Method for producing scandium metal

Abstract

To provide a method of preparing scandium metal.SOLUTION: A method of preparing scandium metal includes: mixing aluminum powder and scandium fluoride powder to form a mixture; heating the mixture in a vacuum environment to react the aluminum powder with the scandium fluoride powder to form aluminum fluoride gas and scandium metal; and removing the aluminum fluoride gas by evacuation to obtain the scandium metal.SELECTED DRAWING: None

Description

Technical Field

[0001] This technical field relates to a method for producing scandium metal.

Background Art

[0002] There are two existing methods for producing scandium metal. They are calciothermic reduction and molten salt electrolysis. The raw materials required for the calciothermic reduction method (such as calcium metal) have low purity. Also, they are difficult to store, and their reaction temperatures can vary drastically, resulting in very low purity of the product (such as scandium metal) (lower than 99 wt%), and the yield of the final product is low. The raw materials used in molten salt electrolysis (such as scandium halide) may severely corrode the electrolytic cell and electrode materials, that is, this method cannot be effectively used in large-scale industrial production operations.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] A novel method for producing scandium metal is needed.

Means for Solving the Problems

[0005] One embodiment of the present disclosure provides a method for producing scandium metal. The method includes mixing aluminum powder and scandium fluoride powder to form a mixture, heating the mixture in a vacuum environment to react the aluminum powder with the scandium fluoride powder to form aluminum fluoride gas and scandium metal, and removing the aluminum fluoride gas by evacuation to obtain scandium metal.

[0006] In some embodiments, the weight ratio of the aluminum powder to the scandium fluoride powder is from 0.27 to 0.4.

[0007] In some embodiments, the pressure of the vacuum environment is greater than 0.1 Pa and less than 1 Pa.

[0008] In some embodiments, the step of heating the mixture includes a first stage and a second stage. The first stage is carried out at a temperature of 900 °C to 1500 °C, and the second stage is carried out at a temperature of 1300 °C to 1800 °C.

[0009] In some embodiments, the first stage is carried out for 20 minutes to 2 hours, and the second stage is carried out for 20 minutes to 2 hours.

[0010] In some embodiments, the step of heating the mixture is a one-stage process carried out at a temperature of 1300 °C to 1500 °C for 40 minutes to 4 hours.

[0011] In some embodiments, the purity of the scandium metal is from 99 wt% to 100 wt%.

[0012] In some embodiments, the method further includes forming a scandium target or a scandium alloy target from the scandium metal.

Advantages of the Invention

[0013] Aluminum fluoride can be removed by evacuation, and there is no need to break the vacuum to remove solid by-products. According to the described method, high-purity (e.g., 99 wt% to 100 wt%) scandium metal can be formed without performing additional purification steps. The degree of vacuum in the vacuum environment of the present disclosure is not extremely high and can be achieved by a general vacuum pump. Further, the method of the present disclosure is simple and not complex, which is advantageous for mass production and cost reduction.

[0014] A detailed description will be given in the following embodiments.

Embodiments for Carrying Out the Invention

[0015] In the following detailed description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, it will be apparent that one or more embodiments may be practiced without these specific details.

[0016] One embodiment of the present disclosure provides a method for producing scandium metal. The method includes a step of mixing aluminum powder and scandium fluoride powder to form a mixture. In some embodiments, the weight ratio of the aluminum powder to the scandium fluoride powder is from 0.27 to 0.4. If the amount of the aluminum powder is too small, the purity of the scandium metal will be insufficient. If the amount of the aluminum powder is too large, the purity of the scandium metal will also be insufficient.

[0017] In the method, the mixture is then heated in a vacuum environment to react the aluminum powder with the scandium fluoride powder to form aluminum fluoride gas and scandium metal. For example, the reaction between the aluminum powder and the scandium fluoride powder is as shown below. Al+ScF 3 →AlF 3 +Sc

[0018] Aluminum fluoride can further react with aluminum as follows. AlF 3 +2Al → 3AlF

[0019] In some embodiments, the pressure of the vacuum environment is greater than 0.1 Pa and less than 1 Pa. If the pressure of the vacuum environment is too high (i.e., the degree of vacuum is insufficient), a part of the scandium metal reacts with oxygen to easily form scandium oxide, thereby hindering chemical reduction. As a result, the purity of the scandium metal product may be insufficient.

[0020] In this method, aluminum fluoride gas (e.g., AlF 3 and AlF) is then removed by evacuation to obtain scandium metal. In some embodiments, the purity of the scandium metal is from 99 wt% to 100 wt%, which can be used to produce a scandium target or a scandium alloy target (e.g., an aluminum scandium alloy target).

[0021] In some embodiments, the step of heating the mixture includes a first stage and a second stage. The first stage is carried out at a temperature of 900 °C to 1500 °C, and the second stage is carried out at a temperature of 1300 °C to 1800 °C. In some embodiments, the first stage is carried out for 20 minutes to 2 hours, and the second stage is carried out for 20 minutes to 2 hours. If the temperature of the first stage is too low or the time of the first stage is too short, the reaction between aluminum and fluorine will be incomplete, resulting in insufficient purity of the scandium metal. If the temperature of the first stage is too high or the time of the first stage is too long, a large amount of aluminum vapor will be generated, causing splash, and since the aluminum vapor cannot react with fluorine, aluminum fluoride cannot be formed. If the temperature of the second stage is too low or the time of the second stage is too short, the aluminum fluoride gas cannot be effectively removed, resulting in insufficient purity of the scandium metal. If the temperature of the second stage is too high or the time of the second stage is too long, the purity of the scandium metal will be insufficient.

[0022] In some embodiments, the step of heating the mixture is a one-step process carried out at a temperature of 1300 °C to 1500 °C for 40 minutes to 4 hours. Scandium metal can also be produced by this one-step process.

[0023] Compared with the existing methods for producing scandium metal, the method of the present disclosure has the following advantages. Since aluminum fluoride can be removed by evacuation, there is no need to break the vacuum to remove solid by-products. According to the described method, high-purity (e.g., 99 wt% to 100 wt%) scandium metal can be formed without performing additional purification steps. The degree of vacuum in the vacuum environment of the present disclosure (e.g., 0.1 Pa to 1 Pa) is not extremely high and can be achieved by a general vacuum pump. Also, the method of the present disclosure is simple and not complex, which is advantageous for mass production and cost reduction.

[0024] Exemplary embodiments will be described in detail below so that those of ordinary skill in the art can easily understand. The inventive concept can be embodied in various forms without being limited to the exemplary embodiments shown herein. For clarity, descriptions of well-known parts are omitted, and like reference numerals throughout indicate like components.

Example

[0025] Comparative Example 1 (Insufficient aluminum powder) Scandium fluoride (ScF 3, 100 g of scandium fluoride (ScF₃, commercially available from Uni-Onward Co.) and 26 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Subsequently, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1200 °C to carry out the first-stage reaction for about 20 minutes. After the first-stage reaction was completed, the temperature of the reaction chamber was raised to 1400 °C, and the pressure inside the reaction chamber was maintained below 1 Pa to carry out the second-stage reaction for about 20 minutes. After the second-stage reaction was completed, the heating device was turned off, and the vacuum pump continued to operate while on to remove aluminum fluoride gas. Subsequently, the reaction chamber was cooled to room temperature, and 45 g of scandium metal was obtained with a purity of 85.2 wt% (measured by EDX). Since the weight ratio of aluminum powder to scandium fluoride powder was too low (0.26), the purity of the scandium metal was insufficient.

[0026] Comparative Example 2 (Excessive Aluminum Powder) Scandium fluoride (ScF₃ 3 , 100 g of scandium fluoride (ScF₃, commercially available from Uni-Onward Co.) and 45 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Subsequently, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1200 °C to carry out the first-stage reaction for about 20 minutes. After the first-stage reaction was completed, the temperature of the reaction chamber was raised to 1400 °C, and the pressure inside the reaction chamber was maintained below 1 Pa to carry out the second-stage reaction for about 20 minutes. After the second-stage reaction was completed, the heating device was turned off, and the vacuum pump continued to operate while on to remove aluminum fluoride gas. Subsequently, the reaction chamber was cooled to room temperature, and 53 g of scandium metal was obtained with a purity of 62.0 wt% (measured by EDX). Since the weight ratio of aluminum powder to scandium fluoride powder was higher than 0.40, the excessive aluminum powder could not completely react, and thus the purity of the scandium metal was insufficient.

[0027] Comparative Example 3 (The reaction temperature in the first stage is excessively low) Scandium fluoride (ScF 3 , commercially available from Uni-Onward Co.) 100 g and aluminum powder (Al, commercially available from Uni-Onward Co.) 29 g were thoroughly mixed and placed in a crucible. Subsequently, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 850 °C to conduct the reaction in the first stage for about 20 minutes. After the reaction in the first stage was completed, the temperature of the reaction chamber was raised to 1300 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to conduct the reaction in the second stage for about 20 minutes. After the reaction in the second stage was completed, the heating device was turned off, and the vacuum pump continued to operate with the power on to remove aluminum fluoride gas. Subsequently, the reaction chamber was cooled to room temperature, and 48 g of scandium metal was obtained with a purity of 57.0 wt% (measured by EDX). Since the reaction temperature in the first stage was too low (850 °C), the purity of the scandium metal was insufficient.

[0028] Comparative Example 4 (The reaction temperature in the second stage is excessively low) Scandium fluoride (ScF 3, 120 g of commercially available (from Uni-Onward Co.) and 44 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Subsequently, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1200 °C to conduct the reaction in the first stage for about 20 minutes. After the reaction in the first stage was completed, the temperature of the reaction chamber was maintained at 1200 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to conduct the reaction in the second stage for about 20 minutes. After the reaction in the second stage was completed, the heating device was turned off, and the vacuum pump continued to operate while on to remove the scandium fluoride gas. Subsequently, the reaction chamber was cooled to room temperature, and 60 g of scandium metal was obtained with a purity of 65 wt% (measured by EDX). Since the reaction temperature in the second stage was too low (1200 °C), the purity of the scandium metal was insufficient.

[0029] Comparative Example 5 (The reaction temperature in the first stage is excessively high) Scandium fluoride (ScF 3, 100 g of (commercially available from Uni-Onward Co.) and 29 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Subsequently, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1600 °C to carry out the first-stage reaction for about 20 minutes. After the first-stage reaction was completed, the temperature of the reaction chamber was maintained at 1600 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to carry out the second-stage reaction for about 20 minutes. After the second-stage reaction was completed, the heating device was turned off, and the vacuum pump continued to operate while on to remove aluminum fluoride gas. Subsequently, the reaction chamber was cooled to room temperature, and 35 g of scandium metal was obtained with a purity of 86 wt% (measured by EDX). Since the reaction temperature in the first stage was too high (1600 °C), the purity of the scandium metal was insufficient. In addition, due to the reaction temperature in the first stage being too high, a large amount of aluminum vapor was formed, causing splashing, and the aluminum vapor could not react with fluorine, so aluminum fluoride was not formed.

[0030] Comparative Example 6 (The reaction temperature in the second stage is excessively high) Scandium fluoride (ScF 3, 100 g of (commercially available from Uni-Onward Co.) and 29 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Then, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1200 °C to carry out the first-stage reaction for about 20 minutes. After the first-stage reaction was completed, the temperature of the reaction chamber was raised to 1820 °C while maintaining the pressure inside the reaction chamber at less than 1 Pa, and the second-stage reaction was carried out for about 20 minutes. After the second-stage reaction was completed, the heating device was turned off, and the vacuum pump was kept operating to remove aluminum fluoride gas. Then, the reaction chamber was cooled to room temperature, and 40 g of scandium metal was obtained with a purity of 97.5 wt% (measured by EDX). Since the reaction temperature in the second stage was too high (1820 °C), the purity of the scandium metal was insufficient.

[0031] Comparative Example 7 (The pressure in the reaction chamber is excessively high) Scandium fluoride (ScF 3 , 100 g of (commercially available from Uni-Onward Co.) and 29 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Then, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to 5 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1200 °C to carry out the first-stage reaction for about 20 minutes. After the first-stage reaction was completed, the temperature of the reaction chamber was raised to 1400 °C while maintaining the pressure inside the reaction chamber at 5 Pa, and the second-stage reaction was carried out for about 20 minutes. After the second-stage reaction was completed, the heating device was turned off, and the vacuum pump was kept operating to remove aluminum fluoride gas. Then, the reaction chamber was cooled to room temperature, and 44 g of scandium metal was obtained with a purity of 72 wt% (measured by EDX). Since the pressure in the reaction chamber was too high (5 Pa), the purity of the scandium metal was insufficient.

[0032] Comparative Example 8 (Calcium and Scandium Fluoride) Scandium fluoride (ScF 3 , commercially available from Uni-Onward Co.) 100 g and calcium powder (Ca, commercially available from Uni-Onward Co.) 65 g were thoroughly mixed and placed in a crucible. Then, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to 0.01 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1650 °C and reacted for about 60 minutes. After the reaction was completed, solid calcium fluoride and liquid scandium were clearly separated into layers. After removing the solid calcium fluoride, the liquid scandium was cooled, and 38 g of scandium metal was obtained with a purity of 96.3 wt% (measured by EDX). Thus, when aluminum is replaced with calcium and the so-called calcium thermal reduction method is performed, the by-product calcium fluoride becomes solid and cannot be removed by evacuation, and the purity of the scandium metal product becomes insufficient.

[0033] Example 1 Scandium fluoride (ScF 3 , commercially available from Uni-Onward Co.) 100 g and aluminum powder (Al, commercially available from Uni-Onward Co.) 29 g were thoroughly mixed and placed in a crucible. Then, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1200 °C and the first-stage reaction was carried out for about 20 minutes. After the first-stage reaction was completed, the temperature of the reaction chamber was raised to 1400 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa, and the second-stage reaction was carried out for about 20 minutes. After the second-stage reaction was completed, the heating device was turned off, and the vacuum pump continued to operate with the power on to remove aluminum fluoride gas. Then, the reaction chamber was cooled to room temperature, and 43 g of scandium metal was obtained with a purity of 99.3 wt% (measured by EDX).

[0034] Example 2 Scandium fluoride (ScF3 120 g of scandium fluoride (ScF₃, commercially available from Uni-Onward Co.) and 44 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Subsequently, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1250 °C to conduct the first-stage reaction for about 20 minutes. After the completion of the first-stage reaction, the temperature of the reaction chamber was raised to 1500 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to conduct the second-stage reaction for about 25 minutes. After the completion of the second-stage reaction, the heating device was turned off, and the vacuum pump continued to operate with the power on to remove aluminum fluoride gas. Subsequently, the reaction chamber was cooled to room temperature, and 50 g of scandium metal was obtained with a purity of 99.5 wt% (measured by EDX).

[0035] Example 3 Scandium fluoride (ScF 3 150 g of scandium fluoride (ScF₃, commercially available from Uni-Onward Co.) and 52 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Subsequently, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, the heating device was turned on, and the raw materials in the crucible were heated to 1400 °C to conduct the first-stage reaction for about 25 minutes. After the completion of the first-stage reaction, the temperature of the reaction chamber was raised to 1500 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to conduct the second-stage reaction for about 30 minutes. After the completion of the second-stage reaction, the heating device was turned off, and the vacuum pump continued to operate with the power on to remove aluminum fluoride gas. Subsequently, the reaction chamber was cooled to room temperature, and 62 g of scandium metal was obtained with a purity of 99.2 wt% (measured by EDX).

[0036] Example 4 Scandium fluoride (ScF 3, 150 g of scandium fluoride (ScF, commercially available from Uni-Onward Co.) and 52 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Then, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, and the heating device was turned on to heat the raw materials in the crucible to 1400 °C, and the reaction in the first stage was carried out for about 25 minutes. After the reaction in the first stage was completed, the temperature of the reaction chamber was maintained at 1400 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to carry out the reaction in the second stage for about 30 minutes. After the reaction in the second stage was completed, the heating device was turned off, and the vacuum pump continued to operate with the power on to remove aluminum fluoride gas. Then, the reaction chamber was cooled to room temperature, and 55 g of scandium metal was obtained with a purity of 99.1 wt% (measured by EDX).

[0037] Example 5 Scandium fluoride (ScF 3 , 100 g of scandium fluoride (ScF, commercially available from Uni-Onward Co.) and 29 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Then, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, and the heating device was turned on to heat the raw materials in the crucible to 900 °C, and the reaction in the first stage was carried out for about 80 minutes. After the reaction in the first stage was completed, the temperature of the reaction chamber was increased to 1400 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to carry out the reaction in the second stage for about 20 minutes. After the reaction in the second stage was completed, the heating device was turned off, and the vacuum pump continued to operate with the power on to remove aluminum fluoride gas. Then, the reaction chamber was cooled to room temperature, and 41 g of scandium metal was obtained with a purity of 99.2 wt% (measured by EDX).

[0038] Example 6 Scandium fluoride (ScF 3, 100 g of scandium fluoride (ScF, commercially available from Uni-Onward Co.) and 29 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Then, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, and the heating device was turned on to heat the raw materials in the crucible to 1200 °C and perform the first-stage reaction for about 20 minutes. After the first-stage reaction was completed, the temperature of the reaction chamber was raised to 1800 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to perform the second-stage reaction for about 20 minutes. After the second-stage reaction was completed, the heating device was turned off, and the vacuum pump continued to operate with the pump on to remove aluminum fluoride gas. Then, the reaction chamber was cooled to room temperature, and 39 g of scandium metal was obtained with a purity of 99.4 wt% (measured by EDX).

[0039] Example 7 Scandium fluoride (ScF 3 , 100 g of scandium fluoride (ScF, commercially available from Uni-Onward Co.) and 29 g of aluminum powder (Al, commercially available from Uni-Onward Co.) were thoroughly mixed and placed in a crucible. Then, the crucible was placed inside the reaction chamber. The pressure inside the reaction chamber was reduced to less than 1 Pa by a vacuum pump, and the heating device was turned on to heat the raw materials in the crucible to 1450 °C and perform the first-stage reaction for about 20 minutes. After the first-stage reaction was completed, the temperature of the reaction chamber was lowered to 1350 °C, and the pressure inside the reaction chamber was maintained at less than 1 Pa to perform the second-stage reaction for about 20 minutes. After the second-stage reaction was completed, the heating device was turned off, and the vacuum pump continued to operate with the pump on to remove aluminum fluoride gas. Then, the reaction chamber was cooled to room temperature, and 40 g of scandium metal was obtained with a purity of 99.2 wt% (measured by EDX).

[0040] It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed methods and materials. The specification and examples are intended to be regarded as merely illustrative, and the true scope of the disclosure is indicated by the following claims and their equivalents.

Claims

1. A method for producing scandium metal, comprising: mixing aluminum powder and scandium fluoride powder to form a mixture; heating the mixture in a vacuum environment to react the aluminum powder with the scandium fluoride powder to form aluminum fluoride gas and scandium metal; removing the aluminum fluoride gas by evacuation to obtain the scandium metal; A method comprising the steps of.

2. The method according to claim 1, wherein the weight ratio of the aluminum powder to the scandium fluoride powder is from 0.27 to 0.

4.

3. The method according to claim 1, wherein the pressure of the vacuum environment is greater than 0.1 Pa and less than 1 Pa.

4. The method according to claim 1, wherein the step of heating the mixture includes a first stage and a second stage, the first stage is carried out at a temperature of 900 ° C to 1500 ° C, and the second stage is carried out at a temperature of 1300 ° C to 1800 ° C.

5. The method according to claim 4, wherein the first stage is carried out for 20 minutes to 2 hours, and the second stage is carried out for 20 minutes to 2 hours.

6. The method according to claim 1, wherein the step of heating the mixture is a one-step process carried out at a temperature of 1300 ° C to 1500 ° C for 40 minutes to 4 hours.

7. The method according to claim 1, wherein the purity of the scandium metal is from 99 wt% to 100 wt%.

8. The method according to claim 1, further comprising the step of forming a scandium target or a scandium alloy target from the scandium metal.