Friction electrostatic spraying preparation method for high-precision ceramic membrane
By grafting methyl groups onto nano-alumina powder through triboelectric electrostatic spraying and then electrostatically adsorbing them onto a ceramic support to prepare a high-precision ceramic film, the problems of uneven film layer and uneven pore size distribution in the prior art are solved. This achieves high uniformity and narrow pore size distribution in the ceramic film, thereby improving the performance of the ceramic film.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZINGKE (CHONGQING) ADVANCED MATERIALS RES INST CO LTD
- Filing Date
- 2023-11-20
- Publication Date
- 2026-04-17
AI Technical Summary
Existing technologies struggle to control the uniformity and pore size distribution of high-precision ceramic films during mass production. In particular, the suspended particle sintering method and ultraviolet curing method still suffer from macropore defects and film inhomogeneity.
High-precision ceramic films are prepared by triboelectric electrostatic spraying. Methyl groups are grafted onto nano-alumina powder, which is then uniformly adsorbed on the surface of a ceramic support. The powder is positively charged through triboelectric effect, and a uniform film layer is formed on the ceramic support after electrostatic adsorption, followed by sintering.
Significant improvements have been achieved in the uniformity and pore size distribution of the ceramic membrane layer. The pore size distribution is narrow and the performance is excellent, making it suitable for practical applications of high-precision ceramic membranes.
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Figure CN121872803A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ceramic film preparation technology, and in particular to a method for preparing high-precision ceramic films by triboelectric electrostatic spraying. Background Technology
[0002] Ceramic membrane technology, a high-tech field that rapidly developed in the early 1960s, uses inorganic porous membranes made from ceramic materials. Driven by a pressure difference, it achieves separation through sieving, offering advantages such as high separation efficiency, stable performance, high temperature resistance, acid and alkali resistance, waste heat recovery, and recyclability. It can be applied in metallurgical, coal, and chemical industries, becoming one of the important filtration materials for high-temperature gas purification. With the development of high-precision ceramics, smaller membrane pore sizes and narrower pore size distributions have enabled ceramic membranes to achieve significant progress in nanofiltration fields such as blood filtration and bacterial separation. However, how to mass-produce high-precision ceramic membranes remains a research challenge.
[0003] Chinese patent No. 201510083781X uses a suspended particle sintering method to prepare ceramic membranes, combining the sol-gel method and the suspended particle sintering method. The sol particles enhance the bonding force between ceramic powders, while the ceramic powders enhance the toughness of the sol particles. The resulting modified layer has good strength and surface smoothness with a small thickness, ensuring high transmittance of the ceramic membrane. Furthermore, this process simplifies the modification process, completing both dip coating and firing in one step. However, the dip coating method cannot guarantee the uniformity of the membrane layer, resulting in widespread large-pore defects. Chinese patent No. 2022108093066 uses a UV curing method to prepare ceramic membranes, incorporating UV-curing resin and a photoinitiator into the ceramic membrane slurry. After coating the slurry onto the substrate surface, it is cured by UV irradiation. This method effectively avoids slurry infiltration and allows for more precise control of the ceramic membrane pore size. However, it still relies on a conventional coating method and cannot achieve uniformity of the membrane layer. Summary of the Invention
[0004] In view of this, the purpose of the present invention is to provide a method for preparing high-precision ceramic films by triboelectric spraying, so that nano-alumina powder can be uniformly adsorbed on the surface of the ceramic film support, and the ceramic film obtained after sintering has a uniform film layer and narrow pore size distribution.
[0005] This invention provides a method for preparing high-precision ceramic films by triboelectric electrostatic spraying, comprising the following steps:
[0006] 1) Synthesis of 2-bromo-2-methyl-n-(3-(triethoxy)propyl)propionamide (BTPAm for short)
[0007] γ-aminopropyltriethoxysilane and triethylamine were dissolved in toluene to obtain mixed solution A. Toluene and 2-bromoisobutyryl bromide were mixed evenly to obtain mixed solution B. Mixed solution A was cooled to 0°C, and mixed solution B was added dropwise to mixed solution A while stirring. The reaction was carried out in an ice-water bath for 2-5 hours, and then at room temperature for 6-12 hours. Impurities were removed by vacuum filtration, and the solvent was removed by vacuum evaporation at 50-60°C to obtain BTPAm.
[0008] 2) Synthetic hair growth agent coated with nano-alumina (abbreviated as: Al2O3-Br)
[0009] BTPAm was added to anhydrous toluene and mixed evenly to obtain a BTPAm mixture. The dried nano-alumina powder was then immersed in the BTPAm mixture and heated to 120°C. The mixture was reacted under reflux for 8-24 hours. The product was collected by centrifugation, washed several times with toluene, and dried under vacuum at 50-60°C for 8-24 hours to obtain the product Al2O3-Br.
[0010] 3) Grafting methyl groups onto nano-alumina (abbreviation: Al2O3-CH3)
[0011] Al₂O₃-Br, CuBr₂, BPY (2,2'-bipyridine), and a polymer monomer containing double bonds and multiple methyl groups were added to a beaker. Anhydrous acetonitrile was added, and the mixture was ultrasonically mixed. Then, the initiator azobisisobutyronitrile (AIBN) was added, followed by 2-bromoisobutyryl bromide. The mixture was subjected to three freeze-thaw cycles with N₂. After degassing, the mixture was reacted under reflux at 60-100℃ for 24-48 h. The mixture was diluted with an aqueous solution of ethylenediaminetetraacetic acid (EDTA), cooled to room temperature, and collected by centrifugation to obtain the product Al₂O₃-CH₃.
[0012] 4) Spray Al2O3-CH3 powder onto the ceramic support.
[0013] Fix and ground the ceramic support, ground the electrostatic spray gun, add Al2O3-CH3 powder to the powder supply tank, and after preparation, turn on the spray gun to evenly spray the Al2O3-CH3 powder onto the surface of the ceramic support. Then sinter in a muffle furnace to obtain a high-precision ceramic film.
[0014] In some embodiments, in step 1), the volume ratio of γ-aminopropyltriethoxysilane, triethylamine and toluene in the mixed solution A is 1-2:1:5-10, and the volume ratio of toluene and 2-bromoisobutyryl bromide in the mixed solution B is 3-5:1.
[0015] In some embodiments, in step 2), the mass ratio of BTPAm, anhydrous toluene, and nano-alumina powder is 1:250-290:2.8-3.2.
[0016] In some embodiments, in step 3), the polymer monomer containing double bonds and having multiple methyl groups is one of polypropylene and N,N,N-trimethylglycine.
[0017] In some embodiments, the mass ratio of Al2O3-Br, CuBr2, BPY, a polymer monomer containing double bonds and multiple methyl groups, anhydrous acetonitrile, AIBN, and 2-bromoisobutyryl bromide is 10:0.2-0.25:0.25-0.32:12-18:300-400:0.15-0.2:0.03-0.04.
[0018] In some embodiments, in step 4), the Al2O3-CH3 powder is sprayed onto the surface of the ceramic support with a thickness of 1-10 μm.
[0019] In some embodiments, in step 4), the sintering conditions are: sintering temperature of 400-600℃ and holding time of 20-240min.
[0020] The beneficial effects of this invention are:
[0021] 1. The present invention uses a triboelectric electrostatic spraying method to prepare ceramic films, which can effectively reduce powder waste during the spraying process and improve the uniformity of the film layer.
[0022] 2. This invention enhances the charge of nano-alumina powder by grafting methyl groups onto it. After friction with the strong cathode material, the powder carries a large amount of positive charge and can adhere more evenly to the grounded ceramic support after being sprayed out. The resulting ceramic film is uniform in size and has a narrow pore size distribution. The most probable pore size distribution of the prepared ceramic film accounts for more than 99%, which can achieve better performance in actual product applications. Attached Figure Description
[0023] Figure 1 This is a schematic diagram illustrating the principle of spraying nanoparticles onto the surface of a ceramic support using triboelectric static electricity.
[0024] Figure 2 This is a surface electron microscope image of the high-precision ceramic film prepared in Example 2 of the present invention;
[0025] Figure 3 This is a pore size distribution diagram of the high-precision ceramic membrane prepared in Example 2 of the present invention;
[0026] Figure 4 This is a pore size distribution diagram of the ceramic membrane prepared in Comparative Example 1 of the present invention. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Unless otherwise specified in the following examples, the conditions are as per standard conditions or the manufacturer's recommendations. Raw materials, equipment, or instruments whose manufacturers are not specified are all commercially available products.
[0029] This invention discloses a method for preparing high-precision ceramic films using triboelectric electrostatic spraying. The method involves spraying modified nano-alumina powder onto a ceramic support using a triboelectric electrostatic spray gun, followed by sintering to obtain the ceramic film. The principle of this method is as follows: a strong cathode material is selected as the spray gun body. During spraying, the nano-alumina powder, propelled by compressed air, rubs against the inner wall of the spray gun and the inner wall of the powder delivery pipe, causing the alumina powder to become positively charged. The ceramic support is grounded. When the positively charged powder particles leave the spray gun body and fly towards the ceramic support, the support becomes negatively charged due to electrostatic effects. The attraction between opposite charges allows the powder to be uniformly adsorbed onto the support surface. The resulting ceramic film after sintering exhibits uniform film layer and narrow pore size distribution, resulting in superior performance in practical applications. Furthermore, compared to ordinary electrostatic spraying, it overcomes the Faraday cage effect, avoiding dead zones during the spraying process. The modified nano-alumina powder is obtained through anti-atom transfer radical polymerization (RATRP), where methyl groups are grafted onto the nano-alumina powder. These methyl groups readily lose electrons and become positively charged during friction.
[0030] Please refer to the following examples for details:
[0031] Example 1
[0032] This embodiment provides a method for preparing high-precision ceramic films by triboelectric electrostatic spraying, the steps of which are as follows:
[0033] Dissolve 60 ml of γ-aminopropyltriethoxysilane and 60 ml of triethylamine in 300 ml of toluene, cool to 0 °C, and add dropwise a mixture of 150 ml of toluene and 50 ml of 2-bromoisobutyryl bromide while stirring. React in an ice-water bath for 2 h and then at room temperature for 6 h. Impurities were removed by vacuum filtration, and the solvent was removed by vacuum evaporation at 50°C to obtain BTPAm. 28g of BTPAm was added to 2500g of anhydrous toluene and mixed thoroughly to obtain a BTPAm mixture. 10g of pre-dried nano-alumina powder was immersed in the mixture, heated to 120°C, and reacted under reflux for 8 hours. The product was collected by centrifugation, washed several times with toluene, and dried under vacuum at 50°C for 8 hours to obtain Al2O3-Br. 10g of Al2O3-Br, 0.2g of CuBr2, 0.25g of BPY, and 12g of polypropylene were placed in a beaker, and 380ml of anhydrous acetonitrile was added. The mixture was ultrasonically mixed thoroughly, and then 0.15g of the initiator azobisisobutyronitrile (AIBN) was added, followed by 0.03g of... 2-Bromoisobutyryl bromide was subjected to three freeze-thaw cycles with N2, degassed, and then reacted at 60°C under reflux for 24 hours. The mixture was diluted with an aqueous solution of ethylenediaminetetraacetic acid (EDTA), cooled to room temperature, and the product was collected by centrifugation to obtain Al2O3-CH3. A cleaned ceramic support was fixed and grounded, and a triboelectric spray gun was grounded. Al2O3-CH3 powder was placed in the powder supply container. Once ready, the spray gun was turned on to spray the powder onto the ceramic support. The principle of spraying nanoparticles onto the surface of the ceramic support using triboelectricity is as follows: Figure 1 As shown, after a 1µm thick layer of powder is uniformly adsorbed on the surface of the support, it is placed in a muffle furnace and sintered at 400℃ for 20 minutes to obtain a high-precision ceramic film.
[0034] Example 2
[0035] This embodiment provides a method for preparing high-precision ceramic films by triboelectric electrostatic spraying, the steps of which are as follows:
[0036] Dissolve 90 ml of γ-aminopropyltriethoxysilane and 60 ml of triethylamine in 300 ml of toluene, cool to 0 °C, and add dropwise a mixture of 200 ml of toluene and 50 ml of 2-bromoisobutyryl bromide while stirring. React in an ice-water bath for 3 h and then at room temperature for 10 h. Impurities were removed by vacuum filtration, and the solvent was removed by vacuum evaporation at 60°C to obtain BTPAm. 30g of BTPAm was added to 2700g of anhydrous toluene and mixed thoroughly to obtain a BTPAm mixture. 10g of pre-dried nano-alumina powder was immersed in the mixture, heated to 120°C, and reacted under reflux for 12 hours. The product was collected by centrifugation, washed several times with toluene, and dried under vacuum at 60°C for 12 hours to obtain Al2O3-Br. 10g of Al2O3-Br, 0.21g of CuBr2, 0.29g of BPY, and 15g of polypropylene were placed in a beaker, and 400ml of anhydrous acetonitrile was added. The mixture was ultrasonically mixed thoroughly, and then 0.16g of the initiator azobisisobutyronitrile (AIBN) was added, followed by 0.032g of... 2-Bromoisobutyryl bromide was subjected to three freeze-thaw cycles with N2, degassed, and then reacted at 80°C under reflux for 48 hours. The mixture was diluted with an aqueous solution of ethylenediaminetetraacetic acid (EDTA), cooled to room temperature, and the product was collected by centrifugation to obtain Al2O3-CH3. A cleaned ceramic support was fixed and grounded, and a triboelectric spray gun was grounded. Al2O3-CH3 powder was placed in the powder supply container. Once ready, the spray gun was turned on to spray the powder onto the ceramic support. The principle of spraying nanoparticles onto the surface of the ceramic support using triboelectricity is as follows: Figure 1 As shown, after a 5µm thick layer of powder is uniformly adsorbed on the surface of the support, it is placed in a muffle furnace and sintered at 500℃ for 120 minutes to obtain a high-precision ceramic film.
[0037] Example 3
[0038] This embodiment provides a method for preparing high-precision ceramic films by triboelectric electrostatic spraying, the steps of which are as follows:
[0039] Dissolve 120 ml of γ-aminopropyltriethoxysilane and 60 ml of triethylamine in 600 ml of toluene, cool to 0 °C, and add dropwise a mixture of 250 ml of toluene and 50 ml of 2-bromoisobutyryl bromide while stirring. React in an ice-water bath for 5 h and then at room temperature for 12 h. Impurities were removed by vacuum filtration, and the solvent was removed by vacuum evaporation at 60℃ to obtain BTPAm. 32g of BTPAm was added to 2900g of anhydrous toluene and mixed thoroughly to obtain a BTPAm mixture. 10g of pre-dried nano-alumina powder was immersed in the mixture, heated to 120℃, and reacted under reflux for 24h. The product was collected by centrifugation, washed several times with toluene, and dried under vacuum at 60℃ for 12h to obtain Al2O3-Br. 10g of Al2O3-Br, 0.25g of CuBr2, 0.32g of BPY, and 18g of polypropylene were placed in a beaker, and 509ml of anhydrous acetonitrile was added. The mixture was ultrasonically mixed thoroughly, and then 0.2g of the initiator azobisisobutyronitrile (AIBN) was added, followed by 0.04g of... 2-Bromoisobutyryl bromide was subjected to three freeze-thaw cycles with N2, degassed, and then reacted at 100°C under reflux for 48 hours. The mixture was diluted with an aqueous solution of ethylenediaminetetraacetic acid (EDTA), cooled to room temperature, and the product was collected by centrifugation to obtain Al2O3-CH3. A cleaned ceramic support was fixed and grounded, and a triboelectric spray gun was grounded. Al2O3-CH3 powder was placed in the powder supply container. Once ready, the spray gun was turned on to spray the powder onto the ceramic support. The principle of spraying nanoparticles onto the surface of the ceramic support using triboelectricity is as follows: Figure 1 As shown, after a 10µm thick layer of powder is uniformly adsorbed on the surface of the support, it is placed in a muffle furnace and sintered at 600℃ for 240 minutes to obtain a high-precision ceramic film.
[0040] Comparative Example 1
[0041] The difference between this comparative example and Example 2 is that this comparative example uses a common spray gun to spray the prepared Al2O3-CH3 onto the ceramic support.
[0042] The pore size and distribution of the high-precision ceramic membrane prepared in Example 2 and the ceramic membrane prepared in Comparative Example 1 were tested at room temperature using the immersion pressing method. Isopropanol was used as the wetting solution. The test results are as follows: Figure 3 , Figure 4 As shown:
[0043] Depend on Figure 3 It can be seen that the high-precision ceramic film prepared in Example 2 has a maximum pore size of 0.135 μm, an average pore size of 0.13 μm, a most probable pore size of 0.13 μm, and a most probable pore size distribution ratio of 99.5%. Figure 4As can be seen, the ceramic film prepared in Comparative Example 1 has a maximum pore size of 0.172 μm, an average pore size of 0.15 μm, and a most probable pore size of 0.16 μm, with the most probable pore size accounting for 33%. This demonstrates that the high-precision ceramic film prepared using the method of this invention exhibits a significantly improved pore size distribution, with a narrower pore size distribution and more uniform pore size, resulting in superior performance in practical product applications. Taking the high-precision ceramic film prepared in Example 2 as an example, its surface electron micrograph is shown below. Figure 2 As shown
[0044] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention. Technologies not described in detail in this invention are known technologies.
Claims
1. A frictional electrostatic spray coating production method for high-precision ceramic membranes, characterized by, Includes the following steps: 1) Synthesis of BTPAm γ-aminopropyltriethoxysilane and triethylamine were dissolved in toluene to obtain mixed solution A. Toluene and 2-bromoisobutyryl bromide were mixed evenly to obtain mixed solution B. Mixed solution A was cooled to 0°C. Mixed solution B was added dropwise to mixed solution A while stirring. The reaction was carried out in an ice-water bath for 2-5 hours, and then at room temperature for 6-12 hours. The generated impurities were removed by vacuum filtration, and the solvent was removed by vacuum evaporation at 50-60°C to obtain BTPAm. 2) Synthesis of Al2O3-Br BTPAm was added to anhydrous toluene and mixed evenly to obtain a BTPAm mixture. The dried nano-alumina powder was then immersed in the BTPAm mixture and heated to 120°C. The mixture was reacted under reflux for 8-24 hours. The product was collected by centrifugation, washed several times with toluene, and vacuum dried at 50-60°C for 8-24 hours to obtain the product Al2O3-Br. 3) Synthesis of Al2O3-CH3 Al2O3-Br, CuBr2, BPY and a polymer monomer containing double bonds and multiple methyl groups were added to a beaker, anhydrous acetonitrile was added, and the mixture was ultrasonically mixed. Then, initiator AIBN was added, followed by 2-bromoisobutyryl bromide. The mixture was subjected to three freeze-thaw cycles with N2. After degassing, the mixture was heated under reflux at 60-100℃ for 24-48 h. The mixture was diluted with an aqueous solution of EDTA, cooled to room temperature, and collected by centrifugation to obtain the product Al2O3-CH3. 4) Preparation of high-precision ceramic films Fix and ground the ceramic support, ground the triboelectric spray gun, add Al2O3-CH3 powder to the powder supply tank, and after preparation, turn on the spray gun to evenly spray the Al2O3-CH3 powder onto the surface of the ceramic support. Then sinter in a muffle furnace to obtain a high-precision ceramic film.
2. The triboelectric spray preparation method of claim 1, wherein, In step 1), the volume ratio of γ-aminopropyltriethoxysilane, triethylamine and toluene in the mixed solution A is 1-2:1:5-10, and the volume ratio of toluene and 2-bromoisobutyryl bromide in the mixed solution B is 3-5:
1.
3. The triboelectric spray preparation method of claim 2, wherein, In step 2), the mass ratio of BTPAm, anhydrous toluene, and nano alumina powder is 2.8-3.2:250-290:
1.
4. The triboelectric spray preparation method of claim 3, wherein, In step 3), the polymer monomer containing double bonds and multiple methyl groups is one of polypropylene and N,N,N-trimethylglycine.
5. The triboelectric spray preparation method of claim 4, wherein, In step 3), the mass ratio of Al2O3-Br, CuBr2, BPY, polymer monomers containing double bonds and multiple methyl groups, anhydrous acetonitrile, AIBN, and 2-bromoisobutyryl bromide is 10:0.2-0.25:0.25-0.32:12-18:300-400:0.15-0.2:0.03-0.
04.
6. The triboelectric spray preparation method of claim 5, wherein, In step 4), the Al2O3-CH3 powder is sprayed onto the ceramic support surface with a thickness of 1-10 μm.
7. A triboelectric spraying production method according to any one of claims 1 to 6, wherein In step 4), the sintering conditions are: sintering temperature of 400-600℃ and holding time of 20-240min.