Ultrahigh performance cooling is one of the important needs of many industries. However, low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for cooling purposes. Nanofluids are engineered by suspending nanoparticles with average sizes below 100 nm in heat transfer fluids such as water, oil, diesel, ethylene glycol, etc. Innovative heat transfer fluids are produced by suspending metallic or nonmetallic nanometer-sized solid particles. Experiments have shown that nanofluids have substantial higher thermal conductivities compared to the base fluids. These suspended nanoparticles can change the transport and thermal properties of the base fluid. As can be seen from the literature, extensive research has been carried out in alumina-water and CuO-water systems besides few reports in Cu-water-, TiO2-, zirconia-, diamond-, SiC-, Fe3O4-, Ag-, Au-, and CNT-based systems. The aim of this review is to summarize recent developments in research on the stability of nanofluids, enhancement of thermal conductivities, viscosity, and heat transfer characteristics of alumina (Al2O3)-based nanofluids. The Al2O3 nanoparticles varied in the range of 13 to 302 nm to prepare nanofluids, and the observed enhancement in the thermal conductivity is 2% to 36%.

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An alumina-5 vol% yttrium aluminum garnet (YAG) composite was obtained through in situ reaction of alumina and yttria during sintering. Analysis of creep experiments together with microstructural data indicated that both pure alumina and alumina-5 vol% YAG composite deform by a Coble grain boundary diffusion creep process. Comparison with other data suggests that at temperatures greater than B1650 K, an isolated or interconnected fine-grained YAG phase does not significantly affect creep in alumina. However, an isolated YAG phase retards both static and dynamic grain growth in the composite. J ournal