CN111423240B - Two-stage sintering method for preparing ceramic and ceramic - Google Patents
Two-stage sintering method for preparing ceramic and ceramic Download PDFInfo
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- CN111423240B CN111423240B CN202010259231.XA CN202010259231A CN111423240B CN 111423240 B CN111423240 B CN 111423240B CN 202010259231 A CN202010259231 A CN 202010259231A CN 111423240 B CN111423240 B CN 111423240B
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/64—Burning or sintering processes
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/453—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zinc, tin, or bismuth oxides or solid solutions thereof with other oxides, e.g. zincates, stannates or bismuthates
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- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
- C04B2235/66—Specific sintering techniques, e.g. centrifugal sintering
- C04B2235/666—Applying a current during sintering, e.g. plasma sintering [SPS], electrical resistance heating or pulse electric current sintering [PECS]
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- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/74—Physical characteristics
- C04B2235/78—Grain sizes and shapes, product microstructures, e.g. acicular grains, equiaxed grains, platelet-structures
- C04B2235/785—Submicron sized grains, i.e. from 0,1 to 1 micron
Abstract
The invention provides a two-section sintering method for preparing ceramics, which comprises the following steps: providing a ceramic green body, and connecting two ends of the ceramic green body with a power supply; communicating the power source to apply a voltage to the ceramic green body; raising the voltage to a preset voltage value to enable the ceramic green body to generate surface discharge or internal discharge, and cutting off the power supply, thereby performing the first-step sintering; and connecting the power supply again, increasing the current flowing through the ceramic green body to a preset current value, maintaining for a preset time period, and then cutting off the power supply, thereby carrying out the second-step sintering to obtain the ceramic. The two-stage sintering method for preparing the ceramic provided by the invention can inhibit the growth of crystal grains. The invention also provides a ceramic sintered by applying the two-stage sintering method for preparing the ceramic.
Description
Technical Field
The invention relates to the technical field of ceramic material preparation, in particular to a two-section type sintering method for preparing ceramic and ceramic sintered by applying the two-section type sintering method for preparing ceramic.
Background
The ceramic material is a non-metal material with a wide application range, and can be used in the scientific and technological advanced fields of electronic instruments, biological medicine, aerospace and the like. The manufacture of ceramic materials requires high temperatures for a long time to sinter an otherwise relatively loose green body to full density. This means that the conventional ceramic manufacturing process requires a large amount of energy consumption and a long time.
The flash firing technology can reduce energy consumption in the ceramic sintering process, and is a novel electric field assisted sintering process, namely, proper alternating current or direct current voltage is applied to two ends of a ceramic green body, so that the ceramic green body can be highly densified within seconds to minutes, and the furnace temperature required by ceramic sintering is greatly reduced. However, the problems of excessive growth of ceramic grains and excessive grain size often occur during the flash firing process, thereby affecting the service performance of the ceramic material.
Disclosure of Invention
In view of the above, the present invention provides a method of sintering a ceramic capable of suppressing grain growth, thereby solving the above problems.
In addition, the invention also provides a ceramic sintered by applying the two-stage sintering method for preparing the ceramic.
The invention provides a two-section sintering method for preparing ceramics, which comprises the following steps:
providing a ceramic green body, and connecting two ends of the ceramic green body with a power supply;
communicating the power source to apply a voltage to the ceramic green body;
raising the voltage to a preset voltage value to enable the ceramic green body to generate surface discharge or internal discharge, and cutting off the power supply, thereby performing the first-step sintering; and
and connecting the power supply again, increasing the current flowing through the ceramic green body to a preset current value, maintaining for a preset time period, and then cutting off the power supply, thereby carrying out the second-step sintering to obtain the ceramic.
The invention also provides a ceramic sintered by applying the two-stage sintering method for preparing the ceramic, wherein the grain diameter of the ceramic is 100-500 nm.
According to the invention, high voltage is applied to two ends of the ceramic green body, the ceramic green body is subjected to surface discharge or internal discharge, and a power supply is cut off after the discharge is generated, so that crystal grains in the ceramic green body are prevented from overgrowing in the discharge process; and then switching on the power supply, increasing the current and maintaining for a period of time to rapidly sinter the ceramic green body. The two-step sintering can rapidly sinter the ceramic at room temperature (0-30 ℃), thereby not only reducing the temperature required by sintering the ceramic, but also inhibiting the growth of crystal grains.
Drawings
FIG. 1 is a flow chart of the preparation of the ceramic according to the preferred embodiment of the present invention.
FIG. 2 is a schematic structural diagram of an apparatus for sintering ceramics according to a preferred embodiment of the present invention.
FIG. 3 is a scanning electron micrograph of the ceramic prepared in example 1 of the present invention.
FIG. 4 is a scanning electron micrograph of the ceramic prepared in example 2 of the present invention.
Description of the main elements
Ceramic green body 10
Conducting wire 30
Fixing bracket 40
The following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection 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 in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Referring to fig. 1 and 2, a two-step sintering method for preparing a ceramic according to a preferred embodiment of the present invention comprises the following steps:
step S11, providing a ceramic green body 10, and connecting both ends of the ceramic green body 10 to a power supply 20.
Specifically, electrodes (not shown) may be formed at two ends of the ceramic green body 10 by gold spraying or conductive silver paste coating, and the two electrodes are respectively wound with wires 30, and the wires 30 are connected to the power source 20, so that the two electrodes are respectively connected to the power source 20. The electrode is made of gold or conductive silver paste.
The wire 30 is a metal wire with a high melting point. Specifically, the metal wire may include a platinum wire. In the present embodiment, the power supply 20 is a high voltage power supply. The power source 20 may be a dc power source or an ac power source. Preferably, the power supply 20 is an alternating current power supply. The ceramic crystal grains obtained by final sintering have better uniformity by using an alternating current power supply. It will be appreciated that the power source 20 may also be a square wave, pulsed or other various forms of power source.
The ceramic green body 10 is at least one of cylindrical, rectangular and dog-bone shaped. It is understood that the shape of the ceramic green body 10 may be other regular shapes. In the present embodiment, the ceramic green sheet 10 has a dog bone shape. The ceramic green body 10 may be made of zinc oxide.
As shown in fig. 2, in the present embodiment, when the ceramic green sheet 10 is connected to the power source 20, the ceramic green sheet 10 is suspended. Specifically, the lead 30 is fixed to the upper ends of the two fixing brackets 40 so that the ceramic green sheet 10 can be suspended between the two fixing brackets 40, the two ends of the ceramic green sheet 10 are connected to the power source 20 through the lead 30, and the ceramic green sheet 10 and the power source 20 form a closed loop through the lead 30. In other embodiments, the ceramic green body 10 may also be placed on a dielectric ceramic plate.
Step S12, the power source 20 is connected to apply a voltage to the ceramic green body 10.
Step S13, raising the voltage to a predetermined voltage value, causing creeping discharge or internal discharge of the ceramic green body 10, and cutting off the power supply 20, thereby performing the first sintering step.
In particular, the voltage is raised to the predetermined voltage value at a rate of 0.1-1 kV/s. Wherein the predetermined voltage value is a variation value, and the predetermined voltage value is related to the length of the ceramic green body 10. After raising the voltage to the predetermined voltage value, the field strength of the ceramic green body 10 is approximately 5 kV/cm.
When the current flowing through the ceramic green sheet 10 suddenly increases and the voltage across the ceramic green sheet 10 drops suddenly, it is judged that the ceramic green sheet 10 has creeping discharge or internal discharge.
Wherein the temperature of the first sintering step is less than or equal to 30 ℃.
Step S14, the power source 20 is turned on again, the current flowing through the ceramic green sheet 10 is increased to a predetermined current value, and the power source 20 is turned off after a predetermined period of time, thereby performing the second sintering to obtain the ceramic.
Wherein the predetermined current value is 10-150mA/mm2The predetermined period of time may be 1 min.
Wherein the temperature of the second sintering step is less than or equal to 30 ℃.
According to the invention, high voltage is applied to two ends of the ceramic green body, the ceramic green body is subjected to surface discharge or internal discharge, and a power supply is cut off after the discharge is generated, so that crystal grains in the ceramic green body are prevented from overgrowing in the discharge process; and then switching on the power supply, increasing the current and maintaining for a period of time to rapidly sinter the ceramic green body. The two-step sintering can rapidly sinter the ceramic at room temperature (0-30 ℃), thereby not only reducing the temperature required by sintering the ceramic, but also inhibiting the growth of crystal grains.
The invention also provides a ceramic sintered by applying the two-section sintering method for preparing the ceramic, wherein the grain diameter of the ceramic is 100-500nm, and the density of the ceramic is not less than 90%.
The present invention will be specifically described below with reference to examples.
Example 1
Firstly, winding wires at two ends of a zinc oxide ceramic green body in the shape of a dog bone, connecting the wires with a power supply, and fixing the wires on a fixing support to suspend the ceramic green body. Wherein the middle part of the dog bone shaped ceramic green body has a thickness of 2mm, a length of 20mm, a width of 3.5mm, and a grain size of 100 nm.
And secondly, switching on the power supply by adopting an alternating current power supply, then increasing the voltage at the rate of 0.5kV/s until the voltage at two ends of the ceramic green body suddenly drops and the passing current suddenly rises, and immediately switching off the power supply.
And thirdly, switching on the power supply again, increasing the current to 600mA, and switching off the power supply after maintaining for 1 minute to finish sintering.
Example 2
The difference from example 1 is: in the first step, the ceramic green body is in a cylindrical shape, wherein the diameter is 4mm, and the length is 20 mm; in the second step, a direct current power supply is adopted; in the third step the current is increased to 1A.
Referring to fig. 3 and 4, the sintered ceramics of examples 1-2 were respectively tested by scanning electron microscopy and compactness by archimedes drainage. The results show that the grain size of the sintered ceramic of example 1 is approximately 300nm, and the compactness is 92%; the grain size of the sintered ceramic of example 2 was approximately 230nm, and the degree of densification was 95%.
The density of the ceramic sintered by the two-stage sintering method for preparing the ceramic provided by the invention can reach more than 90 percent, the defects such as cracks and the like do not occur, the average grain size of the ceramic can be controlled below 500nm, and the growth of grains can be effectively inhibited.
According to the invention, the ceramic is sintered at room temperature, so that the environmental temperature required for sintering the ceramic is greatly reduced, and a large amount of energy consumption is reduced. Meanwhile, the two-section sintering method for preparing the ceramic has simple process flow, and does not need an additional heating device compared with the common flash firing process.
Although the embodiments of the present invention have been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the embodiments of the present invention.
Claims (7)
1. A two-stage sintering method for preparing ceramics is characterized by comprising the following steps:
providing a ceramic green body, and connecting two ends of the ceramic green body with a power supply;
communicating the power source to apply a voltage to the ceramic green body;
raising the voltage to a preset voltage value to enable the ceramic green body to generate surface discharge or internal discharge, and cutting off the power supply, thereby performing the first-step sintering; and
and connecting the power supply again, increasing the current flowing through the ceramic green body to a preset current value, maintaining for a preset time period, and then cutting off the power supply, thereby performing a second-step sintering to obtain the ceramic, wherein the temperature of the first-step sintering and the second-step sintering is less than or equal to 30 ℃.
2. The two-stage sintering process for the preparation of ceramics according to claim 1, characterized in that the rate of raising the voltage to the predetermined voltage value is 0.1-1 kV/s.
3. The two-stage sintering method for producing ceramic according to claim 1, wherein the predetermined current value is 10 to 150mA/mm2。
4. The two-stage sintering method for producing ceramic according to claim 1, wherein connecting both ends of the ceramic green body to the power supply comprises:
forming electrodes at two ends of the ceramic green body respectively; and
and connecting the two electrodes with the power supply respectively by using leads.
5. The two-stage sintering method for preparing ceramic according to claim 4, wherein the material of the electrode comprises gold or conductive silver paste.
6. The two-stage sintering method for producing ceramic according to claim 4, wherein the wire comprises a platinum wire.
7. The two-stage sintering process for preparing ceramic according to claim 1 wherein the power source is a dc power source or an ac power source.
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| CN112683062B (en) * | 2020-12-08 | 2022-09-02 | 国网江西省电力有限公司电力科学研究院 | Ultrafast sintering method and device for ceramic material |
| CN113405362A (en) * | 2021-06-23 | 2021-09-17 | 清华大学深圳国际研究生院 | Ceramic sintering device and ceramic sintering method |
| CN115650736B (en) * | 2022-10-10 | 2023-06-16 | 国网江西省电力有限公司电力科学研究院 | Ceramic room-temperature ultra-fast sintering method based on dielectric barrier discharge glue discharging treatment |
| CN115974560B (en) * | 2022-10-10 | 2024-03-12 | 国网江西省电力有限公司电力科学研究院 | Ceramic room temperature sintering method |
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| CN103708817A (en) * | 2013-12-19 | 2014-04-09 | 桂林电子科技大学 | High pressure-resistance leadless high-temperature ferroelectric ceramic and preparation method thereof |
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| CN103708817A (en) * | 2013-12-19 | 2014-04-09 | 桂林电子科技大学 | High pressure-resistance leadless high-temperature ferroelectric ceramic and preparation method thereof |
| CN108558398A (en) * | 2018-05-08 | 2018-09-21 | 北京科技大学 | A kind of method of pulsed discharge room temperature flash sintering nano ceramic material |
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