Energy-saving thermal-insulation new material and preparation method thereof

Abstract

This invention belongs to the field of building materials technology, specifically relating to a novel energy-saving and thermal insulation material and its preparation method. The method includes: mixing tetraethyl orthosilicate with anhydrous ethanol, adding deionized water and hydrochloric acid to adjust the pH to an acidic range, obtaining an acidic silica sol; mixing cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate hydroxide into a modified powder, adding it to a mixed alkaline solution of dilute ammonia and anhydrous ethanol for ultrasonic dispersion to obtain a modified suspension; adding the modified suspension dropwise into the acidic silica sol to adjust the pH to a weakly alkaline range, and after gel aging, drying under supercritical conditions using anhydrous ethanol as a medium to obtain the energy-saving and thermal insulation material. The cerium-terbium co-doped strontium calcium zinc stannate is prepared by a co-precipitation-hydrothermal-calcination method, and the tin-doped layered magnesium aluminate hydroxide is prepared by a co-flow co-precipitation-hydrothermal method. The material prepared by this invention has low thermal conductivity and excellent flame retardant properties, making it suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a new energy-saving and heat-insulating material and its preparation method. Background Technology

[0002] Building energy consumption accounts for a significant proportion of global total energy consumption. Improving the thermal insulation performance of building envelopes is an effective way to reduce building operating energy consumption and achieve energy conservation and emission reduction goals. Currently, the mainstream thermal insulation materials on the market are mainly divided into two categories: organic thermal insulation materials and inorganic thermal insulation materials. Organic thermal insulation materials, represented by polyurethane foam, polystyrene foam, and phenolic foam, have outstanding advantages such as light weight, low thermal conductivity, and excellent thermal insulation effect, and are widely used in the field of building exterior wall insulation. However, organic thermal insulation materials generally have poor flame retardant properties. These materials contain a large number of hydrocarbon chains, which are highly flammable when exposed to fire, and release a large amount of toxic fumes and molten droplets during combustion, seriously threatening the safety of people and property. In recent years, building fire accidents caused or exacerbated by organic thermal insulation materials have occurred frequently, making improving the fire safety of thermal insulation materials a key technical problem that the industry urgently needs to solve.

[0003] Inorganic insulation materials such as rock wool, glass wool, perlite, and foam glass, while possessing good flame-retardant properties and thermal stability, are not easily combustible, and do not produce toxic fumes when burning, also have significant performance limitations. First, the thermal conductivity of inorganic insulation materials is generally high, typically exceeding 0.03 to 0.05 Kelvin per meter, resulting in significantly lower insulation performance compared to high-quality organic insulation materials. Second, most inorganic insulation materials have a high density, increasing the load on building structures. Furthermore, some inorganic insulation materials are prone to absorbing moisture in humid environments, leading to a severe decline in insulation performance and even phenomena such as powdering and detachment. Therefore, single-component inorganic insulation materials are insufficient to meet the dual demands of modern buildings for high energy efficiency and fire safety.

[0004] To overcome the performance limitations of single materials, researchers have begun exploring organic-inorganic composite insulation materials, attempting to combine the low thermal conductivity of organic components with the excellent flame-retardant properties of inorganic components. Among these, composite materials based on silica aerogel have attracted widespread attention due to their extremely high porosity and extremely low thermal conductivity. However, in existing composite systems, the interfacial compatibility between flame-retardant modifiers and the aerogel matrix is ​​poor, and flame retardants are prone to migration and precipitation during long-term use, leading to a decline in flame-retardant performance. Furthermore, traditional flame-retardant modifiers have relatively limited functions, making it difficult to simultaneously achieve synergistic effects such as flame retardancy, smoke suppression, infrared reflection, and improved thermal stability. While tin-containing compounds exhibit highly efficient flame-retardant and smoke-suppressing effects, the flame-retardant efficiency of pure stannates still has room for improvement. Although layered bimetallic hydroxides can exert flame-retardant effects through endothermic decomposition, existing systems exhibit poor structural stability in acidic environments, making direct composite with acidic silica sols difficult. Therefore, developing novel inorganic modified compounds that are well compatible with aerogel matrices and possess multiple synergistic functions, and designing reasonable composite processes to protect the structure of the modifier from damage, are technical challenges that urgently need to be solved in this field. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a new energy-saving and heat-insulating material and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing a novel energy-saving and heat-insulating material, comprising the following steps:

[0007] S1. By weight, mix 80-120 parts of tetraethyl orthosilicate with 200-350 parts of anhydrous ethanol, stir at room temperature, then add 30-60 parts of deionized water and 2-8 parts of hydrochloric acid to adjust the pH to 2.5-3.5, and continue stirring to obtain an acidic silica sol; mix 2-15 parts of cerium-terbium co-doped strontium calcium zinc stannate and 2-15 parts of tin-doped layered magnesium aluminate hydroxide to obtain a modifier mixed powder; add the modifier mixed powder to a mixed alkaline solution containing 5-15 parts of dilute ammonia and 50-100 parts of anhydrous ethanol, and disperse ultrasonically under an ice-water bath to obtain a modified suspension; while stirring, add the modified suspension dropwise to the acidic silica sol, adjust the pH to 7.6-8.2, stir, pour into a mold and let it stand to gel to obtain a wet gel;

[0008] S2. Age the wet gel at room temperature; after aging, place it in a reaction vessel, add 400-800 parts of anhydrous ethanol, dry at 258-262℃, and cool naturally to room temperature.

[0009] The preparation mechanism of this novel energy-saving and heat-insulating material is based on the sol-gel principle and supercritical drying technology. First, under acidic conditions, tetraethyl orthosilicate undergoes hydrolysis catalyzed by hydrochloric acid, with silanyl ethoxy groups gradually being replaced by hydroxyl groups to generate silanols, accompanied by the release of ethanol. Because the reaction system is in an acidic environment, the hydrolysis rate is relatively fast while the polycondensation rate is relatively slow. Therefore, the hydrolysis products mainly exist in the form of silanol monomers or oligomers, forming a clear acidic silica sol. Subsequently, two modifiers (cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate hydroxide) powders are pre-dispersed in a mixed alkaline solution composed of dilute ammonia and anhydrous ethanol. This alkaline environment protects the layered structure of the tin-doped layered magnesium aluminate hydroxide from damage. When this modified suspension is added dropwise to the acidic silica sol, the pH of the system gradually increases to a weakly alkaline range with the introduction of the alkaline solution. Under weakly alkaline conditions, silanols undergo condensation polymerization, with silanol groups dehydrating to form siloxane bonds, gradually crosslinking to form a three-dimensional network structure. During this process, pre-dispersed modifier powder is uniformly encapsulated within the forming silica gel network. Because the surface of the modifier powder contains abundant hydroxyl groups, these hydroxyl groups can undergo condensation reactions with the silanols, forming chemical bonds and thus enhancing the interfacial bonding between the modifier and the aerogel matrix. After rapid stirring, the sol is poured into a mold and allowed to stand, allowing the condensation reaction to continue and the network structure to continuously improve, ultimately forming a wet gel with a certain mechanical strength. During the long-term aging process at room temperature, the silanols in the network continue to condense, further strengthening the framework. Anhydrous ethanol is replaced multiple times during aging to displace water and unreacted substances from the gel channels, preparing for supercritical drying. Finally, the wet gel is placed in a high-pressure reactor and dried under supercritical conditions using anhydrous ethanol as the drying medium. When the temperature exceeds the critical temperature and pressure of ethanol, the ethanol enters the supercritical state, its gas-liquid interface disappears, and its surface tension approaches zero. Under these conditions, the pressure is released, and the ethanol directly changes from the supercritical state to the gaseous state and escapes. The three-dimensional porous network structure of the gel is completely preserved because it is not affected by capillary forces, thus obtaining a silica aerogel composite material with ultra-high porosity, ultra-low density and extremely low thermal conductivity. The two modifiers are uniformly distributed in the aerogel skeleton, giving the material excellent flame retardant properties and mechanical strength.

[0010] According to a preferred embodiment of the present invention, in step S1, the gel is allowed to stand for 25-50 minutes.

[0011] According to a preferred embodiment of the present invention, in step S2, the wet gel is aged at room temperature for 24-28 hours.

[0012] According to a preferred embodiment of the present invention, the preparation method of the cerium-terbium co-doped strontium calcium zinc stannate includes: A1, dissolving 28-33 parts by weight of zinc acetate dihydrate, 6-7 parts by weight of strontium acetate, 3-4 parts by weight of calcium acetate, 32-38 parts by weight of tin tetrachloride pentahydrate, 1-2 parts by weight of cerium nitrate hexahydrate, 0.8-1.2 parts by weight of terbium nitrate hexahydrate, and 10-20 parts by weight of hydrochloric acid in 1000-1500 parts by weight of deionized water, and stirring in a water bath at 68-72°C to obtain a mixed salt solution. Dissolve 45-55 parts of sodium hydroxide in 500-700 parts of deionized water to obtain a precipitant solution; adjust the pH of 200-300 parts of deionized water to 10.0-11.0 with sodium hydroxide solution to obtain alkaline bottom water; add the mixed salt solution and precipitant solution dropwise to the alkaline bottom water simultaneously with stirring at 74-76℃ to obtain a suspension; transfer the suspension to a reaction vessel and perform a hydrothermal reaction at 195-205℃ to obtain a reaction mixture; A2. Allow the reaction mixture to cool naturally and centrifuge to obtain a precipitate; wash the precipitate alternately with deionized water and anhydrous ethanol; dry in a vacuum drying oven at 78-82℃ to obtain a precursor powder; place the precursor powder in a muffle furnace, heat to 448-452℃ and hold, then heat to 948-952℃ and hold, cool to room temperature with the furnace, grind, and sieve.

[0013] The preparation mechanism of cerium-terbium co-doped strontium calcium zinc stannate in this invention is as follows: The synthesis of this compound adopts a multi-step method of co-precipitation-hydrothermal-calcination. First, under acid-suppressive conditions, zinc acetate dihydrate, strontium acetate, calcium acetate, tin tetrachloride pentahydrate, cerium nitrate hexahydrate, and terbium nitrate hexahydrate are dissolved in sufficient deionized water. The addition of an appropriate amount of hydrochloric acid provides a hydrogen ion environment, effectively inhibiting the premature hydrolysis of tin ions in the aqueous solution, so that all metal ions are uniformly dispersed in the form of hydrated ions. When the mixed salt solution and sodium hydroxide precipitant solution are simultaneously added dropwise to the pre-adjusted strongly alkaline bottom water in a co-current manner, the pH of the reaction system is strictly controlled within a constant strongly alkaline range. Under these conditions, all metal ions undergo instantaneous and synchronous precipitation reactions to generate hydroxides or hydroxyl oxide precursors. Among them, zinc ions, strontium ions, and calcium ions form their respective hydroxides, tin ions form tin hydroxide or stannate ions, and cerium ions and terbium ions form cerium hydroxide and terbium hydroxide. Because the co-current dropwise addition ensured a constant pH throughout the precipitation process, the metal ions achieved uniform mixing at the molecular level, avoiding phase separation caused by stepwise precipitation. Subsequently, under moderate high-temperature hydrothermal conditions, the precursor underwent recrystallization and lattice rearrangement. Tin ions gradually occupied octahedral sites, while zinc, strontium, and calcium ions jointly occupied tetrahedral and octahedral sites. Cerium and terbium ions doped into the zinc sites in the lattice, forming a hydroxide precursor with a spinel structure. Finally, during high-temperature calcination at extremely high temperatures, the precursor underwent dehydration condensation and oxidation reactions, converting hydroxide ions into oxygen anions. The metal ions rearranged to form a stable spinel-type stannate crystal structure, in which zinc, strontium, calcium, cerium, and terbium ions jointly occupied site A, and tin ions occupied site B. The co-doping of cerium and terbium introduced lattice distortion and oxygen vacancies, ultimately yielding cerium-terbium co-doped strontium-calcium-zinc stannate powder.

[0014] According to a preferred embodiment of the present invention, in step A1, the hydrothermal reaction time at 195-205°C is 24-30 hours.

[0015] According to a preferred embodiment of the present invention, in step A2, the time for holding the temperature at 448-452°C is 2-4 hours.

[0016] According to a preferred embodiment of the present invention, the preparation method of the tin-doped layered magnesium aluminate magnesium hydroxide comprises: B1, dissolving 45-55 parts by weight of magnesium nitrate hexahydrate, 20-25 parts by weight of aluminum nitrate nonahydrate, 4-6 parts by weight of calcium nitrate tetrahydrate, 6-8 parts by weight of tin tetrachloride pentahydrate, and 5-10 parts by weight of hydrochloric acid in 700-900 parts by weight of water, stirring in a water bath at 58-62°C to obtain a mixed salt solution A; dissolving 35-45 parts by weight of sodium hydroxide in 700-900 parts by weight of water to obtain a mixed alkaline solution B; and stirring in a nitrogen atmosphere... Under protective conditions and at 68-72℃, mixed salt solution A and mixed alkali solution B are simultaneously added dropwise to a reactor containing 100-200 parts of deionized water, maintaining the pH at 9.6-10.0, and stirred. After the addition is complete, stirring and aging are continued at 68-72℃ to obtain a slurry. The slurry is transferred to a reactor and hydrothermally treated at 138-142℃ to obtain a reaction solution. B2. The reaction solution is centrifuged to obtain a precipitate. The precipitate is washed alternately with deionized water and anhydrous ethanol, vacuum dried at 58-62℃, ground, and sieved.

[0017] The preparation mechanism of tin-doped layered magnesium aluminate hydroxide in this invention is as follows: The compound is synthesized using a co-precipitation method combined with hydrothermal crystallization. Magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, calcium nitrate tetrahydrate, and tin tetrachloride pentahydrate are dissolved in deionized water with the assistance of an appropriate amount of hydrochloric acid. The hydrochloric acid inhibits premature hydrolysis of tin ions, forming a transparent mixed salt solution containing magnesium, aluminum, calcium, and tin ions. Sodium hydroxide, as a precipitant, is added dropwise to the reaction vessel in parallel with the salt solution under strict inert gas protection, maintaining a constant weakly alkaline environment throughout the precipitation process. Under these alkaline conditions, magnesium, aluminum, calcium, and tin ions simultaneously undergo precipitation reactions to generate the corresponding hydroxides. Specifically, magnesium and calcium ions form six-coordinated divalent hydroxide octahedra, while aluminum and tin ions form six-coordinated hypervalent hydroxide octahedra. These octahedrons are connected by shared edges to form a positively charged lamellar structure. Magnesium and calcium ions provide divalent cations, while aluminum and tin ions provide hypervalent cations. The net positive charge of the lamellar structure is balanced by nitrate anions in the interlayer. Simultaneously, water of crystallization molecules are also present in the interlayer. The parallel-drop addition technique ensures synchronous nucleation of metal ions under constant pH, avoiding compositional inhomogeneity caused by different precipitation sequences. After precipitation, the structure is aged for an extended period at an appropriate temperature to further refine the lamellar structure. Subsequently, crystallization is performed under hydrothermal conditions at a higher temperature. The high-temperature, high-pressure environment promotes the orderly arrangement of cations in the lamellar structure and the orderly intercalation of anions in the interlayer. Simultaneously, the solid solubility of tin ions in the lamellar structure is increased. Some tin ions that fail to enter the lamellar structure may form trace amounts of magnesium hydroxystannate cubic phase, forming a hybrid structure with the layered hydroxide. Finally, after thorough washing and drying, tin-doped layered magnesium aluminate calcium hydroxide powder is obtained. The chemical formula of its lamellar structure is magnesium aluminum calcium tin hydroxy complex, and the interlayer consists of nitrate ions and water of crystallization.

[0018] According to a preferred embodiment of the present invention, in step B1, the hydrothermal treatment at 138-142°C is carried out for 12-14 hours.

[0019] According to a preferred embodiment of the present invention, in step B2, the vacuum drying time at 58-62°C is 24-30 hours.

[0020] A second aspect of the present invention provides an energy-saving and heat-insulating novel material prepared according to the preparation method of the described energy-saving and heat-insulating novel material.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The energy-saving and heat-insulating novel material and its preparation method provided by this invention have achieved many beneficial effects. First, in terms of heat insulation performance, the porous material prepared by this invention using silica aerogel as the matrix and combining sol-gel process with supercritical drying technology has extremely high porosity and extremely low solid-state thermal conductivity. The two modifiers, cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate calcium hydroxide, uniformly dispersed in the aerogel matrix, can further scatter and reflect infrared radiation, effectively suppressing radiative heat transfer. The thermal conductivity of the material of this invention is extremely low, far superior to traditional inorganic heat insulation materials, comparable to or even better than high-quality organic heat insulation materials, while overcoming the defect of poor flame retardant performance of organic materials. In addition, the introduction of the two modifiers does not destroy the three-dimensional porous network structure of the aerogel, the material maintains a high specific surface area, and ensures excellent heat insulation performance.

[0023] (2) This invention achieves a synergistic effect of multiple flame-retardant mechanisms through two modified compounds (cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate). Cerium-terbium co-doped strontium calcium zinc stannate can form a complex ceramic protective layer containing multiple elements such as zinc, strontium, calcium, tin, cerium, and terbium at high temperatures. This protective layer is dense and continuous, effectively blocking heat transfer and oxygen penetration, thus delaying the pyrolysis and combustion of the matrix material. Cerium has variable valence states and can undergo redox reactions at high temperatures, catalyzing the formation of char from polymers; terbium has strong infrared reflectivity, which can reduce radiative heat transfer. Meanwhile, tin-doped layered magnesium aluminate undergoes endothermic decomposition upon heating, releasing water vapor to dilute the concentration of combustible gases, while simultaneously forming a dense char layer structure containing tin and aluminum on the material surface. The magnesium and calcium ions in this compound help stabilize the char layer and improve its high-temperature oxidation resistance. The two modifiers work synergistically to achieve full-chain protection from gas-phase flame retardancy to condensed-phase flame retardancy. The material of this invention has excellent flame retardant and smoke-suppressing properties, a high limiting oxygen index, achieves the highest flame retardant level in vertical burning tests, and significantly reduces peak heat release rate and total smoke production, greatly improving the material's safety in fire scenarios.

[0024] (3) This invention employs a process strategy of first dispersing the modifier powder in a mixed alkaline solution of dilute ammonia and anhydrous ethanol, and then mixing it with acidic silica sol. This effectively avoids the disintegration and irreversible decomposition of the layered hydroxides in an acidic environment, ensuring the structural integrity and functional performance of the modifier. In the preparation methods of the two modified compounds, by adding an appropriate amount of hydrochloric acid to the metal salt solution to inhibit the premature hydrolysis of tin ions, and by using co-precipitation technology to achieve the simultaneous nucleation of multiple metal ions, the phase purity and crystal structure integrity of the product are ensured. All raw materials used in this invention are commercially available, requiring no special synthesis or expensive reagents. The preparation process conditions are mild and controllable, suitable for large-scale industrial production. The resulting energy-saving insulation material has good hydrophobic properties and dimensional stability. Its thermal conductivity remains stable after long-term placement in a humid environment, while also possessing sufficient mechanical strength, meeting the basic requirements for mechanical properties of building insulation materials. In summary, this invention successfully solves the long-standing technical problem in the field of insulation materials where flame retardancy and insulation are difficult to achieve simultaneously, providing an ideal technical solution for building energy conservation and fire safety. Detailed Implementation

[0025] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0026] Example 1

[0027] This embodiment provides a method for preparing a novel energy-saving and heat-insulating material, the steps of which include:

[0028] S1. Mix 100g of tetraethyl orthosilicate with 275g of anhydrous ethanol and stir magnetically for 15min at room temperature. Then add 45g of deionized water and 5g of concentrated hydrochloric acid (36% by mass) to adjust the pH to 3.0 and continue stirring for 2.5h to obtain a clear acidic silica sol. Mix 8.5g of cerium-terbium co-doped strontium calcium zinc stannate powder and 8.5g of tin-doped layered magnesium aluminate powder evenly to obtain a modifier mixed powder. Add the modifier mixed powder to a mixed alkaline solution consisting of 10g of dilute ammonia (5% by mass) and 75g of anhydrous ethanol and ultrasonically disperse at 300W for 45min under ice-water bath conditions to obtain a modified suspension. Add the modified suspension dropwise to the acidic silica sol under vigorous stirring, adjust the pH to 7.9, stir rapidly for 30s, pour into a mold and let it stand for 37.5min to obtain a wet gel.

[0029] S2. The obtained wet gel is aged at room temperature for 26 hours, during which 150g of anhydrous ethanol is replaced every 6 hours. After aging, the gel is placed in a high-pressure reactor and dried for 2.5 hours under supercritical conditions of 260℃ and 7.5MPa using 600g of anhydrous ethanol as the drying medium. Then, the pressure is slowly released to atmospheric pressure at a rate of 1.5MPa / h and allowed to cool naturally to room temperature to obtain the new energy-saving and heat-insulating material.

[0030] Preparation of cerium-terbium co-doped strontium calcium zinc stannate:

[0031] A1. Dissolve 30.5g of zinc acetate dihydrate, 6.5g of strontium acetate, 3.5g of calcium acetate, 35.0g of tin tetrachloride pentahydrate, 1.5g of cerium nitrate hexahydrate, 1.0g of terbium nitrate hexahydrate, and 15.0g of concentrated hydrochloric acid (36% by mass) in 1250g of deionized water. Stir magnetically in a 70℃ water bath until completely dissolved to obtain a mixed salt solution. Dissolve 50.0g of sodium hydroxide in 600g of deionized water to prepare a precipitant. Solution: 250g of bottom water was pre-adjusted to pH 10.5 with sodium hydroxide solution to obtain alkaline bottom water; under vigorous stirring, the mixed salt solution and the precipitant solution were simultaneously added dropwise to the alkaline bottom water in a parallel flow, controlling the dropping rate to maintain the pH of the reaction system at 10.5 and the reaction temperature at 75℃. After the addition was completed, stirring was continued for 2.5h to obtain a suspension; the suspension was transferred to a high-pressure reactor and hydrothermally reacted at 200℃ for 27h to obtain the reaction mixture;

[0032] A2. After the reaction is complete, allow the mixture to cool naturally. Wash the precipitate alternately with 800g of deionized water and 800g of anhydrous ethanol until no Cl- residue is detected by AgNO3 solution and the pH of the washing solution is 7. Place the precipitate in an 80℃ vacuum drying oven and dry for 12h to obtain the precursor powder. Place the precursor powder in a muffle furnace and heat it from room temperature to 450℃ at a heating rate of 3℃ / min and hold for 3h. Then heat it to 950℃ at a heating rate of 2℃ / min and hold for 3h. Cool the mixture with the furnace and grind it through a 200-mesh sieve to obtain cerium-terbium co-doped strontium calcium zinc stannate powder.

[0033] Preparation of tin-doped layered magnesium aluminate:

[0034] B1. Dissolve 50.0g of magnesium nitrate hexahydrate, 22.5g of aluminum nitrate nonahydrate, 5.0g of calcium nitrate tetrahydrate, 7.0g of tin tetrachloride pentahydrate, and 7.5g of concentrated hydrochloric acid (36% by mass) in 800g of deionized water. Heat and stir in a 60℃ water bath until completely dissolved to obtain mixed salt solution A. Dissolve 40.0g of sodium hydroxide in 800g of deionized water to obtain mixed alkali solution B. Under nitrogen protection and at 70℃, simultaneously add solutions A and B dropwise in a reactor containing 150g of deionized water in a parallel flow. Control the dropping rate of the two solutions to maintain the pH of the reaction system at 9.8, and stir vigorously. After the addition is complete, continue stirring and aging at 70℃ for 24h. Then transfer the resulting slurry to a high-pressure reactor and hydrothermally treat it at 140℃ for 13h to obtain the reaction solution.

[0035] B2. After the reaction is complete, the precipitate is washed alternately with 600g of deionized water and 600g of anhydrous ethanol until no Cl- residue is detected by AgNO3 solution and the pH of the washing solution is 7. The precipitate is then vacuum dried at 60℃ for 27h and ground through a 200-mesh sieve to obtain tin-doped layered magnesium aluminate magnesium hydroxide powder.

[0036] Example 2

[0037] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing a novel energy-saving and heat-insulating material, the steps of which include:

[0038] S1. Mix 80g of tetraethyl orthosilicate with 200g of anhydrous ethanol and stir magnetically for 15min at room temperature. Then add 30g of deionized water and 2g of concentrated hydrochloric acid (36% by mass) to adjust the pH to 2.5 and continue stirring for 2.5h to obtain a clear acidic silica sol. Mix 2g of cerium-terbium co-doped strontium calcium zinc stannate powder and 2g of tin-doped layered magnesium aluminate powder evenly to obtain a modifier mixed powder. Add the modifier mixed powder to a mixed alkaline solution consisting of 5g of dilute ammonia (5% by mass) and 50g of anhydrous ethanol and ultrasonically disperse at 300W for 45min under ice-water bath conditions to obtain a modified suspension. Add the modified suspension dropwise to the acidic silica sol under vigorous stirring, adjust the pH to 7.6, stir rapidly for 30s, pour into a mold and let it stand for 25min to obtain a wet gel.

[0039] S2. The obtained wet gel is aged at room temperature for 24 hours, during which 100g of anhydrous ethanol is replaced every 6 hours. After aging, the gel is placed in a high-pressure reactor and dried for 2.5 hours under supercritical conditions of 258℃ and 7.0MPa using 400g of anhydrous ethanol as the drying medium. Then, the pressure is slowly released to atmospheric pressure at a rate of 1.5MPa / h and allowed to cool naturally to room temperature to obtain the new energy-saving and heat-insulating material.

[0040] Preparation of cerium-terbium co-doped strontium calcium zinc stannate:

[0041] A1. Dissolve 28.0g of zinc acetate dihydrate, 6.0g of strontium acetate, 3.0g of calcium acetate, 32.0g of tin tetrachloride pentahydrate, 1.0g of cerium nitrate hexahydrate, 0.8g of terbium nitrate hexahydrate, and 10.0g of concentrated hydrochloric acid (36% by mass) in 1000g of deionized water. Stir magnetically in a 68℃ water bath until completely dissolved to obtain a mixed salt solution. Dissolve 45.0g of sodium hydroxide in 500g of deionized water to prepare a precipitant. Solution: 200g of bottom water was pre-adjusted to pH 10.0 with sodium hydroxide solution to obtain alkaline bottom water; under vigorous stirring, the mixed salt solution and the precipitant solution were simultaneously added dropwise to the alkaline bottom water in a parallel flow, controlling the dropping rate to maintain the pH of the reaction system at 10.0 and the reaction temperature at 74℃. After the addition was complete, stirring was continued for 2.5h to obtain a suspension; the suspension was transferred to a high-pressure reactor and hydrothermally reacted at 195℃ for 24h to obtain the reaction mixture;

[0042] A2. After the reaction is complete, allow the mixture to cool naturally. Wash the precipitate alternately with 500g of deionized water and 500g of anhydrous ethanol until the washing solution shows no Cl- residue when tested with AgNO3 solution and the pH of the washing solution is 7. Place the precipitate in a vacuum drying oven at 78℃ and dry for 12h to obtain the precursor powder. Place the precursor powder in a muffle furnace and heat it from room temperature to 448℃ at a heating rate of 3℃ / min and hold for 2h. Then heat it to 948℃ at a heating rate of 2℃ / min and hold for 2h. Cool the mixture with the furnace and grind it through a 200-mesh sieve to obtain cerium-terbium co-doped strontium calcium zinc stannate powder.

[0043] Preparation of tin-doped layered magnesium aluminate:

[0044] B1. Dissolve 45.0g of magnesium nitrate hexahydrate, 20.0g of aluminum nitrate nonahydrate, 4.0g of calcium nitrate tetrahydrate, 6.0g of tin tetrachloride pentahydrate, and 5.0g of concentrated hydrochloric acid (36% by mass) in 700g of deionized water. Heat and stir in a water bath at 58℃ until completely dissolved to obtain mixed salt solution A. Dissolve 35.0g of sodium hydroxide in 700g of deionized water to obtain mixed alkali solution B. Under nitrogen protection and at 68℃, simultaneously add solutions A and B dropwise into a reactor containing 100g of deionized water in a parallel flow. Control the dropping rate of the two solutions to maintain the pH of the reaction system at 9.6, and stir vigorously. After the addition is complete, continue stirring and aging at 68℃ for 24h. Then transfer the resulting slurry to a high-pressure reactor and hydrothermally treat it at 138℃ for 12h to obtain the reaction solution.

[0045] B2. After the reaction is complete, the precipitate is washed alternately with 400g of deionized water and 400g of anhydrous ethanol until no Cl- residue is detected by AgNO3 solution and the pH of the washing solution is 7. The precipitate is then vacuum dried at 58℃ for 24h and ground through a 200-mesh sieve to obtain tin-doped layered magnesium aluminate magnesium hydroxide powder.

[0046] Example 3

[0047] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing a novel energy-saving and heat-insulating material, the steps of which include:

[0048] S1. Mix 120g of tetraethyl orthosilicate with 350g of anhydrous ethanol and stir magnetically for 15min at room temperature. Then add 60g of deionized water and 8g of concentrated hydrochloric acid (36% by mass) to adjust the pH to 3.5 and continue stirring for 2.5h to obtain a clear acidic silica sol. Mix 15g of cerium-terbium co-doped strontium calcium zinc stannate powder and 15g of tin-doped layered magnesium aluminate calcium hydroxide powder evenly to obtain a modifier mixed powder. Add the modifier mixed powder to a mixed alkaline solution consisting of 15g of dilute ammonia water (5% by mass) and 100g of anhydrous ethanol and ultrasonically disperse at 300W for 45min under ice-water bath conditions to obtain a modified suspension. Add the modified suspension dropwise to the acidic silica sol under vigorous stirring, adjust the pH to 8.2, stir rapidly for 30s, pour into a mold and let it stand for 50min to obtain a wet gel.

[0049] S2. The obtained wet gel is aged at room temperature for 28 hours, during which 200g of anhydrous ethanol is replaced every 6 hours. After aging, the gel is placed in a high-pressure reactor and dried for 2.5 hours under supercritical conditions of 262℃ and 8.0MPa using 800g of anhydrous ethanol as the drying medium. Then, the pressure is slowly released to atmospheric pressure at a rate of 1.5MPa / h and allowed to cool naturally to room temperature to obtain the new energy-saving and heat-insulating material.

[0050] Preparation of cerium-terbium co-doped strontium calcium zinc stannate:

[0051] A1. Dissolve 33.0g of zinc acetate dihydrate, 7.0g of strontium acetate, 4.0g of calcium acetate, 38.0g of tin tetrachloride pentahydrate, 2.0g of cerium nitrate hexahydrate, 1.2g of terbium nitrate hexahydrate, and 20.0g of concentrated hydrochloric acid (36% by mass) in 1500g of deionized water. Stir magnetically in a 72℃ water bath until completely dissolved to obtain a mixed salt solution. Dissolve 55.0g of sodium hydroxide in 700g of deionized water to prepare a precipitant. Solution: 300g of bottom water was pre-adjusted to pH 11.0 with sodium hydroxide solution to obtain alkaline bottom water; under vigorous stirring, the mixed salt solution and the precipitant solution were simultaneously added dropwise to the alkaline bottom water in a parallel flow, controlling the dropping rate to maintain the pH of the reaction system at 11.0 and the reaction temperature at 76℃. After the addition was complete, stirring was continued for 2.5h to obtain a suspension; the suspension was transferred to a high-pressure reactor and hydrothermally reacted at 205℃ for 30h to obtain the reaction mixture;

[0052] A2. After the reaction is complete, allow the mixture to cool naturally. Wash the precipitate alternately with 1000g of deionized water and 1000g of anhydrous ethanol until the washing solution shows no Cl- residue when tested with AgNO3 solution and the pH of the washing solution is 7. Place the precipitate in a vacuum drying oven at 82℃ and dry for 12h to obtain the precursor powder. Place the precursor powder in a muffle furnace and heat it from room temperature to 452℃ at a heating rate of 3℃ / min and hold for 4h. Then heat it to 952℃ at a heating rate of 2℃ / min and hold for 4h. Cool the mixture with the furnace and grind it through a 200-mesh sieve to obtain cerium-terbium co-doped strontium calcium zinc stannate powder.

[0053] Preparation of tin-doped layered magnesium aluminate:

[0054] B1. Dissolve 55.0g of magnesium nitrate hexahydrate, 25.0g of aluminum nitrate nonahydrate, 6.0g of calcium nitrate tetrahydrate, 8.0g of tin tetrachloride pentahydrate, and 10.0g of concentrated hydrochloric acid (36% by mass) in 900g of deionized water. Heat and stir in a 62℃ water bath until completely dissolved to obtain mixed salt solution A. Dissolve 45.0g of sodium hydroxide in 900g of deionized water to obtain mixed alkali solution B. Under nitrogen protection and at 72℃, simultaneously add solutions A and B dropwise in a reactor containing 200g of deionized water in a parallel flow. Control the dropping rate of the two solutions to maintain the pH of the reaction system at 10.0, and stir vigorously. After the addition is complete, continue stirring and aging at 72℃ for 24h. Then transfer the resulting slurry to a high-pressure reactor and hydrothermally treat it at 142℃ for 14h to obtain the reaction solution.

[0055] B2. After the reaction is complete, the precipitate is washed alternately with 800g of deionized water and 800g of anhydrous ethanol until no Cl- residue is detected by AgNO3 solution and the pH of the washing solution is 7. The precipitate is then vacuum dried at 62℃ for 30h and ground through a 200-mesh sieve to obtain tin-doped layered magnesium aluminate magnesium hydroxide powder.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is that cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate hydroxide are not added. The remaining steps are the same as in Example 1.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 1 is that only cerium-terbium co-doped strontium calcium zinc stannate is added, without the addition of tin-doped layered magnesium aluminate magnesium hydroxide. The remaining steps are the same as in Example 1.

[0060] Comparative Example 3

[0061] The difference between this comparative example and Example 1 is that only tin-doped layered magnesium aluminate magnesium hydroxide is added, and cerium-terbium co-doped calcium zinc stannate is not added. The remaining steps are the same as in Example 1.

[0062] According to relevant national and industry standards, the performance of the energy-saving and thermal insulation new materials provided in the above embodiments and comparative examples was tested. The test methods are as follows:

[0063] Thermal conductivity test: The thermal conductivity meter was used for the heat flow method. The sample was cut into a flat plate with a size of 300mm×300mm×25mm. The average test temperature was 25℃, with the cold plate temperature set at 15℃ and the hot plate temperature set at 35℃, with a temperature difference of 20℃. After the heat flow stabilized, the thermal conductivity value was recorded. Three parallel samples were tested for each sample. The final result was the arithmetic mean, with the unit being W / (m·K), and the result was retained to three decimal places.

[0064] Limiting oxygen index test: The test was conducted using an oxygen index meter. The sample was cut into strips with dimensions of 80mm×10mm×10mm. The sample was vertically installed in the combustion chamber. The flow rate of the mixed oxygen and nitrogen gas was adjusted so that the mixed gas flowed through the combustion chamber at a speed of 40mm / s. The top of the sample was ignited with an igniter, and the combustion behavior of the sample was observed. The oxygen concentration was gradually reduced until the sample just maintained combustion. The oxygen volume fraction at this point was recorded. Fifteen samples were tested for each sample, and the arithmetic mean was taken. The result was expressed as a percentage and rounded to one decimal place.

[0065] Vertical flammability test: The test was conducted using a vertical flammability tester. The sample was cut into strips measuring 125mm × 13mm × 10mm. The sample was vertically fixed on a fixture, and degreased cotton was placed 300mm from the bottom. A Bunsen burner was used to generate a blue flame with a height of 20mm. The flame was applied for 10 seconds and then immediately removed. The first afterflame time t1 was recorded. After the afterflame extinguished, the flame was applied again for 10 seconds and then removed. The second afterflame time t2 and afterglow time t3 were recorded. At the same time, it was observed whether molten droplets were generated and whether the molten droplets ignited the degreased cotton. Five samples were tested for each sample. The V-0, V-1, or V-2 level was determined based on the maximum afterflame time (the maximum value of t1 or t2), the total afterflame time (t1+t2), and the ignition of molten droplets. V-0 requires that the afterflame time of a single sample be ≤10s, the total afterflame time be ≤50s, and no molten droplets ignite the degreased cotton. V-1 requires that the afterflame time of a single sample be ≤30s, the total afterflame time be ≤250s, and no molten droplets ignite the degreased cotton. V-2 requires that the afterflame time of a single sample be ≤30s, the total afterflame time be ≤250s, but molten droplets are allowed to ignite the degreased cotton.

[0066] Density test: The test was conducted using an electronic balance and vernier calipers. The sample was cut into cubic specimens with dimensions of 50mm×50mm×25mm. The mass was weighed using an electronic balance to an accuracy of 0.01g. The length, width, and height of the specimen were measured three times each using vernier calipers, and the average value was used to calculate the volume. The density was calculated by dividing the mass by the volume. Three parallel samples were tested for each sample, and the arithmetic mean was taken. The unit is g / cm³, and the result is rounded to two decimal places.

[0067] Compressive strength test: The test was conducted using a universal testing machine. The sample was cut into cubic specimens with dimensions of 50mm×50mm×25mm. The specimens were placed in the center of the upper and lower pressure plates of the testing machine and loaded at a constant compression rate of 10mm / min. The compression was stopped when the specimen thickness was reduced to 10%. The maximum compressive stress at that moment was recorded. Five parallel specimens were tested for each sample, and the arithmetic mean was taken. The unit is MPa, and the result is retained to two decimal places.

[0068] The performance test data above are shown in Table 1.

[0069] Table 1 Performance Test Results

[0070]

[0071] As can be seen from the above, Examples 1-3 successfully solved the technical problems of existing thermal insulation materials, such as the difficulty in simultaneously achieving flame retardant and thermal insulation properties, as well as insufficient mechanical properties, compared to Comparative Examples 1-3.

[0072] Specifically, regarding thermal conductivity, the thermal conductivity of Examples 1-3 ranged from 0.022 to 0.027 W / (m·K), which was basically the same as that of Comparative Example 1 (0.021 W / (m·K) without any modifiers. The thermal conductivity was only slightly higher but still within the ultra-low thermal conductivity range, indicating that the introduction of the two modifiers (cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate hydroxide) did not destroy the three-dimensional porous network structure of silica aerogel, and the thermal insulation performance of the material was fully maintained. Although Comparative Examples 2 and 3 added a single modifier, their thermal conductivity was 0.026 and 0.025 W / (m·K), respectively, which was comparable to that of the Examples, but their flame retardant performance was significantly lower than that of the Examples.

[0073] Regarding the limiting oxygen index, Examples 1-3 reached 32.8-36.2%, which is much higher than Comparative Example 1's 22.5%, and also significantly higher than Comparative Example 2's 29.6% and Comparative Example 3's 30.2%. This indicates that although adding cerium-terbium co-doped strontium calcium zinc stannate or adding tin-doped layered magnesium aluminate hydroxide alone can improve flame retardancy to a certain extent, neither can achieve a high flame retardancy level of over 32%. However, the combined use of the two produced a significant synergistic effect, enabling the material to simultaneously exert the dual mechanisms of ceramic protective layer barrier and heat-absorbing decomposition smoke suppression when exposed to fire, thereby greatly improving flame retardant performance.

[0074] Regarding the vertical combustion rating, Examples 1-3 all achieved the highest rating of V-0, while Comparative Example 1 was only V-2, and Comparative Examples 2 and 3 were only V-1. This further confirms that the synergistic effect of the two modifiers (cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate hydroxide) can completely change the combustion behavior of the material, enabling it to self-extinguish rapidly after the flame is removed and without drip ignition, thus meeting the stringent requirements for fire safety of building insulation materials.

[0075] Regarding compressive strength, the compressive strength of Examples 1-3 was 0.55-0.68 MPa, which was significantly higher than 0.42 MPa of Comparative Example 1, and slightly higher than 0.58 MPa of Comparative Example 2 and 0.56 MPa of Comparative Example 3. This indicates that the co-dispersion of the two modifiers in the aerogel matrix can effectively enhance the skeleton structure and make up for the defects of the fragile mechanical properties of pure aerogel. At the same time, the rigid inorganic properties of the two modifiers (cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate hydroxide) help to improve the compressive strength of the material.

[0076] In summary, Examples 1-3, through the synergistic compounding of two modified compounds (cerium-terbium co-doped strontium calcium zinc stannate and tin-doped layered magnesium aluminate calcium hydroxide), significantly improved the flame retardant properties and mechanical strength of the materials without sacrificing thermal insulation performance. This successfully solved the core problems in the prior art, such as insufficient flame retardant efficiency, mutual constraints between flame retardancy and thermal insulation, and poor mechanical properties of composite materials.

Claims

1. A method for preparing a novel energy-saving and heat-insulating material, characterized in that the steps include... include: S1. By weight, mix 80-120 parts of tetraethyl orthosilicate with 200-350 parts of anhydrous ethanol, stir at room temperature, then add 30-60 parts of deionized water and 2-8 parts of hydrochloric acid to adjust the pH to 2.5-3.5, and continue stirring to obtain an acidic silica sol; mix 2-15 parts of cerium-terbium co-doped strontium calcium zinc stannate and 2-15 parts of tin-doped layered magnesium aluminate hydroxide to obtain a modifier mixed powder; add the modifier mixed powder to a mixed alkaline solution containing 5-15 parts of dilute ammonia and 50-100 parts of anhydrous ethanol, and disperse ultrasonically under an ice-water bath to obtain a modified suspension; With stirring, the modified suspension was added dropwise to the acidic silica sol, the pH was adjusted to 7.6-8.2, and after stirring, it was poured into a mold and allowed to stand to gel, thus obtaining a wet gel. S2. Age the wet gel at room temperature; after aging, place it in a reaction vessel, add 400-800 parts of anhydrous ethanol, dry at 258-262℃, and cool naturally to room temperature.

2. The preparation method of the energy-saving and heat-insulating novel material according to claim 1, characterized in that, In step S1, the gel is allowed to stand for 25-50 minutes.

3. The preparation method of the energy-saving and heat-insulating novel material according to claim 1, characterized in that, In step S2, the wet gel is aged at room temperature for 24-28 hours.

4. The preparation method of the energy-saving and heat-insulating novel material according to claim 1, characterized in that, The preparation method of the cerium-terbium co-doped strontium calcium zinc stannate includes: A1, dissolving 28-33 parts by weight of zinc acetate dihydrate, 6-7 parts by weight of strontium acetate, 3-4 parts by weight of calcium acetate, 32-38 parts by weight of tin tetrachloride pentahydrate, 1-2 parts by weight of cerium nitrate hexahydrate, 0.8-1.2 parts by weight of terbium nitrate hexahydrate, and 10-20 parts by weight of hydrochloric acid in 1000-1500 parts by weight of deionized water, stirring in a water bath at 68-72°C to obtain a mixed salt solution; and then dissolving 45-55 parts by weight of strontium calcium zinc stannate in 1000-1500 parts by weight of deionized water. Dissolve 500-700 parts of sodium hydroxide in 500 parts of deionized water to obtain a precipitant solution; adjust the pH of 200-300 parts of deionized water to 10.0-11.0 with sodium hydroxide solution to obtain alkaline bottom water; add the mixed salt solution and precipitant solution dropwise to the alkaline bottom water simultaneously with stirring at 74-76℃ to obtain a suspension; transfer the suspension to a reaction vessel and perform a hydrothermal reaction at 195-205℃ to obtain a reaction mixture; allow the reaction mixture to cool naturally and centrifuge to obtain a precipitate; wash the precipitate alternately with deionized water and anhydrous ethanol; dry it in a vacuum drying oven at 78-82℃ to obtain a precursor powder; place the precursor powder in a muffle furnace, heat it to 448-452℃ and hold it thereafter, then heat it to 948-952℃ and hold it thereafter, cool it to room temperature with the furnace, grind it, and sieve it.

5. The preparation method of the energy-saving and heat-insulating novel material according to claim 4, characterized in that, In step A1, the hydrothermal reaction time at 195-205℃ is 24-30 hours.

6. The method for preparing the new energy-saving and heat-insulating material according to claim 4, characterized in that, In step A2, the temperature is raised to 448-452℃ and held for 2-4 hours.

7. The preparation method of the energy-saving and heat-insulating novel material according to claim 1, characterized in that, The preparation method of the tin-doped layered magnesium aluminate calcium hydroxide includes: B1, dissolving 45-55 parts by weight of magnesium nitrate hexahydrate, 20-25 parts by weight of aluminum nitrate nonahydrate, 4-6 parts by weight of calcium nitrate tetrahydrate, 6-8 parts by weight of tin tetrachloride pentahydrate, and 5-10 parts by weight of hydrochloric acid in 700-900 parts by weight of deionized water, stirring in a water bath at 58-62°C to obtain mixed salt solution A; dissolving 35-45 parts by weight of sodium hydroxide in 700-900 parts by weight of deionized water to obtain mixed alkaline solution B; and stirring in a water bath at 68-70°C under nitrogen protection. At 2℃, mixed salt solution A and mixed alkali solution B are simultaneously added dropwise to a reactor containing 100-200 parts of deionized water, maintaining the pH at 9.6-10.0, and stirred. After the addition is complete, stirring and aging are continued at 68-72℃ to obtain a slurry. The slurry is transferred to a reactor and hydrothermally treated at 138-142℃ to obtain a reaction solution. B2. The reaction solution is centrifuged to obtain a precipitate. The precipitate is washed alternately with deionized water and anhydrous ethanol, vacuum dried at 58-62℃, ground, and sieved.

8. The method for preparing the energy-saving and heat-insulating novel material according to claim 7, characterized in that, In step B1, the hydrothermal treatment at 138-142℃ takes 12-14 hours.

9. The method for preparing the energy-saving and heat-insulating novel material according to claim 7, characterized in that, In step B2, the vacuum drying time at 58-62℃ is 24-30 hours.

10. A novel energy-saving and heat-insulating material, characterized in that, The energy-saving and heat-insulating novel material is prepared by the method according to any one of claims 1-9.

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