Ceramic sintering device and sintering method

Abstract

According to the ceramic sintering device and method, a battery and a graphite electrode are used for rapidly heating a powder medium in a sealed environment, a ceramic material can be sintered without an external power source, meanwhile, sintering can be conducted in the air atmosphere, the heating rate can reach 500 DEG C / min, the highest temperature of 1600 DEG C is achieved, and the sintering time is shortened. The segmented temperature curve is set through the sintering method, the temperature can be dynamically controlled while rapid heating is carried out, the defects of cracking, deformation and the like caused by uneven ceramic heating can be prevented, the sintering efficiency is high, the energy consumption is low, and equipment is simple.

Description

Technical Field

[0001] The present application belongs to the technical field of ceramic manufacturing, and in particular, relates to a ceramic sintering device and a sintering method. Background Art

[0002] Ceramic materials are widely used in the fields of automobile, aerospace, medical, battery, chemical industry, etc. due to their advantages of high wear resistance, heat resistance, low dielectric, chemical stability, mechanical stability, etc. There are many ways to prepare ceramics, usually by molding powder into green bodies, and then densifying them through high-temperature sintering.

[0003] Existing plasma sintering equipment, ultra-high temperature rapid sintering equipment and traditional box-type furnace sintering equipment are relatively complex and must be connected to an external continuous power supply for long-term temperature rise sintering. They have high requirements for sintering materials and low sintering density, which is inconvenient in production. Summary of the invention

[0004] The purpose of the present application is to provide a ceramic sintering device and a sintering method, which can solve at least one of the above problems.

[0005] In the first aspect, the present application provides a ceramic sintering device, including a sintering furnace, an insulation component, a battery, a first electrode, a second electrode and a heating medium. The insulation component is provided with an insulation cavity; the battery is provided outside the insulation component; the sintering furnace is provided in the insulation cavity; the first electrode is provided in the insulation cavity and is electrically connected to the output end of the battery; the second electrode is provided in the insulation cavity and is electrically connected to the input end of the battery, and the sintering furnace is provided between the first electrode and the second electrode; the heating medium wraps the first electrode and the second electrode respectively, and the first electrode and the second electrode are electrically connected to the heating medium respectively.

[0006] By using the battery to quickly heat up the electrodes and the heating medium in a sealed environment, ceramic materials can be sintered without the need for an external continuous voltage-stabilized power supply. At the same time, sintering can be performed directly in an air atmosphere, with an actual heating rate of up to 500°C / min and a maximum temperature of 1600°C. The sintering efficiency is high, the energy consumption is low, and the equipment is simple.

[0007] In some embodiments, the heat insulation component includes a heat insulation layer, and the heat insulation cavity is formed by enclosing the heat insulation layer. The heat insulation cavity is provided to fix the sintering furnace and the heating component and to isolate heat loss.

[0008] In some embodiments, the heat insulation assembly further comprises an insulating shell, which wraps the heat insulation layer. By providing the insulating shell, the current transmitted from the electrode to the heating medium is isolated in the sintering chamber, preventing the current from flowing through the furnace body and causing a short circuit.

[0009] In some embodiments, the ceramic sintering device further includes a temperature control component, the temperature control component includes a thermometer, a sintering chamber is provided in the sintering furnace, the thermometer is fixed to the sintering chamber and is electrically connected to the battery, so that the temperature in the sintering chamber can be monitored at any time.

[0010] In some embodiments, the temperature control assembly includes a current controller, one end of which is connected to the first electrode, and the other end of which is electrically connected to the output end of the battery, thereby being able to control the current intensity of the circuit.

[0011] In some embodiments, the temperature control assembly further includes a temperature controller, which is electrically connected to the battery, the temperature measuring instrument and the current controller, respectively, and is used to obtain the real-time temperature of the temperature measuring instrument, and compare and calculate the actual temperature obtained with the set required temperature, and control the current of the current controller. In this way, the temperature in the furnace can be dynamically adjusted.

[0012] In some embodiments, the temperature measuring device is an infrared temperature measuring device, thereby being able to quickly measure the surface temperature of the ceramic green body.

[0013] In some embodiments, the first electrode and / or the second electrode is a graphite electrode. The use of graphite electrodes can better withstand high temperatures and the impact of rapid temperature rise.

[0014] In a second aspect, a ceramic sintering method is provided, the method comprising: obtaining sintering temperature curve parameters input on a temperature controller, the temperature curve parameters comprising a preset time; controlling the temperature of the temperature controller according to the sintering temperature curve parameters, and monitoring the sintering process to obtain the sintering result; making a status judgment on the sintering result, and when the preset time is reached, judging that the sintering is completed, sending a power-off signal, and allowing the finished ceramic product to cool naturally.

[0015] In some embodiments, the steps of controlling the temperature of a temperature controller according to the sintering temperature curve parameters and monitoring the sintering process to obtain the sintering result specifically include: obtaining the surface temperature value of the ceramic green body through a temperature meter; calculating the temperature adjustment parameters according to the surface temperature value and the temperature curve parameters; controlling the current controller to adjust the current current intensity according to the temperature adjustment parameters to perform temperature control, and monitoring the sintering process to obtain the sintering result. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of a ceramic sintering device according to an embodiment of the present application; Figure 2 is a schematic diagram of component connections of a ceramic sintering device according to an embodiment of the present application; Figure 3 is a schematic flow chart of a ceramic sintering method in an embodiment of the present application; Figure 4 is a schematic flow chart of a ceramic sintering method in an embodiment of the present application; Figure 5 This is a schematic diagram of a sample photo of a zirconia ceramic after forming in an embodiment of the present application; Figure 6 This is a 4 μm electron microscope image of the microstructure of the zirconia ceramic molded sample in the embodiment of the present application. DETAILED DESCRIPTION

[0017] The following description provides specific application scenarios and requirements of this specification, with the purpose of enabling those skilled in the art to make and use the contents of this specification. Various local modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of this specification. Therefore, this specification is not limited to the embodiments shown, but to the widest scope consistent with the claims.

[0018] It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other when there is no conflict in structure or function. The present application is further described in detail below in conjunction with the accompanying drawings.

[0019] For the convenience of presentation, before we begin the description, we will explain the terms that will be used in the following description as follows: Ceramic powder: a combination of one or more oxides, carbides, nitrides and other ceramic composite materials.

[0020] Ceramic slurry: It is made by mixing ceramic powder, solvent, binder, plasticizer, resin, photoinitiator, dispersant, etc.

[0021] Ceramic green body: Made of ceramic powder or ceramic slurry, the maximum size of the ceramic green body does not exceed 40mm in diameter and the height does not exceed 5cm.

[0022] Reference Figure 1 : A ceramic sintering device includes a battery 100, a first electrode 201, a second electrode 202, a thermal insulation component 500 and a heating medium 300.

[0023] The sintering furnace 400 is arranged in the heat-insulating cavity 503; the sintering furnace 400 has a sintering cavity 402, and the ceramic green body can be placed in the sintering cavity 402. The wall of the sintering furnace 400 is made of a material with good high temperature resistance and thermal conductivity, such as silicon carbide, silicon nitride, etc. Preferably, the thickness of the furnace wall 401 is between 1 and 5 mm, the diameter of the cavity inside the furnace wall 401 does not exceed 5 cm, and the height does not exceed 30 cm. By setting the corresponding parameters of the sintering furnace 400, a better sintering effect can be achieved during actual sintering.

[0024] The first electrode 201 is disposed in the heat-insulating cavity 503, and the first electrode 201 is electrically connected to the output end of the battery 100. The second electrode 202 is disposed in the heat-insulating cavity 503, and the second electrode 202 is electrically connected to the input end of the battery 100. The second electrode 202 is spaced apart from the first electrode 201, and the sintering furnace 400 is disposed between the first electrode 201 and the second electrode 202.

[0025] The heat insulation component 500 is provided with a heat insulation cavity 503. The sintering furnace 400 is arranged in the heat insulation cavity 503 in the heat insulation component 500, which is used to isolate heat and seal the device.

[0026] The battery 100 may be disposed outside the heat insulation assembly 500. For example, a rechargeable battery such as a lead-acid battery 100, a lithium battery 100, a graphene battery 100, a lithium iron phosphate battery 100, etc. may be selected, and the specific type may be determined according to demand, and the battery 100 capacity of 20Ah and the voltage of 0-50V may be provided.

[0027] The heating medium 300 wraps the first electrode 201 and the second electrode 202 respectively, and the heating medium on both sides of the first electrode 201 and the second electrode 202 are connected. In this way, the heating medium 300 is connected to form a current loop to prevent short circuit, and the heating medium 300 surrounds the outer periphery of the furnace wall 401, which is more conducive to ensuring temperature uniformity.

[0028] Specifically, since the battery 100 is a DC power supply, after the power is turned on, the current flows through the wire to the first electrode 201, and the current of the first electrode 201 flows through the heating medium 300. The heating medium 300 quickly generates heat under the action of the current. At the same time, the connected heating medium 300 forms a current loop along the second electrode 202. Under the insulation of the insulation component 500, the heat generated by the heating medium 300 is transferred to the furnace wall 401, thereby quickly heating the ceramic sample in the sintering furnace 400. The heat generated is according to the Joule heating principle Q=I 2 Rt, and the temperature calculation formula Q=cm△T. Under good thermal insulation conditions, when the current is 20A, the heating rate can exceed 500℃ / min, and the maximum temperature reaches 1610℃ after 3 minutes.

[0029] In some embodiments, the thermal insulation assembly 500 includes a thermal insulation layer 501. The thermal insulation layer 501 is provided for fixing and heat insulation, and heat can only be conducted to the furnace wall 401 with good thermal conductivity, thereby improving heating efficiency. Exemplarily, the thermal insulation layer 501 can be made of a mixture of one or more materials selected from refractory materials such as polycrystalline alumina fibers and aerogels, so that the thermal insulation layer 501 can withstand high temperatures of 1600°C and rapid thermal shock.

[0030] In some embodiments, since the heat insulation layer 501 cannot completely isolate the heat loss, it mainly diffuses the heat to the outside in the form of heat conduction. Therefore, an insulating shell 502 is provided outside the heat insulation layer 501, and the insulating shell 502 completely wraps the heat insulation layer 501 to further avoid heat loss. Exemplarily, the insulating shell 502 can be a composite of one or more high-temperature resistant insulating materials such as Teflon, ceramic fiber, aluminum silicate, etc. At the same time, by providing the insulating shell 502, the current transmitted by the electrode to the heating medium 300 is isolated in the sintering chamber 402, preventing the current from flowing through the furnace body to cause a short circuit or the device from leaking electricity to cause electric shock. In order to ensure the sealing, the wire can be insulated with polytetrafluoroethylene and sealed with a sealing gasket when connected to the insulating shell.

[0031] Specifically, when the voltage and current remain constant, the temperature gradually increases with time until it remains stable. The theoretical total heat of heating is Q0=I 2 R1t, where I is the current, R1 is the resistance value, t is the time, and the comprehensive thermal conductivity of the insulation layer is 0.1W / (m*K). The insulation layer cannot completely isolate the heat loss. It mainly diffuses heat to the outside in the form of heat conduction. The loss energy is Q1. The heat loss satisfies the formula: Q1=hA(T3-T2), where h is the convection heat transfer coefficient between the air and the outer wall of the insulation layer, A is the heat transfer area, T3 is the outer wall temperature of the insulation layer, ℃, and T2 is the ambient temperature, ℃.

[0032] In some embodiments, reference Figure 1 and Figure 2 The temperature control assembly 600 includes a thermometer 602 for measuring the actual temperature of the ceramic green body. The thermometer can be an infrared thermometer. For example, the infrared thermometer has a temperature measurement range of room temperature to 1600°C and a response speed of 5ms to avoid the temperature rising quickly and the temperature being high during sintering. The error in obtaining the temperature data affects the temperature regulation, thereby affecting the sintering effect.

[0033] Optionally, an infrared temperature measuring device is selected and placed on the top of the sintering furnace 400 at a distance of 15 to 25 cm from the ceramic green body, so as to detect the microwaves generated by the ceramic green body to detect the actual temperature of the ceramic green body in real time. Through the infrared temperature measurement method, on the one hand, the actual temperature of the sample can be detected in real time, and on the other hand, the measured actual temperature can be used for feedback, thereby facilitating subsequent current control.

[0034] In some embodiments, during the heating process of sintering, due to the high temperature and rapid heating speed, the first electrode and the second electrode will melt if ordinary metal electrodes are used, and electrodes that are resistant to high temperature and rapid heating shock must be used, such as graphite electrodes that can work at a high temperature of 1600° C. In order to increase the resistance of the heating medium 300 as much as possible and to form a circuit for the current, the heating medium 300 can be pure graphite powder or a mixture of graphite powder and ceramic powder.

[0035] Among them, the resistance change characteristics of the heating medium are related to the specific material of the heating medium. When other ceramic powders are mixed as heating media, different initial resistance values ​​are shown according to different mixing ratios. The initial resistance value R0 can be measured by the UI curve. When the current is constant, the resistance value of the heating medium shows a good linear relationship with the voltage, and the expression is U=IR0+A, where I is the set value, and A can be calculated by fitting the voltage-resistance test. The initial R0 value is between 2 and 5Ω. In addition, the resistance of the heating medium also decreases with increasing temperature, and the expression is R1=KT+R0, where K is the temperature rise coefficient and T is the actual temperature, which can be calculated by fitting the RT curve.

[0036] In some embodiments, in order to more accurately adjust the temperature in the sintering furnace 400, the temperature control component 600 also includes a current controller 603. Among them, the current controller 603 is used to control the current size of the circuit. According to the different batteries 100 selected, the current can actually be adjusted to 0-20A, and the corresponding current can be adjusted manually. It should be noted that the current controller can use an existing model DIN11L-U2-P1-0z current controller, as long as the relevant parameters such as the adjustable range meet the requirements, and there is no restriction here. More preferably, in order to dynamically and automatically adjust the temperature in the sintering furnace 400, the ceramic sintering device can also be provided with a temperature controller 601, which can also provide the required current and voltage size to the temperature controller 601 when electrically connected to the temperature controller 601. The temperature controller 601 is electrically connected to the temperature meter 602, and can obtain the actual temperature of the temperature meter 602. It is configured to compare and calculate the actual temperature obtained with the set required temperature, and feedback to the current controller 603 to change the size of the current for temperature control. Therefore, by setting the parameters of the segmented temperature curve through the temperature control component 600, the temperature can be controlled while the temperature is rapidly increased, thereby preventing defects such as cracking and deformation of the ceramic caused by uneven temperature increase.

[0037] Specifically, temperature control at different heating rates has different effects. The temperature control method controls the current change according to the difference B between the actual test temperature T1 of the thermometer and the set temperature T0. Data comparison is performed every 100ms. When -a≤B≤a, the current current I0 is kept unchanged; when B>a, I0=0; when B<-a, I1=KI0+C, a is the set value, K and C are constants that can be set. According to the heat calculation formula, Q3=Q0-Q1-Q2=cm(T5-T4), where Q3 is the heat that heats the heating medium to a specific temperature, Q0 is the total heat when the current heats the heating medium, Q1 is the heat loss of the insulation layer, that is, Q1=hA(T3-T2), Q2 is the heat lost when the heating medium heats the sample, c is the specific heat capacity of the heating medium, J / (kg·℃); m is the mass of the heating medium, kg; T5 and T4 are the theoretical temperature after heating and the temperature before heating, ℃, and the formula is derived from this: I0 2 =[cm(T5-T4)+hA(T3-T2)] / (KT5+R0)t. The theoretical temperature of each stage is determined according to the heating curve, and the corresponding current size is obtained according to the formula, so that the current can be controlled.

[0038] In one pair of proportions, two electrodes are spaced apart and arranged on the surface of the ceramic green embryo. An external AC power supply is also required to output voltage to the electrodes on the surface of the ceramic green embryo. By applying different voltages to different electrodes, a voltage difference is formed between the electrodes, generating current for sintering. During actual sintering, different temperatures need to be adjusted according to different sintering periods. It is also necessary to strictly control the voltage and continuously control the power switch to sinter the ceramic green embryo, which makes the operation complicated.

[0039] In another comparative example, in order to ensure the sintering quality of the finished ceramic product, it is necessary to pre-evacuate the sintering chamber and introduce protective gas to ensure an oxygen-free environment, and ensure that the sintered ceramic parts are in full contact with the heating medium, and then use an external continuous power supply to power and heat the conductive parts and the heating medium. At the same time, the existing plasma sintering equipment, ultra-high temperature rapid sintering equipment and traditional box-type furnace sintering equipment require a long time to heat up and sinter, and must be fixed in a specific position and cannot be flexibly moved.

[0040] Compared with the existing related technical solutions, the present application can use rechargeable batteries and electrodes to quickly heat the heating medium in a sealed environment, and perform high-temperature sintering without an external continuous power supply, especially being able to use an independent power supply alone for sintering. The power supply of a traditional sintering furnace is a circuit with a regulated voltage of 220V or 380V, that is, an external continuous regulated power supply is required for sintering, the equipment is complex, and it is inconvenient to use and move.

[0041] At the same time, the present application does not need to evacuate the sintering chamber or discharge protective gas in advance, and can directly carry out sintering in an air atmosphere. The heating rate can reach 500°C / min, and the maximum temperature can reach 1600°C. It can achieve rapid sintering of ceramic materials and reduce sintering energy consumption. The equipment is simple and portable, which is conducive to improving production efficiency and reducing production costs.

[0042] The following will describe in detail the process of sintering a ceramic green body using the above ceramic sintering device.

[0043] See also Figure 3 and Figure 4 A preferred embodiment of the present invention provides a ceramic sintering method, comprising: S100, obtaining sintering temperature curve parameters inputted on a temperature controller, wherein the temperature curve parameters include a preset time; S200, controlling the temperature of the temperature controller according to the sintering temperature curve parameters, and monitoring the sintering process to obtain the sintering result; S300, the sintering result is judged as state, and when the preset time is reached, the sintering is judged to be completed, and a power off signal is issued to allow the ceramic product to cool naturally. See also Figure 4 , wherein step S200 specifically includes: S210, obtaining a surface temperature value of the ceramic green body by using a temperature measuring instrument; S220, calculating a temperature adjustment parameter according to the surface temperature value and the temperature curve parameter; S230, controlling the current controller to adjust the current current intensity according to the temperature adjustment parameter to perform temperature control, and monitoring the sintering process to obtain the sintering result.

[0044] For example, taking sintering zirconia ceramics as an example, the process is specifically carried out according to the following steps: First, 400nm ZrO2 powder was prepared into 60vol% slurry, and a disc with a diameter of 15mm and a thickness of 2mm was prepared by photocuring. The disc was degreased and pre-sintered at 900℃ for 2 hours. At this time, the density of the disc was 40%; then the pre-sintered disc was placed in the sintering chamber; the battery was powered on, and the temperature change curve parameters were set to 1000℃ / 10A / 1min, 1500℃ / 15A / 1min, 1600℃ / 20A / 2min, for a total of four minutes. The temperature measured by the thermometer was compared with the set temperature value. When the measured temperature was lower than the set temperature, the current was increased; when the measured temperature was higher than the set temperature, the current was reduced; until sintering was completed, refer to Figure 5 and Figure 6 The sintering density of the test sample reached 95.6% and the sintering shrinkage rate reached 18.5%.

[0045] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] In addition, certain terms in this application have been used to describe embodiments of the present application. For example, "one embodiment", "embodiment" and / or "some embodiments" mean that a particular feature, structure or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. It can be emphasized and should be understood that two or more references to "embodiment" or "one embodiment" or "alternative embodiment" in various parts of this specification do not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics can be appropriately combined in one or more embodiments of the present application.

[0047] Therefore, the embodiments disclosed in this specification are only examples and not limitations. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present application, and these all fall within the scope of protection of the present application.

Claims

1. A ceramic sintering device, characterized in that: include: A thermal insulation assembly having a thermal insulation cavity; A battery, which is arranged outside the thermal insulation assembly; a sintering furnace, which is arranged in the heat-insulating cavity; a first electrode disposed in the heat-insulating cavity and electrically connected to an output terminal of the battery; a second electrode disposed in the heat-insulating cavity and electrically connected to an input terminal of the battery, wherein the sintering furnace is disposed between the first electrode and the second electrode; A heating medium, wherein the heating medium wraps the first electrode and the second electrode respectively, and the first electrode and the second electrode are electrically connected to the heating medium respectively.

2. The ceramic sintering device according to claim 1, characterized in that: The thermal insulation component comprises a thermal insulation layer, and the thermal insulation cavity is formed by enclosing the thermal insulation layer.

3. The ceramic sintering device according to claim 2, characterized in that: The thermal insulation assembly further comprises an insulating shell, wherein the insulating shell wraps the thermal insulation layer.

4. The ceramic sintering device according to claim 1, characterized in that: It also includes a temperature control component, which includes a thermometer. A sintering chamber is provided in the sintering furnace. The thermometer is fixed on the sintering chamber and is electrically connected to the battery.

5. The ceramic sintering device according to claim 4, characterized in that: The temperature control component includes a current controller, one end of which is connected to the first electrode, and the other end of which is electrically connected to the output end of the battery.

6. The ceramic sintering device according to claim 5, characterized in that: The temperature control component also includes a temperature controller, which is electrically connected to the battery, the temperature meter and the current controller respectively, and is used to obtain the real-time temperature of the temperature meter, calculate the actual temperature obtained and the set required temperature, and control the current size of the current controller.

7. The ceramic sintering device according to claim 4, characterized in that: The thermometer is an infrared temperature measuring device.

8. The ceramic sintering device according to claim 1, characterized in that: The first electrode and / or the second electrode is a graphite electrode.

9. A ceramic sintering method, used for controlling the operation of the ceramic sintering device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Obtaining sintering temperature curve parameters inputted on a temperature controller, wherein the temperature curve parameters include a preset time; The temperature controller is used to control the temperature according to the sintering temperature curve parameters, and the sintering process is monitored to obtain the sintering results; The sintering result is judged as state, and when the preset time is reached, the sintering is judged to be completed, and a power-off signal is issued, allowing the finished ceramic product to cool naturally.

10. The ceramic sintering method according to claim 9, characterized in that: During the sintering process, the temperature controller is controlled according to the sintering temperature curve parameters, and the sintering process is monitored to obtain the sintering result, including: The surface temperature value of the ceramic green body is obtained by a thermometer; The temperature adjustment parameters are calculated based on the surface temperature value and the temperature curve parameters; The current controller is controlled according to the temperature control parameters to adjust the current current intensity to control the temperature, and the sintering process is monitored to obtain the sintering result.

Images