Composite heat-insulating ball and preparation method and application thereof

Abstract

The present application relates to a kind of composite heat insulation ball and its preparation method and application.It includes: ball core, it is porous spherical structure;The material of the ball core is alumina;Insulating layer, it is set on the outer surface of the ball core;The insulating layer can prevent liquid and / or solid seep into the ball core surface;Coating layer, it is bonded in the outer surface of the insulating layer by adhesive A;The material of the coating layer includes alumina and aerogel;The mass ratio of the aerogel and alumina is 1:15~25;And, reflective layer, it is bonded in the outer surface of the coating layer by adhesive B, the material of the reflective layer is the material with the performance of greater than 0.3~0.6 and emissivity is 0.7~0.9 performance of middle far infrared light reflectivity;The thickness of the reflective layer is 80~120 μm.The technical problem to be solved is how to provide a kind of composite heat insulation ball, so that the heat insulation repair molding material made can effectively block the heat transfer process mainly by thermal radiation at 800~1500 ℃ high temperature.

Description

Technical Field

[0001] This invention belongs to the field of aerospace vehicle technology, and in particular relates to a composite heat insulation ball, its preparation method and application. Background Technology

[0002] For reusable aerospace vehicles, thermal protection systems are crucial for flight safety. Due to the unique aerodynamic shape of the aircraft and the complex structure of the engines, existing thermal insulation tiles or pads are limited in size, leading to significant difficulties in their manufacturing and assembly. Furthermore, gaps between adjacent thermal insulation tiles or pads, as well as in areas with complex curved surfaces, can cause localized reductions in insulation capacity, thus posing a threat to flight safety.

[0003] Currently, commonly used materials for repairing gaps mainly include organic polymer foam materials and inorganic ceramic fiber materials. However, inorganic ceramic fiber materials have limited thermal insulation capabilities and cannot provide good insulation at high temperatures of 800–1500℃. Organic polymer foam materials are prone to failure at high temperatures. Although some technical solutions attempt to add foaming components or hollow glass microspheres to enhance thermal insulation performance, they still cannot effectively block the heat transfer process, which is mainly based on thermal radiation, at high temperatures of 800–1500℃. Summary of the Invention

[0004] The main objective of this invention is to provide a composite heat insulation ball, its preparation method, and its application. The technical problem to be solved is how to provide a composite heat insulation ball with a reflective layer that can reflect thermal radiation, so that the resulting heat insulation repair molding material can effectively block the heat transfer process dominated by thermal radiation at high temperatures of 800-1500℃.

[0005] The objective of this invention and the technical problem it solves are achieved through the following technical solution. A composite heat-insulating ball according to this invention comprises:

[0006] The spherical core has a porous spherical structure; the material of the spherical core is aluminum oxide.

[0007] An isolation layer is disposed on the outer surface of the sphere core; the isolation layer can prevent liquids and / or solids from penetrating into the surface of the sphere core; the thickness of the isolation layer is <100μm;

[0008] A coating layer is bonded to the outer surface of the isolation layer by adhesive A; the coating layer is made of alumina and aerogel; the mass ratio of the aerogel to alumina is 1:15–25; the thickness of the coating layer is 300–500 μm; and,

[0009] A reflective layer is bonded to the outer surface of the covering layer by adhesive B. The reflective layer is made of a material with a reflectivity greater than 0.3 to 0.6 for mid- and far-infrared light and an emissivity of 0.7 to 0.9. The thickness of the reflective layer is 80 to 120 μm.

[0010] Preferably, in the aforementioned composite heat-insulating sphere, the pore volume of the sphere core is >0.38 mL / g, and the specific surface area is >200 m². 2 / g, with a diameter of 0.5–5 mm; the surface of the reflective layer is provided with several reinforcing layers; the reinforcing layers include a reinforced coating layer and a reinforced reflective layer stacked together.

[0011] Preferably, in the aforementioned composite heat-insulating ball, the adhesive A is a mixture of aluminum dihydrogen phosphate and magnesium oxide; the mass ratio of aluminum dihydrogen phosphate to magnesium oxide is 1:0.04 to 0.06.

[0012] Preferably, in the aforementioned composite heat-insulating sphere, the sphere core further includes a light-blocking agent disposed on the interior and / or outer surface of the sphere core; the light-blocking agent is titanium dioxide.

[0013] Preferably, in the aforementioned composite heat-insulating ball, the adhesive B is aluminum dihydrogen phosphate; the insulating layer is made of graphite; and the reflective layer is made of natural flake graphite.

[0014] The objective of this invention and the solution to its technical problem are further achieved by the following technical solution. A method for preparing a composite heat-insulating ball according to this invention includes the following steps:

[0015] S1. Preparation of spherical cores: Alumina powder is mixed with binder, sphericalized, dried, and sintered at 600-800℃ to obtain spherical cores; the mass ratio of alumina to binder is 1:0.05-0.1.

[0016] S2. Preparation of the isolation layer: Using graphite paper, an isolation layer is formed on the outer surface of the sphere core by a scraping method to obtain a sphere core with an isolation layer; the thickness of the isolation layer is <100μm;

[0017] S3. Preparation of coating layer: Mix ultrafine alumina powder and ultrafine aerogel powder at a mass ratio of 1:15-25; place the ball core with the isolation layer in adhesive A solution and immerse for 10-30 seconds, then use a roller coating method or scraping method to mix the immersed ball core with the mixture of ultrafine alumina powder and ultrafine aerogel powder, and bake to obtain the ball core with the coating layer;

[0018] S4. Preparation of reflective layer: The sphere core with the coating layer is placed in adhesive B solution and immersed for 10-30 seconds. Then, a reflective layer is formed on the surface of the sphere core with the coating layer by roller coating or scraping method. The material of the reflective layer is a material with a reflectivity of greater than 0.3-0.6 for mid- and far-infrared light and an emissivity of 0.7-0.9, to obtain a composite heat insulation sphere.

[0019] Preferably, in the aforementioned preparation method, alumina powder is mixed with a light-blocking agent and a binder; the mass ratio of alumina to the light-blocking agent is 1:0.01 to 0.1.

[0020] Preferably, in the aforementioned preparation method, ultrafine alumina powder and ultrafine aerogel powder are mixed at a mass ratio of 1:15-25; the sphere core with the reflective layer is placed in adhesive A solution and immersed for 10-30 seconds; then, the immersed sphere core with the reflective layer is mixed with the mixture of ultrafine alumina powder and ultrafine aerogel powder by roller coating or scraping method, and baked to obtain a sphere core with a coating layer; then step S4 is performed; this step is performed N times, where N is a natural number, to obtain a composite heat insulation sphere.

[0021] Preferably, in the aforementioned preparation method, the adhesive is selected from polyethylene glycol; the adhesive A is a mixture of aluminum dihydrogen phosphate and magnesium oxide; the mass ratio of aluminum dihydrogen phosphate to magnesium oxide is 1:0.04 to 0.06; and the adhesive B is aluminum dihydrogen phosphate.

[0022] The objective of this invention and the solution to its technical problem are also achieved by the following technical solution. According to this invention, a heat-insulating repair molding material comprises, by mass percentage: 60-90% composite heat-insulating balls, 0-10% ordinary silicate cement, 0-10% ordinary calcium aluminate cement, 0.1-5% cement accelerator, 0-3% natural flake graphite, 1-15% aluminum dihydrogen phosphate, 0-7% potassium silicate aqueous solution, 0-7% sodium silicate aqueous solution, 0-2% sodium fluorosilicate, 0.1-10% activated alumina powder, and 0.1-10% water; the composite heat-insulating balls are the aforementioned composite heat-insulating balls.

[0023] By employing the above technical solution, the composite heat-insulating ball, its preparation method, and its application proposed in this invention have at least the following advantages:

[0024] The composite heat insulation ball of the present invention uses low-density porous alumina as the core, which is composed of micron / submicron-sized alumina primary crystals stacked together. It has a large number of mesopores / macropores and the contact surface between micron / submicron primary crystals is small, thus effectively reducing heat conduction and convection heat transfer processes.

[0025] The composite heat insulation ball of this invention is provided with a coating layer composed of alumina and aerogel. Since aerogel has low strength, an appropriate amount of alumina is added to provide a certain supporting strength. Furthermore, alumina also provides good heat insulation. In use, dozens, or even hundreds or thousands of composite heat insulation balls need to be used together. During use, the composite heat insulation balls are in close contact, so heat will be transferred through thermal conduction. This invention, by providing a coating layer composed of alumina and aerogel, can effectively prevent heat transfer between the composite heat insulation balls, thereby improving the heat insulation effect of the composite heat insulation ball.

[0026] The composite heat-insulating sphere of this invention is provided with a reflective layer made of smooth graphite. The smooth graphite effectively reflects heat radiation generated at high temperatures, further reducing radiative heat transfer and thus providing heat insulation. During use, several composite heat-insulating spheres are combined together. During stacking, the smooth graphite layers of the spheres collectively form a labyrinthine radiative heat-reflecting structure, causing heat radiation to be reflected multiple times within the labyrinth, thereby effectively isolating heat radiation.

[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the composite heat insulation sphere;

[0029] Figure 2 This is a schematic diagram of the composite heat insulation sphere;

[0030] Figure 3 These are schematic diagrams of composite heat insulation spheres of different sizes;

[0031] Figure 4 This is a schematic diagram of thermal insulation molding materials obtained by combining composite thermal insulation balls of different diameters with adhesives. Detailed Implementation

[0032] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a composite heat-insulating ball, its preparation method, and its application according to the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0033] This invention proposes a composite heat-insulating ball, as shown in the attached figure. Figures 1-4 The above includes:

[0034] Core 1 has a porous spherical structure; the core is made of alumina; the pore volume of the core is >0.38mL / g, and the specific surface area is >200m². 2 / g, with a diameter of 0.5–5 mm;

[0035] The spherical core described in this invention is made of alumina powder. In the preparation process, alumina powder and a binder are first mixed to form a spherical shape, and then sintered at 600–800°C. By controlling the sintering temperature to 600–800°C and sintering without applying pressure, this invention enables the sintered spherical core to have a loose and porous structure. This results in a pore volume > 0.38 mL / g and a specific surface area > 200 m². 2 The performance per g. This invention controls the pore volume of the sphere core to be >0.38 mL / g and the specific surface area to be >200 m². 2 / g, achieving a loose and porous structure. This structure reduces the contact area between micron / submicron primary crystals, thereby effectively reducing heat conduction and convective heat transfer processes.

[0036] In the preparation of the spherical core, a 10% wt polyethylene glycol solution is used as the binder. Polyethylene glycol is a commonly used commercial reagent. The reason for choosing polyethylene glycol as the binder in this invention is that it ensures that the alumina powder forms spherical shapes during the spherical preparation process, preventing it from becoming loose. After spherical preparation, the spherical samples are fed into a heating furnace and sintered at a temperature controlled at 600–800°C. During sintering, the high temperature removes the polyethylene glycol, while the alumina powder grows and forms a spherical structure. To ensure the spherical core has a loose, porous shape and avoid excessive growth leading to reduced porosity, this invention requires controlling the temperature at 600–800°C during sintering and avoiding the application of pressure. Furthermore, the sintering time is 2–6 hours. Excessive sintering time will cause the spherical core to lose its porous structure, resulting in a decrease in the product's thermal insulation performance and ultimately a decline in the performance of the repair molding material.

[0037] Furthermore, the adhesive mentioned in this invention is not limited to polyethylene glycol; other types of adhesives may also be selected, as long as the following two conditions are met: 1) it can be removed during the sintering process to ensure the formation of the core; 2) the removal process does not have a negative impact on the formation of the core.

[0038] An isolation layer 2 is disposed on the outer surface of the sphere core; the isolation layer can prevent liquids and / or solids from penetrating into the surface of the sphere core; the thickness of the isolation layer is <100μm;

[0039] This invention includes an isolation layer made of dense graphite, whose main function is to protect the sphere core. During subsequent fabrication, adhesives A and B are used to fix the coating and reflective layers. The isolation layer prevents these adhesives from seeping into the pores of the sphere core. Furthermore, the isolation layer also prevents solid particles or impurities from penetrating to the sphere core surface during the fabrication of the coating and reflective layers using roller coating or scraping methods. This prevents situations that could degrade the sphere core's performance, while protecting the integrity and performance of the sphere core.

[0040] The insulating layer provided in this invention not only protects the integrity and performance of the sphere core but also provides thermal insulation. Because the insulating layer is made of dense graphite, it reflects some of the radiant heat energy when external heat radiates onto the graphite surface. Thus, the graphite insulating layer prevents heat from being further conducted into the sphere core, reducing heat transfer and absorption.

[0041] A coating layer 3 is bonded to the outer surface of the isolation layer by adhesive A; the coating layer is made of alumina and aerogel; the mass ratio of the aerogel to alumina is 1:15–25; the thickness of the coating layer is 300–500 μm; and,

[0042] The coating layer of this invention is made of ultrafine alumina powder and ultrafine aerogel powder. Among them, the aerogel has low density, high specific surface area and excellent thermal insulation properties. When external heat is conducted to the coating layer, the aerogel can hinder the heat conduction through its tiny pore structure, thereby reducing heat loss and the heat transferred to the core, and improving the thermal insulation effect.

[0043] However, adding aerogel to the coating layer has negative effects because aerogel has low strength, which reduces the strength of the composite insulation ball. Therefore, to solve the problem of low aerogel strength, this invention utilizes the excellent mechanical strength of alumina and mixes aerogel and alumina to form an alumina / aerogel coating layer. This maintains the insulation performance while preventing the coating layer from collapsing.

[0044] The ultrafine alumina powder described in this invention has a mesh size of 30-1600 mesh, and this material is commercially available. The reason for using ultrafine alumina powder is that it has high porosity and a large specific surface area. When heat passes through these pores, it is hindered, resulting in a reduction in heat transfer capacity. Furthermore, the porous structure of ultrafine alumina powder increases surface reflection and scattering effects of thermal radiation and thermal conductivity. These two effects together reduce heat conduction, thereby achieving a thermal insulation effect. In addition, ultrafine alumina powder also has good dispersibility and can be uniformly dispersed in ultrafine aerogel powder. This helps to improve the mechanical strength and structural stability of the composite insulation ball.

[0045] The ultrafine aerogel powder described in this invention is selected from any one of ultrafine silica aerogel powder, ultrafine zirconium dioxide aerogel powder, ultrafine alumina aerogel powder, and ultrafine silica / alumina composite aerogel powder. The mesh size of the ultrafine aerogel powder described in this invention is 30-1600 mesh. The reason for using ultrafine aerogel powder in this invention is that it has high porosity and a large specific surface area, which can reduce heat conduction and transfer, effectively isolating heat flow. Furthermore, ultrafine aerogel powder is lightweight, which can reduce the weight of the composite heat insulation ball, thereby enabling the production of lightweight materials.

[0046] This invention uses adhesive A, a mixture of aluminum dihydrogen phosphate and magnesium oxide, to bond the coating layer to the surface of the insulating layer. Adhesive A effectively bonds the coating layer and the insulating layer together, increasing the strength and stability of the material and ensuring the quality of the bonding interface. Furthermore, both aluminum dihydrogen phosphate and magnesium oxide possess excellent high-temperature resistance and are not removed during subsequent sintering, thus increasing the strength and stability of the material and ensuring the structural stability of the composite heat-insulating ball. Aluminum dihydrogen phosphate has good adhesive properties, forming a strong bond with magnesium oxide, while magnesium oxide has high high-temperature resistance, maintaining stability during subsequent sintering. Therefore, by controlling the mass ratio of aluminum dihydrogen phosphate to magnesium oxide within the range of 1:0.04 to 0.06, this invention ensures that the composition of adhesive A is appropriate, providing sufficient adhesive strength while maintaining material stability. Excessively high or low mass ratios of aluminum dihydrogen phosphate to magnesium oxide may lead to unsatisfactory adhesive performance, affecting the quality and performance of the material.

[0047] The reflective layer 4 is bonded to the outer surface of the covering layer by adhesive B. The reflective layer is made of a material with a reflectivity greater than 0.3 to 0.6 for mid- and far-infrared light and an emissivity of 0.7 to 0.9. The thickness of the reflective layer is 80 to 120 μm.

[0048] At high temperatures (above 800°C), heat transfer is primarily through thermal radiation. Therefore, traditional inorganic ceramic fiber materials or organic materials cannot effectively block thermal radiation. The composite heat-insulating spheres of this invention are equipped with a reflective layer made of a material with a reflectivity greater than 0.3–0.6 for mid- and far-infrared light and an emissivity of 0.7–0.9. This layer reflects external thermal radiation. During use, multiple composite heat-insulating spheres are stacked together, and their reflective layers collectively form a labyrinthine radiative heat-reflecting structure. At high temperatures (above 800°C), this effectively isolates the transfer of radiative heat, thus achieving a heat insulation effect.

[0049] The reflectivity mentioned herein refers to the ratio of the incident intensity to the reflected intensity of thermal radiation in the mid- and far-infrared light band of a material in an environment of 800–1500°C, which reflects the material's ability to reflect thermal radiation in the mid- and far-infrared light band.

[0050] The emissivity described herein refers to the ability of a material to radiate heat outward in the mid- and far-infrared light band in an environment of 800–1500°C. It is a dimensionless indicator and is usually expressed as a decimal between 0 and 1.

[0051] The material of the reflective layer of this invention has a reflectivity of more than 0.3 to 0.6 for mid- and far-infrared light, while also controlling the emissivity to be 0.7 to 0.9. This allows the composite heat insulation ball to emit the heat it absorbs in the form of thermal radiation, reducing the heat of the composite heat insulation ball itself, thereby avoiding heat transfer between the composite heat insulation balls and improving the heat insulation effect of the heat insulation repair molding material.

[0052] The choice of material and thickness of the reflective layer is a key factor in determining the optimal reflection effect and heat insulation performance. In this invention, the reflective layer is preferably made of natural flake graphite, resulting in a smooth reflective layer that reflects heat radiation, effectively blocking it and providing good heat insulation. This invention controls the thickness of the reflective layer to 80–120 μm. Controlling this thickness ensures the composite heat insulation sphere has optimal heat insulation performance and material stability. If the reflective layer is too thick, the strength of the composite heat insulation sphere will decrease, leading to structural damage and rendering it unusable.

[0053] This invention utilizes adhesive B to firmly bond the reflective layer to the outer surface of the coating layer, ensuring the stability and reliability of the reflective layer. It is important to note that selecting a suitable adhesive B is crucial for bonding the reflective layer to the coating layer, ensuring good adhesion and guaranteeing the quality and reliability of the bond. Maintaining the uniformity and flatness of the reflective layer during the bonding process is also paramount.

[0054] The adhesive B described in this invention is aluminum dihydrogen phosphate, which has excellent adhesive properties and can provide high adhesive strength. This is crucial for firmly bonding the reflective layer to the outer surface of the coating layer, ensuring that the reflective layer is not easily detached or damaged during use. Secondly, aluminum dihydrogen phosphate has excellent high-temperature resistance and will not be removed during subsequent sintering, thereby improving the strength of the composite heat-insulating microspheres and ensuring their structural integrity. Compared to adhesive A, adhesive A requires the addition of magnesium oxide because the coating layer contains aerogel, which is weak and brittle. Therefore, magnesium oxide is needed to provide support for the coating layer, thus ensuring the structural integrity of the composite heat-insulating microspheres and resulting in excellent heat insulation performance.

[0055] Preferably, in the aforementioned composite heat insulation ball, the surface of the reflective layer is provided with a plurality of reinforcing layers; the reinforcing layers include a reinforced covering layer and a reinforced reflective layer stacked together.

[0056] This invention provides several reinforcing layers on the surface of the reflective layer. The number of reinforcing layers can be selected according to actual production needs. For example, when the number of reinforcing layers is one, such as... Figure 2 As shown, the structure of the composite heat insulation ball, from the inside out, is as follows: core 1, insulating layer 2, covering layer 3, reflective layer 4, reinforcing covering layer 5, and reinforcing reflective layer 6. When there are two reinforcing layers, the structure of the composite heat insulation ball, from the inside out, is as follows: core, insulating layer, covering layer, reflective layer, reinforcing covering layer, reinforcing reflective layer, reinforcing covering layer, and reinforcing reflective layer. The structure and bonding method of the reinforcing covering layer and the reinforcing reflective layer are the same as those of the covering layer and the reflective layer. For example, when there is one reinforcing layer, the reinforcing covering layer 5 is bonded to the surface of the reflective layer using adhesive A; the reinforcing reflective layer 6 is bonded to the surface of the reinforcing covering layer using adhesive B. This invention, by setting several reinforcing layers on the outer surface of the reflective layer, can improve the reflective performance of the composite heat insulation ball against thermal radiation, thereby improving the thermal insulation effect of the composite heat insulation ball.

[0057] Preferably, in the aforementioned composite heat-insulating sphere, the sphere core further includes a light-blocking agent disposed on the interior and / or outer surface of the sphere core; the light-blocking agent is titanium dioxide.

[0058] The spherical core of this invention may also contain a titanium dioxide light-blocking agent. This titanium dioxide light-blocking agent is distributed in the pores and / or surface of the spherical core. The titanium dioxide light-blocking agent has high reflectivity, reflecting heat radiation back, thereby reducing heat transfer. Secondly, the titanium dioxide light-blocking agent reduces light penetration, thereby reducing heat entry, lowering the surface temperature of the spherical core, and further improving the heat insulation effect of the composite heat-insulating microspheres. The titanium dioxide light-blocking agent added in this invention is a commonly available material. The titanium dioxide used in this invention has a mesh size of 200-800 mesh, preferably 800 mesh.

[0059] Preferably, in the aforementioned composite heat-insulating ball, the adhesive A is a mixture of aluminum dihydrogen phosphate and magnesium oxide; the mass ratio of aluminum dihydrogen phosphate to magnesium oxide is 1:0.04 to 0.06; the adhesive B is aluminum dihydrogen phosphate; the material of the insulating layer is graphite; and the material of the reflective layer is natural flake graphite.

[0060] This invention also proposes a method for preparing composite heat-insulating balls, which includes the following steps:

[0061] S1. Preparation of spherical cores: Alumina powder is mixed with binder, sphericalized, dried, and sintered at 600-800℃ to obtain spherical cores; the mass ratio of alumina to binder is 1:0.05-0.1.

[0062] This invention prepares spherical cores using alumina powder and a binder. Since this invention employs a mass production method for core preparation, the bulk density of the spheres is controlled at 0.6-0.7 g / cm³ to ensure spherical quality. 3 For example, using tools to prepare 200 spherical cores, the bulk density of the 200 spherical cores is 0.6–0.7 g / cm³. 3 By controlling the packing density of the spheres, the quality of the sphere core can be controlled, thereby improving the pass rate.

[0063] Furthermore, the current mass production method of this invention cannot produce spheres with a single diameter. Instead, the diameters of the produced spheres vary. Therefore, this invention requires sieving the produced spheres, with spheres having a diameter of 0.5 to 1 mm being the best, followed by spheres with a diameter of 1 to 2 mm.

[0064] In this invention, the sintering temperature is controlled at 600-800°C. At this temperature, the binder is removed, and the alumina powder can grow slightly, thereby obtaining a spherical shape. Furthermore, hot pressing is not required during the sintering process. Under the combined effect of the above two processes, the resulting spherical core has a loose and porous structure and a low density, thereby enabling the resulting composite heat insulation ball to have a good heat insulation effect.

[0065] S2. Preparation of the isolation layer: Using graphite paper, an isolation layer is formed on the outer surface of the sphere core by a scraping method to obtain a sphere core with an isolation layer; the thickness of the isolation layer is <100μm;

[0066] The specific preparation method of the isolation layer of the present invention is as follows:

[0067] Place the ball core on a large piece of graphite paper, press the ball core with a support, apply pressure to the support of about 0.3 to 1 kg per square centimeter, and make it rub back and forth on the surface of the graphite paper. Repeatedly adjust the scraping direction and the pressing direction of the alumina ball until the target isolation layer is obtained.

[0068] The graphite paper described in this invention is a paper-like material made by pressing graphite, with a size of 30×30cm. This size is the specification used in the experiments of this invention, and the specific size can be adjusted according to actual production needs. The support mentioned in this invention refers to supports such as perforated plates / mesh nets / flexible base plates, etc.

[0069] S3. Preparation of the coating layer: Mix ultrafine alumina powder and ultrafine aerogel powder at a mass ratio of 1:15-25; place the ball core with the isolation layer in adhesive A solution and immerse it for 10-30 seconds; then, using a roller coating or scraping method, mix the immersed ball core with the isolation layer with the mixture of ultrafine alumina powder and ultrafine aerogel powder, and bake to obtain the ball core with the coating layer; the mesh size of the ultrafine alumina powder is 30-1600 mesh; the mesh size of the ultrafine aerogel powder is 30-1600 mesh; the ultrafine aerogel powder is selected from any one of silica ultrafine aerogel powder, zirconium dioxide ultrafine aerogel powder, alumina ultrafine aerogel powder, and silica / alumina composite ultrafine aerogel powder.

[0070] In preparing the coating layer, this invention requires the use of ultrafine aerogel powder and ultrafine alumina powder, with the mass ratio of ultrafine alumina powder to ultrafine aerogel powder controlled at 1:15-25. Excessive addition of ultrafine aerogel powder will lead to a decrease in the product's thermal insulation performance; insufficient addition will result in a decrease in the product's strength. Therefore, controlling the mass ratio of ultrafine alumina powder to ultrafine aerogel powder to 1:15-25 in this invention enables the composite thermal insulation microspheres to possess both good thermal insulation capabilities and mechanical strength. The adhesive A described in this invention can bond the coating layer to the surface of the insulating layer, improving the adhesion between the adhesive and the microsphere core.

[0071] This invention uses a roller coating or scraping method to mix the soaked sphere core with a mixture of ultrafine aerogel powder and ultrafine alumina powder, allowing the ultrafine alumina powder and ultrafine aerogel powder to adhere uniformly to the surface of the sphere core, providing excellent adhesion. Preferably, the coating layer is prepared using a roller coating method. Using a roller coating method to prepare the coating layer allows for precise control of the coating layer thickness, thereby ensuring controllable product performance.

[0072] The specific method for preparing the coating layer using the roller coating method in this invention is as follows:

[0073] Transfer the moistened core ball to a shallow dish containing ultrafine alumina powder and ultrafine aerogel powder. Rotate the dish at a speed of 20–50 rpm for 1–3 minutes. After completion, bake at 120–300°C to obtain the alumina / aerogel coating layer.

[0074] S4. Preparation of reflective layer: The sphere core with the coating layer is placed in adhesive B solution and immersed for 10-30 seconds. Then, a reflective layer is formed on the surface of the sphere core with the coating layer by roller coating or scraping method. The material of the reflective layer is a material with a reflectivity of greater than 0.3-0.6 for mid- and far-infrared light and an emissivity of 0.7-0.9.

[0075] This invention applies a reflective layer using either a roller coating or a scraping method; preferably, a roller coating method is used to prepare the coating layer. Using a roller coating method allows for precise control of the coating layer's thickness, thereby ensuring controllable product performance.

[0076] The specific method for preparing the coating layer using the roller coating method in this invention is as follows:

[0077] Transfer the moistened alumina core to a shallow dish lined with natural flake graphite. Rotate the dish at a speed of 20–50 rpm for 2–5 minutes to encourage the low-density porous alumina spheres to roll and adhere to the natural flake graphite. The friction between the spheres ensures a tight bond between the adhered flake graphite and maintains a smooth surface. Then bake the mixture at 120–300°C to obtain a smooth graphite reflective layer.

[0078] S5. Mix ultrafine alumina powder and ultrafine aerogel powder at a mass ratio of 1:15-25; place the ball core with the reflective layer in adhesive A solution and immerse it for 10-30 seconds; then use a roller coating method or a scraping method to mix the immersed ball core with the ultrafine alumina powder and ultrafine aerogel powder mixture, bake it, and obtain the ball core with the coating layer; then proceed to step S4.

[0079] S6. Execute step S5 N times, where N is a natural number, to obtain a composite heat-insulating ball.

[0080] Steps S5 and S6 of this invention are used to prepare an enhancement layer, which includes an enhancement coating layer and an enhancement reflective layer; wherein the enhancement coating layer is prepared by the same method as the coating layer; and the enhancement reflective layer is prepared by the same method as the reflective layer. Step S5 can be performed N times, where N can be a natural number such as 0, 1, 2, 3, 4, 5, etc. When N is 0, the composite heat insulation sphere, from the inside out, includes: a core, an insulating layer, a covering layer, and a reflective layer; when N is 1, the composite heat insulation sphere, from the inside out, includes: a core, an insulating layer, a covering layer, a reflective layer, a reinforced covering layer, and a reinforced reflective layer; when N is 2, the composite heat insulation sphere, from the inside out, includes: a core, an insulating layer, a covering layer, a reflective layer, a reinforced covering layer, a reinforced reflective layer, a reinforced covering layer, and a reinforced reflective layer; when N is n, the composite heat insulation sphere, from the inside out, includes: a core, an insulating layer, a covering layer, a reflective layer, a reinforced covering layer, a reinforced reflective layer, ..., a reinforced covering layer and a reinforced reflective layer (the nth layer);

[0081] Preferably, in the aforementioned preparation method, alumina powder is mixed with a light-blocking agent and a binder; the mass ratio of alumina to the light-blocking agent is 1:0.01 to 0.1.

[0082] In this invention, the mass ratio of alumina to the opaque agent is controlled to be 1:0.01 to 0.1, because the opaque agent...

[0083] Preferably, in the aforementioned preparation method, the adhesive is selected from polyethylene glycol; the adhesive A is a mixture of aluminum dihydrogen phosphate and magnesium oxide; the mass ratio of aluminum dihydrogen phosphate to magnesium oxide is 1:0.04 to 0.06; and the adhesive B is aluminum dihydrogen phosphate.

[0084] The present invention also proposes a heat insulation repair molding material, which, by mass percentage, comprises: 60-90% composite heat insulation balls, 0-10% ordinary silicate cement, 0-10% ordinary calcium aluminate cement, 0.1-5% cement accelerator, 0-3% natural flake graphite, 1-15% aluminum dihydrogen phosphate, 0-7% potassium silicate aqueous solution, 0-7% sodium silicate aqueous solution, 0-2% sodium fluorosilicate, 0.1-10% activated alumina powder, and 0.1-10% water; wherein the composite heat insulation balls are the aforementioned composite heat insulation balls.

[0085] In practical applications, the composite heat insulation balls added to the heat insulation repair molding material can be composite heat insulation balls of the same specification, or they can be a mixture of composite heat insulation balls of different specifications in a certain proportion. The specifications mentioned here can refer to the size of the ball core, the size of the finished composite heat insulation ball, and the number of layers of the composite heat insulation ball, etc. Preferably, this invention incorporates composite heat insulation balls of different specifications during the preparation of the heat insulation repair molding material; the specifications refer to the size of the ball core.

[0086] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0087] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0088] Example 1

[0089] A method for preparing a composite heat-insulating ball includes the following steps:

[0090] S1. Select low-density porous alumina spheres with a diameter of 1-2 mm and a primary crystal median size D50 of 0.5 μm as the sphere core;

[0091] S2. Place the ball core on a 30cm×30cm graphite paper, press the ball core with a flexible base plate, apply pressure of 0.5kg per square centimeter to the support, and scrape it back and forth on the graphite paper surface more than 10 times. Repeat (more than 5 times) adjusting the scraping direction and the pressing direction of the ball core to scrape the graphite paper surface to obtain an isolation layer.

[0092] S3. Mix aluminum dihydrogen phosphate and magnesium oxide nanoparticles at a mass ratio of 1:0.05 to obtain adhesive A; wet the sphere core with the isolation layer using adhesive A, and then transfer the wetted sphere to a shallow dish containing a mixture of 100-mesh ultrafine alumina powder and 100-mesh ultrafine alumina aerogel powder, wherein the mass ratio of ultrafine alumina powder to ultrafine alumina aerogel powder is 15:1; rotate the shallow dish at a speed of approximately 30 r / min for 3 min. After completion, bake at 180 degrees Celsius for 10 min to obtain the coating layer;

[0093] S4. Place the product obtained in S3 in aluminum dihydrogen phosphate, moisten it, and then transfer it to a shallow dish covered with 50-mesh natural flake graphite. Rotate the shallow dish at a speed of 50 r / min for 3 min. After completion, bake it at 180℃ for 10 min to obtain the reflective layer.

[0094] S5. Repeat steps S3 and S4 once to obtain composite heat insulation balls.

[0095] Example 2

[0096] Compared with Example 1, the diameter of the sphere core in Example 2 is 2-3 mm, the median size D50 of the original crystal is 2.5 μm, and the mass ratio of ultrafine alumina powder to ultrafine alumina aerogel powder and light-shielding agent zirconium oxide is 18:2:1.

[0097] Example 3

[0098] A heat insulation repair molding material, by mass percentage, comprises: 70% composite heat insulation ball, 10% aluminum dihydrogen phosphate, 3% potassium silicate aqueous solution, 5% sodium silicate aqueous solution, 1% sodium fluorosilicate, 1% activated alumina powder and 3% ordinary silicate cement, with the remainder being water; the composite heat insulation ball is the composite heat insulation ball described in Example 1.

[0099] Example 4

[0100] The difference from Example 3 is that in Example 4, the composite heat insulation ball is a mixture of the composite heat insulation balls prepared in Example 1 and Example 2, wherein the ratio of the amount of composite heat insulation ball added in Example 1 to the amount of composite microsphere added in Example 2 is 1:1.3.

[0101] Example 5

[0102] The difference from Example 3 is that the composite heat insulation ball in Example 5 is the composite heat insulation ball prepared in Example 2.

[0103] Comparative Example 1

[0104] Traditional aluminosilicate ceramic fiber cotton is used as the repair molding material.

[0105] Comparative Example 2

[0106] Polyurethane foam is used as the repair molding material.

[0107] A 2cm x 1cm notch was cut in the center of a 1cm thick heat insulation tile to simulate a defect / seam. Materials from Examples 3, 4, 5, Comparative Example 1, and Comparative Example 2 were used to fill the notch. A flat-plate furnace method was used, with the temperature set at 1100℃. The back temperature of the repaired area was recorded after 15 minutes and 30 minutes. Specific data are as follows:

[0108] Table 1

[0109]

[0110]

[0111] The data above shows that, using the flat-plate furnace method, Examples 3, 4, and 5 can all withstand heat radiation at 1100℃. However, Comparative Example 1, using aluminosilicate ceramic fiber cotton as the repair molding material, cannot achieve a good heat insulation effect. Comparative Example 2, using polyurethane foam as the repair molding material, directly carbonizes and burns at high temperatures, failing to complete the test. Therefore, the repair molding material made using the composite heat-insulating ball of this invention can effectively reflect heat radiation at 800–1500℃, thus exhibiting excellent heat insulation performance.

[0112] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0113] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A composite heat-insulating ball, characterized in that, It includes: The spherical core has a porous spherical structure; the material of the spherical core is aluminum oxide. An isolation layer is disposed on the outer surface of the spherical core; The isolation layer prevents liquids and / or solids from penetrating the surface of the core; the thickness of the isolation layer is <100μm. A coating layer is bonded to the outer surface of the isolation layer by an adhesive A; the adhesive A is a mixture of aluminum dihydrogen phosphate and magnesium oxide; the mass ratio of aluminum dihydrogen phosphate to magnesium oxide is 1:0.04 to 0.06; the coating layer is made of alumina and aerogel; the mass ratio of aerogel to alumina is 1:15 to 25; the thickness of the coating layer is 300 to 500 μm. and, A reflective layer is bonded to the outer surface of the covering layer by adhesive B. The reflective layer is made of a material with a reflectivity greater than 0.3 to 0.6 for mid- and far-infrared light and an emissivity of 0.7 to 0.

9. The thickness of the reflective layer is 80 to 120 μm.

2. The composite heat-insulating ball according to claim 1, characterized in that, The sphere core has a pore volume > 0.38 mL / g, a specific surface area > 200 m² / g, and a diameter of 0.5–5 mm; the surface of the reflective layer is provided with several reinforcing layers; the reinforcing layers include a reinforced coating layer and a reinforced reflective layer stacked together.

3. The composite heat-insulating ball according to claim 1, characterized in that, The sphere core also includes a light-blocking agent, which is disposed inside and / or on the outer surface of the sphere core; the light-blocking agent is titanium dioxide.

4. The composite heat-insulating ball according to claim 1, characterized in that, The adhesive B is aluminum dihydrogen phosphate; the material of the isolation layer is graphite; and the material of the reflective layer is natural flake graphite.

5. A method for preparing the composite heat-insulating ball according to any one of claims 1 to 4, characterized in that, It includes the following steps: S1. Preparation of spherical cores: Alumina powder is mixed with binder, sphericalized, dried, and sintered at 600-800℃ to obtain spherical cores; the mass ratio of alumina to binder is 1:0.05-0.

1. S2. Preparation of the isolation layer: Using graphite paper, an isolation layer is formed on the outer surface of the sphere core by a scraping method to obtain a sphere core with an isolation layer; the thickness of the isolation layer is <100μm; S3. Preparation of coating layer: Mix ultrafine alumina powder and ultrafine aerogel powder at a mass ratio of 1:15-25; place the ball core with the isolation layer in adhesive A solution and immerse for 10-30 seconds, then use a roller coating method or scraping method to mix the immersed ball core with the mixture of ultrafine alumina powder and ultrafine aerogel powder, and bake to obtain the ball core with the coating layer; S4. Preparation of reflective layer: The sphere core with the coating layer is placed in adhesive B solution and immersed for 10-30 seconds. Then, a reflective layer is formed on the surface of the sphere core with the coating layer by roller coating or scraping method. The material of the reflective layer is a material with a reflectivity of greater than 0.3-0.6 for mid- and far-infrared light and an emissivity of 0.7-0.9, to obtain a composite heat insulation sphere.

6. The preparation method according to claim 5, characterized in that, In step S1, alumina powder is mixed with a light-blocking agent and an adhesive; the mass ratio of alumina to the light-blocking agent is 1:0.01 to 0.

1.

7. The preparation method according to claim 5, characterized in that, The preparation method further includes: Ultrafine alumina powder and ultrafine aerogel powder are mixed at a mass ratio of 1:15-25. The sphere core with the reflective layer is placed in adhesive A solution and immersed for 10-30 seconds. Then, the immersed sphere core with the reflective layer is mixed with the mixture of ultrafine alumina powder and ultrafine aerogel powder by roller coating or scraping method. After baking, a sphere core with a coating layer is obtained. Then, step S4 is performed. This step is performed N times, where N is a natural number, to obtain a composite heat insulation sphere.

8. The preparation method according to claim 5, characterized in that, The adhesive is selected from polyethylene glycol; the adhesive A is a mixture of aluminum dihydrogen phosphate and magnesium oxide; the mass ratio of aluminum dihydrogen phosphate to magnesium oxide is 1:0.04 to 0.06; the adhesive B is aluminum dihydrogen phosphate.

9. A heat-insulating repair molding material, characterized in that, The composition, by weight percentage, comprises: 60–90% composite insulating balls, 0–10% ordinary silicate cement, 0–10% ordinary calcium aluminate cement, 0.1–5% cement accelerator, 0–3% natural flake graphite, 1–15% aluminum dihydrogen phosphate, 0–7% potassium silicate aqueous solution, 0–7% sodium silicate aqueous solution, 0–2% sodium fluorosilicate, 0.1–10% activated alumina powder, and 0.1–10% water; the composite insulating balls are those described in any one of claims 1–4.

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