Ammonium Metatungstate Price on Nov.29th, 2016

Ammonium metatungstate price with purity over 91.40% from Chinatungsten Online is 35.50 USD/KG, by Chinatungsten FOB Xiamen, Nov.29th, 2016.

AMT photo

Arsenic Doped Ammonium Metatungstate Preparing Nano Tungsten Powder

arsenic doped ammonium metatungstate imageArsenic doped ammonium metatungstate (AMT) is generated by adding ammonium metatungstate into the nitric acid solution of elemental arsenic and stirring, drying and grinding, the excellent raw material for preparing nano tungsten powder. Nano tungsten powder is the tungsten powder which the particle size is fine to nanoscale, at present, the traditional method for manufacturing nano tungsten powder is tungsten oxide reduction method, wherein the reducing agent maybe hydrogen or carbon; with the appearing of nano materials, the manufacture methods of nano tungsten powder are emerging constantly, such as high-energy ball milling, gas evaporation, plasma, self-propagating high-temperature reduction and molten salt electrolysis method.
There is a study to take ammonium metatungstate as raw material, and through doping process to get arsenic doped ammonium metatungstate to finally get nano tungsten powder, with the producing process like the following:
1. Preparation of arsenic doped ammonium metatungstate precursor composite powder
Add a certain amount of elemental arsenic into the nitric acid with a certain concentration, then add ammonium metatungstate into the nitric acid solution of elemental arsenic after the As is completely dissolved with the arsenic content being controlled; electric mix the raw materials, then dry them in a oven under 70~90°C for 8~10 hours, and then, grind to get arsenic doped ammonium metatungstate precursor compound powder.
2. Arsenic doped ammonium metatungstate calcination to prepare yellow tungsten trioxide powder
Put the prepared arsenic doped ammonium metatungstate precursor compound powder in a box type resistance furnace at the temperature of 580~620°C to carry out calcination in air atmosphere for 2~3 hours, then we get yellow tungsten trioxide powder.
3. Tungsten trioxide reduction to generate nano tungsten powder
Put the yellow tungsten trioxide powder in a tube furnace to get reduction by inletting hydrogen, under the reduction temperature of 780~820°C with the heating rate of 5°C/min, and the heat preservation time of 3~4 hours, to finally manufacture nano tungsten powder
The nano tungsten powder get by arsenic doped ammonium metatungstate has the advantages of good dispersion, and uniform particle size distribution, thus to effectively promote the development and application of nano-crystal WC-Co alloy.


Ammonium Metatungstate Price on Nov.25th, 2016

Ammonium metatungstate price with purity over 91.40% from Chinatungsten Online is 35.50 USD/KG, by Chinatungsten FOB Xiamen, Nov.25th, 2016.

AMT photo

Ammonium Metatungstate Preparing Violet Tungsten Oxide Whisker

violet tungsten oxide whisker SEM imageAmmonium metatungstate (AMT) is an important compound in tungsten metallurgy industry, an important raw material for preparing tungsten oxide, such as tungsten trioxide (YTO, WO3), violet tungsten oxide (VTO, WO2.72 or W18O49). Violet tungsten oxide whisker is the micro-nano-short fibers which are generated by the high purity violet tungsten oxide, with the mechanical strength equal to the strength of adjacent atoms between the intensity. The highly oriented structure of W18O49 whisker has not only making itself of high strength, modulus and elongation, but also of the properties of electrical, optical, magnetism, dielectricity, conductivity and superconductivity.
It is pointed out that a process for producing violet tungsten oxide whiskers by coaxial electrostatic spinning method with ammonium metatungstate as a raw material is as follows:
1. Mix 2ml saturated ammonium metatungstate solution and 12% PVA solution in a certain proportion, to prepare spinning solution;
2. Inject the best electrospinning solution into 10ml syringe, and install it in the syringe pump to carry out a single tube electrospinning experiment. In the spinning process, solvent will volatilize partly in the air and form ammonium metatungstate/PVA composite fiber;
3. Calcine the obtained ammonium metatungstate / PVA composite fiber in the air to remove the solvent and the matrix PVA, and the ammonium metatungstate is decomposed by heating to obtain WO3 one-dimensional nanofibers at the same time;
4. The WO3 one-dimensional nanofibers is transformed to some specific crystal type and appearance by a certain heat treatment process, thereby to get W18O49 whisker.
The results showed that 800 ℃ is the optimum temperature for the formation of violet tungsten oxide whisker, and the W18O49 whisker nanorods are different in length. In addition, from the transmission electron microscopy (TEM), SEM, XRD and SAED patterns, we can observe that W18O49 whiskers are growing independently of each other with the smooth surface, with nano-level diameter and micron-length, large aspect ratio, and the is diameter mainly among 170nm-250nm, the length is mainly between 2-3μm, long diameter ratio mainly among 10-17, thus to be with some unique properties.


Ammonium Metatungstate Preparation -- Nitric Acid Neutralization Method

ammonium metatungstate powder pictureAmmonium metatungstate (AMT) is an important intermediate compound during the tungsten wet smelting process, white or yellowish crystals, which has the highest solubility in all tungsten compounds (303g/100mL under 20°C in water). There are many preparation methods of ammonium metatungstate, such as thermal decomposition, tungsten acid, electrodialysis, solvent extraction, ion exchange method, while the thermal decomposition method based on the raw material of APT is the main process for manufacturing AMT in industrial currently.
Being one class of preparation method, acid neutralization method has been focused and widely used in the industry because of its simple process and equipment. Some studies have followed on the nitric acid neutralization method, taken ammonium paratungstate (APT) as raw material to convert and generate AMT in an environment of nitric acid, which is heating a certain amount of deionized water, and slowly adding APT and dilute nitric acid solution with the ratio of 1:20 with stirring, then controlling the transformation temperature within limits to convert APT to AMT in the liquid phase and generate AMT solution, and finally get ammonium metatungstate crystal after the steps of ageing, preconcentration, concentration, crystallization, solid-liquid separation and drying. Wherein, the reaction equations of APT converts to AMT by nitric acid neutralization method is like:
(NH4)10W12O41.xH20+4HNO3= (NH4)6H2W12O40.yH20+4NH4NO3+H2O
The nitric acid in this method can be replaced by organic acids, such as formic acid, acetic acid, citric acid, lactic acid, with the advantages of moderate acidity and easy to operate; but, the expansive price of organic acids makes them hardly to be used in the mass production of AMT in industrial. However, although the nitric acid being used in the nitric acid neutralization method has the benefits of easy to get and low cost; but, because nitric acid has a strong acidity which will make the generation of tungstic acid colloid becoming easily, and introduces impurity of nitrate into AMT, thereby to decrease the converting rate and property of AMT.

Ammonium Metatungstate and Rewriting Paper

rose in rewriting paperAsk: What is the relationship between ammonium metatungstate (AMT) and rewriting paper?
Answer: Nothing direct.
Ask: Then, why you put both of them together?
Answer: Because ammonium metatungstate is the raw material for preparing tungsten dioxide (WO2), while tungsten dioxide is one of the two material of rewriting paper.
Paper wasting is one of the biggest problems we meet in environment protection currently, we know that, the raw materials of papermaking are plant fiber (such as woods, bamboo, grass), mineral fiber (asbestos, glass fiber, etc), other fiber (nylon, metal wire, etc.), and the polymer material which get from oil cracking. At present, papers used for writing, painting and packing are still manufacturing from plant fiber, which will bring huge threat to environment protection.
Recently, one research team came up with an interesting solution – the rewriting paper, which is using two materials of tungsten dioxide (WO2) and polyvinyl pyrrolidone; this rewriting paper not only can save water, energy, space, but also can reduce the emissions of greenhouse gas; in addition, this kind of rewriting paper has non-toxic effect, and has been proved to be used for the field of medicine and food. The rewriting paper is through the appearing and fading of blue to realize function of rewriting, if this material is exposed to UV light for more than 30 seconds, the color will automatically become dark blue; while, the blue will fade when exposed in the outdoor for a or two days, or heated; moreover, the addition of polyvinyl pyrrolidone can extend the duration of blue to 10 days, and increase circulation writing to 40 times.
Ammonium metatungstate is a kind of white or yellowish powder with water solubility, and the solubility can reach to 300g/100ml in the water under 20°C, an important tungsten compound in tungsten metallurgy industry. Ammonium metatungstate is mainly used for preparing tungsten oxide, such as tungsten trioxide (WO3), tungsten dioxide (WO2), blue tungsten oxide (WO2.9) and violet tungsten oxide (WO2.72), tungsten powder, tungsten based carbide; furthermore, AMT is also used in many kinds of petroleum and chemical catalysts, the main raw material of W-based catalyst for oil refineries.


Ammonium Metatungstate Preparing WO3-Fe2O3/TiO2 Composite Photocatalyst

ammonium metatungstate pictureWO3-Fe2O3/TiO2 composite photocatalyst is an inorganic material which can be used in the degradation of pollutants in the environment, the new type of photocatalyst. Traditional photocatalyst is mainly based on titanium dioxide (TiO2), which has the advantages of chemical stability, high catalytic activity, strong oxidizing power, non-toxic, low cost ect.; however, because the spectral response range of titanium dioxide is really narrow, and thus it can only utilize the ultraviolet light (wavelength less than 387nm), which has become the bottleneck and limited the application range of titanium dioxide. Therefore, the development of photocatalyst which has high activity and can utilize the visible light is of very large economic and practical value. 
Research has found that, doping metal ion is an effective way to make TiO2 showing photocatalytic activity under visible light. Generally believed that the metal ions into the TiO2 lattice can be introduced impurity levels in the forbidden band, the band gap is reduced, so that the valence band electrons after receiving a large optical excitation wavelength, the first transition to impurity energy level, by once again absorb the energy, the transition from the impurity level to the conduction band, thereby reducing the energy required by stimulated to achieve so that the spectral response range of TiO2 photocatalytic move to the visible region. 
An invention has pointed out a method to prepare WO3-Fe2O3/TiO2 composite photocatalyst, which bases on the tungsten source of ammonium metatungstate (AMT), with the steps as following:
1. Add water into the ammonium metatungstate solution according to the weight ratio of WO3: water (1:6〜7);
2. And then add ferric nitrate [Fe(NO3)3•9H2O] according to the weight ration of WO3: ferric nitrate (5〜7:1 ) to dissolve and get the impregnation liquid;
3. Add TiO2 powder, which is anatase type with BET specific surface area of 80〜150m2/g, according to the weight ration of WO3: TiO2 (1:6〜7), then dry the mixture at 100°C for 4~6 hours;
4. Calcine the mixture at 580°C〜780°C for 5 hours to finally get WO3-Fe2O3/TiO2 composite photocatalyst.
Compared with the composite materials which dose not dope with metal ions, WO3-Fe2O3/TiO2 composite photocatalyst is showing a better photocatalytic ability; at the same time, the doping of WO3 and Fe2O3 with specific lattice structure is actually modifying the TiO2 particle, thus to extended spectral response range of TiO2, and make it can be widely applied in the fields of environmental purification.


Ammonium Metatungstate Price on Nov.17th, 2016

Ammonium metatungstate price with purity over 91.40% from Chinatungsten Online is 35.50 USD/KG, by Chinatungsten FOB Xiamen, Nov.17th, 2016.

AMT image


Ammonium Metatungstate Preparing Solid Superacid

According to the classical definition, a superacid is an acid with an acidity greater than that of 100% pure sulfuric acid, which has a Hammett acidity function (H0) of −12. According to the modern definition, superacid is a medium in which the chemical potential of the proton is higher than in pure sulfuric acid. The known superacid can be divided into liquid and solid superacid according to the appearance. In petrochemistry, superacidic media are used as catalysts, especially for alkylations. Typical catalysts are sulfated oxides of titanium and zirconium or specially treated alumina or zeolites. The solid acids are used for alkylating benzene with ethylene and propylene as well as difficult acylations, e.g. of chlorobenzene.
In 1998, the presence of supported oxide solid superacid has immediately caused a wave of research in the field of catalyst, which has been reported to have three types, namely WO3, MoO3 and B2O3 oxides, with the acidity showing as the following table:
acidity table of supported oxide solid superacid
The supported oxide solid superacid (WO3/ ZrO2) which Arata firstly studied has the acidity lower than that of SO42- / MxOy-type solid superacid (SO42- / ZrO2) with H0 < -16.0 (while the H0 of WO3/ ZrO2 is lower than 14.5), but its stability in solution and reducing atmosphere and heat is better than that of SO42- / ZrO2 solid superacid; moreover, it is selectivity for some specific reactions, such as isomerization of high-carbon alkanes, is higher than that of SO42- / MxOy catalyst.
The results showed that ammonium metatungstate (AMT) can be used as a tungsten source for the preparation of supported oxide solid superacid (WO3/ ZrO2), with the preparation methods of coprecipitation and sol-gel method; both of the two methods are also called as one-step method since it is introducing WOat the same time of preparation process, the processes are:
1. Coprecipitation method: Pour the ZrOCl2 solution into a mixed solution of ammonium metatungstate and ammonia water to conduct coprecipitation, and adjust the final pH value to 9.0, then carry out filtering, washing, drying and calcination to get the final product.
2. Sol-gel method: Add the zirconium n-propoxide into the mixed solution of ethanol and nitric acid containing with ammonium metatungstate to get gelling; remove the ethanol by carbon dioxide supercritical drying method after the obtained gel is aged for 2 hours; and then dry it in vacuum for 3 hours respectively at temperature of 383 K and 523 K, and finally carry out calcination at high temperature.


Ammonium Metatungstate Preparing Ammonium Dithiotungstate

ammonium metatungstate imageAmmonium metatungstate (AMT) is an important intermediate compound in tungsten metallurgy industry, which is mainly used for manufacturing tungsten oxide, tungsten powder, tungsten wire and other tungsten compound, also, it is used in catalyst of petrochemical industry. Researches have indicated that ammonium metatungstate and ammonium sulfide solution can be used for preparing ammonium dithiotungstate under some specific environment.
There are two methods of ammonium metatungstate preparing ammonium dithiotungstate, as following:
The first method:
1. Dissolve ammonium metatungstate in the deionized water with stirring;
2. Add ammonia water and stir for 20 minutes to speed up the reaction speed under the temperature of 60°C, at this time, the pH value of reaction system may be 9;
3. Add ammonium sulfide solution and stir for 30 minutes under 60°C, then carry out vacuum filtration until the reaction is stop to remove a small amount of blue precipitation which generated during the reaction process;
4. Stand the filtrate for 24 hours under 0°C to get yellow crystal;
5. Carry out vacuum filtration and the precipitation is washed respectively with deionized water and anhydrous ethanol for three times, and finally we get the ammonium dithiotungstate crystal after drying, with the yield of 45%.
The second method:
1. Place the 5g of industrial grade ammonium tungstate which contains 83% of tungsten trioxide into conical beaker, and add 8 wt% of ammonium sulfide solution 35ml slowly, at this time the color of the solution will slowly turns from blue to light yellow;
2. Stir for 30 minute at room temperature after all the ammonium sulfide solution is poured into the conical beaker, and then stand the reactant solution for 12 hours to generate yellow crystal;
3. Precipitate, and wash the precipitation respectively with deionized water and anhydrous ethanol for three times, dry at room temperature in vacuum environment to finally get ammonium dithiotungstate crystal, the yield is 93% in accordance with tungsten content.
Ammonium dithiotungstate [(NH4)2WO2S2] is an important class of thiometal ammonium salt, and the decomposition products include {WOS2}, vulcanization intermediate of tungsten oxide. Studies have found that the thermal decomposition of ammonium dithiotungstate crystal under the atmosphere of hydrogen is mainly occurred among 160~450℃, which firstly transfers to {WOS2} and then to tungsten disulfide.




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