Aluminum nitride-based composite ceramic carrier and method for manufacturing the same

Abstract

The application discloses an aluminum nitride-based composite ceramic carrier and a preparation method thereof, and belongs to the technical field of composite ceramic material preparation. The carrier is prepared from aluminum nitride as a base material, and a specific proportion of beta-Sialon precursor powder and Y2O3-ZrO2 composite sintering aids. The preparation method comprises the following steps: treating raw materials by adopting a high-speed and low-speed ball milling process, and then performing two-stage composite sintering of electric discharge plasma sintering and hot-press sintering in sequence. Through the synergistic design of the material formula and the process, the columnar beta-Sialon grain network and the metastable tetragonal phase ZrO2 generated in situ are utilized to construct a multi-stage toughening system while the super-high thermal conductivity of the aluminum nitride base is maintained, so that the material has high fracture toughness and excellent thermal shock resistance, and is especially suitable for an automobile exhaust treatment system with strict requirements on rapid ignition and long-term reliability.

Description

Technical Field

[0001] This invention relates to the field of advanced ceramic materials technology, and in particular to an aluminum nitride-based composite ceramic carrier and its preparation method. Background Technology

[0002] To meet increasingly stringent vehicle emission regulations, the performance requirements of ceramic supports in automotive exhaust aftertreatment systems, particularly for three-way catalytic converters and particulate filters, are extremely high. The support must possess excellent thermal conductivity to ensure rapid ignition of the catalyst during cold starts, thereby reducing initial pollutant emissions. Aluminum nitride ceramics, due to their ultra-high thermal conductivity and good chemical stability, are considered ideal next-generation support materials, with potential far exceeding that of current cordierite or silicon carbide supports.

[0003] However, pure aluminum nitride ceramics face severe challenges in practical applications: First, they have poor thermal shock resistance and are prone to cracking due to thermal stress concentration during frequent hot and cold cycles in exhaust gas treatment systems; second, sintering aids added to improve density often form a second phase with high thermal resistance at grain boundaries, severely weakening their inherent high thermal conductivity advantage; in addition, the material itself is brittle and has insufficient reliability under long-term mechanical vibration and thermal stress coupling.

[0004] To address these issues, existing technologies typically attempt to introduce a β-Sialon phase to enhance toughness. However, due to insufficient precision in formulation design and process control, the morphology, distribution, and interfacial bonding of the reinforcing phase with the matrix are difficult to optimize, making it impossible to form an effective three-dimensional toughening network. Furthermore, this often results in a significant loss of the material's thermal conductivity. Therefore, developing an aluminum nitride-based composite material that simultaneously possesses ultra-high thermal conductivity, high toughness, and excellent thermal shock resistance through material and process innovation has become a core technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0005] In view of this, the present invention proposes an aluminum nitride-based composite ceramic carrier and its preparation method. This method, through unique material formulation design and an innovative "asymmetric mixing-two-stage sintering" process, maintains the ultra-high thermal conductivity potential of the aluminum nitride matrix while utilizing an in-situ generated columnar β-Sialon grain network and zirconium oxide particles of a specific phase to construct a multi-level toughening system, thereby preparing a ceramic carrier with excellent comprehensive performance, particularly suitable for harsh automotive exhaust environments.

[0006] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides an aluminum nitride-based composite ceramic carrier, the raw materials of which, by mass percentage, comprise: Aluminum nitride powder: 60%~85%; β-Sialon precursor powder: 10%~30%; Composite sintering aid: 3%~10%; The general chemical formula of the β-Sialon precursor powder is Si. 6-z Al z O z N 8-z The value of z ranges from 0.5 to 4.2. The composite sintering aid is a mixed powder of Y2O3 and ZrO2.

[0007] Based on the above technical solutions, preferably, the β-Sialon precursor powder has the general chemical formula Si 6- z Al z O z N 8-z In the given information, z=2.

[0008] More preferably, the β-Sialon precursor powder comprises Si3N4, AlN, and Al2O3; the Si3N4, AlN, and Al2O3 are calculated in a molar ratio of (6-z):z:z.

[0009] More preferably, in the composite sintering aid, the mass ratio of Y2O3 to ZrO2 is 1:2 to 2:1.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned aluminum nitride-based composite ceramic carrier, comprising the following steps: S1. Si3N4, Al2O3 and the composite sintering aid are mixed and subjected to a first ball milling process, followed by the addition of AlN powder for a second ball milling process to obtain a mixed powder. S2. The mixed powder is mixed with an organic carrier and extruded to obtain a porous green body; S3. The green blank is subjected to programmed temperature rise heat treatment under a protective atmosphere; S4. The blank obtained in step S3 is subjected to discharge plasma sintering and hot pressing sintering in sequence.

[0011] Based on the above technical solutions, preferably, in step S1, the rotation speed of the first ball milling treatment is 300~500 rpm, the treatment time is 10~15 h, and the particle size after ball milling is controlled at 0.5~1 µm; the rotation speed of the second ball milling treatment is 100~200 rpm, the treatment time is 2~4 h, and the particle size after ball milling is controlled at 1~1.5 µm.

[0012] The asymmetric mixing process employed in step S1 is based on the coordinated control of energy input and the feeding sequence. The first ball milling process involves high-energy ball milling to deeply integrate the sintering aid with the reinforcing phase precursor, solving the problem of uncontrollable β-Sialon grain morphology caused by uneven aid distribution. The second ball milling process uses low-energy, short-time mixing into the AlN matrix, overcoming the technical bottleneck of excessive lattice oxygen content and a significant decrease in thermal conductivity in AlN due to prolonged high-energy wear in traditional processes.

[0013] More preferably, in step S2, the organic carrier comprises (binder, plasticizer, dispersant, lubricant, and solvent); extrusion is performed using a cemented carbide die with a square or hexagonal hole array, and the wall thickness is controlled at 0.1~0.2 mm. During the extrusion process, due to the shear force, the precursor particles with a large aspect ratio will undergo a certain degree of directional alignment, which is beneficial to the subsequent growth of β-Sialon grains in a specific direction, thereby optimizing the compressive strength of the carrier in the axial direction.

[0014] In a further preferred embodiment, in step S3, a temperature program is performed at a heating rate of 0.2~0.5 ℃ / min, and the temperature is held in the temperature ranges of 250~350 ℃ and 450~600 ℃ respectively, with each temperature program holding for 1~2 h.

[0015] More preferably, step S3 is performed under a flowing nitrogen protective atmosphere. First, the temperature is maintained in the range of 250–350 °C to completely remove small-molecule plasticizers; then, it is maintained in the range of 450–600 °C to allow the macromolecular binder to fully decompose. The protective atmosphere can promptly remove thermal decomposition products from the system, thereby effectively avoiding carbon residue and ensuring the high thermal conductivity of the aluminum nitride matrix in the final sintered body.

[0016] More preferably, in step S4, the discharge plasma sintering is carried out under a nitrogen atmosphere, the sintering temperature is 1550~1650 ℃, the holding time is 10~20 min, and the pressure is 0.1~0.5 MPa.

[0017] More preferably, in step S4, the hot pressing sintering is carried out under a nitrogen atmosphere, the sintering temperature is 1750~1850 ℃, the holding time is 4~6 h, and the pressure is 20~40 MPa.

[0018] Step S4 employs a two-stage sintering process. In the first stage, the transient high heating rate and electric field-assisted diffusion effect of spark plasma sintering (SPS) induce a non-equilibrium solid solution reaction in the precursor, achieving high-density dispersed nucleation of β-Sialon at AlN grain boundaries and suppressing disordered grain coarsening. In the second stage, high-temperature long-term heat preservation and pressure field drive promote the preferential growth of crystal nuclei along specific crystal orientations into columnar crystals with a large aspect ratio (5:1~15:1), constructing a three-dimensional interpenetrating network structure. The fibrous reinforcement effect significantly improves the fracture toughness and thermal shock resistance of the AlN matrix.

[0019] After sintering, the composite ceramic carrier has a network structure formed by needle-like or columnar β-Sialon grains interspersed between AlN grain boundaries; the ZrO2 particles are dispersed in monoclinic or tetragonal phases at the grain boundary triangulation points, playing a role in phase transformation toughening.

[0020] More preferably, after the hot pressing and sintering described in step S4 is completed, a controllable cooling process is performed.

[0021] More preferably, the conditions for the controllable cooling process include controllable cooling at a rate of 30 °C / min within a temperature range of 1000 to 1850 °C.

[0022] The present invention has the following advantages over the prior art: (1) Significantly improved thermal shock resistance: Fiber toughening is achieved through in-situ generated rod-shaped β-Sialon grains, and a multi-level synergistic toughening system is constructed by utilizing the phase transformation toughening mechanism of ZrO2. This material exhibits excellent performance in rapid cooling and heating cycles from 600℃ to room temperature, fundamentally solving the problem of easy cracking of aluminum nitride under drastic temperature fluctuations.

[0023] (2) High thermal conductivity is maintained: The Y2O3-ZrO2 composite sintering aid forms a low-viscosity liquid phase at high temperature, which not only promotes the in-situ growth of β-Sialon, but also effectively removes oxygen impurities on the surface of AlN particles and purifies grain boundaries, so that the thermal conductivity of the composite material is always maintained at 105~118 W·m. -1 ·K -1 .

[0024] (3) High mechanical reliability: β-Sialon has good thermophysical compatibility with AlN, and the interface formed by in-situ growth has high bonding strength, which enables the carrier to have a longer service life in the complex vibration environment of automobile driving.

[0025] (4) The ignition time is significantly shortened: thanks to the thermal conductivity of the carrier which is much higher than that of the traditional cordierite carrier, the carrier prepared by the present invention can quickly transfer the heat of the exhaust gas to the active center of the catalyst, thereby significantly improving the emission performance during the cold start stage. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1: The preparation of an aluminum nitride-based composite ceramic carrier involves the following specific steps: Matrix phase: 72g aluminum nitride (AlN) powder; Reinforcing phase precursor: 25g β-Sialon precursor powder, calculated from Si3N4, AlN and Al2O3 in a molar ratio of 2:1:1, whose chemical formula can usually be represented as Si4Al2O2N6 (z=2); Composite sintering aid: 3g Y2O3-ZrO2 mixed powder, wherein the mass ratio of Y2O3 to ZrO2 is 1:2.

[0028] S1. First, place 16.56g of Si3N4, 6.02g of Al2O3, 1.00g of Y2O3 and 2.00g of ZrO2 in a ball mill jar and ball mill at 400 rpm for 12 h. Then add AlN powder (74.42g, of which 2.42g is the precursor and 72.00g is the matrix phase), reduce the speed to 150 rpm and continue mixing and milling for 3 h.

[0029] S2. The mixed powder obtained in step S1 is thoroughly mixed with the organic carrier (20g deionized water; 3g hydroxypropyl methylcellulose; 2g polyethylene glycol; 1g oleic acid) in a mixer and then vacuum-kneaded to form a billet with good plasticity. Subsequently, using a cemented carbide die with a square channel array, it is formed on an extruder to obtain a honeycomb structure green body with a channel wall thickness controlled at 0.15 mm.

[0030] S3. The formed green body is placed in an atmosphere sintering furnace and subjected to programmed temperature rise heat treatment under the protection of flowing nitrogen at a flow rate of 1 L / min to remove the organic carrier. The temperature rise regime is set as follows: heat to 300℃ at an extremely slow rate of 0.3 ℃ / min and hold for 2 h; then continue to heat to 500℃ at the same rate and hold for 2 h.

[0031] S4. The first stage of sintering employs spark plasma sintering (SPS). The green body is placed in a graphite mold and then placed in a spark plasma sintering furnace. Under a nitrogen atmosphere of 0.3 MPa, the temperature is rapidly increased to 1600 °C at a rate of 120 °C / min and held at this temperature for 15 min. The second stage of sintering employs hot pressing sintering: the SPS-treated green body is transferred to a hot pressing sintering furnace. Under a nitrogen atmosphere of 0.5 MPa, a two-stage heating process is used: first, the temperature is increased to 1600 °C at a rate of 100 °C / min, and then increased at a slower rate of 10 °C / min to the final sintering temperature of 1800 °C, and held at 1800 °C and a pressure of 30 MPa for 5 h.

[0032] S5. After hot pressing and heat preservation, controlled cooling is carried out in the sintering furnace. In the high-temperature range above 1000 ℃, the cooling rate is controlled at approximately 30 ℃ / min to "freeze" the ZrO2 in the composite additive into a metastable tetragonal phase with phase transformation toughening potential. After the temperature drops below 1000 ℃, it is cooled to room temperature in the furnace to obtain the final aluminum nitride-based composite ceramic carrier.

[0033] Experimental Results and Analysis: The obtained sample was tested and found to have a relative density > 99% and a thermal conductivity of 110 W·m. -1 ·K -1 fracture toughness K IC 6.5 MPa·m 1 / 2 Thermal shock resistance was tested using a 600 ℃ water quenching method. After 50 cycles, no visible cracks were found on the sample surface, and the bending strength retention rate was over 92%.

[0034] Example 2: The preparation of an aluminum nitride-based composite ceramic carrier involves the following specific steps: Matrix phase: 60g aluminum nitride (AlN) powder; Reinforcing phase precursor: 30g β-Sialon precursor powder, calculated from Si3N4, AlN, and Al2O3 in a molar ratio of 5.5:0.5:0.5, whose chemical formula can usually be represented as Si 5.5 Al 0.5 O 0.5 N 7.5 (z=0.5); Composite sintering aid: 10g of Y2O3-ZrO2 mixed powder, wherein the mass ratio of Y2O3 to ZrO2 is 1:1.

[0035] S1. First, place 27.46g of Si3N4, 1.81g of Al2O3, 5.00g of Y2O3 and 5.00g of ZrO2 in a ball mill jar and ball mill at 300 rpm for 15 h. Then add AlN powder (60.73g, of which 0.73g is the precursor and 60.00g is the matrix phase), reduce the speed to 100 rpm and continue mixing and milling for 2 h.

[0036] S2. The mixed powder obtained in step S1 is thoroughly mixed with the organic carrier (22g deionized water; 4g hydroxypropyl methylcellulose; 2.5g glycerol; 1.2g stearic acid) in a mixer and then vacuum-kneaded to form a green body with good plasticity. Subsequently, using a cemented carbide die with a square channel array, it is formed on an extruder to obtain a honeycomb structure green body with a channel wall thickness controlled at 0.15 mm.

[0037] S3. The formed green body is placed in an atmosphere sintering furnace and subjected to programmed temperature rise heat treatment under the protection of flowing nitrogen at a flow rate of 1 L / min to remove organic carriers. The temperature rise regime is set as follows: heat to 250℃ at an extremely slow rate of 0.2 ℃ / min and hold for 2 h; then continue to heat to 450 ℃ at the same rate and hold for 2 h.

[0038] S4. The first stage of sintering employs spark plasma sintering (SPS). The green body is placed in a graphite mold and then placed in a spark plasma sintering furnace. Under a nitrogen atmosphere of 0.1 MPa, the temperature is rapidly increased to 1550 °C at a rate of 120 °C / min and held at this temperature for 20 min. The second stage of sintering employs hot pressing sintering: the SPS-treated green body is transferred to a hot pressing sintering furnace. Under a nitrogen atmosphere of 0.5 MPa, a two-stage heating process is used: first, the temperature is increased to 1600 °C at a rate of 100 °C / min, and then increased at a slower rate of 10 °C / min to the final sintering temperature of 1750 °C, and held at 1750 °C and 40 MPa for 4 h.

[0039] S5. After hot pressing and heat preservation, controlled cooling is carried out in the sintering furnace. In the high-temperature range above 1000 ℃, the cooling rate is controlled at approximately 30 ℃ / min to "freeze" the ZrO2 in the composite additive into a metastable tetragonal phase with phase transformation toughening potential. After the temperature drops below 1000 ℃, it is cooled to room temperature in the furnace to obtain the final aluminum nitride-based composite ceramic carrier.

[0040] Experimental Results and Analysis: The obtained sample was tested and found to have a relative density > 98.5% and a thermal conductivity of 105 W·m. -1 ·K -1 fracture toughness K IC Up to 7.2 MPa·m1 / 2 After 50 cycles of water quenching at 600 ℃, the sample showed no visible cracks, and the bending strength retention rate was over 90%.

[0041] Example 3: The preparation of an aluminum nitride-based composite ceramic carrier involves the following specific steps: Matrix phase: 85g aluminum nitride (AlN) powder; Reinforcing phase precursor: 10g β-Sialon precursor powder, calculated from Si3N4, AlN, and Al2O3 in a molar ratio of 1.8:4.2:4.2, whose chemical formula can usually be represented as Si 1.8 Al 4.2 O 4.2 N 3.8 (z=4.2); Composite sintering aid: 5g of Y2O3-ZrO2 mixed powder, wherein the mass ratio of Y2O3 to ZrO2 is 2:1.

[0042] S1. First, place 2.96g of Si3N4, 5.02g of Al2O3, 3.33g of Y2O3 and 1.67g of ZrO2 in a ball mill jar and ball mill at 500 rpm for 10 h. Then add AlN powder (87.02g, of which 2.02g is the precursor and 85.00g is the matrix phase), reduce the speed to 200 rpm and continue mixing and milling for 4 h.

[0043] S2. The mixed powder obtained in step S1 is thoroughly mixed with the organic carrier (18g of deionized water; 2.5g of methylcellulose; 1.5g of polyethylene glycol; 1g of ammonium polyacrylate) in a mixer and then vacuum-kneaded to form a billet with good plasticity. Subsequently, using a hard alloy die with a square channel array, it is formed on an extruder to obtain a honeycomb structure green body with a channel wall thickness controlled at 0.15 mm.

[0044] S3. The formed green body is placed in an atmosphere sintering furnace and subjected to programmed temperature rise heat treatment under the protection of flowing nitrogen at a flow rate of 1 L / min to remove organic carriers. The temperature rise regime is set as follows: the temperature is raised to 350℃ at an extremely slow rate of 0.5 ℃ / min and held for 2 h; then the temperature is raised to 600℃ at the same rate and held for 2 h.

[0045] S4. The first stage of sintering employs spark plasma sintering (SPS). The green body is placed in a graphite mold and then placed in a spark plasma sintering furnace. Under a nitrogen atmosphere of 0.5 MPa, the temperature is rapidly increased to 1650 °C at a rate of 120 °C / min and held at this temperature for 10 min. The second stage of sintering employs hot pressing sintering: the SPS-treated green body is transferred to a hot pressing sintering furnace. Under a nitrogen atmosphere of 0.5 MPa, a two-stage heating process is used: first, the temperature is increased to 1650 °C at a rate of 100 °C / min, and then increased at a slower rate of 10 °C / min to the final sintering temperature of 1850 °C, and held at 1850 °C and a pressure of 20 MPa for 6 h.

[0046] S5. After hot pressing and heat preservation, controlled cooling is carried out in the sintering furnace. In the high-temperature range above 1000 ℃, the cooling rate is controlled at approximately 30 ℃ / min to "freeze" the ZrO2 in the composite additive into a metastable tetragonal phase with phase transformation toughening potential. After the temperature drops below 1000 ℃, it is cooled to room temperature in the furnace to obtain the final aluminum nitride-based composite ceramic carrier.

[0047] Experimental Results and Analysis: The obtained sample was tested and found to have a relative density > 99% and a thermal conductivity of 118 W·m. -1 ·K -1 fracture toughness K IC It is 5.8 MPa·m 1 / 2 After 50 cycles of water quenching at 600 ℃, the sample showed no visible cracks, and the bending strength retention rate was over 89%.

[0048] Example 4: Unlike Example 1, only the ratio of Y2O3-ZrO2 was changed to 2:1, that is, 2.00g of Y2O3 and 1.00g of ZrO2 were added. The remaining steps were the same as in Example 1, and will not be repeated here.

[0049] Experimental Results and Analysis: The obtained sample was tested, and the measured thermal conductivity of the material decreased to 106 W·m. -1 ·K -1 In terms of mechanical properties, the fracture toughness K of the material... IC 5.0 MPa·m 1 / 2 Due to the relatively lower proportion of ZrO2 (the phase transformation toughening phase) in the composite additive, its contribution to the phase transformation toughening effect is weakened compared to the optimal formulation. Nevertheless, the material can still withstand 30 cycles and maintain 88% of its strength retention in the harsh thermal shock test of water quenching at 600 ℃, demonstrating good overall thermal stability.

[0050] Example 5: Unlike Example 1, 25g of β-Sialon precursor powder was added, with the proportions calculated from Si3N4 (21.10g), AlN (1.12g), and Al2O3 (2.79g) in a molar ratio of 5.5:0.5:0.5. Its chemical formula can generally be represented as Si 5.5 Al 0.5 O 0.5 N 7.5 (z=0.5); the remaining steps are the same as in Example 1, and will not be repeated here.

[0051] Experimental Results and Analysis: Testing of the obtained samples revealed that when the z-value was set to a lower level, the number of impurity atoms entering the aluminum nitride (AlN) lattice decreased, weakening phonon scattering and thus increasing the material's thermal conductivity to 117 W·m. -1 ·K -1 This is superior to the previous embodiment. However, the fiber toughening effect of short columnar grains is correspondingly weakened, resulting in a decrease in the fracture toughness K of the material. IC 4.8 MPa·m 1 / 2 While significantly higher than pure AlN ceramics, it is slightly lower than formulations with a superior long columnar structure. Regarding thermal shock resistance, after a 600 ℃ water quenching test, the material began to show microcracks after 20 cycles, with a strength retention rate of 82%.

[0052] Comparative Example 1: Unlike Example 1, β-Sialon precursor powder was not added. The remaining steps were the same as in Example 1, and will not be repeated here.

[0053] Experimental Results and Analysis: Mechanical Properties: Fracture Toughness K IC Only 2.8 MPa m 1 / 2 It exhibits typical brittle fracture characteristics; thermal shock resistance: in the 600 ℃ water quenching test, the sample developed through cracks after 3 cycles, and the strength retention rate was less than 30%.

[0054] Comparative Example 2: Unlike Example 1, in step S4, the first stage sintering, namely spark plasma sintering (SPS), is not performed. The remaining steps are the same as in Example 1, and will not be repeated here.

[0055] Experimental Results and Analysis: Thermal Conductivity: Thermal conductivity is 102 W·m -1 ·K -1 The temperature was lower than in Example 1. Excessive conventional sintering time resulted in uneven distribution of the second phase at grain boundaries and the entry of some impurities into the crystal lattice; Mechanical properties: fracture toughness K IC 4.2 MPa m 1 / 2 .

[0056] Comparative Example 3: Unlike Example 1, in step S4, the second stage of sintering, i.e., hot pressing sintering, is not performed. The remaining steps are the same as in Example 1, and will not be repeated here.

[0057] Experimental Results and Analysis: The obtained samples were tested and found to have a relative density of 92%–95% and a thermal conductivity of 85 W·m. -1 ·K -1 fracture toughness K IC Only 3.5 MPa·m 1 / 2 Microcracks appeared after 10 cycles of water quenching at 600 ℃, and the strength retention rate was <65%.

[0058] Comparative Example 4: Unlike Example 1, this example uses 70g of SiC as the main matrix, 25g of β-Sialon precursor powder, Si4Al2O2N6 (z=2), and 5g of graphite as a key additive. Y2O3-ZrO2 composite additive is not used. The remaining steps are the same as in Example 1, and will not be repeated here.

[0059] Experimental Results and Analysis: Insufficient Densification: Due to the lack of a liquid phase environment formed by oxide additives such as Y₂O₃, the wettability between SiC and the β-Sialon precursor is poor. Although graphite can inhibit SiC grain growth, it cannot provide effective liquid phase sintering kinetics, resulting in high porosity of the sintered body (relative density of only 88%~91%). Thermal Conductivity: Although SiC itself has a certain thermal conductivity, due to the large number of closed pores inside the material and the significant thermal resistance layer formed by the graphite phase at the grain boundaries, the measured thermal conductivity is only 52 W·m. -1 ·K -1 The strength was far below that of Example 1; thermal shock resistance: in the 600 °C water quenching test, due to the lack of ZrO2 phase transformation toughening and the effective construction of β-Sialon fiber network, the sample showed obvious macroscopic cracks after 8 to 10 cycles, and the strength retention rate was less than 45%.

[0060] Comparative Example 5: Unlike Example 1, Si3N4 (59.61g), Al2O3 (21.68g), and AlN (8.71g) were used as raw materials to generate 90% single-phase β-Sialon (z=2) in a stoichiometric ratio of 2:1:1. 10% of a composite additive of Y2O3 (4.00g)-Al2O3 (2.00g)-ZrO2 (4.00g) was added. The remaining steps were the same as in Example 1 and will not be repeated here.

[0061] Experimental Results and Analysis: Thermal Conductivity: Due to the removal of the high thermal conductivity AlN matrix, the material consists of a continuous β-Sialon phase. Because β-Sialon itself has low thermal conductivity, the overall thermal conductivity of the measured sample is only 15 W·m. -1 ·K -1 Ignition simulation test failure: In the simulated cold start test of automobile exhaust, the carrier exhibited extremely slow thermal conductivity, resulting in the catalyst reaching its operating temperature more than five times longer than in Example 1, failing to meet the rapid ignition requirements of the China VI / China VII emission standards; Mechanical properties and thermal shock resistance: The material exhibited extremely high fracture toughness K... IC 6.0 MPa m 1 / 2 It has good thermal shock resistance, but due to its low thermal conductivity, it is prone to local hot spot accumulation under actual exhaust gas scouring, and the structural reliability in long-term service is not as stable as that of Example 1.

[0062] Comparative Examples 6-7: Unlike Example 1, the mass ratio of Y2O3 to ZrO2 is 1:4 (1.00g Y2O3 and 4.00g ZrO2) and 4:1 (4.00g Y2O3 and 1.00g ZrO2), respectively. The remaining steps are the same as in Example 1, and will not be repeated here.

[0063] Experimental Results and Analysis: The relative density of the sample obtained from Comparative Example 6 (Y2O3:ZrO2=1:4) was approximately 97%, and the thermal conductivity was 95 W·m. -1 ·K -1 Fracture toughness 4.5 MPa·m 1 / 2 After 20 water quenchings at 600 ℃, the strength retention rate was 72%. The sample obtained from Comparative Example 7 (Y₂O₃:ZrO₂ = 4:1) had a relative density of approximately 98.5% and a thermal conductivity of 88 W·m⁻¹. -1 ·K -1 Fracture toughness 4.2 MPa·m 1 / 2 After 15 water quenchings at 600℃, the strength retention rate is 60%.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aluminum nitride-based composite ceramic carrier, characterized in that, Its raw materials, by weight percentage, include: Aluminum nitride powder: 60%~85%; β-Sialon precursor powder: 10%~30%; Composite sintering aid: 3%~10%; The general chemical formula of the β-Sialon precursor powder is Si. 6-z Al z O z N 8-z The value of z ranges from 0.5 to 4.

2. The composite sintering aid is a mixed powder of Y2O3 and ZrO2.

2. The composite ceramic carrier as described in claim 1, characterized in that, The general chemical formula of the β-Sialon precursor powder is Si. 6-z Al z O z N 8-z In the given information, z=2.

3. The composite ceramic carrier as described in claim 1, characterized in that, In the composite sintering aid, the mass ratio of Y2O3 to ZrO2 is 1:2 to 2:

1.

4. A method for preparing a composite ceramic carrier as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Si3N4, Al2O3 and the composite sintering aid are mixed and subjected to a first ball milling process, followed by the addition of AlN powder for a second ball milling process to obtain a mixed powder. S2. The mixed powder is mixed with an organic carrier and extruded to obtain a porous green body; S3. The green blank is subjected to programmed temperature rise heat treatment under a protective atmosphere; S4. The blank obtained in step S3 is subjected to discharge plasma sintering and hot pressing sintering in sequence.

5. The preparation method according to claim 4, characterized in that, In step S1, the rotation speed of the first ball milling process is 300~500 rpm, and the processing time is 10~15 h; the rotation speed of the second ball milling process is 100~200 rpm, and the processing time is 2~4 h.

6. The preparation method according to claim 4, characterized in that, In step S3, a programmed temperature rise is performed at a heating rate of 0.2~0.5 ℃ / min, and the temperature is maintained in the temperature ranges of 250~350 ℃ and 450~600 ℃ respectively.

7. The preparation method according to claim 4, characterized in that, In step S4, the discharge plasma sintering is carried out under a nitrogen atmosphere, with a sintering temperature of 1550~1650 ℃, a holding time of 10~20 min, and a pressure of 0.1~0.5 MPa.

8. The preparation method according to claim 4, characterized in that, In step S4, the hot pressing sintering is carried out under a nitrogen atmosphere, with a sintering temperature of 1750~1850 ℃, a holding time of 4~6 h, and a pressure of 20~40 MPa.

9. The preparation method according to claim 4, characterized in that, After the hot pressing and sintering described in step S4 is completed, a controlled cooling process is performed.

10. The preparation method according to claim 9, characterized in that, The conditions for the controlled cooling process include controlled cooling at a rate of 30 °C / min within a temperature range of 1000 to 1850 °C.