CN113121252B - Preparation method of high-thermal-conductivity SiC-AlN composite ceramic - Google Patents
Preparation method of high-thermal-conductivity SiC-AlN composite ceramic Download PDFInfo
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Abstract
The invention belongs to the field of SiC-AlN composite ceramic sintering preparation, and provides a preparation method of high-thermal conductivity SiC-AlN composite ceramic, which comprises the following steps: s1, providing silicon-containing raw material powder, wherein the silicon-containing raw material powder comprises coarse-particle silicon carbide powder and fine-particle silicon powder; s2, carrying out low-energy ball milling and mixing on the silicon-containing raw material powder, an aluminum nitride source and a carbon source to obtain uniformly mixed raw material powder; s3, carrying out synthetic reaction on the uniformly mixed powder to obtain SiC-AlN composite powder containing silicon carbide whiskers; and S4, mixing the SiC-AlN composite powder with a sintering aid and sintering to obtain the SiC-AlN composite ceramic. The process is simple and easy to implement, and has important significance in improving the thermal conductivity, strength and the like of the SiC-AlN composite ceramic.
Description
Technical Field
The invention belongs to the technical field of advanced ceramic preparation, and particularly relates to a preparation method of high-thermal-conductivity SiC-AlN composite ceramic.
Background
With the development of electronic products, especially consumer electronic products and high-power LEDs, the circuit integration level is higher and higher, and the problem of overheating of electronic devices is more and more serious. In most electronic products, an insulating medium is often used before the substrate and the circuit layer, and the insulating medium is mostly organic materials and metal oxides, which have quite low thermal conductivity. Excessive heat buildup can cause substrate deformation and reduce the lifetime of the electronic device. In general, the use of a substrate material with good heat dissipation property is the first choice to solve the problem of heat accumulation, and therefore, how to improve the heat conductivity of the substrate material is the focus of current research.
In recent years, ceramic substrate materials have become one of the best choices for high-power integrated circuit substrates due to their outstanding thermal conductivity compared to other substrate materials. Among the ceramic materials, beryllium oxide (BeO), aluminum oxide (Al) are commonly used as substrates2O3) Aluminum nitride (AlN), silicon carbide (SiC), and the like. Among them, BeO has good comprehensive performance and high heat dissipation, but its use range is limited due to toxicity. Al (Al)2O3Low cost, but thermal conductivityThe ratio is relatively poor, and is only about 30W/m.K. AlN ceramics and SiC ceramics are important advanced ceramic materials. Phase contrast Al2O3AlN has more excellent thermal conductivity, good insulation property and low dielectric constant, and is suitable for high-power circuits. In addition, SiC has the characteristics of high thermal conductivity, high hardness, good wear resistance and corrosion resistance, excellent thermal shock resistance, low thermal expansion coefficient and the like.
However, SiC ceramics and AlN ceramics also have some disadvantages in terms of preparation and performance. The SiC has stronger covalent bond, so that the sintering temperature of the ceramic is high and the ceramic is difficult to compact; AlN raw material is expensive, so the preparation cost of the ceramic is high, and hydrolysis reaction is easy to occur. The SiC-AlN composite ceramic can make up the defects of the two materials independently and keep the original excellent characteristics. Particularly, the composite ceramic product has high density and better mechanical properties such as bending strength and the like due to the similar density and thermal expansion coefficient of the composite ceramic product.
However, compared to the theoretical thermal conductivity of AlN and SiC ceramics, the thermal conductivity of SiC-AlN composite ceramic materials currently prepared is generally lower. Such as: D.H.A. Besisa et al [ Densitification and characterization of SiC-AlN composites for solar Energy applications, D.H.A. Besisa, E.M.EWAIS.Y.M.Z.Ahmed, Recewable Energy 129(2018)201 and 213], the thermal conductivity of the SiC-AlN composite ceramics prepared under different atmospheres is only 51W/m.K at most; gu et al [ Thermal conductivity and high-frequency dielectric properties of compressed SiC-AlN multiphasic ceramics, J.L.Gu, L.L.Sangg, B.Pan, materials.11(2018)969] adopt a pressureless sintering mode, and the obtained SiC-AlN composite ceramic has the highest Thermal conductivity of only 61W/m.K. In conclusion, how to further improve the thermal conductivity of the material is a problem to be solved urgently in the industrial application of the SiC-AlN composite ceramic.
Disclosure of Invention
In view of the above, the application provides a preparation method of the high-thermal conductivity SiC-AlN composite ceramic, and the SiC-AlN composite ceramic with good mechanical property and high thermal conductivity can be obtained by the method.
The invention provides a preparation method of SiC-AlN composite powder, which comprises the following steps:
s1, providing silicon-containing raw material powder, wherein the silicon-containing raw material powder comprises coarse silicon carbide powder and fine silicon powder;
s2, carrying out low-energy ball milling and mixing on the silicon-containing raw material powder, an aluminum nitride source and a carbon source to obtain uniformly mixed powder;
s3, carrying out synthetic reaction on the uniformly mixed powder to obtain SiC-AlN composite powder containing silicon carbide whiskers;
and S4, mixing the SiC-AlN composite powder with a sintering aid and sintering to obtain the high-thermal-conductivity SiC-AlN composite ceramic.
Preferably, in the step S1, the primary particle size range of the coarse silicon carbide powder is 1.5 to 20 μm, and the primary particle size range of the fine silicon carbide powder is 0.1 to 2 μm.
Preferably, the material composition of the silicon-containing raw material powder is 10% -90% of silicon carbide and 10% -90% of silicon.
Preferably, the molar ratio of silicon in the silicon-containing raw material powder silicon powder to carbon in the carbon source is 1: 1-1: 2; the aluminum nitride source accounts for 1-35% of the total mass of the powder in the step.
Preferably, the aluminum nitride source is one or two of aluminum and aluminum nitride; the carbon source can be one or more of inorganic carbon sources such as carbon black, activated carbon, graphite and the like, and can also be one or more of organic carbon sources such as glucose, starch, melamine and the like; the ball-material ratio of the low-energy ball milling mixed material is 3: 1-20: 1, and the ball milling time is 5-24 hours.
Preferably, the reaction temperature is 1300-1600 ℃, and the heat preservation time is 0.5-4 hours; the atmosphere of the synthesis reaction is one of nitrogen, ammonia or argon atmosphere.
Preferably, after the reaction, removing the excessive carbon source by a combustion method to obtain pure SiC-AlN composite powder.
Preferably, in step S4, the sintering aid is a rare earth oxide, preferably one or more of yttrium oxide, lanthanum oxide and strontium oxide; the added mass of the sintering aid is 1-5% of the total mass of the powder in the step.
Preferably, the sintering manner in step S4 is one of vacuum sintering, low-pressure sintering, hot-pressing sintering, spark plasma sintering or microwave sintering; the sintering temperature in the step S4 is 1700-2100 ℃.
The invention has the following advantages and beneficial effects:
(1) according to the invention, the silicon carbide and the silicon with different grain sizes are used as main initial raw materials, so that the material is easy to compact and sinter, and the grain boundary in the unit volume of the material can be reduced, which is beneficial to improving the thermal conductivity of the SiC-AlN composite ceramic.
(2) The SiC-AlN composite powder raw material is prepared in advance, and the composite powder contains the silicon carbide crystal whisker, so that the mechanical property of the SiC-AlN composite ceramic which is subsequently sintered is improved.
(3) According to the invention, the pre-synthesized powder is used as a raw material to sinter the SiC-AlN composite ceramic, and the SiC and the AlN are easy to form a 2H solid solution, so that the strength of the composite ceramic is improved.
(4) The preparation method of the SiC-AlN composite ceramic provided by the invention has the advantages of simple and easy process, low cost of raw materials and good comprehensive performance of materials, and is suitable for industrial large-scale popularization.
Drawings
FIG. 1 is an SEM image of the morphology of a silicon-containing raw material powder in example 1 of the present invention;
FIG. 2 is the EDS diagram corresponding to b in FIG. 1;
FIG. 3 is an EDS diagram corresponding to c in FIG. 1;
FIG. 4 is a graph showing a particle size curve of a silicon-containing raw material powder in example 1 of the present invention;
FIG. 5 is an SEM photograph of the SiC-AlN composite powder obtained in example 1 of the present invention;
FIG. 6 is a TEM image of the silicon carbide whisker obtained in example 1 of the present invention;
FIG. 7 is an HR-TEM image of the silicon carbide whisker obtained in example 1 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of SiC-AlN composite powder, which comprises the following steps:
s1, providing silicon-containing raw material powder, wherein the silicon-containing raw material powder comprises coarse-particle silicon carbide powder and fine-particle silicon powder;
s2, carrying out low-energy ball milling and mixing on the silicon-containing raw material powder, an aluminum nitride source and a carbon source to obtain uniformly mixed raw material powder;
s3, carrying out synthetic reaction on the uniformly mixed powder under a certain atmosphere to obtain SiC-AlN composite powder containing silicon carbide whiskers;
and S4, mixing the SiC-AlN composite powder with a sintering aid and sintering to obtain the high-thermal-conductivity SiC-AlN composite ceramic.
The SiC-AlN composite powder obtained by the invention is beneficial to the sintering preparation of SiC-AlN composite ceramic, and can improve the thermal conductivity and the like of the ceramic material.
The embodiment of the invention firstly provides silicon-containing raw material powder, preferably obtains silicon carbide main raw material by recycling solid photovoltaic crystal silicon waste, and the material composition of the silicon-containing raw material powder comprises coarse-particle silicon carbide powder and fine-particle silicon powder.
The silicon source used for preparing the SiC-AlN composite powder is preferably solid photovoltaic crystal silicon waste, and the silicon source mainly comprises silicon carbide and silicon; and the particle size distribution of the solid photovoltaic crystal silicon waste material is wide, the main particle size of coarse silicon carbide particles is about 10 mu m, and the main particle size of fine silicon particles is about 1.5 mu m. The method takes the solid photovoltaic crystal silicon waste as the raw material, is beneficial to recycling the photovoltaic crystal silicon waste, and has the advantages of low raw material cost and good environmental protection. In the embodiment of the invention, the solid photovoltaic crystalline silicon waste material is waste mortar generated in the photovoltaic crystalline silicon cutting process, the content of silicon carbide or silicon can be close to 10-90%, and almost all the silicon carbide or silicon can be contained in the powder.
The embodiment of the invention takes the waste mortar powder as the following specific substances in percentage by mass: 10 to 90 percent of silicon carbide and 10 to 90 percent of silicon, preferably 15 to 50 percent. The silicon-containing raw material powder has different micro-nano particle size ranges, and specifically comprises the following steps: the coarse particles are silicon carbide, and the main particle size range of the coarse particles is 1.5-20 mu m, for example, the main particle size is about 10 mu m; the fine particles are mainly silicon, and have a main particle diameter in the range of 0.1 to 2 μm, for example, about 1.5 μm.
After the silicon-containing raw material powder is obtained, the silicon-containing raw material powder, an aluminum nitride source and a carbon source are placed in a ball milling tank according to different proportions, and preferably mixed through ball milling to obtain mixed powder. Wherein the aluminum nitride source can be aluminum powder or aluminum nitride powder, and the particle size is 1-3 mu m; wherein the aluminum powder can be synthesized into aluminum nitride in the atmosphere of nitrogen or ammonia gas while silicon-carbon reaction is carried out. The carbon source can be one or more of inorganic carbon sources such as carbon black, activated carbon, graphite and the like, and can also be one or more of organic carbon sources such as glucose, starch, melamine and the like; carbon black is preferably used as a carbon source in the present invention.
In the embodiment of the invention, the molar ratio of silicon in the silicon-containing raw material powder silicon powder to carbon in the carbon source can be 1: 1-1: 2; the invention preferably employs an excess of carbon source to ensure complete reaction. The content of aluminum nitride in the composite powder has a large influence on the performance of subsequent ceramics, and the aluminum nitride powder accounts for 1-35% of the total mass of the powder, and more preferably 5-15%. The mass ratio of the low-energy ball milling ball materials is preferably 3: 1-20: 1, and the ball milling time can be 5-24 hours. After the mixing is finished, the ball material is separated by sieving, and mixed powder with uniform mixing can be obtained.
In the embodiment of the invention, the mixed powder is put in a sintering furnace and is synthesized by reaction in a certain atmosphere. The reaction synthesis temperature is preferably 1300-1600 ℃, and the heat preservation time is 0.5-4 hours; the atmosphere is preferably argon when aluminum nitride powder is used as a raw material, and nitrogen or ammonia is selected when aluminum powder is used as a raw material. After the reaction, the method preferably further comprises the following steps: and removing the excessive carbon source by a combustion method to obtain pure SiC-AlN powder. The temperature for removing by the combustion method can be 600-700 ℃, and the heat preservation time is 0.5-2 hours.
The SiC-AlN composite powder prepared by the invention comprises SiC and AlN; the powder is uniformly dispersed and a certain amount of silicon carbide crystal whiskers are generated. The particle size distribution of the composite powder is not obviously changed compared with the original solid photovoltaic crystal silicon waste material, and the AlN substance accounts for 1-35 percent. The SiC-AlN powder is adopted for sintering, and the SiC-AlN composite ceramic with good mechanical property and high thermal conductivity can be obtained.
The SiC-AlN composite powder is taken out, added with the sintering aid and uniformly mixed, and then placed in a graphite mold for sintering to obtain the SiC-AlN composite ceramic.
Wherein, the sintering aid is preferably rare earth element oxide, and more preferably one or more of yttrium oxide, lanthanum oxide and strontium oxide; the added mass of the sintering aid can be 1-5% of the total mass of the sintering powder. The sintering mode can be one of vacuum sintering, low-pressure sintering, hot-pressing sintering, spark plasma sintering or microwave sintering, and the spark plasma sintering is preferably adopted in the invention. The sintering temperature is preferably 1700-2100 ℃; the heating rate can be 50-300 ℃/min, the heat preservation time is 5-20 min, the pressure is 20-70 MPa, and the atmosphere is vacuum or a small amount of argon.
In the composite ceramic, different aluminum nitride contents have an effect on the bulk properties. The highest value of the thermal conductivity is AlN is 5 wt% (according to the mass fraction of aluminum nitride in the block sintering to the total mass), and the thermal conductivity is slowly reduced when the thermal conductivity is too high; the bending strength is in an ascending trend, and can reach 580MPa after 15 wt%; the compactness can reach 98.6 percent when the compactness is 5 weight percent, and then is maintained at about 99 percent. In general, the aluminum nitride content is preferably 5 to 15 wt%.
In summary, in the embodiment of the invention, a certain amount of solid photovoltaic crystalline silicon waste material composed of silicon carbide and silicon is selected as raw material powder, and then the raw material powder, an aluminum nitride source and carbon black are put into a ball milling tank to be ball milled and mixed, so that uniform mixed powder is obtained. According to the embodiment of the invention, the mixed powder is subjected to reaction synthesis and decarbonization to obtain pure SiC-AlN composite powder; finally, mixing the ceramic powder with a sintering aid, and sintering the ceramic powder in a discharge plasma mode to obtain the composite ceramic. The embodiment of the invention is a novel technical scheme for preparing uniformly mixed composite powder and SiC-AlN composite ceramic with high thermal conductivity and high strength by using solid photovoltaic crystalline silicon waste as a main raw material, and is beneficial to application in products such as a heat-conducting ceramic substrate and the like.
For further understanding of the present application, the following specifically describes the preparation method of the SiC — AlN composite ceramic with high thermal conductivity provided in the present application with reference to examples. It should be understood, however, that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention, which is defined by the following examples.
In the following examples, the silicon-containing raw material powder is waste mortar powder, wherein the content of silicon carbide is 75%, and the balance is silicon; the main particle size range of the coarse silicon carbide powder is 1.5-20 μm, and the main particle size range of the fine silicon powder is 0.1-2 μm. The particle size of the aluminum nitride source is 1-3 mu m.
Example 1
(1) Taking silicon-containing raw material powder with 25 percent of silicon content, adding carbon black (with the purity of 99.9 percent and the particle diameter of about 100 nm) with the molar ratio of 1.2 times and 5 weight percent of aluminum nitride powder into a ball milling tank, and ball milling for 10 hours according to the ball-to-material ratio of 10: 1; after the mixing is finished, the ball material is separated by sieving, and mixed powder with uniform mixing is obtained. The raw material mixture ratio here was 100g of raw material, 5g of aluminum nitride, 86.6g of silicon-containing raw material powder, and 8.4g of carbon black.
(2) And (2) filling the mixed powder in the step (1) into a graphite crucible, putting the graphite crucible into a vacuum sintering furnace, vacuumizing and washing gas, and introducing flowing argon gas with the gas flow of 1L/min. Setting the heating rate at 5 ℃/min, reacting at 1400 ℃, and keeping the temperature for 2 h.
(3) And (3) cooling the system after the reaction in the step (2), taking out the powder, heating to 700 ℃ in the air atmosphere, preserving the heat for 1h, and removing excessive carbon to obtain about 98.6g of pure SiC-AlN composite powder.
(4) And (4) taking out the SiC-AlN composite powder obtained in the step (3), adding 3 wt% of yttrium oxide, uniformly mixing, putting into a graphite mold with the diameter of 30mm, pressing two ends of the mold by using a pressure head, putting into a discharge plasma sintering furnace, vacuumizing and introducing a small amount of argon. Setting the heating rate at 100 ℃/min, and preserving the heat at 1900 ℃ for 10min to finish sintering to obtain the SiC-AlN composite ceramic.
The relative density of the SiC-AlN composite ceramic sample is 99.6 percent; the thermal conductivity is 125W/(m.K); the three-point bending strength is 293 MPa. The test method comprises the following steps: the density was measured by Archimedes drainage method, the thermal conductivity was measured by a laser thermal conductivity meter, and the bending strength was measured by a universal testing machine, and the same applies to the following examples.
In the embodiment, the silicon-containing raw material powder contains 75 wt% of silicon carbide and 25 wt% of silicon; the SEM picture of the powder morphology is shown in figure 1, the corresponding EDS picture is shown in figures 2-3, and the particle size curve of the powder is shown in figure 4. As can be seen from the figure, in the silicon-containing raw material powder, the coarse particles are silicon carbide, and the main particle size is about 10 mu m; the fine particles are silicon powder, and the main particle size is about 1.5 mu m.
The SEM image of the SiC-AlN composite powder obtained in this example is shown in FIG. 5, the TEM image of the whisker obtained is shown in FIG. 6, and the corresponding HR-TEM image is shown in FIG. 7. It can be seen from the figure that the powder has a certain amount of silicon carbide whiskers due to the coexistence of the particle sizes and sizes.
Example 2
(1) Taking silicon-containing raw material powder with 25 percent of silicon content, adding carbon black in a molar ratio of 1.5 times and 15 percent of aluminum powder by weight into a ball milling tank, and ball milling for 10 hours according to a ball-to-material ratio of 20: 1; after the mixing is finished, the ball material is separated by sieving, and mixed powder with uniform mixing is obtained. The raw materials comprise 100g of raw materials, 15g of aluminum powder, 75.8g of silicon-containing raw material powder and 9.2g of carbon black.
(2) And (2) filling the powder mixed in the step (1) into a graphite crucible, putting the graphite crucible into a vacuum sintering furnace, vacuumizing and washing gas, and introducing flowing nitrogen with the gas flow of 1L/min. Setting the heating rate at 5 ℃/min, reacting at 1600 ℃, and keeping the temperature for 2 h.
(3) And (3) cooling the system after the reaction in the step (2), taking out the powder, heating to 700 ℃ in the air atmosphere, preserving the heat for 1h, and removing excessive carbon to obtain about 104.7g of pure SiC-AlN composite powder.
(4) And (4) taking out the SiC-AlN composite powder obtained in the step (3), adding 3 wt% of lanthanum oxide, uniformly mixing, putting into a graphite mold with the diameter of 30mm, pressing two ends of the mold by using a pressure head, putting into a discharge plasma sintering furnace, vacuumizing and introducing a small amount of argon. Setting the heating rate at 100 ℃/min, and preserving the heat at 1900 ℃ for 10min to finish sintering to obtain the SiC-AlN composite ceramic.
The relative density of the SiC-AlN composite ceramic sample is 99.6 percent; the thermal conductivity is 95W/(m.K); the three-point bending strength is 580 MPa.
Example 3
(1) Taking silicon-containing raw material powder with the silicon content of 25 percent, adding 1 time of urea and 35wt percent of aluminum nitride powder in a molar ratio into a ball milling tank, and ball milling for 5 hours according to the ball-to-material ratio of 5: 1; after the mixing is finished, the ball material is separated by sieving, and mixed powder with uniform mixing is obtained. The raw material mixture ratio here is 100g of raw material, 35g of aluminum nitride, 46.3g of silicon-containing raw material powder and 18.7g of urea.
(2) And (2) filling the mixed powder in the step (1) into a graphite crucible, putting the graphite crucible into a vacuum sintering furnace, vacuumizing and washing gas, and introducing flowing argon gas with the gas flow of 1L/min. Setting the heating rate at 5 ℃/min, reacting at 1300 ℃, and keeping the temperature for 1 h.
(3) And (3) cooling the system after the reaction in the step (2), taking out the powder, heating to 600 ℃ in the air atmosphere, preserving the heat for 1h, and removing excessive carbon to obtain about 85g of pure SiC-AlN composite powder.
(4) And (4) taking out the SiC-AlN composite powder obtained in the step (3), adding 1 wt% of yttrium oxide, uniformly mixing, putting into a mold with the diameter of 20mm to prepare a green compact, taking out, putting into a microwave sintering furnace, vacuumizing and introducing argon. Setting the heating rate at 150 ℃/min, and preserving the heat at 1700 ℃ for 5min to complete sintering to obtain the SiC-AlN composite ceramic.
The relative density of the SiC-AlN composite ceramic sample is 99.2 percent; the thermal conductivity is 86W/(m.K); the three-point bending strength is 500 MPa.
Example 4
(1) Taking silicon-containing raw material powder with the silicon content of 25 percent, adding 1.5 times of active carbon and 2 weight percent of aluminum nitride powder into a ball milling tank, and ball milling for 20 hours according to the ball-to-material ratio of 20: 1; after the mixing is finished, the ball material is separated by sieving, and mixed powder with uniform mixing is obtained. The raw material mixture ratio is 100g of raw material, 2g of aluminum nitride, 85.9g of silicon-containing raw material powder and 9.1g of activated carbon.
(2) And (2) filling the mixed powder in the step (1) into a graphite crucible, putting the graphite crucible into a vacuum sintering furnace, vacuumizing and washing gas, and introducing flowing argon gas with the gas flow of 1L/min. Setting the heating rate at 5 ℃/min, reacting at 1600 ℃, and keeping the temperature for 1 h.
(3) And (3) cooling the system after the reaction in the step (2), taking out the powder, heating to 600 ℃ in the air atmosphere, preserving the heat for 1h, and removing excessive carbon to obtain about 97g of pure SiC-AlN composite powder.
(4) And (4) taking out the SiC-AlN composite powder obtained in the step (3), adding 5 wt% of strontium oxide, uniformly mixing, putting into a mold with the diameter of 50mm to manufacture a green compact, taking out, putting into a vacuum sintering furnace, and vacuumizing. Setting the heating rate at 10 ℃/min, and preserving heat for 2h at 2100 ℃ to complete sintering to obtain the SiC-AlN composite ceramic.
The relative density of the SiC-AlN composite ceramic sample is 93.5 percent; the thermal conductivity is 108W/(m.K); the three-point bending strength is 221 MPa.
Example 5
(1) Taking silicon-containing raw material powder with the silicon content of 30 percent, adding glucose with the molar ratio of 1.5 times and aluminum nitride powder with the weight percent of 2 into a ball milling tank, and ball milling for 20 hours according to the ball-to-material ratio of 20: 1; after the mixing is finished, the ball material is separated by sieving, and mixed powder with uniform mixing is obtained. The raw material mixture ratio here was 100g of raw material, 2g of aluminum nitride, 71.5g of silicon-containing raw material powder, and 26.5g of glucose.
(2) And (2) filling the mixed powder in the step (1) into a graphite crucible, putting the graphite crucible into a vacuum sintering furnace, vacuumizing and washing gas, and introducing flowing argon gas with the gas flow of 1L/min. Setting the heating rate at 20 ℃/min, reacting at 1500 ℃, and keeping the temperature for 30 min.
(3) And (3) cooling the system after the reaction in the step (2), taking out the powder, heating to 600 ℃ in the air atmosphere, preserving the temperature for 1h, and removing excessive carbon to obtain about 81.6g of pure SiC-AlN composite powder.
(4) And (4) taking out the SiC-AlN composite powder obtained in the step (3), adding 4 wt% of yttrium oxide, uniformly mixing, putting into a die with the diameter of 30mm to prepare a green compact, taking out, putting into a low-pressure sintering furnace, vacuumizing and introducing 3MPa argon. Setting the heating rate at 10 ℃/min, and preserving heat for 2h at 2000 ℃ to complete sintering to obtain the SiC-AlN composite ceramic.
The relative density of the SiC-AlN composite ceramic sample is 92.8 percent; the thermal conductivity is 106W/(m.K); the three-point bending strength is 245 MPa.
In the prior art, silicon carbide powder and aluminum nitride powder are directly sintered to prepare composite ceramic, wherein the grain diameter of SiC is 0.5 micron, and the thermal conductivity of the composite ceramic is respectively about 50W/(m.K) and 60W/(m.K). The relative density of the SiC-AlN composite ceramic sample prepared by the invention can reach 99.6 percent; the thermal conductivity can reach 125W/(m.K); the three-point bending strength can reach 580 MPa. Therefore, the invention has important significance in improving the thermal conductivity and the strength of the SiC-AlN composite ceramic and is beneficial to application.
The above description is only a preferred embodiment of the present invention, and it should be noted that various modifications to these embodiments can be implemented by those skilled in the art without departing from the technical principle of the present invention, and these modifications should be construed as the scope of the present invention.
Claims (9)
1. A preparation method of SiC-AlN composite ceramic comprises the following steps:
s1, providing silicon-containing raw material powder, wherein the silicon-containing raw material powder comprises coarse-particle silicon carbide powder and fine-particle silicon powder;
s2, carrying out low-energy ball milling and mixing on the silicon-containing raw material powder, an aluminum nitride source and a carbon source to obtain uniformly mixed powder; the molar ratio of silicon in the silicon-containing raw material powder silicon powder to carbon in the carbon source is 1: 1-1: 2; the aluminum nitride source accounts for 1% -35% of the total mass of the powder in the step; the aluminum nitride source is aluminum or aluminum nitride;
s3, carrying out synthetic reaction on the uniformly mixed powder to obtain SiC-AlN composite powder; the SiC-AlN composite powder contains silicon carbide whiskers; the atmosphere of the synthesis reaction is argon when aluminum nitride is used as a raw material, and nitrogen or ammonia is selected when aluminum is used as a raw material;
and S4, mixing the SiC-AlN composite powder with a sintering aid and sintering to obtain the high-thermal-conductivity SiC-AlN composite ceramic.
2. The method according to claim 1, wherein in step S1, the coarse silicon carbide powder has a primary particle size of 1.5 to 20 μm, and the fine silicon powder has a primary particle size of 0.1 to 2 μm.
3. The production method according to claim 1 or 2, wherein the silicon-containing raw material powder has a material composition of: SiC accounts for 10-90%, and Si accounts for 10-90%.
4. The preparation method according to claim 1, wherein the carbon source is one or more of carbon black, activated carbon, graphite, glucose, starch and melamine; the ball-material ratio of the low-energy ball milling mixed material is 3: 1-20: 1, and the ball milling time is 5-24 hours.
5. The preparation method according to claim 4, wherein the reaction temperature is 1300-1600 ℃ and the holding time is 0.5-4 hours.
6. The preparation method according to claim 5, characterized in that the reaction is followed by removing excess carbon source by combustion to obtain pure SiC-AlN composite powder.
7. The method according to claim 1, wherein in the step S4, the sintering aid is one or more of yttrium oxide, lanthanum oxide, and strontium oxide; the mass of the sintering aid is 1-5% of the total mass of the powder in the step.
8. The method according to claim 7, wherein the sintering manner in step S4 is one of vacuum sintering, low-pressure sintering, hot-press sintering, spark plasma sintering, and microwave sintering.
9. The method according to claim 8, wherein the sintering temperature in the step S4 is 1700-2100 ℃.
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