Isothermal kinetics of reduction and carburization of WO 3 –NiO nanocomposite powder by CO/CO 2 Hurieh Mohammadzadeh Valendar 1 • Dawei Yu 2 • Mansoor Barati 3 • HamidReza Rezaie 4 Received: 8 February 2016 / Accepted: 1 October 2016 Ó Akade ´miai Kiado ´, Budapest, Hungary 2016 Abstract Reduction and carburization behavior of com- posite oxide powder of WO 3 –NiO by CO/CO 2 was studied. And also for these reactions, the kinetics was investigated using isothermal thermogravimetric analysis technique under various CO/CO 2 ratios and temperatures. The reac- tion products were analyzed by XRD, TEM and SEM. The effect of CO fraction was investigated at constant tem- perature (950 °C), to obtain an optimum value that results in complete reduction of the oxides and carburization of W, while avoiding deposition of excess carbon. An atmosphere containing 93 % CO yielded the best results above which deposition of carbon on particles was observed. The effect of temperature at constant CO content (80 %), was studied in the range of 775–1100 °C. At higher temperatures car- burization did not happen because of thermodynamic rea- sons, whereas at the lowest temperature the reduction was incomplete due to the slower kinetics. The optimum tem- perature was found to be 850 °C for complete reduction and carburization along with limited agglomeration and carbon deposition. The kinetics of reduction and carbur- ization reactions was evaluated using isoconversional method. The calculated activation energy for different stages of reduction and carburization was 25.2, 92.8, 171.5 and 112.6 kJ mol -1 . & Hurieh Mohammadzadeh Valendar h.mohamadzadeh@urmia.ac.ir HamidReza Rezaie h.rezaie@iust.ac.ir 1 Department of Materials Engineering, Faculty of Engineering, Urmia University, P.O. Box: 5756151818, Urmia, Iran 2 Natural Resources Canada, Ottawa, ON M5S 3E4, Canada 3 Department of Materials Science and Engineering, University of Toronto, 184 College Street, Suite 140, Toronto, ON M5S 3E4, Canada 4 School of Materials and Metallurgy Engineering, Iran University of Science and Technology (IUST), Tehran, Iran 123 J Therm Anal Calorim DOI 10.1007/s10973-016-5883-y