2022年3月17日星期四

Submicron Tungsten Powder Manufacturing Process

Because the grain uniformity of hard alloy mainly depends on the particle size distribution of WC powder, the particle size distribution of WC powder is hereditary in tungsten powder. Therefore, the preparation technology of tungsten powder and tungsten carbide powder by submicron size and narrow size is very important. The key technical indexes of fine grain, submicron, ultrafine or nanocrystalline cemented carbide for WC powder are the purity, particle size and particle size distribution, and it is clearly stipulated that there is no type of type III coarse in WC powder.

submicron tungsten powder image

Some scholars have adopted the following technical schemes to prepare submicron tungsten powder or tungsten carbide powder, including the following steps:

(1) Ammonium paratungstate (APT) is pyrolyzed to ammonium metatungstate (AMT) and dissolved in ammonia solution or deionized water and filtered to obtain ammonium tungstate solution, or using ammonium paratungstate (APT) production line after ion exchange or crystallization liquid as raw material.

(2) In the ammonium tungstate solution, the dispersant solution and the dispersing agent are added simultaneously and stirred evenly.

(3) Spray drying equipment was used for rapid crystallization drying to obtain fine particle hollow thin-walled spherical ammonium tungstate crystals.

(4) In the presence of hydrogen, nitrogen, nitrogen hydrogen mixture or air, the precursor of tungsten oxide, yellow tungsten, blue tungsten or violet tungsten was pyrolyzed at 500~700°C.

(5) Reduction of submicron and narrow particle size distribution of tungsten powder by hydrogen gas.

(6) In situ forming submicron and narrow particle size tungsten carbide powders by carbon mixing, ball milling and carbonization.

The results show that the average particle size of tungsten powder and tungsten carbide powder prepared by these methods is submicron grade, and has a narrow size distribution range, and it is convenient to prepare the tungsten powder and tungsten carbide powder with the purity of 4N or 5N in submicron size distribution.

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Tungsten Oxide Nanorod Regulation Method

At present, the general method of preparing tungsten oxide is liquid phase method. In the process of preparing tungstic acid in liquid phase, the tungstic acid particles are automatically coalesced because of the unstable thermodynamics. In addition, the free water molecules on the surface of the particles form hydrogen bonds with the free hydroxyl groups, and then form a hydrogen chain with the water molecules on the surface of the adjacent particles to produce a bridging action.

tungsten oxide nanorod image

Some scholars have proposed a method of adjusting the length of tungsten oxide nanorod by oxygen, with a surface functionalized carbon nanotube with a diameter of 2-200 nm and a layer of 1-30 layers as the carrier, tungsten metal salt as the tungsten source, the addition of hydrochloric acid in the carbon nanorod glycol suspension and tungsten metal salt system, and the principle of making the weak acid with strong acid to make tungstate granules. It directly forms on the surface of the carbon nanotubes and grows along the surface of the carbon nanotubes to form tungstate / carbon nanotube rod like composites, which mainly include the following steps:

(1) The 1-50 mg diameter of 2-200 nm and 1-30 layers of carbon nanotubes were soaked in strong acid (one or several mixtures in HCl, nitric acid, sulfuric acid), refluxing, filtering, drying, and then being placed in 10-500 mL ethylene glycol at 100-140°C. The ultrasonic dispersion of 8-24h. A uniform carbon nanotube glycol suspension was obtained.

(2) Tungsten metal salt is completely dissolved in solvent (deionized water, ethylene glycol or mixture of both), and a tungsten metal salt solution with a concentration of 0.01-0.5 mol /L is obtained.

(3) The carbon nanoscale glycol suspension is added to the tungsten metal salt solution and is mixed uniformly under the action of mechanical stirring (constant temperature magnetic agitator or ultrasonic oscillator), in which the molar ratio of tungsten metal salt and carbon nanotube is 1:1-40:1, and then added to them (using micro injector, drip tube or hydrochloric acid atomization, etc. The concentration of 1-20 mL was 5-12 mol/L hydrochloric acid, and the pH value of the solution was adjusted to 1-5; 5-48h was reflued under the constant temperature oil bath at 80-140°C, then vacuum filtration, washing and drying were carried out. The drying temperature was 100-150°C, and the drying time was 3-24h, and the tungstate / carbon nanotube rod like complex was obtained.

(4) The composite is spread in the corundum reaction boat and together with the corundum reaction boat together with the horizontal quartz reaction tube in a tubular resistance furnace. When the sample is roasted, different proportions of oxygen and nitrogen are put into the horizontal quartz reaction tube, the flow rate is 30-500 mL/min, and the oxygen content is 0-100% and the heat treatment temperature is at the temperature. At 400-800°C, the heat treatment time is 0.5-12h. When cooled to room temperature, the tungsten oxide nanorods with a length of 20-800nm can be obtained.

With carbon nanotubes as a template, tungstic acid / carbon nanotube nanorods were prepared by liquid phase method. After that, the tungstate / carbon nanotube nanorods were placed in the high temperature reaction zone of the tube furnace. In the process of dehydration of tungstate precursor and conversion of tungsten oxide into the tungsten oxide, the oxidation atmosphere was entered to make the carbon nanotubes burning and generating two oxygen. With the disappearance of carbon nanotubes and the disappearance of the carbon nanotubes, the tungstic acid nanorods break, which interferes with the growth of tungsten oxide along the surface of the tube bundle of carbon nanotubes. Therefore, the preparation of the process is simple and it is easy to popularize.

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Tailings Recycle Wolframite Optimization Design

The wolframite is brittle and easy to smash and produce fine slime, and most of them have fine embedded granularity and more useful metal minerals. The gangue minerals are closely related to tungsten minerals, and the separation is difficult. Many fine grain tungsten can not be recycled. Then it forms tailings.

tailings recycle wolframite image

Some scholars have proposed a comprehensive mineral processing scheme for recycling wolframite from tailings, including the following steps:

(1) Centrifuge gravity separation and tail preconcentration, after the wolframite tailings are adjusted to pulp, the centrifugal concentrator is used to preconcentration and discarding tailings, and the concentrate and tailings of centrifugal gravity separation are obtained.

(2) The concentrate is floated by the first coarse second sweep process, and the flotation tailings and sulfide ore concentrate are obtained.

(3) Magnetic separation of flotation tailings by magnetic separation is carried out, and magnetic separation concentrate and magnetic separation tailings are obtained.

(4) The magnetic separation tailings were enriched by high gradient magnetic separation to obtain wolframite coarse concentrate and high gradient magnetic separation tailings.

(5) Gravity separation of high gradient magnetic separation concentrate was carried out by shaking table separation, and coarse grained tungsten concentrate and grit tailings were obtained.

(6) The floatation tailings were concentrated to 35% ~ 38%, and the flotation flowsheet was made by using coarse crude and fine second sweep.

(7) The wolframite concentrate from gravity separation and flotation to the wolframite concentrate II are combined into the final wolframite concentrate.

In accordance with the characteristics of the separation of coarse fine-grained wolframite, the process has been optimized by the process of "centrifugal enrichment throwing tail - sulphide flotation - magnetic separation iron removal - high gradient magnetic separation - shaking bed gravity separation - black tungsten flotation". The index of mineral separation. Compared with the conventional ore dressing method, the selected ore volume is less than 60% to 65%, and the selection grade is improved and the ore dressing cost is reduced. It is a kind of beneficiation method suitable for the high efficiency recovery of the wolframite from the tailings.

If you have any inquiry of tungsten, please feel free to contact us:
Tel.: +86 592 5129696/+86 592 5129595
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High Purity Tungsten Reduction Technology

High purity tungsten, which means more than 99.995% of the purity of tungsten, is a key material for the formation of the diffusion barrier in the process of mass integrated circuit and PVD coating. High purity tungsten powder has become an indispensable raw material for the microelectronics industry.

high purity tungsten iamge

Some scholars have put forward the preparation method of high purity tungsten powder for scale integrated circuit, which aims to make the production of high purity tungsten powder with purity not less than 99.999%, and to ensure the controllability of the particle size and morphology of tungsten powder. The process is as follows:

(1) Using the industrial 0 grade ammonium parotungstate in GB/T10116-2007 as raw material, the three band rotary tube air furnace is calcined to form yellow tungsten. The temperature of the three zone is 550 + 5°C, 600 + 5°C, 600 + 5°C.  The concentration of yellow tungsten is dissolved in 10% ammonia water at 50-60°C, the initial concentration of solution is 200-300g/L, and the dissolution is about 4-8h, and then the ammonium tungstate solution is formed.

(2) 10μm and1μm polypropylene filters were selected for two stage filtration of Fe (OH)3, Ca (OH)2 and other insoluble substances in ammonium tungstate solution.

(3) The filtered ammonium tungstate solution is evaporated and crystallized at 90-120°C in the enamel reaction kettle. The stirring frequency is 50Hz~80Hz, and the crystal mother liquid density reaches 1.08-1.1g/cm3 and then stops the crystallization. At this time the crystallization rate is 60-70%.

(4) A centrifuge equipped with polypropylene filter is used to separate the wet ammonium metatungstate from the centrifuge, and ammonium metatungstate is cleaned by deionized water to the washing liquid to be transparent and then sent into the hot air circulation oven at 100~120°C for 18 ~ 24h, and the purified ammonium metatungstate after purification is obtained.

(5) The high pure ammonium metatungstate was reduced by a tube reduction furnace with high purity quartz as furnace tube. Hydrogen flux was 60-100L/min, hydrogen dew point was -60°C, reduction temperature was 800-900°C, reduction time 1.5-2h, and the loading thickness was 10-30mm.

The purity of high purity ammonium metatungstate and high purity tungsten powder after purification is detected. The total content of impurities is less than 10ppm, and the purity is more than 99.999%. It can meet the requirements of the large-scale integrated circuit and semiconductor chip packaging industry.

If you have any inquiry of tungsten, please feel free to contact us:
Tel.: +86 592 5129696/+86 592 5129595
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Tungsten Ores Directly Produces Coarse-Grain Tungsten Carbide

At present, 50 to 60% of the world's tungsten is used for the manufacture of tungsten carbide. Among them, rock drills in mining tools, ...