CN118637920A - A preparation method of gel casting pressureless sintered silicon carbide ceramics - Google Patents

Abstract

The present application relates to a preparation method of a gel injection molding pressureless sintered silicon carbide ceramic, comprising the following steps: preparing component A: mixing monomer, cross-linking agent, deionized water, dispersant, suspending agent, and a portion of ceramic powder, stirring, drying after stirring, sieving and powdering to obtain component A; preparing component B: mixing defoamer, catalyst, initiator with the remaining ceramic powder, stirring, drying after stirring, sieving and powdering to obtain component B; preparing silicon carbide ceramics: after mixing component A with component B, adding deionized water to mix to form a slurry as a whole, curing to obtain a green body, drying the green body, and sintering the dried green body without pressure at a temperature range of 2100-2200°C, keeping warm for 2-5h, and obtaining a silicon carbide ceramic product; the monomer includes acrylamide, and the cross-linking agent includes methylene bisacrylamide. When preparing silicon carbide ceramic products, the present application effectively improves the controllability of silicon carbide ceramics during preparation, and is green and environmentally friendly, and the product quality is greatly improved.

Description

A preparation method of gel casting pressureless sintered silicon carbide ceramics

Technical Field

The present application relates to the field of ceramic preparation technology, and in particular to a method for preparing gel-casting pressureless sintered silicon carbide ceramics.

Background Art

Silicon carbide ceramics have excellent room temperature mechanical properties, bending strength, oxidation resistance, corrosion resistance, wear resistance, etc., and also have good high temperature mechanical properties. Ceramic preparation can be done by hot pressing sintering, pressureless sintering, hot isostatic pressing sintering, etc., and the high temperature strength can be maintained up to 1600°C. This year, with the development of sintering theory of silicon carbide products, the improvement of micro powder performance, the diversification and in-depth research of sintering aids, the process of sintering high-performance silicon carbide products using pressureless sintering has begun to develop and improve, and the production cost is low, and there is no restriction on the shape and size of the product.

In recent years, new colloidal molding such as filter press molding, gel injection molding and direct solidification injection molding, etc., in-situ curing is an effective method for preparing high-reliability, complex-shaped ceramic parts. Gel injection molding has been widely studied in the fields of porous materials, composite materials, and functional materials. However, the green body after gel injection curing cannot be used, and the amount of ceramic glue is calculated according to the molded product and volume. For large-sized products, the overall heat generation during curing is large, the curing controllability is low, and the success rate is low.

Summary of the invention

In order to solve the above technical problems, the present application provides a method for preparing gel-casting pressureless sintered silicon carbide ceramics.

The present application provides a method for preparing a gel-injection pressureless sintered silicon carbide ceramic using the following technical solution:

A method for preparing a gel-casting pressureless sintered silicon carbide ceramic comprises the following steps:

Preparation of component A: Mixing monomers, crosslinking agents, deionized water, dispersants, suspending agents, and a portion of ceramic powder, stirring, drying after stirring, and sieving and powdering to obtain component A;

Preparation of component B: mixing the defoamer, catalyst, initiator and remaining ceramic powder, stirring, drying after stirring, sieving and powdering to obtain component B;

Preparation of silicon carbide ceramics: After mixing component A and component B, add deionized water to form a slurry as a whole, solidify to obtain a green body, dry the green body, and perform pressureless sintering at a temperature range of 2100-2200°C for 2-5 hours to obtain a silicon carbide ceramic product;

The monomer includes acrylamide, and the cross-linking agent includes methylene bisacrylamide.

By adopting the above technical solution, component A and component B are configured separately, and solidification can only begin when component A meets component B. The preparation of large-size products can be better controlled, and the parts of component A and component B that are not in contact can be retained and reused in the next preparation, which is more energy-saving and environmentally friendly and reduces production costs.

Preferably, in the step of preparing component A and the step of preparing component B, the stirring temperature is 5-10° C. and the stirring speed is 100-150 r/min.

By adopting the above technical solution, the stirring temperature and stirring speed when component A and component B are in contact are controlled within the above-mentioned limited range, which can further improve the stability of the prepared slurry. When stirring at low temperature and high speed, the cross-linking and curing reaction between the monomer and the cross-linking agent can be suppressed and the contact between component A and component B can be more sufficient, thereby facilitating the subsequent control of the obtained slurry.

Preferably, the dispersant accounts for 2-5% of the total slurry, and the suspending agent accounts for 0.4-0.6% of the total slurry.

By adopting the above technical solution, preferably the content of the dispersant and the suspending agent is within the above range, which can further improve the uniformity and stability of the various components in the overall slurry, and also improve the quality of the prepared silicon carbide ceramic product.

Preferably, the mass ratio between component A and component B in the preparation of silicon carbide ceramic in the step is (3.8-4.2):1.

Preferably, the ceramic powder comprises silicon carbide surface modified ultrafine powder, carbon black and boron nitride, and the mass ratio of the silicon carbide surface modified ultrafine powder, carbon black and boron nitride is (97.2-97.6):2:0.6.

By adopting the above technical scheme, ceramic powder is prepared by mixing silicon carbide surface modified ultrafine powder, carbon black and boron nitride, so that the comprehensive performance of the ceramic powder is improved. By controlling the mass ratio of silicon carbide ultrafine powder, carbon black and boron nitride within the above range, the quality of the product prepared from the ceramic powder can be further improved.

Preferably, the silicon carbide surface modified ultrafine powder is prepared by the following method:

After mixing the silicon carbide ultrafine powder with deionized water, adding a modifier and a surfactant, stirring for reaction and then centrifuging, washing and drying the precipitate, and obtaining the silicon carbide surface modified ultrafine powder.

By adopting the above technical scheme, after using modifiers and surfactants to treat silicon carbide ultrafine powder, the dispersion effect of silicon carbide ultrafine powder in the system can be effectively improved, and the prepared slurry can have good rheological properties and sedimentation stability. At the same time, the solid content of the slurry can be increased, and the product quality of the prepared silicon carbide ceramics can be further improved.

Preferably, the mass ratio of the modifier, surfactant and silicon carbide surface modified ultrafine powder is (0.49-0.51):1:19.8.

By adopting the above technical solution, the mass ratio of the modifier, the surfactant and the surface-modified silicon carbide ultrafine powder is preferably within the above range, which can further improve the comprehensive performance of the modified silicon carbide ultrafine powder.

Preferably, the modifier comprises dimethyl allyl ammonium chloride-acrylamide copolymer.

By adopting the above technical scheme, the dimethyldiallylammonium chloride-acrylamide copolymer is a polyquaternary ammonium salt substance, and its molecular chain contains a large number of amide groups and quaternary ammonium groups. The quaternary ammonium groups have a positive charge and can form high-affinity adsorption with the surface of silicon carbide ultrafine powder. The hydrophilic amide groups can extend into water, so that the modified silicon carbide ultrafine powder particles have good hydrophilicity and steric hindrance, thereby improving the dispersibility of the silicon carbide ultrafine powder particles, thereby improving the product quality of the prepared silicon carbide ceramics.

Preferably, the surfactant comprises sodium lauryl sulfate.

By adopting the above technical scheme, after sodium lauryl sulfate is added as a surfactant, the sulfate ions in the sodium lauryl sulfate can be adsorbed on the surface of the silicon carbide ultrafine powder. While the modifier improves the dispersibility of the silicon carbide ultrafine powder, the sodium lauryl sulfate can spontaneously enrich on the surface of the silicon carbide ultrafine powder, thereby improving the stability of the silicon carbide ultrafine powder and further improving the product quality of the prepared silicon carbide ceramics.

Preferably, the reaction temperature during the stirring reaction is 88-92°C.

By adopting the above technical solution, the reaction temperature during the stirring reaction is preferably within the above range, which can better promote the combination of the modifier, surfactant and silicon carbide ultrafine powder, thereby improving the overall dispersion performance and quality of the prepared silicon carbide ultrafine powder.

In summary, the present application includes at least one of the following beneficial technical effects:

Component A and component B are prepared separately. When component A and component B meet, they are solidified. The controllability of large-sized silicon carbide ceramic preparation is improved. At the same time, during the preparation process, the parts of component A and component B that are not in contact with each other can be recycled and used in the subsequent preparation of silicon carbide ceramic products. It is green and environmentally friendly, and the production cost is reduced.

After surface treatment of silicon carbide ultrafine powder with modifiers and surfactants, the overall dispersibility of silicon carbide ceramic powder can be effectively improved, so that the ceramic powder can be dispersed more evenly in the slurry, the prepared green body can be more stable, and the solid content of the green body can be effectively increased, reducing the collapse of the green body and other phenomena. The quality of the silicon carbide ceramic products prepared subsequently can be effectively improved.

DETAILED DESCRIPTION

The present application discloses a method for preparing a gel-cast pressureless sintered silicon carbide ceramic. The present application is further described in detail below in conjunction with the examples:

Raw material preparation:

Monomer: acrylamide (CAS No.: 79-06-1); cross-linking agent: methylene bisacrylamide (CAS No.: 110-26-9); dispersant: the dispersant is prepared by mixing DolaPIX CE 64 and MQ-5088 in a mass ratio of 1:1; suspending agent: MQ-818; defoaming agent: n-octanol (CAS No.: 111-87-5); catalyst: tetramethylethylenediamine (CAS No.: 110-18-9); initiator: prepared by mixing 5% by mass of ammonium persulfate and the rest of deionized water.

Method for preparing pressureless sintered silicon carbide ceramics by gel casting:

Preparation of component A: Mix the monomer, cross-linking agent, deionized water, dispersant, suspending agent and a portion of ceramic powder, stir at 100-150 r/min for 1.5-2.5 h at a temperature of 5-10°C, then transfer to a vacuum drying oven and dry at 35-45°C for 24 h, sieve and powder to obtain component A.

Preparation of component B: Mix the defoamer, catalyst, initiator and remaining ceramic powder, stir at 100-150 r/min for 1.5-2.5 h at a temperature of 5-10°C, then transfer to a low-temperature drying oven and dry at 35-45°C for 24 h, sieve and powder to obtain component B.

Preparation of silicon carbide ceramics: The components A and B prepared above are poured into a dispensing machine or an injection molding machine at a mass ratio of (3.8-4.2):1. Under the thrust of the dispensing machine or the injection molding machine, the powders of components A and B are mixed. A water inlet is set at the outlet of the dispensing machine or the injection molding machine. After adding deionized water, components A and B are combined together to form a whole, and then cured. The product is formed to obtain a green body, and the remaining components A and B are recovered; the green body after forming is dried at a constant temperature and humidity, and the drying system is shown in Table 1; after the drying technology, the green body is pressurelessly sintered, the sintering temperature is controlled to be 2100-2200°C, and the insulation time is 2-5h to obtain a silicon carbide ceramic product.

Table 1 Green body drying system

Temperature/℃ 30 40 50 50 60 70 90 100 100 70 30 humidity/% 75 70 60 50 40 20 0 0 0 0 0 Time/H 1 20 20 2 10 6 10 5 10 10 4

Example

Preparation of silicon carbide surface modified ultrafine powder:

1890.8g of silicon carbide ultrafine powder was mixed with 2000ml of deionized water, and the pH value was adjusted to 10 with sodium hydroxide. The mixture was stirred at 300rpm for 30min, and then 35.91g of dimethyldiallylammonium chloride-acrylamide copolymer (CAS No.: 26590-05-6) and 73.29g of sodium lauryl sulfate (CAS No.: 151-21-3) were added. The mixture was heated to 88°C and stirred at 400rpm for 4h. After centrifugation, the precipitate was washed with deionized water. After repeated washing twice, the precipitate was dried at 80°C for 24h and ground to obtain silicon carbide surface modified ultrafine powder.

Preparation of ceramic powder: 1753.11 g of the above-prepared silicon carbide surface-modified ultrafine powder, 36.07 g of carbon black and 10.82 g of carbon nitride powder were mixed to obtain ceramic powder.

Preparation of silicon carbide ceramics:

Preparation of component A: Mix 41 g of acrylamide, 4 g of methylenebisacrylamide, 200 g of deionized water, 30 g of dispersant, 7.5 g of suspending agent and 905 g of ceramic powder, stir at 150 r/min for 1.5 h at 5 °C, then transfer to a vacuum drying oven and dry at 40 °C for 24 h, sieve and powder to obtain component A.

Preparation of component B: Mix 0.75 g of defoamer, 0.075 g of catalyst, 0.08 g of initiator and 312 g of ceramic powder, stir at 150 r/min for 1.5 h at 5 °C, then transfer to a vacuum drying oven and dry at 35 °C for 24 h, sieve and powder to obtain component B.

Preparation of silicon carbide ceramics: Weigh 1187.5g of component A and 312.5g of component B prepared above and add them to an injection molding machine. After starting the injection molding machine, fully mix component A and component B. Set a water inlet at the outlet of the injection molding machine, add 200g of deionized water, and component A and component B form a whole and solidify under the action of deionized water. Obtain a green body according to the preparation requirements, and recover the remaining component A and component B; keep the obtained green body at a constant temperature and humidity until it is dry, and the drying system is shown in Table 1; after drying, perform pressureless sintering, control the sintering temperature to 2100°C, and the insulation time to 5h to obtain a silicon carbide ceramic product.

Example

Preparation of silicon carbide surface modified ultrafine powder:

1889.42 g of silicon carbide ultrafine powder was mixed with 2000 ml of deionized water, and the pH value was adjusted to 10 with sodium hydroxide. The mixture was stirred at 300 rpm for 30 min, and then 37.35 g of dimethyldiacrylammonium chloride-acrylamide copolymer and 73.23 g of sodium lauryl sulfate were added. The mixture was heated to 92°C and stirred at 400 rpm for 4 h. After centrifugation, the precipitate was washed with deionized water. After repeated washing twice, the precipitate was dried at 80°C for 24 h and ground to obtain silicon carbide surface modified ultrafine powder.

Preparation of ceramic powder: 1753.29 g of the silicon carbide surface-modified ultrafine powder prepared above, 35.93 g of carbon black and 10.78 g of carbon nitride powder were mixed to obtain ceramic powder.

Preparation of silicon carbide ceramics:

Preparation of component A: Mix 100.7 g of acrylamide, 6.8 g of methylenebisacrylamide, 270 g of deionized water, 150 g of dispersant, 11 g of suspending agent and 1181.5 g of ceramic powder, stir at 100 r/min for 1.5 h at 10°C, then transfer to a vacuum drying oven and dry at 40°C for 24 h, sieve and powder to obtain component A.

Preparation of component B: Mix 6.45 g of defoamer, 0.215 g of catalyst, 0.2 g of initiator and 423 g of ceramic powder, stir at 100 r/min for 1.5 h at 10°C, then transfer to a vacuum drying oven and dry at 45°C for 24 h, sieve and powder to obtain component B.

Preparation of silicon carbide ceramics: Weigh 1720g of component A and 430g of component B prepared above and add them to an injection molding machine. After starting the injection molding machine, fully mix component A and component B. Set a water inlet at the outlet of the injection molding machine, add 200g of deionized water, and component A and component B form a whole and solidify under the action of deionized water. A green body is obtained according to the preparation requirements, and the remaining component A and component B are recovered; the obtained green body is kept at a constant temperature and humidity until dry, and the drying system is shown in Table 1; after drying, pressureless sintering is carried out, the sintering temperature is controlled to 2100°C, and the insulation time is 5h to obtain a silicon carbide ceramic product.

Example

Preparation of silicon carbide surface modified ultrafine powder:

1890.11 g of silicon carbide ultrafine powder was mixed with 2000 ml of deionized water, and the pH value was adjusted to 10 with sodium hydroxide. The mixture was stirred at 300 rpm for 30 min, and then 36.63 g of dimethyldiacrylammonium chloride-acrylamide copolymer and 73.26 g of sodium lauryl sulfate were added. The mixture was heated to 90°C and stirred at 400 rpm for 4 h. After centrifugation, the precipitate was washed with deionized water. After repeated washing twice, the precipitate was dried at 80°C for 24 h and ground to obtain silicon carbide surface modified ultrafine powder.

Preparation of ceramic powder: 1753.2 g of the above-prepared silicon carbide surface-modified ultrafine powder, 36 g of carbon black and 10.8 g of carbon nitride powder were mixed to obtain ceramic powder.

Preparation of silicon carbide ceramics:

Preparation of component A: Mix 68.5 g of acrylamide, 5.5 g of methylenebisacrylamide, 250 g of deionized water, 65 g of dispersant, 9.5 g of suspending agent and 1096.5 g of ceramic powder, stir at 130 r/min at 7°C for 1.5 h, then transfer to a vacuum drying oven and dry at 40°C for 24 h, sieve and powder to obtain component A.

Preparation of component B: Mix 3.7 g of defoamer, 0.15 g of catalyst, 0.15 g of initiator and 351 g of ceramic powder, stir at 130 r/min at 7°C for 1.5 h, then transfer to a vacuum drying oven and dry at 40°C for 24 h, sieve and powder to obtain component B.

Preparation of silicon carbide ceramics: Weigh 1495g of component A and 355g of component B prepared above and add them to an injection molding machine. After starting the injection molding machine, fully mix component A and component B. Set a water inlet at the outlet of the injection molding machine, add 200g of deionized water, and component A and component B form a whole and solidify under the action of deionized water. A green body is obtained according to the preparation requirements, and the remaining component A and component B are recovered; the obtained green body is kept at a constant temperature and humidity until dry, and the drying system is shown in Table 1; after drying, pressureless sintering is carried out, the sintering temperature is controlled to 2100°C, and the insulation time is 5h to obtain a silicon carbide ceramic product.

Example

Example 4 is based on Example 3. The difference between Example 4 and Example 3 is that in Example 4, when preparing the surface-modified silicon carbide ultrafine powder, the dimethyldiacrylammonium chloride-acrylamide copolymer weighed is 33.03 g, and the sodium lauryl sulfate weighed is 73.39 g.

Example

Example 5 is based on Example 3. The difference between Example 5 and Example 3 is that in Example 5, when preparing the surface-modified silicon carbide ultrafine powder, the amount of dimethyl propylene ammonium chloride-acrylamide copolymer weighed is 40.22 g, and the amount of sodium lauryl sulfate weighed is 73.13 g.

Example

Example 6 is based on Example 3. The difference between Example 6 and Example 3 is that in Example 6, when preparing the surface-modified ultrafine powder of silicon carbide, 36.9 g of dimethyl propylene ammonium chloride-acrylamide copolymer is weighed, and 59.04 g of sodium lauryl sulfate is weighed.

Example

Example 7 is based on Example 3. The difference between Example 7 and Example 3 is that in Example 7, when preparing the surface-modified silicon carbide ultrafine powder, 36.36 g of dimethyl propylene ammonium chloride-acrylamide copolymer is weighed, and 87.27 g of sodium lauryl sulfate is weighed.

Example

Example 8 is based on Example 3. The difference between Example 8 and Example 3 is that in Example 8, when preparing the surface-modified ultrafine powder of silicon carbide, sodium lauryl sulfate is replaced by an equal amount of disuccinimidyl suberate (CAS No.: 68528-80-3).

Example

Example 9 is based on Example 3. The difference between Example 9 and Example 3 is that in Example 9, when preparing the surface-modified ultrafine powder of silicon carbide, sodium lauryl sulfate is replaced by an equal amount of sodium dodecylbenzene sulfonate (CAS No.: 25155-30-0).

Example

Example 10 is based on Example 3. The difference between Example 10 and Example 3 is that in Example 10, when preparing the surface-modified ultrafine powder of silicon carbide, the dimethyl propylene ammonium chloride-acrylamide copolymer is replaced with an equal amount of polydimethyldiallylammonium chloride (CAS No.: 26062-79-3).

Example

Example 11 is based on Example 3. The difference between Example 11 and Example 3 is that in Example 11, when preparing the surface-modified silicon carbide ultrafine powder, the reaction temperature is 96°C.

Example

Example 12 is based on Example 3. The difference between Example 12 and Example 3 is that in Example 12, when preparing the surface-modified silicon carbide ultrafine powder, the reaction temperature is 84°C.

Comparative Example 1

Comparative Example 1 is based on Example 3. The difference between Comparative Example 1 and Example 3 is that: in Comparative Example 1, component A and component B are not separated. In Comparative Example 1, all raw materials are directly mixed and then put into the injection molding machine.

Performance testing

For Examples 1-12 and Comparative Example 1, the silicon carbide ceramics prepared were sampled and subjected to the following performance tests:

(1) The density of the samples was tested according to the test standard GB/T 25995-2010 Test method for density and apparent porosity of fine ceramics. Each sample was tested three times, and the average value was taken. The test results were filled in Table 2.

(2) Using GB/T 6569-2006 Fine Ceramics Bending Strength Test Method as the test standard, the samples were tested for bending strength. Each sample was tested three times at room temperature, and the average value was taken. The test results were filled in Table 2.

Table 2 Performance test results of silicon carbide ceramics of Examples 1-12 and Comparative Examples

Data analysis

It can be seen from Table 1 that the average density of the silicon carbide ceramics prepared in Examples 1-3 is 3.13 g/cm ³ or above, the difference between the side wall density and the bottom density is 0.02 g/cm ³ or below, and the compressive strength is above 430 MPa, indicating that the silicon carbide ceramics prepared in this application have good uniformity and the product quality is significantly improved.

When the addition amount of sodium lauryl sulfate is too small, after it is enriched on the surface of silicon carbide ultrafine powder, the positive adsorption phenomenon decreases, and the repulsion effect on silicon carbide ultrafine powder decreases, so the powder dispersion performance and suspension stability of the prepared slurry decrease, affecting the quality of the subsequent prepared products; since sodium lauryl sulfate has certain foaming properties, when the addition amount of sodium lauryl sulfate is too much, the prepared slurry will produce bubbles, and too many bubbles will form air masses, which hinder the fluidity of the slurry, the viscosity of the slurry is too large, and the uniformity of the system decreases, affecting the average density and product quality, so the performance of Examples 4 and 5 are all reduced.

When the addition amount of dimethyl propylene ammonium chloride-acrylamide copolymer is too small, it is difficult to promote the silicon carbide ultrafine powder to obtain better water-clearing property and steric hindrance, so the dispersion performance of the silicon carbide ultrafine powder is reduced, affecting the stability of the system; when the content of dimethyl propylene ammonium chloride-acrylamide copolymer is too much, the excessively high polymer concentration will aggravate the bridging and overlapping of the polymer chains, hinder the fluidity of the slurry, make the slurry viscosity too large, and reduce the uniformity of the system, thereby affecting the product quality. Therefore, the various performances of Example 6 and Example 7 are reduced.

The complete ionization rate of disuccinimidyl suberate sulfonic acid group is low, which hinders the molecular chain from forming a sterically hindered conformation, and thus the effect of improving the dispersion performance of the silicon carbide ultrafine powder is reduced; the hydrogen bonding effect of sodium dodecylbenzene sulfonate is relatively weak, which will also affect the sterically hindered conformation of the silicon carbide ultrafine powder, thereby reducing the dispersion effect of the silicon carbide ultrafine powder. Therefore, the stability improvement effects of the systems of Example 8 and Example 9 are both reduced, and various performances are reduced.

Polydimethyldiallylammonium chloride has too many positively charged groups, and the dispersion performance of the molecular chain is reduced in an alkaline environment. Therefore, it is difficult to improve the dispersion performance modification effect of silicon carbide ultrafine powder. Therefore, the stability of the system in Example 10 is reduced, resulting in a decrease in various performances.

When preparing modified silicon carbide ultrafine powder, when the reaction temperature is too low, the viscosity of the slurry obtained from the subsequent preparation of the silicon carbide ultrafine powder will increase, affecting the fluidity of the slurry and reducing the overall stability of the system; when the reaction temperature is too high, the performance of the high molecular weight polymer in the system will decrease, thereby affecting the modification effect of the silicon carbide ultrafine powder. Therefore, the performance of Examples 11 and 12 are all reduced.

In Comparative Example 1, all the raw materials are directly mixed and put into the injection molding machine. When all the raw materials are mixed and then put into the injection molding machine to prepare large-sized silicon carbide ceramic products, all the raw materials generate heat as a whole during curing, and the curing effect is difficult to control. The curing uniformity decreases, and therefore the quality of the product prepared in Comparative Example 1 decreases.

This specific embodiment is only an explanation of the present application, and it is not a limitation of the present application. Through the above description, relevant staff can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims (10)

1. A preparation method of gel injection molding pressureless sintering silicon carbide ceramic is characterized in that: the method comprises the following steps:

Preparing a component A: mixing a monomer, a cross-linking agent, deionized water, a dispersing agent, a suspending agent and a part of ceramic powder, stirring, drying after stirring, sieving and powdering to obtain a component A;

preparing a component B: mixing the defoaming agent, the catalyst, the initiator and the rest ceramic powder, stirring, drying after stirring, sieving and powdering to obtain a component B;

Preparing silicon carbide ceramics: mixing the component A and the component B, adding deionized water, mixing to form a slurry whole, solidifying to obtain a green body, drying the green body, performing pressureless sintering on the dried green body at the temperature of 2100-2200 ℃, and preserving heat for 2-5h to obtain a silicon carbide ceramic product;

the monomer comprises acrylamide and the crosslinking agent comprises methylene bisacrylamide.

2. The method for preparing the gel injection molding pressureless sintered silicon carbide ceramic according to claim 1, wherein the method comprises the following steps: in the step preparation component A and the step preparation component B, the stirring temperature during stirring is 5-10 ℃, and the stirring speed is 100-150r/min.

3. The method for preparing the gel injection molding pressureless sintered silicon carbide ceramic according to claim 1, wherein the method comprises the following steps: the dispersing agent accounts for 2-5% of the whole slurry, and the suspending agent accounts for 0.4-0.6% of the whole slurry.

4. The method for preparing the gel injection molding pressureless sintered silicon carbide ceramic according to claim 1, wherein the method comprises the following steps: the mass ratio of the component A to the component B in the silicon carbide ceramic preparation is (3.8-4.2) 1.

5. The method for preparing the gel injection molding pressureless sintered silicon carbide ceramic according to claim 1, wherein the method comprises the following steps: the ceramic powder comprises silicon carbide surface modified ultrafine powder, carbon black and boron nitride, wherein the mass ratio of the silicon carbide surface modified ultrafine powder to the carbon black to the boron nitride is (97.2-97.6) 2:0.6.

6. The method for preparing the gel-injection pressureless sintered silicon carbide ceramic according to claim 5, wherein the method comprises the following steps: the silicon carbide surface modified ultrafine powder is prepared by the following method:

Mixing the silicon carbide ultrafine powder with deionized water, adding a modifier and a surfactant, stirring for reaction, centrifuging, washing the precipitate, and drying to obtain the silicon carbide surface modified ultrafine powder.

7. The method for preparing the gel-injection pressureless sintered silicon carbide ceramic according to claim 6, wherein the method comprises the following steps: the mass ratio of the modifier, the surfactant and the silicon carbide surface modified superfine powder is (0.49-0.51) 1:19.8.

8. The method for preparing the gel-injection pressureless sintered silicon carbide ceramic according to claim 7, wherein the method comprises the following steps: the modifier comprises dimethyl allyl ammonium chloride-acrylamide copolymer.

9. The method for preparing the gel-injection pressureless sintered silicon carbide ceramic according to claim 7, wherein the method comprises the following steps: the surfactant comprises sodium lauryl sulfate.

10. The method for preparing the gel-injection pressureless sintered silicon carbide ceramic according to claim 6, wherein the method comprises the following steps: the reaction temperature is 88-92 ℃ during the stirring reaction.