Magnetic field induced entropy change was investigated for La-Fe based NaZn13-type compounds with magnetic first-order phase transition. In view of magnetic refrigeration at room temperature, the developing of the mat...Magnetic field induced entropy change was investigated for La-Fe based NaZn13-type compounds with magnetic first-order phase transition. In view of magnetic refrigeration at room temperature, the developing of the materials and the understanding of the entropy change were., reviewed. For La-Fe-Si compounds, the entropy change about 29 J·kg^- 1·K^-1 was obtained at 190 K under the magnetic field of 5 T.While a large entropy change of about 15 J·kg^-1·K^-1 near room temperature under 5 T can be obtained by the substitution of Co for Fe in the compounds. It is found that the entropy change is mainly composed of that contributed from magnetic ordering and crystal lattice. The large entropy change consumed by lattice contribution is mainly due to the magnetic ordering one.展开更多
Effects of Nd-doping on the magnetic properties and magnetocaloric effects （MCEs） of NdxLa1-xFe11.5Al1.5 have been investigated. Substitution of Nd leads to a weakening of the antiferromagnetic （AFM） coupling and ...Effects of Nd-doping on the magnetic properties and magnetocaloric effects （MCEs） of NdxLa1-xFe11.5Al1.5 have been investigated. Substitution of Nd leads to a weakening of the antiferromagnetic （AFM） coupling and an enhancement of the ferromagnetic （FM） coupling. This in turn results in a complex magnetic behaviour for Nd0.2La0.8Fe11.5Al1.5 characterized by the occurrence of two phase transitions at ～188 K （PM AFM） and ～159 K （AFM-FM）. As a result, a table-like MCE （9 J/kg.K） is found in a wide temperature range （160-185 K） for a field change of 0-5T around the transition temperature, as evidenced by both the magnetic and calorimetric measurements. Based on the analysis of low-temperature heat capacity, it is found that the AFM-FM phase transition modifies the electron density significantly, and the major contribution to the entropy change comes from the electronic entropy change.展开更多
The magnetic properties and the phase transformation of the partial substitution of Pr for La in LaFe11.4Si1.6 have been investigated by the means of X-ray diffraction (XRD) and vibrating sample magnetic (VSM). The re...The magnetic properties and the phase transformation of the partial substitution of Pr for La in LaFe11.4Si1.6 have been investigated by the means of X-ray diffraction (XRD) and vibrating sample magnetic (VSM). The results indicated that the single phase NaZn13-type cubic structure is stabilized for the compound La0.8Pr0.2Fe11.4Si1.6 and large values of the isothermal magnetic entropy change SM around the curie temperature TC～194 K in relative low magnetic fields. The maximum value︱SM︱max～37.07 J/kg·K-1 under a field of 1.5 T. Such large MCEs are attributed to the sharp change of the magnetization at the Curie temperature, the field-induced IEM transition and a strong temperature dependence of the critical field BC.展开更多
The metallic Na has been regarded as the most promising anode for next-generation sodium metal batteries(SMBs)owing to its high theoretical specific capacity,low redox potential,and low cost.The practical applications...The metallic Na has been regarded as the most promising anode for next-generation sodium metal batteries(SMBs)owing to its high theoretical specific capacity,low redox potential,and low cost.The practical applications of Na metal,however,have still been severely hindered by the uncontrolled sodium dendrites growth during Na deposition and stripping processes,which leads to low Coulombic efficiency and poor cycling stability.In this study,sub-nano zinc oxide(ZnO)uniformly dispersed in threedimensional(3D)porous nitrogen-doped(N-doped)carbon nanocube(ZnO@NC)was acquired as a stable host for dendrite-free Na metal anode.Benefiting from the in-situ electrochemically formed sodiophilic nucleation site(NaZn13 alloy)and the enriched pore structure,rapid and uniform sodium deposition behavior can be performed.As expected,the ZnO@NC electrode delivers impressive electrochemical performance,an ultra-high areal capacity of 20 mAh·cm−2 in the half-cell can be maintained for 2,000 h.In the symmetrical-cell,it can also exhibit up to 3,000 h at 3 mA·cm−2 and 3 mAh·cm−2 with low polarization potential.Furthermore,in the full-cell that matches with Prussian blue(PB)cathode,the Na@ZnO@NC anode performs the outstanding long-cycling and rate performance.Therefore,this work provides an effective strategy to inhibit the growth of Na dendrites for the development of high-safety and long-cycling SMBs.展开更多
文摘Magnetic field induced entropy change was investigated for La-Fe based NaZn13-type compounds with magnetic first-order phase transition. In view of magnetic refrigeration at room temperature, the developing of the materials and the understanding of the entropy change were., reviewed. For La-Fe-Si compounds, the entropy change about 29 J·kg^- 1·K^-1 was obtained at 190 K under the magnetic field of 5 T.While a large entropy change of about 15 J·kg^-1·K^-1 near room temperature under 5 T can be obtained by the substitution of Co for Fe in the compounds. It is found that the entropy change is mainly composed of that contributed from magnetic ordering and crystal lattice. The large entropy change consumed by lattice contribution is mainly due to the magnetic ordering one.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 50571112 and 50731007)the National Basic Research Program of China (Grant No 2006CB601101)the Basic Research Program of Chinese Academy of Science (Grant No KJCX2-YW-W02s)
文摘Effects of Nd-doping on the magnetic properties and magnetocaloric effects （MCEs） of NdxLa1-xFe11.5Al1.5 have been investigated. Substitution of Nd leads to a weakening of the antiferromagnetic （AFM） coupling and an enhancement of the ferromagnetic （FM） coupling. This in turn results in a complex magnetic behaviour for Nd0.2La0.8Fe11.5Al1.5 characterized by the occurrence of two phase transitions at ～188 K （PM AFM） and ～159 K （AFM-FM）. As a result, a table-like MCE （9 J/kg.K） is found in a wide temperature range （160-185 K） for a field change of 0-5T around the transition temperature, as evidenced by both the magnetic and calorimetric measurements. Based on the analysis of low-temperature heat capacity, it is found that the AFM-FM phase transition modifies the electron density significantly, and the major contribution to the entropy change comes from the electronic entropy change.
基金Project supported by The National Natural Science Foundation of China (50164003)
文摘The magnetic properties and the phase transformation of the partial substitution of Pr for La in LaFe11.4Si1.6 have been investigated by the means of X-ray diffraction (XRD) and vibrating sample magnetic (VSM). The results indicated that the single phase NaZn13-type cubic structure is stabilized for the compound La0.8Pr0.2Fe11.4Si1.6 and large values of the isothermal magnetic entropy change SM around the curie temperature TC～194 K in relative low magnetic fields. The maximum value︱SM︱max～37.07 J/kg·K-1 under a field of 1.5 T. Such large MCEs are attributed to the sharp change of the magnetization at the Curie temperature, the field-induced IEM transition and a strong temperature dependence of the critical field BC.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Nos.52102222,51920105004,U1805254,and U1705255)Guangzhou Key Laboratory of Low Dimensional Materials and Energy Storage Devices(No.201905010002).
文摘The metallic Na has been regarded as the most promising anode for next-generation sodium metal batteries(SMBs)owing to its high theoretical specific capacity,low redox potential,and low cost.The practical applications of Na metal,however,have still been severely hindered by the uncontrolled sodium dendrites growth during Na deposition and stripping processes,which leads to low Coulombic efficiency and poor cycling stability.In this study,sub-nano zinc oxide(ZnO)uniformly dispersed in threedimensional(3D)porous nitrogen-doped(N-doped)carbon nanocube(ZnO@NC)was acquired as a stable host for dendrite-free Na metal anode.Benefiting from the in-situ electrochemically formed sodiophilic nucleation site(NaZn13 alloy)and the enriched pore structure,rapid and uniform sodium deposition behavior can be performed.As expected,the ZnO@NC electrode delivers impressive electrochemical performance,an ultra-high areal capacity of 20 mAh·cm−2 in the half-cell can be maintained for 2,000 h.In the symmetrical-cell,it can also exhibit up to 3,000 h at 3 mA·cm−2 and 3 mAh·cm−2 with low polarization potential.Furthermore,in the full-cell that matches with Prussian blue(PB)cathode,the Na@ZnO@NC anode performs the outstanding long-cycling and rate performance.Therefore,this work provides an effective strategy to inhibit the growth of Na dendrites for the development of high-safety and long-cycling SMBs.
