Compounds with large magnetic entropy changes and their preparation

A compound, magnetic entropy change technology, applied in magnetic objects, magnetic materials, electrical components and other directions, can solve the problems of restricting magnetic refrigeration, insoluble, insufficient magnetic entropy change, etc., achieving simple manufacturing process, adjustable Curie temperature, The effect of increasing magnetic entropy

Inactive Publication Date: 2005-02-23
UNIV OF SCI & TECH BEIJING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

For a long time, elemental rare earth metal gadolinium has been considered as the best magnetic refrigerant near room temperature, but the magnetic entropy change is not high enough, which restricts the practical application of magnetic refrigeration at room temperature and above
In 1997, Pecharsky and Gschneidner of Ames Laboratory in the United States reported GdSiGe compounds, whose highest magnetic entropy change was much greater than that of gadolinium (Phys. Rev. Lett, 78 (1997) 4494), but the compounds required high purity of raw materials and were insoluble , the preparation process is more complex
The LaFeSi compound (Phys.Rev.B, 64, (2001) 012409) reported by Hu Fengxia, Shen Baogen and others from the Institute of Physics, Chinese Academy of Sciences, has a higher magnetic entropy change than gadolinium, and is comparable to GdSiGe. The problem is that the preparation process is more complicated Difficult to mass produce

Method used

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  • Compounds with large magnetic entropy changes and their preparation
  • Compounds with large magnetic entropy changes and their preparation
  • Compounds with large magnetic entropy changes and their preparation

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] Raw materials such as nickel, manganese, gallium, etc. are classified into chemical components Ni 51.5 mn 22.7 Ga 25.8 Proportion (electron concentration is 7.513), put into vacuum electric arc furnace, induction furnace or other smelting furnace, vacuumize to 10 -1 or above, pass in argon gas, and obtain a compound with uniform composition after repeated melting and cooling. The compound obtained by smelting was homogenized at 900°C for 72 hours, and then annealed at 700°C for 60 hours. In order to prevent sample oxidation, the homogenization treatment and annealing process can be carried out under vacuum or argon protection. The sample was proved by X-ray diffraction to be a non-modulated square structure, belonging to the martensitic phase. SQUID was used to measure the magnetization curve as a function of temperature. The compound obtained through the above steps has a Curie temperature of -77°C. The calculation results show that the magnetic entropy becomes 4...

Embodiment 2

[0022] Raw materials such as nickel, manganese, gallium, etc. are classified into chemical components Ni 54.9 mn 20.5 Ga 24.6 Proportion (electron concentration is 7.663), put into vacuum electric arc furnace, induction furnace or other smelting furnace, vacuumize to 10 -1 or above, pass in argon gas, and obtain a compound with uniform composition after repeated melting and cooling. The compound obtained by smelting was homogenized at 1050°C for 48 hours, and then annealed at 650°C for 72 hours. In order to prevent sample oxidation, the homogenization treatment and annealing process can be carried out under vacuum or argon protection. The sample prepared in this way proves to be non-modulated square structure through X-ray diffraction, belongs to martensitic phase (see figure 1 ). Vibrating sample magnetometer LakeShore-7410 was used to measure the isothermal magnetization curve near the phase transition temperature (see figure 2 ). The compound obtained through the ab...

Embodiment 3

[0024] Raw materials such as nickel, manganese, gallium, etc. are classified into chemical components Ni 55.5 mn 19.8 Ga 24.7 Proportion (electron concentration is 7.677), put it into a vacuum electric arc furnace, induction furnace or other smelting furnace, vacuumize to 10-1 or above, pass in argon gas, and obtain a compound with uniform composition after repeated melting and cooling. The compound obtained by smelting was homogenized at 950°C for 72 hours, and then annealed at 750°C for 48 hours. In order to prevent sample oxidation, the homogenization treatment and annealing process can be carried out under vacuum or argon protection. The sample prepared in this way proves to be non-modulated square structure through X-ray diffraction, belongs to martensitic phase (see Figure 4 ). Vibrating sample magnetometer LakeShore-7410 was used to measure the isothermal magnetization curve near the phase transition temperature (see Figure 5 ). The compound obtained through the...

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Abstract

A big magnetic entropy variation compound and its preparing method are disclosed. It consists of NixMnyGaz (50 is less than or equal to x is less than or equal to 56, 22 is less than or equal to y is less than or equal to 30, 22 is less than or equal to z is less than or equal to 30), with martensite and magnetic conversion under -80deg.C- 80deg.C. When 53 is less than or equal to x is less than or equal to 56, 19 is less than or equal to y is less than or equal to 22, 23 is less than or equal to z is less than or equal to 26, it make austenite phase-transition temperature range and magnetic transition temperature between -20deg.C-80 deg.C by component regulation. It is prepared by proportioning nickel, mangan and gallium etc. raw materials by chemical component, laying vacuum arc furnace or inducing furnace, vacuum pumping up to 10 to the power -1 , passing argon, smelting and cooling to obtain uniform compound, homogeneous treating the compound for 24-120 hrs under 900-1100deg.C, and annealing for 12-72 hrs under 600-800deg.C. Its advantages include simple process, big magnetic entropy and regulating temperature.

Description

technical field [0001] The invention belongs to the technical field of magnetic refrigeration materials, and in particular provides a compound with large magnetic entropy change and a preparation method thereof. Background technique [0002] Magnetic refrigeration is realized by using a magnetic field to change the order degree of the spin orientation spatial distribution of the atoms of the refrigeration working substance, causing a change in magnetic entropy. When the refrigerant is demagnetized adiabatically, the temperature decreases; when the refrigerant is magnetized adiabatically, the temperature increases. It can also be said that when the refrigerated substance is isothermally demagnetized, it absorbs heat; when it is isothermally magnetized, it releases heat. This is the magnetocaloric effect, also known as the magnetic calorie effect, referred to as the magnetic card effect [0003] Magnetic entropy is a characterization of the degree of magnetic order. As long a...

Claims

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Application Information

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IPC IPC(8): C22C19/03H01F1/047H01L37/00
Inventor 张泽玉闻达龙毅叶荣昌万发荣
Owner UNIV OF SCI & TECH BEIJING
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