High-purity tantalum powder and preparation method thereof

Abstract

The present invention relates to a high-purity tantalum powder and a preparation method therefore. The tantalum powder has a purity of more than 99.995%, as analyzed by GDMS. Preferably, the tantalum powder has an oxygen content of not more than 1000 ppm, a nitrogen content of not more than 50 ppm, a hydrogen content of not more than 20 ppm, a magnesium content of not more than 5 ppm, and an average particle diameter D50 of less than 25 m.

Claims

1. A high purity tantalum powder having a purity of greater than 99.995%, as analyzed by Glow Discharge Mass Spectrometry (GDMS); the tantalum powder having an oxygen content of not more than 1000 ppm, and a magnesium content of not more than 5 ppm, and the tantalum powder having a particle diameter D50<25 m, wherein the high purity tantalum powder is prepared by a method comprising the following steps in sequence: 1) subjecting a high purity tantalum ingot to a hydrogenation treatment; 2) crushing the tantalum scraps as prepared after the hydrogenation of the tantalum ingot to tantalum powder, and then purifying the powder by pickling to remove impurity contaminations introduced during ball milling; 3) subjecting the tantalum powder obtained in step 2) to a high-temperature dehydrogenation treatment, wherein the high-temperature dehydrogenation is carried out as follows: tantalum powder is heated at about 800-1000 C. and maintained at this temperature for about 60-300 minutes, cooling the tantalum powder; discharging; and sieving to produce a dehydrogenated tantalum powder; 4) subjecting the tantalum powder obtained in step 3) to a deoxygenation treatment, wherein the deoxygenation temperature is lower than the dehydrogenation temperature by a temperature within the range of from 50-300 C.; 5) subjecting the tantalum powder obtained in step 4) to pickling, washing, baking to dry, and sieving; and 6) subjecting the tantalum powder obtained in step 5) to a low-temperature heat treatment performed by maintaining a temperature within the range of 600-1200 C. for about 15-90 minutes, and then subjecting the treated tantalum powder to cooling, passivating, discharging, and sieving to produce the high purity tantalum powder.

2. The high purity tantalum powder of claim 1, wherein the tantalum powder has: a nitrogen content of not more than 50 ppm, preferably not more than 40 ppm; and a hydrogen content of not more than 20 ppm, preferably not more than 10 ppm.

3. The high purity tantalum powder of claim 1, wherein the tantalum powder has a particle diameter D50<20 m.

4. The high purity tantalum powder of claim 1, wherein the high-temperature dehydrogenation of step 3) is carried out as follows: tantalum powder is heated at about 900-950 C. and the temperature is maintained for about 60-300 minutes; and the tantalum powder is then subjected to cooling, discharging, and sieving operations to achieve the dehydrogenated tantalum powder.

5. The high purity tantalum powder of claim 1, wherein the deoxygenation temperature is lower than the dehydrogenation temperature by about 80-200 C.

6. The high purity tantalum powder of claim 1, wherein said low-temperature heat treatment is performed by maintaining the temperature of about 600-1200 C. for about 60 minutes, and at a vacuum level of 10.sup.3 Pa or higher.

7. The high purity tantalum powder of claim 1, wherein the tantalum scraps are crushed in step 2) to a level that the resultant powder can pass through 400-700-mesh sieves.

8. A method of using the high purity tantalum powder of claim 1 in semiconductor, medical and/or surface spray coating applications.

Description

SPECIFIC MODES FOR CARRYING OUT THE INVENTION

(1) For the purpose of illustration but not limitation, the following examples are provided.

(2) In each embodiment, tantalum powder obtained by the process of reducing potassium ftuotantalate with sodium is used as the raw material (referred to as sodium reduced tantalum powder). However, it should be understood that tantalum powder obtained by other processes also can achieve the object of the present invention.

(3) As appreciated by the skilled in the art, the term bar-compressing described as follow is meant to compress or press the tantalum powder into tantalum bar by the means of static pressure.

Example 1

(4) Sodium reduced tantalum powder was selected as the raw material, which was subjected to bar-compressing, sintering, and electron beam melting to give a tantalum ingot, and the tantalum ingot was subjected to a hydrogenation treatment. Tantalum scraps obtained after the hydrogenation of the tantalum ingot were crushed by the means of ball milling, and sieved with a 500-mesh sieve. The tantalum powder obtained after the ball milling and the sieving was pickled with a mixed acid of HNO.sub.3 and HF (HNO.sub.3, HF and water were mixed in a volume ratio of 4:1:20) to remove metal impurities, and following this, the tantalum powder was baked to dry and sieved. The tantalum powder was placed in a closed furnace and heated while charging argon gas to 900 C., and the temperature was kept for 180 minutes. Following this, the tantalum powder was cooled, then discharged and sieved. After the sieving, the tantalum powder was analyzed for the oxygen content, and the result was shown in Table 1. Subsequently, tantalum powder was mixed with magnesium powder in an amount of 1% by weight of the tantalum powder. The mixture was then heated while charging argon gas to 700 C. in a closed furnace, and the temperature was kept for 2 hours. The mixture was then cooled and discharged. The resultant tantalum powder was washed with nitric acid to remove redundant magnesium and magnesium oxide, then washed with deionic water to neutral, and the tantalum powder was baked to dry and sieved. Further, the above tantalum powder was heated under the vacuum of 10.sup.3 Pa to 700 C., and the temperature was kept for 60 minutes. Following this, the tantalum powder was cooled, passivated, discharged, and sieved to give the sample A. The obtained product was analyzed with a Glow Discharge Mass Spectrometry (GDMS) and its particle size was measured with a Malvern laser particle size analyzer, and the results were shown in Table 1.

Example 2

(5) Sodium reduced tantalum powder was selected as the raw material, which was subjected to bar-compressing, sintering, and electron beam melting to give a tantalum ingot, and the tantalum ingot was subjected to a hydrogenation treatment. Tantalum scraps obtained after the hydrogenation of the tantalum ingot were crushed by the means of ball milling, and sieved with a 500-mesh sieve. The tantalum powder obtained after the ball milling and the sieving was pickled with a mixed acid of HNO.sub.3 and HF (HNO.sub.3, HF and water were mixed in a volume ratio of 4:1:20) to remove metal impurities, and following this, the tantalum powder was baked to dry and sieved. The tantalum powder was placed in a closed furnace and heated while charging argon gas to 900 C., and the temperature was kept for 180 minutes. Following this, the tantalum powder was cooled, then discharged and sieved. After the sieving, the tantalum powder was analyzed for the oxygen content, and the result was shown in Table 1. Subsequently, tantalum powder was mixed with magnesium powder in an amount of 1% by weight of the tantalum powder. The mixture was then heated while charging argon gas to 750 C. in a closed furnace, and the temperature was kept for 2 hours. The mixture was then cooled and discharged. The resultant tantalum powder was washed with nitric acid to remove redundant magnesium and magnesium oxide, then washed with deionic water to neutral, and the tantalum powder was baked to dry and sieved. Further, the above tantalum powder was heated under the vacuum of 10.sup.3 Pa to 800 C., and the temperature was kept for 60 minutes. Following this, the tantalum powder was cooled, passivated, discharged, and sieved to give the sample B. The obtained product was analyzed with a Glow Discharge Mass Spectrometry (GDMS) and its particle size was measured with a Malvern laser particle size analyzer, and the results were shown in Table 1.

Example 3

(6) Sodium reduced tantalum powder was selected as the raw material, which was subjected to bar-compressing, sintering, and electron beam melting to give a tantalum ingot, and the tantalum ingot was subjected to a hydrogenation treatment. Tantalum scraps obtained after the hydrogenation of the tantalum ingot were crushed by the means of ball milling, and sieved with a 500-mesh sieve. The tantalum powder obtained after the ball milling and the sieving was pickled with a mixed acid of HNO.sub.3 and HF (HNO.sub.3, HF and water were mixed in a volume ratio of 4:1:20) to remove metal impurities, and following this, the tantalum powder was baked to dry and sieved. The tantalum powder was placed in a closed furnace and heated while charging argon gas to 900 C., and the temperature was kept for 180 minutes. Following this, the tantalum powder was cooled, then discharged and sieved. After the sieving, the tantalum powder was analyzed for the oxygen content, and the result was shown in Table 1. Subsequently, tantalum powder was mixed with magnesium powder in an amount of 1% by weight of the tantalum powder. The mixture was then heated while charging argon gas to 700 C. in a closed furnace, and the temperature was kept for 2 hours. The mixture was then cooled and discharged. The resultant tantalum powder was washed with nitric acid to remove redundant magnesium and magnesium oxide, then washed with deionic water to neutral, and the tantalum powder was baked to dry and sieved. Further, the above tantalum powder was heated under the vacuum of 10.sup.3 Pa to 1100 C., and the temperature was kept for 30 minutes. Following this, the tantalum powder was cooled, passivated, discharged, and sieved to give the sample C. The obtained product was analyzed with a Glow Discharge Mass Spectrometry (GDMS) and its particle size was measured with a Malvern laser particle size analyzer, and the results were shown in Table 1.

Comparative Example

(7) Sodium reduced tantalum powder was selected as the raw material, which was subjected to bar-compressing, sintering, and electron beam melting to give a tantalum ingot, and the tantalum ingot was subjected to a hydrogenation treatment. Tantalum scraps obtained after the hydrogenation of the tantalum ingot were crushed by the means of ball milling, and sieved with a 500-mesh sieve. The tantalum powder obtained after the ball milling and the sieving was pickled with a mixed acid of HNO.sub.3 and HF (HNO.sub.3, HF and water were mixed in a volume ratio of 4:1:20) to remove metal impurities, and following this, the tantalum powder was baked to dry and sieved. The above tantalum powder was mixed with magnesium powder in an amount of 1% by weight of the tantalum powder. Then, the mixture was heated while charging argon gas to 850 C. in a closed furnace, and the temperature was kept for 2 hours. Subsequently, the mixture was cooled and discharged. The resultant tantalum powder was washed with nitric acid to remove redundant magnesium and magnesium oxide, then washed with deionic water to neutral, and the tantalum powder was baked to dry and sieved to give the sample D. The obtained product was analyzed with a Glow Discharge Mass Spectrometry (GDMS) and its particle size was measured with a Malvern laser particle size analyzer, and the results were shown in Table 1.

(8) TABLE-US-00001 TABLE 1 Performance Comparison of tantalum powder Before the de- After the de- Particle Serial oxygenation O oxygenation O N H Mg Purity size number (ppm) (ppm) (ppm) (ppm) (ppm) (%) D50 m A 1280 650 30 10 1.2 >99.999 10.425 B 950 450 35 10 0.8 >99.999 13.05 C 1300 700 30 10 0.12 >99.999 15.17 D 1200 36 70 33 99.992 13.49

(9) As seen from the above data, the tantalum powder which is treated by the method of the invention had a particle size D50<25 m, and a purity of at least 99.999%.

(10) The analytical devices and types for each parameter in the present application are shown in the following table:

(11) TABLE-US-00002 Analytic items Analysis device name Specification Manufacturer Average particle Malvern laser particle Mastersizer British Malvern diameter (m) size analyzer 2000 Instruments Ltd. O, N, H Oxygen and nitrogen LECO LECO analyzer CS-436 Corporation Mg (ppm)/Purity Glow discharge mass Element GD Thermo Fisher spectrometer Scientific