Preparation method of nearly spherical molybdenum powder

Abstract

The invention relates to a preparation method of nearly-spherical molybdenum powder, belongs to the technical field of rare metal powder metallurgy, and solves the problems that in the prior art, molybdenum powder is prone to sintering, agglomeration is caused, and the morphology is not easy to control. Comprising the following steps: (1) leaching, extracting and reversely extracting molybdenum calcine to obtain a peroxymolybdic acid solution; (2) adding metal cations into the peroxymolybdic acid solution to ensure that the mass concentration C of the metal cations is greater than or equal to 0% and less than or equal to Clt; the preparation method comprises the following steps of: adding the molybdenum peroxide powder with the needle-like crystal structure doped or not doped with metal cations into a material boat of a reduction furnace, and sequentially carrying out primary reduction and secondary reduction to obtain nearly spherical molybdenum powder, wherein the molybdenum peroxide powder with the needle-like crystal structure doped or not doped with the metal cations is added into the material boat of the reduction furnace. The morphology of the molybdenum powder prepared by the method is easy to control.

Description

Technical Field

[0001] This invention relates to the field of rare metal powder metallurgy technology, and in particular to a method for preparing near-spherical molybdenum powder. Background Technology

[0002] Currently, the most common industrial method for preparing molybdenum powder is the hydrogen reduction of molybdenum trioxide or ammonium molybdate. The raw materials for this method are typically in lumps, with a Fisher particle size often concentrated between 5-20 μm. The process generally involves first calcining ammonium molybdate to decompose it into ammonia and water, producing molybdenum trioxide. The molybdenum trioxide then undergoes a two-step hydrogen reduction: the first reduction to molybdenum trioxide is followed by further reduction to molybdenum dioxide at multiple temperature zones, and the second reduction to molybdenum dioxide is followed by further reduction to molybdenum powder at multiple temperature zones. The agglomerated powder also requires sieving during this intermediate step. Several industrial methods for preparing ultrafine / nano-sized molybdenum powder also exist, primarily including the reduction of ammonium octamolybdate, ball milling and chemical pretreatment, and the hydrogen reduction method using sublimated molybdenum trioxide.

[0003] However, existing methods for preparing molybdenum powder are prone to sintering and agglomeration, have complicated reduction processes, and are difficult to control the morphology and particle size of molybdenum powder. Furthermore, the process of roasting ammonium molybdate to produce molybdenum trioxide inevitably generates ammonia nitrogen waste gas. The pungent ammonia nitrogen waste gas not only limits workers' production but also increases the additional cost of exhaust gas recovery. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a method for preparing near-spherical molybdenum powder to solve at least one of the following problems existing in the molybdenum powder preparation method: (1) easy to sinter and cause agglomeration; (2) cumbersome reduction process; (3) difficult to control the morphology and particle size of molybdenum powder; (4) generation of ammonia nitrogen waste gas.

[0005] This invention provides a method for preparing near-spherical molybdenum powder, the method comprising:

[0006] (1) Molybdenum calcinate was leached, extracted, and back-extracted to obtain a peroxymolybdic acid solution:

[0007] (2) Add metal cations to the peroxymolybdic acid solution so that the mass concentration of metal cations C is 0% ≤ C < 0.05%, then evaporate and crystallize. The resulting needle-shaped peroxymolybdic acid powder with or without metal cations is loaded into the boat of the reduction furnace and subjected to one reduction and two reductions in sequence to obtain near-spherical molybdenum powder.

[0008] Preferably, the temperature of the first reduction is 480-530℃.

[0009] Preferably, the mass concentration C of the metal cation is 0.02% ≤ C < 0.05%, and the temperature of the secondary reduction is 730-850℃.

[0010] Preferably, the hydrogen flow rate for the primary reduction is 2-4 m³ / h. 3 / h.

[0011] Preferably, the speed of the boat pusher in one reduction is 15-30 min / pass.

[0012] Preferably, the hydrogen flow rate for the secondary reduction is 5-18 m³ / h. 3 / h.

[0013] Preferably, the mass concentration C of the metal cation is 0% ≤ C < 0.02%, and the temperature of the secondary reduction is 780-850℃ or 930-1050℃.

[0014] Preferably, the hydrogen flow rate for the primary reduction is 1.5-5 m³ / h. 3 / h.

[0015] Preferably, the pushing speed of the boat in one restoration is 35-45 min / pass.

[0016] Preferably, the hydrogen flow rate for the secondary reduction is 20-40 m³ / h. 3 / h.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0018] 1. The raw material of this invention, peroxymolybdic acid, has a needle-like crystal structure. With or without the addition of metal cations, it forms peroxymolybdic acid with or without metal cation doping. The needle-like crystal structure of peroxymolybdic acid exhibits excellent dispersibility and extremely high specific surface area. With or without the introduction of metal cations, the arrangement of the peroxymolybdic acid needle-like crystals changes during the reduction process, altering the difficulty for hydrogen to reach the interior of the crystals. This changes the mechanism of the partial reduction reaction, ultimately resulting in the preparation of molybdenum powder with a near-spherical morphology. This invention uses peroxymolybdic acid with a needle-like crystal structure as a raw material, which has good dispersibility, is not prone to agglomeration, and its morphology is easily controlled.

[0019] 2. When the mass concentration C of the metal cation is 0.02% ≤ C < 0.05%, the needle-like crystal structure of peroxymolybdic acid doped with metal cations gradually enlarges and agglomerates during the first reduction, providing conditions for the new grains to grow larger during the second reduction. During the second reduction, molten metal cation-containing grains (e.g., KOH grains) are formed, providing nucleation sites for molybdenum powder and helping it grow into near-spherical grains. When the mass concentration C of the metal cation is 0% ≤ C < 0.02%, the first reduction at a low temperature prepares polyhedral MoO2 grains with smaller particle size. Then, in the second reduction, a moderate temperature is used to induce pseudomorphic transformation and chemical vapor transport in the polyhedral MoO2 grains, thereby preparing larger near-spherical molybdenum powder. Alternatively, the second reduction can be carried out at a higher temperature to induce chemical vapor transport and prepare near-spherical molybdenum powder with smaller particle size.

[0020] 3. The reduction process of this invention is a single-temperature zone, and the reduction process is simple.

[0021] 4. By controlling the amount of metal cations added and the reduction conditions, this invention can more precisely control the morphology and grain size of near-spherical molybdenum powder.

[0022] 5. The method of the present invention uses peroxymolybdic acid as raw material, and the preparation process does not generate ammonia nitrogen waste gas that affects the environment.

[0023] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0024] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0025] Figure 1 This is a scanning electron microscope image of the near-spherical molybdenum nanoparticles obtained in Example 2;

[0026] Figure 2 This is a scanning electron microscope image of the near-spherical molybdenum nanoparticles obtained in Example 3;

[0027] Figure 3 The image shows a scanning electron microscope (SEM) image of peroxymolybdic acid with a needle-like crystal structure doped with metal cations obtained in Example 1.

[0028] Figure 4 The image shows a scanning electron microscope (SEM) image of peroxymolybdic acid with a needle-like crystal structure doped with metal cations obtained in Example 4.

[0029] Figure 5The image shows a scanning electron microscope (SEM) image of peroxymolybdic acid with a needle-like crystal structure doped with metal cations obtained in Example 5.

[0030] Figure 6 This is a scanning electron microscope image of the near-spherical molybdenum nanoparticles obtained in Example 1. Detailed Implementation

[0031] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0032] This invention provides a method for preparing near-spherical molybdenum powder, characterized in that the preparation method includes:

[0033] (1) Molybdenum calcinate was leached, extracted, and back-extracted to obtain a peroxymolybdic acid solution:

[0034] (2) Add metal cations to the peroxymolybdic acid solution so that the mass concentration of metal cations C is 0% ≤ C < 0.05%, then evaporate and crystallize. The resulting needle-shaped peroxymolybdic acid powder with or without metal cations is loaded into the boat of the reduction furnace and subjected to one reduction and two reductions in sequence to obtain near-spherical molybdenum powder.

[0035] Compared with existing technologies, the peroxymolybdic acid used in this invention has a needle-like crystal structure. When cations are added, it forms a needle-like crystal structure of peroxymolybdic acid doped with metal cations; without cations, it remains a needle-like crystal structure. The needle-like crystal structure of peroxymolybdic acid exhibits excellent dispersibility and extremely high specific surface area. With or without the introduction of metal cations, the arrangement of the peroxymolybdic acid needle-like crystals changes during the reduction process, altering the difficulty for hydrogen to reach the interior of the crystals. This changes the mechanism of the partial reduction reaction, ultimately resulting in a near-spherical molybdenum powder. This invention uses needle-like crystal structure peroxymolybdic acid as a raw material, which has good dispersibility and is not prone to agglomeration.

[0036] In this invention, step (1) includes the following steps:

[0037] (a) Molybdenum calcined sand is leached with inorganic acid to obtain a molybdenum-containing inorganic acid leachate;

[0038] (b) Molybdenum was extracted from the leachate obtained in step (a) using a cationic extractant to obtain a molybdenum acyl cation loaded with molybdenum cations (MoO2). 2+ The organic phase and raffinate;

[0039] (c) Using hydrogen peroxide solution as a back-extraction agent, it is mixed with an organic phase loaded with molybdenum acyl cations to obtain a molybdenum back-extraction solution, namely peroxymolybdic acid solution.

[0040] For example, in step (a), the leaching temperature is 75-96°C, more preferably 85-95°C.

[0041] For example, in step (a), the leaching pressure is atmospheric pressure.

[0042] For example, in step (a), the leaching time is 2-6 hours.

[0043] For example, in step (a), the inorganic acid is one or more of sulfuric acid, nitric acid, and hydrochloric acid.

[0044] For example, in step (a), the concentration of the inorganic acid is 2-4 mol / L, and the leaching liquid-to-solid ratio (L / Kg) is 3:1-10:1.

[0045] For example, in step (b), the cationic extractant is one or more of P507, P204 or Cyanex272.

[0046] For example, in step (b), the cationic extractant is mixed with kerosene to form a kerosene solution and then added to the leachate, wherein the volume fraction of the cationic extractant in the kerosene solution is 10-50%.

[0047] For example, in step (b), the extraction ratio O / A = 2:1-1:3; multi-stage countercurrent extraction is used, with 3-5 extraction stages.

[0048] For example, in step (c), the mass concentration of hydrogen peroxide is 10-20%.

[0049] For example, in step (c), the back-extraction is compared with O / A = 3:1-5:1, and multi-stage countercurrent back-extraction is adopted, with the number of back-extraction stages being 2-5 stages.

[0050] For example, the molybdenum calcined sand can be commercially available.

[0051] For example, the concentration of molybdenum ions in the peroxymolybdic acid solution is 100-200 g / L. Examples include 110 g / L, 130 g / L, 150 g / L, 170 g / L, and 190 g / L. Too low a concentration of molybdenum ions will result in low crystallization rate and smaller, more dispersed needle-like crystals, affecting subsequent particle size distribution; too high a concentration of molybdenum ions will result in excessively large needle-like crystals.

[0052] For example, the metal cation is K. + Na + Ca 2+ and Mg 2+ At least one of the following. Because the national standards require low content of elements such as Ca and Mg, the preferred metal cation is K. + and / or Na +K is further preferred. + .

[0053] For example, the metal cation is added in the form of an alkali.

[0054] For example, the evaporation crystallization temperature is 70-95°C, more preferably 80-95°C. Examples include 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, and 94°C. Too low an evaporation crystallization temperature will result in excessively dispersed and fine crystal grains, while too high a temperature will cause the reaction to be too vigorous.

[0055] Specifically, the evaporation crystallization includes: rotating and stirring a mixture of peroxymolybdic acid solution and metal cations at an evaporation crystallization temperature; after evaporation until a large number of solid particles are suspended in the solution, performing solid-liquid separation; drying the separated solids to obtain peroxymolybdic acid with a needle-like crystal structure doped with metal cations.

[0056] For example, the rotational speed of the stirring is 200-600 r / min, more preferably 200-350 r / min. Examples include 220 r / min, 240 r / min, 260 r / min, 280 r / min, 300 r / min, 320 r / min, and 340 r / min. Too low a speed will result in a large amount of solid adhering to the outer wall, while too high a speed may cause uneven grain development.

[0057] For example, a pressure filter is used for solid-liquid separation, and the separated wet filter cake is dried using a microwave dryer to obtain peroxymolybdic acid with a needle-like crystal structure doped with metal cations.

[0058] The evaporation and crystallization process of this invention is simple and easy to control, resulting in needle-like crystal structures of peroxymolybdic acid with a width of 30-120 nm and a length of over 5 μm. It exhibits excellent dispersibility, with a width of only about 100 nanometers, significantly increasing its specific surface area. Simultaneously, the dispersed and cross-arranged arrangement of the crystal grains creates a porous structure, allowing hydrogen gas to rapidly penetrate the interior of the crystals, thereby accelerating the reduction reaction and reducing the reduction time.

[0059] In this invention, the purpose of the first reduction is to reduce peroxymolybdic acid to molybdenum dioxide.

[0060] For example, the temperature for the first reduction is 480-530℃, such as 490℃, 500℃, 510℃, or 520℃. If the temperature for the first reduction is too high, the material is likely to grow into long strips; if the temperature for the first reduction is too low, reduction is difficult.

[0061] It should be noted that to obtain near-spherical molybdenum powder, different mass concentrations of added metal cations require different reduction processes (while the primary reduction temperature remains the same). These include two cases: metal cation mass concentration C is 0.02% ≤ C < 0.05% and metal cation mass concentration C is 0% ≤ C < 0.02%, as detailed below:

[0062] In one embodiment, the mass concentration C of the metal cation is 0.02% ≤ C < 0.05%, for example, the mass concentration C is 0.02%, 0.03%, or 0.04%. The temperature of the secondary reduction is 730-850℃, for example, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, or 840℃, and more preferably 750-850℃. Near-spherical molybdenum powder with a Fisher particle size of less than 0.5-1.1 μm can be obtained. The particle size of the near-spherical molybdenum powder increases with increasing potassium ion concentration.

[0063] Increasing the secondary reduction temperature within the aforementioned range can effectively increase the near-spherical grain size, but it cannot be increased indefinitely, as excessively high temperatures will alter the morphology. If the secondary reduction temperature is too low, reduction is difficult, and it may also cause the coarse parts of the grains to become nearly spherical; if the secondary reduction temperature is too high, it may cause grain inhomogeneity.

[0064] For example, the hydrogen flow rate for the first reduction is 2-4 m³ / h. 3 / h. If the hydrogen flow rate is too low for a single reduction, the reduction time will increase; if the hydrogen flow rate is too high for a single reduction, it may cause uneven grain size.

[0065] For example, the pushing speed of the boat in one restoration is 15-30 min / pass.

[0066] For example, the reduction time for one cycle is 180-360 minutes. Examples include 200 minutes, 220 minutes, 240 minutes, 260 minutes, 280 minutes, 300 minutes, 320 minutes, and 340 minutes. A reduction time that is too short will result in insufficient reduction and growth, while a time that is too long may cause grain enlargement or even over-reduction.

[0067] After the molybdenum dioxide obtained from the first reduction is cooled to room temperature, it is fed back into the charging boat of the reduction furnace for a second reduction. The purpose of the second reduction is to reduce molybdenum dioxide to molybdenum.

[0068] For example, the hydrogen flow rate for the secondary reduction is 5-18 m³ / h. 3 / h. Excessive hydrogen flow rate during secondary reduction can easily lead to uneven grain size.

[0069] For example, the pushing speed of the secondary restoration is 30-60 min / pass.

[0070] For example, the secondary reduction time is 6-12 hours. If the secondary reduction time is too short, the reduction may be insufficient; if the secondary reduction time is too long, it may cause excessive grain growth.

[0071] In another embodiment, the mass concentration C of the metal cation is 0% ≤ C < 0.02%, for example, the mass concentration C is 0%, 0.01%, or 0.015%, and the temperature of the secondary reduction is 780-850℃ or 930-1050℃, for example, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, or 1040℃. Increasing the secondary reduction temperature can effectively increase the near-spherical grain size, but it cannot be increased indefinitely, as excessively high temperatures will alter the morphology.

[0072] Specifically, when the temperature of the secondary reduction is 780-850℃, the small polyhedral MoO2 grains formed by the primary reduction undergo pseudomorphic transformation and chemical vapor transport, thereby preparing larger near-spherical molybdenum powder with a Fisher particle size of 0.7-0.9μm. Increasing the secondary reduction temperature within this range can effectively increase the near-spherical grain size, but it cannot be increased indefinitely, as excessively high temperatures will alter the morphology.

[0073] When the secondary reduction temperature is 930-1050℃, chemical vapor transport occurs in the small-sized polyhedral MoO2 grains formed in the primary reduction, producing near-spherical molybdenum powder with a small particle size. The Fisher particle size of the near-spherical molybdenum powder is 0.4-0.7 μm (excluding 0.7 μm). Increasing the secondary reduction temperature within this range can effectively increase the near-spherical grain size, but it cannot be increased indefinitely, as excessively high temperatures will alter the morphology.

[0074] It should be noted that when the temperature of the secondary reduction is greater than 850℃ but less than 930℃, inconsistent morphology will occur, resulting in mixed grains with two different morphologies.

[0075] For example, the hydrogen flow rate for the first reduction is 1.5-5 m³ / h. 3 / h. If the hydrogen flow rate is too low during the first reduction, the reaction will be incomplete; if the hydrogen flow rate is too high, the crystals will be uneven.

[0076] For example, the pushing speed of the boat in one restoration is 35-45 min / pass.

[0077] For example, the reduction time for one cycle is 200-420 min. Examples include 220 min, 240 min, 260 min, 280 min, 300 min, 320 min, 340 min, 380 min, and 400 min. A reduction time that is too short will result in insufficient reduction and growth, while a time that is too long may cause grain enlargement or even over-reduction.

[0078] After the molybdenum dioxide obtained from the first reduction is cooled to room temperature, it is fed back into the charging boat of the reduction furnace for a second reduction. The purpose of the second reduction is to reduce molybdenum dioxide to molybdenum.

[0079] For example, the hydrogen flow rate for the secondary reduction is 20-40 m³ / h. 3 / h. Secondary reduction requires a larger hydrogen flow rate to accelerate the reduction speed, but the hydrogen flow rate for secondary reduction cannot be too large, as an excessive flow rate will cause growth to be too fast and affect the morphology.

[0080] For example, the pushing speed of the secondary reduction is 15-60 min / pass.

[0081] For example, the secondary reduction time is 5-15 hours. If the secondary reduction time is too short, the reduction will be insufficient or the oxygen content will be high; if the secondary reduction time is too long, the grains may sinter.

[0082] The near-spherical molybdenum powder prepared by this invention can be used in 3D printing, surface spraying, injection molding, contact materials and other fields.

[0083] The preparation method of the near-spherical molybdenum powder of the present invention will be further illustrated below through specific embodiments.

[0084] Example 1

[0085] This embodiment provides a method for preparing near-spherical molybdenum powder, including:

[0086] (1) Preparation of peroxymolybdic acid solution

[0087] (a) Molybdenum calcined sand was leached with sulfuric acid with a concentration of 3 mol / L, the liquid-to-solid ratio (L / Kg) was 5:1, the temperature was 90℃, the pressure was normal, and the time was 4h to obtain an inorganic acid leaching solution containing molybdenum.

[0088] (b) The cationic extractant P507 was mixed with kerosene to prepare a kerosene solution, which was then added to the leachate to extract molybdenum from the leachate. The extraction ratio O / A = 1:1, the extraction stage was 4 stages, and the volume fraction of the cationic extractant in the kerosene solution was 30%. This yielded a molybdenum-loaded cation (MoO2) solution. 2+ The organic phase and raffinate;

[0089] (c) Using a 15% hydrogen peroxide solution as the back-extraction agent, it is mixed with an organic phase loaded with molybdenum acyl cations. The back-extraction ratio O / A = 3:1 and the number of back-extraction stages is 3, to obtain a molybdenum back-extraction solution, i.e., a peroxymolybdic acid solution, with a molybdenum ion concentration of 100 g / L.

[0090] (2) Preparation of needle-like crystal structure peroxymolybdic acid doped with metal cations: Potassium hydroxide was added to a peroxymolybdic acid solution, and the mass concentration of potassium ions in the mixture was 0.04%. After complete dissolution, the mixture was placed in a crystallization vessel and evaporated at 85°C with a rotating stirring speed of 300 r / min. After evaporation until a large number of solid particles were suspended in the solution, solid-liquid separation was performed using a pressure filter. The separated wet filter cake was then dried using a microwave dryer to obtain needle-like crystal structure peroxymolybdic acid doped with metal cations with a width of 40-120 nm and a length of 5-10 μm. Figure 3 As shown, slight agglomeration occurs, and agglomeration is also part of regulating the subsequent powder particle size.

[0091] (3) Primary reduction: Peroxymolybdic acid powder with a needle-like crystal structure doped with metal cations is loaded into the boat of the reduction furnace for primary reduction at a temperature of 490℃ and a hydrogen flow rate of 3m³ / h. 3 The boat pushing speed is 20 min / pass, and the time is 240 min. After one reduction cycle, the molybdenum dioxide obtained from the reduction is cooled to room temperature in the cooling zone.

[0092] (4) Secondary reduction: The cooled molybdenum dioxide is loaded into a new boat and pushed into a secondary reduction furnace for reduction at a temperature of 810℃ and a hydrogen flow rate of 15m³ / h. 3 The boat pushing speed is 40 min / pass, and the time is 10 h. After the second reduction, the molybdenum powder obtained by reduction is cooled to room temperature in the cooling zone, and the extracted molybdenum powder is passed through a 200-mesh sieve to obtain near-spherical nano-molybdenum powder, such as... Figure 6 As shown, the Fisher particle size is 0.78 μm.

[0093] Example 2

[0094] This embodiment provides a method for preparing near-spherical molybdenum powder, which does not involve the addition of metal cations and includes:

[0095] (1) Preparation of peroxymolybdic acid solution

[0096] (a) Molybdenum calcined sand was leached with sulfuric acid with a concentration of 3 mol / L, the liquid-to-solid ratio (L / Kg) was 5:1, the temperature was 90℃, the pressure was normal, and the time was 4h to obtain an inorganic acid leaching solution containing molybdenum.

[0097] (b) The cationic extractant P507 was mixed with kerosene to prepare a kerosene solution, which was then added to the leachate to extract molybdenum from the leachate. The extraction ratio O / A = 1:1, the extraction stage was 4 stages, and the volume fraction of the cationic extractant in the kerosene solution was 30%. This yielded a molybdenum-loaded cation (MoO2) solution. 2+ The organic phase and raffinate;

[0098] (c) Using a 15% hydrogen peroxide solution as the back-extraction agent, it is mixed with an organic phase loaded with molybdenum acyl cations. The back-extraction ratio O / A = 4.5:1 and the number of back-extraction stages is 3, to obtain a molybdenum back-extraction solution, namely peroxymolybdic acid solution, with a molybdenum ion concentration of 150 g / L.

[0099] (2) Preparation of needle-shaped peroxymolybdic acid doped with metal cations: The peroxymolybdic acid solution was placed in a crystallization vessel and evaporated and crystallized by rotating and stirring at 85°C. The rotation speed of the stirring was 300 r / min. After evaporation until a large number of solid particles were suspended in the solution, solid-liquid separation was performed using a pressure filter. The separated wet filter cake was dried using a microwave dryer to obtain needle-shaped peroxymolybdic acid with a width of 50-100 nm and a length of 5-10 μm.

[0100] (3) Primary reduction: Needle-shaped peroxymolybdic acid powder is loaded into the feed boat of the reduction furnace for primary reduction at a temperature of 510℃ and a hydrogen flow rate of 3m³ / h. 3 The boat pushing speed is 40 min / pass, and the time is 360 min. After one reduction cycle, the molybdenum dioxide obtained from the reduction is cooled to room temperature in the cooling zone.

[0101] (4) Secondary reduction: The cooled molybdenum dioxide is loaded into a new boat and pushed into a secondary reduction furnace for reduction at a temperature of 1000℃ and a hydrogen flow rate of 30m³. 3 The boat pushing speed was 40 min / pass, and the time was 10 h. After the second reduction, the reduced molybdenum powder was cooled to room temperature in the cooling zone, and the extracted molybdenum powder was passed through a 200-mesh sieve to obtain near-spherical nano-molybdenum powder with a Fisher particle size of 0.67 μm. Figure 1 As shown.

[0102] Example 3

[0103] This embodiment provides a method for preparing near-spherical molybdenum powder similar to that of Example 2, except that the secondary reduction temperature is 850°C. The obtained near-spherical nano-molybdenum powder is as follows: Figure 2 As shown, the Fisher particle size of the molybdenum powder is 0.86 μm.

[0104] Example 4

[0105] This embodiment provides a method for preparing near-spherical molybdenum powder similar to that of Example 1, except that the mass concentration of potassium ions is 0.02%. The resulting needle-like crystal structure of peroxymolybdic acid doped with metal cations has a width of 40-100 nm and a length of 5-10 μm. Figure 4 As shown, the Fisher particle size of the nearly spherical molybdenum nanoparticles obtained was 0.59 μm.

[0106] Example 5

[0107] This embodiment provides a method for preparing near-spherical molybdenum powder similar to that of Example 1, except that the mass concentration of potassium ions is 0.03%. The resulting needle-like crystal structure of peroxymolybdic acid doped with metal cations has a width of 40-110 nm and a length of 5-10 μm. Figure 5 As shown, the Fisher particle size of the nearly spherical molybdenum nanoparticles obtained was 0.68 μm.

[0108] Example 6

[0109] This embodiment provides a method for preparing near-spherical molybdenum powder similar to that in Embodiment 1, except that the crystallization evaporation temperature is 70°C.

[0110] The needle-like crystal structure of peroxymolybdic acid doped with metal cations was obtained with a width of 40-80 nm and a length of 5-10 μm.

[0111] Example 7

[0112] This embodiment provides a method for preparing near-spherical molybdenum powder similar to that in Embodiment 1, except that the rotational stirring speed during crystallization evaporation is 450 r / min.

[0113] Needle-shaped peroxymolybdic acid with doped metal cations was obtained, with a width of 30-100 nm and a length of 4-10 μm. Near-spherical molybdenum nanoparticles with a Fisher particle size of 0.55 μm were obtained.

[0114] Example 8

[0115] This embodiment provides a method for preparing near-spherical molybdenum powder similar to that of Example 1, except that the reduction temperature is 600°C. This produces elongated molybdenum powder.

[0116] Example 9

[0117] This embodiment provides a method for preparing near-spherical molybdenum powder similar to that in Example 1, except that the secondary reduction temperature is 840°C. The resulting near-spherical nano-molybdenum powder has a Fisher particle size of 0.80 μm.

[0118] Example 10

[0119] This embodiment provides a method for preparing near-spherical molybdenum powder similar to that of Example 1, except that the secondary reduction temperature is 900°C. A mixture of near-spherical and non-spherical morphologies of molybdenum powder is produced.

[0120] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing near-spherical molybdenum powder, characterized in that, The preparation method includes: (1) Molybdenum calcinate was leached, extracted, and back-extracted to obtain a peroxymolybdic acid solution: (2) Add metal cations to the peroxymolybdic acid solution so that the mass concentration of metal cations C is 0% ≤ C < 0.05%, then evaporate and crystallize. The resulting needle-shaped peroxymolybdic acid powder with or without metal cations is loaded into the boat of the reduction furnace and subjected to one reduction and two reductions in sequence to obtain near-spherical molybdenum powder.

2. The preparation method according to claim 1, characterized in that, The temperature for the first reduction is 480-530℃.

3. The preparation method according to claim 1 or 2, characterized in that, The mass concentration C of the metal cation is 0.02% ≤ C < 0.05%, and the temperature of the secondary reduction is 730-850℃.

4. The preparation method according to claim 3, characterized in that, The hydrogen flow rate for the first reduction is 2-4 m³ / h. 3 / h.

5. The preparation method according to claim 3, characterized in that, The speed of pushing the boat during one restoration is 15-30 minutes per pass.

6. The preparation method according to claim 3, characterized in that, The hydrogen flow rate for the secondary reduction is 5-18 m³ / h. 3 / h.

7. The preparation method according to claim 1 or 2, characterized in that, The mass concentration C of the metal cation is 0% ≤ C < 0.02%, and the temperature of the secondary reduction is 780-850℃ or 930-1050℃.

8. The preparation method according to claim 7, characterized in that, The hydrogen flow rate for the first reduction is 1.5-5 m³ / h. 3 / h.

9. The preparation method according to claim 7, characterized in that, The speed of pushing the boat during one restoration is 35-45 min / track.

10. The preparation method according to claim 7, characterized in that, The hydrogen flow rate for the secondary reduction is 20-40 m³ / h. 3 / h.

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