Great Magnetoresistance of Tungsten Telluride
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- Category: Tungsten's News
- Published on Thursday, 04 February 2016 17:48
- Written by xinyi
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A magnetoresistive material is added with a magnetic field, whose resistance will change, which is a technically useful phenomenon, such as the utilization in sensors to read data of hard disk. Mazhar Ali and his colleagues now identify a kind of material (tungsten telluride), in which the magnetoresistance effect is abnormally large: the resistance can be changed by more than 13 million percent. Its remarkable reluctance will be displayed in very high magnetic fields and very low temperatures, so the actual application is currently impossible. But the discovery proposed new direction for study on the magnetoresistance, which may eventually lead to new applications of this effect.
Tungsten(IV) telluride (WTe2) is an inorganic semimetallic chemical compound. In October 2014, tungsten ditelluride was discovered to exhibit an extremely large magnetoresistance: 13 million percent with no known saturation point. The resistance is proportional to the square of the magnetic field. This may be due to the materiel being the first example of a compensated semimetal, in which the number of mobile holes is the same as the number of electrons. The structure of tungsten ditelluride is layered, and the substance can be exfoliated into thin sheets down to monolayers. However electrons can easily move between the layers, unlike in other two dimensional semiconductors. The fraction of charge carriers is 0.005 per formula unit (WTe2).
When subjected to pressure, the magnetoresistance effect in WTe2 is reduced. At a pressure of 10.5 GPa magnetoresistance disappears. Above this same pressure of 10.5 GPa tungsten ditelluride can become a superconducter. At 13.0 GPa the transition to superconductivity happens below 6.5K. WTe2 was also recently predicted to be a Weyl semimetal and, in particular, to be the first example of a "Type II" Weyl semimetal, where the Weyl nodes exist at the intersection of the electron and hole pockets.
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Isopropyl Alcohol's Widespread Applications
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- Category: Tungsten's News
- Published on Wednesday, 03 February 2016 18:04
- Written by xinyi
- Hits: 660
IPA ,also known as isopropyl alcohol, is used as a low-cost solvent in many industrial and consumer products, it is also used as the extraction agent. According to the European Solvents Industry Group (ESIG) analysis, in 2001 in Europe, the demand of intermediate accounted for 32% of IPA consumption, 14% as anti-icers, 13% for coatings and resins, 9% for medicine , 4% for food, 3% for inks and adhesives. It is also used as solvent for oil and gum, and the preparation of fish feed concentrate.
Low-grade IPA can be used as vehicle fuel. the amount of IPA used as raw materials of acetone in production declines. There are several compounds synthesized by the IPA, the main compounds is methyl isobutyl ketone and many esters. The general purity of Anhydrous IPA is 99%, the premium (used for making perfume and medicine) IPA purity is greater than 99.8%.
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Demand Capacity of Isopropyl Alcohol
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- Category: Tungsten's News
- Published on Wednesday, 03 February 2016 17:59
- Written by xinyi
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Demand and capacity
According to statistics, BP, Sasol and Shell's total production capacity of the European IPA was 424,010 tons in 2001, Western Europe sales was nearly 366,000 tons, and export 46,000 tons in 2001. Annual growth rate of Europe needs was 1% to 2%, it is expected that the growth will be higher in Central and Eastern Europe and Asia. IPA have a great potential for the production of derivatives, the growth of being used as a solvent is little or no.
The world's total production capacity is more than 2.42 million tons per year. Domo and Mitsui Chemicals built solvent (including IPA) combination unit of 80,000 tons per year in Germany Luna, and put into production in 2004.
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Production Technology of Isopropyl Alcohol
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- Category: Tungsten's News
- Published on Wednesday, 03 February 2016 18:01
- Written by xinyi
- Hits: 996
Production Technology
There are two kinds of commercial process of isopropyl alcohol (IPA) preparation, which both use propylene as raw materials. The older method using refinery grade propylene and sulfuric acid catalyst indirect dehydration to produce isopropyl sulfate, then use steam hydrolyzed into sulfuric acid and IPA, crude IPA was purified by distillation. Newer chemical route is using chemical grade propylene (90% to 99%) to direct hydration, avoiding the use of sulfuric acid. Propylene and water through heating, the gas-liquid mixture into the trickle-bed reactor containing sulfonated polystyrene cation exchange resin under pressure.Also phosphoric acid catalyst by manipulation in a fixed bed reaction is carried out in the gas phase.
There is also a liquid line, using a soluble tungsten catalyst. IPA is obtained from the aqueous solution by distillation. Also a small amount of IPA from acetone hydrogenation in the liquid phase, but the process is only applicable to the excess acetone available place.
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High-Quality Low-Cost Single Tungsten Disulfide Realize a Large-Area Preparation II
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- Category: Tungsten's News
- Published on Tuesday, 02 February 2016 17:39
- Written by xinyi
- Hits: 656
On this basis, they proposed the catalytic surface atmospheric pressure chemical vapor deposition method with gold as growth substrate,which achieved the high quality, single uniform and large-area films preparation of millimeter-sized WS2 single crystals. The study found that the catalytic activity of gold and low solubility of tungsten in gold ensure the growth of uniform monolayer high quality WS2 crystals. In the meanwhile, the electrochemical bubbling method may be applied in realization of WS2 high quality transfer without gold substrate damaging. The single WS2 obtained by this method has high crystalline quality, showing optical and electrical properties compared with the material prepared by mechanical exfoliation of the proposed.
In addition, the research proposed non-destructive method of roll-to-roll and electrochemical bubbling combination for transferring, which achieve a low-cost continuous transfer of large-area single WS2 film to flexible transparent substrate, which also realize the preparation of large-area flexible transparent WS2 monolayer’s thin films transistors array and the electrical properties is still not attenuated after being bent hundreds of times .
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