A tantalum pentoxide powder, its preparation method and uses

Abstract

This invention relates to a high-purity tantalum pentoxide powder, its preparation method, and its uses. The powder is characterized by a Fisher particle size to loose packing density ratio greater than 1.5, preferably greater than 2.0, more preferably greater than 2.5, more preferably greater than 3.0, more preferably greater than 3.5, more preferably greater than 4.5; more preferably 2.0-15.0, more preferably 2.0-5.0; and more preferably tantalum oxide with a purity of 99.995% or higher. The preparation method includes: (1) adding fluorotantalic acid (H2TaF7) solution to a reaction vessel, adding sulfuric acid to the fluorotantalic acid solution to make the acidity of the fluorotantalic acid solution exceed 2 mol / L, controlling the temperature of the reaction vessel to exceed 80°C, adding a precipitant until the pH of the reaction solution is 8 to 10, then stopping the ammonia supply, aging, and obtaining tantalum hydroxide slurry; (2) filtering and washing the tantalum hydroxide slurry obtained in step (1), and then performing solid-liquid separation to obtain tantalum hydroxide filter cake; (3) drying the filter cake obtained in step (2) to obtain tantalum hydroxide powder; (4) calcining the tantalum hydroxide powder obtained in step (3), crushing and sieving the calcined sample to obtain tantalum pentoxide powder; and (5) heat-treating the tantalum pentoxide powder obtained in step (4) at a temperature of 1000°C to 1500°C to obtain high-purity tantalum pentoxide powder.

Description

Technical Field

[0001] This invention relates to the field of powder manufacturing, and more specifically to a high-purity tantalum pentoxide powder, its preparation method, and its uses. Background Technology

[0002] Tantalum pentoxide, also commonly known as tantalum oxide (the two terms can be used interchangeably in this article), is a raw material for producing metallic tantalum and also has important applications in other industrial fields.

[0003] Chinese invention CN114057227B discloses a low-carbon, high-purity tantalum pentoxide powder and its manufacturing method, which successfully reduces the carbon content in tantalum oxide to below 15 ppm. However, although the carbon content impurities obtained by this patent are low, the overall purity is not satisfactory, and there is room for improvement in process stability. Moreover, it does not address the relationship between Fisher particle size and bulk density. Summary of the Invention

[0004] According to a first aspect, the present invention provides a tantalum oxide powder suitable as a raw material for the preparation of tantalum powder by magnesium reduction. The tantalum oxide powder has a Fisher particle size (in μm) and a bulk density (in g / cm³). 3 The ratio (in units) is greater than 1.5 (for example: Fisher particle size is 6.78μm, and loose packing density is 2.3g / cm³). 3 The ratio of the two is 6.78 ÷ 2.3 = 2.95.

[0005] The ratio of the Fisher particle size to the loose packing density of the tantalum oxide powder of the present invention is greater than 1.5, preferably greater than 2.0, more preferably greater than 2.5, more preferably greater than 3.0, more preferably greater than 3.5, more preferably greater than 4.5; more preferably 2.0-15.0, and most preferably 3.0-5.0.

[0006] Preferably, the tantalum oxide powder is high-purity tantalum oxide powder with a purity of 99.995% or higher; more preferably, the tantalum oxide powder is high-purity tantalum oxide powder with a purity of 99.999% or higher. The inventors have discovered that higher tantalum oxide purity is more beneficial for improving the electrical properties of tantalum powder.

[0007] A second aspect of the present invention provides a method for preparing tantalum oxide powder, characterized in that, before adding a precipitant to a fluorotantalic acid (H2TaF7) solution, sulfuric acid is added to the fluorotantalic acid solution to make the acidity of the fluorotantalic acid solution exceed 2 mol / L, preferably exceeds 2.2 mol / L, and more preferably 2.5-3.5 mol / L.

[0008] Preferably, the method includes:

[0009] (1) Add fluorotantalic acid (H2TaF7) solution to a reaction vessel, add sulfuric acid to make the acidity of the fluorotantalic acid solution at least 2 mol / L, add a precipitant (e.g., ammonia gas) until the pH of the reaction solution is 8-10 (preferably 8-9.5), then stop adding the precipitant and age (e.g., age for 2-5 hours, preferably 3-4 hours) to obtain tantalum hydroxide slurry;

[0010] (2) The tantalum hydroxide slurry obtained in step (1) is filtered and washed, and then solid-liquid separation is performed to obtain tantalum hydroxide filter cake;

[0011] (3) The filter cake obtained in step (2) is dried to obtain tantalum hydroxide powder;

[0012] (4) The tantalum hydroxide powder obtained in step (3) is calcined, and the calcined sample is crushed and sieved to obtain tantalum pentoxide powder; and

[0013] (5) Heat-treat the tantalum pentoxide powder obtained in step (4) at a temperature of 1000℃~1500℃ to obtain high-purity tantalum pentoxide powder.

[0014] In step (1), the preferred acidity range is 2 mol / L-5 mol / L. More preferably, when the pH of the reaction solution in step (1) is 8-9, the addition of precipitant is stopped.

[0015] In step (1), the fluorotantalic acid solution can be heated, and the temperature of the reaction vessel can be controlled to exceed 60°C, preferably above 80°C, and more preferably 85-95°C.

[0016] In step (1), preferably, the oxide content of the fluorotantalic acid (H2TaF7) solution, calculated as Ta2O5, is 20–120 g / L, more preferably 30–110 g / L, for example 40–100 g / L. Advantageously, this wider range provides greater process flexibility. The term "calculated as Ta2O5" is clear to those skilled in the art. However, to make it easier for those skilled in the art to understand, the inventors explain "calculated as Ta2O5" as follows: This is a commonly used method for expressing the concentration of fluorotantalic acid solution (sometimes simply referred to as "tantalic acid solution" in this document). Tantalum in fluorotantalic acid solution mainly exists in the form of a complex. During the determination process, the tantalum content in fluorotantalic acid is detected and then converted into the Ta2O5 content to express the concentration of the tantalic acid solution, specifically referring to the national standard GB / T15076.1.

[0017] In step (1), the precipitant includes, but is not limited to, one or more of sodium bicarbonate, ammonium carbonate, urea, ammonia water, ammonia gas, and sodium hydroxide. Preferably, ammonia gas is used as the precipitant; in this case, adding the precipitant can also be referred to as introducing ammonia gas. There is no limitation on the rate of ammonia gas introduction, but slow introduction is preferred. In step (1), stirring is preferably carried out in the reaction vessel.

[0018] Preferably, the aging time (also known as the settling time) in step (2) is 2-5 hours. More preferably, the aging time is 3-4 hours. Preferably, the filtration and washing in step (2) are repeated multiple times. For example, the filtration and washing can be carried out as follows: the tantalum hydroxide slurry obtained in step (1) is added to the filtration and washing tank, and then filtered and washed with hot pure water (e.g., hot pure water at 90-100°C). Preferably, solid-liquid separation is performed by negative pressure filtration.

[0019] Preferably, in step (3), the drying is carried out by placing the filter cake in a hot air oven and drying it at 80-180°C (preferably 100-160°C, more preferably 120-140°C) for, for example, 8-12 hours (preferably 10-11.5 hours). The tantalum hydroxide powder obtained in this step is generally white.

[0020] Preferably, the calcination in step (4) is carried out by loading the tantalum pentoxide powder obtained in step (3) into a crucible and placing it in a furnace. The furnace used here is preferably a muffle furnace. Preferably, the calcination temperature is 900℃~1000℃ (preferably 800℃~900℃), and the calcination time is 8h~12h (preferably 9-11h).

[0021] In step (5), the preferred high-temperature calcination heat treatment temperature is 1200℃~1500℃ (e.g., 1400℃), and the preferred time is 1~3h. In step (5), the sintering heat treatment atmosphere includes, but is not limited to, vacuum, inert atmosphere (e.g., helium, argon, neon, etc.), and atmospheric atmosphere. More preferably, it is carried out under vacuum.

[0022] Preferably, the high-temperature vacuum heat treatment temperature in step (5) is 1200℃~1400℃, more preferably 1200~1300℃. Preferably, the heat treatment time is 1h~5h, such as 3h.

[0023] Preferably, the ratio of the Fisher particle size to the loose packing density of the tantalum oxide powder obtained in step (5) is greater than 1.5, more preferably greater than 2.0, more preferably greater than 2.5, more preferably greater than 3.0, more preferably greater than 3.5, more preferably greater than 4.5; more preferably 2.0-15.0, more preferably 3.0-5.0. More preferably, the tantalum oxide powder has a purity of 99.995%, more preferably tantalum oxide with a purity of 99.999% or higher.

[0024] Through extensive experimentation, the inventors discovered that using a higher acidity as described in step (1) can increase the temperature inside the reactor with less external energy consumption due to the exothermic neutralization reaction. Furthermore, the inventors unexpectedly discovered that using such an acidity can stably produce tantalum oxide powder according to the first aspect of the invention. "Stable" means that the tantalum powder produced each time meets the particle size to bulk density ratio and purity requirements defined by the invention, without instances where the requirements are met one time but not the next, or only one of the two requirements is met in a particular instance. Regarding process stability, the selection of acidity (especially with the aid of sulfuric acid) in step (1) has yielded outstanding and unexpectedly beneficial effects.

[0025] The overall purity discussed in this article focuses on the sum of all impurities, rather than being limited to the content of one or more common impurities.

[0026] A third aspect of the invention also relates to the use of the aforementioned tantalum oxide powder, for example, in the electronics industry, for the production of lithium tantalate single crystals and the manufacture of optical glass (especially high-refractive-index, low-dispersion special optical glass), and as a catalyst in the chemical industry. Attached Figure Description

[0027] The following figures are provided to aid in understanding the invention. These figures are not intended to limit the scope of the invention.

[0028] Figure 1 Electron micrographs of tantalum oxide powder according to the first aspect of the present invention or tantalum oxide powder obtained according to the method of the second aspect. The figure shows that the microstructure has been improved. Detailed Implementation

[0029] The following embodiments are provided to better illustrate the present invention. These embodiments are merely intended to enable those skilled in the art to more readily understand the present invention and are not intended to limit the invention.

[0030] Unless otherwise specified in the examples, standard conditions were followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0031] For the purposes of this specification, all figures indicating amounts of ingredients, reaction conditions, etc., in the specification and claims shall in all cases be understood to be modified by the term "about," unless otherwise specified. Accordingly, the numerical parameters given in the following specification and appended claims are approximate values, which may vary according to the desired properties sought to be obtained according to the invention, unless indicated to the contrary. At least, and without limitation, the application of the doctrine of equivalence to the scope of the claims is intended, each numerical parameter shall be interpreted at least according to the number of significant figures reported and in accordance with ordinary rounding techniques.

[0032] The impurity content of tantalum pentoxide powder was analyzed according to the national standard GB / T15076.8, the Fisher particle size was analyzed according to the national standard GB / T3249, and the loose packing density was analyzed according to the national standard GB / T1479.1.

[0033] Example 1:

[0034] 1. Measure 100L of fluorotantalic acid solution, with an oxide content of 90g / L (calculated as Ta₂O₅), and add it to a reaction vessel. Then add sulfuric acid to adjust the acidity of the fluorotantalic acid solution to 2.8mol / L. Heat the fluorotantalic acid solution, controlling the temperature of the reaction vessel at 95℃. Slowly pass ammonia water into the tantalic acid solution until the pH of the reaction solution reaches 9, obtaining tantalum hydroxide slurry, and then age it for 3 hours.

[0035] 2. Transfer the tantalum hydroxide slurry into the filter washing tank, and repeatedly filter and wash the reaction precipitate with hot pure water at 95℃. Finally, use negative pressure filtration to separate the solid and liquid and obtain a white filter cake.

[0036] 3. Place the white filter cake into a tray and put it in a hot air oven. Dry it at 100°C for 10 hours to obtain tantalum hydroxide white powder.

[0037] 4. Put the white tantalum hydroxide powder into a crucible and calcine it in a muffle furnace at a temperature of 900℃ for 10 hours. After calcination, crush and sieve the sample to obtain tantalum pentoxide powder.

[0038] 5. Put tantalum pentoxide powder into a crucible, place it in a high-temperature vacuum furnace, and heat it at 1300℃ for 2 hours to obtain high-purity tantalum pentoxide powder.

[0039] The impurity content of the above tantalum pentoxide powder was analyzed and the purity of tantalum oxide was calculated. The Fisher particle size and loose packing density were analyzed and the ratio of the Fisher particle size to the loose packing density test values ​​was calculated. The results are listed in Table 1.

[0040] Example 2:

[0041] 1. Measure 100L of fluorotantalic acid solution, with an oxide content of 90g / L (calculated as Ta₂O₅), and add it to a reaction vessel. Then add sulfuric acid to adjust the acidity of the fluorotantalic acid solution to 2.2mol / L. Heat the fluorotantalic acid solution, controlling the temperature of the reaction vessel at 85℃. Slowly pass ammonia water into the tantalic acid solution until the pH of the reaction solution reaches 9, obtaining tantalum hydroxide slurry. Aging time is 3 hours.

[0042] 2. Transfer the tantalum hydroxide slurry into the filter washing tank, and repeatedly filter and wash the reaction precipitate with hot pure water at 95℃. Finally, use negative pressure filtration to separate the solid and liquid and obtain a white filter cake.

[0043] 3. Place the white filter cake into a tray and put it in a hot air oven. Dry it at 100°C for 10 hours to obtain tantalum hydroxide white powder.

[0044] 4. Put the white tantalum hydroxide powder into a crucible and calcine it in a muffle furnace at a temperature of 900℃ for 10 hours. After calcination, crush and sieve the sample to obtain tantalum pentoxide powder.

[0045] 5. Put tantalum pentoxide powder into a crucible, place it in a high-temperature vacuum furnace, and heat it at 1350℃ for 2 hours to obtain high-purity tantalum pentoxide powder.

[0046] The impurity content of the above tantalum pentoxide powder was analyzed and the purity of tantalum oxide was calculated. The Fisher particle size and loose packing density were analyzed and the ratio of the Fisher particle size to the loose packing density test values ​​was calculated. The results are listed in Table 1.

[0047] Example 3:

[0048] 1. Measure 100L of fluorotantalic acid solution, with an oxide content of 60g / L (calculated as Ta₂O₅), and add it to the reaction vessel. Then add sulfuric acid to adjust the acidity of the fluorotantalic acid solution to 2.5mol / L. Heat the fluorotantalic acid solution, controlling the temperature of the reaction vessel at 82℃. Slowly pass ammonia water into the tantalic acid solution until the pH of the reaction solution reaches 10, obtaining tantalum hydroxide slurry. Aging time is 3 hours.

[0049] 2. Transfer the tantalum hydroxide slurry into the filter washing tank, and repeatedly filter and wash the reaction precipitate with hot pure water at 95℃. Finally, use negative pressure filtration to separate the solid and liquid and obtain a white filter cake.

[0050] 3. Place the white filter cake into a tray and put it in a hot air oven. Dry it at 100°C for 10 hours to obtain white tantalum hydroxide powder.

[0051] 4. Put the white tantalum hydroxide powder into a crucible and calcine it in a muffle furnace at a temperature of 800℃ for 10 hours. After sintering, crush and sieve the sample to obtain tantalum pentoxide powder.

[0052] 5. Put tantalum pentoxide powder into a crucible, place it in a high-temperature vacuum furnace, and heat it at 1200℃ for 2 hours to obtain high-purity tantalum pentoxide powder.

[0053] The impurity content of the above tantalum pentoxide powder was analyzed and the purity of tantalum oxide was calculated. The Fisher particle size and loose packing density were analyzed and the ratio of the Fisher particle size to the loose packing density test values ​​was calculated. The results are listed in Table 1.

[0054] Example 4:

[0055] 1. Measure 100L of fluorotantalic acid solution, with an oxide content of 50g / L (calculated as Ta₂O₅), and add it to a reaction vessel. Then add sulfuric acid to adjust the acidity of the fluorotantalic acid solution to 2.5mol / L. Heat the fluorotantalic acid solution, controlling the temperature of the reaction vessel at 85℃. Slowly pass ammonia water into the tantalic acid solution until the pH of the reaction solution reaches 10, obtaining tantalum hydroxide slurry. Aging time is 3 hours.

[0056] 2. Transfer the tantalum hydroxide slurry into the filter washing tank, and repeatedly filter and wash the reaction precipitate with hot pure water at 95℃. Finally, use negative pressure filtration to separate the solid and liquid and obtain a white filter cake.

[0057] 3. Place the white filter cake into a tray and put it in a hot air oven. Dry it at 100°C for 10 hours to obtain white tantalum hydroxide powder.

[0058] 4. Put the white tantalum hydroxide powder into a crucible and calcine it in a muffle furnace at a temperature of 800℃ for 10 hours. After sintering, crush and sieve the sample to obtain tantalum pentoxide powder.

[0059] 5. Put tantalum pentoxide powder into a crucible, place it in a high-temperature vacuum furnace, and heat it at 1250℃ for 2 hours to obtain high-purity tantalum pentoxide powder.

[0060] The impurity content of the above tantalum pentoxide powder was analyzed and the purity of tantalum oxide was calculated. The Fisher particle size and loose packing density were analyzed and the ratio of the Fisher particle size to the loose packing density test values ​​was calculated. The results are listed in Table 1.

[0061] Example 5:

[0062] 1. Measure 100L of fluorotantalic acid solution, with an oxide content of 35g / L (calculated as Ta₂O₅), and add it to a reaction vessel. Then add sulfuric acid to adjust the acidity of the fluorotantalic acid solution to 2.5mol / L. Heat the fluorotantalic acid solution, controlling the temperature of the reaction vessel at 85℃. Slowly pass ammonia water into the tantalic acid solution until the pH of the reaction solution reaches 10, obtaining tantalum hydroxide slurry. Aging time is 3 hours.

[0063] 2. Transfer the tantalum hydroxide slurry into the filter washing tank, and repeatedly filter and wash the reaction precipitate with hot pure water at 95℃. Finally, use negative pressure filtration to separate the solid and liquid and obtain a white filter cake.

[0064] 3. Place the white filter cake into a tray and put it in a hot air oven. Dry it at 100°C for 10 hours to obtain white tantalum hydroxide powder.

[0065] 4. Put the white tantalum hydroxide powder into a crucible and calcine it in a muffle furnace at a temperature of 800℃ for 10 hours. After sintering, crush and sieve the sample to obtain tantalum pentoxide powder.

[0066] 5. Put tantalum pentoxide powder into a crucible, place it in a high-temperature vacuum furnace, and heat it at 1150℃ for 2 hours to obtain high-purity tantalum pentoxide powder.

[0067] The impurity content of the above tantalum pentoxide powder was analyzed and the purity of tantalum oxide was calculated. The Fisher particle size and loose packing density were analyzed and the ratio of the Fisher particle size to the loose packing density test values ​​was calculated. The results are listed in Table 1.

[0068] Example 6:

[0069] 1. Measure 100L of fluorotantalic acid solution, with an oxide content of 25g / L (calculated as Ta₂O₅), and add it to the reaction vessel. Then add sulfuric acid to adjust the acidity of the fluorotantalic acid solution to 2.5mol / L. Heat the fluorotantalic acid solution, controlling the temperature of the reaction vessel at 85℃. Slowly pass ammonia water into the tantalic acid solution until the pH of the reaction solution reaches 10, obtaining tantalum hydroxide slurry. Aging time is 3 hours.

[0070] 2. Transfer the tantalum hydroxide slurry into the filter washing tank, and repeatedly filter and wash the reaction precipitate with hot pure water at 95℃. Finally, use negative pressure filtration to separate the solid and liquid and obtain a white filter cake.

[0071] 3. Place the white filter cake into a tray and put it in a hot air oven. Dry it at 100°C for 10 hours to obtain white tantalum hydroxide powder.

[0072] 4. Put the white tantalum hydroxide powder into a crucible and calcine it in a muffle furnace at a temperature of 800℃ for 10 hours. After sintering, crush and sieve the sample to obtain tantalum pentoxide powder.

[0073] 5. Put tantalum pentoxide powder into a crucible, place it in a high-temperature vacuum furnace, and heat it at 1150℃ for 2 hours to obtain high-purity tantalum pentoxide powder.

[0074] The impurity content of the above tantalum pentoxide powder was analyzed and the purity of tantalum oxide was calculated. The Fisher particle size and loose packing density were analyzed and the ratio of the Fisher particle size to the loose packing density test values ​​was calculated. The results are listed in Table 1.

[0075] Table 1. Analysis results of high-purity tantalum pentoxide

[0076]

[0077] As can be seen from Table 1, the ratio of Fisher particle size to bulk density of the tantalum pentoxide powder obtained by the method of the present invention is significantly more ideal. In particular, its purity reaches 99.999%.

Claims

1. A method for preparing tantalum pentoxide powder, the method comprising: (1) Add fluorotantalic acid solution to the reaction vessel, add sulfuric acid to the fluorotantalic acid solution to make the acidity of the fluorotantalic acid solution exceed 2 to 5 mol / L, control the temperature of the reaction vessel above 80℃, add ammonia water as a precipitant until the pH of the reaction solution is 8 to 10, then stop the ammonia flow and age it to obtain tantalum hydroxide slurry. (2) The tantalum hydroxide slurry obtained in step (1) is filtered and washed, and then solid-liquid separation is performed to obtain tantalum hydroxide filter cake; (3) The filter cake obtained in step (2) is dried to obtain tantalum hydroxide powder; (4) The tantalum hydroxide powder obtained in step (3) is calcined, and the calcined sample is crushed and sieved to obtain tantalum pentoxide powder; and (5) Heat-treat the tantalum pentoxide powder obtained in step (4) at a temperature of 1000℃~1500℃ to obtain high-purity tantalum pentoxide powder.

2. The method according to claim 1, wherein in step (1), the temperature of the reactor is controlled above 85°C.

3. The method according to claim 1 or 2, wherein in step (1), the temperature of the reactor is controlled at 85-95°C.

4. The method according to claim 1 or 2, wherein in step (1), ammonia water as a precipitant is added until the pH of the reaction solution is 8-9.

5.

5. The method according to claim 1 or 2, wherein aging is performed for 2-5 hours in step (1).

6. The method according to claim 1 or 2, wherein aging is performed for 3-4 hours in step (1).

7. The method according to claim 1 or 2, wherein stirring is performed in the reaction vessel in step (1).

8. The method according to claim 1 or 2, wherein in step (1), stirring is performed in the reactor for 5-10 min.

9. The method according to claim 1 or 2, wherein the rinsing in step (2) is repeated multiple times.

10. The method according to claim 1 or 2, wherein in step (2), solid-liquid separation is performed by negative pressure filtration.

11. The method according to claim 1 or 2, wherein the drying in step (3) is carried out by placing the filter cake in a hot air oven and drying it at 80 to 180°C.

12. The method according to claim 11, wherein drying is performed at 100-160°C in step (3).

13. The method according to claim 11, wherein drying is performed at 120°C-140°C in step (3).

14. The method according to claim 11, wherein drying is performed for 8 to 12 hours in step (3).

15. The method according to claim 11, wherein drying is performed for 10 to 11.5 hours in step (3).

16. The method according to any one of claims 1-2 and 12-15, wherein the calcination in step (4) is carried out by loading the tantalum hydroxide powder obtained in step (3) into a crucible and placing it in a furnace.

17. The method of claim 16, wherein the furnace used is a muffle furnace.

18. The method according to claim 16, wherein the calcination temperature is 900°C to 1000°C.

19. The method according to claim 16, wherein the calcination time is 8h to 12h.

20. The method according to claim 16, wherein the calcination time is 9-11 h.

21. The method according to any one of claims 1-2, 12-15, and 17-20, wherein in step (5), the heat treatment temperature is 1200°C to 1500°C.

22. The method according to claim 21, wherein the heat treatment temperature is 1200℃~1400℃.

23. The method according to claim 21, wherein the heat treatment temperature is 1200~1300℃.

24. The method according to claim 21, wherein the heat treatment temperature is 1400°C.

25. The method according to claim 21, wherein the heat treatment time is 1-5 hours.

26. The method according to any one of claims 1-2, 12-15, and 17-20, wherein in step (5), the heat treatment atmosphere comprises a vacuum, an inert atmosphere, or an atmospheric atmosphere.

27. The method according to any one of claims 1-2, 12-15, and 17-20, wherein the heat treatment is performed under vacuum.

28. The method of claim 26, wherein the inert atmosphere is selected from one or more of helium, argon, and neon.

29. The method according to claim 1 or 2, wherein when the pH of the reaction solution in step (1) is 8 to 9, the addition of the precipitant is stopped.

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