Method and reaction apparatus for passivating tantalum powder

Abstract

This invention discloses a passivation method for tantalum powder, comprising a reaction apparatus, the reaction apparatus including a furnace body, a gas introduction switch connected to the furnace chamber for controlling whether gas is introduced into the furnace chamber, and a strong cooling device. The passivation method for tantalum powder includes: filling an inert gas into a furnace chamber containing heat-treated tantalum powder at its front end; a primary passivation step, including evacuating the furnace chamber to achieve the initial passivation vacuum level after the tantalum powder is cooled to the initial passivation temperature, then turning on the strong cooling device and repeatedly introducing air into the furnace chamber; a secondary passivation step, including turning on the strong cooling device and repeatedly introducing air into the furnace chamber; and a final passivation step, including detecting the temperature of the tantalum powder in the furnace chamber at the final passivation initiation temperature, then repeatedly introducing filtered air into the furnace chamber, wherein the strong cooling device is not turned on and the temperature difference between the tantalum powder in the furnace chamber and the final passivation initiation temperature is constantly monitored to see if it is greater than a threshold temperature.

Description

Technical Field

[0001] This invention relates to the field of tantalum powder passivation technology, and particularly to a passivation method and reaction apparatus for tantalum powder. Background Technology

[0002] Tantalum, also known as valve metal, is typically extracted from its ores in powder form. For example, tantalum powder suitable for high-performance capacitors can be produced by the chemical reduction of potassium fluorotantalate (e.g., sodium reduction). Because tantalum metal has a high affinity for oxygen, it forms a dense oxide film of tantalum pentoxide upon contact with oxygen, preventing further oxidation. As described in Chinese patent CN102181818A, due to the difference in thermal expansion coefficients between metallic tantalum and tantalum oxide, when tantalum particles covered by the dense oxide film are heated to temperatures above approximately 100°C, the oxide film cracks and is destroyed. When tantalum powder is heated to above 700°C, some oxygen from the oxide film dissolves into the tantalum matrix, while some oxygen escapes and accumulates. Therefore, when tantalum metal powder is heated during heat treatment, deoxidation, granulation, agglomeration, or sintering, the powder will begin to oxidize again from the surface upon contact with an oxygen-containing atmosphere after cooling. Without passivation, the tantalum metal powder will rapidly heat up and even ignite. Passivation is the process of artificially controlling the oxygen supply rate when tantalum metal powder comes into contact with an oxygen-containing atmosphere. This controlled oxygen supply allows for precise control of the oxidation rate and temperature of the tantalum metal powder, resulting in the formation of a passivating oxide film on the powder surface and preventing aggressive oxidation. Tantalum powder releases heat during oxidation, and its oxidation rate is highly dependent on its specific surface area. Tantalum powders with higher specific capacities (i.e., larger specific surface areas) are more sensitive to oxidation and more prone to heat generation. For high-specific-capacity tantalum powders with FTW-100K and above, controlling the passivation process is even more crucial for effective and reliable passivation. Summary of the Invention

[0003] The purpose of this invention is to provide a passivation method and reaction apparatus that can reliably, effectively, and fully achieve passivation of high specific capacitance tantalum powder.

[0004] This invention discloses a passivation method for tantalum powder, comprising a reaction apparatus, the reaction apparatus including a furnace body, a gas introduction switch connected to the furnace chamber for controlling whether to introduce gas into the furnace chamber, and a strong cooling device. The passivation method for tantalum powder includes:

[0005] An inert gas is introduced into the furnace chamber containing heat-treated tantalum powder at the front end.

[0006] The passivation process includes, after the tantalum powder is cooled to the passivation start temperature, evacuating the furnace to achieve the initial passivation vacuum level, then activating the blast cooling device and repeatedly opening the gas inlet switch to allow filtered air to be introduced into the furnace. The blast cooling device includes a blast cooling gas inlet connected to the rear end of the furnace, a heat exchange chamber connected to the blast cooling gas inlet, a buffer tank, a blast cooling gas input device connected to the front end of the furnace, a circulation pump connected between the blast cooling gas inlet and the blast cooling gas input device, and a system connected between the blast cooling gas inlet and the heat exchange chamber. The furnace includes a first pipe, a second pipe connecting the heat exchange chamber and the buffer tank, a third pipe connecting the buffer tank and the refrigeration gas inlet, and a refrigeration device surrounding the heat exchange chamber for cooling the gas inside the heat exchange chamber. An axial heat shield is provided between the refrigeration gas inlet and the front end of the furnace. The axial heat shield is used to insulate and prevent gas from the front end of the furnace from directly entering the refrigeration gas inlet in a direction parallel to the axis of the furnace. During a passivation step, the refrigeration device remains on after being opened.

[0007] The secondary passivation step includes: turning off the strong cooling device and evacuating the furnace to achieve the initial vacuum level for secondary passivation; then turning on the strong cooling device and repeatedly opening the gas inlet switch to allow filtered air to be introduced into the furnace. During the secondary passivation process, the strong cooling device remains on after being turned on, and the gas pressure increase in the furnace caused by each opening of the gas inlet switch during the secondary passivation process is greater than or equal to the gas pressure increase in the furnace caused by each opening of the gas inlet switch during the primary passivation step.

[0008] The final passivation step includes: shutting off the strong cooling device and evacuating the furnace to achieve the final passivation initiation vacuum level; detecting the temperature of the tantalum powder in the furnace at the final passivation initiation temperature; and then repeatedly opening the gas inlet switch to allow filtered air to be introduced into the furnace. During the final passivation step, the strong cooling device is not turned on, and the temperature difference between the tantalum powder in the furnace and the final passivation initiation temperature is constantly monitored to ensure it is greater than a threshold temperature. The increase in gas pressure in the furnace caused by each opening of the gas inlet switch during the final passivation process is greater than or equal to the increase in gas pressure in the furnace caused by each opening of the gas inlet switch during the secondary passivation process.

[0009] In some embodiments, filling an inert gas into a furnace containing heat-treated tantalum powder at the front end includes: reducing the temperature of the heat-treated tantalum powder in the furnace to 300-600°C, and then filling the furnace with inert gas to raise the gas pressure in the furnace to 60-80 kPa, while the forced cooling device remains on during this process.

[0010] In some embodiments, after the tantalum powder is cooled to the passivation start temperature, the furnace is evacuated to achieve the initial passivation vacuum level. Then, the strong cooling device is turned on and the gas inlet switch is opened multiple times to allow filtered air to be introduced into the furnace. This includes: after the tantalum powder is cooled to 30-35°C, the furnace is evacuated to reduce the gas pressure in the furnace to 50 kPa. Then, the strong cooling device is turned on and the gas inlet switch is opened 16 times to allow filtered air to be introduced into the furnace. Each time the gas inlet switch is opened, the gas pressure in the furnace increases by 2 kPa before the gas inlet switch is closed. Between two consecutive openings of the gas inlet switch, after the previous gas inlet switch is closed, the next gas inlet switch is opened again after 15-20 minutes.

[0011] In some embodiments, the method further includes: testing the reaction apparatus before it contains tantalum powder, including evacuating the furnace to bring the gas pressure inside the furnace to 20 kPa, then turning on the strong cooling device and the gas inlet switch to allow filtered air to be introduced into the furnace, and continuously measuring the time S1 when the gas pressure inside the furnace increases from 20 kPa to 30 kPa, the time S2 when the gas pressure inside the furnace increases from 30 kPa to 40 kPa, the time S3 when the gas pressure inside the furnace increases from 40 kPa to 50 kPa, the time S4 ​​when the gas pressure inside the furnace increases from 50 kPa to 60 kPa, the time S5 when the gas pressure inside the furnace increases from 60 kPa to 70 kPa, and the time S6 when the gas pressure inside the furnace increases from 70 kPa. The time S6 for reaching 80 kPa and the time S7 for the gas pressure in the furnace to increase from 80 kPa to 90 kPa; the process of opening the gas inlet switch 16 times to allow filtered air to be introduced into the furnace, with each opening of the gas inlet switch increasing the gas pressure in the furnace by 2 kPa before closing the gas inlet switch includes: the gas inlet switch being kept open for S4 / 5 after the first to fifth openings, the gas inlet switch being kept open for S5 / 5 after the sixth to tenth openings, the gas inlet switch being kept open for S6 / 5 after the eleventh to fifteenth openings, and the gas inlet switch being kept open for S7 / 5 after the sixteenth opening.

[0012] In some embodiments, evacuating the furnace to achieve a secondary passivation initial vacuum, and then repeatedly opening the gas inlet switch to allow filtered air to enter the furnace, includes: evacuating the furnace to reduce the gas pressure inside the furnace to 20 kPa, then activating the strong cooling device and opening the gas inlet switch 16 times to allow filtered air to enter the furnace. Each time the gas inlet switch is opened, the furnace pressure is increased by a preset amount before the gas inlet switch is closed. The first opening of the gas inlet switch increases the furnace pressure by 2 kPa, the second to seventh openings increase the furnace pressure by 3 kPa each time, and the eighth to sixteenth openings increase the furnace pressure by 5 kPa each time. Between two consecutive openings of the gas inlet switch, after the previous opening is closed, the next opening of the gas inlet switch is allowed 10 to 15 minutes.

[0013] In some embodiments, the method further includes: testing the reaction apparatus before it contains tantalum powder, including evacuating the furnace to bring the gas pressure inside the furnace to 20 kPa, then turning on the strong cooling device and the gas inlet switch to allow filtered air to be introduced into the furnace, and continuously measuring the time S1 when the gas pressure inside the furnace increases from 20 kPa to 30 kPa, the time S2 when the gas pressure inside the furnace increases from 30 kPa to 40 kPa, the time S3 when the gas pressure inside the furnace increases from 40 kPa to 50 kPa, the time S4 ​​when the gas pressure inside the furnace increases from 50 kPa to 60 kPa, the time S5 when the gas pressure inside the furnace increases from 60 kPa to 70 kPa, the time S6 when the gas pressure inside the furnace increases from 70 kPa to 80 kPa, and the time S7 when the gas pressure inside the furnace increases from 80 kPa to 80 kPa. The time S7 for the gas pressure to reach 90 kPa from 0 kPa; the process of opening the gas inlet switch 16 times to allow filtered air to be introduced into the furnace includes: the time for which the gas inlet switch is kept open after the first opening is (S1+S2) / 10, the time for which the gas inlet switch is kept open after the second to seventh opening is 3(S1+S2) / 20, the time for which the gas inlet switch is kept open after the eighth to ninth opening is S3 / 2, the time for which the gas inlet switch is kept open after the tenth to eleventh opening is S4 / 2, the time for which the gas inlet switch is kept open after the twelfth to thirteenth opening is S5 / 2, and the time for which the gas inlet switch is kept open after the sixteenth opening is S7 / 2.

[0014] In some embodiments, shutting off the forced cooling device and evacuating the furnace to achieve the final passivation initial vacuum level, followed by repeatedly opening the gas inlet switch to allow filtered air to enter the furnace, includes: evacuating the furnace to reduce the gas pressure inside the furnace to 50 kPa, then opening the gas inlet switch 8 times to allow filtered air to enter the furnace. Each time the gas inlet switch is opened, the furnace pressure is increased by a preset amount before the gas inlet switch is closed. Each time the gas inlet switch is opened, the furnace pressure is increased by 5 kPa. Between two consecutive openings of the gas inlet switch, after the previous opening of the gas inlet switch is closed, 10 minutes are allowed before the next opening of the gas inlet switch.

[0015] In some embodiments, the method further includes: testing the reaction apparatus before it contains tantalum powder, including evacuating the furnace to bring the gas pressure inside the furnace to 20 kPa, then turning on the strong cooling device and the gas inlet switch to allow filtered air to be introduced into the furnace, and continuously measuring the time S1 for the gas pressure inside the furnace to increase from 20 kPa to 30 kPa, the time S2 for the gas pressure inside the furnace to increase from 30 kPa to 40 kPa, the time S3 for the gas pressure inside the furnace to increase from 40 kPa to 50 kPa, the time S4 ​​for the gas pressure inside the furnace to increase from 50 kPa to 60 kPa, and the time S5 for the gas pressure inside the furnace to increase from 60 kPa to 70 kPa. Time S5, time S6 for the gas pressure in the furnace to increase from 70 kPa to 80 kPa, and time S7 for the gas pressure in the furnace to increase from 80 kPa to 90 kPa; the process of opening the gas inlet switch 8 times to allow filtered air to be introduced into the furnace includes: the gas inlet switch being kept open for 2 seconds after the first and second openings, the gas inlet switch being kept open for 2 seconds after the third and fourth openings, the gas inlet switch being kept open for 2 seconds after the fifth and sixth openings, the gas inlet switch being kept open for 2 seconds after the fifth and sixth openings, and the gas inlet switch being kept open for 2 seconds after the seventh and eighth openings, the gas inlet switch being kept open for 2 seconds after the seventh and eighth openings.

[0016] In some embodiments, the final passivation step further includes: when the temperature difference between the tantalum powder located in the furnace and the final passivation starting temperature is detected to be greater than a threshold temperature, repeating the second passivation step, and then proceeding to the final passivation step.

[0017] In some embodiments, the threshold temperature is 3°C.

[0018] A second aspect of the present invention discloses a reaction apparatus for passivation of tantalum powder using any of the methods described above, comprising a furnace body, a gas inlet switch connected to the furnace body for controlling whether gas is introduced into the furnace, and a strong cooling device. The strong cooling device includes a strong cooling gas inlet communicating with the rear end of the furnace, a heat exchange chamber communicating with the strong cooling gas inlet, a buffer tank, a strong cooling gas input device communicating with the front end of the furnace, a circulation pump connected between the strong cooling gas inlet and the strong cooling gas input device, a first pipe connected between the strong cooling gas inlet and the heat exchange chamber, a second pipe connected between the heat exchange chamber and the buffer tank, a third pipe connected between the buffer tank and the strong cooling gas input device, and a refrigeration device arranged around the heat exchange chamber for cooling the gas in the heat exchange chamber. An axial heat insulation screen is provided between the strong cooling gas inlet and the front end of the furnace, the axial heat insulation screen being used to insulate and prevent gas from the front end of the furnace from directly entering the strong cooling gas inlet in a direction parallel to the axis of the furnace.

[0019] In some embodiments, the furnace body is further provided with a multi-layered annular radial heat insulation screen surrounding the furnace body. The forced cooling gas input device includes a main pipe that is connected to the third pipe and arranged around the multi-layered annular radial heat insulation screen, and a plurality of branch pipes arranged at intervals along the circumference. The plurality of branch pipes are connected to the main pipe. The multi-layered radial heat insulation screen includes a first heat insulation screen and a second heat insulation screen located radially inside the furnace body. The first heat insulation screen and the second heat insulation screen are provided with gas channels along the radial direction. The branch pipes pass radially through the heat insulation screens of the multi-layered radial heat insulation screen other than the first heat insulation screen and the second heat insulation screen, and then communicate with the gas channels.

[0020] Based on the tantalum powder passivation method provided by the present invention, by performing a first passivation step, a second passivation step and a final passivation step, the passivation process of tantalum powder can be stably and effectively realized, and the passivation of tantalum powder can be fully and effectively achieved.

[0021] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0023] Figure 1 This is a schematic diagram of the reaction apparatus used in the tantalum powder passivation method of this invention.

[0024] Figure 2 for Figure 1A partially enlarged schematic diagram of the reaction apparatus shown;

[0025] Figure 3 for Figure 1 A schematic diagram of the reaction apparatus from another angle. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0028] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0031] The tantalum powder passivation method of this embodiment includes a reaction device, which includes a furnace body 1, a gas introduction switch 6 connected to the furnace chamber of the furnace body 1 for controlling whether to introduce gas into the furnace chamber, and a strong cooling device. The tantalum powder passivation method includes an inert gas cooling step, a primary passivation step, and a secondary passivation step.

[0032] The inert gas cooling step involves filling the furnace chamber, which contains heat-treated tantalum powder at the front, with an inert gas, such as argon. Figure 1 As shown, tantalum powder is placed in the furnace through crucible 4 for passivation.

[0033] The passivation process includes cooling the tantalum powder to the initial passivation temperature, evacuating the furnace to achieve the initial passivation vacuum level, then activating the strong cooling device and repeatedly opening the gas inlet switch 6 to introduce filtered air into the furnace. As shown in the figure, the reaction apparatus also includes a vacuum pipe 2 connected to the furnace; opening or closing the vacuum pipe 2 allows for evacuation of the furnace. The reaction apparatus also includes a thermocouple 5 for measuring the furnace temperature and a temperature control instrument 9 connected to the thermocouple 5 signal. The gas inlet switch 6 is as follows... Figure 1The system may include an electromagnetic switch. A gas inlet switch 6 is connected to a gas source or exposed to the outside atmosphere via a filter 7. Opening the gas inlet switch 6 introduces oxygen-containing gas into the furnace. The initial passivation temperature is selected from 30 to 35°C, and the initial vacuum level for one passivation step can be set, for example, to a gas pressure of 50 kPa in the furnace. The forced cooling device includes a forced cooling gas inlet 15 connected to the rear end of the furnace, a heat exchange chamber 19 connected to the forced cooling gas inlet 15, a buffer tank 11, a forced cooling gas input device connected to the front end of the furnace, a circulation pump 17 connected between the forced cooling gas inlet 15 and the forced cooling gas input device, a first pipe 16 connected between the forced cooling gas inlet 15 and the heat exchange chamber 19, a second pipe connected between the heat exchange chamber 19 and the buffer tank 11, a third pipe connected between the buffer tank 11 and the forced cooling gas input device, and a refrigeration device 18 surrounding the heat exchange chamber 19 for cooling the gas within the heat exchange chamber 19. An axial heat shield 10 is installed between the gas inlet 15 and the front end of the furnace. The axial heat shield 10 is used to insulate against heat and prevent gas from the front end of the furnace from directly entering the cooling gas inlet 15 in a direction parallel to the furnace axis. After the cooling device is turned on, the circulation pump 17 operates, drawing gas from the furnace through the cooling gas inlet 15. The gas then enters the heat exchange chamber 19 through the first pipe 16, where it is cooled by the cooling device 18. It then enters the buffer tank 11 through the second pipe for buffering, and from the buffer tank 11, it enters the cooling gas input device through the third pipe. The gas then returns to the furnace through the cooling gas input device for the next cycle. During the passivation step, the cooling device remains on after being turned on. Through this passivation step, the tantalum powder can undergo preliminary passivation smoothly and orderly. The continued operation of the cooling device ensures a stable oxidation temperature for the tantalum powder and improves the uniformity of the gas, making the reaction with the tantalum powder more uniform and ensuring a safer and more reliable passivation process. The refrigeration device may include refrigeration cycle systems such as air conditioning systems, and the circulation pump may include an oil-free vacuum pump. An oil-free vacuum pump is a vacuum pump that has both vacuuming and compression functions, and does not produce oil fumes or contaminate the compressed gas.

[0034] The secondary passivation step includes: shutting off the refrigeration device and evacuating the furnace to achieve the initial vacuum level for secondary passivation; then turning on the refrigeration device and repeatedly opening gas inlet switch 6 to introduce filtered air into the furnace. During the secondary passivation process, the refrigeration device remains on after being turned on. Each time gas inlet switch 6 is opened during the secondary passivation process, the increased gas pressure in the furnace is greater than or equal to the increased gas pressure during the first passivation step. After the first passivation process is completed, preliminary oxidation has formed on the surface of the tantalum powder. At this point, oxygen-containing gas at a higher pressure can be introduced to further enhance the degree and effectiveness of surface oxide formation on the tantalum powder. With the refrigeration device on, the tantalum powder can complete deep passivation in the secondary passivation step.

[0035] The final passivation step includes: shutting off the strong cooling device and evacuating the furnace to achieve the initial vacuum level for final passivation; detecting the temperature of the tantalum powder in the furnace at the final passivation initiation temperature; and then repeatedly opening the gas inlet switch 6 to introduce filtered air into the furnace. During the final passivation step, the strong cooling device remains off, and the temperature difference between the tantalum powder in the furnace and the final passivation initiation temperature is constantly monitored to ensure it does not exceed a threshold temperature. Each time the gas inlet switch 6 is opened during the final passivation process, the increased gas pressure in the furnace is greater than or equal to the increased gas pressure during the secondary passivation process. After the high-specific-capacity tantalum metal powder completes the first and second passivation steps, a relatively dense oxide layer has formed on its surface. However, to ensure more complete passivation of the tantalum metal powder and avoid safety hazards such as localized temperature increases, over-oxidation, or combustion due to insufficient passivation, a final passivation is required. The final passivation step involves filling the furnace with oxygen-containing gas at the highest pressure, which enables the tantalum powder to complete a comprehensive and deep passivation process. It also allows for the verification of the passivation effect after the first and second passivation steps. If the temperature difference between the tantalum powder in the furnace and the final passivation starting temperature is greater than the threshold temperature, it indicates that the passivation effect after the first and second passivation steps is not comprehensive or ideal.

[0036] The tantalum powder passivation method of this embodiment, by performing a first passivation step, a second passivation step, and a final passivation step, enables the tantalum powder passivation process to be stable and effective, and ensures that the tantalum powder passivation is sufficient and effective.

[0037] In some embodiments, filling the furnace containing heat-treated tantalum powder with inert gas includes: lowering the temperature of the heat-treated tantalum powder in the furnace to 300–600°C, and then filling the furnace with inert gas to raise the gas pressure in the furnace to 60–80 kPa, while the forced cooling device remains on during this process. After heat treatment, the tantalum metal powder is first cooled to 300–600°C in a vacuum environment inside the furnace (e.g., the gas pressure inside the furnace is less than 0.5 Pa), and then inert gas is filled to 60–80 kPa for further cooling. Rapid cooling of the tantalum powder can be achieved by activating the forced cooling device.

[0038] In some embodiments, after the tantalum powder is cooled to the passivation start temperature, the furnace is evacuated to achieve the initial passivation vacuum level. Then, the strong cooling device is activated, and the gas inlet switch 6 is opened multiple times to allow filtered air to enter the furnace. This includes: after the tantalum powder is cooled to 30-35°C, the furnace is evacuated to reduce the gas pressure inside the furnace to 50 kPa. Then, the strong cooling device is activated, and the gas inlet switch 6 is opened 16 times to allow filtered air to enter the furnace. Each time the gas inlet switch 6 is opened, the gas pressure in the furnace increases by 2 kPa before the gas inlet switch 6 is closed. Between two consecutive openings of the gas inlet switch 6, after the previous opening is closed, the next opening of the gas inlet switch 6 is allowed 15-20 minutes. This passivation step in this embodiment allows the tantalum metal powder to react slowly with oxygen in the air, maintaining a stable temperature and ensuring that air flows evenly to the tantalum metal powder, allowing the tantalum powder to passivate uniformly and sufficiently in a shorter time.

[0039] In some embodiments, the passivation method for tantalum powder further includes: testing the reaction apparatus before it contains tantalum powder, including evacuating the furnace to bring the gas pressure inside the furnace to 20 kPa, then turning on the strong cooling device and the gas inlet switch 6 to allow filtered air to be introduced into the furnace, and continuously measuring the time S1 when the gas pressure inside the furnace increases from 20 kPa to 30 kPa, the time S2 when the gas pressure inside the furnace increases from 30 kPa to 40 kPa, the time S3 when the gas pressure inside the furnace increases from 40 kPa to 50 kPa, the time S4 ​​when the gas pressure inside the furnace increases from 50 kPa to 60 kPa, the time S5 when the gas pressure inside the furnace increases from 60 kPa to 70 kPa, and the time S6 when the gas pressure inside the furnace increases from 70 kPa to 100 kPa. The time S6 is for the gas pressure to reach 80 kPa, and the time S7 is for the gas pressure in the furnace to increase from 80 kPa to 90 kPa. The gas inlet switch 6 is opened 16 times to allow filtered air to enter the furnace. Each time the gas inlet switch 6 is opened, the gas pressure in the furnace increases by 2 kPa before the gas inlet switch 6 is closed. This includes: after the first to fifth openings, the gas inlet switch 6 is kept open for S4 / 5; after the sixth to tenth openings, it is kept open for S5 / 5; after the eleventh to fifteenth openings, it is kept open for S6 / 5; and after the sixteenth opening, it is kept open for S7 / 5. In this embodiment, by measuring the gas pressure process of the reaction device before the passivation operation of tantalum powder, and by studying and establishing the correspondence between the opening time of the gas inlet switch 6 and the gas pressure, the gas pressure in the furnace can be quickly and effectively controlled by controlling the opening time of the gas inlet switch during the passivation operation. This embodiment provides a solution for quickly and accurately controlling the actual charging pressure to match the theoretical charging pressure, facilitating a safe and controllable passivation process for high-specific-capacity tantalum metal powder. It can be applied to the calibration of passivation charging pressure in vacuum equipment, as well as solutions for inconsistencies between the passivation charging pressure and the theoretical charging pressure caused by the commissioning of new vacuum equipment, replacement of furnace shells, or replacement of temperature control instruments.

[0040] In some embodiments, evacuating the furnace to achieve the initial vacuum level for secondary passivation, and then repeatedly opening the gas inlet switch 6 to introduce filtered air into the furnace, includes: evacuating the furnace to reduce the gas pressure inside the furnace to 20 kPa, then activating the strong cooling device and opening the gas inlet switch 6 16 times to introduce filtered air into the furnace. Each time the gas inlet switch 6 is opened, it increases the gas pressure in the furnace by a preset amount before closing it. The first opening of the gas inlet switch 6 increases the gas pressure in the furnace by 2 kPa, the second to seventh openings increase the gas pressure by 3 kPa each time, and the eighth to sixteenth openings increase the gas pressure by 5 kPa each time. Between two consecutive openings of the gas inlet switch 6, after the previous opening is closed, the next opening of the gas inlet switch 6 is allowed 10 to 15 minutes. This embodiment can achieve more thorough passivation of high-specific-capacity tantalum metal powder.

[0041] In some embodiments, the method further includes: testing the reaction apparatus before it contains tantalum powder, including evacuating the furnace to bring the gas pressure inside the furnace to 20 kPa, then turning on the strong cooling device and the gas inlet switch 6 to allow filtered air to be introduced into the furnace, and continuously measuring the time S1 when the gas pressure inside the furnace increases from 20 kPa to 30 kPa, the time S2 when the gas pressure inside the furnace increases from 30 kPa to 40 kPa, the time S3 when the gas pressure inside the furnace increases from 40 kPa to 50 kPa, the time S4 ​​when the gas pressure inside the furnace increases from 50 kPa to 60 kPa, the time S5 when the gas pressure inside the furnace increases from 60 kPa to 70 kPa, the time S6 when the gas pressure inside the furnace increases from 70 kPa to 80 kPa, and the time S7 when the gas pressure inside the furnace increases from 80 kPa to 90 kPa. The time S7 is the time to open the gas inlet switch 6 16 times to allow filtered air to be introduced into the furnace, including: the time to keep the gas inlet switch 6 open after the first opening is (S1+S2) / 10, the time to keep the gas inlet switch 6 open after the second to seventh opening is 3(S1+S2) / 20, the time to keep the gas inlet switch 6 open after the eighth to ninth opening is S3 / 2, the time to keep the gas inlet switch 6 open after the tenth to eleventh opening is S4 / 2, the time to keep the gas inlet switch 6 open after the twelfth to thirteenth opening is S5 / 2, and the time to keep the gas inlet switch 6 open after the sixteenth opening is S7 / 2.

[0042] In some embodiments, shutting off the forced cooling device and evacuating the furnace to achieve the final passivation initial vacuum level, and then repeatedly opening the gas inlet switch 6 to allow filtered air to enter the furnace, includes: evacuating the furnace to reduce the gas pressure inside the furnace to 50 kPa, and then opening the gas inlet switch 6 8 times to allow filtered air to enter the furnace. Each time the gas inlet switch 6 is opened, the furnace pressure is increased by a preset amount, and then the gas inlet switch 6 is closed. Each time the gas inlet switch 6 is opened, the furnace pressure is increased by 5 kPa. Between two consecutive openings of the gas inlet switch 6, after the previous opening of the gas inlet switch 6 is closed, 10 minutes are passed before the next opening of the gas inlet switch 6 is opened.

[0043] In some embodiments, the method further includes: testing the reaction apparatus before it contains tantalum powder, including evacuating the furnace to bring the gas pressure inside the furnace to 20 kPa, then turning on the strong cooling device and the gas inlet switch 6 to allow filtered air to be introduced into the furnace, and continuously measuring the time S1 when the gas pressure inside the furnace increases from 20 kPa to 30 kPa, the time S2 when the gas pressure inside the furnace increases from 30 kPa to 40 kPa, the time S3 when the gas pressure inside the furnace increases from 40 kPa to 50 kPa, the time S4 ​​when the gas pressure inside the furnace increases from 50 kPa to 60 kPa, and the time S5 when the gas pressure inside the furnace increases from 60 kPa to 70 kPa. The time S6 for the gas pressure inside the furnace to increase from 70 kPa to 80 kPa, and the time S7 for the gas pressure inside the furnace to increase from 80 kPa to 90 kPa; the process of opening the gas inlet switch 6 8 times to allow filtered air to be introduced into the furnace includes: the time after opening the gas inlet switch 6 for the first and second times is S4 / 2, the time after opening the gas inlet switch 6 for the third and fourth times is S5 / 2, the time after opening the gas inlet switch 6 for the fifth and sixth times is S6 / 2, and the time after opening the gas inlet switch 6 for the seventh and eighth times is S7 / 2. This embodiment allows for the precise determination of the required gas filling time for each of the primary, secondary, and final passivation steps of a reaction device by statistically analyzing seven time periods from S1 to S7. This time is then sequentially input into the temperature control instrument, achieving a near-identical relationship between the actual and theoretical gas filling pressures of the passivation method. Furthermore, it offers high efficiency and avoids situations where insufficient or excessive gas filling leads to over-oxidation or incomplete oxidation of the tantalum metal powder.

[0044] In some embodiments, the final passivation step further includes: when the temperature difference between the tantalum powder located in the furnace and the final passivation initiation temperature is detected to be greater than a threshold temperature, repeating the second passivation step before proceeding to the final passivation step. This embodiment supplements the passivation step by performing a second passivation step on tantalum powder that has not been sufficiently and uniformly passivated after the first and second passivation steps. This timely second passivation step compensates for previous passivation deficiencies, avoiding loss and waste of ineffectively passivated tantalum powder. Then, re-entering the final passivation step for inspection ensures effective and comprehensive passivation of the tantalum powder.

[0045] In some embodiments, the threshold temperature is 3°C.

[0046] In some embodiments, a reaction apparatus for applying any of the above-described tantalum powder passivation methods is also disclosed. The reaction apparatus includes a furnace body 1, a gas inlet switch 6 connected to the furnace chamber of the furnace body 1 for controlling whether gas is introduced into the furnace chamber, and a strong cooling device. The strong cooling device includes a strong cooling gas inlet 15 connected to the rear end of the furnace chamber, a heat exchange chamber 19 connected to the strong cooling gas inlet 15, a buffer tank 11, a strong cooling gas input device connected to the front end of the furnace chamber, a circulation pump 17 connected between the strong cooling gas inlet 15 and the strong cooling gas input device, and a circulation pump 17 connected to the strong cooling gas inlet 15. The furnace includes a first pipe 16 between the inlet 15 and the heat exchange chamber 19, a second pipe between the heat exchange chamber 19 and the buffer tank 11, a third pipe between the buffer tank 11 and the forced cooling gas input device, and a refrigeration device 18 arranged around the heat exchange chamber 19 for cooling the gas inside the heat exchange chamber 19. An axial heat insulation screen 10 is provided between the forced cooling gas inlet 15 and the front end of the furnace. The axial heat insulation screen 10 is used to insulate and prevent gas from the front end of the furnace from directly entering the forced cooling gas inlet 15 in a direction parallel to the axis of the furnace.

[0047] In some embodiments, such as Figure 2 As shown, the furnace body 1 is also equipped with a multi-layered annular radial heat shield 4 surrounding the furnace body 1. The forced cooling gas input device includes a main pipe 12 connected to the third pipe and arranged around the multi-layered annular radial heat shield 4, and multiple branch pipes 13 arranged circumferentially. The multiple branch pipes 13 are connected to the main pipe 12. The multi-layered radial heat shield 4 includes a first heat shield and a second heat shield located radially inside the furnace body 1. The first heat shield and the second heat shield are provided with gas channels 14 radially. The branch pipes 13 pass radially through the heat shields of the multi-layered radial heat shield 4 other than the first and second heat shields and then connect to the gas channels 14. The branch pipes are preferably made of tantalum or high-temperature molybdenum near the front furnace door of the furnace chamber. The inner diameter of the pipe is 8-14 mm. The outlet end of the pipe is located between the second and third layers of radial heat shields. The number of branch pipes is 3-5, and they are distributed at the upper end. In this embodiment, the reaction apparatus does not blow up volatiles inside the furnace or between radial heat shields during tantalum metal powder passivation, thus avoiding contamination of the furnace chamber and metal powder.

[0048] Example

[0049] (1) Select one ZR-189 vacuum heat treatment furnace equipped with a strong cooling device, evacuate to 20 kPa and fill with gas, and record the time required for each 10 kPa filling from 20 kPa to 90 kPa. Based on the records, obtain the filling time for each segment of the first passivation step, the second passivation step and the final passivation step, and set the time in the passivation time program of the heat treatment furnace temperature control instrument.

[0050] The ZR-189 vacuum furnace operates the passivation program, and the pressure accuracy of each stage of the gas filling process can be controlled within ±0.2 kPa. This verifies that the scheme involved in the passivation method can accurately control the passivation gas filling pressure according to the theoretical value, as shown in Table 1.

[0051] Table 1. Measured Passivation Gas Pressure of ZR-189 Vacuum Furnace

[0052]

[0053] (2) Two batches of tantalum powder of grade FTW-100K obtained by sodium reduction were labeled as 100K-1 and 100K-3, respectively. The tantalum powder had Fe impurities <6ppm and C impurities <15ppm.

[0054] (3) Weigh tantalum powder of batches 100K-1 and 100K-3 evenly into a crucible, place it in a ZR-189 vacuum heat treatment furnace for high-temperature vacuum heat treatment, sintering process 1100-1300℃ / 30-60min, vacuum ≤0.4pa.

[0055] In the ZR-189 furnace at 100K-1, a strong cooling device is used for cooling and passivation, and the passivation method described above is used. In the ZR-189 furnace at 100K-3, a strong cooling device is not used for cooling and passivation, and the old process is used for passivation, with a passivation cycle of 16 hours.

[0056] (4) After sintering, when the temperature drops below 400℃, argon gas is backfilled to 60-80Kpa. A strong cooling device is used to rapidly cool the tantalum metal powder to 35℃ (the passivation temperature). This strong cooling device can prevent the volatiles from being blown up, and the impurity content on the material surface is normal, as shown in Table 2.

[0057] (5) When the temperature drops below 35°C, perform the first passivation step, the second passivation step, and the final passivation step, and fill the furnace with air to passivate the tantalum powder. As shown in Table 2, using a strong cooling device can avoid the temperature rise problem during tantalum powder passivation. Without using a strong cooling device, the material will experience a temperature rise, which will prolong the passivation time (Note: When the temperature rises during passivation to a certain value, passivation must be stopped and the passivation can continue after the temperature drops to the passivation temperature).

[0058] (6) After passivation, the heat-treated 100K-1 and 100K-3 tantalum powders were removed from the crucible, and the oxygen content of the tantalum powder materials was measured. The results are shown in Table 2.

[0059] When tantalum powder is subjected to strong cooling during passivation in a vacuum furnace, no material temperature rise occurs. After passivation, the tantalum metal powder is stable. When passivation is performed without strong cooling, the tantalum powder temperature rises to 43°C, the oxygen content of the tantalum powder increases relatively, and the passivation cycle is longer.

[0060] Table 2 Comparison of data between using and not using forced cooling systems.

[0061]

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method of passivating tantalum powder, characterized by, The apparatus includes a reaction device, which comprises a furnace body, a gas introduction switch connected to the furnace chamber for controlling whether gas is introduced into the furnace chamber, and a forced cooling device. The passivation method for the tantalum powder includes: An inert gas is introduced into the furnace chamber containing heat-treated tantalum powder at the front end. The passivation process includes, after the tantalum powder is cooled to the passivation start temperature, evacuating the furnace to achieve the initial passivation vacuum level, then activating the refrigeration system and repeatedly opening the gas inlet switch to allow filtered air to be introduced into the furnace. The refrigeration system includes a refrigeration gas inlet connected to the rear end of the furnace, a heat exchange chamber connected to the refrigeration gas inlet, a buffer tank, a refrigeration gas input device connected to the front end of the furnace, a circulation pump connected between the refrigeration gas inlet and the refrigeration gas input device, and a circulation pump connected between the refrigeration gas inlet and the heat exchange chamber. The system includes a first pipe between the chambers, a second pipe connecting the heat exchange chamber and the buffer tank, a third pipe connecting the buffer tank and the refrigeration gas input device, and a refrigeration device surrounding the heat exchange chamber for cooling the gas inside the heat exchange chamber. An axial heat shield is provided between the refrigeration gas inlet and the front end of the furnace. The axial heat shield is used to insulate and prevent gas from the front end of the furnace from directly entering the refrigeration gas inlet in a direction parallel to the axis of the furnace. During a passivation step, the refrigeration device remains on after being opened. The secondary passivation step includes: turning off the strong cooling device and evacuating the furnace to achieve the initial vacuum level for secondary passivation; then turning on the strong cooling device and repeatedly opening the gas inlet switch to allow filtered air to be introduced into the furnace. During the secondary passivation process, the strong cooling device remains on after being turned on, and the gas pressure increase in the furnace caused by each opening of the gas inlet switch during the secondary passivation process is greater than or equal to the gas pressure increase in the furnace caused by each opening of the gas inlet switch during the primary passivation step. The final passivation step includes: shutting off the strong cooling device and evacuating the furnace to achieve the final passivation initiation vacuum level; detecting the final passivation initiation temperature of the tantalum powder in the furnace; and then repeatedly opening the gas inlet switch to allow filtered air to be introduced into the furnace. During the final passivation step, the strong cooling device is not turned on, and the temperature difference between the tantalum powder in the furnace and the final passivation initiation temperature is constantly monitored to ensure it is greater than a threshold temperature. The increase in gas pressure in the furnace caused by each opening of the gas inlet switch during the final passivation process is greater than or equal to the increase in gas pressure in the furnace caused by each opening of the gas inlet switch during the secondary passivation process.

2. The method of passivating tantalum powder according to claim 1, wherein The process of filling an inert gas into a furnace containing heat-treated tantalum powder at the front end includes: reducing the temperature of the heat-treated tantalum powder in the furnace to 300-600°C, and then filling the furnace with inert gas to raise the gas pressure in the furnace to 60-80 kPa, while the forced cooling device remains on during this process.

3. The method of passivating tantalum powder according to claim 1, wherein After the tantalum powder is cooled to the passivation start temperature, the furnace is evacuated to achieve the initial passivation vacuum level. Then, the strong cooling device is turned on and the gas inlet switch is opened 16 times to allow filtered air to enter the furnace. This includes: after the tantalum powder is cooled to 30~35℃, the furnace is evacuated to reduce the gas pressure in the furnace to 50Kpa. Then, the strong cooling device is turned on and the gas inlet switch is opened 16 times to allow filtered air to enter the furnace. Each time the gas inlet switch is opened, the gas pressure in the furnace increases by 2Kpa before the gas inlet switch is closed. Between two consecutive openings of the gas inlet switch, after the previous opening of the gas inlet switch is closed, the next opening of the gas inlet switch is allowed to occur after 15~20 minutes.

4. The passivation method for tantalum powder as described in claim 3, characterized in that, Also includes: Before the reaction apparatus is filled with tantalum powder, it is tested, including evacuating the furnace to achieve a gas pressure of 20 kPa, then turning on the strong cooling device and the gas inlet switch to allow filtered air to be introduced into the furnace. The time S1 for the gas pressure in the furnace to increase from 20 kPa to 30 kPa, the time S2 for the gas pressure to increase from 30 kPa to 40 kPa, the time S3 for the gas pressure to increase from 40 kPa to 50 kPa, the time S4 ​​for the gas pressure to increase from 50 kPa to 60 kPa, the time S5 for the gas pressure to increase from 60 kPa to 70 kPa, and the time S6 for the gas pressure to increase from 70 kPa to 80 kPa are continuously measured. The time S6 for gas inlet a, the time S7 for gas pressure in furnace to rise from 80 kPa to 90 kPa; the process of opening the gas inlet switch 16 times to allow filtered air to enter the furnace, with each opening increasing the gas pressure in the furnace by 2 kPa before closing the gas inlet switch includes: the gas inlet switch being kept open for S4 / 5 after the first to fifth openings, the gas inlet switch being kept open for S5 / 5 after the sixth to tenth openings, the gas inlet switch being kept open for S6 / 5 after the eleventh to fifteenth openings, and the gas inlet switch being kept open for S7 / 5 after the sixteenth opening.

5. The passivation method for tantalum powder as described in claim 1, characterized in that, The process of evacuating the furnace to achieve a secondary passivation initial vacuum, followed by repeatedly opening the gas inlet switch to allow filtered air to enter the furnace, includes: evacuating the furnace to reduce the gas pressure to 20 kPa; then activating the strong cooling device and opening the gas inlet switch 16 times to allow filtered air to enter the furnace. Each time the gas inlet switch is opened, it increases the furnace pressure by a preset amount before closing. The first opening of the gas inlet switch increases the furnace pressure by 2 kPa; the second to seventh openings increase the furnace pressure by 3 kPa each time; and the eighth to sixteenth openings increase the furnace pressure by 5 kPa each time. Between two consecutive openings of the gas inlet switch, after the previous opening is closed, the next opening of the gas inlet switch is allowed 10-15 minutes.

6. The passivation method for tantalum powder as described in claim 5, characterized in that, Also includes: Before the reaction apparatus is filled with tantalum powder, it is tested, including evacuating the furnace to bring the gas pressure inside the furnace to 20 kPa, then turning on the strong cooling device and the gas inlet switch to allow filtered air to be introduced into the furnace. The time S1 for the gas pressure inside the furnace to increase from 20 kPa to 30 kPa, the time S2 for the gas pressure inside the furnace to increase from 30 kPa to 40 kPa, the time S3 for the gas pressure inside the furnace to increase from 40 kPa to 50 kPa, the time S4 ​​for the gas pressure inside the furnace to increase from 50 kPa to 60 kPa, the time S5 for the gas pressure inside the furnace to increase from 60 kPa to 70 kPa, the time S6 for the gas pressure inside the furnace to increase from 70 kPa to 80 kPa, and the time S7 for the gas pressure inside the furnace to increase from 80 kPa to 90 kPa. The time S7 is 90 kPa; the process of opening the gas inlet switch 16 times to allow filtered air to be introduced into the furnace includes: the gas inlet switch is kept open for (S1+S2) / 10 after the first opening, the gas inlet switch is kept open for 3(S1+S2) / 20 after the second to seventh opening, the gas inlet switch is kept open for S3 / 2 after the eighth to ninth opening, the gas inlet switch is kept open for S4 / 2 after the tenth to eleventh opening, the gas inlet switch is kept open for S5 / 2 after the twelfth to thirteenth opening, and the gas inlet switch is kept open for S7 / 2 after the sixteenth opening.

7. The passivation method for tantalum powder as described in claim 1, characterized in that, The process involves shutting down the forced cooling device and evacuating the furnace to achieve the final passivation initial vacuum level. Then, the gas inlet switch is opened multiple times to allow filtered air to enter the furnace. This includes: evacuating the furnace to reduce the gas pressure to 50 kPa; then opening the gas inlet switch eight times to allow filtered air to enter the furnace. Each time the gas inlet switch is opened, the furnace pressure is increased by a preset value before the switch is closed. Each time the gas inlet switch is opened, the furnace pressure is increased by 5 kPa. Between two consecutive openings of the gas inlet switch, after the previous opening is closed, the next opening of the gas inlet switch is allowed 10 minutes.

8. The passivation method for tantalum powder as described in claim 7, characterized in that, Also includes: Before the reaction apparatus is filled with tantalum powder, it is tested, including evacuating the furnace to bring the gas pressure inside the furnace to 20 kPa, then turning on the strong cooling device and the gas inlet switch to allow filtered air to be introduced into the furnace. The time S1 for the gas pressure inside the furnace to increase from 20 kPa to 30 kPa, the time S2 for the gas pressure inside the furnace to increase from 30 kPa to 40 kPa, the time S3 for the gas pressure inside the furnace to increase from 40 kPa to 50 kPa, the time S4 ​​for the gas pressure inside the furnace to increase from 50 kPa to 60 kPa, and the time S5 for the gas pressure inside the furnace to increase from 60 kPa to 70 kPa are continuously measured during this process. The time S6 for the gas pressure inside the furnace to increase from 70 kPa to 80 kPa, and the time S7 for the gas pressure inside the furnace to increase from 80 kPa to 90 kPa; the process of opening the gas inlet switch 8 times to allow filtered air to be introduced into the furnace includes: the time after opening the gas inlet switch for the first and second times is S4 / 2, the time after opening the gas inlet switch for the third and fourth times is S5 / 2, the time after opening the gas inlet switch for the fifth and sixth times is S6 / 2, and the time after opening the gas inlet switch for the seventh and eighth times is S7 / 2.

9. The passivation method for tantalum powder as described in claim 1, characterized in that, The final passivation step further includes: when the temperature difference between the tantalum powder in the furnace and the final passivation starting temperature is detected to be greater than the threshold temperature, the second passivation step is repeated, and then the final passivation step is entered.

10. The passivation method for tantalum powder as described in claim 1, characterized in that, The threshold temperature is 3°C.

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