Slidable spring contact device for pressure assisted flash sintering apparatus

Abstract

The application belongs to the technical field of powder metallurgy, and particularly relates to a slidable elastic electric contact device for a pressure-assisted flash sintering equipment, which can be used as a pressure head in the pressure-assisted flash sintering equipment. In the process of pressure-assisted flash sintering, the slidable pressure head in the electric contact device can slide along the protruding cylindrical positioning shaft above the base under the action of axial pressure, and the use of the conductive sliding bearing ensures that the slidable pressure head can maintain good electric contact with the base during the sliding process and continuously transmit electric current. The lower surface of the slidable pressure head is in contact with the spring, which can conduct the axial pressure to the spring, so that the spring is deformed and stores elastic potential energy. Once the flash sintering phenomenon occurs and causes the sample to rapidly shrink, the spring will immediately release the stored elastic potential energy and push the slidable pressure head to rapidly slide upwards, so that good electric contact between each component bearing the axial pressure can be maintained when the flash sintering occurs, and the pressure flash problem is improved.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, specifically to a sliding elastic electrical contact device for pressure-assisted flash sintering equipment. Background Technology

[0002] The conventional flash sintering process for ceramic materials is characterized by the following: at a specific furnace temperature, an electric field of a certain intensity is directly applied to the green body via electrodes. After a certain "incubation period," Joule thermal runaway, rapid temperature rise, intense flashing, and rapid densification occur on the green body. During flash sintering, rapid densification causes a rapid shrinkage of the green body's macroscopic dimensions, posing a challenge to maintaining good electrical contact between the electrodes and the green body. In pressureless flash sintering equipment, the electrodes are typically platinum wires, welded to the green body using conductive metal paste, generally eliminating issues such as electrode detachment. In pressure-assisted flash sintering equipment, the green body is usually placed in an insulated mold, and current and pressure are applied to it via upper and lower electrodes. This type of equipment is usually modified from hot pressing or spark plasma sintering (SPS) equipment. However, the densification rate of hot pressing and SPS is far lower than that of flash sintering. For example, zirconia ceramics typically require tens of minutes to several hours to reach a density of over 95% under hot pressing sintering, several minutes to tens of minutes under SPS, and only seconds to tens of seconds under flash sintering. Due to the low densification rates of hot pressing and SPS, the green body shrinks slowly. Driven by a hydraulic or servo motor system, the pressure head can slowly move along with the green body's shrinkage, ultimately maintaining good contact with it. However, under pressure-assisted flash sintering, once flash sintering occurs, the green body shrinks instantaneously. At this point, the hydraulic or servo motor system cannot instantly move the pressure head and electrodes, leading to a brief loss of contact between the electrodes and the green body. This results in a system pressure collapse (the pressure drops instantly to a small value or even zero), and may even cause discharge between the electrodes and the green body, damaging the sample. While a customized ultra-high sensitivity hydraulic or servo motor system can solve the pressure collapse problem in pressure-assisted flash sintering, such systems are expensive. Therefore, a low-cost solution is urgently needed. Summary of the Invention

[0003] To address the problems existing in the prior art, the main objective of this invention is to propose a sliding elastic electrical contact device for pressure-assisted flash sintering equipment.

[0004] According to one aspect of the present invention, the present invention provides the following technical solution:

[0005] A sliding elastic electrical contact device for a pressure-assisted flash sintering equipment includes:

[0006] Sliding pressure head, base, spring, conductive sliding bearing;

[0007] The conductive sliding bearing, the spring, and the sliding pressure head are sequentially nested on the positioning shaft protruding from the center of the upper part of the base.

[0008] As a preferred embodiment of the sliding elastic electrical contact device for pressure-assisted flash sintering equipment described in this invention, a cylindrical groove is provided below the sliding pressure head, and the conductive sliding bearing is inserted into the groove by means of clearance fit.

[0009] As a preferred embodiment of the slidable elastic electrical contact device for pressure-assisted flash sintering equipment described in this invention, the positioning shaft protruding at the center of the upper part of the base is cylindrical, and the conductive sliding bearing is nested on the cylindrical positioning shaft by a clearance fit.

[0010] In a preferred embodiment of the sliding elastic electrical contact device for a pressure-assisted flash sintering equipment according to the present invention, the spring is nested on the conductive sliding bearing by means of a clearance fit.

[0011] As a preferred embodiment of the slidable elastic electrical contact device for a pressure-assisted flash sintering equipment according to the present invention, wherein: the sum of the depth of the cylindrical groove below the sliding pressure head and the height of the spring when it is not deformed is greater than the height of the cylindrical positioning shaft protruding above the base.

[0012] As a preferred embodiment of the sliding elastic electrical contact device for a pressure-assisted flash sintering equipment according to the present invention, wherein: the difference between the sum of the depth of the cylindrical groove below the sliding pressure head and the height of the spring when it is not deformed, and the height of the cylindrical positioning shaft protruding above the base, is the travel of the sliding pressure head; the travel of the sliding pressure head is less than or equal to the deformation of the spring.

[0013] As a preferred embodiment of the slidable elastic electrical contact device for a pressure-assisted flash sintering equipment according to the present invention, wherein: the depth of the cylindrical groove below the sliding pressure head is less than or equal to the height of the cylindrical positioning shaft protruding above the base.

[0014] As a preferred embodiment of the slidable elastic electrical contact device for a pressure-assisted flash sintering equipment according to the present invention, the height of the spring is less than or equal to the height of the cylindrical positioning shaft protruding above the base.

[0015] As a preferred embodiment of the sliding elastic electrical contact device for pressure-assisted flash sintering equipment described in this invention, the sliding pressure head and the base are made of stainless steel, high-temperature alloy, refractory alloy, or high-strength, high-conductivity copper alloy; the conductive sliding bearing is made of carbon-based or metallic material.

[0016] According to another aspect of the present invention, the present invention provides the following technical solution:

[0017] A pressure-assisted flash sintering apparatus includes the aforementioned slidable elastic electrical contact device for pressure-assisted flash sintering apparatus.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention proposes a sliding elastic electrical contact device for pressure-assisted flash sintering equipment, which can be used as a pressure head in the equipment. During pressure-assisted flash sintering, the sliding pressure head in the electrical contact device can slide along a cylindrical positioning shaft protruding above the base under axial pressure. The use of a conductive sliding bearing ensures that the sliding pressure head maintains good electrical contact with the base during sliding and continuously transmits current. The lower surface of the sliding pressure head contacts a spring, which transmits the axial pressure to the spring, causing it to deform and store elastic potential energy. Once flash sintering occurs and causes the sample to shrink rapidly, the spring immediately releases the stored elastic potential energy and pushes the sliding pressure head to slide upward rapidly. This ensures good electrical contact between the various components (including electrodes and samples) subjected to axial pressure during flash sintering and improves the problem of pressure bursting. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the released state of the sliding elastic electrical contact device of the present invention.

[0022] Figure 2 This is a schematic diagram of the compressed state of the sliding elastic electrical contact device of the present invention.

[0023] Figure 3 This is a perspective view of the pressure-assisted flash sintering equipment of the present invention.

[0024] Figure 4 This is a cross-sectional view of the pressure-assisted flash sintering apparatus of the present invention, excluding the power supply and wires.

[0025] Among them: 1-sliding pressure head, 2-conductive sliding bearing, 3-spring, 4-base, 5-upper pressure head, 6-upper electrode, 7-insulating mold, 8-sample, 9-lower electrode, 10-wire, 11-power supply.

[0026] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.

[0028] This invention proposes a sliding elastic electrical contact device for pressure-assisted flash sintering equipment, which solves problems such as electrical contact failure between electrodes and samples, pressure bursts, and discharge between electrodes and samples caused by rapid shrinkage of green blanks during the rapid densification process of pressure-assisted flash sintering equipment.

[0029] like Figure 1-2 As shown, a sliding elastic electrical contact device for a pressure-assisted flash sintering equipment includes:

[0030] 1. Sliding pressure head; 2. Conductive sliding bearing; 3. Spring; 4. Base.

[0031] The conductive sliding bearing 2, the spring 3, and the sliding pressure head 1 are nested sequentially on the positioning shaft protruding from the center of the upper part of the base 4.

[0032] like Figure 3-4 As shown, a pressure-assisted flash sintering apparatus includes a slidable elastic electrical contact device for the pressure-assisted flash sintering apparatus, wherein... Figure 4 The left-middle image shows a schematic diagram of the retracted state of the sliding elastic electrical contact device. Figure 4The right-middle figure is a schematic diagram of the released state of the sliding elastic electrical contact device; a lower electrode 9 is provided at the upper end of the sliding pressure head 1. The pressure-assisted flash sintering equipment is also provided with an upper pressure head 5 and an upper electrode 6 located below the upper pressure head 5. The sample 8 is placed between the lower electrode 9 and the upper electrode 6. The insulating mold 7 is wrapped around the outside of the sample 8. Both the upper electrode 6 and the lower electrode 9 are partially inserted into the insulating mold 7. The power supply 11 is connected to the upper pressure head 5 and the base 4 through the wire 10. During the flash sintering process, the current is transferred from the upper pressure head 5 to the sample 8 through the upper electrode 6. Due to the large resistance of the sample 8, a large Joule heat is generated, which makes the sample 8 dense. The current is then transferred to the sliding pressure head 1 and the conductive sliding bearing 2 through the lower electrode 9, and finally flows back to the power supply 11 through the base 4 and the wire 10.

[0033] This invention relates to a sliding elastic electrical contact device for a pressure-assisted flash sintering (PAS) apparatus, which serves as the pressure head in the PAS apparatus. During PAS, the sliding pressure head 1 in the electrical contact device can slide along a cylindrical positioning shaft protruding above the base 4 under axial pressure. The use of a conductive sliding bearing 2 ensures that the sliding pressure head 1 maintains good electrical contact with the base 4 during sliding and continuously transmits current. The lower surface of the sliding pressure head 1 contacts a spring 3. Before flash sintering, the axial pressure can be transmitted to the spring 3, causing it to deform and store elastic potential energy. Once flash sintering occurs and causes the sample 8 to contract rapidly, the spring 3 will immediately release the stored elastic potential energy and push the sliding pressure head 1 to slide upward rapidly. This ensures good electrical contact between the various components bearing axial pressure (including the lower electrode 9 and the sample 8) during flash sintering and improves the problem of pressure bursting.

[0034] In one embodiment of the present invention, a cylindrical groove is formed below the sliding pressure head 1, and the conductive sliding bearing 2 is inserted into the groove by means of clearance fit.

[0035] In one embodiment of the present invention, the positioning shaft protruding at the center of the upper part of the base 4 is cylindrical, and the conductive sliding bearing 2 is nested on the cylindrical positioning shaft by means of clearance fit.

[0036] In one embodiment of the present invention, the spring 3 is nested on the conductive sliding bearing 2 by means of clearance fit.

[0037] In one embodiment of the present invention, the sum of the depth of the cylindrical groove below the sliding pressure head 1 and the height of the spring 3 when it is not deformed is greater than the height of the cylindrical positioning shaft protruding above the base 4.

[0038] In one embodiment of the present invention, the difference between the sum of the depth of the cylindrical groove below the sliding pressure head 1 and the height of the spring 3 when it is not deformed, and the height of the cylindrical positioning shaft protruding above the base 4, is the travel distance of the sliding pressure head 1; the travel distance of the sliding pressure head 1 is less than or equal to the deformation of the spring 3.

[0039] In one embodiment of the present invention, the depth of the cylindrical groove below the sliding pressure head 1 is less than or equal to the height of the cylindrical positioning shaft protruding above the base 4.

[0040] In one embodiment of the present invention, the height of the spring 3 is less than or equal to the height of the cylindrical positioning shaft protruding above the base 4.

[0041] In one embodiment of the present invention, the sliding pressure head 1 and the base 4 are made of stainless steel, high-temperature alloy, refractory alloy, or high-strength, high-conductivity copper alloy; the conductive sliding bearing 2 is made of carbon-based or metal material.

[0042] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0043] Example 1

[0044] The flash sintering method using the pressure-assisted flash sintering equipment described in this invention employs W-20Cu powder as the raw material, an insulating mold 7 made of insulating alumina tube, and both the lower electrode 9 and the upper electrode 6 made of high-purity tungsten rods. A pressure of 500 MPa is applied to the sample 8 via a hydraulic device. As the pressure increases, the lower sliding pressure head 1 slides downwards along the cylindrical positioning axis protruding above the base 4 under the action of axial pressure. The lower surface of the sliding pressure head 1 contacts the spring 3, transmitting the axial pressure to the spring 3, causing it to deform and store elastic potential energy. The power supply 11 is then activated, generating approximately 2.3 × 10⁻⁶ MPa of sintered material. 7 A / m 2 A pulsed current of high current density causes flash sintering and rapid contraction of sample 8. Spring 3 immediately releases its stored elastic potential energy and pushes the sliding pressure head 1 above it to slide upwards rapidly, ensuring good electrical contact between the components bearing axial pressure (including the lower electrode 9 and sample 8). After 30 seconds, power supply 11 is turned off and the sample is removed, yielding a W-20Cu composite material block with a density of 99.99%.

[0045] Comparative Example 1

[0046] Using the equipment described in patent CN117363914A, W-20Cu powder is used as the raw material, the insulating mold is an insulating alumina tube, and the electrode is a high-purity tungsten rod. A hydraulic device applies a pressure of 500 MPa to the powder. As the pressure increases, the mica sheets, long copper plates, steel plate gaskets, and electrodes at both ends of the equipment gradually move closer together. The power is then turned on, generating approximately 2.3 × 10⁻⁶ ppm. 7 A / m 2 A pulsed current of high current density causes flash sintering and sample shrinkage. Due to the lack of a springback mechanism, the pressure drops instantaneously, increasing the contact area between the electrode and the sample. This reduces the pressure-assisted effect and increases the contact resistance. Subsequently, driven by the pressurizing device, the pressure head slowly displaces, further pushing the electrode until it regains contact with the sample. After 30 seconds, the power is turned off and the sample is removed, yielding a W-20Cu composite material block with a density of 97.4%.

[0047] The samples prepared in Example 1 and Comparative Example 1 were tested. The density of the sample in Example 1 was 99.99%, and the density of the sample in Comparative Example 1 was 97.4%. The hardness of the sample in Example 1 was 306.02 HV, and the hardness of the sample in Comparative Example 1 was 215.2 HV. The conductivity of the sample in Example 1 was 47.36% IACS, and the conductivity of the sample in Comparative Example 1 was 34.95% IACS. The reason for the decrease in density and performance of the sample in Comparative Example 1 is that its equipment lacks the sliding elastic electrical contact device for pressure-assisted flash sintering equipment described in this invention. Flash sintering has a fast densification rate, and the rapid shrinkage of the sample leads to a sudden drop in pressure. The equipment used in Comparative Example 1 cannot restore the initial pressure in a short time by relying solely on the pressurization device. The effect of pressure assistance is weakened, the ability to fill the voids between material particles decreases, and the grains are prone to coarsening at high temperatures, affecting its mechanical and electrical properties.

[0048] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A pressure-assisted flash sintering apparatus, characterized in that, The device includes a slidable elastic electrical contact for a pressure-assisted flash sintering apparatus, the slidable elastic electrical contact for the pressure-assisted flash sintering apparatus comprising: Sliding pressure head, base, spring, conductive sliding bearing; The conductive sliding bearing, the spring, and the sliding pressure head are sequentially nested on the positioning shaft protruding from the center of the upper part of the base; a cylindrical groove is opened below the sliding pressure head, and the conductive sliding bearing is inserted into the groove by means of clearance fit; the positioning shaft protruding from the center of the upper part of the base is cylindrical; The sum of the depth of the cylindrical groove below the sliding pressure head and the height of the spring when it is not deformed is greater than the height of the cylindrical positioning shaft protruding above the base; the difference between the sum of the depth of the cylindrical groove below the sliding pressure head and the height of the spring when it is not deformed and the height of the cylindrical positioning shaft protruding above the base is the stroke of the sliding pressure head; the stroke of the sliding pressure head is less than or equal to the deformation of the spring. During pressure-assisted flash sintering, the sliding pressure head in the electrical contact device slides along the protruding cylindrical positioning shaft above the base under axial pressure. The use of conductive sliding bearings ensures that the sliding pressure head can maintain good electrical contact with the base during sliding and continuously transmit current. The lower surface of the sliding pressure head contacts the spring, transmitting the axial pressure to the spring, causing it to deform and store elastic potential energy. Once flash sintering occurs and causes the sample to shrink rapidly, the spring will immediately release the stored elastic potential energy and push the sliding pressure head to slide upward rapidly, ensuring good electrical contact between the various components bearing axial pressure, including the electrodes and the sample, during flash sintering and improving the pressure flashover problem.

2. The pressure-assisted flash sintering equipment according to claim 1, characterized in that, The conductive sliding bearing is nested on the cylindrical positioning shaft using a clearance fit.

3. The pressure-assisted flash sintering equipment according to claim 1, characterized in that, The spring is nested on the conductive sliding bearing with a clearance fit.

4. The pressure-assisted flash sintering equipment according to claim 1, characterized in that, The depth of the cylindrical groove below the sliding pressure head is less than or equal to the height of the cylindrical positioning shaft protruding above the base.

5. The pressure-assisted flash sintering equipment according to claim 1, characterized in that, The height of the spring is less than or equal to the height of the cylindrical positioning shaft protruding above the base.

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