Search results
1 – 10 of 194
Abstract
Details
Keywords
Akshya K. Guin, M. Bhadu, Mahua Sinhababu, Ankita Mundhara, T.K. Rout and G. Udayabhanu
– The aim of this work was to study the effect of La(NO
Abstract
Purpose
The aim of this work was to study the effect of La(NO
3
)
3
on the corrosion behavior of sol-gel coating prepared by hydrolysis of 3-glycidoxypropyl)methyldiethoxysilane and 3-aminopropyltriethoxysilane. Generally, galvanized steel is subjected to a hexavalent chromium passivation treatment. Hexavalent chromium passivation is not an environment friendly product and researchers are looking for a suitable alternative for chromium passivation treatment. Some of the potential alternatives are silicate conversion coating or the use of silane-based coatings. In this context, sol-gel coating was investigated as a potential replacement for hazardous hexavalent chromium passivation treatment.
Design/methodology/approach
The sol-gel film was deposited on galvanized steel sheet by the dip coating method. The molecular vibration and chemical properties of sol-gel solution and coated films were obtained by infrared spectroscopy. Images from a scanning electron microscope were obtained to characterize the morphology of the film. The corrosion resistance of the coated samples was evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves and salt spray tests.
Findings
The results indicated that La(NO
3
)
3
-doped coatings were more resistance to corrosion than undoped coating. The coating doped with 0.5 per cent La(NO
3
)
3
offered improved corrosion protection due to the inhibitive action of the La3+ ion.
Originality/value
This result can provide a reference for the development of chromium-free passivation for galvanized sheeting.
Details
Keywords
Karima Derdour, Chafia Bouchelta, Amina Khorief Naser-Eddine, Mohamed Salah Medjram and Pierre Magri
The purpose of this paper is to focus on the removal of hexavalent chromium [Cr(VI)] from wastewater by using activated carbon-supported Fe catalysts derived from walnut shell…
Abstract
Purpose
The purpose of this paper is to focus on the removal of hexavalent chromium [Cr(VI)] from wastewater by using activated carbon-supported Fe catalysts derived from walnut shell prepared using a wetness impregnation process. The different conditions of preparation such as impregnation rate and calcination conditions (temperature and time) were optimized to determine their effects on the catalyst’s characteristics.
Design/methodology/approach
The catalyst samples were characterized using thermogravimetric analysis, scanning electron microscopy and Fourier transform infrared spectroscopy. The adsorption of Cr(VI) by using using activated carbon supported Fe catalysts derived from walnut shell as an adsorbent and catalyst was investigated under different adsorption conditions. The parameters studied were contact time, adsorbent dose, solution pH and initial concentrations.
Findings
Results showed that higher adsorption capacity and rapid kinetics were obtained when the activated walnut shell was impregnated with Fe at 5 per cent and calcined under N2 flow at 400°C for 2 h. The adsorption isotherms data were analyzed with Langmuir and Freundlich models. The better fit is obtained with the Langmuir model with a maximum adsorption capacity of 29.67 mg/g for Cr(VI) on Fe5-AWS at pH 2.0.
Originality/value
A comparison of two kinetic models shows that the adsorption isotherms system is better described by the pseudo-first-order kinetic model.
Details
Keywords
Xiaobo Wang, Zhipeng Li, Wen Zhan, Jesong Tu, Xiaohua Zuo, Xiangyi Deng and Boyi Gui
This study aims to expand the reliability and special functions of lightweight materials for high-end equipment and green manufacturing, so that it is the first such research to…
Abstract
Purpose
This study aims to expand the reliability and special functions of lightweight materials for high-end equipment and green manufacturing, so that it is the first such research to carry out nano-composite technology of nickel-coated carbon nanotubes (Ni-CNTs)-based titanium-zirconium chemical conversion on aluminum alloy substrate.
Design/methodology/approach
Corrosion behavior of various coatings was investigated using dropping corrosion test, linear polarization and electrochemical impedance spectroscopy. The results showed that the corrosion resistance of the nano-composite conversion coatings was significantly improved to compare with the conventional titanium-zirconium conversion coating. The morphology and microdomain characteristics of the nano-composite conversion coatings were characterized by SEM/eds/EPMA, which indicated that the CNT or Ni-CNTs addition promoting the integrity coverage of coatings in a short time.
Findings
Surface morphology of titanium-zirconium (Ti-Zr)/Ni-CNT specimens exhibited smooth, compact and little pores. The nano-composite conversion coatings are mainly composed of Al, O, C and Ti elements and contain a small amount of F and Zr elements, which illuminated that CNT or Ni-CNT addition could co-deposit with aluminum and titanium metal oxides.
Originality/value
The study of corrosion resistance of nano-composite conversion coatings and the micro-zone film-formation characteristics would be provided theoretical support for the development of basic research on surface treatment of aluminum alloys.
Details
Keywords
The ring seal under consideration has come out as a result of the complex research such as the numerical simulation research, introductory quality research involving a real…
Abstract
The ring seal under consideration has come out as a result of the complex research such as the numerical simulation research, introductory quality research involving a real object, comparative research on a tribotester and fundamental research on the real object. It has been found that the essence of excellent tribological properties of the new ring seal lies, in its low value of surface free energy (SFE) of titanium nitride coating on the piston ring and in its high value of energy which is the characteristic of the nitrided surface of the cast iron cylinder sleeve. As a result, when the motion of the ring on the sleeve surface ceases, especially in the outer dead centre (ODC) in expansion stroke, the boundary layer of oil on the sleeve surface prevents metallic contact. In general, it has been found that the SFE can be an important index of material selection for cutting pairs, especially for those working in the reciprocating motion.
Details
Keywords