The present work deals with the synthesis of Ni–SiO2–Al2O3 nanocomposites fabricated by embedding nickel oxide particles, obtained from hexahydrated nickel nitrate [Ni(NO3)2 · 6H2O], in matrixes with different molar percents of Silica/Alumina, through sol–gel method based on hydrolysis and condensation of tetraethylorthosilicate (TEOS) and Aluminum Isopropoxide [Al(OC3H7)3] alkoxides. Due to the various factors, e.g., pH, EtOH/TEOS/H2O ratio, Si/Ni ratio etc., influencing the nickel grain size of the nanocomposites, Taguchi robust design method of system optimization was used to determine the percent of contribution (%ρ) of each factor. The nanocomposites were reduced in a flow of hydrogen and nitrogen gas at 700 °C for half an hour. The nickel grain size in the nanocomposites was determined by utilizing Scherrer`s method and XRD patterns. The smallest nickel grain size obtained from the Taguchi orthogonal array was about 24 nm, later confirmed by TEM observations. After optimization of the controlling factors, a nickel grain size of 15.4 nm was obtained. It was found that the SiO2/Al2O3 molar ratio of the matrix had the most influence on the nickel grain size (29.22%) and the Water/TEOS molar ratio stood in second place (21.44%). It was illustrated that the starting temperature of the aluminum isopropoxide had the least influence on the nickel grain size.

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