Preparation method of thermal insulation coating containing ATO-Nb2O5-at-Al2O3 aerogel and capable of resisting temperature of 1200 DEG C

Abstract

The invention discloses a preparation method of a 1200 DEG C temperature-resistant thermal insulation coating containing ATO-Nb2O5-coated Al2O3 aerogel, and belongs to the technical field of coatings. According to the method, the ATO-Nb2O5-coated Al2O3 aerogel is prepared through a gradient coating technology, nanometer ATO particles form an infrared reflection barrier, Nb2O5 inhibits Al2O3 high-temperature crystal form transformation through a pinning effect, and CO2 supercritical drying (11-14 MPa, 30-45 DEG C and 4-6 h) is combined to obtain the aerogel with high porosity and the alpha phase transition temperature larger than or equal to 1200 DEG C. An organic-inorganic compound adhesive (alkaline silica sol, potassium silicate and modified organic silicon emulsion) is used as a matrix and cooperates with hollow ceramic microbeads and superfine mullite fibers to construct a multi-scale heat insulation system, and the coating is prepared through high-speed dispersion. The heat conductivity coefficient of the coating at 25 DEG C is as low as 0.039 W / (m.K), the temperature resistance reaches 1225 DEG C, the coating has thermal shock resistance and low heat conductivity, the problems of high-temperature phase change densification and coating cracking of traditional Al2O3 aerogel are solved, and the coating is suitable for ultrahigh-temperature heat insulation protection of industrial equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and specifically relates to a preparation method of a heat-insulating coating containing ATO-Nb2O5@Al2O3 aerogel with a temperature resistance of 1200 °C. Nano-ATO powder is a nano-ultrafine particle powder composed of tin oxide and antimony oxide. Background Art

[0002] Traditional heat-resistant, heat-insulating and heat-preserving materials have played a huge role in industrial heat preservation. However, with the advent of China's "dual carbon" era, the requirements for heat-resistant, heat-insulating and heat-preserving materials in industrial heat preservation are becoming increasingly stringent. On the one hand, it should have as small a thermal conductivity or heat transfer coefficient as possible and sufficient temperature resistance to ensure the process temperature and industrial requirements of production. On the other hand, it can save energy, reduce consumption, be environmentally friendly and reduce heat loss. Thirdly, it can reduce environmental heat pollution and ensure the safety and health of personnel. Fourthly, it can ensure the normal operation of equipment, extend the service life of equipment and reduce costs. Such stringent conditions make it difficult for conventional heat-resistant, heat-insulating and heat-preserving materials, including new heat-preserving materials such as glass wool, slag wool, rock wool, aluminum silicate fiber, micro-porous calcium silicate, hollow microspheres, polyurethane foam plastics, etc., to meet the various requirements of modern industrial heat preservation.

[0003] Aerogel is a porous network structure formed by the aggregation of nanoscale particles. It is a porous network solid composite material filled with air in the network skeleton, and has unique properties such as a density lower than that of air, a porosity higher than 98%, and a specific surface area greater than 1000 m 2 / g. Among them, silica (SiO2) aerogel and its derivatives have a long history and are the most widely studied aerogels. However, these aerogels will decompose or sinter at relatively high temperatures.

[0004] Aluminum oxide (Al2O3) aerogel exhibits stronger thermal stability, superior to other oxide aerogels such as silica (SiO2) and titanium dioxide (TiO2). In addition, Al2O3 aerogel has ultra-low thermal conductivity and excellent catalytic activity. Due to its excellent properties, Al2O3 aerogel has great potential applications as a high-temperature thermal insulator and catalyst. However, it is found that Al2O3 aerogel still faces an irreversible α-phase transformation process in a high-temperature environment: when the temperature exceeds the critical value, the crystal form transformation of γ-Al2O3 to α-Al2O3 will cause the densification of the skeleton structure, resulting in a sharp drop in specific surface area, attenuation of porosity and a sharp increase in thermal conductivity. This phase transformation process not only reduces the heat-insulating efficiency of the material, but also causes cracking and peeling of the coating, seriously restricting its application in the ultra-high temperature field.

[0005] Prior art attempts to improve the anti-phase change ability of Al2O3 aerogel through nano-doping modification, but conventional doping systems have problems such as high-temperature element migration and unstable hetero-phase interfaces. The present invention innovatively introduces an ATO-Nb2O5 composite modification system, and realizes a dual action mechanism by constructing a gradient coating structure: on the one hand, the uniform dispersion of nano-ATO particles can form an infrared reflection barrier, effectively blocking radiative heat transfer; on the other hand, the interfacial interaction between Nb2O5 and the Al2O3 matrix can significantly increase the lattice distortion energy, and inhibit the surface diffusion of aluminum ions at high temperatures through the pinning effect, thereby raising the α-phase transformation temperature to above 1200 °C, breaking through the thermal stability bottleneck of existing Al2O3 aerogel materials. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of a heat-insulating coating containing ATO-Nb2O5@Al2O3 aerogel with a temperature resistance of 1200 °C. By applying ATO-Nb2O5@Al2O3 aerogel to the heat-insulating coating, a heat-insulating coating containing ATO-Nb2O5@Al2O3 aerogel is prepared, which has good high-temperature resistance and heat-insulating properties. The Al-O bond energy is high, the crystal structure of Al2O3 aerogel is stable at high temperatures, Nb2O5 further inhibits the high-temperature crystal transformation of Al2O3, and maintains the pore structure of Al2O3 aerogel at high temperatures, that is, maintains the hindrance to heat conduction and heat convection; ATO enhances the reflection and radiation of Al2O3 aerogel to the heat source at high temperatures, that is, maintains the hindrance to thermal radiation. To sum up, this coating solves the problems of poor high-temperature resistance and heat-insulating properties of the coating, and has low production cost, and is a high-quality high-temperature heat-insulating coating.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] The present invention provides a preparation method of a heat-insulating coating containing ATO-Nb2O5@Al2O3 aerogel with a temperature resistance of 1200 °C, which is characterized in that, by mass, 100 parts of an organic-inorganic compound adhesive, 18-30 parts of ATO-Nb2O5@Al2O3 aerogel, 25-40 parts of hollow ceramic microspheres, 12-15 parts of ultra-fine mullite fibers, 2-4 parts of film-forming agent, 0.5-1.5 parts of leveling agent, 1.5-3 parts of quick-drying agent, 0.5-1.5 parts of thickening agent, and 0.5-1.5 parts of wetting agent are mixed, and dispersed and stirred at high speed for 1-2 hours, and deionized water is added to adjust the viscosity of the coating to obtain the heat-insulating coating.

[0009] The present invention also provides a preparation method of a heat-insulating coating containing ATO-Nb2O5@Al2O3 aerogel with a temperature resistance of 1200 °C, which includes using ATO-Nb2O5@Al2O3 aerogel, an organic-inorganic compound adhesive, hollow ceramic microspheres, ultra-fine mullite fibers, deionized water, a film-forming agent, a leveling agent, a quick-drying agent, a thickening agent, and a wetting agent, and is prepared through high-speed dispersion and stirring steps. It is characterized in that:

[0010] (1) The organic-inorganic compound adhesive includes alkaline silica sol, potassium silicate solution, modified silicone emulsion, and silane coupling agent. By mass fraction: 45-55 parts of alkaline silica sol, 25-35 parts of potassium silicate solution, 20-30 parts of modified silicone emulsion, and 2-5 parts of silane coupling agent. At 50 °C and under magnetic stirring, a diluent of silane coupling agent (15%) is slowly added to the modified silicone emulsion to form reaction solution 1, and the reaction is carried out for 30 min; the alkaline silica sol is slowly added to reaction solution 1 to form reaction solution 2, and the reaction is carried out for 30 min; then the potassium silicate solution is slowly added to reaction solution 2 to form reaction solution 3, and the reaction is carried out for 60 min; finally, reaction solution 3 is added to a hydrothermal reaction kettle, and continuous reaction is carried out at 110 °C and a pressure of 1.2 MPa for 3 h to obtain the organic-inorganic compound adhesive;

[0011] (2) The ATO-Nb2O5@Al2O3 aerogel of the present invention is prepared by the following method:

[0012] S1: Add AlCl3·6H2O to water, add nano-Nb2O5 powder and nano-ATO powder, ultrasonically disperse for 10 min, and add ethanol solvent (EtOH) to prepare aluminum precursor solution A;

[0013] S2: Add sodium carboxymethyl cellulose and chitosan to aluminum precursor solution A, and form a yellow suspension B with a certain viscosity after stirring for 3 hours;

[0014] S3: Slowly add propylene oxide dropwise to suspension B and stir for 10 min to obtain ATO-Nb2O5@Al2O3 sol C;

[0015] S4: At room temperature, let the above-mentioned ATO-Nb2O5@Al2O3 sol C stand for 2 h to gelate to obtain ATO-Nb2O5@Al2O3 gel. Immerse it in EtOH, and the liquid level of EtOH should be about 2 cm higher than the upper surface of the ATO-Nb2O5@Al2O3 gel, and replace it every 24 h. Repeat this step 3-4 times to fully displace the residual water and organic matter in the gel to obtain ATO-Nb2O5@Al2O3 wet gel;

[0016] S5: Place the ATO-Nb2O5@Al2O3 wet gel in the drying kettle of a multi-purpose supercritical test device, add an appropriate amount of absolute ethanol to completely submerge it, and perform CO2 supercritical drying to obtain the ATO-Nb2O5@Al2O3 aerogel.

[0017] (3) By mass fraction: 100 parts of the organic-inorganic compound adhesive, 18 - 32 parts of the ATO-Nb2O5@Al2O3 aerogel, 25 - 40 parts of hollow ceramic microspheres, 12 - 15 parts of ultrafine mullite fibers, 2 - 4 parts of film-forming agent, 0.5 - 1.5 parts of leveling agent, 1.5 - 3 parts of quick-drying agent, 0.5 - 1.5 parts of thickening agent, 0.5 - 1.5 parts of wetting agent. Add the above components in sequence, stir at high speed for 1 - 2 h, and adjust the coating viscosity by adding deionized water according to the doctor blade coating requirements to obtain the gray viscous ATO-Nb2O5@Al2O3 aerogel heat-resistant coating at 1200 °C.

[0018] The aluminum precursor solution A of the present invention, by mass fraction: 10 - 15 parts of AlCl3·6H2O, 20 - 25 parts of EtOH, 15 - 20 parts of water, 2 - 3 parts of Nb2O5, 1 - 3 parts of nano-ATO powder.

[0019] The suspension B of the present invention, by mass fraction: 0.1 - 0.2 parts of sodium carboxymethyl cellulose, 0.4 - 0.8 parts of chitosan.

[0020] The dropping rate of propylene oxide in the suspension B of the present invention is 1 - 2 mL / min, and by mass fraction: 3 - 5 parts of propylene oxide.

[0021] The CO2 supercritical drying pressure of the present invention is 11 - 14 MPa, the drying temperature is 30 - 45 °C, and the drying time is 3 - 5 h.

[0022] Compared with the existing preparation methods of high-temperature heat-resistant coatings, the present invention has the following advantages and beneficial effects:

[0023] I. Breakthrough of the high-temperature phase transition problem of Al2O3 aerogel

[0024] The Al2O3 aerogel undergoes a γ→α phase transition when the temperature exceeds 1000 °C, resulting in volume shrinkage, a sharp drop in porosity, and an increase in thermal conductivity. Traditional doping methods (such as Si, La, etc.) have problems of element migration and interface instability.

[0025] The present invention adopts the following solutions to solve:

[0026] ATO-Nb2O5 composite modification:

[0027] An infrared reflection barrier is formed by the uniform dispersion of nano ATO (antimony tin oxide) particles to block radiative heat transfer; meanwhile, a pinning effect is formed at the interface between Nb2O5 and the Al2O3 matrix to inhibit the high-temperature diffusion of aluminum ions and raise the α-phase transition temperature to above 1200 °C.

[0028] Gradient coating structure:

[0029] AlCl3, Nb2O5 and ATO powder are introduced into the precursor solution, the sol network is regulated by sodium carboxymethyl cellulose and chitosan, and the gelation rate is controlled by dropwise addition of propylene oxide (1 - 2 mL / min) to form a stable three-dimensional porous structure.

[0030] CO2 supercritical drying:

[0031] Drying is carried out for 3 - 5 hours under the conditions of 11 - 14 MPa and 35 - 45 °C to eliminate the surface tension, maintain the integrity of the aerogel nano-porous structure and avoid the collapse caused by traditional drying;

[0032] II. Optimization of the interfacial bonding of organic-inorganic adhesives

[0033] Technical problems:

[0034] Conventional adhesives are prone to degradation at high temperatures, and the interfacial bonding force between inorganic and organic is weak, resulting in cracking and peeling of the coating.

[0035] Compound system design:

[0036] Alkaline silica sol (45 - 55 parts) is used to provide an inorganic heat-resistant skeleton, potassium silicate solution (25 - 35 parts) enhances the bonding strength, modified silicone emulsion (20 - 30 parts) improves the flexibility, and silane coupling agent (2 - 5 parts) strengthens the interface through chemical bonding (Si-O-Si);

[0037] Hydrothermal reaction process:

[0038] Hydrothermal reaction is carried out at 110 °C and 1.2 MPa for 3 hours to promote the polycondensation reaction of silica sol and silicone emulsion to form a high-temperature resistant cross-linked network.

[0039] III. Synergistic effect design of heat insulation fillers

[0040] Technical problems:

[0041] A single filler is difficult to balance low thermal conductivity and mechanical strength, traditional hollow microspheres are prone to sedimentation, and fibers are unevenly dispersed.

[0042] The present invention solves the problem by adopting the following scheme:

[0043] Hollow ceramic microspheres (25 - 40 parts):

[0044] Low density (0.4 - 0.6 g / cm3 ) With low thermal conductivity (0.05 W / m·K), it blocks heat convection through a static air layer and reflects infrared radiation;

[0045] Ultrafine mullite fiber: Forms a three-dimensional network, enhancing the thermal shock resistance and mechanical strength of the coating, while reducing the risk of crack propagation;

[0046] Synergistic effect: The nano-pores (<50 nm) of the aerogel block gas heat conduction, the hollow microspheres (micrometer scale) inhibit thermal radiation, and the mullite fibers provide macroscopic support, forming a multi-scale thermal insulation system. Description of the Drawings

[0047] Figure 1 It is the SEM image of ATO-Nb2O5@Al2O3 aerogel;

[0048] Figure 2 It is the SEM image of hollow ceramic microspheres;

[0049] Figure 3 It is the thermal insulation coating with a temperature resistance of 1200 °C containing ATO-Nb2O5@Al2O3 aerogel;

[0050] Figure 4 It is the construction coating of the thermal insulation coating with a temperature resistance of 1200 °C containing ATO-Nb2O5@Al2O3 aerogel;

[0051] Figure 5 It is the infrared transmittance of the coating of the thermal insulation coating with a temperature resistance of 1200 °C containing ATO-Nb2O5@Al2O3 aerogel;

[0052] Figure 6 It is the thermal conductivity of Example 1;

[0053] Figure 7 It is the thermal conductivity of Example 2;

[0054] Figure 8 It is the thermal conductivity of Example 3;

[0055] Figure 9 It is the thermal conductivity of the comparative example;

[0056] Figure 10 It is the comparison table of examples. Detailed Embodiments

[0057] The present invention will be further described below in combination with the experimental scheme, research results and examples, but the scope of protection required by the present invention is not limited thereto.

[0058] Example 1

[0059] This embodiment provides a method for preparing a heat-insulating coating containing ATO-Nb2O5@Al2O3 aerogel with a temperature resistance of 1200 °C, which is prepared by using ATO-Nb2O5@Al2O3 aerogel, an organic-inorganic compound adhesive, hollow ceramic microspheres, ultrafine mullite fibers, deionized water, a film-forming agent, a leveling agent, a quick-drying agent, a thickening agent, and a wetting agent through high-speed dispersion and stirring steps, including the following steps:

[0060] (1) The organic-inorganic compound adhesive includes alkaline silica sol, potassium silicate solution, modified silicone emulsion, and silane coupling agent. By mass fraction: 48 parts of alkaline silica sol, 20 parts of potassium silicate solution, 30 parts of modified silicone emulsion, and 2 parts of silane coupling agent. At 50 °C and under magnetic stirring, a 15% silane coupling agent dilution solution is slowly added to the modified silicone emulsion to form reaction solution 1, and the reaction is carried out for 30 min; the alkaline silica sol is slowly added to reaction solution 1 to form reaction solution 2, and the reaction is carried out for 30 min; then the potassium silicate solution is slowly added to reaction solution 2 to form reaction solution 3, and the reaction is carried out for 60 min; finally, reaction solution 3 is added to a hydrothermal reaction kettle and continuously reacted at 110 °C and a pressure of 1.2 MPa for 3 h to obtain the organic-inorganic compound adhesive;

[0061] (2) The ATO-Nb2O5@Al2O3 aerogel is prepared by the following method:

[0062] S1: Add 10.5 parts of AlCl3·6H2O to 20 parts of water, add 2 parts of Nb2O5 and 1 part of nano-ATO powder, ultrasonically disperse for 10 min, and add 25 parts of ethanol solvent (EtOH) to form aluminum precursor solution A;

[0063] S2: Add 0.1 part of sodium carboxymethylcellulose and 0.4 part of chitosan to aluminum precursor solution A, and after stirring for 3 hours, a yellow suspension B with a certain viscosity is formed;

[0064] S3: Slowly add 5 parts of propylene oxide dropwise to suspension B at a uniform speed (1-2 mL / min) and stir for 10 min to obtain ATO-Nb2O5@Al2O3 sol C;

[0065] S4: At room temperature, let the above ATO-Nb2O5@Al2O3 sol C stand for 2 h to gelate to obtain ATO-Nb2O5@Al2O3 gel. Immerse it in EtOH, and the liquid level of EtOH should be about 2 cm higher than the upper surface of the ATO-Nb2O5@Al2O3 gel, and change it every 24 h. Repeat this step 3-4 times to fully displace the residual water and organic substances in the gel to obtain ATO-Nb2O5@Al2O3 wet gel;

[0066] S5: Place the ATO-Nb2O5@Al2O3 wet gel in the drying kettle of a multi-purpose supercritical test device, add an appropriate amount of absolute ethanol to completely submerge it, and perform CO2 supercritical drying at a CO2 supercritical drying pressure of 11 MPa, a drying temperature of 40 °C, and a drying time of 4 h to obtain ATO-Nb2O5@Al2O3 aerogel;

[0067] By mass fraction: 100 parts of organic-inorganic compound adhesive, 20 parts of ATO-Nb2O5@Al2O3 aerogel, 39 parts of hollow ceramic microspheres, 13 parts of ultrafine mullite fibers, 3 parts of film-forming agent, 0.5 part of leveling agent, 1.5 parts of quick-drying agent, 1.5 parts of thickening agent, 0.5 part of wetting agent. Add the above components in sequence, disperse and stir at high speed for 1 - 2 h, and add deionized water to adjust the coating viscosity according to the scraping requirements to obtain a gray viscous ATO-Nb2O5@Al2O3 aerogel heat-insulating coating with a temperature resistance of 1200 °C.

[0068] The thermal conductivity (25 °C) of the ATO-Nb2O5@Al2O3 aerogel heat-insulating coating with a temperature resistance of 1200 °C is 0.048 W / (m·K), there are no cracks after natural drying at room temperature, and the maximum temperature resistance is 1240 °C.

[0069] Example 2

[0070] This example provides a preparation method of a heat-insulating coating with a temperature resistance of 1200 °C containing ATO-Nb2O5@Al2O3 aerogel, which is prepared by using ATO-Nb2O5@Al2O3 aerogel, organic-inorganic compound adhesive, hollow ceramic microspheres, ultrafine mullite fibers, deionized water, film-forming agent, leveling agent, quick-drying agent, thickening agent, and wetting agent through high-speed dispersion and stirring steps, including the following steps:

[0071] (1) The organic-inorganic compound adhesive includes alkaline silica sol, potassium silicate solution, modified silicone emulsion, and silane coupling agent. By mass fraction: 47 parts of alkaline silica sol, 27 parts of potassium silicate solution, 21 parts of modified silicone emulsion, and 5 parts of silane coupling agent. At 50 °C and under magnetic stirring, slowly add the silane coupling agent diluent (15%) to the modified silicone emulsion to prepare reaction solution 1, and react for 30 min; slowly add the alkaline silica sol to reaction solution 1 to prepare reaction solution 2, and react for 30 min; then slowly add the potassium silicate solution to reaction solution 2 to prepare reaction solution 3, and react for 60 min; finally, add reaction solution 3 to the hydrothermal reaction kettle and continuously react at 110 °C and a pressure of 1.2 MPa for 3 h to obtain the organic-inorganic compound adhesive;

[0072] (2) The ATO-Nb2O5@Al2O3 aerogel is prepared by the following method:

[0073] S1: Add 12.5 parts of AlCl3·6H2O to 18 parts of water, add 3 parts of Nb2O5 and 2 parts of nano-ATO powder, ultrasonically disperse for 10 min, then add 22 parts of ethanol solvent (EtOH) to prepare aluminum precursor solution A.

[0074] S2: Add 0.1 part of sodium carboxymethyl cellulose and 0.5 part of chitosan to aluminum precursor solution A, and form a yellow suspension B with a certain viscosity after stirring for 3 hours.

[0075] S3: Dropwise add 4 parts of propylene oxide to suspension B at a constant speed (1 - 2 mL / min), and stir for 10 min to obtain ATO-Nb2O5@Al2O3 sol C.

[0076] S4: At room temperature, let the above ATO-Nb2O5@Al2O3 sol C stand for 2 h to gel and obtain ATO-Nb2O5@Al2O3 gel. Immerse it in EtOH, and the liquid level of EtOH should be about 2 cm higher than the upper surface of ATO-Nb2O5@Al2O3 gel, and change it every 24 h. Repeat this step 3 - 4 times to fully displace the residual water and organic substances in the gel to obtain ATO-Nb2O5@Al2O3 wet gel.

[0077] S5: Place the ATO-Nb2O5@Al2O3 wet gel in the drying kettle of a multi-purpose supercritical test device, add an appropriate amount of anhydrous ethanol to completely submerge it, and carry out CO2 supercritical drying. The CO2 supercritical drying pressure is 12 MPa, the drying temperature is 32 °C, and the drying time is 5 h to obtain ATO-Nb2O5@Al2O3 aerogel.

[0078] By mass fraction: 100 parts of organic-inorganic compound adhesive, 30 parts of ATO-Nb2O5@Al2O3 aerogel, 25 parts of hollow ceramic microspheres, 13 parts of ultrafine mullite fibers, 2 parts of film-forming agent, 1.5 parts of leveling agent, 1.5 parts of quick-drying agent, 0.5 part of thickening agent, 1.5 parts of wetting agent. Add the above components in sequence, disperse and stir at high speed for 1 - 2 h, and adjust the coating viscosity by adding deionized water according to the scraping requirements to obtain a gray viscous ATO-Nb2O5@Al2O3 aerogel heat-insulating coating with a temperature resistance of 1200 °C.

[0079] The thermal conductivity (25 °C) of the ATO-Nb2O5@Al2O3 aerogel heat-insulating coating with a temperature resistance of 1200 °C is 0.039 W / (m·K), it has no cracks after natural drying at room temperature, and the highest temperature resistance is 1225 °C.

[0080] Example 3

[0081] This embodiment provides a method for preparing a heat-insulating coating based on ATO-Nb2O5@Al2O3 aerogel with a temperature resistance of 1200 °C, which includes using ATO-Nb2O5@Al2O3 aerogel, organic-inorganic composite adhesives, hollow ceramic microspheres, ultra-fine mullite fibers, deionized water, film-forming agents, leveling agents, quick-drying agents, thickeners, and wetting agents, and is prepared through high-speed dispersion and stirring steps, including the following steps:

[0082] (1) The organic-inorganic composite adhesive includes alkaline silica sol, potassium silicate solution, modified silicone emulsion, and silane coupling agent. By mass fraction: 51 parts of alkaline silica sol, 22 parts of potassium silicate solution, 24 parts of modified silicone emulsion, and 3 parts of silane coupling agent. At 50 °C under magnetic stirring, a diluted solution of silane coupling agent (15%) is slowly added to the modified silicone emulsion to form reaction solution 1, and the reaction is carried out for 30 min; the alkaline silica sol is slowly added to reaction solution 1 to form reaction solution 2, and the reaction is carried out for 30 min; then the potassium silicate solution is slowly added to reaction solution 2 to form reaction solution 3, and the reaction is carried out for 60 min; finally, reaction solution 3 is added to a hydrothermal reaction kettle, and continuous reaction is carried out at 110 °C and a pressure of 1.2 MPa for 3 h to obtain the organic-inorganic composite adhesive;

[0083] (2) The ATO-Nb2O5@Al2O3 aerogel is prepared by the following method:

[0084] S1: Add 15 parts of AlCl3·6H2O to 18 parts of water, add 2 parts of Nb2O5 and 3 parts of nano-ATO powder, ultrasonically disperse for 10 min, and add 23 parts of ethanol solvent (EtOH) to form aluminum precursor solution A;

[0085] S2: Add 0.2 part of sodium carboxymethyl cellulose and 0.8 part of chitosan to aluminum precursor solution A, and after stirring for 3 hours, a yellow suspension B with a certain viscosity is formed;

[0086] S3: Slowly add 3.5 parts of propylene oxide to suspension B at a constant speed (1-2 mL / min) and stir for 10 min to obtain ATO-Nb2O5@Al2O3 sol C;

[0087] S4: At room temperature, let the above ATO-Nb2O5@Al2O3 sol C stand for 2 h to gel and obtain ATO-Nb2O5@Al2O3 gel. Immerse it in EtOH, and the liquid level of EtOH should be about 2 cm higher than the upper surface of the ATO-Nb2O5@Al2O3 gel, and replace it every 24 h. Repeat this step 3-4 times to fully displace the residual water and organic matter in the gel to obtain ATO-Nb2O5@Al2O3 wet gel;

[0088] S5: Place the ATO-Nb2O5@Al2O3 wet gel in the drying kettle of a multi-purpose supercritical test device, add an appropriate amount of anhydrous ethanol to completely submerge it, and conduct CO2 supercritical drying. The CO2 supercritical drying pressure is 14 MPa, the drying temperature is 45 °C, and the drying time is 3 h to obtain the ATO-Nb2O5@Al2O3 aerogel.

[0089] By mass fraction: 100 parts of organic-inorganic compound adhesive, 27 parts of ATO-Nb2O5@Al2O3 aerogel, 26.5 parts of hollow ceramic microspheres, 15 parts of ultrafine mullite fiber, 4 parts of film-forming agent, 1.0 part of leveling agent, 2.5 parts of quick-drying agent, 1.0 part of thickening agent, and 1.0 part of wetting agent. Add the above components in sequence, and disperse and stir at high speed for 1 - 2 h. Adjust the coating viscosity by adding deionized water according to the scraping requirements to obtain a gray viscous ATO-Nb2O5@Al2O3 aerogel heat-resistant coating with a temperature resistance of 1200 °C.

[0090] The thermal conductivity (25 °C) of this heat-resistant coating is 0.042 W / (m·K), it has no cracks during natural drying at room temperature, and the maximum temperature resistance is 1270 °C.

[0091] Example 4

[0092] Compared with Example 1, the preparation processes of the organic-inorganic compound adhesive and the ATO-Nb2O5@Al2O3 aerogel are the same. The difference is that the coating formula of Example 1 is replaced with the coating formula of Example 2.

[0093] The thermal conductivity (25 °C) of this heat-resistant coating is 0.043 W / (m·K), it has no cracks during natural drying at room temperature, and the maximum temperature resistance is 1240 °C.

[0094] Example 5

[0095] Compared with Example 3, the preparation processes of the organic-inorganic compound adhesive and the ATO-Nb2O5@Al2O3 aerogel are the same. The difference is that the coating formula of Example 3 is replaced with the coating formula of Example 2.

[0096] The thermal conductivity (25 °C) of this heat-resistant coating is 0.041 W / (m·K), it has no cracks during natural drying at room temperature, and the maximum temperature resistance is 1270 °C.

[0097] Example 6

[0098] Compared with Example 3, the preparation processes of the organic-inorganic compound adhesive and the ATO-Nb2O5@Al2O3 aerogel are the same. The difference is that the coating formula of Example 3 is replaced with the coating formula of Example 2, and the amount of the organic-inorganic compound adhesive in the coating formula is replaced with 70 parts.

[0099] The heat-insulating coating cracks during natural drying at room temperature, making it impossible to measure the thermal conductivity (25 °C) and the maximum heat resistance.

[0100] Comparative example

[0101] This comparative example provides a preparation method of a heat-insulating coating with a heat resistance of 1200 °C, which includes using an organic-inorganic composite adhesive, hollow ceramic microspheres, ultra-fine mullite fibers, deionized water, film-forming agent, leveling agent, quick-drying agent, thickening agent, wetting agent, and is prepared through high-speed dispersion and stirring steps, including the following steps:

[0102] (1) The organic-inorganic composite adhesive is the same as in Example 2;

[0103] (2) By mass fraction: 100 parts of organic-inorganic composite adhesive, 55 parts of hollow ceramic microspheres, 13 parts of ultra-fine mullite fibers, 2 parts of film-forming agent, 1.5 parts of leveling agent, 1.5 parts of quick-drying agent, 0.5 part of thickening agent, 1.5 parts of wetting agent. Add the above components in sequence, and disperse and stir at high speed for 1 - 2 h. Adjust the viscosity of the coating by adding deionized water according to the scraping requirements to obtain a grayish-white viscous heat-insulating coating.

[0104] The thermal conductivity (25 °C) of this heat-insulating coating is 0.060 W / (m·K), there are no cracks during natural drying at room temperature, and the maximum heat resistance is 1225 °C.

[0105] Because the present invention adopts the above technical solutions, it has the following characteristics:

[0106] (1) The present invention adds Al2O3 aerogel, which forms a composite heat-insulating coating porosity / pore size hierarchical design with the micron pores formed by the accumulation of hollow ceramic microspheres to construct a multi-stage heat conduction barrier, and realizes the obstruction of heat transfer (thermal convection) during the heat-insulating process from the perspective of molecular thermodynamics. Al2O3 has a high reflectivity and refractive index, and a large number of nano-skeletons form countless solid-gas interfaces, which reflect and scatter thermal radiation, etc.; doped with nano-ATO powder (nano-tin oxide and antimony oxide powder), using its high refractive index and selective reflection, as well as radiation performance (high infrared emissivity), to synergistically improve the reflection and radiation of ultraviolet and infrared rays with a wider frequency range, and realize the obstruction of heat transfer (thermal radiation) during the heat-insulating process from the optical perspective. Design and prepare the distorted lattice of Al2O3 aerogel and hollow ceramic microspheres, and the micro-nano high-porosity realizes phonon scattering and inhibits electron movement, and realizes the obstruction of heat transfer (thermal conduction) during the heat-insulating process from the perspective of solid physics.

[0107] The two most important performance indicators of heat-resistant and heat-insulating coatings are heat resistance and heat insulation performance. These two performances are contradictory. Generally, materials with good heat resistance have poor heat insulation performance; materials with good heat insulation performance have poor heat resistance. The coating needs to balance this contradiction during the design process. In high-temperature application scenarios, heat resistance is the basis of heat insulation performance. At high temperatures, aerogels such as silica that are not heat-resistant will have their structures collapsed and crystal form transformed, and their heat insulation performance cannot be maintained. This is the pain point of commercially available common aerogel coatings. Commercially available heat-resistant and heat-insulating coatings without aerogels are difficult to form nano-scale pores, and their heat insulation effects in terms of photothermal regulation (radiation), pore confinement (convection), and lattice dissipation (conduction) are far from those of aerogel heat-resistant and heat-insulating coatings.

[0108] In summary, ATO-Nb2O5@Al2O3 aerogel is prepared by modulation to have excellent optical properties, nano-scale pores and high porosity, and ultra-low solid-phase thermal conductivity. Based on high-temperature thermal stability, a heat-insulating coating with "photothermal regulation (radiation) + pore confinement (convection) + lattice dissipation (conduction)" multi-dimensional synergistic heat insulation is formed, realizing the deep decoupling and system integration of cross-scale heat transfer, and thus comprehensively achieving high-performance heat insulation.

[0109] (2) The present invention uses a compounded organic-inorganic adhesive instead of simple mixing. The silane coupling agent is fully hydrolyzed, and the hydrolysis products are silanol groups and amino groups, which react and bond with the hydroxyl groups and carboxyl groups of basic silica sol, potassium silicate, and modified silicone emulsion, playing a coupling and anchoring role to form a hybrid macromolecule of the compounded organic-inorganic adhesive. This not only enhances the heat resistance of the organic adhesive but also enhances the softness of the inorganic adhesive. The adhesive binds more tightly to the substrate, and the stability of the hybrid macromolecule is enhanced at high temperatures, thereby enhancing the bonding force, adhesion, and heat resistance of the adhesive.

[0110] (3) Using ATO-Nb2O5@Al2O3 aerogel to prepare heat-insulating coatings is suitable for large-scale mass production, has simple construction conditions, and excellent heat insulation performance.

Claims

1. A preparation method of an ATO-Nb2O5@Al2O3 aerogel heat-insulating coating resistant to 1200 °C, characterized in that, By mass parts, 100 parts of an organic-inorganic compound adhesive, 18 - 30 parts of ATO-Nb2O5@Al2O3 aerogel, 25 - 40 parts of hollow ceramic microspheres, 12 - 15 parts of ultrafine mullite fibers, 2 - 4 parts of film-forming agent, 0.5 - 1.5 parts of leveling agent, 1.5 - 3 parts of quick-drying agent, 0.5 - 1.5 parts of thickening agent, and 0.5 - 1.5 parts of wetting agent are mixed and stirred at high speed for 1 - 2 hours, and deionized water is added to adjust the viscosity of the coating to obtain the heat-insulating coating.

2. The method according to claim 1, wherein The organic-inorganic compound adhesive: By mass parts, it includes 45 - 55 parts of alkaline silica sol, 20 - 30 parts of potassium silicate solution, 20 - 30 parts of modified silicone emulsion, and 2 - 5 parts of silane coupling agent.

3. The method according to claim 2, wherein The steps for preparing the organic-inorganic compound adhesive include: Step 1.1: Add a silane coupling agent dilution solution with a mass percentage concentration of 15% to the modified silicone emulsion, and stir magnetically at 50°C for 30 minutes to obtain reaction solution 1; Step 1.2: Add the alkaline silica sol to reaction solution 1 and continue reacting for 30 minutes to obtain reaction solution 2; Step 1.3: Add the potassium silicate solution to reaction solution 2 and continue reacting for 60 minutes to obtain reaction solution 3; Step 1.4: Place reaction solution 3 in a hydrothermal reaction kettle and react at 110°C and 1.2 MPa for 3 hours to obtain the organic-inorganic compound adhesive.

4. The method according to claim 1, wherein The preparation of ATO-Nb2O5@Al2O3 aerogel includes the following steps: Step 2.1: Disperse 10 - 15 parts of AlCl3·6H2O, 2 - 3 parts of Nb2O5, and 1 - 3 parts of nano-ATO powder in a mixed solvent of 15 - 20 parts of water and 20 - 25 parts of ethanol, and obtain aluminum precursor solution A after ultrasonic dispersion; Step 2.2: Add 0.1 - 0.2 parts of sodium carboxymethylcellulose and 0.4 - 0.8 parts of chitosan to aluminum precursor solution A in sequence and stir for 3 hours to form suspension B; Step 2.3: Dropwise add 3 - 5 parts of propylene oxide to suspension B and stir for 10 minutes to obtain sol C; Step 2.4: After standing and gelling sol C for 2 hours, soak and displace it with ethanol 3 - 4 times, 24 hours each time, to obtain a wet gel; Step 2.5: Subject the wet gel to CO2 supercritical drying under the conditions of 11 - 14 MPa, 30 - 45°C, and 3 - 5 hours to obtain ATO-Nb2O5@Al2O3 aerogel.

5. The method according to claim 3, wherein The dropping rate of propylene oxide in suspension B is 1 - 2 mL / min.

6. The method according to claim 1, characterized in that, The ATO-Nb2O5@Al2O3 aerogel is 28 parts.

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