阅读说明：本技术 通过碳源改性和反应熔渗制备硅化石墨的方法及硅化石墨 (Method for preparing silicified graphite through carbon source modification and reaction infiltration and silicified graphite ) 是由 王继平 薛蓉 王梓璇 蔺浩然 史忠旗 王波 夏鸿雁 于 2021-10-26 设计创作，主要内容包括：本发明公开了一种通过碳源改性和反应熔渗制备硅化石墨的方法及硅化石墨,通过球形石墨与树脂进行混合,固化炭化得到改性过的碳颗粒,即resin-C@G颗粒,采用resin-C@G颗粒和中间相碳微球为碳源,酚醛树脂为粘结剂,聚丙烯酸树脂为造孔剂,通过冷等静压得到生坯,将生坯进行炭化,炭化后的样品放入真空电阻炉中进行反应熔渗,得到碳含量和致密度较高的硅化石墨材料。本发明所使用的原料价格低廉,制备方法简单,生产周期相对较短,且不需要经历长时间的高温等高能耗工艺。制备得到的硅化石墨材料十分致密,碳含量较高,重复性高。(The invention discloses a method for preparing silicified graphite through carbon source modification and reactive infiltration and the silicified graphite, wherein spherical graphite and resin are mixed, and are solidified and carbonized to obtain modified carbon particles, namely, resin-C @ G particles and mesocarbon microspheres are used as carbon sources, phenolic resin is used as a binder, polyacrylic resin is used as a pore-forming agent, a green body is obtained through cold isostatic pressing, the green body is carbonized, and a carbonized sample is placed into a vacuum resistance furnace for reactive infiltration to obtain the silicified graphite material with higher carbon content and density. The raw materials used in the invention have low price, the preparation method is simple, the production period is relatively short, and the high-energy-consumption process such as high temperature and the like which is long in time does not need to be carried out. The prepared silicified graphite material is very compact, has high carbon content and high repeatability.)

1. A method for preparing graphite silicide by carbon source modification and reaction infiltration is characterized by comprising the following steps:

1) mechanically mixing spherical graphite with liquid phenolic resin, and putting the uniformly mixed materials into an oven for segmented heating and curing;

2) carbonizing the cured material in a protective atmosphere, preserving heat, and crushing to obtain resin carbon coated spherical graphite resin-C @ G particles;

3) taking ethanol as a solvent, carrying out ball milling on the resin-C @ G particles, the mesocarbon microbeads and the phenolic resin, and drying the mixed slurry to obtain a resin-C @ G composite carbon source;

4) mixing and drying a resin-C @ G composite carbon source and polyacrylic resin by taking distilled water as a medium to obtain resin-C @ G composite powder;

5) prepressing and molding the resin-C @ G composite powder, and performing cold isostatic pressing after prepressing to obtain a blank body;

6) carbonizing the blank, carbonizing, and preserving heat to obtain a porous carbon blank;

7) and (3) placing the porous carbon blank on the silicon particles, adding a layer of silicon particles to enable the blank to be completely embedded by the silicon particles, carrying out reaction infiltration, sintering, keeping the temperature, and cooling to room temperature along with the furnace to obtain the silicified graphite material.

2. The method for preparing siliconized graphite through carbon source modification and reaction infiltration according to claim 1, wherein the mass ratio of the spherical graphite to the liquid phenolic resin is 55-65%: and (3) mechanically mixing 35-45%, heating for 2 hours at 70 ℃ in a sectional heating curing mode, and heating for 4 hours at 150 ℃.

3. The method for preparing graphite silicide by carbon source modification and reaction infiltration as claimed in claim 1, wherein the carbonization temperature is 800-.

4. The method for preparing siliconized graphite by carbon source modification and reactive infiltration according to claim 1, wherein the mass ratio of the resin-C @ G particles to the mesocarbon microbeads is 2: 1; the added amount of phenolic resin was 10 wt.% of mesocarbon microbeads.

5. The method for preparing siliconized graphite by carbon source modification and reactive infiltration according to claim 1, wherein the ball-to-feed ratio of mesocarbon microbeads to ethanol, resin-C @ G particles and phenolic resin is 3-4: 1, ball milling for 4-6h at the rotation speed of 400-; drying the mixed slurry at 40-60 ℃; the addition amount of the polyacrylic resin is 30-35% of the total mass of the resin-C @ G composite carbon source.

6. The method for preparing siliconized graphite through carbon source modification and reaction infiltration according to claim 1, wherein the composite powder is pre-pressed at a pressure of 30-40MPa for a dwell time of 20-40s, and then is subjected to cold isostatic pressing at a pressure of 50-60MPa for a dwell time of 2-5 min.

7. The method for preparing graphite silicide by carbon source modification and reaction infiltration as claimed in claim 1, wherein the temperature for carbonization of the blank is 800-.

8. The method for preparing graphite silicide by carbon source modification and reaction infiltration as claimed in claim 1, wherein the infiltration sintering temperature is 1450-1650 ℃, and the holding time is 10-20 min.

9. A graphite silicide produced by modification of a carbon source and reactive infiltration as produced by the method of any one of claims 1 to 8.

10. The method of claim 9, wherein the siliconized graphite has a carbon content of 18 to 33 vol.% and a density of 2.6 to 2.8 g-cm^-3And the open porosity is less than 1%.

Technical Field

The invention belongs to the technical field of preparation of inorganic non-metallic materials, and particularly relates to a method for preparing silicified graphite through carbon source modification and reaction infiltration and the silicified graphite.

Background

The silicified graphite composite material is compounded by three phases of carbon, silicon carbide and silicon, has the advantages of self-lubricating property, good electric and heat conducting properties, excellent high-temperature strength, good thermal shock resistance and the like of the carbon/graphite material, and also has a series of characteristics of high strength, high hardness, oxidation resistance, corrosion resistance and the like of the silicon carbide, so that the silicified graphite composite material is widely applied to the fields of bearing bushes, mechanical seals, thermal structure materials, thermocouple protection tubes and the like. The current method for preparing the siliconized graphite composite material mainly comprises the following steps: chemical vapor infiltration, chemical vapor reaction, precursor impregnation and pyrolysis, and reactive infiltration. The reaction infiltration method for preparing the siliconized graphite ceramic has the advantages of simple forming, low sintering temperature, compact one-time sintering, high sintering speed, near net size and the like. However, since the contact angle of silicon and carbon is very small at high temperature, the reaction is very violent, and a general carbon source is very easy to react with liquid silicon to generate silicon carbide, so that the content of carbon phase in the siliconized graphite material is low. Therefore, the key point of the reaction infiltration method for preparing the siliconized graphite material lies in how to effectively retain the carbon phase in the siliconized graphite material so as to enable the siliconized graphite material to exert the self-lubricating property.

Disclosure of Invention

In order to solve the defects in the prior art, the invention aims to reserve the carbon phase in the siliconized graphite material prepared by the reaction infiltration method, and designs a low-cost and effective carbon source treatment method, thereby realizing the preparation of the siliconized graphite with high carbon content.

The invention is realized by the following technical scheme.

The invention provides a method for preparing graphite silicide by carbon source modification and reaction infiltration, which comprises the following steps:

1) mechanically mixing spherical graphite with liquid phenolic resin, and putting the uniformly mixed materials into an oven for segmented heating and curing;

2) carbonizing the cured material in a protective atmosphere, preserving heat, and crushing to obtain resin carbon coated spherical graphite resin-C @ G particles;

3) taking ethanol as a solvent, carrying out ball milling on the resin-C @ G particles, the mesocarbon microbeads and the phenolic resin, and drying the mixed slurry to obtain a resin-C @ G composite carbon source;

4) mixing and drying a resin-C @ G composite carbon source and polyacrylic resin by taking distilled water as a medium to obtain resin-C @ G composite powder;

5) prepressing and molding the resin-C @ G composite powder, and performing cold isostatic pressing after prepressing to obtain a blank body;

6) carbonizing the blank, carbonizing, and preserving heat to obtain a porous carbon blank;

7) and (3) placing the porous carbon blank on the silicon particles, adding a layer of silicon particles to enable the blank to be completely embedded by the silicon particles, carrying out reaction infiltration, sintering, keeping the temperature, and cooling to room temperature along with the furnace to obtain the silicified graphite material.

Preferably, the mass ratio of the spherical graphite to the liquid phenolic resin is 55-65%: 35-45%.

Preferably, the step-by-step heating curing is carried out at 70 ℃ for 2h, and the temperature is raised to 150 ℃ for 4 h.

Preferably, the carbonization temperature is 800-1200 ℃, the heat preservation time is 2-4h, the heating rate is 1 ℃/min, and the protective atmosphere is nitrogen or argon.

Preferably, the mass ratio of the resin-C @ G particles to the mesocarbon microbeads is 2: 1; the added amount of phenolic resin was 10 wt.% of mesocarbon microbeads.

Preferably, the ball-to-feed ratio of the mesocarbon microbeads to the ethanol, the resin-C @ G particles and the phenolic resin is 3-4: 1, ball milling for 4-6h at the rotation speed of 400-; the drying temperature of the mixed slurry is 40-60 ℃.

Preferably, the addition amount of the polyacrylic resin is 30-35% of the total mass of the resin-C @ G composite carbon source.

Preferably, the composite powder is pre-pressed at a pressure of 30-40MPa for a pressure maintaining time of 20-40s, and then is subjected to cold isostatic pressing at a pressure of 50-60MPa for a pressure maintaining time of 2-5 min.

Preferably, the carbonization temperature of the blank is 800-1200 ℃, and the heat preservation time is 2-4 h.

Preferably, the infiltration sintering temperature is 1450-1650 ℃, and the heat preservation time is 10-20 min.

The invention also provides a method for preparing the siliconized graphite by carbon source modification and reaction infiltration.

Due to the adoption of the technical scheme, the invention has the following beneficial effects:

spherical graphite and resin are mixed, cured, carbonized and crushed to prepare resin carbon coated spherical graphite (namely resin-C @ G) particles, and then the silicified graphite material is prepared by a reaction infiltration method. Because the silicon-carbon reaction is very violent, various untreated carbon sources are difficult to retain in the reaction infiltration, and when resin-C @ G particles prepared by mixing the carbon sources and the liquid resin phase in a certain proportion are used as the carbon sources, the spherical graphite is coated by the dense resin carbon, a dense silicon carbide layer is formed in the reaction infiltration to prevent the further reaction of carbon and silicon, the content of the carbon phase in the siliconized graphite is effectively controlled, and the self-lubricating property of the material is improved.

According to the invention, the spherical graphite and the resin are mixed, and are solidified and carbonized to obtain modified carbon particles, the resin carbon after resin carbonization can be bonded with small particles on one hand, and is very compact on the other hand, and a layer of compact resin carbon is formed on the surface of the spherical graphite, so that a continuous silicon carbide shell is formed on the surface of the carbon particles in the reaction infiltration process, further reaction of silicon and carbon is prevented, and the preservation of a carbon phase in the siliconized graphite material is realized. The content of carbon in the siliconized graphite prepared by the invention reaches 18-33 vol.%, and the density reaches 2.6-2.8 g-cm^-3And the open porosity is less than 1%.

In addition, the raw materials used in the preparation method are low in price, the preparation method is simple, the production period is relatively short, and high-energy-consumption processes such as long-time high temperature and the like are not needed. The prepared silicified graphite material is very compact, has high carbon content and high repeatability, and has wide application prospect in the fields of chemical industry, metallurgy, aerospace, nuclear energy and the like.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention:

FIG. 1 is an XRD pattern of siliconized graphite prepared in accordance with example 2 of the present invention;

FIG. 2 is an SEM image of siliconized graphite prepared in example 2 of the present invention.

Detailed Description

The present invention will now be described in detail with reference to the drawings and specific embodiments, wherein the exemplary embodiments and descriptions of the present invention are provided to explain the present invention without limiting the invention thereto.

The embodiment of the invention provides a method for preparing siliconized graphite through carbon source modification and reaction infiltration, which comprises the following steps:

1) the mass ratio of the spherical graphite to the liquid phenolic resin is 55-65%: and (3) mechanically mixing 35-45%, putting the uniformly mixed materials into an oven, heating and curing in sections, heating at 70 ℃ for 2h, and heating to 150 ℃ for 4 h.

2) Putting the cured material into a tubular furnace, carbonizing at 800-1200 ℃ under the protective atmosphere of nitrogen or argon, keeping the temperature for 2-4h at the heating rate of 1 ℃/min, and crushing to obtain resin carbon coated spherical graphite resin-C @ G particles;

3) taking ethanol as a solvent, putting the resin-C @ G particles, the mesocarbon microbeads and the phenolic resin into a ball milling tank, and carrying out ball milling for 4-6h at the rotating speed of 400-: 1; the added amount of phenolic resin was 10 wt.% of mesocarbon microbeads; the ball material ratio is 3-4: 1; then putting the mixed slurry into an oven, wherein the temperature of the oven is 40-60 ℃, and drying to obtain a resin-C @ G composite carbon source;

4) distilled water is used as a medium, and the mass ratio of the distilled water to the distilled water is 100: (30-35) mixing and drying the resin-C @ G composite carbon source and the polyacrylic resin by using a magnetic heating stirrer to obtain resin-C @ G composite powder;

5) putting the resin-C @ G composite powder into a die, performing prepressing molding by using a hydraulic machine, wherein the prepressing pressure is 30-40MPa, the pressure maintaining time is 20-40s, and performing cold isostatic pressing molding after prepressing, wherein the pressure is 50-60MPa, and the pressure maintaining time is 2-5min to obtain a blank;

6) carbonizing the blank in a tube furnace at 800-1200 deg.C for 2-4h to obtain porous carbon blank;

7) and (3) placing the porous carbon blank on silicon particles, adding a layer of silicon particles to enable the blank to be completely embedded by the silicon particles, carrying out reaction infiltration in a vacuum resistance furnace at the sintering temperature of 1450-.

The invention is further illustrated by the following specific examples.

Example 1:

1) spherical graphite and phenolic resin are mixed according to the weight ratio of 55: 45, mechanically mixing, and putting the mixed materials into an oven for curing under the curing condition of 70 ℃/2h +150 ℃/4 h;

2) putting the cured material into an atmosphere tube furnace, carbonizing for 2h at 1000 ℃ under the protection of nitrogen at the heating rate of 1 ℃/min, and crushing the carbonized sample to obtain resin-C @ G particles;

3) the weight ratio of the main carbon source is resin-C @ G particles: mesocarbon microbeads 2: 1, the weight of the phenolic resin is 10% of the weight of the total carbon source, all the raw materials and absolute ethyl alcohol are put into a sealed plastic tank for ball milling for 5 hours, and the ball-to-material ratio is 4: 1, the rotating speed is 400 r/min, then the ball-milled slurry is put into a tray in an oven to be dried, the temperature of the oven is 40 ℃, and the dried resin-C @ G composite carbon source is dry-milled and passes through a 60-mesh screen;

4) distilled water is used as a medium, and a resin-C @ G composite carbon source and polyacrylic resin are mixed according to the weight percentage of 100: 30, mixing and drying by using a magnetic heating stirrer, and screening by using a 60-mesh screen to obtain resin-C @ G composite powder;

5) prepressing the composite powder at 30MPa for 30s, and performing cold isostatic pressing at 50MPa for 2min to obtain a blank;

6) putting the blank obtained by the compression molding into an atmosphere tube furnace, and carbonizing for 2h at 800 ℃ under the protection of nitrogen;

7) and putting the carbonized green body into a vacuum resistance furnace for reaction sintering, wherein the sintering temperature is 1500 ℃, and the heat preservation time is 15 min. The size of the silicon particles is 0.5-4 mm, and the weight of the silicon particles is 2 times of the total weight of the green body;

the siliconized graphite material prepared by the process has the carbon content of 17.65 vol.% and the density of 2.65g cm^-3And the open porosity is less than 1%.

Example 2:

1) spherical graphite and phenolic resin are mixed according to the weight ratio of 60: 40, mechanically mixing, and putting the mixed materials into an oven for curing under the curing condition of 70 ℃/2h +150 ℃/4 h;

2) putting the cured material into an atmosphere tubular furnace, carbonizing for 3h at 900 ℃ under the protection of nitrogen at the heating rate of 1 ℃/min, and crushing the carbonized sample to obtain resin-C @ G particles;

3) the weight ratio of the main carbon source is resin-C @ G particles: mesocarbon microbeads 2: 1, the weight of the phenolic resin is 10% of the weight of the total carbon source, all the raw materials and absolute ethyl alcohol are put into a sealed plastic tank for ball milling for 4 hours, and the ball-to-material ratio is 3.5: 1, the rotating speed is 500 r/min, then the ball-milled slurry is put into a tray in an oven to be dried, the temperature of the oven is 60 ℃, and the dried resin-C @ G composite carbon source is dry-milled and passes through a 60-mesh screen;

4) distilled water is used as a medium, and a resin-C @ G composite carbon source and polyacrylic resin are mixed according to the weight percentage of 100: 32, mixing and drying by using a magnetic heating stirrer, and screening by using a 60-mesh screen to obtain resin-C @ G composite powder;

5) prepressing the composite powder at 35MPa for 40s, and then carrying out cold isostatic pressing at 55MPa for 5min to obtain a blank;

6) putting the blank obtained by the compression molding into an atmosphere tube furnace, and carbonizing for 3h at 1000 ℃ under the protection of nitrogen;

7) and putting the carbonized green body into a vacuum resistance furnace for reaction sintering, wherein the sintering temperature is 1450 ℃, and the heat preservation time is 15 min. The size of the silicon particles is 0.5-4 mm, and the weight of the silicon particles is 2 times of the total weight of the green body;

the siliconized graphite material prepared by the process has the carbon content of 33.10 vol.% and the density of 2.76g cm^-3And the open porosity is less than 1%.

The resulting product was characterized by X-ray diffractometer (XRD), Field Emission Scanning Electron Microscope (FESEM). Fig. 1 is an XRD pattern of the product, which can be found to be mainly composed of SiC, Si and C. Fig. 2 is a back-scattered photograph of the product, which clearly shows that a large amount of black carbon phase is preserved, no significant pores are found inside the sample, and the sample is very dense.

Example 3:

1) spherical graphite and phenolic resin are mixed according to the weight ratio of 50: 50, mechanically mixing, and putting the mixed materials into an oven for curing under the curing condition of 70 ℃/2h +150 ℃/4 h;

2) putting the cured material into an atmosphere tube furnace, carbonizing for 2h at 800 ℃ under the protection of nitrogen, and crushing a carbonized sample to obtain resin-C @ G particles;

3) the weight ratio of the main carbon source is resin-C @ G particles: mesocarbon microbeads 2: 1, the weight of the phenolic resin is 10% of the weight of the total carbon source, all the raw materials and absolute ethyl alcohol are put into a sealed plastic tank for ball milling for 6 hours, and the ball-to-material ratio is 3: 1, the rotating speed is 600 revolutions per minute, then the ball-milled slurry is put into a tray in an oven to be dried, the temperature of the oven is 50 ℃, and the dried resin-C @ G composite carbon source is dry-milled and passes through a 60-mesh screen;

4) distilled water is used as a medium, and a resin-C @ G composite carbon source and polyacrylic resin are mixed according to the weight percentage of 100: 35, mixing and drying by using a magnetic heating stirrer, and screening by using a 60-mesh screen to obtain resin-C @ G composite powder;

5) pre-pressing the composite powder at 40MPa for 40s, and then carrying out cold isostatic pressing at 60MPa for 4min to obtain a blank;

6) putting the blank obtained by the compression molding into an atmosphere tube furnace, and carbonizing for 4 hours at 1100 ℃ under the protection of nitrogen;

7) and putting the carbonized green body into a vacuum resistance furnace for reaction sintering, wherein the sintering temperature is 1550 ℃, and the heat preservation time is 10 min. The size of the silicon particles is 0.5-4 mm, and the weight of the silicon particles is 2 times of the total weight of the green body;

the siliconized graphite material prepared by the process has the carbon content of 27.20 vol.% and the density of 2.73g cm^-3And the open porosity is less than 1%.

Example 4:

1) spherical graphite and phenolic resin are mixed according to the weight ratio of 65: 35, mechanically mixing, and placing the mixed materials into an oven for curing under the curing conditions of 70 ℃/2h +150 ℃/4 h;

2) putting the cured material into an atmosphere tube furnace, carbonizing for 4h at 950 ℃ under the protection of nitrogen, and crushing a carbonized sample to obtain resin-C @ G particles;

3) the weight ratio of the main carbon source is resin-C @ G particles: mesocarbon microbeads 2: 1, the weight of the phenolic resin is 10% of the weight of the total carbon source, all the raw materials and absolute ethyl alcohol are put into a sealed plastic tank for ball milling for 5.5h, and the ball-material ratio is 4: 1, the rotating speed is 450 rpm, then the ball-milled slurry is put into a tray in an oven to be dried, the temperature of the oven is 60 ℃, and the dried resin-C @ G composite carbon source is dry-milled and passes through a 60-mesh screen;

4) distilled water is used as a medium, and a resin-C @ G composite carbon source and polyacrylic resin are mixed according to the weight percentage of 100: 30, mixing and drying by using a magnetic heating stirrer, and screening by using a 60-mesh screen to obtain resin-C @ G composite powder;

5) pre-pressing the composite powder at 40MPa for 20s, and then carrying out cold isostatic pressing at 58MPa for 3min to obtain a blank;

6) putting the blank obtained by the compression molding into an atmosphere tube furnace, and carbonizing for 2h at 1200 ℃ under the protection of nitrogen;

7) and putting the carbonized green body into a vacuum resistance furnace for reaction sintering, wherein the sintering temperature is 1650 ℃, and the heat preservation time is 20 min. The size of the silicon particles is 0.5-4 mm, and the weight of the silicon particles is 2 times of the total weight of the green body;

the siliconized graphite material prepared by the process has the carbon content of 22.30 vol.% and the density of 2.63g cm^-3And the open porosity is less than 1%.

Comparative example 1

The spherical graphite is not treated and is directly used as a carbon source for reaction, other process parameters are the same as those in example 1, and the carbon content of the finally obtained silicified graphite material is 15.00 vol.%.

As can be seen from the comparison of the above examples 1-4 with the comparative example 1, the siliconized graphite material prepared by the invention is very dense and has the density of 2.6-2.8 g-cm^-3And the open porosity is less than 1%. The carbon content of the siliconized graphite material is not lower than 17.65 vol.%, the carbon content of the siliconized graphite material is obviously improved compared with the carbon content of the siliconized graphite in the comparison example, wherein the carbon content of the siliconized graphite material in the example 1 is improved by 17.67 percent compared with the carbon content of the siliconized graphite in the comparison example 1; example 2 is an improvement of 120.67% over comparative example 1; example 3 is an improvement of 81.33% over comparative example 1; example 4 is an increase of 48.67% compared to comparative example 1. The silicified graphite material prepared by the method is a graphite material with excellent performance, and can be widely applied to the fields of chemical industry, metallurgy, aerospace, nuclear energy and the like.

The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.