Preparation method of high-performance silicon carbide material and product thereof

Abstract

The invention relates to the field of silicon carbide ceramic materials, in particular to a preparation method of a high-performance silicon carbide material and a product thereof. The preparation method of the high-performance silicon carbide material comprises the following steps: mixing and stirring silicon carbide powder, a carbon source, a binder and water to obtain pug, and molding the pug to obtain a silicon carbide green body; carrying out heat treatment on the silicon carbide green body in an inert atmosphere; and embedding the silicon carbide green body subjected to heat treatment into silicon powder, and sintering to obtain the silicon carbide material, the temperature of the heat treatment is 300-500 DEG C; the heat treatment time is 1-2 hours. According to the invention, heat treatment is carried out in an inert atmosphere, and the in-situ active carbon source generated by pyrolysis of the binder is uniformly distributed in the green body, so that the proportion of the active carbon source is effectively increased. And a beta-SiC binding phase is quickly and efficiently generated in a manner of externally adding a carbon source, so that the content of silicon carbide in the product is effectively increased, and the bending strength is improved while the thermal expansion coefficient is reduced.

Description

Technical Field

[0001] The present invention relates to the field of silicon carbide ceramic materials, and in particular to a preparation method of a high-performance silicon carbide material and a product thereof. Background Art

[0002] With the rapid development of modern industry, the demand for high-performance materials is growing, especially in the fields of aerospace, automobile manufacturing, electronic devices, chemical machinery, nuclear energy engineering, and advanced refractory materials. The demand for advanced ceramic materials with excellent high-temperature performance, wear resistance, corrosion resistance, and good thermal stability is rising. Silicon carbide (SiC) ceramics have become an indispensable key material in these high-end fields due to their unique physical and chemical properties. In the field of aerospace, the low density and high strength of silicon carbide make it an ideal choice for manufacturing aircraft engine hot end components, rocket nozzles, and spacecraft thermal protection systems. In the field of electronic devices, the high thermal conductivity and good electrical insulation of silicon carbide make it an ideal material for manufacturing high-temperature electronic devices and power devices, such as LED lighting, semiconductor devices, and sensors. In the field of chemical machinery, the corrosion resistance and wear resistance of silicon carbide make it widely used in seals, pumps, valves and other components of chemical equipment. In the field of nuclear energy engineering, the high temperature resistance and radiation resistance of silicon carbide make it have potential application value in the fuel cladding and heat exchangers of nuclear reactors.

[0003] In the process of reaction sintering silicon carbide, free silicon is inevitably introduced, which will damage its high temperature performance, resulting in high thermal expansion coefficient of silicon carbide, poor creep resistance, and inability to maintain stable shape and mechanical properties under high temperature conditions. At the same time, it will also reduce the mechanical properties of silicon carbide and affect its bending strength. 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 material in the prior art, namely, large thermal expansion coefficient and poor bending strength, thereby providing a preparation method of high-performance silicon carbide material and its product, and reducing the negative impact of free silicon by increasing the silicon carbide content.

[0005] To solve the above problems:

[0006] The present invention provides a method for preparing a high-performance silicon carbide material, comprising the following steps:

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

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

[0009] (3) burying the heat-treated silicon carbide blank in silicon powder and sintering it to obtain the silicon carbide material;

[0010] The temperature of the heat treatment is 300-500°C;

[0011] The heat treatment time is 1-2h.

[0012] Preferably, the silicon carbide powder is α-SiC.

[0013] Preferably, in step (1), the carbon source includes one or two of graphene, carbon nanotubes and nano carbon black; the binder includes one or more of polyethylene glycol, polyvinyl alcohol and carboxymethyl cellulose, preferably two or more.

[0014] Preferably, in step (2), the inert atmosphere comprises nitrogen and / or argon.

[0015] Preferably, in step (3), the sintering is carried out under vacuum conditions; optionally, the vacuum degree of the sintering is <10Pa; the sintering temperature is 1550-1750°C; and the sintering time is 2-3h.

[0016] Preferably, the particle size of the silicon carbide powder is 80-350 mesh; the particle size of the carbon source is ≤200nm; the particle size of the silicon powder is 80-350 mesh; and the silicon powder is polycrystalline silicon powder.

[0017] Preferably, the steps in step (1) include: mixing silicon carbide powder, a carbon source and a binder to obtain a powder, adding water and stirring to obtain a slurry, and molding and drying the slurry to obtain a silicon carbide blank.

[0018] Preferably, the mass ratio of the carbon source to the silicon carbide powder is (6-8): (92-94); the binder accounts for 5%-6% of the powder mass; and the mass solid content of the mud is 80%-90%.

[0019] 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 silicon carbide blank.

[0020] Preferably, in step (1), the forming is extrusion forming, compression molding or slip injection molding.

[0021] 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.

[0022] The present invention also provides a silicon carbide material obtained by the method for preparing the high-performance silicon carbide material.

[0023] The technical solution of the present invention has the following advantages:

[0024] 1. The present invention provides a method for preparing a high-performance silicon carbide material, comprising the following steps: (1) mixing silicon carbide powder, a carbon source, a binder and water to obtain a slurry, and molding the slurry to obtain a silicon carbide blank; (2) heat-treating the silicon carbide blank under an inert atmosphere; (3) burying the heat-treated silicon carbide blank in silicon powder and sintering it to obtain the silicon carbide material; the heat treatment temperature is 300-500°C; and the heat treatment time is 1-2h.

[0025] The present invention heat treats the silicon carbide blank under an inert atmosphere, and the in-situ active carbon source generated by the pyrolysis of the binder is evenly distributed in the blank, effectively increasing the proportion of the active carbon source. It also promotes the growth of β-SiC grains in the subsequent vacuum sintering, thereby increasing the content of silicon carbide in the silicon carbide material, improving the bending resistance of the silicon carbide material, reducing the thermal expansion coefficient, and avoiding the creep of the silicon carbide material under high temperature conditions.

[0026] The temperature of the heat treatment is 300-500°C. Low-temperature heat treatment can make the binder remain. The remaining binder reacts with silicon vapor during the subsequent sintering process to further increase the silicon carbide content.

[0027] The present invention provides a new way to quickly and efficiently generate a β-SiC binding phase by in-situ generating an activated carbon source and an external carbon source, effectively increases the content of silicon carbide in the product, and solves the key problem that the free silicon content in the current reaction-sintered silicon carbide is difficult to reduce.

[0028] The present invention uses an added carbon source as the main active carbon source and utilizes its high reactivity. Under high-temperature sintering conditions, the active carbon source reacts quickly with siliconizing to generate a high volume density β-SiC phase, which is tightly stacked with the original α-SiC particles, and finally a silicon carbide material with high silicon carbide content, high density and uniform grain distribution is obtained.

[0029] 2. The present invention further defines that the binder includes one or more of polyethylene glycol, polyvinyl alcohol and carboxymethyl cellulose. The present invention selects a high molecular weight polymer as the binder, and the amount of in-situ activated carbon produced under an inert atmosphere is greater and evenly distributed in the silicon carbide blank.

[0030] 3. The present invention also provides a silicon carbide material obtained by the method for preparing the high-performance silicon carbide material. The silicon carbide material obtained by the method has a silicon carbide content greater than 93% and a volume density of 3.42-3.50 g / cm 3 , flexural strength> 210MPa, thermal expansion coefficient less than 4.16×10 -6 K -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 is a SEM image of the silicon carbide material of Example 2 of the present invention;

[0033] Figure 2 This is the XRD detection diagram of the silicon carbide material in Example 2 of the present invention. DETAILED DESCRIPTION

[0034] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0035] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0036] The silicon carbide powders used in the following examples are all α-SiC powders, and the silicon powders are all polycrystalline silicon powders.

[0037] Example 1

[0038] This embodiment provides a silicon carbide material:

[0039] Graphene and carbon nanotubes are used as carbon sources, and polyvinyl alcohol and carboxymethyl cellulose are used as binders.

[0040] Based on 100% powder mass, the silicon carbide powder comprises 88.35%, graphene comprises 3.8%, carbon nanotubes comprises 2.85%, polyvinyl alcohol comprises 3%, and carboxymethyl cellulose comprises 2%.

[0041] The method for preparing the above silicon carbide material comprises the following steps:

[0042] (1) Silicon carbide powder (particle size 325 mesh), graphene (particle size 200 nm), carbon nanotubes (particle size 200 nm), polyvinyl alcohol and carboxymethyl cellulose are mixed to obtain a powder, and then water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, and the mud material is extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0043] (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;

[0044] (3) burying the heat-treated silicon carbide blank in silicon powder (particle size 80 mesh) and sintering at 1750°C for 2 hours under vacuum conditions;

[0045] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0046] Example 2

[0047] This embodiment provides a silicon carbide material:

[0048] Graphene and carbon nanotubes are used as carbon sources, and polyvinyl alcohol, carboxymethyl cellulose and polyethylene glycol are used as binders.

[0049] Based on 100% powder mass, the silicon carbide powder accounts for 88.36%, the graphene accounts for 2.82%, the carbon nanotubes accounts for 2.82%, the polyvinyl alcohol accounts for 2%, the carboxymethyl cellulose accounts for 2%, and the polyethylene glycol accounts for 2%.

[0050] The method for preparing the above silicon carbide material comprises the following steps:

[0051] (1) Silicon carbide powder (particle size 300 mesh), graphene (particle size 200 nm), carbon nanotubes (particle size 200 nm), polyvinyl alcohol, carboxymethyl cellulose and polyethylene glycol are mixed to obtain a powder, and then water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 80%, and the mud material is extruded and formed, and dried at 100° C. for 16 hours to obtain a silicon carbide blank;

[0052] (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 1.5 h;

[0053] (3) burying the heat-treated silicon carbide blank in silicon powder (particle size 350 mesh) and sintering at 1600° C. for 2.5 h under vacuum conditions;

[0054] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0055] The silicon carbide material obtained in this example was observed by scanning electron microscope (SEM). Figure 1 shown.

[0056] The silicon carbide material obtained in this example was subjected to XRD detection. Figure 2 shown.

[0057] from Figure 1It can be seen that the silicon carbide material prepared in this embodiment has a dense silicon carbide structure and less free silicon.

[0058] from Figure 2 It can be seen that the diffraction peak of silicon carbide is strong, while the diffraction peak of free silicon is relatively weak, which also indicates that the content of free silicon is low.

[0059] Example 3

[0060] This embodiment provides a silicon carbide material:

[0061] Nano carbon black and carbon nanotubes are used as carbon sources, and polyvinyl alcohol and polyethylene glycol are used as binders.

[0062] Based on 100% powder mass, the silicon carbide powder accounts for 87.42%, the nano carbon black accounts for 3.76%, the carbon nano tube accounts for 2.82%, the polyvinyl alcohol accounts for 3%, and the polyethylene glycol accounts for 3%.

[0063] The method for preparing the above silicon carbide material comprises the following steps:

[0064] (1) Silicon carbide powder (particle size 80 mesh), nano carbon black (particle size 200 nm), carbon nanotubes (particle size 200 nm), polyvinyl alcohol and polyethylene glycol are mixed to obtain a powder, and then water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 90%, and the mud material is extruded and formed, and dried at 100° C. for 16 hours to obtain a silicon carbide blank;

[0065] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in an argon atmosphere at a temperature of 500° C. for 1 h;

[0066] (3) burying the heat-treated silicon carbide blank in silicon powder (particle size 120 mesh) and sintering at 1550° C. for 3 h under vacuum conditions;

[0067] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0068] Example 4

[0069] This embodiment provides a silicon carbide material:

[0070] Graphene and carbon nanotubes are used as carbon sources, and polyvinyl alcohol and polyethylene glycol are used as binders.

[0071] Based on 100% powder mass, the content includes 87.4% silicon carbide powder, 4.75% graphene, 2.85% carbon nanotubes, 3% polyvinyl alcohol and 2% polyethylene glycol.

[0072] The method for preparing the above silicon carbide material comprises the following steps:

[0073] (1) Silicon carbide powder (particle size 145 mesh), graphene (particle size 200 mesh), carbon nanotubes (particle size 200 nm), polyvinyl alcohol and polyethylene glycol are mixed to obtain a powder, and then water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, and the mud material is extruded and formed, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0074] (2) placing the silicon carbide blank into a sintering furnace and performing heat treatment in a nitrogen atmosphere at a temperature of 400° C. for 2 h;

[0075] (3) The heat-treated silicon carbide blank was buried in silicon powder (particle size 200 mesh) and sintered at 1650° C. for 2.5 h under vacuum conditions;

[0076] (4) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0077] Comparative Example 1

[0078] This comparative example provides a silicon carbide material:

[0079] Based on 100% powder mass, the silicon carbide powder accounts for 92% and the graphite accounts for 8%.

[0080] The method for preparing the above silicon carbide material comprises the following steps:

[0081] (1) After mixing silicon carbide powder and graphite to obtain 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) burying the silicon carbide blank in silicon powder and sintering at 1650°C for 2.5 hours under vacuum conditions;

[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] Based on the powder mass being 100%, the powder comprises 94% silicon carbide powder and 6% graphene.

[0087] The method for preparing the above silicon carbide material comprises the following steps:

[0088] (1) After mixing silicon carbide powder and graphene to obtain 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.

[0089] (2) The silicon carbide blank is buried in silicon powder and sintered at 1650°C for 2.5 hours under vacuum conditions.

[0090] (3) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0091] Comparative Example 3

[0092] This comparative example provides a silicon carbide material:

[0093] Based on 100% powder mass, the silicon carbide powder comprises 88.35%, the graphite comprises 6.65%, and the polyvinyl alcohol comprises 5%.

[0094] The method for preparing the above silicon carbide material comprises the following steps:

[0095] (1) Silicon carbide powder, graphite and polyvinyl alcohol are mixed to obtain a powder, and then water is added and stirred for 6 hours to obtain a mud material with a mass solid content of 85%, the mud material is formed into a basic shape, and dried at 80° C. for 24 hours to obtain a silicon carbide blank;

[0096] (2) burying the silicon carbide blank in silicon powder and sintering at 1650°C for 2.5 hours under vacuum conditions;

[0097] (3) Grinding, polishing and cutting the sintered product to obtain silicon carbide material.

[0098] Comparative Example 4

[0099] This comparative example provides a silicon carbide material, which is different from Example 1 in that the heat treatment temperature is 900°C.

[0100] Test Case

[0101] The silicon carbide materials obtained in the above examples and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0102] Table 1 Test results of silicon carbide material properties obtained in the examples and comparative examples

[0103]

[0104] The silicon carbide material obtained by the present invention has a silicon carbide content greater than 93% and a volume density of 3.42-3.50 g / cm 3 , flexural strength> 210MPa, thermal expansion coefficient less than 4.16×10 -6 K -1 As can be seen from Table 1, the thermal expansion coefficient of the silicon carbide material provided by the present invention is significantly lower than that of the comparative example, and the flexural strength is significantly improved, which effectively improves the problems of poor high temperature performance and low mechanical strength caused by low silicon carbide content.

[0105] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing high-performance silicon carbide material, characterized in that: It includes the following steps: (1) mixing silicon carbide powder, a carbon source, a binder and water to obtain a slurry, and molding the slurry to obtain a silicon carbide blank; (2) heat treating the silicon carbide blank under an inert atmosphere; (3) burying the heat-treated silicon carbide blank in silicon powder and sintering it to obtain the silicon carbide material; The temperature of the heat treatment is 300-500°C; The heat treatment time is 1-2h.

2. The method for preparing a high-performance silicon carbide material according to claim 1, characterized in that: In step (1), the carbon source includes one or two of graphene, carbon nanotubes and nano carbon black; And / or, the binder includes one or more of polyethylene glycol, polyvinyl alcohol and carboxymethyl cellulose, preferably two or more.

3. A method for preparing a high-performance silicon carbide material according to claim 1 or 2, characterized in that: In step (2), the inert atmosphere includes nitrogen and / or argon.

4. A method for preparing a high-performance silicon carbide material according to any one of claims 1 to 3, characterized in that: In step (3), the sintering is performed under vacuum conditions; Optionally, the sintering vacuum degree is <10Pa; And / or, the sintering temperature is 1550-1750°C; And / or, the sintering time is 2-3h.

5. A method for preparing a high-performance silicon carbide material according to any one of claims 1 to 4, characterized in that: The particle size of the silicon carbide powder is 80-350 mesh; and / or, the particle size of the carbon source is ≤200 nm; And / or, the particle size of the silicon powder is 80-350 mesh.

6. A method for preparing a high-performance silicon carbide material according to any one of claims 1 to 5, characterized in that: The steps in step (1) include: Silicon carbide powder, a carbon source and a binder are mixed to obtain a powder, and then water is added and stirred to obtain a mud material. The mud material is molded and dried to obtain a silicon carbide blank.

7. The method for preparing a high-performance silicon carbide material according to claim 6, characterized in that: The mass ratio of the carbon source to the silicon carbide powder is (6-8): (92-94); And / or, the binder accounts for 5%-6% of the powder mass; And / or, the mass solid content of the mud is 80%-90%.

8. The method for preparing a high-performance silicon carbide material according to claim 6, characterized in that: The drying temperature is 80-100° C. and the drying time is 16-24 hours.

9. A method for preparing a high-performance silicon carbide material according to any one of claims 1 to 8, characterized in that: In step (1), the forming is extrusion forming, compression molding or slip injection molding.

10. The silicon carbide material obtained by the method for preparing a high-performance silicon carbide material according to any one of claims 1 to 9.

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