Synthesis and mechanical characterization of aligned carbon nanotube metal- and carbon-matrix nanocomposites

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020Cataloged from the official PDF of thesis.Includes bibliographical references (pages 203-224).Carbon nanotube (CNT) assemblies are seeing increasing use in engineering applications due to their advantaged, mass-specific physical properties. The high strength-to-weight ratio, electrical and thermal conductivity, and elastic properties make CNTs ideal for many aerospace, automotive, and electrical applications. In structural materials, CNTs are an outstanding candidate to provide nano-reinforcement, both in hybrid composites and nanocomposites, and they have been found to improve the hardness, yield strength, and conductivity of their matrix material. Additional enhancement of these matrices can be realized by using aligned CNTs (A-CNTs) of increased volume fraction, as explored in this work.In this thesis, ceramic matrix nanocomposites (CMNCs), specifically A-CNT/carbon matrix nanocomposites (A/C-NCs), are synthesized by first infusing a carbon precursor resin into A-CNT arrays with CNT volume fractions (v[subscript f]) ranging from 1-30 vol%, and then pyrolyzing the resin to create a carbon matrix around the A-CNTs. Previous work with A/C-NC hardness suggests that such a lightweight, superhard material may rival the density-normalized hardness of diamond at high v[subscript f]. Various processes were refined and tested in this work, yielding microscale void-free A/CNCs up to 30% v[subscript f], with an ~7% improvement in hardness over baseline pyrolytic carbon (PyC) for 1% v[subscript f] A/C-NCs and