Stereoselective construction of quaternary chiral centers using Ti(III)-mediated opening of 2,3-epoxy alcohols: studies directed toward the synthesis of penifulvins

A trisubstituted α,β-unsaturated ester moiety was suitably placed in a molecule also bearing an epoxy alcohol moiety at its other end to intramolecularly trap the intermediate radical, which was formed when the molecule was treated with Cp₂Ti(III)Cl to regio- and stereoselectively open its epoxy ring, giving rise to a quaternary chiral center. The method was subsequently used in an attempt to construct the bicyclic core framework of potent insecticides penifulvins.     

Nb3Ru5B2 – The First Fully Characterized Ternary Phase in the Nb‐Ru‐B System: Synthesis,Crystal Structure,and Bonding Analysis

The first fully characterized phase in the Nb‐Ru‐B system, Nb₃Ru₅B₂, was successfully synthesized as polycrystalline powders as well as single crystals and characterized by EDX analysis and X‐ray diffraction methods. It is the first ternary phase of the type A₃T₅B₂ adopting the Ti₃Co₅B₂ structure type and containing a group eight transition metal at the T sites. According to COHP bonding analysis the Nb–Nb interactions between two pentagonal prisms are strongly bonding and thus weaken the Nb–Ru interactions, which become significantly weaker than those found in the tetragonal prisms. Furthermore a deep pseudogap is found around the Fermi Level of the calculated DOS and the phase is predicted to be a metallic conductor as expected for this metal‐rich boride.     

Effects of surface nanocrystallization pretreatment on low-temperature ion sulfurization behavior of 1Cr18Ni9Ti stainless steel

A nanocrystalline surface layer of 10 μm thickness was fabricated on 1Cr18Ni9Ti stainless steel by means of supersonic fine particles bombarding (SFPB). The followed low-temperature ion sulfurizing was carried out on the original and the SFPBed (SFPB treated) surface, respectively, forming sulfide layers with certain thickness. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to analyze the phase constituents and grain size of the nanocrystallized surface layer. The surface morphologies and compositions of the sulfide layers were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). X-ray photoelectron spectroscope (XPS) was used to detect the valence states of the sulfide layers. Elemental distribution with depth was measured by augur energy spectroscopy (AES). The results show that the microstructure of the surface layer is refined to nano-grains with the grain size about 30 nm and random crystallographic orientations by SFPB treatment. The surface nanocrystallization pretreatment can significantly improve the thickness, density, and the FeS content ratio of the sulfide layers. The analysis indicates that, the enhancement in efficiency of the ion sulfurization treatment by SFPB surface nanocrystallization treatment is mainly attributed to the high-density crystal defects and the increase of surface chemical activity.     

Modeling the relationship between hydrogen content and mechanical property of Ti600 alloy by using ANFIS

An adaptive network based fuzzy inference system (ANFIS) was used to predict the tensile strength of Ti600 alloy after hydrogenation. In this approach, the whole procedure of structure identification and parameter optimization was carried out automatically and efficiently. Two major influence factors were considered as input variables including hydrogenation temperature ranging of 600–750 °C and hydrogen content ranging of 0–0.502 wt.%, two different membership functions, triangular and Gaussian, were employed as fuzzy subset to compare the model accuracy. After the training and testing process, the predicted values were compared with experimental result and multiple linear regression values. It is found that the ANFIS predicted values with Gaussian and Triangular membership function were in good agreement with the experimental results with relative error of 2.69% and 2.77%, which has a equal accuracy but higher than multiple linear regression method with the error of 16.74%. Such modeling approach for the hydrogenation of titanium alloy can be highly beneficial since it offers the possibility of identifying promising processing parameters without the necessity for extensive experimental test cycles.     

在乙二醇甲醚溶液中合成NiTiO_3超细粉末

在无隔膜电解槽中,加入0.035mol/L（Bu4N）Br的乙二醇甲醚溶液,保持电解温度40℃、电流密度30mA/cm2时,先电解钛片6h,再电解镍片3h,制得镍、钛醇盐配合物,电流效率为95.1%。采用红外、拉曼光谱对其进行了表征。结果表明,前驱体结构为NiTi（OCH2CH2OCH3）6,可以有效克服团聚现象。水解...     

Theoretical Study of the Statistical Properties of Single- and Double-Pass M-Mode Er3+-Ti:LiNbO3 Straight Waveguide Amplifiers

Abstract

In this article, we report a theoretical study concerning some statistical parameters which characterize the single- and double-pass Er³⁺-doped Ti:LiNbO₃ M-mode straight waveguides. For the derivation and the evaluation of the Fano factor, the statistical fluctuation and the spontaneous emission factor we used a quasi two-level model in the small gain approximation and the unsaturated regime. The simulation results show the evolution of these parameters under various pump regimes and waveguide lengths. The obtained results can be used for the design of complex rare earth-doped integrated circuits.     

Highly Active Nickel Nanoparticles Supported on TiO2 Nanotube Electrodes for Methanol Electrooxidation

Nickel nanoparticles/TiO₂ nanotubes/Ti electrodes were prepared by galvanic deposition of nickel nanoparticles on the TiO₂ nanotubes layer on titanium substrates. Titanium oxide nanotubes were fabricated by anodizing titanium foil in a DMSO fluoride‐containing electrolyte. The morphology and surface characteristics of titanium dioxide nanotubes and Ni/TiO₂/Ti electrodes were investigated using scanning electron microscopy and energy‐dispersive X‐ray spectroscopy, respectively. The results indicated that nickel nanoparticles were homogeneously deposited on the surface of TiO₂ nanotubes. The electrocatalytic behaviour of nickel nanoparticles/TiO₂/Ti electrodes for the methanol electrooxidation was studied by electrochemical impedance spectroscopy, cyclic voltammetry, differential pulse voltammetry and chronoamperometry methods. The results showed that Ni/TiO₂/Ti electrodes exhibit a considerably higher electrocatalytic activity toward the oxidation of methanol.     

非铁电巨介电压敏材料CCTO

本文主要介绍了近年来一种新型类钙钛矿型非铁电巨介电非线性压敏陶瓷材料——CaCu3Ti4O12,概述了其在晶体结构、相结构、微观形貌、多条件下介电特性和I-V特性等方面的研究进展。比较了CaCu3Ti4O12陶瓷的各种巨介电性理论和模型,阐述了压敏特性的起源。在讨论CaCu3Ti4O12陶瓷巨介电性和压敏特性机理的同时,指出了CaCu3Ti4O12作为介电材料和压敏材料的研究方向及应用的可能性。掺杂、复合及热处理工艺等对CaCu3Ti4O12电性能影响的系统性研究工作还需要进一步深入;纳米化可能会导致其某项特性的进一步提升,而薄膜化尽早与微电子领域的需要相结合会产生更广阔的应用空间。     

氢对PbZr0．5Ti0．5O3在氮氢混合气氛退火中铁电性能的影响

采用基于密度泛函理论的第一性原理,针对PbZr0.5Ti0.5O3无氧和含氢的顺电相和铁电相的二层超晶胞,分别计算了 Ti 沿 c 轴位移时体系总能量的变化、电子云密度分布和Ti-O、Zr-O和H-O的重叠布居数.结果表明,含氢铁电相的Ti-O键和Zr-O 键相埘无氢铁电相明显减弱,氢氧之间较强的轨道杂化使它们趋于形成共价键;晶格中氧氧键的钉扎效应使含氢情况下的顺电相能昔始终低于铁电相能量,说明氢的引入阻碍了PbZr0.5Ti0.5O3从立方顺电相到四方铁电相的相变,并推断其为含氧气氛退火过程中PbZr0.5Ti0.5O3铁电性能下降的主要原因之一.所得结果对于深入理解铁电材料在氮氢混合气氛退火后铁电件能下降的微观机制具有参考价值.