Preparation method for superfine nano metal powder

Abstract

The invention discloses a preparation method for superfine nano metal powder, which comprises the following steps of: installing a collecting vessel in a closed chamber in advance, placing an adsorbent in the collecting vessel, and then pumping air pressure in the closed chamber to a vacuum state through a vacuum system; closing the vacuum system, and slowly inputting inert gas into the closed cavity; starting a heating device in the closed cavity to evaporate the metal in the closed cavity, and adsorbing and cooling by using a liquid adsorbent to form metal powder; and separating the metal powder deposited in the adsorbent to obtain the superfine nano metal powder. By adopting the preparation method disclosed by the invention, the agglomeration problem and the powder uniformity problem of the superfine nano metal powder are effectively solved, a superfine nano particle product with uniform particles, no agglomeration and good dispersity can be obtained, and large-scale production of the metal powder with high uniformity and high dispersity is facilitated; therefore, the application range of the nano metal powder can be expanded, and the method is suitable for popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of metal powder materials, and in particular to a method for preparing ultrafine nano metal powder. Background Art

[0002] Nanometal powders, due to their surface effects, quantum size effects, and macroscopic quantum effects, possess mechanical, thermal, optical, electrical, magnetic, and chemical properties that differ from those of ordinary metal powders. They hold broad application prospects in materials, information, energy, chemistry, and chemical engineering. However, due to their large surface area and high surface activity, nanometal powders can oxidize during preparation and use due to exposure to the atmosphere. This can affect their surface state and properties, and can even lead to safety issues such as high temperatures or combustion, severely hindering their practical application.

[0003] At present, the manufacturing methods of nano-metal powders mainly include chemical deposition, physical vapor deposition and mechanical pulverization. The appropriate technology can be selected according to the material properties and process requirements. Among them, although the chemical deposition method can be carried out at a lower temperature, it usually faces the problems of slow reaction rate and difficult to control product dispersion and purity. In addition, the chemical reagents used in the chemical deposition method are often harmful to the environment. Although the physical vapor deposition method can produce high-purity metal powder, its equipment cost is high and the production efficiency is low. It is generally only suitable for the laboratory stage and is not suitable for large-scale production. As for the mechanical pulverization method, for the commonly used ball milling method, although the process is simple and the cost is relatively low, it often introduces inevitable impurities, has difficulty in grading, and is prone to agglomeration and powder unevenness, resulting in low powder purity; while the air flow milling method has the advantages of high continuous automation and good particle size uniformity, it has high energy consumption and is only suitable for brittle metals.

[0004] A search revealed that patent document CN1778498A discloses a method and apparatus for preparing organically coated metal nanopowders. The disclosed method allows for coating the surface of metal nanopowders with a hydrocarbon layer several nanometers thick, effectively preventing oxidation. However, the hydrocarbon layer formed by high-pressure plasma is dense and insoluble in any organic solvents. Therefore, the hydrocarbon layer cannot be effectively removed during subsequent use, limiting the further use of metal nanopowders in certain fields. Patent document CN105750540A discloses an apparatus and method for online reversible coating of nanometal powders, while patent document CN119407191A discloses an apparatus and method for continuous automated production of micro-nanometallic powders. The three retrieved patent documents provide methods for preparing nanometal powders from different perspectives.

[0005] Low-melting-point metals are metals that are liquid at room temperature, or have a melting point significantly lower than room temperature. However, there are no reports of technologies that utilize the low melting point of low-melting-point metals as adsorbents to absorb generated metal powders and subsequently separate them to obtain ultrafine nano-metal powders. Therefore, it is highly desirable to provide a preparation method that differs from the prior art to obtain ultrafine nano-metal powders and expand the application range of nano-metal powders. Summary of the Invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to obtain ultrafine nano metal powder, thereby providing a method for preparing ultrafine nano metal powder. By utilizing the low melting point property of low-melting-point metal, the solid metal is converted into liquid metal by heating, so that the generated metal powder is deposited in the liquid metal. Finally, the ultrafine nano metal powder can be obtained by separation, thereby expanding the application range of nano metal powder. Specifically, it is a method for preparing ultrafine nano metal powder.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing ultrafine nano-metal powder, the preparation method comprising the following steps: S1. A collection vessel is installed in a closed chamber in advance, and an adsorbent is placed in the collection vessel. The metal raw material to be processed is then placed in the closed chamber, and the air pressure in the closed chamber is then evacuated to a vacuum state through a vacuum system. S2. Turn off the vacuum system and slowly introduce inert gas into the closed chamber until the closed chamber is filled with inert gas; S3. Activating the heating device in the closed chamber to evaporate the metal placed in the closed chamber. The metal vapor formed by the evaporation of the metal is cooled by the inert gas in the closed chamber to form metal powder. Simultaneously, heating the collection vessel placed in the closed chamber to convert the adsorbent placed in the collection vessel from a solid state to a liquid state. The heating is then stopped, and the liquid adsorbent is used to adsorb and cool the metal powder to form metal powder. During the adsorption stage, the stirring device is activated to stir the adsorbent in the collection vessel so that all the metal powder is deposited in the adsorbent in the collection vessel. S4. After the adsorbent in the collection vessel is cooled and converted from a liquid to a solid state, the closed chamber is opened and the collection vessel is removed from the closed chamber. The metal powder deposited in the adsorbent is then separated to obtain ultrafine nano-metal powder.

[0008] Furthermore, in the method for preparing ultrafine nano metal powder described in the present invention, the adsorbent is a low-melting-point metal, the collecting vessel adopts a basin structure with an open top, and the amount of the adsorbent does not exceed two-thirds of the volume of the collecting vessel.

[0009] Furthermore, in the method for preparing ultrafine nano metal powder described in the present invention, the low melting point metal is metal gallium or metal indium.

[0010] Furthermore, in the method for preparing ultrafine nano metal powder described in the present invention, the inert gas is argon.

[0011] Furthermore, in the method for preparing ultrafine nano-metal powder described in the present invention, the heating device in the closed chamber is any one of plasma heating, magnetron sputtering, multi-arc heating or laser heating to evaporate the metal.

[0012] Furthermore, a method for preparing ultrafine nano-metal powder described in the present invention is adopted, and the separation method is a combination of elution and screening, and separation is performed by utilizing density difference. The specific separation method is to add ethanol or glycerol as an elution liquid to a collection container, heat it during elution, and filter it with a screen, so that the solid adsorbent formed after cooling is converted into a liquid state, while the deposited powder remains in its original solid state. Through the action of gravity, the particles with high density pass through the screen and settle to the bottom of the adsorbent, while the particles with low density float above the adsorbent, thereby realizing solid-liquid separation of the metal powder deposited in the adsorbent.

[0013] Furthermore, by adopting the method for preparing ultrafine nano-metal powder of the present invention, the average particle size of the ultrafine nano-metal powder formed after separation is 10 to 200 nm.

[0014] Compared with the prior art, the method for preparing ultrafine nano-metal powder according to the present invention has the following advantages: utilizing the low melting point property of low-melting-point metals, since the melting point of metal gallium is 29.76°C, it is solid at room temperature, i.e., 20-25°C, and can be converted from solid metal to liquid metal by low-temperature heating; while the melting point of metal indium is 156.61°C, it can be converted from solid metal to liquid metal by only appropriate heating, so that the metal vapor formed by heating the metal to be prepared by the heating device is cooled by the inert gas in the closed chamber to form metal powder, which is then deposited in the liquid metal under the action of gravity, and finally separated by density difference, so that ultrafine nano-metal powder can be obtained by separation. This not only avoids surface oxidation of the nano-metal powder, facilitating the use and storage of the nano-metal powder, but also allows for convenient and effective removal during later use, restoring the clean surface of the nano-metal powder, so that the nano-metal powder exhibits excellent surface properties.

[0015] It can be seen that the preparation method described in the present invention effectively solves the agglomeration problem and powder uniformity problem of ultrafine nano metal powder, and can obtain ultrafine nano-scale particle products with uniform particles, no agglomeration and good dispersion, which is conducive to the large-scale production of metal powder with high uniformity and high dispersion, thereby expanding the application range of nano metal powder and being suitable for promotion and application. DETAILED DESCRIPTION

[0016] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0017] It should be noted that the terms such as "upper", "lower", "left", "right", etc. cited in this specification are only for the convenience of description and are not intended to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as within the scope of implementation of the present invention without substantially changing the technical content.

[0018] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "provided with" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; and direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention.

[0019] It should be noted that the term "comprise" or any other variation is intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus. Example 1

[0020] This embodiment provides a method for preparing ultrafine nano-metal powder, the preparation method comprising the following steps: S1. A collection vessel is pre-installed in a closed chamber and an adsorbent is placed in the collection vessel. The metal material to be processed is then placed in the closed chamber and the chamber is evacuated to a vacuum state using a vacuum system. The adsorbent is a low-melting-point metal, such as gallium. The collection vessel is an open-top basin, and the amount of adsorbent does not exceed two-thirds of the volume of the collection vessel. S2. Turn off the vacuum system and slowly introduce an inert gas into the closed chamber so that the closed chamber is filled with an inert gas, wherein the inert gas is argon; S3. Activating the plasma heating device in the closed chamber to evaporate the metal placed in the closed chamber. The metal vapor formed by the evaporation of the metal is cooled by the inert gas in the closed chamber to form metal powder. Simultaneously, heating the collection vessel placed in the closed chamber to convert the adsorbent placed in the collection vessel from a solid state to a liquid state. The heating is then stopped, and the liquid adsorbent is used to adsorb and cool the metal powder to form metal powder. During the adsorption stage, the stirring device is activated to stir the adsorbent in the collection vessel so that all the metal powder is deposited in the adsorbent in the collection vessel. S4. After the adsorbent in the collection vessel is cooled and converted from liquid to solid, the closed chamber is opened, the collection vessel is removed from the closed chamber, and the metal powder deposited in the adsorbent is separated to obtain ultrafine nano metal powder; the separation method is a combination of washing and screening, and separation is performed using density differences. The specific separation method is to add ethanol as a washing liquid to the collection vessel, heat it during washing, and filter it with a screen to convert the adsorbent formed into a solid state after cooling into a liquid state, while the deposited powder remains in its original solid state. Through the action of gravity, the particles with high density pass through the screen and settle to the bottom of the adsorbent, while the particles with low density float above the adsorbent, thereby realizing solid-liquid separation of the metal powder deposited in the adsorbent, and realizing solid-liquid separation between the metal powder and metal gallium. The mesh size of the screen can be selected according to the actual separation situation. The average particle size of the ultrafine nano metal powder formed after separation is 10 to 200 nm. Example 2

[0021] The difference between this embodiment and embodiment 1 is mainly reflected in the following two aspects: first, in step S1, the low-melting-point metal is metallic indium; second, in step S3, the heating device in the closed chamber uses magnetron sputtering heating to evaporate the metal; third, in step S4, glycerol is added to the collecting vessel as a washing liquid. Example 3

[0022] The main difference between this embodiment and embodiment 1 is that in step S3, the heating device in the closed chamber uses laser heating to evaporate the metal. Example 4

[0023] The main difference between this embodiment and embodiment 2 is that in step S3, the heating device in the closed chamber uses a multi-arc heating method to evaporate the metal. Example 5

[0024] The main difference between this embodiment and embodiment 2 is that in step S1, the low-melting-point metal is a low-melting-point alloy material. The remaining steps are the same. The low-melting-point alloy material is a bismuth-tin alloy, which is a mixture of 58% bismuth and 42% tin, and has a melting point between 60 and 200°C.

[0025] Scanning electron microscopy revealed that the ultrafine nano-metal powders prepared using the methods described in Examples 1 to 5 had uniform particles, a rounded structure, and no agglomeration. However, using a low-melting-point alloy material as an adsorbent is not as effective as using gallium metal directly. This is because gallium metal has a melting point of 29.76°C, which is higher than 25°C. At room temperature, i.e., between 20°C and 25°C, it is solid. Low-temperature heating can convert the solid metal into liquid metal. Indium metal has a melting point of 156.61°C, and commonly used low-melting-point alloy materials have melting points below 200°C. Only moderate heating is required to convert the solid metal into liquid metal. Thus, the metal vapor formed by heating the metal to be prepared by the heating device is cooled by the inert gas in the closed chamber to form metal powder, which is then deposited in the liquid metal under the action of gravity. Finally, separation can produce an ultrafine nano-metal powder with uniform particles and a rounded structure.

[0026] In the preparation method of the present invention, the plasma heating, magnetron sputtering, multi-arc heating or laser heating adopted by the heating device in the closed chamber are all metal vaporization heating methods in the prior art. It is only necessary to select the corresponding heating process according to the specific metal material, so the specific process parameters are not described in detail.

[0027] The innovation of the preparation method described in the present invention is to utilize the low melting point property of low-melting-point metals to transform solid metals into liquid metals through heating, so that the metal vapor formed by heating the metal to be prepared by the heating device is cooled by the inert gas in the closed chamber to form metal powder, which is deposited in the liquid metal under the action of gravity. Finally, it is separated by utilizing the density difference. Ultrafine nano-metal powder can be obtained by separation, which not only avoids surface oxidation of the nano-metal powder and facilitates the use and storage of the nano-metal powder, but also can be conveniently and effectively removed during later use to restore the clean surface of the nano-metal powder, so that the nano-metal powder presents excellent surface properties.

[0028] In summary, the preparation method described in the present invention effectively solves the agglomeration problem and powder uniformity problem of ultrafine nano-metal powder, and can obtain ultrafine nano-scale particle products with uniform particles, no agglomeration and good dispersion, which is conducive to the large-scale production of metal powders with high uniformity and high dispersion, thereby expanding the application range of nano-metal powders and being suitable for promotion and application.

[0029] Other aspects of the present invention that are not described in detail are all conventional techniques known to those skilled in the art.

[0030] The protection scope of the present invention is not limited to the technical solutions disclosed in the specific implementation methods. The above description is only a preferred implementation method of the present invention and does not limit the present invention. Any minor modifications, equivalent replacements and improvements made based on the technical solutions of the present invention should be included in the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing ultrafine nano metal powder, characterized in that: The preparation method comprises the following steps: S1. A collection vessel is installed in a closed chamber in advance, and an adsorbent is placed in the collection vessel. The metal raw material to be processed is then placed in the closed chamber, and the air pressure in the closed chamber is then evacuated to a vacuum state through a vacuum system. S2. Turn off the vacuum system and slowly introduce inert gas into the closed chamber until the closed chamber is filled with inert gas; S3. Activating the heating device in the closed chamber to evaporate the metal placed in the closed chamber. The metal vapor formed by the evaporation of the metal is cooled by the inert gas in the closed chamber to form metal powder. Simultaneously, heating the collection vessel placed in the closed chamber to convert the adsorbent placed in the collection vessel from a solid state to a liquid state. The heating is then stopped, and the liquid adsorbent is used to adsorb and cool the metal powder to form metal powder. During the adsorption stage, the stirring device is activated to stir the adsorbent in the collection vessel so that all the metal powder is deposited in the adsorbent in the collection vessel. S4. After the adsorbent in the collection vessel is cooled and converted from a liquid to a solid state, the closed chamber is opened and the collection vessel is removed from the closed chamber. The metal powder deposited in the adsorbent is then separated to obtain ultrafine nano-metal powder.

2. The method for preparing ultrafine nano metal powder according to claim 1, characterized in that: The adsorbent is a low melting point metal, the collecting container adopts a basin structure with an open top, and the amount of the adsorbent does not exceed two-thirds of the volume of the collecting container.

3. The method for preparing ultrafine nano metal powder according to claim 2, characterized in that: The low melting point metal is metal gallium or metal indium.

4. The method for preparing ultrafine nano metal powder according to claim 1, wherein: The inert gas is argon.

5. The method for preparing ultrafine nano metal powder according to claim 1, characterized in that: The heating device in the closed chamber is any one of plasma heating, magnetron sputtering, multi-arc heating or laser heating to evaporate the metal.

6. The method for preparing ultrafine nano metal powder according to claim 1, characterized in that: The separation method is a combination of elutriation and sieving, and separation is performed using density differences. Specifically, ethanol or glycerol is added to a collecting vessel as an elutriation liquid, which is heated during elutriation and filtered with a sieve, so that the adsorbent formed into a solid state after cooling is converted into a liquid state, while the deposited powder remains in its original solid state. Through the action of gravity, particles with high density pass through the sieve and settle below the adsorbent, while particles with low density float above the adsorbent, thereby achieving solid-liquid separation of the metal powder deposited in the adsorbent.

7. The method for preparing ultrafine nano metal powder according to claim 6, characterized in that: The average particle size of the ultrafine nano metal powder formed after separation is 10 to 200 nm.