Spark plasma sintering device and sintering method for producing large-size advanced ceramics

Abstract

This invention discloses a spark plasma sintering apparatus for producing large-size advanced ceramics, comprising a vacuum chamber, a discharge assembly, and a control assembly. The discharge assembly is composed of multiple discharge modules connected together, with an insulating layer separating adjacent discharge modules. This invention effectively partitions the advanced ceramic sample to be sintered, and the control assembly controls multiple discharge modules to cycle through discharge / de-energization in a set sequence within a very short time. This allows the divided areas of material to cycle through heat release / de-energization in a very short time, achieving plasma sintering of large-size advanced ceramics under conventional current conditions. The sintering method of this invention eliminates the need for granulation or other processing of the advanced ceramic powder, as well as time-consuming debinding processes for molding additives, enabling rapid production of advanced ceramics.

Description

Technical Field

[0001] This invention relates to the field of advanced ceramic production technology, and more specifically, to a spark plasma sintering apparatus and sintering method for producing large-size advanced ceramics. Background Technology

[0002] Advanced ceramics possess advantages such as high hardness, good wear resistance, and stable chemical properties, and are widely used in industries such as semiconductors, photovoltaics, and medical devices. There are various sintering methods for advanced ceramics, including atmospheric pressure sintering and hot pressing sintering. The specific sintering method is generally selected based on a comprehensive consideration of the product's material type, shape, and performance requirements.

[0003] Spark plasma sintering (SPS) is a novel ceramic sintering method. Unlike traditional hot pressing sintering, SPS equipment uses pulsed current released through electrodes to induce electrical sparks between powder particles, generating a large amount of plasma. This plasma generates significant heat in the mold and material, ultimately achieving rapid sintering. During SPS, a low-voltage, high-current parameter combination is typically used. The large amount of plasma generated by the SPS equipment has multiple effects on the powder material, releasing significant heat while removing inert substances from the powder surface and promoting particle bonding. Simultaneously, the induced magnetic field generated by the pulsed current deforms the powder surface, increasing its surface area and further accelerating particle bonding. Therefore, SPS offers advantages such as rapid heating, short sintering time, energy efficiency, and environmental friendliness. Furthermore, the resulting sintered body exhibits uniform grain size, high density, and excellent mechanical properties. Meanwhile, spark plasma sintering can produce a wide variety of materials and is widely used in the preparation of nanomaterials, functionally graded materials, metallic materials, magnetic materials, composite materials, ceramics and other materials.

[0004] Because SPS (Solid Polymer Sintering) requires a low-voltage, high-current pulsed current generated by the power generator, the cross-sectional area of ​​the sintered ceramic products is limited by the power of the power generator during the SPS production process. For large-sized ceramic products with a large cross-sectional area, to ensure the required current density for sintering, the power of the power generator needs to be increased accordingly, and the specifications of various controllers, components, and wires within the device need to be upgraded. This not only rapidly increases the manufacturing cost of the equipment but also places very high demands on the supporting power supply system.

[0005] Therefore, without significantly increasing the manufacturing cost of the equipment and the burden on the power supply system, how to effectively increase the sinterable product size of the discharge plasma sintering equipment and produce large-size advanced ceramics in a more economical way has become an important problem for those skilled in the art. Summary of the Invention

[0006] This invention discloses a spark plasma sintering apparatus for producing large-size advanced ceramics, comprising a vacuum chamber, a discharge assembly, and a control assembly. The vacuum chamber includes a left chamber and a right chamber, which are arranged opposite to each other. The discharge assembly is installed between the left and right chambers. The discharge assembly is composed of multiple discharge modules, with an insulating layer separating adjacent discharge modules. Each discharge module includes, from top to bottom, an upper electrode, an upper pressure head, an upper mold, a lower mold, a lower pressure head, and a lower electrode. The bottom end of the upper electrode is electrically connected to the top end of the upper pressure head. The upper mold includes an upper conductive part and an upper insulating part, with the bottom end of the upper pressure head connected to the top end of the conductive part. The lower mold includes a lower conductive part and a lower insulating part, with the upper insulating part and the lower insulating part opposite to each other. A discharge cavity for accommodating materials is provided between the upper and lower molds. The bottom end of the lower conductive part is electrically connected to the top end of the lower pressure head. The bottom end of the lower pressure head is electrically connected to the top end of the lower electrode.

[0007] The control components include a PLC control system, a current sensor, a temperature sensor, a pressure sensor, and a pulse current generator. The current sensor is connected to the discharge module and is used to detect the operating current of the discharge module. The temperature sensor is used to detect the temperature of the material. The pressure sensor is connected to the upper and lower pressure heads and is used to detect the pressure of the upper and lower pressure heads. The pulse current generator is connected to the upper and lower electrodes and is used to generate pulse current. The PLC control system is connected to the current sensor, the temperature sensor, the pressure sensor, and the pulse current generator, and is used to control the discharge sequence and parameters.

[0008] Preferably, the system further includes a switching assembly connected to the PLC control system. The switching assembly includes a first single-pole double-throw (SPD) switch, a second SPD switch, and a third SPD switch. The first SPD switch includes stationary terminals A1, A2, and A3; the second SPD switch includes stationary terminals B1, B2, and B3; and the third SPD switch includes stationary terminals C1, C2, and C3. The discharge assembly is composed of four discharge modules, namely module A, module B, module C2, and module C3. C and module D; one end of module A, one end of module B, one end of module C and one end of module D are respectively connected in parallel to the pulse current generator; the other end of module A is connected in series with the stationary terminal A1, the other end of module B is connected in series with the stationary terminal A2, the other end of module C is connected in series with the stationary terminal B1, the other end of module D is connected in series with the stationary terminal B2, the moving terminal A3 is connected in series with the stationary terminal C1, the moving terminal B3 is connected in series with the stationary terminal C2, and the moving terminal C3 is connected to the pulse current generator.

[0009] Preferably, the upper electrode and the lower electrode have the same structure. The upper electrode is made of copper or copper alloy with a conductivity of 50–56.5 MS / m and a compressive strength of 200–300 MPa. The upper pressure head and the lower pressure head have the same structure. The upper pressure head is made of stainless steel or manganese alloy steel with a conductivity of 1.25–1.43 MS / m and a compressive strength of 300–500 MPa. The upper mold and the lower mold have the same structure. Both the upper conductive part and the lower conductive part are made of high-strength graphite material with a compressive strength of 100–150 MPa, a resistivity of 7–8 μΩ·m, and a melting point of 3850 ± 50 °C.

[0010] Preferably, the insulating layer is an insulating coating, which is applied to the upper electrode, the upper pressure head, the upper mold, the lower mold, the lower pressure head, and the lower electrode respectively; the insulating coating is alumina or alumina or titanium oxide composite ceramic with a room temperature dielectric constant of 12, and the insulating strength of the insulating coating is 1069V / 0.1mm, and the resistivity is 1014Ω·cm.

[0011] Preferably, the discharge assembly has a rectangular cross-section; four upper electrodes form a cuboid electrode group A1, with adjacent upper electrodes isolated by the insulating layer; four lower electrodes form a cuboid electrode group B1, with adjacent lower electrodes isolated by the insulating layer; four upper pressure heads form a cuboid pressure head group A1, with adjacent upper pressure heads isolated by the insulating layer; four lower pressure heads form a cuboid pressure head group B1, with adjacent lower pressure heads isolated by the insulating layer; and four upper molds form a structure with grooves at the top and bottom. A cuboid mold A1 is formed, with adjacent upper molds separated by the insulating layer; four lower molds form a cuboid mold B1 with grooves on the top and bottom, and adjacent lower molds are separated by the insulating layer; the electrode assembly A1 is connected to the pressure head assembly A1, the pressure head assembly A1 is fitted into the groove on the top of the cuboid mold A1, the groove on the bottom of the cuboid mold A1 is connected to the groove on the top of the cuboid mold B1, the groove on the bottom of the cuboid mold B1 is fitted onto the top of the pressure head assembly B1, and the pressure head assembly B1 is connected to the electrode assembly B1.

[0012] Preferably, the discharge assembly has a rhomboid cross-section; four upper electrodes form a quadrangular prism electrode group A2, with adjacent upper electrodes isolated by the insulating layer; four lower electrodes form a quadrangular prism electrode group B2, with adjacent lower electrodes isolated by the insulating layer; four upper pressure heads form a quadrangular prism pressure head group A2, with adjacent upper pressure heads isolated by the insulating layer; four lower pressure heads form a quadrangular prism pressure head group B2, with adjacent lower pressure heads isolated by the insulating layer; and four upper molds form a quadrangular prism with grooves on the top and bottom. The upper mold A2 is separated from adjacent upper molds by the insulating layer; four lower molds form a quadrangular prism mold B2 with grooves on the top and bottom, and adjacent lower molds are separated from each other by the insulating layer; the electrode group A2 is connected to the pressure head group A2, the pressure head group A2 is fitted into the groove on the top of the quadrangular prism mold A2, the groove on the bottom of the quadrangular prism mold A2 is connected to the groove on the top of the quadrangular prism mold B2, the groove on the bottom of the quadrangular prism mold B2 is fitted onto the top of the pressure head group B2, and the pressure head group B2 is connected to the electrode group B2.

[0013] Preferably, the discharge assembly has a triangular cross-section; four upper electrodes form a triangular prism electrode group A3, with adjacent upper electrodes isolated by the insulating layer; four lower electrodes form a triangular prism electrode group B3, with adjacent lower electrodes isolated by the insulating layer; four upper pressure heads form a triangular prism pressure head group A3, with adjacent upper pressure heads isolated by the insulating layer; four lower pressure heads form a triangular prism pressure head group B3, with adjacent lower pressure heads isolated by the insulating layer; and four upper molds form a triangular structure with grooves on the top and bottom. A cylindrical mold A3 is formed, with adjacent upper molds separated by the insulating layer; four lower molds form a triangular prism mold B3 with grooves on the top and bottom, and adjacent lower molds are separated by the insulating layer; the electrode assembly A3 is connected to the pressure head assembly A3, the pressure head assembly A3 is fitted into the groove on the top of the triangular prism mold A3, the groove on the bottom of the triangular prism mold A3 is connected to the groove on the top of the triangular prism mold B3, the groove on the bottom of the triangular prism mold B3 is fitted onto the top of the pressure head assembly B3, and the pressure head assembly B3 is connected to the electrode assembly B3.

[0014] A sintering method using a spark plasma sintering apparatus for producing large-size advanced ceramics includes the following steps:

[0015] Step S1: Ball milling; Alumina powder, alumina grinding balls toughened with zirconia, and ethanol are placed together in a polytetrafluoroethylene ball milling jar for wet ball milling;

[0016] Step S2: Ultrasonic treatment; The fully ball-milled alumina slurry is ultrasonically treated for 35-45 minutes, and stirring is maintained during the ultrasonic treatment to remove agglomerates in the powder.

[0017] Step S3: Sieving; Place the alumina slurry in a drying oven and dry it at 100℃ for 12 hours. Then sieve it through a 200-mesh sieve to obtain alumina powder of the target fineness.

[0018] Step S4: Set up the spark plasma sintering device, put the processed alumina powder into the graphite mold, and then put the graphite mold into the spark plasma sintering furnace. Evacuate to 4-6 Pa, and apply a pressure of 25 MPa under argon atmosphere for pre-compression.

[0019] Step S5: Heat to sintering temperature; apply pulse current to increase pressure to 40MPa; control device controls 4 discharge modules, and repeatedly cycle through discharge / power off processes in the order of discharge module A, discharge module B, discharge module C, and discharge module D. Under the action of pulse current, discharge is generated between alumina powder particles, which excites plasma and causes the temperature of alumina powder to rise rapidly to the sintering temperature.

[0020] Step S6: Constant temperature sintering; The PLC control system controls the pulse current to be reduced to 750-850A and holds the temperature for 5 minutes.

[0021] Step S7: After sintering is completed, the PLC control system controls the upper and lower electrodes to stop discharging, allowing the material to cool naturally; after the internal temperature of the furnace drops to room temperature, the applied pressure is gradually reduced; after the pressure drops to 0, the material is removed from the graphite mold to obtain the sintered product.

[0022] Preferably, in step S5, the pulse current generator outputs a DC pulse current of 3650–3750 A, a pulse frequency of 40 Hz, and a single discharge time of 0.25–0.75 s.

[0023] Preferably, in step S1, the rotational speed of the ball mill is 185-200 r / min, the forward and reverse rotation frequency is 10 min / time, the ball milling time is 10-13 h, and the ball-to-material ratio is 3-5:1.

[0024] This invention provides a spark plasma sintering apparatus for producing large-size advanced ceramics. By placing alumina powder, after ball milling, ultrasonication, and sieving, into a spark assembly, and utilizing the splicing structure of the spark modules separated by an insulating layer, the material to be sintered is effectively partitioned. A control component controls several spark modules to cycle through discharge / de-energization multiple times in a set sequence within a very short time. This causes the material to be divided into regions to cycle through heat release / de-energization multiple times in a very short time, minimizing temperature differences within the material at any given time. This achieves the goal of sintering large-size products using plasma sintering under conventional current conditions. The sintering method employed in this invention eliminates the need for granulation of the advanced ceramic powder and time-consuming debinding processes for molding additives, enabling rapid production and overcoming the industry pain point of long production cycles for large-size ceramic products using traditional methods. Furthermore, the production process is controlled by a PLC control system, and producing a large-size product only requires one furnace start-up and shutdown, simplifying the operation and effectively reducing manufacturing costs. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the electrical discharge plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0027] Figure 2 This is a partial exploded view of the vacuum chamber and discharge components of the discharge plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0028] Figure 3 This is a schematic diagram showing the splicing effect of the discharge module of the discharge plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0029] Figure 4 This is a schematic diagram of the electric field lines generated by the discharge module of the discharge plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0030] Figure 5 This is a structural diagram of electrode assembly A1 in the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0031] Figure 6 This is a top view of electrode assembly A1 in the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0032] Figure 7 This is a structural diagram of the pressure head assembly A1 of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention;

[0033] Figure 8 This is a top view of the pressure head assembly A1 of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0034] Figure 9 This is a structural diagram of the cuboid mold A1 of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0035] Figure 10 This is a top view of the cuboid mold A1 of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0036] Figure 11 This is a schematic diagram of the light switch structure of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0037] Figure 12 This is a schematic diagram of electrode group A2 of another embodiment of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0038] Figure 13 This is a schematic diagram of the pressure head assembly B2 structure of another embodiment of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0039] Figure 14This is a schematic diagram of the structure of a quadrangular prism mold A2, which is another embodiment of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0040] Figure 15 This is a schematic diagram of electrode group A3 of another embodiment of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0041] Figure 16 This is a schematic diagram of the pressure head assembly B3 in another embodiment of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0042] Figure 17 This is a schematic diagram of the triangular prism mold A3, which is another embodiment of the spark plasma sintering apparatus for producing large-size advanced ceramics according to the present invention.

[0043] The labels in each of the attached figures are as follows:

[0044] 1--Vacuum cavity, 11--Left cavity, 12--Right cavity, 2--Discharge assembly, 21--Discharge module, 211--Upper electrode, 212--Upper pressure head, 213--Upper mold, 2131--Upper conductive part, 2132--Upper insulating part, 214--Lower mold, 2141--Lower conductive part, 2142--Lower insulating part, 215--Lower pressure head, 216--Lower electrode, 22--Insulating layer, 23--Module A, 24--Module B, 25--Module C, 26--Module D, 3--Control Components, 31--PLC control system, 32--current sensor, 33--temperature sensor, 34--pressure sensor, 35--pulse current generator, 36--switch assembly, 361--first single-pole double-throw switch, 3611--stationary terminal A1, 3612--stationary terminal A2, 3613--moving terminal A3, 362--second single-pole double-throw switch, 3621--stationary terminal B1, 3622--stationary terminal B2, 3623--moving terminal B3, 363--third single-pole double-throw switch, 4--materials. Detailed Implementation

[0045] This invention discloses a discharge plasma sintering apparatus and sintering method for producing large-size advanced ceramics. By effectively dividing the advanced ceramic sample to be sintered into zones, the control component controls multiple discharge modules to cycle through discharge / de-energization in a set sequence within a very short time. This causes the divided areas of the material to cycle through heat release / de-energization in a very short time, resulting in small temperature differences between different parts of the material at the same time. This achieves the goal of plasma sintering large-size products under conventional current conditions.

[0046] The technical solutions of the embodiments of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0047] Please see Figures 1 to 17 This invention provides a spark plasma sintering apparatus for producing large-size advanced ceramics, comprising a vacuum chamber 1, a discharge assembly 2, and a control assembly 3. The vacuum chamber 1 includes a left chamber 11 and a right chamber 12, which are arranged opposite to each other. The discharge assembly 2 is installed between the left chamber 11 and the right chamber 12. The discharge assembly 2 is composed of multiple discharge modules 21, with an insulating layer 22 separating adjacent discharge modules 21. Each discharge module 21 includes, from top to bottom, an upper electrode 211, an upper pressure head 212, an upper mold 213, a lower mold 214, a lower pressure head 215, and a lower electrode. 216; The bottom end of the upper electrode 211 is electrically connected to the top end of the upper pressure head 212; The upper mold 213 includes an upper conductive part 2131 and an upper insulating part 2132, and the bottom end of the upper pressure head 212 is connected to the top end of the conductive part; The lower mold 214 includes a lower conductive part 2141 and a lower insulating part 2142, and the upper insulating part 2132 is connected to the lower insulating part 2142; A discharge cavity for accommodating material 4 is provided between the upper mold 213 and the lower mold 214; The bottom end of the lower conductive part 2141 is electrically connected to the top end of the lower pressure head 215; The bottom end of the lower pressure head 215 is electrically connected to the top end of the lower electrode 216;

[0048] The control component 3 includes a PLC control system 31, a current sensor 32, a temperature sensor 33, a pressure sensor 34, and a pulse current generator 35. The current sensor 32 is connected to the discharge module 21 and is used to detect the operating current of the discharge module 21. The temperature sensor 33 is used to detect the temperature of the material 4. The pressure sensor 34 is connected to the upper pressure head 212 and the lower pressure head 215 and is used to detect the pressure of the upper pressure head 212 and the lower pressure head 215. The pulse current generator 35 is connected to the upper electrode 211 and the lower electrode 216 and is used to generate pulse current. The PLC control system 31 is connected to the current sensor 32, the temperature sensor 33, the pressure sensor 34, and the pulse current generator 35 respectively, and the PLC control system 31 is used to control the discharge sequence and parameters.

[0049] In this embodiment of the invention, the vacuum chamber 1 serves to enclose the discharge assembly 2, placing it in a vacuum environment for discharge operations. This helps eliminate the obstruction of electrons by gas molecules, thereby improving the performance and stability of the electronic device. The vacuum chamber 1 consists of a left chamber 11 and a right chamber 12. The two chambers can be joined together. When opened, the discharge assembly 2 can be easily removed and materials 4 can be placed or removed. When closed, the discharge operation area of ​​the discharge assembly 2 is completely enclosed. Furthermore, an observation window is provided on the right chamber 12, through which the discharge assembly 2 operating inside can be directly observed.

[0050] In this embodiment, the discharge assembly 2 adopts a partitioned block structure design, the purpose of which is to divide the material 4 into multiple areas to achieve precise operation. Specifically, the discharge assembly 2 is composed of multiple discharge modules 21 with identical structures spliced ​​together. The discharge modules 21 are isolated from each other by an insulating layer 22, that is, adjacent discharge modules 21 are not electrically conductive to each other.

[0051] The discharge module 21 includes, from top to bottom, an upper electrode 211, an upper pressure head 212, an upper mold 213, a lower mold 214, a lower pressure head 215, and a lower electrode 216. The shapes of the upper electrode 211 and the lower electrode 216 are determined by the shape of the material 4 to be produced. The two electrodes in opposite positions are called an electrode pair. The upper electrode 211 and the lower electrode 216 are respectively connected to the control component 3. The control component 3 manipulates the electrode pair to realize the discharge operation. During the discharge process, an electric field is generated in the powder material 4. The upper pressure head 212 and the lower pressure head 215 have the same function, which is used to extrude the upper mold 213 and the lower mold 214, and also plays a role in current conduction. The upper pressure head 212 and the lower pressure head 215 are respectively provided with conductive areas and insulating areas. The conductive areas have the characteristics of being able to conduct electricity, having high compressive strength, and being economical in cost. The insulating area is covered by the insulating layer 22, separating the conductive area from the insulating area. The conductive area of ​​the upper pressure head 212 corresponds to the adjacent upper electrode 211, and the conductive area of ​​the lower pressure head 215 corresponds to the adjacent lower electrode 216. The upper mold 213 and the lower mold 214 also adopt a paired design. The upper conductive part 2131 of the upper mold 213 connects to the conductive area of ​​the upper pressure head 212, and the lower conductive part 2141 of the lower mold 214 connects to the conductive area of ​​the lower pressure head 215. With the above structural arrangement, after the material 4 is placed into the discharge cavity between the upper mold 213 and the lower mold 214, the current can flow between the upper electrode 211, the upper pressure head 212, the upper mold 213, the material 4, the lower mold 214, the lower pressure head 215, and the lower electrode 216. Since each discharge module 21 is insulated from each other, when one discharge module 21 is energized, the other discharge modules 21 are not conductive, thereby realizing the partitioning of the material 4. It should be noted that the thickness of the insulating layer 22 can be very thin. During the plasma sintering process of a certain block of material 4, some plasma will escape to a small area outside the edge, causing these areas to undergo plasma sintering simultaneously, thus making the produced material 4 uniform and dense. In the specific discharge operation, the current sensor 32 is connected to the electrode pair and the PLC control system 31 to detect the working current of the electrodes. The temperature sensor 33 is connected to the inner wall of the mold and the PLC control system 31 to detect the temperature of the material 4. The pressure sensor 34 is connected to the upper pressure head 212, the lower pressure head 215, and the PLC control system 31 to detect the pressure of the pressure head. The PLC control system 31 is connected to each sensor, the pulse current generator 35, the upper electrode 211, and the lower electrode 216 to control the discharge sequence and the magnitude of various parameters.

[0052] Furthermore, the pulse current generator 35 is used to generate pulse current, with a voltage range of 0–10V, a current range of 0–30kA, a current frequency of 0–5000Hz, and a maximum power of 300KW. These parameters can be adjusted by the PLC control system 31. The electrode discharge time for a single discharge is selected to be 0.25–0.75s. Under normal current conditions, the material temperature rises by approximately 0.2℃ with each discharge, and the heating rate of the pulse current passing continuously through a certain area is approximately 400℃ / min. To ensure that the temperature difference between different areas of the material does not exceed 10℃, the number of discharges by the electrode in a certain area per cycle cannot exceed 50. Since the frequency of the current used is 40–45Hz, 0.25–0.75s meets this condition.

[0053] The working process of this embodiment is as follows: Material 4 is placed into the discharge assembly 2, and then the vacuum chamber 1 is closed. The control assembly 3 applies a pulse current to one of the discharge modules 21 through the pulse current generator 35. The current only passes between the upper electrode 211, upper pressure head 212, upper mold 213, material 4, lower mold 214, lower pressure head 215, and lower electrode 216 within the discharge module 21. When the discharge begins, charge accumulation is formed on the inner surface of the upper and lower molds 214, generating a uniform local electric field with the same cross-sectional area as the block in the corresponding area of ​​the powder material 4, as shown in the appendix. Figure 4 This electric field induces positive and negative electrodes to be generated in the powder particles on both sides of the gap. As the pulsed current is applied, the powder particles in the gap are broken down by the pulsed electric field generated by the accumulation of positive and negative charges, resulting in electric spark discharge and continuously generating a large amount of plasma. Under the action of the electric field, the plasma forms channels in the gaps between the powder particles, forming a circuit in the powder material 4. Because it can move in the gaps between the powder particles, the current carrying efficiency of the charged particles in the plasma is much greater than that of the original charge carriers in the material. Therefore, the plasma generated in the local columnar electric field greatly increases the conductivity of some powder particles in the electric field, and most of the current in the circuit will pass through this part, and the current density can meet the requirements of plasma sintering. Most of the charged particles in the plasma generated in the material 4 in this region move along the direction of the electric field lines perpendicular to the cross-section and hardly escape into the material 4 in other regions. They interact with the surface of the powder particles in the working area of ​​the material 4, generating a large amount of heat and causing the temperature in the region to rise rapidly. Rapid plasma sintering of the target portion of material 4 is achieved through the combined effects of electrothermal heating of the mold and self-heating generated by material 4. Simultaneously, after power is cut off, plasma generation ceases, the conductivity of the power-off region returns to its original level, and almost no current flows during discharge in other regions. By dividing the discharge device into separate areas for plasma sintering, the pulse current is maintained within the acceptable range of the device while ensuring the current density of the sintered portion.

[0054] In addition to controlling the magnitude of various parameters through a control device, this invention can also control multiple discharge modules 21 to cycle through discharge / de-energization in a set sequence within a time interval of 0.25 to 0.75 seconds through a control component 3. This causes the regions of material 4 to cycle through the process of conducting and releasing heat / de-energizing heat release in a very short time in sequence. Within one cycle, material 4 is sintered in different regions, but because the time of one cycle is very short, the overall temperature of material 4 remains consistent at the same time. Therefore, this invention can complete the plasma sintering of large-sized material 4 under a conventional current by using the discharge component 2 and the control device in conjunction, and can avoid the hidden dangers of uneven local heating.

[0055] In actual production, the appropriate combination of discharge components 2 can be flexibly selected according to the shape and size of material 4. Generally, the design is based on the principle of equal division of areas, taking into account the power of the equipment, the required cross-sectional area of ​​the material to be sintered, the sintering temperature, and other actual conditions. Therefore, products of different shapes and sizes can be produced using this plasma sintering device.

[0056] Furthermore, the present invention is not limited to the cross-sectional area of ​​the product to be sintered, and can sinter large-sized products in one go without destructive disassembly and reassembly of the product itself. There is almost no difference between the parts of the plasma sintering. Moreover, since the insulating layer 22 of the upper pressure head 212, lower pressure head 215, upper mold 213 and lower mold 214 is very thin, during the plasma sintering of a certain block of material 4, some of the plasma will escape to a small area outside the edge, causing these areas to also undergo plasma sintering at the same time. These factors make the material 4 produced by the method of the present invention uniform and dense.

[0057] Preferably, the system further includes a switching assembly 36 connected to the PLC control system 31. The switching assembly 36 includes a first single-pole double-throw switch 361, a second single-pole double-throw switch 362, and a third single-pole double-throw switch 363. The first single-pole double-throw switch 361 includes a stationary terminal A13611, a stationary terminal A23612, and a moving terminal A33613. The second single-pole double-throw switch 362 includes a stationary terminal B13621, a stationary terminal B23622, and a moving terminal B33623. The third single-pole double-throw switch 363 includes a stationary terminal C1, a stationary terminal C2, and a moving terminal C3. The discharge assembly 2 is composed of four discharge modules 21 spliced ​​together. The four discharge modules 21 are module A23, module B23, module C24, module C25, module C26 ... 4. Modules C25 and D26; one end of module A23, one end of module B24, one end of module C25, and one end of module D26 are respectively connected in parallel to the pulse current generator 35; the other end of module A23 is connected in series with the stationary terminal A13611, the other end of module B24 is connected in series with the stationary terminal A23612, the other end of module C25 is connected in series with the stationary terminal B13621, the other end of module D26 is connected in series with the stationary terminal B23622, the moving terminal A33613 is connected in series with the stationary terminal C1, the moving terminal B33623 is connected in series with the stationary terminal C2, and the moving terminal C3 is connected to the pulse current generator 35.

[0058] To better integrate the discharge module 21 and the PLC control system 31, this embodiment employs a method where the discharge module 21 is connected in parallel with another identical unit and in series with a single-pole double-throw switch, then in parallel with yet another identical unit and in series with another single-pole double-throw switch, and so on. Each switch is connected to the PLC control system 31. When current needs to flow through a specific zone during the sintering process, the PLC control system 31 controls each switch to the appropriate position, achieving simultaneous discharge of the target discharge module 21 and de-energization of other discharge modules 21. By controlling the changes in the positions of each switch, the PLC control system 31 cycles the current through each zone, achieving the purpose of alternating heating / stopping heating in each zone within a cycle. For example, as shown in the appendix... Figure 11As shown, in one cycle, modules A23, B24, C25, and D26 need to discharge individually and sequentially. The PLC control system 31 controls the first single-pole double-throw switch 361 to position 1-1, the second single-pole double-throw switch 362 to open, and the third single-pole double-throw switch 363 to position 3-1 to discharge module A23. Then, the first single-pole double-throw switch 361 is switched to position 1-2 to discharge module B24. Next, the PLC control system 31 controls the first single-pole double-throw switch 361 to open, the second single-pole double-throw switch 362 to position 2-1, and the third single-pole double-throw switch 363 to position 3-2 to discharge module C25. Finally, the second single-pole double-throw switch 362 is switched to position 2-2 to discharge module D26. The PLC control system 31, by implementing the above logic and method, achieves the purpose of rotating the current of each partition within one cycle.

[0059] Preferably, the upper electrode 211 and the lower electrode 216 have the same structure. The upper electrode 211 is made of copper or copper alloy material, with a conductivity of 50-56.5 MS / m and a compressive strength of 200-300 MPa. The upper pressure head 212 and the lower pressure head 215 have the same structure. The upper pressure head 212 is made of stainless steel or manganese alloy steel material, with a conductivity of 1.25-1.43 MS / m and a compressive strength of 300-500 MPa. The upper mold 213 and the lower mold 214 have the same structure. The upper conductive part 2131 and the lower conductive part 2141 are both made of high-strength graphite material with a compressive strength of 100-150 MPa, a resistivity of 7-8 μΩ·m, and a melting point of 3850±50℃. In this embodiment, the upper electrode 211 and the lower electrode 216 are made of copper or copper alloy, with a conductivity of 50–56.5 MS / m and a compressive strength of 200–300 MPa, possessing advantages such as high conductivity, high compressive strength, and economic cost. The shape of the electrodes is determined by the shape of the material 4 to be produced. The insulating layer 22 between the electrodes is used to insulate and fix the electrodes to form an electrode assembly. The upper pressure head 212 and the lower pressure head 215 are used to transmit the pressure applied to the material 4 and conduct current. They are made of conductive materials such as stainless steel or manganese alloy steel, with a conductivity of 1.25–1.43 MS / m and a compressive strength of 300–500 MPa, possessing advantages such as conductivity, high compressive strength, and economic cost. The upper conductive part 2131 of the upper mold 213 and the lower conductive part 2141 of the lower mold 214 are made of conductive materials such as high-strength graphite. The high-strength graphite material has a compressive strength of 100-150 MPa, a resistivity of 7-8 μΩ·m, and a melting point of 3850±50℃. The upper insulating part 2132 and the lower insulating part 2142 can be made of insulating materials such as ceramic materials. The upper conductive part 2131 is separated by the upper insulating part 2132, and the lower conductive part 2141 is separated by the lower insulating part 2142. Each part corresponds to the other.

[0060] Preferably, the insulating layer 22 is an insulating coating, which is applied to the upper electrode 211, the upper pressure head 212, the upper mold 213, the lower mold 214, the lower pressure head 215, and the lower electrode 216 respectively. The insulating coating is alumina or alumina / titanium oxide composite ceramic with a room temperature dielectric constant of 12, and the insulating strength is 1069V / 0.1mm, with a resistivity of 1014Ω·cm. In this embodiment, all insulating coatings are made of alumina or alumina / titanium oxide composite ceramic with a room temperature dielectric constant of 12, with a maximum insulating strength of 1069V / 0.1mm and a resistivity of 1014Ω·cm. Further, each component of the present invention is dip-coated with a precursor glaze and then heated to 1200-1300℃ and cured for 0.5-1h to obtain an insulating coating with a thickness of 0.2-0.3mm.

[0061] Preferably, the discharge assembly 2 has a rectangular cross-section; four upper electrodes 211 form a cuboid electrode group A1, with adjacent upper electrodes 211 isolated by the insulating layer 22; four lower electrodes 216 form a cuboid electrode group B1, with adjacent lower electrodes 216 isolated by the insulating layer 22; four upper pressure heads 212 form a cuboid pressure head group A1, with adjacent upper pressure heads 212 isolated by the insulating layer 22; four lower pressure heads 215 form a cuboid pressure head group B1, with adjacent lower pressure heads 215 isolated by the insulating layer 22; four upper molds 213 form a... A cuboid mold A1 has grooves on its top and bottom, and adjacent upper molds 213 are separated by the insulating layer 22; four lower molds 214 form a cuboid mold B1 with grooves on its top and bottom, and adjacent lower molds 214 are separated by the insulating layer 22; the electrode group A1 is connected to the pressure head group A1, the pressure head group A1 is fitted into the groove on the top of the cuboid mold A1, the groove on the bottom of the cuboid mold A1 is connected to the groove on the top of the cuboid mold B1, the groove on the bottom of the cuboid mold B1 is fitted onto the top of the pressure head group B1, and the pressure head group B1 is connected to the electrode group B1.

[0062] Please refer to Figures 5 to 10As shown in the figure, the discharge assembly 2 of the present invention adopts an electrode grouping, pressure head partitioning, and mold partitioning method to achieve the purpose of product partitioning sintering. Specifically, there are four discharge modules 21, that is, four upper electrodes 211, four lower electrodes 216, four upper pressure heads 212, four lower pressure heads 215, four upper molds 213, and four lower molds 214. In the horizontal direction, the four upper electrodes 211 form a cuboid electrode group A1, and similarly, the four lower electrodes 216 form an electrode group B1. In contrast, the four upper pressure heads 212 form a cuboid pressure head group A1, the four lower pressure heads 215 form a pressure head group B1, the four upper molds 213 form a cuboid mold A1, and the four lower molds 214 form a cuboid mold B1. Then, electrode assembly A1, pressure head assembly A1, cuboid mold A1, cuboid mold B1, pressure head assembly B1, and electrode assembly B1 are arranged sequentially from top to bottom. Then, material 4 is loaded between cuboid mold A1 and cuboid mold B1. In this embodiment, the discharge assembly 2 adopts an approximately cuboid structure, which facilitates the processing of advanced ceramics with cuboid structures.

[0063] Preferably, the discharge assembly 2 has a rhomboid cross-section; four upper electrodes 211 form a quadrangular prism electrode group A2, with adjacent upper electrodes 211 isolated by the insulating layer 22; four lower electrodes 216 form a quadrangular prism electrode group B2, with adjacent lower electrodes 216 isolated by the insulating layer 22; four upper pressure heads 212 form a quadrangular prism pressure head group A2, with adjacent upper pressure heads 212 isolated by the insulating layer 22; four lower pressure heads 215 form a quadrangular prism pressure head group B2, with adjacent lower pressure heads 215 isolated by the insulating layer 22; four upper molds 213 form a top and... A quadrangular prism mold A2 has grooves on its bottom, and adjacent upper molds 213 are separated by the insulating layer 22; four lower molds 214 form a quadrangular prism mold B2 with grooves on both the top and bottom, and adjacent lower molds 214 are separated by the insulating layer 22; the electrode assembly A2 is connected to the pressure head assembly A2, the pressure head assembly A2 is fitted into the groove on the top of the quadrangular prism mold A2, the groove on the bottom of the quadrangular prism mold A2 is connected to the groove on the top of the quadrangular prism mold B2, the groove on the bottom of the quadrangular prism mold B2 is fitted onto the top of the pressure head assembly B2, and the pressure head assembly B2 is connected to the electrode assembly B2. Please refer to... Figures 12 to 14 Through the above structural setup, a quadrangular prism space is formed between the cuboid mold A2 and the cuboid mold B2, which enables the processing of advanced ceramics with quadrangular prism structures.

[0064] Preferably, the discharge assembly 2 has a triangular cross-section; four upper electrodes 211 form a triangular prism electrode group A3, with adjacent upper electrodes 211 isolated from each other by the insulating layer 22; four lower electrodes 216 form a triangular prism electrode group B3, with adjacent lower electrodes 216 isolated from each other by the insulating layer 22; four upper pressure heads 212 form a triangular prism pressure head group A3, with adjacent upper pressure heads 212 isolated from each other by the insulating layer 22; four lower pressure heads 215 form a triangular prism pressure head group B3, with adjacent lower pressure heads 215 isolated from each other by the insulating layer 22; four upper molds 213 form a top and... A triangular prism mold A3 has grooves on its bottom, and adjacent upper molds 213 are separated by the insulating layer 22; four lower molds 214 form a triangular prism mold B3 with grooves on both the top and bottom, and adjacent lower molds 214 are separated by the insulating layer 22; the electrode assembly A3 is connected to the pressure head assembly A3, the pressure head assembly A3 is fitted into the groove on the top of the triangular prism mold A3, the groove on the bottom of the triangular prism mold A3 is connected to the groove on the top of the triangular prism mold B3, the groove on the bottom of the triangular prism mold B3 is fitted onto the top of the pressure head assembly B3, and the pressure head assembly B3 is connected to the electrode assembly B3. Please refer to... Figures 15 to 17 Through the above structural setup, a triangular prism space is formed between the cuboid mold A3 and the cuboid mold B3, which can process advanced ceramics with triangular prism structures.

[0065] The discharge plasma sintering apparatus of this invention rationally divides the material 4 into zones. A PLC control system 31 uses pulsed current to directionally focus and discharge onto the product to be sintered in designated zones. After a specified discharge time, the control circuit rotates the discharge area to the next designated zone. The control component 3 controls multiple discharge modules 21 to repeatedly discharge / de-energize in a very short time according to a set sequence. This allows the areas of material 4 divided into zones to sequentially and repeatedly cycle through the process of conducting heat release / de-energizing and stopping heat release in a very short time, ensuring that the overall temperature of material 4 remains consistent at the same time. Ultimately, this allows the entire material 4 to undergo plasma sintering. Through the discharge plasma sintering apparatus of this invention, pulsed current can be focused on designated zones without increasing the power of the plasma SPS sintering equipment. This ensures the current density of the sintering section, guarantees sufficient plasma generation in the designated area, ensures the sintering effect within the area, and ultimately achieves the goal of rapid plasma sintering of large-size products, effectively reducing equipment costs.

[0066] A sintering method using a spark plasma sintering apparatus for producing large-size advanced ceramics includes the following steps:

[0067] Step S1: Ball milling; Alumina powder, alumina grinding balls toughened with zirconia, and ethanol are placed together in a polytetrafluoroethylene ball milling jar for wet ball milling;

[0068] Step S2: Ultrasonic treatment; The fully ball-milled alumina slurry is ultrasonically treated for 35-45 minutes, and stirring is maintained during the ultrasonic treatment to remove agglomerates in the powder.

[0069] Step S3: Sieving; Place the alumina slurry in a drying oven and dry it at 100℃ for 12 hours. Then sieve it through a 200-mesh sieve to obtain alumina powder of the target fineness.

[0070] Step S4: Set up the spark plasma sintering device, put the processed alumina powder into the graphite mold, and then put the graphite mold into the spark plasma sintering furnace. Evacuate to 4-6 Pa, and apply a pressure of 25 MPa under argon atmosphere for pre-compression.

[0071] Step S5: Heat to sintering temperature; apply pulse current to increase pressure to 40MPa; control device controls 4 discharge modules, and repeatedly cycle through discharge / power off processes in the order of discharge module A, discharge module B, discharge module C, and discharge module D. Under the action of pulse current, discharge is generated between alumina powder particles, which excites plasma and causes the temperature of alumina powder to rise rapidly to the sintering temperature.

[0072] Step S6: Constant temperature sintering; The PLC control system controls the pulse current to be reduced to 750-850A and holds the temperature for 5 minutes.

[0073] Step S7: After sintering is completed, the PLC control system controls the upper and lower electrodes to stop discharging, allowing the material to cool naturally; after the internal temperature of the furnace drops to room temperature, the applied pressure is gradually reduced; after the pressure drops to 0, the material is removed from the graphite mold to obtain the sintered product.

[0074] Preferably, in step S5, the pulse current generator outputs a DC pulse current of 3650–3750 A, with a pulse frequency of 40 Hz and a single discharge time of 0.25–0.75 s. In this step, discharge is generated between particles under the action of the pulse current, exciting plasma and causing the temperature of the powder material to rise rapidly to 1500 °C at a heating rate of 100 °C / min. When a current of approximately 8000 A continuously passes through a certain section, the heating rate of that section is approximately 1000 °C / min. Since this invention uses a four-electrode cyclic intermittent discharge, in order to achieve a heating rate of 100 °C / min for the material, the pulse current used should satisfy a heating rate of 400 °C / min while continuously passing through a certain area. With the power supply voltage constant, if the heat preservation power is 10% of the input power when the temperature rises at 1000℃ / min, then the heat preservation current is 10% of 8000A, which is 800A. The current required for a temperature rise of 400℃ / min is 800A minus 40% of the heat preservation current, which is 2880A. Therefore, the required pulse current is approximately 3700A when the two are added together.

[0075] Preferably, in step S1, the rotational speed of the ball mill is 185-200 r / min, the forward and reverse rotation frequency is 10 min / time, the ball milling time is 10-13 h, and the ball-to-material ratio is 3-5:1.

[0076] This sintering method offers the following advantages: it eliminates the need for granulation of advanced ceramic powders and time-consuming debinding processes for molding additives, enabling very rapid production and overcoming the industry pain point of long production cycles for large-size ceramic products using traditional methods. Furthermore, the production process is controlled by a control device, and producing a large-size product only requires one furnace start-up and shutdown, simplifying the operation and effectively reducing manufacturing costs.

[0077] The following describes three examples:

[0078] Embodiment 1:

[0079] Step S1: Ball milling; Alumina powder, alumina grinding balls toughened with zirconia, and ethanol are placed together in a polytetrafluoroethylene ball mill jar for wet ball milling; The ball mill speed is 200 r / min, the forward and reverse rotation frequency is 10 min / time, the ball milling time is 10 h, and the ball-to-material ratio is 3:1.

[0080] Step S2: Ultrasonic treatment; The fully ball-milled alumina slurry is ultrasonically treated for 40 minutes, and stirring is maintained during the ultrasonic treatment to remove agglomerates in the powder.

[0081] Step S3: Sieving; Place the alumina slurry in a drying oven and dry it at 100℃ for 12 hours. Then sieve it through a 200-mesh sieve to obtain alumina powder of the target fineness.

[0082] Step S4: Set up the spark plasma sintering device, put the processed alumina powder into the graphite mold, and then put the graphite mold into the spark plasma sintering furnace. Evacuate to 4-6 Pa, and apply a pressure of 25 MPa under argon atmosphere for pre-compression.

[0083] Step S5: Heat to sintering temperature; apply pulsed current to increase pressure to 40MPa; control device controls 4 discharge modules, performing multiple cycles of discharge / power-off in the order of discharge module A, discharge module B, discharge module C, and discharge module D. Under the action of pulsed current, discharge is generated between alumina powder particles, stimulating plasma and rapidly raising the temperature of alumina powder to the sintering temperature; the pulsed current generator outputs a DC pulse current of 3700A, a pulse frequency of 40Hz, and a single discharge time of 0.25–0.75s.

[0084] Step S6: Constant temperature sintering; The PLC control system controls the pulse current to be reduced to 800A and maintains the temperature for 5 minutes.

[0085] Step S7: After sintering is completed, the PLC control system controls the upper and lower electrodes to stop discharging, allowing the material to cool naturally; after the internal temperature of the furnace drops to room temperature, the applied pressure is gradually reduced; after the pressure drops to 0, the material is removed from the graphite mold to obtain the sintered product.

[0086] Example 2:

[0087] Step S1: Ball milling; Alumina powder, alumina grinding balls toughened with zirconia, and ethanol are placed together in a polytetrafluoroethylene ball mill jar for wet ball milling; The ball mill speed is 190 r / min, the forward and reverse rotation frequency is 10 min / time, the ball milling time is 11 h, and the ball-to-material ratio is 4:1.

[0088] Step S2: Ultrasonic treatment; The fully ball-milled alumina slurry is ultrasonically treated for 35 minutes, and stirring is maintained during the ultrasonic treatment to remove agglomerates in the powder.

[0089] Step S3: Sieving; Place the alumina slurry in a drying oven and dry it at 100℃ for 12 hours. Then sieve it through a 200-mesh sieve to obtain alumina powder of the target fineness.

[0090] Step S4: Set up the spark plasma sintering device, put the processed alumina powder into the graphite mold, and then put the graphite mold into the spark plasma sintering furnace. Evacuate to 4-6 Pa, and apply a pressure of 25 MPa under argon atmosphere for pre-compression.

[0091] Step S5: Heat to sintering temperature; apply pulsed current to increase pressure to 40MPa; control device controls 4 discharge modules, performing multiple cycles of discharge / power-off in the order of discharge module A, discharge module B, discharge module C, and discharge module D. Under the action of pulsed current, discharge is generated between alumina powder particles, stimulating plasma and rapidly raising the temperature of alumina powder to the sintering temperature; the pulsed current generator outputs a DC pulse current of 3700A, a pulse frequency of 40Hz, and a single discharge time of 0.25–0.75s.

[0092] Step S6: Constant temperature sintering; The PLC control system controls the pulse current to be reduced to 800A and maintains the temperature for 5 minutes.

[0093] Step S7: After sintering is completed, the PLC control system controls the upper and lower electrodes to stop discharging, allowing the material to cool naturally; after the internal temperature of the furnace drops to room temperature, the applied pressure is gradually reduced; after the pressure drops to 0, the material is removed from the graphite mold to obtain the sintered product.

[0094] Example 3:

[0095] Step S1: Ball milling; Alumina powder, alumina grinding balls toughened with zirconia, and ethanol are placed together in a polytetrafluoroethylene ball mill jar for wet ball milling; The ball mill speed is 185 r / min, the forward and reverse rotation frequency is 10 min / time, the ball milling time is 13 h, and the ball-to-material ratio is 5:1;

[0096] Step S2: Ultrasonic treatment; The fully ball-milled alumina slurry is ultrasonically treated for 45 minutes, and stirring is maintained during the ultrasonic treatment to remove agglomerates in the powder.

[0097] Step S3: Sieving; Place the alumina slurry in a drying oven and dry it at 100℃ for 12 hours. Then sieve it through a 200-mesh sieve to obtain alumina powder of the target fineness.

[0098] Step S4: Set up the spark plasma sintering device, put the processed alumina powder into the graphite mold, and then put the graphite mold into the spark plasma sintering furnace. Evacuate to 4-6 Pa, and apply a pressure of 25 MPa under argon atmosphere for pre-compression.

[0099] Step S5: Heat to sintering temperature; apply pulsed current to increase pressure to 40MPa; control device controls 4 discharge modules, performing multiple cycles of discharge / power-off in the order of discharge module A, discharge module B, discharge module C, and discharge module D. Under the action of pulsed current, discharge is generated between alumina powder particles, stimulating plasma and rapidly raising the temperature of alumina powder to the sintering temperature; the pulsed current generator outputs a DC pulse current of 3700A, a pulse frequency of 40Hz, and a single discharge time of 0.25–0.75s.

[0100] Step S6: Constant temperature sintering; The PLC control system controls the pulse current to be reduced to 800A and maintains the temperature for 5 minutes.

[0101] Step S7: After sintering is completed, the PLC control system controls the upper and lower electrodes to stop discharging, allowing the material to cool naturally; after the internal temperature of the furnace drops to room temperature, the applied pressure is gradually reduced; after the pressure drops to 0, the material is removed from the graphite mold to obtain the sintered product.

[0102] This invention provides a spark plasma sintering apparatus for producing large-size advanced ceramics. By placing alumina powder, after ball milling, ultrasonication, and sieving, into a spark assembly, and utilizing the splicing structure of the spark modules separated by an insulating layer, the material to be sintered is effectively partitioned. A control component controls several spark modules to cycle through discharge / de-energization multiple times in a set sequence within a very short time. This causes the material to be divided into regions to cycle through heat release / de-energization multiple times in a very short time, minimizing temperature differences within the material at any given time. This achieves the goal of sintering large-size products using plasma sintering under conventional current conditions. The sintering method employed in this invention eliminates the need for granulation of the advanced ceramic powder and time-consuming debinding processes for molding additives, enabling rapid production and overcoming the industry pain point of long production cycles for large-size ceramic products using traditional methods. Furthermore, the production process is controlled by a PLC control system, and producing a large-size product only requires one furnace start-up and shutdown, simplifying the operation and effectively reducing manufacturing costs.

[0103] The above provides a detailed description of the spark plasma sintering apparatus for producing large-size advanced ceramics provided by the present invention. For those skilled in the art, based on the ideas of the embodiments of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A spark plasma sintering apparatus for producing large-size advanced ceramics, characterized in that, It includes a vacuum chamber (1), a discharge assembly (2), and a control assembly (3); the vacuum chamber includes a left cavity (11) and a right cavity (12), the left cavity and the right cavity are arranged opposite to each other, and the discharge assembly is installed between the left cavity and the right cavity; the discharge assembly is composed of multiple discharge modules (21) spliced ​​together, and an insulating layer (22) is provided between adjacent discharge modules and is isolated by the insulating layer; the discharge module includes an upper electrode (211), an upper pressure head (212), an upper mold (213), a lower mold (214), and a lower pressure head (215) arranged from top to bottom. The upper electrode (216) is electrically connected to the top of the upper pressure head; the upper mold includes an upper conductive part (2131) and an upper insulating part (2132), and the bottom of the upper pressure head is connected to the top of the conductive part; the lower mold includes a lower conductive part (2141) and a lower insulating part (2142), and the upper insulating part and the lower insulating part are connected to each other; a discharge cavity for accommodating material (4) is provided between the upper mold and the lower mold; the bottom of the lower conductive part is electrically connected to the top of the lower pressure head; the bottom of the lower pressure head is electrically connected to the top of the lower electrode; The control components include a PLC control system (31), a current sensor (32), a temperature sensor (33), a pressure sensor (34), and a pulse current generator (35); the current sensor is connected to the discharge module and is used to detect the operating current of the discharge module; the temperature sensor is used to detect the temperature of the material; the pressure sensor is connected to the upper pressure head and the lower pressure head and is used to detect the pressure of the upper pressure head and the lower pressure head; the pulse current generator is connected to the upper electrode and the lower electrode and is used to generate a pulse current; the PLC control system is connected to the current sensor, the temperature sensor, the pressure sensor, and the pulse current generator respectively, and the PLC control system is used to control the discharge sequence and parameters; It also includes a switching assembly (36) connected to the PLC control system. The switching assembly includes a first single-pole double-throw switch (361), a second single-pole double-throw switch (362), and a third single-pole double-throw switch (363). The first single-pole double-throw switch includes a stationary terminal A1 (3611), a stationary terminal A2 (3612), and a moving terminal A3 (3613). The second single-pole double-throw switch includes a stationary terminal B1 (3621), a stationary terminal B2 (3622), and a moving terminal B3 (3623). The third single-pole double-throw switch includes a stationary terminal C1, a stationary terminal C2, and a moving terminal C3. The discharge assembly is composed of four discharge modules spliced ​​together. The discharge modules are module A (23), module B (24), module C (25) and module D (26); one end of module A, one end of module B, one end of module C and one end of module D are respectively connected in parallel to the pulse current generator; the other end of module A is connected in series with the stationary end A1, the other end of module B is connected in series with the stationary end A2, the other end of module C is connected in series with the stationary end B1, the other end of module D is connected in series with the stationary end B2, the moving end A3 is connected in series with the stationary end C1, the moving end B3 is connected in series with the stationary end C2, and the moving end C3 is connected to the pulse current generator.

2. The spark plasma sintering apparatus for producing large-size advanced ceramics according to claim 1, characterized in that, The upper electrode has the same structure as the lower electrode. The upper electrode is made of copper or copper alloy with a conductivity of 50~56.5 MS / m and a compressive strength of 200~300 MPa. The upper pressure head has the same structure as the lower pressure head. The upper pressure head is made of stainless steel or manganese alloy steel with a conductivity of 1.25~1.43 MS / m and a compressive strength of 300~500 MPa. The upper mold has the same structure as the lower mold. Both the upper conductive part and the lower conductive part are made of high-strength graphite material with a compressive strength of 100~150 MPa, a resistivity of 7~8 μΩ·m, and a melting point of 3850±50℃.

3. The spark plasma sintering apparatus for producing large-size advanced ceramics according to claim 2, characterized in that, The insulating layer is an insulating coating, which is applied to the upper electrode, the upper pressure head, the upper mold, the lower mold, the lower pressure head, and the lower electrode. The insulating coating is alumina or alumina / titanium oxide composite ceramic with a room temperature dielectric constant of 12. The insulating strength of the insulating coating is 1069V / 0.1mm, and the resistivity is 1014Ω·cm.

4. The spark plasma sintering apparatus for producing large-size advanced ceramics according to claim 1, characterized in that, The discharge assembly has a rectangular cross-section; four upper electrodes form a cuboid electrode group A1, with adjacent upper electrodes isolated by the insulating layer; four lower electrodes form a cuboid electrode group B1, with adjacent lower electrodes isolated by the insulating layer; four upper pressure heads form a cuboid pressure head group A1, with adjacent upper pressure heads isolated by the insulating layer; four lower pressure heads form a cuboid pressure head group B1, with adjacent lower pressure heads isolated by the insulating layer; four upper molds form a rectangular mold with grooves on the top and bottom. A cuboid mold A1 is separated from adjacent upper molds by the insulating layer; four lower molds form a cuboid mold B1 with grooves on the top and bottom, and adjacent lower molds are separated from each other by the insulating layer; the electrode group A1 is connected to the pressure head group A1, the pressure head group A1 is fitted into the groove on the top of the cuboid mold A1, the groove on the bottom of the cuboid mold A1 is connected to the groove on the top of the cuboid mold B1, the groove on the bottom of the cuboid mold B1 is fitted onto the top of the pressure head group B1, and the pressure head group B1 is connected to the electrode group B1.

5. The spark plasma sintering apparatus for producing large-size advanced ceramics according to claim 1, characterized in that, The discharge assembly has a rhomboid cross-section; four upper electrodes form a quadrangular prism electrode group A2, with adjacent upper electrodes isolated by the insulating layer; four lower electrodes form a quadrangular prism electrode group B2, with adjacent lower electrodes isolated by the insulating layer; four upper pressure heads form a quadrangular prism pressure head group A2, with adjacent upper pressure heads isolated by the insulating layer; four lower pressure heads form a quadrangular prism pressure head group B2, with adjacent lower pressure heads isolated by the insulating layer; four upper molds form a quadrangular prism with grooves on the top and bottom. Mold A2, adjacent upper molds are isolated by the insulating layer; four lower molds form a quadrangular prism mold B2 with grooves on the top and bottom, adjacent lower molds are isolated by the insulating layer; the electrode group A2 is connected to the pressure head group A2, the pressure head group A2 is fitted into the groove on the top of the quadrangular prism mold A2, the groove on the bottom of the quadrangular prism mold A2 is connected to the groove on the top of the quadrangular prism mold B2, the groove on the bottom of the quadrangular prism mold B2 is fitted onto the top of the pressure head group B2, and the pressure head group B2 is connected to the electrode group B2.

6. The spark plasma sintering apparatus for producing large-size advanced ceramics according to claim 1, characterized in that, The discharge assembly has a triangular cross-section; four upper electrodes form a triangular prism electrode group A3, and adjacent upper electrodes are isolated by the insulating layer; four lower electrodes form a triangular prism electrode group B3, and adjacent lower electrodes are isolated by the insulating layer. Four upper pressure heads form a pressure head group A3 with a triangular prism structure, and adjacent upper pressure heads are isolated from each other by the insulating layer; four lower pressure heads form a pressure head group B3 with a triangular prism structure, and adjacent lower pressure heads are isolated from each other by the insulating layer. Four upper molds form a triangular prism mold A3 with grooves on the top and bottom, and adjacent upper molds are isolated by the insulating layer; four lower molds form a triangular prism mold B3 with grooves on the top and bottom, and adjacent lower molds are isolated by the insulating layer; the electrode group A3 is connected to the pressure head group A3, the pressure head group A3 is fitted into the groove on the top of the triangular prism mold A3, the groove on the bottom of the triangular prism mold A3 is connected to the groove on the top of the triangular prism mold B3, the groove on the bottom of the triangular prism mold B3 is fitted onto the top of the pressure head group B3, and the pressure head group B3 is connected to the electrode group B3.

7. A sintering method for the spark plasma sintering apparatus for producing large-size advanced ceramics as described in any one of claims 1 to 6, characterized in that, It includes the following steps: Step S1: Ball milling; Alumina powder, alumina grinding balls toughened with zirconia, and ethanol are placed together in a polytetrafluoroethylene ball milling jar for wet ball milling; Step S2: Ultrasonic treatment; The fully ball-milled alumina slurry is ultrasonically treated for 35-45 minutes, and stirring is maintained during the ultrasonic treatment to remove agglomerates in the powder. Step S3: Sieving; Place the alumina slurry in a drying oven and dry it at 100℃ for 12 hours. Then sieve it through a 200-mesh sieve to obtain alumina powder of the target fineness. Step S4: Set up the spark plasma sintering device, put the processed alumina powder into the graphite mold, and then put the graphite mold into the spark plasma sintering furnace. Evacuate to 4~6 Pa, and apply a pressure of 25 MPa under argon atmosphere for pre-compression. Step S5: Increase the temperature to the sintering temperature; A pulsed current is applied to raise the pressure to 40MPa. The control device controls four discharge modules, which cycle through the discharge / power-off process multiple times in the order of discharge module A, discharge module B, discharge module C, and discharge module D. Under the action of the pulsed current, discharge is generated between the particles of alumina powder, which excites plasma and causes the temperature of alumina powder to rise rapidly to the sintering temperature. Step S6: Isothermal sintering; The PLC control system reduces the pulse current to 750~850A and maintains the temperature for 5 minutes. Step S7: After sintering is completed, the PLC control system controls the upper and lower electrodes to stop discharging, allowing the material to cool naturally; after the internal temperature of the furnace drops to room temperature, the applied pressure is gradually reduced; after the pressure drops to 0, the material is removed from the graphite mold to obtain the sintered product.

8. The sintering method of the spark plasma sintering apparatus for producing large-size advanced ceramics according to claim 7, characterized in that, In step S5, the pulse current generator outputs a DC pulse current of 3650~3750A, a pulse frequency of 40Hz, and a single discharge time of 0.25~0.75s.

9. The sintering method of the spark plasma sintering apparatus for producing large-size advanced ceramics according to claim 7, characterized in that, In step S1, the ball mill rotates at a speed of 185-200 r / min, the forward and reverse rotation frequency is 10 min / time, the ball milling time is 10-13 h, and the ball-to-material ratio is 3-5:1.

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