A wet doping method for tungsten powder to improve the uniformity of rare earth distribution

Abstract

The application discloses a tungsten powder wet doping method for improving the uniformity of rare earth distribution, and belongs to the technical field of powder metallurgy, and comprises the following steps: heat treating tungsten powder to oxidize the tungsten powder, forming a tungsten oxide layer on the surface of tungsten powder particles, and then putting the tungsten powder into a double helix conical mixer to start mixing; spraying a lanthanum nitrate aqueous solution to the surface of the tungsten powder in the double helix conical mixer, and then heat treating the materials in the mixer below 120 DEG C, evaporating free water of the lanthanum nitrate aqueous solution, and removing the combined water of the separated hydrated lanthanum nitrate; stopping the double helix conical mixer, taking out the materials in the mixer, sintering the loose porous first material in a hydrogen atmosphere at 500-700 DEG C for 1.5-5 hours, and obtaining tungsten powder doped with lanthanum oxide. Compared with the prior art, the application can reduce the segregation and agglomeration risk of rare earth compounds and improve the uniformity of the rare earth distribution in tungsten materials.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy, and more specifically, to a wet doping method for tungsten powder to improve the uniformity of rare earth distribution. Background Technology

[0002] Tungsten materials are widely used in electric light sources, electronic devices, and the nuclear industry due to their high melting point, high strength, and corrosion resistance. Pure tungsten suffers from high-temperature brittleness and low recrystallization temperature, and is usually doped with rare earth elements to refine the grain size and improve the high-temperature performance of tungsten materials.

[0003] Currently, the doping method used in the industry typically involves ball-milling tungsten and rare earth materials (such as La2O3, CeO2, Y2O3, etc.) into powder separately, then mixing them uniformly using a mixer, followed by relevant post-processing. The advantages of this dry doping method are its simplicity, ease of operation, and low cost. However, its disadvantages are also quite obvious: during dry doping, the two phases are in powder form. Although the particle size difference can be reduced by ball milling, the material density is determined by the atomic types and crystal structure, and the surface properties are determined by the molecular structure. The density and surface property differences between the two phases cannot be eliminated by mechanical processing methods such as ball milling, easily leading to segregation and agglomeration, resulting in uneven distribution of the dopant in the tungsten powder.

[0004] Therefore, how to provide a new method for doping rare earth elements into tungsten materials, reduce the risk of segregation and agglomeration, and improve the uniformity of rare earth element distribution in tungsten materials has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a wet doping method for tungsten powder to improve the uniformity of rare earth distribution, so as to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A wet doping method for tungsten powder to improve the uniformity of rare earth distribution, characterized by incorporating lanthanum oxide, a rare earth compound, into the tungsten powder, comprising the following steps: Heat-treated tungsten powder is oxidized to form a tungsten oxide layer on the surface of the tungsten powder particles; The tungsten powder obtained from heat treatment is fed into a double-helix conical mixer, and the double-helix conical mixer is started to mix the materials. Lanthanum nitrate aqueous solution is atomized and sprayed onto the surface of tungsten powder in a double-helix conical mixer; The temperature of the double helix cone mixer is adjusted to heat-treat the material in the double helix cone mixer, evaporate the free water in the lanthanum nitrate aqueous solution, and remove the bound water of the hydrated lanthanum nitrate that precipitates after evaporation. The temperature during the heat treatment process is always below 120℃. Shut down the double helix cone mixer and remove the material inside as the first material; In a hydrogen atmosphere, the loose and porous first material is sintered for 1.5-5 hours at a fifth preset temperature to obtain tungsten powder doped with lanthanum oxide. The fifth preset temperature is 500-700℃.

[0007] Optionally, tungsten powder with a particle size of 0.5–5 μm is subjected to oxidation heat treatment to generate a tungsten oxide layer on the surface of the tungsten powder particles.

[0008] Optionally, the process of heat-treating tungsten powder to form a tungsten oxide layer on the surface of the tungsten powder particles includes the following steps: In an air atmosphere, tungsten powder is heat-treated at a first preset temperature for a first preset time, the first preset temperature being 200-300℃ and the first preset time being 0.5-2 hours.

[0009] Optionally, tungsten powder is fed into a double-helix conical mixer, and the mixer is started to mix for 8-12 minutes. Then, an aqueous solution of lanthanum nitrate is atomized and sprayed onto the surface of the tungsten powder in the double-helix conical mixer.

[0010] Optionally, the double-helix conical mixer is started for mixing, with an orbital speed of 1-2 rpm and a rotational speed of 60-70 rpm.

[0011] Optionally, after the first material is taken out from the double helix conical mixer, the first material is uniaxially molded at 5-15MPa to form a thin layer with a thickness of <5mm. In a hydrogen atmosphere, the first material after sintering and pressing at a fifth preset temperature for 1.5-5 hours is used to obtain tungsten powder doped with lanthanum oxide.

[0012] Optionally, after the first material is removed from the double helix cone mixer, it is screened using a screen with a mesh size of 130-160 mesh. The first material that has been screened is uniaxially molded at 5-10MPa to form a thin layer with a thickness of <5mm; In a hydrogen atmosphere, the first material is sintered and pressed at a fifth preset temperature for 1.5-3 hours to obtain tungsten powder doped with lanthanum oxide.

[0013] Optionally, the heat treatment process for the material in the double-helix conical mixer includes the following steps: The heat treatment is carried out at the second preset temperature for 2-3 hours, then the temperature is raised to the third preset temperature and held at the third preset temperature for 2-3 hours, then the temperature is raised to the fourth preset temperature and held at the fourth preset temperature for 4-5 hours. The second preset temperature is 50-70℃, the third preset temperature is 75-95℃, and the fourth preset temperature is 100-110℃.

[0014] This invention oxidizes tungsten powder through a heat treatment process, forming an oxide layer on the surface of the tungsten powder. A double-helix conical mixer is used for mixing, and a lanthanum nitrate aqueous solution is atomized and sprayed onto the moving tungsten powder surface for wet doping. After atomization and spraying, the internal temperature of the mixer is adjusted to heat-treat the material, thereby evaporating the free water in the lanthanum nitrate aqueous solution and removing the bound water from the hydrated lanthanum nitrate that precipitates after evaporation. The material is then removed from the mixer and sintered at 500-700℃ for 1.5-5 hours in a hydrogen atmosphere. During the heating process, as the temperature rises above 100℃, any remaining bound water is released, forming small droplets of lanthanum nitrate. At this point, due to the relatively low temperature, the tungsten oxide layer on the surface of the tungsten powder has not yet been reduced to tungsten, and the contact angle between lanthanum nitrate and tungsten oxide is smaller than that between lanthanum nitrate and tungsten, resulting in better wettability and reducing the agglomeration effect of rare earth compounds at this stage. As the temperature continues to rise to 150-200℃, the bound water is completely removed, and the anhydrous lanthanum nitrate exists in the form of molten salt and begins to partially decompose into LaONO3. The material is gradually heated to 250-300℃, and the anhydrous lanthanum nitrate is completely thermally decomposed into LaONO3. The material is heated further to 500-700℃, and LaONO3 thermally decomposes into lanthanum oxide. The tungsten oxide layer on the surface of the tungsten powder is fully reduced to tungsten, resulting in tungsten powder uniformly doped with lanthanum oxide.

[0015] Compared to existing technologies, this application first removes most of the free water and bound water of hydrated lanthanum nitrate at low temperature, reducing the number of droplets and the water content of droplets during the sintering thermal decomposition process. At the same time, it ensures that the droplet contact interface at this stage is tungsten oxide rather than tungsten, which has poorer wettability. Both of these measures can effectively suppress the agglomeration and segregation of rare earth phases during the thermal decomposition process of lanthanum nitrate doping, thereby improving the uniformity of rare earth distribution. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the structure of the double-helix conical mixer used in Example 1; Figure 2 This is a schematic diagram of the internal structure of the double-helix conical mixer used in Example 1; Figure 3 This is a radial cross-sectional view of the double-helix conical mixer used in Example 1; Figure 4 This is a partial structural schematic diagram of the atomizing spray device used in Example 1; Figure 5 This is a schematic diagram of the double-helix conical mixer used in Comparative Example 1; Figure 6 This is a schematic diagram of the internal structure of the double-helix conical mixer used in Comparative Example 1; Figure 7 The image shows an electron microscope image of the first material prepared in Example 1. Figure 8 Here is an electron microscope image of the tungsten powder obtained by sintering in Example 1; Figure 9 The image shows an electron microscope image of the first material prepared in Comparative Example 1. Figure 10 The image shows an electron microscope (EM) image of the tungsten powder obtained by sintering in Comparative Example 1.

[0017] Reference numerals: 100, double helical conical mixer; 110, feed inlet; 120, discharge outlet; 130, jacket; 140, nitrogen outlet; 150, driver; 151, revolving spindle; 160, first agitator; 170, second agitator; 180, drive unit; 190, scraper; 200, temperature control device; 300, atomizing spray device; 310, throat; 320, expansion section; 330, container; 331, injection pipe; 340, power source for ejection; 400, nitrogen cylinder. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] This invention provides a wet doping method for tungsten powder to improve the uniformity of rare earth distribution, characterized by incorporating lanthanum oxide, a rare earth compound, into the tungsten powder, comprising the following steps: Heat-treated tungsten powder is oxidized to form a tungsten oxide layer on the surface of the tungsten powder particles; The tungsten powder obtained from heat treatment is fed into a double-helix conical mixer 100 (see [link to specific structure of double-helix conical mixer 100]). Figure 1-4 As shown, a feed inlet 110 is provided at the top, and tungsten powder is fed in through the feed inlet 110. The double helix cone mixer 100 is then started to mix the materials. Lanthanum nitrate aqueous solution is atomized and sprayed onto the surface of tungsten powder in a double-helix conical mixer 100; The temperature of the double helix conical mixer 100 is adjusted to heat-treat the material in the double helix conical mixer 100, evaporate the free water in the lanthanum nitrate aqueous solution, and remove the bound water of the hydrated lanthanum nitrate that precipitates after evaporation. The temperature during the heat treatment process is always below 120°C. Shut down the double helix cone mixer 100 and remove the material inside as the first material; In a hydrogen atmosphere, the loose and porous first material is sintered for 1.5-3 hours at a fifth preset temperature to obtain tungsten powder doped with lanthanum oxide. The fifth preset temperature is 500-700℃.

[0020] This invention oxidizes tungsten powder through a heat treatment process, forming an oxide layer on the surface of the tungsten powder. A double-helix conical mixer 100 is used for mixing, and a lanthanum nitrate aqueous solution is atomized and sprayed onto the moving tungsten powder surface for wet doping. After atomization and spraying, the internal temperature of the mixer is adjusted to heat-treat the material, thereby evaporating the free water in the lanthanum nitrate aqueous solution and removing the bound water from the hydrated lanthanum nitrate that precipitates after evaporation. The material is then removed from the mixer and sintered at 500-700℃ for 1.5-5 hours in a hydrogen atmosphere. During the heating process, as the temperature rises above 100℃, any remaining bound water is released, forming small droplets of lanthanum nitrate. At this point, due to the relatively low temperature, the tungsten oxide layer on the surface of the tungsten powder has not yet been reduced to tungsten, and the contact angle between lanthanum nitrate and tungsten oxide is smaller than that between lanthanum nitrate and tungsten, resulting in better wettability and reducing the agglomeration effect of rare earth compounds at this stage. As the temperature continues to rise to 150-200℃, the bound water is completely removed, and anhydrous lanthanum nitrate exists as a molten salt, which begins to partially decompose into LaONO3, as shown in the following reaction formula: La(NO3)3→LaONO3+2NO2↑+½O2↑; The material is gradually heated to 250-300℃, at which point anhydrous lanthanum nitrate completely decomposes into LaONO3. The material is then further heated to 500-700℃, at which point LaONO3 decomposes into lanthanum oxide, as shown in the following reaction equation: 2LaONO3→La2O3+NO↑+NO2↑+O2↑; The tungsten oxide layer on the surface of the tungsten powder is fully reduced to tungsten, as shown in the following reaction formula: WO3 + H2 → WO2 + H2O↑; WO2 + 2H2 → W + 2H2O↑; The first material after sintering was collected to obtain tungsten powder uniformly doped with lanthanum oxide.

[0021] Compared to existing technologies, this application first removes most of the free water and bound water of hydrated lanthanum nitrate at low temperature, reducing the number of droplets and the water content of droplets during the sintering thermal decomposition process. At the same time, it ensures that the droplet contact interface at this stage is tungsten oxide rather than tungsten, which has poorer wettability. Both of these measures can effectively suppress the agglomeration and segregation of rare earth phases during the thermal decomposition process of lanthanum nitrate doping, thereby improving the uniformity of rare earth distribution.

[0022] It should be noted that the double-helix conical mixer 100, also called a Notta mixer, is a vertical mixing device with an inverted conical cylinder. It contains a main rotating shaft 151, on which one or two cantilevered spiral agitators are mounted. The driver 150 drives the main rotating shaft 151 to rotate around its own axis. Simultaneously, the cantilevered spiral agitators on the radially outer side of its load revolve around the cylinder axis. At the same time, regardless of the direction or location of the cantilevered spiral agitator's revolution, its axis remains parallel to the conical generatrix of the axial section of the inverted conical cylinder (the one on the same radial side of the revolution). Driven by its own drive device 180, it rotates, causing the material to undergo axial lifting, radial convection, and shear mixing within the cylinder for uniform mixing. The "double" in double-helix conical mixer 100 refers to the simultaneous rotation and revolution, and should not be interpreted as requiring two cantilevered spiral agitators to be connected to the main rotating shaft 151. Preferably, this application uses... Figure 1 In the embodiment of the double-helix conical mixer 100, a main rotating shaft 151 is connected to two cantilevered helical stirrers, which are distributed on opposite sides of the main rotating shaft 151 in a radial direction. One of the cantilevered helical stirrers has a longer axial length of helical blades and a larger radius of rotation around the axis of the main rotating shaft 151, and is designated as the first stirrer 160; the other cantilevered helical stirrer has a shorter axial length of helical blades and a smaller radius of rotation around the axis of the main rotating shaft 151, and is designated as the second stirrer 170.

[0023] It should be noted that this application does not specify the relative position of the atomizing nozzle of the lanthanum nitrate aqueous solution to the various components within the double-helix conical mixer 100, nor does it impose specific limitations on the position of the nozzle on the double-helix conical mixer 100, as long as it can be atomized and sprayed onto the surface of the tungsten powder. Preferably, the nozzle's ejection position is located at the inverted conical top of the double-helix conical mixer 100, radially outside the main axis of revolution 151. Preferably, taking an axial section of the double-helix conical mixer 100 passing through this ejection position, along the radial direction of the main axis of revolution 151, when all the cantilevered spiral stirrers revolve to this section, their rotation axes are all located between the axis of the main axis of revolution 151 and the ejection position. The spray direction of the atomizing nozzle can be vertically downward. Preferably, an axial section of the double-helix conical mixer 100 is made at the spray position. The inverted conical cylinder of the double-helix conical mixer 100 is an inverted cone shape. The spray direction of the atomizing nozzle is parallel to a generatrix of the inverted cone in the axial section. The generatrix and the spray position of the atomizing nozzle are located on the same radial side of the main axis of revolution 151.

[0024] It should be noted that the term "cone" in the inverted cone shape of the double-helix conical mixer 100, and the "inverted cone" of the aforementioned cross-section, are industry naming conventions. The actual geometric shape is an inverted frustum, with the top platform area larger than the bottom platform area, and the axis aligning with the direction of gravity. It cannot be connected to form a closed geometric conical cylinder with a conical tip.

[0025] It should be noted that this application does not specifically limit the temperature regulation method and related mechanical structure of the double-helix conical mixer 100, as long as temperature regulation can be achieved, with the principle of uniform heating of the material as the guiding principle. Preferably, the double-helix conical mixer 100 is provided with an outer jacket 130, and the jacket 130 is connected to a temperature control device 200. The temperature control device 200 outputs a heat transfer medium at a preset temperature to the jacket 130 through a circulating pump, which circulates and recovers the heat transfer medium after heat exchange, re-temperatures it, and reuses it. Compared with temperature regulation in a cylindrical tank with a jacket 130, this application can reduce radial temperature difference. The heat transfer medium can be selected as heat transfer oil or water.

[0026] In one possible implementation, tungsten powder with a particle size of 0.5–5 μm is subjected to oxidative heat treatment to generate a tungsten oxide layer on the surface of the tungsten powder particles. Furthermore, before atomizing and spraying the lanthanum nitrate aqueous solution, the process includes a step of preparing the lanthanum nitrate aqueous solution: dissolving La(NO3)3·6H2O in water to obtain the lanthanum nitrate aqueous solution, wherein the mass fraction of La(NO3)3·6H2O in the lanthanum nitrate aqueous solution is 1.5%–2%.

[0027] In one possible implementation, the process of heat-treating tungsten powder to form a tungsten oxide layer on the surface of the tungsten powder particles includes the following steps: heat-treating tungsten powder in an air atmosphere at a first preset temperature for a first preset time, wherein the first preset temperature is 200-300°C and the first preset time is 0.5-2 hours.

[0028] In one possible implementation, a double-helix conical mixer 100 is started to perform mixing operations, with an orbital speed of 1-2 rpm and a rotational speed of 60-70 rpm.

[0029] In one possible implementation, tungsten powder is fed into a double-helix conical mixer 100, and the double-helix conical mixer 100 is started to mix the powder separately for 8-12 minutes to improve the dispersion of the tungsten powder itself. Then, an aqueous solution of lanthanum nitrate is atomized and sprayed onto the surface of the tungsten powder in the double-helix conical mixer 100.

[0030] In one possible implementation, an atomizing injector is used to atomize and spray an aqueous solution of lanthanum nitrate onto the surface of tungsten powder. This atomizing injector is a nitrogen-ejector atomizing spray device 300 based on the Venturi effect, and its throat and expansion section 320 have the following axial cross-sections: Figure 4 As shown, this cannot be interpreted as the atomizing spray device 300 having no shrinkage section. The prepared lanthanum nitrate aqueous solution was placed in... Figure 1In the container 330 shown in the embodiment, an injection pipe 331 inclined to the axis of the throat 310 is connected to the throat 310. An ejector power source 340 axially ejects nitrogen gas from the nitrogen cylinder 400, which sequentially passes through the contraction section, the throat, and the expansion section 320. At the throat, the lanthanum nitrate aqueous solution is driven to obliquely enter the throat. The high-speed nitrogen gas flow shears and breaks the liquid into droplets, which are then atomized and sprayed onto the surface of the tungsten powder within the double-helix conical mixer 100. The inlet position of the lanthanum nitrate aqueous solution is located at the throat, and the inlet direction is inclined to the axis of the throat 310 at an angle of 50°-60°, preferably. Figure 4 55° shown.

[0031] In one possible implementation, after the first material is taken out from the double helix conical mixer 100, the first material is uniaxially molded at 5-15 MPa to form a thin layer with a thickness of <5 mm, preferably <3 mm. In a hydrogen atmosphere, the first material after sintering and pressing at a fifth preset temperature for 1.5-3 hours is used to obtain tungsten powder doped with lanthanum oxide.

[0032] Optionally, after the first material is removed, it is screened using a sieve with a mesh size of 130-160 mesh. The first material that has been screened is uniaxially molded at 5-15MPa to form a thin layer with a thickness of <5mm. In a hydrogen atmosphere, the first material is sintered and pressed at a fifth preset temperature for 1.5-3 hours to obtain tungsten powder doped with lanthanum oxide.

[0033] In one possible implementation, the heat treatment process for the material in the double-helix conical mixer 100 includes the following steps: The heat treatment is carried out at the second preset temperature for 2-3 hours, then the temperature is raised to the third preset temperature and held at the third preset temperature for 2-3 hours, then the temperature is raised to the fourth preset temperature and held at the fourth preset temperature for 4-5 hours. The second preset temperature is 50-70℃, the third preset temperature is 75-95℃, and the fourth preset temperature is 100-110℃.

[0034] During this heat treatment process, the rare earth compound phase is transformed from droplets of lanthanum nitrate aqueous solution into solid particles of La(NO3)3·6H2O. Furthermore, the bound water in the La(NO3)3·6H2O solid particles evaporates upon heating, ultimately yielding tungsten powder doped with La(NO3)3·H2O solid particles.

[0035] Preferably, the first preset temperature is 60°C, the second preset temperature is 80°C, and the third preset temperature is 110°C.

[0036] In one possible implementation, such as Figure 2 , Figure 3As shown, the revolution shaft of the double helix cone mixer 100 is also connected to a scraper 190. After the double helix cone mixer 100 is started, the scraper 190 rotates synchronously with the revolution shaft to scrape off the material on the cone-shaped inner wall of the double helix cone mixer 100.

[0037] To better illustrate the present invention, Comparative Example 1 and Example 1 are provided below.

[0038] Take tungsten powder with a particle size of 3μm and divide it into two parts: one part is the tungsten powder raw material of Example 1, and the other part is the tungsten powder raw material of Comparative Example 1.

[0039] Example 1: In an air atmosphere, tungsten powder is heat-treated at 250°C for 1 hour to oxidize the tungsten powder, thereby generating a tungsten oxide layer on the surface of the tungsten powder particles. La(NO3)3·6H2O was dissolved in water to obtain an aqueous solution of lanthanum nitrate. The mass fraction of La(NO3)3·6H2O in the aqueous solution of lanthanum nitrate was 1.8%. The tungsten powder obtained from heat treatment is added to... Figure 1 In the embodiment, the double helix conical mixer 100 is started to mix materials. The revolution speed of the double helix conical mixer 100 is 2 rpm, and the rotation speed of the two cantilevered spiral stirrers is 60 rpm. After starting the double helix conical mixer 100 for 10 minutes, the lanthanum nitrate aqueous solution is atomized and sprayed onto the surface of the tungsten powder in the double helix conical mixer 100; After the atomization spraying is completed, the temperature of the double helix conical mixer 100 is adjusted, and the material in the double helix conical mixer 100 is heat-treated as follows: the temperature is uniformly increased to 60°C at a heating rate of 2°C / min, and held at 60°C for 2 hours. Then, the temperature is uniformly increased to 80°C at a heating rate of 2°C / min, and held at 80°C for 2 hours. Then, the temperature is uniformly increased to 110°C at a heating rate of 2°C / min, and held at 110°C for 4 hours. Finally, the temperature is uniformly decreased to room temperature at a cooling rate of 5°C / min. Shut down the double-helix conical mixer 100, open the discharge port 120, and take out the material as the first material for scanning electron microscopy (SEM) observation. The SEM image is shown below. Figure 7 ; The first material is removed by screening with a sieve with a mesh size of 150. Only the first material that can pass through the sieve is collected, and the first material that has passed through the sieve is uniaxially molded at 5MPa to form a thin layer of 3mm thickness. The thin layer was placed above a perforated support in a sintering furnace, where a continuous axial flow of hydrogen gas was maintained. The first material (thin layer) was sintered at 600°C for 3 hours in a hydrogen atmosphere to obtain tungsten powder doped with lanthanum oxide. The obtained tungsten powder was observed using a scanning electron microscope (SEM), and the SEM image is shown below. Figure 8 .

[0040] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that: The internal environment of the double-helix conical mixer 100 is ventilated using a nitrogen system to create a nitrogen atmosphere. Tungsten powder is then directly added to... Figure 5 The embodiment of the double-helix conical mixer 100. Figure 5 In this embodiment, a nitrogen cylinder 400 is detachably connected to the discharge port 120, and a nitrogen outlet 140 is provided at the top. The remaining mechanical mechanisms are... Figure 1 The embodiment is consistent; for the radial cross-sectional view of the double-helix conical mixer 100 in this embodiment, please refer to [link / reference]. Figure 3 Using nitrogen cylinder 400 to continuously ventilate the internal environment of double helix cone mixer 100, so that the double helix cone mixer 100 is in a nitrogen atmosphere, the inlet and outlet ports 120 and the nitrogen inlet and outlet are closed, and then the double helix cone mixer 100 is started to mix materials; After the atomization spraying is completed, the temperature of the double-helix conical mixer 100 is adjusted, and the material in the double-helix conical mixer 100 is subjected to heat treatment as follows: the temperature is uniformly increased to 110℃ at a heating rate of 2℃ / min, and held at 110℃ for 8 hours. Then, the temperature is uniformly reduced to room temperature at a cooling rate of 5℃ / min before the double-helix conical mixer 100 is turned off. The material is taken out as the first material and observed by scanning electron microscopy (SEM). The SEM image is shown below. Figure 9 ; The first material is removed by sieving with a sieve under a nitrogen atmosphere; Under the protection of nitrogen atmosphere, the first material that has been screened is uniaxially molded at 5MPa, forming it into a thin layer with a thickness of 3mm.

[0041] Everything else was exactly the same as in Comparative Example 1. The tungsten powder obtained after sintering Comparative Example 1 was observed using a scanning electron microscope (SEM), and its SEM image is shown below. Figure 10 .

[0042] contrast Figure 7 and Figure 9 It can be seen that the doped powder in Example 1 is more uniform and shows no obvious agglomeration, while the doped powder in Comparative Example 1 has agglomeration of large particles of 20-50 μm. Figure 8 and Figure 10It can be seen that the grain boundaries of the sintered product in Example 1 are clearer, and the porosity caused by the agglomeration of rare earth compound phases and the gas aggregation is smaller, resulting in a significant improvement in quality. This proves that tungsten powder oxidation and staged heating dehydration can reduce the agglomeration of rare earth compounds and improve the uniformity of rare earth distribution.

[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A wet doping method for tungsten powder to improve the uniformity of rare earth distribution, characterized in that, Adding lanthanum oxide, a rare earth compound, to tungsten powder includes the following steps: The tungsten powder is heat-treated to oxidize the tungsten powder, thereby generating a tungsten oxide layer on the surface of the tungsten powder particles; The tungsten powder obtained from heat treatment is fed into a double-helix conical mixer, and the double-helix conical mixer is started to mix the materials. A lanthanum nitrate aqueous solution is atomized and sprayed onto the surface of tungsten powder in the double-helix conical mixer; The temperature of the double helix conical mixer is adjusted to heat-treat the material in the double helix conical mixer, evaporate the free water in the lanthanum nitrate aqueous solution, and remove the bound water of the hydrated lanthanum nitrate that precipitates after evaporation. The temperature during the heat treatment process is always below 120°C. Shut down the double helix cone mixer and remove the material inside as the first material; In a hydrogen atmosphere, the loose and porous first material is sintered for 1.5-5 hours at a fifth preset temperature to obtain tungsten powder doped with lanthanum oxide. The fifth preset temperature is 500-700℃.

2. The wet doping method for tungsten powder to improve the uniformity of rare earth distribution according to claim 1, characterized in that, Tungsten powder with a particle size of 0.5–5 μm was subjected to oxidation heat treatment to generate a tungsten oxide layer on the surface of the tungsten powder particles.

3. The wet doping method for tungsten powder to improve the uniformity of rare earth distribution according to claim 1, characterized in that, The process of heat-treating tungsten powder to form a tungsten oxide layer on the surface of tungsten powder particles includes the following steps: In an air atmosphere, tungsten powder is heat-treated at a first preset temperature for a first preset time, wherein the first preset temperature is 200-300℃ and the first preset time is 0.5-2 hours.

4. The wet doping method for tungsten powder to improve the uniformity of rare earth distribution according to claim 1, characterized in that, Tungsten powder is added to a double-helix conical mixer, and the mixer is started to mix for 8-12 minutes. Then, a lanthanum nitrate aqueous solution is atomized and sprayed onto the surface of the tungsten powder in the double-helix conical mixer.

5. The wet doping method for tungsten powder to improve the uniformity of rare earth distribution according to claim 1, characterized in that, The double-helix conical mixer is started to perform mixing operations, with an orbital speed of 1-2 rpm and a rotational speed of 60-70 rpm.

6. The wet doping method for tungsten powder to improve the uniformity of rare earth distribution according to claim 1, characterized in that, After the first material is taken out from the double helix conical mixer, it is uniaxially molded at 5-15MPa to form a thin layer with a thickness of <5mm. In a hydrogen atmosphere, the first material after sintering and pressing at a fifth preset temperature for 1.5-5 hours is used to obtain tungsten powder doped with lanthanum oxide.

7. The wet doping method for tungsten powder to improve the uniformity of rare earth distribution according to claim 6, characterized in that, After the first material is removed from the double helix cone mixer, it is sieved using a screen with a mesh size of 130-160 mesh. The first material that has been screened is uniaxially molded at 5-10MPa to form a thin layer with a thickness of <5mm; In a hydrogen atmosphere, the first material is sintered and pressed at a fifth preset temperature for 1.5-3 hours to obtain tungsten powder doped with lanthanum oxide.

8. The wet doping method for tungsten powder to improve the uniformity of rare earth distribution according to claim 1, characterized in that, The heat treatment process for materials in a double-helix conical mixer includes the following steps: The temperature is held at the second preset temperature for 2-3 hours, then raised to the third preset temperature and held at the third preset temperature for 2-3 hours, then raised to the fourth preset temperature and held at the fourth preset temperature for 4-5 hours. The second preset temperature is 50-70℃, the third preset temperature is 75-95℃, and the fourth preset temperature is 100-110℃.

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