阅读说明：本技术 提高LaFe11.2Co0.7 Si1.1合金居里温度的方法 (Increase of LaFe11.2Co0.7 Si1.1Method for curie temperature of alloy ) 是由 李兆杰 黄焦宏 程娟 金培育 刘翠兰 张英德 王强 戴默涵 郭亚茹 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种提高LaFe-(11.2)Co-(0.7)Si-(1.1)合金居里温度的方法,步骤包括：对LaFeSi材料合金添加Co元素进行熔炼,得到LaFe-(11.2)Co-(0.7)Si-(1.1)合金；通过对LaFe-(11.2)Co-(0.7)Si-(1.1)合金添加间隙原子来进行熔炼,使得合金的晶胞体积膨胀,晶格常数随之逐渐增大。本发明通过Co部分替代Fe原子,引入间隙原子来提高居里温度。(The invention discloses a method for improving LaFe 11.2 Co 0.7 Si 1.1 A method for the curie temperature of an alloy, comprising the steps of: adding Co element into LaFeSi material alloy for smelting to obtain LaFe 11.2 Co 0.7 Si 1.1 Alloying; by the reaction of LaFe 11.2 Co 0.7 Si 1.1 The alloy is smelted by adding interstitial atoms, so that the unit cell volume of the alloy expands, and the lattice constant gradually increases. According to the invention, the Co partially replaces Fe atoms, and interstitial atoms are introduced to improve the Curie temperature.)

1. Improve LaFe_11.2Co_0.7 Si_1.1A method of alloy curie temperature, comprising:

adding Co element into LaFeSi material alloy for smelting to obtain LaFe_11.2Co_0.7 Si_1.1Alloying;

by the reaction of LaFe_11.2Co_0.7 Si_1.1The alloy is smelted by adding interstitial atoms, so that the unit cell volume of the alloy expands, and the lattice constant gradually increases.

2. Elevated LaFe according to claim 1_11.2Co_0.7 Si_1.1The Curie temperature method of the alloy is characterized in that C, B, H interstitial atoms are selected as interstitial atoms.

3. Elevated LaFe according to claim 1_11.2Co_0.7 Si_1.1The method of Curie temperature of the alloy is characterized in that the alloy is subjected to LaFe_11.2Co_0.7 Si_1.1Adding C element into the alloy for smelting to generate LaFe_11.2Co_0.7Si_1.1C_xAlloy of para-LaFe_11.2Co_0.7Si_1.1C_xAnd carrying out heat treatment on the alloy.

4. Elevated LaFe according to claim 3_11.2Co_0.7 Si_1.1The Curie temperature method of the alloy is characterized in that when x is 0, 0.05, 0.10, 0.15 and 0.20, the lattice constants of the alloy are 1.1409nm, 1.1413nm, 1.1418nm, 1.1425nm and 1.1431nm respectively.

5. Elevated LaFe according to claim 3_11.2Co_0.7 Si_1.1Method for the Curie temperature of alloys, characterised in that LaFe_11.2Co_0.7 Si_1.1C_xIn the alloy, five alloy elements all exist alpha-Fe phase, and main phases are NaZn₁₃A cubic structure.

6. Elevated LaFe according to claim 3_11.2Co_0.7 Si_1.1A method for improving the Curie temperature of an alloy, characterized in that interstitial atoms C are added to expand the volume of a unit cell, and the lattice constant is gradually increased.

Technical Field

The invention belongs to the technical field of room temperature magnetic refrigeration, and particularly relates to a method for improving LaFe_11.2Co_0.7 Si_1.1Alloy Curie temperature method.

Background

At present, magnetic refrigeration is to utilize the heat absorption and release when the magnetocaloric effect material enters and exits the magnetic field to achieve the purpose of refrigeration, so the magnetocaloric effect material is the key of the research and development of the magnetic refrigeration technology. Among many materials with magnetocaloric effect, lanthanum-iron-silicon based materials have received a lot of attention due to their high magnetocaloric effect, low price, good thermal conductivity, safety, non-toxicity, etc., and become one of the most potential materials with magnetocaloric effect.

However, a technology for increasing the curie temperature of the lanthanum-iron-silicon-based material to be close to the room temperature to meet the room-temperature magnetic refrigeration is lacked at present.

Disclosure of Invention

The invention aims to provide a method for improving LaFe_11.2Co_0.7 Si_1.1The Curie temperature of the alloy is increased by partially replacing Fe atoms with Co and introducing interstitial atoms.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

increase of LaFe11_.2Co_0.7 Si_1.1A method of alloy curie temperature, comprising:

adding Co element into LaFeSi material alloy for smelting to obtain LaFe_11.2Co_0.7 Si_1.1Alloying;

by the reaction of LaFe_11.2Co_0.7 Si_1.1The alloy is smelted by adding interstitial atoms, so that the unit cell volume of the alloy expands, and the lattice constant gradually increases.

Further, C, B, H interstitial atoms are used as interstitial atoms.

Further, for LaFe_11.2Co_0.7 Si_1.1Adding C element into the alloy for smelting to generate LaFe_11.2Co_0.7 Si_1.1C_xAlloy of para-LaFe_11.2Co_0.7 Si_1.1C_xAnd carrying out heat treatment on the alloy.

Further, when x is 0, 0.05, 0.10, 0.15, 0.20, the lattice constants of the alloys are 1.1409nm, 1.1413nm, 1.1418nm, 1.1425nm, 1.1431nm, respectively.

Further, LaFe_11.2Co_0.7 Si_1.1C_xIn the alloy, five alloy elements all exist alpha-Fe phase, and main phases are NaZn₁₃A cubic structure.

Further, interstitial atoms C are added to expand the unit cell volume, with a gradual increase in lattice constant.

The invention has the technical effects that:

according to the invention, the Curie temperature of the alloy material is adjusted through C atoms, Fe atoms are partially replaced by Co, and C, B, H and other interstitial atoms are introduced to improve the Curie temperature.

The invention provides a solution for the low Curie temperature of the existing LaFeSi material, because interstitial atoms C are added, the volume of a unit cell is expanded, the lattice constant is gradually increased, the Curie temperature is gradually increased, the magnetization intensity is not zero after the alloy is subjected to ferromagnetic state-paramagnetic state transition, the second phase of alpha-Fe is still kept in a ferromagnetic state, the maximum isothermal magnetic entropy change value is gradually reduced, and the annealed LaFe_11.2Co_0.7Si_1.1C_xThe Curie temperature is increased to be near the room temperature by the adiabatic temperature change curve obtained by the alloy passing in and out of the magnetic field under the condition of the external magnetic field.

Drawings

FIG. 1 shows LaFe in the present invention_11.2Co_0.7Si_1.1C_xXRD diffraction pattern of the alloy at room temperature after annealing;

FIG. 2 shows LaFe in the present invention_11.2Co_0.7Si_1.1C_xAn M-T curve chart of the alloy under a 0.05T magnetic field after annealing;

FIG. 3 is a graph of isothermal magnetic entropy change of the alloy after annealing in a magnetic field of 0-1.5T;

FIG. 4 shows LaFe in the present invention_11.2Co_0.7Si_1.1C_xAdiabatic temperature change curve at 1.5T in magnetic field after 72 hours of alloy annealing.

Detailed Description

The following description sufficiently illustrates specific embodiments of the invention to enable those skilled in the art to practice and reproduce it.

The invention provides a method for improving LaFe_11.2Co_0.7 Si_1.1The method for controlling the Curie temperature of the alloy comprises the following specific steps:

adding Co element into LaFeSi material alloy for smelting to obtain LaFe_11.2Co_0.7 Si_1.1Alloying;

by the reaction of LaFe_11.2Co_0.7 Si_1.1The alloy is smelted by adding interstitial atoms, so that the unit cell volume of the alloy expands, and the lattice constant gradually increases.

For LaFe_11.2Co_0.7 Si_1.1Adding C element into the alloy for smelting to obtain LaFe_11.2Co_0.7 Si_1.1C_xAlloy, then LaFe_11.2Co_0.7 Si_1.1C_xThe alloy is heat treated, x is 0, 0.05, 0.10, 0.15, 0.20, the lattice constants of the alloy are 1.1409nm, 1.1413nm, 1.1418nm, 1.1425nm, 1.1431nm respectively.

By partial substitution of Fe atoms by Co, for LaFe_11.2Co_0.7 Si_1.1C, B or H element is added to the alloy for smelting, and C, B, H and other interstitial atoms are further introduced to increase the Curie temperature.

The invention adopts a certain proportion increasing regulation mode to control the LaFe_11.2Co_0.7 Si_1.1Adding interstitial C atoms into the alloy, and then adding LaFe_11.2Co_0.7 Si_1.1C_xThe alloy was annealed, x being 0, 0.05, 0.10, 0.15, 0.20. The five alloy elements all exist in an alpha-Fe phase, and main phases are NaZn₁₃A cubic structure.

In LaFe_11.2Co_0.7 Si_1.1Under the condition that the refrigerating capacity of the alloy is kept unchanged, the Curie temperature is increased by about 24K and reaches the vicinity of the room temperature.

As shown in FIG. 1, it is LaFe in the present invention_11.2Co_0.7Si_1.1C_xXRD diffractogram at room temperature after alloy annealing.

As can be seen, the alloy had LaFe after annealing for 72 hours_11.2Co_0.7Si_1.1C_xThe alloy contains a second phase of alpha-Fe and a main phase of NaZn₁₃And the space group of the cubic structure is Fm-3 c. In the figure, the alpha-Fe phase exists in all five alloys.

In comparison, the alloy without C added has a higher diffraction peak value of alpha-Fe than the alloy with C added. As can be seen from the graph, the diffraction peak gradually moves toward a high angle as the C content increases. The addition of interstitial atoms C causes the cell volume to expand, resulting in a gradual increase in the lattice constant. LaFe was analyzed by fitting_11.2Co_0.7Si_1.1C_x(x ═ 0, 0.05, 0.10, 0.15, 0.20), the lattice constants were 1.1409nm, 1.1413nm, 1.1418nm, 1.1425nm, and 1.1431nm, respectively, and the lattice constants increased stepwise. This is due to the addition of interstitial atoms C which causes the cell volume to expand, resulting in a gradual increase in the lattice constant.

As shown in FIG. 2, it is LaFe in the present invention_11.2Co_0.7Si_1.1C_xM-T plot under 0.05T magnetic field after alloy annealing.

With increasing C content x, are combinedThe curie temperature value of gold gradually increased to around room temperature. Using origin7.0 software to calculate the first-order partial derivative of the curve, and taking the extreme value as LaFe_11.2Co_0.7Si_1.1C_x(x ═ 0, 0.05, 0.10, 0.15, 0.20) curie temperatures for the alloys, 268K, 274K, 280K, 286K, 292K, respectively. It can be seen that for every 0.05 increase in C content x, LaFe, when x ≦ 0.2_11.2Co_0.7Si_1.1C_xThe curie temperature of the alloy rose by about 6K, which was more than 2 times the curie temperature per 0.05 interstitial atoms B added. This is because the atomic radius of C is larger than that of B, and the lattice deformation of unit cell is larger after adding interstitial atoms, so that the coupling effect of Fe-Fe and Fe-Co is enhanced, and the Curie temperature is increased.

It can be seen from the M-T diagram that after the ferromagnetic-paramagnetic transition of the alloy, the magnetization is not zero, since the second phase of α -Fe in the alloy remains in the ferromagnetic state. The magnetization of the alloy with x-0 in fig. 2 after being transformed into paramagnetic state is obviously much higher than that of other alloys with interstitial atoms C added, because the alloy contains the largest amount of the second phase of α -Fe, which is consistent with the XRD test results.

As shown in FIG. 3, it is an isothermal magnetic entropy change curve under a magnetic field of 0-1.5T after the alloy annealing.

It is also apparent from fig. 3 that the maximum isothermal magnetic entropy change value is gradually decreased as the C content increases. The maximum isothermal magnetic entropy change of the alloy is much higher than that of metal Gd (about 3.3J/(kg. K)), and the half-peak width of the alloy is wide.

Calculation of LaFe_11.2Co_0.7Si_1.1C_xThe maximum isothermal magnetic entropy change of the (x ═ 0, 0.05, 0.10, 0.15, 0.20) alloys was 5.99J/(kg · K), 6.39J/(kg · K), 6.23J/(kg · K), 5.96J/(kg · K) and 4.46J/(kg · K), respectively. In addition to the alloy with x being 0, it is also apparent from the figure that the maximum isothermal magnetic entropy change value is gradually reduced as the C content increases. Wherein the variation range between the maximum value of isothermal magnetic entropy variation of the two alloys of which x is 0.15 and x is 0.20 is obviously larger than that of x<Variation range of isothermal magnetic entropy of 0.15 alloy to maximum valueIs large. This is because orbital hybridization occurs between the 1s electrons of the C-interstitial atoms and the 3d layer electrons of the Fe or Co atoms in the alloy, resulting in a decrease in the exchange coupling between Fe-Fe or Fe-Co in the alloy, and this effect begins to manifest. The maximum value of isothermal magnetic entropy change of the series of alloys is much higher than that of metal Gd (about 3.3J/(kg. K)), of which LaFe_11.2Co_0.7Si_1.1C_0.15Maximum isothermal magnetic entropy change and LaFe_11.05Co_0.85Si_1.1B_0.25(about 5.22J/(kg. multidot.K) with Curie temperature around 284K) is higher than the above value. The half-width of the alloy is much wider than that of (LaCe) (FeMnSi)13Hx series alloy, and is much wider than that of La

The half-widths of the (FeCoSi)13Bx series alloys do not differ much.

As shown in FIG. 4, it is LaFe in the present invention_11.2Co_0.7Si_1.1C_xAdiabatic temperature change curve at 1.5T in magnetic field after 72 hours of alloy annealing.

After annealing, interstitial atoms C are added to make LaFe_11.2Co_0.7 Si_1.1C_xWhen the cooling capacity is not changed (x is 0, 0.05, 0.10, 0.15, 0.20), the curie temperature is increased by about 24K. The group of samples basically covers a room temperature area between 268K and 292K, and has high practical application value for room temperature magnetic refrigeration.

As can be seen from comparison of FIG. 3 and FIG. 4, the two rules are substantially consistent.

LaFe_11.2Co_0.7Si_1.1The maximum adiabatic temperature change values of Cx (x ═ 0, 0.05, 0.10, 0.15, 0.20) were 2.0K, 2.3K, 2.2K, 2.1K, and 2.0K, respectively. The adiabatic temperature change values of the alloys are equal when x is 0 and x is 0.20, i.e. after annealing for 72h, interstitial atoms C are added so that LaFe_11.2Co_0.7 Si_1.1Under the condition that the refrigerating capacity is not changed, the Curie temperature is increased by about 24K. The group of samples basically covers a room temperature area between 268K and 292K, and has high practical application value for room temperature magnetic refrigeration.

The terminology used herein is for the purpose of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.