Oxygen-deficient oxide ceramic material and preparation method thereof

Abstract

The invention relates to an anoxic oxide ceramic material and a preparation method thereof. The preparation method comprises the following steps: pressing oxide ceramic powder into a green body; preheating the green body to reach a conductive temperature; turning on a power supply to flash-burn the oxide green body; after flash sintering is finished, the sintered oxide ceramic is crushed and sieved; carrying out secondary sintering in a low oxygen partial pressure environment; and maintaining for a preset time period to obtain the sintered oxygen-deficient oxide ceramic. According to the method, the oxide ceramic material is rapidly deoxidized by utilizing a flash sintering process, and the deoxidized powder is secondarily sintered in a low oxygen partial pressure environment, so that rapid preparation of the oxygen-deficient oxide ceramic material is realized, and a new thought for design and preparation of the oxygen-deficient oxide ceramic material is provided.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and in particular relates to an oxygen-deficient oxide ceramic material and a preparation method thereof. Background Art

[0002] Oxygen-deficient oxide ceramic materials have important application prospects in the fields of gas sensors, solid oxide fuel cells, photocatalysis, etc. For example, when oxygen-deficient oxide ceramic materials are used as photocatalysts, their large number of oxygen vacancy defects enhance the absorption of visible light by oxide ceramics, stimulate the generation of surfactants, and promote redox reactions between active substances and pollutants, which have good application prospects in the field of water pollution control. In addition, oxygen-deficient oxide ceramic materials can also be used in biomedicine. Oxygen-deficient bioceramics are known as the fourth generation of bioceramics. With the presence of oxygen vacancies, they can convert light into heat and active oxygen, which are used for photothermal and photodynamic therapy, respectively, and simultaneously feedback infrared and photoacoustic images.

[0003] When using the traditional high-temperature sintering method to sinter oxide ceramics, it is necessary to keep the temperature in a reducing atmosphere for a long time, which has problems such as high energy consumption, long process, high cost, etc., and the stoichiometry of the oxygen-deficient ceramics prepared is difficult to control. Therefore, it is urgent to propose a new method for preparing oxygen-deficient oxide ceramic materials. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, the present invention provides an oxygen-deficient oxide ceramic material and a preparation method thereof.

[0005] A method for preparing an oxygen-deficient oxide ceramic material comprises the following steps:

[0006] S1. The oxide raw material powder is pressed into a green body and preheated;

[0007] S2. applying direct current to the preheated oxide powder green body to trigger the flash burning phenomenon and rapidly deoxidize the oxide powder green body;

[0008] S3. The oxide ceramic obtained by flash deoxidation is crushed and sieved to obtain an oxygen-deficient oxide powder;

[0009] S4. Under a low oxygen partial pressure environment, the oxygen-deficient oxide powder is subjected to secondary sintering to complete densification, thereby obtaining an oxygen-deficient oxide ceramic material.

[0010] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the oxide raw material powder includes cerium oxide, zirconium oxide, uranium dioxide or yttrium oxide.

[0011] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the preheating temperature is 200-1200°C.

[0012] According to the above aspects and any possible implementation, a further implementation is provided, wherein the electric field strength of the direct current in S2 is 10 to 1000 V / cm, and the current density is 10 to 5000 A / cm 2 .

[0013] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the flash deoxidation time in S4 is 10 to 600 seconds.

[0014] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the secondary sintering method is hot pressing sintering, spark plasma sintering or pressureless sintering.

[0015] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the low oxygen partial pressure environment is a vacuum environment or a gas protection environment.

[0016] According to the above aspects and any possible implementation, an implementation is further provided, wherein the electric field strength of the direct current in S2 is 50 V / cm and the current density is 283 A / cm 2 .

[0017] According to the above aspects and any possible implementation, an implementation is further provided, wherein the electric field strength of the direct current in S2 is 200 V / cm, and the current density is 566 A / cm 2 .

[0018] The invention also provides an oxygen-deficient oxide ceramic material, which is obtained by adopting the preparation method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The preparation method of the oxygen-deficient oxide ceramic material of the present invention comprises: pressing the oxide raw material powder into a green body and preheating it; applying direct current to the preheated oxide powder green body to trigger the flash burning phenomenon and quickly deoxidize the oxide powder green body; crushing and screening the oxide ceramic obtained after flash burning and deoxidation to obtain oxygen-deficient oxide powder; and secondary sintering the oxygen-deficient oxide powder under a low oxygen partial pressure environment to complete densification, thereby obtaining the oxygen-deficient oxide ceramic material. Compared with the prior art, the present invention utilizes the electrochemical reduction effect of the flash burning process to solve the problems of low internal deoxidation efficiency, high production cost and long process flow of oxygen-deficient oxide ceramic green bodies, and effectively improves the preparation efficiency of oxygen-deficient oxide ceramics. In addition, the secondary sintering process under low oxygen partial pressure avoids the problems of pores and difficulty in densification of oxide ceramics caused by deoxidation, and can effectively maintain its stoichiometry. The present invention provides a new idea for the efficient preparation of oxygen-deficient oxide ceramic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0022] In order to better understand the technical solution of the present invention, the content of the present invention includes but is not limited to the specific implementation methods described below, and similar technologies and methods should be considered to be within the scope of protection of the present invention. In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] It should be clear that the embodiments described in the present invention are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0025] like Figure 1 As shown, the present invention provides a method for preparing an oxygen-deficient oxide ceramic material, comprising the following steps:

[0026] S1, pressing the oxide powder into a green body;

[0027] S2, preheating the oxide powder green body and applying direct current to it to trigger the flash burning phenomenon;

[0028] S3, using the electrochemical reduction reaction of the flash burning process to quickly deoxidize the oxide powder green body;

[0029] S4, crushing and sieving the oxide ceramics after flash deoxidation to obtain oxygen-deficient oxide powder;

[0030] S5. Under a low oxygen partial pressure environment, the oxygen-deficient oxide powder is subjected to secondary sintering to complete densification, thereby obtaining an oxygen-deficient oxide ceramic material.

[0031] The present invention adopts a two-step method for preparation. The first step is to introduce defects by flash burning to create oxygen vacancies. The second step is to re-densify the deoxidized powder by hot pressing sintering, spark plasma sintering, pressureless sintering and other means.

[0032] Flash burning is a sintering process that can achieve rapid heating and densification under the assistance of an electric field, greatly shortening the sintering time. The present invention uses it to apply an electric field to the preheated oxide powder green body to produce flash burning; and there is an electrochemical reaction during the flash burning process. At the positive electrode, At the negative electrode, in, is an oxygen atom; is a positively charged oxygen vacancy; e' is an electron; is an uncharged oxygen vacancy.

[0033] Preferably, the oxide ceramic material can be selected from plasma conductors such as cerium oxide, zirconium oxide, uranium dioxide, yttria-stabilized zirconia (8YSZ), etc., with a particle size ranging from 50 to 1000 nm.

[0034] Preferably, the preheating temperature of the oxide ceramic is between 200 and 1200° C. The selection of this temperature range is based on the properties of the oxide ceramic itself. Most oxide ceramics are insulating at room temperature. Only when the temperature is preheated to its conductive temperature can they conduct electricity and achieve flash burning.

[0035] Preferably, the principle of flash electrochemical reaction is used, and an external power source is connected to the oxide ceramic green body to form a closed loop. Under conditions such as sufficient electric field strength, current density and ambient temperature, flash occurs, and the flash process is accompanied by an electrochemical deoxidation process. At the positive electrode of the oxide ceramic, the oxygen atoms in the lattice of the oxide ceramic undergo an electrochemical reaction to form positively charged oxygen vacancies and oxygen molecules. The positively charged oxygen ion vacancies undergo an electrochemical reaction at the negative electrode with the electrons injected by the external electric field to form uncharged oxygen vacancies. The more oxygen vacancies there are, the more deoxidation there is, thereby achieving rapid deoxidation.

[0036] Preferably, the electric field strength of the direct current is 10 to 1000 V / cm, and the current density is 10 to 5000 A / cm 2Within this range, external current can pass through the oxide ceramic material to generate sufficient Joule heat to trigger flash combustion, thereby causing electrochemical reaction to achieve deoxidation. The flash deoxidation time is 10 to 600 seconds. The selection of this range depends on the size and type of the oxide ceramic sample. If the sample size is large and the conductivity is poor, the required deoxidation time will be extended.

[0037] Preferably, the secondary sintering method in a low oxygen partial pressure environment is based on the previously deoxidized material, which is crushed into powder and then re-sintered to prepare a dense sintered body, specifically using hot pressing sintering, spark plasma sintering or pressureless sintering.

[0038] Preferably, the low oxygen partial pressure environment is a vacuum environment or a gas protection environment, and the gas protection environment is, for example, argon, hydrogen, carbon monoxide or nitrogen, or a mixed gas of nitrogen and carbon monoxide.

[0039] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0040] Example 1

[0041] A two-step method for preparing an oxygen-deficient oxide ceramic material comprises the following steps:

[0042] S1. Press cerium oxide powder with a particle size of 50 nm into a green body. The green body of cerium oxide ceramics is in the shape of a "round cake" with a diameter of 15 mm and a thickness of 2 mm.

[0043] S2. Start the induction heating device to preheat the cerium oxide ceramic green body to 700° C. so that the cerium oxide ceramic has a certain conductivity.

[0044] S3, start the DC pulse power supply, apply an electric field to the green body through the positive and negative electrodes, and set the power supply output parameters to 50V and 0.5kA. After the flash start, the voltage gradually decreases from 50V to 12.2V and remains stable. At the same time, the current gradually increases from 0kA to 0.5kA, and the current density is 283A / cm 2 , and maintain for 60s to achieve rapid deoxygenation.

[0045] S4. The deoxidized cerium oxide ceramic is crushed and sieved to obtain an oxygen-deficient oxide powder with a mesh size of 40. Under this mesh size condition, the powder has good fluidity, small particle size, high activity, and is an oxygen-deficient oxide powder.

[0046] S5. Take an appropriate amount of powder and put it into a hot pressing mold with an inner diameter of 10 mm, and hot press and sinter for 30 minutes at 1200° C., 30 MPa and a vacuum degree of 10 Pa to obtain oxygen-deficient cerium oxide ceramics.

[0047] The invention starts with cerium oxide ceramic powder during sintering, which is then pressed into a cerium oxide ceramic green body and finally sintered into a cerium oxide ceramic block.

[0048] The cerium oxide ceramic sintered in Example 1 was tested using the Archimedean drainage method, and the calculation results showed that the density of the ceramic sintered in Example 1 was 96%. The sintered sample was black throughout, indicating that there were a large number of oxygen vacancies. The oxygen vacancies generated by flash burning would cause the cerium ions in the cerium oxide to be partially reduced to a metallic state, resulting in a blackening phenomenon at the cathode. As time accumulates, the blackening area will continue to expand.

[0049] Example 2

[0050] A two-step method for preparing an oxygen-deficient oxide ceramic material comprises the following steps:

[0051] S1. Zirconia powder with a powder particle size of 50 nm is pressed into a green body. The green body of zirconia ceramic is in the shape of a "round cake" with a diameter of 15 mm and a thickness of 5 mm.

[0052] S2. Start the induction heating device to preheat the zirconia ceramic green body to 800° C. so that the zirconia ceramic has a certain conductivity.

[0053] S3, start the DC pulse power supply, apply an electric field to the green body through the positive and negative electrodes, and set the power supply output parameters to 200V and 1kA. After the flash start, the voltage gradually decreases from 200V to 87V and remains stable. At the same time, the current gradually increases from 0kA to 1kA, and the current density is 566A / cm 2 , and maintain for 100s to achieve rapid deoxygenation.

[0054] S4. The deoxidized zirconia ceramic is crushed and sieved to obtain oxygen-deficient oxide powder with a mesh size of 40.

[0055] S5. Take an appropriate amount of powder and put it into a graphite mold with an inner diameter of 10 mm. Use a spark plasma sintering device at a pressure of 20 MPa and a vacuum degree of 10 -1 The oxygen-deficient zirconia ceramics were sintered at 1300 °C for 30 min.

[0056] The cerium oxide ceramic sintered in Example 2 was tested using the Archimedean drainage method, and the calculation results showed that the density of the ceramic sintered in Example 2 was 95%. The sintered sample was black throughout, indicating that there were a large number of oxygen vacancies.

[0057] Example 3

[0058] A two-step method for preparing an oxygen-deficient oxide ceramic material comprises the following steps:

[0059] S1. Press uranium dioxide powder with a particle size of 100 nm into a green body. The uranium dioxide ceramic green body is in the shape of a "round cake" with a diameter of 15 mm and a thickness of 10 mm.

[0060] S2. Start the induction heating device to preheat the uranium dioxide ceramic green body to 200° C. to make it have a certain conductivity.

[0061] S3, start the DC power supply, apply an electric field to the green body through the positive and negative electrodes, and set the power supply output parameters to 10V and 0.5kA. After the flash start, the voltage gradually decreases from 10V to 4.2V and remains stable. At the same time, the current gradually increases from 0kA to 0.5kA, and the current density is 283A / cm 2 , and maintain for 320s to achieve rapid deoxygenation.

[0062] S4. The deoxidized uranium dioxide ceramic is crushed and sieved to obtain oxygen-deficient oxide powder with a mesh size of 40.

[0063] S5. Take an appropriate amount of powder and put it into a hot pressing mold with an inner diameter of 10 mm, and heat it at 1200℃, 30MPa and 10 -3 Pa, and hot-pressed sintering for 20 min gave oxygen-deficient uranium dioxide ceramics.

[0064] The uranium dioxide ceramic sintered in Example 3 was tested using the Archimedean drainage method, and the calculation results showed that the density of the ceramic sintered in Example 3 was 98%.

[0065] Example 4

[0066] A two-step method for preparing an oxygen-deficient oxide ceramic material comprises the following steps:

[0067] S1. Yttria-stabilized zirconia (8YSZ) powder with a powder particle size of 50 nm is pressed into a green body. The 8YSZ ceramic green body is in the shape of a "round cake" with a diameter of 15 mm and a thickness of 10 mm. Positive and negative electrodes are set on both sides of the green body.

[0068] S2. Start the induction heating device to preheat the 8YSZ ceramic green body to 400° C. so that the 8YSZ ceramic has a certain conductivity.

[0069] S3, start the DC pulse power supply, apply an electric field to the green body through the positive and negative electrodes, and set the power supply output parameters to 800V and 0.1kA. After the flash start, the voltage gradually decreases from 800V to 355V and remains stable. At the same time, the current gradually increases from 0kA to 0.1kA, and the current density is 56.6A / cm 2 , and maintain for 100s to achieve rapid deoxygenation.

[0070] S4. The deoxidized 8YSZ ceramic is crushed and sieved to obtain oxygen-deficient oxide powder with a mesh size of 40.

[0071] S5. Take an appropriate amount of powder and put it into a graphite mold with an inner diameter of 10 mm. Sinter it for 30 minutes using a spark plasma sintering device under the conditions of a pressure of 45 MPa, a vacuum degree of 10 Pa, and a temperature of 1400° C. to obtain oxygen-deficient zirconia ceramics.

[0072] The 8YSZ ceramic sintered in Example 4 was tested using the Archimedean drainage method, and the calculation results showed that the density of the ceramic sintered in Example 4 was 96%. The sintered sample was black throughout, indicating that there were a large number of oxygen vacancies.

[0073] It can be seen from the above embodiments that the present invention provides a two-step method for preparing oxygen-deficient oxide ceramic materials, which utilizes a flash firing process to achieve rapid deoxidation of oxide ceramic materials, and performs secondary sintering on the deoxidized powder at a low oxygen partial pressure, thereby achieving rapid preparation of oxygen-deficient oxide ceramic materials, and providing a new idea for the design and preparation of oxygen-deficient oxide ceramic materials.

[0074] The above description shows and describes several preferred embodiments of the present invention, but as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not depart from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing an oxygen-deficient oxide ceramic material, characterized in that: The following steps are involved: S1. The oxide raw material powder is pressed into a green body and preheated; S2. applying direct current to the preheated oxide powder green body to trigger the flash burning phenomenon and rapidly deoxidize the oxide powder green body; S3. The oxide ceramic obtained by flash deoxidation is crushed and sieved to obtain an oxygen-deficient oxide powder; S4. Under a low oxygen partial pressure environment, the oxygen-deficient oxide powder is subjected to secondary sintering to complete densification, thereby obtaining an oxygen-deficient oxide ceramic material.

2. The method according to claim 1, characterized in that The oxide raw material powder includes cerium oxide, zirconium oxide, uranium dioxide or yttrium oxide.

3. The method according to claim 1 or 2, characterized in that: The preheating temperature is 200-1200°C.

4. The method according to claim 2, characterized in that: The electric field strength of the direct current in S2 is 10-1000 V / cm, and the current density is 10-5000 A / cm 2 .

5. The method according to claim 4, characterized in that The flash deoxidation time in S4 is 10 to 600 seconds.

6. The method according to claim 1, characterized in that The secondary sintering method is hot pressing sintering, spark plasma sintering or pressureless sintering.

7. The method according to claim 1, characterized in that The low oxygen partial pressure environment is a vacuum environment or a gas protection environment.

8. The method according to claim 4, characterized in that The electric field strength of the direct current in S2 is 50 V / cm and the current density is 283 A / cm 2 .

9. The method according to claim 4, characterized in that The electric field strength of the direct current in S2 is 200 V / cm and the current density is 566 A / cm 2 .

10. An oxygen-deficient oxide ceramic material, characterized in that: The material is obtained by the preparation method according to any one of claims 1 to 9.

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