High-entropy oxide powder based on self-propagating reaction as well as preparation method and application of high-entropy oxide powder

Abstract

The invention provides a preparation method of high-entropy oxide powder based on self-propagating reaction, which comprises the following steps: firstly, preparing mixed alloy powder containing metal elements of Al, Fe, Cu, Mg and Ni; secondly, the mixed alloy powder and a thermite are mixed to obtain a reactant, the reactant is placed in a reaction container, pyrophoric powder is scattered on the reactant, under the conditions that shielding gas is introduced and a collecting assembly of a collecting device is continuously cooled, the pyrophoric powder is ignited, and the mixed alloy powder is subjected to a high-temperature self-propagating reaction under the action of the thermite; and finally, after the reaction is finished and the reaction device is cooled, high-entropy oxide powder is obtained in a collecting assembly. The preparation method provided by the invention has the advantages of simplicity in operation, easiness in implementation, relatively low material cost and the like. The high-entropy oxide powder prepared by the method has the characteristics of small particles, uniform particle size distribution, good conductivity and thermal stability and the like, and has wide popularization and application prospects in battery materials and catalytic materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of high entropy alloys, and in particular relates to a high entropy oxide powder based on a self-propagating reaction and a preparation method thereof, and also relates to the application of the high entropy oxide powder based on a self-propagating reaction. Background Art

[0002] High entropy oxides are oxides of a single structure obtained by dissolving five or more metal or non-metal oxides in equal or near molar ratios. The high entropy properties of high entropy oxides can effectively improve the cycle stability of electrode materials, making them perform well in applications such as lithium-ion batteries. In applications such as zinc-ion batteries, high entropy oxides can provide multi-path electron transfer and significant structural stability, thereby improving battery performance and cycle stability. High entropy oxides have the advantages of high activity and low cost in catalytic applications, which will help promote the development of green energy conversion devices.

[0003] Currently, the main methods for preparing high entropy oxide powders include thermal decomposition, NSP, FSP, wet chemical method and solution combustion synthesis method, but these methods have problems such as complex operation, expensive raw materials, low yield and low efficiency.

[0004] Based on this, providing a new method for preparing high entropy oxide powder, realizing efficient preparation of high entropy oxide powder in a simpler and faster way, and improving the output rate of target products is a technical problem that needs to be solved urgently. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for preparing high entropy oxide powder which is simple and efficient to operate and can effectively improve the yield of target products and control the particle size of products.

[0006] A second object of the present invention is to provide a high entropy oxide powder based on a self-propagating reaction.

[0007] The third object of the present invention is to provide an application of high entropy oxide powder in battery materials, catalytic materials or adsorption materials.

[0008] The technical solution adopted by the present invention to achieve one of the purposes is: to provide a method for preparing high entropy oxide powder based on a self-propagating reaction, comprising the following steps: S1. preparing a mixed alloy powder containing metal elements Al, Fe, Cu, Mg and Ni; S2, mixing the mixed alloy powder with thermite and CaSO4 to obtain a reactant, placing the reactant in a reaction vessel of a reaction device, and sprinkling ignition powder on the surface of the reactant; S3, under the condition of introducing protective gas and continuously cooling the collecting assembly of the collecting device, igniting the ignition powder, so that the mixed alloy powder undergoes a high-temperature self-propagating reaction under the action of thermite; S4. After the high-temperature self-propagating reaction is completed and the reaction device is cooled, high entropy oxide powder is obtained in the collecting assembly.

[0009] The overall idea and inventive principle of the present invention are as follows: Self-propagating high temperature synthesis, also known as combustion synthesis technology, is a technology that uses the self-heating and self-conduction effect of high chemical reaction heat between reactants to synthesize materials. Once the reactants are ignited, they will automatically spread to the unreacted area until the reaction is complete. It is a new method for preparing inorganic compound high-temperature materials. The present invention innovatively proposes to apply self-propagating high temperature synthesis technology to the preparation process of high entropy oxides to solve the problems of complex operation, expensive raw materials, low yield, low efficiency, etc. in the existing high entropy oxide preparation methods.

[0010] The preparation method provided by the present invention ignites the reactants under the conditions of protective atmosphere and continuous cooling of the collection assembly, and uses a large amount of heat generated by the redox reaction of thermite to realize the preparation of high entropy oxide powder. In terms of the selection of the components of the raw material mixed alloy powder, it is necessary to focus on the relationship between the alloy components and the ratio and the thermite. The raw material mixed alloy powder component ratio of the present invention is determined by the Hume-Rothery rule and related experiments, wherein Al and Cu are the same as the metal elements contained in the thermite component, and will not cause product pollution; selecting Mg as one of the alloy components can meet the coordination requirements of the Hume-Rothery rule in the composite alloy design criteria, and can significantly reduce the density of the alloy, thereby reducing the overall weight. At the same time, the doping of Mg also has the advantages of reducing the melting point of the high entropy alloy, improving the fluidity of the melt, and facilitating powder molding; the addition of Fe and Ni allows the product to form an Fe-Cu-Ni electrolyte corrosion-resistant system. Since Cu has a higher mobility, it will first move to the outer surface to react with oxygen to form an oxide layer, which hinders oxygen from contacting the bulk alloy; at the same time, the area lacking copper can promote the generation of NiFe2O4, further hindering the outward diffusion of Cu and the invasion of oxygen. In addition, in the mixed alloy powder provided by the present invention, the standard Gibbs free energy of the single element oxidation reaction of aluminum, copper, iron, and nickel elements is all negative, and they are easy to oxidize and maintain a stable oxidation state. These characteristics make the high entropy oxide prepared by the present invention perform better in applications under high temperature and harsh environments.

[0011] Furthermore, the present invention optimizes and adjusts the scheme of designing each metal element in the traditional high entropy alloy according to an equimolar ratio, so that the composition of the raw material mixed alloy powder is more suitable for the self-propagating reaction system, and the prepared aluminum-based high entropy oxide can better meet the application requirements. For example, the addition of Mg can significantly reduce the melting point of the high entropy alloy during the molding process, but if excessive Mg is added, the melting point of the high entropy alloy will be too much reduced, affecting its high temperature performance, and Mg-based metal compounds are easily generated inside the material, increasing the brittleness of the material and easy to crack; the addition of Fe, Cu, and Ni allows the product to form an Fe-Cu-Ni electrolyte corrosion-resistant system, and the Cu content is kept in an appropriate range, which plays a vital role in corrosion resistance. Preferably, in step S1, the molar ratio of the metal elements Al, Fe, Cu, Mg and Ni in the mixed alloy powder is (42.5-45.5):(17.5-20.5):(10.5-14.5):(18.5-19.0):(0.5-11.0), and more preferably is (42.5-43.5):(17.5-18.5):(10.5-11.5):(18.5-19.0):(7.5-11.0).

[0012] Furthermore, in step S1, the mixed alloy powder includes at least one of metal powders of Al, Fe, Cu, Mg, Ni or their corresponding metal oxides. Specifically, the metal powders containing the above metal elements can be used directly, or Cu, Mg, Ni therein can be replaced with their corresponding metal oxides CuO, MgO, NiO.

[0013] Furthermore, in step S1, the mixed alloy powder is prepared by subjecting raw material powders containing various metal elements to mechanical alloying treatment; the mechanical alloying treatment is carried out by ball milling, and the particle size of the mixed alloy powder is 350-600 mesh.

[0014] Furthermore, in step S2, the thermite is composed of Al powder and CuO powder, and its composition is similar to that of the high entropy oxide to be prepared. The Al and CuO in the thermite are consistent with the main components of the high entropy oxide, Al and Cu, and will not pollute the product.

[0015] Furthermore, in the self-propagating reaction system, Al powder and CuO powder are used as thermites. If the ratio is too high, it will lead to waste and excessive reaction, and may even cause the shell of the preparation device to burn; while the thermite content is too low, the self-propagating high-temperature reaction cannot be fully carried out. Preferably, the composition of the reactants is calculated by weight percentage, and the mixed alloy powder is 45%-58%, the Al powder is 10%-12.5%, the CuO powder is 30%-37.5%, and the CaSO4 is 2%-5%. Among them, CaSO4 is not only a reactant that reacts with aluminum to release heat, but also a slag-forming agent to generate sulfide waste slag. The above reactant formula is obtained through a large number of experiments and research calculations. Based on the above ratio, the yield and quality of the reaction product high entropy oxide are controllable, and the elemental composition of the thermite is similar to that of the high entropy alloy, so no additional impurity elements are introduced.

[0016] Furthermore, in step S3, the protective gas is formed by mixing an inert gas and air in a volume ratio of (75-80):(20-25), and the flow rate of the protective gas is 5-7 L / min; and the collecting component is cooled by water cooling.

[0017] Furthermore, in step S3, the ignition agent is ignited by electronic ignition. Preferably, the ignition agent is selected from a combination of one or more of potassium chlorate, potassium nitrate and ammonium nitrate.

[0018] Furthermore, in step S4, the collecting assembly is provided with a corrugated plate, and the collecting assembly is connected to the reaction device by fastening screws.

[0019] In the preparation method provided by the present invention, the collecting assembly is firstly continuously water-cooled, and then the fan of the air inlet is started, and the protective gas is continuously introduced into the reaction device by an air pump, and then the electronic ignition device is started to ignite the reactants. Under the condition that Al and CuO in the thermite undergo a violent redox reaction and release a large amount of heat, the mechanically alloyed mixed alloy powder melts and is ejected due to high pressure to form a high entropy oxide, and the high entropy oxide is attached to the collecting device with a corrugated plate. Since the water cooling device takes away the heat of the high entropy oxide in time and cools it rapidly, the further growth of the high entropy oxide product particles is prevented, and the particle size of the high entropy oxide particles finally obtained is maintained between 170-610 nm.

[0020] The following reactions mainly occur in the preparation method of the present invention: Reaction 1 Reaction 2 Reaction 3 The technical solution adopted by the present invention to achieve the second purpose is: to provide a high entropy oxide powder based on a self-propagating reaction, which is prepared by the preparation method described in one of the purposes of the present invention.

[0021] The technical solution adopted by the present invention to achieve the third purpose is: to provide an application of the high entropy oxide powder described in the second purpose of the present invention in battery materials, catalytic materials or adsorption materials.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) Compared with the existing conventional methods for preparing high entropy oxides, the method for preparing high entropy oxide powders based on self-propagating reaction provided by the present invention has the advantages of simple operation, easy implementation, and the ability to prepare nanopowders of various particle sizes, and low material cost. In addition, the preparation method provided by the present invention improves the yield of the target product while ensuring the high efficiency of the preparation process, solving the problems of the existing high entropy oxide powder preparation process, such as the method being time-consuming, the product requiring post-processing, and low efficiency.

[0023] (2) The high entropy oxide powder based on the self-propagating reaction prepared by the present invention has the advantages of small particles, uniform particle size distribution, good conductivity and thermal stability, etc., and has broad promotion and application prospects in battery materials and catalytic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic flow chart of a method for preparing high entropy oxide powder based on a high temperature self-propagating reaction provided in an embodiment of the present invention.

[0025] Figure 2 A schematic diagram of the structure of a device used in an embodiment of the present invention; Figure 3 The XRD pattern of the high entropy oxide powder prepared in Example 1 of the present invention; Figure 4 This is the SEM spectrum of the high entropy oxide powder prepared in Example 1 of the present invention; Figure 5 This is the SEM spectrum of the high entropy oxide powder prepared in Example 2 of the present invention; Figure 6 This is the SEM spectrum of the high entropy oxide powder prepared in Example 3 of the present invention; Among them, 1-graphite crucible; 2-thermites and substances to be reacted; 3-ignition powder; 4-cardboard; 5-waste slag tank; 6-fastening screws; 7-fan; 8-collecting device with corrugated plate; 9-water tank; 10-water cooling pipe; 11-coil electronic ignition head; 12-ignition device capacitor; 13-dry battery. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0028] The present invention provides a method for preparing a high entropy oxide based on a high temperature self-propagating reaction, and the schematic diagram thereof is shown in FIG. Figure 1 As shown, the structural schematic diagram of the device used in the preparation method is as shown Figure 2 shown.

[0029] See also Figure 2 The device is composed of a waste slag tank 5, a graphite crucible 1, a collection component with a corrugated plate, and an electronic ignition component. The waste slag tank 5 is provided with a groove, on which a cardboard 4 is placed, the graphite crucible 1 contains thermite and a substance to be reacted 2, and the surface is sprinkled with ignition powder 3, the graphite crucible 1 is placed above the cardboard 4, and a slag discharge hole is opened at the bottom. The ignition powder 3 is ignited by the electronic ignition component, thereby initiating a self-propagating reaction below. The electronic ignition component includes a coil electronic ignition head 11, an ignition device capacitor 12, and a dry battery 13. The collection component with a corrugated plate includes a top wall and a side wall, and the side wall is detachably connected to the waste slag tank. The top wall is provided with a water tank 9, and the side wall includes a pair of first side walls in an inverted right-angle trapezoid, a second side wall arranged in a vertical direction, and a third side wall arranged obliquely; the second side wall is provided with a fan 7 facing the third side wall for conveying protective gas; the third side wall is provided with a water cooling pipe 10, and the inlet of the water cooling pipe 10 is connected to the outlet of the water tank 9. Corrugated plates for collecting products are respectively arranged on the top wall and the third side wall facing the graphite crucible 1 .

[0030] The above device adds structures such as fans, water tanks, and water cooling pipes, which are conducive to the generation of finer high-entropy oxide particles during the reaction. While the oxidation is relatively complete and aggregation is not likely to occur, it is conducive to the generation of high-entropy oxide products with smaller particle sizes and more uniform distribution. At the same time, the device also connects the four corners of the collection component and the waste slag tank with fastening screws. During the reaction, the waste slag tank and the collection device are an integrated structure, which can effectively prevent the huge pressure generated by the reaction from washing away the collection device, ensuring the smooth progress of the reaction.

[0031] The preparation method comprises the following steps: Step 1: Weigh the corresponding powders of Al powder, Fe powder, Cu powder, Mg powder and Ni powder according to the molar ratio of the metal elements of Al, Fe, Cu, Mg and Ni of (42.5-45.5):(17.5-20.5):(10.5-14.5):(18.5-19.0):(0.5-11.0), mix them evenly and put them into a ball mill for mechanical alloying treatment. The grinding balls are made of 304 stainless steel, with a ball-to-material ratio of 5:1, and the number ratios of grinding balls with diameters of 12 mm, 10 mm and 6 mm are 2-3:13-17:25-36. Ball milling is continued for 3-4 hours to obtain a mixed alloy powder with a particle size of 450-600 mesh.

[0032] Step 2: Mix 45-58 parts of the mechanically alloyed metal powder with 10-12.5 parts of Al powder, 30-37.5 parts of CuO powder, and 2-5 parts of CaSO4 powder by weight and place them in Figure 2 In the graphite crucible 1 shown, ignition powder is sprinkled on the surface.

[0033] Step 3: Place the slag tank 5 on the ground, arrange silicate refractory bricks, place cardboard 4 above the holes of the slag tank 5, place the graphite crucible 1 on the slag tank 5, and align the holes of the graphite crucible 1 with the holes of the slag tank 5. Install the collection assembly above the slag tank 5 and fix it by tightening screws. And install the coil electronic ignition head 11 into the graphite crucible 1. Continuously inject cooling water into the water tank 9 of the device, start the fan of the air inlet, and continuously introduce protective gas with an air pump. The protective gas is a mixture of inert gas and air in a volume ratio of (75-80): (20-25), and the flow rate of the protective gas is controlled to be 5-7L / min. Then start the electronic ignition assembly to ignite the ignition powder, and then the Al in the thermite and CuO undergo a violent redox reaction to release a large amount of heat, so that the mechanically alloyed mixed alloy powder melts and is ejected due to high pressure, forming high entropy oxide particles that adhere to the top wall and side wall of the corrugated plate in the collection assembly under the action of the fan. The cooling water in the water tank and cooling pipe on the back of the corrugated plate can take away the heat of the high-entropy oxide particles in time, thereby preventing the particles from growing further and obtaining high-entropy oxides with uniform and controllable particle size.

[0034] Step 4: After the high-temperature self-propagating reaction is completed and the device is cooled, the target product high-entropy oxide powder is collected on the corrugated plate of the collection component, and then the high-entropy oxide powder is weighed and characterized.

[0035] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0036] In Examples 1-3 of the present invention, the contents of each metal element in the mixed alloy powder in step 1 (in molar fraction) and the composition of the self-propagating reaction system in step 2 (in weight fraction) are shown in Table 1 below.

[0037] Table 1

[0038] Example 1 According to the molar ratio of 42.5:17.5:10.5:18.5:11, weigh the powders of Al, Fe, Cu, Mg, and Ni, mix them evenly, and then put them into a ball mill for 3 hours to obtain mechanically alloyed metal powder. Then take 10 parts of Al powder, 30 parts of CuO powder, 57 parts of mechanically alloyed powder obtained in the previous step, and 3 parts of CaSO4, mix them evenly and put them into the graphite crucible of the reaction device, sprinkle ignition powder on the surface, and then install the reaction device, start the fan at the air inlet, and use an air pump to pass protective gas at a flow rate of 5L / min. Continuously inject cooling water into the water tank, and then close the charging switch to charge the capacitor. After the capacitor is charged, disconnect the charging switch, close the coil switch to ignite the reactants, and after the reaction is completed and the device is cooled, the high entropy oxide powder can be collected on the corrugated plate in the collection device. After collection, the mass is weighed to be 5.65g. After XRD and SEM characterization, it is determined that the obtained powder is the required high entropy oxide powder. The XRD spectrum of the high entropy oxide powder prepared in this embodiment is as follows Figure 3 shown.

[0039] Example 2 According to the molar ratio of 45.5:20.5:14.5:19:0.5, weigh the powders of Al, Fe, Cu, Mg, and Ni, mix them evenly, and put them into a ball mill for 3.5 hours to obtain mechanically alloyed metal powder. Then take 12.5 parts of Al powder, 37.5 parts of CuO powder, 46 parts of the mechanically alloyed powder obtained in the previous step, and 44 parts of CaSO, mix them evenly and put them into the graphite crucible of the reaction device, sprinkle ignition powder on the surface, and then install the reaction device, start the fan at the air inlet, and use an air pump to introduce protective gas with a flow rate of 6L / min. Continuously inject cooling water into the water tank, and then close the charging switch to charge the capacitor. After the capacitor is charged, disconnect the charging switch, close the coil switch to ignite the reactants, and after the reaction is completed and the device is cooled, the high entropy oxide powder can be collected on the corrugated plate in the collection device. The mass after collection is 5.93g. After XRD and SEM characterization, it is determined that the obtained powder is the required high entropy oxide powder.

[0040] Example 3 According to the molar ratio of 45:20:13:18.75:3.25, weigh the powders of Al, Fe, Cu, Mg, and Ni, mix them evenly, and put them into a ball mill for 4 hours to obtain mechanically alloyed metal powder. Then take 12 parts of Al powder, 36 parts of CuO powder, 47 parts of the mechanically alloyed powder obtained in the previous step, and 45 parts of CaSO, mix them evenly, and put them into the graphite crucible of the reaction device. Sprinkle ignition powder on the surface, and then install the reaction device. Start the fan at the air inlet, and use an air pump to introduce protective gas with a flow rate of 7L / min. Continuously inject cooling water into the water tank, and then close the charging switch to charge the capacitor. After the capacitor is charged, disconnect the charging switch, close the coil switch to ignite the reactants, and after the reaction is completed and the device is cooled, the high entropy oxide powder can be collected on the corrugated plate in the collection device. The mass after collection is weighed to be 6.12g. After XRD and SEM characterization, it is determined that the obtained powder is the required high entropy oxide powder.

[0041] The yield of the high entropy oxide powder obtained in Examples 1-3 of the present invention, the yield rate of the target product (the ratio of the yield of the high entropy oxide powder to the total weight of the raw materials in the self-propagating reaction system) and the particle size of the product are shown in Table 2 below.

[0042] Table 2

[0043] Furthermore, the scanning electron microscope images of the high entropy oxides prepared in Examples 1-3 are as follows: Figure 4-6 As shown, Figure 4 The obtained high entropy oxide has a small particle size and many micropores, and can be used in the chemical industry as a nanocatalyst; Figure 5 The particle size of the prepared high entropy oxide particles is slightly larger than Figure 4 The product can be used in the field of microelectronics based on the electrical conductivity and thermal stability of high entropy oxides. Figure 6 The obtained high entropy oxide particles have many micropores and can be used in the preparation of adsorption materials for adsorbing pollutants or impurities.

[0044] In summary, the method for preparing a high entropy oxide powder based on a self-propagating reaction provided by the present invention has the advantages of simple operation, easy implementation, ability to prepare nanopowders of various particle sizes, and low material cost, compared with the existing conventional method for preparing high entropy oxides. The high entropy oxide powder based on a self-propagating reaction prepared by the present invention has small particles, uniform particle size distribution, good conductivity and thermal stability, and has broad promotion and application prospects in battery materials and catalytic materials.

[0045] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing high entropy oxide powder based on self-propagating reaction, characterized in that: The following steps are involved: S1. preparing a mixed alloy powder containing metal elements Al, Fe, Cu, Mg and Ni; S2, mixing the mixed alloy powder with thermite and CaSO4 to obtain a reactant, placing the reactant in a reaction vessel of a reaction device, and sprinkling ignition powder on the surface of the reactant; S3, under the condition of introducing protective gas and continuously cooling the collecting assembly of the collecting device, igniting the ignition powder, so that the mixed alloy powder undergoes a high-temperature self-propagating reaction under the action of thermite; S4. After the high-temperature self-propagating reaction is completed and the reaction device is cooled, high entropy oxide powder is obtained in the collecting assembly.

2. The preparation method according to claim 1, characterized in that: In step S1, the molar ratio of the metal elements Al, Fe, Cu, Mg and Ni in the mixed alloy powder is (42.5-45.5):(17.5-20.5):(10.5-14.5):(18.5-19.0):(0.5-11.0).

3. The preparation method according to claim 1, characterized in that: In step S1, the mixed alloy powder includes at least one of metal powders of Al, Fe, Cu, Mg, Ni or their corresponding metal oxides.

4. The preparation method according to claim 1, characterized in that: In step S1, the mixed alloy powder is prepared by subjecting raw material powders containing various metal elements to mechanical alloying treatment; the mechanical alloying treatment is performed by ball milling, and the particle size of the mixed alloy powder is 350-600 meshes.

5. The preparation method according to claim 1, characterized in that: In step S2, the thermite is composed of Al powder and CuO powder; the composition of the reactants is calculated by weight percentage, and the mixed alloy powder is 45%-58%, the Al powder is 10%-12.5%, the CuO powder is 30%-37.5%, and the CaSO4 is 2%-5%.

6. The preparation method according to claim 1, characterized in that In step S3, the protective gas is a mixture of inert gas and air in a volume ratio of (75-80):(20-25); the flow rate of the protective gas is 5-7 L / min; and the collecting component is cooled by water cooling.

7. The preparation method according to claim 1, characterized in that: In step S3, the ignition agent is ignited by electronic ignition.

8. The preparation method according to claim 1, characterized in that: In step S4, the collecting assembly is provided with a corrugated plate, and the collecting assembly is connected to the reaction device by fastening screws.

9. A high entropy oxide powder based on a self-propagating reaction, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the high entropy oxide powder according to claim 9 in battery materials, catalytic materials or adsorption materials.

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