A wf / rcf / hgm composite fiber mat and a method for manufacturing the same

Abstract

The application discloses a WF / RCF / HGM composite fiber felt and a preparation method thereof, and belongs to the technical field of high-temperature thermal insulation materials and composite fiber materials. The composite fiber felt takes ceramic fibers as a main thermal insulation framework, wood fibers enhance the bonding strength between fibers, and hollow glass microspheres are uniformly dispersed in the fiber network to reduce the overall thermal conductivity. The mass ratio of the wood fibers to the ceramic fibers is 1:1-1:6, the addition amount of the hollow glass microspheres is 1.0%-15.0% of the dry weight of the mixed fibers, and dispersants, forming aids and binders are further added. The preparation method comprises the steps of hollow glass microsphere pre-dispersion, composite fiber slurry preparation, wet web forming and drying forming. The composite fiber felt prepared by the application has the characteristics of high strength and low thermal conductivity, the preparation process is simple and controllable, is suitable for large-scale production, and widens the application range of the ceramic fiber felt in the high-end thermal insulation field.

Description

Technical Field

[0001] This invention relates to the field of high-temperature thermal insulation materials and composite fiber materials, and in particular to a WF / RCF / HGM composite fiber felt and its preparation method. Background Technology

[0002] Ceramic fiber (RCF) felt is widely used in industrial kilns, aerospace, and thermal insulation due to its excellent properties such as high temperature resistance and low thermal conductivity. However, existing ceramic fiber felts mainly rely on mechanical entanglement for fiber bonding, resulting in weak inter-fiber cohesion. This leads to defects such as low strength and poor molding stability, making the products prone to pulverization and cracking during use and handling, severely affecting their performance and service life. To improve the mechanical properties of ceramic fiber felt, existing technologies typically involve adding organic or inorganic binders to the ceramic fibers. However, this method often significantly increases the thermal conductivity of the ceramic fiber felt, compromising its thermal insulation performance. Furthermore, some binders decompose and fail under high-temperature conditions, failing to maintain their mechanical reinforcement effect at high temperatures, making it difficult to simultaneously achieve both mechanical and thermal insulation properties of the ceramic fiber felt.

[0003] Therefore, how to further reduce the thermal conductivity and thermal diffusivity of materials while improving their mechanical properties, and achieve a synergistic improvement in mechanical and thermal insulation performance, has become an urgent technical challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a WF / RCF / HGM composite fiber felt and its preparation method, so as to solve the problems of low strength, poor structural stability, and difficulty in achieving both mechanical and thermal insulation properties in existing ceramic fiber felts mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides a WF / RCF / HGM composite fiber felt, the raw material composition of which includes ceramic fiber (RCF), wood fiber (WF), hollow glass microspheres (HGM) and additives; wherein, the mass ratio of wood fiber to ceramic fiber is 1:1 to 1:6; the amount of hollow glass microspheres added is 1.0% to 15.0% of the dry weight of the mixture of ceramic fiber and wood fiber; the additives are dispersants, molding aids and binders.

[0006] Preferably, the mass ratio of wood fiber to ceramic fiber is 1:3 to 1:5; the amount of hollow glass microspheres added is 2.5% to 10.0% of the dry weight of the mixture of ceramic fiber and wood fiber.

[0007] Preferably, the dispersant is polyacrylamide, and the amount added is 0.2% to 1.0% of the dry weight of the ceramic fiber and wood fiber mixture.

[0008] Preferably, the molding aid is starch, and the amount added is 0.1% to 2.0% of the dry weight of the ceramic fiber and wood fiber mixture.

[0009] Preferably, the binder is carboxymethyl cellulose, which is added in the form of an aqueous solution of carboxymethyl cellulose with a mass fraction of 1-5%, and the amount of solid carboxymethyl cellulose added is 0.5-2.0% of the dry weight of the ceramic fiber and wood fiber mixture.

[0010] This invention also provides a method for preparing WF / RCF / HGM composite fiber felt, which is obtained by wet molding, specifically including the following steps: S1. Pre-dispersion of hollow glass microspheres: Hollow glass microspheres are added to a dispersion medium for pre-dispersion to obtain a uniform suspension of hollow glass microspheres. S2. Preparation of composite fiber slurry: Wood fiber and ceramic fiber are added to water and dispersed by beating. The solid content of the slurry is controlled to be 0.5% to 2.0%. Then, dispersant and molding aid are added and mixed and dispersed. The hollow glass microsphere suspension obtained in step S1 is added and stirred to obtain ternary composite fiber slurry. S3, Wet web forming: The ternary composite fiber slurry obtained in step S2 is injected into a wet forming machine, and a binder is added to form a web by vacuum filtration. S4. Drying and shaping: After dehydrating the wet fiber felt obtained in step S3, dry it until the moisture content is ≤1% to obtain wood fiber / ceramic fiber / hollow glass microsphere composite fiber felt.

[0011] Preferably, in step S1, the mass-to-volume ratio of hollow glass microspheres to dispersion medium is m(hollow glass microspheres):V(dispersion medium) = 1g:30-40mL; the dispersion medium is water, ethanol, or a mixture of water and ethanol, wherein the volume ratio of water to ethanol in the mixture of water and ethanol is 1:9 to 9:1.

[0012] Preferably, in step S2, the slurry solid content is 1%.

[0013] Preferably, in step S3, the vacuum filtration time is 3 to 5 minutes and the pressure is 0.06 to 0.08 MPa.

[0014] Preferably, in step S4, the drying temperature is 80–150°C and the drying time is 6–10 h.

[0015] Therefore, the WF / RCF / HGM composite fiber felt and its preparation method provided by the present invention have the following beneficial effects: (1) By introducing wood fiber, the bonding force between ceramic fibers is enhanced by the fiber characteristics of wood fiber, which solves the problems of low strength and poor molding stability of pure ceramic fiber felt. The tensile strength, bending modulus and bending strength of composite fiber felt are greatly improved, and it is not easy to pulverize or crack during use and handling.

[0016] (2) Hollow glass microspheres are pre-dispersed and uniformly filled into the pores of interwoven fibers, dividing the large pores into multi-level micropores or mesopores, effectively reducing the overall thermal conductivity and thermal diffusivity of the material, and maintaining excellent thermal insulation performance. The thermal conductivity of the composite fiber felt under the optimal ratio is as low as 88 mW·m -1 ·K -1 The thermal diffusivity is as low as 0.20 mm. 2 ·s -1 Furthermore, the introduction of hollow glass microspheres significantly improved the thermal stability of the composite fiber felt, with its 5% weight loss temperature (T5) decreasing. d The temperature range of the material was increased from 543.82℃ in the pure wood / ceramic fiber binary system to 620.85℃, which broadened the application range of the material under high temperature conditions. At the same time, the hollow glass microsphere pre-dispersion process, combined with the use of dispersant, effectively solved the problems of layering and agglomeration when wood fiber and ceramic fiber are wet-processed. The absolute value of the zeta potential of the slurry was significantly improved, the dispersion stability was greatly optimized, and the fiber and hollow glass microsphere formed a uniform three-dimensional network structure.

[0017] (3) The present invention adopts a wet molding process, which is simple and highly controllable, and is suitable for large-scale and industrialized production; moreover, the raw materials used are readily available, the production cost is controllable, and it has good industrialization prospects.

[0018] (4) Expanded application scope: The resulting composite fiber felt has the characteristics of high strength, low thermal conductivity and high thermal stability, which solves the problem that the mechanical and thermal insulation properties of traditional ceramic fiber felt are difficult to balance. It can be widely used in high-end thermal insulation fields such as industrial kilns, aerospace, high-temperature equipment insulation, building insulation and thermal protection, and has broad application prospects.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 The images show the SEM morphology of the composite fiber mats prepared in Comparative Example 2 and Example 1 of the present invention, where (a) is Comparative Example 2 and (b) is Example 1. Figure 2 The graph shows the test results of the Zeta potential (interfacial potential) of different slurry systems in Examples 1-4 and Comparative Examples 1-3 of the present invention. Figure 3This is a comparison diagram of the tensile strength of different fiber felt systems in Examples 1-4 and Comparative Examples 1-2 of the present invention; Figure 4 These are graphs showing the relationship between the flexural modulus and flexural strength of fiber felt and the amount of hollow glass microspheres added in different systems of Examples 1-4 and Comparative Examples 1-3 of the present invention. Figure 5 Thermogravimetric analysis results of different fiber felt systems in Embodiment 1 and Comparative Examples 1-2 of the present invention are shown in the figure. Figure 6 The transient thermal insulation performance diagrams are for different fiber felt systems in Examples 1-4 and Comparative Examples 1-2 of the present invention. Detailed Implementation

[0021] This invention provides a wood fiber (WF) / ceramic fiber (RCF) / hollow glass microsphere (HGM) composite fiber felt. The raw material composition includes ceramic fiber, wood fiber, hollow glass microspheres, and additives. Among them, ceramic fiber serves as the main thermal insulation skeleton, providing the composite fiber felt with high temperature resistance and basic thermal insulation performance. Wood fiber is used to enhance the bonding strength between fibers, improve the mechanical properties and molding stability of the composite fiber felt. Hollow glass microspheres are uniformly dispersed in the fiber network, filling the fiber gaps, reducing the overall thermal conductivity, and optimizing the thermal insulation performance. The additives are dispersants, molding aids, and binders.

[0022] In this invention, the mass ratio of wood fiber to ceramic fiber is 1:1 to 1:6, preferably 1:3 to 1:5, and more preferably 1:4. At this ratio, the wood fiber can be uniformly dispersed within the ceramic fiber, achieving optimal mechanical reinforcement without compromising the basic thermal insulation properties of the ceramic fiber. The amount of hollow glass microspheres added is 1.0% to 15.0% of the dry weight of the mixed ceramic and wood fibers, preferably 2.5% to 10.0%, more preferably 5.0% to 8.0%, and most preferably 7.5%. At this amount, the hollow glass microspheres can uniformly fill the fiber gaps, maximizing the reduction of thermal conductivity, and will not cause material densification due to excessive addition, thus increasing the thermal diffusivity.

[0023] In this invention, the dispersant is polyacrylamide (PAM), added at 0.2%–1.0% of the dry weight of the mixed ceramic fiber and wood fiber, to improve the dispersibility of wood fiber, ceramic fiber, and hollow glass microspheres in the slurry and prevent agglomeration. The molding aid is starch, added at 0.1%–2.0% of the dry weight of the mixed ceramic fiber and wood fiber, to optimize the wet web forming effect and improve the molding stability of the wet fiber felt. The binder carboxymethyl cellulose (CMC) is pre-prepared as an aqueous solution with a mass fraction of 1–5% to improve its dispersion uniformity in the aqueous medium. During the molding process, 25–100 g of this binder solution is added to the fiber slurry and thoroughly mixed under manual stirring to ensure uniform distribution of the binder on the fiber surface, thereby improving the wet web consolidation and molding stability.

[0024] This invention also provides a wet molding method for preparing the above-mentioned wood fiber / ceramic fiber / hollow glass microsphere composite fiber mat, which specifically includes the following steps: S1. Pre-dispersion of hollow glass microspheres: Hollow glass microspheres are added to a dispersion medium for pre-dispersion, wherein the mass-to-volume ratio of hollow glass microspheres to dispersion medium is 1g:30-40mL; the dispersion medium is water, ethanol, or a mixture of water and ethanol, preferably ethanol or a mixture of water and ethanol with a volume ratio of 1:9 to 9:1; the pre-dispersion method includes stirring, ultrasonication, or a combination of both, and a uniform hollow glass microsphere suspension is obtained after full dispersion; pre-dispersion is a necessary feature for obtaining a uniform pore structure and inhibiting the aggregation of hollow glass microspheres.

[0025] S2. Preparation of composite fiber slurry: Wood fiber and ceramic fiber are added to water and dispersed by beating. The solid content of the slurry is strictly controlled to be 0.5% to 2.0%, preferably 1%. Then, polyacrylamide and / or starch are added and mixed to disperse the fibers, thereby improving the fiber dispersibility and formability. The hollow glass microsphere suspension obtained in step S1 is then added and stirred. After thorough mixing, a ternary composite fiber slurry is obtained.

[0026] S3. Wet web forming: The ternary composite fiber slurry is injected into a wet web forming machine and formed into a web by vacuum filtration. Carboxymethyl cellulose solution can be added before or during web forming to further improve the bonding force between fibers. The solid content and filtration conditions together determine the uniformity of web forming during wet web forming, which is the core control point of the process window. In this invention, the vacuum filtration time is 3 to 5 minutes and the pressure is 0.06 to 0.08 MPa.

[0027] S4. Drying and Shaping: The wet felt after wet web forming is dehydrated and then placed in a drying device to dry until the moisture content is ≤1%, thus obtaining a wood fiber / ceramic fiber / hollow glass microsphere composite fiber felt. In this invention, the drying temperature is 80-150℃, preferably 100-120℃; the drying time is 6-10h, preferably 8h.

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.

[0029] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0030] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0031] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art, and the testing standards all use national or international standards commonly used in the field, without further explanation.

[0032] The main raw materials used in the following examples or comparative examples are: Wood fiber (WF, length 1-2mm, Lingshou County Fengfeng Mineral Products Processing Plant); Refractory ceramic fiber (RCF, commercial specification "80 cotton", Shandong Zhongluan New Materials Co., Ltd., main component is SiO2-Al2O3 system; fiber diameter 4-6μm, slag ball content 15.20wt.%); Hollow glass microspheres (HGM, Henan Borun New Materials Co., Ltd., commercial specification "300-400 mesh", main component is borosilicate glass system; particle size range 10-75μm, wall thickness about 1-2μm, true density 0.4g·cm³). -3 Bulk density 0.24 g·cm³ -3 (Softening temperature 620℃).

[0033] Example 1 This embodiment provides a wood fiber / ceramic fiber / hollow glass microsphere composite fiber felt and its preparation method. The main raw material formula is as follows: the mass ratio of wood fiber to ceramic fiber is 1:4, and the total mass is 100g (of which wood fiber is 20g and ceramic fiber is 80g); the amount of hollow glass microspheres added is 7.5% of the dry weight of WF and RCF mixture, i.e., 7.5g; the amount of dispersant polyacrylamide added is 1.0%, i.e. 1g; the amount of molding aid starch added is 1.0%, i.e. 1g; and the mass fraction of 2.0% carboxymethyl cellulose (CMC) solution is 50g (i.e., the amount of CMC solid added is 1.0% of the dry weight of WF and RCF mixture).

[0034] Its preparation method specifically includes the following steps: S1. Pre-dispersion of hollow glass microspheres: Weigh 7.5g of hollow glass microspheres and add them to a mixed solvent with a volume ratio of ethanol to water of 7:3. The total volume of the mixed solvent is 300ml (i.e., m(hollow glass microspheres):V(dispersion medium) = 1g:40mL, of which the volume of ethanol is 210ml and the volume of water is 90ml). Disperse the mixture using ultrasonic dispersion for 30min to obtain a uniform suspension of hollow glass microspheres for later use.

[0035] S2. Preparation of composite fiber pulp: Distilled water is added to a pulper, followed by polyacrylamide and starch, and stirred for 6 minutes until completely dissolved; the above-dispersed hollow glass microsphere suspension is added and mixed evenly; then the proportioned wood fiber and ceramic fiber are added, and stirring and pulping are continued to disperse the pulp, controlling the solid content of the pulp to 1%, to obtain ternary composite fiber pulp.

[0036] S3. Wet web forming: The ternary composite fiber slurry is injected into a wet web forming machine, and 50g of 2% carboxymethyl cellulose solution is added. After manual stirring for 2 minutes, the web is formed by vacuum filtration at 0.08MPa pressure for 4 minutes to obtain wet fiber felt.

[0037] S4. Drying and shaping: After dehydrating the wet fiber felt, place it in a drying oven and dry it at 105℃ for 8 hours until the moisture content is <1%, to obtain wood fiber / ceramic fiber / hollow glass microsphere composite fiber felt.

[0038] Example 2 The only difference between this embodiment and Example 1 is that the amount of hollow glass microspheres added is 2.5% of the dry weight of the mixture of WF and RCF. The other raw material formulations, preparation steps and process parameters are the same as in Example 1, and will not be repeated here.

[0039] Example 3 The only difference between this embodiment and Example 1 is that the amount of hollow glass microspheres added is 5.0% of the dry weight of the mixture of WF and RCF. The other raw material formulations, preparation steps and process parameters are the same as in Example 1, and will not be repeated here.

[0040] Example 4 The only difference between this embodiment and Example 1 is that the amount of hollow glass microspheres added is 10.0% of the dry weight of the mixture of WF and RCF. The other raw material formulations, preparation steps and process parameters are the same as in Example 1, and will not be repeated here.

[0041] Comparative Example 1 This comparative example uses pure ceramic fiber felt, without the addition of wood fiber and hollow glass microspheres. The remaining wet molding process and process parameters are the same as in Example 1, and will not be repeated here.

[0042] Comparative Example 2 This comparative example is a wood fiber / ceramic fiber binary composite felt with a WF to RCF mass ratio of 1:4. No hollow glass microspheres were added. The remaining wet molding process and process parameters are the same as those in Example 1, and will not be repeated here.

[0043] Comparative Example 3 The only difference between this comparative example and Example 1 is that the hollow glass microspheres were not pre-dispersed and were directly added to the slurry. The other raw material formulations, preparation steps and process parameters are the same as in Example 1, and will not be repeated here.

[0044] Figure 1 These are SEM morphology comparison images of the composite fiber mats prepared in Example 1 and Comparative Example 2 of this invention. Figure 1 As shown in (a) of Comparative Example 2, the WF / RCF composite fibers are randomly interwoven, forming a network of large-diameter, highly interconnected pores. The inter-fiber voids are relatively uniformly distributed, with no obvious filling particles. Figure 1 As can be seen from (b) in Example 1, after pre-dispersion, HGM is uniformly filled in the pores of the interwoven fibers in the form of spherical particles. The large pores are divided into multi-level micropores or mesopores, the pore structure is more compact, and there is no obvious agglomeration.

[0045] Figure 2 The results of Zeta potential tests for different slurry systems are presented. The absolute value of the Zeta potential can be used to characterize the dispersion stability of the slurry system. The higher the value, the stronger the electrostatic repulsion between particles or fibers in the system, and the better the slurry dispersion. Figure 2It can be seen that the absolute value of the zeta potential of the pure ceramic fiber slurry in Comparative Example 1 is low, and the dispersion stability is limited. After the introduction of hollow glass microspheres, the zeta potential of the slurry first increases and then decreases with the addition of HGM. The absolute value of the zeta potential of Example 1 (HGM is 7.5%) reaches a high level, and the dispersion stability is optimal. This is because when the hollow glass microspheres are not pre-dispersed, the microspheres are prone to agglomeration, which leads to a reduction in the effective charged surface area in the slurry system, resulting in a lower absolute value of the zeta potential (Comparative Example 3), which is not conducive to maintaining the dispersion stability of the slurry.

[0046] Figures 3-4 Table 1 shows the mechanical properties of fiber felts of different systems.

[0047] in, Figure 3 This is a comparison chart of the tensile strength of fiber felts from different systems. Figure 3 It can be seen that the tensile strength of the single RCF system (Comparative Example 1) is the lowest among all systems; as the amount of HGM added increases, the tensile strength shows a trend of "first increasing and then decreasing". The tensile strength of the HGM-2.5% (Example 2), 5.0% (Example 3), and 7.5% (Example 1) systems is higher than that of pure RCF but lower than that of the RCF&WF system.

[0048] Figure 4 The relationship between flexural modulus and flexural strength and HGM addition amount is shown. Figure 4 It can be seen that 7.5% (Example 1) is the optimal addition ratio for mechanical properties. At this ratio, the flexural modulus reaches 133.03 MPa and the flexural strength reaches 1.53 MPa, which is close to the performance of the WF&RCF binary system (Comparative Example 2) (flexural modulus 137.24 MPa and flexural strength 1.64 MPa).

[0049] Table 1 shows the bending resistance parameters of fiber felts with different components, and lists the mechanical property test results of the samples of Example 1 and Comparative Examples 1-3.

[0050] Table 1: Flexural performance parameters of the samples from Example 1 and Comparative Examples 1-3

[0051] As shown in Table 1, when the interfacial bonding between microspheres and fibers in the composite system is insufficient, the flexural strength of the fiber felt is significantly reduced. This is because poor wetting and interfacial compatibility between microspheres and fibers makes it difficult to form a continuous and uniform interfacial bonding structure, affecting the overall integrity of the fiber network and resulting in a relatively loose internal structure of the felt. Under bending loads, this structure cannot effectively transfer loads, easily leading to interfacial debonding and local structural damage, thus reducing the flexural modulus and flexural strength of the fiber felt.

[0052] Figure 5Thermogravimetric analysis results of different fiber felt systems were presented. Figure 5 It can be seen that the introduction of HGM significantly improved the thermal stability of the system. The 5% weight loss temperature (Td5%) of Example 1 increased from 543.82℃ in Comparative Example 2 to 620.85℃ in Example 1, which is an increase of 77.03℃.

[0053] Figure 6 Table 2 shows the thermal insulation performance of fiber felts of different systems.

[0054] in, Figure 6 The transient thermal insulation performance of fiber felts with different HGM addition amounts was determined by... Figure 6 It can be seen that when the HGM filling amount increases from 2.5% to 7.5%, the thermal diffusivity continuously decreases. However, when the addition amount exceeds 7.5%, excessive HGM leads to material densification, and the thermal diffusivity rebounds. In Example 1, the thermal conductivity of the HGM-7.5% system is as low as 88 mW·m. -1 ·K -1 The thermal diffusivity is as low as 0.20 mm. 2 ·s -1 It has the best thermal insulation performance.

[0055] Table 2 lists the thermal performance parameters of the samples from Example 1 and Comparative Examples 1-3, including the thermal conductivity λ and the thermal diffusivity α. The thermal diffusivity reflects the rate of heat diffusion within the material; the higher the value, the worse the material's thermal insulation performance.

[0056] Table 2: Thermal performance parameters of the samples from Example 1 and Comparative Examples 1-3

[0057] As shown in Table 2, the thermal diffusivity of the composite fiber felt is significantly reduced and its thermal insulation performance is improved after introducing wood fibers and using pre-dispersed hollow glass microspheres. Conversely, when hollow glass microspheres are added directly to the slurry without pre-dispersion in an alcohol-water system, the microspheres are prone to agglomeration and delamination during wet molding, resulting in an uneven internal structure of the fiber felt. The agglomerated areas easily form localized dense heat transfer channels, while the delamination structure may produce a thermal bridging effect, thereby shortening the heat transfer path, increasing the thermal conductivity and thermal diffusivity of the material, and reducing its thermal insulation performance.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A WF / RCF / HGM composite fiber felt, characterized in that: The raw material composition includes ceramic fiber, wood fiber, hollow glass microspheres and additives; wherein, the mass ratio of wood fiber to ceramic fiber is 1:1 to 1:6; the amount of hollow glass microspheres added is 1.0% to 15.0% of the dry weight of the mixture of ceramic fiber and wood fiber; the additives are dispersants, molding aids and binders.

2. The WF / RCF / HGM composite fiber felt according to claim 1, characterized in that, The mass ratio of wood fiber to ceramic fiber is 1:3 to 1:5; the amount of hollow glass microspheres added is 2.5% to 10.0% of the dry weight of the mixture of ceramic fiber and wood fiber.

3. The WF / RCF / HGM composite fiber felt according to claim 1, characterized in that, The dispersant is polyacrylamide, and the amount added is 0.2% to 1.0% of the dry weight of the ceramic fiber and wood fiber mixture.

4. The WF / RCF / HGM composite fiber felt according to claim 1, characterized in that, The molding aid is starch, and the amount added is 0.1% to 2.0% of the dry weight of the ceramic fiber and wood fiber mixture.

5. The WF / RCF / HGM composite fiber felt according to claim 1, characterized in that, The binder is carboxymethyl cellulose, which is added in the form of an aqueous solution of carboxymethyl cellulose with a mass fraction of 1-5%. The amount of solid carboxymethyl cellulose added is 0.5-2.0% of the dry weight of the ceramic fiber and wood fiber mixture.

6. The method for preparing a WF / RCF / HGM composite fiber felt according to any one of claims 1-5, characterized in that, It is produced by wet molding, specifically including the following steps: S1. Pre-dispersion of hollow glass microspheres: Hollow glass microspheres are added to a dispersion medium for pre-dispersion to obtain a uniform suspension of hollow glass microspheres. S2. Preparation of composite fiber slurry: Wood fiber and ceramic fiber are added to water and dispersed by beating. The solid content of the slurry is controlled to be 0.5% to 2.0%. Then, dispersant and molding aid are added and mixed and dispersed. The hollow glass microsphere suspension obtained in step S1 is added and stirred to obtain ternary composite fiber slurry. S3. Wet web forming: The ternary composite fiber slurry obtained in step S2 is injected into a wet forming machine, and a binder is added to form a web by vacuum filtration. S4. Drying and shaping: After dehydrating the wet fiber felt obtained in step S3, dry it until the moisture content is ≤1% to obtain wood fiber / ceramic fiber / hollow glass microsphere composite fiber felt.

7. The method for preparing a WF / RCF / HGM composite fiber felt according to claim 6, characterized in that, In step S1, the mass-to-volume ratio of hollow glass microspheres to dispersion medium is 1g:30-40mL; the dispersion medium is water, ethanol, or a mixture of water and ethanol, wherein the volume ratio of water to ethanol in the mixture of water and ethanol is 1:9-9:

1.

8. The method for preparing a WF / RCF / HGM composite fiber felt according to claim 6, characterized in that, In step S2, the slurry solids content is 1%.

9. The method for preparing a WF / RCF / HGM composite fiber felt according to claim 6, characterized in that, In step S3, the vacuum filtration time is 3 to 5 minutes and the pressure is 0.06 to 0.08 MPa.

10. The method for preparing a WF / RCF / HGM composite fiber felt according to claim 6, characterized in that, In step S4, the drying temperature is 80–150℃ and the drying time is 6–10 hours.

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