Controllable morphology entropy-stable high-entropy oxide powder and low-temperature high-pressure preparation method thereof

Abstract

The present application relates to a controllable morphology entropy-stable high-entropy oxide powder and a low-temperature high-pressure preparation method thereof. By selecting magnesium, cobalt, nickel, copper, zinc, strontium, lanthanum, chromium, iron, manganese, titanium, zirconium, gadolinium and other metal elements, the entropy-stable single-phase high-entropy oxide powder with rock salt, perovskite or fluorite structure can be synthesized under the condition far below the normal pressure phase transition temperature by using 10-300 MPa pressure assisted reaction. The method is based on the precursor morphology control, combined with the high-pressure atmosphere reaction kettle in a specific atmosphere for 0.5-24 hours of heat preservation, successfully overcomes the problem that the traditional pressureless or static pressure sintering is difficult to realize high phase purity and controllable morphology at the same time, and obtains the monodisperse and uniform structure powder. The process has the advantages of low temperature, low energy consumption, easy scaling and the like, and the obtained powder has excellent performance and can meet the application requirements in many fields.

Description

Technical Field

[0001] This invention relates to the field of novel inorganic material preparation technology, specifically to a controllable morphology-stable high-entropy oxide powder and its low-temperature, high-pressure preparation method. Background Technology

[0002] Entropy-stable high-entropy oxides are a class of novel ceramic materials composed of five or more metallic elements in equimolar or near-equimolar ratios, forming a single stable solid solution structure. Since their first report in 2015, their unique "high-entropy effect" has endowed them with excellent thermal stability, mechanical properties, and functional characteristics (such as catalytic, dielectric, and lithium-ion battery properties), making them demonstrate enormous application potential in energy, environment, catalysis, and aerospace fields.

[0003] The performance of materials depends not only on their chemical composition and crystal structure, but also closely on their microstructure. For example, spherical powders are beneficial for improving compact density and sintering activity; fibrous or flake powders, due to their high specific surface area and anisotropy, exhibit excellent performance in catalytic and electrode materials. Therefore, achieving the controllable preparation of entropy-stable high-entropy oxide powders is a key step in promoting their transition from basic research to practical applications.

[0004] Currently, methods for preparing entropy-stable high-entropy oxide powders mainly include co-precipitation, sol-gel methods, hydrothermal methods, and electrospinning. These methods typically involve first synthesizing a precursor with a specific morphology, and then converting it into the target oxide through high-temperature heat treatment (calcination). However, these methods are generally carried out under ambient pressure conditions, which has the following inherent drawbacks: Morphological collapse problem: The precursor undergoes thermal decomposition during heat treatment, releasing a large amount of gas (such as H2O, CO2, NO). x Under normal pressure, the instantaneous and violent release of gas generates strong internal stress, causing the original fine microstructure of the precursor (such as spherical or fibrous) to collapse, crack, or sinter and agglomerate severely, making it difficult to maintain the integrity of the morphology; studies have shown that even at relatively low calcination temperatures of 150°C to 850°C, morphological damage is difficult to avoid. High energy consumption and phase separation risk: In order to obtain pure phase entropy-stable high-entropy oxides, atmospheric pressure methods often require higher temperatures (usually exceeding 800℃, or even above 1000℃) to drive atomic diffusion and crystal growth. This not only leads to a significant increase in energy consumption, but also, at high temperatures, different metal elements are prone to component segregation or phase separation due to differences in diffusion rates, forming impure phases and destroying the core advantage of high-entropy systems—the stability of single-phase structures. To lower the synthesis temperature, pressure has been introduced in existing technologies. For example, some studies have successfully formed a single rock salt phase structure in the (MgCoNiCuZn)O system under an axial pressure of about 30 MPa and a temperature of 800 °C using plasma activated sintering (SPS) technology. Although pressure reduces the phase transformation temperature to some extent, the main purpose of such static pressure sintering methods is to achieve rapid densification of materials to prepare bulk ceramics. The process is accompanied by huge plastic flow and volume shrinkage, and the final result is a dense bulk material, rather than monodisperse powder with a specific morphology.

[0005] In summary, a prominent contradiction exists in existing technologies: atmospheric pressure high-temperature methods capable of preparing powders cannot maintain their morphology, while pressure-assisted methods that can lower temperatures fail to produce powders. Currently, there is a lack of a universal method that can effectively prepare entropy-stable high-entropy oxide powders with controllable morphology and high phase purity at relatively low temperatures.

[0006] Therefore, there is an urgent need to develop a new preparation strategy that can simultaneously solve the three interrelated technical challenges of morphology preservation, low-temperature synthesis, and phase structure purification, so as to promote the practical application of high-performance entropy-stable high-entropy oxide powder materials. Summary of the Invention

[0007] The purpose of this invention is to provide a controllable morphology-stable high-entropy oxide powder and its low-temperature, high-pressure preparation method, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A controllable morphology entropy-stable high-entropy oxide powder, wherein the entropy-stable high-entropy oxide powder is composed of five or more metallic elements and has a single-phase rock salt structure, perovskite structure or fluorite structure; the metallic elements are selected from at least five of magnesium, cobalt, nickel, copper, zinc, chromium, iron, manganese, strontium, lanthanum, titanium, zirconium and gadolinium; the morphology of the entropy-stable high-entropy oxide powder is determined by the specific morphology of the precursor (such as spherical, flake, fibrous or flocculent).

[0009] As a preferred option, entropy-stable high-entropy oxides are selected with a single rock salt phase structure.

[0010] As a preferred approach, the morphology of the entropy-stable high-entropy oxide powder is prepared as spherical particles, fibrous structures, and irregular three-dimensional network-like flocculent structures.

[0011] As a preferred option, the five metallic elements are magnesium, cobalt, nickel, copper and zinc, and the molar ratio of the five metallic elements magnesium, cobalt, nickel, copper and zinc is an equimolar ratio or a near equimolar ratio.

[0012] A method for preparing entropy-stable high-entropy oxide powders with controllable morphology includes the following steps: S1: Prepare entropy-stable and entropy-stable high-entropy oxide precursors with specific morphologies; S2: Place the precursor obtained in step S1 into a high-pressure reaction device; S3: The reaction is carried out in a specific gas atmosphere. The precursor is subjected to a pressure of 10 MPa to 300 MPa and kept at a temperature below atmospheric pressure for 0.5 h to 24 h to carry out a low-temperature high-pressure reaction, resulting in entropy-stable high-entropy oxide powder with a single rock salt phase structure and a specific morphology.

[0013] As a preferred embodiment, step S1 involves preparing an entropy-stable and entropy-stable high-entropy oxide precursor with a specific morphology, specifically including: A particulate precursor can be obtained by preparing a mother salt solution containing a metal element and a precipitant solution through co-precipitation, reacting them in a water bath with mechanical stirring; or by continuously stirring a metal salt containing a metal element and a complexing agent in a solution to form a sol through a sol-gel method, and obtaining a flocculent precursor after drying; or by spinning a polymer precursor solution containing a metal element through electrospinning to obtain a fibrous precursor, etc.

[0014] As a preferred option, the high-pressure reaction device is a high-pressure reactor.

[0015] As can be seen from the technical solution provided by the present invention above, the beneficial effects of the controllable morphology entropy-stable high-entropy oxide powder and its low-temperature high-pressure preparation method provided by the present invention are: By pre-designing and synthesizing precursors with specific morphologies (such as spherical, fibrous, and flocculent), and then subjecting them to low-temperature heat treatment under high pressure, the high-pressure environment effectively inhibited the morphological collapse, agglomeration, or sintering growth of the precursors caused by rapid gas release during thermal decomposition. Simultaneously, the low-temperature conditions prevented excessive grain growth and recrystallization, allowing the original morphology of the precursors to be "frozen" and inherited, successfully obtaining entropy-stable high-entropy oxide powders with regular morphology and good dispersibility. This solved the technical problem of maintaining specific morphologies using traditional atmospheric pressure and high-temperature methods. The high-pressure conditions used in this invention provide an additional driving force for atomic diffusion and effectively suppress the phase separation tendency caused by the difference in diffusion rate of different metal components. Under the synergistic effect of temperature and pressure, it is possible to directly and efficiently form rock salt phase-stable high-entropy oxides with uniform composition and simple structure, avoiding the generation of impurity phases, thereby ensuring the chemical and structural stability of the material in subsequent applications. The method of this invention can synthesize and crystallize entropy-stable high-entropy oxides in a relatively low temperature range of 400℃ to 850℃, which is much lower than many atmospheric pressure sintering methods (which usually require more than 1000℃) and some existing high pressure methods (such as plasma activation sintering at 800℃). The significant reduction in synthesis temperature directly leads to a significant reduction in energy consumption, which is in line with the green and low-carbon manufacturing concept and has a cost advantage for industrial application. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the steps in the low-temperature, high-pressure preparation method of controllable morphology entropy-stable high-entropy oxide powder according to the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0019] like Figure 1 As shown, this embodiment of the invention provides a controllable morphology entropy-stable high-entropy oxide powder. The entropy-stable high-entropy oxide powder is composed of five or more metal elements and has a single rock salt phase crystal structure. The metal elements are selected from at least five of magnesium, cobalt, nickel, copper, zinc, chromium, iron, manganese, titanium, zirconium, and gadolinium. The morphology of the entropy-stable high-entropy oxide powder is determined by the specific morphology of the precursor (such as spherical, flake, fibrous, or flocculent).

[0020] In this embodiment, the morphology of the entropy-stable high-entropy oxide powder is spherical particles, fibrous structure, and irregular three-dimensional network flocculent structure.

[0021] In this embodiment, the five metallic elements are magnesium, cobalt, nickel, copper and zinc, and the molar ratio of the five metallic elements is an equimolar ratio or a near equimolar ratio.

[0022] A method for preparing entropy-stable high-entropy oxide powders with controllable morphology includes the following steps: S1: Prepare entropy-stable and entropy-stable high-entropy oxide precursors with specific morphologies; S2: Place the precursor obtained in step S1 into a high-pressure reaction device; S3: The reaction is carried out in a specific gas atmosphere. The precursor is subjected to a pressure of 10 MPa to 300 MPa and kept at a temperature below atmospheric pressure for 0.5 h to 24 h to carry out a low-temperature high-pressure reaction, resulting in entropy-stable high-entropy oxide powder with a single rock salt phase structure and a specific morphology.

[0023] In this embodiment, step S1, preparing an entropy-stable and entropy-stable high-entropy oxide precursor with a specific morphology, specifically includes: A particulate precursor can be obtained by preparing a mother salt solution containing a metal element and a precipitant solution through co-precipitation, reacting them in a water bath with mechanical stirring; or by continuously stirring a metal salt containing a metal element and a complexing agent in a solution to form a sol through a sol-gel method, and obtaining a flocculent precursor after drying; or by spinning a polymer precursor solution containing a metal element through electrospinning to obtain a fibrous precursor, etc. Furthermore, step S1 aims to construct entropy-stable and entropy-stable high-entropy oxide precursors with specific morphologies such as spherical, flocculent, or fibrous forms by selecting a suitable preparation method. This lays the structural foundation for obtaining the target morphology entropy-stable high-entropy oxide powder through subsequent low-temperature and high-pressure reactions. This step requires consideration of the target powder morphology requirements. This invention will provide several methods for preparing precursors with specific morphologies, as detailed below: Step S1-1: Preparation of particulate precursor by co-precipitation method: Preparation of mother salt solution: Select soluble salts corresponding to the metal elements as raw materials. The metal elements must be selected from at least five of the following: magnesium, cobalt, nickel, copper, zinc, chromium, strontium, lanthanum, iron, manganese, titanium, zirconium, and gadolinium. If magnesium, cobalt, nickel, copper, and zinc are selected, the molar ratio of the five metal elements must be controlled to be equimolar or nearly equimolar. Dissolve the above metal salts in deionized water in proportion and stir until completely dissolved to form a homogeneous mother salt solution containing the target metal element. Preparation of precipitant solution: Select a reagent that can form insoluble hydroxides or carbonates with metal ions as a precipitant, such as sodium hydroxide, sodium carbonate or ammonia water, and dissolve the precipitant in deionized water and stir until a precipitant solution of uniform concentration is formed. Water bath stirring reaction: Place the prepared mother salt solution in a water bath environment, turn on the mechanical stirrer and maintain a stable stirring rate, and then slowly add the precipitant solution; continuously monitor the pH value of the solution during the addition process to ensure that the pH of the reaction system is stable within a suitable range so that the metal ions can precipitate uniformly; after the addition is completed, continue to stir the reaction under water bath conditions for a period of time until uniform granular precipitate is formed. Obtaining particulate precursor: After the reaction, the particulate precipitate in the system is separated into solid and liquid phases. The precipitate is washed multiple times with deionized water to remove residual impurity ions. The washed precipitate is then placed in a drying device and dried to constant weight at a suitable temperature to obtain the particulate precursor. Step S1-2: Preparation of flocculent precursors using the sol-gel method: Mixing metal salts with complexing agents: Select soluble salts of metal elements from the same source as in step S1-1, weigh the metal salts according to the requirement of at least five metal elements and magnesium, cobalt, nickel, copper, and zinc (if selected) in an equimolar or near-equimolar ratio, and dissolve them in deionized water; add a complexing agent to the metal salt solution, the complexing agent must be able to form a stable complex with the metal ions, such as citric acid, ethylene glycol, or ethylenediaminetetraacetic acid, etc., and stir to completely dissolve the complexing agent and mix it thoroughly with the metal ions; Continuous stirring to form a sol: Place the above mixed solution under a stirring device, keep it at room temperature or slightly above room temperature, and stir continuously for a period of time; during the stirring process, the metal ions and complexing agents gradually undergo coordination reactions, and the solution gradually changes from a clear state to a viscous sol state. At this time, it is necessary to control the stirring rate to avoid the sol from layering or agglomerating. Drying process to form flocculent precursor: The formed sol is transferred to a drying container and placed in a drying device for drying; the drying process requires control of temperature and time to allow the solvent in the sol to gradually evaporate and the sol system to gradually gel; continue drying until the gel is completely dehydrated, and finally a flocculent precursor with an irregular three-dimensional network structure is formed. Step S1-3: Preparation of fibrous precursors by electrospinning: Preparation of polymer precursor solution: Select a polymer soluble in organic solvents or water as a carrier, such as polyvinylpyrrolidone, polyacrylonitrile, or polyethylene glycol. Dissolve the polymer in a suitable solvent and stir until completely dissolved to form a polymer solution. Add soluble salts of at least five metal elements as described in step S1-1 to the polymer solution. The molar ratio of the metal elements should follow the requirements of equimolar ratio or near equimolar ratio (if magnesium, cobalt, nickel, copper, and zinc are selected). Continue stirring to completely dissolve the metal salts and form a homogeneous polymer precursor solution containing metal elements. Electrospinning process: The prepared polymer precursor solution is loaded into the syringe of the electrospinning equipment. The distance between the syringe needle and the receiving device is adjusted, and a suitable spinning voltage and solution propulsion rate are set. The electrospinning equipment is turned on. Under the action of the high voltage electric field, the solution at the syringe needle forms a Taylor cone, which is then stretched to form a continuous fibrous jet. During the flight of the jet, the solvent evaporates and finally deposits on the receiving device to form a fibrous structure. Acquisition of fibrous precursor: The fibrous product collected on the receiving device is removed and placed in a drying device for further drying to remove residual solvent; if it is necessary to remove the polymer carrier, the dried fibrous product can be placed in an inert atmosphere or air atmosphere for low-temperature pre-calcination to allow the polymer to decompose and be removed gradually, finally obtaining the fibrous precursor.

[0024] In this embodiment, step S2 serves to provide a stable and suitable reaction support environment for the subsequent low-temperature and high-pressure reaction, ensuring that the precursor can uniformly withstand the pressure and temperature in subsequent steps, avoiding uneven reaction due to equipment problems, and thus ensuring the controllability of the single rock salt phase crystal structure and specific morphology of the final entropy-stable high-entropy oxide powder; the detailed steps are as follows: Step S2-1: Selection and pretreatment of high-pressure reaction equipment: Equipment selection: Based on the morphology of the precursor prepared in step S1 and the reaction scale of the subsequent step S3, a high-pressure reactor is selected; Equipment cleaning: Thoroughly clean the interior of the selected high-pressure reactor to remove residual impurities, oxides or previous reaction products; for high-pressure reactors, special attention should be paid to cleaning the interior of the reactor body and the corrosion-resistant lining (such as PTFE lining). After rinsing with deionized water, place it in a drying device to dry until no moisture remains. Equipment component inspection: Inspect the core functional components of the high-pressure reactor, including the sealing rings (such as metal or flexible sealing rings), valves, pressure gauges, sealing structure, and pressure control system of the high-pressure reactor; confirm that the sealing rings are free from aging and damage, the valves open and close flexibly, the pressure gauges meet the requirements (the error must be within ±2% of the reaction pressure range), the sheath sealing structure is free from cracks, and ensure that the equipment can stably withstand the pressure of 10MPa to 300MPa in the subsequent step S3; Step S2-2: Pretreatment and quantification of precursors: Precursor dispersibility adjustment: Dispersibility treatment is performed on precursors with different morphologies obtained in step S1; if it is a granular precursor and there is slight agglomeration, it needs to be lightly ground with an agate mortar and pestle, and then screened through a 200-300 mesh sieve to ensure uniform particle size distribution; if it is a flocculent precursor, it needs to be gently loosened to avoid clumping, which would lead to uneven heating and pressure during subsequent reactions; if it is a fibrous precursor, it needs to be organized into loose fiber bundles to prevent fiber entanglement from affecting pressure transmission. Precursor quantitative weighing: Based on the effective reaction volume of the high-pressure reactor and the target product yield, accurately weigh the pretreated precursor; weighing should be done using an electronic balance with an accuracy of 0.001g to ensure that the amount of precursor used matches the volume of the reactor—the amount of precursor filling in the high-pressure reactor should not exceed 70% of the effective volume of the reactor, leaving a certain space for possible volume changes during the reaction process, and avoiding a sudden increase in pressure or overflow of the precursor in the reactor; Step S2-3: Placement of the precursor in the high-pressure reactor: Placement inside the high-pressure reactor: Slowly load the metered precursor into the liner of the high-pressure reactor, ensuring that the precursor is evenly spread on the bottom of the liner and avoiding local accumulation; if the precursor is fibrous, the fiber bundles should be placed parallel to the length of the liner to reduce morphological damage to the fibers during the reaction; if the precursor is flocculent, it should be gently compacted (compaction density controlled between 0.8 g / cm³ and 1.2 g / cm³) to ensure close contact of the precursor to facilitate mass transfer in the reaction, while avoiding over-compaction that would prevent gas from escaping; Step S2-4: Assembly and sealing verification of the high-pressure reaction unit: High-pressure reactor assembly: Place the liner containing the precursor into the high-pressure reactor body, ensuring that the liner is centered and without deviation; cover the reactor lid and tighten the lid bolts evenly diagonally. After each round of tightening, use a torque wrench to check the bolt torque to ensure that the torque of all bolts is consistent (the torque value must meet the requirements of the equipment instruction manual, usually 50 N·m to 150 N·m), to avoid reactor seal failure due to uneven force; Sealing verification: Perform a sealing test on the assembled high-pressure reaction device; for high-pressure reactors, introduce a small amount of inert gas (such as argon) into the reactor to make the pressure inside the reactor reach 5MPa to 10MPa. After closing the gas inlet valve, let it stand for 30 minutes and observe the change in the pressure gauge reading. If the pressure drop does not exceed 0.1MPa, the sealing is deemed qualified. Perform an airtightness test on the pressure chamber to ensure that there is no leakage in the pressure chamber and that it meets the requirements of subsequent high-pressure reactions.

[0025] Furthermore, step S3 involves causing the precursor placed in the high-pressure reactor in step S2 to undergo a crystallization reaction under controlled atmosphere, pressure, and temperature conditions, forming entropy-stable high-entropy oxide powder with a single rock salt phase crystal structure, while completely preserving the specific morphology of the precursor, such as spherical, fibrous, or flocculent, ultimately obtaining the target product. The detailed steps are as follows: Step S3-1: Construction and verification of the reaction atmosphere: Atmosphere type selection: The reaction atmosphere is selected based on the chemical properties of the metal elements in the precursor. If the precursor contains easily oxidizable metal elements such as copper and iron, inert gases (such as argon and nitrogen) should be preferred to avoid oxidation of the metal elements at high temperatures. If the metal elements in the precursor (such as magnesium and zirconium) have strong oxidation stability, an air atmosphere can be used to reduce process costs. Atmosphere replacement operation: For high-pressure reactors, first close all exhaust valves, turn on the vacuum system to evacuate the reactor until the vacuum level reaches below 1×10⁻²Pa, then close the vacuum valves and slowly introduce the selected atmosphere gas until the pressure inside the reactor rises to 0.5MPa; after holding for 5 minutes, open the exhaust valves again to release the gas, and repeat the "evacuation-atmosphere introduction" operation 2-3 times to ensure that the residual air inside the reactor is fully replaced; Atmosphere stability verification: After the atmosphere replacement is completed, keep the atmosphere inlet valve slightly open to maintain the atmosphere pressure in the device at 0.1MPa-0.2MPa. Let it stand for 15 minutes, and use the gas composition detector of the device (if it is an inert gas, the oxygen content must be less than 0.1%; if it is air, the humidity must be less than 5%) to confirm that the atmosphere meets the requirements and there is no leakage, so as to ensure that the subsequent reaction is carried out in a stable atmosphere. Step S3-2: Stepped pressure application and stabilization control: Initial low-pressure leak detection: Turn on the pressure control system of the high-pressure reactor and slowly increase the pressure at a rate of 1MPa / min-2MPa / min. When the pressure reaches 20MPa, stop increasing the pressure, close the pressure control valve, and let it stand for 20 minutes. Monitor the pressure change in real time through the pressure sensor of the device. If the pressure drop does not exceed 0.05MPa, the device is considered to have no leaks. If a leak is found, the pressure needs to be released and the sealing components (such as the sealing ring of the high-pressure reactor) need to be re-inspected. After repair, the leak detection should be performed again. Target pressure application: After confirming no leakage, continue to increase the pressure at a rate of 2MPa / min-3MPa / min, and increase the pressure to the range of 10MPa-300MPa according to product requirements (this range can more efficiently promote crystal growth and reduce equipment energy consumption); during the pressure increase process, observe the pressure curve in real time to avoid precursor agglomeration or morphological damage inside the equipment due to sudden pressure increase (such as fibrous precursor breakage, spherical precursor deformation). Continuous pressure stabilization: After reaching the target pressure, switch the pressure control system to "pressure stabilization mode" to maintain pressure fluctuations within ±0.5MPa via an automatic pressure compensation device; for high-pressure reactors, monitor the correlation between reactor wall temperature and pressure to prevent pressure anomalies caused by temperature changes; Step S3-3: Precise temperature control and heat preservation reaction: Gradient heating operation: Turn on the heating system of the high-pressure reactor and raise the temperature using a gradient heating method; initially, raise the temperature to 200℃ at a rate of 5℃ / min and hold for 10 minutes to ensure uniform heating of the precursor and avoid morphological deformation caused by local temperature differences; then continue to raise the temperature at a rate of 8℃ / min-10℃ / min until the target temperature of 500℃-1200℃ is reached (this range ensures that the precursor reacts fully and avoids powder sintering and agglomeration caused by high temperature); Heat preservation time control: After reaching the target temperature, the heat preservation program is started, and the heat preservation time is set to 0.5h-24h (0.5h-24h heat preservation can ensure the complete growth of the crystal structure, while avoiding the increase in energy consumption and morphology deterioration caused by excessive heat preservation time); During the heat preservation process, the temperature is monitored in real time by thermocouples in the device (accuracy ±1℃). If the temperature deviates from the target value by more than ±3℃, the heating system automatically adjusts the power to maintain temperature stability; Crystallization reaction monitoring: During the heat preservation period, the crystal structure changes of the precursor are monitored periodically by the in-situ detection module of the high-pressure reaction device (such as the X-ray diffraction in-situ monitoring unit, if the device is equipped) to confirm its gradual transformation into a single rock salt phase; if the in-situ detection module is not equipped, a fixed heat preservation time can be set according to the previous experimental data to ensure the complete reaction. Step S3-4: Real-time monitoring and parameter fine-tuning of the reaction process: Multi-parameter synchronous monitoring: Throughout the low-temperature, high-pressure reaction process, the device's control system synchronously collects parameters such as pressure, temperature, and atmosphere concentration (detected every 30 minutes) to form real-time data curves. If abnormal pressure fluctuations are detected (such as sudden increases or decreases), it is necessary to first determine whether the fluctuations are caused by temperature changes. If the device is leaking, heating must be stopped immediately, and the pressure must be slowly released to atmospheric pressure before maintenance. If the temperature is abnormal, the heating power must be reduced, and the reaction can continue only after the temperature stabilizes. Parameter fine-tuning strategy: If monitoring reveals a slow crystallization rate of the precursor (e.g., no obvious rock salt phase is detected even after half the holding time), the temperature can be increased by 20℃-30℃ or the pressure by 30MPa-50MPa within the target parameter range to accelerate the reaction process. However, it is necessary to ensure that the adjusted parameters do not exceed 10MPa-300MPa pressure. If slight agglomeration of the precursor is found, the heating rate can be appropriately reduced (e.g., from 10℃ / min to 5℃ / min), and the pressure should be kept stable to reduce the risk of agglomeration. Step S3-5: Cooling and depressurization and obtaining the target product: Slow cooling operation: After the heat preservation reaction is completed, turn off the heating system and use a combination of natural cooling and active temperature control to cool down; first, reduce the temperature to 200℃ at a rate of 2℃ / min-5℃ / min to avoid cracking of the product due to internal stress caused by thermal expansion and contraction caused by excessive cooling; then stop active temperature control and allow the device to cool down naturally to room temperature (25℃±5℃); during the cooling process, maintain a slight positive pressure (0.1MPa) in the reaction atmosphere to prevent outside air from entering the device and contaminating the product; Smooth depressurization operation: After the temperature inside the device drops to room temperature, open the pressure relief valve and slowly depressurize at a rate of 1MPa / min-2MPa / min; during the depressurization process, closely observe the pressure drop curve to avoid sudden pressure drops causing the airflow inside the device to impact the products and damage their morphology (such as the breakage of fibrous products and the fragmentation of flocculent products); when the pressure inside the device drops to atmospheric pressure (0.1MPa), close the pressure relief valve; Target product extraction and preliminary confirmation: Open the high-pressure reaction device and extract the product after reaction; observe the morphology of the product to confirm that it retains the spherical (particle size 50nm-5μm), fibrous (diameter 100nm-2μm, length 1μm-100μm), or flocculent (irregular three-dimensional network) structure of the precursor; perform crystal structure detection on the product using X-ray diffraction to confirm that it is a single rock salt phase crystal structure, thus completing the low-temperature high-pressure reaction process of step S3.

[0026] In this embodiment, the high-pressure reaction device is a high-pressure reactor.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A controllable morphology-stable high-entropy oxide powder, characterized in that: The entropy-stable high-entropy oxide powder is composed of five or more metallic elements and has a single-phase crystal structure; the metallic elements are selected from at least five of magnesium, cobalt, nickel, copper, zinc, chromium, iron, strontium, lanthanum, manganese, titanium, zirconium, and gadolinium; the morphology of the entropy-stable high-entropy oxide powder is determined by the special morphology of the precursor.

2. The controllable morphology entropy-stable high-entropy oxide powder according to claim 1, characterized in that: The morphology of the high-entropy oxide powder is one of the following: spherical particles with special morphology, fibrous structure, and irregular three-dimensional network flocculent structure.

3. A method for preparing entropy-stable high-entropy oxide powder with controllable morphology as described in any one of claims 1, characterized in that, Includes the following steps: S1: Prepare entropy-stable high-entropy oxide precursors with specific morphologies; S2: Place the precursor obtained in step S1 into a high-pressure reaction device; S3: The reaction is carried out in a specific gas atmosphere. The precursor is subjected to a pressure of 10 MPa to 300 MPa and kept at a temperature below atmospheric pressure for 0.5 h to 24 h to carry out a low-temperature high-pressure reaction, resulting in entropy-stable high-entropy oxide powder with a single rock salt phase structure and a specific morphology.

4. The low-temperature, high-pressure preparation method for controllable morphology-entropy-stable high-entropy oxide powder according to claim 3, characterized in that: In step S1, the preparation of an entropy-stable and entropy-stable high-entropy oxide precursor with a specific morphology specifically includes: A mother salt solution containing the metal element and a precipitant solution are prepared by co-precipitation, and reacted under water bath and mechanical stirring to obtain a particulate precursor; or a metal salt containing the metal element and a complexing agent are continuously stirred in solution to form a sol by sol-gel method, and flocculent precursor is obtained after drying; or a polymer precursor solution containing the metal element is spun by electrospinning to obtain a fibrous precursor.

5. The low-temperature, high-pressure preparation method for controllable morphology-entropy-stable high-entropy oxide powder according to claim 3, characterized in that: The high-pressure reaction device is a high-pressure reaction vessel.

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