CN116462511A

CN116462511A - Reaction sintering silicon carbide product containing small amount of free silicon and production method thereof

Info

Publication number: CN116462511A
Application number: CN202310520697.4A
Authority: CN
Inventors: 任云; 任霞; 刘岩哲; 宋思雨; 祁永莲
Original assignee: Shenyang Xinchang Material Co ltd
Current assignee: Shenyang Xinchang Material Co ltd
Priority date: 2023-05-09
Filing date: 2023-05-09
Publication date: 2023-07-21

Abstract

The embodiment of the invention discloses a reaction sintering silicon carbide product containing a small amount of free silicon and a production method thereof. The reaction sintering silicon carbide product comprises the following components in parts by weight: 20-30 parts of purified water, 25-35 parts of silicon carbide micro powder, 40-65 parts of silicon carbide coarse particles, 6-10 parts of carbon black and 1.1-2.3 parts of bonding agent. The content of free silicon in the obtained reaction sintering silicon carbide is less than or equal to 4%, so that excellent high-temperature use stability is achieved, and the high-temperature use limit of the product is improved. The volume density of the green body is 2.38-2.48g/cm ³ The volume density of the finished product is 3.07-3.12g/cm ³ The bending strength at 20 ℃ is about 270-300MPa, and the bending strength at 1200 ℃ is about 290-330MPa. The bending strength of the blank body at different temperatures is greatly improved.

Description

Reaction sintering silicon carbide product containing small amount of free silicon and production method thereof

Technical Field

The embodiment of the invention relates to the technical field of fine ceramic products, in particular to a reaction sintering silicon carbide product containing a small amount of free silicon and a production method thereof.

Background

The reaction sintering silicon carbide product is a novel fine ceramic and has a plurality of excellent properties: high strength, high hardness, good corrosion resistance, thermal shock resistance, high electric conductivity and heat conductivity, etc. Production sites are mainly concentrated in Shandong and Henan area. The silicon carbide products have wide application fields, mainly comprise ceramic kiln furniture, electrons, aerospace, semiconductors, photovoltaics and the like, and the main preparation method comprises the following steps: the method comprises the steps of preparing a blank by using alpha-SiC and carbon black with different granularities through various molding modes under the action of a bonding agent, then sintering, reacting the carbon black in the blank with infiltrated silicon at high temperature to generate beta-SiC, combining the beta-SiC with the alpha-SiC to form a compact sintered body, and enabling redundant silicon to exist in pores in a free silicon form, so that the density of a product is improved.

At present, the main production modes of the reaction sintering silicon carbide are two, one is extrusion molding, the free silicon content in the silicon carbide product is about 20 percent, and the volume density of a blank body is 2.2g/cm ³ The volume density of the finished product is 2.90g/cm ³ About 20 ℃ bending strength of about 240MPa and 1200 ℃ bending strength of about 250MPa. In another slip casting, the free silicon content of the silicon carbide product is about 10%, and the volume density of the blank body is 2.3g/cm ³ The volume density of the finished product is 3.00g/cm ³ About, the bending strength at 20℃is about 250MPa, and the bending strength at 1200℃is about 260MPa. The silicon carbide products obtained by the two forming processes have high free silicon content, so that the high-temperature use effect is poor, and the defect of limited use under a high-temperature environment exists.

Disclosure of Invention

Therefore, the embodiment of the invention provides a reaction sintering silicon carbide product containing a small amount of free silicon and a production method thereof, so as to solve the defect of poor high-temperature service performance caused by high content of free silicon in the existing reaction sintering silicon carbide product.

In order to achieve the above object, the embodiment of the present invention provides the following technical solutions:

according to a first aspect of embodiments of the present invention, there is provided a reaction-sintered silicon carbide article containing a small amount of free silicon, comprising the following raw materials in parts by weight: 20-30 parts of purified water, 25-35 parts of silicon carbide micro powder, 40-65 parts of silicon carbide coarse particles, 6-10 parts of carbon black and 1.1-2.3 parts of bonding agent; wherein, the liquid crystal display device comprises a liquid crystal display device,

d of the silicon carbide micropowder ₁₀ ＝0-1.2μm，D ₅₀ ＝1.8-2.5μm，D ₉₀ ＝5-10μm；

The particle size distribution of the silicon carbide coarse particles is as follows, in weight percent: 0-100 meshes, 0-5%,100-140 meshes, 5-20%,140-200 meshes, 32-45%,200-325 meshes, 30-50% and more than 325 meshes, 2-10%.

The application finds that the volume density of the product has a great relation with the grain composition of the raw material silicon carbide, and the more reasonable the grain composition among silicon carbide grains is, the larger the volume density of the product is, so that the higher the strength is and the longer the service life is. Through a large number of experiments, the applicant finds that the preferable silicon carbide micro powder and silicon carbide coarse particles have large particle size span and reasonable particle grading, and are beneficial to improving the comprehensive performance of the silicon carbide product.

Further, the binding agent consists of 0.2-0.5 part by weight of sodium carboxymethylcellulose, 0.3-0.8 part by weight of dispersing agent and 0.5-1 part by weight of deflocculant.

Carbon black is nano-sized and reacts well with infiltrated silicon to produce beta-SiC, which reduces porosity as the carbon black is converted to silicon carbide of greater volume and mass. And the excessive silicon can generate more beta-SiC by increasing the dosage of the carbon black, so that the compactness of the product is improved, meanwhile, the porosity of the blank is further reduced, and the reduction of the content of free silicon in the reaction sintering silicon carbide product is facilitated. It was found that when the amount of carbon black was increased, the carbon black was liable to agglomerate, was poor in dispersibility, and was not able to effectively reduce the free silicon content.

The bonding agent is used for improving the dispersion performance of the carbon black in water, so that the addition amount of the carbon black can be increased, and the comprehensive performance of the product is improved. The bonding agent commonly used at present is sodium carboxymethyl cellulose or sodium humate, and the like, and the phenomenon of poor dispersibility and poor comprehensive performance of products still exists.

According to the application, a large amount of researches show that a specific amount of sodium carboxymethyl cellulose, a dispersing agent and a deflocculating agent are added, wherein the dispersing agent is a humate-silicate mixture and is used for uniformly dispersing nano-scale carbon black in slurry, and the dispersing agent is preferably DOLAPIX SP NEU produced by the chemical industry of Germany; the deflocculant is phosphate-silicate, which can suspend silicon carbide particles in slurry well and is not easy to precipitate, and the deflocculant is preferably GLESSFIX C91 in the chemical industry of the Sema, germany. The adoption of the bonding agent is more beneficial to obtaining uniform and consistent products while improving the using amount of the carbon black, so that particles can be orderly arranged in the slurry sucking process, the volume density of a blank body is increased, the manufacturing difficulty is reduced, and meanwhile, the carbon black can fully react with silicon to generate beta-SiC, thereby achieving the effect of reducing the content of free silicon in a product.

Further, the carbon black D ₁₀ ＝0-20nm，D ₅₀ ＝30-50nm，D ₉₀ ＝60-150nm。

Further, the conductivity of the purified water is 5 μs/cm or less.

According to a second aspect of embodiments of the present invention, there is provided a method of preparing a reaction-sintered silicon carbide article containing a small amount of free silicon as defined in any one of the above, the method comprising:

dissolving the binding agent in purified water, adding silicon carbide micropowder, stirring for 30-60min, adding silicon carbide coarse particles, stirring for 45-60min, adding carbon black in a small amount and multiple times, rapidly stirring for 48-72h, and then sequentially performing slip casting, demolding, drying and sintering.

Further, when the carbon black added last time is completely blended into the slurry, adding a small amount of carbon black, wherein the adding time of the carbon black is 2-3 hours; the drying temperature is 80-120 ℃.

Further, the sintering process of the sintering is as follows: in a vacuum state, the temperature is between room temperature and 800 ℃ and the heating time is between 3 and 4 hours; heating at 800-1150 deg.c for 3-4 hr; 1150-1350 ℃ and 2-3h; simultaneously filling inert gas, and heating for 5-8h at 1350-1700 ℃; filling inert gas, keeping the temperature at 1700 ℃ for 2-3h; and (3) filling inert gas for cooling at 1700-1300 ℃, and filling helium for rapid cooling after 1300 ℃.

The embodiment of the invention has the following advantages:

the invention carries out intensive research on raw materials and processes of the reaction sintering silicon carbide product, discovers that silicon carbide micro powder, silicon carbide coarse particles and binding agent with specific particle size distribution, obtains a blank through a slip casting process in a stirring mode, sinters at high temperature to obtain the reaction sintering silicon carbide with the free silicon content less than or equal to 4%, achieves excellent high-temperature use stability, and improves the high-temperature use limit of the product.

The volume density of the green body is 2.38-2.48g/cm ³ The volume density of the finished product is 3.07-3.12g/cm ³ The bending strength at 20 ℃ is 270MPa-300MPa, and the bending strength at 1200 ℃ is 290MPa-330MPa, so that the manufacturing strength, the volume density and the bending strength at different temperatures of the blank are greatly improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It will be apparent to those of ordinary skill in the art that the drawings in the following description are exemplary only and that other implementations can be obtained from the extensions of the drawings provided without inventive effort.

FIG. 1 is a graph showing the particle size distribution of fine silicon carbide powder;

FIG. 2 is a graph of the morphology of coarse silicon carbide particles;

FIG. 3 is an XRD pattern for a reaction-sintered silicon carbide article of example 1;

FIG. 4 is an XRD pattern for a reaction-sintered silicon carbide article of comparative example 1;

FIG. 5 is an XRD pattern for a reaction-sintered silicon carbide article of comparative example 2;

FIG. 6 is an XRD pattern for a reaction-sintered silicon carbide article of comparative example 3;

FIG. 7 is a scanning electron microscope image of a reaction sintered silicon carbide article of example 1;

FIG. 8 is a scanning electron microscope image of a reaction sintered silicon carbide article of comparative example 1;

FIG. 9 is a scanning electron microscope image of a reaction sintered silicon carbide article of comparative example 2;

FIG. 10 is a scanning electron microscope image of a reaction sintered silicon carbide article of comparative example 3.

Detailed Description

Other advantages and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, by way of illustration, is to be read in connection with certain specific embodiments, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

The embodiment provides a reaction sintering silicon carbide product, which comprises the following raw materials: 27 parts of purified water, 34 parts of silicon carbide micro powder, 59.5 parts of silicon carbide coarse particles, 7.5 parts of carbon black and 1.5 parts of a bonding agent. Wherein the binding agent consists of 0.4 part by weight of sodium carboxymethylcellulose, 0.6 part by weight of DOLAPIX SPNEU (Germany Sima Huagong) and 0.5 part by weight of GLESSFIX C91 (Germany Sima Huagong). Wherein:

d of silicon carbide micropowder ₁₀ ＝1.08μm，D ₅₀ ＝2.29μm，D ₉₀ =7.47 μm, its manufacturing method: the 3000# silicon carbide powder and the 1500# silicon carbide powder are prepared according to the mass ratio of 1:3, and are sequentially subjected to the procedures of grinding, press filtration, drying, crushing and the like, and the particle size distribution diagram is shown in figure 1.

The particle size distribution of the silicon carbide coarse particles is: 0-100 mesh 3.0%,100-140 mesh 14.6%,140-200 mesh 36.5%,200-325 mesh 43.0% and 325 mesh 2.9%, and its preparation method comprises: the 60-70# granular sand is crushed by an air flow mill, classified, shaped, screened and the like, the granularity is nearly spherical, and the morphology diagram is shown in figure 2.

Median diameter D of carbon black ₁₀ ＝10nm，D ₅₀ ＝47nm，D ₉₀ =85 nm, a carbon content of 93.2% and a specific surface area of 48m ² The volatile content (950 ℃) was 0.6%, the pH value was 9.0 and the ash content was 0.30%.

The preparation method of the reaction sintering silicon carbide product comprises the following steps:

1) Purified water is put into a clean stirring barrel, and stirring is started.

2) Adding the bonding agent into the stirring barrel in the step 1), and stirring for 8min to completely dissolve the bonding agent.

3) Adding the silicon carbide micro powder into the stirring barrel in the step 2), and stirring for 45min.

4) Adding coarse silicon carbide particles into the stirring barrel in the step 3), and stirring for 30min.

5) And (3) continuously adding carbon powder into the stirring barrel in the step (4), wherein the adding process is slow, the carbon powder is added for a small amount of times, whether the carbon powder added last time is fused into the previous slurry or not is observed during each adding, and the carbon powder can be added again after being completely fused, wherein the process needs about 3 hours.

6) After all the carbon powder is added, the mixture is rapidly stirred for 48 hours for use.

7) Gypsum molds with different shapes are selected according to production requirements to carry out slip casting, different time for absorbing the slurry of the product is different, and the time for absorbing the slurry of the product with the thickness of about 5mm is 50 minutes.

8) And (3) demolding, namely, the mud blank which is removed from the gypsum mold needs to be compacted by a tool with good straightness, so that deformation in the drying process is avoided.

9) Drying at 100deg.C.

10 Sintering at room temperature-800 ℃ under vacuum state, and heating for 3h; heating for 4h at 800-1150 ℃; heating to 1150-1350 deg.c for 3 hr; simultaneously filling inert gas, heating for 6h at 1350-1700 ℃, filling inert gas, maintaining the temperature for 2h at 1700 ℃, filling inert gas for cooling at 1700-1300 ℃, and filling helium for rapid cooling after 1300 ℃.

Example 2

This example provides a reaction sintered silicon carbide article that differs from example 1 only in the parts by weight of carbon black. The raw materials of this embodiment are: 27 parts of purified water, 34 parts of silicon carbide micro powder, 59.5 parts of silicon carbide coarse particles, 8 parts of carbon black and 1.5 parts of a binding agent. Wherein the binding agent consists of 0.4 part by weight of sodium carboxymethylcellulose, 0.6 part by weight of DOLAPIX SPNEU (Germany Sima Huagong) and 0.5 part by weight of GLESSFIX C91 (Germany Sima Huagong).

The method of preparing the reaction sintered silicon carbide article of this example is the same as in example 1.

Example 3

This example provides a reaction sintered silicon carbide article that differs from example 1 only in the parts by weight of carbon black. The raw materials of this embodiment are: 27 parts of purified water, 34 parts of silicon carbide micro powder, 59.5 parts of silicon carbide coarse particles, 12 parts of carbon black and 1.5 parts of a binding agent. Wherein the binding agent consists of 0.4 part by weight of sodium carboxymethylcellulose, 0.6 part by weight of DOLAPIX SPNEU (Germany Sima Huagong) and 0.5 part by weight of GLESSFIX C91 (Germany Sima Huagong).

Comparative example 1

This comparative example provides a reaction-sintered silicon carbide article that differs from example 1 only in the use of silicon carbide micropowder and silicon carbide coarse particles. The raw materials used in this comparative example were: 27 parts of purified water, silicon carbide micro powder F1200 (D) ₁₀ ＝0-2.5μm，D ₅₀ ＝3.5-6.5μm，D ₉₀ 34 parts of Shenyang Changxin New Material Co., ltd. =5-9 μm, coarse silicon carbide particles F240 (D ₁₀ ＝10-30μm，D ₅₀ ＝35-75μm，D ₉₀ =50-80 μm, shenyang chang xin new materials limited) 59.5 parts, carbon black 6.5 parts, binder 1.5 parts. Wherein the binding agent consists of 0.4 part by weight of sodium carboxymethylcellulose, 0.6 part by weight of sodium humate and 0.5 part by weight of GLESSFIX162 (German Sima Huagong silicate).

The preparation method of the reaction sintered silicon carbide product of this comparative example is the same as in example 1.

Comparative example 2

This comparative example provides a reaction sintered silicon carbide article that differs from example 1 only in the binder. The raw materials used in this comparative example were: 27 parts of purified water, 34 parts of silicon carbide micro powder of comparative example 1, 59.5 parts of silicon carbide coarse particles of comparative example 1, 6.5 parts of carbon black and 1.5 parts of a binding agent. Wherein the binding agent consists of 0.4 part by weight of sodium carboxymethylcellulose, 0.6 part by weight of DOLAPIX SPNEU (Germany Sima Huagong) and 0.5 part by weight of GLESSFIX C91 (Germany Sima Huagong).

Comparative example 3

This comparative example provides a reaction sintered silicon carbide article that differs from example 1 only in the binder. The raw materials used in this comparative example were: 27 parts of purified water, 34 parts of silicon carbide micro powder of example 1, 59.5 parts of silicon carbide coarse particles of example 1, 6.5 parts of carbon black and 1.5 parts of a binding agent. Wherein the binding agent consists of 0.4 part by weight of sodium carboxymethylcellulose, 0.6 part by weight of sodium humate and 0.5 part by weight of GLESSFIX162 (German Sima Huagong silicate).

Test example 1

Table 1 comparative Table of various properties of the reaction sintered body produced

TABLE 1

While the invention has been described in detail in the foregoing general description and specific examples, it will be apparent to those skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the invention and are intended to be within the scope of the invention as claimed.

Claims

1. A reaction sintered silicon carbide article containing a small amount of free silicon, comprising the following raw materials in parts by weight: 20-30 parts of purified water, 25-35 parts of silicon carbide micro powder, 40-65 parts of silicon carbide coarse particles, 6-10 parts of carbon black and 1.1-2.3 parts of bonding agent, wherein,

The particle size distribution of the silicon carbide coarse particles is as follows, in weight percent: 0-100 meshes, 0-5%,100-140 meshes, 5-20%,140-200 meshes, 32-45%,200-325 meshes, 30-50% and 325 meshes, 2-10%.

2. The reactive sintered silicon carbide article of claim 1 wherein the binder is comprised of, by weight, 0.2 to 0.5 parts sodium carboxymethylcellulose, 0.3 to 0.8 parts dispersant, and 0.5 to 1 part coagulant.

3. The reaction sintered silicon carbide article containing a small amount of free silicon of claim 2, wherein the dispersant is a humate-silicate mixture; the deflocculant is phosphate-silicate.

4. The reaction sintered silicon carbide article containing a small amount of free silicon of claim 1 wherein the carbon black D ₁₀ ＝0-10nm，D ₅₀ ＝30-50nm，D ₉₀ ＝60-150nm。

5. The reaction sintered silicon carbide article containing a small amount of free silicon of claim 1 wherein the purified water has a conductivity of 5 μs/cm or less.

6. A method of producing a reaction sintered silicon carbide article containing a small amount of free silicon as claimed in any one of claims 1 to 5, said method comprising:

dissolving the binding agent in purified water, adding silicon carbide micropowder, stirring for 30-60min, adding silicon carbide coarse particles, stirring for 45-60min, adding carbon black in a small amount and multiple times, rapidly stirring for 48-72h after the addition, and then sequentially performing slip casting, demoulding, drying and sintering.

7. The method of producing a reaction sintered silicon carbide article containing a small amount of free silicon according to claim 6 wherein a small amount of carbon black is added when the last added carbon black is completely blended into the slurry, said carbon black being added for a period of 2 to 3 hours; the drying temperature is 80-120 ℃.

8. The method of producing a reaction sintered silicon carbide article containing a small amount of free silicon according to claim 6 wherein said sintering step is: in a vacuum state, the temperature is between room temperature and 800 ℃ and the heating time is between 3 and 4 hours; heating at 800-1150 deg.c for 3-4 hr; 1150-1350 ℃ and 2-3h; simultaneous filling

Inert gas, 1350-1700 ℃, and heating time of 5-8h; filling inert gas, keeping the temperature at 1700 ℃ for 2-3h;

and (3) filling inert gas for cooling at 1700-1300 ℃, and filling helium for rapid cooling after 1300 ℃.