphene Oxide nanoplatelet stacks.

Selective Oxidation of n‐Butane and Isobutane Catalyzed by Boron Nitride

“…An overall catalytic cycle is displayed in Figure . Based on previous reports on the oxygen functionalization of BN materials, we expect oxygen adsorption to occur along the terminating edges of hBN. Such edges are found in either armchair or zigzag configurations .…”

“…Spectroscopic evidence for the oxygen functionalization of the hBN surface was obtained by using attenuated total reflectance (ATR) FTIR spectroscopy of used (spent) hBN catalysts (Figure ). After 48 h on‐stream, hBN used in both n ‐butane and isobutane ODH showed the appearance of a feature at =3200 cm −1 , which is assigned to B−OH stretching modes . Additionally, a small feature at =1190 cm −1 assigned to B−O stretching appeared, but the strong BN breathing mode at =1365 cm −1 makes further description of this feature difficult.…”

“… ATR‐FTIR spectra of fresh BN (blue line) and BN used (spent) in the ODH of n ‐butane (orange line) and isobutane (purple line). The feature shown at =3200 cm −1 is assigned to B−OH stretching, and that at =1190 cm −1 is assigned to B−O stretching …”

Probing the Transformation of Boron Nitride Catalysts under Oxidative Dehydrogenation Conditions

“…9,10,18 IR spectra of the spent catalysts contain spectroscopic features that are attributed to BO-H and B-O vibrations at ~3200 and 1190 cm -1 , respectively. 3,19 These spectroscopic features are not detected in fresh h-BN, and are only observed at low intensities in fresh BNNTs. 9,10 Given the resistance of h-BN to oxidation in air below 800 °C, 4,18,20 early literature reports of h-BN-catalyzed ODH hypothesized that BN oxidation is confined to edge sites that catalyze the ODH reaction.…”

Strengthening in Boron Nitride Nanotube Reinforced Aluminum Composites Prepared by Roll Bonding

“…Its impressive elastic modulus of up to 1.3 TPa and strength of 61 GPa makes it a promising structural reinforcement for polymer, metal, and ceramic‐matrix composites. Its excellent oxidation resistance (800–1000 °C in air), chemical inertness, and thermal conductivity has attracted aerospace and automobile industries for reinforcement of lightweight aluminum (Al). By adding BNNTs to an aluminum matrix, lighter and stronger materials can be achieved for increased fuel efficiency and tremendous energy savings.…”