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
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.
Sonicate
Stir/Titrate
Stirrer
Magnetic Hotplate
Dry
10
123456789
Minutes to wait
Toluene
Stirrer
Magnetic Hotplate
60
70ooC
C
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Initial toluene volume
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Cold Mix
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“Titration”

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Mixing mixture at temperature lower than melting point
of polyethylene
Adding polyethylene over time
Heat Mix

Stirring and leaving the heat on for additional hour
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Preparation

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…)

Measure out the determined amount of polyethylene
based on the mass ratio.
 5 grams of polyethylene would be needed for a mass ratio of
10:1

Calculate the volume of polyethylene and multiply it by
3.5. Add that amount of toluene to the silicon carbide.
n2
n1
Picture courtesy of Stancil group and
student Charlezetta E. Stokes
Polyethylene (PE)
Silicon Carbide (SiC)
Reflectivity changes with refraction index
S-polarized
P-polarized
Polyethylene
Carbon Black
SiC
Material
Refractive Index
Polyethylene
1.5159 - 1.488
Silicon Carbide
2.69026 - 2.55
Carbon Black
1.11-2
Toluene
1.496
Air
1
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Goal: To see how long it took for enough toluene
to evaporate before it’s presence was not detected
on the FTIR-ATR (Fourier transform infrared
spectroscopy – Attenuated Total Reflectance).
What was expected.
What was observed.
Importance : Refractive index changes as the
components of the nanocomposite changes.
10:1
95
90
Increase in Time
85
80
T%
Day 1
Day 3
75
Day 4
Day 5
70
65
60
760
810
860 Cm-1
910
960
Day 5
1 to 1
15 to 1
30
90
25
85
Day 1
15
Day 2
%T
%T
20
Day 1
80
Day 2
Day 4
10
Day 4
Day 5
Day 5
75
5
0
70
750
800
850
900
950
1000
750
800
850
Cm-1
5 to 1
950
1000
20 to 1
75
94
70
92
65
90
60
Day 1
55
Day 2
50
Day 3
Day 4
45
Day 5
40
35
88
%T
%T
900
Cm-1
86
Day 1
84
Day 4
82
Day 5
80
78
750
800
850
900
cm-1
950
1000
750
800
850
900
Cm-1
950
1000
100
Day 5 Averages across all ratios
90
80
70
60
%T
1 to 1
5 to 1
50
10 to 1
15 to 1
40
20 to 1
30
20
10
Increase with decrease in polyethylene
0
750
800
850
900
Cm-1
950
1000
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Mixing Challenges

Nanoparticles seem to clump together.
This may be caused by the nanoparticles not
dispersing fully.
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Polyethylene/Nanoparticle mixture becomes too
viscous which affects 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. 4 times the volume of polyethylene.
VT = volume total
VNP = volume of
nanoparticles
X = distance between
nanoparticles
Figure of a SiC particle of diameter, D, enclosed by a rectangular
representation of polyethylene of length = height = D+X
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Phonon-Polariton activity happens between the
wavelengths of 766-969 nanometers.
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Day 5 is dried
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Slanting caused by changes in refraction index
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To compare the surface phonon-polariton
response for one mass ratio with time
dependence (Day 1 – Day 5).
To compare the surface phonon-polariton
response for different mass ratios on the same
day.
Table the SEM determined particle separations
versus recipe determined particle separations.
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)