阅读说明：本技术 一种多孔氮化铝陶瓷材料的制备方法 (Preparation method of porous aluminum nitride ceramic material ) 是由 孙卫康 田静 李庆春 汤志强 茹红强 赵东萍 王春华 于 2019-10-12 设计创作，主要内容包括：本发明公开了一种多孔氮化铝陶瓷材料的制备方法,属多孔氮化铝陶瓷材料的制备领域,现有技术普遍使用造孔剂、发泡剂、冷冻干燥等方法制备多孔氮化铝陶瓷材料存在显著的缺陷：孔的形态不稳定有大量随机性的闭孔或大孔,孔径尺寸不统一,且分布不均。本发明为解决以上问题,首先采用空心氧化铝微珠作为反应原料,经离子渗碳氮处理后获得产物空心AlN微珠,且壳壁表面生成纳米级的穿孔；以此产物为原料,不添加任何造孔剂、发泡剂或使用冷冻干燥工艺,就可以烧结制备出具有极高的孔隙率、孔径结构均匀且有纳米尺寸的二级穿孔的多孔AlN材料,极大地改善了材料的过滤吸附、分离净化、载体催化、导热、介电性能,具有非常大的工业实用价值。(The invention discloses a preparation method of a porous aluminum nitride ceramic material, belonging to the field of preparation of porous aluminum nitride ceramic materials, wherein the porous aluminum nitride ceramic material prepared by commonly using methods such as pore-forming agent, foaming agent, freeze drying and the like in the prior art has the remarkable defects that: the pores are unstable in shape, have a large number of random closed pores or large pores, are not uniform in pore size, and are not uniformly distributed. In order to solve the problems, firstly, hollow alumina microspheres are adopted as reaction raw materials, the hollow AlN microspheres are obtained after ion carbonitriding treatment, and nano-scale perforations are generated on the surface of the shell wall; the product is used as a raw material, and a secondary perforated porous AlN material with extremely high porosity, uniform pore-size structure and nanometer size can be prepared by sintering without adding any pore-forming agent and foaming agent or using a freeze-drying process, so that the filtering, adsorption, separation and purification, carrier catalysis, heat conduction and dielectric properties of the material are greatly improved, and the product has great industrial practical value.)

1. A preparation method of a porous aluminum nitride ceramic material is characterized in that,

the method comprises the following steps: pretreatment, ion carbonitriding treatment, sedimentation, mixing and sintering.

2. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

the pretreatment is hollow Al₂O₃The particle size of the micro-beads is 100-500 mu m, the shell wall thickness is 15-75 mu m, and the purity is more than 99.5%.

3. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

the ion carbonitriding treatment and the vacuum ion carbonitriding heat treatment are carried out, the heating rate is 5-20 ℃/min, and the heat preservation time is 30-60 min.

4. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

in the ion carbonitriding treatment, carbon source gases comprise methane, propane and acetylene, a nitrogen source comprises nitrogen, the mass ratio of the carbon source to the nitrogen source is 1 (6-12), and the air pressure of a mixed gas source is 460-1280 Pa.

5. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

and sintering, wherein the heating rate is 3-8 ℃/min, and the highest temperature heat preservation time is 30-90 min.

6. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

the MgO powder has the average granularity of 20nm and the purity of more than 99.9 percent; SiO 2₂The average particle size of the powder is 45nm, and the purity is more than 99.5 percent; al (Al)₂O₃The average particle size of the powder is 30nm, and the purity is more than 99.9%; the concentration of the PVA solution is 0.5-1.5%.

7. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

the sedimentation and ultrasonic cleaning are carried out for 1-5 times, the drying temperature is 50-120 ℃, and the time is 6-12 hours.

8. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

the mixture comprises AlN microbeads, MgO powder and SiO₂Powder, Al₂O₃The mass ratio of the powder is (90-98): (4-8): 3-6): 2-8.

9. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

the porous aluminum nitride ceramic material obtained by the method has the porosity of 63.3-87.5 percent and the specific surface area of 0.95-4.18m²The average diameter of primary pores is 58-294 mu m, the average size of secondary pores is 45-95nm, the bending strength is 155.7-249.6MPa, and the compressive strength is 24.2-43.6 MPa.

10. The method for preparing a porous aluminum nitride ceramic material according to claim 1,

the pretreatment and washing times are 1-3 times, the drying temperature is 50-120 ℃, and the time is 6-12 hours.

Technical Field

The invention belongs to the technical field of porous aluminum nitride ceramic materials, and particularly relates to a preparation method of a porous aluminum nitride ceramic material.

Background

The aluminum nitride ceramic has the characteristics of excellent high-temperature mechanical property, high-temperature oxidation resistance, molten metal corrosion resistance, high heat conductivity, low thermal expansion coefficient, piezoelectric effect and the like, and has a good application prospect in the industrial field. The porous aluminum nitride ceramic not only has the characteristics of the aluminum nitride ceramic, but also can filter and adsorb impurities in molten metal due to the properties of high porosity and large specific surface area, and the displayed piezoelectric effect can be used as an acoustic detector, and an electronic packaging part can be manufactured by excellent heat-conducting property; has great practical value.

At present, additives such as pore-forming agents, foaming agents and the like are commonly used for preparing porous aluminum nitride ceramics, for example, the patent publication number is CN109133986A, namely AlN-SiC porous composite ceramics based on a foaming method and a preparation method thereof, the method not only easily causes uneven distribution of pores inside a ceramic matrix, but also produces a large amount of macropores and small closed pores, and is easy to reduce the mechanical strength of the material, and the pore-forming agents and the foaming agents are high in price, so that the problems of low yield of the porous aluminum nitride ceramics and difficulty in exerting higher practical value are caused.

Patent publication No. CN101734923A, entitled an aluminum nitride porous ceramic and a preparation method thereof, also adopts the basic principle that oxygen in alumina is replaced by reacting with carbon to generate carbon monoxide, and then the carbon reacts with nitrogen to generate aluminum nitride, but the aluminum nitride as a reaction raw material is solid particles, and a carbon source adopts carbon black, so the whole reaction process is uneven, the reaction efficiency is low, the reaction rate is slow, and the reaction is not thorough, and the used carbon black is not only a reaction raw material but also a pore-forming agent, so the prepared porous aluminum nitride is bound to the defect of the pore-forming agent, and the product defect caused by the pore-forming agent cannot be avoided.

Chinese patent No. CN105884372B provides a method for synthesizing AlN ceramic powder by organic network method, in which aluminum is used as raw material, nitrogen is introduced to react to directly generate aluminum nitride at high temperature, and carbon powder only plays a role in buffering and dispersing during the process, i.e. preventing the generated aluminum nitride from being a block, so that solid aluminum nitride particles are generated and the uniformity of the powder particles cannot be guaranteed. Therefore, the purity of the aluminum nitride powder obtained in the process is not high, and the aluminum nitride powder contains a large amount of carbon impurities and needs to be further purified.

The existing porous aluminum nitride ceramics have the following defects: (1) most of the particles are solid particle structures; (2) the pore size is not uniform; (3) low high-temperature mechanical strength.

Disclosure of Invention

The invention aims to solve the problem of poor practical value effect caused by low porosity, uneven pore size distribution, low mechanical strength, high production cost and low yield of the existing porous aluminum nitride ceramics, and provides a preparation method of the porous aluminum nitride ceramics to realize the following purposes:

(1) according to the preparation method of the porous aluminum nitride ceramic material, the porous aluminum nitride ceramic material with a hollow morphology structure is obtained;

(2) according to the preparation method of the porous AlN ceramic material, the prepared porous AlN ceramic material has uniform and evenly distributed aperture size;

(3) the porous aluminum nitride ceramic material prepared by the preparation method of the porous aluminum nitride ceramic material has excellent high-temperature mechanical strength.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a porous aluminum nitride ceramic material is characterized by comprising the following steps: pretreatment, ion carbonitriding treatment, sedimentation, mixing and sintering.

The following are preferred for the technical solution of the present invention:

a method of preparing a porous aluminum nitride ceramic material, the method comprising: pretreatment, ion carbonitriding treatment, sedimentation, mixing, drying, sieving granulation, mould pressing, drying and sintering.

A preparation method of a porous aluminum nitride ceramic material comprises the following steps:

(1) pretreatment: hollow Al is added₂O₃Washing the microbeads with absolute ethyl alcohol, and then putting the microbeads into a drying box for drying;

(2) ion carbonitriding treatment: washing and drying the hollow Al₂O₃Putting the microbeads into a vacuum ion carbonitriding furnace, and introducing carbon source and nitrogen source gases for heat treatment;

(3) and (3) settling: ultrasonically cleaning the heat-treated microbeads by absolute ethyl alcohol, centrifugally settling and drying;

(4) mixing: mixing the dried microbeads with MgO powder and SiO₂Powder, Al₂O₃Stirring and mixing the powder and the PVA solution uniformly;

(5) drying: putting the mixed slurry into a drying box for drying;

(6) sieving and granulating: grinding the dried mixture into powder, and sieving and granulating;

(7) die pressing: compression molding the mixed particles to obtain a green body;

(8) and (3) drying: putting the green body into a drying box for drying and discharging the water in the green body;

(9) and (3) sintering: and placing the blank into a vacuum sintering furnace, and sintering at 1550-1850 ℃ to obtain the porous AlN ceramic material.

In the pretreatment, the particle size of the hollow alumina microspheres is 100-500 mu m, the shell wall thickness is 15-75 mu m, and the purity is more than 99.5%.

In the pretreatment, the washing times are 1-3 times, the drying temperature is 50-120 ℃, and the time is 6-12 hours.

In the ion carbonitriding treatment, the temperature of the vacuum ion carbonitriding heat treatment is 1200-1450 ℃, the heating rate is 5-20 ℃/min, and the heat preservation time is 30-60 min.

In the ion carbonitriding treatment, the carbon source gas is methane, propane and acetylene, the nitrogen source is nitrogen, the mass ratio of the carbon source to the nitrogen source is 1 (6-12), and the air pressure of the mixed gas source is 460-1280 Pa.

In the sedimentation, the ultrasonic cleaning is performed for 1-5 times, the drying temperature is 50-120 ℃, and the time is 6-12 hours.

In the mixing, the average particle size of MgO powder is 20nm, and the purity is more than 99.9%; SiO 2₂The average particle size of the powder is 45nm, and the purity is more than 99.5 percent; al (Al)₂O₃The average particle size of the powder is 30nm, and the purity is more than 99.9%; the concentration of the PVA solution is 0.5-1.5%.

In the above mixture, AlN microbeads, MgO powder, SiO₂Powder, Al₂O₃The mass ratio of the powder is (90-98): (4-8): 3-6): 2-8.

In the mixing, the stirring time is 12-24 h, and the temperature is room temperature.

In the drying, the drying temperature is 75-150 ℃, and the drying time is 18-36 h.

In the sieving granulation, the specification of a screen mesh in the sieving granulation is 20-100 meshes.

In the die pressing, the pressure for die pressing forming is 25-50 MPa, and the pressure maintaining time is 5-10 s.

In the drying, the drying temperature is 120-160 ℃, and the drying time is 6-12 h.

In the sintering, the heating rate is 3-8 ℃/min, and the highest temperature heat preservation time is 30-90 min.

The invention also provides a porous aluminum nitride ceramic material, and the porous aluminum nitride ceramic material prepared by the preparation method has the porosity of 63.3-87.5 percent and the specific surface area of 0.95-4.18m²The average diameter of primary pores is 58-294 mu m, the average size of secondary pores is 45-95nm, the bending strength is 155.7-249.6MPa, and the compressive strength is 24.2-43.6 MPa.

The preparation method comprises the steps of putting washed and dried hollow alumina microspheres into a vacuum ion carbonitriding furnace, ionizing a carbon source and a nitrogen source by heating and high-voltage discharge, wherein carbon atoms and Al are firstly mixed₂O₃The oxygen ions in the aluminum alloy react to generate CO gas, and then nitrogen atoms are combined with aluminum ions to generate AlN, so that the hollow Al is formed₂O₃Converting the micro-beads into hollow AlN micro-beads, ultrasonically cleaning and drying the AlN micro-beads, and then mixing with MgO powder and SiO₂Powder, Al₂O₃The powder and the PVA solution are stirred and mixed uniformly, and are dried, crushed, sieved and granulated, and after compression molding, the porous aluminum nitride ceramic with extremely high porosity, uniform and uniformly distributed matrix pore size and excellent mechanical strength is obtained by vacuum sintering.

Compared with the prior art, the invention has the advantages that:

(1) the preparation method of the porous aluminum nitride ceramic material adopts Al with a hollow structure₂O₃The microbeads are used as AlN source, carbon source and nitrogen source are ionized by heating and high-voltage discharge, and carbon atoms are firstly mixed with Al₂O₃The oxygen ions in the aluminum oxide react to generate CO gas, and then nitrogen atoms are combined with aluminum ions to generate AlN, so that the hollow Al is formed₂O₃The micro-beads are converted into hollow SiC micro-beads without damaging the macroscopic hollow structure of the micro-beads; there is the following reaction equation:

it can be known that: from Al₂O₃The AlN conversion is a mass reduction process, and the reaction gas CO is discharged, which inevitably causes the shell wall of the original cenosphere to generate continuous secondary perforation and become nano-size; the morphology structure is obviously different from the traditional AlN solid particle structure.

(2) According to the preparation method of the porous aluminum nitride ceramic material, the porous AlN ceramic material prepared by the AlN microbeads with the primary-hole hollow structure and the secondary nano-size perforations on the shell wall shows that the pore size of the matrix is uniform and evenly distributed, and the porous AlN ceramic material hardly contains large holes with large size and closed holes with small size, so that the negative influence caused by using a pore-forming agent and a foaming agent is avoided; the porous aluminum nitride ceramic material has the porosity of 63.3-87.5 percent and the specific surface area of 0.95-4.18m²/g，The average diameter of the primary pores is 58-294 μm, and the average size of the secondary pores is 45-95 nm.

(3) According to the porous aluminum nitride ceramic material prepared by the preparation method disclosed by the invention, the pore form of the porous aluminum nitride ceramic material not only maintains the structure of the original hollow microsphere, but also shows excellent high-temperature mechanical strength, wherein the bending strength is 155.7-249.6MPa, and the compression strength is 24.2-43.6 MPa;

(4) the porous aluminum nitride ceramic material obtained by the preparation method of the porous aluminum nitride ceramic material has continuous secondary perforation with nanometer size on the shell wall, which greatly improves the effects of filtration, adsorption, separation and purification, carrier catalysis and heat conduction and radiation, and has wide application in the aspects of high-temperature radiation electronic elements, high-power microwave integrated circuits, power electronic devices, laser diodes and metal-ceramic matrix composite materials.

The invention adopts alumina hollow microspheres with uniform particle size as raw materials, and the introduced carbon source gas reacts with ionized carbon atoms to capture Al under the high-temperature and high-voltage state₂O₃The generated CO molecules are discharged, and then nitrogen atoms ionized by nitrogen gas react with aluminum ions to generate aluminum nitride. This process is not only a process of forming aluminum nitride but also a process of further purifying the raw material, and very high purity of aluminum nitride can be ensured by reaction and bonding of carbon atoms and nitrogen atoms. Because the reaction temperature in the process is far lower than the softening point temperature of the aluminum oxide, the aluminum nitride retains the structure of the aluminum oxide hollow sphere and generates nano-scale perforations on the surface of the spherical shell wall.

The porous aluminum nitride ceramic has extremely high porosity, the pore size of the matrix is uniform and evenly distributed, and macropores with larger size and closed pores with smaller size are hardly contained; the form of the holes not only retains the structure of the original hollow microspheres and shows excellent high-temperature mechanical strength, but also has continuous secondary perforation with nanometer size on the shell wall, thus greatly improving the effects of filtration, adsorption, separation and purification, carrier catalysis and heat conduction and radiation, and having wide application in the aspects of high-temperature radiation electronic elements, high-power microwave integrated circuits, power electronic devices, laser diodes and metal-ceramic matrix composite materials. The process has the advantages of simple operation flow, low equipment requirement, no addition of pore-forming agent and foaming agent, greatly reduced production cost, convenient batch production and great industrial practical value.

Drawings

FIG. 1 is a flow chart illustrating the steps for preparing a porous AlN ceramic material according to an embodiment of the present invention;

FIG. 2 shows carbon atoms, nitrogen atoms and Al in the ion carbonitriding process in an embodiment of the present invention₂O₃Schematic representation of the reaction to AlN.

Detailed Description

The present invention will be further described with reference to the following specific examples. It should be understood that the following examples are illustrative only and are not intended to limit the scope of the present invention.