La_(1.1)Fe_(11.4)Si_(1.55)Ge_(0.05)合金的磁热效应

使用电弧熔炼法制备了La1.1Fe11.4Si1.55Ge0.05合金。研究了用少量的Ge替代Si后,La1.1Fe11.4Si1.55Ge0.05合金的磁性和磁热效应。粉末X射线衍射结果表明:在1273K真空退火处理10d后,合金La1.1Fe11.4Si1.55Ge0.05主相为NaZn13型立方结构,存在微量的α-Fe相。热磁曲线M-T与Arrott曲线表明:在居里温度Tc=205K处发生由铁磁性(TTc)转变为顺磁性(TTc)的二级磁相变。在磁场变化0～1.5T下,根据等温磁化曲线通过Maxwell关系式计算得出最大磁熵变-ΔSmmax=9J.kg-.1K-1。Ge替代Si后该合金在其居里温度Tc处-ΔSm-T曲线半高宽增大,使合金的相对制冷能力RCP(S)有所提高。     

磁热效应合金Gd5(Ge1-xMx)4的结构

用磁控电弧炉在氩气气氛中熔炼了Gd5(Ge1-xMx)4(M=Mo、Al、Cr和Ga)系列合金。对样品的结构、显微组织和磁热性能进行了研究,研究发现随着M元素含量的增加,晶体结构会发生由5∶4型正交结构→5∶2∶2型单斜结构→5∶4型正交结构的转变,晶态组织出现非共晶→共晶→非共晶的转变,样品的磁热效应会随着M元素的含量增大而增大。     

MnFe1-xTixP0.63Ge0.12Si0.25（x=0,0.01,0.02,0.03）系列化合物的磁热效应

通过X射线衍射分析(XRD)和振动磁强计(VSM)磁性测量,研究了替代元素Ti替代Fe元素含量的MnFe1-xTixP0.63Ge0.12Si0.25(x=0,0.01,0.02,0.03)系列化合物的物相结构与磁热效应的影响。结果表明:该系列化合物的结构为Fe2P型六角晶系结构,空间群为P62m。主相均为(Mn,Fe)2(P,Ge,Si),并含有少量的第二相(Mn,Fe)3Si相。随着Ti原子替代Fe原子的增加化合物的晶格常数a增大,晶格常数c略有减小,晶胞体积V基本保持不变。随着Ti含量增加居里温度(TC)减小,热滞ΔThys的大小改进不太明显。MnFeP0.63Ge0.12Si0.25的TC为305 K,当外磁场变化为0～1.5 T时最大磁熵变的绝对值为14.8 J.(kg.K)-1。     

P元素的替代对LaFe_(11.4)Si_(1.6)的磁热效应影响

通过电弧炉熔炼法制备了LaFe11.4Si1.6-x P x(x=0.05,0.1,0.2,0.3)系列合金,XRD分析表明少量P元素替代,LaFe11.4Si1.6-x P x(x=0.05,0.1,0.2和0.3)合金仍然保持NaZn13型结构,但晶格常数减小。在居里温度T c附近磁化曲线表明,该系列合金经历由磁场引起巡游电子由顺磁态到铁磁态变磁转变的一级相变。随着P含量的增加,LaFe11.4Si1.6-x P x(x=0.05,0.1和0.2)的居里温度T c减小,等温磁熵变也减小。在外加磁场变化为0~1.5 T时,等温磁熵变最大值分别为19.3 J/(kg·K),15.3 J/(kg·K)和10.3 J/(kg·K)。     

Si元素的添加对Ni43Mn46Sn11合金磁热效应的影响

通过对合金Ni43Mn46Sn11Six(x=0.0,0.1,0.2,0.3)磁热效应的研究,发现随着Si含量增加,合金的转变温度(TM)从187 K降到160K,合金的磁熵变也略微减小。在外场变化为3 T时,随着x的增加,合金的磁熵变分别为28.7,24.7,26.1和23.3 J.kg-·1K-1。此外,还利用连续和不连续降温两种方法对Ni43Mn46Sn11Six合金的等温磁化曲线进行了测量。发现两种测量方法测量的磁熵变值存在较大的差异,例如,对x=0的样品,在外场变化为3 T时,连续和不连续降温测量方法算得的磁熵变分别为28.74和38.56 J·kg-·1K-1。     

哈斯勒合金Ni-Mn-Sn的磁热效应

采用真空电弧熔炼法和高温淬火法制备了四元哈斯勒合金Ni50-xCuxMn36Sn14(x=0,2,4,6)的化合物。用X射线衍射仪和振动样品磁强计研究了合金的物相与磁热效应。结果表明,部分Cu元素对Ni的替代,并没有改变三元哈斯勒合金Ni-Mn-Sn原有的晶体结构,只是晶格常数开始有减小的趋势,晶胞的体积没有发生太大的变化。M-T曲线的结果表明,该系列哈斯勒合金样品在奥氏体相的铁磁交换作用增强,导致居里温度升高,而结构相变温度降低。此外,通过麦克斯韦方程计算了该系列合金的磁熵变(-ΔSm),在磁场变化为1.5 T的情况下,获得了Ni46Cu4Mn36Sn14合金在330 K附近的最大磁熵变(-ΔSmmax)约为2.0 J·(kg·K)-1。     

Gd_5Si_(1.8)Ge_(1.8)Sn_(0.4)合金的高温相变

为认识合金的高温相变,采用热分析技术对Gd5Si1.8Ge1.8Sn0.4合金可能的高温相变进行了定性研究,并利用高温XRD研究了合金在200～400℃之间的相结构。研究结果表明:升温过程中,Gd5Si1.8Ge1.8Sn0.4合金在200～300℃之间发生了由Gd5Si2Ge2-型单斜结构向Gd5Si4-型正交结构的转变。从而为探索材料方便快捷的制备工艺提供技术支持。     

LaGd_(0.1)Fe_(11.4-x)Co_xSi_(1.6)(x=0.1,0.3,0.5,0.7,0.9)合金的磁热效应

研究了LaGd0.1Fe11.4-xCoxSi1.6(x=0.1,0.3,0.5,0.7,0.9)系列合金的结构以及磁热效应。室温XRD分析表明该系列合金除微量的α-Fe相外,均具有立方NaZn13型立方单相晶体结构,空间群为Fm-3c。晶格常数没有明显变化,分别为1.1458,1.1454,1.1458,1.1459,1.469nm。磁性测量表明该系列合金的Tc随着Co含量的增加而增加,分别为212,231,253,281,302K。在外磁场变化ΔB=1.5T时,最大的磁熵变随着Co含量的增加而减少,由x=0.1的13.8J降为x=0.9J.kg-.1K-1的1.5J.kg-.1K-1。并且随着Co含量的增加存在由一级相变转为二级相变的趋势。     

Gd含量对Gd5Si2Ge2晶体结构和磁性能的影响

用非自耗电弧炉熔炼了Gd5 xSi2Ge2系列样品。用X射线粉末衍射(XRD)和Rietveld方法研究了Gd5 xSi2Ge2系列样品的晶体结构。用自制的仪器测量了样品的居里温度,用振动样品磁强计研究了样品的磁卡效应。对样品的晶体结构分析结果表明:Gd的含量x的变化对Gd5Si2Ge2化合物的晶体结构有较大的影响,当x>0时,样品中含有Gd5(Si,Ge)4和Gd5(Si,Ge)3两个相,并且随着x的增加Gd5(Si,Ge)4相会减少,Gd5(Si,Ge)3相会增加;当x<0时,样品会形成Gd5(Si,Ge)4和Gd(Si,Ge)两相,并且随着x的减少Gd5(Si,Ge)4相会减少,Gd(Si,Ge)相会增多。对样品的磁性能分析结果表明:Gd的含量x>0和x<0时都会降低样品的磁卡效应,样品的居里温度会随着x的增加而增加。     

La0.8Ce0.2(Fe1-xCox)10.5Si2.5金属间化合物晶体结构和磁熵变特性研究

通过X射线衍射和磁性测量等手段对金属间化合物La0.8Ce0.2(Fe1-xCox)10.5Si2.5(x=0,0.02,0.04,0.06)系的结构、磁性以及磁熵变进行了研究.实验发现,La0.8Ce0.2(Fe1-xCox)10.5Si2.5系的晶体结构均保持立方NaZn13型结构.随着Co含量x的不断增大,晶格常数将单调减小,居里温度TC呈单调增加.当x=0.02时,该化合物在居里温度TC～239K具有较高的磁熵变︱ΔSM︱,在1 T的磁场下(ΔSM)max为2.87 J·kg-1·K-1.当x=0.04和0.06时,居里温度在室温附近,磁熵变有了一定程度的降低,但仍有可观的磁熵变.最后,对该系列合金作为近室温磁制冷工质的可能性作了适当地探讨.     

YMn_6Sn_(6-x)M_x(M=Ga,Ti)化合物的结构和磁性研究

:制备了 YMn6 Sn6 - x Gax( x =0 .3,0 .6 ,0 .9,1.2 ,1.5 ,1.8)和 YMn6 Sn6 - x Tix( x=0 ,0 .2 ,0 .4,0 .6 ,0 .8,1.0 )化合物 ,通过 X射线衍射和磁性测量手段对其结构和磁性进行了研究 ,实验表明 ,所有这些化合物均为 Ca Cu5型六方结构。对 YMn6 Sn6 - x Gax 研究表明 ,晶格参数和晶胞体积均随 Ga含量的增加而线性减小 ,磁性测量表明 :当x≥ 0 .3时 ,化合物由反铁磁性转变为铁磁性或亚铁磁性 ,随 Ga含量增加 ,该化合物的居里温度先增高 ,在 x=0 .6达到最大值 ,然后居里温度又逐渐降低。饱和磁化强度开始随 Ga含量的增加而增大 ,当 x>1.2时 ,随 Ga含量的增加而减小。对 YMn6 Sn6 - x Tix 研究表明 ,晶格参数和晶胞体积均随 Ti含量的增加而线性增大 ,磁性测量表明 ,当 x≥ 0 .6时 ,化合物由反铁磁性转变为铁磁性或亚铁磁性 ,随 Ti含量增加居里温度 (或奈耳温度 )呈线性下降 ,饱和磁化强度开始随 Ti含量的增加而增大 ,当 x>0 .6时 ,随 Ti含量的增加而减小     

The Stability of Rare Earth-Iron-Nitrides Sm_2(Fe,M)_(17)N_y,Permanent Magnets

The effects of the partial substitution of element M(M=Cr,V,Mn,x=0.05;Zr,Ga,x=0.017;Si,x=0.15;Co,x=0.10)for Fe in samarium-iron-nitride Sm_2(Fe_(1-x)M_x)_(17)N_y compounds on their stabilitiesand Curie temperatures have been studied.It is found that Co,Ga can raise the Curie temperature of thecompounds.The initial decomposition temperatures cannot be raised significantly by all the studied elementsexcept Co.The result contradicts the formation enthalpy consideration.The final decomposition tempera-tures can be raised by all of the substitution elements.The effects of atmospheres on their decomposition be-havior were also studied.The results show that oxidation is the major reason for magnetic deterioration ofthe powder heated in air.Compared with nitrogen atmosphere,argon or vacuum helps to delay the decompo-sition of the compounds.     

Research Advance on Magnetocaloric Effect of La-Fe-M(Al, Si) Compounds

Inviewofenergysavingandenvironmentalpro tection ,magneticrefrigerationnearroomtemperaturehasastrongimpactonconventionalgascompressiontechnology .However ,coolingefficiencyofthesystemformagneticrefrigerationismainlydecidedbythemagnitudeofmagnetocaloriceffectformagneticrefrig eratingmaterialsinthesystemunderacertainmagnet icfieldchange .Therefore ,developmentofnewrefrig eratingmaterialswithgreatmagnetocaloriceffectnearroomtemperatureisespeciallyimportant .Therearetwoparameterswhichareusedtochara…     

氧压酸浸法从脱锌氧化硬锌渣中选择性浸出锗和铟

以含锗、铟的锌精炼脱锌氧化硬锌渣为原料,采用氧压酸浸工艺选择性回收其中的锗和铟,并对锗、铟、铜、锡、锑等元素的溶出行为进行了研究。结果表明,锗、铟及锌溶出率分别达到95%、91%及98%以上,大部分铅、硅、锡、锑等则留于残渣中。     

Influence of magnesium content on structure and electrochemical properties of La_(1-x)Mg_xNi_(1.75)Co_(2.05) hydrogen storage alloys

La_(1-x)Mg_xNi_(1.75)Co_(2.05)(x=0.07, 0.08, 0.10, 0.13, 0.15) alloys were prepared by high-frequency inductive method, and then their structure and electrochemical properties were investigated systematically. The XRD analysis revealed that the alloys consisted of LaNi_5 phase and La_4MgNi_(19)(Ce_5Co_(19) + Pr_5Co_(19)) phase, and the introduction of Mg could promote the formation of La_4MgNi_(19) phase. The observation of microstructure showed that all the alloys processed dendritic structure, which was refined with the increase of x value. The electrochemical measurements showed that all the alloys could be activated within 2 cycles, and with increasing x, the maximum discharge capacity obviously increased from 254.00 m Ah/g(x=0.07) to 351.51 mAh/g(x=0.15), but the cycling stability(S_(80)) decreased somehow from 78.4% to 73.9%. Meanwhile, the appropriate addition of Mg could improve the high-rate discharge capacity(HRD) of the alloy electrodes, which was mainly controlled by the electrochemical reaction rate on the surface of the alloys.     

Preparation and luminescence properties of Eu²⁺-doped CASN-sinoite multiphase system for LED

A series of Eu2+-doped CASN-sinoite multiphase system with a formula of(CaAlSiN3)(1-x)-(Si2N2O)x were successfully synthesized by the high temperature solid-state method.The crystal structure and morphology of the phosphors and their photoluminescence(PL) were investigated.For the Eu2+-doped samples the PL intensity approached its maximum when the molar ratio of Si2N2O in the samples was about 0.15.With increase of the concentration of Si2N2O,the emission peak shifted from 645 to 605 nm.It was because the spectroscopic polarizability(αsp) became smaller with the increase of Si/Al ratio or the adding of O atoms,which caused the change of crystal field strength.In addition,the full width at half maximum(FWHM) widened with the increase of x value,which was favor of the improvement of the color rendering index.     

气态源分子束外延生长GexSi1-x/Si异质结合金

采用气态源分子束外延法成功地生长了ＧｅｘＳｉ１－ｘ／Ｓｉ异质结合金材料，所使用的气体分别是乙硅烷和锗烷。高能电子衍射被用于原位监控生长层的表面重构状态。在一定的生长温度下，ＧｅｘＳｉ１－ｘ合金组分ｘ取决于锗烷和乙硅烷的流量比。外延层的表面形貌与锗组分的大小、生长层的厚度及生长温度有关。结果表明，较大的锗组分和较高的生长温度利于由二维模式向三维模式转变的外延生长。     

Effects of manganese doping on magnetocaloric effect in Ge-rich Gd_5Ge_（2.05）Si_（1.95） alloy

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.