Hollow ceramic microbead thermal insulation coating containing liquid phase deposition TiO2 and preparation method of hollow ceramic microbead thermal insulation coating

Abstract

The invention relates to the technical field of coatings, and particularly discloses a hollow ceramic microbead heat-insulating coating containing liquid-phase deposited TiO2 and a preparation method of the hollow ceramic microbead heat-insulating coating. The coating is prepared from the following components in parts by weight: 100 parts of organic-inorganic compound adhesive, 25 to 35 parts of hollow ceramic microbeads of liquid-phase deposited TiO2, 20 to 35 parts of In2O3 coated Al2O3 aerogel and the like, wherein the adhesive is prepared from 30 to 45 parts of alkaline silica sol, 25 to 40 parts of lithium silicate solution, 20 to 30 parts of modified organic silicon emulsion and 2 to 5 parts of silane coupling agent. During preparation, the adhesive is prepared through a three-step liquid phase reaction, a (NH4) 2TiF6-H3BO3 system is adopted for oscillation at 30-50 DEG C for 12-24 h to achieve TiO2 deposition on the surfaces of the hollow ceramic microbeads, and a coating layer is formed after calcination at 400-550 DEG C. The coating combines the infrared reflectivity of TiO2, the heat insulation property of hollow microspheres and the nano-pore structure of Al2O3 aerogel, the heat conductivity coefficient at 25 DEG C reaches 0.032-0.037 W / (m.K), the temperature resistance reaches 900 DEG C, and no coating cracks exist. By controlling the TiO2 deposition thickness and the aerogel doping ratio, the synergistic interaction of heat reflection and heat insulation is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to a heat-insulating coating of hollow ceramic microspheres containing liquid-phase deposited TiO2 and a preparation method thereof. Background Art

[0002] With the development of industry and the improvement of economy, the requirements for energy conservation, emission reduction, low-carbon environmental protection are increasing. New thermal insulation materials in the industrial and construction fields emerge in an endless stream, and heat-insulating coatings are one of the representative functional materials. Heat-insulating coatings are widely used because of their low thermal conductivity and excellent mechanical properties. Common thermal insulation coatings can be divided into three categories: organic, inorganic, and organic-inorganic composites. Among them, the thermal insulation materials mainly used in industrial furnaces attach great importance to heat insulation performance and high temperature resistance (1000°C).

[0003] As is well known, the heat conduction rate in air is very low, and the thermal conductivity of air is 0.026 W / (m·K). Aerogel, as a high-nano porous material with a porosity exceeding 90%, usually has structural characteristics such as a high specific surface area, a large pore volume, a low density, and a high porosity, and at the same time has excellent heat insulation performance. 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] Titanium dioxide (TiO2) has a high reflectivity to infrared light and at the same time has high-temperature thermal stability, and can be used in temperature-resistant heat-insulating materials. However, the thermal conductivity of TiO2 itself is high, and if the addition amount is too large, it will cause the thermal conductivity of the temperature-resistant heat-insulating material to rise, which is not worth the loss. Hollow ceramic microspheres have a hollow chamber, which plays a role of heat preservation like a "thermos bottle" at high temperatures and hinders heat conduction. However, hollow ceramic microspheres cannot effectively reflect infrared light and cannot hinder thermal radiation. By liquid-phase deposition, TiO2 is deposited on the surface of hollow ceramic microspheres to form a thin coating layer, so as to achieve a larger area distribution of TiO2 without increasing the amount of TiO2 used, and endow the hollow ceramic microspheres with the ability to hinder thermal radiation.

[0005] Aluminum oxide (Al2O3) aerogel exhibits enhanced thermal stability, which is better than other oxide aerogels, such as zirconia and silica (SiO2). 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 a catalyst. In2O3@Al2O3 aerogel can form an efficient reflection of infrared waves and effectively inhibit the radiative propagation of heat, further improving the heat insulation performance.

[0006] Therefore, by combining the hollow ceramic microspheres with liquid-phase deposited TiO2, the ultra-low thermal conductivity and strong thermal stability of In2O3@Al2O3 aerogel, the heat insulation and high-temperature resistance of the coating can be greatly improved. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method of a heat-insulating coating containing hollow ceramic microspheres with liquid-phase deposited TiO2. By applying the hollow ceramic microspheres with liquid-phase deposited TiO2 and In2O3@Al2O3 aerogel to the heat-insulating coating, a heat-insulating coating containing hollow ceramic microspheres with liquid-phase deposited TiO2 is prepared, which has good high-temperature resistance and heat-insulating performance, solves the problem of poor high-temperature resistance and heat-insulating performance of the coating, and has low production cost. It is a high-quality high-temperature heat-insulating coating.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a heat-insulating coating containing hollow ceramic microspheres with liquid-phase deposited TiO2, which includes, by mass fraction:

[0010] 100 parts of organic-inorganic compound adhesive, 25 - 35 parts of hollow ceramic microspheres with liquid-phase deposited TiO2, 25 - 32 parts of In2O3@Al2O3 aerogel, 10 - 15 parts of high-aluminum ceramic fiber, 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.

[0011] In the above scheme, the organic-inorganic compound adhesive includes, by mass fraction: 30 - 45 parts of alkaline silica sol, 25 - 40 parts of lithium silicate solution, 20 - 30 parts of modified silicone emulsion, 2 - 5 parts of silane coupling agent.

[0012] The present invention also provides a preparation method of a heat-insulating coating containing hollow ceramic microspheres with liquid-phase deposited TiO2, which includes using hollow ceramic microspheres with liquid-phase deposited TiO2, In2O3@Al2O3 aerogel, organic-inorganic compound adhesive, high-aluminum ceramic fiber, deionized water, film-forming agent, leveling agent, quick-drying agent, thickening agent, wetting agent, and preparing through high-speed dispersion and stirring steps:

[0013] (1) The organic-inorganic compound adhesive comprises alkaline silica sol, lithium silicate solution, modified silicone emulsion, and silane coupling agent. By mass fraction: 30 - 45 parts of alkaline silica sol, 25 - 40 parts of lithium silicate solution, 20 - 30 parts of modified silicone emulsion, and 2 - 5 parts of silane coupling agent. At 50°C under magnetic stirring, a silane coupling agent dilution (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 lithium 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 115°C and a pressure of 1.3 MPa for 2 h to obtain the organic-inorganic compound adhesive. The organic-inorganic compound adhesive affects the anti-cracking performance and the highest heat resistance of the coating. According to product requirements, the coating dries naturally without cracking, and the highest heat resistance is ≥900°C;

[0014] (2) The hollow ceramic microspheres with liquid-phase deposited TiO₂ are prepared by the following method:

[0015] S1: Wash the hollow ceramic microspheres with an aqueous hydrochloric acid solution with a pH of 1 - 3, then wash the hollow ceramic microspheres with pure water, and perform vacuum drying at a drying temperature of 60 - 80°C and a vacuum degree of 133 Pa;

[0016] S2: Put the dried hollow ceramic microspheres into a PTFE container, and successively add an aqueous solution of (NH₄)₂TiF₆ and an aqueous solution of H₃BO₃ to obtain mixture A;

[0017] S3: Continuously carry out a constant-temperature oscillation reaction on mixture A in a constant-temperature oscillation water bath to deposit TiO₂ on the surface of the hollow ceramic microspheres;

[0018] S4: Wash the hollow ceramic microspheres with liquid-phase deposition with pure water, put them into a tubular furnace, heat them to the set temperature at a rate of 10 K / min, and perform constant-temperature drying to obtain the hollow ceramic microspheres with liquid-phase deposited TiO₂.

[0019] In the present invention, the pH value of the aqueous hydrochloric acid solution for washing the hollow ceramic microspheres is 1 - 3.

[0020] In the present invention, mixture A, by mass fraction: 50 - 100 parts of hollow ceramic microspheres, 10 - 15 parts of (NH₄)₂TiF₆, and 30 - 50 parts of H₃BO₃.

[0021] In the present invention, the temperature for constant-temperature oscillation heating is 30 - 50°C, and the oscillation time is 12 - 24 h.

[0022] In the present invention, the set temperature of the tubular furnace is 400 - 550°C, and the constant-temperature drying time is 2 - 3 h.

[0023] Compared with the preparation methods of existing high-temperature resistant thermal insulation coatings, the present invention has the following advantages and beneficial effects:

[0024] (1) The present invention adds hollow ceramic microspheres with liquid-phase deposited TiO2 and Al2O3 aerogel doped with nano-In2O3 powder. By integrating the optical performance advantages of TiO2, Al2O3, and In2O3 powders, it can reflect infrared wavelengths with obvious thermal effects back; it has the high porosity and temperature resistance of nano-powders and aerogels. The nano-pores are smaller than the mean free path of air molecules, achieving high-performance thermal insulation; compared with SiO2 aerogel, Al2O3 aerogel can withstand high temperatures and still maintain the nano-porous structure of the aerogel at high temperatures without losing its thermal insulation performance.

[0025] (2) The present invention uses a compound organic-inorganic adhesive. The silane coupling agent is fully hydrolyzed, and the hydrolysis product is silanol, which plays a role in coupling and anchoring alkaline silica sol, lithium silicate, and modified silicone emulsion. At high temperatures, multi-component silanols cross-polycondense to form a strengthened network structure, enhancing the bonding force, adhesion, and temperature resistance of the adhesive.

[0026] (3) Using hollow ceramic microspheres with liquid-phase deposited TiO2 and In2O3@Al2O3 aerogel to prepare thermal insulation coatings is suitable for large-scale production, has simple construction conditions, and excellent thermal insulation performance.

[0027] (4) The synergistic thermal barrier effect of hollow ceramic microspheres and TiO2 coating layer

[0028] Traditional hollow ceramic microspheres only reduce heat conduction through the hollow chamber but lack infrared reflection ability; while TiO2 has a high infrared reflectivity, but excessive addition will increase the overall thermal conductivity due to its high thermal conductivity.

[0029] The present invention innovatively coats TiO2 on the hollow microspheres: through a liquid-phase deposition process (such as the hydrolysis of (NH4)2TiF6 to generate a TiO2 film), a uniform thin layer (thickness ≤ 0.5 μm) is formed on the surface of the microspheres. Without increasing the overall TiO2 dosage, it gives high reflectivity to infrared waves and solves the defect that traditional hollow ceramic microspheres cannot inhibit thermal radiation.

[0030] (5) The composite of In2O3@Al2O3 aerogel: Al2O3 aerogel provides ultra-low thermal conductivity and high-temperature stability (the structure remains stable at 1000 °C), while doping In2O3 nanoparticles (such as introduced by the sol-gel method) can further reflect infrared radiation, forming a dual thermal insulation mechanism of "aerogel barrier + metal oxide reflection".

[0031] Synergistic effect: The thermal conductivity of the coating at 1000 °C is reduced by about 50% compared with the traditional SiO2 aerogel system (the thermal conductivity of Examples 1-3 is 0.032-0.037 W / (m·K), while that of the comparative example reaches 0.043 W / (m·K)).

[0032] (6) Optimization of component ratio and balance of construction performance

[0033] Solution to technical problems: Although a high filler content improves the heat insulation performance, it easily leads to an increase in the viscosity of the coating and difficulty in coating.

[0034] Ratio of liquid-phase deposited microspheres to aerogel: The synergistic ratio of hollow ceramic microspheres to In2O3@Al2O3 aerogel ensures both the porosity of the coating (>70%) and avoids a decrease in mechanical strength caused by excessive aerogel. Description of the drawings

[0035] Figure 1 is the SEM image of the hollow ceramic microsphere heat-insulating coating containing liquid-phase deposited TiO2;

[0036] Figure 2 is the SEM image of In2O3@A12O3 aerogel;

[0037] Figure 3 is the coating of the heat-insulating coating containing In2O3@Al2O3 aerogel with a temperature resistance of 1000 °C;

[0038] Figure 4 is the thermal conductivity of Example 1;

[0039] Figure 5 is the thermal conductivity of Example 2;

[0040] Figure 6 is the thermal conductivity of Example 3;

[0041] Figure 7 is the thermal conductivity of the comparative example. Detailed implementation manners

[0042] The present invention will be further described below in conjunction with the test scheme, research results and examples, but the scope claimed by the present invention is not limited thereto.

[0043] Example 1

[0044] This example provides a preparation method of a hollow ceramic microsphere heat-insulating coating containing liquid-phase deposited TiO2, which includes using hollow ceramic microspheres with liquid-phase deposited TiO2, In2O3@Al2O3 aerogel, organic-inorganic compound adhesives, high-aluminum ceramic fibers, deionized water, film-forming agents, leveling agents, quick-drying agents, thickening agents, wetting agents, and is prepared through high-speed dispersion and stirring steps, including the following steps:

[0045] (1) The organic-inorganic compound adhesive contains alkaline silica sol, lithium silicate solution, modified silicone emulsion, and silane coupling agent. By mass fraction: 32 parts of alkaline silica sol, 36 parts of lithium silicate solution, 30 parts of modified silicone emulsion, and 2 parts of silane coupling agent. At 50 °C under magnetic stirring, the silane coupling agent dilution (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 lithium 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 115 °C and a pressure of 1.3 MPa for 2 h to obtain the organic-inorganic compound adhesive;

[0046] (2) The hollow ceramic microspheres with liquid-phase deposited TiO2 are prepared by the following method:

[0047] S1: Wash the hollow ceramic microspheres with an aqueous hydrochloric acid solution with a pH of 1.1, and then wash the hollow ceramic microspheres with pure water, and perform vacuum drying at a drying temperature of 65 °C and a vacuum degree of 133 Pa;

[0048] S2: Put the dried hollow ceramic microspheres into a PTFE container, and sequentially add an aqueous solution of (NH4)2TiF6 and an aqueous solution of H3BO3. 60 parts of hollow ceramic microspheres, 10 parts of (NH4)2TiF6, and 35 parts of H3BO3 to obtain mixture A;

[0049] S3: Continuously carry out a constant-temperature oscillation reaction on mixture A in a constant-temperature oscillation water bath. The constant-temperature oscillation heating temperature is 35 °C, and the oscillation time is 16 h to carry out liquid-phase deposition of TiO2 on the surface of the hollow ceramic microspheres;

[0050] S4: Wash the hollow ceramic microspheres with liquid-phase deposition with pure water, put them into a tube furnace, heat them to 440 °C at a rate of 10 K / min, and carry out constant-temperature drying for 2 h to obtain the hollow ceramic microspheres with liquid-phase deposited TiO2.

[0051] By mass fraction: 100 parts of organic-inorganic compound adhesive, 27.5 parts of hollow ceramic microspheres with liquid-phase deposited TiO2, 26 parts of In2O3@Al2O3 aerogel, 13 parts of high-aluminum ceramic fiber, 3 parts of film-forming agent, 1.5 parts of leveling agent, 1.5 parts of quick-drying agent, 1.5 parts of thickening agent, and 0.5 part of wetting agent. Add the above components in sequence, and carry out high-speed dispersion and stirring for 1 - 2 h. Adjust the coating viscosity by adding deionized water according to the scraping requirements to obtain a gray viscous heat-insulating coating.

[0052] The thermal conductivity (25 °C) of this heat-insulating coating is 0.037 W / (m·K), there are no cracks during normal-temperature natural drying, and the maximum heat resistance is 920 °C.

[0053] Example 2

[0054] This example provides a preparation method of a heat-insulating coating for hollow ceramic microspheres containing liquid-phase deposited TiO₂, which includes using hollow ceramic microspheres with liquid-phase deposited TiO₂, In₂O₃@Al₂O₃ aerogel, organic-inorganic compound adhesives, high-aluminum ceramic 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:

[0055] (1) The organic-inorganic compound adhesive includes alkaline silica sol, lithium silicate solution, modified silicone emulsion, and silane coupling agent. By mass fraction: 35 parts of alkaline silica sol, 40 parts of lithium silicate solution, 22 parts of modified silicone emulsion, and 3 parts of silane coupling agent. At 50 °C and under magnetic stirring, the silane coupling agent dilution (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 lithium 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 115 °C and a pressure of 1.3 MPa for 2 h to obtain the organic-inorganic compound adhesive;

[0056] (2) The hollow ceramic microspheres with liquid-phase deposited TiO₂ are prepared by the following method:

[0057] S1: Wash the hollow ceramic microspheres with an aqueous hydrochloric acid solution with a pH of 1.6, then wash the hollow ceramic microspheres with pure water, and perform vacuum drying at a drying temperature of 70 °C and a vacuum degree of 133 Pa;

[0058] S2: Put the dried hollow ceramic microspheres into a PTFE container, and sequentially add an aqueous solution of (NH₄)₂TiF₆ and an aqueous solution of H₃BO₃, 72 parts of hollow ceramic microspheres, 11 parts of (NH₄)₂TiF₆, and 44 parts of H₃BO₃ to obtain mixture A;

[0059] S3: Continuously carry out constant-temperature oscillation reaction of mixture A in a constant-temperature oscillation water bath, with a constant-temperature oscillation heating temperature of 40 °C and an oscillation time of 22 h to deposit TiO₂ on the surface of the hollow ceramic microspheres in a liquid phase;

[0060] S4: Wash the hollow ceramic microspheres with liquid-phase deposition with pure water, put them into a tubular furnace, heat up to 480 °C at a rate of 10 K / min, and carry out constant-temperature drying for 2.5 h to obtain the hollow ceramic microspheres with liquid-phase deposited TiO₂.

[0061] By mass fraction: 100 parts of organic-inorganic compound adhesive, 34 parts of hollow ceramic microspheres with liquid-phase deposited TiO2, 31 parts of In2O3@Al2O3 aerogel, 10 parts of high-aluminum ceramic fiber, 2 parts of film-forming agent, 0.5 part of leveling agent, 2.5 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 doctor blade coating requirement to obtain a gray viscous heat-insulating coating.

[0062] The thermal conductivity (25 °C) of this heat-insulating coating is 0.032 W / (m·K), it has no cracks after natural drying at room temperature, and the maximum heat resistance is 975 °C.

[0063] Example 3

[0064] This example provides a preparation method of a heat-insulating coating containing hollow ceramic microspheres with liquid-phase deposited TiO2, which includes using hollow ceramic microspheres with liquid-phase deposited TiO2, In2O3@Al2O3 aerogel, organic-inorganic compound adhesive, high-aluminum ceramic fiber, 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:

[0065] (1) The organic-inorganic compound adhesive includes alkaline silica sol, lithium silicate solution, modified silicone emulsion, and silane coupling agent. By mass fraction: 41 parts of alkaline silica sol, 26 parts of lithium silicate solution, 28 parts of modified silicone emulsion, 5 parts of silane coupling agent. Under 50 °C and magnetic stirring, slowly add the silane coupling agent dilution solution (15%) to the modified silicone emulsion to form reaction solution 1, and react for 30 min; slowly add the alkaline silica sol to reaction solution 1 to form reaction solution 2, and react for 30 min; then slowly add the lithium silicate solution to reaction solution 2 to form reaction solution 3, and react for 60 min; finally, add reaction solution 3 to the hydrothermal reaction kettle and continuously react at 115 °C and a pressure of 1.3 MPa for 2 h to obtain the organic-inorganic compound adhesive;

[0066] (2) The hollow ceramic microspheres with liquid-phase deposited TiO2 are prepared by the following method:

[0067] S1: Wash the hollow ceramic microspheres with hydrochloric acid aqueous solution with pH = 2.4, then wash the hollow ceramic microspheres with pure water, and perform vacuum drying at a drying temperature of 72 °C and a vacuum degree of 133 Pa;

[0068] S2: Put the dried hollow ceramic microspheres into a PTFE container, and sequentially add (NH4)2TiF6 aqueous solution and H3BO3 aqueous solution, 90 parts of hollow ceramic microspheres, 12 parts of (NH4)2TiF6, and 45 parts of H3BO3 to obtain mixture A;

[0069] S3: Continuously carry out a constant-temperature oscillation reaction on mixture A in a constant-temperature oscillation water bath at a constant temperature of 45°C and an oscillation time of 24 h to perform liquid-phase deposition of TiO2 on the surface of hollow ceramic microspheres;

[0070] S4: Wash the hollow ceramic microspheres with liquid-phase deposition with pure water, put them into a tube furnace, heat them to 520°C at a rate of 10 K / min, and dry them at a constant temperature for 3 h to obtain hollow ceramic microspheres with liquid-phase deposited TiO2.

[0071] By mass fraction: 100 parts of organic-inorganic compound adhesive, 30 parts of hollow ceramic microspheres with liquid-phase deposited TiO2, 29 parts of In2O3@Al2O3 aerogel, 14 parts of high-alumina ceramic fiber, 4 parts of film-forming agent, 1.0 part of leveling agent, 1.5 parts of quick-drying agent, 1.0 part of thickening agent, 1.0 part 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 doctor blade coating requirements to obtain a gray viscous heat-insulating coating.

[0072] The thermal conductivity (25°C) of this heat-insulating coating is 0.035 W / (m·K), it has no cracks after natural drying at room temperature, and the maximum heat resistance is 960°C.

[0073] Example 4

[0074] Compared with Example 1, the preparation processes of the organic-inorganic compound adhesive and the liquid-phase deposited TiO2 are the same. The difference lies in: replacing the coating formula of Example 1 with the coating formula of Example 2.

[0075] The thermal conductivity (25°C) of this heat-insulating coating is 0.035 W / (m·K), it has no cracks after natural drying at room temperature, and the maximum heat resistance is 920°C.

[0076] Example 5

[0077] Compared with Example 3, the preparation processes of the organic-inorganic compound adhesive and the liquid-phase deposited TiO2 are the same. The difference lies in: replacing the coating formula of Example 3 with the coating formula of Example 2.

[0078] The thermal conductivity (25°C) of this heat-insulating coating is 0.033 W / (m·K), it has no cracks after natural drying at room temperature, and the maximum heat resistance is 960°C.

[0079] Example 6

[0080] Compared with Example 3, the preparation processes of the organic-inorganic compound adhesive and the liquid-phase deposited TiO2 are the same. The difference lies in: replacing the coating formula of Example 3 with the coating formula of Example 2, and changing the dosage of the organic-inorganic compound adhesive in the coating formula to 65 parts.

[0081] 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.

[0082] Comparative Example

[0083] This comparative example provides a method for preparing a heat-insulating coating with a heat resistance of 1000°C, which includes using hollow ceramic microspheres, In2O3@Al2O3 aerogel, organic-inorganic compound adhesives, high-aluminum ceramic 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:

[0084] (1) The organic-inorganic compound adhesive is the same as in Example 1;

[0085] (2) By mass fraction: 100 parts of organic-inorganic compound adhesive, 27.5 parts of ordinary hollow ceramic microspheres, 26 parts of In2O3@Al2O3 aerogel, 13 parts of high-aluminum ceramic fibers, 3 parts of film-forming agent, 1.5 parts of leveling agent, 1.5 parts of quick-drying agent, 1.5 parts of thickener, and 0.5 part 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 grayish-white viscous heat-insulating coating.

[0086] The thermal conductivity (25°C) of this heat-insulating coating is 0.043 W / (m·K), there are no cracks during natural drying at room temperature, and the maximum heat resistance is 920°C. Comparative table of examples:

[0087]

[0088]

Claims

1. A heat-insulating coating for hollow ceramic microspheres containing liquid-phase deposited TiO2, characterized in that, Comprising by mass fraction: 100 parts of organic-inorganic compound adhesive, 25 - 35 parts of hollow ceramic microspheres with liquid-phase deposited TiO₂, 25 - 32 parts of In₂O₃@Al₂O₃ aerogel, 10 - 15 parts of high-aluminum ceramic fiber, 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.

2. The heat-insulating coating for hollow ceramic microspheres containing liquid-phase deposited TiO2 according to claim 1, wherein The organic-inorganic compound adhesive comprises by mass fraction: 30 - 45 parts of alkaline silica sol, 25 - 40 parts of lithium silicate solution, 20 - 30 parts of modified silicone emulsion, 2 - 5 parts of silane coupling agent.

3. A preparation method of a heat-insulating coating for hollow ceramic microspheres containing liquid-phase deposited TiO2, characterized in that, By mass fraction: Add 100 parts of organic-inorganic compound adhesive, 25 - 35 parts of hollow ceramic microspheres with liquid-phase deposited TiO₂, 25 - 32 parts of In₂O₃@Al₂O₃ aerogel, 10 - 15 parts of high-aluminum ceramic fiber, 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 in sequence, and disperse and stir at high speed for 1 - 2 h. Add deionized water to adjust the coating viscosity according to the scraping requirements, and then a gray viscous heat-insulating coating containing hollow ceramic microspheres with liquid-phase deposited TiO₂ is obtained.

4. The preparation method according to claim 3, wherein The organic-inorganic compound adhesive by mass fraction includes: 30 - 45 parts of alkaline silica sol, 25 - 40 parts of lithium silicate solution, 20 - 30 parts of modified silicone emulsion, 2 - 5 parts of silane coupling agent; At 50 °C under magnetic stirring, slowly add the silane coupling agent diluent (15%) into the modified silicone emulsion to prepare reaction solution 1, and react for 30 min; Slowly add the alkaline silica sol into reaction solution 1 to prepare reaction solution 2, and react for 30 min; Then slowly add the lithium silicate solution into reaction solution 2 to prepare reaction solution 3, and react for 60 min; Finally, add reaction solution 3 into a hydrothermal reaction kettle, and continuously react at 115 °C and a pressure of 1.3 MPa for 2 h to obtain the organic-inorganic compound adhesive.

5. The preparation method according to claim 4, characterized in that, The hollow ceramic microspheres with liquid-phase deposited TiO₂ are prepared by the following method: S1: Wash the hollow ceramic microspheres with an aqueous hydrochloric acid solution with pH = 1 - 3, then wash the hollow ceramic microspheres with pure water, and perform vacuum drying at a drying temperature of 60 - 80 °C and a vacuum degree of 133 Pa; S2: Put the dried hollow ceramic microspheres into a PTFE container, and sequentially add an aqueous solution of (NH₄)₂TiF₆ and an aqueous solution of H₃BO₃ to obtain mixture A; S3: Continuously carry out constant-temperature oscillating reaction on mixture A in a constant-temperature oscillating water bath to deposit TiO₂ on the surface of the hollow ceramic microspheres; S4: Wash the hollow ceramic microspheres with liquid-phase deposition with pure water, put them into a tube furnace, heat up to the set temperature at a rate of 10 K / min, and perform constant-temperature drying to obtain the hollow ceramic microspheres with liquid-phase deposited TiO₂.

6. The preparation method according to claim 5, characterized in that, Mixture A by mass fraction: 50 - 100 parts of hollow ceramic microspheres, 10 - 15 parts of (NH₄)₂TiF₆, 30 - 50 parts of H₃BO₃.

7. The preparation method according to claim 5, characterized in that, The temperature of constant-temperature oscillating heating is 30 - 50 °C, and the oscillating time is 12 - 24 h.

8. The preparation method according to claim 5, characterized in that, The set temperature of the tube furnace is 400 - 550 °C, and the constant temperature drying time is 2 - 3 h.

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