The effect of carboxylic group concentration on the stability and thermal conductivity of carbon nanotub fluid as heat transfer media

The nanofluid does not simply refer to a liquid-solid mixture. In general, these are effective methods used for preparation of suspensions: (1) to change the pH value of suspensions; (2) to use surface activators and/or dispersants; (3) to use ultrasonic vibration. In this work, Distilled water and Multi-walled carbon nanotubes were used to produce nanofluids. The carbon nanotubes were provided by the Research Institute of Petroleum Industry, Iran. They were synthesized by catalytic decomposition of 20% methane in hydrogen over catalysts at 1000°C. (a) and (b) show respectively the SEM image and Raman spectroscopy (Philips, 200kV) of the sample. It can be seen that the nanotubes are entangled and some are in the format of agglomerates.