The thermal decompositions (including TG and DSC) of nickel carbide were studied under different atmospheres of Ar, air and H-2. X-ray diffraction combined with element analysis indicated that nickel metal, together with solid amorphous carbon, was formed during Ni3C decomposition in Ar atmosphere, accompanying mass invariant in this process. While in H-2 atmosphere nickel metal was the only residual from reactions. The carbon component of nickel carbide reacted with H-2 to form methane as the main volatile gases. Both the nickel and carbon components of Ni3C reacted with O-2 in the air to form their corresponding oxides. Moreover, we calculated the activation energy for the decomposition process and the molar enthalpy of formation of Ni3C based on the thermal analysis. (C) 2008 Elsevier B.V. All rights reserved.