CN110395996B - Preparation method for improving electric field auxiliary sintering capacity - Google Patents
Preparation method for improving electric field auxiliary sintering capacity Download PDFInfo
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- CN110395996B CN110395996B CN201910724308.3A CN201910724308A CN110395996B CN 110395996 B CN110395996 B CN 110395996B CN 201910724308 A CN201910724308 A CN 201910724308A CN 110395996 B CN110395996 B CN 110395996B
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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
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- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
- C04B41/51—Metallising, e.g. infiltration of sintered ceramic preforms with molten metal
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- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
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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]
Abstract
A preparation method for improving electric field auxiliary sintering capacity comprises the following steps: providing a ceramic green body; arranging an insulating layer on the outer surface of the ceramic green body, and attaching the insulating layer to the ceramic green body to form a sintering precursor; and applying an electric field and heating treatment to the sintering precursor to obtain the ceramic. According to the preparation method for improving the auxiliary sintering capacity of the electric field, provided by the embodiment of the invention, the insulating layer is arranged on the surface of the ceramic green body, so that the generation of creeping discharge can be inhibited, the electric field intensity generated by the electric field applied to the ceramic green body is increased, and the threshold value of creeping discharge generated by the ceramic green body is increased; the preparation method can carry out electric field auxiliary sintering on ceramic green bodies with various sizes; and the preparation method has simple process flow.
Description
Technical Field
The invention relates to the technical field of ceramic material preparation, in particular to a preparation method for improving electric field auxiliary sintering capacity.
Background
Electric field assisted sintering is an emerging sintering technique in recent decades for sintering dense metal or ceramic powders. In the electric field assisted sintering process, not only the ceramic green body or the metal green body needs to be heated and insulated, but also an electric field with certain strength can uniformly pass through the green body as much as possible. Compared with the traditional sintering technology, the electric field assisted sintering has the advantages of low sintering densification temperature, short sintering time, smaller sintered product crystal grain and the like.
In the reported electric field assisted sintering research of ceramic materials, the electric field intensity applied to the green body is generally not high, because when a high-intensity electric field is applied to the electric field assisted sintering of ceramic, the surface of the green body may generate surface flashover due to overhigh voltage, that is, air breakdown occurs on the surface of the green body, and current does not flow through the green body, so that the sintering fails, and the experiment or application cannot be carried out. For example, when YSZ flash firing studies were conducted, the green body surface broke down when the voltage across the green body reached 7kV and the green body temperature exceeded 300 ℃. In addition, currently, only axially symmetric shaped ceramic green bodies can be processed using electric field assisted sintering techniques.
Disclosure of Invention
In view of the above, it is desirable to provide a preparation method for suppressing creeping discharge, thereby improving the electric field assisted sintering capability.
A preparation method for improving electric field auxiliary sintering capacity comprises the following steps:
providing a ceramic green body;
arranging an insulating layer on the outer surface of the ceramic green body, and attaching the insulating layer to the ceramic green body to form a sintering precursor; and
and applying an electric field and heating treatment to the sintering precursor to obtain the ceramic.
Further, disposing the insulating layer includes applying an insulating paint to a surface of the ceramic green body.
Further, the temperature of the heating treatment of the sintering precursor is lower than 300 ℃.
Further, disposing the insulating layer includes embedding the ceramic green body in an insulating powder and performing tableting so that the ceramic green body is not exposed to the insulating powder.
Further, the chemical composition of the insulating powder is the same as that of the ceramic green body.
Further, the shape of the ceramic green body is an axisymmetric cubic structure.
Further, before the insulating layer is provided on the surface of the ceramic green body, a step of providing an electrode to the ceramic green body is further included.
Further, the step of disposing an electrode includes:
coating metal slurry on two ends of the ceramic green body;
and solidifying the metal slurry to form the electrode.
Further, the step of disposing electrodes comprises attaching metal sheets to both ends of the ceramic green body, the metal sheets being closely attached to the ceramic green body.
According to the preparation method for improving the auxiliary sintering capacity of the electric field, provided by the embodiment of the invention, the insulating layer is arranged on the surface of the ceramic green body, so that the generation of creeping discharge can be inhibited, the electric field intensity generated by the electric field applied to the ceramic green body is increased, and the threshold value of creeping discharge generated by the ceramic green body is increased; the preparation method can carry out electric field auxiliary sintering on ceramic green bodies with various sizes; and the preparation method has simple process flow.
Drawings
Fig. 1 is a flowchart of a preparation method for improving electric field assisted sintering capability according to an embodiment of the present invention.
FIG. 2 is a scanning electron microscope test chart of the ceramics prepared by the embodiment of the present invention.
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.
Referring to fig. 1, a flow chart of a manufacturing method for improving electric field assisted sintering capability according to an embodiment of the present invention includes the following steps:
step S1: providing a ceramic green body;
step S2: arranging an insulating layer on the outer surface of the ceramic green body, wherein the insulating layer is tightly attached to the ceramic green body to form a sintering precursor;
step S3: and applying an electric field and heating the sintering precursor to obtain the ceramic.
Through set up the insulating layer on the surface of ceramic green, right when ceramic green carries out the electric field treatment of exerting, the insulating layer avoids ceramic green and air contact makes the electric current that discharges and produce flows along ceramic green, prevents that the electric current from the green surface flow through the breakdown air and produce creeping discharge.
In step S1, the shape of the ceramic green body is an arbitrary shape. Preferably, the ceramic green body is in the shape of an axisymmetric cube, such as a rectangular parallelepiped, a cube, a prism, a cylinder, a sphere, and the like.
The ceramic green body is formed by tabletting ceramic powder through a pressing process, and the pressing process of the ceramic green body, the chemical components and the particle size of the ceramic powder and the binder removal process after tabletting can be selected at will.
In step S2, the providing of the insulating layer includes at least one of coating an insulating coating on a surface of the ceramic green body, embedding the ceramic green body in an insulating powder, and tabletting. Through the arrangement of the insulating layer, the edge surface of the ceramic green body in contact with air is reduced or eliminated, so that the generation of edge surface discharge when the ceramic green body is discharged is effectively inhibited.
In a specific embodiment, a surface of the ceramic green body is coated with a silicon sulfide rubber coating, after the silicon sulfide rubber coating is cured, the silicon sulfide rubber coating forms the insulating layer on the surface of the ceramic green body, and the insulating layer can increase a threshold of a flashover voltage, effectively inhibit surface discharge of the ceramic green body, and improve electric field intensity applied to a sintering precursor.
Further, the insulating coating does not chemically react with the ceramic green body at normal temperature or when an electric field is applied.
Further, in this embodiment, the temperature at which the ceramic is sintered is less than 300 ℃, and if the temperature is too high, the silicone sulfide rubber coating will be burned before sintering begins, and the surface insulation performance will be affected.
In another embodiment, the ceramic green body is embedded in an insulating powder having the same chemical composition as the ceramic green body, the ceramic green body is not exposed to the insulating powder, pressure is applied to the insulating powder and the ceramic green body, the insulating powder is tightly loaded on the ceramic green body, the insulating powder and the ceramic green body are in sufficient contact, and contact between the ceramic green body and air is reduced or eliminated, so that creeping discharge is suppressed. By adopting the method for arranging the insulating layer on the ceramic green body in the embodiment, the sintering precursor can be heated and insulated in a wider range, for example, more than 300 ℃.
The pressure is 0.1MPa-10 MPa.
Further, in the present embodiment, the structure of the ceramic green body is preferably an equiaxed symmetrical structure of a rectangular parallelepiped, a cube, a cylinder, and a sphere, and the ceramic green body is prevented from being broken or crushed due to excessive pressure when pressure is applied.
Before the surface of the ceramic green body is provided with the insulating layer, the method further comprises the step of arranging electrodes on the ceramic green body, namely arranging metal conducting layers at two ends of the ceramic green body, and connecting the ceramic green body to two ends of a power supply through the metal conducting layers and a lead, so that an electric field can be applied to the sintering precursor through the lead.
In one embodiment, the step of disposing the electrodes includes coating metal paste, such as metal material, for example, gold paste, silver paste, and platinum paste, on both ends of the ceramic green body, and then performing a heat treatment on the ceramic green body coated with the metal paste to cure the metal paste on both ends of the ceramic green body.
In another embodiment, the step of disposing the electrodes comprises attaching metal sheets to both ends of the ceramic green body, wherein the metal sheets and the ceramic green body need to be tightly attached to each other, otherwise the sintering quality of the ceramic is affected.
In step S3, the voltage applied to the sintering precursor includes various forms such as dc voltage, ac voltage, and pulse voltage, and the higher the electric field intensity of the voltage, the better.
The present invention will be specifically described below with reference to examples.
Examples
Providing zirconium oxide ceramic powder, wherein the average particle size of the zirconium oxide ceramic powder is 100nm, and tabletting the zirconium oxide ceramic powder to form a ceramic green body; then coating silver paste on two ends of the ceramic green body, and after heat treatment, loading the silver paste on two ends of the ceramic green body to form silver electrodes; embedding a ceramic green body with a silver electrode into insulating powder and applying pressure to enable the insulating powder to be loaded on the ceramic green body to obtain a sintering precursor; and finally, applying an electric field to the sintered precursor through the electrode to obtain the sintered ceramic, wherein the electric field intensity generated by the voltage is 6kV/cm at most, and the time for applying the electric field is 30 s.
Comparative example
In contrast to the examples: the surface of the ceramic green body is not coated with the insulating powder.
Other steps are the same as the embodiment and are not described herein again.
The ceramics prepared in the examples are rapidly sintered and densified within a short time, the compactness of the ceramics is 93%, please refer to fig. 2, fig. 2 is a scanning electron microscope test chart of the ceramics prepared in the examples, and as can be seen from fig. 2, the dense structure of the ceramics prepared after electric field assisted sintering. The ceramics sintered in the comparative example underwent planar flashover at an electric field strength of 5.5kV/cm, resulting in failure to achieve electric field assisted sintering of the ceramic green body.
According to the preparation method for improving the auxiliary sintering capacity of the electric field, provided by the embodiment of the invention, the insulating layer is arranged on the surface of the ceramic green body, so that the generation of creeping discharge can be inhibited, the electric field intensity generated by the electric field applied to the ceramic green body is increased, and the threshold value of creeping discharge generated by the ceramic green body is increased; the preparation method can carry out electric field auxiliary sintering on ceramic green bodies with various sizes; and the preparation method has simple process flow.
Although the present invention has been described in detail with reference to the preferred embodiments, it will 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 invention.
Claims (5)
1. A preparation method for improving electric field auxiliary sintering capacity is characterized by comprising the following steps:
providing a ceramic green body;
arranging an insulating layer on the outer surface of the ceramic green body, wherein the insulating layer is attached to the ceramic green body to form a sintering precursor, and the insulating layer is used for avoiding the ceramic green body from contacting air; and
applying an electric field and heating treatment to the sintering precursor to obtain ceramic;
wherein the step of arranging the insulating layer comprises the step of coating an insulating coating on the surface of the ceramic green body, and the temperature for heating the sintering precursor is lower than 300 ℃; or disposing the insulating layer includes embedding the ceramic green body in an insulating powder and tabletting so that the ceramic green body is not exposed to the insulating powder, the ceramic green body having an axisymmetric cubic structure.
2. The method for preparing electric field assisted sintering capable of being enhanced according to claim 1, wherein the chemical composition of the insulating powder is the same as that of the ceramic green body.
3. The method according to claim 1, further comprising a step of providing an electrode on the ceramic green body before providing an insulating layer on the surface of the ceramic green body.
4. The method for preparing electric field assisted sintering capable of being enhanced according to claim 3, wherein the step of arranging electrodes comprises:
coating metal slurry on two ends of the ceramic green body;
and solidifying the metal slurry to form the electrode.
5. The method according to claim 3, wherein the step of disposing electrodes comprises attaching metal sheets to both ends of the ceramic green body, wherein the metal sheets are closely attached to the ceramic green body.
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