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Influence of NaCl Additive on the Reduction Process of MoO3 to Mo2C by High-Purity CO Gas

Que Biao-Hua, Wang Lu, Wang Bao, Chen Yi, Xue Zheng-Liang

Archives of Metallurgy and Materials

2022

Vol. 67, iss. 2

787--796

In this work, influence of NaCl additive on the transformation process of MoO3 to Mo2C under pure CO atmosphere in the range of room temperature to 1170 K was investigated. The results showed that transformation of MoO3 to Mo2C can be roughly divided into two stages: the reduction of MoO3 to MoO2 (the first stage) and the carburization of MoO2 to Mo2C (the second stage). As to the first stage, it was found that increasing the content of NaCl (from 0 to 0.5 wt.%) was beneficial for the increase of reaction rate due to the nucleation effect; while when the content of NaCl increased to 2 wt.%, the reaction rate will be decreased in turn. As to the second stage, the results showed that reaction rate was decreased with the increase of NaCl, which may be due to the formation of low-melting point eutectic. The work also found that morphology of as-prepared Mo2C was irregular and particle size of it was gradually increased with increasing the NaCl content. According to the results, the possible reaction mechanism was proposed.

Analiza procesu syntezy Mo2C w układzie (NH4)6Mo7O24ź4H2O-węgiel aktywny

Sabara M., Biedunkiewicz A.

Inżynieria Materiałowa

2011

Vol. 32, nr 4

699-702

Przedstawiono analizę syntezy węglika molibdenu (Mo2C) przy różnych parametrach wyjściowych procesu. Na podstawie diagramów równowagi fazowej układu MoO3-C ustalano skład początkowy próbek. Metodą zol-żel (Stobera) otrzymano próbki do karbotermicznej redukcji. Jako prekursory stosowano (NH4)5Mo7O24ź4H2O i węgiel aktywny. Karbotermiczną redukcję prowadzono w argonie w 1000 i 1250°C w piecu i w aparacie TG. Skład fazowy próbek określono metodą XRD. Na podstawie pomiarów termograwimetrycznych, podczas których identyfikowano także produkty gazowe metodą spektrometrii masowej, przeanalizowano kinetykę procesu.

Analysis of the synthesis of molybdenum carbide (Mo2C) at various initial parameters of the process had been presented. Basing on phase equilibrium diagrams of MoO3-C the composition of initial samples has been determined. Samples to carbothermal reduction was obtained by sol-gel method (Stober). (NH4)5Mo7O24ź4H2O and active carbon were used as precursors. Carbothermal reduction was carried in argon at 1000 and 1250°C in the furnace and in the TG apparatus. Phase composition of samples was determined by XRD method. Basing on thermogravimetric measurements combined with mass spectrometry was determined kinetics of process.