Mechanism and kinetics of decomposition reaction of ultrafine ammonium molybdate for preparing ultrafine MoO3 powder

• Published in: Materials chemistry and physics Vol. 302; p. 127760
• Main Authors: Yang, Xiao-Hui, Zuo, Yu-Fei, Feng, Peng-Fa, Wang, Na, Li, Jing, Wang, Yu-Qing, Zhang, Guo-Hua, Chou, Kuo-Chih
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2023
• Subjects: Kinetics; Powders; Ultrafine ammonium molybdate; Ultrafine MoO3; Powders; Ultrafine MoO3; Kinetics; Ultrafine ammonium molybdate
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2023.127760

The decomposition reaction of ammonium molybdate to prepare molybdenum trioxide (MoO3) is a crucial step for the production of molybdenum powder. In this study, ultrafine MoO3 was prepared by calcining ultrafine ammonium molybdate in air atmosphere. The decomposition of ultrafine ammonium molybdate to generate MoO3 was proved to be a single-step reaction without intermediates in air atmosphere. Furthermore, the effects of temperature and reaction time on the phase composition, morphology and particle size distribution of products were also studied. The results showed that the temperature (in the range of 350 °C–450 °C) had a significant influence on the reaction rate, and the time required for completing the decomposition reaction was shortened as the temperature increased. However, the particle size of produced MoO3 was almost unchanged. It was also found that the phase compositions of products at different material layers (up, middle and bottom layers) were different, because the mass transfer of gaseous product in material layers affected the decomposition reaction. Additionally, a kinetic model considering the mass transfer of gaseous product in the material layer as well as the interface chemical reaction was proposed. Application of the developed model validated that the model could well describe the decomposition kinetics of ultrafine ammonium molybdate. •Ultrafine MoO3 was prepared by calcining ultrafine ammonium molybdate in air.•The temperature had a significant influence on the reaction rate.•A kinetic model considering mass transfer of gaseous product in material layer was proposed.