Mechanochemical Reduction of MoS 2 by Zn in Presence of Lime to Produce Nano-CaMoO 4 and -ZnS Simultaneously
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NTRODUCTION
THE ability of Molybdenum (Mo) metal to withstand extreme temperatures without being expanded or softened significantly makes it useful in the applications that involve intense heat, including jet engine parts, armor, and filaments.[1–6] Ferromolybdenum (Fe-Mo) is the most applicable form of Mo, which is used for alloying of high-temperature steels, cast iron, and super alloys to increase their mechanical strength, swiftness, and resistance to corrosion. However, employing ferromolybdenum to alloy steels includes some disadvantages[7–9]: a. The chemical composition of Fe-Mo pellets differs from each other due to their eutectic solidification. b. It contains nonmetallic inclusions like quartz, glass, and silicates. c. The density of the pellets decreases due to presence of porosities leading the Fe-Mo pellets to climb through melting and the subsequent Mo entrapping in the slag. Recently, MoO3 has been introduced as an alternative source of Mo for the alloying of steels.[10,11] However, the low melting and boiling temperatures of MoO3 lead to its sublimation during the steel making process, thereby decreasing the yield of Mo in the steel.[10,12] The
MALIHE MOHAMMADI BEZANAJ and ARMAN HOSEINPUR, Students, and JALIL VAHDATI KHAKI, Professor, are with the Department of Materials Engineering, Ferdowsi University of Mashhad, P.O. Box 91775-1111, Mashhad, Islamic Republic of Iran. Contact e-mails: [email protected], [email protected] Manuscript submitted September 15, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
evaporated MoO3 would be entrapped in the slag, resulting in the Mo loss. Nevertheless, several researches have shown that the presence of alkalis and alkaline earth oxides, as well as carbonates, will restrain the evaporation of MoO3, resulting from the formation of molybdates at about 873 K (600 °C). Besides, this problem can be surmounted by directly using some molybdates like FeMoO4 and CaMoO4 rather than MoO3.[10,13,14] These compounds would be more stable during alloying due to their higher melting temperatures. Researchers have utilized CaMoO4 to alloy steel in industrial scale and they have been successful in reaching the high rate of nearly 95 pct of Mo yield.[10] Furthermore, it is noteworthy that in case of using FeMo, the alloying time would be prolonged. Thus, an important advantage of using CaMoO4 is the decrease of the alloying time that is crucial from the economical point of view. Nonetheless, the industrial production of CaMoO4 by heating MoO3 and CaO is a challenging issue because of the sublimation problem of MoO3. Molybdenum trioxide (MoO3) is the product of the roasting process of MoS2, in which high amount of SO2 gas is emitted into the air atmosphere leading to environmental pollution.[15–17] With regard to the aforementioned information, the main aim of this research is the in situ synthesis of CaMoO4 from MoS2 by employing ball milling as a room temperature process and entrapping sulfur in the form a solid compound. Hence, the sulfur emission into the atmosphere wou
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