| Due to its energy-efficiency and environmentally friendliness,room-temperature magnetic refrigeration technology has great potential in substituting conventional vapor-compression one.La(Fe1-xSix)13 series compounds with NaZn13-type cubic structure are widely concerned because of their low raw material costs,non-toxiccinstituting,continuously adjustable Curie temperature(Tc)and good magnetocaloric effects(MCE),which is one of the most promising candidate for magnetic refrigerant.So,to accelerate the application of rare earth magnetic refrigerant material in both practical and scientific ways,it has great significance to investigate the magnetocaloric and mechanical properties of these materials.In this paper,the MCEs of La0.8Ce0.2Fe11.5-xCoxSi1.5C0.2 alloys,hydrides and their bonded samples of La(Fe1-xSix)13 series compounds are investigated.1.La0.8Ce0.2Fe11.5-xCoxSi1.5C0.2(x=0.3,0.5,0.7)alloys were prepared by doping Ce,Co and C elements.The samples have the same major phase of NaZn13 type cubic structure,and there is a small amount of α-Fe as impurity phase in the samples.With the increase of Co content,the Tc of alloys increases remarkably from 238 to 276 K.the relative cooling ability of three alloy samples were 267.1 J/kg,289.8 J/kg,290.2 J/kg in 2T,the difference between the maximum and minimum values of RCP is less than 9%.Therefore,the Curie temperature of La0.8Ce0.2Fei11.5-xCoxSi1.5C0.2 alloy can be effectively adjusted by adjusting the content of Co element,meanwhile,the alloys can maintaine the high magnetocaloric effect.In addition,it is found that the hysteresis is very small by observing the isothermal magnetization curve and La0.8Ce0.2Fe11-5-xCoxSi1.5C0.2 alloys are potential magnetic refrigeration materials.2.LaFe11.6Si1.4 alloys were crushed to coarse particles for hydrogenation,and then the powder bonded sample of hydride was prepared by powder metallurgy technology.The binder samples were prepared with metal Bi.The samples with binder mass fraction of 5%,10%and 15%were prepared.The samples have the same major phase of NaZn13-type cubic structure before and after bonding,and there is a small amount of α-Fe as impurity phase in their hydride and powder bonded samples.When the sample was bonded with Bi alloy,the Curie temperature of the bonded sample decreased from 298K to 263K compared with that of the hydride,which was due to dehydrogenation in the preparation process.The magnetic entropy change(ΔSm)of the bonded sample decreases compared with that of the hydride.ΔSm of the composites with 5wt%,10wt%and 15wt%Bi metal are 7.8 J/kg K,7.4 J/kg K and 6.1 J/kg K respectively under afield change from 0 to 2 T.By calculation,the effective cooling capacity values of the three kinds of binder are 78J/kg,81.4J/kg and 87.89J/kg,respectively,and the magnetocaloric effect(MCE)are reduced.The maximum compressive strength of bulk LaFe11.6Si1.4 alloy is 155 MPa,and the compressive strength of the composites with 5%,10wt%and 15%wt Bi metal are 263 MPa,306 MPa and.358 Mpa respectively,which is about 70%,97%and 131%,respectively,higher than that of the bulk LaFe11.6Si1.4 alloy.The MCE and Tc of the bonded samples decrease,but the mechanical properties are greatly improved.3.The binder samples were prepared with low-melting alloy Pb-Bi-Cd.The samples with binder mass fraction of 5%,10%and 15%were prepared.The samples have the same major phase of NaZn13-type cubic structure before and after bonding,and there is a small amount of a-Fe as impurity phase in their hydride and powder bonded samples.The Tc and ΔS of the LaFe11.6Si1.4H1.4/Pb-Bi-Cd bonded sample has no change compared with that of hydride.ΔSm of the composites with 5wt%,10wt%and 15wt%Pb-Bi-Cd low-melting alloy are 11.9 J/kg K,11.1 J/kg K and 9.6 J/kg K respectively under afield change from 0 to 2 T.The maximum compressive strength of bulk LaFe11.6Si1.4 alloy is 155 MPa,and the compressive strength of the composites with 5%,10wt%and 15%Bi metal are 259 MPa,344 MPa and 495 MPa,respectively,which is is about 69%,122%and 219%,respectively,higher.than that of the bulk LaFe11.6Si1.4 alloy.The bonded samples not only maintain high magnetocaloric effect,but also have higher mechanical properties.Therefore,the bonded sample LaFe11.6Si1.4H1.4/Pb-Bi-Cd can be effectively applied to the magnetic refrigerator,and it is a very promising magnetic refrigeration material. |
