A three-dimensional reticulated ceramic fiber mat reinforced ceramic shell and a method of making the same

Abstract

The application provides a three-dimensional reticular ceramic fiber felt reinforced ceramic shell and a preparation method thereof, and relates to the technical field of ceramic shell preparation. The preparation method comprises the following steps: preparing a cloth-like ceramic precursor fiber felt; preparing a back layer slurry, and performing slurry immersion treatment on the fiber felt so that the back layer slurry is adsorbed in the fiber felt; preparing a surface layer slurry, and preparing a surface layer shell on the surface of a wax mold; alternately performing slurry hanging and fiber felt pasting on the surface layer shell to form a multi-layer composite back layer structure, and obtaining a ceramic shell preform after drying; and sequentially performing sealing, demolding and calcination treatment on the ceramic shell preform to obtain the three-dimensional reticular ceramic fiber felt reinforced ceramic shell. The application realizes three-dimensional continuous network distribution of the fiber reinforcement in the back layer of the ceramic shell, significantly improves the normal temperature strength, high temperature thermal shock resistance, interlayer bonding strength and air permeability of the ceramic shell, and is suitable for high temperature alloy precision casting.

Description

Technical Field

[0001] This application relates to the field of ceramic shell preparation technology, specifically to a three-dimensional mesh ceramic fiber felt reinforced ceramic shell and its preparation method. Background Technology

[0002] With the rapid development of the aviation industry, the requirements for the temperature resistance of aero engines are increasing. Turbine blades, as a core component of the engine, are becoming increasingly complex in shape and larger in size, placing extremely high demands on the materials and structures of ceramic molds used in precision casting. Throughout the entire process of pouring molten high-temperature alloys, the ceramic mold not only needs to possess sufficient strength to withstand the impact of the high-temperature molten metal, but also should have high permeability to ensure the quality of the casting.

[0003] Currently, most research focuses on adding various ceramic fibers to enhance the high-temperature strength of ceramic shells, and this has yielded good results. There are essentially two existing methods for fiber addition: one is mechanical mixing in silica sol or shell slurry, but mechanical mixing makes it difficult to achieve uniform fiber dispersion, easily leading to agglomeration and resulting in lower-than-expected performance enhancement of the ceramic shell; the other is distributing the fibers on the shell backing layer using a sand-sprinkling method, but this method still causes uneven fiber distribution, affecting the strengthening effect. Therefore, the fiber dispersion effect achieved by the above methods is poor, and the strengthening effect is limited.

[0004] Existing patent CN110434288A discloses a fiber-ceramic shell and its preparation method, using glass fiber as the backing layer sand material, alternately sprinkled with mullite sand to form the backing layer, so that the fiber is wrapped by the slurry to form a layered stress-bearing skeleton, which enhances the shell strength to a certain extent. However, in this method, the fiber is distributed in discrete particles, which cannot form a continuous reinforcing network, and the uniformity of fiber distribution and interlayer continuity are still limited. Existing patent CN112062516A discloses a novel gradient engineering material, using alumina ceramic spheres as the reinforcing phase and steel fibers as the toughening phase. Through the gradient design of the backing layer, intermediate layer, and surface layer, the content of ceramic spheres decreases and the content of fibers increases, realizing the gradient reinforcement of the material. However, this material system is a cement-based composite material used in the field of building protection, and its fibers are short-cut steel fibers, introduced by layered spreading or mixing, which cannot form a continuous fiber-reinforced structure.

[0005] Therefore, it is necessary to develop new fiber distribution and reinforcement methods to enhance the strength and permeability of ceramic shells, which is of great significance for promoting the development of ceramic shell technology and high-temperature alloy precision casting. Summary of the Invention

[0006] Based on the above-mentioned prior art, this application proposes a three-dimensional mesh ceramic fiber felt reinforced ceramic shell and its preparation method, in order to solve the technical problem that the fiber reinforcement in the existing ceramic shell is discontinuously distributed and has limited reinforcement effect.

[0007] To achieve the above objectives, the first aspect of this application proposes a method for preparing a ceramic shell reinforced with a three-dimensional mesh ceramic fiber felt, the specific technical solution of which is as follows: A method for preparing a ceramic shell reinforced with a three-dimensional mesh ceramic fiber felt includes the following steps: S1. Preparation of cloth-like ceramic precursor fiber mat; S2. Prepare backing slurry by impregnating the fiber felt with slurry to allow the backing slurry to adhere to the interior of the fiber felt. S3. Prepare the surface layer slurry and prepare the surface layer shell on the surface of the wax model; S4. Alternately apply slurry and fiber felt to the surface shell to form a multi-layer composite backing structure. After drying, a ceramic shell preform is obtained. S5. The ceramic shell preform is sequentially subjected to sealing, demolding and calcination treatments to obtain a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt.

[0008] Furthermore, in step S1, the cloth-like ceramic precursor fiber felt is prepared by electrospinning. The spinning solution includes a precursor salt, a spinning aid, and a solvent. The precursor salt is one or more of zirconium salt, yttrium salt, and aluminum salt, or a combination of aluminum salt and ethyl silicate.

[0009] Furthermore, the spinning voltage of the electrospinning process is 10-35kV, and the distance between the receiving rollers is 12-30cm.

[0010] Furthermore, in step S2, the backing slurry comprises refractory powder, inorganic binder, dispersant and deionized water, wherein by mass percentage, the refractory powder comprises 65% to 70%, the inorganic binder comprises 20% to 22%, the dispersant comprises 0.8% to 1%, and the deionized water comprises 9% to 13%.

[0011] Furthermore, in step S3, the surface shell is formed by coating the wax mold surface with a surface slurry and sprinkling sand; the surface slurry includes refractory powder, inorganic binder, dispersant and deionized water; by mass percentage, the refractory powder is 60% to 70%, the inorganic binder is 5% to 10%, the dispersant is 0.2% to 1%, and the deionized water is 19% to 34.8%.

[0012] Furthermore, in step S3, the coating thickness of the surface layer slurry on the wax mold surface is 0.1 to 0.5 mm.

[0013] Furthermore, in step S4, the alternating operation of slurry application and fiber felt laying is as follows: first, slurry is applied using pre-made backing slurry, then the fiber felt after slurry absorption is bonded together to form a composite backing layer, and then the slurry application and fiber felt laying operation is repeated; the thickness of the backing slurry each time is 0.2 to 2 mm.

[0014] Furthermore, the repeated slurry application and fiber felt laying operations form 3 to 11 layers of composite backing.

[0015] Furthermore, in step S5, the sealing treatment uses a sealing material with the same composition as the back layer slurry in step S2 for sealing 1 to 2 times; the demolding treatment uses heating demolding, raising the temperature to 250 to 450°C to melt and remove the wax mold; the calcination treatment uses a segmented heating process, finally raising the temperature to 1300 to 1650°C, holding the temperature, and then cooling it with the furnace.

[0016] The second aspect of this application proposes a ceramic shell reinforced with a three-dimensional mesh ceramic fiber felt, the specific technical solution of which is as follows: A three-dimensional mesh ceramic fiber felt reinforced ceramic shell is prepared by the method for preparing a three-dimensional mesh ceramic fiber felt reinforced ceramic shell as described in the first aspect above, comprising: The inner surface layer; At least one composite backing layer is located in the middle, wherein a continuous three-dimensional mesh ceramic fiber felt is embedded in the composite backing layer, the fiber felt having a three-dimensional through network structure and being tightly bonded to the interface of the backing layer slurry matrix; And the outermost sealing layer.

[0017] By applying the above-described technical solution of this application, at least the following technical effects are achieved: 1. This application utilizes electrospinning to prepare a ceramic precursor fiber mat with a three-dimensional network structure, which is then embedded as a continuous reinforcing phase within the back layer of the mold shell to form a spatially interconnected reinforcing skeleton. Compared to traditional discontinuous distribution methods such as chopped fibers or sprinkled fibers, this continuous network can effectively transfer and disperse stress, significantly improve the room temperature strength, firing strength, and residual strength of the mold shell, inhibit crack initiation and propagation, and prevent deformation or breakage of the mold shell during high-temperature casting.

[0018] 2. This application employs a cyclic composite process of slurry application and bonding, ensuring that the fiber felt is fully in contact with and compacted with the backing slurry after impregnation, guaranteeing a wrinkle-free and bubble-free interface between the fiber felt and the slurry matrix. During calcination, the precursor fibers are transformed in situ into ceramic fibers and chemically bonded and physically integrated with the matrix, forming a seamless, delamination-free, and tightly bonded interface. This significantly improves the interlayer bonding strength, eliminates interface defects common in traditional reinforcement methods, and ensures the structural integrity of the shell at high temperatures.

[0019] 3. The cloth-like fiber felt used in this application has a three-dimensional interconnected porous network structure. After calcination, this structure is interconnected with the micropores in the backing matrix to form a uniform and continuous exhaust channel, which significantly improves the air permeability of the ceramic shell. Good air permeability is conducive to the rapid discharge of gas inside the shell during the casting process, reducing defects such as porosity and looseness in the casting, and improving the forming quality of precision castings.

[0020] 4. The preparation method described in this application is simple to operate in each step, and the process parameters can be flexibly adjusted according to different material systems, specifications, and structures of precision castings. By controlling conditions such as electrospinning parameters, slurry composition, and number of circulation layers, customized designs for shell reinforcement and permeability can be achieved. It has a wide range of applications, is easy to achieve industrial-scale production, and effectively improves the yield and economic benefits of precision casting.

[0021] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application. The illustrative embodiments and descriptions of the application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 A schematic flowchart of the preparation method of a three-dimensional mesh ceramic fiber felt reinforced ceramic shell proposed in this application is shown; Figure 2 A SEM schematic diagram of the three-dimensional network alumina precursor fiber mat prepared in Example 1 of this application is shown. Figure 3 A CT schematic diagram of the cross-section of the ceramic shell reinforced with three-dimensional mesh ceramic fiber felt prepared according to Embodiment 1 of this application is shown. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0025] To address the technical problem of discontinuous distribution and limited reinforcement effect of fiber reinforcement in existing ceramic shells, this application proposes a three-dimensional mesh ceramic fiber felt reinforced ceramic shell and its preparation method. The method involves preparing a cloth-like three-dimensional mesh ceramic precursor fiber felt using electrospinning. After pre-impregnation, the felt is repeatedly applied and coated during the back layer construction of the ceramic shell to form a multi-layer composite back layer structure. Following sealing, demolding, and calcination, the precursor fibers are transformed in situ into ceramic fibers, achieving three-dimensional continuous network reinforcement. This significantly improves the strength, thermal shock resistance, and interlayer continuity of the ceramic shell.

[0026] The first aspect of this application proposes a method for preparing a ceramic shell reinforced with a three-dimensional mesh ceramic fiber felt, see reference. Figure 1 As shown, the preparation method includes the following steps: S1. Fabric-like ceramic precursor fiber mat was prepared by electrospinning process. S2. Immerse the cloth-like ceramic precursor fiber felt into the pre-made backing slurry, and the backing slurry is fully adsorbed into the interior of the cloth-like ceramic precursor fiber felt. S3. Apply pre-made surface slurry to the wax model and sprinkle sand to form a surface shell; S4. Apply the pre-made back layer slurry to the surface shell and attach the cloth-like ceramic precursor fiber felt from step S2 to the surface shell to form the first back layer shell. Then repeat the cycle of applying the back layer slurry and attaching the cloth-like ceramic precursor fiber felt to form a multi-layer composite back layer structure and obtain the ceramic shell preform. S5. The ceramic shell preform is sequentially sealed, demolded, and calcined to obtain a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt.

[0027] In this embodiment, step S1 specifically involves preparing a fabric-like ceramic precursor fiber mat using electrospinning. The spinning solution comprises a precursor salt solution, a spinning aid, and a solvent, which are mixed in a mass ratio of 40-60:5-15:25-55 and then magnetically stirred until homogeneous. Optionally, the precursor salt solution is one of zirconium salt, yttrium salt, or aluminum salt, or a combination of zirconium salt and yttrium salt, or a combination of aluminum salt and ethyl silicate. The spinning aid is polyvinyl alcohol (PVA) or polyethylene glycol (PEG). The solvent is deionized water or anhydrous ethanol. In the electrospinning process, the process parameters are controlled as follows: spinning voltage 10-35kV, receiving roller distance 12-30cm, feed rate 0.5-8mL / h, ambient temperature 20-35℃, and ambient humidity 30%-65%. After spinning, a continuous, three-dimensionally interconnected fabric-like ceramic precursor fiber mat is obtained.

[0028] In this embodiment, step S2 specifically involves immersing the fabric-like ceramic precursor fiber felt in a pre-prepared backing slurry, ensuring the slurry fully penetrates and adsorbs into the fiber felt. The backing slurry is prepared by ball milling a mixture of refractory powder, inorganic binder, dispersant, and deionized water, with the following mass percentages: 65%–70%, 20%–22%, 0.8%–1%, and 9%–13%, respectively. Optionally, the refractory powder is one of alumina, yttrium oxide, quartz, or mullite; the inorganic binder is one of silica sol, alumina sol, or yttrium sol; and the dispersant is one of polyethylene glycol, ammonium citrate, polyvinylpyrrolidone, or sodium polyacrylate. The immersion and adsorption time for the fabric-like ceramic precursor fiber felt is 8–35 minutes, supplemented by ultrasonic vibration during immersion to accelerate the filling of the fiber felt pores with the slurry and ensure uniform adsorption.

[0029] In this embodiment, step S3 specifically involves: applying a pre-prepared surface slurry to the wax model used for investment casting, followed by sand application to form a surface shell. The surface slurry is a ceramic surface slurry for investment casting, and it is prepared by ball milling a mixture of refractory powder, inorganic binder, dispersant, and deionized water, with the following mass percentages: 60%–70%, 5%–10%, 0.2%–1%, and 19%–34.8%, respectively. The refractory powder is one of alumina, yttrium oxide, quartz, or mullite. The inorganic binder is one of silica sol, alumina sol, or yttrium sol; the dispersant is one of polyethylene glycol, ammonium citrate, polyvinylpyrrolidone, or sodium polyacrylate. During application, the coating thickness of the surface slurry on the wax model surface is controlled to be 0.1–0.5 mm. The sand used for sand spreading is alumina sand, quartz sand, or mullite sand, with a particle size of 100–220 mesh; optionally, the sand can be a single type or a mixture of two or more types. After spreading, the sand is left to dry at room temperature for 2–10 hours.

[0030] In this embodiment, step S4 specifically involves: applying a pre-made backing slurry to the surface shell, then attaching the cloth-like ceramic precursor fiber felt (after slurry adsorption in step S2) to the surface shell to form the first backing shell. This process of applying backing slurry and attaching the cloth-like ceramic precursor fiber felt is repeated to form a multi-layer composite backing structure. Finally, another layer of backing slurry is applied. After the composite backing is formed, it is dried and cured at room temperature for 4–20 hours to ensure the stability of the multi-layer backing structure. The thickness of each backing slurry application is 0.2–2 mm. When attaching the cloth-like ceramic precursor fiber felt, it is essential to ensure that there are no wrinkles or air bubbles and that it is completely compacted to the shell surface.

[0031] In this embodiment, step S5 specifically involves sequentially performing sealing, demolding, and calcination treatments on the ceramic shell preform to ultimately obtain a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt. Specifically, the sealing treatment uses a sealing material with the same composition as the backing slurry, performing 1-2 sealing operations, followed by drying for 4-8 hours. The demolding treatment employs a heated demolding method, raising the temperature to 250-450℃ and holding it for 1-4 hours to completely melt and remove the wax mold. The calcination treatment uses a segmented heating process: the first stage raises the temperature to 600-800℃ and holds it for 1-3 hours; the second stage raises the temperature to 1300-1650℃ and holds it for 2-7 hours; the heating rate is controlled at 2-10℃ / min. After calcination, the material is cooled in the furnace.

[0032] The following provides an exemplary description of this application in conjunction with specific raw material combinations and process parameters.

[0033] Example 1

[0034] S1. Aluminum nitrate, polyvinyl alcohol, and anhydrous ethanol are mixed at a mass ratio of 40:5:55 and magnetically stirred to obtain a homogeneous spinning solution. The spinning solution is injected into a syringe, connected to a high-voltage power supply, and electrospinning is performed. The spinning voltage is set to 20kV, the receiving roller distance is 18cm, the feed rate is 2mL / h, the ambient temperature is 25℃, and the ambient relative humidity is 45%. After spinning, a three-dimensional network alumina precursor fiber mat is obtained.

[0035] S2. Prepare the backing slurry by ball milling 70% mullite powder, 20% silica sol binder, 1% sodium polyacrylate dispersant, and 9% deionized water until homogeneous. Immerse the fiber felt obtained in step S1 into the backing slurry and ultrasonically soak for 15 minutes to ensure that the backing slurry is fully absorbed into the fiber felt.

[0036] S3. Preparation of the surface layer slurry: By mass percentage, ball mill and mix 60% alumina, 5% aluminum sol, 0.2% polyethylene glycol, and 34.8% deionized water evenly. Apply the zirconia surface layer slurry to the surface of the wax pattern for investment casting to a thickness of 0.3 mm, immediately sprinkle with 150-mesh mullite sand, and then let it stand and dry at room temperature for 4 hours to form the surface layer shell.

[0037] S4. Apply a backing slurry to the surface of the surface shell, with a slurry thickness of 0.4 mm. Attach the fiber felt of the adsorbent slurry obtained in step S2 to the surface shell and compact it until there are no air bubbles, forming the first backing shell. Then, repeat the cycle of applying the backing slurry and attaching the cloth-like ceramic precursor fiber felt to form a three-layer composite backing structure. Finally, apply the backing slurry again. After the composite backing is formed, dry and cure it at room temperature for 8 hours to obtain the ceramic shell preform.

[0038] S5. The ceramic shell preform is sealed with a slurry containing the same components as the backing slurry, and dried for 5 hours. Then, a demolding process is performed: the temperature is raised to 350℃ and held for 2 hours to completely melt and remove the wax mold. Finally, a staged heating process is used for calcination: at a heating rate of 5℃ / min, the first stage is heated to 700℃ and held for 2 hours; the second stage is heated to 1500℃ and held for 4 hours. After calcination, the shell is cooled in the furnace to obtain a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt.

[0039] The ceramic shell prepared in this embodiment was subjected to performance tests. The test results were as follows: room temperature strength was 16.9 MPa, calcination strength was 35.8 MPa, residual strength was 25.4 MPa, and shell permeability was 40.6%.

[0040] Example 2

[0041] S1. Zirconium nitrate, polyvinyl alcohol, and deionized water are mixed at a mass ratio of 60:15:25 and magnetically stirred to obtain a homogeneous spinning solution. The spinning solution is injected into a syringe, connected to a high-voltage power supply, and electrospinning is performed. The spinning voltage is set to 25kV, the receiving roller distance is 22cm, the feed rate is 3mL / h, the ambient temperature is 28℃, and the relative humidity is 40%. After spinning, a three-dimensional network zirconia precursor fiber mat is obtained.

[0042] S2. Prepare the backing slurry by ball milling 65.1% yttrium oxide powder, 22.0% yttrium sol binder, 0.8% ammonium citrate dispersant, and 12.1% deionized water until homogeneous. Immerse the fiber felt obtained in step S1 into the backing slurry and ultrasonically soak for 20 minutes to ensure the slurry is fully absorbed into the fiber felt.

[0043] S3. Preparation of the surface layer slurry: By mass percentage, mix 70% yttrium oxide, 10% yttrium sol, 1% polyethylene glycol, and 19% deionized water, and ball mill for 2 hours to mix evenly. Apply the yttrium oxide surface layer slurry to the surface of the wax pattern for investment casting to a thickness of 0.4 mm, immediately sprinkle with 180-mesh yttrium oxide sand, and then let it stand and dry at room temperature for 5 hours to form the surface layer shell.

[0044] S4. Apply a backing slurry to the surface of the surface shell, with a slurry thickness of 1 mm. Attach the fiber felt of the adsorbent slurry obtained in step S2 to the surface shell and compact it until there are no air bubbles, forming the first backing shell. Then, repeat the cycle of applying the backing slurry and attaching the cloth-like ceramic precursor fiber felt to form a five-layer composite backing structure. Finally, apply the backing slurry again. After the composite backing is formed, dry and cure it at room temperature for 10 hours to obtain the ceramic shell preform.

[0045] S5. The ceramic shell preform is sealed twice with a slurry having the same composition as the backing slurry, and dried for 6 hours. Then, a demolding process is performed: the temperature is raised to 400℃ and held for 1.5 hours to allow the wax mold to completely melt and be removed. Finally, a staged heating process is used for calcination: at a heating rate of 7℃ / min, the first stage is heated to 800℃ and held for 2 hours; the second stage is heated to 1650℃ and held for 5 hours. After calcination, the shell is cooled in the furnace to obtain a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt.

[0046] The ceramic shell prepared in this embodiment was subjected to performance tests. The test results were as follows: room temperature strength was 17.5 MPa, calcination strength was 32.5 MPa, residual strength was 21.3 MPa, and shell permeability was 48.2%.

[0047] Example 3

[0048] S1. Zirconium nitrate, polyvinyl alcohol (PVA), and deionized water are mixed at a mass ratio of 50:10:40 and magnetically stirred to obtain a homogeneous spinning solution. The spinning solution is injected into a syringe, connected to a high-voltage power supply, and electrospinning is performed. The spinning voltage is set to 35kV, the receiving roller distance is 30cm, the feed rate is 7mL / h, the ambient temperature is 35℃, and the relative humidity is 65%. After spinning, a three-dimensional network zirconia precursor fiber mat is obtained.

[0049] S2. Prepare the backing slurry by ball milling 66.6% alumina powder, 21.0% aluminum sol binder, 0.8% ammonium citrate dispersant, and 11.6% deionized water until homogeneous. Immerse the fiber felt obtained in step S1 into the backing slurry and ultrasonically soak for 30 minutes to ensure that the backing slurry is fully absorbed into the fiber felt.

[0050] S3. Preparation of the surface layer slurry: By mass percentage, ball mill and mix 65% mullite, 8% silica sol, 0.5% ammonium citrate, and 26.5% deionized water evenly. Apply the alumina surface layer slurry to the surface of the wax pattern for investment casting to a thickness of 0.5 mm, immediately sprinkle with 220-mesh mullite sand, and then let it stand and dry at room temperature for 8 hours to form the surface layer shell.

[0051] S4. Apply a backing slurry to the surface of the surface shell, with a slurry thickness of 0.5 mm. Attach the fiber felt of the adsorbent slurry obtained in step S2 to the surface shell and compact it until there are no air bubbles, forming the first backing shell. Then, repeat the cycle of applying the backing slurry and attaching the cloth-like ceramic precursor fiber felt to form an eight-layer composite backing structure. Finally, apply the backing slurry again. After the composite backing is formed, dry and cure at room temperature for 20 hours to obtain the ceramic shell preform.

[0052] S5. The ceramic shell preform is sealed twice with a slurry having the same composition as the backing slurry, and dried for 6 hours. Then, a demolding process is performed: the temperature is raised to 450℃ and held for 3.5 hours to allow the wax mold to completely melt and be removed. Finally, a staged heating process is used for calcination: at a heating rate of 7℃ / min, the first stage is heated to 800℃ and held for 2 hours; the second stage is heated to 1400℃ and held for 5 hours. After calcination, the shell is cooled in the furnace to obtain a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt.

[0053] The ceramic shell prepared in this embodiment was subjected to performance tests. The test results were as follows: room temperature strength was 21.5 MPa, calcination strength was 39.1 MPa, residual strength was 23.5 MPa, and shell permeability was 45.5%.

[0054] Example 4

[0055] S1. Zirconium nitrate, yttrium nitrate, polyvinyl alcohol (PVA), and deionized water are mixed at a mass ratio of 55:15:30 and magnetically stirred to obtain a homogeneous spinning solution. The spinning solution is injected into a syringe, connected to a high-voltage power supply, and electrospinning is performed. The spinning voltage is set to 10kV, the receiving roller distance is 12cm, the feed rate is 1mL / h, the ambient temperature is 20℃, and the relative humidity is 35%. After spinning, a three-dimensional network yttrium oxide stabilized zirconia precursor fiber mat is obtained.

[0056] S2. Prepare the backing slurry by ball milling 65.0% yttrium oxide powder, 22.0% yttrium sol binder, 0.8% ammonium citrate dispersant, and 12.2% deionized water until homogeneous. Immerse the fiber felt obtained in step S1 into the backing slurry and ultrasonically soak for 10 minutes to ensure the slurry is fully absorbed into the fiber felt.

[0057] S3. Preparation of the surface layer slurry: By mass percentage, ball mill and mix 62% mullite, 6% silica sol, 0.8% polyvinylpyrrolidone, and 31.2% deionized water evenly. Apply the quartz surface layer slurry to the surface of the wax pattern for investment casting to a thickness of 0.1 mm, immediately sprinkle with 100-mesh quartz sand, and then let it stand and dry at room temperature for 8 hours to form the surface layer shell.

[0058] S4. Apply a backing slurry to the surface of the surface shell, with a slurry thickness of 1.5 mm. Attach the fiber felt of the adsorbent slurry obtained in step S2 to the surface shell and compact it until there are no air bubbles, forming the first backing shell. Then, repeat the cycle of applying the backing slurry and attaching the cloth-like ceramic precursor fiber felt to form a ten-layer composite backing structure. Finally, apply the backing slurry again. After the composite backing is formed, dry and cure it at room temperature for 10 hours to obtain the ceramic shell preform.

[0059] S5 performs a sealing treatment on the ceramic shell preform, using a slurry with the same composition as the backing slurry, sealing twice and drying for 6 hours. Then, a demolding process is performed: the temperature is raised to 250℃ and held for 1.5 hours to completely melt and remove the wax mold. Finally, a staged heating process is used for calcination: at a heating rate of 3℃ / min, the first stage is heated to 600℃ and held for 2 hours; the second stage is heated to 1300℃ and held for 5 hours. After calcination, the mold is cooled in the furnace to obtain a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt.

[0060] The ceramic shell prepared in this embodiment was subjected to performance tests. The test results were as follows: room temperature strength was 19.1 MPa, calcination strength was 34.6 MPa, residual strength was 24.8 MPa, and shell permeability was 52.1%.

[0061] Comparative Example 1

[0062] The difference between this comparative example and the above embodiment is that short-cut alumina fibers are directly mixed into the backing slurry and the backing layer is formed by sprinkling sand, instead of using a multi-layer composite structure with cloth-like fiber felt. The specific steps are as follows: S1. Coat the surface of the wax pattern for investment casting with a quartz surface layer slurry with a coating thickness of 0.3 mm, immediately sprinkle with 180-mesh quartz sand, and then let it stand and dry at room temperature for 8 hours to form a surface shell.

[0063] S2. Prepare the backing slurry by mixing 60.0% yttrium oxide powder, 5.0% alumina fiber, 22.0% yttrium sol binder, 0.8% ammonium citrate dispersant and 12.2% deionized water by mass percentage, and ball mill for 5 hours to mix evenly.

[0064] S3. Apply a back layer slurry to the surface of the surface shell with a slurry thickness of 0.5 mm, then sprinkle mullite sand with a particle size of 1 mm, and dry and cure at room temperature for 10 hours to form a back layer shell.

[0065] S4. The ceramic shell is sealed twice with slurry and dried for 6 hours. Then, a demolding process is performed: the temperature is raised to 400℃ and held for 1.5 hours to completely melt and remove the wax mold. Finally, a staged heating process is used for calcination: the first stage is heated to 800℃ and held for 2 hours at a heating rate of 5℃ / min; the second stage is heated to 1600℃ and held for 5 hours. After calcination, the shell is cooled in the furnace to obtain a ceramic fiber reinforced ceramic shell.

[0066] The ceramic shell prepared in this comparative example was subjected to performance tests. The test results were as follows: room temperature strength was 10.1 MPa, calcination strength was 14.6 MPa, residual strength was 11.8 MPa, and shell permeability was 40.1%.

[0067] The present application will be further described in conjunction with the accompanying drawings. It should be noted that although the fiber materials and process parameters of the various embodiments are different, the fiber felts produced are all continuous three-dimensional mesh through-structures, and the microstructure characteristics of the ceramic shell cross-section are basically the same. Therefore, only Example 1 is shown as a representative example.

[0068] See Figure 2 The image shown is an SEM image of the three-dimensional network alumina precursor fiber mat prepared in Example 1 of the present invention. As can be seen from the image, the fiber mat is composed of a large number of micro and nanofibers overlapping each other. The fibers have a continuous three-dimensional network structure with a large number of pores distributed between the fibers.

[0069] See Figure 3 The image shows a CT scan of the cross-section of the ceramic shell reinforced with three-dimensional mesh ceramic fiber felt obtained in Example 1 of this invention. As can be seen from the image, the cross-section of the ceramic shell exhibits a clear multi-layered composite structure, where A is the surface layer, B is the three-dimensional mesh ceramic fiber felt layer, and C is the backing slurry layer. The fiber felt layers are continuously distributed between the backing slurry layers, with tight bonding between each layer, clear interfaces, and no obvious gaps or delamination.

[0070] In summary, the method for preparing a three-dimensional mesh ceramic fiber felt-reinforced ceramic shell provided in the first aspect of this application achieves a three-dimensional continuous network distribution of the fiber reinforcement through the above steps, effectively improving the comprehensive performance of the ceramic shell. This results in significant improvements in room temperature mechanical strength, high temperature thermal shock resistance, interlayer continuity, and air permeability, meeting the stringent requirements of high-temperature alloy precision casting such as complex hollow blades for high-performance ceramic shells.

[0071] The second aspect of this application discloses a ceramic shell reinforced with a three-dimensional mesh ceramic fiber felt. The ceramic shell is a multi-layer composite structure, comprising, from the inside out, a surface layer, at least one backing composite layer, and an outermost sealing layer. The backing composite layer consists of a backing slurry matrix and at least one layer of three-dimensional mesh ceramic fiber felt embedded therein, with the fiber felt and the backing slurry matrix being alternately stacked.

[0072] Specifically, the surface and back layers of the ceramic shell are each independently composed of one of alumina, yttrium oxide, mullite, or quartz, while the fiber material of the three-dimensional mesh ceramic fiber felt is one of alumina, zirconium oxide, yttrium oxide-stabilized zirconium oxide, or mullite. The three-dimensional mesh ceramic fiber felt has a continuous fabric structure, with fibers spatially overlapping to form a three-dimensional interconnected network. This fiber felt is continuously distributed within the back layer of the ceramic shell, extending substantially parallel to the shell surface, and exhibiting a layered distribution along the shell's thickness. A tight chemical bond and physical interlocking interface exists between the fiber felt and the back layer slurry matrix. Scanning electron microscopy reveals that the fiber surface is uniformly coated with the matrix material, with no visible gaps, delamination, or debonding at the interface.

[0073] Compared with the prior art, the ceramic shell proposed in this application uses a three-dimensional mesh ceramic fiber felt as an independent continuous reinforcing phase, rather than discrete short-cut fibers, to achieve continuous stress transmission and uniform distribution in the fiber network; the composite structure formed by the alternating arrangement of fiber felt layers and slurry layers significantly improves the resistance to interlaminar cracking; the three-dimensional through pores of the fiber felt itself are connected to the micropores in the matrix, giving the shell excellent air permeability; at the same time, since the fiber felt is co-sintered with the matrix using a precursor in-situ conversion process, the interface is tightly bonded, without cracks or delamination, ensuring the structural integrity of the shell at high temperatures.

[0074] The above are merely several specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and inventive concept of this application, should be included within the scope of protection of this application.

[0075] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0076] It should be noted that, in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A method for preparing a ceramic shell reinforced with a three-dimensional mesh ceramic fiber felt, characterized in that, Includes the following steps: S1. Preparation of cloth-like ceramic precursor fiber mat; S2. Prepare backing slurry by impregnating the fiber felt with slurry to allow the backing slurry to adhere to the interior of the fiber felt. S3. Prepare the surface layer slurry and prepare the surface layer shell on the surface of the wax model; S4. Alternately apply slurry and fiber felt to the surface shell to form a multi-layer composite backing structure. After drying, a ceramic shell preform is obtained. S5. The ceramic shell preform is sequentially subjected to sealing, demolding and calcination treatments to obtain a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt.

2. The method for preparing a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt according to claim 1, characterized in that: In step S1, the cloth-like ceramic precursor fiber felt is prepared by electrospinning. The spinning solution includes a precursor salt, a spinning aid, and a solvent. The precursor salt is one or more of zirconium salt, yttrium salt, and aluminum salt, or a combination of aluminum salt and ethyl silicate.

3. The method for preparing a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt according to claim 2, characterized in that: The electrospinning process uses a spinning voltage of 10–35 kV and a receiving roller distance of 12–30 cm.

4. The method for preparing a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt according to claim 1, characterized in that: In step S2, the backing slurry comprises refractory powder, inorganic binder, dispersant and deionized water. By mass percentage, the refractory powder accounts for 65% to 70%, the inorganic binder accounts for 20% to 22%, the dispersant accounts for 0.8% to 1%, and the deionized water accounts for 9% to 13%.

5. The method for preparing a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt according to claim 1, characterized in that: In step S3, the surface shell is formed by coating the wax mold surface with a surface slurry and sprinkling sand; the surface slurry includes refractory powder, inorganic binder, dispersant and deionized water; by mass percentage, the refractory powder is 60% to 70%, the inorganic binder is 5% to 10%, the dispersant is 0.2% to 1%, and the deionized water is 19% to 34.8%.

6. The method for preparing a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt according to claim 5, characterized in that: In step S3, the coating thickness of the surface layer slurry on the wax mold surface is 0.1 to 0.5 mm.

7. The method for preparing a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt according to claim 1, characterized in that: In step S4, the alternating slurry application and fiber felt laying operation is as follows: first, slurry is applied using pre-made backing slurry, then the fiber felt after slurry absorption is laminated to form a composite backing layer, and then the slurry application and fiber felt laying operation is repeated; the thickness of the backing slurry each time is 0.2 to 2 mm.

8. The method for preparing a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt according to claim 7, characterized in that: The repeated slurry application and fiber felt laying process forms a composite backing layer of 3 to 11 layers.

9. The method for preparing a ceramic shell reinforced with three-dimensional mesh ceramic fiber felt according to claim 1, characterized in that: In step S5, the sealing treatment uses a sealing material with the same composition as the back layer slurry in step S2 for sealing 1 to 2 times; the demolding treatment uses heating demolding, raising the temperature to 250 to 450°C to melt and remove the wax mold; the calcination treatment uses a segmented heating process, finally raising the temperature to 1300 to 1650°C, holding the temperature, and then cooling it with the furnace.

10. A ceramic shell reinforced with a three-dimensional mesh ceramic fiber felt, prepared by the method described in any one of claims 1 to 9, characterized in that, include: The inner surface layer; At least one composite backing layer is located in the middle, wherein a continuous three-dimensional mesh ceramic fiber felt is embedded in the composite backing layer, the fiber felt having a three-dimensional through network structure and being tightly bonded to the interface of the backing layer slurry matrix; And the outermost sealing layer.

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