Date of Award

8-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Engineering Science

Major Professor

Dayakar Penumadu

Committee Members

Roberto S. Benson, Kevin M. Kit, Charles L. Melcher, Laurence F. Miller

Abstract

Due to the shortage of 3He (helium-3), there is a great demand to develop alternative technologies for thermal neutron detection. The Department of Homeland security is interested in applications with polymeric scintillation detectors that can directly discriminate between neutron and gamma radiation using manufacturing techniques that are both inexpensive and which can be effectively implemented to produce large-area detectors. The 6Li (lithium-6) isotope has a significant thermal neutron cross-section and produces highenergy charged particles upon thermal neutron absorption. This research focuses on the development of small-diameter fibers (micro-/nanoscale) loaded with 6Li for thermal neutron detection by electrospinning and melt-spinning methods. Electrospun polymer nanofibers are attractive due to their unique volume-to-surface area as well as their chemical, electrical, and optical properties. The fibers are characterized by polymeric properties, including microstructure evaluation, response to thermal neutrons, and alpha, beta, and gamma radiation using suitable radiation facilities. 6Li-loaded polyethylene naphthalate (PEN) oriented microfibers were fabricated by melt-spinning and tested for thermal neutron detection. Additionally, (PEN)-based microfibers were integrated with carbon fiber/vinyl ester-reinforced backing to form a composite laminate with the dual function of serving as a scintillator and a structural composite material. Laminate scintillators were evaluated to study the mechanical properties and the effect of scintillation performance. Important microstructural information using a digital optical microscope and mechanical behavior, including the modulus, are both reported.

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