A textured processable silicon nitride ceramic and method of making the same

Abstract

The application relates to a textured processable silicon nitride ceramic and a preparation method thereof. The preparation method of the textured processable silicon nitride ceramic comprises the following steps: (1) mixing Si3N4 powder, h-BN powder and a sintering aid to obtain mixed powder; adding a dispersant, a binder, a plasticizer and a solvent into the mixed powder, mixing through ball milling to obtain a casting slurry; (2) vacuum deaerating the casting slurry and carrying out casting forming to obtain a ceramic film strip, and then carrying out lamination and cutting according to a specified size; (3) carrying out debinding on the ceramic film strip to obtain a green ceramic; and (4) carrying out hot-pressing sintering on the green ceramic to obtain the textured processable silicon nitride ceramic.

Description

Technical Field

[0001] This invention belongs to the technical field of silicon nitride ceramic materials, and relates to a textured processable silicon nitride ceramic and its preparation method. Background Technology

[0002] Silicon nitride (Si3N4) ceramics possess high strength, high fracture toughness, excellent thermal shock resistance, and high-temperature oxidation stability, making them widely used in aerospace, high-end equipment, and other fields. However, their high hardness and strong covalent bond characteristics result in poor machinability, making the forming and processing of complex-shaped parts difficult. Introducing hexagonal boron nitride (h-BN) is an effective strategy to improve the machinability of Si3N4 ceramics. The layered structure of h-BN can undergo interlaminar slip and shear deformation under external forces, which is beneficial for crack deflection and micro-area spalling. However, the introduction of h-BN usually leads to a significant reduction in strength, especially when h-BN is randomly distributed. Therefore, for Si3N4 ceramics, achieving both good machinability and high strength remains a significant challenge.

[0003] Both h-BN and β-Si3N4 exhibit structural anisotropy; h-BN presents a layered, lamellar structure, while β-Si3N4 exhibits slender, rod-shaped grains. Texture design is an effective method for optimizing the properties of multiphase ceramics, and oriented grains are beneficial for improving properties such as thermal conductivity and flexural strength in specific directions. However, existing research mostly focuses on the orientation evolution of a single phase, and achieving simultaneous texture design of two phases in the same composite material system remains challenging. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention aims to provide a textured, machinable silicon nitride ceramic and its preparation method. This invention achieves a dual reorientation effect of h-BN and β-Si3N4 in the h-BN / Si3N4 multiphase ceramic through a combination of tape casting and hot pressing sintering, thereby improving mechanical strength while maintaining good machinability.

[0005] On the one hand, the present invention provides a method for preparing textured processable silicon nitride ceramics, comprising the following steps: (1) mixing Si3N4 powder, h-BN powder and sintering aid to obtain mixed powder; adding dispersant, binder and plasticizer and solvent to the mixed powder, and mixing by ball milling to obtain casting slurry; (2) Vacuum degassing and casting of the cast slurry to obtain ceramic film strips, and then stacking and cutting according to the specified dimensions; (3) The ceramic membrane belt is degreased to obtain a ceramic green body; (4) The ceramic green body is hot-pressed and sintered to obtain the textured processable silicon nitride ceramic.

[0006] In this invention, by combining tape casting and hot pressing sintering, simultaneous texturing of the two phases in h-BN / Si3N4 multiphase ceramics is achieved. Tape casting induces in-plane orientation of the lamellar particles through shear force, while hot pressing sintering promotes directional grain growth through applied pressure. The ordered β-Si3N4 grains form an interlocking network structure, providing excellent mechanical support.

[0007] Preferably, in step (1), based on a total content of 100 vol% of the mixed powder, the total content of the Si3N4 powder and the sintering aid is 72-95 vol%, and the content of the h-BN powder is 5-28 vol%.

[0008] Preferably, the median particle size of the Si3N4 powder is 0.3–0.5 μm; and the particle size of the h-BN powder is 0.1–10 μm.

[0009] Preferably, the sintering agent is a rare earth oxide and MgO powder; the rare earth oxide is selected from at least one of Y2O3, Sc2O3, Lu2O3, La2O3, CeO2, and Yb2O3, preferably Y2O3; the particle size of the MgO powder is 0.2 to 0.4 μm. Preferably, the mass ratio of the rare earth oxide to the MgO powder is (1-4):(3-10).

[0010] Preferably, the dispersant is selected from at least one of castor oil, trioleic acid glyceride, TX-10, and triethyl phosphate; the binder is selected from at least one of PVB, ethyl cellulose, acrylic resin, and polyvinyl acetate; the plasticizer is selected from at least one of dibutyl phthalate, polyethylene glycol, tricresyl phosphate, and glycerol; and the solvent is selected from at least two of butanone, anhydrous ethanol, toluene, ethyl acetate, and dimethyl carbonate, preferably a mixture of butanone and anhydrous ethanol in a mass ratio of 2:1.

[0011] Preferably, the mass ratio of the mixed powder, dispersant, binder, plasticizer and solvent is 1: (0.01~0.05): (0.03~0.15): (0.05~0.3): (0.3~0.7).

[0012] Preferably, the parameters for ball milling include: using Si3N4 balls as the milling medium, a milling speed of 100–500 rpm, and a milling time of 6–48 h; the solid content of the cast slurry is 30–70 wt%.

[0013] Preferably, in step (2), the parameters for casting include: a scraper height of 100-800 μm and a casting speed of 20-60 cm / min.

[0014] Preferably, in step (3), the ceramic membrane belt is subjected to warm isostatic pressing before degreasing; the pressure of the warm isostatic pressing is 30-80 MPa and the temperature is 60-100 ℃. The degreasing temperature is 400–600℃, and the time is 5–40 h; preferably, the heating rate is 1–10℃ / min.

[0015] Preferably, in step (4), the hot pressing sintering temperature is 1600-1800 ℃, the sintering pressure is 10-40 MPa, and the holding time is 1-3 hours; preferably, the ambient atmosphere is a 1-2 atm nitrogen atmosphere, and the heating rate is 3-10 ℃ / min.

[0016] On the other hand, the present invention also provides a textured processable silicon nitride ceramic prepared according to the above preparation method, wherein the textured processable silicon nitride ceramic has Si3N4 and h-BN as the main crystalline phases, and the h-BN and β-Si3N4 grains are oriented.

[0017] Preferably, the textured machinable silicon nitride ceramic has a Vickers hardness of 5.23–12.24 GPa, a flexural strength of 600–874 MPa, and a fracture toughness of 7.60–10.68 MPa·m. 1 / 2 . Beneficial effects

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention combines tape casting and hot pressing sintering to achieve simultaneous texturing of h-BN and β-Si3N4 in h-BN / Si3N4 multiphase ceramics. Through the directional arrangement of the two phases, the directionally grown β-Si3N4 grains provide mechanical support, while the directionally arranged h-BN sheets play an interlayer slip role, thus maintaining high mechanical strength while having good machinability. Attached Figure Description

[0019] Figure 1 The phase analysis diagrams of silicon nitride ceramics prepared in Examples 2-4 and Comparative Examples 1-2 of this invention are perpendicular to the hot-pressing direction. Figure 2 The phase analysis diagrams of silicon nitride ceramics prepared in Examples 2-4 and Comparative Examples 1-2 of this invention are shown parallel to the hot-pressing direction. Figure 3 The cross-sectional morphology of the silicon nitride ceramics prepared in Example 4 and Comparative Example 1 of this invention is shown. Figure 4 The images show the morphology of the silicon nitride ceramic prepared in Example 4 of this invention after drilling with cemented carbide drill bits at different drilling speeds. Detailed Implementation

[0020] To further illustrate the invention's content, features, and practical effects, the invention will be described in detail below with reference to embodiments. It should be noted that the modification methods of the invention are not limited to these specific implementation methods. Equivalent substitutions and modifications made by those skilled in the art based on their reading of the invention's content, without departing from the spirit and essence of the invention, are also within the scope of protection claimed by this invention.

[0021] First, this invention provides a method for preparing textured, machinable silicon nitride ceramics. Through tape casting and hot pressing sintering, the simultaneous texturing of h-BN and Si3N4 in the h-BN / Si3N4 multiphase ceramic is achieved. Specifically, tape casting induces in-plane orientation of sheet-like h-BN particles through shear force, while hot pressing sintering promotes the directional growth of rod-shaped β-Si3N4 grains through applied pressure. This results in an interlocking network structure of orderly arranged β-Si3N4 grains, providing excellent mechanical support.

[0022] In this invention, simultaneous texturing of both h-BN and β-Si3N4 phases is achieved through a combination of tape casting and hot pressing sintering. During tape casting, shear force induces in-plane pre-orientation of the lamellar h-BN particles. During hot pressing sintering, unidirectional pressure further promotes the orientation of h-BN, while simultaneously inducing the preferential growth of β-Si3N4 rod-shaped grains perpendicular to the pressure direction. This dual-orientation structure enables β-Si3N4 to form an interlocking network, enhancing mechanical strength, while the oriented h-BN lamellars facilitate interlayer slip, imparting good processability to the material.

[0023] To simultaneously achieve the two-phase texturing of β-Si3N4 and h-BN in the same composite material, the following three main obstacles need to be overcome: (1) h-BN is more dependent on shear force orientation, while β-Si3N4 is more dependent on pressure orientation, and their orientation mechanisms are different; (2) h-BN introduces and disrupts the β-Si3N4 interlocking network, and its existence as a weak interface phase leads to a decrease in strength; (3) the tape casting process and the high-temperature sintering process are difficult to control in a coordinated manner. In order to overcome the above technical obstacles, this invention adopts a two-step method of "tape casting pre-orientation + hot pressing post-orientation", so that h-BN is pre-oriented in-plane in tape casting by strong shear force, and β-Si3N4 is preferentially grown as a template during hot pressing sintering; by adjusting the h-BN content and particle size, the β-Si3N4 rod-shaped crystal interlocking network is used to compensate for part of the strength loss; the tape casting parameters and sintering regime are optimized to ensure that the pre-oriented structure is retained and to promote the coordinated orientation of the two phases.

[0024] The following exemplifies the preparation method of textured processable silicon nitride ceramics provided by the present invention.

[0025] Si3N4 powder, h-BN powder and sintering aid are mixed to obtain a mixed powder; dispersant, binder, plasticizer and solvent are added to the mixed powder, and the mixture is ball-milled to obtain a casting slurry.

[0026] In an optional embodiment, the median particle size of the Si3N4 powder is 0.3–0.5 μm; the particle size of the h-BN powder is 0.1–10 μm. If the particle size of the h-BN powder is too small, the particles are prone to agglomeration, which will not only significantly reduce the processability of the system and make casting difficult, but also weaken its interlayer slip effect; if the particle size of the h-BN powder is too large, stress concentration is easily generated in the matrix, which acts as a crack source, destroys the β-Si3N4 interlocking structure, and greatly reduces the mechanical strength.

[0027] In an optional embodiment, the sintering agent is rare earth oxide powder and MgO powder; the rare earth oxide powder is selected from at least one of Y2O3, Sc2O3, Lu2O3, La2O3, CeO2, and Yb2O3, preferably Y2O3, the particle size of the Y2O3 powder is 0.15-5 μm, and the particle size of the MgO powder is 0.2-0.4 μm; preferably, the mass ratio of the rare earth oxide to the MgO powder is (1-4):(3-10).

[0028] In an optional embodiment, with a total content of 100 vol% of the mixed powder, the total content of the Si3N4 powder and sintering aid is 72–95 vol%, and the content of the h-BN powder is 5–28 vol%. If the content of h-BN powder is too low, it is difficult to form continuous interlayer slip channels, and the improvement in processability is not significant; if the content of h-BN powder is too high, it will significantly destroy the β-Si3N4 interlocking structure, hinder the densification process, and lead to a significant decrease in mechanical strength.

[0029] In an optional embodiment, the dispersant is selected from at least one of castor oil, triolein, TX-10, and triethyl phosphate; the binder is selected from at least one of PVB, ethyl cellulose, acrylic resin, and polyvinyl acetate; the plasticizer is selected from at least one of dibutyl phthalate, polyethylene glycol, tricresyl phosphate, and glycerin; and the solvent is selected from at least two of butanone, anhydrous ethanol, toluene, ethyl acetate, and dimethyl carbonate, preferably a mixture of butanone and anhydrous ethanol in a mass ratio of 2:1. The mass ratio of the mixed powder, dispersant, binder, plasticizer, and solvent is 1:(0.01-0.05):(0.03-0.15):(0.05-0.3):(0.3-0.7).

[0030] In an optional embodiment, the parameters for ball milling include: using Si3N4 balls as the milling medium, a milling speed of 100–500 rpm, and a milling time of 6–48 h. The solid content of the cast slurry is 30–70 wt%.

[0031] The cast slurry is vacuum defoamed and cast to form a ceramic film tape, which is then stacked and cut to the specified dimensions.

[0032] In an optional embodiment, the parameters of the casting process include: a scraper height of 100–800 μm and a casting speed of 20–60 cm / min.

[0033] The ceramic film strip is first subjected to warm isostatic pressing, and then degreased to obtain a ceramic green body.

[0034] In an optional embodiment, the pressure of the isostatic pressing is 30–80 MPa, and the temperature is 60–100°C. The degreasing temperature is 400–600°C, and the time is 5–40 h; preferably, the heating rate is 1–10°C / min.

[0035] The textured, machinable silicon nitride ceramic is obtained by hot pressing and sintering the ceramic green body.

[0036] In an optional embodiment, the hot-pressing sintering temperature is 1600–1800°C, the sintering pressure is 10–40 MPa, and the holding time is 1–3 hours; preferably, the ambient atmosphere is a 1–2 atm nitrogen atmosphere, and the heating rate is 3–10°C / min. If the sintering temperature is too low, the β-Si3N4 phase transformation is insufficient, grain growth is limited, and fracture toughness and machinability decrease significantly; if the sintering temperature is too high, β-Si3N4 becomes abnormally coarse, the interlocking structure effect is weakened, resulting in a decrease in mechanical strength.

[0037] The textured machinable silicon nitride ceramics prepared by the above method are mainly composed of Si3N4 and h-BN crystal phases, and the h-BN and β-Si3N4 grains are oriented. The textured machinable silicon nitride ceramics have a Vickers hardness of 5.23–12.24 GPa, a flexural strength of 600–874 MPa, and a fracture toughness of 7.60–10.68 MPa·m. 1 / 2 .

[0038] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Examples 1-4

[0039] A total of 5 g of Y₂O₃ and MgO powder (mass ratio 2:5) was weighed as a sintering aid and mixed with Si₃N₄ and h-BN powder (total mass 95 g) (7.21 g h-BN powder volume fraction of 10 vol%, 14.86 g h-BN powder volume fraction of 20 vol%). Using 200 g Si₃N₄ balls as the ball milling medium, 2.75 g castor oil (dispersant), 10 g PVB (binder), and 15 g dibutyl phthalate (plasticizer) were added. A 2:1 (mass ratio) azeotrope of butanone and anhydrous ethanol was used as the solvent to adjust the slurry solid content to 55 wt%. The mixture was ball-milled for 24 h to obtain a casting slurry. After vacuum degassing, the obtained casting slurry was cast on an experimental strip forming machine at a doctor blade height of 300 μm and a casting speed of 45 cm / min. Subsequently, it was subjected to a 40°C process. The film was dried at ℃; the dried film strip was stacked and cut into 40 mm × 40 mm squares, and then isostatically pressed at 80℃ and 50 MPa. It was then debinded in air at 500℃ for 24 h to remove organic matter and obtain a ceramic green body; the obtained green body was placed in a graphite mold coated with BN, and the hot pressing direction was perpendicular to the casting direction. It was hot-pressed and sintered in a 0.1 MPa N2 atmosphere with a heating rate of 5 ℃ / min, a sintering temperature of 1800℃, a holding time of 2 h, and a sintering pressure of 30 MPa. The difference between Examples 1-4 lies in the h-BN content and particle size, as detailed in Table 1. The mechanical properties of the prepared materials were tested perpendicular to the hot-pressing direction, and the results are shown in Table 1. Example 5

[0040] The preparation process of the textured processable silicon nitride ceramic in Example 5 is the same as in Example 4, except that the hot pressing sintering temperature is 1750℃. Example 6

[0041] The preparation process of the textured processable silicon nitride ceramic in Example 6 is the same as in Example 4, except that the hot pressing sintering temperature is 1700℃. Example 7

[0042] The preparation process of textured processable silicon nitride ceramics in Example 7 is the same as in Example 4, except that the hot pressing sintering temperature is 1650℃. Comparative Example 1

[0043] The raw material ratio and sintering process of the silicon nitride ceramic in Comparative Example 1 are the same as those in Example 4, the only difference being the molding method. The specific steps are as follows: 80.14 g of Si3N4 and 14.86 g of h-BN powder, totaling 95 g (where the h-BN content is 20 vol%), are weighed and mixed with 5 g of Y2O3 and MgO powder (mass ratio of 2:5) as sintering aids. 100 g of anhydrous ethanol is added as a solvent, and Si3N4 balls are used as the ball milling medium. The mixture is then mixed in a planetary ball mill for 4 h to obtain a ceramic slurry. The obtained slurry is dried at 80°C and passed through a 100-mesh sieve to obtain a mixed powder. The mixed powder is then dry-pressed under a pressure of 20 MPa to obtain a green body. Comparative Example 2

[0044] The raw material ratio and sintering process of the silicon nitride ceramic in Comparative Example 2 are the same as those in Example 3, the only difference being the molding method. The specific steps are as follows: 87.79 g of Si3N4 and 7.21 g of h-BN powder, totaling 95 g (where the h-BN content is 10 vol%), are weighed and mixed with 5 g of Y2O3 and MgO powder (mass ratio of 2:5) as sintering aids. 100 g of anhydrous ethanol is added as a solvent, and Si3N4 balls are used as the ball milling medium. The mixture is then mixed in a planetary ball mill for 4 h to obtain a ceramic slurry. The obtained slurry is dried at 80°C and passed through a 100-mesh sieve to obtain a mixed powder. The mixed powder is then dry-pressed under a pressure of 20 MPa to obtain a green body. Comparative Example 3

[0045] The preparation process of the textured processable silicon nitride ceramic in Comparative Example 3 is the same as in Example 3, except that the content of h-BN powder is 30 vol.

[0046] Figure 1 and Figure 2 The XRD patterns of textured processable Si3N4 ceramics prepared in Examples 2-4 and Comparative Examples 1-2 are shown in different directions. As can be seen from the figures, Si3N4 in all samples was completely transformed into β-Si3N4. Figure 1 In the plane perpendicular to the hot-pressing direction, the (200) and (210) diffraction peaks are relatively strong, and their intensity is significantly higher than that of the (101) peak; Figure 2In the plane parallel to the hot-pressing direction, the intensity of the (101) diffraction peak is significantly higher than that of the (200) and (210) peaks. The intensity ratio of the diffraction peaks of β-Si3N4 in the two directions shows a significant difference. In Examples 3-4, the (002) diffraction peak of h-BN has a high intensity in the plane perpendicular to the hot-pressing direction, but an extremely low intensity in the parallel direction, making it almost undetectable. However, in Example 2, using nano-h-BN (0.2 μm), the difference in diffraction peak intensity between different directions is small, indicating that the orientation is not significant. Furthermore, Figure 1 In the direction perpendicular to hot pressing, the intensity of the (002) diffraction peak of h-BN in Example 4 (cast molding) is significantly higher than that in Comparative Example 1 (dry pressing), indicating that h-BN in Example 4 has a higher degree of texture. Meanwhile, the difference in the diffraction peak intensity of β-Si3N4 also shows that the orientation of β-Si3N4 in Example 4 is significantly better than that in Comparative Example 1, further illustrating that cast molding is beneficial for promoting the synergistic directional alignment of the h-BN and β-Si3N4 phases.

[0047] Figure 3 The figures show the cross-sectional morphology of the silicon nitride ceramics prepared in Example 4 and Comparative Example 1 of this invention. As can be seen from the figures, the orientation of β-Si3N4 and h-BN in Example 4, which was formed by tape casting, is significantly better than that in Comparative Example 1, which was formed by dry pressing. The grains show obvious directional arrangement, and the h-BN sheets are in-plane parallel orientation.

[0048] Figure 4 The figures show the morphology of the silicon nitride ceramic prepared in Example 4 of this invention after drilling with carbide drill bits at different drilling speeds. As can be seen from the figures, the silicon nitride multiphase ceramic can be drilled using conventional carbide drill bits under both low and high drilling speed conditions. The machined holes have intact edges without chipping or cracking, exhibiting good processing quality and demonstrating the excellent machinability of this material.

[0049] Table 1 lists the preparation process and performance parameters (perpendicular to the hot pressing direction) of silicon nitride ceramics in Examples 1-7 and Comparative Examples 1-3 of the present invention.

[0050] Table 1: .

[0051] Table 1 shows that increasing the h-BN content reduces the mechanical strength of the multiphase ceramic, but simultaneously reduces hardness and improves machinability. Using larger-sized h-BN particles helps improve its orientation during the tape casting process, thus enhancing the material's machinability, but also slightly decreases the mechanical strength. Lowering the sintering temperature inhibits the phase transformation process and grain growth of β-Si3N4, leading to reduced flexural strength and fracture toughness. Compared to the preparation method of dry pressing combined with hot pressing sintering, the sample obtained by tape casting combined with hot pressing sintering exhibits a higher degree of texture, effectively improving the mechanical strength of the multiphase ceramic.

[0052] In summary, this invention achieves simultaneous texturing of both h-BN and β-Si3N4 phases through a combination of tape casting and hot pressing sintering. Specifically, a tape casting process is used to induce in-plane orientation of sheet-like h-BN particles by utilizing the shear force generated by the slurry flow, followed by hot pressing sintering. The unidirectional pressure promotes the directional growth of rod-shaped β-Si3N4 grains along a specific direction. This dual-orientation structure helps to fully utilize the interlayer slip toughening mechanism of h-BN and the rod-shaped crystal interlocking strengthening mechanism of β-Si3N4, enhancing mechanical properties while maintaining good processability. Compared to traditional randomly distributed or single-phase oriented composite materials, this invention achieves comprehensive optimization of mechanical properties and processability.

[0053] The above description represents only some preferred embodiments of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content and spirit of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing textured, processable silicon nitride ceramics, characterized in that, Includes the following steps: (1) Si3N4 powder, h-BN powder and sintering aid are mixed to obtain mixed powder; dispersant, binder and plasticizer and solvent are added to the mixed powder and ball milled to obtain casting slurry; (2) Vacuum degassing and casting of the cast slurry to obtain ceramic film strips, and then stacking and cutting according to the specified dimensions; (3) The ceramic membrane belt is degreased to obtain a ceramic green body; (4) The ceramic green body is hot-pressed and sintered to obtain the textured processable silicon nitride ceramic.

2. The preparation method according to claim 1, characterized in that, In step (1), with the total content of the mixed powder being 100 vol%, the total content of the Si3N4 powder and sintering aid is 72-95 vol%, and the content of the h-BN powder is 5-28 vol%.

3. The preparation method according to claim 1 or 2, characterized in that, The median particle size of the Si3N4 powder is 0.3–0.5 μm; the particle size of the h-BN powder is 0.1–10 μm. The sintering agent is a rare earth oxide and MgO powder; the rare earth oxide is selected from at least one of Y2O3, Sc2O3, Lu2O3, La2O3, CeO2, and Yb2O3, preferably Y2O3; the particle size of the MgO powder is 0.2 to 0.4 μm; preferably, the mass ratio of the rare earth oxide to the MgO powder is (1 to 4):(3 to 10).

4. The preparation method according to any one of claims 1-3, characterized in that, The dispersant is selected from at least one of castor oil, trioleic acid glyceride, TX-10, and triethyl phosphate; the binder is selected from at least one of PVB, ethyl cellulose, acrylic resin, and polyvinyl acetate; the plasticizer is selected from at least one of dibutyl phthalate, polyethylene glycol, tricresyl phosphate, and glycerin; the solvent is selected from at least two of butanone, anhydrous ethanol, toluene, ethyl acetate, and dimethyl carbonate, preferably a mixture of butanone and anhydrous ethanol in a mass ratio of 2:

1. Preferably, the mass ratio of the mixed powder, dispersant, binder, plasticizer and solvent is 1: (0.01~0.05): (0.03~0.15): (0.05~0.3): (0.3~0.7).

5. The preparation method according to any one of claims 1-4, characterized in that, In step (1), the parameters for ball milling include: using Si3N4 balls as the ball milling medium, a ball milling speed of 100-500 rpm, and a ball milling time of 6-48 h; the solid content of the cast slurry is 30-70 wt%.

6. The preparation method according to any one of claims 1-5, characterized in that, In step (2), the parameters for casting include: a scraper height of 100-800 μm and a casting speed of 20-60 cm / min.

7. The preparation method according to any one of claims 1-6, characterized in that, In step (3), the ceramic membrane belt is subjected to warm isostatic pressing before degreasing; the pressure of the warm isostatic pressing is 30-80 MPa and the temperature is 60-100 ℃. The degreasing temperature is 400–600 °C, and the time is 5–40 h; preferably, the heating rate is 1–10 °C / min.

8. The preparation method according to any one of claims 1-7, characterized in that, In step (4), the hot pressing sintering temperature is 1600-1800 ℃, the sintering pressure is 10-40 MPa, and the holding time is 1-3 hours; preferably, the ambient atmosphere is a 1-2 atm nitrogen atmosphere, and the heating rate is 3-10 ℃ / min.

9. A textured, processable silicon nitride ceramic prepared by the preparation method according to any one of claims 1-8, characterized in that, The textured processable silicon nitride ceramic is dominated by Si3N4 and h-BN crystal phases, and the h-BN and β-Si3N4 grains are oriented.

10. The textured, processable silicon nitride ceramic according to claim 9, characterized in that, The textured, machinable silicon nitride ceramic has a Vickers hardness of 5.23–12.24 GPa, a flexural strength of 600–874 MPa, and a fracture toughness of 7.60–10.68 MPa·m. 1 / 2 .

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