A review on preparation methods and challenges of nanofluids

Nanofluid, as a kind of new engineering material consisting of nanometer-sized additives and base fluids, has attracted great attention from investigators for its superior thermal properties and many potential applications. In this review, we summarize the nanofluid preparation methods reported by different investigators in an attempt to find a suitable method for preparing stable nanofluids. Nanofluids are classified according to material type as metallic and nonmetallic nanoparticles since different nanoparticles need their own stability method. Various nanoparticle types with different basefluids are investigated. Moreover, challenges and future directions of applications of nanofluids have been reviewed and presented in this paper. The aim of this review is to summarize recent developments in research on the synthesis and characterization of stationary nanofluids and to try finding some challenging issues that need to be solved for future research.