Zerstörungsfreie Aktivierungsanalyse von Sonderwerkstoffen

Die instrumentelle Neutronen-Aktivierungsanalyse wird zur Bestimmung von Elementen in Sonderwerkstoffen im Bereich von 0,1 bis 20 Masse-% eingesetzt, Die Proben und Eichnormnale werden im Rossendorfer Kernreaktor bestrahlt und mit Hilfe der Gamma-Spektrometrie und eines Ge(Li)-Detektors ausgezählt. Wesentliche Fehlerquellen, die die Analysengenauigkeit beeinflussen, werden anhand der Bestimmung von Co in WC-Hartwerkstoffen und der Bestimmung von Sn und Cu in Supraleitungswerkstoffen diskutiert.     

Band structure and lattice vibration properties of III-P ternary alloys

Electronic band structure, optical and vibrational properties of zinc-blende GaP_xSb_1−x and GaAs_1−xP_x ternary alloys are obtained from pseudo-potential calculations. Comparisons are made with the available experimental values and with data obtained in previous theoretical studies. These comparisons show generally good agreement between the present results and experiment. The direct and indirect band-gap energies, the transverse effective charge, and the longitudinal and transversal optical phonon energies show a non-linear behavior with varying the composition x. The ionicity of the materials of interest is discussed in terms of the antisymmetric gap.     

Spinodal Composition of the System Water + Chloroform + Acetic Acid at 25 °C

A theoretical spinodal curve for the system water + chloroform + acetic acid at 25 °C is derived using a lattice model for ternary amphiphilic solutions: rod-like molecules covering the bonds of the honeycomb lattice with three-body interactions between the molecular ends associated to the same lattice site. The molecular model is equivalent to the standard Ising model on the same lattice; its mean-field solution is the most appropriate for reproducing, by local fitting, the experimental data for the binodal composition. The derived spinodal curve is in very good agreement with the spinodal composition determined also in the present work from the measured diffusion coefficients recently reported for the same system.     

A comparative study of PFP and BAB models in predicting the excess thermo-acoustical and its allied properties of liquid ternary mixtures at 298.15 K

Densities and speed of sound were measured for six binaries and three ternary liquid systems. Excess acoustical and its allied properties like excess internal pressure, excess thermal pressure coefficient, excess pseudo-Gruneisen parameter, excess speed of sound and excess ultrasonic impendence, were evaluated with the help of perspective of two liquid models i.e. Prigogine–Flory–Patterson (PFP) and Bertrand–Acree–Bruchfield (BAB) at 298.15 K over a wide range of composition. The results so obtained from two liquid models are very much comparable and are in good agreement. A molecular interaction study has also been made successfully in the light of these excess acoustical properties.     

Structure and electrical transport properties of the ordered skutterudites MGe1.5S1.5 (M=Co, Rh, Ir)

High-resolution powder neutron diffraction data collected for the skutterudites MGe_1.5S_1.5 (M=Co, Rh, Ir) reveal that these materials adopt an ordered skutterudite structure (space group R3¯), in which the anions are ordered in layers perpendicular to the [111] direction. In this ordered structure, the anions form two-crystallographically distinct four-membered rings, with stoichiometry Ge₂S₂, in which the Ge and S atoms are trans to each other. The transport properties of these materials, which are p-type semiconductors, are discussed in the light of the structural results. The effect of iron substitution in CoGe_1.5S_1.5 has been investigated. While doping of CoGe_1.5S_1.5 has a marked effect on both the electrical resistivity and the Seebeck coefficient, these ternary skutterudites exhibit significantly higher electrical resistivities than their binary counterparts.     

Synthesis and properties of colloidal ternary ZnGa2O4:Eu nanocrystals

A nonhydrolytic hot solution synthesis technique was used to grow monodisperse ternary oxide nanocrystals of ZnGa₂O₄:Eu³⁺. The shape of ZnGa₂O₄:Eu³⁺ nanocrystals was a function of the type of precursor, and their size was controlled by changing the concentration ratio of Zn precursor to surfactant. The crystal structure of synthesized ZnGa₂O₄ nanocrystals was a cubic spinel with no detectable secondary phases. Photoluminescence of red-emitting ZnGa₂O₄:Eu³⁺ nanocrystals resulted in a high (⁵D₀-⁷F₂)/(⁵D₀-⁷F₁) intensity ratio, suggesting that the Eu³⁺ ions occupy tetrahedral Zn²⁺ sites or distorted octahedral Ga³⁺ sites with no inversion symmetry in ZnGa₂O₄ nanocrystals.     

The Ternary Goldbach Problem with Primes in Arithmetic Progressions

In this paper, we give an explicit numerical upper bound for the moduli of arithmetic progressions, in which the ternary Goldbach problem is solvable. Our result implies a quantitative upper bound for the Linnik constant. Received November 4, 1998, Accepted March 6, 2001     

CsCl-C2H5OH-H2O三元体系多温下平衡溶解度的研究

采用自制微型平衡溶解度测定装置,测定了CsCl-C₂H₅OH-H₂O三元体系全温度范围内的平衡溶解度,绘制成相应的相图.首次报道氯化铯在乙醇水混合溶剂中于30,40和50℃时的分层现象,通过实验得到氯化铯在乙醇水混合溶剂中的分层温度.用Schreinemarkers"湿渣结线法"确定实验温度范围的平衡固相为无水CsCl.     

三元金属二硫化物纳米管的制备

1992年和 1 993年 ,Tenne等[1,2 ] 先后报道了具有类富勒烯和纳米管状结构的 WS2 和无机类富勒烯 Mo S2 .此后 ,无机类富勒烯化合物的制备与合成成为国内外学者的关注热点之一 .但采用化学方法制备纳米金属二硫化物时 ,多面体或洋葱状结构的 Mo S2 或 WS2 晶体的形成概率小 (这与碳的情况相似 ,也许通过扩展反应区内的温度梯度可以增加形成上述两种结构的可能性 [3] ) .另外 ,采用气固相反应制备洋葱状 WS2 的过程中 ,当每批次的量超过 1 5g时 ,无机类富勒烯 (IF)纳米颗粒的质量降低 ;同时 ,若滤筛中粉末厚度过大 ,相当大的凝聚团块开…     

Tunable Electronic Memory Performances Based on Poly(Triphenylamine) and Its Metal Complex via a SuFEx Click Reaction

A triphenylamine derivative decorated with an azobenzene group (TDA) was synthesized via a SuFEx click reaction and its polymer, poly(triphenylamine) (PTDA), was polymerized through a redox polymerization. More interestingly, its polymeric metal complex, PTDA‐Fe, can be simply obtained via one‐pot reaction between TDA and FeCl₃ owing to TDA showing a strong affinity to the Fe^III ion. The sandwich memory device based on PTDA nanofilms as active layers exhibited a binary memory performance. However, the memory device based on its polymeric metal complex exhibited a unique ternary memory behavior. The different memory performances should come from the different conductive mechanism. The mechanism of such ternary memory devices is illustrated based on both the theoretical calculation and experiments. Our work provides new insights into the preparation of novel materials for multilevel memory devices.