2023 AIChE Annual Meeting
Fundamental Structural Study of Boron Nitride (BN)-Based Materials at Low and High Temperatures
In the recent past, boron nitride (BN)-based materials have raised interests due to their physical and chemical properties (i.e., wide band gap (5-6 eV), high oxidation resistance, high thermal conductivity, high mechanical strength, and high surface area). Amongst these BN-based materials, boron nitride nanotubes (BNNTs) and hexagonal-boron nitride (h-BN) have acquired great attention due to unique structures. The BNNTs have a tubular structure with boron and nitrogen atoms in hexagonal lattice, whereas the h-BN showed 2D geometry in a hexagonal configuration. This work aims to study the stability of BNNTs and h-BN materials under broad temperature range (-50 to 800 oC) in terms of weight and molecular structure. The BN-based materials were tested using thermogravimetric analysis (TGA), Fourier Transform Infrared spectroscopy (FTIR), and ex-situ/in-situ Raman spectroscopic techniques to understand the thermal and structural properties under harsh conditions. Raman spectroscopy results reveal that BNNTs responded well only to the UV (325 nm) laser, whereas structure of h-BN was well layered and detected by all (UV, visible and near IR) lasers. Low temperature (room temperature to -50 oC) in-situ Raman studies were performed for BNNTs and h-BN revealing their stable molecular structure in these conditions. On the other hand, h-BN showed a red-shift in Raman spectra when treated at 800 oC under inert (N2) and oxidative (O2) conditions confirming expansion in the hexagonal layers. This was further confirmed by FTIR analysis which showed structure modification at higher temperatures for h-BN due to structural expansion, while no changes were observed for BNNTs. The collected characterization data confirm the stability of BNNTs under high and low temperature with inert/oxidative conditions. Future scope of this work is the use of stable BNNTs as an effective support material for catalysts synthesis and use for various gas phase chemical reactions.