In the present work we reported the phase formation, microstructure, magnetocaloric effect and hydrogenation behavior of La-rich La1.7Fe11.6Si1.4alloy. In this off-stoichiometric La（Fe,Si）13alloy, the Na Zn13-type L...In the present work we reported the phase formation, microstructure, magnetocaloric effect and hydrogenation behavior of La-rich La1.7Fe11.6Si1.4alloy. In this off-stoichiometric La（Fe,Si）13alloy, the Na Zn13-type La（Fe,Si）13matrix phase shows faceted grains, with the Cr5B3-type La5Si3 used as the secondary phase distributed intergranularly. Such a peculiar morphology quickly forms upon one day annealing. In La1.7Fe11.6Si1.4alloy, we have observed a significant field dependence of magnetostructural transition temperature（～ 6.3 K/T）, resulting in a large and table-like entropy change（△S～ 18 J/kg·K in 2 T） over a broad temperature range（～ 10 K）. Upon hydrogenation, the maximum value of △S keeps almost unchanged, while the Curie temperature increases up to 350 K. These results indicate that the investigated offstoichiometric La（Fe,Si）13alloy is a promising magnetic material for magnetic refrigerators.展开更多
研究了热处理对La Fe Si化合物组织结构的影响。结果表明,热处理保温时间在24h以内及温度在900～1300℃之间,铸态试样在两个温度点发生相变,即900～1200℃为一个相变点,α Fe相从铸态的非主相变为主相;1300℃为另一个相变点。在900～110...研究了热处理对La Fe Si化合物组织结构的影响。结果表明,热处理保温时间在24h以内及温度在900～1300℃之间,铸态试样在两个温度点发生相变,即900～1200℃为一个相变点,α Fe相从铸态的非主相变为主相;1300℃为另一个相变点。在900～1100℃范围材料中α Fe相的晶胞常数逐渐减小,当热处理温度继续增加,其α Fe相的晶胞常数缓慢增加。展开更多
介绍了La Fe M(M=Al,Si)化合物在磁热性能研究方面的最新进展。具有NaZn13型晶体结构,含高浓度Fe的La Fe M(M=Al,Si)化合物为良好的软磁材料;用少量的Co替代化合物中Si,Al元素可以将化合物的居里温度提高至室温;对La(Fe1-yCoy)xSi13-x...介绍了La Fe M(M=Al,Si)化合物在磁热性能研究方面的最新进展。具有NaZn13型晶体结构,含高浓度Fe的La Fe M(M=Al,Si)化合物为良好的软磁材料;用少量的Co替代化合物中Si,Al元素可以将化合物的居里温度提高至室温;对La(Fe1-yCoy)xSi13-x化合物,适量的Si,Co组合可使化合物在室温产生可与Gd5Si2Ge2比拟的磁热效应;加入适量的间隙原子H,也可使La(FexSi1-x)13在室温的磁热性能远远大于金属Gd;对含Si量低及含Si量高的La(FexSi1-x)13化合物在相转变点附近由温度和磁场诱导相变的本质做了详细阐述。展开更多
A sub-rapidly solidified LaFe11.6Si1.4 plate was fabricated directly from liquid by centrifugal casting method. The phase constitution, microstructure and magnetocaloric effect were investigated using backscatter scan...A sub-rapidly solidified LaFe11.6Si1.4 plate was fabricated directly from liquid by centrifugal casting method. The phase constitution, microstructure and magnetocaloric effect were investigated using backscatter scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and phys- ical property measurement system. When the plate was annealed at 1373 K, rl phase was formed by a solid-state peritectoid reaction. A first-order magnetic phase transition occurred in the vicinity of 188 K, and the effective refrigeration capacities reached 203.5J/kg and 209.7J/kg in plates annealed for I h and 3 h, respectively, under a magnetic field change of 3T. It is suggested that centrifugal casting may become a new approach to prepare high-performance La-Fe-Si magnetocaloric plates for prac- tical applications, which could largely accelerate the formation of rl phase during high-temperature heat-treatment process due to refined and homogeneous honeycombed microstructure.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
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
Recent research progress on magnetocaloric effect of La-Fe-M (M = Al, Si) compounds was presented. La-Fe-M (M = Al, Si) compounds of high Fe content are excellent soft magnetic materials with NaZn13 structure. The Cur...Recent research progress on magnetocaloric effect of La-Fe-M (M = Al, Si) compounds was presented. La-Fe-M (M = Al, Si) compounds of high Fe content are excellent soft magnetic materials with NaZn13 structure. The Curie temperature of the compounds can be increased by substituting small amount of Co for Si, Al. The La(Fe1-xCoy)(x)Si13-x compounds with an appropriate ratio of Co and Si can produce giant magnetocaloric effect comparable to that for Gd5Si2Ge2 at room temperature. The La (FexSi1-x)(13) doped with H can also produce giant magnetocaloric effect at room temperature, which is much greater than that for Gd. For La (FexSi1-x)(13) compounds with low Si or high Si contents. The nature of phase transition near Curie temperature induced by temperature and magnetic field was described in detail.展开更多
The ingots with the composition oi LaFe13-x Six （ 1.2 〈 x 〈 2.2） were prepared by arc-melting, and subsequently homogenized by annealing for a long time. The sample was mainly composed of a single NaZn13-type phas...The ingots with the composition oi LaFe13-x Six （ 1.2 〈 x 〈 2.2） were prepared by arc-melting, and subsequently homogenized by annealing for a long time. The sample was mainly composed of a single NaZn13-type phase. The dependence of magnetization on the magnetic field was measured at different temperatures for LaFe13- xSix （ 1.2 ≤ x ≤ 2.2） compound, and the entropy change （△S） was calculated using Maxwell relation. The variation of AS with H was discussed according to both the Landau second-order phase transition theory and the scaling law under mean-field approximation. The results show that the relation of △S ∝ H^2/3 is satisfied for the LaFe13-x Six compounds. The parameters obtained by the simulation of peak value of entropy change can be used to determine the degree of first-order magnetic phase transition. The present work may be useful for the research of the magnetic refrigeration.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51371184)the Outstanding Youth Fund of Zhejiang Province,China(Grant No.LR14E010001)
文摘In the present work we reported the phase formation, microstructure, magnetocaloric effect and hydrogenation behavior of La-rich La1.7Fe11.6Si1.4alloy. In this off-stoichiometric La（Fe,Si）13alloy, the Na Zn13-type La（Fe,Si）13matrix phase shows faceted grains, with the Cr5B3-type La5Si3 used as the secondary phase distributed intergranularly. Such a peculiar morphology quickly forms upon one day annealing. In La1.7Fe11.6Si1.4alloy, we have observed a significant field dependence of magnetostructural transition temperature（～ 6.3 K/T）, resulting in a large and table-like entropy change（△S～ 18 J/kg·K in 2 T） over a broad temperature range（～ 10 K）. Upon hydrogenation, the maximum value of △S keeps almost unchanged, while the Curie temperature increases up to 350 K. These results indicate that the investigated offstoichiometric La（Fe,Si）13alloy is a promising magnetic material for magnetic refrigerators.
文摘介绍了La Fe M(M=Al,Si)化合物在磁热性能研究方面的最新进展。具有NaZn13型晶体结构,含高浓度Fe的La Fe M(M=Al,Si)化合物为良好的软磁材料;用少量的Co替代化合物中Si,Al元素可以将化合物的居里温度提高至室温;对La(Fe1-yCoy)xSi13-x化合物,适量的Si,Co组合可使化合物在室温产生可与Gd5Si2Ge2比拟的磁热效应;加入适量的间隙原子H,也可使La(FexSi1-x)13在室温的磁热性能远远大于金属Gd;对含Si量低及含Si量高的La(FexSi1-x)13化合物在相转变点附近由温度和磁场诱导相变的本质做了详细阐述。
基金financially supported by the National Natural Science Foundation of China(No.51474144)the Shanghai Sailing Program(No.17YF1405900)
文摘A sub-rapidly solidified LaFe11.6Si1.4 plate was fabricated directly from liquid by centrifugal casting method. The phase constitution, microstructure and magnetocaloric effect were investigated using backscatter scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and phys- ical property measurement system. When the plate was annealed at 1373 K, rl phase was formed by a solid-state peritectoid reaction. A first-order magnetic phase transition occurred in the vicinity of 188 K, and the effective refrigeration capacities reached 203.5J/kg and 209.7J/kg in plates annealed for I h and 3 h, respectively, under a magnetic field change of 3T. It is suggested that centrifugal casting may become a new approach to prepare high-performance La-Fe-Si magnetocaloric plates for prac- tical applications, which could largely accelerate the formation of rl phase during high-temperature heat-treatment process due to refined and homogeneous honeycombed microstructure.
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.
文摘Recent research progress on magnetocaloric effect of La-Fe-M (M = Al, Si) compounds was presented. La-Fe-M (M = Al, Si) compounds of high Fe content are excellent soft magnetic materials with NaZn13 structure. The Curie temperature of the compounds can be increased by substituting small amount of Co for Si, Al. The La(Fe1-xCoy)(x)Si13-x compounds with an appropriate ratio of Co and Si can produce giant magnetocaloric effect comparable to that for Gd5Si2Ge2 at room temperature. The La (FexSi1-x)(13) doped with H can also produce giant magnetocaloric effect at room temperature, which is much greater than that for Gd. For La (FexSi1-x)(13) compounds with low Si or high Si contents. The nature of phase transition near Curie temperature induced by temperature and magnetic field was described in detail.
文摘The ingots with the composition oi LaFe13-x Six （ 1.2 〈 x 〈 2.2） were prepared by arc-melting, and subsequently homogenized by annealing for a long time. The sample was mainly composed of a single NaZn13-type phase. The dependence of magnetization on the magnetic field was measured at different temperatures for LaFe13- xSix （ 1.2 ≤ x ≤ 2.2） compound, and the entropy change （△S） was calculated using Maxwell relation. The variation of AS with H was discussed according to both the Landau second-order phase transition theory and the scaling law under mean-field approximation. The results show that the relation of △S ∝ H^2/3 is satisfied for the LaFe13-x Six compounds. The parameters obtained by the simulation of peak value of entropy change can be used to determine the degree of first-order magnetic phase transition. The present work may be useful for the research of the magnetic refrigeration.
