半导体硅上电沉积Cu/Co层状薄膜

由磁性层和非磁性层组成的人工调制层状结构多层膜,其物性和磁性都表现出与其它结构的多层膜显著不同的特点,如巨磁阻效应［’,‘l、易磁性方向的改变等”］．其性能的研究不但在磁性理论上具有重大意义,而且有望应用于高性能的磁阻敏感设备及提高磁记录密度等．因而近年来有关这方面的研究越来越引起人们的重视．目前,磁性多层膜的制备主要采用气相沉积、磁控溅射、分子束外延等真空技术．由于电沉积技术具有设备简单、操作方便等特点而成为制备多层膜的颇具活力的工艺．CO／Cll多层膜在C。层厚度较薄时具有较高室温巨磁阻（GMR）…     

半导体Si上电沉积Cu-Co颗粒膜及其巨磁电阻效应

采用电化学沉积方法在半导体Si上制备Cu-Co金属颗粒膜. XRD测试结果表明制备态的薄膜形成了单相亚稳态面心合金结构, 薄膜经退火后, XRD谱图中出现了析出的纯金属Co的衍射峰, 这表明薄膜在退火过程中发生了相分离. TEM测试结果也进一步证实了磁性的Co颗粒从非磁性的铜基体中析出. 随着退火温度的增加, 颗粒膜巨磁电阻(GMR)效应不断增大, 当退火温度为450 ℃时, Co0.20Cu0.80薄膜的巨磁电阻效应达到最大, 磁阻率为8.21％. 之后, 磁阻率又随退火温度的升高而降低. 退火前后样品磁滞回线的变化表明薄膜中发生了从超顺磁性到铁磁性的转变, 矫顽力、剩余磁化强度和饱和磁化强度均随退火温度的增高而逐渐增大. 超顺磁性颗粒的作用导致了GMR－H与M－H曲线的不同.     

硼酸系电结晶制[Co/Pt]_n(n≥40)金属多层膜的研究

于钝铜片及玻碳上采用双电解池恒电位结晶制取了［Ｃｏ（０．５ｎｍ～２．２ｎｍ）／Ｐｔ（２．０ｎｍ）］ｎ（ｎ≥４０）金属多层膜．低角度Ｘ射线衍射表明多层膜有良好的周期性调制结构,其Ｂｒａｇｇ峰的半幅值随着钴层电结晶电位的负移和铂层电结晶电位正移而减小．中角度Ｘ射线衍射表明界面上存在ＣｏＰｔ３金属化合物．多层膜的磁滞回线表明该多层膜的易磁化轴平行于膜面,表现出平面磁各向异性．以低过电位镀Ｃｏ（厚度约０．５ｎｍ）的多层膜的垂直方向磁滞回线形状较好,有望表现出垂直磁各向异性．     

La2／3Ca1／3MnO3／YBa2Cu4O8／La2／3Cal／3MnO3三层薄膜中的各向异性磁电阻

研究了La2/3Ca1/3MnO3(LCMO)／YBa2Cu4O8(YBCO)／LCMO三层薄膜中的各向异性磁电阻。LCMO单层膜和三层膜都表现出面内各向异性，磁电阻对θ(磁场方向和偏置电流方向的夹角)和Ф(磁场方向和薄膜表面的夹角)表现出正弦三角函数的依赖关系。在低场下，无论在面内还是面外都发现了正的磁电阻。     

线型异核三金属M－E－M（M＝Mo，W；E＝Hg，Zn）化合物的研究──［η~5－RC_5H_4（CO）_3M］_2Zn（M＝Mo，W；R＝CO_2Me，CO_2Et）的合成、性质及结构

研究了含汞三金属化合物［η_５－ＲＣ_５Ｈ_４（ＣＯ）_３Ｍ］_２Ｈｇ（Ｍ＝Ｍｏ，Ｗ；Ｒ＝Ｍｅ，Ｅｔ，ＣＯ_２Ｍｅ，ＣＯ_２Ｅｔ）与锌粉的置换反应，发现当取代基Ｒ为给电子的Ｍｅ和Ｅｔ时底物不发生反应，而取代基Ｒ为拉电子的ＣＯ_２Ｍｅ和ＣＯ_２Ｅｔ时，则底物中的汞可被锌置换，生成带有机官能团的三金属化合物［η_５－ＲＣ_５Ｈ_４（ＣＯ）_３Ｍ］_２Ｚｎ；另外，还发现Ｒ为ＣＯ_２Ｅｔ，Ｍ为Ｍｏ的产物［η_５－ＲＣ_５Ｈ_４（ＣＯ）_３Ｍ］_２Ｚｎ可在室温下被分解为相应的氯代物η_５－ＥｔＯ_２ＣＣ_５Ｈ_４ＭｏＣｌ．     

非晶态分子合金低温制备纳米复合氧化物La~1~-~xCa~xMnO~3

钙钛矿型稀土锰氧化物La~1~-~xCa~xMnO~3(RE=La,Pr,Nd,Gd;T=Ca,Sr,Ba,Pb等)因其特殊的巨磁电阻效应,引起人们广泛的关注。用非晶态的分子合金为前驱体,制备了一系列具有纳米尺寸的La-Ca-Mn-O复合氧化物颗粒。研究表明,前驱体的晶化温度对纳米颗粒的形貌和大小均有影响。当晶化温度为450℃-600℃时,从透射电子显微镜观察到的颗粒大小约为25nm-100nm。该纳米材料的磁及磁电阻行为不同于其体相体系,其交流磁化率表现出较较强的尺寸依赖性,而磁电阻具有本征型和自旋隧穿型的巨磁电阻行为。     

可录型光盘(CD-R)中染料膜层的光谱性质和光学特性

本文利用光在多层膜介质中的传播模型,计算了可录型光盘（ＣＤ Ｒ）中染料媒体的光学特性．表明在适合于ＣＤ Ｒ光盘记录的７８０ｎｍ波长处,由于多层膜中光的干涉作用,样品反射率随薄膜的厚度变化发生振荡．振荡的幅度和周期依赖于染料薄膜的复数折射率（ｎ＋ｉｋ）．当记录介质层的复数折射率在２．１＋ｉ０．０２至２．８＋ｉ０．１２之间时,能够满足ＣＤ Ｒ光盘对染料介质的要求．通过对三种菁染料薄膜的光谱性质分析及光学参数的模拟计算,证实了该方法用于染料薄膜光学特性研究的合理性．并为选择适合于光记录的染料薄膜的厚度范围提供了简便的方法     

Nd-Sr-Mn-O钙态矿锰氧化物的低场磁电阻效应

采用固相烧结法和脉冲激光沉积法分别制备了钙态矿型锰氧化物Nd1-xSrxMnO3(x=0．1，0．2，0．3，0．4，0．5)大块多晶和Nd0．7Sr0．3MnO3在(100)LaAlO3基片上的单取向薄膜样品，分别研究了这些样品的磁电阻效应。研究表明，在多晶样品中，x=0．3时具有最大的磁电阻比，其值在240K和1T磁场下可达24．2％。对于同一成分的外延薄膜，发现磁电阻随着沉积时基片温度Ts的升高而下降，当Ts=500℃时的制备态薄膜在同样条件下的磁电阻可达84％，随着外加磁场增大到5T，磁电阻将线性增大到275％。并讨论了造成单取向膜和块材磁电阻不同的原因。     

新型五甲基茂基三苄氧基钛/甲基铝氧烷催化剂合成苯乙烯-乙烯共聚物及其表征

以五甲基茂基三苄氧基钛［Ｃｐ＊ Ｔｉ（ＯＢｚ）３］ 和甲基铝氧烷（ ＭＡＯ） 组成的催化体用本体法合成出苯乙烯 乙烯共聚物Ｐｏｌｙ（Ｓ ｃｏ Ｅ） ．考察了共聚温度,共聚时间,Ａｌ／Ｔｉ 摩尔比,主催化剂浓度［Ｔｉ］ 等条件对共聚反应的影响．共聚产物经沸丁酮,沸四氢呋喃（ＴＨＦ） 连续抽提分离,发现共聚物主要存在于ＴＨＦ 可溶级分中．可溶级分经ＤＳＣ,１３Ｃ ＮＭＲ,ＷＡＸＤ,ＤＭＡ 等手段分析,证明苯乙烯 乙烯共聚物为具有单一玻璃化转变温度（ Ｔｇ） 无熔融温度的无规共聚物,显示弹性体的粘弹性行为．     

CH自由基共振增强多光子电离光谱

ＣＨ自由基在燃烧化学、星际化学、化学发光和化学激光研究中占有重要的地位,并且作为最简单的碳氢化合物,ＣＨ自由基是理想的理论计算模型分子,在理论研究领域中也有着重要的地位．因此 ,多年来人们对ＣＨ自由基进行了大量的研究［１ -９］,但是对于ＣＨ自由基,到目前为止大部分局限于低激发态的研究,对于较高激发态的研究报导则很少见．Ｃｈｕｐｋａ等［２ -６］用(２ １)ＲＥＭＰＩ方法获得了ＣＨＤ态的ｖ＝２振动能级光谱．然而后来Ｔｊｏｓｓｅｍ和Ｓｍｙｔｈ［７］测量了同波段的ＲＥＭＰＩ光谱,发现他们测得的光谱谱峰强度与…     

电沉积条件对钴-锰合金结构和磁性能的影响

以柠檬酸为络合剂和硼酸为缓冲剂的酸性硫酸盐镀液中电沉积Co-Mn合金,循环伏安实验显示Co-Mn的起始共沉积电位约-1.282 V(vs.Hg-Hg2SO4 , sat.K2SO4)。借助扫描电镜(SEM)、能谱分析(EDS) 、X射线衍射(XRD)和振动样品磁强计(VSM) 研究了沉积条件对镀层结构和磁性能的影响。结果表明,Co-Mn镀层的组成受沉积条件影响较大;在镀液pH 4.0时,随着阴极电流密度从10 mA•cm-2增加到40 mA•cm-2,镀层中锰含量从0.3 at%增大到6.6 at%;镀层结构由hcp的固溶体转为fcc的固溶体;随着镀层中锰含量增加,膜的饱和磁化强度开始增大,然后降低,最大饱和磁化强度为1926.0 kA•m-1,膜的矫顽力在31.6 ~ 33.9 kA•m-1范围。     

热处理对[NiFe/Cu/Co/Cu]_n多层纳米线磁性能的影响

采用双槽控电位法在阳极氧化铝(AAO)模板中制备了有序均一的[NiFe/Cu/Co/Cu]n多层纳米线阵列,并在不同温度下进行了热处理.利用X射线衍射(XRD)对热处理前后多层线的晶体结构进行了测试.考察了不同退火温度对多层线矫顽力、剩磁比、巨磁电阻(GMR)效应、磁灵敏度的影响.随热处理温度升高,多层纳米线中磁性微晶晶型取向越来越明显,晶体结构更均匀;多层纳米线的矫顽力和剩磁比先增大后减小.300°C下多层纳米线矫顽力达到最大值,GMR最大值可达59%,对应的磁电阻灵敏度(SV)为0.233%Oe-1.     

自旋阀多层膜的电化学制备及其巨磁电阻效应

采用双槽控电位电沉积法在n-Si(111)基体上以NiFe 薄膜为缓冲层制备了[Ni80Fe20/Cu/Co/Cu]n自旋阀多层膜, 并确定了电沉积的工艺条件. 利用X射线衍射(XRD)表征了自旋阀多层膜的超晶格结构, 研究了NiFe缓冲层对自旋阀生长取向的影响. 采用四探针法研究了各子层厚度对自旋阀巨磁电阻效应的影响, 通过振动样品磁强计(VSM)测试了自旋阀的磁滞回线. 自旋阀的巨磁电阻(GMR)值最初随着铜层厚度的变化并发生周期性振荡, Cu 层厚度为3.6 nm时, GMR 达到最大值,随后逐渐减小. 随着Co层和NiFe 层厚度的增大, GMR 值的变化趋势均为先增大后减小. 当自旋阀的结构为NiFe(25 nm)/[Cu(3.6 nm)/Co(1.2 nm)/Cu(3.6 nm)/NiFe(2.8 nm)]30时, GMR 值可达5.4%, 对应的磁电阻灵敏度(SV)为0.2%·Oe-1, 饱和磁场仅为350 Oe.     

电结晶铜/钴纳米多层膜结构与磁性能研究

以n型Si(111)为基底, 在硼酸镀液体系中采用双槽法电结晶制备Cu/Co纳米多层膜, 确定了工艺条件. 用扫描电镜(SEM)和X射线衍射(XRD)对纳米多层膜的结构和形貌进行了表征, 显示多层膜具有良好周期性和超晶格结构. 并用物性测量系统PPMS测试了不同结构 Cu/Co纳米多层膜的磁性能. 磁滞回线表明: 不同周期数的纳米多层膜其矫顽力均较小. 巨磁阻(GMR)性能与纳米多层膜结构有关. GMR值随Co磁性层厚度增长先增大后减小, 有一极值; 随着Cu非磁性层厚度的增加GMR值发生周期性的振荡; 随周期数N的增大, GMR值先增大, 在N为60时达到了90%, 随着N的继续增加而减小, 当达到80周期时, GMR值趋于稳定.     

退火处理对新型无镁Y0.7La0.3Ni3.25Al0.1Mn0.15储氢合金结构和电化学性能的影响

通过电弧熔炼制备了无镁La-Y-Ni系A₂B₇型Y_0.7La_0.3Ni_3.25Al_0.1Mn_0.15合金, 并在高纯0.2 MPa Ar气氛下分别对合金进行850~1050 ℃真空24 h退火热处理. 通过X射线衍射(XRD)、 中子衍射(ND)、 扫描电子显微镜/能量分散谱(SEM/EDS)和电化学测试方法研究了退火温度对合金结构和性能的影响. 结构分析表明, 铸态合金由CaCu₅, Ce₅Co₁₉, Gd₂Co₇, Ce₂Ni₇多相构成, 随着退火温度升高, CaCu₅, Ce₅Co₁₉, Gd₂Co₇相逐步减少直至消失, Ce₂Ni₇主相相丰度逐步增加. 900~950 ℃退火时, 合金为单相Ce₂Ni₇结构. 退火温度继续升高, 合金中出现少量PuNi₃相. 合金电极的最大放电容量随着退火温度的升高先增加后降低. 从铸态的307.6 mA·h/g增加到900 ℃退火时的最大值393.1 mA·h/g, 后又降到1050 ℃退火时的366.4 mA·h/g. 合金电极的电化学循环稳定性随退火温度的升高而升高, 循环100次后电化学容量保持率(S₁₀₀)从铸态的66%上升到1050 ℃退火后的88.5%, 900~950 ℃退火时, 合金电极具有较好的综合电化学性能.     

Characteristics of organic transformations in a confined dendritic core: studies on the AIBN-initiated reaction of dendrimer cobalt(II) porphyrins with alkynes

Cobalt(II) complexes of poly(aryl ester) dendrimer porphyrins [(m-[Gn]TPP)Co(II)] (generation number n=0-4), in the presence of azobisisobutyronitrile (AIBN) at 60 degrees C, underwent alkenylation with several alkynes at the metal center. A complete inhibition of double-bond migration (secondary transformation) was observed for [(m-[Gn]TPP)Co(II)] (n=3 and 4), which gave [(m-[Gn]TPP)Co(III)-C(=CH(2))R] (n=3 and 4) exclusively. Overall reaction rates for [(m-[Gn]TPP)Co(II)] (n=0-3) were hardly dependent on the size of the dendritic substituents, while a notable retardation was observed for the largest dendrimer, [(m-[G4]TPP)Co(II)]. Mechanistic studies on double-bond migration with pure [(m-[Gn]TPP)Co(III)-C(=CH(2))Bu] (n=0-4) demonstrated that the secondary transformation involves participation of [(m-[Gn]TPP)Co(III)H] (n=0-4), derived from [(m-[Gn]TPP)Co(II)] and AIBN, rather than [(m-[Gn]TPP)Co(II)] alone. Crossover experiments using [(m-[Gn]TPP)Co(III)-C(=CH(2))Bu] (n=2-4), in combination with nondendritic [(m-[G0]TPP)Co(II)] and AIBN, indicated a high level of steric protection of the active center by a robust [G4]-dendritic cage, as suggested by a (1)H NMR pulse relaxation time profile of m-[G4]TPPH(2).     

Synthesis of silicon doped SrMO3 (M = Mn, Co): stabilization of the cubic perovskite and enhancement in conductivity

In this paper we report the successful incorporation of silicon into SrMO(3) (M = Co, Mn) leading to a structural change from a hexagonal to a cubic perovskite. For M = Co, the cubic phase was observed for low doping levels (3%), and these doped phases showed very high conductivities (up to ≈350 Scm(-1) at room temperature). However, annealing studies at intermediate temperatures (700-800 °C), indicated that the cubic phase was metastable with a gradual transformation to a hexagonal cell on annealing. Further work showed that co-doping with Fe resulted in improved stability of the cubic phase; a composition SrCo(0.85)Fe(0.1)Si(0.05)O(3-y) displayed good stability at intermediate temperatures and a high conductivity (≈150 Scm(-1) at room temperature). For M = Mn, the work showed that higher substitution levels were required to form the cubic perovskite (≈15% Si doping), although in these cases the phases were shown to be stable to annealing at intermediate temperatures. Conductivity measurements again showed an enhancement in the conductivity on Si doping, although the conductivities were lower (≈0.3-14 Scm(-1) in the range 20-800 °C) than the cobalt containing systems. The conductivities of both systems suggest potential for use as cathode materials in solid oxide fuel cells.     

The dependence of slow crack growth in a polyethylene copolymer on test temperature and morphology

The slow crack growth resistance was measured in an ethylene-octene copolymer as a function of the morphological changes produced by varying the thermal history. Morphology was varied by annealing the quenched state at temperatures between 86°C and the melting point. The slow crack growth behavior was measured by the lifetime of a notched tensile specimen under a constant load. In general, the lifetime exhibited a maximum at a critical value of the annealing temperature. This critical annealing temperature decreased with a decrease in the temperature at which the lifetime was measured. The former result is understandable in terms of the increase in crystal strength as the annealing temperature is increased and the decrease in the number of tie molecules when more material is melted as the annealing temperature increases. The latter result depends on the relationship between crystal size and the effect of testing temperature. Differential scanning calorimetry data played a key part in analyzing the results. © 1992 John Wiley & Sons, Inc.     

Pt–M (M=Fe,Co, Ni and Cu) electrocatalysts synthesized by an aqueous route for proton exchange membrane fuel cells

Nanostructured Pt–M (M=Fe, Co, Ni, and Cu) alloy catalysts synthesized by a low temperature (70 °C) reduction procedure with sodium formate in aqueous medium have been investigated for oxygen reduction in sulfuric acid and as cathodes in single proton exchange membrane fuel cells (PEMFC). The Pt–M alloy catalysts show improved catalytic activity towards oxygen reduction compared to pure platinum. Among the various alloy catalysts investigated, the Pt–Co catalyst shows the best performance with the maximum catalytic activity and minimum polarization occurring at a Pt:Co atomic ratio of around 1:7. While mild heat treatments at moderate temperatures (200 °C) improve the catalytic activity due to a cleaning of the surface oxides, annealing at elevated temperatures (900 °C) degrade the activity due to an increase in particle size.