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CN-121990830-A - Silicon carbide ceramic slurry grouting forming method based on gypsum mold

CN121990830ACN 121990830 ACN121990830 ACN 121990830ACN-121990830-A

Abstract

The invention relates to the technical field of advanced ceramic material molding, and provides a slip casting method of silicon carbide ceramic slurry based on a gypsum mold, which aims to solve the technical defects in slip casting of the existing silicon carbide (SiC), and has the advantages of (1) slurry preparation, (2) slurry injection and solidification, (3) demolding and drying, (4) sintering, simple process, low cost, high green body strength and good sintering performance.

Inventors

  • HU WEIPENG
  • CHENG DONGYUAN

Assignees

  • 浙江富乐德半导体材料科技有限公司

Dates

Publication Date
20260508
Application Date
20251231

Claims (10)

  1. 1. The silicon carbide ceramic slurry grouting molding method based on the gypsum mold is characterized by comprising the following steps of: (1) Mixing silicon carbide micro powder, a sintering aid, a dispersing agent and deionized water, and performing ball milling to obtain uniform, stable and high-solid-content water-based slurry; (2) Vacuum degassing the slurry, and then injecting the slurry into a porous gypsum mold to form a blank; (3) Demoulding after the blank reaches the strength of 7-15Mpa, and then drying in a sectional mode; (4) And (3) sintering the dried green body at a high temperature in a protective atmosphere, and obtaining a compact silicon carbide ceramic product through a sintering curve.
  2. 2. The slip casting method of silicon carbide ceramic slurry based on gypsum mold according to claim 1, wherein the particle size of the silicon carbide micro powder in the step (1) is 10-30um and 80-100um, respectively, and the mass ratio of the fine micro powder to the coarse micro powder is 0.3-0.6:0.4-0.7.
  3. 3. The slip casting method of the gypsum mold-based silicon carbide ceramic slurry according to claim 1, wherein the sintering aid in the step (1) is selected from carboxymethyl cellulose, and the use amount is 5-20% of the mass of the silicon carbide micro powder.
  4. 4. The slip casting method of the gypsum mold-based silicon carbide ceramic slurry according to claim 1, wherein the dispersant in the step (1) is selected from sodium silicate, and the use amount is 1-8% of the mass of the silicon carbide micro powder.
  5. 5. The slip casting method of a gypsum mold-based silicon carbide ceramic slurry according to claim 1 or 2, wherein the water-based slurry in step (1) has a solids content of 80 to 90% and a low viscosity of <1000mpa.s.
  6. 6. The gypsum mold-based silicon carbide ceramic slurry slip casting method of claim 1, wherein the mold environment temperature and humidity in step (2) is 60-80% rh.
  7. 7. The slip casting method of the silicon carbide ceramic slurry based on the gypsum mold according to claim 1, wherein the step (3) is performed before the step of sectional drying, and aging is performed for 24 hours in a high humidity (more than 85% RH) environment at 20-25 ℃.
  8. 8. The slip casting method of the silicon carbide ceramic slurry based on the gypsum mold according to claim 1, wherein in the step (3), the step of sectional drying is performed by heating to 35 ℃ at 1-2 ℃ per minute, heating to 50 ℃ at 2-4 ℃ per minute, heating to 150 ℃ at 3-6 ℃ per minute, and reducing the temperature to 25-30 ℃ at 1-2 ℃ per minute.
  9. 9. The slip casting method of the silicon carbide ceramic slurry based on the gypsum mold according to claim 1, wherein the sintering curve in the step (4) is that the temperature is firstly increased from 25 ℃ to 1000 ℃ at 1-2 ℃ per minute under the protection of nitrogen, then increased to 1500 ℃ at 2-3 ℃ per minute under the protection of N 2 , then increased to 2000 ℃ at 4-5 ℃ per minute under the protection of argon, and finally increased to 2200-2300 ℃ at 1-2 ℃ per minute under the protection of argon.
  10. 10. The slip casting method of the silicon carbide ceramic slurry based on the gypsum mold according to claim 1, wherein the sintering temperature in the step (4) is 2200-2300 ℃ and the sintering time is 48-55 h.

Description

Silicon carbide ceramic slurry grouting forming method based on gypsum mold Technical Field The invention relates to the technical field of advanced ceramic material molding, in particular to a slip casting method based on a gypsum mold for preparing silicon carbide ceramic. Background Silicon carbide ceramics are widely used in the fields of mechanical sealing, aerospace, chemical metallurgy, electronic semiconductors and the like because of the excellent performances of high strength, high hardness, excellent wear resistance, corrosion resistance, high thermal conductivity, high chemical stability and the like. One of the key processes for preparing silicon carbide ceramic articles is shaping. It has been found that the current common molding methods include dry press molding, isostatic pressing, injection molding, slip casting, and the like. Among them, slip casting, particularly slip casting using a porous gypsum mold, is favored because of its simple equipment, low cost, and capability of producing a component having a complicated shape and a large size. However, the application of slip casting to silicon carbide ceramics has a plurality of technical difficulties (1) the stability of the slurry is that the surface energy of silicon carbide particles is high, the silicon carbide particles are easy to agglomerate in water, and the slurry with high solid content, low viscosity and long-term stability is difficult to prepare. Poor slurry stability can lead to uneven green body density, and is easy to generate deformation and cracking after sintering. (2) The green strength of the cured pure silicon carbide slurry is low, the green strength is easy to damage in the demolding and subsequent treatment processes, and the yield is low. (3) The problem of matching with the mould is that if the water absorption rate and the capillary structure of the gypsum mould are not matched with the solidification characteristics of the sizing agent, the internal stress of the blank body is concentrated, and cracks are generated. (4) Sintering activity problems pure silicon carbide is a strongly covalent compound, sintering difficulty is great (i.e. sintering activity is low), it is often necessary to add sintering aids and to increase the sintering density by optimizing the grain size distribution. In the prior art, although some researches relate to slip casting of silicon carbide (SiC), most of the problems are complex process flow (if a large amount of organic binder needs to be added), poor green body performance or limited to laboratory scale. Therefore, the development of the SiC gypsum mold slip casting method which has simple process and high blank quality and is suitable for industrial production has important significance. Disclosure of Invention In order to solve the technical defects in the existing slip casting of silicon carbide (SiC), the invention provides a slip casting method of silicon carbide ceramic slurry based on a gypsum mold, which has the advantages of simple process, low cost, high green body strength and good sintering property. In order to achieve the purpose, the technical scheme provided by the invention is that the silicon carbide ceramic slurry grouting molding method based on the gypsum mold comprises the following steps of: (1) The preparation of slurry, namely mixing silicon carbide micro powder, a sintering aid, a dispersing agent and deionized water, and obtaining uniform, stable and high-solid-content water-based slurry through ball milling; Preferably, the particle diameters of the silicon carbide micro powder are respectively 10-30um and 80-100um, and the mass ratio of the fine micro powder to the coarse micro powder is 0.3-0.6:0.4-0.7. Preferably, the sintering aid is selected from carboxymethyl cellulose (CMC), the use amount is 5-20% of the mass of the silicon carbide micro powder, and the addition of the sintering aid not only promotes the subsequent sintering densification, but also plays a certain role in bonding in slurry, improves the strength of green bodies and reduces the breakage rate in the processes of demoulding and carrying. Preferably, the dispersing agent is selected from sodium silicate, and the use amount is 1-8% of the mass of the silicon carbide micro powder. Preferably, the water-based slurry has a solids content of 80-90% and a low viscosity <1000mpa.s. Through particle size distribution design and dispersant selection, slurry with high solid content (mass fraction 80-90%), low viscosity less than 1000mPa.s and good stability is prepared, and a foundation is laid for obtaining high-density and uniform blanks and final products. (2) Grouting and curing, namely vacuum degassing the slurry, and then injecting the slurry into a porous gypsum mold to form a blank; Preferably, the temperature and humidity of the mold environment are 60-80% RH. Preferably, the porosity of the porous gypsum mold is 30-50%, the dehydration rate is regulated and controlled to be 0.1-0.5