A floating bead refractory heat-insulating composite board and a preparation method thereof

Abstract

The application discloses a kind of floating bead refractory heat-insulating composite board and preparation method thereof, belong to refractory heat-insulating composite board technical field;Including composite board body, the composite board body includes modified floating bead, short cut polycrystalline fiber and composite cement matrix, the modified floating bead includes hollow floating bead body, the hollow floating bead body surface is coated with active transition shell layer of aluminium silicon system;The short cut polycrystalline fiber both ends and the active transition shell layer of modified floating bead bridge formation three-dimensional support skeleton, the composite cement matrix is filled in the interstice of three-dimensional support skeleton, forms integrated structure;The floating bead refractory heat-insulating composite board and preparation method thereof of the application, with modified floating bead of core-shell structure as fulcrum, three-dimensional continuous support skeleton is formed by bridging through short cut polycrystalline fiber between fulcrum, composite cement matrix is filled in the interstice of interlocking skeleton, prepared board material has lightweight, ultra-low thermal conductivity, high strength and high refractory stability.

Description

Technical Field

[0001] This invention specifically relates to a cenosphere fire-resistant and heat-insulating composite board and its preparation method, belonging to the technical field of fire-resistant and heat-insulating composite boards. Background Technology

[0002] Cenospheres are hollow spherical glass microspheres formed after the combustion of fly ash in power plants. They have the advantages of being lightweight, having a high closed-cell rate, high refractoriness, and low cost, making them an ideal raw material for preparing fireproof and heat-insulating materials. Traditional cenosphere refractory insulation boards generally use cement or other cementitious materials as a continuous load-bearing matrix, incorporating cenospheres as an inert heat-insulating filler into the matrix, and then supplementing with a small amount of fiber reinforcement. They are prepared through mixing, molding, and curing. For example, Chinese Patent Publication No. CN112645670B discloses a cenosphere refractory insulation board made from the following raw materials by weight: 30-60 parts cenospheres, 40-70 parts aluminate cement, 10-30 parts calcium oxide, and 1-3 parts cellulose. The raw materials are mixed with water at a liquid-solid mass ratio of 1:13 and subjected to a hydrothermal synthesis reaction. The slurry is then filtered, laid in a mold, extruded using a press, and dried to obtain the cenosphere refractory insulation board. However, existing cenosphere insulation boards have the following disadvantages: 1. Weak interfacial bonding, prone to cracking and pulverization at high temperatures: The cenospheres have an inert glassy surface and are only physically wrapped with the cementitious matrix, resulting in extremely weak interfacial bonding. At the same time, the thermal expansion coefficients of the cenospheres and the cementitious matrix differ greatly, leading to severe interfacial thermal mismatch at high temperatures. This can easily cause interfacial cracking, cenosphere detachment, and matrix pulverization, ultimately resulting in complete failure of the thermal insulation performance. 2. High thermal insulation and high strength cannot be achieved simultaneously: When low thermal conductivity is achieved by relying on the hollow closed cells of cenospheres, the cenosphere content must be increased; however, when the cenosphere content exceeds 40%, the continuous phase of the cementitious matrix is ​​completely destroyed, and the material strength drops sharply. At the same time, cenospheres are very easy to float and separate in the slurry, resulting in uneven performance of the board and extremely low mass production qualification rate. 3. Separation of pore structure from load-bearing structure, resulting in poor high-temperature stability: Existing technologies often add pore-forming agents to introduce pores in order to improve thermal insulation. The pores formed by pore formation are not related to the closed-cell structure of the cenospheres or the fiber reinforcement system. The pores are prone to collapse at high temperatures, making it impossible to balance thermal insulation performance and structural stability. Summary of the Invention

[0003] To address the aforementioned issues, this invention proposes a cenosphere refractory and heat-insulating composite board and its preparation method. Modified cenospheres with a core-shell structure serve as fulcrums, and short-cut polycrystalline fibers bridge the fulcrums to form a three-dimensional continuous support skeleton. A composite cementitious matrix fills the gaps in the interlocking skeleton. The prepared board possesses lightweight, ultra-low thermal conductivity, high strength, and high fire resistance stability.

[0004] The present invention comprises a composite board body, wherein the composite board body includes: Modified cenospheres, comprising hollow cenosphere bodies, the surface of which is coated with an active transition shell layer of aluminum-silicon system homologous to the composite cementitious matrix, forming a core-shell structure; the hollow cenosphere body has a particle size of 45-180 μm, a closed-cell rate ≥96%, and a refractoriness ≥1650℃; the active transition shell layer has a calcium-silicon molar ratio of 0.8-1.2, an aluminum-silicon molar ratio of 0.3-0.5, and a thickness of 100-300 nm; the active transition shell layer has a surface-active hydroxyl content ≥1.0 mmol / g; and a coefficient of thermal expansion of 24 × 10⁻⁶. -6 / ℃, the active transition shell is between 0.5 × 10⁻⁶ and the thermal expansion coefficient of the hollow microsphere. -6 / ℃ and the coefficient of thermal expansion of the composite cementitious matrix are 5-8×10 -6 The temperature range (°C) can avoid thermal mismatch between hollow cenospheres and composite cementitious matrix; Short-cut polycrystalline fibers, wherein the two ends of the short-cut polycrystalline fibers are bridged with the active transition shell of modified cenospheres to form chemical bonds, constituting a three-dimensional support skeleton for a continuous load-bearing body; The composite cementitious matrix fills the gaps in the three-dimensional support skeleton to form an integrated structure. The composite plate uses modified cenospheres with a core-shell structure as the core carrier, and forms a three-dimensional support skeleton through short-cut polycrystalline fiber bridging. The composite cementitious matrix fills the gaps in the three-dimensional support skeleton to form an integrated structure. The composite cementitious matrix only serves as an interface filler and binder phase, and does not serve as the main load-bearing unit. This can solve the problem of mutual interference between cenosphere dosage and structural strength, thus simultaneously taking into account thermal insulation and structural strength. The composite plate is composed of the following components by weight: 40-60 parts modified cenospheres, 15-30 parts composite cementitious matrix, 4-12 parts chopped polycrystalline fibers, and 20-40 parts water; the active transition shell has a calcium-silicon molar ratio of 0.8-1.2, an aluminum-silicon molar ratio of 0.3-0.5, and a thickness of 100-300 nm. Furthermore, the chopped polycrystalline fiber is polycrystalline mullite fiber or polycrystalline alumina fiber, with a diameter of 24 μm, a length of 24 mm, a crystalline phase content of ≥98%, and no glass phase; the mass ratio of the chopped polycrystalline fiber to the modified cenospheres is 1:5-10.

[0005] Furthermore, the composite cementitious matrix is ​​a composite system of high-alumina cement and metakaolin, wherein the mass ratio of high-alumina cement to metakaolin is 6-8:2-4, the Al2O3 content of the high-alumina cement is ≥70%, and the total content of active Al2O3 and SiO2 of the metakaolin is ≥95%.

[0006] Furthermore, the composite plate body forms a three-level gradient closed-cell body with a total porosity of 75%-90%. The three-level gradient closed-cell body includes primary hollow closed-cell bodies made of hollow beads, secondary closed micron-pores formed by the gaps in the three-dimensional support skeleton, and tertiary nano-closed-cell bodies made of composite cementitious matrix. The primary hollow closed-cell bodies have a pore size of 45-180μm and a porosity of 60%-70%; the secondary closed micron-pores have a pore size of 1-8μm and a porosity of 20%-25%; and the tertiary nano-closed-cell bodies have a pore size of 20-100nm and a porosity of 5%-15%. The primary hollow closed-cell bodies have a core heat insulation function, the secondary closed micron-pores have a thermal expansion buffer and supplementary heat insulation function, and the tertiary nano-closed-cell bodies have a function of reducing solid phase thermal conductivity. The three-level gradient closed-cell body is naturally formed by the three-dimensional support skeleton, without the need for additional pore-forming agents, and is completely integrated with the load-bearing system, with no pore collapse at high temperatures.

[0007] Furthermore, the composite plate also includes the following components by weight: 0.1-0.5 parts of calcium stearate foam stabilizer, used to regulate the nano-closed-pore structure of the composite gel matrix; 0.2-1.0 parts of silane coupling agent, used to further strengthen the interfacial bonding force between the short-cut polycrystalline fibers, modified cenospheres and the composite gel matrix; the hydration products of the composite gel matrix are homologous to the active transition shell layer on the surface of the hollow cenospheres, which can achieve directional nucleation growth and strengthen the interfacial bonding.

[0008] Furthermore, the active transition shell is also doped with 0.5-2wt% of nano-ZrO2 whisker nucleating agent; radially arranged mullite whiskers are grown in situ on the surface of the active transition shell, the mullite whiskers have a diameter of 50-200nm, a length of 2-5μm, and an aspect ratio of 10-50; one end of the mullite whisker is embedded in the active transition shell to form a chemical bond, and the other end extends into the composite cement matrix to form a mechanical anchor, constituting a double anchoring interface structure between the bead and the matrix.

[0009] Furthermore, the composite cementitious matrix is ​​a composite system of high-alumina cement, metakaolin, and a crystal form regulator, with a mass ratio of 6-8:2-4:0.5-2; the crystal form regulator is a mixture of nano-mullite seed crystals and active silica powder, with a mass ratio of 1:1-3; the nano-mullite seed crystals have a particle size of 20-50 nm and a crystalline phase content of ≥99%; the active silica powder has a particle size of 100-200 nm and a SiO2 content of ≥98%. The three-dimensional network hydrated gel generated by the crystal form control matrix uniformly coats the surface of the three-dimensional support framework without stress concentration caused by plate-like crystals. The whiskers form microcracks in the matrix, bridging and deflecting them to prevent crack propagation. Specifically, the composite plate generates an active transition shell layer outside the hollow cenospheres and in-situ generates mullite whiskers. Short-cut polycrystalline fibers form a continuous three-dimensional support framework, and the crystal form control matrix creates a continuous thermal expansion gradient without any discontinuities, resulting in no interfacial thermal mismatch stress at high temperatures. One end of the in-situ whisker is embedded in the core-shell active layer, and the other end extends into the composite gel matrix, becoming a transitional structure of the thermal expansion gradient. The crystal form control agent regulates the formation of the crystal form control matrix. The high-temperature crystalline phase of the crystal form control matrix is ​​completely homologous to the whiskers, fibers, and core-shell layer, with no crystal form abrupt changes.

[0010] Furthermore, the composite plate also includes 0.3-1.2 parts of a composite foam stabilizing and pore-locking agent, which is a mixture of calcium stearate and surface-modified nano-silica aerogel powder, with a mass ratio of 1:2-4; the surface of the surface-modified nano-silica aerogel powder is grafted with aluminum-silicon active groups, with a particle size of 1-5 μm and a closed-cell rate of ≥90%; the composite plate forms a four-level gradient closed-cell body with a total porosity of 80%-92%, and the four-level gradient closed-cell body also includes four-level mesopores composed of aerogel powder, with a total closed-cell rate of ≥95%.

[0011] A method for preparing a cenosphere refractory and heat-insulating composite board, comprising the following steps: S1. Preparation of modified cenospheres: First, fly ash is washed with water to remove dust and impurities, passed through a 100-200 mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenospheres; then, the hollow cenospheres are immersed in an aluminum-silicon composite sol and stirred at room temperature for 1-2 hours to allow the sol to be uniformly adsorbed on the surface of the cenospheres; after filtration, they are dried at 60-80℃ for 1-2 hours to obtain modified cenospheres; S2. Slurry preparation: First, add the composite gel matrix to water and stir at 1000-2000 rpm for 5-10 minutes to obtain a uniform slurry; then add chopped polycrystalline fibers and stir at 600-800 rpm for 3-5 minutes to uniformly disperse the chopped polycrystalline fibers and form a network structure; finally, add modified cenospheres and stir at 300-500 rpm for 2-3 minutes to fully overlap the ends of the chopped polycrystalline fibers with the modified cenospheres to form a slurry containing a three-dimensional support skeleton. S3. Molding and curing: The slurry prepared in the previous step is injected into a flat mold and molded under a pressure of 0.2-0.8 MPa or directly cast to obtain a wet blank with a thickness of 5-50 mm. S4. In-situ hydration curing and drying: The wet blank is placed in an environment with a normal temperature of 20-30℃ and a humidity of ≥85% for in-situ hydration curing for 48-72 hours, so that the composite cementitious matrix can be directionally nucleated and grown on the surface of the active transition shell of the modified cenospheres, and the three-dimensional support skeleton is fixed. Then, after demolding, it is dried at 80-110℃ to constant weight to obtain the finished composite board. During drying, continuous drying in a tunnel kiln is adopted, and the drying temperature is set in stages to adapt to large-scale mass production.

[0012] Furthermore, the aluminum-silicon composite sol has a solid content of ≥20%, a calcium-silicon molar ratio of 0.8-1.2, and an aluminum-silicon molar ratio of 0.3-0.5; the chopped polycrystalline fibers are pre-modified with an aqueous solution of 1%-3% silane coupling agent and then dried before use.

[0013] Furthermore, the sol is an aluminum-silicon composite sol doped with nano-ZrO2 whisker nucleating agent, wherein the doping amount of the aluminum-silicon composite sol is 0.5-2 wt% of the sol solid content, the sol solid content is ≥20%, the calcium-silicon molar ratio is 0.8-1.2, and the aluminum-silicon molar ratio is 0.3-0.5.

[0014] Compared with the prior art, the cenosphere refractory and heat-insulating composite board and its preparation method of the present invention have the following advantages: 1. Improves interfacial bonding strength: Modified cenospheres achieve a continuous gradient transition of thermal expansion coefficients between the cenospheres and the matrix through a gradient thermal expansion active core-shell structure. At the same time, the active transition shell layer enables the directional nucleation and growth of the matrix on the cenosphere surface, forming a chemical bonding interface, which greatly improves the interfacial bonding strength.

[0015] 2. Combining high thermal insulation and high strength: A three-dimensional support skeleton is formed by modified cenospheres and short-cut polycrystalline fibers. Even with a high cenosphere content, a stable continuous load-bearing structure can still be formed. The dry density can be as low as 120kg / m³, the thermal conductivity is as low as 0.025W / (m•K), and the flexural strength is ≥2.2MPa.

[0016] 3. Further improve the strength of the composite plate: Under the premise of online contact and overlap of the three-dimensional support skeleton, after the addition of in-situ whiskers, the overlap point forms a three-dimensional surface contact combination of chemical bonding and mechanical anchoring of whiskers, and the strength of the skeleton node is further improved.

[0017] 4. Capable of combining thermal insulation and high-temperature stability: The three-level gradient closed-cell structure is an interlocking skeleton that is naturally formed and completely integrated with the load-bearing system. No additional pore-forming agent is required. It achieves ultra-low thermal conductivity through multi-level closed cells and ensures that the pores do not collapse at high temperatures through the skeleton structure. The linear shrinkage rate is ≤1.2% after 3 hours of insulation at 1200℃, the maximum service temperature is increased to 1300℃, and the fire resistance limit is ≥5 hours. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the cenosphere fire-resistant and heat-insulating composite board of the present invention.

[0019] Figure 2 This is a schematic diagram of the preparation process of the cenosphere refractory and heat-insulating composite board of the present invention.

[0020] Figure labels: 1. Modified cenospheres, 2. Short-cut polycrystalline fibers, 3. Composite cementitious matrix. Detailed Implementation

[0021] like Figure 1 and Figure 2 As shown, the cenosphere fire-resistant and heat-insulating composite board of the present invention includes a composite board body, wherein the composite board body comprises: Modified cenospheres 1, comprising hollow cenospheres, the surface of which is coated with an active transition shell layer of aluminum-silicon system homologous to the composite cementitious matrix, forming a core-shell structure; the hollow cenospheres have a particle size of 45-180 μm, a closed-cell rate ≥96%, and a refractoriness ≥1650℃; the active transition shell layer has a calcium-silicon molar ratio of 0.8-1.2, an aluminum-silicon molar ratio of 0.3-0.5, and a thickness of 100-300 nm; the active transition shell layer has a surface-active hydroxyl content ≥1.0 mmol / g; and a coefficient of thermal expansion of 24 × 10⁻⁶. -6 / ℃, the active transition shell is between 0.5 × 10⁻⁶ and the thermal expansion coefficient of the hollow bead. -6 / ℃ and the coefficient of thermal expansion of the composite cementitious matrix are 5-8×10 -6 The temperature range (°C) can avoid thermal mismatch between hollow cenospheres and composite cementitious matrix; Short-cut polycrystalline fibers 2, the two ends of which are bridged with the active transition shell of modified cenospheres 1 to form chemical bonds, constituting a three-dimensional support skeleton for continuous load-bearing body; The composite cementitious matrix 3 fills the gaps in the three-dimensional support skeleton to form an integrated structure. The composite plate uses modified cenospheres 1 with a core-shell structure as the core carrier, and is bridged by short-cut polycrystalline fibers 2 to form a three-dimensional support skeleton. The composite cementitious matrix 3 fills the gaps in the three-dimensional support skeleton to form an integrated structure. The composite cementitious matrix 3 only serves as an interface filler and binder phase, and does not serve as the main carrier unit. This can solve the problem of mutual interference between cenosphere dosage and structural strength, thereby simultaneously taking into account thermal insulation and structural strength. The composite plate is composed of the following components by weight: 140-60 parts modified cenospheres, 315-30 parts composite cementitious matrix, 24-12 parts chopped polycrystalline fibers, and 20-40 parts water; the active transition shell has a calcium-silicon molar ratio of 0.8-1.2, an aluminum-silicon molar ratio of 0.3-0.5, and a thickness of 100-300 nm. The chopped polycrystalline fiber 2 is a polycrystalline mullite fiber or a polycrystalline alumina fiber with a diameter of 24 μm, a length of 24 mm, a crystalline phase content of ≥98%, and no glass phase; the mass ratio of the chopped polycrystalline fiber 2 to the modified cenosphere 1 is 1:5-10.

[0022] The composite cementitious matrix 3 is a composite system of high-alumina cement and metakaolin, with a mass ratio of high-alumina cement to metakaolin of 6-8:2-4. The high-alumina cement has an Al2O3 content of ≥70%, and the metakaolin has a total active Al2O3 and SiO2 content of ≥95%.

[0023] The composite plate contains a three-level gradient closed-cell body with a total porosity of 75%-90%. This three-level gradient closed-cell body comprises primary hollow closed-cells (hollow beads), secondary closed micron-pores (the gaps in the three-dimensional support framework), and tertiary nano-closed-cells (the composite cementitious matrix 3). The primary hollow closed-cells have a pore size of 45-180 μm and a porosity of 60%-70%; the secondary closed micron-pores have a pore size of 1-8 μm and a porosity of 20%-25%; and the tertiary nano-closed-cells have a pore size of 20-100 nm and a porosity of 5%-15%. The primary hollow closed-cells provide core thermal insulation, the secondary closed micron-pores provide thermal expansion buffering and supplementary thermal insulation, and the tertiary nano-closed-cells reduce solid-phase thermal conductivity. The three-level gradient closed-cell body is naturally formed by the three-dimensional support framework, requiring no additional pore-forming agent, and is completely integrated with the load-bearing system, preventing pore collapse at high temperatures.

[0024] The composite plate also includes the following components by weight: 0.1-0.5 parts of calcium stearate foam stabilizer, used to regulate the nano-closed-pore structure of the composite gel matrix 3; 0.2-1.0 parts of silane coupling agent, used to further strengthen the interfacial bonding force between the short-cut polycrystalline fiber 2, the modified cenosphere 1 and the composite gel matrix 3; the hydration products of the composite gel matrix 3 are homologous to the active transition shell layer on the surface of the hollow cenosphere, which can achieve directional nucleation growth and strengthen the interfacial bonding.

[0025] The active transition shell is also doped with 0.5-2wt% of nano ZrO2 whisker nucleating agent; radially arranged mullite whiskers are grown in situ on the surface of the active transition shell, the mullite whiskers have a diameter of 50-200nm, a length of 2-5μm, and an aspect ratio of 10-50; one end of the mullite whisker is embedded in the active transition shell to form a chemical bond, and the other end extends into the composite cement matrix 3 to form a mechanical anchor, thus forming a double anchoring interface structure between the float and the matrix.

[0026] The composite cementitious matrix 3 is a composite system of high-alumina cement, metakaolin, and crystal form regulator, with a mass ratio of 6-8:2-4:0.5-2. The crystal form regulator is a mixture of nano-mullite seed crystals and active silica powder, with a mass ratio of 1:1-3. The nano-mullite seed crystals have a particle size of 20-50 nm and a crystal phase content of ≥99%, while the active silica powder has a particle size of 100-200 nm and a SiO2 content of ≥98%. The three-dimensional network hydrated gel generated by the crystal form control matrix uniformly coats the surface of the three-dimensional support framework without stress concentration caused by plate-like crystals. The whiskers form microcracks in the matrix, bridging and deflecting them to prevent crack propagation. Specifically, the composite plate generates an active transition shell layer outside the hollow cenospheres and in-situ generates mullite whiskers. Short-cut polycrystalline fibers 2 form a continuous three-dimensional support framework, and the crystal form control matrix forms a continuous thermal expansion gradient without any discontinuities, resulting in no interfacial thermal mismatch stress at high temperatures. One end of the in-situ whisker is embedded in the core-shell active layer, and the other end extends into the composite gel matrix 3, becoming a transition structure of the thermal expansion gradient. The crystal form control agent regulates the formation of the crystal form control matrix. The high-temperature crystalline phase of the crystal form control matrix is ​​completely homologous to the whiskers, fibers, and core-shell layer, with no crystal form abrupt changes.

[0027] The composite plate also includes 0.3-1.2 parts of a composite foam stabilizing and pore-locking agent, which is a mixture of calcium stearate and surface-modified nano-silica aerogel powder, with a mass ratio of 1:2-4. The surface of the surface-modified nano-silica aerogel powder is grafted with aluminum-silicon active groups, with a particle size of 1-5 μm and a closed-cell rate of ≥90%. The composite plate forms a four-level gradient closed-cell body with a total porosity of 80%-92%, which also includes four-level mesopores composed of aerogel powder, with a total closed-cell rate of ≥95%.

[0028] A method for preparing a cenosphere refractory and heat-insulating composite board, comprising the following steps: S1. Preparation of modified cenospheres 1: First, fly ash is washed with water to remove dust and impurities, passed through a 100-200 mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenospheres; then, the hollow cenospheres are immersed in an aluminum-silicon composite sol and stirred at room temperature for 1-2 hours to allow the sol to be uniformly adsorbed on the surface of the cenospheres; after filtration, they are dried at 60-80℃ for 1-2 hours to obtain modified cenospheres 1. S2. Slurry preparation: First, add the composite gel matrix 3 to water and stir at 1000-2000 rpm for 5-10 minutes to obtain a uniform slurry; then add the chopped polycrystalline fibers 2 and stir at 600-800 rpm for 3-5 minutes to uniformly disperse the chopped polycrystalline fibers 2 to form a network structure; finally, add the modified cenospheres 1 and stir at 300-500 rpm for 2-3 minutes to fully overlap the two ends of the chopped polycrystalline fibers 2 with the modified cenospheres 1 to form a slurry containing a three-dimensional support skeleton. S3. Molding and curing: The slurry prepared in the previous step is injected into a flat mold and molded under a pressure of 0.2-0.8 MPa or directly cast to obtain a wet blank with a thickness of 5-50 mm. S4. In-situ hydration curing and drying: The wet blank is placed in an environment with a normal temperature of 20-30℃ and a humidity of ≥85% for in-situ hydration curing for 48-72 hours, so that the composite cementitious matrix 3 can be oriented to nucleate and grow on the surface of the active transition shell layer of the modified cenospheres 1, and fix the three-dimensional support skeleton. Then, after demolding, it is dried at 80-110℃ to constant weight to obtain the finished composite board. During drying, continuous drying in a tunnel kiln is adopted, and the drying temperature is set in stages to adapt to large-scale mass production.

[0029] The aluminum-silicon composite sol has a solid content of ≥20%, a calcium-silicon molar ratio of 0.8-1.2, and an aluminum-silicon molar ratio of 0.3-0.5; the short-cut polycrystalline fibers 2 are pre-modified with an aqueous solution of 1%-3% silane coupling agent and then dried before use.

[0030] The sol is an aluminum-silicon composite sol doped with nano-ZrO2 whisker nucleating agent. The doping amount of the aluminum-silicon composite sol is 0.5-2 wt% of the sol solid content, the sol solid content is ≥20%, the calcium-silicon molar ratio is 0.8-1.2, and the aluminum-silicon molar ratio is 0.3-0.5.

[0031] The raw materials used in the embodiments of this invention are all commercially available industrial-grade products, as detailed below: Hollow fly ash cenospheres: power plant solid waste, particle size 45-180μm, closed cell rate ≥96%, refractoriness ≥1650℃; Industrial-grade aluminum-silicon composite sol: solid content 25%, calcium-silicon molar ratio 1:1, aluminum-silicon molar ratio 0.4:1. High-alumina cement: CA-50 type, Al2O3 content ≥70%, #625; Metakaolin: 1250 mesh, total active Al2O3 and SiO2 content ≥95%; Short-cut polycrystalline mullite fiber: 24μm in diameter, 24mm in length, crystalline phase content ≥98%, no glass phase; Short-cut polycrystalline alumina fibers: 24μm in diameter, 24mm in length, crystalline phase content ≥98%, no glass phase; Silane coupling agent: KH-550, industrial grade; Calcium stearate: Industrial grade foam stabilizer.

[0032] Example 1: The cenosphere fire-resistant and heat-insulating composite board of this embodiment is a general-purpose mass-produced cenosphere fire-resistant and heat-insulating composite board, suitable for building fire protection and conventional industrial heat insulation applications. The composite board includes the following components by weight: 150 parts modified cenospheres, 325 parts composite cementitious matrix (17.5 parts high-alumina cement, 7.5 parts metakaolin), 8 parts short-cut polycrystalline mullite fiber, 0.3 parts calcium stearate foam stabilizer, 0.5 parts KH-550 silane coupling agent, and 30 parts water. The preparation method includes the following steps: S1. Preparation of modified cenospheres 1: Hollow cenospheres made from fly ash were washed with water to remove impurities, passed through a 150-mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenosphere bodies; the hollow cenosphere bodies were immersed in industrial-grade aluminum-silicon composite sol and stirred at room temperature for 1.5 hours to allow the sol to be uniformly adsorbed onto the surface of the cenospheres; after filtration, they were dried at 70℃ for 1.5 hours to obtain core-shell structure modified cenospheres 1, with an active transition shell thickness of 150-200 nm and a coefficient of thermal expansion of 3×10⁻⁶. -6 / ℃; S2. Slurry preparation: Add composite gel matrix 3, calcium stearate, and silane coupling agent to water and stir at high speed of 1500 rpm for 8 minutes to obtain a uniform slurry; first add short-cut polycrystalline mullite fibers pre-modified with silane coupling agent and stir at medium speed of 700 rpm for 4 minutes to make the fibers uniformly dispersed to form a network structure; then add modified cenospheres 1 and stir at low speed of 400 rpm for 2.5 minutes to make the ends of the fibers fully overlap with the modified cenospheres 1 to form a slurry containing a three-dimensional support skeleton. S3. Molding and curing: The slurry is injected into a flat mold, molded under low pressure of 0.5MPa, and held under pressure for 20s to obtain a wet blank with a thickness of 10mm. S4 In-situ hydration curing and drying: The wet blank is placed in an environment with a normal temperature of 25℃ and a humidity of ≥90% for in-situ hydration curing for 60 hours, with an additional pressure of 0.12MPa applied every 12 hours; after demolding, it is dried at 100℃ to constant weight to obtain the cenosphere refractory and heat-insulating composite board.

[0033] Example 2: The cenosphere refractory and heat-insulating composite board of this embodiment is a lightweight cenosphere refractory and heat-insulating composite board, which is suitable for scenarios such as ships and high-speed railways with strict weight requirements. The composite board includes the following components by weight: 160 parts modified cenospheres, 318 parts composite cementitious matrix (12.6 parts high alumina cement, 5.4 parts metakaolin), 5 parts short-cut polycrystalline mullite fiber, 0.5 parts calcium stearate foam stabilizer, 0.3 parts KH-550 silane coupling agent, and 35 parts water. The preparation method includes the following steps: S1. Preparation of modified cenosphere 1: Hollow cenospheres made from fly ash were washed with water to remove impurities, passed through a 100-mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenospheres; the hollow cenospheres were immersed in industrial-grade aluminum-silicon composite sol, stirred and soaked at room temperature for 1 hour, filtered, and dried at 60℃ for 2 hours to obtain modified cenosphere 1, with an active transition shell thickness of 100-150 nm. S2. Slurry preparation: Add composite gel matrix 3, calcium stearate and silane coupling agent to water, stir at high speed of 1200 rpm for 10 min to obtain a uniform slurry; first add short-cut polycrystalline mullite fiber, stir at medium speed of 600 rpm for 5 min, then add modified cenosphere 1, stir at low speed of 300 rpm for 3 min to form a slurry containing a three-dimensional support skeleton. S3. Molding and curing: The slurry is injected into a flat mold, molded under low pressure of 0.3MPa, and held under pressure for 30s to obtain a wet blank with a thickness of 15mm. S4 In-situ hydration curing and drying: The wet blank is placed in an environment with a normal temperature of 20℃ and a humidity of ≥85% for in-situ hydration curing for 72 hours; after demolding, it is dried at 80℃ for 6 hours, and then heated to 105℃ to dry to constant weight to obtain the cenosphere fire-resistant and heat-insulating composite board.

[0034] Example 3: The cenosphere refractory insulation composite board of this embodiment is a high fire-resistant cenosphere refractory insulation composite board. It is a high fire-resistant product and is suitable for ultra-high temperature scenarios such as metallurgical kilns, high-temperature pipelines, and new energy high-temperature equipment. The raw materials prepared by weight are as follows: 140 parts modified cenospheres, 330 parts composite cementitious matrix (21 parts high-alumina cement and 9 parts metakaolin), 12 parts short-cut polycrystalline alumina fibers, 0.2 parts calcium stearate foam stabilizer, 0.8 parts KH-560 silane coupling agent, and 40 parts water. The preparation method includes the following steps: S1. Preparation of core-shell structure modified cenospheres 1: Hollow cenospheres made from fly ash were washed with water to remove impurities, passed through a 200-mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenospheres; the hollow cenospheres were immersed in industrial-grade aluminum-silicon composite sol, stirred and soaked at room temperature for 2 hours, filtered, and dried at 80℃ for 1 hour to obtain core-shell structure modified cenospheres 1, with an active transition shell thickness of 200-300 nm; S2. Slurry preparation: Add composite gel matrix 3, calcium stearate and silane coupling agent to water, stir at high speed of 2000 rpm for 5 min to obtain a uniform slurry; first add short-cut polycrystalline alumina fibers, stir at medium speed of 800 rpm for 3 min, then add core-shell structure modified cenospheres 1, stir at low speed of 500 rpm for 2 min to form a slurry containing a three-dimensional support skeleton. S3. Molding and curing: The slurry is injected into a flat mold, molded under low pressure of 0.8MPa, and held under pressure for 15s to obtain a wet blank with a thickness of 20mm. S4. In-situ hydration curing and drying: The wet blank is placed in an environment with a normal temperature of 30℃ and a humidity of ≥90% for in-situ hydration curing for 48 hours; after demolding, it is dried at 110℃ to constant weight to obtain the cenosphere fire-resistant and heat-insulating composite board.

[0035] Comparative Example 1: The cenosphere refractory and heat-insulating composite board in this comparative example is a traditional cenosphere refractory and heat-insulating board. This comparative example is a commercially available traditional cenosphere board. Unmodified cenospheres 1 are used as filler, and cement is used as a continuous load-bearing matrix without an interlocking skeleton structure. According to the component weight parts, the raw materials are the same as those in Example 1: 50 parts of unmodified fly ash cenospheres, 25 parts of high-alumina cement, 8 parts of short-cut polycrystalline mullite fiber, and 30 parts of water. The preparation method adopts the traditional process: all raw materials are mixed, stirred at high speed of 2000 rpm for 10 min, cast into shape, cured at room temperature for 7 days, and dried at 100℃ to constant weight to obtain a cenosphere board with a thickness of 10 mm.

[0036] Comparative Example 2: The cenosphere refractory and heat-insulating composite board in this comparative example is a conventional fiber-reinforced cenosphere board. This comparative example uses an existing conventional fiber-reinforced structure, with unmodified cenospheres and only fiber reinforcement. It lacks a core-shell structure and interlocking skeleton. The raw materials prepared by weight are the same as in Example 1: 50 parts of unmodified fly ash cenospheres, 17.5 parts of high-alumina cement, 7.5 parts of metakaolin, 8 parts of short-cut polycrystalline mullite fiber, 0.5 parts of KH-550 silane coupling agent, and 30 parts of water. The preparation method is as follows: all raw materials are mixed, stirred stepwise, molded, cured at room temperature for 3 days, and dried at 100°C to constant weight to obtain a cenosphere board with a thickness of 10 mm.

[0037]

[0038] All embodiments and comparative examples of this invention were tested using the following national standards: 1. Dry density: GB / T5486-2008 "Test Methods for Inorganic Rigid Thermal Insulation Products"; 2. Thermal conductivity: GB / T10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method", test temperature 25℃; 3. Flexural strength and compressive strength: GB / T5486-2008; 4. Impact resistance: GB / T25975-2010 "Rock wool products for external wall insulation of buildings"; 5. Fire resistance rating: GB / T9978-2008 "Test Methods for Fire Resistance of Building Components"; 6. High-temperature linear shrinkage: GB / T5486-2008, test conditions: 1200℃ for 3 hours; 7. Combustion performance: GB8624-2012 "Classification of Combustion Performance of Building Materials and Products"; 8. Density deviation: Take three samples (top, middle, and bottom) evenly along the thickness direction of the board, test the dry density, and calculate the relative deviation.

[0039] The test results in Table 1 show that the composite boards prepared in Examples 1-3 of this invention have significantly lower thermal conductivity while maintaining a much lower dry density than the comparative example. Simultaneously, their flexural strength and impact strength are increased by more than 150%, achieving a complete balance between high thermal insulation and high strength. The density deviation of the boards in these examples is ≤3%, and the mass production qualification rate is ≥96%, completely solving the problems of floating and delamination of traditional beaded boards and low mass production qualification rates. The linear shrinkage rate at 1200℃ in Examples 1-3 is ≤1.2%, with no cracking or pulverization at 1300℃, a fire resistance limit of ≥4.5h, and high-temperature stability that is more than 3 times higher than the comparative example, fully meeting the requirements for use in ultra-high temperature scenarios. Compared to Comparative Example 2, the flexural strength of Example 1 is increased by 85.7%, the thermal conductivity is reduced by 34.9%, and the linear shrinkage rate at 1200℃ is reduced by 72.2%.

[0040] The raw materials used in the embodiments of the present invention also include the following components: Nano ZrO2 whisker nucleating agent: particle size 30-50nm, monoclinic phase content ≥95%; nano mullite seed crystals: particle size 20-50nm, crystalline phase content ≥99%; active silica micro powder: 1250 mesh, SiO2 content ≥98%, activity ≥90%; surface modified nano silica aerogel micro powder: particle size 1-5μm, closed-pore rate ≥90%, surface grafted with aluminum-silicon active groups.

[0041] Example 4: The cenosphere refractory and heat-insulating composite board of this embodiment is an improvement on the general mass-produced cenosphere refractory and heat-insulating composite board of Example 1. Specifically, it includes the following components by weight: 150 parts modified cenospheres, 326 parts composite cementitious matrix (17.5 parts high-alumina cement, 7.5 parts metakaolin, 0.5 parts nano mullite seed crystals, 0.5 parts active silica powder), 8 parts short-cut polycrystalline mullite fibers, 0.8 parts composite foam stabilizing and pore-locking agent (0.2 parts calcium stearate, 0.6 parts modified aerogel powder), 0.5 parts KH-550 silane coupling agent, and 30 parts water. The preparation method includes the following steps: S1. Preparation of modified cenosphere 1: Hollow cenospheres made from fly ash were washed with water to remove impurities, passed through a 150-mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenospheres; the hollow cenospheres were immersed in an industrial-grade aluminum-silicon composite sol doped with 1wt% nano ZrO2 whisker nucleating agent, stirred and soaked at room temperature for 1.5h, filtered, and dried at 70℃ for 1.5h to obtain modified cenosphere 1 with a core-shell structure; S2. Slurry preparation: Add composite gel matrix 3, composite foam stabilizer and pore lock agent, and silane coupling agent to water, and stir at high speed of 1500 rpm for 8 min to obtain a uniform slurry; first add short-cut polycrystalline mullite fibers pre-modified with silane coupling agent, and stir at medium speed of 700 rpm for 4 min to form a network structure; then add core-shell structure modified cenosphere 1 precursor, and stir at low speed of 400 rpm for 2.5 min to form a slurry containing a three-dimensional support skeleton. S3. Molding and curing: The slurry is injected into a flat mold, molded under low pressure of 0.5MPa, and held under pressure for 20s to obtain a wet blank with a thickness of 10mm. S4. In-situ hydration curing and simultaneous growth of whiskers: The wet blank is placed in an environment with a room temperature of 25℃ and a humidity of ≥90% for in-situ hydration curing for 60h, with a pressure of 0.12MPa applied every 12h; after demolding, it is dried at 100℃ to constant weight to obtain a cenosphere refractory and heat-insulating composite board.

[0042] Example 5: The cenosphere refractory and heat-insulating composite board of this embodiment is an improvement on the lightweight cenosphere refractory and heat-insulating composite board of Example 2. Specifically, it includes the following components by weight: 160 parts modified cenospheres, 319 parts composite cementitious matrix (12.6 parts high alumina cement, 5.4 parts metakaolin, 0.3 parts nano mullite seed crystals, 0.7 parts active silica powder), 5 parts short-cut polycrystalline mullite fibers, 1.2 parts composite foam stabilizing and pore-locking agent (0.3 parts calcium stearate, 0.9 parts modified aerogel powder), 0.3 parts KH-550 silane coupling agent, and 35 parts water. The preparation method includes the following steps: S1. Preparation of modified cenosphere 1: Hollow cenospheres made from fly ash were washed with water to remove impurities, passed through a 100-mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenospheres; the hollow cenospheres were immersed in an industrial-grade aluminum-silicon composite sol doped with 0.5wt% nano ZrO2 whisker nucleating agent, stirred and soaked at room temperature for 1 hour, filtered, and dried at 60℃ for 2 hours to obtain modified cenosphere 1 with a core-shell structure; Preparation of S2 interlocking precursor slurry: Add composite gel matrix 3, composite foam stabilizer and pore lock agent and silane coupling agent to water, stir at high speed of 1200 rpm for 10 min to obtain a uniform slurry; first add short-cut polycrystalline mullite fiber, stir at medium speed of 600 rpm for 5 min, then add core-shell structure modified cenosphere 1 precursor, stir at low speed of 300 rpm for 3 min to form a slurry containing a three-dimensional support skeleton; S3 Molding and Curing: The interlocking precursor slurry is injected into a flat mold, molded under low pressure of 0.3MPa, and held under pressure for 30s to obtain a wet blank with a thickness of 15mm. S4 In-situ hydration curing and simultaneous whisker growth: The wet blank is placed in an environment with a room temperature of 20℃ and a humidity of ≥85% for in-situ hydration curing for 72 hours; after demolding, it is dried at 80℃ for 6 hours, and then heated to 105℃ to dry to constant weight to obtain the cenosphere fire-resistant and heat-insulating composite board.

[0043] Example 6: The cenosphere refractory and heat-insulating composite board of this embodiment is a further improvement on the high fire-resistant cenosphere refractory and heat-insulating composite board of Example 3. Specifically, it includes the following components by weight: 140 parts modified cenospheres, 331 parts composite cementitious matrix (21 parts high alumina cement, 9 parts metakaolin, 0.7 parts nano mullite seed crystals, 0.3 parts active silica powder), 12 parts short-cut polycrystalline alumina fibers, 0.5 parts composite foam stabilizing and pore-locking agent (0.15 parts calcium stearate, 0.35 parts modified aerogel powder), 0.8 parts KH-560 silane coupling agent, and 40 parts water; The preparation method includes the following steps: S1. Preparation of modified cenospheres 1: Hollow cenospheres made from fly ash were washed with water to remove impurities, passed through a 200-mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenospheres; the hollow cenospheres were immersed in an industrial-grade aluminum-silicon composite sol doped with 2wt% nano ZrO2 whisker nucleating agent, stirred and soaked at room temperature for 2 hours, filtered, and dried at 80℃ for 1 hour to obtain modified cenospheres 1 with a core-shell structure; S2. Slurry preparation: Add composite gel matrix 3, composite foam stabilizer and pore lock agent and silane coupling agent to water, stir at high speed of 2000 rpm for 5 min to obtain a uniform slurry; first add short-cut polycrystalline alumina fibers, stir at medium speed of 800 rpm for 3 min, then add core-shell structure modified cenosphere 1 precursor, stir at low speed of 500 rpm for 2 min to form a slurry. S3. Molding and curing: The interlocking precursor slurry is injected into a flat mold, and low-pressure molding is performed at 0.8MPa for 15s to obtain a wet blank with a thickness of 20mm. S4 In-situ hydration curing and simultaneous growth of whiskers: The wet blank is placed in an environment with a room temperature of 30℃ and a humidity of ≥90% for in-situ hydration curing for 48 hours; after demolding, it is dried at 110℃ to constant weight to obtain a cenosphere refractory and heat-insulating composite board.

[0044] Comparative Example 3: Comparative Example 3, which is the same as Example 1, is a cenosphere composite plate with only added whiskers and no synergistic system. Only nano ZrO2 whisker nucleating agent is added, without crystal form regulator and composite foam stabilizer and pore lock agent, and without core-shell structure modification. The other raw materials and preparation methods are the same as in Example 1.

[0045] Comparative Example 4: Comparative Example 4, which is the same as Example 1, is a floating bead plate with only aerogel and no synergistic system. Only unmodified aerogel powder is added, without whisker anchoring structure and crystal form regulator. The other raw materials and preparation methods are the same as in Example 1.

[0046] The performance of the composite panels produced in Examples 4 to 6, and Comparative Examples 3 and 4 was tested, and the test results are shown in Table 2.

[0047] The test results in Table 2 show that, compared with Example 1, the composite plate prepared in Example 4 of this invention has a 5% lower dry density, a 7.1% lower thermal conductivity at 25℃, a 19.2% higher flexural strength, a 20% lower linear shrinkage rate at 1200℃, and a 20% higher fire resistance limit. Furthermore, as can be seen from Comparative Examples 3 and 4, adding whiskers or aerogel alone can only achieve a slight performance improvement.

[0048] The above embodiments are merely preferred embodiments of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention are included within the scope of the present invention.

Claims

1. A type of cenosphere fire-resistant and heat-insulating composite board, characterized in that: Includes a composite panel, the composite panel comprising: Modified cenospheres, comprising hollow cenosphere bodies, the surface of which is coated with an aluminum-silicon based active transition shell; the hollow cenosphere body has a particle size of 45-180 μm and a closed-cell rate of ≥96%; the active transition shell has a surface-active hydroxyl content of ≥1.0 mmol / g; the active transition shell has a calcium-silicon molar ratio of 0.8-1.2, an aluminum-silicon molar ratio of 0.3-0.5, and a thickness of 100-300 nm; Short-cut polycrystalline fibers, wherein the two ends of the short-cut polycrystalline fibers are bridged with the active transition shell of modified cenospheres to form a three-dimensional support framework. A composite cementitious matrix, wherein the composite cementitious matrix fills the gaps in the three-dimensional support skeleton to form an integrated structure; The composite plate is composed of the following components by weight: 40-60 parts modified cenospheres, 15-30 parts composite cementitious matrix, 4-12 parts chopped polycrystalline fibers, and 20-40 parts water. The active transition shell has a calcium-to-silicon molar ratio of 0.8-1.2, an aluminum-to-silicon molar ratio of 0.3-0.5, and a thickness of 100-300 nm.

2. The perlite refractory and heat-insulating composite board according to claim 1, characterized in that: The chopped polycrystalline fibers are polycrystalline mullite fibers or polycrystalline alumina fibers, with a diameter of 24 μm, a length of 24 mm, a crystalline phase content of ≥98%, and no glass phase.

3. The perlite refractory and heat-insulating composite board according to claim 1, characterized in that: The composite cementitious matrix is ​​a composite system of high-alumina cement and metakaolin, wherein the mass ratio of high-alumina cement to metakaolin is 6-8:2-4, the Al2O3 content of the high-alumina cement is ≥70%, and the total content of active Al2O3 and SiO2 of the metakaolin is ≥95%. The composite plate body forms a three-level gradient closed-cell body with a total porosity of 75%-90%. The three-level gradient closed-cell body includes primary hollow closed pores of hollow beads, secondary closed micron pores of three-dimensional supporting skeleton gaps, and tertiary nano closed pores of composite cementitious matrix. The primary hollow closed pores have a pore size of 45-180μm and a porosity of 60%-70%; the secondary closed micron pores have a pore size of 1-8μm and a porosity of 20%-25%; and the tertiary nano closed pores have a pore size of 20-100nm and a porosity of 5%-15%.

4. The perlite refractory and heat-insulating composite board according to claim 1, characterized in that: The composite plate also includes the following components in parts by weight: 0.1-0.5 parts of calcium stearate foam stabilizer and 0.2-1.0 parts of silane coupling agent.

5. The perlite refractory and heat-insulating composite board according to claim 1, characterized in that: The active transition shell is also doped with 0.5-2wt% of nano ZrO2 whisker nucleating agent; radially arranged mullite whiskers are grown in situ on the surface of the active transition shell, the mullite whiskers have a diameter of 50-200nm, a length of 2-5μm, and an aspect ratio of 10-50.

6. The cenosphere fire-resistant and heat-insulating composite board according to claim 1, characterized in that: The composite cementitious matrix is ​​a composite system of high-alumina cement, metakaolin, and crystal form regulator, with a mass ratio of 6-8:2-4:0.5-2. The crystal form regulator is a mixture of nano-mullite seed crystals and active silica powder, with a mass ratio of 1:1-3. The nano-mullite seed crystals have a particle size of 20-50 nm and a crystalline phase content of ≥99%, while the active silica powder has a particle size of 100-200 nm and a SiO2 content of ≥98%.

7. The perlite refractory and heat-insulating composite board according to claim 1, characterized in that: The composite plate also includes 0.3-1.2 parts of a composite foam stabilizing and pore-locking agent, which is a mixture of calcium stearate and surface-modified nano-silica aerogel powder, with a mass ratio of 1:2-4. The surface of the surface-modified nano-silica aerogel powder is grafted with aluminum-silicon active groups, with a particle size of 1-5 μm and a closed-cell rate of ≥90%. The composite plate forms a four-level gradient closed-cell body with a total porosity of 80%-92%, which also includes four-level mesopores composed of aerogel powder, with a total closed-cell rate of ≥95%.

8. A method for preparing a cenosphere refractory and heat-insulating composite board, used to prepare the cenosphere refractory and heat-insulating composite board according to any one of claims 1 to 7, characterized in that: Includes the following steps: S1. Preparation of modified cenospheres: First, fly ash is washed with water to remove dust and impurities, passed through a 100-200 mesh sieve, and dried at 105℃ to constant weight to obtain hollow cenospheres; then, the hollow cenospheres are immersed in an aluminum-silicon composite sol and stirred at room temperature for 1-2 hours to allow the sol to be uniformly adsorbed on the surface of the cenospheres; after filtration, they are dried at 60-80℃ for 1-2 hours to obtain modified cenospheres; S2. Slurry preparation: First, add the composite gel matrix to water and stir at 1000-2000 rpm for 5-10 minutes to obtain a uniform slurry; then add chopped polycrystalline fibers and stir at 600-800 rpm for 3-5 minutes to uniformly disperse the chopped polycrystalline fibers and form a network structure; finally, add modified cenospheres and stir at 300-500 rpm for 2-3 minutes to overlap the ends of the chopped polycrystalline fibers with the modified cenospheres to form a slurry containing a three-dimensional support skeleton. S3. Molding and curing: Inject the slurry prepared in the previous step into a flat mold, and mold it under a pressure of 0.2-0.8 MPa, or directly cast it to obtain a wet blank with a thickness of 5-50 mm. S4. In-situ hydration curing and drying: Place the wet blank in an environment with a room temperature of 20-30℃ and a humidity of ≥85% for in-situ hydration curing for 48-72 hours. Then, after demolding, dry at 80-110℃ to constant weight to obtain the finished composite board.

9. The method for preparing the cenosphere refractory and heat-insulating composite board according to claim 8, characterized in that: The aluminum-silicon composite sol has a solid content of ≥20%, a calcium-silicon molar ratio of 0.8-1.2, and an aluminum-silicon molar ratio of 0.3-0.5; the short-cut polycrystalline fibers are pre-modified with an aqueous solution of 1%-3% silane coupling agent and then dried before use.

10. The method for preparing the cenosphere refractory and heat-insulating composite board according to claim 8, characterized in that: The sol is an aluminum-silicon composite sol doped with nano-ZrO2 whisker nucleating agent. The doping amount of the aluminum-silicon composite sol is 0.5-2 wt% of the sol solid content, the sol solid content is ≥20%, the calcium-silicon molar ratio is 0.8-1.2, and the aluminum-silicon molar ratio is 0.3-0.5.

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