Ceramic sintering apparatus and ceramic sintering method

Abstract

The application provides a ceramic sintering device and a ceramic sintering method for sintering a ceramic green body, the ceramic sintering device comprising a power supply device, a first insulating plate and a second insulating plate, the first insulating plate being used for supporting the ceramic green body; the power supply device being used for electrically connecting with both ends of the ceramic green body, the power supply device being used for providing a voltage for the ceramic green body to generate an electric arc above the ceramic green body to sinter the ceramic green body; the second insulating plate being spaced apart on the first insulating plate, the second insulating plate being used for being spaced apart on the ceramic green body at a preset interval, and the second insulating plate being used for binding the electric arc above the ceramic green body. In the application, the power supply device is electrically connected with both ends of the ceramic green body, and a voltage is provided for the ceramic green body to generate an electric arc above the ceramic green body, so that the ceramic green body is rapidly sintered in a short time under the action of the electric arc and forms a densified ceramic, thereby realizing the sintering of the ceramic green body at room temperature and improving the traditional long-time sintering mode.

Description

Technical Field

[0001] This application relates to the field of ceramic material preparation technology, and in particular to a ceramic sintering apparatus and a ceramic sintering method. Background Technology

[0002] Currently, ceramic materials, as the most promising inorganic materials after metals and non-metals, have broad application and development prospects and are essential key materials in modern society and construction. In the electrical field, dielectric ceramics have gained widespread application due to their excellent mechanical strength, insulation properties, and high-temperature resistance. The manufacturing of ceramic materials is still mainly based on traditional sintering. Traditional sintering processes involve very high sintering temperatures and long sintering times; for example, the sintering temperature of alumina ceramics is as high as 1650℃~1990℃, and the sintering time requires several hours. Therefore, traditional sintering processes cannot limit the unlimited growth of grains, and the energy loss caused by traditional sintering methods is enormous, resulting in low energy utilization efficiency. Therefore, finding a method for rapid densification of ceramic blanks is crucial.

[0003] Flash sintering is a novel ceramic preparation method with advantages such as low energy consumption and fast sintering speed. However, currently, the range of ceramic materials that can be applied by flash sintering is limited. For example, alumina ceramics and YSZ ceramics cannot yet be flash sintered at room temperature, which restricts the development and application of ceramics. Summary of the Invention

[0004] In view of this, this application provides a ceramic sintering apparatus and a ceramic sintering method.

[0005] To achieve the above objectives, this application provides a ceramic sintering apparatus for sintering ceramic green bodies. The ceramic sintering apparatus includes a power supply device, a first insulating plate, and a second insulating plate. The first insulating plate supports the ceramic green body. The power supply device is electrically connected to both ends of the ceramic green body and provides voltage to the ceramic green body to generate an electric arc above it for sintering. The second insulating plate is spaced apart from the first insulating plate and is positioned at a predetermined interval on the ceramic green body to confine the electric arc above it.

[0006] In some possible implementations, the preset spacing is 2 to 15 mm.

[0007] In some possible implementations, the ceramic sintering apparatus further includes a current-limiting resistor and a voltage and current measuring device, wherein the current-limiting resistor is used to limit the current of the power supply device, and the voltage and current measuring device is used to detect the voltage in the power supply device in real time.

[0008] In some possible implementations, the first insulating plate and the second insulating plate respectively comprise alumina ceramic, aluminum nitride ceramic, or beryllium nitride ceramic.

[0009] In some possible implementations, the power supply device includes a first electrode and a second electrode, which are respectively connected to the two ends of the ceramic green body, and the first electrode and the second electrode are respectively made of tungsten wire or molybdenum wire.

[0010] This application also provides a ceramic sintering method, comprising: placing a ceramic green body on a first insulating plate, and then placing a second insulating plate at intervals above the first insulating plate to obtain an intermediate body; placing the intermediate body in a preset gas atmosphere; at room temperature, connecting a power supply device to both ends of the ceramic green body, applying a voltage to the ceramic green body through the power supply device, and generating an electric arc above the ceramic green body to sinter the ceramic green body.

[0011] In some possible implementations, the current density flowing through the ceramic green body is 75–150 mA / mm². 2 The sintering time of the ceramic green body is less than or equal to 2.5 min.

[0012] In some possible implementations, the thickness of both the first insulating plate and the second insulating plate is greater than or equal to 1 cm.

[0013] In some possible implementations, the boost rate of the power supply is 0.1 to 5 kV / s.

[0014] In some possible implementations, the preset gas atmosphere includes air, oxygen, nitrogen, or argon.

[0015] In this application, a ceramic sintering apparatus is electrically connected to both ends of a ceramic green body via a power supply device, providing voltage to the green body and generating an electric arc above it. This allows the green body to rapidly sinter under the influence of the electric arc, forming a dense ceramic structure. This achieves sintering of the green body at room temperature, improving upon traditional long-duration sintering methods and reducing energy consumption. Furthermore, the current flowing through the green body not only ensures uniform sintering but also reduces damage to the surface of the green body caused by the electric arc. Additionally, the power supply device provided in this application achieves sintering simply by applying voltage to the green body and generating an electric arc, eliminating the need for additional heating devices. This process can be completed at room temperature and is structurally simple. Moreover, in the ceramic sintering apparatus provided in this application, a second insulating plate is spaced above the first insulating plate to confine the electric arc to the surface of the green body, improving the efficiency of the electric arc's action on the green body and preventing the arc from spreading outwards. The ceramic sintering apparatus provided in this application has a simple structure, is easy to operate, and can be applied to ceramic green bodies of different materials. It has strong applicability and helps to promote the development of flash sintering of ceramics. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a ceramic sintering apparatus provided in an embodiment of this application.

[0017] Figure 2 In the image, (A) is a scanning electron microscope image of the alumina ceramic prepared in Example 1, (B) is an X-ray energy dispersive spectroscopy (EDS) image of the alumina ceramic in (A), (C) is an Al element distribution map of the alumina ceramic in (A), and (D) is a Zn element distribution map of the alumina ceramic in (A).

[0018] Figure 3 The image shows a scanning electron microscope image of the YSZ ceramic prepared in Example 2.

[0019] Figure 4 This is a scanning electron microscope image of the alumina ceramic prepared in an argon atmosphere in Example 3.

[0020] Figure 5 This is a scanning electron microscope image of the alumina ceramic green body in Comparative Example 1.

[0021] Explanation of main component symbols

[0022] Ceramic sintering device 100

[0023] Power supply unit 10

[0024] First electrode 11

[0025] Second electrode 12

[0026] Wire 13

[0027] First insulating board 20

[0028] Second insulating board 30

[0029] 200 ceramic green bodies Detailed Implementation

[0030] The embodiments of the present invention are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0031] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] See Figure 1 This embodiment provides a ceramic sintering apparatus 100, which includes a power supply device 10, a first insulating plate 20, and a second insulating plate 30. The first insulating plate 20 can be disposed on a platform (not shown). A ceramic green body 200 is placed on the first insulating plate 20. The second insulating plate 30 is disposed directly above the first insulating plate 20 via a bracket (not shown). The power supply device 10 is electrically connected to both ends of the ceramic green body 200 and provides voltage to the ceramic green body 200 to generate an electric arc above the ceramic green body 200 and sinter the ceramic green body 200, thereby achieving sintering of the ceramic green body 200 at room temperature. In this application, the second insulating plate 30 confines the electric arc above the ceramic green body 200, thereby allowing the electric arc to sinter the entire ceramic green body 200 through its upper surface.

[0033] The second insulating plate 30 is disposed on the ceramic green body 200 at a preset interval, the preset interval between the second insulating plate 30 and the ceramic green body 200 being 2–15 mm. Under this condition, not only can the ceramic green body 200 be fully subjected to electric arc treatment, but the electric arc can also be constrained to prevent it from spreading outward. For example, the interval can be 2 mm, 3 mm, 5 mm, 7 mm, 10 mm, or 15 mm.

[0034] In some embodiments, the power supply device 10 includes a power source (not shown), a first electrode 11, a second electrode 12, and a wire 13. The first electrode 11 and the second electrode 12 are respectively connected to the power source via the wire 13. Both the first electrode 11 and the second electrode 12 are connected to the ceramic green body 200. Furthermore, in the above process, it is not necessary to coat both ends of the ceramic green body 200 with conductive silver paste. The first electrode 11 and the second electrode 12 directly achieve electrical connection with the ceramic green body 200 by clamping it, simplifying the process steps.

[0035] In some embodiments, both the first insulating plate 20 and the second insulating plate 30 are made of high-temperature resistant materials to prevent the first insulating plate 20 and the second insulating plate 30 from cracking caused by the electric arc generated by the subsequent ceramic green body 200. In some embodiments, the first insulating plate 20 and the second insulating plate 30 are respectively made of alumina ceramic, aluminum nitride ceramic, or beryllium nitride ceramic. The first insulating plate 20 and the second insulating plate 30 may be made of the same material or different materials. In other embodiments, other high-temperature resistant insulating materials may also be used.

[0036] In some embodiments, the thickness of both the first insulating plate 20 and the second insulating plate 30 is greater than or equal to 1 cm, thereby preventing the first insulating plate 20 and the second insulating plate 30 from being broken by an electric arc, causing them to explode. In some embodiments, the thickness of the first insulating plate 20 and the second insulating plate 30 may be the same or different. For example, the thickness of both the first insulating plate 20 and the second insulating plate 30 may be 1 cm, 2 cm, 3 cm, 4 cm, or 5 cm.

[0037] In some embodiments, the first electrode 11 and the second electrode 12 are respectively made of tungsten wire or molybdenum wire. The melting point of both tungsten wire and molybdenum wire is higher than 2000°C, and the diameter of the first electrode 11 and the second electrode 12 is greater than 0.4 mm, so that the first electrode 11 and the second electrode 12 will not melt under high voltage, thus ensuring the normal operation of the power supply device 10.

[0038] In some embodiments, the power supply device 10 is further provided with a current-limiting resistor (not shown) and a voltage and current measuring device (not shown). The current-limiting resistor can be a current-limiting resistor, and the voltage and current measuring device can include a voltage and current data acquisition card. The current-limiting resistor is used to limit the current of the power supply device 10 and protect the safety of the power supply device 10. The voltage and current measuring device is used to measure the voltage in the power supply device 10 in real time, and can also adjust the voltage of the entire power supply device 10 as needed to meet application requirements.

[0039] This application also provides a ceramic sintering method, including the following steps:

[0040] S1. Provide a ceramic green body.

[0041] Ceramic green bodies can be one of alumina ceramic green bodies, zinc oxide ceramic green bodies, or yttrium-stabilized zirconia green bodies.

[0042] The specific preparation steps of ceramic green body include: granulating ceramic powder by ball milling, grinding the granulated ceramic powder through an 80-mesh sieve to obtain the final powder, pressing it into tablets using a uniaxial press, and debinding it in a muffle furnace at 400℃ for 30 minutes to obtain the ceramic green body.

[0043] S2. Place the ceramic green body on the first insulating plate, and then place the second insulating plate at intervals directly above the first insulating plate to obtain an intermediate body.

[0044] In this step, the first insulating plate supports the ceramic green body, and the second insulating plate is spaced above the first insulating plate. This allows the electric arc generated on the surface of the ceramic green body to be restricted and restrained during subsequent processing, preventing the arc from spreading outward and enabling the arc to concentrate on the surface of the ceramic green body. This also improves the efficiency of the arc acting on the ceramic green body.

[0045] S3. Place the intermediate in a preset gas atmosphere.

[0046] The first insulating plate, the second insulating plate, and the ceramic green body are simultaneously placed in a preset gas atmosphere. In practical applications, different gas atmospheres can be selected according to requirements to control the electric arc, change the heat energy acting on the ceramic green body, and thus change the sintering effect on the ceramic green body. In some embodiments, the preset gas atmosphere includes air, oxygen, nitrogen, or argon.

[0047] S4. At room temperature, the two ends of the ceramic green body are connected to a power supply device, and a current loop is formed between the power supply device and the ceramic green body. A voltage is applied to the ceramic green body through the power supply device, and an electric arc is generated above the ceramic green body to sinter the ceramic green body.

[0048] In the above steps, power supply devices are installed at both ends of the ceramic green body. These devices provide voltage to the green body, forming a current loop with it. Applying voltage generates a high-energy electric arc on the surface of the green body. At room temperature, the arc converts electrical energy into heat, rapidly heating the surface and penetrating the entire green body, thus achieving flash firing. This method is applicable to ceramic green bodies of different materials and has universality. Furthermore, in the ceramic sintering method provided in this application, the current flows through the entire green body, ensuring uniform sintering and reducing damage to the surface of the green body caused by the electric arc.

[0049] In some embodiments, the power supply device boosts the voltage at a rate of 0.1–5 kV / s until an electric arc is generated, and the current density flowing through the ceramic green body is 75–150 mA / mm². 2 The sintering time of the ceramic green body is less than or equal to 2.5 min. This time range ensures that the surface of the ceramic green body can undergo high-energy arc treatment, while avoiding excessive time that could damage the power supply. Too low a current density will not guarantee rapid densification of the ceramic green body; too high a current density may cause the ceramic green body to shrink rapidly, leading to localized overheating and breakage. In some embodiments, the voltage ramp rate is 0.1 kV / s, 0.2 kV / s, 0.5 kV / s, 1 kV / s, 2 kV / s, 3 kV / s, or 4 kV / s; the current density is 75 mA / mm². 2 90mA / mm 2 100mA / mm 2 120mA / mm 2 Or 150mA / mm 2 The sintering time for the ceramic green body is 0.5 min, 1 min, 1.5 min or 2 min.

[0050] In some embodiments, the rated capacity of the power supply is greater than or equal to 100kVA, and the rated output current is greater than or equal to 2A. The rated output voltage of the power supply is 50kV, and the permissible operating time is greater than or equal to 30 minutes at the rated voltage and current.

[0051] The ceramics mentioned include one of alumina ceramics, zinc oxide ceramics, and yttrium-stabilized zirconium oxide. Alumina ceramics, as the most widely used and produced oxide ceramics, are currently extensively used in power grid equipment such as vacuum electronic devices, ceramic components, circuit boards, thyristors, and solid-state circuit housings. In the power industry, alumina ceramics have a broad application base due to their significant advantages such as high mechanical strength, high insulation resistance, and low dielectric loss. The ceramic sintering method provided in this application can promote the development of flash sintering of ceramics.

[0052] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the invention. Unless otherwise stated, reagents, software, and instruments involved in the following embodiments that are not specifically described are all conventional commercially available products or open-source materials.

[0053] Example 1

[0054] The steps for preparing alumina ceramics are as follows:

[0055] (1) Alumina ceramic powder containing 5% zinc oxide is granulated, ball-milled, pressed into sheets and debinded to obtain alumina ceramic green body. The alumina ceramic green body has a length of 14.5 mm, a width of 3.3 mm and a height of 1.7 mm.

[0056] (2) Place the ceramic green body on the first insulating plate and make it in close contact with the electrodes on both sides, keeping the power supply off. Place the second insulating plate on top of the first insulating plate, with a 10mm gap between the ceramic green body and the second insulating plate.

[0057] (3) In an atmospheric pressure environment, turn on the high-voltage AC power supply and uniformly increase the voltage at a rate of 0.2 kV / s until a high-energy electric arc is generated and penetrates the surface of the ceramic green body. At this time, adjust the voltage to stabilize the current at 113.5 mA / mm. 2 After maintaining the temperature for 30 seconds, the power was turned off to obtain alumina ceramic with a density of 97.6%.

[0058] Example 2

[0059] The steps for preparing yttrium-stabilized zirconium oxide are as follows:

[0060] (1) 3YSZ ceramic powder is granulated, ball-milled, pressed into sheets and debinded to obtain 3YSZ ceramic green body. The length of the 3YSZ ceramic green body is 14.5 mm, the width is 3.3 mm and the height is 1.7 mm.

[0061] (2) Place the ceramic green body on the first insulating plate and make it in close contact with the electrodes on both sides, keeping the power supply off. Place the second insulating plate on top of the first insulating plate, with a 10mm gap between the ceramic green body and the second insulating plate.

[0062] (3) In an atmospheric pressure environment, turn on the high-voltage AC power supply and uniformly increase the voltage at a rate of 0.2 kV / s until a high-energy electric arc is generated and penetrates the surface of the ceramic green body. At this time, adjust the voltage to stabilize the current at 90 mA / mm. 2 After maintaining the temperature for 30 seconds, the power was turned off, resulting in YSZ ceramic with a density of 99.4%.

[0063] Example 3

[0064] The difference between Example 3 and Example 1 is that an electric arc is generated in an argon atmosphere. The remaining steps are the same as in Example 1.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 1 is that the alumina ceramic green body was not subjected to electric arc treatment.

[0067] This application also includes scanning electron microscopy tests on the ceramics prepared in Examples 1-3 and Comparative Example 1.

[0068] See Figure 2 (A) is a scanning electron microscope image of the alumina ceramic prepared in Example 1; (B) is an X-ray energy dispersive spectroscopy (EDS) image of the alumina ceramic in (A); (C) is an Al element distribution map of the alumina ceramic in (A); and (D) is a Zn element distribution map of the alumina ceramic in (A). Compared to unsintered alumina ceramic green bodies (see... Figure 5 From the above Figure 2 As can be seen from (A) in the figure, the surface of the alumina ceramic after arc sintering is uniform and dense. Figure 2 As shown in (B), (C), and (D), Al and Zn elements are distributed on the surface of the alumina ceramic. Some pores still exist on the surface, and the grain size is 9.68 ± 0.67 μm.

[0069] See Figure 3 , Figure 3 The image shows a scanning electron microscope image of the YSZ ceramic prepared in Example 2. Figure 3 As can be seen, the surface of YSZ ceramic is dense, with virtually no pores, and the grain size is 174.32±4.38μm.

[0070] See Figure 4 , Figure 4 The image shown is a scanning electron microscope image of the alumina ceramic prepared in an argon atmosphere in Example 3. Figure 4 As can be seen, in an argon atmosphere, the surface of the alumina ceramic green body after arc sintering is dense, and the grain size is 1.13±0.35μm.

[0071] This application also tested the ceramics prepared in Examples 1-2 and Comparative Example 1 using the Archimedes' displacement method. The tests showed that, compared to the density of 58.3% for the unsintered ceramic green body, the alumina ceramic prepared in Example 1 achieved a density of 97.6%. The YSZ ceramic prepared in Example 2 achieved a density of 99.4%. This demonstrates that sintering ceramic green bodies under an electric arc can yield dense ceramics. The alumina ceramic prepared in Example 1 meets both the requirements of high-performance materials for power grid equipment and the needs of dual-carbon development.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention should not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A ceramic sintering apparatus for sintering ceramic green bodies, characterized in that, The ceramic sintering apparatus includes: A first insulating plate is used to support the ceramic green body; A power supply device is provided for electrical connection to both ends of the ceramic green body. The power supply device provides voltage to the ceramic green body to generate an electric arc above it for sintering. The power supply device ensures that the current density flowing through the ceramic green body is 90~113.5 mA / mm². 2 It is also used to make the sintering time of the ceramic green body 30s; A first electrode and a second electrode are respectively connected to both ends of the ceramic green body, and the first electrode is made of tungsten wire or molybdenum wire, and the second electrode is made of tungsten wire or molybdenum wire; The second insulating plate is disposed at intervals on the first insulating plate. The second insulating plate is used to be disposed at preset intervals on the ceramic green body. The second insulating plate is used to confine the electric arc above the ceramic green body. The preset interval is 2~15mm.

2. The ceramic sintering apparatus as described in claim 1, characterized in that, The ceramic sintering apparatus further includes a current-limiting resistor and a voltage and current measuring device. The current-limiting resistor is used to limit the current of the power supply device, and the voltage and current measuring device is used to detect the voltage in the power supply device in real time.

3. The ceramic sintering apparatus as described in claim 1, characterized in that, The first insulating plate and the second insulating plate respectively comprise alumina ceramic, aluminum nitride ceramic or beryllium nitride ceramic.

4. A ceramic sintering method employing a ceramic sintering apparatus as described in any one of claims 1 to 3, characterized in that, include: A ceramic green body is placed on a first insulating plate, and then a second insulating plate is placed at intervals above the first insulating plate to obtain an intermediate body; The intermediate is placed in a preset gas atmosphere; At room temperature, the two ends of the ceramic green body are connected to a power supply device, and a voltage is applied to the ceramic green body through the power supply device to generate an electric arc above the ceramic green body to sinter the ceramic green body.

5. The ceramic sintering method as described in claim 4, characterized in that, The thickness of both the first insulating plate and the second insulating plate is greater than or equal to 1 cm.

6. The ceramic sintering method as described in claim 4, characterized in that, The voltage boost rate of the power supply device is 0.1~5kV / s.

7. The ceramic sintering method as described in claim 4, characterized in that, The preset gas atmosphere includes air, oxygen, nitrogen, or argon.

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