A method and apparatus for reducing defects in a disc ceramic membrane coating

Abstract

The application provides a method and device for reducing defects of a disc ceramic membrane coating, comprising the following steps: installing a clamp in a forward direction on a spraying station, rotating a ceramic membrane dynamically, cleaning and activating a positive surface of the ceramic membrane by using low-temperature plasma technology; while rotating the ceramic membrane dynamically, performing negative pressure suction on the ceramic membrane, and spraying a membrane liquid on the positive surface of the ceramic membrane by using ultrasonic atomization; rotating the ceramic membrane dynamically, and performing negative pressure suction on the ceramic membrane, so that the ceramic membrane arc part is dynamically immersed in the membrane liquid. By using the cooperation of ceramic membrane dynamic rotation, negative pressure and ultrasonic spraying, when the ultrasonic atomized liquid droplets contact the surface of the ceramic membrane, they are "sucked" into the microporous structure or the surface gap, so that pinholes or defects of the membrane layer are avoided, and a uniform, dense and defect-free membrane layer is formed; contactless treatment of the ceramic membrane is realized, and coating defects caused by improper contact before drying of the membrane layer are effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of disc-type ceramic film technology, and more particularly to a method and apparatus for reducing defects in disc-type ceramic film coatings. Background Technology

[0002] Disk-shaped ceramic membranes are disc-shaped filter media made of ceramic materials. They have advantages such as high mechanical strength, high temperature resistance, corrosion resistance, and good chemical stability, and are widely used in water treatment, food and beverage, biopharmaceutical, and chemical separation fields.

[0003] In the application of disc-type ceramic membranes, the high-speed rotation of the ceramic membrane and the high-speed shearing action on the material accelerate membrane damage, especially at the curved edges where the linear velocity is highest and damage is more likely. Therefore, high quality requirements are placed on the membrane layer. However, in the traditional ceramic membrane coating process, especially when there are processing defects at the curved edges of the ceramic membrane or improper contact with the membrane, membrane defects such as uneven coating, cracks, and large pores can occur. These defects significantly affect filtration efficiency and greatly limit the industrial application of disc-type ceramic membranes, particularly in the filtration and separation of high-end products such as semiconductors, biomedicine, and new energy. Therefore, designing a method and device to reduce coating defects in disc-type ceramic membranes is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to disclose a method and apparatus for reducing defects in disc-type ceramic film coatings. First, it employs a combination of dynamic rotation of the ceramic film and low-temperature plasma technology to clean and activate the surface of the ceramic film, efficiently removing surface contaminants and improving the wettability and coating adhesion of the ceramic film surface. Second, it utilizes a combination of dynamic rotation of the ceramic film, negative pressure, and ultrasonic spraying. When ultrasonically atomized droplets contact the ceramic film surface, they are "absorbed" into the microporous structure or surface gaps, improving the adhesion of the film-forming solution without impacting or damaging the already formed film area, thus avoiding pinholes or defects in the film layer. First, it ensures the uniformity of the membrane's microstructure, forming a uniform, dense, and defect-free membrane layer, thus improving filtration efficiency. Second, by using dynamic rotation and negative pressure to dip-coat the curved parts of the ceramic membrane, a uniform and dense membrane layer can be covered on the surface of the curved parts, optimizing the membrane formation process at the curved corners, reducing the processing requirements for the curved corners, improving the yield of the ceramic membrane, reducing the processing cost of the ceramic membrane, and improving the filtration accuracy. Third, the ceramic membrane is fixed by a clamp, achieving non-contact treatment of the ceramic membrane throughout the process, effectively preventing coating defects caused by improper contact before the membrane layer dries.

[0005] To achieve the above objectives, the present invention provides a method for reducing defects in disc-type ceramic film coatings, comprising the following steps:

[0006] Step 1: Prepare the film-forming solution;

[0007] Step 2: Install the ceramic diaphragm onto the fixture and clean and dry it;

[0008] Step 3: Install the fixture in the forward position on the spraying station, causing the ceramic diaphragm to rotate dynamically. Use low-temperature plasma technology to clean and activate the front surface of the ceramic diaphragm.

[0009] Step 4: While the ceramic diaphragm is rotating dynamically, negative pressure suction is applied to the ceramic diaphragm, and ultrasonic atomization is used to spray the film-forming solution onto the front surface of the ceramic diaphragm. After spraying, drying is performed.

[0010] Step 5: Install the fixture in reverse on the spraying station, and repeat steps 3 and 4;

[0011] Step 6: Then install the fixture on the dip coating station, so that the ceramic diaphragm rotates dynamically and is subjected to negative pressure suction, so that the arc part of the ceramic diaphragm is dynamically dipped in the film coating solution.

[0012] Step 7: Dry the ceramic diaphragm together with the fixture, then remove the ceramic diaphragm and fire it.

[0013] In some embodiments, in step one, the film-forming solution comprises the following components in parts by weight: 0.001-0.5 parts of dispersant, 0.1-1 parts of binder, 0.0001-0.01 parts of defoamer, 0.01-0.2 parts of sintering aid, and 1 part of metal compound; the above components are ultrasonically dispersed in a constant temperature water bath at 10-40°C for 5-60 minutes to obtain the film-forming solution, wherein the solid content of the film-forming solution is 0.1-40 wt%.

[0014] In some embodiments, the dispersant is one or more of sodium polyacrylate, polyacrylamide, and polyacrylic acid; the binder is one or more of PVA, PVB, PEG, and HPC; the defoamer is one or more of alcohols, organosilicones, polyethers, and esters; the sintering aid is one or more of yttrium nitrate, cerium nitrate, lanthanum nitrate, alumina, titanium dioxide, zirconium oxide, and silicon dioxide; and the metal compound is one or more of alumina, titanium dioxide, zirconium oxide, silicon dioxide, cerium oxide, yttrium oxide, and lanthanum oxide.

[0015] In some embodiments, in step two, the ceramic membrane is rinsed or soaked in an organic solvent for 5–120 min, then rinsed, soaked and ultrasonically cleaned with pure water 2–3 times, each time for 5–120 min, and finally dried at 50–200°C for 10–240 min.

[0016] In some embodiments, in step three, the ceramic diaphragm and fixture are preheated to 50-200°C in an oven, and then removed and installed on the spraying station. The dynamic rotation speed of the ceramic diaphragm is 2-100 RPM. Low-temperature plasma technology is used, with air as the gas source, to ionize and generate a mixture of electrons, ions, atoms and atomic groups to clean and activate the surface of the ceramic diaphragm for 5-120 seconds, removing surface contaminants.

[0017] In some embodiments, in step four, the spraying environment temperature is controlled at 20–60°C and the relative humidity is controlled at 20–80%; a negative pressure generating device is used to perform negative pressure suction on the ceramic diaphragm, and the pressure is controlled at -100–0 kPa; the dynamic rotation speed of the ceramic diaphragm is controlled at 2–100 RPM; the film-forming solution is magnetically stirred under a constant temperature water bath at 10–40°C, and a peristaltic pump is used for liquid injection, with the injection flow rate controlled at 0–65 ml / min; an ultrasonic atomizing spraying device is used to spray the surface of the ceramic diaphragm for 1–60 min; after spraying, the ceramic diaphragm and fixture are removed together and placed in a constant temperature and humidity chamber, with the ceramic diaphragm in a suspended state, for drying for 30–300 min, with the temperature of the constant temperature and humidity chamber controlled at 20–80°C and the relative humidity controlled at 20–80%.

[0018] In some embodiments, in step six, the ambient temperature for immersion coating is controlled at 20–60°C and the relative humidity is controlled at 20–80%; a negative pressure generating device is used to perform negative pressure suction on the ceramic diaphragm, and the pressure is controlled at -100–0 kPa; the dynamic rotation speed of the ceramic diaphragm is controlled at 2–50 RPM; and the dynamic immersion time of the arc-shaped part of the ceramic diaphragm in the film-forming solution is controlled at 0–240 s.

[0019] In some embodiments, in step seven, after the dip coating is completed, the ceramic film is dried together with the fixture. During the drying process, the ceramic film is suspended in the air and dried in a constant temperature and humidity chamber for 30 to 300 minutes. The temperature of the constant temperature and humidity chamber is controlled at 20 to 80°C and the relative humidity is controlled at 20 to 80%. Then, it is calcined at 400 to 1300°C for 10 to 240 minutes.

[0020] To achieve the above objectives, the present invention also provides an apparatus for reducing defects in disc-type ceramic film coatings, characterized in that it includes a ceramic film surface spraying mechanism and a ceramic film arc portion dip coating mechanism.

[0021] The ceramic diaphragm surface spraying mechanism includes a spraying chamber, a fixed plate installed inside the spraying chamber, a first motor installed on the fixed plate, a hollow rotating shaft driven by the first motor, a clamp connected to the hollow rotating shaft, a ceramic diaphragm installed on the clamp, a track located above the ceramic diaphragm, and a movable seat sliding on the track.

[0022] It also includes a vacuum pump and a rotary joint connected to the vacuum pump; the rotary joint is connected to a hollow shaft.

[0023] It also includes a magnetic stirrer, a peristaltic pump connected to the magnetic stirrer, and a first ultrasonic nozzle and a second ultrasonic nozzle connected to the peristaltic pump; the first ultrasonic nozzle is disposed facing the arc portion of the ceramic diaphragm, and the second ultrasonic nozzle is mounted on a movable base and disposed facing the surface of the ceramic diaphragm.

[0024] It also includes a low-temperature plasma treatment machine, wherein the plasma spray gun of the low-temperature plasma treatment machine is mounted on a movable base and arranged facing the surface of the ceramic membrane.

[0025] The ceramic diaphragm arc portion dip coating mechanism includes a second motor, a clamp driven by the second motor, a ceramic diaphragm mounted on the clamp, a rotary joint connected to the clamp, a vacuum pump connected to the rotary joint, a lifting platform, and a film-forming liquid tank placed on the lifting platform; the ceramic diaphragm arc portion is dynamically dipped in the film-forming liquid.

[0026] In some embodiments, the clamp includes two hollow tubes and flanges connected to the hollow tubes; the ceramic diaphragm is clamped by the two flanges, which are connected by bolts and nuts, a sealing ring is provided between the ceramic diaphragm and the flanges, and the hollow tubes are provided with internal threads.

[0027] In some embodiments, in the ceramic diaphragm surface spraying mechanism, one hollow tube of the clamp is screwed to a hollow shaft, and the other hollow tube of the clamp is sealed by bolts, with a sealing ring provided between the bolts and the hollow tube.

[0028] In some embodiments, the fixing plate is provided with a fixing seat, the fixing seat is provided with a groove, and the hollow rotating shaft and the hollow tube both extend into the groove for connection.

[0029] In some embodiments, the track is a lead screw, the movable seat is a nut seat, and a third motor is also included to drive the lead screw to rotate.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] I. The ceramic diaphragm surface is cleaned and activated by a combination of dynamic rotation of ceramic diaphragms and low-temperature plasma technology, which effectively removes surface contaminants and improves the wettability and coating adhesion of the ceramic diaphragm surface.

[0032] Second, by using dynamic rotation of ceramic membrane, negative pressure and ultrasonic spraying in synergy, when ultrasonic atomized droplets come into contact with the surface of ceramic membrane, they are "absorbed" into the microporous structure or surface gaps, which improves the adhesion of the membrane-forming solution and does not cause impact damage to the already formed membrane area, avoiding pinholes or defects in the membrane layer, ensuring the uniformity of the membrane layer microstructure, forming a uniform, dense and defect-free membrane layer, and improving filtration efficiency.

[0033] Third, by using dynamic rotation and negative pressure to dip and coat the arc-shaped part of the ceramic membrane, a uniform and dense membrane layer can be covered on the surface of the arc-shaped part of the ceramic membrane. This optimizes the film formation process of the arc corner, reduces the processing requirements of the arc corner, improves the yield of ceramic membranes, reduces the processing cost of ceramic membranes, and improves the filtration accuracy.

[0034] Fourth, the ceramic diaphragm is fixed by a clamp, which allows for non-contact treatment of the ceramic diaphragm throughout the process, effectively preventing coating defects caused by improper contact before the film dries. Attached Figure Description

[0035] Figure 1 This is a comparison chart of the bubble point pressure (a) of the ceramic diaphragm coating shown in this invention and the bubble point pressure (b) of the conventional ceramic diaphragm coating;

[0036] Figure 2 This is a comparison diagram of the bubble point pore size distribution (c) of the ceramic membrane coating shown in this invention and the bubble point pore size distribution (d) of a traditional ceramic membrane coating;

[0037] Figure 3 SEM images (e) of the ceramic film coating surface shown in this invention and (f) of the conventional ceramic film coating surface are shown.

[0038] Figure 4 SEM images of cross-sections of ceramic membrane coatings according to the present invention (g) and conventional ceramic membrane coatings (h) are shown.

[0039] Figure 5 A comparison of the surface roughness of the ceramic membrane coating, ceramic membrane (support), and traditional ceramic membrane coating shown in this invention;

[0040] Figure 6 This is a comparison diagram of the pore size distribution of ceramic membrane coatings after plasma activation treatment (I) and without plasma activation treatment (J) as shown in this invention.

[0041] Figure 7 This is a comparison diagram of the pore size distribution of the ceramic membrane coating under different ambient humidity conditions as shown in this invention.

[0042] Figure 8 This is a schematic diagram of the fixture shown in this invention;

[0043] Figure 9 This is a schematic diagram of the ceramic diaphragm surface spraying mechanism shown in this invention;

[0044] Figure 10 This is a schematic diagram of the structure of the ceramic diaphragm arc-shaped part dip-coating mechanism shown in this invention. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent changes or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0046] Example 1:

[0047] This embodiment discloses a method for reducing defects in disc-type ceramic film coatings, comprising the following steps:

[0048] Step 1: Prepare the film-forming solution;

[0049] Specifically, the film-forming solution comprises the following components in parts by weight: 0.5 parts dispersant, 1 part binder, 0.01 parts defoamer, 0.2 parts sintering aid, and 1 part metal compound; the above components are ultrasonically dispersed in a constant temperature water bath at 40°C for 30 minutes to obtain the film-forming solution. The dispersant is sodium polyacrylate, the binder is PVA, the defoamer is an alcohol, the sintering aid is yttrium nitrate, and the metal compound is alumina.

[0050] Dispersants ensure uniform dispersion of metal compound particles in the liquid phase, preventing agglomeration and forming a stable suspension system. Uniform component dispersion improves the consistency of the film's chemical and physical properties. Ultrasonic dispersion further breaks up particle agglomeration through cavitation, improving dispersion uniformity, especially effective for nanoscale metal compounds. Uniform component dispersion further enhances the consistency of the film's chemical and physical properties. Low-temperature water baths prevent solvent evaporation or component degradation caused by high temperatures, maintaining system stability. Binders provide mechanical strength, enhance film flexibility and adhesion, and prevent cracking during drying or sintering. Defoamers eliminate bubbles introduced by stirring and ultrasound, reducing film defects such as pinholes and cracks, and improving surface smoothness. Defoamers and binders synergistically reduce microscopic defects, enhancing film reliability. Sintering aids lower the sintering temperature of metal compounds, promote interparticle diffusion, form a denser structure, and improve the film's mechanical or electrical properties. Sintering aids optimize grain boundary structure, potentially improving film hardness, thermal stability, or electrical conductivity.

[0051] Step 2: Install the ceramic diaphragm onto the fixture and clean and dry it;

[0052] Specifically, the ceramic membrane is rinsed or soaked in an organic solvent for 80 minutes, then rinsed, soaked, and ultrasonically cleaned with pure water three times, each time for 60 minutes, and finally dried at 100°C for 120 minutes.

[0053] Organic solvent treatment can remove organic pollutants, dissolve and remove grease, residual binders, or organic additives such as dispersants and defoamers in the membrane preparation solution from the membrane surface; it can improve the porosity, as the membrane has a porous structure and organic solvents such as ethanol and acetone can unclog the channels blocked by organic matter and restore the porosity; it can also adjust the surface, as solvent cleaning may change the wettability of the membrane surface, laying the foundation for subsequent water washing or functionalization treatment.

[0054] Multiple washes with pure water thoroughly remove solvent residues, preventing secondary contamination or surface defects caused by organic solvents during drying. Ionic impurities are also removed; water washing dissolves and washes away inorganic salt impurities such as sintering aid residues and metal ions, improving the chemical purity of the membrane. Furthermore, the synergistic effect of ultrasound, with ultrasonic cavitation, strips away particulate contaminants, enhancing pore cleanliness, and providing more significant cleaning effects for complex structures such as asymmetrical or tortuous pores.

[0055] High-temperature drying completely removes moisture, preventing residual moisture from causing bubbles or cracks during subsequent applications such as coating deposition; it also stabilizes the structure, as drying at an appropriate temperature reduces shrinkage stress on the membrane caused by rapid drying, maintaining geometric stability; and it serves as a pretreatment stage, with 100°C drying acting as a preheating phase to reduce the risk of thermal shock.

[0056] This cleaning and drying process significantly improves the performance of ceramic membranes through step-by-step treatment, resulting in high surface cleanliness, good restoration of pore function, and improved flux of porous ceramic membranes such as permeability and filtration efficiency; optimized interface performance, with the cleaned surface enhancing the adhesion and uniformity of subsequent modifications such as coatings and activation; and improved reliability, reducing performance degradation caused by impurities such as membrane fouling.

[0057] Step 3: Install the fixture in the forward position on the spraying station, causing the ceramic diaphragm to rotate dynamically. Use low-temperature plasma technology to clean and activate the front surface of the ceramic diaphragm.

[0058] Specifically, the ceramic diaphragm and fixture are preheated to 200°C in an oven, then removed and installed on the spraying station. The dynamic rotation speed of the ceramic diaphragm is 60 RPM. Low-temperature plasma technology is used, with air as the gas source, to ionize and generate a mixture of electrons, ions, atoms and atomic groups to clean and activate the surface of the ceramic diaphragm for 100 seconds, removing surface contaminants and improving the wettability and coating adhesion of the diaphragm surface.

[0059] Preheating can remove adsorbed moisture and volatile pollutants. High-temperature baking can evaporate adsorbed moisture and residual organic solvents on the surface of the membrane and fixture, avoiding interference with reaction activity during subsequent plasma treatment. It can also reduce thermal stress, as preheating reduces the temperature gradient between the membrane and subsequent plasma treatment (which may be accompanied by local temperature rise), preventing cracking or deformation caused by sudden heating. Furthermore, it can initially improve surface energy: high temperature can partially remove weakly bound pollutants such as grease, providing a cleaner initial surface for plasma activation.

[0060] The effects of dynamic rotation of ceramic diaphragms are as follows: 1. Uniform treatment: Rotation ensures that the plasma acts on the entire surface of the diaphragm, avoiding uneven treatment such as edge effects or shadow areas caused by static spraying; 2. Enhanced contaminant removal: Centrifugal force assists in removing particulate contaminants desorbed during plasma cleaning, improving cleaning efficiency; 3. Optimized coating pre-coverage: The activated surface in the rotating state is more conducive to the uniform adhesion of the coating.

[0061] Utilizing low-temperature plasma cleaning and activation, this method offers several advantages: 1. Deep cleaning of ceramic diaphragms: During production, ceramic diaphragms may accumulate oil on their surface due to skin contact and equipment contact. This oil directly affects the adhesion of the coating solution during subsequent application, resulting in incomplete coating. Some oils, such as those from equipment, require alcohol soaking for removal. However, alcohol residue remains on the ceramic diaphragm surface, hindering coating solution adsorption. In contrast, the high-energy ions and electrons in the plasma bombard the ceramic diaphragm surface, physically stripping away nanoscale contaminants such as organic matter and dust. Furthermore, the active oxygen atoms (O) and free radicals (·OH) generated by the air plasma oxidize and decompose organic contaminants such as oil. First, plasma can remove grease, residual binders, and volatile products such as CO2 and H2O. Second, it can activate the surface of ceramic films: plasma introduces polar groups such as -OH and -COOH on the surface of ceramic films, which significantly increases the surface energy, making the film hydrophilic and improving its wettability to water-based solutions or coatings. Plasma etching can form nanoscale uneven structures, increasing the specific surface area and further enhancing adhesion, i.e., the mechanical anchoring effect. Third, it can provide chemical bonding sites for ceramic films: the activated surface generates dangling bonds or active sites, which form stronger chemical bonds with subsequent coatings (such as Si-O-C, Ti-O-N), rather than just physical adsorption, thus increasing the adhesion of the coating.

[0062] This process achieves efficient and uniform surface modification while ensuring the integrity of the ceramic diaphragm substrate through the synergistic effect of heat, force, and plasma.

[0063] Step 4: While the ceramic diaphragm is rotating dynamically, negative pressure suction is applied to the ceramic diaphragm, and ultrasonic atomization is used to spray the film-forming solution onto the front surface of the ceramic diaphragm. After spraying, drying is performed.

[0064] Specifically, the spraying environment temperature was controlled at 50℃ and the relative humidity at 70%; a negative pressure generating device was used to perform negative pressure suction on the ceramic diaphragm, controlling the pressure at -100kPa; the dynamic rotation speed of the ceramic diaphragm was controlled at 60RPM; the film-forming solution was magnetically stirred under a constant temperature water bath at 40℃, and a peristaltic pump was used for liquid injection, with the injection flow rate controlled at 55ml / min; an ultrasonic atomizing spraying device was used to spray the ceramic diaphragm surface for 30 minutes; after spraying, the ceramic diaphragm and fixture were removed together and placed in a constant temperature and humidity chamber, with the ceramic diaphragm suspended, for drying for 200 minutes. The temperature of the constant temperature and humidity chamber was controlled at 50℃ and the relative humidity at 70%. The suspended drying of the ceramic diaphragm, without contact, effectively prevents coating defects caused by improper contact before the film layer dries.

[0065] By employing negative pressure suction, a negative pressure is generated inside the ceramic membrane, causing the sprayed atomized droplets to be "suctioned" into the microporous structure or surface gaps when they reach the ceramic membrane surface. This significantly enhances the droplet permeability and anchoring effect, reduces surface droplet bounce and splashing, improves initial adhesion, and promotes a more uniform and continuous underlayer spreading. This is crucial for forming a defect-free, low-porosity, dense separation layer.

[0066] The dynamic rotation of the ceramic membrane ensures that the atomized droplets can be uniformly deposited on the surface of the ceramic membrane from all angles. This effectively avoids the "shadow effect" (some areas are not sprayed) and "coffee ring effect" (solution migrates and accumulates towards the edge) caused by static spraying, resulting in a membrane layer with extremely high thickness distribution consistency.

[0067] Ultrasonic atomization produces smaller droplets, typically reaching the micrometer or even submicrometer level, with narrower distribution, lower flight speed, and lower momentum. These smaller droplets are more easily "sucked" into the pores of the ceramic membrane by negative pressure, which is beneficial for forming a thinner, homogeneous separation layer. At the same time, the low momentum reduces the impact damage of droplets on the already formed film area, avoiding pinholes or defects and ensuring the uniformity of the film's microstructure.

[0068] Step 5: Install the fixture in reverse on the spraying station, and repeat steps 3 and 4 to allow both sides of the ceramic diaphragm to be cleaned and coated with the film-forming solution. The ceramic diaphragm fixture is designed with the front and back sides switchable, and the ceramic diaphragms do not come into contact during production, effectively preventing coating defects caused by improper contact before the film dries.

[0069] Step 6: Then install the fixture on the dip coating station, so that the ceramic diaphragm rotates dynamically and is subjected to negative pressure suction, so that the arc part of the ceramic diaphragm is dynamically dipped in the film coating solution.

[0070] Specifically, the ambient temperature for immersion coating is controlled at 50℃ and the relative humidity is controlled at 70%; a negative pressure generating device is used to perform negative pressure suction on the ceramic diaphragm, and the pressure is controlled at -100kPa; the dynamic rotation speed of the ceramic diaphragm is controlled at 40RPM; and the dynamic immersion time of the arc part of the ceramic diaphragm in the film-forming solution is controlled at 200s.

[0071] By employing negative pressure suction, a negative pressure is generated inside the ceramic membrane. When the arc-shaped part of the ceramic membrane comes into contact with the membrane-forming liquid, the liquid is "drawn" into the microporous structure or surface gaps. This significantly enhances the permeability and anchoring effect of the droplets, reduces the rebound and splashing of surface droplets, improves the initial adhesion, and promotes a more uniform and continuous spread of the underlying layer. This is crucial for forming a dense separation layer with no defects and low porosity.

[0072] The dynamic rotation of the ceramic membrane ensures that the arc-shaped part of the ceramic membrane is dynamically immersed in the coating solution, so that the arc-shaped part can be uniformly immersed in the coating solution. This effectively avoids the "shadow effect" (some areas are not sprayed) and "coffee ring effect" (solution migrates and accumulates towards the edge) caused by static spraying, resulting in a membrane layer with extremely high thickness distribution uniformity.

[0073] It can make the surface of the arc part of the ceramic membrane covered with a uniform and dense membrane layer, optimize the arc corner film formation process, reduce the processing requirements of the arc corner, improve the processing yield of ceramic membranes, reduce the processing cost of ceramic membranes, and improve the filtration accuracy of disc ceramic membranes.

[0074] Step 7: Dry the ceramic diaphragm together with the fixture, then remove the ceramic diaphragm and fire it.

[0075] Specifically, after the dip coating is completed, the ceramic film is dried together with the fixture. During the drying process, the ceramic film is suspended in the air and dried in a constant temperature and humidity chamber for 200 minutes. The temperature of the constant temperature and humidity chamber is controlled at 60℃ and the relative humidity is controlled at 70%. Then, it is calcined at 800℃ for 180 minutes.

[0076] The ceramic diaphragm is suspended and dried without contact, which can effectively prevent coating defects caused by improper contact before the diaphragm dries.

[0077] Bubble point is an indicator used to detect the pore size of a membrane. The test pressure is increased from low to high, and the pressure at which the first bubble appears is the bubble point pressure of the membrane. The lower the bubble point pressure, the larger the pore size. (Combined with...) Figure 1 and Figure 2It is known that the ceramic membrane coating of this invention has a high bubble point pressure and a small bubble point pore size, while traditional ceramic membrane coatings have a low bubble point pressure and a large bubble point pore size. The ceramic membrane surface of this invention is more likely to maintain the uniformity of the microstructure and form a film layer with low surface roughness and no defects. The high bubble point pressure and small bubble point pore size of the ceramic membrane coating of this invention is due to the use of dynamic rotation of the ceramic membrane, negative pressure and ultrasonic synergistic spraying. When the ultrasonic atomized droplets come into contact with the surface of the ceramic membrane, they are "absorbed" into the microporous structure or surface gaps. The adhesion of the film-forming solution is strong, the surface of the ceramic membrane is filled and there are no defects, which can form a dense and uniform film that can withstand strong pressure.

[0078] Combination Figure 3 , Figure 4 and Figure 5 It can be seen that the ceramic diaphragm coating obtained by the present invention has a uniform surface, low roughness, and no defects, while the traditional ceramic diaphragm coating has an uneven surface, pits, cracks, and large pores, resulting in high roughness.

[0079] from Figure 6 It can be seen that, under the same conditions, the ceramic membrane coating treated with plasma activation (I) has a smaller pore size and better filtration effect, while the ceramic membrane coating without plasma activation (J) has a larger pore size.

[0080] from Figure 7 It can be seen that, under the same conditions, when the ambient humidity H = 70%, the ceramic membrane coating has a smaller pore size and a better filtration effect.

[0081] Example 2:

[0082] This embodiment discloses an apparatus for reducing defects in disc-type ceramic film coatings to achieve the method of Embodiment 1, including a ceramic film surface spraying mechanism and a ceramic film arc portion dip coating mechanism.

[0083] like Figure 8 As shown, the clamp 1 includes two hollow tubes 11 and flanges 12 connected to the hollow tubes 11. The ceramic diaphragm 2 is clamped by the two flanges 12, which are connected by bolts and nuts, so that the ceramic diaphragm 2 and the clamp 1 form an integral structure that can rotate synchronously.

[0084] A sealing ring 13 is provided between the ceramic diaphragm 2 and the flange 12 to ensure airtightness and prevent air leakage when the ceramic diaphragm 2 is subjected to negative pressure suction. The hollow tube 11 is provided with internal threads to facilitate connection.

[0085] By using clamp 1, non-contact operation can be achieved during the coating process of ceramic film 2. During disassembly, assembly, and drying, the above operations can be achieved by contacting clamp 1, thereby effectively preventing coating defects caused by improper contact before the film is dried.

[0086] like Figure 9 As shown, the ceramic diaphragm surface spraying mechanism includes a spraying chamber 8, a fixed plate 41 installed in the spraying chamber 8, a first motor 42 installed on the fixed plate 41, a hollow rotating shaft 45 driven by the first motor 42, a clamp 1 connected to the hollow rotating shaft 45, and a ceramic diaphragm 2 installed on the clamp 1.

[0087] It also includes a vacuum pump 4 and a rotary joint 44 connected to the vacuum pump 4. One end of the hollow shaft 45 is connected to the clamp 1, and the other end of the hollow shaft 45 is connected to the rotary joint 44.

[0088] The vacuum pump 4 generates negative pressure, which is used to draw the ceramic diaphragm 2 through the hollow rotating shaft 45 and the clamp 1. This creates negative pressure inside the ceramic diaphragm 2, causing the sprayed atomized droplets to be "drawn" into the microporous structure or surface gaps when they reach the surface of the ceramic diaphragm 2. This significantly enhances the droplet permeability and anchoring effect, reduces the rebound and splashing of surface droplets, improves the initial adhesion, and promotes a more uniform and continuous spread of the underlying layer. This is crucial for forming a defect-free, low-porosity, dense separation layer.

[0089] The first motor 42 shaft and the hollow shaft 45 are driven by a belt 43. The first motor 42 drives the hollow shaft 45 to rotate, and the hollow shaft 45 drives the ceramic diaphragm 2 to rotate dynamically. The speed of the first motor 42 can be adjusted according to the actual situation, thereby controlling the speed of the ceramic diaphragm 2.

[0090] One hollow tube 11 of the clamp 1 is screwed to a hollow rotating shaft 45, which is convenient for assembly and disassembly. On the one hand, it connects the clamp 1 and the hollow rotating shaft 45, allowing the ceramic diaphragm 2 to rotate with the hollow rotating shaft 45. On the other hand, the connection between the hollow rotating shaft 45 and the hollow tube 11 allows for negative pressure adsorption of the ceramic diaphragm 2. The other hollow tube 11 of the clamp 1 is screwed and sealed with a bolt 14. A sealing ring 15 is provided between the bolt 14 and the hollow tube 11 to ensure airtightness and prevent air leakage when the ceramic diaphragm 2 is suctioned under negative pressure. A fixing seat 46 is provided on the fixing plate 41. The fixing seat 46 has a groove 460, and both the hollow rotating shaft 45 and the hollow tube 11 extend into the groove 460 for connection.

[0091] It also includes a track 7 located above the ceramic diaphragm 2, and a movable seat 71 that slides on the track 7. Specifically, the track 7 is a lead screw, the movable seat 71 is a nut seat, and a third motor for driving the lead screw to rotate is also included. The movable seat 71 can move back and forth on the track 7.

[0092] It also includes a low-temperature plasma treatment machine 6, which uses air as a gas source to ionize and generate a mixture of electrons, ions, atoms and atomic groups to clean and activate the surface of the ceramic membrane 2, remove contaminants from the surface of the ceramic membrane 2, and improve the wettability and coating adhesion of the surface of the ceramic membrane 2.

[0093] The plasma spray gun 61 of the low-temperature plasma treatment machine 6 is mounted on the movable base 71 and faces the surface of the ceramic membrane 2, thereby cleaning and activating the surface of the ceramic membrane 2. The plasma spray gun 61 is either rotary or direct-injection type. The plasma spray gun 61 moves back and forth within a small range on the track 7 with the movable base 71, allowing the plasma spray gun 61 to move back and forth within the radius of the ceramic membrane 2, thus enabling the plasma spray gun 61 to thoroughly clean and activate the surface of the ceramic membrane 2. The movement of the plasma spray gun 61 is uniformly accelerated, with an initial speed of 0-20 mm / s and an acceleration of -5-5 mm / s. 2 .

[0094] While the ceramic membrane 2 rotates dynamically, a low-temperature plasma treatment machine 6 cleans and activates the surface of the ceramic membrane 2. The dynamic rotation of the ceramic membrane 2 ensures that the plasma acts on the entire surface of the ceramic membrane 2, avoiding uneven treatment such as edge effects or shadow areas caused by static spraying; it can also enhance the removal of contaminants, and centrifugal force assists in removing particulate contaminants desorbed during plasma cleaning, thereby improving cleaning efficiency.

[0095] It also includes a magnetic stirrer 5, a peristaltic pump 51 connected to the magnetic stirrer 5, and a first ultrasonic nozzle 52 and a second ultrasonic nozzle 54 connected to the peristaltic pump 51. The magnetic stirrer 5 contains a film-forming solution, which is transported by the peristaltic pump 51 to the first ultrasonic nozzle 52 and the second ultrasonic nozzle 54 for atomization. The ultrasonic atomization produces smaller droplets, typically reaching the micrometer or even submicrometer level, with a narrower distribution, lower flight speed, and lower momentum. These small droplets are more easily "sucked" into the pores of the ceramic membrane by negative pressure, which is beneficial for forming a thinner, homogeneous separation layer. At the same time, the low momentum reduces the impact damage of the droplets on the already formed film area, avoiding pinholes or defects and ensuring the uniformity of the film's microstructure.

[0096] The first ultrasonic nozzle 52 is connected to the fixed plate 41 via the bracket 53. The first ultrasonic nozzle 52 is positioned facing the arc portion of the ceramic diaphragm 2, thereby spraying the film-forming liquid onto the arc portion of the ceramic diaphragm 2 to form a uniform and dense film on the surface of the arc portion.

[0097] The second ultrasonic nozzle 54 is mounted on the movable base 71 and faces the surface of the ceramic diaphragm 2, thereby spraying the film-forming liquid onto both sides of the ceramic diaphragm 2 to form a uniform and dense film on both sides. The second ultrasonic nozzle 54 reciprocates within a small range on the track 7 along with the movable base 71, allowing it to move within the radius of the ceramic diaphragm 2, thus ensuring that the film-forming liquid sprayed from the second ultrasonic nozzle 54 uniformly covers the ceramic diaphragm 2. The movement of the second ultrasonic nozzle 54 is a uniformly accelerated movement, with an initial speed of 0–20 mm / s and an acceleration of -5–5 mm / s. 2 .

[0098] While the ceramic membrane 2 rotates dynamically, it is subjected to negative pressure suction, and ultrasonic atomization is used to spray the film-forming solution onto the surface of the ceramic membrane 2, thereby forming a uniform, dense, and defect-free film layer. The dynamic rotation of the ceramic membrane 2 ensures that the atomized droplets can be uniformly deposited on the surface of the ceramic membrane 2 from all angles. This effectively avoids the "shadow effect" (unspecified areas) and "coffee ring effect" (solution migration and accumulation towards the edges) caused by static spraying, resulting in a film layer with extremely high thickness distribution uniformity.

[0099] The working process of the ceramic diaphragm surface spraying mechanism is as follows: the fixture 1 is installed in the forward direction, the first motor 42 drives the ceramic diaphragm 2 to rotate dynamically, the plasma spray gun 61 sprays plasma to clean and activate the surface of the ceramic diaphragm 2, after the cleaning and activation is completed, the low temperature plasma treatment machine 6 stops working, the vacuum pump 4 starts working to generate negative pressure inside the ceramic diaphragm 2, and at the same time the first ultrasonic nozzle 52 and the second ultrasonic nozzle 54 perform atomized spraying on the ceramic diaphragm 2. After the spraying is completed, the fixture 1 is installed in the reverse direction, and the above operation is repeated to complete the spraying of the front and back sides of the ceramic diaphragm 2.

[0100] Finally, remove the clamp 1 from the hollow rotating shaft 45, remove the bolt 14, and then install it into the ceramic diaphragm arc-shaped part dipping mechanism.

[0101] like Figure 10 As shown, the ceramic diaphragm arc portion dip coating mechanism includes a bracket 33, a second motor 34 mounted on the bracket 33, a clamp 1 driven by the second motor 34, and a ceramic diaphragm 2 mounted on the clamp 1.

[0102] It also includes a lifting platform 31 and a film-forming solution tank 32 placed on the lifting platform 31. The film-forming solution tank 32 is filled with film-forming solution, and the arcuate portion of the ceramic membrane 2 is immersed in the film-forming solution. The height of the film-forming solution tank 32 can be adjusted by the lifting platform 31 to facilitate the immersion coating operation.

[0103] The clamp 1 has a hollow tube 11 connected to the shaft of the second motor 34. Specifically, the shaft of the second motor 34 has external threads, and the hollow tube 11 and the shaft of the second motor 34 are screwed together, making disassembly and assembly convenient. The second motor 34 can drive the clamp 1, thereby realizing the dynamic rotation of the ceramic diaphragm 2. The dynamic rotation of the ceramic diaphragm 2 ensures that droplets can be uniformly deposited on the surface of the arc portion of the ceramic diaphragm 2, effectively avoiding the "shadow effect" (unspecified areas) caused by static spraying, and obtaining a film layer with extremely high uniformity of thickness distribution.

[0104] It also includes a vacuum pump 35 and a rotary joint 36 connected to the vacuum pump 35. Another hollow tube 11 of the fixture 1 is screwed to the rotary joint 36, so as not to affect the rotation of the fixture 1. The vacuum pump 35 generates negative pressure, which is drawn into the ceramic membrane 2 through the hollow tube 11, thereby creating negative pressure inside the ceramic membrane 2. When the droplets of the film-forming solution come into contact with the arc surface of the ceramic membrane 2, they are "drawn" into the microporous structure or surface gaps, which significantly enhances the permeability and anchoring effect of the droplets, reduces the rebound and splashing of surface droplets, improves the initial adhesion, and promotes a more uniform and continuous spread of the bottom layer. This is crucial for forming a defect-free, low-porosity, dense separation layer.

[0105] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

[0106] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for reducing defects in disc-type ceramic film coatings, characterized in that, Includes the following steps: Step 1: Prepare the film-forming solution; Step 2: Install the ceramic diaphragm onto the fixture and clean and dry it; Step 3: Install the fixture in the forward position on the spraying station, causing the ceramic diaphragm to rotate dynamically. Use low-temperature plasma technology to clean and activate the front surface of the ceramic diaphragm. Step 4: While the ceramic diaphragm is rotating dynamically, negative pressure suction is applied to the ceramic diaphragm, and ultrasonic atomization is used to spray the film-forming solution onto the front surface of the ceramic diaphragm. After spraying, drying is performed. Step 5: Install the fixture in reverse on the spraying station, and repeat steps 3 and 4; Step 6: Then install the fixture on the dip coating station, so that the ceramic diaphragm rotates dynamically and is subjected to negative pressure suction, so that the arc part of the ceramic diaphragm is dynamically dipped in the film coating solution. Step 7: Dry the ceramic diaphragm together with the fixture, then remove the ceramic diaphragm and fire it.

2. The method for reducing defects in disc-type ceramic film coatings according to claim 1, characterized in that, In step one, the film-forming solution comprises the following components in parts by weight: 0.001-0.5 parts dispersant, 0.1-1 parts binder, 0.0001-0.01 parts defoamer, 0.01-0.2 parts sintering aid, and 1 part metal compound; the above components are ultrasonically dispersed in a constant temperature water bath at 10-40°C for 5-60 minutes to obtain the film-forming solution, wherein the solid content of the film-forming solution is 0.1-40 wt%.

3. The method for reducing defects in disc-type ceramic film coatings according to claim 2, characterized in that, The dispersant is one or more of sodium polyacrylate, polyacrylamide, and polyacrylic acid; the binder is one or more of PVA, PVB, PEG, and HPC; the defoamer is one or more of alcohols, organosilicones, polyethers, and esters; the sintering aid is one or more of yttrium nitrate, cerium nitrate, lanthanum nitrate, alumina, titanium dioxide, zirconium oxide, and silicon dioxide; and the metal compound is one or more of alumina, titanium dioxide, zirconium oxide, silicon dioxide, cerium oxide, yttrium oxide, and lanthanum oxide.

4. The method for reducing defects in disc-type ceramic film coatings according to claim 1, characterized in that, In step two, the ceramic membrane is rinsed or soaked in an organic solvent for 5–120 minutes, then rinsed, soaked and ultrasonically cleaned with pure water 2–3 times, each time for 5–120 minutes, and finally dried at 50–200℃ for 10–240 minutes.

5. The method for reducing defects in disc-type ceramic film coatings according to claim 1, characterized in that, In step three, the ceramic diaphragm and fixture are preheated to 50-200°C in an oven, then removed and installed on the spraying station. The dynamic rotation speed of the ceramic diaphragm is 2-100 RPM. Low-temperature plasma technology is used, with air as the gas source, to ionize and generate a mixture of electrons, ions, atoms and atomic groups to clean and activate the surface of the ceramic diaphragm for 5-120 seconds, removing surface contaminants.

6. A method for reducing defects in disc-type ceramic film coatings according to claim 2, characterized in that, In step four, the spraying environment temperature is controlled at 20–60℃ and the relative humidity at 20–80%. A negative pressure generating device is used to perform negative pressure suction on the ceramic diaphragm, controlling the pressure at -100–0 kPa. The dynamic rotation speed of the ceramic diaphragm is controlled at 2–100 RPM. The film-forming solution is magnetically stirred under a constant temperature water bath at 10–40℃, and a peristaltic pump is used for liquid injection, with the injection flow rate controlled at 0–65 ml / min. An ultrasonic atomizing spraying device is used to spray the surface of the ceramic diaphragm for 1–60 minutes. After spraying, the ceramic diaphragm and fixture are removed together and placed in a constant temperature and humidity chamber, with the ceramic diaphragm in a suspended state, for drying for 30–300 minutes. The temperature of the constant temperature and humidity chamber is controlled at 20–80℃ and the relative humidity at 20–80%.

7. The method for reducing defects in disc-type ceramic film coatings according to claim 1, characterized in that, In step six, the ambient temperature for immersion coating is controlled at 20–60℃ and the relative humidity is controlled at 20–80%. A negative pressure generating device is used to perform negative pressure suction on the ceramic diaphragm, and the pressure is controlled at -100–0 kPa. The dynamic rotation speed of the ceramic diaphragm is controlled at 2–50 RPM. The dynamic immersion time of the arc part of the ceramic diaphragm in the film-forming solution is controlled at 0–240 s.

8. A method for reducing defects in disc-type ceramic film coatings according to claim 1, characterized in that, In step seven, after the dip coating is completed, the ceramic film is dried together with the fixture. During the drying process, the ceramic film is suspended in the air and dried in a constant temperature and humidity chamber for 30 to 300 minutes. The temperature of the constant temperature and humidity chamber is controlled at 20 to 80°C and the relative humidity is controlled at 20 to 80%. Then, it is calcined at 400 to 1300°C for 10 to 240 minutes.

9. A device for reducing defects in disc-type ceramic film coatings, characterized in that, This includes a ceramic diaphragm surface spraying mechanism and a ceramic diaphragm arc-shaped part dip coating mechanism; The ceramic diaphragm surface spraying mechanism includes a spraying chamber, a fixed plate installed inside the spraying chamber, a first motor installed on the fixed plate, a hollow rotating shaft driven by the first motor, a clamp connected to the hollow rotating shaft, a ceramic diaphragm installed on the clamp, a track located above the ceramic diaphragm, and a movable seat sliding on the track. It also includes a vacuum pump, and a rotary joint for connecting the vacuum pump; the rotary joint is connected to the hollow shaft; It also includes a magnetic stirrer, a peristaltic pump connected to the magnetic stirrer, and a first ultrasonic nozzle and a second ultrasonic nozzle connected to the peristaltic pump; the first ultrasonic nozzle is disposed facing the arc portion of the ceramic diaphragm, and the second ultrasonic nozzle is mounted on a movable base and disposed facing the surface of the ceramic diaphragm. It also includes a low-temperature plasma treatment machine, wherein the plasma spray gun of the low-temperature plasma treatment machine is mounted on a movable base and arranged facing the surface of the ceramic membrane. The ceramic diaphragm arc portion dip coating mechanism includes a second motor, a clamp driven by the second motor, a ceramic diaphragm mounted on the clamp, a rotary joint connected to the clamp, a vacuum pump connected to the rotary joint, a lifting platform, and a film-forming liquid tank placed on the lifting platform; the ceramic diaphragm arc portion is dynamically dipped in the film-forming liquid.

10. The apparatus for reducing defects in disc-type ceramic film coatings according to claim 9, characterized in that, The clamp includes two hollow tubes and flanges connected to the hollow tubes; the ceramic diaphragm is clamped by the two flanges, which are connected by bolts and nuts, and a sealing ring is provided between the ceramic diaphragm and the flanges; the hollow tubes are provided with internal threads.

11. The apparatus for reducing defects in disc-type ceramic film coatings according to claim 10, characterized in that, In the ceramic diaphragm surface spraying mechanism, one hollow tube of the fixture is screwed to a hollow shaft, and the other hollow tube of the fixture is sealed by bolts. A sealing ring is provided between the bolts and the hollow tube.

12. The apparatus for reducing defects in disc-type ceramic film coatings according to claim 11, characterized in that, The fixing plate is provided with a fixing seat, the fixing seat is provided with a groove, and the hollow rotating shaft and the hollow tube both extend into the groove and are connected.

13. The apparatus for reducing defects in disc-type ceramic film coatings according to claim 9, characterized in that, The track is a lead screw, the movable seat is a nut seat, and a third motor is also included to drive the lead screw to rotate.

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