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在140~180℃利用水热合成法制备了Co Fe2O4纳米颗粒。使用X射线衍射仪和振动磁强计检测Co Fe2O4纳米颗粒。结果表明:随着合成温度的升高,该颗粒的矫顽力先增大后减小,在160℃时出现峰值,晶粒尺寸和饱和磁化强度则持续增加。对上述Co Fe2O4纳米颗粒进行磁分离处理,结果表明:该颗粒的晶粒尺寸和矫顽力都有一定程度的提高,其中原产物晶粒尺寸越小,晶粒尺寸和矫顽力提高的效果越明显。说明磁分离可以去除样品中的超顺磁颗粒,减小样品的晶粒尺寸分布,提高样品的矫顽力。     

Co1-xNixFe2O4／SiO2纳米复合材料的磁性

采用溶胶-凝胶法制备了Co1-xNixFe2O4/SiO2(0≤x≤1.0)纳米复合材料.利用XRD,TEM,振动样品磁强计(VSM)和M(o)ssbauer谱测试了900℃热处理样品的结构,晶粒尺寸和磁性.结果表明,样品中Co1-xNixFe2O4铁氧体的平均晶粒尺寸在15-20 nm之间,Ni2+的掺杂引起CoFe2O4晶胞体积减小.VSM结果表明,随Ni2+含量的增加,样品的比饱和磁化强度和矫顽力变小.M(o)ssbauer谱表明,室温下各样品均处于磁有序状态,样品的内磁场随N2+含量的增加而变小.     

纳米晶Fe0．13[Co20Ni80]0．87合金微细纤维的制备及磁性能

以柠檬酸和金属盐为原料,采用有机凝胶一热还原法制各了Fe0.13[Co20Ni80]0.87三元合金微细纤维.采用FTIR、XRD、TG/DSC、SEM和EDS等对纤维前驱体和热还原产物的结构、物相、形貌和组成进行了分析.采用振动样品磁强计(VSM)对纤维的磁性能进行了测试.结果表明:Fe0.13[Co20Ni80]0.87合金纤维的直径为0.3～.0 μm,表面光滑、长径比大;组成合金纤维的晶粒大小与还原温度密切相关,当温度为300～700℃时,晶粒尺寸由约20 nm增加到约50 nm;该合金纤维显铁磁性,其矫顽力主要受合金中C含量及晶粒大小的影响,随制备温度的升高而降低;饱和磁化强度则主要与合金的组分相关,随还原温度的升高和合金纯度的提高而增大;经700℃热还原后,合金纤维的饱和磁化强度ms为120A·m2/kg,矫顽力Hc为10.4 kA/m.     

纳米NixZn1-xFe2O4颗粒的制备及其磁性能

采用水热法制备了不同镍锌比的纳米NixZn1-xFe2O4粉体.采用X射线衍射、透射电镜(TEM)、振动样品磁强计(VSM)等方法对制备的样品进行了表征,物相分析结果表明,在200℃水热5 h可以得到纯的纳米NiFe2O4粉体,在200℃水热5 h制备的Ni0.5Zn0.5Fe2O4中含有γ-Fe2O3,在220℃水热5 h可以得到纯Ni0.5Zn0.5Fe2O4纳米粉体.水热温度为220℃时制备的ZnFe2O4中仍然存在γ-Fe2O3.TEM结果表明,NixZn1-xFe2O4粒子为球形,粒径为10～20nm.磁滞回线结果表明纳米NixZn1-xFe2O4具有较好的磁性能,其中Ni0.5Zn0.5Fe2O4纳米粒子具有最大的饱和磁化强度(Ms),ZnFe2O4具有最大的矫顽力(Hc)值.     

低温烧结合成Ni-Cu铁氧体粉体

以新鲜鸡蛋清作为复合络合剂,利用蛋清合成Ni0.6Cu0.4Fe2O4尖晶石铁氧体粉体。此方法反应条件温和、工艺简单、成本低廉,且容易控制。通过X射线衍射仪(XRD)和透射电子显微镜(TEM)分析样品的微观结构和形貌特征,并结合差热-热重联合分析仪(TG-DTA)研究样品的晶化过程,用激光粒度仪(LPSA)测量样品的粒度分布,用振动磁强计(VSM)测量样品在室温下的磁学性能参数。结果表明:Ni0.6Cu0.4Fe2O4氧体粉体较佳的制备工艺参数为采用两阶段式的烧结工艺:240℃保温1 h,升温至440℃保温2 h,最终介于520~550℃焙烧6 h。在该条件下合成得到的Ni0.6Cu0.4Fe2O4铁氧体粉体为纳米级的、单相的,平均晶粒尺寸约为16.31 nm,平均颗粒尺寸约为2.19μm,饱和磁化强度可达37 emu/g,平均矫顽力为68.53 Oe。     

热处理制度对纳米晶Mn0．6Zn0．4Fe2O4铁氧体纤维结构和磁性能的影响

以柠檬酸及金属盐为原料,采用有机凝胶先驱体转化法制备直径0.5～3.0 μm、平均晶粒尺寸为8.7～31.8 nm的Mn0.6Zn0.4Fe2O4铁氧体纤维.利用XRD、SEM和VSM分别对前驱体凝胶的结构、热处理产物的物相、形貌及磁性能进行表征.结果表明:Mn-Zn铁氧体相的稳定性主要受热处理气氛中氧含量的影响,在空气气氛中将发生部分分解,而在氮气气氛中能获得纯的尖晶石型铁氧体相;在400 ℃时获得的Mn0.6Zn0.4Fe2O4铁氧体纤维因晶粒尺寸小于临界尺寸而表现出超顺磁特性,但随热处理温度的升高和保温时间的延长,Mn0.6Zn0.4Fe2O4铁氧体纤维的饱和磁化强度、矫顽力和晶粒尺寸均逐渐提高,特别是在500 ℃以后,增长尤为显著.     

机械合金化制备Al_(65)Fe_(25)Ni_(10)纳米合金粉的磁性研究

用机械合金化法制备A165Fe25Ni10纳米合金粉末.采用X射线衍射(XRD)、振动样品磁强计(VSM)研究了其结构和磁性随球磨时间的演变.结果表明:在球磨初期,粉末晶粒尺寸急剧减小,内应变迅速增大:球磨50 h后晶粒尺寸、内应变基本保持稳定.矫顽力(Hc)随球磨时间的增加先增大,球磨50 h后急剧减小.在晶粒尺寸较小时,矫顽力与晶粒尺寸的六次方成正比;晶粒尺寸较大时,矫顽力与晶粒尺寸成反比.     

Co~(2+)取代Ni~(2+)对MgNiCuZn铁氧体纳米微粒磁学性能的影响

通过化学共沉淀法制备了纳米级的Mg0.05CoxNi0.35-xCu0.2Zn0.4Fe2O4铁氧体超细粉末,采用X射线衍射仪和振动样品磁强计分析研究了Co2+取代Ni2+对铁氧体结构和饱和磁化强度的影响。结果表明,试样的晶格参数a和平均粒径Dx随Co2+取代量的增加而增大;饱和磁化强度Ms随Co2+取代量的增加单调增大。     

纳米晶Ni-Zn铁氧体纤维的制备与磁性能

以柠檬酸和金属盐为原料,采用有机凝胶先驱体转化法成功制备了纳米晶Nix-Zn1-x(x=0.25～0.75)铁氧体纤维.通过FTIR,TG/DSC,XRD及SEM对纤维先驱体凝胶的结构、热分解过程及热处理产物的物相、形貌进行了表征.采用VSM研究了铁氧体纤维的磁性能.结果表明这种Ni-Zn铁氧体纤维表面光滑,直径均匀,有较大的长径比,最细纤维直径可达1μm以下;组成Nix-Zn1-x(x=0.25～0.75)铁氧体纤维的晶粒大小在15.2～86 nm,主要受焙烧温度的影响;纤维的饱和磁化强度与矫顽力与其成分和焙烧温度有关,经800℃焙烧2 h后得到的Ni0.5-Zn0.5铁氧体纤维的饱和磁化强度为12.723 A·m2·kg-1矫顽力为5851 A·m-1.     

中空Mn_(0.4-x)Mg_xZn_(0.6)Fe_2O_4(x=0.0,0.2)铁氧体纤维的制备和磁性能

以柠檬酸和金属盐为原料.采用有机凝胶-热分解法成功制备出了具有中空结构的Mn0.4-xMgxZn0.6Fe2O4(x=0.0,0.2)铁氧体纤维.通过 XRD、SEM和VSM对目标纤维进行了表征,并初步研究了纤维中空结构的形成机制以及Mg2+掺杂对Mn-Zn铁氧体纤维的结构、微观形貌和磁性能的影响.结果表明,所得纤维样品都为单一的立方尖晶石结构,直径在0.5-3 μm之间,长径比较大,纤维表面都较为光滑、致密.Mg2+掺杂改善了纤维的微观结构和磁性能,与未掺杂的Mn-Zn铁氧体相比.20 mol%Mg2+掺杂的Mn-Mg-Zn铁氧体纤维的晶格常数、晶粒尺寸、饱和磁化强度和矫顽力都有不同程度的提高.     

(1-4x)NBT-3xKBT-xBT系无铅压电陶瓷性能研究

采用传统固相法制备了(1-4x)NBT-3xKBT-xBT(x=0.020～0.035)体系压电陶瓷.通过XRD分析,发现该体系陶瓷都能形成单一的钙钛矿型固溶体,并在0.025≤x≤0.032范围内具有三方和四方共存结构,为该体系的准同型相界.当x=0.028时,d_(33)=162 pC/N,Q_m=203.29,k_p=0.234.同时分析了该体系陶瓷材料在1, 10, 100 kHz下介电常数-温度曲线和介电损耗-温度曲线,发现该体系陶瓷样品的介电温谱都存在两个介电反常峰,且介电常数和介电损耗与频率存在很强的依赖性,表明该体系材料具有弛豫型铁电体性质.     

(0.96Bi_(0.5)Na_(0.5)TiO_3~-0.04BaTiO_3)-(0.98K_(0.5)Na_(0.5)NbO_3~-0.02LiTaO_3)无铅压电陶瓷的结构分析与性能研究

研究了(1-x)(0.96Bi_0.5Na_0.5TiO_3-0.04BaTiO_3)-x(0.98K_0.5Na_0.5NbO_3-0.02LiTaO_3)(BNTBT-KNNLT)体系在0≤x≤0.07这一组分区域的结构和性能.X射线衍射谱发现,这一系列组分在室温下形成纯钙钛矿型固溶体,没有其他杂相产生.(111)峰的峰位和峰形随组分的变化有规律的变化.随着KNNLT组分的加入,压电及介电等性能有比较明显的改变.压电性能随KNNLT的加入出现最大值.当x=0.02时,压电常数d_(33)=125 pC/N.介电常数在室温下随组分的增加而增加.电滞回线的结果显示,尽管在BNTBT中掺杂了KNNLT,这一系列的压电陶瓷仍然具有较大的矫顽场.当x=0.02时,室温下介电常数和剩余极化强度分别为:ε_r=1455,P_r=32.3 μC/cm~2.实验结果表明适量的KNNLT掺杂进BNTBT中可以改善BNTBT的压电和介电性能.     

Electrochemical performance of LiNi_(0.5)Mn_(0.5)O_2 with different synthesis methods

Li Ni0.5Mn0.5O2 as a cathode material for Li-ion battery was prepared by the metal acetate decomposition method, sol–gel method, and carbonate co-precipitation method, respectively. The influences of synthesis methods on the physical and electrochemical behaviors of Li Ni0.5Mn0.5O2 were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and electrochemical tests. XRD patterns show that both the sol–gel and carbonate co-precipitation methods can form single phase of layered structure, while a trace of Ni O impurity is observed via the metal acetate decomposition method. SEM results show the as-prepared carbonate particle has a spherical morphology with an average diameter of 10 lm, consisted of primary nano-sized particles with particle diameter of200 nm. The sample prepared by the carbonate co-precipitation method exhibits the highest discharge specific capacity and the best cycling stability, which results from the steady homogeneity of precursor constant by the fixation of CO2-3group. It can deliver an initial discharge specific capacity of 186.3 m Ahág-1, and retain 170 m Ahág-1after100 cycles at a current rate of 20 m Aág-1in the voltage range of 2.5–4.7 V at 25 °C. Moreover, even at the high temperature of 55 °C, it still delivers a reversible specific capacity of 222.6 m Ahág-1with little capacity loss after 30 cycles.     

BaTiO_3-Na_(0.5)Bi_(0.5)TiO_3无铅PTCR陶瓷研究

以BaTiO_3-Na_0.5Bi_0.5TiO_3(BT-NBT)陶瓷系统为研究对象,采用固相法制备了(1-x)BT+xNBT(0.01＜x＜0.06)系统陶瓷.通过DSC、XRD、SEM等分析手段研究了NBT的加入量以及烧成气氛对BaTiO_3基PTCR陶瓷的显微结构及阻温特性的影响.研究结果表明:加入低含量(x＜0.03)NBT时,能明显提高烧成陶瓷的居里温度(T_c),当加入x=0.01NBT时,T_c提高到150 ℃.氮气中烧成的陶瓷室温电阻率低于空气中烧成的,但其PTC效应减弱.     

Tunable characteristics of (Ba0.5Sr0.5) TiO3 (BST) capacitors using (Ba0.5Sr0.5) RuO3 (BSR) interfacial layers onto Pt/Ti/SiO2/Si substrates

The conducting oxide electrodes (Ba, Sr) RuO₃ (BSR) similar in structure and chemical composition to (Ba, Sr) TiO₃ (BST) were deposited by metalorganic chemical vapor deposition (MOCVD) onto Pt/Ti/SiO₂/Si substrates to improve the structural and dielectric properties of BST films. The BSR interfacial layers between the BST and Pt bottom electrode influenced the preferred orientation, surface morphologies, and dielectric properties of BST films. The structural and dielectric properties of BST films depended on the thickness of the BSR layers. BST films with (100) texturing up to 150 Å thickness of BSR showed a smoother and smaller grain size than those without interfacial layers, and a tunability and dielectric constant of about 70% and 1300 at an interfacial layer of 150 Å, respectively. On the other hand, BST films with above 300 Å thickness in BSR layers showed a (110) texturing similar to those without BSR layers and a slight decrease of tunability and dielectric constant compared with those of (100) texturing BST films. The increase of the dielectric loss of BST films with BSR layers was attributed to the carbon contamination diffused from MOCVD-BSR layers.     

Sm_(0.5)Ca_(0.5)MnO_3薄膜的光诱导弛豫特性(英文)

采用射频磁控溅射方法在LaAlO3（100）基片上制备了电荷有序态锰氧化物Sm0．5Ca0.5MnO3薄膜,X射线衍射分析表明所制备薄膜具有较好的外延特性。测试了薄膜的低电阻-温度关系,表明薄膜在测量温度范围内呈现半导体导电特性。施加磁场和激光辐照均可引起电荷有序态的退局域化,从而导致电阻减小。研究了激光诱导电阻变化弛豫特性,表明电阻随时间的变化符合指数关系,通过拟合得到的时间常数随着温度的升高而增加,分析表明其主要可归结于外在热效应的影响。     

Magnetic properties and crystallization kinetics of Zn_(0.5) Ni_(0.5) Fe_2O_4

Precursor of nanocrystalline Zn0.5Ni0.5Fe2O4 was obtained by grinding mixture of ZnSO4·7H2O,NiSO4·6H2O,FeSO4·7H2O,and Na2CO3·10H2O under the condition of surfactant polyethylene glycol(PEG)-400 being present at room temperature,washing the mixture with water to remove soluble inorganic salts and drying it at 373 K.The spinel Zn0.5Ni0.5Fe2O4 was obtained via calcining precursor above 773 K.The precursor and its calcined products were characterized by differential scanning calorimetry(DSC) ,Fourier transform ...     

Switching characteristics of MPB compositions of (Bi0.5Na0.5)TiO3–BaTiO3–(Bi0.5K0.5)TiO3 lead-free ferroelectric ceramics

The polarization switching characteristics of lead-free a(Bi_0.5Na_0.5)TiO₃–bBaTiO₃–c(Bi_0.5K_0.5)TiO₃ (abbreviated as BNBK 100a/100b/100c) ferroelectric ceramics are investigated. For the first time, the strain hystereses of BNBK compositions inside and outside the morphotropic phase boundary (MPB) are presented. The total induced electrostrain (ε_33,total) and apparent piezoelectric coefficient (d₃₃) first increase dramatically and then decrease gradually as the BNBK composition moves from the tetragonal phase to the MPB and then to the rhombohedral phase. The measured polarization hystereses indicate that the BNBK compositions situated near the rhombohedral side of the MPB typically possess higher coercive field (E_c) and remanent polarization (P_r), while the compositions situated near the tetragonal side of the MPB possess higher apparent permittivity. BNBK 85.4/2.6/12 a composition well within the MPB, exhibits an ε_33,total of ∼0.14%, an apparent d₃₃ of 295 pCN⁻¹ and a P_r of 22.5 μC cm⁻². These property values suggest a candidate material for lead-free actuator applications.     

Fe_(4.5)Co_(67.5)Nb_(0.5)Mn_(0.5)Si_(12)B_(15)丝材中的巨磁阻抗效应

报道了淬火态Fe45Co675Nb05Mn05Si12B15丝中GMI效应,发现淬火态非晶丝GMI(Z)=|(Z(65Oe)-Z(0))/Z(0)|可高达73%。我们也对简单退火下对Fe45Co675Nb05Mn05Si12B15钴基材料中GMI效应的影响也进行了深入细致的研究,发现GMI峰值随退火温度从300℃增加到450℃而先上升,达到一个最大值,然后下降。350℃退火的效果较佳。同时发现低于1MHz时,淬火态对应的GMI效应优于退火态的值,而高于1MHz时,350℃退火材料的GMI(Z)值相应的要高。     

Structural and magnetic properties of (Sm_0.5Nd_0.5)_2(Fe_(1-x)Co_x)_(17)compounds

The structure, magnetization, and magnetocrystalline anisotropy were investigated using X-ray diffraction, vibrating sample magnetometer, and AC susceptibility-meter. It is found that the microstructure of (Sm0.5Nd0.5)2(Fe1-xCox)17 alloys is an (Sm,Nd)2(Fe,Co)17 phase with the rhombohedral Th2Zn17-type structure. The Curie temperature Tc increases with the Co concentration increasing, and the magnetization first increases as the Co content increases in (Sm0.5Nd0.5)2(Fe1-xCox)17 alloys and then decreases slowly. The easy magnetization direction (EMD) of (Sm0.5Nd0.5)2(Fe0.25Co0.75)17 is along the c-axis and a strong enhancement of the crystalline anisotropy energy constant K is produced by the addition of some Co atoms. The anisotropy energy constant reaches the maximum when x = 0.75 and then decreases slowly with the Co content further increasing. The (Sm0.5Nd0.5)2(Fe0.25Co0.75)17compound is an optical candidate for the new permanent magnet, which possesses a high magnetization, a high Curie temperature,