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Recentlytherehasbeenaninterestinmagneticrefrigerationstudiesduetoitspotentialasanenergysavingtechnology[1~ 5] .Theefficiencyofmagneticre frigerationcriticallydependuponmagneticrefriger ants .Forthebestrefrigerantperformance ,verylargeisothermalmagneticentropychangeΔSisrequired ,andthemaximumvalueofΔSmustexistoverawiderrangeoftemperatures[2 ] .Recentdiscoveryofgiantmagnetocaloriceffect(MCE)ΔSinfirst ordertransi tionmaterialsgivesfurtherimpulsetowardsthedevel opmentofbothnewmaterialsandmag… 相似文献
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Inviewofenergysavingandenvironmentalpro tection ,magneticrefrigerationnearroomtemperaturehasastrongimpactonconventionalgascompressiontechnology .However ,coolingefficiencyofthesystemformagneticrefrigerationismainlydecidedbythemagnitudeofmagnetocaloriceffectformagneticrefrig eratingmaterialsinthesystemunderacertainmagnet icfieldchange .Therefore ,developmentofnewrefrig eratingmaterialswithgreatmagnetocaloriceffectnearroomtemperatureisespeciallyimportant .Therearetwoparameterswhichareusedtochara… 相似文献
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简述了室温磁制冷材料的发展历史和纳米技术,概述了磁制冷材料研究的重点。总结了室温磁制冷工质材料具有优良性能的标准,并且给出了从微观、唯象和纳米方面研究室温磁制冷材料的新思路。介绍了纳米技术在室温磁制冷材料研究中的应用,重点讲述了纳米化对室温磁制冷材料的影响,预测了磁制冷材料的发展趋势。 相似文献
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The magnetocaloric effect was discovered in 1881by Warburg[1]. When a magnetic field is applied to amagnetic material, the unpaired spins are aligned par allel to the magnetic field, which lowers the magneticentropy and causes the sample to heat up. I… 相似文献
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WU Wei Feng Zai Guo Lijun 《中国稀土学报(英文版)》2005,23(4):441-441
Magnetic Entropy Change of (Gd_(1-x)RE_x)_5Si_4(RE=Dy, Ho) Alloys 相似文献
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依据X射线衍射(XRD)与等温磁化曲线和等磁场变温磁化曲线,主要研究了Tb3NiSi2合金相结构与磁性相变和磁热性能。XRD表明,采用800℃保温14天,然后炉冷至室温的热处理方法制备的R3NiSi2(R=Tb,Dy,Ho,Er)合金中,主相均为Gd3NiSi2型正交结构(空间群:Pnma,No.62)相,但杂相R5Si3含量存在差异,其规律是从Er到Tb,含量依次减少,Tb3NiSi2合金样品基本为一个单相,其相应晶格常数分别为a=1.1240(8)nm,b=0.41009(8)nm,c=1.12058(1)nm。等温磁化曲线显示在50~300 K温度范围内,Tb3NiSi2合金仅展现出铁磁-顺磁相变,并没有在130,82,66,53 K等观察到相关文献报道的多重的反常反铁磁态-铁磁态(AFM-FM)相变。0.01 T磁场下的磁化强度对温度求导曲线(d M/d T)和0~2 T磁场下的Arrott图结果证实合金铁磁-顺磁二级磁相变居里温度(Tc)=88 K。居里外斯定理拟合表明合金中Tb3+粒子的有效磁矩为9.90μB(μB为玻尔磁子),同期望值μeff/Tb3+=g(J(J+1))1/2=9.72μB基本一致。在磁热性方面,Tb3NiSi2合金在0~2 T磁场范围内,低场响应性较差,铁磁态分子的有效磁矩远低于顺磁分子有效磁矩,最大磁熵变(-ΔSMmax)为3.2 J·kg-1·K-1;在对应的半高宽温跨(δTFWHM)=35.5K范围内,相对制冷量为113 J·kg-1。 相似文献
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Recently,researchonmagnetocaloriceffect(MCE)hasattractedagreatdealofinterestinrare earth(RE)basedcompoundsbecauseoftheirenergy efficiencyandenvironmentalsafetyformagneticrefrig eration.Afirst ordermagneticphasetransitionwas foundintheintermetalliccompoundsRECo2(RE=Er,Ho,Dy)withMgCu2typestructure[1,2],leadingtoa largemagneticentropychangeforthesecompounds,whereasasecond ordertransitionwasfoundinTbCo2andGdCo2.IntheintermetalliccompoundsRECo2,theloweringofd electronconcentrationbythesubst… 相似文献
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The structure, magnetic and magnetocaloric properties of the Ge-rich Gd5Ge2.05-xSi1.95-xMn2x (x=0.01 and 0.03) alloys were investigated by scanning electron microscopy, X-ray powder diffraction, differential scanning calorimeter (DSC) and magnetization measurements. The results of energy dispersive X-ray analysis (EDX) and X-ray diffraction analyses showed that the composition and crystal structure of the alloys were desired. DSC measurements were performed to determine the transformation temperatures for each alloy. Both alloys exhibited the first order phase transition around room temperature. The alloys showed an anti-ferromagnetic transition around 60 K. The isothermal magnetic entropy changes of the alloys were determined from the isothermal magnetization measurements by using the Maxwell relation. The maximum values of isothermal magnetic entropy change of the Gd5Ge2.05-xSi1.95-xMn2x alloy with x=0.01 was found to be -12.1 and -19.8 J/(kg·K) using Maxwell equation around 268 K in applied fields of 2 and 5 T, respectively. 相似文献
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Magnetocaloric Effect of Ni56Mn18.8Ga24.5 Gd0.7 Alloy 总被引:1,自引:0,他引:1
Zhang Zeyu ~ Long Yi ~ Duan Jingfang ~ Huang Peng ~ Wu Guangheng ~ Chang Yongqin ~ 《中国稀土学报(英文版)》2006,24(5):579-581
Inrecent years materials with high magnetocaloriceffect (MCE) have attracted considerable attention ow-ingto its potential application as a magnetic refriger-ant .Many material systemsthat underwentthefirst-or-der magnetic transition have been found to exhibit agiant MCE. Their typical representatives areGd5(SixGe1 -x)4[1 ,2]and La (FexSi1 -x)13[3 ,4]alloys .Ni MnGa is aferromagnetic shaped memory alloy whichundergoes a reversible first-order structural phase tran-sition (SPT) with the … 相似文献
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M-T curves, p-T curves, and MR-T curves of La0.67-xErxSr0.33MnO3 (x=0.00, 0.10, 0.20) system were studied by experiments. The experiments showed that: with increasing the doping amount, the magnetic structure of the system transformed from long-range ferromag-netic ordering to spin-cluster glass state, and M-T curves bent up in the extremely low temperature range; the resistivity of the system in-creased with increasing doping amount and exhibited the minimum phenomenon of low-temperature resistivity. The variation of the mag-netic and electric properties came from the extra magnetic coupling induced by the doping and from the Kondo effect induced by the lattice distortion and local magnetic moments which was similar to that induced by the mattering of magnetic impurities on electron spins. 相似文献
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Large Magnetic Entropy Effect in La2/3Ca1/3MnO3 总被引:2,自引:0,他引:2
彭振生 《中国稀土学报(英文版)》2004,22(2):232-234
The magnetocaloric effect in the colossal magnetoresistance material La2/3Ca1/3MnO3 was studied. From the measurements of temperature dependence of magnetization in various magnetic fields, the large magnetic entropy change associated with the ferromagnetic-paramagnetie transition was discovered. This result suggests that perovskite manganites are suitable candidates as working substance in magnetie refrigeration technology. 相似文献
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The magnetic and magnetocaloric properties for the Nd12Co6Pb compound were investigated. The Curie temperature TC of the magnetic transition of Nd12Co6Pb compound is 194 K. The experimentally determined magnetic effective paramagnetic moment is μeff=12.36 μB per formula unit (3.49 μB per Nd atom). The maximum magnetic entropy change in the low magnetic field changes of 0~2 T for the Nd12Co6Pb compound is about 215.0 J·mole-1·K-1. 相似文献
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T.I. Ivanova S.A. Nikitin W. Suski GA. Tskhadadze I.A. Ovtchenkova D. Badurski 《中国稀土学报(英文版)》2009,27(4):684-687
The results of magnetization, magnetoresistivity and magnetocaloric effect (MCE) studies performed on polycrystalline samples of the GdxLa1−xMnSi (x=0.5, 0.6, 0.7, 0.8, 0.9, 1.0) compounds were presented. Complex measurements were carried out on the GdxLa1−xMnSi compounds to determine the influence of substitution in the rare earth (R) sublattice on the magnetic and related properties of these compounds. The compounds with x≤0.6 demonstrated two magnetic phase transitions (ferromagnetic to paramagnetic and antiferro-magnetic to ferromagnetic) both of which were first order. Anomalies in the magnetocaloric effect, electroresistivity and magnetoresistivity were observed in the temperature ranges of the magnetic phase transitions. The temperature dependences of MCE and magnetoresistivity for these compounds correlated with the temperature dependence of magnetization. 相似文献
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Magnetocaloric effect and magnetic properties of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 and its hydride La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 were investigated. The Curie temperature of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 was increased by hydrogen absorption. XRD patterns showed that the structure of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 remained NaZn13-type. The Curie temperature (TC) of the sample was increased from 174 K to 331 K. The homogeneity of the hydrogen absorption for La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 was proven very well by the random measurement of DSC. The magnetic entropy △SM of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 had peak at 326 K. The peak value of-△SM-was 12.3 and 7.8 J/(kg.K) under magnetic field change of 0-2 T and 0-1 T,respectively,which was comparable with Gd5Si2Ge2. The negative slope and inflection point of the Arrott curve indicated that the first-order magnetic transition of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 was reserved after hydrogen absorption. 相似文献
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E.Yüzüak 《中国稀土学报(英文版)》2010,28(3):477-480
The influence of the manganese-alloying on the structure and magnetocaloric properties of the Gd5Si2.05Ge1.95 compound was studied by X-ray powder diffraction and magnetization measurements.The Gd5Si2.05-xGe1.95-xMn2x(2x=0,0.03 and 0.08) compounds crystallized in the Gd5Si2Ge2-type monoclinic structure.In all X-ray powder diffraction patterns,a minor hexagonal Gd5Si3 phase was observed as a second phase.With increasing Mn content,the unit cell volume increased.For the compounds with x=0,0.03 and 0.08,the fi... 相似文献