Slidable elastic electric contact device for pressure-assisted flash sintering equipment

Abstract

The invention belongs to the technical field of powder metallurgy, and particularly relates to a slidable elastic electric contact device for pressure-assisted flash sintering equipment, which can be used as a pressure head in the pressure-assisted flash sintering equipment. In the pressure-assisted flash sintering process, the sliding pressure head in the electric contact device can slide along the cylindrical positioning shaft protruding out of the upper portion of the base under the action of axial pressure, and due to the use of the conductive sliding bearing, it is guaranteed that the sliding pressure head can keep good electric contact with the base in the sliding process, and current is continuously transmitted. The lower surface of the sliding pressure head is in contact with the spring, axial pressure can be conducted to the spring, and then the spring deforms and stores elastic potential energy. Once the flash sintering phenomenon occurs and the sample is rapidly shrunk, the spring immediately releases the stored elastic potential energy and pushes the sliding pressure head to rapidly slide upwards, so that good electric contact between parts bearing axial pressure can be ensured when the flash sintering phenomenon occurs, and the problem of pressure flash collapse is solved.

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy, in particular to a slidable elastic electric contact device for pressure-assisted flash sintering equipment. Background Art

[0002] The characteristics of the conventional flash sintering process of ceramic materials are: at a certain furnace temperature, a certain electric field strength is directly applied to the green body through the electrode. After a certain period of "incubation period", Joule thermal runaway, rapid temperature rise, strong flash and rapid densification will occur on the green body. During the flash sintering process, rapid densification will cause rapid shrinkage of the macroscopic size of the green body, which poses a challenge to maintaining good electrical contact between the electrode and the green body. In pressureless flash sintering equipment, the electrode is usually a platinum wire, which is welded to the green body through conductive metal slurry, and there is usually no problem of electrode falling off. In pressure-assisted flash sintering equipment, the green body is usually placed in an insulating mold, and current and pressure are applied to it through upper and lower electrodes. Such equipment is usually modified based on hot pressing or spark plasma sintering (SPS) equipment. However, the densification rate of hot pressing and SPS is far less than that of flash sintering. For example, zirconia ceramics usually take tens of minutes to hours to reach a density of more than 95% under hot pressing conditions, and it takes minutes to tens of minutes to reach the same density under SPS conditions, while it only takes seconds to tens of seconds to complete the densification process under flash sintering conditions. Due to the low densification rate of hot pressing and SPS, the green body shrinks slowly. Driven by the hydraulic or servo motor system, the pressure head can slowly move along with the green body shrinkage, and finally can maintain good contact with the green body. Under the conditions of pressure-assisted flash sintering, once the flash sintering phenomenon occurs, the green body will shrink instantly, but at this time the hydraulic or servo motor system cannot instantly push the pressure head and electrode to move, which will cause the electrode to lose contact with the green body for a short time, and then cause the system pressure to flash collapse (the pressure drops to a small value or even zero instantly), and even cause discharge between the electrode and the green body and damage the sample. The pressure flash collapse problem in the pressure-assisted flash sintering process can be solved by customizing an ultra-high sensitivity hydraulic or servo motor system, but the high-sensitivity hydraulic or servo motor system is expensive, so a low-cost solution is urgently needed. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a slidable 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: A slidable elastic electrical contact device for a pressure-assisted flash sintering device, comprising: Sliding head, base, spring, conductive sliding bearing; The conductive sliding bearing, the spring and the sliding pressure head are sequentially nested on a positioning shaft protruding from the center position above the base.

[0005] As a preferred solution of the slidable elastic electrical contact device for pressure-assisted flash sintering equipment described in the present invention, a cylindrical groove is opened under the sliding pressure head, and the conductive sliding bearing is inserted into the groove by a clearance fit.

[0006] As a preferred solution of a slidable elastic electrical contact device for pressure-assisted flash sintering equipment described in the present invention, the positioning shaft protruding at the center position above the base is cylindrical, and the conductive sliding bearing is nested on the cylindrical positioning shaft by means of clearance fit.

[0007] As a preferred solution of the slidable elastic electrical contact device for pressure-assisted flash sintering equipment described in the present invention, the spring is nested in the conductive sliding bearing by means of clearance fit.

[0008] As a preferred embodiment of a slidable elastic electrical contact device for a pressure-assisted flash sintering device described in the present invention, the sum of the depth of the cylindrical groove below the sliding pressure head and the height of the spring when not deformed is greater than the height of the cylindrical positioning shaft protruding above the base.

[0009] As a preferred embodiment of a slidable elastic electrical contact device for a pressure-assisted flash sintering device described in the present invention, 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 movement stroke of the sliding pressure head; the movement stroke of the sliding pressure head is less than or equal to the deformation of the spring.

[0010] As a preferred solution of the slidable elastic electrical contact device for pressure-assisted flash sintering equipment described in the present invention, 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.

[0011] As a preferred solution of the slidable elastic electrical contact device for pressure-assisted flash sintering equipment described in 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.

[0012] As a preferred embodiment of the slidable elastic electrical contact device for pressure-assisted flash sintering equipment described in the present invention, the sliding pressure head and the base are made of stainless steel, high-temperature alloy, refractory alloy, high-strength and high-conductivity copper alloy; the conductive sliding bearing is made of carbon-based or metal material.

[0013] According to another aspect of the present invention, the present invention provides the following technical solution: A pressure-assisted flash sintering device comprises the above-mentioned slidable elastic electrical contact device for the pressure-assisted flash sintering device.

[0014] The beneficial effects of the present invention are as follows: The present invention proposes a slidable elastic electrical contact device for pressure-assisted flash sintering equipment, which can be used as a pressure head in the pressure-assisted flash sintering equipment. During the pressure-assisted flash sintering process, the sliding pressure head in the electrical contact device can slide along the cylindrical positioning shaft protruding above the base under the action of axial pressure. The use of conductive sliding bearings ensures that the sliding pressure head can maintain good electrical contact with the base during the sliding process and continuously transmit current. The lower surface of the sliding pressure head is in contact with the spring, which can transmit the axial pressure to the spring, thereby causing it to deform and store elastic potential energy. Once the flash sintering phenomenon 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 rapidly upward, which can ensure that when flash sintering occurs, the various components that are subjected to axial pressure (including electrodes and samples) maintain good electrical contact and improve the pressure flash collapse problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0016] Figure 1 It is a schematic diagram of the released state of the slidable elastic electric contact device of the present invention.

[0017] Figure 2 It is a schematic diagram of the compressed state of the slidable elastic electric contact device of the present invention.

[0018] Figure 3 It is a three-dimensional diagram of the pressure-assisted flash sintering equipment of the present invention.

[0019] Figure 4 This is a cross-sectional view of the structure of the pressure-assisted flash sintering equipment of the present invention excluding the power supply and the wires.

[0020] Wherein: 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.

[0021] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0022] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention proposes a slidable elastic electrical contact device for a pressure-assisted flash sintering device, which is used to solve the problems of electrical contact failure between an electrode and a sample, pressure flash collapse, and discharge between an electrode and a sample caused by rapid shrinkage of a green body during the rapid densification process of the pressure-assisted flash sintering device.

[0024] like Figure 1-2 As shown, a slidable elastic electrical contact device for a pressure-assisted flash sintering device comprises: Sliding pressure head 1, conductive sliding bearing 2, spring 3, base 4; The conductive sliding bearing 2 , the spring 3 and the sliding pressure head 1 are sequentially nested on a positioning shaft protruding from the center position above the base 4 .

[0025] like Figure 3-4 As shown, a pressure-assisted flash sintering device comprises a slidable elastic electrical contact device for a pressure-assisted flash sintering device, wherein: Figure 4 The middle left picture is a schematic diagram of the retracted state of the slidable elastic electric contact device. Figure 4 The middle right figure is a schematic diagram of the released state of the slidable elastic electric contact device; a lower electrode 9 is provided at the upper end of the sliding pressure head 1, and 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 arranged between the lower electrode 9 and the upper electrode 6, and the insulating mold 7 is wrapped around the outside of the sample 8. 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 respectively through the wire 10. During the flash sintering process, the current is transmitted from the upper pressure head 5 to the sample 8 through the upper electrode 6. Since the resistance of the sample 8 is large, a large Joule heat is generated to make the sample 8 dense. The current is then transmitted 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.

[0026] The slidable elastic electric contact device for pressure-assisted flash sintering equipment of the present invention is used as a pressure head in the pressure-assisted flash sintering equipment. During the pressure-assisted flash sintering process, the sliding pressure head 1 in the electric contact device can slide along the cylindrical positioning shaft protruding above the base 4 under the action of axial pressure. The use of the conductive sliding bearing 2 ensures that the sliding pressure head 1 can maintain good electrical contact with the base 4 during the sliding process and continuously transmit current. The lower surface of the sliding pressure head 1 is in contact with the spring 3. Before flash sintering, the axial pressure can be transmitted to the spring 3, thereby causing it to deform and store elastic potential energy. Once the flash sintering phenomenon occurs and causes the sample 8 to shrink rapidly, the spring 3 will immediately release the stored elastic potential energy and push the sliding pressure head 1 to slide rapidly upward, which can ensure that when flash sintering occurs, the various components that bear the axial pressure (including the lower electrode 9 and the sample 8) maintain good electrical contact and improve the pressure flash collapse problem.

[0027] 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 a clearance fit.

[0028] In one embodiment of the present invention, the positioning shaft protruding at the center position above the base 4 is cylindrical, and the conductive sliding bearing 2 is nested on the cylindrical positioning shaft by means of clearance fit.

[0029] In one embodiment of the present invention, the spring 3 is nested on the conductive sliding bearing 2 by means of clearance fit.

[0030] 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 not deformed is greater than the height of the cylindrical positioning shaft protruding above the base 4 .

[0031] 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 not deformed, minus the height of the cylindrical positioning shaft protruding above the base 4, is the movement stroke of the sliding pressure head 1; the movement stroke of the sliding pressure head 1 is less than or equal to the deformation amount of the spring 3.

[0032] 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.

[0033] 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 .

[0034] 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, high-strength and high-conductivity copper alloy; the conductive sliding bearing 2 is made of carbon-based or metal material.

[0035] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0036] Example 1 The flash sintering method is carried out by using the pressure-assisted flash sintering equipment of the present invention, with W-20Cu powder as the raw material powder, the insulating mold 7 is an insulating alumina tube, and the lower electrode 9 and the upper electrode 6 are both high-purity tungsten rods. A pressure of 500MPa is applied to the sample 8 by a hydraulic device. As the pressure rises, the lower sliding head 1 slides downward along the cylindrical positioning shaft protruding above the base 4 under the action of axial pressure. The lower surface of the sliding head 1 contacts the spring 3, which can transmit the axial pressure to the spring 3, thereby causing it to deform and store elastic potential energy. Start the power supply 11, generate about 2.3×10 7 A / m 2 The pulse current of current density is high, flash sintering occurs and causes sample 8 to shrink rapidly. Spring 3 immediately releases the stored elastic potential energy and pushes the sliding pressure head 1 above it to slide upward rapidly, ensuring good electrical contact between the various components under axial pressure (including lower electrode 9 and sample 8). After 30 seconds, power supply 11 is turned off and the sample is taken out to obtain a W-20Cu composite block with a density of 99.99%.

[0037] Comparative Example 1 The equipment in patent CN117363914A was used, with W-20Cu powder as raw material powder, insulating mold as insulating alumina tube, and electrode as high-purity tungsten rod. A hydraulic device applied 500MPa pressure to the powder. As the pressure increased, the mica sheets, long copper plates, steel plate gaskets and electrodes at the upper and lower ends of the equipment gradually moved closer. The power supply was turned on, generating about 2.3×10 7 A / m 2 The pulse current of the current density is high, and flash sintering occurs and causes the sample to shrink. Due to the lack of a rebound device, the pressure will drop in an instant, and the contact area between the electrode and the sample will become larger, resulting in a decrease in the pressure-assisting effect and an increase in the contact resistance. Subsequently, driven by the pressurizing device, the pressure head slowly moves, and the displacement of the pressure head further pushes the electrode, and finally restores contact with the sample. After 30 seconds, the power is turned off and the sample is taken out to obtain a W-20Cu composite material block with a density of 97.4%.

[0038] 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 why the density and performance of the sample in Comparative Example 1 decreased is that its equipment lacks the slidable elastic electrical contact device for pressure-assisted flash sintering equipment described in the present invention. The flash sintering densification rate is fast, and the sample shrinks rapidly, resulting in 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 pressurizing device, the effect of pressure assistance is weakened, the gap filling ability between material particles is reduced, and the grains are easily coarsened at high temperatures, affecting its mechanical and electrical properties.

[0039] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A slidable elastic electrical contact device for pressure-assisted flash sintering equipment, characterized in that: include: Sliding head, base, spring, conductive sliding bearing; The conductive sliding bearing, the spring and the sliding pressure head are sequentially nested on a positioning shaft protruding from the center position above the base.

2. The slidable elastic electrical contact device for pressure-assisted flash sintering equipment according to claim 1, characterized in that: A cylindrical groove is provided below the sliding pressure head, and the conductive sliding bearing is inserted into the groove in a clearance fit manner.

3. The slidable elastic electrical contact device for pressure-assisted flash sintering equipment according to claim 2, characterized in that: The positioning shaft protruding at the center position above the base is cylindrical, and the conductive sliding bearing is nested on the cylindrical positioning shaft by means of clearance fit.

4. The slidable elastic electrical contact device for pressure-assisted flash sintering equipment according to claim 1, characterized in that: The spring is nested on the conductive sliding bearing by means of clearance fit.

5. The slidable elastic electrical contact device for pressure-assisted flash sintering equipment according to claim 3, characterized in that: The sum of the depth of the cylindrical groove below the sliding pressure head and the height of the spring when not deformed is greater than the height of the cylindrical positioning shaft protruding above the base.

6. The slidable elastic electrical contact device for pressure-assisted flash sintering equipment according to claim 3, characterized in that: 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, minus the height of the cylindrical positioning shaft protruding above the base, is the movement stroke of the sliding pressure head; the movement stroke of the sliding pressure head is less than or equal to the deformation of the spring.

7. The slidable elastic electrical contact device for pressure-assisted flash sintering equipment according to claim 3, 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.

8. The slidable elastic electrical contact device for pressure-assisted flash sintering equipment according to claim 3, 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.

9. The slidable elastic electrical contact device for pressure-assisted flash sintering equipment according to claim 1, characterized in that: The sliding pressure head and the base are made of stainless steel, high-temperature alloy, refractory alloy, high-strength and high-conductivity copper alloy; the conductive sliding bearing is made of carbon-based or metal material.

10. A pressure-assisted flash sintering device, characterized in that: The invention comprises a slidable elastic electrical contact device for a pressure-assisted flash sintering device as described in any one of claims 1 to 9.

Images