A lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration and a preparation method thereof

Abstract

The present invention discloses a lanthanum iron silicon based alloy for room temperature magnetic refrigeration, the general chemical formula of which is La 1+x Fe 11 Co 0.9 Si 1.1 , where x=0.2~0.8; the preparation steps are to first use La, Fe, Co, Si single powder as starting materials, obtain precursor powder by mechanical alloying solid phase reaction under protective atmosphere, then obtain bulk alloy by spark plasma sintering, and finally encapsulate in quartz tube under anaerobic conditions, and then perform annealing and quenching treatment to obtain lanthanum iron silicon-based alloy. The lanthanum iron silicon-based alloy synthesized by the preparation method of the present invention has low cost, short production cycle, simple process, and has the potential for large-scale application in the field of room temperature magnetic refrigeration.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic refrigeration materials, and in particular relates to a lanthanum-iron-silicon-based alloy for room-temperature magnetic refrigeration, and a preparation method thereof. Background Art

[0002] Due to the needs of daily life, business and technological development, refrigeration technology has become indispensable. Traditional air compression refrigeration technology is very mature, but due to its high energy consumption, use of harmful refrigerants and strong greenhouse effect, it will eventually be replaced by new energy-saving and environmentally friendly refrigeration technology in the future.

[0003] Magnetic refrigeration technology, which is developed by utilizing the isothermal entropy change or adiabatic temperature rise phenomenon generated by magnetic materials during the excitation or demagnetization process, has attracted widespread attention at home and abroad due to its advantages such as energy saving, environmental protection, noiselessness and easy miniaturization. In the field of room temperature magnetic refrigeration technology, lanthanum iron silicon-based alloys are one of the most promising magnetic refrigeration fluids, which are non-toxic, environmentally friendly, low-cost, and can achieve high relative cooling capacity at room temperature.

[0004] At present, a large number of researchers have reported on the work of lanthanum iron silicon based alloys in terms of composition regulation and preparation methods. Patent (CN1450190A) discloses a preparation method for doping La, Fe and interstitial sites in LaFeSi based magnetic refrigeration alloys. The Curie point of the LaFeSi based alloy prepared by smelting, rapid quenching, annealing and further absorption and degassing treatment is continuously adjustable over a wide range, and a magnetic entropy change of more than 2 times higher than that of metal Gd can be obtained near room temperature. Patent (CN109266951B) discloses a LaFeSiCu magnetic refrigeration alloy and its preparation method. The LaFeSiCu alloy is successfully prepared by multiple smelting of raw material powder and subsequent annealing and quenching. Patent (CN111755187A) discloses a preparation method for broadening the working temperature range of lanthanum iron silicon alloy magnetic refrigeration. The LaFeSi alloy with a wide temperature range is successfully prepared by sequentially smelting, belt throwing, annealing, quenching, grinding and high pressure annealing of raw material powder. The patent (CN115323248B) discloses a method for preparing a high-entropy doped lanthanum iron silicon-based magnetic refrigeration material with a wide refrigeration temperature range. The LaFeCoNiCrMnSi magnetic refrigeration alloy is successfully prepared by smelting, annealing and quenching the raw material powder.

[0005] Based on the above disclosed patents, the existing process routes for preparing LaFeSi-based alloys are mainly to prepare precursor ingots by melting raw material powder multiple times. Although the vacuum melting-annealing-quenching preparation method is very mature, it also limits the large-scale application of LaFeSi-based alloys. On the one hand, the precursor ingot requires long-term high-temperature annealing to form a functional phase, which has high energy consumption and a long production cycle; on the other hand, the subsequent stripping, absorption / degassing and other processes are complicated, which can easily lead to a decrease in the effective solid solubility of the alloy.

[0006] Therefore, it is very necessary to develop a preparation method for lanthanum-iron-silicon-based alloys with high effective solid solubility in the alloy and short preparation time for room temperature magnetic refrigeration, and to provide key materials for the application of room temperature magnetic refrigeration technology. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, one of the objectives of the present invention is to disclose a lanthanum-iron-silicon based alloy for room temperature magnetic refrigeration.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a lanthanum iron silicon based alloy for room temperature magnetic refrigeration, the chemical formula of which is La 1+x Fe 11 Co 0.9 Si 1.1 , wherein x=0.2~0.8, the magnetic refrigeration functional phase in the alloy material has NaZn 13 Cubic crystal structure.

[0009] The second purpose of the present invention is to disclose a method for preparing a lanthanum iron silicon based alloy for room temperature magnetic refrigeration, by which a lanthanum iron silicon based alloy with large magnetic entropy change in the room temperature range and uniform composition can be prepared.

[0010] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a lanthanum iron silicon-based alloy for room temperature magnetic refrigeration, comprising the following steps: 1) Using La, Fe, Co, and Si powder as starting materials, according to La 1+x Fe 11 Co 0.9 Si 1.1 The precursor powder is obtained by configuring the precursor powder in a stoichiometric ratio and undergoing a mechanical alloying solid phase reaction under a protective atmosphere. 2) Pre-pressing the precursor powder into a shape and then subjecting it to spark plasma sintering to obtain a bulk alloy; 3) The bulk alloy is encapsulated in a quartz tube under anaerobic conditions, and then subjected to high temperature annealing and quenching treatment to obtain a lanthanum iron silicon based alloy for room temperature magnetic refrigeration.

[0011] Furthermore, the purity of the elemental powder is ≥99.5%, and the protective atmosphere is argon, helium, argon-hydrogen mixed gas or helium-hydrogen mixed gas.

[0012] Furthermore, the mechanical alloying solid phase reaction adopts stainless steel or tungsten carbide ball mill tank material, the grinding ball material is zirconium oxide, aluminum oxide, tungsten carbide or stainless steel, the grinding ball diameter is 6 to 20 mm, the ball-to-material ratio is 10 to 50:1, the ball mill speed is 200 to 550 rpm, and the reaction time is 10 to 24 hours.

[0013] Furthermore, in the step 2), the mold material for spark plasma sintering is graphite or tungsten carbide, the sintering pressure is 20-70 MPa, the pressure increase time is 5-15 min, and the pressure holding time is 40-80 min; the sintering temperature increase process is to increase the temperature to 800-1200°C at a rate of not less than 50°C / min, keep the temperature for 5-30 min, and then air cool to room temperature.

[0014] Furthermore, the anaerobic condition is a vacuum or inert gas protection condition; the annealing process is: first heating to 700-900°C at a rate of 5-10°C / min and keeping warm for 30-60min, then heating to 1000-1200°C at a rate not faster than 5°C / min, and the annealing time is 0.5-16 days; the quenching medium is commercial quenching oil, salt solution or ice-water mixture.

[0015] Compared with the prior art, the preparation method of the present invention has the following advantages: 1. Starting from the preparation method of the precursor, the effective solid solubility of the alloy is improved;

[0016] 2. Shorten the production cycle, save energy and time;

[0017] 3. The precursor powder composition is uniform and highly repeatable;

[0018] 4. The prepared lanthanum iron silicon based alloy has a relatively high refrigeration capacity in the room temperature range;

[0019] Therefore, the lanthanum iron silicon-based alloy synthesized according to the preparation method of the present invention has low cost, short production cycle and simple process, and has the potential for large-scale application in the field of room temperature magnetic refrigeration. DETAILED DESCRIPTION

[0020] The embodiments of the present invention are described in detail below, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions.

[0021] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art. Example 1

[0022] The present embodiment discloses a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration, the nominal composition of which is La 1.2 Fe 11 Co 0.9 Si 1.1 The specific steps of the preparation method are as follows.

[0023] 1) Under the protection of high-purity argon atmosphere, La, Fe, Co, and Si single powders were used as starting materials. 1.2 Fe11 Co 0.9 Si 1.1 10g of the mixed powder was placed in a stainless steel ball mill with a stoichiometric ratio, and 350g of Φ6, Φ10 and Φ20 zirconium oxide balls were added. The mixture was first mixed at 200rpm for 30min, and then ball milled at 550rpm for 20h. After ball milling, the precursor powder was taken out under the protection of a high-purity argon atmosphere.

[0024] 2) Under the protection of high-purity argon atmosphere, weigh 4g of the above powder into a graphite mold, and then quickly put the graphite mold into the spark plasma sintering system to start the sintering process. The sintering pressure is 30MPa, the pressure increase time is 5min, and the pressure holding time is 45min; the sintering temperature rise process is to increase the temperature to 1000℃ at 50℃ / min, keep the temperature for 8min, and then air cool to room temperature to obtain a bulk alloy.

[0025] 3) Place the above-mentioned bulk alloy into a clean quartz tube under the protection of high-purity argon atmosphere and evacuate to 1*10 -4 Pa or less. After sealing, place it in a muffle furnace for high-temperature annealing. The annealing process is: first heat up to 850℃ at a rate of 10℃ / min and keep it for 30min, then heat up to 1050℃ at a rate of 5℃ / min and keep it for 4 days. After quenching with ice water, a lanthanum-iron-silicon-based alloy with a high functional phase content is obtained.

[0026] 4) The obtained samples were subjected to phase analysis and magnetic property testing. Example 2

[0027] The present embodiment discloses a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration, the nominal composition of which is La 1.4 Fe 11 Co 0.9 Si 1.1 The specific steps of the preparation method are as follows.

[0028] 1) Under the protection of high-purity helium atmosphere, La, Fe, Co, and Si single powders were used as starting materials. 1.4 Fe 11 Co 0.9 Si 1.1 10g of the mixed powder was placed in a tungsten carbide ball mill according to the stoichiometric ratio, and 100g of Φ6, Φ10 and Φ20 alumina balls were added. The mixture was first mixed at 300rpm for 30min, and then ball milled at 400rpm for 9.5h. After ball milling, the precursor powder was taken out under the protection of high-purity argon atmosphere.

[0029] 2) Under the protection of high-purity helium atmosphere, weigh 4g of the above powder into a tungsten carbide mold, and then quickly put the tungsten carbide mold into the spark plasma sintering system to start the sintering process. The sintering pressure is 20MPa, the pressure increase time is 10min, and the pressure holding time is 45min; the sintering temperature rise process is to increase the temperature to 800℃ at 80℃ / min, keep the temperature for 5min, and then air cool to room temperature to obtain a bulk alloy.

[0030] 3) Place the above-mentioned bulk alloy into a clean quartz tube under the protection of high-purity argon atmosphere and evacuate to 1*10 -4 Pa or less. After sealing, it was placed in a muffle furnace for high-temperature annealing. The annealing process was: firstly, the temperature was raised to 700°C at a rate of 5°C / min and kept at that temperature for 60 minutes, then the temperature was raised to 1000°C at a rate of 4°C / min and kept at that temperature for 0.5 days. After quenching with commercial quenching oil, a lanthanum-iron-silicon-based alloy with a high functional phase content was obtained.

[0031] 4) The obtained samples were subjected to phase analysis and magnetic property testing. Example 3

[0032] The present embodiment discloses a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration, the nominal composition of which is La 1.8 Fe 11 Co 0.9 Si 1.1 The specific steps of the preparation method are as follows.

[0033] 1) Under the protection of high-purity argon-hydrogen mixed gas or helium-hydrogen mixed gas, La, Fe, Co, Si single powders are used as starting materials. 1.8 Fe 11 Co 0.9 Si 1.1 10g of the mixed powder was placed in a stainless steel ball mill with a stoichiometric ratio, and 500g of Φ6, Φ10 and Φ20 tungsten carbide or stainless steel balls were added. The mixture was first mixed at 200rpm for 30min, and then ball milled at 550rpm for 23.5h. After ball milling, the precursor powder was taken out under the protection of high-purity argon atmosphere.

[0034] 2) Under the protection of high-purity argon-hydrogen mixed gas or helium-hydrogen mixed gas, weigh 4g of the above powder into a graphite mold, and then quickly put the graphite mold into the spark plasma sintering system to start the sintering process. The sintering pressure is 70MPa, the pressure increase time is 15min, and the pressure holding time is 85min; the sintering temperature rise process is to increase the temperature to 1200℃ at 70℃ / min, keep the temperature for 30min, and then air cool to room temperature to obtain a bulk alloy.

[0035] 3) Place the above-mentioned bulk alloy into a clean quartz tube under the protection of high-purity argon atmosphere and evacuate to 1*10-4 Pa or less. After sealing, it is placed in a muffle furnace for high-temperature annealing. The annealing process is: first, the temperature is raised to 900°C at a rate of 8°C / min and kept at this temperature for 50 minutes, then the temperature is raised to 1200°C at a rate of 2°C / min and kept at this temperature for 16 days. After quenching with a salt solution, a lanthanum-iron-silicon-based alloy with a high functional phase content is obtained.

[0036] 4) The obtained samples were subjected to phase analysis and magnetic property testing.

[0037] Comparative Example 1: This comparative example discloses a lanthanum iron silicon-based alloy for room temperature magnetic refrigeration, whose nominal composition is LaFe 11 Co 0.9 Si 1.1 The specific steps of the preparation method are as follows.

[0038] 1) Under the protection of high-purity argon atmosphere, La, Fe, Co, and Si single powders were used as starting materials. 11 Co 0.9 Si 1.1 10g of the mixed powder was placed in a stainless steel ball mill with a stoichiometric ratio, and 350g of Φ6, Φ10 and Φ20 zirconium oxide balls were added. The mixture was first mixed at 200rpm for 30min, and then ball milled at 550rpm for 20h. After ball milling, the precursor powder was taken out under the protection of a high-purity argon atmosphere.

[0039] 2) Under the protection of high-purity argon atmosphere, weigh 4g of the above powder into a graphite mold, and then quickly put the graphite mold into the spark plasma sintering system to start the sintering process. The sintering pressure is 30MPa, the pressure increase time is 5min, and the pressure holding time is 45min; the sintering temperature rise process is to increase the temperature to 1000℃ at 50℃ / min, keep the temperature for 8min, and then air cool to room temperature to obtain a bulk alloy.

[0040] 3) Place the above-mentioned bulk alloy into a clean quartz tube under the protection of high-purity argon atmosphere and evacuate to 1*10 -4 Pa or less. After sealing, place it in a muffle furnace for high-temperature annealing. The annealing process is: first heat up to 850℃ at a rate of 10℃ / min and keep it for 30min, then heat up to 1050℃ at a rate of 5℃ / min and keep it for 4 days. After quenching with ice water, a lanthanum-iron-silicon-based alloy with a high functional phase content is obtained.

[0041] 4) The obtained samples were subjected to phase analysis and magnetic property testing.

[0042] Comparative Example 2: This comparative example discloses a lanthanum iron silicon-based alloy for room temperature magnetic refrigeration, whose nominal composition is La 1.4 Fe 11 Co 0.9 Si1.1 The specific steps of the preparation method are as follows.

[0043] 1) Under the protection of high-purity argon atmosphere, La, Fe, Co, and Si single powders were used as starting materials. 1.4 Fe 11 Co 0.9 Si 1.1 10g of the mixed powder was placed in a stainless steel ball mill with a stoichiometric ratio, and 350g of Φ6, Φ10 and Φ20 zirconium oxide balls were added. The mixture was first mixed at 200rpm for 30min, and then ball milled at 550rpm for 20h. After ball milling, the precursor powder was taken out under the protection of a high-purity argon atmosphere.

[0044] 2) Under the protection of high-purity argon atmosphere, weigh 4g of the above powder, press it into a clean quartz tube, and evacuate it to 1*10 -4 Pa or less. After sealing, place it in a muffle furnace for high-temperature annealing. The annealing process is: first heat up to 850℃ at a rate of 10℃ / min and keep it for 30min, then heat up to 1050℃ at a rate of 5℃ / min and keep it for 4 days. After quenching with ice water, a lanthanum-iron-silicon-based alloy with a high functional phase content is obtained.

[0045] 3) The obtained samples were subjected to phase analysis and magnetic property testing.

[0046] The phase analysis and magnetic property test results of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 are summarized as follows.

[0047] 1. A large number of functional phases were detected in all samples, and the positions of all diffraction peaks of the marked phases were consistent with the corresponding PDF cards. Among them, the functional phase 1:13 phase of Example 1, Example 2 and Example 3 was the main phase, and its content was significantly higher than that of the comparative example.

[0048] 2. The maximum magnetic entropy changes of the samples obtained in Example 1, Example 2, Example 3 and the comparative example under a magnetic field of 2.0 T are 2.77 J×kg -1 ×K -1 @307K, 2.84J×kg -1 ×K -1 @298K, 2.53J×kg -1 ×K -1 @319K and 1.91J×kg -1 ×K -1 @292K.

[0049] The above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here, so the obvious changes or modifications derived are still within the protection scope of the invention.

Claims

1. A lanthanum iron silicon based alloy for room temperature magnetic refrigeration, characterized in that: The chemical formula is La 1+x Fe 11 Co 0.9 Si 1.1 , where x = 0.2 ~ 0.8, the magnetic refrigeration functional phase in the alloy has NaZn 13 Cubic crystal structure.

2. A method for preparing the lanthanum-iron-silicon based alloy as claimed in claim 1, characterized in that: The following steps are involved: 1) Using La, Fe, Co, and Si single-substance powders as starting materials, they are configured according to a stoichiometric ratio, and a precursor powder is obtained by mechanical alloying solid phase reaction under a protective atmosphere; 2) Pre-pressing the precursor powder into a shape and then subjecting it to spark plasma sintering to obtain a bulk alloy; 3) The bulk alloy is encapsulated in a quartz tube under anaerobic conditions, and then subjected to high temperature annealing and quenching treatment to obtain a lanthanum iron silicon based alloy for room temperature magnetic refrigeration.

3. The method for preparing a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration according to claim 2, characterized in that: In the step 1), the purity of the elemental powder is ≥99.5%, and the protective atmosphere is argon, helium, argon-hydrogen mixed gas or helium-hydrogen mixed gas.

4. The method for preparing a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration according to claim 3, characterized in that: The mechanical alloying solid phase reaction adopts a stainless steel or tungsten carbide ball mill body, the grinding ball material is zirconium oxide, aluminum oxide, tungsten carbide or stainless steel, the grinding ball diameter is 6 to 20 mm, the ball-to-material ratio is 10 to 50:1, the ball mill speed is 200 to 550 rpm, and the reaction time is 10 to 24 hours.

5. The method for preparing a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration according to claim 4, characterized in that: In the step 2), the mold material for spark plasma sintering is graphite or tungsten carbide, the sintering pressure is 20-70 MPa, the pressure increase time is 5-15 minutes, and the pressure holding time is 40-80 minutes; the sintering temperature increase process is to increase the temperature to 800-1200°C at a rate of not less than 50°C / min, keep the temperature for 5-30 minutes, and then air cool to room temperature.

6. The method for preparing a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration according to claim 5, characterized in that: The anaerobic condition is a vacuum or inert gas protection condition.

7. The method for preparing a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration according to claim 5, characterized in that: The annealing process is: firstly heating to 700-900°C at a rate of 5-10°C / min and keeping the temperature for 30-60min, then heating to 1000-1200°C at a rate no faster than 5°C / min, and the annealing time is 0.5-16 days.

8. The method for preparing a lanthanum-iron-silicon-based alloy for room temperature magnetic refrigeration according to claim 5, characterized in that: The quenching medium is commercial quenching oil, salt solution or ice-water mixture.