Flexible thermal barrier fibrous ceramic aerogel having core-sheath structure and method of making

Abstract

The application discloses a kind of flexible heat-insulating fibrous ceramic aerogel with core-sheath structure and preparation method, belong to new material technical field.Preparation steps are: with Zr, Y, La preparation precursor, nanofiber ceramic aerogel core layer is prepared by electrostatic spinning and high temperature annealing;Again according to Zr, Y, La, Ti preparation nanoparticle precursor, after dispersing core layer, obtain initial gel by sol-gel;After ladder water bath aging, hydrophobic modification and solvent replacement, normal temperature and pressure drying and high temperature annealing again, obtain Zr-Y-La-Ti core-sheath structure fibrous ceramic aerogel.The inner layer of single fiber is nanofiber ceramic aerogel, and the outer layer is nanoparticle ceramic aerogel, closely adhere, and the surface is smooth.The aerogel has excellent flexibility and heat insulation performance, the minimum thermal conductivity is 21.96 mW / m·K, the maximum elastic compression deformation is 80%, the maximum working temperature is 1200 DEG C, and is suitable for high temperature heat protection and flexible deformation scene, which widens the application range of aerogel material.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure and its preparation method. Background Technology

[0002] Aerogels, with their low density, high porosity, and large specific surface area, have been widely used in thermal insulation, adsorption, and sound insulation. As research into aerogel materials deepens, various novel aerogels are constantly being developed and applied, leading to a continuous increase in the types of aerogels and the formation of a vast material system. Aerogels can be classified according to the size of their basic constituent units into zero-dimensional aerogels (such as SiO2 nanoparticle aerogels and ZrO2 nanoparticle aerogels), one-dimensional aerogels (such as mullite nanofiber aerogels and SiC nanoribbon aerogels), and two-dimensional aerogels (such as graphene aerogels and boron nitride aerogels). Different types of aerogels exhibit performance differences in thermal insulation, mechanical properties, and sound insulation, necessitating the use of different types of aerogels for different application scenarios (such as high-temperature scenarios primarily for thermal protection and expansion joint components primarily for flexibility). Therefore, developing novel multi-dimensional aerogels to meet the versatility of multiple application scenarios has always been a major research direction and development prospect for the scientific and industrial communities.

[0003] Among the three types of aerogels, zero-dimensional nanoparticle aerogels have a low thermal conductivity, while one-dimensional nanofiber aerogels have high flexibility. Therefore, combining the basic units of the two types of aerogels to prepare nanofiber-reinforced nanoparticle aerogels is currently the main approach for developing novel aerogels that possess both good flexibility and thermal insulation properties. For example, Chinese Patent Publication No. CN108467276A, Invention Title: A Method for Preparing Electrospun Nanofiber-Reinforced Silica Aerogel; and Chinese Patent Publication No. CN119430851A, Invention Title: A High-Entropy Nanoceramic Fiber-Reinforced Silica Aerogel and Its Preparation Method. By using nanofiber reinforcement, the thermal insulation properties of nanoparticle aerogels are basically retained while appropriately enhancing the flexibility of the aerogel. However, during use, structural damage such as aerogel particle shedding and aerogel delamination often occurs, which greatly limits the application scenarios of nanofiber-reinforced aerogels. To further enhance the flexibility of aerogels and ensure their integrity during use, increasing the proportion of nanofibers in the overall aerogel and thus preparing nanofiber aerogels rich in nanoparticles is a suitable research approach. For example, Chinese Patent Publication No.: CN119505357A, Invention Title: A Nano-Calcium Aluminum Particle Reinforced Aramid Nanofiber Aerogel and Its Preparation Method and Application. However, as the proportion of nanofibers in the aerogel continues to increase, the pore size in the aerogel gradually increases, leading to a gradual loss of its thermal insulation performance and a continuous increase in thermal conductivity until it exceeds 28 mW / m·K. Summary of the Invention

[0004] Based on the above shortcomings, this invention provides a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure and its preparation method. By designing the microstructure of the basic aerogel unit and combining it with a suitable production method, the multi-dimensional construction process of the basic aerogel unit is completed, and a novel aerogel with both flexibility and heat insulation properties is prepared. This solves the important technical problem of insufficient universality of traditional aerogels in multiple application scenarios, thereby expanding the application range of aerogels and opening up new aerogel material systems.

[0005] The technical solution adopted in this invention is as follows: A method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure, comprising the following steps:

[0006] S1. Preparation of Zr-Y-La nanofiber ceramic aerogel;

[0007] S2. Prepare a nanoparticle precursor solution with a molar ratio of Zr:Y:La:Ti = 1:0.05~0.5:0.5~2:0.5~2, disperse Zr-Y-La nanofiber ceramic aerogel in it, add gel control agent and gel promoter to carry out condensation reaction, and obtain fibrous initial gel Zr-Y-La-Ti.

[0008] S3. The initial gel was placed in an aging solution and aged in a stepped water bath at 30℃, 45℃ and 60℃. Then, hydrophobic modification and solvent replacement were performed to obtain wet gel Zr-Y-La-Ti.

[0009] S4. Place the wet gel in a sealed desiccator at room temperature, then remove the solvent atmosphere from the desiccator until the solution in the wet gel is completely converted into a gas phase and detached from the gel to form a fibrous aerogel. Then, anneal at a high temperature of 800-1000℃ to obtain a Zr-Y-La-Ti core-sheath structure fibrous ceramic aerogel. The inner layer of each fiber is a nanofiber ceramic aerogel core layer, and the outer layer is a nanoparticle ceramic aerogel sheath layer. The two are closely bonded together, and the fiber surface is smooth.

[0010] Further, in step S1, a precursor solution is prepared according to a molar ratio of Zr:Y:La = 1:0.05~0.5:1~2, and Zr-Y-La nanofiber ceramic aerogel is prepared by electrospinning and high-temperature annealing at 800~1000℃. The receiving distance of electrospinning is 0.6~0.9m and the voltage is 15~25kV.

[0011] Furthermore, in step S1, the molar ratio of the precursor solution is Zr:Y:La = 1:0.1:1.

[0012] Furthermore, in step S2, the gel control agent is a mixture of polyethylene glycol and formamide, with a molar ratio of Zr:polyethylene glycol:formamide = 1:0.1:0.1; the gel promoter is propylene oxide, with a molar ratio of Zr:propylene oxide = 1:4 to 6.

[0013] Furthermore, the characteristic feature is that, in step S2, the molar ratio of the nanoparticle precursor solution is Zr:Y:La:Ti = 1:0.1:1:1.

[0014] Furthermore, in step S2, the molar ratio of Zr to propylene oxide is 1:4.5.

[0015] Furthermore, in step S3, the aging solution is an ethanol solution containing 10% tetraethyl orthosilicate by volume, and the aging time is 12-24 hours.

[0016] Furthermore, in step S3, the hydrophobic modification solution is a hexane solution containing 20% ​​by volume of trimethylethoxysilane, the modification temperature is 30-60°C, and the solution is soaked for 12-24 hours.

[0017] Furthermore, in step S3, the replacement solution is a mixed solution of anhydrous ethanol and n-hexane with a volume ratio of 1:9, and the number of replacements is 12 to 24.

[0018] The present invention also provides a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure prepared by the method described above. The aerogel is a Zr-Y-La-Ti system, with a single fiber having a double-layer tightly bonded structure. The inner layer is a nanofiber ceramic aerogel core, and the outer layer is a nanoparticle ceramic aerogel sheath. The fiber surface is smooth and without defects.

[0019] The beneficial effects and advantages of this invention are as follows: This invention prepares a fibrous aerogel with a "core-sheath" structure by designing the microstructure of the basic unit of fibrous aerogel, combined with far-field electrospinning and sol-gel methods. It retains the thermal insulation performance of nanoparticle aerogel: the lowest thermal conductivity can reach 21.96mW / m·K, while also having excellent flexibility: the maximum elastic compressive deformation can reach 80%. This invention is suitable for high-temperature thermal protection and flexible deformation scenarios, thus broadening the application range of aerogel materials. Attached Figure Description

[0020] Figure 1 These are optical images (a) and single fiber SEM images (b) of the "core-sheath" structured fibrous ceramic aerogel prepared in Example 1.

[0021] Figure 2 The images show the compression mechanical properties (a) and torsional optical photographs (b) of the core-sheath structured fibrous ceramic aerogel prepared in Example 1.

[0022] Figure 3 The bar charts (a) showing the room temperature thermal conductivity and (b) showing the maximum resilient compressible deformation of the "core-sheath" structured fibrous ceramic aerogels prepared in Examples 1, 2, 3, and 4 are shown. Detailed Implementation

[0023] To provide a clearer and more detailed explanation of the preparation method and process described in this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to specific examples and accompanying drawings. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention. The raw materials used in the examples are all conventional commercially available products or prepared according to existing techniques.

[0024] Example 1:

[0025] A method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure includes the following steps:

[0026] S1. At room temperature, a precursor solution was prepared according to a molar ratio of Zr:Y:La = 1:0.1:1. The precursor solution was added to an electrospinning device. The distance of the receiver in the electrospinning device was adjusted to 0.6m, and the voltage was adjusted to 20kV. After the precursor solution was used up, the nanofiber aerogel in the collector was taken out and subjected to high-temperature annealing at 1000℃ to prepare Zr-Y-La nanofiber ceramic aerogel.

[0027] S2. At room temperature, a nanoparticle precursor solution is prepared according to a molar ratio of Zr:Y:La:Ti = 1:0.1:1:1. The Zr-Y-La nanofiber ceramic aerogel obtained in step S1 is added and stirred slowly until the Zr-Y-La nanofiber ceramic aerogel is uniformly dispersed in the nanoparticle precursor solution. Then, a gel control agent is added and stirred thoroughly. The gel control agent is a mixture of polyethylene glycol and formamide with a molar ratio of Zr:polyethylene glycol:formamide = 1:0.1:0.1. Finally, a gel accelerator is added to the solution to promote the polycondensation reaction and obtain a fibrous initial gel. The gel accelerator is propylene oxide with a molar ratio of Zr:propylene oxide = 1:4.5.

[0028] S3. The initial gel obtained in step S2 is immersed in an aging solution and heated in a water bath, aged at 30℃, 45℃, and 60℃ for 12–24 hours respectively. After aging, the wet gel is removed and added to a hydrophobic modification solution, and fully immersed in a water bath at 30–60℃ for 12–24 hours. Then, the wet gel is removed and added to a replacement solution for solvent replacement, a total of 12–24 replacements to ensure that the solution in the wet gel has been completely replaced. The aging solution is an ethanol solution containing 10% tetraethyl orthosilicate by volume; the hydrophobic modification solution is a hexane solution containing 20% ​​trimethylethoxysilane by volume; the replacement solution is a mixed solution of anhydrous ethanol and hexane by volume ratio of 1:9, and the number of replacements is 12–24.

[0029] S4. Place the wet gel obtained in step S3 into a desiccator, then place the desiccator in a room temperature environment and seal it. Extract the solvent atmosphere from the desiccator until all the solution in the wet gel is converted into a gas phase and detaches from the gel to form a fibrous aerogel. Finally, remove the fibrous aerogel from the desiccator and perform high-temperature annealing at 800-1000℃ to finally prepare a Zr-Y-La-Ti "core-sheath" structured fibrous ceramic aerogel. The single fiber constituting the ceramic aerogel exhibits a double-layer structure: an inner layer of nanofiber ceramic aerogel "core" and an outer layer of nanoparticle ceramic aerogel "sheath," which are tightly bonded together, and the fiber surface is smooth and defect-free.

[0030] The core-sheath fibrous ceramic aerogel prepared in this embodiment has a uniform morphology. Compared with existing aerogel products, the core-sheath fibrous ceramic aerogel has excellent flexibility: the maximum resilient compressive deformation can reach 80%, and excellent thermal insulation performance: the lowest thermal conductivity can reach 21.96mW / m·K. Specific data are shown in Table 1.

[0031] Table 1 compares the performance of the aerogel of this invention with existing aerogels.

[0032] category Thermal conductivity (mW / m·K) Maximum operating temperature (°C) Maximum resilient compressive deformation (%) Mullite aerogel 27.03 1000 20 Glass fiber reinforced silica aerogel 23.98 450 16 3D printing cellulose aerogel 62.5 325 80 Polymer fiber aerogel 25.21 300 80 Core-Sheath Structure Fibrous Ceramic Aerogel 21.96 1200 80

[0033] Example 2:

[0034] A method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure includes the following steps:

[0035] At room temperature, a precursor solution was prepared at a molar ratio of Zr:Y:La = 1:0.5:1 and added to an electrospinning apparatus. The distance of the receiver in the electrospinning apparatus was adjusted to 0.8 m, and the high-voltage DC power supply was turned on and the voltage was adjusted to 25 kV. After all the precursor solution had been used, the nanofiber aerogel in the collector was removed and subjected to high-temperature annealing at 900 °C to prepare Zr-Y-La nanofiber ceramic aerogel.

[0036] At room temperature, a nanoparticle precursor solution was prepared in a molar ratio of Zr:Y:La:Ti = 1:0.5:1:1, and the previously prepared Zr-Y-La nanofiber ceramic aerogel was added. The mixture was slowly stirred until the Zr-Y-La nanofiber ceramic aerogel was uniformly dispersed in the solution. Then, polyethylene glycol and formamide, with a molar ratio of Zr:polyethylene glycol:formamide = 1:0.1:0.1, were added as gel control agents and stirred thoroughly. Finally, propylene oxide, with a molar ratio of Zr:propylene oxide = 1:6, was added to the solution to promote the polycondensation reaction and obtain a fibrous initial gel.

[0037] The prepared initial gel was immersed in an aging solution and heated in a water bath, and aged for 12 hours at 30℃, 45℃, and 60℃ respectively, following a stepwise increasing temperature range. After aging, the wet gel was removed and added to a hydrophobic modification solution, and fully immersed in a water bath at 60℃ for 24 hours. Then, the wet gel was removed and added to a displacement solution for solvent displacement, a total of 12 displacements to ensure that the solution in the wet gel was completely replaced. The aging solution was an ethanol solution containing 10% tetraethyl orthosilicate by volume; the hydrophobic modification solution was a hexane solution containing 20% ​​trimethylethoxysilane by volume; the displacement solution was a mixed solution of anhydrous ethanol and hexane at a volume ratio of 1:9, and the number of displacements was 12 to 24.

[0038] The prepared wet gel was placed in a desiccator, which was then placed at room temperature and sealed. A small vacuum filtration apparatus was used to periodically extract the solvent atmosphere from the desiccator until all the solution in the wet gel was converted to a gaseous phase and detached from the gel, forming a fibrous aerogel. Finally, the fibrous aerogel was removed from the desiccator and subjected to high-temperature annealing at 800–1000℃ to prepare a Zr-Y-La-Ti core-sheath structured fibrous ceramic aerogel.

[0039] The prepared core-sheath structured fibrous ceramic aerogel has a uniform morphology, moderate flexibility (maximum resilient compressible deformation of 60%), moderate thermal insulation performance (minimum thermal conductivity of 24.37 mW / m·K), and certain deformability.

[0040] Example 3: Comparative Experiment

[0041] A method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure includes the following steps:

[0042] At room temperature, a precursor solution was prepared at a molar ratio of Zr:Y:La = 1:0.05:1 and added to an electrospinning apparatus. The distance of the receiver in the electrospinning apparatus was adjusted to 0.8 m, and the high-voltage DC power supply was turned on and the voltage was adjusted to 25 kV. After all the precursor solution had been used, the nanofiber aerogel in the collector was removed and subjected to high-temperature annealing at 900 °C to prepare Zr-Y-La nanofiber ceramic aerogel.

[0043] At room temperature, a nanoparticle precursor solution was prepared in a molar ratio of Zr:Y:La:Ti = 1:0.1:1:2, and the previously prepared Zr-Y-La nanofiber ceramic aerogel was added. The mixture was slowly stirred until the Zr-Y-La nanofiber ceramic aerogel was uniformly dispersed in the solution. Then, polyethylene glycol and formamide, with a molar ratio of Zr:polyethylene glycol:formamide = 1:0.1:0.1, were added as gel control agents and stirred thoroughly. Finally, propylene oxide, with a molar ratio of Zr:propylene oxide = 1:6, was added to the solution to promote the polycondensation reaction and obtain a fibrous initial gel.

[0044] The prepared initial gel was immersed in an aging solution and heated in a water bath, and aged for 24 hours at 30℃, 45℃, and 60℃ respectively, following a stepwise increasing temperature range. After aging, the wet gel was removed and added to a hydrophobic modification solution, and fully immersed in a water bath at 60℃ for 24 hours. Then, the wet gel was removed and added to a displacement solution for solvent displacement, a total of 24 displacements to ensure that the solution in the wet gel was completely replaced. The aging solution was an ethanol solution containing 10% tetraethyl orthosilicate by volume; the hydrophobic modification solution was a hexane solution containing 20% ​​trimethylethoxysilane by volume; the displacement solution was a mixed solution of anhydrous ethanol and hexane at a volume ratio of 1:9, and the number of displacements was 12 to 24.

[0045] The prepared wet gel was placed in a desiccator, which was then placed at room temperature and sealed. A small vacuum filtration apparatus was used to periodically extract the solvent atmosphere from the desiccator until all the solution in the wet gel was converted to a gaseous phase and detached from the gel, forming a fibrous aerogel. Finally, the fibrous aerogel was removed from the desiccator and subjected to high-temperature annealing at 1000℃ to prepare a Zr-Y-La-Ti core-sheath structured fibrous ceramic aerogel.

[0046] The prepared core-sheath structured fibrous ceramic aerogel has a uniform morphology, moderate flexibility (maximum resilient compressible deformation of 65%), moderate thermal insulation performance (minimum thermal conductivity of 25.46 mW / m·K), and certain deformability.

[0047] Example 4: Comparative Experiment

[0048] like Figure 3 As shown, a method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure includes the following steps:

[0049] At room temperature, a precursor solution was prepared at a molar ratio of Zr:Y:La = 1:0.5:2 and added to an electrospinning apparatus. The distance of the receiver in the electrospinning apparatus was adjusted to 0.9 m, and the high-voltage DC power supply was turned on and the voltage was adjusted to 25 kV. After all the precursor solution had been used, the nanofiber aerogel in the collector was removed and subjected to high-temperature annealing at 1000 °C to prepare Zr-Y-La nanofiber ceramic aerogel.

[0050] At room temperature, a nanoparticle precursor solution was prepared in a molar ratio of Zr:Y:La:Ti = 1:0.5:2:2, and the previously prepared Zr-Y-La nanofiber ceramic aerogel was added. The mixture was slowly stirred until the Zr-Y-La nanofiber ceramic aerogel was uniformly dispersed in the solution. Then, polyethylene glycol and formamide, with a molar ratio of Zr:polyethylene glycol:formamide = 1:0.1:0.1, were added as gel control agents and stirred thoroughly. Finally, propylene oxide, with a molar ratio of Zr:propylene oxide = 1:4, was added to the solution to promote the polycondensation reaction and obtain a fibrous initial gel.

[0051] The prepared initial gel was immersed in an aging solution and heated in a water bath, and aged for 24 hours at 30℃, 45℃, and 60℃ respectively, following a stepwise increasing temperature range. After aging, the wet gel was removed and added to a hydrophobic modification solution, and fully immersed in a water bath at 60℃ for 24 hours. Then, the wet gel was removed and added to a displacement solution for solvent displacement, a total of 24 displacements to ensure that the solution in the wet gel was completely replaced. The aging solution was an ethanol solution containing 10% tetraethyl orthosilicate by volume; the hydrophobic modification solution was a hexane solution containing 20% ​​trimethylethoxysilane by volume; the displacement solution was a mixed solution of anhydrous ethanol and hexane at a volume ratio of 1:9, and the number of displacements was 12 to 24.

[0052] The prepared wet gel was placed in a desiccator, which was then placed at room temperature and sealed. A small vacuum filtration apparatus was used to periodically extract the solvent atmosphere from the desiccator until all the solution in the wet gel was converted to a gaseous phase and detached from the gel, forming a fibrous aerogel. Finally, the fibrous aerogel was removed from the desiccator and subjected to high-temperature annealing at 1000℃ to prepare a Zr-Y-La-Ti core-sheath structured fibrous ceramic aerogel.

[0053] The prepared core-sheath structured fibrous ceramic aerogel has a uniform morphology, moderate flexibility (maximum resilient compressive deformation can reach 70%), moderate thermal insulation performance (minimum thermal conductivity is 27.82mW / m·K), and excellent deformability.

Claims

1. A method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure, characterized in that, The steps are as follows: S1. Preparation of Zr-Y-La nanofiber ceramic aerogel: A precursor solution was prepared with a molar ratio of Zr:Y:La = 1:0.05~0.5:1~2. The solution was then electrospun and annealed at a high temperature of 800~1000℃ to prepare Zr-Y-La nanofiber ceramic aerogel. The receiving distance of the electrospinning was 0.6~0.9m and the voltage was 15~25kV. S2. Prepare a nanoparticle precursor solution with a molar ratio of Zr:Y:La:Ti = 1:0.05~0.5:0.5~2:0.5~2, disperse Zr-Y-La nanofiber ceramic aerogel in the solution, add a gel control agent and a gel accelerator to carry out a condensation reaction, and obtain a fibrous initial gel Zr-Y-La-Ti; the gel control agent is a mixture of polyethylene glycol and formamide with a molar ratio of Zr:polyethylene glycol:formamide = 1:0.1:0.1; the gel accelerator is propylene oxide with a molar ratio of Zr:propylene oxide = 1:4~6; S3. The initial gel is placed in an aging solution and aged in a stepped water bath at 30℃, 45℃, and 60℃, followed by hydrophobic modification and solvent replacement to obtain a wet gel Zr-Y-La-Ti. The aging solution is an ethanol solution containing 10% tetraethyl orthosilicate by volume, and the aging time is 12-24 hours. The hydrophobic modification solution is a hexane solution containing 20% ​​trimethylethoxysilane by volume, and the modification temperature is 30-60℃, with thorough soaking for 12-24 hours. The replacement solution is a mixed solution of anhydrous ethanol and hexane by volume ratio of 1:9, and the number of replacements is 12-24. S4. Place the wet gel in a sealed desiccator at room temperature, then remove the solvent atmosphere from the desiccator until the solution in the wet gel is completely converted into a gas phase and detached from the gel to form a fibrous aerogel. Then, anneal at a high temperature of 800-1000℃ to obtain a Zr-Y-La-Ti core-sheath structure fibrous ceramic aerogel. The inner layer of each fiber is a nanofiber ceramic aerogel core layer, and the outer layer is a nanoparticle ceramic aerogel sheath layer. The two are closely bonded together, and the fiber surface is smooth.

2. The method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure according to claim 1, characterized in that, In step S1, the molar ratio of the precursor solution is Zr:Y:La = 1:0.1:

1.

3. The method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure according to claim 1, characterized in that, In step S2, the molar ratio of the nanoparticle precursor solution is Zr:Y:La:Ti = 1:0.1:1:

1.

4. The method for preparing a flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure according to claim 1, characterized in that, In step S2, the molar ratio of Zr to propylene oxide is 1:4.

5.

5. A flexible, heat-insulating fibrous ceramic aerogel with a core-sheath structure, characterized in that, The aerogel is prepared by the method described in any one of claims 1 to 4; the aerogel is a Zr-Y-La-Ti system, with a single fiber having a double-layer tightly bonded structure, the inner layer being a nanofiber ceramic aerogel core and the outer layer being a nanoparticle ceramic aerogel sheath, and the fiber surface being smooth and without defects.

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