Magnetic Refrigeration Comprehensive Properties Of LaFeSi Hydride And Metal Composites

At present,NaZn₁₃-type La?Fe,Si?₁₃-based alloy with first-order phase transformation has become one of the most promising magnetic refrigeration materials recognized internationally.However,the thermal conductivity,compressive strength,and corrosion resistance of La?Fe,Si?₁₃ hydride are not enough for long-term use on an active magnetic cold storage prototype.This article has carried out research to solve this problem.La_0.9Ce_0.1Fe_11.7-xMn_xSi_1.3?x=0 and 0.35?hydride bulks having a Curie temperature near room temperature were prepared by sintering under a hydrogen pressure of 50 MPa;the mixed powder was refined by ball milling La_0.5Pr_0.5Fe_11.4Si_1.6B_0.2/Al hydrogenated composite samples were prepared by sintering using high-pressure heat treatment equipment;La_0.7Ce_0.3Fe_11.45Mn_0.2Si_1.35 with low?-Fe phase was sintered using high-pressure heat treatment equipment.Hydride bulk,and its surface is chemically plated with a Ni-P film.XRD patterns were used to analyze the phase composition;the scanning electron microscope was used to characterize the sample surface and fractures;the superconducting quantum interferometer was used to measure the magnetism;the electrochemical workstation was used to measure the corrosion parameters.The effects of excessive?-Fe,Al and Ni-P coatings on the comprehensive magnetic cooling properties of La?Fe,Si?₁₃ hydride were studied.La_0.9Ce_0.1Fe_11.7-xMn_xSi_1.3?x=0 and 0.35?hydride bulks were prepared under sintering conditions of 50 MPa,500°C and 48 h.The Curie temperature of La_0.9Ce_0.1Fe_11.7-xMn_xSi_1.3?x=0 and 0.35?bulk was increased to 354 K and 301 K by saturated hydrogen absorption,under the 5 T magnetic field,the magnetic entropy changes are 16.4 J/kg·K and 10.3 J/kg·K.By increasing the sintering pressure from 40 to 50 MPa,the?-Fe phase content increased from 5.1%and 5.8%of the master alloy to 18.5%and 20.1%,and the compressive strength was increased to 245 and 421 MPa.The results show that the sintered La_0.9Ce_0.1Fe_11.7-xMn_x Si_1.3?x=0 and 0.35?hydride bulk has excellent mechanical properties.After sintering at 290?and 40 MPa for 10 minutes,and then the temperature was lowered to 200?and maintained for 1 h,we prepared La_0.5Pr_0.5Fe_11.4Si_1.6B_0.2/Al composite hydrogenated bulk?weight ratio of 5:1,10:1,60:1?.The results show that the compressive strength and thermal conductivity are significantly improved by the compounding of Al powder,but the adiabatic temperature change is greatly reduced due to the formation of the second phase such as Al_0.3Fe₃Si_0.7 and Al₅Fe₂ and the reduction of particle size.The compressive strength of the samples with ratios of 5:1 and 10:1 reached388 and 287 MPa,respectively,which is much larger than the 40 MPa of the 1:60 sample.In addition,the thermal conductivity of the 1:5 sample is 11.1 Wm^-1K^-1,which is 5 times that of the 1:60 sample of 2.3 Wm^-1K^-1.La_0.7Ce_0.3Fe_11.45Mn_0.2Si_1.35 flaky hydride was prepared by sintering at 500?,40MPa and 10 min,and the surface was chemically plated with Ni-P film.The Ni-P film significantly improved the corrosion resistance and thermal conductivity of La_0.7Ce_0.3Fe_11.45Mn_0.2Si_1.35 flaky bulks.The results show that the magnetic entropy changes of the samples coated for 40 min and for 60 min are still maintained at 17.2 J/kg·K and 15.8 J/kg·K under the 5 T magnetic field,which are less than the body's 19.4J/kg·K.The thermal conductivity of the sample coated for 60 min is 5.4 Wm^-1K^-1,and the thermal conductivity of the sample coated for 40 min is 2.8 Wm^-1K^-1,which are both greater than the body's 1.8 Wm^-1K^-1.The self-corrosion current density of the sample coated for 40 min increased by 7 times and the impedance increased by 12 times.