تهيه پودر كاربيد تنگستن نانوساختاري و مطالعه مشخصات آن در حين كربوريزاسيون

Optimization of SSAFT Equation of State Parameters to Study the Phase Equilibria of Preparation of Nanostructured Tungsten Carbide Powder and its Characterization During Carburization

Nanostructured tungsten carbide powder is a new product in nanotechnology, and it may substitute platinum in many catalytic reactions, due to its exceptional properties. Here, the effect of temperature and heating rate on carburization and phase transition of ammonium paratungstate has been studied. The ammonium paratungstate was carburized in 20% CH4 in H2 atmosphere in a quartz reactor. The temperature of the reactor was increased with different slopes of 0.33 and 1.0°C/min. The samples were weighed and characterized by XRD, SEM, BET and density measurement in 50-100°C intervals during the carburization. Results indicate the formation of amorphous carbon and metallic tungsten and surface area rising at about 550°C. At higher temperatures, up to 950°C, the tungsten is converted to W2C and then to WC, without significant changes in its specific surface area. The amount of amorphous carbon shows a minimum at about 750°C that seems to be due to methanation of the carbon .As compared to 1.0, the 0.33°C/min heating rate does not change the nanostructures considerably, except in the 750-850°C temperature range. However, the 0.33°C/min heating rate preserves the pristine microstructures of the ammonium paratungstate more than 1.0°C/min heating rate.