CN110845241A

CN110845241A - Preparation method of porous aluminum nitride ceramic material

Info

Publication number: CN110845241A
Application number: CN201910969142.1A
Authority: CN
Inventors: 孙卫康; 田静; 李庆春; 汤志强; 茹红强; 赵东萍; 王春华
Original assignee: Shenzhen Dongtao New Material Co Ltd; Shandong Dongda New Materials Research Institute Co Ltd
Current assignee: Shenzhen Dongtao New Material Co Ltd; Shandong Dongda New Materials Research Institute Co Ltd
Priority date: 2019-10-12
Filing date: 2019-10-12
Publication date: 2020-02-28

Abstract

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.

Description

Preparation method of porous aluminum nitride ceramic material

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.

Example 1

(1) hollow Al with particle size of 200 μm and shell wall thickness of 45 μm₂O₃Washing the microbeads with absolute ethyl alcohol for 2 times, and then putting the washed microbeads into a drying oven at 120 ℃ for drying for 6 hours;

(2) washing and drying the hollow Al₂O₃Putting the microbeads into a vacuum ion carbonitriding furnace, heating to 1300 ℃ at a speed of 15 ℃/min in vacuum, then introducing a mixed gas of methane and nitrogen according to a mass ratio of 1:8 for heat treatment, keeping the air pressure at 950Pa, and keeping the temperature for 60 min;

(3) ultrasonically cleaning AlN microbeads obtained after heat treatment for 3 times by using absolute ethyl alcohol, centrifugally settling, and then putting the microbeads into a drying oven at 120 ℃ for drying for 6 hours;

(4) mixing the dried AlN microbeads with MgO powder and SiO according to the mass ratio₂Powder, Al₂O₃Mixing the powder =93:4:3:2, mixing the powder with a PVA solution with the concentration of 0.5% according to the proportion of 100:120 to form slurry, and stirring the slurry for 20 hours until the mixture is uniformly mixed;

(5) putting the mixed slurry into a drying oven at 80 ℃ for drying for 30 h;

(6) grinding the dried mixture into powder, and sieving the powder by a 50-mesh sieve for granulation;

(7) pouring the mixed particles into a mold, carrying out compression molding by a press under the pressure of 35MPa, and maintaining the pressure for 5s to obtain a green body; (ii) a

(8) Putting the green body into a drying oven at 150 ℃ for drying for 6h, and discharging the water in the green body;

(9) and putting the blank body into a vacuum sintering furnace, heating to 1650 ℃ at the speed of 8 ℃/min, and preserving the heat at 1650 ℃ for 60min to obtain the porous AlN ceramic material.

Tests show that the porosity of the porous AlN ceramic material is 81.4 percent, and the specific surface area is 2.35m²(g), the average diameter of primary pores was 108 μm, the average size of secondary pores was 60nm, the flexural strength was 206.5MPa, and the compressive strength was 37.1 MPa.

Example 2

(1) hollow Al with particle size of 100 μm and shell wall thickness of 20 μm₂O₃Washing the microbeads with absolute ethyl alcohol for 3 times, and then drying the microbeads in a drying oven at 60 ℃ for 12 hours;

(2) washing and drying the hollow Al₂O₃Putting the microbeads into a vacuum ion carbonitriding furnace, heating to 1350 ℃ at the speed of 5 ℃/min in vacuum, then introducing a mixed gas of propane and nitrogen according to the mass ratio of 1:6 for heat treatment, keeping the air pressure at 1250Pa, and keeping the temperature for 45 min;

(3) ultrasonically cleaning AlN microbeads obtained after heat treatment for 5 times by using absolute ethyl alcohol, centrifugally settling, and then putting the microbeads into a drying oven at 80 ℃ for drying for 12 hours;

(4) mixing the dried AlN microbeads with MgO powder and SiO according to the mass ratio₂Powder, Al₂O₃Mixing the powder =98:7:4:8, mixing the powder with a PVA solution with the concentration of 1.0% according to the proportion of 100:180 to form slurry, and stirring the slurry for 24 hours until the mixture is uniformly mixed;

(5) putting the mixed slurry into a drying oven at 100 ℃ for drying for 36 hours;

(6) grinding the dried mixture into powder, and sieving the powder by a 100-mesh sieve for granulation;

(7) pouring the mixed particles into a mold, carrying out compression molding by a press under the pressure of 50MPa, and maintaining the pressure for 10s to obtain a green body; (ii) a

(8) Putting the green body into a drying oven at 120 ℃ for drying for 12h, and discharging the water in the green body;

(9) and (3) putting the blank into a vacuum sintering furnace, heating to 1750 ℃ at the speed of 5 ℃/min, and preserving the heat at 1750 ℃ for 45min to obtain the porous AlN ceramic material.

Tests show that the porosity of the porous AlN ceramic material is 87.5 percent, and the specific surface area is 4.18m²(g), the average diameter of primary pores was 58 μm, the average size of secondary pores was 45nm, the flexural strength was 249.6MPa, and the compressive strength was 43.6 MPa.

Example 3

(1) hollow Al with particle size of 500 μm and shell wall thickness of 100 μm₂O₃Washing the microbeads with absolute ethyl alcohol for 1 time, and then putting the microbeads into a drying oven at 80 ℃ for drying for 7 hours;

(2) washing and drying the hollow Al₂O₃Putting the microbeads into a vacuum ion carbonitriding furnace, heating to 1150 ℃ at the speed of 20 ℃/min in vacuum, introducing mixed gas of acetylene and nitrogen according to the mass ratio of 1:12 for heat treatment, keeping the air pressure at 750Pa, and keeping the temperature for 60 min;

(3) ultrasonically cleaning AlN microbeads obtained after heat treatment for 2 times by using absolute ethyl alcohol, centrifugally settling, and then putting the microbeads into a drying oven at 100 ℃ for drying for 10 hours;

(4) mixing the dried AlN microbeads with MgO powder and SiO according to the mass ratio₂Powder, Al₂O₃Mixing the powder =90:8:6:5, mixing the powder with a PVA solution with the concentration of 1.4% according to the proportion of 100:220 to form slurry, and stirring the slurry for 15 hours until the mixture is uniformly mixed;

(5) putting the mixed slurry into a drying oven at 140 ℃ for drying for 18 h;

(6) grinding the dried mixture into powder, and sieving the powder by a 24-mesh sieve for granulation;

(7) pouring the mixed particles into a mold, carrying out compression molding by a press under the pressure of 25MPa, and maintaining the pressure for 7s to obtain a green body;

(8) putting the green body into a 135 ℃ drying oven for drying for 9 hours, and discharging the water in the green body;

(9) and (3) putting the blank into a vacuum sintering furnace, heating to 1550 ℃ at the speed of 3 ℃/min, and preserving the temperature at 1550 ℃ for 90min to obtain the porous AlN ceramic material.

Tests show that the porosity of the porous AlN ceramic material is 63.3 percent, and the specific surface area is 0.95m²In terms of a specific volume of the pores, the average diameter of primary pores was 294 μm, the average size of secondary pores was 95nm, the flexural strength was 155.7MPa, and the compressive strength was 24.2 MPa.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the present invention, and various changes may be made in the above embodiment of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.

Claims

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.