Preparation and stability of hybrid nanofluids

This chapter discusses the synthesis, stability evaluation, and stability enhancement methods of hybrid nanofluids in brief. Proper preparation of hybrid nanofluids is necessary for enhancing thermophysical properties and their stability. The stability of nanofluids plays a vital role in their proper working in thermal systems. To gain important indicative information about the stability of nanofluids, various stability evaluation methods like sedimentation, zeta potential, spectral absorbance, and electron microscopy are deliberated. For improving the stability of nanofluids, various stability enhancement techniques such as ultrasonication, surfactant addition, surface modifications of nanoparticles, and pH change are also described in this chapter. Proper selection of nanomaterials is obligatory for preparing hybrid nanofluids according to their synergy level. At the end of the chapter, some challenges and outlooks concerned with hybrid nanofluids have been discussed for their worldwide applications.