Y. Jin
,
X.G. Bi
,
S.R. Yu
,
null
,
null
,
null
金属学报(英文版)
The kinetic model for desulfurization using CaO-based powder injection has been proposed, which accords with the actual process of the experiment. For the model, a comparison between CaO-based flux and Mg-based flux was made and the results show that the desulfurization rate of the Mg-based flux is far more than that of CaO-based flux. On the basis of the model calculation, on comparison of CaO-CaF2 flux and calcium aluminate flux, the desulfurization rates of the two fluxes are close to each other. In addition, the effects of some operational factors on the kinetics of desulfurization are discussed.
关键词:
powder injection
,
null
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null
Acta Physica Sinica
In this work, La(0.1)Bi(0.9-x)Eu(x)FeO(3) compounds were prepared by solid-state reaction. The phase relation at room temperature was investigated by X-ray powder diffraction. A rhombohedral (R3c) phase exists for x <= 0.05; for 0.08 <= x <= 0.12 a pseudo-R3c phase is found; for x >= 0.15 it is an orthorhombic (Pbnm) phase, while the distortion of the Pbnm phase was observed for the composition range of 0.15 <= x <= 0.20. Magnetic measurements indicate that weak ferromagnetism exists in all the compounds, and for the compounds with x <= 0.20 the magnetic moment has the maximum value at x = 0.12. The composition dependence of dielectric constant was investigated at room temperature. The relationship between the structure and the physical properties was discussed.
关键词:
La(0.1)Bi(0.9-x)Eu(x)FeO(3);X-ray diffraction;magnetism;dielectric;constant;transition;ceramics;bifeo3
Chinese Physics B
Different magnetodielectric effects were observed in Bi(1-x)Gd(x)FeO(3) ceramics depending on gadolinium content. A positive one was observed in the samples with x <= 0.10 at 295 K and 16 K, and a negative one in the sample with x = 0.4 at 16 K. Structure analysis by x-ray diffraction (XRD) reveals that the samples crystallize in the R3c structure (ferroelectrics) for x < 0.08 and in the Pbnm structure (paraelectrics) for x >= 0 : 3 at room temperature. Temperature-dependent dielectric response and x-ray diffraction confirm the occurrence of a structural transition in the Pbnm phase at low temperature for the samples with x <= 0.4. While the positive magnetodielectric effects can be attributed to a coupling of magnetic and crystallographic structures of the R 3 c phase, the observed negative magnetodielectric effect in the Pbnm phase can be associated with a low-temperature modification of the Pbnm structure. The observed dual-signed magnetodielectric effects suggest that the Bi(1-x)Gd(x)FeO(3) oxides are a good prototype for understanding the magnetodielectric coupling mechanism in this kind of materials.
关键词:
multiferroic;magnetodielectric effect;x-ray diffraction;Bi(1-x)Gd(x)FeO(3) ceramics;temperature-dependence;bifeo3;crystal;ferrite;system
龚晓钟
,
曾艳芳
,
叶洞君
,
田鹏
,
罗智宇
,
汤皎宁
稀有金属材料与工程
在尿素-NaBr-KBr-甲酰胺体系中用脉冲电沉积的方法制备Bi_2Sb_3Ce_x及Bi_2Sb_3Nd_x合金薄膜.通过X射线能谱(EDS)及X射线衍射(XRD)分别确定其化学成分、分析其晶型结构.在最佳工艺条件下,稀土元素达到最大填充量,合金薄膜的组成为Bi_2Sb_3Ce_2及Bi_2Sb_3Nd_(0.1).合金薄膜是由斜方六面体BiSb和四面立方结构的单质Ce、Nd组成.探索了不同稀土填充的Bi-Sb半导体热电材料的电学性能.
关键词:
电沉积
,
稀土元素
,
热电材料
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非水体系
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电学性能
李宇涵
,
吕康乐
,
何咏基
,
赵再望
,
黄宇
催化学报
doi:10.1016/S1872-2067(16)62573-1
采用一种原位合成工艺制备了具有类石榴结构的金属铋(Bi)单质修饰的g-C3N4复合材料(Bi-CN),并用于可见光氧化NO反应中.金属Bi单质镶嵌在CN层间形成的复合物,由于金属Bi单质显著的表面等离子体共振(SPR)作用可将光吸收范围由紫外光延展至近红外,极大地提高了复合物的光吸收.此外,由于Bi单质存在于复合物界面可产生内建莫特-肖特基效应,从而加快光生载流子的分离与转移.由此,Bi-CN复合物光催化剂展现出超强的光催化去除NO性能.我们提出了类石榴结构的形成以及相应的Bi-CN复合物光催化活性的提高机理.这不仅为高效的金属铋单质改性的g-C3N4基光催化剂提供了一种新的设计方案,也对g-C3N4基光催化的机制理解提出了新的见解.通过X射线衍射、红外光谱和X射线光电子能谱结果发现Bi是以金属单质的形式存在于Bi-CN复合物中,这得益于我们采用了二水合铋酸钠(NaBiO3·2H2O)作为铋前驱体,从而成功避免了氧化态铋的形成.Bi-CN复合物中金属铋单质的存在有诸多优点.首先,金属铋单质具有显著的表面SPR效应,它的引入可大大提高复合物的光吸收能力和太阳光利用率.有研究表明,直径为150–200 nm的铋球能够在紫外-可见漫反射图谱(UV-vis)在λ=500 nm处呈现出典型的SPR峰,但本样品在λ=200–800 nm区间内并未发现该SPR峰.由于铋单质的共振受限于其尺寸大小、颗粒形状和构造环境.本文中球形铋单质的直径约为1μm,其可能发生共振效应的峰位置应超过800 nm,因此未发现相应的SPR峰.其次,金属铋单质分散在CN层表面上构建的肖特基垫垒能够高效地阻止光生电子与空穴的复合,促进了光生载流子的分离与转移,从而提高光氧化NO进程.再者,金属铋单质的介入成功构造了Bi-CN异质结,在可见光照射下NO氧化反应中,Bi-CN复合物活性显著高于CN(22.2%)、CN-EG(36.4%)和Bi(14.1%),其中以10%Bi-CN活性最佳,NO去除率到70.4%,远远超过K插层的g-C3N4、Ag掺杂的g-C3N4和氧化石墨烯修饰的g-C3N4.当复合物中金属铋单质含量超过10%时,其活性明显下降.这是因为大量的金属铋单质积聚在Bi-CN复合物表面上而造成物理堵塞,妨碍了CN吸收可见光,从而降低了其可见光吸收能力;同时导致只会吸收更多的紫外光(λ<280 nm)而不是可见光,因而其可见光催化氧化NO能力下降.
关键词:
金属铋
,
表面等离子体共振
,
光氧化
,
一氧化氮
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可见光
,
石墨型碳化氮
Chinese Physics Letters
The magnetoresistance (MR) behavior of La(2-x/)3Bi(x/3)Ca(1/3)MnO(3) (x = 0.4) compound was investigated. The compound exhibits complex magnetic transitions, i.e., paramagnetic-canted ferromagnetic-ferromagnetic-spin glass transitions. The temperature dependence of resistivity of the compound indicates a semiconducting behavior, and no semiconductor-metal transition was associated with these magnetic transitions. The magnetoresistance ratio exhibits a critical maximum corresponding to the canted ferromagnetic transition. A MR ratio as large as 86% was observed at 85 K. The temperature dependence of MR ratio is well described by the relation of (rho(o)-rho(H))/rho(o) = A(M/M-s)(2).
关键词:
films
Journal of Molecular Structure-Theochem
The local structures and the electron paramagnetic resonance (EPR) g factors g(parallel to) and g(perpendicular to) for the substitutional V(4+) and Cr(4+) at the Ge(4+) sites in Bi(4)Ge(3)O(12) are theoretically investigated from the perturbation formulas of the g factors for 3d(1) and 3d(2) ions under tetragonally elongated tetrahedra. In the calculations, the ligand orbital and spin-orbit coupling contributions are taken into account from the cluster approach in view of the covalency of the systems. The local impurity-ligand bond angles beta related to the C(4) axis in the V(4+) and Cr(4+) centers are found to be about 5 degrees and 6 degrees, respectively, lower than the host angle beta(H) in the pure crystal. So the ligand tetrahedra transform from original compression at the host Ge(4+) site into elongation in the impurity centers due to the size mismatching substitution of the smaller Ge(4+) by the larger impurities. Meanwhile, the Jahn-Teller effect also brings forward some contribution to the local structure of the V(4+) center. The calculated g factors are in good agreement with the experimental data. The local structures of both centers are discussed. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Electron paramagnetic resonance;V(4+);Cr(4+);Bi(4)Ge(3)O(12);atomic screening constants;superposition model;sillenite crystals;single-crystals;scf functions;ions;parameters;spectrum;impurity;vanadium
Rui XIONG
材料科学技术（英文）
The electronic structure of the quasi-two-dimensional (2D) semiconducting molybdenum purple bronze Bi0.2MoO3 was presented by X-ray photoemission spectroscopy. The valence band of Bi0.2MoO3 is made up of Opπ non-bonding level, π and σ bonding bands. The peak at 1.5 eV and the shoulder at 0.5 eV in the forbidden band may be formed from the non-bonding dxy orbitals of some Mo atoms. The O1s core-level spectrum demonstrates the presence of two inequivalent bonds of oxygen ions in Bi0.2MoO3. Bi4f core-level spectrum shows two bonding characters of Bi atoms in bismuth molybdenum single crystal. Mo3d core-level spectrum confirms two kinds of valence states of Molybdenum (Mo+5 and Mo+6). Ar+ ion irradiation induces more significant distortion of MoO6 octahedra.
关键词:
Bi0.2MoO3 single crystal
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null
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null
