Two-dimensional compounds (like graphite or MoS2) are capable of bending their layers and forming a closed cage structure, which is denoted the inorganic-fullerene-like (IF) phase in the case of inorganic materials. Simultaneous thermal analysis (TG-DTA) of a number of nanomaterials (IF-MoS2, IF-NbS2, and IF-WS2) and their bulk counterparts was carried out in inert and oxidizing environments at various heating rates. Oxidation occurred at 295 °C for the smallest particle size (100 nm) but the oxidation temperature increased to 440 °C for the largest particle size (3 μm). At low heating rates, the oxidation occurred through sulfates and lower oxides, while at high heating rates mostly one-step oxidation to the highest oxide was observed. The stability in N2 atmosphere depended on the criterion of stability chosen: Choosing the onset temperatures of the decomposition step (between 1200 °C and 1390 °C), the stability decreased in the order WS2
≈ MoS2 > NbS2; and the bulk material reacted mostly at higher temperatures compared to the IF-phase. Choosing the extent of decomposition as a measure of stability, no specific trend could be found. Surprisingly, a single IF-WS2 sample was found to be most stable by both methods.This study shows that IF nanoparticles are comparably (though somewhat less) stable against oxidation as well as decomposition than the bulk material exhibiting the usual plate-like structure.
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