Samarium-iron-nitrogen powder with loose porous structure and preparation method of samarium-iron-nitrogen powder

Abstract

The invention discloses samarium-iron-nitrogen powder with a loose porous structure and a preparation method thereof.The preparation method comprises the steps that samarium-iron-nitrogen raw material powder is mixed with organic and inorganic grinding media in proportion, and a mixed material is obtained; in an oxygen-free environment, grinding the mixed material to obtain ground slurry; and carrying out powder drying on the ground slurry to obtain the samarium-iron-nitrogen powder with a loose porous structure. The problem that an existing samarium-iron-nitrogen powder material cannot obtain a loose and porous structure is solved, the prepared powder has the large specific surface area and good wave absorbing performance, and the preparation technology is simple, short in consumed time and low in cost.

Description

Technical Field

[0001] The present invention belongs to the field of microwave absorbing materials, and particularly relates to a samarium iron nitride powder with a loose porous structure and a preparation method thereof. Background Art

[0002] Microwave absorbing materials are a type of materials that can absorb or significantly weaken the energy of electromagnetic waves, thereby reducing electromagnetic wave interference. With the development of modern science and technology, microwave absorbing materials have important applications in physiotherapy devices, aerospace, national defense, and military industries. Microwave absorbing materials have also become a major topic in materials engineering.

[0003] Samarium iron nitride materials were discovered in 1990 and have been attracting much attention due to the microwave absorbing properties generated after nitrogen atoms enter the samarium iron lattice to form interstitial compounds. Similar to conventional microwave absorbing materials, specific surface area is also an important factor affecting the microwave absorbing effect of samarium iron nitride materials. Generally, the larger the specific surface area, the better the microwave absorbing effect. Because when the specific surface area is large, the internal porosity is appropriate, which can form good electromagnetic wave channels in the material, enabling electromagnetic waves to enter the material interior greatly and thus be fully absorbed. As is well known, particle size and particle morphology are two important factors affecting the specific surface area of powders. Generally speaking, the smaller the particle diameter, the looser the particle structure or the more pores in the particles, the larger the specific surface area of the powder, the more excellent the surface properties of the material, and the more excellent the microwave absorbing properties. This is also the main reason why microwave absorbing materials such as samarium iron nitride and many catalytic materials are developed towards small particle sizes and loose porous materials.

[0004] Currently, the main preparation technologies for samarium iron nitride powder materials include mechanical ball milling method, melt spinning method, powder metallurgy method, chemical diffusion reduction method, and spraying method. In these technologies, the main way to increase the specific surface area of samarium iron nitride powder materials is the small particle size approach of reducing the particle diameter to sub-micron or nano-scale. However, in the actual application process, the problem with this small particle size approach is that it not only has high requirements for equipment or processes, especially high requirements for oxygen prevention control, but also increases the process complexity and lengthens the process time, ultimately resulting in high costs, complex processes, and long flowcharts. Therefore, people have always hoped to achieve a loose porous structure in samarium iron nitride materials through new technology regulation and control. However, due to the influence of the chemical structure, mechanical properties, and preparation technology of samarium iron nitride itself, the samarium iron nitride powder materials obtained by the existing technology are all dense structures with relatively flat surfaces and no holes on the surface and inside. Whether a loose porous structure can be obtained and how to obtain it have always been a major problem in the development of samarium iron nitride materials.

[0005] Therefore, it is of great significance to provide a samarium iron nitride powder material with a loose porous structure and a preparation method thereof. Summary of the Invention

[0006] To overcome the problem in the prior art that it is impossible to obtain a samarium iron nitride powder material with a loose and porous structure, the purpose of the present invention is to provide a samarium iron nitride powder with a loose and porous structure and a preparation method thereof. This method solves the problem that the conventional preparation method of samarium iron nitride powder materials cannot obtain a loose and porous structure, and at the same time solves the problems of high cost, many processes, and long time consumption in the preparation of conventional compact structures, especially small particle sizes.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A samarium iron nitride powder with a loose and porous structure, the samarium iron nitride powder has a loose and porous structure.

[0009] Further, the loose and porous structure includes an aggregated loose and porous structure and an independent loose and porous structure.

[0010] Further, the aggregated loose and porous structure is formed by small particles and large particles together, and / or independently formed by the aggregation of small particles; the independent loose and porous structure is formed by the large particles themselves; the small particles are of a dense structure, with irregular shapes, and the particle sizes range from nanometers to sub-microns; the large particles have irregular shapes, the particle sizes are in the micron scale, and the particle surfaces are flat and smooth structures, or uneven porous structures with undulations.

[0011] Further, the pores of the loose and porous structure come from the aggregation pores of small particles, and / or when the surface of the large particle is an uneven porous structure, from the pores on the surface of the large particle; the aggregation pores of small particles include the aggregation pores between small particles and the aggregation pores between small particles and large particles.

[0012] A preparation method of a samarium iron nitride powder with a loose and porous structure, comprising the following steps:

[0013] (1) Mix the samarium iron nitride raw material powder with organic and inorganic grinding media in proportion to obtain a mixed material;

[0014] (2) Grind the mixed material in an oxygen-free environment to obtain a ground slurry;

[0015] (3) After drying the powder of the ground slurry, obtain a samarium iron nitride powder with a loose and porous structure.

[0016] Further, it also includes the following steps:

[0017] (4) Put the samarium iron nitride powder with a loose and porous structure into a spraying device for treatment, and collect the particles at the bottom layer.

[0018] Further, the average particle size of the samarium iron nitride raw material powder does not exceed 200 microns.

[0019] Furthermore, the organic grinding medium includes a solvent, a surfactant, and a coupling agent. The solvent is one or more of gasoline, n-hexane, cyclohexane, cyclopentane, isooctane, n-heptane, n-pentane, and octane; the surfactant is one or more of oleic acid, oleylamine, stearic acid, palmitic acid, linoleic acid, arachidic acid, and behenic acid; the inorganic grinding medium includes grinding balls.

[0020] Furthermore, the grinding balls are steel balls, agate balls, cast iron balls, alloy balls, or ceramic balls; the grinding time is 5 - 1000 min; the ball-to-material ratio is 1:1 - 25:1; the coupling agent is a silane coupling agent.

[0021] Furthermore, the dosage of the solvent is (10 - 200)% of the mass of the samarium iron nitride raw material powder, the dosage of the surfactant is (0 - 200)% of the mass of the samarium iron nitride raw material powder, the dosage of the coupling agent is (0 - 10)% of the mass of the samarium iron nitride raw material powder, and the surfactant and the coupling agent are not both 0 at the same time.

[0022] Furthermore, the dosage of the solvent is (30 - 70)% of the mass of the samarium iron nitride raw material powder, the dosage of the surfactant is (1 - 50)% of the mass of the samarium iron nitride raw material powder, and the dosage of the coupling agent is (0.2 - 2)% of the mass of the samarium iron nitride raw material powder.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] Starting from comprehensively regulating the fracture mechanics behavior of samarium iron nitride powder and the powder aggregation force, the present invention effectively matches the organic and inorganic grinding media during the grinding process, weakens the crack propagation ability of samarium iron nitride powder after being impacted by grinding, and changes the crack propagation and powder fragmentation from the conventional through-powder type to the local superficial type, thereby inducing the generation of small surface-shedding particles and remaining large particles (the surface of the large particles is a flat and smooth structure, or an uneven and porous structure with undulations); and the generated small surface-shedding particles, driven by the aggregation force, re-aggregate around the large particles before fragmentation without cold welding. Finally, a loose and porous structure is formed through the consumption of large particles and the accumulation of voids in the aggregation of small particles. This structure has a large specific surface area. The present invention solves the problem that the existing samarium iron nitride powder materials cannot obtain a loose and porous structure, and compared with the conventional small-particle-size scheme for increasing the specific surface area, the preparation process of the present invention is simple, takes a short time, and has a low cost, and is very suitable for practical application.

[0025] The samarium iron nitride powder with a loose and porous structure prepared by the present invention has a pore structure, thus having a large specific surface area and good wave-absorbing performance. Description of the Drawings

[0026] Figure 1 It is the SEM image of the ball-milled samarium iron nitride powder obtained in Example 1 of the present invention;

[0027] Figure 2 SEM image of the hierarchical samarium iron nitride powder obtained in Example 2 of the present invention. Detailed implementation manners

[0028] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0029] A preparation method of a samarium iron nitride powder of the present invention is as follows: First, mix the samarium iron nitride raw material powder with organic and inorganic grinding media in a certain proportion, then grind the mixed powder in an oxygen-free environment, and finally obtain the samarium iron nitride powder with a loose and porous structure after washing and drying.

[0030] The samarium iron nitride powder with a loose and porous structure is an agglomerated loose and porous structure powder or an independent loose and porous structure powder.

[0031] Specifically, the preparation method of the agglomerated loose and porous structure powder in the present invention is as follows:

[0032] (1) Mix the samarium iron nitride raw material powder with organic and inorganic grinding media in a certain proportion to obtain a ground mixed material;

[0033] (2) Place the mixed material on a grinding device in an oxygen-free environment for grinding to obtain a ground slurry;

[0034] (3) Take out the ground slurry, and obtain the target samarium iron nitride powder with an agglomerated loose and porous structure after powder drying. Preferably, washing is required before drying, and the washing liquid is alcohol and / or acetone.

[0035] The average particle size of the samarium iron nitride raw material powder in the present invention does not exceed 200 microns.

[0036] The organic grinding media mainly refer to solvents, surfactants and coupling agents. Among them, solvents include, but are not limited to, one or several mixtures of gasoline, n-hexane, cyclohexane, cyclopentane, isooctane, n-heptane, n-pentane, octane, etc.; surfactants include, but are not limited to, one or several mixtures of oleic acid, oleylamine, stearic acid, palmitic acid, linoleic acid, arachidic acid, behenic acid, etc.; the coupling agent is a silane coupling agent, and the models include, but are not limited to, one or several mixtures of KH550, KH560 or KH570.

[0037] The inorganic grinding media are grinding balls. Preferably, the grinding balls include, but are not limited to, steel balls, agate balls, cast iron balls, alloy balls or ceramic balls, etc.

[0038] The equipment used for grinding includes, but is not limited to, vibrating ball mills, planetary ball mills, and three-dimensional vibrating ball mills.

[0039] Preferably, the time is 5 - 1000 min, and more preferably the grinding time is 5 - 240 min.

[0040] Preferably, the dosage of the solvent is (10 - 200)% of the mass of the samarium iron nitride raw material powder, the dosage of the surfactant is (0 - 200)% of the mass of the samarium iron nitride raw material powder, the dosage of the coupling agent is (0 - 10)% of the mass of the samarium iron nitride raw material powder, and the dosages of the surfactant and the coupling agent are not both 0 at the same time.

[0041] More preferably, the dosage of the solvent is (30 - 70)% of the mass of the samarium iron nitride raw material powder, the dosage of the surfactant is (1 - 50)% of the mass of the samarium iron nitride raw material powder, the dosage of the coupling agent is (0.2 - 2)% of the mass of the samarium iron nitride raw material powder; the ball-to-material ratio is 1:1 - 25:1, preferably 3:1 - 15:1.

[0042] Specifically, for the preparation method of the independent loose porous structure powder in the present invention, the steps include:

[0043] (1) Take the samarium iron nitride raw material powder and mix it with organic and inorganic grinding media in proportion to obtain a grinding mixture.

[0044] (2) Under an oxygen-free environment, place the mixture on a grinding device for grinding to obtain a grinding slurry.

[0045] (3) Take out the grinding slurry, and after powder drying, obtain agglomerated loose porous structure samarium iron nitride powder.

[0046] (4) Take out the agglomerated loose porous structure samarium iron nitride powder, put it into a spraying device for classification, collect the bottom layer particles, and obtain the target independent loose porous samarium iron nitride powder.

[0047] Among them, steps (3) and (4) can also be combined, omitting one drying step, that is, take out the grinding slurry, put it into a spraying device for classification, collect the bottom layer particles, and obtain the loose porous samarium iron nitride powder with an independent structure.

[0048] The samarium iron nitride powder prepared by the present invention has a loose porous structure. Among them, the loose porous structure is a porous and loose structure formed by small and large surface particles, including both an agglomerated loose porous structure and an independent loose porous structure.

[0049] The agglomerated loose porous structure includes an agglomerated loose porous structure formed by small particles and large particles together, and / or a loose porous structure formed only by the agglomeration of small particles; the independent loose porous structure includes a loose porous structure formed only by large particles themselves;

[0050] Most of the small particles are of a dense structure, with irregular shapes, and the particle sizes range from nanometers to sub-microns, mostly sub-microns;

[0051] The large particles have irregular shapes, and the particle sizes are mostly in the micron scale. The surface of the particles can be a flat and smooth structure or an uneven porous structure with many bumps and depressions.

[0052] The pores in the loose porous structure come from the pores formed by the agglomeration of small particles (the pores formed by the agglomeration of small particles include the pores between small particles and the pores between small particles and large particles), and / or when the surface of the large particle is an uneven porous structure, the pores from the surface of the large particle.

[0053] In the present invention, surfactants and coupling agents not only play an important role in regulating the mechanical behavior of powder fragmentation and the powder agglomeration force, but also have the advantages of maintaining the powder structure and reducing powder oxidation. Surfactants and coupling agents are first molecular bridges connecting polar powders and non-polar solvents. This is because, in essence, both surfactants and coupling agents have polar groups that are hydrophilic to polar powders and non-polar groups that are hydrophilic to non-polar solvents. The reason why they play an important role in regulating the mechanical behavior of powder fragmentation is that after they are dissolved in the solvent, they can not only cause changes in the solution viscosity and thus change the impact kinetic energy of the grinding balls, but also form an effective barrier between the magnetic powders and between the powders and the grinding balls. By forming the barrier, the actual impact energy of the powders is further weakened, ultimately triggering unconventional phenomena such as the powder fragmentation tending to occur on the surface and the large particles being gradually consumed into a flat structure or a surface porous structure in the present invention; after the powder is fragmented, they can form a barrier between the powders through rapid adsorption on the fresh surface, so that the newly fragmented powders do not cold-weld together but form loose agglomerates. This is also the main reason why surfactants and coupling agents regulate the powder agglomeration force and promote the formation of porous structures.

[0054] Meanwhile, the functions of surfactants and coupling agents are not entirely the same and are distinguishable, mainly due to the different molecular chain structures and compositions of surfactants and coupling agents. Specifically, surfactants have a single-chain structure, while coupling agents have a multi-chain structure. There is one binding and adsorption point between the surfactant and the powder, while there are multiple binding and adsorption points between the coupling agent and the powder. Therefore, relatively speaking, surfactants move faster in the solvent and are more likely to be preferentially adsorbed between newly formed fracture surfaces. As a result, they play a more obvious role in preferentially promoting the further expansion of fracture cracks, preferentially determining the morphology of large particles after surface fracture, and preferentially preventing the adverse cold welding of newly formed particles. This law of the morphology of large particles determined by the movement speed of surfactants is also the main reason why different morphologies of large particles can be obtained by combining the same surfactant with different solvents. However, limited by the single-point adsorption characteristics and long molecular structure of surfactants with the powder, the adsorption point density generated by surfactants is lower than that of coupling agents. Therefore, coupling agents have more advantages in increasing the powder adsorption point density and stabilizing the final agglomeration state of crushed powder.

[0055] The following are specific embodiments of the present invention.

[0056] Example 1

[0057] (1) Take isooctane at 52% of the mass of the samarium iron nitride raw material powder, oleic acid at 2% of the mass of the samarium iron nitride raw material powder, and silane coupling agent KH550 at 0.5% of the mass of the samarium iron nitride raw material powder as organic grinding media, and mix them with inorganic grinding media to obtain a grinding mixture.

[0058] (2) Under an oxygen-free environment, place the mixture on a three-dimensional vibrating ball mill and grind it with grinding balls. The ball-to-material ratio is 10:1. After ball milling for 30 minutes, a crushed powder slurry is obtained.

[0059] (3) Take out the grinding slurry and dry it at 60 °C for 20 minutes to obtain ball-milled samarium iron nitride powder.

[0060] (4) Take out the ball-milled samarium iron nitride powder and put it into a spraying device for classification. Collect the particles at the bottom layer to obtain classified samarium iron nitride powder.

[0061] Observation of the ball-milled samarium iron nitride powder obtained in Example 1 by SEM shows that the samarium iron nitride powder obtained in this example presents an agglomerated loose porous structure (see Figure 1 ). The surface of the structure is a loose agglomeration of many sub-micron small particles, while the large particles have a dense structure with a smooth surface and no pores. Therefore, the pores in the loose structure only come from the agglomeration pores of small particles.

[0062] Example 2

[0063] (1) Take 52% of the mass of the samarium iron nitride raw material powder as n-hexane, 100% of the mass of the samarium iron nitride raw material powder as oleic acid, and 0.5% of the mass of the samarium iron nitride raw material powder as the silane coupling agent KH550 as the organic grinding medium, and mix them with the inorganic grinding medium to obtain a grinding mixture.

[0064] (2) Under an anaerobic environment, place the mixed material on a three-dimensional vibrating ball mill for ball milling to obtain a crushed powder slurry; the ball-to-material ratio is 10:1; the ball milling time is 120 min.

[0065] (3) After the grinding is completed, take out the powder slurry, wash it with acetone and alcohol, and then dry it under vacuum at 60 °C for 20 min to obtain the ball-milled samarium iron nitride powder.

[0066] (4) Take out the ball-milled samarium iron nitride powder, put it into a spraying device for classification, collect the particles at the bottom layer to obtain the classified samarium iron nitride powder.

[0067] Observation of the ball-milled and classified samarium iron nitride powders obtained in this example by SEM shows that the ball-milled samarium iron nitride powder obtained in this example presents an aggregated loose porous structure, and the surface of the structure is a loose aggregation of many sub-micron small particles; the obtained classified samarium iron nitride powder presents an independent loose porous structure (see Figure 2 ), indicating that the large particles corresponding to the aggregated loose porous structure in the ball-milled state at this time have a rough surface structure, and the surface of the large particles is a porous structure with pore sizes ranging from nanometers to sub-microns. Therefore, the loose porous structure obtained in this example includes both an aggregated loose porous structure and an independent loose porous structure, and the pores in the loose structure come from both the aggregated pores of small particles and the surface uneven pores of large particles.

[0068] Example 3

[0069] (1) Take 52% of the mass of the samarium iron nitride raw material powder as cyclohexane, 2% of the mass of the samarium iron nitride raw material powder as oleic acid, and 0.5% of the mass of the samarium iron nitride raw material powder as the silane coupling agent KH550 as the organic grinding medium, and mix them with the inorganic grinding medium to obtain a grinding mixture.

[0070] (2) Under an anaerobic environment, place the mixed material on a three-dimensional vibrating ball mill for grinding to obtain a crushed powder slurry; the ball-to-material ratio is 10:1; the ball milling time is 30 min.

[0071] (3) After the grinding is completed, take out the powder slurry, wash it with acetone and alcohol, and then dry it under nitrogen protection at 60 °C for 20 min to obtain the ball-milled samarium iron nitride powder.

[0072] (4) Take out the ball-milled samarium iron nitride powder, put it into a spray device for classification treatment, collect the particles at the bottom layer, and obtain the classified samarium iron nitride powder;

[0073] By observing the ball-milled and classified samarium iron nitride powders obtained in this example using SEM, it is found that the samarium iron nitride powders obtained in this example are indeed of a loose and porous structure. The surface of the structure is composed of many sub-micron small particles loosely agglomerated, while the large particles have a dense structure with a smooth surface and no pores. Therefore, the pores in the loose structure only come from the agglomeration pores of the small particles.

[0074] Example 4

[0075] (1) Take the samarium iron nitride raw material powder, 52% of the mass of the samarium iron nitride raw material powder of cyclopentane, 2% of the mass of the samarium iron nitride raw material powder of oleic acid, and 2% of the mass of the samarium iron nitride raw material powder of silane coupling agent KH550 as the organic grinding medium, mix it with the inorganic grinding medium, and obtain the grinding mixture;

[0076] (2) Under an oxygen-free environment, place the mixture on a three-dimensional vibrating ball mill for grinding to obtain a crushed powder slurry; the ball-to-material ratio is 10:1; the ball milling time is 30 min;

[0077] (3) After the grinding is completed, take out the powder slurry, wash it with acetone and alcohol, and then dry it in vacuum at 60 °C for 20 min to obtain the ball-milled samarium iron nitride powder.

[0078] (4) Take out the ball-milled samarium iron nitride powder, put it into a spray device for classification treatment, collect the particles at the bottom layer, and obtain the classified samarium iron nitride powder;

[0079] By observing the ball-milled and classified samarium iron nitride powders obtained in this example using SEM, it is found that the samarium iron nitride powders obtained in this example are indeed of a loose and porous structure. The surface of the structure is composed of many sub-micron small particles loosely agglomerated, while the large particles have a dense structure with a smooth surface and no pores. Therefore, the pores in the loose structure only come from the agglomeration pores of the small particles.

[0080] Example 5

[0081] (1) Take the samarium iron nitride raw material powder, 100% of the mass of the samarium iron nitride raw material powder of hexane, 50% of the mass of the samarium iron nitride raw material powder of oleic acid, and 2% of the mass of the samarium iron nitride raw material powder of silane coupling agent KH550 as the organic grinding medium, mix it with the inorganic grinding medium, and obtain the grinding mixture;

[0082] (2) Under an oxygen-free environment, place the mixture on a three-dimensional vibrating ball mill for grinding to obtain a crushed powder slurry; the ball-to-material ratio is 3:1; the ball milling time is 120 min;

[0083] (3) After the grinding is completed, the powder slurry is taken out, washed with acetone and alcohol, and then dried under argon protection at 60 °C for 20 min to obtain ball-milled samarium iron nitride powder.

[0084] (4) The ball-milled samarium iron nitride powder is put into a spraying device for classification treatment, and the particles at the bottom layer are collected to obtain classified samarium iron nitride powder;

[0085] By observing the ball-milled and classified samarium iron nitride powders obtained in this example using SEM, it is known that the samarium iron nitride powder obtained in this example is indeed a loose and porous structure, and its structural morphology is similar to that of Example 2, that is, the surface of the structure is a loose aggregation of many sub-micron small particles, and the surface of the large particles is uneven with many holes. Therefore, the loose and porous structure obtained in this example also includes both aggregated loose and porous structures and independent loose and porous structures, and the holes in the loose structure come from both the aggregated holes of small particles and the surface uneven holes of large particles.

[0086] Comparative Example 1

[0087] (1) Take 100% of n-heptane by the mass of the samarium iron nitride raw material powder, 100% of oleic acid by the mass of the samarium iron nitride raw material powder, and 5% of the silane coupling agent KH550 by the mass of the samarium iron nitride raw material powder as the organic grinding medium, and mix it with the inorganic grinding medium to obtain a grinding mixture;

[0088] (2) In an oxygen-free environment, the mixture is placed on a three-dimensional vibration ball mill for grinding to obtain a crushed powder slurry; the ball-to-material ratio is 30:1; the ball milling time is 720 min;

[0089] (3) After the grinding is completed, the powder slurry is taken out, washed with acetone and alcohol, and then dried at 60 °C for 20 min to obtain ball-milled samarium iron nitride powder.

[0090] (4) The ball-milled samarium iron nitride powder is put into a spraying device for classification treatment, and the particles at the bottom layer are collected to obtain classified samarium iron nitride powder;

[0091] By observing the ball-milled and classified samarium iron nitride powders obtained in Comparative Example 1 using SEM, it is known that the samarium iron nitride powder obtained in this example, whether in the ball-milled state or the classified state, does not have the loose and porous structure described in the present invention.

[0092] The samarium iron nitride powders prepared in the above Examples 1 to 5 and the comparative examples are observed by SEM, and the results are summarized in Table 1.

[0093] Table 1 SEM observation results of the samarium iron nitride powders obtained in Examples 1-5 and Comparative Example 1

[0094] Example Porous structure Surface morphology of large particles Source of holes in the porous structure Example 1 Yes Smooth and non-porous Holes formed by agglomeration of small particles Example 2 Yes Concave-convex porous Holes formed by agglomeration of small particles + surface holes of large particles Example 3 Yes Smooth and non-porous Holes formed by agglomeration of small particles Example 4 Yes Smooth and non-porous Holes formed by agglomeration of small particles Example 5 Yes Concave-convex porous Holes formed by agglomeration of small particles + surface holes of large particles Comparative Example 1 No Smooth and non-porous No porous structure

[0095] Through Examples 1 - 5, it can be found that by the above technical solution of the present invention, samarium iron nitride powder with a loose and porous structure can be effectively obtained, and the preparation process is simple, with few steps, low cost, and is easy to scale up production.

[0096] Example 6

[0097] (1) Take 10% of gasoline by the mass of the samarium iron nitride raw material powder and 200% of oleylamine by the mass of the samarium iron nitride raw material powder as organic grinding media, and mix them with inorganic grinding media to obtain a grinding mixture.

[0098] (2) Under an oxygen - free environment, place the mixture on a three - dimensional vibrating ball mill and grind it with grinding balls. The ball - to - material ratio is 1:1. After ball - milling for 5 minutes, a crushed powder slurry is obtained.

[0099] (3) Take out the grinding slurry, dry it at 60 °C for 30 minutes to obtain ball - milled samarium iron nitride powder.

[0100] Example 7

[0101] (1) Take 200% of n - hexane by the mass of the samarium iron nitride raw material powder, 1% of stearic acid by the mass of the samarium iron nitride raw material powder, and 10% of silane coupling agent KH550 by the mass of the samarium iron nitride raw material powder as organic grinding media, and mix them with inorganic grinding media to obtain a grinding mixture.

[0102] (2) Under an oxygen - free environment, place the mixture on a three - dimensional vibrating ball mill and grind it with grinding balls. The ball - to - material ratio is 25:1. After ball - milling for 700 minutes, a crushed powder slurry is obtained.

[0103] (3) Take out the grinding slurry, dry it at 80 °C for 20 minutes to obtain ball - milled samarium iron nitride powder.

[0104] Example 8

[0105] (1) Take 30% of cyclohexane by the mass of the samarium iron nitride raw material powder, 50% of palmitic acid by the mass of the samarium iron nitride raw material powder, and 0.2% of silane coupling agent KH570 by the mass of the samarium iron nitride raw material powder as organic grinding media, and mix them with inorganic grinding media to obtain a grinding mixture.

[0106] (2) Under an oxygen - free environment, place the mixture on a three - dimensional vibrating ball mill and grind it with grinding balls. The ball - to - material ratio is 3:1. After ball - milling for 300 minutes, a crushed powder slurry is obtained.

[0107] (3) Take out the grinding slurry, dry it at 70 °C for 25 minutes to obtain ball - milled samarium iron nitride powder.

[0108] Example 9

[0109] (1) Take 70% of the mass of the samarium iron nitride raw material powder as n-heptane, 100% of the mass of the samarium iron nitride raw material powder as linoleic acid, and 2% of the mass of the samarium iron nitride raw material powder as the silane coupling agent KH560 as the organic grinding medium, and mix with the inorganic grinding medium to obtain a grinding mixture.

[0110] (2) Under an oxygen-free environment, place the mixed material on a three-dimensional vibrating ball mill and grind it with grinding balls. The ball-to-material ratio is 15:1. After ball milling for 60 minutes, a crushed powder slurry is obtained.

[0111] (3) Take out the grinding slurry, dry it at 65 °C for 26 minutes to obtain the ball-milled samarium iron nitride powder.

[0112] Example 10

[0113] (1) Take 100% of the mass of the samarium iron nitride raw material powder as octane, 70% of the mass of the samarium iron nitride raw material powder as arachidic acid, and 1% of the mass of the samarium iron nitride raw material powder as the silane coupling agent KH570 as the organic grinding medium, and mix with the inorganic grinding medium to obtain a grinding mixture.

[0114] (2) Under an oxygen-free environment, place the mixed material on a three-dimensional vibrating ball mill and grind it with grinding balls. The ball-to-material ratio is 7:1. After ball milling for 500 minutes, a crushed powder slurry is obtained.

[0115] (3) Take out the grinding slurry, dry it at 70 °C for 23 minutes to obtain the ball-milled samarium iron nitride powder.

[0116] Example 11

[0117] (1) Take 60% of the mass of the samarium iron nitride raw material powder as cyclopentane, 40% of the mass of the samarium iron nitride raw material powder as oleic acid, and 2% of the mass of the samarium iron nitride raw material powder as the silane coupling agent KH550 as the organic grinding medium, and mix with the inorganic grinding medium to obtain a grinding mixture.

[0118] (2) Under an oxygen-free environment, place the mixed material on a three-dimensional vibrating ball mill for grinding to obtain a crushed powder slurry; the ball-to-material ratio is 12:1; the ball milling time is 55 minutes;

[0119] (3) After grinding, take out the powder slurry, wash it with acetone and alcohol, and then dry it under nitrogen protection at 80 °C for 20 minutes to obtain the ball-milled samarium iron nitride powder.

[0120] (4) Take the ball-milled samarium iron nitride powder, put it into a spraying device for classification treatment, collect the particles at the bottom layer to obtain the classified samarium iron nitride powder.

[0121] Example 12

[0122] (1) Take 40% of the mass of the samarium iron nitride raw material powder as cyclopentane, 20% of the mass of the samarium iron nitride raw material powder as oleic acid, and 0.8% of the mass of the samarium iron nitride raw material powder as the silane coupling agent KH550 as the organic grinding medium, and mix it with the inorganic grinding medium to obtain a grinding mixture.

[0123] (2) Under an oxygen-free environment, place the mixture on a three-dimensional vibrating ball mill for grinding to obtain a crushed powder slurry; the ball-to-material ratio is 8:1; the ball milling time is 240 min.

[0124] (3) After grinding, take out the powder slurry, put it into a spraying device for treatment, collect the bottom layer particles, and obtain the classified samarium iron nitride powder.

[0125] In addition, in the manner of referring to Examples 1 - 5, other raw materials and conditions listed in this specification were used for experiments in other examples, and samarium iron nitride powder with a loose and porous structure could also be prepared.

[0126] It should be understood that the above examples are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

[0127] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention.

Claims

1. A samarium iron nitride powder with a loose porous structure, characterized in that the samarium iron nitride powder has a loose porous structure.

2. The samarium iron nitride powder with a loose porous structure according to claim 1, characterized in that the loose porous structure includes an agglomerated loose porous structure and an independent loose porous structure.

3. The samarium iron nitride powder with a loose porous structure according to claim 2, characterized in that the agglomerated loose porous structure is formed by small particles and large particles together, and / or is independently formed by agglomeration of small particles; the independent loose porous structure is formed by the large particles themselves; the small particles have a dense structure, irregular shapes, and particle sizes ranging from nanometers to sub-microns; the large particles have irregular shapes, particle sizes on the micron scale, and the particle surfaces are flat and smooth structures or uneven porous structures with undulations.

4. The samarium iron nitride powder with a loose porous structure according to claim 1, characterized in that the pores of the loose porous structure come from the agglomeration pores between small particles, and / or when the surface of the large particles is an uneven porous structure, from the pores on the surface of the large particles; the agglomeration pores between small particles include the agglomeration pores between small particles and the agglomeration pores between small particles and large particles.

5. A preparation method of a samarium iron nitride powder with a loose porous structure, characterized by comprising the following steps: (1) Mixing the samarium iron nitride raw material powder with organic and inorganic grinding media in a certain proportion to obtain a mixed material; (2) Grinding the mixed material in an oxygen-free environment to obtain a grinding slurry; (3) After drying the grinding slurry, obtaining a samarium iron nitride powder with a loose porous structure.

6. The preparation method of the samarium iron nitride powder according to claim 1, characterized by further comprising the following steps: (4) Putting the samarium iron nitride powder with a loose porous structure into a spraying device for classification treatment, and collecting the particles at the bottom layer.

7. The preparation method according to claim 5, characterized in that the average particle size of the samarium iron nitride raw material powder does not exceed 200 microns.

8. The preparation method according to claim 5, characterized in that the organic grinding medium includes a solvent, a surfactant, and a coupling agent. The solvent is one or more of gasoline, n-hexane, cyclohexane, cyclopentane, isooctane, n-heptane, n-pentane, and octane; the surfactant is one or more of oleic acid, oleylamine, stearic acid, palmitic acid, linoleic acid, arachidic acid, and behenic acid; the inorganic grinding medium includes grinding balls.

9. The preparation method according to claim 8, characterized in that the grinding balls are steel balls, agate balls, cast iron balls, alloy balls, or ceramic balls; the grinding time is 5 - 1000 min; the ball-to-material ratio is 1:1 - 25:1; the coupling agent is a silane coupling agent.

10. The preparation method according to claim 5, characterized in that the dosage of the solvent is (10 - 200)% of the mass of the samarium iron nitride raw material powder, the dosage of the surfactant is (0 - 200)% of the mass of the samarium iron nitride raw material powder, the dosage of the coupling agent is (0 - 10)% of the mass of the samarium iron nitride raw material powder, and the surfactant and the coupling agent are not both 0 at the same time.

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