CN119894624A - Method for producing tantalum powder for capacitor by reducing tantalum oxide with alkaline earth metal - Google Patents
Method for producing tantalum powder for capacitor by reducing tantalum oxide with alkaline earth metal Download PDFInfo
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Abstract
本发明涉及一种碱土金属还原氧化钽生产电容器用钽粉的方法。具体涉及一种采用碱土金属例如镁(优选镁颗粒)还原氧化钽制备钽粉的方法，其特征是该方法包括在含氢气氛中进行的还原、保温过程，优选地，所述的含氢气氛是纯氢或者是氢与惰性气体的混合气体；和/或所述含氢气体通过通入气态含氢气体得到的，或通过加入含氢物质并使其释放氢气得到。
The present invention relates to a method for producing tantalum powder for capacitors by reducing tantalum oxide with alkaline earth metals. Specifically, it relates to a method for preparing tantalum powder by reducing tantalum oxide with alkaline earth metals such as magnesium (preferably magnesium particles), characterized in that the method includes a reduction and heat preservation process in a hydrogen-containing atmosphere, preferably, the hydrogen-containing atmosphere is pure hydrogen or a mixed gas of hydrogen and an inert gas; and/or the hydrogen-containing gas is obtained by introducing a gaseous hydrogen-containing gas, or by adding a hydrogen-containing substance and causing it to release hydrogen.
Description
Technical Field
The invention belongs to the field of rare metal functional material smelting, and particularly relates to tantalum powder for manufacturing a high-voltage high-reliability capacitor and a manufacturing method thereof.
Background
The tantalum electrolytic capacitor (hereinafter referred to as tantalum capacitor) has the advantages of high capacity, small volume, strong self-healing capability, high reliability and the like, and is widely applied to the high-end technical fields of communication, computers, automobile electronics, medical appliances, radars, aerospace, automatic control devices and the like. Tantalum powder is a key material for manufacturing tantalum capacitors, and only tantalum powder with higher voltage resistance can be used for manufacturing tantalum capacitors with better reliability. Therefore, only the tantalum powder for the capacitor with higher voltage resistance is continuously broken, and the produced tantalum capacitor can continuously meet the requirements of high-reliability development of electronic devices and electronic circuits.
The current industrialized preparation method of the capacitor-grade tantalum powder mainly comprises a sodium reduction potassium fluotantalate method, a magnesium reduction tantalum oxide method, a tantalum ingot hydrogenation method and the like. The sodium-reduced potassium fluorotantalate method is easy to prepare high specific volume tantalum powder, but has the problem that the pressure resistance of tantalum powder is generally low. The tantalum powder prepared by the tantalum ingot hydrogenation method has excellent pressure resistance, but has the problem that the specific volume of the tantalum powder is generally low. In order to continuously improve the pressure resistance of tantalum powder and simultaneously improve the specific volume of tantalum powder, the magnesium reduction tantalum oxide method is successfully developed and continuously developed, and the magnesium reduction tantalum oxide method has obvious advantages when preparing tantalum powder for a capacitor, wherein the specific volume and the pressure resistance of the tantalum powder are simultaneously improved due to the change of the state of reactants.
CN114192791B discloses a method for producing tantalum powder for capacitors by reducing tantalum oxide with alkaline earth metal. The method is to add alkali metal or alkali earth metal halide in the reduction process, reduce the alkali earth metal in a heating furnace filled with inert gas at a high temperature of more than 700 ℃, separate the excessive alkali earth metal from tantalum-containing materials after the reduction is finished, and sinter the materials at a high temperature of more than 750 ℃, but the method has the problems that a large amount of alkali earth metal is used, fire possibly occurs when the materials are discharged from the heating furnace after the reduction, and potential safety hazards exist. Moreover, the process is complex, requires a separate sintering step and has high energy consumption
CN1308566a (application No. 99808374.7), CN105033283a (application No. 201510310262.2) and CN1251325A also disclose methods for producing tantalum powder by reducing tantalum oxide with alkaline earth metal (including magnesium vapor) or rare earth metal, but the tantalum powder produced by the methods has large specific surface, strong activity and poor burning resistance, and the produced tantalum powder for the capacitor has poor specific volume no matter breakdown voltage or high-voltage energized tantalum powder, and does not obviously improve the voltage resistance of the tantalum powder for the capacitor.
There are also methods in the prior art for preparing tantalum powder by self-propagating high temperature synthesis (SHS). However, this process needs to be carried out at temperatures above at least 2000 ℃, and the reaction is too fast, not only difficult to control, but also too demanding for process equipment. In addition, the tantalum powder obtained is also non-uniform and cannot meet the requirements for manufacturing highly reliable capacitors.
Without being bound to a general theory, the inventor finds that the existing tantalum powder preparation process uses a large amount of alkaline earth metal, so that the potential safety hazard of ignition of the alkaline earth metal exists, the process is complex, and the energy consumption is high. Moreover, the overall electrical performance is not ideal.
Disclosure of Invention
It is an object of the present invention to provide a method for producing tantalum powder by reducing tantalum oxide with an alkaline earth metal such as magnesium in a hydrogen-containing atmosphere, by which the amount of alkaline earth metal added can be reduced and the safety risk of ignition of alkaline earth metal at the tapping after the completion of reduction can be reduced.
Another object of the present invention is to provide a method for producing tantalum powder for capacitors that is simple in process, easier to operate and control and safer in process. Accordingly, the present invention provides a method for preparing tantalum powder by reducing tantalum oxide with an alkaline earth metal such as magnesium, comprising the steps of:
(1) Mixing tantalum oxide with excessive alkaline earth metal reducing agent, mixing at least one alkali metal and/or alkaline earth metal halide with the weight of tantalum oxide being 10-200%, loading into a closed reaction container, extracting air from the container, and placing the container into a heating furnace;
(2) Raising the temperature of the heating furnace to 700-1000 ℃, and preserving heat for 1-3 hours, for example, so that the tantalum oxide and the reducing agent fully undergo a reduction reaction;
(3) After the heat preservation is finished, the temperature of the heating furnace is set at 600-750 ℃ (preferably 620-680 ℃, such as 640 ℃), the inside of the heating furnace is evacuated, for example, to be less than 10Pa, and the heating furnace is kept at a negative pressure (for example, kept for 1-10 hours);
(4) Then, filling inert gas into a reaction container, keeping the reaction container at positive pressure, cooling to room temperature and performing passivation treatment to obtain a mixed material containing halide and tantalum powder;
(5) Tantalum powder is separated from the resulting mixture, for example by washing with water, pickling, filtering, drying,
Wherein in step (1) after the air is withdrawn, the vessel is provided with a hydrogen-containing gas, for example by passing through the hydrogen-containing gas, or by adding a liquid or solid (preferably solid) hydrogen-containing substance and letting it release hydrogen. Preferably, in the latter case, the hydrogen-containing species is separated from other raw materials such as tantalum oxide powder, alkali metal and/or alkaline earth metal halides, which may be accomplished, for example, by placing the hydrogen-containing species (preferably hydrogen-containing tantalum powder) separately in a crucible.
Preferably, the hydrogen-containing substance is, for example, a substance that can release hydrogen at high temperature, such as tantalum powder (also referred to as hydrogen-containing tantalum powder) adsorbed with hydrogen, niobium-containing powder, titanium-containing powder, and a hydrogen-containing compound.
The alkaline earth metal reducing agent in the step (1) is preferably magnesium, more preferably magnesium particles of 3N5 or more (purity 99.95% or more), and the higher the purity of the magnesium particles, the better. The particle size of the magnesium particles is not limited. However, the applicant has found through extensive research that magnesium particles having a particle size of 150-4000 μm are more suitable for the present technique, and tantalum powder obtained by reduction has better pressure resistance. The magnesium particles with the particle size range are beneficial to the safety of the magnesium metal in the storage and transportation process and are beneficial to uniform mixing. If the magnesium particles are too fine, the activity is too strong, the spontaneous combustion and ignition are easy, and if the magnesium particles are too coarse, the uniform mixing is not facilitated, and the performance optimization of tantalum powder is not facilitated. The addition amount of the excessive reducing agent means an amount exceeding the theoretical amount for completely reducing tantalum oxide. In general, the theoretical amount of fully reduced tantalum oxide is 0.273 kg. In the present invention, the amount is preferably 5 to 50%, preferably 10 to 48%, more preferably 10 to 45%, still more preferably 10 to 15% or 5 to 10% or 15 to 20% exceeding the theoretical amount.
In step (2), due to the occurrence of reduction heat, sintering of tantalum powder inevitably occurs to some extent. The presence of hydrogen-containing gas in the container further enhances the sintering phenomenon of the tantalum powder, so that a separate subsequent sintering step can be omitted. The present invention undoubtedly simplifies the process, since the prior art often has a separate sintering step. In addition, sintering and reduction under the conditions are carried out simultaneously, and tantalum powder with improved microstructure is more easily obtained by compounding together.
The alkali metal and/or alkaline earth metal halide(s) described in step (1) are preferably added in an amount of 10 to 180%, preferably 25 to 120%, more preferably 70 to 120% or 100 to 180%, most preferably 15 to 80%, for example 25 to 80% by weight of tantalum oxide. The alkali metal or alkaline earth halide is preferably analytically pure, preferably of higher purity. The alkali metal or alkaline earth halide is preferably in particulate form. The particle size is not limited, but the applicant found that 70-4000 μm particles are more suitable for the technology, and the tantalum powder obtained by reduction has better pressure resistance.
Preferably, the alkali or alkaline earth metal halide of step (1) is one or more of NaCl, KCl, KF, KI, and/or MgCl 2. The alkali metal halide may be sodium chloride and/or potassium chloride. Preferably a mixture of sodium chloride and potassium chloride, more preferably the mass ratio of sodium chloride to potassium chloride in the mixture is from 1:1 to 10, most preferably about 1:1.
Preferably, one or more compounds containing B, P and/or N element may be further added as an additive in step (1) to dope the tantalum powder. The amount of the element B added is preferably 1 to 100ppm, more preferably 20 to 60ppm, the amount of the element P added is preferably 10 to 200ppm, more preferably 30 to 90ppm, and the amount of the element N added is preferably 300 to 2500ppm, more preferably 500 to 1200ppm, based on the amount of the effective element. It should be understood that although compounds are added here, the effective elements are B, P, and/or N, so the amounts mentioned here are calculated as amounts of B, P, and/or N.
Preferably, in the step (2), the temperature of the heating furnace is raised to 750-1000 ℃. More preferably, the temperature of the heating furnace is raised to 900-965 ℃.
Unlike inert atmosphere commonly used in the prior art, the hydrogen-containing gas used in the step (1) is pure hydrogen or a mixed gas of hydrogen and inert gas, and the hydrogen can be gaseous hydrogen or hydrogen released by heating other liquid or solid hydrogen-containing substances. Importantly, in the present invention, a hydrogen-containing gas is used as the atmosphere.
Although hydrogen is a common reducing agent, hydrogen is not capable of reducing tantalum oxide. That is, hydrogen gas cannot function as a reducing agent in the present invention. However, the inventors have unexpectedly found that since hydrogen enhances sintering that accompanies the reduction process, the process can be significantly simplified by omitting the sintering step. Furthermore, the introduction of a hydrogen-containing gas in an inert atmosphere can reduce the addition amount of alkaline earth metal as a reducing agent and can also improve the overall electrical properties of the product.
Preferably, in step (1), a positive pressure is maintained in the reaction vessel. In the reaction vessel, the partial pressure of hydrogen exceeds 0.050KPa, preferably 0.1 to 200KPa, more preferably 0.3 to 50KPa, more preferably 10 to 20KPa, even more preferably 0.5 to 10KPa or 10 to 15KPa, even more preferably 0.1 to 0.3KPa. The inventors have found that too low a hydrogen partial pressure does not sufficiently promote the reduction effect, so that it is preferable not to excessively low a hydrogen partial pressure from the viewpoint of not, and conversely, too high a hydrogen partial pressure reduces the improvement of the reduction effect, and from the viewpoint of ensuring absolute safety with hydrogen, it is preferable to avoid too high a hydrogen partial pressure.
Inert gases generally refer to noble gases such as helium, neon, and argon. Although nitrogen is sometimes used as an inert gas because of its stable properties, nitrogen is generally considered to be unsuitable as an inert shielding gas in the art because of its relatively high reduction temperature, and its high activity at such high temperatures. However, the inventors have found through extensive studies that nitrogen doping of tantalum powder can be achieved by the inclusion of a small amount of nitrogen in the above inert gas without impairing the inert protective atmosphere. In the case where a mixture of a hydrogen-containing gas (e.g., pure hydrogen) and an inert gas is used in the step (1), nitrogen may be preferably contained in an amount of 0.5 to 10% based on the total amount of the hydrogen-containing gas and the inert gas, from the viewpoint of achieving a better nitrogen-doping effect of the tantalum powder.
In step (3), since the melting point of magnesium metal is relatively high, magnesium vapor is difficult to diffuse to the outside of the reactor, but is condensed into solid in the low temperature region of the reactor, thereby achieving separation.
Preferably, in the step (3), the temperature of the heating furnace is 600-750 ℃. More preferably, the temperature of the heating furnace is increased to 620-680 ℃, for example 640 ℃. Preferably, the heating furnace is evacuated to 5Pa or less, preferably 0.5Pa or less.
The hydrogen-containing gas in step (1) may be a mixture of hydrogen and an inert gas, and in this case, the inert gas in step (1) and step (4) may be the same or different. Preferably, in step (1) and/or (4), a positive pressure is maintained in the furnace. Preferably, a positive pressure in the reactor is avoided in step (3), since if a positive pressure is detrimental to achieving a separation of excess alkaline earth metal, e.g. magnesium.
Preferably, the method of the present invention further comprises a heat treatment such as a high temperature high vacuum heat treatment (or a high temperature high vacuum heat treatment after the molten salt assisted sintering according to the invention of patent CN 114210973B), oxygen reduction, acid washing, and then separating out the tantalum powder, such as by filtration and drying, so that the tantalum powder suitable for manufacturing a high-reliability tantalum capacitor can be obtained. These treatments are all processes known in the art. In other words, any process known in the art may be used for these treatments. For example, the high temperature and high vacuum heat treatment and passivation may be carried out by the methods provided in the patents CN201110039272.9, CN201120077798.1, CN201120077680.9, CN201120077305.4, etc., the oxygen reduction may be carried out by the method provided in the patent CN201420777210.7, and the acid washing may be carried out by the methods provided in the patents CN201210548101.3, CN201280077499.5, CN201210548008.2, etc.
Instead of incorporating N, P and/or B elements in step (1), a step of incorporating these elements may also be included separately in the present invention, for example after step (5). Of course, the raw materials containing these elements may be used as they are. These elements may also be added in the aforementioned high temperature high vacuum heat treatment step. It is particularly preferable to add the P element. The addition of the P element can improve the specific volume, so long as the total amount of the doped P is well controlled, the effect of improving the specific volume is the same whenever the P element is added.
The tantalum powder is pressed into blocks and sintered, energized under high pressure condition, and the electric performance of the energized blocks is tested, so that the energized blocks are found to have better overall electric performance, and the tantalum powder manufactured by the method is more suitable for manufacturing high-voltage high-reliability tantalum capacitors.
Moreover, the invention has simple process and easy control. For example, microwaves are not used in all steps of the invention, nor are excessive temperatures above 1000 ℃ used, and the alkaline earth metal used for reduction is lower in proportion. Therefore, the used equipment is simpler, and the safety of the tantalum powder preparation process is better.
Without being bound to a general theory, in combination with the theory analysis theory of powder liquid phase sintering, the inventors believe that the reason for the excellent effect achieved by the present invention is that in step (2), in the presence of hydrogen in the atmosphere, reduction occurs more easily and sintering is enhanced, so that a space structure suitable for a capacitor is more easily built between tantalum powder particles, the tantalum powder particles are uniform in size, and the particles are smooth, the sintering neck is coarse, and ultrafine particles are few. Thereafter, the tantalum powder obtained is subjected to high temperature and high vacuum heat treatment (or the high temperature and high vacuum heat treatment is performed after fused salt assisted sintering according to the invention of patent CN 114210973B), oxygen reduction and acid washing treatment according to the prior art, and then the tantalum powder suitable for preparing the high-voltage high-reliability capacitor is obtained.
As used herein, "more easily constructing a space structure suitable for a capacitor" means that after the resulting tantalum powder is pressed and sintered into an anode block, no ultra-fine pores are present in the resulting anode block. These ultrafine voids are detrimental to electrical properties, in particular leakage current and ESR (equivalent series resistance).
The invention also relates to the tantalum powder prepared by the method, an anode block prepared from the tantalum powder and the application of the tantalum powder and/or the anode block in the preparation of capacitors.
Drawings
The following drawings are provided for a better understanding of the present invention. These drawings are illustrative and are not intended to limit the scope of the invention.
Fig. 1 shows a scanning electron microscope photograph of tantalum powder obtained according to the present invention.
The figure shows that the obtained tantalum powder has more uniform particle size, smooth particles, coarse sintering neck and less ultrafine particles.
Detailed Description
The objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments of the invention, which is to be read in connection with the accompanying examples. The description is only intended to further illustrate the features and advantages of the invention, and is not intended to be limiting. The examples were conducted under conventional conditions, except that the specific conditions were not specified. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
For the purposes of this specification, all numbers expressing quantities of ingredients, reaction conditions, and so forth in the specification and claims are to be understood as being modified in all instances by the term "about" unless otherwise specified. Accordingly, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention unless indicated to the contrary. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
The analysis of the impurity content in the tantalum powder is carried out according to Chinese standard GB/T15076.1-15076.15, and the physical properties are regulated according to industry standard YS/T573-2015. The test of the electrical performance in tantalum powder is carried out according to the specification of Chinese standard GB/T3137.
Example 1
Taking 10.0kg of tantalum oxide, adding 3.1kg of metal magnesium particles, adding 3.0kg of potassium chloride (KCl) at the same time, mixing uniformly, filling into a reaction container, and separating (i.e. extracting) air in the reaction container. Introducing mixed gas of hydrogen and argon into a reaction container, controlling the partial pressure of the hydrogen to be 50KPa, heating the reaction container in a heating furnace under the condition of keeping positive pressure in the reaction container, heating to 940 ℃, and preserving heat for 2.0 hours to fully reduce the tantalum oxide. Then, the temperature was lowered to 640℃for evacuation, the pressure in the reaction vessel was lowered to 5.7Pa, and the evacuation was stopped after 3 hours of incubation. Then argon is introduced into the reaction vessel, the temperature is reduced to the room temperature, the passivation treatment is carried out, the furnace is discharged after the passivation is finished, the metal magnesium is stable and has no ignition and smoke phenomenon when discharged, and then the obtained mixture of the halide and the tantalum powder is washed with water, washed with acid, filtered and dried, so that the tantalum powder is separated.
Then, 50ppm of P is doped into the tantalum powder, high-temperature high-vacuum heat treatment is carried out for 1.0 hour at 1450 ℃ and the pressure of less than 5.0X10 -3 Pa, and then oxygen reduction and acid washing are carried out, so that the final tantalum powder is obtained. The anode block mass, pressed density, anode block sintering temperature, sintering time were specified in table 1, other conditions were in accordance with the foregoing GB/T3137 requirements, the resulting final tantalum powder was fabricated into anode blocks, energized at 250V, and then tested for electrical properties in accordance with the foregoing GB/T3137 requirements, in the specific capacitance test, after testing with 30% h 2SO4 solution, with 10% h 3PO4 solution, and the measured results are set forth in table 1.
Example 2
Taking 10.0kg of tantalum oxide, adding 3.85kg of metal magnesium particles, adding 3.0kg of potassium chloride (KCl), mixing uniformly, filling into a reaction vessel, and separating out air in the reaction vessel. Introducing mixed gas of hydrogen and argon into a reaction container, controlling the partial pressure of the hydrogen to be 0.5KPa, heating the reaction container in a heating furnace under the condition of keeping positive pressure, heating to 940 ℃, preserving heat for 2.0 hours, then reducing the temperature to 650 ℃ for evacuation, reducing the pressure in the reaction container to 5.7Pa, preserving heat for 8 hours, and stopping the evacuation. Then argon is introduced into the reaction vessel and cooled to room temperature, passivation treatment is carried out, the furnace is discharged after passivation is finished, magnesium metal is stable when the furnace is discharged, the magnesium metal is stable when the furnace is discharged and has no phenomenon of ignition and smoke, and the obtained mixed material of halide and tantalum powder is washed, pickled, filtered and dried to separate tantalum powder.
Then, 50ppm of P is doped into the tantalum powder, high-temperature high-vacuum heat treatment is carried out for 1.0 hour at 1450 ℃ and the pressure of less than 5.0X10 -3 Pa, and then oxygen reduction and acid washing are carried out, so that the final tantalum powder is obtained. The anode block mass, pressed density, anode block sintering temperature, sintering time were specified in table 1, other conditions were in accordance with the foregoing GB/T3137 requirements, the resulting final tantalum powder was fabricated into anode blocks, energized at 250V, and then tested for electrical properties in accordance with the foregoing GB/T3137 requirements, in the specific capacitance test, after testing with 30% h 2SO4 solution, with 10% h 3PO4 solution, and the measured results are set forth in table 1.
Example 3
Taking 10.0kg of tantalum oxide, adding 3.50kg of metal magnesium particles, adding 3.0kg of potassium chloride (KCl), mixing uniformly, filling into a reaction vessel, and separating out air in the reaction vessel. Introducing mixed gas of hydrogen and argon into a reaction container, controlling the partial pressure of the hydrogen to be 100KPa, heating the reaction container in a heating furnace under the condition of keeping positive pressure in the reaction container, heating to 940 ℃, preserving heat for 2.0 hours, then reducing the temperature to 640 ℃ for evacuation, reducing the pressure in the reaction container to 5.7Pa, preserving heat for 5 hours, and stopping the evacuation. Then argon is introduced into the reaction vessel, the temperature is reduced, the reaction vessel is cooled to the room temperature, passivation treatment is carried out, the reaction vessel is discharged after passivation, and the magnesium metal is stable and has no ignition and smoke phenomenon when discharged. And (3) washing, pickling, filtering and drying the obtained mixed material of the halide and the tantalum powder to separate the tantalum powder.
Then, 50ppm of P is doped into the tantalum powder, high-temperature high-vacuum heat treatment is carried out for 1.0 hour at 1450 ℃ and the pressure of less than 5.0X10 -3 Pa, and then oxygen reduction and acid washing are carried out, so that the final tantalum powder is obtained. The anode block mass, pressed density, anode block sintering temperature, sintering time were specified in table 1, other conditions were in accordance with the foregoing GB/T3137 requirements, the resulting final tantalum powder was fabricated into anode blocks, energized at 250V, and then tested for electrical properties in accordance with the foregoing GB/T3137 requirements, in the specific capacitance test, after testing with 30% h 2SO4 solution, with 10% h 3PO4 solution, and the measured results are set forth in table 1.
Example 4
10.0Kg of tantalum oxide is taken, 3.90kg of metal magnesium particles are mixed, 2.0kg of potassium chloride (KCl) is mixed, the mixture is filled into a reaction vessel, and air in the reaction vessel is separated. Introducing mixed gas of hydrogen and argon into a reaction container, controlling the partial pressure of the hydrogen to be 0.1KPa, heating the reaction container in a heating furnace under the condition of keeping positive pressure in the reaction container, heating to 940 ℃, preserving heat for 2.0 hours, then reducing the temperature to 640 ℃ for evacuating, reducing the pressure in the reaction container to 5.7Pa, preserving heat for 7 hours, and stopping evacuating. Then argon is introduced into the reaction vessel and cooled to room temperature, the reaction vessel is subjected to passivation treatment, the metal magnesium is discharged from the furnace after the passivation is finished, the metal magnesium is stable and has no ignition and smoke phenomenon when discharged from the furnace, and the obtained mixed material of the halide and the tantalum powder is subjected to water washing, acid washing, filtering and drying to separate the tantalum powder.
Then, 50ppm of P is doped into the tantalum powder, high-temperature high-vacuum heat treatment is carried out for 1.0 hour at 1450 ℃ and the pressure of less than 5.0X10 -3 Pa, and then oxygen reduction and acid washing are carried out, so that the final tantalum powder is obtained. The anode block mass, pressed density, anode block sintering temperature, sintering time were specified in table 1, other conditions were in accordance with the foregoing GB/T3137 requirements, the resulting final tantalum powder was fabricated into anode blocks, energized at 250V, and then tested for electrical properties in accordance with the foregoing GB/T3137 requirements, in the specific capacitance test, after testing with 30% h 2SO4 solution, with 10% h 3PO4 solution, and the measured results are set forth in table 1.
Example 5
Taking 10.0kg of tantalum oxide, adding 3.1kg of metal magnesium particles, adding 3.0kg of potassium chloride (KCl), mixing uniformly, filling into a reaction vessel, and separating out air in the reaction vessel. Introducing mixed gas of hydrogen and argon into a reaction container, controlling the partial pressure of the hydrogen to be 0.3KPa, heating the reaction container in a heating furnace under the condition of keeping positive pressure in the reaction container, heating to 940 ℃, preserving heat for 2.0 hours, then reducing the temperature to 640 ℃ for evacuating, reducing the pressure in the reaction container to 5.7Pa, preserving heat for 3 hours, and stopping evacuating. Then argon is introduced into the reaction vessel and cooled to room temperature, the reaction vessel is subjected to passivation treatment, the metal magnesium is discharged from the furnace after the passivation is finished, the metal magnesium is stable and has no ignition and smoke phenomenon when discharged from the furnace, and the obtained mixed material of the halide and the tantalum powder is subjected to water washing, acid washing, filtering and drying to separate the tantalum powder.
Then, 50ppm of P is doped into the tantalum powder, high-temperature high-vacuum heat treatment is carried out for 1.0 hour at 1450 ℃ and the pressure of less than 5.0X10 -3 Pa, and then oxygen reduction and acid washing are carried out, so that the final tantalum powder is obtained. The anode block mass, pressed density, anode block sintering temperature, sintering time were specified in table 1, other conditions were in accordance with the foregoing GB/T3137 requirements, the resulting final tantalum powder was fabricated into anode blocks, energized at 250V, and then tested for electrical properties in accordance with the foregoing GB/T3137 requirements, in the specific capacitance test, after testing with 30% h 2SO4 solution, with 10% h 3PO4 solution, and the measured results are set forth in table 1.
Example 6
Taking 10.0kg of tantalum oxide, adding 3.1kg of metal magnesium particles, adding 1.5kg of potassium chloride (KCl) and 1.5kg of sodium chloride (NaCl), mixing uniformly, filling into a reaction vessel, and separating out air in the reaction vessel. Introducing mixed gas of hydrogen and argon into a reaction container, controlling the partial pressure of the hydrogen to be 1.0KPa, heating the reaction container in a heating furnace under the condition of keeping positive pressure in the reaction container, heating to 940 ℃, preserving heat for 2.0 hours, then reducing the temperature to 640 ℃ for evacuating, reducing the pressure in the reaction container to 5.7Pa, preserving heat for 3 hours, stopping evacuating, then introducing argon into the reaction container, reducing the temperature to room temperature, passivating, discharging the reaction container after the passivation is finished, stabilizing metal magnesium without ignition and smoke phenomenon when discharging the reaction container, and washing, pickling, filtering and drying the obtained mixed material of halide and tantalum powder to separate tantalum powder.
Then, 50ppm of P is doped into the tantalum powder, high-temperature high-vacuum heat treatment is carried out for 1.0 hour at 1450 ℃ and the pressure of less than 5.0X10 -3 Pa, and then oxygen reduction and acid washing are carried out, so that the final tantalum powder is obtained. The anode block mass, pressed density, anode block sintering temperature, sintering time were specified in table 1, other conditions were in accordance with the foregoing GB/T3137 requirements, the resulting final tantalum powder was fabricated into anode blocks, energized at 250V, and then tested for electrical properties in accordance with the foregoing GB/T3137 requirements, in the specific capacitance test, after testing with 30% h 2SO4 solution, with 10% h 3PO4 solution, and the measured results are set forth in table 1.
Example 7
Taking 10.0kg of tantalum oxide, adding 3.1kg of metal magnesium particles, adding 1.5kg of potassium chloride (KCl) and 1.5kg of sodium chloride (NaCl), mixing uniformly, then filling into a reaction container, putting into a crucible, putting 1.5kg of tantalum powder containing 3500ppm of hydrogen into the crucible, and separating out air in the reaction container. Introducing argon into the reaction container, heating the reaction container in a heating furnace under the condition of keeping positive pressure, heating the reaction container to 940 ℃, preserving heat for 2.0 hours, then reducing the temperature to 640 ℃ for evacuating, reducing the pressure in the reaction container to 5.7Pa, preserving heat for 3 hours, stopping evacuating, then introducing argon into the reaction container, reducing the temperature to room temperature, passivating, discharging after the passivation is finished, ensuring that the magnesium metal is stable without ignition and smoke phenomenon when discharging, and washing, pickling, filtering and drying the obtained halide and tantalum powder mixed material to separate tantalum powder.
Then, 50ppm of P is doped into the tantalum powder, high-temperature high-vacuum heat treatment is carried out for 1.0 hour at 1450 ℃ and the pressure of less than 5.0X10 -3 Pa, and then oxygen reduction and acid washing are carried out, so that the final tantalum powder is obtained. The anode block mass, pressed density, anode block sintering temperature, sintering time were specified in table 1, other conditions were in accordance with the foregoing GB/T3137 requirements, the resulting final tantalum powder was fabricated into anode blocks, energized at 250V, and then tested for electrical properties in accordance with the foregoing GB/T3137 requirements, in the specific capacitance test, after testing with 30% h 2SO4 solution, with 10% h 3PO4 solution, and the measured results are set forth in table 1.
Comparative example 1
Taking 10.0kg of tantalum oxide, mixing 5.46kg of metal magnesium particles, mixing 2.5kg of potassium chloride (KCl) and 2.5kg of sodium chloride (NaCl), mixing uniformly, filling into a reaction vessel, and separating out air in the reaction vessel. And (3) only introducing argon into the reaction container, heating the reaction container in a heating furnace under the condition of keeping positive pressure, heating to 940 ℃, preserving heat for 1.0 hour, then reducing the temperature to 650 ℃ for evacuation, reducing the pressure in the reaction container to 5.7Pa, preserving heat for 8 hours, stopping evacuation, introducing argon into the reaction container, heating to 940 ℃ under the condition of keeping positive pressure, and preserving heat for 3 hours. Cooling to room temperature after heat preservation, passivating, discharging from the furnace after passivation, discharging from the furnace, igniting and smoking metal magnesium, washing the obtained mixed material of halide and tantalum powder with water, pickling, filtering, drying, and separating tantalum powder.
Then, 50ppm of P is doped into the tantalum powder, high-temperature high-vacuum heat treatment is carried out for 1.0 hour at 1450 ℃ and the pressure of less than 5.0X10 -3 Pa, and then oxygen reduction and acid washing are carried out, so that the final tantalum powder is obtained. The anode block mass, pressed density, anode block sintering temperature, sintering time were specified in table 1, other conditions were in accordance with the foregoing GB/T3137 requirements, the resulting final tantalum powder was fabricated into anode blocks, energized at 250V, and then tested for electrical properties in accordance with the foregoing GB/T3137 requirements, in the specific capacitance test, after testing with 30% h 2SO4 solution, with 10% h 3PO4 solution, and the measured results are set forth in table 1.
TABLE 1 electric property data of tantalum powder finished product
As can be seen from table 1:
After the consumption of magnesium metal is reduced, the tantalum powder can be energized under the high-voltage condition of 250V (the voltage below 200V is generally adopted in the prior art), the obtained energized block has high specific volume, and in the specific capacitance test, the difference between the test result of adopting 30% H 2SO4 solution and the test result of adopting 10% H 3PO4 solution is smaller, and the higher breakdown voltage is shown in the breakdown voltage test.
It can also be seen from table 1 that the anode blocks made from the tantalum powder of the present invention have less difference in specific capacitance after being energized, as measured by different acid solutions. It is believed that the surface tension of phosphoric acid and sulfuric acid are different and the ability to penetrate into the ultra-fine pores in the anode block is also different. Thus, the difference in specific capacitance reflects the presence of ultrafine voids in the anode block. This therefore demonstrates that anode blocks with less ultrafine porosity and better microstructure can be obtained with the tantalum powder according to the invention.
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