Abstract
A graphitic carbon, referred to as graphite from the University of Idaho thermolyzed asphalt reaction (GUITAR), was coated in silica nanosprings and silicon substrates via the pyrolysis of commercial roofing tar at 800 °C in an inert atmosphere. Scanning electron microscopy and transmission electron microscopy images indicate that GUITAR is an agglomeration of carbon nanospheres formed by the accretion of graphitic flakes into a ~100 nm layer. Raman spectroscopic analyses, in conjunction with scanning electron microscopy and transmission electron microscopy, indicate that GUITAR has a nanocrystalline structure consisting of ~1–5 nm graphitic flakes interconnected by amorphous sp3 bonded carbon. The electrical resistivities of 11 single GUITAR-coated nanospring devices were measured over a temperature range of 10–80 °C. The average resistivity of all 11 devices at 20 °C was 4.3 ± 1.3 × 10−3 Ω m. The GUITAR coated nanospring devices exhibited an average negative temperature coefficient of resistivity at 20 °C of −0.0017 ± 0.00044 °C−1, which is consistent with the properties of nanocrystalline graphite.
Highlights
The carbon material dubbed graphite from the University of Idaho thermolyzed asphalt reaction (GUITAR) was first observed as the carbonaceous residue from the combustion of oil shale
We used a combination of Raman spectroscopy, scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) images, and the electrical characterization of 11 single GUITAR-coated NS (G-NS) devices to study the nanostructure, surface morphology, electrical resistivity, and negative temperature coefficient of resistivity (TCOR) of GUITAR in order to classify GUITAR within the spectrum of carbon materials
The Raman spectra of GUITAR were consistent with nanocrystalline graphite (nc-G), in that it had low sp3 content with an estimated crystalline size of ~1.5–3.6 nm
Summary
The carbon material dubbed graphite from the University of Idaho thermolyzed asphalt reaction (GUITAR) was first observed as the carbonaceous residue from the combustion of oil shale. Materials 2019, 12, 3794 which results in better corrosion resistance relative to other graphitic materials [2,4] These features make GUITAR an excellent candidate for use in applications such as sensors [5], energy storage and conversion [6], and water purification [3]. The unique electrochemical properties of GUITAR suggest that it is not just another form of graphite; further investigation of its morphology and electrical properties is required to classify GUITAR within the spectrum of carbon materials. The use of silica NSs allowed us to precisely characterize the morphology of GUITAR and correlate it with its electrical properties. While this approach is not well-suited to single crystal materials, it is ideal for characterizing the electrical properties of amorphous and polycrystalline materials such as GUITAR
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