Tungstensulfide

DescriptionTungsten sulfide (S2W) is a chemical compound that exists naturally in the form of a rare mineral called tungstenite. It is used as a principal component of catalysts in processes such as hydrogenation of crude oil, hydrodesulfurization and hydrodenitrification reactions. It is widely employed as additives in solid lubricants to improve lubricants and extreme pressure properties and antiwear properties especially in environments of high temperature, high pressure, high vacuum, high load and with radiation and corrosive media. Due to the above property, the nanoscale of tungsten sulfide can be also added in the casting process which helps make cast metal have a certain self-lubricating properties and have an excellent adsorption capacity on the metal surface. It can also be used as solid-state secondary lithium battery cathodes and other electrochemical devices. Besides, it is found that the friction coefficient of tungsten sulfide is relatively small, which makes it an additive in other metal powder for a stable friction coefficient. It also finds application in semiconductor materials, inorganic nanotubes, etc.

UsesTungsten disulfide (WS2) in bulk has been used for many years as a dry lubricant due to how it exhibits properties of a low coefficient of friction, high chemical stability, and thermal stability. In 1992, it was discovered that the structure of WS2 made it capable of forming nanotube structures. These nanotubes were the first examples of WS2 being used as a low-dimensional material. After the discovery of simple mechanical exfoliation techniques to isolate single layers of 2-D materials, it was possible to study the properties of WS2 flakes. It was shown that, just like MoS2, the band-gap of WS2 change from an indirect band-gap of 1.4eV to a direct band-gap of 2eV when changing from a bulk material to a 2-D material. Due to its band-gap, WS2 is seen as a significantly interesting material for many areas of application. WS2 possesses a high on/off ratio in field-effect transistors, controllable spin and valley polarisation, strong geometrical confinement of excitons, and tunable photoluminescence. Additionally, WS2 could lead to increased interest in areas such as photodetectors and multi-junction photovoltaics. Besides, WS2 is used, in conjunction with other materials, as catalyst for hydrotreating of crude oil. Lamellar tungsten disulfide is used as a dry lubricant for fasteners, bearings, and molds under the brand name Dicronite.

DescriptionFew-layertungsten disulfide (WS2) film has a 2D-layered structure with a narrow indirect bandgap of of 1.35 eV. In contrast, the monolayer film possesses a direct bandgap of 2.1 eV.