KR100257478B1 - Method for forming a tungsten powder having a high degree of purity from (5(nh4)2o 12wo3 5h2o) by self-propargating high-temperature synthesis - Google Patents

Abstract

PURPOSE: A method is provided to manufacture high purity tungsten (W) by leaching tungsten (W)-magnesium oxide (MgO) composite powder obtained as a byproduct of the reduction using about 20% hydrochloric acid (HCl) after reducing a raw material powder of ammonium paratungstate (5(NH4)2O·12WO3·5H2O) using magnesium (Mg) powder as a reductant in the self-propagating high temperature synthesis. CONSTITUTION: The method for manufacturing high purity tungsten powder comprises the steps of mixing ammonium paratungstate and magnesium in a mole ratio of 1:35; forming the formed mixture into a pellet by applying a forming pressure of 4 to 41 tons to the mixture; charging the pellet into a self-propagating high temperature synthesizing reactor under an inert gas atmosphere; burning the pellet in the self-propagating high temperature synthesizing reactor; discharging the manufactured burned product from the self-propagating high temperature synthesizing reactor; leaching the burned product using hydrochloric acid (HCl) which is diluted to 20%; filtering the leached exudation; and washing the filtered tungsten (W) powder.

Description

Process for producing high purity tungsten powder from ammonium paratungstate using self-burning reaction

The present invention uses a self-propagating High-temperature Synthesis (hereinafter referred to as SHS) ammonium paratungstate (5 (NH ₄ ) ₂ O. 12WO ₃ · 5H ₂ O) and magnesium (Mg) And tungsten (W) powder from the above, and in particular, ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ · 5H ₂ O) and magnesium (Mg) in a constant molar ratio and using SHS The present invention relates to a method for producing high purity tungsten (W) powder through a leaching process after preparing a mixed powder of tungsten (W) and magnesium oxide (Mg).

Generally, tungsten (W) is an off-white, face-centered cubic structure of metal with a specific gravity of 19.3 and a melting point of 3410 ± 20 ° C. Tungsten (W) is stable at room temperature and poor in processability, but it is oxidized when it is in contact with oxygen or water vapor at high temperatures, and it forms carbide when it is in contact with powdered carbon, carbon monoxide, carbon dioxide, etc., and when it is in contact with a halogen compound, it makes a halogen compound. Tungsten (W) is not eroded by sulfuric acid and hydrochloric acid at room temperature, but is gradually soluble in thermal nitric acid and aqua regia and severely eroded when oxygen coexists in molten alkali. Moreover, since specific heat is extremely small (0.32ca1 / g, 20 degreeC), even if it heats only a little, it will become high temperature.

Tungsten (W) having such physical properties may be hot worked in a protective atmosphere at a temperature of 100 ° C. to 1,000 ° C. or more. Therefore, it is processed into an ultrafine wire and is widely used for the filament or the electron tube of an incandescent electric bulb and a vacuum tube. In addition, since hardness and strength are maintained even at a high temperature, they are used for electrical contacts, welding electrodes, precision mechanical parts, and the like. In addition, tungsten (W) has been spotlighted as an aviation material such as nozzle materials for space rockets due to its excellent high temperature characteristics such as thermal shock resistance, high temperature strength, and wear resistance.

To date, tungsten (W) has a high melting point and is difficult to dissolve so that ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) is obtained from ore, and then tungsten oxide (WO ₃ ) is produced. Tungsten (W) was produced by heating to a temperature of about 1,200 ℃ or more in an electric furnace and hydrogen reduction. However, in the case of producing tungsten (W) through such a process, not only the manufacturing process is complicated but also a large amount of energy must be supplied, so that there is a drawback in that a large burden must be taken economically.

The present invention has been made to solve the conventional problems as described above, an object of the present invention by using magnesium (Mg) powder as a reducing agent in the self-combustion reaction of the raw material powder of ammonium paratungstate (5 (NH ₄ )) _{2 O · 12WO 3 · 5H 2} O) , tungsten (W) obtained as a by-product was reduced - by a magnesium oxide (MgO) composite powder leaching using hydrochloric acid (HCl) in about 20% of high-purity tungsten (W) It is to provide a method for producing a powder.

1 is a manufacturing process chart of the high purity tungsten (W) powder according to the present invention.

2 is a diagram schematically showing the configuration of a self-burning reactor used to carry out the present invention.

3 is a powder in which ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) and magnesium (Mg) are mixed in a molar ratio of 1: (30-40) according to a preferred embodiment of the present invention. Is a graph showing the X-ray diffraction results of the reaction product obtained by the self-combustion reaction. And

4 is a powder in which ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) and magnesium (Mg) are mixed in a molar ratio of 1: (30-40) according to a preferred embodiment of the present invention. Is a graph showing the results of X-ray diffraction after leaching the reaction product obtained by the self combustion reaction.

* Explanation of symbols for main parts of the drawings

10: preheat 12: green pellets

14: Thermocouple 16: Data Collector

20 computer 22 tungsten (W) filament

24: power supply 26: heat-resistant glass

28 vacuum pump 30 inert gas supply source

32: vent 34: cooling device

36: vacuum instrument panel 100: self-burning reactor

102: reactor chamber

In order to achieve the above object, the present invention, the step of mixing the ammonium paratungstate and magnesium in a constant ratio (S1);

Molding the mixture formed in the step (S1) into pellets (S2);

Charging said pellets into a self-combustion reactor (S3);

Combusting the pellets in the self-burning reactor (S4);

Taking out the combustion product made in the step (S4) from the self-combustion reactor (S5);

Leaching the combustion product (S6);

Filtering the leachate leaching in step S6 (S7); And

It provides a method for producing high purity tungsten powder comprising the step (S8) of washing the tungsten (W) powder filtered in the step (S7).

The ammonium paratungstate and magnesium are represented by the following reaction formula

5 (NH ₄ ) ₂ O. 12WO ₃ .5H ₂ O + 36Mg → 12W + 36MgO to mix.

Preferably, the mixing ratio of the ammonium paratungstate (5 (NH ₄ ) ₂ O. 12WO ₃ .5H ₂ O) and the magnesium (Mg) is 1: (30 to 40).

Preferably, the ammonium paratungstate (5 (NH ₄ ) ₂ O. 12WO ₃ .5H ₂ O) has a particle size through 100 mesh and a purity of at least 99.74%.

The self-combustion reactor is maintained at atmospheric pressure, under vacuum or below argon (Ar) gas.

As mentioned above, in the method for producing high purity tungsten (W) powder according to the present invention, ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) is reduced and then obtained as a by-product. A tungsten (W) -magnesium oxide (MgO) composite powder is leached with about 20% hydrochloric acid (HCl) to prepare a high purity tungsten (W) powder.

Hereinafter, a process of manufacturing high purity tungsten (W) powder according to the present invention with reference to the accompanying drawings in more detail.

First, FIG. 2 is a diagram schematically showing the configuration of a self-burning reactor used to carry out the present invention. Referring to FIG. 2, the self-burning reactor 100 consists mainly of the reactor chamber 102 and its peripheral devices. The self-burning reactor 100 may have any structure as long as it can create a vacuum or inert gas atmosphere in the reactor chamber 102 and ignite the specimen located in the reactor chamber 102.

The preheating furnace 10 is located at the center inside the reactor chamber 102 of the self-combustion reactor 100. Preferably, the preheating furnace 10 has a cylindrical shape having a diameter of 30 cm and a length of 40 cm. In the preheater 10 is placed a green pellet 12 composed of ammonium paratungstate (5 (NH ₄ ) ₂ O. 12WO ₃ .5H ₂ O) and magnesium (Mg). One side of the preheating furnace 10 is equipped with a thermocouple 14 for measuring the temperature of the green pellet 12 to be burned in the preheating furnace 10. Thermocouple 14 is electrically connected to computer 20 via data collector 16.

Within the reactor chamber 102, tungsten filaments 22 for igniting the green pellets 12 located in the preheater 10 are located just above the preheater 10. Tungsten filament 22 receives current from a power supply 24 located outside the reactor chamber 102. On one side wall of the reactor chamber 102 is a heat-resistant glass 26 of a disc shape that can be opened and closed. The heat-resistant glass 26 performs the inlet and outlet of the green pellet 12 while opening and closing as needed, and allows the operator to check the combustion state of the green pellet 12 with the naked eye through the heat-resistant glass 26. .

At the bottom of the reactor chamber 102 is connected a vacuum hose 29 for establishing a vacuum in the reactor chamber 102. The vacuum hose 29 extends to a vacuum pump 28 located outside the reactor chamber 102. The vacuum pump 28 draws air in the reactor chamber 102 as needed to create a vacuum. In addition, an inert gas supply hose 31 for introducing an inert gas into the reactor chamber 102 is connected to a lower end of the reactor chamber 102. The inert gas supply hose 31 extends to an inert gas supply source 30 located outside the reactor chamber 102. Inert gas source 30 provides inert gas, such as hydrogen (H ₂ ) or argon (Ar), into reactor chamber 102 as needed. Alternatively, the reactor chamber 102 may be maintained under atmospheric pressure.

In addition, the vent 32 formed on one side of the lower end of the reactor chamber 102 maintains a constant pressure in the reactor chamber 102 or discharges the pressure in the reactor chamber 102 to the outside when the heat-resistant glass 26 is opened. Let's do it. Cooling devices 34 for maintaining a constant temperature in the reactor chamber 102 are installed in the upper and lower portions of the reactor chamber 102. Above the outer side of the reactor chamber 102, a vacuum instrument panel 36 is provided for notifying the vacuum state formed in the reactor chamber 102.

1 is a manufacturing process chart of the high purity tungsten (W) powder according to the present invention. A process for producing high purity tungsten (W) powder using the self-burning reactor 100 having the configuration as described above with reference to FIGS. 1 and 2 will be described.

In the present invention, ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ · 5H ₂ O) and magnesium (Mg) are mixed in a constant molar ratio to obtain tungsten (W) and magnesium oxide (MgO) by SHS. It is a method of obtaining high purity tungsten (W) by removing magnesium oxide (MgO) by leaching it with about 20% hydrochloric acid (HCl). In general, the SHS used in the present invention is a self-combustion reaction method in which a chemical reaction between a solid and a solid is an exothermic reaction and synthesizes a material using its own heat of chemical reaction after ignition of the material without supplying energy from the outside.

The raw material powders used in the present invention include ammonium paratungstate (5 (NH ₄ ) ₂ O · 12WO ₃ · 5H ₂ O) having a particle size passed through 100 mesh and a purity having a particle size of 44 μm or less. 99.5% of magnesium (Mg) is employed. At this time, the purity of the raw powder of ammonium paratungstate (5 (NH ₄ ) ₂ O. 12WO ₃ · 5H ₂ O) is closely related to the purity of the high-purity tungsten (W) powder to be obtained in the present invention. That is, as the purity of ammonium paratungstate (5 (NH ₄ ) ₂ O · 12WO ₃ · 5H ₂ O) is increased, the purity of tungsten (W) increases. Preferably, the purity of ammonium paratungstate (5 (NH ₄ ) ₂ O. 12WO ₃ .5H ₂ O) is at least 99.74%.

After preparing the ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) and magnesium (Mg), ammonium paratungstate (5 (NH ₄ ) ₂ O as shown in the following reaction formula (I). 12WO ₃ 5H ₂ O) and magnesium (Mg) are uniformly mixed in a constant composition ratio.

5 (NH ₄ ) ₂ O 12 WO ₃ 5H ₂ O + 36 Mg → 12 W + 36 MgO. … … … … (I)

Ammonium paratungstate (5 (NH ₄ ) ₂ O. 12WO ₃ .5H ₂ O) and magnesium (Mg) are uniformly mixed in a molar ratio of 1: (30-40), preferably 1:35. Next, a mixture of ammonium paratungstate (5 (NH ₄ ) ₂ O. 12WO ₃ .5H ₂ O) and magnesium (Mg) is compressed by applying a predetermined molding pressure. Preferably, it compresses by applying molding pressure of 4-14t. This is because, when a molding pressure of 4t or less is applied, the pellet may be easily broken due to a low pressure, and when a molding pressure of 14t or more is applied, the pellet may not be ignited well.

After compacting the mixture of ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) and magnesium (Mg), the heat-resistant glass 26 of the self-combustion reactor 100 is opened and paratungstic acid Green pellet 12 consisting of ammonium (5 (NH ₄ ) ₂ O. 12WO ₃ .5H ₂ O) and magnesium (Mg) is charged into the reactor chamber 102. That is, the green pellet 12 is located in the preheating furnace 10. After closing the heat-resistant glass 26 under these conditions, the vacuum pumps 28 are operated to create a vacuum in the reactor chamber 102, to maintain the atmospheric pressure, or to operate the inert gas source 30 to operate the reactor chamber 102. Inert gas, preferably argon (Ar) gas, is introduced into the shell. Thereafter, a current is applied from the power supply source 24 to the tungsten filament 22 to ignite and burn the green pellets 12.

In this way, p-tungstic acid, ammonium _{(5 (NH 4) 2 O} · 12WO 3 · 5H 2 O) and magnesium after obtaining a tungsten (W) and magnesium oxide (MgO) from the green pellets 12 made of a (Mg) is , Leaching with about 20% hydrochloric acid (HCl) as shown in the reaction scheme (II) to remove magnesium oxide (MgO) to obtain high purity tungsten (W).

12 W + 36 MgO + (HCl) (L)-12 W ↓ + (36 MgO + HCl) (L). … … … … (II)

The tungsten (W) powder thus precipitated is recovered using a filter paper and washed several times to obtain pure tungsten (W) powder. The finally produced tungsten (W) has a high purity of 99.948% or more because the impurities volatilized during the combustion process.

Hereinafter, the preferred embodiment of the present invention will be briefly described.

EXAMPLE

As a raw material powder, a molar ratio of ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) and magnesium (Mg) (reagent grade) of 1: (30-40), preferably 1:35, respectively. Put in a ball mill and mix for at least 3 hours. Next, the mixed powder is subjected to a pressure of 4 to 14 tons to form pellets having a diameter of 20 mm. The pellets thus formed are ignited and burned in an inert gas atmosphere, preferably in an argon (Ar) gas atmosphere, in a self-combustion reactor. Thereafter, the generated sample is analyzed using X-ray diffraction (hereinafter referred to as XRD).

3 is a powder in which ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) and magnesium (Mg) are mixed in a molar ratio of 1: (30-40) according to a preferred embodiment of the present invention. Is a graph showing the X-ray diffraction results of the reaction product obtained by the self-combustion reaction. Referring to FIG. 3, it can be seen that tungsten (W) and magnesium oxide (MgO) are produced.

Alternatively, the reaction product produced by igniting and burning the molded pellets is leached with about 20% hydrochloric acid (HCl), and then tungsten (W) that has been precipitated by using filter paper is recovered. Then, after washing tungsten (W) several times to produce pure tungsten (W), it is analyzed by XRD.

4 is a powder in which ammonium paratungstate (5 (NH ₄ ) ₂ O.12WO ₃ .5H ₂ O) and magnesium (Mg) are mixed in a molar ratio of 1: (30-40) according to a preferred embodiment of the present invention. Is a graph showing the results of X-ray diffraction after leaching the reaction product obtained by the self combustion reaction. Referring to FIG. 4, it can be seen that magnesium oxide (MgO) shown in FIG. 3 is removed by leaching and only tungsten (W) is present as a final product. In addition, when the microstructure is observed with a scanning electron microscope (SEM), it can be seen that the crystal phase particles of the reaction product have a particle size distribution of about 0.2 to 10 μm. In addition, the final product was measured by atomic absorption spectrometer, it was confirmed that the high purity powder of more than 99.948%.

As mentioned above, in the method for producing tungsten (W) powder according to the present invention, by using magnesium (Mg) powder as the reducing agent, ammonium paratungstate (5 (NH ₄ ) ₂ O. 12 WO ₃ · 5H ₂ O ) Powder is reduced and magnesium oxide (MgO) obtained as a by-product is leached with about 20% hydrochloric acid (HCl) to prepare tungsten (W) powder. Therefore, the high temperature reactor required by the conventional method for producing tungsten (W) powder becomes unnecessary, and the manufacturing process is simplified. In addition, since the combustion reaction of the reactant proceeds automatically by the self-heating amount, high-efficiency tungsten (W) powder can be obtained because the energy efficiency is high, and the exothermic temperature is very high, and impurities are volatilized. In addition, since the reaction itself starts from the oxide, it is possible to synthesize the tungsten (W) without the need for smelting separately, and to synthesize it in the air.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (4)

Mixing ammonium paratungstate and magnesium in a molar ratio of 1:35 (S1); Molding the mixture formed in the step S1 into pellets by applying a molding pressure of 4 to 14 t (S2); Charging the pellets into a self-combustion reactor having an inert gas atmosphere (S3); Combusting the pellets in the self-burning reactor (S4); Taking out the combustion product made in the step (S4) from the self-combustion reactor (S5); Leaching the combustion product with hydrochloric acid (HCL) diluted to 20% (S6); Filtering the leachate leaching in step S6 (S7); And washing the tungsten (W) powder filtered in the step (S7) (S8). The high purity of claim 1, wherein the ammonium paratungstate (5 (NH ₄ ) ₂ O · 12WO ₃ · 5H ₂ O) has a particle size that passes through 100 mesh and a purity of 99.74% or more. Method for producing tungsten powder. The method of claim 1, wherein the inert gas atmosphere is an argon (Ar) gas atmosphere. The method for producing high purity tungsten (W) powder according to claim 1, wherein the tungsten (W) powder has a particle size distribution of 0.2 to 10 µm and a purity of 99.948% or more.

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