Plasma assisted ceramic sintering device and 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 the fields of electronics, chemical industry, space and medicine. Sintering is an important step in the production of ceramic materials. Ceramic materials produced by high-temperature sintering have the disadvantages of large crystal grains and high energy. Small crystal grains can improve the mechanical and electrical performance of ceramics, so it is of great practical significance to produce high-performance ceramics. 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 contains 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 device is electrically connected to the ceramic green compact, and applies a voltage to the ceramic green compact to sinter it and obtain a ceramic.

[0005] The plasma-assisted ceramic sintering apparatus according to the embodiment of the present application generates plasma by discharging 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. The gas supply device communicates with the plasma generation chamber through a gas inlet, and the output gas can supply a working gas for plasma generation, while entering the sealed container through a gas outlet to provide a sintering atmosphere for sintering the ceramic green body. The generated exhaust gas can be discharged from an exhaust port of the sealed container. In addition, the gas outlet of the plasma generation chamber can be provided in the sealed container, and the generated plasma can 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, and can more suitably realize performance optimization 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. The actuation power supply is used to generate plasma.

[0008] According to some embodiments of the present application, the power supply is a high voltage AC power supply, which can provide currents of different magnitudes as required. The power supply 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. The power supply device of the present application may use only a voltage measuring device, may use only a current measuring device, or may use a voltage measuring device and a current measuring device simultaneously.

[0010] An example of the voltage measuring device is a voltmeter, and an example of the current measuring device is an ammeter. The voltage measuring device and the current measuring device can be used to measure and control the voltage and current applied to the ceramic green body.

[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 is provided according to a second aspect of the present application, comprising the steps of: Providing a ceramic green body; generating plasma using a plasma jet device, spraying and treating the surface of the ceramic green body with the plasma generated by the plasma jet device, 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 preset time range within a preset range to obtain a ceramic by sintering; or applying a voltage to the ceramic green body, increasing the voltage to a target voltage, and then maintaining a current density flowing through the ceramic green body within a predetermined range within a predetermined time range; spraying and treating the plasma generated from the plasma jet device onto a surface of the ceramic green body within a predetermined time range, and sintering the surface to obtain a ceramic.

[0016] In the ceramic sintering method according to the embodiment of the present application, a voltage is applied to the ceramic green compact, and the voltage is gradually increased to a target voltage. When the voltage is increased to the target voltage, a creeping discharge occurs on the ceramic green compact, the electrical conductivity of the ceramic green compact changes, and the ceramic green compact can form an internal conductive path through creeping flashover. The Joule heating effect realizes rapid sintering of the ceramic, and rapid densification of the ceramic material at room temperature is achieved. In addition, in the present application, the performance of the ceramic can be optimized by applying plasma to perform auxiliary sintering, and the plasma application process can be performed in two stages. One is to use plasma to induce discharge before increasing the applied voltage to the ceramic green compact to the target voltage to generate creeping discharge on the ceramic green compact, and the flash start voltage of the ceramic is reduced with the assistance of plasma. The other is to use plasma to treat the surface of the ceramic after the target voltage is reached and the electrical conductivity of the ceramic green compact changes, so that the ceramic green compact interacts with the active particles in the plasma at a high temperature during sintering to modify the ceramic surface, thereby controlling the performance of the ceramic and achieving the purpose of 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 through 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 to the occurrence of flash sintering. If the pressure rise rate is more than 5 kV / s, the pressure rise is too fast, which causes direct destruction arcs at both ends of the ceramic green compact, and the lead wires connected to both ends of the ceramic green compact are melted. The current density flowing through the ceramic green compact is 10 to 150 mA / mm 2 Too low a current density will not allow the rapid densification of the ceramic green body to be maintained, whereas too high a current density will cause the ceramic to shrink rapidly and may be locally overheated and fractured.

[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 creepage flashover voltage is 3 to 4 kV at normal pressure, changing the electrical conductivity of the ceramic green body to generate a current path, and the sintering is rapidly densified to obtain ceramics. 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 material of the first electrode and the second electrode is one selected from gold and conductive silver paste. The electrodes may be formed by spraying gold or applying conductive silver paste onto the ceramic green compact, so that they can be electrically connected to a power supply device.

[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 description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram showing the structure of a plasma-assisted ceramic sintering apparatus according to an embodiment of the present application. [Diagram 2] 4 is a trend graph of voltage and current in the ceramic sintering method according to the first embodiment of the present application, in which the ceramic green body is subjected to plasma surface treatment. [Diagram 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] 1 shows scanning electron microscope (SEM) images of ceramics obtained by the ceramic sintering method according to the second embodiment of the present application, where a shows an SEM image of a ceramic produced with plasma surface treatment and a flash sintering time of 90 s, b shows an SEM image of a ceramic produced without plasma surface treatment and a flash sintering time of 120 s, c shows an SEM image of a ceramic produced without plasma surface treatment and a flash sintering time of 90 s, and d shows an SEM image of a ceramic produced without plasma surface treatment and a flash sintering time of 60 s. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 to be noted that the described embodiments are only a part of the embodiments of the present application, and are not all 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 those skilled in the art to which the present disclosure pertains. The terms used in the present specification are for the purpose of describing specific examples only and are not intended to be limiting of the present application.

[0026] Referring to FIG. 1, a plasma-assisted ceramic sintering apparatus according to an 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 housing a ceramic green body 500, and a gas exhaust port 110 is opened in the sealed container 100. The plasma jet device 200 includes an operating power supply 210 and a plasma generation chamber 220. A gas inlet 221 and a gas outlet 222 are opened in the plasma generation chamber 220. The gas outlet 222 is located in the sealed container 100, and the plasma or gas output from the gas outlet 222 enters the sealed container 100 and processes the ceramic green body 500 therein. In this embodiment, the plasma generation chamber 220 is housed in the sealed container 100. The plasma generating chamber 220 is provided with a working electrode 230, which has a first end 231 and a second end 232, the first end 231 being electrically connected to the working power supply 210, and the second end 232 being adjacent to the gas outlet 222. The gas supplying device 300 is connected to the gas inlet 221 of the plasma generating chamber 220 through an air guide tube, and supplies a working gas to the plasma generating 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 to generate plasma, and the generated plasma is output from the gas outlet 222 and sprayed onto the surface of the ceramic green compact 500. In addition, since the gas outlet 222 is located in 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 by sintering is exhausted through the 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 to each other and the power is 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 compact 500 is changed, and by controlling the current density flowing through the ceramic green compact 500, ceramics of a certain density can be formed by electric field sintering by 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. One is to turn on the operating power source 210 to generate plasma before generating a creeping discharge on the ceramic green compact 500, induce discharge of the ceramic green compact, and reduce the flash sintering start voltage of the ceramic. The other is to turn on the operating power source 210 to generate plasma after the electrical conductivity of the ceramic green compact 500 has changed, and the generated plasma is sprayed onto the surface of the ceramic to control the performance of the ceramic.

[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 enabling 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 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 compact 500, making it easy for the generated plasma to be sprayed from the gas outlet 222 onto the surface of the ceramic green compact 500. For example, the position of the gas outlet 222 is specifically located above the ceramic green compact 500, and plasma can be sprayed from above the ceramic green compact 500.

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

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

[0034] In some embodiments, the following method is adopted to manufacture the ceramic green body. Zinc oxide powder is selected, and the zinc oxide powder is ball milled, dried, granulated, sieved, tableted, and fired to remove the binder, to obtain 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 dog-bone shaped, with the entire dog-bone length being 21 mm, the entire width being 3.3 mm, and the thickness of the middle part being 1.7 mm. Step S2: The ceramic green compact 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 compact 500, both ends of the ceramic green compact 500 and the power supply 400 are electrically connected via the lead wires, the lead wires are fixed to a fixed holder so that the ceramic green compact 500 is floating, the power supply 400 is used as a high-voltage AC power source, and the power supply 400 is kept in the OFF state. Step S3: Generate plasma using the plasma jet device. Specifically, open the valve of the gas supply device 300, adjust the flowmeter 310 until the output volumetric flow rate of the working gas is 10 L / min, and turn on the working power supply 210. The working electrode 230 discharges with the assistance 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 (min) of plasma treatment, turn off the plasma jet, turn on the power supply 400, and uniformly increase the voltage to the target voltage at a rate of 0.2 kV / s to generate a creeping flashover on the surface of the ceramic green compact 500, and this voltage value is the flash sintering start voltage. After that, the voltage across the ceramic drops sharply and the current increases instantaneously, and then the current density is maintained within a predetermined range to generate a stable conductive path inside the green, entering the stable sintering stage. After sintering for a predetermined time (e.g., 1 minute), turn off the power and record the voltage / current experimental data. A voltage / current trend graph is shown in Figure 2.

[0036] Step S5: Turn off the operating 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 FIG. 3. That is, the ceramic green body 500 is flash-sintered without surface-treating it with plasma to obtain another set of comparative experimental data. Comparing FIG. 2 with FIG. 3, it can be seen that the flash-sintering start voltage of ceramics can be effectively reduced by applying plasma before the ceramic green body generates a creeping discharge.

[0037] A second embodiment of the present application further provides a ceramic sintering method using the above 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 adopted to manufacture the ceramic green compact. Zinc oxide powder is selected and tested, and the ceramic green compact 500 is obtained through processes such as powder ball milling, drying, granulation, sieving, tableting, and firing to remove the binder, which can be used for subsequent testing. High-temperature silver paste is brushed on both sides of the ceramic green compact 500 and dried at an appropriate temperature to form the first and second electrodes. The ceramic green compact is approximately dog-bone shaped, with the entire dog-bone length being 21 mm, the entire width being 3.3 mm, and the thickness of the middle part being 1.7 mm.

[0041] Step S2: The ceramic green compact 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 compact 500, both ends of the ceramic green compact 500 and the power supply 400 are electrically connected via the lead wires, the lead wires are fixed to a fixed holder so that the ceramic green compact 500 is floating, the power supply 400 is used as 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 to the target voltage at a rate of 0.2 kV / s to generate a creeping flashover on the surface of the ceramic green compact 500, and set this voltage value as the flash sintering start voltage. After that, the voltage across the ceramic drops suddenly and the current increases instantaneously, and a stable conductive path is generated inside the green, 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 flowmeter 310 until the output volumetric flow rate of the working gas is 10 L / min, and then turn on the working power supply 210. The working electrode 230 discharges with the assistance 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: Turn off the power supply 400 after firing for 1 minute. In the second embodiment, the ceramic green body was flash sintered for 90 s, and the scanning electron microscope image of the prepared ceramic sample is shown in FIG. 4a. A ceramic sample that has not been subjected to plasma surface treatment is obtained using steps S1, S2, S3, and S5 similar to those of the second embodiment. When the ceramic sample was subjected to an electron microscope scanning test, FIG. 4b shows an electron microscope scanning image of a ceramic sample with a flash sintering time of 120 s, FIG. 4c shows an electron microscope scanning image of a ceramic sample with a flash sintering time of 90 s, and FIG. 4d shows an electron microscope scanning image of a ceramic sample with a flash sintering time of 60 s. According to FIG. 4, it can be seen that the crystallite size of the ceramic sample becomes smaller after plasma treatment, and the crystallite size distribution is more concentrated.

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

[0046] In some embodiments, the voltage rise rate during the ceramic sintering process is 0.1 to 5 kV / s, and the voltage rise 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 having different densities can be produced by flash sintering.

[0047] The above embodiment is merely a preferred embodiment of the present application and does not limit the present application in any manner. The preferred embodiment is disclosed as above, but is not intended to limit the present application. As long as it does not deviate from the technical solution of the present application, equivalent embodiments created by some changes and modifications using the technical solution disclosed above, any simple changes, equivalent changes and modifications of the above-mentioned embodiment essentially belong to the technical solution of the present application, as long as it does not deviate from the technical solution of the present application. [Explanation of symbols]

[0048] 100 Airtight Container 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 Flow meter 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 contains a ceramic green body and has an exhaust port. The plasma jet device includes an operating power source 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 actuating electrode having a first end and a second end; the first end is electrically connected to the operating power source; the second end is proximate 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 device is electrically connected to the ceramic green bodies, and applies a voltage to the ceramic green bodies to sinter them to obtain ceramics.

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. 1. A ceramic sintering method comprising the steps of: Providing a ceramic green body; 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 preset time range within a preset range to obtain a ceramic by sintering; or applying a voltage to the ceramic green body, gradually increasing the voltage to a target voltage, and then 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 compact is 10 to 150 mA / mm 2 8. The method of claim 7, wherein the temperature is maintained at 100.degree.

9. 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 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.

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