Recently, the Bulgarian Gas Company said that Bulgaria is negotiating with Gazprom on resuming natural gas supply, and there is a possibility that Russia will resume natural gas supply to Bulgaria.
Since the outbreak of the conflict between Russia and Ukraine, the European Union has imposed several rounds of sanctions on Russia. Russian President signed a presidential decree on March 31, requiring "unfriendly" countries and regions to pay for Russian natural gas in rubles, otherwise gas supplies will be suspended. Bulgaria has been out of breath since the end of April for refusing to comply with the rouble settlement order. Affected by natural gas supply shortages and soaring energy costs, Bulgarian natural gas companies have applied to the Bulgarian government to raise Bulgarian natural gas prices by 60% in August, RIA Novosti reported.
On August 3, local time, the US Senate passed a resolution by a vote of 95 to 1, agreeing to the application of Finland and Sweden to join NATO.
NATO signed a protocol on the accession of Finland and Sweden to NATO on July 5. In accordance with the procedures, NATO members will examine and approve the protocol in accordance with their own procedures. The US House of Representatives passed a resolution supporting Finland and Sweden to join NATO on July 18. After it is passed by the Senate, the Biden administration will submit approval documents to NATO.
Because of the turbulent international situation, the supply and prices of many international bulk tungsten disulfide are still very uncertain.
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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