CN104495929B - Niobium suboxide powder and process for producing the same - Google Patents

Niobium suboxide powder and process for producing the same Download PDF

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CN104495929B
CN104495929B CN201410829667.2A CN201410829667A CN104495929B CN 104495929 B CN104495929 B CN 104495929B CN 201410829667 A CN201410829667 A CN 201410829667A CN 104495929 B CN104495929 B CN 104495929B
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niobium suboxide
suboxide powder
niobium
powder
oxygen
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陈学清
程越伟
马跃忠
李刚
马海燕
李霞
郭孝民
马玉婷
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Ningxia Orient Tantalum Industry Co Ltd
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Abstract

The invention provides niobium suboxide powder with uniform oxygen content, which is screened into n particle size intervals, wherein n is an integer larger than or equal to 1, and the standard deviation of the oxygen content in the niobium suboxide powder in each particle size interval is smaller than or equal to 0.7 wt%. The niobium suboxide powder containing oxygen uniformly has uniform particle size distribution and improved leakage current.

Description

Niobium suboxide powder and process for producing the same
Technical Field
The invention belongs to the field of niobium oxide powder, and particularly relates to low-valence niobium oxide powder and a preparation method thereof.
Background
Niobium suboxide is a ceramic material that can form Nb on its surface by anodic oxidation due to its metallic conductivity2O5The dielectric oxide film of (3) is further processed into a niobium suboxide electrolytic capacitor. As a novel electrolytic capacitor, the niobium suboxide electrolytic capacitor can be used as a substitute of partial tantalum and aluminum capacitors. The capacitor has the characteristics of high safety, easy miniaturization, large capacity, chip type and the like, shows sharp in the field of low-voltage capacitors, and is widely applied to products such as mobile phones, notebook computers, game machines, digital cameras, automobiles and the like. The key to the development of high performance niobium suboxide electrolytic capacitors is the preparation of high performance niobium suboxide powders.
Chinese patent CN101139110A describes a method for preparing niobium suboxide or niobium powder, which comprises: carrying out heat treatment on the raw material niobium oxide and a reducing agent, then carrying out acid cleaning to remove the redundant reducing agent, carrying out high-temperature heat treatment under vacuum or inert atmosphere, and screening to obtain the low-valence niobium oxide or niobium powder.
Chinese patent CN1587066A describes a method for producing niobium suboxide, which is to mix niobium oxide and capacitor-grade niobium powder uniformly, then carry out low-temperature heat treatment, then mix the obtained powder with a certain proportion of capacitor-grade niobium powder uniformly, and then carry out high-temperature heat treatment.
There is also a need in the art for niobium suboxide powders of better quality.
Disclosure of Invention
It is an object of the present invention to provide a uniform niobium suboxide powder containing oxygen, and it is another object of the present invention to provide a method for preparing a uniform niobium suboxide powder containing oxygen. It is still another object of the present invention to provide a porous sintered body. It is yet another object of the present invention to provide a capacitor anode. It is yet another object of the present invention to provide an electrolytic capacitor. It is a further object of the invention to provide an electronic circuit or an electronic instrument.
Further, the present invention provides a uniform niobium suboxide powder containing oxygen having one or more of the following advantages:
(1) lower leakage current (DCL);
(2) lower Equivalent Series Resistance (ESR);
(3) a higher specific capacitance;
(4) the powder has uniform particle size distribution and improved over-sintering phenomenon.
The inventors have found that the physical and electrical properties of niobium suboxide powders can be significantly improved after increasing the uniformity of their oxygen content.
The inventors have further discovered that niobium suboxide powders that contain uniform oxygen also have good nitrogen content uniformity after nitrogen doping, which also have improved physical and electrical properties.
To this end, the present invention provides, in a first aspect, a niobium suboxide powder containing oxygen uniformly, which is sieved into n size intervals, n being an integer of 1 or more, and the standard deviation of the oxygen content in the niobium suboxide powder in each size interval is 0.7 wt% or less, preferably 0.6 wt% or less, more preferably 0.5 wt% or less, further preferably 0.4 wt% or less, 0.3 wt% or less, 0.2 wt% or less, or 0.15 wt% or less.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of the first aspect of the present invention has a very small difference in oxygen content of 1.6 wt% or less, preferably 1.2 wt% or less, more preferably 1 wt% or less, still more preferably 0.8 wt% or less, and particularly preferably 0.5 wt% or less in the niobium suboxide powder in each particle size range.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the preceding first aspect of the present invention has an oxygen content of 13 to 16 wt%, preferably 14.6 to 15.4 wt% or 14 to 15 wt% in the niobium suboxide powder in each particle size interval.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the preceding first aspects of the invention has the formula consisting of NbOxWherein x is 0.99 to 1.06.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the preceding first aspects of the invention, which contains elemental nitrogen, has a sample standard deviation of the nitrogen content of the niobium suboxide powder of less than or equal to 280ppm, e.g., less than or equal to 250ppm, less than or equal to 230ppm, less than or equal to 200ppm, less than or equal to 180ppm, less than or equal to 150ppm, less than or equal to 120ppm, less than or equal to 100ppm, less than or equal to 80ppm, or less than or equal to 70ppm for each particle size interval.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the first aspect of the present invention has a nitrogen content of 50 to 10000ppm, for example 1000 to 5000ppm, 2000 to 4000ppm, or 2800 to 3200ppm, in each particle size range.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the foregoing first aspects of the present invention has a nitrogen content in the niobium suboxide powder in each particle size interval that varies by a very small amount of 700ppm or less, such as 600ppm or less, or 500ppm or less, or 400ppm or less, or 300ppm or less, 200ppm or less, or 180ppm or less.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the preceding first aspects of the invention, wherein n-5.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the first aspect of the present invention has a particle size range of 60 to 80 mesh, 80 to 200 mesh, 200-.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the foregoing first aspects of the invention has a leakage current of 2nA/μ FV or less, e.g., 1nA/μ FV or less, 0.5nA/μ FV or less, and 0.3nA/μ FV or less.
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the preceding first aspect of the invention has a bulk density of 0.5 to 1.5g/cm3For example, 0.7 to 1.3g/cm3。
In one embodiment, the oxygen-containing uniform niobium suboxide powder of any one of the preceding first aspects of the invention has a particle size of ≦ 60 mesh.
In one embodiment, the oxygen-containing uniform niobium suboxide powder according to any one of the first aspect of the present invention has a specific capacitance (CV value) of 40000 to 250000 μ FV/g.
A second aspect of the present invention provides a method for producing the oxygen-containing uniform niobium suboxide powder of any one of the preceding first aspects of the present invention, which comprises:
1) uniformly mixing raw material niobium suboxide powder, heating to 700-1000 ℃ (preferably 750-980 ℃, 750-900 ℃ or 850-950 ℃) in a hydrogen atmosphere, preserving heat for 3-8 hours (preferably 3-6 hours, 3-5 hours or 4-6 hours), evacuating, discharging hydrogen, filling inert gas for protection, cooling and passivating, and discharging, or,
uniformly mixing raw material niobium suboxide powder, heating to 700-1000 ℃ (preferably 750-980 ℃, 750-900 ℃ or 850-950 ℃) in hydrogen atmosphere, preserving heat for 3-8 hours (preferably 3-6 hours, 3-5 hours or 4-6 hours), reducing the temperature to 500-700 ℃ (for example 550-650 ℃ or 600 ℃), replacing the hydrogen atmosphere with nitrogen atmosphere, preserving heat for 100-140 minutes (for example 120 minutes), discharging after cooling and passivating,
2) heat treating the product of step 1) to obtain the uniform oxygen-containing niobium suboxide powder of any one of the first aspect of the present invention.
In one embodiment, the method of the second aspect of the present invention, wherein the starting niobium suboxide powder of step 1) is prepared from a powder of the formula NbOxIs shown in whichx is 0.8 to 1.2 (for example, x is 0.9 to 1.1).
The raw niobium suboxide powder of the present invention can be obtained by those skilled in the art according to the prior art and the means of ordinary skill in the art, for example, according to the methods of patent CN101139110A or CN 1587066A. The present invention is incorporated by reference in its entirety.
In one embodiment, the above-mentioned production method of the second aspect of the present invention, wherein the raw material niobium suboxide powder in step 1) is a niobium suboxide powder obtained by reducing niobium pentoxide with a reducing agent, or a niobium suboxide powder obtained by disproportionating niobium with niobium pentoxide.
In one embodiment, the method of any one of the second aspect of the present invention, wherein the step 1) further comprises a step of removing the reducing agent by acid washing. Preferably, after niobium pentoxide is reduced by a reducing agent, the reduced powder is sieved by a 60-mesh sieve, then hydrochloric acid with the mass ratio of 1:4 is added into the powder for acid washing, after acid washing, the powder is filtered by pure water and then dried, and the powder is sieved by the 60-mesh sieve, so that the raw material niobium pentoxide powder with low valence is obtained.
In one embodiment, the raw material niobium suboxide powder in step 1) is obtained by uniformly mixing niobium pentoxide with a reducing agent (e.g., at least one of calcium, strontium, barium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or an alloy thereof, or a mixture thereof, or a hydride thereof, or a mixture thereof), and reacting in a vacuum or an inert atmosphere (e.g., an argon atmosphere) or/and a hydrogen atmosphere at a temperature of 600 to 1300 ℃ (e.g., 700 to 1000 ℃ or 850 to 950 ℃), wherein the reaction time may be 120 to 900 minutes (e.g., 300 to 600 minutes).
In one embodiment, the raw material niobium suboxide powder of step 1) is obtained by granulating a certain amount of capacitor-grade niobium powder with niobium pentoxide, subjecting the granulated powder to a low-temperature heat treatment (preferably, the temperature of the low-temperature heat treatment is 600 to 1000 ℃, more preferably, the temperature of the low-temperature heat treatment is 800 to 1000 ℃, more preferably, 650 to 980 ℃, 800 to 950 ℃, or 850 to 900 ℃) in a non-oxidizing atmosphere (for example, vacuum, or inert gas (for example, argon) atmosphere, pulverizing and sieving the product of the low-temperature heat treatment, mixing the pulverized and sieved product with a proper amount of capacitor-grade niobium powder, and subjecting the mixture to a high-temperature heat treatment (preferably, the temperature of the high-temperature heat treatment is 1100 to 1600 ℃, more preferably, the temperature of the high-temperature heat treatment is 1200 to 1400 ℃, for example, 1100 to 1350 ℃, or 1250 ℃) in a non-oxidizing atmosphere. The time of the low-temperature heat treatment may be 60 to 150 minutes (e.g., 90 to 120 minutes). The time of the high-temperature heat treatment can be 30-180 minutes.
In the present invention, the pressure of the hydrogen atmosphere is not particularly required, but the pressure should not exceed 0.1MPa from the viewpoint of production safety.
In the present invention, the inert gas atmosphere refers to an inert gas atmosphere, and the inert gas may be argon, helium, or the like.
The production method of any one of the foregoing second aspects of the invention, wherein the heat treatment described in the step 2) is a heat treatment technique well known in the art, in order to change the extremely fine particles present in the powder into 2-order particles having a relatively large particle diameter. In one embodiment, the heat treatment is to heat the product powder of the step 1) to 1100-1500 ℃ in vacuum or inert atmosphere, and keep the temperature for 1-2 hours. The product of step 1) may also be pre-agglomerated prior to heat treatment by methods well known in the art and then heat treated. After heat treatment, cooling the product to room temperature, introducing argon for protection, and discharging the product after passivation. After heat treatment, the low-valence niobium oxide powder with proper apparent density and good fluidity can be obtained.
The niobium suboxide powder provided by the invention can be used for preparing a porous sintered body with stable performance, and the porous sintered body can be used as an anode, so that a highly reliable solid electrolytic capacitor can be manufactured.
Accordingly, a third aspect of the present invention provides a porous sintered body made of the uniform niobium suboxide powder containing oxygen of the first aspect of the present invention.
In one embodiment, the porous sintered body of the third aspect of the present invention may be formed into a porous sintered body by a technique well known in the art. For example, 1 to 5 wt% of a binder is added to the niobium suboxide powder containing uniform oxygen, and the mixture is pressed and molded, and then heated at 1200 to 1550 ℃ for 10 minutes to sinter the mixture into a sintered body.
In a fourth aspect, the present invention provides a capacitor anode made of the porous sintered body according to any one of the above third aspects.
In one embodiment, the capacitor anode of the fourth aspect of the invention may be made as follows: in the niobium suboxide powder of the first aspect of the present invention, which contains uniform oxygen, the lead wire is embedded therein, and then the resulting product is press-molded and sintered to integrate the sintered body with the lead wire. The sintered body is then immersed in an electrolyte solution such as: and (3) anodizing in 0.1 wt% phosphoric acid solution at 85 deg.C and 150mA/g current density for 1-3 hr to 30V to obtain the anode of the solid electrolytic capacitor.
In a fifth aspect, the present invention provides an electrolytic capacitor comprising a capacitor anode according to the fourth aspect of the present invention.
In one embodiment, the electrolytic capacitor according to the fifth aspect of the present invention may be obtained by successively forming a layer of a solid electrolyte (such as manganese oxide, lead oxide or a conductive polymer), a graphite layer, a silver layer, a cathode terminal and then a resin case on the anode according to a method of the art. The electrolytic capacitor has a capacity of about 40000 to 250000 mu FV/g and a leakage current of not more than 1 nA/leakage current (for example, not more than 0.5 nA/mu FV or not more than 0.3 nA/mu FV).
A sixth aspect of the present invention provides an electronic circuit or an electronic instrument comprising the electrolytic capacitor of the fifth aspect of the present invention.
As used herein and as is well known to those skilled in the art, when the particle size of the powder is expressed by a mesh number, "60-80 mesh" means the powder passed through a 60 mesh screen but not an 80 mesh screen, "80-200 mesh", "200-. "particle size of-60 mesh" means that the powder particle size may be-m mesh (m may be an integer of 60 or more), for example, the particle size is-60 mesh, -80 mesh, etc. In the present invention, the term "mesh" has the general meaning known in the art, the physics of which is defined as the particle size or thickness of the material, and the general definition refers to the number of holes in a 1 inch line of a screen.
In the present invention, the standard deviation (and the range deviation) of the oxygen content in the niobium suboxide powder in each particle size range is measured as follows:
the niobium suboxide powder is classified (e.g., sieved) into A according to the size of the powder1、A2、A3…AnN intervals in total, wherein n is an integer more than or equal to 1, and the oxygen element mass percentage content (wt%) of the powder in the n intervals is respectively measured to obtain a1、a2、a3…anN oxygen elements in total, a1、a2、a3…anThe sample standard deviation (and range) of (a) is the sample standard deviation (and range) of the oxygen content in the niobium suboxide powder of each particle size interval of the present invention.
In the invention, the sample standard deviation or the range deviation of the nitrogen content in the niobium suboxide powder in each granularity interval is measured by the following method:
the niobium suboxide powder is classified (e.g., sieved) into B according to the size of the powder1、B2、B3…BnN intervals in total, and respectively measuring the mass parts per million (ppm) of the nitrogen element of the powder in the n intervals to obtain b1、b2、b3…bnN total nitrogen elements in percentage by mass, b1、b2、b3…bnThe sample standard deviation (and range) of (a) is the sample standard deviation (and range) of the nitrogen content in the niobium suboxide powder of each grain size interval of the present invention.
The calculation formula of the standard deviation of the sample is as follows:
wherein
Figure BDA0000644520510000072
(x is a or b).
The calculation formula of the range difference is as follows:
x1、x2、x3…xnminus the minimum value of (a); (x is a or b).
In one embodiment, the oxygen-containing uniform niobium suboxide powder of the first aspect of the present invention is sieved into 5 size intervals, i.e., n-5. Preferably A1Is 60-80 mesh, A2Is 80-200 mesh, A3Is 200-325 mesh interval, A4Is 325-400 mesh interval, A5Is in the range of-400 meshes. Preferably B1In the interval of 60-80 meshes, B2In the interval of 80-200 meshes, B3Is 200-mesh and 325-mesh region, B4Is 325-400 mesh interval, B5Is in the range of-400 meshes.
In the present invention, analysis of oxygen content of niobium suboxide powder was carried out by thermogravimetry commonly used in the field of analysis, analysis of nitrogen content was carried out by LECO CS-436 type oxygen-nitrogen analyzer, and microstructure analysis was carried out by testing using JSM-5600LV type low vacuum scanning electron microscope, apparent density (SBD, g/cm)3) Is obtained by testing according to the method specified in Chinese national standard GB 5060-85.
In the present invention, the electrical properties of niobium suboxide powders were tested as follows: pressing the niobium suboxide powder into the powder with the density Dg of 2.8g/cm3The green compact of (1) was vacuum-sintered at 1350 to 1460 ℃ for 10 minutes (the specific sintering temperatures used in the electrical property test of the niobium suboxide powders of examples 1 to 6 and comparative examples 1 to 3 are shown in tables 1 and 2), to obtain a sintered body. The sintered body was immersed in a 0.1 wt% phosphoric acid aqueous solution at 85 ℃ and anodized at 30V, and then measured for specific Capacitance (CV) in an 18 wt% sulfuric acid aqueous solution at 25 ℃. The leakage current (DCL) test was carried out at 21V in a 0.3 wt% phosphoric acid aqueous solution at 25 ℃ and the specific test results are shown in tables 1 and 2.
The invention has the advantages of
The niobium suboxide powder of the first aspect of the present invention contains oxygen uniformly, and has a uniform oxygen content in each particle size region. The niobium suboxide powder of the first aspect of the present invention has improved physical properties and electrical properties as described in the following items (1) to (4):
(1) lower leakage current (DCL);
(2) lower Equivalent Series Resistance (ESR);
(3) a higher specific capacitance;
(4) the powder has uniform particle size distribution and no over-sintering phenomena such as agglomeration and the like.
The inventors have found that the uniformity of the oxygen content among the niobium suboxide particles also greatly affects the uniformity of the nitrogen content of the niobium suboxide powder after nitrogen doping. The niobium suboxide has good uniformity of oxygen content in each granularity, and the niobium suboxide powder has relatively uniform nitrogen content in each granularity interval after nitrogen doping, and also has improved physical properties and electrical properties in the items (1) to (4).
The inventors have also found that when the oxygen content is extremely different between the respective particle sizes by more than 0.5 wt%, particularly by more than 1 wt%, the powder having a low oxygen content is not resistant to firing because of its niobium powder characteristic, and thus excessive sintering is likely to occur during sintering, which increases the leak current, increases the ESR, and deteriorates the stability of the dielectric film. Nb or NbO is readily present when the oxygen content is less than 14.6 wt% or greater than 15.4 wt%2In addition, the properties of the niobium monoxide powder are also easily deteriorated.
In one embodiment, the niobium suboxide powder containing uniform oxygen provided by the invention contains uniform oxygen, the extreme difference of the oxygen content is below 0.5 wt%, the standard deviation of a sample is below 0.5 wt%, the oxygen content is between 14.6 wt% and 15.4 wt%, the oxygen content is moderate, the composition of the niobium suboxide powder is closer to NbO, and the niobium suboxide powder can reflect the characteristics of niobium monoxide. The bulk density of the niobium suboxide powder provided by the invention is preferably 0.7-1.3 g/cm3In the meantime.
The low-valence niobium oxide powder containing uniform oxygen has greatly improved electrical performance indexes such as leakage current, ESR and the like, and is beneficial to molding and sintering during anode manufacturing.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
FIG. 1 is a scanning electron micrograph (2500 Xmagnification) of a uniform niobium suboxide powder containing oxygen of example 1.
FIG. 2 is a scanning electron micrograph (2500 Xmagnification) of a niobium suboxide powder of comparative example 1.
FIG. 3 is a graph showing the relationship between the standard deviation of the oxygen content in each particle size region of the niobium suboxide powders of examples 1 to 6 and comparative examples 1 to 3 and the leakage current of the niobium suboxide powder.
Detailed Description
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Example 1
According to the content disclosed in example 5 of Chinese patent CN101139110A, niobium pentoxide and yttrium hydride powder which pass through 60 meshes are uniformly mixed according to the weight ratio of 1:1.05, and then the mixture is subjected to heat treatment under argon, the temperature is raised to 900 ℃, the temperature is kept for 8 hours, and the mixture is cooled and discharged from a furnace. And (3) after the powder is discharged out of the furnace, sieving the powder with a 60-mesh sieve, adding 10 wt% of hydrochloric acid according to the mass ratio of 1:4 for acid washing, filtering the acid washed powder with pure water, drying the filtered powder, and sieving the dried powder with the 60-mesh sieve to obtain the raw material niobium suboxide powder.
And (3) oxygen homogenization treatment: loading the raw material niobium suboxide powder into a reaction bomb, filling hydrogen to positive pressure, heating to 900 ℃, preserving heat for 4 hours, evacuating, discharging hydrogen, filling argon for protection, cutting off power, cooling to room temperature, passivating, and discharging.
Vacuum heat treatment: pre-agglomerating the discharged materials, then loading the materials into a vacuum furnace, firstly vacuumizing to the vacuum degree required by the vacuum furnace, then heating to 1400 ℃, and preserving the heat for 60 minutes. Then cooling to room temperature, filling argon, discharging after passivation, and sieving with a 60-mesh sieve after discharging. The oxygen-containing uniform niobium suboxide powder of example 1 was obtained.
Fig. 1 shows a scanning electron micrograph (2500 x) of the oxygen-containing uniform niobium suboxide powder of example 1.
Comparative example 1
The niobium suboxide powder of comparative example 1 was obtained by directly subjecting the niobium suboxide powder of example 1 as a raw material to the same vacuum heat treatment step as in example 1 without subjecting the powder to an oxygen homogenization treatment.
FIG. 2 shows a scanning electron micrograph (2500 Xmagnification) of a niobium suboxide powder in comparative example 1.
As is apparent from a comparison of FIGS. 1 and 2, the oxygen content distribution of the niobium suboxide powder of the present invention (FIG. 1) is uniform, the over-sintering phenomenon is improved, and the particle size distribution is relatively uniform.
Example 2
According to the content disclosed in the Chinese patent CN101139110A, niobium pentoxide and lanthanum hydride powder which pass through 60 meshes are uniformly mixed according to the weight ratio of 1:1.15, the mixture is heated to 900 ℃ in a hydrogen atmosphere, the temperature is kept for 8 hours, and the mixture is cooled and discharged from a furnace. And (3) after the powder is discharged out of the furnace, sieving the powder with a 60-mesh sieve, adding 10% hydrochloric acid according to the mass ratio of 1:4 for acid washing, filtering the acid washed powder with pure water, drying the filtered powder, and sieving the dried powder with the 60-mesh sieve to obtain the raw material niobium suboxide powder.
And (3) oxygen homogenization treatment: loading the raw material niobium suboxide powder into a reaction bomb, filling hydrogen to positive pressure, heating to 750 ℃, preserving heat for 6 hours, evacuating and discharging hydrogen, filling argon for protection, then cutting off power and cooling to room temperature, and discharging after passivation.
The vacuum heat treatment step was the same as in example 1, and the oxygen-containing uniform niobium suboxide powder of example 2 was obtained.
Example 3
According to the content disclosed in the Chinese patent CN101139110A, niobium pentoxide and lanthanum hydride powder which pass through 60 meshes are uniformly mixed according to the weight ratio of 1:1.2, the temperature is raised to 880 ℃, the temperature is kept for 8 hours, and the mixture is cooled and discharged from the furnace. And (3) after the powder is discharged out of the furnace, sieving the powder with a 60-mesh sieve, adding 10% hydrochloric acid according to the mass ratio of 1:4 for acid washing, filtering the powder with pure water after the acid washing, drying the powder, and sieving the powder with the 60-mesh sieve to obtain the raw material niobium suboxide powder.
And (3) oxygen homogenization treatment: loading the raw material niobium suboxide powder into a reaction bomb, filling hydrogen to positive pressure, heating to 800 ℃, preserving heat for 5 hours, evacuating, discharging hydrogen, filling argon for protection, cooling to room temperature, passivating, and discharging.
Vacuum heat treatment: pre-agglomerating the discharged material, loading the material into a vacuum furnace, vacuumizing to the vacuum degree required by the vacuum furnace, heating to 1380 ℃, and preserving the heat for 90 minutes. Then, the mixture was cooled to room temperature, and then argon gas was introduced, and after passivation, the mixture was discharged, and after discharge, the mixture was sieved through a 60-mesh sieve, thereby obtaining the uniform oxygen-containing niobium suboxide powder of example 3.
Example 4
Example 4 all the raw materials and procedures were the same as in example 3 except that the discharged material after the oxygen homogenization treatment was directly charged into a vacuum furnace without pre-agglomeration and subjected to a vacuum heat treatment procedure to obtain the niobium suboxide powder of example 4 which contained uniform oxygen.
Example 5
The method of example 1 in Chinese patent CN1587066A is followed. Specifically, 400g of niobium pentoxide and 200g of capacitor-grade niobium powder are uniformly mixed, granulated, vacuumized to the vacuum degree required by a vacuum furnace in a vacuum heat treatment furnace, heated to 920 ℃, kept for 120 minutes, cooled to room temperature, filled with argon, passivated and discharged from the furnace. And (3) after the niobium powder is discharged out of the furnace and sieved by a 60-mesh sieve, adding 200g of capacitor-grade niobium powder, uniformly mixing, putting into a vacuum furnace, heating to 1300 ℃, preserving the temperature for 60 minutes, cooling to room temperature, then filling argon, discharging after passivation, and after discharge, sieving by a 60-mesh sieve to obtain the raw material niobium suboxide powder.
And (3) oxygen homogenization treatment: loading the raw material niobium suboxide powder into a reaction bomb, filling hydrogen to positive pressure, heating to 850 ℃, keeping the temperature for 4 hours, pumping to discharge hydrogen, filling argon for protection, cutting off power, cooling to room temperature, discharging after passivation, and sieving with a 60-mesh sieve after discharging.
Vacuum heat treatment: and (3) loading the material subjected to the oxygen homogenization treatment into a vacuum furnace, vacuumizing to the vacuum degree required by the vacuum furnace, heating to 1400 ℃, and preserving the heat for 60 minutes. Then cooling to room temperature, filling argon, discharging after passivation, and sieving with a 60-mesh sieve after discharging. The oxygen-containing uniform niobium suboxide powder of example 5 was obtained.
Comparative example 2
The niobium suboxide powder of example 5 was used as the niobium suboxide powder of comparative example 2, and the oxygen content measurement and the electrical property test were conducted as they are.
Example 6
According to the content disclosed in Chinese patent CN101139110A, niobium pentoxide and lanthanum hydride powder which pass through 60 meshes are uniformly mixed according to the weight ratio of 1:1.2, the temperature is raised to 920 ℃, the temperature is kept for 8 hours, and the mixture is cooled and discharged from the furnace. And (3) after the powder is discharged out of the furnace, sieving the powder with a 60-mesh sieve, adding 10% hydrochloric acid according to the mass ratio of 1:4 for acid washing, filtering the acid washed powder with pure water, and drying to obtain the raw material niobium suboxide powder.
Oxygen homogenization treatment and nitrogen doping treatment: loading the raw material niobium suboxide powder into a reaction bomb, filling hydrogen to positive pressure, raising the temperature to 980 ℃, preserving the heat for 4 hours, then reducing the temperature to 600 ℃, evacuating and replacing, filling nitrogen, preserving the heat for 120 minutes, cutting off the power and cooling to room temperature, and discharging the material after passivation.
Vacuum heat treatment: pre-agglomerating the discharged materials, then loading the materials into a vacuum furnace, firstly vacuumizing to the vacuum degree required by the vacuum furnace, then heating to 1350 ℃, and preserving the heat for 100 minutes. Then, the mixture was cooled to room temperature, argon gas was introduced, the mixture was discharged after passivation, and the discharge was sieved through a 60-mesh sieve, thereby obtaining the uniform oxygen-containing niobium suboxide powder of example 6.
Comparative example 3
The raw material niobium suboxide powder of example 6 was taken, and subjected to nitrogen doping treatment without oxygen homogenization treatment: charging the raw material niobium suboxide powder into a reaction bomb, charging nitrogen to positive pressure, heating to 600 ℃, keeping the temperature for 120 minutes, cutting off power, cooling to room temperature, and discharging after passivation. Then, vacuum heat treatment was performed in the same manner as in example 6 to obtain a niobium suboxide powder of comparative example 3.
The oxygen content values in each particle size region of the niobium suboxide powders of examples 1 to 6 and comparative examples 1 to 3 were measured. Specifically, the niobium suboxide powders prepared in examples 1 to 6 and comparative examples 1 to 3 were respectively sieved into 60 to 80 mesh, 80 to 200 mesh, 200-. In addition, the niobium suboxide powder was sintered to form a sintered body, and electrical property data including leakage current (DCL) and specific Capacitance (CV) were measured. Specific oxygen content value data, electrical property data and sintering temperatures are shown in table 1.
The nitrogen content values of the niobium suboxide powders of example 6 and comparative example 3 in each grain size interval were measured at the same time, specifically, the niobium suboxide powders were respectively sieved into 60-80 mesh, 80-200 mesh, 200-. In addition, the niobium suboxide powders of example 6 and comparative example 3 were sintered into sintered bodies, and their electrical property data, including leakage current (DCL) and specific Capacitance (CV), were tested. Specific nitrogen content value data, electrical property data and sintering temperature are shown in table 2.
Based on the data in tables 1 and 2, the relationship between the standard deviation of the oxygen content sample and the leakage current of the niobium suboxide powder in each particle size interval of examples 1 to 6 and comparative examples 1 to 3 of the present invention is plotted, as shown in fig. 3. As can be seen from fig. 3, the leakage current value is significantly in positive correlation with the sample standard deviation, that is, the smaller the sample standard deviation of the oxygen content in each particle size region of the niobium suboxide powder is, the lower the leakage current value is. It is well known in the art that the smaller the sample standard deviation, the better the data uniformity. Therefore, the present invention has succeeded in obtaining niobium suboxide powder having a uniform oxygen content, which has improved leakage current, after subjecting the raw material niobium suboxide to oxygen homogenization heat treatment.
Meanwhile, the niobium suboxide powder containing uniform oxygen not only obviously reduces the leakage current, but also improves the microstructure. As can be seen from the comparison of FIGS. 1 and 2, the niobium suboxide powder of the present invention containing uniform oxygen has a very uniform particle size distribution and an improved over-sintering phenomenon.
As shown in table 2, the standard deviation of the nitrogen content in each grain size interval is lower after the niobium suboxide powder of the present invention is doped with nitrogen, which indicates that the nitrogen content in each grain interval is also very uniform after the niobium suboxide powder of the present invention is doped with nitrogen, and the nitrogen-doped niobium suboxide powder containing uniform oxygen also has lower leakage current.
In conclusion, the present invention provides a niobium suboxide powder that contains oxygen uniformly. It has one or more of the following advantages: (1) lower leakage current (DCL); (2) lower Equivalent Series Resistance (ESR); (3) a higher specific capacitance; (4) the powder has uniform particle size distribution and improved over-sintering phenomenon.
Figure BDA0000644520510000141
Figure BDA0000644520510000151
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.

Claims (68)

1. Sieving the niobium suboxide powder with uniform oxygen content into 5 granularity intervals, wherein each granularity interval is respectively 60-80 meshes, 80-200 meshes, 200-325 meshes, 325-400 meshes and-400 meshes, the sample standard deviation of the oxygen content in the niobium suboxide powder in each granularity interval is less than or equal to 0.5 wt%, and the sample standard deviation of the nitrogen content in the niobium suboxide powder in each granularity interval is less than or equal to 250 ppm;
the preparation method of the niobium suboxide powder comprises the following steps:
1) uniformly mixing the raw material niobium suboxide powder, heating to 700-1000 ℃ in a hydrogen atmosphere, preserving heat for 3-8 hours, then reducing the temperature to 500-700 ℃, replacing the hydrogen atmosphere with a nitrogen atmosphere, preserving heat for 100-140 minutes, discharging the mixture after cooling and passivation,
2) heat treating the product of step 1);
the raw material niobium suboxide powder in the step 1) is niobium suboxide powder obtained by reducing niobium pentoxide with a reducing agent, or niobium suboxide powder obtained by disproportionating niobium and niobium pentoxide;
wherein, in the step 2), the heat treatment is to heat to 1100-1500 ℃ in vacuum or inert atmosphere, and the temperature is kept for 1-2 hours.
2. The niobium suboxide powder of claim 1, wherein the standard deviation of the oxygen content of the niobium suboxide powder for each size interval is 0.4 wt% or less.
3. The niobium suboxide powder of claim 1, wherein the standard deviation of the oxygen content of the niobium suboxide powder for each size interval is 0.3 wt% or less.
4. The niobium suboxide powder of claim 1, wherein the standard deviation of the oxygen content of the niobium suboxide powder for each size interval is 0.2 wt% or less.
5. The niobium suboxide powder of claim 1, wherein the standard deviation of the oxygen content of the niobium suboxide powder for each size interval is 0.15 wt% or less.
6. The niobium suboxide powder of claim 1, wherein the niobium suboxide powder has a range of 1.6 wt.% or less oxygen content for each size range.
7. The niobium suboxide powder of claim 1, wherein the niobium suboxide powder has a range of 1.2 wt.% or less oxygen content for each size range.
8. The niobium suboxide powder of claim 1, wherein the niobium suboxide powder has an oxygen content within each size range of 1 wt% or less.
9. The niobium suboxide powder of claim 1, wherein the niobium suboxide powder has a range of oxygen content within each size range of 0.8 wt% or less.
10. The niobium suboxide powder of claim 1, wherein the niobium suboxide powder has a range of oxygen content within each size range of 0.5 wt% or less.
11. The niobium suboxide powder of claim 1, wherein the niobium suboxide powder has an oxygen content of from 13 to 16% by weight for each size interval.
12. The niobium suboxide powder of claim 1, wherein the niobium suboxide powder has an oxygen content of from about 14.6 to about 15.4 weight percent for each size interval.
13. The niobium suboxide powder of claim 1, wherein the niobium suboxide powder has an oxygen content of from 14 to 15 wt% in each size range.
14. The oxygen-containing homogeneous niobium suboxide powder of claim 1, said niobium suboxide powder having the formula consisting of NbOxWherein x is 0.99 to 1.06.
15. The oxygen-containing homogeneous niobium suboxide powder of claim 14, said niobium suboxide powder having the formula consisting of NbOxWherein x is 0.99.
16. The oxygen-containing homogeneous niobium suboxide powder of claim 14, said niobium suboxide powder having the formula consisting of NbOxWherein x is 1.06.
17. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content within each size interval of 230ppm or less.
18. The niobium suboxide powder of claim 15, having a uniform oxygen content, wherein the sample standard deviation of the nitrogen content of the niobium suboxide powder for each size interval is 200ppm or less.
19. The niobium suboxide powder of claim 15, having a uniform oxygen content, wherein the standard deviation of the nitrogen content of the niobium suboxide powder for each size interval is less than or equal to 180 ppm.
20. The niobium suboxide powder of claim 15, having a uniform oxygen content, wherein the sample standard deviation of the nitrogen content of the niobium suboxide powder for each size interval is 150ppm or less.
21. The niobium suboxide powder of claim 15, having a uniform oxygen content, wherein the sample standard deviation of the nitrogen content of the niobium suboxide powder for each size interval is 120ppm or less.
22. The niobium suboxide powder of claim 15, having a uniform oxygen content, wherein the standard deviation of the nitrogen content of the niobium suboxide powder for each size interval is 100ppm or less.
23. The niobium suboxide powder of claim 15, having a uniform oxygen content, wherein the sample standard deviation of the nitrogen content of the niobium suboxide powder for each size interval is 80ppm or less.
24. The niobium suboxide powder of claim 15, having a uniform oxygen content, wherein the sample standard deviation of the nitrogen content of the niobium suboxide powder for each size interval is 70ppm or less.
25. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content of 50 to 10000ppm for each size range.
26. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content of 1000 to 5000ppm in each size range.
27. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content of 2000 to 4000ppm for each size range.
28. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content of 2800 to 3200ppm in each size range.
29. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content within each size range of no greater than 700 ppm.
30. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content within each size range of 600ppm or less.
31. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content within each size range of no more than 500 ppm.
32. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content within each size range of no more than 400 ppm.
33. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content within each size range of no greater than 300 ppm.
34. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content within each size range of 200ppm or less.
35. The niobium suboxide powder of claim 15, wherein the niobium suboxide powder has a nitrogen content within each size range of 180ppm or less.
36. The oxygen-containing uniform niobium suboxide powder as claimed in any one of claims 1 to 35, which has a leakage current of 2nA/μ FV or less.
37. The oxygen-containing uniform niobium suboxide powder as claimed in any one of claims 1 to 35, which has a leakage current of 1nA/μ FV or less.
38. The oxygen-containing uniform niobium suboxide powder as claimed in any one of claims 1 to 35, which has a leakage current of 0.5nA/μ FV or less.
39. The oxygen-containing uniform niobium suboxide powder as claimed in any one of claims 1 to 35, which has a leakage current of 0.3nA/μ FV or less.
40. The oxygen-containing uniform niobium suboxide powder of any one of claims 1 to 35, having a particle size of ≦ -60 mesh.
41. The oxygen-containing uniform niobium suboxide powder as claimed in any one of claims 1 to 35, which has a specific capacitance of 40000 to 250000 μ FV/g.
42. The oxygen-containing uniform niobium suboxide powder as claimed in any one of claims 1 to 35, wherein the bulk density is 0.7 to 0.95g/cm3。
43. The oxygen-containing uniform niobium suboxide powder as claimed in any one of claims 1 to 35, wherein the bulk density is 0.5 to 1.5g/cm3。
44. The oxygen-containing uniform niobium suboxide powder as claimed in any one of claims 1 to 35, wherein the bulk density is 0.7 to 1.3g/cm3。
45. A method of making the oxygen containing uniform niobium suboxide powder of any one of claims 1 to 44, comprising:
1) uniformly mixing the raw material niobium suboxide powder, heating to 700-1000 ℃ in a hydrogen atmosphere, preserving heat for 3-8 hours, then reducing the temperature to 500-700 ℃, replacing the hydrogen atmosphere with a nitrogen atmosphere, preserving heat for 100-140 minutes, discharging the mixture after cooling and passivation,
2) heat treating the product of step 1) to obtain the uniform oxygen-containing niobium suboxide powder of any one of claims 1 to 44;
the raw material niobium suboxide powder in the step 1) is niobium suboxide powder obtained by reducing niobium pentoxide with a reducing agent, or niobium suboxide powder obtained by disproportionating niobium and niobium pentoxide;
wherein in the step 2), the heat treatment is to heat to 1100-1500 ℃ in vacuum or inert atmosphere, and the temperature is kept for 1-2 hours.
46. The production method according to claim 45, wherein in step 1), the raw material niobium suboxide powder is uniformly mixed and then heated to 750 to 950 ℃ in a hydrogen atmosphere.
47. The production method according to claim 45, wherein in step 1), the raw material niobium suboxide powder is uniformly mixed and then heated to 750 to 900 ℃ in a hydrogen atmosphere.
48. The production method of claim 45, wherein in step 1), the raw material niobium suboxide powder is uniformly mixed and heated to 700 to 1000 ℃ in a hydrogen atmosphere, and the temperature is maintained for 3 to 6 hours.
49. The method of claim 45, wherein step 1) is followed by reducing the temperature to 550-650 ℃.
50. The method of claim 45, wherein step 1) is followed by reducing the temperature to 600 ℃.
51. The method for preparing a uniform niobium suboxide powder containing oxygen as claimed in claim 45, wherein in step 1), the atmosphere of hydrogen is replaced by a nitrogen atmosphere, the temperature is maintained for 120 minutes, and the niobium suboxide powder is discharged after cooling and passivation.
52. The preparation method of claim 45, wherein said raw material niobium suboxide powder of step 1) is obtained by granulating niobium pentoxide with a predetermined amount of capacitor-grade niobium powder, subjecting to low-temperature heat treatment in a non-oxidizing atmosphere, pulverizing and sieving the product of the low-temperature heat treatment, mixing with a predetermined amount of capacitor-grade niobium powder, and subjecting to high-temperature heat treatment in a non-oxidizing atmosphere.
53. The preparation method of claim 52, wherein the reducing agent is at least one of calcium, strontium, barium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, or an alloy thereof, or a mixture thereof, or a hydride thereof, or a mixture thereof.
54. The method of claim 52, wherein the non-oxidizing atmosphere is vacuum, an inert gas atmosphere, or a hydrogen gas atmosphere.
55. The method of claim 52, wherein the low-temperature heat treatment is performed at a temperature of 600 to 1000 ℃.
56. The method of claim 52, wherein the low-temperature heat treatment is carried out at a temperature of 800 to 1000 ℃.
57. The method according to claim 52, wherein the high-temperature heat treatment is carried out at a temperature of 1100 to 1600 ℃.
58. The method of claim 52, wherein the high temperature heat treatment is carried out at a temperature of 1200 to 1400 ℃.
59. The method of claim 45, wherein step 2) is followed by a heat treatment after pre-agglomerating the product of step 1) prior to the heat treatment using methods well known in the art.
60. The method of claim 45, wherein in step 2), after the heat treatment, the product is cooled to room temperature, argon is introduced for passivation, and then the product is discharged.
61. A porous sintered body comprising the uniform niobium suboxide powder containing oxygen according to any one of claims 1 to 44.
62. A capacitor anode comprising the porous sintered body according to claim 61.
63. An electrolytic capacitor comprising the capacitor anode of claim 62.
64. The electrolytic capacitor of claim 63, having a capacity of 40000 to 250000 μ FV/g.
65. The electrolytic capacitor of claim 63 having a leakage current of ≤ 1nA/μ FV.
66. The electrolytic capacitor of claim 63, having a leakage current of 0.5nA/μ FV or less.
67. The electrolytic capacitor of claim 63, having a leakage current of ≤ 0.3nA/μ FV.
68. An electronic circuit or an electronic instrument comprising the electrolytic capacitor as claimed in any one of claims 63 to 67.
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