Avi Natan
Advisor: Prof. Scott Danielsen
will defend a doctoral thesis entitled,
Solution-Processed Boron Nitride Materials for High-Temperature Composites
On
Tuesday, June 16th at 10 a.m.
Dissertation Defense Room
Price Gilbert 4222
and
Virtually via MS Teams
Committee
Prof. Scott Danielsen – School of MSE (advisor)
Dr. Kishor Gupta – School of MSE (co-advisor)
Prof. Natalie Stingelin – School of MSE (co-advisor)
Prof. Satish Kumar – School of MSE
Prof. Satish Kumar – School of ME
Dr. Cheol Park – Senior Researcher, NASA Langley
Abstract
High-temperature composite materials are critical for applications requiring thermal stability and mechanical performance. This dissertation establishes a solution-processing methods for boron nitride (BN)-based fibers and BN-filled elastomer composites, providing an alternative approach to conventional processing routes while advancing understanding of their processing-structure-property relationships.
The first two studies focus on the development of BN-based fibers for potential use in fiber-reinforced composites and ceramic matrix composites. A novel solution-spun polyacrylonitrile/boron oxide/boron nitride nanotube (PAN/BO/BNNT) precursor was developed to produce hybrid hexagonal-boron nitride (h-BN)/BNNT fibers. This work represents the first reported route for producing h-BN fibers from solution-spun PAN/BO precursors. The effects of precursor composition and ammonia heat-treatment conditions on fiber chemistry and microstructure were examined, and the incorporation of BNNTs, combined with processing and formulation improvements, resulted in significant enhancements in mechanical performance.
Next, the thermal stability of pilot-scale BNNT fibers produced from solution-spun PAN/BNNT precursors was investigated as a function of processing conditions. Thermal treatment studies revealed that precursor processing adversely affected BNNT thermal stability, likely due to defect formation during sonication. Evidence of oxidation was identified as the fibers were treated to 800 °C in air. These findings provide insight into the influence of processing-induced defects on BNNT fiber stability and identify potential approaches for improving high-temperature thermal oxidative stability for the fibers.
The second thrust of this work examines solution-processed fluoroelastomer (FKM) composites containing BN and carbon-based fillers. A systematic comparison of filler chemistries and morphologies demonstrated that all fillers provided mechanical reinforcement, while high-aspect-ratio fillers, including carbon nanotubes (CNTs) and BNNTs, produced the largest increases in modulus and tensile strength. BN-based fillers also yielded greater improvements in thermal conductivity than carbon fillers at comparable filler fraction. These results establish clear relationships between filler chemistry and shape and functional performance. Building on these findings, hybrid filler systems combining low- and high-aspect-ratio fillers were evaluated through screening studies and statistical analyses. One-way and bivariate analyses were used to quantify the individual and combined effects of filler type and loading on composite properties, providing insight into the design of multifunctional elastomer composites.
Collectively, this work advances the understanding of solution-processed materials for high-temperature composite applications by linking processing conditions to resulting structures and properties. The findings provide foundational knowledge for the continued development and scalable manufacturing of BN-based fibers and novel elastomer composites for high-temperature applications.