“…The latter result can be attributed to the enhanced dielectric properties caused by the interfacial polarization between the CNF aggregates and the PP . 19 Figure 6.AC complex conductivity σ ´ (ω) (a) and σ ´´ (ω) (b) versus frequency of PP and PP/CNF composites. The red solid lines in the inset figures are the least-square linear fits to UPL equations (6) and (7) of 0.9 vol.…”
Section: Resultsmentioning
confidence: 99%
“…The direct current conductivity σ DC at room temperature was performed using an experimental setup composed by a picoammeter Keitheley model 6487 and a digital control DC power supply TENMA model 72–10,495 as described in a previous work 19 . The capacitance (C) and dielectric losses tan δ (w) at room temperature were measured by using a Quadtech 1929 LCR precision meter at frequencies (f) between 430 Hz and 2 MHz, with an applied signal of 0.5 V. The real ε′(w) and the imaginary ε″(w) parts of the complex dielectric permittivity ε(w) were calculated by the equations…”
Section: Methodsmentioning
confidence: 99%
“…The latter result can be attributed to the enhanced dielectric properties caused by the interfacial polarization between the CNF aggregates and the PP . 19…”
Section: Ac Conductivity Analysis By the Universal Power Lawsmentioning
confidence: 99%
“…18 It is in this context that we have undertaken this study, which complements a former study focused on the dielectric spectroscopy analysis at room temperature of melt-extruded polypropylene (PP) with as-grown CNFs by the universal power laws (UPLs). 19 In the present work, the AC electrical conductivity at room temperature of the same type of PP/CNF composites is used to test the validity of the GEM model. Moreover, the potential of a modified GEM 20 that takes into consideration the effect of the interphase between the CNFs and the PP is also examined.…”
The morphology, crystallinity, and electrical conductivity (σ′ and σ″) as a function of frequency of polypropylene (PP) melt-extruded with different amounts of as-grown carbon nanofibers (CNFs) from 0 to 1.4 vol. % are examined. The PP/CNF composites present CNF aggregates randomly distributed within the PP and an insulator–conductor transition at CNF contents near 0.9 vol. %. The degree of crystallinity of PP/CNF composites with loadings of 1.4 vol. % increases ∼15% with respect to the neat PP (∼34%), with σ´ ∼ 8.6 × 10−5 S m−1 (σ″ ∼ 8.3 × 10−4 S m−1) at 2 MHz. In addition, the values of the electrical conductivity σint´ ∼2.9 × 10−6 S m−1 (σint″∼3.7 × 10−4 S m−1) at 2 MHz, as a result of the interphase (ϕint ∼0.05 vol. %) of the 1.4 vol. % PP/CNF composites, are estimated by the use of a modified generalized effective medium model (GEM). The analysis gathered in here indicates that the interphase between the polymer and the conducting particle may have a quantifiable effect on the electrical properties of carbon-based polymer composites, and this fact should not be neglected in the production of conducting polymer composites (CPCs) with enhanced electrical properties.
“…The latter result can be attributed to the enhanced dielectric properties caused by the interfacial polarization between the CNF aggregates and the PP . 19 Figure 6.AC complex conductivity σ ´ (ω) (a) and σ ´´ (ω) (b) versus frequency of PP and PP/CNF composites. The red solid lines in the inset figures are the least-square linear fits to UPL equations (6) and (7) of 0.9 vol.…”
Section: Resultsmentioning
confidence: 99%
“…The direct current conductivity σ DC at room temperature was performed using an experimental setup composed by a picoammeter Keitheley model 6487 and a digital control DC power supply TENMA model 72–10,495 as described in a previous work 19 . The capacitance (C) and dielectric losses tan δ (w) at room temperature were measured by using a Quadtech 1929 LCR precision meter at frequencies (f) between 430 Hz and 2 MHz, with an applied signal of 0.5 V. The real ε′(w) and the imaginary ε″(w) parts of the complex dielectric permittivity ε(w) were calculated by the equations…”
Section: Methodsmentioning
confidence: 99%
“…The latter result can be attributed to the enhanced dielectric properties caused by the interfacial polarization between the CNF aggregates and the PP . 19…”
Section: Ac Conductivity Analysis By the Universal Power Lawsmentioning
confidence: 99%
“…18 It is in this context that we have undertaken this study, which complements a former study focused on the dielectric spectroscopy analysis at room temperature of melt-extruded polypropylene (PP) with as-grown CNFs by the universal power laws (UPLs). 19 In the present work, the AC electrical conductivity at room temperature of the same type of PP/CNF composites is used to test the validity of the GEM model. Moreover, the potential of a modified GEM 20 that takes into consideration the effect of the interphase between the CNFs and the PP is also examined.…”
The morphology, crystallinity, and electrical conductivity (σ′ and σ″) as a function of frequency of polypropylene (PP) melt-extruded with different amounts of as-grown carbon nanofibers (CNFs) from 0 to 1.4 vol. % are examined. The PP/CNF composites present CNF aggregates randomly distributed within the PP and an insulator–conductor transition at CNF contents near 0.9 vol. %. The degree of crystallinity of PP/CNF composites with loadings of 1.4 vol. % increases ∼15% with respect to the neat PP (∼34%), with σ´ ∼ 8.6 × 10−5 S m−1 (σ″ ∼ 8.3 × 10−4 S m−1) at 2 MHz. In addition, the values of the electrical conductivity σint´ ∼2.9 × 10−6 S m−1 (σint″∼3.7 × 10−4 S m−1) at 2 MHz, as a result of the interphase (ϕint ∼0.05 vol. %) of the 1.4 vol. % PP/CNF composites, are estimated by the use of a modified generalized effective medium model (GEM). The analysis gathered in here indicates that the interphase between the polymer and the conducting particle may have a quantifiable effect on the electrical properties of carbon-based polymer composites, and this fact should not be neglected in the production of conducting polymer composites (CPCs) with enhanced electrical properties.
“…47,48 Moreover, they have been also used in numerous nanostructured composites to properly capture the complex impedance performance. 49,50 For this reason, the C elements will be substituted, in this case, by constant phase elements (CPEs), as shown in the schematics of Figure 4d.…”
The temperature effect on electronic transport mechanisms in graphene nanoplatelet (GNP) doped polydimethylsiloxane (PDMS) for temperature sensing applications has been investigated under electrical impedance spectroscopy (EIS) analysis. AC measurements showed a very prevalent frequency-dependent behavior in low filled nanocomposites due to the lower charge density. In fact, 4 wt % GNP samples showed a nonideal capacitive behavior due to scattering effects. Therefore, the standard RC-LRC circuit varies with the substitution of capacitive elements by CPEs, where a CPE is a constant phase element which denotes energy dissipation. In this regard, the temperature promotes a prevalence of scattering effects, with an increase of resistance and inductance and a decrease of capacitance values in both RC (intrinsic and contact mechanisms) and LRC (tunneling mechanisms) elements and, even, a change from ideal to nonideal capacitive behavior as in the case of 6 wt % GNP samples. In this way, a deeper understanding of electronic mechanisms depending on GNP content and temperature is achieved in a very intuitive way. Finally, a proof-of-concept carried out as temperature sensors showed a huge sensitivity (from 0.05 to 11.7 °C−1 ) in comparison to most of the consulted studies (below 0.01 °C−1 ), proving, thus, excellent capabilities never seen before for this type of application.
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