Synthesis & characterization of boron nitride nanostructures and application in nanocomposites

Lightweight, high temperature resistivity and high strength materials are areas of interest in industry and academy for advanced composite applications. Boron Nitride (BN) nanostructures such as nanofibers and nanotubes are very important classes of materials, due to their high surface area, high aspect ratio and extreme material characteristics. BN nanomaterials are promising reinforcement materials for several nanocomposite applications because of their unique properties. This study focuses on the synthesis, optimization, and characterization of advanced BN nanostructures including BN nanotubes, nanofibers as well as fuzzy architectures to develop enhanced polymer nanocomposites. This study can be summarized in two main section;  synthesis, optimization and characterization of BN nanostructures  fabrication of BN based polymer nanocomposites The first section of this study consists of synthesis of boron nitride nanofibers (BNNFs) and boron nitride nanotubes (BNNTs) by using different boron precursors and methods on various substrates. To achieve BNNFs, electrospinning method is used and followed by a nitriding process, respectively. Electrospinning solution was prepared with polyvinlybutyral (PVB) as polymeric material, boric oxide (B2O3) as boron source and ethanol as solvent. Nanofibers containing of boron source, labelled as BOFs, were obtained by conventional electrospinning set-up. Then, in NH3, O2, N2 atmosphere, heat treatment process was applied to BOFs and BNNFs were produced, respectively. Optimization studies of time durations of process and wt. % of boron source and polymer were performed and parameters were optimized within the existing system. In parallel to BNNFs studies, BNNTs were synthesized by a chemical vapour deposition (CVD) method under Ar and NH3 atmosphere. Process parameters and precursor amounts were optimized for fabrication of advanced nanostructures. Synthesis of fuzzy BNNTs on different substrates such as BNNFs and single ceramic fibers was performed to achieve more surface area and increase laminar strength in the existing CVD system. For fabrication of fuzzy BNNTs, catalysis studies were done and an optimized process was applied to the substrates. In the second section of this study, BN based polymer nanocomposites were fabricated. Regarding the lack of the researches about the BNNF/polymer nanocomposites, BNNFs were used as reinforcement material and epoxy sheet as matrix material. In literature, chemical or physical functionalization process is applied to the BN's to increase wettability since BN nanomaterials have low wettability and are super hydrophobic. The aim of the polymer nancomposites section in this study is to increase conjunction between the reinforcement surface and the matrix material by using mechanical force instead of functionalization process, which is done in other BN material/polymer nanocomposites studies and resulted as poor property nanocomposites. The polymer nanocompsoites were fabricated by hot press moulding and vacuum infusion methods, respectively. Scanning electron microscopy (SEM) was performed to investigate the morphological properties of BN nanostructures. Fourier transformation infrared ray spectrum (FTIR) was performed to investigate bonding nature of the materials. Thermal gravimetric analysis (TGA) was used to investigate the thermal properties and oxidation resistance properties of BN nanostructures.