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Indexed by:期刊论文

Date of Publication:2013-11-01

Journal:POLYMER JOURNAL

Included Journals:SCIE、EI、Scopus

Volume:45

Issue:11

Page Number:1120-1134

ISSN No.:0032-3896

Key Words:conductive polymer composite; electron transport; fluctuation-induced tunneling conduction; nonparabolic potential barrier width; visco-elastic property

Abstract:The conductivity of composites with a carbon fiber (CF) content slightly higher than the percolation threshold was measured at increasing temperatures up to -10 degrees C. The tunneling effect was theoretically calculated using a rigorous nonparabolic potential barrier. The tunneling barrier width D and the surface area A were determined. For a polyethylene (PE) matrix, good agreement between theoretical and experimental results was obtained using D=1.00 nm and A=1.35 to 1.68 nm(2) at a 30-vol% CF content and using D=1.30 nm and A=1.25 to 1.28 nm(2) at a 25-vol% CF content. That is, almost perfect agreement between experiment and theory was obtained by adjusting the parameters except over the temperature ranges in which the beta and gamma relaxation peaks appeared. Dynamic loss modulus and positron annihilation measurements were also conducted. However, a theoretical analysis that was derived using a parabolic potential barrier produced inconsistent results. That is, the tunneling barrier width D was less than the c-axis length of a PE crystal unit, and the surface area A was considerably less than the a-b plane area of a PE crystal unit.