Reaction bonded silicon carbide ceramic membrane and method of making

Abstract

The application discloses a reaction-bonded silicon carbide ceramic membrane and a preparation method thereof, and belongs to the technical field of porous ceramics. The preparation method of the reaction-bonded silicon carbide ceramic membrane comprises the following steps: uniformly mixing first silicon carbide powder, first silicon powder and first titanium-silicon-iron alloy powder, adding an organic binder and a polyhydric alcohol plasticizer, granulating and forming to obtain a support green body; uniformly mixing second silicon carbide powder, second silicon powder, second titanium-silicon-iron alloy powder, a water-based polymer dispersant and water to obtain a slurry, and coating the slurry on the surface of the support green body to obtain a support green body containing a membrane layer; and sintering the support green body containing the membrane layer at 1200 DEG C to 1400 DEG C in a nitrogen-containing gas atmosphere to obtain the reaction-bonded silicon carbide ceramic membrane. The reaction-bonded silicon carbide ceramic membrane prepared by the application has excellent thermal shock resistance.

Description

Technical Field

[0001] This invention relates to the field of porous ceramics technology, and more specifically to a reaction-bonded silicon carbide ceramic membrane and its preparation method. Background Technology

[0002] SiC ceramic membranes possess characteristics such as low bulk density, low coefficient of thermal expansion, high mechanical strength, good fracture toughness, and excellent thermal shock resistance. They also exhibit excellent hydrophilicity, high temperature resistance, and resistance to acid and alkali corrosion. These superior properties make SiC ceramic membranes a novel material for solving environmental problems related to industrial wastewater, high-temperature corrosive gases, and precision filtration and separation.

[0003] However, due to the strong covalent nature of Si-C bonds, the sintering temperature is relatively high. For example, Chinese invention patent CN118307337A discloses a candle-type porous silicon carbide ceramic membrane and its preparation method, which uses two different particle sizes of silicon carbide powder as raw materials and prepares the porous silicon carbide ceramic membrane by sintering at 1750-2000℃ in an argon atmosphere.

[0004] To lower the sintering temperature of porous silicon carbide ceramics, sintering aids are added to the SiC ceramic system, and sintering is carried out in an air atmosphere. The oxidation of the silicon carbide surface and its chemical reaction with the sintering aids form bonding phases such as mullite, cordierite, silica, and a glassy phase. For example, in their paper "The Influence of ρ-Al2O3 Addition Amount on the Performance of In-situ Reactively Bonded Silicon Carbide Film Supports" published in the *Journal of Process Engineering*, Luo Zhiyong et al. used ρ-Al2O3 and basic magnesium carbonate as sintering aids, sintering at 1430℃ in an air atmosphere, utilizing the in-situ reaction between alumina and SiO2 formed by the oxidation of the SiC surface to form mullite bonding. In his master's thesis "Preparation and Performance Study of Low-Cost Tubular SiC Ceramic Membranes," Wang Yongda used coal gangue waste as a sintering aid and graphite as a pore-forming agent, sintering at 1300℃ in an air atmosphere to prepare a SiC support with a porosity of 47%. Chinese invention patent CN118108524A discloses a method for preparing a highly corrosion-resistant silicon carbide porous ceramic membrane support and the resulting product. Silicon carbide powder is used as aggregate, alumina and titanium dioxide as sintering aids, and walnut shell powder as a pore-forming agent. Sintering is performed in air at 1150–1300°C, and mullite bonding is formed through the in-situ reaction of the sintering aids with SiO2 formed by oxidation on the silicon carbide surface. Chinese invention patent CN117700232A discloses a silicon manganese slag-reinforced acid and alkali resistant silicon carbide ceramic membrane support and its preparation method. Silicon manganese slag is used as a sintering aid, and sintering is performed in air at 900–1200°C to form a mullite, anorthite, and rhodochrosite bond. Chinese invention patent CN113999045A discloses a silicon carbide-based porous ceramic filter membrane and its preparation method. Fly ash is used as a sintering aid, and sintering is performed at 1200–1400°C to form a mullite bond. In his master's thesis entitled "Preparation and Performance Characterization of Si3N4-SiC-Bound Porous Ceramic Supports", Romaia prepared a silicon nitride-bonded silicon carbide porous ceramic support with a porosity of 41.8% and a flexural strength of 17.3 MPa by sintering at 1440℃ in a nitrogen atmosphere using 75% SiC and 5% Si powder as raw materials, 4% Y2O3 and 3% Al2O3 as composite sintering aids, and starch as a pore-forming agent. However, the sample mass loss was about 2% in standard acid solution and about 4% in standard alkaline solution.

[0005] Oxide sintering aids can significantly reduce the sintering temperature of SiC ceramics. However, the composite oxides formed by these aids are easily dissolved under strong acids and alkalis, resulting in mass loss. This adversely affects the mechanical properties and pore structure of the support, leading to damage during long-term service. Furthermore, the bound phase is prone to reacting with particulate matter in high-temperature flue gas at high temperatures, forming a low-melting-point phase that clogs the ceramic membrane pores and affects its separation performance.

[0006] Chinese invention patent CN113999046A discloses a method for preparing low-temperature reaction-sintered silicon carbide ceramic membranes. Using NaCl-KCl as the molten salt medium and SiC powder, silicon powder, kaolin, etc., as raw materials, the silicon carbide ceramic membrane is prepared by reaction sintering in the molten salt medium. However, the volatilization of chloride molten salt during the high-temperature sintering process causes severe corrosion to the equipment, and the immersion desalination process generates a large amount of saline wastewater. Furthermore, the mismatch between the thermal expansion coefficient and thermal conductivity of the oxide-bonded phase and the thermal properties of silicon carbide materials also leads to a decrease in the thermal shock resistance of the silicon carbide ceramic membrane. Summary of the Invention

[0007] To address the above problems, this invention provides a reaction-bonded silicon carbide ceramic membrane and its preparation method. The prepared reaction-bonded silicon carbide ceramic membrane exhibits excellent thermal shock resistance.

[0008] The first objective of this invention is to provide a method for preparing a reaction-bonded silicon carbide ceramic film, comprising the following steps:

[0009] After uniformly mixing the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder, an organic binder and a polyol plasticizer are added, and the mixture is granulated and molded to obtain a green support body.

[0010] The second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, the water-based polymer dispersant and water are mixed evenly to obtain a slurry. The slurry is then coated on the surface of the support green body to obtain a support green body containing a film layer.

[0011] In a nitrogen-containing gas atmosphere, a green body containing a film layer is sintered at 1200℃~1400℃ to obtain a reaction-bonded silicon carbide ceramic film.

[0012] For example, sintering temperatures are 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, etc., but are not limited to the listed values. Other unlisted values ​​within the above range also apply.

[0013] In a preferred embodiment of the present invention, the mass ratio of the first silicon carbide powder to the first silicon powder is 70-95:5-30; for example, the mass ratio of the first silicon carbide powder to the first silicon powder is 70:5, 70:10, 70:20, 70:30, 80:5, 80:10, 80:20, 80:30, 90:5, 90:10, 90:20, 90:30, 95:5, 95:10, 95:20, 95:30, etc.

[0014] The mass of the first titanium-silicon-iron alloy powder is 0.1% to 50% of the mass of the silicon powder. For example, the mass of the first titanium-silicon-iron alloy powder is 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% of the mass of the first silicon powder, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0015] In a preferred embodiment of the present invention, the mass ratio of the second silicon carbide powder to the second silicon powder is 80-90:10-20; for example, the mass ratio of the second silicon carbide powder to the second silicon powder is 80:10, 80:15, 80:20, 85:10, 85:15, 85:20, 90:10, 90:15, 90:20, etc.

[0016] The mass of the second titanium-silicon-iron alloy powder is 0.1% to 50% of the mass of the second silicon powder. For example, the mass of the second titanium-silicon-iron alloy powder is 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% of the mass of the second silicon powder, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0017] In a preferred embodiment of the present invention, the sintering time is 0.5h to 7h. For example, the sintering time is 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0018] In a preferred embodiment of the present invention, the coating thickness is 150μm to 200μm, for example, the coating thickness is 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0019] In a preferred embodiment of the present invention, the amount of organic binder added is 2 to 6% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; for example, the amount of organic binder added is 2%, 3%, 4%, 5%, 6%, etc. of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder, but it is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0020] The organic binder is one of phenolic resin, epoxy resin, aqueous solution of polyvinyl alcohol, aqueous solution of polyethylene glycol, carboxymethyl cellulose, and liquid paraffin.

[0021] In a preferred embodiment of the present invention, the amount of polyol plasticizer added is 1% to 30% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder. For example, the amount of polyol plasticizer added is 1%, 5%, 10%, 15%, 20%, 25%, 30% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0022] The polyol plasticizer is glycerol or diethylene glycol.

[0023] In a preferred embodiment of the present invention, the amount of aqueous polymeric dispersant added is 0.5% to 5% of the total mass of the slurry; the amount of aqueous polymeric dispersant added is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% of the total mass of the slurry, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0024] The aqueous polymeric dispersant is one of polyethylene glycol, polyvinyl alcohol, hydroxypropyl methylcellulose, polyacrylamide, and polypyrrolidone.

[0025] In a preferred embodiment of the present invention, the average particle size of the first silicon carbide powder is 3μm to 45μm; for example, the average particle size of the first silicon carbide powder is 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, etc.

[0026] The average particle size of the first silicon powder is 1μm to 45μm; for example, the average particle size of the first silicon powder is 1μm, 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, etc.

[0027] The average particle size of the first titanium-silicon-iron alloy powder is 3μm to 5μm; for example, the average particle size of the first titanium-silicon-iron alloy powder is 3μm, 4μm, 5μm, etc.

[0028] The particle size span of the first silicon carbide powder is ≤2.5; the particle size span of the second silicon carbide powder is ≤2.5.

[0029] The particle size span of the first silicon powder is ≤2.5; the particle size span of the second silicon powder is ≤2.5.

[0030] The average particle size of the second titanium-silicon-iron alloy powder is ≤5μm.

[0031] The average particle size of the second silicon powder is ≤5μm.

[0032] The average particle size of the second silicon carbide powder is ≤5μm.

[0033] A second objective of this invention is to provide a reaction-bonded silicon carbide ceramic film prepared by the above-described preparation method.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This invention introduces silicon powder and titanium-silicon-iron alloy powder into the raw materials. Utilizing the in-situ nitriding reaction of silicon powder and titanium-silicon-iron alloy powder in a nitrogen atmosphere, a reactive bond is formed, significantly reducing the sintering temperature of silicon carbide ceramics by more than 350°C compared to pure porous silicon carbide ceramics. The silicon powder and titanium-silicon-iron alloy exhibit significant volume expansion during nitriding, which helps refine the pores. The bonding phases formed by silicon powder and titanium-silicon-iron alloy during the reactive sintering process are TiN and Si3N4. These two bonding phases have high thermal property compatibility with SiC materials, which is beneficial to the thermal shock resistance of silicon carbide ceramics. Simultaneously, both bonding phases possess excellent chemical stability and can withstand strong acid and alkali corrosion, allowing the resulting reactive-bonded silicon carbide ceramic film to be used in strong acid and alkali environments.

[0036] This invention introduces titanium-silicon-iron alloy powder into the raw materials. The titanium-silicon-iron alloy has a low nitriding temperature and catalyzes the nitriding of silicon powder, promoting its nitriding and further reducing the nitriding temperature. The catalytic nitriding of silicon by the titanium-silicon-iron alloy promotes the growth of Si3N4 whiskers. The formation of a large number of silicon nitride whiskers not only strengthens and toughens the ceramic support and improves the mechanical properties of the membrane, but also, the interlocking silicon nitride whiskers further segment and refine the pores, improving the pore structure of the support and membrane, thus giving the ceramic membrane superior separation performance.

[0037] In this invention, the volume expansion during the nitriding reaction of titanium-silicon-iron alloy and silicon powder, as well as the segmentation of pores by whiskers, can optimize the pore size. The pore size of the support and film can be controlled by the ratio of raw materials and the particle size distribution.

[0038] The technical solution adopted in this invention is a near-net-shape method, which results in small dimensional changes in the green body during sintering, which is beneficial for the structural control of ceramic membrane components.

[0039] The sintering temperature of this invention is lower than the melting point of silicon powder, which avoids the formation of liquid phase during the silicon powder nitriding process. Since no liquid phase is involved in the sintering process, the volume shrinkage during the sintering process is avoided. The resulting reaction-bonded silicon carbide ceramic film has a similar apparent porosity to the green body. The reaction-bonded silicon carbide ceramic film can maintain a high porosity and has a high pure water flux and gas flux.

[0040] This invention prepares SiC ceramic supports and films through one-step sintering, which can further reduce production costs.

[0041] Compared with the existing two-step sintering preparation method of ceramic film support and film layer, the present invention prepares SiC ceramic support and film layer by one-step sintering, which can significantly reduce the energy consumption of the production process. Attached Figure Description

[0042] Figure 1 Scanning electron microscope image of the reaction-bonded silicon carbide ceramic film prepared in Example 2.

[0043] Figure 2 Scanning electron microscope image of the reaction-bonded silicon carbide ceramic film prepared in Example 1.

[0044] Figure 3 Scanning electron microscope image of the reaction-bonded silicon carbide ceramic film prepared in Example 5.

[0045] Figure 4 The XRD pattern of the reaction-bonded silicon carbide ceramic film prepared in Example 2.

[0046] Figure 5 The XRD pattern of the reaction-bonded silicon carbide ceramic film prepared in Comparative Example 1. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] A method for preparing a silicon carbide ceramic film includes the following steps:

[0049] After uniformly mixing the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder, an organic binder and a polyol plasticizer are added, and the mixture is granulated and molded to obtain a green support body.

[0050] The second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, the water-based polymer dispersant and water are mixed evenly to obtain a slurry. The slurry is then coated on the surface of the support green body to obtain a support green body containing a film layer.

[0051] Under a nitrogen-containing gas atmosphere, the green support is sintered at 1200℃~1400℃ to obtain a silicon carbide ceramic film. The nitrogen-containing gas is nitrogen, ammonia, or a nitrogen-hydrogen mixture.

[0052] During the fabrication process, the green support needs to have high porosity, large pore size, and high strength; the membrane layer needs to have small pore size and narrow pore size distribution; and the membrane layer needs to be thin to improve flux. Membrane flux is affected by parameters such as pore size, porosity, membrane thickness, and tortuosity factor. Therefore, in the fabrication process, the green support is prepared first, and then the membrane layer is coated.

[0053] During sintering, the silicon powder undergoes a significant drop in sintering temperature under the catalytic nitriding effect of the titanium-silicon-iron alloy. At sintering temperatures of 1200–1400℃, it maintains high apparent porosity while exhibiting high compressive strength, thus significantly reducing production costs. During sintering, a nitrogen-containing gas atmosphere serves as the reaction gas source, where silicon or the alloy reacts with nitrogen to form products such as silicon nitride and titanium nitride, thereby forming a bonded phase.

[0054] The catalytic nitriding process promotes the growth of Si3N4 whiskers, which enhances and toughens the ceramic support and film. At the same time, the silicon nitride whiskers can refine the pores.

[0055] The reaction bonding phases are TiN and Si3N4, both of which have excellent acid and alkali corrosion resistance. The reaction-bonded silicon carbide ceramic films prepared under the conditions of each embodiment have a very high retention rate of compressive strength after being corroded by strong acids and alkalis, indicating that the reaction-bonded silicon carbide ceramic films prepared by the present invention have excellent acid and alkali corrosion resistance.

[0056] The technical solution adopted in this invention is a near-net-shape method. The reaction-bonded silicon carbide ceramic film obtained after sintering has a linear change of less than 0.1% relative to the green body, exhibiting extremely high volume stability, which is beneficial for the precise design and preparation of the film structure.

[0057] Therefore, the reaction-bonded silicon carbide ceramic membrane prepared by this invention has the characteristics of high porosity, adjustable pore size, excellent resistance to strong acid and alkali corrosion, good thermal shock resistance, and excellent mechanical properties.

[0058] The ratio of silicon powder, silicon carbide powder, and alloy will have a certain influence on the strength and pore size distribution of the product. Therefore, in the preparation process, the mass ratio of the first silicon carbide powder to the first silicon powder is 70-95:5-30; the mass of the first titanium-silicon-iron alloy powder is 0.1%-50% of the mass of the silicon powder.

[0059] The mass ratio of the second silicon carbide powder to the second silicon powder is 80-90:10-20; the mass of the second titanium-silicon-iron alloy powder is 0.1%-50% of the mass of the silicon powder.

[0060] In one embodiment of the present invention, the sintering time is 0.5 h to 7 h. During the sintering process, the sintering time has a certain influence on the degree of nitriding reaction, that is, it affects the strength and pore size distribution.

[0061] In one embodiment of the present invention, the coating thickness is 150 μm to 200 μm.

[0062] In one embodiment of the present invention, the amount of organic binder added is 2 to 6% of the total mass of silicon carbide powder, silicon powder and titanium-silicon-iron alloy powder.

[0063] The organic binder is one of phenolic resin, epoxy resin, aqueous solution of polyvinyl alcohol, aqueous solution of polyethylene glycol, carboxymethyl cellulose, and liquid paraffin.

[0064] The addition of polyol plasticizers can affect the molding of the product and also affect its porosity. Therefore, during the preparation process, the amount of polyol plasticizer added is 1 to 30% of the total mass of silicon carbide powder, silicon powder and titanium-silicon-iron alloy powder.

[0065] The polyol plasticizer is glycerol or diethylene glycol.

[0066] Waterborne polymeric dispersants affect the properties of the slurry, which in turn affects the coating and the separation performance of the film. Therefore, the amount of waterborne polymeric dispersant added during the preparation process is 0.5% to 5% of the total mass of the slurry.

[0067] The aqueous polymeric dispersant is one of polyethylene glycol, polyvinyl alcohol, hydroxypropyl methylcellulose, polyacrylamide, and polypyrrolidone.

[0068] In one embodiment of the present invention, the average particle size of the first silicon carbide powder is 3 μm to 45 μm.

[0069] The average particle size of the first silicon powder is 1μm to 45μm.

[0070] The average particle size of the first titanium-silicon-iron alloy powder is 3μm to 45μm.

[0071] The particle size span of the first silicon carbide powder is ≤2.5; the particle size span of the second silicon carbide powder is ≤2.5.

[0072] The particle size span of the first silicon powder is ≤2.5; the particle size span of the second silicon powder is ≤2.5.

[0073] The average particle size of the second titanium-silicon-iron alloy powder is ≤5μm.

[0074] The average particle size of the second silicon powder is ≤5μm.

[0075] The average particle size of the first silicon carbide powder is ≤5μm.

[0076] It is understood that the particle size span values ​​of the first silicon carbide powder and the second silicon carbide powder used in this invention can be the same or different, as long as the particle size span value requirement is met.

[0077] The particle size span values ​​of the first silicon powder and the second silicon powder can be the same or different, as long as the particle size span value requirement is met.

[0078] During the preparation process, a high-porosity product is obtained through appropriate particle size distribution.

[0079] The titanium-silicon-iron alloy powder contains ≥20% (w) Ti and 3-15% (w) Fe.

[0080] The reaction-bonded silicon carbide ceramic membrane prepared by this invention can be used for separation and filtration. For example, a 200nm membrane can be used for emulsified oil-water separation; a 400nm membrane can be used for papermaking wastewater filtration and reuse; and an 800nm ​​membrane can be used for whey protein filtration. Membranes with different pore sizes can also be used for solid-liquid separation of mineral slurries and powder slurries, as well as flue gas filtration, depending on the application scenario and actual production needs.

[0081] The silicon carbide powder and silicon powder used in this invention were purchased from the market.

[0082] The titanium-silicon-iron alloy powder was prepared according to invention patent ZL2005100196643, and the specific preparation method is as follows:

[0083] The selected titanium-containing blast furnace slag has the following chemical composition: CaO 24.62 wt%, SiO2 27.97 wt%, Al2O3 13.40 wt%, MgO 7.68 wt%, Fe2O3 3.19 wt%, TiO2 20.59 wt%, and MnO 0.89 wt%. A reducing agent, a mixture of aluminum, carbon, magnesium, and iron, is added at 40% of the mass of the titanium-containing blast furnace slag in a mass ratio of 4:6:1.5:1.

[0084] After the components are mixed evenly, the alloy is subjected to a molten reduction reaction at 2300℃ for 1 hour in a plasma furnace under Ar gas protection. The alloy and the melt are then separated in the hot state and cooled to obtain an iron-silicon-titanium alloy.

[0085] Example 1

[0086] This embodiment provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0087] Step 1: Preparation of the support

[0088] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 70:30; weigh the first titanium-silicon-iron alloy powder according to a mass of 5% of the mass of the first silicon powder; weigh the organic binder phenolic resin 2130 according to an addition amount of 4% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; and weigh the polyol plasticizer glycerin according to an addition amount of 15% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder.

[0089] It should be noted that the average particle size of the first silicon carbide powder is 5.0 μm, the average particle size of the first titanium-silicon-iron alloy powder is 7.8 μm, and the average particle size of the first silicon powder is 6.4 μm.

[0090] Step 1.2: Mix the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder in proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. The agglomerates are shaped and dried to obtain a green support body.

[0091] Step 2, Film Preparation

[0092] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to a mass ratio of 80:20; weigh the second titanium-silicon-iron alloy powder according to a mass ratio of 50% of the second silicon powder; weigh the water-based polymer dispersant polyethylene glycol 2000 according to an addition amount of 4.0% of the total mass of the slurry.

[0093] It should be noted that the average particle size of the second silicon carbide powder is 5.0 μm, the average particle size of the second silicon powder is 0.4 μm, and the average particle size of the second titanium-silicon-iron alloy powder is 1.0 μm.

[0094] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, deionized water, and water-based polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 30% (w).

[0095] Then, the green support blank is immersed in the slurry for a period of time by the impregnation method and then pulled out and dried. A film layer with a thickness of about 150 μm is prepared on the outer surface of the green support blank. After drying, it is sintered at 1400℃ for 7 h in a nitrogen atmosphere to obtain the reaction-bonded silicon carbide ceramic film.

[0096] In this embodiment, the particle size distribution (D) of the first silicon carbide powder is as follows: 90 -D 10 ) / D 50 The particle size distribution of the second silicon carbide powder is 1.6 (D).90 -D 10 ) / D 50 It is 1.7.

[0097] In this embodiment, the particle size range (D) of the first silicon powder 90 -D 10 ) / D 50 The particle size distribution of the second silicon powder is 2.0 (D). 90 -D 10 ) / D 50 It is 2.2.

[0098] The reaction-bonded silicon carbide ceramic membrane prepared in this embodiment has a compressive strength of 52 MPa, with a support porosity of 39% and an average pore size of 1.2 μm, an average pore size of 140 nm in the membrane layer, and a pure water flux of 0.5 m³ / min. 3 / (m 2 (·h·bar). After immersion in a 37.5% (w) hydrochloric acid solution at 20°C for 120 h, the compressive strength retention rate is >99.5%. After immersion in a 40% (w) NaOH solution at 20°C for 120 h, the compressive strength retention rate is >99.5%.

[0099] The reaction-bonded silicon carbide ceramic membrane prepared in this embodiment was used in an oil-water separation test of emulsified oil with a mineral oil concentration of 200 mg / L. The rejection rate was 99.2% when the transmembrane pressure difference was 0.01 MPa and 95.3% when the transmembrane pressure difference was 0.05 MPa. This ceramic membrane was also used to treat carbon black wastewater with a turbidity of 30 NTU and a chemical oxygen demand (COD) of 380 mg / L. After membrane separation, the turbidity removal rate was approximately 100%, and the COD decreased to 62 mg / L.

[0100] Example 2

[0101] This embodiment provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0102] Step 1: Preparation of the support

[0103] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 75:25; weigh the first titanium-silicon-iron alloy powder according to a mass ratio of 10% of the first silicon powder; weigh the organic binder epoxy resin E44 according to an organic binder addition amount of 5% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; and weigh the polyol plasticizer diethylene glycol according to an organic binder addition amount of 25% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder.

[0104] It should be noted that the average particle size of the first silicon carbide powder is 9.6 μm, the average particle size of the first titanium-silicon-iron alloy powder is 13.2 μm, and the average particle size of the first silicon powder is 15 μm.

[0105] Step 1.2: Mix the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder in proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. The agglomerates are shaped and dried to obtain a green support body.

[0106] Step 2, Film Preparation

[0107] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to the mass ratio of the second silicon carbide powder to the second silicon powder of 82:18; weigh the second titanium-silicon-iron alloy powder according to the mass of the second silicon powder of 10%; weigh the water-based polymer dispersant polyvinyl alcohol 1788 according to the amount of water-based polymer dispersant added of 5% of the total mass of the slurry.

[0108] It should be noted that the average particle size of the second silicon carbide powder is 3.6 μm, the average particle size of the second silicon powder is 0.5 μm, and the average particle size of the second titanium-silicon-iron alloy powder is 0.8 μm.

[0109] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, deionized water, and water-based polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 40 (w).

[0110] Then, the green support blank is immersed in the slurry for a period of time by the impregnation method and then pulled out and dried. A film layer with a thickness of about 150 μm is prepared on the outer surface of the green support blank. After drying, it is sintered at 1200℃ for 6 hours in an ammonia atmosphere to obtain the reaction-bonded silicon carbide ceramic film.

[0111] In this embodiment, the particle size distribution (D) of the first silicon carbide powder is as follows: 90 -D 10 ) / D 50 The value is 2.2, and the particle size range of the second silicon carbide powder (D) is... 90 -D 10 ) / D 50 It is 2.4.

[0112] In this embodiment, the particle size range (D) of the first silicon powder 90 -D 10 ) / D 50 The particle size distribution of the second silicon powder is 2.5 (D). 90 -D 10 ) / D 50 It is 2.3.

[0113] like Figure 4 As shown in the XRD pattern, TiN and Si3N4 were generated in this embodiment. The presence of TiN and Si3N4 effectively improves the strength of the reaction-bonded silicon carbide ceramic membrane. The reaction-bonded silicon carbide ceramic membrane obtained in this embodiment has a compressive strength of 48 MPa, with a support porosity of 42% and an average pore size of 1.8 μm, an average pore size of 280 nm in the membrane layer, and a pure water flux of 0.9 m³ / s. 3 / (m 2 (·h·bar). After immersion in a 37.5% (w) hydrochloric acid solution at 20°C for 120 h, the compressive strength retention rate is >99.5%. After immersion in a 40% (w) NaOH solution at 20°C for 120 h, the compressive strength retention rate is >99.5%.

[0114] Example 3

[0115] This embodiment provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0116] Step 1: Preparation of the support

[0117] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 80:20; weigh the first titanium-silicon-iron alloy powder according to a mass ratio of 20% of the first silicon powder; weigh the organic binder polyvinyl alcohol aqueous solution according to an addition amount of 6% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; and weigh the polyol plasticizer diethylene glycol acetate according to an addition amount of 30% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder.

[0118] It should be noted that the average particle size of the first silicon carbide powder is 12.3 μm, the average particle size of the first titanium-silicon-iron alloy powder is 11.5 μm, and the average particle size of the first silicon powder is 9.0 μm. The mass fraction of the polyvinyl alcohol aqueous solution is 3%, and the polyvinyl alcohol is polyvinyl alcohol 1788.

[0119] Step 1.2: Mix the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder in proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. The agglomerates are shaped and dried to obtain a green support body.

[0120] Step 2, Film Preparation

[0121] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to a mass ratio of 84:16; weigh the second titanium-silicon-iron alloy powder according to a mass ratio of 20% of the second silicon powder; weigh the water-based polymer dispersant hydroxypropyl methylcellulose according to an addition amount of 3.2% of the total mass of the slurry. The molecular weight of the hydroxypropyl methylcellulose used in this embodiment is 86,000.

[0122] It should be noted that the average particle size of the second silicon carbide powder is 2.4 μm, the average particle size of the second silicon powder is 0.9 μm, and the average particle size of the second titanium-silicon-iron alloy powder is 0.6 μm.

[0123] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, deionized water, and water-based polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 50% (w).

[0124] Then, the green support was immersed in the slurry for a period of time using an impregnation method, then pulled out and dried. A film layer with a thickness of approximately 150 μm was prepared on the outer surface of the green support. After drying, it was sintered at 1250 °C for 4 hours in a nitrogen-hydrogen mixed atmosphere to obtain a reaction-bonded silicon carbide ceramic film. It should be noted that in this embodiment, the volume ratio of hydrogen in the nitrogen-hydrogen mixed atmosphere is 4%.

[0125] In this embodiment, the particle size distribution (D) of the first silicon carbide powder is as follows: 90 -D 10 ) / D 50 The particle size distribution of the second silicon carbide powder is 2.3 (D). 90 -D 10 ) / D 50 It is 2.5.

[0126] In this embodiment, the particle size range (D) of the first silicon powder 90 -D 10 ) / D 50 The particle size distribution of the second silicon powder is 1.9 (D). 90 -D 10 ) / D 50 It is 1.6.

[0127] The reactive-bonded silicon carbide ceramic membrane obtained in this embodiment has a pressure resistance of 40 MPa, with a support porosity of 40% and an average pore size of 1.6 μm, an average pore size of 340 nm in the membrane layer, and a pure water flux of 1.1 m³ / min. 3 / (m 2(·h·bar). After immersion in a 37.5% (w) hydrochloric acid solution at 20°C for 120 h, the compressive strength retention rate is >99.5%. After immersion in a 40% (w) NaOH solution at 20°C for 120 h, the compressive strength retention rate is >99.5%.

[0128] Example 4

[0129] This embodiment provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0130] Step 1: Preparation of the support

[0131] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 85:15; weigh the first titanium-silicon-iron alloy powder according to a mass ratio of 30% of the first silicon powder; weigh the organic binder polyethylene glycol 2000 aqueous solution according to an organic binder addition amount of 2% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; weigh the polyol plasticizer glycerin according to an organic binder addition amount of 5% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder.

[0132] It should be noted that the average particle size of the first silicon carbide powder is 18 μm, the average particle size of the first titanium-silicon-iron alloy powder is 16.4 μm, and the average particle size of the first silicon powder is 0.5 μm.

[0133] Step 1.2: Mix the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder in proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. The agglomerates are shaped and dried to obtain a green support body.

[0134] Step 2, Film Preparation

[0135] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to a mass ratio of 86:14; weigh the second titanium-silicon-iron alloy powder according to a mass ratio of 30% of the second silicon powder; weigh the water-based polymer dispersant polyacrylamide according to an addition amount of 0.8% of the total mass of the slurry.

[0136] It should be noted that the average particle size of the second silicon carbide powder is 0.8 μm, the average particle size of the second silicon powder is 0.9 μm, and the average particle size of the second titanium-silicon-iron alloy powder is 0.4 μm. The polyacrylamide used in this embodiment was purchased and is a non-ionic polyacrylamide with a molecular weight of 2,000,000-14,000,000.

[0137] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, deionized water, and water-based polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 60 (w).

[0138] Then, the green support blank is immersed in the slurry for a period of time by the impregnation method and then pulled out and dried. A film layer with a thickness of about 150 μm is prepared on the outer surface of the green support blank. After drying, it is sintered at 1300℃ for 1 h in a nitrogen atmosphere to obtain the reaction-bonded silicon carbide ceramic film.

[0139] In this embodiment, the particle size distribution (D) of the first silicon carbide powder is as follows: 90 -D 10 ) / D 50 The particle size distribution of the second silicon carbide powder is 1.8 (D). 90 -D 10 ) / D 50 It is 2.3.

[0140] In this embodiment, the particle size span (D) between the first silicon powder and the second silicon powder 90 -D 10 ) / D 50 Both are 1.5.

[0141] The reactive-bonded silicon carbide ceramic membrane obtained in this embodiment has a pressure resistance of 33 MPa, with a support porosity of 48% and an average pore size of 2.6 μm, an average pore size of 520 nm in the membrane layer, and a pure water flux of 1.5 m³ / min. 3 / (m 2 (·h·bar). After immersion in a 37.5% (w) hydrochloric acid solution at 20°C for 120 h, the compressive strength retention rate is >99.5%. After immersion in a 40% (w) NaOH solution at 20°C for 120 h, the compressive strength retention rate is >99.5%.

[0142] Example 5

[0143] This embodiment provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0144] Step 1: Preparation of the support

[0145] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 90:10; weigh the first titanium-silicon-iron alloy powder according to a mass ratio of 40% of the first silicon powder; weigh the organic binder carboxymethyl cellulose according to an organic binder addition amount of 3% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; weigh the polyol plasticizer glycerin according to an organic binder addition amount of 10% of the total powder mass. The viscosity of the carboxymethyl cellulose used in this embodiment is 800-1000 mPa·s.

[0146] It should be noted that the average particle size of the first silicon carbide powder is 19.6 μm, the average particle size of the first titanium-silicon-iron alloy powder is 1.2 μm, and the average particle size of the first silicon powder is 2.8 μm.

[0147] Step 1.2: Mix the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder in proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. The agglomerates are shaped and dried to obtain a green support body.

[0148] Step 2, Film Preparation

[0149] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to a mass ratio of 88:12; weigh the second titanium-silicon-iron alloy powder according to a mass ratio of 40% of the second silicon powder; weigh the water-based polymer dispersant polypyrrolidone K90 according to an addition amount of 0.5% of the total mass of the slurry.

[0150] It should be noted that the average particle size of the second silicon carbide powder is 1.0 μm, the average particle size of the second silicon powder is 1.8 μm, and the average particle size of the second titanium-silicon-iron alloy powder is 0.2 μm.

[0151] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, deionized water, and water-based polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 70% (w).

[0152] Then, the green support blank is immersed in the slurry for a period of time by the impregnation method and then pulled out and dried. A film layer with a thickness of about 150 μm is prepared on the outer surface of the green support blank. After drying, it is sintered at 1320℃ for 5.5 h in an ammonia atmosphere to obtain the reaction-bonded silicon carbide ceramic film.

[0153] In this embodiment, the particle size distribution (D) of the first silicon carbide powder is as follows: 90 -D 10 ) / D 50The particle size distribution of the second silicon carbide powder is 1.8 (D). 90 -D 10 ) / D 50 It is 1.6.

[0154] In this embodiment, the particle size range (D) of the first silicon powder 90 -D 10 ) / D 50 The particle size distribution of the second silicon powder is 1.8 (D). 90 -D 10 ) / D 50 It is version 2.0.

[0155] The reactive-bonded silicon carbide ceramic membrane obtained in this embodiment has a pressure resistance of 35 MPa, with a support porosity of 38% and an average pore size of 2.1 μm, an average membrane pore size of 370 nm, and a pure water flux of 1.2 m³ / min. 3 / (m 2 (·h·bar). After immersion in a 37.5% (w) hydrochloric acid solution at 20°C for 120 h, the compressive strength retention rate is >99.5%. After immersion in a 40% (w) NaOH solution at 20°C for 120 h, the compressive strength retention rate is >99.5%.

[0156] Example 6

[0157] This embodiment provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0158] Step 1: Preparation of the support

[0159] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 95:5; weigh the first titanium-silicon-iron alloy powder according to a mass ratio of 50% of the first silicon powder; weigh the organic binder liquid paraffin according to an organic binder addition amount of 4.5% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; weigh the polyol plasticizer diethylene glycol according to an organic alcohol plasticizer addition amount of 1.0% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder.

[0160] It should be noted that the average particle size of the first silicon carbide powder is 25 μm, the average particle size of the first titanium-silicon-iron alloy powder is 20 μm, and the average particle size of the first silicon powder is 1.0 μm.

[0161] Step 1.2: Mix the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder in proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. The agglomerates are shaped and dried to obtain a green support body.

[0162] Step 2, Film Preparation

[0163] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to a mass ratio of 90:10; weigh the second titanium-silicon-iron alloy powder according to a mass ratio of 3% of the second silicon powder; weigh the water-based polymer dispersant polyvinyl alcohol 2000 according to an addition amount of 2.0% of the total mass of the slurry.

[0164] It should be noted that the average particle size of the second silicon carbide powder is 0.3 μm, the average particle size of the second silicon powder is 2 μm, and the average particle size of the second titanium-silicon-iron alloy powder is 0.2 μm.

[0165] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, deionized water, and water-based polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 45% (w).

[0166] Then, the green support was immersed in the slurry for a period of time using an impregnation method, then pulled out and dried. A film layer with a thickness of approximately 150 μm was prepared on the outer surface of the green support. After drying, it was sintered at 1280 °C for 10 h in a nitrogen and hydrogen mixed atmosphere to obtain a reaction-bonded silicon carbide ceramic film. It should be noted that in this embodiment, the volume ratio of hydrogen in the nitrogen-hydrogen mixed gas is 1.5%.

[0167] In this embodiment, the particle size distribution (D) of the first silicon carbide powder is as follows: 90 -D 10 ) / D 50 The particle size distribution of the second silicon carbide powder is 1.4 (D). 90 -D 10 ) / D 50 It is 1.2.

[0168] In this embodiment, the particle size range (D) of the first silicon powder 90 -D 10 ) / D 50 The particle size distribution of the second silicon powder is 1.6 (D). 90 -D 10 ) / D 50 It is 1.3.

[0169] The reactive-bonded silicon carbide ceramic membrane obtained in this embodiment has a pressure resistance of 23 MPa, with a support porosity of 50% and an average pore size of 2.8 μm, an average membrane pore size of 760 nm, and a pure water flux of 1.8 m³ / s. 3 / (m 2(·h·bar). After immersion in a 37.5% (w) hydrochloric acid solution at 20°C for 120 h, the compressive strength retention rate is >99.5%. After immersion in a 40% (w) NaOH solution at 20°C for 120 h, the compressive strength retention rate is >99.5%.

[0170] Example 7

[0171] This embodiment provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0172] Step 1: Preparation of the support

[0173] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 80:20; weigh the first titanium-silicon-iron alloy powder according to a mass ratio of 0.1% of the first silicon powder; weigh the organic binder liquid paraffin according to an organic binder addition amount of 5% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; weigh the polyol plasticizer diethylene glycol acetate according to a polyol plasticizer addition amount of 5% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder.

[0174] It should be noted that the average particle size of the first silicon carbide powder is 45 μm, the average particle size of the first titanium-silicon-iron alloy powder is 45 μm, and the average particle size of the first silicon powder is 45 μm.

[0175] Step 1.2: Mix the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder in proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. The agglomerates are shaped and dried to obtain a green support body.

[0176] Step 2, Film Preparation

[0177] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to a mass ratio of 85:15; weigh the second titanium-silicon-iron alloy powder according to a mass ratio of 0.1% of the second silicon powder; weigh the water-based polymer dispersant polyvinyl alcohol 2000 according to an addition amount of 2% of the total mass of the slurry.

[0178] It should be noted that the average particle size of the second silicon carbide powder is 5 μm, the average particle size of the second silicon powder is 5 μm, and the average particle size of the second titanium-silicon-iron alloy powder is 3 μm.

[0179] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, deionized water, and water-based polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 45% (w).

[0180] Then, a slurry was sprayed onto the surface of the green support using a spraying method to prepare a film layer with a thickness of approximately 170 μm on the outer surface of the green support. After drying, it was sintered at 1200 °C for 5 h in a nitrogen and hydrogen mixed atmosphere to obtain a reaction-bonded silicon carbide ceramic film. It should be noted that in this embodiment, the volume ratio of hydrogen in the nitrogen-hydrogen mixed gas is 1.5%.

[0181] In this embodiment, the particle size span (D) of the first silicon carbide powder and the second silicon carbide powder is as follows: 90 -D 10 ) / D 50 Both are 1.5.

[0182] In this embodiment, the particle size range (D) of the first silicon powder 90 -D 10 ) / D 50 The particle size distribution of the second silicon powder is 1.4 (D). 90 -D 10 ) / D 50 It is 1.7.

[0183] Example 8

[0184] This embodiment provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0185] Step 1: Preparation of the support

[0186] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 80:20; weigh the first titanium-silicon-iron alloy powder according to a mass ratio of 0.1% of the first silicon powder; weigh the organic binder liquid paraffin according to an organic binder addition amount of 5% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder; weigh the polyol plasticizer diethylene glycol acetate according to a polyol plasticizer addition amount of 5% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder.

[0187] It should be noted that the average particle size of the first silicon carbide powder is 3 μm, the average particle size of the first titanium-silicon-iron alloy powder is 3 μm, and the average particle size of the first silicon powder is 1 μm.

[0188] Step 1.2: Mix the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder in proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. Then, extrude them into tubular shapes and dry them to obtain a green support body.

[0189] Step 2, Film Preparation

[0190] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to a mass ratio of 85:15; weigh the second titanium-silicon-iron alloy powder according to a mass ratio of 0.1% of the second silicon powder; weigh the water-based polymer dispersant polyvinyl alcohol 2000 according to an addition amount of 2% of the total mass of the slurry.

[0191] It should be noted that the average particle size of the second silicon carbide powder is 5 μm, the average particle size of the second silicon powder is 4 μm, and the average particle size of the second titanium-silicon-iron alloy powder is 5 μm.

[0192] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, the second titanium-silicon-iron alloy powder, deionized water, and water-based polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 45% (w).

[0193] Then, the green support was immersed in the slurry for a period of time using an impregnation method, then pulled out and dried. A film layer with a thickness of approximately 160 μm was prepared on the inner surface of the green support. After drying, it was sintered at 1400 °C for 0.5 h in a nitrogen and hydrogen mixed atmosphere to obtain a reaction-bonded silicon carbide ceramic film. It should be noted that in this embodiment, the volume ratio of hydrogen in the nitrogen-hydrogen mixed gas is 1.5%.

[0194] In this embodiment, the particle size distribution (D) of the first silicon carbide powder is as follows: 90 -D 10 ) / D 50 The particle size distribution of the second silicon carbide powder is 1.5 (D). 90 -D 10 ) / D 50 It is version 2.0.

[0195] In this embodiment, the particle size span (D) between the first silicon powder and the second silicon powder 90 -D 10 ) / D 50 Both are 1.6.

[0196] Comparative Example 1

[0197] This comparative example provides a method for preparing a reaction-bonded silicon carbide ceramic film, and the specific preparation steps are as follows:

[0198] Step 1: Preparation of the support

[0199] Step 1.1: Weigh the first silicon carbide powder and the first silicon powder according to a mass ratio of 70:30; weigh the organic binder phenolic resin 2130 according to an organic binder addition amount of 4% of the total mass of the first silicon carbide powder and the first silicon powder; weigh the polyol plasticizer glycerin according to an organic binder addition amount of 15% of the total mass of the first silicon carbide powder and the first silicon powder.

[0200] It should be noted that the average particle size of the first silicon carbide powder is 5.0 μm, and the average particle size of the first silicon powder is 6.4 μm.

[0201] Step 1.2: Mix the first silicon carbide powder and the first silicon powder in a certain proportion and mix them evenly in a high-speed mixer. Add an organic binder and a polyol plasticizer, and then spray granulate to obtain agglomerates with a particle size of 20μm to 130μm. The agglomerates are shaped and dried to obtain a green support body.

[0202] Step 2, Film Preparation

[0203] Step 2.1: Weigh the second silicon carbide powder and the second silicon powder according to a mass ratio of 80:20; weigh the water-based polymer dispersant polyethylene glycol 2000 according to an addition amount of 4.0% of the total mass of the slurry.

[0204] It should be noted that the average particle size of the second silicon carbide powder is 5.0 μm, and the average particle size of the second silicon powder is 0.4 μm.

[0205] Step 2.2: Mix the second silicon carbide powder, the second silicon powder, deionized water and the aqueous polymer dispersant, and disperse them evenly using a ball mill or a high-speed shear mill to prepare a uniform slurry with a solid content of 30% (w).

[0206] Then, the green support blank is immersed in the slurry for a period of time by the impregnation method and then pulled out and dried. A film layer with a thickness of about 150 μm is prepared on the outer surface of the green support blank. After drying, it is sintered at 1400℃ for 7 h in a nitrogen atmosphere to obtain the reaction-bonded silicon carbide ceramic film.

[0207] In this comparative example, the particle size distribution (D) of the first silicon carbide powder is as follows: 90 -D 10 ) / D 50 The particle size distribution of the second silicon carbide powder is 1.6 (D). 90 -D 10 ) / D 50 It is 1.7.

[0208] In this comparative example, the particle size distribution (D) of the first silicon powder is as follows:90 -D 10 ) / D 50 The particle size distribution of the second silicon powder is 2.0 (D). 90 -D 10 ) / D 50 It is 2.2.

[0209] The reaction-bonded silicon carbide ceramic membrane obtained in this comparative example has a pressure resistance of 2.5 MPa, with a support porosity of 26% and an average pore size of 9.6 μm, an average pore size of 6.3 μm in the membrane layer, and a pure water flux of 1.4 m³ / s. 3 / (m 2 ·h·bar). For example Figure 5 As shown, XRD analysis of the support and film revealed that, apart from SiC, only a small amount of Si3N4 was observed to form, and a large amount of Si remained in the sample without nitriding.

[0210] Compared to Example 1, Comparative Example 1, by omitting the first and second titanium-silicon-iron alloy powders, showed a decrease in the compressive strength of the reaction-bonded silicon carbide ceramic membrane. This further demonstrates that the titanium-silicon-iron alloy's catalytic nitridation of silicon can promote the growth of Si3N4 whiskers. The formation of silicon nitride whiskers enhances the toughening effect, improves the mechanical properties of the ceramic support and membrane, and further refines and segments the pores through silicon nitride whiskers, improving the pore structure of the support and membrane, thus giving the ceramic membrane superior separation performance.

[0211] Figure 1 The image shows a scanning electron microscope (SEM) image of the reaction-bonded silicon carbide ceramic film support prepared in Example 2. As can be seen from the image, a large number of interleaved Si3N4 whiskers are formed on the surface of the SiC particles. These whiskers enhance and toughen the support. Simultaneously, the interleaved whiskers between the SiC particles act as cutters to the pores.

[0212] Figure 2 The image shows a SEM image of the reaction-bonded silicon carbide ceramic film prepared in Example 1. As can be seen from the image, a large number of Si3N4 whiskers and granular TiN particles are formed interspersed among the fine SiC particles. The whiskers and particles fill part of the pores between the SiC particles, and the interspersed whiskers divide the pores, further refining the pores.

[0213] Figure 3 The image shows a SEM image of the reaction-bonded silicon carbide ceramic film prepared in Example 5. As can be seen from the image, a large number of Si3N4 whiskers are interwoven and connected to form a uniform sieve structure, and the porosity between SiC particles is significantly optimized.

[0214] In this invention, under the catalytic nitriding effect of a titanium-silicon-iron alloy, the alloy itself and silicon powder react with nitrogen gas to form silicon nitride whiskers and granular TiN. This process is accompanied by volume expansion, which fills and occupies the space of the original pores created by particle accumulation, causing a decrease in pore size. Furthermore, the overlapping whiskers also form a sieve-like structure, further segmenting the pore size, and the effective pore size during the separation process further decreases. The smaller the pore size, the higher its application value in the field of membrane separation.

[0215] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0216] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a reaction-bonded silicon carbide ceramic film, characterized in that, Includes the following steps: After uniformly mixing the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder, an organic binder and a polyol plasticizer are added, and the mixture is granulated and molded to obtain a support green body; the mass ratio of the first silicon carbide powder to the first silicon powder is 70~95:5~30; the mass of the first titanium-silicon-iron alloy powder is 0.1~50% of the mass of the first silicon powder; A second silicon carbide powder, a second silicon powder, a second titanium-silicon-iron alloy powder, an aqueous polymeric dispersant, and water are mixed evenly to obtain a slurry. The slurry is then coated onto the surface of a green support to obtain a green support containing a film layer. The mass ratio of the second silicon carbide powder to the second silicon powder is 80-90:10-20. The mass of the second titanium-silicon-iron alloy powder is 0.1-50% of the mass of the second silicon powder. Under a nitrogen-containing gas atmosphere, a green body containing a film layer is sintered at 1200℃~1400℃ to obtain a reaction-bonded silicon carbide ceramic film. The organic binder is one of phenolic resin, epoxy resin, polyvinyl alcohol aqueous solution, polyethylene glycol aqueous solution, carboxymethyl cellulose, and liquid paraffin; The polyol plasticizer is glycerol or diethylene glycol; The aqueous polymeric dispersant is one of polyethylene glycol, polyvinyl alcohol, hydroxypropyl methylcellulose, polyacrylamide, and polypyrrolidone; The average particle size of the first silicon carbide powder is 3μm~45μm; The average particle size of the first silicon powder is 1μm~45μm; The average particle size of the first titanium-silicon-iron alloy powder is 3μm~45μm; The particle size range of the first silicon carbide powder is ≤2.5; The particle size range of the second silicon carbide powder is ≤2.5; The particle size range of the first silicon powder is ≤2.5; The particle size range of the second silicon powder is ≤2.5; The average particle size of the second titanium-silicon-iron alloy powder is ≤5μm; The average particle size of the second silicon powder is ≤5μm; The average particle size of the second silicon carbide powder is ≤5μm.

2. The method for preparing a reaction-bonded silicon carbide ceramic film according to claim 1, characterized in that, The sintering time is 0.5h to 7h.

3. The method for preparing a reaction-bonded silicon carbide ceramic film according to claim 1, characterized in that, The coating thickness is 150μm~200μm.

4. The method for preparing a reaction-bonded silicon carbide ceramic film according to claim 1, characterized in that, The amount of organic binder added is 2% to 6% of the total mass of the first silicon carbide powder, the first silicon powder, and the first titanium-silicon-iron alloy powder.

5. The method for preparing a reaction-bonded silicon carbide ceramic film according to claim 1, characterized in that, The amount of polyol plasticizer added is 1% to 30% of the total mass of the first silicon carbide powder, the first silicon powder and the first titanium-silicon-iron alloy powder.

6. The method for preparing a reaction-bonded silicon carbide ceramic film according to claim 1, characterized in that, The amount of water-based polymeric dispersant added is 0.5% to 5% of the total mass of the slurry.

7. A reaction-bonded silicon carbide ceramic membrane prepared by the preparation method according to any one of claims 1-6.

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