Ionic liquids enhance electrical conductivity of greases: an impedance spectroscopy studyShow others and affiliations
2024 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 683, article id 132875Article in journal (Refereed) Published
Abstract [en]
Ionic liquids (ILs) have emerged as viable solutions for developing new-age lubricants, both as neat lubricants and lubricant additives. Enabled by the presence of discrete ions, ILs have the possibility to render electrically conductive lubricants, which is a feasible strategy for developing lubricant systems compatible with modern e-drive conditions. However, this requires the characterization of the electrical properties of lubricants, which is a bottleneck for developing electrically conductive greases, given their complex architecture. This work introduces an electrochemical impedance spectroscopy measurement methodology to evaluate grease samples’ electrical properties. Compared to the commonly used conductivity meters, this method, through its multi-frequency alternating current (AC) impedance approach, can effectively distinguish the individual contributions of the bulk and the sample-electrode interface to the measured electrical response. Impedance spectra of grease samples are obtained using an electrochemical cell with parallel plate electrodes, mounted on a temperature-controlled cell stand and coupled with a potentiostat. The grease's bulk conductivity is extracted by fitting the impedance data to relevant equivalent electrical circuits. The bulk conductivity of lithium complex grease doped with ILs is evaluated and compared to greases with conventional conductivity additives (copper powder and conductive carbon black). The analysis of temperature-dependent conductivity reveals the rather different conductivity mechanisms for different additives. For greases doped with ILs, a comparison against the electrical conductivity of neat ILs reveals that, in addition to the ion dissociation, the interaction of the ions with the different grease components (base oil, thickener) is crucial in defining the grease conductivity.
Place, publisher, year, edition, pages
Elsevier BV , 2024. Vol. 683, article id 132875
Keywords [en]
Electrical conductivity, Grease, Impedance spectroscopy, Ionic liquid
National Category
Other Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-342183DOI: 10.1016/j.colsurfa.2023.132875Scopus ID: 2-s2.0-85181141582OAI: oai:DiVA.org:kth-342183DiVA, id: diva2:1827935
Note
QC 20240115
2024-01-152024-01-152025-02-14Bibliographically approved