Porous carbide ceramic preparation method based on combination of stacking process and template method

Abstract

The invention belongs to the technical field of porous ceramic material preparation, and particularly relates to a porous carbide ceramic preparation method based on combination of a stacking process and a template method, which comprises the following steps: S1, uniformly coating carbide slurry on two sides of a polyurethane foam template, and drying at room temperature to form a sheet green body; the carbide slurry is composed of the following components: 75-85 wt% of carbide powder, 2-5 wt% of a binder, 1-3 wt% of a composite dispersant, 1-3 wt% of a sintering aid, and the balance of a solvent. S2, uniformly coating the single side of the sheet green body with oxide slurry to form a transition layer; the oxide slurry is composed of the following components: 70-80 wt% of oxide powder, 2-5 wt% of a binder, 1-2 wt% of a dispersant, and the balance of a solvent; according to the sandwich type stacking method for controlling the thickness and the reaction transition layer for forming chemical bonds in the sintering process, the structural integrity is improved, and the cracking risk is reduced.

Description

Technical Field

[0001] This invention relates to the field of porous ceramic material preparation technology, and in particular to a method for preparing porous carbide ceramics based on a combination of stacking process and template method. Background Technology

[0002] In the growth of semiconductor single crystals (such as SiC and GaN), porous ceramic materials are required in the PVT furnace to control the airflow distribution and adsorb impurities, thereby improving crystal quality. Traditional porous ceramic preparation methods (such as template methods) have the following problems: 1. Thickness limitation: When preparing high-thickness ceramics, if the solid content of the slurry is too low, it will easily lead to uneven slurry coating, while if the solid content is too high, it will lead to poor slurry fluidity; 2. Stress cracking: Cracking occurs due to uneven shrinkage stress during the drying and sintering process of large-sized billets. Summary of the Invention

[0003] This invention provides a method for preparing porous carbide ceramics based on a combination of stacking process and template method, aiming to solve at least one of the above-mentioned technical problems.

[0004] This invention provides the following technical solution: A method for preparing porous carbide ceramics based on a combination of stacking and template methods includes the following steps: Step S1: The carbide slurry is evenly coated on both sides of the polyurethane foam template and dried at room temperature to form a thin sheet green blank. The carbide slurry is composed of the following components: 75-85 wt% carbide powder, 2-5 wt% binder, 1-3 wt% composite dispersant, 1-3 wt% sintering aid, and the balance being solvent. Step S2: Uniformly coat one side of the thin sheet green blank with oxide slurry to form a transition layer; The oxide slurry is composed of the following components: 70-80 wt% oxide powder, 2-5 wt% binder, 1-2 wt% dispersant, and the balance being solvent; Step S3: Stack multiple layers of green sheets, with a transition layer between two adjacent green sheets, dry at room temperature and then heat up gradually to solidify; hot press and sinter, then cool to produce porous carbide ceramics.

[0005] Preferably, in step S1, the carbide powder is one of silicon carbide, hafnium carbide, and tantalum carbide; the binder is one of PVA1788 and PVB; the composite dispersant is one of PVPK30+PEG6000 and PAA+PEG; the sintering aid is one of nickel powder and molybdenum disilicide; and the solvent is two of ethanol, ethylene glycol, and benzyl alcohol.

[0006] Preferably, in step S1, the method for preparing the carbide slurry is as follows: Two carbide powders with different particle sizes are thoroughly mixed, and then solvent, binder, composite dispersant and sintering aid are added in sequence. After mixing evenly, the mixture is placed in a planetary ball mill and ball-milled for 4-5 hours to obtain a carbide slurry. The slurry has a particle size D50 of 0.8-1 μm, a solid content of 40-50 vol%, a viscosity of 100-150 mPa.s, and a pH of 8-9.

[0007] Preferably, in step S2, the oxide powder is one of silicon oxide, hafnium oxide, and tantalum oxide; the binder is one of PVA1788 and PVB; the dispersant is one of PAA-NH4 and PEI; and the solvent is two of ethanol, isopropanol, and benzyl alcohol.

[0008] Preferably, in step S2, the method for preparing the oxide slurry is as follows: Two tantalum pentoxide powders with different particle sizes are thoroughly mixed. Then, solvent, binder and dispersant are added in sequence. After mixing evenly, the mixture is placed in a planetary ball mill and ball-milled for 3-4 hours to obtain an oxide slurry. The particle size of the slurry is D50=1-2μm, the solid content is 30-40vol%, and the viscosity is 100-200mPa·s.

[0009] Preferably, in step S3, after drying at room temperature, the temperature is gradually increased and cured. The temperature is maintained at 40-60℃ for 1-3 hours, then increased to 80-120℃ at 4-7℃ / min and maintained for 3-4 hours, and then increased to 120-160℃ at 1-3℃ / min and maintained for 1-3 hours.

[0010] Preferably, in step S3, the sintering conditions are: in a hot press furnace, the vacuum degree is less than 10. -3 At a pressure of 3-10 MPa, the temperature is increased to 300-450℃ at a rate of 3-5℃ / min and held for 2-3 hours; then increased to 800-1000℃ at a rate of 5-10℃ / min and held for 2-3 hours; then increased to 1500-1700℃ at a rate of 5-10℃ / min and held for 1-2 hours; then increased to 2000-2300℃ at a rate of 1-5℃ / min and held for 2-3 hours, followed by cooling to room temperature at a rate of 3-5℃ / min.

[0011] Preferably, the coating method can be one of brushing, dipping, or spraying.

[0012] Preferably, the polyurethane foam template is an open-cell polyurethane foam, cylindrical in shape, with dimensions including diameters of 150mm, 200mm, 250mm, 300mm, etc., thicknesses of 2.5mm, 3mm, 3.5mm, 4mm, etc., and a pore size range of 0.1-1mm.

[0013] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit the invention.

[0014] Compared with traditional preparation methods, the "sandwich" stacking method used in this invention to control thickness and the reaction transition layer that forms chemical bonds during sintering improve structural integrity and reduce the risk of cracking.

[0015] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This invention provides a schematic flowchart of a method for preparing porous carbide ceramics based on a combination of stacking and template methods. Figure 2 : A schematic diagram of a porous carbide ceramic stacking method according to an embodiment of the present invention; Figure 3 One of the scanning electron microscope images of the porous tantalum carbide ceramic stacking interface obtained by the porous carbide ceramic preparation method based on the combination of stacking process and template method in this invention; Figure 4 The second image is a scanning electron microscope image of the stacked interface of porous tantalum carbide ceramics obtained by the present invention based on a porous carbide ceramic preparation method combining stacking process and template method. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0019] To better understand the purpose, function, and specific design of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0020] Example 1: This embodiment provides a method for preparing porous tantalum carbide ceramics based on a combination of stacking technology and template method. The specific preparation process is as follows: Step S1: Thoroughly mix two tantalum carbide powders with different particle sizes. Specifically, thoroughly mix 120g of tantalum carbide powder with a particle size of 0.8-1.2μm and 30g of tantalum carbide powder with a particle size of 1.2-5μm. Then, add 15ml of ethylene glycol, 50ml of ethanol, 1.2g of cobalt powder, 1.5g of PVB, 0.6g of PVPK30, and 0.4g of PEG6000 in sequence. After mixing evenly, place the mixture in a planetary ball mill, using a grinding jar and balls made of silicon nitride or tungsten carbide. For example, the grinding jar and balls are made of silicon nitride. The ball-to-material ratio is 2:1, the rotation speed is 300 rpm, and the ball milling time is 4 hours to obtain a tantalum carbide slurry. The slurry has a particle size D50 of 0.8, a solid content of 40 vol%, a viscosity of 100 mPa·s, and a pH of 8. Step S2: Thoroughly mix two tantalum pentoxide powders with different particle sizes (120g with a particle size of 1-2μm and 30g with a particle size of 2-5μm), then add 20ml benzyl alcohol, 60ml ethanol, 1.2g PVB, and 0.8PAA-NH4 in sequence. After mixing evenly, place the mixture in a planetary ball mill. The grinding balls are silicon nitride, the ball-to-powder ratio is 2:1, the rotation speed is 200 rpm, and the ball milling time is 3-4 hours to obtain tantalum pentoxide slurry. The particle size of the slurry is D50=1μm, the solid content is 30vol%, and the viscosity is 100mPa·s. Step S3: Apply tantalum carbide slurry evenly to both sides of polyurethane foam (dimensions include diameter 150mm and thickness 3mm), and after drying at room temperature for 24 hours, the green body weight is 128g.

[0021] Step S4: The transition layer is air-sprayed using a pneumatic spray gun, and tantalum pentoxide slurry is evenly sprayed onto one side of the green sheet (spraying parameters: air pressure 0.3 MPa, spray distance 15cm). The transition layer increases in weight by about 5g. Then, another sheet is placed on top of the transition layer, and the two sheets are stacked with a transition layer in between, resulting in a total of 2 sheets.

[0022] Step S5: Perform a drying process on the stacked blocks. The drying conditions are as follows: hold at 60℃ for 2 hours, then increase the temperature to 120℃ at 5℃ / min and hold for 4 hours, then increase the temperature to 150℃ at 2℃ / min and hold for 2 hours. Step S6: The dried green body is heat-treated and then hot-pressed and sintered. The sintering conditions are: vacuum degree less than 10 in a hot press furnace. -3The temperature was increased to 300℃ at 3℃ / min and held for 2 hours; then increased to 800℃ at 5℃ / min and held for 2 hours; then increased to 1500℃ at 5℃ / min and held for 1 hour; then increased to 2000℃ at 2℃ / min and held for 2 hours, while maintaining a pressure of 5MPa, and then cooled to room temperature at 3℃ / min.

[0023] This embodiment prepares a porous tantalum carbide ceramic with a diameter of 145.8 mm and a thickness of 5.2 mm through the above steps, such as... Figure 3 The image shows the microstructure of the porous tantalum carbide ceramic stacked interface. There are uniformly distributed through pores between the two thin layers, which meets the requirements for crystal growth. The thin layer interface is tightly bonded. The test results show that the porosity of the ceramic is 71% and the compressive strength is 6.2 MPa.

[0024] Example 2: This embodiment provides a method for preparing porous tantalum carbide ceramics based on a combination of stacking technology and template method. The specific preparation process is as follows: Step S1: Thoroughly mix 120g of tantalum carbide powder with a particle size of 0.8-1.2μm and 30g of tantalum carbide powder with a particle size of 1.2-5μm. Then, add 15ml of ethylene glycol, 50ml of ethanol, 1.2g of cobalt powder, 1.5g of PVB, 0.6g of PVPK30, and 0.4g of PEG6000 in sequence. After mixing evenly, place the mixture in a planetary ball mill. The grinding jar and balls are made of tungsten carbide. The ball-to-material ratio is 2:1, the rotation speed is 300 rpm, and the ball milling time is 5 hours to obtain tantalum carbide slurry. The slurry has a particle size D50=1μm, a solid content of 50vol%, a viscosity of 150mPa.s, and a pH=9. Step S2: Thoroughly mix 120g of tantalum pentoxide powder with a particle size of 1-2μm and 30g of tantalum pentoxide powder with a particle size of 2-5μm. Then, add 15ml of benzyl alcohol, 55ml of ethanol, 1g of PVB, and 0.8PAA-NH4 in sequence and mix evenly. Place the mixture in a planetary ball mill with silicon nitride grinding balls, a ball-to-material ratio of 2:1, a rotation speed of 200 rpm, and a ball milling time of 4 hours to obtain tantalum pentoxide slurry. The particle size of the slurry is D50=2μm, the solid content is 40vol%, and the viscosity is 200mPa·s. Step S3: Apply tantalum carbide slurry evenly to both sides of polyurethane foam with a diameter of 180mm and a thickness of 3mm. After drying at room temperature for 24 hours, the green body weighs 140g.

[0025] Step S4: The transition layer is air-sprayed using a pneumatic spray gun. The tantalum pentoxide slurry is evenly sprayed onto one side of the green sheet. The spraying parameters are air pressure 0.3 MPa, spray distance 15cm, and the weight gain of the transition layer is about 10g. Then, another sheet is placed on top of the transition layer, and the sheets are stacked with a transition layer in between the two sheets. Finally, there are a total of 4 sheets.

[0026] Step S5: Perform a drying process on the stacked blocks. The drying conditions are as follows: hold at 60℃ for 2 hours, then increase the temperature to 120℃ at 5℃ / min and hold for 4 hours, then increase the temperature to 150℃ at 2℃ / min and hold for 2 hours. Step S6: The dried green body is heat-treated and then hot-pressed and sintered. The sintering conditions are: vacuum degree less than 10 in a hot press furnace. -3 The temperature was increased to 450℃ at 5℃ / min and held for 2 hours; then increased to 1000℃ at 10℃ / min and held for 3 hours; then increased to 1700℃ at 10℃ / min and held for 2 hours; then increased to 2300℃ at 5℃ / min and held for 3 hours, while maintaining a pressure of 3MPa, and then cooled to room temperature at 3℃ / min.

[0027] In this embodiment, a porous tantalum carbide ceramic with a diameter of 176.7 mm and a thickness of 5.4 mm was prepared through the above steps. The test results showed that the porosity of the ceramic was 68% and the compressive strength was 5.1 MPa.

[0028] Comparative Example 1: This comparative example is exactly the same as Example 1, except that step S2 is not used as a transition layer in the preparation process, that is, the sheet stacking method is adjusted to "sheet-sheet" and no transition layer is added.

[0029] The porous tantalum carbide ceramic obtained in this comparative example is as follows: Figure 4 As shown, through Figure 4 It is known that after hot pressing and sintering, delamination occurs due to discontinuity at the interface of the thin sheets. This indicates that the addition of the transition layer during the stacking of the thin sheet green bodies must be strictly carried out in accordance with the requirements of this invention. Failure to add the transition layer or its addition amount not within the above requirements will directly lead to discontinuity at the interface during subsequent hot pressing and sintering, which in turn leads to a decrease in the mechanical properties of the ceramic material, and in severe cases, porous ceramics cannot be formed.

[0030] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. In the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing porous carbide ceramics based on a combination of stacking process and template method, characterized in that, Includes the following steps: Step S1: The carbide slurry is evenly coated on both sides of the polyurethane foam template and dried at room temperature to form a thin sheet green blank. The carbide slurry is composed of the following components: 75-85 wt% carbide powder, 2-5 wt% binder, 1-3 wt% composite dispersant, 1-3 wt% sintering aid, and the balance being solvent. Step S2: Uniformly coat one side of the thin sheet green blank with oxide slurry to form a transition layer; The oxide slurry is composed of the following components: 70-80 wt% oxide powder, 2-5 wt% binder, 1-2 wt% dispersant, and the balance being solvent; Step S3: Stack multiple layers of green sheets, with a transition layer between two adjacent green sheets, dry at room temperature and then heat up gradually to solidify; hot press and sinter, then cool to produce porous carbide ceramics.

2. The method for preparing porous carbide ceramics based on a combination of stacking process and template method according to claim 1, characterized in that, In step S1, the carbide powder is one of silicon carbide, hafnium carbide, and tantalum carbide; the binder is one of PVA1788 and PVB; the composite dispersant is one of PVPK30+PEG6000 and PAA+PEG; the sintering aid is one of nickel powder and molybdenum disilicide; and the solvent is two of ethanol, ethylene glycol, and benzyl alcohol.

3. The method for preparing porous carbide ceramics based on a combination of stacking process and template method according to claim 2, characterized in that, In step S1, the method for preparing the carbide slurry is as follows: Two carbide powders with different particle sizes are thoroughly mixed, and then solvent, binder, composite dispersant and sintering aid are added in sequence. After mixing evenly, the mixture is placed in a planetary ball mill and ball-milled for 4-5 hours to obtain a carbide slurry.

4. The method for preparing porous carbide ceramics based on a combination of stacking process and template method according to claim 3, characterized in that, In step S2, the oxide powder is one of silicon oxide, hafnium oxide, and tantalum oxide; the binder is one of PVA1788 and PVB; the dispersant is one of PAA-NH4 and PEI; and the solvent is two of ethanol, isopropanol, and benzyl alcohol.

5. The method for preparing porous carbide ceramics based on a combination of stacking process and template method according to claim 4, characterized in that, In step S2, the method for preparing the oxide slurry is as follows: Two tantalum pentoxide powders with different particle sizes are thoroughly mixed, and then solvent, binder and dispersant are added in sequence. After mixing evenly, the mixture is placed in a planetary ball mill and ball-milled for 3-4 hours to obtain an oxide slurry.

6. The method for preparing porous carbide ceramics based on a combination of stacking process and template method according to claim 5, characterized in that, In step S3, after drying at room temperature, the temperature is gradually increased and cured. The temperature is maintained at 40-60℃ for 1-3 hours, then increased to 80-120℃ at 4-7℃ / min and maintained for 3-4 hours. Finally, the temperature is increased to 120-160℃ at 1-3℃ / min and maintained for 1-3 hours.

7. The method for preparing porous carbide ceramics based on a combination of stacking process and template method according to claim 6, characterized in that, In step S3, the sintering conditions are: in the hot press furnace, the vacuum degree is less than 10. -3 At a pressure of 3-10 MPa, the temperature is increased to 300-450℃ at a rate of 3-5℃ / min and held for 2-3 hours; then increased to 800-1000℃ at a rate of 5-10℃ / min and held for 2-3 hours; then increased to 1500-1700℃ at a rate of 5-10℃ / min and held for 1-2 hours; then increased to 2000-2300℃ at a rate of 1-5℃ / min and held for 2-3 hours, followed by cooling to room temperature at a rate of 3-5℃ / min.

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