阅读说明：本技术 一种常压烧结抗辐照碳化硅陶瓷材料及其制备方法 (Normal pressure sintered anti-irradiation silicon carbide ceramic material and preparation method thereof ) 是由 陈健 祝明 黄政仁 陈文辉 姚秀敏 陈忠明 刘学建 于 2021-01-05 设计创作，主要内容包括：本发明公开一种常压烧结抗辐照碳化硅陶瓷材料及其制备方法。所述抗辐照碳化硅陶瓷材料包括碳化硅基体和原位固溶进入碳化硅晶格的～(11)B-4C；其中,～(11)B-4C占抗辐照碳化硅陶瓷材料的质量比为1wt%以下。原位生成的B-4C容易固溶进碳化硅晶格,能以极少量的B元素使晶界能降至足够低,促进碳化硅陶瓷烧结致密化,克服了SiC的自扩散性差以及强共价键的存在使其烧结性差的缺陷。(The invention discloses a normal pressure sintered anti-irradiation silicon carbide ceramic material and a preparation method thereof. The anti-irradiation silicon carbide ceramic material comprises a silicon carbide matrix and a silicon carbide crystal lattice which is in-situ solid-dissolved 11 B 4 C; wherein the content of the first and second substances, 11 B 4 the mass ratio of C in the anti-radiation silicon carbide ceramic material is less than 1 wt%. In situ generated B 4 C is easy to be dissolved into the silicon carbide crystal lattice, the crystal boundary can be reduced to be low enough by using a small amount of B element, the sintering densification of the silicon carbide ceramic is promoted, and the defects that the self-diffusivity of SiC is poor and the sinterability of SiC is poor due to the existence of strong covalent bonds are overcome.)

1. The normal pressure sintered anti-irradiation silicon carbide ceramic material is characterized by comprising a silicon carbide substrate and a silicon carbide crystal lattice which is subjected to in-situ solid solution¹¹B₄C; wherein the content of the first and second substances,¹¹B₄the mass ratio of C in the anti-radiation silicon carbide ceramic material is less than 1 wt%.

2. The radiation-resistant silicon carbide ceramic material of claim 1, wherein the ceramic material is selected from the group consisting of silicon carbide¹¹B₄The mass ratio of C in the anti-radiation silicon carbide ceramic material is 0.4-1 wt%.

3. Root of herbaceous plantThe radiation-resistant silicon carbide ceramic material as claimed in claim 1 or 2, wherein the density of the radiation-resistant silicon carbide ceramic material is 3.1-3.2 g-cm^-3The compactness is more than 99 percent, and the bending strength is 300-500 MPa.

4. The method for preparing the atmospheric-pressure-sintered radiation-resistant silicon carbide ceramic material according to any one of claims 1 to 3, wherein the method comprises the following steps:

(1) uniformly mixing raw materials including silicon carbide powder, a boron source and a carbon source to prepare mixed slurry;

(2) drying and sieving or spray granulating the mixed slurry to obtain raw material powder;

(3) and (3) forming the raw material powder obtained in the step (2), then carrying out vacuum de-bonding treatment, and finally carrying out high-temperature sintering to obtain the silicon carbide ceramic material.

5. The method of claim 4, wherein the boron source is¹¹Boric acid with the B abundance of 95-100%.

6. The production method according to claim 4 or 5, wherein the boric acid accounts for 1.8 to 4.5wt% of the silicon carbide powder.

7. The production method according to any one of claims 4 to 6, wherein the carbon source is a mixture of one or more of carbon black, phenol resin, and fructose; the carbon source accounts for 10-16 wt% of the silicon carbide powder.

8. The production method according to any one of claims 4 to 7, wherein the molding is dry press molding and/or cold isostatic press molding; preferably, the pressure of the dry pressing is 5-50MPa, the pressure of the cold isostatic pressing is 150-250MPa, and the pressure maintaining time is 1-5 minutes.

9. The method as claimed in any one of claims 4 to 8, wherein the temperature for vacuum de-binding is 900-1200 ℃ and the holding time is 30-120 minutes.

10. The preparation method as claimed in any one of claims 4 to 9, wherein the sintering manner is normal pressure sintering, the sintering temperature is 2050-.

Technical Field

The invention relates to a normal pressure sintered anti-irradiation silicon carbide ceramic material and a preparation method thereof, belonging to the field of silicon carbide ceramic.

Background

In a nuclear energy system and a nuclear energy space, materials are easy to be bombarded by high-energy particles, and the phenomena of irradiation hardening, irradiation catalysis, irradiation segregation and the like, which cause instability of material phases, or irradiation growth, irradiation swelling and the like, occur, thereby causing device faults. The Single Event Effect (SEE) of irradiation of high-energy particles and rays from nuclear fusion and nuclear fission, universe and sun on materials, namely, after single high-energy particles (such as heavy ions, protons, neutrons and the like) are incident on nuclear protection materials or integrated circuit electronic substrates for spaceflight, the properties of the materials are changed and the materials fail.

Silicon carbide (SiC) ceramics have excellent properties of high strength, high hardness, high elastic modulus, high wear resistance, high thermal conductivity, oxidation resistance, corrosion resistance and the like, and the series of remarkable advantages enable the silicon carbide (SiC) ceramics to have important application in the fields of military and national defense, nuclear industry, aerospace and the like. In particular, since SiC ceramics have a low neutron absorption cross section, it can be applied to an irradiation resistant system such as a nuclear power system or an integrated circuit electronic substrate for aerospace. However, SiC has poor self-diffusibility and poor sinterability due to the presence of strong covalent bonds, and therefore, it is often necessary to add a sintering aid to densify the SiC ceramic during sintering. The sintering method of silicon carbide ceramics can be divided into liquid phase sintering and solid phase sintering. The liquid phase sintered SiC ceramic needs to be added with alumina and/or rare earth oxide and other lower melting point oxides, but the low melting point limits the high temperature application of the silicon carbide ceramic, and meanwhile, the high neutron absorption cross section of the rare earth element also limits the application of the rare earth element in an anti-radiation system. Relatively speaking, solid phase sintered SiC ceramics can be adapted to higher service temperature, however, the solid phase sintering needs to add B₄C-C system auxiliary agent. B is₄In C, B is¹¹B and¹⁰two isotopes of B, 80.2 at% of natural B¹¹B absorbs almost no neutrons, although only about 19.8 at%¹⁰B absorbs neutrons, but¹⁰B absorbs neutrons and reacts to produce lithium and high energy alpha particles, the reaction equation is as follows:this effect is reported to cause expansion of the solid state sintered SiC ceramic, leading to failure of the structural member.

Disclosure of Invention

In a first aspect, the invention provides an atmospheric pressure sintered radiation-resistant silicon carbide ceramic material. The anti-irradiation silicon carbide ceramic material comprises a silicon carbide matrix and a silicon carbide crystal lattice which is in-situ solid-dissolved¹¹B₄C. In situ generated B₄C is easy to be dissolved into the silicon carbide crystal lattice, the crystal boundary can be reduced to be low enough by using a small amount of B element, the sintering densification of the silicon carbide ceramic is promoted, and the defects that the self-diffusivity of SiC is poor and the sinterability of SiC is poor due to the existence of strong covalent bonds are overcome.

Wherein the content of the first and second substances,¹¹B₄the mass ratio of C in the anti-radiation silicon carbide ceramic material is less than 1 wt%. Generated in situ in the invention¹¹B₄C content is very small, and¹¹B₄c may undergo a solid solution reaction with SiC. Residual in the sample under combined action¹¹B₄C content is very small, so B is not observed in XRD₄Characteristic peak of C. In some technical schemes, the generation can be adjusted by controlling the adding amount of the boric acid¹¹B₄C content is controlled to be less than 1wt% in the sample, so that sintering densification of the silicon carbide ceramic is realized. At the same time, control¹¹B₄The smaller amount of C can also avoid the increase of preparation cost.

Preferably, the¹¹B₄The mass ratio of C in the anti-radiation silicon carbide ceramic material is 0.4-1 wt%.

Preferably, the density of the radiation-resistant silicon carbide ceramic is 3.1-3.2 g-cm^-3The compactness is more than 99 percent, and the bending strength is 300-500 MPa.

In a second aspect, the invention further provides a preparation method of the atmospheric pressure sintering irradiation-resistant silicon carbide ceramic material. The preparation method comprises the following steps:

(1) uniformly mixing raw materials including silicon carbide powder, a boron source and a carbon source to prepare mixed slurry;

(2) drying and sieving or spray granulating the mixed slurry to obtain raw material powder;

(3) and (3) forming the raw material powder obtained in the step (2), then carrying out vacuum de-bonding treatment, and finally carrying out high-temperature sintering to obtain the silicon carbide ceramic material.

The preparation method of the invention provides a new idea for the preparation of the anti-irradiation silicon carbide ceramic material. In particular, the preparation method of the invention is high in¹¹Boronic acid introduction of B abundance¹¹B element which can be decomposed into B in the vacuum debonding process₂O₃Generation of B₂O₃Can react with added carbon source to generate in the sintering process¹¹B₄C. The relevant reaction equation is as follows: 2H₃BO₃＝3H₂O+B₂O₃；2B₂O₃+7C＝B₄C +6 CO. B formed in the preparation method₄Since C has a very small particle size and is more likely to be dissolved in the silicon carbide lattice, the grain boundary energy can be sufficiently reduced with a very small amount of B element, and sintering densification can be promoted. Meanwhile, the introduced boron source is¹¹B, will not react with the neutron, can avoid the expansion of solid phase sintering SiC pottery.

Preferably, the boron source is¹¹Boric acid with the B abundance of 95-100%. If the abundance of boric acid is too low, then¹⁰The B content is too high so that the sintered sample absorbs a large amount of neutrons, causing damage to the structural member.

Preferably, the mass ratio of the boric acid to the silicon carbide powder is 1.8-4.5 wt%. The boric acid content is controlled within the above range so that the product will be produced¹¹B₄The mass ratio of C in the anti-radiation silicon carbide ceramic material is controlled to be 0.4-1 wt%.

Preferably, the carbon source is a mixture of one or more of carbon black, phenolic resin and fructose; the carbon source accounts for 10-16 wt% of the silicon carbide powder.

Preferably, the silicon carbide powder is 6H-SiC powder.

Preferably, the grain diameter of the silicon carbide powder is 0.1-1.5 μm.

Preferably, the forming is dry pressing and/or cold isostatic pressing; preferably, the pressure of the dry pressing is 5-50MPa, the pressure of the cold isostatic pressing is 150-250MPa, and the pressure maintaining time is 1-5 minutes.

Preferably, the temperature for vacuum debonding is 900-.

Preferably, the sintering mode is normal pressure sintering, the sintering temperature is 2050-.

Preferably, the raw material in step (1) further comprises a binder. The binder can be one or a mixture of several of phenolic resin, polyvinyl alcohol and polyvinyl butyral. Preferably, the binder is 10-20 wt% of the mass of the silicon carbide powder.

Drawings

FIG. 1 is an XRD pattern of an atmospheric pressure sintered radiation-resistant silicon carbide ceramic material according to an embodiment of the present invention;

FIG. 2 is a SEM image of a fracture of an atmospheric pressure sintered irradiation-resistant silicon carbide ceramic material according to an embodiment of the present invention.

Detailed Description

The present invention is described in further detail by the following embodiments with reference to the attached drawings, and it should be understood that the following embodiments are merely illustrative of the present invention and are not limitative of the present invention, and any technical solution that does not substantially alter the present invention still falls within the scope of the present invention.

The preparation method of the radiation-resistant silicon carbide ceramic is exemplarily described below. The method selects and uses the super high¹¹B-abundant boric acid, produced by pyrolysis thereof¹¹B₄And C, thereby promoting sintering densification of the SiC ceramic.

Preparing raw materials for preparing the anti-radiation silicon carbide ceramic material. The raw material comprises silicon carbide powder, a boron source and a carbon source.

The particle size of the silicon carbide powder may be 0.5 μm.

The ordinary boric acid with high content of 10B element (10B accounts for about 19.8 at% in natural B) will react with neutrons to cause structural damage. The boron source of the present invention is high¹¹B-abundant boronic acid. The advantages of introducing abundant boric acid as a boron source are: generated B₄The grain size of C is extremely small, and the C is more easily dissolved in the silicon carbide crystal lattice, so that the grain boundary can be sufficiently lowered with an extremely small amount of B element, and the sintering densification of the silicon carbide ceramic is promoted. Meanwhile, the introduced boron source is¹¹B, the silicon carbide ceramic material can not react with neutrons, so that the prepared silicon carbide ceramic material meets the requirement of radiation resistance. In some embodiments, the boric acid is present in an amount of 1.8 to 4.5wt% of the silicon carbide powder.

The carbon source includes, but is not limited to, a mixture of one or more of carbon black, phenolic resin, and fructose. The mass ratio of the carbon source to the silicon carbide powder can be 10-16 wt%. Among them, the phenol resin functions as a carbon source and a binder.

A mixed slurry is prepared. Raw materials including silicon carbide powder, a boron source and a carbon source are uniformly mixed to prepare a mixed slurry. For example, silicon carbide powder, a boron source and a carbon source are used as raw materials, absolute ethyl alcohol is added as a solvent, a proper amount of silicon carbide balls are used as ball milling balls, and the ball milling is carried out on a planetary ball mill for 4 to 24 hours to obtain uniformly mixed slurry.

In some embodiments, the feedstock may also include additional added binders. The binder can be one or more of polyvinyl alcohol and polyvinyl butyral. In some embodiments, the binder is 10-20 wt% of the mass of the silicon carbide powder.

And drying the mixed slurry to obtain the silicon carbide ceramic powder. The drying temperature can be 60-80 deg.C, and the drying time can be 12-24 hr. For example, the obtained mixed slurry is placed in an oven to be dried to remove absolute ethyl alcohol, and then the dried raw material is sieved by a 100-mesh sieve to obtain silicon carbide ceramic powder. In some embodiments, the oven temperature is controlled at 60 ℃ and the drying time is 24 hours.

And (3) carrying out vacuum debonding treatment on the silicon carbide ceramic powder after molding. For example, silicon carbide ceramic powder is subjected to dry pressing, cold isostatic pressing and vacuum de-bonding. The pressure of the dry pressing molding is 5-50MPa, the pressure of the cold isostatic pressing is 150-250MPa, and the pressure maintaining time of the cold isostatic pressing is 1-5 minutes. The vacuum de-bonding temperature can be 900-.

Finally, the anti-irradiation silicon carbide ceramic material is obtained through high-temperature sintering. The sintering is preferably pressureless. The sintering temperature is 2050-.

And grinding the obtained silicon carbide ceramic material, processing the silicon carbide ceramic material into a specific size, and then carrying out related tests. The density was measured by the archimedes method. The bending strength was measured by a three-point bending method. In some embodiments, the radiation resistant silicon carbide ceramic has a density of 3.163 to 3.168 g-cm^-3The compactness is 99.4-99.6%, and the bending strength is 340-380 MPa.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

Taking 100 g of silicon carbide powder, adding¹¹The boric acid with B abundance is used as a boron source, and phenolic resin is added as a binder and is also used as a carbon source. The concrete contents are as follows: the adding amount of boric acid is 1.8 g; the phenolic resin was added in an amount of 12 grams. The raw materials are added into a certain amount of absolute ethyl alcohol, 100 g of silicon carbide ball milling balls are added, and ball milling is carried out on a planet ball mill for 4 hours, so as to obtain mixed slurry. And drying the mixed slurry, and sieving the dried mixed slurry with a 100-mesh sieve to obtain the silicon carbide ceramic powder. Weighing a proper amount of powder, dry-pressing and molding the powder under the pressure of 20MPa, and then carrying out cold isostatic pressing under the pressure of 200MPa for 3 minutes. Vacuum-debonding the obtained molded block at 1100 deg.C, and keeping the temperature for a certain timeThe binder is removed fully for 1 hour, and then the mixture is sintered at the temperature of 2150 ℃ under normal pressure and is kept warm for 1 hour to obtain the anti-radiation silicon carbide ceramic material. And grinding the obtained anti-irradiation silicon carbide ceramic material, processing the ceramic material into a specific size, and performing related tests, including density measurement by an Archimedes method and bending strength measurement by a three-point bending method. Wherein the density is 3.166g cm^-3The relative density was 99.5% and the bending strength was 353.2 MPa.

Example 2

Taking 100 g of silicon carbide powder, adding¹¹The boric acid with B abundance is used as a boron source, and phenolic resin is added as a binder and is also used as a carbon source. The concrete contents are as follows: the adding amount of boric acid is 2.7 g; the phenolic resin was added in an amount of 13 grams. The raw materials are added into a certain amount of absolute ethyl alcohol, 100 g of silicon carbide ball milling balls are added, and ball milling is carried out on a planet ball mill for 4 hours, so as to obtain mixed slurry. And drying the mixed slurry, and sieving the dried mixed slurry with a 100-mesh sieve to obtain the silicon carbide ceramic powder. Weighing a proper amount of powder, dry-pressing and molding the powder under the pressure of 20MPa, and then carrying out cold isostatic pressing under the pressure of 200MPa for 3 minutes. And (3) carrying out vacuum debonding on the obtained molded block at 1100 ℃, keeping the temperature for 1 hour to fully remove the binder, and then carrying out normal pressure sintering at 2150 ℃ for 1 hour to obtain the anti-irradiation silicon carbide ceramic material. And grinding the obtained anti-irradiation silicon carbide ceramic material, processing the ceramic material into a specific size, and performing related tests, including density measurement by an Archimedes method and bending strength measurement by a three-point bending method. Wherein the density is 3.166g cm^-3The relative density was 99.5% and the flexural strength was 342.7 MPa.

Example 3

Taking 100 g of silicon carbide powder, adding¹¹The boric acid with B abundance is used as a boron source, and phenolic resin is added as a binder and is also used as a carbon source. The concrete contents are as follows: the adding amount of boric acid is 3.6 g; the phenolic resin was added in an amount of 14 grams. The raw materials are added into a certain amount of absolute ethyl alcohol, 100 g of silicon carbide ball milling balls are added, and ball milling is carried out on a planet ball mill for 4 hours, so as to obtain mixed slurry. And drying the mixed slurry, and sieving the dried mixed slurry with a 100-mesh sieve to obtain the silicon carbide ceramic powder. Weighing appropriate amount of powder, and pressing under 20MPaThe mixture was dry-pressed to shape and then cold-isostatically pressed at a pressure of 200MPa for a dwell time of 3 minutes. And (3) carrying out vacuum debonding on the obtained molded block at 1100 ℃, keeping the temperature for 1 hour to fully remove the binder, and then carrying out normal pressure sintering at 2150 ℃ for 1 hour to obtain the anti-irradiation silicon carbide ceramic material. And grinding the obtained anti-irradiation silicon carbide ceramic material, processing the ceramic material into a specific size, and performing related tests, including density measurement by an Archimedes method and bending strength measurement by a three-point bending method. Wherein the density is 3.163g cm^-3The relative density was 99.4% and the flexural strength was 375.7 MPa.

Example 4

Taking 100 g of silicon carbide powder, adding¹¹The boric acid with B abundance is used as a boron source, and phenolic resin is added as a binder and is also used as a carbon source. The concrete contents are as follows: the adding amount of boric acid is 4.5 g; the phenolic resin was added in an amount of 15 grams. The raw materials are added into a certain amount of absolute ethyl alcohol, 100 g of silicon carbide ball milling balls are added, and ball milling is carried out on a planet ball mill for 4 hours, so as to obtain mixed slurry. And drying the mixed slurry, and sieving the dried mixed slurry with a 100-mesh sieve to obtain the silicon carbide ceramic powder. Weighing a proper amount of powder, dry-pressing and molding the powder under the pressure of 20MPa, and then carrying out cold isostatic pressing under the pressure of 200MPa for 3 minutes. And (3) carrying out vacuum debonding on the obtained molded block at 1100 ℃, keeping the temperature for 1 hour to fully remove the binder, and then carrying out normal pressure sintering at 2150 ℃ for 1 hour to obtain the anti-irradiation silicon carbide ceramic material. And grinding the obtained anti-irradiation silicon carbide ceramic material, processing the ceramic material into a specific size, and performing related tests, including density measurement by an Archimedes method and bending strength measurement by a three-point bending method. Wherein the density is 3.168g cm^-3The relative density was 99.56% and the bending strength was 340.7 MPa.

Comparative example

Taking 100 g of silicon carbide powder, adding¹¹The boric acid with B abundance is used as a boron source, and phenolic resin is added as a binder and is also used as a carbon source. The concrete contents are as follows: the adding amount of boric acid is 0.9 g; the phenolic resin was added in an amount of 11 grams. Adding the raw materials into a certain amount of absolute ethyl alcohol, and adding 100 g of silicon carbide ball grinding balls into the mixture to form a planetBall milling is carried out for 4 hours on a ball mill, and mixed slurry is obtained. And drying the mixed slurry, and sieving the dried mixed slurry with a 100-mesh sieve to obtain the silicon carbide ceramic powder. Weighing a proper amount of powder, dry-pressing and molding the powder under the pressure of 20MPa, and then carrying out cold isostatic pressing under the pressure of 200MPa for 3 minutes. And (3) carrying out vacuum debonding on the obtained molded block at 1100 ℃, keeping the temperature for 1 hour to fully remove the binder, and then carrying out normal pressure sintering at 2150 ℃ for 1 hour to obtain the anti-irradiation silicon carbide ceramic material. And grinding the obtained anti-irradiation silicon carbide ceramic material, processing the ceramic material into a specific size, and performing related tests, including density measurement by an Archimedes method and bending strength measurement by a three-point bending method. Wherein the density is 3.067g cm^-3The relative density was 96.4% and the bending strength was 272.2 MPa.

The comparative example shows that when the boric acid accounts for a lower mass percentage of the silicon carbide powder, the density and the compactness of the obtained sample are obviously lower, and the sample has higher porosity. Generated in situ at this time¹¹B₄The mass ratio of C in the silicon carbide ceramic material is about 0.2 wt%, and the densification of the silicon carbide ceramic material cannot be guaranteed. This is because the content of B element is low, the content of B element dissolved in silicon carbide is too small, and there is no significant effect of reducing the surface energy thereof, which is not favorable for the sintering process. Accordingly, the bending strength of the obtained sample is also low. The above is not beneficial to the application in the anti-irradiation environment.