?ukasz SCHELLER1, Bertrand JÓ?WIAK2, Justyna DZIADOSZ1, Adrian GOLBA1, Grzegorz DZIDO2, Rafa? FLAMHOLC3, Anna KOLANOWSKA2, Rafa? J?DRYSIAK2, Krzysztof CWYNAR1, Edward ZOR?BSKI1, Maria José V. LOURENÇO4, Carlos A. NIETO DE CASTRO4, S?awomir BONCEL2, Marzena DZIDA1
1University of Silesia in Katowice, Institute of Chemistry, Katowice, Poland
2Silesian University of Technology, Faculty of Chemistry, Gliwice, Poland
3Anton Paar Poland, Warszawa, Poland
4Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal
Ionanofluids (INFs) being dispersions of multi-walled carbon nanotubes (MWCNTs) in ionic liquids (ILs) display remarkable thermal conductivity, thermal stability and optimal viscosity [1]. Such interesting properties suggest the possibility of INFs to replace commonly used heat-transfer fluids (HTFs) and meet the needs of modern industrial energy management. We present thermophysical study of INFs composed of 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and long in-house MWCNTs (aspect ratio of 11,000) or short, commercially available MWCNTs (aspect ratio 150) at MWCNTs' weight percent range from 0.25% to 5.00%. The INFs were prepared by two-step method using sonication. The samples were stored in different conditions (295.15 K under and without sunlight, 353.15 K without sunlight). As a result all INFs with at least 0.50 wt.% of MWCNTs were over 3-years stable. The thermal conductivity was measured at temperatures from 298.15 to 323.15 K. Rheological characteristics, including viscosity and flow curves (shear rate range from 0.1 to 100 s-1), hysteresis loops (range from 5 to 131 s-1) as well as storage and loss moduli have been performed at 298.15 K. The density measurements were conducted in the temperature range from 278.15 K to 348.15 K. The isobaric heat capacity was studied from 293.15 to 363.15 K. As a result a remarkable thermal conductivity enhancement of 41% compared to pure IL was obtained. Studied INFs are shear-thinning non-Newtonian media, however long MWCNTs-based INFs have substantially lower viscosity than their short MWCNTs-based counterparts. A thixotropic behavior was observed for INFs containing ≥0.50 wt.% of short MWCNTs and for 1 wt.% of long MWCNTs. The density of INFs increases linearly with the MWCNTs load. The isobaric heat capacity changes were within the device uncertainty of ±2%. Excellent thermal conductivity and optimal rheology of long MWCNTs-based INFs allow to consider them as a potential alternatives for modern HTFs, namely for temperatures above water applications.
[1] M. Dzida, S. Boncel, B. Jó?wiak, H.F. Greer, M. Dulski, ?. Scheller, A. Golba, R. Flamholc, G. Dzido, J. Dziadosz, A. Kolanowska, R. J?drysiak, K. Cwynar, E. Zor?bski, C.E.S. Bernardes, M.J.V. Lourenço, C.A.N.de Castro, ACS Appl. Mater. Interfaces 2022, 14, 45, 50836-50848.
This work was financially supported by the National Science Centre (Poland) Grant No. 2017/27/B/ST4/02748. M.J.V. Lourenço and C.A.N. de Castro would like to thank Fundação para a Ciência e Tecnologia, Portugal, for partial financing through projects UIDB/00100/2020 and UIDP/00100/2020 to Centro de Química Estrutural and LA/P/0056/2020 to Institute of Molecular Sciences.