Thermal stability of carbon nanotube-based nanofluids for solar thermal collectors

Carbon nanotube dispersions are promising candidates for use as working fluids in high-performance solar collectors. However, one major stumbling block in the way of their widespread application is the difficulty in achieving stable nanofluid suspensions at elevated temperatures. In this study, the stability of plasma- and acid-functionalised multi-walled carbon nanotube dispersions at temperatures up to 150°C was investigated. Therminol 55 and propylene glycol were used as the main solvents, while water was used as a reference solvent. The results of UV-VIS-NIR absorption spectroscopy showed that no agglomeration occurred in the plasma-functionalised multi-walled carbon nanotube nanofluids heated to 150°C. However, minor variations were observed in the absorbance of acid-functionalised multi-walled carbon nanotubes in propylene glycol and therminol 55 base fluids at high temperatures.