CN117655338A - Preparation method of low-impurity-content flaky tantalum powder - Google Patents
Preparation method of low-impurity-content flaky tantalum powder Download PDFInfo
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- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 title claims abstract description 125
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 36
- 238000000498 ball milling Methods 0.000 claims abstract description 35
- 238000005406 washing Methods 0.000 claims abstract description 29
- 238000010438 heat treatment Methods 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims abstract description 24
- 239000002253 acid Substances 0.000 claims abstract description 23
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 23
- 238000000227 grinding Methods 0.000 claims abstract description 23
- 239000001301 oxygen Substances 0.000 claims abstract description 23
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 23
- 229910001362 Ta alloys Inorganic materials 0.000 claims abstract description 18
- VMJRMGHWUWFWOB-UHFFFAOYSA-N nickel tantalum Chemical compound [Ni].[Ta] VMJRMGHWUWFWOB-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000000843 powder Substances 0.000 claims abstract description 16
- 239000002994 raw material Substances 0.000 claims abstract description 15
- 230000009467 reduction Effects 0.000 claims abstract description 13
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 238000005554 pickling Methods 0.000 claims abstract description 6
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 3
- 239000000243 solution Substances 0.000 claims description 29
- 229910052715 tantalum Inorganic materials 0.000 claims description 29
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 24
- 238000006722 reduction reaction Methods 0.000 claims description 18
- 238000001816 cooling Methods 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 239000000463 material Substances 0.000 claims description 13
- 229910052786 argon Inorganic materials 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 12
- 238000012360 testing method Methods 0.000 claims description 12
- 239000010935 stainless steel Substances 0.000 claims description 11
- 229910001220 stainless steel Inorganic materials 0.000 claims description 11
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 8
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 8
- 229910017604 nitric acid Inorganic materials 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 8
- 239000002904 solvent Substances 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 7
- 238000004321 preservation Methods 0.000 claims description 7
- 238000007599 discharging Methods 0.000 claims description 6
- 238000011010 flushing procedure Methods 0.000 claims description 6
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- 238000007873 sieving Methods 0.000 claims description 5
- 239000003990 capacitor Substances 0.000 claims description 4
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- 230000008569 process Effects 0.000 abstract description 15
- 230000015556 catabolic process Effects 0.000 abstract description 13
- 229910052751 metal Inorganic materials 0.000 abstract description 9
- 239000002184 metal Substances 0.000 abstract description 9
- 239000008204 material by function Substances 0.000 abstract description 2
- 238000003466 welding Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 13
- 238000005245 sintering Methods 0.000 description 9
- 238000001514 detection method Methods 0.000 description 8
- LYCAIKOWRPUZTN-UHFFFAOYSA-N ethylene glycol Substances OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 8
- 239000000047 product Substances 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 239000006228 supernatant Substances 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 238000003892 spreading Methods 0.000 description 3
- 230000007480 spreading Effects 0.000 description 3
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000010963 304 stainless steel Substances 0.000 description 1
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Abstract
The invention belongs to the technical field of functional materials, and particularly relates to a preparation method of low-impurity-content flaky tantalum powder; it comprises the following steps: mixing raw material tantalum powder, a ball grinding agent and a grinding medium, performing ball milling and flaking, performing acid washing and impurity removal on the flaked tantalum powder after ball milling, and then performing heat treatment and oxygen reduction; wherein the grinding medium is a nickel-tantalum alloy ball. In the application, the nickel-tantalum alloy balls are selected as grinding media, so that the content of Fe, cr, C and other impurities in the finished tantalum powder can be effectively reduced, ni impurities introduced due to cold welding are also easily washed out by a subsequent pickling process in the collision friction process of raw material powder and the media balls, the residual quantity is small, the performance of the finished tantalum powder cannot be influenced, and the problems of large leakage current, low pressure resistance, poor reliability and the like of the tantalum powder caused by the large introduction of metal impurities in the processing process are effectively solved. In addition, the nickel-tantalum alloy ball has high hardness and good wear resistance, the surface of the flaky tantalum powder after ball milling is flat and smooth, the flaky shape is uniform, the thickness and the specific surface area are moderate, and the finished tantalum powder is ensured to have higher breakdown voltage and specific volume.
Description
Technical Field
The invention belongs to the technical field of functional materials, and particularly relates to a preparation method of low-impurity-content flaky tantalum powder.
Background
Tantalum is a valve metal used for various purposes and has the characteristics of high melting point, good chemical stability, large dielectric constant of a surface oxide film and the like, and is mostly processed into tantalum powder or tantalum wire for manufacturing tantalum capacitors for electronic circuits of high-precision weapon equipment and the like. The flake tantalum powder can have higher breakdown voltage and larger porosity due to the inherent characteristics of flake shape, and is generally used for producing medium-high voltage solid and liquid tantalum capacitors.
In the production and manufacturing process of the flaky tantalum powder, the raw material powder is required to be subjected to a ball milling and flaking process, a stainless steel ball is generally adopted as a ball milling medium in the prior art to prepare the flaky tantalum powder, and impurities such as Fe, cr, C and the like are introduced in a large amount in the process and cannot be thoroughly removed in the subsequent pickling process, so that the leakage current and breakdown voltage of the finished product powder are affected.
Disclosure of Invention
The invention provides a preparation method of flake tantalum powder with low impurity content for solving the problems.
The method is realized by the following technical scheme:
1. the preparation method of the flaky tantalum powder with low impurity content is characterized by comprising the following steps of:
(1) Ball milling: mixing raw materials of tantalum powder, a ball grinding agent and a grinding medium, performing ball milling at a ball milling rotating speed of 120-170r/min for 30-50h, flushing the tantalum powder on the surfaces of the ball mill and the medium ball into a stainless steel disc after ball milling is finished, settling and standing, pouring out upper absolute ethyl alcohol clear liquid, and placing the ball milled tantalum powder into a blast oven for drying at 60-80 ℃;
further, the purity of the raw material tantalum powder is more than or equal to 4N, the impurity content Fe is less than or equal to 5ppm, ni is less than or equal to 5ppm, cr is less than or equal to 5ppm, and C is less than or equal to 20ppm.
Further, the ball milling solvent is absolute ethyl alcohol; the grinding medium is nickel-tantalum alloy ball, and the diameter of the medium ball is 2-5mm.
Further, the raw materials of tantalum powder, ball milling solvent and grinding medium are mixed according to the mass ratio of 1:1-2:5-7.
(2) Acid washing: mixing the tantalum powder dried in the step (1) with an acid washing solution, stirring and washing in a constant-temperature water bath for 2-3 hours, standing and settling, pouring out an upper acid solution, repeatedly washing for 2-3 times, washing with water until the conductivity of a washing solution is less than 20 mu s/cm, and drying; the sedimentation time is not specifically required and is calculated based on sedimentation.
Further, the constant temperature water bath is 30-40 ℃; the stirring speed is 100-150r/min.
Further, the pickling solution is a mixed solution of nitric acid and hydrofluoric acid, the volume concentration of the nitric acid is 12-18%, and the volume concentration of the hydrofluoric acid is 0.4-0.7%. The inventor researches show that by adopting the specific pickling solution, redundant metal impurities can be effectively washed away, and meanwhile, the product yield is ensured.
(3) And (3) heat treatment: placing the material obtained in the step (2) into a tantalum crucible, placing the tantalum crucible into a heat treatment furnace, vacuumizing and continuously heating, preserving heat for 1-2.5 hours, cooling, taking out the material when cooling to room temperature, crushing, and sieving with a 50-mesh sieve to obtain tantalum powder particles;
further, the vacuum is continuously increased in temperature, and the vacuum degree is lower than 3 multiplied by 10 -3 Pa, continuously heating to 1350-1500 ℃.
(4) And (3) reducing oxygen: and (3) removing redundant oxygen on the surface of the tantalum powder by utilizing an oxygen reduction process, mixing the tantalum powder particles subjected to the heat treatment in the step (3) with the reduced magnesium powder, placing the mixture in an oxygen reduction crucible, hanging the mixture into an oxygen reduction furnace, carrying out leak rate test on an oxygen reduction reaction bomb, charging argon after the test is qualified, starting heating and heat preservation treatment, charging argon, cooling to room temperature, and discharging from the furnace.
Further, the temperature rise and heat preservation treatment is to heat the temperature to 950 ℃ for 3 hours and vacuumize the water for 3 hours.
Further, the mass ratio of the tantalum powder particles to the reduced magnesium powder is 1:0.02-0.03.
The low-impurity-content flaky tantalum powder finished powder prepared by the method has the impurity contents of Fe less than or equal to 20ppm, ni less than or equal to 10ppm, cr less than or equal to 10ppm and C less than or equal to 30ppm, can have lower leakage current and higher reliability, and can be widely applied to the fields of missile, space vehicle, automobile electronics, 5G communication and the like.
In summary, the beneficial effects of the invention are as follows: according to the invention, the nickel-tantalum alloy balls which are easy to process, high in hardness and good in wear resistance are selected as the grinding medium, the surfaces of the ball-milled flaky tantalum powder are flat and smooth, the flaky tantalum powder is uniform in thickness and specific surface area, the finished tantalum powder can have good quality and electrical property, and because the nickel-tantalum alloy balls are simple in composition and contain few impurities, the introduction of a large amount of impurities which cannot be removed in subsequent procedures such as Fe, cr and C due to interface cutting action is avoided in the collision friction process of raw material powder and medium balls, ni impurities which are introduced due to cold welding action are also easy to be washed out in the subsequent pickling process in the collision friction process of the raw material powder and medium balls, the residual quantity is small, the influence on the performance of the finished tantalum powder is avoided, and the technical problems of high leakage current, low pressure resistance, poor reliability and the like caused by the excessive content of the metal impurities of the tantalum powder in the prior art are solved. In addition, the nickel-tantalum alloy ball has high hardness and good wear resistance, the surface of the flaky tantalum powder after ball milling is flat and smooth, the flaky shape is uniform, the thickness and the specific surface area are moderate, and the tantalum powder can have higher breakdown voltage and specific volume, so that the good quality and electrical property of the finished tantalum powder are ensured.
According to the invention, tantalum powder particles are contracted and mutually connected through a high-temperature heat treatment process, so that tantalum powder particles with certain strength, sintering neck and porosity are formed, and metal impurities are volatilized continuously under the action of high temperature, so that the impurity content of the tantalum powder is further reduced, and the leakage current performance is improved.
Drawings
Fig. 1 is an SEM image of the low impurity content flake tantalum powder prepared in example 1.
Detailed Description
The following detailed description of the invention is provided in further detail, but the invention is not limited to these embodiments, any modifications or substitutions in the basic spirit of the present examples, which still fall within the scope of the invention as claimed.
Example 1
The embodiment provides a preparation method of low-impurity-content flaky tantalum powder, which comprises the following steps:
1. putting 1kg of raw material tantalum powder into a phi 30cm ball mill filled with 6kg of nickel-tantalum alloy balls with the diameter of 2.5mm, adding 1.5L of absolute ethyl alcohol serving as a ball milling solvent, ball milling for 40 hours at the rotating speed of 150r/min, flushing the tantalum powder in the ball mill and on the surfaces of medium balls into a stainless steel disc by using the absolute ethyl alcohol after the ball milling process is finished, settling and standing for about 30min, pouring out supernatant of the absolute ethyl alcohol on the upper layer, and putting the ball-milled tantalum powder at the bottom of the stainless steel disc into a blast oven for drying at 60 ℃.
2. Pouring the dried material into 2L of mixed acid washing solution of nitric acid (volume concentration is 15%), hydrofluoric acid (volume concentration is 0.5%), placing in constant-temperature water bath at 35 ℃, stirring and acid washing for 2h at a rotating speed of 120r/min, then standing until tantalum powder is settled, pouring out acid liquor after reaction, repeating the above operation for two times to ensure that redundant metal impurities are completely reacted with acid, washing the lower tantalum powder settled by the system by deionized water until the conductivity of washing liquid is less than 20 mu s/cm, and placing in a blast oven for drying.
3. The tantalum powder is spread in a tantalum crucible, heat treated for 1h at 1340 ℃, cooled to room temperature, and then the furnace door can be opened to take out the material, the material is crushed by a crusher and is sieved by a 50-mesh sieve.
4. According to the mass ratio of tantalum powder to reduced magnesium powder of 1:0.027, placing in an oxygen reduction crucible, hanging into an oxygen reduction furnace, carrying out leak rate test on an oxygen reduction reaction bomb, after the leak rate test is qualified, charging argon, raising the temperature to 950 ℃ for heat preservation for 3 hours, vacuumizing for 3 hours, charging argon for cooling, and discharging after cooling to room temperature to obtain the finished tantalum powder.
In this example, a nickel-tantalum alloy ball with a diameter of 2.5mm was used as the grinding medium, the ball milling time was 40 hours,the heat treatment temperature is 1340 ℃, and the heat treatment time is 1h, wherein the impurity content of the finished product is Fe=21 ppm, ni=3 ppm, cr=5 ppm and C=11 ppm. The finished powder is pressed into tantalum blocks for electrical property detection, and the conditions are as follows by weight: 0.147g, pressed density: 5.5g/cm 3 Sintering conditions: 1500 ℃/30min, energizing solution: h with volume concentration of 0.01% 3 PO 4 -ethylene glycol solution, energizing voltage: tantalum block specific volume 12562. Mu.F.V/g at 250V, K value 2.54 x 10 -4 μA/μF.V, breakdown voltage 326.4V.
Example 2
The embodiment provides a preparation method of low-impurity-content flaky tantalum powder, which comprises the following steps:
1. putting 1kg of raw material tantalum powder into a phi 30cm ball mill filled with 6kg of nickel-tantalum alloy balls with the diameter of 2.5mm, adding 1.5L of absolute ethyl alcohol serving as a ball milling solvent, ball milling for 50 hours at the rotating speed of 150r/min, flushing the tantalum powder in the ball mill and on the surfaces of medium balls into a stainless steel disc by using the absolute ethyl alcohol after the ball milling process is finished, settling and standing for about 30min, pouring out supernatant of the absolute ethyl alcohol on the upper layer, and putting the ball-milled tantalum powder at the bottom of the stainless steel disc into a blast oven for drying at 60 ℃.
2. Pouring the dried material into 2L of mixed acid washing solution of nitric acid (volume concentration is 15%), hydrofluoric acid (volume concentration is 0.5%), placing in constant-temperature water bath at 35 ℃, stirring and acid washing for 2h at a rotating speed of 120r/min, then standing until tantalum powder is settled, pouring out acid liquor after reaction, repeating the above operation for two times to ensure that redundant metal impurities are completely reacted with acid, washing the lower tantalum powder settled by the system by deionized water until the conductivity of washing liquid is less than 20 mu s/cm, and placing in a blast oven for drying.
3. Spreading tantalum powder in a tantalum crucible, heat treating at 1340 deg.C for 1 hr, cooling to room temperature, opening furnace door to take out material, crushing with crusher, and sieving with 50 mesh sieve
4. According to the mass ratio of tantalum powder to reduced magnesium powder of 1:0.027, placing in an oxygen reduction crucible, hanging into an oxygen reduction furnace, carrying out leak rate test on an oxygen reduction reaction bomb, after the leak rate test is qualified, charging argon, raising the temperature to 950 ℃ for heat preservation for 3 hours, vacuumizing for 3 hours, charging argon for cooling, and discharging after cooling to room temperature to obtain the finished tantalum powder.
In this example, nickel-tantalum alloy balls with a diameter of 2.5mm are used as grinding media, the ball milling time is 50 hours, the heat treatment temperature is 1340 ℃, and when the heat treatment time is 1 hour, the impurity contents of finished products are Fe=24 ppm, ni=4 ppm, cr=6ppm and C=16 ppm. The finished powder is pressed into tantalum blocks for electrical property detection, and the conditions are as follows by weight: 0.147g, pressed density: 5.5g/cm 3 Sintering conditions: 1500 ℃/30min, energizing solution: h with volume concentration of 0.01% 3 PO 4 -ethylene glycol solution, energizing voltage: at 250V, the specific volume of tantalum block is 13084 mu F.V/g, and K value is 2.62 x 10 -4 μA/μF.V, breakdown voltage 313.8V.
Example 3
The embodiment provides a preparation method of low-impurity-content flaky tantalum powder, which comprises the following steps:
1. putting 1kg of raw material tantalum powder into a phi 30cm ball mill filled with 6kg of nickel-tantalum alloy balls with the diameter of 2.5mm, adding 1.5L of absolute ethyl alcohol serving as a ball milling solvent, ball milling for 40 hours at the rotating speed of 150r/min, flushing the tantalum powder in the ball mill and on the surfaces of medium balls into a stainless steel disc by using the absolute ethyl alcohol after the ball milling process is finished, settling and standing for about 30min, pouring out supernatant of the absolute ethyl alcohol on the upper layer, and putting the ball-milled tantalum powder at the bottom of the stainless steel disc into a blast oven for drying at 60 ℃.
2. Pouring the dried material into 2L of mixed acid washing solution of nitric acid (volume concentration is 15%), hydrofluoric acid (volume concentration is 0.5%), placing in constant-temperature water bath at 35 ℃, stirring and acid washing for 2h at a rotating speed of 120r/min, then standing until tantalum powder is settled, pouring out acid liquor after reaction, repeating the above operation twice to ensure that redundant metal impurities completely react with acid, washing the lower tantalum powder settled by the system by deionized water until the conductivity of washing liquid is less than 20 mu s/cm, and placing in a blast oven for drying
3. Spreading tantalum powder in a tantalum crucible, heat treating at 1380deg.C for 1 hr, cooling to room temperature, opening furnace door to take out material, crushing with crusher, and sieving with 50 mesh sieve
4. According to the mass ratio of tantalum powder to reduced magnesium powder of 1:0.027, placing in an oxygen reduction crucible, hanging into an oxygen reduction furnace, carrying out leak rate test on an oxygen reduction reaction bomb, after the leak rate test is qualified, charging argon, raising the temperature to 950 ℃ for heat preservation for 3 hours, vacuumizing for 3 hours, charging argon for cooling, and discharging after cooling to room temperature to obtain the finished tantalum powder.
In this example, nickel-tantalum alloy balls with a diameter of 2.5mm are used as grinding media, the ball milling time is 40 hours, the heat treatment temperature is 1380 ℃, and when the heat treatment time is 1 hour, the impurity content of the finished product is Fe=19 ppm, ni=3 ppm, cr=4 ppm and C=10 ppm. The finished powder is pressed into tantalum blocks for electrical property detection, and the conditions are as follows by weight: 0.147g, pressed density: 5.5g/cm 3 Sintering conditions: 1500 ℃/30min, energizing solution: h with volume concentration of 0.01% 3 PO 4 -ethylene glycol solution, energizing voltage: tantalum block specific volume 11942 mu F.V/g at 250V, K value 2.45 x 10 -4 μA/μF.V, breakdown voltage 333.7V.
Example 4
The embodiment provides a preparation method of low-impurity-content flaky tantalum powder, which comprises the following steps:
1. putting 1kg of raw material tantalum powder into a phi 30cm ball mill filled with 6kg of nickel-tantalum alloy balls with the diameter of 2.5mm, adding 1.5L of absolute ethyl alcohol serving as a ball milling solvent, ball milling for 40 hours at the rotating speed of 150r/min, flushing the tantalum powder in the ball mill and on the surfaces of medium balls into a stainless steel disc by using the absolute ethyl alcohol after the ball milling process is finished, settling and standing for about 30min, pouring out supernatant of the absolute ethyl alcohol on the upper layer, and putting the ball-milled tantalum powder at the bottom of the stainless steel disc into a blast oven for drying at 60 ℃.
2. Pouring the dried material into 2L of mixed acid washing solution of nitric acid (volume concentration is 15%), hydrofluoric acid (volume concentration is 0.5%), placing in constant-temperature water bath at 35 ℃, stirring and acid washing for 2h at a rotating speed of 120r/min, then standing until tantalum powder is settled, pouring out acid liquor after reaction, repeating the above operation twice to ensure that redundant metal impurities completely react with acid, washing the lower tantalum powder settled by the system by deionized water until the conductivity of washing liquid is less than 20 mu s/cm, and placing in a blast oven for drying
3. Spreading tantalum powder in a tantalum crucible, heat treating at 1340 deg.C for 2.5 hr, cooling to room temperature, opening furnace door to take out material, crushing with crusher, and sieving with 50 mesh sieve
4. According to the mass ratio of tantalum powder to reduced magnesium powder of 1:0.027, placing in an oxygen reduction crucible, hanging into an oxygen reduction furnace, carrying out leak rate test on an oxygen reduction reaction bomb, after the leak rate test is qualified, charging argon, raising the temperature to 950 ℃ for heat preservation for 3 hours, vacuumizing for 3 hours, charging argon for cooling, and discharging after cooling to room temperature to obtain the finished tantalum powder.
In this example, nickel-tantalum alloy balls with a diameter of 2.5mm are used as grinding media, the ball milling time is 40 hours, the heat treatment temperature is 1340 ℃, and the heat treatment time is 2.5 hours, when the impurity content of the finished product is Fe=19 ppm, ni=2 ppm, cr=4 ppm and C=10 ppm. The finished powder is pressed into tantalum blocks for electrical property detection, and the conditions are as follows by weight: 0.147g, pressed density: 5.5g/cm 3 Sintering conditions: 1500 ℃/30min, energizing solution: h with volume concentration of 0.01% 3 PO 4 -ethylene glycol solution, energizing voltage: tantalum block specific volume 11915 μF.V/g at 250V, K value 2.47 x 10 -4 μA/μF.V, breakdown voltage 331.9V.
Comparative example 1
This comparative example is substantially identical to example 1 except that 304 stainless steel balls having a diameter of 2.5mm are used as the grinding medium in this comparative example.
Finished impurity content fe=29 ppm, ni=7ppm, cr=7ppm, c=20 ppm. The finished powder is pressed into tantalum blocks for electrical property detection, and the conditions are as follows by weight: 0.147g, pressed density: 5.5g/cm 3 Sintering conditions: 1500 ℃/30min, energizing solution: h with volume concentration of 0.01% 3 PO 4 -ethylene glycol solution, energizing voltage: at 250V, the specific volume of tantalum block is 12122 mu F.V/g, and the K value is 3.08 x 10 -4 μA/μF.V, breakdown voltage 312.5V.
Comparative example 2
This comparative example is substantially the same as example 1 except that zirconia grinding balls having a diameter of 2.5mm are used as the grinding medium in this comparative example.
Finished impurity content fe=17 ppm, ni=5 ppm, cr=4 ppm, c=17 ppm. The finished powder is pressed into tantalum blocks for electrical property detection, and the conditions are as follows by weight: 0.147g, pressed density: 5.5g/cm 3 Sintering conditions: 1500 ℃/30min, energizing solution: h with volume concentration of 0.01% 3 PO 4 -ethylene glycol solution, energizing voltage: at 250V, the specific volume of tantalum block is 11785 mu F.V/g, and K value is 1.43 x 10 -1 μA/μF.V, breakdown voltage 241.3V.
Comparative example 3
This comparative example is essentially the same as example 1, except that a nickel-tantalum alloy ball having a diameter of 5mm is used as the grinding medium in this comparative example.
Finished impurity content fe=18 ppm, ni=4 ppm, cr=4 ppm, c=11 ppm. The finished powder is pressed into tantalum blocks for electrical property detection, and the conditions are as follows by weight: 0.147g, pressed density: 5.5g/cm 3 Sintering conditions: 1500 ℃/30min, energizing solution: h with volume concentration of 0.01% 3 PO 4 -ethylene glycol solution, energizing voltage: at 250V, the specific volume of tantalum block is 11028 mu F.V/g, and K value is 2.49 x 10 -4 μA/μF.V, breakdown voltage 335.1V.
Comparative example 4
This comparative example is substantially identical to example 1, except that only 3kg of the nickel-tantalum alloy balls having a grinding medium diameter of 2.5mm are added.
Finished impurity content fe=18 ppm, ni=3 ppm, cr=3 ppm, c=9 ppm. The finished powder is pressed into tantalum blocks for electrical property detection, and the conditions are as follows by weight: 0.147g, pressed density: 5.5g/cm 3 Sintering conditions: 1500 ℃/30min, energizing solution: h with volume concentration of 0.01% 3 PO 4 -ethylene glycol solution, energizing voltage: at 250V, the specific volume of tantalum block is 10493 mu F.V/g, and K value is 2.51 x 10 -4 μA/μF.V, breakdown voltage 342.8V.
Comparative example 1 and comparative examples 1-4 above, it can be seen that the specific grinding media used in the present application, in combination with the ball milling parameters, heat treatment temperature and time, have a higher breakdown voltage while being beneficial to increasing the specific volume of the final tantalum powder, and have a suitable chemical impurity content.
Claims (10)
1. The preparation method of the flaky tantalum powder with low impurity content is characterized by comprising the following steps of:
(1) Ball milling: mixing raw materials of tantalum powder, a ball grinding agent and a grinding medium, performing ball milling at a ball milling rotating speed of 120-170r/min for 30-50h, flushing the tantalum powder on the surfaces of the ball mill and the medium ball into a stainless steel disc after ball milling is finished, settling and standing, pouring out upper absolute ethyl alcohol clear liquid, and placing the ball milled tantalum powder into a blast oven for drying at 60-80 ℃;
(2) Acid washing: mixing the tantalum powder dried in the step (1) with an acid washing solution, stirring and washing in a constant-temperature water bath for 2-3 hours, standing and settling, pouring out an upper acid solution, repeatedly washing for 2-3 times, washing with water until the conductivity of a washing solution is less than 20 mu s/cm, and drying;
(3) And (3) heat treatment: placing the material obtained in the step (2) into a tantalum crucible, placing the tantalum crucible into a heat treatment furnace, vacuumizing and continuously heating, preserving heat for 1-2.5 hours, cooling, taking out the material when cooling to room temperature, crushing, and sieving with a 50-mesh sieve to obtain tantalum powder particles;
(4) And (3) reducing oxygen: mixing the tantalum powder particles subjected to the heat treatment in the step (3) with the reduced magnesium powder, placing the mixture in an oxygen reduction crucible, hanging the mixture into an oxygen reduction furnace, performing leak rate test on an oxygen reduction reaction bomb, charging argon after the test is qualified, starting heating and heat preservation treatment, charging argon, cooling to room temperature, and discharging.
2. The method for preparing high-pressure high-specific volume tantalum powder for capacitors according to claim 1, wherein the purity of the raw material tantalum powder is more than or equal to 4N, the impurity content Fe is less than or equal to 5ppm, ni is less than or equal to 5ppm, cr is less than or equal to 5ppm, and C is less than or equal to 20ppm.
3. The method for preparing the low-impurity-content flaky tantalum powder according to claim 1, wherein the ball milling solvent is absolute ethyl alcohol; the grinding medium is nickel-tantalum alloy ball, and the diameter of the medium ball is 2-5mm.
4. The preparation method of the low-impurity-content flaky tantalum powder as claimed in claim 1, wherein the raw materials of tantalum powder, a ball milling solvent and a grinding medium are mixed according to the mass ratio of 1:1-2:5-7.
5. The method for preparing a tantalum flake powder with low impurity content according to claim 1, wherein said constant temperature water bath in said step (2) is 30-40 ℃; the stirring speed is 100-150r/min.
6. The method for preparing the low-impurity-content flaky tantalum powder according to claim 1, wherein the pickling solution is a mixed solution of nitric acid and hydrofluoric acid, the volume concentration of the nitric acid is 12-18%, and the volume concentration of the hydrofluoric acid is 0.4-0.7%.
7. The method for producing a tantalum flake powder having a low impurity content according to claim 1, wherein said vacuum-pumping in said step (3) is continuously elevated in temperature to a degree of vacuum of less than 3X 10 -3 Pa, continuously heating to 1350-1500 ℃.
8. The method for preparing the low-impurity-content flaky tantalum powder according to claim 1, wherein the heating and heat-preserving treatment in the step (4) is to heat-preserving for 3 hours at a temperature of 950 ℃ and vacuumize for 3 hours.
9. The method for preparing the low-impurity-content flaky tantalum powder according to claim 1, wherein the mass ratio of the tantalum powder particles to the reduced magnesium powder in said step (4) is 1:0.02-0.03.
10. Use of a low impurity content flake tantalum powder produced by the method for producing a low impurity content flake tantalum powder as defined in any one of claims 1 to 9 for producing electronic circuits such as electrolytic capacitors, high-precision weapons and the like.
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