Research on annealing temperature in the process of MoS2 nanostructure synthesis from nanoscale powder

To see the formation process of inorganic fullerene-like structures from MoS₂ the thermal annealing of superfine nanoscale MoS₂ powder was performed in neutral argon atmosphere. The grain size of MoS₂ powder is about 3 nm. The annealing temperature varied in the range of 500°C-1000°C, and the annealing time varied between 4 hours and 5 minutes for low and high annealing temperatures, respectively. PXRD and TEM analyses were made to observe the change of the character of the crystallization process and of the curvature of [002] MoS₂ planes. The rise of the annealing temperature leads to an increase of the crystalline phase and a simultaneous decrease of the amorphous phase in the MoS₂ powder. The sample annealed at T_ann=500°C reveals a weak curvature of the [002] planes, and the grains become larger as compared with the pristine MoS₂ powder. Increasing the annealing temperature up to T_ann=700°C leads to a stronger curvature of the [002] planes. The character of the curved planes varies from quite large planes with a large curvature radius up to U-shaped and rectangularly shaped structures. An increase of the annealing temperature up to T_ann=1000°C, finally, leads to a pronounced crystallization of the powder, with some part being left over in an amorphous phase.