34 results about "Magnetic transition temperature" patented technology

A magnetocaloric effect heterostructure having a core layer of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, and a constricting material layer coated on at least one surface of the magnetocaloric material core layer. The constricting material layer may enhance the magnetocaloric effect by restriction of volume changes of the core layer during application of a magnetic field to the heterostructure. A magnetocaloric effect heterostructure powder comprising a plurality of core particles of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, wherein each of the core particles is encapsulated within a coating of a constricting material is also disclosed. A method for enhancing the magnetocaloric effect within a giant magnetocaloric material including the step of coating a surface of the magnetocaloric material with a constricting material is disclosed.

The invention discloses a temperature measurement method based on trivalent rare earth ferrous oxides as temperature sensing materials, and belongs to the technical field of thermally responsive materials. The trivalent rare earth ferrous oxides are prepared through a pressureless sintering technology by using trivalent rare earth oxides and ferric oxides as the raw materials. Under the excitation of THz waves, the trivalent rare earth ferrous oxides can radiate out narrow band THz waves, and the center frequency of the narrow band THz waves obviously change along with temperature, so the trivalent rare earth ferrous oxides can be used as the temperature sensing materials and applied to temperature measurement. In the temperature measuring process, a circuit does not need to be led in, and the measurement effect can be good at low temperature. The working temperature range of the temperature sensing materials is wider, theoretically, 0K to antiferromagnetic-paramagnetic transition temperature (650-750K) can be achieved, and the working mode can be in a transmission type or a reflection type. In addition, due to the fact that the THz waves have a good permeance property to most of materials except for metal and strong polar materials, the THz waves can be used for measuring the internal temperature of a closed space.

A method for classifying articles comprising magnetocalorically active material according to magnetic transition temperature comprises providing a source of articles to be classified, the source comprising articles comprising magnetocalorically active materials having differing magnetic transition temperatures, sequentially applying a magnetic field at differing temperatures to the source, the magnetic field being sufficient to exert a magnetic force on the source that is greater than the inertia of a fraction of the articles causing the fraction of the articles to move and produce an article fraction, and collecting the article fraction at each temperature to provide a plurality of separate article fractions of differing magnetic transition temperature, thus classifying the articles comprising magnetocalorically active material according to magnetic transition temperature.

An Er-based amorphous low-temperature magnetic refrigeration material and a preparation method thereof; the general chemical formula of the material is: EraTbAlc, wherein T is one of Fe, Co, Ni or Cu, a is 56-63, and b is 18- 33, c is 16 to 28, and a+b+c=100; method: 1) prepare materials, slightly excessive Er; 2) arc melting under inert gas conditions until it is completely melted, naturally cool after heat preservation, and repeatedly smelt to obtain a uniform composition Alloy ingot; 3) After the surface is cleaned, it is broken into small pieces of alloy ingot; 4) The ingot is completely melted under the condition of inert gas by using an induction melting and throwing belt device, and the belt is thrown after heat preservation to obtain Er-based amorphous low temperature Magnetic refrigeration material; the material of the present invention has a width of 2-2.8mm and a thickness of 35-42m; under a magnetic field change of 0-7T, the magnetic transition temperature is 8-18K, the maximum magnetic entropy change is 12.6-22.5J / kgK, and the magnetic refrigeration capacity is 480- 620J / kg; glass transition temperature 550-640K, crystallization temperature 640-700K, cold liquid phase width 33-65K.

A kind of ferromagnetic metal material, the chemical formula of this ferromagnetic metal material is La 3 MnAs 5 , the crystal structure is hexagonal, the space group is P63 / mcm, and the corresponding space group number is 193. The crystal structure of the ferromagnetic metal material is composed of trimerized MnAs along the c-axis direction 6 Octahedrons are connected by face sharing, forming a one-dimensional chain structure; the ab plane is composed of MnAs 6 The chains form a triangular lattice, the chains are arranged in parallel, and the distance between the chains is the lattice constant a. The ferromagnetic metal material is prepared by the following method: First, the metal La powder, the metal Mn powder and the As powder are fully ground and mixed according to the molar ratio of 3:1:5, and then the ground mixture is pressed into shape by a tablet machine, and finally in the The ferromagnetic metal material is obtained by sintering at a pressure of 3-8GPa and at a temperature of 1200-1400°C. The ferromagnetic metal material of the invention has a typical one-dimensional crystal structure, high magnetic transition temperature and good magnetic anisotropy.

The invention discloses a Gd-Ni-Al-based amorphous and nanocrystalline composite material. The molecular formula of the Gd-Ni-Al-based amorphous and nanocrystalline composite material is GdaNibAlc, wherein a, b and c represent atom contents of corresponding elements, 80<=a<=90, 5.8<=b<=11.6, 4.2<=c<=8.4, and the equation that a+b+c=100 is satisfied. The Gd-Ni-Al-based amorphous and nanocrystalline composite material is of an amorphous / nanocrystalline complex phase structure and has two refrigeration temperature zones and one or two magnetic entropy change platforms, the high-temperature magnetic order temperature is 270 K or above, and the magnetic entropy change under a 5T magnetic field can reach 6.7 J / kg / K. Because magnetic transition temperature intervals are wide, the refrigeration capacity reaches up to 640 J / kg or above, and the Gd-Ni-Al-based amorphous and nanocrystalline composite material is a good magnetic refrigeration material and can be used as a magnetic refrigeration working material in the two intervals of the two refrigeration temperature zones.

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.

The invention discloses a single-phase rhodium-based alloy magnetic refrigeration material, the general formula of which is R 3 Rh 2 , wherein R is any one of the rare earth elements Ho or Er, and its composition is a single phase; the single phase is Y 3 Rh 2 type of crystal structure. The preparation method comprises the following steps: 1) melting of rhodium-based alloy magnetic refrigeration alloy ingot; 2) annealing treatment of rhodium-based magnetic refrigeration material. As a magnetic refrigeration material, it is a two-stage phase change material without thermal hysteresis; the magnetic entropy change value is in the range of 14-20 J kg under a 0-5 T magnetic field ‑1 K ‑1 , the refrigeration capacity is up to 380‑390 J / kg. The invention has the following advantages: good single-phase property; it is a single two-stage phase change material, and only magnetic structure transition occurs near the magnetic transition temperature without thermal hysteresis; it is a very ideal magnetic refrigeration material in low temperature region; and the process is simple, Suitable for industrial production.

The invention discloses a rare-earth cobalt-nickel-based low-temperature amorphous magnetic refrigeration material and a preparation method thereof; the general formula of the material is (Ho a Er b T m c ) 60 co x Ni y , where a is 0~1, b is 0~1, c is 0~1, and a+b+c=1; x is 14~28, y is 12~26, and x+y=40. The method of the present invention is as follows: prepare materials, slightly excessive rare earth; smelt to complete melting under inert gas conditions, naturally cool after heat preservation, and repeatedly smelt to obtain an alloy ingot with uniform composition; after the surface is cleaned, it is broken into small pieces of alloy ingot; The smelting and throwing belt device completely melts the ingot under the condition of inert gas, and throws the belt after heat preservation to obtain a low-temperature amorphous magnetic refrigeration material. The low-temperature amorphous magnetic refrigeration material of the present invention has large magnetic entropy change near its magnetic transition temperature, and has low cost, simple preparation method and good magnetic and thermal reversible properties, and has good application prospects in the field of low-temperature magnetic refrigeration.

The invention discloses a rare-earth palladium-magnesium low-temperature magnetic refrigeration material and a preparation method thereof. The material has the chemical general formula as follows: RE4-Pd-Mg, wherein RE is one or two selected from Ho, Er and Tm, and the atomic ratio of RE to Pd to Mg is equal to 4:1:1; and the preparation method comprises the steps of (1) mixing; (2) sealing an environment by using inert gases; (3) sintering, namely keeping a quartz vessel at the temperature of 850-920 DEG C for 10-20min, then, cooling to 650-720 DEG C, keeping the temperature for 3-5h, and naturally cooling; (4) tabletting and molding; and (5) sealing and annealing, namely sealing the molded material into a quartz tube, annealing at the temperature of 660-700 DEG C for 36-48h, and naturally cooling to obtain a finished product. The material disclosed by the invention is obvious in magnetic entropy change, high in magnetic refrigeration capacity and favorable in magnetic and thermal reversibility; and the change of magnetic transition temperature and the maximum magnetic entropy change value along with components within the temperature range of 5-40K is continuously adjustable. Slow temperature rise and step-by-step reaction are adopted in the method disclosed by the invention, so that Mg volatilization is overcome; and the method is simple in process and easy to realize.

Present invention refers to method determining sparse magnetic semiconductor gallium manganese arsenium ferromagnetic transition thermometric through measuring transport property. It features 1, etching gallium manganese sample to Hall element shape, making electrode adopting indium pressure welding technology, said electrode connected with constant current source and voltmeter, 2, putting Hall element in closed loop refrigeration system, 3, measuring Hall element tangential grinder resistance with thermometric relation curve, determining gallium manganese arsenium conduct characteristic, phase transition temperature from insulativity converting to metallicity, thereby determining gallium manganese arsenium thin-film ferromagnetic transition temperature.

The invention discloses a lanthanum strontium copper manganese sulfur oxygen diluted magnetic semiconductor material of which the chemical formula is La1-xSrxCu1-yMnySO. The invention also discloses a preparation method of the lanthanum strontium copper manganese sulfur oxygen diluted magnetic semiconductor material. The preparation method comprises the following steps of: mixing raw materials; sufficiently grinding under the argon shield; subsequently stamping under certain pressure intensity; sealing an obtained tablet into a vacuum container; putting the container in a tubular furnace to be heated up; and further calcining in constant temperature so as to obtain the lanthanum strontium copper manganese sulfur oxygen diluted magnetic semiconductor material. According to the preparation method, a magnetic moment is introduced by using a method that Cu+ is replaced by Mn2+, subsequently the La is partially replaced by Sr so as to introduce a cavity type carrier, and through such doping, the electrical conductivity and the magnetism of the semiconductor can be controlled well, a diluted magnetic semiconductor in a ZrCuSiAs type structure with higher Curie temperature is obtained, the diluted magnetic semiconductor has very high ferromagnetic transformation temperature, the Curie temperature TC is increased to 199K, and the diluted magnetic semiconductor is free of toxic elements such as As.