Composite thermal insulation ceramic and preparation method and application thereof

Abstract

The application belongs to the technical field of refractory materials, and discloses a composite heat-insulating ceramic as well as a preparation method and application thereof. 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy ceramic, and the functional composite layer is corundum and mullite, the method is that high-entropy powder, active alumina, silicon dioxide and deionized water are mixed and cast to form an anti-corrosion layer green body; corundum particles, alumina powder, alumina hollow spheres, mullite, kaolin, silicon dioxide, sodium silicate, active alumina, calcium aluminate cement and wood fibers are added into deionized water, and then cast and solidified on the anti-corrosion layer green body to be formed, and then sintered at 1500-1700 DEG C to obtain the composite heat-insulating ceramic. The composite heat-insulating ceramic has excellent comprehensive properties such as low thermal conductivity, high strength, high thermal shock resistance and high-temperature corrosion resistance, and can be applied to the field of gas turbine combustion chambers.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, and more specifically, relates to a composite heat-insulating ceramic, its preparation method and application. Background Technology

[0002] A gas turbine mainly consists of an axial compressor, a combustion chamber, a turbine, and a control and protection system. The combustion chamber and turbine are the hot-end components of the gas turbine. In heavy-duty gas turbines, the metal casing of the combustion chamber, which is in the highest temperature range, is not resistant to high temperatures and is usually protected by high-temperature resistant ceramic insulation materials.

[0003] The performance and service behavior of insulating ceramics have a decisive impact on the safe and efficient operation of gas turbines. Under the interaction of high-temperature gas, solid, and liquid components, insulating materials are subjected to thermal, mechanical, and chemical shocks and losses. Ceramic insulating materials have a relatively short high-temperature service life and are prone to failures such as thermal shock damage, erosion, structural damage, and functional degradation. Currently, insulating ceramics struggle to meet the requirements of thermomechanical performance and thermal shock resistance while simultaneously reducing thermal conductivity. Therefore, there is an urgent need to develop new insulating ceramic materials with excellent comprehensive properties, including low thermal conductivity, high strength, high thermal shock resistance, and resistance to high-temperature corrosion. Summary of the Invention

[0004] To address the aforementioned technical problems, the primary objective of this invention is to provide a composite thermal insulation ceramic. This ceramic possesses excellent comprehensive properties, including low thermal conductivity, high strength, high thermal shock resistance, and resistance to high-temperature corrosion.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned composite thermal insulation ceramic.

[0006] Another object of the present invention is to provide the application of the above-mentioned composite thermal insulation ceramic.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A composite thermal insulation ceramic comprises an anti-corrosion layer and a functional composite layer, wherein the anti-corrosion layer is composed of mullite and (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 The high-entropy ceramic is 2Ce2O7, wherein the functional composite layer is corundum and mullite, and the anti-corrosion layer is in direct contact with the hot surface.

[0009] Preferably, the composite thermal insulation ceramic has an apparent porosity of 13-20%, a thermal conductivity of 0.8-2 W / mK, and a flexural strength of 14-18 MPa; the thickness of the anti-corrosion layer is 0.5-1 mm.

[0010] Preferably, the anti-corrosion layer is prepared by mixing La2O3 powder, Y2O3 powder, Yb2O3 powder, Ho2O3 powder, Er2O3 powder, and CeO2 powder in a stoichiometric ratio and then preparing a single-phase (La2O3) coating at 1450-1650°C. 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy powder is prepared by mixing the high-entropy powder, activated alumina, silicon dioxide and deionized water, casting it into a mold, and sintering it at 1500~1700℃.

[0011] More preferably, the particle size of the La2O3 powder, Y2O3 powder, Yb2O3 powder, Ho2O3 powder, Er2O3 powder and CeO2 powder is 0.1~0.4 µm; the mass ratio of the high-entropy powder, activated alumina and silica is (90~96):(3~7):(1~3).

[0012] Preferably, the functional composite layer is prepared by adding a mixture of corundum particles, alumina powder, hollow alumina spheres, mullite, kaolin, silica, sodium silicate, activated alumina, calcium aluminate cement, and wood fiber to deionized water, casting and solidifying the mixture, and sintering it at 1500~1700℃.

[0013] Preferably, the corundum particles constitute 20-50 wt% of the mixed powder, the alumina powder constitutes 20-35 wt% of the mixed powder, the hollow alumina spheres constitute 3-6 wt% of the mixed powder, the mullite constitutes 25-50 wt% of the mixed powder, the kaolin constitutes 3-6 wt% of the mixed powder, the silica constitutes 1-5 wt% of the mixed powder, the sodium silicate constitutes 0.2-0.6 wt% of the mixed powder, the activated alumina constitutes 1-5 wt% of the mixed powder, the calcium aluminate cement constitutes 1-5 wt% of the mixed powder, and the wood fiber constitutes 2-6 wt% of the mixed powder.

[0014] Preferably, the corundum particles have a particle size of 0.2~4mm, including particles with a particle size of 0.2~0.8mm, 1~2mm, and 3~4mm; the alumina powder has a particle size of 0.5~1µm; the hollow alumina spheres have a particle size of 1~2mm; the mullite has a particle size of 0.5mm~100µm, including particles with a particle size of 0.5~1mm, 50~100µm, and 100~500µm; and the wood fibers have a length of 25~100µm.

[0015] More preferably, the corundum particles with a particle size of 3-4 mm account for 5-10 wt% of the mixed powder, the corundum particles with a particle size of 1-2 mm account for 5-20 wt% of the mixed powder, and the corundum particles with a particle size of 0.2-0.8 mm account for 10-20 wt% of the mixed powder; the mullite particles with a particle size of 0.5-1 mm account for 5-10 wt% of the mixed powder, the mullite particles with a particle size of 100-500 µm account for 10-20 wt% of the mixed powder, and the mullite particles with a particle size of 50-100 µm account for 10-20 wt% of the mixed powder.

[0016] The preparation method of the composite thermal insulation ceramic includes the following steps:

[0017] S1. Mix La2O3 powder, Y2O3 powder, Yb2O3 powder, Ho2O3 powder, Er2O3 powder, and CeO2 powder according to (La 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 (La) is prepared by mixing 2Ce2O7 in stoichiometric ratio and heating at 1450~1650℃. 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy powder;

[0018] S2. The above-mentioned high-entropy powder, activated alumina and silica are added to deionized water and mixed, then cast into a mold to obtain a corrosion-resistant layer blank.

[0019] S3. Add corundum particles, alumina powder, hollow alumina spheres, mullite, kaolin, silica, sodium silicate, activated alumina, calcium aluminate cement, and wood fiber to deionized water and mix evenly. Pour the mixture onto the corrosion-resistant green body and solidify it. Sinter at 1500~1700℃ for 2~5 hours to obtain composite heat-insulating ceramic.

[0020] The application of the composite thermal insulation ceramic in the field of gas turbine combustion chambers.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention uses mullite and (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2The high-entropy ceramic composite of A₂Ce₂O₇ serves as the contact surface for the hot-faced structure. The reaction between activated alumina and silica generates mullite, which exhibits excellent thermal shock resistance, thus enhancing the thermal shock resistance of the composite insulating ceramic. Due to the corrosion-resistant properties of Y, Yb, Ho, and Er compounds, A₂Ce₂O₇ pyrochlore-type oxides possess low thermal conductivity and excellent thermal insulation properties; furthermore, La… 3+ Y with a larger ionic radius and a smaller ionic radius 3+ Yb 3+ Ho 3+ Er 3+ Through high-entropy doping, the interionic spacing of high-entropy ceramics is reduced, the lattice energy is increased, and the coefficient of thermal expansion is lowered. Compared with mullite, which has a lower coefficient of thermal expansion, it has better thermal shock resistance. At the same time, due to the high-entropy effect, lattice distortion effect, hysteresis diffusion effect, and "cocktail" effect, high-entropy ceramics have higher mechanical strength, excellent fracture toughness, higher chemical stability and thermal stability, and lower thermal conductivity, which significantly improves the mechanical and thermal insulation properties of composite thermal insulation ceramics.

[0023] This invention combines corundum particles, hollow alumina spheres, and mullite. The corundum particles enhance the mechanical strength of the composite insulating ceramic, while the hollow alumina spheres, with their slow heat transfer, provide excellent insulation. Mullite, possessing superior thermal shock resistance, further improves the thermal shock resistance of the composite insulating ceramic. Furthermore, the addition of a small amount of sodium silicate serves two purposes: firstly, sodium silicate and calcium aluminate cement act as excellent refractory binders, increasing the strength of the green body after molding and promoting bonding between the matrix (fine powder, excluding large particles) and the larger particles (alumina and mullite) during high-temperature sintering; secondly, sodium silicate promotes the in-situ synthesis of mullite whiskers from kaolin, silica, and activated alumina. The whisker pull-out and crack bridging mechanisms enhance and toughen the composite insulating ceramic. The introduction of an appropriate amount of wood fiber ensures the apparent porosity of the composite insulating ceramic while simultaneously preventing crack propagation and reducing thermal conductivity.

[0024] The composite thermal insulation ceramic prepared by this invention has excellent comprehensive properties such as low thermal conductivity, high strength, high thermal shock resistance and high temperature corrosion resistance. Its apparent porosity is 13~20%, thermal conductivity is 0.8~2W / mK, flexural strength is 14~18MPa, and it shows no cracks after 50 cycles of thermal shock resistance test. It can be applied to the combustion chamber of gas turbine. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the composite thermal insulation ceramic of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0027] The corundum particles used in this embodiment of the invention have a particle size of 0.2~4mm, including corundum particles with a particle size of 0.2~0.8mm, corundum particles with a particle size of 1~2mm, and corundum particles with a particle size of 3~4mm; the alumina powder has a particle size of 0.5~1µm, the alumina hollow spheres have a particle size of 1~2mm, the mullite has a particle size of 0.5mm~100µm, including mullite with a particle size of 0.5~1mm, mullite with a particle size of 50~100µm, and mullite with a particle size of 100~500µm; and the wood fibers have a length of 25~100µm. Example 1

[0028] Press (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 In a stoichiometric ratio, La₂O₃ powder, Y₂O₃ powder, Yb₂O₃ powder, Ho₂O₃ powder, Er₂O₃ powder, and CeO₂ powder were mixed and synthesized at 1450℃ to form a single-phase (La₂O₃)₂O₇. 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high entropy powder, 92wt% high entropy powder, 5wt% activated alumina, 3wt% silica, and then 10wt% deionized water are added and cast to form a corrosion-resistant preform.

[0029] The mixture consists of 5 wt% 3-4 mm corundum particles, 10 wt% 1-2 mm corundum particles, 10 wt% 0.2-0.8 mm corundum particles, 25 wt% alumina powder, 5 wt% hollow alumina spheres, 10 wt% 0.5-1 mm mullite, 10 wt% 100-500 µm mullite, 10 wt% 50-100 µm mullite, 3.5 wt% kaolin, 2.3 wt% silica, 0.2 wt% sodium silicate, 3 wt% activated alumina, 1 wt% calcium aluminate cement, and 5 wt%... A mixture of wt% wood fiber powder and 7wt% deionized water was added and mixed evenly. This mixture was then poured onto a raw anti-corrosion layer and solidified. The mixture was sintered at 1600℃ for 2 hours to obtain a composite thermal insulation ceramic. This composite thermal insulation ceramic consists of an anti-corrosion layer 1 and a functional composite layer 2. The thickness of the anti-corrosion layer 1 is 1 mm. The anti-corrosion layer 1 is composed of mullite and (La...0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy ceramic, the functional composite layer 2 is corundum and mullite, and the anti-corrosion layer 1 is in direct contact with the hot surface, its structure is as follows Figure 1 As shown.

[0030] The composite thermal insulation ceramic of this embodiment has an apparent porosity of 19%, a thermal conductivity of 0.86 W / mK, a flexural strength of 14.8 MPa, and no cracks after 50 cycles of thermal shock resistance test. Example 2

[0031] Press (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 In a stoichiometric ratio, La₂O₃ powder, Y₂O₃ powder, Yb₂O₃ powder, Ho₂O₃ powder, Er₂O₃ powder, and CeO₂ powder were mixed and synthesized at 1500℃ to form a single-phase (La₂O₃)₂Ce₂O₇. 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high entropy powder, 93wt% high entropy powder, 4wt% activated alumina, 3wt% silica, and then 10wt% deionized water are added and cast to form a corrosion-resistant preform.

[0032] 2. A mixture of 5 wt% 3-4 mm corundum particles, 15 wt% 1-2 mm corundum particles, 10 wt% 0.2-0.8 mm corundum particles, 30 wt% alumina powder, 3 wt% hollow alumina spheres, 5 wt% 0.5-1 mm mullite, 10 wt% 100-500 µm mullite, 10 wt% 50-100 µm mullite, 4 wt% kaolin, 2.3 wt% silica, 0.2 wt% sodium silicate, 1.5 wt% activated alumina, 1 wt% calcium aluminate cement, and 3 wt% wood fiber powder is mixed with 8 wt% deionized water and poured onto a corrosion-resistant green body to solidify and sinter at 1650℃ for 3 hours to obtain a composite thermal insulation ceramic. This composite thermal insulation ceramic consists of an anti-corrosion layer and a functional composite layer. The thickness of the anti-corrosion layer is 0.8 mm; the anti-corrosion layer is composed of mullite and (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy ceramic, with a functional composite layer of corundum and mullite, and an anti-corrosion layer in direct contact with the hot surface.

[0033] The composite thermal insulation ceramic of this embodiment has an apparent porosity of 16%, a thermal conductivity of 1.9 W / mK, a flexural strength of 16.9 MPa, and no cracks after 50 cycles of thermal shock resistance test. Example 3

[0034] 1. Press (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 In a stoichiometric ratio, La₂O₃ powder, Y₂O₃ powder, Yb₂O₃ powder, Ho₂O₃ powder, Er₂O₃ powder, and CeO₂ powder were mixed and synthesized at 1500℃ to form a single-phase (La₂O₃)₂Ce₂O₇. 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high entropy powder, 93wt% high entropy powder, 5wt% activated alumina, 2wt% silica, and then 10wt% deionized water are added and cast to form a corrosion-resistant preform.

[0035] 2. A mixture of 8 wt% 3-4 mm corundum particles, 10 wt% 1-2 mm corundum particles, 15 wt% 0.2-0.8 mm corundum particles, 20 wt% alumina powder, 3.5 wt% hollow alumina spheres, 5 wt% 0.5-1 mm mullite, 14 wt% 100-500 µm mullite, 14 wt% 50-100 µm mullite, 3 wt% kaolin, 2 wt% silica, 0.3 wt% sodium silicate, 2 wt% activated alumina, 1.2 wt% calcium aluminate cement, and 2 wt% wood fiber powder is mixed with 8 wt% deionized water and stirred evenly. The mixture is then poured onto a corrosion-resistant green body and solidified. After sintering at 1550℃ for 3 hours, a composite thermal insulation ceramic is obtained. This composite thermal insulation ceramic consists of an anti-corrosion layer and a functional composite layer. The thickness of the anti-corrosion layer is 1 mm; the anti-corrosion layer is composed of mullite and (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy ceramic, with a functional composite layer of corundum and mullite, and an anti-corrosion layer in direct contact with the hot surface.

[0036] The composite thermal insulation ceramic of this embodiment has an apparent porosity of 14%, a thermal conductivity of 1.7 W / mK, a flexural strength of 17.6 MPa, and no cracks after 50 cycles of thermal shock resistance test. Example 4

[0037] Press (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 In a stoichiometric ratio, La₂O₃ powder, Y₂O₃ powder, Yb₂O₃ powder, Ho₂O₃ powder, Er₂O₃ powder, and CeO₂ powder were mixed and synthesized at 1450℃ to form a single-phase (La₂O₃)₂O₇. 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high entropy powder, 93wt% high entropy powder, 5wt% activated alumina, 2wt% silica, and then 10wt% deionized water are added and cast to form a corrosion-resistant preform.

[0038] A mixture of 6 wt% 3-4 mm corundum particles, 8 wt% 1-2 mm corundum particles, 10 wt% 0.2-0.8 mm corundum particles, 18 wt% alumina powder, 3.5 wt% hollow alumina spheres, 10 wt% 0.5-1 mm mullite, 15 wt% 100-500 µm mullite, 15 wt% 50-100 µm mullite, 5 wt% kaolin, 1 wt% silica, 0.5 wt% sodium silicate, 4 wt% activated alumina, 1 wt% calcium aluminate cement, and 3 wt% wood fiber powder is mixed with 9 wt% deionized water and stirred evenly. This mixture is then poured onto a corrosion-resistant green body and solidified, and sintered at 1600℃ for 2 hours to form a composite heat-insulating ceramic. This composite thermal insulation ceramic consists of an anti-corrosion layer and a functional composite layer. The thickness of the anti-corrosion layer is 0.6 mm; the anti-corrosion layer is composed of mullite and (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy ceramic, with a functional composite layer of corundum and mullite, and an anti-corrosion layer in direct contact with the hot surface.

[0039] The composite thermal insulation ceramic of this embodiment has an apparent porosity of 16%, a thermal conductivity of 1.2 W / mK, a flexural strength of 16.4 MPa, and no cracks after 50 cycles of thermal shock resistance test. Example 5

[0040] Press (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2In a stoichiometric ratio, La₂O₃ powder, Y₂O₃ powder, Yb₂O₃ powder, Ho₂O₃ powder, Er₂O₃ powder, and CeO₂ powder were mixed and synthesized at 1450℃ to form a single-phase (La₂O₃)₂O₇. 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high entropy powder, 95wt% high entropy powder, 3wt% activated alumina, 2wt% silica, and then 10wt% deionized water are added, and the mixture is cast into a mold to obtain an anti-corrosion layer.

[0041] A mixture of 5 wt% 3-4 mm corundum particles, 10 wt% 1-2 mm corundum particles, 12 wt% 0.2-0.8 mm corundum particles, 25 wt% alumina powder, 6 wt% hollow alumina spheres, 6 wt% 0.5-1 mm mullite, 12 wt% 100-500 µm mullite, 10 wt% 50-100 µm mullite, 3 wt% kaolin, 2 wt% silica, 0.5 wt% sodium silicate, 3.5 wt% activated alumina, 2 wt% calcium aluminate cement, and 3 wt% wood fiber powder is mixed with 6 wt% deionized water and stirred evenly. The mixture is then poured onto an anti-corrosion layer and solidified, and sintered at 1600℃ for 2 hours to obtain a composite thermal insulation ceramic. This composite thermal insulation ceramic consists of an anti-corrosion layer and a functional composite layer. The thickness of the anti-corrosion layer is 1 mm; the anti-corrosion layer is composed of mullite and (La) 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy ceramic, with a functional composite layer of corundum and mullite, and an anti-corrosion layer in direct contact with the hot surface.

[0042] The composite thermal insulation ceramic of this embodiment has an apparent porosity of 18%, a thermal conductivity of 0.98 W / mK, a flexural strength of 15.6 MPa, and no cracks after 50 cycles of thermal shock resistance test.

[0043] The composite thermal insulation ceramic of the present invention has excellent comprehensive properties such as low thermal conductivity, high strength, high thermal shock resistance and high temperature corrosion resistance. Its apparent porosity is 13~20%, thermal conductivity is 0.8~2W / mK, flexural strength is 14~18MPa, and the thickness of the anti-corrosion layer is 0.5~1mm. After 50 cycles of thermal shock resistance test, there are no cracks. It can be applied to the field of gas turbine combustion chamber.

[0044] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A composite insulating ceramic, characterized by, The composite heat insulation ceramic is composed of a corrosion-resistant layer and a functional composite layer, the corrosion-resistant layer is mullite and (La 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy ceramic, the functional composite layer is corundum and mullite, and the corrosion-resistant layer is in direct contact with the hot surface. The anticorrosion layer is prepared by mixing La2O3 powder, Y2O3 powder, Yb2O3 powder, Ho2O3 powder, Er2O3 powder and CeO2 powder in stoichiometric ratio, and sintering at 1450-1650 DEG C to obtain (La 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy powder, mixing the high-entropy powder, active alumina, silicon dioxide and deionized water, and then pouring and forming, and sintering at 1500-1700 DEG C to obtain; the mass ratio of the high-entropy powder, active alumina and silicon dioxide is (90-96):(3-7):(1-3). The functional composite layer is prepared by adding mixed powders of corundum particles, alumina powder, alumina hollow spheres, mullite, kaolin, silicon dioxide, sodium silicate, active alumina, calcium aluminate cement and wood fiber into deionized water, pouring and solidifying into shape, and sintering at 1500-1700 DEG C. The corundum particles are 20-50 wt% of the mixed powders, the alumina powder is 20-35 wt% of the mixed powders, the alumina hollow spheres are 3-6 wt% of the mixed powders, the mullite is 25-50 wt% of the mixed powders, the kaolin is 3-6 wt% of the mixed powders, the silicon dioxide is 1-5 wt% of the mixed powders, the sodium silicate is 0.2-0.6 wt% of the mixed powders, the active alumina is 1-5 wt% of the mixed powders, the calcium aluminate cement is 1-5 wt% of the mixed powders, and the wood fiber is 2-6 wt% of the mixed powders.

2. The composite insulating ceramic according to claim 1, wherein The composite heat-insulating ceramic has an apparent porosity of 13-20%, a thermal conductivity of 0.8-2 W / mK, and a bending strength of 14-18 MPa; and the corrosion-resistant layer has a thickness of 0.5-1 mm.

3. The composite insulating ceramic of claim 1, wherein, The particle size of the La2O3 powder, the Y2O3 powder, the Yb2O3 powder, the Ho2O3 powder, the Er2O3 powder and the CeO2 powder is 0.1-0.4 µm.

4. The composite insulating ceramic of claim 1, wherein, The particle size of the corundum particles is 0.2-4 mm, including 0.2-0.8 mm, 1-2 mm and 3-4 mm; the particle size of the alumina powder is 0.5-1 µm, the particle size of the alumina hollow spheres is 1-2 mm, the particle size of the mullite is 0.5 mm-100 µm, including 0.5-1 mm, 50-100 µm and 100-500 µm; and the length of the wood fiber is 25-100 µm.

5. The composite insulating ceramic according to claim 4, wherein, The mass of the corundum particles with a particle size of 3-4 mm is 5-10 wt% of the mixed powders, the mass of the corundum particles with a particle size of 1-2 mm is 5-20 wt% of the mixed powders, and the mass of the corundum particles with a particle size of 0.2-0.8 mm is 10-20 wt% of the mixed powders; the mass of the mullite with a particle size of 0.5-1 mm is 5-10 wt% of the mixed powders, the mass of the mullite with a particle size of 100-500 µm is 10-20 wt% of the mixed powders, and the mass of the mullite with a particle size of 50-100 µm is 10-20 wt% of the mixed powders.

6. The method for preparing a composite insulating ceramic according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: S1. La2O3 powder, Y2O3 powder, Yb2O3 powder, Ho2O3 powder, Er2O3 powder and CeO2 powder are mixed in a stoichiometric ratio of (La 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7, and (La 0.2 Y 0.2 Yb 0.2 Ho 0.2 Er 0.2 )2Ce2O7 high-entropy powder is prepared at 1450-1650°C. S2. The high-entropy powders, active alumina and silicon dioxide are mixed into deionized water, poured into shape, and a corrosion-resistant layer green body is prepared; the mass ratio of the high-entropy powders, active alumina and silicon dioxide is (90-96):(3-7):(1-3); S3. Corundum particles, alumina powder, alumina hollow sphere, mullite, kaolin, silicon dioxide, sodium silicate, active alumina, calcium aluminate cement and wood fiber are added into deionized water and mixed uniformly, and then poured and solidified on the anticorrosive layer element blank to form a composite thermal insulation ceramic after sintering at 1500-1700℃ for 2-5h; the corundum particles are 20-50 wt% of the mixed powder, the alumina powder is 20-35 wt% of the mixed powder, the alumina hollow sphere is 3-6 wt% of the mixed powder, the mullite is 25-50 wt% of the mixed powder, the kaolin is 3-6 wt% of the mixed powder, the silicon dioxide is 1-5 wt% of the mixed powder, the sodium silicate is 0.2-0.6 wt% of the mixed powder, the active alumina is 1-5 wt% of the mixed powder, the calcium aluminate cement is 1-5 wt% of the mixed powder, and the wood fiber is 2-6 wt% of the mixed powder.

7. Use of the composite thermal insulation ceramic according to any one of claims 1-5 in the field of gas turbine combustion chambers.

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