Al2O3 composite ceramic with TiCxOyNz spherical shell structure as toughening phase and preparation method of Al2O3 composite ceramic

Abstract

The invention discloses Al2O3 composite ceramic with a spherical shell structure formed by TiCxOyNz as a toughening phase, the Al2O3 composite ceramic is composed of the toughening phase and a matrix phase, the matrix phase is filled with the toughening phase, and the Al2O3 composite ceramic comprises, by mass, 0.6%-4% of the toughening phase and 96%-99.4% of the matrix phase; the matrix phase is Al2O3, and the toughening phase is of a spherical shell structure formed by TiCxOyNz. The Al2O3 composite ceramic provided by the invention has a brand-new toughening structure, a spherical shell structure formed by TiCxOyNz is used as a toughening phase, and the closed spherical shell is still filled with an Al2O3 matrix phase, that is, the Al2O3 matrix phase is separated by the TiCxOyNz spherical shell, so that the fracture toughness of the Al2O3 composite ceramic is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a method for preparing a ceramic material comprising TiC x O y N z Al2O3 composite ceramics with spherical shell structure as toughening phase and preparation method thereof. Background Art

[0002] Al2O3 ceramics have the advantages of high hardness, high strength, excellent corrosion resistance, good electrical insulation, high thermal stability and machinability, so Al2O3 ceramics are widely used in machinery, optical fiber, cutting tools, medical, food, chemical, aerospace and other industries. However, the low fracture toughness of Al2O3 ceramics limits its further widespread application. Therefore, exploring new toughening methods to improve fracture toughness has always been an important research direction of Al2O3 materials.

[0003] In recent years, Al2O3 ceramics are commonly toughened by particle dispersion toughening, fiber toughening, whisker toughening, etc. For example, CN119143515A discloses a SiC whisker toughened Al2O3 ceramic tool with a maximum fracture toughness of 5.52MPa·m 1 / 2 In addition, Felice Rubino et al. used P 2 C sintering process was sintered at 1250℃ for 10min to obtain Al2O3-TiB2 composite ceramics. Compared with pure Al2O3 ceramics, the fracture toughness increased by 25.58% and reached 5.4MPa·m 1 / 2 The above toughening methods are all to introduce particles or fibers into Al2O3 ceramics, and to perform toughening by crack deflection and fiber pullout. The fracture toughness of Al2O3 ceramics is improved, but since the toughening phase is traditional particles or whiskers, the toughening effect is not significant. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a TiC x O y N z The Al2O3 composite ceramic with the formed spherical shell structure as the toughening phase and the preparation method thereof effectively improve the fracture toughness of the Al2O3 composite ceramic.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is:

[0006] A TiC x O y N zThe Al2O3 composite ceramic with a spherical shell structure as a toughening phase is composed of a toughening phase and a matrix phase. In terms of mass percentage, the toughening phase is 0.6% to 4% and the matrix phase is 96% to 99.4%. The matrix phase is Al2O3 and the toughening phase is titanium oxycarbonitride (TiC x O y N z ) formed a spherical shell structure.

[0007] The above TiC x O y N z The method for preparing Al2O3 composite ceramics with a spherical shell structure as a toughening phase comprises first preparing Al2O3 powder coated with carbonized polydopamine, and then converting the carbonized polydopamine into titanium oxynitride (TiC x O y N z ), and TiC x O y N z Encapsulated Al2O3(Al2O3@TiC x O y N z The powder of the core-shell structure is then mixed with the Al2O3 matrix powder, and the target composite ceramic is obtained by pressurized rapid sintering (preferably spark plasma sintering). x O y N z The formed spherical shell structure is used as the toughening phase of Al2O3 composite ceramics.

[0008] The above TiC x O y N z The preparation method of Al2O3 composite ceramics with the formed spherical shell structure as the toughening phase mainly includes the following steps:

[0009] (1) Al2O3 powder and dopamine hydrochloride are mixed in a weak alkaline buffer solution, and then dopamine hydrochloride undergoes a self-polymerization reaction under the weak alkaline condition of the buffer solution to generate polydopamine, which adheres to the surface of the Al2O3 powder, and then centrifuges, washes, and dries to obtain a composite powder A; the composite powder A is heated to 800-1000° C. in a high-temperature tube furnace under a protective atmosphere, kept warm for 1-2 hours, and cooled to room temperature with the furnace to obtain Al2O3 powder coated with carbonized polydopamine;

[0010] (2) Carbonized polydopamine-coated Al2O3 powder and nano-Ti powder are used as raw materials, NaCl and KCl are used as molten salt media, and anhydrous ethanol is used as a liquid medium. After being uniformly mixed, the mixed powder B is dried to obtain a mixed powder B; the mixed powder B is heated to 1300-1400°C in a high-temperature tube furnace under a protective atmosphere, kept warm for 1-2 hours, cooled to room temperature with the furnace, washed and dried, and Al2O3@TiC is obtained. x O y N z Core-shell powder;

[0011] (3) According to the mass percentage, Al2O3@TiC x O y N z Core-shell powder 2% to 8% and Al2O3 powder 92% to 98% (TiC in core-shell powder x O y N z The Al2O3 matrix powder accounts for 0.6% to 4% of the mass, and the mass percentage is calculated based on the amount of nano-Ti powder consumed in the preparation process of the core-shell powder) is mixed in anhydrous ethanol and dried to obtain a mixed powder C; the mixed powder C is heated to a sintering temperature of 1400 to 1600°C and maintained for 5 to 8 minutes, wherein a uniaxial pressure of 40 to 60 MPa is applied when the temperature is raised to 800°C and continued until the sintering is completed to obtain a TiC x O y N z The formed spherical shell structure is used as the toughening phase of Al2O3 composite ceramics.

[0012] According to the above scheme, in step (1), the particle size of Al2O3 powder is 1-2um, and the purity is ≥99.9%; the mass ratio of Al2O3 powder to dopamine hydrochloride is 2:1-2.5:1.

[0013] According to the above scheme, in step (1), the weak alkaline buffer solution uses Tris-HCl buffer with a pH of 8 to 8.5; in steps (1) and (2), the heating rate of the high-temperature tube furnace is 1 to 3°C / min.

[0014] According to the above scheme, in step (2), the particle size of the nano-Ti powder is about 20 to 100 nm, and the purity is ≥99.8%; the mass ratio of the Al2O3 powder coated with carbonized polydopamine to the nano-Ti powder is 2.5:1 to 3:1; the mass ratio of the total mass of the molten salt medium to the total mass of the raw materials (i.e., the sum of the masses of the Al2O3 powder coated with carbonized polydopamine and the nano-Ti powder) is 4:1 to 8:1; and the molar ratio of NaCl to KCl is 4:1 to 1:4.

[0015] According to the above scheme, in step (3), the particle size of the Al2O3 matrix powder is about 100-300nm, and the purity is ≥99.9%; it is heated to 1400-1600℃ at a heating rate of 100-200℃ / min.

[0016] The TiC prepared by the above method x O y N z The Al2O3 composite ceramic with a spherical shell structure as the toughening phase has a density of 3.963-3.976 g / cm 3 , relative density is 99.57~99.89%, and has good mechanical properties, hardness is 18.06~19.07GPa, fracture toughness is 5.56~6.47MPa·m 1 / 2 .

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) Different from the existing Al2O3 ceramics toughened by particles, fibers, and plates, the Al2O3 composite ceramic proposed in the present invention has a brand-new toughening structure. x O y N z The formed spherical shell structure is used as a toughening phase, and the interior of the closed spherical shell is still filled with Al2O3 matrix phase, i.e. TiC x O y N z The spherical shell isolates the Al2O3 matrix phase, and the diameter of the spherical shell is concentrated between 1 and 2 μm. Among them, the micron-sized TiC x O y N z The spherical shell structure is formed by the accumulation of nano-scale particles, which has a size difference with the Al2O3 phase. Due to the special arc structure of the toughening phase spherical shell structure, and the physical properties and grain size differences in its micro-region, complex stress distribution is generated in the micro-region, inducing multi-dimensional crack expansion, so as to achieve the purpose of improving the fracture toughness of Al2O3 composite ceramics.

[0019] (2) The present invention firstly coats a layer of polydopamine on the surface of Al2O3 particles by chemical method, and then prepares TiC by molten salt method. x O y N z The core-shell structure powder wrapped with Al2O3 has the same phase of Al2O3 in its core as the matrix phase of the target ceramic. The core-shell structure powder is used as a raw material and mixed with the matrix Al2O3 powder to prepare TiC by pressure rapid sintering. x O y N zAl2O3 composite ceramics with spherical shell structure as toughening phase. During the sintering process, due to rapid sintering and pressure sintering, the TiC x O y N z The spherical shell is destroyed, so that the spherical shell structure can be completely retained in the Al2O3 matrix to form a spherical shell toughening phase. Based on the above specific preparation process, TiC x O y N z The formed spherical shell structure toughened Al2O3 composite ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Made of TiC x O y N z Schematic diagram of the microstructure of Al2O3 composite ceramics with the formed spherical shell structure as the toughening phase;

[0021] Figure 2 is the SEM spectrum of the carbonized polydopamine-coated Al2O3 powder in Example 3;

[0022] Figure 3 It is Al2O3@TiC in Example 3 x O y N z SEM spectrum of core-shell structure powder;

[0023] Figure 4 It is Al2O3@TiC in Example 3 x O y N z XRD spectrum of core-shell structure powder;

[0024] Figure 5 In Example 3, TiC x O y N z The BSE spectra of the polished surface of the Al2O3 composite ceramic with the formed spherical shell structure as the toughening phase and the crack passing through the core-shell structure;

[0025] Figure 6 In Example 3, TiC x O y N z XRD spectrum of Al2O3 composite ceramics with the formed spherical shell structure as the toughening phase. DETAILED DESCRIPTION

[0026] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the present invention is not limited to the following embodiments.

[0027] Example 1

[0028] A TiC x O y N z The Al2O3 composite ceramic with a spherical shell structure as a toughening phase is composed of a toughening phase and a matrix phase. In terms of mass percentage, TiC x O y N z Spherical shell structure 0.7%, matrix phase 99.3%; the matrix phase is Al2O3, and the toughening phase is TiC x O y N z Spherical shell structure; the spherical shell structure is titanium oxycarbonitride (TiC x O y N z ) forms a closed spherical shell.

[0029] like Figure 1 As shown, the toughening phase is composed of TiC x O y N z The spherical shell structure is formed, and the inside of the spherical shell is filled with Al2O3, and the inside and outside of the closed spherical shell are both Al2O3 matrix phases, that is, the TiCxOyNz spherical shell separates the Al2O3 matrix phase. The structural schematic diagram is shown in Figure 1 As shown; the diameter of the spherical shell is in the micron order, and it is formed by the accumulation of nanoscale particles.

[0030] The above TiC x O y N z The preparation method of Al2O3 composite ceramics with the formed spherical shell structure as the toughening phase comprises the following specific steps:

[0031] (1) Al2O3 powder and dopamine hydrochloride are placed in a Tris-HCl buffer (pH 8) at a mass ratio of 2:1. Dopamine hydrochloride undergoes a self-polymerization reaction under magnetic stirring to generate polydopamine. The generated polydopamine adheres to the surface of the Al2O3 powder, and then the composite powder A is obtained after centrifugation, washing, and drying. The particle size of the Al2O3 powder is about 1.5 um.

[0032] (2) The composite powder A obtained in step (1) is placed in a semicircular corundum crucible with a lid, and heated to 800° C. at a heating rate of 1° C. / min in a high-temperature tube furnace with a flow rate of 50 ml / min under Ar gas protection, and kept warm for 1 h. The mixture is cooled to room temperature with the furnace to obtain Al2O3 powder coated with carbonized polydopamine.

[0033] (3) Carbonized polydopamine-coated Al2O3 powder and nano-Ti powder are used as raw materials (the mass ratio of carbonized polydopamine-coated Al2O3 powder to nano-Ti powder is 3:1), NaCl and KCl with a molar ratio of 4:1 are used as molten salt medium, the mass ratio of molten salt medium to raw materials is 8:1, and anhydrous ethanol is used as liquid medium. The mixture is magnetically stirred and mixed on a magnetic stirrer, the solution is evaporated by rotary evaporation, and vacuum dried to obtain a mixed powder B; wherein the particle size of the nano-Ti powder is about 60 nm, and the purity is ≥99.8%.

[0034] (4) The mixed powder B obtained in step 1 is placed in a semicircular corundum crucible with a lid, and heated to 1300°C at a heating rate of 1°C / min in a high-temperature tube furnace with a flow rate of 50 ml / min under Ar gas protection, kept at this temperature for 1 h, and cooled to room temperature with the furnace to obtain Al2O3@TiC x O y N z The core-shell powder was washed with water several times to remove the molten salt and then dried in a vacuum oven.

[0035] (5)Al2O3@TiC x O y N z The mass ratio of core-shell structure powder to Al2O3 powder is 2:98 (TiC x O y N z The mass of the spherical shell structure powder accounts for about 0.7% of the Al2O3 matrix powder) is magnetically stirred in anhydrous ethanol solution for 24 hours and then directly evaporated to dryness, and dried in a vacuum oven to obtain a mixed powder C.

[0036] (6) The mixed powder C obtained in step (5) is subjected to spark plasma sintering, wherein the sintering system is to heat to 1400° C. at a heating rate of 100° C. / min and maintain for 8 min, wherein a uniaxial pressure of 40 MPa is applied at 800° C. and continued until the sintering is completed; after the sintering is completed, the mixed powder C is cooled to room temperature, the power is turned off and the pressure is released, and a TiC x O y N z The formed spherical shell structure is used as the toughening phase of Al2O3 composite ceramics.

[0037] After testing, the density of the composite ceramic prepared in this embodiment is 3.963g / cm 3 , relative density is 99.57%, hardness is 18.06GPa, fracture toughness is 5.56MPa·m 1 / 2 The density of the composite ceramics was measured by the Archimedean method, and the relative density was calculated by dividing the actual density by the theoretical density. The Vickers hardness was evaluated by applying a load of 10×9.8N for 15s on the polished surface of the composite ceramics, and the fracture toughness was calculated by the length of the Vickers indentation crack.

[0038] Example 2

[0039] The difference from Example 1 is that: in step (1), the mass ratio of Al2O3 powder to dopamine hydrochloride is 2.5:1; in step (2), the mixture is heated to 1000°C at a heating rate of 3°C / min in a high-temperature tube furnace and kept warm for 1 h; in step (3), the mass ratio of molten salt to raw material is 6:1, and the molar ratio of NaCl to KCl is 1:4; in step (6), Al2O3@TiC x O y N z The mass ratio of core-shell structure powder to Al2O3 powder was changed to 4:96 (among which TiC x O y N z The mass of the spherical shell structure powder accounts for about 1.4% of the Al2O3 matrix powder).

[0040] The density of the composite ceramic prepared in this example is 3.971 g / cm 3 , relative density is 99.77%, hardness is 18.31GPa, fracture toughness is 5.89MPa·m 1 / 2 .

[0041] Example 3

[0042] A TiC x O y N z The preparation method of Al2O3 composite ceramics with the formed spherical shell structure as the toughening phase comprises the following specific steps:

[0043] (1) Al2O3 powder and dopamine hydrochloride are placed in a Tris-HCl buffer (pH 8.5) at a mass ratio of 2:1. Dopamine hydrochloride undergoes a self-polymerization reaction under magnetic stirring to generate polydopamine, which is attached to the Al2O3 powder. Composite powder A is then obtained after centrifugation, washing, and drying. The particle size of the Al2O3 powder is about 1.5 um.

[0044] (2) The composite powder A obtained in step (1) is placed in a semicircular corundum crucible with a lid, and heated to 800°C at a heating rate of 3°C / min in a high-temperature tube furnace with a flow rate of 50 ml / min under Ar gas protection, and kept warm for 2 h. The mixture is then cooled to room temperature to obtain carbonized polydopamine-coated Al2O3 powder.

[0045] (3) Carbonized polydopamine-coated Al2O3 powder and nano-Ti powder are used as raw materials (the mass ratio of carbonized polydopamine-coated Al2O3 powder to nano-Ti powder is 2.5:1), NaCl and KCl with a molar ratio of 1:1 are used as molten salt media, the mass ratio of molten salt medium to raw materials is 4:1, and anhydrous ethanol is used as liquid medium. The mixture is magnetically stirred and mixed on a magnetic stirrer, the solution is evaporated by rotary evaporation, and vacuum dried to obtain a mixed powder B; wherein the particle size of the nano-Ti powder is about 60 nm, and the purity is ≥99.8%.

[0046] (4) The mixed powder B obtained in step 1 is placed in a semicircular corundum crucible with a lid, and heated to 1300°C at a heating rate of 3°C / min in a high-temperature tube furnace with a flow rate of 50 ml / min under Ar gas protection, kept at this temperature for 2 h, and cooled to room temperature with the furnace to obtain Al2O3@TiC x O y N z The core-shell powder was washed with water several times to remove the molten salt and then dried in a vacuum oven.

[0047] (5) Al2O3@TiC x O y N z The core-shell powder and Al2O3 powder are in a mass ratio of 8:92 (TiC x O y N z The mass of the spherical shell structure powder accounts for about 2.9% of the Al2O3 matrix powder), and after magnetic stirring in anhydrous ethanol solution for 24 hours, it is directly evaporated to dryness and dried in a vacuum oven to obtain a mixed powder C.

[0048] (6) The mixed powder C obtained in step (5) is subjected to spark plasma sintering, wherein the sintering system is to heat to 1500° C. at a heating rate of 100° C. / min and hold for 5 min, wherein a uniaxial pressure of 60 MPa is applied at 800° C. and continued until the sintering is completed; after the sintering is completed, the mixed powder C is cooled to room temperature, the power is turned off and the pressure is released, and a TiC x O y N z The formed spherical shell structure is used as the toughening phase of Al2O3 composite ceramics.

[0049] The density of the composite ceramic prepared in this example is 3.976 g / cm 3 , relative density is 99.89%, hardness is 18.69GPa, fracture toughness is 6.47MPa·m 1 / 2 .

[0050] Depend on Figure 2It can be seen that the smooth surface of Al2O3 powder becomes rough, the size is concentrated between 1 and 2 um, and the average particle size is about 1.6 um. This is because polydopamine is attached to the surface of Al2O3 powder.

[0051] Depend on Figure 3 It can be seen that the figure shows Al2O3@TiC with cracks x O y N z The core-shell powder has a diameter concentrated between 1 and 2 μm, with an average particle size of about 1.7 μm. It can be seen from the figure that TiC x O y N z The shell is composed of nano-scale particles stacked together.

[0052] Depend on Figure 4 It can be seen that the XRD spectrum detected Al2O3 and TiC x O y N z The corresponding peaks indicate that Al2O3@TiC x O y N z The core-shell structure powder is mainly composed of Al2O3, TiC x O y N z And a small amount of Ti3O5. Figure 5 The successful synthesis of core-shell powders was confirmed. Figure 5 It can be seen that the shiny white area corresponds to TiC x O y N z The gray area corresponds to Al2O3, and there are almost no pores on the ceramic surface, showing the high density of the ceramic, and the complete TiC x O y N z The spherical shell structure is clearly discernible, with a diameter between 1 and 2 um.

[0053] Depend on Figure 6 It can be seen that the XRD spectrum analysis confirms that Al2O3 and TiC in the composite ceramic prepared in this embodiment x O y N z The existence of TiC x O y N z The spherical shell structure is retained after sintering in the Al2O3 matrix.

[0054] Example 4

[0055] The difference from Example 3 is that: in step (2), the mass ratio of carbonized polydopamine-coated Al2O3 powder to nano-Ti powder is 3:1; in step (4), the high-temperature tube furnace is heated to 1400°C at a heating rate of 1°C / min and kept warm for 1 hour; in step (6), the sintering system is heated to 1600°C at a heating rate of 200°C / min, maintained for 5 minutes, and a uniaxial pressure of 40 MPa is applied at 800°C, and the sintering is continued until completion.

[0056] The density of the composite ceramic prepared in this example is 3.973 g / cm 3 , relative density is 99.82%, hardness is 19.07GPa, fracture toughness is 5.87MPa·m 1 / 2 .

[0057] Comparative Example 1

[0058] The difference from Example 3 is that pure Al2O3 powder is rapidly sintered under the same sintering system to obtain Al2O3 ceramics.

[0059] The density of pure Al2O3 ceramic prepared in this example is 3.967 g / cm 3 , relative density is 99.67%, hardness is 18.03GPa, fracture toughness is 4.67MPa·m 1 / 2 .

[0060] Comparative Example 2

[0061] TiC x O y N z The preparation method of Al2O3 composite ceramics with powder as toughening phase, the specific steps are as follows:

[0062] (1) dopamine hydrochloride is placed in a Tris-HCl buffer solution (pH 8.5), and dopamine hydrochloride undergoes a self-polymerization reaction in a weakly alkaline solution under magnetic stirring to generate polydopamine, which is then centrifuged, washed, and dried to obtain powder A;

[0063] (2) The powder A obtained in step (1) is placed in a semicircular corundum crucible with a lid, and heated to 800° C. at a heating rate of 3° C. / min in a high-temperature tube furnace with a flow rate of 50 ml / min under Ar gas protection, and kept warm for 2 h, and then cooled to room temperature with the furnace to obtain carbonized polydopamine powder.

[0064] (3) Carbonized polydopamine and nano-Ti powder are used as raw materials (the mass ratio of carbonized polydopamine to nano-Ti powder is 1:1.2), NaCl and KCl with a molar ratio of 1:1 are used as molten salt medium, the mass ratio of molten salt medium to raw materials is 4:1, and anhydrous ethanol is used as liquid medium. The mixture is magnetically stirred and mixed on a magnetic stirrer, the solution is rotary evaporated, and vacuum dried to obtain a mixed powder B; wherein the particle size of the nano-Ti powder is about 60 nm, and the purity is ≥99.8%.

[0065] (4) The mixed powder B obtained in step 1 is placed in a semicircular corundum crucible with a lid, and heated to 1300°C at a heating rate of 3°C / min in a high-temperature tube furnace with a flow rate of 50 ml / min under Ar gas protection, kept at this temperature for 2 hours, and cooled to room temperature with the furnace to obtain TiC x O y N powder was washed with water several times to remove the molten salt and then dried in a vacuum oven.

[0066] (5) TiC x O y N powder and Al2O3 powder were magnetically stirred in anhydrous ethanol solution at a mass ratio of 2.9:97.1 for 24 hours, then directly evaporated to dryness and dried in a vacuum oven to obtain mixed powder C.

[0067] (6) The mixed powder C obtained in step (5) is subjected to spark plasma sintering, wherein the sintering system is to heat to 1500° C. at a heating rate of 100° C. / min and hold for 5 min, wherein a uniaxial pressure of 60 MPa is applied at 800° C. and continued until the sintering is completed; after the sintering is completed, the mixed powder C is cooled to room temperature, the power is turned off and the pressure is released, and TiC x O y N z Al2O3 composite ceramics with powder as toughening phase.

[0068] The density of the composite ceramic prepared in this example is 3.974 g / cm 3 , relative density is 99.85%, hardness is 18.57GPa, fracture toughness is 5.13MPa·m 1 / 2 .

[0069] Compared with the pure Al2O3 ceramic prepared in Comparative Example 1, the composite ceramic prepared in Example 3 has a slightly higher hardness and a significantly higher fracture toughness, which is increased by about 38.55%. Compared with the composite ceramic prepared in Comparative Example 2, the fracture toughness of Example 3 is increased by about 26.12% under the condition of equivalent relative density and hardness. x O y N z The addition of powder will slightly increase the fracture toughness of the ceramic, and when TiC x Oy N z When the powder is added to Al2O3 ceramics in the form of a spherical shell structure, the fracture toughness of the composite ceramics will be significantly improved.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and changes without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A TiC x O y N z The Al2O3 composite ceramic with a spherical shell structure as a toughening phase is characterized by: The toughening phase is filled in the matrix phase, and the toughening phase is 0.6% to 4% by mass, and the matrix phase is 96% to 99.4% by mass. The matrix phase is Al2O3, and the toughening phase is TiC x O y N z The formed spherical shell structure has a matrix phase inside and outside, and a diameter of the spherical shell structure of 1 to 2 um.

2. A TiC x O y N z The method for preparing Al2O3 composite ceramics with a spherical shell structure as a toughening phase is characterized in that: First, prepare Al2O3 powder coated with carbonized polydopamine, and then convert carbonized polydopamine into TiC x O y N z , and obtain Al2O3@TiC x O y N z The core-shell structured powder is then x O y N z The core-shell structure powder and Al2O3 matrix powder are mixed evenly and sintered under pressure to obtain TiC x O y N z The formed spherical shell structure is used as the toughening phase of Al2O3 composite ceramics.

3. A TiC-based x O y N z The method for preparing Al2O3 composite ceramics with a spherical shell structure as a toughening phase is characterized in that: The steps include: (1) Al2O3 powder and dopamine hydrochloride are mixed in a weak alkaline buffer solution, and dopamine hydrochloride undergoes a self-polymerization reaction under the weak alkaline condition of the buffer solution to generate polydopamine, which adheres to the surface of the Al2O3 powder, and then centrifuges, washes, and dries to obtain a composite powder A; the composite powder A is heated to 800-1000° C. under a protective atmosphere and kept warm for 1-2 hours to obtain Al2O3 powder coated with carbonized polydopamine; (2) Carbonized polydopamine-coated Al2O3 powder and nano-Ti powder are used as raw materials, NaCl and KCl are used as molten salt media, and mixed evenly to obtain a mixed powder B; the mixed powder B is heated to 1300-1400°C under a protective atmosphere, kept warm for 1-2 hours, washed and dried to obtain Al2O3@TiC x O y N z Core-shell powder; (3) According to the mass percentage, Al2O3@TiC x O y N z 2% to 8% of the core-shell powder and 92% to 98% of the matrix powder are uniformly mixed to obtain a mixed powder C; the mixed powder C is heated to a sintering temperature of 1400 to 1600°C and maintained for 5 to 8 minutes, wherein a uniaxial pressure of 40 to 60 MPa is applied when the temperature is raised to 800°C and continued until the sintering is completed to obtain a TiC x O y N z The formed spherical shell structure is used as the toughening phase of Al2O3 composite ceramics.

4. The TiC-based x O y N z The method for preparing Al2O3 composite ceramics with a spherical shell structure as a toughening phase is characterized in that: In step (1), the particle size of Al2O3 powder is 1-2 um, and the mass ratio of Al2O3 powder to dopamine hydrochloride is 2:1-2.5:

1.

5. The TiC-based x O y N z The method for preparing Al2O3 composite ceramics with a spherical shell structure as a toughening phase is characterized in that: In step (1), the weakly alkaline buffer solution is a Tris-HCl buffer solution with a pH of 8 to 8.5; in both steps (1) and (2), the temperature is increased to the insulation temperature at a heating rate of 1 to 3°C / min.

6. The TiC-based x O y N z The method for preparing Al2O3 composite ceramics with a spherical shell structure as a toughening phase is characterized in that: In step (2), the mass ratio of Al2O3 powder coated with carbonized polydopamine to nano-Ti powder is 2.5:1-3:1; the mass ratio of the total mass of the molten salt medium to the total mass of the raw materials is 4:1-8:1; and the molar ratio of NaCl to KCl is 4:1-1:

4.

7. The TiC-based x O y N z The method for preparing Al2O3 composite ceramics with a spherical shell structure as a toughening phase is characterized in that: In step (3), heating is performed to 1400-1600° C. at a heating rate of 100-200° C. / min.

8. The Al2O3 composite ceramic prepared by the method of claim 3, characterized in that: Density: 3.963~3.976g / cm 3 , relative density is 99.57~99.89%, hardness is 18.06~19.07GPa, fracture toughness is 5.56~6.47MPa·m 1 / 2 .

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