Magnetocaloric Effect Of Fe-based Bulk Metallic Glasses

Different from the traditional refrigeration technology,magnetic refrigeration is a new cooling mode based on magnetocaloric effect,which has the advantages of high efficiency,low noise,green and pollution-free.Fe-based bulk metallic glasses（BMGs）have become one of the hotspots of magnetocaloric materials in recent years due to their low hysteresis and thermal hysteresis,good corrosion resistance and low cost.The work of this thesis focuses on the magnetic properties of Fe-based BMGs,including the following two parts:（1）Study on magnetocaloric properties of Fe₇1Mo₉P₁3C₇ BMG with near room-temperature magnetocaloric effect.In this part of work,Fe₇1Mo₉P₁3C₇BMG with a critical dimension of 1.3 mm are successfully prepared by fluxing and J-Quenching techniques.The saturation magnetization of the Fe₇1Mo₉P₁3C₇BMG is 0.55 T.At the maximum applied magnetic field of 5 T,the peak value of the magnetic entropy change of this BMG is 2.57 J/（kg K）,and the cooling capacity is305.57 J/kg.Compared with other Fe-based amorphous alloys,the magnetocaloric properties of Fe₇1Mo₉P₁3C₇ are not outstanding,which may be caused by the antiferromagnetic coupling between Fe atoms and Mo atoms.However,the Curie temperature of Fe₇1Mo₉P₁3C₇ BMG is as low as 355 K,which is close to room temperature,so it is expected to be used for room temperature magnetic refrigeration,which has great significance in practical applications.（2）StudyonmagnetocaloricpropertiesofFe₂5Co₂5Ni₂5Mo₅P₁0B₁0high-entropy bulk metallic glass（HE-BMG）.Fe₂5Co₂5Ni₂5Mo₅P₁0B₁0HE-BMG rod with a diameter of about 1.2 mm is successfully prepared by fluxing purificationandJ-quenchingtechniques.TheCurie temperatureofthe Fe₂₅Co₂₅Ni₂₅Mo₅P₁₀B₁₀0 HE-BMG is 560 K,the peak value of the magnetic entropy change and the refrigerant capacity are 0.80 J/（kg K）and 135.4 J/kg under the applied field of 1.5 T,1.88 J/（kg K）and 310.2 J/kg under the applied field of 5 T,respectively.Comparedwithothertransitionmetal-basedBMGs,thepresent Fe₂5Co₂5Ni₂5Mo₅P₁0B₁0 HE-BMG does not exhibit a relatively larger magnetic entropy change.However,the high-entropy effect seems enlarge the wider full width at half maximum temperature of the magnetic entropy change curve,thus a larger refrigerant capacity.