In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an incr...In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an increase of the aluminum content, the compounds exhibit successively an antiferromagnetic （AFM） state, a ferromagnetic （FM） state, and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13 -xAlx can be converted to an FM one by substituting Si for A1, Co for Fe, and magnetic rare-earth R for La, or introducing interstitial C or H atoms. However, low doping levels lead to FM clusters embedded in an AFM matrix, and the resultant compounds can undergo, under appropriate applied fields, first an AFM-FM and then an FM-AFM phase transition while heated, with significant magnetic relaxation in the vicinity of the transition temperature. The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co, C, or H, and a strong magnetocaloric effect can be obtained around the transition temperature. For example, for the LaFel 1.5All.5Co.2Hl.o compound, the maximal entropy change reaches 13.8 J.kg-1.K-1 for a field change of 0-5 T, occurring around room temperature. It is 42% higher than that of Gd, and therefore, this compound is a promising room-temperature magnetic refrigerant.展开更多
Due to the hydrogen embrittlement effect,La(Fe,Si)_(13)-based hydrides can only exist in powder form,which limits their practical application.In this work,ductile and thermally conductive Al metal was homogeneously mi...Due to the hydrogen embrittlement effect,La(Fe,Si)_(13)-based hydrides can only exist in powder form,which limits their practical application.In this work,ductile and thermally conductive Al metal was homogeneously mixed with La_(0.5)Pr_(0.5)Fe_(11.4)Si_(1.6)B_(0.2)using the ball milling method.Then hydrogenation and compactness shaping of the magnetocaloric composites were performed in one step via a sintering process under high hydrogen pressure.As the Al content reached 9 wt.%,the La_(0.5)Pr_(0.5)Fe_(11.4)Si_(1.6)B_(0.2)H_(y)/Al composite showed the mechanical behavior of a ductile material with a yield strength of~44 MPa and an ultimate strength of 269 MPa accompanied by a pronounced improvement in thermal conductivity.Due to the ease of formation of Fe-Al-Si phases and the several micron and submicron sizes of the composite particles caused by ball milling process,the magnetic entropy change of the composites was substantially reduced to~1.2 J/kg·K-1.5 J/kg·K at 0 T-1.5 T.展开更多
Magnetic properties and structures in La1-zPrz(Fe0.895–xCoxSi0.105)13 (x=0.07, 0.08; z=0, 0.2, 0.4) compounds were investigated. When Pr and Co substituted for La and Fe, the Curie temperature of the compounds was ad...Magnetic properties and structures in La1-zPrz(Fe0.895–xCoxSi0.105)13 (x=0.07, 0.08; z=0, 0.2, 0.4) compounds were investigated. When Pr and Co substituted for La and Fe, the Curie temperature of the compounds was adjusted to around room temperature. The magnetic phase transition was driven from first-order to second-order due to Co substitution. As a second-order phase transition material, the MCE of La0.6Pr0.4(Fe0.825Co0.07Si0.105)13, whose relative cooling power was 175 J/kg under a field change of 2 T, ...展开更多
La（Fe, Si）13-based compounds have been considered as promising candidates for magnetic refrigerants particularly near room temperature. Herein we review recent progress particularly in the study of the effects of in...La（Fe, Si）13-based compounds have been considered as promising candidates for magnetic refrigerants particularly near room temperature. Herein we review recent progress particularly in the study of the effects of interstitial H and/or C atoms on the magnetic and magnetocaloric properties of La（Fe, Si）13 compounds. By introducing H and/or C atoms, the Curie temperature Tc increases notably with the increase of lattice expansion which makes the Fe 3d band narrow and reduces the overlap of the Fe 3d wave functions. The first-order itinerant-electron metamagnetic transition is conserved and the MCE still remains high after hydrogen absorption. In contrast, the characteristic of magnetic transition varies from first-order to second-order with the increase of C concentration, which leads to remarkable reduction of thermal and magnetic hysteresis. In addition, the introduc- tion of interstitial C atoms promotes the formation of NaZnl3-type （1：13） phase in La（Fe, Si）13 compounds, and thus reducing the annealing time significantly from 40 days for LaFe11.7Sil.3 to a week for LaFell.7Sil.3C0.2. The pre-occupied interstitial C atoms may depress the rate of hydrogen absorption and release, which is favorable to the accurate control of hydrogen content. It is found that the reduction of particle size would greatly depress the hysteresis loss and improve the hydrogenation process. By the incorporation of both H and C atoms, large MCE without hysteresis loss can be obtained in La（Fe, Si）13 compounds around room temperature, for instance, La0.7Pr0.3Fe115Si15C0.2H12 exhibits a large IASM[ of 22.1 J/（kg＇K） at Tc = 321 K without hysteresis loss for a field change of 0-5 T.展开更多
We present a simple hot press-based method for processing La(Fe,Si)13-based compounds consisting of La–Fe–Co–Si–C particles and phenolic resin. The magnetic entropy change △S per unit mass for the La Fe_(10.87)Co...We present a simple hot press-based method for processing La(Fe,Si)13-based compounds consisting of La–Fe–Co–Si–C particles and phenolic resin. The magnetic entropy change △S per unit mass for the La Fe_(10.87)Co_(0.63)Si_(1.5)C_(0.2)/phenolic resin compounds have nearly the same magnitude with the base materials. With the content of phenolic resin of 5.0 wt%, the compound conductivity is 3.13 W·m^(-1)·K^(-1). In order to measure the cooling performance of La(Fe,Si)13-based compounds,the La(Fe_(11.6-x)Co_(x))Si_(1.4)C_(0.15)(x =0.60, 0.65, 0.75, 0.80, 0.85)/phenolic resin compounds were pressed into thin plates and tested in a hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling cycle refrigeration effect. The test results showed that a maximum cooling power of 41 W was achieved over a temperature span of 30 K.展开更多
Data-mining techniques using machine learning are powerful and efficient for materials design, possessing great potential for discovering new materials with good characteristics. Here, this technique has been used on ...Data-mining techniques using machine learning are powerful and efficient for materials design, possessing great potential for discovering new materials with good characteristics. Here, this technique has been used on composition design for La（Fe,Si/Al）（13）-based materials, which are regarded as one of the most promising magnetic refrigerants in practice. Three prediction models are built by using a machine learning algorithm called gradient boosting regression tree（GBRT） to essentially find the correlation between the Curie temperature（TC）, maximum value of magnetic entropy change（（？SM）（max））,and chemical composition, all of which yield high accuracy in the prediction of TC and（？SM）（max）. The performance metric coefficient scores of determination（R^2） for the three models are 0.96, 0.87, and 0.91. These results suggest that all of the models are well-developed predictive models on the challenging issue of generalization ability for untrained data, which can not only provide us with suggestions for real experiments but also help us gain physical insights to find proper composition for further magnetic refrigeration applications.展开更多
A comparative study of Na2MoO4·2H2O and Na2HPO4·12H2O as inhibitors for magnetic refrigeration material La-Fe-Co-Si compound corrosion in distilled water at room temperature was carried out.Moreover,the inhi...A comparative study of Na2MoO4·2H2O and Na2HPO4·12H2O as inhibitors for magnetic refrigeration material La-Fe-Co-Si compound corrosion in distilled water at room temperature was carried out.Moreover,the inhibiting behavior of the mixture of Na2MoO4·2H2O and Na2HPO4·12H2O was investigated.Potentiodynamic polarization curves and electrochemical impedance spectroscopy （EIS） measurements were applied to study the corrosion behavior of the compound in the absence or presence of different concentrations of these inhibitors under the same experimental conditions.The study revealed that the mixture of 3.0×10–3 kg/L Na2MoO4·2H2O and 5.0×10–3 kg/L Na2HPO4·12H2O was the best inhibitor reaching the value of inhibition efficiency （ε%） up to 93.9%.Polarization curves showed that the studied compounds acted as anodic inhibitors.The potential of zero charge （PZC） of La-Fe-Co-Si compound was determined in distilled water in the absence of the studied inhibitors.Corrosion inhibition mechanisms for inhibitors were proposed in this work.展开更多
In this paper, we study the effects of Pr substitution on the hydrogenating process and magnetocaloric properties of La（1-x）PrxFe11.4Si1.6Hy hydrides. The powder x-ray diffraction patterns of the La1-xPrxFe11.4Si1.6...In this paper, we study the effects of Pr substitution on the hydrogenating process and magnetocaloric properties of La（1-x）PrxFe11.4Si1.6Hy hydrides. The powder x-ray diffraction patterns of the La1-xPrxFe11.4Si1.6 and its hydrides show that each of the alloys is crystallized into the single phase of cubic Na Zn13-type structure. There are hydrogen-absorbing plateaus under 0.4938 MPa and 0.4882 MPa in the absorbing curves for the La0.8Pr0.2Fe11.4Si1.6 and La0.6Pr0.4Fe11.4Si1.6 compounds. The releasing processes lag behind the absorbing process, which is obviously different from the coincidence between absorbing and releasing curves of the La Fe11.4Si1.6 compound. The remnant hydrogen content for La0.6Pr0.4Fe11.4Si1.6 is significantly more than that for La0.8Pr0.2Fe11.4Si1.6 after hydrogen desorption, indicating that more substitutions of Pr for La are beneficial to retaining more hydrogen atoms in the alloys. The values of maximum magnetic entropy change are 14.91 J/kg·K and 17.995 J/kg·K for La0.8Pr0.2Fe11.4Si1.6H0.13 and La0.6Pr0.4Fe11.4Si1.6H0.87,respectively.展开更多
基金Project supported by the National Natural Science Foundation of Chinathe Key Research Program of the Chinese Academy of Sciences+1 种基金the National Basic Research Program of Chinathe National High Technology Research and Development Program of China
文摘In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an increase of the aluminum content, the compounds exhibit successively an antiferromagnetic （AFM） state, a ferromagnetic （FM） state, and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13 -xAlx can be converted to an FM one by substituting Si for A1, Co for Fe, and magnetic rare-earth R for La, or introducing interstitial C or H atoms. However, low doping levels lead to FM clusters embedded in an AFM matrix, and the resultant compounds can undergo, under appropriate applied fields, first an AFM-FM and then an FM-AFM phase transition while heated, with significant magnetic relaxation in the vicinity of the transition temperature. The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co, C, or H, and a strong magnetocaloric effect can be obtained around the transition temperature. For example, for the LaFel 1.5All.5Co.2Hl.o compound, the maximal entropy change reaches 13.8 J.kg-1.K-1 for a field change of 0-5 T, occurring around room temperature. It is 42% higher than that of Gd, and therefore, this compound is a promising room-temperature magnetic refrigerant.
基金Project supported by the Open Research Project of State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilizationthe National Natural Science Foundation of China(Grant Nos.51771197 and 52171187)。
文摘Due to the hydrogen embrittlement effect,La(Fe,Si)_(13)-based hydrides can only exist in powder form,which limits their practical application.In this work,ductile and thermally conductive Al metal was homogeneously mixed with La_(0.5)Pr_(0.5)Fe_(11.4)Si_(1.6)B_(0.2)using the ball milling method.Then hydrogenation and compactness shaping of the magnetocaloric composites were performed in one step via a sintering process under high hydrogen pressure.As the Al content reached 9 wt.%,the La_(0.5)Pr_(0.5)Fe_(11.4)Si_(1.6)B_(0.2)H_(y)/Al composite showed the mechanical behavior of a ductile material with a yield strength of~44 MPa and an ultimate strength of 269 MPa accompanied by a pronounced improvement in thermal conductivity.Due to the ease of formation of Fe-Al-Si phases and the several micron and submicron sizes of the composite particles caused by ball milling process,the magnetic entropy change of the composites was substantially reduced to~1.2 J/kg·K-1.5 J/kg·K at 0 T-1.5 T.
基金Project supported by the National Basic Research Program of China (2006CB601101)the National High Technology Research and Development Program of China (2007AA03Z440)the National Natural Science Foundation of China (50731007)
文摘Magnetic properties and structures in La1-zPrz(Fe0.895–xCoxSi0.105)13 (x=0.07, 0.08; z=0, 0.2, 0.4) compounds were investigated. When Pr and Co substituted for La and Fe, the Curie temperature of the compounds was adjusted to around room temperature. The magnetic phase transition was driven from first-order to second-order due to Co substitution. As a second-order phase transition material, the MCE of La0.6Pr0.4(Fe0.825Co0.07Si0.105)13, whose relative cooling power was 175 J/kg under a field change of 2 T, ...
基金supported by the National Natural Science Foundation of Chinathe Hi-Tech Research and Development program of China+2 种基金the Key Research Program of the Chinese Academy of Sciencesthe National Basic Research Program of Chinathe Fundamental Research Funds for the Central Universities
文摘La（Fe, Si）13-based compounds have been considered as promising candidates for magnetic refrigerants particularly near room temperature. Herein we review recent progress particularly in the study of the effects of interstitial H and/or C atoms on the magnetic and magnetocaloric properties of La（Fe, Si）13 compounds. By introducing H and/or C atoms, the Curie temperature Tc increases notably with the increase of lattice expansion which makes the Fe 3d band narrow and reduces the overlap of the Fe 3d wave functions. The first-order itinerant-electron metamagnetic transition is conserved and the MCE still remains high after hydrogen absorption. In contrast, the characteristic of magnetic transition varies from first-order to second-order with the increase of C concentration, which leads to remarkable reduction of thermal and magnetic hysteresis. In addition, the introduc- tion of interstitial C atoms promotes the formation of NaZnl3-type （1：13） phase in La（Fe, Si）13 compounds, and thus reducing the annealing time significantly from 40 days for LaFe11.7Sil.3 to a week for LaFell.7Sil.3C0.2. The pre-occupied interstitial C atoms may depress the rate of hydrogen absorption and release, which is favorable to the accurate control of hydrogen content. It is found that the reduction of particle size would greatly depress the hysteresis loss and improve the hydrogenation process. By the incorporation of both H and C atoms, large MCE without hysteresis loss can be obtained in La（Fe, Si）13 compounds around room temperature, for instance, La0.7Pr0.3Fe115Si15C0.2H12 exhibits a large IASM[ of 22.1 J/（kg＇K） at Tc = 321 K without hysteresis loss for a field change of 0-5 T.
基金supported by the National Natural Science Foundation of China (Grant Nos. 52171054 and 52171195)the National Natural Science Foundation for Distinguished Young Scholars (Grant No. 51925605)。
文摘We present a simple hot press-based method for processing La(Fe,Si)13-based compounds consisting of La–Fe–Co–Si–C particles and phenolic resin. The magnetic entropy change △S per unit mass for the La Fe_(10.87)Co_(0.63)Si_(1.5)C_(0.2)/phenolic resin compounds have nearly the same magnitude with the base materials. With the content of phenolic resin of 5.0 wt%, the compound conductivity is 3.13 W·m^(-1)·K^(-1). In order to measure the cooling performance of La(Fe,Si)13-based compounds,the La(Fe_(11.6-x)Co_(x))Si_(1.4)C_(0.15)(x =0.60, 0.65, 0.75, 0.80, 0.85)/phenolic resin compounds were pressed into thin plates and tested in a hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling cycle refrigeration effect. The test results showed that a maximum cooling power of 41 W was achieved over a temperature span of 30 K.
基金supported by the National Basic Research Program of China(Grant No.2014CB643702)the National Natural Science Foundation of China(Grant No.51590880)+1 种基金the Knowledge Innovation Project of the Chinese Academy of Sciences(Grant No.KJZD-EW-M05)the National Key Research and Development Program of China(Grant No.2016YFB0700903)
文摘Data-mining techniques using machine learning are powerful and efficient for materials design, possessing great potential for discovering new materials with good characteristics. Here, this technique has been used on composition design for La（Fe,Si/Al）（13）-based materials, which are regarded as one of the most promising magnetic refrigerants in practice. Three prediction models are built by using a machine learning algorithm called gradient boosting regression tree（GBRT） to essentially find the correlation between the Curie temperature（TC）, maximum value of magnetic entropy change（（？SM）（max））,and chemical composition, all of which yield high accuracy in the prediction of TC and（？SM）（max）. The performance metric coefficient scores of determination（R^2） for the three models are 0.96, 0.87, and 0.91. These results suggest that all of the models are well-developed predictive models on the challenging issue of generalization ability for untrained data, which can not only provide us with suggestions for real experiments but also help us gain physical insights to find proper composition for further magnetic refrigeration applications.
基金Project supported by the National High Technology Research and Development Program of China,the National Basic Research Program of China, and the National Natural Science Foundation of China (50971022, 50731007)
文摘A comparative study of Na2MoO4·2H2O and Na2HPO4·12H2O as inhibitors for magnetic refrigeration material La-Fe-Co-Si compound corrosion in distilled water at room temperature was carried out.Moreover,the inhibiting behavior of the mixture of Na2MoO4·2H2O and Na2HPO4·12H2O was investigated.Potentiodynamic polarization curves and electrochemical impedance spectroscopy （EIS） measurements were applied to study the corrosion behavior of the compound in the absence or presence of different concentrations of these inhibitors under the same experimental conditions.The study revealed that the mixture of 3.0×10–3 kg/L Na2MoO4·2H2O and 5.0×10–3 kg/L Na2HPO4·12H2O was the best inhibitor reaching the value of inhibition efficiency （ε%） up to 93.9%.Polarization curves showed that the studied compounds acted as anodic inhibitors.The potential of zero charge （PZC） of La-Fe-Co-Si compound was determined in distilled water in the absence of the studied inhibitors.Corrosion inhibition mechanisms for inhibitors were proposed in this work.
基金supported by the National Natural Science Foundation of China(Grant Nos.51301008 and 51171003)the Beijing Natural Science Foundation,China(Grant No.1112005)
文摘In this paper, we study the effects of Pr substitution on the hydrogenating process and magnetocaloric properties of La（1-x）PrxFe11.4Si1.6Hy hydrides. The powder x-ray diffraction patterns of the La1-xPrxFe11.4Si1.6 and its hydrides show that each of the alloys is crystallized into the single phase of cubic Na Zn13-type structure. There are hydrogen-absorbing plateaus under 0.4938 MPa and 0.4882 MPa in the absorbing curves for the La0.8Pr0.2Fe11.4Si1.6 and La0.6Pr0.4Fe11.4Si1.6 compounds. The releasing processes lag behind the absorbing process, which is obviously different from the coincidence between absorbing and releasing curves of the La Fe11.4Si1.6 compound. The remnant hydrogen content for La0.6Pr0.4Fe11.4Si1.6 is significantly more than that for La0.8Pr0.2Fe11.4Si1.6 after hydrogen desorption, indicating that more substitutions of Pr for La are beneficial to retaining more hydrogen atoms in the alloys. The values of maximum magnetic entropy change are 14.91 J/kg·K and 17.995 J/kg·K for La0.8Pr0.2Fe11.4Si1.6H0.13 and La0.6Pr0.4Fe11.4Si1.6H0.87,respectively.
