MSE Poster Competition

  • View
    55

  • Download
    0

Embed Size (px)

Text of MSE Poster Competition

  • Materials Characterization in Polymer/CNT Fibers using Raman Spectroscopy

    Lindsey Thomson

    Advisor: Dr. Satish Kumar

    Project Mentor: Bradley Newcomb

    Conclusions

    Acknowledgements I wish to thank Dr. Satish Kumar for accepting me onto his

    research team and his support as my faculty advisor, and Dr.

    Fred Cook for his advice and encouragement during my

    undergraduate research. Special thanks to Brad Newcomb for

    his guidance, patience, and assistance as my project mentor.

    Introduction Resonance Raman Spectroscopy (RRS) was used

    to determine CNT chiralities of single-walled

    (SWNT) and few-walled carbon nanotubes (FWNT).

    An incident laser ( = 785 nm, E = 1.58 eV) was

    used, which allowed for the determination of SWNT

    and FWNT chiralities in CNT powders and

    PVA/SWNT, PAN/SWNT, and PAN,FWNT gel spun

    composite fibers. Frequency shifts of the rbm peak

    positions and intensity shifts were observed after

    preparing the composite polymer/CNT fibers. rbm

    frequency shifts were attributed to the surrounding

    polymeric material (environmental effect), while

    intensity shifts (up or down) are attributed to

    differences in the bundling state of the CNTs within

    the polymeric/CNT fibers as compared to the as-

    received CNT. Stress transfer by single filament

    straining of polyacrylonitrile/ carbon nanotube

    (PAN/CNT) and polyvinyl alcohol/carbon nanotube

    (PVA/CNT) fibers was observed by monitoring G

    mode downshifts as a function of fiber strain.

    Changes in energy band gap also occur, allowing

    for the precise determination of SWNT chiralites.

    Bundling Effects in Polymer/CNT Fibers

    5 nm

    GT PAN CF

    = 2 + 3 [ 1 + cos 3 + sin 3 ]

    Best fit line

    Type of polymer and type of CNT effect the

    environmental coefficient

    Same chiralities are present in the fiber as in the

    powder, but with an upshift in peak position

    Bundling changes the electronic transition energy

    of CNTs

    Table of Peak Position, Chiralities, and Diameter

    Straining Effects in Polymer/CNT

    Fibers

    High intensity peaks have E value approaching 0

    E is the difference between lasers energy and ECNT

    High intensity in (10,2) peak represents a bundled state

    E moves farther off resonance from laser when the (10,2)

    peak is debundled

    Debundled CNTs can improve mechanical and electrical

    properties of polymer/CNT composites

    Vertical shift due to bundling effect

    Horizontal shift due to environmental effect

    Raman Spectroscopy

    O'Connell, M. J.; Sivaram, S.; Doorn, S. K., Near-infrared resonance Raman excitation profile studies of single-walled carbon nanotube

    intertube interactions: A direct comparison of bundled and individually dispersed HiPco nanotubes. Physical Review B 2004, 69 (23).

    Horizontal shifts of G mode due to straining along

    axial direction

    G peak shifts left because stretching/straining

    weakens the C-C bond

    Shift in G peak shows that the CNT within the fiber

    is being strained, not just polymer sliding past the

    CNT as the fiber is strained

    Future Work/ Application Industry: use Raman to monitor bundling behavior

    of CNTs on a systems line

    Control over changes in energy band gap for use

    in tunable electronic devices