Addition of a Second Metal (Co) to Molybdenum Carbide: Effect of the Doping Route.

Molybdenum carbide is an interesting and versatile material, which has important applications in the metal matrix industry as a reinforcement material, as well as in the catalytic field. Though many papers suggest different methodologies for adding cobalt to the carbide structure aiming either to increase catalytic activity or enhancing mechanical proprieties such as ductility, etc. no straightforward evaluation is available. In the present paper two doping methodologies were studied: via solid state mixture of powders and via wet impregnation. Ammonium molybdate [(NH4)2MoO4] and cobalt nitrate [Co(NO3)2·6H2O] were used as starting materials and the doping process was carried out before carburization reaction. Those materials were characterized by FT-IR, SEM, XRF and XRD. The carbo-reduction products' were evaluated on XRD and XRF basis. Doped precursors' evaluation showed that the wet impregnated doped materials presented smaller particle sizes, were more homogeneous and retained more cobalt than the solid state doped ones. However, final products' assessment indicated that the solid state methodology was able to retain a greater dopant percentage according to XRF evaluation, and XRD data indicated a more intrinsic addition of the dopant to the carbide structure. In addition, no significant changes on particle size could be attributed to any of the methodologies, both producing Mo2C of approximately 30 nm.