2019年6月24日星期一

Zirconium Tungstate Thin Film

A thin film material is a film material with a thickness less than 1 microns. It is mainly used for semiconductor functional devices and optical coatings.

At present, the field has been involved in computer storage equipment, pharmaceuticals, high temperature insulation products, thin-film batteries, solar cells etc..

Compared with traditional block materials, thin film materials have incomparable advantages, such as small grains, large specific surface area and special surface structure. Therefore, zirconium tungstate is a kind of excellent negative thermal expansion material. The thin films prepared with zirconium tungstate can be conveniently used in the compensation layer of thermal stable structures or into large capacity heat driven devices, This is also the other general material is difficult to take advantage of it, so these years the zirconium tungstate thin film or zirconium tungstate composite thin film has also been concerned and research hot spots. 

It is well known that zirconium tungstate is mainly produced by the synthesis of ammonium paratungstate and zirconium oxychloride, and the difficulty of making the powder is a major obstacle to the popularization of zirconium tungstate thin film.

zirconium tungstate thin film solar cell image

The research shows that the methods of preparing zirconium tungstate thin film are mainly current beam evaporation powder method, wet chemical method, radio frequency magnetron sputtering method, alternating radio frequency magnetron sputtering method. Among them, the evaporation process of the current beam evaporation method is not well controlled, and the WO3 is easy to volatilize at high temperature, the stoichiometry of the film element is inconsistent with the Zr2W2O8 target; The purity of zirconium tungstate thin film made by wet chemical method and radio frequency magnetron sputtering method is not very high; The only thing worth mentioning is the alternating magnetron sputtering method based on RF magnetron sputtering, the method of preparation of zirconium tungstate thin films on quartz substrate deposition and annealing process, the sample obtained is cubic phase zirconium tungstate thin film, the purity and quality are improved, but the corresponding increase in procedure leads to higher cost.

To sum up, the zirconium tungstate thin film will take a place in the future high and new technology field with its excellent performance, but immature, inexpensive schemes also limit its use. However, as a new thing, the study of zirconium tungstate thin film is still in the initial stage, it is worth looking forward to the future.

If you have any inquiry of tungsten, please feel free to contact us:
Tel.: +86 592 5129696/+86 592 5129595
Fax: +86 592 5129797

Scan QR code of Chinatungsten Wechat platform to follow up the daily latest price and market of tungsten, molybdenum and rare earth.


Bismuth Tungstate Photocatalytic Degradation of Tetracycline Wastewater

China is a major producer of antibiotics and one of the most serious countries that abuse antibiotics.

Livestock farming is the hardest hit by the use of antibiotics, with the rapid development of aquaculture, the residues of antibiotics in water, sediment and soil become more and more serious.

Tetracycline is the most common antibiotic used in livestock farming. Its main characteristics are broad-spectrum antibacterial and cheap, unlike other organic wastewater contamination, tetracycline and other antibiotic compounds usually have a shorter degradation half-life in the environment, however, the use of tetracyclines in livestock and aquaculture has never ceased to allow them to enter the environment, manifested as "persistent". Such a consequence is that antibiotics selectively inhibit some environmental microorganisms in the environment and induce the emergence of some antibiotic resistance groups, thus triggering a particular ecotoxicological effect, this is why some large pharmaceutical factories and farms become the main pollution factors and ecological extinction of the surrounding rivers.

In recent years, photocatalytic degradation technology has been paid more and more attention to environmental pollution control, and photocatalytic treatment of antibiotic pollution seems to be a good solution, thus, some areas began to use photocatalytic technology to control tetracycline pollution.

bismuth tungstate photocatalytic degradation of tetracycline wastewater image

The photocatalysts include tungstate series, titanium series and bismuth series. Tungstate is one of the best known photocatalysts, and bismuth tungstate is one of the best. In recent years, bismuth tungstate photocatalyst has attracted much attention in the field of environmental protection, mainly due to its following advantages: (1) Good UV and visible light response; (2) Thermal stability; (3) Photocatalytic stability; (4) The material sources are easy and the cost is relatively low; (5) Environmental friendly.

Some scholars used bismuth tungstate catalyst and doped with small amounts of ZnFe2O4 to degrade tetracycline wastewater, in the process of photocatalytic reaction, the oxidation of hydroxyl radical promotes the deamination, demethylation and other oxidation reactions of tetracycline, in the long photocatalytic reaction time, the intermediates of the macromolecules will eventually be mineralized into CO2, H2O and NH4+, and the photocatalytic degradation efficiency will reach 98%.

Studies have shown that bismuth tungstate is the bane of antibiotic wastewater such as tetracycline, and its importance to human survival is self-evident. As we all know, avian influenza and super drug resistant bacteria occur frequently in recent years, which is associated with the abuse of antibiotics in the aquaculture industry. We do not expect the pursuit of profit businessmen can find their conscience, but only hope that the rivers and lakes, the sea can be more clean, the development of light degradation technology also allows people to have more expectations of the environment.

If you have any inquiry of tungsten, please feel free to contact us:
Tel.: +86 592 5129696/+86 592 5129595
Fax: +86 592 5129797

Scan QR code of Chinatungsten Wechat platform to follow up the daily latest price and market of tungsten, molybdenum and rare earth.


Bismuth Tungstate Preparation by Microemulsion Method

Bismuth tungstate (Bi2WO6) is an oxide with perovskite like structure, and is a typical n type semiconductor. Bismuth tungstate has become a new hot spot of photocatalysis because of its unique crystal structure.

The preparation methods of bismuth tungstate include solvothermal method, precipitation method, microemulsion method, hydrothermal method, etc.. Among them, microemulsion method is a new method for preparing ultrafine powders, which can be used to prepare nanometer bismuth tungstate, which is relatively simple and the powder morphology is easy to control.

Microemulsion refers to two mutually insoluble reaction solutions which form isotropic and thermodynamically stable emulsions under the influence of surfactants, the reactants are nucleated, agglomerated, agglomerated, crystallized and grown in tiny vacuoles and then treated at high temperatures (usually less than 240 degrees) to form nanoparticles.

Microemulsion can be divided into three types: water-in-oil and oil-in-water type, intermediate state, also known as positive phase microemulsion (O / W), reverse microemulsion (W / O) and double continuous phase microemulsion.

bismuth tungstate preparation by microemulsion method image

Some scholars have prepared Bi2Wo6 photocatalyst by microemulsion mediated hydrothermal method: The oil phase of n-butanol and cyclohexane is mixed with an aqueous phase consisting of dilute nitric acid solutions and Na2WO4 solutions, and the magnetic stirring for 15 minutes, forming precursor, adjust pH value, pour into the high pressure reactor, the hydrothermal reaction was carried out at a temperature of 180 °C for 24 hours, the product is naturally cooled to room temperature, and the product is dried at 80 °C by centrifugal separation and washing, and then Bi2WO6 photocatalyst is obtained.

Microemulsion is characterized by the formation of tiny reactors under the action of amphiphilic molecules of surfactant, which prevents the formation of agglomerated nanocrystals. Compared with other liquid phase methods, microemulsion method has the advantages of simple process, good product dispersion, and the surface active agent can be used to modify the surface of nanomaterials, the prepared bismuth tungstate has controllable particle size and uniform morphology, so the photocatalytic property of bismuth tungstate produced by microemulsion method is highly recognized.

If you have any inquiry of tungsten, please feel free to contact us:
Tel.: +86 592 5129696/+86 592 5129595
Fax: +86 592 5129797

Scan QR code of Chinatungsten Wechat platform to follow up the daily latest price and market of tungsten, molybdenum and rare earth.


Bismuth Tungstate Preparation by Solvothermal Method

Bismuth tungstate (Bi2WO6) is an oxide with perovskite like structure, and is a typical n-type semiconductor.

Because of its unique crystal structure, Bi2WO6 has the properties of thermoelectric, ferroelectric, piezoelectric, oxygen ion conductor, luminescence, nonlinear dielectric induction and catalysis.

The preparation methods of bismuth tungstate include solvothermal method, precipitation method, microemulsion method, hydrothermal method, etc.. Among the many methods of liquid phase preparation, hydrothermal process has high utilization ratio of material and less energy consumption because of its simple operation process. But there is a clear flaw in hydrothermal methods, that is, the water sensitive compounds are not satisfactory, so people will use organic solvents instead of "water" in hydrothermal method, which is called solvothermal method.

bismuth tungstate preparation by solvothermal method image

The principle of solvothermal method is similar to thydrothermal method. It also works in a special sealed reaction vessel (autoclave), the difference is that other organic solvents are used instead of water as the reaction medium, organic solvents also play a role in the media, mineralization and transmission of pressure.

The main difference between solvothermal and hydrothermal methods is that: 1. The solvothermal method uses organic solvent, while hydrothermal method uses water; 2. Under normal circumstances, the boiling point of organic solvents is relatively low, so the reaction temperature required in the preparation process is relatively low, less energy consumption; 3. The reaction activity of the solvent is high, and the quality of the synthesized bismuth tungstate is better; 4. Organic solvents used in solvothermal methods are toxic and less environmentally friendly.

The most common organic solvent used in the preparation of bismuth tungstate is ethylene glycol, Bi2WO6 with an average grain size of 12 nm was synthesized by solvothermal method using ethylene glycol as solvent, the Bi2WO6 samples prepared by hydrothermal method were compared under the same conditions, it is found that the Bi2WO6 powder prepared by solvothermal method has smaller grain size and larger specific surface area than hydrothermal method, so the photocatalytic degradation of B powder is better under visible light.

In recent years, the use of solvothermal method is more and more widespread, but the gap is still very obvious. Organic solvent as reaction solvent will bring security risks to the stability of reaction system, in addition, organic solvents are generally toxic, improper use is liable to harm the body and the environment, so for the use of this method, enterprises often have to consider carefully.

If you have any inquiry of tungsten, please feel free to contact us:
Tel.: +86 592 5129696/+86 592 5129595
Fax: +86 592 5129797

Scan QR code of Chinatungsten Wechat platform to follow up the daily latest price and market of tungsten, molybdenum and rare earth.