Aluminium Nanofluids Stability: A Comparison between the Conventional Two-Step Fabrication Approach and the Controlled Sonication Bath Temperature Method

Abstract

This study investigates the shelving stability of dispersed aluminium nanoparticles in water mixtures fabricated by the conventional and the controlled bath temperature two-step methods. The nanofluids were prepared with water of pH 9 and nanoparticles of 0.1–1.0 vol.%. A bath type ultrasonicator was employed for dispersing the nanoparticles into the base fluid. The sonication process, for all as-prepared samples, lasted for 4 hours and was either device bath temperature uncontrolled or controlled in the range of 10–60°C. Furthermore, the stability of the as-produced nanosuspensions was evaluated using the sedimentation photograph capturing method by capturing images at equal intervals of time for 12 hours then analysing the data based on the sample sedimentation height ratios. It was found that the sedimentation behaviour of the nanofluids fabricated via the controlled temperatures of less than 30°C was of dispersed sedimentation type, while those produced by the conventional method and the fixed temperatures of 30°C and higher were of flocculated sedimentation type. In addition, increasing the controlled sonication temperature has shown to increase the settling process of the sediments. Moreover, the rise in nanoparticle concentration was seen to reduce the variation in sedimentation height ratio between the fixed temperature samples. A comparison between the two fabrication methods has shown that the 30°C nanofluids had better short- and long-term stability than the conventionally produced suspensions.

Novel Surface-Modified Bilosomes as Functional and Biocompatible Nanocarriers of Hybrid Compounds

“…In the ultrasonic bath, the sonic signals diverge unevenly, which can have a significant impact on the value of the polydispersity index. Furthermore, the temperature in the bath itself rises, which may also result in different characteristics of the obtained carriers [ 34 ]. Furthermore, the colloidal nanoparticles as bilosomes dispersed in the liquid solvent are in continuous motion (called Brownian motion) and are bombarded by particles of the dispersing phase.…”

Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

“…A study revealed that parameters such as the ultrasonication time [ 10 ] can affect the aforementioned properties and also the rheological properties of the nanofluids. Moreover, predefining and monitoring the sonication bath temperature leads to the preparation of more stable nanofluids [ 11 ]. However, the introduction of NPs into the base fluids is claimed to significantly enhance the stability and heat transfer performance [ 1 , 2 , 3 , 4 , 5 , 6 ].…”

Carbon-Based Nanofluids and Their Advances towards Heat Transfer Applications—A Review

“…Regardless of the type of two-step mixing approach used, this method is still considered as a cost-effective process that is appropriate for both small- and large-scale production of any type of nanofluids, which is seen as a favorable approach to many researchers in the field [ 140 ]. However, some of the critical issues associated with this method during nanofluids fabrication are the agglomeration of the nanoparticles due to the very high surface energy between the particles, and the notable increase in the process temperature with fabrication time when using some of the mixing devices (e.g., bath type ultrasonic device) [ 8 , 13 ]. The first obstacle causes the suspension to be in a weak physical stability state that results from the nanoparticles undergoing agglomeration, which is followed by separation of the particles from the base fluid in the form of sediments.…”

“…This is due to the dispersed solid particles’ significantly higher thermal conductivity compared to their hosting fluid, which would enhance the effective thermal conductivity of the colloidal. The term ‘effective’ is generally used when referring to the net property of a solid–liquid suspension [ 8 ]. However, it was found that in flow areas of low velocities, the particles hosted by the suspension tended to deposit from its carrier liquid.…”

“…Thus, it is highly unlikely that similar nanofluids can be produced through the conventional two-step route without simultaneously fabricating the products at the same preparation conditions. A more convenient two-step method employed for nanofluid production would be the two-step controlled sonicator bath temperature approach, as was reported by Ali et al [ 8 , 11 ] and Song et al [ 38 ]. The aforementioned approach would eliminate the rise in bath temperature obstacle, and hence will ensure an optimum level of nanofluids reproducibility to the manufacturer at any surrounding atmospheric conditions, and even when using different types of bath sonicators.…”