Calculated structure, elastic and electronic properties of Mg2Pb at high pressure

The effects of high pressure on structure,elastic and electronic properties of the intermetallic Mg₂Pb were calculated by the first-principles plane wave pseudo-potential method in the scheme of density functional theory（DFT）within the generalized gradient approximation.The elastic constants and Debye temperature obtained at 0 GPa are in good agreement with the available experiment data and other theoretical results.The electronic properties calculated suggest that the electronic density of states（DOS）at the Fermi level decreases under high pressure.     

First-principles Investigation of the Structural,Electronic and Elastic Properties of Al2Ca and Al4Sr Phases in Mg-Al-Ca（Sr） Alloy

First-principles calculations have been carried out to investigate the structural stabilities, electronic structures and elastic properties of Mg17Al12, Al2Ca and Al4Sr phases. The optimized structural parameters are in good agreement with the experimental and other theoretical values. The calculated formation enthalpies and cohesive energies show that Al2Ca has the strongest alloying ability, and Al4Sr has the highest structural stability. The densities of states （DOS）, Mulliken electronic populations, and electronic charge density difference are obtained to reveal the underlying mechanism of structural stability. The bulk modulus, shear modulus, Young＇s modulus, and Poisson＇s ratio are estimated from the calculated elastic constants. The mechanical properties of these phases are further analyzed and discussed. The Gibbs free energy and Debye temperature are also calculated and discussed.     

Electronic Structure and Thermoelectric Properties of Na and Ni-doped Ca3Co2O6

The electronic structures of Ca3Co2O6, Na and Ni doped models were studied by the quantum chemical software of Cambride Serial Total Energy Package （CASTEP） that is based on deusity function theory （DFT） and psendo-potential. The electronic conductivity, seebeck coefficient, thermal conduetivity and figure of merit （Z） were computed. The energy band structure reveals the form of the impurity levels due to the substitutional imapurity in semiconductors. Na-doped model stunts the character of p-type semiconductor, but Xi-doped model is n-type semiconductor. The calculation results show that the electric conduetirity of the doped model is higher than that of the non-doped model, while the Seebeck coefficient and thermal conductivity of the doped model are lower than those of the non-doped one. Because of the great increase of the electric conductivity, Z of Na- doped model is enhanced and thermoelectric properties are improved. On the other hand, as the large decline of Seebeck coefficient, Z of Ni-doped model is less than that of the non-doped model.     

Thermoelectric Properties and Electronic Structure of Ca3Co2O6

The nanosized Ca3Co2O6 powder was synthesized via sol-gel process.The phase composition was characterized by means of X-ray diffraction.Polycfrystalline swnples of Ca3Co2O6 were prepared by a sintering procedure of nanosized power.The seebeck cofficient and electrical conductivity of the samples were measured from 450K up to 750 K.The results show that the Seebeck coefficient increases with the increasing temperature.The electronic structures were calculated using the self-cwtsistent full-potential linearized augmentedc plane-wave (LAPW) method within the density functional theory.The relationship between thermoelectric property and electronic structures was discussed.     

Electrochemical Characterization of Surface-modified LiMn2O4 Cathode Materials for Li-ion Batteries

To improve the performance, the surface of 12Mn2O4 was coated with very fine MgO , Al2O3 and ZnO by solgel method, respectively. The structure and morphology of the coated materials were investigated by X-ray diffraction （ XRD ）, X-ray photoelectron spectroscopy （ XPS ） and scanning electron microscopy （SEM）. The charge and discharge performance of uncoated and surfnce modified 12Mn2O4 spinel at 25℃ and 55 ℃ were tested, using a voltage window of 3.0-4.35 V and a current deasity of 0. 1 C rate. There is a slight decrease in the initial discharge capacity relative to that of uncoated UMn2 O4, bat the cycle ability of 12 12Mn2O4 coated by metal-oxide has remarkably been improved. The EIS measuremeuts of uncoated and Al2O3 -coated 12Mn2O4 were carried out by a model 273 A potentiostatl galvanistat controUed by a computer using M270 software, and using a freqnency response analyzer （ Zsimpwin ） combined with a potentiostate （ PAR 273）. Coaseqnently, the reason for the improved cycle properties is that the surface modification reduces the dissolution of Mn , which results from the suppression of the electrolyte decomposition, and suppresses the formation of passivation film that acts as an electronic insulating layer. In conclusion, the use of surface modification is an effective way to improve the electrochemical performance of 12Mn2O4 cathode material for lithium batteries.     

Investigation of the 6H-SiC （0001） surface by AFM

Micropipe and step structures on 6H-SiC （0001） surface were investigated by an atomic force microscopy （AFM）. On the facet,all micropipes examined are the origins of spiral steps,indicating that dislocations intersect the surface at these points. Micropipes are empty-core super-dislocations as originally described by Frank. The micropipe radius increases with the square of the dislocation Burgers vector. From the center to the periphery,step structures change with different surface inclinations. Regular step is observed within the central faceted area. Step bunching and atomically rough surfaces are observed within the peripheral convex area. If the inclination with respect to the （0001） plane is large enough,step bunching of 15R-SiC can be observed.     

Enhanced Low-field Magnetoresistence in the Absence of Mn Content in Polycrystalline La0.67Ca0.33MnO3

Magnetic and electrical transport properties of the La0.67Ca0.33Mn1-xO3 （x=0-0.16）, which were prepared by the sol-gel method followed by sintering treatment at 1 450, 1 100 and 900 ℃, respectively, were investigated. Experimental results show that, with the increase of x, the resistivity of samples increases and the insulator-metal transition temperature shifts towards lower temperature. Meanwhile, the intrinsic megnetoresistance effect is weakened and the extrinsic magnetoresistance is enhanced. For the samples with x=0.16 and 0.10 sintered at 1 100 ℃ and 900 ℃, respectively, low field magnetoresistance as high as about 50% can be observed. Furthermore, for the samples sintered at 1 100 ℃ and 900 ℃, the grain size is not only controlled by about sintering temperature, but also by the absence of Mn content x.     

Structure and Mixed Electronic-ionic Conducting Properties of La0.6Sr0.4Co1-yFeyO3（y= 0-1.0） Ceramics Made by a Citrate Method

La0.6Sr0.4Co1-yFeyO3（y= 0-1.0） powders were synthesized by a citrate method, and the structure and mixed electronic-ionic conducting properties of the resulting ceramics were investigated. The synthesized La0.6Sr0.4Co1-yFeyO3 powders have a pure perovskite structure and consist of uniform and fine particles. A perovskite struciure with rhombohedral symmetry was certified for the La0.6Sr0.4Co1-yFeyO3 ceramics. The increase of Co/Fe ratio significantly promoted the grain growth and microstructural densification. The La0.6Sr0.4Co1-yFeyO3 compositions with relatively higher Co/Fe ratio exhibit superior mixed conducting properties. The electronic structure and microstructure of the ceramics are responsible for the variation of the mixed conducting properties with Co/Fe ratio.     

Effect of microstructure on the mechanical,thermal, and electronic property measurement ofceramic coatings

Ceramic materials were investigated as thermal barrier coatings and electrolytes. Electrophoretic deposition（EPD） and physical vapor deposition（PVD） were employed to fabricate samples, and the mechanical properties and microstructure were examined by nanoindentation and microscopy, respectively. Yttria-stabilized zirconia/alumina（YSZ/Al2O3） composite coatings, a candidate for thermal barrier coatings, yield a kinky, rather than smooth, load–displacement curve. Scanning electron microscope（SEM） examination reveals that the kinky curve is because of the porous microstructure and cracks are caused by the compression of the indenter. Li0.34La0.51 Ti O2.94（LLTO） on Si/Sr Ru O3（Si/SRO） substrates, an ionic conductor in nature, demonstrates electronic performance. Although SEM images show a continuous and smooth microstructure, a close examination of the microstructure by transmission electron microscopy（TEM） reveals that the observed spikes indicate electronic performance. Therefore, we can conclude that ceramic coatings could serve multiple purposes but their properties are microstructure-dependent.     

Performances of lithium manganese oxide prepared by hydrothermal process

A simple hydrothermal process followed by heat treatment was applied to the preparation of spinel Li1.05Mn1.95O4. In this process, electrolytic manganese dioxide（EMD） and LiOH·H2O were used as starting materials. The physiochemical properties of the synthesized samples were investigated by thermogravimetry-differential scanning calorimetry（TG-DSC）, X-ray diffractometry（XRD）, and scanning electronic microscopy（SEM）. The results show that the hydrothermally synthesized precursor is an essential amorphous. The precursor can be easily transferred to spinel powders with a homogeneous structure and a regularly-shaped morphology by heat treatment. Li1.05Mn1.95O4 powder obtained by heat treating the precursor at 430 °C for 12 h and then calcining at 800 °C for 12 h shows an excellent cycling performance with an initial charge capacity of 118.2 mA·h·g-1 obtained at 0.5C rate and 93.8% of its original value retained after 100 cycles.     

Electronic structures and properties of Ti, Zr and Hf metals

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Structures and properties of Sc and Y metals

Ａｔｒｏｏｍｔｅｍｐｅｒａｔｕｒｅａｎｄａｍｂｉｅｎｔｐｒｅｓｓｕｒｅ ,ｔｈｅｓｔａ ｂｌｅｃｒｙｓｔａｌｌｉｎｅｓｔａｔｅｏｆＳｃａｎｄＹｈａｓａｈｅｘａｇｏｎａｌｃｏｌｓｅ ｐａｃｋｅｄ(ｈｃｐ)ｓｔｒｕｃｔｕｒｅ(αｐｈａｓｅ) .Ａｔｈｉｇｈｔｅｍｐｅｒａｔｕｒｅ ,ｂｏｔｈｍｅｔａｌｓｕｎｄｅｒｇｏａｐｈａｓｅｔｒａｎｓｆｏｒｍａｔｉｏｎｉｎｔｏａｂｏｄｙ ｃｅｎｔｅｒｅｄｃｕｂｉｃ(ｂｃｃ)ｓｔｒｕｃｔｕｒｅ( βｐｈａｓｅ) .Ｔｈｅｐｈａｓｅｓｔａ ｂｉｌｉｔｙａｎｄｐｈａｓｅｔｒａｎｓｆｏｒｍａ…     

稀土磁致冷Gd5Ge2(Si2-xMnx)化合物的结构及微观机制

利用X射线衍射和扫描电镜对Gd5Ge2(Si2-xMnx)结构及表面形貌进行了研究.并利用差示量热法对Gd5Ge2(Si2-xMnx)的磁热性能进行了研究.x射线衍射(XRD)测量分析表明Mn的替代不会影响母体Gd5Si2Ge2的晶体结构,样品中的主相仍然具有单斜结构(P1121/a),其晶体对称性不会随Mn含量的增加而改变.随着Mn含量的增加,晶粒逐渐变大,晶常数增大,体积膨胀,同时Mn和杂质相的析出量也在增加.少量的Mn元素替代Si可以提高Gd5Si2Ge2化合物的居里温度.     

几种二元弱酸的电离常数及其与CU2＋形成配合物的稳定常数的测定

用电位滴定法测定几种二元弱酸在离子强度μ =0.1（KNO3）,V（乙醇）/V（水）=10％混合溶剂中的电离常数及其与Cu2＋形成的MAB（M=Cu2＋;A=水杨酸、5-硝基水杨酸、5-甲氧基水杨酸;B=丙二酸、苯丁基丙二酸）型配合物的稳定常数.讨论弱酸中取代基官能团对电离常数及配位稳定性的影响.结果表明：在含有芳环的配体水杨酸中引入吸电子基团时电离常数降低,引入推电子基团时电离常数升高.对于丙二酸配体,增长碳链电离常数增加,配体芳环之间的堆砌作用可以增强配合物的稳定性.     

掺氮3C-SiC电子结构的第一性原理研究

采用广义梯度近似方案处理电子间相互作用的交换关联能量泛函,电子波函数采用平面波基矢展开,并采用超软赝势近似离子实与价电子间相互作用,对掺氮(3×3×3)3C-SiC超晶胞电子结构进行了第一性原理研究．对不同掺氮浓度3C-SiC超晶胞的能带结构和态密度进行计算,结果表明氮原子的2p态和2s态分别占据价带顶和导带底,随着掺杂浓度的增加,导带底和价带顶的位置逐渐向低能端移动,导带底移动速度要大于价带顶,导致禁带宽度减小．     

电子鼻与电子舌在饮料品质评价中的应用

随着传感技术的发展,电子鼻与电子舌以其独特的优越性广泛应用于食品的品质评价中.阐述了电子鼻与电子舌的结构组成及其在饮料的种类识别、品质控制、定量分析和感官评价等方面的应用,并指出了其在发展过程中需要解决的问题.     

聚并吡啶电子性质的理论研究

采用量子化学半经验ＭＮＤＯ,ＣＮＤＯ／２晶体轨道方法,对聚并吡啶分子结构进行探讨,找出了结构稳定性和电子性质的变化发规律,能带结构分析表明：分子的准一维体系向二维拓宽,将使能隙趋于变小,本征电导率增加。此与裂解温度高则聚合度和电导率相应增加的实验结果相一致。     

电导率法测定非1∶1型难溶电解质的溶度积常数

以电导率法测定了非１∶１型难溶电解质饱和溶液的电导率，确定溶液离子浓度。从而根据溶度积规则可以计算出难溶电解质的溶度积常数．     

Electronic structure of FCC phase in Fe-Mn-Si based shape memory alloys and its stability

The relationship between the electronic structure of FCC phase in Fe-Mn-Si alloy and its stability has been studied by using the discrete variational method based on the first principle. The reason why Mn and Si elements have different influences on the stacking fault energy may be related to the electron concentration ( e/a). Si reduces the hole number of 3d band while Mn is rather complicated . The binding energy has been calculated and the experimental results that martensite start temperature (Ms) varies with Si and Mn are explained. When the external stress is exerted in three directions, the electronic structure, the total density of states, the energy gap at Fermi energy level( EF) and the energy degeneracy will change into other states. When the different external stresses are exerted in one direction, 3d or 4s orbital occupations of the central atom decrease, the partial density of states seems to be thinner and its peak increases at EF, the bond orbit shrinks in the direction of the external st