CN102674354B - Preparation method of mesoporous silicon carbide material - Google Patents

Abstract

The invention belongs to the field of inorganic materials and material synthesis technology, and relates to a preparation method of a mesoporous silicon carbide material. The invention uses resorcinol, formaldehyde and tetraethyl orthosilicate as reactants, acid and alkali as catalysts to carry out sol-gel reaction to prepare wet gel, and the wet gel is aged and dried under normal pressure to obtain silicon carbide precursor , the silicon carbide precursor undergoes carbothermal reduction under the protection of an inert gas to generate silicon carbide, and then undergoes calcination, pickling, water washing, filtration, and drying to obtain mesoporous silicon carbide materials. The invention has the advantages of cheap and easy-to-obtain raw materials, simple equipment, small silicon carbide particle size and large specific surface area.

Description

A kind of preparation method of mesoporous silicon carbide material

technical field

The invention belongs to the field of inorganic materials and material synthesis technology, and relates to a preparation method of a mesoporous silicon carbide material.

Background technique

Silicon carbide (SiC) material has many excellent properties such as good thermal conductivity and electrical conductivity, high temperature resistance and chemical stability, thermal shock resistance, low thermal expansion coefficient, high hardness, etc. It is used in ceramic composite materials, wear-resistant materials, catalysts and The field of optoelectronic materials has great application potential.

SiC can be prepared by traditional Acheson process, precursor immersion cracking method and shape memory synthesis method, but these synthesis methods have relatively high carbothermal reduction temperature, such as the reaction temperature of Acheson process is generally above 2000 °C. In addition, the porous SiC materials synthesized by the above methods have larger particles and pore diameters (generally at the micron level) and smaller specific surface areas (generally no more than 70m ² /g). Sol-gel method combined with carbothermal reduction process is an effective way to prepare SiC mesoporous materials or nanoparticles with high specific surface area. This method usually uses sol-gel method to synthesize carbon-silicon dioxide composite as a precursor , the precursor synthesizes SiC through high-temperature carbothermal reduction reaction. The mesoporous SiC material obtained by this method has small particles and large specific surface area, as reported by Nicholas Leventis et al. (Chem. Mater. 2010, 22, 2790-2803) A method for preparing mesoporous SiC by using a sol-gel method and a carbothermal reduction process, with an average particle diameter of 7-17nm, but a relatively low specific surface area of no more than 100m ² /g. In addition, the preparation processes of the SiC precursors reported so far are relatively complicated, and most of them need to mix the separately prepared carbon sol and SiO ₂ sol.

Contents of the invention

The object of the present invention is to provide a kind of preparation method of mesoporous silicon carbide material in order to improve the deficiencies existing in the prior art. A mesoporous silicon carbide material with high specific surface area and small particle size is prepared.

The technical scheme of the present invention is: a kind of preparation method of mesoporous silicon carbide material, and its specific steps are as follows:

(1) Mix resorcinol, formaldehyde, tetraethyl orthosilicate, acid catalyst, anhydrous sodium carbonate, deionized water, and absolute ethanol in a molar ratio of 1:2: (0.25~2): (0.04~ 0.15): (0.003~0.01): (1~8): (20~160) Mix evenly, stir at 50~70°C for 30~90 minutes, add ammonia water to adjust the pH value to 7.8~9.5, at 50~70° The sol-gel reaction is carried out under C to obtain a wet gel, and the wet gel is dried under normal pressure after aging to obtain a silicon carbide precursor;

(2) Heat the silicon carbide precursor obtained in step (1) to 1450-1600°C at a heating rate of 2-4°C/min under the protection of an inert gas, keep it warm for 3-10 hours, and then lower the temperature to 500~700°C, replace the inert gas with air, keep warm for 2~4 hours to remove residual carbon, cool to room temperature, take out the sample, then soak in hydrofluoric acid to remove silicon dioxide, wash with water, filter, bake After drying, light green mesoporous silicon carbide was obtained.

Preferably, the acidic catalyst described in step (1) is one of hydrochloric acid or nitric acid.

The preferred step (1) sol-gel reaction time is 10-30 minutes; the aging condition in step (1) is: aging at 50-75°C for 1-7 days; the drying condition in step (1) is: 40-60 Dry at °C for 24-48 hours.

Preferably, the inert gas described in step (2) is one of helium or argon. Preferably, the mass fraction of hydrofluoric acid described in step (2) is 10-30%, and the soaking time is 1-3 hours.

The mesoporous silicon carbide material prepared by the invention can be used in the fields of catalyst materials, ceramic composite materials, wear-resistant materials, optoelectronic materials, high-temperature heat insulation materials and the like.

Beneficial effect:

The mesoporous silicon carbide material prepared by the method of the present invention has the following characteristics:

(1) The raw materials are cheap and easy to obtain, the equipment is simple, and it is easy to realize large-scale production.

(2) The particle size and distribution of silicon carbide are uniform, with typical mesoporous structure characteristics.

Description of drawings

Fig. 1 is the XRD spectrum of the mesoporous silicon carbide material prepared in Example 2.

Fig. 2 is the HRTEM photo of the mesoporous silicon carbide material prepared in Example 2.

Fig. 3 is the SEM photo of the mesoporous silicon carbide material prepared in Example 2.

Fig. 4 is the nitrogen adsorption-desorption curve of the mesoporous silicon carbide material prepared in Example 2, wherein ● and ○ are the adsorption curve and the desorption curve, respectively.

Detailed ways

Example 1

(1) Mix resorcinol, formaldehyde, tetraethyl orthosilicate, hydrochloric acid, anhydrous sodium carbonate, deionized water, and absolute ethanol in a molar ratio of 1:2:1.5:0.06:0.008:6:100 Evenly, stir at 50°C for 90 minutes, add ammonia water to adjust the pH value to 7.8, carry out sol-gel reaction at 60°C for 20 minutes to obtain a wet gel, and the wet gel is aged at 70°C for 3 days, and then in Dry in an oven at 50°C for 36 hours to obtain a silicon carbide precursor.

(2) The silicon carbide precursor was heated to 1600°C at a heating rate of 4°C/min under the protection of argon, and kept for 3 hours, then the temperature was lowered to 500°C, and the argon was replaced with air, and kept for 4 hours to remove residual carbon, cool to room temperature, take out the sample, and then soak in 30% hydrofluoric acid aqueous solution for 1 hour to remove silicon dioxide in silicon carbide, after washing, filtering, and drying, a light green mesoporous silicon carbide.

The prepared mesoporous silicon carbide material has a pore size distribution of 5-26 nm, a specific surface area of 196 m ² /g, and an average particle size of 6.5 nm.

Example 2

(1) Mix resorcinol, formaldehyde, tetraethyl orthosilicate, hydrochloric acid, anhydrous sodium carbonate, deionized water, and absolute ethanol in a molar ratio of 1:2:1:0.09:0.01:4:120 Evenly, stir at 60°C for 60 minutes, add ammonia water to adjust the pH value to 8.5, carry out sol-gel reaction at 60°C for 30 minutes to obtain a wet gel, and the wet gel is aged at 75°C for 5 days, and then in Dry in an oven at 40°C for 48 hours to obtain a silicon carbide precursor.

(2) The silicon carbide precursor was heated to 1500°C at a heating rate of 2°C/min under the protection of argon, and kept for 6 hours, then the temperature was lowered to 600°C, and the argon was replaced with air, and kept for 3 hours. hours to remove residual carbon, cool to room temperature, take out the sample, and then soak in 20% hydrofluoric acid aqueous solution for 2 hours to remove silicon dioxide in silicon carbide, after washing, filtering and drying, a light green mesoporous silicon carbide.

The pore size distribution of the prepared mesoporous silicon carbide material is 4-13nm, the BET specific surface area is 366m ² /g, and the average particle size is 5.2nm.

The XRD spectrum of the silicon carbide mesoporous material prepared in this example is shown in FIG. 1 . The XRD analysis was carried out on the ARLX'TRA X-ray diffractometer of ARL Company of the American Thermoelectric Group; using CuKα diffraction, λ=0.15406nm, scanning rate 2(°)/min, scanning angle 10-80 degrees. It can be seen from Figure 1 that the prepared mesoporous silicon carbide is β-SiC, and the corresponding average particle size can be calculated according to the Scherrer formula to be 5.2nm.

The HRTEM photo of the silicon carbide mesoporous material prepared in this example is shown in FIG. 2 . TEM analysis was performed using a JEM-2010 transmission electron microscope from Japan Electronics Corporation. From the HRTEM photo of the sample, it can be seen that the prepared mesoporous silicon carbide has a crystal plane spacing of 0.252nm, which is consistent with the crystal plane spacing of the (111) crystal plane of β-SiC, which also indicates that the prepared silicon carbide is β-SiC .

The SEM photo of the silicon carbide mesoporous material prepared in this example is shown in FIG. 3 . The SEM test adopts the LEO-1530VP field emission scanning electron microscope of German Carl Zeiss Company. It can be seen from the SEM photo that the particle size and distribution of the silicon carbide mesoporous material prepared by the present invention are uniform.

The nitrogen adsorption-desorption curve of the silicon carbide mesoporous material prepared in this example is shown in FIG. 4 . The nitrogen adsorption and desorption test adopts the ASAP2020 automatic specific surface area analyzer of American Micromeritics Company. It can be seen from the figure that the prepared silicon carbide material has typical mesoporous structure characteristics, and the BET specific surface area of the sample can be calculated to be 366m ² /g through the data of the adsorption-desorption curve.

Example 3

(1) Mix resorcinol, formaldehyde, tetraethyl orthosilicate, nitric acid, anhydrous sodium carbonate, deionized water, and absolute ethanol in a molar ratio of 1:2:0.5:0.04:0.003:1:20 Evenly, stir at 60°C for 30 minutes, add ammonia water to adjust the pH value to 8.5, carry out sol-gel reaction at 50°C for 10 minutes to obtain a wet gel, and the wet gel is aged at 50°C for 3 days, and then in Dry in an oven at 50°C for 36 hours to obtain a silicon carbide precursor.

(2) The silicon carbide precursor was heated to 1450°C at a heating rate of 2°C/min under the protection of argon, and kept for 10 hours, then the temperature was lowered to 600°C, and the argon was replaced with air, and kept for 3 hours to remove residual charcoal, cool to room temperature, take out the sample, and then soak in 10% hydrofluoric acid aqueous solution for 3 hours to remove silicon dioxide in silicon carbide, after washing, filtering and drying, a light green mesoporous silicon carbide.

The prepared mesoporous silicon carbide material has a pore size distribution of 25-35 nm, a specific surface area of 173 m ² /g, and an average particle size of 6.9 nm.

Example 4

(1) Mix resorcinol, formaldehyde, tetraethyl orthosilicate, hydrochloric acid, anhydrous sodium carbonate, deionized water, and absolute ethanol in a molar ratio of 1:2:1:0.15:0.004:2:160 Evenly, stir at 70°C for 30 minutes, add ammonia water to adjust the pH value to 9.5, carry out sol-gel reaction at 70°C for 30 minutes to obtain a wet gel, and the wet gel is aged at 75°C for 7 days, and then in Dry in an oven at 60°C for 24 hours to obtain a silicon carbide precursor.

(2) The silicon carbide precursor was heated to 1500°C at a heating rate of 2°C/min under the protection of argon, and kept for 4 hours, then the temperature was lowered to 500°C, and the argon was replaced with air, and kept for 4 hours. hours to remove residual carbon, cool to room temperature, take out the sample, and then soak in 20% hydrofluoric acid aqueous solution for 2 hours to remove silicon dioxide in silicon carbide, after washing, filtering and drying, a light green mesoporous silicon carbide.

The prepared mesoporous silicon carbide material has a pore size distribution of 5-25 nm, a specific surface area of 298 m ² /g, and an average particle size of 4.7 nm.

Example 5

(1) Mix resorcinol, formaldehyde, tetraethyl orthosilicate, nitric acid, anhydrous sodium carbonate, deionized water, and absolute ethanol in a molar ratio of 1:2:1:0.1:0.006:2:40 Evenly, stir at 50°C for 60 minutes, add ammonia water to adjust the pH value to 8.2, carry out sol-gel reaction at 50°C for 25 minutes to obtain a wet gel, and age the wet gel at 60°C for 1 day, then in Dry in an oven at 50°C for 36 hours to obtain a silicon carbide precursor.

(2) The silicon carbide precursor was heated to 1550°C at a heating rate of 3°C/min under the protection of argon, and kept for 6 hours, then the temperature was lowered to 700°C, and the argon was replaced with air, and kept for 2 hours to remove residual charcoal, cool to room temperature, take out the sample, and then soak in 10% hydrofluoric acid aqueous solution for 3 hours to remove silicon dioxide in silicon carbide, after washing, filtering and drying, a light green mesoporous silicon carbide.

The prepared mesoporous silicon carbide material has a pore size distribution of 10-30 nm, a specific surface area of 221 m ² /g, and an average particle size of 5.6 nm.

Example 6

(1) Mix resorcinol, formaldehyde, tetraethyl orthosilicate, hydrochloric acid, anhydrous sodium carbonate, deionized water, and absolute ethanol in a molar ratio of 1:2:1.5:0.13:0.005:8:80 Evenly, stir at 60°C for 50 minutes, add ammonia water to adjust the pH value to 8.8, carry out sol-gel reaction at 60°C for 20 minutes to obtain a wet gel, and the wet gel is aged at 70°C for 5 days, and then in Dry in an oven at 40°C for 48 hours to obtain a silicon carbide precursor.

(2) The silicon carbide precursor was heated to 1500°C at a heating rate of 2°C/min under the protection of argon, and kept for 8 hours, then the temperature was lowered to 600°C, and the argon was replaced with air, and kept for 3 hours to remove residual carbon, cool to room temperature, take out the sample, and then soak in 30% hydrofluoric acid aqueous solution for 1 hour to remove silicon dioxide in silicon carbide, after washing, filtering, and drying, a light green mesoporous silicon carbide.

The pore size distribution of the prepared mesoporous silicon carbide material is 5-35nm, the specific surface area is 177m ² /g, and the average particle size is 7nm.

Claims (7)

1. a preparation method of mesoporous silicon carbide material, its concrete steps are as follows: (1) Mix resorcinol, formaldehyde, tetraethyl orthosilicate, acid catalyst, anhydrous sodium carbonate, deionized water, and absolute ethanol in a molar ratio of 1:2: (0.25～2):(0.04～ 0.15):(0.003～0.01):(1～8):(20～160) Mix evenly, stir at 50～70℃ for 30～90 minutes, add ammonia water to adjust the pH value to 7.8～9.5, at 50～70℃ The sol-gel reaction is carried out to obtain a wet gel, and the wet gel is dried to obtain a silicon carbide precursor after aging; (2) Heat the silicon carbide precursor obtained in step (1) to 1450-1600°C at a heating rate of 2-4°C/min under the protection of an inert gas, keep it warm for 3-10 hours, and then lower the temperature to 500- 700°C, replace the inert gas with air, keep warm for 2 to 4 hours to remove residual carbon, cool to room temperature, take out the sample, then soak in hydrofluoric acid, wash with water, filter, and dry to obtain light green medium porous silicon carbide. 2. The preparation method according to claim 1, characterized in that the acidic catalyst described in step (1) is one of hydrochloric acid or nitric acid. 3. The preparation method according to claim 1, characterized in that step (1) sol-gel reaction time is 10-30 minutes. 4. The preparation method according to claim 1, characterized in that the aging condition in step (1) is: aging at 50-75°C for 1-7 days. 5. The preparation method according to claim 1, characterized in that the drying condition in step (1) is: drying at 40-60°C for 24-48 hours. 6. The preparation method according to claim 1, characterized in that the inert gas in step (2) is one of helium or argon. 7. The preparation method according to claim 1, characterized in that the mass fraction of hydrofluoric acid in step (2) is 10-30%, and the soaking time is 1-3 hours.

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