Influence of SiC Polytype on the Thermal Conductivity of SiC Nanofluids: A Critical Review

Nanofluids are suspensions of nanoparticles in a base fluid. Water, ethylene glycol, engine oil, and others are often used as base fluids, whereas inorganic additives include metals, metal oxides, carbon-based materials, and non-oxide inorganic materials. According to recent research, a small amount of nanoparticles with high thermal conductivity can improve heat transfer in nanofluids. The expectations for nanofluids are increasing, making them the subject of intense research. Current interest is focused on materials that, in addition to high thermal conductivity, also have other favorable features, such as chemical resistance or resistance to high temperatures. Silicon carbide SiC, a material with many advantageous properties, is being considered as a candidate that may meet such expectations. Among the different polymorphs of SiC, the most common are numerous hexagonal α-SiC varieties with anisotropic properties and the only isotropic cubic β-SiC polytype. The latter was reported to have a thermal conductivity of 500 W/mK. The use of nanoparticles from different SiC polytypes in nanofluid studies often leads to incomparable results. Studies on nanofluids prepared from nanoparticles of various silicon carbide polytypes discussed in this article indicate that isotropic β-SiC nanoparticles may be a promising material. When nanofluids for diverse heat transfer applications are prepared, more detailed studies of all the nanoparticles used should be considered.