Fiscal Year	2023
Division	Research & Sponsored Programs
Department	Naval Research Program
Investigator(s)	Miller, Scot A.
Sponsor	NPS Naval Research Program (Navy)
Summary	Boron nitride nanotubes (BNNTs) exhibit high in-plane thermal conductivity and high out-of-plane thermal insulation. BNNTs have also been shown to have high thermal stability at elevated temperatures (< 1000 °C). The ability of BNNT to direct heat at elevated temperatures offers an opportunity for protecting critical components, like those exposed to high temperatures in hypersonic applications. This work will explore the feasibility of integrating BNNTs into a ceramic matrix composite (CMC) with complex geometries. Further, the high temperature thermal and dielectric properties will be investigated to determine if these composites can be shown to be transparent to long wavelength radiation, i.e., microwaves, at elevated temperatures (up to 1000 °C or 1832 °F). Fabrication of complex BNNT-CMCs will be accomplished using ceramic 3D-printing. The BNNTs will be mixed with the non-oxide ceramic slurry of silicon nitride (Si3N4) and printed in complex shapes. The heat flow and dielectric properties will then be measured at high temperatures. Instrumented indentation will be used to measure material hardness, elastic moduli, and plasticity of BNNT-CMCs. Optical and electron microscopy will be utilized to study the microstructure of the composites and confirm whether the BNNTs are orienting randomly (undesired) or parallel to the CMC surfaces (ideal). All results will be compiled in student theses and a final report with recommendations for or against integration of BNNTs in CMCs for high temperature applications.
Keywords	Joint fires, COMPACFLT, AOR
Publications	Publications, theses (not shown) and data repositories will be added to the portal record when information is available in FAIRS and brought back to the portal
Data	Publications, theses (not shown) and data repositories will be added to the portal record when information is available in FAIRS and brought back to the portal