Electroactive conducting polymers for corrosion control

There is an intensive effort underway to develop new corrosion control coatings for structural metals. In part, this effort has been motivated by the desire to replace chromium(VI)-containing coatings currently used for corrosion control of iron and aluminum alloys. Cr(VI) has been shown to be hazardous to the environmental and to human health, and its use in many countries will be sharply curtailed in the coming years. Electroactive conducting polymers (ECPs) represent a class of interesting materials currently being explored for use in corrosion control coating systems, possibly as a replacement for Cr(VI)-based coatings. The electroactivity and the electronic conductivity (or semiconductivity) of ECPs set them apart from traditional organic coatings. As with chromate, interesting and potentially beneficial interactions of ECPs with active metal alloys such as steel and aluminum are anticipated, with concomitant alteration of their corrosion behavior. A review of this active research area will be presented in two parts. Here in Part 1, a general introduction to the topic of corrosion control by ECPs will be presented, including an overview of corrosion and its control by traditional methods, an introduction to ECPs and their properties, and a discussion of the processing issues surrounding the use of ECPs as coatings. Part 1 also includes a review of the literature on the use of ECPs as coatings (or components of coatings) on non-ferrous active metals, principally aluminum and aluminum alloys, although some work on zinc, copper, silver, titanium and silicon will also be described. In Part 2 of this review (to be published in the next issue of this journal), the rather extensive literature on the use of ECPs for the corrosion control of ferrous alloys (steels) will be reviewed. Electronic Publication     

Effects of retrograde-zoning of garnet on Sm-Nd isotopic dating of eclogite and oxygen isotopic disequilibrium between eclogitic minerals

The compositional zoning of the garnet in a strongly deformed eclogite from Raobazhai foliated peridotite has been recognized. The CaO concentrations of the garnet are decreased from the core to the rim, while its MnO concentrations are increased, suggesting the retrograde origin of such CaO—MnO zoning. The tie line of garnet + omphacite from this eclogite gives a Sm-Nd age of (187 ± 5) Ma, which is less significant than the Sm-Nd ages of (221±5)—(228 ± 3) Ma and (210 ± 6)—(214 ± 6) Ma for ultrahigh-pressure eclogites in the southern Dabie zone and in the northern Dabie zone, respectively. This younger Sm-Nd age could result from the¹⁴³Nd/¹⁴⁴ Nd ratio decrease of the retrograde zone in the garnet. The δ¹⁸O values of the garnet and omphacite show that their fractionation values are less than the equilibrium fractionation value between the garnet and omphacite at 500—900°C, which suggests an oxygen isotopic disequilibrium between them.     

毛细管气相色谱法测定油中植物甾醇和胆固醇

采用2.0mol/L的氢氧化钾乙醇溶液在85℃水浴上皂化45min，石油醚萃取，毛细管气相色谱法分离植物甾醇和胆固醇的分析方法，讨论并确定了样品皂化的最佳条件。用该法测定了芝麻油中甾醇的含量，相对标准偏差为0.86%-4.13%；回收率为89.59%-103.09%。结果表明：采用该方法具有操作快速、简便、准确等优点。     

电化学溶解金属铜制备纳米CuO

有机电解合成;铜电极;水解;电化学溶解金属铜制备纳米CuO     

新颖无限三股螺旋钴配位聚合物{[Co(4,4''''-bipyridine)(4,4''''azobispyridine)_2(NCS)_2]·H_2O}_n的合成、结构和性质的研究(英文)

0IntroductionThereisagreatcurrentinterestforthecrystalengineeringofcoordinationframeworks犤1,2犦,notonlybecauseoftheirpotentialapplicationsaszeolite-likematerialsinmolecularselection,ionexchange,andcatalysis,butalsobecauseoftheirintriguingvarietyofarchitecturesandnewtopologies.Uptonow,themostimportantdrivingforcesincrystalengineeringarecoordinationbondingandhydrogenbondinginteract-ion犤3～5犦.Theuniquedirectionality,strength,andcom-plementaryofnon-covalenthydrogenandcoordinatedbondingplayanimp…     

碳纤维微电极负载金纳米粒子用于绿茶中儿茶素的检测

本文开发了基于纳米金修饰的碳纤维超微电极(CFME)用于儿茶素的定量检测。通过使用柠檬酸三钠还原氯金酸制得纳米金粒子(AuNPs),采用恒电位电沉积法将纳米金修饰在CFME表面。在pH 2.00的Tris-HCl缓冲溶液中,采用差分脉冲法和循环伏安法考察了修饰前后电极对儿茶素的电催化性能。结果表明,纳米金修饰电极对儿茶素具有明显的电催化效果。在优化实验条件下,纳米金修饰的碳纤维超微电极(AuNPs/CFME)与儿茶素浓度在1.00×10^-3~10.0μmol/L范围内呈良好的线性关系,且AuNPs/CFME的电化学性能非常稳定,具有良好的重现性。该方法操作简单,准确性高,可用于对儿茶素进行定量检测。     

Achieving Superior Electrocatalytic Performance by Surface Copper Vacancy Defects during Electrochemical Etching Process

Vacancy defects of catalysts have been extensively studied and proven to be beneficial to various electrocatalytic reactions. Herein, an ultra‐stable three‐dimensional PtCu nanowire network (NNW) with ultrafine size, self‐supporting rigid structure, and Cu vacancy defects has been developed. The vacancy defect‐rich PtCu NNW exhibits an outstanding performance for the oxygen reduction reaction (ORR), with a mass activity 14.1 times higher than for the commercial Pt/C catalyst (20 %.wt, JM), which is currently the best performance. The mass activity of the PtCu NNW for methanol oxidation reaction (MOR) is 17.8 times higher than for the commercial Pt/C catalyst. Density‐functional theory (DFT) calculations indicate that the introduction of Cu vacancies enhances the adsorption capacity of Pt atoms to the HO* intermediate and simultaneously weakens the adsorption for the O* intermediate. This work presents a facile strategy to assemble efficient electrocatalysts with abundant vacancy defects, at the same time, provides an insight into the ORR mechanism in acidic solution.     

3D-structured carbon-coated MnO/graphene nanocomposites with exceptional electrochemical performance for Li-ion battery anodes

MnO has a high theoretical capacity, moderate discharge plateau, and low polarization when it is used as the anode material in lithium battery. However, the issues that limit its application are its poor conductivity and large volume changes, which can easily result in the collapse of electrode structure during long-term cycling. In the present work, a carbon-coated MnO/graphene 3D-network anode material is synthesized by an electrostatic adsorption of dispersed precipitates precipitation method. The MnO nanoparticles coated by carbon are uniformly distributed on the surface of graphene nanosheets and form a 3D sandwich-like nanostructure. A carbon layer is coated on the surface of MnO nanoparticles, which slows down the volume expansion in the process of lithium intercalation. The graphene nanosheets are cross-linked through carbons in this 3D nanostructure, which provides mechanical support and effective electron conduction pathways during the charge-discharge. The electrochemical tests indicate that the prepared 3D carbon-coated MnO/graphene electrode exhibits an excellent rate capacity of 1247.3 and 713.2 mAh g^?1 at 100 and 1000 mA g^?1, respectively. The capacity is 792.2 mAh g^?1 after long cycle at a current density of 1000 mA g^?1. The specific capacity is higher than that of MnO-based composite lithium anode materials currently reported. The superior rate and cycling performances are attributed to the unique 3D-network structure, which provides an effectively conductive network, buffers volume expansion, and prevents falling and aggregation of MnO in the charge and discharge process of the electrode materials. The 3D-structured carbon-coated MnO/graphene anode material will have an excellent application prospect.

Open image in new window

Graphical abstract Cyclic performance at 1 A g^?1 and SEM images (inset) of the 3D-structured carbon-coated MnO/graphene nanocomposite.

     

Low-temperature heat capacity and standard thermodynamic functions of 1-butyl-3-methylimidazolium lactate

The heat capacities of 1-butyl-3-methylimidazolium lactate ionic liquids ([C₄mim][Lact]) were measured with a highly accurate automatic adiabatic calorimeter over the temperature range from 79 to 406 K. And the experimental values of molar heat capacities were fitted to a polynomial equation using least square method in the appropriate temperature ranges. The standard molar heat capacity was determined to be 1734.46?±?5.12 J K^?1 mol^?1 at 298.15 K. The molar enthalpy and molar entropy of the transition were determined to be 15.575?±?0.045 and 64.44?±?0.14 J K^?1 mol^?1. Other thermodynamic properties, such as (H_T???H_298.15) and (S_T???S_298.15), were also calculated. Furthermore, when the temperature reaches 241.87 K, the strongest peaks appeared by analysis of the heat capacity curve. This phenomenon could be explained from the interionic interaction, which is the hydrogen bond between the anions and cations.     

Structural diversity of isothiocyanato Cd(II) and Zn(II) Girard’s T hydrazone complexes in solution and solid state: effect of H-bonding on coordination number and supramolecular assembly of Cd(II) complex in solid state

The isothiocyanato Zn(II) complex (1) and mixed isothiocyanato/thiocyanato Cd(II) complex (2) with the condensation product of 2-acetylpyridine and trimethylammoniumacetohydrazide chloride (Girard’s T reagent) (HLCl) were investigated both experimentally and theoretically. The crystal structures of both complexes showed tridentate N₂O coordination of hydrazine ligand. In complex 1 square-pyramidal coordination surrounding of Zn(II) consists of deprotonated hydrazone ligand and two isothiocyanato ligands, while in octahedral Cd(II) complex ligand is coordinated without deprotonation as a positively charged species and coordination geometry is completed with two N-coordinated and one S-coordinated NCS^? anions. NMR spectroscopy and molar conductivity results for Cd(II) and Zn(II) complexes indicated their instability in solution. DFT calculations were performed to explain coordination preference and stability of complexes 1 and 2 in solid state and in solution. The obtained Cd(II) complex is the first reported mononuclear pseudohalide/halide Cd(II) complex with quinoline-/pyridine-based hydrazone ligands possessing octahedral geometry in solid state. In this complex, H-bonding has significant impact on coordination number and supramolecular assembly in solid state.