In the present study, Ni-x-Co(1-x) (x = 0, 0.2, 0.4, 0.6, 0.8,1) nanoparticles(NPs) were synthesized using the thermogravimetric method. The production of these NPs was carried out through the reduction reaction of nickel and cobalt oxides, as metal precursors, and methane gas, as a reducing agent, under atmospheric pressure. The raw materials and the products were characterized using XRD, FESEM, XRF, EDS and Map analysis. Initially, the duration of the reduction reaction and conversion of NiO and CoO to Ni and Co NPs was predicted using a grain model simulation. The effect of different parameters such as methane volume percentage and reduction temperature on the duration of conversion were investigated by this model in order to properly choose the optimum temperature and volume percentage of methane gas for the experiments. The experimental results demonstrated that the reaction time of nickel and cobalt oxides with 23 vol.% methane at 830 degrees C for the production of Ni and Co NPs was 14 and 39 min, respectively, which was in good agreement with the predicted results. Investigation of the reaction time for (NiO)(x)-(Co3O4)((1-x)) binary mixture with methane was evaluated by considering the relative compositions of NiO(x = 0, 0.2, 0.4, 0.6, 0.8, 1). The results showed that as the content of NiO in the binary mixture increased, the duration of Ni-x-Co(1-x) NPs production decreased. XRD and EDS analysis confirmed the formation of about 96% of Ni-0.6-Co-0.4 BNPs and over 97% of Ni and Co NPs. In addition, the effect of methane diffusion into the pellets was investigated on (NiO)(0.4)-(CoO)(0.6) with sintered and non-sintered modes. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.