Synthesis and crystal structure of a new organic metal with honeycomb dithiooxalato-bridged anionic network, β″-(ET)2{[NMe3Ph]NaCr(C2S2O2)3(MeCN)}

The first bis(ethylenedithio)tetrathiafulvalene (ET) based radical cation salt with a bimetallic dithiooxalato-bridged anionic network, β″-(ET)₂{[NMe₃Ph]NaCr(C₂S₂O₂)₃(MeCN)} has been prepared. The compound is metallic down to 60 K, at lower temperatures the resistance grows smoothly. The structure of β″-(ET)₂{[NMe₃Ph]NaCr(C₂S₂O₂)₃(MeCN)} has been determined from single-crystal X-ray diffraction and is characterized by alternation a conducting donor layer of the β″-type packing with three insulating layers, two of which are {[NaCr(dto)₃]²⁻}_∞ anionic networks and the third one, interleaving them, is formed by [NMe₃Ph]⁺organic cations and acetonitrile solvent molecules.     

A new organic/inorganic electroluminescent material with a silsesquioxane core

This paper describes a new polyhedral oligomeric silsesquioxane (POSS)-based blue-light electroluminescent nanoparticle, octakis[N-(9-ethyl-9H-carbazol-3-yl)undecanamide-11-dimethylsiloxy]silsesquioxane (POSS-C11-Cz), which contains eight carbazole chromophore arms, synthesized through the hydrosilation reaction of octakis(dimethylsiloxy)silsesquioxane with the terminal olefin Cz-C11ene. POSS-C11-Cz exhibits good thermal and electrochemical stabilities and good film-forming properties. The optical and photoluminescence spectra of POSS-C11-Cz in solution and in the solid state indicate a reduction in the degrees of aggregation and excimer formation because inter-chain interactions were prohibited by the bulky POSS core. Moreover, photoluminescence spectra of a POSS-C11-Cz (3 wt.%)/polyfluorene (97 wt.%) blend revealed that the color was stable after heating the sample at 200 °C for 5 h; in contrast, the pure polyfluorene exhibited a significant green emission at 530 nm. A triple-layer device based on this blend exhibited higher maximum brightness and luminance efficiencies relative to those of the pure polyfluorene. Thus, the organic/inorganic POSS-C11-Cz/polyfluorene blend has potential for use in polymeric light-emitting diodes because of its improved thermal and optoelectronic characteristics.     

A new lubricant carrier for metal forming

A lubricant carrier for metal forming processes is developed. Surfaces with pores of micrometer size for entrapping lubricant are generated by electrochemical deposition of an alloy, consisting of two immiscible metals, of which one metal subsequently is etched away leaving 5 μm layers with a sponge-like structure. The pores will act as lubricant reservoirs during severe forming processes. The deposited microporous layer is evaluated by friction tests in the form of ring compression tests and double cup extrusion tests. Furthermore the anti-seizure properties are investigated by single cup extrusion at high reduction and excessive stroke comparing with conventionally lubrication using phosphate coating and soap.     

一种新型的金属板材柔性加工系统

在制造业中,生产批量与生产效率、质量、成本、生产周期经常是一个突出的矛盾。特别是随着人们对需求的差异,小批量生产与单件生产所占的比重日益增大。为了解决这个矛盾,柔性加工技术应运而生。20多年前,萨瓦尼尼公司采用全新的理念设计并制造出了世界上第一套金属板材柔性加工系统。近20年来,萨瓦尼尼公司综合自身积累的经验,为用户提供先进的技术和工艺,及计算机技术、数字控制技术、自动化生产技术和远程通讯方面的最新发展,对柔性加工系统进行不断地改进与完善,使其在板材加工领域中始终处于世界先进行列。1　金属板材柔性加工系统的优…     

A new functionalized conductive polymer poly(2-methyl-5-amino-1,4-naphthoquinone) (PMANQ) with two distinct redox systems

The electrooxidation of 2-methyl-5-amino-1,4-naphthoquinone (MANQ) on platinum or glassy carbon (GC) electrodes in acetonitrile leads to poly(2-methyl-5-amino-1,4-naphthoquinone) (PMANQ) films. Films were characterized by UV–VIS, X-ray photoelectron spectroscopy (XPS), ex situ FT-IR and in situ multiple internal reflection FT-IR spectroscopies (MIRFT-IRS). Results converge to a definition of the polymer structure, which is of the polyaniline type, bearing one methylquinone group per monomer unit. The electrochemical properties of PMANQ film in organic and aqueous media were studied by MIRFT-IRS and in situ d.c. conductivity. The film is conducting in negative as well as in positive potential range.     

Corrosion prevention with an organic metal (polyaniline): Surface ennobling,passivation, corrosion test results

Progress on the area of passivation of metallic materials by polyaniline is being presented. The redoxcatalytic reaction leading to the formation of a passivating oxide layer has been evaluated, and a reaction scheme is shown. Results of corrosion tests are described as well.     

A new approach to the processing of metal hydrides

In this paper we show that severe plastic deformation techniques could be used to enhance hydrogen sorption properties of metal hydrides. Commercial magnesium hydride was processed in a vertical cold rolling apparatus. After only five rolling passes hydrogen sorption kinetics at 623 K were greatly enhanced without noticeable loss of capacity. The improvement in sorption kinetics is probably due to the nanocrystalline structure and number of defects. Investigation of the powder morphology and crystal structure indicates that cold rolling is equivalent to ball milling.     

A new approach to optimal design of multi-stage metal forming processes with micro genetic algorithms

This paper describes a new method for design optimization of process variables in multi-stage metal forming processes. The selected forming processes are multi-pass cold wire drawing, multi-pass cold drawing of a tubular profile and cold forging of an automotive outer race preform. An adaptive micro genetic algorithm (μGA) scheme has been implemented for minimizing a wide variety of objective-cost functions relevant to the respective processes. The chosen design variables are die geometry, area reduction ratios and the total number of forming stages. Significant improvements in the simulated product quality and reduction in the number of passes has been observed as a result of the micro genetic algorithms-based optimization process.     

Synthesis,structure of a new acceptor TBA2S6 and preparation,physical properties of ET3S6

A general procedure for the synthesis of the tetrabutylammoium hexasulphide, TBA₂S₆, is first described. The structure of TBA₂S₆ has been determined by X-ray crystallography. Lattice parameters and space group information are as follows: a=15.039(5) Å, b=16.086(5) Å, c=17.078(6) Å, α=β=γ=90.00°, V=4131.5(24) ų, orthorhombic, Pbnb (Z=4). Diffraction data (MoK_α radiation, 2θ_max=50) is collected by Rigaku-AFC6 diffract meter. The structure was solved and refined by direct method and full-matrix least-squares procedures to R-value of 0.0645. The complex ET₃S₆ has been prepared through electrocrystallization ways. The conductivity of this salt at room temperature is 2.3 S cm⁻¹. It shows weak metallic behavior above 240 K. Below this temperature, it becomes a semiconductor. The XPS spectra indicated the presence of three different kinds of S atoms in the salt. The ESR line width is found to be 44.478 G at room temperature.     

A new joining by forming process to produce lap joints in metal sheets

This paper proposes a new joining by forming process to produce lap joints in metal sheets. The process combines partial cutting and bending with mechanical interlocking by sheet-bulk compression of tabs in the direction perpendicular to thickness. The lap joints are flat with all the plastically deforming material contained within the thickness of the two sheets partially placed over one another. The design of the lap joints is performed by a simple analytical model and the overall concept is validated by means of numerical modelling and experimentation. Destructive shear tests demonstrate the effectiveness and performance of the new proposed lap joints.     

A methodology for off-line evaluation of new environmentally friendly tribo-systems for sheet metal forming

Increasing focus on environmental issues in industrial production has urged sheet stamping companies to look for new tribo-systems in order to substitute hazardous lubricants such as chlorinated paraffin oils. Production testing of new lubricants is, however, costly and makes industry reluctant towards testing alternative solutions. The present paper presents a methodology for off-line testing of new tribo-systems based on numerical modelling of production process as well as laboratory test to adjust the latter combined with testing of selected tribo-systems on a new automatic sheet-tribo-tester emulating typical sheet forming production processes. Final testing of the tribo-systems in production verifies the methodology.     

A new semiconductor Al2Fe3Si3 with complex crystal structure

Al₂Fe₃Si₃, a new semiconductor with complex triclinic structure was synthesized by arc melting and spark plasma sintering, followed by heat treatment. The nominal compositions of samples have been changed to compensate Al evaporation during synthesis process, and single Al₂Fe₃Si₃ phase has been obtained with the nominal composition of Al: Fe: Si = 26: 37: 37 (6 at.% Al excess against stoichiometry). In this study, we measured the sound velocity, thermal expansion coefficient, Vickers hardness, fracture toughness, electrical conductivity, Seebeck coefficient, and thermal conductivity of the new semiconductor Al₂Fe₃Si₃. The Al₂Fe₃Si₃ sample displayed positive Seebeck coefficient from 300 to 850 K, with a maximum Seebeck coefficient of 110 μV/K at 430 K. The Debye temperature of Al₂Fe₃Si₃ was 640 K, which was similar to or higher than those of other Al, Fe, Si based thermoelectric materials, but the lattice thermal conductivity was lower, 4–5 W/mK, due to the complex crystal structure of Al₂Fe₃Si₃. The maximum ZT value was 0.06 at 580 K.     

TiO_2可见光催化H_2O_2降解水中的有机污染物

以活性艳红X-3B及苯酚作模型污染物,研究催化剂晶型(锐钛矿和金红石)及H2O2对TiO2可见光催化性能的影响,并研究Fe3+在这一反应体系中的协同效应。结果表明:在H2O2存在条件下,锐钛矿和金红石TiO2均能可见光催化降解活性艳红X-3B,且TOC的去除率达65%,反应并不限于发色基团的破坏,但当TiO2的吸附点位吸附CO32?达到饱和后,则对活性艳红X-3B基本无降解效果;TiO2能可见光催化H2O2降解苯酚,金红石TiO2显示出较锐钛矿TiO2更高的催化活性,反应120 min后,对苯酚的降解率达80%,且反应体系生成的环状中间产物的浓度明显较锐钛矿TiO2的高;以Fe3+协同TiO2可见光催化H2O2降解苯酚时,反应效率显著加快,经20 min反应,对苯酚的降解率可达100%,而金红石TiO2显示更为明显的协同效应。     

Poly(1,4-bis[2-(4-hexylthiophene)]-2,5-dimethylphenylene): a new conjugated electroluminescent polymer

We report the synthesis of the conjugated polymer, poly(1,4-bis[2-(4-hexylthiophene)]-2,5-dimethylphenylene), by FeCl₃ oxidation in high yield. The polymer has perfect head-to-head (HH) linkages between the thiophene rings, exhibits good solubility in conventional organic solvents, and exhibits high thermal stability. The optical band gap is ∼2.76 eV. The polymer emits greenish-blue light under UV irradiation with the emission maximum at 507 nm; the photoluminescence (PL) efficiency (solid thin film) is ∼10%. The external electroluminescence efficiency was measured to be 0.0012% for single layer devices using Al as the cathode material and 0.0035% for single layer devices using Ca as the cathode material.     

A new ternary compound YbZn2As2 with mixed valency of Yb

A new compound with chemical formula YbZn₂As₂ and ‘anti’-La₂O₃-type crystal structure (space group P3m1) has been synthesized for the first time. The trigonal lattice constants of the compound are a=0.4157 and c=0.6954 nm. In the temperature range 77–500 K, the magnetic susceptibility of YbZn₂As₂ follows the Curie–Weiss law, indicating antiferromagnetic interactions of the Yb ions and yielding a Curie temperature θ=−52.8 K and an effective magnetic moment μ_eff=2.35 μ_B (the Bohr magneton) per Yb ion. This means that a part of the Yb ions has valency 3+, instead of 2+ for all the Yb ions, as would be expected from their formal oxidation number, i.e. YbZn₂As₂ is a compound with mixed valency of Yb. YbZn₂As₂ exhibits p-type conductivity with a room temperature electrical resistivity of 0.15 Ω cm which decreases when lowering temperature and reaches a practically constant value of 0.08 Ω cm below 20 K.     

A new experimental methodology to analyse the friction behaviour at the tool-chip interface in metal cutting

This paper investigates a new test to analyse the friction behaviour of the tool-chip interface under conditions that usually appear in metal cutting. The developed test is basically an orthogonal cutting process, that was modified to a high speed forming and friction process by using an extreme negative rake angle and a very high feed. The negative rake angle suppresses chip formation and results in plastic metal flow on the tool rake face. Through the modified kinematics and in combination with a feed velocity that is five to ten times higher than in conventional metal cutting, the shear and normal stresses are only acting in a simple inclined plane, allowing to calculate the mean friction coefficient analytically. In addition, the test setup allows to obtain the coefficient of friction for different temperatures, forces and sliding velocities. Experiments showed, that the coefficient of friction is strongly dependent on the sliding velocity for the example workpiece/tool material combination of C45E+N (AISI 1045) and uncoated cemented carbide.     

A new theoretical model of material inhomogeneity for prediction of surface roughening in micro metal forming

For prediction and prevention of surface roughening in micro metal formings, a new model to represent material inhomogeneity and an original method to determine the material inhomogeneous parameters were proposed. A series of micro deep drawing were carried out by employing metal foils with thickness of 0.05 mm and average grain size of 16.7 μm. The validity of the proposed model and method were verified with respect to prediction of surface roughening in the tested micro deep drawings. It has become clear that the proposed model and method for predicting product accuracy in manufacturing medical and electrical micro parts.     

Characterization of sheet metal components by using an upsetting test with miniaturized cylindrical specimen

Especially for safety-relevant components local characterization of the mechanical properties is necessary for product testing. For sheet metal parts with a complicated geometry conventional specimens for standardized tests cannot be extracted due to size limitations. Thus, a novel extraction procedure of miniaturized upsetting specimens is investigated. Taking a miniaturized upsetting specimen out of the sheet component allows for the first time the characterization of sheet metals in a standardized upsetting test under uniaxial compression stresses. Furthermore, this enables the analysis of strain hardening behavior of components and a direct validation of finite element simulations based on the true stress.     

A wear resistant ductile metal-toughened Cr13Ni5Si2 ternary metal silicide alloy

A ductile metal-toughened Cr–Ni–Si ternary metal silicide wear resistant alloy with a dual-phase microstructure consisting of Cr₁₃Ni₅Si₂ ternary metal silicide primary dendrites and the interdendritic nickel-base solid solution (γ) was designed and fabricated by the laser melting/continuous deposition process. Wear resistance of the γ-toughened Cr₁₃Ni₅Si₂ intermetallic alloy was evaluated on an MM-200 block-on-wheel dry sliding wear tester at room temperature. The γ-toughened Cr₁₃Ni₅Si₂ intermetallic alloy has excellent wear resistance and extremely low load-sensitivity of wear under dry sliding wear test conditions due to the inherent high hardness, abnormal hardness–temperature relation and strong covalent-dominant atomic bonds. The isolated toughening γ phase played a positive role in reducing volume wear rate by retarding crack propagation and preventing pull-out of the broken Cr₁₃Ni₅Si₂ fragments from the wear surface.