52 results about "Magnetic phase transition" patented technology

The magnetic material for magnetic refrigeration according to the present invention has an NaZn₁₃-type crystalline structure and comprises iron (Fe) as a principal element (more specifically, Fe is substituted for the position of “Zn”) and hydrogen (H) in an amount of 2 to 18 atomic % based on all constitutional elements. Preferably, the magnetic material for magnetic refrigeration preferably contains 61 to 87 atomic % of Fe, 4 to 18 atomic % of a total amount of Si and Al, 5 to 7 atomic % of La. The magnetic material for magnetic refrigeration exhibits a large entropy change in a room temperature region and no thermal hysteresis in a magnetic phase transition. Therefore, when a magnetic refrigeration cycle is configured using the magnetic material for magnetic refrigeration, a stable operation can be performed.

The invention discloses a magnetic phase transition microcapsule and a preparation method thereof. Nanometer magnetic powder is filled in a microcapsule material to form a shell, and a core material is wrapped in the shell. The magnetic phase transition microcapsule is prepared by the following steps: firstly, adding urea to a formaldehyde solution to dissolve or adding melamine to the formaldehyde solution, or adding the urea to the formaldehyde solution and adding melamine after fully dissolving the urea; then, reacting under stirring at a constant temperature to obtain a prepolymer solution; adding the nanometer magnetic powder to the prepolymer solution and dispersing the solution under ultrasound; dissolving an emulsifying agent in the water, adding an organic phase transition material and cutting and emulsifying the organic phase transition material at a high speed to prepare an emulsion; and uniformly mixing the emulsion and the prepolymer solution after ultrasonic dispersion and reacting under stirring at the constant temperature to obtain the magnetic phase transition microcapsule. The magnetic phase transition microcapsule has magnetism and can reach specific parts under the guide of an external magnetic field while the magnetic phase transition microcapsule is applied to a latent heat type functional fluid so as to control the flow of the fluid.

The invention provides a MnCoGe-based magnetic material with a giant piezocaloric effect as well as a preparation method and application thereof. A chemical general formula of the MnCoGe-based magnetic material is MnCoGe1-xInx, wherein x is more than 0 and less than or equal to 0.03, and the MnCoGe-based magnetic material has a Ni2In type hexagonal structure. The MnCoGe-based magnetic material has the characteristic that martensitic structural phase transition and magnetic phase transition are coupled, and coupling is carried out at the temperature close to room temperature. The MnCoGe-based magnetic material shows an adverse piezocaloric effect under the action of pressure, the amplitude of entropy change under the action of pressure of 3kbar and at the temperature close to room temperature is at least 50J/(Kg.K). Along with change of In content, the magnetic structure coupling temperature Tmstru of the material is adjustable at a wide temperature region close to room temperature, so that the giant piezocaloric effect appears in the wide temperature region close to room temperature. The MnCoGe-based magnetic material has the advantages of simple preparation method, green and environmental-friendly raw materials, high efficiency and energy conservation.

This invention relates to magnetocaloric materials comprising ternary alloys useful for magnetic refrigeration applications. The disclosed ternary alloys are Cerium, Neodymium, and/or Gadolinium based compositions that are fairly inexpensive, and in some cases exhibit only 2^nd order magnetic phase transitions near their curie temperature, thus there are no thermal and structural hysteresis losses. This makes these compositions attractive candidates for use in magnetic refrigeration applications. The performance of the disclosed materials is similar or better to many of the known expensive rare-earth based magnetocaloric materials.

The invention relates to the technical field of high-entropy alloys and discloses a six-element high-entropy alloy with a first-order magnetic phase transition and a preparation method thereof. The six-element high-entropy alloy with the first-order magnetic phase transition has a general formula structure of MgaMnbFecCodNieGdf and is obtained by electrochemical reduction deposition, wherein an electrolyte in the electrochemical reduction deposition comprises the following components: dimethyl sulfoxide, tetraethylammonium hexafluorophosphate, vitamin C, GdCl3, FeCl2, CoCl2, NiCl2, MnCl2 and MgCl2. The prepared alloy is an amorphous alloy, the magnetic transition of the prepared alloy is the magnetic transition caused by strong electron correlation without being restrained by the crystal form transformation of a material, and therefore, the high-entropy alloy has the advantages of large temperature range of magnetic phase transition, controllable critical transition temperature and reversibility.

The invention relates to a method for realizing the mono-disperse modification and the optimal orientation array of a hypovanadic oxide nano wire. The method is as follows: two-step surface function treatment is carried out on a VO2 nano wire by stearic acid and hexadecyl trimethyl ammonium bromide, thus the VO2 nano wire achieves mono-disperse in chloroform and does not precipitate in case of one-month standing; the obtained VO2 nano wire LB film realizes (001) crystal orientation array and local region orientation array, and has quasi-persistent photoconductivity and typical magnetic phase transition and paramagnetic property. The method has simple process, low requirements for equipment, good reproducibility, high controllable degree, meets environmental requirements, and is applicable to the assembly, the integration and the application of sensing, photoelectric and biological novel nano devices.

The invention provides a magnetic recording material compounded by iron-platinum nano-particle self-assembly monofilm and B4C and a preparation method thereof. The preparation method comprises the following steps: the mono-disperse nanometer FePt particles with adjustable grain diameters are spread on an inorganic material substrate to form a self-assembly monofilm structure, a B4C protective layer with thickness of 10-50 nanometers is sputtered on the monofilm by the magnetron sputtering technology, and the B4C protective layer covers and protects the iron-platinum nano-particle monofilm; after high temperature annealing, the complex film magnetic recording material formed by the FePt nano-particles with magnetic phase transition and stable self-assembly is formed. The material has the advantages of good stability, high coercive force, high integration, high repeatability, and the like, which can greatly improve recording density.

The invention relates to a magnetic phase change microcapsule and a preparation method thereof. The preparation method comprises the steps that an oil-in-water emulsion is prepared; a prepolymer solution is prepared; in-situ polymerization is carried out; and a magnetic additive is further added. According to the phase change microcapsule, a wall material of the phase change microcapsule can protect a core material well, and the phase change is enabled to play a better role; and magnetic materials such as Fe/Fe3O4/CrO2 are doped into the wall material to enable the thermal conductivity of themicrocapsule to be increased and the latent heat of phase change to be increased, and the magnetic property is imparted to the magnetic phase change microcapsule, so that the functions of heat conduction, heat preservation and magnetic property are achieved.

The invention discloses a (Hf,Ta)Fe2 magnetic phase transition alloy with a zero thermal expansion effect in a wide temperature range and applications thereof. The atomic expression of the magnetic phase transition alloy is Hf0.87Ta0.13Fe2, and the magnetic phase transition alloy has a zero thermal expansion effect in a temperature range of 15K-250K. Hf0.87Ta0.13Fe2 has an extremely low thermal expansion coefficient (alpha=1.5*10<-7>K<-1>) in a temperature range of 124-250K. In the prior art, an alloy with a zero thermal expansion effect is usually prepared by compounding a negative thermal expansion material and a positive thermal expansion material, the preparation technology is complicated, the equipment requirements are high, thus the cost is high, and the prepared alloy only has a zero thermal expansion effect in a narrow temperature range and a large thermal expansion coefficient, so the practical application of the alloy is very difficult. The provided (Hf,Ta)Fe2 magnetic phasetransition alloy has a zero thermal expansion effect in a wide temperature range and an extremely low thermal expansion coefficient and can effectively meet the use requirements therefore.

A magnetic phase-transformation material with the formula Ni_a−mMn_b−nCo_m+nTi_c is provided, wherein a+b+c=100, 20<a≦90, 5≦b<50, 5≦c≦30, 0≦m≦a, 0≦n≦b, 0<m+n<a+b, and wherein, any one or combination of a, b, c, m, n represent an atomic percentage content. The magnetic phase-transformation material has properties of high toughness, high deformation rate, ferromagnetism and magnetic field-driven martensitic phase transformation, which can be widely used in various fields including high-strength and high-toughness actuators, temperature and/or magnetic sensitive elements, magnetic refrigeration devices and equipments, magnetic heat pump devices, magnetic memories, micro-electromechanical devices and systems, and thermomagnetic power generators or transducers.

A method of working an article includes providing an article containing at least one magnetocalorically active phase having a magnetic phase transition temperature T_c and removing at least one portion of the article while the article remains at a temperature above the magnetic phase transition temperature T_c or below the magnetic phase transition temperature T_c.

The invention discloses a method for the even hydrogenation of NaZn13 structured rare earth-iron cobalt silicon material, which comprises the step: putting rare earth-iron cobalt silicon compound having NaZn13 structure in a hydrogenation furnace for hydrogenation thermal treatment for 2 to 4 hours at the temperature ranging from 400 to 600 DEG C. The method can also comprise the step of putting the rare earth-iron cobalt silicon compound having NaZn13 structure in the hydrogenation furnace for activation once or many times and then for hydrogenation thermal treatment at the temperature ranging from 80 to 600 DEG C for 2 to 4 hours so as to result in the finished product. The rare earth-iron cobalt silicon hybride obtained after hydrogenation according to the preparation method has a crystal structure taking the NaZn13 structure as main phase, which is identical to the crystal structure of original rare earth-iron cobalt silicon compound. The method has the advantages that: the hydrogenation time is short, the rare earth-iron cobalt silicon compound can be certainly subject to even hydrogenation, and all the hybrides of the resultant rare earth-iron cobalt silicon compound have only one magnetic phase transition temperature. Thus, outstanding refrigerating effect of the hybrides of the rare earth-iron cobalt silicon compound during the use thereof in a magnetic refrigerator can be ensured.

The present invention concerns, in particular, a method for obtaining a product with magnetocaloric effect from a single piece of material having a magnetic phase transition, the method comprising irradiation of at least one part of the material with ions, the irradiation being carried out with a suitable flux so that, after the irradiation, the material has various magnetic phase transition temperatures in the various parts of the material.

The invention provides an inelastic neutron scattering data analysis method for a strong correlation material, and the method comprises the following steps: (a) diagonalizing the Hamiltonian quantityof a conventional crystal field, and calculating an eigenvalue A and an eigenvector A; (b) diagonalizing the total Hamiltonian quantity by integrating phonon contribution and magnetoelastic coupling interaction factors, and calculating an eigenvalue B and an eigenvector B; (c) calculating a matrix element according to the eigenvector B obtained in the step (b); and (d) calculating a neutron scattering function according to the eigenvalue B obtained in the step (b) and the matrix element obtained in the step (c), and fitting neutron scattering experimental data to obtain a magnetoelastic coupling coefficient g. The method is suitable for fitting the non-elastic neutron scattering data observed above the magnetic phase transition temperature of the strongly correlated material, and can be used for analyzing the crystal field excitation and phonon coupling phenomenon in the material.