Edwin Gonzalez ¹ , Eli Block ² , Michael Moberg ² , Jonathan Phillips³, and Claudia Luhrs²

1. 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. Microstructural Characterization Scanning Electron Microscopy (SEM) Carbon fiber Growth Tube Furnace Electrical Testing Resistance (Ohms) vs. Volume (mm³) Loading Catalyst onto Cloth Impregnation Method High T Abstract Nickel catalyst (80mg) Catalyst Ethanol (1ml) + CNF Negative wire Multimeter The Zeiss Neon 40 SEM was used to determine fiber diameter, approximate length, catalyst distribution, and cloth characteristics Carbon Source 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 sonicatedmixture 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 multimeterto 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. Ethylene, N2, O2 @ 350C Ar/H2 @ 350C Carbon Nanofibers Ethylene, N2, O2 @ 550C Sonication Positive wire N2 Purge Measures Resistivity in Ohms N2 Cool Down Ni Nanopowder Sonicated mixture applied to cloth by dropper Carbon Nanofiber Nickel Foil plate soldered to wire Solvent evaporated until dry Distance compressed Measured by digital calipers Thermo SCIENTIFIC Lindberg Blue M Tube Furnace used to grow Carbon Nanotubes Syringe Results Conclusion Conclusion Carbon fiber Growth Tube Furnace Microstructural Characterization Scanning Electron Microscopy (SEM) Electrical Testing Resistance (Ohms) vs. Volume (mm³) Loading Catalyst onto Cloth Impregnation Method Using a variety of loading methods and catalysts, it was determined that the best set up for growing carbon nanofiberson 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. Catalyst Loaded Silica Cloth on Combustion boat inside quartz tube furnace 500x Magnification (a) Bare Silica Cloth 1000x Magnification Carbon Nanofiber Growth in Tube Furnace (b) Catalyst Loaded Silica Cloth 2,500x Magnification Carbon Nanofiber Growth The three phase process is shown here. (a) 3M Fiberglass cloth (b) 3M Fiberglass cloth impregnated with 80 mg of Nickel Nanopowder. 10,000x Magnification 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 Literature Cited Acknowledgements For Further Information Moberg, M.J. 2012. Carbon Fiber and Tungsten Disulfide Nanoscale Architectures for Ballistic Armor Applications. >. Accessed 2012 June 24 Please contact ccluhrs@nps.edu More information on this and related projects can be obtained at http://www.nps.edu/Academics/Centers/CMR/index.htmlor the author at edwin7gonzalez@gmail.com