| Magnetic refrigeration based on the magnetocaloric effect(MCE)is an environmentfriendly,high-efficiency technology.But its commercial application is limited due to its high cost of magnetocaloric materials and high volume of the external magnetic field device.However,the form for magnetic refrigeration in biomedical applications is coating or metal film with a relatively low cost.In addition,price is not a major consideration which promise that biomedical applications will be an ideal application for magnetocaloric effect.Magnetic drug targeting by controlling the phase transition of thermosensitive polymer,which means a negative magnetocaloric effect,is a new method for postoperative treatment of implants.Low magnetic field intensity is harmless to human tissues or cells and has a strong magnetic field penetrates,which is expected to realize the automatic and accurate control of local cooling Among them,Fe-Rh alloy with large magneto-thermal effect and stability of microstructure will be the key technology to the application of magnetic refrigeration in biomedical science.The structure,magnetic and magneto-thermal effects of Fe-Rh alloy particles prepared by liquid phase coreduction,room temperature solid-phase method,and high-temperature solid-phase method were investigated.Through preparation technology optimization,composition optimization,optimization annealing technology,studied the excitation and the demagnetization process of the change of the sample under the steady-state of magnetic,annealing for the regulation of alloy structure,obtained the first order antiferromagnetic ferromagnetic phase change characteristic and the magnetocaloric effect of Fe-Rh alloy particles,and the preparation process of green environmental protection can satisfy the Fe-Rh alloy in targeted for the prescription application below.The main research results of this paper are as follows:1.In the process of preparing Fe-Rh alloy particles by liquid phase reduction,the unannealed Fe-Rh sample is the disordered phase structure of face-centered cube.After annealing,the disordered phase of the face-centered cube disappears and the CsCl structural phase of body-centered cube appears.Superlattice diffraction peaks were observed in the annealed samples,which indicated that the The CsCl type body centered cubic phase is highly ordered.Fe-Rh samples prepared by liquid phase reduction still retain some ferromagnetism at low temperature after annealing.The magnetization increases with the increase of Rh atomic content,which showed that the increase of Rh atom content was beneficial to the inhibition of the presence of the ferromagnetic aqueous phase at low temperature.2.The Fe-Rh alloy particles prepared by solid-phase method at room temperature are characterized by simple preparation method and low requirement for experimental conditions.Fe3+ is difficult to fully reduce to Fe atoms,but is lost as Fe2+ due to the fast experiment process.As a result,the composition of Fe Rh alloy particle is difficult to control.But the structure of the alloy can be effectively regulated through the subsequent annealing process,3.Fe-Rh alloy particles with antiferromagnetic ferromagnetic first order phase transition and magnetothermal effect were prepared successfully by high temperature solid state method.The Fe-Rh alloy with a single phase is more easily obtained with the ratio of 1:1.Simultaneous annealing is necessary for the elimination of hydrogen atoms.With a higher annealing temperature and a longer annealing time,the content of antiferromagnetic phase in the sample and the magnetothermal effect will increase.The preparation of Fe-Rh alloy microparticles with oxide as the raw material can better regulate the composition of the sample.This study is conducive to deepening the understanding of the phase change and magnetothermal effect of Fe-Rh alloy,and is of great significance in promoting the application of magnetothermal effect in the high-end biomedical field. |
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