Aerogel composite fiber felt and preparation method thereof

Abstract

The invention relates to the technical field of thermal insulation materials, in particular to aerogel composite fiber felt and a preparation method thereof. The aerogel composite fiber felt comprises a plurality of layers of fiber felt bodies which are compounded together, the composite interfaces of the adjacent fiber felt bodies are filled with chopped fibers and heat insulation powder, the mass ratio of the chopped fibers to the heat insulation powder is (3-5): 100, and the heat insulation powder comprises, by mass, 50%-70% of silicon dioxide aerogel powder, 10%-20% of fumed silica and 20%-35% of opacifier. The silicon dioxide aerogel powder, the fumed silica, the opacifying agent and the chopped fibers are filled in the composite interface of the fibrofelt, the chopped fibers are beneficial to fixing the heat insulation powder, the opacifying agent can absorb infrared radiation to reduce solid-phase heat conduction, a more coherent barrier network is formed, and the heat insulation effect is improved. The silicon dioxide aerogel powder can inhibit gas-phase heat conduction scattering infrared radiation, and gas-phase silicon dioxide assists in heat insulation and improves the flowability, the compressibility and the strength of the powder mixture at the same time.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology, specifically to an aerogel composite fiber felt and its preparation method. Background Technology

[0002] Aerogel production costs are relatively high. Currently, aerogel powder and other heat-insulating powders are usually mixed with water or alcohol solvents to form a slurry. Then, a substrate such as fiber felt is immersed in the slurry and dried to obtain aerogel felt. However, due to the excellent heat insulation properties of aerogel, it is difficult to evaporate the moisture during drying, and the required drying process is long. Furthermore, the phenomenon of aerogel microparticles and dust falling off is easy to occur, which affects the performance and service life of aerogel felt and causes environmental pollution.

[0003] Chinese invention patent application CN118441409A, published on August 6, 2024, discloses a method for preparing an aerogel thermal insulation composite material. The method involves adding 10-50 parts by weight of silica aerogel powder and 50-90 parts by weight of porous or high-surface-area powder to a mixer and mixing at high speed to obtain a composite powder. Aluminum-magnesium fibers are arranged into a thin felt, and the composite powder is evenly sprayed onto the thin felt through a nozzle. The powder-coated thin felt is then layered and pressed under pressure to obtain a fiber felt, thus filling the interior of the material with powder. The porous or high-surface-area powder is selected from one or more of expanded perlite powder, expanded vermiculite powder, 4A zeolite powder, porous diatomaceous earth, and ultrafine talc powder. The silica aerogel powder accounts for 25%-35% of the weight of the composite powder. When silica aerogel powder is mixed at high speed with porous materials or high surface area powders in a high-speed mixer, the powders collide and rub against each other, breaking the powder and creating new interfaces and broken chemical bonds. These broken chemical bonds have extremely high reactivity and recombine to form new aggregates. The aggregates are then sprayed into fiber felt through a nozzle, where they adhere to the fiber felt under the action of force, thus preventing air from flowing through the fiber gaps and avoiding heat transfer caused by air convection. This results in a nanoporous composite material with low thermal conductivity. Furthermore, the process does not use solvents or supercritical processes and can be achieved using conventional equipment, making it low-cost and easy to promote and apply.

[0004] However, the aforementioned aerogel composite materials still have high thermal conductivity, low tensile strength, and poor flexibility. Summary of the Invention

[0005] The first objective of this invention is to provide an aerogel composite fiber felt that solves the problems of high thermal conductivity, low strength, and poor flexibility of existing aerogel composite fiber felts.

[0006] The second objective of this invention is to provide a method for preparing aerogel composite fiber felt, thereby solving the problems of high thermal conductivity, low strength, and poor flexibility of existing aerogel composite fiber felt.

[0007] To solve the above-mentioned technical problems, the technical solution of the aerogel composite fiber felt of the present invention is as follows: An aerogel composite fiber felt includes multiple layers of fiber felts composited together. The composite interface between adjacent fiber felts is filled with chopped fibers and heat-insulating powder. The mass ratio of chopped fibers to heat-insulating powder is (3~5):100. The heat-insulating powder includes 50~70% silica aerogel powder, 10~20% fumed silica and 20~35% light-blocking agent by mass fraction.

[0008] This invention improves upon existing technology by providing an aerogel composite fiber felt. It involves filling the composite interface between adjacent fiber felts with chopped fibers and insulating powder. The insulating powder comprises a certain proportion of silica aerogel powder, fumed silica, and a light-blocking agent. The light-blocking agent fills the voids in the fiber felt, absorbs infrared radiation, reduces solid-phase heat conduction, and significantly lowers thermal conductivity. Some of the light-blocking agent even overlaps with the chopped fibers or fiber felt, forming a more coherent barrier network. The silica aerogel powder inhibits gas-phase heat conduction, and the aerogel skeleton itself also has a certain scattering effect on infrared radiation, ensuring the final product maintains excellent heat insulation performance. Fumed silica, as an inexpensive filler and auxiliary insulating material, simultaneously improves the flowability, compressibility, and strength of the powder mixture. The chopped fibers help fix the insulating powder, reducing migration and delamination during the composite process. The combination of insulating powder and chopped fibers maintains the strength and flexibility of the fiber felt, reducing powder shedding during bending.

[0009] Preferably, the silica aerogel powder is selected from one or two types of silica aerogel powder with an average pore size of <20nm and an average pore size of 40~70nm.

[0010] Preferably, the silica aerogel powder is composed of 70-85% by mass of silica aerogel powder with an average pore size <20nm and 15-30% by mass of silica aerogel powder with an average pore size of 40-70nm. Small-pore silica aerogel powder can suppress gas-phase heat conduction, while large-pore silica aerogel powder can improve flowability during the mixing process. This protects the fine nanostructure of the small-pore aerogel powder from damage during pressing, ensuring that the final product maintains excellent thermal insulation performance. Furthermore, the aerogel frameworks of different pore sizes themselves also have a certain scattering effect on infrared radiation.

[0011] Preferably, the light-blocking agent is selected from one or more of the following: nanoscale light-blocking agents with absorption wavelength <5μm, submicron-scale light-blocking agents with absorption wavelength 5~10μm, and micron-scale light-blocking agents with absorption wavelength >10μm; the nanoscale light-blocking agent with absorption wavelength <5μm is selected from one or more of the following: carbon black, iron oxide, silicon carbide, and rutile titanium dioxide with a particle size of 20~50nm; the submicron-scale light-blocking agent with absorption wavelength 5~10μm is selected from one or more of the following: rutile titanium dioxide, zirconium oxide, carbon black, iron oxide, and silicon carbide with a particle size of 0.5~2μm; and the micron-scale light-blocking agent with absorption wavelength >10μm is selected from one or more of the following: mica powder, flake alumina, and silicon carbide with a particle size of 5~15μm.

[0012] Preferably, the light-blocking agent consists of 60-70% by mass of a nanoscale light-blocking agent with an absorption wavelength <5μm and 30-40% by mass of a micrometer-scale light-blocking agent with an absorption wavelength >10μm; or it consists of 10-20% by mass of a nanoscale light-blocking agent with an absorption wavelength <5μm, 40-60% by mass of a submicrometer-scale light-blocking agent with an absorption wavelength of 5-10μm and 30-40% by mass of a micrometer-scale light-blocking agent with an absorption wavelength >10μm. The combination of light-blocking agents with different particle sizes achieves a synergistic blocking effect, forming a full-band barrier against infrared radiation of different wavelengths. This significantly reduces thermal conductivity, resulting in a more balanced density and thermal conductivity. It avoids the severe agglomeration of light-blocking agent particles caused by excessive use of a single agent, which increases solid-phase heat conduction, or the increased porosity due to excessively large particles, which increases gas-phase heat conduction and reduces strength. Particles of different sizes can better fill the gaps and can even partially overlap with short fibers or substrate fibers, forming a more coherent barrier network. The presence of gradient pore sizes in silica aerogel may further complicate the radiation propagation path, working synergistically with the particle size-combined light-blocking agents to more effectively attenuate radiative heat flux. By using dual-pore-size silica aerogel powder combined with multi-scale light-blocking agent blends, effective shielding against full-band infrared radiation is achieved, significantly improving thermal insulation performance at 500℃.

[0013] Preferably, 40-70% of the total chopped fibers at the composite interface are needle-punched to insert 40-70% of their length into the fiber felt; the length of the chopped fibers is 1-3 mm. This embedding of 40-70% of the chopped fibers into the substrate fiber felt, with the remainder exposed on the surface to form a "felt-like" structure, provides excellent "anchoring points" for the subsequently applied thermal insulation powder. Needling the short fibers into the substrate first, followed by applying the thermal insulation powder, makes the fiber insertion effect more controllable, preventing the powder from being carried away or over-encapsulated during the needle-punching process.

[0014] Preferably, the amount of chopped fibers at the composite interface is 5~10 g / m². 2 The amount of heat insulation powder used is 190~220g / m².2 The specific surface area of ​​fumed silica is >150 m². 2 / g.

[0015] The technical solution of the preparation method of the aerogel composite fiber felt of the present invention is as follows: A method for preparing an aerogel composite fiber felt as described includes the following steps: laying a first chopped fiber on the surface of the fiber felt, followed by laying a mixed powder to form a stacked unit; after at least one stacked unit is stacked, a fiber felt is laid on the outermost layer of mixed powder and then pressed to obtain an aerogel composite fiber felt; the mixed powder includes a heat-insulating powder and a second chopped fiber; the heat-insulating powder is composed of raw materials including 50-70% silica aerogel powder, 10-20% fumed silica and 20-35% light-blocking agent by mass fraction, and the mass ratio of the first chopped fiber and the second chopped fiber to the heat-insulating powder is (3-5):100.

[0016] The method for preparing aerogel composite fiber felt provided by this invention involves laying short-cut fibers on the surface of the fiber felt, then laying heat-insulating powder, and finally laying another layer of fiber felt on the outermost layer of heat-insulating powder before pressing to obtain the aerogel composite fiber felt. The short-cut fibers help fix the heat-insulating powder, reducing migration and delamination during the pressing process. By pressing the heat-insulating powder into the interior of the fiber felt, the light-blocking agent can absorb infrared radiation and reduce solid-phase heat conduction. Some of the light-blocking agent overlaps on the short fibers or fiber felt, forming a more coherent barrier network. The silica aerogel powder can inhibit gas-phase heat conduction and scatter infrared radiation, further improving the heat insulation performance and reducing the thermal conductivity. The fumed silica also improves the flowability, compressibility, and strength of the powder mixture while assisting in heat insulation.

[0017] Preferably, when laying the chopped fibers, a needle-punching method is used to insert 40-70% of the length of the first chopped fiber into the fiber felt; the first chopped fiber accounts for 40-70% of the total mass of the first and second chopped fibers. This embeds 40-70% of the chopped fiber length into the substrate fiber felt, with the remaining portion exposed on the surface to form a "felt-like" structure. This provides excellent "anchoring points" for the subsequently laid insulating powder. Punching the short fibers into the substrate first, followed by laying the insulating powder, makes the fiber insertion effect more controllable, and the powder is less likely to be carried away or over-encapsulated during the needle-punching process. By controlling the needle-punching depth and retaining sufficient free fiber segments, a small number of chopped fibers are directionally needle-punched into the continuous fiber felt, forming an interlayer anchoring reinforcement system between the laid main fibers and the needled fibers. This effectively solves the problems of easy delamination, powder shedding, and loose structure of multilayer aerogel felts without sacrificing flexibility.

[0018] Preferably, the pressing temperature is ≤40℃, the pressure is 2~3MPa, and the holding time is 30~90s. Low-temperature pressing avoids damaging the softness of the wet-process fiberglass mat (adhesive aging).

[0019] This invention uses flexible fiber felt as the matrix. The entire preparation process does not require the addition of rigid organic binders such as phenolic resin and epoxy. The molding process uses low-temperature and low-pressure pressing, which can avoid fiber embrittlement or aerogel sintering and hardening. The powder is fixed by physical interlocking and short fiber anchoring, maintaining the overall flexibility. The interface layer design takes into account both bonding and flexibility. The thermal insulation powder filling the interlayer is a loose particle mixture that can slightly slip when bent, without generating stress concentration. The amount of short chopped fibers is extremely low, which plays an anchoring role but does not form a rigid network, and has a very weak impact on thermal insulation performance. Detailed Implementation

[0020] The technical concept of the aerogel composite fiber felt provided by this invention is as follows: Existing aerogel composite fiber felt technology is obtained by layering and pressing silica aerogel powder and porous or high surface area powder onto the surface of aluminum-magnesium fiber felt. This prevents air from flowing between the fibers, thus avoiding heat transfer caused by air convection. However, it still suffers from problems such as relatively high thermal conductivity and low tensile strength.

[0021] This invention uses a certain proportion of silica aerogel powder, fumed silica, and a light-blocking agent as heat-insulating powder and fills the composite interface of adjacent fiber felts with chopped fibers. The chopped fibers help fix the heat-insulating powder, the light-blocking agent can absorb infrared radiation to reduce solid-phase heat conduction, and partially overlap with the chopped fibers or fiber felt to form a more coherent barrier network. The silica aerogel powder can inhibit gas-phase heat conduction and the aerogel skeleton scatters infrared radiation. The fumed silica assists in heat insulation while improving the flowability, compressibility, and strength of the powder mixture. The three work synergistically to further reduce the thermal conductivity of the composite fiber felt.

[0022] The aerogel composite fiber felt provided by the present invention includes a multi-layer composite fiber felt, with chopped fibers and heat insulation powder filling the composite interface of adjacent fiber felts. The mass ratio of chopped fibers to heat insulation powder is (3~5):100. The heat insulation powder includes 50~70% silica aerogel powder, 10~20% fumed silica and 20~35% light-blocking agent by mass fraction.

[0023] The amount of short-cut fibers used at the composite interface is 5~10 g / m². 2 The amount of heat insulation powder used is 190~220 g / m². 2 The specific surface area of ​​fumed silica is >150 m². 2 / g.

[0024] Of the total chopped fibers at the composite interface, 40-70% by weight of the chopped fibers are inserted into the fiber mat by needle punching, with 40-70% of the chopped fiber length being inserted; the length of the chopped fibers is 1-3 mm. More preferably, 40-50% of the chopped fiber length is inserted into the fiber mat by needle punching.

[0025] The preparation method of aerogel composite fiber felt provided by the present invention includes the following steps: 1) The total chopped fibers are divided into two parts, including needle-punched chopped fibers (first chopped fibers) and mixed chopped fibers (second chopped fibers). The first chopped fibers account for 40 to 70% of the total mass of the first and second chopped fibers.

[0026] Mixed powder: The mixed powder consists of heat-insulating powder and second chopped fibers. The length of the second chopped fibers is 1~3mm.

[0027] Thermal insulation powder: The thermal insulation powder consists of 50-70% silica aerogel powder, 10-20% fumed silica, and 20-35% opacifier by mass. The silica aerogel powder consists of 70-85% silica aerogel powder with an average pore size of 10-15 nm and 15-30% silica aerogel powder with an average pore size of 40-70 nm by mass. The silica aerogel powder is selected from one or both of the silica aerogel powders with an average pore size <20 nm and an average pore size of 40-70 nm. When the silica aerogel powder consists of two components with different pore sizes, it consists of 70-85% silica aerogel powder with an average pore size <20 nm and 15-30% silica aerogel powder with an average pore size of 40-70 nm by mass.

[0028] The light-blocking agent is selected from one or more of the following: nanoscale light-blocking agents with absorption wavelength <5μm, submicron-scale light-blocking agents with absorption wavelength 5~10μm, and micron-scale light-blocking agents with absorption wavelength >10μm. The light-blocking agent consists of 60~70% by mass of nanoscale light-blocking agents with absorption wavelength <5μm and 30~40% by mass of micron-scale light-blocking agents with absorption wavelength >10μm; or it consists of 10~20% by mass of nanoscale light-blocking agents with absorption wavelength <5μm, 40~60% by mass of submicron-scale light-blocking agents with absorption wavelength 5~10μm, and 30~40% by mass of micron-scale light-blocking agents with absorption wavelength >10μm.

[0029] The purpose of compounding silica aerogel powder is to suppress gas phase conduction. The characteristics of silica aerogel powder with different pore sizes are as follows: Small pore size aerogel powder: average pore size <20 nm (preferably 10~15 nm), effectively restricts the free movement of air molecules (N2, O2 mean free path ~68 nm) under normal pressure. Core function: significantly suppresses gas phase conduction and provides basic low thermal conductivity.

[0030] Medium / large pore size aerogel powder: average pore size 40-70 nm. Key preparation methods: moderately increasing silicon source concentration or shortening aging time. Improved powder flowability: larger pore sizes typically correspond to a more robust network structure, resulting in better flowability during dry mixing and spreading, reducing the likelihood of breakage and fine dust generation, and facilitating uniform spreading and pressing. Buffer layer / stress dispersion: during pressing, large pore size aerogel powder, due to its relatively large pore size and strength, can better withstand pressure, reducing excessive breakage of small pore size aerogel powder (breakage increases pore size and reduces thermal insulation performance).

[0031] When compounding silica aerogel powder, small-pore aerogel powder should be the dominant component to ensure a low thermal conductivity core. A sufficient proportion of large-pore aerogel powder is needed to improve processability, but it should not be too high to avoid significantly increasing the average pore size. The technical effects of the compounding are as follows: Small-pore aerogel powder inhibits gas-phase heat conduction; its pore size is much smaller than the mean free path of gas molecules at normal pressure, resulting in a much higher frequency of collisions between gas molecules and pore walls than intermolecular collisions, thus greatly reducing heat transfer efficiency. Large-pore aerogel powder significantly improves the feasibility of dry processing (good flowability, less dust) and protects the fine nanostructure of small-pore aerogel powder from damage during pressing, ensuring the final product maintains excellent thermal insulation performance. Overall, while maintaining low gas-phase heat conduction, the compounded system is easier to produce and process than pure small-pore aerogel powder, improving product stability and yield. Synergistic effect with opacifiers: Aerogel frameworks of different pore sizes also have a certain scattering effect on infrared radiation. The presence of gradient apertures may further complicate the radiation propagation path, and in conjunction with light-blocking agents with particle size distribution, more effectively attenuate radiative heat flux.

[0032] Preferably, the nanoscale opaque agent with an absorption wavelength <5μm is selected from one or more of carbon black, iron oxide, silicon carbide, and rutile titanium dioxide with a particle size of 20-50nm. It has a high specific surface area and infrared absorption efficiency; it mainly absorbs short-wave and mid-wave infrared radiation <5μm.

[0033] The submicron-sized opacifier with an absorption wavelength of 5-10 μm is selected from one or more of rutile titanium dioxide, zirconium oxide, carbon black, iron oxide, and silicon carbide with a particle size of 0.5-2 μm. It can effectively scatter and absorb mid-wave infrared radiation, has a good matching degree between particle size and thermal radiation wavelength, and has high scattering efficiency (absorbing waves of 5-10 μm).

[0034] Micron-sized light-blocking agents with absorption wavelengths >10μm are selected from one or more of the following: mica powder, flake alumina, and silicon carbide with a particle size of 5~15μm. Their main function is to block long-wave infrared radiation and extend the light path through multiple reflections / scatterings. The flake-shaped light-blocking agents can form a physical barrier layer (absorbing waves >10μm).

[0035] More preferably, the light-blocking agent is composed of 10-20% by mass of carbon black with a particle size of 20-50 nm, 40-60% by mass of rutile titanium dioxide with a particle size of 0.5-2 μm, and 30-40% by mass of mica powder with a particle size of 5-15 μm; or it is composed of 10-20% by mass of iron oxide with a particle size of 20-50 nm, 40-60% by mass of zirconium oxide with a particle size of 0.5-2 μm, and 30-40% by mass of flake alumina with a particle size of 5-15 μm.

[0036] The technical effects of compounded opaque agents are as follows: The compounding of opaque agents with different particle sizes achieves a synergistic blocking effect, forming a full-band barrier against infrared radiation of different wavelengths, significantly reducing thermal conductivity; the compounding of submicron and micron particles enhances strong scattering, increases the propagation path of radiation within the powder layer, and enhances infrared absorption; the compounding of opaque agents with different particle sizes results in a more balanced density and thermal conductivity, avoiding severe agglomeration of opaque agent particles due to excessive use of a single opaque agent, which increases solid-phase thermal conduction, or increased porosity due to the use of excessively large particles, increasing gas-phase thermal penetration and reducing strength; it also provides better synergy with fiber felt substrates or fibers: in the flat powder, particles of different sizes can better fill the gaps, and micron-sized flake particles can even partially overlap with short fibers or substrate fibers, forming a more coherent barrier network. Short fibers help fix these particles of different sizes, reducing migration and delamination during the pressing process.

[0037] Preferably, the specific surface area of ​​fumed silica is >150 m². 2 / g, mainly used as a cheap filler and auxiliary heat insulation, while improving the flowability, compressibility and strength of powder mixtures.

[0038] Preferably, when mixing the powder, the opacifier, one-third to one-half (by weight) of fumed silica and the second chopped fiber are first mixed, and then silica aerogel and the remaining fumed silica are added for a second mixing.

[0039] More preferably, the mixing is a dry mixing process, and the temperature of the dry mixing process is room temperature; the dry mixing process involves first mixing the opaque agent, one-third to one-half of the fumed silica and the second chopped fiber for 30 to 50 minutes, and then adding the silica aerogel and the remaining fumed silica for a second mixing process for 40 to 80 minutes; the rotation speed during the dry mixing process is 20 to 80 rpm.

[0040] 2) Powder spreading and layering: After laying the first chopped fiber on the surface of the fiber felt, the mixed powder is then laid to form a layered unit. After at least one layered unit is stacked, a fiber felt is laid on the outermost layer of mixed powder to form a layered structure. The mass ratio of the first chopped fiber and the second chopped fiber to the heat insulation powder is (3~5):100.

[0041] Preferably, after laying the first chopped fiber on the surface of the fiber felt, the mixed powder is laid to form a stacked unit, two stacked units are stacked, and then a fiber felt is laid on the outermost layer of mixed powder to form a stacked structure.

[0042] Preferably, when laying the chopped fibers, a needle punching method is used to insert 40-70% of the length of the first chopped fiber into the fiber felt; the first chopped fiber accounts for 40-70% of the total mass of the first and second chopped fibers.

[0043] Preferably, the fiber mat is a wet-laid mat, selected from one or both of basalt fiber mat and wet-laid glass fiber mat, which facilitates the incorporation of aerogel powder into the fiber mat. During the molding process, the wet-laid mat can control the fiber lay-up and directional distribution, blocking heat conduction between intersecting fibers. The fiber mat has a thickness of 0.2~0.5mm and ≥2 layers.

[0044] Preferably, the total amount of the first and second chopped fibers is 5~10 g / m². 2 The amount of heat insulation powder used is 190~220 g / m². 2 .

[0045] 3) Pressing: The laminated structure is pressed at a temperature ≤40℃, a pressure of 2~3MPa, and a holding time of 30~90s. Low-temperature pressing is used to avoid damaging the softness of the wet-process fiberglass mat (adhesive aging).

[0046] The embodiments of the present invention will be further described below with reference to specific examples. Unless otherwise specified, the chemical reagents involved in the following examples are all commercially available conventional products.

[0047] I. Specific Embodiments of the Aerogel Composite Fiber Felt and its Preparation Method of the Present Invention Example 1 The preparation method of the aerogel composite fiber felt in this embodiment is as follows: 1) Mixed powder The mixed powder is prepared as follows: by weight, it consists of 100 parts of heat-insulating powder and 1 part of basalt short-cut fibers (2 mm in length). The heat-insulating powder consists of 60 parts of silica aerogel powder, 30 parts of opacifier, and 10 parts of fumed silica. Specifically, 45 parts are silica aerogel powder with an average pore size of 10-15 nm, and 15 parts are silica aerogel powder with an average pore size of 40-70 nm. The opacifier consists of 4.5 parts of nano-sized carbon black with a particle size of 20-50 nm, 15 parts of submicron-sized rutile TiO2 with a particle size of 0.5-2 μm, and 10.5 parts of micron-sized mica powder with a particle size of 5-15 μm. The specific surface area of ​​the fumed silica is >150 m². 2 / g. Basalt short-cut fiber length 2mm.

[0048] A dry mixing method was employed using a V-type mixer: 30 parts of opacifier, 3.3 parts of fumed silica, and 1 part of basalt chopped fibers were mixed in the mixer at room temperature for 30 minutes. Then, 60 parts of silica aerogel powder and the remaining fumed silica were added, and mixing continued for 45 minutes (25 rpm, room temperature) to obtain a mixed powder. Sampling tests were conducted to ensure the consistency of the components in different mixed samples, with a component deviation of <±2%. The angle of repose test showed an angle of repose ≤35°, and no agglomeration was observed.

[0049] 2) Spreading powder and layering Clean the dust from the surface of the wet-laid fiberglass mat (0.3 mm thick, 3 layers). Then, evenly spread two portions of basalt chopped fibers (2 mm in length) onto the surface of the wet-laid fiberglass mat. Use a needle-punching device to embed approximately 40% of the length of the basalt chopped fibers into the substrate, forming anchor points. Evenly spread the mixed powder from step 1) onto the surface of the wet-laid fiberglass mat, wherein the amount of thermal insulation powder in the spread mixed powder is 190 g / m². 2 The total amount of needle-punched basalt short-cut fibers and basalt short-cut fibers in the mixed powder is 5.7 g / m³. 2 Then, following the aforementioned method, another layer of wet-process glass fiber mat is laid, needle-punched basalt short fibers are laid, and mixed powder is laid. Finally, another layer of wet-process glass fiber mat is laid on the outermost layer, forming a sandwich structure of wet-process glass fiber mat-mixed powder-wet-process glass fiber mat-mixed powder-wet-process glass fiber mat, with a total thickness of 2mm.

[0050] By using short-cut fibers and needle punching, interlayer mechanical interlocking is achieved, forming Z-axis fiber bridges, which improves interlayer bonding strength (prevents delamination) and overall tensile / tear resistance (especially in the transverse and Z-axis directions). The silica aerogel powder can be hydrophobically treated, which further enhances its thermal insulation performance.

[0051] 3) Suppression The laminated structure obtained in step 2) is transferred to the press platform at a temperature of 40°C and a pressure of 2.5 MPa for a holding time of 60 s. After depressurization, the sample is removed to obtain the aerogel composite fiber felt.

[0052] The pressing pressure is lower than the traditional 3 MPa, the temperature is ≤40°C, and the holding time is short. It is only used to promote the initial curing of the binder and the positioning of the powder, avoiding excessive compression that could lead to fiber breakage or hardening and brittleness of the felt, thus preserving the original flexibility and strength of the base felt.

[0053] The aerogel composite fiber felt obtained in this embodiment is the aerogel composite fiber felt provided by the present invention, comprising three layers of wet-process glass fiber felt composited together. The composite interface between adjacent fiber felts is filled with basalt chopped fibers (2 mm) and heat-insulating powder. The heat-insulating powder consists of 60 parts silica aerogel powder, 10 parts fumed silica, and 30 parts light-blocking agent. Of the silica aerogel powder, 75% has an average pore size of 10-15 nm, and 25% has an average pore size of 40-70 nm. The light-blocking agent consists of 15% carbon black with a particle size of 20-50 nm, 50% rutile titanium dioxide with a particle size of 0.5-2 μm, and 35% mica powder with a particle size of 5-15 μm. The specific surface area of ​​the fumed silica is >150 m². 2 / g. The mass ratio of thermal insulation powder to basalt chopped fibers is 100:3; of the total chopped fibers at the composite interface, two-thirds of the basalt chopped fibers are inserted into the fiber felt using a needle-punching method, with approximately 40% of the chopped fiber length inserted; the total amount of basalt chopped fibers used at the composite interface is 5.7 g / m. 2 The amount of heat insulation powder used is 190 g / m². 2 .

[0054] Example 2 The preparation method of the aerogel composite fiber felt in this embodiment is basically the same as that in Example 1, except that in step 1), the heat insulation powder is composed of 60 parts of silica aerogel powder, 30 parts of light-blocking agent, and 10 parts of fumed silica. Among them, 60 parts are silica aerogel powder with an average pore size of 40~70nm.

[0055] Example 3 The preparation method of the aerogel composite fiber felt in this embodiment is basically the same as that in Example 1, except that in step 1), the heat insulation powder is composed of 60 parts of silica aerogel powder, 30 parts of light-blocking agent, and 10 parts of fumed silica. Among them, 60 parts are silica aerogel powder with an average pore size of 10~15nm.

[0056] Example 4 The preparation method of the aerogel composite fiber felt in this embodiment is basically the same as that in Example 1, except that in step 1), the heat insulation powder is composed of 60 parts of silica aerogel powder, 30 parts of opacifier, and 10 parts of fumed silica. The opacifier is composed of 19.5 parts of nano-sized carbon black with a particle size of 20-50 nm and 10.5 parts of micron-sized mica powder with a particle size of 5-15 μm.

[0057] Example 5 The preparation method of the aerogel composite fiber felt in this embodiment is basically the same as that in Example 1, except that in step 1), the heat insulation powder is composed of 60 parts of silica aerogel powder, 30 parts of light-blocking agent, and 10 parts of fumed silica. Among them, the light-blocking agent is 30 parts of micron-sized mica powder with a particle size of 5~15μm.

[0058] Example 6 The preparation method of the aerogel composite fiber felt in this embodiment is basically the same as that in Example 1, except that in step 1), the mixed powder consists of 100 parts of heat insulation powder and 3 parts of basalt short-cut fibers (2 mm in length). The heat insulation powder consists of 60 parts of silica aerogel powder, 30 parts of opacifier, and 10 parts of fumed silica.

[0059] In step 2), dust is cleaned from the surface of the wet-laid fiberglass mat. Then, two portions of basalt chopped fibers (2mm in length) are evenly spread on the surface of the wet-laid fiberglass mat. A needle-punching device is used to embed approximately 40% of the length of the basalt chopped fibers into the substrate, forming anchor points. The mixed powder from step 1) is then evenly spread on the surface of the wet-laid fiberglass mat, wherein the amount of thermal insulation powder in the spread mixed powder is 190 g / m². 2 The total amount of needle-punched basalt short-cut fibers and basalt short-cut fibers in the mixed powder is 9.5 g / m³. 2 .

[0060] II. Comparative Example Comparative Example 1 The preparation method of the aerogel composite fiber felt in this comparative example is basically the same as that in Example 1, except that: in step 1), no basalt short-cut fibers are added to the mixed powder, and the composition of the mixed powder is the same as that of the heat insulation powder, which consists of 60 parts of silica aerogel powder, 30 parts of opacifier and 10 parts of fumed silica.

[0061] In step 2), without needle-punching the basalt short-cut fibers, clean the dust from the surface of the wet-laid glass fiber mat, and then evenly spread the mixed powder from step 1) onto the surface of the wet-laid glass fiber mat. The amount of the spread insulating powder is 190 g / m². 2 .

[0062] Comparative Example 2 The preparation method of the aerogel composite fiber felt in this comparative example is basically the same as that in Example 1, except that: in step 1), no basalt short-cut fibers are added to the mixed powder, and the composition of the mixed powder is the same as that of the heat insulation powder, which consists of 60 parts of silica aerogel powder, 30 parts of opacifier and 10 parts of fumed silica.

[0063] In step 2), dust is cleaned from the surface of the wet-laid fiberglass mat. Then, three portions of basalt chopped fibers (2mm in length) are evenly spread on the surface of the wet-laid fiberglass mat. A needle-punching device is used to embed approximately 40% of the length of the basalt chopped fibers into the substrate, forming anchor points. The thermal insulation powder from step 1) is then evenly spread on the surface of the wet-laid fiberglass mat, with the amount of thermal insulation powder in the mixed powder being 190 g / m². 2 The amount of needle-punched basalt short-cut fiber used was 5.7 g / m². 2 .

[0064] Comparative Example 3 The preparation method of the aerogel composite fiber felt in this comparative example is basically the same as that in Example 1. The difference is that when preparing the mixed powder in step 1), the stepwise mixing method is not adopted. All raw materials are added to the V-type mixer at one time for mixing. The specific method is as follows: 30 parts of opaque agent, 10 parts of fumed silica, 1 part of basalt short chopped fiber and 60 parts of silica aerogel powder are mixed in the mixer at room temperature for 75 minutes (speed 25 rpm) to obtain the mixed powder.

[0065] III. Experimental Examples Performance tests were conducted on the aerogel composite fiber mats of the examples and comparative examples. Specific test parameters are as follows: The bending performance was assessed by bending the aerogel composite fiber felt at a 45° angle along its width and observing its appearance.

[0066] Thermal conductivity: The thermal conductivity at 500℃ was tested according to GB / T 10295 Determination of steady-state thermal resistance and related properties of thermal insulation materials by heat flow meter method; the thermal conductivity at 25℃ was tested according to GB / T 10294 Determination of steady-state thermal resistance and related properties of thermal insulation materials by protective hot plate method. The test results are shown in Table 1.

[0067] Table 1 Performance test results of aerogel composite fiber felt Thermal conductivity (25℃) Thermal conductivity (500℃) Bending performance Example 1 0.020 0.027 No cracks, virtually no powder shedding Example 2 0.024 0.030 No cracks, virtually no powder shedding Example 3 0.022 0.028 No cracks, virtually no powder shedding Example 4 0.023 0.032 No cracks, virtually no powder shedding Example 5 0.022 0.030 No cracks, virtually no powder shedding Example 6 0.022 0.030 No cracks, virtually no powder shedding Comparative Example 1 0.019 0.027 The cracks are quite severe, and there is significant powder shedding. Comparative Example 2 0.020 0.027 Minor cracks, virtually no powder falling off. Comparative Example 3 Poor numerical stability Poor numerical stability It has slight cracks and is shedding a lot of powder. As can be seen from Table 1, compared with Comparative Examples 1-3, the aerogel composite fiber felt of the present invention has excellent thermal conductivity, no cracks when bent, and basically no powder shedding, indicating that it has excellent flexibility and strength as well as the bonding ability between the powder and the matrix.

[0068] In Comparative Example 1, the insulating powder did not contain any fibers, nor were there any fibers inserted into the fiber felt. The powder was filled into the pores of the fiber felt by pressure, relying entirely on the bonding force between the powder and the fiber felt. Compared to Example 1, the cracks were more severe, and the powder shedding was also very serious, indicating that the bonding force between the powder and the matrix was also very poor. However, when only all the short-cut fibers were inserted into the fiber felt, but not into the mixed powder (Comparative Example 2), the resulting aerogel composite fiber felt did not shed powder when bent, but still showed cracks, indicating that its flexibility and strength improvement were limited.

[0069] Comparative Example 3, due to the one-time mixing method, resulted in uneven powder mixing, poor numerical stability of the obtained aerogel composite fiber felt, and poor bonding force between the powder and the matrix.

[0070] Aerogels themselves have poor skeletal continuity and few contact points, resulting in extremely low solid-phase thermal conductivity. Short-cut fibers, acting as highly thermally conductive pathways, form thermal bridges within the aerogel matrix. The incorporation of fibers can also create localized connections, enhancing overall thermal conductivity. While short-cut fibers may reduce insulation performance, they can strengthen the fiber felt and improve its formability. Furthermore, the combination of the insulating powder and short-cut fibers in this invention can improve the strength and formability of the fiber felt while maintaining a low thermal conductivity, preserving the original flexibility and strength of the base felt.

[0071] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aerogel composite fiber felt, characterized in that, It includes a multi-layered fiber felt, with chopped fibers and heat-insulating powder filling the composite interface between adjacent fiber felts. The mass ratio of chopped fibers to heat-insulating powder is (3~5):

100. The heat-insulating powder includes 50~70% silica aerogel powder, 10~20% fumed silica and 20~35% light-blocking agent by mass fraction.

2. The aerogel composite fiber felt as described in claim 1, characterized in that, The silica aerogel powder is selected from one or two types of silica aerogel powder with an average pore size of <20nm and an average pore size of 40~70nm.

3. The aerogel composite fiber felt as described in claim 2, characterized in that, Silica aerogel powder consists of 70-85% by mass of silica aerogel powder with an average pore size <20nm and 15-30% by mass of silica aerogel powder with an average pore size of 40-70nm.

4. The aerogel composite fiber felt as described in claim 1, characterized in that, The light-blocking agent is selected from one or more of the following: nanoscale light-blocking agents with absorption wavelength <5μm, submicron-scale light-blocking agents with absorption wavelength 5~10μm, and micron-scale light-blocking agents with absorption wavelength >10μm; the nanoscale light-blocking agent with absorption wavelength <5μm is selected from one or more of the following: carbon black, iron oxide, silicon carbide, and rutile titanium dioxide with a particle size of 20~50nm; the submicron-scale light-blocking agent with absorption wavelength 5~10μm is selected from one or more of the following: rutile titanium dioxide, zirconium oxide, carbon black, iron oxide, and silicon carbide with a particle size of 0.5~2μm; and the micron-scale light-blocking agent with absorption wavelength >10μm is selected from one or more of the following: mica powder, flake alumina, and silicon carbide with a particle size of 5~15μm.

5. The aerogel composite fiber felt as described in claim 4, characterized in that, The light-blocking agent consists of 60-70% by mass of nanoscale light-blocking agent with an absorption wavelength <5μm and 30-40% by mass of microscale light-blocking agent with an absorption wavelength >10μm; or it consists of 10-20% by mass of nanoscale light-blocking agent with an absorption wavelength <5μm, 40-60% by mass of submicron-scale light-blocking agent with an absorption wavelength of 5-10μm and 30-40% by mass of microscale light-blocking agent with an absorption wavelength >10μm.

6. The aerogel composite fiber felt as described in claim 1, characterized in that, Of the total chopped fibers at the composite interface, 40-70% by weight of the chopped fibers are inserted into the fiber felt by needle punching, with 40-70% of the length of the chopped fibers being inserted; the length of the chopped fibers is 1-3 mm.

7. The aerogel composite fiber felt as described in claim 6, characterized in that, The amount of short-cut fibers used at the composite interface is 5~10 g / m². 2 The amount of heat insulation powder used is 190~220 g / m². 2 The specific surface area of ​​fumed silica is >150 m². 2 / g.

8. A method for preparing an aerogel composite fiber mat as described in any one of claims 1-7, characterized in that, Includes the following steps: After laying the first chopped fiber on the surface of the fiber felt, a mixed powder is laid to form a stacked unit. After at least one stacked unit is stacked, a fiber felt is laid on the outermost mixed powder and then pressed to obtain an aerogel composite fiber felt. The mixed powder includes heat-insulating powder and second chopped fiber. The heat-insulating powder is made of raw materials including 50-70% silica aerogel powder, 10-20% fumed silica and 20-35% light-blocking agent by mass fraction. The mass ratio of the first chopped fiber and the second chopped fiber to the heat-insulating powder is (3-5):

100.

9. The method for preparing aerogel composite fiber felt as described in claim 8, characterized in that, When laying chopped fibers, the needle punching method is used to insert 40-70% of the length of the first chopped fiber into the fiber felt; the first chopped fiber accounts for 40-70% of the total mass of the first and second chopped fibers.

10. The method for preparing aerogel composite fiber felt as described in claim 9, characterized in that, The pressing temperature is ≤40℃, the pressure is 2~3MPa, and the holding time is 30~90s.