Silicon carbide regulated porous silicon carbide membrane material generated by in-situ reaction and preparation method and application thereof

Abstract

The invention relates to the field of porous materials, in particular to a silicon carbide regulated porous silicon carbide film material generated through in-situ reaction and a preparation method and application thereof. According to the porous silicon carbide film material blank, a framework is formed by original silicon carbide particle aggregate, a silicon-containing component and a carbon-containing component are contained in macropore gaps formed among particles, and in the sintering preparation process of the film material, the silicon-containing component and the carbon-containing component are subjected to an in-situ reaction to generate nanoscale or submicron silicon carbide crystal grains to fill the macropore gaps and form small pores. The original silicon carbide particles and / or the nano-scale or submicron-scale silicon carbide crystal grains are connected through sintering to obtain a hole-embedded hole structure. The innovation of the invention lies in that sintering among silicon carbide particles is promoted by adopting the activity of in-situ reaction, the problem that the pore structure cannot be regulated and controlled when macropores among aggregate particles in the transition layer of the silicon carbide film material are simply stacked and filled by small particles is solved, and the permeability of the silicon carbide film material is favorably improved.

Description

Technical Field

[0001] The invention relates to the field of porous materials, in particular to a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, and a preparation method and application thereof. Background Art

[0002] Porous silicon carbide materials are widely used. They are light in weight, large in specific surface area, high in porosity, good in biocompatibility, and easy to modify in structure. Silicon carbide membranes have high hardness, large flux, long life, and are resistant to harsh environments. They have been widely studied and applied in catalysis, pharmaceuticals, sensors and other fields.

[0003] The membrane can be divided into a support layer, a transition layer and a functional layer, wherein the functional layer realizes functions such as separation and filtration, and the functional layer is very thin and needs to be supported by the support layer, and the two are connected with the help of the transition layer. The transition layer needs to have a strong bonding force with the functional layer and the support layer, but the existing silicon carbide ceramic membranes often use nano silicon carbide particles to make the transition layer. These nano silicon carbide particles can only be partially embedded in the superficial part of the support layer composed of the original silicon carbide particle aggregate, and have poor mechanical bonding strength and thermal shock resistance. They are easy to fall off together with the functional layer, resulting in loss of membrane function; on the other hand, the production cost of nano silicon carbide powder is high, and the cost of using nano silicon carbide to make the transition layer material is high, and the pores are formed by accumulation, which has poor controllability and is easy to be filled during the preparation process.

[0004] In the existing silicon carbide sintering technology, the silicon carbide grains are not completely connected by sintering, but sintering aids such as silicon dioxide and alumina are added. The use of sintering aids can reduce the difficulty of silicon carbide sintering, but the oxide components in the sintering aids are easy to partially melt under high-temperature working conditions, causing the silicon carbide particles to change their distribution, deforming the pore structure, and reducing the membrane strength. Changes in pore size and porosity will also cause changes in membrane flux; the introduction of oxides makes the internal components of doped silicon carbide have different thermal expansion coefficients, which easily accumulates internal stress and produces defects, and has poor thermal shock resistance; the chemical properties of oxides are not as stable as silicon carbide, and they are easily corroded by acids and alkalis and are not resistant to harsh environments. Therefore, it is urgent to prepare a silicon carbide membrane material that is not easy to fall off and deform and can be used under harsh working conditions. Summary of the invention

[0005] The purpose of the present invention is to provide a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, and a preparation method and application thereof, so as to solve the problem that the pore structure cannot be regulated when the large pores between aggregate particles in the transition layer of conventional silicon carbide membrane materials are simply filled with small particles, which is beneficial to improving the permeability of silicon carbide membrane materials.

[0006] The technical solution of the present invention is:

[0007] A porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide. The green body of the porous silicon carbide membrane material forms a framework with original silicon carbide particle aggregates. The macroporous voids formed between the particles contain a silicon-containing component and a carbon-containing component. During the sintering preparation process of the membrane material, the silicon-containing component and the carbon-containing component undergo an in-situ reaction to generate nanoscale or sub-micron-scale silicon carbide grains to fill the macroporous voids and form small pores. Connections are formed between the original silicon carbide particles and the nanoscale or sub-micron-scale silicon carbide grains through sintering to obtain a "pore-in-pore" structure.

[0008] For the porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, the original silicon carbide particles are composed of α-SiC and / or β-SiC, and the size of the original silicon carbide particles is 1 μm to 500 μm.

[0009] For the porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, the porosity p of the macroporous voids formed between the original silicon carbide particles is 0 < p ≤ 70%, and the macropore diameter is 0.5 μm to 300 μm.

[0010] For the porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, the size of the nanoscale or sub-micron-scale silicon carbide grains generated by in-situ reaction is 20 nm to 1 μm, and it is composed of β-SiC and / or α-SiC generated by the polymorphic transformation of β-SiC after high-temperature treatment.

[0011] A preparation method of a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide. The preparation method of the porous silicon carbide membrane material includes the following steps:

[0012] (1) Prepare a dispersion: Disperse the silicon-containing component in solvent A to form dispersion A, and disperse the carbon-containing component in solvent B to form dispersion B. Dispersion A or dispersion B is one of a solution, a sol, and a suspension.

[0013] (2) Aging of the dispersion: Under continuous stirring, place dispersion A and / or dispersion B at a constant temperature of 20°C to 200°C for 1 to 24 h, or adjust the pH value of dispersion A and / or dispersion B to 2 to 12 and age for 1 to 12 h.

[0014] (3) Blending of the dispersions: By weight, under continuous stirring, blend 100 parts of dispersion A in step (1) or step (2) with 5 to 200 parts of dispersion B, or blend 100 parts of dispersion A or dispersion B in step (1) with 5 to 200 parts of dispersion B or dispersion A in step (2) to form a blend containing a silicon-containing component and a carbon-containing component.

[0015] (4) removing the solvent from the mixed solution of step (3), drying at 100° C. to 200° C. for 1 h to 2 h, and then pyrolyzing at 800° C. for 1 h to 3 h under inert gas protection to form a pyrolyzed precursor;

[0016] (5) ball-milling 100 parts of the original silicon carbide particles with 5 to 200 parts of one or more of the following systems to form a blended powder or slurry: the dispersion A or / and the dispersion B obtained in step (1), the dispersion A or / and the dispersion B obtained in step (2), the blended liquid obtained in step (3), and the pyrolyzed precursor obtained in step (4);

[0017] (6) forming the blended powder or slurry obtained in step (5) by one or a combination of two or more of the following methods:

[0018] (i) Isostatic pressing: the blended powder or slurry obtained in step (5) is baked at 30°C to 100°C for 1 to 6 hours and then loaded into a molding mold, and then densified by one or more methods of unidirectional molding, bidirectional molding, hot isostatic pressing, and cold isostatic pressing to obtain a multi-level porous silicon carbide membrane material blank;

[0019] (ii) Grouting method: the blended powder or slurry obtained in step (5), water or alcohol solvent or ketone solvent or ether solvent, binder and additive are uniformly mixed to form slurry, which is then poured into a container and heated to 50-300° C. to completely solidify, thereby obtaining a porous silicon carbide membrane material blank;

[0020] (iii) Extrusion molding method: the blended powder or slurry obtained in step (5), water or alcohol solvent or ketone solvent or ether solvent, binder, and additive are uniformly mixed to form a slurry-like mixture, and then molded by an extruder to obtain a porous silicon carbide membrane material blank;

[0021] (iv) Dip coating method: the blended powder or slurry obtained in step (5), water or alcohol solvent or ketone solvent or ether solvent, binder and additive are uniformly mixed to prepare slurry, and the porous silicon carbide membrane material body is obtained by dip coating;

[0022] (v) Spraying method: the blended powder or slurry obtained in step (5), water or alcohol solvent or ketone solvent or ether solvent, binder and additive are uniformly mixed to form slurry, and a porous silicon carbide membrane material blank is obtained by air pressure spraying or high pressure airless spraying;

[0023] (7) Sintering: Sintering the porous silicon carbide membrane material blank obtained in step (6) at a high temperature of 900 to 2500° C. for a holding time of 10 min to 6 h under a protective atmosphere; the protective atmosphere is selected from one or more of high-purity argon, high-purity hydrogen, high-purity nitrogen, a high-purity hydrogen-argon mixture, and vacuum conditions;

[0024] (8) Post-treatment process: The product obtained by high-temperature sintering in step (7) is subjected to one or more of the following operations: acid solution cleaning, alkaline solution cleaning, deionized water cleaning, anhydrous ethanol cleaning, acetone cleaning, and calcination in air to obtain a porous silicon carbide membrane material.

[0025] The method for preparing a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, wherein the silicon-containing component is selected from one or a combination of two or more of the following substances: silane, silane hydrolysate, orthosilicic acid and mixtures thereof, silicate compounds, and silica sol; and the carbon-containing component is selected from one or a combination of two or more of the following substances: sugar, starch, starch derivatives, cellulose, and organic polymers.

[0026] The method for preparing a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, the sugar includes sucrose, glucose, fructose, invert sugar, maltose, and the organic polymer includes phenolic resin, furfural resin, urea-formaldehyde resin and their corresponding mixtures or modified derivatives.

[0027] The method for preparing a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, in steps (ii) to (v), the binder contains one or more of the following substances: polyvinyl alcohol, polyvinyl butyral, carboxymethyl cellulose, phenolic resin, furfural resin, urea-formaldehyde resin, polyurethane resin, polyethylene glycol, nitrocellulose, cellulose acetate, carboxymethyl cellulose, rosin phenolic resin, modified starch, asphalt, petroleum coke.

[0028] The method for preparing a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, in steps (ii) to (v), the auxiliary agent contains one or more of the following substances: hydrochloric acid, nitric acid, ammonia water, sodium metasilicate, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate, sodium carbonate, sodium silicate, sodium chloride, sodium stearate, sodium citrate, sodium humate, sodium tannate, ammonium oxalate, sodium oxalate, sodium alkylbenzene sulfonate, urotropine, sodium ethylenediaminetetraacetic acid, sulfonates, polyacrylamide, polyacrylic acid and its salts, hydroxymethyl cellulose salts, fish oil, and fatty acids.

[0029] An application of a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide. The porous silicon carbide membrane material is used to prepare an inorganic membrane material support layer, transition layer or functional layer, and is applied in gas-solid separation, catalytic carrier, extraction, fluid distribution or composite material preparation process.

[0030] The design idea of ​​the present invention is:

[0031] The present invention creatively uses the activity of in-situ reaction to promote sintering between silicon carbide particles, prompting the original silicon carbide particles to form connections with nano-scale or submicron silicon carbide grains through sintering to obtain a "hole-in-hole" structure, which is one of the main innovations of the present invention.

[0032] The pure porous silicon carbide membrane produced by the present invention has a structural feature that the original silicon carbide particle aggregate forms a skeleton and macroporous voids, and the nanoscale / submicron silicon carbide grains generated by the in-situ reaction fill the macroporous voids to form small pores. The support layer skeleton structure is extended by the original silicon carbide particle skeleton described in the patent of the present invention, and the overlap between the nanoscale / submicron silicon carbide grains in the macroporous voids and the support layer skeleton structure is increased, thereby improving the mechanical bonding strength between the two and preventing them from falling off easily; in addition, the small pore structure formed by the nanoscale / submicron silicon carbide grains generated by the in-situ reaction is a non-stacked pore structure, which is easy to control, so that the membrane has better permeability and higher flux under the allowable pressure, and has broad research value and application prospects.

[0033] The present invention has the following advantages and beneficial effects:

[0034] 1. The silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide has a "hole-embedded-hole" structure: the original silicon carbide particle aggregate forms a skeleton and macroporous voids, and the nano-scale or submicron-scale silicon carbide grains generated by in-situ reaction fill the macroporous voids and form small holes. The introduction of the "hole-embedded-hole" structure of the present invention is conducive to broadening the range of pore structure regulation of silicon carbide membrane materials.

[0035] 2. The present invention utilizes the activity of in-situ reaction to promote sintering between silicon carbide particles, thereby improving the mechanical strength of the membrane material.

[0036] 3. The porous silicon carbide membrane material of the present invention solves the problem that the pore structure cannot be controlled when the large pores between aggregate particles in the transition layer of the silicon carbide membrane material are simply filled with small particles, which is beneficial to improving the permeability of the silicon carbide membrane material.

[0037] 4. The porous silicon carbide membrane material described in the present invention is heat-resistant, pressure-resistant, acid-resistant, alkali-resistant, and corrosion-resistant, and can produce strong economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of the membrane material of the present invention when used as a transition layer, in which the original silicon carbide particle aggregate forms a skeleton, macroporous voids, and in-situ reaction generates nano-scale or submicron-scale silicon carbide grains to form small pores. In the figure, 1 is a functional layer, 2 is a porous silicon carbide membrane material (structure of the present invention), and 3 is a support layer.

[0039] Figure 2It is a microscopic morphology diagram of the original silicon carbide particle aggregate forming a skeleton and in-situ reaction to generate nano-scale or submicron-scale silicon carbide grains according to the present invention.

[0040] Figure 3 The microscopic morphology of the region where nanometer-scale or submicrometer-scale silicon carbide grains are generated by in-situ reaction at 1400° C. to fill macropores and form small pores is shown in the present invention.

[0041] Figure 4 The microscopic morphology of the region where nanometer-scale or submicrometer-scale silicon carbide grains are generated by in-situ reaction at 1700° C. to fill macropores and form small pores is shown in the present invention. DETAILED DESCRIPTION

[0042] like Figure 1 As shown, when the membrane material of the present invention is used as a transition layer, the original silicon carbide particle aggregate forms a skeleton, macroporous voids and in-situ reactions generate nano-scale or submicron silicon carbide grains to form a porous silicon carbide membrane material 2 with a small pore structure. The upper and lower surfaces of the porous silicon carbide membrane material 2 are the functional layer 1 and the supporting layer 3, respectively. The functional layer 1 and the supporting layer 3 are connected by the porous silicon carbide membrane material 2 as a transition layer.

[0043] like Figure 2 As shown in FIG. 1 , the microscopic morphology of the original silicon carbide particle aggregate forming a skeleton and in-situ reaction to generate nano-scale or submicron-scale silicon carbide grains according to the present invention is shown in FIG. Figure 2 It can be seen that macroporous voids are formed between the original SiC particle aggregates, and the nano-scale or submicron-scale SiC grains generated by the in-situ reaction are interconnected and fill the macroporous voids and form small pores, forming a “hole-embedded-hole” structure.

[0044] In a specific embodiment, the preparation process of the silicon carbide film material regulated by the in-situ reaction to generate silicon carbide according to the present invention is listed in the following embodiments:

[0045] Example 1

[0046] This embodiment is a preparation process of a silicon carbide film material regulated by in-situ reaction to generate silicon carbide, which is specifically as follows:

[0047] (1) preparing a dispersion: dispersing tetraethyl silicate in ethanol to form a solution A with a mass fraction of 50%, and dispersing phenolic resin in ethanol to form a solution B with a mass fraction of 30%;

[0048] (2) Dispersion aging: Solution B was kept at 90°C for 1 h under continuous stirring;

[0049] (3) Dispersion blending: blending 100 g of solution A in step (1) with 100 g of solution B in step (2) under continuous stirring to form a blended liquid;

[0050] (4) removing the solvent from the sample blended in step (3), drying at 110° C. for 1 h, and then pyrolyzing at 800° C. for 3 h under inert gas protection to form a pyrolyzed precursor;

[0051] (5) ball-milling 100 g of original silicon carbide particles with an average particle size of 400 μm and 80 g of the following system to form a blended powder slurry: solution B obtained in step (2) and the pyrolysis precursor obtained in step (4);

[0052] (6) The blended slurry obtained in step (5) is baked at 80° C. for 1 h, and the resulting powder is loaded into a molding mold, first subjected to uniaxial molding at 100 MPa, and then subjected to cold isostatic pressing at 300 MPa to densify the blended powder, thereby obtaining a multi-level porous silicon carbide membrane material blank;

[0053] (7) Sintering: The porous silicon carbide membrane material blank obtained in step (6) is sintered at high temperature in a high-purity argon (volume purity 99.999%) atmosphere at 900° C. for 1 hour, and then heated to 1400° C. for 2 hours.

[0054] (8) Post-treatment process: The sample obtained in step (7) is sequentially cleaned with a 0.1 M nitric acid solution, cleaned with deionized water, and dried to prepare a porous silicon carbide membrane material.

[0055] The obtained porous silicon carbide membrane material has a porosity of 55% and an average pore size of 100 μm. The microscopic morphology of the area where nano-scale or submicron-scale silicon carbide grains are generated by in-situ reaction to fill the macropores and form small pores is as follows: Figure 3 As shown, the average pore size is 300nm. The grains are connected by sintering. Its chemical composition is mainly silicon carbide. The membrane compressive strength is 2MPa and the membrane flux is 200L / (m 2 h).

[0056] Example 2

[0057] This embodiment is a preparation process of a silicon carbide film material regulated by in-situ reaction to generate silicon carbide, which is different from Embodiment 1 in that:

[0058] In step (1), a dispersion is prepared: tetraethyl silicate is dispersed in ethanol to form a solution A with a mass fraction of 80%, and a phenolic resin is dispersed in ethanol to form a solution B with a mass fraction of 50%;

[0059] Step (5) ball-milling 100 g of original silicon carbide particles with an average particle size of 40 μm and 90 g of the following system to form a blended slurry: solution B obtained in step (2) and the pyrolysis precursor obtained in step (4);

[0060] Step (6) is formed by a slip injection method: 100 g of the blended slurry obtained in step (5), 5 g of ethanol, 10 g of phenolic resin, and 1 g of urotropine are uniformly mixed to prepare a slip injection molding slurry, which is injected into a container and heated to 100° C. to completely solidify, thereby obtaining a porous silicon carbide membrane material blank;

[0061] Step (7) sintering: The porous silicon carbide membrane material blank obtained in step (6) is sintered at high temperature in a high-purity argon (volume purity 99.999%) atmosphere at 900°C for 1 hour, and then heated to 1700°C for 1 hour.

[0062] The obtained porous silicon carbide membrane material has a porosity of 45%, an average pore size of 20 μm, and the microscopic morphology of the area where nano-scale or submicron-scale silicon carbide grains are generated by in-situ reaction to fill the macropores and form small pores is as follows: Figure 4 As shown, the average pore size is 500nm. The grains are connected by sintering. Its chemical composition is mainly silicon carbide. The membrane compressive strength is 1.5MPa and the membrane flux is 150L / (m 2 h).

[0063] Example 3

[0064] This embodiment is a preparation process of a silicon carbide film material regulated by in-situ reaction to generate silicon carbide, which is different from Embodiment 1 in that:

[0065] In step (1), a dispersion is prepared: tetraethyl silicate is dispersed in ethylene glycol to form a solution A with a mass fraction of 50%, and a phenolic resin is dispersed in ethanol to form a solution B with a mass fraction of 50%;

[0066] Step (5) ball-milling 100 g of original silicon carbide particles with an average particle size of 10 μm and 90 g of the following system to form a blended slurry: solution B obtained in step (2) and the pyrolyzed precursor obtained in step (4);

[0067] Step (6) adopts air pressure spraying molding: 100g of the blended slurry obtained in step (5), 5g of ethanol, 20g of phenolic resin, and 2g of urotropine are uniformly mixed to prepare an air pressure spraying slurry, which is sprayed on the surface of the supporting membrane material for molding, and after being completely cured at 100°C, a porous silicon carbide membrane material blank is obtained;

[0068] Step (7) sintering: The porous silicon carbide membrane material blank obtained in step (6) is sintered at high temperature in a high-purity argon (volume purity 99.999%) atmosphere at 900° C. for 1 hour, and then heated to 1300° C. for 3 hours.

[0069] The obtained porous silicon carbide membrane material has a porosity of 40%, an average pore size of 10μm, and nano-scale or submicron silicon carbide grains are generated by in-situ reaction to fill the macropores and form small pores with an average pore size of 200nm. The grains are connected by sintering, and its chemical composition is mainly silicon carbide. The membrane compressive strength is 2.5MPa, and the membrane flux is 100L / (m 2 h).

[0070] Example 4

[0071] This embodiment is a preparation process of a silicon carbide film material regulated by in-situ reaction to generate silicon carbide, which is different from Embodiment 1 in that:

[0072] In step (1), a dispersion is prepared: tetraethyl silicate is dispersed in a 30% (volume ratio) ethanol aqueous solution to form a sol A with a mass fraction of 50%, and a phenolic resin is dispersed in ethanol to form a solution B with a mass fraction of 50%;

[0073] Step (3) dispersion blending: blending 100 g of sol A in step (1) with 100 g of solution B in step (2) under continuous stirring to form a blended liquid;

[0074] Step (5) ball-milling 80 g of original silicon carbide particles with an average particle size of 10 μm and 100 g of the following system to form a blended slurry: solution B obtained in step (2) and the pyrolysis precursor obtained in step (4);

[0075] Step (6) adopts air pressure spraying molding: 100g of the blended slurry obtained in step (5), 25g of ethanol, 20g of phenolic resin, and 2g of urotropine are uniformly mixed to prepare an air pressure spraying slurry, which is sprayed on the surface of the supporting membrane material for molding, and after being completely cured at 70°C, a porous silicon carbide membrane material blank is obtained;

[0076] Step (7) sintering: The porous silicon carbide membrane material blank obtained in step (6) is sintered at high temperature in a high-purity argon (volume purity 99.999%) atmosphere at 900°C for 1 hour, and then heated to 1350°C for 3 hours.

[0077] The obtained porous silicon carbide membrane material has a porosity of 47% and an average pore size of 8μm. The nano-scale or submicron silicon carbide grains generated by in-situ reaction fill the macropores and form small pores with an average pore size of 300nm. The grains are connected by sintering. Its chemical composition is mainly silicon carbide. The membrane compressive strength is 1.7MPa and the membrane flux is 80L / (m 2 h).

[0078] Example 5

[0079] This embodiment is a preparation process of a silicon carbide film material regulated by in-situ reaction to generate silicon carbide, which is different from Embodiment 1 in that:

[0080] In step (1), a dispersion is prepared: tetraethyl silicate is dispersed in a 30% (volume ratio) ethanol aqueous solution to form a sol A with a mass fraction of 50%, and a mixed resin of phenolic resin and furfural resin (mass ratio of 1:1) is dispersed in ethanol to form a solution B with a mass fraction of 50%;

[0081] Step (3) dispersion blending: blending 100 g of sol A in step (1) with 100 g of solution B in step (2) under continuous stirring to form a blended liquid;

[0082] Step (5) ball-milling 120 g of original silicon carbide particles with an average particle size of 10 μm and 100 g of the following system to form a blended slurry: solution B obtained in step (2) and the pyrolysis precursor obtained in step (4);

[0083] Step (6) adopts air pressure spraying molding: 100g of the blended slurry obtained in step (5), 25g of ethanol, and 20g of polyurethane prepolymer are evenly mixed to prepare an air pressure spraying slurry, which is sprayed on the surface of the supporting membrane material for molding, and after being completely cured at 110°C, a porous silicon carbide membrane material blank is obtained;

[0084] Step (7) sintering: The porous silicon carbide membrane material blank obtained in step (6) is sintered at high temperature under vacuum conditions, at 900° C. for 1 hour, and then heated to 1350° C. for 3 hours.

[0085] The obtained porous silicon carbide membrane material has a porosity of 52% and an average pore size of 5μm. The in-situ reaction generates nano-scale or submicron silicon carbide grains to fill the macropores and form small pores with an average pore size of 200nm. The grains are connected by sintering. Its chemical composition is mainly silicon carbide. The membrane compressive strength is 2.1MPa and the membrane flux is 130L / (m 2 h).

[0086] Example 6

[0087] This embodiment is a preparation process of a silicon carbide film material regulated by in-situ reaction to generate silicon carbide, which is different from Embodiment 1 in that:

[0088] In step (1) of preparing a dispersion liquid: a silica sol with a mass fraction of 30% is selected as sol A, and a mixed resin of phenolic resin and microcrystalline cellulose (mass ratio of 10:1) is dispersed in ethanol to form a solution B with a mass fraction of 50%;

[0089] Step (3) Dispersion blending: 100 g of sol A in step (1) and 80 g of solution B are blended under continuous stirring to form a blended liquid;

[0090] Step (5) ball-milling 90 g of original silicon carbide particles with an average particle size of 7 μm and 100 g of the following system to form a blended slurry: solution B obtained in step (2) and the pyrolyzed precursor obtained in step (4);

[0091] Step (6) isostatic pressing: 100 g of the blended slurry obtained in step (5) is kept at 90° C. for 1 hour, and then put into a mold and isostatically pressed at 300 MPa to obtain a porous silicon carbide membrane material blank;

[0092] Step (7) sintering: The porous silicon carbide membrane material blank obtained in step (6) is sintered at high temperature under vacuum conditions, at 900° C. for 1 hour, and then heated to 1550° C. for 2 hours.

[0093] The obtained porous silicon carbide membrane material has a porosity of 49% and an average pore size of 3μm. The nano-scale or submicron silicon carbide grains generated by in-situ reaction fill the macropores and form small pores with an average pore size of 220nm. The grains are connected by sintering. Its chemical composition is mainly silicon carbide. The membrane compressive strength is 2.3MPa and the membrane flux is 110L / (m 2 h).

[0094] Example 7

[0095] This embodiment is a preparation process of a silicon carbide film material regulated by in-situ reaction to generate silicon carbide, which is different from Embodiment 1 in that:

[0096] In step (1) of preparing a dispersion liquid, a silica sol with a mass fraction of 30% is selected as sol A, and a mixed resin of phenolic resin and starch (mass ratio of 10:3) is dispersed in ethanol to form a solution B with a mass fraction of 50%;

[0097] Step (3) dispersion blending: blending 100 g of sol A in step (1) with 80 g of solution B in step (2) under continuous stirring to form a blended liquid;

[0098] Step (5) 90 g of original silicon carbide particles with an average particle size of 5 μm are ball-milled and mixed with 100 g of the following system to form a blended slurry: solution B obtained in step (2) and the mixed solution obtained in step (3);

[0099] Step (6) isostatic pressing: 100 g of the blended slurry obtained in step (5) is kept at 70° C. for 1 hour, and then put into a mold and isostatically pressed at 200 MPa to obtain a porous silicon carbide membrane material blank;

[0100] Step (7) sintering: The porous silicon carbide membrane material blank obtained in step (6) is sintered at high temperature in high-purity argon (volume purity 99.999%) at 900°C for 1 hour, and then heated to 1650°C for 1.5 hours.

[0101] The obtained porous silicon carbide membrane material has a porosity of 40% and an average pore size of 3μm. The nano-scale or submicron silicon carbide grains generated by in-situ reaction fill the macropores and form small pores with an average pore size of 200nm. The grains are connected by sintering. Its chemical composition is mainly silicon carbide. The membrane compressive strength is 2.7MPa and the membrane flux is 105L / (m 2 h).

[0102] The results of the embodiments show that the silicon carbide membrane material regulated by the in-situ reaction generated by silicon carbide described in the present invention has a membrane material blank formed by the original silicon carbide particle aggregate to form a skeleton, and the macroporous voids formed between the particles contain silicon-containing components and carbon-containing components. During the sintering preparation process of the membrane material, the silicon-containing component and the carbon-containing component react in situ to generate nano-scale or submicron silicon carbide grains to fill the macroporous voids and form small holes. The original silicon carbide particles and / or nano-scale or submicron silicon carbide grains are connected by sintering to obtain a "hole-embedded-hole" structure. Compared with the traditional porous silicon carbide pore structure regulation process that completely uses nano-silicon carbide, it is more economical, solves the problem that the pore structure cannot be regulated when the macropores between the aggregate particles in the transition layer of the silicon carbide membrane material are simply filled with small particles, and is beneficial to improving the permeability of the silicon carbide membrane material.

Claims

1. A porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide, characterized in that: The porous silicon carbide membrane material green body forms a framework from the original silicon carbide particle aggregate. The large pore voids formed between the particles contain a silicon-containing component and a carbon-containing component. During the sintering preparation process of the membrane material, the silicon-containing component and the carbon-containing component undergo an in-situ reaction to generate nano-scale or sub-micron-scale silicon carbide grains that fill the large pore voids and form small pores. A connection is formed between the original silicon carbide particles and the nano-scale or sub-micron-scale silicon carbide grains through sintering, obtaining a "pore-in-pore" structure.

2. The porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide according to claim 1, characterized in that: The original silicon carbide particles are composed of α-SiC and / or β-SiC, and the size of the original silicon carbide particles is 1μm - 500μm.

3. The porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide according to claim 1, characterized in that: The porosity p of the large pore voids formed between the original silicon carbide particles is 0 < p ≤ 70%, and the large pore diameter is 0.5μm - 300μm.

4. The porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide according to claim 1, characterized in that: The in-situ reaction generates nano-scale or sub-micron-scale silicon carbide grains with a size of 20nm - 1μm, which are composed of β-SiC and / or α-SiC formed by the polymorphic transformation of β-SiC after high-temperature treatment.

5. A method for preparing a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide according to any one of claims 1 to 4, characterized in that: The preparation method of the porous silicon carbide membrane material includes the following steps: (1) Prepare the dispersion: Disperse the silicon-containing component in solvent A to form dispersion A, and disperse the carbon-containing component in solvent B to form dispersion B. Dispersion A or dispersion B is one of a solution, a sol, or a suspension respectively; (2) Aging of the dispersion: Under continuous stirring, place dispersion A and / or dispersion B at a constant temperature of 20°C - 200°C for 1 - 24h, or adjust the pH value of dispersion A and / or dispersion B to 2 - 12 and age for 1 - 12h; (3) Blend the dispersions: By weight, under continuous stirring, blend 100 parts of dispersion A in step (1) or step (2) with 5 - 200 parts of dispersion B, or under continuous stirring, blend 100 parts of dispersion A or dispersion B in step (1) with 5 - 200 parts of dispersion B or dispersion A in step (2) to form a blend liquid containing a silicon-containing component and a carbon-containing component; (4) Remove the solvent from the blend liquid in step (3), dry at 100°C - 200°C for 1 - 2h, and then pyrolyze at 800°C for 1 - 3h under inert gas protection to form a pyrolyzed precursor; (5) By weight, ball-mill and mix 100 parts of the original silicon carbide particles with one or more of the following systems in an amount of 5 - 200 parts to form a blend powder or slurry: dispersion A or / and dispersion B obtained in step (1), dispersion A or / and dispersion B obtained in step (2), the blend liquid obtained in step (3), the pyrolyzed precursor obtained in step (4); (6) Shape the blend powder or slurry obtained in step (5) by one or more combinations of the following methods: (i) Isostatic pressing method: Bake the blend powder or slurry obtained in step (5) at 30°C - 100°C for 1 - 6h, then load it into a shaping mold, and use one or more of the methods of unidirectional die pressing, bidirectional die pressing, hot isostatic pressing, and cold isostatic pressing to densify the blend powder or slurry to obtain a multi-porous silicon carbide membrane material green body; (ii) Grouting method: the blended powder or slurry obtained in step (5), water or alcohol solvent or ketone solvent or ether solvent, binder and additive are uniformly mixed to form slurry, which is then poured into a container and heated to 50-300° C. to completely solidify, thereby obtaining a porous silicon carbide membrane material blank; (iii) Extrusion molding method: the blended powder or slurry obtained in step (5), water or alcohol solvent or ketone solvent or ether solvent, binder, and additive are uniformly mixed to form a slurry-like mixture, and then molded by an extruder to obtain a porous silicon carbide membrane material blank; (iv) Dip coating method: the blended powder or slurry obtained in step (5), water or alcohol solvent or ketone solvent or ether solvent, binder and additive are uniformly mixed to prepare slurry, and the porous silicon carbide membrane material body is obtained by dip coating; (v) Spraying method: the blended powder or slurry obtained in step (5), water or alcohol solvent or ketone solvent or ether solvent, binder and additive are uniformly mixed to form slurry, and a porous silicon carbide membrane material blank is obtained by air pressure spraying or high pressure airless spraying; (7) Sintering: Sintering the porous silicon carbide membrane material blank obtained in step (6) at a high temperature of 900 to 2500° C. for a holding time of 10 min to 6 h under a protective atmosphere; the protective atmosphere is selected from one or more of high-purity argon, high-purity hydrogen, high-purity nitrogen, a high-purity hydrogen-argon mixture, and vacuum conditions; (8) Post-treatment process: The product obtained by high-temperature sintering in step (7) is subjected to one or more of the following operations: acid solution cleaning, alkaline solution cleaning, deionized water cleaning, anhydrous ethanol cleaning, acetone cleaning, and calcination in air to obtain a porous silicon carbide membrane material.

6. The method for preparing a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide according to claim 5, characterized in that: The silicon-containing component is selected from one or a combination of two or more of the following substances: silane, silane hydrolyzate, orthosilicic acid and mixtures thereof, silicate compounds, and silica sol; the carbon-containing component is selected from one or a combination of two or more of the following substances: sugar, starch, starch derivatives, cellulose, and organic polymers.

7. The method for preparing a porous silicon carbide membrane material regulated by in-situ reaction generation of silicon carbide according to claim 6, characterized in that: Sugars include sucrose, glucose, fructose, invert sugar, and maltose; organic polymers include phenolic resins, furfural resins, urea-formaldehyde resins, and corresponding mixtures or modified derivatives thereof.

8. The method for preparing a porous silicon carbide membrane material regulated by in-situ reaction generation of silicon carbide according to claim 5, characterized in that: In steps (ii) to (v), the binder contains one or more of the following substances: polyvinyl alcohol, polyvinyl butyral, carboxymethyl cellulose, phenolic resin, furfural resin, urea-formaldehyde resin, polyurethane resin, polyethylene glycol, nitrocellulose, cellulose acetate, carboxymethyl cellulose, rosin phenolic resin, modified starch, asphalt, and petroleum coke.

9. The method for preparing a porous silicon carbide membrane material regulated by in-situ reaction generation of silicon carbide according to claim 5, characterized in that: In steps (ii) to (v), the auxiliary agent contains one or more of the following substances: hydrochloric acid, nitric acid, ammonia water, sodium metasilicate, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium phosphate, sodium carbonate, sodium silicate, sodium chloride, sodium stearate, sodium citrate, sodium humate, sodium tannate, ammonium oxalate, sodium oxalate, sodium alkylbenzene sulfonate, urotropine, sodium edetate, sulfonate, polyacrylamide, polyacrylic acid and its salts, hydroxymethyl cellulose salt, fish oil, fatty acid.

10. An application of a porous silicon carbide membrane material regulated by in-situ reaction to generate silicon carbide according to any one of claims 1 to 4, characterized in that: The porous silicon carbide membrane material is used for preparing an inorganic membrane material support layer, a transition layer or a functional layer, and is applied in gas-solid separation, catalytic carrier, extraction, fluid distribution or composite material preparation processes.

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