Corrosion inhibition of carbon steel in hydrochloric acid by cationic arylthiophenes as new eco-friendly inhibitors: Experimental and quantum chemical study

This study describes the adsorption behavior of three arylthiophene derivatives namely: 2-(4-amidino-3-fluorophenyl)-5-[4-methoxy phenyl] thiophene dihydrochloride salt (MA-1217), 2-(4-amidinophenyl)-5-[4-chlorophenyl] thiophene dihydrochloride salt (MA-1316) and 2-(4-amidino-3-fluorophenyl)-5-[4-chlorophenyl]thiophene dihydrochloride salt (MA-1312) at C-steel in 1.0 mol·L^-1 HCl interface using experimental and theoretical studies. Electrochemical and mass loss measurements showed that the inhibition efficiency (IE) of the arylthiophene derivatives increases with increasing concentrations and exhibited maximum efficiency 89% at 21×10^-6 mol·L^-1 (MA-1217) by mass loss method. The investigated arylthiophene derivatives obey the Langmuir adsorption isotherm. From polarization studies the arylthiophene derivatives act as mixed-type inhibitors. Surface analysis were carried out and discussed. The mode of orientation and adsorption of inhibitor molecules on C-steel surface was studied using molecular dynamics (MD) simulations. Quantum chemical parameters as well as the radial distribution function indices and binding energies confirm the experimental results.     

The dynamic evolution of aggregated lithium dendrites in lithium metal batteries

Lithium (Li) metal anodes promise an ultrahigh theoretical energy density and low redox potential,thus being the critical energy material for next-generation batteries.Unfortunately,the formation of Li den-drites in Li metal anodes remarkably hinders the practical applications of Li metal anodes.Herein,the dynamic evolution of discrete Li dendrites and aggregated Li dendrites with increasing current densities is visualized by in-situ optical microscopy in conjunction with ex-situ scanning electron microscopy.As revealed by the phase field simulations,the formation of aggregated Li dendrites under high current den-sity is attributed to the locally concentrated electric field rather than the depletion of Li ions.More specif-ically,the locally concentrated electric field stems from the spatial inhomogeneity on the Li metal surface and will be further enhanced with increasing current densities.Adjusting the above two factors with the help of the constructed phase field model is able to regulate the electrodeposited morphology from aggregated Li dendrites to discrete Li dendrites,and ultimately columnar Li morphology.The methodol-ogy and mechanistic understanding established herein give a significant step toward the practical appli-cations of Li metal anodes.     

Studying the formation process of chromate conversion coatings on aluminium using continuous electrochemical noise resistance measurements

A unique electrochemical technique, namely continuous noise resistance calculation (CNRC), was used to obtain electrochemical kinetic information from the formation process of chromate conversion coatings (CCC) on aluminium electrodes. It was found that the noise resistance (R_n) of aluminium electrodes remained almost unchanged during electrodes' immersion in a chromate containing acidic solution where the CCC films were supposed to form rapidly. This result indicates that the formation of CCC was associated with continuous corrosion of the aluminium electrodes and that the CCC films formed on aluminium surface were not intact barrier films, but most likely porous layers. The CCCs became protective only after they were aged in the environment. Based on these findings, the formation and inhibition mechanisms of CCC have been discussed.     

Hydroxyl-and-carboxyl ligand concatenating multi-lanthanide substituted tellurotungstates and electrochemical detection of noradrenaline

Developing and exploring organic–inorganic hybrid multi-lanthanide (Ln) implanted heteropolyoxometalates (HPOMs) has bloomed into an emerging research field. In this article, two neoteric d-gluconic acids (H₆GA) concatenating multi-Ln^III implanted heteropolytungstates K₁₄H₁₀[Ln₄(H₂O)₄W₆(H₂GA)₄O₁₂(B-α-TeW₉O₃₃)₄]·60H₂O (Ln = La³⁺ (1), Pr³⁺ (2)) were obtained in acidic aqueous system. Attractively, in the polyanion structure of 1 and 2, six W^VI and four Ln^III centers are connected by four flexible H₂GA^4? ligands via carboxyl and hydroxyl groups, resulting in the heterometallic [Ln₄(H₂O)₄W₆(H₂GA)₄O₁₂]⁸⁺ cluster and then the heterometallic cluster is surrounded by four [B-α-TeW₉O₃₃]^8– segments. Electrochemical measurements for the 1@CFMCN/GCE sensor (CFMCN = carboxyl-functionalized multiwalled carbon nanotube; GCE = glass carbon electrode) demonstrate that 1@CFMCN/GCE shows benign recognition response to detecting noradrenaline (NDA). This research expands the structural diversity of Ln-implanted HPOMs and presents an electrochemical platform of recognizing NDA in the field of biosensors.     

Effects of rapid solidification on the phase structures and electrochemical properties of a V3TiNi0.56Co0.14Nb0.047Ta0.047 alloy

The crystal structures and electrochemical properties of a V₃TiNi_0.56Co_0.14Nb_0.047Ta_0.047 alloy prepared by the melt-spinning method were studied. The rapidly solidified alloy consists of a major Vanadium-based solid solution phase and a secondary Ti₂Ni-based phase. The secondary phase exists between the dendritic arms of the major phase, showing a typical eutectic characteristic. With increasing cooling rate, the amount of the secondary phase decreases but the lattice parameters of both the major phase and the secondary phase show no obvious change. Because the disappearance of the catalytic effect of the secondary phase, the rapidly solidified alloy shows bad electrochemical properties except cycle stability.     

Passivation of Fe-Cr alloys studied with ICP-AES and EQCM

The response of sputter deposited Fe-15Cr and Fe-25Cr alloys to a rapid potential increase in the passive region was studied using two in situ methods: electrochemical quartz crystal microbalance and inductive coupled plasma-atomic emission spectroscopy (ICP-AES). Both methods indicated an increase in the dissolution rate of iron following the potential change; the total amount of material dissolved being higher for the Fe-15Cr alloy. For both alloys, about 10% of the total dissolved material was Cr. This result compared well with experiments on a 430 stainless steel. ICP-AES is shown to be useful for the in situ determination of partial currents of metal dissolution using solution analysis in a flow cell.     

锻模型腔的电解加工技术

通过电解加工与其它常用加工方法的比较，以及电解加工应用的实例，论证了电解加工是提高锤模型腔加工水平的重要工艺手段。     

L－半胱氨酸的电化学还原制备（Ⅰ）

研究了包括电极材料、电解方式和电流密度在内的几个因素对Ｌ－胱氨酸电化学还原为Ｌ－半胱氨酸的影响。结果表明，经处理后的Ｓｎ能明显地提高反应速度；恒电位电解可使Ｌ－半胱氨酸的产率和电流效率分别达到９８％和１００％；恒电流电解的适宜电流密度为１２～１６Ａ·ｄｍ－３，产率和电流效率各为９７．６～９８；５％和７０～７８％；分段控制电流法的产率为９６．４％，电流效率为９２％。     

Study of the coupling reactions between electrochemically generated aromatic radical anions and methyl, alkyl and benzyl radicals

Alkyl radicals produced in the indirect reduction of alkyl halides or alkyldimethylsulfonium salts by electrochemically generated aromatic radical anions couple fast with the latter and alkylated or dialkylated dihydro compounds are formed. Rate constants measured for the coupling reaction between on one hand methyl, primary, secondary and tertiary alkyl radicals as well as benzyl and cumyl radicals and on the other hand a wide spectrum of electrochemically generated aromatic radical anions are found to be about 1×10⁹ M⁻¹ s⁻¹. Previous measurements of coupling rate constants for primary alkyl radicals have been re-evaluated since they were affected by the presence of an S_N2 reaction occurring between the alkyl halides used as radical precursors and the aromatic radical anions. New experiments are also included using alkyldimethylsulfonium salts as precursors in order to prevent such S_N2 artefacts. It is concluded that sterical hindrance does not play a significant role for the radical-radical anion coupling reactions. In general the rate constants for the coupling reactions are all close to 10⁹ M⁻¹ s⁻¹.     

Carbon nanofibers: Synthesis, characterization, and electrochemical properties

Carbon nanofibers (CNFs) have been synthesized by co-catalyst deoxidization process by a reaction between C₂H₅OC₂H₅, Zn and Fe powder at 650 °C for 10 h. These nanofibers exhibit diameters of ∼80 nm and lengths ranging from several micrometers to tens of micrometers. X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy indicate that as-prepared CNFs possess low graphitic crystallinity. The resultant CNFs as electrode shows capacity of ∼220 mAh/g and high reversibility with little hysteresis in the insertion/deintercalation reactions of lithium-ion. In addition, the possible growth of CNFs is discussed.