Method for purifying metal scandium by using vacuum distillation method and treatment method of tantalum collector

Abstract

The invention relates to the technical field of high-purity material preparation, and provides a treatment method of a tantalum collector for purifying metal scandium through a vacuum distillation method, the tantalum collector is a semi-closed cylinder, the lower end face of the tantalum collector is an open side and serves as a collecting opening, and the inner wall of the tantalum collector serves as a collecting face; a protective layer used for preventing scandium metal from being bonded with the tantalum collector is prepared on the collecting face of the tantalum collector, specifically, the protective layer extends inwards from a collecting opening, and the extending depth is 2 / 5-3 / 5 of the height of the tantalum collector. The protective layer is prepared at the bottom of the tantalum collector, so that the metal scandium is effectively prevented from being bonded with the tantalum collector; according to the tantalum collector treated by the method, the purity of metal scandium purified by a vacuum distillation method can be improved, and the difficulty of post-treatment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of high-purity material preparation, and specifically to a method for purifying metallic scandium by vacuum distillation and a method for treating a tantalum collector thereof. Background Art

[0002] Metallic scandium is an important rare earth element. Due to its special physical and chemical properties, it has a wide range of applications in multiple fields such as aluminum-scandium alloys, fuel cell electrolytes, scandium-sodium halide lamps, special glasses, and tracers. In addition, it also has broad application prospects in high-tech industrial fields such as 5G communication filters, superconductivity, high-performance ceramics, and catalysts. With the development and application of scandium in various fields, scandium has gradually become an irreplaceable element in new materials, and the market demand for high-purity scandium is increasing year by year. Metallic scandium has been widely used in national defense, metallurgy, chemical industry, aerospace, nuclear energy production, superconductivity, electric light sources, electrical components, medical science, and many other fields. In particular, its applications in laser crystals, new light source materials, and high-definition television picture tubes are the most remarkable. At the same time, these new applications also have higher and higher requirements for the purity of metallic scandium.

[0003] Distilling and purifying metallic scandium under vacuum conditions is one of the most commonly used and effective methods in industrial production. Its principle is to achieve separation and purification based on the differences in the melting points, boiling points, and vapor pressures of rare earth elements and impurities. Usually, tantalum sheets are used as collectors. However, since the metallic scandium distilled at high temperatures will penetrate and bond with the tantalum sheets, when the metallic scandium is peeled off, the tantalum skin will also be peeled off, resulting in too high a tantalum content in the metallic scandium and making it impossible to prepare high-purity scandium metal.

[0004] Generally, a vacuum carbon tube distillation furnace is usually used to purify metallic scandium. For example, CN217483263U discloses a metallic scandium distillation carbon tube furnace, which includes a heat-insulating outer shell, a crucible and a collection cylinder arranged inside the heat-insulating outer shell. The upper end of the collection cylinder is closed and the lower end is open. The upper end of the steam outlet of the crucible is connected to the lower end of the collection cylinder. A cooling device is arranged around the outside of the collection cylinder, and the height of the cooling device is not less than 2 / 3 of the height of the collection cylinder. The above patent also mentions in the specification: "The metallic scandium penetrates into the collection cylinder made of tantalum sheets, making it difficult to separate the tantalum sheets from the metallic scandium during the later processing. It is very difficult for workers to process the tantalum sheets on the surface of the metallic scandium, and there is also a situation where the processing is not clean, resulting in a high tantalum content in the metallic scandium and being unable to meet the customer's requirements." Thus, the problem that the collected high-purity rare earth metal will bond with the collector occurs.

[0005] In practical applications, we found that the bottom of the collection cylinder is more prone to adhesion. One of the causes of this problem is that during the high-temperature distillation of scandium metal, due to equipment limitations, a part of the bottom of the collection cylinder will inevitably be located below the insulation layer and have a higher temperature, which leads to the bottom of the tantalum collection cylinder being prone to adhesion with scandium vapor. The situation is similar to two pieces of alloy sticking together at high temperatures.

[0006] Based on this, the technical problem to be solved in this case is: how to solve the problem of adhesion between scandium metal and the tantalum collector during the purification of scandium metal by vacuum distillation, especially the adhesion to the bottom of the tantalum collector. Summary of the Invention

[0007] To solve the above technical problem, the present invention provides a method for purifying scandium metal by vacuum distillation and a method for treating the tantalum collector thereof. This solution effectively prevents the adhesion between scandium metal and the tantalum collector by preparing a protective layer at the bottom of the tantalum collector. The tantalum collector treated by the above method can improve the purity of scandium metal purified by vacuum distillation and reduce the difficulty of post-treatment.

[0008] The technical solution of the present invention is:

[0009] A method for treating a tantalum collector for purifying scandium metal by vacuum distillation, wherein the tantalum collector is a semi-closed cylinder, the lower end face thereof is an open side and serves as a collection port, and the inner wall thereof serves as a collection surface;

[0010] Prepare a protective layer on the collection surface of the tantalum collector to prevent the adhesion between scandium metal and the tantalum collector. Specifically, the protective layer extends inward from the collection port, and the extension depth is 2 / 5 to 3 / 5 of the height of the tantalum collector, including but not limited to 2 / 5, 1 / 2, 3 / 5.

[0011] In the actual process of purifying scandium metal by vacuum distillation in the present invention, a protective layer is prepared at the bottom of the tantalum collector. The protective layer can reduce the contact between the high-temperature scandium vapor and the bottom of the tantalum collector, thereby avoiding the adhesion between scandium metal and the collector. And the protective layer is preferably a boron nitride coating because the boron nitride coating itself has certain lubricating properties, which further avoids the occurrence of adhesion between scandium metal and the collector.

[0012] At the same time, in order to prevent the protective layer from reducing the purity of the scandium metal product, the present invention limits the extension direction and extension depth of the protective layer, specifically: extending inward from the collection port, and the extension depth is 2 / 5 to 3 / 5 of the height of the tantalum collector. Thus, the purity and quality of the scandium metal product are ensured to meet the standards.

[0013] In the above method for treating a tantalum collector for purifying scandium metal by vacuum distillation, the preparation method of the boron nitride coating includes the following steps:

[0014] Step 1: Shield the collection surface of the tantalum collector. After shielding, only the area with a height of 2 / 5 to 3 / 5 of the height of the tantalum collector is exposed on the collection surface.

[0015] Step 2: Spray boron nitride release agent on the exposed collection surface and let it stand for 30 - 60 s.

[0016] Step 3: Dry the tantalum collector, and the preparation of the boron nitride coating is completed. Preferably, the drying temperature is 100 - 200 °C.

[0017] In the above method for treating the tantalum collector in the purification of metallic scandium by vacuum distillation, in Step 1, the collection surface is shielded with pearl cotton wrapped in dust-free paper.

[0018] In the above method for treating the tantalum collector in the purification of metallic scandium by vacuum distillation, the specific spraying method in Step 2 is as follows: Place the tantalum collector horizontally; then align the nozzle of the spraying device filled with boron nitride release agent with the collection port of the tantalum collector; finally, while rotating the tantalum collector along its own axis, spray the boron nitride release agent using the spraying device.

[0019] In the above method for treating the tantalum collector in the purification of metallic scandium by vacuum distillation, the surface density of the boron nitride coating after drying in Step 3 is 3.0 - 4.5 mg / cm 2 , including but not limited to 3.0 mg / cm 2 、3.2 mg / cm 2 、3.5 mg / cm 2 、3.8 mg / cm 2 、4.0 mg / cm 2 、4.3 mg / cm 2 、4.5 mg / cm 2 .

[0020] In the above method for treating the tantalum collector in the purification of metallic scandium by vacuum distillation, before Step 1, the tantalum collector is first cleaned and the net weight W1 of the clean tantalum collector is weighed; after Step 3, the net weight W2 of the dried tantalum collector is weighed;

[0021] If (W2 - W1) / the surface area of the collection surface = 3.0 - 4.5 mg / cm 2 , the preparation of the boron nitride coating is completed; if (W2 - W1) / the surface area of the collection surface < 3.0 - 4.5 mg / cm 2 , return to Step 2; if (W2 - W1) / the surface area of the collection surface > 3.0 - 4.5 mg / cm 2 , clean the tantalum collector and then return to Step 1.

[0022] In addition, the present application also discloses a method for purifying scandium metal by vacuum distillation, using the above tantalum collector. The subsequent treatment of the prepared scandium metal product is simple, and the Ta content of the scandium metal product after subsequent treatment is < 10 ppm.

[0023] One of the technical solutions in the above technical solutions of the present invention has at least one of the following advantages or beneficial effects:

[0024] By preparing a protective layer at the bottom of the tantalum collector, the present invention reduces the contact between the high-temperature scandium vapor and the bottom of the tantalum collector, thereby avoiding the adhesion of scandium metal to the collector; at the same time, the present invention defines the extension direction and extension depth of the protective layer, thereby preventing the protective layer from reducing the purity of the prepared scandium metal product.

[0025] Using the tantalum collector of the present invention to purify scandium metal by vacuum distillation, the subsequent treatment of the prepared scandium metal product is simple, and the Ta content of the scandium metal product after subsequent treatment is < 10 ppm. Description of the Drawings

[0026] Figure 1 Appearance diagram of the scandium metal prepared in Example 4 of the present invention (not polished);

[0027] Figure 2 Appearance diagram of the scandium metal prepared in Comparative Example 3 of the present invention (not polished);

[0028] Figure 3 Appearance diagram of the scandium metal prepared in Comparative Example 3 of the present invention (polished). Detailed Description of the Invention

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. 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.

[0030] It should be noted that the implementation method also includes purifying scandium metal by vacuum distillation using the tantalum collector treated in the above examples and comparative examples. The results are shown in Figures 1 to 3 and Table 1.

[0031] Example 1

[0032] A processing method for a tantalum collector for purifying scandium metal by vacuum distillation. The tantalum collector is a semi-closed cylinder, the lower end surface of which is an open side and serves as a collection port, and the inner wall serves as a collection surface;

[0033] Prepare a protective layer on the collection surface of the tantalum collector to prevent the bonding of scandium metal to the tantalum collector. Specifically, the protective layer extends inward from the collection port, and the extension depth is 2 / 5 of the height of the tantalum collector. In this embodiment, the protective layer is preferably a boron nitride coating.

[0034] The processing method of this embodiment is as follows:

[0035] First, clean the tantalum collector;

[0036] Then, use the EPE wrapped with dust-free paper to cover the collection surface of the tantalum collector, and only expose the bottom part of the tantalum collector, which is 2 / 5 of the height of the tantalum collector in this embodiment; after covering, install the tantalum collector on the external tooling, place the tantalum collector horizontally, and then align the nozzle of the spraying device filled with boron nitride release agent with the collection port of the tantalum collector; it should be noted that the model of the boron nitride release agent selected in this embodiment is Jiadan JD-3028; during spraying, the distance between the collection port and the nozzle is about 15 cm, and the nozzle should be located on the axis of the tantalum collector.

[0037] Then, drive the tantalum collector to rotate along its own axis through the external tooling and spray boron nitride release agent at the same time. The number of rotation circles is two, and after spraying, let it stand for 60 s. This spraying operation can not only prevent the top and middle parts of the tantalum collector from being contaminated with boron nitride release agent, but also help to ensure the uniformity of the boron nitride coating.

[0038] Then, place the tantalum collector after spraying into an oven at 100 °C and dry it for 10 min.

[0039] Example 2

[0040] A processing method of a tantalum collector for purifying metallic scandium by vacuum distillation is basically the same as that of Example 1, except that: the boron nitride coating extends inward from the collection port, and the extension depth is 3 / 5 of the height of the tantalum collector.

[0041] Example 3

[0042] A processing method of a tantalum collector for purifying metallic scandium by vacuum distillation, the tantalum collector is a semi-closed cylinder, its lower end face is the open side and serves as the collection port, and its inner wall serves as the collection surface;

[0043] Prepare a protective layer on the collection surface of the tantalum collector to prevent the bonding of scandium metal to the tantalum collector. Specifically, the protective layer extends inward from the collection port, and the extension depth is 3 / 5 of the height of the tantalum collector. In this embodiment, the protective layer is preferably a boron nitride coating.

[0044] The processing method of this embodiment is as follows:

[0045] First, clean the tantalum collector, then weigh the net weight of the clean tantalum collector and record it as W1;

[0046] Then, use the pearl cotton wrapped with dust-free paper to block the collection surface of the tantalum collector, and only expose the bottom part of the tantalum collector, which is 2 / 5 of the height of the tantalum collector in this embodiment; after the blocking is completed, install the tantalum collector on the peripheral tooling, place the tantalum collector horizontally, and then align the nozzle of the spraying device filled with boron nitride release agent with the collection port of the tantalum collector; it should be noted that the model of the boron nitride release agent selected in this embodiment is Jiadan JD-3028; during spraying, the distance between the collection port and the nozzle is about 15 cm, and the nozzle should be located on the axis of the tantalum collector.

[0047] Then, drive the tantalum collector to rotate along its own axis through the peripheral tooling and spray boron nitride release agent at the same time. The number of rotation circles is two, and after spraying, let it stand for 60 s. This spraying operation can not only prevent the top and middle parts of the tantalum collector from being contaminated with boron nitride release agent, but also help to ensure the uniformity of the boron nitride coating.

[0048] Then, place the tantalum collector after spraying into an oven at 100 °C and dry it for 10 min, take it out and weigh it again and record it as W2; then compare W1 and W2. If (W2 - W1) / the surface area of the collection surface = 3.0 - 4.5 mg / cm 2 , that is, the preparation of the boron nitride coating is completed; if (W2 - W1) / the surface area of the collection surface < 3.0 - 4.5 mg / cm 2 , then spray the tantalum collector again; if (W2 - W1) / the surface area of the collection surface > 3.0 - 4.5 mg / cm 2 , it is judged that there is a problem of excessive boron nitride content in the finished product, and it should be cleaned and the above process should be repeated.

[0049] Example 4

[0050] A processing method for a tantalum collector used in the purification of metallic scandium by vacuum distillation method. The tantalum collector is a semi-closed cylinder, the lower end surface of which is an open side and serves as the collection port, and the inner wall serves as the collection surface;

[0051] Prepare a protective layer on the collection surface of the tantalum collector to prevent the bonding of scandium metal and the tantalum collector. Specifically, the protective layer extends inward from the collection port, and the extension depth is 3 / 5 of the height of the tantalum collector. In this embodiment, the protective layer is preferably a boron nitride coating.

[0052] The processing method of this embodiment is as follows:

[0053] First, clean the tantalum collector, then weigh the net weight of the clean tantalum collector and record it as W1;

[0054] Then, use the EPE wrapped with lint-free paper to block the collection surface of the tantalum collector, and only expose the bottom part of the tantalum collector, which is 2 / 5 of the height of the tantalum collector in this embodiment; after the blocking is completed, install the tantalum collector on the external tooling, place the tantalum collector horizontally, and then align the nozzle of the spraying device filled with boron nitride release agent with the collection port of the tantalum collector; it should be noted that the model of the boron nitride release agent selected in this embodiment is Jiadan JD-3028; during spraying, the distance between the collection port and the nozzle is about 15 cm, and the nozzle should be located on the axis of the tantalum collector.

[0055] Then, drive the tantalum collector to rotate along its own axis through the external tooling and spray boron nitride release agent at the same time. The number of rotation circles is two, and after spraying, let it stand for 60 s. This spraying operation can not only prevent the top and middle parts of the tantalum collector from being contaminated with boron nitride release agent, but also help to ensure the uniformity of the boron nitride coating.

[0056] Then, place the tantalum collector after spraying into an oven at 100 °C, dry it for 10 min, take it out and weigh it again and record it as W2; then compare W1 and W2. If (W2 - W1) / the surface area of the collection surface = 3.0 - 4.5 mg / cm 2 , the preparation of the boron nitride coating is completed; if (W2 - W1) / the surface area of the collection surface < 3.0 - 4.5 mg / cm 2 , then spray the tantalum collector again; if (W2 - W1) / the surface area of the collection surface > 3.0 - 4.5 mg / cm 2 , it is judged that the finished product has a problem of excessive boron nitride content and should be washed and the above process should be repeated.

[0057] Comparative Example 1

[0058] A method for treating a tantalum collector for purifying metallic scandium by vacuum distillation is basically the same as that of Example 4, except that: the boron nitride coating extends inward from the collection port, and the extension depth is 1 / 5 of the height of the tantalum collector.

[0059] Comparative Example 2

[0060] A method for treating a tantalum collector for purifying metallic scandium by vacuum distillation is basically the same as that of Example 4, except that: the boron nitride coating extends inward from the collection port, and the extension depth is 4 / 5 of the height of the tantalum collector.

[0061] Comparative Example 3

[0062] A method for treating a tantalum collector for purifying metallic scandium by vacuum distillation does not prepare a boron nitride coating.

[0063] Test: Refer to Figures 1 to 3, the scandium metal is purified by using a vacuum distillation method and a tantalum collector treated by the above examples and comparative examples.

[0064] Table 1: Adhesion of scandium metal to tantalum collectors in each example and Ta content in scandium metal

[0065]

[0066]

[0067] Result analysis:

[0068] No adhesion phenomenon occurred in both Example 1 and Example 2, and the subsequent grinding treatment was relatively easy. However, in multiple tests, the impurity content occasionally exceeded the quality control standard, especially for element B. It is speculated that the cause is the lack of standardization of the spraying thickness of the boron nitride coating.

[0069] No adhesion phenomenon occurred in both Example 3 and Example 4, and the subsequent grinding treatment was easier than that in Example 1 and Example 2. Due to the control of the areal density of the boron nitride coating, the detected impurity Ta element was less than 10 ppm and the contents of other impurities were stably in line with the specified standards. In addition, during actual application, the secondary spraying operation in Example 4 could effectively reduce the number of reworks and prepare a boron nitride coating with a suitable areal density, improving the production efficiency.

[0070] The boron nitride coating prepared in Comparative Example 1 did not completely cover the heat preservation area of the vacuum distillation, resulting in adhesion of part of the collector to the surface of the scandium metal obtained by subsequent distillation, increasing the number of reworks and the detected impurity Ta element being greater than 60 ppm, even greater than 100 ppm.

[0071] The boron nitride coating prepared in Comparative Example 2 occupied a relatively large area of the collection surface of the tantalum collector. Although no adhesion phenomenon occurred, the subsequent grinding treatment was relatively easy and the detected impurity Ta element was less than 10 ppm, but some elements, especially element B, exceeded the specified standards.

[0072] No boron nitride coating was prepared in Comparative Example 3, resulting in complete adhesion between the collector and the scandium metal obtained by distillation, which was difficult to remove. After subsequent grinding, the detected impurity Ta element seriously exceeded the standard, far higher than the specified standard.

[0073] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for treating a tantalum collector for purifying metallic scandium by vacuum distillation, characterized in that: The tantalum collector is a semi-enclosed cylinder, the lower end surface of which is an open side and serves as a collecting port, and the inner wall of which serves as a collecting surface; A protective layer is prepared on the collecting surface of the tantalum collector to prevent the scandium metal from adhering to the tantalum collector. Specifically, the protective layer extends inward from the collecting port, and the extending depth is 2 / 5 to 3 / 5 of the height of the tantalum collector.

2. The method for treating a tantalum collector for purifying metal scandium by vacuum distillation according to claim 1, characterized in that: The protective layer is a boron nitride coating.

3. The method for treating a tantalum collector for purifying metal scandium by vacuum distillation according to claim 2, characterized in that: The method for preparing the boron nitride coating comprises the following steps: Step 1: shielding the collecting surface of the tantalum collector, so that only 2 / 5 to 3 / 5 of the height of the tantalum collector is exposed; Step 2: Spray boron nitride release agent on the exposed collection surface and let it stand for 30 to 60 seconds; Step 3: Drying the tantalum collector completes the preparation of the boron nitride coating.

4. The method for treating a tantalum collector for purifying metal scandium by vacuum distillation according to claim 3, characterized in that: In the step 1, pearl cotton wrapped by dust-free paper is used for shielding.

5. The method for treating a tantalum collector for purifying metal scandium by vacuum distillation according to claim 3, characterized in that: The specific spraying method of step 2 is as follows: the tantalum collector is placed horizontally; then the nozzle of the spraying device equipped with the boron nitride release agent is directed toward the collection port of the tantalum collector; finally, the tantalum collector is rotated along its own axis while the boron nitride release agent is sprayed using the spraying device.

6. The method for treating a tantalum collector for purifying metal scandium by vacuum distillation according to claim 3, characterized in that: The surface density of the boron nitride coating after drying in step 3 is 3.0-4.5 mg / cm 2 .

7. The method for treating a tantalum collector for purifying metal scandium by vacuum distillation according to claim 6, characterized in that: Before step 1, the tantalum collector is cleaned and the net weight W1 of the clean tantalum collector is weighed; after step 3, the net weight W2 of the dried tantalum collector is weighed; If (W2-W1) / surface area of ​​collection surface = 3.0-4.5 mg / cm 2 , the preparation of the boron nitride coating is completed; if (W2-W1) / the surface area of ​​the collection surface is less than 3.0-4.5 mg / cm 2 , then return to step 2; if (W2-W1) / surface area of ​​the collection surface>3.0~4.5mg / cm 2 , then clean the tantalum collector and return to step 1.

8. A method for purifying metallic scandium by vacuum distillation, characterized in that: The tantalum collector as claimed in claims 1 to 7 is used.

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