Low carbon high purity tantalum pentoxide powder and method for preparing same and use thereof

Abstract

The present invention relates to a low carbon high purity tantalum pentoxide powder and a method for preparing the same and its use. The powder has a carbon content of 15 ppm or less, preferably 10 ppm to 15 ppm, more preferably 3 ppm to 10 ppm. The preparation method includes the following steps: (1) adding fluorotantalic acid (H2TaF7) solution into a reaction vessel, controlling the temperature of the reaction vessel at 30-60°C, adding a precipitant until the pH of the reaction solution is 8-10, then stopping the introduction of ammonia, and aging to obtain a tantalum hydroxide slurry; (2) filtering and washing the tantalum hydroxide slurry obtained in step (1), and then carrying out solid-liquid separation to obtain a tantalum hydroxide filter cake; (3) drying the filter cake obtained in step (2) to obtain a white tantalum hydroxide powder; (4) calcining the tantalum hydroxide powder obtained in step (3), and pulverizing and sieving the calcined sample to obtain a tantalum pentoxide powder; and (5) subjecting the tantalum pentoxide powder obtained in step (4) to a heat treatment at a temperature of 1000-1500°C to obtain a high-purity tantalum pentoxide powder.

Description

[Technical field]

[0001] The present invention relates to the field of powder production, in particular to low carbon high purity tantalum pentoxide powder and methods for preparing same and uses thereof. [Background technology]

[0002] Tantalum pentoxide (also commonly known as tantalum oxide) is the raw material for producing metallic tantalum and is also used in the electronics industry to produce lithium tantalate single crystals and to produce optical glasses (especially high refractive index, low dispersion specialty optical glasses) and in the chemical industry as a catalyst.

[0003] In the prior art, tantalum oxide is mainly prepared by neutralization precipitation. This method includes the steps of using tantalum-niobium concentrate as raw material to separate tantalum and niobium by liquid-liquid extraction to form tantalum liquid containing tantalum in the form of H2TaF7 and a certain amount of HF and H2SO4, neutralizing the tantalum liquid with ammonia water to pH=8-10 to obtain water-insoluble white tantalum hydroxide, and then drying and calcining to obtain tantalum oxide. CN104386751A and CN104310323A disclose related technologies. However, these technologies have the disadvantage that it is difficult to sufficiently remove carbon from tantalum oxide. Unfortunately, too high carbon content, in particular, adversely affects the purity of tantalum pentoxide, thereby limiting the use of tantalum pentoxide in the preparation of high-purity materials, such as the preparation of high-purity tantalum powder and the growth of high-purity lithium tantalate crystals. Summary of the Invention [Problem to be solved by the invention]

[0004] Although much research has been done in the prior art, the problem of further reducing the carbon content of tantalum pentoxide has not yet been solved. [Means for solving the problem]

[0005] The present invention relates to low-carbon high-purity tantalum pentoxide. As used herein, "low-carbon high-purity" tantalum pentoxide or "high-purity" tantalum pentoxide refers to tantalum pentoxide having a carbon content of 15 ppm or less. Preferably, the carbon content is 10 ppm to 15 ppm, preferably 3 ppm to 10 ppm.

[0006] Tantalum oxide is the common name for tantalum pentoxide, but for accuracy, tantalum pentoxide will be primarily used in this specification to refer to it as Tb2O5. The present invention relates to a method for preparing tantalum pentoxide powder comprising the steps of:

[0007] (1) adding a fluorotantalic acid (H2TaF7) solution to a reaction vessel, controlling the temperature of the reaction vessel to 30 to 60°C (preferably 40 to 50°C), adding a precipitating agent until the pH of the reaction solution becomes 8 to 10 (preferably 8 to 9.5), and then stopping the introduction of ammonia and aging (e.g., aging for 2 to 5 hours, preferably 3 to 4 hours) to obtain a tantalum hydroxide slurry; (2) filtering and washing the tantalum hydroxide slurry obtained in step (1), and then carrying out solid-liquid separation to obtain a tantalum hydroxide filter cake; (3) drying the filter cake obtained in step (2) to obtain a white tantalum hydroxide powder; (4) calcining the tantalum hydroxide powder obtained in step (3), and grinding and sieving the calcined sample to obtain tantalum pentoxide powder; and (5) A step of subjecting the tantalum pentoxide powder obtained in step (4) to a heat treatment at a temperature of 1000 to 1500°C to obtain a high-purity tantalum pentoxide powder. The present invention relates to a method, including

[0008] More preferably, when the pH of the reaction solution in step (1) is 8 to 9, the addition of the precipitant is stopped. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In step (1), the fluorotantalic acid (H2TaF7) solution preferably has an oxide content calculated as Ta2O5 of 20-80 g / L, more preferably 35-65 g / L. The term "calculated as Ta2O5" will be clear to those skilled in the art. However, in order to make it easier for those skilled in the art to understand, the applicant will explain the term "calculated as Ta2O5" as follows. This is a common method for expressing the concentration of a fluorotantalic acid solution (sometimes referred to herein as a "tantalic acid solution"), in which the content of tantalum present mainly in complex form in the fluorotantalic acid solution is detected during the measurement, and then converted to a Ta2O5 content to express the concentration of the tantalic acid solution. This method is carried out in detail in accordance with the National Standard GB / T15076.1 of the People's Republic of China.

[0010] In step (1), the precipitating agent includes, but is not limited to, one or more selected from the group consisting of sodium bicarbonate, ammonium carbonate, urea, ammonia water, ammonia gas, and sodium hydroxide. Preferably, ammonia water is used as the precipitating agent, and in this case, the addition of the precipitating agent is also referred to as the introduction of ammonia gas. The introduction rate of ammonia water is not limited, but slow introduction is preferred. In step (1), stirring is preferably performed in a reaction kettle. More preferably, the stirring time is 5 to 10 minutes.

[0011] Preferably, the aging time (also referred to as rest time) in step (2) is 2 to 5 hours. More preferably, the aging time is 3 to 4 hours. Preferably, the filtration and washing in step (2) are repeated multiple times. For example, the filtration and washing can be carried out by adding the tantalum hydroxide solution obtained in step (1) to a filtration and washing tank, and then filtering and washing with hot pure water (for example, hot pure water at 90 to 100°C). Preferably, solid-liquid separation is carried out by negative pressure suction filtration.

[0012] Preferably, 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 (preferably 100 to 160°C, more preferably 120 to 140°C) for, for example, 8 to 12 hours (preferably 10 to 11.5 hours).

[0013] Preferably, the calcination in step (4) is carried out by placing the tantalum hydroxide powder obtained in step (3) in a crucible and placing it in a furnace. The furnace used herein is preferably a muffle furnace. Preferably, the calcination temperature is 900-1000°C (preferably 800-900°C), and the calcination time is 8-12 hours (preferably 9-11 hours).

[0014] The temperature of the high-temperature calcination heat treatment in step (5) is preferably 1200 to 1500°C (e.g., 1400°C), and the time is preferably 1 to 3 hours. In step (5), the sintering heat treatment atmosphere includes, but is not limited to, a vacuum, an inert atmosphere (e.g., helium, argon, neon, etc.), and an air atmosphere. A vacuum is more preferred.

[0015] The temperature of the high-temperature vacuum heat treatment in step (5) is preferably 1200 to 1400° C., more preferably 1200 to 1300° C. The heat treatment time is preferably 1 to 3 hours.

[0016] The high purity tantalum pentoxide powder obtained in step (5) preferably has a carbon content of 10 to 15 ppm, more preferably 3 to 10 ppm. The present invention also relates to the use of the above-mentioned tantalum pentoxide powder for producing lithium tantalate single crystals and catalysts, and for producing optical glasses, such as high refractive index, low dispersion optical glasses.

[0017] Without being bound by any general theory, after thorough research, the inventors believe that the main reason why it is difficult to further reduce the carbon content in the prior art is that in the manufacturing process of preparing high-purity tantalum pentoxide by neutralization precipitation, a large amount of organic substances are mostly used as the extractant in the early liquid-liquid extraction process, and in the subsequent process, the extractant cannot be completely removed, so that the high-purity tantalum pentoxide powder has a high carbon content. Due to the "inheritance" of the carbon impurity content, in the process of preparing tantalum powder using tantalum pentoxide, the carbon content of the tantalum powder will exceed the standard.

[0018] After extensive research, the present inventors have found that the method of the present invention can provide desirable low carbon, high purity tantalum pentoxide powder. EXAMPLES

[0019] In order to better illustrate the present invention, the following examples are provided. These examples are only for the purpose of a better understanding of the present invention by those skilled in the art, and are not intended to limit the present invention.

[0020] The examples were carried out under conventional conditions unless specific conditions were specified. Reagents or equipment used were of conventional, commercially available origin unless the manufacturer was specified. For purposes of this specification, all numbers expressing quantities of ingredients, reaction conditions, and the like in the specification and claims are to be understood as being modified in all instances by the term "about," unless otherwise indicated. Accordingly, the numerical parameters given in the following specification and appended claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention, unless otherwise indicated. At the very least, there is no intention to limit the application of the doctrine of equivalents to the scope of the claims, and each numerical parameter should be construed in accordance with, at the very least, the number of reported significant digits and ordinary rounding techniques.

[0021] Comparative Example 1 1. 100L of fluorotantalic acid solution with an oxide content of 50g / L calculated as Ta2O5 was added into the reaction kettle, and the reaction kettle was controlled at a temperature of 40°C. Ammonia water was slowly introduced into the tantalic acid solution until the reaction solution had a pH=9 to obtain a tantalum hydroxide slurry, which was then aged for 3 hours.

[0022] 2. The tantalum hydroxide slurry was transferred to a filtration and washing tank, and the reaction precipitate was repeatedly filtered and washed with hot pure water at a temperature of 95°C. Finally, solid-liquid separation was carried out by negative pressure suction filtration to obtain a white filter cake.

[0023] 3. The white filter cake was placed on a material tray and then dried in a hot air oven at a temperature of 100° C. for 10 hours to obtain a white tantalum hydroxide powder. 4. The white tantalum hydroxide powder was placed in a crucible and calcined in a muffle furnace at a temperature of 900°C for 10 hours, and then the sintered sample was crushed and sieved to obtain tantalum pentoxide powder.

[0024] The carbon content of the tantalum pentoxide powder was analyzed according to the national standard of the People's Republic of China GB / T15076.8, and the results are shown in Table 1. Example 1 1. 100L of fluorotantalic acid solution with an oxide content of 50g / L calculated as Ta2O5 was added into the reaction kettle, and the reaction kettle was controlled at a temperature of 40°C. Ammonia water was slowly introduced into the tantalic acid solution until the reaction solution had a pH=9 to obtain a tantalum hydroxide slurry, which was then aged for 3 hours.

[0025] 2. The tantalum hydroxide slurry was transferred to a filtration and washing tank, and the reaction precipitate was repeatedly filtered and washed with hot pure water at a temperature of 95°C. Finally, solid-liquid separation was carried out by negative pressure suction filtration to obtain a white filter cake.

[0026] 3. The white filter cake was placed on a material tray and then dried in a hot air oven at a temperature of 100° C. for 10 hours to obtain a white tantalum hydroxide powder. 4. The white tantalum hydroxide powder was placed in a crucible and calcined in a muffle furnace at a temperature of 900°C for 10 hours, and then the sintered sample was crushed and sieved to obtain tantalum pentoxide powder.

[0027] 5. The tantalum pentoxide powder was placed in a crucible and heat-treated in a high-temperature vacuum furnace at 1200°C for 2 hours to obtain low-carbon tantalum pentoxide powder. The carbon content of the tantalum pentoxide powder was analyzed according to the national standard of the People's Republic of China GB / T15076.8, and the results are shown in Table 1.

[0028] Comparative Example 2 1. 100L of fluorotantalic acid solution with an oxide content of 35g / L calculated as Ta2O5 was added into the reaction kettle, and the reaction kettle was controlled at a temperature of 60°C. Ammonia water was slowly introduced into the tantalic acid solution until the reaction solution had a pH=10 to obtain a tantalum hydroxide slurry, which was then aged for 3 hours.

[0029] 2. The tantalum hydroxide slurry was transferred to a filtration and washing tank, and the reaction precipitate was repeatedly filtered and washed with hot pure water at a temperature of 95°C. Finally, solid-liquid separation was carried out by negative pressure suction filtration to obtain a white filter cake.

[0030] 3. The white filter cake was placed on a material tray and then dried in a hot air oven at a temperature of 100° C. for 10 hours to obtain a white tantalum hydroxide powder. 4. The white tantalum hydroxide powder was placed in a crucible and calcined in a muffle furnace at a temperature of 800°C for 10 hours, and then the sintered sample was crushed and sieved to obtain tantalum pentoxide powder.

[0031] The carbon content of the tantalum pentoxide powder was analyzed according to the national standard of the People's Republic of China GB / T15076.8, and the results are shown in Table 1. Example 2 1. 100L of fluorotantalic acid solution with an oxide content of 35g / L calculated as Ta2O5 was added into the reaction kettle, and the reaction kettle was controlled at a temperature of 60°C. Ammonia water was slowly introduced into the tantalic acid solution until the reaction solution had a pH=10 to obtain a tantalum hydroxide slurry, which was then aged for 3 hours.

[0032] 2. The tantalum hydroxide slurry was transferred to a filtration and washing tank, and the reaction precipitate was repeatedly filtered and washed with hot pure water at a temperature of 95°C. Finally, solid-liquid separation was carried out by negative pressure suction filtration to obtain a white filter cake.

[0033] 3. The white filter cake was placed on a material tray and then dried in a hot air oven at a temperature of 100° C. for 10 hours to obtain a white tantalum hydroxide powder. 4. The white tantalum hydroxide powder was placed in a crucible and calcined in a muffle furnace at a temperature of 800°C for 10 hours, and then the sintered sample was crushed and sieved to obtain tantalum pentoxide powder.

[0034] 5. The tantalum pentoxide powder was placed in a crucible and heat-treated in a high-temperature vacuum furnace at 1350°C for 2 hours to obtain low-carbon tantalum pentoxide powder. The carbon content of the tantalum pentoxide powder was analyzed according to the national standard of the People's Republic of China GB / T15076.8, and the results are shown in Table 1.

[0035] [Table 1]

[0036] As can be seen from Table 1, the carbon content of the tantalum pentoxide powder obtained according to the method of the present invention is unexpectedly reduced by an order of magnitude.

Claims

1. 1. A method for preparing tantalum pentoxide powder comprising the steps of: (1) Fluorotantalic acid (H ２ TaF ７ ) adding the solution into a reaction vessel, controlling the temperature of the reaction vessel at 30-60°C, adding a precipitating agent until the pH of the reaction solution is 8-10, then stopping the introduction of the precipitating agent, and aging for 3-4 hours to obtain a tantalum hydroxide slurry; (2) filtering and washing the tantalum hydroxide slurry obtained in step (1), and then carrying out solid-liquid separation to obtain a tantalum hydroxide filter cake; (3) drying the filter cake obtained in step (2) to obtain a white tantalum hydroxide powder; (4) calcining the tantalum hydroxide powder obtained in step (3), and grinding and sieving the calcined sample to obtain tantalum pentoxide powder; and (5) A step of subjecting the tantalum pentoxide powder obtained in the step (4) to a heat treatment at a temperature of 1000 to 1500° C. to obtain tantalum pentoxide powder. A method comprising:

2. The method according to claim 1, wherein in the step (1), the precipitant is added until the pH of the reaction solution becomes 8 to 9.

3. In the step (1), the fluorotantalic acid (H ２ TaF ７ ) solution is Ta ２ O ５ 3. The method according to claim 1, wherein the oxide content, calculated as:

4. 3. The method according to claim 1 or 2, wherein in the step (1), the precipitating agent is one or more selected from the group consisting of sodium bicarbonate, ammonium carbonate, urea, ammonia water, ammonia gas, and sodium hydroxide.

5. The method according to claim 1 or 2, wherein in the step (1), stirring is carried out in the reaction vessel for 5 to 10 minutes.

6. The method of claim 4 , wherein the precipitating agent is aqueous ammonia.

7. The precipitating agent is aqueous ammonia, The method according to claim 1 or 2, wherein the drying in the step (3) is carried out by placing the filter cake in a hot air oven and drying it at 100 to 160° C. for 8 to 12 hours.

8. 3. The method according to claim 1 or 2, wherein the calcination in step (4) is carried out by placing the tantalum hydroxide powder obtained in step (3) in a crucible and placing it in a furnace.

9. The method according to claim 8, wherein the calcination temperature is 900-1000° C. and the calcination time is 8-12 hours.

10. The method according to claim 1 or 2, wherein in the step (5), the temperature of the heat treatment is 1200 to 1500° C.

11. 3. The method according to claim 1 or 2, wherein in the step (5), the atmosphere of the heat treatment is selected from the group consisting of a vacuum, an inert atmosphere, and an air atmosphere.

12. The method according to claim 10 or 11, wherein the heat treatment is carried out for 1 to 3 hours.

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