CN115028962A - Preparation method of NiMnGa particle/polymer composite material with magnetic anisotropy - Google Patents
Preparation method of NiMnGa particle/polymer composite material with magnetic anisotropy Download PDFInfo
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
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- C08K3/10—Metal compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/01—Magnetic additives
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Abstract
The invention discloses a preparation method of a NiMnGa particle/polymer composite material with magnetic anisotropy, belonging to the technical field of magnetic refrigeration. The invention aims to solve the technical problems of particle deposition in the preparation process, difficult orientation of particles after a magnetic field is applied and the like. The invention is characterized in that a nickel-manganese-gallium alloy cast ingot is smelted in a multi-induction smelting mode, then cutting, polishing, ultrasonic cleaning, drying, crushing, grinding and screening are carried out to obtain single crystal micro particles, and then the micro particles are directionally embedded in a polymer under a magnetic field to prepare the nickel-manganese-gallium/polymer composite material with magnetic anisotropy. The composite material prepared by the invention has high particle orientation degree, good magnetic anisotropy and good mechanical stability, and is applied to rotary magnetic refrigeration.
Description
Technical Field
The invention belongs to the technical field of magnetic refrigeration, and particularly relates to a preparation method of a NiMnGa particle/polymer composite material with magnetic anisotropy.
Background
Magnetic refrigeration is an energy-saving and environment-friendly refrigeration technology, and compared with traditional gas compression refrigeration, the magnetic refrigeration system has the characteristics of high efficiency, energy conservation, environmental friendliness, high magnetic entropy density, low vibration and noise, long service life, wide application temperature range and the like. In the field of low temperature, magnetic refrigeration technology has been widely used, for example, in the fields of liquid hydrogen preparation, space astronomical exploration, low-temperature biomedicine, low-temperature physics, magnetic resonance imaging and the like, but in the field of room temperature, the magnetic refrigeration technology is still in the research stage due to the limitation of materials, magnetic fields, equipment and the like, but the technology still has wide development prospects, for example, room-temperature magnetic refrigeration materials can be applied to equipment such as automatic vending cold drink machines, refrigerators, air conditioners, alternators and the like, so that the equipment is developed to be light, cheap and efficient, and the application of the magnetic refrigeration technology in the field of room temperature still has high research value and application value.
Although the magnetic refrigeration technology has significant advantages, the current magnetic refrigerator involves applying and removing a magnetic field, or repeatedly taking out a magnetic material from the refrigerator, and the like, which inevitably causes the problems of complex structure, large volume, large energy consumption, low refrigeration efficiency, incapability of realizing high-frequency refrigeration, and the like. The ferromagnetic phase of the Ni-Mn-Ga ferromagnetic memory alloy is a martensite phase (c < a ≈ b) with low symmetry, and strong magnetocrystalline anisotropy (different magnetization properties in different crystal directions) exists, so that the magnetic entropy generated in the easy magnetization direction (c axis) and the difficult magnetization direction (a/b axis) is different, namely, under a constant magnetic field, a large magnetic entropy change can be generated only by rotating the alloy, thereby achieving the aim of refrigeration. However, bulk polycrystalline alloys have large hysteresis and strong tendency to fracture along the crystal, and single crystal alloys have good properties but are difficult and costly to prepare, limiting applications.
Disclosure of Invention
The invention provides a preparation method of a Ni-Mn-Ga particle/polymer composite material with magnetic anisotropy, aiming at the problems of poor mechanical stability, difficult single crystal preparation and the like of a nickel-manganese-gallium alloy in the magnetic refrigeration process.
The invention aims to prepare the nickel-manganese-gallium/polymer composite material with magnetic anisotropy energy by preparing the nickel-manganese-gallium alloy into single crystal micro-particles and directionally embedding the micro-particles in a polymer under a magnetic field, thereby providing a solution for the problems of the alloy in the aspect of room-temperature rotating magnetic refrigeration.
The method mainly solves the technical problems of particle deposition in the preparation process of the composite material, difficult orientation of particles after a magnetic field is applied, and the like, achieves the aim of preparing the particle/polymer composite material with good mechanical stability and excellent magnetic anisotropy, and lays a foundation for solving a series of problems of the nickel-manganese-gallium alloy in the application of rotating magnetic refrigeration.
In order to solve the above technical problems, the method for preparing the NiMnGa particle/polymer composite material having magnetic anisotropy of the present invention is realized by the following steps:
step one, weighing metal raw materials according to design components, wherein the Mn element is excessive by 1.5-2.0 wt%;
secondly, smelting a metal ingot in a multi-induction smelting mode, and carrying out heat preservation treatment for at least 24 hours after smelting is finished;
cutting and polishing the cast ingot, ultrasonically cleaning, drying, crushing, grinding and screening to obtain alloy particles with the particle size of 60-80 microns;
step four, carrying out vacuum heat treatment on the alloy particles obtained in the step three in an inert atmosphere;
step five, filling the alloy particles into a soft mold with the inner surface coated with a release agent, heating the epoxy resin to 100 ℃ while stirring, adding a curing agent, immediately pouring the uniformly stirred mixture into the soft mold, when the temperature is reduced to 50 ℃, the soft mould is placed between two poles of the magnetic field generator, the magnetic field generator is electrified by using a voltage-stabilizing direct current power supply, the air gap of the longitudinal magnetic field is controlled to be 15-20 mm, the output current of the regulated power supply is regulated to make the magnetic field between two poles of the magnetic field generator reach above 1T, after the magnetic field is applied, the alloy particles are gradually changed from disordered arrangement to chain arrangement under the action of magnetic force, the easy magnetization axes of the alloy particles are turned to the direction of a magnetic field, and curing the polymer at room temperature in the state, keeping for at least 45h, taking out from the magnetic field, demolding, and keeping the temperature for at least 2h to obtain the composite material.
Further, the design composition was 25.44 at.% Ni, 4.86 at.% Mn, and 38.83 at.% Ga.
And further smelting for at least 4 times in the second step.
And further, the temperature of the second step is kept at 1000 ℃ for 24 h.
And further, ultrasonically cleaning the substrate for 5-10 min by using acetone in the third step.
And further, drying at 393K for 10 min.
Further, crushing in the third step until the grain size of the alloy is below 1 mm.
Further, the vacuum degree in the vacuum heat treatment process in the step four is 0.3 multiplied by 10 -3 Pa～0.5×10 -3 Pa, heating to 725 ℃, preserving heat for 2h, then cooling to 700 ℃ and preserving heat for 10h, then cooling to 500 ℃ and preserving heat for 20h, and finally cooling along with the furnace, wherein the cooling rate is 7-10 ℃/min.
Further, in the fifth step, the curing agent is polyamine ether.
Further, in the fifth step, the mass ratio of the curing agent to the epoxy resin is 1: 3.
Further, the addition amount of the alloy particles in the fifth step is not more than 30 wt.%.
And further, the temperature of the step five is kept at 100 ℃ for 2-3 h.
Compared with the prior art, the invention has the following beneficial effects:
the alloy particles in the composite material prepared by the invention are single crystal particles.
The alloy particles in the composite material prepared by the invention are subjected to macroscopic directional arrangement under the action of an external magnetic field to form particle beams like alloy fibers, each particle beam is composed of a plurality of micron alloy particles, a certain distance is maintained between the particle beams, and for two adjacent particle beams, the particle beams are almost not distributed, so that the composite material has good mechanical stability.
The composite material prepared by the invention has high particle orientation degree and good magnetic anisotropy.
Drawings
FIG. 1 is a microstructure of an alloy particle, a) an SEM image; b) metallographic polarized light images;
FIG. 2 is a) cross-section of a magnetic field cured composite; b) longitudinally slicing; c) amplifying the image by 50 times of the longitudinal section; d) amplifying the image by 100 times on the longitudinal section;
FIG. 3 is a graph of magnetization curves in different directions for a composite material having an alloy mass fraction of 10 wt.%, a) no magnetic field solidification, wherein the G direction is the direction of gravity during solidification; b) there is a magnetic field to solidify.
Detailed Description
The invention will be better understood by reference to the following examples. The invention is not limited to what has been described in the detailed description.
Example 1: the following is a specific method for preparing a NiMnGa particle/polymer composite material having magnetic anisotropy.
1. And (5) preparing an alloy ingot. In order to obtain a nickel manganese gallium alloy with a transformation temperature around room temperature, according to an empirical formula, the transformation temperature of the nickel manganese gallium alloy can be roughly expressed as:
M s (K)＝25.44Mi(at.％)-4.86Mn(at.％)-38.83Ga(at.％) (1)
the content of each element in the nickel-manganese-gallium alloy is calculated according to the formula (1), and 1.5 wt.% of Mn element is additionally added on the basis of design components in consideration of volatilization of Mn element in ingot smelting and heat treatment processes. Weighing the metal raw materials according to design components, smelting a metal ingot in an induction smelting mode, and remelting the ingot for 3-5 times to ensure that the components are uniform. And then, placing the cast ingot in a vacuum furnace, and preserving heat for 24 hours at the temperature of 1000 ℃ to further realize component homogenization and alloy grain growth.
2. And (4) preparing alloy particles. The alloy particles are prepared by using an ingot casting grinding method in the following specific preparation mode. The large cylindrical alloy is subjected to linear cutting, the cutting direction is perpendicular to the axial direction of the cylindrical alloy, and the thickness of a cutting sample is 20-25 mm and is used for grinding particles. And (3) polishing the surface of the alloy by using No. 240 abrasive paper to remove oxide scales generated in the heat treatment process, and polishing the two ends of the cut gold wire by using No. 240 abrasive paper to eliminate the trace of the wire cutting. Then, the alloy is immersed in an acetone solution, placed in an ultrasonic cleaning machine for ultrasonic cleaning for 5-10 minutes, taken out, placed on dry filter paper, placed in a drying box and dried for 10 minutes at 393K. And crushing the dried alloy by using a universal testing machine until the particle size of the alloy is 1mm, and then putting the alloy into an agate mortar for grinding. And finally, screening the ground particles by using a standard sample sieve, and finally screening alloy particles with the particle size of 60-80 mu m.
3. And (4) carrying out heat treatment on the alloy particles. The purpose of the heat treatment is to promote the degree of ordering of the alloy and to remove residual stresses during mechanical grinding. A quartz tube with one end sealed and the other end open, the diameter of the quartz tube being 6-9 mm and the length of the quartz tube being 150-200 mm is used as a container for heat treatment alloy particles, 40-50 mg of Mn particles are added into the container to make up for volatilization of Mn at high temperature caused by too high particle comparison area in the heat treatment process, and 0.5-1 g of Ti wires are added to absorb more oxygen in the heat treatment process. The specific operation is as follows: firstly, placing the alloy particles screened in the step 2) at the sealing end of a quartz tube, wherein the filling height of the alloy particles is lower than 1/2 of the length of the quartz tube; then weighing Mn particles and Ti wires, and placing the Mn particles and the Ti wires in the middle of a quartz tube to ensure that the Mn particles and the Ti wires cannot contact with alloy particles; the tube was then evacuated to 0.5X 10 -3 Introducing high-purity argon after Pa, and vacuumizing to 0.5 multiplied by 10 -3 Introducing high-purity argon after Pa, repeating the process for 3-4 times, and finally vacuumizing to 0.5 multiplied by 10 -3 Pa, the quartz tube was sealed with an oxyacetylene flame at a tube length from the open end 1/4 of the quartz tube. And (3) heat treatment process: firstly, heating a heating furnace to 725 ℃, putting the sealed quartz tube into the furnace after the temperature is reached, preserving the heat for 2 hours, then cooling the furnace to 700 ℃ and preserving the heat for 10 hours, then cooling the furnace to 500 ℃ and preserving the heat for 20 hours, and finally cooling along with the furnace. The cooling rate is kept to be 7-10 ℃/min in the process of cooling from 725 ℃ to 700 ℃ and from 700 ℃ to 500 ℃.
4. And (4) directional solidification of the composite material. Firstly, curing mold pretreatment: uniformly spraying a furin release agent on the inner surface of a soft rubber mold with the diameter of 30mm and the height of 20mm, baking the mold at 100 ℃, and then spraying a layer of furin release agent on the inner surface of the mold. Weighing the particles: weighing the alloy particles subjected to heat treatment in the step 3), calculating the weighing mass according to the designed mass percentage, and putting the weighed particles into a pretreated die for standby application in order to ensure the particle dispersibility and the mass percentage is not more than 30 wt.%. Preparation of matrix polymer: using epoxy resin as a matrix, heating the epoxy resin to 100 ℃ and continuously stirring the epoxy resin by using a glass rod until bubbles in the resin are basically disappeared, and then stopping heating. Immediately adding a polyamine ether curing agent into the resin after heating is stopped, wherein the mass ratio of the polyamine ether curing agent to the epoxy resin is 1:3, and rapidly stirring the mixture for 1-2 min by using a glass rod until the polymer is uniform and has no floating substances. The stirred mixture was then immediately poured into a flexible mold containing alloy particles. The mass of the poured mixture was determined as a percentage of the designed mass. Magnetic field directional solidification: mechanically stirring by a glass rod until the particles are uniformly dispersed in the polymer matrix, monitoring the temperature of the mixture of the liquid epoxy resin, the polyamine ether curing agent and the particles in real time by using a temperature sensor, and placing the flexible mold between two poles of a magnetic field generator when the temperature is reduced to 50 ℃. And electrifying the magnetic field generator by using a voltage-stabilizing direct current power supply, controlling the air gap of the longitudinal magnetic field to be 15-20 mm, and adjusting the output current of the voltage-stabilizing power supply to enable the magnetic field between two electrodes of the magnetic field generator to reach more than 1T. After the magnetic field is applied, the alloy particles are gradually changed into chain-shaped arrangement from disordered arrangement under the action of magnetic force, the easy-magnetization axes of the particles are turned to the direction of the magnetic field, the polymer is cured at room temperature in the state, the curing is kept for 45-48 hours, and the primary curing is completed. And then taking the composite material out of the magnetic field for demolding, preserving the temperature of the demolded composite material at 100 ℃ for 2-3 h, further enhancing the crosslinking of the polymer matrix, and realizing final curing.
The effect of the invention is illustrated by taking the example of the composite material prepared by curing with an external magnetic field. FIG. 1(a) is an SEM image of alloy particles used in the present invention, and it can be seen that the size distribution of the alloy particles is relatively uniform, substantially between 60-90 μm, after mechanical grinding, stress-relief heat treatment and sizing. Fig. 1(b) is a polarization image of the alloy particles under a metallographic microscope, and very significant martensite bosses can be observed on the surfaces of the particles, and the bosses are uniformly oriented, which indicates that the prepared alloy particles are single-crystal particles.
FIGS. 2(a) and (b) are transverse and longitudinal slices, respectively, of a magnetic field-cured composite material. As seen from the transverse slicing, the alloy particles are distributed more uniformly on a plane vertical to the direction of the external magnetic field; as seen from the longitudinal section of the composite material, the alloy particles are macroscopically arranged in an oriented manner under the action of the external magnetic field to form particle beams as the alloy fibers, and the distance between the particle beams is maintained at about 0.5 mm.
Fig. 2(c) and (d) are 50-fold and 100-fold magnified images, respectively, of a longitudinal slice. As can be seen from the micro-morphology of the composite material, each particle beam is composed of a plurality of micron alloy particles, and the sizes of the particles are mainly distributed in the range of 60-90 μm. For two adjacent particle beams, there is little particle distribution between the particle beams. The distribution state of the particles in the polymer is mainly influenced by the curing conditions and the properties of the polymer, and the main control parameters are as follows: curing time, curing temperature (which determines the viscosity of the polymer), and the magnitude of the magnetic field. The parameters used in this example are: and (3) adding a 1T magnetic field, curing for 48h at room temperature, and then keeping the temperature of the composite material at 100 ℃ for 2 h. Under the parameter, the viscosity of the polymer is moderate before curing, the problems of particle deposition or difficult directional arrangement and the like can not occur, and high-temperature treatment is carried out after primary curing is finished, so that the crosslinking among polymer macromolecules is further enhanced, and the composite material shows good mechanical stability.
FIG. 3 is a graph of the magnetization curves in different directions for a composite material cured without and with a magnetic field at a particle mass fraction of 10 wt.%. For the sample without magnetic field solidification, the magnetization curves obtained by testing in different directions are basically superposed; magnetic field-cured composite materials prepared according to the method used in this patent, magnetic in the direction of the magnetic field-cure and perpendicular to that directionThe chemical curves are not overlapped, which shows that the material has magnetic anisotropy; the magnetic anisotropy of the composite material can be obtained by calculating the integral area of the two curves to make a difference. The magnetic anisotropy energy K of the composite material is calculated when the particle content is 10 wt% u Can reach 1.05480 multiplied by 10 5 J/m 3 This value is already close to K of Ni-Mn-Ga single crystal u The values show that the composite material prepared by the process flow has high particle orientation degree and good magnetic anisotropy, and a better rotating magnetocaloric effect is expected to appear.
Claims (10)
1. A method for preparing NiMnGa particle/polymer composite material with magnetic anisotropy is characterized in that the preparation method is realized by the following steps:
step one, weighing metal raw materials according to design components, wherein the Mn element is excessive by 1.5-2.0 wt%;
secondly, smelting a metal ingot in a multi-induction smelting mode, and carrying out heat preservation treatment for at least 24 hours after smelting is finished;
cutting and polishing the cast ingot, ultrasonically cleaning, drying, crushing, grinding and screening to obtain alloy particles with the particle size of 60-80 microns;
step four, carrying out vacuum heat treatment on the alloy particles obtained in the step three in an inert atmosphere;
step five, filling alloy particles into a soft mold with the inner surface coated with a release agent, heating the epoxy resin to 100 ℃ while stirring, adding a curing agent, immediately pouring the uniformly stirred mixture into the soft mold, when the temperature is reduced to 50 ℃, the flexible mould is placed between two poles of the magnetic field generator, the magnetic field generator is electrified by using a voltage-stabilizing direct current power supply, the air gap of the longitudinal magnetic field is controlled to be 15-20 mm, the output current of the regulated power supply is regulated to make the magnetic field between two poles of the magnetic field generator reach above 1T, after the magnetic field is applied, the alloy particles are gradually changed from disordered arrangement to chain arrangement under the action of magnetic force, the easy magnetization axes of the alloy particles are turned to the direction of a magnetic field, and curing the polymer at room temperature in the state, keeping for at least 45h, taking out from the magnetic field, demolding, and keeping the temperature for at least 2h to obtain the composite material.
2. The method of claim 1, wherein the design components are 25.44 at.% Ni, 4.86 at.% Mn, and 38.83 at.% Ga.
3. The method for preparing a NiMnGa particle/polymer composite material with magnetic anisotropy as recited in claim 1, wherein the second melting is performed at least 4 times.
4. The method for preparing a NiMnGa particle/polymer composite material with magnetic anisotropy as recited in claim 1, wherein the second step is performed by holding at 1000 ℃ for 24 h.
5. The method for preparing a NiMnGa particle/polymer composite material with magnetic anisotropy as claimed in claim 1, wherein the third step employs acetone ultrasonic cleaning for 5-10 min.
6. The method for preparing a NiMnGa particle/polymer composite material with magnetic anisotropy as recited in claim 1, wherein the third step is drying at 393K for 10 min.
7. The method for preparing NiMnGa particle/polymer composite with magnetic anisotropy according to claim 1, characterized in that the three-step crushing is carried out until the alloy particle size is below 1 mm.
8. The method for preparing NiMnGa particle/polymer composite material with magnetic anisotropy as claimed in claim 1, characterized in that the degree of vacuum in the four-step vacuum heat treatment process is 0.3 x 10 -3 Pa～0.5×10 -3 Pa, raising the temperature to 725 ℃, preserving heat for 2h, then lowering the temperature to 700 ℃ and preserving heat for 10h, then lowering the temperature to 500 ℃ and preserving heat for 20h, finally cooling along with the furnace, lowering the temperatureThe temperature rate is 7-10 deg.c/min.
9. The method for preparing a NiMnGa particle/polymer composite material with magnetic anisotropy as recited in claim 1, wherein in step five, the curing agent is polyamine ether, the mass ratio of the curing agent to the epoxy resin is 1:3, and the addition amount of the alloy particles is not more than 30 wt.%.
10. The method for preparing NiMnGa particle/polymer composite material with magnetic anisotropy as claimed in claim 1, wherein the temperature of step five is kept at 100 ℃ for 2-3 h.
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| CN116478540A (en) * | 2023-04-24 | 2023-07-25 | 北京科技大学 | Composite material with flexibility and magnetostriction performance as well as preparation method and application thereof |
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| JP2004277764A (en) * | 2003-03-13 | 2004-10-07 | Furukawa Techno Material Co Ltd | Composite material of shape memory alloy and plastics |
| CN101724224A (en) * | 2009-12-02 | 2010-06-09 | 哈尔滨工程大学 | Composite material of NiMnGa magnetic memorial alloy and epoxide resin and preparation method thereof |
| CN102764887A (en) * | 2012-08-02 | 2012-11-07 | 西安市嘉闻材料技术有限公司 | Method for preparing polymer-bonded magnetic refrigerating composite material |
| CN106011713A (en) * | 2016-06-17 | 2016-10-12 | 哈尔滨工业大学 | Preparation method of nickel-manganese-gallium alloy microparticles high in refrigerating capacity |
| WO2016198741A1 (en) * | 2015-06-07 | 2016-12-15 | Aalto University Foundation | A method to produce magnetic shape memory material, composites and their uses |
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| JP2004277764A (en) * | 2003-03-13 | 2004-10-07 | Furukawa Techno Material Co Ltd | Composite material of shape memory alloy and plastics |
| CN101724224A (en) * | 2009-12-02 | 2010-06-09 | 哈尔滨工程大学 | Composite material of NiMnGa magnetic memorial alloy and epoxide resin and preparation method thereof |
| CN102764887A (en) * | 2012-08-02 | 2012-11-07 | 西安市嘉闻材料技术有限公司 | Method for preparing polymer-bonded magnetic refrigerating composite material |
| WO2016198741A1 (en) * | 2015-06-07 | 2016-12-15 | Aalto University Foundation | A method to produce magnetic shape memory material, composites and their uses |
| CN106011713A (en) * | 2016-06-17 | 2016-10-12 | 哈尔滨工业大学 | Preparation method of nickel-manganese-gallium alloy microparticles high in refrigerating capacity |
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| CN116478540A (en) * | 2023-04-24 | 2023-07-25 | 北京科技大学 | Composite material with flexibility and magnetostriction performance as well as preparation method and application thereof |
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