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Doppler Broadening Spectroscopy:

Doppler Broadening Spectroscopy:. Analysis of Rubber Composites. Chun Yang Mentor: Dr. C.A. Quarles. Initial Goal. To confirm non-uniformity found in rubber samples by V.O. Jobando and John Rhoads from previous Lifetime Analysis work.

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Doppler Broadening Spectroscopy:

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  1. Doppler BroadeningSpectroscopy: Analysis of Rubber Composites Chun Yang Mentor: Dr. C.A. Quarles

  2. Initial Goal • To confirm non-uniformity found in rubber samples by V.O. Jobando and John Rhoads from previous Lifetime Analysis work. • Composite rubber used in industry are possibly not homogeneous. • Positron Annihilation Spectroscopy could be used to find non-uniformities in mixed rubber. • Doppler Broadening was chosen in particular for better analysis of composition differences.

  3. Some Background… • Doppler Broadening PAS involves the momentum distribution of electrons annihilated with positrons. • Greater momentums of annihilation increase Doppler shift in the signal of the photon energy released. • Para-positronium formed have a very low momentum of annihilation. • Increasing carbon will decrease positronium formation. • Fewer low-momentum distributions. • DB signals directly related to uniformity.

  4. Unexpected Challenges…

  5. …Overcome! • S-Parameter fluctuation appeared to be related to dead time.

  6. Rate Dependency • Counting rate, which is dependent on the amplifier settings, is directly affected by the distance of the sample from the detector. • Dead Time is affected by both the number of channels counted and counting rate. • The number of channels counted is dependent on the MCA card settting.

  7. Once Again… • Reexamined SnSSBR rubber with a reasonably stable counting rate.

  8. Uniformity Data • Rubber with differing phr (parts per hundred rubber) of N774 carbon black analyzed.

  9. Concentration Data • Analysis conducted on N774 and N115 samples. • Concentration of Carbon Black affects S-parameter.

  10. Technique Refinement Metal Covering Consider Temperature Look for non-uniformity based on mixing time. Possible application for faster material analysis due to rate dependence. Looking Ahead…

  11. Acknowledgements • I would like to thank: • The NSF for providing the funding for this program (and paying me). • The TCU Department of Physics and Astronomy for their support. • Dr. C.A. Quarles for guiding me on this project.

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