A method for preparing a high-performance ceramic membrane

Abstract

This invention relates to the field of ceramic membrane preparation technology, specifically to a method for preparing a high-performance ceramic membrane, comprising the following steps: Step 1, powder pretreatment: ceramic raw materials are prepared into ceramic powder, and the ceramic powder, temporary pore-forming agent, sintering aid, and dispersion medium are mixed to obtain a support blank; Step 2, support forming: the support blank is formed, dried, and pre-fired to obtain a porous support with interconnected channels; Step 3, confined pore sealing; Step 4, gradient film formation; Step 5, slow-release drying; Step 6, segmented sintering; Step 7, hydrophilic modification. This invention solves the problems of easy infiltration of membrane slurry into the support channels, insufficient bonding stability of the separation layer, and difficulty in simultaneously achieving filtration flux and antifouling performance during ceramic membrane preparation by pre-sealing the pores, followed by film formation, and releasing the pores during the sintering stage.

Description

Technical Field

[0001] This invention relates to the field of ceramic membrane preparation technology, and more specifically to a method for preparing a high-performance ceramic membrane. Background Technology

[0002] Ceramic membranes, as an important component of inorganic membrane materials, are widely used in water treatment, food processing, chemical separation, biopharmaceutical separation, and oily wastewater treatment. Their pore structure, membrane integrity, support strength, and surface wettability directly affect filtration flux, separation accuracy, operational stability, and antifouling capabilities.

[0003] The paper "Preparation of high-permeability ceramic microfiltration membranes using a pore-sealing method" (Wu Qin, Yi Zhang, Jianqing Wu, 2020) proposes a method to sequentially coat a polyvinyl alcohol acetal (PVB) layer and an alumina membrane precursor onto the surface of a macroporous alumina support. The PVB interlayer temporarily seals the pores on the support surface during coating, and the PVB layer is removed by pyrolysis after membrane formation. This allows for the direct acquisition of high-permeability alumina microfiltration membranes without an intermediate layer. The intermediate-layer-free ceramic membrane prepared by this method has an average pore size of 0.26 micrometers and a significantly higher water permeability than that obtained using traditional methods. The improved permeability is mainly due to the reduction in filtration resistance. While this method represents an improvement, it still does not systematically solve the problem of continuous and synergistic control among pore sealing, membrane formation, and surface modification.

[0004] Therefore, the fundamental deficiency of existing ceramic membrane preparation technologies lies in the lack of continuous and coordinated process control between the support pores, the separation layer film formation process, and subsequent surface modification. This leads to the membrane slurry easily penetrating into the support pores, insufficient bonding stability between the separation layer and the support, and a tendency to sacrifice filtration flux when improving antifouling performance. Therefore, it is necessary to propose a method for preparing high-performance ceramic membranes to solve these problems. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing a high-performance ceramic membrane. This method utilizes a process sequence of sealing the pores before forming the membrane and releasing the pores during the sintering stage. This addresses the issues of membrane slurry easily penetrating the support pores, insufficient bonding stability of the separation layer, and the difficulty in simultaneously achieving high filtration flux and antifouling performance during the ceramic membrane preparation process.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing a high-performance ceramic membrane, comprising the following steps: Step 1, powder pretreatment: ceramic raw materials are made into ceramic powder by a preparation device, and the ceramic powder, temporary pore-forming agent, sintering aid and dispersion medium are mixed to obtain a support blank.

[0007] Step 2, support body forming: The support body blank is formed, dried and pre-fired to obtain a porous support body with interconnected channels.

[0008] Step 3, confined sealing: Prepare a sealing solution containing pyrolytic organic matter, nano-oxide precursor, and wetting agent; place the porous support and sealing solution in a vacuum impregnation container, ensuring the sealing solution completely covers the porous support; use a vacuum pump to evacuate the vacuum impregnation container to create a negative pressure environment, allowing air to escape from the surface pores of the porous support; stop the vacuum pump and release the negative pressure, allowing the sealing solution to enter the surface pores of the porous support; remove the porous support from the sealing solution, remove excess sealing solution from the surface, and perform low-temperature curing to form a confined sealing layer covering the surface pores of the porous support and having micro-recessed areas on the outer surface.

[0009] Step 4, gradient film formation: a low-solids-content film layer slurry and a high-solids-content film layer slurry are sequentially coated on the outer surface of the confined sealing layer. The low-solids-content film layer slurry fills the micro-recessed area on the outer surface of the confined sealing layer, and the high-solids-content film layer slurry forms a continuous film layer, thus obtaining a composite film preform.

[0010] Step 5, slow-release drying: The composite film preform is placed in an environment with decreasing humidity to dry, resulting in a dried composite preform.

[0011] Step 6, Segmented sintering: The dried composite green body is sequentially treated with a debinding section, a conversion section, and a dense connection section, which decomposes the pyrolytic organic matter and releases the pores of the porous support, transforms the nano-oxide precursor into oxide transition particles, and allows the continuous film layer to combine with the porous support through the oxide transition particles, thus obtaining a ceramic film substrate.

[0012] Step 7, hydrophilic modification: The ceramic film substrate is placed in a modification solution containing silicon, titanium or zirconium source for hydrothermal treatment, so that hydrophilic nano-modification points are formed on the outer surface of the continuous film layer and the inner wall of the near-surface pores that are connected to the pores on the outer surface of the continuous film layer. After cleaning and drying, a high-performance ceramic film is obtained.

[0013] The technical principles of the above solution are as follows: First, a sealing liquid containing pyrolytic organic matter and nano-oxide precursors is introduced into the pores and near-surface channels of the pre-sintered porous support. This liquid is then cured at low temperature to form a temporary confined sealing layer. This sealing layer acts as a physical barrier during subsequent coating of the film slurry, preventing slurry particles from penetrating into the support. Second, a gradient film-forming strategy is employed, sequentially coating low-solids and high-solids slurries. The low-solids slurry preferentially fills the micro-recesses on the surface of the sealing layer, while the high-solids slurry forms a continuous film layer on top, improving film smoothness and avoiding defects caused by single-coat thick layers. Subsequently, during segmented sintering, organic matter is removed sequentially, and the oxide precursors are converted into transition particles. These transition particles allow the continuous film layer to firmly bond with the support, while the previously blocked pores are re-exposed, ensuring channel connectivity. Finally, hydrothermal treatment forms hydrophilic nano-modification points in situ on the outer surface of the film and the inner walls of the near-surface channels, enhancing its anti-fouling ability.

[0014] The above approach has the following beneficial effects: 1. This invention, through the continuous combination of confined sealing, gradient film formation, and segmented sintering, makes it difficult for a large amount of film slurry to enter the support pores during coating, and releases the temporarily blocked pores after sintering. This can reduce pore blockage and film defects, and is conducive to obtaining ceramic films with high flux and stable structure.

[0015] 2. This invention first uses a low-solids-content film layer slurry to fill the surface micro-recessed areas, and then uses a high-solids-content film layer slurry to form a continuous film layer. Combined with humidity-decreasing drying and segmented sintering, it can reduce the risk of cracking caused by drying shrinkage, glue release and gas release, and high-temperature bonding, and improve the stability of the preparation process.

[0016] 3. In this invention, hydrophilic modification is performed on the ceramic membrane substrate after its formation, so that hydrophilic nano-modification points are formed on the outer surface of the continuous membrane layer and on the inner wall of the near-surface pores that are connected to the pores on the outer surface of the continuous membrane layer. This can reduce the tendency of pollutants to adhere to the membrane surface and pores, making it easier for the ceramic membrane to maintain a stable separation effect during filtration.

[0017] Furthermore, in step one, the ceramic raw materials include one or more of alumina, zirconium oxide, titanium oxide, silicon carbide, kaolin, halloysite, and fly ash-based ceramic raw materials, and the particle size of the ceramic powder is 0.1μm-50μm.

[0018] Beneficial effects: The ceramic raw materials cover oxide ceramics, silicon carbide ceramics, and mineral-based ceramics, allowing for the selection of acid and alkali resistant, wear-resistant, or low-cost raw materials according to different application scenarios. Limiting the ceramic powder particle size to the range of 0.1μm-50μm can balance the requirements of powder sintering activity and support pore structure formation, avoiding insufficient molding strength due to excessively coarse powder, and avoiding difficulties in mixing and debinding due to excessively fine powder.

[0019] Furthermore, in step one, the temporary pore-forming agent includes one or more of starch, polymethyl methacrylate microspheres, graphite powder, and cellulose, and the temporary pore-forming agent accounts for 5%-30% of the ceramic powder mass.

[0020] Beneficial effects: Temporary pore-forming agents, made from materials such as starch, polymethyl methacrylate microspheres, graphite powder, or cellulose, can be removed during subsequent heat treatment and form interconnected channels. Limiting the amount of temporary pore-forming agent to 5%-30% of the ceramic powder mass allows the support to form sufficient porosity without significantly reducing the strength of the green body due to excessive pore-forming agent, thereby improving the stability of support forming and subsequent pre-firing.

[0021] Furthermore, in step two, the pre-firing temperature is 700℃-1100℃, the pre-firing time is 1h-4h, and the resulting porous support has an open porosity of 25%-55% and an average pore size of 0.2μm-20μm.

[0022] Beneficial effects: With pre-firing temperature and time limited, the porous support can achieve preliminary sintering strength before complete densification and retain a large number of open pores. The limited range of open porosity and average pore size allows the support to provide low-resistance channels for the filtration process and a stable bearing surface for subsequent confined sealing and gradient film formation, which helps reduce local collapse and uncontrolled seepage into the pores during membrane preparation.

[0023] Furthermore, in step three, the pyrolytic organic matter includes one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, and cellulose derivatives, and the nano-oxide precursor includes one or more of silica sol, titanium sol, zirconium sol, and aluminum sol. When preparing the sealing solution, the pyrolytic organic matter is first added to deionized water or an alcohol-water mixture and stirred to dissolve, then the nano-oxide precursor and wetting agent are added and stirred to disperse, thus obtaining the sealing solution.

[0024] Beneficial effects: Pyrolytic organic matter can form a temporary sealing framework after low-temperature solidification, which can be removed during subsequent sintering, thereby reducing the risk of permanent pore blockage. Nano-oxide precursors can be transformed into oxide transition particles after heat treatment, eliminating the need for an additional thick intermediate layer and enhancing the bonding between the continuous membrane layer and the support, enabling the ceramic membrane to balance filtration channel retention and membrane adhesion stability.

[0025] Furthermore, in step three, the vacuum pump evacuates the vacuum impregnation container to a vacuum level of -0.03MPa to -0.09MPa, the negative pressure impregnation time is 1min to 20min, and the low-temperature curing temperature is 40℃ to 120℃.

[0026] Beneficial effects: With the vacuum degree and wetting time limited by negative pressure, the sealing liquid can enter the surface pores and near-surface channels, without easily penetrating too deeply into the support. The low-temperature curing temperature is limited to 40℃-120℃, which allows the sealing liquid to form a stable, confined sealing layer, while preventing excessively high temperatures from prematurely damaging the structure of pyrolytic organic materials, thus maintaining the stable barrier effect of the sealing layer during the subsequent gradient film formation stage.

[0027] Furthermore, in step four, the solid content of the low-solids film layer slurry is 5%-20%, and the solid content of the high-solids film layer slurry is 20%-45%. Both the low-solids film layer slurry and the high-solids film layer slurry include ceramic fine powder, dispersant, binder and solvent.

[0028] Beneficial effects: Low-solids-content film layer slurry first penetrates the micro-recessed areas on the surface of the confined sealing layer, which can improve the local unevenness of the support surface; high-solids-content film layer slurry then forms a continuous film layer, which can reduce excessive film penetration and improve the stability of film thickness. Both slurries are composed of ceramic fine powder, dispersant, binder and solvent, which facilitates the formation of a compatible interlayer interface and reduces the risk of film delamination.

[0029] Furthermore, in step five, the humidity-reducing environment is formed by a constant temperature and humidity drying oven. After the composite film preform is placed in the constant temperature and humidity drying oven, it goes through the first drying stage, the second drying stage and the third drying stage in sequence. The relative humidity of the first drying stage is 70%-95%, the relative humidity of the second drying stage is 45%-70%, and the relative humidity of the third drying stage is 20%-45%.

[0030] Beneficial effects: The humidity-reducing environment gradually decreases humidity through the first, second, and third drying stages, allowing the solvent in the composite membrane preform to transition from slow evaporation to sizing and drying. This process reduces shrinkage stress caused by rapid water loss from the membrane surface, ensuring good adhesion between the confined sealing layer and the continuous membrane layer during drying, thereby reducing the probability of cracking, warping, and pinholes.

[0031] Furthermore, in step six, the treatment temperature of the glue removal section is 250℃-450℃, the treatment temperature of the conversion section is 450℃-750℃, and the treatment temperature of the dense bonding section is 900℃-1350℃. In step seven, the hydrothermal treatment temperature is 80℃-180℃, and the hydrothermal treatment time is 0.5h-8h.

[0032] Beneficial effects: The descaling section, conversion section, and dense connection section respectively perform the functions of organic matter removal, precursor conversion, and membrane layer bonding, which can avoid membrane rupture caused by the concentrated occurrence of multiple thermal changes. After limiting the hydrothermal treatment temperature and time, hydrophilic nano-modification points can form on the outer surface of the continuous membrane layer and on the inner wall of the near-surface pores that communicate with the pores on the outer surface of the continuous membrane layer, without excessively clogging the deep pores, thus maintaining a good balance between antifouling performance and filtration flux of the ceramic membrane.

[0033] Furthermore, the preparation device includes a dual-head drive unit, with a grinding component for grinding raw materials at one output end of the dual-head drive unit, and a cleaning component for reducing clogging of the grinding component at the other output end of the dual-head drive unit.

[0034] The grinding assembly includes a filter cage coaxially fixedly connected to one output end of a dual-head drive unit. Several grinding balls are placed inside the filter cage. An outer sleeve is fitted around the outside of the filter cage. One output end of the dual-head drive unit passes through one side wall of the outer sleeve and rotates with it. Several fixing columns are fixedly connected between the outer sleeve and the dual-head drive unit. A discharge trough is opened at the bottom of the outer sleeve. A feed port is opened on the side wall of both the outer sleeve and the filter cage away from the dual-head drive unit. A cover is detachably connected to the feed port on the outer sleeve. Support plates are fixedly connected to the bottom of both the dual-head drive unit and the outer sleeve. A collection frame is fixedly connected between the support plates.

[0035] The cleaning assembly includes a piston cylinder with a slide rail fixedly connected to its top and several support columns fixedly connected to its bottom. A rotating rod is fixedly connected to the output end of a dual-head drive unit away from the fixed columns. A transmission rod is rotatably connected to the other end of the rotating rod, and a slider is rotatably connected to the other end of the transmission rod. The slider slides against the slide rail. A piston rod is fixedly connected to the side wall of the slider. A piston plate is fixedly connected to the other end of the piston rod, passing through the top of the piston cylinder and inside the cylinder. A partition is fixedly connected to the inner side wall of the piston cylinder. Several suction holes are opened on the side wall of the piston cylinder, all located above the partition. The partition has through holes. An exhaust hole is opened at the bottom of the piston cylinder. Several air jet holes are opened on the side wall of the outer sleeve, all communicating with the exhaust hole. Each suction hole is equipped with an intake one-way valve, with airflow from outside to inside the piston cylinder. An exhaust one-way valve is installed in the through hole, with airflow from the upper chamber to the lower chamber of the partition. A solenoid valve is installed in the exhaust hole, electrically connected to a controller. A pressure sensor is fixedly connected to the bottom of the partition, and electrically connected to the controller.

[0036] Beneficial effects: The dual-head drive unit simultaneously rotates the filter cage and moves the piston plate back and forth, allowing the raw material grinding and filter cage air cleaning to proceed synchronously. Inside the filter cage, grinding balls collide and grind the raw material; qualified powder enters the collection frame through the discharge chute. The cleaning component sprays air into the filter cage after the air pressure reaches a threshold, clearing pore blockages and encouraging retained material to re-participate in the grinding process, thus improving powder pretreatment efficiency. Attached Figure Description

[0037] Figure 1 This is a step diagram illustrating an embodiment of the method for preparing the high-performance ceramic membrane of the present invention.

[0038] Figure 2 This is a schematic diagram of the preparation apparatus in an embodiment of the high-performance ceramic membrane preparation method of the present invention.

[0039] Figure 3 This is a cross-sectional view of the preparation apparatus in an embodiment of the method for preparing high-performance ceramic membranes according to the present invention.

[0040] The reference numerals in the accompanying drawings of the instruction manual include: 1. Dual-head drive unit; 2. Outer sleeve; 3. Filter cage; 4. Cover; 5. Inlet; 6. Fixed column; 7. Support plate; 8. Support column; 9. Collection frame; 10. Rotating rod; 11. Transmission rod; 12. Slider; 13. Slide rail; 14. Piston rod; 15. Piston plate; 16. Piston cylinder; 17. Partition plate; 18. Suction hole; 19. Through hole; 20. Exhaust hole; 21. Air jet hole; 22. Discharge trough. Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0042] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0043] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] The following detailed description illustrates the specific implementation method: Example 1:

[0045] As attached Figure 1 As shown: A method for preparing a high-performance ceramic membrane includes the following steps: Step 1, Powder Pretreatment: The ceramic raw material is processed into ceramic powder using a preparation device. The ceramic powder, temporary pore-forming agent, sintering aid, and dispersion medium are then mixed to obtain the support blank. In this embodiment, a ball mill can be used as the preparation device.

[0046] In step one, the ceramic raw materials include one or more of the following: alumina, zirconium oxide, titanium oxide, silicon carbide, kaolin, halloysite, and fly ash-based ceramic raw materials. In this embodiment, kaolin is selected. The particle size of the ceramic powder is 0.1 μm-50 μm.

[0047] In step one, the temporary pore-forming agent includes one or more of starch, polymethyl methacrylate microspheres, graphite powder, and cellulose; in this embodiment, graphite powder is selected. The temporary pore-forming agent accounts for 5%-30% of the ceramic powder mass.

[0048] Step 2, support body forming: The support body blank is formed, dried and pre-fired to obtain a porous support body with interconnected channels.

[0049] In step two, the pre-firing temperature is 700℃-1100℃, the pre-firing time is 1h-4h, and the resulting porous support has an open porosity of 25%-55% and an average pore size of 0.2μm-20μm.

[0050] Step 3, confined sealing: Prepare a sealing solution containing pyrolytic organic matter, nano-oxide precursor, and wetting agent; place the porous support and sealing solution in a vacuum impregnation container, ensuring the sealing solution completely covers the porous support; use a vacuum pump to evacuate the vacuum impregnation container to create a negative pressure environment, allowing air to escape from the surface pores of the porous support; stop the vacuum pump and release the negative pressure, allowing the sealing solution to enter the surface pores of the porous support; remove the porous support from the sealing solution, remove excess sealing solution from the surface, and perform low-temperature curing to form a confined sealing layer covering the surface pores of the porous support and having micro-recessed areas on the outer surface.

[0051] In step three, the pyrolytic organic compounds include one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, and cellulose derivatives. In this embodiment, polyvinyl alcohol is selected.

[0052] The nano-oxide precursor includes one or more of silica sol, titanium sol, zirconium sol and aluminum sol. In this embodiment, silica sol is selected.

[0053] The method for preparing the sealing solution is as follows: First, add the pyrolytic organic matter to one of the deionized water or alcohol-water mixture and stir to dissolve it. Then, add the nano-oxide precursor and wetting agent and continue stirring to disperse to obtain the sealing solution.

[0054] In step three, the vacuum pump evacuates the vacuum impregnation container to a vacuum level of -0.03MPa to -0.09MPa, the negative pressure impregnation time is 1min to 20min, and the low-temperature curing temperature is 40℃ to 120℃.

[0055] Step 4, gradient film formation: a low-solids-content film layer slurry and a high-solids-content film layer slurry are sequentially coated on the outer surface of the confined sealing layer. The low-solids-content film layer slurry fills the micro-recessed area on the outer surface of the confined sealing layer, and the high-solids-content film layer slurry forms a continuous film layer, thus obtaining a composite film preform.

[0056] In step four, the solid content of the low-solids film layer slurry is 5%-20%, and the solid content of the high-solids film layer slurry is 20%-45%. Both the low-solids film layer slurry and the high-solids film layer slurry include ceramic fine powder, dispersant, binder and solvent.

[0057] Step 5, slow-release drying: The composite film preform is placed in an environment with decreasing humidity to dry, resulting in a dried composite preform.

[0058] In step five, the humidity-reducing environment is formed by a constant temperature and humidity drying oven. After the composite film preform is placed in the constant temperature and humidity drying oven, it goes through the first drying stage, the second drying stage and the third drying stage in sequence. The relative humidity of the first drying stage is 70%-95%, the relative humidity of the second drying stage is 45%-70%, and the relative humidity of the third drying stage is 20%-45%.

[0059] Step 6, Segmented sintering: The dried composite green body is sequentially treated with a debinding section, a conversion section, and a dense connection section, which decomposes the pyrolytic organic matter and releases the pores of the porous support, transforms the nano-oxide precursor into oxide transition particles, and allows the continuous film layer to combine with the porous support through the oxide transition particles, thus obtaining a ceramic film substrate.

[0060] In step six, the processing temperature of the glue removal section is 250℃-450℃, the processing temperature of the conversion section is 450℃-750℃, and the processing temperature of the dense bonding section is 900℃-1350℃.

[0061] Step 7, hydrophilic modification: The ceramic film substrate is placed in a modification solution containing silicon, titanium or zirconium source for hydrothermal treatment, so that hydrophilic nano-modification points are formed on the outer surface of the continuous film layer and the inner wall of the near-surface pores that are connected to the pores on the outer surface of the continuous film layer. After cleaning and drying, a high-performance ceramic film is obtained.

[0062] In step seven, the hydrothermal treatment temperature is 80℃-180℃, and the hydrothermal treatment time is 0.5h-8h.

[0063] The specific implementation process is as follows: In the first step, during powder pretreatment, ceramic raw materials are processed into ceramic powder using a preparation device. The ceramic powder is then thoroughly mixed with a temporary pore-forming agent, a sintering aid, and a dispersion medium to obtain a uniform support blank. The temporary pore-forming agent forms the source of pores during subsequent pre-firing, the sintering aid improves the bonding state between powder particles, and the dispersion medium ensures that the components are uniformly dispersed during the mixing stage.

[0064] The second step involves shaping and drying the support blank to form a stable blank, and then pre-firing it to give it initial strength while retaining the connecting channels, resulting in a porous support with connecting channels, which provides a load-bearing foundation for subsequent confined sealing and film coating.

[0065] The third step is confined sealing: The porous support is immersed in the sealing liquid, and a vacuum pump is started to evacuate the vacuum impregnation container, creating a negative pressure environment. This negative pressure environment can expel air from the surface pores and near-surface pores of the porous support. After the negative pressure impregnation time is reached, the vacuum pump is turned off and the negative pressure is released, allowing the vacuum impregnation container to return to normal pressure. During the pressure recovery process, the sealing liquid enters the surface pores and near-surface pores of the porous support. Subsequently, the porous support is removed from the sealing liquid, and excess sealing liquid on the surface is removed by scraping, wiping, or blowing, so that the sealing liquid mainly remains in the surface pores and near-surface pores. Then, it is cured at low temperature to form a confined sealing layer. This confined sealing layer cures and shapes along the surface pores and surface undulations of the porous support, forming localized concave areas, i.e., micro-recesses, on its outer surface. During the subsequent coating of the film slurry, the confined sealing layer acts as a temporary barrier.

[0066] The fourth step is gradient film formation: a low-solids-content film layer slurry and a high-solids-content film layer slurry are sequentially coated on the outer surface of the confined sealing layer. The low-solids-content film layer slurry preferentially fills the micro-recesses on the outer surface of the confined sealing layer, while the high-solids-content film layer slurry mainly forms a continuous film layer on its surface, thereby reducing the penetration of the film layer slurry into the deep pores of the support, resulting in a composite membrane preform.

[0067] Step 5, slow-release drying: The composite membrane preform is dried in an environment with decreasing humidity. The composite membrane preform is first slowly dried in a high humidity environment to remove some of the solvent, then transferred to a medium humidity environment to continue drying, and finally shaped in a low humidity environment. This allows the continuous film layer to gradually shrink during the drying process, avoiding cracking, and resulting in a dried composite preform.

[0068] Step 6, Segmented Sintering: The dried composite green body is sequentially treated with a debinding section, a conversion section, and a dense bonding section. The debinding section decomposes the pyrolytic organic matter and releases the temporarily blocked pores; the conversion section transforms the nano-oxide precursor into oxide transition particles; the dense bonding section allows the continuous film layer to bond with the porous support through the oxide transition particles, thus obtaining a ceramic film substrate.

[0069] Step 7, hydrophilic modification: The ceramic film substrate is placed in a modification solution containing silicon, titanium, or zirconium sources for hydrothermal treatment, forming hydrophilic nano-modification points on the outer surface of the continuous film layer and on the inner walls of the near-surface pores that communicate with the pores on the outer surface of the continuous film layer. After cleaning and drying, a high-performance ceramic film is obtained.

[0070] In this embodiment, a confined sealing layer prevents the deep penetration of the membrane slurry during the film formation stage, and releases the pores and forms oxide transition particles during the segmented sintering stage, so that the continuous membrane can be stably bonded to the surface of the porous support while retaining the interconnecting channels of the support. Furthermore, hydrophilic modification improves the wettability of the membrane surface, thereby achieving a comprehensive improvement in the flux, structural stability and antifouling performance of the ceramic membrane.

[0071] Example 2:

[0072] The difference from Example 1 is as follows: Figure 2 and attached Figure 3 As shown, the apparatus for preparing high-performance ceramic films includes a dual-head drive unit 1. One output end of the dual-head drive unit 1 is provided with a grinding component for grinding raw materials, and the other output end of the dual-head drive unit 1 is provided with a cleaning component for reducing clogging of the grinding component.

[0073] The grinding assembly includes a filter cage 3 coaxially bolted to one output end of the dual-head drive 1. Several grinding balls are placed inside the filter cage 3. An outer sleeve 2 is fitted on the outside of the filter cage 3. One output end of the dual-head drive 1 passes through one side wall of the outer sleeve 2 and rotates with it. Several fixing posts 6 are bolted between the outer sleeve 2 and the dual-head drive 1.

[0074] The bottom of the outer sleeve 2 has a discharge trough 22. The outer sleeve 2 and the filter cage 3 both have a feed port 5 on the side wall away from the double-head drive component 1. The feed port 5 on the outer sleeve 2 is detachably connected to a cover 4.

[0075] Both the dual-head drive unit 1 and the outer sleeve 2 are bolted to the bottom of a support plate 7, and a collection frame 9 is bolted between the support plates 7.

[0076] The cleaning assembly includes a piston cylinder 16, with a slide rail 13 bolted to the top of the piston cylinder 16 and several support columns 8 bolted to the bottom of the piston cylinder 16; a rotating rod 10 is bolted to the output end of the dual-head drive unit 1 away from the fixed column 6, and a transmission rod 11 is rotatably engaged at the other end of the rotating rod 10, and a slider 12 is rotatably engaged at the other end of the transmission rod 11, with the slider 12 slidingly engaged with the slide rail 13.

[0077] A piston rod 14 is bolted to the side wall of slider 12. The other end of piston rod 14 passes through the top of piston cylinder 16 and is bolted to piston plate 15 inside piston cylinder 16. A partition plate 17 is bolted to the inner side wall of piston cylinder 16.

[0078] The piston cylinder 16 has several suction holes 18 on its side wall, all of which are located above the partition plate 17. The partition plate 17 has through holes 19. The piston cylinder 16 has an exhaust hole 20 at its bottom. The outer sleeve 2 has several jet holes 21 on its side wall, all of which are connected to the exhaust holes 20. Each suction hole 18 is equipped with an intake one-way valve, and the airflow direction is from the outside of the piston cylinder 16 to the inside of the piston cylinder 16. An exhaust one-way valve is equipped in the through hole 19, and the airflow direction is from the upper chamber of the partition plate 17 to the lower chamber of the partition plate 17. An exhaust hole 20 is equipped with a solenoid valve, which is electrically connected to a controller. A pressure sensor is attached to the bottom of the partition plate 17, and the pressure sensor is electrically connected to the controller.

[0079] Specifically, during use, the device is placed on a flat surface by the support plate 7 and the support column 8, so that the outer sleeve 2, the double-headed drive component 1 and the piston cylinder 16 remain stable.

[0080] After opening the cover 4, add the ceramic raw material into the filter cage 3 through the feed inlet 5, and then close the cover 4.

[0081] After the dual-head drive unit 1 is activated, one output end of the dual-head drive unit 1 drives the filter cage 3 to rotate inside the outer sleeve 2. The grinding balls inside the filter cage 3 tumble with the filter cage 3 and collide with and squeeze the ceramic raw material, so that the ceramic raw material is gradually ground into powder. The powder that meets the conditions for passing through the pores of the filter cage 3 falls from the filter cage 3 into the bottom of the outer sleeve 2 under the action of gravity, and enters the collection frame 9 through the discharge chute 22.

[0082] The output end of the other end of the dual-head drive unit 1 synchronously drives the rotating rod 10 to rotate. When the rotating rod 10 rotates, it drives the transmission rod 11 to swing. The transmission rod 11 then pushes the slider 12 to slide back and forth along the slide rail 13. When the slider 12 moves back and forth, it drives the piston rod 14 to move. The piston rod 14 drives the piston plate 15 to move back and forth inside the piston cylinder 16.

[0083] When the piston plate 15 returns, the air outside the piston cylinder 16 enters the upper chamber of the partition 17 through the intake port 18 and the intake check valve; when the piston plate 15 is compressed, the air in the upper chamber of the partition 17 enters the lower chamber of the partition 17 through the through hole 19 and the exhaust check valve, thereby gradually forming compressed air in the lower chamber of the partition 17.

[0084] A preset air pressure threshold of 0.15 MPa is set in the controller. The air pressure sensor detects the air pressure in the chamber below the partition 17 and transmits the air pressure signal to the controller. When the detected air pressure reaches 0.15 MPa, the controller controls the solenoid valve to open, and the compressed air in the chamber below the partition 17 is sequentially sprayed into the filter cage 3 through the exhaust port 20 and the jet port 21. The sprayed gas can impact the powder attached to the pores of the filter cage 3, causing the powder clogging the pores of the filter cage 3 to fall off; at the same time, the airflow can also disturb the raw material near the pore wall in the filter cage 3, causing some of the insufficiently ground raw material to return to the collision range of the grinding balls to participate in secondary grinding. After the compressed air is released, the controller closes the solenoid valve, and the piston plate 15 continues to reciprocate and replenishes the chamber below the partition 17 with compressed air.

[0085] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-performance ceramic membrane, characterized in that, Includes the following steps: Step 1, Powder pretreatment: The ceramic raw materials are made into ceramic powder using a preparation device, and the ceramic powder, temporary pore-forming agent, sintering aid and dispersion medium are mixed to obtain the support blank; Step 2, Support Forming: The support blank is formed, dried and pre-fired to obtain a porous support with interconnected channels; Step 3, confined sealing: Prepare a sealing solution containing pyrolytic organic matter, nano-oxide precursor and wetting agent; The porous support and sealing liquid are placed in a vacuum impregnation container, and the sealing liquid is submerged in the porous support. A vacuum pump is used to evacuate the vacuum impregnation container to create a negative pressure environment, so that the air in the pores on the surface of the porous support is discharged. Stop the vacuum pump and release the negative pressure to allow the sealing liquid to enter the surface orifices of the porous support. After removing the porous support from the sealing liquid, remove the excess sealing liquid from the surface and perform low-temperature curing to form a confined sealing layer that covers the surface orifices of the porous support and has micro-recesses on the outer surface. Step 4, gradient film formation: a low-solids-content film layer slurry and a high-solids-content film layer slurry are sequentially coated on the outer surface of the confined sealing layer. The low-solids-content film layer slurry fills the micro-recessed area on the outer surface of the confined sealing layer, and the high-solids-content film layer slurry forms a continuous film layer, thus obtaining a composite film preform. Step 5, slow-release drying: The composite film preform is placed in an environment with decreasing humidity to dry, resulting in a dried composite preform; Step 6, Segmented sintering: The dried composite green body is sequentially treated with a debinding section, a conversion section and a dense connection section, so that the pyrolytic organic matter decomposes and releases the pores of the porous support, the nano-oxide precursor is transformed into oxide transition particles, and the continuous film layer is combined with the porous support through the oxide transition particles to obtain a ceramic film matrix. Step 7, hydrophilic modification: The ceramic film substrate is placed in a modification solution containing silicon, titanium or zirconium source for hydrothermal treatment, so that hydrophilic nano-modification points are formed on the outer surface of the continuous film layer and the inner wall of the near-surface pores that are connected to the pores on the outer surface of the continuous film layer. After cleaning and drying, a high-performance ceramic film is obtained.

2. The method for preparing a high-performance ceramic membrane according to claim 1, characterized in that, In step one, the ceramic raw materials include one or more of alumina, zirconium oxide, titanium oxide, silicon carbide, kaolin, halloysite, and fly ash-based ceramic raw materials, and the particle size of the ceramic powder is 0.1μm-50μm.

3. The method for preparing a high-performance ceramic membrane according to claim 2, characterized in that, In step one, the temporary pore-forming agent includes one or more of starch, polymethyl methacrylate microspheres, graphite powder, and cellulose; the temporary pore-forming agent accounts for 5%-30% of the ceramic powder mass.

4. The method for preparing a high-performance ceramic membrane according to claim 3, characterized in that, In step two, the pre-firing temperature is 700℃-1100℃, the pre-firing time is 1h-4h, and the resulting porous support has an open porosity of 25%-55% and an average pore size of 0.2μm-20μm.

5. The method for preparing a high-performance ceramic membrane according to claim 4, characterized in that, In step three, the pyrolytic organic compounds include one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, and cellulose derivatives. Nano-oxide precursors include one or more of silica sol, titanium sol, zirconium sol, and aluminum sol; The method for preparing the sealing solution is as follows: First, add the pyrolytic organic matter to one of the deionized water or alcohol-water mixture and stir to dissolve it. Then, add the nano-oxide precursor and wetting agent and continue stirring to disperse to obtain the sealing solution.

6. The method for preparing a high-performance ceramic membrane according to claim 5, characterized in that, In step three, the vacuum pump evacuates the vacuum impregnation container to a vacuum level of -0.03MPa to -0.09MPa, the negative pressure impregnation time is 1min to 20min, and the low-temperature curing temperature is 40℃ to 120℃.

7. The method for preparing a high-performance ceramic membrane according to claim 6, characterized in that, In step four, the solid content of the low-solids film layer slurry is 5%-20%, and the solid content of the high-solids film layer slurry is 20%-45%. Both low-solids-content and high-solids-content film layer slurries include ceramic fine powder, dispersant, binder and solvent.

8. The method for preparing a high-performance ceramic membrane according to claim 7, characterized in that, In step five, the humidity-reducing environment is formed by a constant temperature and humidity drying oven. After the composite film preform is placed in the constant temperature and humidity drying oven, it goes through the first drying stage, the second drying stage and the third drying stage in sequence. The relative humidity during the first drying stage is 70%-95%; The relative humidity during the second drying stage is 45%-70%; The relative humidity during the third drying stage is 20%-45%.

9. The method for preparing a high-performance ceramic membrane according to claim 8, characterized in that, In step six, the processing temperature of the glue removal section is 250℃-450℃, the processing temperature of the conversion section is 450℃-750℃, and the processing temperature of the dense bonding section is 900℃-1350℃. In step seven, the hydrothermal treatment temperature is 80℃-180℃, and the hydrothermal treatment time is 0.5h-8h.

10. The method for preparing a high-performance ceramic membrane according to claim 9, characterized in that, The preparation device includes a dual-head drive unit (1), one end of which is provided with a grinding component for grinding raw materials, and the other end of which is provided with a cleaning component for reducing clogging of the grinding component; The grinding assembly includes a filter cage (3) coaxially fixedly connected to one output end of the dual-head drive (1). Several grinding balls are placed inside the filter cage (3). An outer sleeve (2) is fitted on the outside of the filter cage (3). One output end of the dual-head drive (1) passes through one side wall of the outer sleeve (2) and rotates with it. Several fixing columns (6) are fixedly connected between the outer sleeve (2) and the dual-head drive (1). A discharge groove (22) is opened at the bottom of the outer sleeve (2). A feed port (5) is opened on the side wall of the outer sleeve (2) and the filter cage (3) away from the dual-head drive (1). A cover (4) is detachably connected to the feed port (5) on the outer sleeve (2). The bottom of the dual-head drive unit (1) and the outer sleeve (2) are both fixedly connected to a support plate (7), and a collection frame (9) is fixedly connected between the support plates (7). The cleaning assembly includes a piston cylinder (16), with a slide rail (13) fixedly connected to the top of the piston cylinder (16) and several support columns (8) fixedly connected to the bottom of the piston cylinder (16); a rotating rod (10) is fixedly connected to the output end of the dual-head drive unit (1) away from the fixed column (6), and a transmission rod (11) is rotatably engaged at the other end of the rotating rod (10), and a slider (12) is rotatably engaged at the other end of the transmission rod (11). The slider (12) is slidably engaged with the slide rail (13), and a piston rod (14) is fixedly connected to the side wall of the slider (12). The other end of the piston rod (14) passes through the top of the piston cylinder (16) and is fixedly connected to a piston plate (15) inside the piston cylinder (16). A partition plate (17) is fixedly connected to the inner side wall of the piston cylinder (16); the piston cylinder (16) side The wall has several air intake holes (18), all of which are located above the partition (17). The partition (17) has through holes (19). The bottom of the piston cylinder (16) has an exhaust hole (20). The side wall of the outer sleeve (2) has several air jet holes (21), all of which are connected to the exhaust hole (20). Each air intake hole (18) is equipped with an air intake one-way valve, and its airflow direction is from outside the piston cylinder (16) to inside the piston cylinder (16). The through hole (19) is equipped with an exhaust one-way valve, and its airflow direction is from the upper chamber of the partition (17) to the lower chamber of the partition (17). The exhaust hole (20) is equipped with a solenoid valve, which is electrically connected to a controller. The bottom of the partition (17) is fixedly connected to a pressure sensor, which is electrically connected to the controller.

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