Thermal analysis and kinetics of oxidation of molybdenum sulfides

Abstract

The thermal oxidation process of stoichiometric MoS 2 and nonstoichiometric "M02S3", together with the kinetics of oxidation of MoS2, were studied by using TG and DTA techniques in the Po 2 range 1~).0890 atm. MoS 2 was oxidized completely to MoO3 in one step:MoS 2 + 7/20 2 -,MOO 3 + 2 SO 2Irrespective of Po2 and the heating rate, "M02S3" was oxidized finally to MOO3, via the following four steps:where (sur) refers to the surface layer. The kinetic study revealed that the oxidation (x = 0.01~).90) of MoS 2 to MoO 3 was controlled by the kinetics l-(1-ct) t/a = kt and that the apparent activation energies determined with the isothermal and the nonisotbermal (10degmin-0 method were 98.1+2.2 and 93.5+3.0kJmol -~, respectively, over the temperature range 540-625 ~ and the Po 2 range 0.6124).129 atm. The relationship between the rate constant k and Po E was determined.In the Mo-S system, the hexagonal 2H-MoS2, the monoclinic "Mo2S3" and metallic Mo can be obtained in solid-gas equilibrium reactions at temperatures higher than 610 ~ [1-3]. In recent years, MoS 2 has been the subject of much interest as a lubricant for rotating and sliding components [4].The oxidation and the kinetics of oxidation of MoS 2 are generally studied from the point of view of recovering molybdenum from molybdenite concentrate (ca. 90% MoS2). Ong [5] reported an investigation on the oxidation of molybdenite compressed into pellets over the temperature range 360--461~ He suggested that the John Wiley & Sons, Limited, Chichester Akad~miai Kiad6, Budapest

How stable are inorganic fullerene-like particles? Thermal analysis (STA) of inorganic fullerene-like NbS2, MoS2, and WS2in oxidizing and inert atmospheres in comparison with the bulk material

“…Shigegaki et al 15 used a similar approach for the investigation of MoS 2 . They report oxidation of MoS 2 to MoO 3 in one step in airflow starting slowly at 450 1C for mm-sized powder.…”

Sonochemical edge functionalisation of molybdenum disulfide

“…Literature about mechanically cleaved MoS2 24 suggests the broadening may be associated with a higher defect density. The peak at 521 cm -1 is the silicon wafer substrate and the peak at 447 As seen in literature [31][32][33] , the chemical reaction for oxidation of MoS2 in presence of oxygen gas is:…”

Accelerator-based production of the 99mTc-186Re diagnostic-therapeutic pair using metal disulfide targets (MoS2, WS2, OsS2)

“…Only the strong oxidizing agent, 30% H 2 O 2 , showed signs of dissolution with slow effervescence at the MoS 2 -H 2 O 2 interface. Molybdenum disulfide is hydrophobic and remained suspended on top of the aqueous solutions until oxidation was initiated by gentle heating (50° C), and then was self-sustaining (exothermic) according to the following reaction (Shigegaki 1988):…”

“…A small quantity of a dark colored precipitate was observed following reaction completion, likely molybdenum dioxide generated by the following competing reaction (Shigegaki 1988):…”