Visible-light-catalytic antibacterial ceramic coating and preparation method thereof

Abstract

The application relates to the technical field of antibacterial ceramics, and particularly discloses a visible-light-catalyzed antibacterial ceramic coating and a preparation method thereof. The antibacterial ceramic coating is located on the surface layer of a ceramic glaze, and is formed by spraying an antibacterial sol on the surface layer of the ceramic glaze and then performing heat treatment. The antibacterial sol comprises the following raw materials in mass fraction: 16-35% of tetrabutyl titanate, 20-45% of organic borate, 5-15% of ethyl acetoacetate, 0.5-1% of copper chloride dihydrate, 2-3% of water, 1-2% of hydrochloric acid, 25-35% of anhydrous ethanol and 0-2% of a dispersant. The antibacterial sol can be used for producing the antibacterial ceramic coating, and the coating has the advantages of being firmly coated on the ceramic glaze, having acid and alkali resistance, wear resistance and easy-to-clean property, and having high-efficiency antibacterial performance under visible light.

Description

Technical Field

[0001] This application relates to the technical field of antibacterial ceramics, and in particular to a visible light catalytic antibacterial ceramic coating and its preparation method. Background Technology

[0002] In the 1990s, Japan's TOTO Corporation pioneered the development of TiO2 ultraviolet photocatalytic antibacterial ceramic tiles. This technology opened up a new technical path for loading TiO2 photocatalytic thin films onto ceramic surfaces, giving ceramics highly efficient antibacterial and self-cleaning functions.

[0003] Compared with traditional antibacterial materials, nano-TiO2 coating materials have significant advantages: excellent UV photocatalytic antibacterial performance, stable chemical properties, abundant sources, and low cost. Its antibacterial mechanism is as follows: under UV light excitation, electron-hole pairs are generated, catalyzing water in the air or dissolved oxygen in water into hydroxyl radicals (·OH) and superoxide anions (·O2). - Reactive oxygen species such as hydrogen peroxide (H2O2) destroy the cell membranes, proteins, and DNA structures of microorganisms through biochemical reactions, effectively killing common pathogens such as Escherichia coli and Staphylococcus aureus. However, traditional TiO2 ceramic coatings still have significant drawbacks: their large band gap means they can only be excited by ultraviolet light, posing a health hazard due to ultraviolet radiation, and the high recombination rate of photogenerated electrons and holes results in low photocatalytic sterilization efficiency; at the same time, the coating has weak adhesion to the ceramic substrate, making it prone to peeling and failure.

[0004] The literature "Preparation of Antibacterial Ceramics and Study on Antibacterial Properties of Zn / Ce and Zn / Y Ion-Doped TiO2" (Northeastern University, 2014) prepared Zn / Ce-TiO2 and Zn / Y-TiO2 sols using the sol-gel method. Using commercially available ceramic sheets as carriers, antibacterial ceramics were prepared by coating method. The effects of surfactant doping amount, number of coating layers, coating thickness, and calcination temperature on its antibacterial properties were investigated. The results showed that with a surfactant addition of 0.25 g, two coating layers, a coating thickness of 15 nm, and a calcination temperature of 600℃, the ceramic exhibited good antibacterial rate and strong acid and alkali resistance under visible light excitation. However, the wear resistance and easy-to-clean properties of the coating were not studied, and the high price of rare earth metals resulted in high industrialization costs.

[0005] The literature "Antibacterial Properties of Co, Li, and Zn / Co Doped TiO2 Nanomaterials and Their Application in Antibacterial Ceramics" (Northeastern University, 2021) prepared Co-doped, Li-doped, and Zn / Co co-doped TiO2 antibacterial sols using the sol-gel method. These sols were then coated onto ceramic surfaces using ultrasonic spraying. The effects of spray height, spray time, and calcination temperature on the antibacterial properties of the ceramics were investigated, along with the coating's stain resistance and adhesion. The study found that Zn / Co-TiO2 antibacterial ceramics with a spray height of 5 cm, 3 coating layers, a coating time of 45 min, and a calcination temperature of 600℃ exhibited significantly better antibacterial performance against *Escherichia coli* and *Staphylococcus aureus* under visible light than Co-TiO2 and Li-TiO2 antibacterial ceramics, with antibacterial rates exceeding 90%. Furthermore, the coating showed stronger stain resistance and resistance to natural water erosion. However, the acid and alkali resistance of the coating was not investigated.

[0006] Chinese patent document CN111266128A discloses a visible light-excited composite photocatalytic antibacterial ceramic and its preparation method. The composite photocatalytic material is prepared using copper nitrate, silver nitrate, and titanium dioxide and then loaded onto cordierite honeycomb ceramic. This ceramic exhibits excellent antibacterial effects under visible light. However, this material is directly loaded onto the ceramic without subsequent heat treatment, resulting in weak bonding with the ceramic. Furthermore, the wear resistance and acid / alkali resistance of the ceramic were not investigated.

[0007] For example, TOTO disclosed a sanitary ceramic with a photocatalyst layer in its patent application (application number CN201610809150.6). The durability of the photocatalyst layer is improved by adding an intermediate layer between the glaze layer and the photocatalyst layer. The intermediate layer is composed of 98%-85% by mass of silicon dioxide and 2%-15% by mass of titanium oxide and / or zirconium oxide. The sanitary ceramic is prepared by heat treatment at 700-900℃. It has excellent acid and alkali stability, wear resistance and high photocatalytic activity in response to ultraviolet light. However, this process requires multiple steps such as the preparation of base glaze, intermediate layer, TiO2 sol and coating. The production process is complicated and the cost is high. It fails to achieve visible light photocatalytic antibacterial function.

[0008] In existing technologies, pure TiO2 coatings on sanitary ceramics only exert their photocatalytic antibacterial effect under ultraviolet light irradiation. However, this technology suffers from drawbacks such as a narrow spectral range, low utilization rate, and the health and safety risks associated with ultraviolet radiation. Furthermore, the need for regular replacement of ultraviolet lamps leads to high maintenance costs. Additionally, after heat treatment, the adhesion between the coating and the ceramic substrate is typically weak, making it prone to detachment and exhibiting poor wear resistance. Moreover, the TiO2 coating formed by traditional sol-gel coating methods has anatase crystals, resulting in poor acid resistance. Therefore, broadening the absorption threshold of TiO2 coatings into the visible light region, while simultaneously improving wear resistance, bonding strength, ease of cleaning, and acid and alkali resistance, is the key technology for the ceramic industry to overcome the bottleneck of visible light photocatalysis and achieve truly effective antibacterial applications. Summary of the Invention

[0009] In order to broaden the absorption threshold of TiO2 coatings into the visible light region, and at the same time improve the bonding strength, wear resistance, easy cleaning and acid and alkali resistance of ceramic coatings, this application provides a TiO2 antibacterial coating that can be firmly coated on ceramic glaze, has wear resistance, easy cleaning and acid and alkali resistance, and has high-efficiency antibacterial properties under visible light, and a method for preparing the same.

[0010] In a first aspect, this application provides a visible light catalytic antibacterial ceramic coating, employing the following technical solution:

[0011] A visible light catalytic antibacterial ceramic coating, wherein the antibacterial ceramic coating is located on the surface of a ceramic glaze, and the antibacterial ceramic coating is formed by spraying an antibacterial sol onto the surface of the ceramic glaze and then heat-treating it, wherein the antibacterial sol comprises the following raw materials in the indicated mass fractions:

[0012] 16-35% tetrabutyl titanate, 20-45% organoboroester, 5-15% ethyl acetoacetate, 0.5-1% copper chloride dihydrate, 2-3% water, 1-2% hydrochloric acid, 25-35% anhydrous ethanol and 0-2% dispersant.

[0013] Optionally, the antibacterial sol comprises the following raw materials in the indicated mass fractions:

[0014] 20% tetrabutyl titanate, 40% organoborolate, 7% ethyl acetoacetate, 1% copper chloride dihydrate, 2% water, 2% hydrochloric acid, 27% anhydrous ethanol and 1% dispersant.

[0015] Optionally, the antibacterial sol comprises the following raw materials in the indicated mass fractions:

[0016] 25% tetrabutyl titanate, 30% organoborolate, 10% ethyl acetoacetate, 1% copper chloride dihydrate, 2% water, 1% hydrochloric acid, 30% anhydrous ethanol and 1% dispersant.

[0017] Optionally, the antibacterial sol comprises the following raw materials in the indicated mass fractions:

[0018] 30% tetrabutyl titanate, 25% organoborolate, 13% ethyl acetoacetate, 0.5% copper chloride dihydrate, 3% water, 1.5% hydrochloric acid, 25% anhydrous ethanol and 2% dispersant.

[0019] By adopting the above technical solution, this application prepares a composite TiO2 sol through alcoholysis reaction, sprays it onto the ceramic glaze surface, and forms a photocatalytic antibacterial coating after low-temperature heat treatment, which can significantly improve the photocatalytic antibacterial performance of ceramics. The reason for not directly introducing TiO2 into the ceramic glaze is that at high temperatures, TiO2 easily forms low-melting-point substances with various components in the glaze, thus failing to exert its antibacterial effect on the ceramic glaze surface. The antibacterial coating prepared on the surface of the ceramic glaze in this application can achieve the effects of firmly adhering to the ceramic glaze surface, strong acid and alkali resistance, good wear resistance and easy cleaning, and highly efficient antibacterial performance under visible light.

[0020] In the antibacterial sol, tetrabutyl titanate is used as the titanium source, organoboroester ester as the boron source, copper chloride dihydrate as the copper source, ethyl acetoacetate as the chelating agent, hydrochloric acid as the pH adjuster, and sodium dodecylbenzenesulfonate as the dispersant. This achieves the synergistic doping of titanium dioxide with both metallic element copper and non-metallic element boron, and precisely constructs the Cu / B-TiO2 sol formulation system to prepare a uniformly dispersed and highly stable composite Cu / B-TiO2 sol.

[0021] In this application, copper chloride dihydrate is used as the copper source for two reasons. First, hydrochloric acid, as a pH adjuster, introduces chloride ions into the system. Using copper chloride, which also contains chloride ions, will not introduce other impurity ions into the system. Second, the type of anion has a significant impact on the alcoholysis rate of tetrabutyl titanate. If copper salts such as copper acetate or copper sulfate are used, the alcoholysis process will be accelerated, and the sol will rapidly cross-link and solidify in a short time, forming a network structure, thickening, and clumping, which is not conducive to subsequent spraying processes. In contrast, the use of chloride ions does not cause rapid thickening, and the sol has good stability, making it suitable for spraying.

[0022] Optionally, the organoboroester is trimethyl borate.

[0023] By adopting the above technical solution, this application selects trimethyl borate, an organic compound, which forms stable Ti-OB bonds with tetrabutyl titanate in the same system through alcoholysis. During subsequent heat treatment, some boron is converted into amorphous B2O3 liquid phase, which fills the pores, inhibits grain growth, and makes the grains more refined and dense, significantly improving the density and structural stability of the coating. In addition, trimethyl borate, copper chloride dihydrate, and tetrabutyl titanate form a uniformly dispersed and highly stable Cu / B-TiO2 sol system through alcoholysis reaction. This system acts as a flux at low temperatures, lowers the melting point of the system, and promotes the formation of stable rutile titanium dioxide at lower temperatures, thereby improving the acid and alkali resistance of the coating. This allows the coating to have excellent acid and alkali resistance, wear resistance, and easy cleaning properties while being highly effective in antibacterial treatment.

[0024] Optionally, the dispersant is sodium dodecylbenzenesulfonate.

[0025] Optionally, the temperature of the heat treatment is 500-700℃.

[0026] Optionally, the heat treatment temperature can be 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, 650℃, 680℃, 700℃, etc.

[0027] Optionally, the thickness of the antibacterial ceramic coating is 0.1 μm-1 μm.

[0028] Optionally, the thickness of the antibacterial ceramic coating can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0029] Optionally, the ceramic glaze is a vitreous vitrified glaze layer formed after sintering.

[0030] Optionally, the molar ratio of Ti:B:Cu in the antibacterial sol is 1:(2.5-5.5):(0.064-0.1).

[0031] Optionally, the molar ratio of Ti:B:Cu in the antibacterial sol can be 1:2.5:0.064, 1:3:0.07, 1:4:0.078, 1:4.5:0.085, 1:5:0.09, 1:5.5:0.1, etc.

[0032] Secondly, this application provides a method for preparing a visible light catalytic antibacterial ceramic coating, employing the following technical solution:

[0033] A method for preparing a visible light catalytic antibacterial ceramic coating includes the following steps:

[0034] (1) Preparation of antibacterial sol

[0035] (a) Add 16-35% tetrabutyl titanate, 20-45% trimethyl borate and 5-15% ethyl acetoacetate to 18-22% anhydrous ethanol and stir thoroughly to obtain solution ①.

[0036] (b) First, add 2-3% water and 1-2% hydrochloric acid to 7-13% anhydrous ethanol, then add 0.5-1% copper chloride dihydrate, and then add 0-2% dispersant. Stir to obtain solution ②.

[0037] (c) Slowly add solution ② to solution ① while it is being stirred. After the addition is complete, stir for 2.5-3.5 h in the absence of air, and let it stand and age for 23-25 ​​h to obtain Cu / B-TiO2 sol;

[0038] (2) Coating preparation

[0039] (a) Glaze surface preparation: Clean and wipe the ceramic glaze surface with distilled water and anhydrous ethanol respectively, and then dry it;

[0040] (b) Spraying sol: The obtained Cu / B-TiO2 sol is sprayed onto the surface of the ceramic glaze using a spray gun. The spray gun is 15-20 cm away from the ceramic glaze, and the spraying is done 1-2 times.

[0041] (c) Low-temperature heat treatment: After drying the Cu / B-TiO2 sol on the surface of the ceramic glaze, heat treatment is carried out by raising the temperature to 500℃-700℃ at a rate of 4-6℃ / min and holding for 1-1.2 h to obtain a visible light catalytic antibacterial ceramic coating.

[0042] Optionally, the nozzle diameter of the spray gun is 0.2-0.4 mm.

[0043] By adopting the above technical solution, in the process of preparing antibacterial sol, tetrabutyl titanate and trimethyl borate are first dissolved in a portion of anhydrous ethanol and mixed evenly to form solution ①. Then, copper chloride dihydrate is dissolved in a small amount of water to form solution ②. Finally, the two solutions are mixed and Cu / B-TiO2 sol is obtained through alcoholysis reaction. This ensures that trimethyl borate and tetrabutyl titanate form stable Ti–O–B bonds in the same system. During subsequent heat treatment, some boron is converted into amorphous B2O3 liquid phase, which plays a role in fluxing, filling pores, and inhibiting grain growth, thereby significantly improving the density and structural stability of the coating.

[0044] In summary, this application has the following beneficial effects:

[0045] 1. This application uses tetrabutyl titanate as the titanium source, organoboroester as the boron source, copper chloride dihydrate as the copper source, ethyl acetoacetate as the chelating agent, hydrochloric acid as the pH adjuster, and sodium dodecylbenzenesulfonate as the dispersant to achieve synergistic doping of titanium dioxide with both metallic copper and non-metallic boron, accurately constructing a Cu / B-TiO2 sol formulation system, and preparing a uniformly dispersed and highly stable composite Cu / B-TiO2 sol.

[0046] 2. By optimizing the synergistic doping ratio and performing heat treatment at 500℃-700℃, the degree of crystallization, crystal phase ratio and vitrification of the coating are controlled, the diffusion of fluxing elements from the ceramic glaze substrate to the TiO2 thin film layer is suppressed, crystallization defects are effectively avoided, and a high-strength bond between the coating and the glaze is achieved.

[0047] 3. The introduction of B element into trimethyl borate reduces the band gap of TiO2 and broadens the response range to visible light. The introduction of Cu element into copper chloride dihydrate forms a trapping center, which traps photogenerated electrons and inhibits electron-hole recombination. The dual effect synergistically improves the photocatalytic performance and endows the ceramic with efficient and stable antibacterial properties under visible light.

[0048] 4. By lowering the glass transition temperature through the fluxing effect of element B, a strong bond is achieved between the coating and the glaze, effectively reconciling the contradictory balance between easy cleaning, wear resistance, high vitrification, and antibacterial properties with high crystallinity. This significantly improves wear resistance, ease of cleaning, and acid and alkali resistance. The coating preparation method of this application has the advantages of simple production process, strong adhesion between the coating and the ceramic substrate, and excellent and stable antibacterial properties under visible light, giving it significant advantages in large-scale production. Attached Figure Description

[0049] Figure 1 This is the X-ray diffraction (XRD) pattern of the coated powder in Example 5.

[0050] Figure 2 The images are scanning electron microscope (SEM) images of Example 5 and Comparative Examples 2 and 6 (scale bar is 400 nm).

[0051] Figure 3 The UV-Vis absorption spectra of Example 5 and Comparative Examples 2 and 6 are shown.

[0052] Figure 4 The graph shows the coefficient of friction (COF) variation curves for Example 5 and Comparative Examples 2 and 6.

[0053] Figure 5 The load-scratch location curves are for Example 5 and Comparative Examples 2 and 6.

[0054] Figure 6 Atomic force microscopy (AFM) images of Example 5 and Comparative Examples 2 and 6. Detailed Implementation

[0055] The present invention will be clearly described below with reference to the accompanying drawings, and will be further illustrated by embodiments. However, the present invention is not limited to the following embodiments, and the described embodiments are only a part of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0056] Source of raw materials

[0057] Tetrabutyl titanate: CAS number 5593-70-4;

[0058] Trimethyl borate: CAS number 121-43-7;

[0059] Copper chloride dihydrate: Molecular formula CuCl2·2H2O, CAS number 10125-13-0;

[0060] Hydrochloric acid: Concentrated hydrochloric acid with a concentration of 36%-38%;

[0061] Sodium dodecylbenzenesulfonate: CAS number 25155-30-0.

[0062] Example

[0063] Example 1

[0064] This embodiment provides a visible light catalytic antibacterial ceramic coating. The coating is formed by spraying and heat treatment of an antibacterial sol. Based on a total weight of 100 g of antibacterial sol, it includes the following raw materials by mass:

[0065] 16.2 g tetrabutyl titanate, 40.2 g trimethyl borate, 8.9 g ethyl acetoacetate, 1 g copper chloride dihydrate, 2.3 g water, 1.2 g hydrochloric acid, 29.7 g anhydrous ethanol and 0.5 g sodium dodecylbenzenesulfonate.

[0066] A method for preparing a visible light catalytic antibacterial ceramic coating includes the following steps:

[0067] (1) Preparation of antibacterial sol

[0068] (a) 16.2 g tetrabutyl titanate, 40.2 g trimethyl borate and 8.9 g ethyl acetoacetate were added to 20 g anhydrous ethanol and stirred thoroughly for 30 min to obtain a light yellow transparent solution ①.

[0069] (b) Add 2.3 g of water and 1.2 g of hydrochloric acid to 9.7 g of anhydrous ethanol, add 1 g of copper chloride dihydrate, and add 0.5 g of sodium dodecylbenzenesulfonate. Stir to obtain solution ②.

[0070] (c) Slowly add solution ② to solution ① while it is being stirred. After the addition is complete, stir for 3 h in the absence of air and let it stand for 24 h to obtain Cu / B-TiO2 sol.

[0071] (2) Coating preparation

[0072] (a) Glaze surface pretreatment: Clean and wipe the ceramic glaze surface (the ceramic glaze surface after sintering and vitrification at 1200℃) with distilled water and anhydrous ethanol respectively, and dry it in a drying oven at 100℃.

[0073] (b) Spraying the sol: Using a 0.3 mm spray gun, spray the sol onto the surface of the ceramic glaze. The spray gun should be 15-20 cm away from the glaze. Spray 1-2 times.

[0074] (c) Low-temperature heat treatment: The sol on the surface of the ceramic glaze is dried and placed in a muffle furnace for heat treatment. The temperature is increased to 500℃ at a rate of 5℃ / min and held for 1 h to obtain a visible light catalytic antibacterial ceramic coating with a thickness of 0.8±0.05 μm.

[0075] Example 2

[0076] A visible-light catalytic antibacterial ceramic coating differs from Example 1 in that it comprises the following raw materials by weight: 21.2 g tetrabutyl titanate, 35.2 g trimethyl borate, 8.9 g ethyl acetoacetate, 1 g copper chloride dihydrate, 2.3 g water, 1.2 g hydrochloric acid, 29.7 g anhydrous ethanol, and 0.5 g sodium dodecylbenzenesulfonate. The remaining preparation steps are the same as in Example 1.

[0077] Example 3

[0078] A visible-light catalytic antibacterial ceramic coating differs from Example 1 in that it comprises the following raw materials by weight: 26.2 g tetrabutyl titanate, 30.2 g trimethyl borate, 8.9 g ethyl acetoacetate, 1 g copper chloride dihydrate, 2.3 g water, 1.2 g hydrochloric acid, 29.7 g anhydrous ethanol, and 0.5 g sodium dodecylbenzenesulfonate. The remaining preparation steps are the same as in Example 1.

[0079] Example 4

[0080] A visible-light catalytic antibacterial ceramic coating differs from Example 1 in that it comprises the following raw materials by weight: 31.2 g tetrabutyl titanate, 25.2 g trimethyl borate, 8.9 g ethyl acetoacetate, 1 g copper chloride dihydrate, 2.3 g water, 1.2 g hydrochloric acid, 29.7 g anhydrous ethanol, and 0.5 g sodium dodecylbenzenesulfonate. The remaining preparation steps are the same as in Example 1.

[0081] As shown in Table 1, the main difference between Examples 1-4 lies in the different proportions of raw materials used in the antibacterial sol in the antibacterial ceramic coating.

[0082] Table 1. Amount of antibacterial sol raw materials used in Examples 1-4 (unit: g)

[0083]

[0084] Example 5

[0085] A method for preparing a visible light catalytic antibacterial ceramic coating differs from Example 3 in that the heat treatment temperature in step (2) of the coating preparation step is 600℃. The remaining steps are the same as in Example 3.

[0086] Example 6

[0087] A method for preparing a visible light catalytic antibacterial ceramic coating differs from Example 3 in that the heat treatment temperature in step (2) of the coating preparation step is 700℃. The remaining steps are the same as in Example 3.

[0088] Comparative Example 1

[0089] A visible light catalytic antibacterial ceramic coating, the coating being made of a sol, wherein the sol comprises the following raw materials by weight, based on a total weight of 100 g:

[0090] 30.6 g tetrabutyl titanate, 11.4 g ethyl acetoacetate, 1 g copper chloride dihydrate, 3.5 g water, 1.5 g hydrochloric acid, 51.5 g anhydrous ethanol, and 0.5 g sodium dodecylbenzenesulfonate.

[0091] A method for preparing a visible light catalytic antibacterial ceramic coating is as follows:

[0092] (1) Sol preparation

[0093] (a) Add 30.6 g tetrabutyl titanate and 11.4 g ethyl acetoacetate to 34 g anhydrous ethanol and stir thoroughly for 30 min to obtain a light yellow transparent solution ①.

[0094] (b) Add 3.5 g of water and 1.5 g of hydrochloric acid to 17.5 g of anhydrous ethanol, add 1 g of copper chloride dihydrate, and add 0.5 g of sodium dodecylbenzenesulfonate. Stir to obtain solution ②.

[0095] (c) Slowly add solution ② to solution ① while it is being stirred. After the addition is complete, stir for 3 h in the absence of air and let it stand for 24 h to obtain Cu-TiO2 sol.

[0096] (2) Coating preparation

[0097] (a) Before spraying the sol, the glaze surface should be pretreated: clean and wipe the glaze surface with distilled water and anhydrous ethanol respectively, and dry it in a drying oven at 100°C.

[0098] (b) Using a 0.3 mm spray gun, apply the sol to the surface of the ceramic tile glaze (the ceramic glaze after sintering and vitrification at 1200℃), with the spray gun 15-20 cm away from the glaze, and spray 1-2 times.

[0099] (c) The sol on the surface of the ceramic glaze is dried and placed in a muffle furnace for heat treatment. The temperature is increased to 500°C at a rate of 5°C / min and held for 1 h to obtain a visible light catalytic antibacterial coating ceramic.

[0100] Comparative Example 2

[0101] A method for preparing a visible light catalytic antibacterial ceramic coating differs from Comparative Example 1 in that the heat treatment temperature in the coating preparation step is 600℃.

[0102] Comparative Example 3

[0103] A method for preparing a visible light catalytic antibacterial ceramic coating differs from Comparative Example 1 in that the heat treatment temperature in the coating preparation step is 700℃.

[0104] Comparative Example 4

[0105] A visible-light catalytic antibacterial ceramic coating differs from Example 3 in that trimethyl borate is replaced with an equal amount of boric acid. All other steps are the same.

[0106] Comparative Example 5

[0107] A visible-light catalytic antibacterial ceramic coating differs from Example 3 in that copper chloride is replaced with an equal amount of copper sulfate. All other steps are the same.

[0108] Comparative Example 6

[0109] This comparative example is a commercially available TOTO toilet with a photocatalytic (ultraviolet) antibacterial coating, brand name NEOREST NX2CS901K V4.

[0110] Performance testing

[0111] The antibacterial properties, UV-Vis absorption, abrasion resistance, bonding strength, easy cleaning, and corrosion resistance of the above embodiments and comparative examples under visible light were tested.

[0112] 1. Antibacterial properties

[0113] The antibacterial rate of the ceramic coating was tested according to the method specified in GB / T 30706-2014 "Test Method and Evaluation of Antibacterial Performance of Photocatalytic Antibacterial Materials and Products under Visible Light Irradiation". The results are shown in Table 2.

[0114] 2. Phase analysis

[0115] Phase analysis of the ceramic coating powder was performed using an X-ray diffractometer (Rigaku Ultima IV XRD, Japan). The results are as follows: Figure 1 As shown.

[0116] 3. Microscopic morphology analysis

[0117] The ceramic coating was analyzed using a field emission scanning electron microscope (ZEISS Gemini SEM 300, Germany), and the results are as follows. Figure 2 As shown.

[0118] Figure 2 In the figures, A1 (uncorroded), A2 (acid corrosion), and A3 (alkali corrosion) are the coating test results of Example 5, respectively; Figure 2 B1 (uncorroded), B2 (acid corrosion), and B3 (alkali corrosion) are the coating test results of Comparative Example 2, respectively. Figure 2C1 (uncorroded), C2 (acid-corroded), and C3 (alkali-corroded) are the coating test results of Comparative Example 6.

[0119] 4. Ultraviolet-Visible Absorption Analysis

[0120] The ultraviolet-visible absorption of the ceramic coating was analyzed using a UV-Vis near-infrared spectrophotometer (Hitachi UH4150, Japan). The results are as follows: Figure 3 As shown.

[0121] 5. Abrasion resistance

[0122] The wear resistance of the ceramic coating was tested using a friction and wear testing machine (Brook UMT-5), and the results are as follows: Figure 4 As shown.

[0123] 6. Bond strength

[0124] The bonding strength between the coating and the ceramic substrate was tested using a nano-scratch tester (RTEC SMT-5000, USA), and the results are as follows: Figure 5 As shown.

[0125] 7. AFM Analysis

[0126] The surface morphology of the ceramic coating was analyzed using an atomic force microscope (Bruker Dimension Icon, Germany), and the results are as follows. Figure 6 As shown.

[0127] 8. Corrosion resistance

[0128] The acid and alkali resistance of the ceramic coating was tested according to the Australian standard AS1976-1992.

[0129] Table 2. Antibacterial properties of Examples 1-6 and Comparative Examples 1-6 under visible light.

[0130]

[0131] As shown in Table 2, Examples 2, 3, 5, and 6, as well as Comparative Example 1, all achieved visible light catalytic antibacterial activity, with Example 5 exhibiting the best antibacterial rate. Examples 2 and 3 demonstrated superior antibacterial effects under visible light compared to Comparative Example 1. This may be because the molar ratio of Ti:B:Cu in Examples 2 and 3 was within the range of 1:(2.5-5.5):(0.064-0.1). Doping with an appropriate amount of B element can reduce the band gap of TiO2, thus broadening its response range to visible light; Cu element doping in TiO2 crystals... 2+ As a photogenerated electron capture center, it inhibits electron-hole recombination, and together they significantly improve the efficient and stable antibacterial performance of visible light catalysis.

[0132] Combining Example 1 and Comparative Example 1 with Table 2, it can be seen that the antibacterial effect of Example 1 under visible light is worse than that of Comparative Example 1. The reason for this is that, at a heat treatment temperature of 500℃, the molar ratio of Ti:B:Cu in the antibacterial sol of Example 1 is 1:8.13:0.12, resulting in an excess of boron. This leads to the formation of a large amount of glassy phase, which encapsulates TiO2, thus reducing the antibacterial effect under visible light. In contrast, Comparative Example 1, despite only doping titanium dioxide with copper at a treatment temperature of 500℃, also exhibits a certain antibacterial effect under visible light.

[0133] Based on Examples 1-3 and Comparative Examples 4 and 5, and referring to Table 2, it can be seen that at the same heat treatment temperature (500℃), Example 3 exhibits better antibacterial effects under visible light than Examples 1 and 2. This may be because excessive introduction of element B as a flux leads to a higher degree of vitrification in the composite sol, resulting in TiO2 being largely encapsulated by the glass phase, thus significantly reducing its antibacterial performance. Furthermore, at the same heat treatment temperature, Example 3 shows better antibacterial effects under visible light than Comparative Examples 4 and 5. The reason for this may be that when boric acid is used instead of trimethyl borate as the boron source (as in Comparative Example 4), boric acid is insoluble in organic matter and difficult to adapt to the sol system of this application, leading to a significant decrease in the antibacterial rate of the coating under visible light. Conversely, when copper sulfate is used instead of copper chloride dihydrate as the copper source (as in Comparative Example 5), the sulfate anions cause the sol to agglomerate and solidify, hindering spraying and making it difficult to form a dense and continuous antibacterial coating, thus resulting in poor antibacterial performance under visible light.

[0134] Based on the results of Examples 5 and 6, Comparative Examples 2 and 3, and the test results in Table 2, it can be seen that the antibacterial efficiency of Examples 5 and 6 is better than that of Comparative Examples 2 and 3. The reason for this is that Cu-TiO2 sol particles are prone to agglomeration after heat treatment at 600℃ and 700℃ (as in Comparative Examples 2 and 3). This phenomenon reduces the photocatalytic specific surface area of ​​the coating and weakens the visible light photocatalytic antibacterial effect of the ceramic coating. At the same temperature, the Cu / B-TiO2 sol system, due to the addition of an appropriate amount of B (as in Example 5), can significantly inhibit the coarsening of anatase and rutile grains, resulting in a narrower and more uniform grain size distribution. This increases the specific surface area and light scattering efficiency, enhances visible light absorption, and strengthens the photocatalytic antibacterial effect. However, excessively high heat treatment temperatures of 700°C (as in Example 6) cause flux components in the glaze to diffuse into the TiO2 coating, resulting in low crystallinity of TiO2 or almost complete transformation of anatase crystals into rutile, which is not conducive to electron-hole pair separation, reduces photocatalytic activity, and decreases antibacterial properties.

[0135] Based on Examples 3, 5, and 6 and Table 2, the antibacterial rate shows a trend of first increasing and then decreasing: Example 5 > Example 3 > Example 6. This may be because the increased heat treatment temperature is conducive to the formation of a heterojunction mixed crystal structure of anatase and rutile TiO2, which can effectively suppress photogenerated electron-hole recombination and significantly improve photocatalytic activity. However, excessively high heat treatment temperature causes the flux components in the glaze to diffuse into the TiO2 coating, resulting in low crystallinity of TiO2, or the anatase crystals are almost completely transformed into rutile, which is not conducive to electron-hole pair separation, thus reducing photocatalytic activity and decreasing antibacterial performance.

[0136] The commercially available product in Comparative Example 6 is an ultraviolet photocatalytic antibacterial product, therefore its antibacterial properties were not tested under visible light.

[0137] The XRD analysis results of the coating powder in Example 5 are as follows: Figure 1 As shown, after heat treatment at 600℃, the main crystalline phase of Cu / B-TiO2 powder is a mixed crystal form of anatase TiO2 (40.2%) and rutile TiO2 (52.8%), with sharp crystal peaks and a very complete crystalline structure. CuCO3 crystals (4.1%) and a small amount of amorphous phases (2.9%) are also present. No boron-related phases were observed. This is likely because most of the incorporated boron melts into the glaze surface, significantly enhancing the adhesion between the coating and the glaze, and improving wear resistance, chemical corrosion resistance, and ease of cleaning. Therefore, this explains why XRD only detected a small amount of amorphous phase in the coating.

[0138] By SEM Figure 2 It can be seen that the coating grains in Comparative Example 2 are severely agglomerated, while those in Example 5 are uniformly sized and distributed. The coating surface in Comparative Example 6 is also uniformly sized and distributed, with a relatively dense surface, but some pits are present. This indicates that the Cu-TiO2 sol particles in Comparative Example 2 are prone to agglomeration after heat treatment at 600℃. This phenomenon reduces the photocatalytic specific surface area of ​​the coating, weakening the visible light photocatalytic antibacterial effect of the ceramic coating. In Example 5, the addition of an appropriate amount of B to Cu-TiO2 significantly inhibits the coarsening of anatase and rutile grains, resulting in a narrower and more uniform grain size distribution. This increases the specific surface area and light scattering efficiency, enhances visible light absorption, and strengthens the photocatalytic antibacterial effect.

[0139] After acid and alkali corrosion, the grain morphology of Comparative Examples 2 and 6 changed, and cracks appeared in the coatings; in Example 5, the grains maintained their original morphology, were evenly distributed, and the coating was undamaged. This indicates that adding an appropriate amount of B can improve the structural stability of TiO2, reduce the reactivity of acid and alkali media with the TiO2 lattice, and also act as a flux, significantly improving the interfacial bonding strength between the coating and the substrate, preventing the coating from detaching from the substrate. The two work synergistically to ensure the durability of acid and alkali resistance.

[0140] Analysis by ultraviolet-visible absorption light Figure 3 It can be seen that all samples exhibit strong ultraviolet absorption and relatively weak visible light absorption. From the absorption peak intensity, Examples 5 and Comparative Example 2 show an increase compared to Comparative Example 6; from the red shift of the absorption band edge, Examples 5 and Comparative Example 2 show a significant red shift at the light absorption edge compared to Comparative Example 6, indicating that the coating's response to visible light is enhanced. These phenomena suggest that adding an appropriate amount of B reduces the band gap width of TiO2, generating more charge carriers under low-energy excitation, thus enhancing the coating's response to visible light; while Cu doping of TiO2 crystals... 2+ As a photogenerated electron trapping center, it suppresses photoinduced electron-hole recombination, improves quantum efficiency, and the co-doping synergistic effect significantly enhances visible light response.

[0141] Figure 4 The graphs show the coefficient of friction (COF) variation curves for Example 5, Comparative Examples 2 and 6. The COF value is directly related to the wear resistance of the coating. A small COF value and a stable curve indicate a smooth coating surface, low frictional resistance, excellent wear resistance, and less susceptibility to peeling or failure due to friction during service. Figure 5 It can be seen that the friction coefficient of Example 5 is lower than that of Comparative Example 2 and Comparative Example 6. Compared with Comparative Example 2, the friction coefficient of Example 5 is smaller. This may be because after B is incorporated into TiO2 crystals, it plays an efficient fluxing role, effectively reducing the glass transition temperature, promoting dense sintering of the coating, and achieving a uniform and smooth coating with low frictional resistance and excellent wear resistance.

[0142] Figure 5 The load-scratch location curves for Examples 5, 2, and 6 are shown below. Figure 5 As can be seen from the data, the critical load Lc values, from highest to lowest, are: Example 5 > Comparative Example 2 > Comparative Example 6. The critical load Lc is the critical failure load at which the coating exhibits significant peeling or crack propagation, and is used to quantify the bonding strength between the coating and the substrate. Compared with Comparative Examples 2 and 6, the coating in Example 5 has a stronger bonding force with the ceramic glaze substrate. This may be because the incorporation of B into TiO2 crystals can inhibit grain coarsening, making the grains more compact, increasing the coating density, reducing the density of surface defects, eliminating scratch initiation sites, and simultaneously inhibiting crack propagation along grain boundaries, thus enhancing the coating's scratch resistance. It can also act as a flux, promoting the interfacial diffusion reaction between TiO2 and ceramics during sintering, forming a continuous, non-porous intermediate layer, enhancing the bonding force between the coating and the glaze, resulting in a larger Lc value and making the coating less prone to peeling.

[0143] Figure 6 The AFM diagrams for Example 5, Comparative Examples 2 and 6 are shown below. Figure 6As can be seen, the coatings of Comparative Examples 2 and 6 exhibit significant irregular wrinkles and folds, failing to form a smooth and dense coating surface, with roughness Ra values ​​of 3.03 and 3.96, respectively. The coating surface of Example 5 shows no obvious unevenness, with uniformly distributed nano-needle-like structures, forming a unique nanostructure. The peak-valley values ​​are only between -14.1 nm and 8.9 nm, with a smaller peak-valley difference than Comparative Examples 2 and 6, and a roughness Ra of 1.34. This may be because the appropriate amount of B incorporated into TiO2 crystals refines the TiO2 grains, reducing the surface grain protrusion area, resulting in a more uniform surface morphology, lowering the height of micro-undulations, and improving surface smoothness; or because B acts as a flux, and its appropriate introduction helps balance the ratio of glassy phase to crystalline phase in the system, effectively reducing coating porosity, significantly promoting dense sintering of the coating, reducing roughness, minimizing the contact area between water or contaminants and the ceramic, resulting in lower adhesion and superior easy-cleaning properties.

[0144] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A visible light catalytic antibacterial ceramic coating, characterized in that: The antibacterial ceramic coating is located on the surface of the ceramic glaze. The antibacterial ceramic coating is formed by spraying an antibacterial sol onto the surface of the ceramic glaze and then heat-treating it. The antibacterial sol comprises the following raw materials in the indicated mass fractions: 16-35% tetrabutyl titanate, 20-45% organoboroester, 5-15% ethyl acetoacetate, 0.5-1% copper chloride dihydrate, 2-3% water, 1-2% hydrochloric acid, 25-35% anhydrous ethanol and 0-2% dispersant.

2. The visible light catalytic antibacterial ceramic coating according to claim 1, characterized in that: The organoboroester is trimethyl borate.

3. The visible light catalytic antibacterial ceramic coating according to claim 1, characterized in that: The dispersant is sodium dodecylbenzenesulfonate.

4. The visible light catalytic antibacterial ceramic coating according to claim 1, characterized in that: The heat treatment temperature is 500℃-700℃.

5. The visible light catalytic antibacterial ceramic coating according to claim 1, characterized in that: The thickness of the antibacterial ceramic coating is 0.1 μm-1 μm.

6. The visible light catalytic antibacterial ceramic coating according to claim 1, characterized in that: The ceramic glaze is a vitreous vitrified glaze layer formed after sintering.

7. The visible light catalytic antibacterial ceramic coating according to claim 1, characterized in that: The molar ratio of Ti:B:Cu in the antibacterial sol is 1:(2.5-5.5):(0.064-0.1).

8. A method for preparing a visible light catalytic antibacterial ceramic coating according to any one of claims 1-7, characterized in that: Includes the following steps: (1) Preparation of antibacterial sol (a) Add 16-35% tetrabutyl titanate, 20-45% trimethyl borate and 5-15% ethyl acetoacetate to 18-22% anhydrous ethanol and stir thoroughly to obtain solution ①. (b) First, add 2-3% water and 1-2% hydrochloric acid to 7-13% anhydrous ethanol, then add 0.5-1% copper chloride dihydrate, and then add 0-2% dispersant. Stir to obtain solution ②. (c) Slowly add solution ② to solution ① while it is being stirred. After the addition is complete, stir for 2.5-3.5 h in the absence of air, and let it stand and age for 23-25 ​​h to obtain Cu / B-TiO2 sol; (2) Coating preparation (a) Glaze surface preparation: Clean and wipe the ceramic glaze surface with distilled water and anhydrous ethanol respectively, and then dry it; (b) Spraying sol: The obtained Cu / B-TiO2 sol is sprayed onto the surface of the ceramic glaze using a spray gun. The spray gun is 15-20 cm away from the ceramic glaze, and the spraying is done 1-2 times. (c) Low-temperature heat treatment: After drying the Cu / B-TiO2 sol on the surface of the ceramic glaze, heat treatment is carried out by raising the temperature to 500℃-700℃ at a rate of 4-6℃ / min and holding for 1-1.2 h to obtain a visible light catalytic antibacterial ceramic coating.

9. The method for preparing a visible light catalytic antibacterial ceramic coating according to claim 8, characterized in that: The nozzle diameter of the spray gun is 0.2-0.4 mm.

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