A method for producing a reaction-sintered silicon carbide material by introducing an active carbon source and a product thereof

Abstract

The application relates to the field of silicon carbide materials, in particular to a preparation method of a silicon carbide material sintered by introducing an active carbon source and a product thereof. The preparation method comprises the following steps: (1) mixing silicon carbide powder, a silicon source, a carbon source, a binder and water to form a mud, and forming the mud to obtain a silicon carbide blank; (2) performing heat treatment on the silicon carbide blank under an inert atmosphere; (3) laying graphite powder on the silicon carbide blank after the heat treatment until the graphite powder wraps the whole silicon carbide blank, and sintering to obtain the silicon carbide material; the carbon source comprises graphene and / or nano carbon black; the temperature of the heat treatment is 550-650 DEG C; and the time of the heat treatment is 1-2 h. The silicon carbide material has high bulk density and bending strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of silicon carbide materials, in particular to a preparation method of a silicon carbide material sintered by introducing active carbon source and a product thereof. BACKGROUND

[0002] Silicon carbide (SiC) material has great application potential in many fields due to its excellent physical and chemical properties, such as high hardness, high thermal conductivity, corrosion resistance and high temperature resistance. These properties make silicon carbide an ideal material for manufacturing high-performance electronic devices, especially in the fields of power electronics, optoelectronic devices, energy conversion and radio frequency applications. The band gap of silicon carbide is three times that of silicon, the breakdown field strength is ten times that of silicon, and the thermal conductivity is more than three times that of silicon. These characteristics make it have obvious advantages in high temperature, high pressure and high frequency applications.

[0003] However, the existing silicon carbide has large brittleness and low bending strength, and is prone to fracture under bending load, which limits its application in the fields of aerospace, automobile manufacturing, nuclear energy engineering, etc. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defects of large brittleness and low bending strength of the existing silicon carbide ceramic material. A preparation method of a silicon carbide material sintered by introducing active carbon source is provided, which increases the content of silicon carbide to solve the problem of large brittleness.

[0005] In order to solve the above problems:

[0006] The present application provides a preparation method of a silicon carbide material sintered by introducing active carbon source, comprising the following preparation steps:

[0007] (1) mixing silicon carbide powder, silicon source, carbon source, binder and water to form a mud, and molding the mud to obtain a silicon carbide body;

[0008] (2) heat treating the silicon carbide body under an inert atmosphere;

[0009] (3) laying graphite powder on the heat-treated silicon carbide body until the entire silicon carbide body is wrapped, and sintering to obtain the silicon carbide material;

[0010] The carbon source includes graphene and / or nano carbon black;

[0011] The temperature of the heat treatment is 550-650℃;

[0012] The time of the heat treatment is 1-2h.

[0013] Preferably, in step (2), the inert atmosphere includes nitrogen and / or argon.

[0014] Preferably, in step (3), the specific steps are as follows: placing the silicon carbide blank in a crucible and uniformly spreading graphite powder on the blank until the blank is entirely covered, and then placing the blank in a sintering furnace for sintering.

[0015] Preferably, in step (3), the sintering temperature is 1400-1550℃, and the sintering time is 2-3h.

[0016] Preferably, step (1) comprises the following steps:

[0017] After mixing the silicon carbide powder, the silicon source, the carbon source and the binder to form a powder, water is added to stir the powder to form a slurry, the slurry is shaped and dried to obtain the silicon carbide blank.

[0018] Preferably, the mass ratio of the silicon carbide powder, the silicon source and the carbon source is (70-80):(14-21):(6-9), the mass of the binder accounts for 7%-8% of the mass of the powder, and the mass solid content of the slurry is 80%-90%.

[0019] Preferably, the silicon source comprises monocrystalline silicon and / or polycrystalline silicon, and the binder comprises one or more of polyethylene glycol, polyvinyl alcohol and carboxymethyl cellulose, preferably two or more.

[0020] Preferably, the particle size of the silicon carbide powder is 80-350 mesh, the particle size of the silicon source is 80-350 mesh, and the particle size of the carbon source is ≤200nm.

[0021] Preferably, in step (1), the shaping is extrusion molding, die pressing or grouting.

[0022] Preferably, the drying temperature is 80-100℃, and the drying time is 16-24h. The purpose of drying is to remove the water in the blank.

[0023] Preferably, the skilled person can finish the product according to the selection after sintering and packaging, and the finishing includes grinding, polishing and cutting.

[0024] The application also provides a silicon carbide material prepared by the method for preparing the silicon carbide material by introducing the active carbon source reaction sintering.

[0025] The technical scheme of the application has the following advantages:

[0026] 1.The present application provides a preparation method of a reactive sintering silicon carbide material with active carbon source, comprising the following preparation steps: (1) mixing silicon carbide powder, silicon source, carbon source, binder and water to form a slurry, and molding the slurry to obtain a silicon carbide body; (2) heat treating the silicon carbide body under an inert atmosphere; (3) laying graphite powder on the heat-treated silicon carbide body until the entire silicon carbide body is wrapped, and sintering to obtain the silicon carbide material; the carbon source comprises graphene and / or nano-carbon black; the heat treatment temperature is 550-650℃; and the heat treatment time is 1-2h.

[0027] The present application performs heat treatment under an inert atmosphere, and the in-situ active carbon source generated by pyrolysis of the binder increases the proportion of the carbon source and promotes the subsequent sintering to generate more β-SiC, so that the β-SiC grain growth and densification have better effects, thereby significantly improving the bulk density and bending strength of the silicon carbide material.

[0028] The present application utilizes the high reactivity of the carbon source with high specific surface area, and under high-temperature sintering conditions, the carbon atoms of the carbon source can rapidly react with the silicon carbide powder and the silicon powder in the silicon source to generate a high-bulk-density β-SiC phase, which is tightly stacked with the original silicon carbide powder, and finally realizes a high-purity and high-density silicon carbide material with uniform grain distribution.

[0029] The preparation method provided by the present application does not require any sintering aid, reduces the possibility of impurity phase residues, effectively avoids the generation of low-melting-point glass phases, and improves the purity of the silicon carbide material. At the same time, it also avoids the potential threat of harmful components in the sintering aid to the environment, and meets the demand for environmentally friendly production processes.

[0030] 2.The present application also provides a silicon carbide material obtained by the preparation method of the reactive sintering silicon carbide material with active carbon source, wherein the silicon carbide content is greater than 98%, the bulk density is 3.41-3.50g / cm 3 , the bending strength is >100MPa, and the thermal expansion coefficient is (4.7-4.31)×10 -6 K -1 . DETAILED DESCRIPTION

[0031] Example 1

[0032] The present embodiment provides a silicon carbide material:

[0033] Graphene and nano-carbon black are used as the carbon source, monocrystalline silicon and polycrystalline silicon are used as the silicon source, and polyvinyl alcohol and carboxymethyl cellulose are used as the binder.

[0034] Silicon carbide powder 73.6%, graphene 1.84%, nano carbon black 3.68%, monocrystalline silicon 3.68%, polycrystalline silicon 9.2%, polyvinyl alcohol 4%, carboxymethyl cellulose 4%, based on 100% of the mass of the powder.

[0035] The preparation method of the silicon carbide material is as follows:

[0036] (1) Silicon carbide powder (particle size 350 mesh), monocrystalline silicon (particle size 200 mesh), polycrystalline silicon (particle size 200 mesh), graphene (particle size 200 nm), nano carbon black (particle size 200 nm), polyvinyl alcohol and carboxymethyl cellulose are mixed to form a powder, then water is added and stirred for 6 hours to obtain a mass solid content of 85% of the slurry, the slurry is extruded and molded, and dried at 80°C for 24 hours to obtain a silicon carbide body;

[0037] (2) The silicon carbide body is placed in a sintering furnace and heat treated in a nitrogen atmosphere, with a heat treatment temperature of 650°C and a time of 1 hour;

[0038] (3) The heat treated silicon carbide body is placed in a crucible and uniformly coated with graphite powder until the entire silicon carbide body is covered, then placed in a sintering furnace and sintered at 1450°C for 3 hours;

[0039] (4) The sintered product is ground, polished and cut to obtain a silicon carbide material.

[0040] Example 2

[0041] The silicon carbide material provided in this embodiment is:

[0042] Graphene and nano carbon black are used as carbon sources, monocrystalline silicon and polycrystalline silicon are used as silicon sources, and polyvinyl alcohol and carboxymethyl cellulose are used as binders.

[0043] Silicon carbide powder 73.6%, graphene 1.84%, nano carbon black 3.68%, monocrystalline silicon 3.68%, polycrystalline silicon 9.2%, polyvinyl alcohol 4%, carboxymethyl cellulose 4%, based on 100% of the mass of the powder.

[0044] The preparation method of the silicon carbide material is as follows:

[0045] (1) Silicon carbide powder (particle size 350 mesh), monocrystalline silicon (particle size 200 mesh), polycrystalline silicon (particle size 200 mesh), graphene (particle size 200 nm), nano carbon black (particle size 200 nm), polyvinyl alcohol and carboxymethyl cellulose are mixed to form a powder, then water is added and stirred for 6 hours to obtain a mass solid content of 85% of the slurry, the slurry is extruded and molded, and dried at 80°C for 24 hours to obtain a silicon carbide body;

[0046] (2) Put the silicon carbide blank into a sintering furnace and heat treat it under a nitrogen atmosphere, with a heat treatment temperature of 600°C and a time of 1h;

[0047] (3) Put the heat treated silicon carbide blank into a crucible and evenly spread graphite powder on it until the entire silicon carbide blank is covered, then put it into a sintering furnace and sinter it at 1550°C for 2h;

[0048] (4) Grind, polish and cut the sintered product to obtain a silicon carbide material.

[0049] Example 3

[0050] The present embodiment provides a silicon carbide material:

[0051] Graphene and nano-carbon black are used as carbon sources, and single crystal silicon and polycrystalline silicon are used as silicon sources. Polyvinyl alcohol and polyethylene glycol are used as binders.

[0052] Based on 100% of the mass of the powder, the silicon carbide powder is 69%, the graphene is 2.76%, the nano-carbon black is 4.14%, the single crystal silicon is 6.9%, the polycrystalline silicon is 9.2%, the polyvinyl alcohol is 5%, and the polyethylene glycol is 3%.

[0053] The preparation method of the above-mentioned silicon carbide material:

[0054] (1) After mixing the silicon carbide powder (particle size 80 mesh), single crystal silicon (particle size 350 mesh), polycrystalline silicon (particle size 80 mesh), graphene (particle size 200 nm), nano-carbon black (particle size 200 nm), polyvinyl alcohol and polyethylene glycol to form a powder, add water and stir for 6h to obtain a mass solid content of 80% of the mud, extrude the mud into a shape, dry it at 80°C for 24h to obtain a silicon carbide blank;

[0055] (2) Put the silicon carbide blank into a sintering furnace and heat treat it under a nitrogen atmosphere, with a heat treatment temperature of 600°C and a time of 1.5h;

[0056] (3) Put the heat treated silicon carbide blank into a crucible and evenly spread graphite powder on it until the entire silicon carbide blank is covered, then put it into a sintering furnace and sinter it at 1500°C for 2.5h;

[0057] (4) Grind, polish and cut the sintered product to obtain a silicon carbide material.

[0058] Example 4

[0059] The present embodiment provides a silicon carbide material:

[0060] Graphene and nano-carbon black are used as carbon sources, and single crystal silicon and polycrystalline silicon are used as silicon sources. Polyvinyl alcohol and polyethylene glycol are used as binders.

[0061] Silicon carbide powder 73.6%, graphene 1.84%, nano carbon black 3.68%, monocrystalline silicon 3.68%, polycrystalline silicon 9.2%, polyethylene glycol 5%, carboxymethyl cellulose 3%, based on 100% of the mass of the powder.

[0062] The preparation method of the silicon carbide material is as follows:

[0063] (1) Silicon carbide powder (particle size 200 mesh), monocrystalline silicon (particle size 200 mesh), polycrystalline silicon (particle size 80 mesh), graphene (particle size 200 nm), nano carbon black (particle size 200 nm), polyethylene glycol and carboxymethyl cellulose are mixed to form a powder, then water is added and stirred for 6 hours to obtain a mass solid content of 90% of the mud, the mud is extruded and shaped, and dried at 80°C for 24 hours to obtain a silicon carbide body;

[0064] (2) The silicon carbide body is placed in a sintering furnace and heat treated in a nitrogen atmosphere, with a heat treatment temperature of 550°C and a time of 2 hours;

[0065] (3) The heat-treated silicon carbide body is placed in a crucible and evenly coated with graphite powder until the entire silicon carbide body is wrapped, then placed in a sintering furnace and sintered at 1550°C for 2 hours;

[0066] (4) The sintered product is ground, polished and cut to obtain a silicon carbide material.

[0067] Example 5

[0068] The silicon carbide material provided in this embodiment is:

[0069] Graphene and nano carbon black are used as carbon sources, monocrystalline silicon and polycrystalline silicon are used as silicon sources, and polyvinyl alcohol and carboxymethyl cellulose are used as binders.

[0070] Silicon carbide powder 64.4%, graphene 2.76%, nano carbon black 5.52%, monocrystalline silicon 5.52%, polycrystalline silicon 13.8%, polyvinyl alcohol 4%, carboxymethyl cellulose 4%, based on 100% of the mass of the powder.

[0071] The preparation method of the silicon carbide material is as follows:

[0072] (1) Silicon carbide powder (particle size 300 mesh), monocrystalline silicon (particle size 300 mesh), polycrystalline silicon (particle size 150 mesh), graphene (particle size 200 nm), nano carbon black (particle size 200 nm), polyvinyl alcohol and carboxymethyl cellulose are mixed to form a powder, then water is added and stirred for 6 hours to obtain a mass solid content of 85% of the mud, the mud is extruded and shaped, and dried at 80°C for 24 hours to obtain a silicon carbide body;

[0073] (2) Put the silicon carbide blank into the sintering furnace and heat treat it under nitrogen atmosphere, the heat treatment temperature is 600℃, and the time is 1h;

[0074] (3) Put the heat treated silicon carbide blank into the crucible, evenly spread the graphite powder on it until the whole silicon carbide blank is wrapped, then put it into the sintering furnace, sinter at 1450℃ for 3h;

[0075] (4) Grind, polish and cut the sintered product to obtain the silicon carbide material.

[0076] Comparative Example 1

[0077] The comparative example provides a silicon carbide material:

[0078] Graphite is used as the carbon source, and single crystal silicon and polycrystalline silicon are used as the silicon source.

[0079] The silicon carbide powder is 70%, the graphite is 9%, the single crystal silicon is 6%, and the polycrystalline silicon is 15% based on 100% of the mass of the powder.

[0080] The preparation method of the above-mentioned silicon carbide material:

[0081] (1) After mixing the silicon carbide powder, single crystal silicon, polycrystalline silicon and graphite to form a powder, water is added and stirred for 6h to obtain a mass solid content of 85% of the mud, the mud is extruded and shaped, and dried at 80℃ for 24h to obtain a silicon carbide blank;

[0082] (2) Put the silicon carbide blank into the crucible, evenly spread the graphite powder on it until the whole silicon carbide blank is wrapped, then put it into the sintering furnace, sinter at 1400℃ for 2h;

[0083] (3) Grind, polish and cut the sintered product to obtain the silicon carbide material.

[0084] Comparative Example 2

[0085] The comparative example provides a silicon carbide material:

[0086] Graphene and nano carbon black are used as the carbon source, and single crystal silicon and polycrystalline silicon are used as the silicon source.

[0087] The silicon carbide powder is 70%, the graphene is 3%, the nano carbon black is 6%, the single crystal silicon is 6%, and the polycrystalline silicon is 15% based on 100% of the mass of the powder.

[0088] The preparation method of the above-mentioned silicon carbide material:

[0089] (1) After mixing the silicon carbide powder, single crystal silicon, polycrystalline silicon, graphene and nano carbon black to form a powder, water is added and stirred for 6h to obtain a mass solid content of 85% of the mud, the mud is extruded and shaped, and dried at 80℃ for 24h to obtain a silicon carbide blank;

[0090] (2) Put the silicon carbide blank into a sintering furnace and heat treat under a nitrogen atmosphere, with a heat treatment temperature of 450°C and a time of 1 h;

[0091] (3) Put the heat treated silicon carbide blank into a crucible and evenly spread graphite powder over it until the entire silicon carbide blank is covered, then put it into a sintering furnace and sinter at 1400°C for 2 h;

[0092] (4) Grind, polish and cut the sintered product to obtain a silicon carbide material.

[0093] Comparative Example 3

[0094] This comparative example provides a silicon carbide material:

[0095] Graphite is used as the carbon source, monocrystalline silicon and polycrystalline silicon are used as the silicon source, and polyvinyl alcohol and carboxymethyl cellulose are used as the binder.

[0096] Based on 100% of the mass of the powder, the silicon carbide powder is 73.6%, the graphite is 5.52%, the monocrystalline silicon is 3.68%, the polycrystalline silicon is 9.2%, the polyvinyl alcohol is 5%, and the carboxymethyl cellulose is 3%.

[0097] The preparation method of the above-mentioned silicon carbide material:

[0098] (1) After mixing the silicon carbide powder, monocrystalline silicon, polycrystalline silicon, graphite, polyvinyl alcohol and carboxymethyl cellulose to form a powder, add water and stir for 6 h to obtain a slurry with a mass solid content of 85%, extrude the slurry into a shape, dry it at 80°C for 24 h, and obtain a silicon carbide blank;

[0099] (2) Put the silicon carbide blank into a sintering furnace and heat treat under a nitrogen atmosphere, with a heat treatment temperature of 500°C and a time of 1 h;

[0100] (3) Put the heat treated silicon carbide blank into a crucible and evenly spread graphite powder over it until the entire silicon carbide blank is covered, then put it into a sintering furnace and sinter at 1500°C for 2 h;

[0101] (4) Grind, polish and cut the sintered product to obtain a silicon carbide material.

[0102] Test Example

[0103] The silicon carbide materials obtained in the examples and comparative examples were tested for performance, and the results are shown in Table 1.

[0104] Table 1 Performance test results of silicon carbide materials obtained in the examples and comparative examples

[0105]

[0106] As shown in Table 1, the flexural strength of the silicon carbide material provided by the present application is above 100 MPa, which is significantly improved compared with the flexural strength of the comparative examples, and effectively solves the problem of large brittleness of the silicon carbide material. As shown in Table 1, the thermal expansion coefficient of the silicon carbide material prepared by the present application is (4.7-4.31) x 10 -6 K -1 , which is obviously reduced compared with the comparative examples, and can improve the thermal shock resistance. The bulk density of the silicon carbide material prepared by the present application is 3.41-3.50 g / cm 3 , which is obviously improved compared with the comparative examples, and the compactness of the silicon carbide material is improved. Obviously, the above examples are only examples for clearly illustrating, and are not limitation to the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for producing a reaction-sintered silicon carbide material which introduces an active carbon source, characterized by, The preparation method comprises the following steps: (1) mixing silicon carbide powder, silicon source, carbon source, binder and water to form a slurry, and molding the slurry to obtain a silicon carbide blank; (2) performing heat treatment on the silicon carbide blank under an inert atmosphere; (3) laying graphite powder on the heat-treated silicon carbide blank until the entire silicon carbide blank is wrapped, and sintering to obtain the silicon carbide material; The carbon source comprises graphene and / or nano-carbon black. The heat treatment temperature is 550-650℃. The heat treatment time is 1-2h. In step (3), the sintering temperature is 1400-1550℃; and the sintering time is 2-3h. The binder comprises a plurality of polyethylene glycol, polyvinyl alcohol and carboxymethyl cellulose.

2. The method of claim 1, wherein the method further comprises the step of: In step (2), the inert atmosphere comprises nitrogen and / or argon. ​ 3. The method of claim 1, wherein the active carbon source is introduced by a reaction sintering process. The steps in step (1) comprise: After mixing the silicon carbide powder, silicon source, carbon source and binder to form a powder, water is added and stirred to form a slurry, and the slurry is molded and dried to obtain a silicon carbide blank.

4. The method of claim 3, wherein the active carbon source is introduced by a reaction sintering process. The mass ratio of the silicon carbide powder, silicon source and carbon source is (70-80):(14-21):(6-9). And / or, the mass of the binder accounts for 7%-9% of the mass of the powder; And / or, the mass solid content of the slurry is 80%-90%.

5. The method for preparing a reaction-sintered silicon carbide material by introducing an active carbon source according to claim 1, characterized in that, The silicon source comprises single crystal silicon and / or polycrystalline silicon.

6. The method of claim 1, wherein the method further comprises the step of: The particle size of the silicon carbide powder is 80-350 mesh, the particle size of the silicon source is 80-350 mesh, and the particle size of the carbon source is ≤200nm. ​ 7. The method of claim 1, wherein the method further comprises the step of: In step (1), the molding is extrusion molding, die pressing or grouting. ​ 8. The method of claim 3, wherein the active carbon source is introduced by a reaction sintering process. The drying temperature is 80-100℃. And / or, the drying time is 16-24h.

9. The silicon carbide material obtained by the preparation method of claim 1-8.

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