A high solid content slurry for silicon carbide workpiece and preparation method thereof

Abstract

The invention discloses a high solid content slurry for a silicon carbide workpiece and a preparation method thereof. The high solid content slurry for a silicon carbide workpiece comprises silicon carbide powder, a sintering aid, a dispersant, a suspending agent, a binder and a solvent; the dispersant comprises at least one or more of a block copolymer and a phosphate ester salt; the binder comprises at least one or more of polyvinyl butyral (PVB) and polyethylene glycol (PEG‑4000). The invention can prepare a uniform slurry with high solid content and good fluidity.

Description

Technical Field

[0001] The invention relates to the technical field of silicon carbide workpieces, and in particular to a silicon carbide workpiece high solid content slurry and a preparation method thereof. Background Art

[0002] Silicon carbide (SiC), as the core basic raw material of the third-generation semiconductor materials, is a covalent compound. Due to its excellent high-temperature mechanical properties, high thermal conductivity, low thermal expansion coefficient and excellent chemical stability, it has shown irreplaceable application value in power electronic devices, aerospace thermal protection systems, nuclear reactor cladding materials and other fields. With the rapid development of high-tech industries such as 5G communications and new energy vehicles, the market has put forward more stringent requirements on the dimensional accuracy, structural density and reliability of high-performance silicon carbide workpieces.

[0003] At present, wet molding processes such as gel casting and tape casting have become key technologies for preparing complex-shaped silicon carbide workpieces. The core lies in obtaining a stable slurry system with suitable rheological properties and high solid content. Among them, good fluidity should be good, that is, low viscosity, so that the slurry can fill every corner of the model; good stability and high uniformity, that is, the slurry can remain stable for a long time and is not easy to precipitate and stratify; low water content and high solid content, that is, while ensuring fluidity, the water content is as small as possible to reduce molding time and drying shrinkage, reduce deformation and cracking of the green body, and increase green body density.

[0004] However, the existing technologies generally have the following technical bottlenecks: the solid phase volume fraction is mostly limited to the range of 45%-50%. Excessive increase will cause the slurry viscosity to rise sharply, causing casting difficulties and defects in the molded body.

[0005] Therefore, developing a silicon carbide slurry system with both high solid content (≥55 vol%) and excellent process adaptability has become a key technical challenge to break through the bottleneck of high-performance silicon carbide workpiece preparation. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a high solid content slurry for silicon carbide workpieces and a preparation method thereof, which can effectively solve the above-mentioned problems of the prior art.

[0007] Technical Solution

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0009] The present invention provides a high solid content slurry for a silicon carbide workpiece, which comprises silicon carbide powder, a sintering aid, a dispersant, a suspending agent, a binder and a solvent;

[0010] The dispersant includes a block copolymer and a phosphate salt;

[0011] The binder includes polyvinyl butyral (PVB) and polyethylene glycol (PEG-4000).

[0012] Furthermore, the silicon carbide powder includes one or more of the particle sizes of 0.3-0.4 μm, 0.5-0.6 μm, 0.8-1 μm, 50-100 μm, 300-500 μm, and 600-1000 μm.

[0013] Furthermore, the silicon carbide powder is composed of 0.8-1.0 μm submicron SiC and 300-500 μm SiC in a mass ratio of 2-5:1.

[0014] Preferably, the silicon carbide powder is composed of 0.8-1.0 μm submicron SiC and 300-500 μm SiC in a mass ratio of 4:1.

[0015] Furthermore, the sintering aid includes one or more of aluminum nitrate, yttrium acetate, graphite powder, wollastonite mineral fiber, silicon powder of different mesh sizes, white carbon black, and phenolic resin.

[0016] Furthermore, the sintering aid comprises aluminum nitrate, yttrium acetate and phenolic resin; the weight proportion of phenolic resin in the sintering aid is 10-18%; the aluminum nitrate [Al(NO 3 ) 3 9H 2 O] and yttrium acetate [Y(CH 3 COO 3 ·4H 2 O] are mixed in a weight ratio of 8:3.

[0017] Preferably, the aluminum nitrate [Al(NO 3 ) 3 9H 2 O], yttrium acetate [Y(CH 3 COO 3 ·4H 2 O] and phenolic resin are mixed in a weight ratio of 8:3:2.

[0018] Further, the dispersant is composed of a block copolymer and a phosphate salt, and the weight ratio of the block copolymer to the phosphate salt is 2:1-5:1;

[0019] Preferably, the weight ratio of the block copolymer to the phosphate salt is 7:3;

[0020] Wherein, the block copolymer adopts the brand of DISPERBYK-2010;

[0021] The phosphate salt is an alkyl phosphate salt; the alkyl phosphate salt is at least one or more of potassium dodecyl phosphate, potassium tetradecyl phosphate or potassium hexadecyl phosphate; preferably, the phosphate salt is potassium tetradecyl phosphate.

[0022] Further, the suspending agent includes one or more of triethylhexyl phosphate, sodium lauryl sulfate, cellulose derivatives, and polyacrylamide methylpentyl alcohol;

[0023] Preferably, the suspending agent is a cellulose derivative, which can be selected from one or more of cellulose nitrate, cellulose acetate, cellulose acetate butyrate, cellulose xanthate, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, cyanoethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose.

[0024] Most preferably, the suspending agent is hydroxypropyl methylcellulose.

[0025] Furthermore, the weight ratio of polyvinyl butyral (PVB) to polyethylene glycol (PEG-4000) in the binder is 2:1-3:1;

[0026] The solvent is isopropanol and deionized water, and the volume ratio thereof is 7:3-6:4.

[0027] Furthermore, in parts by weight, it includes 60-80 parts of silicon carbide powder, 1-5 parts of sintering aid, 0.5-5 parts of dispersant, 0.1-1 parts of suspending agent, 3-10 parts of binder and 10-30 parts of solvent.

[0028] Preferably, in parts by weight, it includes 75 parts of silicon carbide powder, 1.3 parts of sintering aid, 1 part of dispersant, 0.2 parts of suspending agent, 4.8 parts of binder and 16 parts of solvent.

[0029] A method for preparing a high solid content slurry for a silicon carbide workpiece, the preparation steps comprising:

[0030] Step 1: Add the dispersant and suspending agent into the solvent and perform ultrasonic treatment (40kHz, 30min) to form a homogeneous solution;

[0031] Step 2: Add SiC powder to the homogenized solution and use planetary ball milling (zirconia ball, rotation speed 300 rpm, time 2 h) to achieve particle surface coating and graded filling;

[0032] Step 3: dissolving aluminum nitrate + yttrium acetate in ethanol to obtain a precursor solution, and adding the precursor solution and phenolic resin into step 2, and stirring magnetically for 1 hour;

[0033] Step 4: Add binder and perform vacuum degassing (-0.095MPa, 30min) to obtain the final slurry.

[0034] The purpose of the present invention is to prepare a slurry with a high solid content for a silicon carbide workpiece. Slip casting is one of the most commonly used methods for preparing recrystallized silicon carbide devices. The key technology of slip casting is to prepare a uniform slurry with a high solid content and good fluidity. Recrystallized silicon carbide is made by evaporating and condensing silicon carbide with coarse and fine grading as raw materials at high temperature. The small particle size of silicon carbide powder is easy to cause agglomeration. Therefore, it is necessary to divide the silicon carbide powder into a particle size gradient, and at the same time add a binder and a dispersant to prevent the occurrence of agglomeration. Although silicon carbide particles (the present invention is silicon carbide powder with a particle size of ≥300μm) are not easy to agglomerate, due to their large mass, they will quickly settle under the action of gravity after being dispersed in water, making them difficult to use for slip casting. The main way to solve this problem is to rely on the force formed between the powders to offset the gravity of the particles and add a suspending agent so that the powder is suspended in the slurry system. In order to form a uniform silicon carbide slurry, the silicon carbide powder must have good fluidity after being prepared into a slurry, and must have a certain buoyancy to prevent the particles from settling, so that the particles and silicon carbide powders of different particle sizes can form a uniform and stable slurry.

[0035] Beneficial Effects

[0036] Compared with the known public technology, the technical solution provided by the present invention has the following beneficial effects:

[0037] (1) The present invention uses aluminum nitrate and yttrium acetate precursors, which decompose to generate Y during high temperature sintering. 2 O 3 -Al 2 O 3 Liquid phase, through reaction sintering to form YAG (Y 3 Al 5 O 12 ) phase, significantly reducing the sintering temperature (1600-1800℃); in addition, phenolic resin is pyrolyzed to generate activated carbon, which reacts with SiO on the surface of SiC 2 The reaction generates CO gas (C + SiO 2 → SiO↑ + CO↑), achieving in-situ purification and improving product purity.

[0038] (2) In the present invention, the block copolymer is adsorbed on the surface of SiC particles, which reduces the thixotropic index of the slurry; the phosphate salt forms hydrogen bonds with the hydroxyl groups on the SiC surface, synergistically enhancing the electrostatic-steric dual stabilization mechanism, so that the slurry still maintains a viscosity of <2 Pa·s (shear rate 100 s) when the solid content is 55-59 vol%. -1 );

[0039] (3) In the present invention, PVB provides a high-strength bonding network, and its glass transition temperature (60-70°C) and the plasticizing effect of PEG synergistically regulate the rheological properties of the slurry; PVB and PEG can be completely thermally decomposed at 400-600°C, avoiding the oxygen inhibition and residual pollution problems caused by the polymerization of traditional acrylic monomers. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The present invention will be further described below in conjunction with the embodiments.

[0042] The manufacturers and models of the raw materials used in the embodiments and comparative examples are as follows:

[0043] Block copolymer: brand DISPERBYK-2010;

[0044] 1. Implementation

[0045] Embodiment 1:

[0046] A high solid content slurry for a silicon carbide workpiece, comprising, by weight, 75 parts of silicon carbide powder, 1.3 parts of a sintering aid, 1 part of a dispersant, 0.2 parts of a suspending agent, 4.8 parts of a binder and 16 parts of a solvent;

[0047] The silicon carbide powder is composed of 60 parts of 0.8-1.0 μm submicron SiC and 15 parts of 300-500 μm SiC.

[0048] The sintering aid includes 0.8 parts of aluminum nitrate [Al(NO 3 ) 3 •9H 2 O], 0.3 parts of yttrium acetate [Y(CH 3 COO 3 •4H 2 O] and 0.2 parts of phenolic resin;

[0049] The dispersant includes 0.7 parts of a block copolymer and 0.3 parts of potassium tetradecyl phosphate, and the block copolymer is of the brand DISPERBYK-2010;

[0050] The suspending agent is 0.2 parts of hydroxypropyl methylcellulose;

[0051] The binder includes 3.5 parts of polyvinyl butyral (PVB) and 1.3 parts of polyethylene glycol (PEG-4000).

[0052] The solvent includes isopropyl alcohol and deionized water in a volume ratio of 7:3.

[0053] A method for preparing a high solid content slurry for a silicon carbide workpiece, the preparation steps comprising:

[0054] Step 1: Add the dispersant and suspending agent into the solvent and perform ultrasonic treatment (40kHz, 30min) to form a homogeneous solution;

[0055] Step 2: Add SiC powder to the homogenized solution and use planetary ball milling (zirconia ball, rotation speed 300 rpm, time 2 h) to achieve particle surface coating and graded filling;

[0056] Step 3: Dissolve the aluminum nitrate and yttrium acetate in 3 parts of ethanol by weight to obtain a precursor solution, and add the precursor solution and phenolic resin to step 2, and stir magnetically for 1 hour;

[0057] Step 4: Add binder and perform vacuum degassing (-0.095MPa, 30min) to obtain the final slurry.

[0058] Comparative Example 1:

[0059] The only difference from Example 1 is that the dispersant is different. Specifically, by weight, the dispersant only includes 1 part of the block copolymer, and the block copolymer is of the brand DISPERBYK-2010.

[0060] Comparative Example 2:

[0061] The only difference from Example 1 is that the dispersant is different. Specifically, the dispersant includes only 1 part of potassium tetradecyl phosphate by weight.

[0062] Comparative Example 3:

[0063] The only difference from Example 1 is that the binder is different. Specifically, the binder includes only 4.8 parts of polyvinyl butyral (PVB) by weight.

[0064] Comparative Example 4:

[0065] The only difference from Example 1 is that the binder is different. Specifically, by weight, the binder includes only 4.8 parts of polyethylene glycol (PEG-4000).

[0066] Comparative Example 5:

[0067] The only difference from Example 1 is that the sintering aid is different. Specifically, by weight, the sintering aid includes only 1.3 parts of phenolic resin.

[0068] Comparative Example 6:

[0069] The only difference from Example 1 is that the sintering aid is different. Specifically, by weight, the sintering aid only includes aluminum nitrate [Al(NO 3 ) 3 •9H 2 O] and yttrium acetate [Y(CH 3 COO 3 •4H 2 O], the sum of the weight parts of aluminum nitrate and yttrium acetate is 1.3 parts, and the weight ratio of aluminum nitrate to yttrium acetate is 8:3.

[0070] (II) Performance test

[0071] (1) Solid content: Determined by drying-burning method. The specific determination method is as follows:

[0072] Step 1: Sampling: Use a precision syringe to take 1.0±0.01g of slurry sample (recorded as m 1 ), dropped into a constant weight platinum crucible (m 0 );

[0073] Step 2: Drying: Place the crucible in a forced air drying oven and dry it at 80°C for 4 hours to remove the volatile solvent; cool to room temperature and weigh (m 2 );

[0074] Step 3: High temperature calcination: transfer the dried sample to a muffle furnace, heat it to 600°C at 5°C / min, and keep it at that temperature for 2h; weigh it after cooling (m 3 ).

[0075]

[0076] Among them, ρ 浆料 : Slurry density (determined by pycnometer method);

[0077] ρ SiC： Theoretical density of silicon carbide (3.21g / cm 3 ).

[0078] (2) Stability refers to the height of the liquid precipitated after the slurry is left to stand for 24 hours. 0 The ratio to the original height h of the slurry.

[0079] The performance test results of the slurry prepared by Example 1 and Comparative Examples 1-6 are as follows:

[0080]

[0081] It can be seen from Example 1 and Comparative Examples 1-4 that when only block copolymer or potassium tetradecyl phosphate is used as the dispersant, or when only polyvinyl butyral (PVB) or polyethylene glycol (PEG-4000) is used as the binder, although the solid content is greater than 50 vol%, the slurry viscosity is greater than 2 Pa·s (shear rate 100 s -1 ); It can be seen from Example 1 and Comparative Examples 5-6 that although the slurry viscosity is relatively small, its solid content is significantly lower than that of Example 1. In addition, the slurry stability of Comparative Examples 1-6 is poorer than that of Example 1. It can be seen that when the slurry contains block copolymer, potassium tetradecyl phosphate, polyvinyl butyral (PVB), and polyethylene glycol (PEG-4000) at the same time, its solid content, slurry viscosity and stability can achieve better results.

[0082] In summary, in the present invention, the block copolymer is adsorbed on the surface of SiC particles, which reduces the thixotropic index of the slurry; the phosphate salt forms hydrogen bonds with the hydroxyl groups on the SiC surface, synergistically enhancing the electrostatic-steric dual stabilization mechanism, so that the slurry still maintains a viscosity of <2 Pa·s (shear rate 100 s) when the solid content is 55-59 vol%. -1 ); PVB provides a high-strength bonding network, and its glass transition temperature (60-70°C) and the plasticizing effect of PEG synergistically regulate the rheological properties of the slurry.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high solid content slurry for silicon carbide workpiece, characterized in that: In parts by weight, it includes 60-80 parts of silicon carbide powder, 1-5 parts of sintering aid, 0.5-5 parts of dispersant, 0.1-1 parts of suspending agent, 3-10 parts of binder and 10-30 parts of solvent; The dispersant is composed of a block copolymer and a phosphate salt, and the block copolymer is of the brand DISPERBYK-2010; the weight ratio of the block copolymer to the phosphate salt is 2:1-5:1; wherein the phosphate salt is an alkyl phosphate salt; the alkyl phosphate salt is at least one of potassium dodecyl phosphate, potassium tetradecyl phosphate or potassium hexadecyl phosphate; The binder includes polyvinyl butyral and polyethylene glycol; The silicon carbide powder is composed of 0.8-1.0 μm submicron SiC and 300-500 μm SiC in a mass ratio of 2-5:1; The sintering aid includes aluminum nitrate, yttrium acetate and phenolic resin; the weight proportion of phenolic resin in the sintering aid is 10-18%; the aluminum nitrate is Al(NO3)3·9H2O, the yttrium acetate is Y(CH3COO)3·4H2O, and the two are mixed at a weight ratio of 8:1-5; The weight ratio of polyvinyl butyral to polyethylene glycol in the binder is 2:1-3:1; the volume ratio of isopropanol to deionized water is 7:3-6:

4.

2. The high solid content slurry for silicon carbide workpiece according to claim 1, characterized in that: The suspending agent includes one or more of triethylhexyl phosphoric acid, sodium lauryl sulfate, cellulose derivatives, polyacrylamide, and methyl amyl alcohol.

3. A method for preparing a high solid content slurry for a silicon carbide workpiece as claimed in any one of claims 1 to 2, characterized in that: The preparation steps include: Step 1: adding a dispersant and a suspending agent into a solvent and subjecting the solvent to ultrasonic treatment to form a homogeneous solution; Step 2: Add SiC powder to the homogenous solution, and use planetary ball milling to achieve particle surface coating and graded filling; Step 3: dissolving aluminum nitrate and yttrium acetate in ethanol to obtain a precursor solution, and adding the precursor solution and phenolic resin into step 2, and stirring magnetically; Step 4: Add binder and perform vacuum degassing to obtain the final slurry.

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