Process for preparing tantalum powder with high specific surface area through cooperation of microwave-assisted magnesium reduction and graded oxidation

Abstract

The invention relates to the technical field of tantalum powder preparation, in particular to a process for preparing tantalum powder with a high specific surface area through cooperation of microwave-assisted magnesium reduction and graded oxidation. The process comprises the following steps that S1, tantalum pentoxide and magnesium are proportioned as raw materials and subjected to ball milling and mixing under argon protection; s2, the mixed raw materials are pressed and molded into raw material briquettes; s3, carrying out microwave heating on the raw material briquette, and reducing to obtain primary tantalum powder; s4, performing oxidation reaction on the primary tantalum powder in a relatively low-temperature and low-oxygen atmosphere to generate a tantalum oxide film on the surface; s5, performing acid pickling treatment with an HCl solution to obtain impurity-removed tantalum powder; s6, carrying out etching treatment on the impurity-removed tantalum powder by using HF + HNO3 mixed acid liquor, dissolving the tantalum oxide film on the surface to form porous tantalum powder, and carrying out water washing and suction filtration to obtain pure tantalum powder; s7, graded oxidation pore forming; S4-S6 circulation is carried out for more than three times, and finally the tantalum powder with the high specific surface area is obtained. According to the process, selective and rapid overall heating can be achieved, the temperature rise efficiency is high, rapid formation of nanometer tantalum cores is promoted, growth of tantalum particles is inhibited, and generation of superfine tantalum powder is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of tantalum powder preparation, and in particular relates to a process for synergistically preparing tantalum powder with high specific surface area by microwave-assisted magnesium reduction and graded oxidation. Background Art

[0002] Tantalum is a rare metal with a high melting point. It has excellent properties such as high melting point, high ductility, corrosion resistance, high electrical and thermal conductivity, excellent high-temperature strength, high dielectric constant of the oxide film, and excellent biocompatibility. It is widely used in the electronic information industry, steel machinery, aerospace and nuclear industry, superconducting technology, 3D printing, biomedical additive manufacturing, etc. Among the above application areas, the biocompatibility of tantalum gives it important development potential in the medical field. Because pure tantalum has been proven to be biologically active and can form a biological bond with bones, pure tantalum and its oxides have low solubility and toxicity in the body, have no rejection reaction in the human body, can promote bone cell growth, and are ideal materials for orthopedic implants (such as artificial joints and intervertebral fusion devices).

[0003] Porous tantalum implants can immediately bear weight and support bone deep into the internal structure, achieving good long-term fixation. Porous tantalum implants have the following advantages: (1) good bone conduction performance and higher normalized fatigue strength; (2) modulus matching the human body, effectively avoiding stress shielding; (3) excellent corrosion resistance and biocompatibility; (4) sufficient mechanical support and long fatigue life; (5) simulating bone mass transfer, supporting bone cell attachment, proliferation, differentiation and mineralization, and having excellent bone integration properties. Research generally believes that porous tantalum powder (20-80μm) can be used to prepare porous bone implants through laser powder bed fusion (LPBF) technology. Its biomimetic structure can promote bone ingrowth. Clinical data show that the postoperative recovery period is shortened by 30%, which is an excellent tantalum powder form for biocompatible materials. When tantalum is prepared as a porous biological implant, it is necessary to increase the porosity to reduce the elastic modulus so as to achieve the purpose of being similar to human bone and increase affinity.

[0004] Among the mainstream industrial nano-tantalum powder preparation processes, the sodium reduction potassium fluorotantalate method is mature, but it uses external heating and electrolysis methods, which have severe heat release that is difficult to control, resulting in coarse and uneven particles; the tantalum ingot hydrogenation-dehydrogenation method can be used to prepare ultrafine nano-tantalum powder, but the oxygen content of the finished product is too high, affecting the leakage current and breakdown voltage. At the same time, the tantalum powder is easy to agglomerate and requires additional spheroidization treatment, which increases costs; the magnesium / calcium thermal reduction method can achieve deep reduction, but it is easy to produce the by-product magnesium tantalate, and the reaction temperature needs to be precisely controlled to avoid excessive sintering; the plasma spheroidization method is easy to produce spherical tantalum powder, but the equipment is expensive and the energy consumption is high.

[0005] The preparation of tantalum powder in the existing technology has the following problems: it is difficult to balance ultrafine particle size and low oxygen content, the introduction of halide diluents leads to high pickling pressure, and the porosity of ultrafine tantalum powder is low. The above process does not have obvious advantages in controlling the morphology and porosity of tantalum powder, and is slightly weak for the preparation of porous tantalum for biomedical use. The existing tantalum powder preparation processes each have their own advantages and disadvantages, and there are limitations in achieving the goal of producing porous tantalum powder. For example, the process is cumbersome and the cycle is long, and the stable control of the optimal reaction temperature needs to be explored. There are problems such as fluoride salt contamination, low porosity of tantalum powder, uneven pore size and high closed porosity, and poor structure. As a result, the existing tantalum powder on the market is not conducive to the application of biomaterial additive manufacturing, and it is difficult to form industrialization. As a result, the application of tantalum in the biomedical field is limited by processing technology rather than biological performance. Therefore, the development of a low-cost, high-purity porous tantalum powder preparation process is a key direction to break through the current technical bottleneck. Summary of the Invention

[0006] In response to the above situation, the present invention provides a process for the coordinated preparation of high specific surface area tantalum powder by microwave-assisted magnesium reduction and graded oxidation, which can selectively and rapidly heat the entire product, has a high temperature rise efficiency, promotes the rapid formation of nano-tantalum nuclei, inhibits the growth of tantalum particles, and facilitates the production of ultrafine tantalum powder.

[0007] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0008] A process for preparing tantalum powder with high specific surface area by microwave-assisted magnesium reduction and graded oxidation comprises the following steps: S1, raw material pretreatment; tantalum pentoxide and magnesium are mixed in proportion to obtain a mixed raw material, and the mixed raw material is ball-milled under inert gas protection;

[0009] S2, briquette forming: pressing the mixed raw materials after ball milling into raw material briquette;

[0010] S3, microwave-assisted reduction; placing the raw material briquette in a reactor, introducing a protective gas for protection, and then subjecting the raw material briquette to microwave power treatment, so that the tantalum pentoxide and magnesium in the raw material briquette are heated as a whole to initiate a magnesium thermal reduction reaction, and then rapidly cooling after the reaction is completed to obtain primary tantalum powder;

[0011] S4, low-temperature oxidation; subjecting the primary tantalum powder obtained by reduction to an oxidation reaction in a relatively low-temperature environment and a low-oxygen atmosphere to form a tantalum oxide film on the surface of the primary tantalum powder to obtain impurity-containing tantalum powder;

[0012] S5, pickling and removing impurities; pickling the impurity-containing tantalum powder obtained after low-temperature oxidation with an HCl solution to remove the by-product magnesium oxide in the impurity-containing tantalum powder, then filtering out the residual HCl solution, and washing with water to remove the magnesium chloride produced during the pickling process to obtain a de-impurity tantalum powder;

[0013] S6, selective etching; etching the obtained decontaminated tantalum powder with a mixed acid solution of HF+HNO3, preferentially dissolving the tantalum oxide film on the surface of the decontaminated tantalum powder to form a porous tantalum powder with a mesoporous structure, then filtering out the remaining mixed acid solution, washing with water, and then filtering to obtain pure tantalum powder;

[0014] S7, graded oxidation to form pores; repeat steps S4-S6 for multiple times, wash and filter the pure tantalum powder obtained after etching, and dry the pure tantalum powder to finally obtain tantalum powder with a high specific surface area.

[0015] Preferably, in step S1, tantalum pentoxide and magnesium are prepared in a molar ratio of n(Ta2O5):n(Mg)=1:10, and the entire preparation process needs to be completed in a glove box filled with inert gas.

[0016] Preferably, the inert gas in step S1 is argon, and the mixed raw material obtained after tantalum pentoxide and magnesium are prepared is placed in a sealed mixing tank and then ball milled for 30 minutes.

[0017] Preferably, the briquette forming in step S2 is to quickly put the ball-milled mixed raw materials into a mold, and then use an automatic tablet press to press and form the raw material briquette into a specific shape at a pressure of 50 MPa.

[0018] Preferably, the reactor in step S3 is a graphite reactor, the protective gas is argon, and the reactor is rapidly cooled to room temperature after the magnesium thermal reduction reaction is completed.

[0019] Preferably, the relatively low temperature environment in step S4 refers to a temperature range of 200-300°C, and the low-oxygen atmosphere refers to an argon atmosphere containing 0.5wt% O2, in which an oxidation reaction is carried out to form a 1-2nm thick tantalum oxide film on the surface of the primary tantalum powder, and the obtained impure tantalum powder also contains magnesium oxide as a by-product.

[0020] Preferably, the pickling in step S5 is to place the impure tantalum powder obtained after low-temperature oxidation in a glass beaker, then add a certain concentration of HCl solution and stir and pickle for a certain period of time to fully dissolve the magnesium oxide, then filter the upper acid solution, add pure water and stir and wash for a certain period of time, and then filter to obtain the impurity-free tantalum powder.

[0021] Preferably, in step S6, a certain concentration of HF+HNO3 mixed acid solution is used to etch the decontaminated tantalum powder, preferentially dissolving the surface tantalum oxide film to form a porous tantalum powder containing a certain size and number of mesoporous structures. At the same time, it also has a certain dissolving effect on fine particles of tantalum powder, making the tantalum powder particle size more uniform. The porous tantalum powder is then ultrasonically washed to remove the dissolved tantalum oxide film to obtain pure tantalum powder.

[0022] Preferably, the graded oxidation pore formation in step S7 is to repeat steps S4-S6 for more than three times, repeatedly wash the pure tantalum powder obtained after the final selective etching, and then filter out the pure tantalum powder and vacuum dry it to obtain tantalum powder with a high specific surface area.

[0023] The present invention also includes other components that enable normal use, which are conventional means in the field. In addition, devices or components not limited in the present invention all adopt existing technologies in the field.

[0024] The beneficial effects of the present invention are as follows:

[0025] The present invention provides a process for preparing high-surface-area tantalum powder using microwave-assisted magnesium reduction and graded oxidation. The principle of microwave-assisted reduction is to stimulate molecular vibrations within the raw materials using microwave radiation, thereby generating heat and enabling the reaction to occur and continue. This method achieves selective and rapid overall heating with high temperature rise efficiency, promotes the rapid formation of tantalum nanoparticles, inhibits the growth of tantalum particles, and facilitates the production of ultrafine tantalum powder.

[0026] Meanwhile, the graded oxidation pore-forming technology selectively oxidizes tantalum powder at low temperatures, forming a controlled, thin tantalum oxide film to protect the tantalum particles from further oxidation. Acid then preferentially dissolves the tantalum oxide film, creating a mesoporous structure of varying sizes and increasing the porosity of the tantalum powder. This repetitive process allows for graded manipulation of the morphology of the tantalum powder, effectively increasing both specific surface area and porosity.

[0027] The tantalum powder preparation process of the present invention has a shorter microwave reaction time and higher production efficiency. No molten salt dilution is required, significantly reducing the degree of corrosion to equipment. Compared with existing technologies, the tantalum powder produced by the present invention has a specific surface area that is more than four times higher than that of traditional processes, and a significantly improved specific volume, while also meeting the performance requirements of high-voltage capacitors. In terms of morphology and structure, the tantalum powder produced by the present invention has a multi-mesoporous structure, a porosity increased by more than 45%, and a nanometer particle size, making it suitable for high-performance tantalum capacitors, 3D printing, and catalytic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a process flow chart for preparing tantalum powder with high specific surface area according to the present invention. DETAILED DESCRIPTION

[0029] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments.

[0030] Example 1

[0031] like Figure 1 As shown in FIG, the process for preparing tantalum powder with high specific surface area by microwave-assisted magnesium reduction and graded oxidation is as follows:

[0032] S1. Raw material pretreatment: Tantalum pentoxide and magnesium were prepared in a molar ratio of n(Ta2O5):n(Mg)=1:10 in a glove box filled with argon atmosphere to obtain a mixed raw material, and the mixed raw material was placed in a sealed mixing tank equipped with grinding balls, and then ball milled for 30 minutes;

[0033] S2, block forming; the mixed raw material after ball milling is quickly placed into a mold, and then an automatic tablet press is used to press the raw material into a cylindrical block with a diameter of 12.5 mm and a thickness of about 1 cm at a pressure of 50 MPa;

[0034] S3, microwave-assisted reduction; placing the raw material block into a graphite reactor, inserting a thermocouple for temperature measurement, then introducing argon gas for 5 minutes until the gas replacement is complete, then adjusting the microwave power to 800W (2.45GHz) to microwave heat the graphite reactor, and controlling the temperature at about 900°C for 45 minutes, so that the tantalum pentoxide and magnesium in the raw material block are heated as a whole to initiate a magnesium thermal reduction reaction, and after the reaction is completed, it is quickly water-cooled, and the product is taken out after cooling to room temperature to obtain primary tantalum powder;

[0035] S4, low-temperature oxidation; the primary tantalum powder obtained by reduction is subjected to a relatively low-temperature environment of 250°C in a tube furnace and then introduced into an argon gas containing 0.5 wt% O2. The atmosphere is maintained at this temperature for 10 minutes to form a dense tantalum oxide film with a thickness of 1-2 nm on the surface of the primary tantalum powder. The obtained impurity-containing tantalum powder also contains a small amount of by-product - magnesium oxide;

[0036] S5, pickling and removing impurities; placing the impure tantalum powder obtained after low-temperature oxidation in a glass beaker, adding a 10wt% HCl solution and stirring to acid-leach for 1 hour to fully dissolve the magnesium oxide, and pickling to remove the by-product magnesium oxide in the impure tantalum powder; then filtering out the residual HCl solution, adding pure water and stirring to wash for 10 minutes, and then filtering to remove the magnesium chloride produced during the pickling process, thereby obtaining the impurity-free tantalum powder;

[0037] S6, selective etching; the obtained decontaminated tantalum powder is subjected to an etching treatment by acid leaching with a 2.5wt% HF+10wt% HNO3 mixed acid solution for 1 hour, preferentially dissolving the tantalum oxide film on the surface of the decontaminated tantalum powder to form a porous tantalum powder with a mesoporous structure, and then filtering out the remaining mixed acid solution, and then ultrasonically washing for 5 minutes and then filtering, and filtering out the upper solution after precipitation, thereby obtaining pure tantalum powder;

[0038] S7, graded oxidation pore formation; repeat steps S4-S6 three times, and wash and filter the pure tantalum powder obtained after the final etching process, and repeatedly wash the pure tantalum powder obtained after the final selective etching process until the washing solution is neutral, and then filter out the pure tantalum powder and vacuum dry it. The main performance indicators of the high specific surface area tantalum powder finally obtained are as follows: oxygen content <1500ppm, specific surface area of 18-25m 2 / g range, and the average particle size range is 50-100nm; compared with the traditional sodium reduction method and magnesium reduction method, the porosity of the product obtained by the present invention is increased by more than 30%, and the specific surface area is greatly improved.

[0039] Example 2

[0040] The microwave-assisted magnesium reduction and graded oxidation process for preparing high specific surface area tantalum powder differs from that of Example 1 mainly in that the ratio of the HF+HNO3 mixed acid solution used in the etching step is different, and accordingly, the main performance indicators of the high specific surface area tantalum powder obtained are also different. The specific steps are as follows:

[0041] S1. Raw material pretreatment: Tantalum pentoxide and magnesium were prepared in a molar ratio of n(Ta2O5):n(Mg)=1:10 in a glove box filled with argon atmosphere to obtain a mixed raw material, and the mixed raw material was placed in a sealed mixing tank equipped with grinding balls, and then ball milled for 30 minutes;

[0042] S2, block forming; the mixed raw materials after ball milling are quickly placed into a mold, and then an automatic tablet press is used to press the raw material into a cylindrical block with a diameter of 12.5 mm and a thickness of about 1 cm at a pressure of 50 MPa;

[0043] S3, microwave-assisted reduction; placing the raw material block into a graphite reactor, inserting a thermocouple for temperature measurement, then introducing argon gas for 5 minutes until the gas replacement is complete, then adjusting the microwave power to 800W (2.45GHz) to microwave heat the graphite reactor, and controlling the temperature at about 900°C for 45 minutes, so that the tantalum pentoxide and magnesium in the raw material block are heated as a whole to initiate a magnesium thermal reduction reaction, and after the reaction is completed, it is quickly water-cooled, and the product is taken out after cooling to room temperature to obtain primary tantalum powder;

[0044] S4, low-temperature oxidation; the primary tantalum powder obtained by reduction is subjected to a relatively low-temperature environment of 250°C in a tube furnace and then introduced into an argon gas containing 0.5 wt% O2. The atmosphere is maintained at this temperature for 10 minutes to form a dense tantalum oxide film with a thickness of 1-2 nm on the surface of the primary tantalum powder. The obtained impurity-containing tantalum powder also contains a small amount of by-product - magnesium oxide;

[0045] S5, pickling and removing impurities; placing the impure tantalum powder obtained after low-temperature oxidation in a glass beaker, adding a 10wt% HCl solution and stirring to acid-leach for 1 hour to fully dissolve the magnesium oxide, and pickling to remove the by-product magnesium oxide in the impure tantalum powder; then filtering out the residual HCl solution, adding pure water and stirring to wash for 10 minutes, and then filtering to remove the magnesium chloride produced during the pickling process, thereby obtaining the impurity-free tantalum powder;

[0046] S6, selective etching; the obtained decontaminated tantalum powder is subjected to an etching treatment by acid leaching with a mixed acid solution of (5wt% HF+10wt% HNO3) for 1 hour, preferentially dissolving the tantalum oxide film on the surface of the decontaminated tantalum powder to form a porous tantalum powder with a mesoporous structure, and then filtering out the remaining mixed acid solution, and then ultrasonically washing for 5 minutes and then filtering, and filtering out the upper solution after precipitation to obtain pure tantalum powder;

[0047] S7, graded oxidation pore formation; repeat steps S4-S6 three times, and wash and filter the pure tantalum powder obtained after the final etching process, and repeatedly wash the pure tantalum powder obtained after the final selective etching process until the washing solution is neutral, and then filter out the pure tantalum powder and vacuum dry it. The main performance indicators of the high specific surface area tantalum powder finally obtained are as follows: oxygen content <1200ppm, specific surface area of 15-20m 2 / g range, and the average particle size range is 50-100nm.

[0048] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Without departing from the scope and spirit of the described embodiments, many modifications and changes are obvious to ordinary technicians in this technical field. Any technical deformation made within the spirit and principles of the present invention falls within the scope of protection of the present invention.

Claims

1. A process for preparing tantalum powder with high specific surface area by microwave-assisted magnesium reduction and graded oxidation, characterized in that: The following steps are involved: S1, raw material pretreatment; tantalum pentoxide and magnesium are mixed in proportion to obtain a mixed raw material, and the mixed raw material is ball-milled under the protection of an inert gas; S2, briquette forming: pressing the mixed raw materials after ball milling into raw material briquette; S3, microwave-assisted reduction; The raw material briquette is placed in a reactor and a protective gas is introduced for protection. The briquette is then subjected to microwave power treatment to heat the tantalum pentoxide and magnesium in the raw material briquette as a whole and initiate a magnesium thermal reduction reaction. After the reaction is completed, the briquette is rapidly cooled to obtain primary tantalum powder. S4, low-temperature oxidation; subjecting the primary tantalum powder obtained by reduction to an oxidation reaction in a relatively low-temperature environment and a low-oxygen atmosphere to form a tantalum oxide film on the surface of the primary tantalum powder to obtain impurity tantalum powder; S5, pickling and removing impurities; pickling the impurity-containing tantalum powder obtained after low-temperature oxidation with an HCl solution to remove the by-product magnesium oxide in the impurity-containing tantalum powder, then filtering out the residual HCl solution, and washing with water to remove the magnesium chloride produced during the pickling process to obtain a de-impurity tantalum powder; S6, selective etching; etching the obtained decontaminated tantalum powder with a mixed acid solution of HF+HNO3, preferentially dissolving the tantalum oxide film on the surface of the decontaminated tantalum powder to form a porous tantalum powder with a mesoporous structure, then filtering out the remaining mixed acid solution, washing with water, and then filtering to obtain pure tantalum powder; S7, graded oxidation to form pores; repeat steps S4-S6 for multiple times, and wash, filter and dry the pure tantalum powder obtained after etching to finally obtain tantalum powder with a high specific surface area.

2. The process for preparing high specific surface area tantalum powder by microwave-assisted magnesium reduction and graded oxidation according to claim 1, characterized in that: In step S1, tantalum pentoxide and magnesium are prepared in a molar ratio of n(Ta2O5):n(Mg)=1:10, and the entire preparation process must be completed in a glove box filled with inert gas.

3. The process for preparing high specific surface area tantalum powder by microwave-assisted magnesium reduction and graded oxidation according to claim 1 or 2, characterized in that: In step S1, the inert gas is argon, and the mixed raw material obtained after tantalum pentoxide and magnesium are placed in a sealed mixing tank, and then ball milled for 30 minutes.

4. The process for preparing high specific surface area tantalum powder by microwave-assisted magnesium reduction and graded oxidation according to claim 1, characterized in that: In step S2, the briquette forming is to quickly put the ball-milled mixed raw materials into a mold, and then use an automatic tablet press to press the raw material briquette at a pressure of 50 MPa.

5. The process for preparing high specific surface area tantalum powder by microwave-assisted magnesium reduction and graded oxidation according to claim 1, characterized in that: The reactor in step S3 is a graphite reactor, and the protective gas is argon. After the magnesium thermal reduction reaction is completed, it is quickly cooled to room temperature with water.

6. The process for preparing high specific surface area tantalum powder by microwave-assisted magnesium reduction and graded oxidation according to claim 1, characterized in that: The relatively low temperature environment in step S4 refers to a temperature range of 200-300°C, and the low-oxygen atmosphere refers to an argon atmosphere containing 0.5wt% O2, in which an oxidation reaction is carried out to form a tantalum oxide film on the surface of the primary tantalum powder. The obtained impure tantalum powder also contains magnesium oxide as a by-product.

7. The process for preparing high specific surface area tantalum powder by microwave-assisted magnesium reduction and graded oxidation according to claim 1, characterized in that: In step S5, the acid washing is to place the impure tantalum powder obtained after low-temperature oxidation in a glass beaker, then add 10wt% HCl solution and stir to acid-leach to fully dissolve the magnesium oxide, then filter the upper acid solution, add pure water and stir to wash and filter to obtain the impurity-free tantalum powder.

8. The process for preparing high specific surface area tantalum powder by microwave-assisted magnesium reduction and graded oxidation according to claim 1, characterized in that: In step S6, the decontaminated tantalum powder is etched with a mixed acid solution of HF+HNO3 to preferentially dissolve the surface tantalum oxide film to form a porous tantalum powder with a mesoporous structure. The porous tantalum powder is then ultrasonically washed to remove the dissolved tantalum oxide film to obtain pure tantalum powder.

9. The process for preparing tantalum powder with high specific surface area by microwave-assisted magnesium reduction and graded oxidation according to claim 8, characterized in that: In step S7, the graded oxidation pore formation is to repeat steps S4-S6 for more than three times, repeatedly wash the pure tantalum powder obtained after the final selective etching, and then filter out the pure tantalum powder and vacuum dry it to obtain tantalum powder with a high specific surface area.

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