Plasma-assisted ceramic sintering device and ceramic sintering method

Abstract

The present application provides a plasma-assisted ceramic sintering apparatus and a ceramic sintering method. The plasma-assisted ceramic sintering apparatus includes a sealed container, a plasma jet device, a gas supply device, and a power supply device. The sealed container houses a ceramic green compact and has an exhaust port. The plasma jet device includes an operating power supply and a plasma generation chamber having a gas inlet and a gas outlet. The gas inlet is located in the sealed container, and a working electrode is provided in the plasma generation chamber. The working electrode has a first end and a second end, the first end is electrically connected to the operating power supply, and the second end is adjacent to the gas outlet. The gas supply device communicates with the gas outlet and supplies a working gas to the plasma generation chamber. The power supply device is electrically connected to the ceramic green compact and applies a voltage to the ceramic green compact to sinter it to obtain a ceramic. The sintering apparatus provided by the present application provides plasma to assist sintering, and can more effectively realize performance optimization of ceramic materials.

Description

[Technical Field]

[0001] The present application relates to the technical field of manufacturing ceramic materials, and in particular to a plasma-assisted ceramic sintering apparatus and method. [Background technology]

[0002] Ceramic materials are widely used in fields such as electronics, chemical industry, aerospace, and medicine. Sintering is an important step in the production of ceramic materials. Ceramic materials produced by high-temperature sintering have disadvantages such as large crystal grains and high energy consumption. However, small crystal grains can improve the mechanical and electrical properties of ceramics, so producing high-performance ceramics is of great practical significance. Summary of the Invention [Problem to be solved by the invention]

[0003] Therefore, it is necessary to provide a ceramic sintering apparatus and a ceramic sintering method that can solve the above problems. [Means for solving the problem]

[0004] A plasma-assisted ceramic sintering apparatus according to a first aspect of the present application includes a sealed container, a plasma jet device, a gas supply device, and a power supply device, The sealed container accommodates a ceramic green body and has an exhaust port. The plasma jet device includes an operating power supply and a plasma generation chamber having a gas inlet and a gas outlet, the gas inlet being located within the sealed container, and an operating electrode being provided within the plasma generation chamber, the operating electrode having a first end and a second end, the first end being electrically connected to the operating power supply, and the second end being adjacent to the gas outlet; the gas supply device is in communication with the gas outlet and supplies a working gas to the plasma generation chamber; The power supply is electrically connected to the ceramic green body, and applies a voltage to the ceramic green body to sinter it and obtain a ceramic.

[0005] A plasma-assisted ceramic sintering apparatus according to an embodiment of the present application generates plasma by discharging electricity in a working gas using a working electrode. The generated plasma is used to treat a ceramic green body in a sealed container to optimize ceramic performance. A gas supply device communicates with a plasma generation chamber via a gas inlet. The output gas supplies the working gas for plasma generation and enters the sealed container via a gas outlet to provide a sintering atmosphere for sintering the ceramic green body. The generated exhaust gas can be discharged through an exhaust port of the sealed container. Furthermore, a gas outlet of the plasma generation chamber can be provided within the sealed container, allowing the generated plasma to be introduced into the sealed container to treat the ceramic green body. The sintering apparatus provided by the present application can provide plasma to assist sintering, thereby more effectively optimizing the performance of ceramic materials.

[0006] According to some embodiments of the present application, the plasma generation chamber is housed within the sealed vessel.

[0007] According to some embodiments of the present application, the actuation power supply is a high frequency jet power supply, which is used to generate plasma.

[0008] According to some embodiments of the present application, the power supply is a high voltage AC power supply that can supply currents of different magnitudes as required, and is used to apply voltage to the ceramic green body for sintering.

[0009] According to some embodiments of the present application, the power supply device includes a voltage measuring device and / or a current measuring device, and the power supply device of the present application may use only a voltage measuring device, only a current measuring device, or both a voltage measuring device and a current measuring device.

[0010] An example of the voltage measuring device is a voltmeter, and an example of the current measuring device is an ammeter. The voltage and current applied to the ceramic green body can be measured and controlled using the voltage and current measuring devices.

[0011] According to some embodiments of the present application, the plasma generation chamber is an organic glass tube.

[0012] According to some embodiments of the present application, the actuation electrode is a tungsten wire.

[0013] According to some embodiments of the present application, the position of the gas outlet corresponds to the position of the ceramic green body, facilitating the process of spraying the plasma output from the gas outlet onto the surface of the ceramic green body.

[0014] According to some embodiments of the present application, the working gas is nitrogen gas or helium gas.

[0015] A ceramic sintering method provided by a second aspect of the present application comprises: Providing a ceramic green body; generating plasma using a plasma jet device, spraying the plasma generated by the plasma jet device onto the surface of the ceramic green body, applying a voltage to the ceramic green body, gradually increasing the voltage to a target voltage, and maintaining a current density flowing through the ceramic green body within a predetermined range within a predetermined time range to obtain a ceramic; or applying a voltage to the ceramic green body, increasing the voltage to a target voltage, maintaining a current density flowing through the ceramic green body within a predetermined range within a predetermined time range, and spraying plasma generated from the plasma jet device onto the surface of the ceramic green body within a predetermined time range to treat it, and sintering it to obtain a ceramic.

[0016] In a ceramic sintering method according to an embodiment of the present application, a voltage is applied to a ceramic green body and gradually increased to a target voltage. When the voltage reaches the target voltage, a surface discharge occurs in the ceramic green body, changing the electrical conductivity of the ceramic green body. The ceramic green body undergoes surface flashover, forming an internal conductive path. Rapid sintering of the ceramic is achieved through the Joule heating effect, resulting in rapid densification of the ceramic material at room temperature. Furthermore, in this application, the performance of the ceramic can be optimized by applying plasma for auxiliary sintering. The plasma application process can be carried out in two stages. First, before increasing the applied voltage to the ceramic green body to the target voltage to generate a surface discharge in the ceramic green body, the plasma is used to induce the discharge, thereby lowering the flashover onset voltage of the ceramic. Second, after the target voltage is reached and the electrical conductivity of the ceramic green body changes, plasma is used to treat the ceramic surface. This allows the ceramic green body to interact with active particles in the plasma at high temperatures during sintering, thereby modifying the ceramic surface and controlling and optimizing the performance of the ceramic.

[0017] According to some embodiments of the present application, the voltage rise rate is 0.1 to 5 kV / s, and the current density flowing in the ceramic green body is 10 to 150 mA / mm 2 If the pressure rise rate is less than 0.1 kV / s, the sintering process is too slow, which is unfavorable for flash sintering. If the pressure rise rate is more than 5 kV / s, the pressure rise is too fast, which causes direct breakdown arcs at both ends of the ceramic green compact, melting the lead wires connected to both ends of the ceramic green compact. The current density flowing through the ceramic green compact is 10 to 150 mA / mm 2 Too low a current density will not allow rapid densification of the ceramic green body, while too high a current density may cause the ceramic to shrink rapidly, resulting in localized overheating and fracture.

[0018] According to some embodiments of the present application, the target voltage is 3 to 4 kV. The voltage is gradually increased so that the surface flashover voltage is 3 to 4 kV at normal pressure, changing the conductivity of the ceramic green body to create a current path, rapidly densifying the sintering process to obtain a ceramic. The target voltage is related to the length of the ceramic green body, and when the voltage is increased to the target voltage, the current density flowing through the ceramic green body is 10 to 150 mA / mm 2 By controlling the target voltage value so as to satisfy the above condition, the ceramic green body can be rapidly densified.

[0019] According to some embodiments of the present application, a method of connecting the ceramic green body to a power supply device includes providing a first electrode and a second electrode on the ceramic green body, and connecting the first electrode and the second electrode to the power supply device.

[0020] According to some embodiments of the present application, the first electrode and the second electrode are made of a material selected from the group consisting of gold and conductive silver paste. The electrodes may be formed by spraying gold or applying conductive silver paste onto the ceramic green body, allowing them to be electrically connected to a power supply.

[0021] According to some embodiments of the present application, the ceramic green body has at least one of a cylindrical shape, a rectangular parallelepiped shape, and a dogbone shape. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram illustrating the structure of a plasma-assisted ceramic sintering apparatus according to an embodiment of the present application. [Figure 2] 1 is a trend graph of voltage and current in a ceramic sintering method according to a first embodiment of the present application, in which a ceramic green body is subjected to plasma surface treatment. [Figure 3] 1 is a trend graph of voltage and current in a ceramic sintering method according to a comparative example of the present application, in which the ceramic green body is not subjected to plasma surface treatment. [Figure 4] 1A and 1B are scanning electron microscope (SEM) images of ceramics obtained by the ceramic sintering method according to a second embodiment of the present application. (a) shows an SEM image of a ceramic produced by plasma surface treatment and a flash sintering time of 90 seconds. (b) shows an SEM image of a ceramic produced by no plasma surface treatment and a flash sintering time of 120 seconds. (c) shows an SEM image of a ceramic produced by no plasma surface treatment and a flash sintering time of 90 seconds. (d) shows an SEM image of a ceramic produced by no plasma surface treatment and a flash sintering time of 60 seconds. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present disclosure is further explained in the following detailed description in conjunction with the above-mentioned drawings.

[0024] The technical solutions in the embodiments of the present application are clearly and completely described below with reference to the drawings in the embodiments of the present application. It is clear that the described embodiments are only a part of the embodiments of the present application, and are not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts are within the scope of the present application.

[0025] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. The terminology used herein is for the purpose of describing specific examples only and is not intended to be limiting of the present application.

[0026] Referring to FIG. 1 , a plasma-assisted ceramic sintering apparatus according to one embodiment of the present application includes a sealed container 100, a plasma jet device 200, a gas supply device 300, and a power supply device 400. The sealed container 100 is for accommodating a ceramic green body 500 and has a gas exhaust port 110. The plasma jet device 200 also includes an operating power supply 210 and a plasma generation chamber 220. The plasma generation chamber 220 has a gas inlet 221 and a gas outlet 222. The gas outlet 222 is located within the sealed container 100, and plasma and gas output from the gas outlet 222 enter the sealed container 100 and treat the ceramic green body 500 therein. In this embodiment, the plasma generation chamber 220 is housed within the sealed container 100. A working electrode 230 is installed in the plasma generation chamber 220. The working electrode 230 has a first end 231 and a second end 232. The first end 231 is electrically connected to the working power supply 210, and the second end 232 is adjacent to the gas outlet 222. The gas supply device 300 is connected to the gas inlet 221 of the plasma generation chamber 220 via an air conduit and supplies a working gas to the plasma generation chamber 220. When the working power supply 210 is turned on, the working electrode 230 discharges at the second end 232 under the assistance of the working gas, generating plasma. The generated plasma is output from the gas outlet 222 and sprayed onto the surface of the ceramic green body 500. In addition, since the gas outlet 222 is located within the sealed container 100, the working gas output from the gas delivery device 300 is output to the sealed container 100 through the gas outlet 222 to provide a sintering atmosphere, and exhaust gas generated during sintering is discharged through an exhaust port 110 opened in the sealed container 100. The power supply device 400 is electrically connected to the ceramic green compact 500 and applies a voltage and a current to the ceramic green compact 500. During use, the power supply device 400 and the ceramic green compact 500 are electrically connected and turned on, and the voltage applied to the ceramic green compact 500 is gradually increased until a creeping discharge or an internal discharge occurs in the ceramic green compact 500.The electrical conductivity of the ceramic green body 500 can be changed, and by controlling the current density flowing through the ceramic green body 500, ceramics of a certain density can be formed by electric field sintering using the flash firing method. The plasma generated by the plasma jet device 200 is used to assist the above-mentioned ceramic sintering process and optimize the ceramic properties. The plasma application process can be performed in two stages. First, before generating a surface discharge on the ceramic green body 500, the operating power supply 210 is turned on to generate plasma, which induces discharge in the ceramic green body and reduces the ceramic's flash sintering initiation voltage. Second, after the electrical conductivity of the ceramic green body 500 has changed, the operating power supply 210 is turned on to generate plasma, which is then sprayed onto the ceramic surface to control the ceramic's performance.

[0027] In some embodiments, the power supply device 400 includes a voltage measuring device 410 that measures and controls the voltage applied to the ceramic green body 500, and a current measuring device 420 that measures the current flowing through the ceramic green body 500. By controlling the applied voltage and the current passing through the ceramic green body 500, the ceramic green body 500 can be turned into ceramic by flash sintering, thereby achieving rapid densification of the ceramic.

[0028] In some embodiments, the plasma generation chamber 220 is an organic glass tube and the working electrode 230 is a tungsten wire.

[0029] In some embodiments, the working gas output by the gas supply device 300 is nitrogen gas or helium gas, and is used to generate plasma and to supply a gas atmosphere to the sealed vessel 100 .

[0030] In some embodiments, a flow meter 310 is connected to the gas supply device 300 to control the flow rate of the working gas.

[0031] In some embodiments, the position of the gas outlet 222 corresponds to the position of the ceramic green body 500, making it easy for the generated plasma to be injected from the gas outlet 222 onto the surface of the ceramic green body 500. For example, the gas outlet 222 is specifically positioned above the ceramic green body 500, and plasma can be injected from above the ceramic green body 500.

[0032] The first embodiment of the present application further provides a ceramic sintering method using the plasma-assisted ceramic sintering apparatus, which includes the following steps:

[0033] Step S1: Provide a ceramic green body.

[0034] In some embodiments, the ceramic green body is manufactured using the following method. Zinc oxide powder is selected, and the zinc oxide powder is subjected to processes such as ball milling, drying, granulation, sieving, tableting, and firing to remove the binder, resulting in a ceramic green body 500 that can be used for subsequent testing. High-temperature silver paste is brushed onto both sides of the ceramic green body and dried at an appropriate temperature to form the first and second electrodes. The ceramic green body is roughly dogbone-shaped, with the overall dogbone length being 21 mm, the overall width being 3.3 mm, and the thickness of the middle portion being 1.7 mm. Step S2: The ceramic green body 500 is placed in the sealed container 100, lead wires are wound around the first and second electrodes at both ends of the ceramic green body 500, the ceramic green body 500 is electrically connected to both ends of the power supply 400 via the lead wires, the lead wires are fixed to a fixed holder so that the ceramic green body 500 floats, the power supply 400 is a high-voltage AC power source, and the power supply 400 is kept in the OFF state. Step S3: Plasma is generated using the plasma jet device. Specifically, the valve of the gas supply device 300 is opened, and the flow meter 310 is adjusted until the volumetric flow rate of the output working gas reaches 10 L / min. At this time, the working power supply 210 is turned on. The working electrode 230 discharges with the aid of the working gas to generate a stable plasma jet, and the generated plasma current is sprayed onto the surface of the ceramic green body 500 for treatment. In this embodiment, the gas supply device 300 is a nitrogen gas cylinder, and the working power supply 210 is a high-frequency jet power supply.

[0035] Step S4: After 30 minutes of plasma treatment, turn off the plasma jet and turn on the power supply 400. The voltage is uniformly increased to the target voltage at a rate of 0.2 kV / s, generating a surface flashover on the ceramic green compact 500 surface. This voltage is the flash sintering start voltage. The voltage across the ceramic then drops sharply, and the current momentarily increases. The current density is then maintained within a predetermined range, creating a stable conductive path within the green compact, marking the stable sintering stage. After sintering for a predetermined time (e.g., 1 minute), turn off the power supply and record the voltage and current experimental data. A voltage and current trend graph is shown in Figure 2.

[0036] Step S5: Turn off the power supply 210, replace the ceramic green body with a new one, and repeat steps S2 and S4 to obtain another set of voltage-current comparative experimental data. A voltage-current trend graph of the comparative experimental data is shown in Figure 3. That is, the ceramic green body 500 is flash-sintered without surface treatment with plasma to obtain another set of comparative experimental data. Comparing Figures 2 and 3, it can be seen that applying plasma before the ceramic green body generates surface discharge can effectively reduce the ceramic flash-sintering initiation voltage.

[0037] A second embodiment of the present application further provides a ceramic sintering method using the plasma-assisted ceramic sintering apparatus.

[0038] The ceramic sintering method includes the following steps:

[0039] Step S1: A ceramic green body 500 is prepared.

[0040] In some embodiments, the following method is used to manufacture the ceramic green body. Zinc oxide powder is selected and tested, and then the powder is ball milled, dried, granulated, sieved, tableted, and fired to remove the binder, resulting in a ceramic green body 500 that can be used for subsequent testing. A high-temperature silver paste is brushed onto both sides of the ceramic green body 500 and dried at an appropriate temperature to form the first and second electrodes. The ceramic green body is roughly dogbone-shaped, with the entire dogbone measuring 21 mm in length, 3.3 mm in width, and 1.7 mm thick at the middle.

[0041] Step S2: The ceramic green body 500 is placed in the sealed container 100, lead wires are wound around the first and second electrodes at both ends of the ceramic green body 500, the ceramic green body 500 is electrically connected to both ends of the power supply 400 via the lead wires, the lead wires are fixed to a fixed holder so that the ceramic green body 500 floats, the power supply 400 is a high-voltage AC power source, and the power supply 400 is kept in the OFF state.

[0042] Step S3: Turn on the power supply 400 and increase the voltage uniformly to the target voltage at a rate of 0.2 kV / s to generate a surface flashover on the surface of the ceramic green compact 500. This voltage value is the flash sintering start voltage. After that, the voltage across the ceramic suddenly drops and the current momentarily increases, forming a stable conductive path inside the green compact, entering the stable sintering stage.

[0043] Step S4: Generate plasma using the plasma jet device. Specifically, open the valve of the gas supply device 300, adjust the flow meter 310 until the volumetric flow rate of the output working gas reaches 10 L / min, and then turn on the working power supply 210. The working electrode 230 discharges with the aid of the working gas to generate a stable plasma jet, and the generated plasma current is sprayed onto the surface of the sample being sintered. In this embodiment, the gas supply device 300 is a nitrogen gas cylinder, and the working power supply 210 is a high-frequency jet power supply.

[0044] Step S5: After firing for 1 minute, the power supply 400 is turned off. In the second example, the ceramic green body was flash sintered for 90 seconds. The scanning electron microscope image of the resulting ceramic sample is shown in Figure 4a. A ceramic sample without plasma surface treatment was obtained using steps S1, S2, S3, and S5, similar to those in the second embodiment. Scanning electron microscope tests were performed on the ceramic sample. Figure 4b shows the scanning electron microscope image of a ceramic sample with a flash sintering time of 120 seconds, Figure 4c shows the scanning electron microscope image of a ceramic sample with a flash sintering time of 90 seconds, and Figure 4d shows the scanning electron microscope image of a ceramic sample with a flash sintering time of 60 seconds. Figure 4 shows that the crystallite size of the ceramic sample became smaller after plasma treatment, and the crystallite size distribution became more concentrated.

[0045] As can be seen from the test results of the second example, by applying plasma after the ceramic green body has entered the stable sintering stage, the high-temperature ceramic green body interacts with the active particles in the plasma, resulting in a more uniform distribution of crystal grain size, smaller crystal grain size, and optimized ceramic performance.

[0046] In some embodiments, the voltage increase rate during the ceramic sintering process is 0.1 to 5 kV / s, and the voltage increase rate is adjusted so that the current density of the ceramic green body 500 is 10 to 150 mA / mm 2By controlling the temperature, ceramics with different densities can be formed by flash sintering.

[0047] The above-described embodiments are merely preferred embodiments of the present application and are not intended to limit the present application in any way. Although preferred embodiments are disclosed as above, they are not intended to limit the present application. Equivalent embodiments created by some changes and modifications using the technical solutions disclosed above, as long as they do not deviate from the technical solutions of the present application, any simple changes, equivalent changes, and modifications of the above-described embodiments essentially belong to the technical solutions of the present application, as long as they do not deviate from the technical solutions of the present application. [Explanation of symbols]

[0048] 100 airtight containers 110 Exhaust port 200 Plasma jet device 210 Operating power supply 220 Plasma Generation Chamber 221 Gas inlet 222 Gas outlet 230 Working Electrode 231 1st end 232 2nd end 300 Gas supply equipment 310 Flowmeter 400 power supply 410 Voltage measuring device 420 Current measuring device 500 Ceramic green compact

Claims

1. A plasma-assisted ceramic sintering apparatus comprising a sealed container, a plasma jet device, a gas supply device, and a power supply device; The sealed container accommodates a ceramic green body and has an exhaust port. The plasma jet device includes an operating power supply and a plasma generation chamber having a gas inlet and a gas outlet. the gas inlet is located within the sealed vessel; A working electrode is provided in the plasma generation chamber, the actuation electrode has a first end and a second end; the first end is electrically connected to the operating power source; the second end is adjacent to the gas outlet; the gas supply device is in communication with the gas outlet and supplies a working gas to the plasma generation chamber; The plasma-assisted ceramic sintering apparatus is characterized in that the power supply device is electrically connected to the ceramic green compact, and applies a voltage to the ceramic green compact to sinter it and obtain ceramic.

2. 2. The plasma-assisted ceramic sintering apparatus according to claim 1, wherein the power supply device includes a voltage measuring device and / or a current measuring device.

3. 2. The plasma-assisted ceramic sintering apparatus according to claim 1, wherein the plasma generation chamber is an organic glass tube.

4. 2. The plasma-assisted ceramic sintering apparatus according to claim 1, wherein the working electrode is a tungsten wire.

5. 5. The plasma-assisted ceramic sintering apparatus according to claim 1, wherein the position of the gas outlet corresponds to the position of the ceramic green body.

6. 5. The plasma-assisted ceramic sintering apparatus according to claim 1, wherein the working gas is nitrogen gas or helium gas.

7. A ceramic sintering method comprising: Providing a ceramic green body; a step of spraying plasma generated by a plasma jet device onto the surface of the ceramic green body to treat it, applying a voltage to the ceramic green body, gradually increasing the voltage to a target voltage, and maintaining a current density flowing through the ceramic green body within a predetermined range within a predetermined time range to obtain a ceramic by sintering; or applying a voltage to the ceramic green body, gradually increasing the voltage to a target voltage, maintaining a current density flowing through the ceramic green body within a predetermined range within a predetermined time range, spraying plasma generated from the plasma jet device onto a surface of the ceramic green body within a predetermined time range to treat it, and sintering the surface to obtain a ceramic.

8. the voltage rise rate is 0.1 to 5 kV / s; The current density flowing through the ceramic green body is 10 to 150 mA / mm 2 8. The ceramic sintering method according to claim 7, wherein the temperature is maintained at 1000.degree.

9. 8. The ceramic sintering method according to claim 7, wherein the target voltage is 3 to 4 kV.

10. The ceramic sintering method according to claim 7, characterized in that the method of connecting the ceramic green body to a power supply device comprises providing a first electrode and a second electrode on the ceramic green body, and connecting the first electrode and the second electrode to the power supply device.

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