European Commission President Ursula von der Leyen recently called on India and other countries to support sanctions against Russia over the Ukraine incident. At The Raisina Dialogue forum, von der Leyen said, "We earnestly appeal to all members of the international community to support our efforts to achieve lasting peace."
Von der Leyen says countries around the world that have been suffering from the virus for two years must now deal with higher food, energy, and fertilizer prices. What is happening in Ukraine will not only determine the future of Europe, but also have profound implications for the rest of the world.
Because of the Russia-Ukraine conflict, the prices of many other commodities like the tungsten disulfide are expected to continue to rise in the future.
Tungsten disulfide and tungsten diselenide are both typical compounds of rare metal tungsten and are inorganic compounds composed of transition metal elements (tungsten) and oxygen group elements. they have good physical, chemical and thermal properties and are widely used in the field of optoelectronics.
However, there are still great differences between the two in terms of specific concepts, nature and uses.
Note: sulfur and selenium both belong to group Ⅵ An elements and oxygen group elements.
Tungsten disulfide is a kind of two-dimensional transition metal layered material, which is a blue-gray fine grain or powder with metallic luster composed of tungsten and sulfur elements. it is the main component of pyroxene. Tungsten disulfide formula is WS2.
Tungsten diselenide is a kind of layered material composed of tungsten and selenium, which is a black or gray solid powder composed of positive tetravalent tungsten ion (W4 +) and negative divalent selenium ion (Se2-). It is a kind of porous material (or thermal insulator) with low thermal conductivity. Tungsten diselenide formula is WSe2.
The structure of WS2 is hexagonal layered structure, with a hexagonal network formed by S-W-S molecular clusters on the surface, connected by van der Waals force between the layers, and linked by Wmuri S covalent bond within the layer.
The structure of WSe2 is hexagonal, one tungsten atom and six selenium atoms are bonded by a prism, each selenium atom is a pyramidal configuration and three tungsten bonds, and the layers are combined by van der Waals force.
Tungsten disulfide melting point is about 1250℃. Tungsten disulfide density is about 7.6g/cm3, and its friction coefficient is 0.03-0.07. Insoluble in water, non-magnetic, non-conductive, good semiconductivity, excellent lubrication and wear resistance, good thermochemical stability, good lithium storage properties, excellent diamagnetism, oxidation and reducibility.
The appearance of WSe2 is black or gray powder. Tungsten diselenide density is about 9.32g/cm3, the thermal conductivity is poor (the thermal conductivity is 1/100000 of that of diamond), the band gap is between wide gap semiconductor and zero band gap graphene, and has excellent electrical and optical properties and high quantum yield.
The common production methods of WS2 are roasting decomposition and direct synthesis. Among them, the roasting decomposition method refers to the process that ammonium tetrathiotungstate (NH4) 2WS4 is decomposed into WS3 and WS2 successively after high temperature roasting.
The preparation steps of WSe2 are as follows: tungsten films of different thickness are deposited on the substrate by magnetron sputtering, and some of the tungsten films are annealed; then the annealed and unannealed tungsten films and selenium powder are heated in a vacuum quartz tube and selenized.
Both of them can be used in the fields of lubrication, energy storage battery, semiconductor and photovoltaic, and can be used as additives for lubricants, modifiers for cathode materials of lithium-sulfur batteries, transistors, etc.
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The war in Russia and Ukraine is roiling global financial markets. Russia and Ukraine are important commodity suppliers in the world, so their conflict is bound to make a full impact on the global commodity supply. In view of this, the price of the tungsten disulfide may continue to rise in the future.
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