LaY0.1Fe11.4T0.1Si1.5（T=Cr,Mn,Fe,Co,Ni）合金的磁热效应

用电弧熔炼法制备了LaY0.1Fe11.4T0.1Si1.5(T=Cr,Mn,Fe,Co,Ni)系列合金。室温XRD分析与SEM成分分析表明,该系列合金中除存在一个明显的杂相峰(富La相,P4/nmm)和α-Fe相外,主相为NaZn13型立方相。除T=Cr外,Fe位原子替代使合金的晶格常数随着替代原子T的原子半径的减小而减小。磁性测量表明,该系列合金除T=Mn以外,随着替代原子T的原子半径减小,合金的居里温度(TC)有增加的趋势。在外磁场变化ΔB=1.5T时,利用Maxwell方程计算得出,该系列合金磁熵变最大值分别为5.1,13.0,20.7,12.7和7.4J·kg-1·K-1。由此可以看出,T=Fe时合金的磁熵变最大值最大,且该系列合金的磁熵变峰值随着外磁场增加向高温区不对称展宽;TC以上磁场引起的变磁转变是磁熵变峰值不对称展宽的原因。     

Mn_(1.35)Fe_(0.65)P_(0.45)Si_(0.55)B_x合金的磁热效应

对Mn1.35Fe0.65P0.45Si0.55Bx(x=0,0.01,0.02,0.03,0.04)合金的结构和磁热效应(MCE)进行了研究。XRD分析结果表明:Mn1.35Fe0.65P0.45Si0.55Bx(x=0,0.01,0.02,0.03,0.04)的合金均为Fe2P型六角结构,空间群为P6-2 m,并随着B元素(原子分数)的增加,晶格常数a增大,c/a减小,晶胞体积V略有减小。磁性测量表明:随着B元素(原子分数)的增加,Curie温度(Tc)从228K升高到315K,热滞(ΔThys)变化不大。0~1.5T外磁场下最大磁熵变(-ΔSmax M)下降,分别为3.6,2.5,2.0,1.7,1.9J/(kg·K)。     

(Mn1-xFex)5Sn3合金晶体结构和居里温度

用粉末冶金法(磁场压制烧结)制备(Mn1-xFex)5Sn3(x=0.1～0.5)合金,对其晶体结构、居里温度进行研究。室温XRD分析表明,该系列合金均保持Mn5Sn3的InNi2型相结构,计算发现合金的晶格常数随着x量增大而减小。通过M-T曲线测量结果表明:居里温度TC在室温附近244～391K连续可调,且随着Fe含量的增加而提高,居里温度随成分近似呈线性变化;成分为(Mn0.70Fe0.30)5Sn3合金的居里温度为295K,在外加磁场为0～1.5T下,最大磁熵变约为0.87J·(kg·K)-1,是一种成本低廉的室温磁制冷候选材料。     

La_(0.9)Ce_(0.1)Fe_(11.44)Si_(1.56)H_y合金及其粉末粘结块体的磁热效应

对La0.9Ce0.1Fe11.44Si1.56合金进行饱和吸氢,之后在不同放氢温度(Td=200~250℃)下进行3 h放氢处理,得到H含量不同即具有不同Curie温度(TC)的氢化物,对其相结构和磁热效应进行测试分析.结果表明,合金在吸氢前后有相同的相结构,主相为Na Zn13型立方结构,同时含有少量a-Fe杂相;随着放氢温度的提高,TC近似线性的降低;由于H原子的引入消弱了一级巡游电子变磁(IEM)转变,等温磁熵变较母合金有所降低,当Td230℃时,磁熵变随着放氢温度的升高明显降低,磁滞减小,当Td=250℃时,磁熵变曲线宽化,一级相变特性弱化.饱和吸氢后的La0.9Ce0.1Fe11.44Si1.56Hy粉末经固化后得到的粘结样品在0~1.5 T的磁场下,绝热温变和等温磁熵变的最大值分别达到2.7 K和7.5 J/(kg·K).     

(Nd_(0.7)Pr_(0.3))_(60-x)Fe_(30)Al_(10)Cu_x(x=0,1,2,4)大块非晶合金磁性及矫顽力机理

采用铜模吸铸法制备了(Nd0.7Pr0.3)60-x Fe30Al10Cux(x=0,1,2,4)大块非晶合金,利用振动样品磁强计(VSM)研究了该合金的磁性能和磁粘滞行为。结果表明,这几种合金都呈现出较好的硬磁性。随着Cu元素的添加,矫顽力略有增加,但是合金的剩磁却没有变化。利用扫描速率法研究了(Nd0.7Pr0.3)60-x Fe30Al10Cux(x=0,1,2,4)大块非晶合金的磁粘滞行为,得到了这几种合金的相关磁性参数:热扰动场Hf为12.1~15.2 m T,热激活体积va为1.5×10-18~1.9×10-18 cm3。在所研究的合金中都存在明显的铁磁交换耦合作用,同时矫顽力与温度之间的关系符合Gaunt提出的畴壁钉扎模型,合金的硬磁性可能是这两方面共同作用的结果。     

LaFe11.9-xCoxSi1.1B0.2(x=0.7,0.8,0.9)合金的磁热效应

使用电弧熔炼法制备了LaFe11.9-xCoxSi1.1B0.2(x=0.7,0.8,0.9)系列合金.XRD分析表明该系列合金除微量的α-Fe相外,均由NaZn13型立方结构单相组成.晶格常数随着Co含量的增加而增大,分别为1.1487,1.1496,1.1498nm;磁性测量表明该系列合金的Curie温度在室温附近,并且也随着Co含量的增加而分别增加到270,290,300 K.在外场变化△B=1.5 T时,该系列合金的最大磁熵变均为金属Gd的2倍左右,相对制冷能力与金属Gd基本相同.     

退火对(La_(0.8)Nd_(0.2))_2Mg(Ni_(0.8-x)Co_(0.1)Mn_(0.1)Al_x)_9合金储氢性能的影响

(La0.8Nd0.2)2Mg(Ni0.8-xCo0.1Mn0.1Alx)9(x=0~0.15)系列合金经退火处理,合金电极具有较好的活化性能,经1~4次充放电循环就可达到最大放电容量,合金电极的最大放电容量Cmax得到提高,最大值为399.2 mA·h/g(x=0)。并随着Al替代量的增加,合金电极的吸放氢平台压降低,而吸氢滞后增大。同时,退火处理能明显改善合金电极的循环稳定性,经60次充放电循环后,合金电极的容量保持率(S60)最大值为76.7%(x=0.1)。     

La_(0.9)Ce_(0.1)Fe_(11.7-x)Mn_xSi_(1.3)H_y(x=0.21,0.25)粘结复合物的磁热效应

通过高频悬浮炉反复熔炼,在1 363K纯氩环境下退火144h后淬火,饱和吸氢后得到母合金样品La0.9Ce0.1Fe11.7-xMnxSi1.3Hy(x=0.21,0.25)。对其进行等质量塑性粘结,得到复合物。XRD相图结果表明,母合金的主相均为NaZn13型立方结构(空间点群为Fm-3c)。由热磁曲线和磁熵变曲线可以明显看出,复合物的温变区间与两母合金相比有所增大,并且其熵变值在1.5T磁场下依然比Gd的要高很多,最高约为6.4J/(kg·K)。复合物的相对制冷能力RCP(S)值与两母合金相比略大。     

Sn的加入对MnFe(P,Si)合金显微组织和磁性的影响

用高能球磨和固态烧结法制备了Mn_(1.3)Fe_(0.7)P_(0.5)Si_(0.5-x)Sn_x(x=0、0.02、0.04,原子分数)系列合金,系统研究了Sn的加入对合金显微组织、磁性和磁热效应的影响。结果表明,所有合金中都存在少量的(Fe,Mn)_3Si相,在含Sn的合金中,Sn原子并没有进入到Fe_2P晶体结构的晶格点阵位置,而是与Mn和Fe形成了Sn_2(Mn,Fe)相。Sn的加入也使合金中形成了2种成分的(Fe,Mn)_2(P,Si)相,导致样品在升温过程中出现2次铁磁-顺磁转变,对应为2个连续磁熵变峰,从而有利于合金磁制冷温区的扩展和制冷容量的提升。Mn_(1.3)Fe_(0.7)P_(0.5)Si_(0.5)合金具有优异的室温磁热效应,1.5 T磁场变化下的最大磁熵变为12.1 J/(kg·K),最大绝热温变为2.4 K,合金的热滞为3 K,Curie温度为273 K,可作为室温磁制冷的理想候选材料。     

MAGNETOSTRICTION IN ANTIFERROMAGNETIC Fe1-xMnx (0.30 ≤ x ≤ 0.55) ALLOYS

采用真空感应熔炼法,制备Fe1-xMnx(x=O.30,0.35,0.40,0.50,0.55(原子分数))合金,在1000℃保温24h,炉冷至室温.研究了不同结构Fe1-xMnx合金样品的室温磁致伸缩性能.结果表明,x≤0.40时,Fe1-xMnx合金样品为,γ ε双相结构,并且ε相体积分数随Mn含量增加而减小,磁致伸缩性能较差;x>0.40时,合金样品为单一的γ相,具有良好的磁致伸缩性能.Fe0.50Mn0.50合金样品在1.9T磁场中的磁致伸缩可达8.73x 10-4     

快速共沉淀过程pH值对Ni_(0.8)Co_(0.1)Mn_(0.1)(OH)_2及LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2性能的影响

采用快速共沉淀法制备Ni0.8Co0.1Mn0.1(OH)2前驱体,利用前驱体与LiOH.H2O的高温固相反应得到锂离子电池层状正极材料LiNi0.8Co0.1Mn0.1O2,探讨pH值对材料结构和电化学性能的影响。通过X射线衍射(XRD)、扫描电镜(SEM)和电化学测试对合成样品进行表征。结果表明,pH值为11.00~12.00时,合成的Ni0.8Co0.1Mn0.1(OH)2前驱体均无杂相;pH值为11.50时,合成的前驱体制备出的正极材料具有良好的电化学性能,0.1C倍率下首次放电比容量为192.4 mA.h/g;经过40次循环,容量保持率为91.56%。     

Fe_(0.85)Mn_(0.15)Ti_(0.9)M_(0.1)(M=Zr,V,Ca)合金的贮氢性能

系统地研究了 Fe0 .85 Mn0 .1 5 Ti0 .9M0 .1 (M=Zr,V,Ca)合金的贮氢性能。研究结果表明 :Fe0 .85 Mn0 .1 5 Ti0 .9Zr0 .1 合金在室温下经几分钟的孕育期就可吸氢 ,但合金在氢化过程中形成了氢含量很高的α相 ,导致合金的贮氢量降低 ,同时还使 p- c- T曲线的平台特性变差 ;Fe0 .85 Mn0 .1 5 Ti0 .9V0 .1 合金的活化性能进一步得到改善 ,在室温下几乎不需要孕育期就可以吸氢 ,但同时要降低合金的贮氢量 ,而对合金的 p- c- T曲线平台特性影响不明显 ;用 Ca取代 Fe0 .85 Mn0 .1 5 Ti合金中的部分 Ti则对合金的贮氢性能影响不明显。通过 XRD分析认为 ,上述性能的变化主要与合金中出现第二相有关     

新型复合贮氢合金Zr_(0.9)Ti_(0.1)(Ni,Co,Mn,V)_(2.1)的制备与电化学性能

采用熔铸方法制备母合金Zr0 .9Ti0 .1(Ni,Co ,Mn ,V) 2 .1,进而在母合金基础上添加吸氢剂B ,利用球磨制得 4种复合贮氢合金。X射线衍射结果表明 ,随着球磨时间的增加 ,复合合金由晶态转化为非晶态 ;电化学测试结果表明 ,复合合金经过 1～ 2次球磨就能完全活化 ,具有很好的活化性能 ;在 6 0mA/g电流下 ,复合贮氢合金C和D的稳定容量均可达到 44 0mA·h/ g左右 ,比母合金高出 80mA·h/ g ;但随着球磨时间的延长 ,所得的复合合金容量比铸态母合金的还低 ;在 30 0mA/g电流下 ,复合合金D具有较好的循环稳定性 ,经过 2 0 0次循环后其容量仅衰减 3 %。     

Correlation of microstructure and magnetic properties in Sm(Co_(bal)Fe_(0.1)Cu_(0.1)Zr_(0.033))_(6.93) magnets solution-treated at different temperatures

The correlation of microstructure and magnetic properties in Sm(Co_(bal)Fe_(0.1)Cu_(0.1)Zr_(0.033))_(6.93) magnets solution-treated at different temperatures was systematically investigated. It is found that the magnets solution-treated at 1219℃ possess a single 1:7 H phase, exhibiting the homogeneous cellular structure during further aging treatment, leading to the optimum magnetic properties. However, for the magnets solution-treated at 1211 and 1223℃,2:17 H or 1:5 H secondary phase will also form besides 1:7 H main phase, which cannot transform into cellular structure,thus deteriorating the magnetic properties greatly. The irreversible magnetization investigations with recoil loops also propose a non-uniform pinning in the magnets induced by the secondary precipitates. At proper solution temperature, Zr is supposed to occupy the Fe-Fe dumbbell sites in the form of Zr-vacancy pairs, leading to the minimum c/a ratio and thus stabilizing the 1:7 H phase. Finally,Sm(Co_(bal)Fe_(0.1)Cu_(0.1)Zr_(0.033))_(6.93) magnets with the maximum energy product and intrinsic coercivity at 550℃ up to 60.73 kJ·m~(-3) and 553.88 kA·m~(-1) were prepared by powder metallurgy method.     

Hydrogen desorption kinetics of amorphous Mg0.9Ti0. 1Ni1-xPdx （x=0, 0.05, 0.1 and 0.15） electrode alloys

1 Introduction Mg-based alloy is a kind of promising hydrogen storage materials used for fuel cell. It is also a potential candidate as cathode materials of Ni-MH rechargeable batteries due to its large discharge capacity[1]. However, its cyclic stabilit…     

Metastable magnetic behavior in La_(0.9)Tb_(0.1)MnO_3

The linear and nonlinear magnetizations of La_(0.9)Tb_(0.1)MnO_3 at low temperatures were reported in detail.The temperature dependence of magnetization shows peaks at 50,100 and 150 K,respectively.When LaMnO_3 is Tb-doped,its magnetic structure exhibits a canted antiparallel spin order.This is different from classical antiferromagnetic(AFM) in which the relaxation behavior takes place at about 150 K.At 50 K,Tb-doped LaMnO_3 exhibits canonical spin glass behavior,arising from the competition of exchange and super-exchange between spins.The peak at 100 K shows neither spin glass behavior nor canted AFM behavior.Its peak value increases with frequency increasing,and the transition temperature of the peak shifts to higher temperatures with frequency increasing.The study of aging behavior at 100 K shows a periodical variable metastability,which is ascribed to the competition between ferromagnetic(FM)-,AFM-and sinusoidal-order interactions.This work should shed a light on understanding the complex magnetic structure of the nerovskite oxides.     

FCC/L12共格高熵合金Al0.1CoCrFeNiTi0.1热压缩PLC变形行为

采用真空感应熔炼(VIM)方法,结合特定的热处理工艺,制备具有FCC/L1₂两相共格的Al_0.1CoCrFeNiTi_0.1高熵合金,在宽温度(298K-973K)内进行系统的准静态单轴恒温压缩试验。使用SEM和XRD测试方法对高熵合金微观结构形貌进行观察;根据热力学和晶体学理论计算FCC固溶体相和L1₂相纳米沉淀相的晶格参数和热力学参数,并解释其形成原因;通过Image j图像处理软件自动统计L1₂相在晶内和晶界处的尺寸、间距以及体积分数。结果表明：L1₂相与FCC相晶格常数和晶面间距的比值分别约为1.008和0.605;该高熵合金的平均原子半径 ;平均混合熵 ;平均混合焓 ;价电子浓度 ;由EDS能谱分析得到L1₂沉淀相粒子化学式为 ;在热压缩变形过程中,在同一温度下的初始应变阶段,随着应变的增大,PLC锯齿屈服强化现象的A型锯齿波逐渐消失;而当温度大于873K,应变大于0.213时,则有B型锯齿波出现。这主要与合金各阶段的变形机制有关。     

ZMT614-xY(x=0,0.1,0.5,1.0)镁合金加工硬化行为研究

利用光学金相显微镜(OM)、X射线衍射(XRD)、扫描电镜(SEM)以及能谱(EDS)对不同Y含量的ZMT614-x Y(x=0,0.1,0.5,1.0)合金挤压态和时效态的微观组织和加工硬化行为进行了研究。结果表明:ZMT614-x Y(x=0,0.1,0.5,1.0)合金挤压态和时效态的晶粒尺寸随着Y含量的增加而减小。当Y质量分数达到1%时,出现新的不规则块状Mg Sn Y相。通过ZMT614-x Y(x=0,0.1,0.5,1.0)合金挤压态和时效态的真应力-应变曲线得到加工硬化率(θ)和加工硬化指数(n)。由于晶粒细化,合金挤压态和时效态的加工硬化率θ随着Y含量的增加而减小。在合金的塑性变形过程中,发生位错的动态回复,合金挤压态和时效态的加工硬化率θ随着变形量的增加而减小。     

Dielectric,magnetic and microwave absorbing properties of polyaniline-Co_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4 composites

The spinel cobalt chromium zinc ferrites(Co_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4) and the polyaniline(PANI)-(Co_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4 composites were prepared by polyacrylamide gel and an in situ polymerization method,respectively.The structure of the synthesized material was characterized by X-ray diffraction(XRD) and Fourier transform infrared spectrometer(FTIR),which shows that the spinel Co_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4 ferrites and the PANICo_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4 composites are obtained.As a small amount of Co~(2+) in the octahedron ferrite is replaced by Cr~(3+),the lattice constant of Co_(0.8)Zn_(0.2)Fe_2O_4 ferrites reduces from0.8409 to 0.8377 nm.The magnetic properties of the two materials were investigated by vibrating sample magnetometer(VSM).The VSM results confirm that the saturation magnetization(M_s),remanent magnetization(M_r) and coercive force(H_c) of the PANI-Co_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4composites are 8.80 mA·m~2·g~(-1),3.14 mA·m~2·g~(-1) and37.22 kA·m~(-1),respectively,which are smaller than those of the Co_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4 ferrites.The microwave absorbing capability of the two materials was studied by waveguide method.In the frequency range of 5-20 GHz,two reflection loss maximum values of the PANI-Co_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4composites appear at 14.1 and 17.9 GHz with-13.17 and-15.36 dB,respectively,which are obviously higher than those of the Co_(0.7)Cr_(0.1)Zn_(0.2)Fe_2O_4 ferrites.     

Thermoelectric properties of Bi_(0.5)Sb_(1.4-x)Na_xIn_(0.1)Te_3 alloys

The Bi_(0.5)Sb_(1.4-x)Na_xIn_(0.1)Te_3(x=0.02-0.20)alloys were fabricated by high vacuum melting and hotpressing technique.The phase structures and morphology of the bulk samples were characterized by X-ray diffraction(XRD) and scanning electron microscope(SEM),respectively.Effects of In and Na co-doping on the electrical and thermal transport properties were studied from room temperature to 500 K.Seebeck coefficient of the Bi_(0.5)Sb_(1.5)Te_3 can be enhanced by substituting Sb with In and Na at near room temperature.The electrical conductivity of the In and Na co-doped samples is lower than that of the Bi_(0.5)Sb_(1.5)Te_3 alloy from room temperature to 500 K.In and Na co-doping of appropriate percentage optimizes the thermal conductivity of the Bi_(0.5)Sb_(1.5)Te_3 alloy.The minimum value of thermal conductivity of Bi_(0.5)Sb_(1.36)Na_(0.04)In_(0.1)Te_3 alloy is 0.45 W·m~(-1) K~(-1) at 323 K.which leads to a great improvement in the thermoelectric figure of merit(zT).The maximum zT value reaches 1.42 at 323 K.