High-heat-shock-resistant hafnium oxide ceramic, and preparation method and application thereof

Abstract

This invention provides a high thermal shock resistant hafnium oxide ceramic, its preparation method, and its application, belonging to the technical field of high-temperature resistant ceramic materials. Specifically, the high thermal shock resistant hafnium oxide ceramic provided by this invention comprises a hafnium oxide matrix and tetragonal zirconia whiskers, wherein the mass of the tetragonal zirconia whiskers is 2%~5% of the hafnium oxide matrix, and the hafnium oxide matrix comprises 90~95 parts of hafnium oxide and 8~10 parts of crystal stabilizer by mass. This invention achieves high thermal shock resistance and mechanical strength of hafnium oxide ceramics through the incorporation of yttrium oxide and tetragonal zirconia whiskers. Furthermore, the preparation method provided by this invention can achieve a smaller average grain size of the hafnium oxide ceramic through a specific sintering process. The technical solution provided by this invention is of great significance for the development of high-heat protection fields such as aerospace.

Description

Technical Field

[0001] This invention relates to the field of high-temperature resistant ceramic materials technology, specifically to a high thermal shock resistant hafnium oxide ceramic, its preparation method, and its application. Background Technology

[0002] Hafnium oxide possesses high melting point, excellent ablation resistance, and good chemical stability, making it an ideal structural ceramic material for extreme high-temperature applications such as aerospace. However, hafnium oxide faces two extremely difficult-to-overcome physical performance bottlenecks in practical engineering applications: First, when the temperature reaches around 1700℃, hafnium oxide undergoes a structural phase transformation from monoclinic to tetragonal phases during heating and cooling. This phase transformation is typically accompanied by a 5% to 7% volume change. When subjected to repeated thermal shocks, the volume change induced by the phase transformation generates significant internal stress within the hafnium oxide, accelerating the initiation and propagation of microcracks, ultimately leading to the fracture or disintegration of the hafnium oxide ceramic. Second, the conventional processes used to produce hafnium oxide ceramics... The density of ceramics is typically 90% to 92%, and they have a lot of pores inside. This leads to insufficient mechanical properties of hafnium oxide ceramics. For example, the room temperature flexural strength of hafnium oxide ceramics is only about 63 MPa, and the flexural strength drops to about 44 MPa at 1500℃. In the thermal shock cycle test from room temperature to 2100℃, conventional hafnium oxide ceramics break after the first to third cycle. This means that the durability of current hafnium oxide ceramics is poor, which seriously limits the research and development and large-scale use of high-temperature resistant devices.

[0003] To improve the performance of hafnium oxide ceramics, existing technologies attempt to dope them with alkaline earth metal oxides or rare earth metal oxides as crystal stabilizers to stabilize the high-temperature phase. However, while the introduction of crystal stabilizers can improve the thermal shock resistance of hafnium oxide ceramics to some extent, the brittleness of hafnium oxide ceramics remains, and crack propagation in the ceramic matrix cannot be suppressed. This results in poor toughness of hafnium oxide ceramics, which will still fracture due to stress concentration when exposed to ultra-high temperature thermal shock environments.

[0004] In addition, the current conventional sintering process for hafnium oxide involves slow heating and long holding times, which easily leads to coarsening of hafnium oxide, further limiting the engineering application of hafnium oxide ceramics. Summary of the Invention

[0005] One of the technical problems to be solved by this invention is: how to improve the thermal shock resistance and mechanical strength of hafnium oxide ceramics.

[0006] To address the aforementioned technical problems, the first aspect of this invention provides a high thermal shock resistant hafnium oxide ceramic, comprising a hafnium oxide matrix and tetragonal zirconia whiskers, wherein the mass of the tetragonal zirconia whiskers is 2% to 5% of the hafnium oxide matrix, and the hafnium oxide matrix comprises, by mass, a portion of... 90-95 parts hafnium oxide; 8-10 parts crystal stabilizer.

[0007] This invention employs a crystal stabilizer to effectively stabilize the hafnium oxide lattice and suppress volume distortion caused by phase transformation. Simultaneously, it uses tetragonal zirconia whiskers to toughen the hafnium oxide ceramic. Zirconia and hafnium are elements in the same group, exhibiting excellent chemical compatibility. Zirconia and hafnium oxide share high similarity in crystal structure and atomic radius, allowing for infinite solid solution and tight interfacial bonding. In the technical solution provided by this invention, zirconia whiskers continuously enhance the matrix toughness through multiple mechanisms, including whisker bridging, crack deflection, and phase transformation toughening. Furthermore, zirconia has a high melting point and good high-temperature compatibility with hafnium oxide, enabling it to withstand long-term high-temperature alternating conditions up to 2100℃. The similar coefficients of thermal expansion result in low interfacial thermal stress during thermal cycling, leading to excellent overall thermal shock resistance of the material.

[0008] Preferably, the crystal stabilizer is selected from any one or more of magnesium oxide, calcium oxide, yttrium oxide, and cerium oxide.

[0009] Preferably, the tetragonal zirconia whiskers have a diameter of 0.5~3μm and an aspect ratio of 10~50.

[0010] The second technical problem to be solved by this invention is: how to refine the average grain size of hafnium oxide ceramics in order to improve the performance of hafnium oxide ceramics.

[0011] To solve the above-mentioned technical problems, a second aspect of the present invention provides a method for preparing the high thermal shock resistant hafnium oxide ceramic described in the first aspect, specifically including the following steps: S1. Preparation of matrix powder: Weigh hafnium oxide powder and crystal stabilizer, add solvent to obtain slurry, grind the slurry to obtain matrix powder; S2. Powder Mixing Preparation: The matrix powder and tetragonal zirconia whiskers are mixed by mechanical resonance to obtain powder mixture; S3. Granulation powder preparation: Add plasticizer to the mixed powder, stir and seal, and carry out aging treatment. After aging, perform cold isostatic pressing to obtain green blank, crush the green blank and ball mill the crushed material to obtain granulation powder. S4. Sintering: The granulated powder is filled into a mold and sintered to obtain hafnium oxide ceramic with high thermal shock resistance.

[0012] Preferably, in step S1, the solvent is selected from any one or more of ethanol, isopropanol, n-propanol, n-butanol, isobutanol, acetone, and water.

[0013] Preferably, the plasticizer is selected from any one or more of PVA, maltodextrin, and PVB.

[0014] Preferably, the parameters of the cold isostatic pressing are: pressure of 20~30MPa and holding time of 60~120s.

[0015] Preferably, in step S4, the sintering procedure is as follows: A1: Vacuum degree ≤ 1×10 -3 Pre-compression at 20~30MPa for 1~5min; A2: Maintain a pressure of 20~30MPa and raise the temperature to 950~1020℃ at a heating rate of 60~100℃ / min; A3: Maintain a pressure of 20~30MPa, raise the temperature to 1790~1820℃ at a heating rate of 30~50℃ / min, and hold for 10~30min; A4: Maintain a pressure of 20~30MPa and reduce the temperature to below 100℃ at a cooling rate of 40~70℃ / min to complete sintering.

[0016] Preferably, the preparation method further includes an annealing step, the annealing step comprising: S5. Annealing: The hafnium oxide ceramic obtained in step S4 is subjected to annealing treatment, wherein... The annealing procedure is as follows: place the ceramic in a muffle furnace and hold at 800~1000℃ for 30~60 minutes to complete the annealing.

[0017] Furthermore, a third aspect of the present invention provides an application of the high thermal shock resistant hafnium oxide ceramic described in the first aspect, wherein the application is to use the high thermal shock resistant hafnium oxide ceramic in the preparation of thermal protection components.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The hafnium oxide ceramic provided by the present invention can effectively improve the thermal shock resistance and toughness of the hafnium oxide ceramic by doping with crystal stabilizer and tetragonal zirconia whiskers. The hafnium oxide ceramic provided by the present invention has high thermal shock resistance and can be used as a raw material for thermal protection components, which is of great significance to the development of fields with high thermal protection requirements such as aerospace. 2. The present invention also provides a method for preparing the aforementioned high thermal shock resistant hafnium oxide ceramic. The preparation method has a high sintering rate, and the hafnium oxide ceramic obtained by sintering has the characteristics of high density, small average grain size, strong grain boundary and interface bonding, and excellent comprehensive mechanical properties, and is suitable for a variety of complex scenarios. 3. Meanwhile, the preparation method of high thermal shock resistant hafnium oxide ceramics provided by the present invention has a simple overall process, controllable parameters, and is suitable for laboratory research and development as well as industrial mass production, and has the advantage of strong process practicality. Detailed Implementation

[0019] The embodiments of the technical solution of the present invention will be described in detail below. These embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.

[0020] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] As described in the background art, current hafnium oxide ceramics suffer from defects such as poor thermal shock resistance, low toughness, insufficient mechanical strength at ultra-high temperatures, and susceptibility to phase transformation cracking. In view of this, the present invention provides a hafnium oxide ceramic with high thermal shock resistance. This high thermal shock resistance hafnium oxide ceramic comprises a hafnium oxide matrix and tetragonal zirconia whiskers, wherein the mass of the tetragonal zirconia whiskers is 2% to 5% of the hafnium oxide matrix. By mass, the hafnium oxide matrix comprises... 90-95 parts hafnium oxide; 8-10 parts crystal stabilizer.

[0022] In the above embodiments, the crystal stabilizer is selected from any one or more of magnesium oxide, calcium oxide, yttrium oxide, and cerium oxide.

[0023] More specifically, in the above embodiments, the crystal stabilizer may also be other rare earth oxides.

[0024] In the above embodiments, the diameter of the tetragonal zirconia whiskers is 0.5~3μm and the aspect ratio is 10~50.

[0025] The high thermal shock resistant hafnium oxide ceramic provided by the specific embodiments of the present invention incorporates a crystal stabilizer and tetragonal zirconia whiskers. The incorporation of the crystal stabilizer effectively stabilizes the hafnium oxide lattice and suppresses volume distortion caused by phase transformation. The incorporation of tetragonal zirconia whiskers toughens the hafnium oxide ceramic. In the above embodiments, zirconium and hafnium are both group IVB elements, exhibiting excellent chemical compatibility, highly similar atomic radii and crystal structures. They can achieve infinite solid solution during high-temperature sintering and service, forming an interface with extremely strong bonding. Simultaneously, the thermal expansion coefficients of zirconium and hafnium are highly matched, maintaining structural integrity during long-term high-temperature service under high-temperature alternating cycles.

[0026] In the above embodiments, tetragonal zirconia whiskers were chosen as the toughening material instead of the more common alumina whiskers because: the melting point of alumina whiskers is much lower than that of zirconia and hafnium oxide, making them prone to softening and weakening in mechanical strength under high-temperature conditions; the crystal structures of alumina and hafnium oxide are significantly different, making it impossible to form an effective solid solution, resulting in low interfacial bonding strength and easy interface separation under high-temperature conditions, which greatly weakens the toughening effect. In addition, the coefficient of thermal expansion of alumina differs significantly from that of the matrix, and repeated thermal shocks will generate large interfacial stresses, accelerating crack initiation and propagation, ultimately leading to component failure.

[0027] In the above embodiments, tetragonal zirconia whiskers are chosen as the toughening material instead of zirconia powder directly because hafnium oxide and zirconia are naturally associated and have similar chemical properties, and industrial-grade high-purity hafnium oxide raw materials themselves contain trace amounts of zirconia. If ordinary zirconia powder is added to the hafnium oxide ceramic matrix, only basic particle dispersion strengthening can be achieved, and toughening effects such as whisker bridging and crack deflection cannot be achieved. Whisker morphology has extremely high high-temperature load-bearing and energy dissipation capabilities. For example, when microcracks are generated and propagated inside the hafnium oxide matrix, tetragonal zirconia whiskers with a specific diameter and aspect ratio can play a multiple crack-resistant toughening mechanism, specifically manifested as (a) whisker bridging: whiskers spanning the two wings of the crack provide closing stress, hindering crack opening and deformation; (b) crack deflection: when the crack propagates and is hindered by whiskers, it will be forced to change the extension path, significantly consuming the surface energy of crack propagation, thereby reducing the driving force of crack propagation and achieving the crack-resistant effect. Zirconia powder has limited effect on improving the fracture toughness, high-temperature strength, and thermal shock resistance of ceramics. If zirconia powder is used to replace tetragonal zirconia whiskers in the matrix, the fracture toughness, mechanical strength, and thermal shock resistance of the material will be significantly reduced, making it unable to meet the harsh conditions of high-temperature alternating thermal shock.

[0028] The present invention also provides a method for preparing the aforementioned high thermal shock resistant hafnium oxide ceramic, which specifically includes the following steps: S1. Preparation of matrix powder: Weigh hafnium oxide powder and crystal stabilizer, add solvent to obtain slurry, grind the slurry to obtain matrix powder; S2. Powder Mixing Preparation: The matrix powder and tetragonal zirconia whiskers are mixed by mechanical resonance to obtain powder mixture; S3. Granulation powder preparation: Add plasticizer to the mixed powder, stir and seal, and carry out aging treatment. After aging, perform cold isostatic pressing to obtain green blank, crush the green blank and ball mill the crushed material to obtain granulation powder. S4. Sintering: The granulated powder is filled into a mold and sintered to obtain hafnium oxide ceramic with high thermal shock resistance.

[0029] In step S1 of the above embodiments, the solvent is selected from any one or more of ethanol, isopropanol, n-propanol, n-butanol, isobutanol, acetone, and water.

[0030] In step S3 of the above embodiment, the plasticizer is selected from any one or more of PVA, maltodextrin, and PVB.

[0031] In step S3 of the above embodiment, the parameters of cold isostatic pressing are: pressure of 20~30MPa and holding time of 60~120s.

[0032] In step S4 of the above embodiment, the sintering process is as follows: A1: Vacuum degree ≤ 1×10 -3 Pre-compression at 20~30MPa for 1~5min; A2: Maintain a pressure of 20~30MPa and raise the temperature to 950~1020℃ at a heating rate of 60~100℃ / min; A3: Maintain a pressure of 20~30MPa, raise the temperature to 1790~1820℃ at a heating rate of 30~50℃ / min, and hold for 10~30min; A4: Maintain a pressure of 20~30MPa and reduce the temperature to below 100℃ at a cooling rate of 40~70℃ / min to complete sintering.

[0033] In the above embodiments, the preparation method further includes an annealing step, the annealing step comprising: S5. Annealing: The hafnium oxide ceramic obtained in step S4 is subjected to annealing treatment, wherein... The annealing procedure is as follows: place the ceramic in a muffle furnace and hold at 800~1000℃ for 30~60 minutes to complete the annealing.

[0034] More specifically, in the above embodiments, the purity of hafnium oxide powder is preferably 99.9% or higher, and the particle size of hafnium oxide powder is preferably 1~3μm.

[0035] More specifically, in the above embodiments, the crystal form stabilizer is preferably yttrium oxide. If the crystal form stabilizer is yttrium oxide, the purity of the yttrium oxide powder is preferably 99.9% or higher, and the particle size of the yttrium oxide powder is preferably 30 to 100 nm.

[0036] More specifically, in the above embodiments, the purity of the tetragonal zirconia whiskers is preferably 99.9% or higher.

[0037] More specifically, in step S2 of the above embodiment, mechanical resonance is preferably acoustic resonance. Acoustic resonance can generate high-intensity sound waves that create a macroscopic vibration and microscopic acoustic flow coupling effect in the mixed multiphase flow, thereby achieving uniform dispersion of whiskers and effectively preventing whisker agglomeration.

[0038] More specifically, in step S3 of the above embodiment, the aging time is preferably 12 to 24 hours.

[0039] More specifically, in the above embodiments, the amount of plasticizer added is preferably 1% to 3% by weight of the mixed powder.

[0040] More specifically, in step S3 of the above embodiment, the particle size of the granulated powder is preferably 15 to 50 mesh, and most preferably 20 mesh.

[0041] More specifically, in step S4 of the above embodiment, the sintering equipment is preferably a spark plasma sintering equipment, and correspondingly, the mold is preferably a graphite mold. Spark plasma sintering can achieve rapid densification of hafnium oxide ceramics by activating grain boundaries with pulsed plasma.

[0042] More specifically, in the above embodiments, one purpose of annealing is to remove the carburization introduced during the sintering process; another purpose of annealing is to release the residual thermal stress inside the ceramic, thereby further improving the toughness and thermal shock resistance of hafnium oxide ceramics.

[0043] The high thermal shock resistant hafnium oxide ceramics prepared by the preparation method provided in the above embodiments have the characteristics of excellent thermal shock resistance and excellent mechanical properties at high temperature. The prepared hafnium oxide ceramic components can meet the stringent requirements of ultra-high temperature thermal protection and thermal shock.

[0044] The technical solutions of the present invention are further described below through specific embodiments. Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art. In some cases, terms with conventional meanings are limited herein for clarification or ease of reference, and such limitations should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and have been employed by conventional methods. Unless otherwise stated, the use of commercially available reagents and instruments shall be performed according to the manufacturer's instructions and parameters.

[0045] In the following examples, the hafnium oxide powder was sourced from Beijing Deco Island Gold Co., Ltd., with a purity of over 99.9% and a particle size of 1~3μm; In the following examples, yttrium oxide was obtained from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of over 99.9% and a particle size of 30~100nm; In the following examples, the tetragonal zirconia whiskers were sourced from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of over 99.9%, a diameter of 0.5~3μm, and an aspect ratio of 10~50. In the following examples, the alumina whiskers were sourced from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of over 99.9%, a diameter of 3 μm, and an aspect ratio of 50. In the following examples, the zirconium oxide powder was sourced from Beijing Deco Island Gold Co., Ltd., with a purity of over 99.9% and a particle size of 600 mesh.

[0046] Example 1

[0047] Preparation of high thermal shock resistant hafnium oxide ceramics S1. Preparation of matrix powder: Weigh 91 parts by mass of hafnium oxide powder with a particle size of 3μm and 9 parts by mass of yttrium oxide powder with a particle size of 50nm. Use anhydrous ethanol as the ball milling medium and control the mass ratio of grinding balls, powder and anhydrous ethanol to be 2:1:1. Perform planetary ball milling for 10 hours. After ball milling, dry the slurry and sieve it using a 100-mesh standard sieve to obtain the matrix powder. S2. Powder Mixing Preparation: By using the acoustic resonance method, 100 parts by mass of matrix powder and 3 parts by mass of tetragonal zirconia whiskers with a diameter of 3μm and an aspect ratio of 50 are mixed to obtain powder mixing. S3. Granulation powder preparation: Add 1% by weight of PVA plasticizer to the mixed powder, stir and seal, and perform aging treatment for 18 hours. After aging, put the material into a rubber sleeve and press it under cold isostatic pressure of 25MPa for 80s to obtain a green blank. Crush the green blank and ball mill it for 3 hours at a powder to grinding ball mass ratio of 1:1. Then pass it through a 20-mesh sieve to obtain qualified granulated powder. S4. Sintering: Select a graphite mold, evenly coat the inner wall and punch surface with BN release agent, fill the mold with granulated powder and flatten and compact it, then place the whole thing into the spark plasma sintering equipment, and evacuate the equipment cavity to a vacuum degree of 1×10⁻⁶. -3 Below Pa, apply a uniaxial pressure of 30 MPa for 3 min to pre-compress, then raise the temperature to 1000℃ at a rate of 80℃ / min, and then raise it to 1800℃ at a rate of 40℃ / min, maintaining a constant pressure of 30 MPa throughout the process, and hold for 20 min. After sintering, disconnect the power, maintain the pressure, and cool with the furnace at a rate of 60℃ / min. Remove the sample when the cavity temperature drops below 100℃. S5. Annealing: The sintered sample is placed in an air muffle furnace and annealed at 880℃ for 40 minutes to remove surface carburized impurities and release internal residual stress; finally, the green body is polished and finished to obtain the finished ceramic.

[0048] Example 2

[0049] Preparation of high thermal shock resistant hafnium oxide ceramics S1. Preparation of matrix powder: Weigh 90 parts by mass of hafnium oxide powder with a particle size of 3μm and 10 parts by mass of yttrium oxide powder with a particle size of 50nm. Use anhydrous ethanol as the ball milling medium and control the mass ratio of grinding balls, powder and anhydrous ethanol to be 2:1:1. Perform planetary ball milling for 10 hours. After ball milling, dry the slurry and sieve it using a 100-mesh standard sieve to obtain the matrix powder. S2. Powder Mixing Preparation: By using the acoustic resonance method, 100 parts by mass of matrix powder and 2 parts by mass of tetragonal zirconia whiskers with a diameter of 2μm and an aspect ratio of 40 are mixed to obtain powder mixing. S3. Granulation powder preparation: Add 3% by weight of PVB plasticizer to the mixed powder, stir and seal, and perform aging treatment for 12 hours. After aging, put the material into a rubber sleeve and press it under cold isostatic pressure of 20MPa for 60s to obtain a green blank. Crush the green blank and ball mill it for 3 hours according to the mass ratio of powder to grinding ball of 1:1. Then pass it through a 20-mesh sieve to obtain qualified granulated powder. S4. Sintering: Select a graphite mold, evenly coat the inner wall and punch surface with BN release agent, fill the mold with granulated powder and flatten and compact it, then place the whole thing into the spark plasma sintering equipment, and evacuate the equipment cavity to a vacuum degree of 1×10⁻⁶. -3 Below Pa, apply a uniaxial pressure of 30 MPa for 3 min to pre-compress, then raise the temperature to 1000℃ at a rate of 60℃ / min, and then raise it to 1800℃ at a rate of 30℃ / min, maintaining a constant pressure of 30 MPa throughout the process, and hold for 10 min. After sintering, disconnect the power, maintain the pressure, and cool with the furnace at a rate of 60℃ / min. Remove the sample when the cavity temperature drops below 100℃. S5. Annealing: The sintered sample is placed in an air muffle furnace and annealed at 800℃ for 60 minutes to remove surface carburized impurities and release internal residual stress; finally, the green body is polished and finished to obtain the finished ceramic.

[0050] Example 3

[0051] Preparation of high thermal shock resistant hafnium oxide ceramics S1. Preparation of matrix powder: Weigh 92 parts by mass of hafnium oxide powder with a particle size of 3μm and 8 parts by mass of yttrium oxide powder with a particle size of 50nm. Use anhydrous ethanol as the ball milling medium and control the mass ratio of grinding balls, powder and anhydrous ethanol to be 2:1:1. Perform planetary ball milling for 12 hours. After ball milling, dry the slurry and sieve it using a 100-mesh standard sieve to obtain the matrix powder. S2. Powder Mixing Preparation: By using the acoustic resonance method, 100 parts by mass of matrix powder and 5 parts by mass of tetragonal zirconia whiskers with a diameter of 2μm and an aspect ratio of 30 are mixed to obtain powder mixing. S3. Granulation powder preparation: Add 2% by weight of maltodextrin plasticizer to the mixed powder, stir and seal, and age for 24 hours. After aging, put the material into a rubber sleeve and press it under cold isostatic pressure of 30MPa for 100s to obtain a green blank. Crush the green blank and ball mill it for 4 hours at a powder to grinding ball mass ratio of 1:1. Then pass it through a 20-mesh sieve to obtain qualified granulated powder. S4. Sintering: Select a graphite mold, evenly coat the inner wall and punch surface with BN release agent, fill the mold with granulated powder and flatten and compact it, then place the whole thing into the spark plasma sintering equipment, and evacuate the equipment cavity to a vacuum degree of 1×10⁻⁶. -3 Below Pa, apply a uniaxial pressure of 30 MPa for 3 min to pre-compress, then raise the temperature to 1000℃ at a rate of 100℃ / min, and then raise it to 1800℃ at a rate of 50℃ / min, maintaining a constant pressure of 30 MPa throughout the process, and hold for 20 min. After sintering, disconnect the power, maintain the pressure, and cool the furnace at a rate of 60℃ / min until the cavity temperature drops below 100℃, then remove the sample. S5. Annealing: The sintered sample is placed in an air muffle furnace and annealed at 1000℃ for 30 minutes to remove surface carburized impurities and release internal residual stress; finally, the green body is polished and refined to obtain the finished ceramic.

[0052] Comparative Example 1 Preparation of hafnium oxide ceramics with zirconium oxide powder S1. Preparation of matrix powder: Weigh 91 parts by mass of hafnium oxide powder with a particle size of 3μm and 9 parts by mass of yttrium oxide powder with a particle size of 50nm. Use anhydrous ethanol as the ball milling medium and control the mass ratio of grinding balls, powder and anhydrous ethanol to be 2:1:1. Perform planetary ball milling for 10 hours. After ball milling, dry the slurry and sieve it using a 100-mesh standard sieve to obtain the matrix powder. S2. Powder Mixing Preparation: By using the acoustic resonance method, 100 parts by weight of matrix powder and 3 parts by weight of zirconium oxide powder with a particle size of 600 mesh and a purity of ≥99.9% are mixed to obtain powder mixture; S3. Granulation powder preparation: Add 1% by weight of PVA plasticizer to the mixed powder, stir and seal, and perform aging treatment for 18 hours. After aging, put the material into a rubber sleeve and press it under cold isostatic pressure of 25MPa for 80s to obtain a green blank. Crush the green blank and ball mill it for 3 hours at a powder to grinding ball mass ratio of 1:1. Then pass it through a 20-mesh sieve to obtain qualified granulated powder. S4. Sintering: Select a graphite mold, evenly coat the inner wall and punch surface with BN release agent, fill the mold with granulated powder and flatten and compact it, then place the whole thing into the spark plasma sintering equipment, and evacuate the equipment cavity to a vacuum degree of 1×10⁻⁶. -3Below Pa, apply a uniaxial pressure of 30 MPa for 3 min to pre-compress, then raise the temperature to 1000℃ at a rate of 80℃ / min, and then raise it to 1800℃ at a rate of 40℃ / min, maintaining a constant pressure of 30 MPa throughout the process, and hold for 20 min. After sintering, disconnect the power, maintain the pressure, and cool with the furnace at a rate of 60℃ / min. Remove the sample when the cavity temperature drops below 100℃. S5. Annealing: The sintered sample is placed in an air muffle furnace and annealed at 880℃ for 40 minutes to remove surface carburized impurities and release internal residual stress; finally, the green body is polished and finished to obtain the finished ceramic.

[0053] Comparative Example 2 Preparation of hafnium oxide ceramics with alumina whiskers S1. Preparation of matrix powder: Weigh 91 parts by mass of hafnium oxide powder with a particle size of 3μm and 9 parts by mass of yttrium oxide powder with a particle size of 50nm. Use anhydrous ethanol as the ball milling medium and control the mass ratio of grinding balls, powder and anhydrous ethanol to be 2:1:1. Perform planetary ball milling for 10 hours. After ball milling, dry the slurry and sieve it using a 100-mesh standard sieve to obtain the matrix powder. S2. Powder Mixing Preparation: By using the acoustic resonance method, 100 parts by mass of matrix powder and 3 parts by mass of alumina whiskers with a diameter of 3μm and an aspect ratio of 50 are mixed to obtain powder mixing. S3. Granulation powder preparation: Add 1% by weight of PVA plasticizer to the mixed powder, stir and seal, and perform aging treatment for 18 hours. After aging, put the material into a rubber sleeve and press it under cold isostatic pressure of 25MPa for 80s to obtain a green blank. Crush the green blank and ball mill it for 3 hours at a powder to grinding ball mass ratio of 1:1. Then pass it through a 20-mesh sieve to obtain qualified granulated powder. S4. Sintering: Select a graphite mold, evenly coat the inner wall and punch surface with BN release agent, fill the mold with granulated powder and flatten and compact it, then place the whole thing into the spark plasma sintering equipment, and evacuate the equipment cavity to a vacuum degree of 1×10⁻⁶. -3 Below Pa, apply a uniaxial pressure of 30 MPa for 3 min to pre-compress, then raise the temperature to 1000℃ at a rate of 80℃ / min, and then raise it to 1800℃ at a rate of 40℃ / min, maintaining a constant pressure of 30 MPa throughout the process, and hold for 20 min. After sintering, disconnect the power, maintain the pressure, and cool with the furnace at a rate of 60℃ / min. Remove the sample when the cavity temperature drops below 100℃. S5. Annealing: The sintered sample is placed in an air muffle furnace and annealed at 880℃ for 40 minutes to remove surface carburized impurities and release internal residual stress; finally, the green body is polished and finished to obtain the finished ceramic.

[0054] Comparative Example 3 Preparation of Hafnium Oxide Ceramics without Whisker Doping S1. Preparation of matrix powder: Weigh 91 parts by mass of hafnium oxide powder with a particle size of 3μm and 9 parts by mass of yttrium oxide powder with a particle size of 50nm. Use anhydrous ethanol as the ball milling medium and control the mass ratio of grinding balls, powder and anhydrous ethanol to be 2:1:1. Perform planetary ball milling for 10 hours. After ball milling, dry the slurry and sieve it using a 100-mesh standard sieve to obtain the matrix powder. S2. Granulation powder preparation: Add 1% by weight of PVA plasticizer to the matrix powder, stir and seal, and perform aging treatment for 18 hours. After aging, put the material into a rubber sleeve and press it under cold isostatic pressure of 25MPa for 80s to obtain a green blank. Crush the green blank and ball mill it for 3 hours at a powder to grinding ball mass ratio of 1:1. Then pass it through a 20-mesh sieve to obtain qualified granulated powder. S3. Sintering: Select a graphite mold, evenly coat the inner wall and punch surface with BN release agent, fill the mold with granulated powder and flatten and compact it, then place the whole thing into the spark plasma sintering equipment, and evacuate the equipment cavity to a vacuum degree of 1×10⁻⁶. -3 Below Pa, apply a uniaxial pressure of 30 MPa for 3 min to pre-compress, then raise the temperature to 1000℃ at a rate of 80℃ / min, and then raise it to 1800℃ at a rate of 40℃ / min, maintaining a constant pressure of 30 MPa throughout the process, and hold for 20 min. After sintering, disconnect the power, maintain the pressure, and cool with the furnace at a rate of 60℃ / min. Remove the sample when the cavity temperature drops below 100℃. S4. Annealing: The sintered sample is placed in an air muffle furnace and annealed at 880℃ for 40 minutes to remove surface carburized impurities and release internal residual stress; finally, the green body is polished and finished to obtain the finished ceramic.

[0055] Comparative Example 4 Preparation of pure hafnium oxide ceramics S1. Preparation of matrix powder: Weigh 100 parts by weight of hafnium oxide powder with a particle size of 3μm, use anhydrous ethanol as the ball milling medium, control the mass ratio of grinding balls, powder and anhydrous ethanol to be 2:1:1, and ball mill for 10 hours. After ball milling, dry the slurry and sieve it with a 100-mesh standard sieve to obtain the matrix powder. S2. Granulation powder preparation: Add 1% by weight of PVA plasticizer to the matrix powder, stir and seal, and perform aging treatment for 18 hours. After aging, put the material into a rubber sleeve and press it under cold isostatic pressure of 25MPa for 80s to obtain a green blank. Crush the green blank and ball mill it for 3 hours at a powder to grinding ball mass ratio of 1:1. Then pass it through a 20-mesh sieve to obtain qualified granulated powder. S3. Sintering: Select a graphite mold, evenly coat the inner wall and punch surface with BN release agent, fill the mold with granulated powder and flatten and compact it, then place the whole thing into the spark plasma sintering equipment, and evacuate the equipment cavity to a vacuum degree of 1×10⁻⁶.-3 Below Pa, apply a uniaxial pressure of 30 MPa for 3 min to pre-compress, then raise the temperature to 1000℃ at a rate of 80℃ / min, and then raise it to 1800℃ at a rate of 40℃ / min, maintaining a constant pressure of 30 MPa throughout the process, and hold for 20 min. After sintering, disconnect the power, maintain the pressure, and cool with the furnace at a rate of 60℃ / min. Remove the sample when the cavity temperature drops below 100℃. S4. Annealing: The sintered sample is placed in an air muffle furnace and annealed at 880℃ for 40 minutes to remove surface carburized impurities and release internal residual stress; finally, the green body is polished and finished to obtain the finished ceramic.

[0056] Test case All ceramic products prepared in the examples and comparative examples were subjected to fracture toughness tests (GB / T 44304-2024), density tests (GB / T 3850-2015), room temperature compressive strength tests (GB / T 4740-1999), room temperature flexural strength tests (GB / T 4741-1999), 1500℃ flexural strength tests (GB / T 14390-2008), room temperature Vickers hardness tests (GB / T16534-2009), 2100℃ thermal shock cycle tests (GB / T 37246-2018), and average grain size tests (GB / T45974-2025). Each ceramic product was tested three times, and the average value was taken as the final result. The results are shown in Table 1.

[0057] Table 1

[0058] The results above show that yttrium oxide modification alone can significantly optimize the density, mechanical properties, and thermal shock resistance of hafnium oxide ceramics, but the toughening effect is limited. Introducing alumina whiskers only slightly improves the room-temperature mechanical properties, but due to its low melting point, poor solid solution capacity, and thermal expansion mismatch, its ultra-high temperature thermal shock resistance at 2100℃ remains unimproved, at the same level as pure hafnium oxide ceramics. Introducing zirconia powder, although zirconia powder and zirconia whiskers are made of the same material, results in a relatively low improvement in toughness and thermal shock resistance because the whiskers cannot utilize their unique toughening mechanism. This invention employs a composite toughening method using zirconia whiskers and a crystal stabilizer. Relying on their good solid solution compatibility and high-temperature adaptability, the resulting hafnium oxide ceramics exhibit significantly improved properties across all aspects.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A hafnium oxide ceramic with high thermal shock resistance, characterized in that, The high thermal shock resistant hafnium oxide ceramic comprises a hafnium oxide matrix and tetragonal zirconia whiskers, wherein the mass of the tetragonal zirconia whiskers is 2% to 5% of the hafnium oxide matrix, and the hafnium oxide matrix comprises, by mass, parts of... 90-95 parts hafnium oxide; 8-10 parts crystal stabilizer.

2. The high thermal shock resistant hafnium oxide ceramic as described in claim 1, characterized in that, The crystal stabilizer is selected from any one or more of magnesium oxide, calcium oxide, yttrium oxide, and cerium oxide.

3. The high thermal shock resistant hafnium oxide ceramic as described in claim 1, characterized in that, The tetragonal zirconia whiskers have a diameter of 0.5~3μm and an aspect ratio of 10~50.

4. A method for preparing the high thermal shock resistant hafnium oxide ceramic according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Preparation of matrix powder: Weigh hafnium oxide powder and crystal stabilizer, add solvent to obtain slurry, grind the slurry to obtain matrix powder; S2. Powder Mixing Preparation: The matrix powder and tetragonal zirconia whiskers are mixed by mechanical resonance to obtain powder mixture; S3. Granulation powder preparation: Add plasticizer to the mixed powder, stir and seal, and carry out aging treatment. After aging, perform cold isostatic pressing to obtain green blank, crush the green blank and ball mill the crushed material to obtain granulation powder. S4. Sintering: The granulated powder is filled into a mold and sintered to obtain hafnium oxide ceramic with high thermal shock resistance.

5. The preparation method according to claim 4, characterized in that, In step S1, the solvent is selected from any one or more of ethanol, isopropanol, n-propanol, n-butanol, isobutanol, acetone, and water.

6. The preparation method according to claim 4, characterized in that, The plasticizer is selected from any one or more of PVA, maltodextrin, and PVB.

7. The preparation method according to claim 4, characterized in that, The parameters for the cold isostatic pressing are: pressure of 20~30MPa and holding time of 60~120s.

8. The preparation method according to claim 4, characterized in that, In step S4, the sintering procedure is as follows: A1: Vacuum degree ≤ 1×10 -3 Pre-compression at 20~30MPa for 1~5min; A2: Maintain a pressure of 20~30MPa and raise the temperature to 950~1020℃ at a heating rate of 60~100℃ / min; A3: Maintain a pressure of 20~30MPa, raise the temperature to 1790~1820℃ at a heating rate of 30~50℃ / min, and hold for 10~30min; A4: Maintain a pressure of 20~30MPa and reduce the temperature to below 100℃ at a cooling rate of 40~70℃ / min to complete sintering.

9. The preparation method according to claim 4, characterized in that, The preparation method further includes an annealing step, which includes: S5. Annealing: The hafnium oxide ceramic obtained in step S4 is subjected to annealing treatment, wherein... The annealing procedure is as follows: place the ceramic in a muffle furnace and hold at 800~1000℃ for 30~60 minutes to complete the annealing.

10. An application of the high thermal shock resistant hafnium oxide ceramic according to any one of claims 1 to 3, characterized in that, The highly thermally shock resistant hafnium oxide ceramic is used in the preparation of thermal protection components.

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