CN112939607B - High-thermal-conductivity aluminum nitride ceramic and preparation method thereof - Google Patents
High-thermal-conductivity aluminum nitride ceramic and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of ceramic materials, and provides high-thermal-conductivity aluminum nitride ceramic and a preparation method thereof, wherein the preparation method comprises the following steps: (1) performing primary ball milling; (2) calcining; (3) performing secondary ball milling; (4) removing bubbles in vacuum; (5) tape casting; (6) isostatic pressing; (7) removing glue; (8) and hot-pressing and sintering to obtain the aluminum nitride ceramic, wherein the thermal conductivity of the obtained aluminum nitride ceramic is 200-230W/(m.K), the bending strength is 470-540 MPa, and the volume density is 3.3-3.5 g/cm, so that the problem that the conventional aluminum nitride ceramic only has outstanding performance in one aspect of thermal conductivity, strength and the like and cannot give consideration to the performance of each aspect at the same time is solved.
Description
Technical Field
The invention relates to the technical field of ceramic materials, in particular to an aluminum nitride ceramic with high thermal conductivity and a preparation method thereof.
Background
The ceramic substrate material mainly comprises aluminum nitride (AlN) and aluminum oxide (Al)203) Beryllium oxide (BeO), silicon carbide (SiC), Boron Nitride (BN), silicon nitride (Si)3N4) And the like. Al (aluminum)2O3The ceramic is used as a traditional substrate material, the thermal conductivity of the ceramic is low, the linear expansion coefficient is not matched with Si, and the thermal mismatch phenomenon between a substrate and a Si sheet is easily caused; although the BeO ceramic has high thermal conductivity which can reach 310W/(m.K), the raw materials of the BeO ceramic have high toxicity and high production cost, and the BeO ceramic is gradually eliminated. Although the SiC substrate has high thermal conductivity, the insulating property is poor; BN is difficult to sinter and compact, the preparation process is complex, the thermal conductivity is low, and the mechanical strength is poor. Compared with other materials, AlN has excellent heat conducting performance, low dielectric constant, linear expansion coefficient matched with Si, excellent electric insulating property, no toxicity and other excellent comprehensive performance, and is an ideal substrate and packaging material for new generation of high integration level and power devices.
The theoretical thermal conductivity of the AlN ceramic is as high as 320W/(m.K), and the AlN ceramic is Al2O35-10 times of the ceramic can effectively improve the operation reliability of the electronic device. However, the thermal conductivity of AlN ceramics actually produced is far from the theoretical value, and for this situation, a lot of research has been conducted at home and abroad on alumina ceramics, such as chinese patent application No.: 201510276618.5 discloses a high thermal conductivity nitrideThe preparation method of the aluminum nitride ceramic with high thermal conductivity takes aluminum nitride powder as a basic raw material and adopts rare earth metal fluoride EuF3、LaF3、SmF3Or the mixture of the aluminum nitride and the aluminum nitride is used as a sintering aid, the addition amount of the rare earth fluoride used as the sintering aid is 2-8% of the mass of the aluminum nitride powder, the aluminum nitride ceramic is formed through wet grinding, mixing, drying, forming, degreasing and sintering, the thermal conductivity of the obtained aluminum nitride ceramic is more than 200W/(m.K), but the bending strength is only 300-350 MPa, and the wider application of the AlN ceramic is limited. In order to improve the mechanical property of the aluminum nitride ceramic, the Chinese patent application number: 200710063448.8 discloses a method for preparing aluminum nitride/boron nitride complex phase ceramic by using boron nitride precursor C3N6H12B2O6Calcining the powder and aluminum nitride particles together in a non-oxygen environment to generate pure aluminum nitride/boron nitride composite powder, wherein the boron nitride is uniformly dispersed in an aluminum nitride matrix without agglomeration; the rare earth oxide as sintering additive is fully mixed with the composite powder and is placed in a spark plasma sintering furnace for sintering, the sintering of the system is realized by utilizing the characteristic of low temperature and high speed of the spark plasma sintering technology, the aluminum nitride is densified to form a structure with crystal grains in close contact, and the boron nitride has smaller length and amplitude in the sintering process, so that the fine crystal grains of the boron nitride are uniformly dispersed in the crystal boundary of the aluminum nitride matrix. The bending strength of the aluminum nitride/boron nitride complex phase ceramic obtained by the method is up to more than 450Mpa, but the thermal conductivity is only 95-130W/(m.K). In recent years, with the development of science and technology, the performance requirements of materials used are higher and higher, and in some specific fields, aluminum nitride materials are required to have high bending strength together with high thermal conductivity, but there are few reports on aluminum nitride ceramics having both high strength and high thermal conductivity (thermal conductivity is more than or equal to 200W/(m · K)), and therefore, AlN ceramics having both high thermal conductivity and high strength are urgently required to be developed to meet the use requirements.
Disclosure of Invention
Therefore, in view of the above, the present invention provides an aluminum nitride ceramic with high thermal conductivity and a preparation method thereof, which solve the problem that the existing aluminum nitride ceramic has outstanding performance only in one aspect of thermal conductivity, strength, etc., and cannot simultaneously give consideration to the performance in each aspect.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a preparation method of aluminum nitride ceramic with high thermal conductivity comprises the following steps:
(1) primary ball milling: adding aluminum nitride powder, calcium carbonate, lithium nitrate and ethanol into a ball mill for primary ball milling, dispersing for 6-15h by ball milling, drying after ball milling, and sieving to obtain intermediate powder;
(2) and (3) calcining: calcining the intermediate powder obtained in the step (1) at 950-1050 ℃ for 30-90 min in a nitrogen atmosphere, and sieving to obtain mixed powder;
(3) secondary ball milling: adding the mixed powder obtained in the step (2), molybdenum disulfide, a solvent, a dispersing agent, a plasticizer and a binder into a ball mill for secondary ball milling for 10-20 hours;
(4) removing bubbles in vacuum: vacuumizing and defoaming the ball-milled materials by using a vacuum defoaming machine to obtain ceramic slurry with the viscosity of 12000-15000 mPa & s;
(5) tape casting: carrying out tape casting on the ceramic slurry obtained in the step (4) to obtain a ceramic green body, and cutting the ceramic green body into a required shape and size by using a mold to obtain a ceramic green sheet;
(6) isostatic pressing: putting the ceramic blank sheet obtained in the step (5) into a cold isostatic press for pressing, wherein the pressure is 200-280 MPa, and the pressure maintaining time is 5-15 min;
(7) rubber discharging: coating a layer of adhesive powder on the surface of the ceramic blank sheet, laminating the ceramic blank sheet, preheating the ceramic blank sheet at the temperature of 130-150 ℃ for 80-120 min, and then putting the ceramic blank sheet into a glue discharging furnace for vacuum glue discharging;
(8) hot-pressing and sintering: and carrying out hot-pressing sintering on the ceramic blank sheet subjected to vacuum binder removal under the protection of nitrogen atmosphere, cooling to room temperature after sintering, and then carrying out powder removal polishing process to obtain the high-thermal-conductivity aluminum nitride ceramic.
The further improvement is that: the mass ratio of the aluminum nitride powder to the calcium carbonate to the lithium nitrate is 85-90: 5-8: 3 to 6.
The further improvement is that: the addition amount of the molybdenum disulfide is 30-50% of the mass of the mixed powder.
The further improvement is that: the solvent is a mixed solvent composed of absolute ethyl alcohol and isopropanol, and the addition amount of the solvent is 40-60% of the mass of the mixed powder.
The further improvement is that: the dispersing agent is any one of sodium polyacrylate, fish oil and polyethylene glycol, and the addition amount of the dispersing agent is 1.5-3% of the mass of the mixed powder.
The further improvement is that: the adhesive consists of polyvinyl butyral resin, an ethylene acrylic acid copolymer and linear low-density polyethylene, and the addition amount of the adhesive is 2-4% of the mass of the mixed powder.
The further improvement is that: the mass ratio of the polyvinyl butyral resin to the ethylene acrylic acid copolymer to the linear low-density polyethylene is (20-30): 3-6: 2 to 4.
The further improvement is that: the plasticizer is at least one of dimethyl phthalate, diethyl phthalate and trioctyl phosphate, and the addition amount of the plasticizer is 0.5-1% of the mass of the mixed powder.
The further improvement is that: and (4) carrying out isostatic pressing in the step (6) at a pressure of 230-250 MPa for a pressure maintaining time of 7-10 min.
The further improvement is that: the step (7) of vacuum glue discharging comprises the following specific steps: heating to 280-360 ℃ at the speed of 1-3 ℃/min, then preserving heat for 2-3 h, heating to 420-480 ℃ at the speed of 4-6 ℃/min, then preserving heat for 1-2 h, heating to 540-580 ℃ at the speed of 3-5 ℃/min, and then preserving heat for 1-2 h.
The further improvement is that: the specific conditions of the hot-pressing sintering in the step (8) are as follows: raising the temperature to 1000-1100 ℃ at a temperature raising rate of 2-4 ℃/min under the pressure of 30-50 MPa, preserving the heat for 1-2 h, then continuing raising the temperature to 1700-1800 ℃, increasing the temperature and simultaneously pressurizing to 80-100 MPa, preserving the heat and keeping the pressure for 4-8 h.
The invention also provides the aluminum nitride ceramic prepared by the preparation method.
The further improvement is that: the aluminum nitride ceramic has a thermal conductivity of 200-230W/(m.K), a bending strength of 470-540 MPa, and a specific surface areaThe bulk density is 3.3-3.5 g/cm3。
By adopting the technical scheme, the invention has the beneficial effects that:
1. the sintering aid reacts with impurities in the crystal lattice to generate a crystal boundary phase, so that the impurities migrate from the interior of the crystal grains to the crystal boundary to reduce the content of solid solution in the interior of the crystal lattice, thereby improving the thermal conductivity. In addition, the sintering aid reacts with the aluminum nitride powder to form a liquid phase, liquid phase sintering is completed, particles are rearranged under the action of surface tension of the liquid phase, the liquid phase promotes the mass transfer process, and the densification process is completed along with the rearrangement and grain growth of the particles. Compared with a single sintering aid, the heat conductivity can be effectively improved by compounding multiple sintering aids, and the sintering temperature can be reduced. The temperature for sintering the aluminum nitride ceramic by adopting a single sintering aid is higher, the sintering temperature is generally higher than 1800 ℃, and the invention adopts CaO-Li2The O binary sintering aid composite system greatly reduces the sintering temperature, can realize low-temperature sintering, reduces energy consumption and saves cost. The addition mode of the sintering aid is generally that the sintering aid is directly mixed with aluminum nitride powder, so that the sintering aid is easily mixed with the aluminum nitride powder unevenly, and the prepared ceramic blank sheet has the condition that the local sintering aid is excessive or insufficient, so that liquid phases formed in all areas are uneven, liquid phases in partial areas are excessive, an overburning state is formed after sintering, and crystal grains grow excessively; partial area has liquid phase loss, and the sintered ceramic is in an under-sintered state, and ceramic grains are not grown or are not completely developed. The sintering aid is added in the form of nitrate and carbonate, and is calcined after being ball-milled and mixed uniformly to generate the calcium oxide-lithium oxide binary sintering aid which is uniformly distributed on the surface of the aluminum nitride powder, and liquid phases formed in all areas are uniform.
2. The invention adds molybdenum disulfide powder into the formula, the molybdenum disulfide has good chemical stability and thermal stability, and has good anisotropy and lower friction factor, and the characteristics of easy processing and good lubricity of the molybdenum disulfide are utilized to improve the toughness of the aluminum nitride ceramic material and simultaneously improve the processing performance of the aluminum nitride. 3. The ceramic slurry is formed in one step by casting, the stress of the blank sheet in all directions can not be ensured to be consistent, and the integral performance of the aluminum nitride ceramic finished product is easy to be different, so that the ceramic blank sheet after casting is subjected to isostatic pressing treatment, the pressed blank body is uniform in stress and high in density, the product performance is improved, the internal stress of the ceramic blank body is small, and the defects of blank body cracking, layering and the like are reduced.
4. In the production process, the binder enables the ceramic particles to be tightly bonded, plays the roles of stabilizing slurry and inhibiting particle sedimentation, and enables the ceramic green body to have certain strength. The adhesive of the invention is preferably a mixture of polyvinyl butyral resin, ethylene acrylic acid copolymer and linear low-density polyethylene, and the adhesive is further added with the ethylene acrylic acid copolymer on the premise of common adhesive polyvinyl butyral to improve the adhesive property of the adhesive; the addition of the linear low density polyethylene can enhance the fluidity of the binder, so that the components in the ceramic slurry are uniformly mixed. The glue is easy to remove when being discharged, and no residue is left.
Detailed Description
The following detailed description will be provided for the embodiments of the present invention with reference to specific embodiments, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented.
Unless otherwise indicated, the techniques employed in the examples are conventional and well known to those skilled in the art, and the reagents and products employed are also commercially available.
Example one
A preparation method of aluminum nitride ceramic with high thermal conductivity comprises the following steps:
(1) primary ball milling: adding aluminum nitride powder, calcium carbonate, lithium nitrate and ethanol into a ball mill for primary ball milling, performing ball milling dispersion for 6 hours, drying and sieving after ball milling to obtain intermediate powder, wherein the mass ratio of the aluminum nitride powder to the calcium carbonate to the lithium nitrate is 85: 5: 3, the mass of the ethanol is 60 percent of that of the aluminum nitride powder;
(2) and (3) calcining: calcining the intermediate powder obtained in the step (1) at 950 ℃ for 90min in a nitrogen atmosphere, and sieving to obtain mixed powder;
(3) secondary ball milling: adding the mixed powder obtained in the step (2), molybdenum disulfide, a solvent, sodium polyacrylate, dimethyl phthalate and a binder into a ball mill for secondary ball milling for 10 hours;
the adding amount of the molybdenum disulfide is 30% of the mass of the mixed powder, and the solvent is absolute ethyl alcohol and isopropanol according to a mass ratio of 1: 1, wherein the addition amount of the solvent is 40% of the mass of the mixed powder, the addition amount of the sodium polyacrylate dispersant is 1.5% of the mass of the mixed powder, and the binder is prepared from polyvinyl butyral resin, ethylene acrylic acid copolymer and linear low density polyethylene according to the mass ratio of 20: 3: 2, the mass of the binder is 2 percent of the mass of the mixed powder, and the addition amount of the dimethyl phthalate plasticizer is 0.5 percent of the mass of the mixed powder;
(4) removing bubbles in vacuum: vacuumizing and defoaming the ball-milled materials by using a vacuum defoaming machine to obtain ceramic slurry with the viscosity of 12000mPa & s;
(5) tape casting: carrying out tape casting on the ceramic slurry obtained in the step (4) to obtain a ceramic green body, and cutting the ceramic green body into a required shape and size by using a mold to obtain a ceramic green sheet;
(6) isostatic pressing: putting the ceramic blank sheet obtained in the step (5) into a cold isostatic press for pressing, wherein the pressure is 200MPa, and the pressure maintaining time is 5 min;
(7) rubber discharging: coating a layer of adhesive powder on the surface of the ceramic blank sheet, laminating the ceramic blank sheet, preheating the ceramic blank sheet at 130 ℃ for 80min, and then putting the ceramic blank sheet into a glue discharging furnace for vacuum glue discharging; the vacuum rubber discharge method comprises the following specific steps: firstly heating to 280 ℃ at the speed of 1 ℃/min, then preserving heat for h, then heating to 420 ℃ at the speed of 4 ℃/min, then preserving heat for 1h, then heating to 540 ℃ at the speed of 3 ℃/min, and then preserving heat for 1 h.
(8) Hot-pressing and sintering: carrying out hot-pressing sintering on the ceramic blank sheet subjected to vacuum binder removal under the protection of nitrogen atmosphere, cooling to room temperature after sintering, and then carrying out a powder removal polishing process to obtain the high-thermal-conductivity aluminum nitride ceramic, wherein the specific conditions of the hot-pressing sintering are as follows: heating to 1000 deg.C at a temperature rise rate of 2 deg.C/min under 30MPa, maintaining for 1h, heating to 1700 deg.C, pressurizing to 80MPa while heating, and maintaining for 4 h.
Example two
A preparation method of aluminum nitride ceramic with high thermal conductivity comprises the following steps:
(1) primary ball milling: adding aluminum nitride powder, calcium carbonate, lithium nitrate and ethanol into a ball mill for primary ball milling, performing ball milling dispersion for 10 hours, drying and sieving after ball milling to obtain intermediate powder, wherein the mass ratio of the aluminum nitride powder to the calcium carbonate to the lithium nitrate is 88: 6: 5, the mass of the ethanol is 70 percent of that of the aluminum nitride powder;
(2) and (3) calcining: calcining the intermediate powder obtained in the step (1) at 1000 ℃ for 60min in a nitrogen atmosphere, and sieving to obtain mixed powder;
(3) secondary ball milling: adding the mixed powder obtained in the step (2), molybdenum disulfide, a solvent, fish oil, diethyl phthalate and a binder into a ball mill for secondary ball milling for 15 hours;
the addition amount of the molybdenum disulfide is 40% of the mass of the mixed powder, and the solvent is absolute ethyl alcohol and isopropanol in a mass ratio of 1: 2, the addition amount of the solvent is 50 percent of the mass of the mixed powder, the addition amount of the fish oil dispersing agent is 2 percent of the mass of the mixed powder, and the binder is prepared from polyvinyl butyral resin, ethylene acrylic acid copolymer and linear low density polyethylene according to the mass ratio of 25: 5: 3, the addition amount of the binder is 3 percent of the mass of the mixed powder, and the addition amount of the diethyl phthalate plasticizer is 0.8 percent of the mass of the mixed powder.
(4) Removing bubbles in vacuum: vacuumizing and defoaming the ball-milled materials by using a vacuum defoaming machine to obtain ceramic slurry with the viscosity of 13000mPa & s;
(5) tape casting: carrying out tape casting on the ceramic slurry obtained in the step (4) to obtain a ceramic green body, and cutting the ceramic green body into a required shape and size by using a mold to obtain a ceramic green sheet;
(6) isostatic pressing: putting the ceramic blank sheet obtained in the step (5) into a cold isostatic press for pressing, wherein the pressure is 230MPa, and the pressure maintaining time is 7 min;
(7) rubber discharging: coating a layer of adhesive powder on the surface of the ceramic blank sheet, laminating the ceramic blank sheet, preheating the ceramic blank sheet at the temperature of 140 ℃ for 100min, and then putting the ceramic blank sheet into a glue discharging furnace for vacuum glue discharging; the vacuum rubber discharge method comprises the following specific steps: firstly heating to 320 ℃ at the speed of 2 ℃/min, then preserving heat for 2.5h, then heating to 450 ℃ at the speed of 5 ℃/min, then preserving heat for 1.5h, then heating to 560 ℃ at the speed of 4 ℃/min, and then preserving heat for 1.5 h.
(8) Hot-pressing and sintering: and carrying out hot-pressing sintering on the ceramic blank sheet subjected to vacuum binder removal under the protection of nitrogen atmosphere, cooling to room temperature after sintering, and then carrying out powder removal polishing process to obtain the high-thermal-conductivity aluminum nitride ceramic. The specific conditions of hot-pressing sintering are as follows: heating to 1050 ℃ at the heating rate of 3 ℃/min under the pressure of 40MPa, preserving heat for 1.5h, then continuously heating to 1750 ℃, pressurizing to 90MPa while heating, preserving heat and keeping pressure for 6 h.
EXAMPLE III
A preparation method of aluminum nitride ceramic with high thermal conductivity comprises the following steps:
(1) primary ball milling: adding aluminum nitride powder, calcium carbonate, lithium nitrate and ethanol into a ball mill for primary ball milling, performing ball milling dispersion for 15 hours, drying after ball milling, and sieving to obtain intermediate powder, wherein the mass ratio of the aluminum nitride powder to the calcium carbonate to the lithium nitrate is 90: 8: 6;
(2) and (3) calcining: calcining the intermediate powder obtained in the step (1) at 1050 ℃ for 30min in a nitrogen atmosphere, and sieving to obtain mixed powder;
(3) secondary ball milling: adding the mixed powder obtained in the step (2), molybdenum disulfide, a solvent, polyethylene glycol 400, a plasticizer and a binder into a ball mill for secondary ball milling for 20 hours;
the adding amount of the molybdenum disulfide is 50% of the mass of the mixed powder, and the solvent is absolute ethyl alcohol and isopropanol according to a mass ratio of 1: 3, wherein the addition amount of the solvent is 60% of the mass of the mixed powder, the addition amount of the polyethylene glycol 400 is 3% of the mass of the mixed powder, and the binder is prepared from polyvinyl butyral resin, an ethylene acrylic acid copolymer and linear low density polyethylene according to the mass ratio of 30: 6: 4, the addition amount of the binder is 4 percent of the mass of the mixed powder, and the addition amount of the trioctyl phosphate plasticizer is 1 percent of the mass of the mixed powder.
(4) Removing bubbles in vacuum: vacuumizing and defoaming the ball-milled materials by using a vacuum defoaming machine to obtain ceramic slurry with the viscosity of 15000mPa & s;
(5) tape casting: carrying out tape casting on the ceramic slurry obtained in the step (4) to obtain a ceramic green body, and cutting the ceramic green body into a required shape and size by using a mold to obtain a ceramic green sheet;
(6) isostatic pressing: putting the ceramic blank sheet obtained in the step (5) into a cold isostatic press for pressing, wherein the pressure is 250MPa, and the pressure maintaining time is 10 min;
(7) rubber discharging: coating a layer of adhesive powder on the surface of the ceramic blank sheet, laminating the ceramic blank sheet, preheating the ceramic blank sheet at 1150 ℃ for 120min, and then putting the ceramic blank sheet into a glue discharging furnace for vacuum glue discharging; the vacuum rubber discharge method comprises the following specific steps: firstly heating to 360 ℃ at the speed of 3 ℃/min, then preserving heat for 3h, then heating to 480 ℃ at the speed of 6 ℃/min, then preserving heat for 2h, then heating to 580 ℃ at the speed of 5 ℃/min, and then preserving heat for 2 h.
(8) Hot-pressing and sintering: and carrying out hot-pressing sintering on the ceramic blank sheet subjected to vacuum binder removal under the protection of nitrogen atmosphere, cooling to room temperature after sintering, and then carrying out powder removal polishing process to obtain the high-thermal-conductivity aluminum nitride ceramic. The specific conditions of hot-pressing sintering are as follows: heating to 1100 deg.C at a heating rate of 4 deg.C/min under 50MPa, maintaining for 2h, heating to 1800 deg.C, pressurizing to 100MPa while heating, and maintaining for 8 h.
Comparative example one (direct addition of calcium oxide and lithium oxide)
Calcium carbonate and lithium nitrate are replaced by equal molar weight of calcium oxide and lithium oxide, and the calcination is skipped after the primary ball milling, and the secondary ball milling is directly carried out. The proportions of other components and the process steps are the same as in the first embodiment.
Comparative example two (without molybdenum disulfide)
Molybdenum disulfide is not added during secondary ball milling, and the proportion and the process steps of other components are the same as those in the first embodiment.
Performance detection
The aluminum nitride ceramics prepared in examples one to three and comparative examples one to two were subjected to the test of thermal conductivity, flexural strength and bulk density, and the test results are shown in table 1.
| Thermal conductivity (W/(m.K)) | Bending Strength (MPa) | Bulk Density (g/cm)3) | |
| Example one | 205 | 486 | 3.38 |
| Example two | 213 | 505 | 3.42 |
| EXAMPLE III | 221 | 531 | 3.44 |
| Comparative example 1 | 177 | 429 | 3.25 |
| Comparative example No. two | 185 | 454 | 3.26 |
The above description is only an embodiment utilizing the technical content of the present disclosure, and any modification and variation made by those skilled in the art can be covered by the claims of the present disclosure, and not limited to the embodiments disclosed.
Claims (13)
1. A preparation method of aluminum nitride ceramics with high thermal conductivity is characterized by comprising the following steps: the method comprises the following steps:
(1) primary ball milling: adding aluminum nitride powder, calcium carbonate, lithium nitrate and ethanol into a ball mill for primary ball milling, dispersing for 6-15h by ball milling, drying after ball milling, and sieving to obtain intermediate powder;
(2) and (3) calcining: calcining the intermediate powder obtained in the step (1) at 950-1050 ℃ for 30-90 min in a nitrogen atmosphere, and sieving to obtain mixed powder;
(3) secondary ball milling: adding the mixed powder obtained in the step (2), molybdenum disulfide, a solvent, a dispersing agent, a plasticizer and a binder into a ball mill for secondary ball milling for 10-20 hours, wherein the binder consists of polyvinyl butyral resin, an ethylene acrylic acid copolymer and linear low-density polyethylene;
(4) removing bubbles in vacuum: vacuumizing and defoaming the ball-milled materials by using a vacuum defoaming machine to obtain ceramic slurry with the viscosity of 12000-15000 mPa & s;
(5) tape casting: carrying out tape casting on the ceramic slurry obtained in the step (4) to obtain a ceramic green body, and cutting the ceramic green body into a required shape and size by using a mold to obtain a ceramic green sheet;
(6) isostatic pressing: putting the ceramic blank sheet obtained in the step (5) into a cold isostatic press for pressing, wherein the pressure is 200-280 MPa, and the pressure maintaining time is 5-15 min;
(7) rubber discharging: coating a layer of adhesive powder on the surface of the ceramic blank sheet, laminating the ceramic blank sheet, preheating the ceramic blank sheet at the temperature of 130-150 ℃ for 80-120 min, and then putting the ceramic blank sheet into a glue discharging furnace for vacuum glue discharging;
(8) hot-pressing and sintering: and carrying out hot-pressing sintering on the ceramic blank sheet subjected to vacuum binder removal under the protection of nitrogen atmosphere, cooling to room temperature after sintering, and then carrying out powder removal polishing process to obtain the high-thermal-conductivity aluminum nitride ceramic.
2. The method for preparing high thermal conductivity aluminum nitride ceramic according to claim 1, wherein: the mass ratio of the aluminum nitride powder to the calcium carbonate to the lithium nitrate is 85-90: 5-8: 3 to 6.
3. The method for preparing the aluminum nitride ceramic with high thermal conductivity according to claim 1, wherein the method comprises the following steps: the addition amount of the molybdenum disulfide is 30-50% of the mass of the mixed powder.
4. The method for preparing high thermal conductivity aluminum nitride ceramic according to claim 1, wherein: the solvent is a mixed solvent composed of absolute ethyl alcohol and isopropanol, and the addition amount of the solvent is 40-60% of the mass of the mixed powder.
5. The method for preparing the aluminum nitride ceramic with high thermal conductivity according to claim 1, wherein the method comprises the following steps: the dispersing agent is any one of sodium polyacrylate, fish oil and polyethylene glycol, and the addition amount of the dispersing agent is 1.5-3% of the mass of the mixed powder.
6. The method for preparing high thermal conductivity aluminum nitride ceramic according to claim 1, wherein: the addition amount of the binder is 2-4% of the mass of the mixed powder.
7. The method for preparing high thermal conductivity aluminum nitride ceramic according to claim 6, wherein: the mass ratio of the polyvinyl butyral resin to the ethylene acrylic acid copolymer to the linear low-density polyethylene is (20-30): 3-6: 2 to 4.
8. The method for preparing the aluminum nitride ceramic with high thermal conductivity according to claim 1, wherein the method comprises the following steps: the plasticizer is at least one of dimethyl phthalate, diethyl phthalate and trioctyl phosphate, and the addition amount of the plasticizer is 0.5-1% of the mass of the mixed powder.
9. The method for preparing high thermal conductivity aluminum nitride ceramic according to claim 1, wherein: and (4) carrying out isostatic pressing in the step (6) at a pressure of 230-250 MPa for a pressure maintaining time of 7-10 min.
10. The method for preparing the aluminum nitride ceramic with high thermal conductivity according to claim 1, wherein the method comprises the following steps: the step (7) of vacuum glue discharging comprises the following specific steps: heating to 280-360 ℃ at the speed of 1-3 ℃/min, then preserving heat for 2-3 h, heating to 420-480 ℃ at the speed of 4-6 ℃/min, then preserving heat for 1-2 h, heating to 540-580 ℃ at the speed of 3-5 ℃/min, and then preserving heat for 1-2 h.
11. The method for preparing high thermal conductivity aluminum nitride ceramic according to claim 1, wherein: the specific conditions of the hot-pressing sintering in the step (8) are as follows: raising the temperature to 1000-1100 ℃ at a temperature raising rate of 2-4 ℃/min under the pressure of 30-50 MPa, preserving the heat for 1-2 h, then continuing raising the temperature to 1700-1800 ℃, increasing the temperature and simultaneously pressurizing to 80-100 MPa, preserving the heat and keeping the pressure for 4-8 h.
12. An aluminum nitride ceramic produced by the production method according to any one of claims 1 to 11.
13. The aluminum nitride ceramic of claim 12, wherein: the aluminum nitride ceramic has a thermal conductivity of 200-230W/(m.K), a bending strength of 470-540 MPa, and a bulk density of 3.3-3.5 g/cm3。
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