Deep cryogenic storage material erni spherical particles and preparation method and application thereof

Abstract

The application relates to the technical field of powder processing technology, and provides a deep-low-temperature cold storage material ErNi spherical particle and a preparation method and application thereof.The method comprises the following steps: 1) powder mixing: pure Er powder and pure Ni powder are mixed until uniform ErNi powder raw materials are obtained; 2) sintering: the ErNi powder obtained in the step 1 is dried, is loaded into a mold, is placed into a discharge plasma sintering system, is subjected to electric discharge under vacuum conditions, is pressurized and heated to be sintered, is cooled in a furnace after sintering is completed, and then is machined to obtain ErNi rod materials; and 3) spheroidization forming: the ErNi rod material obtained in the step 2 is used as a consumable electrode, is rotated at high speed in an inert atmosphere, is subjected to plasma rotating electrode atomization, and ErNi spherical particles are obtained.The ErNi particles have high sphericity, narrow particle size distribution, no hollow powder and satellite powder, excellent low-temperature specific heat performance, and can be applied to cold storage type gas refrigerators as cold storage materials.

Description

Technical Field

[0001] This invention relates to the field of powder processing technology, and more specifically to a high sphericity ErNi cold storage particle for a small cold storage gas refrigerator, its preparation method, and its application. Background Technology

[0002] Small-scale cryogenic gas refrigerators have been widely used in cryogenic applications due to their small size, light weight, and high efficiency. These refrigerators fill the accumulator with spherical cryogenic storage materials with high specific heat capacity. During the refrigeration cycle, this material exchanges heat with helium as the working fluid, thus achieving refrigeration within a low-temperature range. Preparing the filling material into regular spheres not only ensures a sufficiently large contact area between the material and the working fluid in the refrigeration cycle but also reduces the flow resistance of the working fluid within the accumulator, significantly improving refrigeration efficiency. Therefore, currently, both domestic and international cryogenic storage materials are prepared as regular spheres and filled into small-scale cryogenic refrigerators.

[0003] Among various cold storage materials, ErNi has a large specific heat capacity around 10K, making it one of the important cold storage materials used in the cold storage units of small-scale cold storage gas refrigerators. However, this alloy is extremely brittle, has poor mechanical properties, and is very difficult to machine. Achieving efficient spherical preparation is a technical bottleneck that the industry urgently needs to overcome. Currently, research on the preparation of ErNi spherical particles in China is relatively scarce. The mainstream preparation method is to use a rotating disk centrifugal atomization method to prepare ErNi spherical particles. However, the spherical particles prepared by this method have drawbacks such as a large amount of satellite powder, poor sphericity, and low production efficiency. In addition, the inherent defects of the material itself, such as high brittleness, easy breakage, and high molding difficulty, seriously restrict its large-scale and efficient application in the field of small-scale cold storage gas refrigerators.

[0004] In contrast, the powder prepared by plasma rotating electrode atomization technology has high sphericity, low impurities, good flowability, and excellent overall quality, fully meeting the performance and usage requirements of cold storage material particles under refrigeration conditions. It is one of the most advantageous processes currently available for preparing spherical particles of cold storage materials. However, due to the characteristics of plasma rotating electrode atomization technology, the material needs to be processed into rods before powder preparation. However, ErNi itself is an intermetallic compound with extremely high brittleness, making preparation and processing extremely difficult. The inventors discovered that the material prepared by traditional melting and casting methods has a large grain size, further increasing its brittleness. Therefore, traditional melting and casting methods are almost incapable of processing ErNi into rods with sufficient mechanical strength. Summary of the Invention

[0005] Technical issues To address the problem of difficulty in spherizing ErNi in existing technologies, this invention provides a method for preparing spherical ErNi particles for cryogenic cold storage and its application. The ErNi particles prepared by the method according to this invention exhibit high sphericity, narrow particle size distribution, and few hollow and satellite particles, resulting in excellent low-temperature specific heat properties. Therefore, they can be used as a cold storage material in cryogenic gas refrigerators.

[0006] Technical solution According to a first aspect of the present invention, a method for preparing ErNi spherical particles is provided, comprising the following steps: Step 1, Powder Mixing: Put pure Er powder and pure Ni powder into a V-type mixer, a drum mixer, or a planetary ball mill for powder mixing until a uniformly mixed ErNi powder raw material is obtained. Step 2, Sintering: The ErNi powder obtained in Step 1 is dried, molded, and placed in a spark plasma sintering system. It is sintered under vacuum conditions with electricity, pressure and temperature. After sintering, it is cooled with the furnace and then machined to obtain ErNi rods. Step 3, Spheroidization: The ErNi rod obtained in Step 2 is used as a consumable electrode and rotated at high speed in an inert gas atmosphere to perform plasma rotating electrode atomization to obtain ErNi spherical particles.

[0007] Preferably, the purity of the pure Er powder in step 1 is above 99.9%, and the particle size is 15~60 μm.

[0008] Preferably, the purity of the pure Ni powder in step 1 is above 99.9%, and the particle size is 15~60 μm.

[0009] Preferably, in step 1, the atomic ratio of pure Er powder to pure Ni powder is 1:1.

[0010] Preferably, in step 2, the vacuum degree is ≤10Pa.

[0011] Preferably, the sintering parameters in step 2 are: The axial pressure is 20~50 MPa, preferably 30~40 MPa; The heating rate is 10~50 ℃ / min, preferably 20~40 ℃ / min; The sintering temperature is 750~1000 ℃, preferably 850~950 ℃; The heat preservation time is 5~20 minutes, preferably 10~15 minutes.

[0012] Preferably, in step 2, the ErNi rod has a diameter of 30-50 mm and a length of 100-120 mm.

[0013] Preferably, in step 2, the ErNi bar stock, after processing, has a diameter slightly smaller than the inner diameter of the mold, a surface roughness ≤0.8 μm, a roundness deviation ≤0.05 mm, and a straightness deviation ≤0.01 mm.

[0014] Preferably, in step 3, when the vacuum degree of the vacuum treatment is ≤3×10 -3 After Pa, the pressure after introducing the protective gas is 0.1 MPa, and the protective gas is argon.

[0015] Preferably, in step 3, the plasma rotating electrode atomization technology involves controlling the ErNi electrode rod rotation speed at 4000~8000 rpm, the current intensity at 300~700 A, and the rod feed speed at 1.5~2.5 mm / s.

[0016] Preferably, the ErNi spherical particles obtained in step 3 have a particle size of 150~500 μm and a D90 of less than 400 μm.

[0017] Preferably, in the ErNi spherical particles obtained in step 3, the proportion of ErNi spherical particles with a particle size of 150~500 μm is 95wt% or more, more preferably 98wt% or more, and even more preferably 99wt% or more.

[0018] In the method for preparing ErNi spherical particles according to the present invention, the spark plasma sintering technology has outstanding advantages in processing such brittle materials due to its fast sintering rate and short sintering time. The prepared ErNi rods have small grain size and high mechanical strength, which can meet the requirements of plasma rotating electrode atomization technology for rods.

[0019] Therefore, this invention uses spark plasma sintering technology to prepare ErNi rods, and then uses plasma rotating electrode atomization technology to prepare ErNi spherical particles with narrow particle size distribution, high sphericity, smooth surface, and high specific heat at low temperature, with a high yield.

[0020] According to a second aspect of the present invention, the present invention provides ErNi spherical particles obtained according to a method for preparing ErNi spherical particles.

[0021] Preferably, the ErNi spherical particles are single-phase pure, have a sphericity of ≥98%, and are free of satellite powder and hollow powder.

[0022] Preferably, the ErNi spherical particles have a particle size of 150~500 μm.

[0023] Preferably, the D90 of the ErNi spherical particles is less than 400 μm.

[0024] Preferably, the ErNi spherical particles have a peak specific heat capacity of 0.94 J / cm³ in the temperature range of 2–12 K. 3 ·K.

[0025] According to a third aspect of the present invention, the present invention provides a cold storage gas refrigerator that uses ErNi spherical particles as described in the present invention as a cold storage material.

[0026] Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses a combination of spark plasma sintering and plasma rotating electrode atomization to prepare ErNi spherical particles. The prepared spherical particles are single-phase pure, with a sphericity ≥98%, virtually no satellite powder or hollow powder, and a particle size concentrated in the range of 150~500 μm; the peak specific heat capacity in the temperature range of 2~12K reaches 0.94 J / cm 3 K is particularly suitable for use as a cold storage material in the cold storage accumulators of small cryogenic refrigerators.

[0027] (2) By designing experiments, this invention controls the particle size distribution of powder by controlling parameters such as the rotation speed of the electrode rod, the current intensity, and the feed speed, and prepares ErNi spherical particles with a pass rate of over 95% and a D90 of less than 400μm. Attached Figure Description

[0028] Figure 1 The particle size distribution diagram of ErNi spherical particles prepared according to Example 1 of the present invention; Figure 2 X-ray diffraction pattern of ErNi spherical particles prepared according to Example 1 of the present invention; Figure 3 This is a low-magnification scanning electron microscope image of ErNi spherical particles prepared according to Example 2 of the present invention; Figure 4 This is a high-magnification scanning electron microscope image of ErNi spherical particles prepared according to Example 2 of the present invention; Figure 5 Specific heat capacity curves of Pb and ErNi spherical particles prepared according to Example 3 of the present invention in the temperature range of 2~20 K; Figure 6 The output cooling curve of the ErNi spherical particles prepared according to Example 3 of the present invention during application. Detailed Implementation

[0029] The present invention will be further described clearly and completely below with reference to the embodiments. However, the following embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; and unless otherwise specified, the reagents used are commercially available.

[0031] Example 1 ErNi spherical particles, a cryogenic cold storage material, were prepared using the following steps. Step 1: Weigh pure Er powder with a purity of ≥99.9% and pure Ni powder in an atomic ratio of 1:1 and put them into a V-type mixer. Add grinding balls and stir to mix evenly.

[0032] Step 2: The uniformly mixed powder is placed into a graphite mold for pre-compaction at a pressure of 10 MPa. The inner diameter of the graphite mold is 32 mm, and the height is 250 mm. The graphite mold containing the compacted powder is then placed into a spark plasma sintering system. When the vacuum degree is ≤10 Pa, the system is electrically pressurized and heated at an axial pressure of 40 MPa. The heating rate is 30 ℃ / min, the sintering temperature is 900 ℃, and the holding time is 10 min. The ErNi rod prepared by spark plasma sintering is then precision-machined into a metal electrode rod that meets the requirements of plasma rotating electrode atomization technology. The rod diameter is 30 mm, and the rod length is 120 mm. The surface roughness is ≤0.8 μm, the roundness deviation is ≤0.05 mm, and the straightness deviation is ≤0.01 mm.

[0033] Step 3: Place the ErNi rod inside the plasma rotating electrode atomization device, clamp it on the rod rotation and axial movement mechanism, and evacuate the entire powder-making equipment. The vacuum level during the vacuum treatment should be ≤3×10⁻⁶. -3 After Pa, argon gas is introduced as a protective gas, with a pressure of 0.1 MPa. The operating current of the plasma rotating electrode atomizer is set to 400 A, the electrode rod rotation speed to 4000 rpm, and the rod feed speed to 2.5 mm / s. The atomization function is activated, and the plasma beam is received while rotating at high speed, causing the consumable electrode tip to melt. The molten liquid metal forms small droplets under centrifugal force, and due to surface tension, the droplets solidify into spherical ErNi particles.

[0034] Step 4: Collect ErNi spherical particles prepared by plasma rotating electrode atomization technology.

[0035] The particle size distribution of the collected ErNi spherical particles is as follows: Figure 1 As shown, 99% of the powder is concentrated in the range of 150-500 μm, with a D50 of 288 μm and a D90 of 390 μm.

[0036] The XRD patterns of the spherical particles were analyzed using an X-ray diffractometer, and the results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the diffraction peaks of ErNi basically coincide with the Bragg positions, proving that the material is a single phase of ErNi.

[0037] Example 2 ErNi spherical particles, a cryogenic cold storage material, were prepared using the following steps. Step 1: Weigh pure Er powder with a purity of ≥99.9% and pure Ni powder in an atomic ratio of 1:1 and put them into a V-type mixer. Add grinding balls and stir to mix evenly.

[0038] Step 2: The uniformly mixed powder is placed into a graphite mold for pre-compaction at a pressure of 10 MPa. The inner diameter of the graphite mold is 42 mm, and the height is 250 mm. The graphite mold containing the compacted powder is then placed into a spark plasma sintering system. When the vacuum degree is ≤10 Pa, the system is electrically pressurized and heated at an axial pressure of 30 MPa. The heating rate is 20 ℃ / min, the sintering temperature is 850 ℃, and the holding time is 15 min. The ErNi rod prepared by spark plasma sintering is then precision-machined into a metal electrode rod that meets the requirements of plasma rotating electrode atomization technology. The rod diameter is 40 mm, and the rod length is 100 mm. The surface roughness is ≤0.8 μm, the roundness deviation is ≤0.05 mm, and the straightness deviation is ≤0.01 mm.

[0039] Step 3: Place the ErNi rod inside the plasma rotating electrode atomization device, clamp it on the rod rotation and axial movement mechanism, and evacuate the entire powder-making equipment until the vacuum degree is ≤3×10⁻⁶. -3 After Pa, argon gas is introduced as a protective gas, with a pressure of 0.1 MPa. The operating current of the plasma rotating electrode atomizer is set to 300 A, the electrode rod rotation speed to 6000 rpm, and the rod feed speed to 2 mm / s. The atomization function is activated, and the plasma beam is received while rotating at high speed, causing the consumable electrode tip to melt. The molten liquid metal forms small droplets under centrifugal force, and due to surface tension, the droplets solidify into spherical ErNi particles.

[0040] Step 4: Collect ErNi spherical particles prepared by plasma rotating electrode atomization technology. The particle size of the ErNi spherical particles is 150~500 μm.

[0041] The microstructure of the ErNi spherical particles was examined using scanning electron microscopy, as shown in the images. Figure 3 and Figure 4As shown in the figure, the ErNi spherical particles prepared by the discharge plasma sintering combined with plasma rotating electrode atomization technology have good sphericity, with almost no ellipsoids or irregular spheres. The particle surface is smooth and rounded, with virtually no satellite powder.

[0042] Example 3 ErNi spherical particles, a cryogenic cold storage material, were prepared using the following steps. Step 1: Weigh pure Er powder with a purity of ≥99.9% and pure Ni powder in an atomic ratio of 1:1 and put them into a V-type mixer. Add grinding balls and stir to mix evenly.

[0043] Step 2: The uniformly mixed powder is placed into a graphite mold for pre-compaction at a pressure of 10 MPa. The inner diameter of the graphite mold is 52 mm, and the height is 250 mm. The graphite mold containing the compacted powder is then placed into a spark plasma sintering system. When the vacuum degree is ≤10 Pa, the system is electrically pressurized and heated at an axial pressure of 35 MPa. The heating rate is 40 ℃ / min, the sintering temperature is 950 ℃, and the holding time is 10 min. The ErNi rod prepared by spark plasma sintering is then precision-machined into a metal electrode rod that meets the requirements of plasma rotating electrode atomization technology. The rod diameter is 50 mm, and the rod length is 100 mm. The surface roughness is ≤0.8 μm, the roundness deviation is ≤0.05 mm, and the straightness deviation is ≤0.01 mm.

[0044] Step 3: Place the ErNi rod inside the plasma rotating electrode atomization device, clamp it on the rod rotation and axial movement mechanism, and evacuate the entire powder-making equipment until the vacuum degree is ≤3×10⁻⁶. -3 After Pa, argon gas is introduced as a protective gas, with a pressure of 0.1 MPa. The operating current of the plasma rotating electrode atomizer is set to 700 A, the electrode rod rotation speed to 8000 rpm, and the rod feed speed to 1.5 mm / s. The atomization function is activated, and the plasma beam is received while rotating at high speed, causing the consumable electrode tip to melt. The molten liquid metal forms small droplets under centrifugal force, which solidify into spherical ErNi particles due to surface tension.

[0045] Step 4: Collect ErNi spherical particles prepared by plasma rotating electrode atomization technology. The particle size of the ErNi spherical particles is 150~500 μm.

[0046] The specific heat capacity variation curves of ErNi spherical particles in the temperature range of 2–20 K were tested using the PPMS comprehensive physical property measurement platform. The results are as follows: Figure 5 As shown. From Figure 5As can be seen, compared with conventional cold storage material Pb, ErNi has a larger specific heat capacity in the range of 2–12 K, with the largest specific heat peak at 9.65 K, which is 0.94 J / cm³. 3 Its relatively large specific heat capacity makes it a significant advantage as a cold storage material in the temperature range of 2~12 K.

[0047] The ErNi spherical particles prepared in Example 3 were filled into the secondary regenerator of a GM RDK-408D2 model refrigerator manufactured by Sumitomo Corporation of Japan, and actual installed performance tests were conducted. This model refrigerator is driven by an F-50H compressor with an input power of 6.5kW. The results were compared with those of the same model GM refrigerator without ErNi spherical particles. Figure 6 As shown, the cooling capacity of the sample with ErNi added is significantly better than that without ErNi below 14K. At 10K, the cooling capacity with ErNi is 10.43W, while that without ErNi is 6.45W. Compared with the sample without ErNi, the cooling capacity at 10K is improved by 61.7%.

[0048] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0049] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing ErNi spherical particles, comprising the following steps: Step 1, Powder Mixing: Put pure Er powder and pure Ni powder into a V-type mixer, a drum mixer, or a planetary ball mill for powder mixing until a uniformly mixed ErNi powder raw material is obtained. Step 2, Sintering: The ErNi powder obtained in Step 1 is dried, molded, and placed in a spark plasma sintering system. It is sintered under vacuum conditions with electricity, pressure and temperature. After sintering, it is cooled with the furnace and then machined to obtain ErNi rods. Step 3, Spheroidization: The ErNi rod obtained in Step 2 is used as a consumable electrode and rotated at high speed in an inert atmosphere to perform plasma rotating electrode atomization to obtain ErNi spherical particles.

2. The method for preparing ErNi spherical particles according to claim 1, wherein, In step 1, the purity of the pure Er powder is above 99.9%, and the particle size is 15~60 μm; In step 1, the purity of the pure Ni powder is above 99.9%, and the particle size is 15~60 μm; In step 1, the atomic ratio of pure Er powder to pure Ni powder is 1:

1.

3. The method for preparing ErNi spherical particles according to claim 1 or 2, wherein, In step 2, the vacuum degree is ≤10Pa; The sintering parameters in step 2 are: The axial pressure is 20~50 MPa; The heating rate is 10~50 ℃ / min; The sintering temperature is 750~1000 ℃; The heat preservation time is 5~20 minutes.

4. The method for preparing ErNi spherical particles according to claim 1 or 2, wherein, In step 2, the ErNi rod has a diameter of 30-50 mm and a length of 100-120 mm; and / or In step 2, the ErNi bar stock, after processing, has a diameter slightly smaller than the inner diameter of the mold, a surface roughness ≤ 0.8 μm, a roundness deviation ≤ 0.05 mm, and a straightness deviation ≤ 0.01 mm.

5. The method for preparing ErNi spherical particles according to claim 1 or 2, wherein, In step 3, when the vacuum degree of the vacuum treatment is ≤3×10 -3 After Pa, the pressure after introducing the protective gas is 0.1 MPa, and the protective gas is argon.

6. The method for preparing ErNi spherical particles according to claim 1 or 2, wherein, In step 3, the plasma rotating electrode atomization technology controls the ErNi electrode rod rotation speed at 4000~8000 rpm, the current intensity at 300~700 A, and the rod feed speed at 1.5~2.5 mm / s.

7. The method for preparing ErNi spherical particles according to claim 1 or 2, wherein, The ErNi spherical particles obtained in step 3 have a particle size of 150~500 μm and a D90 of less than 400 μm; and / or In the ErNi spherical particles obtained in step 3, the proportion of ErNi spherical particles with a particle size of 150~500 μm is more than 95wt%.

8. An ErNi spherical particle, obtained according to the method for preparing ErNi spherical particles according to any one of claims 1 to 7.

9. The ErNi spherical particles according to claim 8, wherein, The ErNi spherical particles are single-phase pure, with a sphericity ≥98%, and free of satellite powder and hollow powder; and / or The ErNi spherical particles have a particle size of 150~500 μm; and / or The D90 of the ErNi spherical particles is less than 400 μm; and / or The ErNi spherical particles exhibit a peak specific heat capacity of 0.94 J / cm³ in the temperature range of 2–12 K. 3 ·K.

10. A cold storage gas refrigerator that uses ErNi spherical particles as described in claim 8 or 9 as the cold storage material.

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