Preparation method of reactive sintering silicon carbide material by introducing active carbon source and product thereof

Abstract

The invention relates to the field of silicon carbide materials, in particular to a preparation method for reactive sintering of a silicon carbide material 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 pug, and molding the pug to obtain a silicon carbide green body; (2) carrying out heat treatment on the silicon carbide green body in an inert atmosphere; and (3) laying graphite powder on the silicon carbide green body subjected to heat treatment until the whole silicon carbide green body is wrapped, 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; the heat treatment time is 1-2 hours. The silicon carbide material disclosed by the invention has relatively high volume density and breaking strength.

Description

Technical Field

[0001] The invention relates to the field of silicon carbide materials, and in particular to a preparation method of silicon carbide materials by introducing an active carbon source for reaction sintering and a product thereof. Background Art

[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 power electronics, optoelectronic devices, energy conversion and radio frequency applications. The band gap width of silicon carbide is three times that of silicon, the breakdown electric field strength is ten times that of silicon, and the thermal conductivity is more than three times that of silicon. These properties give it obvious advantages in high temperature, high pressure and high frequency applications.

[0003] However, existing silicon carbide is very brittle, has low flexural strength, is prone to breakage when subjected to bending loads, and has poor reliability, which limits its application in aerospace, automobile manufacturing, nuclear energy engineering and other fields. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the silicon carbide ceramic material in the prior art, namely, the high brittleness and low flexural strength. Thus, a preparation method of silicon carbide material by introducing an active carbon source for reaction sintering is provided, which solves the problem of high brittleness by increasing the silicon carbide content.

[0005] To solve the above problems:

[0006] The present invention provides a method for preparing a silicon carbide material by introducing an active carbon source for reaction sintering, comprising the following preparation steps:

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

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

[0009] (3) laying graphite powder on the heat-treated silicon carbide blank until the entire silicon carbide blank is covered, 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°C;

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

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

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

[0015] Preferably, in step (3), the sintering temperature is 1400-1550° C.; and the sintering time is 2-3 hours.

[0016] Preferably, the steps in step (1) include:

[0017] Silicon carbide powder, silicon source, carbon source and binder are mixed to form powder, water is added and stirred to form mud, and the mud is molded and dried to obtain a silicon carbide blank.

[0018] Preferably, the mass ratio of the silicon carbide powder, silicon source and 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 mud is 80%-90%.

[0019] Preferably, the silicon source includes single crystal silicon and / or polycrystalline silicon; the binder includes one or more of polyethylene glycol, polyvinyl alcohol, and carboxymethyl cellulose; preferably more than two.

[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 ≤200 nm.

[0021] Preferably, the molding in step (1) is extrusion molding, compression molding or slip injection molding.

[0022] Preferably, the drying temperature is 80-100°C and the drying time is 16-24 hours. The purpose of drying is to remove moisture from the green body.

[0023] Preferably, those skilled in the art can perform fine processing and packaging on the sintered product according to their choice, wherein the fine processing includes grinding, polishing and cutting.

[0024] The present invention also provides a silicon carbide material obtained by the preparation method of the silicon carbide material by introducing an active carbon source and reacting and sintering the silicon carbide material.

[0025] The technical solution of the present invention has the following advantages:

[0026] 1. The present invention provides a method for preparing a silicon carbide material by introducing an active carbon source for reaction sintering, comprising the following preparation steps: (1) mixing silicon carbide powder, a silicon source, a carbon source, a binder and water to form a slurry, and molding the slurry to obtain a silicon carbide blank; (2) heat-treating 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°C; and the heat treatment time is 1-2h.

[0027] The present invention 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, promotes subsequent sintering to produce more β-SiC, and achieves better effects on β-SiC grain growth and densification, thereby significantly improving the volume density and flexural strength of the silicon carbide material.

[0028] The present invention utilizes the high reactivity brought by the high specific surface area of ​​the carbon source. Under high-temperature sintering conditions, the carbon atoms of the carbon source can react quickly with the silicon carbide powder and the silicon powder in the silicon source to generate a high volume density β-SiC phase, which is tightly stacked with the original silicon carbide powder, ultimately achieving a highly purified, highly dense, and uniformly distributed silicon carbide material.

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

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

[0031] Example 1

[0032] This embodiment provides a silicon carbide material:

[0033] Graphene and nano carbon black are used as carbon sources, single crystal silicon and polycrystalline silicon are used as silicon sources, and polyvinyl alcohol and carboxymethyl cellulose are used as binders.

[0034] Based on 100% powder mass, silicon carbide powder is 73.6%, graphene is 1.84%, nano carbon black is 3.68%, single crystal silicon is 3.68%, polycrystalline silicon is 9.2%, polyvinyl alcohol is 4%, and carboxymethyl cellulose is 4%.

[0035] Preparation method of the above silicon carbide material:

[0036] (1) Silicon carbide powder (particle size 350 mesh), single crystal 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, water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, the mud material is extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0037] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in a nitrogen atmosphere at a temperature of 650° C. for 1 h;

[0038] (3) placing the heat-treated silicon carbide blank in a crucible and evenly spreading graphite powder on it until the entire silicon carbide blank is covered, and then placing it in a sintering furnace and sintering it at 1450° C. for 3 h;

[0039] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0040] Example 2

[0041] This embodiment provides a silicon carbide material:

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

[0043] Based on 100% powder mass, silicon carbide powder accounts for 64.4%, graphene accounts for 2.76%, nano carbon black accounts for 5.52%, single crystal silicon accounts for 5.52%, polycrystalline silicon accounts for 13.8%, polyvinyl alcohol accounts for 5%, and carboxymethyl cellulose accounts for 3%.

[0044] Preparation method of the above silicon carbide material:

[0045] (1) Silicon carbide powder (particle size 300 mesh), single crystal silicon (particle size 300 mesh), polycrystalline silicon (particle size 180 mesh), graphene (particle size 200 nm), nano carbon black (particle size 200 nm), polyvinyl alcohol and carboxymethyl cellulose were mixed to form a powder, and water was added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, and the mud material was extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0046] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in a nitrogen atmosphere at a temperature of 600° C. for 1 h;

[0047] (3) placing the heat-treated silicon carbide blank in a crucible and evenly spreading graphite powder on it until the entire silicon carbide blank is covered, and then placing it in a sintering furnace and sintering at 1550° C. for 2 h;

[0048] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0049] Example 3

[0050] This embodiment provides a silicon carbide material:

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

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

[0053] Preparation method of the above silicon carbide material:

[0054] (1) 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 are mixed to form a powder, water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 80%, the mud material is extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0055] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in a nitrogen atmosphere at a temperature of 600° C. for 1.5 h;

[0056] (3) placing the heat-treated silicon carbide blank in a crucible and evenly spreading graphite powder on it until the entire silicon carbide blank is covered, and then placing it in a sintering furnace and sintering it at 1500° C. for 2.5 h;

[0057] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0058] Example 4

[0059] This embodiment provides a silicon carbide material:

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

[0061] Based on 100% powder mass, silicon carbide powder is 73.6%, graphene is 1.84%, nano carbon black is 3.68%, single crystal silicon is 3.68%, polycrystalline silicon is 9.2%, polyethylene glycol is 5%, and carboxymethyl cellulose is 3%.

[0062] Preparation method of the above silicon carbide material:

[0063] (1) Silicon carbide powder (particle size 200 mesh), single crystal 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, water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 90%, the mud material is extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0064] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in a nitrogen atmosphere at a temperature of 550° C. for 2 h;

[0065] (3) placing the heat-treated silicon carbide blank in a crucible and evenly spreading graphite powder on it until the entire silicon carbide blank is covered, and then placing it in a sintering furnace and sintering at 1550° C. for 2 h;

[0066] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0067] Example 5

[0068] This embodiment provides a silicon carbide material:

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

[0070] Based on 100% powder mass, silicon carbide powder accounts for 64.4%, graphene accounts for 2.76%, nano carbon black accounts for 5.52%, single crystal silicon accounts for 5.52%, polycrystalline silicon accounts for 13.8%, polyvinyl alcohol accounts for 4%, and carboxymethyl cellulose accounts for 4%.

[0071] Preparation method of the above silicon carbide material:

[0072] (1) Silicon carbide powder (particle size 300 mesh), single crystal 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 were mixed to form a powder, and water was added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, and the mud material was extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0073] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in a nitrogen atmosphere at a temperature of 600° C. for 1 h;

[0074] (3) placing the heat-treated silicon carbide blank in a crucible and evenly spreading graphite powder on it until the entire silicon carbide blank is covered, and then placing it in a sintering furnace and sintering it at 1450° C. for 3 h;

[0075] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0076] Comparative Example 1

[0077] This 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] Based on 100% powder mass, the content includes 70% silicon carbide powder, 9% graphite, 6% single crystal silicon and 15% polycrystalline silicon.

[0080] Preparation method of the above silicon carbide material:

[0081] (1) Silicon carbide powder, single crystal silicon, polycrystalline silicon, and graphite are mixed to form a powder, water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, the mud material is extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0082] (2) placing the silicon carbide blank in a crucible and evenly spreading graphite powder on it until the entire silicon carbide blank is covered, then placing it in a sintering furnace and sintering it at 1400° C. for 2 h;

[0083] (3) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0084] Comparative Example 2

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

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

[0087] Based on 100% powder mass, silicon carbide powder accounts for 70%, graphene accounts for 3%, nano carbon black accounts for 6%, single crystal silicon accounts for 6%, and polycrystalline silicon accounts for 15%.

[0088] Preparation method of the above silicon carbide material:

[0089] (1) Silicon carbide powder, single crystal silicon, polycrystalline silicon, graphene, and nano-carbon black are mixed to form a powder, water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, the mud material is extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0090] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in a nitrogen atmosphere at a temperature of 450° C. for 1 h;

[0091] (3) placing the heat-treated silicon carbide blank in a crucible and evenly spreading graphite powder on it until the entire silicon carbide blank is covered, and then placing it in a sintering furnace and sintering it at 1400° C. for 2 h;

[0092] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0093] Comparative Example 3

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

[0095] Graphite is used as a carbon source, single crystal silicon and polycrystalline silicon are used as silicon sources, and polyvinyl alcohol and carboxymethyl cellulose are used as binders.

[0096] Based on 100% powder mass, the content includes 73.6% silicon carbide powder, 5.52% graphite, 3.68% single crystal silicon, 9.2% polycrystalline silicon, 5% polyvinyl alcohol and 3% carboxymethyl cellulose.

[0097] Preparation method of the above silicon carbide material:

[0098] (1) Silicon carbide powder, single crystal silicon, polycrystalline silicon, graphite, polyvinyl alcohol, and carboxymethyl cellulose are mixed to form a powder, water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, the mud material is extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0099] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in a nitrogen atmosphere at a temperature of 500° C. for 1 h;

[0100] (3) placing the heat-treated silicon carbide blank in a crucible and evenly spreading graphite powder on it until the entire silicon carbide blank is covered, and then placing it in a sintering furnace and sintering it at 1500° C. for 2 h;

[0101] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0102] Test Case

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

[0104] Table 1 Test results of silicon carbide material properties obtained in the examples and comparative examples

[0105]

[0106] As can be seen from Table 1, the flexural strength of the silicon carbide material provided by the present invention is above 100 MPa, which is significantly improved compared with the flexural strength of the comparative example, and effectively solves the problem of high brittleness of the silicon carbide material. And as can be seen from Table 1, the thermal expansion coefficient of the silicon carbide material prepared by the present invention is (4.7-4.31)×10 -6 K -1 , which is significantly lower than the control group, and can improve thermal shock resistance. The bulk density is 3.41-3.50g / cm 3 , which is significantly improved compared with the comparative example, and the density of the silicon carbide material of the present invention is improved. Obviously, the above embodiments are only examples for clear explanation, and are not limitations on the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the invention.

Claims

1. A method for preparing silicon carbide material by introducing an active carbon source for reaction sintering, characterized in that: The method comprises the following preparation steps: (1) mixing silicon carbide powder, a silicon source, a carbon source, a binder and water to form a mud material, and molding the mud material to obtain a silicon carbide blank; (2) heat treating 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 covered, and sintering to obtain the silicon carbide material; The carbon source includes graphene and / or nano carbon black; The temperature of the heat treatment is 550-650°C; The heat treatment time is 1-2h.

2. The method for preparing silicon carbide material by introducing an active carbon source and reacting and sintering the material according to claim 1, characterized in that: In step (2), the inert atmosphere includes nitrogen and / or argon.

3. The method for preparing a silicon carbide material by introducing an active carbon source and reacting and sintering the material according to claim 1 or 2, characterized in that: In step (3), the sintering temperature is 1400-1550° C. and the sintering time is 2-3 hours.

4. The method for preparing a silicon carbide material by introducing an active carbon source and reacting and sintering the material according to any one of claims 1 to 3, characterized in that: The steps in step (1) include: Silicon carbide powder, silicon source, carbon source and binder are mixed to form powder, water is added and stirred to form mud, and the mud is molded and dried to obtain a silicon carbide blank.

5. The method for preparing silicon carbide material by introducing an active carbon source and reacting and sintering the material according to claim 4, characterized in that: The mass ratio of the silicon carbide powder, the silicon source and the 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 mud is 80%-90%.

6. A method for preparing a silicon carbide material by introducing an active carbon source and reacting and sintering the material according to any one of claims 1 to 5, characterized in that: The silicon source includes single crystal silicon and / or polycrystalline silicon; And / or, the binder includes one or more of polyethylene glycol, polyvinyl alcohol, and carboxymethyl cellulose; preferably two or more.

7. A method for preparing a silicon carbide material by introducing an active carbon source and reacting and sintering the material according to any one of claims 1 to 6, characterized in that: The particle size of the silicon carbide powder is 80-350 meshes, the particle size of the silicon source is 80-350 meshes, and the particle size of the carbon source is ≤200nm.

8. The method for preparing a silicon carbide material by introducing an active carbon source and reacting and sintering the material according to any one of claims 1 to 7, characterized in that: The molding in step (1) is extrusion molding, compression molding or injection molding.

9. The method for preparing silicon carbide material by introducing an active carbon source and reacting and sintering the material according to claim 4, characterized in that: The drying temperature is 80-100°C; And / or, the drying time is 16-24 hours.

10. The silicon carbide material obtained by the method for preparing the silicon carbide material by introducing an active carbon source and reactively sintering the silicon carbide material according to any one of claims 1 to 9.

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