Study of thermally induced phase transformations and microstructural changes in porous MoO3 nanostructures for the design of tribological additives

Abstract The thermal behavior of MoO3-nanostructures is relevant for the design of tribological additives containing Mo-oxides. We report on thermal behavior of porous MoO3-nanostructures analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The nanostructures were grown by gas condensation under H2. Our results revealed 3 stages of phases behavior as a function of temperature. We found dehydration of MoO3∙0,33 H2O after 180 °C followed by the formation of β-MoO3 after 230 °C, then to α-MoO3 after 280 °C, and finally formation of suboxide γ-Mo4O11 at ~330 °C. The formation of the latter is mainly due to the crystallization and reduction of the porous oxide matrix. Our results highlight that both thermal and chemical processes must be taken into account when designing tribological additives that contain MoO3.