Influence of nitrogen and magnesium doping on the properties of ZnO films

Undoped ZnO and doped ZnO films were deposited on the MgO(111) substrates using oxygen plasma-assisted molecular beam expitaxy. The orientations of the grown ZnO thin film were investigated by in situ reflection high-energy electron diffraction and ex situ x-ray diffraction(XRD). The film roughness was measured by atomic force microscopy, which was correlated with the grain sizes determined by XRD. Synchrotron-based x-ray absorption spectroscopy was performed to study the doping effect on the electronic properties of the ZnO films, compared with density functional theory calculations.It is found that, nitrogen doping would hinder the growth of thin film, and generate the NOdefect, while magnesium doping promotes the quality of nitrogen-doped ZnO films, inhibiting(N_2)Oproduction and increasing nitrogen content.     

高分散性片状阻燃型氢氧化镁的制备

以轻烧氧化镁为原料, 通过水化水热法制备高分散性片状氢氧化镁. 考察了不同的水化温度、水化时间、水热时间和分散剂体系对氢氧化镁材料形貌的影响. 采用X射线衍射(XRD)、扫描电子显微镜(SEM)、全自动氮物理吸附仪(ASAP)等对所制得的氢氧化镁颗粒的物相、形貌和比表面积进行了分析. 结果表明, 通过水热反应控制和分散剂的加入, 可以得到高分散性片状的阻燃型氢氧化镁.     

SrO/Al2O3比率对Sr2AlO4:Eu,Dy发光性能的影响

采用高温固相法合成稀土离子掺杂碱土铝酸盐发光粉,通过改变原料配比分别合成出富Sr和富Al的Sr2AlO4：Eu,Dy发光粉样品。XRD分析结果表明,SrO／Al2O3比率的微小变化不会影响样品的晶相组成。样品的发光性能和长余辉特性测试结果表明,富Al的Sr2AlO4：Eu,Dy发光粉具有较高的荧光强度及较长的余辉时间,说明Sr2AlO4晶格中SrO／Al2O3比率对Sr2AlO4：Eu,Dy发光性能和长余辉特性有很大的影响。激发与发射光谱、发射峰余辉衰减以及热释光谱分析表明,SrO／Al2O3比率的微小变化,导致晶格中发光中心Eu^2 浓度和陷阱的深度与密度发生改变。在富Sr体系中,稀土掺杂离子Eu^2 ,Dy^3 较难进入Sr^2 的晶格位置,晶格中发光中心Eu^2 浓度和陷阱密度都较低,使得粉体发光强度较低,余辉时间较短。     

Ab initio studies on n-type and p-type Li4Ti5O12

This paper studies the structure and electronic properties of Li4Ti5O12, as anode material for lithium ion batteries, from first principles calculations. The results suggest that there are two kinds of unit cell of Li4Ti5O12: n-type and p-type. The two unit cells have different structures and electronic properties:the n-type with two 16d site Li ions is metallic by electron, while the p-type with three 16d Li ions is metallic by hole. However, the Li4Ti5O12 is an insulator. It is very interesting that one n-type cell and two p-type cells constitute one Li4Ti5O12 supercell which is insulating. The results show that the intercalation potential obtained with a p-type unit cell with one additional electron is quite close to the experimental value of 1.5 V.     

Clewlike ZnV2O4 Hollow Spheres: Nonaqueous Sol–Gel Synthesis,Formation Mechanism,and Lithium Storage Properties

Hollow ZnV₂O₄ microspheres with a clewlike feature were synthesized by reacting zinc nitrate hexahydrate and ammonium metavanadate in benzyl alcohol at 180 °C for the first time. GC–MS analysis revealed that the organic reactions that occurred in this study were rather different from those in benzyl alcohol based nonaqueous sol–gel systems with metal alkoxides, acetylacetonates, and acetates as the precursors. Time‐dependent experiments revealed that the growth mechanism of the clewlike ZnV₂O₄ hollow microspheres might involve a unique multistep pathway. First, the generation and self‐assembly of ZnO nanosheets into metastable hierarchical microspheres as well as the generation of VO₂ particles took place quickly. Then, clewlike ZnV₂O₄ hollow spheres were gradually produced by means of a repeating reaction–dissolution (RD) process. In this process, the outside ZnO nanosheets of hierarchical microspheres would first react with neighboring vanadium ions and benzyl alcohol and also serve as the secondary nucleation sites for the subsequently formed ZnV₂O₄ nanocrystals. With the reaction proceeding, the interior ZnO would dissolve and then spontaneously diffuse outwards to nucleate as ZnO nanocrystals on the preformed ZnV₂O₄ nanowires. These renascent ZnO nanocrystals would further react with VO₂ and benzyl alcohol, ultimately resulting in the final formation of a hollow spatial structure. The lithium storage ability of clewlike ZnV₂O₄ hollow microspheres was studied. When cycled at 50 mA g^?1 in the voltage range of 0.01–3 V, this peculiarly structured ZnV₂O₄ electrode delivered an initial reversible capacity of 548 mAh g^?1 and exhibited almost stable cycling performance to maintain a capacity of 524 mAh g^?1 over 50 cycles. This attractive lithium storage performance suggests that the resulting clewlike ZnV₂O₄ hollow spheres are promising for lithium‐ion batteries.     

Synthesis and structure of anhydrous complexes of magnesium(II) with β-ketoesters of higher alcohols

Methods for the synthesis of anhydrous complexes of magnesium(II) with β-ketoesters of higher alcohols have been developed. A number of novel magnesium complexes of the general formula MgL₂ (where HL is hexyl-, dodecyl-, tert-butyl-, cyclohexyl-, bornyl- and 1-adamantyl acetoacetate), which are readily soluble in organic media, have been synthesized. It has been found by X-ray crystallography that bis(1-adamantyl acetoacetato)magnesium(II) has a trimeric structure. The structure of the complexes in solutions is discussed.     

尖晶石LiMn2O4中锂离子嵌入脱出过程的电化学阻抗谱研究

运用电化学阻抗谱(EIS)研究了尖晶石LiMn2O4电极的首次充放电过程. 发现EIS谱高频区域拉长压扁的半圆是由两个半圆相互重叠而成的, 分别归属于与锂离子通过固体电解质相界面膜(SEI膜)的迁移和与尖晶石LiMn2O4材料的电子电导率相关的特征. 通过选取适当的等效电路, 对实验所得的电化学阻抗谱数据进行拟合, 获得尖晶石LiMn2O4电极首次充放电过程中SEI膜电阻、电子电阻和电荷传递电阻等随电极极化电位变化的规律. 根据研究结果提出了嵌锂物理机制模型.     

硫酸镁为原料制备三水碳酸镁晶须的研究

以MgSO4·7H2 O和Na2 CO3为原料制备了三水碳酸镁晶须,考察了MgSO4浓度、MgSO4和Na2 CO3摩尔加料比例、反应时间以及反应温度对产物的影响,并对产物进行了分析和表征。确定了适宜的反应条件为温度50℃、MgSO4浓度1.2 mol/L、MgSO4和Na2 CO3摩尔比1∶1.2、反应时间40 min,此条件下,镁离子的转化率可达82.35;。当Na2 CO3浓度升高、反应时间延长、反应温度升高时,三水碳酸镁会向碱式碳酸镁转变。同时也探索了以白钠镁矾作为镁源制备三水碳酸镁晶须的条件,并进行了母液循环工艺的设计。     

Measurement of mass attenuation coefficients for undoped and boron nitride–doped magnesium diboride superconductors in the x-ray region 8.04–59.5 keV

In this study, mass attenuation coefficients of the undoped and 2% boron nitride–doped magnesium diboride superconductor samples were investigated. Mass attenuation coefficients were measured at 8.04–59.5?keV x-ray energies by using a high-purity germanium detector with a resolution of 182?eV at 5.9?keV. It is observed that mass attenuation coefficients in undoped and doped magnesium diboride samples decrease with increasing photon energy, and doping with the boron nitride leads to increase the absorption of the electromagnetic radiation.     

ChemInform Abstract: Prediction and Characterization of the HMgH···LiX (X: H,OH, F,CCH, CN,and NC) Complexes: A Lithium—Hydride Lithium Bond

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