Superfine capacitance-grade tantalum powder and preparation method thereof

Abstract

The embodiment of the invention discloses superfine capacitance-level tantalum powder and a preparation method thereof. The method comprises the following steps: S1, reacting alkaline earth / rare earth metal oxide or alkaline earth / rare earth metal carbonate with tantalum oxide to generate tantalum composite oxide; the alkaline earth / rare earth metal oxide comprises MgO, CaO, Ce2O3, Y2O3 and La2O3, and the alkaline earth / rare earth metal carbonate comprises MgCO3, CaCO3, Ce2O3, Y2 (CO3) 3 and La2 (CO3) 3; the tantalum composite oxide is BxTayOz, and B is Mg, Ca, Y, Ce or La; s2, the tantalum composite oxide reacts with a metal reducing agent containing metal elements in the tantalum composite oxide, and by-products of metal oxide and tantalum powder are obtained; s3, the by-product metal oxide and the tantalum powder are washed with an acid solution to be separated, the metal oxide is removed, and superfine capacitance-level tantalum powder is obtained; the tantalum capacitor with excellent performance can be prepared by using the superfine capacitance-level tantalum powder, and the tantalum capacitor has a good application prospect in the field of capacitors.

Description

Technical Field

[0001] The invention belongs to the technical field of high specific capacitance capacitors, and in particular relates to ultrafine capacitor-grade tantalum powder and a preparation method thereof. Background Art

[0002] Tantalum capacitors are widely used in electronic circuits due to their small size, large capacity, high thermal stability, low leakage current, high reliability and many other advantages. Key areas such as new generation information technology and intelligent manufacturing have put forward higher requirements on the performance of tantalum capacitors. The specific capacitance of tantalum capacitors is inversely proportional to the particle size of tantalum powder, so ultrafine tantalum powder is favored by high specific capacitance tantalum capacitors.

[0003] The particle size of tantalum powder is closely related to its preparation process. The sodium reduction of potassium fluorotantalate is the mainstream production process for preparing tantalum powder at home and abroad. However, the sodium reduction of potassium fluorotantalate is a violent exothermic reaction, which will lead to local heat accumulation, making it easy for the crystal nucleus to grow during the preparation of tantalum powder, resulting in coarse primary particles of tantalum powder; in addition, liquid-liquid reduction leads to a large potassium fluorotantalate concentration gradient in the reaction system, and low concentration leads to the production of fine particles, making it difficult to improve the uniformity of the primary particles of sodium-reduced tantalum powder, which limits the application of sodium-reduced tantalum powder in high-voltage and high-reliability tantalum capacitors. At present, a large amount of diluents such as NaCl, KCl, KF, or halide salts or mixtures thereof or mechanical stirring are usually added to enhance heat dissipation, thereby inhibiting the rapid growth of grains, but these methods introduce a large amount of impurities into the tantalum powder, resulting in a decrease in the purity of the tantalum powder.

[0004] In order to meet the high requirements of automated production of capacitors, and the rise of some emerging technologies, such as surface mount technology, tantalum capacitors are being driven towards miniaturization and thinning, and their performance is being improved towards higher specific capacitance and smaller volume. This poses a greater challenge to the development of tantalum capacitor manufacturing raw material "tantalum powder for capacitors", which requires high specific capacitance, small particle size, and good fluidity to meet the needs of miniaturization and high capacity of capacitors.

[0005] Current tantalum powder cannot meet the manufacturing requirements of high energy density tantalum capacitors. Summary of the invention

[0006] In view of this, on the one hand, some embodiments disclose a method for preparing ultrafine capacitor-grade tantalum powder, comprising the steps of:

[0007] S1, alkaline earth / rare earth metal oxides or alkaline earth / rare earth metal carbonates, react with tantalum oxide to generate tantalum composite oxides; alkaline earth / rare earth metal oxides include MgO, CaO, Ce2O3, Y2O3, La2O3, and alkaline earth / rare earth metal carbonates include MgCO3, CaCO3, Ce2O3, Y2(CO3)3, La2(CO3)3; tantalum composite oxide is BxTayOz, wherein B is Mg, Ca, Y, Ce or La;

[0008] S2, the tantalum composite oxide reacts with a metal reducing agent containing the metal element in the tantalum composite oxide to obtain a by-product metal oxide and tantalum powder;

[0009] S3, the secondary metal oxide and tantalum powder are washed with an acid wash solution to remove the metal oxide and obtain ultrafine capacitor-grade tantalum powder.

[0010] On the other hand, some embodiments disclose ultrafine capacitor grade tantalum powder obtained by a method for preparing ultrafine capacitor grade tantalum powder, wherein the particle size of the ultrafine capacitor grade tantalum powder is less than 100 nm.

[0011] The method for preparing ultrafine capacitor-grade tantalum powder disclosed in the embodiment of the present invention uses alkaline earth / rare earth oxides or carbonates and tantalum oxide to prepare tantalum composite oxides, and uses the tantalum composite oxides as a precursor to further react with a metal reducing agent. Since the reaction thermal effect of the tantalum composite oxides and the metal reducing agent is small, heat concentration in the product is avoided, and the coarse grains of the generated tantalum powder are effectively prevented, thereby obtaining ultrafine capacitor-grade tantalum powder; the preparation reaction temperature range is wide, and it can be applied to solid-solid reactions, liquid-solid reactions, and gas-solid reactions; the ultrafine capacitor-grade tantalum powder can be used to prepare tantalum capacitors with excellent performance, and has good application prospects in the capacitor field. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a scanning electron microscope image of the ultrafine capacitor-grade tantalum powder of Example 1;

[0013] Figure 2 This is a scanning electron microscope image of tantalum metal powder in the prior art;

[0014] Figure 3 This is a scanning electron microscope image of the ultrafine capacitor-grade tantalum powder of Example 2. DETAILED DESCRIPTION

[0015] The word "embodiment" used herein as an "exemplary" does not necessarily mean that any embodiment described is superior or better than other embodiments. Performance index tests in the embodiments of the present invention are performed using conventional test methods in the art unless otherwise specified. It should be understood that the terms described in the embodiments of the present invention are only used to describe specific implementation methods and are not intended to limit the contents disclosed in the embodiments of the present invention.

[0016] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by ordinary technicians in the technical field to which the embodiments of the present invention belong; other experimental methods and technical means not specifically specified in the embodiments of the present invention refer to experimental methods and technical means commonly used by ordinary technicians in the field.

[0017] The terms "substantially" and "approximately" used herein are used to describe small fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. The numerical data represented or presented in the range format herein are used only for convenience and brevity, and should therefore be flexibly interpreted as including not only the values ​​clearly listed as the limits of the range, but also all independent values ​​or sub-ranges contained in the range. For example, the numerical range of "1-5%" should be interpreted as including not only the clearly listed values ​​of 1% to 5%, but also the independent values ​​and sub-ranges within the range shown. Therefore, independent values ​​such as 2%, 3.5% and 4% and sub-ranges such as 1%-3%, 2%-4% and 3%-5% are included in this numerical range. This principle also applies to the range of only one numerical value. In addition, such an interpretation applies regardless of the width of the range or the characteristics described.

[0018] In this document, including in the claims, transitional words such as "comprises," "includes," "with," "having," "containing," "involving," "accommodating," etc. are understood to be open-ended, i.e., meaning "including but not limited to." Only the transitional words "consisting of" and "composed of" are closed transitional words.

[0019] In order to better illustrate the present invention, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the gist of the present invention.

[0020] Under the premise of no conflict, the technical features disclosed in the embodiments of the present invention may be arbitrarily combined, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present invention.

[0021] In some embodiments, the method for preparing ultrafine capacitor grade tantalum powder comprises the steps of:

[0022] S1, alkaline earth / rare earth metal oxides or alkaline earth / rare earth metal carbonates, react with tantalum oxide to generate tantalum composite oxides; alkaline earth / rare earth metal oxides include MgO, CaO, Ce2O3, Y2O3, La2O3, and alkaline earth / rare earth metal carbonates include MgCO3, CaCO3, Ce2O3, Y2(CO3)3, La2(CO3)3; tantalum composite oxide is BxTayOz, wherein B is Mg, Ca, Y, Ce or La;

[0023] Generally, the reaction temperature of alkaline earth / rare earth metal oxides or alkaline earth / rare earth metal carbonates and tantalum oxide to form tantalum composite oxides is 600-1500°C; the reaction temperature needs to be determined according to the reaction properties of the alkaline earth metal and the rare earth metal;

[0024] S2, the tantalum composite oxide reacts with a metal reducing agent containing the metal element in the tantalum composite oxide to obtain a by-product metal oxide and tantalum powder; usually, the metal reducing agent is a single substance of the metal element in the tantalum composite oxide or an alloy formed by the single substance and other alkaline earth metals or rare earth metals; the metal single substance reducing agent is Mg, Ca, Y, Ce, La or an alloy thereof;

[0025] Typically, the reduction reaction is carried out in an inert atmosphere at a reaction temperature of 600 to 1500°C.

[0026] In some embodiments, the alkaline earth metal oxide MgO reacts with tantalum oxide to generate tantalum-magnesium composite oxide, or magnesium tantalate, and the reducing agent to be selected is Mg, or an alloy of Mg and any one or more metals of Ca, Y, Ce or La;

[0027] S3. The by-product metal oxide and tantalum powder are washed with an acid solution to remove the metal oxide and obtain ultrafine capacitor-grade tantalum powder.

[0028] Usually, tantalum composite oxide is prepared by using oxides or carbonates of alkaline earth or rare earth and tantalum oxide, and the tantalum composite oxide is used as a precursor to further react with a metal reducing agent. Since the tantalum composite oxide decomposes and absorbs heat at high temperature, and the metal oxide generated by the decomposition has a large heat capacity, the thermal effect of the reaction process of the tantalum composite oxide and the metal reducing agent is small, which avoids heat concentration in the product, and the tantalum powder grains grow slowly, which effectively prevents the coarse grains of the generated tantalum powder, and obtains ultrafine capacitor-grade tantalum powder.

[0029] Generally, the pickling solution is hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid or any combination thereof.

[0030] In some embodiments, the particle size of the ultrafine capacitor-grade tantalum powder obtained by the method for preparing the ultrafine capacitor-grade tantalum powder is less than 100 nm.

[0031] In some embodiments, ultrafine capacitor-grade tantalum powder is used to prepare tantalum capacitors. The ultrafine capacitor-grade tantalum powder prepared in the embodiment of the present invention has a particle size of less than 100nm, a high specific capacitance, a small particle size, and better fluidity, and can be suitable for the preparation of miniaturized and thin tantalum capacitors. Based on current emerging technologies, such as surface mount technology, ultrafine capacitor-grade tantalum powder with a particle size of less than 100nm can be used to prepare miniaturized thin tantalum capacitors.

[0032] The technical details are further illustrated below in conjunction with embodiments.

[0033] Example 1

[0034] In Example 1, the method for preparing ultrafine capacitor-grade tantalum powder includes:

[0035] S1, magnesium oxide and tantalum oxide are fully mixed in a molar ratio of 4:1, and pressed into blocks under a certain pressure, and then magnesium tantalate Mg4Ta2O9, a composite oxide of tantalum, is synthesized at a high temperature;

[0036] S2, using the precursor magnesium tantalate Mg4Ta2O9 as a tantalum-containing raw material and metallic magnesium as a reducing agent to prepare ultrafine capacitor-grade tantalum powder;

[0037] Specifically, 3.016 g of magnesium tantalate Mg4Ta2O9 and 0.911 g of Mg powder were weighed, the two were fully mixed and spread flat in a corundum crucible, and then the crucible was placed horizontally in a horizontal tube furnace. The sealing flanges at both ends of the furnace tube were installed and checked for air tightness. Then argon was introduced as an inert protective gas, and the gas was washed by vacuuming + introducing argon. The gas washing was circulated three times to ensure that there were no other gases affecting the reaction in the furnace tube. After the atmosphere in the device was replaced with normal pressure argon, the heating was turned on after maintaining a stable flow rate of 200 mL / min, so that the temperature of the reaction zone containing the mixed raw materials reached 900 ° C and was kept warm for 3 hours, so that the magnesium remained in a liquid state during the reaction. After the reaction is completed and the reaction zone is completely cooled to room temperature, the ventilation is stopped; a certain vacuum is drawn and a certain amount of room temperature air is introduced for passivation. The product is taken out after the passivation is completed. The obtained product is acid-washed and washed with water, and then the tantalum powder is dried.

[0038] Figure 1 This is an electron scanning microscope photo of the metal tantalum powder obtained in Example 1. After phase composition identification and microscopic morphology observation, pure tantalum powder was obtained after acid washing. Figure 1 It shows that the particle size of tantalum powder is relatively fine, reaching the level of 40 to 60 nm. The overall particle shape is spherical and has good fluidity.

[0039] Figure 2This is an electron scanning microscope photo of tantalum powder obtained by reducing tantalum pentoxide with liquid magnesium using the traditional method. After phase composition identification and microscopic morphology observation, pure tantalum powder was obtained after acid washing. Compared with the morphology of tantalum powder in Example 1, Figure 2 It shows that the particle size of tantalum powder is coarser, and more particles reach the scale of 200nm.

[0040] Depend on Figure 1 , Figure 2 It can be seen from the particle size distribution data that the tantalum powder prepared by the new process of reducing magnesium tantalate with liquid magnesium in Example 1 has a significantly smaller particle size, and the ultrafine capacitor-grade tantalum powder prepared by the method of Example 1 has a better particle size distribution.

[0041] The ultra-fine capacitor grade tantalum powder was used to prepare a miniaturized thin tantalum capacitor sample. The specific capacitance of the thin tantalum capacitor was 36967μFV·g -1 .

[0042] Example 2

[0043] In Example 2, the method for preparing ultrafine capacitor-grade tantalum powder includes:

[0044] S1, magnesium oxide and tantalum oxide are fully mixed in a molar ratio of 1:1, and pressed into blocks under a certain pressure, and then magnesium tantalate MgTa2O6, a composite oxide of tantalum, is synthesized at a high temperature;

[0045] S2, using the precursor magnesium tantalate as a tantalum-containing raw material and metallic magnesium as a reducing agent to prepare ultrafine capacitor-grade tantalum powder;

[0046] High-temperature synthesized precursor magnesium tantalate MgTa2O6 is used as the tantalum-containing raw material, and metallic magnesium is used as the reducing agent. A double-layer stainless steel crucible connected by threads is used, and the two layers are separated by a porous plate. The upper layer contains the raw material MgTa2O6 and also serves as a reaction zone. The lower layer contains magnesium powder. The lower layer is connected to an external gas system through a ventilated stainless steel pipe for carrier gas purging, which is convenient for carrying evaporated magnesium vapor into the reaction zone for reaction.

[0047] First, weigh 0.911g of Mg powder and spread it on the bottom of the lower crucible, then weigh 2.411g of magnesium tantalate MgTa2O6 and spread it on the porous plate, tighten the upper and lower structures through threads to ensure that there is no powder leakage; place the crucible horizontally in the horizontal tube furnace, install the sealing flanges at both ends of the furnace tube, and check the air tightness; then introduce argon as an inert protective gas, and wash the gas by vacuuming + introducing argon, and cycle the washing three times to ensure that there is no other gas that affects the reaction in the furnace tube. After the atmosphere in the device is replaced with atmospheric pressure argon, connect the pipeline of the crucible with the external gas line, introduce argon as a carrier gas, and maintain a stable flow of 200mL / min to carry the evaporated magnesium vapor; then officially start heating, so that the temperature of the reaction zone containing the raw materials reaches 1000℃ and then keeps warm for 3h, so that magnesium remains in a gaseous state during the contact reaction with the magnesium tantalate raw material. After the reaction is completed and the reaction zone is completely cooled to room temperature, the ventilation is stopped; a certain vacuum is drawn and a certain amount of room temperature air is introduced for passivation. After the passivation is completed, the product is taken out, the product is acid-washed and water-washed, and then the tantalum powder is dried.

[0048] Figure 3 This is an electron scanning microscope photo of the metal tantalum powder obtained in Example 2. After phase composition identification and microscopic morphology observation, pure tantalum powder was obtained after pickling. The tantalum powder prepared by this process has a fine particle size, and the particle size of the tantalum powder is basically at the level of 100nm.

[0049] The micro-sized thin tantalum capacitor samples were prepared using ultra-fine capacitor-grade tantalum powder. The specific capacitance of the thin tantalum capacitor was measured to be 38478μFV·g -1 .

[0050] The method for preparing ultrafine capacitor-grade tantalum powder disclosed in the embodiment of the present invention uses alkaline earth / rare earth oxides or carbonates and tantalum oxide to prepare tantalum composite oxides, and uses the tantalum composite oxides as a precursor to further react with a metal reducing agent. Since the reaction thermal effect of the tantalum composite oxides and the metal reducing agent is small, heat concentration in the product is avoided, and the coarse grains of the generated tantalum powder are effectively prevented, thereby obtaining ultrafine capacitor-grade tantalum powder; the preparation reaction temperature range is wide, and it can be applied to solid-solid reactions, liquid-solid reactions, and gas-solid reactions; the ultrafine capacitor-grade tantalum powder can be used to prepare tantalum capacitors with excellent performance, and has good application prospects in the capacitor field.

[0051] The technical solutions disclosed in the embodiments of the present invention and the technical details disclosed in the embodiments are merely illustrative of the inventive concept of the present invention and do not constitute a limitation on the technical solutions of the embodiments of the present invention. Any conventional changes, replacements or combinations of the technical details disclosed in the embodiments of the present invention have the same inventive concept as the present invention and are within the protection scope of the claims of the present invention.

Claims

1. A method for preparing ultrafine capacitor-grade tantalum powder, characterized in that: Includes steps: S1, alkaline earth / rare earth metal oxide or alkaline earth / rare earth metal carbonate, reacts with tantalum oxide to generate tantalum composite oxide; the alkaline earth / rare earth metal oxide includes MgO, CaO, Ce2O3, Y2O3, La2O3, the alkaline earth / rare earth metal carbonate includes MgCO3, CaCO3, Ce2O3, Y2(CO3)3, La2(CO3)3; the tantalum composite oxide is BxTayOz, wherein B is Mg, Ca, Y, Ce or La; S2, the tantalum composite oxide reacts with a metal reducing agent containing the metal element in the tantalum composite oxide to obtain a by-product metal oxide and tantalum powder; S3, the accessory metal oxide and tantalum powder are washed with an acid solution to remove the metal oxide and obtain ultrafine capacitor-grade tantalum powder.

2. The method for preparing ultrafine capacitor-grade tantalum powder according to claim 1, characterized in that: The metal reducing agent is a single substance or alloy of the metal element in the tantalum composite oxide.

3. The method for preparing ultrafine capacitor-grade tantalum powder according to claim 2, characterized in that: The metal reducing agent is Mg, Ca, Y, Ce, La or an alloy thereof.

4. The method for preparing ultrafine capacitor-grade tantalum powder according to claim 1, characterized in that: In step S1, the reaction temperature for generating tantalum composite oxide is 600 to 1500°C.

5. The method for preparing ultrafine capacitor-grade tantalum powder according to claim 1, characterized in that: In step S2, step S2 is carried out in an inert atmosphere, and the reaction temperature is 600-1500°C.

6. The method for preparing ultrafine capacitor-grade tantalum powder according to claim 1, characterized in that: In step S3, the pickling solution is hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid or any combination thereof.

7. Ultrafine capacitor grade tantalum powder, characterized in that: The ultrafine capacitor-grade tantalum powder is obtained by the preparation method of any one of claims 1 to 6, wherein the particle size of the ultrafine capacitor-grade tantalum powder is less than 100 nm.

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