| As a kind of energy-efficient and environmentally-friendly refrigeration technology,magnetic refrigeration technology has attracted people’s attention and is considered to be one of the most promising alternatives to traditional gas compression refrigeration.The key to magnetic refrigeration technology is magnetic refrigeration materials.It is important to explore materials with large MCE that can operate over different temperature ranges,especially near room temperature.La(Fe,Si)13-based alloys are the most interesting,they have excellent magnetic properties and relatively inexpensive price,non-toxic constituent elements.La(Fe,Si)13 alloy is based on the face-centered cubic NaZn13 structure(space group is Fm-3c),and it is considered to be one of the most promising room temperature magnetic refrigeration materials.In this paper,the effects of Co content on the crystal structure and MCE of Pr and Tb doped La(Fe,Si)13 based magnetic refrigeration materials were investigated.In addition,the mechanical properties and MCEs of low melting point alloy bonded LaFe11.6Si1.4H1.6/Sn69.5Bi30Cu0.5 composites was also investigated.In this paper,the addition of Co element with x=0.3,0.5,0.7 in the preparation of La0.8Rr0.2Fe11.8-xCoxSi1.2C0.2(x=0.3,0.5,0.7)alloys is doped with Pr and C elements.The crystal structure and magnetocaloric effect of the La(Fe,Si)13-based magnetic refrigeration materials were investigated.For the alloy samples with different Co element content,the main phase is the NaZn13 phase,and a small amount of second phase α-Fe is formed.With the increase of Co content,the lattice constant of the series alloys decreased slightly,and the Tc increased from 241 K to 261 K and 288 K.At 0-7 T,the magnetic entropy change decreased from 16.07 J/kg K to 14.68 J/kg K and 10.18 J/kg K.The isothermal magnetic entropy of the sample gradually decreased,but the cooling temperature range of the sample became wider,and the half width δT became larger.The value of RCP remains essentially unchanged.Adjusting the properties of the La0.8Pr0.2Fe11.8-xCoxSi1.2C0.2 alloy by Co element can not only improve the Tc of the material,but also maintain the high cooling capacity of the alloy.Finally,the critical index of the La0.8Pr0.2Fe11.1Co0.7Si1.2C0.2 sample obtained by calculation is close to the Hesienberg model(short-range interaction).A series of Lao.9Tb0.1Fe11.4-xCoxSi1.6(x=0.3,0.5,0.7)alloys were prepared by doping Tb and Co elements.The main phases of the three samples are all NaZn13 type cubic structure and contain a small amount of second phase Tb2Fe17.With the increase of Co content,the lattice constant of La0.9Tb0.1Fe11.4-xCoxSi1.6(x=0.3,0.5,0.7)series alloys decreased slightly,and the Tc increased continuously,which was 243K,263K and 284K,respectively.At the same time,the isothermal magnetic entropy change of the sample also gradually decreased.At 0-7 T,the magnetic entropy of the sample decreased from 12.99 J/kg K to 10.85 J/kg K and 9.67 J/kg K,but the cooling temperature range of the sample became wider and the half width was half,δT becomes larger.Adjusting the properties of the La0.9Tb0.1Fe11.4-xCoxSi1.6 alloy by Co element can not only improve the Tc of the material,but also maintain the high cooling capacity of the alloy.Finally,the critical index of the La0.9Tb0.1Fe10.7Co0.7Si1.6 sample obtained by calculation is close to the mean-field model(long-range interaction).In addition,this paper describes the preparation of different mass fractions of LaFe11.6Si1.4H1.6/Sn69.5Bi3oCu0.5 composites by hot pressing,and the mechanical properties and magnetocaloric properties of all samples were measured.The microstructure of the 14.8 wt.%sample showed that the Sn69.5Bi30Cu0.5 alloy was filled in the gap of the LaFe11.6Si1.4H1.6 particles.The maximum compressive strength with 8.6 wt.%,14.8 wt.%and 19.4 wt.%is 259 MPa,344 MPa and 361 MPa,which is larger than the bulk LaFe11.6Si1.4 alloy.The compressive strength was increased by about 67%,115%and 133%,respectively.With the increase of the low melting point alloy,the maximum magnetic entropy change of the sample at 0-2 T was 8.2 J/kg K,8.5 J/kg K and 7.8 J/kg K,respectively.Compared with LaFe11.6Si1.4H1.6,the magnetothermal performance of the composites is reduced,but compared with other room temperature magnetic refrigeration materials,the bonded sample not only have higher magnetic entropy change,but also the ΔTadmax reached 2.89 K,3.1 K and 3.12 K at Tc,respectively.Therefore,the bonded samples LaFe11.6Si1.4H1.6/Sn69.5Bi30Cu0.5 can be effectively applied to the magnetic refrigerator,which is a very promising magnetic refrigeration material. |
PDF Full Text Request