Nucleophilic Activation of Sulfur Hexafluoride by N-Heterocyclic Carbenes and N-Heterocyclic Olefins: A Computational Study

Sulfur hexafluoride (SF₆) is considered as a potent greenhouse gas, whose effective degradation is challenging. Here we report a computational study on the nucleophilic activation of sulfur hexafluoride by N-heterocyclic carbenes and N-heterocyclic olefins. The result shows that the activation of SF₆ is both thermodynamically and kinetically favorable at mild condition using NHOs with fluoro-substituted azolium and sulfur pentafluoride anion being formed. The Gibbs free energy barrier during the activation of SF₆ has a linear relationship with the energy of HOMO of substrates, which could be a guideline for applying those compounds that feature higher energy in HOMO to activate SF₆ in high efficiency.     

Tensile behaviour of corroded and hydrogen embrittled 2024 T351 aluminum alloy specimen

The synergetic effect of corrosion and corrosion induced hydrogen embrittlement damage processes which occur at local scale has been found to result in a dramatic macroscopic tensile ductility loss of the 2024 aluminum alloy. In the present work, the tensile behaviour of corroded 2024 T351 specimens has been estimated on the basis of FE analysis by taking into account the local material properties in the damaged areas. A parametric study is involved to account for the effect of thickness in the results. Calculated tensile properties obtained with the analysis agree well with experimental data.     

线缆护套材料在我国西部环境中的试验研究

本文通过对线缆外护套材料在我国西部地区严酷环境试验站中土壤和大气1～5年的试验结果分析，总结了塑料护套材料的耐蚀性能。为线缆护套的防护设计、合理选材及制定标准提供科学依据。     

A biocatalytic route to enantioenriched, sulfanyl aldol products

The aldol products derived from sulfur- or selenium containing acceptors were prepared by kinetic resolution in the presence of antibody 84G3 with enantiomeric excesses ranging from 56 to 70%. Much higher level of enantioselectivity was obtained (enantiomeric excesses all superior to 96%) for sulfanyl aldol products derived from thiomethoxyacetone with three different acceptors.     

CID-ICP-AES检测煤中不同形态的硫

研究了CID-ICP-AES检测煤中硫酸盐和硫铁矿形态硫的方法。较现有国标方法快速、简便，常见元素不干扰，加标回收率在98．5％-103．0％之间，10次测定的RSD在0．76％-1．59％之间。     

离子束混合工艺对材料抗蚀性能的影响

本文介绍了离子束混合工艺方法。与直接注入相比较,离子束混合所使用的设备造价低1/4—1/2,而生产效率可提高1—2个数量级,因而使生产成本大幅度降低,这无疑对离子束工艺的实际应用将产生巨大的促进作用。 通过对轴承材料(GCr15和Cr4Mo4V)经Cr、N、Ta不同元素的混合处理后,在0.5M H_2SO_4和0.1M NaCl的缓冲溶液中的阳极极化曲线表明经混合处理后的两种材料试样,其抗蚀能力和抗点蚀能力均大大提高,这与直接注入的试样效果是一致的。 通过俄歇谱仪和透射电镜的分析结果表明混合是成功的,且在一定的条件下,形成非晶组织。 本文的结论是,无论是离子的直接注入还是离子束混合,对提高轴承材料的抗腐蚀性能都是有效的方法,特别是离子束混合技术具有更大的应用前景。     

Characterization of ceramic PVD thin films on AZ31 magnesium alloys

Ceramic thin films have been widely used to protect the metal substrate as coatings in the past years. In order to improve the poor corrosion resistance of AZ31 magnesium alloy, the study in this paper used the electron beam evaporation method to prepare ceramic PVD films on its surface with TiO₂ and Al₂O₃ as donors, respectively. Atomic force microscopy (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) were used to investigate the surface morphology, composition and microstructure of the thin films. Both films deposited on AZ31 took on compact top surface morphologies and grew as amorphous structures on substrate. AES test not only showed that films compositions deviated the standard stoichiometric ratios, but also found that element Mg diffused into films and existed as magnesium oxide in the TiO_x film as well as the AlO_x film. In the electrochemical corrosion test, the AlO_x coating on AZ31 exhibited the largest electrochemical impedance in a 3.5% NaCl solution. But it did not show better corrosion resistance than others for the poorer adhesion. Even if its thickness was small, the TiO_x coating on AZ31 exhibited the best corrosion resistance in this study. According to the observation and analysis, the damage of these films on AZ31 in aggressive solutions was mainly due to the existence of pores, microcracks, vacancies and poor adhesion between coating and substrate.     

Slow positron beam study of corrosion-related defects in pure iron

Corrosion-related defects of pure iron were investigated by measuring Doppler broadening energy spectra (DBES) of positron annihilation and positron annihilation lifetime (PAL). Defect profiles of the S-parameter from DBES as a function of positron incident energy up to 30 keV (i.e. ∼1 μm depth) were analyzed. The DBES data show that S-parameter increases as a function of positron incident energy (mean depth) after corrosion, and the increase in the S-parameter is larger near the surface than in the bulk due to corrosion. Furthermore, information on defect size from PAL data as a function of positron incident energy up to 10 keV (i.e. ∼0.2 μm depth) was analyzed. In the two-state trapping model, the lifetime τ₂ = 500 ps is ascribed to annihilation of positrons in voids with a size of the order of nanometer. τ₁, which decreases with depth from the surface to the bulk, is ascribed to the annihilation of positrons in dislocations and three-dimensional vacancy clusters. The corroded samples show a significant increase in τ₁ and the intensity I₂, and near the surface the corroded iron introduces both voids and large-size three-dimensional vacancy clusters. The size of vacancy clusters decreases with depth.     

Holographic interferometry as electrochemical emission spectroscopy of a carbon steel in 5–20 ppm TROS C-70 inhibited seawater

In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the number of the fringe evolutions during the corrosion test of a carbon steel in blank seawater and seawater with different concentrations of a corrosion inhibitor. In other words, the anodic dissolution behaviors (corrosion) of the carbon steel were determined simultaneously by holographic interferometry, as an electromagnetic method, and by the electrochemical impedance (EI) spectroscopy, as an electronic method. So, the abrupt rate change of the number of the fringe evolutions during corrosion tests, EI spectroscopy, of the carbon steel is called electrochemical emission spectroscopy. The corrosion process of the steel samples was carried out in blank seawater and seawater with different concentrations, 5–20 ppm, of TROS C-70 corrosion inhibitor using the EI spectroscopy method, at room temperature. The electrochemical-emission spectra of the carbon steel in different solutions represent a detailed picture of the rate change of the anodic dissolution of the steel throughout the corrosion processes. Furthermore, the optical interferometry data of the carbon steel were compared to the data, which was obtained from the EI. spectroscopy. Consequently, holographic interferometry is found very useful for monitoring the anodic dissolution behaviors of metals, in which the number of the fringe evolutions of the steel samples can be determined in situ.     

Determination of the boiling point distribution of sulfur compounds in light cycle oil using GC with a flame photometric detector and pyrolyzer

A method has been developed to determine the boiling point distribution of sulfur compounds in light cycle oils (LCO'S). The method chosen for this analysis was GC with a flame photometric detector (FPD) and pyrolyzer. Tests were carried out to evaluate the recovery efficiency, repeatability, and accuracy of the method. Repeatabilities within 2% were obtained. The recovery of benzothiophenes and dibenzothiophenes was close to 100%; this was important because these are the major sulfur components in LCO's. No hydrocarbon or solvent interferences were observed with the use of the pyrolyzer, even for a 95% solvent level. Comparison with results from other techniques showed that the method accurately determined the levels of sulfur compounds in the LCO boiling point range.