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 B.V. , 2024. Vol. 683, article id 132875
Keywords [en]
Carbon black; Digital storage; Electric conductivity; Electric impedance measurement; Electrochemical electrodes; Electrochemical impedance spectroscopy; Ions; Lithium compounds; carbon; copper; grease; ionic liquid; lithium; lubricating agent; unclassified drug; Bulk conductivities; Complex architectures; Condition; Electrical conductivity; Electrically conductive; Impedance spectroscopy; Lubricant additives; Lubricant systems; New age; Viable solutions; alternating current; Article; chemical interaction; conductance; dissociation; electric conductivity; impedance spectroscopy; temperature; Ionic liquids
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:ri:diva-76058DOI: 10.1016/j.colsurfa.2023.132875Scopus ID: 2-s2.0-85181141582OAI: oai:DiVA.org:ri-76058DiVA, id: diva2:1912039
Note
The Swedish Foundation for Strategic Research (project EM16-0013 ), the Swedish Research Council (project 2018-05017 ), the Swedish Energy Agency, Sweden (project 2019-002238 ), and the Knut and Alice Wallenberg Foundation, Sweden (project KAW2012.0078 ) are gratefully acknowledged for financial support. The authors also would like to thank Dr. Marcel Druschler and Dr. Jens Wallauer from RHD instruments GmbH & Co. KG, Germany, for their invaluable insight into EIS measurements.
2024-11-112024-11-112025-09-23Bibliographically approved