CN112404439A - High-voltage tantalum powder for capacitor, preparation method thereof and capacitor - Google Patents
High-voltage tantalum powder for capacitor, preparation method thereof and capacitor Download PDFInfo
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- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 title claims abstract description 169
- 239000003990 capacitor Substances 0.000 title claims abstract description 42
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 238000000498 ball milling Methods 0.000 claims abstract description 54
- 238000005406 washing Methods 0.000 claims abstract description 32
- 239000002253 acid Substances 0.000 claims abstract description 27
- 238000010438 heat treatment Methods 0.000 claims abstract description 19
- 238000005554 pickling Methods 0.000 claims abstract description 17
- 238000001035 drying Methods 0.000 claims abstract description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000000034 method Methods 0.000 claims description 25
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 24
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical group CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 17
- 229910001220 stainless steel Inorganic materials 0.000 claims description 17
- 239000010935 stainless steel Substances 0.000 claims description 17
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 12
- 229910017604 nitric acid Inorganic materials 0.000 claims description 12
- 238000005245 sintering Methods 0.000 claims description 12
- 239000002904 solvent Substances 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 3
- 230000015556 catabolic process Effects 0.000 abstract description 26
- 229910052715 tantalum Inorganic materials 0.000 abstract description 25
- 239000012535 impurity Substances 0.000 abstract description 19
- 239000000843 powder Substances 0.000 abstract description 19
- 239000002994 raw material Substances 0.000 abstract description 19
- 229910052751 metal Inorganic materials 0.000 abstract description 14
- 239000002184 metal Substances 0.000 abstract description 14
- 239000008204 material by function Substances 0.000 abstract description 2
- 238000007669 thermal treatment Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 15
- 238000003825 pressing Methods 0.000 description 9
- 238000001514 detection method Methods 0.000 description 8
- 239000007788 liquid Substances 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- 229910000831 Steel Inorganic materials 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 210000003739 neck Anatomy 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/06—Metallic powder characterised by the shape of the particles
- B22F1/068—Flake-like particles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/142—Thermal or thermo-mechanical treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/145—Chemical treatment, e.g. passivation or decarburisation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/0029—Processes of manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/022—Electrolytes; Absorbents
- H01G9/025—Solid electrolytes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/043—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by ball milling
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Abstract
The invention discloses high-voltage tantalum powder for a capacitor, a preparation method thereof and the capacitor, and relates to the technical field of functional materials. The preparation method of the high-voltage tantalum powder for the capacitor comprises the following steps: ball-milling spherical tantalum powder into sheets, carrying out acid washing on the ball-milled sheet tantalum powder, washing the acid-washed tantalum powder with water, drying, and then carrying out heat treatment; wherein the average grain diameter of the spherical tantalum powder is 5-10 μm. Spherical tantalum powder is selected for use as the raw materials in this application, spherical tantalum powder outward appearance is smooth, no edge closed angle, has fine mobility, the breakdown voltage of finished product powder has effectively been improved, its impurity content is low, the surface is smooth, the influence of metal impurity to finished product powder breakdown voltage has been reduced by a wide margin, the electrical property of product has further been improved, through with spherical tantalum powder high-voltage tantalum powder for the condenser that step processing such as ball-milling pickling thermal treatment was made, can realize increasing by a wide margin of finished product powder breakdown voltage, can satisfy novel tantalum capacitor to the demand of high-voltage tantalum powder.
Description
Technical Field
The invention relates to the technical field of functional materials, in particular to high-voltage tantalum powder for a capacitor, a preparation method of the high-voltage tantalum powder and the capacitor.
Background
The dense oxide film formed on the surface of tantalum powder has the property of one-way conductive valve metal, and is mainly used for manufacturing high-quality electrolytic capacitors (the capacitance is more than 5 times larger than the common capacitance with the same size). The method is widely applied to military equipment and high-tech fields. Such as missiles, space vehicles, televisions, electronic computers, and the like.
In the prior art, sheet tantalum powder is generally used as a raw material to prepare tantalum powder with high specific surface area, high specific heat capacity and high breakdown voltage. However, the inventor finds that the breakdown voltage of the finished tantalum powder prepared from the conventional flaky tantalum powder is still not high, and the finished tantalum powder cannot be effectively applied to capacitors.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The invention aims to provide high-voltage tantalum powder for a capacitor, a preparation method of the high-voltage tantalum powder and the capacitor.
The invention is realized by the following steps:
in a first aspect, an embodiment of the present invention provides a method for preparing high-voltage tantalum powder for a capacitor, including: ball-milling the spherical tantalum powder into sheet tantalum powder, and then performing heat treatment to form a sintering neck;
wherein the average grain diameter of the spherical tantalum powder is 5-10 μm.
In an optional embodiment, the purity of the spherical tantalum powder is more than or equal to 4N, wherein the impurity content of Fe is less than or equal to 5ppm, Ni is less than or equal to 5ppm, Cr is less than or equal to 5ppm, W is less than or equal to 5ppm, Mo is less than or equal to 5ppm, and Nb is less than or equal to 5 ppm.
In an alternative embodiment, the ball milling comprises placing the spherical tantalum powder in a ball mill with stainless steel balls, adding a ball milling solvent, and ball milling for 6-12h at a rotation speed of 100-.
In an alternative embodiment, the ball milling solvent is absolute ethanol.
In an alternative embodiment, the flaky tantalum powder has a flake diameter of 5 to 45 μm and a thickness of 1.5 to 6.9 μm.
In an optional embodiment, after the ball milling, before the heat treatment, the method further comprises placing the ball-milled and dried material in an acid washing solution to be washed for 2-3h at a stirring speed of 180-;
preferably, the acid washing solution is a mixed acid solution of nitric acid and hydrofluoric acid, wherein the volume concentration of the nitric acid is 14-15%, and the volume concentration of the hydrofluoric acid is 0.4-0.6%.
In an alternative embodiment, after the acid washing and before the heat treatment, the acid washing system is settled and kept still for 10-30min, then the tantalum powder after the lower layer of acid washing is taken out, washed by water until the conductivity of the washing liquid is less than 20us/cm, and then dried at 80-90 ℃.
In an alternative embodiment, the heat treatment comprises heat treatment at 1400-1800 ℃ for 20-40 min.
In a second aspect, embodiments of the present invention provide a high-voltage tantalum powder for capacitors, which is prepared by the method for preparing a high-voltage tantalum powder for capacitors according to any one of the foregoing embodiments.
In a third aspect, embodiments of the present invention provide a capacitor including the high-voltage tantalum powder for capacitors as described in any one of the previous embodiments.
The invention has the following beneficial effects:
this application chooses spherical tantalum powder as the raw materials for use, spherical tantalum powder outward appearance is smooth, no edge closed angle, has fine mobility, the breakdown voltage of finished product powder has effectively been improved, its impurity content is low, the surface is smooth, the influence of metal impurity to finished product powder breakdown voltage has been reduced by a wide margin, the electrical property of product has further been improved, through with spherical tantalum powder high-voltage tantalum powder for the condenser that step processing such as ball-milling pickling thermal treatment was made, can realize the improvement by a wide margin of finished product powder breakdown voltage, can satisfy novel tantalum capacitor to the demand of high-voltage tantalum powder, under the equal specific volume condition with the solution, the not high technical problem of current finished product tantalum powder breakdown voltage.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a SEM illustration of spherical tantalum powder provided in example 1 of the present invention;
FIG. 2 is a SEM illustration of the high-voltage tantalum powder for capacitors prepared in example 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The embodiment of the invention provides a preparation method of high-voltage tantalum powder for a capacitor, which comprises the following steps:
s1, selecting raw materials.
According to the method, spherical tantalum powder with extremely high purity is selected as a raw material, the purity of the spherical tantalum powder is more than or equal to 4N, the impurity content of Fe is less than or equal to 5ppm, Ni is less than or equal to 5ppm, Cr is less than or equal to 5ppm, W is less than or equal to 5ppm, Mo is less than or equal to 5ppm, Nb is less than or equal to 5ppm, and the average particle size of the spherical tantalum powder is 5-10 mu m.
And S2, ball milling.
The method comprises the following steps of ball-milling spherical tantalum powder into sheets, specifically, placing the spherical tantalum powder into a ball mill with stainless steel balls, adding a ball-milling solvent, and ball-milling for 6-12h at the rotation speed of 100-150 r/min. Preferably, the ball milling solvent used herein is absolute ethanol. After the ball milling process is finished, washing the tantalum powder in the ball mill and on the surface of the steel ball into a stainless steel disc by using absolute ethyl alcohol, settling and standing for 2-3h, pouring out the upper layer absolute ethyl alcohol clear liquid, and drying the ball-milled tantalum powder at the bottom of the stainless steel disc in a blast oven at 80-90 ℃.
The spherical tantalum powder has smooth surface, no sharp edge and good fluidity, but is not suitable for the production and manufacturing process of the tantalum capacitor because of the incapability of forming, and meanwhile, the spherical tantalum powder has small specific surface area, so that the spherical tantalum powder cannot have enough specific volume if being used for the production and manufacturing of the tantalum capacitor. Therefore, in the prior art, spherical tantalum powder is not generally adopted as a raw material, but the spherical tantalum powder with specific particle size and high purity is selected, so that the impurity content is low, the surface is smooth, and the spherical tantalum powder is processed into flaky tantalum powder with the flaky particle size concentrated at 5-45 mu m and the thickness concentrated at 1.5-6.9 mu m by ball milling, so that the specific volume is large and the breakdown voltage is high.
Due to the existence of metal impurities such as Fe, Ni, Cr, W, Mo, Nb and the like, in the production and manufacturing process of the tantalum capacitor, the phenomena of increased leakage current and reduced breakdown voltage of the product caused by oxide film defects are easily caused, so that the electrical property of the tantalum powder is reduced. Therefore, the lowest content of metal impurities is more beneficial to the improvement of the performance of the tantalum powder, and in view of the above situation, the content of metal impurities in the spherical tantalum powder of the present application should be as low as possible within a controllable range.
S3, acid washing.
And (3) putting the ball-milled and dried material into an acid washing solution to be acid-washed for 2-3h at the stirring speed of 180-220 r/min.
The pickling solution in the application is a mixed acid solution of nitric acid and hydrofluoric acid, wherein the volume concentration of the nitric acid is 14-15%, and the volume concentration of the hydrofluoric acid is 0.4-0.6%. The characteristic that acid can corrode metal is utilized to remove metal impurities introduced in the ball milling step. The inventor researches and discovers that the specific pickling solution can effectively remove metal impurities under the condition of ensuring less quality loss of finished products.
And S4, washing with water, and drying.
And settling and standing the acid washing system for 10-30min, then taking the tantalum powder after the lower layer of acid washing, washing with water until the conductivity of the washing liquid is less than 20us/cm, and then drying at 80-90 ℃.
And S5, heat treatment.
Heat treatment at 1400-1800 deg.C for 20-40 min. In the application, sintering necks with certain strength are formed among tantalum powder particles through high-temperature heat treatment, and a good pore structure is formed.
When the energized voltage of the high-voltage tantalum powder for the capacitor prepared by the method is 200V, the breakdown voltage of a tantalum block can reach over 287V, the specific volume can reach over 5310 muf.V/g, and the high-voltage tantalum powder can be widely applied to the fields of electrolytic capacitors, missiles, space vehicles, televisions, electronic computers and the like.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The embodiment provides a preparation method of high-pressure tantalum powder for a capacitor, which selects high-purity spherical tantalum powder as a raw material, and performs a ball milling flaking process on the high-purity spherical tantalum powder to prepare high-pressure finished tantalum powder, and the preparation method specifically comprises the following steps: 1kg of raw spherical tantalum powder (see FIG. 1) having an average particle size of 5 μm was placed in a stainless steel ball 3kg
Adding 2L of ball milling solvent absolute ethyl alcohol into a ball mill, ball milling for 6h at the rotating speed of 100r/min, after the ball milling process is finished, washing tantalum powder in a ball mill and on the surface of a steel ball into a stainless steel disc by absolute ethyl alcohol, settling and standing for 2 hours, pouring out an upper layer absolute ethyl alcohol clear solution, drying the ball-milled tantalum powder at the bottom of the stainless steel disc in a blast oven at 85 ℃, pouring the dried powder into a 2L mixed acid system of 15% nitric acid and 0.5% hydrofluoric acid in volume concentration, pickling for 2 hours at a stirring speed of 200r/min, settling and standing for 20 minutes, pouring out an upper layer pickling clear solution, and filtering and washing the residual bottom tantalum powder by using deionized water until the conductivity is less than 20us/cm, drying the tantalum powder in a forced air oven at 85 ℃, and finally performing heat treatment for 30min at 1600 ℃ to obtain the finished product tantalum powder (see figure 2).
In this example, 5 μm spherical tantalum powder was usedWhen the ball milling time is 6h, the prepared ball milling sheet tantalum powder is concentrated at 5-15 μm in diameter and 2-5 μm in thickness, and the metal impurity content Fe is 3ppm, Ni is 1ppm, and Cr is 1ppm after acid washing. And pressing the finished powder into a tantalum block for electrical property detection, wherein the conditions are as follows by weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solution: h at a concentration of 0.01% by volume3PO4Solution, energizing voltage: at 200V, the breakdown voltage of the tantalum block is 295V, and the specific volume is 5450 muf.V/g.
Example 2
The embodiment provides a preparation method of high-pressure tantalum powder for a capacitor, which selects high-purity spherical tantalum powder as a raw material, and performs a ball milling flaking process on the high-purity spherical tantalum powder to prepare high-pressure finished tantalum powder, and the preparation method specifically comprises the following steps: 1kg of raw material spherical tantalum powder with the average grain diameter of 5 mu m is placed in a container with 3kg of stainless steel ball
Adding 2L of ball milling solvent absolute ethyl alcohol into a ball mill, carrying out ball milling for 12h at the rotating speed of 120r/min, after the ball milling process is finished, washing tantalum powder in the ball mill and on the surface of a steel ball into a stainless steel disc by using the absolute ethyl alcohol, settling and standing for 2h, pouring out the upper layer absolute ethyl alcohol clear liquid, drying the ball milling tantalum powder at the bottom of the stainless steel disc in a blast oven at 85 ℃, pouring the dried ball milling tantalum powder into a 2L mixed acid system of 15% nitric acid and 0.5% hydrofluoric acid at the stirring speed of 200r/min for pickling for 2h, settling and standing for 20min, pouring out the upper layer pickling clear liquid, filtering and washing the residual bottom tantalum powder by using deionized water until the conductivity is less than 20us/cm, drying the tantalum powder at 85 ℃ in the blast oven, and finally carrying out heat treatment for 30min at 1600 ℃ to obtain the finished product tantalum powder.
In the example, when 5 μm spherical tantalum powder is used as a raw material, the ball milling time is prolonged to 12h, the prepared ball milling sheet type tantalum powder sheet has the diameter of 7-20 μm and the thickness of 1.5-3.5 μm, the metal impurity content Fe after acid washing is 5ppm, Ni is 1ppm, and Cr is 2 ppm. And pressing the finished powder into a tantalum block for electrical property detection, wherein the conditions are as follows by weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solutionLiquid: h at a concentration of 0.01% by volume3PO4Solution, energizing voltage: at 200V, the breakdown voltage of the tantalum block is 287V, and the specific volume is 5930 muf.V/g.
Example 3
The embodiment provides a preparation method of high-pressure tantalum powder for a capacitor, which selects high-purity spherical tantalum powder as a raw material, and performs a ball milling flaking process on the high-purity spherical tantalum powder to prepare high-pressure finished tantalum powder, and the preparation method specifically comprises the following steps: 1kg of raw material spherical tantalum powder with the average grain diameter of 10 mu m is placed in a container with 3kg of stainless steel ball
Adding 2L of ball milling solvent absolute ethyl alcohol into a ball mill, carrying out ball milling for 12h at the rotating speed of 140r/min, after the ball milling process is finished, washing tantalum powder in the ball mill and on the surface of a steel ball into a stainless steel disc by using the absolute ethyl alcohol, settling and standing for 2h, pouring out the upper layer absolute ethyl alcohol clear liquid, drying the ball milling tantalum powder at the bottom of the stainless steel disc in a blast oven at 85 ℃, pouring the dried ball milling tantalum powder into a 2L mixed acid system of 15% nitric acid and 0.5% hydrofluoric acid at the stirring speed of 200r/min for pickling for 2h, settling and standing for 20min, pouring out the upper layer pickling clear liquid, filtering and washing the residual bottom tantalum powder by using deionized water until the conductivity is less than 20us/cm, drying the tantalum powder at 85 ℃ in the blast oven, and finally carrying out heat treatment for 30min at 1600 ℃ to obtain the finished product tantalum powder.
In the example, when 10 μm spherical tantalum powder is used as a raw material and the ball milling time is 12 hours, the prepared ball-milled sheet-type tantalum powder sheet has the diameter of 13-45 μm and the thickness of 2.7-6.9 μm, and the metal impurity content after acid washing is 5ppm, 1ppm, 2 ppm. And pressing the finished powder into a tantalum block for electrical property detection, wherein the conditions are as follows by weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solution: h at a concentration of 0.01% by volume3PO4When the solution is energized at 200V, the breakdown voltage of the tantalum block is 306V, and the specific volume is 5310 muf.V/g.
Example 4
This example provides a method for preparing high-voltage tantalum powder for capacitors, which comprises selecting high-purity spherical tantalum powder as raw materialThe ball milling flaking process is carried out to prepare high-pressure finished tantalum powder, and the preparation steps are as follows: 1kg of raw material spherical tantalum powder with the average grain diameter of 10 mu m is placed in a container with 3kg of stainless steel ball
Adding 2L of ball milling solvent absolute ethyl alcohol into a ball mill, carrying out ball milling for 10h at the rotating speed of 150r/min, after the ball milling process is finished, washing tantalum powder in the ball mill and on the surface of a steel ball into a stainless steel disc by using the absolute ethyl alcohol, settling and standing for 3h, pouring out an upper layer absolute ethyl alcohol clear solution, drying ball milling tantalum powder at the bottom of the stainless steel disc in a blast oven at 90 ℃, pouring the dried ball milling tantalum powder into a 2L mixed acid system of 14% nitric acid and 0.6% hydrofluoric acid at the volume concentration for pickling for 2.5h at the stirring speed of 220r/min, settling and standing for 30min, pouring out an upper layer acid cleaning clear solution, filtering and washing the residual bottom tantalum powder by using deionized water until the conductivity is less than 20us/cm, drying at 90 ℃ in the blast oven, and finally carrying out heat treatment for 25min at 1800 ℃ to obtain the finished tantalum powder.
In the example, spherical tantalum powder of 10 μm is used as a raw material, when the ball milling time is 10 hours, the prepared ball-milled tantalum powder sheet is concentrated in the diameter of 13-40 μm and the thickness of 3.1-6.8 μm, the metal impurity content after acid washing is 5ppm, Ni is 1ppm, and Cr is 2 ppm. And pressing the finished powder into a tantalum block for electrical property detection, wherein the conditions are as follows by weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solution: h at a concentration of 0.01% by volume3PO4When the solution is energized at 200V, the breakdown voltage of tantalum block is 308V, and the specific volume is 5220 f.V/g.
Comparative example 1
This comparative example is substantially the same as example 1 except that the spherical tantalum powder raw material used in this comparative example has a particle size of 30 μm.
And pressing the finished powder into a tantalum block for electrical property detection, wherein the conditions are as follows by weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solution: h at a concentration of 0.01% by volume3PO4When the solution is energized at 200V, the breakdown voltage of the tantalum block is 316V, and the specific volume is 3240 muf.V/g.
Comparative example 2
This comparative example is substantially the same as example 1 except that the raw material used in this comparative example was conventional flaky tantalum powder.
And pressing the finished powder into a tantalum block for electrical property detection, wherein the conditions are as follows by weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solution: h at a concentration of 0.01% by volume3PO4When the solution is energized at 200V, the breakdown voltage of the tantalum block is 281V, and the specific volume is 5400 muf.V/g.
Comparative example 3
This comparative example is substantially the same as example 1 except that the purity of the spherical tantalum powder in this comparative example was 3N or more, and the impurity contents of Fe was 15ppm, Ni was 2ppm, Cr was 7ppm, W was 3ppm, Mo was 2ppm, and Nb was 14 ppm.
And pressing the finished powder into a tantalum block for electrical property detection, wherein the conditions are as follows by weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solution: h at a concentration of 0.01% by volume3PO4When the solution is energized at 200V, the breakdown voltage of the tantalum block is 277V, and the specific volume is 5430 muf.V/g.
Comparative example 4
The comparative example is substantially the same as example 1 except that ball milling is carried out at a rotation speed of 100r/min for 15 hours, and the prepared ball-milled flaky tantalum powder is concentrated at 9-24 μm in diameter and 1.2-3.3 μm in thickness.
And pressing the finished powder into a tantalum block for electrical property detection, wherein the conditions are as follows by weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solution: h at a concentration of 0.01% by volume3PO4When the solution is energized at 200V, the breakdown voltage of the tantalum block is 278V, and the specific volume is 5950 muf.V/g.
Comparative example 5
This comparative example is substantially the same as example 1 except that the acid cleaning solution in this comparative example is a mixed acid solution of nitric acid and hydrofluoric acid, in which the volume concentration of nitric acid is 16% and the volume concentration of hydrofluoric acid is 4%.
Pressing the finished powder into tantalum blocksAnd (3) detecting the electrical property under the conditions of weight: 2g, pressed density: 6.5g/cm3And sintering conditions are as follows: 1800 ℃/30min, energized solution: h at a concentration of 0.01% by volume3PO4When the energizing voltage of the solution is 200V, the breakdown voltage of the tantalum block is 304V, the specific volume is 5480 muf.V/g, and the mass loss rate is 18.7 percent.
As can be seen from the comparison of example 1 and the above comparative examples 1-5, in the present application, the tantalum powder with a specific particle size and purity is used as a raw material, and specific ball milling and acid washing parameters are matched, so that the tantalum powder with a higher breakdown voltage and specific volume can be obtained under the condition of ensuring less quality loss of the finished product.
In conclusion, the spherical tantalum powder is selected as the raw material, the spherical tantalum powder is smooth in appearance, free of sharp corners of edges and good in flowability, the breakdown voltage of the finished product powder is effectively improved, the purity of the spherical tantalum powder is limited, the impurity content of the spherical tantalum powder is low, the surface of the spherical tantalum powder is smooth, the influence of metal impurities on the breakdown voltage of the finished product powder is greatly reduced, the electrical property of a product is further improved, the high-voltage tantalum powder for the capacitor is processed by the spherical tantalum powder through the steps of ball-milling, pickling, heat treatment and the like, the breakdown voltage of the finished product powder can be greatly improved, the requirement of a novel tantalum capacitor on the high-voltage tantalum powder can be met, and the technical problem that the breakdown voltage of the existing finished product.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of high-voltage tantalum powder for capacitors is characterized by comprising the following steps: ball-milling the spherical tantalum powder into sheet tantalum powder, and then performing heat treatment to form a sintering neck;
wherein the average grain diameter of the spherical tantalum powder is 5-10 μm.
2. The method of claim 1, wherein the spherical tantalum powder has a purity of 4N or more, and contains Fe 5ppm or less, Ni 5ppm or less, Cr 5ppm or less, W5 ppm or less, Mo 5ppm or less, and Nb 5ppm or less.
3. The method for preparing high-voltage tantalum powder for capacitors as claimed in claim 1, wherein the ball milling comprises placing the spherical tantalum powder in a ball mill with stainless steel balls, adding a ball milling solvent, and ball milling for 6-12h at a rotation speed of 100-.
4. The method for preparing high-voltage tantalum powder for capacitors as claimed in claim 3, wherein the ball milling solvent is absolute ethyl alcohol.
5. The method for preparing high-voltage tantalum powder for capacitors as claimed in claim 3, wherein the flaky tantalum powder has a flake diameter of 5 to 45 μm and a thickness of 1.5 to 6.9 μm.
6. The method for preparing high-voltage tantalum powder for capacitors as claimed in claim 1, wherein after the ball milling, before the heat treatment, the method further comprises pickling the ball-milled and dried material in a pickling solution at a stirring speed of 180-;
preferably, the acid washing solution is a mixed acid solution of nitric acid and hydrofluoric acid, wherein the volume concentration of the nitric acid is 14-15%, and the volume concentration of the hydrofluoric acid is 0.4-0.6%.
7. The method of claim 6, further comprising settling the pickling system for 10-30min after the pickling and before the heat treatment, removing the tantalum powder after the pickling, washing the tantalum powder with water until the conductivity of the washing solution is less than 20us/cm, and drying the tantalum powder at 80-90 ℃.
8. The method as claimed in claim 1, wherein the heat treatment comprises heat treatment at 1800 ℃ for 20-40 min.
9. A high-voltage tantalum powder for capacitors, which is produced by the production method of the high-voltage tantalum powder for capacitors as claimed in any one of claims 1 to 8.
10. A capacitor comprising the high-voltage tantalum powder for capacitors as claimed in claim 9.
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