A high solid content and low viscosity SiC ceramic double-cured slurry and a low shrinkage green body preparation method

Abstract

The application discloses a kind of high solid content low viscosity SiC ceramic double solidification slurry and low shrinkage green body preparation method, it is related to SiC ceramic additive manufacturing technical field.For solving the problem of existing slurry solid content low, viscosity high, green body shrinkage big, green body strength low, the modified SiC powder of surface in-situ growth SiO2 / phenolic resin composite core-shell is used in the present application, with photosensitive resin and thermal gel matrix, build double solidification slurry system;After photo-curing layering, thermal gel secondary reinforcement, ladder debinding and pressureless sintering, obtain low shrinkage, high strength SiC green body and dense ceramic.The application realizes slurry solid content 65~72vol%, viscosity≤1200mPa·s, green body linear shrinkage rate≤8%, green body strength≥8MPa, and is suitable for semiconductor precision ceramic component additive manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide ceramic preform preparation and additive manufacturing technology. Specifically, it relates to a high-solids-content, low-viscosity SiC ceramic dual-curing slurry formulation and a process for preparing low-shrinkage, high-strength SiC preforms by photocuring-thermogel composite shaping. It is applicable to additive manufacturing of semiconductor structural ceramics, precision silicon carbide parts, and complex-configuration SiC ceramic components. Background Technology

[0002] SiC ceramics possess excellent properties such as high hardness, high thermal conductivity, high temperature resistance, and low expansion, and are widely used in semiconductor carriers, aerospace hot-end components, and other fields. Current mainstream methods for preparing SiC preforms include photopolymerization 3D printing, gel casting, and extrusion molding.

[0003] Currently, the industry faces significant technical bottlenecks: conventional photocurable SiC slurries generally have a solid content of less than 55 vol, resulting in large shrinkage, easy cracking, and low sintering density in the green blanks after debinding and sintering; increasing the solid content leads to a sharp increase in slurry viscosity, poor fluidity, difficulty in layup, and a significant decrease in printing accuracy; single photocuring relies solely on photosensitive resin crosslinking, resulting in low green blank strength, easy damage during demolding and post-processing, and single gel casting makes it difficult to form fine and complex structures.

[0004] Existing technologies lack integrated solutions for powder surface modification, dual-curing systems, and step-by-step shaping and reinforcement, making it impossible to simultaneously achieve high solids content, low viscosity, high precision, low shrinkage, and high green body strength. Existing patents primarily focus on single resin systems and optimization of conventional dispersant ratios, failing to fundamentally resolve the contradiction between high solids content and low viscosity. Furthermore, there is no known process for integral green body molding that combines photocuring and thermogelation, indicating a significant technological gap and room for innovation.

[0005] Purpose of the invention

[0006] This invention aims to overcome the technical defects of existing SiC ceramic slurries, such as low solid content, high viscosity, large shrinkage of green body, low green body strength, easy cracking during molding, and difficulty in preparing complex structures. It provides a core-shell modified SiC powder combined with a dual-curing composite slurry system, which uses photocuring for rapid shaping combined with thermogel in-situ reinforcement to prepare low-shrinkage, high-strength, and high-density SiC ceramic green bodies. It is suitable for DLP, SLA photocuring additive manufacturing and mass production of precision ceramics.

[0007] Technical solution

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A high-solids-content, low-viscosity SiC ceramic dual-curing slurry is composed of modified SiC powder, photosensitive resin monomer, thermogel matrix, photoinitiator, thermosetting accelerator, and dispersant. The modified SiC powder has an in-situ grown nano-SiO2 / phenolic resin composite core-shell structure on the surface of SiC particles, with a shell thickness of 20-50 nm. The overall solids content of the slurry is 65-72 vol%, and the viscosity of the slurry at 25℃ is ≤1200 mPa·s. The slurry simultaneously possesses dual curing characteristics of ultraviolet light curing and medium-temperature thermogelation.

[0010] Preferably, the proportions by weight are: 70-85 parts modified SiC powder, 8-18 parts photosensitive resin monomer, 3-8 parts thermogel matrix, 0.3-1.2 parts photoinitiator, 0.2-0.8 parts thermosetting accelerator, and 0.5-1.5 parts dispersant.

[0011] Preferably, the particle size of SiC powder is controlled between 0.5 and 5 μm, and nano-SiO2 accounts for 30 to 60% of the shell mass in the composite core-shell structure.

[0012] A method for preparing low-shrinkage green bodies using a high-solids-content, low-viscosity SiC ceramic dual-curing slurry includes the following steps:

[0013] (1) Powder modification: The original SiC powder is subjected to surface hydroxylation treatment, and 20-50nm SiO2 / phenolic resin core-shell coated modified powder is generated by in-situ deposition;

[0014] (2) Slurry mixing: The modified SiC powder is ball-milled and fully dispersed with photosensitive resin, thermogel matrix, photoinitiator, thermosetting accelerator and dispersant to obtain a high solids content and low viscosity dual-curing slurry;

[0015] (3) Photopolymerization and layer-by-layer shaping: DLP / SLA photopolymerization 3D printing is used, with a layer thickness of 0.05-0.1mm. UV light exposure is used to cure layer by layer to obtain the initial blank;

[0016] (4) Thermogel reinforcement: The raw green body is placed in a constant temperature environment of 50-80℃ for 1-3 hours to trigger the formation of a cross-linked network in the thermogel system, thereby achieving secondary strength enhancement of the green body;

[0017] (5) Low-temperature pre-calcination and step degreasing: Heat to 450℃ at 1℃ / min and hold for 2 hours, then heat to 600-800℃ at 3-5℃ / min for low-temperature pre-calcination to remove organic matter;

[0018] (6) Pressureless sintering: The pre-fired green blank is placed in a high-temperature sintering furnace and kept at 1800-1950℃ for 2-4 hours to obtain a dense SiC ceramic product.

[0019] Preferably, the printing exposure power in step (3) is 8-20 mW / cm 2 Single-layer exposure time is 3-8 seconds.

[0020] Preferably, the prepared SiC green blank has a linear shrinkage rate ≤8%, a green blank bending strength ≥8MPa, and a bulk density ≥3.15g / cm³ after sintering. 3 .

[0021] Beneficial effects

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention uses SiC powder surface nano core-shell coating modification to greatly improve powder dispersion compatibility, break through the traditional upper limit of slurry solid content, maintain low viscosity under the premise of high solid content, and take into account printing flowability and molding density.

[0024] 2. Construct a dual curing system of photocuring + thermogelling, with one-time slurry adaptation and two-step molding. Photocuring ensures rapid shaping and structural accuracy, while thermogelling significantly improves the strength of the green body and makes it less prone to breakage and deformation during demolding.

[0025] 3. The matching stepped degreasing and pressureless sintering process effectively releases organic volatiles and sintering thermal stress, significantly reduces the linear shrinkage rate of the green blank, and ensures that the components are free from cracking and warping.

[0026] 4. The formulation composition, structural parameters and process range form a complete protection chain, with a clear innovation mechanism, which is different from the existing conventional ratio improvement, with outstanding creativity and excellent licensing prospects;

[0027] 5. The process is compatible with existing photopolymer additive manufacturing equipment, requiring no large-scale equipment modification, and can be directly implemented for mass production, suitable for the preparation of high-end precision silicon carbide components in semiconductors and aerospace. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the SiO2 / phenolic resin composite core-shell structure of the modified SiC powder of this invention.

[0029] Figure 2 This is a flowchart illustrating the process for preparing low-shrinkage green bodies using the high-solids-content, low-viscosity SiC ceramic dual-curing slurry of the present invention.

[0030] Specifically, Figure 1The microscopic core-shell hierarchical structure of modified SiC powder is shown. The core of the powder is high-purity SiC particles, and the surface of the particles is successively coated with an inner layer of nano-SiO2 and an outer layer of phenolic resin. Active modified groups are distributed on the surface of the powder, which can form a good wetting interface with the dual-curing resin system, effectively improving the dispersibility and compatibility of SiC powder in the resin system, and solving the problems of high viscosity and easy agglomeration of high solids slurry.

[0031] 1—SiC powder core particles; 2—Nano SiO2 inner coating layer; 3—Phenolic resin outer coating layer; 4—Surface-active modified groups; 5—Dual-curing resin wetting interface.

[0032] Specifically, Figure 2 The invention demonstrates the complete preparation process, which includes SiC powder surface hydroxylation pretreatment, in-situ deposition preparation of composite core-shell modified powder, ball milling and mixing of dual-curing slurry, photopolymerization 3D printing layer shaping, medium-temperature thermogel isothermal crosslinking enhancement, low-temperature pre-firing and step-by-step debinding, and high-temperature pressureless sintering. Finally, a low-shrinkage, high-strength, and high-density SiC ceramic product is obtained. Each process works in a step-by-step manner to achieve the core technical effects of high solids and low viscosity slurry and low shrinkage and high strength green body.

[0033] S1—SiC powder surface hydroxylation pretreatment; S2—In-situ deposition preparation of SiO2 / phenolic resin composite core-shell modified SiC powder; S3—Ball milling and mixing of modified powder with photosensitive resin, thermogel and additives to prepare dual-curing ceramic slurry; S4—DLP / SLA photopolymerization 3D printing layered UV setting to prepare primary green body; S5—Medium-temperature thermogel isothermal crosslinking to enhance the secondary strength of the green body; S6—Low-temperature pre-firing + stepwise debinding to remove organic components; S7—High-temperature pressureless sintering; S8—Low-shrinkage, high-strength, dense SiC ceramic finished product. Detailed Implementation

[0034] Example 1

[0035] A method for preparing a high-solids-content, low-viscosity SiC ceramic dual-curing slurry and a low-shrinkage green body, wherein the SiC powder has a particle size of 1-3 μm and a 35 nm SiO2 / phenolic resin core-shell layer is generated in situ after surface hydroxylation.

[0036] The formula is as follows (by weight): 78 parts modified SiC, 12 parts photosensitive resin, 5 parts thermogel matrix, 0.6 parts photoinitiator, 0.4 parts thermosetting accelerator, and 1.0 part dispersant.

[0037] The prepared slurry had a solid content of 69 vol% and a viscosity of 960 mPa·s at 25℃.

[0038] DLP photopolymerization printing was used, with a layer thickness of 0.08mm and an exposure power of 12mW / cm. 2 Single-layer exposure for 5 seconds;

[0039] After printing, maintain the temperature at 65℃ for 2 hours using a thermal gel.

[0040] After stepwise degreasing, the material was sintered at 1900℃ without pressure for 3 hours.

[0041] Performance testing: Green body linear shrinkage rate 7.2%, green body flexural strength 9.1 MPa, sintered density 3.18 g / cm³ 3 The components are free of cracks and obvious pores, and have excellent dimensional accuracy.

Claims

1. A high-solids-content, low-viscosity SiC ceramic dual-curing slurry, characterized in that: It is composed of modified SiC powder, photosensitive resin monomer, thermogel matrix, photoinitiator, thermosetting accelerator, and dispersant; The modified SiC powder is a nano-SiO2 / phenolic resin composite core-shell structure grown in situ on the surface of SiC particles, with a shell thickness of 20-50 nm. The slurry has an overall solid content of 65-72 vol%, and a viscosity of ≤1200 mPa·s at 25℃. The slurry possesses both UV curing and medium-temperature thermogel curing properties.

2. The high-solids-content, low-viscosity SiC ceramic dual-curing slurry according to claim 1, characterized in that, The formula is as follows (by weight): 70-85 parts modified SiC powder, 8-18 parts photosensitive resin monomer, 3-8 parts thermogel matrix, 0.3-1.2 parts photoinitiator, 0.2-0.8 parts thermosetting accelerator, and 0.5-1.5 parts dispersant.

3. The high-solids-content, low-viscosity SiC ceramic dual-curing slurry according to claim 1, characterized in that: The SiC powder has a particle size of 0.5–5 μm, and nano-SiO2 accounts for 30–60% of the shell mass in the composite core-shell.

4. A method for preparing low-shrinkage green bodies using a high-solids-content, low-viscosity SiC ceramic dual-curing slurry as described in any one of claims 1 to 3, characterized in that, It includes the following steps: (1) Powder modification: The original SiC powder is subjected to surface hydroxylation treatment, and 20-50nm SiO2 / phenolic resin core-shell coated modified powder is generated by in-situ deposition; (2) Slurry mixing: Modified SiC powder is ball-milled and dispersed with photosensitive resin, thermogel matrix, photoinitiator, thermosetting accelerator and dispersant to prepare a high solids content and low viscosity dual-curing slurry; (3) Photopolymerization and layer-by-layer shaping: DLP / SLA photopolymerization 3D printing is used, with a layer thickness of 0.05-0.1mm. UV light exposure is used to cure layer by layer to obtain the initial blank; (4) Thermogel reinforcement: The raw green body is placed in a constant temperature environment of 50-80℃ for 1-3 hours to trigger the cross-linking network of the thermogel system and achieve secondary reinforcement of the green body; (5) Low-temperature pre-calcination + stepwise degreasing: Heat to 450℃ at 1℃ / min and hold for 2 hours, then heat to 600-800℃ at 3-5℃ / min to remove organic matter; (6) Pressureless sintering: Hold at 1800~1950℃ for 2~4h to obtain dense SiC ceramic products.

5. The method according to claim 4, characterized in that: Step (3) Printing exposure power 8-20mW / cm 2 Single-layer exposure time is 3-8 seconds.

6. The method according to claim 4, characterized in that: The prepared SiC green blank has a linear shrinkage rate ≤8%, a green bending strength ≥8MPa, and a bulk density ≥3.15g / cm³ after sintering. 3 .

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