Method for preparing ceramic nanofiber aerogel with precise structure through cold field 3D printing and ceramic nanofiber aerogel

Abstract

The invention relates to a method for preparing ceramic nanofiber aerogel with a precise structure through cold field 3D printing, which comprises the following steps: mixing an ice crystal constraining agent with deionized water to form a general printing ink precursor for inhibiting freezing volume expansion; ceramic nanofiber short fibers and an inorganic binder are added, and efficient dispersion and directional arrangement of the ceramic short fibers are achieved through a high-pulse pneumatic vortex field; the ceramic fiber printing ink with high solid content and shear thinning characteristics is obtained by adopting a gradient heating evaporation coupling process; an ice crystal instantaneous freezing shaping technology and a nonlinear temperature control technology are utilized to realize micron-sized structure shape preservation; and drying and calcining to obtain the interconnected ceramic nanofiber aerogel. Compared with the prior art, the method has the advantages that the dependence of traditional printing ink on a high-content organic tackifier, a solution with complex characteristics or a special initiator is broken through, a general printing ink precursor is obtained, and in-situ, rapid and high-fidelity 3D printing of the ceramic nanofiber aerogel with a precise structure is realized.

Description

Technical Field

[0001] This invention relates to the field of advanced ceramic materials and additive manufacturing technology, and in particular to a method for preparing precision-structured ceramic nanofiber aerogels by cold field 3D printing, and ceramic nanofiber aerogels. Background Technology

[0002] Ceramic aerogels, as a new generation of high-performance porous materials, possess the inherent high-temperature resistance, corrosion resistance, and wear resistance of ceramic materials. They also exhibit unique advantages such as high porosity, ultra-low bulk density, large specific surface area, tunable elastic modulus, and ultra-lightweight and ultra-elastic properties, making them widely applicable in high-temperature insulation, oil-water separation, sound absorption and noise reduction, and catalytic degradation. Ceramic aerogels are primarily prepared using sol-gel or ceramic particle / fiber dispersions via direct freeze-drying molding technology. However, their macroscopic structure relies on mold forming or secondary machining, resulting in low processing efficiency and poor precision for complex irregular components. Furthermore, their internal microstructure exhibits randomly distributed mesh, through-pore, or gradient pore morphology, exhibiting defects such as uneven pore size distribution, difficulty in controlling pore size, and poor pore connectivity. This makes it difficult to meet the customized requirements of precision devices in high-precision fields such as aerospace, medical devices, and energy development for the internal and external topological structures of materials.

[0003] Additive manufacturing technology provides a new way to overcome the above limitations. Among them, 3D printing technology realizes the moldless forming of three-dimensional solid structures through digital modeling, which has outstanding advantages such as short manufacturing cycle and simple manufacturing process, especially for the rapid prototyping of complex and irregular structural parts. However, existing research focuses on organic polymer materials and carbon-based material systems, such as selective laser sintering (SLS), two-photon stereolithography (SLA), and mapping-acoustic wave forming technology, which face the challenge of adaptability in the field of ceramic materials. Researchers adopted an organic-inorganic hybrid strategy to disperse ceramic particles in the existing mature organic ink system and successfully prepared silica aerogel (ACS Applied Material & Interfaces, 2018, 10(26): 22718-22730). However, this scheme is essentially an organic-inorganic hybrid material, which has problems such as easy decomposition at high temperature and cannot meet the high-temperature application scenarios of ceramic materials. Subsequently, ceramic aerogel materials were prepared by mixing ceramic materials with photoinitiators such as photosensitive resins or photosensitive monomers, followed by photocuring and high-temperature calcination (CN116425561A). However, this method suffers from drawbacks such as poor matching between photoinitiators and light sources, constraints on the shape and size of raw materials, and limited solid content in the slurry. Recently, thermosetting and gel curing mechanisms have been applied to the 3D printing of ceramic aerogels, improving printing precision and fidelity. For example, CN114213142A prepared printing ink by mixing nano-silica powder with aluminum sol and urea, and induced gelation of aluminum sol through urea thermal decomposition and ammoniation to prepare silica-alumina oxide ceramic aerogels; CN104108131A obtained ceramic materials by mixing ceramic powder with a slurry with cryogelation properties. However, the above methods merely transform the dependence on photoinitiators or complex chemical components into a dependence on thermosensitive / chemical triggers, and the slow curing speed of single layers leads to easy fusion between layers, resulting in low printing resolution and poor fidelity. Furthermore, existing technologies mostly involve the mixed printing of ceramic particles. The ceramic aerogels prepared based on the particle stacking principle have a microscopic structure of beaded structures with particle-particle neck connections. Under stress, they produce a significant stress concentration effect, exhibiting typical brittle fracture characteristics, which impairs the reliability of aerogel applications.

[0004] Therefore, the rapid, high-precision, and high-fidelity 3D printing technology of existing ceramic nanofiber aerogels still needs to be solved. Specifically, it faces the following problems: 1) Existing photocuring / thermal curing / gel curing processes require specific chemical components or precise reaction conditions, which severely restricts the universal development of printing inks; 2) Traditional photocuring / thermal curing methods have slow response speeds, resulting in excessive interlayer fusion and low feature resolution; 3) Traditional printing inks have high organic thickener content, causing severe volume shrinkage after sintering of the printed body; 4) High-solids-content ceramic nanofiber inks are difficult to disperse, prone to shear thickening and printhead clogging, while low-solids-content systems have difficulty maintaining the integrity and mechanical reliability of the formed structure. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a method for preparing precision-structured ceramic nanofiber aerogels using cold-field 3D printing, and a method for preparing ceramic nanofiber aerogels. This invention utilizes the low-temperature rapid freezing properties of water and controls its anomalous expansion during freezing, breaking through the dependence of traditional printing inks on complex solutions or special initiators. At the same time, it introduces a gradient heating evaporation coupling process to replace the use of traditional high-solids-content organic thickeners, effectively avoiding structural sintering shrinkage, obtaining a universal printing ink precursor, greatly expanding the application field of 3D printing, and realizing in-situ, rapid, and high-fidelity 3D printing of ceramic nanofiber aerogels with precision structures.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The first aspect of this invention provides a method for preparing precision-structured ceramic nanofiber aerogels using cold field 3D printing, comprising the following steps:

[0008] S1: By using the molecular bonding between the ice crystal restraint agent and deionized water, the volume expansion during the freeze crystallization process is suppressed, forming a universal printing ink precursor with zero volume expansion during freeze crystallization;

[0009] S2: Add ceramic nanofiber short fibers and inorganic binder to the general-purpose printing ink precursor obtained in S1, peel off the fiber aggregates through the cavitation effect generated by the high-pulse aerodynamic vortex field, and achieve the directional arrangement of individual fibers in the three-dimensional turbulent field;

[0010] S3: For the dispersion system obtained in S2, a gradient heating evaporation coupling process is used to regulate the solvent evaporation kinetics, and the fiber solid content is increased in stages to obtain a printable ink that has both high solid content and shear thinning properties.

[0011] S4: The printable ink obtained in S3 is extruded through the print head to the ultra-low temperature semiconductor cold stage. The fiber position is locked in the micron-level space by using ice crystal instant freezing and shaping technology, and nonlinear temperature control technology is used to maintain the same freezing rate of each printed layer to obtain a ceramic fiber-ice crystal composite.

[0012] S5: The ceramic fiber-ice crystal composite obtained in S4 is vacuum dried and sublimated to remove the ice crystal template, and then calcined at high temperature to promote the in-situ condensation of the inorganic binder at the fiber interlacing points, constructing a three-dimensional inorganic topological network, and obtaining an interconnected ceramic nanofiber aerogel with a precise structure.

[0013] Furthermore, S1 specifically includes the following steps:

[0014] The ice crystal restraining agent was uniformly mixed with deionized water at room temperature by magnetic stirring at a speed of 50 rpm to 200 rpm for 1 h to 5 h to form a general-purpose printing ink precursor that can suppress volume expansion during the freezing crystallization process.

[0015] The amount of ice crystal restraining agent added is 0.01% to 20% of the total weight of ice crystal restraining agent and deionized water. Further, in S1, the ice crystal restraining agent is selected from one of antifreeze, ice crystal inhibitor, and eutectic forming agent.

[0016] When ice crystal inhibitors are selected as the ice crystal restraining agent, the amount of ice crystal inhibitor added is 0.01% to 0.1% of the total weight of the ice crystal inhibitor and deionized water.

[0017] The antifreeze agent is selected from one of ethanol, tert-butanol, ethylene glycol, and glycerin;

[0018] The ice crystal inhibitor is polyvinyl alcohol or polyacrylamide;

[0019] The eutectic forming agent is sodium chloride or calcium chloride.

[0020] Further, in S2, the diameter of the ceramic nanofiber short fiber is 50nm to 500nm, the aspect ratio is greater than 1000, and the ceramic nanofiber short fiber is obtained by one of electrospinning, melt spinning or wet spinning processes.

[0021] More preferably, the diameter of the ceramic nanofiber short fibers is 100nm to 500nm.

[0022] The ceramic nanofiber short fibers are selected from one of oxide ceramic short fibers, nitride ceramic short fibers, and carbide ceramic short fibers;

[0023] The oxide ceramic short fibers are alumina or silicon oxide, the nitride ceramic short fibers are aluminum nitride or boron nitride, and the carbide ceramic short fibers are silicon carbide or titanium carbide.

[0024] The inorganic binder is selected from one of silica sol, aluminum sol, aluminum dihydrogen phosphate sol, and aluminum borosilicate sol;

[0025] The amount of ceramic nanofiber short fibers added is 0.1% to 1% of the total weight of the mixture, and the amount of inorganic binder added is 1% to 10% of the fiber content.

[0026] More preferably, the amount of inorganic binder added is 5% to 10% of the fiber content.

[0027] Furthermore, in S2, during the treatment of the mixing system using a high-pulse aerodynamic vortex field, the pulse frequency is controlled at 10–100 Hz, the stirring speed is 100–2000 rpm, and the vortex shear velocity is 500–2000 s⁻¹. -1 Continue stirring for 0.5–3 hours;

[0028] More preferably, the pulse frequency is controlled between 40 and 100 Hz.

[0029] In S2, the fiber aggregates are stripped away by the cavitation effect generated by the high-pulse aerodynamic vortex field, and the individual fibers are oriented in a three-dimensional turbulent field to obtain a uniformly dispersed system with oriented fibers.

[0030] Furthermore, S3 specifically includes the following steps:

[0031] The dispersion system obtained by S2 was placed in a temperature-controlled reaction device and first fluidized dispersion treatment was carried out at a temperature of 25℃~110℃ to fully disperse the fibers in the system and form a stable suspension state. The fluidized dispersion treatment time was 0.5h~2h.

[0032] The temperature was then raised to 110℃~135℃ for interface stabilization treatment, so that a stable interface was formed between the active groups on the fiber surface and the dispersion medium. The treatment time was 0.5h~2h.

[0033] Finally, the temperature is further increased to 135℃~155℃ for concentration and viscosity enhancement treatment. Through solvent evaporation, the fiber solids content is gradually increased to 5%~30%, while the ink acquires shear-thinning properties, i.e., a static viscosity of 100mPa·s~500mPa·s and a shear rate of 100s. -1 The viscosity is 10 mPa·s to 30 mPa·s, and the processing time is 0.5 h to 2 h, thereby obtaining a printable ink that has both high solids content and shear thinning properties.

[0034] More preferably, the static viscosity is 100–300 mPa·s.

[0035] Furthermore, S4 specifically includes the following steps:

[0036] The printable ink obtained from S3 is loaded into the print head of the 3D printer. The initial temperature of the ultra-low temperature semiconductor cold stage is set to -5℃ to -15℃, preferably -10℃ to -15℃. As the number of printing layers increases, the cold stage temperature is non-linearly reduced to -30℃ to -50℃, preferably -30℃ to -40℃.

[0037] The printing speed is controlled at 1mm / s to 30mm / s, the air extrusion pressure is 0.1MPa to 0.6MPa, and the printing environment humidity is maintained at 10RH% to 30RH%. This allows the ink to be extruded from the printhead and quickly freeze on the cold stage surface for less than 1 second, achieving precise positioning and shaping of ceramic fibers in the micron-level space. Layer by layer printing is then used to build up a ceramic fiber-ice crystal composite with a precise structure.

[0038] Furthermore, S5 specifically includes the following steps:

[0039] The vacuum drying conditions are: vacuum degree -0.05 to -0.1 MPa, drying time 12 to 48 h;

[0040] The conditions for high-temperature calcination are: calcination temperature of 600–900℃, preferably 600–800℃, and calcination time of 0.5–3 hours.

[0041] It should be noted separately that the precision-structured interconnected ceramic nanofiber aerogel in this invention is an advanced aerogel material with a high-precision, complex structure, prepared using cold-field 3D printing technology. This aerogel uses ceramic nanofibers as its basic building blocks, employing ice crystal instant freezing and shaping technology and nonlinear temperature control technology to achieve precise positioning and orientation of the fibers within a micrometer-level space, forming a highly ordered precision structure. At the fiber interweaving points, an inorganic binder undergoes in-situ condensation during high-temperature calcination, constructing a three-dimensional inorganic topological network, endowing the material with excellent mechanical properties and stability. This aerogel not only possesses a precision structure with a printing resolution of less than 30 μm, a layer thickness deviation of less than 30 μm, and a fidelity greater than 95%, but also exhibits superelasticity with less than 5% plastic deformation after 1000 cycles of compression. This achieves lightweight, high-strength, and multifunctional ceramic materials, and can be widely applied in aerospace, medical devices, energy development, and other fields that demand high-performance precision ceramic materials.

[0042] It should be noted separately that the universal printing ink precursor with zero volume expansion during freezing in this invention refers to a mixed solution formed by uniformly mixing an ice crystal restraining agent with deionized water at a speed of 50 rpm to 200 rpm under room temperature conditions using magnetic stirring, and continuously stirring for 1 to 5 hours. The amount of ice crystal restraining agent added is 0.01% to 20% of the total weight of the ice crystal restraining agent and deionized water (wherein, when an ice crystal inhibitor is used as the ice crystal restraining agent, the amount of the ice crystal inhibitor added is limited to 0.01% to 0.1%). This ink precursor utilizes the properties of the ice crystal restraining agent to prevent water molecules from forming a regular lattice arrangement through chemical bonds or molecular chains during the freezing and crystallization process, thereby inhibiting the volume expansion of water molecules caused by freezing and achieving zero volume expansion of the mixed liquid after freezing.

[0043] It should be noted separately that the gradient temperature evaporation coupling process in this invention is a process that adjusts solvent evaporation and ink viscosity by precisely controlling temperature changes. The specific process is as follows: A dispersion system containing ceramic nanofiber short fibers and inorganic binders is placed in a temperature-controlled reaction device. First, fluidization dispersion treatment is performed at a temperature of 25℃~110℃ to fully disperse the fibers in the system and form a stable suspension state, with a treatment time of 0.5h~2h. Then, the temperature is raised to 110℃~135℃ for interface stabilization treatment, so that a stable interface is formed between the active groups on the fiber surface and the dispersion medium, with a treatment time of 0.5h~2h. Finally, the temperature is further raised to 135℃~155℃ for concentration and thickening treatment. Through solvent evaporation, the fiber solid content is gradually increased to 5%~30%, while the ink acquires shear-thinning characteristics, that is, a static viscosity of 100mPa·s~500mPa·s and a shear rate of 100s. -1 The viscosity is 10 mPa·s to 30 mPa·s, and the processing time is 0.5 h to 2 h, thus obtaining a printable ink that has both high solids content and shear thinning properties, avoiding the use of high solids content organic thickeners.

[0044] It should be noted separately that, in this invention, the cavitation effect generated by the high-pulse aerodynamic vortex field to strip away fiber aggregates and achieve the directional alignment of individual fibers in a three-dimensional turbulent field specifically refers to: utilizing high-pulse aerodynamic vortex field technology, with a pulse frequency of 10–100 Hz, a stirring speed of 100–2000 rpm, and an vortex shear velocity of 500–2000 s⁻¹. -1 The dispersion system containing short ceramic nanofibers was treated under specific conditions and stirred continuously for 0.5–3 hours. During this process, the cavitation effect generated by the high-pulse aerodynamic vortex field effectively stripped the fiber aggregates, allowing the fibers to be fully dispersed. At the same time, the three-dimensional turbulent field provided the fibers with multi-directional shear forces and collision opportunities, prompting the individual fibers to undergo topological orientation during the flow.

[0045] It should be noted separately that, in this invention, the synergistic use of ice crystal instant freezing and solidification technology refers to the process where, during cold-field 3D printing, printable ink is extruded onto an ultra-low temperature semiconductor cold stage. The water in the ink rapidly freezes due to the low temperature, forming ice crystals. Simultaneously, by controlling the ink supply, printing speed (1–30 mm / s), and cold stage temperature (initial temperature -5°C to -10°C, highest layer temperature -30°C to -50°C), the ink achieves instantaneous freezing and solidification on the cold stage surface in less than one second. This rapid ice crystal formation allows for precise positioning of ceramic fibers within a micrometer-level space, and nonlinear temperature control technology maintains a consistent freezing rate across all printed layers.

[0046] It should be noted separately that, in this invention, the nonlinear temperature control technology maintains a consistent freezing rate for each printed layer by employing the following method: During the cold-field 3D printing process, a real-time temperature compensation system installed on the ultra-low temperature semiconductor cold stage monitors and provides feedback on the temperature changes on the cold stage surface in real time. As the number of printed layers increases, the system automatically and precisely controls the cold stage temperature according to a preset nonlinear cooling program, reducing it nonlinearly from the initial -5℃ to -10℃ to -30℃ to -50℃ for the highest layer. The real-time temperature compensation system dynamically adjusts the cooling power of the cold stage based on the monitoring data, ensuring a consistent freezing rate for each printed layer. This effectively avoids the problem of excessive interlayer fusion or inconsistent freezing rates caused by the actual temperature decreasing with increasing printing thickness, ensuring that the ceramic fiber-ice crystal bond formed in each printed layer is under the same and stable freezing conditions.

[0047] It should be noted separately that the ceramic fiber-ice crystal composite in this invention refers to the process during cold field 3D printing, where, when printing ink containing short ceramic nanofibers is extruded onto the surface of an ultra-low temperature semiconductor cold stage, the water in the ink rapidly freezes due to the low temperature, forming ice crystals. These ice crystals, together with the ceramic nanofibers, constitute a composite structure. In this composite, the ice crystals not only provide immediate support and shaping for the ceramic nanofibers, enabling them to maintain a predetermined shape and position with micron-level precision, but also ensure the fineness and integrity of the printed structure through their instantaneous freezing characteristics. Subsequently, the ice crystals are removed by vacuum drying, leaving a porous aerogel structure composed of ceramic nanofibers. This process realizes the transformation from the ceramic fiber-ice crystal composite to a precision-structured ceramic nanofiber aerogel.

[0048] A second aspect of the present invention provides a ceramic nanofiber aerogel prepared by the method described above.

[0049] Furthermore, the ceramic nanofiber aerogel has a precision structure, including: a printing resolution of less than 30 μm, a layer thickness deviation of less than 30 μm, and a fidelity of more than 95%.

[0050] The ceramic nanofiber aerogel exhibits less than 5% plastic deformation after 1000 compression cycles.

[0051] The ceramic nanofiber aerogel has a three-dimensional inorganic topological network structure at the fiber interlacing points, which is formed by in-situ condensation polymerization of an inorganic binder during high-temperature calcination.

[0052] The mechanism of this invention is described below:

[0053] The precursor for printing inks made from ceramic nanofiber aerogels is an aqueous solution. During the printing process, when liquid water freezes, it transforms from a dynamically disordered network of hydrogen bonds into a hexagonal tetrahedral structure, leading to increased intermolecular spacing and volume expansion, which is detrimental to high fidelity and high resolution printing. The ice crystal confinement agent introduced in this invention can effectively suppress the anomalous volume expansion of water. By establishing a molecular-scale volume compensation mechanism through chemical bonds or molecular chains and directionally regulating the dynamic balance of hydrogen bonds in water molecules, it achieves zero volume expansion of the printing ink during freezing, thereby improving the printing resolution.

[0054] The high-pulse aerodynamic vortex field employed in this invention addresses the bottleneck of traditional mechanical dispersion (such as ball milling and shear dispersion) in damaging the intrinsic structure of ceramic nanofibers. By constructing a non-contact energy transfer system, the cavitation effect generated by high-frequency pulses is used to peel off fiber aggregates, and a three-dimensional turbulent field is used to achieve topological orientation of individual fibers, thereby improving the retention rate of fiber aspect ratio and realizing non-destructive dispersion of ceramic nanofibers.

[0055] Highly efficient and stable printing requires inks with a certain viscosity. This is often achieved by adding polymers, gel materials, or carbon-based powders to increase ink viscosity and aid in printing. However, ceramic materials contain a certain amount of non-inorganic components, causing ceramic aerogels to shrink in volume after calcination, which is detrimental to the stable formation of precise structures. Gradient heating and evaporation coupling, through precise control of solvent evaporation kinetics, directly achieves fluidization, interface stabilization, and high solids content in the fiber dispersion, thereby controlling the printable viscosity of the ink and effectively avoiding structural sintering shrinkage.

[0056] During the printing process, a nonlinear ultra-low temperature semiconductor cold stage is used for curing. The temperature of the cold stage ranges from -5℃ to -10℃ for the first layer to -30℃ to -50℃ for the highest layer. This nonlinear cooling achieves the same freezing rate for each layer, compensating for the defects caused by excessive interlayer fusion due to the decrease in actual temperature as the printing thickness increases. This improves printing precision and yields high-resolution, precision-structured ceramic nanofiber heterogeneous aerogels.

[0057] During the calcination process, the ceramic nanofibers do not undergo ceramic transformation, but the inorganic binders on their surface and at the interlacing points undergo thermal condensation reaction. The hydroxyl groups on them condense due to heat, forming a three-dimensional inorganic topological network in situ between the fibers, which enhances the structural stability of the aerogel material, and finally yields a high-strength, superelastic ceramic nanofiber heterogeneous aerogel.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) This invention relies on the ultra-low temperature rapid freezing properties of water to prepare water-based ink, breaking through the dependence of traditional photocuring / thermal curing / gel curing printing inks on complex chemical components, characteristic solutions and special initiators; and through the synergistic effect of ice crystal restraint agent and ultra-low temperature rapid freezing, it completely suppresses the volume expansion phenomenon of water-based ink during freezing, greatly improves the printing resolution and fidelity, realizes the universality and simplicity of 3D printing ink precursor, and greatly expands the application field of 3D printing.

[0060] (2) During material preparation, the high-pulse pneumatic vortex dispersion and gradient evaporation coupling technology are combined to overcome the problem of difficult dispersion and easy agglomeration of high solid content nanofiber dispersions. This replaces the use of traditional high solid content organic binders and achieves synergistic optimization of the stability, fluidity and printability of fiber inks, effectively avoiding structural sintering shrinkage.

[0061] (3) By utilizing the instantaneous shaping characteristics of ice crystal templates, the forming efficiency and resolution of complex three-dimensional structures have been significantly improved, providing an innovative solution for the rapid manufacturing of precision ceramic devices such as aerospace micro thermal protection devices and high-efficiency flexible catalyst carriers. Attached Figure Description

[0062] Figure 1 : A flowchart of the method for preparing ceramic nanofiber aerogel by cold field 3D printing in this invention;

[0063] Figure 2 : Schematic diagram of the pre-printed mesh model of ceramic nanofiber aerogel in Example 1;

[0064] Figure 3 Macroscopic optical image of the cold-field 3D printed ceramic nanofiber aerogel in Example 1;

[0065] Figure 4 SEM image of the microstructure of the cold-field 3D printed ceramic nanofiber aerogel in Example 1;

[0066] Figure 5 Macroscopic optical image of the cold-field 3D printed ceramic nanofiber aerogel in Comparative Example 1;

[0067] Figure 6Macroscopic optical image of the cold-field 3D printed ceramic nanofiber aerogel in Comparative Example 2. Detailed Implementation

[0068] Overall, the method for preparing ceramic nanofiber aerogel by cold field 3D printing in this invention includes the following steps: First, an ice crystal confinement agent is mixed with deionized water to form a general-purpose printing ink precursor that inhibits freezing volume expansion; short ceramic nanofibers and an inorganic binder are added to the printing ink precursor, and the short ceramic fibers are efficiently dispersed and oriented through a high-pulse aerodynamic vortex field; a gradient heating evaporation coupling process is used to obtain a ceramic fiber printing ink with both high solids content and shear thinning properties; the ink is extruded onto the surface of an ultra-low temperature semiconductor cold stage through a printing nozzle, and the shape preservation of the micron-level structure is achieved by using ice crystal instant freezing and shaping technology and nonlinear temperature control technology; after vacuum drying and high-temperature calcination, a high-fidelity, precision-structured interconnected ceramic nanofiber aerogel is obtained. Compared with existing technologies, this invention utilizes the low-temperature rapid freezing properties of water and controls its anomalous expansion during freezing, breaking through the dependence of traditional printing inks on complex solutions or special initiators, and obtaining a universal printing ink precursor, which greatly expands the application field of 3D printing and realizes in-situ, rapid, and high-fidelity 3D printing of ceramic nanofiber aerogels with precise structures.

[0069] The specific implementation includes the following steps:

[0070] (1) Mix ice crystal restraint agent with deionized water to form a general-purpose printing ink precursor that inhibits frozen volume expansion;

[0071] (2) Add ceramic nanofiber short fibers and inorganic binder to the printing ink precursor, and achieve efficient dispersion and directional arrangement of ceramic short fibers through a high-pulse aerodynamic vortex field;

[0072] (3) The solvent evaporation rate and ink viscosity are controlled by gradient heating evaporation coupling process to obtain ceramic fiber printing ink with both high solid content and shear thinning characteristics.

[0073] (4) The ink is extruded onto the surface of the ultra-low temperature semiconductor cold stage through the print head, and the micron-level structure is preserved by using the ice crystal instant freezing and shaping technology and nonlinear temperature control technology to obtain the ceramic fiber / ice crystal composite.

[0074] (5) The ice crystal template is removed by vacuum drying, and then inorganic bonding points are formed between the fibers by high-temperature calcination to obtain a high-fidelity, precision-structured interconnected ceramic nanofiber aerogel.

[0075] In one embodiment of the present invention, in step (1), the ice crystal restraining agent refers to a type of material that can prevent water molecules from forming a regular lattice arrangement and a volume expansion structure through chemical bonds or molecular chains, thereby ensuring zero volume expansion after the mixed liquid is frozen.

[0076] In specific implementation, in step (1), the ice crystal inhibitor includes an antifreeze agent, an ice crystal inhibitor, or a cocrystallizing agent. The antifreeze agent includes one or more of the following: ethanol, tert-butanol, ethylene glycol, 1,3-propanediol, glycerol, trehalose, dimethyl sulfoxide, etc. The ice crystal inhibitor includes one or more of the following: polyvinyl alcohol, polyacrylamide, antifreeze protein, γ-polyglutamic acid, etc. The cocrystallizing agent includes sodium chloride, calcium chloride, sodium nitrate, ammonium acetate, sodium citrate, choline chloride, betaine, etc.

[0077] In specific implementation, in step (1), the general-purpose water-based printing ink precursor is uniformly mixed with ice crystal inhibitor and deionized water by magnetic stirring at room temperature. The stirring speed is 50-200 rpm, and the stirring time is 1-5 hours. The amount of ice crystal inhibitor added is 0.01-20 wt% (wherein, the amount of ice crystal inhibitor added is limited to 0.01 wt%-0.1 wt%, preferably 0.05 wt%-0.1 wt%. If it is higher than 0.1 wt%, it will shrink and become brittle, and if it is lower than 0.01 wt%, the effect of ice crystal inhibitor will be not obvious).

[0078] In specific implementation, in step (2), the ceramic nanofiber short fibers can be obtained by any process such as electrospinning, melt spinning, or wet spinning. The ceramic nanofiber membrane obtained by electrospinning can be cut into small pieces of 1cm×1cm and then initially dispersed in a pulping machine or homogenizer. The discrete fiber bundles obtained by electrospinning or other processes can be initially sheared and dispersed directly in a homogenizer.

[0079] In specific implementation, in step (2), the ceramic nanofiber short fibers include one or more types such as oxide ceramic short fibers, nitride ceramic short fibers, and carbide ceramic short fibers. Among them, oxides include one or more types such as alumina, silicon oxide, zirconium oxide, gadolinium oxide, mullite, and spinel; nitrides include one or more types such as aluminum nitride, boron nitride, silicon nitride, and seron; and carbides include one or more types such as silicon carbide, zirconium carbide, and titanium carbide. The diameter of the ceramic nanofiber short fibers is 50-500 nm, and the aspect ratio is >1000.

[0080] In specific implementation, in step (2), the inorganic binder is dehydrogenated at high temperature to construct a three-dimensional inorganic topological network in situ between fibers; the inorganic binder includes silicates, phosphates, oxides, sulfates and borates, such as silica sol, aluminum sol, aluminum dihydrogen phosphate sol, aluminum borosilicate sol, boric acid and one or more.

[0081] In specific implementation, in step (2), the high-pulse aerodynamic vortex field is dispersed with a pulse frequency of 10-100Hz, a stirring speed of 100-2000rpm, and a vortex shear velocity of 500-2000s.-1 The stirring time is 0.5 to 3 hours; the content of short ceramic nanofibers is 0.1 to 1 wt%, and the content of inorganic binder is 1 to 10 wt% of the fiber content.

[0082] In specific implementation, step (3) involves three stages: a fluidization dispersion stage (25-110℃), an interface stabilization stage (110-135℃), and a concentration and thickening stage (135-155℃).

[0083] In specific implementation, in step (3), the ceramic nanofiber printing ink with high spacing, high solid content, and shear-thinning characteristics has a short ceramic nanofiber content increased to 5-30 wt%; the printing ink has shear-thinning characteristics, with a static viscosity of 100-500 mPa·s and a shear rate of 100 s. -1 The ink viscosity is 10–30 mPa·s.

[0084] In specific implementation, in step (4), the instantaneous freezing and shaping technology of ice crystals is controlled by adjusting the printing liquid supply, printing speed, and cold plate temperature. Specifically, the ultra-low temperature semiconductor cold stage temperature is -1℃ to -50℃, and the printing speed is 1 to 30 mm / s. -1 The air compression pressure is 0.1–0.6 MPa, and the printing environment humidity is 10–30% RH.

[0085] In specific implementation, in step (4), the nonlinear temperature control technology achieves stability of the printing temperature gradient field and the freezing rate at the printing layer through a real-time temperature measurement and compensation system. The cold stage temperature ranges from -5℃ to -10℃ for the first layer to -30℃ to -50℃ for the highest layer; the instantaneous freezing and curing time of all layers is <1s, and the printing height can be from micrometers to 20cm.

[0086] In specific implementation, in step (5), the vacuum drying has a vacuum degree of -0.05 to -0.1 MPa and a drying time of 12 to 48 hours. The ice in the ceramic nanofiber / ice crystal composite is removed by gaseous sublimation, which will not produce capillary action and affect the structural stability.

[0087] In specific implementation, in step (5), the high-temperature calcination is carried out at a temperature of 600-900℃ and a calcination time of 0.5-3h. After calcination, an inorganic network with a three-dimensional topological structure is formed between the fibers of the ceramic nanofiber aerogel.

[0088] In specific implementation, in step (5), the high-fidelity, precision-structured interconnected ceramic nanofiber aerogel has diverse structures and advantages such as printing resolution <30μm, layer thickness deviation <30μm, and fidelity >95%. Furthermore, the ceramic nanofiber aerogel exhibits plastic deformation <5% after 1000 cycles of compression.

[0089] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Any preparation methods, materials, structures, or compositional ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0090] Example 1:

[0091] like Figure 1 As shown, tert-butanol crystals were first heated at 40°C to dissolve the tert-butanol solution. 15 wt% tert-butanol was mixed with deionized water and stirred for 0.5 h. Then, 0.05 wt% polyacrylamide was added and stirred at 50 rpm for 2 h to obtain a general-purpose water-based printing ink precursor with zero volume expansion during freezing.

[0092] Tetraethyl orthosilicate, deionized water, and phosphoric acid were mixed and stirred for 8 hours at a mass ratio of 1:1:0.01 to obtain a precursor solution. A 10 wt% polyvinyl alcohol solution was added to the precursor solution and stirring continued for 4 hours, with the mass ratio of the precursor solution to the polyvinyl alcohol solution being 1:1, to obtain a spinning solution. Nanofiber membranes were prepared by electrospinning at an infusion rate of 1 mL / h under a 22 kV voltage. Calcination at 800℃ for 2 hours under aerobic conditions yielded a 350 μm thick silica nanofiber membrane with an average fiber diameter of 500 nm. The silica nanofiber membrane was cut into 1 cm × 1 cm pieces and dispersed at 1000 rpm for 5 minutes to obtain a silica fiber dispersion with an aspect ratio >1000. Short silica nanofibers were obtained through freeze-drying. 0.3 wt% short fibers and 5 wt% silica sol by weight of the fibers were added to a general-purpose water-based printing ink precursor. The pulse frequency was 100 Hz, the rotation speed was 1000 rpm, and the vortex speed was 500 s. -1 Stir for 1 hour to obtain a uniformly dispersed low-solids nanofiber dispersion.

[0093] A pulsed aerodynamic vortex field was subjected to temperature control. The mixture was first stirred at 30°C for 30 min, then the temperature was increased to 110°C and stirred for 1 h, followed by stirring at 130°C for 30 min to obtain a printing ink containing 5 wt% nanofibers. The ink had a static viscosity of 300 mPa·s and a shear rate of 100 s⁻¹. -1 At that time, the viscosity was 10 mPa·s.

[0094] Ceramic nanofiber printing ink is placed in the printing cylinder, and the prepared mesh slice model is then placed inside. Figure 2 Import the data into the printer and set the printing speed to 5 mm / s. -1 The air extrusion pressure is 0.2 MPa, the initial temperature of the cold stage is -10℃ and decreases non-linearly to -30℃ over time, the ambient humidity is 15% RH%, the ink curing time is <1s, and the total printing time is 2 hours.

[0095] The printed silica nanofiber / ice crystal model was transferred to a vacuum dryer and vacuum dried for 48 hours, then calcined in air at 800℃ for 1 hour. Figure 3 and Figure 4 As shown, a silica nanofiber aerogel with a fine mesh structure was obtained, with a structure printing accuracy of <30μm and fidelity >95%, which can be used in the field of high-temperature thermal insulation.

[0096] Example 2:

[0097] 20wt% ethanol was mixed with deionized water and stirred for 0.5h to obtain a general-purpose water-based printing ink precursor with zero volume expansion during freezing.

[0098] Aluminum nitride particles, ammonium chloride particles, and iron powder were mixed in a mass ratio of 4:3:6 and placed in a crucible. The mixture was heated to 1550℃ and held for 30 min under an argon atmosphere. Nitrogen gas was then introduced, and the temperature was further increased to 1650℃ and held for 5 h to prepare an aluminum nitride single-crystal nanofiber aggregate with a fiber diameter of 100–200 nm. The aluminum nitride nanofiber aggregate was placed in an ethanol solution, ultrasonically dispersed for 5 h, filtered, and then dried at 100℃ for 24 h to obtain short aluminum nitride single-crystal nanofibers. 0.1 wt% of the short fibers and 5 wt% of the fiber weight of aluminum dihydrogen phosphate sol were added to a general-purpose water-based printing ink precursor. The pulse frequency was 80 Hz, the rotation speed was 500 rpm, and the vortex speed was 500 s. -1 Stir for 1 hour to obtain a uniformly dispersed low-solids nanofiber dispersion.

[0099] A pulsed aerodynamic vortex field was subjected to temperature control. The mixture was first stirred at 30°C for 30 min, then the temperature was increased to 110°C and stirred for 1 h, followed by stirring at 130°C for 30 min to obtain a printing ink containing 2 wt% nanofibers. The ink had a static viscosity of 300 mPa·s and a shear rate of 100 s⁻¹. -1 At that time, the viscosity was 30 mPa·s.

[0100] The ceramic nanofiber printing ink was placed in the printing cartridge, and the prepared Sierpinski fractal pyramid slice model was imported into the printer. The printing speed was set to 10 mm / s. -1 The air extrusion pressure is 0.4 MPa, the initial temperature of the cold stage is -10℃ and decreases non-linearly to -25℃ over time, the ambient humidity is 12% RH%, the ink curing time is <1s, and the total printing time is 1.5h.

[0101] The printed aluminum nitride single-crystal nanofiber / ice crystal model was transferred to a vacuum dryer and dried under vacuum for 48 hours, then calcined in air at 700℃ for 0.5 hours. An aluminum nitride single-crystal nanofiber aerogel with a Sierpinski fractal pyramid structure was obtained, with a printing accuracy of <30μm and fidelity >95%. The macro / microscopic structural connections of the aerogel exhibited strong physical adhesion, resulting in improved mechanical strength; after 1000 compression cycles, the plastic deformation was <5%. Furthermore, the aerogel possessed a directional structure, making it suitable for thermal cooling applications in extreme environments.

[0102] Example 3:

[0103] 0.1 wt% polyacrylamide was mixed with deionized water and stirred for 3 hours to obtain a general-purpose water-based printing ink precursor with zero volume expansion when frozen.

[0104] Polycarbosilane, polyvinylpyrrolidone, ethanol, tetrahydrofuran, ammonium dodecyl sulfate, and zirconium acetate were mixed in a mass ratio of 2.8:1.2:8:2:0.02:0.3 and stirred continuously at 25°C for 8 hours to prepare a spinning solution. Nanofiber membranes were prepared by electrospinning at a voltage of 17 kV and an injection rate of 0.2 mL / h. Subsequently, the obtained precursor nanofiber membrane was thermally crosslinked in air at 200°C for 2 hours and then crosslinked again in an argon atmosphere at 400°C for 2 hours to obtain silicon carbide nanofiber short fibers. 0.2 wt% of the short fibers and 3 wt% of the fiber weight of aluminoborosilicate sol were added to a general-purpose water-based printing ink precursor, with a pulse frequency of 40 Hz, a rotation speed of 200 rpm, and a vortex speed of 500 s. -1 Stir for 1 hour to obtain a uniformly dispersed low-solids nanofiber dispersion.

[0105] A pulsed aerodynamic vortex field was subjected to temperature control. The ink was first stirred at 30°C for 30 min, then the temperature was increased to 110°C and stirred for 1 h, followed by stirring at 130°C for 30 min to obtain a printing ink containing 3 wt% nanofibers. The ink had a static viscosity of 150 mPa·s and a shear rate of 100 s⁻¹. -1 At that time, the viscosity was 25 mPa·s.

[0106] The ceramic nanofiber printing ink was placed in the printing cartridge, and the prepared spiral layered square honeycomb slice model was imported into the printer. The printing speed was set to 1 mm / s. -1 The air extrusion pressure is 0.1 MPa, the initial temperature of the cold stage is -15℃ and decreases non-linearly to -40℃ over time, the ambient humidity is 15% RH%, the ink curing time is <1 second, and the total printing time is 3 hours.

[0107] The printed silicon carbide nanofiber / ice crystal model was transferred to a vacuum dryer and dried under vacuum for 48 hours, then calcined in air at 600℃ for 0.5 hours. A silicon carbide nanofiber aerogel with a helical layered square honeycomb structure was obtained. The structure printing accuracy was <30μm, and the fidelity was >95%. The aerogel exhibits impact resistance and thermal shock resistance, making it suitable for applications in aerospace fields such as reentry capsules.

[0108] Comparative Example 1:

[0109] A method for preparing silica ceramic nanofiber aerogel by cold field 3D printing, the only difference between this method and Example 1 is that:

[0110] 0.05 wt% polyacrylamide was added directly to deionized water and stirred at 50 rpm for 2 hours to obtain a water-based printing ink precursor.

[0111] The rest is the same as in Example 1.

[0112] The final product is a silica fiber aerogel with a mesh structure, achieving a printing accuracy >100μm and fidelity <70% (e.g., Figure 5 ).

[0113] Comparative Example 2:

[0114] A method for preparing silica ceramic nanofiber aerogel by cold field 3D printing, the only difference between this method and Example 1 is that:

[0115] 0.2 wt% polyacrylamide was added to a tert-butanol / deionized water mixture and stirred at 50 rpm for 2 h to obtain a conventional printing ink precursor containing a high-solids-content tackifier. 5 wt% short fibers and 5 wt% silica sol (based on the fiber weight) were added to the high-solids-content tackifier printing ink precursor to obtain a ceramic nanofiber printing ink with a static viscosity of 200 mPa·s and a shear rate of 100 s⁻¹. -1 At that time, the viscosity was 50 mPa·s.

[0116] The rest is the same as in Example 1.

[0117] The final product is a silica fiber aerogel with a mesh structure, a printing accuracy of <50μm, and a volume shrinkage rate of nearly 20% after calcination (e.g., Figure 6 ), fidelity <80%.

[0118] In summary, in practical implementation, the printing ink system of this invention leverages the ultra-low temperature rapid freezing properties of water. By introducing an ice crystal confining agent, it effectively suppresses the volume expansion of water in water-based inks during the freezing process. Furthermore, by introducing gradient evaporation coupling technology to replace high-solids-content organic thickeners, it suppresses structural shrinkage during the sintering process of inorganic printing materials. Specific advantages include:

[0119] Ice crystal confinement agents prevent water molecules from forming a regular lattice arrangement through chemical bonds or molecular chains, thereby regulating the freezing behavior of water at the molecular level and giving printing ink precursors broad versatility. They are not only applicable to various types of ceramic nanofibers, but also allow for flexible adjustment of ink composition and performance according to actual needs, without relying on complex chemical initiators or special solution systems. This breaks the limitations of traditional photocuring and thermocuring printing inks on specific chemical components.

[0120] This invention's ink system replaces high-solids-content organic thickeners with evaporation coupling technology and exhibits excellent rheological properties during printing. It has shear-thinning characteristics, with high viscosity at static conditions to maintain structural stability, and reduced viscosity during shearing for easy flow and extrusion. This meets the stringent requirements of high-precision printing for ink flowability and effectively suppresses the shrinkage problem of sintered structures, providing a reliable guarantee for the stable printing of complex and precision structures.

[0121] Water, as the primary solvent, is widely available and inexpensive, significantly reducing the manufacturing cost of printing inks compared to organic solvents or complex chemical reagents. Furthermore, water-based ink systems offer high safety, are environmentally friendly, align with the principles of green manufacturing, and are conducive to large-scale production and widespread practical application.

[0122] On the other hand, in practical implementation, this invention has made several key optimizations to the printing process, achieving high-precision and high-fidelity printing of ceramic nanofiber aerogels:

[0123] To address the challenges of easy agglomeration and poor dispersion of ceramic nanofibers, a high-pulse aerodynamic vortex field treatment was employed. Utilizing the cavitation effect and three-dimensional turbulent field generated by high-frequency pulses, fiber agglomerates were effectively exfoliated, and the topological orientation of individual fibers was achieved. This significantly improved the fiber aspect ratio retention rate and dispersion uniformity, providing a high-quality printing raw material for the preparation of high-performance ceramic nanofiber aerogels. It also solved the problems of easy agglomeration, poor dispersion, and printhead clogging in high-solids-content ceramic nanofiber inks, overcoming the shortcomings of traditional mechanical dispersion methods that easily damage the intrinsic structure of the fibers.

[0124] By precisely controlling solvent evaporation kinetics and gradually increasing fiber solids content, the printing ink maintains good fluidity while progressively increasing its solids content, ultimately yielding an ink that combines high solids content with excellent printing performance. This process avoids the fiber agglomeration and ink performance instability problems caused by direct high solids content preparation, achieving synergistic optimization of fiber ink stability, fluidity, and printability, laying the foundation for precise printing of complex structures.

[0125] This invention utilizes an ultra-low temperature semiconductor cooling stage to achieve instantaneous freezing and shaping of ink during the printing process. By precisely controlling parameters such as cooling stage temperature, printing speed, and ambient humidity, it ensures that each layer of ink solidifies rapidly after extrusion, forming a stable micron-scale structure. Simultaneously, nonlinear temperature control technology dynamically adjusts the cooling stage temperature according to the number of printed layers, ensuring that each printed layer has the same freezing rate. This effectively prevents problems such as excessive interlayer fusion and structural deformation caused by temperature differences, significantly improving printing accuracy and fidelity. The printed ceramic nanofiber aerogel can accurately reproduce the complex structure and fine features of the design model.

[0126] On the other hand, in practical implementation, the ceramic nanofiber aerogel prepared by this invention exhibits significant advantages in terms of performance and application:

[0127] The printed ceramic nanofiber aerogel exhibits extremely high printing resolution (less than 30 μm), layer thickness deviation (less than 30 μm), and fidelity (greater than 95%), ensuring the consistency between the microstructure and the macroscopic design of the aerogel. After high-temperature calcination, a three-dimensional inorganic topological network structure is formed at the fiber interweaving points, endowing the material with excellent mechanical properties. Even after 1000 cycles of compression, its plastic deformation remains less than 5%, demonstrating good elasticity and fatigue resistance, meeting the stringent requirements of high-performance precision ceramic materials in aerospace, medical device, and other fields.

[0128] By changing the type of ceramic fiber, aerogel materials can be customized to perform various functions such as thermal insulation, electrical conductivity, wave absorption, and electromagnetic shielding. For example, using ceramic fibers with specific properties, alumina fiber aerogels suitable for thermal insulation in high-temperature environments and aluminum nitride fiber aerogels with good electromagnetic shielding effects can be prepared. This fully meets the personalized needs of different application scenarios for material functional properties, expands the application fields of ceramic nanofiber aerogels, and provides new solutions for solving material challenges in high-end technology fields.

[0129] Based on the 3D printing process of this invention, ceramic nanofiber aerogels with complex and irregular structures can be rapidly manufactured without the need for traditional molds, significantly shortening the production cycle and reducing manufacturing costs. This makes rapid customized production according to specific application needs possible, especially in fields such as aerospace component manufacturing and personalized medical device fabrication. It can effectively improve production efficiency, meet market demands for rapid response and personalized products, and has significant industrial value and market competitiveness.

[0130] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a precise structure ceramic nanofiber aerogel by cold field 3D printing, characterized in that, The method comprises the following steps: S1: Inhibiting volume expansion in the freezing crystallization process by molecular bonding of ice crystal constraint agent and deionized water, to form a general printing ink precursor with zero volume expansion in freezing; S2: Adding ceramic nanofiber short fibers and inorganic binder to the general printing ink precursor obtained in S1, and stripping the fiber agglomerates by cavitation effect generated by high pulse pneumatic vortex field, and realizing directional arrangement of single fibers in three-dimensional turbulent flow field; S3: For the dispersion system obtained in S2, gradient temperature evaporation coupling process is used to control solvent volatilization kinetics, and the fiber solid content is increased in stages to obtain a printable ink with high solid content and shear thinning property; S4: The printable ink obtained in S3 is extruded through a printing nozzle to an ultralow temperature semiconductor cold table, and the fiber position is locked in a micron-level space by using ice crystal instantaneous freezing and shaping technology, and the freezing rate of each printing layer is maintained uniform by using nonlinear temperature control technology, to obtain a ceramic fiber-ice crystal combination; S5: The ceramic fiber-ice crystal combination obtained in S4 is subjected to vacuum drying and sublimation to remove the ice crystal template, and then high temperature calcination is performed to promote in-situ polycondensation of the inorganic binder at the fiber interweaving place, to build a three-dimensional inorganic topological network, and obtain an interconnected ceramic nanofiber aerogel with precise structure.

2. The method of claim 1, wherein the ceramic nanofiber aerogel is a precision structure ceramic nanofiber aerogel. In S1, the following steps are specifically included: The ice crystal constraint agent is uniformly mixed with deionized water by magnetic stirring at a speed of 50 rpm to 200 rpm in a room temperature environment, and the stirring is continued for 1 h to 5 h, to form a general printing ink precursor capable of inhibiting volume expansion in the freezing crystallization process; The addition amount of the ice crystal constraint agent is 0.01% to 20% of the total weight of the ice crystal constraint agent and the deionized water.

3. The method of claim 1, wherein the ceramic nanofiber aerogel is a precision structure ceramic nanofiber aerogel. In S1, the ice crystal constraint agent is selected from one of an antifreeze agent, an ice crystal inhibitor, and a eutectic forming agent; The antifreeze agent is selected from one of ethanol, tert-butyl alcohol, ethylene glycol, and glycerol; The ice crystal inhibitor is polyvinyl alcohol or polyacrylamide; The eutectic forming agent is sodium chloride or calcium chloride.

4. The method of claim 1, wherein the ceramic nanofiber aerogel is a precision structure ceramic nanofiber aerogel. In S2, the ceramic nanofiber short fibers have a diameter of 50 nm to 500 nm and an aspect ratio greater than 1000, and are obtained by one of electrospinning, melt spinning, or wet spinning process; The ceramic nanofiber short fibers are selected from one of oxide ceramic short fibers, nitride ceramic short fibers, and carbide ceramic short fibers; The oxide ceramic short fibers are alumina or silicon oxide, the nitride ceramic short fibers are aluminum nitride or boron nitride, and the carbide ceramic short fibers are silicon carbide or titanium carbide; The inorganic binder is selected from one of silica sol, aluminum sol, aluminum dihydrogen phosphate sol, and aluminum-boron-silicon sol; The addition amount of the ceramic nanofiber short fibers is 0.1% to 1% of the total weight of the mixed solution, and the addition amount of the inorganic binder is 1% to 10% of the fiber content.

5. The method of claim 1, wherein the ceramic nanofiber aerogel is a precision structure ceramic nanofiber aerogel. In S2, the pulse frequency is controlled at 10-100 Hz, the stirring speed is 100-2000 rpm, and the vortex shear speed is 500-2000 s -1 during the treatment of the mixed system by using high pulse aerodynamic vortex field, and the stirring lasts for 0.5-3 h. In S2, the fiber agglomerates are stripped by cavitation effect generated by high pulse pneumatic vortex field, and directional arrangement of single fibers is realized in three-dimensional turbulent flow field, to obtain a dispersion system with uniform dispersion and directional arrangement of fibers.

6. The method of claim 1, wherein the ceramic nanofiber aerogel is a precision structure ceramic nanofiber aerogel. In S3, the following steps are specifically included: The dispersion system obtained in S2 is placed in a temperature-controllable reaction device, and first fluidized dispersion treatment is performed at a temperature of 25-110°C to fully disperse the fibers in the system and form a stable suspension state, and the fluidized dispersion treatment time is 0.5-2h; Subsequently, the temperature is raised to 110-135°C for interface stabilization treatment to form a stable interface between the active groups on the fiber surface and the dispersion medium, and the treatment time is 0.5-2h; Finally, the temperature is further increased to 135°C-155°C for concentration and viscosity increasing treatment, the fiber solid content is gradually increased to 5%-30% through solvent evaporation, and the ink has shear thinning property, i.e. the viscosity is 100 mPa·s-500 mPa·s at static state, the viscosity is 10 mPa·s-30 mPa·s at shear speed of 100 s -1 , the treatment time is 0.5 h-2 h, so that the printable ink with high solid content and shear thinning property is obtained.

7. The method of claim 1, wherein the ceramic nanofiber aerogel is a precision structure ceramic nanofiber aerogel. In S4, the following steps are specifically included: The printable ink obtained in S3 is loaded into the printing nozzle of a 3D printer, and the initial temperature of the ultra-low temperature semiconductor cold table is set to -5 to -10°C, and as the number of printing layers increases, the cold table temperature is nonlinearly reduced to -30 to -50°C; The printing speed is controlled to be 1-30mm / s, the air extrusion pressure is 0.1-0.6MPa, and the printing environment humidity is maintained at 10-30RH%, so that the ink is extruded from the nozzle and rapidly forms a transient freezing solidification time of less than 1s on the surface of the cold table, realizing precise positioning and shaping of the ceramic fibers in the micron-level space, and layer-by-layer printing accumulation forms a ceramic fiber-ice crystal combination body with precise structure.

8. The method of claim 1, wherein the ceramic nanofiber aerogel is a precision structure ceramic nanofiber aerogel. In S5, the following steps are specifically included: The vacuum drying conditions are: vacuum degree -0.05 to -0.1MPa, and drying time 12-48h; The high-temperature calcination conditions are: calcination temperature 600-900°C, and calcination time 0.5-3h.

9. A ceramic nanofiber aerogel prepared by the method of any one of claims 1-8.

10. The ceramic nanofibrous aerogel according to claim 9, wherein, The ceramic nanofiber aerogel has a precise structure, including: printing resolution less than 30μm, layer thickness deviation less than 30μm, and fidelity greater than 95%; After 1000 cycles of compression, the plastic deformation of the ceramic nanofiber aerogel is less than 5%; The fiber interweaving part of the ceramic nanofiber aerogel has a three-dimensional inorganic topological network structure formed by in-situ polycondensation of the inorganic binder during high-temperature calcination.

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