Preparation method of SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating with netlike and gradient structures for sandstone cultural relics

Abstract

The invention discloses a preparation method of a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating with a mesh structure and a gradient structure for sandstone cultural relics. The preparation method comprises the following steps: 1, preparing hydrophilic SiO2 nanoparticles; 2, preparation of hydrophobic SiO2 nano particles; 3, preparing a hydrophilic SiO2 nano particle / polydimethylsiloxane dispersion liquid; 4, preparing a hydrophilic / hydrophobic SiO2 nano particle / polydimethylsiloxane dispersion liquid; 5, preparing a hydrophobic SiO2 nano particle / polydimethylsiloxane dispersion liquid; and 6, fixing grids on the surface of the sandstone, and sequentially spraying the dispersion liquid prepared in the steps 3, 4 and 5 as a bottom layer, a middle layer and a top layer. The bottom layer enhances the combination of the coating and a sandstone matrix through hydrogen bonds, the hydrophilic SiO2 of the middle layer is beneficial to dispersing hydrophobic SiO2 and enhancing bonding transition and stress transfer between the bottom layer and the top layer, and the top layer provides rich low-surface-energy groups and endows the bottom layer with synergistically enhanced adhesive force, stability and mechanical durability; the net structure ensures the hydrophobicity of the coating and enhances the wear resistance of the coating.

Description

Technical Field

[0001] The present invention belongs to cultural relic protection technology and relates to a coating preparation method, in particular to a method for preparing a SiO2 transparent, high-adhesion, wear-resistant, super-hydrophobic coating with both a mesh and gradient structure for sandstone cultural relics. Background Art

[0002] Sandstone architecture, stone paintings, and carvings are an integral part of the world's cultural heritage, embodying ancient scientific, artistic, and historical significance. However, due to their porous intrinsic structure and exposure to the elements, they are constantly impacted by environmental factors such as temperature fluctuations, rainwater erosion, and bacterial invasion, as well as by human activities. Among these factors, water has been identified as the primary culprit for degradation, as it not only weakens the sandstone's internal adhesion by dissolving soluble components but also contributes to weathering, soluble salt crystallization, freeze-thaw cycles, microbial attachment, and other pathologies. Inspired by the lotus effect, superhydrophobic surfaces, featuring a precise synergy of low surface energy and hierarchical micro / nanostructures, are highly sought after in surface engineering. However, the micro / nanostructures of superhydrophobic surfaces are easily destroyed by external forces, resulting in a loss of superhydrophobicity, severely limiting their practical applications. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing a SiO2 transparent, high-adhesion, wear-resistant super-hydrophobic coating with both a mesh and gradient structure for sandstone cultural relics. The transparency and super-hydrophobicity of the coating are achieved through the mesh structure, and the adhesion between the coating and the substrate is enhanced through the gradient structure, so that the coating has excellent mechanical durability.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A method for preparing a SiO2 transparent, high-adhesion, wear-resistant, super-hydrophobic coating having both a mesh and gradient structure for sandstone cultural relics comprises the following steps:

[0006] Step 1: Preparation of hydrophilic SiO2 nanoparticles

[0007] γ-aminopropyltriethoxysilane dispersion was added dropwise to SiO2 / ethanol dispersion at a mass ratio of 1:(0.6-1), and after the reaction, hydrophilic SiO2 nanoparticles were obtained by centrifugation, ethanol washing and drying.

[0008] Step 2: Preparation of hydrophobic SiO2 nanoparticles

[0009] Alkoxysiloxane / ethanol solution is added dropwise to SiO2 dispersion in a mass ratio of 1:(2-5), and after the reaction, hydrophobic SiO2 nanoparticles are obtained by centrifugation, ethanol washing and drying.

[0010] Step 3, dispersing the hydrophilic SiO2 nanoparticles prepared in step 1 in an organic solvent to obtain a hydrophilic SiO2 / organic solvent dispersion, stirring evenly, adding a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent, stirring and dispersing evenly to obtain a hydrophilic SiO2 nanoparticle / polydimethylsiloxane dispersion for standby use;

[0011] Step 4, mixing the hydrophilic SiO2 nanoparticles prepared in step 1 and the hydrophobic SiO2 nanoparticles prepared in step 2 in a mass ratio of 1: (20-100) to obtain hydrophilic / hydrophobic SiO2 nanoparticles, dispersing the hydrophilic / hydrophobic SiO2 nanoparticles in an organic solvent to obtain a hydrophilic / hydrophobic SiO2 / organic solvent dispersion, stirring evenly, adding a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent, stirring and dispersing evenly to obtain a hydrophilic / hydrophobic SiO2 nanoparticle / polydimethylsiloxane dispersion for standby use;

[0012] Step 5: Dispersing the hydrophobic SiO2 nanoparticles prepared in step 2 in an organic solvent to obtain a hydrophobic SiO2 / organic solvent dispersion, stirring evenly, adding a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent, stirring and dispersing evenly to obtain a hydrophobic SiO2 nanoparticle / polydimethylsiloxane dispersion for standby use;

[0013] The mass ratio of the hydrophilic SiO2 nanoparticles, the hydrophilic / hydrophobic SiO2 nanoparticles, and the hydrophobic SiO2 nanoparticles to the organic solvent in steps 3 to 5 is 1:(30-50); the mass ratio of the hydrophilic SiO2 / organic solvent dispersion, the hydrophilic / hydrophobic SiO2 / organic solvent dispersion, and the hydrophobic SiO2 / organic solvent dispersion to the PDMS-CA mixture is 1:(0.05-0.2); the mass ratio of polydimethylsiloxane to the curing agent in the PDMS-CA mixture is 10:1;

[0014] Step 6. Fix the grid on the sandstone surface. First, spray the hydrophilic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 3 as the bottom layer. After standing at room temperature, spray the hydrophilic / hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 4 as the middle layer. After standing at room temperature, spray the hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 5 as the top layer. Curing at room temperature obtains a network structure SiO2 transparent, high adhesion, wear-resistant super hydrophobic coating.

[0015] Furthermore, the SiO2 / ethanol dispersion in step 1 is obtained by uniformly dispersing SiO2 and ethanol by ultrasonication in a mass ratio of (1:5) to (1:30), wherein the particle size of the SiO2 nanoparticles is 50 to 200 nm.

[0016] Furthermore, the γ-aminopropyltriethoxysilane dispersion in step 1 is obtained by uniformly dispersing γ-aminopropyltriethoxysilane, ethanol and deionized water by ultrasonication in a mass ratio of 1:(3-5):(0.5-1).

[0017] Furthermore, in step 1, the reaction temperature is 50-70° C., the reaction time is 2-4 h, the centrifugal speed is 6000-10000 rpm, the ethanol washing is 3-5 times, the drying temperature is 60-80° C., and the drying time is 2-4 h.

[0018] Furthermore, the SiO2 dispersion in step 2 is obtained by uniformly dispersing SiO2, ammonia water and deionized water in a mass ratio of 1:(1-1.5):(5-10) by ultrasonication, wherein the particle size of the SiO2 nanoparticles is 5-20 nm.

[0019] Furthermore, the alkoxysiloxane / ethanol solution in step 2 is obtained by mixing alkoxysiloxane and ethanol solution in a mass ratio of 1:(30-100), wherein the alkoxysiloxane is a long-chain perfluoroalkylalkoxysilane with a carbon number ≥8 and a long-chain alkylalkoxysilane with a carbon number ≥12.

[0020] Furthermore, the alkoxysiloxane includes perfluorodecyltriethoxysilane, perfluorooctyltriethoxysilane, dodecyltriethoxysilane or hexadecyltriethoxysilane.

[0021] Furthermore, in step 2, the reaction temperature is 40-60° C., the reaction time is 12-36 h, the centrifugal speed is 6000-10000 rpm, the ethanol washing is 3-5 times, the drying temperature is 60-80° C., and the drying time is 2-4 h.

[0022] Furthermore, in steps 3 to 5, the organic solvent is tetrahydrofuran, dimethylformamide, ethanol or dichloromethane, and the stirring time is 15 to 30 minutes.

[0023] Furthermore, in step 6, the mesh aperture is 50-500 mesh, the material is stainless steel, nylon or polyester fiber, the spraying time is 2-6 seconds, and the room temperature curing time is 36-72 hours.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The network structure constructed by the present invention can effectively increase the roughness of the coating surface and improve the hydrophobicity of the coating; in addition, the surface network structure can reduce coating wear and enhance the stability of the coating.

[0026] (2) The gradient structure constructed by the present invention can improve the adhesion of the superhydrophobic coating to sandstone and enhance the stability and mechanical durability of the coating. The bottom layer strengthens the bonding between the coating and the sandstone substrate through hydrogen bonding. The appropriate amount of hydrophilic SiO2 in the middle layer can better disperse the hydrophobic SiO2 and enhance the bonding transition and stress transfer between the bottom and top layers. The top layer provides abundant low surface energy groups, giving it synergistically enhanced adhesion, stability, and mechanical durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 For photos of the original sandstone;

[0028] Figure 2 This is a photo of the sandstone modified with a SiO2 transparent, high-adhesion, wear-resistant, super-hydrophobic coating having both a mesh and gradient structure, prepared in Example 1 of the present invention;

[0029] Figure 3 This is a photo of the sandstone modified with a SiO2 transparent, high-adhesion, wear-resistant, super-hydrophobic coating having both a mesh and gradient structure, prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1:

[0032] This embodiment provides a method for preparing a SiO2 transparent, high-adhesion, wear-resistant, super-hydrophobic coating having both a mesh and gradient structure for sandstone cultural relics, which specifically comprises the following steps:

[0033] Step 1, preparation of hydrophilic SiO2 nanoparticles: SiO2 with a particle size of 118 nm and ethanol are ultrasonically dispersed in a mass ratio of 1:10 to obtain a SiO2 / ethanol dispersion, to which is added dropwise a γ-aminopropyltriethoxysilane dispersion obtained by mixing γ-aminopropyltriethoxysilane, ethanol, and deionized water in a mass ratio of 1:3.9:0.5, the mass ratio of the SiO2 / ethanol dispersion to the γ-aminopropyltriethoxysilane dispersion being 1:0.6, and the mixture is reacted at 60°C for 3h, centrifuged at 8000rpm, washed three times with ethanol, and dried at 80°C for 3h to obtain hydrophilic SiO2;

[0034] Step 2, preparation of hydrophobic SiO2 nanoparticles: SiO2 with a particle size of 10 nm, ammonia water and deionized water in a mass ratio of 1:1.2:5 were ultrasonically dispersed to obtain a SiO2 dispersion, to which a perfluorodecyltriethoxysilane / ethanol solution obtained by mixing perfluorodecyltriethoxysilane and an ethanol solution in a mass ratio of 1:75 was added dropwise, the mass ratio of the SiO2 dispersion to the perfluorodecyltriethoxysilane / ethanol solution being 1:3.2. After reacting at 40°C for 24 hours, the mixture was centrifuged at 8000 rpm, washed three times with ethanol and dried at 80°C for 3 hours to obtain hydrophobic SiO2;

[0035] Step 3, dispersing the hydrophilic SiO2 nanoparticles prepared in step 1 in tetrahydrofuran at a mass ratio of 1:44 to obtain a hydrophilic SiO2 / tetrahydrofuran dispersion, stirring for 15 minutes, adding a PDMS-CA mixture composed of polydimethylsiloxane and a curing agent at a mass ratio of 10:1, and the mass ratio of the hydrophilic SiO2 / tetrahydrofuran dispersion to the PDMS-CA mixture is 1:0.1, stirring for 15 minutes and then setting aside;

[0036] Step 4, according to a mass ratio of 1:20, the hydrophilic SiO2 prepared in step 1 and the hydrophobic SiO2 nanoparticles prepared in step 2 are mixed to obtain hydrophilic / hydrophobic SiO2 nanoparticles, and the hydrophilic / hydrophobic SiO2 nanoparticles are dispersed in tetrahydrofuran to obtain a hydrophilic / hydrophobic SiO2 / tetrahydrofuran dispersion, wherein the mass ratio of the hydrophilic / hydrophobic SiO2 nanoparticles to tetrahydrofuran is 1:44. After stirring for 15 minutes, a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent in a mass ratio of 10:1 is added, and the mass ratio of the hydrophilic / hydrophobic SiO2 / tetrahydrofuran dispersion to the PDMS-CA mixture is 1:0.1. The mixture is stirred for 15 minutes and then used.

[0037] Step 5, dispersing the hydrophobic SiO2 nanoparticles prepared in step 2 in tetrahydrofuran at a mass ratio of 1:44 to obtain a hydrophobic SiO2 / tetrahydrofuran dispersion, stirring for 15 minutes, adding a PDMS-CA mixture composed of polydimethylsiloxane and a curing agent at a mass ratio of 10:1, and the mass ratio of the hydrophobic SiO2 / tetrahydrofuran dispersion to the PDMS-CA mixture is 1:0.1, stirring for 15 minutes and then set aside;

[0038] Step 6. Fix a stainless steel grid with a pore size of 200 mesh on the sandstone surface. First, spray the hydrophilic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 3 for 3s as the bottom layer. After leaving it at room temperature for 2 hours, spray the hydrophilic / hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 4 for 3s as the middle layer. After leaving it at room temperature for 6 hours, spray the hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 5 for 3s as the top layer. Curing it at room temperature for 48 hours obtains a SiO2 transparent, high-adhesion, wear-resistant super-hydrophobic coating with both a network and gradient structure.

[0039] Figure 1 Original sandstone, Figure 2 The sandstone cultural relic prepared in Example 1 is coated with a SiO2 transparent, high-adhesion, wear-resistant super-hydrophobic coating with both a mesh and gradient structure. In comparison, the color of the sandstone does not change significantly. After tape adhesion, sandpaper abrasion, gravel erosion, and acid rain / alkaline water erosion, its contact angle is still greater than 150°, showing excellent mechanical durability.

[0040] Example 2:

[0041] This embodiment provides a method for preparing a SiO2 transparent, high-adhesion, wear-resistant, super-hydrophobic coating having both a mesh and gradient structure for sandstone cultural relics, which specifically comprises the following steps:

[0042] Step 1, preparation of hydrophilic SiO2 nanoparticles: SiO2 with a particle size of 50 nm and ethanol are ultrasonically dispersed in a mass ratio of 1:15 to obtain a SiO2 / ethanol dispersion, to which is added dropwise a γ-aminopropyltriethoxysilane dispersion obtained by mixing γ-aminopropyltriethoxysilane, ethanol, and deionized water in a mass ratio of 1:3:0.5, the mass ratio of the SiO2 / ethanol dispersion to the γ-aminopropyltriethoxysilane dispersion being 1:0.8, and the mixture is reacted at 60°C for 3 hours, centrifuged at 6000 rpm, washed three times with ethanol, and dried at 80°C for 2 hours to obtain hydrophilic SiO2;

[0043] Step 2, preparation of hydrophobic SiO2 nanoparticles: SiO2 with a particle size of 5 nm, ammonia water and deionized water in a mass ratio of 1:1.3:6 were ultrasonically dispersed to obtain a SiO2 dispersion, to which a perfluorooctyltriethoxysilane / ethanol solution obtained by mixing perfluorooctyltriethoxysilane and an ethanol solution in a mass ratio of 1:70 was added dropwise, the mass ratio of the SiO2 dispersion to the perfluorooctyltriethoxysilane / ethanol solution being 1:3.5. After reacting at 40°C for 36 hours, the mixture was centrifuged at 6000 rpm, washed three times with ethanol, and dried at 80°C for 2 hours to obtain hydrophobic SiO2;

[0044] Step 3, the hydrophilic SiO2 nanoparticles prepared in step 1 are dispersed in dimethylformamide at a mass ratio of 1:40 to obtain a hydrophilic SiO2 / dimethylformamide dispersion, and after stirring for 30 minutes, a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent at a mass ratio of 10:1 is added, and the mass ratio of the hydrophilic SiO2 / dimethylformamide dispersion to the PDMS-CA mixture is 1:0.15. After stirring for 30 minutes, the mixture is set aside;

[0045] Step 4, according to a mass ratio of 1:100, the hydrophilic SiO2 prepared in step 1 and the hydrophobic SiO2 nanoparticles prepared in step 2 are mixed to obtain hydrophilic / hydrophobic SiO2 nanoparticles, and the hydrophilic / hydrophobic SiO2 nanoparticles are dispersed in dimethylformamide to obtain a hydrophilic / hydrophobic SiO2 / dimethylformamide dispersion, wherein the mass ratio of the hydrophilic / hydrophobic SiO2 nanoparticles to dimethylformamide is 1:40, and after stirring for 30 minutes, a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent in a mass ratio of 10:1 is added, and the mass ratio of the hydrophilic / hydrophobic SiO2 / dimethylformamide dispersion to the PDMS-CA mixture is 1:0.15. Stir for 30 minutes and then standby;

[0046] Step 5, dispersing the hydrophobic SiO2 nanoparticles prepared in step 2 in dimethylformamide at a mass ratio of 1:40 to obtain a hydrophobic SiO2 / dimethylformamide dispersion, stirring for 30 minutes, adding a PDMS-CA mixture composed of polydimethylsiloxane and a curing agent at a mass ratio of 10:1, and the mass ratio of the hydrophobic SiO2 / dimethylformamide dispersion to the PDMS-CA mixture is 1:0.15, stirring for 30 minutes and then set aside;

[0047] Step 6: Fix a stainless steel grid with an aperture of 190 mesh on the sandstone surface, first spray the hydrophilic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 3 for 3s as the bottom layer, let it stand at room temperature for 2h, spray the hydrophilic / hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 4 for 3s as the middle layer, let it stand at room temperature for 6h, spray the hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 5 for 3s as the top layer, and cure it at room temperature for 48h to obtain a SiO2 transparent, high-adhesion, wear-resistant super-hydrophobic coating with both a network and gradient structure.

[0048] Figure 3 A sandstone cultural relic prepared in Example 2 is coated with a SiO2 transparent high adhesion wear-resistant super hydrophobic coating with both a mesh and gradient structure. Figure 1 The color of the sandstone did not change significantly. After tape adhesion, sandpaper abrasion, gravel erosion, and acid rain / alkaline water erosion, its contact angle was still greater than 150°, showing excellent mechanical durability.

[0049] Example 3:

[0050] This embodiment provides a method for preparing a SiO2 transparent, high-adhesion, wear-resistant, super-hydrophobic coating having both a mesh and gradient structure for sandstone cultural relics, which specifically comprises the following steps:

[0051] Step 1, preparation of hydrophilic SiO2 nanoparticles: SiO2 with a particle size of 200 nm and ethanol are ultrasonically dispersed in a mass ratio of 1:5 to obtain a SiO2 / ethanol dispersion, to which is added dropwise a γ-aminopropyltriethoxysilane dispersion obtained by mixing γ-aminopropyltriethoxysilane, ethanol, and deionized water in a mass ratio of 1:3:0.8, the mass ratio of the SiO2 / ethanol dispersion to the γ-aminopropyltriethoxysilane dispersion being 1:0.6, and the mixture is reacted at 70°C for 2h, centrifuged at 10,000 rpm, washed 5 times with ethanol, and dried at 60°C for 4h to obtain hydrophilic SiO2;

[0052] Step 2, preparation of hydrophobic SiO2 nanoparticles: SiO2 with a particle size of 20 nm, ammonia water and deionized water in a mass ratio of 1:1:5 are ultrasonically dispersed to obtain a SiO2 dispersion, to which a dodecyltriethoxysilane / ethanol solution obtained by mixing dodecyltriethoxysilane and an ethanol solution in a mass ratio of 1:30 is added dropwise, the mass ratio of the SiO2 dispersion to the dodecyltriethoxysilane / ethanol solution being 1:2. After reacting at 60°C for 12 hours, the mixture is centrifuged at 10,000 rpm, washed with ethanol 5 times and dried at 60°C for 4 hours to obtain hydrophobic SiO2;

[0053] Step 3, the hydrophilic SiO2 nanoparticles prepared in step 1 are dispersed in ethanol at a mass ratio of 1:30 to obtain a hydrophilic SiO2 / ethanol dispersion, and after stirring for 20 minutes, a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent at a mass ratio of 10:1 is added, and the mass ratio of the hydrophilic SiO2 / ethanol dispersion to the PDMS-CA mixture is 1:0.05. After stirring for 20 minutes, the mixture is set aside;

[0054] Step 4, according to a mass ratio of 1:50, the hydrophilic SiO2 prepared in step 1 and the hydrophobic SiO2 nanoparticles prepared in step 2 are mixed to obtain hydrophilic / hydrophobic SiO2 nanoparticles, and the hydrophilic / hydrophobic SiO2 nanoparticles are dispersed in ethanol to obtain a hydrophilic / hydrophobic SiO2 / ethanol dispersion, wherein the mass ratio of the hydrophilic / hydrophobic SiO2 nanoparticles to ethanol is 1:30. After stirring for 20 minutes, a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent in a mass ratio of 10:1 is added, and the mass ratio of the hydrophilic / hydrophobic SiO2 / ethanol dispersion to the PDMS-CA mixture is 1:0.05. After stirring for 20 minutes, the mixture is set aside.

[0055] Step 5, the hydrophobic SiO2 nanoparticles prepared in step 2 were dispersed in ethanol at a mass ratio of 1:30 to obtain a hydrophobic SiO2 / ethanol dispersion, and after stirring for 20 minutes, a PDMS-CA mixture of polydimethylsiloxane and a curing agent at a mass ratio of 10:1 was added, and the mass ratio of the hydrophobic SiO2 / ethanol dispersion to the PDMS-CA mixture was 1:0.05. After stirring for 20 minutes, the mixture was set aside;

[0056] Step 6. Fix a nylon mesh with a pore size of 50 mesh on the sandstone surface. First, spray the hydrophilic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 3 for 2s as the bottom layer. After leaving it at room temperature for 2h, spray the hydrophilic / hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 4 for 3s as the middle layer. After leaving it at room temperature for 6h, spray the hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 5 for 2s as the top layer. Curing it at room temperature for 36h obtains a SiO2 transparent, high-adhesion, wear-resistant super-hydrophobic coating with both a mesh and gradient structure.

[0057] Example 4:

[0058] This embodiment provides a method for preparing a SiO2 transparent, high-adhesion, wear-resistant, super-hydrophobic coating having both a mesh and gradient structure for sandstone cultural relics, which specifically comprises the following steps:

[0059] Step 1, preparation of hydrophilic SiO2 nanoparticles: SiO2 with a particle size of 100 nm and ethanol are ultrasonically dispersed in a mass ratio of 1:30 to obtain a SiO2 / ethanol dispersion, to which is added dropwise a γ-aminopropyltriethoxysilane dispersion obtained by mixing γ-aminopropyltriethoxysilane, ethanol, and deionized water in a mass ratio of 1:5:1, the mass ratio of the SiO2 / ethanol dispersion to the γ-aminopropyltriethoxysilane dispersion being 1:1, and the mixture is reacted at 50°C for 4 hours, centrifuged at 9000 rpm, washed four times with ethanol, and dried at 70°C for 3 hours to obtain hydrophilic SiO2;

[0060] Step 2, preparation of hydrophobic SiO2 nanoparticles: SiO2 with a particle size of 15 nm, ammonia water and deionized water in a mass ratio of 1:1.5:10 are ultrasonically dispersed to obtain a SiO2 dispersion, to which a hexadecyltriethoxysilane / ethanol solution obtained by mixing hexadecyltriethoxysilane and an ethanol solution in a mass ratio of 1:100 is added dropwise, the mass ratio of the SiO2 dispersion to the hexadecyltriethoxysilane / ethanol solution being 1:5. After reacting at 50°C for 24 hours, the mixture is centrifuged at 9000 rpm, washed four times with ethanol and dried at 70°C for 3 hours to obtain hydrophobic SiO2;

[0061] Step 3, the hydrophilic SiO2 nanoparticles prepared in step 1 are dispersed in dichloromethane at a mass ratio of 1:50 to obtain a hydrophilic SiO2 / dichloromethane dispersion, and after stirring for 30 minutes, a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent at a mass ratio of 10:1 is added, and the mass ratio of the hydrophilic SiO2 / dichloromethane dispersion to the PDMS-CA mixture is 1:0.2. After stirring for 30 minutes, the mixture is set aside;

[0062] Step 4, according to a mass ratio of 1:80, the hydrophilic SiO2 prepared in step 1 and the hydrophobic SiO2 nanoparticles prepared in step 2 are mixed to obtain hydrophilic / hydrophobic SiO2 nanoparticles, and the hydrophilic / hydrophobic SiO2 nanoparticles are dispersed in dichloromethane to obtain a hydrophilic / hydrophobic SiO2 / dichloromethane dispersion, wherein the mass ratio of the hydrophilic / hydrophobic SiO2 nanoparticles to dichloromethane is 1:50. After stirring for 30 minutes, a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent in a mass ratio of 10:1 is added, and the mass ratio of the hydrophilic / hydrophobic SiO2 / dichloromethane dispersion to the PDMS-CA mixture is 1:0.2. After stirring for 30 minutes, the mixture is set aside.

[0063] Step 5, dispersing the hydrophobic SiO2 nanoparticles prepared in step 2 in dichloromethane at a mass ratio of 1:50 to obtain a hydrophobic SiO2 / dichloromethane dispersion, stirring for 30 minutes, adding a PDMS-CA mixture composed of polydimethylsiloxane and a curing agent at a mass ratio of 10:1, and the mass ratio of the hydrophobic SiO2 / dichloromethane dispersion to the PDMS-CA mixture is 1:0.2, stirring for 30 minutes and then set aside;

[0064] Step 6. Fix a polyester fiber grid with a pore size of 500 mesh on the sandstone surface. First, spray the hydrophilic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 3 for 6 seconds as the bottom layer. After leaving it at room temperature for 2 hours, spray the hydrophilic / hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 4 for 3 seconds as the middle layer. After leaving it at room temperature for 6 hours, spray the hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 5 for 6 seconds as the top layer. Curing it at room temperature for 72 hours obtains a SiO2 transparent, high-adhesion, wear-resistant super-hydrophobic coating with both a mesh and gradient structure.

Claims

1. A method for preparing a SiO2 transparent, high-adhesion, wear-resistant super-hydrophobic coating having both a mesh and gradient structure for sandstone cultural relics, characterized in that: The steps include: Step 1: Preparation of hydrophilic SiO2 nanoparticles γ-aminopropyltriethoxysilane dispersion was added dropwise to SiO2 / ethanol dispersion at a mass ratio of 1:(0.6-1), and after the reaction, hydrophilic SiO2 nanoparticles were obtained by centrifugation, ethanol washing and drying. Step 2: Preparation of hydrophobic SiO2 nanoparticles Alkoxysiloxane / ethanol solution is added dropwise to SiO2 dispersion in a mass ratio of 1:(2-5), and after the reaction, hydrophobic SiO2 nanoparticles are obtained by centrifugation, ethanol washing and drying. Step 3, dispersing the hydrophilic SiO2 nanoparticles prepared in step 1 in an organic solvent to obtain a hydrophilic SiO2 / organic solvent dispersion, stirring evenly, adding a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent, stirring and dispersing evenly to obtain a hydrophilic SiO2 nanoparticle / polydimethylsiloxane dispersion for standby use; Step 4, mixing the hydrophilic SiO2 nanoparticles prepared in step 1 and the hydrophobic SiO2 nanoparticles prepared in step 2 in a mass ratio of 1: (20-100) to obtain hydrophilic / hydrophobic SiO2 nanoparticles, dispersing the hydrophilic / hydrophobic SiO2 nanoparticles in an organic solvent to obtain a hydrophilic / hydrophobic SiO2 / organic solvent dispersion, stirring evenly, adding a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent, stirring and dispersing evenly to obtain a hydrophilic / hydrophobic SiO2 nanoparticle / polydimethylsiloxane dispersion for standby use; Step 5: Dispersing the hydrophobic SiO2 nanoparticles prepared in step 2 in an organic solvent to obtain a hydrophobic SiO2 / organic solvent dispersion, stirring evenly, adding a PDMS-CA mixture consisting of polydimethylsiloxane and a curing agent, stirring and dispersing evenly to obtain a hydrophobic SiO2 nanoparticle / polydimethylsiloxane dispersion for standby use; The mass ratio of the hydrophilic SiO2 nanoparticles, the hydrophilic / hydrophobic SiO2 nanoparticles, and the hydrophobic SiO2 nanoparticles to the organic solvent in steps 3 to 5 is 1:(30-50); the mass ratio of the hydrophilic SiO2 / organic solvent dispersion, the hydrophilic / hydrophobic SiO2 / organic solvent dispersion, and the hydrophobic SiO2 / organic solvent dispersion to the PDMS-CA mixture is 1:(0.05-0.2); the mass ratio of polydimethylsiloxane to the curing agent in the PDMS-CA mixture is 10:1; Step 6. Fix the grid on the sandstone surface. First, spray the hydrophilic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 3 as the bottom layer. After standing at room temperature, spray the hydrophilic / hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 4 as the middle layer. After standing at room temperature, spray the hydrophobic SiO2 nanoparticles / polydimethylsiloxane dispersion prepared in step 5 as the top layer. Curing at room temperature obtains a network structure SiO2 transparent, high adhesion, wear-resistant super hydrophobic coating.

2. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 1, wherein: The SiO2 / ethanol dispersion in step 1 is obtained by uniformly dispersing SiO2 and ethanol by ultrasonication in a mass ratio of (1:5) to (1:30), wherein the particle size of the SiO2 nanoparticles is 50 to 200 nm.

3. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 1, wherein: The γ-aminopropyltriethoxysilane dispersion in step 1 is obtained by uniformly dispersing γ-aminopropyltriethoxysilane, ethanol and deionized water by ultrasonication in a mass ratio of 1:(3-5):(0.5-1).

4. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 1, wherein: In the step 1, the reaction temperature is 50-70° C., the reaction time is 2-4 hours, the centrifugal speed is 6000-10000 rpm, the ethanol is washed 3-5 times, the drying temperature is 60-80° C., and the drying time is 2-4 hours.

5. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 1, wherein: In step 2, the SiO2 dispersion is uniformly obtained by ultrasonically dispersing SiO2, ammonia water and deionized water in a mass ratio of 1: (1-1.5): (5-10), wherein the particle size of the SiO2 nanoparticles is 5-20 nm.

6. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 1, wherein: The alkoxysiloxane / ethanol solution in step 2 is obtained by mixing alkoxysiloxane and ethanol solution in a mass ratio of 1:(30-100), wherein the alkoxysiloxane is a long-chain perfluoroalkylalkoxysilane with a carbon number of ≥8 and a long-chain alkylalkoxysilane with a carbon number of ≥12.

7. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 6, wherein: The alkoxysiloxane includes perfluorodecyltriethoxysilane, perfluorooctyltriethoxysilane, dodecyltriethoxysilane or hexadecyltriethoxysilane.

8. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 1, wherein: In step 2, the reaction temperature is 40-60° C., the reaction time is 12-36 hours, the centrifugal speed is 6000-10000 rpm, the ethanol is washed 3-5 times, the drying temperature is 60-80° C., and the drying time is 2-4 hours.

9. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 1, wherein: In steps 3 to 5, the organic solvent is tetrahydrofuran, dimethylformamide, ethanol or dichloromethane, and the stirring time is 15 to 30 minutes.

10. The method for preparing a SiO2 transparent high-adhesion wear-resistant super-hydrophobic coating having both a reticular and gradient structure for sandstone cultural relics according to claim 1, characterized in that: In step 6, the mesh aperture is 50-500 mesh, the material is stainless steel, nylon or polyester fiber, the spraying time is 2-6 seconds, and the room temperature curing time is 36-72 hours.

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