By
Jesse L. Gray, III
Mentors:
Dr. Kimani A. Stancil
Dr. James S. Hammonds
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Goal and Importance
What are Surface Phonon-Polaritons?
Making of Nanocomposite
Analysis
Preliminary Results
Discussion
Next Steps
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Goal – To make tunable bulk nanocomposite
comprised of Silicon Carbide & Polyethylene
that exhibits Surface Phonon-Polariton
coupling.
Importance – The results will be used to give
the capability to tune and dictate the thermal
conductance of a material based on
nanoparticle spacing.
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Electromagnetic waves that propagate along
the interfaces of polar dielectrics.
Results from an evanescent wave’s electric field
coupling of infrared photons and optical
phonons like two coupled oscillators with the
same frequency.
They can enhance fields near the interfaces at
infrared frequencies.
Toluene
Stirrer
Magnetic Hotplate
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Preparation
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Measure out a predetermined ratio of silicon carbide
nanoparticles to polyethylene.
 .5 grams of nanoparticles is a base reference for all mass
ratios (1:1, 5:1, 10:1, etc…)
Mix
Heat / Stir
Stirrer
Magnetic Hotplate
Dry
Small samples from dried composite are analyzed using
an FTIR (Fourier transform infrared spectroscopy)ATR (Attenuated Total Reflectance) machine.
Picture courtesy of Stancil group and
student Charlezetta E. Stokes
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Mixing Challenges
Nanoparticles seem to clump together.
This may be caused by the nanoparticles not dispersing
fully.
 Proper mixing will have nanoparticles ~70nm apart.
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Polyethylene/Nanoparticle mixture becomes too viscous
which effects the mixing of additional polyethylene.
 Idea: Toluene is evaporating too fast.
 Improvement: Starting out with a greater amount of Toluene may
solve the predicament. Use toluene volume that is approx. 3 times
the volume of polyethylene.
SiC Nanoparticles
Picture courtesy of Cory Davis
Polyethylene
Figure of a SiC particle of diameter, D, enclosed by a rectangular
representation of polyethylene of length = height = D+X
Picture courtesy of Cory Davis
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Ratios 10:1 and lower cracked up when force
was applied to them for FTIR measurement
resulting in sloping graphs.
Nanoparticles did not mix well in ratios 5:1 and
below.
Phonon-Polariton activity happens between the
wavelengths of 766-969 nanometers.
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To use a titration method for mixing
polyethylene and silicon carbide.
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Limit toluene evaporation using a lid.
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Stir with heat over longer time periods.
I would like to thank
Dr. Kimani A. Stancil, Dr. James S. Hammonds
Cory Davis, Josh Brown
Howard University Physics & Astronomy
National Science Foundation
(funding the HU Physics REU)
Virginia Union University
(and Dr. Francis Mensah)