CN-121972648-A - High-purity pressure-resistant high-specific-volume tantalum powder and preparation method thereof

Abstract

The invention provides a high-purity pressure-resistant high-specific-volume tantalum powder and a preparation method thereof, wherein the high-purity pressure-resistant high-specific-volume tantalum powder is prepared by material preparation, three-section high-temperature sintering, smelting, hydrogen absorption crushing, three-section heat treatment, airflow crushing and reduction deoxidization, according to the invention, the internal structure of the powder is controlled to be in the shape of crushed polygonal blocks, so that fine powder contained in the powder is reduced, a powder structure with high pressure resistance, high capacity and high specific volume is formed, the high specific volume is further excited through three-stage heat treatment, the pressure resistance is improved, and the tantalum powder with high pressure resistance and high specific volume is further obtained.

Inventors

• BAO XIFANG
• LI HUIYING
• CHEN LIN
• WANG DONGXIN
• LI SHURONG
• ZHANG ZIFU
• ZHANG JING
• CHEN XUEQING
• LI ZHONGXIANG
• YANG LONG

Assignees

• 中色（宁夏）东方集团有限公司

Dates

Publication Date

20260505

Application Date

20260203

Claims (7)

1. 1. A high-purity pressure-resistant high-specific-volume tantalum powder is characterized in that the granularity of the powder is 2.0-3.5 mu m, the apparent density is 1.50-1.90g/cm 3 , the specific volume reaches 8000-12000 mu FV/g under 1850 ℃/30min and 200V energizing condition, the leakage current is not more than 1.5 uV/g, and the breakdown voltage reaches more than 230V.
2. 2. The method for preparing the high-purity pressure-resistant high-specific volume tantalum powder according to claim 1, which is characterized by comprising the following steps: Preparing raw materials, namely selecting metal tantalum raw powder prepared by a magnesium reduction tantalum oxide method; Performing three-stage high-temperature sintering, namely performing isostatic pressing on tantalum raw powder to obtain tantalum rod blanks, placing the tantalum rod blanks in a high-temperature high-vacuum heat treatment furnace to perform three-stage heat preservation process high-temperature sintering, wherein the first-stage heat preservation temperature is 650-850 ℃, the heat preservation time is 2-3h, the second-stage heat preservation temperature is 1250-1450 ℃, the heat preservation time is 1-2h, the third-stage heat preservation temperature is 1750-1950 ℃, the heat preservation time is 3-5h, and the vacuum degree in the furnace is below 9X 10 -4 MPa in the heating and heat preservation processes; Smelting, namely smelting the sintered metal tantalum rod by adopting an electron beam furnace to obtain a high-purity tantalum ingot; Hydrogen absorption crushing, namely, carrying out hydrogenation and hydrogen absorption on the high-purity tantalum ingot, and crushing by adopting nitrogen protection air flow to obtain multi-edge angular block powder with the granularity of 2-4 mu m; The three-stage heat treatment, namely washing powder by nitric acid, hydrofluoric acid and pure water to remove impurities, and performing vacuum heat treatment by adopting a three-stage heat preservation process, wherein the heat preservation temperature of the first stage is 650-850 ℃ and the heat preservation time is 1.5-3h, the heat preservation temperature of the second stage is 1100-1250 ℃ and the heat preservation time is 1-2h, the heat preservation temperature of the third stage is 1400-1550 ℃ and the heat preservation time is 1-2h, and the vacuum degree in a furnace is below 5 multiplied by 10 -4 MPa in the heating and heat preservation processes; air flow crushing, namely crushing sintered powder by nitrogen protection air flow; deoxidizing, namely, performing magnesium deoxidizing treatment on the powder to prepare the high-purity pressure-resistant high-specific-volume tantalum powder.
3. 3. The method of claim 2, wherein the average particle size of the tantalum powder is 1.0-2.5 μm and the apparent density is 1.3-1.6g/cm 3 .
4. 4. The method of claim 2, wherein the tantalum flake is covered above the rod blank in the three-stage high-temperature sintering step.
5. 5. The method of claim 2, wherein a gap is reserved between the tantalum sheet and the rod blank for forming a channel for exhausting gas inside the rod blank, and the tantalum sheet has a curved surface structure with a low middle and high two ends along the length direction of the rod blank.
6. 6. The method for preparing high-purity pressure-resistant high-specific volume tantalum powder according to claim 2, wherein in the smelting step, a 1200KW electron beam furnace is adopted for smelting twice, and the purity of the metal tantalum is improved to more than 4N 5.
7. 7. The method for preparing the high-purity pressure-resistant high-specific-volume tantalum powder according to claim 2, wherein in the smelting step, a nitrogen protection airflow is adopted for crushing in the hydrogen absorption crushing step, the air inlet pressure is controlled to be 0.55-0.85MPa, the frequency of a classifying wheel is controlled to be 20-30Hz, the air inlet pressure of the airflow crushing is controlled to be 0.35-0.45MPa, the frequency of the classifying wheel is controlled to be 15-25Hz under the nitrogen protection atmosphere, and the powder with the granularity of 2.0-3.5 mu m is prepared.

Description

High-purity pressure-resistant high-specific-volume tantalum powder and preparation method thereof Technical Field The invention relates to the technical field of preparation of high specific volume tantalum powder and high purity tantalum powder for tantalum capacitors, in particular to high-purity pressure-resistant high specific volume tantalum powder and a preparation method thereof. Background Tantalum metal is widely used in the field of electrolytic capacitor fabrication due to its excellent corrosion resistance, chemical stability and dielectric properties. High purity, high specific capacity tantalum powder is a key material for preparing high performance electrolytic capacitors, and its quality directly affects the electrical performance and reliability of the capacitors. In the preparation of tantalum metal, U.S. patent No. 4169722a discloses a thermite reduction process employing induction furnace smelting to effect thermite reduction of reactive metal oxides, with reactant addition rates and power input being controlled to maintain melt temperature. US4727928a describes a process for refining tantalum or niobium by first converting tantalum powder or blocks containing volatile impurities into a raw cast metal by plasma smelting and then refining the raw cast metal by electron beam smelting. These techniques provide an effective way to obtain high purity tantalum metal. In the aspect of tantalum powder preparation technology, U.S. patent No. 10737320B2 discloses a preparation method of high-purity tantalum powder, which relates to a hydrogenation crushing process, a vacuum dehydrogenation treatment, a magnesium reduction deoxidization technology and a multistage heat treatment process, and the tantalum powder with the purity of more than 99.995% is prepared. U.S. patent No. 4508563a proposes a process for reducing the oxygen content of tantalum by reacting an alkali metal halide with tantalum metal, forming and discharging the tantalum halide and alkali metal oxide in a non-oxidizing atmosphere at 1200 ℃. Chinese patent CN1035852a describes a technology for preparing capacitor-grade high-pressure high-specific volume tantalum powder by using a carbon reduction method, which includes two-stage carbon reduction, hydraulic classification, partial doping, dehydrogenation heat treatment, and other processes. Regarding the hydrogenation and dehydrogenation behavior of tantalum metal, related studies have shown that the hydrogenation and dehydrogenation processes are affected by various factors such as temperature, pressure, and atmospheric conditions. SCIENCEDIRECT the published research paper details the hydrogenation behaviour of tantalum metal and the dehydrogenation behaviour of tantalum hydride powder under different conditions. Further studies have shown that 5N grade high purity tantalum can be produced by electron beam melting, which removes or significantly reduces nearly 60 impurity elements by four consecutive melting cycles. Although the prior art has developed to some extent in the aspects of tantalum metal preparation and tantalum powder processing, the problems still exist that the existing tantalum powder preparation process is difficult to realize high purity, accurate granularity control and excellent electrical performance at the same time, the traditional heat treatment process parameters are not accurate enough, ideal powder morphology and structure cannot be obtained, the parameter control of the hydrogenation crushing process is not accurate enough, the pressure resistance of the powder is influenced, and the tantalum powder prepared by the prior art is difficult to meet the performance requirements of a high-end capacitor in terms of specific capacity and breakdown voltage. Therefore, a new tantalum powder preparation method needs to be developed, and the high-performance tantalum powder with high specific capacity and high breakdown voltage is prepared by optimizing parameter control of each process link. Disclosure of Invention In view of the defects, the invention provides the high-purity pressure-resistant high-specific volume tantalum powder, wherein the granularity of the powder is 2.0-3.5 mu m, the apparent density is 1.50-1.90g/cm 3, the specific volume reaches 8000-12000 mu FV/g under 1850 ℃/30min and 200V energizing condition, and the breakdown voltage reaches more than 230V. Also provides a preparation method of the high-purity pressure-resistant high-specific-volume tantalum powder, which comprises the following steps: Preparing raw materials, namely selecting metal tantalum raw powder prepared by a magnesium reduction tantalum oxide method; Performing three-stage high-temperature sintering, namely performing isostatic pressing on tantalum raw powder to obtain tantalum rod blanks, placing the tantalum rod blanks in a high-temperature high-vacuum heat treatment furnace to perform three-stage heat preservation process high-temperature sintering, wherein the first-stag