In this paper, we report an in situ silicidizing method to prepare nickel silicide nanowire arrays with varied structures and phases. The in situ reaction (silicidation) between Si and NiCl2 led to conversion of Si nanowires to nickel suicide nanowires. Structures and phases of the obtained nickel suicides could be varied by changing the reaction temperature. At a relatively lower temperature of 700 degrees C, the products are Si/NiSi core/shell nanowires or NiSi nanowires, depending on the concentration of NiCl2 solution. At a higher temperature (800 degrees C and 900 degrees C), other phases of the nickel silicides, including Ni2Si, Ni31Si12, and NiSi2, were obtained. It is proposed that the different diffusion rates of Ni and Si atoms at different temperatures played a critical role in the formation of nickel suicide nanowires with different phases. (C) 2012 Elsevier Ltd. All rights reserved.