Thesis Title

Ion Implantation and Characterization of High Temperature and High Performance Polymers

Date of Graduation

Fall 1991

Degree

Master of Science in Materials Science

Department

Physics, Astronomy and Materials Science

Committee Chair

Ryan Giedd

Subject Categories

Materials Science and Engineering

Abstract

In this paper, over ten different polymers, having high temperature and high performance properties either from commercial sources or custom made, are modified by ion implantation technology. Over ten different ions from ⁴He to ¹³⁷Xe with a wide range of energies of 50 keV to 42 MeV have been implanted with a dose range of 10¹³ to 10¹⁷ ions/cm². Surface electrical conductivities of these originally insulating polymers have been drastically enhanced after the ion implantation. Structural and compositional changes that accompanied these electrical enhancements were observed using Infrared (IR), Raman, and electron spin resonance (ESR) spectroscopies, scanning electron microscopy (SEM), Rutherford back scattering (RBS) spectroscopy, and elastic recoil detection analysis (ERDA) methods. Electrical conduction mechanisms in the implanted polymers are discussed in detail based on the results of the temperature dependence of surface conductivity. A dual-hopping conduction model has been introduced to explain the experimental results of these ion damaged polymers. According to this model, the electrical conduction process in ion damaged polymers is a mixture contribution both from one-dimensional variable-range hopping along polymer chains and three-dimensional variable-range hopping among the ion created conducting islands. The structure of the island looks like a "Calabash" that has a soft conducting inner-part (graphite-like-carbon) created by the electronic energy disposition and wrapped by a hard non-conducting shell (diamond-like-carbon) produced by the nuclear energy deposition process. We found that the relative importance of 1-D and 3-D hopping is determined by two independent factors: the degree of disorder of the samples and the temperature. The 1-D hopping portion in highly disordered samples produced by high dose irradiations is obviously less than that in less disordered samples produced by low dose irradiations. For a given irradiated sample, the 1-D hopping process is more important in the low temperature range, whereas the 3-D hopping starts to dominate at high temperatures. Finally, the future outlook of polymer research with ion beams is presented.

Copyright

© Yongqiang Wang

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