Carbon Nanofiber Pressure Transducer
Edwin Gonzalez¹, Eli Block², Michael Moberg², Jonathan Phillips³, and Claudia Luhrs²
¹Engineering Department, Hartnell College, Salinas, CA 93908
²Mechanical and Aerospace Department, Naval Postgraduate School, Monterey, CA.
³Physics Department, Naval Postgraduate School, Monterey, CA.
Introduction
Materials and Methods
A Pressure Transducer is an instrument that detects changes in
pressure in a mechanical or electrical signal. In resistive pressure
transducers, pressure is measured by an element that changes its
electrical resistance a function of pressure.
Loading Catalyst onto Cloth
Carbon fiber Growth
Microstructural Characterization
Electrical Testing
Impregnation Method
Tube Furnace
Scanning Electron Microscopy (SEM)
Resistance (Ohms) vs. Volume (mm³)
Nickel
catalyst
(80mg)
Abstract
The electrical properties of carbon nanofibers and carbon nanotubes
(CNF/CNT) make them suitable candidates for use in pressure transducer
applications. The goal of this research is to engineer carbon nanotubes on
fiberglass cloth with controlled CNF/CNT diameter and spacing in a way that
resistivity can be measured as a function of pressure. carbon nanotube
must be grown in a controlled environment. The major growth factors are
temperature, catalyst, and carbon source. Current experimentation used
temperature ranges from 350 to 750 degrees Celsius, Nickel or Iron was
used as a catalyst, and ethylene gas was used as the Carbon source over
different time intervals ranging from 15 to 90 minutes. Fiberglass cloth and
catalyst samples were prepared utilizing diverse methods. Synthesis
process for Nickel consisted of impregnation of direct ethanol-nickel
sonicated mixture deposition to fiberglass cloth by dropper. Characterization
was conducted by scanning electron microscopy and pressure testing.
Electrical testing consisted of carbon nanofibers in a 10 ml syringe with
electrical contacts and metal disks ant both ends. Two wires were run
through the syringe and connected to a multimeter to obtain resistivity as
the syringe pump compressed the fibers; the distance compressed was
measured by digital calipers. The volume versus resistivity plots achieved in
this experiment suggest potential for producing inexpensive, lightweight
pressure transducers for medical applications.
+
Ethanol
(1ml)
CNF
Carbon Source
Ar/H2
@ 350C
Sonication
Negative wire
The Zeiss Neon 40 SEM was used to
determine fiber diameter, approximate length,
catalyst distribution, and cloth characteristics
Ethylene, N2, O2
@ 350C
Carbon
Nanofibers
Ethylene, N2, O2
@ 550C
Positive wire
N2 Purge
Measures
Resistivity in
Ohms
N2 Cool Down
Sonicated mixture
applied to cloth by
dropper
Ni
Nanopowder
Carbon Nanofiber
Nickel Foil
plate
soldered to
wire
Solvent
evaporated until
dry
Thermo SCIENTIFIC
Lindberg Blue M
Tube Furnace used
to grow Carbon
Nanotubes
Syringe
Results
Carbon fiber Growth
Microstructural Characterization
Electrical Testing
Impregnation Method
Tube Furnace
Scanning Electron Microscopy (SEM)
Resistance (Ohms) vs. Volume (mm³)
Bare Silica
Cloth
Catalyst
Loaded Silica
Cloth on
Combustion
boat inside
quartz tube
furnace
500x Magnification
Resisitance of CNF with change in Volume
Resisitance…
120
100
(b)
Catalyst
Loaded Silica
Cloth
2,500x Magnification
Resistance (Ohms)
1000x Magnification
Carbon
Nanofiber
Growth in
Tube
Furnace
80
60
40
20
The three phase process is shown here. (a)
3M Fiberglass cloth (b) 3M Fiberglass cloth
impregnated with 80 mg of Nickel
Nanopowder.
Literature Cited
Moberg, M.J. 2012. Carbon Fiber and Tungsten
Disulfide Nanoscale Architectures for
Ballistic Armor Applications. >. Accessed
2012 June 24
Carbon
Nanofiber
Growth
Distance compressed
Measured by digital
calipers
Conclusion
Loading Catalyst onto Cloth
(a)
Multimeter
0
10,000x Magnification
0
500
1000
1500
2000
Volume (mm^3)
2500
Acknowledgements
Thanks to Claudia Luhrs, Michael Moberg, Jonathan Phillips, and Eli Block of the Naval Postgraduate
School.
Andy Newton and Joe Welch of Hartnell College
This internship was funded by a National Science Foundation Advanced Technology Education Grant
3000
3500
Using a variety of loading methods and catalysts, it was
determined that the best set up for growing carbon nanofibers on
fiberglass cloth was to use the impregnation method to load
Nickel nanopowder in a mixture of 80mg Nickel and 1 ml ethanol.
Once the cloth was impregnated and dry we used the 90 minute
growth phase to grow Carbon Nanofibers. This procedure yielded
the best growth of fibers on the fiberglass cloth.
Electrical testing was conducted using a syringe
compressor, a digital multimeter, test leads, silver paint, nickel
foil, and digital calipers to test the resistivity as the volume was
compressed in a syringe. The data indicted that there was a
direct relationship between resistivity and volume. As the volume
decreased the resistivity decreased. his suggests that as the
fibers are closer together, they come into contact more thus
creating better conductor than if they were not compressed. As
the conductivity increases the resistivity deceases. This
relationship can be used to create a pressure transducer. The
pressure can be measured by how much the fibers are
compressed.
Uses for this type of pressure transducer include medical
applications in the form of a bandage. Bandages have to be
applied at a certain pressure in order to heal with optimal results.
Having a bandage that can read pressure directly would be of
great benefit to wounded individuals. It is expected that this
research continue to produce such a pressure transducer in the
near future.
For Further Information
Please contact ccluhrs@nps.edu More information on
this and related projects can be obtained at
http://www.nps.edu/Academics/Centers/CMR/index.html
or the author at edwin7gonzalez@gmail.com