2022年2月16日星期三

Ammonium Paratungstate Purification from Complex Scheelite Ore

Tungsten ore is mainly scheelite. The world's scheelite accounts for more than 2/3 of total, and China accounts for 72.1%. Some scholars have improved the method of using ammonium sulphate to decompose scheelite to prepare ammonium partrungstate.

ammonium paratungstate image

(1) Tungsten containing sulphuric acid and phosphorus mixed acid solution, wherein the concentration of tungsten trioxide is 25-150g/L, the concentration of phosphoric acid is 10 ~ 200g/L, and the concentration of sulphuric acid is 1.5 ~ 2.5mol/L.

(2) The obtained tungsten containing mixed solution of sulphuric acid and phosphoric acid was mixed with oil to extract the two phase volume ratio of oil phase: water phase = 3:1-1:3, and the loading organic phase was obtained.

(3) The obtained load organic phase was extracted by distilling water with volume ratio as oil phase: water phase = 3:1-10:1, and the stripping solution was obtained.

(4) Ammonia was added to the stripping solution to control the free ammonia in the solution at 1-2mol/L and the ammonium tungstate solution was obtained.

(5) Ammonium paratungstate was obtained from ammonium tungstate solution by conventional phosphorus removal and evaporation crystallization.

The improved method can be used as an extractant by increasing the acidity of the material and the alcohols with low concentration. Because the alcohol extractant is a weak neutral extractant, the extractants of iron, calcium, manganese, sulfate and phosphate are not extracted, so the high content of impurities can be processed. A high concentration of phosphotungstic acid solution is obtained by using water as a stripping agent, and then ammonia is added to avoid the problem that the organic phase emulsification can be easily caused by the direct contact between the alkaline reflux and the load organic phase in the traditional process, and the blank organic phase after the extraction of water can be directly extracted without the need of the recycling process of the organic phase. The organic phase after stripping does not have the problem of introducing impurities into the original liquid, the process is short, the manufacturing cost is low, the product yield is high, and the green is pollution-free, and it can be industrialized on a large scale.


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Tungsten Tin Ore Dressing Guide

Tungsten tin ore is a brittle mineral, which is extremely easy to be milled and polished during mineral processing, causing inconvenience to mineral processing.

tungsten tin ore dressing image

Some scholars have proposed a method of mineral processing for tungsten tin ores. The content of Sn in the mineral materials is 0.083 to 0.32% and the content of WO3 is 0.035 ~ 0.46%. The steps and the pharmaceutical system are as follows:

(1) The tungsten tin minerals are removed to some monomers and the jigging branch separation technology is used to separate the minerals into coarse heavy minerals and fine grain aggregates, and then the coarse and fine grain aggregate minerals are reselected.

(2) Coarse and heavy minerals are selected by spiral chute, and the coarse concentrate and spiral chute tailings are obtained, and the spiral chute coarse concentrate rocking bed is selected. The coarse tungsten and tin concentrate 1, the rocking bed middle mine 1 and the rocking tailings tailings 1 are obtained.

(3) The fine aggregate mineral is recycled by shaking table and coarse and fine process. Tungsten tin concentrate 2, rocking bed middling 2 and shaking table tailings 2 are obtained.

(4) The spiral chute tailings, the rocking bed middling 1 and the rocking bed tailings 1 and the shaking table middling 2 are combined to regrinding, and the tungsten tin coarse concentrate 3 is obtained.

(5) Tungsten tin coarse concentrate 1, tungsten tin coarse concentrate 2 and tungsten tin concentrate 3 are combined, the sulphuric acid solution of 1000 ~ 2000g/t with mass concentration of 5%, 100 ~ 300g/t of copper sulfate solution with mass concentration, 5% of Ding Ji xanthate solution of mass concentration 1% and 30 to 50g/t of 2# oil raw liquid are used to remove sulfide ore and obtain tungsten tin mixture.

(6) Tungsten tin mixed concentrate was selected under the condition of magnetic field strength 10000 ~ 13500Gs wet strong magnetic separation. Tungsten tin separation was selected under the condition of 8000 ~ 10000Gs wet strong magnetic separation, and tungsten concentrate and tin concentrate were obtained respectively.

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Tungsten Carbide Nitride Conversion Method

Compared with ordinary powder, WC nano powder has advantages of small particle size, large surface area and high reactive activity. It has remarkable advantages in chemical synthesis, fuel cell and other fields. Therefore, it is of great significance to study a method for preparing high-quality single phase tungsten carbide nano powders.

tungsten carbide nitride conversion method image

Some scholars have provided a method for preparing tungsten carbide nitride nanopowders based on nitride conversion method, including the following steps:

10mmol deionized AMT and 50mmol citric acid were dissolved in 100ml deionized water to get clarified mixed solution; complex reaction was carried out at 70°C for 5 hours; filtration and drying for 12 hours at 120°C, the precursor of tungsten oxide was obtained. The WO3 powder was obtained by calcining at 650°C for 3 hours.

The WO3 powder is placed in a tube furnace and nitrided through ammonia gas. The flow rate of ammonia is controlled at 3L/min, the temperature is 700°C, the heating rate is 2°C/min, and the heat preservation is 2 hours, and the W2N powder is obtained.

10 g of tungsten nitride powder is mixed with 0.62g carbon black, with ethanol as solvent and tungsten carbide ball as ball milling medium, mixed for 24 hours on roll ball mill, rotary evaporation drying, W2N/C mixed powder, W2N/C mixed powder in graphite crucible, and heated to 1100°C under the condition of pressure below 200Pa in carbon tube furnace. The WC nanopowders were obtained at 3°C and the average particle size was 120nm.

Using nitrides conversion method, not only is the raw material cheap and easy to be obtained, but also greatly reduces the synthesis temperature, reduces the cost and energy consumption of raw materials, and the preparation process is simple, practical, controllable and easy to realize scale production.

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Microwave Ball Milling Nano Tungsten Powder

Tungsten powder is the main raw material for the processing of powder metallurgy tungsten products and tungsten alloys. With the rapid development of the microelectronics industry, energy, aviation, machinery industry and other fields, the demand of ultrafine tungsten powder is increasing day by day.

microwave ball milling nano tungsten powder image

At present, the main process methods of nano tungsten powder include hydrogen reduction, sol-gel, high energy ball milling, freeze-drying, molten salt electrolysis, self propagating high temperature reduction and spray drying fluidized bed. In order to solve the problem of preparing ultrafine tungsten powder, scholars have provided a processing technology for nanometer tungsten powder.

(1) Ceramic ball mill can be put into a microwave oven by placing a metal powder, a 10-20 micron blue tungsten or yellow tungsten powder, a ceramic ball with a particle size of 0.5 millimeters and the ratio of deionized water to a ceramic ball mill in a proportion of 1:5.

(2) The motor and microwave oven that start the ceramic ball can make tungsten trioxide reduce to tungsten oxide at 500~700°C.

(3) At 700~900°C, tungsten oxide is reduced to tungsten powder. Reduction is often carried out in tubular electric furnace or rotary furnace.

(4) The tungsten based alloy oxide mixed powder was reduced and the tungsten carbon reduction method was used. The reduction temperature was higher than 1050°C, the atmosphere was hydrogen atmosphere and hydrogen, and the ultrafine tungsten based alloy powder less than 0.05μm was obtained.

The tungsten based alloy oxide was prepared by microwave mechanical ball milling, and then the tungsten based alloy oxide was reduced. The nanometer superfine tungsten based alloy powder was obtained. It not only greatly reduced the high temperature of nano oxide powder, but also successfully solved the serious pollution in dry ball milling and the easy agglomeration of the powder.

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2022年2月9日星期三

High Purity Phosphotungstic Acid Preparation

Heteropoly acid is one of the most active catalysts in acid catalytic reaction and redox reaction. Phosphotungstic acid H3PW12O40•nH2O is the most widely used in heteropoly acid. The purity of phosphotungstic acid directly affects the conversion rate of the catalytic system. Therefore, the preparation of high purity phosphotungstic acid is especially important.

high purity phosphotungstic acid image

Some scholars have proposed a purification method for phosphotungstic acid crystals.

(1) The crystal of industrial phosphotungstic acid is dissolved in water and the inorganic acid is added to the solution of phosphotungstic acid containing inorganic acid. The concentration of tungsten trioxide is 50-150g/L, and the volume molar concentration of the inorganic acid is 0.5 ~ 6mol/L.

(2) In the solution of phosphotungstic acid containing inorganic acids, the oil phase organic alcohol extractant was extracted with the volume concentration of 5-50%, and the volume ratio of the two phase was oil phase = 1:1-10:1, and the organic phase loaded with tungsten was obtained.

(3) The organic phase containing tungsten is extracted by distilling water with volume ratio as oil phase: water phase = 3:1-10:1, and the stripping solution is obtained.

(4) High purity phosphotungstic acid crystals can be obtained by heating evaporating crystals or spray drying, and the yield is more than 95.4%.

The new process is short, the preparation cost is low, the environment is not polluted, and it is easier for large-scale industrial production.

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Ammonium Paratungstate Purification from Complex Scheelite Ore

Tungsten ore is mainly scheelite. The world's scheelite accounts for more than 2/3 of total, and China accounts for 72.1%. Some scholars have improved the method of using ammonium sulphate to decompose scheelite to prepare ammonium partrungstate.

ammonium paratungstate image

(1) Tungsten containing sulphuric acid and phosphorus mixed acid solution, wherein the concentration of tungsten trioxide is 25-150g/L, the concentration of phosphoric acid is 10 ~ 200g/L, and the concentration of sulphuric acid is 1.5 ~ 2.5mol/L.

(2) The obtained tungsten containing mixed solution of sulphuric acid and phosphoric acid was mixed with oil to extract the two phase volume ratio of oil phase: water phase = 3:1-1:3, and the loading organic phase was obtained.

(3) The obtained load organic phase was extracted by distilling water with volume ratio as oil phase: water phase = 3:1-10:1, and the stripping solution was obtained.

(4) Ammonia was added to the stripping solution to control the free ammonia in the solution at 1-2mol/L and the ammonium tungstate solution was obtained.

(5) Ammonium paratungstate was obtained from ammonium tungstate solution by conventional phosphorus removal and evaporation crystallization.

The improved method can be used as an extractant by increasing the acidity of the material and the alcohols with low concentration. Because the alcohol extractant is a weak neutral extractant, the extractants of iron, calcium, manganese, sulfate and phosphate are not extracted, so the high content of impurities can be processed. A high concentration of phosphotungstic acid solution is obtained by using water as a stripping agent, and then ammonia is added to avoid the problem that the organic phase emulsification can be easily caused by the direct contact between the alkaline reflux and the load organic phase in the traditional process, and the blank organic phase after the extraction of water can be directly extracted without the need of the recycling process of the organic phase. The organic phase after stripping does not have the problem of introducing impurities into the original liquid, the process is short, the manufacturing cost is low, the product yield is high, and the green is pollution-free, and it can be industrialized on a large scale.

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Carbon Nanotube Supported Platinum Electrocatalysts Coated with Titanium Tungsten Oxide

Carbon supported platinum catalysts are regarded as ideal fuel cell catalysts. However, the interaction between the carbon carrier and platinum is weak, the carbon carrier is easy to corrode. The nano platinum particles can easily migrate on the surface of the carrier, grow up and even lose, which leads to the degradation of the catalyst activity, and eventually leads to the shorter service life of the fuel cell.

titanium tungsten oxide image

In view of the disadvantages of poor stability and activity of existing fuel cell cathode catalysts, some scholars have used sol-gel method to evenly coat titanium tungsten oxide on the surface of carbon nanotubes, and then heat treatment to form titanium tungsten with high crystallinity and high electrical conductivity. The oxide coating, and thus the platinum catalyst, its main process is as follows:

(1) 1 gram of carbon nanotubes, adding 160 ml of concentrated nitric acid, reheating for 3 hours, cooling, diluted by ultra pure water, filtering out the supernatant, centrifuging and washing, drying, and grinding the purified carbon nanotubes.

(2) The mass ratio of 1: 2.5: 1 was called the purification of carbon nanotubes, butyl titanate and sodium tungstate, respectively, according to the volume ratio of 1: 0.2: 0.008, ethanol, ammonia and hydrogen peroxide respectively, of which the concentration of ammonia water was 28%, the mass concentration of the hydrogen peroxide solution was 30%, and the carbon nanotubes were dispersed in the anhydrous ethanol, and the carbon nanotubes were added to the anhydrous ethanol. The dispersion of n-butyl titanate in carbon nanotubes was obtained by ultrasonic stirring for 40 minutes. Sodium tungstate was dissolved in the ammonia water and added to the hydrogen peroxide solution. The ultrasonic oscillation was 15 minutes, and sodium tungstate solution was obtained. The sodium tungstate solution was slowly dripped into the above carbon nanotube titanate dispersion solution. After stirring reaction for 48 hours, the drying was dried. The amorphous titanium tungsten oxide coated carbon nanotube was coated, and the amorphous titanium tungsten oxide coated carbon nanotube was calcined at 650 C in nitrogen or argon atmosphere for 2 hours, cooling to room temperature, washing two times and washing for two times, drying and grinding to obtain the titanium tungsten oxide coated carbon nanotube.

(3) The mass ratio of 1: 1.1: 0.76: 10 was called titanium tungsten oxide coated carbon nanotubes, chloroplatinated acid, citric acid three sodium and sodium borohydride, and the obtained titanium tungsten oxide coated carbon nanotubes were dispersed in ethylene glycol, and ultrasonic stirring for 40 minutes, forming a mass concentration of 3 mg / ml of titanium tungsten oxide coated carbon nanotube dispersions. Then chloroplatin was slowly added to the titanium tungsten oxide coated carbon nanotube dispersions, stirring for 6 hours, and then adding sodium citrate three for 4 hours. Then the sodium hydroxide solution with mass concentration of 5% was adjusted to pH value to 9, and then slowly added to sodium borohydride and stirring for 4 hours, and then centrifuged, washed, washed, vacuum and vacuum. Titanium and tungsten oxide coated carbon nanotube supported platinum electrocatalysts were obtained by drying and grinding.

Titanium tungsten oxide coated carbon nanotube platinum electrocatalysts can be applied to fuel cells with proton exchange membranes as electrolytes, such as hydrogen oxygen proton exchange membrane fuel cells, direct methanol fuel cells and other gas electrodes. It can also be used in various spacecrafts, portable electronic devices, such as cameras, notebook computers, electric toys, etc.

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Tungsten Doped Vanadium Dioxide

Tungsten doping is a promising and effective way to reduce the phase transition temperature of vanadium didioxide. Doping can improve the electrical properties of vanadium dididioxide thin films, reduce the square resistance of the films, and improve the resistance temperature coefficient of the films. Common methods of doping include evaporation, ion implantation, sol-gel and magnetron sputtering.

vanadium dioxide image

Researchers have developed a method for preparing tungsten doped vanadium dioxide thin films, including the following steps:

(1) The substrate is cleaned, and the cleaned substrate is put into the high real chamber.

(2) Preparation of VOx/W/VOx composite film: The argon, metal vanadium target and tungsten metal target are placed in the vacuum chamber, and the metal vanadium target and tungsten target surface are pre sputtered by the sputtering power source of vanadium target and the tungsten target sputtering power, respectively. When the vanadium target is sputter target, the tungsten target is shielded with tungsten target and sputter tungsten targets. Vanadium target is covered with vanadium target baffle. The oxygen is passed into the vacuum chamber, the substrate baffle is opened, the tungsten target baffle is closed, the vanadium target sputtering power is opened, and the bottom dioxide vanadium dioxide (VOx) film is deposited. After the deposition of the vanadium dioxide film at the bottom, the oxygen is closed, the sputtering power supply and the vanadium target baffle are closed, the tungsten target sputtering power and the tungsten target baffle are opened, and the middle layer tungsten (W) thin film is deposited. After the tungsten thin film is deposited, the tungsten target sputtering power and the tungsten target baffle are closed, the oxygen is rejoined, the vanadium target sputtering power and the vanadium target baffle are opened, and the upper layer of vanadium dioxide (VOx) film is deposited.

(3) The deposited VOx/W/VOx composite films were annealed in situ. After the VOx/W/VOx composite film was deposited, the argon and oxygen were closed and the vacuum chamber was restored to high vacuum. The oxygen was added to the substrate and the substrate temperature was raised. After the interlayer oxygen diffusion between the VOx/W/VOx composite films is sufficient, the oxygen flowmeter is closed, and the vanadium doped vanadium dioxide film is cooled to room temperature in a high vacuum environment. The improved technology can overcome the traditional magnetron sputtering method to prepare the tungsten dioxide doped tungsten dioxide thin film in the process of double target co sputtering. The sputtering process can only prepare the doped thin film, and the sputtering process is stable and compatible with the micromechanical electronic system.

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Lithium Ion Battery Used Nano Tungstic Acid Price on SEPT.16, 2022

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