Nd_(0.5)Sr_(0.5)Co_(1-x)Mn_xO_3的晶体结构和电磁性能研究

采用固相反应法制备了Nd0.5Sr0.5Co1–xMnxO3多晶样品(0≤x≤1)。利用X射线衍射仪和Rietveld方法精修程序分析了样品的晶体结构;对样品的磁性和电输运性能进行了测量。结果表明:样品均为斜方晶系单相结构,空间群为Imma。样品的晶格常数a、b、c,晶格平均扭曲率D和有效磁矩μeff随着Mn含量x的增加而增大,促使Co离子向高自旋态转变。在x≥0.6时,样品中Co离子都处于高自旋态。在样品中,Mn替代了Co,Mn—O—Co的反铁磁性超交换作用与Co3+—O2–—Co4+的铁磁性双交换作用相互竞争破坏了样品的金属导电行为,致使当x≥0.2时,样品表现出半导体导电行为。     

(Ni、Li)掺杂ZnO薄膜的制备及其性能

采用溶胶-凝胶技术和旋涂的方法,在Si(100)衬底上制备了Ni掺杂和(Ni、Li)共掺的3种ZnO薄膜(Ni0.10Zn0.90O、Ni0.10Li0.05Zn0.85O和Ni0.10Li0.10Zn0.80O)。X射线衍射分析表明,所有薄膜样品均为纤锌矿结构,未发现其他杂相。光致发光研究表明,(Ni、Li)共掺后出现了410nm左右的紫外发光峰,并随Li浓度的增加发光峰变强,该峰与Li杂质能级有关,同时观察到O2-空位引起的610nm和740nm的两个红色发光峰。薄膜中Ni离子为+2价,取代Zn离子的位置。掺杂的ZnO薄膜呈现室温铁磁性,单个Ni原子的饱和磁矩可达到0.210μB,掺入Li或在N2气氛中退火后,都导致单个Ni原子的饱和磁矩降低。铁磁性来源于电子调制的机制。     

高温超导氧化物(Y0.6Ca0.4)(Sr2-xBax)(Cu0.5B0.5)Cu7O7-δ的电子衍射研究

在超导材料YBa2Cu3O7-δ中,用Ca、Sr、B原子分别部分取代Y、Ba、Cu,制成(Y0.6Ca0.4)(Sr.Ba)(Cu0.5B0.5)Cu2O7-δ晶体.随着B掺入量的增加,晶体的超导电性逐渐消失,但如果同时掺入Ba和Ca其超导性则可恢复[1].本文用电子衍射方法,测定了x=0.5、x=1.0、x=1.5三种样品的晶胞参数和可能空间群.     

多层Z型六方铁氧体磁导率频率特性研究

采用普通陶瓷工艺,制备了Co2Z(Ba3Co2Fe24O41)六方铁氧体及Ba2+被Sr2+部分取代的Z型六方铁氧体[Ba3(1-x)Sr3xCo2Fe24O41],并将烧结好的铁氧体粉料压制成多层结构样品。其中间层为纯Co2Z粉料,上下两层为掺Sr2+粉料。研究了样品在300MHz~4GHz下的磁导率频率特性。结果表明:多层结构设计能优化甚高频(UHF)下Co2Z材料的磁性性能,使共振频率和复数磁导率动态可调。当掺Sr2+层参数x为0.4时,多层样品获得了最佳的甚高频性能。此时,共振频率达到2.25GHz,且2GHz下μ'和μ"分别为9.03和10.49。     

Cr离子取代Co2Z六角铁氧体的磁特性研究

采用固相反应法制备了Cr离子取代的Co2Z平面六角结构(Sr3Co2Fe24-xCrxO41)软磁铁氧体,并对其磁特性进行了研究。分析了样品的物相组成,并计算了样品的晶格常数;用扫描电镜分析了样品的形貌特征;测试了样品的磁滞回线。实验结果表明,掺杂Cr离子后,晶格常数变化不大,当Cr取代量x≥0.3时,Z相开始分解;在x≤0.2时,随着x的提高,样品的饱和磁化强度(Ms〖WTBZ〗)逐渐增加;当x＞0.2时,随着x的增加,样品的饱和磁化强度减小。由此可见,通过掺入适量的Cr离子可以提高Z型六角铁氧体的磁特性。     

Ti、Zn掺杂对Co2Z电磁性能的影响

用固相反应法制备了Ti4+、Zn2+取代的Co2Z(Ba3Co2Fe24-xMO41,M=Ti、Zn, x=0.2～0.6)平面六角结构软磁铁氧体并对其电磁特性进行了研究.X-射线衍射结果表明样品表现出典型的Z型平面六角铁氧体构型.Ti4+、Zn2+ 取代会增加铁氧体内载流子的浓度,从而影响Co2Z的电磁性能.实验中用4991A阻抗/材料分析仪测试室温条件下Ba3Co2Fe24-xTixO41(x=0、0.2、0.4)和Ba3Co2Fe24-xZnxO41(x=0、0.2、0.4、0.6)样品在5 MHz～1 GHz 范围内的磁导率频谱和介电常数频谱.实验结果表明,Ti4+取代Fe3+会增加Co2Z的起始磁导率,降低Co2Z的介电共振.而Zn2+取代Fe3+会引起起始磁导率的下降,增加Co2Z的介电共振,且在共振频率附近介电常数为负值.Co2Z的负介电常数特性使它可作为负介电常数介质用于左手材料的制备.     

溶胶-凝胶法制备Co,Cu共掺杂ZnO薄膜 结构及光学特性

采用溶胶-凝胶法在玻璃基片上制备了纯ZnO薄膜和高浓度Cu掺杂的Co,Cu共掺ZnO(Zn0.90CoxCu0.1-xO,x=0.01,0.03,0.05)薄膜。扫描电镜观察到无论是纯ZnO还是掺杂ZnO薄膜表面都有均匀分布的颗粒,但是在Cu含量较高时均匀性更好。X射线衍射揭示所有样品都具有纤锌矿结构,但是Cu掺杂量的增加使晶格常数略有减小,而晶粒尺寸却略有增大。XPS测试结果表明样品中Co离子的价态为+2价和+3价,Cu离子的价态为+2价和+1价共存。室温光致发光测量在所有样品中均观察到较强的紫外发光峰、蓝光双峰和较弱的绿光发光峰。     

锂离子电池正极材料LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2的合成及电化学性能

采用碳酸盐共沉淀法合成了Ni0.4Co0.2Mn0.4CO3前驱体,然后以Ni0.4Co0.2MnCO3和LiOH为原料,合成出了层状锂离子电池正极材料LiNi0.4Co0.2Mn0.4O2.通过XRD,SEM和电化学测试对LiN0.4Co0.2Mn0.4O2材料的结构、形貌及电化学性能进行了测试和表征.结果表明,800℃下烧结12 h所得到的样品,以0.2 c放电,其首次放电容量151 mAh·g-1,循环30次后容量为138 mAh·g-1,电化学性能好.     

Mg_(0.15)Zn_(0.85)O:Tb合金薄膜的阴极射线发光性质研究

采用溶胶凝胶方法成功地制备了掺杂稀土铽离子的 Zn O和 Mg0 .1 5Zn0 .85薄膜。通过对 X射线衍射结果的分析表明 ,稀土离子替代了 Zn2 +的格位 ,进入了半导体基质的晶格中。从阴极射线发光结果可以发现 ,在Mg0 .1 5Zn0 .85O基质中 ,可以观察到来源于稀土铽离子各能级的发射 ,而 Zn O:Tb的薄膜只能观察到较强的铽离子 5D4 — 7F5能级的跃迁。这可能是由于 Mg0 .1 5Zn0 .85O基质的能隙 (3 .65 e V)比 Zn O更宽 (3 .3 e V) ,其对铽离子的能量传递更有效的缘故。     

(001)Si衬底上La0.9Sr0.1MnO3/SrTiO3外延生长薄膜的界面电子显微学研究

本文利用高分辨电子显微术、电子能量损失谱和电子全息技术对Si基体上生长的SrTiO3（STO）和La0.9Sr0.1MnO3（LSMO）薄膜及其STO层和Si基体之间的界面结构进行了深入研究,结果表明在Si和STO层之间由于氧扩散会形成一层过渡的SiOx无序层,且随沉积条件不同界面原子无序层厚度稍有不同;选区电子衍射结果表明薄膜和基体之间的外延生长关系为[001]LSMO//[^-110]Si,[110]LSMO//[001]Si[001]STO,//[001]Si,[010]STO//[110]Si;电子能量损失谱分析表明界面无序层中Si离子的氧化态处于Si^2＋和Si^0之间;电子全息结果清晰地显示了基体与薄膜之间存在明显的相位和势垒变化,负电荷聚集在界面SiOx的无序层中。     

Structural study of an Al73Ni22Fe5 decagonal quasicrystal by high-angle annular dark-field scanning transmission electron microscopy

A water-quenched Al73Ni22Fe5 decagonal quasicrystal was investigated by the selected-area electron diffraction, convergent-beam electron diffraction and high-angle annular dark-field scanning transmission electron microscope methods. The alloy shows very sharp spots and nearly no diffuse scattering in the diffraction patterns, belongs to centrosymmetric space group P10(5)/mmc and is constructed almost by one type of 2 nm diameter atom cluster having mirror symmetry with a highly quasicrystalline order arrangement. Although a small number of 2 nm atom clusters having five-fold symmetry exists, which are similar to those observed in melt-quenched Al70Ni15Fe15, the structure of Al73Ni22Fe5 is considered to basically be the same as that of water-quenched Al72Ni20Co8, which is constructed only by mirror symmetry clusters arranged with a very high quasiperiodicity. The number of valence electrons per atom (e/a) of the present alloy (1.92) is very close to that of Al72Ni20Co8 (1.90), but differs from those of phases constructed by only the five-fold symmetry clusters. This implies that these alloys are Hume-Rothery electron compounds, whose structures are determined primarily by e/a value.     

Ni(OH)2及Co(OH)2片状纳米晶体的合成与表征

使用强碱氢氧化钾为沉淀剂,通过水热法成功合成了具有六角形貌的过渡金属氢氧化物Ni（OH）2及Co（OH）2片状纳米晶.利用X射线粉末衍射仪和透射电子显微镜对样品的结构和形貌进行了表征.透射电镜观察结果显示：Ni（OH）2相为规则六角纳米片,Co（OH）2相为纳米片和纳米棒的混合物.选区衍射结果指出：Ni（OH）2及Co（OH）2纳米晶体均为单晶体.Ni（OH）2及Co（OH）2纳米片的产率分别达到了70%和90%.将实验结果同前人的过渡族金属氢氧化物纳米片报道进行了比较,提出了一个新的片状纳米晶的形成机制,指出在正常的沉淀条件下,Ni（OH）2及Co（OH）2纳米晶的稳定形貌总为六角片状.     

Time resolved study on Co/Ni/a-Si phase transition during isothermal annealing at 400 °C

An approach based on in situ sheet resistance analyses during isothermal annealing processes is proposed to find out the critical stages of Co/Ni phase transition on amorphous silicon. Unlike the case of conventional Co/Si systems, it was found that Co/Ni/Si reaction produces a double-peak in the resistance versus time curve. This behaviour was studied by energy filtered transmission electron microscopy (EFTEM), energy dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED) analyses. It was found that cobalt atoms prefer to diffuse through the grain boundaries of the underlying Ni₂Si layer that forms at very low temperature in contact with silicon. The diffusion process stops when cobalt atoms reach the deeper NiSi layer which is located at the interface with the substrate. Finally, CoSi and NiSi phases form separately, and Co(Ni)Si₂ grains nucleate in contact with silicon differently from what is known for thick layer systems.     

Preparation and Photo—properties of Nanosize ZnS and Zn（en）2S

The precursore Zn(en)2 S (en=ethylenediamine) were prepared via a solvothermal process from elemental sulfur and zinc using ethylenediamine as a solvent. Detailed characterizations of the infrared (IR) absorption spectrum, powder X-- ray diffraction (XRD) and thermogravimetric analysis (TG) confirmed two en coordinated with Zn^2 to form a complex cation. The morphological property was also characterized by transmission electron microscopy (TEM) and electron diffraction analysis (ED). Phase—pure hexagonal wurtzite ZnS products were obtained by annealing the precursor in nitrogen stream at about 900 ℃ Zn(en)2S showed a nanosize of about 30 nm, and ZnS of about 60 nm. The fluorescence spectra were also studied. PL results showed that Zn(en)2S excited a fluorescence at 452 nm.     

Microstructural characteristics and vibration fracture properties of Sn-Ag-Cu-TM (TM=Co, Ni, and Zn) alloys

This study investigated microstructure thermal behavior, and mechanical properties of Sn-3.3Ag-0.5Cu alloys (SAC) with the addition of transition metals (TM, Ni, Co, and Zn). Results show that alloying with TM elements was able to reduce the degree of undercooling and strengthen SAC alloys. Among these elements, only Zn can raise the ductility. CoSn and Cu-Ni-Sn intermetallics appeared, respectively, in the Co-containing and Ni-containing samples while coarse Sn dendrites and a large area of eutectic phases could be observed in the specimens with Zn. These microstructural changes led to an inferior vibration fracture resistance under resonant vibration with a constant pull force.     

基于24析因设计的重金属胁迫蛋白核小球藻联合毒性研究

设计实验研究多种重金属胁迫藻类的联合毒性,更有利于阐明真实环境中重金属与藻类的毒性作用过程和机理。采用叶绿素荧光分析技术结合24析因设计方法研究重金属Hg2+、Cd2+、Cu2+和Zn2+胁迫蛋白核小球藻的联合毒性作用,得到主效应Hg、Cd、Cu、Zn以及交互作用Hg*Cu、Hg*Zn和Hg*Cu*Zn对蛋白核小球藻潜在最大量子效率Fv/Fm具有显著性影响（Sig.<0.05）的结论;通过多元线性回归拟合得到联合重金属浓度与藻类光合活性抑制率间的剂量-效应关系,得到模型表达式：y[%]= -22.557+19.926Hg+5.282Cu+0.015Zn+0.029Hg*Zn-0.002Hg*Cu*Zn,并对联合重金属胁迫蛋白核小球藻的机理做出解释;通过对模型进行统计学检验和实验验证,证明该模型可用于实验室条件下已知种类重金属Hg2+、Cd2+、Cu2+、Zn2+胁迫蛋白核小球藻的联合毒性估计。     

半磁半导体Zn_0.97Co_(0.03)S的红外磁光研究(英文)

The absorption spectra of ternary mixed crystal Zn0.97Co0.03.S SMSC have been measured by using a Fourier transform spectrometer and a high field sup3rconducting magnet.The absorption lines shift or split when magnetic field is added. The widthes and the positions of lines also change with temperature. These phenomena can be interpreted by S-L interaction of d-electrons in Co2+ and Jahn-Teller effect because of coupling between electrons, vibration modes of Co2+ and their neighborhood atoms. The absorption spectra of samples with different Co concentrations are also measured at different temperature, and the phenomena are well discussed.     

High-resolution transmission electron microscopy study of Ca(3)Co(4)O(9)

The crystal structure of Ca(3)Co(4)O(9) was investigated using high-resolution transmission electron microscopy (HRTEM) and the image-simulation method. The c(*) was 10.8A and the b parameters were 4.56A for the Ca(2)CoO(3) block and 2.82A for the CoO(2) sheet. The [110] zone axis HRTEM images confirmed that Ca(3)Co(4)O(9) has a modulated layered structure with modulation. For the first time, the atomic positions of the Ca and Co atoms in the Ca(2)CoO(3) block were identified, corresponding to three rows of dark spots in the [110] direction. The observed HRTEM images for Ca(2)CoO(3) agreed well with the calculated images based on the structural model obtained by the Rietveld refinement method.