A dual-phase inlayed meso-oxide ablation-resistant ceramic and a method of making the same

Abstract

The application relates to a dual-phase mosaic middle-entropy oxide anti-ablation ceramic and a preparation method thereof, and belongs to the technical field of ceramic materials. The method comprises the following steps: firstly, high-temperature heat treatment is adopted to prepare dual-phase middle-entropy oxide ceramic powders ((Hf, Zr, Ti)O2 and (Hf, Zr)TiO4) with different proportions; and then, a composite-phase mosaic structure ceramic is prepared by means of pressureless sintering. The method not only provides a theoretical basis for optimal anti-cyclic ablation performance component design of Hf-Zr-Ti-based multicomponent ultrahigh-temperature ceramic, but also lays a material foundation for the application of the prepared ceramic powder in substrate modification and coating preparation in the future. In addition, the pressureless sintering preparation of the dual-phase mosaic middle-entropy oxide anti-ablation ceramic block can realize low-cost and large-scale production. The process can not only realize low-cost and large-scale production, but also obtain uniformly distributed dual-phase middle-entropy oxides, fully exert the mutual synergistic effect among multicomponent oxides, and simultaneously improve the resistance to cyclic thermal shock and the anti-ablation performance of the ceramic block.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic material preparation, and particularly relates to a dual-phase embedded medium-entropy oxide ablation-resistant ceramic and a preparation method thereof. BACKGROUND

[0002] Traditional Hf / Zr-based ultra-high temperature ceramics (HfC, HfB2, ZrC, ZrB2, etc.) are widely used as ablation-resistant materials in ultra-high temperature environments (above 2000℃) due to their high melting points (above 3000℃), good chemical stability, excellent oxidation / ablation resistance, and the fact that their oxidation products also have high melting points (HfO2: ~2810℃ and ZrO2: ~2670℃) and good high-temperature stability. However, after long-term cyclic ablation, HfO2 / ZrO2 can undergo phase changes, resulting in significant stress, which causes the oxidation film to become loose and even form defects (pores, cracks, and peeling), ultimately exacerbating the damage to the oxidation film and weakening its cyclic ablation resistance. Therefore, the poor cyclic ablation resistance limits its further development. Currently, low-melting-point oxides (TiO2: ~1870℃, Ta2O5: ~1800℃, and Nb2O5: ~1460℃, etc.) are used to densify the loose framework of high-melting-point HfO2 / ZrO2 during the ablation process. Among them, TiO2 has a high melting point and good high-temperature stability, gradually attracting the attention of researchers.

[0003] Patent CN 114853506 B and the document "J. Li, Y. Zhang, Y. Zhao, et al. A novel (Hf 1 / 3 Zr 1 / 3Ti 1 / 3 )C medium-entropy carbide coating with excellent long-life ablation resistance applied above 2100℃, Compos. Part B-Eng. 251 (2023) 110467." reported a novel (Hf 1 / 3 Zr 1 / 3 Ti 1 / 3 )C medium-entropy carbide coating, which forms a dense and stable (Hf, Zr, Ti)O2 medium-entropy oxide by mutual solid solution of complex oxides (HfO2, ZrO2, and TiO2) during ablation, showing excellent ablation resistance. However, as the cyclic ablation time increases, (Hf, Zr, Ti)O2 will cause ablation defects to form due to phase changes, leading to coating failure and weakening its ablation resistance.

[0004] The document "J. Li, Y. Zhang, J. Lv, et al. Sealing role of Ti-rich phase in HfC-ZrC-TiC coating for C / C composites during ablation above 2100℃, Corros. Sci. 205 (2022) 110474." reports that during the ablation process of the multi-phase HfC-ZrC-TiC coating, the entropy oxide in the low-melting point (Hf, Zr) TiO4 formed by the solid solution reaction of multi-phase oxides (HfO2, ZrO2 and TiO2) can self-heal the defects formed in the coating during the ablation process and densify the oxide film, but due to its low melting point, it cannot resist long-term mechanical erosion, ultimately leading to coating damage.

[0005] The cyclic ablation resistance of multi-element ultra-high temperature ceramics mainly depends on the surface autogenous oxide film generated during service, therefore, how to obtain a stable and dense oxide film during ablation is the key to solving the problem of poor cyclic ablation resistance of multi-element ultra-high temperature ceramics. SUMMARY

[0006] The purpose of the present application is to overcome the above-mentioned shortcomings of the prior art, and to provide a dual-phase inlaid entropy oxide ablation-resistant ceramic and a preparation method thereof, in order to solve the problems of narrow ablation-resistant temperature range, poor cyclic thermal shock resistance and difficulty in repeated use of the prior art ultra-high temperature ceramic material.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A preparation method of a dual-phase inlaid entropy oxide ablation-resistant ceramic, comprising the following steps:

[0009] S1, mixing HfO2 powder, ZrO2 powder and TiO2 powder and ball milling to obtain an oxide ceramic mixed powder; wherein the molar ratio of HfO2 powder and ZrO2 powder is 1:2, and the molar ratio of TiO2 powder in the oxide ceramic mixed powder is 15mol.% to 25mol.%;

[0010] S2, high-temperature heat treatment of the oxide ceramic powder to obtain a dual-phase entropy oxide powder; the dual-phase entropy oxide powder is (Hf, Zr, Ti)O2-(Hf, Zr)TiO4 powder;

[0011] S3, mixing the dual-phase entropy oxide powder and a polyvinyl alcohol solution and grinding to obtain a to-be-pressed powder;

[0012] S4, pressing the to-be-pressed powder into a block to obtain a dual-phase entropy oxide ceramic block;

[0013] S5, obtaining the meso-oxide ceramic bulk (Hf,Zr,Ti)O2-(Hf,Zr)TiO4 after pressureless heat treatment of the process two-phase meso-oxide ceramic bulk.

[0014] Further improvement of the present application is:

[0015] Preferably, in S2, the high-temperature heat treatment process is to heat to 800℃ at 2℃ / min, then heat to 1500-1700℃ at 0.5-1℃ / min and keep for 12-24h, and the heat treatment reaction atmosphere is air atmosphere.

[0016] Preferably, in S2, after high-temperature heat treatment, the furnace is cooled to room temperature at 1-2℃ / min.

[0017] Preferably, in S3, the polyvinyl alcohol solution is composed of polyvinyl alcohol and water, and the mass concentration of polyvinyl alcohol is 1.5%-2%.

[0018] Preferably, in S4, the pressing pressure for pressing the powder to be pressed into a bulk is 20-25MPa, and the pressing time is 5-20min.

[0019] Preferably, in S5, the pressureless heat treatment process is to heat to 800℃ at 2℃ / min, then heat to 1500-1600℃ at 0.5-1℃ / min and keep for 4-8h, and the heat treatment reaction atmosphere is air atmosphere.

[0020] Preferably, in S5, after pressureless heat treatment, the furnace is cooled to room temperature at 1-2℃ / min.

[0021] Preferably, in S1, the purity of HfO2 powder, ZrO2 powder and TiO2 powder is 99.00%, and the particle size is 1-3μm.

[0022] A two-phase mosaic meso-oxide (Hf,Zr,Ti)O2-(Hf,Zr)TiO4 obtained by any one of the above preparation methods.

[0023] Preferably, when the oxygen-ethyne heat flow density is 2.4MW / m 2 , the ablation protection temperature range of the two-phase mosaic meso-oxide is room temperature-2500℃; when continuous ablation is applied, the total effective protection time can reach 30s; when 15s cyclic ablation is applied, the total effective protection time reaches 60s, and the cyclic number can reach 4 times.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The application relates to a preparation method of a dual-phase mosaic meso-entropy oxide anti-ablation ceramic material prepared by pressureless sintering, which comprises the following steps: first, different proportions of dual-phase meso-entropy oxide ceramic powders ((Hf, Zr, Ti)O2 and (Hf, Zr)TiO4) are prepared by high-temperature heat treatment; then, the dual-phase mosaic structure ceramic is prepared by pressureless sintering. In the preparation process, the mixing proportion of the HfO2 powder, the ZrO2 powder and the TiO2 powder is strictly limited, so that the final (Hf, Zr, Ti)O2-(Hf, Zr)TiO4 powder can be generated. The preparation method not only provides a theoretical basis for the optimal anti-cyclic ablation performance component design of the Hf-Zr-Ti-based multicomponent ultrahigh-temperature ceramic, but also lays a material foundation for the application of the prepared ceramic powder in the later substrate modification and coating preparation. In addition, the dual-phase mosaic meso-entropy oxide anti-ablation ceramic bulk prepared by pressureless sintering can realize low-cost and large-scale production. The process not only can realize low-cost and large-scale production, but also can obtain the uniformly distributed dual-phase meso-entropy oxide, fully play the mutual synergistic effect among the multicomponent oxides, and simultaneously improve the cyclic thermal shock resistance and the anti-ablation performance of the ceramic bulk.

[0026] The application further discloses a dual-phase mosaic meso-entropy oxide anti-ablation ceramic. The dual-phase meso-entropy oxide ceramic is directly prepared into the ablation-resistant oxide ceramic without adopting the traditional ceramic system (carbide, boride and nitride, etc.) ablation analysis oxide film mode. The ablation-resistant performance of the ceramic is good. The ceramic strictly limits the content and distribution between (Hf, Zr, Ti)O2 and (Hf, Zr)TiO4. The melting point of (Hf, Zr)TiO4 is lower than the ablation temperature, and the phase is in a molten state in the ablation process. The phase not only can inhibit the damage of the (Hf, Zr, Ti)O2 oxide skeleton caused by thermal stress and mechanical ablation, but also can be used as a crack and pore in the molten phase healing coating, so that the ceramic bulk can be prevented from being broken due to the thermal shock caused by the cyclic ablation, the high-temperature stability of the Hf-Zr-Ti-based multicomponent oxide is improved, and the cyclic ablation resistance of the Hf-Zr-Ti-based multicomponent ultrahigh-temperature ceramic material is improved.

[0027] The ceramic material realizes the ultrahigh-temperature cyclic ablation resistance at room temperature-2500 DEG C. When the continuous ablation is applied, the effective protection total length reaches 30s; when the 15s cyclic ablation is applied, the effective protection total length reaches 60s, and the cyclic number reaches 4 times. 2 BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the XRD of the ceramic bulk prepared by different molar ratios;

[0029] Figure 2 is the macroscopic morphology of different ceramic bulks before and after ablation. DETAILED DESCRIPTION​

[0030] The present invention is described in further detail below with reference to the accompanying drawings:

[0031] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0032] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0033] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0034] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0035] The present invention discloses a method for preparing a dual-phase inlaid medium entropy oxide ablation-resistant ceramic material by pressureless sintering as follows:

[0036] Step 1: Take commercial HfO2, ZrO2, and TiO2 powders with a purity of 99.00% and a particle size of 1-3 μm in different molar ratios as raw materials, place the mixed powder in a planetary ball mill, and grind it by dry ball milling at a speed of 400-450 r / min for 4-6 hours, and then sieve the oxide ceramic mixed powder with a 300-mesh sieve.

[0037] As a preferred solution, the molar ratio of HfO2 and ZrO2 powders in the mixed powder is 1:2, and the molar ratio of TiO2 phase in the mixed powder is 15 mol.% to 25 mol.%.

[0038] The process directly mixes the raw material powder, so that the corresponding oxides can be generated in-situ by subsequent heat treatment reactions, and the two phases in the generated powder are uniform, which helps to prepare a ceramic block with uniform composition later and improves its ablation resistance. At the same time, by limiting the proportion of each substance, the final target oxide ceramic can be generated.

[0039] Step 2: Put the screened mixed powder into a high-temperature box furnace with air, heat to 800℃ at a rate of 2℃ / min, then heat to 1500-1700℃ at a rate of 0.5-1℃ / min, and keep for 12-24h, high-temperature heat treatment to obtain a dual-phase meso-entropy oxide ceramic powder, finally reduce to room temperature at a rate of 1-2℃ / min, and then take out the dual-phase meso-entropy oxide powder.

[0040] In this process, the internal powder is heated uniformly, and the ceramic block is cooled in the furnace, which can prevent the ceramic block from cracking due to too fast cooling speed.

[0041] Step 3: Dry ball milling is used to grind the dual-phase meso-entropy oxide ceramic powder at a speed of 400-450r / min for 2-4h, the ground dual-phase meso-entropy oxide ceramic powder is placed on a 300 mesh screen, 5-6g of powder is screened, 1-2 drops of polyvinyl alcohol (PVA) solution with a mass ratio of 1.5%-2% is added, then poured into a mortar, and manually ground for 20-30min until uniformly mixed.

[0042] Step 4: Put the mixed dual-phase meso-entropy oxide ceramic powder into a dry press machine mold, apply a loading rate of 20-25MPa / min and a load pressure of 20-25MPa for 5-10min, to obtain an unheated dual-phase meso-entropy oxide ceramic block with a diameter of 20mm.

[0043] Step 5: Put the obtained unheated dual-phase meso-entropy oxide ceramic block into a high-temperature box furnace with air, first heat to 800℃ at a rate of 2℃ / min, then heat to 1500-1600℃ at a rate of 0.5-1℃ / min, and keep for 4-8h, high-temperature heat treatment sintering to obtain a meso-entropy oxide ceramic block, finally reduce to room temperature at a rate of 1-2℃ / min, and then take out the dual-phase meso-entropy oxide ceramic block.

[0044] A dual-phase mosaic meso-entropy oxide ablation-resistant ceramic block of "(Hf,Zr,Ti)O2-(Hf,Zr)TiO4" is directly prepared, the former is a solid phase, and the latter is a liquid phase, both of which are uniformly distributed and tightly combined, and have excellent ablation resistance.

[0045] A dual-phase embedded middle-entropy oxide ablation-resistant ceramic bulk with composition of (Hf, Zr, Ti)O2-(Hf, Zr)TiO4 is prepared by pressureless sintering. When the oxygen-ethyne heat flow density is 2.4 MW / m 2 When the continuous ablation is applied, the total effective protection time reaches 30 s; when the 15-s cycle ablation is applied, the total effective protection time reaches 60 s, and the cycle number reaches 4 times. The ceramic bulk can meet the above two ablation conditions at the same time.

[0046] During the ablation process, (Hf, Zr)TiO4 becomes a liquid phase at a high temperature. Due to the uniform doping of the two phases of the bulk, the liquid phase (Hf, Zr)TiO4 can quickly and fully fill the cracks and pores generated during the phase transition of (Hf, Zr, Ti)O2 in the ablation process. Combined with the method of the application, the two phases are uniform, and the ablation resistance of the whole bulk is strong.

[0047] Example 1 and Example 3

[0048] Step 1, take HfO2, ZrO2 powder with a molar ratio of 1:2, and TiO2 phase accounts for 15 mol.% of the mixed powder (the purity is 99.5%, and the particle size is 3 μm), put the mixed powder into a planetary ball mill, and adopt dry ball milling at a speed of 400 r / min for 6 h, and then screen the oxide ceramic mixed powder through a 300-mesh screen.

[0049] Step 2, put the screened mixed powder into a high-temperature box furnace with air, heat to 800℃ at a rate of 2℃ / min, then heat to 1500℃ at a rate of 1℃ / min and keep for 24 h, and obtain the dual-phase middle-entropy oxide ceramic powder by high-temperature heat treatment, and finally reduce to room temperature at a rate of 1℃ / min, and then take out the dual-phase middle-entropy oxide powder.

[0050] Step 3, adopt dry ball milling at a speed of 400 r / min for 4 h for the dual-phase middle-entropy oxide ceramic powder, put the milled dual-phase middle-entropy oxide ceramic powder into a 300-mesh screen, screen 6 g of powder, add 1 drop of polyvinyl alcohol (PVA) solution with a mass ratio of 2%, then pour into a mortar, and manually grind for 30 min until uniformly mixed.

[0051] Step 4, put the uniformly mixed dual-phase middle-entropy oxide ceramic powder into a dry press machine mold, apply a loading rate of 20 MPa / min and a load pressure of 20 MPa for 10 min, and obtain a dual-phase middle-entropy oxide ceramic bulk with a diameter of 20 mm without heat treatment.

[0052] Step 5: Place the obtained unheat-treated dual-phase medium-entropy oxide ceramic block into a high-temperature box furnace ventilated with air, first heat it to 800°C at 2°C / min, then heat it to 1500°C at 1°C / min and keep it warm for 8 hours, and sinter it to obtain a medium-entropy oxide ceramic block through high-temperature heat treatment. Finally, cool it to room temperature at 1°C / min, and then take out the dual-phase medium-entropy oxide ceramic block.

[0053] The heat flux density of oxyacetylene is 2.4MW / m 2 When the ceramic block is subjected to continuous ablation and cyclic ablation, the ablation is performed respectively, corresponding to Examples 1 and 3.

[0054] Implementation Case 2 and Example 4

[0055] Step 1: Take a mixed powder (purity of 99.5% and particle size of 3 μm) with a molar ratio of HfO2 and ZrO2 powder of 1:2 and a molar ratio of TiO2 phase to the mixed powder of 25 mol%. Place the mixed powder in a planetary ball mill and grind it by dry ball milling at a speed of 450 r / min for 6 hours. Then, sieve the oxide ceramic mixed powder with a 300-mesh sieve.

[0056] Step 2: Place the sieved mixed powder into a high-temperature box furnace ventilated with air, heat it to 800°C at 2°C / min, then heat it to 1500°C at 0.5°C / min and keep it warm for 24 hours. High-temperature heat treatment is performed to obtain a dual-phase medium-entropy oxide ceramic powder. Finally, the temperature is lowered to room temperature at 2°C / min, and the dual-phase medium-entropy oxide powder is then taken out.

[0057] Step 3: Grind the dual-phase medium entropy oxide ceramic powder by dry ball milling at a speed of 450 r / min for 4 hours, place the ground dual-phase medium entropy oxide ceramic powder on a 300-mesh sieve, sieve out 6 g of powder, add 2 drops of 2% polyvinyl alcohol (PVA) solution by mass, then pour it into a mortar and grind it manually for 30 minutes until evenly mixed.

[0058] Step 4: Place the mixed dual-phase medium entropy oxide ceramic powder in a dry pressing mold, apply a loading rate of 25 MPa / min and a load pressure of 20 MPa and maintain the pressure for 10 minutes to obtain an unheat-treated dual-phase medium entropy oxide ceramic block with a diameter of 20 mm.

[0059] Step 5: Place the obtained unheat-treated dual-phase medium-entropy oxide ceramic block into a high-temperature box furnace ventilated with air, first heat it to 800°C at 1°C / min, then heat it to 1550°C at 1°C / min and keep it warm for 8 hours, and sinter it to obtain a medium-entropy oxide ceramic block through high-temperature heat treatment. Finally, cool it to room temperature at 2°C / min, and then take out the dual-phase medium-entropy oxide ceramic block.

[0060] The ceramic block was subjected to continuous ablation and cyclic ablation, respectively corresponding to Examples 2 and 4, when the oxygen-ethyne heat flow density was 2.4 MW / m 2

[0061] Referring to Figure 1 , Figure 1 are XRD of ceramic blocks prepared at different molar ratios, wherein the "(Hf, Zr, Ti)O2-(Hf, Zr)TiO4" dual-phase mosaic entropic oxide ablation-resistant ceramic blocks were successfully prepared in Examples 1-4.

[0062] Referring to Figure 2 , Figure 2 are macroscopic morphologies of different ceramic blocks before and after ablation, wherein the ceramic blocks in Examples 1-4 all remained intact after continuous ablation and cyclic ablation, respectively.

[0063] Table 1 is a comparison of the cyclic ablation resistance of different examples.

[0064] Comparative Examples 1 and 2

[0065] Step 1, take HfO2, ZrO2 powder molar ratio of 1:2, and take TiO2 phase accounting for 15 mol.% (Comparative Example 1) and 25 mol.% (Comparative Example 2) of the mixed powder (purity of 99.5%, particle size of 3 μm) respectively, place the mixed powder in a planetary ball mill, and adopt dry ball milling at a speed of 450 r / min for 6 h, then screen the oxide ceramic mixed powder with a 300 mesh screen.

[0066] Step 2, adopt dry ball milling at a speed of 450 r / min for 4 h to grind the oxide ceramic powder, place the ground oxide ceramic powder in a 300 mesh screen, screen 6 g of powder, and add 2 drops of polyvinyl alcohol (PVA) solution with a mass ratio of 2%, then pour into a mortar, and manually grind for 30 min until uniformly mixed.

[0067] Step 3, place the uniformly mixed oxide ceramic powder in a dry press machine mold, apply a loading rate of 25 MPa / min and a load pressure of 20 MPa for 10 min, and obtain an unheat-treated oxide ceramic block with a diameter of 20 mm.

[0068] Step 4, place the obtained unheat-treated oxide ceramic block in a high-temperature box furnace with air, first heat to 800℃ at a rate of 1℃ / min, then heat to 1500℃ at a rate of 1℃ / min and keep for 8 h, sinter the oxide ceramic block through high-temperature heat treatment, finally reduce to room temperature at a rate of 2℃ / min, and then take out the oxide ceramic block.

[0069] ​Without 1500℃ mixed powder high temperature pre-treatment, directly using HfO2, ZrO2, TiO2 mixed powder pressureless sintering, the prepared TiO2 phase accounts for 15 mol.% and 25 mol.% of the molar ratio of the mixed powder ceramic block, corresponding to Comparative Example 1 and Comparative Example 2, respectively.

[0070] Comparative Example 3 and Comparative Example 4

[0071] Step 1, take HfO2, ZrO2 powder molar ratio of 1:2, and take TiO2 phase accounts for 15 mol.% (Comparative Example 3) and 25 mol.% (Comparative Example 4) of the mixed powder (purity is 99.5%, particle size is 3μm) respectively, put the mixed powder into the planetary ball mill, dry ball milling at a speed of 400r / min for 4h, then screen the oxide ceramic mixed powder through a 300 mesh screen.

[0072] Step 2, put the screened mixed powder into a high temperature box furnace with air, heat to 800℃ at a rate of 2℃ / min, then heat to 1200℃ at a rate of 1℃ / min and keep for 24h, high temperature heat treatment to obtain oxide ceramic powder, finally reduce to room temperature at a rate of 1℃ / min, then take out the oxide powder.

[0073] Step 3, dry ball milling of oxide ceramic powder at a speed of 400r / min for 4h, put the milled oxide ceramic powder into a 300 mesh screen, screen 6g powder and add 1 drop of polyvinyl alcohol (PVA) solution with a mass ratio of 1.5%, then pour into a mortar and manually grind for 30min until uniform mixing.

[0074] Step 4, put the mixed oxide ceramic powder into a dry press machine mold, apply a loading rate of 20MPa / min and a load pressure of 20MPa for 10min, obtain an unheated oxide ceramic block with a diameter of 20mm.

[0075] Step 5, put the obtained unheated oxide ceramic block into a high temperature box furnace with air, first heat to 800℃ at a rate of 1℃ / min, then heat to 1200℃ at a rate of 1℃ / min and keep for 8h, high temperature heat treatment sintering to obtain a medium entropy oxide ceramic block, finally reduce to room temperature at a rate of 1℃ / min, then take out the oxide ceramic block.

[0076] 1200℃ powder pre-treatment and 1200℃ ceramic sintering, the prepared TiO2 phase accounts for 15 mol.% and 25 mol.% of the molar ratio of the mixed powder ceramic block, corresponding to Comparative Example 3 and Comparative Example 4, respectively.

[0077] Comparative Example 5 and Comparative Example 7

[0078] Step 1, take the mixed powder of HfO2, ZrO2 powder with a molar ratio of 1:2 (purity is 99.5%, particle size is 3 μm), put the mixed powder into a planetary ball mill, adopt dry ball milling at a speed of 450 r / min for 6 h, and then screen the oxide ceramic mixed powder through a 300 mesh screen.

[0079] Step 2, put the screened mixed powder into a high-temperature box furnace with air, heat to 800℃ at a rate of 2℃ / min, then heat to 1500℃ at a rate of 0.5℃ / min and keep for 24 h, high-temperature heat treatment to obtain a dual-phase entropy oxide ceramic powder, and finally reduce to room temperature at a rate of 1℃ / min, then take out the dual-phase entropy oxide powder.

[0080] Step 3, adopt dry ball milling at a speed of 400 r / min for 4 h for the dual-phase entropy oxide ceramic powder, put the milled dual-phase entropy oxide ceramic powder into a 300 mesh screen, screen 6 g of powder, add 2 drops of polyvinyl alcohol (PVA) solution with a mass ratio of 2%, then pour into a mortar and manually grind for 30 min until uniform mixing.

[0081] Step 4, put the uniformly mixed dual-phase entropy oxide ceramic powder into a dry press machine mold, apply a loading rate of 20 MPa / min and a load pressure of 20 MPa for 10 min, to obtain a non-heat-treated dual-phase entropy oxide ceramic bulk body with a diameter of 20 mm.

[0082] Step 5, put the obtained non-heat-treated dual-phase entropy oxide ceramic bulk body into a high-temperature box furnace with air, first heat to 800℃ at a rate of 2℃ / min, then heat to 1550℃ at a rate of 1℃ / min and keep for 8 h, high-temperature heat treatment sintering to obtain an entropy oxide ceramic bulk body, and finally reduce to room temperature at a rate of 2℃ / min, then take out the dual-phase entropy oxide ceramic bulk body.

[0083] When the oxygen-ethane heat flow density is 2.4 MW / m 2 , the ceramic bulk bodies prepared without adding TiO2 were subjected to continuous ablation and cyclic ablation, corresponding to Comparative Examples 5 and 7, respectively.

[0084] Comparative Example 6 and Comparative Example 8

[0085] Step 1, take the mixed powder of HfO2, ZrO2 powder with a molar ratio of 1:2, and TiO2 phase accounting for 5 mol.% of the mixed powder (purity is 99.5%, particle size is 3 μm), put the mixed powder into a planetary ball mill, adopt dry ball milling at a speed of 400 r / min for 4 h, and then screen the oxide ceramic mixed powder through a 300 mesh screen.

[0086] Step 2: Place the sieved mixed powder into a high-temperature box furnace ventilated with air, heat it to 800°C at 2°C / min, then heat it to 1500°C at 1°C / min and keep it warm for 24 hours. High-temperature heat treatment is performed to obtain a dual-phase medium-entropy oxide ceramic powder. Finally, the temperature is lowered to room temperature at 2°C / min, and the dual-phase medium-entropy oxide powder is then taken out.

[0087] Step 3: Grind the dual-phase medium entropy oxide ceramic powder by dry ball milling at a speed of 450 r / min for 4 hours, place the ground dual-phase medium entropy oxide ceramic powder on a 300-mesh sieve, sieve out 6 g of powder, add 1 drop of 2% polyvinyl alcohol (PVA) solution by mass, then pour it into a mortar and grind it manually for 30 minutes until evenly mixed.

[0088] Step 4: Place the mixed dual-phase medium entropy oxide ceramic powder in a dry pressing mold, apply a loading rate of 20 MPa / min and a load pressure of 20 MPa and maintain the pressure for 10 minutes to obtain an unheat-treated dual-phase medium entropy oxide ceramic block with a diameter of 20 mm.

[0089] Step 5: Place the obtained unheat-treated dual-phase medium-entropy oxide ceramic block into a high-temperature box furnace ventilated with air, first heat it to 800°C at 1°C / min, then heat it to 1500°C at 1°C / min and keep it warm for 8 hours, and sinter it to obtain a medium-entropy oxide ceramic block through high-temperature heat treatment. Finally, cool it to room temperature at 2°C / min, and then take out the dual-phase medium-entropy oxide ceramic block.

[0090] The heat flux density of oxyacetylene is 2.4MW / m 2 When 5 mol.% TiO2 was added, the ceramic blocks prepared were subjected to continuous ablation and cyclic ablation, corresponding to Examples 6 and 8, respectively.

[0091] The results of the above examples and comparative examples are shown in Table 1, and the corresponding results and analysis are shown below:

[0092] (1) Comparative Example 1 (15 mol.% TiO2) and Comparative Example 2 (25 mol.% TiO2) were not subjected to 1500°C high-temperature preheating treatment of the mixed powder, and were directly pressureless sintered using the HfO2, ZrO2, TiO2 mixed powder. The HfO2, ZrO2, and TiO2 powders were not completely dissolved, and the prepared ceramic blocks still had residual HfO2, ZrO2, and TiO2 powders. The "(Hf, Zr, Ti)O2-(Hf, Zr)TiO4" dual-phase mosaic medium entropy oxide anti-ablation ceramic block was not successfully prepared.

[0093] (2), Comparative Example 3 (15 mol.% TiO2) and Comparative Example 4 (25 mol.% TiO2) were pre-sintered at 1200 °C, then sintered at 1200 °C. The HfO2, ZrO2, TiO2 powders were not completely dissolved, and the ceramic blocks still contained HfO2, ZrO2, TiO2 powders. The ceramic blocks were not successfully prepared as "(Hf,Zr,Ti)O2-(Hf,Zr)TiO4" dual-phase mosaic entropic oxide ablation-resistant ceramic blocks.

[0094] (3), Comparative Example 5 and Comparative Example 7, no TiO2 was added to the mixed powders, Figure 1 XRD showed that after sintering, the ceramic did not form "(Hf,Zr,Ti)O2-(Hf,Zr)TiO4" dual-phase mosaic entropic oxide, but only (Hf,Zr)O2. After continuous ablation (Comparative Example 5) and cyclic ablation (Comparative Example 7), the coating cracked due to the phase change of (Hf,Zr)O2, causing the ceramic to break down Figure 2 )。

[0095] (4), Comparative Example 6 and Comparative Example 8, only 5 mol.% TiO2 was added to the mixed powders, Figure 1 XRD showed that after sintering, the ceramic only formed (Hf,Zr,Ti)O2, but not (Hf,Zr)TiO4. Without the (Hf,Zr)TiO4 low-melting phase to self-heal the defects in the coating during ablation, the ceramic cracked due to the phase change of (Hf,Zr,Ti)O2 after continuous ablation (Comparative Example 6) and cyclic ablation (Comparative Example 8), causing the ceramic to break down Figure 2 )。

[0096] (5), Example 1 and Example 3, 15 mol.% TiO2 was added to the mixed powders, Figure 1 XRD showed that after sintering, the ceramic formed "(Hf,Zr,Ti)O2-(Hf,Zr)TiO4" dual-phase mosaic entropic oxide. (Hf,Zr,Ti)O2 as an ablation skeleton can withstand the mechanical stress generated by ablation, and (Hf,Zr)TiO4 as a low-melting phase can not only reduce the damage to the (Hf,Zr,Ti)O2 oxide skeleton caused by thermal stress and mechanical ablation, but also can heal cracks and pores in the molten phase, thereby avoiding the thermal shock caused by cyclic ablation of the ceramic block, and thus maintaining the integrity of the ceramic block after continuous ablation (Example 1) and cyclic ablation (Example 3) Figure 2 )。

[0097] (6), Example 2 and Example 4, 25 mol.% TiO2 was added to the mixed powders, Figure 1XRD shows that the ceramic after sintering forms a dual-phase entropic oxide of "(Hf,Zr,Ti)02-(Hf,Zr)Ti04", (Hf,Zr,Ti)02as an ablative skeleton can reduce the mechanical stress generated by ablation, while as (Hf,Zr)Ti04low-melting phase can not only reduce the damage to the (Hf,Zr,Ti)02oxide skeleton due to thermal stress and mechanical ablation, but also can heal cracks and pores in the molten phase coating, thereby avoiding the thermal shock of the ceramic bulk due to the cyclic ablation, thus maintaining the density and integrity after continuous ablation (Example 2) and cyclic ablation (Example 4). Figure 2

[0098] Table 1

[0099]

[0100] Example 5

[0101] Step 1, take Hf02, Zr02powder molar ratio of 1:2, and Ti02phase accounts for 20 mol.% of the mixed powder (purity is 99.5%, particle size is 3 μm), the mixed powder is placed in the planetary ball mill, dry ball milling at a speed of 420 r / min for 4 h, then the oxide ceramic mixed powder is screened by 300 mesh screen.

[0102] Step 2, the screened mixed powder is put into a high temperature box furnace with air, heated to 800℃ at a rate of 2℃ / min, then heated to 1600℃ at a rate of 0.5℃ / min and kept for 20 h, high temperature heat treatment to obtain dual-phase entropic oxide ceramic powder, finally reduced to room temperature at a rate of 1.5℃ / min, then the dual-phase entropic oxide powder is taken out.

[0103] Step 3, dry ball milling of dual-phase entropic oxide ceramic powder at a speed of 450 r / min for 4 h, the ground dual-phase entropic oxide ceramic powder is placed in a 300 mesh screen, 6 g of powder is screened and 2 drops of polyvinyl alcohol (PVA) solution with a mass ratio of 1.5% are added, then poured into a mortar and hand ground for 30 min until uniformly mixed.

[0104] Step 4, the uniformly mixed dual-phase entropic oxide ceramic powder is placed in a dry press machine mold, a loading rate of 25 MPa / min and a load pressure of 25 MPa are applied for 5 min, obtaining a diameter of 20 mm of unheat-treated dual-phase entropic oxide ceramic bulk.

[0105] ​Step 5, the obtained non-heat-treated dual-phase entropy oxide ceramic bulk body is placed into a high-temperature box furnace with air, first heated to 800℃ at a rate of 1℃ / min, then heated to 1500℃ at a rate of 0.8℃ / min and kept for 6h, high-temperature heat treatment sintering is performed to obtain the entropy oxide ceramic bulk body, finally reduced to room temperature at a rate of 1℃ / min, and then the dual-phase entropy oxide ceramic bulk body is taken out.

[0106] Example 6

[0107] Step 1, take HfO2, ZrO2 powder with a molar ratio of 1:2, and TiO2 phase accounting for 18mol.% of the mixed powder (the purity is 99.5%, and the particle size is 3μm), place the mixed powder in a planetary ball mill, dry ball mill at a speed of 430r / min for 5h, and then screen the oxide ceramic mixed powder through a 300 mesh screen.

[0108] Step 2, the screened mixed powder is placed into a high-temperature box furnace with air, heated to 800℃ at a rate of 2℃ / min, then heated to 1700℃ at a rate of 0.5℃ / min and kept for 12h, high-temperature heat treatment is performed to obtain the dual-phase entropy oxide ceramic powder, finally reduced to room temperature at a rate of 2℃ / min, and then the dual-phase entropy oxide powder is taken out.

[0109] Step 3, dry ball mill the dual-phase entropy oxide ceramic powder at a speed of 450r / min for 4h, place the milled dual-phase entropy oxide ceramic powder in a 300 mesh screen, screen 6g of powder, add 2 drops of polyvinyl alcohol (PVA) solution with a mass ratio of 1.8%, then pour into a mortar, and manually grind for 30min until uniform mixing.

[0110] Step 4, place the uniformly mixed dual-phase entropy oxide ceramic powder in a dry press machine mold, apply a loading rate of 25MPa / min and a load pressure of 22MPa for 20min, obtain a non-heat-treated dual-phase entropy oxide ceramic bulk body with a diameter of 20mm.

[0111] Step 5, the obtained non-heat-treated dual-phase entropy oxide ceramic bulk body is placed into a high-temperature box furnace with air, first heated to 800℃ at a rate of 1℃ / min, then heated to 1600℃ at a rate of 1℃ / min and kept for 4h, high-temperature heat treatment sintering is performed to obtain the entropy oxide ceramic bulk body, finally reduced to room temperature at a rate of 1.5℃ / min, and then the dual-phase entropy oxide ceramic bulk body is taken out.

[0112] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing ablation-resistant ceramics of dual-phase inlaid entropy oxide, characterized in that: The following steps are involved: S1, mixing HfO2 powder, ZrO2 powder, and TiO2 powder and then ball-milling to obtain oxide ceramic mixed powder; wherein the molar ratio of HfO2 powder to ZrO2 powder is 1:2, and the molar ratio of TiO2 powder to the oxide ceramic mixed powder is 15 mol.% to 25 mol.%; S2, subjecting the oxide ceramic powder to a high-temperature heat treatment to obtain a dual-phase medium-entropy oxide powder; the dual-phase medium-entropy oxide powder is (Hf, Zr, Ti)O2-(Hf, Zr)TiO4 powder; S3, mixing the dual-phase entropy oxide powder and the polyvinyl alcohol solution and grinding them to obtain a powder to be pressed; S4, pressing the powder to be pressed into a block to obtain a process dual-phase medium entropy oxide ceramic block; S5, subjecting the process dual-phase medium-entropy oxide ceramic block to pressureless heat treatment to obtain a medium-entropy oxide ceramic block (Hf, Zr, Ti)O2-(Hf, Zr)TiO4.

2. The method for preparing ablation-resistant ceramic of a dual-phase inlaid medium entropy oxide according to claim 1, characterized in that: In S2, the high temperature heat treatment process is to increase the temperature to 800°C at 2°C / min, then increase the temperature to 1500-1700°C at 0.5-1°C / min and keep the temperature for 12-24h. The heat treatment reaction atmosphere is air atmosphere.

3. The method for preparing ablation-resistant ceramic of a dual-phase inlaid medium entropy oxide according to claim 1, characterized in that: In S2, after high temperature heat treatment, the temperature is cooled to room temperature at a rate of 1-2°C / min.

4. The method for preparing ablation-resistant ceramics of a dual-phase inlaid medium entropy oxide according to claim 1, characterized in that: In S3, the polyvinyl alcohol solution consists of polyvinyl alcohol and water, wherein the mass concentration of the polyvinyl alcohol is 1.5% to 2%.

5. The method for preparing ablation-resistant ceramic of a dual-phase inlaid medium entropy oxide according to claim 1, characterized in that: In S4, the powder to be pressed is pressed into a block shape at a pressing pressure of 20-25 MPa and a pressing time of 5-20 min.

6. The method for preparing ablation-resistant ceramics of a dual-phase inlaid medium entropy oxide according to claim 1, characterized in that: In S5, the process of the pressureless heat treatment is to increase the temperature to 800°C at 2°C / min, then increase the temperature to 1500-1600°C at 0.5-1°C / min and keep the temperature for 4-8 hours. The heat treatment reaction atmosphere is air atmosphere.

7. The method for preparing ablation-resistant ceramic of a dual-phase inlaid medium entropy oxide according to claim 1, characterized in that: In S5, after the autoclave heat treatment, the temperature is cooled to room temperature in the furnace at a rate of 1-2°C / min.

8. The method for preparing ablation-resistant ceramics of a dual-phase inlaid medium entropy oxide according to claim 1, characterized in that: In S1, the purity of HfO2 powder, ZrO2 powder, and TiO2 powder is 99.00%, and the particle size is 1-3 μm.

9. An ablation-resistant ceramic of dual-phase inlaid medium entropy oxide obtained by the method for preparing an ablation-resistant ceramic according to any one of claims 1 to 8, characterized in that: The heat flux density of oxyacetylene is 2.4MW / m 2 When the ablation protection temperature zone of the entropy oxide in the dual-phase mosaic is room temperature-2500°C; when continuous ablation is applied, the total effective protection time can reach 30s; when 15s cyclic ablation is applied, the total effective protection time reaches 60s, and the number of cycles can reach 4 times.

Images