43results about How to "Large magnetic entropy change" patented technology

The invention discloses a fluorine bridged rare earth molecular cluster magnetic refrigeration material and a preparation method thereof. By adopting a solvothermal synthesis method, an air-stable fluorine bridged rare earth molecular cluster magnet is obtained through the reaction of a rare earth metal salt and a fluorine source. Refrigeration material, the unique weak ferromagnetic exchange makes the magnetic entropy change more difficult to saturate under low temperature and low field, and the magnetic refrigeration effect is better. The magnetic refrigeration material of fluorine bridged rare earth molecular cluster is a cluster compound, which is soluble in organic solvents, easy to process, and easy to combine with other materials or refrigeration sites, which can accurately reduce the specified temperature. The temperature in the region has a large magnetic entropy change in the low temperature region, which is an ideal material for low-temperature magnetic refrigeration materials. Due to the weak ferromagnetic exchange between rare earth ions in the cluster compound, the magnetic entropy change of the material at low temperature and low magnetic field is caused. high.

The invention discloses a method for preparing a MnFePSi-based magnetic refrigeration composite material, which belongs to the technical field of magnetic refrigeration materials. The steps include: screening MnFePSi-based magnetic refrigeration material powders with a particle size of 30-120 μm, and performing pickling pretreatment; The powder after the pickling pretreatment is suspended in a mixed solution of copper sulfate and sodium citrate at a certain concentration, and after dip-plating at room temperature for a period of time, it is taken out, cleaned and dried to obtain a core-shell MnFePSi / Cu composite powder material; The composite powder material is hot-pressed and molded under vacuum, the hot-pressing temperature is 950-1100° C., the hot-pressing pressure is 250-500 MPa, and the hot-pressing time is 1-5 minutes. The invention can obtain the MnFePSi / Cu composite magnetic refrigeration material with high thermal conductivity, high compressive strength and excellent magneto-caloric performance, which helps to promote the practical application of this type of magnetic refrigeration material.

The invention relates to a preparation method of a thin film material, and more specifically relates to a preparation method of a La0.7Ca0.25Sr0.05MnO3 ferromagnetic thin film. The preparation method comprises following steps: 1, lanthanum nitrate is added into a mixed solution of glacial acetic acid and ethylene glycol monomethyl ether so as to obtain a solution A; 2, a mixture of calcium acetate and strontium nitrate is added into the mixed solution of glacial acetic acid and ethylene glycol monomethyl ether so as to obtain a solution B; 3, manganese acetate is added into the solution B so as to obtain a solution C; 4, the solution A is mixed with the solution C, and 1 to 10ml of acetic acid is added so as to obtain a La0.7Ca0.25Sr0.05MnO3 solution; 5, a substrate is subjected to ultrasonic processing in acetone and absolute ethyl alcohol successively; 6, the La0.7Ca0.25Sr0.05MnO3 solution is added onto the processed substrate dropwise for spin coating so as to obtain a thin film D; 7, the thin film D is subjected to presintering so as to obtain a thin film E; 8, the thin film E is delivered into a rapid heat treatment furnace for roasting, and is cooled with the rapid heat treatment furnace to room temperature so as to obtain the La0.7Ca0.25Sr0.05MnO3 ferromagnetic thin film. The preparation method is capable of solving problems of existing technology used for preparing the La0.7Ca0.25Sr0.05MnO3 (LCSMO) ferromagnetic thin film that performance is poor, purity is low, density is low, and sintering temperature is too high in preparation processes. The LCSMO ferromagnetic thin film with uniform film thickness and excellent magnetocaloric effects is prepared via modified sol-gel method.

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.

A preparation method for manganese-ferrum-phosphorus-silicon magnetic cooling alloy belongs to the technical field of magnetic material preparation. At first, manganese powder, ferrum powder, phosphorus powder and silicon powder, which serve as raw materials, are mixed according to the mole ratio of 2-x : x : 1-y : y to obtain a nominal composition: Mn2-xFexP1-ySiy, wherein x is larger than or equal to 0.8 and less than or equal to 1.0, and y is larger than or equal to 0.4 and less than or equal to 0.6; then, the high energy ball milling is conducted and the spark plasma sintering is performed under vacuum so as to obtain a manganese-ferrum-phosphorus-silicon alloy block body; and finally, the obtained manganese-ferrum-phosphorus-silicon alloy block body is subjected to heat treatment under the protection of argon so as to obtain the manganese-ferrum-phosphorus-silicon magnetic cooling alloy with an excellent magnetocaloric property. The curie temperature of the manganese-ferrum-phosphorus-silicon magnetic cooling alloy is adjusted through regulating the manganese-ferrum ratio and the phosphorus-silicon ratio within the temperature range from 50 DEG C below zero to 50 DEG C; and the obtained manganese-ferrum-phosphorus-silicon alloy has a greater magnetic entropy change under a 2 tesla field, thereby being beneficial to be used in a room-temperature area magnetic cooling technology.