Ceramic sintering device and method

Abstract

The invention provides a ceramic sintering device and method which are used for sintering ceramic green bodies. The sintering device comprises a support, electrodes and a power source. The bracket includes a first end and a second end. The bracket is configured to place a ceramic green body. The number of the electrodes is two, the two electrodes penetrate through the first end and the second end respectively and are oppositely arranged on the support, and the ceramic green body is arranged between the two electrodes. The power supply is electrically connected with the electrode, forms a discharge path with the ceramic green body, and is configured to apply an electric field to the electrode to heat the ceramic green body until sintering. An electric field is applied to the ceramic green body through a working power supply, the conductivity of the ceramic green body is rapidly reduced through electric breakdown and thermal runaway of Joule heating, the current is rapidly increased to a set value, and rapid sintering under the action of current Joule heating is started. By means of the ceramic room-temperature rapid sintering device, room-temperature rapid sintering of a large piece of ceramic can be achieved.

Description

Technical Field

[0001] The present application relates to the technical field of ceramic preparation, and particularly relates to a ceramic sintering device and method. Background Art

[0002] Ceramic materials have been widely used in the fields of construction, electricity, medical treatment, and environmental protection. In the preparation process of ceramic materials, sintering is an important link and has a great influence on the performance of ceramics. The traditional ceramic sintering process has disadvantages such as long time consumption, low energy efficiency, and large sintered ceramic grains. However, there is currently a lack of research on the rapid sintering of large sheet ceramics at room temperature, which limits the application of rapid sintering at room temperature. Summary of the Invention

[0003] In order to solve at least one of the above technical problems, an embodiment of the present application provides a ceramic sintering device with a short reaction time and a simple structure.

[0004] In addition, an embodiment of the present application further provides a ceramic sintering method using the ceramic sintering device.

[0005] An embodiment of the present application provides a ceramic sintering device for sintering a ceramic green body. The ceramic sintering device includes a bracket, two electrodes, and a power source. The bracket includes a first end and a second end. The bracket is configured to place the ceramic green body. The two electrodes respectively pass through the first end and the second end and are oppositely arranged on the bracket, and the ceramic green body is arranged between the two electrodes. The power source is electrically connected to the electrodes and forms a discharge path with the ceramic green body. The power source is configured to apply an electric field to the electrodes to sinter the ceramic green body.

[0006] In some embodiments of the present application, through holes are provided on the first end and the second end. The two electrodes include a first electrode and a second electrode. The polarities of the first electrode and the second electrode are opposite. The first electrode and the second electrode are movably inserted into the through holes. The ceramic green body includes a first surface and a second surface arranged oppositely. The first electrode is configured to abut against the first surface, and the second electrode is configured to abut against the second surface.

[0007] In some embodiments of the present application, both the first electrode and the second electrode include an integrally formed abutting end and a connecting portion. The connecting portion is inserted into the through hole, and the abutting end is configured to abut against the ceramic green body.

[0008] In some embodiments of the present application, two conductive members are further included, and the two conductive members respectively cover the first surface and the second surface.

[0009] In some embodiments of the present application, the surface area of the conductive member is configured to be larger than the surface area of the ceramic green body.

[0010] In some embodiments of the present application, the material of the conductive member is graphite, and the material of the electrode is copper-zinc alloy.

[0011] In some embodiments of the present application, the electrode is connected to the power supply through a wire. A voltage measurer and a current measurer are also provided between the power supply and the electrode. The voltage measurer is configured to measure and control the voltage applied by the power supply, and the current measurer is configured to measure and control the current applied by the power supply.

[0012] The present application also provides a ceramic sintering method, which uses the aforementioned ceramic sintering device and includes the following steps: providing a green ceramic body; applying a target voltage to the green ceramic body, and adjusting the first current to a target current at a constant current growth rate, and maintaining the target current for 1 minute to 10 minutes to complete the sintering of the green ceramic body.

[0013] In some embodiments of the present application, the voltage value of the target voltage is 50 V to 500 V. The current value of the first current is 0.5 A to 2 A, and the current value of the target current is 1 A to 10 A. The current growth rate is 0.5 A / s to 2 A / s.

[0014] In some embodiments of the present application, when the thickness of the green ceramic body is 1.7 mm, the target voltage is 100 V. When the diameter of the green ceramic body is 20 mm, the target current is 1 A.

[0015] Compared with the prior art, the ceramic sintering device provided by the embodiments of the present application applies an electric field to the green ceramic body through a working power supply, and the conductivity of the green ceramic body rapidly decreases and the current rapidly rises to the set value through electrical breakdown and thermal runaway of Joule heating, and rapid sintering under the action of current Joule heating is started, shortening the reaction time. Using the ceramic room-temperature rapid sintering device provided by the present application, the room-temperature rapid sintering of large ceramic sheets can be realized, the sintered samples have finer grain sizes and higher densities, and the structure of the ceramic sintering device is simpler. Description of the Drawings

[0016] Figure 1 is a schematic diagram of a ceramic sintering device according to an embodiment of the present application.

[0017] Main Element Symbol Description: Bracket 100, Electrode 200, Power Supply 300, Green Ceramic Body 400, First End 101, Second End 102, First Electrode 201, Second Electrode 202, Through Hole 110, First Surface 401, Second Surface 402, Contact End 210, Connection Portion 220, Conductive Member 500, Voltage Measurer 600, Current Measurer 700. Detailed Embodiments

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0019] In order to solve the problems existing in the existing ceramic sintering methods, such as long reaction time, high energy consumption, low efficiency, and inability to sinter at room temperature. The inventors of the present application have found that rapid sintering of ceramic green bodies can be achieved through thermal runaway by Joule heating.

[0020] In view of this, please refer to Figure 1 , an embodiment of the present application provides a ceramic sintering device for sintering a ceramic green body 400. The sintering device includes a bracket 100, electrodes 200, and a power supply 300. The bracket 100 includes a first end 101 and a second end 102. The bracket 100 is configured to place the ceramic green body 400. There are two electrodes 200, and the two electrodes 200 respectively pass through the first end 101 and the second end 102 and are oppositely arranged on the bracket 100, and the ceramic green body 400 is arranged between the two electrodes 200. The power supply 300 is electrically connected to the electrodes 200 and forms a discharge path with the ceramic green body 400. The power supply 300 is configured to apply an electric field to the electrodes 200 to heat the ceramic green body 400 to sintering. By applying an electric field to the ceramic green body through the working power supply 300, the electrical conductivity of the ceramic green body rapidly decreases due to electrical breakdown and thermal runaway of Joule heating, the current rapidly rises to a set value, and rapid sintering under the action of current Joule heating begins. Using the ceramic room-temperature rapid sintering device provided by the present application, rapid sintering of large ceramic sheets at room temperature can be achieved. The sintered samples have finer grain sizes and higher densities, and the device is easy to implement. The electric field heating is more uniform, reducing the risk of deformation or cracking of the sheet ceramics during the sintering process. In some embodiments, the electric field can be a direct current electric field or an alternating current electric field.

[0021] In some embodiments of the present application, the bracket 100 is provided with a through hole 110. The electrode 200 includes a first electrode 201 and a second electrode 202. The polarities of the first electrode 201 and the second electrode 202 are opposite. The first electrode 201 and the second electrode 202 are movably inserted into the through hole 110. The ceramic green body 400 includes a first surface 401 and a second surface 402. The first electrode 201 abuts against the first surface 401, and the second electrode 202 abuts against the second surface 402. By providing the through hole 110 in the bracket 100 and movably inserting the first electrode 201 and the second electrode 202 into the through hole 110, stable fixation and reliable electrical connection of the ceramic green body 400 can be achieved. The opposite polarities of the first electrode 201 and the second electrode 202 can form a symmetrical electric field distribution, so that the ceramic green body 400 is more evenly affected by the electric field during the sintering process, improving the uniformity and quality of sintering. The first electrode 201 and the second electrode 202 are movably inserted into the through hole 110, which can ensure the maximum contact area between the electrode and the ceramic green body 400, thereby reducing the contact resistance and ensuring the uniform distribution of current. The setting of the through hole 110 can also prevent the problem of poor contact caused by excessive bending or movement of the electrode, further improving the reliability of the electrical connection. In some embodiments, the first electrode 201 is the positive electrode and the second electrode 202 is the negative electrode. In some other embodiments, the first electrode 201 is the negative electrode and the second electrode 202 is the positive electrode.

[0022] In some embodiments of the present application, both the first electrode 201 and the second electrode 202 include an integrally formed abutting end 210 and a connecting portion 220. The connecting portion 220 is inserted into the through hole 110, and the abutting end 210 is configured to place the ceramic green body 400. By designing the first electrode 201 and the second electrode 202 as an integrally formed abutting end 210 and a connecting portion 220, the structure and function of the electrode are further optimized. First, the abutting end 210 is configured to place the ceramic green body 400, which can ensure the stable placement of the ceramic green body 400 and avoid the problem of uneven sintering caused by unstable placement. Second, the connecting portion 220 is inserted into the through hole 110, which can provide a stable fixing effect and ensure the stability of the electrode during the sintering process.

[0023] In some embodiments of the present application, the ceramic sintering device further includes two conductive members 500, which are respectively disposed on the first surface 401 and the second surface 402. By respectively disposing the conductive members 500 on the first surface 401 and the second surface 402 of the green ceramic body 400, the sintering uniformity and stability are further improved. The arrangement of the conductive members 500 can enhance the electrical conductivity of the green ceramic body 400, ensuring that the current can be evenly distributed on the surface of the green ceramic body 400, thereby avoiding the risk of uneven sintering. The two conductive members 500 are respectively disposed on the first surface 401 and the second surface 402, which can form a symmetric electric field distribution, further improving the sintering uniformity and significantly improving the sintering quality and success rate. It can also improve the electrical contact and avoid the influence of uneven current distribution or partial discharge on the sintering uniformity. The sintering is initiated by the heating effect of the high-temperature plasma, and the sintering is completed by the thermal effect of the current, which is applicable to sintering large-area sheet ceramic materials of various shapes.

[0024] In some embodiments of the present application, the surface area of the conductive member 500 is larger than the surface area of the green ceramic body 400. By setting the surface area of the conductive member 500 to be larger than the surface area of the green ceramic body 400, the uniformity during the sintering process of the green ceramic body can be improved. On the other hand, the larger surface area of the conductive member 500 can more comprehensively cover the surface of the green ceramic body 400. The shape is not restricted on the premise of completely covering the green ceramic body, and it can be replaced with other flexible materials.

[0025] In some embodiments of the present application, the electrode 200 is connected to the power supply 300 through a wire. A voltage measurer 600 and a current measurer 700 are also disposed between the power supply 300 and the electrode 200. The voltage measurer 600 is configured to measure and control the voltage applied by the power supply 300, and the current measurer 700 is configured to measure and control the current applied by the power supply 300.

[0026] In some embodiments of the present application, the conductive member 500 includes one or both of graphite felt and graphite paper, and the material of the electrode 200 is brass. In some embodiments, the graphite felt can be replaced with flexible conductive materials such as metal wire braids or conductive aerogels. Flexible materials such as graphite felt are used to prevent the sample from adhering to the surface of the metal electrode during sintering, which may cause the sample to break. Graphite paper is used to improve the electrical contact between the sample and the flexible electrode.

[0027] In some embodiments, the thickness of the graphite felt is 5 mm to 10 mm. In some possible embodiments, the thickness of the graphite felt can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any value within the range formed by any two of the above values. The thickness of the graphite paper is 0.1 mm to 0.2 mm. In some possible embodiments, the thickness of the graphite paper can be 0.1 mm, 0.15 mm, 0.2 mm, or any value within the range formed by any two of the above values. In some embodiments, the porosity of the graphite felt is 60% to 95%. In some possible embodiments, the porosity of the graphite felt can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any value within the range formed by any two of the above values. If the thickness of the graphite felt and the graphite paper is too large, the cost will be high; if the thickness is too small, it is easy to break during the sintering process. If the porosity of the graphite felt is too high, the strength is insufficient and it is easy to collapse; if the porosity is too low, the uniformity of ceramic sintering is poor.

[0028] Compared with the prior art, the ceramic sintering device provided by the embodiments of the present application has the following beneficial effects: 1. Through electrical breakdown and thermal runaway of Joule heating, the electrical conductivity of the green ceramic body rapidly decreases, the current rapidly rises to the set value, and rapid sintering under the action of current Joule heating begins. Using the room-temperature rapid sintering device for ceramics provided by the present application, rapid sintering of large ceramic sheets at room temperature can be achieved. The sintered samples have finer grain sizes and higher densities, and the device is easy to implement.

[0029] 2. The ceramic sintering device provided by the present application is inexpensive and widely used for rapid sintering of large sheet ceramics at room temperature.

[0030] The embodiments of the present application also provide a ceramic sintering method, which uses the aforementioned ceramic sintering device, and specifically includes the following steps: Step 1: Provide a green ceramic body 400.

[0031] In some embodiments, the preparation method of the green ceramic body 400 includes selecting zinc oxide powder, and subjecting the zinc oxide powder to granulation, sieving, tabletting, and debinding processes to obtain a disc-shaped green ceramic body 400.

[0032] Step 2: Apply a target voltage to the green ceramic body 400, and adjust the first current to the target current at a constant current growth rate, and maintain the target current for 1 min to 10 min to complete the sintering of the green ceramic body 400.

[0033] In some embodiments of the present application, the voltage value of the target voltage is 50 V to 500 V. The current value of the first current is 0.5 A to 2 A, and the current value of the target current is 1 A to 10 A. The current growth rate is 0.5 A / s to 2 A / s. An excessively high target voltage may cause the sample to break down violently and shatter, while an excessively low target voltage cannot achieve breakdown. If the highest-level target current is too large, the sample cannot withstand the large current and shatters; if the highest-level target current is too small, it is not sufficient to sinter the sample. If the target rate is too fast, the sample cannot withstand the electrothermal shock and shatters; if the target rate is too slow, the efficiency of sintering the sample densely is low. If the target time is too short, the sintering is insufficient; if the target time is too long, the energy consumption is high.

[0034] In some embodiments, the voltage value of the target voltage is 50 V, 60 V, 70 V, 80 V, 90 V, 100 V, 200 V, 300 V, 400 V, 500 V, 600 V, or any value within the range formed by any two of the above values. In some embodiments, the current value of the first current can be 0.5 A, 0.7 A, 0.9 A, 1 A, 2 A, or any value within the range formed by any two of the above values. The current value of the target current can be 1 A, 2 A, 3 A, 4 A, 5 A, 6 A, 7 A, 8 A, 9 A, 10 A, or any value within the range formed by any two of the above values. In some embodiments, the growth rate of the current can be 0.5 A / s, 0.7 A / s, 0.9 A / s, 1 A / s, 2 A / s, or any value within the range formed by any two of the above values. In some embodiments, the holding time of the target current can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any value within the range formed by any two of the above values.

[0035] In some embodiments of the present application, when the thickness of the green ceramic body 400 is 1.7 mm, the target voltage is 100 V. When the diameter of the green ceramic body 400 is 20 mm, the target current is 1 A.

[0036] In some embodiments, the target voltage is related to the longitudinal dimension of the green ceramic body, and the target current and target rate are related to the transverse dimension of the green ceramic body. Taking a disc-shaped green body as an example, the target voltage is related to the thickness of the green ceramic body. When the thickness of the green ceramic body is 1.7 mm, the target voltage should be set to 100 V; the target current and target rate are related to the diameter of the green ceramic body. When the diameter of the green ceramic body is 20 mm, the target current should be divided into five levels. The first-level target current should be set to 1 A, and the highest-level target current should be set to 5 A. The target rate should be 1 A / s.

[0037] The foregoing ceramic sintering device will be further described below through specific embodiments.

[0038] Example 1 Step 1: Provide a green ceramic body. Select zinc oxide powder, and through processes such as granulation, sieving, pressing, and debinding of the zinc oxide powder, a disc-shaped ceramic green body 400 with a diameter of 20 mm and a thickness of 1.7 mm is obtained.

[0039] Step 2: Close to both sides of the ceramic green body 400, graphite papers with a diameter of 20 mm and a thickness of 0.1 mm are attached. The ceramic green body 400 covered with the graphite papers is clamped by two cubic graphite felts with a bottom side length of 25 mm and a thickness of 8 mm, and then placed between the first electrode 201 and the second electrode 202. By adjusting the distance between the first electrode 201 and the second electrode 202, the abutting end 210 is made to closely adhere to the graphite felt. The power supply 300, the first electrode 201, and the second electrode 202 are electrically connected with wires.

[0040] Step S3: Preset the target voltage of the voltage measuring device 600 and the current measuring device 700 to 100 V and the target current to 1 A. Turn on the power supply 300. At this time, the voltage across the ceramic green body 400 rises to the target voltage of 100 V within 1 s and discharges and high-temperature plasma appears. The current flowing through the ceramic green body 400 rapidly rises to the first-stage target current of 1 A within the subsequent 1 s, and then the current is gradually adjusted to the highest fifth-stage target current of 5 A at a target rate of 1 A / s and maintained for the target time of 1 min to complete sintering, and then the power supply 300 is turned off. After natural cooling to room temperature, the sintered ceramic green body 400 is taken out.

[0041] Example 2 Step 1: Provide a green ceramic body. Select zinc oxide powder, and through processes such as granulation, sieving, pressing, and debinding of the zinc oxide powder, a disc-shaped ceramic green body 400 with a diameter of 10 mm and a thickness of 1 mm is obtained.

[0042] Step 2: Close to both sides of the ceramic green body 400, graphite papers with a diameter of 20 mm and a thickness of 0.1 mm are attached. The ceramic green body 400 covered with the graphite papers is clamped by two cubic graphite felts with a bottom side length of 25 mm and a thickness of 8 mm, and then placed between the first electrode 201 and the second electrode 202. By adjusting the distance between the first electrode 201 and the second electrode 202, the abutting end 210 is made to closely adhere to the graphite felt. The power supply 300, the first electrode 201, and the second electrode 202 are electrically connected with wires.

[0043] Step S3: Preset the target voltage of the voltage measurer 600 and the current measurer 700 to 80 V and the target current to 0.5 A. Turn on the power supply 300. At this time, the voltage across the green ceramic blank 400 rises to the target voltage of 80 V within 1 s, and discharge and high-temperature plasma occur. The current flowing through the green ceramic blank 400 rapidly rises to the first-stage target current of 0.5 A within the subsequent 1 s, and then the current is gradually adjusted to the highest fifth-stage target current of 3 A at a target rate of 0.7 A / s and maintained for the target time of 2 min to complete sintering, and then turn off the power supply 300. After natural cooling to room temperature, take out the sintered green ceramic blank 400.

[0044] Example 3 Step 1: Provide a green ceramic blank. Select zinc oxide powder, and obtain a disc-shaped green ceramic blank 400 with a diameter of 50 mm and a thickness of 4 mm through processes such as granulation, sieving, pressing, and debinding of the zinc oxide powder.

[0045] Step 2: Closely attach graphite paper with a diameter of 20 mm and a thickness of 0.1 mm to both sides of the green ceramic blank 400, clamp the green ceramic blank 400 covered with the graphite paper with two cubic graphite felts with a bottom side length of 25 mm and a thickness of 8 mm, and then place it between the first electrode 201 and the second electrode 202. By adjusting the distance between the first electrode 201 and the second electrode 202, make the abutting end 210 closely contact the graphite felt. Electrically connect the power supply 300, the first electrode 201, and the second electrode 202 with wires.

[0046] Step S3: Preset the target voltage of the voltage measurer 600 and the current measurer 700 to 400 V and the target current to 2 A. Turn on the power supply 300. At this time, the voltage across the green ceramic blank 400 rises to the target voltage of 400 V within 1 s, and discharge and high-temperature plasma occur. The current flowing through the green ceramic blank 400 rapidly rises to the first-stage target current of 2 A within the subsequent 1 s, and then the current is gradually adjusted to the highest fifth-stage target current of 10 A at a target rate of 2 A / s and maintained for the target time of 10 min to complete sintering, and then turn off the power supply 300. After natural cooling to room temperature, take out the sintered green ceramic blank 400.

[0047] It can be seen that for the ceramic sintering device provided by the present application, an electric field is applied to the green ceramic body through a working power supply. Due to electric breakdown and thermal runaway of Joule heating, the conductivity of the green ceramic body rapidly decreases, and the current rapidly rises to a set value, and rapid sintering under the action of current Joule heating begins. By using the rapid room-temperature sintering device for ceramics provided by the present application, rapid room-temperature sintering of large ceramic sheets can be achieved. The sintered samples have finer grain sizes and higher densities, and the device is easy to implement. By applying a target voltage to the green ceramic body, discharge and breakdown occur on the side of the green ceramic body. The discharge spreads and generates a high-temperature plasma between the flexible graphite felt and the graphite paper. Its heating effect causes the temperature of the green ceramic body to rapidly increase, the conductivity to rapidly decrease, and the current flowing through the green ceramic body to rise to the target current, realizing rapid and uniform sintering of large ceramic sheets at room temperature through the current thermal effect. The electrode design of the flexible graphite felt and the graphite paper can improve electrical contact and avoid the influence of uneven current distribution or partial discharge on the sintering uniformity. The initiation of sintering relies on the heating effect of the high-temperature plasma, and the completion of sintering relies on the thermal effect of the current. The method can be used to sinter large-area sheet ceramic materials of various shapes.

[0048] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present invention. However, the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered within the protection scope of the present invention.

Claims

1. A ceramic sintering device for sintering green ceramic blanks, characterized in that The ceramic sintering device includes: A bracket, the bracket includes a first end and a second end, and the bracket is configured to place the green ceramic body; Two electrodes, the two electrodes respectively pass through the first end and the second end and are oppositely arranged on the bracket, and the green ceramic body is arranged between the two electrodes; and A power supply, the power supply is electrically connected to the electrodes and forms a discharge path with the green ceramic body, and the power supply is configured to apply an electric field to the electrodes to sinter the green ceramic body.

2. The ceramic sintering device according to claim 1, wherein Through holes are provided on the first end and the second end. The two electrodes include a first electrode and a second electrode. The polarities of the first electrode and the second electrode are opposite. The first electrode and the second electrode are movably inserted into the through holes. The green ceramic body includes a first surface and a second surface arranged oppositely. The first electrode is configured to abut against the first surface, and the second electrode is configured to abut against the second surface.

3. The ceramic sintering device according to claim 2, characterized in that, Both the first electrode and the second electrode include an integrally formed abutting end and a connecting portion. The connecting portion is inserted into the through hole, and the abutting end is configured to abut against the green ceramic body.

4. The ceramic sintering device according to claim 2, wherein It further includes two conductive members, and the two conductive members respectively cover the first surface and the second surface.

5. The ceramic sintering device according to claim 4, characterized in that, The surface area of the conductive member is configured to be larger than the surface area of the green ceramic body.

6. The ceramic sintering device according to claim 4, wherein The material of the conductive member is graphite, and the material of the electrode is copper-zinc alloy.

7. The ceramic sintering device according to claim 1, characterized in that, The electrode is connected to the power supply through a wire. A voltage measuring device and a current measuring device are further provided between the power supply and the electrode. The voltage measuring device is configured to measure and control the voltage applied by the power supply, and the current measuring device is configured to measure and control the current applied by the power supply.

8. A ceramic sintering method, characterized in that, Using the ceramic sintering device according to any one of claims 1-7, includes the following steps: Providing a green ceramic body; Applying a target voltage to the green ceramic body, and adjusting the first current to the target current at a constant current growth rate, and maintaining the target current for 1 min to 10 min to complete the sintering of the green ceramic body.

9. The ceramic sintering method according to claim 8, characterized in that, The voltage value of the target voltage is 50 V to 500 V; The current value of the first current is 0.5 A to 2 A, and the current value of the target current is 1 A to 10 A; The current growth rate is 0.5 A / s to 2 A / s.

10. The ceramic sintering method according to claim 8, characterized in that, When the thickness of the green ceramic body is 1.7 mm, the target voltage is 100 V; When the diameter of the green ceramic body is 20 mm, the target current is 1 A.

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