A high negative silicon carbide flat membrane material and a preparation method thereof
Phosphorus silicon compounds were generated on the surface of silicon carbide flat sheet membranes by phytic acid modification and heat treatment, which solved the problem of insufficient negative charge of silicon carbide flat sheet membranes, realized silicon carbide flat sheet membrane materials with high negative charge and stability, and improved anti-fouling and separation performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG JIANMO TECH CO LTD
- Filing Date
- 2026-04-09
- Publication Date
- 2026-06-16
AI Technical Summary
The existing silicon carbide flat sheet membranes have insufficient negative charge, which leads to reduced anti-fouling performance and selective separation performance. Furthermore, the commonly used polymer coating or grafting methods have poor stability and are prone to pore blockage.
Phytic acid aqueous solution is mixed with a polar organic solvent, and after pH adjustment, it is impregnated onto a silicon carbide flat sheet membrane substrate and subjected to staged heat treatment, including low-temperature reaction and high-temperature carbonization. Phytic acid molecules react on the membrane surface to generate phosphosilicate compounds, which provide negative charge and pore support.
The negative charge and stability of silicon carbide flat sheet membranes were improved, flux attenuation was reduced, antifouling ability and separation performance were enhanced, and the stability of the pore structure was improved.
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Figure CN121990844B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of silicon carbide flat sheet film technology, and in particular relates to a highly negatively charged silicon carbide flat sheet film material and its preparation method. Background Technology
[0002] Silicon carbide possesses high hardness, excellent chemical resistance, good thermal conductivity, and high mechanical strength, making it widely used in the preparation of flat sheet membranes, tubular membranes, and porous supports. Silicon carbide membranes exhibit high stability during separation processes under high temperature, high pressure, organic solvents, and extreme pH conditions.
[0003] The zeta potential on the surface of silicon carbide flat sheet membranes is a key factor determining the membrane's antifouling performance and retention efficiency. Typically, when the surface of a silicon carbide flat sheet membrane has high negative charge, it can effectively prevent negatively charged pollutants from being adsorbed and deposited on the membrane surface through electrostatic repulsion, thereby maintaining high flux and long service life.
[0004] Silicon carbide flat sheet membranes are typically prepared using solid-state sintering, and their surface is often covered with an amorphous silica layer. Although the silica layer dissociates into silanol groups in water, generating a certain degree of negative charge, this negative charge is often insufficient. To improve the negative charge, polymers that can provide negative charges are often coated or grafted onto the membrane. However, these polymers are prone to detachment, have poor stability, and may clog the pores, leading to a decrease in the flux of the silicon carbide membrane and a reduction in its antifouling ability and selective separation performance. Therefore, there is an urgent need to develop a silicon carbide flat sheet membrane material with stable structure, strong negative charge, and good durability to meet the requirements of efficient separation in complex systems. Summary of the Invention
[0005] To address the aforementioned issues, this application provides a highly electronegative silicon carbide flat sheet film material and its preparation method.
[0006] This application first provides a method for preparing a highly electronegative silicon carbide flat sheet film material, comprising the following steps:
[0007] S1: Mix phytic acid aqueous solution with a polar organic solvent and adjust the pH to 2.5-4.0 to obtain a precursor solution;
[0008] S2: After impregnating the silicon carbide flat sheet film substrate with a precursor solution, a reaction is carried out to obtain a phytic acid modified silicon carbide flat sheet film.
[0009] S3: Perform staged heat treatment on the above-mentioned phytic acid modified silicon carbide flat sheet film: First stage: heat up to 180-250℃ at a rate of 1-2℃ / min and hold for 1-2 hours; Second stage: heat up to 300-450℃ at a rate of 2-3℃ / min and hold for 1-3 hours; heat up to 600-750℃ at a rate of 3-5℃ and hold for 1-2 hours. After the heat treatment is completed, allow it to cool naturally.
[0010] Furthermore, in step S1, the polar organic solvent is one or more of ethanol, isopropanol, and ethylene glycol;
[0011] And / or, in step S1, the mass fraction of phytic acid in the phytic acid aqueous solution is 10%-90%;
[0012] And / or, in step S1, the mass ratio of phytic acid to polar organic solvent is 1:(5-20).
[0013] Furthermore, in step S2, the reaction conditions are as follows: under vacuum, the reaction is first carried out at 60-80℃ for 2-6 hours, and then the temperature is increased to 120-180℃ at a rate of 2-5℃ / min for 1-3 hours.
[0014] Furthermore, in step S2, the method for preparing the silicon carbide flat film substrate is as follows: silicon carbide powder and auxiliary materials are added to water, and a mixed slurry is prepared by ball milling. The mixed slurry is then aged at room temperature, and then shaped, dried, cut, and sintered at high temperature.
[0015] Furthermore, the mass ratio of silicon carbide powder to auxiliary materials is 100:(5-25).
[0016] Furthermore, the auxiliary material comprises the following components in parts by weight: 5-20 parts of silica sol, 0.1-6 parts of pore-forming agent, 0.5-3 parts of dispersant, 0.5-5 parts of sintering aid, and 0.1-1 parts of defoamer.
[0017] Furthermore, the pore-forming agent is one or more of glucose powder, starch, and polyethylene microspheres.
[0018] Furthermore, the dispersant is one or more of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and polyvinylpyrrolidone.
[0019] Furthermore, the sintering aid is one or more of graphite, alumina, and silicon dioxide.
[0020] Furthermore, the defoamer is dimethyl silicone oil.
[0021] This application also provides a highly negatively charged silicon carbide flat sheet film material, which is prepared by the above-described method.
[0022] Compared with the prior art, this application has the following beneficial effects:
[0023] 1. This application utilizes the reaction of phytic acid macromolecules with the silanol groups on the surface of silicon carbide, which are then anchored on the membrane surface and pore walls. Simultaneously, inositol rings are introduced to provide steric hindrance at low temperatures, opening up the pores. At high temperatures, they decompose into gas, generating a micro-positive pressure within the pores, supporting the pores, and preventing collapse or shrinkage. This effectively prevents the silicon carbide membrane pores from being blocked, thereby reducing the flux attenuation of the silicon carbide flat sheet membrane material.
[0024] 2. This application involves a staged heating heat treatment under an inert atmosphere, which carbonizes the inositol ring in the phytic acid molecules to form a conductive carbon skeleton, maintaining the pore structure. The phosphate groups react with the silicon carbide surface to form phosphosilicate compounds, generating negative charge centers and providing high negative charge, thereby improving the antifouling performance of the silicon carbide flat sheet membrane material. Attached Figure Description
[0025] Figure 1 The Zeta potential-pH curves of the highly negatively charged silicon carbide flat sheet film materials in the embodiments and control groups of this application are shown.
[0026] Figure 2 The flux decay curves of the highly negatively charged silicon carbide flat sheet membrane materials in the embodiments of this application and the control group are shown. Detailed Implementation
[0027] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments, clearly and completely describing the technical solutions in the embodiments of this application. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0029] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.
[0030] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.
[0031] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.
[0032] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.
[0033] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.
[0034] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.
[0035] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.
[0036] In this application, room temperature refers to 0-40°C, including but not limited to 10-40°C, or further to 20-30°C.
[0037] This application, based on extensive experimental research, provides a method for preparing a highly electronegative silicon carbide flat sheet film material, comprising the following steps:
[0038] S1: Mix phytic acid aqueous solution with a polar organic solvent and adjust the pH to 2.5-4.0 to obtain a precursor solution;
[0039] S2: After impregnating the silicon carbide flat sheet film substrate with a precursor solution, a reaction is carried out to obtain a phytic acid modified silicon carbide flat sheet film.
[0040] S3: Perform staged heat treatment on the above-mentioned phytic acid modified silicon carbide flat sheet film: First stage: heat up to 180-250℃ at a rate of 1-2℃ / min and hold for 1-2 hours; Second stage: heat up to 300-450℃ at a rate of 2-3℃ / min and hold for 1-3 hours; heat up to 600-750℃ at a rate of 3-5℃ and hold for 1-2 hours. After the heat treatment is completed, allow it to cool naturally.
[0041] In some embodiments of this application, under these weakly acidic conditions, phytic acid can react with the silanol groups on the silicon carbide surface without excessively etching the silicon carbide flat sheet film substrate framework. During the reaction, phytic acid molecules first adsorb onto the surface or pore walls of the silicon carbide flat sheet film substrate and react with the silanol groups. Simultaneously, the inositol ring provides steric hindrance, effectively preventing the closure of the membrane pores. Then, a staged heat treatment is performed. The first stage mainly removes physically adsorbed water and bound water, and the phytic acid reacts to become polyphosphoric acid. The second stage mainly involves the carbonization of the inositol ring, generating small molecule gas, and simultaneously generating initial phosphosilicon compounds in situ, amorphous... Carbon formation can improve the stability and conductivity of silicon carbide flat sheet membrane materials. Small molecule gases can form a micro-positive pressure in the channels, which can not only prevent external oxygen from entering, but also support the mesh and effectively reduce the shrinkage phenomenon. The third stage mainly involves the formation of phosphosilicate composite ceramics and the fixation of negative charge centers, which gives the silicon carbide flat sheet membrane high negative charge and stability. This not only prevents membrane pore blockage of the silicon carbide flat sheet membrane material and reduces flux attenuation, but also improves the negative charge of the silicon carbide flat sheet membrane material, thereby improving the antifouling ability and separation performance of the silicon carbide flat sheet membrane material.
[0042] In some embodiments of this application, in step S3, the first stage heating rate can be 1℃ / min, 1.5℃ / min, or 2℃ / min, the temperature can be 180℃, 200℃, 230℃, or 250℃, and the holding time can be 1h, 1.5h, or 2h; the second stage heating rate can be 2℃ / min, 2.5℃ / min, or 3℃ / min, the temperature can be 300℃, 350℃, 400℃, or 450℃, and the holding time can be 1h, 2h, or 3h; the third stage heating rate can be 3℃ / min, 4℃ / min, or 5℃ / min, the temperature can be 600℃, 650℃, 700℃, or 750℃, and the holding time can be 1h, 1.5h, or 2h.
[0043] In some embodiments of this application, in step S1, the polar organic solvent is one or more of ethanol, isopropanol, and ethylene glycol. Alcoholic organic solvents facilitate the penetration of phytic acid molecules into the pores of the silicon carbide membrane.
[0044] In some embodiments of this application, in step S1, the mass fraction of phytic acid in the phytic acid aqueous solution is 10%-90%; for example, it can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.
[0045] In some embodiments of this application, in step S1, the mass ratio of phytic acid to polar organic solvent is 1:(5-20), for example, it can be 1:5, 1:8, 1:10, 1:12, 1:16, 1:18, or 1:20.
[0046] In some embodiments of this application, the reaction conditions in step S2 are as follows: under vacuum, the reaction is first carried out at 60-80°C for 2-6 hours, for example, the reaction temperature can be 60°C, 70°C, or 80°C, and the reaction time can be 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours; then the temperature is increased to 120-180°C at a rate of 2-5°C / min, and the reaction is carried out for 1-3 hours, for example, the heating rate is 2°C / min, 3°C / min, 4°C / min, or 5°C / min, the temperature can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C, and the reaction time can be 1 hour, 2 hours, or 3 hours. Vacuuming removes air from the pores, preventing further oxidation of the silicon carbide film during the reaction.
[0047] In some specific embodiments of this application, the preparation method of the silicon carbide flat film substrate in step S2 is as follows: silicon carbide powder and auxiliary materials are added to water, and a mixed slurry is prepared by ball milling. The mixed slurry is then aged at room temperature, and then shaped, dried, cut, and sintered at high temperature.
[0048] In some specific embodiments of this application, the mass ratio of silicon carbide powder to auxiliary materials is 100:(5-25), for example, it can be 100:5, 100:10, 100:15, 100:20, or 100:25.
[0049] In some specific embodiments of this application, the excipients comprise the following components in parts by weight: 5-20 parts silica sol, 0.1-6 parts pore-forming agent, 0.5-3 parts dispersant, 0.5-5 parts sintering aid, and 0.1-1 parts defoamer. The addition of silica sol can introduce oxygen vacancy defects into the silicon carbide lattice, thereby forming stable, high-density negative charge centers on the film surface, thus improving the antifouling performance of the silicon carbide flat sheet film material.
[0050] In some specific embodiments of this application, the pore-forming agent is one or more of glucose powder, starch, and polyethylene microspheres.
[0051] In some specific embodiments of this application, the dispersant is one or more of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and polyvinylpyrrolidone.
[0052] In some specific embodiments of this application, the sintering aid is one or more of graphite, alumina, and silicon dioxide; the sintering aid can form a solid solution with silicon carbide, reduce the oxygen vacancy formation energy, improve defect stability, and thus improve the negative charge of the silicon carbide flat sheet film material.
[0053] In some specific embodiments of this application, the defoamer is dimethyl silicone oil.
[0054] In addition, this application also provides a highly negatively charged silicon carbide flat sheet film material, which is prepared by the above-described method.
[0055] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.
[0056] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.
[0057] Example 1
[0058] The preparation method of the highly negatively charged silicon carbide flat sheet film material in this embodiment includes the following steps:
[0059] S1: Weigh 50g of 50% phytic acid aqueous solution and 400g of anhydrous ethanol, mix them evenly, add ammonia solution dropwise, adjust the pH to 3, and obtain the precursor solution.
[0060] S2: The precursor solution is uniformly coated on the silicon carbide flat sheet film substrate using the dip-coating technique. Then, it is placed in a box-type microwave dryer, vacuumed, and reacted at 70°C for 3 hours. Then, the temperature is increased to 150°C at a rate of 3°C / min and held for 1.5 hours. After natural cooling to room temperature, it is taken out, washed with deionized water, and dried with nitrogen to obtain phytic acid modified silicon carbide flat sheet film.
[0061] S3: Place the above-mentioned phytic acid modified silicon carbide flat sheet film into a high-temperature sintering furnace and perform staged heating according to the following procedure: first, heat to 200℃ at a rate of 2℃ / min and hold for 1 hour; then heat to 400℃ at a rate of 3℃ / min and hold for 2 hours; finally, heat to 700℃ at a rate of 3℃ / min and hold for 1 hour, and then allow the furnace to cool naturally to room temperature.
[0062] The method for preparing the silicon carbide flat sheet film substrate in this embodiment is as follows:
[0063] (1) Weigh 1000g of high-purity silicon carbide powder, 300g of deionized water, 20g of starch, 10g of hexadecyltrimethylammonium bromide, 15g of silicon dioxide and 5g of dimethyl silicone oil, and process them at a ball milling rate of 300rpm for 4h to obtain a mixed slurry.
[0064] (2) The mixed slurry was aged at 25℃ and 60%RH for 24h, and then dry-pressed at 20MPa to form a green body. The green body was dried at 60℃ for 12h and then cut into flat film samples.
[0065] (3) Place the flat sheet membrane sample in a high-temperature sintering furnace at an oxygen partial pressure of 10. -2 Sintering is carried out in three steps under ATM: first, the temperature is raised from room temperature to 600℃ at a rate of 5℃ / min and held for 2 hours; then, the temperature is raised to 1000℃ at a rate of 8℃ / min and held for 1 hour; then, the temperature is raised to 1400℃ at a rate of 3℃ / min and held for 3 hours. After sintering, the temperature is naturally cooled to room temperature to obtain the final product.
[0066] Example 2
[0067] The preparation method of the highly negatively charged silicon carbide flat sheet film material in this embodiment is the same as that in Example 1;
[0068] The difference between the preparation method of the silicon carbide flat film substrate in this embodiment and that in Example 1 is as follows:
[0069] (1) Weigh 1000g of high-purity silicon carbide powder, 100g of silica sol, 300g of deionized water, 20g of starch, 10g of hexadecyltrimethylammonium bromide, 15g of silicon dioxide and 5g of dimethyl silicone oil, and process them at a ball milling rate of 300rpm for 4h to obtain a mixed slurry.
[0070] The remaining steps are the same as in Example 1.
[0071] Control group 1
[0072] The preparation method of the highly negatively charged silicon carbide flat sheet film material in this control group includes the following steps:
[0073] Weigh 350mL of concentrated sulfuric acid into a beaker, and slowly add 100mL of 30% hydrogen peroxide while stirring. After mixing evenly, coat the mixture evenly onto the silicon carbide flat film substrate, then place it in a box-type microwave dryer, vacuum it, and react it at 70℃ for 3 hours. After removing it, let it cool naturally to room temperature, wash it with deionized water, and blow it dry with nitrogen.
[0074] The preparation method of the silicon carbide flat film substrate in this control group is the same as that in Example 1.
[0075] Control group 2
[0076] The preparation method of the highly negatively charged silicon carbide flat sheet film material in this control group includes the following steps:
[0077] S1: Weigh 50g of 50% phytic acid aqueous solution and 400g of anhydrous ethanol, mix them evenly, add ammonia solution dropwise, adjust the pH to 3, and obtain the precursor solution.
[0078] S2: The precursor solution is uniformly coated on the silicon carbide flat film substrate using the dip-coating technique. Then, it is placed in a box-type microwave dryer, vacuumed, and reacted at 70°C for 3 hours. After being removed, it is naturally cooled to room temperature, washed with deionized water, and dried with nitrogen.
[0079] The preparation method of the silicon carbide flat film substrate in this control group is the same as that in Example 1.
[0080] Performance testing
[0081] 1. Zeta potential test
[0082] ① Prepare phosphate buffer solutions with pH=3, pH=5, pH=7, and pH=9;
[0083] ② Highly electronegative silicon carbide flat sheet membrane materials from Examples 1-2 and Control Groups 1-2 were immersed in different pH buffer solutions and placed in the sample cell of a Zeta potential meter. The parameters were set to 25℃ and equilibration time to 120s. Each sample was measured three times, and the average value was taken. A Zeta potential-pH curve was plotted. Figure 1 As shown.
[0084] from Figure 1 As can be seen, compared with the control group, the silicon carbide flat sheet membrane material of Example 1 has a stronger negative charge over a wider pH range. When silica sol is added during the preparation of the silicon carbide flat sheet membrane substrate, the negative charge of the silicon carbide flat sheet membrane material is also increased, possibly because oxygen vacancies are generated during the sintering process of the silica sol.
[0085] 2. Water permeability flux and antifouling performance test
[0086] ① Using terminal filtration, ultrapure water was pre-pressurized for 0.5 hours at a pressure of 0.1 MPa. After the water flow stabilized, the permeation flux of the water passing through for 0.5 hours was tested and used as the initial flux, denoted as η0.
[0087] ② Prepare a humic acid solution with a concentration of 100 mg / L as the permeate, run it at a pressure of 0.1 MPa for 0.5 h, and then backwash it with ultrapure water for 0.5 h at a backwash pressure of 0.2 MPa. Measure the pure water flux through it again for 0.5 h and take it as the flux of the first cycle, denoted as η1.
[0088] ③ Repeat step ②, repeating the contamination-cleaning cycle 5 times, and plot the flux decay curve, as shown. Figure 2 As shown.
[0089] from Figure 2 As can be seen, compared with the control group, the high-electrostatic silicon carbide flat sheet membrane material of the embodiment has a higher initial flux, and after multiple contamination-cleaning cycles, the flux decay of the high-electrostatic silicon carbide flat sheet membrane material of the embodiment is less. This may be because the pores of the high-electrostatic silicon carbide flat sheet membrane material of the embodiment are unobstructed and not blocked, and the high electronegativity can effectively hinder the adsorption and deposition of pollutants. However, if strong oxidation is carried out alone, it may lead to a reduction in the number of membrane pores or condensation blockage. If only phytic acid macromolecules are grafted without high-temperature pyrolysis, it may not only block the pores, but the phosphate groups may also be wrapped by the sterically hindered inositol ring, thereby reducing the electronegativity.
[0090] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for preparing a highly electronegative silicon carbide flat sheet film material, characterized in that: Includes the following steps: S1: Mix phytic acid aqueous solution with a polar organic solvent and adjust the pH to 2.5-4.0 to obtain a precursor solution; S2: After impregnating the silicon carbide flat sheet film substrate with a precursor solution, a reaction is carried out to obtain a phytic acid modified silicon carbide flat sheet film. S3: Perform staged heat treatment on the above-mentioned phytic acid modified silicon carbide flat sheet film: First stage: heat up to 180-250℃ at a rate of 1-2℃ / min and hold for 1-2 hours; Second stage: heat up to 300-450℃ at a rate of 2-3℃ / min and hold for 1-3 hours; heat up to 600-750℃ at a rate of 3-5℃ and hold for 1-2 hours. After the heat treatment is completed, allow it to cool naturally.
2. The method for preparing a highly electronegative silicon carbide flat sheet film material according to claim 1, characterized in that: In step S1, the polar organic solvent is one or more of ethanol, isopropanol, and ethylene glycol; And / or, in step S1, the mass fraction of phytic acid in the phytic acid aqueous solution is 10%-90%; And / or, in step S1, the mass ratio of phytic acid to polar organic solvent is 1:(5-20).
3. The method for preparing a highly electronegative silicon carbide flat sheet film material according to claim 1, characterized in that: In step S2, the reaction conditions are as follows: under vacuum, the reaction is first carried out at 60-80℃ for 2-6 hours, and then the temperature is increased to 120-180℃ at a rate of 2-5℃ / min for 1-3 hours.
4. The method for preparing a highly electronegative silicon carbide flat sheet film material according to claim 1, characterized in that: In step S2, the preparation method of silicon carbide flat film substrate is as follows: silicon carbide powder and auxiliary materials are added to water, and a mixed slurry is prepared by ball milling. The mixed slurry is then aged at room temperature, and then shaped, dried, cut and sintered at high temperature.
5. The method for preparing a highly electronegative silicon carbide flat sheet film material according to claim 4, characterized in that: The mass ratio of silicon carbide powder to auxiliary materials is 100:(5-25).
6. The method for preparing a highly electronegative silicon carbide flat sheet film material according to claim 4, characterized in that: The auxiliary material comprises the following components in parts by weight: 5-20 parts silica sol, 0.1-6 parts pore-forming agent, 0.5-3 parts dispersant, 0.5-5 parts sintering aid, and 0.1-1 parts defoamer.
7. The method for preparing a highly electronegative silicon carbide flat sheet film material according to claim 6, characterized in that: The pore-forming agent is one or more of glucose powder, starch, and polyethylene microspheres.
8. The method for preparing a highly electronegative silicon carbide flat sheet film material according to claim 6, characterized in that: The dispersant is one or more of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and polyvinylpyrrolidone.
9. The method for preparing a highly electronegative silicon carbide flat sheet film material according to claim 6, characterized in that: The sintering aid is one or more of graphite, alumina, and silicon dioxide; the defoamer is dimethyl silicone oil.
10. A highly electronegative silicon carbide flat sheet film material, characterized in that: It is prepared by any one of the preparation methods described in claims 1-9.