A method for preparing metal oxide nanopowder by molten salt quenching

Abstract

The application discloses a method for preparing metal oxide nanopowder by molten salt quenching, which comprises the following steps: firstly, heating a reaction system to make a precursor salt in a molten state; secondly, adding a metal source salt into the reaction system and reacting for a period of time; thirdly, taking out the reaction system and quenching in a liquid; fourthly, cooling the product to room temperature, centrifuging, cleaning, and completely drying to obtain a metal oxide nanopowder material; and the mass ratio of the precursor salt and the metal source salt is 100-0.5:1. The method can prepare metal oxide nanopowder with various morphologies and sizes, and the morphology and size can be controlled by the ratio of the precursor salt and the metal source salt, the ratio of the quenching liquid, and the reaction temperature and time. The prepared metal oxide nanopowder can be applied in the fields of energy and environment, such as catalysis, energy storage, degradation, ion exchange, desulfurization and denitrification, and the production process is simple and easy to implement, without the need of complex special equipment, and the industrial production can be easily realized.

Description

Technical Field

[0001] This invention belongs to the field of powder material preparation technology, specifically relating to a method for preparing metal oxide nanopowders by molten salt quenching. Background Technology

[0002] Metal oxides are diverse and widely used. Different metal oxides possess unique advantages in terms of redox activity, valence state changes, environmental friendliness, and stability, showing great potential and prospects in catalysis, energy storage, and sensing. The nanopowder morphology of metal oxides, with its superior properties compared to bulk materials, has been extensively explored by researchers. Particularly in the energy storage field, nanopowders can adapt to various current collector shapes to construct rigid or flexible energy storage devices. Compared to nanofilms, nanopowders offer greater flexibility in controlling loading to meet industry demands. In catalysis and sensing, nanopowders can be better distributed within the target material, exposing more reaction sites and effectively enhancing performance.

[0003] Currently, the preparation of metal oxide nanopowders includes solvothermal methods and chemical precipitation methods. For example, patent CN201710216261.0 discloses a method for preparing transition metal oxide electrode materials with various morphologies. This method prepares transition metal oxides via a solvothermal process under the action of a precipitant and a surfactant, using alcohol or water as a solvent. This results in a large amount of waste liquid, and the synthesis process requires high temperature and pressure, leading to high energy consumption, high production costs, and difficulty in control, which is not conducive to large-scale production. Therefore, although the solvothermal method can obtain various metal oxides with special morphologies, the preparation conditions are complex and demanding, and the morphology and size control is difficult, which is not conducive to industrial production. Another example is patent CN202410040131.6, which discloses a method for preparing nano-metal oxide materials via chemical precipitation. This method has less demanding preparation conditions, but requires the addition of multiple reagents for multi-step reactions, resulting in numerous preparation steps and a long process cycle. For example, patent CN200410077946.4 discloses a method for preparing layered composite metal oxide supercapacitor electrode materials. This method utilizes a fully reverse mixed-liquid membrane reactor to conduct a co-precipitation reaction of a cobalt-aluminum mixed salt solution and an alkaline solution, separating the nucleation and crystallization processes. The conditions for both nucleation and growth processes are controlled separately, and the final step is high-temperature calcination. Therefore, while similar chemical precipitation methods are currently one of the most commonly used methods for industrial production of metal oxides, the production process is cumbersome, generates large amounts of waste liquid, requires high temperatures, and the co-precipitation conditions are difficult to control, resulting in severe environmental pollution and high costs.

[0004] Compared with the traditional preparation techniques mentioned above, the molten salt method is simple and efficient, and the preparation process does not require an aqueous medium, thus avoiding water pollution, lower energy consumption, and environmental friendliness. The molten salt used in the molten salt method can be recycled, further reducing costs. In the field of nanopowder preparation, the molten salt method can currently be used to prepare metal oxides and ion-intercalated two-dimensional materials. For example, CN107697888A discloses a method for preparing metal oxides or metal composite oxides. This method uses the molten salt method to prepare metal oxides or metal composite oxides, but the preparation process requires the addition of a dispersion carrier and a template agent, resulting in multiple steps and difficulty in control. Another example is CN106629613A, which discloses a method for preparing ion-intercalated two-dimensional material powder. The structure of the ion-intercalated two-dimensional material prepared by the molten salt method is a powder formed by the intercalation of cations, anions, or water molecules between layers.

[0005] The material prepared by this invention is a metal oxide nanopowder. Metal oxides have a simple composition, wide applications, and can be directly used as functional materials, showing great potential in many fields. Therefore, this invention not only provides a method for efficiently preparing metal oxide nanopowders using molten salt quenching, but also eliminates the need for dispersants and templates, reduces the number of steps, shortens the preparation cycle, and makes the process easy to control, applicable to a variety of metal oxides. By adjusting the type and amount of salt added to the molten salt, controlling the quenching liquid ratio, and regulating the reaction time and temperature, the type, morphology, size, and quality of the metal oxides can be easily controlled. The obtained powder can be directly used as a functional material, facilitating industrialization. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing metal oxide nanopowders by molten salt quenching, achieving rapid and efficient preparation. The nanopowders prepared by this method exhibit controllable morphology and size, strong versatility, low cost, low energy consumption, and excellent performance. The method includes the following steps:

[0007] (1) Place the precursor salt from room temperature into an environment with a set temperature;

[0008] (2) Heat the precursor salt to keep it in a molten state;

[0009] (3) After the precursor salt in step (2) is completely melted, the metal source salt is added. The reaction is carried out at a preset temperature for a predetermined time. The preset temperature is not lower than the temperature of the molten state in step (2). The purpose of raising the temperature in step (3) is to ensure that the molten salt does not decompose, while the metal salt has enough energy (thermal energy) to make the molten salt reaction system react uniformly and fully, thereby ensuring nucleation and growth in the later stage. The specific temperature can be adjusted according to the type and ratio of the molten salt. After the type and ratio of the molten salt in the reaction system are determined, its decomposition temperature is also determined. Below the decomposition temperature, compared with the reaction temperature in step (2), the higher the temperature is raised, the more intense the movement of ions in the reaction system, the easier it is to nucleate but not easy to grow, the more product particles there are and the smaller the grain size.

[0010] (4) Take out the reaction system of step (3) and quench it in liquid; quenching can make the grain size of the product more uniform and fine. Adjusting the reaction temperature and time can control the morphology and size of the product. The growth of nanoparticles conforms to the theoretical law of crystal growth. The higher the temperature and the longer the time, the more fully the nucleation and growth, and the easier it is to form a three-dimensional structure with a certain orientation and the larger the size.

[0011] (5) Cool the product from step (4) to room temperature and wash it by centrifugation with deionized water.

[0012] (6) The washed product is completely dried to obtain metal oxide nanopowder material.

[0013] Preferably, the precursor salt refers to a salt with a melting point below 800°C, including any one or more of the following: nitrates, chlorides, sulfates, phosphates, acetates, and carbonates.

[0014] Preferably, the metal source salt is a nitrate, sulfate, chloride, phosphate, titanate, tungstate, acetate, molybdenum, tin, vanadium, chromium, molybdenum, ruthenium, tungsten, zirconium, lanthanum, or carbonate of any one of the following metal elements: copper, manganese, nickel, cobalt, zinc, iron, titanium, aluminum, tin, vanadium, chromium, molybdenum, ruthenium, tungsten, zirconium, lanthanum, or cerium.

[0015] Preferably, in step (4), the liquid used for quenching is deionized water or an aqueous ethanol solution; the ethanol concentration of the aqueous ethanol solution is less than 10%; the morphology of the metal oxide nanopowder is controlled by adjusting the ethanol concentration of the aqueous ethanol solution: within the range of ethanol concentration less than 10%, increasing the ethanol concentration causes the metal oxide nanopowder to form a spherical structure, and decreasing the ethanol concentration causes the metal oxide nanopowder to form a polyhedral structure.

[0016] Preferably, the set temperature in step (1) and the heat preservation and heating temperature in step (2) are the same, both being the melting point temperature of the precursor salt.

[0017] Preferably, in step (3), the preset temperature ranges from the melting point of the precursor salt to a second temperature, where the second temperature is the lower of the decomposition temperature and boiling point of the precursor salt, and the preset time is 3 seconds to 3600 seconds.

[0018] The number of metal oxide nanoparticles and the grain size in step (6) can be controlled by adjusting the second temperature: compared with the reaction temperature in step (2), the higher the second temperature, the more vigorous the movement of ions in the reaction system, the easier it is to nucleate but not easy to grow, and the more metal oxide nanoparticles there are and the smaller the grain size.

[0019] Preferably, in step (1), the mass ratio of the precursor salt to the metal source salt is 100 to 0.5:1. Within the above range, the phase and particle size of the metal oxide nanopowder in step (6) are adjusted by regulating the ratio of the precursor salt to the metal source salt: the higher the mass ratio of the reactants, the larger the size of the metal oxide nanopowder.

[0020] The main advantages of this invention are as follows:

[0021] (1) This invention enables rapid and efficient preparation of various metal oxide nanopowder materials, which are easy to mass-produce;

[0022] (2) By adjusting the ratio of precursor salt to metal source salt, the ratio of quenching liquid, and the reaction temperature and time, the type, morphology, and size of nanopowder can be controlled. Specifically, by adjusting the ratio of precursor salt to metal source salt, the phase and size of the product can be adjusted. The higher the mass of reactants, the larger the product size. By adjusting the reaction temperature and time, the morphology and size of the product can be controlled. The growth of nanoparticles conforms to the theoretical law of crystal growth. The higher the temperature and the longer the time, the more complete the nucleation and growth, and the easier it is to form a three-dimensional structure with a certain orientation, and the larger the size. Within the scope of this invention, the higher the ethanol content in the quenching liquid, the smaller the grain size and the more particles.

[0023] (3) This invention utilizes the characteristics of enhanced fluidity when salt melts, as well as the high viscosity and polarity of ions in molten salt that quickly form a good matching degree. Therefore, high concentrations of precursor salts and metal source salts can be used to make the reaction efficient and synthesize a large amount of uniform pure phase nanopowder, which can be directly used as functional materials such as electrodes and catalysts.

[0024] (4) Compared with wet chemical synthesis, the complex ions in the molten salt medium of the present invention have smaller Stokes radii than hydrated ions, resulting in lower reaction barriers and faster reaction rates.

[0025] (5) The preparation method of the present invention is simple, efficient and fast, environmentally friendly and low cost. The morphology and size of the nanopowder can be controlled. The nanopowder prepared is expected to be widely used in the fields of energy and environment such as electrode materials, catalyst or adsorbent carriers, magnetic materials, desulfurization and denitrification. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Some specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings indicate the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0027] Figure 1 Field emission scanning electron microscope image of CuO nanocones prepared in Example 1.

[0028] Figure 2 Field emission scanning electron microscope image of the Fe2O3 nanodiscs prepared in Example 2.

[0029] Figure 3 Field emission scanning electron microscope image of the MnO2 nanoflowers prepared in Example 3.

[0030] Figure 4 Field emission scanning electron microscope image of the NiO nanospheres prepared in Example 4.

[0031] Figure 5 Cyclic voltammetry curves of MnO2 nanosheets prepared in Example 5 as the positive electrode of a zinc ion supercapacitor.

[0032] Figure 6 The X-ray diffraction patterns of the metal oxide nanopowders prepared in Examples 6-12 are as follows: a is TiO2 prepared in Example 6, b is Co3O4 prepared in Example 7, c is ZnO prepared in Example 8, d is SnO2 prepared in Example 9, e is Fe2O3 prepared in Example 10, f is MnO2 prepared in Example 11, and g is MnO2 prepared in Example 12. Detailed Implementation

[0033] The present invention is further illustrated below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0034] Example 1

[0035] (1) Transfer 10g of sodium nitrate from room temperature to a constant temperature environment of 350℃; (2) Heat the sodium nitrate at 350℃ until it is completely melted; (3) After the sodium nitrate is completely melted, add 0.1g of copper sulfate, maintain the system temperature, and react for 1 minute; (4) Take out the reaction system from step (3) and quench it in deionized water; (5) Cool the product from step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely to obtain CuO nanocone material. Field emission scanning electron microscope images of the obtained nanopowder material are shown below. Figure 1 As shown, the surface morphology observation results indicate that the nanopowder has an octagonal pyramidal structure with a particle size of approximately 20 nm in length and approximately 10 nm in width and thickness.

[0036] Example 2

[0037] (1) Mix 0.4g potassium nitrate and 0.1g potassium chloride evenly, and then move the mixture from room temperature to a constant temperature environment of 380℃; (2) Heat the mixed precursor salt of potassium nitrate and potassium chloride at 380℃ until it is completely melted; (3) After the precursor salt is completely melted, add 1g ferric chloride, maintain the system temperature, and react for 3 seconds; (4) Take out the reaction system of step (3) and quench it in a 10% ethanol aqueous solution; (5) Cool the product of step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely to obtain Fe2O3 nanodisc material. The field emission scanning electron microscope image of the obtained nanopowder material is shown below. Figure 2 As shown, the surface morphology observation results indicate that the nanopowder has a hexagonal disk structure, and the nanodisc is formed by stacking multiple layers of nanosheets. The diameter of the nanodisc is about 40 nm and the thickness is about 3 nm.

[0038] Example 3

[0039] (1) Transfer 5g of potassium nitrate from room temperature to a constant temperature environment of 380℃; (2) Heat the potassium nitrate at 380℃ until it is completely melted; (3) After the precursor salt is completely melted, add 1g of manganese nitrate, raise the temperature of the reaction system by 20℃ to 400℃, and react for 60 seconds; (4) Take out the reaction system of step (3) and quench it in a 5% ethanol aqueous solution; (5) Cool the product of step (4) to room temperature and wash it by centrifugation with deionized water; (6) Dry the washed product completely to obtain MnO2 nanoflower material. Field emission scanning electron microscope images of the obtained nanopowder material are shown below. Figure 3 As shown, the surface morphology observation results indicate that the nanopowder has a spherical nanoflower structure, the surface of the nanoflower has a fine sheet-like structure, the nanoflower has a fluffy appearance, the diameter of the nanoflower is about 10-50 nm, and the thickness of the fine sheet-like structure on the surface is about 0.5 nm.

[0040] Example 4

[0041] (1) Mix 5g of potassium chloride and 1g of sodium chloride evenly, and then move the mixture from room temperature to a constant temperature environment of 800℃; (2) Heat the mixed precursor salt of potassium chloride and sodium chloride at 800℃ until it is completely melted; (3) After the precursor salt is completely melted, add 1g of nickel nitrate, maintain the system temperature, and react for 60 seconds; (4) Take out the reaction system of step (3) and quench it in deionized water; (5) Cool the product of step (4) to room temperature and centrifuge and wash it with 10% ethanol aqueous solution; (6) Dry the washed product completely to obtain NiO nanospheres. The field emission scanning electron microscope image of the obtained nanopowder material is shown below. Figure 4 As shown, the surface morphology observation results indicate that the nanopowder has a spherical structure, the nanospheres are well dispersed, and the diameter of the nanospheres is approximately 10 nm.

[0042] Example 5

[0043] (1) Transfer 5g of potassium nitrate from room temperature to a constant temperature environment of 380℃; (2) Heat the potassium nitrate at 380℃ until it is completely melted; (3) After the precursor salt is completely melted, add 1g of manganese nitrate, maintain the system temperature, and react for 60 seconds; (4) Take out the reaction system of step (3) and quench it in a 5% ethanol aqueous solution; (5) Cool the product of step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely to obtain MnO2 nanosheet material. The obtained MnO2 nanosheet active material, Ketjen black and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 7:2:1 and stirred thoroughly for 2 hours with a magnetic stirrer to make the slurry uniform. The obtained slurry is evenly coated in a 1cm×1cm square area at one end of a 1cm×2cm carbon cloth and dried horizontally in an oven to obtain the test electrode. Its cyclic voltammetry curve is shown in the figure. Figure 5 As shown, the electrochemical performance results indicate that in a 2M zinc sulfate electrolyte, at a voltage of 2 mV / s... -1 The voltage was scanned at a certain speed, and the areal capacitance was calculated to be 925.455 mF / cm² based on the resulting cyclic volt-ampere curve. -2 This indicates that the MnO2 nanosheets prepared by this method have excellent electrochemical performance and good prospects for electrochemical energy storage applications.

[0044] Example 6

[0045] (1) A mixture of 0.5g potassium nitrate and 0.5g sodium nitrate precursor salts was moved from room temperature to a constant temperature environment of 280℃; (2) Potassium nitrate was heated at 280℃ until it was completely melted; (3) After the precursor salts were completely melted, 1g titanium oxysulfate was added, and the reaction temperature was increased to 500℃ for 60 seconds; (4) The reaction system from step (3) was removed and quenched in deionized water; (5) The product from step (4) was cooled to room temperature and washed by centrifugation with deionized water; (6) The washed product was completely dried. The X-ray diffraction pattern of the obtained nanopowder material is shown below. Figure 6 As shown in curve a, the results indicate that the oxide is titanium dioxide.

[0046] Example 7

[0047] (1) Transfer 5g of potassium nitrate from room temperature to a constant temperature environment of 380℃; (2) Heat the potassium nitrate at 380℃ until it is completely melted; (3) After the precursor salt is completely melted, add 0.2g of cobalt chloride, raise the reaction temperature to 400℃, and react for 60 seconds; (4) Take out the reaction system of step (3) and quench it in deionized water; (5) Cool the product of step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely. The X-ray diffraction pattern of the obtained nanopowder material is as follows. Figure 6 As shown in curve b, the results indicate that the oxide is cobalt tetroxide.

[0048] Example 8

[0049] (1) Transfer the mixed precursor salt of 0.5g potassium nitrate and 5g sodium chloride from room temperature to a constant temperature environment of 450℃; (2) Heat the precursor salt at 450℃ until it is completely melted; (3) After the precursor salt is completely melted, add 1g zinc sulfate, raise the reaction temperature to 600℃, and react for 600 seconds; (4) Take out the reaction system of step (3) and quench it in deionized water; (5) Cool the product of step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely. The X-ray diffraction pattern of the obtained nanopowder material is as follows. Figure 6 As shown in curve c, the results indicate that the oxide is zinc oxide.

[0050] Example 9

[0051] (1) Transfer the mixed precursor salt of 10g potassium nitrate and 10g sodium nitrate from room temperature to a constant temperature environment of 250℃; (2) Heat the precursor salt at 250℃ until it is completely melted; (3) After the precursor salt is completely melted, add 1g tin chloride, maintain the system temperature, and react for 30 seconds; (4) Take out the reaction system of step (3) and quench it in deionized water; (5) Cool the product of step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely. The X-ray diffraction pattern of the obtained nanopowder material is as follows. Figure 6 As shown in curve d, the results indicate that the oxide is tin oxide.

[0052] Example 10

[0053] (1) Transfer 10g of potassium nitrate from room temperature to a constant temperature environment of 380℃; (2) Heat the potassium nitrate at 380℃ until it is completely melted; (3) After the precursor salt is completely melted, add 2g of ferric chloride, maintain the system temperature, and react for 1800 seconds; (4) Take out the reaction system of step (3) and quench it in a 5% ethanol aqueous solution; (5) Cool the product of step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely. The X-ray diffraction pattern of the obtained nanopowder material is as follows. Figure 6 As shown in curve e, the results indicate that the oxide is ferric oxide.

[0054] Example 11

[0055] (1) Transfer the mixed precursor salt of 10g sodium nitrate and 3g sodium chloride from room temperature to a constant temperature environment of 350℃; (2) Heat the precursor salt at 350℃ until it is completely melted; (3) After the precursor salt is completely melted, add 1g manganese chloride, maintain the system temperature, and react for 180 seconds; (4) Take out the reaction system of step (3) and quench it in a 2% ethanol aqueous solution; (5) Cool the product of step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely. The X-ray diffraction pattern of the obtained nanopowder material is as follows. Figure 6 As shown in curve f, the results indicate that the oxide is manganese dioxide.

[0056] Example 12

[0057] (1) Transfer 10g of potassium nitrate from room temperature to a constant temperature environment of 380℃; (2) Heat the potassium nitrate at 380℃ until it is completely melted; (3) After the precursor salt is completely melted, add 1g of manganese chloride, maintain the system temperature, and react for 180 seconds; (4) Take out the reaction system of step (3) and quench it in a 2% ethanol aqueous solution; (5) Cool the product of step (4) to room temperature and wash it with deionized water by centrifugation; (6) Dry the washed product completely. The X-ray diffraction pattern of the obtained nanopowder material is as follows. Figure 6 As shown in curve g, the results indicate that the oxide is manganese dioxide.

[0058] The X-ray diffraction patterns of the metal oxide nanofilm materials prepared in Examples 6-12 of this invention are as follows: a) TiO2 prepared in Example 6, b) Co3O4 prepared in Example 7, c) ZnO prepared in Example 8, d) SnO2 prepared in Example 9, e) Fe2O3 prepared in Example 10, f) MnO2 prepared in Example 11, and g) MnO2 prepared in Example 12. (Comparison) Figure 6 The curves show that by adjusting different preparation parameters and raw materials, this technique can prepare a variety of metal oxides; in comparison... Figure 6 The relative peak intensities of the diffraction peaks in the f and g curves show that the crystallinity and quality of manganese oxide nanopowder can be controlled by adjusting the preparation parameters. Higher reaction temperature results in better product crystallinity. When the amount of precursor salt in the reaction system is large and the amount of metal source salt is sufficient, the metal source salt participates in the reaction more fully, resulting in a higher product mass.

[0059] This invention prepares metal oxide nanopowders with low-cost, readily available raw materials, a wide range of applications, and a simple, efficient preparation process. It requires minimal equipment and atmosphere control, and the resulting product can be directly used as a functional material, demonstrating significant potential in numerous fields. Unlike traditional methods that typically require multiple steps and often necessitate high-temperature sintering, this invention's synthesis method is rapid and efficient, with lower energy consumption. The process eliminates the need for water as a solvent, preventing water pollution and offering environmental friendliness. The reaction slurry medium can be recycled and reused using appropriate technologies. Therefore, this invention not only provides a rapid method for preparing metal oxide nanopowders but is also applicable to various metal oxides. By adjusting the type and amount of raw materials, reaction time, and temperature, the type, morphology, size, and quality of the metal oxides can be easily controlled. The resulting powder can be directly used as a functional material, facilitating industrialization.

[0060] The embodiments and applications described above are specific implementations of the technical solutions of the present invention and are further detailed descriptions of the technical solutions of the present invention. However, the design concept of the present invention is not limited thereto. Any simple modifications, equivalent changes or improvements made to the present invention based on its technical essence should still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for producing metal oxide nanopowder by molten salt quenching, characterized by, The method comprises the following steps: (1) placing the precursor salt from room temperature into an environment with a set temperature; (2) heating the precursor salt to make it in a molten state; (3) after the precursor salt is completely molten in step (2), adding a metal source salt, and reacting for a predetermined time at a preset temperature, which is not lower than the temperature in the molten state in step (2); (4) taking out the reaction system in step (3) and quenching it in a liquid; (5) cooling the product in step (4) to room temperature and cleaning it by centrifugation with deionized water; (6) completely drying the cleaned product to obtain a metal oxide nanopowder material; The precursor salt refers to a salt with a melting point lower than 800℃, including any one or a combination of the following: nitrate, chloride, sulfate, phosphate, acetate, carbonate; The metal source salt is a nitrate, sulfate, chloride, phosphate, titanate, tungstate, acetate, molybdate or carbonate of any one of the following metal elements: copper, manganese, nickel, cobalt, zinc, iron, titanium, aluminum, tin, vanadium, chromium, molybdenum, ruthenium, tungsten, zirconium, lanthanum and cerium; The set temperature in step (1) and the temperature for heating in step (2) are the same, both being the melting point temperature of the precursor salt; in step (1), the mass ratio of the precursor salt to the metal source salt is 100~0.5:1; In step (3), the preset temperature ranges from the melting point of the precursor salt to a second temperature, which is the lower value between the decomposition temperature and the boiling point of the precursor salt, and the predetermined time is 3 seconds~3600 seconds; In step (4), the liquid used for quenching is deionized water or an ethanol aqueous solution; the mass concentration of ethanol in the ethanol aqueous solution is lower than 10 %.

2. The method for producing metal oxide nanopowder by molten salt quenching according to claim 1, characterized by, By controlling the mass concentration of ethanol in the ethanol aqueous solution, the morphology of the metal oxide nanopowder is controlled: within the range of a mass concentration of ethanol lower than 10 %, increasing the mass concentration of ethanol makes the morphology of the metal oxide nanopowder form a spherical structure, and decreasing the mass concentration of ethanol makes the morphology of the metal oxide nanopowder form a polyhedral structure.

3. The method for preparing a metal oxide nanopowder by a molten salt quenching method according to claim 2, characterized in that, By controlling the high and low of the second temperature, the particle number and grain size of the metal oxide nanopowder in step (6) are controlled: compared to the reaction temperature in step (2), the higher the second temperature, the more the particle number of the metal oxide nanopowder and the smaller the grain size.

4. The method of claim 2, wherein the molten salt quenching process is performed at a temperature of 800 to 1,200°C. By controlling the ratio of the precursor salt to the metal source salt, the particle size of the metal oxide nanopowder in step (6) is adjusted: within the range of the mass ratio of the precursor salt to the metal source salt being 100~0.5:1, the higher the mass ratio of the reactants, the larger the size of the metal oxide nanopowder.

Images