CZ306250B6 - Method of passivating tantalum metal surface and apparatus therefor - Google Patents

Abstract

In the present invention, there is provided a method of passivating tantalum metal surface, wherein the method comprises cooling tantalum metal to or below 32 degC and/or passivating tantalum metal surface by oxygen-containing gas with a temperature of 0 degC. or below. Also provided is an apparatus for passivating tantalum metal surface for applying the method, comprising a heat treatment furnace, an argon forced-cooling device and/or a device for cooling oxygen-containing gas.

Description

A method of passivating a tantalum metal surface and an apparatus for carrying out the method

Field of technology

The present invention relates to the field of tantalum metal production, and in particular to a method and apparatus for producing tantalum powder or porous tantalum metal for an electrolytic capacitor.

Prior art

Tantalum metal is mainly used for the production of tantalum electrolytic capacitors. However, a method of making tantalum electrolytic capacitors usually comprises pressing tantalum powder into a molding, sintering the molding in a vacuum furnace into a porous body in which the particles are bonded together, subjecting the porous agglomerate to anodic oxidation in a suitable electrolyte to form a homogeneous, bonded dielectric oxidation film. surface of the porous particles, i.e., an anode covering the cationic material on the surface of the oxide film is formed, and then the anode and cathode of the capacitors are coated and formed. The parameters used to evaluate tantalum electrolytic capacitors mainly include capacitive resistance, DC (leakage direct current) and equivalent series of resistors (ESR). The development tendency of capacitors is to have a high capacitance, a low leakage current and a low equivalent series of resistors (low tg6 anodes). The amount of impurities in the level of tantalum powder capacitors, which is the main starting product of tantalum electrolytic capacitors, especially the amount of oxygen, has the greatest effect on the leakage current. The low leakage current requires that the tantalum powder have a low oxygen content.

Typically, tantalum powders for electrolytic capacitors should be subjected to heat treatment to purify the tantalum powders on the one hand and condense the tantalum microparticles into porous particles on the other hand to improve physical properties such as the flowability of the tantalum powders. properties of electrolytic capacitors made from them, such as capacitance, leakage current and equivalent series resistors (ESR) of capacitors. U.S. Pat. No. 3,473,915 discloses the heat treatment of tantalum powders comprising heat condensing 2 to 30 microns of tantalum powders at 1200 to 1500 ° C under an inert atmosphere to form multiple bonded porous particles to obtain condensed tantalum powders. In the last few decades, tantalum powder manufacturers and capacitor manufacturers have conducted extensive studies of the heat treatment of tantalum powders during the development of tantalum powders having a high specific surface area and small types of capacitors. The state of the art concerning the agglomeration (condensation) of heat treatment of tantalum powders can be found in the following patent documents: JP 2-34701, US 5,954,856, WO 99/61,184, CN 1,197,707 A, CN 1,238,251 A, CN 1,899 730 A.

The deoxidizing heat treatment of tantalum powders usually involves mixing an appropriate amount of an alkali or rare earth metal reducing agent or hydride thereof with tantalum powders, heat treating at 700 to 1100 ° C under vacuum or an inert atmosphere to condense the tantalum powders and remove oxygen. The prior art relating to the deoxidizing heat treatment of tantalum powders can be found in the following patent documents. U.S. 4,483,819, U.S. 4,537,641, CN 1,052,070 A, etc.

Because tantalum metal is a metal having a strong affinity for oxygen, tantalum and oxygen are chemically bonded to Ta ₂ O ₅ , which is an exothermic reaction. If the surface of the tantalum powders has a layer of dense oxygen film, the tantalum can be protected against further oxidation. When such tantalum particles coated with a dense oxygen film are heated to a temperature above 300 ° C, the tantalum oxide cracks and is damaged, some oxygen dissolves in the tantalum substrate, and some oxygen is dispersed or concentrated. Therefore, the heated tantalum powders are oxidized after cooling away from the surface and in contact with the oxygen-containing medium. The powders adsorb new oxygen and the oxygen content increases. If. i.

the rate of oxygen adsorption cannot be effectively controlled, tantalum powders ignite automatically. Therefore, the technology of passivation of tantalum powders with controlled oxidation has developed. Such tantalum passivation means that when the oxidation film of tantalum powders is damaged in contact with the oxygen-containing medium, the oxygen supply rate is artificially controlled to control the oxidation rate and temperature of the tantalum powders under controlled conditions to form a passivated oxide film on the tantalum surface. powders and prevented oxidative oxidation. Therefore, tantalum powders having a high specific surface area (specific surface area above 0.1 m ² / g) should be subjected to passivation after heat treatment.

The tantalum metal surface passivation described in the present disclosure includes surface passivation of tantalum powders and surface passivation of a porous body formed by compressing tantalum powders.

As electronic components evolve toward miniaturization, tantalum microparticles having a larger specific surface area are needed. In the case of tantalum powders having a high specific surface area, when the tantalum powder per unit volume generated more heat during passivation, the temperature of the tantalum powder increases much faster during passivation. During the passivation of tantalum powder after heat treatment, it has often been found that the temperature rises abruptly. This is due to the fact that tantalum powders begin to oxidize violently, and aeration passivation must stop immediately. After the temperature dropped, the aeration passivation could proceed slowly. After passivation and emptying, white tantalum oxide plates were found on the surface of the tantalum powders, and the tantalum powder, which had no white tantalum oxide, also had a high oxygen content. If the passivation is not precisely controlled, the tantalum powder may ignite. Therefore, passivation of tantalum powder and a key technology for the development of tantalum powders with a high specific surface area become difficult.

Although the surface area of porous moldings formed from tantalum powders having a high specific surface area, e.g., tantalum moldings for making anode electrolytic capacitors, decreases after sintering, the area of the porous agglomerate also oxidizes and forms a high temperature to produce a porous agglomerate containing excess oxygen and tantalum brittle wires, or even caused sharp oxidation of the porous tantalum agglomerate. The tantalum anode made with such a tantalum agglomerate has a high leakage current. Thus, a porous agglomerate formed from tantalum powders with a high specific surface area should be subjected to a passivation treatment after sintering.

Known state comprising US 6,927,967 B2, US 6,435,161 B1, US 6,238,456 B1, CN 1,919,508 A, CN 101,404,213 A, US 6,992,881 B2, US 7,485,256 B2 and CN 1,899,728 A describes the passivation of tantalum powders. However, this prior art requires the introduction of an oxygen-containing gas at room temperature into a vacuum furnace subjected to heat treatment and cooled to room temperature or higher to passivate the tantalum powders. Such processing and passivation takes a long time and causes violent oxidation of tantalum powders. Chinese Patent Application CN 101348891 A discloses a method of reducing oxygen by controlled passivation of tantalum powder and processing magnesium, wherein the passivation treatment is performed using pure oxygen. This method is not suitable for the passivation of tantalum powders with a high specific surface area and the passivation treatment takes a long time and has a low yield.

Due to the above problems of the prior art, it is therefore desirable to provide a method and apparatus for producing low oxygen tantalum powders and porous tantalum agglomerates, and this method and apparatus can prevent violent oxidation during passivation of the tantalum metal surface.

. 7 CZ 306250 B6

The essence of the invention

In view of the problems existing in the prior art, it is an object of the present invention to provide a method for passivating a tantalum metal surface which can prevent violent oxidation during passivation. Another object of the invention is to provide an apparatus for carrying out a method for passivating a tantalum metal surface.

The present invention achieves the above objects by providing a method and apparatus for passivating a tantalum metal surface. In this method, the tantalum metal is subjected to a heat treatment and then cooled, and the passivation is performed using low-temperature oxygen-containing gases.

In particular, the present invention provides the following technical solutions:

(1) A method of passivating a tantalum metal surface, characterized in that it comprises the following steps:

(a) forming a tantalum metal that has been heat treated;

(b) reducing the temperature of the tantalum metal to a temperature of 32 ° C or lower, preferably below 30 ° C and even more preferably to 10 to 30 ° C, using cooled inert gases;

(c) introducing an oxygen-containing gas to passivate the tantalum metal surface;

(d) optionally repeating step (c) one or more times.

(2) A method of passivating a tantalum metal surface, characterized in that it comprises the following steps:

(a) forming a tantalum metal that has been heat treated;

(b) lowering the temperature of the tantalum metal to room temperature;

(c) introducing an oxygen-containing gas at a temperature of 0 ° C or lower, preferably 0 to -40 ° C, to passivate the tantalum metal surface; and (d) optionally repeating step (c) one or more times.

(3) A method of passivating a tantalum metal surface, characterized by the following steps:

(a) forming a tantalum metal that has been heat treated;

(b) lowering the temperature of the tantalum metal to a temperature of 32 ° C or lower, preferably below 30 ° C, and even more preferably 10 to 30 ° C, using cooled inert gases;

(c) introducing an oxygen-containing gas at a temperature of 0 ° C or lower, and preferably 0 to -40 ° C, to passivate the tantalum metal surface; and (d) optionally repeating step (c) one or more times.

(4) The method for passivating a tantalum metal surface according to the technical solution (1) or (2) or (3), characterized in that the oxygen-containing gas is air, a mixed gas of inert gas and oxygen, or a mixed gas of inert gas and air.

(5) The method for passivating a tantalum metal surface according to the technical solution (1) or (2) or (3), characterized in that the oxygen-containing gas is a mixed gas of argon and air.

(6) The method for passivating a tantalum metal surface according to the technical solution (1) or (2) or (3), characterized in that the oxygen concentration in the gas-containing gas is 21% by volume or less, preferably 5 to 20% by volume.

(7) The method for passivating a tantalum metal surface according to the technical solution (1) or (3), characterized in that the inert gas is argon.

(8) Equipment for passivation of tantalum metal surface containing heat treatment furnace and equipment for forced cooling of argon, where heat treatment furnace contains: hearth, casing

-3GB 306250 B6 with a water-cooled jacket forming a hearth, a supply of oxygen-containing passivation air, a supply of argon entering the hearth, an argon outlet located at the top of the heat treatment furnace, a heating element arranged in the hearth and a heat treatment crucible for locating the tantalum metal being processed ; the argon forced cooling device comprises a condenser, a heat exchanger chamber, a cooled argon inlet, a cooled argon outlet, and a circulation pump;

wherein the supply of cooled argon is connected to the outlet of argon at the top of the hearth of the heat treatment furnace; during the passivation treatment, the high temperature argon in the heat treatment furnace exits the argon outlet, passes through a connecting pipe cooled by cooling water on the periphery, and enters the exchanger chamber on one side of the exchanger chamber; in the exchanger chamber, the incoming argon is cooled, and then exits the argon outlet on the other side of the exchanger chamber and is fed to a circulating pump, the cooled argon is extruded by a circulating pump and passed through a connecting pipe to a heat treatment furnace from an argon inlet at the bottom of the heat furnace. processing to reduce the passivated tantalum metal to a temperature of 32 ° C or lower to passivate it with an oxygen-containing gas.

(9) Apparatus for passivating a tantalum metal surface comprising a heat treatment furnace and a cooling system for oxygen-containing gases, the heat treatment furnace comprising: a hearth, a jacket with a water-cooled jacket forming the hearth, an oxygen-containing gas supply for passivating the interior of the hearth; tubes, a heater arranged inside the hearth and a heat treatment crucible for locating the tantalum metal to be processed; the oxygen-containing gas cooling system comprises: a condenser, an exchanger chamber, an oxygen-containing gas inlet connected to one side of the exchanger chamber, an argon inlet, and an oxygen-containing gas outlet connected to the other side of the exchanger chamber;

where, during the passivation treatment, the oxygen-containing gases and argon are fed from their respective inlets to the exchanger chamber and mixed, the mixed gases are cooled to below 0 ° C by heat exchange with a medium tube in the exchanger chamber, the oxygen-containing cooled gases leaving a different outlet Oxygen-containing gases from the exchanger chamber are passed through thermal insulation pipes and fed to a heat treatment furnace from the top of the heat treatment furnace for passivation of passivated tantalum metal.

(10) An apparatus for passivating a tantalum metal surface comprising a heat treatment furnace, an argon forced cooling apparatus, and an oxygen-containing gas cooling system, the heat treatment furnace comprising: a hearth, a shell with a water-cooled jacket forming the hearth, a gas supply containing oxygen for passivation to be introduced into the hearth, an argon supply to the hearth, an argon outlet located at the top of the heat treatment furnace, a heater arranged inside the hearth, and a heat treatment crucible for locating the tantalum metal being processed;

the forced argon cooling device comprises a condenser, an exchanger chamber, a cooled argon inlet, a cooled argon outlet and a circulation pump; where the supply of cooled argon is connected to the outlet of argon at the top of the hearth of the heat treatment furnace, during the passivation of high temperature argon in the heat treatment furnace exits the argon outlet, passes through cooling water cooled by connecting pipes around the perimeter and enters the exchanger chamber on one side exchanger chambers; in the exchanger chamber, the supplied argon is cooled, and then leaves the argon outlet on the other side of the exchanger chamber and is fed to the circulation pump, the cooled argon is forced out by the circulation pump and fed through a connecting pipe to the heat treatment furnace from the argon supply in the lower parts of a heat treatment furnace to reduce passivated tantalum metal to a temperature of 32 ° C or lower; and the oxygen-containing gas cooling system comprises a condenser, a heat exchanger chamber, an oxygen-containing gas inlet connected to one end of the exchanger chamber, an argon inlet, and an oxygen-containing gas outlet connected to the other end of the exchanger chamber; during the passivation treatment, the oxygen-containing gases and argon enter the exchanger chamber from their respective inlets and mix, the mixed gases are cooled to below 0 ° C by heat exchange with the medium line in the exchanger chamber, the oxygen-containing cooled gases exit the outlets on the other side of the exchanger. chambers, pass through thermal insulation pipes and enter the furnace from the top of the heat treatment furnace to passivate the passivated tantalum metal.

(11) Apparatus for passivating the surface of tantalum metal according to technical solution (8) or (10), characterized in that the tantalum metal is cooled to 10 to 30 ° C by means of a forced argon cooling device so as to passivate oxygen-containing gases.

(12) Apparatus for passivating a tantalum metal surface according to technical solution (9) or (10), characterized in that the mixed gases are cooled to form an oxygen-containing gas for passivation at -40 to 0 ° C.

The advantages of the method for passivating the tantalum metal surface are safety, reliability and high yield, and the obtained tantalum powders have a low oxygen and hydrogen content and the anodes and tantalum electrolytic capacitors made of tantalum powders show good electrical properties.

It is to be understood that the foregoing general descriptions and the following detailed description taken in conjunction with the drawings and detailed description of the preferred examples are illustrative descriptions that are used to further explain the claimed invention, not to limit the invention.

Explanation of drawings

Giant. 1 is a diagram of a device for passivating a tantalum metal surface according to the prior art.

Giant. 2 shows an apparatus for passivating a tantalum metal surface with an apparatus for forcibly cooling an inert gas according to the present invention.

Giant. 3 shows an example of an apparatus for passivating a tantalum metal surface with an oxygen-containing gas cooling system according to the present invention.

Giant. 4 shows an example of an apparatus for passivating a tantalum metal surface with an apparatus for forcibly cooling an inert gas and an oxygen-containing gas cooling system according to the present invention.

Giant. 5 shows another diagram of a device for passivating a tantalum metal surface according to the prior art.

Giant. 6 shows another example of an apparatus for passivating a tantalum metal surface with an inert gas cooling apparatus according to the present invention.

Giant. 7 shows another example of an apparatus for passivating a tantalum metal surface with an oxygen-containing gas cooling system according to the present invention.

Giant. 8 shows another example of an apparatus for passivating a tantalum metal surface with an apparatus for forcibly cooling an inert gas and an oxygen-containing gas cooling system according to the present invention.

Examples of embodiments of the invention

The present invention is further described with reference to the drawings and preferred examples:

-5i

In the description, the unit ppm refers to "parts per million based on weight ratio, unless otherwise explicitly stated.

The present invention provides a method for passivating a tantalum metal surface. In the process of the present invention, the tantalum metal to be heat treated and passivated may be chemically reduced tantalum powders that have not been heat treated, e.g., tantalum powders prepared by reducing tantalum fluoride with sodium, raw material powder obtained by hydrogenation and grinding of tantalum ingots and heat processed tantalum powders and porous tantalum agglomerates formed by compressing tantalum powders, etc. Prior to the heat treatment, the tantalum powders are preferably pelletized, in particular subjected to spheroid granulation. During the granulation of tantalum powders, any chemical beneficial for controlling the shrinkage rate of tantalum powders at high sintering temperature and reducing surface area loss at the desired ratio can be added as a refractory such as phosphorus, nitrogen, boron, oxygen. In the process according to the invention, the tantalum powders can be subjected to heat treatment by known technologies, for example, the processes mentioned in CN 1410 209 A, CN 1 238 251 A and CN 1 899 730 A, which are incorporated herein by reference.

In the process according to the invention, the inert gas forced cooling device can be used to cool the heat-treated tantalum metal to a temperature below 32 ° C. The inert gas may be argon, helium, xenon or a mixture thereof. However, from a cost point of view, argon is preferably used to perform the forced cooling.

According to the method of the present invention, the particle shape of the tantalum powders to be heat-treated is not limited; they can be grainy, flat, polygonal, or any combination thereof. The specific surface area of the tantalum powders is not particularly necessary and may be 0.1 m ² / g to 10 ² / g, preferably 0.2 to 5 m ² / g.

The deoxidizing heat treatment of tantalum powders in a reducing atmosphere can be carried out by technologies known per se. Typically, small amounts of a reducing agent having an affinity for oxygen greater than tantalum for oxygen, such as rare earth alkali metals, rare earth metals and their hydrides, can be added to tantalum powders; most commonly, magnesium metal powder is added to the tantalum powders in an amount of 0.5 to 4% by weight of the tantalum.

Giant. 1 is a diagram of an apparatus 100 for passivating a surface of heat-treated tantalum metal according to the prior art. The device for passivating the surface of heat-treated tantalum metal comprises: a hearth HO, a jacket 111 with a water-cooled jacket having a water inlet 111-1 and a water outlet 111-2, the shell forming a hearth 110 and a vacuum gauge 112 connected to the hearth 110, a passivation gas inlet 120 containing oxygen entering the hearth HO, an argon inlet 140, a suction line 141, a thermal insulation screen 130 arranged in the hearth, a heater 150 arranged in the thermal insulation screen 130, a thermocouple 160 for measuring temperature, a crucible 180 for heat treatment and tantalum powder 170, which to be heat treated in the crucible 180.

Giant. 2 is a diagram of an apparatus for passivating a tantalum metal surface with an argon forced cooling apparatus according to the present invention. The tantalum metal surface passivation device comprises: a hearth 210, a jacket 211 with a water-cooled jacket having a water inlet 211-1 and a water outlet 211-2, the jacket forming a hearth 20, and a vacuum gauge 212 connected to the hearth 210, an oxygen-containing gas supply for passivation, argon inlet 240, suction line 241, thermal insulation screen 230 arranged in the hearth 210, heater 250 arranged in the thermal insulation screen 230, thermocouple 260 for temperature measurement, heat treatment crucible 280 and processed tantalum powder 270 filled in the crucible 280. The tantalum metal surface passivation device further includes an argon forced cooling device 200A; the components in the argon forced cooling device 200A and their functions are as follows: outlet 207 at the top of the heat treatment furnace, high temperature argon exits the argon outlet 207, passes through connecting pipes 208, cooled by cooling water at the periphery, and fed to the exchanger. chamber 201 from the argon inlet 202 on one side of the exchanger chamber. In the exchanger chamber 201, the medium line 204 is cooled by a cooler 200, the cooler 200 allowing the cooling medium to pass through the exchanger chamber 201; in the exchanger chamber 201, the argon is cooled and then exits the outlet 205 and led to the circulation pump 209, the cooled argon is extruded by the circulation pump 209 and fed through connecting pipes to the heat treatment furnace from the argon outlet 240 at the bottom of the heat treatment furnace, wherein the cooling water on the circumference of the tube 208 enters 208-1 on one side of the exchanger chamber next to the cooling exchanger chamber and exits 208-2 next to one side of the heat treatment furnace, before the tantalum powder is passivated, it is forced cooled by a forced cooling the argon to reduce the temperature of the tantalum powder to 30 ° C or lower, preferably to 10 to 30 ° C, to effectively control the oxidation of the tantalum powder and prevent abrupt oxidation of the tantalum powder. During forced argon cooling, the system pressure is maintained between 0.09 and 0.11 MPa by feeding argon to the circulating system or by suction.

Giant. 3 shows an apparatus for passivating a tantalum metal surface with an oxygen-containing gas cooling system for passivating a tantalum metal surface. The tantalum metal surface passivation device comprises: a hearth 310. a shell 311 with a water-cooled jacket having a water inlet 3111 and a water outlet 311-2, the shell forming a hearth 310 and a vacuum gauge 312 connected to the hearth 310, an oxygen-containing gas inlet 320 for passivation in upper part of the hearth, argon inlet 340, suction tubes 341, heat-insulating screen arranged in the hearth, heating element 350 arranged in the heat-insulating screen 330, thermocouple 360 for measuring temperature, crucible 380 for heat treatment and processed tantalum powder 370 contained in the crucible 380. The tantalum metal surface passivation device further includes an oxygen-containing gas cooling system 390A for passivation, the oxygen-containing gas cooling system 390A for passivation comprising: a condenser 390, an exchanger chamber 391, the condenser-cooled medium passing through the exchanger chamber 391; a gas containing oxygen and argon enters from inlet 392, and resp. supply 393, argon to the exchanger chamber 391 and mixed, the mixed gas-containing gas and refrigerant line 394 connected to the condenser 390 is subjected to heat exchange, the cooled oxygen-containing gas exits the outlet 395 on the other side of the exchanger chamber 391, passes through heat insulating tubes 396 connecting the outlet 395 and the inlet 320 at the top of the heat treatment furnace and leading to the hearth 310; in which a pressure gauge 398 is connected to the exchanger chamber 391, the thermometer 397 is arranged near the oxygen-containing gas outlet 395; and a water outlet 399 arranged at the bottom of the heat exchanger 391. When the passivation of the tantalum metal batch is completed, each component in the heat exchanger is cleaned using hot air, the dissolved water flowing out through the water outlet 399. The oxygen-containing gases are cooled below 0 ° C, preferably below -10 ° C, more preferably -10 ° C to -40 ° C.

Giant. 4 is a diagram of an apparatus for passivating a tantalum metal surface with an argon cooling device and an oxygen-containing gas cooling system according to the present invention, comprising: a hearth 410, a shell 411 with a water-cooled jacket having a water inlet 411-1 and a water outlet 411-2; the jacket consists of a hearth 410 and a vacuum gauge 412 connected to the hearth 410, an oxygen-containing gas supply 420 for passivation, an argon inlet 440, suction tubes 441. a thermal insulation screen 430 arranged in the hearth, a heater 450 arranged in the thermal insulation screen 430, a thermocouple 460 for a temperature measuring crucible 480 for heat treatment and the treated tantalum powder 470 contained in the crucible 480, characterized in that the tantalum metal surface passivation device further comprises: an argon 400A forced cooling device and an oxygen-containing gas cooling system 490A. forced cooling of argon and its functions are as follows: outlet 407 of argon at the top of the furnace p for heat treatment, argon at high temperature in the furnace exits the argon outlet 407, passes through the connecting pipes 408, cools with cooling water, is fed from the 408-1 and exits the 408-2 on the periphery and is fed to the exchanger chamber 401 from one side exchanger chamber 401, in the exchanger chamber 401 there is a cooler-cooled medium line 404, in the exchanger chamber 401 the argon is cooled and leaves the argon outlet 405 on the other side of the exchanger chamber 401, passes through the line 406 and enters the circulation pump 409, the cooled argon is expelled circulating pump 409 and fed through connecting pipes to the heat treatment furnace 410 from the inlet 440 at the bottom of the heat treatment furnace, components in the gas cooling system 490A containing. 7.

oxygen and their functions are as follows: the cooling medium is cooled by a condenser 490; the cooled medium flows and passes through the medium line 494 into the exchanger chamber 491, in which the pressure gauge 498 is connected to the exchanger chamber 491; in the exchanger chamber 491, the oxygen-containing gas and argon are fed from their respective inlets 492, respectively. 493, into the exchanger chamber 491 and mixed; the oxygen-containing mixed gas is cooled by heat exchange with a medium line 494 in the exchanger chamber 491, the oxygen-containing cooled gas exits another outlet 495 of the exchanger chamber 491, passes through heat insulating lines 496 and is fed to a heat treatment furnace 410 from outlet 420 at the top a heat treatment furnace, a thermometer 497 is arranged near the outlet of the oxygen-containing gas, the thermometer is used to measure the temperature of the oxygen-containing gas; the water outlet 499 is arranged at the bottom of the exchanger chamber 491. When the passivation of the tantalum metal dose is completed, each component in the heat exchanger is dried using hot air, the dissolved water flowing out of the water outlet 499.

Giant. 5 is a diagram of a known apparatus for passivating a tantalum metal surface after a tantalum powder has been subjected to deoxidation heat treatment by external heating (not shown), comprising: a deoxidation heat treatment reactor 510, a top cover 511, an argon inlet pipe 540 arranged on the top cover 511; suction line 541, nitrogen inlet pipe 542, oxygen-containing gas inlet pipe 520 for passivation, vacuum pressure gauge 512 for measuring reactor pressure, tantalum crucible 580 arranged in reactor 510, tantalum powder mixed with magnesium powder contained in crucible 580, thermocouple 561, 562 and 563 for measuring the temperature of the upper part, the middle part and resp. the bottom of the reactor and the thermal insulation screen assembly 550 located at the top of the crucible 580.

Giant. 6 is a diagram of an apparatus for passivating a tantalum metal surface after a tantalum powder has been subjected to deoxidation heat treatment by external heating (not shown) with an inert gas forced cooling apparatus according to the present invention, comprising: deoxidation heat treatment reactor 610, argon inlet pipe 640 arranged on the top cover 611 and extending to the bottom of the reactor 610, a discharge line 641, a nitrogen inlet pipe 642, an oxygen-containing gas inlet pipe 620 for passivation, a vacuum pressure gauge 612 for measuring reactor pressure, a tantalum crucible 680 arranged in the reactor, tantalum powder 670 mixed with magnesium powder contained in the crucible 680, thermocouple 661, 662 and 663 for measuring the temperature in the upper part, the middle part and resp. the bottom of the reactor and a thermal insulation screen assembly 650 located on top of the crucible 680, further comprising an argon forced cooling device 600A, the argon forced cooling device 600A comprising: an argon outlet 607 at the top of the reactor 610, high argon temperature arises from the argon outlet 607, passes through a connecting pipe 608, cooled by cooling water supplied from 608-1 and exiting the circuit 608-2, and is fed to the exchanger chamber 601 on one side of the exchanger chamber 601, in the exchanger chamber 601 there is a pipe 604 cooler-cooled medium, the argon supplied in the exchanger chamber 601 is cooled and exits the argon outlet 605 on the other side of the exchanger chamber 601, passes through line 607 and is fed to a circulation pump 609, the cooled argon is expelled by a circulation pump 609, and supplied by passing through connecting pipes to the heat treatment furnace 610 from the outlet 640 at the bottom of the heat treatment furnace. By forced cooling with argon, the temperature of the tantalum powder is reduced to 30 ° C or lower, preferably to 10 to 20 ° C, before the passivation of the tantalum powder.

Giant. 7 is a diagram of an apparatus for passivating a tantalum metal surface after a tantalum powder has been subjected to deoxidation heat treatment by external heating (not shown) with an oxygen-containing gas cooling system of the present invention, comprising: a deoxidation heat treatment reactor 710, top cover 711, inlet argon tube 740 disposed on top cover 711, suction line 741, nitrogen inlet tube 742, oxygen-containing gas inlet tube 720 for passivation, vacuum pressure gauge 712 for measuring reactor pressure, tantalum crucible 780 arranged in reactor 710, tantalum powder 770 mixed with magnesium powder contained in the crucible 780, thermocouples 761, 762 and 763 for measuring the temperature of the upper part, the middle part and resp. the bottom of the reactor and the thermal insulation screen assembly 750, located on top of the crucible 780, further comprising a cooling system 790A

Q of oxygen-containing gas for passivation, the oxygen-containing gas cooling system 790A includes: a condenser 490 for cooling the cooling medium; the cooled medium flows through the medium line 794 into the exchanger chamber 791, in which the pressure gauge 798 is connected to the exchanger chamber 791; in the exchanger chamber 791, oxygen-containing gas and argon are fed from their respective inlets 792 and 793 to the exchanger chamber 791 and mixed; the mixed oxygen-containing gas is heat-treated with the medium line 794 in the exchanger chamber 791 and thus cooled, the oxygen-containing gas exits the outlet 795 on the other side of the exchanger chamber 791, passes through thermal insulation lines 796 and is fed to the reactor 710 from outlet 720 at the top of the reactor, a thermometer 797 is arranged near the outlet of the oxygen-containing gas, the thermometer being used to measure the temperature of the oxygen-containing gas; the water outlet 799 is arranged at the bottom of the exchanger chamber 791.

When the passivation of the tantalum metal batch is complete, each component of the heat exchanger is dried using hot air, the dissolved water flowing out of the water outlet 799.

Giant. 8 is a diagram of an apparatus for passivating a surface of tantalum metal after the tantalum powder has been subjected to deoxidation heat treatment with an inert gas forced cooling device and an oxygen-containing gas cooling system according to the present invention, comprising: deoxidation heat treatment reactor 810, top cover 811; argon inlet pipe 840 arranged on the upper cover 811 and passing into the lower part of the reactor 810, suction line 841, nitrogen inlet 842, oxygen-containing gas inlet pipe 820 for passivation, vacuum pressure gauge 812 for measuring reactor pressure, tantalum crucible 880 arranged in the reactor 810, tantalum powder 870 mixed with magnesium powder contained in a crucible 880, thermocouples 861, 862 and 863 for measuring the temperature of the upper part, the middle part and the resp. the bottom of the reactor and the thermal insulation screen assembly 850 located at the top of the crucible 880, further comprising an argon forced cooling device 800A and an oxygen-containing gas cooling system 890A, argon forced cooling device 800A components, and functions: an argon outlet 807 arranged at the top of the reactor 810, the high temperature argon in the furnace exits the argon outlet 807, passes through cooling water cooled piping pipes 808 entering 808-1 and exiting 808-2 on the periphery, and enters the exchanger chamber 801 from on one side of the exchanger chamber 801, in the exchanger chamber 801 there is a cooler-cooled medium line 804, the argon supplied in the exchanger chamber is cooled and exits the argon outlet 805 on the other side of the exchanger chamber 801, passes through the line 807 and is supplied to the circulating pump 809 is extruded by a circulation pump 809 and fed through connecting pipes to a furnace 810 for heat processing from outlet 840 at the bottom of the reactor. The components in the oxygen-containing gas cooling system 890A and their functions are as follows: the cooling medium is cooled by a condenser 890; the cooled medium flows through the medium line 894 into the exchanger chamber 891, in which the pressure gauge 898 is connected to the exchanger chamber 891; in the exchanger chamber 891, the oxygen- and argon-containing gas enters the exchanger chamber 891 from its respective inlets 892 and 893 and mixes; the oxygen-containing mixed gas undergoes heat exchange with the medium line 894 in the exchanger chamber 891 and is thereby cooled; the oxygen-containing cooled gas exits the outlet 895 on the other side of the exchanger chamber 891, passes through thermal insulation lines 896 and enters the reactor 810 from the inlet 820 to the upper part of the reactor, a thermometer 897 is arranged near the outlet of the oxygen-containing gas, the thermometer being used to measure the temperature of the oxygen-containing gas; the water outlet 899 is arranged at the bottom of the exchanger chamber 891.

When the passivation of the tantalum metal batch is complete, each component in the heat exchanger is dried using hot air, the dissolved water flowing out of the water outlet 899.

In the present invention, the dosing of tantalum powder into the heat treatment furnace is not particularly limited. However, with respect to heat uniformity, nitriding and passivation uniformity and performance, the thickness of the tantalum powder is preferably 60 mm or less, and preferably 40 to 50 mm. For safety and higher yields, the tantalum powder is preferably slowly dosed into a crucible and leveled. The present invention typically utilizes a circular or square crucible

-9EN 306250 B6 with a shallow depth, such as a tantalum crucible, having a length x width x depth of about 350 x 210 x 75 mm.

The heat treatment temperature and the residence time of the tantalum powder are determined based on different types of tantalum powders and requirements, the usual residence time is 30 to 90 minutes at 900 to 1400 ° C and the vacuum is less than 1.33 x 10 ^-1 Pa.

The heat-treated tantalum powder is optimally nitrided by supplying nitrogen during cooling.

After the tantalum powder has been exposed to a holding temperature of 900 to 1400 ° C, it is cooled in a vacuum oven, and then cooled with a water-cooled jacket, the tantalum powder is cooled with argon at room temperature to about 80 ° C or lower, and then subjected to forced circulating cooling with argon below room temperature so that the tantalum powder is cooled to a temperature of 30 ° C or lower, preferably 20 ° C or lower, for example to 10 to 20 ° C, and then subjected to a passivation treatment by introducing an oxygen-containing gas.

The oxygen-containing gas is mixed with the argon-oxygen-containing gas and, in view of economics, the oxygen-containing gas is preferably a mixed gas containing air and argon. According to the present invention, the oxygen concentration of the oxygen-containing effect is 21% by volume or less; the lower the oxygen concentration, the more effectively the oxidation of tantalum can be controlled. Because the lower the specific heat of the gas, in view of the effect, it is desirable that the oxygen concentration in the oxygen-containing gas be as low as possible. However, in view of yield and economy, at the beginning of the passivation, the oxygen content of the oxygen-containing gas is preferably 5 to 15% by volume.

In the case of tantalum powder having a small specific surface area, it is sufficient that the passivation be performed once. In the case of tantalum powder having a considerable specific surface area, it is preferable that the passivation be performed twice or more. The first passivation is performed using a low oxygen gas, and then the concentration of the oxygen-containing gas is gradually increased, up to an oxygen concentration in the air, about 21% by volume.

According to the present invention, the oxygen-containing gas and the make-up gas, e.g. argon, are fed from their respective inlets to the exchanger chamber in a volume ratio calculated from the gas pressure, the gases are mixed and passed by heat exchange in the heat exchanger, the temperature of the oxygen-containing exhaust gas being measured at output. The temperature of the oxygen-containing gas described in the present invention means the temperature of the exhaust gas measured at the outlet.

When the tantalum powder was passivated, the heat treatment furnace was depleted to about 200 Pa, and then the oxygen-containing gas was continuously or intermittently introduced into the heat treatment furnace so that the final pressure in the heat treatment furnace reached about 0.1 MPa.

The heat treatment described herein means heating the tantalum powder at a temperature above 300 ° C in a vacuum or inert atmosphere or reducing atmosphere and includes sintering the porous tantalum molding, e.g., sintering to produce an anode of the tantalum electrolytic capacitor, and equipment similar to tantalum powder heat treatment. e.g. the device shown in Figs. 2 to 4.

The oxygen content of the tantalum powder described herein was determined using the common determinant TC-436 oxygen nitrogen; the hydrogen content of the tantalum powder was determined using the hydrogen content determinant RH-404. The wet electronic properties of the tantalum powder described herein were measured as follows: The tantalum powder was compressed into a cylindrical compact with a density of 4.5 g / cm ³ , a diameter of 3.0 mm and a height of 4.72 mm, into which 0.3 mm tantalum wire, each molding contained about 150 mg of tantalum powder; the compact was sintered at 1320 ° C for 10 minutes to form an agglomerate; the agglomerate was placed in 0.1 wt. phosphoric acid at 80 ° C, the voltage was increased to 30 V at a current density of 60 mA / g and the voltage was maintained for 120 ml

Λ to form an anode in which the surface of the tantalum particles has been covered with a dielectric film; the leakage current of the anode was determined in 0.1 wt. phosphoric acid at 25 ° C and the specific electrical capacity (specific capacity) and losses were determined in 20 wt. sulfuric acid solution.

To further explain the present invention, preferred embodiments of the present invention are described as follows by combining examples and drawings. However, it is to be understood that these descriptions are merely further explanations of the features and advantages of the present invention, but are not intended to limit the scope of the invention.

Examples of embodiments of the invention

Example 1

A starting powder was formed which was prepared by reducing potassium tantalum fluoride with sodium; the starting powder had a specific surface area of 1.82 m ² / g, a bulk density of 0.51 g / cm ³ and an oxygen content of 6200 ppm. The crude powder was mixed with 120 ppm of phosphorus, based on the weight of the tantalum powder, granulated by soft annealing to obtain spherical particles having a bulk density of 1.02 g / cm ³ . The soft-annealed granular tantalum powder was metered into a crucible, and the crucible was placed in a passivation device by heat treating the tantalum powder, as shown in Fig. 4, heated under vacuum at 1.33 x 10 ¹ Pa at 1200 ° C, and held for 30 minutes, and then the heating was stopped and the temperature was reduced to 200 ° C; argon was introduced to reduce the temperature to 80 ° C, a system 400A for forced cooling of argon was put into operation, argon with high temperature in the heat treatment furnace came out of outlet 407, passed through pipe 408 cooled by cooling water, it was introduced into the exchanger chamber 401 from the gas supply 402 and underwent heat exchange with a refrigerant pipe 404 connected to the condenser; the argon was cooled by heat exchange, the cooled argon exiting the outlet 405, pumped using a circulating pump 409 to pass through line 406 and fed to the heat treatment furnace from the heat treatment furnace gas inlet 440, which represents the circulation of argon. Circulating argon caused the crucible and tantalum powder to cool in the heat treatment furnace, after cooling for about 2 hours, the temperature in the furnace was reduced to 25 ° C and the tantalum powder was passivated. The passivation method includes discharging the gas from the furnace through an aeration line 441 to a vacuum of about 200 Pa, and an oxygen-containing gas cooling system 490A is actuated to supply air and argon to the exchanger chamber 491 of 492 and 492, respectively. 493 under the following conditions, are mixed, heat exchanged with 494, and then exit the outlet 495, pass through a thermally insulating pipe 496 and be fed to the hearth 410 from the inlet 420; first, an oxygen-containing gas with an oxygen concentration of about 5% by volume (1 part by volume of air and 3 parts by volume of argon were introduced by a pressure gauge from inlet 492 and outlet 493 into exchanger chamber 491) was heat exchanged with a refrigerant tube 494 connected to The oxygen-containing gas at -10 to -20 ° C exits the oxygen-containing gas outlet 495, passes through the heat insulating tube 496, and is fed to the heat treatment furnace from the gas supply 420 at the top of the heat furnace. processing, the pressure increased in 8 stages and in 3 hours from 200 Pa to 0.1 MPa: (200 Pa to 0.005 MPa) / 30 minutes, (0.005 to 0.01 MPa) / 30 minutes, (0.1 to 0 .02 MPa) / 20 minutes, (0.02 to 0.03 MPa) / 20 minutes, 0.03 to 0.045 MPa) / 20 minutes, (0.045 to 0.06 MPa) / 20 minutes, 0.06 to 0 .08 MPa) / 20 minutes, (0.08 to 0.1 MPa) / 20 minutes, total 3 hours; second, the oxygen-containing gas at -10 to -20 ° C with an oxygen concentration of 10% by volume (1 part by volume of air and 1 part by volume of argon were mixed) increased from 200 Pa to 0.1 MPa in 3 hours to the first aeration procedure; third, the pressure was increased from 200 Pa to 0.1 MPa in 3 hours using air at -10 to -20 ° C in the same manner as in the first procedure; fourth, the pressure was increased from 200 Pa to 0.1 MPa in four stages for a total of 2 hours using air at -10 to -20 ° C: (200 Pa to 0.01 MPa) / 30 minutes, (0.01 to 0.03 MPa) / 30 minutes, (0.03 to 0.06 MPa) / 30 minutes, (0.06 to 0.10 MPa) / 30 minutes. Four passivations were performed in a total of 11 hours. Throughout the process, the temperature in the furnace first gradually increased to 28 ° C, then the temperature was gradually constant and changed between 25 and 28 ° C, and finally the temperature gradually decreased to 25 ° C. After emptying, the tantalum powder was removed and no violent oxidation occurred. Te

The finely treated tantalum powder was sieved through an 80-mesh sieve to obtain an S-1h tantalum powder. The oxygen and hydrogen contents of the tantalum powder were analyzed, the results being shown in Table 1. 2 wt. magnesium powder, based on the tantalum powder, was mixed to form a mixed powder, the mixed powder was fed to a tantalum powder deoxidation reactor as shown in Fig. 6, held at 850 ° C for 3 hours to perform deoxidation treatment. the heating was stopped and the temperature was reduced, and the treated tantalum powder was nitrided at 280 ° C, quenched with argon when the temperature of the tantalum powder was reduced to 15 ° C, and an oxygen-containing gas was introduced at 31 ° C according to a passivation procedure similar to the above heat treatment passivation was performed 4 times using an oxygen-containing gas with an oxygen concentration of about 5% by volume, 10% by volume, 21% by volume and 21% by volume, the first 3 passivations were performed each for 3 hours and the last passivation was performed for 2 hours, a total of 11 hours. After emptying, the passivated tantalum powder was pickled, washed with water and dried to obtain an S-Id tantalum powder. The oxygen and hydrogen contents of the tantalum powder were analyzed, the results are shown in Table 1. The electrical power of the tantalum powder was determined, and the results are shown in Table 2.

Example 2

The starting tantalum powder used in Example 1 was fed to a tantalum powder heat treatment furnace with an argon forced cooling device as shown in Fig. 2 and subjected to heat treatment under the same conditions as in Example 1 when the temperature reduced the amount of tantalum powder to about 200 ° C, argon was introduced and the argon forced cooling system 200A was started, high temperature argon in the heat treatment furnace exited the outlet 207 at the top of the furnace, passed through water-cooled line 208, to the exchanger chamber 201 from the gas supply 202 and subjected to heat exchange with a refrigerant pipe 204 connected to the condenser 200; the argon was cooled by heat exchange, the cooled argon exiting the outlet 205, passing through line 206, pumped using a circulation pump 209 to be fed to the heat treatment furnace 210 from the heat treatment furnace gas inlet 240, which represents the circulation of argon; circulating argon causes the crucible and tantalum powder in the heat treatment furnace to cool when cooling for 4 hours, the crucible and tantalum powder are forcibly cooled with argon to 10 ° C, and the tantalum powder is passivated. The heat treatment furnace was emptied to about 200 Pa; first, the oxygen-containing gas at 32 ° C with an oxygen concentration of about 5% by volume increased in 8 steps and 4 hours from 200 Pa to 0.1 MPa: (200 Pa to 0.005 MPa) / 30 minutes, (0.005 to 0, 01 MPa) / 30 minutes, (0.01 to 0.02 MPa) / 30 minutes, (0.02 to 0.03 MPa) / 30 minutes, (0.03 to 0.045 MPa) / 30 minutes, (0.045 to 0.06 MPa) / 30 minutes, (0.06 to 0.08 MPa) / 30 minutes, (0.08 to 0.1 MPa) / 30 minutes; second, the oxygen-containing gas at 32 ° C with an oxygen concentration of about 10% by volume was increased from 200 Pa to 0.1 MPa in 4 hours according to the first aeration procedure; third: the pressure was increased from 200 Pa to 0.1 MPa in 4 hours using air at 32 ° C according to the same procedure as in the first procedure; fourth, the oxygen-containing gas was increased from 200 Pa to 0.1 MPa in 4 stages for a total of 2 hours using air at 32 ° C: (200 Pa to 0.01 MPa) / 30 minutes, (0.01 to 0 .03 MPa) / 30 minutes, (0.03 to 0.06 MPa) / 30 minutes, (0.06 to 0.10 MPa) / 30 minutes. Four passivations were performed for a total of 14 hours. Throughout the process, the oven temperature is first raised gradually to 33 ° C, then the temperature has gradually stabilized and varied between 28 and 32 ° C. After emptying, the tantalum powder was removed, no sign of violent oxidation. The heat-treated tantalum powder was passed through an 80-mesh sieve to obtain S-2h tantalum powder. The oxygen and hydrogen contents of the tantalum powder were analyzed, the results being shown in Table 1. 2 wt. magnesium powder relative to the tantalum powder was mixed in the tantalum powder S-2h to form a mixed powder, the mixed powder was metered into the tantalum powder deoxidation reactor as shown in Fig. 7, held at 850 ° C for three hours to deoxidation treatment was performed, heating was stopped and the temperature was reduced, and the treated tantalum powder was nitrided at 280 ° C, and then the temperature of the tantalum powder in the reactor was reduced to 31 ° C, the oxygen-containing gas at -10 to -40 ° C was four times, according to a passivation procedure similar to the heat treatment described above, and the tantalum powder was passivated using an oxygen-containing gas having an oxygen concentration of about 5% by volume, 10% by volume, 21% by volume and 21% by volume, the first three passivations being performed every 3 hours and the last passivation was performed for 2 hours, a total of 11 hours. After emptying, the passivated tant. and?.

the fishing powder was pickled, washed with water and dried to obtain tantalum powder S-2d. The oxygen and hydrogen contents of the tantalum powder were analyzed, the results are shown in Table 1. The electrical power of the tantalum powder was determined, and the results are shown in Table 2.

Example 3

The heat treatment apparatus shown in Fig. 3 was used, and the same tantalum powder as in Example 1 was heat treated under the same conditions as described in Example 1. After the heat treatment, the jacket was cooled with water to a lower temperature and argon was added for 12 hours. to reduce the temperature to 30 ° C and passivate the tantalum powder. The passivation process comprises: aspirating argon in a furnace to about 200 Pa, an oxygen-containing gas cooling system 390A is activated to supply air and argon to the exchanger chamber 391 of 392 and 393 under the following conditions, mixed and subjected to heat exchange with 394; and then it was discharged through an outlet 395, passed through a thermal insulation pipe 396 and fed to a hearth 310 from an inlet 320; first, an oxygen-containing gas with a concentration of about 5% by volume was cooled to -2 to -40 ° C and increased in eight steps from 200 Pa to 0.1 MPa: (200 Pa to 0.005 MPa) / 30 minutes, (0.005 to 0.01 MPa) / 30 minutes, (0.01 to 0.02 MPa) / 30 minutes, (0.02 to 0.03 MPa) / 30 minutes, (0.03 to 0.045 MPa) / 30 minutes, (0.045 to 0.06 MPa) / 30 minutes, (0.06 to 0.08 MPa) / 30 minutes, (0.08 to 0.1 MPa) / 30 minutes, total 4 hours; second, the oxygen-containing gas at -20 to -40 ° C with an oxygen concentration of about 10% by volume was increased from 200 Pa to 0.1 MPa in 4 hours according to the first aeration procedure; third, the pressure was increased from 200 Pa to 0.1 MPa in 4 hours using air at -20 to -40 ° C according to the same procedure as the first procedure; fourth, the pressure was increased from 200 Pa to 0.1 MPa in 4 stages using air at -20 to -40 ° C: (200 Pa to 0.01 MPa) / 30 minutes, (0.01 to 0.03 MPa) / 30 minutes, (0.03 to 0.06 MPa) / 30 minutes, (0.06 to 0.10 MPa) / 30 minutes. Four passivations were performed for a total of 14 hours. The oven temperature first rose gradually to 35 ° C, then gradually stabilized and varied between 32 and 35 ° C. After emptying, the tantalum powder was removed, no sign of violent oxidation. The heat-treated tantalum powder was passed through an 80-mesh sieve to obtain tantalum powder S-3h. The oxygen and hydrogen contents of the tantalum powder were analyzed, the results being shown in Table 1. 2 wt. magnesium powder, based on tantalum powder, was mixed in tantalum powder S-3h to form a mixed powder, the mixed powder was metered into a tantalum powder deoxidation reactor as shown in Fig. 8, kept at 850 ° C for 3 hours, to perform the deoxidation treatment, the heating was stopped and the temperature was lowered, and the treated tantalum powder was nitrided at 280 ° C, and then forcibly cooled with argon, when the temperature of the tantalum powder decreased to 15 ° C, an oxygen-containing gas was introduced at -10 to -40 ° C four times, according to a passivation procedure similar to the heat treatment as described above, the tantalum powder was passivated with an oxygen-containing gas with an oxygen concentration of about 5% by volume, 10% by volume, 21% by volume and 21% by volume, the first 3 passivations were each performed for 3 hours and the last passivation was performed for 2 hours, for a total of 11 hours. After emptying, the passivated tantalum powder was pickled, washed with water and dried to obtain S-3d tantalum powder. The oxygen and hydrogen contents of the tantalum powder were analyzed, and the results are shown in Table 1. The electrical power of the tantalum powder was determined, and the results are shown in Table 2.

Comparative Example 1

The same tantalum powder as in Example 1 was used and the heat treatment was performed at the same temperature, after the heating was stopped, the temperature was reduced to 200 ° C in vacuo, argon was fed for cooling for 12 hours when the temperature was reduced to 32 ° C. , passivation began; the passivation process includes: suction of argon in the furnace to about 200 Pa, first, air is fed to the furnace for heat treatment in 8 stages to increase the talk in the furnace from 200 Pa to 0.1 MPa: (200 Pa to 0.005 MPa) / 120 minutes, (0.005 to 0.01 MPa) / 60 minutes, (0.01 to 0.02 MPa) / 60 minutes, (0.02 to 0.03 MPa) / 60 minutes, (0.03 to 0.045 MPa) ) / 30 minutes, (0.045 to 0.06 MPa) / 30 minutes, (0.06 to 0.08 MPa) / 30 minutes, (0.08 MPa to 0.1 MPa) / 30 minutes, a total of 7 hours, when the temperature increased suddenly 6 times during aeration, the highest temperature was up to 60 ° C; When it was found that the temperature rose suddenly, aeration took place immediately

- 13 CZ 306250 B6 stopped; and after the temperature dropped to about 32 ° C, the aeration was performed in the furnace again. Second, air at 31 ° C was introduced into the 8-stage heat treatment furnace to increase the pressure in the furnace from 200 Pa to 0.1 MPa: (200 Pa to 0.005 MPa) / 60 minutes, (0.005 to 0, 01 MPa) / 60 minutes, (0.01 to 0.02 MPa) / 60 minutes, (0.02 to 0.03 MPa) / 60 minutes, (0.03 to 0.045 MPa) / 30 minutes, (0.045 to Δ 0.06 MPa) / 30 minutes, (0.06 to 0.08 MPa) / 30 minutes, (0.08 to 0.1 MPa) / 30 minutes, total 6 hours;

the temperature suddenly rising suddenly to 50 ° C. The third operation is the same as the second operation, air at 31 ° C was fed to a heat treatment furnace, and passivation was performed for 6 hours. Fourth, the pressure was increased from 200 Pa to 0.1 MPa in 4 stages using air at 31 ° C: (200 Pa to 0.01 MPa) / 30 minutes, (0.01 to 0.03 MPa) / 30 minutes , (0.03 to 0.06 MPa) / 30 minutes, (0.06 to 10.10 MPa) / 30 minutes, for a total of 2 hours. Four passivations were performed for a total of 21 hours. After passivation, the tantalum powder was removed and heat was actually generated. The heat-treated tantalum powder was sieved through an 80-mesh sieve to obtain tantalum powder E-1h. The oxygen and hydrogen contents of the tantalum powder were analyzed, the results being shown in Table 1.2% by weight. magnesium powder, relative to the tantalum powder, was mixed to form a mixed powder, the mixed powder was fed to a reactor for deoxidizing the tantalum powder as shown in Fig. 5, kept at 850 ° C for 3 hours to perform deoxidation. treatment, heating was stopped and the temperature was reduced, and the treated tantalum powder was nitrided at 280 ° C, by a passivation procedure similar to the above-described heat treatment, when the temperature was reduced at 31 ° C, air at 31 ° C was introduced 4 times to perform passivation. . The first three passivations were performed in 8 steps each for 5 to 20 hours, and the fourth passivation was performed in 4 steps for 2 hours, for a total of 17 hours. The passivated tantalum powder was pickled, washed with water and dried to obtain tantalum powder E-ld. The oxygen and hydrogen contents of the tantalum powder were analyzed, the results are shown in Table 1. The electrical power of the tantalum powder was determined, and the results are shown in Table 2.

Table 1: Oxygen and hydrogen contents of tantalum powder

Tantalum powder no. O H S-lh 10600 70 S-ld 3800 140 S-2h 11300 78 S-2d 4100 140 S-3h 11600 60 S-3d 400 130 E-lh 16500 180 E-ld 5800 200

Table 2: Measurement of the electrical power result of tantalum powder

Tantalum powder no. Leakage current nA / g Specific capacity pF.v / g Losses (tg6)% S-ld 58 85860 30.5 S-2d 59 85800 31.1 S-3d 59 84900 32.8 E-ld 126 85000 45.2

As can be seen from the results shown in Tables 1 and 2, the process of the present invention has the advantage of short production times and the prepared tantalum powder has low oxygen and hydrogen contents and a low leakage current.

Example 4

After deoxidation heat treatment, the tantalum powder S-1d in Example 1 was pressed into a cylindrical molding with a density of 4.5 g / cm ³ , a diameter of 3.0 mm and a height of 4.72 mm, into which a tantalum wire of 0.3 mm was inserted. each compact contained about 150 mg of tantalum powder; in the apparatus shown in Fig. 4, the molding was sintered at 1320 ° C for 10 minutes to form a tantalum agglomerate, and then the heating was stopped, the temperature was reduced to 200 ° C, argon was introduced, and the 400A apparatus was operated for forced cooling of argon, cooling was performed for 3 hours to reduce the furnace temperature to 20 ° C, and the tantalum agglomerate was passivated. The passivation process comprises: aspirating argon in a furnace to a vacuum of about 200 Pa; first, an oxygen-containing gas at -10 to -40 ° C at a concentration of about 10% by volume was introduced into a heat treatment furnace in 5 stages in 3 hours to increase the pressure in the furnace from 200 Pa to 0.1 MPa: ( 200 Pa to 0.01 MPa) / 40 minutes, (0.01 to 0.03 MPa) / 40 minutes, (0.03 to 0.05 MPa) / 40 minutes, (0.5 to 0.07 MPa) / 30 minutes, (0.07 to 0.1 MPa) / 30 minutes. Second, air at -10 to -40 ° C was fed to the furnace for heat treatment in 4 stages and in 2 hours to increase the pressure in the furnace from 200 Pa to 0.1 MPa: (200 Pa to 0.01 MPa ) / 30 minutes, (0.01 to 0.03 MPa) / 30 minutes, (0.03 to 0.06 MPa) / 30 minutes, (0.06 to 0.10 MPa) / 30 minutes. Both passivations were performed for a total of 5 hours. Throughout the process, the oven temperature was first gradually raised to 32 ° C, then the temperature gradually stabilized and varied between 29 and 31 ° C, and finally the temperature gradually decreased to 29 ° C. After emptying, the tantalum powder was removed to obtain a tantalum agglomerate S-4. The oxygen and hydrogen contents of the tantalum agglomerate were analyzed, the results are shown in Table 3. The agglomerate was placed in 0.1 wt. phosphoric acid at 80 ° C, the voltage was increased at a current density of 60 mA / g to 30 V and kept at a constant pressure for 120 minutes to form the tantalum anode S-4a; the leakage current of the anode was determined in 0.1 wt. phosphoric acid at 25 ° C and the specific electrical capacity (specific capacity) and losses were determined in 20 wt. phosphoric acid solution, the results are shown in Table 4.

Comparative Example 2

The same tantalum powder as in Example 4 was compressed into the same tantalum compact, and sintered under the same conditions, the temperature was reduced to 200 ° C, argon was added to cool in about 6 hours to reduce the furnace temperature to 33 ° C. and the tantalum agglomerate was passivated. The passivation process includes: aspirating argon in a furnace to a vacuum of about 200 Pa, first, air at 32 ° C was introduced into the furnace for heat treatment in 6 stages and in 4.5 hours to increase the pressure in the furnace from 200 Pa to 0 1 MPa: (200 Pa to 0.005 MPa) / 60 minutes, (0.005 to 0.02 MPa) / 30 minutes, (0.02 to 0.03 MPa) / 30 minutes, (0.03 to 0.05 MPa) / 30 minutes, (0.03 to 0.05 MPa) / 30 minutes, (0.05 to 0.06 MPa) / 30 minutes, (0.06 to 0.08 MPa) / 30 minutes, (0.08 up to 0.1 MPa) / 30 minutes. Second, air at 32 ° C was introduced into the heat treatment furnace in 4 stages and 2 hours to increase the pressure in the furnace from 200 Pa to 0.1 MPa: (200 Pa to 0.01 MPa) / 30 minutes. (0.01 to 0.03 MPa) / 30 minutes, (0.03 to 0.06 MPa) / 30 minutes, (0.06 to 0.10 MPa) 30 minutes. The two passivations were performed for a total of 6.5 hours. Throughout the process, the oven temperature first rose gradually to 41 ° C. After emptying, the tantalum agglomerate was removed to obtain tantalum agglomerate E-2s. The oxygen and hydrogen contents of the tantalum agglomerate were analyzed and the results are shown in Table 3. The agglomerate was formed into the anode E-2a under the same conditions as described in Example 3. The electrical power of the agglomerate was determined and the results are shown in Table 4.

- 15 CZ 306250 B6

Table 3: Oxygen and hydrogen contents of tantalum powder

Tantalum agglomerate no. O H S-4 5200 30 E-2 6500 70

Table 4: Results of measuring the electrical power of tantalum agglomerate

Tantalum powder no. Leakage current nA / g Specific capacity pF.v / g Loss (tg6)% S-4 48 85800 30.1 E-2 93 84000 44.8

From the above it is clear that the heat treatment of tantalum powder according to the invention is safe and reliable, has a high yield and tantalum powder does not burn and the prepared tantalum powder has low oxygen and hydrogen contents and the anode prepared from tantalum powder has low leakage current and good electrical performance .

In the above description, although the description is mainly directed to tantalum powder, those skilled in the art will appreciate that the present invention is also suitable for other active metal powders, such as niobium powder.

Claims (10)

PATENT CLAIMS A method of passivating a tantalum metal surface, characterized in that it comprises the following steps: (a) forming a tantalum metal that has been heat treated; (b) lowering the temperature of the tantalum metal to room temperature; (c) introducing an oxygen-containing gas at 0 ° C or lower, preferably 0 to -40 ° C, to passivate the tantalum metal surface; and (d) optionally repeating step (c) one or more times. A method of passivating a tantalum metal surface according to claim 1, characterized in that in step b) the temperature of the tantalum metal is reduced to 32 ° C or less, preferably below 30 ° C, and even more preferably to 10 to 30 ° C, using cooled inert gases. A method of passivating a tantalum metal surface according to claims 1 and 2, characterized in that the oxygen-containing gas supplied is air, a mixed gas of inert gas and oxygen or a mixed gas of inert gas and air. A method of passivating a tantalum metal surface according to claims 1 to 3, characterized in that the oxygen-containing gas is a mixed gas of argon and air. 1Á _ Process for passivating a tantalum metal surface according to one of Claims 1 and 2, characterized in that the oxygen concentration in the oxygen-containing gas is 21% by volume or less, preferably 5 to 20% by volume. A method of passivating a tantalum metal surface according to claim 2, characterized in that the inert gas is argon. An apparatus for carrying out the method according to claim 1, comprising a heat treatment furnace, said heat treatment furnace comprising: a hearth (310), a shell (311) with a water-cooled jacket forming the hearth (310), a passivation gas inlet (320) comprising oxygen for supply to the hearth (310), an aeration line, a heater disposed within the hearth (310), and a heat treatment crucible (380) for locating the tantalum metal being processed; characterized in that it further comprises an oxygen-containing gas cooling system (390A), the oxygen-containing cooling system (390A) comprising: - an oxygen-containing gas supply (320) which is used to supply an oxygen-containing gas to passivate the tantalum metal; - a heat exchanger chamber (391) in which the oxygen-containing gas is cooled by heat exchange; and - an oxygen-containing gas outlet (395), wherein the cooled oxygen-containing gas leaves the exchanger chamber (391) through the outlet (395) and is fed to the heat treatment furnace from the top of the heat treatment furnace through heat insulating connecting pipes (396). The apparatus for carrying out the method according to claim 2, wherein the apparatus is the apparatus according to claim 7, further comprising an inert gas cooling device, characterized in that the inert gas forced cooling device comprises: - an inlet (240) of cooled inert gases, wherein the inlet (240) of cooled inert gases is connected to an outlet (207) of inert gases at the top of the argon heat treatment furnace; - a heat exchanger chamber (201) for supplying (202) high temperature inert gases from the heat treatment furnace through the supply (240) of cooled inert gases for cooling by the heat exchange method; - an outlet (205) of cooled inert gases, wherein the cooled inert gases in the exchanger chamber are discharged from the outlet (205) of inert gases; and - a circulation pump (209), where cooled inert gases from the cooled inert gas outlet (240) are fed to the circulation pump, and supplies cooled inert gases to the heat treatment furnace from the inert gas supply at the bottom of the heat treatment furnace through connecting pipes (208 ). Device according to claim 8, characterized in that the device for forced cooling of inert gases is preferably a device for forced cooling of argon for cooling the surface of tantalum metal to 32 ° C. Apparatus according to claim 7 or 8, characterized in that the oxygen-containing gas cooling system (390A) is configured to cool the oxygen-containing gas to passivate the tantalum metal surface at a temperature of 0 ° C or lower, preferably - 40 to 0 ° C. .