阅读说明：本技术 一种锰钴锗基合金室温磁制冷材料及其制备方法 (Manganese-cobalt-germanium-based alloy room-temperature magnetic refrigeration material and preparation method thereof ) 是由 钱凤娇 缪雪飞 杨浩 于 2020-05-14 设计创作，主要内容包括：本发明涉及一种锰钴锗基合金室温磁制冷材料及其制备方法,所述室温磁制冷材料的化学通式为Mn<Sub>1-<I>x</I></Sub>Zr<Sub><I>x</I></Sub>CoGe,式中0.04≤<I>x</I>≤0.06,其制备方法为：将锰片、锆片、钴块、锗块按化学通式中各元素的摩尔比称重,并熔炼成合金锭；将熔炼后的合金锭在真空条件下(真空度≤10<Sup>-2</Sup>Pa)进行退火处理,退火温度为1123~1273K,保温时间为75~100小时,保温结束后淬火至室温。本发明通过将MnCoGe母合金中Mn原子部分替代为Zr原子,使得原本分离的铁磁相变和马氏体结构相变在室温附近发生耦合,获得了优异的磁热性能,有望应用于室温磁制冷领域。(The invention relates to a manganese-cobalt-germanium-based alloy room-temperature magnetic refrigeration material and a preparation method thereof, wherein the general chemical formula of the room-temperature magnetic refrigeration material is Mn x 1‑ Zr x CoGe, in the formula, 0.04 is less than or equal to x Less than or equal to 0.06, and the preparation method comprises the following steps: weighing the manganese piece, the zirconium piece, the cobalt block and the germanium block according to the molar ratio of each element in the chemical general formula, and smelting into an alloy ingot; the alloy ingot after smelting is processed under the vacuum condition (the vacuum degree is less than or equal to 10) ‑2 Pa) annealing at 1123-1273K for 75-100 h, and quenching to room temperature after heat preservation. The Mn atoms in the MnCoGe master alloy are partially replaced by Zr atoms, so that the originally separated ferromagnetic phase change and martensite are realizedThe bulk phase change is coupled near the room temperature, so that excellent magnetocaloric performance is obtained, and the bulk phase change is expected to be applied to the field of room-temperature magnetic refrigeration.)

1. The manganese-cobalt-germanium-based alloy room-temperature magnetic refrigeration material is characterized in that the chemical general formula of the manganese-cobalt-germanium-based alloy room-temperature magnetic refrigeration material is Mn _x1-Zr _x CoGe, in the formula, 0.04 is less than or equal tox≤ 0.06，x=The alloy is a TiNiSi-type orthogonal martensite phase at room temperature at 0.04 deg.C;xthe alloy consists of TiNiSi-type orthogonal martensite and N at room temperature when the alloy is 0.05 =₂In-type hexagonal austenite two-phase composition;xalloy is N at room temperature when the alloy is 0.06₂An In-type hexagonal austenite phase.

2. The preparation method of the manganese-cobalt-germanium-based alloy room-temperature magnetic refrigeration material as claimed in claim 1, characterized by comprising the following steps:

1) weighing the manganese piece, the zirconium piece, the cobalt block and the germanium block according to the molar ratio of each element in the chemical general formula, and smelting into an alloy ingot;

2) and annealing the smelted alloy ingot under a vacuum condition.

3. The method for preparing a Mn-Co-Ge-based alloy room-temperature magnetic refrigeration material according to claim 2, wherein the melting in step 1) is performed by a vacuum arc melting furnace.

4. The method for preparing the Mn-Co-Ge-based alloy room-temperature magnetic refrigeration material according to claim 2, wherein the melting in step 1) is performed by a vacuum induction melting furnace.

5. The method for preparing the Mn-Co-Ge-based alloy room-temperature magnetic refrigeration material according to claim 2, wherein the vacuum condition in the step 2) is that the vacuum degree is less than or equal to 10^-2Pa。

6. The method for preparing the Mn-Co-Ge-based alloy room-temperature magnetic refrigeration material according to claim 2, wherein the annealing treatment in the step 2) is carried out at an annealing temperature of 1123-1273K, the heat preservation time at the annealing temperature is 75-100 hours, and the Mn-Co-Ge-based alloy room-temperature magnetic refrigeration material is quenched to room temperature after the heat preservation.

Technical Field

The invention relates to a room temperature magnetic refrigeration material, in particular to a manganese-cobalt-germanium-based alloy room temperature magnetic refrigeration material and a preparation method thereof.

Background

Refrigeration technology plays a very important role in modern social life, from household refrigerators, air conditioners and food cold storage cabinets used in daily life to gas liquefaction, central air conditioners and the like in industrial production. The refrigeration technology which is commonly applied at present is the traditional vapor compression refrigeration, and the Freon refrigerant which is widely used in the technology has great damage effect on the atmospheric ozone layer. Although non-fluorine substitute refrigerants (such as halogenated substances of ammonia, carbon dioxide and other light hydrocarbons) have been used, a large amount of greenhouse gases are still emitted, and the environment is polluted. Another key problem of the conventional refrigeration technology is low refrigeration efficiency and high energy consumption. Under the environment of global warming and energy shortage, the seeking of a novel refrigeration technology which is environment-friendly, efficient and energy-saving is particularly urgent.

In recent years, a novel refrigeration technology (i.e. magnetic refrigeration technology) based on the magnetocaloric effect is widely regarded by researchers at home and abroad and the industry because the novel refrigeration technology is efficient and environment-friendly and meets the low-carbon economic requirements. Magnetic refrigeration technology relies on the magnetocaloric effect characteristic of magnetic materials, which results from a strong coupling between the magnetic moment and the crystal lattice in the magnetic material. When an external magnetic field of a certain magnitude is applied to a magnetic material, the magnetic moment arrangement of the magnetic material is changed from disorder to order, namely, the magnetic entropy is reduced. Under adiabatic conditions, since the total entropy of the material is not changed, in order to compensate for the decrease of the magnetic entropy, the lattice entropy of the material is increased, so that the temperature of the material is increased; conversely, if the external magnetic field is removed, the magnetic moments can restore disorganized arrangement, namely the magnetic entropy is increased, and under an adiabatic condition, the lattice entropy is reduced, so that the temperature of the material is reduced. This phenomenon, in which the temperature of the material changes significantly due to the change in the applied magnetic field, is referred to as the magnetocaloric effect. The key to the application of magnetic refrigeration technology lies in the selection and development of suitable magnetic refrigeration materials. Compared with the second-level magnetic phase change material, the first-level magnetic phase change alloy (such as Gd)₅(Si,Ge)₄, (Mn,Fe)₂(P, As) and La (Fe, Si)₁₃Etc.) because the magnetic phase change is accompanied with the crystal structure phase change (namely the magnetic-structure coupling phase change), the inherent latent heat of phase change brings more remarkable magnetocaloric effect, and has great application prospect in the field of room-temperature magnetic refrigeration. It can be seen that in the magnetic materialThe realization of the coupled primary magnetic phase change of a magnetic-structure is an important way for obtaining excellent magnetocaloric performance at present.

The thermal effect brought by the huge lattice volume change of the MnCoGe alloy during phase change makes the MnCoGe alloy become one of strong competitors of room-temperature magnetic cooling materials. However, the MnCoGe alloy generates martensite structure phase transformation at about 430K and generates ferromagnetic phase transformation at about 323K, and the structure phase transformation temperature is far away from the ferromagnetic phase transformation temperature, so that the magnetic-structure phase transformation coupling is difficult to generate. Therefore, it is necessary to provide a way to couple originally separated magnetic-structure phase transitions in the MnCoGe alloy, so as to obtain excellent magnetocaloric properties in the alloy system. Relevant researches show that the phase transition temperature of a martensite structure can be reduced by replacing magnetic atoms Mn or Co with 3d metal atoms such as V, Cu, Zn and the like, so that the phase transition temperature coincides with the ferromagnetic phase transition temperature, and the giant magnetocaloric effect is realized. However, it has been reported that a room temperature magnetic refrigeration material having excellent magnetocaloric properties can be obtained by introducing 4d metal atom Zr into a MnCoGe-based alloy to realize magnetic-structural phase change coupling at around room temperature.

Disclosure of Invention

The invention aims to provide a MnCoGe-based alloy room-temperature magnetic refrigeration material which realizes magnetic-structure phase change coupling near room temperature and obtains excellent magnetocaloric performance and a preparation method thereof.

The purpose of the invention can be realized by the following technical scheme:

a manganese-cobalt-germanium-based alloy room temperature magnetic refrigeration material has a chemical general formula as follows: mn _x1-Zr _x CoGe, in the formula, 0.04 is less than or equal tox≤0.06。

According to the manganese-cobalt-germanium-based alloy room-temperature magnetic refrigeration material, Zr atoms are used for partially replacing Mn atoms, so that the phase transition temperature of a martensite structure can be quickly reduced, and the ferromagnetic phase transition temperature can be slowly reduced. When the Zr content is less than or equal to 0.04xWhen the temperature is less than or equal to 0.06, the superposition of martensite structure phase transformation and ferromagnetic phase transformation near room temperature can be realized, and the phase transformation temperature zone is reduced along with the increase of Zr content and can be regulated and controlled near room temperature. The magnetocaloric effect is remarkably improved by the magnetic-structure phase change coupling near room temperature, and compared with MnCoGe master alloy without Zr, Mn _x1-Zr _x CoGe in 1T and 2T magnetic field variationThe maximum entropy change of the cells is improved by more than 2 times.

The preparation method of the manganese-cobalt-germanium-based alloy room-temperature magnetic refrigeration material comprises the following steps:

1) weighing the manganese piece, the zirconium piece, the cobalt block and the germanium block according to the molar ratio of each element in the chemical general formula, and smelting into an alloy ingot;

2) and annealing the smelted alloy ingot under a vacuum condition.

Preferably, the melting in step 1) is melting by a vacuum arc melting furnace.

Preferably, the smelting in step 1) is smelting by a vacuum induction smelting furnace.

Preferably, the vacuum condition in the step 2) is that the vacuum degree is less than or equal to 10^-2Pa。

Preferably, the annealing treatment in the step 2) is carried out at an annealing temperature of 1123-1273K, the heat preservation time is 75-100 hours at the annealing temperature, and the steel plate is quenched to room temperature after the heat preservation is finished.

Compared with the prior art, the invention has the following advantages:

1) according to the invention, Zr atoms are used for partially replacing Mn atoms in the MnCoGe master alloy, so that the phase transition temperature of a martensite structure is reduced to be close to room temperature, and magnetic phase transition is coupled with structural phase transition, thereby obviously improving the magnetocaloric effect.

2) The alloy has the characteristics of simple preparation method, easy realization, excellent magnetic refrigeration performance, wide application prospect and the like. Can be applied to the fields of household appliances, medical instruments, high-energy physics, aerospace, precise instruments, petrochemical industry and the like.

Drawings

FIG. 1 shows a Mn room temperature magnetic refrigerant material of the present invention _x1-Zr _x CoGe (x =0.04,0.05, 0.06) and Zr-free base alloys (i.e. Zr-freexThermal analysis (DSC) curve of =0) and thermomagnetic (C: =0)M-T) Curve line.

FIG. 2 shows Mn as a room temperature magnetic refrigerant material of the present invention _x1-Zr _x CoGe (x=0.04,0.05, 0.06) and Zr-free raw alloy (i.e. Zr-free raw alloyxRoom temperature X-ray diffraction (XRD) derivatives of =0)And (4) shooting.

FIG. 3 shows Mn as a room temperature magnetic refrigerant material of the present invention _x1-Zr _x CoGe (x= 0.06) Scanning Electron Microscopy (SEM) and energy spectroscopy (EDS) images.

FIG. 4 shows Mn as a room temperature magnetic refrigerant material of the present invention _x1-Zr _x CoGe (x=0.04,0.05, 0.06) and Zr-free raw alloy (i.e. Zr-free raw alloyx=0) isothermal entropy curve (cooling process) under 1T and 2T magnetic field variation.

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.