Aluminum titanate composite ceramic material with low thermal expansion coefficient and preparation method thereof

Abstract

The invention discloses an aluminum titanate composite ceramic material with a low thermal expansion coefficient. The aluminum titanate composite ceramic material comprises the following components in percentage by mass: 75-85% of an aluminum titanate base material, 10-20% of synthetic mullite and 0-5% of a sintering aid. Wherein the crystal phase of the aluminum titanate base material is an Al2 (Ti < 1-x > Ce < x >) phase, and x is 0.08-0.12. The invention further discloses a preparation method of the aluminum titanate composite ceramic material with the low thermal expansion coefficient, cerium ions exist in crystal lattices in a solid solution form through the synergistic effect of the raw materials and a sintering process, and a three-dimensional bridging structure is formed by the synthesized mullite and an Al2 (Ti1-xCex) phase of an aluminum titanate base material. According to the invention, the decomposition of aluminum titanate is inhibited, the excellent low thermal expansion characteristic of the material is maintained, and the thermal shock resistance is enhanced, so that the linear expansion coefficient of the composite ceramic material at 20-1000 DEG C is less than 1.0 * 10 <-6 > / DEG C, and the thermal shock resistance cycle index is more than or equal to 30 times. The method is high in process controllability and suitable for manufacturing high-temperature-resistant thermal shock devices.

Description

Technical Field

[0001] The present invention relates to the field of high-temperature structural ceramic materials, and in particular to an aluminum titanate composite ceramic material with a low thermal expansion coefficient and a preparation method thereof. Background Art

[0002] Aluminum titanate (Al2TiO5) has an ultra-low thermal expansion coefficient (α=0.5-1.5×10 -6 / °C, 20-1000°C) and excellent thermal shock resistance make it irreplaceable in extreme operating conditions such as high-temperature thermal barrier coatings and internal combustion engine exhaust purifier substrates. However, this material undergoes irreversible phase decomposition (Al2TiO5 → Al2O3 + TiO2) when used for a long time at temperatures above 800°C, resulting in a strength drop of over 50%, severely limiting its engineering applications.

[0003] The existing technology mainly uses Mg doping 2+ 、Fe 3+ Low-valent ions replace Al 3+ To inhibit decomposition, this method has the following significant drawbacks: (1) The introduction of additives such as MgO will increase the thermal expansion coefficient of the material, α≥2.0×10 -6 / ℃, losing the low thermal expansion characteristics; (2) secondary phases such as magnesium aluminum spinel (MgAl2O4) are formed at high temperature, reducing the purity of the material (XRD detection shows that the proportion of impurity phase is >8%); (3) the ion solubility is limited (<5mol%), and deep stabilization cannot be achieved.

[0004] In summary, the existing technology is not effective in inhibiting the decomposition of aluminum titanate and cannot maintain the low thermal expansion performance of the material. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the existing technology, the present invention addresses the technical bottlenecks of high-temperature phase decomposition of aluminum titanate materials and increased thermal expansion coefficient caused by traditional doping processes, and proposes a synergistic stabilization strategy based on cerium oxide lattice engineering and mullite gradient composite.

[0006] The technical solution adopted by the present invention is as follows: a low thermal expansion coefficient aluminum titanate composite ceramic material, which comprises, by mass percentage, 75%-85% of an aluminum titanate base material, 10%-20% of synthetic mullite, and 0-5% of a sintering aid; wherein the aluminum titanate base material comprises aluminum oxide, titanium dioxide, and cerium oxide, and the molar ratio of the three is Al2O3:TiO2:CeO2=(8.3-12.5):(7.3-11.5):1; the crystal phase of the aluminum titanate base material is Al2(TiO2) 1-x Ce x ) phase, x=0.08-0.12.

[0007] Furthermore, the aluminum titanate base material is obtained by the following preparation method: nano-alumina with a particle size of 10-50 nm, rutile titanium dioxide with a particle size of 0.2-1 μm, and cerium oxide are mixed in a molar ratio; the mixed powder is subjected to high-energy ball milling to reduce the particle size to ≤1 μm; after ball milling, it is dry-pressed into a green body, and the temperature is raised to 1350°C-1400°C at 3-5°C / min under an argon atmosphere to carry out an in-situ solid solution reaction to obtain the aluminum titanate base material. In some preferred embodiments, zirconium oxide balls are used as the grinding medium (ball-to-material ratio 4-5:1), the mixture is ball milled in anhydrous ethanol for 6-12 hours, and the green body is dry-pressed under a pressure of 50-100 MPa.

[0008] Preferably, the particle size of the aluminum titanate base material is 2-5 μm; and the particle size of the synthetic mullite is 5-15 μm.

[0009] Preferably, the specific surface area of ​​the cerium oxide is ≥50m 2 / g.

[0010] Furthermore, the sintering aid comprises 1-3% MgO, 1-2% ZnO, and 1-2% Fe2O3. Preferably, the particle size of the sintering aid is 0.5-2 μm.

[0011] In some preferred embodiments, the synthetic mullite comprises kaolin and α-Al2O3, which are mixed in a molar ratio of Al2O3 / SiO2=3:2, and the Al2O3 in the kaolin is ≥38wt%.

[0012] The present invention also provides a method for preparing a low thermal expansion coefficient aluminum titanate composite ceramic material, comprising the following steps:

[0013] Step 1, preparing the aluminum titanate base material;

[0014] Step 2: ball-mill the aluminum titanate base material and synthetic mullite, spray-dry and dry-press to form, and then perform gradient sintering; the gradient sintering includes a pre-sintering stage and a final sintering stage; the pre-sintering stage is in an oxygen / argon mixed atmosphere, with an oxygen volume proportion of 5-10%, and the temperature is increased at a rate of 2-3°C / min to 950°C-1000°C and kept for 1 hour; the final sintering stage is to heat to 1450°C-1550°C in argon and sinter for 1-3 hours, with a heating rate of 2-3°C / min.

[0015] In some preferred embodiments, a sintering aid is added to the aluminum titanate base material and synthetic mullite for ball milling in step 2. The sintering aid is a mixture of MgO, ZnO, and Fe2O3. Preferably, a planetary ball mill is used, polycarboxylate ammonium is used as a dispersant, a ball-to-material ratio of 3-4:1, and wet mixing is performed for 2-4 hours.

[0016] Preferably, the inlet temperature of the spray drying in step 2 is 180-220° C., and the atomization pressure is 0.3-0.5 MPa; after dry pressing at a pressure of 100-200 MPa, cold isostatic pressing is performed, with a cold isostatic pressing parameter of 200-300 MPa and a holding pressure of 3-5 minutes.

[0017] Beneficial effect: The present invention induces lattice distortion by in-situ doping with cerium oxide to form a stable Al2(Ti 1-x Ce x )O5 solid solution phase, and then introduce synthetic mullite combined with gradient sintering process to form a three-dimensional bridge structure, which solves the limitation of low solid solubility, adds higher concentration of cerium oxide, forms a deeper stable phase, and enhances the high temperature stability of the material

[0018] (1) The aluminum titanate composite ceramic material obtained by the present invention has a linear expansion coefficient of 0.65×10 -6 / ℃~0.72×10 -6 By adjusting the mullite content and the amount of cerium oxide doped in the aluminum titanate matrix, the average thermal expansion coefficient of the composite ceramic material at 20-1000℃ changes gradually (Δα≤0.3×10 -6 / ℃), and finally achieve overall α≤1.0×10 -6 / ℃.

[0019] (2) The aluminum titanate composite ceramic material obtained by the present invention has a thermal shock resistance of ≥30 cycles without cracking ( Water quenching), stabilizes the aluminum titanate lattice structure and inhibits high-temperature decomposition.

[0020] (3) Crack deflection strengthening mechanism: Micron mullite particles induce crack bifurcation during thermal shock, increasing the number of thermal shock resistance cycles to more than 30 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a SEM image of an embodiment of the present application.

[0022] Figure 2 This is the XRD spectrum of Example 1 of the present application after water quenching. After water quenching, the solid solution phase is still maintained and Al2O3 and TiO2 are not decomposed.

[0023] Figure 3 This is the XRD spectrum of comparative example 1 of the present application after water quenching. Al2O3 and TiO2 are decomposed after water quenching. DETAILED DESCRIPTION

[0024] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0025] It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0026] The materials used in the present invention include aluminum titanate base material and synthetic mullite, and the preparation of the two is as follows:

[0027] (A) Aluminum titanate base material

[0028] Nano-alumina with a particle size of 10-50 nm, rutile titanium dioxide with a particle size of 0.2-1 μm, and cerium oxide are mixed in a molar ratio of Al2O3:TiO2:CeO2 = (8.3-12.5):(7.3-11.5):1. High-energy ball milling is used to achieve uniform nanoscale dispersion, yielding a mixed powder with a particle size D50 less than 1 μm. This powder is then dry-pressed under a pressure of 50-100 MPa to form a green body. High-energy ball milling parameters include: zirconia balls, a ball-to-material ratio of 4-5:1, anhydrous ethanol as the medium, milling for 6-12 hours, and a rotation speed of 300 rpm.

[0029] The green body is sintered at high temperature for in-situ solid solution reaction: the temperature is raised to 1350-1400℃ at 3-5℃ / min in argon atmosphere, kept at this temperature for 3 hours and then crushed to D50 of 2-5μm to obtain cerium ion doped aluminum titanate base material. 4+ The substitutional solid solution induces lattice distortion, and the cerium ions exist in the lattice in the form of solid solution to form a stable Al2(Ti 1-x Ce x )O5 solid solution phase, where x represents the substitution amount, x = 0.08-0.12. When the substitution amount is less than 0.08, the obtained composite ceramic material is easy to decompose and the thermal shock resistance is less than 5 times. The thermal shock resistance test is carried out using Water quenching. There are also reports on the use of cerium oxide to modify aluminum titanate, but the solid solubility is low and there is no significant improvement in the thermal stability of the material.

[0030] In one preferred embodiment, the specific surface area is greater than or equal to 50m 2 / g of cerium oxide. If the specific surface area is less than 50m 2 / g of cerium oxide, its reaction activity is slightly poor, and its replacement amount and specific surface area are greater than or equal to 50m 2 / g is relatively low.

[0031] (B) Synthetic mullite

[0032] Kaolin containing ≥38 wt% Al2O3 is mixed with α-Al2O3 in a molar ratio of Al2O3 / SiO2 of 3:2. The mixture is calcined in air at 1500-1550°C for 2-4 hours and crushed and sieved to a size of 5-15 μm. The resulting micron-sized mullite particles induce crack bifurcation during thermal shock, improving the thermal shock resistance of the composite ceramic material.

[0033] The method for preparing aluminum titanate composite ceramic material of the present invention is as follows: aluminum titanate base material and synthetic mullite are subjected to high-energy ball milling, spray drying and granulation, dry pressing and gradient sintering. This process promotes the Al2(Ti 1-x Ce x )O5 solid solution phase forms a three-dimensional bridge structure, further improving the high-temperature stability of aluminum titanate. In some preferred embodiments, sintering aids can also be added to perform ball milling, granulation and gradient sintering.

[0034] More specifically, gradient sintering includes a pre-firing stage and a final sintering stage; in the pre-firing stage, in an oxygen / argon mixed atmosphere, the oxygen volume accounts for 5-10%, and the temperature is increased at a rate of 2-3°C / min to 950°C-1000°C and kept warm for 1 hour; then the temperature is increased to 1450°C-1550°C in argon and sintered for 1-3 hours, with a heating rate of 2-3°C / min.

[0035] Preferably, the parameters of spray drying granulation are set as follows: inlet temperature 180-220°C, atomization pressure 0.3-0.5 MPa, to obtain granulated powder with fluidity ≥30s / 50g; dry pressing at a pressure of 100-200 MPa, followed by cold isostatic pressing, with a cold isostatic pressing parameter of 200-300 MPa and holding pressure for 3-5 minutes.

[0036] Example 1 provides an aluminum titanate composite ceramic material with a low thermal expansion coefficient, the raw material ratio of which (in mass percentage) is as follows: aluminum titanate base material (D50 = 3.2 μm) accounts for 75% of the total mass, synthetic mullite (Al2O3 / SiO2 = 3:2, D50 = 10 μm) accounts for 20% of the total mass, and a sintering aid accounting for 5% of the total mass is taken, more specifically MgO 1.5%, ZnO 1.5%, and Fe2O32%.

[0037] The preparation process of this embodiment includes the following steps:

[0038] First, prepare aluminum titanate base material. The raw materials are: nano-Al2O3 (particle size 30nm), rutile TiO2 (particle size 0.5μm), CeO2 (specific surface area 60m 2 / g) and mixed in a molar ratio of Al2O3:TiO2:CeO2 = 12.5:11.5:1. These raw materials were ball-milled in an anhydrous ethanol medium using zirconia balls (ball-to-material ratio of 5:1) for 8 hours to obtain a powder with a particle size D50 = 0.8 μm. This powder was then dry-pressed under a pressure of 50-100 MPa to form a green body. The green body was sintered in an argon atmosphere at a rate of 4°C / min to 1380°C and held for 3 hours. This yielded a cerium-doped aluminum titanate base material. Calculations indicate that the cerium substitution in the aluminum titanate base material ranges from 0.08% to 0.12%.

[0039] Next, aluminum titanate base material, synthetic mullite, and sintering aids were added to a planetary ball mill for mixing and granulation. Ammonium polycarboxylate was used as a dispersant, with a ball-to-material ratio of 3:1. The mixture was wet-mixed for 3 hours, spray-dried, and then dry-pressed. The spray drying inlet temperature was 200°C, the atomization pressure was 0.4 MPa, and the granulated powder flowability was 32 seconds per 50 grams. The dry pressing pressure was 150 MPa, and the cold isostatic pressing was performed at 250 MPa for 4 minutes.

[0040] The composite ceramic material of the present invention was then produced using a gradient sintering process, including a pre-firing stage and a final sintering stage. The pre-firing stage involved heating in an oxygen / argon (O28%) atmosphere at 2°C / min to 950°C and holding for 1 hour. The pre-firing stage produced a residual carbon content of 0.08 wt%. The final sintering stage involved heating in a pure argon atmosphere at 3°C / min to 1480°C and holding for 2.5 hours. The resulting aluminum titanate composite ceramic material had a relative density of 98.5% (measured using the Archimedean method).

[0041] Performance test: thermal expansion coefficient (20-1000℃) is 0.72×10 -6 / ℃; Thermal shock resistance: There is no cracking after 30 water quenchings, and the strength retention rate is 93.3%.

[0042] Example 2 provides an aluminum titanate composite ceramic material with a low thermal expansion coefficient, the raw material ratio of which (in mass percentage) is: aluminum titanate base material (D50 = 4.5 μm) accounts for 80% of the total mass, synthetic mullite (Al2O3 / SiO2 = 3:2, D50 = 12 μm) accounts for 15% of the total mass, and a sintering aid accounting for 5% of the total mass is taken, more specifically 2% MgO, 2% ZnO and 1% Fe2O3.

[0043] The preparation process of this embodiment includes the following steps:

[0044] First, prepare aluminum titanate base material. The raw materials are: nano-Al2O3 (particle size 50nm), rutile TiO2 (particle size 0.8μm), CeO2 (specific surface area 70m 2 / g) and mixed in a molar ratio of Al2O3:TiO2:CeO2 = 10:9:1. These raw materials were ball-milled in an anhydrous ethanol medium using zirconia balls (ball-to-material ratio of 5:1) for 10 hours to obtain a powder with a particle size D50 = 0.6 μm. This powder was then dry-pressed under a pressure of 50-100 MPa to form a green body. The green body was sintered in an argon atmosphere at a rate of 5°C / min to 1400°C and held for 3 hours. This yielded a cerium-doped aluminum titanate matrix. Calculations indicate that the cerium substitution in the aluminum titanate matrix ranges from 0.08% to 0.12%.

[0045] Next, aluminum titanate base material, synthetic mullite, and sintering aids were added to a planetary ball mill for mixing and granulation. Ammonium polycarboxylate was used as a dispersant, with a ball-to-material ratio of 3:1. The mixture was wet-mixed for 4 hours, spray-dried, and then dry-pressed. The spray drying inlet temperature was 200°C, the atomization pressure was 0.5 MPa, and the granulated powder flowability was 32 seconds per 50 grams. The dry pressing pressure was 180 MPa, and the cold isostatic pressing was performed at 300 MPa for 5 minutes.

[0046] The composite ceramic material of the present invention was then produced using a gradient sintering process, including a pre-sintering stage and a final sintering stage. The pre-sintering stage involved heating in an oxygen / argon (O2 10%) atmosphere at 3°C / min to 1000°C and holding for 1 hour. The final sintering stage involved heating in a pure argon atmosphere at 3°C / min to 1550°C and holding for 1 hour. This resulted in an aluminum titanate composite ceramic material.

[0047] Performance test: thermal expansion coefficient (20-1000℃) is 0.68×10 -6 / ℃; Thermal shock resistance: There is no cracking after 35 water quenchings, the strength retention rate is 91.7%; the relative density is 99.1% (tested by the Archimedes method).

[0048] Example 3 provides an aluminum titanate composite ceramic material with a low thermal expansion coefficient, the raw material ratio of which (in mass percentage) is: aluminum titanate base material (D50 = 3.8 μm) accounts for 85% of the total mass, synthetic mullite (Al2O3 / SiO2 = 3:2, D50 = 8 μm) accounts for 10% of the total mass, and a sintering aid accounting for 5% of the total mass is taken, more specifically 2.2% MgO, 1.8% ZnO and 1% Fe2O3.

[0049] The preparation process of this embodiment includes the following steps:

[0050] First, prepare aluminum titanate base material. The raw materials are: nano-Al2O3 (particle size 40nm), rutile TiO2 (particle size 0.6μm), CeO2 (specific surface area 80m 2 / g) and mixed in a molar ratio of Al2O3:TiO2:CeO2 = 8.3:7.3:1. These raw materials were ball-milled in an anhydrous ethanol medium using zirconia balls (ball-to-material ratio 4:1) for 7 hours to obtain a powder with a particle size D50 = 0.7 μm. This powder was then dry-pressed under a pressure of 50-100 MPa to form a green body. The green body was sintered in an argon atmosphere at a rate of 3.5°C / min to 1370°C and held for 3 hours. This yielded a cerium-doped aluminum titanate matrix. Calculations indicate that the cerium substitution in the aluminum titanate matrix ranges from 0.08% to 0.12%.

[0051] Next, aluminum titanate base material, synthetic mullite, and sintering aids were added to a planetary ball mill for mixing and granulation. Ammonium polycarboxylate was used as a dispersant, with a ball-to-material ratio of 3:1. The mixture was wet-mixed for 3.5 hours, spray-dried, and then dry-pressed. The spray drying inlet temperature was 210°C, the atomization pressure was 0.45 MPa, and the granulated powder flowability was 35 seconds per 50 grams. The dry pressing pressure was 170 MPa, and the cold isostatic pressing was performed at 280 MPa for 4.5 minutes.

[0052] The composite ceramic material of the present invention was then produced using a gradient sintering process, including a pre-sintering stage and a final sintering stage. The pre-sintering stage involved heating in an oxygen / argon (O27%) atmosphere at 2.5°C / min to 980°C and holding for 1 hour. The final sintering stage involved heating in a pure argon atmosphere at 2.8°C / min to 1500°C and holding for 2 hours. This resulted in an aluminum titanate composite ceramic material.

[0053] Performance test: thermal expansion coefficient (20-1000℃) is 0.65×10 -6 / ℃; Thermal shock resistance: After 41 water quenching cycles, there was no cracking, the strength retention rate was 89.1%, and the relative density was 98.8% (tested using the Archimedes method).

[0054] Example 4 (No Sintering Aid Added) provides a low thermal expansion coefficient aluminum titanate composite ceramic material. The raw material ratio (by mass percentage) is as follows: aluminum titanate base material (D50 = 3.8 μm) accounts for 85% of the total mass, and synthetic mullite (Al2O3 / SiO2 = 3:2, D50 = 8 μm) accounts for 15% of the total mass. No sintering aid is added in this example.

[0055] The preparation process of this embodiment includes the following steps:

[0056] First, prepare aluminum titanate base material. The raw materials are: nano-Al2O3 (particle size 40nm), rutile TiO2 (particle size 0.6μm), CeO2 (specific surface area 80m 2 / g) and mixed in a molar ratio of Al2O3:TiO2:CeO2 = 8.3:7.3:1. These raw materials were ball-milled in an anhydrous ethanol medium using zirconia balls (ball-to-material ratio 4:1) for 7 hours to obtain a powder with a particle size D50 = 0.7 μm. This powder was then dry-pressed under a pressure of 50-100 MPa to form a green body. The green body was sintered in an argon atmosphere at a rate of 3.5°C / min to 1370°C and held for 3 hours. This yielded a cerium-doped aluminum titanate matrix. Calculations indicate that the cerium substitution in the aluminum titanate matrix ranges from 0.08% to 0.12%.

[0057] Next, the aluminum titanate base material and synthetic mullite were added to a planetary ball mill for granulation. Ammonium polycarboxylate was used as a dispersant, with a ball-to-material ratio of 3:1. The mixture was wet-mixed for 3.5 hours, spray-dried, and then dry-pressed. The spray drying inlet temperature was 210°C, the atomization pressure was 0.45 MPa, and the granulated powder flowability was 35 seconds per 50 grams. The dry pressing pressure was 170 MPa, and the cold isostatic pressing was performed at 280 MPa for 4.5 minutes.

[0058] The composite ceramic material of the present invention was then produced using a gradient sintering process, including a pre-firing stage and a final firing stage. The pre-firing stage involved heating in an oxygen / argon (O27%) atmosphere at 2.5°C / min to 980°C and holding for 1 hour. The final firing stage involved heating in a pure argon atmosphere at 2.8°C / min to 1500°C and holding for 2 hours. The resulting aluminum titanate composite ceramic material had a relative density of 95.8% (measured using the Archimedean method).

[0059] Performance test: thermal expansion coefficient (20-1000℃) is 0.68×10 -6 / ℃; Thermal shock resistance: There was no cracking after 33 water quenchings, and the strength retention rate was 87.2%.

[0060] By comparing Example 3 with Example 4, the present invention has a lower thermal expansion coefficient without adding a sintering aid, and the number of thermal shock resistance cycles exceeds 30 times.

[0061] Comparative Example 1 employed a one-step sintering method. The raw material ratios were the same as in Example 1: 75% by mass of the aluminum titanate base material (D50 = 3.2 μm), 20% by mass of the synthetic mullite (Al2O3 / SiO2 = 3:2, D50 = 10 μm), and 5% by mass of the sintering aid, specifically 1.5% MgO, 1.5% ZnO, and 2% Fe2O3.

[0062] The preparation process of this embodiment includes the following steps:

[0063] First, prepare aluminum titanate base material. The raw materials are: nano-Al2O3 (particle size 30nm), rutile TiO2 (particle size 0.5μm), CeO2 (specific surface area 60m 2 / g) and mixed in a molar ratio of Al2O3:TiO2:CeO2 = 12.5:11.5:1. These raw materials were ball-milled in an apparatus using zirconium oxide balls (ball-to-material ratio of 5:1) and anhydrous ethanol for 8 hours to obtain a powder with a particle size D50 = 0.8 μm. This powder was dry-pressed under a pressure of 50-100 MPa to form a green body. The green body was sintered in an argon atmosphere at a rate of 4°C / min to 1380°C and held for 3 hours. This yielded a cerium-doped aluminum titanate base material.

[0064] Next, aluminum titanate base material, synthetic mullite, and sintering aids were added to a planetary ball mill for mixing and granulation. Ammonium polycarboxylate was used as a dispersant, with a ball-to-material ratio of 3:1. The mixture was wet-mixed for 3 hours, spray-dried, and then dry-pressed. The spray drying inlet temperature was 200°C, the atomization pressure was 0.4 MPa, and the granulated powder flowability was 32 seconds per 50 grams. The dry pressing pressure was 150 MPa, and the cold isostatic pressing was performed at 250 MPa for 4 minutes.

[0065] Then, the sintering was carried out using a one-step sintering method. In a pure argon protective atmosphere, the temperature was raised at 3°C / min to 1480°C and held for 2.5 hours to obtain an aluminum titanate composite ceramic material with a relative density of 93.5% (measured by the Archimedean method).

[0066] Performance test: thermal expansion coefficient (20-1000℃) is 0.71×10 -6 / ℃; Thermal shock resistance: There was no cracking after 24 water quenchings, and the strength retention rate was 86.1%.

[0067] Figure 1 This is the SEM picture of the embodiment of the present application, synthesizing mullite and Al2(Ti 1-x Ce x )O5 solid solution phase forms a bridging structure.

[0068] Figure 2 This is the XRD spectrum of Example 1 after water quenching. After water quenching, the solid solution phase (indicated by AT in the figure) is still maintained, and Al2O3 and TiO2 are not decomposed. Figure 3 The XRD spectrum of Example 1 after water quenching shows that Al2O3 and TiO2 are decomposed after water quenching. From the XRD results of Example 1 and Comparative Example 1, it is obvious that the gradient sintering process in the present invention can improve the thermal stability of aluminum titanate and further inhibit its decomposition.

[0069] During the research and development process, the inventors also found that only adding cerium oxide modification without adding synthetic mullite, during the thermal shock resistance test, Microcracks appeared after about 10 water quenchings, which had a certain effect on inhibiting the decomposition of aluminum titanate, but the effect was not as good as the combined effect of cerium oxide and synthetic mullite. Moreover, compared with the case of mixing cerium oxide, mullite and aluminum titanate simultaneously, the present invention first added cerium oxide to complete the replacement solid solution and then added synthetic mullite, resulting in a composite ceramic material with better thermal stability.

[0070] The present invention induces lattice distortion by in-situ doping with cerium oxide to form a stable Al2(Ti 1-x Ce x )O5 solid solution phase; then introduce synthetic mullite, adjust the ratio of synthetic mullite and aluminum titanate base material, especially the doping amount of cerium oxide, and combine with gradient sintering process to promote the synthesis of synthetic mullite and Al2(Ti 1-x Ce x )O5 solid solution phase forms a three-dimensional bridging structure, further increasing the high-temperature stability of aluminum titanate. At the same time, the three-dimensional bridging structure solves the limitation of low solid solubility. The addition of higher concentration of cerium oxide forms a deeper stable phase, enhancing the high-temperature stability of the material, and ultimately making the average thermal expansion coefficient gradient change of aluminum titanate composite ceramic material at 20-1000℃ Δα≤0.3×10 -6 / ℃, the overall thermal expansion coefficient is less than 1.0×10 -6 / ℃.

[0071] On the other hand, the micron-sized synthetic mullite particles used induce crack bifurcation during the thermal shock process, generating a crack deflection strengthening mechanism, which increases the number of thermal shock cycles to more than 30 times without cracking, stabilizes the aluminum titanate lattice structure of the present invention, and inhibits high-temperature decomposition.

[0072] The above description is merely a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of protection of the present invention.

Claims

1. A low thermal expansion coefficient aluminum titanate composite ceramic material, characterized in that: The invention relates to a sintering agent comprising 75% to 85% of an aluminum titanate base material, 10% to 20% of synthetic mullite, and 0% to 5% of a sintering aid, wherein the aluminum titanate base material comprises aluminum oxide, titanium dioxide, and cerium oxide, and the molar ratio of the three is Al2O3:TiO2:CeO2=(8.3-12.5):(7.3-11.5):1; the crystal phase of the aluminum titanate base material is Al2(TiO2) 1-x Ce x ) phase, x=0.08-0.

12.

2. The low thermal expansion coefficient aluminum titanate composite ceramic material according to claim 1, characterized in that: The aluminum titanate base material is obtained by the following preparation method: nano-alumina with a particle size of 10-50nm, rutile titanium dioxide with a particle size of 0.2-1μm, and cerium oxide are mixed in a molar ratio; the mixed powder is subjected to high-energy ball milling to make its particle size ≤1μm; after ball milling, it is dry-pressed into a green body, and the temperature is raised to 1350°C-1400°C at 3-5°C / min in an argon atmosphere to carry out an in-situ solid solution reaction to obtain the aluminum titanate base material.

3. The low thermal expansion coefficient aluminum titanate composite ceramic material according to claim 1, characterized in that: The particle size of the aluminum titanate base material is 2-5 μm; the particle size of the synthetic mullite is 5-15 μm.

4. The low thermal expansion coefficient aluminum titanate composite ceramic material according to claim 1, characterized in that: The specific surface area of ​​cerium oxide is ≥50m 2 / g.

5. The low thermal expansion coefficient aluminum titanate composite ceramic material according to claim 1, characterized in that: The sintering aid comprises 1-3% MgO, 1-2% ZnO, and 1-2% Fe2O3.

6. The low thermal expansion coefficient aluminum titanate composite ceramic material according to claim 5, characterized in that: The particle size of the sintering aid is 0.5-2 μm.

7. The low thermal expansion coefficient aluminum titanate composite ceramic material according to claim 1, characterized in that: The synthetic mullite comprises kaolin and α-Al2O3, which are mixed in a molar ratio of Al2O3 / SiO2=3:2, and the Al2O3 in the kaolin is ≥38wt%.

8. A method for preparing a low thermal expansion coefficient aluminum titanate composite ceramic material according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, preparing the aluminum titanate base material according to claim 1; Step 2: ball-mill the aluminum titanate base material and synthetic mullite, spray-dry and dry-press to form, and then perform gradient sintering; the gradient sintering includes a pre-sintering stage and a final sintering stage; the pre-sintering stage is in an oxygen / argon mixed atmosphere, with an oxygen volume proportion of 5-10%, and the temperature is increased at a rate of 2-3°C / min to 950°C-1000°C and kept for 1 hour; the final sintering stage is to heat to 1450°C-1550°C in argon and sinter for 1-3 hours, with a heating rate of 2-3°C / min.

9. The method for preparing a low thermal expansion coefficient aluminum titanate composite ceramic material according to claim 8, characterized in that: In step 2, a sintering aid is added to the aluminum titanate base material and the synthetic mullite for ball milling, and the sintering aid is a mixture of MgO, ZnO and Fe2O3.

10. The method for preparing a low thermal expansion coefficient aluminum titanate composite ceramic material according to claim 8, characterized in that: The inlet temperature of the spray drying in step 2 is 180-220° C., and the atomization pressure is 0.3-0.5 MPa. After dry pressing at a pressure of 100-200 MPa, cold isostatic pressing is performed, with a cold isostatic pressing parameter of 200-300 MPa and a pressure holding time of 3-5 minutes.

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