CN111440002A - Ceramic sintering method and ceramic sintering device - Google Patents

Ceramic sintering method and ceramic sintering device Download PDF

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Publication number
CN111440002A
CN111440002A CN202010258787.7A CN202010258787A CN111440002A CN 111440002 A CN111440002 A CN 111440002A CN 202010258787 A CN202010258787 A CN 202010258787A CN 111440002 A CN111440002 A CN 111440002A
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sintering
ceramic green
green body
electrode
voltage
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CN111440002B (en
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王希林
李想
张若兵
贾志东
王黎明
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Shenzhen International Graduate School of Tsinghua University
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Shenzhen International Graduate School of Tsinghua University
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    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64Burning or sintering processes
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27FURNACES; KILNS; OVENS; RETORTS
    • F27DDETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00Arrangement of elements for electric heating in or on furnaces
    • F27D11/08Heating by electric discharge, e.g. arc discharge
    • F27D11/10Disposition of electrodes
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27FURNACES; KILNS; OVENS; RETORTS
    • F27DDETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00Arrangements of controlling devices
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/65Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
    • C04B2235/66Specific sintering techniques, e.g. centrifugal sintering
    • C04B2235/666Applying a current during sintering, e.g. plasma sintering [SPS], electrical resistance heating or pulse electric current sintering [PECS]
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27FURNACES; KILNS; OVENS; RETORTS
    • F27DDETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00Arrangements of controlling devices
    • F27D2019/0028Regulation
    • F27D2019/0034Regulation through control of a heating quantity such as fuel, oxidant or intensity of current
    • F27D2019/0037Quantity of electric current

Abstract

The invention provides a ceramic sintering method, which comprises the following steps: obtaining a ceramic green body; arranging a first electrode and at least two second electrodes which are mutually spaced to the ceramic green body; and applying a first voltage to the first electrode and a second voltage to the at least two second electrodes at different times to sinter the ceramic green body. The invention also provides a ceramic sintering device.

Description

Ceramic sintering method and ceramic sintering device
Technical Field
The invention relates to the technical field of ceramic sintering, in particular to a ceramic sintering method and a ceramic sintering device used by the ceramic sintering method.
Background
Ceramic materials have found wide application in various fields, for example, in the manufacture of solar cells, piezoelectric devices, and the like. The formation of the ceramic material requires that the ceramic powder is changed into a green body through a forming technology, and then the grain migration and growth of the green body and the contraction of the green body are realized through a sintering technology. The traditional sintering technology generally needs high temperature of more than 1000 ℃, and has higher energy consumption and cost.
In recent years, a number of new ceramic sintering techniques have emerged. Among them, "Flash Sintering" (Flash Sintering) is a new Sintering process that reduces the Sintering temperature of ceramics with the assistance of electric field and greatly shortens the time required for Sintering. How to further reduce the temperature required for flash firing to low temperatures (< 400 ℃) and even room temperature is a big hotspot of research. However, low temperature flash memory suffers from the limitation of conditions: for a fixed green-electrode structure, to further reduce the temperature required for flash firing, the voltage must be increased to increase the pressure, but this also increases the current through the flash-fired sample when flash firing occurs, and excessive current can cause the flash-fired sample to break. In addition, the conventional sintering technology or the flash firing technology cannot realize integral ceramic sintering.
Disclosure of Invention
In order to overcome the defects of the existing flash firing technology, the invention provides a porcelain sintering method which comprises the following steps:
obtaining a ceramic green body;
arranging a first electrode and at least two second electrodes which are mutually spaced to the ceramic green body; and
a first voltage is applied to the first electrode and a second voltage is applied to the at least two second electrodes in a time-sharing manner to sinter the ceramic green body.
Preferably, the step of disposing a first electrode and at least two second electrodes spaced apart from each other to the ceramic green body includes:
and arranging a first electrode and at least two second electrodes which are mutually spaced to the ceramic green body in a spraying or bonding mode.
Preferably, the first voltage is higher than the second voltage.
Preferably, the number of the second electrodes is two;
the step of applying a first voltage to the first electrode and applying a second voltage to the at least two second electrodes in a time-sharing manner specifically includes:
during a first sintering period, applying the first voltage to the first electrode and simultaneously applying the second voltage to one of the second electrodes;
during a second sintering period, the first voltage is applied to the first electrode and the second voltage is simultaneously applied to the other second electrode.
Preferably, the ceramic green body is heated during the first sintering period and the second sintering period.
Preferably, the ceramic green body is placed in an atmosphere of air, inert gas or reducing gas during the first sintering period and the second sintering period.
Another aspect of the present invention provides a ceramic sintering apparatus for sintering a ceramic green body; the ceramic sintering apparatus includes:
the sintering furnace is used for accommodating the ceramic green body;
a power source electrically connected to the ceramic green body for applying a first voltage and a second voltage to the ceramic green body; and
and the switch module is electrically connected with the power supply and the ceramic green body and is used for electrically connecting the power supply to different positions of the ceramic green body in a time-sharing manner.
Preferably, the ceramic green body sintering furnace further comprises a heating module arranged outside the sintering furnace, wherein the heating module is used for heating the ceramic green body in the process of sintering the ceramic green body.
According to the ceramic sintering method, the second voltages are applied to the different second electrodes in different time-sharing ways in different sintering time periods, so that different sections on the ceramic green body can be sintered in different time periods, different sintering temperatures and the like of the different sections of the ceramic green body are different, and different sections on the whole ceramic green body can be different in structure and property so as to meet subsequent application requirements. In addition, the ceramic green bodies are sintered in a time-sharing and sectional mode, voltage during sintering is reduced for the ceramic green bodies with large overall sizes (the larger the sintering size is, the higher the voltage requirement is), the voltage during sintering is reduced, the problem that the ceramic green bodies are broken due to high voltage is solved, and energy consumption is saved.
Drawings
Fig. 1 is a schematic structural diagram of a ceramic sintering apparatus and a ceramic green body according to a preferred embodiment of the present invention.
FIG. 2 is a flow chart of a ceramic sintering method according to a preferred embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a ceramic sintering apparatus and a ceramic green body according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of a grain structure formed in one of the segments after sintering of the ceramic green body in accordance with one embodiment of the present invention.
FIG. 5 is a schematic illustration of a grain structure formed in another section after sintering of a ceramic green body in accordance with one embodiment of the present invention.
Fig. 6 is a schematic structural diagram of a ceramic sintering apparatus and a ceramic green body according to a second embodiment of the present invention.
FIG. 7 is a schematic illustration of the grain structure formed in one of the segments after sintering of the ceramic green body in accordance with the second embodiment of the present invention.
FIG. 8 is a schematic illustration of the grain structure formed in another section after sintering of the ceramic green body in example two of the present invention.
Description of the main elements
Ceramic sintering device 10
Sintering furnace 11
Sintering chamber 111
Power supply 12
Switch module 13
A first electrode 14,
Second electrode 1, n-1, n, 171, 172, 181, 182
Heating module 16
Ceramic green bodies 20, 30, 40
Steps S1, S2, S3
The following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. In addition, the embodiments and features of the embodiments of the present application may be combined with each other without conflict. In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention, and the described embodiments are merely a subset of the embodiments of the present invention, rather than a complete embodiment. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes all and any combination of one or more of the associated listed items.
In various embodiments of the present invention, for convenience in description and not in limitation, the term "coupled" as used in the specification and claims of the present application is not limited to physical or mechanical couplings, either direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.
Referring to fig. 1, a ceramic sintering apparatus 10 according to a preferred embodiment of the present invention is provided for sintering a ceramic green body 20 into a target ceramic structure. The ceramic sintering device 10 comprises a sintering furnace 11, a power supply 12 and a switch module 13, wherein the power supply 12 is arranged outside the sintering furnace 11, and the switch module 13 is electrically connected with the power supply 12.
The ceramic green compact 20 is formed by putting ceramic powder (with grain diameter of 1nm-10 μm) into a die for extrusion molding (with pressure range of 40MPa-800 MPa). The shape of the ceramic green body 20 is set according to the mold, and may include, but is not limited to: the dog bone shape, the cylinder shape, the cuboid shape and other regular or irregular geometric shapes. In this example, a ceramic green body 20 having a substantially "dog-bone" shape is exemplified. The ceramic powder is processed by ball milling and granulation processes, so that the ceramic powder has small particle size, high fluidity and easy molding.
Referring to fig. 1, the ceramic sintering device 10 further includes a first electrode 14 and n second electrodes, which are the second electrode 1, the second electrode 2, …, the second electrode n-1 and the second electrode n, where n is greater than or equal to 2. The first electrode 14 and the n second electrodes are disposed on the surface of the ceramic green sheet 20. The first electrode 14 and each second electrode are spaced apart from each other and insulated from each other, and the first electrode 14 and the second electrode n are fixed to both ends of the ceramic green sheet 20, respectively. In this embodiment, the first electrode 14 and the n second electrodes are equally spaced on the surface of the ceramic green sheet 20 in the axial direction or the major axis direction. That is, the intervals between every adjacent two electrodes on the surface of the ceramic green sheet 20 are equal. The first electrode 14 and the n second electrodes are distributed on the surface of the ceramic green body 20 at equal intervals, which is favorable for simplifying the electrode arrangement process. In other embodiments, the first electrode 14 and the n second electrodes may be distributed differently. The first electrode 14, the n second electrodes are distributed in a manner dependent upon, among other factors, the material of the ceramic powder forming the ceramic green compact 20, the shape and size of the ceramic green compact 20, and the target ceramic structure to be sintered to form. The first electrode 14 and the n second electrodes are formed on the surface of the extruded ceramic green body 20 by spraying or adhering conductive materials. The method of forming the electrode on the surface of the ceramic green body by spraying or adhering the conductive material is a conventional method in the art, and the details are not described herein.
With continued reference to fig. 1, the sintering furnace 11 has a sintering chamber 111, and the sintering chamber 111 is used for accommodating the ceramic green body 20.
With continued reference to fig. 1, the power source 12 and the switch module 13 are electrically connected to the ceramic green sheet 20 by wires extending into the sintering chamber 111, so that the power source 12 can apply a voltage to the ceramic green sheet 20. In this embodiment, the power source 12 applies a first voltage to the first electrode 14 on the ceramic green body 20 and applies a second voltage to the n second electrodes on the ceramic green body 20 in a time-sharing manner, i.e., the power source 12 applies the second voltage to different second electrodes at different time periods. The first voltage is higher than the second voltage, so as to generate a required voltage difference between the first electrode 14 and each of the second electrodes. In this embodiment, when the first voltage is applied to the first electrode 14, each of the second electrodes is grounded in a time sharing manner. The power source 12 may be a dc, ac or pulsed power source. The voltage supplied by the power supply 12 may be regulated in the range of 0-500 kV. The frequency of the alternating current or pulse power supply can be adjusted within the range of 1Hz-50 kHz. In other embodiments, the maximum frequency of the AC or pulsed power source should be lower than the microwave frequency (300 MHz).
With continued reference to fig. 1, the switch module 13 is electrically connected to the power source 12 at one end, and electrically connected to the first electrode 14 and the n second electrodes of the ceramic green body 20 through wires at the other end, so as to establish an electrical connection between the power source 12 and the ceramic green body 20. During the sintering of the ceramic green body 20, the switching module 13 controls the first voltage output by the power supply 12 to be applied to the first electrode 14 of the ceramic green body 20, and controls the second voltage output by the power supply 12 to be applied to each second electrode of the ceramic green body 20 in a time-sharing manner. That is, during sintering of the ceramic green body 20, the switching module 13 is configured to switch a second electrode of the ceramic green body 20 that receives a second voltage output by the power source 12.
With continued reference to fig. 1, the ceramic sintering device 10 further includes a heating module 16. The heating module 16 is disposed outside the sintering chamber 111 of the sintering furnace 11, and is used for heating the ceramic green body 20 during sintering of the ceramic green body 20. Under the same other conditions, the heating module 16 assists heating when sintering the ceramic green sheet 20, and the voltage at the time of sintering can be reduced. Therefore, the auxiliary heating by the heating module 16 during sintering of the ceramic green body 20 is advantageous in solving the problem that the ceramic green body 20 is broken due to high pressure during sintering, and in saving energy consumption. In this embodiment, the heating module 16 may be a heating plate, a box furnace, or the like.
It should be understood that in other embodiments of the present invention, the ceramic sintering device 10 may not include the heating module 16.
The process of sintering the ceramic green sheet 20 using the above-described ceramic sintering apparatus 10 will be described in detail below.
Referring to fig. 2, a method for sintering a ceramic according to a preferred embodiment of the present invention includes:
step S1, obtaining a ceramic green body;
step S2, arranging a first electrode and at least two second electrodes which are mutually spaced to the ceramic green body; and
step S3, applying a first voltage to the first electrode and applying a second voltage to the at least two second electrodes in a time-sharing manner to sinter the ceramic green body.
Referring to fig. 1 and 2, in step S1, the ceramic powder is ball milled and granulated as described above, and then placed in a mold (not shown) to be extruded and formed into a ceramic green body 20.
Continuing with fig. 1 and fig. 2, in step S2, a first electrode 14 and n second electrodes, including a second electrode 1, a second electrode 2 … …, a second electrode n-1 and a second electrode n, are disposed on the surface of the ceramic green body 20, where n is greater than or equal to 2. The first electrode 14 and the n second electrodes are arranged on the surface of the ceramic green body 20 at intervals and are insulated from each other. The first electrode 14 and the n second electrodes are distributed on the surface of the ceramic green body 20 at equal intervals. That is, on the surface of the ceramic green sheet 20, the distance between each of the two electrodes arranged adjacent to each other among the first electrode 14 and the n second electrodes is equal. The first electrode 14 and the n second electrodes are formed by spraying a conductive material onto the ceramic green sheet 20 or by adhering a conductive material to the surface of the ceramic green sheet 20.
Continuing to refer to fig. 1 and 2 simultaneously, in step S3, in the first sintering period, the power source 12 outputs a first voltage and a second voltage, and the switching module 13 controls the first voltage output by the power source 12 to be applied to the first electrode 14 of the ceramic green body 20 and controls the second voltage output by the power source 12 to be applied to the second electrode 1 on the surface of the ceramic green body 20. A voltage difference is created between the first electrode 14 and the second electrode 1, and an electric current is generated to sinter the section of the ceramic green body 20 between the first electrode 14 and the second electrode 1.
In the (n-1) th sintering period, the switching module 13 controls the first voltage output from the power supply 12 to be applied to the first electrode 14 of the ceramic green body 20 and controls the second voltage output from the power supply 12 to be applied to the second electrode n-1 on the surface of the ceramic green body 20. A voltage differential is created between the first electrode 14 and the second electrode n-1, which generates an electrical current that sinters the section of the ceramic green body 20 between the first electrode 14 and the second electrode n-1.
After the n-1 th sintering period, in the nth sintering period, the switching module 13 controls the first voltage output by the power supply 12 to be applied to the first electrode 14 of the ceramic green body 20, and controls the second voltage output by the power supply 12 to be applied to the second electrode n on the surface of the ceramic green body 20. A voltage difference is created between the first electrode 14 and the second electrode n, and an electric current is generated to sinter the section of the ceramic green body 20 between the first electrode 14 and the second electrode n.
The switching module 13 controls the second voltage outputted by the power supply 12 to be sequentially applied to each second electrode on the surface of the ceramic green body 20 in a time-sharing manner, and then the ceramic green body 20 is sintered.
The above-mentioned sequence of the switch module 13 controlling the second voltage outputted by the power source 12 to be applied to each second electrode on the surface of the ceramic green body 20 is only an example and is not intended to limit the present invention. The order in which the switching modules 13 switch the respective second electrodes is determined by the target ceramic structure that is desired to be sintered to form.
During each of the above-described sintering periods, the ceramic green body 20 may be in an atmosphere of air, an inert gas, a reducing gas, or a mixture of the above gases. The gas environment is selected based on the material of the ceramic green body 20.
As described above, in different sintering periods, the switching module 13 switches different second electrodes in a time-sharing manner to apply the second voltage, so that different sections of the ceramic green body 20 can be sintered in a time-sharing manner, and therefore, different sections of the ceramic green body 20 have different sintering time lengths, different sintering temperatures, and the like, so that different sections of an integral ceramic green body 20 can have different structures and properties, that is, a structural gradient distribution can be obtained after the sintering of the integral ceramic green body 20 is completed, so as to meet the subsequent diversified application requirements. In addition, the time-sharing and sectional sintering of one ceramic green body 20 is beneficial to reducing the voltage during sintering (the voltage requirement is higher when the sintering size is larger) for the ceramic green body 20 with larger overall size, and the voltage during sintering is reduced, so that the problem that the ceramic green body 20 is fractured due to high voltage is solved, and the energy consumption is saved.
An example of a ceramic sintering method using the ceramic sintering apparatus 10 according to the present invention will be specifically described below with reference to examples.
Example one
Referring to fig. 3, in the present embodiment, the ceramic sintering apparatus 10 includes two second electrodes, which are a second electrode 171 and a second electrode 172, respectively, and the first electrode 14, the second electrode 171, and the second electrode 172 are spaced apart from each other and are disposed on the surface of the "dog bone" shaped ceramic green compact 30 at equal intervals and are insulated from each other, wherein the first electrode 14 and the second electrode 172 are respectively fixed at two ends of the ceramic green compact 30, the ceramic powder forming the ceramic green compact 30 is zinc oxide powder with an average particle size of 30nm, a cubic size between the electrodes at two ends of the ceramic green compact 30 is 13mm × 3.3.3 mm × 0.8.8 mm, and the power supply 12 is a power frequency ac power supply.
In the first sintering period, the switching module 13 controls the first voltage output by the power supply 12 to be applied to the first electrode 14 of the ceramic green body 30, controls the second voltage output by the power supply 12 to be applied to the second electrode 171, forms a voltage difference between the first electrode 14 and the second electrode 171, generates a current, sinters the section of the ceramic green body 20 located between the first electrode 14 and the second electrode 171, gradually increases the first voltage applied to the first electrode 14 from zero to 4kV and maintains the first voltage, gradually increases the current passing through the ceramic green body 30 within 2min until the flash firing occurs, the current passing through the ceramic green body 30 during the flash firing is 600mA, and the first voltage returns to zero after the flash firing is maintained for 30 s. In the first sintering period, the second voltage output to the second electrode 171 is continuously maintained at the ground voltage.
During the second sintering period, the switching module 13 controls the first voltage output by the power supply 12 to be applied to the first electrode 14 of the ceramic green body 30, and controls the second voltage output by the power supply 12 to be applied to the second electrode 172, a voltage difference is formed between the first electrode 14 and the second electrode 172, a current is generated, the section of the ceramic green body 30 located between the first electrode 14 and the second electrode 172 is sintered, and the first voltage applied to the first electrode 14 gradually increases from zero. The first voltage is flashed when the first voltage is not higher than 4kV, the voltage is continuously boosted until the current passing through the ceramic green body 30 is 600mA, the first voltage returns to zero after the flashing for 30s, and the power supply 12 is disconnected. During the second sintering period, the second voltage output to the second electrode 172 is continuously maintained at the ground voltage.
The ceramic green compact 30 after the sintering process is cooled to room temperature, and then is taken out and stored, and the sintering is completed. In the sintering process, the current passing through the ceramic green body 30 shows a tendency of change which is rapidly decreased → slowly increased → sudden rise (when flash firing occurs) → substantially constant; the density, conductivity, mechanical properties and the like of the ceramic green body 30 show a changing trend that the density, conductivity, mechanical properties and the like are constantly increased to be basically unchanged; the surface temperature of the ceramic green body 30 gradually increases to 300 ℃ or higher with the increase of the first voltage, and suddenly increases to 1000 ℃ or higher in flash firing and is substantially maintained.
In a comparative example, a voltage of 7kV or more is required to be used by using a ceramic sintering apparatus and a ceramic sintering method different from those of the present example. The ceramic sintering device 10 and the ceramic sintering method provided by the embodiment greatly reduce the voltage (first voltage) during sintering; and the present embodiment can achieve the step sintering of the ceramic green body 30 by using two second electrodes (171 and 172), so that after the sintering of the ceramic green body 30 is completed, the grain sizes of different sections are obviously different. Specifically, the grain structure after sintering of the section between the first electrode 14 and the second electrode 171 is shown in fig. 4, and the grain structure after sintering of the section between the second electrode 171 and the second electrode 172 is shown in fig. 5.
Example two
Referring to fig. 6, in the present embodiment, the ceramic sintering apparatus 10 includes two second electrodes, which are a second electrode 181 and a second electrode 182, respectively, and the first electrode 14, the second electrode 181, and the second electrode 182 are disposed on the surface of the ceramic green body 40 at an interval and at an equal interval and are insulated from each other, wherein the ceramic green body 40 is cylindrical, the first electrode 14 and the second electrode 182 are respectively fixed at two ends of the ceramic green body 30, and the ceramic green body 40 has a diameter of 10mm and a height of 80 mm; the ceramic green body 40 is press-molded from zinc oxide powder having an average particle diameter of 30 nm; the power supply 12 is a power frequency alternating current power supply.
In the ceramic sintering method of the embodiment, in step S3, in the first sintering period, the power source 12 outputs a first voltage and a second voltage, the switching module 13 controls the first voltage output by the power source 12 to be applied to the first electrode 14 of the ceramic green body 40 and controls the second voltage output by the power source 12 to be applied to the second electrode 181 of the ceramic green body 40, a voltage difference is formed between the first electrode 14 and the second electrode 181, a current is generated, a section of the ceramic green body 40 located between the first electrode 14 and the second electrode 181 is sintered, the first voltage is gradually increased from zero to 4.5kV and is maintained, thereafter, the current passing through the ceramic green body 40 gradually increases within 2min until flash firing occurs, the current passing through the ceramic green body 40 during flash firing is 640mA, and the first voltage returns to zero after flash firing for 30S. In the first sintering period, the second voltage output to the second electrode 181 is continuously maintained at the ground voltage.
After the first sintering period is over, in the second sintering period, the switching module 13 controls the first voltage output by the power supply 12 to be applied to the first electrode 14 of the ceramic green body 40 and controls the second voltage output by the power supply 12 to be applied to the second electrode 182 of the ceramic green body 40. A voltage difference is formed between the first electrode 14 and the second electrode 182 to generate a current, the section of the ceramic green body 40 between the first electrode 14 and the second electrode 182 is sintered, the first voltage is gradually increased from zero, flash firing occurs when the voltage does not reach 4.5kV, the voltage is continuously increased until the current passing through the ceramic green body 40 is 640mA, the first voltage returns to zero after flash firing for 30s, and the power supply 12 is disconnected. In the second sintering period, the second voltage output to the second electrode 182 is continuously maintained at the ground voltage.
And taking down and storing the ceramic green body 40 after the ceramic green body is cooled to room temperature, and completing sintering. The current passing through the ceramic green body 40 in the above process shows a tendency of change that rapidly decreases → slowly increases → sharply increases (when flash firing occurs) → remains substantially unchanged; the density, conductivity, mechanical properties and the like of the ceramic green body 40 are in a changing trend of constantly increasing to be basically unchanged in the process; the surface temperature of the ceramic green body 40 gradually rises to above 300 ℃ with the rise of the first voltage during the process, and suddenly rises to above 1000 ℃ during flash firing and is substantially maintained.
In a comparative example, a voltage of 7kV or more is required to be used by using a ceramic sintering apparatus and a ceramic sintering method different from those of the present example. The ceramic sintering device 10 and the ceramic sintering method provided by the embodiment greatly reduce the voltage (first voltage) during sintering; and the present embodiment can realize the step sintering of the ceramic green body 40 by using two second electrodes (181 and 182), so that after the sintering of the ceramic green body 40 is completed, the grain sizes of different sections are obviously different. Specifically, the grain structure after sintering of the region between the first electrode 14 and the second electrode 181 is shown in fig. 7, and the grain structure after sintering of the region between the second electrode 181 and the second electrode 182 is shown in fig. 8.
It will be appreciated by those skilled in the art that the above embodiments are illustrative only and not intended to be limiting, and that suitable modifications and variations may be made to the above embodiments without departing from the true spirit and scope of the invention.

Claims (10)

1. A method of sintering a ceramic, comprising the steps of:
obtaining a ceramic green body;
arranging a first electrode and at least two second electrodes which are mutually spaced to the ceramic green body; and
a first voltage is applied to the first electrode and a second voltage is applied to the at least two second electrodes in a time-sharing manner to sinter the ceramic green body.
2. The method of sintering a ceramic of claim 1 wherein the first electrode and the at least two second electrodes are equally spaced on the ceramic green body.
3. The method of claim 1, wherein the step of providing a first electrode and at least two second electrodes spaced apart from each other to the green ceramic body comprises:
and arranging a first electrode and at least two second electrodes which are mutually spaced to the ceramic green body in a spraying or bonding mode.
4. The method of claim 1, wherein the first voltage is higher than the second voltage.
5. The ceramic sintering method according to claim 1, wherein the second electrodes are two;
the step of applying a first voltage to the first electrode and applying a second voltage to the at least two second electrodes in a time-sharing manner specifically includes:
during a first sintering period, applying the first voltage to the first electrode and simultaneously applying the second voltage to one of the second electrodes;
during a second sintering period, the first voltage is applied to the first electrode and the second voltage is simultaneously applied to the other second electrode.
6. The method of sintering a ceramic of claim 5 wherein the ceramic green body is heated during the first sintering period and the second sintering period.
7. The method of claim 5, wherein the ceramic green body is placed in an atmosphere of air, inert gas, or reducing gas during the first sintering period and the second sintering period.
8. A ceramic sintering apparatus for sintering a ceramic green body; characterized in that the ceramic sintering device comprises:
the sintering furnace is used for accommodating the ceramic green body;
a power source electrically connected to the ceramic green body for applying a first voltage and a second voltage to the ceramic green body; and
and the switch module is electrically connected with the power supply and the ceramic green body and is used for electrically connecting the power supply to different positions of the ceramic green body in a time-sharing manner.
9. The ceramic sintering apparatus of claim 8, further comprising a first electrode and at least two second electrodes spaced apart and insulated from each other on the ceramic green body;
the power supply is used for applying the first voltage to the first electrode and applying the second voltage to the at least two second electrodes in a time-sharing manner.
10. The ceramic sintering apparatus of claim 8, further comprising a heating module disposed outside the sintering furnace, the heating module being configured to heat the ceramic green body during sintering of the ceramic green body.
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