An electrical conductivity translator for carbons

doi:10.1016/j.measurement.2014.07.003

Measurement

Volume 56, October 2014, Pages 215-218

https://doi.org/10.1016/j.measurement.2014.07.003 Get rights and content

Highlights

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Four points probe is adequate for small amount of carbon samples.
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Compression method is preferable for anisotropic carbons.
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Carbon conductivities from both methods can be correlated allowing comparison.

Abstract

The variety of methodologies used to determine the electrical conductivity of carbons makes it very difficult to compare samples and establish reference values. In this study, the electrical conductivity of a wide range of carbons was determined using two different methods: four-point probe and compression. Although the methodologies and the operating conditions are very different, linear correlations between the values measured by these two methods can be established for some of the materials studied. Only materials with a very high conductivity (graphite and carbon black) could not be correlated.

Introduction

Electrical conductivity (i.e. the ability of a material to conduct electric current), is a very important property, especially in materials used for energy storage [1], [2], metal–polymer composites manufacture [3], electronic devices, etc. For this reason, it is essential to employ a simple and reliable method to determine the electrical conductivity as a control property of many solid materials after their production. However, as yet, there is no worldwide accepted method for carrying out such control, as there is for other properties. The disparities between the methodologies employed to determine electrical conductivity (i.e. impedance spectroscopy [4], the Van der Pauw method [5], the measurement of conductivity by compression [6]) make it necessary to find values that can be used to compare different materials. Although all of these methods provide electrical conductivity data, the procedure, the measuring device, the operating conditions, etc. are different, and so the so-called “conductivity” value of the material needs to be treated differently in each case.

In this study, the electrical conductivity of various carbonaceous materials was determined using the two most common methods that can be found in the literature, four-point probe technique and measure under compression [5], [6], [7], [8], with the aim of finding out whether they can be correlated. The first method consists in preparing disk-shaped pellets and measuring their sheet resistivity by means of the four-point probe (FPP) technique (based on the Van der Pauw equation), whereas the second involves monitoring the electrical conductivity of powdery samples under compression (COM) in a specific pressure range. The results are compared and various aspects related to the operating conditions are evaluated taking into account the advantages and disadvantages of each method.

Section snippets

Materials and methods

The following commercial carbons were selected for this research: 7 activated carbons applied in electrochemical systems (Supra 30, Super 30 and Supra 50 from NORIT, YEC-8A and YEC-8B from Fuzhou Yihuan Carbon, SO-15A from TDA Research and YP-50F from Kuraray); 2 generic carbon xerogels (XER-HMV and XER-HSA supplied by Xerolutions); carbon fibers (AS4C-3K from Hexcel Core); a graphite (TIMREX SLP50) and a carbon black (Super P-Li from Timcal). Some in-lab samples obtained from anthracites by

Results

The electrical conductivities of the materials measured by FPP and COM are presented in Table 1. As can be seen, the values determined by these two methods are very different in all cases. The COM method provides values that are much higher than the corresponding data obtained by the FPP method, except for the graphite. The reason for these higher conductivity measurements is that the COM method determines the electrical conductivity through a column of sample, whilst the FPP method measures

Conclusions

The results discussed have highlighted some of the advantages of each method. Thus, FPP has the great advantage that it is very rapid and simple to perform under ambient conditions, and only a small amount of sample is needed to evaluate the electrical conductivity of the carbon materials, while the COM method is particularly useful for either non-compact or graphitic materials with a high degree of anisotropy.

In summary, it has been demonstrated that by applying the correlations defined in

Acknowledgements

Financial support from the Ministerio de Economía y Competitividad of Spain MINECO (under Projects MAT2011-23733, IPT-2012-0689-420000 and ENE2011-28318) is greatly acknowledged. NRR is also grateful to MINECO for her predoctoral research grant.

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Technical noteAn electrical conductivity translator for carbons

Highlights

Abstract

Introduction

Section snippets

Materials and methods

Results

Conclusions

Acknowledgements

J. Power Sources

Compos. A Appl. Sci. Manuf.

Solid State Ionics

Powder Technol.

Carbon

Technical note
An electrical conductivity translator for carbons