Electrodeposition of polyaniline, poly(2-iodoaniline), and poly(aniline-co-2-iodoaniline) on steel surfaces and corrosion protection of steel

Polyaniline (PANi), poly(2-iodoaniline) (PIANi), and poly(aniline-co-2-iodoaniline) (co-PIANi) were synthesized using cyclic voltammetry in acetonitrile solution containing tetrabuthylammonium perchlorate (TBAP) and perchloric acid (HClO₄) on 304-stainless steel electrodes. Adherent and black polymer films were obtained on the electrodes. The structure and properties of these polymer films were characterized by FTIR and UV-vis spectroscopy and electrochemical method. The corrosion performance of PANi, PIANi, and co-PIANi coated electrodes were investigated in 0.5 M hydrochloric acid (HCl) solutions by potentiodynamic polarization technique, open circuit potential-time curves and electrochemical impedance spectroscopy, EIS. It was found that the PANi film could provide much better protection than PIANi, and co-PIANi and PANi films have barrier property as well as acting as passivator. On the other hand PIANi and co-PIANi films are acting as barrier coatings which were related with the prevention of cathodic reaction taking place at metal\electrolyte interface. EIS measurement shows that every coating gives protection efficiency of greater than 75% after 48 h of immersion time in corrosive test solution.     

Initial oxidation of duplex stainless steel

Three different techniques were used to produce thin oxide layers on polished and sputter-cleaned duplex stainless-steel samples. These samples were exposed to 10⁻⁵ mbar of pure oxygen inside the vacuum chamber, exposed to ambient conditions for 24 h, and plasma oxidized. The oxide layers thus produced were analysed using XPS depth profiling in order to determine the oxide layers’ compositions with depth. We found that all the techniques produce oxide layers with different traces of metallic components and with the maximum concentration of chromium oxide shifted towards the oxide-layer-bulk-metal interface. A common characteristic of all the oxide layers investigated is a double-oxide stratification, with regions closer to the surface exhibiting higher concentrations of iron oxide and those more in-depth exhibiting higher concentrations of chromium oxide. A simple non-destructive Thickogram procedure was used to corroborate the thickness estimates for the thinnest oxide layers.     

Microstructural analysis of carbonitrided austenitic steels

An austenitic heat resisting steel containing 25% Cr and 19% Ni was internally carbonitrided in an atmosphere of 0.5% C₃H₆, 9.5% H₂ and 90% N₂. Immediately below the alloy surface, globular precipitates were observed. At greater depth, two zones of lamellar morphology precipitates were observed to form. M₇C₃ was found directly beneath the surface and M₂₃C₆ was found closer to the reaction front. The lamellar carbide morphology is more typically characteristic of the precipitates formed during nitriding rather than carburising, suggesting that nitrogen plays some role in the precipitation process. A focused ion beam (FIB) miller was used to create thin, electron transparent locations at specific regions in the precipitation zone in order to characterise, via transmission electron microscopy, the crystallography and composition of the phases present. In this study, thin areas were produced in the lamellar region at the transition between the M₂₃C₆ and M₇C₃ regions. The composition, crystal structure, and orientation relationships are reported and compared to those found previously at both the internal precipitation front and the sample surface.     

含Nb微合金钢应变诱导析出的模拟

基于物理冶金原理建立了微合金钢在热轧过程中流变应力、回复、再结晶和析出模型，模拟了含Nb微合金钢Nb（C,N）析出动力学，并利用Thermo-Calc软件计算了不同条件下析出粒子形核驱动力和元素平衡含量值，同时考虑了回复和再结晶对析出的影响.计算结果表明，该模型对含Nb微合金钢在不同热轧形变条件下模拟结果与实验结果符合较好，因此可以有效预测在不同热轧形变条件下析出粒子体积分数和析出粒子尺寸. 关键词： 微合金钢 位错密度 回复 再结晶     

Fissile core and Tritium-Breeding Blanket: structural materials and their requirements

High radiation resistant structural materials for fusion and fission nuclear power plants are a key issue for the development of both types of reactors. Selection criteria, elements of metallurgy of the selected materials, and the major issues as they are revealed by the results of the present development programmes, are presented. At low temperature (300 °C) ferritic/martensitic steels are suffering from He-embrittlement, associated with possible hardening due to α/α^′ unmixing. The kinetics of hardening and embrittlement versus dose, especially saturation with dose, are still open key issues, difficult to settle on the basis of a purely experimental programme. Important progress is still to be made in mastering the initial microstructure, inclusion cleanness and joining techniques of oxide dispersion strengthened steels for higher heat resistance. Physics modeling as presented in this issue should promote guidance to the understanding of the mechanisms involved, provide solutions to master the initial microstructure and phase stability, and mitigate the in-service property degradation. To cite this article: J.-L. Boutard et al., C. R. Physique 9 (2008).     

醋酸介质中溶解氧对不锈钢和磷脱氧铜腐蚀行为影响

应用极化曲线法和溶解氧测量技术研究不锈钢_2 0 6和磷脱氧铜在醋酸介质中的腐蚀行为以及过程的控制特征 .分析在含氧及采用抗坏血酸去除部分溶解氧的醋酸介质中 ,醋酸浓度、氯度、温度对上述两种金属腐蚀行为的影响因素 ,为石油化工中的醋酸设备的正确选材及有效防腐提供理论和实验依据     

Spectroscopic, energetic and metallographic investigations of the laser lap welding of AISI 304 using the response surface methodology

Spectroscopic signals originated by the laser-induced plasma optical emission have been simultaneously investigated together with energetic and metallographic analyses of CO₂ laser welded stainless steel lap joint, using the Response Surface Methodology. This statistical approach allowed us to study the influence of the laser beam power and the laser welding speed on the following response parameters: plasma plume electron temperature, joint penetration depth and melted area. A clear correlation has been found between all the investigated response parameters. The results have been shown to be consistent with quantitative considerations on the energy supplied to the workpiece as far as the laser power and travel speed were varied. The regression model obtained in this way could be a valuable starting point to develop a closed loop control of the weld penetration depth and the melted area in the investigated process window.     

Surface microstructures and antimicrobial properties of copper plasma alloyed stainless steel

Bacterial adhesion to stainless steel surfaces is one of the major reason causing the cross-contamination and infection in many practical applications. An approach to solve this problem is to enhance the antibacterial properties on the surface of stainless steel. In this paper, novel antibacterial stainless steel surfaces with different copper content have been prepared by a plasma surface alloying technique at various gas pressures. The microstructure of the alloyed surfaces was investigated using glow discharge optical emission spectroscopy (GDOES) and scanning electron microscopy (SEM). The viability of bacteria attached to the antibacterial surfaces was tested using the spread plate method. The antibacterial mechanism of the alloyed surfaces was studied by X-ray photoelectron spectroscopy (XPS). The results indicate that gas pressure has a great influence on the surface elements concentration and the depth of the alloyed layer. The maximum copper concentration in the alloyed surface obtained at the gas pressure of 60 Pa is about 7.1 wt.%. This alloyed surface exhibited very strong antibacterial ability, and an effective reduction of 98% of Escherichia coli (E. coli) within 1 h was achieved by contact with the alloyed surface. The maximum thickness of the copper alloyed layer obtained at 45 Pa is about 6.5 μm. Although the rate of reduction for E. coli of this alloyed surface was slower than that of the alloyed surface with the copper content about 7.1 wt.% over the first 3 h, few were able to survive more than 12 h and the reduction reached over 99.9%. The XPS analysis results indicated that the copper ions were released when the copper alloyed stainless steel in contact with bacterial solution, which is an important factor for killing bacteria. Based on an overall consideration of bacterial killing rate and durability, the alloyed surface with the copper content of 2.5 wt.% and the thickness of about 6.5 μm obtained at the gas pressure of 45 Pa is expected to be useful as antimicrobial materials that may have a promising future in antimicrobial applications.     

Finite element and experimental method for analyzing the effects of martensite morphologies on the formability of DP steels

Abstract

In this article, we investigated the effect of martensite morphology on the mechanical properties and formability of dual phase steels. At first, three heat treatment cycles were subjected to a low-carbon steel to produce ferrite–martensite microstructure with martensite morphology of blocky-shaped, continuous, and fibrous. Tensile tests were then carried out so as to study mechanical properties, particularly the strength and strain hardening behavior of dual phase steels. In order to study the formability of dual phase samples, Forming Limit Diagram was obtained experimentally and numerically. Experimental forming limit diagram was obtained using Nakazima forming test, while Finite Element Method was utilized to numerically predict the forming limit diagram. The results indicated that the dual phase samples with fibrous martensite morphology had the highest tensile properties and strain rate hardening out of the three different microstructures. Blocky-shaped martensite morphology, on the other hand, had the worst mechanical properties. The study of the strain hardening behavior of dual phase sample by Kocks–Mecking-type plots, evinced two stages of strain hardening for all specimens with different microstructures: stages III and IV. The forming limit diagram of dual phase steels also proved that samples with fibrous martensite morphology had the best formability compared to other two microstructures. The simulated forming limit diagram manifested that there is a good agreement between experimental results and those obtained by FEM.     

Vacancy-solute complexes and their clusters in iron

In this contribution, several vacancy-solute complexes in iron are investigated theoretically from the viewpoint of positron annihilation. In particular, V-Si, V-P, V-Cr, V-Mn, V-Ni, V-Cu and V-Mo complexes are examined. In addition, nano-sized vacancy-Cu clusters in the Fe matrix are also studied. We concentrate on positron lifetimes and coincidence Doppler broadening profiles that bring complementary information about the studied complexes and their clusters. Positron calculations are carried out using the atomic superposition method employing realistic atomic configurations obtained recently using an ab initio pseudopotential method (vacancy-solute complexes) and Monte Carlo/molecular dynamics methods (vacancy-Cu clusters). The main aim of this study is to predict as to what extent such defects are detectable and differentiable using positron annihilation techniques. The results obtained are discussed in the context of experimental data available in the literature.