Preparation method of magnetic refrigeration device

Abstract

The invention discloses a preparation method of a magnetic refrigeration device, which comprises the following steps: uniformly mixing magnetic material powder with a binder to form composite particles; the composite particles are printed through a single-screw extrusion 3D printer, and a three-dimensional prefabricated body is formed; and the three-dimensional prefabricated body is degreased and sintered under atmosphere protection, and the magnetic refrigeration device is formed. Compared with a traditional mode, the preparation method is low in cost and more environmentally friendly, printing of the prefabricated body structure can be achieved only through one binder, use of chemicals can be reduced, environmental pollution can be avoided, and the material utilization rate can reach 99%; secondly, a mold is not needed, and printing can be carried out after a device structure slice is constructed through three-dimensional cartographic software; and finally, the precision is high, the printing precision is within 0.1 mm, the shrinkage rate in all directions after sintering can be controlled to be about 12%, in conclusion, the magnetic refrigeration device is prepared through the single-screw extrusion 3D printing technology, the cost is low, repeatability is good, and the manufacturing precision is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printed magnetic refrigeration devices, and in particular relates to a method for preparing a magnetic refrigeration device based on single-screw extrusion 3D printing technology. Background Art

[0002] Magnetic refrigeration has the advantages of high refrigeration cycle efficiency, easy miniaturization, no need for compressors, stability and reliability, long life, and low noise. At the same time, it does not pollute the atmosphere, and its advantages in environmental protection and energy saving are very obvious. It can avoid environmental problems such as ozone layer depletion and greenhouse effect caused by traditional refrigeration technology. In the context of energy shortages, rising global temperatures, and increasingly serious environmental impacts, it has become one of the most promising high-tech green alternative refrigeration technologies.

[0003] The magnetocaloric effect refers to the phenomenon that under the action of a magnetic field, the temperature of a magnetocaloric material changes with the change of the magnetic field strength. The elastocaloric effect is similar to the magnetocaloric effect. The driving force changes from the magnetic field to the stress field, and the temperature of the magnetocaloric material changes with the change of the stress. In order to improve the efficiency of its temperature change, magnetic refrigeration devices based on the magnetocaloric effect and the elastocaloric effect need to be molded into a geometric shape that can quickly and efficiently transfer heat and heat to the transmission fluid. Traditional manufacturing methods such as vacuum arc melting and molding cannot better produce magnetic refrigeration devices with complex shapes and structures due to their limitations.

[0004] The use of 3D printing technology can solve the above-mentioned problems very well. 3D printing technology can quickly and accurately manufacture parts of any complex shape and structure on a single device, while also reducing costs by more than 20%-40% and shortening the product development cycle. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing a magnetic refrigeration device to overcome the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0007] The present invention provides a method for preparing a magnetic refrigeration device, comprising:

[0008] The magnetic material powder and the binder are kneaded and mixed uniformly and then crushed to obtain composite particles, wherein the binder is a thermoplastic resin random copolymer polypropylene;

[0009] The composite particles are heated to a viscous flow state by a single-screw extrusion 3D printer and then extruded from a nozzle, and the nozzle and a receiving substrate of the printing material are moved relative to each other in a three-dimensional space, so that the filamentary material extruded by the nozzle is superimposed on the receiving substrate to form a three-dimensional preform;

[0010] The three-dimensional preform is subjected to degreasing treatment and sintering treatment in sequence in a protective atmosphere to obtain a magnetic refrigeration device.

[0011] Furthermore, the mass ratio of the magnetic material powder to the binder is 75% to 94%: 6% to 25%.

[0012] The present invention adjusts the ratio of the binder and the magnetic material powder to make it have sufficient rheological properties and can flow and extrude through a nozzle of a certain caliber; when the binder content is too low, the viscosity of the composite material particles is small and the preform structure cannot be formed. At the same time, the porosity between the powders is large, which affects the performance of the magnetic refrigeration device and increases the difficulty of printing. Therefore, the mass fraction of the magnetic material powder does not exceed 94%.

[0013] Furthermore, the average diameter of the magnetic material powder is 0.01 to 20 μm.

[0014] Magnetic material powder with a diameter greater than 20 μm will form larger pores after high-temperature heat treatment, affecting the accuracy of the prepared structure. Preferably, the average diameter of the magnetic material powder is 0.01 to 20 μm. The appropriate magnetic material powder size can avoid clogging the nozzle and reduce the shrinkage rate of the magnetic refrigeration device during subsequent heat treatment.

[0015] Furthermore, the melt flow rate of the thermoplastic resin random copolymer polypropylene is 8.0±2.5g / 10min. This resin does not require other plasticizers, surfactants, lubricants, etc. when mixed with magnetic material powder. A single-component binder can be used to prepare composite material particles with good fluidity and strong adhesion.

[0016] Furthermore, the preparation method of the magnetic refrigeration device specifically includes: placing the composite particles into the barrel of a single-screw extrusion 3D printer, and heating the bottom of the screw to the melting temperature of the composite particles to convert the composite particles into a viscous flow state, and rotating the screw to extrude the viscous flow material from the nozzle.

[0017] Furthermore, the heating temperature of the bottom of the screw is 190-215°C. Too low a processing temperature will result in too high a viscosity of the material, while too high a heating temperature will result in too low a viscosity of the adhesive, causing the product to bulge and crack during molding. Polypropylene does not have a definite melting temperature when it changes from a crystalline state to a viscous flow state. The melting process occurs between 160 and 170°C. As the solid content of the magnetic powder increases, in order to make it filamentary, it is necessary to increase the speed of its transformation to a viscous flow state. Therefore, the heating temperature of the bottom of the screw is set between 190 and 215°C.

[0018] Furthermore, the temperature of the receiving substrate is 90-115°C. When polypropylene is extruded on the receiving substrate, it needs to be cooled while being firmly fixed on the receiving substrate to avoid warping due to too fast cooling speed or deformation due to inconsistent shrinkage rates up and down. Therefore, a hot substrate temperature of 110°C is more appropriate.

[0019] Furthermore, the degreasing treatment includes: firstly heating the three-dimensional preform to 120-150°C at a heating rate of 0.1-5°C / min and keeping it warm for 24-72h to perform low-temperature pre-degreasing, so that 60%-80% of the binder is removed; then, in a protective atmosphere, heating the pre-degreased three-dimensional preform to 400-500°C at a heating rate of 0.1°C-5 / min and keeping it warm for 3-6h to perform high-temperature thermal degreasing, so that the binder is completely removed.

[0020] The present invention first performs pre-degreasing at 120-150°C with a heating rate of 0.1-5°C / min and a holding time of 24-72h to remove part of the binder so that in the subsequent thermal degreasing process, the internal binder can be decomposed and released through the pores left by the decomposition of the surface binder. Too fast a heating rate or too high a pre-degreasing temperature will cause defects in the three-dimensional preform structure, such as expansion and cracking.

[0021] In order to completely remove the binder contained in the three-dimensional preform, the temperature needs to be further increased. Under the protection of argon, the temperature is increased to 400-500°C at a heating rate of 0.1°C-5 / min and kept warm for 3-6 hours to completely remove the binder inside while avoiding collapse or expansion.

[0022] Furthermore, the sintering process comprises: heating the degreased three-dimensional preform to 900-1000° C. at a heating rate of 0.1-5° C. / min and keeping the temperature in an inert atmosphere for 2-4 hours.

[0023] The total shrinkage rate of the magnetic refrigeration device prepared by the present invention is related to the content of the binder and the pre-degreasing rate. The higher the binder content and the pre-degreasing rate, the higher the overall shrinkage rate. At the same time, the density of the prepared magnetic refrigeration device can reach up to 95% of the relative density.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The preparation method of the magnetic refrigeration device based on the single-screw extrusion 3D printing technology provided by the present invention can realize the preparation of the device through four steps of mixing, printing, degreasing and sintering. Compared with the traditional method, it has many advantages. First, the cost is low. Only one binder is needed to realize the printing of the preform structure, and the material utilization rate can reach 99%; second, no mold is required, and the device structure slice can be constructed through three-dimensional mapping software before printing; finally, the precision is high, the printing precision is within 0.1mm, and the shrinkage rate in all directions after sintering can be controlled at about 12%; in summary, the single-screw extrusion 3D printing technology is used to prepare the magnetic refrigeration device, which has low cost, good repeatability and high production precision, which is helpful to reduce enterprise costs and realize the miniaturized production of magnetic refrigeration devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1-Figure 4 It is a schematic diagram of the process of a method for preparing a magnetic refrigeration device in one embodiment of the present application.

[0028] Figure 5 This is a physical picture of a three-dimensional preform of a screw extrusion 3D printed magnetic refrigeration device in one embodiment of the present application.

[0029] Figure 6 This is a physical picture of a magnetic refrigeration device that is 3D printed by screw extrusion in one embodiment of the present application.

[0030] Explanation of the reference numerals: 1. polypropylene, 2. magnetic material powder, 3. internal mixer, 4. composite particles, 5. barrel, 6. hot substrate, 7. nozzle, 8. filament, 9. three-dimensional preform, 10. degreasing equipment, 11. air inlet, 12. air outlet. DETAILED DESCRIPTION

[0031] In order to overcome the shortcomings of the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The present invention provides a method for preparing a magnetic refrigeration device based on single-screw extrusion 3D printing technology, which relies on heating the bottom of the screw to transform the single-component binder composite particles into a viscous flow state, and relies on the screw to rotate and extrude the material from the nozzle to form a prefabricated three-dimensional structure of the magnetic refrigeration device, and then undergoes degreasing and sintering processes to form the expected magnetic refrigeration device, so that the magnetic refrigeration device prepared in this way can simultaneously meet the complex heat exchange structure while improving the heat absorption and release rate, and can also greatly reduce costs and reduce the use of chemicals. It is a new type of sustainable solution. The technical solution, its implementation process and principles will be further explained as follows.

[0032] One aspect of an embodiment of the present invention provides a method for preparing a magnetic refrigeration device, comprising:

[0033] The magnetic material powder and the binder are kneaded and mixed evenly and then crushed to obtain composite particles, wherein the binder is a thermoplastic resin random copolymer polypropylene; the composite particles are heated to a viscous flow state by a single-screw extrusion 3D printer and then extruded from a nozzle, and the nozzle is made

[0034] The head and the receiving substrate of the printing material move relative to each other in three-dimensional space, so that the filamentary material extruded by the nozzle is superimposed on the receiving substrate to form a three-dimensional preform;

[0035] The three-dimensional preform is subjected to degreasing treatment and sintering treatment in sequence in a protective atmosphere to obtain a magnetic refrigeration device.

[0036] In some preferred embodiments, the mass ratio of the magnetic material powder to the binder is 75% to 94%: 6% to 25%.

[0037] The embodiment of the present invention adjusts the ratio of the binder and the magnetic material powder so that it has sufficient rheological properties and can flow and extrude through a nozzle of a certain caliber. When the binder content is too low, the viscosity of the composite material particles is too low to form a preform structure. At the same time, the porosity between the powders is too large, which affects the performance of the magnetic refrigeration device and increases the difficulty of printing. Therefore, the mass fraction of the magnetic material powder does not exceed 94%.

[0038] In some more preferred embodiments, the magnetic material powder is in the shape of spherical particles or ellipsoidal particles with an aspect ratio of less than 5, and the average diameter of the magnetic material powder is 0.01-20 μm.

[0039] Magnetic material powder with a diameter greater than 20 μm will form larger pores after high-temperature heat treatment, affecting the accuracy of the prepared structure. Preferably, the average diameter of the magnetic material powder is 0.01-20 μm. The appropriate magnetic material powder size can avoid clogging the nozzle and reduce the shrinkage rate of the magnetic refrigeration device during subsequent heat treatment.

[0040] In some more preferred embodiments, the melt flow rate of the thermoplastic resin random copolymer polypropylene is 8.0±2.5g / 10min. When this resin is mixed with magnetic material powder, no other plasticizers, surfactants and lubricants are required. A single-component binder can be used to prepare composite material particles with good fluidity and strong adhesion. The reused composite material particles are stable in nature and are not affected by the ratio between different components of the binder, and the material utilization rate can be increased to 99%. At the same time, its decomposition products contain harmful substances such as sulfides and nitrides, which are more environmentally friendly.

[0041] In some more preferred embodiments, the diameter of the composite particles is 0.01-150 μm.

[0042] In some preferred embodiments, the kneading temperature is 190° C. to 215° C. and the kneading time is 0.5 h to 1 h.

[0043] In some preferred embodiments, the method for preparing the magnetic refrigeration device specifically includes: placing the composite particles into the barrel of a single-screw extrusion 3D printer, and heating the bottom of the screw to the melting temperature of the composite particles to convert the composite particles into a viscous flow state, and rotating the screw to extrude the viscous flow material from the nozzle.

[0044] In some more preferred embodiments, the heating temperature of the bottom of the screw is 190-215°C. Too low a processing temperature will result in too high a viscosity of the material, while too high a heating temperature will result in too low a viscosity of the adhesive, causing the product to bulge and crack during molding. Polypropylene does not have a definite melting temperature when it changes from a crystalline state to a viscous flow state. The melting process occurs between 160 and 170°C. As the solid content of the magnetic powder increases, in order to make it filamentary, it is necessary to increase the speed of its transformation to a viscous flow state. Therefore, the heating temperature of the bottom of the screw is set between 190 and 215°C.

[0045] In some more preferred embodiments, the temperature of the receiving substrate is 90-115°C. When polypropylene is extruded on the receiving substrate, it needs to be cooled while being firmly fixed on the receiving substrate to avoid warping due to too fast cooling speed or deformation due to inconsistent shrinkage rates up and down. Therefore, a receiving substrate temperature of 110°C is more appropriate.

[0046] In some more preferred embodiments, the receiving substrate may be a thermal substrate, but is not limited thereto.

[0047] In some preferred embodiments, the degreasing treatment includes: firstly heating the three-dimensional preform to 120-150°C at a heating rate of 0.1-5°C / min and keeping it warm for 24-72h to perform low-temperature pre-degreasing, so that 60%-80% of the binder is removed; then, in a protective atmosphere, heating the pre-degreased three-dimensional preform to 400-500°C at a heating rate of 0.1°C-5 / min and keeping it warm for 3-6h to perform high-temperature thermal degreasing, so that the binder is completely removed.

[0048] If the low-temperature pre-degreasing time is too short and the binder is removed by less than 60%, it will cause deformation, blistering, cracking of the molded parts, and melting during the subsequent sintering process, affecting the precision of the molded parts; if the time is too long and the binder is removed by more than 80%, it will cause incomplete shrinkage of the molded parts, affecting the precision and strength of the molded parts.

[0049] The embodiment of the present invention first performs pre-debinding at 120-150°C with a heating rate of 0.1-5°C / min and a holding time of 24-72h to remove part of the binder so that in the subsequent thermal debinding process, the internal binder can be decomposed and released through the pores left by the decomposition of the surface binder. Too fast a heating rate or too high a pre-debinding temperature will cause defects in the three-dimensional preform structure, such as expansion and cracking.

[0050] In some preferred embodiments, the sintering process may include normal pressure sintering or hot isostatic pressing sintering.

[0051] In some more preferred embodiments, the sintering process comprises: heating the degreased three-dimensional preform to 900-1000° C. at a heating rate of 0.1-5° C. / min and keeping the temperature in an inert atmosphere for 2-4 hours.

[0052] In order to completely remove the binder contained in the three-dimensional preform, the temperature needs to be further increased. Under the protection of argon, the temperature is increased to 500°C at a heating rate of 1°C / min and kept warm for 3 hours to completely remove the binder inside while avoiding collapse or expansion.

[0053] In some preferred embodiments, the sintering method may include atmospheric pressure sintering or hot isostatic pressing sintering, but is not limited thereto.

[0054] In some preferred embodiments, the preparation method of the magnetic refrigeration device includes: heating the degreased three-dimensional preform to 900-1000°C at a heating rate of 0.1-5°C / min, keeping it warm for 2-4 hours under the protection of a rare gas atmosphere, and performing a sintering process to combine the magnetic material powders with each other to form a magnetic refrigeration device.

[0055] The total shrinkage rate of the magnetic refrigeration device prepared in the embodiment of the present invention is related to the binder content and the pre-degreasing rate. The higher the binder content and the pre-degreasing rate, the higher the overall shrinkage rate. At the same time, the density of the prepared magnetic refrigeration device can reach up to 95% of the relative density.

[0056] To further illustrate the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0057] Example 1

[0058] See also Figure 1-Figure 4 The present embodiment provides a method for preparing a magnetic refrigeration device, comprising the following steps:

[0059] (1) Preparation of composite particles

[0060] 25wt% polypropylene (F800E) and 75wt% magnetic material powder (Ni 45 Mn 44 Sn 11 ) is poured into an internal mixer 3 for mixing, the internal mixing temperature is 190°C, the internal mixing time is 30 minutes, and then the mixed material after internal mixing is crushed in a grinder for 1 minute, sieved with a 100-mesh screen, and then dried in an oven at 50°C for 12 hours to form composite particles 4 with a diameter of 0.01-150μm.

[0061] (2) Printing a 3D preform using a single-screw extrusion 3D printer

[0062] Draw the required three-dimensional structure and slice it. Load the composite particles 4 prepared in step (1) into the barrel 5 of a single-screw extruder 3D printer. Heat the bottom of the screw to 195°C to transform the composite particles into a viscous flow state. Rotate the screw to extrude the composite particles from the nozzle 7 to form filaments 8. Move the nozzle 7 at the same time to stack the filaments 8 on a hot substrate 6 preheated to 110°C to form a three-dimensional preform 9 of a magnetic refrigeration device. Figure 5 As shown, the prepared three-dimensional preform has high precision and the microchannel diameter can reach 140 to 180 pm.

[0063] (3) Degreasing treatment

[0064] The three-dimensional preform 9 obtained in step (2) is placed in a degreasing device 10, and the three-dimensional preform 9 is first pre-degreased at 140°C at a heating rate of 1°C / min for 48 hours. Then, under the protection of an argon atmosphere, the temperature is increased to 500°C at a heating rate of 1°C / min and kept for 3 hours to completely degrease the preform.

[0065] (4) Figure 4As shown, the three-dimensional preform 9 is sintered in a tubular sintering furnace. The sintering needs to be carried out under the protection of a flowing atmosphere (argon gas). The gas enters from the air inlet 11 and flows out from the air outlet 12. The three-dimensional preform 9 after degreasing in step (3) is directly heated to 900°C at a heating rate of 5°C / min and kept at this temperature for 2h for sintering to obtain a magnetic refrigeration device with uniform shrinkage (16%) in all directions and compactness, such as Figure 6 shown.

[0066] Example 2

[0067] The preparation method of a magnetic refrigeration device provided in this embodiment is basically the same as that in embodiment 1, except that the raw materials used are 20wt% polypropylene (F800E) and 80wt% magnetic material powder (Ni 45 Mn 44 Sn 11 ).

[0068] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment in all directions is 14%.

[0069] Example 3

[0070] The preparation method of a magnetic refrigeration device provided in this embodiment is basically the same as that in embodiment 1, except that the raw materials used are 15wt% polypropylene (F800E) and 85wt% magnetic material powder (Ni 45 Mn 44 Sn 11 ).

[0071] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment is 12% in all directions.

[0072] Example 4

[0073] This embodiment provides a method for preparing a magnetic refrigeration device which is basically the same as that in Embodiment 1, except that the raw materials used are 10 wt% polypropylene (F800E) and 90 wt% magnetic material powder (Ni 45 Mn 44 Sn 11 ).

[0074] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment is 10% in all directions.

[0075] Example 5

[0076] This embodiment provides a method for preparing a magnetic refrigeration device, which is the same as the preparation process of Example 1, except that the raw materials used are 6wt% polypropylene (F800E) and 94wt% magnetic material powder 2 with a diameter of 0.1 to 20μm.

[0077] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment in all directions is 9%.

[0078] Example 6

[0079] This embodiment provides a method for preparing a magnetic refrigeration device which is basically the same as that in Embodiment 1, except that the low-temperature pre-degreasing temperature is 140° C. and the pre-degreasing time is 72 h.

[0080] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment in all directions is 16%.

[0081] Example 7

[0082] This embodiment provides a method for preparing a magnetic refrigeration device which is basically the same as that in Embodiment 1, except that the low-temperature pre-degreasing temperature is 140° C. and the pre-degreasing time is 48 h.

[0083] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment is 13% in all directions.

[0084] Example 8

[0085] This embodiment provides a method for preparing a magnetic refrigeration device which is basically the same as that in Embodiment 1, except that the low-temperature pre-degreasing temperature is 140° C. and the pre-degreasing time is 24 h.

[0086] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment in all directions is 9%.

[0087] Example 9

[0088] This embodiment provides a method for preparing a magnetic refrigeration device which is basically the same as that in Embodiment 1, except that the low-temperature pre-degreasing temperature is 150° C. and the pre-degreasing time is 72 h.

[0089] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment in all directions is 17%.

[0090] Example 10

[0091] This embodiment provides a method for preparing a magnetic refrigeration device which is basically the same as that in Embodiment 1, except that the low-temperature pre-degreasing temperature is 120° C. and the pre-degreasing time is 72 h.

[0092] After degreasing and sintering, the shrinkage rate of the obtained magnetic refrigeration device in this embodiment in all directions is 11%.

[0093] Embodiment 11

[0094] See also Figure 1-Figure 4 The present embodiment provides a method for preparing a magnetic refrigeration device, comprising the following steps:

[0095] (1) Preparation of composite particles

[0096] 25wt% polypropylene (F800E) and 75wt% magnetic material powder (Ni 45 Mn 44 Sn 11 ) is poured into an internal mixer 3 for mixing. The internal mixing temperature is 215°C and the internal mixing time is 1 hour. The internally mixed material is then crushed in a grinder for 1 minute and sieved with a 100-mesh screen. It is then dried in an oven at 50°C for 12 hours to form composite particles 4 with a diameter of 0.01-150 μm.

[0097] (2) Printing a 3D preform using a single-screw extrusion 3D printer

[0098] Draw the required three-dimensional structure and slice it, load the composite particles 4 prepared in step (1) into the barrel 5 of a single-screw extruder 3D printer, heat the bottom of the screw to 190°C to transform the composite particles into a viscous flow state, and extrude them from the nozzle 7 to form filaments 8 by rotating the screw. At the same time, move the nozzle 7 so that the filaments 8 are stacked layer by layer on a hot substrate 6 that has been preheated to 90°C to form a three-dimensional preform 9 of the magnetic refrigeration device.

[0099] (3) Degreasing treatment

[0100] The three-dimensional preform 9 obtained in step (2) is placed in a degreasing device 10, and the three-dimensional preform 9 is first pre-degreased at 120°C at a heating rate of 0.1°C / min for 24 hours. Then, under the protection of an argon atmosphere, the temperature is increased to 400°C at a heating rate of 0.1°C / min and kept for 4 hours to completely degrease the preform.

[0101] (4) Figure 4 As shown, the three-dimensional preform 9 is sintered in a tubular sintering furnace. The sintering needs to be carried out under the protection of a flowing atmosphere (argon), and the gas enters from the air inlet 11 and flows out from the air outlet 12; the three-dimensional preform 9 after degreasing in step (3) is directly heated to 950°C at a heating rate of 0.1°C / min and kept warm for 3 hours for sintering to obtain a magnetic refrigeration device with uniform shrinkage (18%) in all directions and compactness.

[0102] Example 12

[0103] See also Figure 1-Figure 4 The present embodiment provides a method for preparing a magnetic refrigeration device, comprising the following steps:

[0104] (1) Preparation of composite particles

[0105] 25wt% polypropylene (F800E) and 75wt% magnetic material powder (Ni 45 Mn 44 Sn 11 ) is poured into an internal mixer 3 for mixing, the internal mixing temperature is 200°C, the internal mixing time is 45 minutes, and then the mixed material after internal mixing is crushed in a grinder for 1 minute, sieved with a 100-mesh screen, and then dried in an oven at 50°C for 12 hours to form composite particles 4 with a diameter of 0.01-150μm.

[0106] (2) Printing a 3D preform using a single-screw extrusion 3D printer

[0107] Draw the required three-dimensional structure and slice it, load the composite particles 4 prepared in step (1) into the barrel 5 of a single-screw extruder 3D printer, heat the bottom of the screw to 215°C to transform the composite particles into a viscous flow state, and extrude them from the nozzle 7 to form filaments 8 by rotating the screw. At the same time, move the nozzle 7 so that the filaments 8 are stacked layer by layer on a hot substrate 6 preheated to 100°C to form a three-dimensional preform 9 of the magnetic refrigeration device.

[0108] (3) Degreasing treatment

[0109] The three-dimensional preform 9 obtained in step (2) is placed in a degreasing device 10, and the three-dimensional preform 9 is first pre-degreased at 150°C at a heating rate of 5°C / min for 72 hours. Then, under the protection of an argon atmosphere, the temperature is increased to 450°C at a heating rate of 5°C / min and kept for 6 hours to completely degrease the preform.

[0110] (4) Figure 4 As shown, the three-dimensional preform 9 is sintered in a tubular sintering furnace. The sintering needs to be carried out under the protection of a flowing atmosphere (argon), and the gas enters from the air inlet 11 and flows out from the air outlet 12; the three-dimensional preform 9 after degreasing in step (3) is directly heated to 1000°C at a heating rate of 1°C / min and kept at this temperature for 4 hours for sintering, thereby obtaining a magnetic refrigeration device with uniform shrinkage (21%) in all directions and compactness.

[0111] Comparative Example 1

[0112] This comparative example provides a method for preparing a magnetic refrigeration device which is basically the same as that in Example 1, except that the low-temperature pre-degreasing is performed at a temperature between 120° C. and 150° C. for 12 hours.

[0113] After high-temperature thermal degreasing and sintering, the magnetic refrigeration device obtained in this comparative example was cracked and contracted unevenly in all directions, which affected the precision and structure of the molded part.

[0114] Comparative Example 2

[0115] This comparative example provides a method for preparing a magnetic refrigeration device which is basically the same as that of Example 1, except that: multi-stage degreasing is not used, and high-temperature thermal degreasing is directly performed.

[0116] After high-temperature thermal degreasing and sintering, the magnetic refrigeration device obtained in this comparative example melts and produces defects such as severe deformation. The original shape of the magnetic refrigeration device cannot be maintained, and a magnetic refrigeration device with a high-precision and complex structure cannot be formed.

[0117] Comparative Example 3

[0118] This comparative example provides a method for preparing a magnetic refrigeration device which is basically the same as that in Example 1, except that: the composite particles are heated to a molten state.

[0119] In this comparative example, after the composite particles are heated to a molten state, the fluidity of the thermoplastic resin and the magnetic material powder is affected, resulting in nozzle clogging, thereby affecting the printing accuracy and the preparation of the three-dimensional preform.

[0120] Comparative Example 4

[0121] This comparative example provides a preparation method of a magnetic refrigeration device which is basically the same as that of Example 1, except that a multi-component adhesive (POM (M90) + PP (F800E)) with a mass ratio of 4:3 is used instead of random copolymer polypropylene with a melt flow rate of 8.0±2.5 g / 10 min.

[0122] In this comparative example, after the composite particles are heated to a molten state, the obtained preform has poor precision, large surface roughness, and many cracks; at the same time, after the POM is decomposed, toxic and harmful gases such as formaldehyde are generated, which is not conducive to environmental protection.

[0123] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0124] Although the present invention has been described with reference to illustrative embodiments, it will be appreciated by those skilled in the art that various other changes, omissions and / or additions may be made without departing from the spirit and scope of the present invention and that the elements of the embodiments may be replaced by substantial equivalents. In addition, many modifications may be made without departing from the scope of the present invention to adapt specific circumstances or materials to the teachings of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for performing the present invention, but it is intended that the present invention will include all embodiments within the scope of the appended claims. In addition, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another.

Claims

1. A method for preparing a magnetic refrigeration device, characterized in that include: The magnetic material powder and the binder are kneaded and mixed uniformly and then crushed to obtain composite particles, wherein the binder is a thermoplastic resin random copolymer polypropylene; The composite particles are heated to a viscous flow state by a single-screw extrusion 3D printer and then extruded from a nozzle, and the nozzle and a receiving substrate of the printing material are moved relative to each other in a three-dimensional space, so that the filamentary material extruded by the nozzle is superimposed on the receiving substrate to form a three-dimensional preform; The three-dimensional preform is subjected to degreasing treatment and sintering treatment in sequence in a protective atmosphere to obtain a magnetic refrigeration device.

2. The method for preparing a magnetic refrigeration device according to claim 1, characterized in that: The average diameter of the magnetic material powder is 0.01-20 μm; and / or the flow rate of the thermoplastic resin random copolymer polypropylene is 8.0±2.5 g / 10 min; and / or the diameter of the composite particles is 0.01-150 μm.

3. The method for preparing a magnetic refrigeration device according to claim 1 or 2, characterized in that: The mass ratio of the magnetic material powder to the binder is 75% to 94%: 6% to 25%.

4. The method for preparing a magnetic refrigeration device according to claim 1 or 2, characterized in that: The temperature of the banburying is 190° C. to 215° C., and the time is 0.5 h to 1 h.

5. The method for preparing a magnetic refrigeration device according to claim 1, characterized in that: Specifically include: The composite particles are placed in the barrel of a single-screw extrusion 3D printer, and the bottom of the screw is heated to the melting temperature of the composite particles to convert the composite particles into a viscous flow state, and the screw is rotated to extrude the viscous flow material from the nozzle.

6. The method for preparing a magnetic refrigeration device according to claim 5, characterized in that: The temperature of the screw bottom heating is 190-215°C.

7. The method for preparing a magnetic refrigeration device according to claim 1 or 5, characterized in that: The temperature of the receiving substrate is 90-110°C.

8. The method for preparing a magnetic refrigeration device according to claim 1, characterized in that: The degreasing treatment includes: firstly heating the three-dimensional preform to 120-150°C at a heating rate of 0.1-5°C / min and keeping it warm for 24-72h to perform low-temperature pre-degreasing, so that 60%-80% of the binder is removed; then, in a protective atmosphere, heating the pre-degreased three-dimensional preform to 400-500°C at a heating rate of 0.1°C-5 / min and keeping it warm for 3-6h to perform high-temperature thermal degreasing, so that the binder is completely removed.

9. The method for preparing a magnetic refrigeration device according to claim 1, characterized in that: The sintering treatment method includes normal pressure sintering or hot isostatic pressing sintering.

10. The method for preparing a magnetic refrigeration device according to claim 1 or 9, characterized in that: The sintering process comprises: heating the degreased three-dimensional preform to 900-1000° C. at a heating rate of 0.1-5° C. / min and keeping the temperature in an inert atmosphere for 2-4 hours.

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