CN107032765B - Method for rapidly sintering alumina ceramic in solid phase at high temperature - Google Patents

Method for rapidly sintering alumina ceramic in solid phase at high temperature Download PDF

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CN107032765B
CN107032765B CN201710244327.7A CN201710244327A CN107032765B CN 107032765 B CN107032765 B CN 107032765B CN 201710244327 A CN201710244327 A CN 201710244327A CN 107032765 B CN107032765 B CN 107032765B
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sintering
temperature
alumina
alumina ceramic
rapid
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CN107032765A (en
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张金咏
汪信志
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Wuhan University of Technology WUT
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Wuhan University of Technology WUT
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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
    • C04B35/10—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 aluminium oxide
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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
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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
    • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
    • C04B2235/6562—Heating rate
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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
    • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
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Abstract

The invention belongs to the technical field of ceramic sintering, and particularly relates to a method for rapidly sintering alumina ceramic in a high-temperature solid phase manner. The method comprises the following steps: drying the alumina powder to prepare a wafer-shaped blank; rapidly heating to a set sintering temperature at a heating rate of 500-600 ℃/s under a pressureless condition, wherein the sintering temperature is 200-300 ℃ higher than the conventional sintering temperature but lower than the melting point of the alumina ceramic, keeping the temperature for a short time, and naturally cooling to obtain the high-density alumina ceramic. Compared with the traditional sintering method, the rapid high-temperature solid-phase sintering alumina ceramic technology has the advantages of high heating rate, high sintering temperature, short sintering time and short production period.

Description

Method for rapidly sintering alumina ceramic in solid phase at high temperature
Technical Field
The invention belongs to the technical field of ceramic sintering, and particularly relates to a method for rapidly sintering alumina ceramic in a high-temperature solid phase manner.
Background
The alumina ceramic is one of ceramic materials with the widest application, the widest application and the largest output in oxide ceramics, has the superior performances of high mechanical strength, high resistivity, good electrical insulation performance, high hardness and melting point, good corrosion resistance, good chemical stability, good optical property, good ionic conductivity and the like under certain conditions, and has wide application prospects in the fields of machinery, electrical engineering, chemical engineering, medicine, buildings and the like.
The alumina sintering is a long process, and the traditional pressureless sintering process requires high sintering temperature and long heat preservation time, so that the problems of serious time and energy consumption exist. In response to this situation, numerous researchers have proposed solutions to improve the sintering process. Firstly, a sintering aid is doped. The sintering aid can form a liquid phase with the aluminum oxide material in the sintering process to promote the particle rearrangement and mass transfer process so as to ensure the mass transferThe mass mechanism is changed from solid phase diffusion to liquid phase diffusion. However, the sintering aid affects the air vent discharge in the sintering process of the alumina ceramic, such as: addition of TiO2The alumina product is easy to form crystal inner holes, thereby influencing the compactness of the green body. Second, new sintering methods have emerged that do not require sintering aids. Such as Spark Plasma Sintering (SPS), Flash Plasma Sintering (FS), and Flash Sintering. The new sintering method is that an external electric field directly passes through a die or sintering powder, and the powder is heated by joule heat, so that the heating mode is more efficient. The heating rate of the traditional sintering method, such as pressureless sintering and hot-pressing sintering, is 10-50 ℃/min, and compared with the traditional sintering method, the heating rate of the new sintering method is higher, and the heating rate reaches more than hundreds of degrees centigrade per minute, so that the rapid densification of the material can be realized. However, since these new sintering methods depend on the conductivity of the powder, the applied auxiliary electric field, the applied pressure, the mold, and so on, this limits the wide application of these new sintering methods. Therefore, the attention of the researchers is paid to whether the rapid densification can be realized under the conditions of no pressure and no action of any external auxiliary field. Brook et al proposed a non-pressure rapid sintering technique (fast sintering) where the sample was heated up to several hundred degrees celsius per minute under non-pressure conditions, confirming that rapid heating promotes the densification process. However, the pressureless rapid sintering technique does not ultimately achieve densification of the material because of the many closed pores in the article, which takes more time to eliminate.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for quickly sintering alumina ceramic in a solid phase at a high temperature.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for rapidly sintering alumina ceramics in a high-temperature solid phase comprises the following steps:
(1) weighing a certain amount of alumina powder, drying, and then carrying out rough blank molding to prepare a wafer-shaped blank;
(2) placing the disk-shaped blank formed in the step (1) in a rapid heating device;
(3) and (3) rapidly heating to a set sintering temperature at a certain heating rate, keeping the temperature for a short time, and naturally cooling to obtain the high-density alumina ceramic.
In the scheme, the heating rate is 500-600 ℃/s.
In the scheme, the sintering temperature is 200-300 ℃ higher than the conventional sintering temperature but lower than the melting point temperature of the alumina ceramic, and is specifically 1650-1850 ℃.
In the scheme, the time for rapid temperature rise is 3-4 s.
In the scheme, the short heat preservation time is 1-2 min.
In the above scheme, the drying in step (1) is: drying under vacuum at 60 deg.C for 24 hr.
In the scheme, the rough blank in the step (1) is formed into: pressing aluminum oxide powder into a disk-shaped blank under the pressure of 200MPa, wherein the density of the blank is 60%.
In the above scheme, the rapid heating device in step (2) is a non-pressure environment heating device.
The invention has the beneficial effects that: (1) compared with the traditional sintering method, the rapid high-temperature solid-phase sintering alumina ceramic technology has the advantages of high heating rate, high sintering temperature, short sintering time and short production period; (2) in the method, the used raw materials are pure or commercial grade powder, and the purity and the grain diameter are not required, so that the production cost can be reduced; (3) the method has simple process and short production period, and the prepared alumina ceramic has higher density, meets the requirements of industrial use, and is beneficial to mass production of the alumina ceramic.
Detailed Description
In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.
Example 1
A preparation method for preparing alumina ceramic under ultra-fast pressure comprises the following steps:
(1) powder treatment: and putting the alumina powder raw materials used in the experiment into a drying oven to be dried for 24 hours.
(2) Preparing an alumina rough blank: weighing 1.5g of the dried alumina powder in the step (1), and pressing into a wafer-shaped rough blank with the diameter of 1.5cm by using a tablet press, wherein the pressure is 8MPa, and the pressure maintaining time is 2 min; and (3) placing the pressed disc-shaped rough blank into a cold isostatic press, carrying out cold isostatic pressing treatment on the sample under the pressure of 200MPa, and keeping the pressure for 5min to ensure that the blank has higher initial density (the compactness of the initial blank is about 60 percent) so as to be beneficial to sintering of subsequent products.
(3) And (3) sintering: placing the treated alumina primary blank in the step (2) into TiB in a rapid heating device2And (3) starting to heat up in a sintering heating tank, wherein the heating rate is over 500-600 ℃/s, the sintering temperature is set to be 1693 ℃ in the embodiment, the sintering temperature is reached within 3s, then the temperature is kept for 1min at the temperature, and then the high-density alumina ceramic is obtained through natural cooling, wherein the measured relative density reaches 99.4%.
Wherein, the measuring method of the relative density comprises the following steps: ceramic samples generally have open pores and closed pores therein, and the apparent density of the sample to be measured, which is the mass of the sample/(the actual volume of the sample + the volume of the open pores + the volume of the closed pores), can be determined by including almost all the pores in the sample. The relative density can be calculated by adopting the apparent density, so that more accurate density can be calculated. The apparent density and relative density are calculated by the formula:
ρ＝ρwater (W)W1/(W3-W2)
ρRelative to each other＝ρ/ρTrue
Where ρ is the apparent density; rhoWater (W)Density of water, W1-the mass of the sample in air; w2-the mass of the sample immersed in water; w3-the mass of the sample in air after immersion; rhoTrueTrue density of alumina ceramics
Example 2
A preparation method for preparing alumina ceramic under ultra-fast pressure comprises the following steps:
(1) powder treatment: and putting the alumina powder raw materials used in the experiment into a drying oven to be dried for 24 hours.
(2) Preparing an alumina rough blank: weighing 1.5g of the dried alumina powder in the step 1), and pressing into a wafer-shaped rough blank with the diameter of 1.5cm by using a tablet press, wherein the pressure is 8MPa, and the pressure maintaining time is 2 min; and placing the pressed disc-shaped rough blank into a cold isostatic press, carrying out cold isostatic pressing treatment on the sample under the pressure of 200MPa, and keeping the pressure for 5min to ensure that the sample has higher initial density so as to be beneficial to sintering of subsequent products.
(3) And (3) sintering: wrapping the alumina rough blank treated in the step (2) with graphite paper, putting the wrapped alumina rough blank into a graphite mold in a rapid heating device, starting to heat up, wherein the heating rate is more than 500-600 ℃/s, the sintering temperature is 1798 ℃ in the embodiment, reaching the sintering temperature within 3-4 s, preserving the heat for 1min at the temperature, and then naturally cooling to obtain the high-density alumina ceramic, wherein the relative density is 99.6% through measurement.
It is apparent that the above embodiments are only examples for clearly illustrating and do not limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications are therefore intended to be included within the scope of the invention as claimed.

Claims (4)

1. A method for rapidly sintering alumina ceramics in a high-temperature solid phase manner is characterized by comprising the following steps:
(1) weighing a certain amount of alumina powder, drying, and then carrying out rough blank molding to prepare a wafer-shaped blank;
(2) placing the wafer-shaped blank formed in the step (1) into a rapid heating device, wherein the rapid heating device is a non-pressure environment heating device;
(3) rapidly heating to a set sintering temperature at a certain heating rate, keeping the temperature for a short time, and naturally cooling to obtain high-density alumina ceramic; the heating rate is 500 ℃/s-600 ℃/s, the sintering temperature is 1650-1850 ℃, the time of rapid heating is 3-4 s, and the time of transient heat preservation is 1-2 min.
2. The method for rapid high-temperature solid-phase sintering of alumina ceramics according to claim 1, wherein the drying in step (1) is: drying under vacuum at 60 deg.C for 24 hr.
3. The method for rapid high-temperature solid-phase sintering of alumina ceramics according to claim 1, wherein the rough blank of step (1) is formed into: the alumina powder was pressed into a disk-like green body under a pressure of 200 MPa.
4. The method for rapid high-temperature solid-phase sintering of alumina ceramics according to claim 1, wherein the compactness of the green body in the step (1) is 60%.
CN201710244327.7A 2017-04-14 2017-04-14 Method for rapidly sintering alumina ceramic in solid phase at high temperature Expired - Fee Related CN107032765B (en)

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Publication number Priority date Publication date Assignee Title
CN112174644B (en) * 2020-09-07 2022-05-31 中国科学院上海光学精密机械研究所 Method for rapidly sintering compact nanocrystalline ceramic under no pressure

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
"Ultra-fast firing: Effect of heating rate on sintering of 3YSZ, with and without an electric field";W. Ji等;《Journal of the European Ceramic Society》;20170207;第37卷;第2549页3.1. Heating rates，2551页5. Conclusions *
Fancheng Meng等.Rapid Densification of Nano-Grained Alumina by High Temperature and Pressure with a Very High Heating Rate.《J. Am. Ceram. Soc.》.2007,第90卷(第4期),摘要，II. Experimental Procedure. *
Rapid Densification of Nano-Grained Alumina by High Temperature and Pressure with a Very High Heating Rate;Fancheng Meng等;《J. Am. Ceram. Soc.》;20070320;第90卷(第4期);摘要，II. Experimental Procedure *

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