Investigation of the effect of disulfiram on corrosion of mild steel in hydrochloric acid solution

The corrosion inhibition properties of disulfiram (DSR) for mild steel in HCl solution were analyzed by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, atomic force microscopy, scanning electron microscopy and gravimetric methods. Physical adsorption is proposed for the inhibition and the process followed the Langmuir adsorption isotherm and kinetic/thermodynamic model of El-Awady et al. Constant phase elements describing the non-ideal characteristics of the electrochemical interface are introduced. The occurrence of inductive loop is also dealt with, through the introduction of an inductive element L. The use of these elements significantly improved the quality of fit of simulation to the EIS data.     

多形式特征向量脑网络分类方法研究

目前已有的脑网络分类方法大多是通过处理收集的信号来构建脑网络,并根据一个或多个脑区之间的脑网络特征属性来进行分类。该分类方法只考虑一个特征属性,忽略了脑网络的其他特征属性,而被忽略的特征属性很可能会对实验结果产生较大的影响。为了克服已有分类方法的缺陷,文中考虑多种特征属性提出了一种基于多形式特征向量的脑网络分类方法并使用了新型图核,该分类方法由4步构成：将原始实验数据经过预处理后完成脑网络构建;根据不同的阈值来提取脑网络中多种脑网络属性值;利用支持向量机训练所有数据,根据训练结果的优劣,在每种网络属性值里挑选分类效果最优的阈值参数,并将它们进行特征融合;使用支持向量机训练融合后的特征向量。通过实验数据分析并与已有分类方法进行了对比,验证该方法在轻度认知障碍数据集上脑网络分类的有效性。     

Corrosion inhibition of mildsteel in sulphuric acid by methanol extract of Luffa aegyptiaca leaves – electrochemical and statistical view

An electrochemical and statistical view of methanol extract of Luffa aegyptiaca leaves (MLA) on the corrosion inhibition of mild steel (MS) in 0.5 M H₂SO₄ medium were investigated by potentiodynamic polarisation and electrochemical impedance spectroscopy. Polarization studies showed that the MLA acts as mixed type inhibitor with predominant cathodic behaviour. The percentage inhibition efficiency was found to increase with MLA concentration and decreased with the temperature. Thermodynamic parameter such as free energy value was negative, that indicates spontaneous adsorption of inhibitor on MS surface. Adsorption of MLA was found to obey Langmuir isotherm. The analysis of variance studies showed that the inhibition efficiencies calculated from the different electrochemical parameters are statistically significant. Surface studies were performed by Fourier transform infrared spectroscopy and atomic force microscopy.     

Quinolin-5-ylmethylene-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide as an effective inhibitor of mild steel corrosion in HCl solution

Quinolin-5-ylmethylene-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide (QMQTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in 1 M and 2 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Polarization resistances calculated from the EIS measurements were in good agreement with those obtained from direct current (DC) polarization measurements. The mild steel samples were also analyzed by scanning electron microscopy (SEM). The results showed that QMQTPH is an excellent inhibitor for mild steel in acid medium. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. It acts as an anodic inhibitor. In the 30° to 60 °C temperature range, the QMQTPH adsorption follows Langmuir isotherm model. The protection efficiency increased with increasing inhibitor concentration in the range 10⁻⁵ − 10⁻³ M, but slightly decreased with increasing temperature.     

Operational based corrosion analysis in naval ships

Life extension of ageing steel structures such as naval ships requires consideration of plate thickness losses due to corrosion, particularly when protective measures such as paint coatings and sacrificial protection are not entirely effective. Traditionally, corrosion prediction models for ships take no account of the operational profile. Consequently, the corrosion models have an inherently high variability with poor corrosion prediction capability. A new corrosion model for the prediction of corrosion loss in the seawater ballast tanks of naval vessels has been developed. The model incorporates previously available corrosion models for immersion corrosion and atmospheric corrosion and takes account of operational and environmental variables. Experimental validation is presented for a trial on an operational naval vessel.     

Electrochemical characterization of polythiophene-coated steel

In situ electropolymerization leading to polythiophene coating has been found to be a new option for providing corrosion protection to mild steel surface. The polythiophene coating thus coated has been diagnosed through polarization and AC impedance analysis, which has demonstrated the passivation role of conducting polythiophene coating. The determination of volume fraction, water uptake and delamination area have been used to further support the corrosion protection of conducting polythiophene coating.     

A correlation study on the phenolic profiles and corrosion inhibition properties of mangrove tannins (Rhizophora apiculata) as affected by extraction solvents

The objective of this study was to investigate the correlation of phenolic compositions and corrosion inhibition properties of Rhizophora apiculata bark extracts as affected by nine solvent systems. Several phenolic compositions, namely, total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC) were investigated. In addition, the inhibitive actions of tannin extracts on mild steel in 1 M HCl solution were studied by potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that extraction solvents had significant effects on TPC, TFC, CTC and inhibition properties of extracts. A correlation between CTC and inhibition properties of R. apiculata bark extracts was revealed.     

A surface wear model for hypoid gear pairs

In this paper, a methodology was proposed for simulation of surface wear of face-milled or face-hobbed hypoid gear pairs. The methodology combines Archard's wear model with a finite-element based hypoid gear contact model. The wear model requires the sliding distances and contact pressures to be computed along the contact zones at each rotational gear position. Formulations were proposed for computation of sliding distance along the tooth contact zones based on hypoid gear kinematics and geometry of the tooth surfaces, and the contact model was used to predict the normal contact pressure distributions. An example hypoid gear pair was analyzed for its wear behavior. Influences of gear position errors on wear patterns were demonstrated. An approximate method that is computationally more efficient was also proposed at the end.     

有限板多孔MSD的应力强度因子计算

首先阐明组合法求解有限板多孔MSD( multiple site damage)应力强度因子的基本原理,然后就组合法运用中比较难以解决的多孔边裂纹间的修正系数问题,提出一种基于复变函数法的有效解决方法.将完善后的组合法应用于有限板多孔MSD应力强度因子的求解,计算某型飞机典型铆接壁板无主裂纹和含主裂纹两种情况的数值算例.通过与有限元结果的比较可知,该方法的计算结果精确、可靠,计算过程简单、易行.提出的近似解析方法能很好地应用于任意分布的有限板多孔MSD裂纹结构,在工程断裂问题中有较好的应用价值.     

On the role of plastic deformation during the mild wear of alumina

Polycrystalline -alumina was worn against Mg-partially stabilized zirconia (Mg-PSZ), using water lubrication, a sliding speed of 0.24 m/s and a load of 10 N. Differential wear between grains (maximum 33 nm) and fine (0.3–1.9 μm diameter) abrasive grooves were found on the worn surface. TEM of back-thinned samples indicated widespread dislocation flow at the surface, heterogeneously distributed between grains, and largely associated with abrasive grooves. Those grains standing proud of the surface invariably contained extensive dislocation damage. The dominant slip system was pyramidal ( , , and ) although occasional basal slip was also found. No prism slip was observed. The pyramidal slip planes were concentrated at angles of 6–33° to the worn surface. Basal slip was frequently associated with basal twinning on planes at 72–73° to the worn surface. Dislocation pile-ups at grain boundaries often coincided with grain boundary cracking. The extent of damage from abrasive grooves varied from grain to grain and was dictated by crystallographic orientation more than the grain height. No evidence of mechanical damage was found in those grains that had suffered the highest wear, indicating that material removal had been controlled by tribochemical mechanisms. The origin of the differential wear between grains is considered and the implications of the experimental observations on the time-dependent transition to severe wear in aluminas are discussed.