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1 – 10 of over 1000Of the many unrelated types of microbes that can initiate or stimulate the corrosion of metals, the most important economically are the sulphate‐reducing bacteria. They flourish…
Abstract
Of the many unrelated types of microbes that can initiate or stimulate the corrosion of metals, the most important economically are the sulphate‐reducing bacteria. They flourish in the soil, in fresh and salt water (including heating and cooling systems) and in oil storage tanks and associated pipelines; and they have been found in all the continents including Antarctica.
M. Mobin and S.K. Hasan
The purpose of this paper is to present the results of studies on the reaction of metal oxides such as Cr2O3 and Al2O3 with Na2SO4 in flowing SO2 (g) at 1,100 and 1,200 K.
Abstract
Purpose
The purpose of this paper is to present the results of studies on the reaction of metal oxides such as Cr2O3 and Al2O3 with Na2SO4 in flowing SO2 (g) at 1,100 and 1,200 K.
Design/methodology/approach
The oxides chosen for the studies were initial scaling products during the oxidation of industrial alloys and invariably are involved in hot‐corrosion reactions in the presence of molten salts. The thermo‐gravimetric studies for the system were carried out as a function of Na2SO4 in the mixture. The different constituents in the reaction products were identified by XRD analysis and morphologies of the reaction products were discussed on the basis of optical metallography and scanning electron microscopic studies. The pH and conductivity of the aqueous solutions of reaction products were measured and an attempt made to functionalize these parameters with Na2SO4 concentration in the mixture. Quantitative estimation of the soluble metal was carried out using an atomic absorption spectrophotometer. The formation of products was investigated by thermodynamic computation of free energies of the reactions and the study of relevant phase stability diagrams.
Findings
Looking at the complex nature of the reactions, it is difficult to generalize the conductance studies, as many complex species are liable to hydrolyze in the aqueous solution. However, the break in few curves at certain mole fraction of Na2SO4 indicates the presence of soluble complex species.
Originality/value
The paper provides information regarding the reaction between a pertinent oxide and Na2SO4 and proper identification of reaction products, useful for understanding the occurrence and importance of fluxing reactions and in the interpretation of hot corrosion mechanism and the development of new protective materials.
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Carbon steels are abundantly employed in our day‐to‐day engineering services, the automotive industry, and in various domestic usages. Service life of carbon steel assumes…
Abstract
Carbon steels are abundantly employed in our day‐to‐day engineering services, the automotive industry, and in various domestic usages. Service life of carbon steel assumes importance, as faults bring either costly industrial downtime or embarrassing domestic inconvenience. It appears that these materials are dependent completely on the solubility of carbon in their solid‐solutions. Instabilities and destabilization mainly occur due to separation of various forms of carbides, which embrittles the matrix in the time domain. The presence of residual stress which is trapped inside the matrix, having originated from the previous deformation stresses of the wrought products, accelerates such precipitation. Thermal treatment, such as the subcritical stress relieving process, may also accelerate such an embrittlement process, although this exercise is meant for the relief of the matrix residual stresses only. Concludes that there is simultaneous precipitation of brittle phases and also deactivation of the matrix, owing to stress relieving. A surface becomes electrochemically more active when the precipitation component more than compensates the deactivation component and vice versa. Improvement of the matrix ductility also works against such deterioration processes. Suggests that imposition of the environmental constraints, such as aggressive and corrosive media, can only accelerate deterioration, by activating the brittle precipitation cycle.
Xiaoping Lin, Xiaoyan Li, Jiming Yao, Xianghong Li and Jianlin Xu
To develop electrode materials for supercapacitor with superior electrochemical performance and simple preparation process, the purpose of this study is to prepare flexible…
Abstract
Purpose
To develop electrode materials for supercapacitor with superior electrochemical performance and simple preparation process, the purpose of this study is to prepare flexible CC/NiS/a-NiS electrodes with self-supporting structure by loading hydrothermally synthesized a-NiS particles along with nano-NiS on carbon cloth by electroplating method.
Design/methodology/approach
The effects of current densities, temperatures and pH values on the loading amount and uniformity of the active substances during the plating process were investigated on the basis of optimization of surface morphology, crystalline structure and electrochemical evaluation as the cyclic voltammetry curves, constant current charge–discharge curves and AC impedance.
Findings
The a-NiS particles on CC/NiS/a-NiS were mostly covered by the plated nano-NiS, which behaved as a bulge and provided a larger specific surface area. The CC/NiS/a-NiS electrode prepared with the optimized parameter exhibited a specific capacitance of 115.13 F/g at a current density of 1 A/g and a Coulomb efficiency of 84% at 5 A/g, which is superior to that of CC/NiS electrode prepared by electroplating at a current density of 10 mA/cm2, a temperature of 55°C and a pH of 4, demonstrating its fast charge response of the electrode and potential application in wearable electronics.
Originality/value
This study provides an integrated solution for the development of specifically structured NiS-based electrode for supercapacitor with simple process, low cost and high electrochemical charge/discharge performance, and the simple and easy-to-use method is also applicable to other electrochemically active composites.
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Baskara Sethupathi P. and Chandradass J.
This study aims to compare the influence of different solid lubricants on the friction stability of a non-asbestos disc brake pad.
Abstract
Purpose
This study aims to compare the influence of different solid lubricants on the friction stability of a non-asbestos disc brake pad.
Design/methodology/approach
Three brake pads were developed using three lubricants, namely, non-asbestos brake pad with sulfide mix (NASM), non-asbestos brake pad with bismuth sulfide (NABS) and non-asbestos brake pad with molybdenum disulfide (NAMO). Sulfide mix was indigenously developed by physically mixing friction modifiers, alkaline earth chemicals and various metallic sulfides homogeneously dispersed in graphite medium. The physical, chemical, mechanical and thermal properties of brake pads were characterized as per industrial standards. The tribological performances were studied using the Chase testing machine as SAE-J661-2012. The worn surface of the pads was studied using scanning electron microscope to analyze the dominating wear mechanism.
Findings
NASM was excellent in fade as well as wear resistance. NABS was better from a wear point of view, but fade resistance was moderate despite its higher cost. NAMO fared average in fade and wear despite its excellent dry lubricating properties. NASM was excellent in terms of fade as well as wear resistance.
Originality/value
Among the selected metal sulfides, the indigenously developed sulfide mix was better than the other two sulfides, which indicates that the synergetic effect of metal sulfides was always preferable to the individual sulfides.
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Sathickbasha K., Selvakumar A.S., Surya Rajan Balachandran and Hariharasakthisudhan P.
The purpose of this study is the influence of various combinations of metal sulfides on the tribological performance of brake pads.
Abstract
Purpose
The purpose of this study is the influence of various combinations of metal sulfides on the tribological performance of brake pads.
Design/methodology/approach
Three brake pads were prepared using the possible combination of any two of the solid lubricants from Bismuth trisulfide (Bi2S3); Tin disulfide (SnS2) and Antimony trisulfide (Sb2S3) are chosen and blended with molybdenum disulfide and graphite. The tribological performance was compared with the brake pad containing aftermarket sulfide mixture. The tribological performance parameters such as performance coefficient of friction, fade percent, recovery percent, wear thickness loss, time is taken to reach the maximum temperature and fluctuation of friction were investigated using Chase tribometer adopting IS 2742 Part-4 (1994) test procedure.
Findings
The friction stability of the brake pad with 4Wt% of MoS2, Bi2S3 and SnS2 was observed to be better, but it showed poor wear performance and aggressive towards the rotor, whereas the brake pad contained 4Wt% of MoS2, Bi2S3 and Sb2S3 exhibited improved wear performance.
Originality/value
This paper explains the influence of the combination of multiple metal sulfide in the tribological performance of the copper-free brake friction composite.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0249/
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Vijay R., Manoharan S., Nagarajan S. and Lenin Singaravelu D.
The purpose of this study is to deals with the effect of premixed dual metal sulfides (tin disulfide + iron disulfide) as a replacement for antimony trisulfide on the tribological…
Abstract
Purpose
The purpose of this study is to deals with the effect of premixed dual metal sulfides (tin disulfide + iron disulfide) as a replacement for antimony trisulfide on the tribological performance of brake friction materials.
Design/methodology/approach
In this study, brake friction materials were developed by using premixed dual metal sulfides as a replacement for antimony trisulfide in the formulation. The brake friction materials were developed in the form of standard brake pads as per the industrial practice. Thermal stability was measured for varying ingredients and developed brake pads using thermogravimetric analysis. The physical, mechanical and thermal properties of the developed brake pads were tested as per the industrial standards. The tribological properties were analyzed using the Chase test as per SAE J661. Worn surface analysis was done using a scanning electron microscope.
Findings
The experimental results indicate that the brake pads filled with premixed dual metal sulfides had good thermal stability, physical, chemical and mechanical properties with stable friction and less wear rate due to better lubrication preventing friction undulations.
Originality/value
This paper explains the influence of premixed dual metal sulfides as a replacement for antimony trisulfide in brake pads formulation to enhance the tribological performance by preventing friction undulations.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0144/
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Lin Liu, Xiaona Pan, Jinjuan Xing and Jianhua Qian
This paper aims to evaluate the inhibition efficiency of thiadiazole derivatives, such as 2,5-dimercapto-1,3,4-thiadiazole (DMTD), 5-methly-2-mercapto-1,3,4-thiadiazole (MMTD) and…
Abstract
Purpose
This paper aims to evaluate the inhibition efficiency of thiadiazole derivatives, such as 2,5-dimercapto-1,3,4-thiadiazole (DMTD), 5-methly-2-mercapto-1,3,4-thiadiazole (MMTD) and 2,5-dithiododecyl-1,3,4-thiadiazole (DDTD), in 50 mg/L hydrogen sulfide for silver strip.
Design/methodology/approach
Evaluation was carried out by corrosion-inhibiting test, electrochemical measurement and surface analysis techniques. 3D surface profiler, atom force microscopy, scanning electron microscopy and energy-dispersive X-ray analysis were applied and finally confirmed the existence of the adsorbed film.
Findings
The electrochemical measurement showed that the inhibition efficiency increases with increasing inhibitor concentration in 50 mg/L hydrogen sulfide solution, while the corrosion rate and the corrosion current decrease. Weight-gained measurements also indicated that inhibitor decreases the corrosion rate in the studied solution. The adsorption of DMTD and MMTD on the silver surface obeys Temkin’s adsorption isotherm, but the adsorption of DDTD follows Langmuir’s adsorption isotherm. That means that the inhibition mechanism is different between DMTD, MMTD and DDTD. The ΔG0ad values of DMTD, MMTD and DDTD were −37.47, −37.29 and −38.69 kJ/mol, respectively. It showed that there was an adsorption bond between silver surface and inhibitor, and the adsorption belongs to chemical adsorption.
Originality/value
The inhibitors have an excellent inhibition efficiency, and the best inhibition efficiency is 91.76 per cent. Inhibitors can effectively inhibit metal corrosion in the oil and gas.
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The corrosion behaviour of copper in dilute HCl solution of pH 1.8‐2, in the absence and presence of different additives of Na2S, was studied by open circuit potential…
Abstract
The corrosion behaviour of copper in dilute HCl solution of pH 1.8‐2, in the absence and presence of different additives of Na2S, was studied by open circuit potential measurement, scanning electron microscopy and polarisation techniques. A complete covering of the surface with the strongly chemisorbed HS− is achieved at ≥10 ppm Na2S concentration. The addition of different concentrations of ethylene diamine (EDA) to HCl of pH 1.8‐2 promoted the dissolution rate, due to an increase in autocatalytic dissolution at the Cu metal surface. However, the synergistic inhibition effect between EDA and Na2S, resulting from the adsorption of HS− on the Cu metal, facilitated the adsorption of EDA.
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Lin Xueyang, Liu Rutie, Wang Lin, Li Zhengzhou, Xiong Xiang, Liao Ning and Chen Jie
This study aims to investigate the effect of combined use of granular graphite and petroleum coke on the properties of copper-based friction materials and the friction and wear…
Abstract
Purpose
This study aims to investigate the effect of combined use of granular graphite and petroleum coke on the properties of copper-based friction materials and the friction and wear mechanisms.
Design/methodology/approach
Copper-based friction materials with different proportions of petroleum coke and granular graphite were prepared by using powder metallurgy. The friction surfaces were analyzed.
Findings
Changing the ratio of petroleum coke/granular graphite affects the formation of oxides and sulfides on the surface of the materials. Increasing the petroleum coke promotes the production of metal sulfide and sulfate in the friction materials and reduces coefficient of friction (COF) and wear. Increasing petroleum coke also increases the amount of carbonic oxide (CO) released during the braking process and promotes the reduction process of iron oxide on the friction surface.
Originality/value
The synergistic effect of carbon materials on copper-based friction materials was studied in terms of the tribological chemical reaction. This research provides useful information for the selection of carbon materials in friction materials.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0075/