Tungsten disulfide is a kind of dark gray crystal or powder with similar lubricating property to graphite. Its CAS No. is 12138-09-9; Chemical formula is WS2; Melting point is 1250°C.
Structure
WS2 has a layered structure related to MoS2, with W atoms situated in trigonal prismatic coordination sphere. Owing to this layered structure, WS2 forms inorganic nanotubes.
Properties
1. WS2 converts to tungsten trioxide if heated in oxygen-containing atmosphere.
2. WS2 does not melt but decomposes to tungsten and sulfur if heated in absence of oxygen (Only at 1250°C).
3. It is chemically fairly inert but is attacked by a mixture of nitric and hydrofluoric acids.
Producing Method - Roasting Method
Step one: Tungstic acid and ammonia are reacted under stirring at the temperature range of 57~60°C for 3h. And make the mixed liquor free settling above 16h in heat preservation to generate ammonium tungstate:
H2WO4+2NH3?H2O→(NH4)2WO4+2H2O
Step two: The generated ammonium tungstate reacts with hydrogen sulfide gas to generate ammonium tetrathiotungstate:
(NH4)2WO4+4H2S→(NH4)2WS4+4H2O
Step three: The generated ammonium tetrathiotungstate roasted by high temperature and decomposed into tungsten disulfide.
2(NH4)2WS4+3O2→2WS2+4NH3+2S+2SO2+H2O
Applications
1. A component of certain catalysts used for hydrodesulfurization and hydrodenitrification.
2. Lamellar tungsten disulfide is used as a dry lubricant for fasteners, bearings, and molds.
3. To form inorganic nanotubes.
4. Exist in the form of atomically thin sheets. Such materials exhibit room-temperature photoluminescence in the monolayer limit.
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