Characterization of carbon aerogels by transport measurements

Journal Article · Sun Aug 01 04:00:00 EDT 1993 · Journal of Materials Research; (United States)

DOI:https://doi.org/10.1557/JMR.1993.1875· OSTI ID:6145383

Fung, A W.P. ^[1]; Wang, Z H ^[2]; Lu, K ^[1]; Dresselhaus, M S ^[3]; Pekala, R W ^[4]

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1. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
2. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
3. Department of Electrical Engineering and Computer Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
4. Chemistry and Materials Science Department, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

Carbon aerogels are a special class of low-density microcellular foams. These materials are composed of interconnected carbon particles with diameters of approximately 10 nm. The temperature dependence of the dc electrical resistivity and magnetic susceptibility ([chi]) from 4 K to room temperature, magnetoresistance (MR) in a magnetic field up to 15 T, and Raman scattering were measured as a function of aerogel density. While Raman scattering measurements are not sensitive to variations in density, the [chi] data show that there are more free carriers in samples of higher density. Aerogel samples with different densities all show a negative temperature coefficient of resistivity and a positive MR. The less dense samples exhibit a stronger temperature dependence of resistivity and a stronger field dependence of the MR, indicating that with decreasing density and increasing porosity, charge carriers are more localized. Data analysis precludes variable-range hopping in favor of nearest-neighbor hopping and fluctuation-induced tunneling as the most likely conduction mechanisms for carbon aerogels.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6145383
• Journal Information: Journal of Materials Research; (United States), Journal Name: Journal of Materials Research; (United States) Vol. 8:8; ISSN JMREEE; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
CARBON
COLLOIDS
DISPERSIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
FOAMS
GELS
MAGNETIC PROPERTIES
MAGNETIC SUSCEPTIBILITY
MAGNETORESISTANCE
NONMETALS
PHYSICAL PROPERTIES
RAMAN EFFECT
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K