Optimization of synthesis conditions of boron nitride nanotubes (BNNTS) and their effects on epoxy resin curing
Yorulmaz, Yelda (2018) Optimization of synthesis conditions of boron nitride nanotubes (BNNTS) and their effects on epoxy resin curing. [Thesis]
Boron nitride nanotubes (BNNTs) are structural analogues of carbon nanotubes (CNTs). The interest in them and their nanocomposites have been growing due to their unique properties. Chemical vapor deposition (CVD) is a relatively cheap and lab scale technique employed in inorganic material synthesis. This thesis work aims to achieve two fundamental goals in two separate chapters. In the first chapter, the process parameters determining the quality and amount of BNNT synthesis by CVD are evaluated in a response surface methodology framework. A three-level full factorial design where process factors such as reaction temperature, heating rate and reactive gas flow are considered in three levels forming a design space with 27 experiment points. Through a systematic experimentation scheme, three responses determined by sophisticated RAMAN and SEM analysis (namely BNNT diameter, BNNT aspect ratio and wafer coverage) are then fitted into polynomial based surrogate models. Performed ANOVA analyzes suggest that surrogate models are mostly able to predict the change in response with respect to changing process factors. Optimized process conditions aiming to achieve high aspect ratio and high substrate coverage are then presented. Second part of the thesis focuses on a composite application example of in-house synthesized BNNTs. BNNTs manufactured at the optimized process conditions are introduced to epoxy resin with altering amounts. Specific attention is given to their effect on the curing kinetics of a thermoset system. BNNTs may give alternate fast curing recipes. Through dynamic and isothermal vi DSC scans of BNNT/epoxy resin, the curing behavior is firstly studied in detail. Then governing curing mechanism and the effects of BNNT addition is explored by the fitting of appropriate kinetic models onto experimental data.
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