WO2015100519A1

WO2015100519A1 - Preparation method of high-nitrogen-content capacitor grade tantalum powder and tantalum powder prepared therefrom and tantalum capacitor

Info

Publication number: WO2015100519A1
Application number: PCT/CN2013/090820
Authority: WO
Inventors: 郑爱国; 杨国启; 郭涛; 王治道; 任萍
Original assignee: 宁夏东方钽业股份有限公司; 国家钽铌特种金属材料工程技术研究中心
Priority date: 2013-12-30
Filing date: 2013-12-30
Publication date: 2015-07-09
Also published as: CN104936729B; CN104936729A

Abstract

A method of adding part nitrogen-containing salts in the synthetic process of potassium fluotantalate is provided. Since the procedure of nitrogen doping is conducted during the synthetic process of potassium fluotantalate, the nitrogen content that is more uniform than those obtained from other methods is obtained, and moreover, nitrogen is doped at the early stage, so primary particles are directly affected and accordingly become finer, the specific volume of tantalum powder is higher, and smaller leakage current and loss are realized. The method improves the qualified rate of capacitor products.

Description

Preparation method of high-nitrogen capacitor grade bismuth powder and bismuth powder and tantalum capacitor prepared thereby

The invention relates to the field of high specific capacitance capacitor grade tantalum powder and high specific capacitance capacitor fabrication. Background technique

Metal ruthenium is a valve metal that forms a dense oxide film on the surface and has a unidirectional conductive property. Anode film made of tantalum is chemically stable (especially stable in acidic electrolytes), electrical resistance

The dielectric constant is large (27.6) and the leakage current is small. In addition, it has a wide operating temperature range (-80 ~ 200), high reliability, shock resistance and long service life. It is an ideal material for making small and reliable tantalum capacitors.

Tantalum capacitors are electronic devices in which a tantalum metal anode is used to directly form a dielectric oxide film on the tantalum surface by anodization. The specific surface area of the tantalum powder is high, and even after pressing and sintering, a high specific surface area is maintained due to its special pore structure, so that a high ratio (electrical) capacity of the capacitor is obtained.

In the process of manufacturing ^ ^, the potassium fluoroantimonate sodium reduction process is the most widely used and the most mature technology in the current production process.

The potassium fluoroantimonate sodium reduction process, also known as the pyrometallurgical reduction process, is a capacitor grade prepared by using K ₂ TaF ₇ and Na as main raw materials, using a halogen salt such as NaCl or KC1 or a mixture of halogen salts as a diluent. The main reaction mechanism of the method is as follows:

K ₂ TaF ₇ +5Na = Ta+5NaF+2KF (1) K ₂ TaF ₇ reacts with liquid sodium under argon gas protection and at a certain temperature. The reduced tantalum powder is subjected to heat treatment after washing with water and pickling, and then deoxidized by magnesium to obtain a final high-purity tantalum powder.

Traditionally, K ₂ TaF ₇ has been synthesized by the synthesis of gas phthalic acid and KC1. KC1 was added to gas citrate to synthesize K ₂ TaF ₇ , and the following reaction occurred:

H ₂ TaF ₇ + 2KC1 = K ₂ TaF ₇ + HC1 (2) Specifically, KC1 is added to H ₂ TaF ₇ , HF is added to adjust L L , the mixture is evenly stirred, and the heat preservation time is not less than 20 minutes. After the heat preservation, the crystal is cooled, washed, and dried at 120 to 160 ° C. A potassium citrate powder was obtained.

A more detailed method for synthesizing potassium fluoroantimonate and a method for preparing bismuth powder by fire method can be referred to the 钽铌 Metallurgical Industry unearthed in 1982, published by Xing Liangzuo, etc., published in 1986 by Wu Ming et al., "The Metallurgical Technology of Minmetals" and the "Modern Metallurgy" edited by Guo Qingwei and others, which was unearthed in the metallurgical industry in 2009.

At present, capacitor-grade tantalum powder is developing in the direction of high specific volume and high purity. It is well known that the specific volume of tantalum powder is proportional to its specific surface area, that is, the smaller the average particle size of tantalum powder, the larger the specific surface area and the higher the specific volume. To achieve high specific volume of tantalum powder, the key technology is to produce tantalum powder with a smaller average particle size. For the sodium fluoroantimonate sodium reduction process, the core of the study is to control the nucleation of the nano-reduction process by controlling the reduction conditions, including the composition of the potassium fluoroantimonate and the diluent dissolved salt, the reduction temperature, the rate of sodium injection, and the like. Forming, distributing and growing, the desired tantalum powder having a certain specific surface area and particle size is prepared. The mechanical method is to obtain finer particles of tantalum powder by controlling the conditions of hydrogenation milling or ball milling. The hydrogen reduction method of the halide adopts the preparation technology of nanometer powder, and the prepared degree of 钽 is in the nanometer order and has a large specific surface area.

Doping is a high specific volume of tantalum powder. It is used in the production and research of high specific volume tantalum powder. It is doped in the process of making 1⁄4 powder. The main purpose is to refine the tantalum powder. The second is to inhibit the growth of the tantalum powder grains during high temperature treatment, and to maximize the possible specific surface area of the tantalum powder and reduce the loss of tantalum powder specific volume. Doping can be carried out in different processes. Common doping elements are N, Si, P, B, C, S, Al, O, etc. and their compounds. The doping element is generally segregated at the grain boundary surface, and reacts with cerium at a high temperature to form various cerium compounds. Doping not only incorporates one element in one process of the process, but also multi-step multi-element doping. This not only refines the tantalum powder, but also reduces the specific volume loss of the tantalum powder.

Nitrogen doping in tantalum powder is a popular practice in the industry, especially in high specific volume production.

US Pat. No. 6,875,542 proposes a method for preparing a nitrogen-containing metal powder and using the metal powder The obtained porous sintered body and solid electrolytic capacitor, the patent proposes a nitrogen-containing metal powder having a nitrogen content W (ppm) and a specific surface area S (m ² /g) measured by the BET method, W/S ratio 500 - 3000. The patent also teaches a method of introducing nitrogen into the reduction to increase the nitrogen content.

U.S. Patent No. 7,066,975 discloses a nitrogen-containing metal powder, a process for the preparation thereof, and a porous sintered body and a solid electrolytic capacitor obtained by using the metal powder. This patent proposes a nitrogen-containing metal powder containing 50 to 20,000 ppm of solid solution nitrogen, especially yttrium, which contains ? , B, O or a combination thereof, characterized in that nitrogen is present in the form of a solid solution, and the average particle diameter of the nitrogen-containing metal powder is from 80 to 360 nm.

U.S. Patent No. 7,473,294 discloses a nitrogen-containing metal powder, a process for the preparation thereof, and a porous sintered body and electrolytic capacitor prepared using the metal powder. The patent proposes a nitrogen-containing metal powder (having a gas and an inner layer) containing 50 to 20,000 ppm of nitrogen in the form of a solid solution, the nitrogen being in a solid solution form, the metal being ruthenium, The nitrogen gas is uniformly infiltrated into the inner layer from the metal, and the metal powder has a particle diameter of ≤ 250 legs.

U.S. Patent No. 6,432,161 discloses another method for preparing a nitrogen-containing metal powder and a porous sintered body and electrolytic capacitor prepared using the metal powder. The patent proposes a method for producing a nitrogen-containing metal powder, which comprises reducing a ruthenium or osmium compound with a reducing agent, and simultaneously introducing a nitrogen gas to the reaction system to form a nitrogen-containing ruthenium or osmium in the form of a solid solution. Nitrogen is simultaneously incorporated into the ruthenium or osmium. This patent is an extension of the sodium reduction fluoroantimonate method to make it suitable for other ruthenium or osmium compounds to be nitrogen-doped.

Chinese patent application CN1498144A relates to a method for producing sintered pellets which is prepared by mixing a refractory metal and a refractory metal nitride and found to be higher than those made of refractory metal or refractory metal nitride alone. The proportion of the inner aggregated pores results in an improved capacitor grade powder, an anode and thus a capacitor crucible. When the mixture is in the range of 50-75 W/W% refractory metal nitride, the pellet porosity and total volume are maximized. The total pellet pore surface area is relatively independent of the 50% concentration of the refractory metal nitride. A substrate consisting of a 50/50 or 25〃5 \¥/\¥% refractory metal/refractory metal nitride powder mixture will produce a solid capacitor with a higher capacitance recovery and lower ESR. In short, it is directly mixed with tantalum nitride or tantalum or tantalum nitride, and then press molded to form the anode of the capacitor. Thus, the method of nitrogen doping in tantalum powder used in the prior art focuses on introducing a nitrogen-containing gas into the reaction system, and nitrogen is present in a solid solution. However, the nitrogen-doping method has low effectiveness, cannot obtain high-content nitrogen powder, and cannot accurately control the nitrogen-doping amount. Therefore, a niobium-doped nitrogen-doping process with good effect and high controllability is still needed. Summary of the invention

SUMMARY OF THE INVENTION An object of the present invention is to provide a high nitrogen content tantalum powder, a method for preparing the same, and a tantalum capacitor produced from the tantalum powder. Moreover, the nitrogen content in the tantalum powder can be accurately controlled.

The object of the present invention is achieved by the following aspects.

In a first aspect of the invention, a method of preparing a tantalum powder is provided, comprising the steps of:

(a) adding KN0 ₃ or a mixture of KN0 ₃ and KC1 to the H ₂ TaF ₇ solution;

(b) adjusting the J1⁄2 liquid for heat preservation;

(c) cooling the crystals to obtain a K ₂ TaF ₇ powder;

(d) Using the K ₂ TaF ₇ powder obtained in the step (c), the preparation was carried out by a potassium phthalate sodium reduction process. The invention adds a nitrogen-containing salt in the synthesis process of potassium fluoroantimonate, so that the nitrogen-doping process is carried out in the synthesis process of potassium fluoroantimonate, which is more uniform than the conventional method. And because nitrogen is incorporated in the early stage, it directly affects the primary particles, making the primary particles finer, the specific volume of the tantalum powder higher, and the leakage current and loss are smaller. Therefore, the pass rate of the capacitor product is improved.

The sodium bismuth citrate reduction process in the step (d) of the first aspect of the present invention is a process generally employed in the prior art, and can be specifically referred to the description in the background section. The reduced material can be subjected to a conventional treatment such as crushing, washing, and/or pickling.

In one embodiment, in step (a), the amounts of KN0 ₃ and KC1 are calculated according to formulas (4) and (5):

The amount of KC1 (g) = concentration of solution of _{_{H 2 TaF 7 (g / l}} ) xH 2 TaF 7 solution volume (1) ΧΟ · 67ΧΝ1

(4)

KN0 ₃ dosage (g) = H ₂ TaF ₇ solution content (g / l) x H ₂ TaF ₇ solution volume (1) X0.91XN2 Where Nl+N2 = ll ~ 1.3, and N2 is not 0.

It should be noted that 0.67 and 0.91 are molecular weight ratios of KC1 to potassium nitrate.

In one embodiment, in step (a), the acidity of the H ₂ TaF ₇ solution is adjusted to 0.7 - 1.2 mol/l before the addition of KN0 ₃ or a mixture of KN0 ₃ and KC1.

In one embodiment, in step (b), the pH of the reaction solution is adjusted using HF. In one embodiment, in step (b), the acidity of the reaction liquid is adjusted to 1.2 - 1.65 mol/l. In one embodiment, in step (b), the holding time is not less than 20 minutes. In one embodiment, in step (c), the product is also dried after cooling and crystallization. In one embodiment, the drying is included at 120-160. C drying. In one embodiment, the drying also includes a second drying at 250 - 350 'C.

According to a second aspect of the invention, there is provided a tantalum powder obtained by the production method according to the first aspect of the invention. According to a third aspect of the invention, there is provided a tantalum capacitor manufactured from tantalum powder according to the second aspect of the invention. In the tantalum powder of the present invention and the tantalum capacitor manufactured therefrom, the nitrogen content is high, and the nitrogen doping amount can be accurately controlled, so that the electrical performance is superior to the tantalum powder and tantalum capacitors in the prior art.

The various embodiments described above can be combined as needed, and the resulting technical solution is still within the scope of the present invention. Detailed description of the invention

The present invention provides a method of producing a high nitrogen content niobium powder, comprising the steps of:

In the production of potassium citrate, using KN0 ₃ moiety or 4^ instead of KC1 to synthesize K ₂ TaF ₇ , the following occurs

H ₂ TaF ₇ + 2KN0 ₃ = K ₂ TaF ₇ +HN0 ₃ (3) Specifically, after adjusting the H ₂ TaF ₇ solution to 0.7 - 1.2 mol / l, add KN0 ₃ and / or KC1, and according to Equations (4) and (5) are used to calculate the amount of KN0 ₃ and KC1:

(4)

KN0 ₃ dosage (g) = H ₂ TaF ₇ solution content (g / l) x H ₂ TaF ₇ solution volume (1) X0.91XN2 Wherein, N1+N2 = 1.1 - 1.3, and N2 is not 0; 0.67 and 0.91 are molecular weight ratios of KC1 to potassium nitrate.

Add HF to adjust the acidity of the reaction solution to 1.2 ~ 1.65mol / l, stir evenly, heat preservation, heat preservation time is not less than 20 minutes, after cooling, crystallize, wash, dry at 120 ~ 160 'C, optionally in 250 ~ 350. The second drying of C gave K ₂ TaF ₇ powder. Analysis of the N content of ₂ TaF ₇ K, to obtain the synthesis of K ₂ TaF ₇ very fine needles.

In the fire reduction stage of the formula (1), K ₂ TaF ₇ synthesized with KC1 was replaced with potassium citrate produced by KN0 ₃ . The remaining types and amounts of molten salt systems such as NaCl, KC1, KF, and the reducing additives and reduction processes are all in accordance with conventional processes in the prior art. The result is a raw powder which is uniformly nitrogen-doped. This gives a fine grain of the first time.

Then, the reduced material is subjected to steps of crushing, washing, pickling, etc. to obtain a desired nitrogen-doping product. In order to further illustrate the invention, the embodiments of the present invention are described in the accompanying drawings and the accompanying drawings. Example 1:

H ₂ TaF ₇ having a concentration of 50 g/K of 0.9 mol/l was dissolved in a tank, and the air was condensed for ^6 time. The purpose is to float part of the organic solution dissolved in the H ₂ TaF ₇ solution to? The upper layer of the solution in the tank is pumped away, which can effectively reduce the carbon content in the final potassium fluoroantimonate. The H ₂ TaF ₇ solution 10001 after ^k was added to the synthesis tank, where the effective volume of the synthesis tank was 13001.

This embodiment of potassium nitrate was added from about 5 ⁴ .6k _g (i.e., m is 0, N ² is ^1.2). Then, the stirring paddle was turned on, and the acidity was adjusted to 1.55 mol/l by adding HF 53 liter. Insulation is carried out by steaming, and the holding time is 20 min. After the completion of the heat preservation, the synthetic liquid UV cooling tank was cooled and crystallized, and the cooling time was 24 hours. After cooling and crystallization, it will be crystallized; centrifuge, rinse with pure water, centrifuge, and separate the separation solution with the mother liquor. Crystallization after separation, and then drying twice, the first use of far infrared dryer, drying temperature 150. C, after the drying is finished, continue the second drying, using vacuum rotary drying, drying temperature 300 ^e C, after drying 3⁄4 sodium reduction process.

Install KC1 120kg, KF 100kg in the reduction furnace, and then heat up according to the set program, when the temperature reaches 900. At time C, K ₂ TaF ₇ 50 Kg was added from the feed port. The temperature was raised to 930 after the feed. C, start calculating the holding time. After lh holding, raise the stirring paddle 10cm, and cool down to 820. C, then start to inject sodium smoothly, while stirring, ^3⁄4 degrees ^ at 900 ^. The amount of sodium added to J^J1⁄2 is 16Kg. i£ Original ^1⁄2 knot ^, , and baked. Then, the reduced material is subjected to steps of crushing, washing, pickling, agglomeration, and the like to obtain a desired nitrogen-doping product. Example 2:

The H ₂ TaF ₇ having a concentration of 50 g/K of 0.9 mol/l was dissolved in the tank, and the air was condensed and the time was 0 h. The H ₂ TaF ₇ solution 10001 after the addition was added to the synthesis tank synthesis, where the effective volume of the synthesis tank was 13001.

In this example, potassium nitrate was added at about 38.2 kg and KC1 at 12 kg (i.e., N1 was 0.36 and N2 was 0.84). Then open the stirring paddle, add HF 53 liters to adjust the acidity to 1.55mol / l, steaming for heat preservation, holding time 30min, after the end of the heat, the synthesis solution ^ cooling tank for cooling crystallization, cooling time 24h. After cooling and crystallization, the crystals are placed in a centrifuge, and the crystals are rinsed with pure water, centrifuged, and the separation liquid is treated together with the mother liquor. After separation, the crystal is crystallization, and then dried twice. The first time, the far-infrared dryer is used, and the drying temperature is 150 Ό. After the drying is finished, the second drying is continued, and the vacuum drying is performed, and the drying temperature is 300. C, after drying, enter the sodium reduction process.

Install KC1 120kg, KF 100kg in the reduction furnace, and then heat up according to the set program, when the temperature reaches 900. At time C, K ₂ TaF ₇ 50 Kg was added from the feed port. The temperature was raised to 930 after the feed. C, start calculating the holding time. After lh holding, raise the stirring paddle 10cm, and cool down to 820. C, then start to inject sodium smoothly, while stirring, ^3⁄4 degrees ^ at 900 ^. The amount of sodium added to J^J1⁄2 is 16Kg. i£ Original ^1⁄2 knot ^, , and baked. Then, the reduced material is subjected to steps of crushing, washing, pickling, agglomeration, and the like to obtain a desired nitrogen-doping product. Example 3:

A H ₂ TaF ₇ solution having a concentration of 50 g/K of 0.9 mol/l was placed in a stripping tank, and compressed air was passed through for 0 hours. The H ₂ TaF ₇ solution 10001 after the addition was added to the synthesis tank synthesis, where the effective volume of the synthesis tank was 13001.

In this example, potassium nitrate was added at about 27.3 Kg and KC1 at 20 Kg (i.e., N1 was 0.6 and N2 was 0.6). Then open the stirring paddle, add HF 53 liters to adjust the acidity to 1.55mol / l, steaming for heat preservation, holding time 30min, after the end of the heat, the synthesis solution ^ cooling tank for cooling crystallization, cooling time 24h. After cooling and crystallization, the crystals are placed in a centrifuge, and the crystals are rinsed with pure water, centrifuged, and the separation liquid is treated together with the mother liquor. After separation, the crystal is crystallization, and then dried twice. The first time, the far-infrared dryer is used, and the drying temperature is 150 Ό. After the drying is finished, the second drying is continued, and the vacuum drying is performed, and the drying temperature is 300. C, after drying, enter the sodium reduction process.

Install KC1 120kg, KF 100kg in the reduction furnace, and then heat up according to the set program, when the temperature reaches 900. At time C, K ₂ TaF ₇ 50 Kg was added from the feed port. The temperature was raised to 930 after the feed. C, start calculating the holding time. After holding lh for heating, raise the stirring paddle 10cm, ? SU^" warm to 820. C, then start to inject sodium smoothly, while stirring, ^3⁄4 degrees ^ at 900 ^. The amount of sodium added to J^J1⁄2 is 16Kg. i£ original ^1⁄2 knot ^, , baked. Next, The reduced material is subjected to steps of crushing, washing, pickling, agglomeration, etc. to obtain a desired nitrogen-doping product.

In this example, potassium acid was added at about 16.4 Kg and KC 128 Kg (i.e., N1 was 0.84 and N2 was 0.36). Then open the stirring paddle, add HF 53 liters to adjust the acidity to 1.55mol / l, pass steam to keep warm, the holding time is 35min, after the end of the heat preservation, the synthetic liquid cooling tank is cooled and crystallized, and the crystallization cooling tank is cooled by external circulation of circulating water. Cooling time 30h. After cooling and crystallizing, the crystal is placed in a centrifuge, plus The pure water is rinsed and crystallized, centrifuged, and the separation liquid is treated together with the mother liquor. Crystallization after separation, and then drying twice, the first time using a far-infrared dryer, drying temperature 150. C. After the drying is finished, the drying is continued for 2 times, and the drying is performed by vacuum spinning, and the drying temperature is 300. C, after drying, enter the sodium reduction process.

Install KC1 120kg, KF 100kg in the reduction furnace, and then heat up according to the set program, when the temperature reaches 900. At time C, K ₂ TaF ₇ 50 Kg was added from the feed port. The temperature was raised to 930 after the feed. C, start calculating the holding time. After holding lh for heating, raise the stirring paddle 10cm, ? SU^" warm to 820. C, then start to inject sodium smoothly, while stirring, ^3⁄4 degrees ^ at 900 ^. The amount of sodium added to J^J1⁄2 is 16Kg. i£ original ^1⁄2 knot ^, , baked. Next, The reduced material is crushed, washed, pickled, agglomerated, etc. to obtain the desired nitrogen-doped product. Comparative Example 5:

In this example, KC1 40Kg was added (i.e., N1 was ^1.2 , and N2 was 0). Then open the stirring paddle, add HF 53 liters to adjust the acidity to 1.55mol / l, steaming for heat preservation, holding time 40min, after the end of the heat preservation, the cooling solution is cooled and crystallized, and the crystal cooling tank is cooled by external circulation of circulating water. After cooling for 30 hours, the crystals are placed in a centrifuge, and the crystals are rinsed with pure water, centrifuged, and the separation liquid is treated together with the mother liquor. After separation, the crystal is crystallization, and then dried twice. The first time, the far-infrared dryer is used, the drying temperature is 150, and the second drying is continued after the drying is completed. The drying is performed by vacuum spinning, and the drying temperature is 300 Ό. After drying, it enters the sodium reduction process.

Install KC1 120 kg, KF lOO kg in the reduction furnace, and then heat up according to the set program, when the temperature reaches 900. At time C, K ₂ TaF ₇ 50 Kg was added from the feed port. The temperature was raised to 930 after the feed. C, start calculating the holding time. After holding lh for heating, raise the stirring paddle 10cm, ? SU^" warm to 820. C, then start to inject sodium smoothly, while stirring, ^3⁄4 degrees ^ at 900 ^. The amount of sodium added to J^J1⁄2 is 16Kg. i£ original ^1⁄2 knot ^, , baked. Next, The reduced material is crushed, washed, pickled, and agglomerated The steps are followed to obtain the desired nitrogen-doped product.

Five sets of examples were analyzed using the reaction system, and the results of the final sample were compared as shown in the following table. Table 1: Physical properties of tantalum powder

in FIG. 1:

FSSS represents the Fourier particle size of the particles.

The apparent density of powders of SBD powder refers to the bulk density measured after the powder is filled under standard conditions, that is, the mass per unit volume when the powder is filled, expressed in _g /cm ³ . It is a process property of powder. The measurement method used here is the funnel method, even if the powder is free to fall from the funnel hole to a full height to fill the cup.

+80 (%) indicates the ratio of particles larger than 80 mesh to the total particles, and -400 (%) indicates the ratio of particles smaller than 400 to all particles. The mesh refers to the number of meshes per inch (25.4 mm) of the screen. Table 2: Main element content in 4 ^ (unit: ppm)

Example 4 5810 37 980 18 12 162 36 Comparative Example 5 6560 38 460 17 15 165 38 The detection methods of the elements in the bismuth powder are all derived from GB/T 15076.8-2008, GB/T 15076.9-2008, GB/T 15076.12-2008. , GB/T 15076.14-2008, GB/T 15076.15-2008, GB/T 15076.16-2008, "Chemical Analysis Methods" and other national standards.

It can be seen from the data in 2 that the highest nitrogen doping amount is obtained by using potassium nitrate when producing potassium citrate (Example 1), and as the amount of potassium nitrate is decreased and the amount of KC1 is increased, the nitrogen doping amount is reduced, when all The amount of nitrogen doping was the lowest when KC1 was used (Comparative Example 5). It can be seen that the nitrogen doping effect of the present invention is better than the conventional nitrogen doping method, and the high nitrogen content tantalum powder can be obtained by the method of the present invention. Table 3: Comparison of electrical properties (sintering 1270. C/10min Vf: 20V D pressure: 5.0g/cc)

The method and equipment for testing the electrical properties of tantalum powder refer to the national standard GB/T 3137-2007, "Test method for electrical properties of tantalum powder".

In Table 3:

Sintered ^ 1270. C/10min means 4^ at 1270. C sintering for 10 minutes gave an anode block.

Vf: 20V means energization at a voltage of 20V.

D pressure: 5.0g / cc means that the anode block has a compact density of 5.0g / cc.

ΚΧ10- ⁴ (μΑ / μΡν) representative of leakage current, hereinafter referred Κ values. Since the capacitance can not be absolutely non-conductive, when the capacitor is applied with a DC voltage, the capacitor will have leakage current. If the leakage current is too large, The capacitor will be damaged by heat. Applying a rated DC operating voltage to the capacitor will observe that the change in charging current begins to increase, decreases over time, and reaches a more stable state at a certain final value. This final value current is called leakage current.

CV (FV/g) represents the specific capacity, that is, the amount of electricity that can be discharged per unit weight of the battery or active material. Tg6 (%) represents the loss of the capacitor. The loss of the capacitor is actually the reactive power consumed by the capacitor, so it can also be defined as follows: The loss of the capacitor also refers to the ratio of the reactive power consumed by the capacitor under the electric field to the total power consumed. The expression is: Capacitor loss angle Tangent value = reactive power ÷ total power, or capacitor loss tangent = reactive power χΐ ο ÷ total power (the resulting value is a percentage).

SHV (%) represents the volumetric shrinkage of the capacitor anode block.

The analytical data show that the nitrogen doping in the potassium fluoroantimonate used for the manufacture can also improve the performance of the capacitor grade tantalum powder as well as the direct doping of nitrogen. As the amount of nitrogen increases, the specific volume increases, the leakage current decreases, and the loss decreases, indicating that the electrical performance is expected to increase.

The method of the invention can achieve nitrogen doping in the process, and can effectively control the nitrogen content in the process, and the obtained product is satisfactory.

The specification and the embodiments of the present invention are set forth in the description of the preferred embodiments of the invention .

Claims

Claim

A method for preparing a tantalum powder, comprising the steps of:

(a) a mixture of KN0 ₃ or KN0 ₃ and KC1 to H ₂ TaF ₇ i^3⁄4;

(b) adjusting the J1⁄2 liquid for heat preservation;

(c) cooling the crystals to obtain a K ₂ TaF ₇ powder;

(d) Using the K ₂ TaF ₇ powder obtained in the step (c), the preparation was carried out by a potassium phthalate sodium reduction process.

The production method according to claim 1, wherein in the step (a), the amounts of KN0 ₃ and KC1 are calculated according to the formulas (4) and (5):

(4)

KN0 ₃ dosage (g) = H ₂ TaF ₇ solution content (g / l) x H ₂ TaF ₇ solution volume (1) X0.91XN2

(5) where Nl+N2 = l.l ~ 1.3, and N2 is not 0.

The preparation method according to claim 1 or 2, wherein in the step (a), the acidity of the H ₂ TaF ₇ solution is adjusted to 0.7 - 1.2 mol/l before adding KN0 ₃ or a mixture of KN0 ₃ and KC1. .

The production method according to claim 1 or 2, wherein in the step (b), the HF adjusting solution is used

The preparation method according to claim 1 or 2, wherein in the step (b), the liquid is adjusted to 1.2 - 1.65 mol / l.

The preparation method according to claim 1 or 2, wherein in the step (b), the holding time is not less than 20 minutes.

The production method according to claim 1 or 2, wherein in the step (c), the product is further dried after cooling and crystallization.

The preparation method according to claim 7, wherein the drying is performed at 120 - 160. C drying.

The preparation method according to claim 8, wherein the drying further comprises a second drying at 250 to 350 °C.

The process for producing according to any one of claims 1-9.