Tantalum metal recovery and preparation method and high-purity tantalum ingot

Abstract

The invention discloses a tantalum metal recycling and preparing method and a high-purity tantalum ingot, and belongs to the technical field of tantalum target material design. The tantalum metal recycling and preparing method comprises the following steps that a recycled tantalum target material is subjected to desoldering treatment and then is cut into strips; the strip-shaped tantalum target material and the machined tantalum turning material are dried after being subjected to gradient acid pickling; the dried tantalum turning material is loaded into a mold to be pressed and formed, and a tantalum blank is obtained; the strip-shaped tantalum target material and the tantalum blank are welded and fixed, then smelting is conducted through electron beams, a coarse tantalum ingot is formed, and after the coarse tantalum ingot is scalped, a high-purity tantalum ingot is formed; polyether phosphazene is added in the second-stage pickling process, the molecular structure of the polyether phosphazene comprises ether bonds and hydrocarbon chains, the surface tension of hydrofluoric acid and nitric acid can be remarkably reduced in the pickling process, the tantalum metal surface can be wetted more easily, the hydrofluoric acid and the nitric acid rapidly permeate into microcracks and pores of an oxide layer, chemical reaction of acid liquor and the oxide layer on the tantalum metal surface is accelerated, and the tantalum metal surface corrosion resistance is improved. Therefore, the metal impurity content and the oxygen content on the tantalum surface can be removed more quickly and efficiently, and the purity of the prepared tantalum ingot can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tantalum target materials, and particularly relates to a method for recycling and preparing tantalum metal and a high-purity tantalum ingot. Background Art

[0002] Tantalum has a series of excellent properties such as high melting point, low vapor pressure, good cold working performance, high chemical stability, strong resistance to liquid metal corrosion, and large dielectric constant of the surface oxide film. Therefore, tantalum has important applications in high-tech fields such as electronics, metallurgy, iron and steel, chemical industry, cemented carbide, atomic energy, superconducting technology, automotive electronics, aerospace, medical and health, and scientific research.

[0003] Tantalum is one of the rare metal mineral resources and is an indispensable strategic raw material for the development of the electronics industry and space technology. With the continuous development of high-tech industries, the use and consumption of tantalum resources are also increasing continuously. However, the quantity of tantalum and its compounds extracted from natural minerals is limited. Tantalum chips and scraps will be generated during the cutting process of tantalum products. In addition, the target materials made of high-purity tantalum metal can be used as the diffusion barrier layer between copper interconnects and silicon substrates in advanced semiconductor technology, and are the key materials in the copper interconnect process.

[0004] Tantalum sputtering targets have become the key raw materials in the semiconductor industry and are irreplaceable, with a very broad application prospect. The preparation of tantalum targets has many and great difficulties, which are the key points and difficulties in the industry. Therefore, a large number of tantalum target development experimental products are required to damage and detect the grain crystal orientation index and its uniformity. After being damaged, the tantalum target blanks cannot be used as products and can only be remelted into tantalum ingots to become tantalum raw materials. However, this remelting method not only consumes a large amount of cost, but also the obtained tantalum ingots have low purity and are difficult to meet the use requirements of high-purity tantalum ingots. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for recycling and preparing tantalum metal and a high-purity tantalum ingot, and solve the following technical problems:

[0006] How to improve the purity of the tantalum ingots obtained by recycling and preparing waste tantalum target materials.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] In a first aspect, the present invention discloses a method for recycling and preparing tantalum metal, including the following steps:

[0009] Step 1: Perform a de-welding treatment on the recycled tantalum target material, and then cut it into strips;

[0010] Step 2: Gradiently pickle the strip-shaped tantalum target material and the machined tantalum turning stock, and then dry them;

[0011] Step 3: Load the dried tantalum turning stock into a mold and press it into shape to obtain a tantalum blank;

[0012] Step 4: Weld and fix the strip-shaped tantalum target to the tantalum blank, and then melt it by electron beam to form a rough tantalum ingot. After peeling the rough tantalum ingot, a high-purity tantalum ingot is formed.

[0013] Further, in Step 1, the method for removing the weld of the recycled tantalum target is as follows: Heat the recycled tantalum target to 170 - 200 °C, use a scraper to scrape off the molten slag on the surface, and after cooling, wash the surface of the tantalum target with a neutral water-based cleaning agent to remove the residual slag;

[0014] Preferably, the recycled tantalum target is heated to 180 °C.

[0015] Further, in Step 1, use a water jet cutting machine to cut the tantalum target into strips. The cutting abrasive is garnet, the cutting water pressure is 220 - 250 MPa, and the cutting feed rate is 10 - 30%;

[0016] Preferably, the cutting water pressure is 230 MPa and the cutting feed rate is 20%.

[0017] Further, in Step 2, the gradient pickling is successively the first-stage pickling, the second-stage pickling, and the third-stage pickling.

[0018] Further, the method for the first-stage pickling is as follows: Mix hydrofluoric acid with a mass fraction of 10 - 20% and dilute nitric acid with a mass fraction of 20 - 40% in a volume ratio of 1:1 to form pickling solution 1, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock in pickling solution 1 for 15 - 30 min;

[0019] Preferably, the method for the first-stage pickling is as follows: Mix hydrofluoric acid with a mass fraction of 15% and dilute nitric acid with a mass fraction of 30% in a volume ratio of 1:1 to form pickling solution 1, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock in pickling solution 1 for 20 min.

[0020] Further, the method for the second-stage pickling is as follows: Mix hydrofluoric acid with a mass fraction of 25 - 45% and dilute nitric acid with a mass fraction of 65 - 75% in a volume ratio of 1:1, add 0.1 - 0.5 wt% of polyether phosphazene to form pickling solution 2, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock that have undergone the first-stage pickling in pickling solution 2 for 5 - 10 min;

[0021] Preferably, the method for the second-stage pickling is as follows: Mix hydrofluoric acid with a mass fraction of 35% and dilute nitric acid with a mass fraction of 70% in a volume ratio of 1:1, add 0.3 wt% of polyether phosphazene to form pickling solution 2, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock that have undergone the first-stage pickling in pickling solution 2 for 8 min.

[0022] Further, the method for pickling in the third stage is as follows: Immerse the strip tantalum target and the machined tantalum turning stock after pickling in the second stage in isopropyl alcohol and ultrasonically clean for 10 - 20 min.

[0023] Further, in step three, the method for pressing the dried tantalum turning stock into a mold is as follows: Load the dried tantalum turning stock into an alloy steel mold, first press with a pressure of 500 - 800 tons for 1 - 2 min, then press with a pressure of 800 - 1300 tons for 1 - 3 min, and finally press with a pressure of 1300 - 2000 tons for 3 - 5 min;

[0024] Preferably, the method for pressing the dried tantalum turning stock into a mold is as follows: Load the dried tantalum turning stock into an alloy steel mold, first press with a pressure of 650 tons for 1.5 min, then press with a pressure of 1000 tons for 2 min, and finally press with a pressure of 1800 tons for 4 min.

[0025] Further, in step four, the method for melting by electron beam is as follows: First, perform horizontal melting with a vacuum degree ≤ 5×10 -3 Pa, a power of 200 - 400 W, and a rate of 50 - 80 kg / h, and after cooling for 3 - 5 h, perform vertical melting under the same conditions;

[0026] Preferably, first perform horizontal melting with a vacuum degree ≤ 5×10 -3 Pa, a power of 300 W, and a rate of 65 kg / h, and after cooling for 4 h, perform vertical melting under the same conditions.

[0027] Based on this, a preferred method for recovering and preparing tantalum metal is obtained, including the following steps:

[0028] Step one: Heat the recovered tantalum target to 180°C, use a scraper to scrape off the molten slag on the surface, and after cooling, use a neutral water-based cleaning agent to clean the surface of the tantalum target to remove the residual slag. Then, use a water jet cutting machine to cut the tantalum target into strips. The cutting abrasive is garnet, the cutting water pressure is 230 MPa, and the cutting feed ratio is 20%.

[0029] Step two: Gradient pickling;

[0030] (1) Pickling in the first stage: Mix hydrofluoric acid with a mass fraction of 15% and dilute nitric acid with a mass fraction of 30% in a volume ratio of 1:1 to form pickling solution one, and then immerse the strip tantalum target and the machined tantalum turning stock in pickling solution one for 20 min;

[0031] (2) Second-stage pickling: Mix hydrofluoric acid with a mass fraction of 35% and dilute nitric acid with a mass fraction of 70% in a volume ratio of 1:1, and add 0.3 wt% of polyether phosphazene to form pickling solution two. Then immerse the strip-shaped tantalum target and machined tantalum turning stock after the first-stage pickling in pickling solution two for 8 minutes;

[0032] (3) Third-stage pickling: Immerse the strip-shaped tantalum target and machined tantalum turning stock after the second-stage pickling in isopropyl alcohol and ultrasonically clean for 5 minutes;

[0033] (4) Dry the strip-shaped tantalum target and machined tantalum turning stock after the third-stage pickling.

[0034] Step three: Load the dried tantalum turning stock into an alloy steel mold, first press it at a pressure of 650 tons for 1.5 minutes, then press it at a pressure of 1000 tons for 2 minutes, and finally press it at a pressure of 1800 tons for 4 minutes to obtain a tantalum billet;

[0035] Step four: First, horizontally melt the tantalum billet at a vacuum degree ≤ 5×10 -3 Pa, a power of 300 W, and a rate of 65 Kg / h, cool it for 4 hours, and then vertically melt it under the same conditions. After peeling the rough tantalum ingot, a high-purity tantalum ingot is formed.

[0036] In the second aspect, the present invention also discloses a high-purity tantalum ingot prepared by using the tantalum metal recovery preparation method as described above, which can be used for product preparation and experimental development, greatly increasing the utilization value and economic value of tantalum metal, realizing the recycling of tantalum resources, and reducing the raw material procurement cost.

[0037] Advantages of the present invention: In the tantalum metal recovery preparation method of the present invention, by recycling the waste tantalum target and machined tantalum turning stock together, a high-purity tantalum ingot is obtained. During the recycling process, impurities on the surface of the tantalum target and in the tantalum turning stock are removed by gradient pickling; among them, polyether phosphazene is added during the second-stage pickling. Its molecular structure contains a hydrophilic group ether bond and a hydrophobic chain hydrocarbon chain, which can significantly reduce the surface tension of hydrofluoric acid and nitric acid during pickling, making it easier to wet the surface of tantalum metal and quickly penetrate into the microcracks and pores of the oxide layer, accelerating the chemical reaction between the acid solution and the oxide layer on the surface of tantalum metal. At the same time, polyether phosphazene forms charged micelles or steric hindrance effects by adsorbing on the surface of oxide layer fragments, which can prevent the peeled oxide particles from reattaching to the surface of tantalum metal. This dispersion effect can reduce secondary pollution and ensure that the surface of tantalum after pickling is cleaner, thereby more quickly and efficiently removing the metal impurity content and oxygen content on the surface of tantalum, improving the purity of the prepared tantalum ingot; a gradient pressing method is also used to manufacture the tantalum billet, avoiding crack caused by stress concentration, thereby improving the strength of the prepared high-purity tantalum ingot. Detailed implementation mode

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] In the experimental methods in the following embodiments, unless otherwise specified, they are all conventional methods and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The materials, reagents, etc. used in the following embodiments, unless otherwise specified, can all be obtained from commercial channels.

[0040] Example 1

[0041] This embodiment discloses a high-purity tantalum ingot, which is prepared by the following tantalum metal recovery preparation method, including the following steps:

[0042] Step 1: Heat the recovered tantalum target to 180 °C, use a scraper to scrape off the molten slag on the surface, and after cooling, use a neutral water-based cleaning agent to clean the surface of the tantalum target to remove the residual slag. Then, use a water jet cutting machine to cut the tantalum target into strips. The cutting abrasive is garnet, the cutting water pressure is 230 MPa, and the cutting feed rate is 20%.

[0043] Step 2: Gradient pickling;

[0044] (1) First-stage pickling: Mix hydrofluoric acid with a mass fraction of 15% and dilute nitric acid with a mass fraction of 30% in a volume ratio of 1:1 to form pickling solution 1, and then immerse the strip-shaped tantalum target and machined tantalum turning waste in pickling solution 1 for 20 min;

[0045] (2) Second-stage pickling: Mix hydrofluoric acid with a mass fraction of 35% and dilute nitric acid with a mass fraction of 70% in a volume ratio of 1:1, and add 0.3 wt% of polyether phosphazene to form pickling solution 2. Then, immerse the strip-shaped tantalum target and machined tantalum turning waste after the first-stage pickling in pickling solution 2 for 8 min;

[0046] (3) Third-stage pickling: Immerse the strip-shaped tantalum target and machined tantalum turning waste after the second-stage pickling in isopropyl alcohol and ultrasonically clean at 20 Hz for 15 min;

[0047] (4) Place the strip-shaped tantalum target and machined tantalum turning waste after the third-stage pickling in an oven and dry at 120 °C for 1 h.

[0048] Step 3: Load the dried tantalum turning stock into an alloy steel mold, press it at a pressure of 650 tons for 1.5 minutes, then press it at a pressure of 1000 tons for 2 minutes, and finally press it at a pressure of 1800 tons for 4 minutes to obtain a tantalum billet;

[0049] Step 4: Horizontally smelt the tantalum billet at a vacuum degree of 5×10 -3 Pa, a power of 300 W, and a rate of 65 kg / h. After cooling for 4 hours, vertically smelt it under the same conditions. After peeling the rough tantalum ingot, a high-purity tantalum ingot is formed.

[0050] Example 2

[0051] This example discloses a high-purity tantalum ingot, which is prepared by the following tantalum metal recovery preparation method, including the following steps:

[0052] Step 1: Heat the recycled tantalum target to 170 °C, use a scraper to scrape off the molten slag on the surface, and after cooling, use a neutral water-based cleaning agent to clean the surface of the tantalum target to remove the residual slag. Then, use a water jet cutting machine to cut the tantalum target into strips. The cutting abrasive is garnet, the cutting water pressure is 220 MPa, and the cutting feed rate is 10%.

[0053] Step 2: Gradient pickling;

[0054] (1) First-stage pickling: Mix hydrofluoric acid with a mass fraction of 10% and dilute nitric acid with a mass fraction of 20% in a volume ratio of 1:1 to form pickling solution 1, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock in pickling solution 1 for 30 minutes;

[0055] (2) Second-stage pickling: Mix hydrofluoric acid with a mass fraction of 25% and dilute nitric acid with a mass fraction of 65% in a volume ratio of 1:1, and add 0.3 wt% of polyether phosphazene to form pickling solution 2. Then, immerse the strip-shaped tantalum target and the machined tantalum turning stock after the first-stage pickling in pickling solution 2 for 10 minutes;

[0056] (3) Third-stage pickling: Immerse the strip-shaped tantalum target and the machined tantalum turning stock after the second-stage pickling in isopropyl alcohol and ultrasonically clean them at 20 Hz for 10 minutes;

[0057] (4) Place the strip-shaped tantalum target and the machined tantalum turning stock after the third-stage pickling in an oven and dry them at 120 °C for 1 hour.

[0058] Step 3: Load the dried tantalum turning stock into an alloy steel mold, press it at a pressure of 500 tons for 2 minutes, then press it at a pressure of 800 tons for 3 minutes, and finally press it at a pressure of 1300 tons for 5 minutes to obtain a tantalum billet;

[0059] Step 4: Horizontally smelt the tantalum billet at a vacuum degree of 5×10 -3 Pa, a power of 200 W, and a rate of 50 kg / h, cool for 3 h, then vertically smelt under the same conditions, and peel the rough tantalum ingot to form a high-purity tantalum ingot.

[0060] Example 3

[0061] This example discloses a high-purity tantalum ingot, which is prepared by the following tantalum metal recovery preparation method, including the following steps:

[0062] Step 1: Heat the recovered tantalum target to 200°C, use a scraper to scrape off the molten slag on the surface, wait for cooling, then use a neutral water-based cleaning agent to clean the surface of the tantalum target to remove the residual slag, and then use a water jet cutting machine to cut the tantalum target into strips. The cutting abrasive is garnet, the cutting water pressure is 250 MPa, and the cutting feed rate is 30%.

[0063] Step 2: Gradient pickling;

[0064] (1) First-stage pickling: Mix hydrofluoric acid with a mass fraction of 20% and dilute nitric acid with a mass fraction of 40% in a volume ratio of 1:1 to form pickling solution 1, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock in pickling solution 1 for 15 min;

[0065] (2) Second-stage pickling: Mix hydrofluoric acid with a mass fraction of 45% and dilute nitric acid with a mass fraction of 75% in a volume ratio of 1:1, add 0.3 wt% of polyether phosphazene to form pickling solution 2, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock after the first-stage pickling in pickling solution 2 for 5 min;

[0066] (3) Third-stage pickling: Immerse the strip-shaped tantalum target and the machined tantalum turning stock after the second-stage pickling in isopropanol and ultrasonically clean at 20 Hz for 20 min;

[0067] (4) Place the strip-shaped tantalum target and the machined tantalum turning stock after the third-stage pickling in an oven and dry at 120°C for 1 h.

[0068] Step 3: Load the dried tantalum turning stock into an alloy steel mold, first press at a pressure of 800 tons for 1 min, then press at a pressure of 1300 tons for 1 min, and finally press at a pressure of 2000 tons for 3 min to obtain a tantalum billet;

[0069] Step 4: Horizontally smelt the tantalum billet at a vacuum degree of 5×10 -3 Pa, a power of 400 W, and a rate of 80 kg / h, cool for 5 h, then vertically smelt under the same conditions, and peel the rough tantalum ingot to form a high-purity tantalum ingot.

[0070] Example 4

[0071] This example discloses a high-purity tantalum ingot, which is prepared by the following tantalum metal recycling preparation method, including the following steps: Compared with Example 1, the difference is only that: the addition amount of polyether phosphazene in the second-stage pickling in Step 2 is adjusted to 0.1 wt%; other steps and conditions remain the same, and finally a high-purity tantalum ingot is obtained.

[0072] Example 5

[0073] This example discloses a high-purity tantalum ingot, which is prepared by the following tantalum metal recycling preparation method, including the following steps: Compared with Example 1, the difference is only that: the addition amount of polyether phosphazene in the second-stage pickling in Step 2 is adjusted to 0.5 wt%; other steps and conditions remain the same, and finally a high-purity tantalum ingot is obtained.

[0074] Comparative Example 1

[0075] Compared with Example 1, the difference is only that: the first-stage pickling and the second-stage pickling in Step 2 are cancelled; other steps and conditions remain the same, and finally a high-purity tantalum ingot is obtained.

[0076] Comparative Example 2

[0077] Compared with Example 1, the difference is only that: the first-stage pickling in Step 2 is cancelled; other steps and conditions remain the same, and finally a high-purity tantalum ingot is obtained.

[0078] Comparative Example 3

[0079] Compared with Example 1, the difference is only that: polyether phosphazene in the second-stage pickling in Step 2 is cancelled; other steps and conditions remain the same, and finally a high-purity tantalum ingot is obtained.

[0080] Comparative Example 4

[0081] Compared with Example 1, the difference is only that Step 3 is adjusted to: loading the dried tantalum turning material into an alloy steel mold and directly pressing it at a pressure of 1000 tons for 7.5 minutes to obtain a tantalum billet; other steps and conditions remain the same, and finally a high-purity tantalum ingot is obtained.

[0082] Perform performance tests on the high-purity tantalum ingots obtained in Examples 1-5 and Comparative Examples 1-4, including purity tests and strength tests. The test methods are as follows:

[0083] Purity test: Refer to GB / T 3628-2020 "Methods for Chemical Analysis of Tantalum and Tantalum Alloys" to test the contents of "W + Mo" and O;

[0084] Strength test: Refer to GB / T 228.1-2021 "Tensile Testing of Metallic Materials - Part 1: Method of Test at Room Temperature" to test the tensile strength.

[0085] The test results are listed in Table 1 as follows:

[0086] Table 1

[0087]

[0088]

[0089] By analyzing the data in Table 1, it can be seen that compared with Comparative Examples 1-3, the high-purity tantalum ingots of Examples 1-5 have significantly higher purity; compared with Comparative Example 4, the high-purity tantalum ingots of Examples 1-5 have significantly higher strength.

[0091] The above has described in detail multiple embodiments of the present invention, but the above content is only the preferred embodiments of the present invention and cannot be considered as used to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for recycling and preparing tantalum metal, characterized in that, It includes the following steps: Step 1: Deweld the recycled tantalum target, and then cut it into strips; Step 2: Gradiently pickle the strip-shaped tantalum target and machined tantalum turning stock, and then dry them; Step 3: Load the dried tantalum turning stock into a mold and press it into shape to obtain a tantalum blank; Step 4: Weld and fix the strip-shaped tantalum target to the tantalum blank, and then melt it by electron beam to form a rough tantalum ingot. After peeling the rough tantalum ingot, a high-purity tantalum ingot is formed.

2. The tantalum metal recovery and preparation method according to claim 1, characterized in that In Step 1, the method for dewelding the recycled tantalum target is: heat the recycled tantalum target to 170 - 200 °C, use a scraper to scrape off the molten slag on the surface, and after cooling, use a neutral water-based cleaning agent to clean the surface of the tantalum target to remove the residual slag.

3. The tantalum metal recovery and preparation method according to claim 1, characterized in that, In Step 1, use a water jet cutting machine to cut the tantalum target into strips. The cutting abrasive is garnet, the cutting water pressure is 220 - 250 MPa, and the cutting feed rate is 10 - 30%.

4. The tantalum metal recovery and preparation method according to claim 1, characterized in that, In Step 2, the gradient pickling is successively the first-stage pickling, the second-stage pickling, and the third-stage pickling.

5. The tantalum metal recovery and preparation method according to claim 4, characterized in that, The method for the first-stage pickling is: Mix hydrofluoric acid with a mass fraction of 10 - 20% and dilute nitric acid with a mass fraction of 20 - 40% in a volume ratio of 1:1 to form pickling solution 1, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock in pickling solution 1 for 15 - 30 min.

6. The tantalum metal recovery and preparation method according to claim 4, characterized in that, The method for the second-stage pickling is: Mix hydrofluoric acid with a mass fraction of 25 - 45% and dilute nitric acid with a mass fraction of 65 - 75% in a volume ratio of 1:1, add 0.1 - 0.5 wt% of polyether phosphazene to form pickling solution 2, and then immerse the strip-shaped tantalum target and the machined tantalum turning stock after the first-stage pickling in pickling solution 2 for 5 - 10 min.

7. The tantalum metal recovery and preparation method according to claim 4, characterized in that, The method for the third-stage pickling is: Immerse the strip-shaped tantalum target and the machined tantalum turning stock after the second-stage pickling in isopropanol and ultrasonically clean for 10 - 20 min.

8. The tantalum metal recovery and preparation method according to claim 1, characterized in that In Step 3, the method for loading the dried tantalum turning stock into a mold and pressing it into shape is: Load the dried tantalum turning stock into an alloy steel mold, first press it with a pressure of 500 - 800 tons for 1 - 2 min, then press it with a pressure of 800 - 1300 tons for 1 - 3 min, and finally press it with a pressure of 1300 - 2000 tons for 3 - 5 min.

9. The tantalum metal recovery and preparation method according to claim 1, characterized in that In step four, the method of smelting by electron beam is as follows: first, horizontal smelting is carried out with a vacuum degree ≤ 5×10 -3 Pa, a power of 200 - 400 W, and a rate of 50 - 80 kg / h, and after cooling for 3 - 5 h, vertical smelting is carried out under the same conditions.

10. A high-purity tantalum ingot, characterized in that, Prepared by using the tantalum metal recycling preparation method described in any one of claims 1 - 9.

Images