Method for producing tantalum powder by reducing tantalum oxide with alkaline earth metal

Abstract

A method for producing a tantalum powder by reducing tantalum oxide with an alkaline earth metal, a tantalum powder manufactured thereby, an anode block made from the tantalum powder, and the use thereof in the manufacture of a capacitor. In the method for preparing a tantalum powder by reducing a tantalum oxide powder raw material with an alkaline earth metal, such as magnesium, preferably magnesium particles, the tantalum oxide powder raw material used is a tantalum oxide powder having a ratio of Fisher particle size (in μm) to apparent density (in g / cm3) of greater than 1.5; a hydrogen-containing gas is used during the reduction process; and the ratio of Fisher particle size to apparent density of the tantalum oxide powder is preferably greater than 2.0, preferably greater than 3.0, more preferably greater than 3.5, and more preferably greater than 4.5; for example, 2.0-15.0, and more preferably 3.0-5.0.

Description

Method for producing tantalum powder by reducing tantalum oxide with alkaline earth metals Technical Field

[0001] This invention belongs to the field of rare metal functional material smelting, specifically relating to the production of tantalum powder for high-voltage, high-reliability capacitors and its manufacturing method. Background Technology

[0002] Tantalum electrolytic capacitors (hereinafter referred to as tantalum capacitors) have advantages such as high capacitance, small size, strong self-healing ability, and high reliability, and are widely used in high-end technology fields such as communications, computers, automotive electronics, medical devices, radar, aerospace, and automatic control devices. Tantalum powder is the key material for making tantalum capacitors; only by using capacitor-grade tantalum powder with higher voltage withstand performance can tantalum capacitors with better reliability be produced. Therefore, only by continuously developing capacitor-grade tantalum powder with higher voltage withstand performance can the produced tantalum capacitors continuously meet the high reliability requirements of electronic devices and electronic circuits.

[0003] Currently, the main industrial methods for preparing capacitor-grade tantalum powder include the sodium reduction of potassium fluorotantalate, the tantalum ingot hydrogenation method, and the magnesium reduction of tantalum oxide method. The sodium reduction of potassium fluorotantalate method easily produces tantalum powder with high specific capacitance, but it suffers from low specific capacitance, high leakage current, and low breakdown voltage under relatively high voltage conditions. The tantalum ingot hydrogenation method produces tantalum powder with excellent withstand voltage, but its specific capacitance is generally low. To continuously improve both the withstand voltage and specific capacitance of tantalum powder, the magnesium reduction of tantalum oxide method has been successfully developed and continues to evolve. Because it alters the state of the reactants, the magnesium reduction of tantalum oxide method holds promise for producing tantalum powder for capacitors with improved specific capacitance and withstand voltage.

[0004] CN114192791B discloses a method for producing tantalum powder for capacitors using alkaline earth metal reduction of tantalum oxide. This method involves adding alkali metal or alkaline earth metal halides during the reduction process. In a furnace filled with inert gas, excess alkaline earth metal is used for reduction at temperatures above 700°C. After reduction, the excess alkaline earth metal is separated from the tantalum-containing material, and then the material is further sintered at temperatures above 750°C. However, this method is not perfect. Potential problems include the limited impact on the specific capacitance of tantalum powder can be achieved by adjusting temperature and time, the amount of halide and magnesium added, and the amount of additives, as described in the patent. Excessive adjustments can even lead to a deterioration in key performance characteristics such as breakdown voltage and leakage current. Therefore, this method cannot meet the diverse market demands for tantalum powder with different specific capacitances. Furthermore, the process is complex, requiring a separate sintering step, resulting in high energy consumption. There is also room for improvement in the safety of this process.

[0005] Existing technologies include a self-propagating high-temperature synthesis (SHS) method for preparing tantalum powder. However, this method requires temperatures above 2000°C, and the reaction is too rapid, making it difficult to control and placing excessive demands on the process equipment. Furthermore, the resulting tantalum powder is not uniform and cannot meet the requirements for manufacturing high-reliability capacitors.

[0006] Unbound by conventional theories, the inventors, after extensive research, discovered that existing processes for preparing tantalum powder are complex, energy-intensive, and / or pose a fire hazard during reduction due to the use of large amounts of alkaline earth metals. Furthermore, their electrical properties (especially residual current and / or breakdown voltage) are not ideal.

[0007] Summary of the Invention

[0008] One object of the present invention is to provide a method for preparing tantalum powder by reducing tantalum oxide powder with an alkaline earth metal such as magnesium in a hydrogen-containing atmosphere, wherein the tantalum oxide powder has a Fisher particle size (in μm) and a bulk density (in g / cm³). 3 The ratio of (calculated) particles to the total particle size is greater than 1.5 (e.g., a Fisher particle size of 6.78 μm and a loose packing density of 2.3 g / cm³). 3 The ratio of the two is 6.78 ÷ 2.3 = 2.95, and the purity is preferably above 99.95%. Using this method to produce tantalum powder reduces the amount of alkaline earth metals added, and the safety risk of alkaline earth metals igniting when the powder is removed from the furnace after reduction is significantly reduced.

[0009] The tantalum oxide powder used as a raw material in this invention is characterized by having a Fisher particle size to loose packing density ratio greater than 1.5, preferably greater than 2.0, more preferably greater than 2.5, more preferably greater than 3.0, more preferably greater than 3.5, and even more preferably greater than 4.5. In a preferred embodiment, this ratio is 2.0-15.0, more preferably 3.0-5.0. Preferably, the tantalum oxide powder has a purity of 99.95% or higher, more preferably 99.995% or higher. Generally, higher purity of tantalum oxide is more beneficial to improving the electrical properties of tantalum powder.

[0010] Tantalum oxide is a common name for tantalum pentoxide. In this article, the two terms can be used interchangeably, both referring to Ta2O5.

[0011] The method of this invention is simple, easier to operate and control, and safer. Furthermore, the resulting tantalum powder exhibits excellent overall electrical properties.

[0012] Specifically, the present invention provides a method for preparing tantalum powder by reducing tantalum oxide with an alkaline earth metal such as magnesium, comprising the following steps:

[0013] (1) Select tantalum oxide powder with a ratio of Fehler particle size to loose density greater than 1.5 as raw material, mix tantalum oxide powder with an excess of alkaline earth metal reducing agent, and simultaneously mix in at least one alkali metal and / or alkaline earth metal halide at 10-200% by weight of tantalum oxide, pack it into a sealed reaction container, extract the air from the container, and place the container in a heating furnace.

[0014] (2) Raise the temperature of the heating furnace to 700-1000℃ and keep it at that temperature for 1-3 hours to allow tantalum oxide to fully undergo a reduction reaction with the reducing agent;

[0015] (3) After the heat preservation is completed, the temperature of the heating furnace is kept at 600-750℃ (preferably 620-680℃, such as 640℃), the furnace is evacuated, for example, evacuated to below 10Pa, and heat preservation is carried out under negative pressure (for example, heat preservation for 1-10h).

[0016] (4) Then, inert gas is introduced into the reaction vessel to maintain positive pressure. The reaction vessel is then cooled to room temperature and passivated to obtain a mixture containing halides and tantalum powder.

[0017] (5) Separate the tantalum powder from the obtained mixture, for example by washing with water, acid washing, filtration, and drying.

[0018] In step (1), after the air in the container is evacuated, the reaction vessel is filled with hydrogen-containing gas. This is achieved, for example, by introducing hydrogen-containing gas, or by adding a liquid or solid hydrogen-containing substance (preferably a solid hydrogen-containing substance) and causing it to release hydrogen gas. Preferably, in the latter case, the hydrogen-containing substance is separated from other raw materials such as tantalum oxide powder, alkali metal and / or alkaline earth metal halides. This can be achieved, for example, by placing the hydrogen-containing substance separately in a crucible. Preferably, the hydrogen-containing substance is, for example, a substance that can release hydrogen gas at high temperatures, such as hydrogen-adsorbed tantalum powder (also called hydrogen-containing tantalum powder), hydrogen-containing niobium powder, hydrogen-containing titanium powder, and hydrogen-containing compounds. Preferably, hydrogen-containing tantalum powder is used.

[0019] Preferably, the tantalum oxide used as raw material in step (1) has a Fisher particle size to loose packing density ratio greater than 2.0, more preferably greater than 3.0, more preferably greater than 3.5, and even more preferably greater than 4.5. In a preferred embodiment, this ratio is 2.0-15.0, more preferably 3.0-5.0. Preferably, its purity is 99.95% or higher, more preferably 99.995% or higher. Generally speaking, higher purity of tantalum oxide is more beneficial to improving the electrical properties of tantalum powder.

[0020] The alkaline earth metal reducing agent mentioned in step (1) is preferably magnesium, more preferably magnesium particles, and even more preferably magnesium particles with a purity of 3N5 (i.e., 99.95%) or higher, and the higher the purity of the magnesium particles, the better. There is no limitation on the particle size of the magnesium particles. However, the inventors have found through extensive research that magnesium particles with a particle size of 150-4000 μm are more suitable for this technology, and the tantalum powder obtained by reduction has better pressure resistance. Magnesium particles in this particle size range are not only beneficial to the safety of the storage and transportation of metallic magnesium, but also to the uniform mixing. If the magnesium particles are too fine, they are too active and prone to spontaneous combustion; if the magnesium particles are too coarse, they are not conducive to uniform mixing and are not conducive to the optimization of tantalum powder performance. The amount of excess reducing agent added refers to the amount exceeding the theoretical amount required to completely reduce tantalum oxide. In this invention, it is preferred to exceed the theoretical amount by 5-50%, more preferably 10-48%, more preferably 10-45%, even more preferably 10-15% or 5-10%, or 15-20%. Generally speaking, the theoretical amount of magnesium required to completely reduce one kilogram of tantalum oxide is approximately 0.273 kilograms.

[0021] In step (2), tantalum powder inevitably undergoes a certain degree of sintering due to the heat of reduction. The presence of hydrogen gas in the container further enhances the sintering phenomenon of tantalum powder, thus eliminating the need for a separate subsequent sintering step. Since a separate sintering step is often required in the prior art, this undoubtedly simplifies the process compared to the prior art. Moreover, the simultaneous and coordinated sintering and reduction under the conditions described in this invention makes it easier to obtain tantalum powder with an improved microstructure, which is unexpected.

[0022] The weight of the alkali metal and / or alkaline earth metal halide added in step (1) is preferably 10-180% of the weight of tantalum oxide, more preferably 25-120%, more preferably 70-120% or 100-180%, and most preferably 15-80%, for example 25-80%. The alkali metal or alkaline earth halide is preferably of analytical grade, and preferably of higher purity. The alkali metal or alkaline earth halide is preferably in particulate form. There is no limitation on its particle size, but the inventors have found that particles of 70 μm-4000 μm are more suitable for this technology, and the tantalum powder obtained from the reduction has better pressure resistance.

[0023] Preferably, the alkali metal or alkaline earth metal halide mentioned in step (1) is one or more of NaCl, KCl, KF, KI, and / or MgCl2. The alkali metal halide can be sodium chloride and / or potassium chloride. Preferably, it is a mixture of sodium chloride and potassium chloride; more preferably, the ratio of sodium chloride to potassium chloride in the mixture is 1:1-10; most preferably, it is about 1:1.

[0024] Preferably, in step (1), one or more compounds containing elements B, P, and / or N may be added as additives to dope the tantalum powder. Based on the amount of effective elements, the amount of B added is preferably 1-100 ppm, more preferably 20-60 ppm; the amount of P added is preferably 10-200 ppm, more preferably 30-90 ppm; and the amount of N added is preferably 300-2500 ppm, more preferably 500-1200 ppm. 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 based on the amounts of B, P, and / or N.

[0025] Preferably, in step (2), the furnace is heated to 750–1000°C. More preferably, the furnace is heated to 900–965°C.

[0026] The hydrogen-containing gas used in step (1) is pure hydrogen or a mixture of hydrogen and an inert gas. The hydrogen can be gaseous or other liquid or solid hydrogen-containing substances heated to release hydrogen. Although hydrogen is a common reducing agent, it cannot reduce tantalum oxide. That is, hydrogen does not act as a reducing agent in this invention. However, the inventors unexpectedly discovered that because hydrogen enhances the sintering process that accompanies reduction, the process can be significantly simplified by omitting the sintering step. Furthermore, introducing hydrogen as a medium may reduce the amount of alkaline earth metal added as a reducing agent and may also improve the electrical properties of the product, particularly residual current and / or breakdown voltage.

[0027] Preferably, the gas pressure in the reaction vessel is positive in step (1). The partial pressure of hydrogen in the vessel exceeds 0.050 kPa, preferably 0.1-200 kPa, more preferably 0.3-50 kPa, even more preferably 10-20 kPa, and even more preferably 0.5-10 kPa or 10-15 kPa, and even more preferably 0.1-0.3 kPa. Too low a partial pressure of hydrogen cannot effectively promote the reduction effect, so the partial pressure of hydrogen should not be too low; conversely, once the partial pressure of hydrogen is increased to a certain level, the ability to further improve it weakens, and from the perspective of ensuring the absolute safety of hydrogen use, it is preferable to avoid excessively high partial pressures of hydrogen.

[0028] Inert gases generally refer to rare gases, such as helium, neon, and argon. Although nitrogen is sometimes considered an inert gas due to its stable properties, it is generally considered unsuitable as an inert protective gas in this field because of its high reduction temperature and high reactivity at this temperature. However, after extensive research, the inventors discovered that the presence of a small amount of nitrogen in the aforementioned inert gases does not compromise the overall inert protective atmosphere and can also incidentally achieve nitrogen doping of tantalum powder. From the perspective of achieving better nitrogen doping effect of tantalum powder, in step (1), when using a mixture of hydrogen-containing gas and inert gas, the mixture can preferably contain 0.5-10% nitrogen, calculated based on the total amount of hydrogen and inert gas.

[0029] In step (3), since the melting point of magnesium is relatively high, magnesium vapor is difficult to diffuse to the outside of the reactor, but condenses into a solid in the low temperature zone of the reactor, thus achieving separation.

[0030] Preferably, in step (3), the furnace temperature is 600–750°C. More preferably, the furnace temperature is 620–680°C. Preferably, the furnace is evacuated to below 5 Pa, more preferably below 0.5 Pa.

[0031] If a mixture of inert gas and hydrogen is introduced in step (1) as a hydrogen-containing atmosphere, the inert atmosphere may be the same as or different from the inert gas in step (4). Preferably, a positive pressure is maintained in the reactor in steps (1) and / or (4). Preferably, a positive pressure is avoided in the reactor in step (3) because a positive pressure is not conducive to the separation of excess alkaline earth metals such as magnesium.

[0032] Preferably, the method of the present invention further includes, after step (5), heat treatment such as high-temperature high-vacuum heat treatment (or, according to patent CN114210973B, high-temperature high-vacuum heat treatment after sintering), oxygen reduction, acid washing, and then separating tantalum powder, for example by filtration and drying, to obtain tantalum powder suitable for manufacturing high-reliability tantalum capacitors. These processes are all known in the prior art. In other words, these processes can employ any process known in the prior art. For example, the high-temperature high-vacuum heat treatment and passivation here can be performed using the methods provided by patents CN201110039272.9, CN201120077798.1, CN201120077680.9, CN201120077305.4, etc.; the oxygen reduction can be performed using the method provided by patent CN201420777210.7; and the pickling can be performed using the methods provided by patents CN201210548101.3, CN201280077499.5, CN201210548008.2, etc.

[0033] As an alternative to incorporating N, P, and / or B elements in step (1), the present invention may also include a separate step of incorporating these elements, for example, after step (5). Of course, raw materials containing these elements can also be used directly. These elements can also be added during the aforementioned high-temperature, high-vacuum heat treatment step. Incorporating P is particularly preferred. Adding P can increase the specific volume; as long as the total amount of P is controlled, the effect of increasing the specific volume is the same regardless of when it is added.

[0034] The tantalum powder described above was pressed into blocks, sintered, and energized under high voltage conditions. The electrical performance of the energized blocks was tested, revealing that they exhibited good electrical properties, particularly residual current. Therefore, the tantalum powder manufactured using this invention is more suitable for producing high-voltage, high-reliability tantalum capacitors.

[0035] Moreover, the process of this invention is simple and easy to control. For example, microwaves and excessively high temperatures are not used in any step of this invention, and the proportion of alkaline earth metals used for reduction is lower. Therefore, the equipment used is also relatively simple, and the tantalum powder preparation process is safer.

[0036] Without being bound by general theories, and combining the analysis principles of powder liquid phase sintering theory, the inventors believe that the reason for the excellent effect of this invention is as follows: In step (2), in the presence of hydrogen-containing gas in the reactor atmosphere, the hydrogen-containing gas makes reduction easier to occur and can also enhance sintering, making it easier for tantalum powder particles to construct a spatial structure suitable for capacitor manufacturing. The tantalum powder particles are more uniform in size, and the particles are smooth, with a large sintering neck and fewer ultrafine particles. Subsequently, the obtained tantalum powder is subjected to high-temperature and high-vacuum heat treatment according to existing technology (or first sintering according to patent CN114210973B and then high-temperature and high-vacuum heat treatment), oxygen reduction, and acid washing treatment to obtain tantalum powder suitable for preparing high-voltage and high-reliability capacitors.

[0037] The phrase "easier to construct a suitable spatial structure for capacitors" refers to the absence of ultrafine pores in the anode block after the obtained tantalum powder is pressed and sintered. These ultrafine pores are detrimental to electrical performance, particularly leakage current and ESR (equivalent series resistance).

[0038] The present invention also relates to tantalum powder obtained by the above method, an anode block made from the tantalum powder, and the use of the tantalum powder and / or the anode block in the manufacture of capacitors. Attached Figure Description

[0039] The following figures are provided to better understand the invention. These figures are exemplary and are not intended to limit the scope of the invention.

[0040] Figure 1 shows a scanning electron microscope image of the tantalum powder obtained according to the present invention.

[0041] The attached figure illustrates that the obtained tantalum powder particles are more uniform in size, with smooth particles, large sintering necks, and fewer ultrafine particles. Detailed Implementation

[0042] To further illustrate the present invention, preferred embodiments are described below with reference to examples, which clearly demonstrate the purpose, features, and advantages of the present invention. However, these descriptions are merely for further illustrating the features and advantages of the present invention and are not intended to limit the invention. Unless otherwise specified in the examples, conventional conditions were followed. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0043] For the purposes of this specification, all figures indicating amounts of ingredients, reaction conditions, etc., in the specification and claims shall in all cases be understood to be modified by the term "about," unless otherwise specified. Accordingly, the numerical parameters given in the following specification and appended claims are approximate values, which may vary according to the desired properties sought to be obtained according to the invention, unless indicated to the contrary. At least, and without limitation, the application of the doctrine of equivalence to the scope of the claims is intended, each numerical parameter shall be interpreted at least according to the number of significant figures reported and in accordance with ordinary rounding techniques.

[0044] The analysis of impurity content in tantalum powder was conducted according to Chinese standards GB / T15076.1~15076.15, and the physical properties were performed according to industry standard YS / T573-2015. The testing of electrical properties in tantalum powder was conducted according to Chinese standard GB / T3137.

[0045] Example 1

[0046] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 10.92 μm and a loose packing density of 2.6 g / cm³. 3The ratio of their values ​​is 10.92 ÷ 2.6 = 4.2, and the purity is 99.997%. 15.5 kg of metallic magnesium granules, along with 5.0 kg of potassium chloride (KCl) and 5.0 kg of sodium chloride (NaCl), are added and mixed thoroughly. The mixture is then placed in a sealed reaction vessel, and the air inside the vessel is removed (i.e., extracted). A mixture of hydrogen and argon gas is introduced into the reaction vessel, controlling the hydrogen partial pressure to 50 kPa. Under positive pressure, the reaction vessel is placed in a furnace and heated to 950°C, held for 2.0 hours to allow for complete reduction of tantalum oxide. Then, the temperature is lowered to 640°C and evacuated, reducing the pressure in the reaction vessel to 5.7 Pa. This temperature is maintained for 18 hours, after which evacuation is stopped. Then, argon gas was introduced into the reaction vessel and the temperature was lowered to room temperature for passivation treatment. After passivation, the product was removed from the furnace. The magnesium metal was stable and showed no signs of ignition or smoke upon removal. The resulting mixture of halide and tantalum powder was then washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0047] Then, the tantalum powder was subjected to temperatures of 1450°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 300V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0048] Comparative Example 1

[0049] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 3.41 μm and a loose packing density of 2.5 g / cm³. 3The ratio of their values ​​is 3.41 ÷ 2.5 = 1.36, and the purity is 99.997%. 15.5 kg of metallic magnesium granules, along with 5.0 kg of potassium chloride (KCl) and 5.0 kg of sodium chloride (NaCl), are added and mixed thoroughly. The mixture is then placed in a sealed reaction vessel, and the air inside the vessel is removed (i.e., evacuated). Argon gas is introduced into the reaction vessel, and under positive pressure, the vessel is placed in a furnace and heated to 950°C, held for 2.0 hours to allow for complete reduction of tantalum oxide. Then, the temperature is lowered to 640°C and evacuated to reduce the pressure inside the reaction vessel to 5.7 Pa. This temperature is maintained for 18 hours, after which evacuation is stopped. Then, argon gas was introduced into the reaction vessel and the temperature was lowered to room temperature for passivation treatment. After passivation, the product was removed from the furnace. The magnesium metal was stable and showed no signs of ignition or smoke upon removal. The resulting mixture of halide and tantalum powder was then washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0050] Then, the tantalum powder was subjected to temperatures of 1450°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 300V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0051] Example 2

[0052] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 10.92 μm and a loose packing density of 2.6 g / cm³. 3The ratio of their values ​​is 10.92 ÷ 2.6 = 4.2, and the purity is 99.997%. 15.5 kg of metallic magnesium granules, along with 5.0 kg of potassium chloride (KCl) and 5.0 kg of sodium chloride (NaCl), are added and mixed thoroughly. The mixture is then placed in a sealed reaction vessel, and the air inside the vessel is removed (i.e., extracted). A mixture of hydrogen and argon gas is introduced into the reaction vessel, controlling the hydrogen partial pressure to 50 kPa. Under positive pressure, the reaction vessel is placed in a furnace and heated to 950°C, held for 2.0 hours to allow for complete reduction of tantalum oxide. Then, the temperature is lowered to 640°C and evacuated, reducing the pressure in the reaction vessel to 5.7 Pa. This temperature is maintained for 18 hours, after which evacuation is stopped. Then, argon gas was introduced into the reaction vessel and the temperature was lowered to room temperature for passivation treatment. After passivation, the product was removed from the furnace. The magnesium metal was stable and showed no signs of ignition or smoke upon removal. The resulting mixture of halide and tantalum powder was then washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0053] Then, the tantalum powder was subjected to temperatures of 1450°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 300V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0054] Comparative Example 2

[0055] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 10.92 μm and a loose packing density of 2.6 g / cm³. 3The ratio of their values ​​is 10.92 ÷ 2.6 = 4.2, and the purity is 99.997%. 15.5 kg of metallic magnesium granules, along with 5.0 kg of potassium chloride (KCl) and 5.0 kg of sodium chloride (NaCl), are added and mixed thoroughly. The mixture is then placed in a sealed reaction vessel, and the air inside the vessel is removed (i.e., evacuated). Argon gas is introduced into the reaction vessel, and under positive pressure, the vessel is placed in a furnace and heated to 950°C, held for 2.0 hours to allow for complete reduction of tantalum oxide. Then, the temperature is lowered to 640°C and evacuated to reduce the pressure inside the reaction vessel to 5.7 Pa. This temperature is maintained for 18 hours, after which evacuation is stopped. Then, argon gas was introduced into the reaction vessel and the temperature was lowered to room temperature for passivation treatment. After passivation, the product was removed from the furnace. The magnesium metal was stable and showed no signs of ignition or smoke upon removal. The resulting mixture of halide and tantalum powder was then washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0056] Then, the tantalum powder was subjected to temperatures of 1450°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 300V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0057] Example 3

[0058] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 9.72 μm and a loose packing density of 2.1 g / cm³. 3The ratio of the tested values ​​was 9.72 ÷ 2.1 = 4.63, and the purity was 99.999%. 15.5 kg of metallic magnesium granules, along with 6.5 kg of potassium chloride (KCl) and 6.5 kg of sodium chloride (NaCl), were added and mixed thoroughly before being placed in a reaction vessel. Air was removed from the reaction vessel. A mixture of hydrogen and argon was introduced into the reaction vessel, controlling the hydrogen partial pressure to 30 kPa. Under positive pressure, the reaction vessel was placed in a furnace and heated to 940°C, held for 2.0 hours, then the temperature was lowered to 650°C and evacuated to reduce the pressure to 5.7 Pa. This temperature was maintained for 18 hours before evacuation was stopped. Argon was then introduced into the reaction vessel and the temperature was lowered to room temperature for passivation. After passivation, the vessel was removed from the furnace; a small amount of smoke was emitted from the magnesium granules upon removal. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The values ​​of tantalum oxide Fisher particle size, loose packing density, purity, and reduction temperature are listed in Table 1.

[0059] Then, tantalum powder was added to 50 ppm of P, and the mixture was heated at 1400°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 200V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0060] Comparative Example 3

[0061] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 2.04 μm and a loose packing density of 2.0 g / cm³. 3The ratio of their values ​​is 2.04 ÷ 2.0 = 1.02, and the purity is 99.999%. 19.5 kg of metallic magnesium granules, along with 6.5 kg of potassium chloride (KCl) and 6.5 kg of sodium chloride (NaCl), were added and mixed thoroughly before being placed in a reaction vessel. Air was then removed from the reaction vessel. Argon gas was introduced into the reaction vessel, and under positive pressure, the vessel was placed in a furnace and heated to 940°C, held for 2.0 hours, then the temperature was lowered to 650°C and evacuated to reduce the pressure to 5.7 Pa. This temperature was maintained for 18 hours before evacuation was stopped. Argon gas was then introduced into the reaction vessel again, and the temperature was lowered to room temperature for passivation treatment. After passivation, the vessel was removed from the furnace. Upon removal, the metallic magnesium exhibited a fire and smoke problem. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The values ​​of tantalum oxide Fisher particle size, loose packing density, purity, and reduction temperature are listed in Table 1.

[0062] Then, tantalum powder was added to 50 ppm of P, and the mixture was heated at 1400°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 200V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0063] Example 4

[0064] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 5.43 μm and a loose packing density of 1.8 g / cm³. 3The ratio of their values ​​is 5.43 ÷ 1.8 = 3.02, and the purity is 99.9993%. 15.5 kg of metallic magnesium granules, along with 8.0 kg of potassium chloride (KCl) and 8.0 kg of sodium chloride (NaCl), were added and mixed thoroughly before being placed in a reaction vessel. Air was then removed from the reaction vessel. A mixture of hydrogen and argon was introduced into the reaction vessel, controlling the hydrogen partial pressure to 50 kPa. Under positive pressure, the reaction vessel was placed in a furnace and heated to 920°C, held for 2.0 hours, then the temperature was lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This temperature was held for 18 hours before evacuation was stopped. Argon was then introduced into the reaction vessel and the temperature was lowered to room temperature for passivation. After passivation, the magnesium was removed from the furnace; upon removal, the metallic magnesium was stable and showed no signs of ignition or smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0065] Then, tantalum powder was added to 50 ppm of P, and the mixture was heated at 1320°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 100V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0066] Comparative Example 4

[0067] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 1.66 μm and a loose packing density of 1.83 g / cm³. 3The ratio of their values ​​is 1.66 ÷ 1.83 = 0.91, and the purity is 99.9993%. 18.5 kg of metallic magnesium granules, along with 8.0 kg of potassium chloride (KCl) and 8.0 kg of sodium chloride (NaCl), were added and mixed thoroughly before being placed in a reaction vessel. Air was then removed from the reaction vessel. Argon gas was introduced into the reaction vessel, and under positive pressure, the vessel was placed in a furnace and heated to 920°C, held for 2.0 hours, then the temperature was lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This temperature was maintained for 18 hours before evacuation was stopped. Argon gas was then introduced into the reaction vessel again, and the temperature was lowered to room temperature for passivation treatment. After passivation, the magnesium granules were removed from the furnace, where they exhibited a fire and smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The values ​​of tantalum oxide Fisher particle size, loose packing density, purity, and reduction temperature are listed in Table 1.

[0068] Then, tantalum powder was added to 50 ppm of P, and the mixture was heated at 1320°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 100V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0069] Example 5

[0070] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 3.86 μm and a loose packing density of 1.4 g / cm³. 3The test ratio was 3.86 ÷ 1.4 = 2.75, and the purity was 99.9993%. 14.5 kg of metallic magnesium granules were added, along with 9.0 kg of potassium chloride (KCl) and 9.0 kg of sodium chloride (NaCl). After mixing thoroughly, the mixture was placed into a reaction vessel, and the air in the reaction vessel was separated. A mixture of hydrogen and argon was introduced into the reaction vessel, controlling the hydrogen partial pressure at 20 kPa. Under positive pressure, the reaction vessel was placed in a furnace and heated to 900°C, held for 2.0 hours, then the temperature was lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This was held for 18 hours, and then evacuation was stopped. Argon was then introduced into the reaction vessel and the temperature was lowered to room temperature for passivation. After passivation, the vessel was removed from the furnace; the magnesium metal was stable and showed no signs of ignition or smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0071] Then, tantalum powder was added to 50 ppm of P, and the mixture was heated at 1280°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 80V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0072] Example 6

[0073] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 3.86 μm and a loose packing density of 1.4 g / cm³. 3The ratio of their values ​​is 3.86 ÷ 1.4 = 2.75, and the purity is 99.9993%. 13.0 kg of metallic magnesium granules, along with 9.0 kg of potassium chloride (KCl) and 9.0 kg of sodium chloride (NaCl), are added, mixed thoroughly, and then placed into a reaction vessel. The air in the reaction vessel is then separated. A mixture of hydrogen and argon was introduced into the reaction vessel, controlling the hydrogen partial pressure at 20 kPa. Under positive pressure, the reaction vessel was placed in a furnace and heated to 900°C, held for 2.0 hours, then the temperature was lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This was held for 18 hours, and then evacuation was stopped. Argon was then introduced into the reaction vessel and the temperature was lowered to room temperature for passivation. After passivation, the vessel was removed from the furnace; the magnesium metal was stable and showed no signs of ignition or smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0074] Then, tantalum powder was added to 50 ppm of P, and the mixture was heated at 1280°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 80V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0075] Example 7

[0076] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 2.62 μm and a loose packing density of 0.79 g / cm³. 3The ratio of their values ​​is 2.62 ÷ 0.79 = 3.32, and the purity is 99.9993%. 14.5 kg of metallic magnesium granules were added, along with 9.0 kg of potassium chloride (KCl) and 9.0 kg of sodium chloride (NaCl). After mixing thoroughly, the mixture was placed into a reaction vessel, and the air in the reaction vessel was separated. A mixture of hydrogen and argon gas was introduced into the reaction vessel, controlling the hydrogen partial pressure to be 20 kPa. Under positive pressure, the reaction vessel was placed in a furnace and heated to 860°C, held for 2.0 hours, then the temperature was lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This was held for 18 hours, and then evacuation was stopped. Argon gas was then introduced into the reaction vessel and the temperature was lowered to room temperature for passivation. After passivation, the vessel was removed from the furnace; the magnesium metal was stable and showed no signs of ignition or smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0077] Then, tantalum powder was added to 70 ppm of P, and the mixture was heated at 1230°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 60V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0078] Example 8

[0079] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 2.62 μm and a loose packing density of 0.79 g / cm³. 3The ratio of their values ​​is 2.62 ÷ 0.79 = 3.32, and the purity is 99.9993%. 12.0 kg of metallic magnesium granules, along with 9.0 kg of potassium chloride (KCl) and 9.0 kg of sodium chloride (NaCl), are added, mixed thoroughly, and then placed into a reaction vessel. The air in the reaction vessel is then separated. A mixture of hydrogen and argon gas was introduced into the reaction vessel, controlling the hydrogen partial pressure to be 20 kPa. Under positive pressure, the reaction vessel was placed in a furnace and heated to 860°C, held for 2.0 hours, then the temperature was lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This was held for 18 hours, and then evacuation was stopped. Argon gas was then introduced into the reaction vessel and the temperature was lowered to room temperature for passivation. After passivation, the vessel was removed from the furnace; the magnesium metal was stable and showed no signs of ignition or smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0080] Then, tantalum powder was added to 70 ppm of P, and the mixture was heated at 1230°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 60V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0081] Example 9

[0082] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 2.62 μm and a loose packing density of 0.79 g / cm³. 3The ratio of their values ​​is 2.62 ÷ 0.79 = 3.32, and the purity is 99.9993%. 14.5 kg of metallic magnesium granules, along with 9.0 kg of potassium chloride (KCl) and 9.0 kg of sodium chloride (NaCl), are added and mixed thoroughly. The mixture is then placed into a reaction vessel, and another crucible containing 1.0 kg of tantalum powder with a hydrogen content of 3500 ppm is placed inside. The air in the reaction vessel is then separated. Argon gas was introduced into the reaction vessel, and under positive pressure, the vessel was placed in a furnace and heated to 860°C for 2.0 hours. The temperature was then lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This evacuation was maintained for 18 hours, after which evacuation was stopped. Argon gas was then introduced again and the vessel was cooled to room temperature for passivation. After passivation, the vessel was removed from the furnace; the magnesium metal was stable and showed no signs of ignition or smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0083] Then, tantalum powder was added to 70 ppm of P, and the mixture was heated at 1230°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 60V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0084] Example 10

[0085] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 1.27 μm and a loose packing density of 0.50 g / cm³. 3The ratio of their values ​​is 1.27 ÷ 0.50 = 2.54, and the purity is 99.9993%. 14.5 kg of metallic magnesium granules, along with 10.0 kg of potassium chloride (KCl) and 10.0 kg of sodium chloride (NaCl), are added, mixed thoroughly, and then placed into a reaction vessel. The air in the reaction vessel is then separated. A mixture of hydrogen and argon gas was introduced into the reaction vessel, controlling the hydrogen partial pressure to be 20 kPa. Under positive pressure, the reaction vessel was placed in a furnace and heated to 850°C, held for 2.0 hours, then the temperature was lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This was held for 18 hours, and then evacuation was stopped. Argon gas was then introduced into the reaction vessel and the temperature was lowered to room temperature for passivation. After passivation, the vessel was removed from the furnace; the magnesium metal was stable and showed no signs of ignition or smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0086] Then, tantalum powder was added to 70 ppm of P, and the mixture was heated at 1180°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 40V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0087] Example 11

[0088] Take 40.0 kg of tantalum oxide, with a Fisher particle size of 1.27 μm and a loose packing density of 0.50 g / cm³. 3The ratio of their values ​​is 1.27 ÷ 0.50 = 2.54, and the purity is 99.9993%. 14.5 kg of metallic magnesium granules, along with 10.0 kg of potassium chloride (KCl) and 10.0 kg of sodium chloride (NaCl), are added and mixed thoroughly before being placed into a reaction vessel. Another crucible is placed in which 1.0 kg of tantalum powder containing 3500 ppm hydrogen is added to separate the air from the reaction vessel. Argon gas was introduced into the reaction vessel, and under positive pressure, the vessel was placed in a furnace and heated to 850°C for 2.0 hours. The temperature was then lowered to 640°C and evacuated to reduce the pressure to 5.7 Pa. This evacuation was continued for 18 hours, after which argon gas was introduced again and the vessel was cooled to room temperature for passivation. After passivation, the vessel was removed from the furnace; the magnesium metal was stable and showed no signs of ignition or smoke. The resulting mixture of halide and tantalum powder was washed with water, acid-washed, filtered, and dried to separate the tantalum powder. The Fisher particle size, loose packing density, purity, and reduction temperature of tantalum oxide are listed in Table 1.

[0089] Then, tantalum powder was added to 70 ppm of P, and the mixture was heated at 1180°C and below 5.0 × 10⁻⁶. -3 The tantalum powder was subjected to high-temperature, high-vacuum heat treatment for 1.0 hour under a pressure of Pa, followed by deoxygenation and acid washing to obtain the final tantalum powder. The final tantalum powder was fabricated into anode blocks according to the anode block mass, pressing density, anode block sintering temperature, and sintering time specified in Table 1, with other conditions conforming to the aforementioned GB / T3137 requirements. The anode blocks were then energized at 40V, and their electrical properties were tested according to the aforementioned GB / T3137 requirements. In the specific capacitance test, the test was conducted using a 30% H2SO4 solution followed by a 10% H3PO4 solution. The results are listed in Table 2.

[0090] Table 1 Main Process Parameters

[0091] Table 2 Electrical Performance Data of Finished Tantalum Powder

[0092] As can be seen from Table 2:

[0093] This invention is suitable for manufacturing tantalum powder for high-voltage, high-reliability capacitors with higher specific capacitance. Compared to the comparative example, the energized block obtained in the embodiment exhibits high specific capacitance and high breakdown voltage in the breakdown voltage test, under relatively high voltage conditions.

[0094] Table 1 also shows that, after energization, the anode blocks made with the tantalum powder described in this invention exhibit smaller differences in specific capacity compared to the prior art (i.e., the corresponding comparative examples) when tested with different acid solutions (30% H2SO4 solution and 10% H3PO4 solution). It is generally believed that phosphoric acid and sulfuric acid have different surface tensions and therefore different abilities to penetrate the ultrafine pores in the anode block. Thus, the specific capacity difference reflects the amount of ultrafine pores in the anode block. Therefore, the results in the table corroborate that anode blocks with fewer ultrafine pores can be obtained using the tantalum powder according to this invention.

Claims

1. A method for preparing tantalum powder by reducing tantalum oxide powder raw material with an alkaline earth metal such as magnesium (preferably magnesium particles), characterized in that: The tantalum oxide powder raw material used has a Fisher particle size (in μm) and a bulk density (in g / cm³). 3 The high-purity tantalum oxide powder has a ratio of 1.5 (by weight) to 1.5, and the reduction process is carried out in an atmosphere containing hydrogen gas. Preferably, the ratio of the Fisher particle size to the loose packing density of the high-purity tantalum oxide powder is greater than 2.0, more preferably greater than 3.0, more preferably greater than 3.5, and more preferably greater than 4.5; for example, 2.0-15.0, more preferably 3.0-5.

0.

2. The method according to claim 1, wherein the tantalum oxide powder raw material is tantalum oxide with a purity of 99.995% or higher, more preferably 99.999% or higher.

3. A method for preparing tantalum powder by reducing tantalum oxide with an alkaline earth metal such as magnesium (preferably magnesium particles), comprising the following steps: (1) Select the Fisher particle size (in μm) and the loose packing density (in g / cm³). 3 Using tantalum oxide powder with a ratio greater than 1.5 (by weight) as raw material, the tantalum oxide powder is mixed with an excess of alkaline earth metal reducing agent, and at the same time, 10-200% by weight of at least one alkali metal and / or alkaline earth metal halide of tantalum oxide is mixed in. The mixture is then placed in a sealed reaction container, the air in the container is extracted, and the container is placed in a heating furnace. (2) Raise the temperature of the heating furnace to 700-1000℃ and keep it at that temperature for 1-3 hours to allow tantalum oxide to fully undergo a reduction reaction with the reducing agent; (3) After the heat preservation is completed, the temperature of the heating furnace is kept at 600-750℃, the furnace is evacuated, for example, evacuated to below 10Pa, and heat preservation is carried out under negative pressure (for example, heat preservation for 1-10h). (4) Then, inert gas is introduced into the reaction vessel to maintain positive pressure. The reaction vessel is then cooled to room temperature and passivated to obtain a mixture containing halides and tantalum powder. (5) Separate the tantalum powder from the obtained mixture, for example by washing with water, acid washing, filtration, and drying. In step (1), after the air in the container is extracted, the atmosphere in the container is made to contain hydrogen gas, for example by introducing hydrogen gas (e.g., pure hydrogen, or a mixture of hydrogen and an inert gas), or by adding a hydrogen-containing substance (e.g., tantalum metal adsorbed with hydrogen) and causing it to release hydrogen gas.

4. The manufacturing method according to claim 3, characterized in that: The amount of reducing agent added in step (1) is 5-50% more than the theoretical amount required for complete reduction of tantalum oxide, preferably 10-48%, more preferably 10-45%, even more preferably 10-15% or 5-10%, or 15-20%.

5. The manufacturing method according to claim 3 or 4, characterized in that: The alkali metal chloride added in step (1) is 10-180% by weight of tantalum oxide, preferably 25-120%, more preferably 70-120% or 100-180%, and most preferably 15-80%, for example 25-80%.

6. The manufacturing method according to any one of claims 3-5, characterized in that: The alkali metal or alkaline earth metal halide mentioned in step (1) is one or more of NaCl, KCl, KF, KI, and MgCl2, preferably a mixture of NaCl and KCl, more preferably a mixture in which the mass ratio of sodium chloride to potassium chloride is 1:1-10, and most preferably about 1:

1.

7. The manufacturing method according to any one of claims 3-6, characterized in that: In step (1), one or more compounds containing elements B, P, and / or N are added as additives to dope tantalum powder. Preferably, the amount of element B added is 1-100 ppm, more preferably 20-60 ppm, based on the amount of effective elements. And / or the added P element is 10-200 ppm, more preferably 30-90 ppm; And / or the added nitrogen element is 300-2500 ppm, more preferably 500-1200 ppm.

8. The manufacturing method according to any one of claims 3-7, characterized in that: The partial pressure of hydrogen in step (2) exceeds 0.050 kPa, preferably 0.1-200 kPa, more preferably 0.3-50 kPa, more preferably 0.3-20 kPa, even more preferably 0.5-2 kPa or 2-8 kPa, and even more preferably 0.1-0.3 kPa.

9. The manufacturing method according to any one of claims 3-8, further comprising, after step 5): High-temperature, high-vacuum heat treatment; To reduce oxygen levels, for example, by adding a small amount of magnesium particles; and Separation can be achieved, for example, through acid washing, filtration, and drying.

10. Tantalum powder manufactured by the manufacturing method according to any one of claims 2-9, an anode block made from the tantalum powder, and its use in the manufacture of capacitors.

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