Ceramic aerogel and preparation method thereof

Abstract

The invention provides wrinkled microsphere ceramic aerogel and a preparation method thereof, and belongs to the field of ceramic aerogel. The method comprises the following steps: respectively preparing a continuous phase solution, a dispersed phase solution and a collection solution, introducing the continuous phase solution and the dispersed phase solution into a micro-fluidic chip according to a specific flow velocity ratio through a dual-channel micro-fluidic injection pump, shearing to form microspheres, fixing a wrinkle structure in the collection solution, and freeze-drying the obtained microspheres to obtain the wrinkle microsphere aerogel. Sintering the wrinkled microsphere aerogel at a high temperature in a nitrogen atmosphere, and removing impurities through ceramic transformation to obtain the wrinkled microsphere ceramic aerogel. According to the preparation method, a microfluidic-coagulating bath technology is combined with a segmented heating sintering process, so that a product forms a uniformly distributed wrinkle structure, strain is stored in advance to resist external shrinkage stress, the problem of insufficient structural stability of a traditional ceramic material is effectively improved, and the mechanical property and the heat insulation property are improved; and continuous production can be realized.

Description

Technical Field

[0001] This invention relates to the field of ceramic aerogels, and particularly to a wrinkled microsphere ceramic aerogel and its preparation method. Background Technology

[0002] Ceramic aerogels, as advanced materials with low thermal conductivity and lightweight properties, have shown broad application prospects in the field of high-temperature thermal insulation. Based on their preparation methods and structural characteristics, they can be classified into various types, such as ceramic precursor-converted aerogels, polymer-based composite aerogels, and ordinary microsphere-based ceramic aerogels. With the increasing demands for performance of thermal protection materials in extreme environments from aerospace, defense, and other fields, ceramic aerogels that combine high structural stability, excellent shrinkage resistance, and continuous production capabilities have become a core research direction for the future. Among these, wrinkled microsphere structures have become a key structural design focus due to their ability to optimize material mechanics and thermal insulation properties.

[0003] Aerogels prepared by traditional ceramic precursor conversion methods are prone to stress concentration due to uneven volume shrinkage during high-temperature pyrolysis, leading to the generation and propagation of microcracks. Polymer-based wrinkled microspheres exhibit poor temperature resistance, easily decomposing and failing above 500°C, making them unsuitable for harsh high-temperature environments. Ordinary ceramic microspheres are prone to surface cracking after high-temperature pyrolysis, resulting in insufficient structural integrity. Furthermore, existing preparation processes often rely on batch reactions, leading to low structural controllability and significant batch-to-batch variations, making it difficult to precisely control the wrinkle morphology while simultaneously ensuring material shrinkage resistance and continuous production requirements. In addition, the carbon component in carbon-ceramic composite systems is easily oxidized in aerobic environments above 400°C, further limiting its application in high-temperature fields. Therefore, this invention introduces a wrinkled microsphere ceramic aerogel that combines controllable wrinkled structure, excellent high-temperature stability, and continuous production characteristics to address the current technical challenges.

[0004] Currently, most research on wrinkled microspheres uses polymer materials as raw materials, and significant challenges remain in achieving precise control of fiber morphology and large-scale continuous production. For example, while Chinese patent CN202411984714.0 can prepare embolic microspheres with wrinkled morphology, increasing the contact area between the microspheres and the drug through wrinkle accumulation and enhancing structural stability, this method is limited by the inherent poor temperature resistance and easy softening and decomposition of polymer materials at high temperatures, making it difficult to maintain structural stability and functional reliability under long-term high temperature or thermal shock environments. Furthermore, its preparation process relies on batch reactions and complex post-processing steps, resulting in long process cycles and low structural controllability.

[0005] Patent CN117623768A uses gel microspheres, after washing or initial drying, as raw materials. These microspheres undergo a first soaking solution, followed by a second vacuum drying pretreatment, and are then sintered in stages in an oxidizing atmosphere to prepare ceramic microspheres. However, shrinkage easily occurs during sintering, resulting in poor stability and decreased mechanical properties. Furthermore, the production cycle is long, hindering efficient large-scale production. Precise control of vacuum levels is also required, limiting the adaptability to production equipment.

[0006] Under the influence of high-temperature sintering, traditional ceramic aerogels and ordinary microsphere-based ceramic materials are prone to significant volume shrinkage and structural cracking, making it difficult to stably retain the wrinkled morphology and resulting in insufficient structural integrity. However, current technologies struggle to precisely control the morphology of wrinkled microspheres while simultaneously achieving the desired shrinkage resistance, excellent mechanical properties, and continuous production requirements; achieving a balance between these two aspects remains challenging. Therefore, preparing wrinkled microsphere ceramic aerogels with controllable wrinkled structures, excellent high-temperature stability, and strong mechanical properties presents a significant challenge. Thus, developing a method for preparing wrinkled microsphere ceramic aerogels that allows for precise control of the wrinkled structure, good mechanical properties, high-temperature stability, and continuous production is of significant research value and application importance. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this patent describes the preparation of a wrinkled microsphere ceramic aerogel. The uniformly distributed wrinkled structure endows the ceramic aerogel with excellent shrinkage resistance and mechanical properties. This invention proposes a simple and efficient preparation process route. Through precise programmed control of process parameters, it is possible to achieve both accurate control of microsphere morphology and continuous production, effectively meeting the core requirements of practical application scenarios.

[0008] 1. The ceramic aerogel and its preparation method according to the present invention include the following steps:

[0009] S1. Preparation of continuous phase solution: Organic solvent 1 is mixed with deionized water and then functional filler 1 is added and stirred to disperse, resulting in a homogeneous and stable continuous phase solution;

[0010] S2. Preparation of dispersed phase solution: The ceramic precursor is fully dissolved in organic solvent 2, and after thorough stirring, a homogeneous and stable dispersed phase solution is obtained;

[0011] S3. Preparation of the collected liquid: Dissolve the functional additive 2 completely in the organic solvent 3, and stir thoroughly to obtain the collected liquid;

[0012] S4. Preparation of wrinkled microsphere aerogel: The spinning solution was subjected to microfluidic-coagulation bath operation and then freeze-dried to obtain wrinkled microsphere aerogel.

[0013] S5. Ceramization: The above-mentioned wrinkled microsphere aerogel is placed in a heating furnace and sintered at high temperature under a nitrogen atmosphere. After removing impurities through ceramization transformation, wrinkled microsphere ceramic aerogel is obtained.

[0014] 2. In step S1, the preferred range of materials is characterized by including:

[0015] Organic solvent 1 is selected from one or more of glycerol, divinylbenzene, n-hexane, N,N-dimethylformamide, N-methyl-2-pyrrolidone, ethanol, dimethyl sulfoxide, and tetrahydrofuran. Functional additive 1 is selected from one or more of graphene oxide, reduced graphene oxide, MXene (transition metal carbide), boron nitride nanosheets, nano-silica, and carbon nanotubes.

[0016] 3. In step S2, the preferred range of materials is characterized by including:

[0017] The ceramic precursor is selected from one or more of polycarbosilane, polysilazane, polysiloxane, polyborosiloxane, and polyborosilazane; the organic solvent 2 is selected from one or more of toluene, xylene, divinylbenzene, n-hexane, N,N-dimethylformamide, N-methyl-2-pyrrolidone, ethanol, and tetrahydrofuran.

[0018] 4. In step S3, the preferred range of materials is characterized by including:

[0019] The functional filler 2 is selected from one or more of the following: aminated polyhedral oligomeric silsesquioxane, mercapto polyhedral oligomeric silsesquioxane, graphene oxide nano-silica, carbon nanotubes, and carboxylated polyhedral oligomeric silsesquioxane; the organic solvent 3 is selected from one of the following: n-hexane, cyclohexane, petroleum ether, and deionized water.

[0020] 5. The preparation method according to 1-3, characterized in that:

[0021] The amounts of organic solvent 1 (A), functional additive 1 (B), ceramic precursor (C), and organic solvent 2 (D) shall simultaneously satisfy the following relationships:

[0022] (A+B) 2 =15.3(C+1.36D)

[0023] This formula does not involve unit conversions.

[0024] 6. In step S4, the method described in S4 is characterized by comprising:

[0025] The dual-channel microfluidic coagulation bath conditions were controlled as follows: the flow rate of the continuous phase solution in channel 1 was 350 μL / min to 950 mL / min; the flow rate of the dispersed phase in channel 2 was 30 μL / min to 100 mL / min; the flow rate ratio was maintained at 2:1 to 10:1; the stirring speed in the coagulation bath was 30 to 100 rpm throughout the process; the collected solution containing microspheres was allowed to stand for 1 to 5 hours; it was then frozen at -85℃ for 1 to 5 hours; and dried continuously at 80℃ for 8 to 14 hours.

[0026] 7. The preparation method according to S5, characterized in that the high-temperature sintering temperature is 800℃~1200℃.

[0027] The above technical solution addresses the problems of low shrinkage resistance and insufficient thermal insulation performance of existing ceramic microspheres and wrinkled microspheres by providing a wrinkled microsphere ceramic aerogel with excellent shrinkage resistance and thermal insulation performance. It improves the shortcomings of traditional ceramic aerogels, such as poor strength, and enables continuous production. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. The following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope.

[0029] Figure 1 This is a scanning electron microscope image of the ceramic aerogel after high-temperature pyrolysis of the wrinkled microspheres prepared in Example 1 of this application;

[0030] Figure 2 Scanning electron microscope image of the precursor polymer aerogel microsphere unit with a wrinkled structure prepared in Example 1 of this application; Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] In Examples 1-5 and Comparative Examples 1-3, the microfluidic chip ends all used 0.34 mm metal capillaries as electrodes. The sintering operation of the samples was carried out in a high-temperature oxygen-containing environment. Sodium dodecyl sulfate (SDS) solid powder was uniformly added to the continuous phase solution.

[0033] The ceramic precursors include, but are not limited to, at least one of polycarbosilane, polysilazane, polysiloxane, polyborosiloxane, and polyborosilazane. Different ceramic precursors have a decisive influence on the overall structure and properties of the material. This invention preferably uses the above-mentioned ceramic precursors to formulate the precursor solution to ensure the excellent overall performance of the material.

[0034] The solvents include, but are not limited to, one or more of glycerol, divinylbenzene, n-hexane, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, tetrahydrofuran, toluene, xylene, ethanol, cyclohexane, petroleum ether, and deionized water. The type of solvent affects the dispersion uniformity of the dispersed phase, the interfacial tension between the continuous and dispersed phases, and the miscibility of the solvent, thus affecting the shearing and shaping of microspheres and the fixation of their wrinkled morphology in microfluidics. Different types of solvents have different polarities and volatility; a suitable solution ensures that the microspheres have a uniform morphology during shearing, guaranteeing the integrity and fixation of the wrinkled structure and the structural stability during subsequent ceramization.

[0035] This invention prepares a microfluidic precursor solution by mixing polymers, solvents, and other raw materials in a specific ratio. During the preparation process, strict control of the raw material ratios, the order of addition, and the stirring parameters is required to ensure sufficient dispersion of the precursor solution, prevent damage to the rheological properties of the mixed solution, and thus guarantee the excellent stability of the precursor solution.

[0036] During the preparation process, the microspheres are subjected to shear forces from the continuous and dispersed phases, stirring forces from the collecting bath, and interfacial electrostatic forces between the filler and the solvent. The flow rate ratio of the continuous to the dispersed phases, solvent concentration, stirring speed in the coagulation bath, freezing temperature, and drying time directly affect the wrinkled morphology and structural stability of the microspheres. A higher flow rate ratio results in more pronounced wrinkles on the microsphere surface. Higher solvent concentrations lead to stronger interfacial complexation. A moderate stirring speed in the collecting bath results in uniform microsphere dispersion and structural stability. Sufficiently low freezing temperatures and adequate drying time prevent structural collapse caused by solvent residue.

[0037] Preferred process parameters:

[0038] The continuous phase solution flow rate in channel 1 is 350 μL / min to 950 μL / min;

[0039] The dispersed phase flow rate in channel 2 is 30 μL / min to 100 μL / min;

[0040] Maintain the flow rate ratio of 2:1 to 10:1; keep the stirring speed of the coagulation bath at 30 to 100 rpm throughout the process;

[0041] The collected liquid containing microspheres was left to stand for 1–5 hours, then frozen at -85℃ for 1–5 hours, and then dried continuously at 80℃ for 8–14 hours.

[0042] Each phase of the fluid is delivered to the microfluidic chip via a dual-channel microfluidic injection pump. Because the continuous phase velocity is significantly higher than the dispersed phase velocity, the dispersed phase fluid is sheared by the continuous phase fluid at the cross-channel, forming microspheres of uniform size. After flowing out from the chip end, the microspheres immediately enter a collection bath, which is magnetically stirred throughout to ensure uniform dispersion and prevent aggregation of the microspheres. Electrostatic interactions occur between the filler and the ligands in the coagulation bath, forming an interfacial layer that shapes the wrinkled structure. The microspheres are then allowed to settle in the collection bath to allow for sufficient interfacial complexation. Residual solvent is then removed by freezing, followed by multiple soakings to replace residual solvent. Finally, vacuum drying solidifies the microspheres, yielding a wrinkled microsphere aerogel.

[0043] The mechanism of the wrinkled microsphere structure of the present invention is as follows: During the high-temperature ceramicization process, the surface wrinkles of the microspheres with wrinkled structures can store strain in advance. When the ceramic precursor undergoes thermal shrinkage, the wrinkles effectively buffer and offset thermal stress through the stretching effect, inhibiting disordered shrinkage. In addition, the spherical morphology can disperse the surface shrinkage tension, avoid cracking caused by local stress concentration, and significantly improve the dimensional stability and shrinkage resistance of the ceramic aerogel. The wrinkled structure on the surface of the microspheres forms an alternating convex and concave morphology. When constructing a three-dimensional aerogel network, the mechanical interlocking effect between the wrinkles enhances the bonding strength between the microspheres. At the same time, the spherical microspheres, as dispersion units, can hinder crack propagation through stress dispersion effect and promote crack path deflection.

[0044] The following is a further detailed description with reference to specific embodiments:

[0045] Example 1

[0046] Preparation of continuous phase solution: Glycerol and deionized water were mixed at a volume ratio of 1:4.0 and stirred thoroughly. Then, an appropriate amount of sodium dodecyl sulfate (SDS) solid powder was added and stirred with a magnetic stirrer for about 30 minutes to dissolve it completely. Graphene oxide (GO) particles were added to the above solution and ultrasonically dispersed for 30 minutes to obtain a continuous phase solution of 1 mg / mL.

[0047] Preparation of dispersed phase solution: Polycarbosilane (PCS) was added to toluene solvent and stirred with a magnetic stirrer for about 2 hours until the PCS was completely dissolved, resulting in a homogeneous and stable PCS ceramic precursor mixed dispersed phase solution with a mass fraction of 1%.

[0048] Preparation of the collection solution: Take the aminated polyhedral oligomeric silsesquioxane (POSS-NH2) ligand, add it to n-hexane, and stir with a magnetic stirrer for about 1 hour until the ligand is completely dissolved to obtain a 1 mg / mL POSS-NH2-n-hexane collection solution.

[0049] Preparation of wrinkled microsphere aerogel: Using a dual-channel injection pump, the continuous phase and dispersed phase were introduced into the cross channel of a microfluidic chip at flow rates of 650 μL / min and 100 μL / min (flow rate ratio 6.5:1). The continuous phase sheared the dispersed phase into uniform droplets, which were then introduced into a collection bath. Magnetic stirring was performed at 100 rpm throughout the process to fix the wrinkled structure on the microsphere surface. After collection, the microsphere-containing collection solution was allowed to stand for 2 hours; then frozen at -85℃ for 2 hours; and finally dried at 80℃ for 10 hours to obtain the wrinkled microsphere aerogel.

[0050] Aerogel ceramization: The wrinkled microsphere aerogel was placed in a heating furnace and sintered in a nitrogen atmosphere. The temperature was increased to 1000℃ at a rate of 5℃ / min and held for 3 hours. Then it was naturally cooled to room temperature to obtain the wrinkled microsphere ceramic aerogel.

[0051] Example 2

[0052] Preparation of continuous phase solution: Divinylbenzene (DVB) and deionized water were mixed at a volume ratio of 1:4.0 and stirred thoroughly. Then, an appropriate amount of sodium dodecyl sulfate (SDS) solid powder was added and stirred with a magnetic stirrer for about 30 minutes to dissolve it completely. Reduced graphene oxide (rGO) particles were added to the above solution and ultrasonically dispersed for 30 minutes to obtain a continuous phase solution of 1 mg / mL.

[0053] Preparation of dispersed phase solution: Polyborosilazane (PBSZ) was added to toluene solvent and stirred with a magnetic stirrer for about 2 hours until PCS was completely dissolved, resulting in a homogeneous and stable PCS ceramic precursor mixed dispersed phase solution with a mass fraction of 1%.

[0054] Preparation of the collection solution: Take the ligand of mercaptopolyhedral oligomeric silsesquioxane (POSS-SH) and add it to n-hexane. Stir with a magnetic stirrer for about 1 hour until the ligand is completely dissolved to obtain a 1 mg / mL POSS-SH-n-hexane collection solution.

[0055] Preparation of wrinkled microsphere aerogel: Using a dual-channel injection pump, the continuous phase and dispersed phase were introduced into the cross channel of a microfluidic chip at flow rates of 400 μL / min and 50 μL / min (flow rate ratio 8:1). The continuous phase sheared the dispersed phase into uniform droplets, which were then introduced into a collection bath. Magnetic stirring was performed at 50 rpm throughout the process to fix the wrinkled structure on the microsphere surface. After collection, the microsphere-containing collection solution was allowed to stand for 1 h; then frozen at -85℃ for 1 h; and finally dried at 80℃ for 8 h to obtain the wrinkled microsphere aerogel.

[0056] Aerogel ceramization: The wrinkled microsphere aerogel was placed in a heating furnace and sintered in a nitrogen atmosphere. The temperature was increased to 1200℃ at a rate of 5℃ / min and held for 3 hours. Then it was naturally cooled to room temperature to obtain the wrinkled microsphere ceramic aerogel.

[0057] Example 3

[0058] Preparation of continuous phase solution: Glycerol and deionized water were mixed at a volume ratio of 1:4.0 and stirred thoroughly. Then, an appropriate amount of sodium dodecyl sulfate (SDS) solid powder was added and stirred with a magnetic stirrer for about 30 minutes to dissolve it completely. Graphene oxide (GO) particles were added to the above solution and ultrasonically dispersed for 30 minutes to obtain a continuous phase solution of 1 mg / mL.

[0059] Preparation of dispersed phase solution: Polycarbosilane (PCS) was added to toluene solvent and stirred with a magnetic stirrer for about 2 hours until the PCS was completely dissolved, resulting in a homogeneous and stable PCS ceramic precursor mixed dispersed phase solution with a mass fraction of 1%.

[0060] Preparation of the collection solution: Take the aminated polyhedral oligomeric silsesquioxane (POSS-NH2) ligand, add it to n-hexane, and stir with a magnetic stirrer for about 1 hour until the ligand is completely dissolved to obtain a 1 mg / mL POSS-NH2-n-hexane collection solution.

[0061] Preparation of wrinkled microsphere aerogel: Using a dual-channel injection pump, the continuous phase and dispersed phase were introduced into the cross channel of a microfluidic chip at flow rates of 900 μL / min and 90 μL / min respectively (flow rate ratio 10:1). The continuous phase sheared the dispersed phase into uniform droplets, which were then introduced into a collection bath. Magnetic stirring was performed at 80 rpm throughout the process to fix the wrinkled structure on the microsphere surface. After collection, the microsphere-containing collection solution was allowed to stand for 3 h; then frozen at -85℃ for 3 h; and finally dried at 80℃ for 12 h to obtain the wrinkled microsphere aerogel.

[0062] Aerogel ceramization: The wrinkled microsphere aerogel was placed in a heating furnace and sintered in a nitrogen atmosphere. The temperature was increased to 800℃ at a rate of 5℃ / min and held for 3 hours. Then it was naturally cooled to room temperature to obtain the wrinkled microsphere ceramic aerogel.

[0063] Example 4

[0064] Preparation of continuous phase solution: Deionized water and divinylbenzene (DVB) were mixed at a weight ratio of 1:4.0 and stirred thoroughly. Then, an appropriate amount of sodium dodecyl sulfate (SDS) solid powder was added and stirred with a magnetic stirrer for about 30 minutes to dissolve it completely. Reduced graphene oxide (rGO) particles were added to the above solution and ultrasonically dispersed for 30 minutes to obtain a continuous phase solution of 1 mg / mL.

[0065] Preparation of dispersed phase solution: Polycarbosilane (PCS) was added to toluene solution and stirred with a magnetic stirrer for about 2 hours until the PCS was completely dissolved, resulting in a homogeneous and stable PCS ceramic precursor mixed dispersed phase solution with a mass fraction of 1%.

[0066] Preparation of the collection solution: Take the aminated polyhedral oligomeric silsesquioxane (POSS-NH2) ligand, add it to n-hexane, and stir with a magnetic stirrer for about 1 hour until the ligand is completely dissolved to obtain a 1 mg / mL POSS-NH2-n-hexane collection solution.

[0067] Preparation of wrinkled microsphere aerogel: Using a dual-channel injection pump, the continuous phase and dispersed phase were introduced into the cross channel of a microfluidic chip at flow rates of 490 μL / min and 70 μL / min (flow rate ratio 7:1). The continuous phase sheared the dispersed phase into uniform droplets, which were then introduced into a collection bath. Magnetic stirring was performed at 60 rpm throughout the process to fix the wrinkled structure on the microsphere surface. After collection, the microsphere-containing collection solution was allowed to stand for 4 h; then frozen at -85℃ for 4 h; and finally dried at 80℃ for 12 h to obtain the wrinkled microsphere aerogel.

[0068] Aerogel ceramization: The wrinkled microsphere aerogel was placed in a heating furnace and sintered in a nitrogen atmosphere. The temperature was increased to 1000℃ at a rate of 5℃ / min and held for 3 hours. Then it was naturally cooled to room temperature to obtain the wrinkled microsphere ceramic aerogel.

[0069] Example 5

[0070] Preparation of continuous phase solution: Tetrahydrofuran and deionized water were mixed at a volume ratio of 1:4.0 and stirred thoroughly. Then, an appropriate amount of sodium dodecyl sulfate (SDS) solid powder was added and stirred with a magnetic stirrer for about 30 minutes to dissolve it completely. Carbon nanotubes were added to the above solution and ultrasonically dispersed for 30 minutes to obtain a continuous phase solution of 1 mg / mL.

[0071] Preparation of dispersed phase solution: Polysilazane (PSN) was added to xylene solvent and stirred with a magnetic stirrer for about 2 hours until PCS was completely dissolved, resulting in a homogeneous and stable PCS ceramic precursor mixed dispersed phase solution with a mass fraction of 1%.

[0072] Preparation of the collection solution: Take the aminated polyhedral oligomeric silsesquioxane (POSS-NH2) ligand, add it to n-hexane, and stir with a magnetic stirrer for about 1 hour until the ligand is completely dissolved to obtain a 1 mg / mL POSS-NH2-n-hexane collection solution.

[0073] Preparation of wrinkled microsphere aerogel: Using a dual-channel injection pump, the continuous phase and dispersed phase were introduced into the cross channel of a microfluidic chip at flow rates of 540 μL / min and 60 μL / min (flow rate ratio 9:1). The continuous phase sheared the dispersed phase into uniform droplets, which were then introduced into a collection bath. Magnetic stirring was performed at 70 rpm throughout the process to fix the wrinkled structure on the microsphere surface. After collection, the microsphere-containing collection solution was allowed to stand for 5 h; then frozen at -85℃ for 5 h; and finally dried at 80℃ for 10 h to obtain the wrinkled microsphere aerogel.

[0074] Aerogel ceramization: The wrinkled microsphere aerogel was placed in a heating furnace and sintered in a nitrogen atmosphere. The temperature was increased to 800℃ at a rate of 5℃ / min and held for 3 hours. Then it was naturally cooled to room temperature to obtain the wrinkled microsphere ceramic aerogel.

[0075] Comparative Example 1

[0076] Preparation of continuous phase solution: Deionized water and divinylbenzene (DVB) were mixed at a weight ratio of 1:5.0 and stirred thoroughly. Then, an appropriate amount of sodium dodecyl sulfate (SDS) solid powder was added and stirred with a magnetic stirrer for about 30 minutes to dissolve it completely. Reduced graphene oxide (rGO) particles were added to the above solution and ultrasonically dispersed for 30 minutes to obtain a continuous phase solution of 1 mg / mL.

[0077] Preparation of dispersed phase solution: Polycarbosilane (PCS) was added to toluene solution and stirred with a magnetic stirrer for about 2 hours until the PCS was completely dissolved, resulting in a homogeneous and stable PCS ceramic precursor mixed dispersed phase solution with a mass fraction of 1%.

[0078] Preparation of the collection solution: Take the aminated polyhedral oligomeric silsesquioxane (POSS-NH2) ligand, add it to n-hexane, and stir with a magnetic stirrer for about 1 hour until the ligand is completely dissolved to obtain a 1 mg / mL POSS-NH2-n-hexane collection solution.

[0079] Preparation of wrinkled microsphere aerogel: Using a dual-channel injection pump, the continuous phase and dispersed phase were introduced into the cross channel of a microfluidic chip at flow rates of 500 μL / min and 100 μL / min (flow rate ratio 5:1). The continuous phase sheared the dispersed phase into uniform droplets, which were then introduced into a collection bath. Magnetic stirring was performed at 150 rpm throughout the process to fix the wrinkled structure on the microsphere surface. After collection, the microsphere-containing collection solution was allowed to stand for 6 h; then frozen at -85℃ for 5 h; and finally dried at 80℃ for 12 h to obtain the final wrinkled microsphere aerogel.

[0080] Aerogel ceramization: The wrinkled microsphere aerogel was placed in a heating furnace and sintered in a nitrogen atmosphere. The temperature was increased to 1400℃ at a rate of 5℃ / min and held for 3 hours. Then it was naturally cooled to room temperature to obtain the wrinkled microsphere ceramic aerogel.

[0081] Comparative Example 2

[0082] Preparation of continuous phase solution: Take n-hexane and deionized water at a volume ratio of 1:6.0, mix thoroughly, add an appropriate amount of sodium dodecyl sulfate (SDS) solid powder, stir with a magnetic stirrer for about 30 min to dissolve it completely, add reduced graphene oxide (rGO) particles to the above solution, and sonicate for 30 min to obtain a 1 mg / mL continuous phase solution.

[0083] Preparation of dispersed phase solution: Polycarbosilane (PCS) was added to tetrahydrofuran solvent and stirred with a magnetic stirrer for about 2 hours until the PCS was completely dissolved, resulting in a homogeneous and stable PCS ceramic precursor mixed dispersed phase solution with a mass fraction of 1%.

[0084] Preparation of the collection solution: Take the aminated polyhedral oligomeric silsesquioxane (POSS-NH2) ligand, add it to n-hexane, and stir with a magnetic stirrer for about 1 hour until the ligand is completely dissolved to obtain a 1 mg / mL POSS-NH2-n-hexane collection solution.

[0085] Preparation of wrinkled microsphere aerogel: Using a dual-channel injection pump, the continuous phase and dispersed phase were introduced into the cross channel of a microfluidic chip at flow rates of 850 μL / min and 100 μL / min (flow rate ratio 8.5:1). The continuous phase sheared the dispersed phase into uniform droplets, which were then introduced into a collection bath. Magnetic stirring was performed at 150 rpm throughout the process to fix the wrinkled structure on the microsphere surface. After collection, the microsphere-containing collection solution was allowed to stand for 4 h; then frozen at -85℃ for 7 h; and finally dried at 80℃ for 14 h to obtain the final wrinkled microsphere aerogel.

[0086] Aerogel ceramization: The wrinkled microsphere aerogel was placed in a heating furnace and sintered in a nitrogen atmosphere. The temperature was increased to 1200℃ at a rate of 5℃ / min and held for 3 hours. Then it was naturally cooled to room temperature to obtain the wrinkled microsphere ceramic aerogel.

[0087] Comparative Example 3

[0088] Preparation of continuous phase solution: Ethanol and deionized water were mixed at a volume ratio of 1:7.0 and stirred thoroughly. Then, an appropriate amount of sodium dodecyl sulfate (SDS) solid powder was added and stirred with a magnetic stirrer for about 30 minutes to dissolve it completely. Graphene oxide (GO) particles were added to the above solution and ultrasonically dispersed for 30 minutes to obtain a continuous phase solution of 1 mg / mL.

[0089] Preparation of dispersed phase solution: Polycarbosilane (PCS) was added to toluene solvent and stirred with a magnetic stirrer for about 2 hours until the PCS was completely dissolved, resulting in a homogeneous and stable PCS ceramic precursor mixed dispersed phase solution with a mass fraction of 1%.

[0090] Preparation of the collection solution: Take the ligand of mercaptopolyhedral oligomeric silsesquioxane (POSS-SH) and add it to ethanol. Stir with a magnetic stirrer for about 1 hour until the ligand is completely dissolved to obtain a 1 mg / mL POSS-SH-n-hexane collection solution.

[0091] Preparation of wrinkled microsphere aerogel: Using a dual-channel injection pump, the continuous phase and dispersed phase were introduced into the cross channel of a microfluidic chip at flow rates of 1200 μL / min and 300 μL / min (flow rate ratio 4:1). The continuous phase sheared the dispersed phase into uniform droplets, which were then introduced into a collection bath. Magnetic stirring was performed at 200 rpm throughout the process to fix the wrinkled structure on the microsphere surface. After collection, the microsphere-containing collection solution was allowed to stand for 6 h; then frozen at -85℃ for 6 h; and finally dried at 80℃ for 15 h to obtain the final wrinkled microsphere aerogel.

[0092] Aerogel ceramization: The wrinkled microsphere aerogel was placed in a heating furnace and sintered in a nitrogen atmosphere. The temperature was increased to 1400℃ at a rate of 5℃ / min and held for 3 hours. Then it was naturally cooled to room temperature to obtain the wrinkled microsphere ceramic aerogel.

[0093] The present invention tests the comprehensive performance of the wrinkled microsphere ceramic aerogel materials finally prepared in Examples 1-5 and Comparative Examples 1-3.

[0094] The volume shrinkage rate was determined according to GB / T10295-2008 standard. The test results are shown in Table 1; comparative example 4 refers to the method of patent CN117623768A; as can be seen from Table 1, the wrinkled microsphere structure ceramic aerogel material obtained by the preparation route described in this invention has a low thermal conductivity, as low as 0.032 W / m·K, a sphericity higher than 85%, and a volume shrinkage rate of less than 20%; the symbol " / " in Table 1 indicates that this performance index was not tested.

[0095] The volume shrinkage rate is calculated using the following formula: Volume shrinkage rate = (volume of aerogel material before ceramization transformation - volume of ceramic aerogel material after ceramization transformation) / volume of aerogel material before ceramization transformation × 100%, where the volumes of the material before and after ceramization transformation are tested according to the GB / T17911-2018 standard.

[0096] The number of folds is calculated using the following formula:

[0097] Number of folds = Total number of folds in the statistical area ÷ Actual surface area of ​​the statistical area

[0098] Examples 1-5 systematically verified the technical feasibility and structural performance advantages of preparing wrinkled microsphere ceramic aerogels using a dual-channel microfluidic-coagulation bath technology combined with sintering. Each example differentiated the ceramic precursor system, the type of functional additives, and the core process parameters. Despite significant differences in variable settings, all examples ultimately yielded uniform microsphere structures with clear wrinkled morphology. Basic performance tests showed that this series of materials possesses high specific surface area, excellent sphericity, and low thermal conductivity, while the sintering process imparts good structural stability. These results fully demonstrate that the proposed preparation method can effectively achieve controllable regulation of the wrinkled microsphere structure, significantly improving its thermal insulation performance while ensuring structural stability, providing key technical support for the subsequent application of this type of material.

[0099] The preparation results and system performance analysis of Comparative Examples 1-3 show that if the preferred microfluidic extrusion parameters, sintering heating rates, and other optimized process parameters described in this invention are not fully followed, and the constraints of the correlation formula for wrinkle structure control are not met, the overall performance of the obtained ceramic aerogel samples all show a significant decline. Specifically, the specific surface area of ​​the material is significantly reduced compared to the sample in the example, it is prone to cracking during pyrolysis, and the thermal conductivity at room temperature increases. The microscopic morphology observation results also show that the integrity of the surface wrinkle structure of such samples is damaged, with defects such as disordered wrinkle distribution and local depressions, and the connectivity of the internal ceramic three-dimensional porous network also decreases. This phenomenon fully illustrates that any deviation from the process conditions will directly interfere with the orderly construction of wrinkled microspheres, destroy the skeletal stability of the ceramic network, and ultimately lead to the deterioration of the core performance of the material.

[0100] Comparative Example 4 shows that the microspheres prepared by the direct sintering method have high thermal conductivity, making continuous production difficult. The method described in this patent, however, can effectively achieve continuous production and possesses good process continuity and stability.

[0101] Current mainstream research mostly focuses on wrinkled microspheres and ceramic microspheres. Although similar to this research, their material and structural limitations hinder their application in the field of high-temperature insulation. The main differences between the wrinkled microsphere ceramic aerogel of this invention are:

[0102] The core difference between this patent and polymer-based microspheres or carbon-ceramic composite systems lies in the different material systems and performance objectives. Polymer-based microspheres have poor heat resistance (easily decomposed and degraded above 500℃), and the carbon component in carbon-ceramic composite systems is easily oxidized and degraded in an aerobic environment above 400℃. Furthermore, the high-temperature crystallization of the ceramic phase easily forms cracks, destroying the overall structure. This patent focuses on an all-ceramic aerogel system, using microfluidic technology to prepare wrinkled microspheres, which are then sintered at high temperatures to transform them into a ceramic structure. Leveraging its all-ceramic properties, it possesses high-temperature resistance, oxidation resistance, and structural stability, making it suitable for harsh conditions such as ultra-high temperatures. The wrinkled morphology can pre-store strain; when the ceramic precursor undergoes high-temperature pyrolysis and shrinkage, the expansion of the wrinkles can directly offset some of the shrinkage stress, preventing structural collapse and ultimately ensuring structural integrity. On the other hand, spherical surfaces tend to shrink more due to their atomic arrangement characteristics, while the uneven morphology of the wrinkles can disperse surface shrinkage tension, alleviating this shrinkage problem.

[0103] Secondly, this process employs a dual-channel microfluidic injection pump to ensure a stable supply of the continuous / dispersed phase, enabling continuous production of wrinkled microspheres and subsequent ceramic aerogels without interrupting operations. Furthermore, the degree of wrinkling can be flexibly controlled by adjusting the flow rate ratio. Simultaneously, the process avoids batch-to-batch variations, reduces manual intervention, and improves production efficiency and product consistency. The precise control characteristics of microfluidic technology also address the challenge of traditional processes in continuously and stably preparing wrinkled microspheres with uniform morphology. Other applications and research objectives for wrinkled microspheres or ceramic microspheres often focus on specific functional adaptations, such as in the medical field, building insulation, and areas experiencing significant volume shrinkage during ceramization. However, the core research objective of this study, focusing on wrinkled microsphere ceramic aerogels, is to address the inherent volume shrinkage and cracking issues during the high-temperature pyrolysis of ceramic precursors. Its application focuses on thermal insulation and structural protection in ultra-high temperature and harsh environments, filling the application gap of traditional microsphere materials in ultra-high temperature and harsh scenarios, clearly distinguishing it from the functional positioning and applicable scenarios of other microspheres.

[0104] Table 1: Performance indicators of samples obtained in Examples 1-5 and Comparative Examples 1-4

[0105]

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing ceramic aerogel, characterized in that, Includes the following steps: S1. Mix organic solvent 1 with deionized water, then add functional filler 1 and stir to disperse, to obtain a homogeneous and stable continuous phase solution; S2. The ceramic precursor polymer is fully dissolved in organic solvent 2, and after thorough stirring, a homogeneous and stable dispersed phase solution is obtained. S3. Dissolve the functional additive 2 completely in the organic solvent 3, and stir thoroughly to obtain the collected liquid; S4. The spinning solution is subjected to microfluidic-coagulation bath operation and then freeze-dried to obtain wrinkled microsphere aerogel. S5. The above-mentioned wrinkled microsphere aerogel is placed in a heating furnace and sintered at high temperature under a nitrogen atmosphere. After removing impurities through ceramic transformation, wrinkled microsphere ceramic aerogel is obtained.

2. The method according to claim 1, characterized in that, Step S1 includes: Organic solvent 1 is selected from one or more of glycerol, divinylbenzene, n-hexane, N,N-dimethylformamide, N-methyl-2-pyrrolidone, ethanol, dimethyl sulfoxide, and tetrahydrofuran. Functional additive 1 is selected from one or more of graphene oxide, reduced graphene oxide, MXene (transition metal carbide), boron nitride nanosheets, nano-silica, and carbon nanotubes.

3. The method according to claim 1, characterized in that, Step S2 includes: The ceramic precursor polymer is selected from one or more of polycarbosilane, polysilazane, polysiloxane, polyborosiloxane, and polyborosilazane; the organic solvent 2 is selected from one or more of toluene, xylene, divinylbenzene, n-hexane, N,N-dimethylformamide, N-methyl-2-pyrrolidone, ethanol, and tetrahydrofuran.

4. The method according to claim 1, characterized in that, Step S3 includes: The functional filler 2 is selected from one or more of the following: aminated polyhedral oligomeric silsesquioxane, mercapto polyhedral oligomeric silsesquioxane, graphene oxide nano-silica, carbon nanotubes, and carboxylated polyhedral oligomeric silsesquioxane; the organic solvent 3 is selected from one of the following: n-hexane, cyclohexane, petroleum ether, and deionized water.

5. The preparation method according to claim 1, characterized in that: The amounts of organic solvent 1 (A), functional additive 1 (B), ceramic precursor (C), and organic solvent 2 (D) shall simultaneously satisfy the following relationships: (A+B) 2 =15.3(C+1.36D)。 6. The method according to claim 1, characterized in that, Step S4 includes: The dual-channel microfluidic coagulation bath conditions were controlled as follows: the flow rate of the continuous phase solution in channel 1 was 350 μL / min to 950 μL / min; the flow rate of the dispersed phase in channel 2 was 30 μL / min to 100 μL / min; the flow rate ratio was maintained at 2:1 to 10:1; the stirring speed in the coagulation bath was 30 to 100 rpm throughout the process; the collected liquid containing microspheres was allowed to stand for 1 to 5 hours; it was frozen at -85℃ for 1 to 5 hours; and it was continuously dried at 80℃ for 8 to 14 hours.

7. The preparation method according to claim 1, characterized in that, The high-temperature sintering temperature range in step S5 is 800℃~1200℃.

8. A wrinkled microsphere ceramic aerogel, characterized in that... Prepared according to the preparation method described in claims 1-7.

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