Tungsten(IV) sulfide
Tungsten(IV) sulfide is the chemical compound with the formula WS2. It occurs naturally as the rare mineral tungstenite. This material is a component of certain catalysts used for hydrodesulfurization and hydrodenitrification.
WS2 adopts a layered structure related to MoS2, with W atoms situated in trigonal prismatic coordination sphere. Owing to this layered structure, WS2 forms inorganic nanotubes, which were discovered on an example of WS2 in 1992.
Properties
Bulk WS2 forms dark gray hexagonal crystals with a layered structure. Like the closely related MoS2, it exhibits properties of a dry lubricant. It is chemically fairly inert but is attacked by a mixture of nitric and hydrofluoric acids. When heated in oxygen-containing atmosphere, WS2 converts to tungsten trioxide. When heated in absence of oxygen, WS2 does not melt but decomposes to tungsten and sulfur, but only at 1250 °C.
The material undergoes exfoliation by treatment with various reagents such as chlorosulfonic acid.
Tungsten
Tungsten, also known as wolfram, is a chemical element with symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten, which directly translates to heavy stone. Its name in Swedish is volfram, however, in order to distinguish it from scheelite, which in Swedish is alternatively named tungsten.
A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as a metal in 1783. Its important ores include wolframite and scheelite. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the elements. Its high density is 19.3 times that of water, comparable to that of uranium and gold, and much higher (about 1.7 times) than that of lead. Polycrystalline tungsten is an intrinsically brittle and hard material, making it difficult to work. However, pure single-crystalline tungsten is more ductile, and can be cut with a hard-steel hacksaw.
Tungsten (music)
A Tungsten or Tungs-Tone is a type of phonograph stylus. They are constructed from tungsten wire, which is held in a metal shank. Unlike a steel stylus, a tungsten stylus has a cylindrical rather than a conical shape, meaning that the cross-section of the stylus remains the same as the stylus wears down, which in turn means that tungsten styluses may be used for several plays.
Typically, a new steel needle is required for every record played on an old acoustic phonograph. This is because the record contains abrasive material. In the first few silent tracks this abrasion hones the steel needle to a profile that tracks the grooves properly. The needle continues to wear as it plays the record, so that by the end its diameter has increased to the point where the sharp edges may damage the grooves on subsequent plays.
One famous brand of tungsten stylus was the Tungs-Tone stylus, manufactured by the Victor Talking Machine Company in the 1910s and 1920s.
References
Palm Tungsten
The Tungsten series was Palm, Inc.'s line of business-class Palm OS-based PDAs.
Details
The Tungsten series was introduced in October 2002, created as a "prosumer" line priced at $199 to $300 to compete with the popular Sony Clie and Windows Mobile PDAs. The first device in the line was the Tungsten T, making it the first Palm PDA to be labeled with a letter rather than a number and to run Palm OS 5.
All of the Tungsten PDAs have a few attributes in common:
All models except the Tungsten C, W, and E have Bluetooth. The Tungsten C has Wi-Fi and it is optional on the E2, T3, and T5 via the Palm Wi-Fi Card placed in their SD card slot).
With the exception of the Tungsten W, all Tungsten PDAs run Palm OS 5 "Garnet" on an ARM processor and have non-user-replaceable lithium-ion batteries. Some users replace battery packs with third-party units. The T3, for example, is shipped with a 900 mAh capacity battery but third-party 1100 mAh or 1150 mAh LI-poly batteries of the same physical dimensions are available. Tungsten models use a five-way navigator pad, in the shape of a rounded rectangle, circle, or oval and have four buttons for built-in applications.
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