Abstract
The effect of temperature on the electrical conductivity(a)and Seebeck coefficient(S)of n-type vapor grown carbon nanofibers(CNFs)and poly(vinylidene fluoride)(PVDF)melt-mixed with 15 wt％of those CNFs is analyzed.At 40 ℃,the CNFs show stable n-type character(S=-4.8μV·K-1)with an σof ca.165 S·m-1,while the PVDF/CNF composite film shows an σ of ca·9 S·m-1 and near-zero S(S=-0.5 μV·K-1).This experimental reduction in S is studied by the density functional tight binding(DFTB)method revealing a contact electron transfer from the CNFs to the PVDF in the interface.Moreover,in the temperature range from 40 ℃ to 100 ℃,the σ(T)of the CNFs and PVDF/CNF film,successfully described by the 3D variable range hopping(VRH)model,is explained as consequence of a thermally activated backscattering mechanism.On the contrary,the S(T)from 40 ℃ to 100 ℃ of the PVDF/CNF film,which satisfactorily matches the model proposed for some multi-walled carbon nanotube(MWCNT)doped mats;however,it does not follow the increase in S(T)found for CNFs.All these findings are presented with the aim of discerning the role of these n-type vapor grown carbon nanofibers on the σ and S of their melt-mixed polymer composites.
维普
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